Time and Brain Region-Dependent Excitatory Neurochemical Alterations in Bilateral Common Carotid Artery Occlusion Global Ischemia Model.

Strict metabolic regulation in discrete brain regions leads to neurochemical changes in cerebral ischemia. Accumulation of extracellular glutamate is one of the early neurochemical changes that take place during cerebral ischemia. Understanding the sequential neurochemical processes involved in cerebral ischemia-mediated excitotoxicity before the clinical intervention of revascularization and reperfusion may greatly influence future therapeutic strategies for clinical stroke recovery. This study investigated the influence of time and brain regions on excitatory neurochemical indices in the bilateral common carotid artery occlusion (BCCAO) model of global ischemia. Male Wistar rats were subjected to BCCAO for 15 and 60 min to evaluate the effect of ischemia duration on excitatory neurochemical indices (dopamine level, glutamine synthetase, glutaminase, glutamate dehydrogenase, aspartate aminotransferase, monoamine oxidase, acetylcholinesterase, and Na+ K+ ATPase activities) in the discrete brain regions (cortex, striatum, cerebellum, and hippocampus). BCCAO without reperfusion caused marked time and brain region-dependent alterations in glutamatergic, glutaminergic, dopaminergic, monoaminergic, cholinergic, and electrogenic homeostasis. Prolonged BCCAO decreased cortical, striatal, and cerebellar glutamatergic, glutaminergic, dopaminergic, cholinergic, and electrogenic activities; increased hippocampal glutamatergic, glutaminergic, dopaminergic, and cholinergic activities, increased cortical and striatal monoaminergic activity; decreased cerebellar and hippocampal monoaminergic activity; and decreased hippocampal electrogenic activity. This suggests that excitatory neurotransmitters play a major role in the tissue-specific metabolic plasticity and reprogramming that takes place between the onset of cardiac arrest-mediated global ischemia and clinical intervention of recanalization. These tissue-specific neurochemical indices may serve as diagnostic and therapeutic strategies for mitigating the progression of ischemic damage before revascularization.

Polyphenol-rich Spondias mombin leaf extract abates cerebral ischemia/reperfusion-induced disturbed glutamate-ammonia metabolism and multiorgan toxicity in rats.

Introduction: This study investigated the protective properties of Spondias mombin leaf extract (SML), in cerebral ischemia/reperfusion (I/R) mediated toxicity in the brain, liver, and kidney of male Wistar rats. Materials and methods: Animals were subjected to 30 min of bilateral common carotid artery occlusion followed by 24 h of reperfusion (BCCAO/R). The animals were divided into sham, I/R, and I/R treated with SML (25, 50 and 100 mg/kg) or quercetin (20 mg/kg) groups. Animals were sacrificed after 24 h of reperfusion and markers of organ toxicity (urea creatinine, glutamine synthetase (GS), glutaminase (GA), aspartate aminotransferase (AST), alanine aminotransferase (ALT), acetylcholinesterase (AChE)) were measured in the brain regions (cortex, striatum, and hippocampus), liver, and kidney. Results and discussion: BCCAO/R significantly (p < 0.0001) inhibited the glutamate-glutamine cycle and mediated toxicity in the cerebral cortex, striatum, hippocampus, liver, and kidney of rats. Post-treatment with SML significantly (p < 0.0001) reversed glutamate-glutamine cycle inhibition and ameliorated cerebrohepatorenal toxicity in ischemic rats. Conclusion: Cerebral I/R significantly mediated cerebral, hepatic, and renal toxicity through the inhibition of glutamate-ammonia detoxification in rats, and SML protected against this post-ischemic glutamate-ammonia mediated multiorgan toxicity.

Comparative influence of kolaviron and coenzyme Q10 on complex I activity, glutamate clearance, 3,4-dihydroxyphenethylamine metabolism, and redox stress in rotenone-induced neurotoxicity.

3,4-dihydroxyphenethylamine (dopamine) depletion, inhibition of complex I activity, oxidative stress, and glutamate excitotoxicity are cardinal biochemical features of neurotoxicity induced by systemic unilateral infusion of rotenone. Kolaviron (KV), a biflavonoid from Garcinia kola seeds, has been proven to have pharmacological effects against neurotoxicity. Coenzyme Q10 plays an essential role in mitochondrial oxidative phosphorylation and as an antioxidant. This study examined the comparative influence of kolaviron and coenzyme Q10 on complex I activity, dopamine metabolism, glutamate clearance, and redox stress in rotenone-induced neurotoxicity in the cortex, hippocampus, and striatum of the brain of rats. Adult Male Wistar rats were pretreated with 200 mg/kg KV or 100 mg/kg coenzyme Q10 for 7 days followed by administration of a progressive six doses of 1.5 mg/kg rotenone within the next 48 h after which the animals were euthanized and the brain excised. On the cortical, hippocampal, and striatal regions of the brain, complex I activity, dopamine metabolism, oxidative stress markers, as well as glutamate metabolism were carried out and analyzed. In all brain regions examined, KV and coenzyme Q10 pretreatment modulated complex I activity, ameliorated redox imbalance, and enhanced dopamine metabolism via increasing the activity of tyrosine hydroxylase and decreasing monoamine oxidase activity. KV facilitated glutamate clearance through augmentation of glutamate dehydrogenase and glutamine synthetase activities.  The activity of KV was comparable to that of the mitochondrial membrane antioxidant compound, coenzyme Q10, this indicates that KV is a promising therapeutic agent in the treatment of Parkinson's disease and its activity compares well with coenzyme Q10.

Reduction of anoxia-induced bioenergetic disturbance in astrocytes by methanol fruit extract of Tetrapleura tetraptera and in silico evaluation of the effect of its antioxidative constituents on excitotoxicity.

Oxidative stress and excitotoxicity are some of the pathophysiological abnormalities in hypoxia-induced brain injury. This study evaluated the intrinsic antioxidant property of methanol fruit extract of Tetrapleura tetraptera (TT), traditionally used for managing brain diseases such as cerebral infarction in West Africa, and its ability to protect primary astrocytes from anoxia-induced cell death. The effect of the phytochemicals present in TT on excitotoxicity was assessed in silico, through docking with human glutamate synthetase (hGS). Chromatographic and spectrophotometric analyses of TT were performed. Primary astrocytes derived from neural stem cells were treated with TT and its effect on astrocyte viability was assessed. TT-treated astrocytes were then subjected to anoxic insult and, cell viability and mitochondrial membrane potential were evaluated. Molecular docking of hGS with detected phytochemicals in TT (aridanin, naringenin, ferulic acid, and scopoletin) was performed and the number of interactions with the lead compounds, aridanin, analyzed. HPLC-DAD analysis of TT revealed the presence of various bioactive phytochemicals. TT demonstrated notable antioxidant and radical scavenging activities. TT also protected astrocytes from anoxic insult by restoring cell viability and preventing alteration to mitochondrial membrane integrity. Aridanin, naringenin, ferulic acid, and scopoletin demonstrated good binding affinities with hGS indicating that Tetrapleura tetraptera is a potential source of new plant-based bioactives relevant in the therapy of neurodegenerative diseases.

Neurotherapeutic potential of kolaviron on neurotransmitter dysregulation, excitotoxicity, mitochondrial electron transport chain dysfunction and redox imbalance in 2-VO brain ischemia/reperfusion injury.

This study investigated the effects of post-treatment with kolaviron on a 2-Vessel Occlusion (2-VO) model of cerebral ischemia/reperfusion (I/R) injury in rats to ascertain its level of efficacy as a potential therapeutic agent for stroke. Male Wistar rats submitted to 30 min of bilateral common carotid artery occlusion and 24 h of reperfusion were treated with kolaviron (25-100 mg/kg) or 20 mg/kg quercetin immediately after reperfusion and 2 h post reperfusion. At the end of the period of reperfusion, animals were scored for motor and cognitive deficits. Brain relative weight and water content were determined. Cortices, striata and hippocampi were dissected and processed for estimation of markers of oxidative stress, inflammation, neurotransmitter dysregulation and excitotoxicity. In addition, assessment of hippocampal mitochondrial integrity and histopathological examination of the cortical, striatal and hippocampal regions were carried out. There was reversal of 2-VO ischemia/reperfusion (I/R) induced motor and cognitive deficits by kolaviron post-treatment. Post-treatment with kolaviron also attenuated I/R-induced oxidative stress, neuroinflammatory events, excitotoxicity as well as mitochondrial dysfunction in brain tissues. Histopathological findings showed amelioration of I/R-induced neuronal cell damage by kolaviron post-treatment. The results revealed the multi-target neurotherapeutic activity of kolaviron and suggest that it is a promising candidate for drug development against stroke.

Catechin, quercetin and taxifolin improve redox and biochemical imbalances in rotenone-induced hepatocellular dysfunction: Relevance for therapy in pesticide-induced liver toxicity?

Hepatotoxicity occurs as a result of adverse effects of some xenobiotics on the liver, which is often the target tissue of toxicity for environmental chemicals. Rotenone, used as a natural pesticide, is an environmental poison reported to cause organ toxicity. This study investigated the protective effect of three flavonoids, catechin, quercetin and taxifolin (2,3-Dihydroquercetin) in rotenone-induced hepatotoxicity. Male Wistar rats were administered rotenone for 10 days followed by post treatment with catechin (5, 10 and 20 mg/kg), quercetin (5, 10 and 20 mg/kg) or taxifolin (0.25, 0.5 and 1 mg/kg), respectively, for 3 days. Bioindices of oxidative stress and hepatocellular injury were measured in serum and tissue homogenate of animals. Rotenone intoxication produced liver damage in rats as reflected in alterations to activities/levels of enzymic and non-enzymic oxidative stress markers and enzymes linked with inflammation, as well as the transaminases, gamma glutamyl transpeptidase, bilirubin, and lactate dehydrogenase. Catechin, quercetin and taxifolin post treatment significantly attenuated these (p < 0.0001) rotenone-induced imbalances. Comparatively, quercetin displayed the best apparent ameliorative activity. It clearly showed superior activity to catechin. However, taxifolin appeared to show comparable activity to quercetin and better activity than catechin in some of the assays despite being administered at considerably lower doses. The results provide insight on the relative efficacy and structure-activity relationships of the selected flavonoids in ameliorating liver damage and also indicate that additional structural and metabolic factors may be involved in the structure-activity relationships of flavonoids.

Improvement of 2-Vessel Occlusion Cerebral Ischaemia/Reperfusion-Induced Corticostriatal Electrolyte and Redox Imbalance, Lactic Acidosis and Modified Acetylcholinesterase Activity by Kolaviron Correlates with Reduction in Neurobehavioural Deficits.

BACKGROUND: Disruption of electrolyte, redox and neurochemical homeostasis alongside cellular energy crisis is a hallmark of cerebral ischaemia and reperfusion injury. PURPOSE: This study investigated the effect of kolaviron (KV) on cortical and striatal cation imbalance, oxidative stress and neurochemical disturbances as well as neurobehavioural deficits in animals subjected to bilateral common carotid artery occlusion (BCCAO)-induced ischaemia/reperfusion injury. METHODS: KV was administered at a dose of 100 or 200 mg/kg to male Wistar rats 1 h before a 30 min BCCAO/4 h reperfusion (I/R). This was followed by neurobehavioral assessment and biochemical evaluations of cation levels, oxidative stress indicators, lactate dehydrogenase activity and acetylcholinesterase (AChE) activity in the brain of animals. CONCLUSION: KV significantly restored altered cortical and striatal Ca2+, Na+, K+ and Mg2+ levels, ameliorated redox imbalance, lactic acidosis and modified AChE activity caused by I/R injury. The favourable neurobehavioural effects of KV correlated with biochemical outcomes. The pharmacological potential of KV in the treatment and management of ischemic stroke and allied pathological conditions via multiple targets (neurotransmitter metabolism, bioenergetic failure and ionic homeostasis) is highlighted by the study.