Ebselen attenuates oxidative stress-induced apoptosis via the inhibition of the c-Jun N-terminal kinase and activator protein-1 signalling pathway in PC12 cells

Carnosic Acid Shows Higher Neuroprotective Efficiency than Edaravone or Ebselen in In Vitro Models of Neuronal Cell Damage

This study compared the neuroprotective efficacy of three antioxidants-the plant-derived carnosic acid (CA), and two synthetic free radical scavengers: edaravone (ED) and ebselen (EB)-in in vitro models of neuronal cell damage. Results showed that CA protected mouse primary neuronal cell cultures against hydrogen peroxide-induced damage more efficiently than ED or EB. The neuroprotective effects of CA were associated with attenuation of reactive oxygen species level and increased mitochondrial membrane potential but not with a reduction in caspase-3 activity. None of the tested substances was protective against glutamate or oxygen-glucose deprivation-evoked neuronal cell damage, and EB even increased the detrimental effects of these insults. Further experiments using the human neuroblastoma SH-SY5Y cells showed that CA but not ED or EB attenuated the cell damage induced by hydrogen peroxide and that the composition of culture medium is the critical factor in evaluating neuroprotective effects in this model. Our data indicate that the neuroprotective potential of CA, ED, and EB may be revealed in vitro only under specific conditions, with their rather narrow micromolar concentrations, relevant cellular model, type of toxic agent, and exposure time. Nevertheless, of the three compounds tested, CA displayed the most consistent neuroprotective effects.

Promising therapeutic mechanism for Chinese herbal medicine in ameliorating renal fibrosis in diabetic nephropathy

Diabetic nephropathy (DN) is one of the most serious chronic microvascular abnormalities of diabetes mellitus and the major cause of uremia. Accumulating evidence has confirmed that fibrosis is a significant pathological feature that contributes to the development of chronic kidney disease in DN. However, the exact mechanism of renal fibrosis in DN is still unclear, which greatly hinders the treatment of DN. Chinese herbal medicine (CHM) has shown efficacy and safety in ameliorating inflammation and albuminuria in diabetic patients. In this review, we outline the underlying mechanisms of renal fibrosis in DN, including oxidative stress (OS) generation and OS-elicited ASK1-p38/JNK activation. Also, we briefly summarize the current status of CHM treating DN by improving renal fibrosis. The treatment of DN by inhibiting ASK1 activation to alleviate renal fibrosis in DN with CHM will promote the discovery of novel therapeutic targets for DN and provide a beneficial therapeutic method for DN.

Ebselen, a multi-target compound: its effects on biological processes and diseases

Ebselen is a well-known synthetic compound mimicking glutathione peroxidase (GPx), which catalyses some vital reactions that protect against oxidative damage. Based on a large number of in vivo and in vitro studies, various mechanisms have been proposed to explain its actions on multiple targets. It targets thiol-related compounds, including cysteine, glutathione, and thiol proteins (e.g., thioredoxin and thioredoxin reductase). Owing to this, ebselen is a unique multifunctional agent with important effects on inflammation, apoptosis, oxidative stress, cell differentiation, immune regulation and neurodegenerative disease, with anti-microbial, detoxifying and anti-tumour activity. This review summarises the current understanding of the multiple biological processes and molecules targeted by ebselen, and its pharmacological applications.

The Protective Effect of Aspirin Eugenol Ester on Oxidative Stress to PC12 Cells Stimulated with H2O2 through Regulating PI3K/Akt Signal Pathway

Aspirin eugenol ester (AEE) is a new pharmaceutical compound esterified by aspirin and eugenol, which has anti-inflammatory, antioxidant, and other pharmacological activities. This study is aimed at identifying the protective effect of AEE against H₂O₂-induced apoptosis in rat adrenal pheochromocytoma PC12 cells and the possible mechanisms. The results of cell viability assay showed that AEE could increase the viability of PC12 cells stimulated by H₂O₂, while AEE alone had no significant effect on the viability of PC12 cells. Compared with the control group, the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were significantly decreased, and the content of malondialdehyde (MDA) was significantly increased in the H₂O₂ group. By AEE pretreatment, the level of MDA was reduced and the levels of SOD, CAT, and GSH-Px were increased in H₂O₂-stimulated PC12 cells. In addition, AEE could reduce the apoptosis of PC12 cells induced by H₂O₂ via reducing superoxide anion, intracellular ROS, and mitochondrial ROS (mtROS) and increasing the levels of mitochondrial membrane potential (ΔΨm). Furthermore, the results of western blotting showed that compared with the control group, the expression of p-PI3K, p-Akt, and Bcl-2 was significantly decreased, while the expression of Caspase-3 and Bax was significantly increased in the H₂O₂ group. In the AEE group, AEE pretreatment could upregulate the expression of p-PI3K, p-Akt, and Bcl-2 and downregulate the expression of Caspase-3 and Bax in PC12 cells stimulated with H₂O₂. The silencing of PI3K with shRNA and its inhibitor-LY294002 could abrogate the protective effect of AEE in PC12 cells. Therefore, AEE has a protective effect on H₂O₂-induced PC12 cells by regulating the PI3K/Akt signal pathway to inhibit oxidative stress.

Radiofrequency radiation at 2.856 GHz does not affect key cellular endpoints in neuron-like PC12 cells

To investigate the potential cytotoxicity of radiofrequency (RF) radiation on central nervous system, rat pheochromocytoma (PC12) cells were exposed to 2.856 GHz RF radiation at a specific absorption rate (SAR) of 4 W/kg for 8 h a day for 2 days in 35 mm Petri dishes. During exposure, the real-time variation of the culture medium temperature was monitored in the first hour. Reactive oxygen species (ROS) production, intracellular Ca²⁺ concentration, and cell apoptosis rate were assessed immediately after exposure by flow cytometry. The results showed that the medium temperature raised about 0.93 °C, but no significant changes were observed in apoptosis, ROS levels or intracellular Ca²⁺ concentration after treatment. Although several studies suggested that RF radiation does indeed cause neurological effects, this study presented inconsistent results, indicating that 2.856 GHz RF radiation exposure at a SAR of 4 W/kg does not have a dramatic impact on PC12 cells, and suggests the need for further investigation on the key cellular endpoints of other nerve cells after exposure to RF radiation.

Ebselen suppresses inflammation induced by Helicobacter pylori lipopolysaccharide via the p38 mitogen-activated protein kinase signaling pathway

Ebselen is a seleno-organic compound that has been demonstrated to have antioxidant and anti-inflammatory properties. A previous study determined that ebselen inhibits airway inflammation induced by inhalational lipopolysaccharide (LPS), however, the underlying molecular mechanism remains to be elucidated. The present study investigated the effect of ebselen on the glutathione peroxidase (GPX)‑reactive oxygen species (ROS) pathway and interleukin‑8 (IL‑8) expression induced by Helicobacter pylori LPS in gastric cancer (GC) cells. Cells were treated with 200 ng/ml H. pylori‑LPS in the presence or absence of ebselen for various durations and concentrations (µmol/l). The expression of toll‑like receptor 4 (TLR4), GPX2, GPX4, p38 mitogen‑activated protein kinase (p38 MAPK), phosphorylated‑p38 MAPK, ROS production and IL‑8 expression were detected with western blotting or ELISA. The present study revealed that TLR4 expression was upregulated; however, GPX2 and GPX4 expression was reduced following treatment with H. pylori LPS, which led to increased ROS production, subsequently altering the IL‑8 expression level in GC cells. Additionally, it was determined that ebselen prevented the reduction in GPX2/4 levels induced by H. pylori LPS, however, TLR4 expression was not affected. Ebselen may also block the expression of IL‑8 by inhibiting phosphorylation of p38 MAPK. These data suggest ebselen may inhibit ROS production triggered by H. pylori LPS treatment via GPX2/4 instead of TLR4 signaling and reduce phosphorylation of p38 MAPK, resulting in altered production of IL‑8. Ebselen may, therefore, be a potential therapeutic agent to mediate H. pylori LPS-induced cell damage.

Protective Effect of miR-374a on Chemical Hypoxia-Induced Damage of PC12 Cells In Vitro via the GADD45α/JNK Signaling Pathway

To explore the effect of microRNA-374a (miR-374a) on chemical hypoxia-induced pheochromocytoma (PC12) cell damage by mediating growth arrest and the DNA damage-45 alpha (GADD45α)/c-Jun N-terminal kinase (JNK) signaling pathway. PC12 cells were divided into a Control group (no treatment), Model group (treated with CoCl₂ for 24 h), negative control (NC) group (transfected with miR-374a negative control sequence and treated with CoCl₂ for 24 h), and miR-374a mimic group (transfected with miR-374a mimics and treated with CoCl₂ for 24 h). The viability and apoptosis of PC12 cells were determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and flow cytometry, while the mitochondrial membrane potential (MMP) and reactive oxygen species (ROS) content were assessed by Rh123 and dichloro-dihydro-fluorescein diacetate (DCFH-DA) methods. The expression of miR-374a and GADD45α/JNK proteins was detected using quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and Western blot. A significant decrease was found in the survival rate, MMP and miR-374a expression, while an increase was shown in the ROS content and GADD45α and p-JNK expression in hypoxic PC12 cells (all P < 0.05). A luciferase reporter gene assay demonstrated that GADD45α is the target gene of miR-374a. When transfected with miR-374a mimics, hypoxic PC12 cells showed an obvious elevation in survival rate and MMP but a great reduction in cell apoptosis and ROS content, as well as in the expression of GADD45α and p-JNK proteins (all P < 0.05). MiR-374a can protect PC12 cells against hypoxia-induced injury by inhibiting the GADD45α/JNK pathway, enhancing cell viability, suppressing oxidative stress, and inhibiting cell apoptosis, thereby becoming a potential therapeutic target for hypoxic damage.

Reactive Oxygen Species: Physiological and Physiopathological Effects on Synaptic Plasticity

In the mammalian central nervous system, reactive oxygen species (ROS) generation is counterbalanced by antioxidant defenses. When large amounts of ROS accumulate, antioxidant mechanisms become overwhelmed and oxidative cellular stress may occur. Therefore, ROS are typically characterized as toxic molecules, oxidizing membrane lipids, changing the conformation of proteins, damaging nucleic acids, and causing deficits in synaptic plasticity. High ROS concentrations are associated with a decline in cognitive functions, as observed in some neurodegenerative disorders and age-dependent decay of neuroplasticity. Nevertheless, controlled ROS production provides the optimal redox state for the activation of transductional pathways involved in synaptic changes. Since ROS may regulate neuronal activity and elicit negative effects at the same time, the distinction between beneficial and deleterious consequences is unclear. In this regard, this review assesses current research and describes the main sources of ROS in neurons, specifying their involvement in synaptic plasticity and distinguishing between physiological and pathological processes implicated.

Ebselen Is a Potential Anti-Osteoporosis Agent by Suppressing Receptor Activator of Nuclear Factor Kappa-B Ligand-Induced Osteoclast Differentiation In vitro and Lipopolysaccharide-Induced Inflammatory Bone Destruction In vivo

Ebselen is a non-toxic seleno-organic drug with anti-inflammatory and antioxidant properties that is currently being examined in clinical trials to prevent and treat various diseases, including atherosclerosis, stroke, and cancer. However, no reports are available for verifying the pharmacological effects of ebselen on major metabolic bone diseases such as osteoporosis. In this study, we observed that ebselen suppressed the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells in an osteoblast/osteoclast co-culture by regulating the ratio of receptor activator of nuclear factor kappa-B ligand (RANKL)/osteoprotegerin secreted by osteoblasts. In addition, ebselen treatment in the early stage of osteoclast differentiation inhibited RANKL-dependent osteoclastogenesis by decreasing the phosphorylation of IκB, PI3K, and Akt in early signaling pathways and by subsequently inducing c-Fos and nuclear factor of activated T-cells c1. Further, ebselen induced apoptosis of osteoclasts in the late stage of osteoclast differentiation. In addition, ebselen treatment suppressed filamentous actin ring formation and bone resorption activity of mature osteoclasts. Reflecting these in vitro effects, administration of ebselen recovered bone loss and its µ-CT parameters in lipopolysaccharide-mediated mouse model. Histological analysis confirmed that ebselen prevented trabecular bone matrix degradation and osteoclast formation in the bone tissues. Finally, it was proved that the anti-osteoclastogenic action of ebselen is achieved through targeting N-methyl-D-aspartate (NMDA) receptor. These results indicate that ebselen is a potentially safe drug for treating metabolic bone diseases such as osteoporosis.

Different dose-dependent effects of ebselen in sciatic nerve ischemia-reperfusion injury in rats

Ebselen is an organoselenium compound which has strong antioxidant and anti-inflammatory effects. We investigated the neuroprotective role of ebselen pretreatment in rats with experimental sciatic nerve ischemia-reperfusion (I/R) injury. Adult male Sprague Dawley rats were divided into four groups (N = 7 in each group). Before sciatic nerve I/R was induced, ebselen was injected intraperitoneally at doses of 15 and 30 mg/kg. After a 2 h ischemia and a 3 h reperfusion period, sciatic nerve tissues were excised. Tissue levels of malondialdehyde (MDA) and nitric oxide (NO), and activities of superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase (CAT) were measured. Sciatic nerve tissues were also examined histopathologically. The 15 mg/kg dose of ebselen reduced sciatic nerve damage and apoptosis (p<0.01), levels of MDA, NO, and inducible nitric oxide synthase (iNOS) positive cells (p<0.01, p<0.05, respectively), and increased SOD, GPx, and CAT activities (p<0.001, p<0.01, p<0.05, respectively) compared with the I/R group that did not receive ebselen. Conversely, the 30 mg/kg dose of ebselen increased sciatic nerve damage, apoptosis, iNOS positive cells (p<0.01, p<0.05, p<0.001) and MDA and NO levels (p<0.05, p<0.01) and decreased SOD, GPx, and CAT activities (p<0.05) compared with the sham group. The results of this study suggest that ebselen may cause different effects depending on the dose employed. Ebselen may be protective against sciatic nerve I/R injury via antioxidant and antiapoptotic activities at a 15 mg/kg dose, conversely higher doses may cause detrimental effects.

Advances in revealing the molecular targets downstream of oxidative stress-induced proapoptotic kinase signaling in diabetic embryopathy

Preexisting maternal diabetes is a high-risk factor of diabetic embryopathy, such as neural tube defects and congenital heart defects. Maternal diabetes significantly increases the production of reactive oxygen species, resulting in oxidative stress and diabetic embryopathy. Multiple cellular and metabolic factors contribute to these processes. Forkhead box O (FoxO)-3a has been demonstrated as a key transcription factor in the signaling transduction pathways responsible for maternal diabetes-induced birth defects. Apoptosis signal-regulating kinase 1 (ASK1) activated by oxidative stress stimulates nuclear translocation of FoxO3a, resulting in the overexpression of tumor necrosis factor receptor 1-associated death domain protein, which, in turn, leads to caspase-8 activation and apoptosis. Maternal diabetes-activated c-Jun N-terminal kinase (JNK)-1/2, downstream effectors of ASK1, can be blocked by superoxide dismutase-1 overexpression, suggesting that oxidative stress is responsible for JNK1/2 signaling activation. Deletion of JNK1/2 significantly suppressed the activity of FoxO3a. These observations indicate that maternal diabetes-induced oxidative stress stimulates the activation of ASK1, JNK1/2, FoxO3a, tumor necrosis factor receptor 1-associated death domain protein, caspase-8 cleavage, and finally, apoptosis and diabetic embryopathy.

SENIEUR status of the originating cell donor negates certain 'anti-immunosenescence' effects of ebselen and N-acetyl cysteine in human T cell clone cultures

Background

Damage to T cells of the immune system by reactive oxygen species may result in altered cell function or cell death and thereby potentially impact upon the efficacy of a subsequent immune response. Here, we assess the impact of the antioxidants Ebselen and N-acetyl cysteine on a range of biological markers in human T cells derived from a SENIEUR status donor. In addition, the impact of these antioxidants on different MAP kinase pathways in T cells from donors of different ages was also examined.

Methods

T cell clones were derived from healthy 26, 45 and SENIEUR status 80 year old people and the impact of titrated concentrations of Ebselen or N-acetyl cysteine on their proliferation and in vitro lifespan, GSH:GSSG ratio as well as levels of oxidative DNA damage and on MAP kinase signaling pathways was examined.

Results

In this investigation neither Ebselen nor N-acetyl cysteine supplementation had any impact on the biological endpoints examined in the T cells derived from the SENIEUR status 80 year old donor. This is in contrast to the anti-immunosenescent effects of these antioxidants on T cells from donors of 26 or 45 years of age. The analysis of MAP kinases showed that pro-apoptotic pathways become activated in T cells with increasing in vitro age and that Ebselen or N-acetyl cysteine could decrease activation (phosphorylation) in T cells from 26 or 45 year old donors, but not from the SENIEUR status 80 year old donor.

Conclusions

The results of this investigation demonstrate that the biological phenotype of SENIEUR status derived human T cells negates the anti-immunosenescence effects of Ebselen and also N-acetyl cysteine. The results highlight the importance of pre-antioxidant intervention evaluation to determine risk-benefit.

Electronic supplementary material

The online version of this article (doi:10.1186/s12979-014-0017-5) contains supplementary material, which is available to authorized users.

Baicalein prevents human prion protein-induced neuronal cell death by regulating JNK activation

Prion diseases are neurodegenerative disorders characterized by the accumulation of an abnormal isoform of the protease-insensitive isoform (PrPSc) of prion protein. Human prion protein fragment 106‑126 [PrP (106‑126)] contains most of the pathological characteristics associated with PrPSc. Although a number of compounds have been identified to inhibit PrP accumulation or dissolve fibrils and aggregates in vitro, there is currenlty no treatment available for these progressive neurodegenerative diseases. Baicalein, the dried root of Scutellaria baicalensis (S. baicalensis) Georgi (known as Huang-qin in traditional Chinese medicine) has been reported to exert neuroprotective effects on neurodegenerative diseases. In the present study, we investigated the effects of baicalein on the development of prion diseases using SH-SY5Y and SK-N-SH cells in vitro. We found that baicalein protected the cells against PrP‑induced neuronal cell death by inhibiting the production of reactive oxygen species (ROS) and mitochondrial dysfunction using ROS detection assay and MTP assay. We demonstrated that baicalein treatment regulated the phosphorylation of c-Jun N-terminal kinase (JNK) by using western blot analysis and Annexin V assay. Our data suggest that baicalein has potential for use as a therapeutic drug for the treatment of various neurodegenerative diseases, including prion diseases.

Pinocembrin protects human brain microvascular endothelial cells against fibrillar amyloid-β(1-40) injury by suppressing the MAPK/NF-κB inflammatory pathways

Cerebrovascular accumulation of amyloid-β (Aβ) peptides in Alzheimer's disease (AD) may contribute to disease progression through Aβ-induced microvascular endothelial pathogenesis. Pinocembrin has been shown to have therapeutic effects in AD models. These effects correlate with preservation of microvascular function, but the effect on endothelial cells under Aβ-damaged conditions is unclear. The present study focuses on the in vitro protective effect of pinocembrin on fibrillar Aβ₁₋₄₀ (fAβ₁₋₄₀) injured human brain microvascular endothelial cells (hBMECs) and explores potential mechanisms. The results demonstrate that fAβ₁₋₄₀-induced cytotoxicity in hBMECs can be rescued by pinocembrin treatment. Pinocembrin increases cell viability, reduces the release of LDH, and relieves nuclear condensation. The mechanisms of this reversal from Aβ may be associated with the inhibition of inflammatory response, involving inhibition of MAPK activation, downregulation of phosphor-IKK level, relief of IκBα degradation, blockage of NF-κB p65 nuclear translocation, and reduction of the release of proinflammatory cytokines. Pinocembrin does not show obvious effects on regulating the redox imbalance after exposure to fAβ₁₋₄₀. Together, the suppression of MAPK and the NF-κB signaling pathways play a significant role in the anti-inflammation of pinocembrin in hBMECs subjected to fAβ₁₋₄₀. This may serve as a therapeutic agent for BMEC protection in Alzheimer's-related deficits.

Neuroprotective effect of ebselen against intracerebroventricular streptozotocin-induced neuronal apoptosis and oxidative stress in rats

The goal of this study was to examine the neuroprotective effect of ebselen against intracerebroventricular streptozotocin (ICV-STZ)-induced oxidative stress and neuronal apoptosis in rat brain. A total of 30 adult male Sprague-Dawley rats were randomly divided into 3 groups of 10 animals each: control, ICV-STZ, and ICV-STZ treated with ebselen. The ICV-STZ group rats were injected bilaterally with ICV-STZ (3 mg/kg) on days 1 and 3, and ebselen (10 mg/kg/day) was administered for 14 days starting from 1st day of ICV-STZ injection to day 14. Rats were killed at the end of the study and brain tissues were removed for biochemical and histopathological investigation. Our results demonstrated, for the first time, the neuroprotective effect of ebselen on Alzheimer's disease (AD) model in rats. Our present study, in ICV-STZ group, showed significant increase in tissue malondialdehyde levels and significant decrease in enzymatic antioxidants superoxide dismutase and glutathione peroxidase in the frontal cortex tissue. The histopathological studies in the brain of rats also supported that ebselen markedly reduced the ICV-STZ-induced histopathological changes and well preserved the normal histological architecture of the frontal cortex tissue. The number of apoptotic neurons was increased in frontal cortex tissue after ICV-STZ administration. Treatment of ebselen markedly reduced the number of degenerating apoptotic neurons. The study demonstrates the effectiveness of ebselen, as a powerful antioxidant, in preventing the oxidative damage and morphological changes caused by ICV-STZ in rats. Thus, ebselen may have a therapeutic value for the treatment of AD.

An investigation of the effects of the antioxidants, ebselen or N-acetyl cysteine on human peripheral blood mononuclear cells and T cells

BACKGROUND

The research literature has documented age-related increases in genetic damage, including oxidative DNA damage, in human T lymphocytes, in vitro and ex vivo. Such damage has the potential to interfere with the ability of the T cells to proliferate at times when they need to, such as when antigen challenged. The consequence of this could be a sub-optimal immune response in vivo.

CONTEXT AND PURPOSE

The purpose of the research reported in this paper was to investigate the impact of two antioxidants, which can be administered in vivo, Ebselen and N-acetyl L-cysteine, on the age-related increase in genetic damage, and on T cell proliferation and lifespan. In vitro human T cell clones, ex vivo peripheral blood mononuclear cells or T cells were supplemented with different concentrations of antioxidants, under standard conditions and for different periods of time. A range of assays were then applied in order to determine any impact of the antioxidants.

RESULTS

30 μM ebselen or 7.5 mM N-acetyl L-cysteine supplementation resulted in a significantly higher intracellular GSH: GSSG ratio. This increased ratio was accompanied by reduced levels of oxidative DNA damage in established CD4+ human T cell clones, from a young or a middle-aged donor. Additionally, cultures of primary human peripheral blood mononuclear cells and CD4+ T cells from donors aged 25-30 or 55-60 years were also supplemented with these agents. Cells from all sources exhibited increased proliferation, and in the case of the T cell clones, an increase in cumulative population doublings. Neither ebselen nor N-acetyl L-cysteine had such effects on clones supplemented from the midpoint of their in vitro lifespan.

CONCLUSIONS

Ebselen and N-acetyl L-cysteine, under certain conditions, may have anti-immunosenescent potential in T cells in in vitro clonal and ex vivo polyclonal culture models.

Novel pathways and therapies in experimental diabetic atherosclerosis

Diabetic subjects are at a greater risk of developing major vascular complications due to abnormalities pertinent to the diabetic milieu. Current treatment options achieve significant improvements in glucose levels and blood pressure control, but do not necessarily prevent or retard diabetes-mediated macrovascular disease. In this review, we highlight several pathways that are increasingly being appreciated as playing a significant role in diabetic vascular injury. We focus particularly on the advanced glycation end product/receptor for advanced glycation end product (AGE/RAGE) axis and its interplay with the nuclear protein HMGB1. We discuss evidence implicating a significant role for the renin-angiotensin system, urotensin II and PPAR, as well as the importance of proinflammatory mediators and oxidative stress in cardiovascular complications. The specific targeting of these pathways may lead to novel therapies to reduce the burden of diabetic vascular complications.

The adaptor protein SH2B1β reduces hydrogen peroxide-induced cell death in PC12 cells and hippocampal neurons

Background

SH2B1β is a signaling adaptor protein that has been shown to promote neuronal differentiation in PC12 cells and is necessary for the survival of sympathetic neurons. However, the mechanism by which SH2B1β may influence cell survival is not known.

Results

In this study, we investigated the role of SH2B1β in oxidative stress-induced cell death. Our results suggest that overexpressing SH2B1β reduced H₂O₂-induced, caspase 3-dependent apoptosis in PC12 cells and hippocampal neurons. In response to H₂O₂, overexpressing SH2B1β enhanced PI3K (phosphatidylinositol 3-kinas)-AKT (protein kinase B) and MEK (MAPK/ERK kinase)-extracellular-signal regulated kinases 1 and 2 (ERK1/2) signaling pathways. We further demonstrated that SH2B1β was able to reduce H₂O₂-induced nuclear localization of FoxO1 and 3a transcription factors, which lie downstream of PI3K-AKT and MEK-ERK1/2 pathways. Moreover, overexpressing SH2B1β reduced the expression of Fas ligand (FasL), one of the target genes of FoxOs.

Conclusions

Overexpressing the adaptor protein SH2B1β enhanced H₂O₂-induced PI3K-AKT and MEK-ERK1/2 signaling, reduced nucleus-localized FoxOs and the expression of a pro-apoptotic gene, FasL.

Antioxidants induce apoptosis of rat ovarian theca-interstitial cells

Regulation of growth of ovarian theca-interstitial tissues is essential for normal ovarian development and function. Reactive oxygen species are involved in modulation of signal transduction pathways, including regulation of tissue growth and apoptosis. Previously, we have demonstrated that antioxidants inhibit proliferation of theca-interstitial cells. This report evaluates the effects of antioxidants on apoptosis of rat theca-interstitial cells. The cells were cultured in chemically defined media without or with vitamin E succinate and ebselen. Apoptosis was evaluated by cytochemical assessment of nuclear morphology, activity of executioner caspases 3 and 7, and determination of staining with annexin V in combination with propidium iodide. Both tested antioxidants induced significant morphological changes consistent with apoptosis, including chromatin condensation, nuclear shrinkage, and pyknosis. Antioxidants also induced other hallmarks of apoptosis including increased activity of caspases 3/7 as well as increased staining with annexin V. The present findings demonstrate that antioxidants with distinctly different mechanisms of action induce a series of events consistent with the process of apoptosis in ovarian mesenchyme. These observations may be of translational-clinical relevance, providing mechanistic support for the use of antioxidants in the treatment of PCOS, a condition associated with excessive growth and activity of theca-interstitial cells.

Effect of angiotensin II on iron-transporting protein expression and subsequent intracellular labile iron concentration in human glomerular endothelial cells

Angiotensin II (Ang II)-induced endothelial injury, which is associated with atherosclerosis, is believed to be mediated by intracellular reactive oxygen species (ROS) through stimulation of nicotinamide adenine dinucleotide phosphate oxidase (NOX). Iron is essential for the amplification of oxidative stress. In this study, we investigated whether Ang II altered iron metabolism and whether the Ang II-induced endothelial injury is attributable to changes in iron metabolism of human glomerular endothelial cells (HGECs). When 90% iron-saturated human transferrin (90% Tf) was applied to HGECs without Ang II, the labile ferrous iron level was same as the effect of control in spite of a significant increase in the total cellular iron concentration. Treatment with Ang II and 30% Tf or 90% Tf significantly (P<0.01) increased the intracellular iron concentration, as well as labile ferrous iron and protein oxidation levels, compared with the effect of separate administration of each compound. Ang II treatment facilitated the protein expression of the Tf receptor, divalent metal transporter 1, and ferroportin 1 in a dose- and time-dependent manner. It was also found that simultaneous exposure of HGECs to Ang II and 90% Tf accelerated hydroxyl radical production, as shown by using an electron paramagnetic resonance spectrometer. These results suggest that Ang II not only induces production of ROS by NOX activation but also iron incorporation followed by an increase in labile iron in HGECs. Both of these events may participate in the progression of oxidative stress because of endothelial cell dysfunction through ferrous iron-mediated ROS generation.

Protection by tetrahydroxystilbene glucoside against cerebral ischemia: involvement of JNK, SIRT1, and NF-kappaB pathways and inhibition of intracellular ROS/RNS generation

Many natural polyphenolic compounds have been shown to attenuate reactive oxygen/nitrogen species (ROS/RNS) formation and protect against ischemia/reperfusion injury both in vitro and in vivo. 2,3,5,4'-tetrahydroxystilbene-2-O-beta-D-glucoside (TSG), an active component of the rhizome extract from Polygonum multiflorum, exhibits antioxidative and anti-inflammatory effects. Here, we used an in vitro ischemic model of oxygen-glucose deprivation followed by reperfusion (OGD-R) and an in vivo ischemic model of middle cerebral artery occlusion (MCAO) to investigate the neuroprotective effects of TSG on ischemia/reperfusion brain injury and the related mechanisms. We demonstrated that OGD-R-induced neuronal injury, intracellular ROS generation, and mitochondrial membrane potential dissipation were reversed by TSG. The elevation of H2O2-induced [Ca2+]i was also attenuated by TSG. Inhibition of the c-Jun N-terminal kinase (JNK) and Bcl-2 family-related apoptotic signaling pathway was involved in the neuroprotection afforded by TSG. Meanwhile, TSG inhibited iNOS mRNA expression induced by OGD-R, which may be mediated by the activation of SIRT1 and inhibition of NF-kappaB activation. In vivo studies further demonstrated that TSG significantly reduced the brain infarct volume and the number of positive cells by TUNEL staining in the cerebral cortex compared to the MCAO group. Our study indicates that TSG protects against cerebral ischemia/reperfusion injury through multifunctional cytoprotective pathways.

Blockade of the translocation and activation of c-Jun N-terminal kinase 3 (JNK3) attenuates dopaminergic neuronal damage in mouse model of Parkinson's disease

Increasing evidence suggests that c-Jun N-terminal kinase (JNK) is an important kinase mediating neuronal death in Parkinson's disease (PD) model induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). JNK3, the only neural-specific isoform, may play an important role in mediating the neurotoxic effects of MPTP in dopaminergic neuronal injury. To analyze the variation in JNK3 activation, the levels of phospho-JNK3 were measured at the various time points of occurrence of MPTP-induced lesions. In our study, we observed that during MPTP intoxication, two peaks of JNK3 activation appeared at 8 and 24h. To further define the mechanism of JNK3 activation and translocation, the antioxidant N-acetylcysteine (NAC), the N-methyl-D-aspartate (NMDA) receptor antagonist ketamine, and the alpha-amino-3-hydroxyl-5-methyl-4-isoxazolepropionic acid (AMPA)/kainate (KA) receptor antagonist 6,7-dinitroquinoxaline-2,3(1H,4H)-dione (DNQX) were administered to the mice 30 min after each of the four MPTP injections. The results revealed that NAC clearly inhibited JNK3 activation during the early intoxication, whereas ketamine preferably attenuated JNK3 activation during the latter intoxication. DNQX had no significant effects on JNK3 activation during intoxication. Consequently, reactive oxygen species (ROS) and the NMDA receptor were closely associated with JNK3 activation following MPTP intoxication. NAC and ketamine exerted a preventive effect against MPTP-induced loss of tyrosine hydroxylase-positive neurons and suppressed the nuclear translocation of JNK3, suggesting that NAC and ketamine can prevent MPTP-induced dopaminergic neuronal death by suppressing JNK3 activation.

Satratoxin H generates reactive oxygen species and lipid peroxides in PC12 cells

Satratoxin H, a mycotoxin, is thought to induce apoptosis of PC12 cells through the activation of p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) in a glutathione (GSH)-sensitive manner. The present study was undertaken to further elucidate the mechanism by which satratoxin H induces cell death in PC12 cells. Satratoxin H caused apoptosis of PC12 cells within 24-h, as determined by DNA fragmentation and flow cytometric analysis. Satratoxin H increased reactive oxygen species (ROS) production and lipid peroxidation, as determined by malondialdehyde formation. These effects were attenuated by incubation of cells with GSH, suggesting that satratoxin H-induced increase in apoptosis of serum-deprived PC12 cells may be partially mediated through the generation of ROS.

Selenium compounds counteract the stimulation of ecto-nucleotidase activities in rat cultured cerebellar granule cells: putative correlation with neuroprotective effects

Glutamate is the main excitatory neurotransmitter in brain involved in pathophysiology of several brain injuries. In this context, glutamate showed to stimulate ecto-nucleotidase activities in cerebellar granule cells increasing extracellular adenosine levels, an important neuromodulator in the CNS able to prevent cell damage. The organoselenium compounds, such as ebselen and diphenyl diselenide [(PhSe)(2)], display neuroprotective activities mediated at least in part by their antioxidant and anti-inflammatory properties. Ebselen was described to prevent glutamate-induced lipid peroxidation and cell death in cerebellar granule cells and (PhSe)(2) modify glutamatergic synapse parameters in vitro and in vivo. In the present study, we investigated the effects of ebselen or (PhSe)(2) on glutamate-induced stimulation of ecto-nucleotidase activities in rat cultured cerebellar granule cells. Glutamate increased nucleotide hydrolysis at lower concentrations (10 and 100 microM) than described in the literature and this effect was counteracted by both organoselenium compounds tested. Based on these results, we investigated the association of organoselenium effects with their antioxidant properties searching for redox site modulation by using the alkylant agent N-ethylmaleimide (NEM). Our results suggest that selenium compounds, as well as the well-known antioxidant trolox, can avoid the increase on glutamate-induced stimulation of ecto-nucleotidase activities probably due to their antioxidant properties.

Defects in tongue papillae and taste sensation indicate a problem with neurotrophic support in various neurological diseases

Neurotrophic support of developing neurons by neurotrophins is of critical importance in the development of fungiform papillae and taste buds. A number of neurological disorders show a decrease or increase in fungiform papillae or taste sensation. These can be grouped into disorders with reduced papillae (Machado-Joseph disease, Stüve-Wiedemann syndrome, familial dysautonomia, dystonia musculorum, and Behçet's disease) and those with taste defects only (Alzheimer's disease, Huntington's disease, hereditary sensory and autonomic neuropathy type IV, and diabetes mellitus). In addition, Parkinson's disease results in increased taste sensation. Here, we hypothesize that the main problem in these disorders is either not enough or too much neurotrophic support. Proneurotrophic drugs such as some antidepressants and aldose reductase inhibitors may prove useful in the treatment of these sensory and central nervous system disorders. Similarly, antineurotrophic drugs may also be useful in Parkinson's disease. Here we show that the protein involved in familial dysautonomia, IKAP, localizes to keratin filaments in HeLa cells, suggesting a role for the keratin cytoskeleton in neurotrophic support.

Cocoa procyanidins protect PC12 cells from hydrogen-peroxide-induced apoptosis by inhibiting activation of p38 MAPK and JNK

Oxidative stress induced by reactive oxygen species has been strongly associated with the pathogenesis of neurodegenerative disorders, including Alzheimer's disease. In this study, we investigated the possible protective effects of a cocoa procyanidin fraction (CPF) and procyanidin B2 (epicatechin-(4beta-8)-epicatechin) - a major polyphenol in cocoa - against apoptosis of PC12 rat pheochromocytoma (PC12) cells induced by hydrogen peroxide (H(2)O(2)). CPF (1 and 5 microg/ml) and procyanidin B2 (1 and 5 microM) reduced PC12 cell death caused by H(2)O(2), as determined by MTT and trypan blue exclusion assays. CPF and procyanidin B2 attenuated the H(2)O(2)-induced fragmentation of nucleus and DNA in PC12 cells. Western blot data demonstrated that H(2)O(2) induced cleavage of poly(ADP-ribose)polymerase (PARP), downregulated Bcl-X(L) and Bcl-2 in PC12 cells. Pretreatment with CPF or procyanidin B2 before H(2)O(2) treatment diminished PARP cleavage and increased Bcl-X(L) and Bcl-2 expression compared with those only treated with H(2)O(2). Activation of caspase-3 by H(2)O(2) was inhibited by pretreatment with CPF or procyanidin B2. Furthermore, H(2)O(2)-induced rapid and significant phosphorylation of c-Jun N-terminal protein kinase (JNK) and p38 mitogen-activated protein kinase (MAPK), and both of these effects were attenuated by CPF or procyanidin B2 treatment. These results suggest that the protective effects of CPF and procyanidin B2 against H(2)O(2)-induced apoptosis involve inhibiting the downregulation of Bcl-X(L) and Bcl-2 expression through blocking the activation of JNK and p38 MAPK.

Nitric oxide-induced apoptosis in cultured rat astrocytes: protection by edaravone, a radical scavenger

Nitric oxide induces apoptosis-like cell death in cultured astrocytes, but the exact mechanism is not known. This study further characterized the mechanism of nitric oxide-induced cytotoxicity, and examined the effect of edaravone, a radical scavenger, on cytotoxicity. Treatment of cultured rat astrocytes with sodium nitroprusside (SNP), a nitric oxide donor, for 72 h, decreased cell viability by causing apoptosis-like cell death. The injury was accompanied by increases in the production of reactive oxygen species and in the level of nuclear apoptosis-inducing factor, but not in caspase activity. SNP-induced cytotoxicity was blocked by the c-jun N-terminal protein kinase (JNK) inhibitor SP600125 (20 microM), the p38 mitogen-activated protein (MAP) kinase inhibitor SB203580 (20 microM), and the extracellular signal-regulating kinase (ERK) inhibitor U0126 (10 microM), and the nitric oxide donor stimulated the phosphorylation of p38 MAP kinase, JNK, and ERK. Edaravone (10 microM) protected astrocytes against SNP-induced cell injury and it inhibited SNP-induced phosphorylation of p38 MAP kinase, JNK, and ERK, and the production of reactive oxygen species. Edaravone also attenuated SNP-induced increase in nuclear apoptosis-inducing factor levels. These results suggest that MAP kinase pathways play a key role in nitric oxide-induced apoptosis and that edaravone protects against nitric oxide-induced cytotoxicity by inhibiting nitric oxide-induced MAP kinase activation in astrocytes.

Calcium release by ryanodine receptors mediates hydrogen peroxide-induced activation of ERK and CREB phosphorylation in N2a cells and hippocampal neurons

Hydrogen peroxide, which stimulates ERK phosphorylation and synaptic plasticity in hippocampal neurons, has also been shown to stimulate calcium release in muscle cells by promoting ryanodine receptor redox modification (S-glutathionylation). We report here that exposure of N2a cells or rat hippocampal neurons in culture to 200 microM H2O2 elicited calcium signals, increased ryanodine receptor S-glutathionylation, and enhanced both ERK and CREB phosphorylation. In mouse hippocampal slices, H2O2 (1 microM) also stimulated ERK and CREB phosphorylation. Preincubation with ryanodine (50 microM) largely prevented the effects of H2O2 on calcium signals and ERK/CREB phosphorylation. In N2a cells, the ERK kinase inhibitor U0126 suppressed ERK phosphorylation and abolished the stimulation of CREB phosphorylation produced by H2O2, suggesting that H2O2 enhanced CREB phosphorylation via ERK activation. In N2a cells in calcium-free media, 200 microM H2O2 stimulated ERK and CREB phosphorylation, while preincubation with thapsigargin prevented these enhancements. These combined results strongly suggest that H2O2 promotes ryanodine receptors redox modification; the resulting calcium release signals, by enhancing ERK activity, would increase CREB phosphorylation. We propose that ryanodine receptor stimulation by activity-generated redox species produces calcium release signals that may contribute significantly to hippocampal synaptic plasticity, including plasticity that requires long-lasting ERK-dependent CREB phosphorylation.

Synthesis and enhanced neuroprotective activity of C60-based ebselen derivatives

A C60-based ebselen derivative 4 was synthesized through the cycloaddition of C60 with the azide (3) containing the ebselen component. It was obtained in a four-step synthesis starting from 2-(chloroseleno)benzoyl chloride and 2-(2-aminoethoxy)ethanol in 53% yield (based on consumed C60). Its structure was characterized by 1H NMR, 13C NMR, IR, UV, and FAB-MS. To verify that the C60-based ebselen derivative 4 had enhanced antioxidative and neuroprotective activity, the C60 derivative 5 and the ebselen derivative 6 were selected to treat cortical neuronal cells using the same procedures as with the C60-based ebselen derivative 4. The cellular viability of different derivative treatment groups was estimated by LDH leakage assay and MTT assay. At the same final concentration (30 µmol/L), the results showed that the antioxidative and protective potencies of the C60-based ebselen derivative 4 (MTT (OD) 0.340 ± 0.035, LDH release (UL–1) 4.80 ± 0.16) against H2O2-mediated neuronal injury have an advantage over those of C60 derivative 5 (MTT (OD) 0.297 ± 0.036, LDH release (UL–1) 5.37 ± 0.31) and ebselen derivative 6 (MTT (OD) 0.267 ± 0.027, LDH release (UL–1) 5.85 ± 0.26). Correspondingly, the GPX activity of 4 (1.62 U/µmol) was higher than that of 5 (0.77 U/µmol) and 6 (1.24 U/µmol). These findings demonstrate that the incorporation of two components with similar biological activity (C60 component and ebselen component) may be a desirable way of obtaining a new and more biologically effective C60-based compound.Key words: fullerene, ebselen derivative, azide, neuroprotective activity, cellular viability.

A role for reactive oxygen/nitrogen species and iron on neuronal synaptic plasticity

A great body of experimental evidence collected over many years indicates that calcium has a central role in a variety of neuronal functions. In particular, calcium participates in synaptic plasticity, a neuronal process presumably correlated with cognitive brain functions such as learning and memory. In contrast, only recently, evidence has begun to emerge supporting a physiological role of reactive oxygen (ROS) and nitrogen (RNS) species in synaptic plasticity. This subject will be the central topic of this review. The authors also present recent results showing that, in hippocampal neurons, ROS/RNS, including ROS generated by iron through the Fenton reaction, stimulate ryanodine receptor-mediated calcium release, and how the resulting calcium signals activate the signaling cascades that lead to the transcription of genes known to participate in synaptic plasticity. They discuss the possible participation of ryanodine receptors jointly stimulated by calcium and ROS/RNS in the normal signaling cascades needed for synaptic plasticity, and how too much ROS production may contribute to neurodegeneration via excessive calcium release. In addition, the dual role of iron as a necessary, but potentially toxic, element for normal neuronal function is discussed.

Selenazoles (selenium compounds) facilitate survival of cultured rat pheochromocytoma PC12 cells after serum-deprivation and stimulate their neuronal differentiation via activation of Akt and mitogen-activated protein kinase, respectively

The activation of extracellular receptor kinase (ERK) is one of the checkpoints to assess the activation of the classical Ras/mitogen-activated protein kinase (MAPK) cascade. Therefore, we tested more than 100 selenium-containing compounds for their ability to activate the MAPK signal pathway. Among them, we found that three selenazoles, 5-chloroacetyl-2-piperidino-1,3-selenazole (CS1), 5-chloroacetyl-2-morpholino-1,3-selenazole (CS2), and 5-chloroacetyl-2-dimethylamino-1,3-selenazole (CS3), induced the phosphorylation of ERK. These compounds also enhanced the phosphorylation of Akt, a signal transducing protein kinase for cell survival; and this phosphorylation was followed by suppression of cell death, thus suggesting that they had anti-apoptotic effects. Moreover, CSs 1-3 induced neurite outgrowth and facilitated the expression of neurofilament-M of PC12 cells, demonstrating that they induced neuronal differentiation of these cells. On the other hand, the CS-induced phosphorylation of MAPK was enhanced by buthionine sulfoximine (BSO), an activator of protein tyrosine phosphatases (PTPs), but inhibited by N-acetyl-l-cysteine (NAC), an inhibitor of receptor tyrosine kinase. These results imply that activation of some receptor tyrosine kinase(s) is involved in the mechanism of action of CSs 1-3. The activation of MAPK by CSs 1-3 was suppressed by U0126, a MEK inhibitor, but not by K252a, an inhibitor of TrkA; AG1478, an antagonist of epidermal growth factor receptor (EGFR); or by pertussis toxin. These results demonstrate that the CS-induced phosphorylation of Akt and MAP kinase (receptor tyrosine kinase(s)-MEK1/2-ERK1/2) cascades was responsible for suppression of apoptosis and facilitation of neuronal differentiation of PC12 cells, respectively. Our results suggest that CSs 1-3 are promising candidates as neuroprotective and/or neurotrophic agents for the treatment of various neurodegenerative neurological disorders.

Antioxidant N-acetylcysteine inhibits the activation of JNK3 mediated by the GluR6-PSD95-MLK3 signaling module during cerebral ischemia in rat hippocampus

Cerebral ischemia induces kainate receptor glutamate receptor 6 (GluR6) binding to the postsynaptic density protein 95 (PSD95), which in turn anchors mixed lineage kinase 3 (MLK3) via SH3 domain in rat brain. MLK3 subsequently activates c-Jun NH(2)-terminal kinase (JNK) via MAP kinase kinases (MKKs). In this study, we investigated the association of PSD95 with GluR6 and MLK3, the autophosphorylation of MLK3, the combination of MLK3 with JNK3, and the phosphorylation of JNK3 during cerebral ischemia in rat hippocampus CA1. Our results indicate that the GluR6-PSD95-MLK3 complex quickly enhanced at 5 min of ischemia and peaked at 10 min of ischemia, and then gradually reduced with the prolonged time of ischemia. Interestingly, the combination of MLK3 and JNK3 gradually increased from 5 min to 30 min of ischemia. JNK3 phosphorylation first increased and then attenuated in cytosol, suggesting the translocation of activated JNK3 to nucleus during ischemia. To further investigate the possible mechanism of JNK3 activation, antioxidant N-acetylcysteine (NAC) was given to the rats 20 min prior to ischemia. Results indicate that NAC distinctly inhibited the association of PSD95 with GluR6 and MLK3, the autophosphorylation of MLK3, the combination of MLK3 with JNK3 and JNK3 activation. Taken together, these finding indicate that ischemic stimulation results in JNK3 activation through the GluR6-PSD95-MLK3 signaling module, and that the activation of JNK3 is closely related to oxidative stress.

Horseradish peroxidase inhibition and antioxidant activity of ebselen and related organoselenium compounds

Horseradish peroxidase (HRP) inhibition and glutathione peroxidase (GPx) activities of ebselen and some related derivatives are described. These studies show that ebselen and ebselen ditelluride (EbTe(2)) with significant antioxidant activity, inhibit the HRP-catalyzed oxidation reactions. In addition, inhibition of lipid peroxidation and singlet oxygen quenching studies were carried out. Although the inhibition of HRP by ebselen is comparable with that of EbTe(2), the inhibitory effect on gamma-radiation induced lipid peroxidation and the GPx activity of ebselen is found to be much higher than that of EbTe(2).

Blockade of the translocation and activation of mitogen-activated protein kinase kinase 4 (MKK4) signaling attenuates neuronal damage during later ischemia-reperfusion

Mitogen-activated protein kinase kinase 4 (MKK4), as an upstream activator of c-Jun NH(2)-terminal kinase (JNK), plays a critical role in response to cellular stresses and pro-inflammatory cytokines. In this study, we investigated the subcellular localization and activation of MKK4 in response to global cerebral ischemia. Our results indicated that MKK4 had two activation peaks in both the cytosol and the nucleus, and translocated from the cytosol to the nucleus at 30 min and 6 h of reperfusion. We also detected the interaction of JNK-interacting protein 3 (JIP3) and MKK4, which reached a maximum at 6 h of reperfusion. To elucidate the mechanism of translocation and activation, we administered N-acetylcysteine, an antioxidant reagent, and a glutamate receptor 6 C-terminus-containing peptide (Tat-GluR6-9c) to rats. The data showed that N-acetylcysteine limited the translocation and activation at 30 min of reperfusion; however, the peptide perturbed the subcellular localization and activation at 6 h of reperfusion, and subsequently provided a protective role against delayed neuronal cell death. Taken together, these results demonstrate that the translocation and activation of MKK4 during early reperfusion are closely associated with reactive oxygen species, whereas, at late reperfusion, MKK4 activation may be involved in brain ischemic injury.

N-acetylcysteine selectively protects cerebellar granule cells from 4-hydroxynonenal-induced cell death

4-hydroxynonenal (HNE), an aldehydic product of membrane lipid peroxidation, has been shown to induce neurotoxicity accompanied by multiple events. To clarify mechanisms of neuroprotective compounds on HNE-induced toxicity, the protective effects of N-acetylcysteine (NAC), alpha-tocopherol (TOC), ebselen and S-allyl-L-cysteine (SAC) were compared in cerebellar granule neurons. The decrease in MTT reduction induced by HNE was significantly suppressed by pretreatment of the neurons with 1000 microM NAC or 10 and 100 microM TOC; however, lactate dehydrogenase (LDH) release and propidium iodide (PI) fluorescence studies revealed that neuronal death was suppressed by NAC but not by TOC. Treatment of these neurons with HNE resulted in a drastic reduction of mitochondrial membrane potential, and this reduction was also prevented by NAC but not by TOC. Ebselen and SAC, a garlic compound, were unable to protect these neurons against HNE-induced toxicity. Pretreatment with NAC also prevented HNE-induced depletion of intracellular glutathione (GSH) levels in these neurons. These results suggest that NAC, but not other antioxidants such as TOC, SAC and ebselen, exerts significant protective effects against HNE-induced neuronal death in cerebellar granule neurons, and that this neuroprotective effect is due, at least in part, to preservation of mitochondrial membrane potential and intracellular GSH levels.