Cilnidipine mediates a neuroprotective effect by scavenging free radicals and activating the phosphatidylinositol 3-kinase pathway

Tacrolimus Decreases Cognitive Function by Impairing Hippocampal Synaptic Balance: a Possible Role of Klotho

The influence of long-term tacrolimus treatment on cognitive function remains to be elucidated. Using a murine model of chronic tacrolimus neurotoxicity, we evaluated the effects of tacrolimus on cognitive function, synaptic balance, its regulating protein (Klotho), and oxidative stress in the hippocampus. Compared to vehicle-treated mice, tacrolimus-treated mice showed significantly decreased hippocampal-dependent spatial learning and memory function. Furthermore, tacrolimus caused synaptic imbalance, as demonstrated by decreased excitatory synapses and increased inhibitory synapses, and downregulated Klotho in a dose-dependent manner; the downregulation of Klotho was localized to excitatory hippocampal synapses. Moreover, tacrolimus increased oxidative stress and was associated with activation of the PI3K/AKT pathway in the hippocampus. These results indicate that tacrolimus impairs cognitive function via synaptic imbalance, and that these processes are associated with Klotho downregulation at synapses through tacrolimus-induced oxidative stress in the hippocampus.

Dependence of PINK1 accumulation on mitochondrial redox system

Accumulation of PINK1 on the outer mitochondrial membrane (OMM) is necessary for PINK-mediated mitophagy. The proton ionophores, like carbonyl cyanide m-chlorophenylhydrazone (CCCP) and carbonyl cyanide-4-(trifluoromethoxy)phenylhydrazone (FCCP), inhibit PINK1 import into mitochondrial matrix and induce PINK1 OMM accumulation. Here, we show that the CHCHD4/GFER disulfide relay system in the mitochondrial intermembrane space (IMS) is required for PINK1 stabilization when mitochondrial membrane potential is lost. Activation of CHCHD4/GFER system by mitochondrial oxidative stress or inhibition of CHCHD4/GFER system with antioxidants can promote or suppress PINK1 accumulation, respectively. Thus data suggest a pivotal role of CHCHD4/GFER system in PINK1 accumulation. The amyotrophic lateral sclerosis-related superoxide dismutase 1 mutants dysregulated redox state and CHCHD4/GFER system in the IMS, leading to inhibitions of PINK1 accumulation and mitophagy. Thus, the redox system in the IMS is involved in PINK1 accumulation and damaged mitochondrial clearance, which may play roles in mitochondrial dysfunction-related neurodegenerative diseases.

Mitochondria damaged by Oxygen Glucose Deprivation can be Restored through Activation of the PI3K/Akt Pathway and Inhibition of Calcium Influx by Amlodipine Camsylate

Amlodipine, a L-type calcium channel blocker, has been reported to have a neuroprotective effect in brain ischemia. Mitochondrial calcium overload leads to apoptosis of cells in neurologic diseases. We evaluated the neuroprotective effects of amlodipine camsylate (AC) on neural stem cells (NSCs) injured by oxygen glucose deprivation (OGD) with a focus on mitochondrial structure and function. NSCs were isolated from rodent embryonic brains. Effects of AC on cell viability, proliferation, level of free radicals, and expression of intracellular signaling proteins were assessed in OGD-injured NSCs. We also investigated the effect of AC on mitochondrial structure in NSCs under OGD by transmission electron microscopy. AC increased the viability and proliferation of NSCs. This beneficial effect of AC was achieved by strong protection of mitochondria. AC markedly enhanced the expression of mitochondrial biogenesis-related proteins and mitochondrial anti-apoptosis proteins. Together, our results indicate that AC protects OGD-injured NSCs by protecting mitochondrial structure and function. The results of the present study provide insight into the mechanisms underlying the protective effects of AC on NSCs.

Sublethal Doses of Zinc Protect Rat Neural Stem Cells Against Hypoxia Through Activation of the PI3K Pathway

Cerebral infarction is one of the major causes of severe morbidity and mortality, and thus, research has focused on developing treatment options for this condition. Zinc (Zn) is an essential element in the central nervous system and has several neuroprotective effects in the brain. In this study, we examined the neuroprotective effects of Zn on neural stem cells (NSCs) exposed to hypoxia. After treatment with several concentrations of Zn, the viability of NSCs under hypoxic conditions was measured by a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, Trypan blue staining, and a lactate dehydrogenase assay. To evaluate the effect of Zn on the proliferation of NSCs, bromodeoxyuridine/5-bromo-2'-deoxyuridine (BrdU) labeling and colony formation assays were performed. Apoptosis was also examined in NSCs exposed to hypoxia with and without Zn treatment. In addition, a western blot analysis was performed to evaluate the effect of Zn on intracellular signaling proteins. NSC viability and proliferation were decreased under hypoxic conditions, but treatment with sublethal doses of Zn restored viability and proliferation. Sublethal doses of Zn reduced apoptosis caused by hypoxia, increased the expression levels of proteins related to the phosphatidylinositol-3 kinase (PI3K) pathway, and decreased the expression levels of proteins associated with neuronal cell death. These findings confirm that in vivo, sublethal doses of Zn protect NSCs against hypoxia through the activation of the PI3K pathway. Thus, Zn could be employed as a therapeutic option to protect NSCs in ischemic stroke.

Inhalation of high concentration hydrogen gas improves short-term outcomes in a rat model of asphyxia induced-cardiac arrest

Cardiogenic global brain hypoxia-ischemia is a devastating medical problem that is associated with unfavorable neurologic outcomes. Low dose hydrogen gas (up to 2.9%) has been shown to be neuroprotective in a variety of brain diseases. In the present study, we investigated the protective effect of water by electrolysis-derived high concentration hydrogen gas (60%) in a rat model of asphyxia induced-cardiac arrest and global brain hypoxia-ischemia. High concentration hydrogen gas was either administered starting 1 hour prior to cardiac arrest for 1 hour and starting 1 hour post-resuscitation for 1 hour (pre- & post-treatment) or starting 1 hour post-resuscitation for 2 hours (post-treatment). In animals subjected to 9 minutes of asphyxia, both therapeutic regimens tended to reduce the incidence of seizures and neurological deficits within 3 days post-resuscitation. In rats subjected to 11 minutes of asphyxia, significantly worse neurological deficits were observed compared to 9 minutes asphyxia, and pre- & post-treatment had a tendency to improve the success rate of resuscitation and to reduce the seizure incidence within 3 days post-resuscitation. Findings of this preclinical study suggest that water electrolysis-derived 60% hydrogen gas may improve short-term outcomes in cardiogenic global brain hypoxia-ischemia.

Maternal n-3 polyunsaturated fatty acid dietary supply modulates microglia lipid content in the offspring

The brain is highly enriched in long chain polyunsaturated fatty acids (LC-PUFAs) that are esterified into phospholipids, the major components of cell membranes. They accumulate during the perinatal period when the brain is rapidly developing. Hence, the levels of LC-PUFAs in the brains of the offspring greatly depend on maternal dietary intake. Perinatal n-3 PUFA consumption has been suggested to modulate the activity of microglial cells, the brain's innate immune cells which contribute to the shaping of neuronal network during development. However, the impact of maternal n-3 PUFA intake on microglial lipid composition in the offspring has never been studied. To investigate the impact of maternal dietary n-3 PUFA supply on microglia lipid composition, pregnant mice were fed with n-3 PUFA deficient, n-3 PUFA balanced or n-3 PUFA supplemented diets during gestation and lactation. At weaning, microglia were isolated from the pup's brains to analyze their fatty acid composition and phospholipid class levels. We here report that post-natal microglial cells displayed a distinctive lipid profile as they contained high levels of eicosapentaenoic acid (EPA), more EPA than docosahexaenoic acid (DHA) and large amount of phosphatidylinositol (PI) / phosphatidylserine (PS). Maternal n-3 PUFA supply increased DHA levels and decreased n-6 docosapentaenoic acid (DPA) levels whereas the PI/PS membrane content was inversely correlated to the quantity of PUFAs in the diet. These results raise the possibility of modulating microglial lipid profile and their subsequent activity in the developing brain.

Neuroserpin Attenuates H2O2-Induced Oxidative Stress in Hippocampal Neurons via AKT and BCL-2 Signaling Pathways

Oxidative stress plays a critical role in neuronal injury and is associated with various neurological diseases. Here, we explored the potential protective effect of neuroserpin against oxidative stress in primary cultured hippocampal neurons. Our results show that neuroserpin inhibits H2O2-induced neurotoxicity in hippocampal cultures as measured by WST, LDH release, and TUNEL assays. We found that neuroserpin enhanced the activation of AKT in cultures subjected to oxidative stress and that the AKT inhibitor Ly294002 blocked this neuroprotective effect. Neuroserpin increased the expression of the anti-apoptotic protein BCL-2 and blocked the activation of caspase-3. Neuroserpin did not increase the level of neuroprotection over levels seen in neurons transduced with a BCL-2 expression vector, and an inhibitor of Trk receptors, K252a, did not block neuroserpin's effect. Taken together, our study demonstrates that neuroserpin protects against oxidative stress-induced dysfunction and death of primary cultured hippocampal neurons through the AKT-BCL-2 signaling pathway through a mechanism that does not involve the Trk receptors and leads to inhibition of caspase-3 activation.

The role of multifunctional drug therapy as an antidote to combat experimental subacute neurotoxicity induced by organophosphate pesticides

Organophosphate pesticides are used in agriculture where they are associated with numerous cases of intentional and accidental misuse. These toxicants are potent inhibitors of cholinesterases leading to a massive build-up of acetylcholine which induces an array of deleterious effects, including convulsions, oxidative damage and neurobehavioral deficits. Antidotal therapies with atropine and oxime yield a remarkable survival rate, but fail to prevent neuronal damage and behavioral problems. It has been indicated that multifunction drug therapy with potassium channel openers, calcium channel antagonists and antioxidants (either single-agent therapy or combination therapy) may have the potential to prevent cell death and/or slow down the processes of secondary neuronal damage. The aim of the present study, therefore, was to make a relative assessment of the potential effects of nicorandil (2 mg/kg), clinidipine (10 mg/kg), and grape seed proanthocyanidin (GSPE) extract (200 mg/kg) individually against subacute chlorpyrifos induced toxicity. The test drugs were administered to Wistar rats 2 h after exposure to Chlorpyrifos (CPF). Different behavioral studies and biochemical estimation has been carried in the study. The results showed that chronic administration of CPF significantly impaired learning and memory, along with motor coordination, and produced a marked increase in oxidative stress along with significantly reduced acetylcholine esterase (AChE) activity. Treatment with nicorandil, clinidipine and GSPE was shown to significantly improve memory performance, attenuate oxidative damage and enhance AChE activity in rats. The present study also suggests that a combination of nicorandil, clinidipine, and GSPE has a better neuroprotective effect against subacute CPF induced neurotoxicity than if applied individually. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1017-1026, 2016.

Neural stem cells injured by oxidative stress can be rejuvenated by GV1001, a novel peptide, through scavenging free radicals and enhancing survival signals

Oxidative stress is a well-known pathogenic mechanism of a diverse array of neurological diseases, and thus, numerous studies have attempted to identify antioxidants that prevent neuronal cell death. GV1001 is a 16-amino-acid peptide derived from human telomerase reverse transcriptase (hTERT). Considering that hTERT has a strong antioxidant effect, whether GV1001 also has an antioxidant effect is a question of interest. In the present study, we aimed to investigate the effects of GV1001 against oxidative stress in neural stem cells (NSCs). Primary culture NSCs were treated with different concentrations of GV1001 and/or hydrogen peroxide (H2O2) for various time durations. The H2O2 decreased the viability of the NSCs in a concentration-dependent manner, with 200μM H2O2 significantly decreasing both proliferation and migration. However, treatment with GV1001 rescued the viability, proliferation and migration of H2O2-injured NSCs. Consistently, free radical levels were increased in rat NSCs treated with H2O2, while co-treatment with GV1001 significantly reduced these levels, especially the intracellular levels. In addition, GV1001 restored the expression of survival-related proteins and reduced the expression of death-associated ones in NSCs treated with H2O2. In conclusion, GV1001 has antioxidant and neuroprotective effects in NSCs following treatment with H2O2, which appear to be mediated by scavenging free radicals, increasing survival signals and decreasing death signals.

Neuroprotective effects of amlodipine besylate and benidipine hydrochloride on oxidative stress-injured neural stem cells

Hypertension is associated with oxidative stress. Amlodipine besylate (AB) and benidipine hydrochloride (BH), which are Ca(2+) antagonists, have been reported to reduce oxidative stress. In this study, we examined the neuroprotective effects of AB and BH on oxidative stress-injured neural stem cells (NSCs), with a focus on the phosphatidylinositol 3-kinase (PI3K) pathway and the extracellular signal-regulated kinase (ERK) pathway. After treatment with H2O2, the viability of NSCs decreased in a concentration-dependent manner; however, co-treatment with AB or BH restored the viability of H2O2-injured NSCs. H2O2 increased free radical production and apoptosis in NSCs, whereas co-treatment with AB or BH attenuated these effects. To evaluate the effects of AB or BH on the H2O2-inhibited proliferation of NSCs, we performed BrdU labeling and colony formation assays and found that NSC proliferation decreased upon H2O2 treatment but that combined treatment with AB or BH restored this proliferation. Western blot analysis showed that AB and BH increased the expression of cell survival-related proteins that were linked with the PI3K and ERK pathways but decreased the expression of cell death-related proteins. To investigate whether the PI3K and ERK pathways were directly involved in the neuroprotective effects of AB and BH on H2O2-treated NSCs, NSCs were pretreated with the PI3K inhibitor, LY294002, or the ERK inhibitor, FR180204, which significantly blocked the effects of AB and BH. Together, our results suggest that AB and BH restore the H2O2-inhibited viability and proliferation of NSCs by inhibiting oxidative stress and by activating the PI3K and ERK pathways.

Novel vaccine peptide GV1001 effectively blocks β-amyloid toxicity by mimicking the extra-telomeric functions of human telomerase reverse transcriptase

GV1001 is a 16-amino-acid vaccine peptide derived from the human telomerase reverse transcriptase sequence. We investigated the effects of GV1001 against β-amyloid (Aβ) oligomer-induced neurotoxicity in rat neural stem cells (NSCs). Primary culture NSCs were treated with several concentrations of GV1001 and/or Aβ₂₅₋₃₅ oligomer for 48 hours. GV1001 protected NSCs against the Aβ₂₅₋₃₅ oligomer in a concentration-dependent manner. Aβ₂₅₋₃₅ concentration dependently decreased viability, proliferation, and mobilization of NSCs and GV1001 treatment restored the cells to wild-type levels. Aβ₂₅₋₃₅ increased free radical levels in rat NSCs while combined treatment with GV1001 significantly reduced these levels. In addition, GV1001 treatment of Aβ₂₅₋₃₅-injured NSCs increased the expression level of survival-related proteins, including mitochondria-associated survival proteins, and decreased the levels of death and inflammation-related proteins, including mitochondria-associated death proteins. Together, these results suggest that GV1001 possesses neuroprotective effects against Aβ₂₅₋₃₅ oligomer in NSCs and that these effects are mediated through mimicking the extra-telomeric functions of human telomerase reverse transcriptase, including the induction of cellular proliferation, anti-apoptotic effects, mitochondrial stabilization, and anti-aging and anti-oxidant effects.

Involvement of α7 nAChR signaling cascade in epigallocatechin gallate suppression of β-amyloid-induced apoptotic cortical neuronal insults

Excessive generation and accumulation of the β-amyloid (Aβ) peptide in selectively vulnerable brain regions is a key pathogenic event in the Alzheimer's disease (AD), while epigallocatechin gallate (EGCG) is a very promising chemical to suppress a variety of Aβ-induced neurodegenerative disorders. However, the precise molecular mechanism of EGCG responsible for protection against neurotoxicity still remains elusive. To validate and further investigate the possible mechanism involved, we explored whether EGCG neuroprotection against neurotoxicity of Aβ is mediated through the α7 nicotinic acetylcholine receptor (α7 nAChR) signaling cascade. It was shown in rat primary cortical neurons that short-term treatment with EGCG significantly attenuated the neurotoxicity of Aβ1-42, as demonstrated by increased cell viability, reduced number of apoptotic cells, decreased reactive oxygen species (ROS) generation, and downregulated caspase-3 levels after treatment with 25-μM Aβ1-42. In addition, EGCG markedly strengthened activation of α7nAChR as well as its downstream pathway signaling molecules phosphatidylinositol 3-kinase (PI3K) and Akt, subsequently leading to suppression of Bcl-2 downregulation in Aβ-treated neurons. Conversely, administration of α7nAChR antagonist methyllycaconitine (MLA; 20 μM) to neuronal cultures significantly attenuated the neuroprotection of EGCG against Aβ-induced neurototoxicity, thus presenting new evidence that the α7nAChR activity together with PI3K/Akt transduction signaling may contribute to the molecular mechanism underlying the neuroprotective effects of EGCG against Aβ-induced cell death.

Enhanced phosphatidylinositol 3-kinase (PI3K)/Akt signaling has pleiotropic targets in hippocampal neurons exposed to iron-induced oxidative stress

The PI3K/Akt pathway is a key component in synaptic plasticity and neuronal survival. The aim of this work was to investigate the participation of the PI3K/Akt pathway and its outcome on different molecular targets such as glycogen synthase kinase 3β (GSK3β) and Forkhead box-O (FoxO) transcription factors during mild oxidative stress triggered by iron overload. The exposure of mouse hippocampal neurons (HT22) to different concentrations of Fe(2+) (25-200 μm) for 24 h led us to define a mild oxidative injury status (50 μm Fe(2+)) in which cell morphology showed changes typical of neuronal damage with increased lipid peroxidation and cellular oxidant levels but no alteration of cellular viability. There was a simultaneous increase in both Akt and GSK3β phosphorylation. Levels of phospho-FoxO3a (inactive form) increased in the cytosolic fraction of cells treated with iron in a PI3K-dependent manner. Moreover, PI3K and Akt translocated to the nucleus in response to oxidative stress. Iron-overloaded cells harboring a constitutively active form of Akt showed decreased oxidants levels. Indeed, GSH synthesis under oxidative stress conditions was regulated by activated Akt. Our results show that activation of the PI3K/Akt pathway during iron-induced neurotoxicity regulates multiple targets such as GSK3β, FoxO transcriptional activity, and glutathione metabolism, thus modulating the neuronal response to oxidative stress.

Comparison of the effects of cilnidipine and amlodipine on cardiac remodeling and diastolic dysfunction in Dahl salt-sensitive rats

OBJECTIVE

The L/N-type calcium channel blocker (CCB) cilnidipine suppresses sympathetic nerve activity and has a superior renoprotective effect compared with L-type CCBs such as amlodipine. The cardioprotective action of cilnidipine has remained largely uncharacterized, however. We have now investigated the effects of cilnidipine, in comparison with amlodipine, on cardiac pathophysiology in rats with salt-sensitive hypertension.

METHODS

Dahl salt-sensitive rats fed a high-salt diet from 6 weeks of age were treated with vehicle (LVH group), amlodipine (3 mg/kg per day), or cilnidipine (3 mg/kg per day) from 7 to 11 weeks.

RESULTS

The salt-induced increase in SBP apparent in LVH rats was attenuated to a similar extent by treatment with amlodipine or cilnidipine. The two drugs also similarly inhibited the development of left ventricular (LV) hypertrophy. However, cilnidipine attenuated the increase in relative wall thickness as well as ameliorated LV perivascular and interstitial fibrosis and diastolic dysfunction to a greater extent than did amlodipine. In addition, cilnidipine treatment was associated with greater inhibition of cardiac oxidative stress, inflammation, and renin-angiotensin system (RAS) gene expression. The decrease in cardiac norepinephrine content apparent in LVH rats was similarly inhibited by both drugs.

CONCLUSIONS

Cilnidipine attenuated LV fibrosis and diastolic dysfunction as well as LV concentricity to a greater extent than did amlodipine in Dahl salt-sensitive rats. The superior cardioprotective action of cilnidipine is likely attributable, at least in part, to the greater antioxidant and anti-inflammatory effects associated with inhibition of cardiac RAS gene expression observed with this drug.

The early activation of PI3K strongly enhances the resistance of cortical neurons to hypoxic injury via the activation of downstream targets of the PI3K pathway and the normalization of the levels of PARP activity, ATP, and NAD⁺

Phosphatidylinositol 3-kinase (PI3K) plays several important roles in neuronal survival. Activation of the pathway is essential for the neuroprotective mechanisms of materials that shield neuronal cells from many stressful conditions. However, there have been no reports to date about the effect of the direct activation of the pathway in hypoxic injury of neuronal cells. We investigated whether the direct activation of the PI3K pathway inhibits neuronal cell death induced by hypoxia. Primary cultured cortical neurons (PCCNs) were exposed to hypoxic conditions (less than 1 mol% O2) and/or treated with PI3K activator. Hypoxia reduced the viability of PCCNs in a time-dependent manner, but treatment with PI3K significantly restored viability in a concentration-dependent manner. Among the signaling proteins involved in the PI3K pathway, those associated with survival, including Akt and glycogen synthase kinase-3β, were decreased shortly after exposure to hypoxia and those associated with cell death, including BAX, apoptosis-induced factor, cytochrome c, caspase-9, caspase-3, and poly(ADP-ribose) polymerase (PARP), were increased. However, treatment with PI3K activator normalized the expression levels of those signaling proteins. PARP activity and levels of ATP and NAD(+) altered by hypoxia were also normalized with direct PI3K activation. All these findings suggest that direct and early activation is important for protecting neuronal cells from hypoxic injury.

Powerful vascular protection by combining cilnidipine with valsartan in stroke-prone, spontaneously hypertensive rats

Cilnidipine is an L- and N-type calcium channel blocker (CCB), and amlodipine is an L-type CCB. Valsartan (10 mg kg(-1)), valsartan (10 mg kg(-1)) and amlodipine (1 mg kg(-1)), and valsartan (10 mg kg(-1)) and cilnidipine (1 mg kg(-1)) were administered once daily for 2 weeks to stroke-prone, spontaneously hypertensive rats (SHR-SPs). Blood pressure was significantly reduced by valsartan, and it was further reduced by the combination therapies. Vascular endothelial dysfunction was significantly attenuated in all therapeutic groups, and further significant attenuation was observed in the valsartan+cilnidipine-treated group, but not in the valsartan+amlodipine-treated group. Vascular nicotinamide adenine dinucleotide phosphate (NADPH) oxidase subunit NOX1 gene expression was significantly attenuated in all therapeutic groups, and significantly greater attenuation was observed in the valsartan+cilnidipine-treated group than in the valsartan-treated group. Compared with the valsartan-treated group, the positive areas for 4-hydroxy-2-nonenal were significantly lower only in the valsartan+cilnidipine-treated group. Plasma renin activity was significantly augmented in the valsartan-treated group, and it was significantly attenuated in the valsartan+cilnidipine-treated group. A significant increase in the ratio of plasma angiotensin-(1-7) to angiotensin II was observed only in the valsartan+cilnidipine-treated group. Vascular angiotensin-converting enzyme (ACE) gene expression was significantly attenuated only in the valsartan+cilnidipine-treated group, but ACE2 gene expression was significantly higher in all of the therapeutic groups. Thus, valsartan and cilnidipine combination therapy might have a powerful protective effect in the vascular tissues via increases in the angiotensin-(1-7)/angiotensin II ratio in plasma.

Coenzyme Q10 protects neural stem cells against hypoxia by enhancing survival signals

Recanalization and secondary prevention are the main therapeutic strategies for acute ischemic stroke. Neuroprotective therapies have also been investigated despite unsuccessful clinical results. Coenzyme Q10 (CoQ10), which is an essential cofactor for electron transport in mitochondria, is known to have an antioxidant effect. We investigated the protective effects of CoQ10 against hypoxia in neural stem cells (NSCs). We measured cell viability and levels of intracellular signaling proteins after treatment with several concentrations of CoQ10 under hypoxia-reperfusion. CoQ10 protected NSCs against hypoxia-reperfusion in a concentration-dependent manner by reducing growth inhibition and inhibiting free radical formation. It increased the expression of a number of survival-related proteins such as phosphorylated Akt (pAkt), phosphorylated glycogen synthase kinase 3-β (pGSK3-β), and B-cell lymphoma 2 (Bcl-2) in NSCs injured by hypoxia-reperfusion and reduced the expression of death-related proteins such as cleaved caspase-3. We conclude that CoQ10 has effects against hypoxia-reperfusion induced damage to NSCs by enhancing survival signals and decreasing death signals.

Amlodipine besylate and amlodipine camsylate prevent cortical neuronal cell death induced by oxidative stress

We examined the neuroprotective effects of the long-acting third-generation dihydropyridine Ca(2+) antagonists, amlodipine besylate (AB) and amlodipine camsylate (AC), on neuronal cell death induced by oxidative stress. Cell viability and levels of free radicals and intracellular signaling proteins were measured after treating primary cultures of cortical neurons with AB, AC, and/or hydrogen peroxide (H(2) O(2) ) under various conditions. Cell viability was not affected by concentrations of AB or AC up to 5 μM but decreased at higher concentrations. Following H(2) O(2) exposure, the viability of cortical neurons decreased in a concentration-dependent manner; however, treatment with AB or AC up to 5 μM restored the viability of H(2) O(2) -injured cortical neurons. Treatment with H(2) O(2) increased the level of free radicals in cortical neurons, and pre-treatment with AB or AC counteracted this in a dose-dependent manner. Similarly, treatment with AB or AC reduced the declines in p85aPI3K, phosphorylated Akt, phosphorylated GSK-3β, heat-shock transcription factor-1, and Bcl-2 induced by H(2) O(2) , as well as the increases in cyclooxygenase-2, cytosolic cytochrome c, cleaved caspase 9, and cleaved caspase 3. Our results indicate that AB and AC exert similar neuroprotective effects by reducing oxidative stress, enhancing survival signals, and inhibiting death signals.