Diazoxide triggers cardioprotection against apoptosis induced by oxidative stress

Although mitochondrial ATP-sensitive potassium (mitoK(ATP)) channels have been reported to reduce the extent of apoptosis, the critical timing of mitoK(ATP) channel opening required to protect myocytes against apoptosis remains unclear. In the present study, we examined whether the mitoK(ATP) channel serves as a trigger of cardioprotection against apoptosis induced by oxidative stress. Apoptosis of cultured neonatal rat cardiomyocytes was determined by flow cytometry (light scatter and propidium iodide/annexin V-FITC fluorescence) and by nuclear staining with Hoechst 33342. Mitochondrial membrane potential (DeltaPsi) was measured by flow cytometry of cells stained with rhodamine-123 (Rh-123). Exposure to H(2)O(2) (500 microM) induced apoptosis, and the percentage of apoptotic cells increased progressively and peaked at 2 h. This H(2)O(2)-induced apoptosis was associated with the loss of DeltaPsi, and the time course of decrease in Rh-123 fluorescence paralleled that of apoptosis. Pretreatment of cardiomyocytes with diazoxide (100 microM), a putative mitoK(ATP) channel opener, for 30 min before exposure to H(2)O(2) elicited transient and mild depolarization of DeltaPsi and consequently suppressed both apoptosis and DeltaPsi loss after 2-h exposure to H(2)O(2). These protective effects of diazoxide were abrogated by the mitoK(ATP) channel blocker 5-hydroxydecanoate (500 microM) but not by the sarcolemmal K(ATP) channel blocker HMR-1098 (30 microM). Our results suggest for the first time that diazoxide-induced opening of mitoK(ATP) channels triggers cardioprotection against apoptosis induced by oxidative stress in rat cardiomyocytes.     

Glutamate Neurotoxicity and the Inhibition of Protein Synthesis in the Hippocampal Slice

In some animal models of ischemia, neuronal degeneration can be prevented by the selective antagonism of the N-methyl-D-aspartate (NMDA) glutamate receptor subtype, suggesting that glutamate released during ischemia causes injury by activating NMDA receptors. The rat hippocampal slice preparation was used as an in vitro model to study the pharmacology of glutamate toxicity and investigate why NMDA receptors are critical in ischemic injury. Acute toxicity was assessed by quantifying the inhibition of protein synthesis, which we confirmed by autoradiography to be primarily neuronal. The effect of NMDA was prevented by the specific antagonists MK-801 and ketamine, as well as by the less selective antagonist kynurenic acid. The less selective antagonists kynurenic acid and 6,7-dinitroquinoxaline-2,3-dione antagonized the effects of quisqualate and NMDA. In contrast to previous observations with dissociated neurons in tissue culture, the toxicity of glutamate was unaffected by antagonists, regardless of the glutamate concentration, the duration of exposure, or the presence of magnesium. The high concentration of glutamate required to inhibit protein synthesis and the inability of receptor antagonists to block the effect of glutamate suggest that either glutamate acts through a non-receptor-mediated mechanism, or that the receptor-mediated nature of glutamate effects are masked in the slice preparation, perhaps by the glial uptake of glutamate. The altered physiology induced by ischemia must potentiate the neurotoxicity of glutamate, because we observed with a brain slice preparation that only high concentrations of glutamate caused neurotoxicity in the presence of oxygen and glucose and that these effects were not reversed by glutamate receptor antagonists.     

Insulin-like growth factor I rescues SH-SY5Y human neuroblastoma cells from hyperosmotic induced programmed cell death

Insulin-like growth factor I (IGF-I) and the type I IGF receptor are widely distributed in developing and adult mammalian nervous systems. In vitro, IGF-I is a mitogen for primary neurons and also for cells from the SH-SY5Y human neuroblastoma cell line, a well-characterized model system of neuronal growth. In the current study, we examined the effects of osmotic stress on SH-SY5Y cell viability and the mechanism by which IGF-I serves as a neuronal osmoprotectant. Within 24 hr, exposure of SH-SY5Y cells to hyperosmotic serum-free media decreased (1) the number of viable cells, (2) the rate of ³H-thymidine incorporation, and (3) cell cycle progression. The inclusion of 10 nM IGF-I with hyperosmotic media prevented the loss of cell viability. The osmoprotective effects of IGF-I were inhibited by α-IR_J, a blocking antibody of the type I IGF receptor. The observed loss of SH-SY5Y cell viability following hyperosmotic shock was due to an induction of programmed cell death as determined by flow cytometry and gel electrophoresis. Our results suggest that IGF-I can protect SH-SY5Y cells from hyperosmotic induced programmed cell death. © 1996 Wiley-Liss, Inc.     

Domoic Acid Neurotoxicity in Cultured Cerebellar Granule Neurons Is Mediated Predominantly by NMDA Receptors that Are Activated as a Consequence of Excitatory Amino Acid Release

Abstract: The participation of NMDA and non-NMDA receptors in domoic acid-induced neurotoxicity was investigated in cultured rat cerebellar granule cells (CGCs). Neurons were exposed to 300 µMl -glutamate or 10 µM domoate for 2 h in physiologic buffer at 22°C followed by a 22-h incubation in 37°C conditioned growth media. Excitotoxic injury was monitored as a function of time by measurement of lactate dehydrogenase (LDH) activity in both the exposure buffer and the conditioned media. Glutamate and domoate evoked, respectively, 50 and 65% of the total 24-h increment in LDH efflux after 2 h. Hyperosmolar conditions prevented this early response but did not significantly alter the extent of neuronal injury observed at 24 h. The competitive NMDA receptor antagonist d (?)-2-amino-5-phosphonopentanoic acid and the non-NMDA receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(f)quinoxaline (NBQX) reduced glutamate-induced LDH efflux totals by 73 and 27%, respectively, whereas, together, these glutamate receptor antagonists completely prevented neuronal injury. Domoate toxicity was reduced 65–77% when CGCs were treated with competitive and noncompetitive NMDA receptor antagonists. Unlike the effect on glutamate toxicity, NBQX completely prevented domoate-mediated injury. HPLC analysis of the exposure buffer revealed that domoate stimulates the release of excitatory amino acids (EAAs) and adenosine from neurons. Domoate-stimulated EAA release occurred almost exclusively through mechanisms related to cell swelling and reversal of the glutamate transporter. Thus, whereas glutamate-induced injury is mediated primarily through NMDA receptors, the full extent of neurodegeneration is produced by the coactivation of both NMDA and non-NMDA receptors. Domoate-induced neuronal injury is also mediated primarily through NMDA receptors, which are activated secondarily as a consequence of α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)/kainate receptor-mediated stimulation of EAA efflux.     

ATP-sensitive potassium channel opener iptakalim protected against the cytotoxicity of MPP+ on SH-SY5Y cells by decreasing extracellular glutamate level

Mounting evidence reveals that ATP-sensitive potassium (K(ATP)) channel openers (KCOs) exert significant neuroprotection in vivo and in vitro in several models of Parkinson's disease (PD). However, the mechanisms are not well understood. In this study, we demonstrated that SH-SY5Y cells expressed mRNA and proteins for Kir6.1, Kir6.2, SUR1 and SUR2 subunits of K(ATP) channels. Moreover, our results showed that 1-methyl-4-phenyl-pyridinium ion (MPP+) induced up-regulation of mRNA for the Kir6.2 subunit and down-regulation of SUR1. It was further found that pretreatment with iptakalim, a novel K(ATP) channel opener, could attenuate increased extracellular glutamate level and decreased cell survival in SH-SY5Y cell culture after exposure to MPP+. Trans-pyrrolidine-2, 4-dicarboxylic acid (t-PDC), a glutamate transporter inhibitor, partially blocked the effect of iptakalim decreasing extracellular glutamate level. Additionally, iptakalim prevented MPP+-induced inhibition of glutamate uptake in primary cultured astrocytes. The beneficial effects of iptakalim on glutamate uptake of astrocytes were abolished by selective mitochondrial K(ATP) (mitoK(ATP)) channel blocker 5-HD. These results suggest (i) K(ATP) channel dysfunction may be involved in the mechanisms of MPP+-induced cytotoxicity and (ii) iptakalim may modulate glutamate transporters and subsequently alleviate the increase of extracellular glutamate levels induced by MPP+ through opening mitoK(ATP) channels, thereby protecting SH-SY5Y cells against MPP+-induced cytotoxicity.     

6,7-Dinitroquinoxaline-2,3-Dione Blocks the Cytotoxicity of N-Methyl-D-Aspartate and Kainate, but Not Quisqualate, in Cortical Cultures

Based on radioligand binding and electrophysiological studies, quinoxalinediones such as 6,7-dinitroquinoxaline-2,3-dione (DNQX) have been shown to be potent competitive antagonists at the quisqualate and kainate subtypes of the glutamate receptor. In this report we have examined the effects of DNQX on excitatory amino acid neurotoxicity and evoked neurotransmitter release. DNQX was found to be a potent neuroprotective agent against glutamate and N-methyl-D-aspartate (NMDA) neurotoxicity. The data suggest that this neuroprotective activity of DNQX is due to its antagonism of the coagonist activity of glycine at the NMDA receptor-channel complex. The specificity of DNQX for the glycine site associated with the NMDA receptor-channel complex was confirmed in radioligand binding and neurotransmitter release studies. DNQX also prevented kainate neurotoxicity and kainate-evoked neurotransmitter release, presumably by direct competition for the kainate receptor. DNQX, however, did not prevent quisqualate neurotoxicity, suggesting that a novel quisqualate-preferring receptor insensitive to DNQX may mediate quisqualate toxicity.     

Plasticity of glutamatergic control of striatal acetylcholine release in experimental parkinsonism: opposite changes at group-II metabotropic and NMDA receptors

To investigate whether adaptive changes of glutamatergic transmission underlie dysfunction of the cholinergic system in experimental parkinsonism, the effects of group-II metabotropic glutamate and NMDA receptor ligands on acetylcholine release was studied in striatal slices and synaptosomes obtained from naive rats, 6-hydroxydopamine hemi-lesioned rats and 6-hydroxydopamine hemi-lesioned rats chronically treated with levodopa (L-DOPA) plus benserazide (non-dyskinetic). Group-II metabotropic glutamate receptor agonists LY354740, DCG-IV and L-CCG-I inhibited the electrically-evoked endogenous acetylcholine release from slices, while NMDA facilitated it. LY354740 also inhibited K+-evoked acetylcholine release from synaptosomes. LY354740-induced inhibition was prevented by the group-II metabotropic glutamate receptor antagonist LY341495. In hemi-parkinsonian rats, sensitivity towards LY354740 was reduced while that to NMDA was enhanced in the lesioned (denervated) compared with unlesioned striatum. Moreover, dizocilpine inhibited acetylcholine release in the lesioned compared with unlesioned striatum. Chronic treatment with L-DOPA normalized sensitivity towards glutamatergic agonists. We conclude that striatal dopamine denervation results in plastic changes at group-II metabotropic glutamate and NMDA receptors that may shift glutamatergic control of acetylcholine release towards facilitation. From a clinical perspective, L-DOPA and NMDA antagonists appear effective in counteracting overactivity of striatal cholinergic interneurones associated with Parkinson's disease.     

Striatal glutamate release evoked in vivo by NMDA is dependent upon ongoing neuronal activity in the substantia nigra, endogenous striatal substance P and dopamine

The aim of the present microdialysis study was to investigate whether the increase in striatal glutamate levels induced by intrastriatal perfusion with NMDA was dependent on the activation of extrastriatal loops and/or endogenous striatal substance P and dopamine. The NMDA-evoked striatal glutamate release was mediated by selective activation of the NMDA receptor-channel complex and action potential propagation, as it was prevented by local perfusion with dizocilpine and tetrodotoxin, respectively. Tetrodotoxin and bicuculline, perfused distally in the substantia nigra reticulata, prevented the NMDA-evoked striatal glutamate release, suggesting its dependence on ongoing neuronal activity and GABA(A) receptor activation, respectively, in the substantia nigra. The NMDA-evoked glutamate release was also dependent on striatal substance P and dopamine, as it was antagonized by intrastriatal perfusion with selective NK(1) (SR140333), D(1)-like (SCH23390) and D(2)-like (raclopride) receptor antagonists, as well as by striatal dopamine depletion. Furthermore, impairment of dopaminergic transmission unmasked a glutamatergic stimulation by submicromolar NMDA concentrations. We conclude that in vivo the NMDA-evoked striatal glutamate release is mediated by activation of striatofugal GABAergic neurons and requires activation of striatal NK(1) and dopamine receptors. Endogenous striatal dopamine inhibits or potentiates the NMDA action depending on the strength of the excitatory stimulus (i.e. the NMDA concentration).     

Proteasome inhibition in oxidative stress neurotoxicity: implications for heat shock proteins

Recent studies have demonstrated that inhibition of the proteasome, an enzyme responsible for the majority of intracellular proteolysis, may contribute to the toxicity associated with oxidative stress. In the present study we demonstrate that exposure to oxidative injury (paraquat, H(2)O(2), FeSO(4)) induces a rapid increase in reactive oxygen species (ROS), loss of mitochondrial membrane potential, inhibition of proteasome activity, and induction of cell death in neural SH-SY5Y cells. Application of proteasome inhibitors (MG115, epoxomycin) mimicked the effects of oxidative stressors on mitochondrial membrane potential and cell viability, and increased vulnerability to oxidative injury. Neural SH-SY5Y cells stably transfected with human HDJ-1, a member of the heat shock protein family, were more resistant to the cytotoxicity associated with oxidative stressors. Cells expressing increased levels of HDJ-1 displayed similar degrees of ROS formation following oxidative stressors, but demonstrated a greater preservation of mitochondrial function and proteasomal activity following oxidative injury. Cells transfected with HDJ-1 were also more resistant to the toxicity associated with proteasome inhibitor application. These data support a possible role for proteasome inhibition in the toxicity of oxidative stress, and suggest heat shock proteins may confer resistance to oxidative stress, by preserving proteasome function and attenuating the toxicity of proteasome inhibition.     

鱼藤酮诱导线粒体轻度损伤细胞氧化应激时硫氧还蛋白转录水平降低

观察鱼藤酮诱导的线粒体轻度损伤细胞氧化应激时硫氧还蛋白转录水平的变化,探讨细胞氧化损伤的可能机制。通过荧光素发光法检测ATP生成、细胞内活性氧(ROS)水平的变化,流式细胞术检测线粒体膜电位,了解低剂量鱼藤酮对线粒体功能的影响;继而用H2O2诱导细胞氧化损伤,MTT法检测细胞活性,观察正常及线粒体缺陷细胞氧化应激时,胞内硫氧还蛋白(Trx)mRNA水平的变化。结果表明,鱼藤酮以剂量依赖方式抑制线粒体ATP的产生、降低线粒体膜电位,而细胞内ROS水平增高;当线粒体损伤细胞氧化应激时胞内Trx mRNA水平降低,提示鱼藤酮诱导线粒体轻度损伤细胞抗氧化能力降低与Trx转录受到抑制有关。     

Interaction of NMDA and Dopamine D2L Receptors in Human Neuroblastoma SH-SY5Y Cells

Abstract: To understand the mechanism of interaction of the dopamine D_2L receptors with NMDA receptors, we have developed a model by transfecting human neuroblastoma SH-SY5Y cells with the human dopamine D_2L receptor gene. In vitro blockade of NMDA receptors by the specific antagonists MK-801 and (±)-3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP) on human neuroblastoma SH-SY5Y cells expressing human dopamine D_2L receptors resulted in a significant increase in the density of D_2L receptors without a significant change in receptor affinity. Moreover, the dopamine receptor mRNA level increased by ∼50% by the blockade of NMDA with MK-801. These results suggest a possible interaction of NMDA and dopamine D_2L receptors in neuroblastoma SH-SY5Y cells. This system would serve as an excellent model to study the molecular mechanisms involved in the interaction of these two receptors.     

The Role of Ca<Superscript>2+</Superscript> Imbalance in the Induction of Acute Oxidative Stress and Cytotoxicity in Cultured Rat Cerebellar Granule Cells Challenged with Tetrabromobisphenol A

Using primary cultures of rat cerebellar granule cells (CGC) we examined the role of calcium transients induced by tetrabromobisphenol A (TBBPA) in triggering oxidative stress and cytotoxicity. CGC were exposed for 30 min to 10 or 25 µM TBBPA. Changes in intracellular calcium concentration ([Ca²⁺]_i), in the production of reactive oxygen species (ROS), and in the potential of mitochondria (?Ψm) were measured fluorometrically during the exposure. The intracellular glutathione (GSH) and catalase activity were determined after the incubation; cell viability was evaluated 24 h later. TBBPA concentration-dependently increased [Ca²⁺]_i and ROS production, and reduced GSH content, catalase activity, ?Ψm and neuronal viability. The combination of NMDA and ryanodine receptor antagonists, MK-801 and bastadin 12 with ryanodine, respectively, prevented Ca²⁺ transients and partially reduced cytotoxicity induced by TBBPA at both concentrations. The antagonists also completely inhibited oxidative stress and depolarization of mitochondria evoked by 10 µM TBBPA, whereas these effects were only partially reduced in the 25 µM TBBPA treatment. Free radical scavengers prevented TBBPA-induced development of oxidative stress and improved CGC viability without having any effect on the rises in Ca²⁺ and drop in ?Ψm. The co-administration of scavengers with NMDA and ryanodine receptor antagonists provided almost complete neuroprotection. These results indicate that Ca²⁺ imbalance and oxidative stress both mediate acute toxicity of TBBPA in CGC. At 10 µM TBBPA Ca²⁺ imbalance is a primary event, inducing oxidative stress, depolarization of mitochondria and cytotoxicity, whilst at a concentration of 25 µM TBBPA an additional Ca²⁺-independent portion of oxidative stress and cytotoxicity emerges.     

Direct Evidence That Excitotoxicity in Cultured Neurons Is Mediated via N-Methyl-D-Aspartate (NMDA) as well as Non-NMDA Receptors

Cultured GABAergic cerebral cortex neurons were exposed to the excitatory amino acid (EAA) L-glutamate, kainate (KA), N-methyl-D-aspartate (NMDA), or RS-alpha-amino-3-hydroxy-5-methyl-4-isoxazolopropionate (AMPA). To ensure a constant glutamate concentration in the culture media during the exposure periods, the glutamate uptake inhibitor L-aspartic acid beta-hydroxamate was added at 500 microM to the cultures that were exposed to glutamate. Each of these EAAs was able to induce neurotoxicity. It was not possible to reduce or prevent glutamate-induced cytotoxicity by blocking only one of the glutamate receptor subtypes with either the NMDA receptor antagonist D-(-)-2-amino-5-phosphonopentanoate (APV) or with one of the specific non-NMDA antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6,7-dinitroquinoxaline-2,3-dione (DNQX). However, if the cultures were exposed simultaneously to glutamate and the antagonists in combination, i.e., APV plus CNQX or APV plus DNQX, the toxicity was completely prevented. Furthermore, CNQX and DNQX were shown to be selective blockers of cytotoxic phenomena induced by non-NMDA glutamate agonists with no effect on NMDA-induced cell death. Likewise, APV prevented NMDA-induced cell death without affecting the KA- or AMPA-induced neurotoxicity. It is concluded that EAA-dependent neurotoxicity is induced by NMDA as well as non-NMDA receptors.     

Carnosine Protects Against Aβ42-induced Neurotoxicity in Differentiated Rat PC12 Cells

(1) The present study was designed to investigate whether histamine is involved in the protective effect of carnosine on Aβ42-induced impairment in differentiated PC12 cells. (2) PC12 cells were exposed to Aβ42 (5 μM) for 24 h after carnosine (5 mM) applied for 18 h. Histamine receptor antagonists (diphenhydramine, zolantidine, thioperamide, clobenpropit) or histidine decarboxylase inhibitor (α-fluoromethylhistidine) were added 15 min before carnosine. Cell viability, glutamate release or cell surface expression of NMDA receptor was examined. (3) Aβ42 caused a concentration-dependent reduction of viability in PC12 cells and pretreatment with carnosine ameliorated this impairment. This amelioration was reversed by the H₃ receptor antagonists thioperamide and clobenpropit, but not by either the H₁ receptor antagonist diphenhydramine or the H₂ receptor antagonist zolantidine. Further, α-fluoromethylhistidine, an irreversible inhibitor of histidine decarboxylase, also had no effect. In the presence of Aβ42, carnosine significantly decreased glutamate release and carnosine increased the surface expression of NMDA receptor. (4) These results indicate that the mechanism by which carnosine attenuates Aβ42-induced neurotoxicity is independent of the carnosine–histidine–histamine pathway, but may act through regulation of glutamate release and NMDA receptor trafficking.     

Increase in External Glutamate and NMDA Receptor Activation Contribute to H2O2-Induced Neuronal Apoptosis

The present study aims to investigate the role of extracellular glutamate and NMDA receptor stimulation in the neuronal death induced by a transient exposure to H2O2 of cultured neurons originating from mouse cerebral cortex. Most of the neuronal loss following a transient exposure to H2O2 of cortical neurons results from an apoptotic process involving a secondary stimulation of NMDA receptors, which occurs after H2O2 washout. Indeed, (a) the neurotoxic effect of H2O2 was strongly reduced by antagonists of NMDA receptors, (b) the neurotoxic effect of H2O2 was enhanced in the absence of Mg2+, (c) the protective effect of MK-801 progressively decayed when it was applied with increasing delay time after H2O2 exposure, and (d), finally, the extracellular concentration of glutamate was increased after H2O2 exposure. The major part of H2O2-induced neurotoxicity is mediated by the formation of hydroxyl radicals, which might be involved in (a) the delayed accumulation of extracellular glutamate and NMDA receptor activation and (b) the poly(ADP-ribose) polymerase activation and the related NAD content decrease. The combination of these two mechanisms could lead to both an increase in ATP consumption and a decrease of ATP synthesis. The resulting large decrease in ATP content might be finally responsible for the neuronal death.     

Magnetic Resonance Spectroscopy Studies on Changes in Cerebral Calcium and Zinc and the Energy State Caused by Excitotoxic Amino Acids

Under control conditions, superfused hippocampal slices exhibited a significantly higher phosphocreatine (PCr)/ATP ratio than cortical slices; the evidence suggests that this is due to lower concentrations of ATP, rather than higher concentrations of PCr. Glutamate caused relatively rapid decreases in PCr and ATP levels to approximately 45%, accompanied or immediately followed by an increased free intracellular calcium concentration ([Ca2+]i) and the release of Zn2+ in the cortex. In the hippocampus PCr and ATP decreased further to approximately 20% of control values, but the changes in [Ca2+]i and Zn2+ content were slower. This is in contrast to the effects of depolarisation, which produced the same rapid changes in the energy state and [Ca2+]i, with no detectable Zn2+, in both tissues. NMDA causes effects similar to those of glutamate in the cortex (decreases in the energy state, increased [Ca2+]i, and release of Zn2+). Pretreatment of the cortex for 1 h with the NMDA blocker MK-801 prevented all of the observed effects of NMDA. In contrast, pretreatment with MK-801 had no detectable effect on the increase in [Ca2+]i or the decreases in PCr and ATP caused by glutamate, although it prevented the release of zinc. The results are discussed in relation to the function of the NMDA subtype of glutamate receptor in excitotoxicity.     

Flow cytometric analysis of mitochondrial populations in HL-CMS systems of rice under H2O2 stress

Cytoplasmic male sterility (CMS) has often been associated with mitochondrial dysfunction. In this report, the heterogeneity of mitochondria was analyzed in both Honglian (HL) CMS (YtA) rice seedlings and those of its corresponding maintainers (YtB) by flow cytometry and staining with rhodamine-123 (Rh-123). Both lines revealed two distinct fluorescence populations: high fluorescence populations (HFP) and light fluorescence populations (LFP), and a somewhat lower LFP/HFP ratio was detected in conjunction with the higher reactive oxygen species (ROS) content in YtA. In addition, use of the specific effector hydrogen peroxide (H₂O₂) demonstrated a correlation between the LFP/HFP ratio and ROS levels in both lines. Higher ROS content caused a more swift decrease of F₀F₁-ATPase activity and ATP contents in YtA than those in YtB, which accompanied with an obvious decline of the LFP/HFP ratio in YtA. Furthermore, a mitochondrial genomic DNA smear was detected by pulsed field gel electrophoresis. Taken together, these results implied that HL-CMS line rice seedlings and those of its corresponding maintainer have different proportion of Rh-123 staining mitochondria populations, which may be accounted for by ROS contents on the basis of ATPase activity and ATP contents.     

Taurine prevented cell cycle arrest and restored neurotrophic gene expression in arsenite-treated SH-SY5Y cells

The study investigated the effect of taurine on cell viability and neurotrophic gene expression in arsenite-treated human neuroblastoma SH-SY5Y cells. Arsenite-induced intracellular reactive oxygen species (ROS) and interrupted cell cycle in SH-SY5Y cells. In addition, arsenite reduced mitochondria membrane potential (MMP) and decreased neurotrophic gene expressions such as n-myc downstream-regulated gene 4 (NDRG-4), brain-derived neurotrophic factor (BDNF) and sirtuin-1 (SIRT-1) in SH-SY5Y cells. In parallel, taurine prevented cell cycle, restored MMP and reduced the intracellular ROS level, and taurine recovered NDRG-4, BDNF and SIRT-1 gene expressions in arsenite-treated SH-SY5Y cells while taurine alone has no effect on these parameters.     

Neuroprotective effect of GMP in hippocampal slices submitted to an in vitro model of ischemia

1. Guanosine-5-monophosphate (GMP) was evaluated as a neuroprotective agent against the damage observed in rat hippocampal slices submitted to an in vitro model of ischemia with or without the presence of the ionotropic glutamate receptor agonist, Kainic acid (KA).2. Cellular injury was evaluated by MTT reduction, lactate dehydrogenase (LDH) release assay, and measurement of intracellular ATP levels.3. In slices submitted to ischemic conditions, 1 mM GMP partially prevented the decrease in cell viability induced by glucose and oxygen deprivation and the addition of KA.4. KA or N-methyl-D-aspartate (NMDA) receptor antagonists, -D-glutamylamino-methylsulfonate (GAMS) or (+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate (MK-801, 20 M) also prevented toxicity in hippocampal slices under ischemic conditions, respectively.5. The association of GMP with GAMS or MK-801 did not induce additional protection than that observed with GMP or that classical glutamate receptor antagonists alone.6. GMP, probably by interacting with ionotropic glutamate receptors, attenuated the damage caused by glucose and oxygen deprivation in hippocampal slices. This neuroprotective action of GMP in this model of excitotoxicity is of outstanding interest in the search for effective therapies against ischemic injury.