Effects of L-Type Voltage-Gated Calcium Channel (LTCC) Inhibition on Hippocampal Neuronal Death after Pilocarpine-Induced Seizure.

Epilepsy, marked by abnormal and excessive brain neuronal activity, is linked to the activation of L-type voltage-gated calcium channels (LTCCs) in neuronal membranes. LTCCs facilitate the entry of calcium (Ca2+) and other metal ions, such as zinc (Zn2+) and magnesium (Mg2+), into the cytosol. This Ca2+ influx at the presynaptic terminal triggers the release of Zn2+ and glutamate to the postsynaptic terminal. Zn2+ is then transported to the postsynaptic neuron via LTCCs. The resulting Zn2+ accumulation in neurons significantly increases the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunits, contributing to reactive oxygen species (ROS) generation and neuronal death. Amlodipine (AML), typically used for hypertension and coronary artery disease, works by inhibiting LTCCs. We explored whether AML could mitigate Zn2+ translocation and accumulation in neurons, potentially offering protection against seizure-induced hippocampal neuronal death. We tested this by establishing a rat epilepsy model with pilocarpine and administering AML (10 mg/kg, orally, daily for 7 days) post-epilepsy onset. We assessed cognitive function through behavioral tests and conducted histological analyses for Zn2+ accumulation, oxidative stress, and neuronal death. Our findings show that AML's LTCC inhibition decreased excessive Zn2+ accumulation, reactive oxygen species (ROS) production, and hippocampal neuronal death following seizures. These results suggest amlodipine's potential as a therapeutic agent in seizure management and mitigating seizures' detrimental effects.

A phosphodiesterase 4 (PDE4) inhibitor, amlexanox, reduces neuroinflammation and neuronal death after pilocarpine-induced seizure.

Epilepsy, a complex neurological disorder, is characterized by recurrent seizures caused by aberrant electrical activity in the brain. Central to this study is the role of lysosomal dysfunction in epilepsy, which can lead to the accumulation of toxic substrates and impaired autophagy in neurons. Our focus is on phosphodiesterase-4 (PDE4), an enzyme that plays a crucial role in regulating intracellular cyclic adenosine monophosphate (cAMP) levels by converting it into adenosine monophosphate (AMP). In pathological states, including epilepsy, increased PDE4 activity contributes to a decrease in cAMP levels, which may exacerbate neuroinflammatory responses. We hypothesized that amlexanox, an anti-inflammatory drug and non-selective PDE4 inhibitor, could offer neuroprotection by addressing lysosomal dysfunction and mitigating neuroinflammation, ultimately preventing neuronal death in epileptic conditions. Our research utilized a pilocarpine-induced epilepsy animal model to investigate amlexanox's potential benefits. Administered intraperitoneally at a dose of 100 â€‹mg/kg daily following the onset of a seizure, we monitored its effects on lysosomal function, inflammation, neuronal death, and cognitive performance in the brain. Tissue samples from various brain regions were collected at predetermined intervals for a comprehensive analysis. The study's results were significant. Amlexanox effectively improved lysosomal function, which we attribute to the modulation of zinc's influx into the lysosomes, subsequently enhancing autophagic processes and decreasing the release of inflammatory factors. Notably, this led to the attenuation of neuronal death in the hippocampal region. Additionally, cognitive function, assessed through the modified neurological severity score (mNSS) and the Barnes maze test, showed substantial improvements after treatment with amlexanox. These promising outcomes indicate that amlexanox has potential as a therapeutic agent in the treatment of epilepsy and related brain disorders. Its ability to combat lysosomal dysfunction and neuroinflammation positions it as a potential neuroprotective intervention. While these findings are encouraging, further research and clinical trials are essential to fully explore and validate the therapeutic efficacy of amlexanox in epilepsy management.

The Protective Role of Glutathione on Zinc-Induced Neuron Death after Brain Injuries.

Glutathione (GSH) is necessary for maintaining physiological antioxidant function, which is responsible for maintaining free radicals derived from reactive oxygen species at low levels and is associated with improved cognitive performance after brain injury. GSH is produced by the linkage of tripeptides that consist of glutamic acid, cysteine, and glycine. The adequate supplementation of GSH has neuroprotective effects in several brain injuries such as cerebral ischemia, hypoglycemia, and traumatic brain injury. Brain injuries produce an excess of reactive oxygen species through complex biochemical cascades, which exacerbates primary neuronal damage. GSH concentrations are known to be closely correlated with the activities of certain genes such as excitatory amino acid carrier 1 (EAAC1), glutamate transporter-associated protein 3-18 (Gtrap3-18), and zinc transporter 3 (ZnT3). Following brain-injury-induced oxidative stress, EAAC1 function is negatively impacted, which then reduces cysteine absorption and impairs neuronal GSH synthesis. In these circumstances, vesicular zinc is also released into the synaptic cleft and then translocated into postsynaptic neurons. The excessive influx of zinc inhibits glutathione reductase, which inhibits GSH's antioxidant functions in neurons, resulting in neuronal damage and ultimately in the impairment of cognitive function. Therefore, in this review, we explore the overall relationship between zinc and GSH in terms of oxidative stress and neuronal cell death. Furthermore, we seek to understand how the modulation of zinc can rescue brain-insult-induced neuronal death after ischemia, hypoglycemia, and traumatic brain injury.

Combined Treatment of Dichloroacetic Acid and Pyruvate Increased Neuronal Survival after Seizure.

During seizure activity, glucose and Adenosine triphosphate (ATP) levels are significantly decreased in the brain, which is a contributing factor to seizure-induced neuronal death. Dichloroacetic acid (DCA) has been shown to prevent cell death. DCA is also known to be involved in adenosine triphosphate (ATP) production by activating pyruvate dehydrogenase (PDH), a gatekeeper of glucose oxidation, as a pyruvate dehydrogenase kinase (PDK) inhibitor. To confirm these findings, in this study, rats were given a per oral (P.O.) injection of DCA (100 mg/kg) with pyruvate (50 mg/kg) once per day for 1 week starting 2 h after the onset of seizures induced by pilocarpine administration. Neuronal death and oxidative stress were assessed 1 week after seizure to determine if the combined treatment of pyruvate and DCA increased neuronal survival and reduced oxidative damage in the hippocampus. We found that the combined treatment of pyruvate and DCA showed protective effects against seizure-associated hippocampal neuronal cell death compared to the vehicle-treated group. Treatment with combined pyruvate and DCA after seizure may have a therapeutic effect by increasing the proportion of pyruvate converted to ATP. Thus, the current research demonstrates that the combined treatment of pyruvate and DCA may have therapeutic potential in seizure-induced neuronal death.

Korean Red Ginseng Improves Astrocytic Mitochondrial Function by Upregulating HO-1-Mediated AMPKα-PGC-1α-ERRα Circuit after Traumatic Brain Injury.

Heme oxygenase-1 (HO-1) exerts beneficial effects, including angiogenesis and energy metabolism via the peroxisome proliferator-activating receptor-γ coactivator-1α (PGC-1α)-estrogen-related receptor α (ERRα) pathway in astrocytes. However, the role of Korean red ginseng extract (KRGE) in HO-1-mediated mitochondrial function in traumatic brain injury (TBI) is not well-elucidated. We found that HO-1 was upregulated in astrocytes located in peri-injured brain regions after a TBI, following exposure to KRGE. Experiments with pharmacological inhibitors and target-specific siRNAs revealed that HO-1 levels highly correlated with increased AMP-activated protein kinase α (AMPKα) activation, which led to the PGC-1α-ERRα axis-induced increases in mitochondrial functions (detected based on expression of cytochrome c oxidase subunit 2 (MTCO2) and cytochrome c as well as O2 consumption and ATP production). Knockdown of ERRα significantly reduced the p-AMPKα/AMPKα ratio and PGC-1α expression, leading to AMPKα-PGC-1α-ERRα circuit formation. Inactivation of HO by injecting the HO inhibitor Sn(IV) protoporphyrin IX dichloride diminished the expression of p-AMPKα, PGC-1α, ERRα, MTCO2, and cytochrome c in the KRGE-administered peri-injured region of a brain subjected to TBI. These data suggest that KRGE enhanced astrocytic mitochondrial function via a HO-1-mediated AMPKα-PGC-1α-ERRα circuit and consequent oxidative phosphorylation, O2 consumption, and ATP production. This circuit may play an important role in repairing neurovascular function after TBI in the peri-injured region by stimulating astrocytic mitochondrial biogenesis.

Reinforced-hydrogel encapsulated hMSCs towards brain injury treatment by trans-septal approach.

Encapsulated stem cells in various biomaterials have become a potentially promising cell transplantation strategy in the treatment of various neurologic disorders. However, there is no ideal cell delivery material and method for clinical application in brain diseases. Here we show silk fibroin (SF)-based hydrogel encapsulated engineered human mesenchymal stem cells (hMSCs) to overproduce brain-derived neurotrophic factor (BDNF) (BDNF-hMSC) is an effective approach to treat brain injury through trans-septal cell transplantation in the rat model. In this study, we observed SF induced sustained BDNF production by BDNF-hMSC both in 2D (9.367 ± 1.969 ng/ml) and 3D (7.319 ± 0.1025 ng/ml) culture conditions for 3 days. Through immunohistochemistry using α-tubulin, BDNF-hMSCs showed a significant increased average neurite length of co-cultured neuro 2a (N2a) cells, suggested that BDNF-hMSCs induced neurogenesis in vitro. Encapsulated BDNF-hMSC, pre-labeled with the red fluorescent dye PKH-26, exhibited intense fluorescence up to 14 days trans-septal transplantation, indicated excellent viability of the transplanted cells. Compared to the vehicle-treated, encapsulated BDNF- hMSC demonstrated significantly increased BDNF level both in the sham-operated and injured hippocampus (Hip) through immunoblot analysis after 7 days implantation. Transplantation of the encapsulated BDNF-hMSC promoted neurological functional recovery via significantly reduced neuronal death in the Hip 7 days post-injury. Using magnetic resonance imaging (MRI) analysis, we demonstrated that encapsulated BDNF-hMSC reduced lesion area significantly at 14 and 21 days in the damaged brain following trans-septal implantation. This stem cell transplantation approach represents a critical set up towards brain injury treatment for clinical application.

Transient Receptor Potential Melastatin 2 (TRPM2) Inhibition by Antioxidant, N-Acetyl-l-Cysteine, Reduces Global Cerebral Ischemia-Induced Neuronal Death.

A variety of pathogenic mechanisms, such as cytoplasmic calcium/zinc influx, reactive oxygen species production, and ionic imbalance, have been suggested to play a role in cerebral ischemia induced neurodegeneration. During the ischemic state that occurs after stroke or heart attack, it is observed that vesicular zinc can be released into the synaptic cleft, and then translocated into the cytoplasm via various cation channels. Transient receptor potential melastatin 2 (TRPM2) is highly distributed in the central nervous system and has high sensitivity to oxidative damage. Several previous studies have shown that TRPM2 channel activation contributes to neuroinflammation and neurodegeneration cascades. Therefore, we examined whether anti-oxidant treatment, such as with N-acetyl-l-cysteine (NAC), provides neuroprotection via regulation of TRPM2, following global cerebral ischemia (GCI). Experimental animals were then immediately injected with NAC (150 mg/kg/day) for 3 and 7 days, before sacrifice. We demonstrated that NAC administration reduced activation of GCI-induced neuronal death cascades, such as lipid peroxidation, microglia and astroglia activation, free zinc accumulation, and TRPM2 over-activation. Therefore, modulation of the TRPM2 channel can be a potential therapeutic target to prevent ischemia-induced neuronal death.

Role of Excitatory Amino Acid Carrier 1 (EAAC1) in Neuronal Death and Neurogenesis After Ischemic Stroke.

Although there have been substantial advances in knowledge regarding the mechanisms of neuron death after stroke, effective therapeutic measures for stroke are still insufficient. Excitatory amino acid carrier 1 (EAAC1) is a type of neuronal glutamate transporter and considered to have an additional action involving the neuronal uptake of cysteine, which acts as a crucial substrate for glutathione synthesis. Previously, our lab demonstrated that genetic deletion of EAAC1 leads to decreased neuronal glutathione synthesis, increased oxidative stress, and subsequent cognitive impairment. Therefore, we hypothesized that reduced neuronal transport of cysteine due to deletion of the EAAC1 gene might exacerbate neuronal injury and impair adult neurogenesis in the hippocampus after transient cerebral ischemia. EAAC1 gene deletion profoundly increased ischemia-induced neuronal death by decreasing the antioxidant capacity. In addition, genetic deletion of EAAC1 also decreased the overall neurogenesis processes, such as cell proliferation, differentiation, and survival, after cerebral ischemia. These studies strongly support our hypothesis that EAAC1 is crucial for the survival of newly generated neurons, as well as mature neurons, in both physiological and pathological conditions. Here, we present a comprehensive review of the role of EAAC1 in neuronal death and neurogenesis induced by ischemic stroke, focusing on its potential cellular and molecular mechanisms.

A Novel Zinc Chelator, 1H10, Ameliorates Experimental Autoimmune Encephalomyelitis by Modulating Zinc Toxicity and AMPK Activation.

Previous studies in our lab revealed that chemical zinc chelation or zinc transporter 3 (ZnT3) gene deletion suppresses the clinical features and neuropathological changes associated with experimental autoimmune encephalomyelitis (EAE). In addition, although protective functions are well documented for AMP-activated protein kinase (AMPK), paradoxically, disease-promoting effects have also been demonstrated for this enzyme. Recent studies have demonstrated that AMPK contributes to zinc-induced neurotoxicity and that 1H10, an inhibitor of AMPK, reduces zinc-induced neuronal death and protects against oxidative stress, excitotoxicity, and apoptosis. Here, we sought to evaluate the therapeutic efficacy of 1H10 against myelin oligodendrocyte glycoprotein 35-55-induced EAE. 1H10 (5 µg/kg) was intraperitoneally injected once per day for the entire experimental course. Histological evaluation was performed three weeks after the initial immunization. We found that 1H10 profoundly reduced the severity of the induced EAE and that there was a remarkable suppression of demyelination, microglial activation, and immune cell infiltration. 1H10 also remarkably inhibited EAE-associated blood-brain barrier (BBB) disruption, MMP-9 activation, and aberrant synaptic zinc patch formation. Furthermore, the present study showed that long-term treatment with 1H10 also reduced the clinical course of EAE. Therefore, the present study suggests that zinc chelation and AMPK inhibition with 1H10 may have great therapeutic potential for the treatment of multiple sclerosis.

Zinc transporter 3 modulates cell proliferation and neuronal differentiation in the adult hippocampus.

The subgranular zone of the dentate gyrus is a subregion of the hippocampus that has two uniquely defining features; it is one of the most active sites of adult neurogenesis as well as the location where the highest concentrations of synaptic zinc are found, the mossy fiber terminals. Therefore, we sought to investigate the idea that vesicular zinc plays a role as a modulator of hippocampal adult neurogenesis. Here, we used ZnT3-/- mice, which are depleted of synaptic-vesicle zinc, to test the effect of targeted deletion of this transporter on adult neurogenesis. We found that this manipulation reduced progenitor cell turnover as well as led to a marked defect in the maturation of newborn cells that survive in the DG toward a neuronal phenotype. We also investigated the effects of zinc (ZnCl2 ), n-acetyl cysteine (NAC), and ZnCl2 plus 2NAC (ZN) supplement on adult hippocampal neurogenesis. Compared with ZnCl2 or NAC, administration of ZN resulted in an increase in proliferation of progenitor cells and neuroblast. ZN also rescued the ZnT3 loss-associated reduction of neurogenesis via elevation of insulin-like growth factor-1 and ERK/CREB activation. Together, these findings reveal that ZnT3 plays a highly important role in maintaining adult hippocampal neurogenesis and supplementation by ZN has a beneficial effect on hippocampal neurogenesis, as well as providing a therapeutic target for enhanced neuroprotection and repair after injury as demonstrated by its ability to prevent aging-dependent cognitive decline in ZnT3-/- mice. Therefore, the present study suggests that ZnT3 and vesicular zinc are essential for adult hippocampal neurogenesis.

Insulin induces phosphorylation of pyruvate dehydrogenase through RhoA activation pathway in HepG2 cells.

Insulin is a critical signaling molecule in reducing blood glucose levels, and pyruvate dehydrogenase (PDH) is an essential enzyme in regulating glucose metabolism. However, the insulin effect on PDH function has not been well established. We observed that insulin attenuated the phosphorylation (p) of Ser264 (p-Ser264) in the PDH E1α subunit (PDHA1) in normal rat hepatocyte. In contrast, insulin induced an increase of p-Ser264 PDHA1 levels in hepatocellular carcinoma HepG2 and Huh7 cells. Insulin activated RhoA and Rho-dependent coiled coil kinase, an effector protein of active RhoA, which regulated p-Ser264 PDHA1 levels, along with both p-Ser9 and p-Tyr216 forms of glycogen synthase kinase-3ß (GSK-3ß) in HepG2 cells. Only p-Tyr216 GSK-3ß, the active form was involved in an increase of p-Ser264 PDHA1. Akt was also engaged in p-Ser9 of GSK-3ß, but neither in p-Tyr216 of GSK-3ß nor p-Ser264 of PDHA1 upon insulin. Reconstituted dephospho-mimic forms PDHA1 S264A and GSK-3ß Y216F impaired, but wild-types PDHA1 and GSK-3ß and phospho-mimic forms PDHA1 S264D and GSK-3ß Y216E increased cell proliferation upon insulin through expression of c-Myc and cyclin D1. Therefore, we propose that insulin-mediated p-PDHA1 is involved in the regulation of HepG2 cell proliferation through RhoA signaling pathway.-Islam, R., Kim, J.-G., Park, Y., Cho, J.-Y., Cap, K.-C., Kho, A.-R., Chung, W.-S., Suh, S.-W., Park, J.-B. Insulin induces phosphorylation of pyruvate dehydrogenase through RhoA activation pathway in HepG2 cells.

EAAC1 gene deletion reduces adult hippocampal neurogenesis after transient cerebral ischemia.

Several studies have demonstrated that excitatory amino acid carrier-1 (EAAC1) gene deletion exacerbates hippocampal and cortical neuronal death after ischemia. However, presently there are no studies investigating the role of EAAC1 in hippocampal neurogenesis. In this study, we tested the hypothesis that reduced cysteine transport into neurons by EAAC1 knockout negatively affects adult hippocampal neurogenesis under physiological or pathological states. This study used young mice (aged 3-5 months) and aged mice (aged 11-15 months) of either the wild-type (WT) or EAAC1 -/- genotype. Ischemia was induced through the occlusion of bilateral common carotid arteries for 30 minutes. Histological analysis was performed at 7 or 30 days after ischemia. We found that both young and aged mice with loss of the EAAC1 displayed unaltered cell proliferation and neuronal differentiation, as compared to age-matched WT mice under ischemia-free conditions. However, neurons generated from EAAC1 -/- mice showed poor survival outcomes in both young and aged mice. In addition, deletion of EAAC1 reduced the overall level of neurogenesis, including cell proliferation, differentiation, and survival after ischemia. The present study demonstrates that EAAC1 is important for the survival of newly generated neurons in the adult brain under physiological and pathological conditions. Therefore, this study suggests that EAAC1 plays an essential role in modulating hippocampal neurogenesis.

Effects of Protocatechuic Acid (PCA) on Global Cerebral Ischemia-Induced Hippocampal Neuronal Death.

Global cerebral ischemia (GCI) is one of the main causes of hippocampal neuronal death. Ischemic damage can be rescued by early blood reperfusion. However, under some circumstances reperfusion itself can trigger a cell death process that is initiated by the reintroduction of blood, followed by the production of superoxide, a blood⁻brain barrier (BBB) disruption and microglial activation. Protocatechuic acid (PCA) is a major metabolite of the antioxidant polyphenols, which have been discovered in green tea. PCA has been shown to have antioxidant effects on healthy cells and anti-proliferative effects on tumor cells. To test whether PCA can prevent ischemia-induced hippocampal neuronal death, rats were injected with PCA (30 mg/kg/day) per oral (p.o) for one week after global ischemia. To evaluate degenerating neurons, oxidative stress, microglial activation and BBB disruption, we performed Fluoro-Jade B (FJB), 4-hydroxynonenal (4HNE), CD11b, GFAP and IgG staining. In the present study, we found that PCA significantly decreased degenerating neuronal cell death, oxidative stress, microglial activation, astrocyte activation and BBB disruption compared with the vehicle-treated group after ischemia. In addition, an ischemia-induced reduction in glutathione (GSH) concentration in hippocampal neurons was recovered by PCA administration. Therefore, the administration of PCA may be further investigated as a promising tool for decreasing hippocampal neuronal death after global cerebral ischemia.

Administration of placenta-derived mesenchymal stem cells counteracts a delayed anergic state following a transient induction of endogenous neurogenesis activity after global cerebral ischemia.

BACKGROUND: Global cerebral ischemia (GCI) is a major obstacle for cardiac arrest survival. Recent studies have suggested the possibility of mesenchymal stem cell (MSC) as a novel therapeutic option for GCI, but these results were limited to the neuroprotective effects of MSCs. Therefore, we aimed to investigate specific characteristics of neurogenesis after transient GCI, and to assess the effect of MSC on these characteristics. METHODS: Adult male Sprague-Dawley rats were subjected to 7 min of transient GCI and randomized into 7 groups: baseline, MSC, and control administered groups, to be analyzed at 2, 3, and 4 weeks after GCI, respectively. The same interventions were repeated for sham operated animals. Rats were euthanized at the designated time after GCI. RESULTS: A comparison of GCI and sham groups without MSC treatment, showed that the counts of bromodeoxyuridine (BrdU)- and doublecortin (DCX)-positive cells were significantly increased in the GCI group at 1 week after insult, but the trend was reversed at 3 weeks after insult. The counts of BrdU-, Ki67- and DCX-positive cells and the intensity of zinc translocator 3 (ZnT3) were all significantly higher in the MSC-treated group than those in the control group at 3 weeks after GCI. The count of NeuN-positive cells in the hippocampus was significantly increased in the MSC group at 4 weeks after GCI. CONCLUSIONS: GCI induces transient neurogenesis, followed by an anergic state. MSC may counteract this anergy of neurogenesis and result in an increase in intact neurons in later stages.

Combined Treatment With Dichloroacetic Acid and Pyruvate Reduces Hippocampal Neuronal Death After Transient Cerebral Ischemia.

Transient cerebral ischemia (TCI) occurs when blood flow to the brain is ceased or dramatically reduced. TCI causes energy depletion and oxidative stress, which leads to neuronal death and cognitive impairment. Dichloroacetic acid (DCA) acts as an inhibitor of pyruvate dehydrogenase kinase (PDK). Additionally, DCA is known to increase mitochondrial pyruvate uptake and promotes glucose oxidation during glycolysis, thus enhancing pyruvate dehydrogenase (PDH) activity. In this study, we investigated whether the inhibition of PDK activity by DCA, which increases the rate of pyruvate conversion to adenosine triphosphate (ATP), prevents ischemia-induced neuronal death. We used a rat model of TCI, which was induced by common carotid artery occlusion and hypovolemia for 7 min while monitoring the electroencephalography for sustained isoelectric potential. Male Sprague-Dawley rats were given an intraperitoneal injection of DCA (100 mg/kg) with pyruvate (50 mg/kg) once per day for 2 days after insult. The vehicle, DCA only or pyruvate on rats was injected on the same schedule. Our study demonstrated that the combined administration of DCA with pyruvate significantly decreased neuronal death, oxidative stress, microglia activation when compared with DCA, or pyruvate injection alone. These findings suggest that the administration of DCA with pyruvate may enhance essential metabolic processes, which in turn promotes the regenerative capacity of the post-ischemic brain.

Protective Effects of Protocatechuic Acid on Seizure-Induced Neuronal Death.

Protocatechuic acid (PCA) is a type of phenolic acid found in green tea and has been shown to have potent antioxidant and anti-inflammatory properties. However, the effect of PCA on pilocarpine seizure-induced neuronal death in the hippocampus has not been evaluated. In the present study, we investigated the potential therapeutic effects of PCA on seizure-induced brain injury. Epileptic seizure was induced by intraperitoneal (i.p.) injection of pilocarpine (25 mg/kg) in adult male rats, and PCA (30 mg/kg) was injected into the intraperitoneal space for three consecutive days after the seizure. Neuronal injury and oxidative stress were evaluated three days after a seizure. To confirm whether PCA increases neuronal survival and reduced oxidative injury in the hippocampus, we performed Fluoro-Jade-B (FJB) staining to detect neuronal death and 4-hydroxynonenal (4HNE) staining to detect oxidative stress after the seizure. In the present study, we found that, compared to the seizure vehicle-treated group, PCA administration reduced neuronal death and oxidative stress in the hippocampus. To verify whether a decrease of neuronal death by PCA treatment was due to reduced glutathione (GSH) concentration, we measured glutathione with N-ethylmaleimide (GS-NEM) levels in hippocampal neurons. A seizure-induced reduction in the hippocampal neuronal GSH concentration was preserved by PCA treatment. We also examined whether microglia activation was affected by the PCA treatment after a seizure, using CD11b staining. Here, we found that seizure-induced microglia activation was significantly reduced by the PCA treatment. Therefore, the present study demonstrates that PCA deserves further investigation as a therapeutic agent for reducing hippocampal neuronal death after epileptic seizures.

ZnT3 Gene Deletion Reduces Colchicine-Induced Dentate Granule Cell Degeneration.

Our previous study demonstrated that colchicine-induced dentate granule cell death is caused by blocking axonal flow and the accumulation of intracellular zinc. Zinc is concentrated in the synaptic vesicles via zinc transporter 3 (ZnT3), which facilitates zinc transport from the cytosol into the synaptic vesicles. The aim of the present study was to identify the role of ZnT3 gene deletion on colchicine-induced dentate granule cell death. The present study used young (3-5 months) mice of the wild-type (WT) or the ZnT3-/- genotype. Colchicine (10 µg/kg) was injected into the hippocampus, and then brain sections were evaluated 12 or 24 h later. Cell death was evaluated by Fluoro-Jade B; oxidative stress was analyzed by 4-hydroxy-2-nonenal; and dendritic damage was detected by microtubule-associated protein 2. Zinc accumulation was detected by N-(6-methoxy-8-quinolyl)-para-toluenesulfonamide (TSQ) staining. Here, we found that ZnT3-/- reduced the number of degenerating cells after colchicine injection. The ZnT3-/--mediated inhibition of cell death was accompanied by suppression of oxidative injury, dendritic damage and zinc accumulation. In addition, ZnT3-/- mice showed more glutathione content than WT mice and inhibited neuronal glutathione depletion by colchicine. These findings suggest that increased neuronal glutathione by ZnT3 gene deletion prevents colchicine-induced dentate granule cell death.

The cancer chemotherapeutic agent paclitaxel (Taxol) reduces hippocampal neurogenesis via down-regulation of vesicular zinc.

Chemotherapy-induced cognitive impairment (CICI) is increasingly recognized as a major unwanted side effect of an otherwise highly valuable life-saving technology. In part, this awareness is a result of increased cancer survival rates following chemotherapy. Altered hippocampal neurogenesis may play a role in mediating CICI. In particular, zinc could act as a key regulator of this process. To test this hypothesis, we administered paclitaxel (Px) to male C57BL/6 mice for set time periods and then evaluated the effects of Px treatment on hippocampal neurogenesis and vesicular zinc. We found that vesicular zinc levels and expression of zinc transporter 3 (ZnT3) were reduced in Px-treated mice, compared to vehicle-treated mice. Moreover, Px-treated mice demonstrated a significant decrease in the number of neuroblasts present. However, no difference in the number of progenitor cells were observed. In addition, zinc supplementation by treatment with ZnCl2 ameliorated the Px-induced decrease in hippocampal neurogenesis and cognitive impairment. These results suggest that via disruption of vesicular zinc stores in hippocampal mossy fiber terminals, chemotherapy may impinge upon one or more of the sequential stages involved in the maturation of new neurons derived via adult neurogenesis and thereby leads to the progressive cognitive decline associated with CICI.

Effect of Adipose-Derived Mesenchymal Stem Cell Administration and Mild Hypothermia Induction on Delayed Neuronal Death After Transient Global Cerebral Ischemia.

OBJECTIVES: Global cerebral ischemia is a cause of poor prognosis after resuscitation from cardiac arrest. Various attempts have been made to minimize global cerebral ischemia but none been more effective than mild hypothermia induction. A few studies have shown the effect of mesenchymal stem cells on global cerebral ischemia, but no studies have compared this effect with mild hypothermia or assessed any possible interaction. We aimed to show the effect of mesenchymal stem cells on delayed neuronal death after global cerebral ischemia and to compare this effect with mild hypothermia. DESIGN: Experimental study. SETTING: Animal research laboratory. SUBJECTS: Adult male Sprague-Dawley rats weighing 250-300 g. INTERVENTIONS: Rats were subjected to 7 minutes of transient global cerebral ischemia and randomized into four groups: control, mild hypothermia, injection of human adipose-derived mesenchymal stem cells, and combined application of mild hypothermia and mesenchymal stem cells, along with four sham groups treated identically. Rats were euthanized 7 days after global cerebral ischemia. MEASUREMENTS AND MAIN RESULTS: Degree of neuronal death in hippocampus was significantly higher in control than in other groups. The number of activated microglia was higher in control group than in other groups and was higher in mild hypothermia than shams, mesenchymal stem cells, mild hypothermia/mesenchymal stem cells. Degree of blood-brain barrier disruption and the count of infiltrated neutrophils were significantly higher in control than in other groups. Degree of oxidative injury was significantly higher in control than other groups. It was higher in mild hypothermia than sham groups, mesenchymal stem cells, mild hypothermia/mesenchymal stem cells and was higher in mesenchymal stem cells group than sham groups. Significantly, worse functional results were found in control than in other groups. CONCLUSIONS: Administration of mesenchymal stem cells after transient global cerebral ischemia has a prominent protective effect on delayed neuron death, even compared with mild hypothermia.

Prevention of hypoglycemia-induced hippocampal neuronal death by N-acetyl-L-cysteine (NAC).

Type 1 and type 2 diabetic patients who are treated with insulin or other blood glucose reducing agents for tight control of blood glucose levels are frequently at risk of experiencing severe hypoglycemia which can lead to seizures, loss of consciousness and death. Hypoglycemic neuronal cell death is not a simple result of low glucose supply to the brain, but, instead, results from a cell death signaling pathway that is started by the re-administration of glucose after glucose deprivation. Zinc is a biologically important element for physiological function of central nervous system. However, excessive zinc release from the presynaptic terminals and subsequent translocation into the postsynaptic neurons may contribute to neuronal death following hypoglycemia. N-acetyl-L-cysteine (NAC) acts as a zinc chelator that alleviates zinc-induced neuronal death processes. In addition, NAC restores levels of neuronal glutathione (GSH), a potent antioxidant, by providing a cell-permeable source of cysteine. Thus, we hypothesized that NAC treatment can reduce neuronal cell death, not only by increasing GSH concentration but also by zinc chelation. As a result, we found that NAC decreased the oxidative stress, zinc release and translocation, and improved the level of glutathione. Therefore, NAC administration alleviated hippocampal neuron death in hypoglycemia-induced rats.