Effects of pyruvate administration on infarct volume and neurological deficits following permanent focal cerebral ischemia in rats

Voacangine mitigates oxidative stress and neuroinflammation in middle cerebral artery occlusion-induced cerebral ischemia/reperfusion injury by averting the NF-κBp65/MAPK signaling pathways in rats

Ischemic stroke is a leading cause of human mortality. Cerebral ischemia-reperfusion injury (CI/RI) is a primary cause of stroke. Ischemia-reperfusion (I/R) resulting in oxidative stress and inflammatory events may lead to severe neuronal impairments. Thus, anti-oxidative and anti-inflammatory mediators that can alleviate post-I/R neuronal injuries are required for the treatment of CI/RI. An alkaloid, voacangine (VCG) is a recognized antioxidant, anti-inflammatory, and anticancer agent. Hence, the current study intended to explore the neuroprotective potential and the principal mechanisms of VCG in CI/RI. The experimental rats were divided into four sets: control, I/R-induced, I/R + VCG (2.5 mg/kg), I/R + VCG (5 mg/kg). CI/RI was induced by implanting a thread into the middle cerebral artery occlusion (MCAO) model. Brain damages were assessed on the basis of brain edema, brain infarct volume, neurological deficit score, histopathology, oxidative stress, and neuroinflammation. Results revealed that VCG inhibited the triggering of NLRP3 inflammasome, pro-inflammatory cytokines, lipid peroxidation, but enhanced the antioxidant status in MCAO rats. Furthermore, VCG treatment averted brain damage by I/R, neuroinflammation, and oxidative stress by suppressing NF-κBp65/MAPK pathways. The results of the study provide pertinent insights pertaining to the role of VCG as a potential neuroprotective agent against ischemic stroke.

Multi-omics reveals specific host metabolism-microbiome associations in intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is the most devastating subtype of stroke, but effective prevention and treatment strategies are lacking. Recently, gut microbiome and its metabolitesis are considered to be an influencing factor of stroke. However, little is known about the effects of the gut microbiome on ICH and host metabolic activity. Therefore, we used 16S sequencing, macrogenomics sequencing and untargeted metabolomics to explore the differences in gut microbial-metabolome interactions between patients with intracerebral hemorrhage and healthy control populations. We found a significant decrease in the phylum of Firmicutes and a significant increase of Bacteroidetes in ICH patients. At the genus level, Streptococcus, Bifidobacterium, Akkermansia, and Lactobacillus were more abundant in ICH patients. Macrogenomic analysis revealed active glycosaminoglycan degradation, heme synthesis, galactose degradation, lipopolysaccharide core region synthesis, and beta-Lactam resistance in ICH patients. Serum untargeted metabolomic analysis combined with ROC curves showed that octanoylcarnitine, decanoylcarnitine, dodecanoylcarnitine, glyceric acid, pyruvic acid, aspartic acid, methylcysteine, pyroglutamic acid, 9E-tetradecenoic acid, N-Acetylneuraminic acid, and aconitic acid were the best markers for the diagnosis of ICH. Correlation analysis showed that microbiome enriched in the gut of ICH patients were significantly correlated with serum metabolites, revealing a close correlation between the gut microbiome of ICH patients and the host metabolome, and significant differences from the healthy population. microbiota-host co-metabolites including pyruvic acid and 9E-tetradecenoic acid is associated with the the National Institutes of Health Stroke Scale (NIHSS) scores. In conclusion, microbiome-related metabolites in ICH patients was associated with the severity of ICH, the microbiota-host co-metabolites may be a potential may be potential therapeutic targets.

Lactate Neuroprotection against Transient Ischemic Brain Injury in Mice Appears Independent of HCAR1 Activation

Lactate can protect against damage caused by acute brain injuries both in rodents and in human patients. Besides its role as a metabolic support and alleged preferred neuronal fuel in stressful situations, an additional signaling mechanism mediated by the hydroxycarboxylic acid receptor 1 (HCAR1) was proposed to account for lactate’s beneficial effects. However, the administration of HCAR1 agonists to mice subjected to middle cerebral artery occlusion (MCAO) at reperfusion did not appear to exert any relevant protective effect. To further evaluate the involvement of HCAR1 in the protection against ischemic damage, we looked at the effect of HCAR1 absence. We subjected wild-type and HCAR1 KO mice to transient MCAO followed by treatment with either vehicle or lactate. In the absence of HCAR1, the ischemic damage inflicted by MCAO was less pronounced, with smaller lesions and a better behavioral outcome than in wild-type mice. The lower susceptibility of HCAR1 KO mice to ischemic injury suggests that lactate-mediated protection is not achieved or enhanced by HCAR1 activation, but rather attributable to its metabolic effects or related to other signaling pathways. Additionally, in light of these results, we would disregard HCAR1 activation as an interesting therapeutic strategy for stroke patients.

Acetyl-CoA production by specific metabolites promotes cardiac repair after myocardial infarction via histone acetylation

Myocardial infarction (MI) is accompanied by severe energy deprivation and extensive epigenetic changes. However, how energy metabolism and chromatin modifications are interlinked during MI and heart repair has been poorly explored. Here, we examined the effect of different carbon sources that are involved in the major metabolic pathways of acetyl-CoA synthesis on myocardial infarction and found that elevation of acetyl-CoA by sodium octanoate (8C) significantly improved heart function in ischemia reperfusion (I/R) rats. Mechanistically, 8C reduced I/R injury by promoting histone acetylation which in turn activated the expression of antioxidant genes and inhibited cardiomyocyte (CM) apoptosis. Furthermore, we elucidated that 8C-promoted histone acetylation and heart repair were carried out by metabolic enzyme medium-chain acyl-CoA dehydrogenase (MCAD) and histone acetyltransferase Kat2a, suggesting that 8C dramatically improves cardiac function mainly through metabolic acetyl-CoA-mediated histone acetylation. Therefore, our study uncovers an interlinked metabolic/epigenetic network comprising 8C, acetyl-CoA, MCAD, and Kat2a to combat heart injury.

Astragalin alleviates cerebral ischemia-reperfusion injury by improving anti-oxidant and anti-inflammatory activities and inhibiting apoptosis pathway in rats

BACKGROUND

Astragalin (AG), a flavonoid from many traditional herbs and medicinal plants, has been described to exhibit in vitro anti-inflammatory activity. The paper aimed to study the effects of astragalin on anti-inflammatory, anti-oxidative ability and apoptosis signaling pathway in brain tissue of rats with cerebral ischemia-reperfusion injury, and to explore its possible mechanism.

METHODS

The rat model of focal cerebral ischemia-reperfusion injury was established by suture method. It was randomly divided into 5 groups, sham operation group, ischemia-reperfusion (I/R) treatment group, and astragalin treatment I / R group (12.5, 25, 50 mg / kg). After 24 h of reperfusion, the neurological deficits of the rats were analyzed and HE staining was performed. The volume of cerebral infarction was calculated by triphenyltetrazolium chloride (TTC) staining, and the apoptosis of nerve cells was detected by TUNEL staining. In addition, the content of malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), glutathione (GSH) assay and glutathione peroxidase (GSH-Px) were measured in rat brain tissue. Western blot analysis was used to determine the expression of related proteins.

RESULTS

Compared with I/R group, the neurological deficit score and infarct volume of I/R rats were reduced in the astragalin treatment group. In the astragalin treatment group, MDA and NO levels in I/R rats were reduced, antioxidant enzymes and superoxide dismutase (SOD) activity were increased. In the astragalin treatment group, NF-κB (p65) and cyclooxygenase-2 (COX-2) expression levels were down-regulated, NF-E2-related factor 2 (Nrf2) nucleus and heme oxygenase-1 (HO-1) protein expression levels were up-regulated. In addition, the astragalin treatment can inhibit apoptosis, down-regulate Bax and cleaved caspase-3 expression, up-regulate Bcl-Xl expression.

CONCLUSION

The antioxidant properties of astragalin may play an important role in improving cerebral ischemia-reperfusion injury.

Real-time ex-vivo measurement of brain metabolism using hyperpolarized [1-13C]pyruvate

The ability to directly monitor in vivo brain metabolism in real time in a matter of seconds using the dissolution dynamic nuclear polarization technology holds promise to aid the understanding of brain physiology in health and disease. However, translating the hyperpolarized signal observed in the brain to cerebral metabolic rates is not straightforward, as the observed in vivo signals reflect also the influx of metabolites produced in the body, the cerebral blood volume, and the rate of transport across the blood brain barrier. We introduce a method to study rapid metabolism of hyperpolarized substrates in the viable rat brain slices preparation, an established ex vivo model of the brain. By retrospective evaluation of tissue motion and settling from analysis of the signal of the hyperpolarized [1-13C]pyruvate precursor, the T1s of the metabolites and their rates of production can be determined. The enzymatic rates determined here are in the range of those determined previously with classical biochemical assays and are in agreement with hyperpolarized metabolite relative signal intensities observed in the rodent brain in vivo.

Effects of the combined treatment of bone marrow stromal cells with mild exercise and thyroid hormone on brain damage and apoptosis in a mouse focal cerebral ischemia model

This study examined whether post-stroke bone marrow stromal cells (BMSCs) therapy combined with exercise (EX) and/or thyroid hormone (TH) could reduce brain damage in an experimental ischemic stroke in mice. Focal cerebral ischemia was induced under Laser Doppler Flowmetry (LDF) guide by 45 min of middle cerebral artery occlusion (MCAO), followed by 7 days of reperfusion in albino mice. BMSCs were injected into the right cerebral ventricle 24 h after MCAO, followed by daily injection of T3 (20 μg/100 g weight S.C) and 6 days of running on a treadmill. Infarct size, neurobehavioral test, TUNEL and BrdU positive cells were evaluated at 7 days after MCAO. Treatment with BMSCs and mild EX alone significantly reduced the infarct volume by 23% and 44%, respectively (both, p < 0.001). The BMSCs + TH, BMSCs + EX, and BMSCs + EX + TH combination therapies significantly reduced the infarct volume by 26%, 51%, and 70%, respectively (all, p < 0.001). A significant improvement in the neurobehavioral functioning was observed in the EX, BMSCs + EX, and BMSCs + EX+ TH groups (p < 0.001). The number of TUNEL-positive cells (a marker of apoptosis) was significantly reduced in the EX, BMSCs, BMSCs + EX, BMSCs + TH, and BMSCs + EX + TH groups (all, p < 0.001). Moreover, the combination therapy considerably increased BrdU-labeled cells in the subventricular zone (SVZ) (p < 0.01). Our findings indicated that the combined treatment of BMSCs with mild EX and TH more efficiently reduces the cerebral infarct size after stroke. More likely, these effects mediate via enchaining generation of new neuronal cells and the attenuation of apoptosis in ischemia stroke in young mice.

l-Lactate mediates neuroprotection against ischaemia by increasing TREK1 channel expression in rat hippocampal astrocytes in vitro

Brain ischaemia is a highly debilitating condition where shortage of oxygen and glucose leads to profuse cell death. Lactate is a neuroprotective metabolite whose concentrations increase up to 15-30 mmol/L during ischaemia and TREK1 is a neuroprotective potassium channel which is upregulated during ischaemia. The aim of this study was to investigate the effect of l-lactate on TREK1 expression and to evaluate the role of l-lactate-TREK1 interaction in conferring neuroprotection in ischaemia-prone hippocampus. We show that 15-30 mmol/L l-lactate increases functional TREK1 protein expression by 1.5-3-fold in hippocampal astrocytes using immunostaining and electrophysiology. Studies with transcription blocker actinomycin-D and quantitative PCR indicate that the increase in TREK1 expression is due to enhanced TREK1 mRNA transcription. We further report that l-lactate-mediated increase in TREK1 expression is via protein kinase A (PKA)-dependent pathway. This is the first report of an ischaemic metabolite affecting functional expression of an ion channel. Our studies in an in vitro model of ischaemia using oxygen glucose deprivation show that 30 mmol/L l-lactate fails to reduce cell death in rat hippocampal slices treated with TREK1 blockers, PKA inhibitors and gliotoxin. The above effects were specific to l-lactate as pyruvate failed to increase TREK1 expression and reduce cell death. l-Lactate-induced TREK1 upregulation is a novel finding of physiological significance as TREK1 channels contribute to neuroprotection by enhancing potassium buffering and glutamate clearance capacity of astrocytes. We propose that l-lactate promotes neuronal survival in hippocampus by increasing TREK1 channel expression via PKA pathway in astrocytes during ischaemia. Insufficient blood supply to the brain leads to cerebral ischaemia and increase in extracellular lactate concentrations. We incubated hippocampal astrocytes in lactate and observed increase in TREK1 channel expression via protein kinase A (PKA). Inhibition of TREK1, PKA and metabolic impairment of astrocytes prevented lactate from reducing cell death in ischaemic hippocampus. This pathway serves as an alternate mechanism of neuroprotection. Cover image for this issue: doi: 10.1111/jnc.13326.

Exogenous lactate infusion improved neurocognitive function of patients with mild traumatic brain injury

BACKGROUND

Many studies showed a better recovery of cognitive function after administration of exogenous lactate during moderate-severe traumatic brain injury. However, the study evaluating lactate effect on mild traumatic brain injury is still limited.

AIMS

To evaluate the effect of exogenous lactate on cognitive function in mild traumatic brain injury patients.

SETTINGS AND DESIGN

Prospective, single blind, randomized controlled study on 60 mild traumatic brain injury patients who were undergoing neurosurgery.

MATERIALS AND METHODS

Subjects were randomly assigned into hyperosmolar sodium lactate (HSL) group or hyperosmolar sodium chloride (HSS) group. Patients in each group received either intravenous infusion of HSL or NaCl 3% at 1.5 ml/KgBW within 15 min before neurosurgery. During the surgery, patients in both groups received maintenance infusion of NaCl 0.9% at 1.5 ml/KgBW/hour.

STATISTICAL ANALYSIS

Cognitive function, as assessed by Mini-Mental State Examination (MMSE) score at 24 h, 30 and 90 days post-surgery, was analyzed by Anova repeated measures test.

RESULTS

The MMSE score improvement was significantly better in HSL group than HSS group (P < 0.001). In HSL group the MMSE score improved from 16.00 (13.75-18.00) at baseline to 21.00 (18.75-22.00); 25.00 (23.75-26.00); 28.00 (27.00-29.00) at 24 h, 30, 90 days post-surgery, respectively. In contrast, in HSS group the MMSE score almost unchanged at 24 h and only slightly increased at 30 and 90 days post-surgery.

CONCLUSIONS

Hyperosmolar sodium lactate infusion during mild traumatic brain injury improved cognitive function better than sodium chloride 3%.

Identification of proteins in hyperglycemia and stroke animal models

BACKGROUND

Stroke is a major cause of disability and death in adults. Diabetes mellitus is a metabolic disorder that strongly increases the risk of severe vascular diseases. This study compared changes in proteins of the cerebral cortex during ischemic brain injury between nondiabetic and diabetic animals.

METHODS

Adult male rats were injected with streptozotocin (40 mg/kg) via the intraperitoneal route to induce diabetes and underwent surgical middle cerebral artery occlusion (MCAO) 4 wk after streptozotocin treatment. Cerebral cortex tissues were collected 24 h after MCAO and cerebral cortex proteins were analyzed by two-dimensional gel electrophoresis and mass spectrometry.

RESULTS

Several proteins were identified as differentially expressed between nondiabetic and diabetic animals. Among the identified proteins, we focused on the following metabolism-related enzymes: isocitrate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, adenosylhomocysteinase, pyruvate kinase, and glucose-6-phosphate isomerase (neuroleukin). Expression of these proteins was decreased in animals that underwent MCAO. Moreover, protein expression was reduced to a greater extent in diabetic animals than in nondiabetic animals. Reverse transcription-polymerase chain reaction analysis confirmed that the diabetic condition exacerbates the decrease in expression of metabolism-related proteins after MCAO.

CONCLUSIONS

These results suggest that the diabetic condition may exacerbate brain damage during focal cerebral ischemia through the downregulation of metabolism-related proteins.

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.

Pyruvate minimizes rtPA toxicity from in vitro oxygen-glucose deprivation and reoxygenation

Clinical application of recombinant tissue plasminogen activator (rtPA) for stroke is limited by hemorrhagic transformation, which narrows rtPA's therapeutic window. In addition, mounting evidence indicates that rtPA is potentially neurotoxic if it traverses a compromised blood brain barrier. Here, we demonstrated that pyruvate protects cultured HT22 neuronal and primary microvascular endothelial cells co-cultured with primary astrocytes from oxygen glucose deprivation (OGD)/reoxygenation stress and rtPA cytotoxicity. After 3 or 6h OGD, cells were reoxygenated with 11mmol/L glucose±pyruvate (8mmol/L) and/or rtPA (10µg/ml). Measured variables included cellular viability (calcein AM and annexin-V/propidium iodide), reactive oxygen species (ROS; mitosox red and 2',7'-dichlorofluorescein diacetate), NADPH, NADP(+) and ATP contents (spectrophotometry), matrix metalloproteinase-2 (MMP2) activities (gelatin zymography), and cellular contents of MMP2, tissue inhibitor of metalloproteinase-2 (TIMP2), and phosphor-activation of anti-apoptotic p70s6 kinase, Akt and Erk (immunoblot). Pyruvate prevented the loss of HT22 cells after 3h OGD±rtPA. After 6h OGD, rtPA sharply lowered cell viability; pyruvate dampened this effect. Three hours OGD and 4h reoxygenation with rtPA increased ROS formation by about 50%. Pyruvate prevented this ROS formation and doubled cellular NADPH/NADP(+) ratio and ATP content. In endothelial cell monolayers, 3h OGD and 24h reoxygenation increased FITC-dextran leakage, indicating disruption of intercellular junctions. Although rtPA exacerbated this effect, pyruvate prevented it while sharply lowering MMP2/TIMP2 ratio and increasing phosphorylation of p70s6 kinase, Akt and Erk. Pyruvate protects neuronal cells and microvascular endothelium from hypoxia-reoxygenation and cytotoxic action of rtPA while reducing ROS and activating anti-apoptotic signaling. These results support the proposed use of pyruvate as an adjuvant to dampen the side effects of rtPA treatment, thereby extending rtPA's therapeutic window.

Energy depletion in seizures: anaplerosis as a strategy for future therapies

Seizure activity can lead to energy failure and neuronal injury, resulting in neurological and cognitive sequelae. Moreover, mutations affecting genes encoding for proteins that maintain energy homeostasis within the cell often result in an epileptic phenotype, implying that energy failure can contribute to epileptogenesis. Indeed, there is evidence to indicate that the efficacy of the ketogenic diet, a treatment for refractory epilepsy, can be partly explained by its effect on increasing energetic substrates. The ATP level, reflecting the energy level of a cell, is maintained by the potential gradient across the mitochondrial membrane. This potential gradient is maintained by NADH/H(+) equivalents, produced by reactions within the tricarboxylic acid cycle (TCA-cycle). Anaplerosis, the replenishment of TCA-cycle substrates, therefore represents an appealing strategy to address energy failure such as occurs in seizures. There is accumulating evidence that pyruvate, a classical anaplerotic substrate, has seizure suppressive effects and protects against seizure induced cell death. This review summarizes the evidence for the contribution of TCA cycle deficits in generating seizures. We highlight the role for TCA substrate supplementation in protecting against seizures and seizure induced cell death, and propose that these are important targets for future translational research addressing energy depletion in seizures. This article is part of the Special Issue entitled 'New Targets and Approaches to the Treatment of Epilepsy'.

Excitatory action of GABA on immature neurons is not due to absence of ketone bodies metabolites or other energy substrates

Brain slices incubated with glucose have provided most of our knowledge on cellular, synaptic, and network driven mechanisms. It has been recently suggested that γ-aminobutyric acid (GABA) excites neonatal neurons in conventional glucose-perfused slices but not when ketone bodies metabolites, pyruvate, and/or lactate are added, suggesting that the excitatory actions of GABA are due to energy deprivation when glucose is the sole energy source. In this article, we review the vast number of studies that show that slices are not energy deprived in glucose-containing medium, and that addition of other energy substrates at physiologic concentrations does not alter the excitatory actions of GABA on neonatal neurons. In contrast, lactate, like other weak acids, can produce an intracellular acidification that will cause a reduction of intracellular chloride and a shift of GABA actions. The effects of high concentrations of lactate, and particularly of pyruvate (4-5 mm), as used are relevant primarily to pathologic conditions; these concentrations not being found in the brain in normal "control" conditions. Slices in glucose-containing medium may not be ideal, but additional energy substrates neither correspond to physiologic conditions nor alter GABA actions. In keeping with extensive observations in a wide range of animal species and brain structures, GABA depolarizes immature neurons and the reduction of the intracellular concentration of chloride ([Cl(-)](i)) is a basic property of brain maturation that has been preserved throughout evolution. In addition, this developmental sequence has important clinical implications, notably concerning the higher incidence of seizures early in life and their long-lasting deleterious sequels. Immature neurons have difficulties exporting chloride that accumulates during seizures, leading to permanent increase of [Cl(-)](i) that converts the inhibitory actions of GABA to excitatory and hampers the efficacy of GABA-acting antiepileptic drugs.

Metabolic and histologic effects of sodium pyruvate treatment in the rat after cortical contusion injury

This study determined the effects of intraperitoneal sodium pyruvate (SP) treatment on the levels of circulating fuels and on cerebral microdialysis levels of glucose (MD(glc)), lactate (MD(lac)), and pyruvate (MD(pyr)), and the effects of SP treatment on neuropathology after left cortical contusion injury (CCI) in rats. SP injection (1000 mg/kg) 5 min after sham injury (Sham-SP) or CCI (CCI-SP) significantly increased arterial pyruvate (p < 0.005) and lactate (p < 0.001) compared to that of saline-treated rats with CCI (CCI-Sal). Serum glucose also increased significantly in CCI-SP compared to that in CCI-Sal rats (p < 0.05), but not in Sham-SP rats. MD(pyr) was not altered after CCI-Sal, whereas MD(lac) levels within the cerebral cortex significantly increased bilaterally (p < 0.05) and those for MD(glc) decreased bilaterally (p < 0.05). MD(pyr) levels increased significantly in both Sham-SP and CCI-SP rats (p < 0.05 vs. CCI-Sal) and were higher in left/injured cortex of the CCI-SP group (p < 0.05 vs. sham-SP). In CCI-SP rats the contralateral MD(lac) decreased below CCI-Sal levels (p < 0.05) and the ipsilateral MD(glc) levels exceeded those of CCI-Sal rats (p < 0.05). Rats with a single low (500 mg/kg) or high dose (1000 mg/kg) SP treatment had fewer damaged cortical cells 6 h post-CCI than did saline-treated rats (p < 0.05), but three hourly injections of SP (1000 mg/kg) were needed to significantly reduce contusion volume 2 weeks after CCI. Thus, a single intraperitoneal SP treatment increases circulating levels of three potential brain fuels, attenuates a CCI-induced reduction in extracellular glucose while increasing extracellular levels of pyruvate, but not lactate, and can attenuate cortical cell damage occurring within 6 h of injury. Enduring (2 week) neuronal protection was achieved only with multiple SP treatments within the first 2 h post-CCI, perhaps reflecting the need for additional fuel throughout the acute period of increased metabolic demands induced by CCI.

Beneficial effects of sodium or ethyl pyruvate after traumatic brain injury in the rat

Sodium pyruvate (SP) treatment initiated within 5 min post-injury is neuroprotective in a rat model of unilateral cortical contusion injury (CCI). The current studies examined: (1) effects of delayed SP treatments (1000 mg/kg, i.p., at 1, 12 and 24h), (2) effects of single (1h) or multiple (1, 12 and 24h) ethyl pyruvate treatments (EP; at 20 or 40 mg/kg, i.p.), and (3) mechanisms of action for pyruvate effects after CCI. In Experiment 1, both SP and EP treatment(s) significantly reduced the number of dead/dying cells in the ipsilateral hippocampus (dentate hilus+CA3(c) and/or CA3(a-b) regions) at 72 h post-CCI. Pyruvate treatment(s) attenuated CCI-induced reductions of cerebral cytochrome oxidase activity at 7 2h, significantly improving activity in peri-contusional cortex after multiple SP or EP treatments. Optical density measures of ipsilateral CD11b immuno-staining were significantly increased 72 h post-CCI, but these measures of microglia activation were not different from sham injury values in SP and EP groups with three post-CCI treatments. In Experiment 2, three treatments (1, 12 and 24h) of SP (1000 mg/kg) or EP (40 mg/kg) significantly improved recovery of beam-walking and neurological scores in the first 3 weeks after CCI, and EP treatments significantly improved spatial working memory 1 week post-CCI. Ipsilateral CA3(b) neuronal loss, but not cortical tissue loss, was significantly reduced 1 month post-CCI with pyruvate treatments begun 1h post-CCI. Thus, delayed pyruvate treatments after CCI are neuroprotective and improve neurobehavioral recovery; these effects may be mediated by improved metabolism and reduced inflammation.

Cerebral ischemia promotes rich pseudopalisading necrosis in the rat c6 glioblastoma model

The effect of hypoxia on glioma growth including pathological changes was investigated in an experimental model of brain ischemia in the rat C6 glioma model. C6 glioma cells were inoculated into the subcortex of adult Wistar rats. Focal cerebral ischemia near the implanted glioma area was induced by permanent middle cerebral artery occlusion (PMCAO). Ten days later, the rats were sacrificed to compare tumor volume of C6 glioma without PMCAO (control group) versus C6 glioma with PMCAO (hypoxia group). The histological features were also observed. The mean tumor volume in the hypoxia group was significantly larger than that in the control group. The most prominent histological finding in the hypoxia group was abundant formation of pseudopalisading around the necrotic areas. Immunohistological examinations showed intensive staining for vascular endothelial growth factor and hypoxia-inducible factor in these pseudopalisading cells. These findings suggest that cerebral ischemia positively modulates glioma mass growth by the formation of pseudopalisading necrosis, a characteristic histological finding of glioblastoma.

Pyruvate protects against experimental stroke via an anti-inflammatory mechanism

Pyruvate, a key intermediate in glucose metabolism, was explored as a potential treatment in models of experimental stroke and inflammation. Pyruvate was administered to rodents after the onset of middle cerebral artery occlusion (MCAO). Since the extent of inflammation is often proportional to the size of the infarct, we also studied a group of animals given lipopolysaccharide (LPS) to cause brain inflammation without cell death. Following MCAO, pyruvate did not affect physiological parameters but significantly reduced infarct volume, improved behavioral tests and reduced numbers of neutrophils, microglial and NFkappaB activation. Animals given LPS showed increased microglial and NFkappaB activation which was almost completely abolished by pyruvate. Lactate, a major metabolite of pyruvate, was increased after pyruvate administration. However, administration of lactate itself did not have any anti-inflammatory effects. Pyruvate protects against ischemia possibly by blocking inflammation, but lactate itself does not appear to explain pyruvate's anti-inflammatory properties.

Peripheral administration of carbenoxolone reduces ischemic reperfusion injury in transient model of cerebral ischemia

Carbenoxolone (CBX) has a neuroprotective effect in experimental models of brain ischemia and trauma. However, systemic effect of CBX on ischemic reperfusion injuries has not been investigated in a temporary model of focal cerebral ischemia. Male Wistar rats (n = 32) were divided into control and CBX-treated (100, 200, or 400 mg/kg, intraperitoneally) groups. Transient focal cerebral ischemia was induced by 60-minute middle cerebral artery occlusion by filament method, followed by 23-hour reperfusion. At the end of 24-hour ischemia, neurologic deficit score was tested and infarct volumes were determined using triphenyltetrazolium chloride staining. Administration of CBX (100, 200, or 400 mg/kg) at the beginning of ischemia significantly reduced cortical infarct volumes by 48%, 58%, and 63%, and striatal infarct volumes by 34%, 63%, and 63%, respectively. Nevertheless, CBX has no effect on neurologic dysfunction. Our findings indicated that peripheral administration of CBX has a neuroprotective effect on postischemic damage in a temporary model of focal cerebral ischemia in rat.

Transient benefits but lack of protection by sodium pyruvate after 2-hour middle cerebral artery occlusion in the rat

Sodium pyruvate has shown protective effects in various experimental models of brain ischemia. The main holdup of this drug is that most of the benefits are reported with a very narrow time window for intervention. Here we investigated whether pyruvate could protect the brain against ischemic damage using a model of 2-hour middle cerebral artery occlusion in the rat. The time course of blood pyruvate after i.p. administration of sodium pyruvate (400 mg/kg) was studied. Animals were treated with the drug or with vehicle 45 min after reperfusion following 2-hour ischemia. Tissue ATP content was determined 5 and 10 h after ischemia onset, and infarct volume was measured at days 1 and 2. The neurological score was evaluated before and after treatment in the different experimental groups. Pyruvate prevented the drop of cortical ATP induced by ischemia in the ipsilateral cortex and ameliorated the neurological deficit at 5 h after the onset of ischemia, supporting some beneficial effects of the treatment. However, these effects were not sustained at 10 h. Furthermore, pyruvate failed to significantly reduce infarct volume and the neurological deficit at 24 and 48 h, in spite of some trend to smaller infarction after pyruvate administration. Therefore, under the present experimental conditions, systemic administration of sodium pyruvate at 3 h after the beginning of ischemia exerted only a transient benefit but not a persistent protection against brain damage.

Neuroprotective effects of ethyl pyruvate on brain energy metabolism after ischemia-reperfusion injury: a 31P-nuclear magnetic resonance study

The neuroprotective effects of ethyl pyruvate (EP), a stable derivative of pyruvate, on energy metabolism of rat brain exposed to ischemia-reperfusion stress were investigated by (31)P-nuclear magnetic resonance ((31)P-NMR) spectroscopy. Recovery level of phosphocreatine after ischemia was significantly greater when superfused with artificial cerebrospinal fluid (ACSF) with 2 mM EP than when superfused with ACSF without EP. EP was neuroprotective against ischemia only when administered before the ischemic exposure. Intracellular pH during ischemia was less acidic when superfused ahead of time with EP. EP did not show neuroprotective effects in neuron-rich slices pretreated with 100 microM fluorocitrate, a selective glial poison. It was suggested that both the administration of EP before ischemic exposure and the presence of astrocytes are required for EP to exert neuroprotective effects. We suggest the potential involvement of multiple mechanisms of action, such as less acidic intracellular pH, glial production of lactate, and radical scavenging ability.

Bioenergetics of cerebral ischemia: a cellular perspective

In cerebral ischemia survival of neurons, astrocytes, oligodendrocytes and endothelial cells is threatened during energy deprivation and/or following re-supply of oxygen and glucose. After a brief summary of characteristics of different cells types, emphasizing the dependence of all on oxidative metabolism, the bioenergetics of focal and global ischemia is discussed, distinguishing between events during energy deprivation and subsequent recovery attempt after re-circulation. Gray and white matter ischemia are described separately, and distinctions are made between mature and immature brains. Next comes a description of bioenergetics in individual cell types in culture during oxygen/glucose deprivation or exposure to metabolic inhibitors and following re-establishment of normal aerated conditions. Due to their expression of NMDA and non-NMDA receptors neurons and oligodendrocytes are exquisitely sensitive to excitotoxicity by glutamate, which reaches high extracellular concentrations in ischemic brain for several reasons, including failing astrocytic uptake. Excitotoxicity kills brain cells by energetic exhaustion (due to Na(+) extrusion after channel-mediated entry) combined with mitochondrial Ca(2+)-mediated injury and formation of reactive oxygen species. Many (but not all) astrocytes survive energy deprivation for extended periods, but after return to aerated conditions they are vulnerable to mitochondrial damage by cytoplasmic/mitochondrial Ca(2+) overload and to NAD(+) deficiency. Ca(2+) overload is established by reversal of Na(+)/Ca(2+) exchangers following Na(+) accumulation during Na(+)-K(+)-Cl(-) cotransporter stimulation or pH regulation, compensating for excessive acid production. NAD(+) deficiency inhibits glycolysis and eventually oxidative metabolism, secondary to poly(ADP-ribose)polymerase (PARP) activity following DNA damage. Hyperglycemia can be beneficial for neurons but increases astrocytic death due to enhanced acidosis.

Detrimental effects of tropisetron on permanent ischemic stroke in the rat

Background

Recent in vitro evidence indicates that blockade of 5-hydroxytryptamine (5-HT) receptor 3 (5-HT₃) is able to confer protection in different models of neuronal injury. The purpose of the present study was to investigate the effect of tropisetron, a 5-HT₃ receptor antagonist, on infarct size and neurological score in a model of ischemic stroke induced by permanent middle cerebral artery occlusion (pMCAO) in the rat.

Methods

Two different doses of tropisetron (5 and 10 mg/kg) or vehicle were administered intraperitoneally 30 min before pMCAO. Neurological deficit scores, mortality rate and infarct volume were determined 24 h after permanent focal cerebral ischemia.

Results

Tropisetron failed to reduce cerebral infarction. Animals receiving tropisetron showed a significant increase (p < 0.05) in neurological deficits and mortality rate.

Conclusion

Data from this study indicate that blockade of 5-HT₃ receptors with tropisetron worsens ischemic brain injury induced by pMCAO. These findings could have important clinical implications. Patients taking tropisetron, and possibly other 5-HT₃ antagonists, could potentially have a worse outcome following a brain infarct.

Ethyl pyruvate: a novel anti-inflammatory agent

Ethyl pyruvate (EP) is a simple derivative of the endogenous metabolite, pyruvic acid. Treatment with EP has been shown to improve survival and/or ameliorate organ dysfunction in a wide variety of preclinical models of critical illnesses, such as severe sepsis, acute respiratory distress syndrome, acute pancreatitis and stroke. EP was originally regarded as simply a way to administer pyruvate anion, whilst avoiding some of the problems associated with the instability of pyruvate in aqueous solutions. Increasingly, however, it is becoming apparent that certain pyruvate esters, including EP, have pharmacological effects, such as suppression of inflammation, that are quite distinct from those exerted by pyruvate anion. EP has been tested in human volunteers and shown to be safe at clinically relevant doses. It remains to be determined whether EP can be used successfully to treat human diseases.

Post-ischaemic treatment with the cyclooxygenase-2 inhibitor nimesulide reduces blood-brain barrier disruption and leukocyte infiltration following transient focal cerebral ischaemia in rats

Several studies suggest that cyclooxygenase (COX)-2 plays a pivotal role in the progression of ischaemic brain damage. In the present study, we investigated the effects of selective inhibition of COX-2 with nimesulide (12 mg/kg) and selective inhibition of COX-1 with valeryl salicylate (VAS, 12-120 mg/kg) on prostaglandin E(2) (PGE(2)) levels, myeloperoxidase (MPO) activity, Evans blue (EB) extravasation and infarct volume in a standardized model of transient focal cerebral ischaemia in the rat. Post-ischaemic treatment with nimesulide markedly reduced the increase in PGE(2) levels in the ischaemic cerebral cortex 24 h after stroke and diminished infarct size by 48% with respect to vehicle-treated animals after 3 days of reperfusion. Furthermore, nimesulide significantly attenuated the blood-brain barrier (BBB) damage and leukocyte infiltration (as measured by EB leakage and MPO activity, respectively) seen at 48 h after the initial ischaemic episode. These studies provide the first experimental evidence that COX-2 inhibition with nimesulide is able to limit BBB disruption and leukocyte infiltration following transient focal cerebral ischaemia. Neuroprotection afforded by nimesulide is observed even when the treatment is delayed until 6 h after the onset of ischaemia, confirming a wide therapeutic window of COX-2 inhibitors in experimental stroke. On the contrary, selective inhibition of COX-1 with VAS had no significant effect on the evaluated parameters. These data suggest that COX-2 activity, but not COX-1 activity, contributes to the progression of focal ischaemic brain injury, and that the beneficial effects observed with non-selective COX inhibitors are probably associated to COX-2 rather than to COX-1 inhibition.

Cerebral metabolism of glucose and pyruvate in soman poisoning

Organophosphates, such as the nerve gas soman, cause inhibition of acetylcholine esterase, accumulation of acetylcholine in synaptic clefts, and excessive activation of cholinergic receptors, causing central nervous symptoms such as tremor and seizures. Soman-poisoned animals have low brain levels of ATP, indicating that energy demand is greater than energy supply. We investigated whether soman poisoning is accompanied by an increased brain metabolism of glucose, as can be inferred from the accumulation of radiolabeled 2-deoxyglucose found in previous studies, or whether soman poisoning entails impairment of cerebral energy metabolism. We performed 13C nuclear magnetic resonance spectroscopy on brain extracts from soman-poisoned mice (160 microg/kg; 1 LD50) that had been dosed with 13C-labeled glucose or pyruvate intravenously. Formation of 13C-labeled glutamate, GABA and glutamine from [1-(13)C]glucose was reduced by approximately 30% in awake, soman-intoxicated animals, but formation of these amino acids from [3-(13)C]pyruvate was not different in soman-intoxicated animals and controls. These results suggest that soman intoxication entails inhibition of glycolysis, but not of tricarboxylic acid cycle activity in the brain. However, when brain metabolism was depressed by a sedative dose of diazepam (5 mg/kg) soman intoxication caused increased metabolism of 13C-labeled glucose. The latter finding shows that the soman-poisoned brain has a high energy requirement even during anticonvulsant therapy. We conclude that metabolic inhibition, as seen in awake, soman-intoxicated animals, may lower seizure threshold and contribute to soman-related neurodegeneration and lethality.

Systemic pyruvate administration markedly reduces infarcts and motor deficits in rat models of transient and permanent focal cerebral ischemia

Pyruvate markedly reduces neuronal death following transient global ischemia. In the present study, we investigated the possible neuroprotective effect of pyruvate in focal ischemia. Pyruvate (62.5-250 mg/kg) treatment, regardless of whether given intraperitoneally (ip) or intravenously (iv), decreased infarct volume by more than 50% in both transient (1 h) and permanent occlusion models. The infarct-reducing effects of pyruvate were maintained 14 days (d) after MCAO. Interestingly, higher doses failed to reduce the infarct size. Pyruvate administration also reduced motor deficits. Magnetic resonance (MR) spectroscopy revealed that protective doses of pyruvate, but not the non-protective doses, were associated with a reduction in the level of lactate compared with saline controls. Diffusion-weighted MR images further confirmed infarct reduction in pyruvate-treated rats. Pyruvate is an endogenous metabolite of glycolysis, and hence is unlikely to have serious side effects. Considering its substantial neuroprotective capacity in focal cerebral ischemia, a clinical trial is warranted.

Brain metabolism of exogenous pyruvate

Pyruvate given in large doses may be neuroprotective in stroke, but it is not known to what degree the brain metabolizes pyruvate. Intravenous injection of [3-13C]pyruvate led to dose-dependent labelling of cerebral metabolites so that at 5 min after injection of 18 mmoles [3-13C]pyruvate/kg (2 g sodium pyruvate/kg), approximately 20% of brain glutamate and GABA were labelled, as could be detected by 13C nuclear magnetic resonance spectrometry ex vivo. Pyruvate, 9 mmoles/kg, was equivalent to glucose, 9 mmoles/kg, as a substrate for cerebral tricarboxylic acid (TCA) cycle activity. Inhibition of the glial TCA cycle with fluoroacetate did not affect formation of [4-13C]glutamate or [2-13C]GABA from [3-13C]pyruvate, but reduced formation of [4-13C]glutamine by 50%, indicating predominantly neuronal metabolism of exogenous pyruvate. Extensive formation of [3-13C]lactate from [2-13C]pyruvate demonstrated reversible carboxylation of pyruvate to malate and equilibration with fumarate, presumably in neurones, but anaplerotic formation of TCA cycle intermediates from exogenous pyruvate could not be detected. Too rapid injection of large amounts of pyruvate led to seizure activity, respiratory arrest and death. We conclude that exogenous pyruvate is an excellent energy substrate for neurones in vivo, but that care must be taken to avoid the seizure-inducing effect of pyruvate given in large doses.

Anti-inflammatory mechanism is involved in ethyl pyruvate-mediated efficacious neuroprotection in the postischemic brain

Ethyl pyruvate (EP) is a pyruvate derivative, and has recently been reported to prevent lethality in mice with established lethal sepsis and systemic inflammation. In a previous study, we reported that EP has a neuroprotective effect in a rat cerebral ischemia model of middle cerebral artery occlusion (MCAO), in which it was found to be effective when injected as late as 12 h after MCAO/reperfusion. In the present study, we show that therapeutic window of pyruvate in this MCAO animal model is limited to 1 h (30 min before and 30 min after MCAO). Moreover, both pyruvate and EP have a neuroprotective effect during oxygen-glucose deprivation (OGD) or H2O2 challenge in primary cortical culture. In contrast, EP suppressed the LPS-induced activation of primary microglia in culture, but pyruvate did not. The suppression of microglia activation was evidenced by a reduction in nitric oxide release and by a proinflammatory factor induction in primary microglia culture, which were accompanied by the repression of nuclear factor-kappaB activation. These results suggest that EP has a strong protective effect and a wide therapeutic window, and that this protective effect of EP is related to its anti-inflammatory action.

Astrocytic contributions to bioenergetics of cerebral ischemia

Astrocytes are multifunctional cells that interact with neurons and other astrocytes in signaling and metabolic functions, and their resistance to pathophysiological conditions can help restrict loss of tissue after an ischemic event provided adequate nutrients are supplied to support their requirements. Astrocytes have substantial oxidative capacity and mechanisms to upregulate glycolytic capability when respiration is impaired. An astrocytic enzyme that synthesizes a powerful activator of glycolysis is not present in neurons, endowing astrocytes with the ability to sustain ATP production under restrictive conditions. The monocarboxylic acid transporter (MCT) isoforms predominating in astrocytes are optimized to facilitate very large increases in lactate flux as lactate concentration increases within (1-3 mM) and above (>3 mM) the normal range. In sharp contrast, the major neuronal MCT serves as a barrier to increased transmembrane transport as lactate rises above 1 mM, restricting both entry and efflux. Lactate can serve as fuel during recovery from ischemia but direct evidence that lactate is oxidized by neurons (vs. astrocytes) to maintain synaptic function is lacking. Astrocytes have critical roles in regulation of ionic homeostasis and control of extracellular glutamate levels, and spreading depression associated with ischemia places high demands on energy supplies in astrocytes and contributes to metabolic exhaustion and demise. Disruption of Ca2+ homeostasis, generation of oxygen free radicals and nitric oxide, and mitochondrial depolarization contribute to astrocyte death during and after a metabolic insult. Novel pharmaceutical agents targeted to astrocytes and hyperoxic therapy that restores penumbral oxygen level during energy failure might improve postischemic outcome.

Effects of the cyclooxygenase-2 inhibitor nimesulide on cerebral infarction and neurological deficits induced by permanent middle cerebral artery occlusion in the rat

Background

Previous studies suggest that the cyclooxygenase-2 (COX-2) inhibitor nimesulide has a remarkable protective effect against different types of brain injury including ischemia. Since there are no reports on the effects of nimesulide on permanent ischemic stroke and because most cases of human stroke are caused by permanent occlusion of cerebral arteries, the present study was conducted to assess the neuroprotective efficacy of nimesulide on the cerebral infarction and neurological deficits induced by permanent middle cerebral artery occlusion (pMCAO) in the rat.

Methods

Ischemia was induced by permanent occlusion of the middle cerebral artery in rats, via surgical insertion of a nylon filament into the internal carotid artery. Infarct volumes (cortical, subcortical and total) and functional recovery, assessed by neurological score evaluation and rotarod performance test, were performed 24 h after pMCAO. In initial experiments, different doses of nimesulide (3, 6 and 12 mg/kg; i.p) or vehicle were administered 30 min before pMCAO and again at 6, 12 and 18 h after stroke. In later experiments we investigated the therapeutic time window of protection of nimesulide by delaying its first administration 0.5–4 h after the ischemic insult.

Results

Repeated treatments with nimesulide dose-dependently reduced cortical, subcortical and total infarct volumes as well as the neurological deficits and motor impairment resulting from permanent ischemic stroke, but only the administration of the highest dose (12 mg/kg) was able to significantly (P < 0.01) diminish infarct volume. The lower doses failed to significantly reduce infarction but showed a beneficial effect on neurological function. Nimesulide (12 mg/kg) not only reduced infarct volume but also enhanced functional recovery when the first treatment was given up to 2 h after stroke.

Conclusions

These data show that nimesulide protects against permanent focal cerebral ischemia, even with a 2 h post-treatment delay. These findings have important implications for the therapeutic potential of using COX-2 inhibitors in the treatment of stroke.

Wide therapeutic time window for nimesulide neuroprotection in a model of transient focal cerebral ischemia in the rat

Results from several studies indicate that cyclooxygenase-2 (COX-2) is involved in ischemic brain injury. The purpose of this study was to evaluate the neuroprotective effects of the selective COX-2 inhibitor nimesulide on cerebral infarction and neurological deficits in a standardized model of transient focal cerebral ischemia in rats. Three doses of nimesulide (3, 6 and 12 mg/kg; i.p.) or vehicle were administered immediately after stroke and additional doses were given at 6, 12, 24, 36 and 48 h after ischemia. In other set of experiments, the effect of nimesulide was studied in a situation in which its first administration was delayed for 3-24 h after ischemia. Total, cortical and subcortical infarct volumes and functional outcome (assessed by neurological deficit score and rotarod performance) were determined 3 days after ischemia. The effect of nimesulide on prostaglandin E(2) (PGE(2)) levels in the injured brain was also investigated. Nimesulide dose-dependently reduced infarct volume and improved functional recovery when compared to vehicle. Of interest is the finding that neuroprotection conferred by nimesulide (reduction of infarct size and neurological deficits and improvement of rotarod performance) was also observed when treatment was delayed until 24 h after ischemia. Further, administration of nimesulide in a delayed treatment paradigm completely abolished PGE(2) accumulation in the postischemic brain, suggesting that COX-2 inhibition is a promising therapeutic strategy for cerebral ischemia to target the late-occurring inflammatory events which amplify initial damage.