Effect of gamma-hydroxybutyrate in two rat models of focal cerebral damage

The IC87201 (a PSD95/nNOS Inhibitor) Attenuates Post- Stroke Injuries

N-methyl-D-aspartate receptor-dependent excitotoxicity is one of the most important mechanisms underlying stroke injury and the resulting neuronal death. In the present study, in order to reduce post-stroke brain injury and improve behavioral performance, a new molecule named IC87201, which acts as an inhibitor of PSD95/nNOS interaction in the intracellular signaling pathway of NMDA receptors, was administered. Using the middle cerebral artery occlusion (MCAO) technique, 24 adult male rats were subjected to one hour of cerebral ischemia. Animals were randomly divided into sham, MCAO, MCAO + DXM, and MCAO + IC87201 groups, and in the last two groups, intraperitoneal injection of dextromethorphan hydrobromide monohydrate (DXM), as an NMDA antagonist, and IC87201 was performed after ischemia. Neurobehavioral scores were evaluated for seven days, and on the last two days, the rats' memory performance was appraised using the passive avoidance test. On seventh day, the brain tissue was properly prepared for stereological analysis. Stereological studies of the hippocampus CA1 and CA3 regions revealed that changes in the total and infarcted volumes, total number of neurons, non-neurons, and dead neurons are the consequences of cerebral ischemia. Also, following cerebral ischemia, neurobehavioral and memory function impairments which were assessed by modified neurological severity scores (mNSS) and passive avoidance test, were observed. The aforementioned impairments were recovered after administration of IC87201 significantly and more potently than DXM. Based on our findings, IC87201 successfully attenuated post-ischemia damages. Therefore, this molecule can be considered as a new therapeutic approach in future research.

The Alzheimer's Disease Brain, Its Microvasculature, and NADPH Oxidase

The deterioration of the brain's microvasculature, particularly in the hippocampus, appears to be a very early event in the development of Alzheimer's disease (AD), preceding even the deposition of amyloid-β. A damaged microvasculature reduces the supply of oxygen and glucose to this region and limits the production of energy, ATP. The damage may be a function of the rise with age in the expression and activity of NADPH oxidase (NOX) in these microvessels. This rise renders these vessels vulnerable to the effects of oxidative stress and inflammation. The rise in NOX activity with age is even more marked in the AD brain where an inverse correlation has been demonstrated between NOX activity and cognitive ability. Apocynin, a putative NOX inhibitor, has been shown to block the damaging effects of NOX activation. Apocynin acts as a strong scavenger of H2O2, and as a weak scavenger of superoxide. Like apocynin, sodium oxybate (SO) has also been shown to block the toxic effects of NOX activation. The application of SO generates NADPH and ATP. SO inhibits oxidative stress and maintains normal cerebral ATP levels under hypoxic conditions. Moreover, it acts epigenetically to attenuate the expression of NOX. SO may delay the onset and slow the progress of AD by suppling energy and maintaining an antioxidative environment in the brain throughout the night. The slow wave activity produced by SO may also activate the glymphatic system and promote the clearance of amyloid-β from the brain.

CaMKIIα as a Promising Drug Target for Ischemic Grey Matter

Ca2+/calmodulin-dependent protein kinase II (CaMKII) is a major mediator of Ca2+-dependent signaling pathways in various cell types throughout the body. Its neuronal isoform CaMKIIα (alpha) centrally integrates physiological but also pathological glutamate signals directly downstream of glutamate receptors and has thus emerged as a target for ischemic stroke. Previous studies provided evidence for the involvement of CaMKII activity in ischemic cell death by showing that CaMKII inhibition affords substantial neuroprotection. However, broad inhibition of this central kinase is challenging because various essential physiological processes like synaptic plasticity rely on intact CaMKII regulation. Thus, specific strategies for targeting CaMKII after ischemia are warranted which would ideally only interfere with pathological activity of CaMKII. This review highlights recent advances in the understanding of how ischemia affects CaMKII and how pathospecific pharmacological targeting of CaMKII signaling could be achieved. Specifically, we discuss direct targeting of CaMKII kinase activity with peptide inhibitors versus indirect targeting of the association (hub) domain of CaMKIIα with analogues of γ-hydroxybutyrate (GHB) as a potential way to achieve more specific pharmacological modulation of CaMKII activity after ischemia.

Cognitive Impairment Following Clinical or Recreational Use of Gammahydroxybutyric Acid (GHB): A Systematic Review

BACKGROUND

GHB (gamma-hydroxybutyric acid; sodium oxybate) is a general anaesthetic that is clinically used for the treatment of narcolepsy, cataplexy, alcohol withdrawal and alcohol relapse prevention. In addition, GHB is recreationally used. Most clinical and recreational users regard GHB as an innocent drug devoid of adverse effects, despite its high dependence potential and possible neurotoxic effects. At high doses, GHB may lead to a comatose state. This paper systematically reviews possible cognitive impairments due to clinical and recreational GHB use.

METHODS

PubMed and PsychINFO were searched for literature data about the acute and residual cognitive deficits following GHB use. This review is conducted using the PRISMA protocol.

RESULTS

A total of 43 reports covering human and animal data on GHB-induced cognitive impairments were eligible and reviewed. This systematic review found no indication for cognitive impairments after clinical GHB use. However, it supports the view that moderate GHB use may result in acute short-term cognitive impairments, whereas regular high-dose GHB use and/or multiple GHB-induced comas are probably neurotoxic resulting in long-term residual cognitive impairments.

CONCLUSION

These results emphasize the need for awareness among clinicians and recreational users to minimize negative health consequences of recreational GHB use, particularly when high doses are used and GHB-induced comas occur.

GHB analogs confer neuroprotection through specific interaction with the CaMKIIα hub domain

GHB is a natural brain metabolite of GABA, previously reported to be neuroprotective. However, the high-affinity binding site for GHB has remained elusive for almost 40 y. We here unveil CaMKIIα, a highly important neuronal kinase, as the long-sought-after GHB high-affinity target. Via a specific interaction within the central hub domain of CaMKIIα, GHB analogs act to stabilize the hub oligomer complex. This interaction potentially explains pronounced neuroprotective effects of GHB analogs in cultured neurons exposed to a chemical insult and in mice exposed to ischemia. The postischemic treatment effects of GHB analogs underline these compounds as selective and high-affinity potential drug candidates and CaMKIIα as a relevant pharmacological target for stroke therapy.

Ca²⁺/calmodulin-dependent protein kinase II alpha subunit (CaMKIIα) is a key neuronal signaling protein and an emerging drug target. The central hub domain regulates the activity of CaMKIIα by organizing the holoenzyme complex into functional oligomers, yet pharmacological modulation of the hub domain has never been demonstrated. Here, using a combination of photoaffinity labeling and chemical proteomics, we show that compounds related to the natural substance γ-hydroxybutyrate (GHB) bind selectively to CaMKIIα. By means of a 2.2-Å x-ray crystal structure of ligand-bound CaMKIIα hub, we reveal the molecular details of the binding site deep within the hub. Furthermore, we show that binding of GHB and related analogs to this site promotes concentration-dependent increases in hub thermal stability believed to alter holoenzyme functionality. Selectively under states of pathological CaMKIIα activation, hub ligands provide a significant and sustained neuroprotection, which is both time and dose dependent. This is demonstrated in neurons exposed to excitotoxicity and in a mouse model of cerebral ischemia with the selective GHB analog, HOCPCA (3-hydroxycyclopent-1-enecarboxylic acid). Together, our results indicate a hitherto unknown mechanism for neuroprotection by a highly specific and unforeseen interaction between the CaMKIIα hub domain and small molecule brain-penetrant GHB analogs. This establishes GHB analogs as powerful tools for investigating CaMKII neuropharmacology in general and as potential therapeutic compounds for cerebral ischemia in particular.

Baihui Point Laser Acupuncture Ameliorates Cognitive Impairment, Motor Deficit, and Neuronal Loss Partly via Antioxidant and Anti-Inflammatory Effects in an Animal Model of Focal Ischemic Stroke

Stroke is recognized as one of the most dangerous killer diseases in Thailand and other countries worldwide. The development of a novel strategy for treating stroke patients is therefore urgently required. The present study investigated the effect of laser acupuncture at the Baihui point on cognitive and functional recovery, neuronal loss, antioxidant enzyme activities, and interleukin-6 (IL-6) activity in the hippocampus in an animal model of focal ischemic stroke. Male Wistar rats were randomly divided into 4 groups: sham operation; permanent occlusion of the right middle cerebral artery (Rt.MCAO); Rt.MCAO with sham laser acupuncture; and Rt.MCAO with Baihui point laser acupuncture. Laser acupuncture at the Baihui point and sham acupuncture at a nonacupoint were performed once daily (10 min at each point) for 14 days after Rt.MCAO. Half of the rats in each group were examined to determine neuron density by Cresyl violet staining, while the other half were examined by biochemical assays to measure glutathione peroxidase (GSH-Px) in the hippocampus, superoxide dismutase (SOD) in mitochondria and interleukin-6 (IL-6) activity in the hippocampus. Laser acupuncture treatment was found to significantly enhance memory and neuron density in CA1 and CA3. Improved neurological score, improved GSH-Px and SOD activities, and decreased density ratio of IL-6 to β-actin were also observed in the hippocampus. In conclusion, Baihui point laser acupuncture alleviates cognitive impairment and motor deficits via antioxidant and anti-inflammatory effects in focal ischemic rats. Further study is warranted to investigate other possible mechanisms of action.

Sleep-Wake Disturbances After Traumatic Brain Injury: Synthesis of Human and Animal Studies

Sleep-wake disturbances following traumatic brain injury (TBI) are increasingly recognized as a serious consequence following injury and as a barrier to recovery. Injury-induced sleep-wake disturbances can persist for years, often impairing quality of life. Recently, there has been a nearly exponential increase in the number of primary research articles published on the pathophysiology and mechanisms underlying sleep-wake disturbances after TBI, both in animal models and in humans, including in the pediatric population. In this review, we summarize over 200 articles on the topic, most of which were identified objectively using reproducible online search terms in PubMed. Although these studies differ in terms of methodology and detailed outcomes; overall, recent research describes a common phenotype of excessive daytime sleepiness, nighttime sleep fragmentation, insomnia, and electroencephalography spectral changes after TBI. Given the heterogeneity of the human disease phenotype, rigorous translation of animal models to the human condition is critical to our understanding of the mechanisms and of the temporal course of sleep-wake disturbances after injury. Arguably, this is most effectively accomplished when animal and human studies are performed by the same or collaborating research programs. Given the number of symptoms associated with TBI that are intimately related to, or directly stem from sleep dysfunction, sleep-wake disorders represent an important area in which mechanistic-based therapies may substantially impact recovery after TBI.

Energy and the Alzheimer brain

The high energy demands of the poorly myelinated long axon hippocampal and cortical neurons render these neurons selectively vulnerable to degeneration in Alzheimer's disease. However, pathology engages all of the major elements of the neurovascular unit of the mature Alzheimer brain, the neurons, glia and blood vessels. Neurons present with retrograde degeneration of the axodendritic tree, capillaries with string vessels and markedly reduced densities and glia with signs of inflammatory activation. The neurons, capillaries and astrocytes of the mature Alzheimer brain harbor structurally defective mitochondria. Clinically, reduced glucose utilization, decades before cognitive deterioration, betrays ongoing energy insufficiency. β-hydroxybutyrate and γ-hydroxybutyrate can both provide energy to the brain when glucose utilization is blocked. Early work in mouse models of Alzheimer's disease demonstrate their ability to reverse the pathological changes in the Alzheimer brain and initial clinical trials reveal their ability to improve cognition and every day function. Supplying the brain with energy holds great promise for delaying the onset of Alzheimer's disease and slowing its progress.

The Neurobiological Mechanisms of Gamma-Hydroxybutyrate Dependence and Withdrawal and Their Clinical Relevance: A Review

OBJECTIVE

x03B3;-Hydroxybutyrate (GHB) has gained popularity as a drug of abuse. In the Netherlands the number of patients in treatment for GHB dependence has increased sharply. Clinical presentation of GHB withdrawal can be life threatening. We aim, through this overview, to explore the neurobiological pathways causing GHB dependency and withdrawal, and their implications for treatment choices.

METHODS

In this work we review the literature discussing the findings from animal models to clinical studies focused on the neurobiological pathways of endogenous but mainly exogenous GHB.

RESULTS

Chronic abuse of GHB exerts multifarious neurotransmitter and neuromodulator effects on x03B3;-aminobutyric acid (GABA), glutamate, dopamine, serotonin, norepinephrine and cholinergic systems. Moreover, important effects on neurosteroidogenesis and oxytocin release are wielded. GHB acts mainly via a bidirectional effect on GABAB receptors (GABABR; subunits GABAB1 and GABAB2), depending on the subunit of the GIRK (G-protein-dependent ion inwardly rectifying potassium) channel involved, and an indirect effect of the cortical and limbic inputs outside the nucleus accumbens. GHB also activates a specific GHB receptor and β1-subunits of α4-GABAAR. Reversing this complex interaction of neurobiological mechanisms by the abrupt cessation of GHB use results in a withdrawal syndrome with a diversity of symptoms of different intensity, depending on the pattern of GHB abuse.

CONCLUSION

The GHB withdrawal symptoms cannot be related to a single mechanism or neurological pathway, which implies that different medication combinations are needed for treatment. A single drug class, such as benzodiazepines, gabapentin or antipsychotics, is unlikely to be sufficient to avoid life-threatening complications. Detoxification by means of titration and tapering of pharmaceutical GHB can be considered as a promising treatment that could make polypharmacy redundant.

Volatile Organic Compound Gamma-Butyrolactone Released upon Herpes Simplex Virus Type -1 Acute Infection Modulated Membrane Potential and Repressed Viral Infection in Human Neuron-Like Cells

Herpes Simplex Virus Type -1 (HSV-1) infections can cause serious complications such as keratitis and encephalitis. The goal of this study was to identify any changes in the concentrations of volatile organic compounds (VOCs) produced during HSV-1 infection of epithelial cells that could potentially be used as an indicator of a response to stress. An additional objective was to study if any VOCs released from acute epithelial infection may influence subsequent neuronal infection to facilitate latency. To investigate these hypotheses, Vero cells were infected with HSV-1 and the emission of VOCs was analyzed using two-dimensional gas chromatograph/mass spectrometry (2D GC/MS). It was observed that the concentrations of gamma-butyrolactone (GBL) in particular changed significantly after a 24-hour infection. Since HSV-1 may establish latency in neurons after the acute infection, GBL was tested to determine if it exerts neuronal regulation of infection. The results indicated that GBL altered the resting membrane potential of differentiated LNCaP cells and promoted a non-permissive state of HSV-1 infection by repressing viral replication. These observations may provide useful clues towards understanding the complex signaling pathways that occur during the HSV-1 primary infection and establishment of viral latency.

Comprehensive Application of Time-of-flight Secondary Ion Mass Spectrometry (TOF-SIMS) for Ionic Imaging and Bio-energetic Analysis of Club Drug-induced Cognitive Deficiency

Excessive exposure to club drug (GHB) would cause cognitive dysfunction in which impaired hippocampal Ca²⁺-mediated neuroplasticity may correlate with this deficiency. However, the potential changes of in vivo Ca²⁺ together with molecular machinery engaged in GHB-induced cognitive dysfunction has never been reported. This study aims to determine these changes in bio-energetic level through ionic imaging, spectrometric, biochemical, morphological, as well as behavioral approaches. Adolescent rats subjected to GHB were processed for TOF-SIMS, immunohistochemistry, biochemical assay, together with Morris water maze to detect the ionic, molecular, neurochemical, and behavioral changes of GHB-induced cognitive dysfunction, respectively. Extent of oxidative stress and bio-energetics were assessed by levels of lipid peroxidation, Na⁺/K⁺ ATPase, cytochrome oxidase, and [¹⁴C]-2-deoxyglucose activity. Results indicated that in GHB intoxicated rats, decreased Ca²⁺ imaging and reduced NMDAR1, nNOS, and p-CREB reactivities were detected in hippocampus. Depressed Ca²⁺-mediated signaling corresponded well with intense oxidative stress, diminished Na⁺/K⁺ ATPase, reduced COX, and decreased 2-DG activity, which all contributes to the development of cognitive deficiency. As impaired Ca²⁺-mediated signaling and oxidative stress significantly contribute to GHB-induced cognitive dysfunction, delivering agent(s) that improves hippocampal bio-energetics may thus serve as a promising strategy to counteract the club drug-induced cognitive dysfunction emerging in our society nowadays.

Hypoxia and GABA shunt activation in the pathogenesis of Alzheimer's disease

We have previously observed that the conversion of mild cognitive impairment to definitive Alzheimer's disease (AD) is associated with a significant increase in the serum level of 2,4-dihydroxybutyrate (2,4-DHBA). The metabolic generation of 2,4-DHBA is linked to the activation of the γ-aminobutyric acid (GABA) shunt, an alternative energy production pathway activated during cellular stress, when the function of Krebs cycle is compromised. The GABA shunt can be triggered by local hypoperfusion and subsequent hypoxia in AD brains caused by cerebral amyloid angiopathy. Succinic semialdehyde dehydrogenase (SSADH) is a key enzyme in the GABA shunt, converting succinic semialdehyde (SSA) into succinate, a Krebs cycle intermediate. A deficiency of SSADH activity stimulates the conversion of SSA into γ-hydroxybutyrate (GHB), an alternative route from the GABA shunt. GHB can exert not only acute neuroprotective activities but unfortunately also chronic detrimental effects which may lead to cognitive impairment. Subsequently, GHB can be metabolized to 2,4-DHBA and secreted from the brain. Thus, the activation of the GABA shunt and the generation of GHB and 2,4-DHBA can have an important role in the early phase of AD pathogenesis.

Exhaled breath volatile biomarker analysis for thyroid cancer

Compared with other types of cancer, thyroid cancer incidence rates have increased rapidly worldwide in the past few decades. In recent years, potential thyroid cancer biomarkers have been studied, but these biomarkers have neither specificity nor good positive predictive value. Exhaled breath analysis is a recently developed convenient and noninvasive method for screening and diagnosing the disease. In this study, potential thyroid cancer biomarkers in volatile organic compounds (VOCs) were detected. Exhaled breath was collected from 64 patients with histologically confirmed cases of thyroid disease (including 39 individuals with papillary thyroid carcinoma and 25 individuals with nodular goiters) and 32 healthy volunteers. Solid-phase microextraction-gas chromatography and mass spectrometry was used to assess the exhaled VOCs of the study participants. The statistical methods of principal component analysis and partial least-squares discriminant analysis were performed to process the final data. The VOCs exhibited significant differences between nodular goiter patients and normal controls, papillary thyroid carcinoma patients and normal controls, and papillary thyroid carcinoma patients and nodular goiter patients; 7, 7, and 3 characteristic metabolites played decisive roles in sample classification, respectively. Breath analysis may provide a new, noninvasive, and directly qualitative method for the clinical diagnosis of thyroid disease.

Mitochondrial dysfunction induced by nuclear poly(ADP-ribose) polymerase-1: a treatable cause of cell death in stroke

Many drugs targeting excitotoxic cell death have demonstrated robust neuroprotective effects in animal models of cerebral ischemia. However, these neuroprotective effects have almost universally required drug administration at relatively short time intervals after ischemia onset. This finding has translated to clinical trial results; interventions targeting excitotoxicity have had no demonstrable efficacy when initiated hours after ischemia onset, but beneficial effects have been reported with more rapid initiation. Consequently, there continues to be a need for interventions with efficacy at later time points after ischemia. Here, we focus on mitochondrial dysfunction as both a relatively late event in ischemic neuronal death and a recognized cause of delayed neuronal death. Activation of poly(ADP-ribose) polymerase-1 (PARP-1) is a primary cause of mitochondrial depolarization and subsequent mitochondria-triggered cell death in ischemia reperfusion. PARP-1 consumes cytosolic NAD(+), thereby blocking both glycolytic ATP production and delivery of glucose carbon to mitochondria for oxidative metabolism. However, ketone bodies such as pyruvate, beta- and gamma-hydroxybutyrate, and 1,4-butanediol can fuel mitochondrial metabolism in cells with depleted cytosolic NAD(+) as long as the mitochondria remain functional. Ketone bodies have repeatedly been shown to be highly effective in preventing cell death in animal models of ischemia, but a rigorous study of the time window of opportunity for this approach remains to be performed.

Possible long-term effects of γ-hydroxybutyric acid (GHB) due to neurotoxicity and overdose

In several countries, including the Netherlands, the use of GHB seems to be rising. GHB is regarded by recreational users as an innocent drug without any side effects. Recently, the number of patients in treatment due to GHB addiction sharply increased. In addition, various studies report incidents following risky GHB use or GHB overdosing. Other sedative drugs, like ketamine and alcohol have been shown to result in unintended neurotoxic harm at the level of memory and cognitive function. As outlined in the present review, GHB and ketamine have a common mode of action, which suggests that GHB may also lead to similar neurotoxicity as ketamine. GHB overdosing, as well as binge drinking (and high ketamine doses), induce profound coma which is probably neurotoxic for the brain especially in the maturing brain of young adults. It is therefore advocated to investigate possible long-term neurotoxic effects in recreational GHB users e.g. by studying the residual effects on cognition and memory.

Comparing Treatments of Alcoholism on Craving and Biochemical Measures of Alcohol Consumptions

An open randomized study was conducted to compare different treatments of alcoholism on ethanol intake, craving, and on biochemical measures of alcohol consumptions. Eighty-six alcoholics were abstinent for a mean of two weeks prior to random assignment to g-hydroxybutyrate (GHB, 50 mg/kg of body weight t.i.d), naltrexone (NTX, 50 mg/day) or disulfiram (DSF, 200 mg/ day) treatment for 12 months. All treatments were equally effective in reducing alcohol intake and in maintaining abstinence. In all patients, the treatments were able to reduce both craving and the altered biological markers of alcohol abuse. The maximum effects were observed in GHB-treated patients. The results of the present study suggest that GHB might act both as anticraving and cellular protector agent.

A single acute pharmacological dose of γ-hydroxybutyrate modifies multiple gene expression patterns in rat hippocampus and frontal cortex

γ-Hydroxybutyrate (GHB) is a natural brain neuromodulator that has its own enzymatic machinery for synthesis and degradation, release, and transport systems and several receptors that belong to the G protein-coupled receptor (GPCR) family. Targeting of this system with exogenous GHB is used in therapy to induce sleep and anesthesia and to reduce alcohol withdrawal syndrome. GHB is also popular as a recreational drug for its anxiolytic and mild euphoric effects. However, in both cases, GHB must be administered at high doses in order to maintain GHB concentrations in brain of ∼800-1,000 μM. These high concentrations are thought to be necessary for interactions with low-affinity sites on GABA(B) receptor, but the molecular targets and cellular mechanisms modulated by GHB remain poorly characterized. Therefore, to provide new insights into the elucidation of GHB mechanisms of action and open new tracks for future investigations, we explored changes of GHB-induced transcriptomes in rat hippocampus and prefrontal cortex by using DNA microarray studies. We demonstrate that a single acute anesthetic dose of 1 g/kg GHB alters a large number of genes, 121 in hippocampus and 53 in prefrontal cortex; 16 genes were modified simultaneously in both brain regions. In terms of molecular functions, the majority of modified genes coded for proteins or nucleotide binding sites. In terms of Gene Ontology (GO) functional categories, the largest groups were involved in metabolic processing for hippocampal genes and in biological regulation for prefrontal cortex genes. The majority of genes modified in both structures were implicated in cell communication processes. Western blot and immunohistochemical studies carried out on eight selected proteins confirmed the microarray findings.

Neurotoxic effects induced by gammahydroxybutyric acid (GHB) in male rats

Gammahydroxybutyric acid (GHB) is an endogenous constituent of the central nervous system that has acquired great social relevance for its use as a recreational 'club drug'. GHB, popularly known as 'liquid ecstasy', is addictive when used continuously. Although the symptoms associated with acute intoxication are well known, the effects of prolonged use remain uncertain. We examined in male rats the effect of repeated administration of GHB (10 and 100 mg/kg) on various parameters: neurological damage, working memory and spatial memory, using neurological tests, the Morris water maze and the hole-board test. The results showed that repeated administration of GHB, especially at doses of 10 mg/kg, causes neurological damage, affecting the 'grasping' reflex, as well as alteration in spatial and working memories. Stereological quantification showed that this drug produces a drastic neuronal loss in the CA1 hippocampal region and in the prefrontal cortex, two areas clearly involved in cognitive and neurological functions. No effects were noted after quantification in the periaqueductal grey matter (PAG), a region lacking GHB receptors. Moreover, NCS-382, a putative antagonist of GHB receptor, prevented both neurological damage and working- memory impairment induced by GHB. This suggests that the effects of administration of this compound may be mediated, at least partly, by specific receptors in the nervous system. The results show for the first time that the repeated administration of GHB, especially at very low doses, produces neurotoxic effects. This is very relevant because its abuse, especially by young persons, could produce considerable neurological alterations after prolonged abuse.

Pharmacological doses of gamma-hydroxybutyrate (GHB) potentiate histone acetylation in the rat brain by histone deacetylase inhibition

Several small chain fatty acids, including butyrate, valproate, phenylbutyrate and its derivatives, inhibit several HDAC activities in the brain at a several hundred micromolar concentration. Gamma-hydroxy-butyrate (GHB), a natural compound found in the brain originating from the metabolism of GABA, is structurally related to these fatty acids. The average physiological tissue concentration of GHB in the brain is below 50 microM, but when GHB is administered or absorbed for therapeutic or recreative purposes, its concentration reaches several hundred micromolars. In the present scenario, we demonstrate that pharmacological concentrations of GHB significantly induce brain histone H3 acetylation with a heterogeneous distribution in the brain and reduce in vitro HDAC activity. The degree of HDAC inhibition was also different according to the region of the brain considered. Taking into account the multiple physiological and functional roles attributed to the modification of histone acetylation and its consequences at the level of gene expression, we propose that part of the therapeutic or toxic effects of high concentrations of GHB in the brain after therapeutic administration of the drug could be partly due to GHB-induced epigenetic factors. In addition, we hypothesize that GHB, being naturally synthesized in the cytosolic compartment of certain neurons, could penetrate into the nuclei and may reach sufficient levels that could significantly modulate histone acetylation and may participate in the epigenetic modification of gene expression.

Vagus nerve mediates the protective effects of melanocortins against cerebral and systemic damage after ischemic stroke

A vagus nerve-mediated, efferent cholinergic protective pathway activated by melanocortins is operative in circulatory shock and myocardial ischemia. Moreover, melanocortins have neuroprotective effects against brain damage after ischemic stroke. Here we investigated cerebral and systemic pathophysiologic reactions to focal cerebral ischemia in rats induced by intrastriatal microinjection of endothelin-1, and the possible protective role of the melanocortin-activated vagal cholinergic pathway. In the striatum and liver of saline-treated control rats, the activation of extracellular signal-regulated kinases, c-jun N-terminal kinases, and caspase-3, the increase in tumor necrosis factor-alpha (TNF-alpha) concentration and DNA fragmentation, as well as the increase in TNF-alpha plasma levels, occurred 10 and 20 h after the ischemic insult suggesting an activation of inflammatory and apoptotic responses. Treatment with [Nle(4), D-Phe(7)]alpha-melanocyte-stimulating hormone (NDP-alpha-MSH; 3 or 9 h after stroke) suppressed the inflammatory and apoptotic cascades at central and peripheral level. Bilateral vagotomy and pharmacologic blockade of peripheral nicotinic acetylcholine receptors blunted the protective effect of NDP-alpha-MSH. The present results show that focal brain ischemia in rats causes significant effects not only in the brain, but also in the liver. Moreover, our data support the hypothesis that a protective, melanocortin-activated, vagal cholinergic pathway is likely operative in conditions of ischemic stroke.

The Continued Promise of Neuroprotection for Acute Stroke Treatment

Stroke is the second leading cause of death. However, effective pharmocologic treatment options are still extremely limited and applicable to only a small fraction of patents. The translational failure in finding an effective neuroprotectant for ischemic strokes has generated an active discussion in this field. One focus has been on validating systems for testing neuroprotectants. This review discusses some fundamental issues in experimental stroke that are worthy of further exploration. We begin with a general review of the current status of experimental stroke research and then move on to a discussion of the determining factors and processes that control and differentiate the fate of ischemic ischemic cells and tissue. We propose several strategies of neuroprotection for ischemic strokes with an emphasis on manipulating cellular energy state.

Neuroprotection in focal cerebral ischemia owing to delayed treatment with melanocortins

In gerbils subjected to transient global cerebral ischemia, melanocortin peptides produce long-lasting protection with a broad time window, and through the activation of central nervous system melanocortin MC(4) receptors. Here we aimed to investigate whether melanocortins are neuroprotective also in a rat model of focal cerebral ischemia induced by intrastriatal microinjection of endothelin-1. The vasoconstrictor agent endothelin-1 caused a significant impairment in spatial learning and memory, as well as in sensory-motor orientation and limb use, associated with severe striatal morphological damage including intense neuronal death and an almost complete myelin degradation. Treatment of ischemic rats with a nanomolar dose (340 microg/kg/day i.p. for 11 days, beginning 3 h or 9 h after endothelin-1 microinjection) of the melanocortin analog [Nle(4), D-Phe(7)]alpha-melanocyte-stimulating hormone (NDP-alpha-MSH) significantly reduced striatal damage, and improved subsequent functional recovery, with all scheduled NDP-alpha-MSH treatments. Pharmacological blockade of melanocortin MC(4) receptors prevented the protective effect of NDP-alpha-MSH. Our findings give evidence that melanocortins are neuroprotective, with a broad time window, also in a severe model of focal cerebral ischemia, and suggest that melanocortin MC(4) receptor agonists could produce neuroprotection in different experimental models of ischemic stroke.

Gamma-Hydroxybutyrate (GHB), gamma-butyrolactone (GBL), and 1,4-butanediol (1,4-BD) reduce the volume of cerebral infarction in rodent transient middle cerebral artery occlusion

gamma-Hydroxybutyric acid (GHB), an endogenous organic acid catabolite of gamma-aminobutyric acid (GABA), has been shown to have tissue-protective effects in various organs, including the brain. We examined the potential neuroprotective effect of GHB and its chemical precursors, gamma-butyrolactone (GBL) and 1,4-butanediol (1,4-BD), in the rodent ischemic stroke model by intraluminal filament middle cerebral artery occlusion (MCAO). Adult male Sprague-Dawley rats underwent transient left-sided MCAO and received intraperitoneal treatment with 300 mg/kg of GHB, GBL, 1,4-BD, or control vehicle given at 30 min before, as well as 180 and 360 min after the onset of ischemia. Infarct volumes were determined 24 h after MCAO. In transient MCAO, the mean volume of infarction for control rats was 464.4 +/- 17.9 cu.mm versus 273.6 +/- 53.1, 233.3 +/- 44.7, and 275.4 +/- 39.9 cu.mm for rats treated with 1,4-BD (P < 0.05), GBL (P < 0.05), and GHB (P < 0.05), respectively. We conclude that GHB, GBL, and 1,4-BD protect against rat focal cerebral ischemia from transient MCAO.

Alzheimer' s disease, oxidative stress and gammahydroxybutyrate

Although the cause of Alzheimer's disease is unknown, oxidative stress, energy depletion, excitotoxicity and vascular endothelial pathology are all considered to play a part in its pathogenesis. In reaction to these adverse events, the Alzheimer brain appears to deploy a highly conserved biological response to tissue stress. Oxidative metabolism is turned down, the expression of antioxidative enzymes is increased and intermediary metabolism is shifted in the direction of the pentose phosphate shunt to promote reductive detoxification, repair and biosynthesis. Gathering evidence suggests that the release of beta-amyloid and the formation of neurofibrillary tangles, the two hallmarks of Alzheimer's disease, are components of this protective response. Gammahydroxybutyrate (GHB), an endogenous short chain fatty acid, may be able to buttress this response. GHB can reduce glucose utilization, shift intermediary metabolism in the direction the pentose phosphate shunt and generate NADPH, a key cofactor in the activity of many antioxidative and reductive enzymes. GHB has been shown to spare cerebral energy utilization, block excitotoxicity and maintain vascular integrity in the face of impaired perfusion. Most important, GHB has repeatedly been shown to prevent the tissue damaging effects of oxidative stress. It may therefore be possible to utilize GHB to strengthen the brain's innate defences against the pathological processes operating in the Alzheimer brain and, in this way, stem the advance of Alzheimer's disease.

Broad therapeutic treatment window of [Nle(4), D-Phe(7)]alpha-melanocyte-stimulating hormone for long-lasting protection against ischemic stroke, in Mongolian gerbils

Melanocortin peptides have been shown to produce neuroprotection in experimental ischemic stroke. The aim of the present investigation was to identify the therapeutic treatment window of melanocortins, and to determine whether these neuropeptides chronically protect against damage consequent to brain ischemia. A 10-min period of global cerebral ischemia in gerbils, induced by occluding both common carotid arteries, caused impairment in spatial learning and memory (Morris test: four sessions from 4 to 67 days after the ischemic episode), associated with neuronal death in the hippocampus. Treatment with a nanomolar dose (340 microg/kg i.p., every 12 h for 11 days) of the melanocortin analog [Nle(4), D-Phe(7)]alpha-melanocyte-stimulating hormone (NDP-alpha-MSH), starting 3-18 h after the ischemic episode, reduced hippocampal damage with improvement in subsequent functional recovery. The protective effect was long-lasting (67 days, at least) with all schedules of NDP-alpha-MSH treatment; however, in the latest treated (18 h) gerbils, some spatial memory deficits were detected. Pharmacological blockade of melanocortin MC(4) receptors prevented the protective effects of NDP-alpha-MSH. Our findings indicate that, in conditions of brain ischemia, melanocortins can provide strong and long-lasting protection with a broad therapeutic treatment window, and with involvement of melanocortin MC(4) receptors, 18 h being the approximately time-limit for stroke late treatment to be effective.

Experimental model of hemorrhagic stroke: Rabbit immunization with HL-60 promyelocytic cell differentiation factor

Rabbits immunized with synthetic HLDF differentiation factor developed hemorrhagic stroke with thrombosis of small cerebral vessels and destruction of vascular endotheliocytes. The severity of stroke correlated with serum level of antibodies to differentiation factor. The role of different sites of HLDF molecule in the induction of clinical signs of hemorrhagic stroke was studied.

Comparison of the behavioral effects of gamma-hydroxybutyric acid (GHB) and its 4-methyl-substituted analog, gamma-hydroxyvaleric acid (GHV)

Gamma-hydroxybutyrate (GHB), a metabolite of GABA, is a drug of abuse and a therapeutic. The illicit use of GHB precursors and analogs reportedly has increased worldwide. Gamma-hydroxyvaleric (GHV) is a 4-methyl-substituted analog of GHB that reportedly is abused and is marketed as a dietary supplement and replacement for GHB. The purpose of these studies was to compare the pharmacological and behavioral profiles of GHV and GHB. In radioligand binding studies, GHV completely displaced [(3)H]NCS-382 with approximately 2-fold lower affinity than GHB and did not markedly displace [(3)H]GABA from GABA(B) receptors at a 20-fold larger concentration. In drug discrimination procedures, GHV did not share discriminative stimulus effects with GHB or baclofen. GHV shared other behavioral effects with GHB, such as sedation, catalepsy, and ataxia, although larger doses of GHV were required to produce these effects. Lethality (50%) was observed after the largest dose of GHV (5600mg/kg), a dose that produced less-than-maximal catalepsy and ataxia. To the extent that large doses of GHV might be taken to in an attempt to produce GHB-like effects (e.g., hypnosis) GHV toxicity may pose a greater public health concern than GHB.

Pyruvate dehydrogenase complex: metabolic link to ischemic brain injury and target of oxidative stress

The mammalian pyruvate dehydrogenase complex (PDHC) is a mitochondrial matrix enzyme complex (greater than 7 million Daltons) that catalyzes the oxidative decarboxylation of pyruvate to form acetyl CoA, nicotinamide adenine dinucleotide (the reduced form, NADH), and CO(2). This reaction constitutes the bridge between anaerobic and aerobic cerebral energy metabolism. PDHC enzyme activity and immunoreactivity are lost in selectively vulnerable neurons after cerebral ischemia and reperfusion. Evidence from experiments carried out in vitro suggests that reperfusion-dependent loss of activity is caused by oxidative protein modifications. Impaired enzyme activity may explain the reduced cerebral glucose and oxygen consumption that occurs after cerebral ischemia. This hypothesis is supported by the hyperoxidation of mitochondrial electron transport chain components and NAD(H) that occurs during reperfusion, indicating that NADH production, rather than utilization, is rate limiting. Additional support comes from the findings that immediate postischemic administration of acetyl-L-carnitine both reduces brain lactate/pyruvate ratios and improves neurologic outcome after cardiac arrest in animals. As acetyl-L-carnitine is converted to acetyl CoA, the product of the PDHC reaction, it follows that impaired production of NADH is due to reduced activity of either PDHC or one or more steps in glycolysis. Impaired cerebral energy metabolism and PDHC activity are associated also with neurodegenerative disorders including Alzheimer's disease and Wernicke-Korsakoff syndrome, suggesting that this enzyme is an important link in the pathophysiology of both acute brain injury and chronic neurodegeneration.

Gamma-hydroxybutyric acid: neurobiology and toxicology of a recreational drug

gamma-Hydroxybutyric acid (GHB) is a short-chain fatty acid that occurs naturally in mammalian brain where it is derived metabolically from gamma-aminobutyric acid (GABA), the primary inhibitory neurotransmitter in the brain. GHB was synthesised over 40 years ago and its presence in the brain and a number of aspects of its biological, pharmacological and toxicological properties have been elucidated over the last 20-30 years. However, widespread interest in this compound has arisen only in the past 5-10 years, primarily as a result of the emergence of GHB as a major recreational drug and public health problem in the US. There is considerable evidence that GHB may be a neuromodulator in the brain. GHB has multiple neuronal mechanisms including activation of both the gamma-aminobutyric acid type B (GABA(B)) receptor, and a separate GHB-specific receptor. This complex GHB-GABA(B) receptor interaction is probably responsible for the protean pharmacological, electroencephalographic, behavioural and toxicological effects of GHB, as well as the perturbations of learning and memory associated with supra-physiological concentrations of GHB in the brain that result from the exogenous administration of this drug in the clinical context of GHB abuse, addiction and withdrawal. Investigation of the inborn error of metabolism succinic semialdehyde deficiency (SSADH) and the murine model of this disorder (SSADH knockout mice), in which GHB plays a major role, may help dissect out GHB- and GABA(B) receptor-mediated mechanisms. In particular, the mechanisms that are operative in the molecular pathogenesis of GHB addiction and withdrawal as well as the absence seizures observed in the GHB-treated animals.