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US20090311340A1 - Use of xenon as neuroprotectant in a neonatal subject - Google Patents

Use of xenon as neuroprotectant in a neonatal subject Download PDF

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US20090311340A1
US20090311340A1 US11/667,065 US66706505A US2009311340A1 US 20090311340 A1 US20090311340 A1 US 20090311340A1 US 66706505 A US66706505 A US 66706505A US 2009311340 A1 US2009311340 A1 US 2009311340A1
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xenon
anesthetic
sevoflurane
subject
isoflurane
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Nicholas Peter Franks
Mervyn Maze
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Ip2ipo Innovations Ltd
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Protexeon Ltd
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Priority to US14/618,667 priority Critical patent/US9326996B2/en
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K33/00—Medicinal preparations containing inorganic active ingredients
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K31/00—Medicinal preparations containing organic active ingredients
    • A61K31/075—Ethers or acetals
    • A61K31/08—Ethers or acetals acyclic, e.g. paraformaldehyde
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K45/00—Medicinal preparations containing active ingredients not provided for in groups A61K31/00 - A61K41/00
    • A61K45/06—Mixtures of active ingredients without chemical characterisation, e.g. antiphlogistics and cardiaca
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P23/00—Anaesthetics
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P25/00—Drugs for disorders of the nervous system
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P25/00—Drugs for disorders of the nervous system
    • A61P25/04—Centrally acting analgesics, e.g. opioids
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P25/00—Drugs for disorders of the nervous system
    • A61P25/28—Drugs for disorders of the nervous system for treating neurodegenerative disorders of the central nervous system, e.g. nootropic agents, cognition enhancers, drugs for treating Alzheimer's disease or other forms of dementia
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P39/00—General protective or antinoxious agents
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
    • A61P43/00—Drugs for specific purposes, not provided for in groups A61P1/00-A61P41/00

Definitions

  • the present invention relates to the field of anesthetics. More specifically, the invention relates to anesthetic agents suitable for use in newborn and/or fetal subjects.
  • One such area may be neonatal anesthesia, where xenon may lack harmful side effects seen with other commonly used neonatal anesthetics e.g. nitrous oxide (Layzer, 1978; Amos et al., 1982; Jevtovic-Todorovic et al., 1998).
  • neonatal anesthesia where xenon may lack harmful side effects seen with other commonly used neonatal anesthetics e.g. nitrous oxide (Layzer, 1978; Amos et al., 1982; Jevtovic-Todorovic et al., 1998).
  • Synaptogenesis (the brain growth spurt) is a period of a rapid establishment of synapses, characterised by a high level of physiological cell death (up to 1% (Olney et al., 2002b)). This includes the formation of extensive corticothalamic and thalamocortical projections (Moolar and Blakemore, 1995). Despite the immense complexity of inter-species embryology, it has been shown that comparisons can be made because milestones in neurodevelopment tend to occur in the same sequence (Clancy et al., 2001).
  • Apoptosis is an essential feature of normal neurodevelopment in processes such as sculpturing, trimming, control of cell numbers and cellular disposal. It is characterised as “active cell death” comprising initiation, commitment and execution by dedicated cellular proteins (Sloviter, 2002). The crucial role of apoptosis is highlighted by the fact that genetic upregulation or downregulation of apoptosis results in a lethal genotype (Yoshida et al., 1998; Rinkenberger et al., 2000).
  • PCD physiological cell death
  • Bcl-2 and cAMP response binding protein or pro-apoptotic (e.g. Bad, Bax and the caspase family) which determine cell fate.
  • Bcl-2 and its associated peptides are thought to be particularly important in the developing CNS (Yuan and Yanker, 2000), as evidenced by the high levels of expression in the neonate and the fact that experimental over-expression of Bcl-2 can both override lack of trophic support (Garcia et al., 1992), and even prevent PCD altogether (Miartinou et al., 1994).
  • a variant of Bcl-2 (Bcl-X L ) may have a specialised role in maintaining developing neurones before they have found their synaptic targets (Motoyama et al., 1995).
  • Jevtovic-Todorovic et al. showed that neonatal rats are vulnerable to harmful side effects of anesthesia during the synaptogenic period. They demonstrated up to a 68-fold increase in the number of degenerating neurones above baseline in areas such as the laterodorsal and anteroventral thalamic nuclei (and to some extent layer II of the parietal cortex) after exposure to anesthetic agents (Jevtovic-Todorovic et al., 2003), which resulted in a functional neurological deficit in behaviour tests later in life.
  • GABAergic anesthetic isoflurane produced dose-dependent neurodegeneration in its own right, with synergistic neurodegeneration with the successive addition of midazolam (a double GABAergic cocktail) and then N 2 O (a triple cocktail) (Jevtovic-Todorovic et al., 2003).
  • This process has been shown to occur with exposure to GABAergic agents in areas other than anesthesia, such as anticonvulsant therapy and maternal drug abuse in rats (Bittigau et al., 2002; Farber and Olney, 2003).
  • a clinical manifestation of this type of neurodegeneration is detected in 1 to 2 infants per 1000 livebirths as Fetal Alcohol Syndrome (FAS) (Moore and Persaud, 1998)—characterised by abnormal facial features, microencephaly and mental retardation (Olney et al., 2002c). It is thought that binge drinking by pregnant mothers produces very high levels of ethanol (a dual GABAergic agent and NMDA receptor antagonist (Farber and Olney, 2003)) in the fetal brain, which in turn triggers the type of neurodegeneration discussed above (Ikonomidou et al., 2000). It is worth noting that this mechanism of action closely resembles that of current anesthetic procedures.
  • FAS Fetal Alcohol Syndrome
  • the present invention seeks to provide an anesthetic agent suitable for use in the newborn that is safe, efficacious, and does not have any adverse effects on neurodevelopment. More specifically, the invention seeks to provide an anesthetic agent for neonatal subjects that is suitable for use in combination with other anesthetics know to adversely affect neurodevelopment. In particular, the invention seeks to provide anesthetic combinations for use in neonates which comprise an agent capable of preventing or alleviating the adverse effects of known anesthetic agents such as isoflurane and/or sevoflurane, and/or desflurane.
  • the present invention relates to the use of xenon for treating and/or preventing and/or alleviating one or more anesthetic-induced neurological deficits in a subject, preferably a neonatal subject.
  • a first aspect of the invention relates to the use of xenon in the preparation of a medicament for treating and/or preventing and/or alleviating one or more anesthetic-induced neurological deficits in a subject, preferably a neonatal subject.
  • NMDA receptor antagonists such as N 2 O, ketamine and other agents such as isoflurane
  • xenon itself an NMDA receptor antagonist, not only lacks the characteristic toxicity produced by ketamine and N 2 O in adult rats, but also ameliorates their toxicity.
  • the experiments detailed herein have investigated xenon's properties in a neonatal rat model of neurodegeneration.
  • N 2 O considerably enhanced isoflurane-induced apoptosis (232.0'19.9; p ⁇ 0.001 vs air) while xenon reduced the injury (26.7 ⁇ 3.9; p>0.05 vs air).
  • xenon unlike other anesthetics that exhibit NMDA receptor blockade, does not enhance apoptotic neurodegeneration in the neonatal rat. In fact, xenon appears to protect against isoflurane-induced apoptosis.
  • the term “neonatal subject” refers to a newborn subject.
  • the neonatal subject is a mammal in the first four weeks after birth. More preferably, the neonatal subject is a mammal in the first two weeks, more preferably still, the first week after birth.
  • the neonatal subject is a human.
  • the neonatal subject is a subject which is undergoing, or requires, fetal surgery.
  • the neonatal subject is a subject having a life-threatening condition requiring emergent or elective surgery later in life
  • the neonatal subject receives xenon indirectly as part of an anesthetic or analgesic regimen administered to the mother during labour, or during cesarean section.
  • the medicament is for preventing and/or alleviating one or more anesthetic-induced neurological deficits in a subject, preferably a neonatal subject.
  • preventing and/or alleviating neurological deficits refers to reducing the severity of one or more neurological deficits as compared to a subject having undergone treatment with an anesthetic in the absence of xenon.
  • the neurological deficit is a learning, memory, neuromotor, neurocognitive and/or psychocognitive deficit.
  • the neurological deficit may be a neuromotor or neurocognitive, deficit.
  • neuromotor deficit is given its meaning as understood by the skilled artisan so as to include deficits in strength, balance and mobility.
  • neurocognitive deficit is given its meaning as understood by the skilled artisan so as to include deficits in learning and memory.
  • Such neurocognitive deficits may typically be assessed by well-established criteria such as the short-story module of the Randt Memory Test [Randt C, Brown E. Administration manual: Randt Memory Test. New York: Life Sciences, 1983], the Digit Span subtest and Digit Symbol subtest of the Wechsler Adult Intelligence Scale-Revised [Wechsler D.
  • the neurological deficit is neurodegeneration.
  • neurodegeneration refers to cell shrinkage, chromatin-clumping with margination and formation of membrane-enclosed apoptotic bodies; on application of caspase 3 antibody the neurodegenerating neurones stair black on application of 3,3′-diamino-benzidine (dab).
  • the neurological deficit is associated with neuronal apoptosis.
  • the neurological deficit is associated Ash neuronal necrosis.
  • the neurological deficit is a learning, memory, neuromotor or psychocognitive deficit.
  • a second aspect of the invention relates to the use of xenon in the preparation of a medicament for treating and/or alleviating and/or preventing anesthetic-induced neurodegeneration in a subject, preferably a neonatal subject.
  • a third aspect of the invention relates to the use of xenon in the preparation of a medicament for treating and/or alleviating and/or preventing anesthetic-induced neuronal apoptosis in a subject, preferably a neonatal subject.
  • a third aspect of the invention relates to the use of xenon in the preparation of a medicament for preventing and/or alleviating anesthetic-induced neuronal injury in a subject, preferably a neonatal subject.
  • the anesthetic is a volatile anesthetic agent.
  • volatile anesthetics include isoflurane, sevoflurane and desflurane.
  • the anesthetic is either a GABAergic agent such as isoflurane, sevoflurane or desflurane, or an NMDA receptor antagonist anesthetic (eg ketamine or nitrous oxide).
  • a GABAergic agent such as isoflurane, sevoflurane or desflurane
  • an NMDA receptor antagonist anesthetic eg ketamine or nitrous oxide
  • the anesthetic is isoflurane, sevoflurane, or desflurane.
  • Isoflurane is a halogenated volatile anesthetic which induces and maintains general anesthesia by depression of the central nervous system and resultant loss of consciousness. Throughout maintenance of anesthesia, a high proportion of the isoflurane is eliminated by the lungs. When administration is stopped, the bulk of the remaining isoflurane is eliminated unchanged from the lungs. As solubility of isoflurane is low, recovery from isoflurane anesthesia in man is rapid.
  • isoflurane has a mild pungency, inhalation is usually preceded by the choice of a short-acting barbiturate, or other intravenous induction agent, to prevent coughing.
  • Isoflurane can induce increased salivation and coughing in small children upon administration.
  • Adverse reactions encountered with isoflurane are similar to those observed with other halogenated anesthetics and include hypotension, respiratory depression and arrhythmias.
  • Other minor side-effects encountered while using isoflurane are an increase in the white blood cell count (even in the absence of surgical stress) and also shivering, nausea and vomiting during the post-operative period.
  • Isoflurane causes an increase in cerebral blood flow at deeper levels of anesthesia; this may give rise to an increase in cerebral spinal fluid pressure. Where appropriate, this can be prevented or reversed by hyperventilating the patient before or during anesthesia. As with other halogenated anesthetics, isoflurane must be used with caution in patients with increased intracranial pressure.
  • Isoflurane is a powerful systemic and coronary arterial dilator.
  • the effect on systemic arterial pressure is easily controlled in the normal healthy patient and has been used specifically as a means of inducing hypotension.
  • the phenomenon of “coronary steal” means that isoflurane should be used with caution in patients with coronary artery disease. In particular, patients with subendocardial ischaemia might be anticipated to be more susceptible.
  • Sevoflurane a fluorinated methyl-isopropyl ether is relatively pleasant and non-pungent and is used to cause general anesthesia before and during surgery. It is administered by inhalation. As it has a blood/gas partition coefficient of only 0.6, onset and recovery times are fast.
  • the dose of sevoflurane required varies from patient to patient, depending on age, physical condition, interactions with other medicines and the type of surgery being performed. Side effects include bradycardia, hypotension, tachycardia, agitation, laryngospasm, airway obstruction, cough, dizziness, drowsiness, increased amount of saliva, nausea, shivering, vomiting, fever, hypothermia, movement, headache. As sevoflurane is metabolized very slowly in the human body there is a high risk of renal toxicity. When used in children sevoflurane has been known to cause increased agitation.
  • xenon may be administered to the subject simultaneously, in combination, sequentially or separately with the anesthetic agent.
  • “simultaneously” is used to mean that the xenon is administered concurrently with the anesthetic agent, whereas the term “in combination” is used to mean the xenon is administered, if not simultaneously, then “sequentially” within a timeframe in which the xenon and the anesthetic both exhibit a therapeutic effect, i.e. they are both are available to act therapeutically within the same time-frame.
  • administration “sequentially” may permit the xenon to be administered within 5 minutes, 10 minutes or a matter of hours before or after the anesthetic.
  • the xenon is administered to the subject prior to the volatile anesthetic agent. Studies have indicated that xenon is capable of changing the vulnerability of the subject to all kinds of injury of an apoptotic or necrotic variety.
  • the xenon is administered before hypoxic-ischaemic injury or any other injury which is apoptosis-dependent (i.e. in which apoptosis is the pathway to cell death) or necrosis-dependent (i.e. in which necrosis is the pathway to cell death), i.e. the xenon functions as a preconditioning agent.
  • the xenon is administered after the volatile anesthetic agent.
  • the xenon is administered after hypoxic-ischaemic injury or any other injury which is apoptosis-dependent (i.e. in which apoptosis is the pathway to cell death) or necrosis-dependent (i.e. in which necrosis is the pathway to cell death).
  • “separately” is used herein to mean that the gap between administering the xenon and exposing the subject to anesthetic agent is significant i.e. the xenon may no longer be present in the bloodstream in a therapeutically effective amount when the subject is exposed to the anesthetic agent, or the anesthetic may no longer be present in the bloodstream in a therapeutically effective amount when the subject is exposed to the xenon.
  • the xenon is administered sequentially or simultaneously with the anesthetic agent, more preferably simultaneously.
  • the xenon is administered prior to, or simultaneously with, the anesthetic agent, more preferably simultaneously.
  • the xenon is administered in a therapeutically effective amount.
  • the xenon is administered in a sub-therapeutically effective amount.
  • sub-therapeutically effective amount means an amount which is lower than that typically required to produce anesthesia. Generally, an atmosphere of about 70% xenon is sufficient to induce or maintain anesthesia. Accordingly, a sub-therapeutic amount of xenon corresponds to less than about 70% xenon.
  • the combination of Xenon and anesthetic agent has a synergistic effect, i.e., the combination is synergistic.
  • Another aspect of the invention relates to the use of (i) xenon, and (ii) an anesthetic selected from isoflurane, sevoflurane and desflurane, in the preparation of a medicament for alleviating and/or preventing isoflurane-induced and/or sevoflurane-induced and/or desflurane-induced neuronal injury in a subject, preferably a neonatal subject.
  • Another aspect of the invention relates to the use of (i) xenon, and (ii) isoflurane, in the preparation of a medicament for alleviating and/or preventing isoflurane-induced neuronal injury in a subject, preferably a neonatal subject.
  • Another aspect of the invention relates to the use of (i) xenon, and (ii) sevoflurane, in the preparation of a medicament for alleviating and/or preventing sevoflurane-induced neuronal injury in a subject, preferably a neonatal subject.
  • Another aspect of the invention relates to the use of (i) xenon, and (ii) desflurane, in the preparation of a medicament for alleviating and/or preventing desflurane-induced neuronal injury in a subject, preferably a neonatal subject.
  • Yet another aspect of the invention relates to the use of xenon in the preparation of a medicament for alleviating and/or preventing isoflurane-induced and/or sevoflurane-induced and/or desflurane-induced neuronal injury in a subject, preferably a neonatal subject.
  • Yet another aspect of the invention relates to the use of (i) xenon, and (ii) an anesthetic selected from isoflurane, sevoflurane and desflurane, in the preparation of a medicament for providing anesthesia in a subject, preferably a neonatal subject, wherein the amount of xenon is sufficient to alleviate or prevent anesthetic-induced injury.
  • Another aspect of the invention relates to the use of xenon and isoflurane in the preparation of a medicament for providing anesthesia in a subject, preferably a neonatal subject, wherein the amount of Xenon is sufficient to alleviate or prevent isoflurane-induced neuronal injury.
  • Another aspect of the invention relates to the use of xenon and sevoflurane in the preparation of a medicament for providing anesthesia in a subject, preferably a neonatal subject, wherein the amount of xenon is sufficient to alleviate or prevent sevoflurane-induced neuronal injury.
  • Another aspect of the invention relates to the use of xenon and desflurane in the preparation of a medicament for providing anesthesia in a subject, preferably a neonatal subject, wherein the amount of xenon is sufficient to alleviate or prevent desflurane-induced neuronal injury.
  • the xenon is administered in combination with a pharmaceutically acceptable diluent, excipient and/or carrier.
  • Acceptable carriers or diluents for therapeutic use are well known in the pharmaceutical art, and are described, for example, in Remington's Pharmaceutical Sciences, Mack Publishing Co. (A. R. Gennaro edit. 1985).
  • suitable carriers include lactose, starch, glucose, methyl cellulose, magnesium stearate, mannitol, sorbitol and the like.
  • suitable diluents include ethanol, glycerol and water.
  • compositions may comprise as, or in addition to, the carrier, excipient or diluent any suitable binder(s), lubricant(s), suspending agent(s), coating agent(s), solubilising agent(s).
  • Suitable binders include starch, gelatin, natural sugars such a, glucose, anhydrous lactose, free-flow lactose, beta-lactose, corn sweeteners, natural and synthetic gums, such as acacia, tragacanth or sodium alginate, carboxymethyl cellulose and polyethylene glycol.
  • Suitable lubricants include sodium oleate, sodium stearate, magnesium stearate, sodium benzoate, sodium acetate, sodium chloride and the like.
  • Preservatives, stabilizers and dyes may be provided in the pharmaceutical composition.
  • preservatives include sodium benzoate, sorbic acid and esters of p-hydroxybenzoic acid.
  • Antioxidants and suspending agents may be also used.
  • the xenon may also be administered in combination with another pharmaceutically active agent.
  • the agent may be any suitable pharmaceutically active agent including anesthetic or sedative agents which promote GABAergic activity. Examples of such GABAergic agents include propofol and benzodiazapines.
  • the xenon may also be administered in combination with other active ingredients such as L-type calcium channel blockers, N-type calcium channel blockers, substance P antagonists, sodium channel blockers, purinergic receptor blockers, or combinations thereof.
  • active ingredients such as L-type calcium channel blockers, N-type calcium channel blockers, substance P antagonists, sodium channel blockers, purinergic receptor blockers, or combinations thereof.
  • the xenon may be administered by any suitable delivery mechanism, or two or more suitable delivery mechanisms.
  • the xenon is administered by perfusion.
  • perfusion refers to the introduction of an oxygen/xenon mixture into, and the removal of carbon dioxide from, a patient using a specialised heart-lung machine.
  • the heart-lung machine replaces the function of the heart and lungs and provides a bloodless, motionless surgical field for the surgeon.
  • the perfusionist ventilates the patient's blood to control the level of oxygen and carbon dioxide.
  • the perfusionist also introduces xenon into the patient's blood. The perfusionist then propels the blood back into the arterial system to provide nutrient blood flow to all the patient's vital organs and tissues during heart surgery.
  • the medicament is in gaseous form.
  • the xenon is administered by inhalation.
  • the medicament further comprises oxygen, nitrogen or mixtures thereof, more particularly air.
  • the medicament further comprises helium, NO, CO, CO 2 , N 2 O, other gaseous compounds and/or inhalable medicaments.
  • the xenon is mixed with another inert gas, such as argon or krypton.
  • the xenon is mixed with oxygen, or an oxygen-containing gas.
  • the medicament is a binary gaseous mixture which comprises from about 10 to about 80% xenon by volume, more preferably from about 20 to about 80% xenon by volume, with the remainder comprising oxygen. In another preferred embodiment, the medicament comprises from about 30 to about 75% xenon by volume, with the remainder comprising oxygen.
  • the medicament is a ternary gaseous mixture which comprises from about 10 to about 80% xenon by volume, more preferably from about 20 to about 80% xenon by volume, with the remainder comprising oxygen and nitrogen. In another preferred embodiment, the medicament comprises from about 30 to about 75% xenon by volume, with the remainder comprising oxygen and nitrogen.
  • the medicament comprises about 5 to about 90% by volume of xenon, more preferably, about 10 to about 80% by volume of xenon, more preferably still, about 10 to about 50% by volume of xenon, more preferably still, about 10 to about 30% by volume of xenon.
  • the medicament is in the form of a liquid or solution. In one particularly preferred embodiment, the medicament is in the form of a lipid emulsion.
  • the liquid is administered in the form of a solution or an emulsion prepared from sterile or sterilisable solutions, which may be injected intravenously, intraarterially, intrathecally, subcutaneously, intradermally, intraperitoneally or intramuscularly.
  • the xenon is administered in the form of a lipid emulsion.
  • the intravenous formulation typically contains a lipid emulsion (such as the commercially available Intralipid®10, Intralipid®20, Intrafat®, Lipofundin®S or Liposyn® emulsions, or one specially formulated to maxinise solubility) which sufficiently increases the solubility of the xenon to achieve the desired clinical effect. Further information on lipid emulsions of this sort may be found in G. Kleinberger and H. Pamperl, Infusionstherapie, 108-117 (1983) 3.
  • the lipid phase of the present invention which dissolves or disperses the gas is typically formed from saturated and unsaturated long and medium chain fatty acid esters containing 8 to 30 carbon atoms. These lipids form liposomes in aqueous solution. Examples include fish oil, and plant oils such as soya bean oil, thistle oil or cottonseed oil.
  • the lipid emulsions of the invention are typically oil-in-water emulsions wherein the proportion of fat in the emulsion is conventionally 5 to 30% by weight, and preferably 10 to 20% by weight. Oil-in-water emulsions of this sort are often prepared in the presence of an emulsifying agent such as a soya phosphatide.
  • the lipids which form the liposomes of the present invention may be natural or synthetic and include cholesterol, glycolipids, sphingomyelin, glucolipids, glycosphingolipids, phosphatidylcholine, phosphatidylethanolamine, phosphatidyl-serine, phosphatidyglycerol, phosphatidylinositol.
  • the lipid emulsions of the present invention may also comprise additional components. These may include antioxidants, additives which make the osmolarity of the aqueous phase surrounding the lipid phase isotonic with the blood, or polymers which modify the surface of the liposomes.
  • xenon can be dissolved or dispersed in concentrations of 0.2 to 10 ml or more per ml of emulsion.
  • concentration of dissolved gas is dependent on a number of factors, including temperature, pressure and the concentration of lipid.
  • the lipid emulsions of the present invention may be loaded with gaseous xenon.
  • a device is filled with the emulsion and anesthetics as gases or vapours passed through sintered glass bubblers immersed in the emulsion.
  • the emulsion is allowed to equilibrate with the anesthetic gas or vapour at a chosen partial pressure.
  • these lipid emulsions show sufficient stability for the anesthetic not to be released as a gas over conventional storage periods.
  • the lipid emulsions of the present invention may be loaded so that the xenon is at the saturation level.
  • the xenon may be present in lower concentrations, provided, for example, that the administration of the emulsion produces the desired pharmaceutical activity.
  • the concentration of xenon employed in the invention may be the minimum concentration required to achieve the desired clinical effect. It is usual for a physician to determine the actual dosage that will be most suitable for an individual patient, and this dose will vary with the age, weight and response of the particular patient. There can, of course, be individual instance where higher or lower dosage ranges are merited, and such are within the scope of this invention.
  • the medicament is in a form suitable for intravenous, neuraxial or transdermal delivery.
  • a further aspect of the invention relates to a method of preventing and/or alleviating anesthetic-induced neurological deficits in a subject, preferably a neonatal subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • a further aspect of the invention relates to a method of treating and/or alleviating and/or preventing anesthetic-induced neurodegeneration in a subject, preferably a neonatal subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • a further aspect of the invention relates to a method of treating and/or alleviating and/or preventing anesthetic-induced neuronal apoptosis in a subject, preferably a neonatal subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • a further aspect of the invention relates to a method of treating and/or alleviating and/or preventing anesthetic-induced neuronal injury in a subject, preferably a neonatal subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • a method of preventing and/or alleviating isoflurane-induced neuronal injury in a subject comprising administering to said subject xenon and isoflurane.
  • a method of preventing and/or alleviating sevoflurane-induced neuronal injury in a subject comprising administering to said subject xenon and sevoflurane.
  • Yet another aspect of the invention relates to an anesthetic formulation for preventing and/or alleviating one or more anesthetic-induced neurological deficits in a subject, preferably a neonatal subject, said formulation comprising xenon and a pharmaceutically acceptable diluent, excipient and/or carrier.
  • Yet another aspect of the invention relate to an anesthetic formulation for treating and/or alleviating and/or preventing anesthetic-induced neurodegeneration in a subject, preferably a neonatal subject, said formulation comprising xenon and a pharmaceutically acceptable diluent, excipient and/or carrier.
  • a further aspect of the invention relates to an anesthetic formulation for treating and/or alleviating and/or preventing anesthetic-induced neuronal apoptosis in a subject, preferably a neonatal subject, said formulation comprising xenon and a pharmaceutically acceptable diluent, excipient and/or carrier.
  • a further aspect of the invention relates to an anesthetic formulation for treating and/or alleviating and/or preventing anesthetic-induced neuronal necrosis in a subject, preferably a neonatal subject, said formulation comprising xenon and a pharmaceutically acceptable diluent, excipient and/or carrier.
  • the anesthetic formulation of the invention further comprises an anesthetic agent.
  • the anesthetic agent is a GABAergic agent.
  • the anesthetic agent is isoflurane, sevoflurane or desflurane.
  • Another aspect of the invention relates to an anesthetic formulation comprising 60% xenon, 0.75% isoflurane, 25% oxygen and with the balance as nitrogen.
  • xenon exhibits many desirable qualities including cardiostability (Stowe et al., 2000), a low blood-gas coefficient (Nakata et al., 1997) (the explanation for xenon's fast induction and emergence times), and a potent analgesic effect (Ma et al., 2004). Given the inevitable restricted application of this extremely rare and costly gas, xenon may find a niche as a prophylactic intra-operative neuroprotective anesthetic (Mayumi Homi et al., 2003).
  • Xenon was a more efficacious neuroprotective agent than either gavestinel (Ma et al, 2005) or dizolcipine (Ma et al 2003a), two other NMDA antagonists that have been clinically tested.
  • xenon can protect against both glutamate and oxygen glucose deprivation induced excitotoxicity (Wilhelm et al., 2002; Ma et al., 2003a). At anesthetic concentrations it vivo (75%), xenon has been shown to dose-dependently protect against excitotoxic insults with the same neuroprotective efficacy as MK3801 (Ma et al., 2002). Additionally, the same experiments showed that even at this relatively high dose of xenon, there is no evidence of any neurotoxicity in the posterior cingulate or retrosplenial corticies. More recent studies have shown that xenon based anesthesia provides a functional neurological improvement in rats subjected to cardio-pulmonary bypass (Ma et al., 2003b).
  • Electrophysiology experiments have characterised xenon as a potent post-synaptic (De Sousa et al., 2000) non-competitive inhibitor of NMDA receptors with little or no GABA mediated effects (Franks et al., 1998). Although this may be the mechanism behind the anesthetic effect, it is almost certain that xenon has other sites of action that are yet to be elucidated. This theory is supported by xenon's ability to act in opposition to other NMDA receptor antagonists, by attenuating their neurotoxic effects (Nagata et al., 2001).
  • xenon in contrast to N 2 O, does not interfere with PKC control of the extending axon in vitro (Fukura et al., 2000) or exhibit teratogenic properties in vivo (Lane et al., 1980). Concerning efficacy, xenon has been shown to be an effective analgesic agent in neonatal rats (Ma et al., 2004).
  • Sprague-Dawley are an inbred strain which display certain phenotypic differences to rats used in earlier studies. Specifically, when attempting to replicate previously used high-dose regimens (Jevtovic-Todorovic et al., 2003), e.g. 75% N 2 O+1% isoflurane+6 mg/kg midazolam, the rats exhibited a high degree of susceptibility—mortality rates would have been 100% in the absence of intervention to end anesthetic exposure. Thus, gas concentrations for each group had to be adapted to induce a state of anesthesia without causing apnoea.
  • the Cupric-Silver technique (DeOlmos Silver Staining) has repeatedly been shown to be excellent for highlighting the density and distribution of neurodegeneration (Beltramino et al., 1993; Jevtovic-Todorovic et al., 2003).
  • the process highlights argyrophilia (a generalised CNS response to injury (O'Callaghan and Jensen, 1992)) to reveal cumulative neurodegeneration, so issues surrounding the small timeframe of marker expression, as in other techniques identifying gene products and enzyme activation, do not apply (DeOlmos and Ingram, 1971).
  • Caspase-3 immunohistochemistry appeared to be acting as a suitable marker of neuronal apoptosis.
  • activated caspase-3 stained cells were stained in their entirety, hence making quantification relatively straightforward.
  • caspase-9 activates caspase-3 (a cysteine protease), and thus caspase-3 is a marker of those cells that are downstream of the apoptotic commitment point. While broadly paralleling silver staining, caspase-3 immunohistochemistry is superior for both quantification purposes, and characterisation of physiological cell death (Olney et al., 2002b).
  • C-Fos is one of the immediate early genes that has a role in linking cytoplasmic events to nuclear gene transcription Walton et al., 1998).
  • c-Fos indicates a state of neuronal activation, a result of several possible different external stimuli, including apoptotic cell death (Dragunow and Preston, 1995) and pain (reviewed in Duckhyun and Barr, 1995).
  • C-Fos has previously been shown to be a sensitive marker of the neurotoxicity of NA receptor antagonists in adult rats (Ma et al., 2002) and is valid for assessment of NMDA receptor activation (Hasegawa et al., 1998).
  • the c-Fos immunohistochemistry protocol (Mia et al., 2002), formed the entire basis of quantification in the spinal cord formalin tests, staining activated nuclei black.
  • the hippocampus a specialised fold of cortical tissue forming part of the limbic system, has an important function in memory formation (Aggleton and Brown, 1999).
  • LTP long term potentiation
  • the blood brain barrier effectively blocks the translocation of many water-soluble substances from the blood to the CNS. It achieves this via a network of tight-junctions, overlapping astrocyte cover, and the relative absence of transport mechanisms.
  • none of these measures are an effective obstacle to xenon, a small and apolar atom, which can rapidly attain anesthetic concentrations in the brain (Sanders et al., 2003). Once at the synapse, xenon is thought to produce its anesthetic effect through non-competitive blockade of the NMDA receptor, albeit by a mechanism that does not produce a typical open-channel block.
  • xenon a potent NMDA receptor antagonist (with 75% xenon equivalent to MK801 in some contexts (Ma et al., 2002)), does not induce similar apoptotic neurodegeneration.
  • xenon has a novel anti-apoptotic property, mediated by an as-yet undefined target (which could be membranous, cytoplasmic, mitochondrial or nuclear given xenon's unusual pharmacodynamic and pharmacokinetic properties).
  • NMDA receptors Whilst at least in theory xenon's unusual block of NMDA receptors could be responsible (e.g. via an NMDA receptor subunit that has a different distribution or level of expression in the neonate such as NR2B or NR2D, or even a preferential effect at extra-synaptic NMDA receptors (Hardingham et al., 2002)), xenon's capacity to diametrically oppose NMDA receptor antagonist mediated neurotoxicity suggests that there are other systems involved (Nagata et al., 2001).
  • xenon could be inducing a degree of pro-apoptotic signalling via an intracellular signalling cascade, whilst the theoretical anti-apoptotic action simultaneously disrupts the very same cascade at a downstream position (and thus also blocking isoflurane-induced signalling).
  • a further aspect of the invention relates to a combination comprising xenon and sevoflurane.
  • the combination is a synergistic combination.
  • the protective effect is anti-necrotic, rather than anti-apoptotic, i.e. the protective effect arises from the prevention of cell death by necrosis.
  • Cell death can occur by apoptosis or necrosis.
  • a stimulus initiates a cascade of events which ultimately leads to cell death; apoptosis is often referred to as “programmed cell death” and is a part of normal physiological development.
  • necrosis involves a stimulus which directly induces the death of the cell and is always a pathologic process.
  • the xenon is administered in a sub-therapeutically effective amount.
  • sub-therapeutically effective amount means an amount which is lower than that typically required to produce anesthesia. Generally, an atmosphere of about 70% xenon is sufficient to induce or maintain anesthesia. Accordingly, a sub-therapeutic amount of xenon corresponds to less than about 70% xenon.
  • the sevoflurane is administered in a sub-therapeutically effective amount.
  • the term “sub-therapeutically effective amount” means an amount which is lower than that typically required to produce anesthesia. Generally, an atmosphere of about 2.5% sevoflurane is sufficient to maintain anesthesia. Accordingly, a sub-therapeutic amount of sevoflurane corresponds to less than about 2.5% sevoflurane.
  • Another aspect of the invention relates to a pharmaceutical composition
  • a pharmaceutical composition comprising xenon and sevoflurane and a pharmaceutically acceptable diluent, excipient or carrier.
  • the pharmaceutical composition is an anesthetic formulation.
  • the formulation comprises from about 10 to about 30% xenon and from about 1 to about 5% sevoflurane (v/v), with the balance comprising oxygen or nitrogen, or a mixture thereof. More preferably, the formulation comprises from about 10 to about 20% xenon and from about 2 to about 4% sevoflurane, with the balance comprising oxygen or nitrogen, or a mixture thereof.
  • the formulation comprises about 12.5% xenon, about 0.67% sevoflurane, about 25% oxygen and the balance nitrogen.
  • a further aspect of the invention relates to an anesthetic formulation for preventing and/or alleviating one or more sevoflurane-induced neurological deficits in a subject, said formulation comprising xenon and a pharmaceutically acceptable diluent, excipient and/or carrier.
  • Another aspect of the invention relates to an anesthetic formulation for treating and/or alleviating and/or preventing sevoflurane-induced neurodegeneration in a subject, said formulation comprising xenon and a pharmaceutically acceptable diluent, excipient and/or carrier.
  • Yet another aspect of the invention relates to an anesthetic formulation for treating and/or alleviating and/or preventing sevoflurane-induced neuronal apoptosis in a subject, said formulation comprising xenon and a pharmaceutically acceptable diluent, excipient and/or carrier.
  • One aspect of the invention relates to the use of xenon and sevoflurane in the preparation of a medicament for providing neuroprotection and/or anesthesia and/or analgesia.
  • Another aspect of the invention relates to the use of xenon in the preparation of a medicament for providing neuroprotection and/or anesthesia and/or analgesia, wherein said medicament is for use in combination with sevoflurane.
  • Another aspect of the invention relates to the use of sevoflurane in the preparation of a medicament for providing neuroprotection and/or anesthesia and/or analgesia, wherein said medicament is for use in combination with xenon.
  • a further aspect of the invention relates to the use of (i) xenon, and (ii) sevoflurane, in the preparation of a medicament for alleviating and/or preventing sevoflurane-induced neuronal injury in a subject.
  • Another aspect of the invention relates to the use of xenon in the preparation of a medicament for preventing and/or alleviating one or more sevoflurane-induced neurological deficits in a subject.
  • the neurological deficit is associated with neuronal necrosis.
  • Another aspect of the invention relates to the use of xenon in the preparation of a medicament for treating and/or alleviating and/or preventing sevoflurane-induced neurodegeneration in a subject.
  • Another aspect of the invention relates to the use of xenon in the preparation of a medicament for treating and/or alleviating and/or preventing neuronal necrosis in a subject.
  • Another aspect of the invention relates to the use of xenon in the preparation of a medicament for treating and/or alleviating and/or preventing sevoflurane-induced neuronal apoptosis in a subject.
  • Another aspect of the invention relates to the use of xenon in the preparation of a medicament for preventing and/or alleviating sevoflurane-induced neuronal injury in a subject.
  • Another aspect of the invention relates to the use of xenon and sevoflurane in the preparation of a medicament for providing anesthesia in a subject, wherein the amount of xenon is sufficient to alleviate or prevent sevoflurane-induced neuronal injury.
  • Yet another aspect of the invention relates to the use of xenon in the preparation of a medicament for treating and/or alleviating and/or preventing neuronal necrosis, or a condition associated with neuronal necrosis.
  • Conditions associated with neuronal necrosis include, for example, ischaemic infarction and traumatic infarction.
  • a further aspect of the invention relates to a method of providing neuroprotection and/or anesthesia and/or analgesia in a subject, said method comprising administering to said subject a therapeutically effective amount of a combination of xenon and sevoflurane.
  • the xenon and sevoflurane are administered prior to hypoxic-ischaemic injury, more preferably, at least 1 hour, more preferably at least 2 hours prior to hypoxic-ischaemic injury. In one particularly preferred embodiment, the xenon and sevoflurane are administered from about 2 to about 24 hours prior to hypoxic-ischaemic injury.
  • the subject is a mammal, more preferably, a human.
  • the subject is a neonatal subject.
  • the xenon and sevoflurane are administered to the neonatal subject by administering to the mother prior to and/or during labour, or prior to and/or during a cesarean section.
  • Another aspect of the invention relates to a method of preventing and/or alleviating sevoflurane-induced neurological deficits in a subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • Another aspect of the invention relates to a method of treating and/or alleviating and/or preventing sevoflurane-induced neurodegeneration in a subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • Another aspect of the invention relates to a method of treating and/or alleviating and/or preventing sevoflurane-induced neuronal apoptosis in a subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • Another aspect of the invention relates to a method of treating and/or alleviating and/or preventing sevoflurane-induced neuronal necrosis in a subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • Another aspect of the invention relate to a method of treating and/or alleviating and/or preventing sevoflurane-induced neuronal injury in a subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • Yet another aspect of the invention relates to a method of preventing and/or alleviating sevoflurane-induced neuronal injury in a subject, said method comprising administering to said subject xenon and sevoflurane.
  • Another aspect of the invention relates to a method of providing anesthesia and/or analgesia in a subject, said method comprising administering xenon in combination with sevoflurane, wherein the amount of xenon is sufficient to alleviate and/or prevent sevoflurane-induced neuronal injury.
  • Another aspect of the invention relates to a method of treating and/or alleviating and/or preventing neuronal necrosis, or a condition associated with neuronal necrosis, in a subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • Another aspect of the invention relates to a method of treating and/or alleviating and/or preventing neuronal necrosis, or a condition associated with neuronal necrosis, in a subject, said method comprising administering a therapeutically effective amount of xenon to said subject.
  • Yet another aspect of the invention relates to the use of xenon and isoflurane in the preparation of a medicament for use as a preconditioning agent for protecting against hypoxic injury.
  • preconditioning agent refers to a medicament that is capable of alleviating and/or preventing neuronal damage that may arise from a subsequent hypoxic injury.
  • preconditioning agents may be administered prior to potentially injurious events such as invasive surgery, cardiopulmonary bypass (CPB), organ transplant, labour, prior to uterine implantation of fertilized embryo (as part of in vitro fertilization), neuromuscular surgical procedures, brain tumour resection and the like.
  • Preconditioning agents may also be administered after one or more injurious events where the subject may be at risk of subsequent further injurious events, for example, stroke patients.
  • the xenon when used as a preconditioning agent, is administered prior to hypoxic-ischaemic injury, more preferably, at least 1 hour, more preferably at least 2 hours prior to hypoxic-ischaemic injury. In one particularly preferred embodiment, the xenon is administered from about 2 to about 24 hours prior to hypoxic-ischaemic injury.
  • Yet another aspect of the invention relates to the use of xenon in the preparation of a medicament for use as a preconditioning agent for protecting against hypoxic injury, wherein said medicament is for use in combination with sevoflurane.
  • Yet another aspect of the invention relates to the use of sevoflurane in the preparation of a medicament for use as a preconditioning agent for protecting against hypoxic injury, wherein said medicament is for use in combination with xenon.
  • a further aspect of the invention relates to a method of protecting a subject from hypoxic injury, said method comprising administering to said subject a therapeutically effective amount of a combination of xenon and sevoflurane.
  • FIG. 1 shows rats anesthetised for a period of 6 hrs (neurodegeneration experiments) or 105 min (formalin test). Once the brains were removed, sections were cut to include the region of interest: a coronal section ⁇ 3.6 mm from the bregma (neurodegeneration experiments) or a transverse section of the lumbar enlargement of the spinal cord (formalin test).
  • FIG. 1A Set-up for closed-circuit xenon anesthesia.
  • FIG. 1B Diagram depicting a sagittal view through the neonatal rat brain, and the transverse slice used for counting.
  • FIG. 1C Diagram of a transverse section through the lumbar enlargement of the spinal cord of the neonatal rat—dotted lines represent boundaries of counting regions, taken from a previously used protocol (Duckhyun and Barr, 1995).
  • FIG. 2 shows silver stained sections. DeOlmos silver staining was employed to determine potential areas of interest for immunohistochemistry. Rats were anesthetised with various gas combinations, had their brains removed, and sections cut for DeOlmos silver staining. Areas of non-specific neurodegeneration are stained black ( ⁇ 4 magnification).
  • FIG. 2A Photomicrograph of the cortex of a control animal, showing low silver uptake.
  • FIG. 2B Photomicrograph of the cortex of a rat exposed to 75% nitrous oxide+0.75% isoflurane, showing silver uptake in specific cortical layers.
  • FIG. 2C Photomicrograph of the hippocampus of a control animal, showing low silver uptake.
  • FIG. 2D Photomicrograph of the hippocampus of a rat exposed to 75% nitrous oxide+0.75% isoflurane, showing extensive silver uptake.
  • FIG. 3 shows cortical and hippocampal apoptotic neurodegeneration induced by exposure to anesthetics in neonatal rats: mean data.
  • FIG. 4 shows cortical apoptotic neurodegeneration in neonatal rats exposed to individual anesthetic agents.
  • Photomicrographs ( ⁇ 4 magnification) showing caspase-3 immunostaining of the cortex, highlighting cells destined for apoptosis (black staining).
  • Photomicrographs ( ⁇ 4 magnification) correspond to gas exposure: air (A), 75% nitrous oxide (B), 75% xenon (C), or 0.75% isoflurane (D) for 6 hrs.
  • FIG. 5 shows cortical apoptotic neurodegeneration in neonatal rats C-posed to combinations of anesthetic agents.
  • Photomicrographs ⁇ 4 magnification
  • both nitrous oxide and xenon are characterised as NMDA receptor antagonists, they exhibit diametrically opposite properties when modulating isoflurane-induced apoptosis (enhancing and attenuating respectively).
  • High power light microscopy ( ⁇ 20 magnification) confirmed that entire neurones where being stained, in keeping with caspase-3 being a cytoplasmic enzyme (C).
  • FIG. 6 shows hippocampal apoptotic neurodegeneration induced by exposure to anesthetics in neonatal rats. Following a 6 hr gas exposure, caspase-3 immunostaining of the hippocampus was performed to highlight cells destined for apoptosis (black staining). Photomicrographs (at ⁇ 4 magnification) correspond to gas exposure: air (A), 75% nitrous oxide (B), 75% xenon (C), 0.75% isoflurane (D), 75% nitrous oxide+0.75% isoflurane (E), and 60% xenon+0.75% isoflurane (F).
  • FIG. 7 shows the results from formalin testing.
  • the analgesic potential of (75% nitrous oxide+0.75% isoflurane) was compared to (60% xenon+0.75% isoflurane) using a formalin test to quantify the nociceptive response to a formalin injection to the left-hind paw via c-Fos expression in the spinal cord.
  • FIG. 7B Photomicrograph of spinal cord slice for 75% nitrous oxide+0.75% isoflurane.
  • FIG. 7C Photomicrograph of spinal cord slice for 60% xenon+0.75% isoflurane.
  • FIG. 8 shows the flow diagram of LDH assay protocol.
  • FIG. 9 shows the flow diagram of the protocol to assess the necrotic, viable and apoptotic cell populations after preconditioning.
  • FIG. 10 shows the graph of LDH release against xenon concentration.
  • the cells were preconditioned for 2 hours followed by OGD) (oxygen glucose deprivation).
  • FIG. 11 shows the graph of LDH release against sevoflurane concentrations. The cells were preconditioned for 2 hours followed by OGD.
  • FIG. 12 shows the graph of LDH release against Xenon preconditioning, sevoflurane preconditioning an combination of preconditioning.
  • the cells were preconditioned for 2 hours followed by OGD.
  • FIG. 13 shows combination preconditioning, using FACS analysis of necrotic, viable and apoptotic cell populations.
  • NMDA receptor antagonists have their maximal neurodegenerative affect 7 days after birth (Ikonomidou et al., 1999).
  • Group B received 75% nitrous oxide and 25% oxygen as delivered by a calibrated anesthetic machine
  • group C received 75% xenon along with 25% oxygen through a customised anesthetic machine modified for xenon delivery (Ohmeda, modified by Air Products, Surrey, UK).
  • Group D were exposed to 25% oxygen along with 0.75%; isoflurane.
  • the remaining 2 groups were exposed to combinations of gases—namely 25% oxygen+75% A nitrous oxide+0.75% isoflurane (group E) and 25% oxygen+60% xenon+15% nitrogen+0.75% isoflurane (group F).
  • the high cost of xenon precludes its use in an open-circuit, consequently group C and group F received gases using a closed-circuit system ( FIG. 1A ), whereas gases for all other groups were delivered in a high-flow open-circuit.
  • Rats destined for immunohistochemistry were sacrificed with 100 mg kg ⁇ 1 sodium pentobarbital IP immediately post-anesthesia, whereas those rats for DeOlmos silver staining were allowed to recover for 18 hrs before undergoing the same procedure.
  • a thoracotomy was performed, and the aorta cannulated via a needle inserted into the apex of the heart.
  • the pup was then perfused with 10 ml of 1% heparin solution, with the excess solution leaving through an incision in the right atrium.
  • 20 ml of 4% paraformaldehyde in 0.1M phosphate buffer was injected by the same transcardial route.
  • the whole brain was then removed and allowed to fix in paraformaldehyde perfusate and refrigerated at 4° C. 24 hours later, the brains were transferred to a solution of 30% sucrose with phosphate buffer and 1% sodium azide, and were kept refrigerated until the brains sank (approximately 48 hours).
  • a block was cut to safely include the area of interest—a coronal section ⁇ 3.6 mm from the bregma ( FIG. 1B ).
  • the blocks were then embedded and frozen into O.C.T. solution.
  • the block was then cut coronally into approximately 120 slices, each 30 ⁇ m thick, with a cryostat (Bright Instrument Company Ltd., Huntingdon, UK).
  • the cut sections were transferred to a 6 well plate containing phosphate buffered saline (PBS).
  • PBS phosphate buffered saline
  • DeOlmos silver staining was carried out according to an established protocol (DeOlmos and Ingram, 1971). The floating sections were mounted onto adhesive polysine slides, washed in distilled water, and then incubated in a copper-silver mixture (1000 ml 2.5% silver nitrate, 15 ml 0.5% cupric nitrate, 40 ml of pyridine and 30 ml of 95% ethyl alcohol).
  • ammoniacal silver nitrate stock 300 ml of distilled water, 200 ml of 0.36% NaOH, 90 ml concentrated ammonium hydroxide and 10 ml of 20% silver nitrate
  • the slides were placed in a reducer solution made of 24 ml 10% non-neutralised formalin, 14 ml of 1% citric acid, 200 ml of 100% ethanol and 1762 ml of distilled water for 2 min.
  • the sections had their background stained yellow with 0.5% potassium ferricyanide, were bleached for 1 min in 1% sodium thiosulphate and then washed in distilled water. They were then gently dehydrated in 70%, 90% and 100% ethanol. The ethanol was then cleared with two 5 min exposures to 100% xylene. While still wet with xylene, the slides had 2 drops of styrolite coverslip media (BDH, Poole, UK) added, and were then coverslipped. Having tapped out the air bubbles, the slides were allowed to dry overnight before light microscopy.
  • BDH styrolite coverslip media
  • the sections were then washed in 5 ml of PBS for 5 min on a shaker set at 75 rpm. This washing procedure was repeated twice more, replacing the PBS each time.
  • To quench the sections they were incubated at room temperature on a shaker for 30 min in a solution comprising 35 ml methanol, 15 ml of PBS and 500 ⁇ l of stock 30% H 2 O 2 . The quenching solution was then removed, and the sections washed three times in PBS.
  • Sections were blocked for 60 min at room temperature with 50 ml of PBST (PB containing 0.5% Triton-X (Promega Corporation, Madison, Wis.)), and 1500 ⁇ l of normal goat serum (NGS) (Vector Laboratories Inc., Burlingame, Calif.).
  • PBST PB containing 0.5% Triton-X (Promega Corporation, Madison, Wis.)
  • NGS normal goat serum
  • the sections were kept overnight at 4° C. on a shaker set at 50 rpm in a solution made up of 16 ⁇ l (1:1500) rabbit anti-cleaved caspase-3 antibody (New England Biolabs, Hertfordshire, UK), 50 ml of PBST and 500 ⁇ l of NGS.
  • the sections were washed 3 times in PBST and then incubated with the secondary antibody for 60 min in a solution made up with 50 ml of PBST, 750 ⁇ l of NGS and 250 ⁇ l of goat anti-rabbit IgG antibody (Chemicon International, Temecula, Calif.). Following a further 3 washes in PBST, the sections were incubated in freshly prepared ABC solution from a Vectastain ABC kit (Vector Laboratories Inc., Burlingame, Calif.) for 60 min.
  • Vectastain ABC kit Vector Laboratories Inc., Burlingame, Calif.
  • the ABC solution was then washed off with 3 changes of PBS, whilst fresh 3,3′-diamino-benzidine (DAB) solution was prepared, which included distilled water, buffer, DAB stock, H 2 O 2 and nickel solution from a peroxidase substrate kit (Vector Laboratories Inc. Burlingame, Calif.).
  • DAB 3,3′-diamino-benzidine
  • the slices were immersed in DAB solution for 4 min at room temperature, immediately washed 3 times with PBS to end staining, and then washed 3 times with distilled water.
  • the well contents were floated into distilled water and the individual sections transferred to superfrost slides using a fine paintbrush. Once mounted, slides were allowed to dry overnight. To complete processing of the slides, the samples slides were then dehydrated, cleared and coverslipped as for the DeOlmos silver staining.
  • the c-Fos immunohistochemistry was performed in parallel with the caspase-3 immunohistochemistry with only three changes to the protocol. Whereas NGS was used in the caspase-3 protocol, normal donkey serum (NDS) (Chemicon International, Temecula, Calif.) was used for the c-Fos wells.
  • NGS normal donkey serum
  • the primary antibody used was 20 ⁇ l (1:2500) of goat anti-c-Fos antibody (Santa Cruz Biotechnology, Santa Cruz, Calif.), and the secondry antibody was 250 ⁇ l of donkey anti-goat antibody (Chemicon International, Temecula, Calif.). All other stages of c-Fos immunostaining were identical to caspase-3 immunohistochemistry protocol.
  • the number of degenerating or activated neurones was determined by counting the number of DAB stained (black) cells in a coronal section of one hemisphere around ⁇ 3.6 mm from the bregma visualised on a BX-60 light microscope (Olympus, Southall, UK) and example photomicrographs were taken with a Axiocam digital camera (Zeiss, Göttingen, Germany). Data was collected for both the cortex and the hippocampus across 3 slices, after which the mean number of degenerating neurones was calculated. Those sections stained with the silver staining method were photographed down the microscope without any formal counting.
  • Formalin testing was carried out according to an established protocol (Ma et al., 2004) to compare group E with group F. Rats from one litter were randomised to one of 4 groups to receive different injections and gases: air+formalin, air+saline, 60% xenon+0.75% isoflurane+formalin or 75% nitrous oxide+0.75% isoflurane+formalin. All rats were exposed to the respective gas mixture for 15 min, and then had the left-hind paw injected with either formalin (10 ⁇ l of 5% formalin) or an equivalent volume of saline. Following a further 90 min of gas exposure, the animals/spinal cord samples were sacrificed, perfused and fixed as in the main study.
  • a block was cut, comprising the lumbar enlargement.
  • 30 ⁇ m transverse sections were cut on a cryostat, and the sections processed for c-Fos immunohistochemistry. After staining, 3 sections exhibiting maximal c-Fos expression were selected and photographed from each group, and the spinal cord divided into regions as reported previously ( FIG. 1C ) (Ducklyuan and Barr, 1995). The mean number of c-Fos positive cells was then calculated by region for statistical analysis.
  • the DeOlmos silver staining particularly highlighted both the hippocampus and specific cortical layers. These areas showed extensive silver uptake, denoted by black staining in sections exposed to anesthetics, as opposed to controls subjected to mock anesthesia where uptake was minimal ( FIG. 2 ).
  • neocortices (devoid of the hippocampus, basal ganglia and meninges) were obtained from early post natal (1-2 day old) pups of BALB/c mice. The pups were anaesthetised with isoflurane and then decapitated with the heads placed immediately into 4° C. HSG solution, an isotonic, high sucrose glucose solution made primarily from Hank's balanced salt solution (HBSS, GibroBRL) enhanced with NaHCO 3 (0.04 M), sucrose (0.2 M) and D-Glucose (0.3 M) also containing antibiotic-anti-mycotic solution (AAS, GibroBRL). Throughout the micro dissection process, brain tissues were kept in 4° C. HSG solution.
  • the brain tissue was then immersed in 0.25% trypsin and a placed in a shaking air chamber for 50 minutes at 37° C. filled with 5% CO 2 and 95% room air. DNase was then added to the mixture and placed back into the shaking air chamber for a further 15 minutes. The mixture was then centrifuged at 1600 rpm for 10 minutes at 4° C. and the supernatant was carefully discarded.
  • the cells were then resuspended and then plated at a density of 6.25 ⁇ 10 4 cells/cm 2 on 24-multiwell plates (Costar, Cambridge, Mass.) and cultured in a medium consisting of Eagle's minimum essential medium augmented with 20 mM glucose, 26 mM NaHCO 3 , 10% foetal bovine serum, 10% heat-inactivated horse serum, AAS (Gibco, Paisley, UK), 2 mM glutamine (Sigma, Poole, UK) and 10 ng/ml murine epidermal growth factor (EGF) (GibcoBRL). Glial cells reached confluence about one week after plating.
  • Eagle's minimum essential medium augmented with 20 mM glucose, 26 mM NaHCO 3 , 10% foetal bovine serum, 10% heat-inactivated horse serum, AAS (Gibco, Paisley, UK), 2 mM glutamine (Sigma, Poole, UK) and 10 ng/ml murine epidermal growth factor (EGF
  • cortical neuronal cells were obtained from fetal BALB/c mice at 14-16 days of gestation and plated at a density of 1.25 ⁇ 10 5 cells per cm 2 on the confluent monolayer of glial cells derived from the corresponding genetic strain. Neuronal cells reached confluence 10 days after plating.
  • Neuronal cells were harvested from 19 day old embryonic mice by caesarean section for pregnant BALB/c mice. 6-9 mouse brains were removed from fetal mice and dissected to isolate whole cerebral neocortices devoid of the hippocampus, basal ganglia and meninges. Again throughout the micro dissection process, brain tissues were kept in 4° C. HSG solution. From here, a similar plating procedure described above was performed. The cells were plated at a density of 1.2 ⁇ 10 5 cells, per cm 2 on 24-multiwell plates (Cater, Cambridge, Mass.) and the cultures were maintained at 37° C. in a humidified 5% CO 2 environment.
  • Neurobasal Media supplemented with B27, glutamine and AAS was used to resuspend the neuronal cells and as culture medium. For every 10 ml of Neurobasal Media, the following supplements were added: 200 ⁇ l B27, 100 ⁇ l antibiotic and 25 ⁇ l glutamine. Medium replacement for these cells was performed on day 2, 5 and 7 with pre-warmed 37° C. culture medium (Neurobasal Media, B27, Glutamine and AAS). On day 5 after neuronal plating, 100 ⁇ l/10 ml cytosine arabinoside (CA hydrochloride, Sigma) was added to the cell cultures to halt non-neuronal cell division. Neuronal cell cultures were ready to use on day 7.
  • Cells were preconditioned using a purpose built 1.4 litre airtight, temperature controlled gas chambers.
  • the chambers had inlet and outlet valves and an internal electric fan to ensure effective and continuous delivery of gases.
  • Gas flow rate was 100 ml/min, and so chambers were flushed and allowed to equilibrate for 45 minutes before establishing a closed system.
  • Cells were preconditioned for 2 hours inside the closed system with the appropriate gas concentrations using flow meters. Sevoflurane was delivered using a vaporiser (Datex-Ohmeda).
  • BSS Deoxygenated balanced salt solution
  • HEPES buffer solution 120 mM NaCl, 5.4 mM KCL, 0.8 mM MgCl 2 , 15 mM glucose and 20 mM HEPES, titrated to pH 7.4 using 1M NaOH).
  • Oxygen glucose deprivation was terminated by removing the cultures from the gas chamber and changing the media; cultures destined for lactate dehydrogenase (LDH) assay were washed once and replaced with Eagle's minimal essential medium enhanced with 25 mM glucose and 38 mM NaHCO 3 , whereas pure neuronal cultures for FACS were washed once and replaced with Neurobasal Media supplemented with B27, glutamine and AAS.
  • LDH lactate dehydrogenase
  • the amount of neuronal damage was assessed by the amount of LDH released into the culture medium, using a standardised colorimetric enzyme kit (Sigma Poole, UK). This technique has been previously described (Wilhelm et al 2002). LDH assessment was performed 16 hours after oxygen glucose deprivation ( FIG. 8 ).
  • a FACSCalibur (Becton Dickinson, Sunnyvale, Calif.) with a single argon laser was used for flow cytometric analysis. Excitation was carried out at 488 nm and the emission filters used were 515-545 BP (green; FITC) and 600LP (red; PI). At least 10,000 cells per sample were analysed. Data acquisition was performed with Cell Quest 3.3 (Becton Dickinson) and data analysis was performed with Cell Quest Pro (Becton Dickinson) ( FIG. 9 ).
  • Preconditioning with xenon for 2 hours produces a concentration dependent reduction in LDH release following oxygen glucose deprivation ( FIG. 10 ).
  • LDH release was significantly reduced by xenon at 50% and at 75%, to 55+/ ⁇ 12% and to 49+/ ⁇ 12% of control values respectively (p ⁇ 0.05).
  • Xenon at 12.5% reduced LDH release to 83+/ ⁇ 7% and xenon at 25% reduced LDH release to 70+/ ⁇ 11% of controls.
  • Xenon at 12.5% and 25% displayed a trend of decreasing LDH release with increasing concentrations, however the results were not significant (p>0.05).
  • Sevoflurane preconditioning for 2 hours also produces a concentration dependent reduction in LDH release ( FIG. 11 ).
  • Concentrations of sevoflurane greater than 1.9% produced a significant reduction in LDH release.
  • Concentrations of sevoflurane less than 1.9% did not significantly reduce LDH release and thus did not offer neuronal cells any protection from oxygen glucose deprivation p>0.05).
  • Sevoflurane at 2.7% resulted in a significant decrease of LDH to 64+/ ⁇ 6% of control (p ⁇ 0.05).
  • LDH release was maximally reduced at concentrations of 3.3% sevoflurane to 37+/ ⁇ 5% of controls (p ⁇ 0.001).
  • Sevoflurane at 0.67% was found to be ineffective, producing a reduction of LDH release to 97+/ ⁇ 5% of controls, and sevoflurane at 1.3% also did not produce any reduction in LDH release (100+/ ⁇ 11% of controls).
  • FACS Fluorescence Activated Cell Sorting
  • Controls were unstained cells with no injury and no preconditioning, in order to determine whether viable cells gave off fluorescence and to define a viable cell region.
  • the effectiveness of xenon and sevoflurane combination used as preconditioners to reduce the amount of neuronal injury following oxygen glucose deprivation is consistent with data from the LDH assay ( FIG. 13 ). Sham preconditioning (injured cells with no preconditioning), 12.5% xenon and 0.67% sevoflurane had a significantly smaller viable cell population compared to controls (p ⁇ 0.001).
  • Combination preconditioning had a viable cell population of 23+/ ⁇ 1%, confirming synergy of the two gases in reducing the amount of neuronal injury in an oxygen glucose deprivation model compared to 9% in 12.5% xenon and 0.67% sevoflurane (P ⁇ 0.001).
  • Control groups had a necrotic population of 17+/ ⁇ 1%, whereas sham preconditioning, 12.5% xenon preconditioning, 0.67% sevoflurane preconditioning had necrotic populations of 70+/ ⁇ 2%, 75+/ ⁇ 2%, and 81+/2% respectively.
  • xenon and sevoflurane in combination had a higher apoptotic population of 35%+/ ⁇ 3%, compared to xenon alone and sevoflurane alone, with apoptotic populations of 9+/ ⁇ 1% (p ⁇ 0.001) and 17+/ ⁇ 1% (p ⁇ 0.001) respectively.

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US20160199406A1 (en) * 2013-08-19 2016-07-14 Klaus Michael SCHMIDT Non-anesthetic protective gases in combination with liquid anesthetic agents for organ protection
US20170095505A1 (en) * 2014-05-21 2017-04-06 L'Air Liquide, Société Anonyme pour I'Etude et I'Exploitation des Procédés Georges Claude Combination of xenon and an antioxidant to control a parkinson's disease-type neurodegenerative disease
US20170312460A1 (en) * 2016-04-05 2017-11-02 Vanderbilt University Administering the Noble Gas Argon during Cardiopulmonary Resuscitation
US10098340B2 (en) 2011-02-07 2018-10-16 Rich Technologies Holding Company, Llc Method for preserving cells and cell cultures
US10369103B2 (en) 2012-08-10 2019-08-06 The Board Of Regents Of The University Of Texas System Neuroprotective liposome compositions and methods for treatment of stroke
US11166451B2 (en) 2011-09-26 2021-11-09 Rich Technologies Holding Company, Llc Method for living tissue preservation
US20220087970A1 (en) * 2019-01-18 2022-03-24 The Johns Hopkins University Prevention of anesthetic-induced neurocognitive dysfunction
US11491184B2 (en) 2013-03-15 2022-11-08 The Board Of Regents Of The University Of Texas System Liquids rich in noble gas and methods of their preparation and use

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EP1980260A1 (fr) 2007-04-10 2008-10-15 Nicholas Peter Franks Utilisation de conditions hyperbares pour fournir une neuroprotection
EP1980261A1 (fr) 2007-04-10 2008-10-15 Nicholas Peter Franks Utilisation de l'hélium avec de l'oxgène pour fournir une neuroprotection
CA3106611A1 (fr) * 2018-07-18 2020-01-23 Likeminds, Inc. Methode pour accelerer la penetration tissulaire de composes dans le cerveau
US12280096B2 (en) 2021-07-12 2025-04-22 Penland Foundation Treatments of cancer using nitrous oxide and botulinum toxin

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US10098340B2 (en) 2011-02-07 2018-10-16 Rich Technologies Holding Company, Llc Method for preserving cells and cell cultures
US11166451B2 (en) 2011-09-26 2021-11-09 Rich Technologies Holding Company, Llc Method for living tissue preservation
US10369103B2 (en) 2012-08-10 2019-08-06 The Board Of Regents Of The University Of Texas System Neuroprotective liposome compositions and methods for treatment of stroke
US10973764B2 (en) 2012-08-10 2021-04-13 The Board Of Regents Of The University Of Texas System Neuroprotective liposome compositions and methods for treatment of stroke
US20210378959A1 (en) * 2012-08-10 2021-12-09 The Board Of Regents Of The University Of Texas System Neuroprotective liposome compositions and methods for treatment of stroke
US11872312B2 (en) * 2012-08-10 2024-01-16 The Board Of Regents Of The University Of Texas Systems Neuroprotective liposome compositions and methods for treatment of stroke
US11491184B2 (en) 2013-03-15 2022-11-08 The Board Of Regents Of The University Of Texas System Liquids rich in noble gas and methods of their preparation and use
US20160199406A1 (en) * 2013-08-19 2016-07-14 Klaus Michael SCHMIDT Non-anesthetic protective gases in combination with liquid anesthetic agents for organ protection
US20170095505A1 (en) * 2014-05-21 2017-04-06 L'Air Liquide, Société Anonyme pour I'Etude et I'Exploitation des Procédés Georges Claude Combination of xenon and an antioxidant to control a parkinson's disease-type neurodegenerative disease
US20170312460A1 (en) * 2016-04-05 2017-11-02 Vanderbilt University Administering the Noble Gas Argon during Cardiopulmonary Resuscitation
US10828436B2 (en) * 2016-04-05 2020-11-10 Vanderbilt University Administering the noble gas argon during cardiopulmonary resuscitation
US20220087970A1 (en) * 2019-01-18 2022-03-24 The Johns Hopkins University Prevention of anesthetic-induced neurocognitive dysfunction

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