过氧化氢预处理对抗氧化应激诱导的PC12细胞凋亡

氧化应激可明显地诱导细胞凋亡。本研究旨在探讨H2O2预处理能否对H2O2诱导的PC12细胞凋亡生产保护作用及ATP敏感性K^ （ATP-sensitive potassinm,KATP）通道在其中的作用。采用PI染色流式细胞仪（flow cytometry, FCM）检测PC12细胞凋亡。结果表明,经10μmol/L H2O2预处理90min的PC12细胞,分别在20、30、50和100μmol/L H2O2作用24h后,其细胞凋亡率明显下降,与未经H2O2的预处理的PC12细胞相比,差异极显著（P＜0.01）,表明H2O2预处理对H2O2诱导PC12细胞凋亡具有保护作用。用10μmol/L的KATP通道激动齐pinacidil(Pin)可显著减少30和50μmol/L H2O2诱导的PC12细胞凋亡,10μmol/L的KATP通道拮抗齐glybenclamide（Gly）则可显著地抑制甚至取消KATP通道激动剂Pin对H2O3诱导PC12细胞凋亡的保护作用,但并不影响H2O2预处理对H2O2诱导PC12细胞凋亡的保护作用;然而,当联合应用H2O2预处理与Pin时,对PC12细胞凋亡的保护作用显大于各自的细胞凋亡作用。提示KATP通道开放不仅对H2O2诱导PC12细胞凋亡具有保护作用,而且与H2O2预处理一起产生抗PC12细胞凋亡的协同作用。但KATP通道开放可能不参与H2O2预处理的适应性保护作用。     

Protective effect of resveratrol on beta-amyloid-induced oxidative PC12 cell death

Beta-amyloid peptide is considered to be responsible for the formation of senile plaques that accumulate in the brains of patients with Alzheimer's disease. There has been compelling evidence supporting the idea that beta-amyloid-induced cytotoxicity is mediated through the generation of reactive oxygen intermediates (ROIs). Considerable attention has been focused on identifying phytochemicals that are able to scavenge excess ROIs, thereby protecting against oxidative stress and cell death. Resveratrol (3,5,4'-trihydroxy-trans-stilbene), a phytoalexin found in the skin of grapes, has strong antioxidative properties that have been associated with the protective effects of red wine consumption against coronary heart disease ("the French paradox"). In this study, we have investigated the effects of resveratrol on beta-amyloid-induced oxidative cell death in cultured rat pheochromocytoma (PC12) cells. PC12 cells treated with beta-amyloid exhibited increased accumulation of intracellular ROI and underwent apoptotic death as determined by characteristic morphological alterations and positive in situ terminal end-labeling (TUNEL staining). Beta-amyloid treatment also led to the decreased mitochondrial membrane potential, the cleavage of poly(ADP-ribose)polymerase, an increase in the Bax/Bcl-X(L) ratio, and activation of c-Jun N-terminal kinase. Resveratrol attenuated beta-amyloid-induced cytotoxicity, apoptotic features, and intracellular ROI accumulation. Beta-amyloid transiently induced activation of NF-kappaB in PC12 cells, which was suppressed by resveratrol pretreatment.     

Bcl-2 protects against Abeta(25-35)-induced oxidative PC12 cell death by potentiation of antioxidant capacity

A substantial body of data indicates that reactive oxygen intermediates (ROIs) are implicated in pathogenesis of diverse human diseases. Oxidative stress induced by ROIs often causes cell death via apoptosis that is regulated by a plenty of functional genes and their protein products. Bcl-2 is one such protein that blocks apoptosis induced by various death stimuli. In spite of extensive research, the molecular mechanisms underlying antiapoptotic function of Bcl-2 are not fully clarified. In the present work, we have investigated the role of bcl-2 in protecting against beta-amyloid (Abeta)-induced oxidative death in rat pheochromocytoma (PC12) cells. Transfection with the antiapoptotic bcl-2 gene rescued PC12 cells from apoptotic death induced by Abeta. Addition of an NF-kappaB inhibitor, such as pyrrolidine dithiocarbamate or N-tosyl-l-phenylalanine chloromethyl ketone, to the media aggravated Abeta-induced PC12 cell death. PC12 cells overexpressing bcl-2 exhibited higher levels of constitutively activated NF-kappaB compared with vector-transfected controls, which appear to be mediated by the elevated activation of Akt/protein kinase B. The ectopic expression of bcl-2 enhanced both the expression and the activity of catalase, which were attenuated by NF-kappaB blockers. These results suggest that NF-kappaB plays a role in bcl-2-mediated protection against Abeta-induced apoptosis in PC12 cells through augmentation of cellular antioxidant capacity.     

Piceatannol attenuates hydrogen-peroxide- and peroxynitrite-induced apoptosis of PC12 cells by blocking down-regulation of Bcl-XL and activation of JNK

There is mounting evidence implicating the accumulation of intracellular reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the pathogenesis of neurodegenerative disorders, including Alzheimer's disease. Recently, considerable attention has been focused on identifying naturally occurring antioxidants that are able to reduce excess ROS and RNS, thereby protecting against oxidative stress and neuron death. The present study investigated the possible protective effects of piceatannol (trans-3,4,3',5'-tetrahydroxystilbene), which is present in grapes and other foods, on hydrogen-peroxide- and peroxynitrite-induced oxidative cell death. PC12 rat pheochromocytoma (PC12) cells treated with hydrogen peroxide or SIN-1 (a peroxynitrite-generating compound) exhibited apoptotic death, as determined by nucleus condensation and cleavage of poly(ADP-ribose)polymerase (PARP). Piceatannol treatment attenuated hydrogen-peroxide- and peroxynitrite-induced cytotoxicity, apoptotic features, PARP cleavage and intracellular ROS and RNS accumulation. Treatment of PC12 cells with hydrogen peroxide or SIN-1 led to down-regulation of Bcl-X(L) and activation of caspase-3 and -8, which were also inhibited by piceatannol treatment. Hydrogen peroxide or SIN-1 treatment induced phosphorylation of the c-Jun-N-terminal kinase (JNK), which was inhibited by piceatannol treatment. Moreover, SP600125 (a JNK inhibitor) significantly inhibited hydrogen-peroxide- and peroxynitrite-induced PC12 cell death, revealing inactivation of the JNK pathway as a possible molecular mechanism for the protective effects of piceatannol against hydrogen-peroxide- and peroxynitrite-induced apoptosis of PC12 cells. Collectively, these findings suggest that the protective effect of piceatannol against hydrogen-peroxide- and peroxynitrite-induced apoptosis of PC12 cells is associated with blocking the activation of JNK and the down-regulation of Bcl-XL.     

Hydrogen peroxide preconditioning protects PC12 cells against apoptosis induced by dopamine

Dopamine (DA), one of the major sources of reactive oxygen species (ROS), is implicated in neuronal death associated with Parkinson's disease (PD). Preconditioning with oxidative stress has been shown to provide cytoprotection similar to ischemic preconditioning (IPC), against cell apoptosis. In this study, using the model neurosecretory cell line, PC12, we investigated whether hydrogen peroxide (H(2)O(2)) at low concentration (10 microM) can protect PC12 cells against apoptosis induced by DA. PC12 cells were preconditioned with 10 microM H(2)O(2) for 90 min, followed by 24-h recovery and subsequent exposures to different concentrations (20, 50, 100 and 200 microM) of DA for 24-h, respectively. DA induced apoptotic cell death with significant morphological nuclear changes and DNA fragmentation as well as the dysfunction of mitochondria. Preconditioning with H(2)O(2) at 10 microM significantly reduced the percentage of apoptotic cells and partly blocked the decreases in 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) reduction and mitochondrial membrane potential (MMP) induced by DA. These results suggest that preconditioning with low concentration of H(2)O(2) protected PC12 cells against DA-induced apoptosis, the part restoration of the damaged mitochondrial functions might be one of the underlying mechanisms of this cytoprotection.     

A novel apoptotic cascade mediated by CDK4 in rat pheochromocytoma PC12 cells.

Apoptosis induced by serum withdrawal in pheochromocytoma PC12 cells is promoted by overexpression of cyclin-dependent kinase 4 (CDK4). We compared CDK4-promoted apoptosis with that induced by serum withdrawal alone in PC12 cells. Protein synthesis inhibitors did not prevent apoptosis in parental cells, but prevented the promotion of apoptosis by CDK4 overexpression. Nerve growth factor, basic-fibroblast growth factor, and Bcl-2 proteins protected both parental and CDK4-overexpressing cells from apoptosis. However, insulin-like growth factor-I and Bcl-X(L) protein only partially inhibited apoptosis in the CDK4-overexpressing cells. Bcl-2 or Bcl-X(L) had no significant effect on CDK4 kinase activity in both cell lines. These results suggest a novel CDK4-mediated apoptotic cascade which is normally restrained, but which is activated by CDK4 overexpression. This apoptotic cascade should eventually converge with the cascade induced by serum withdrawal in normal PC12 cells. We discuss the interactions among these apoptotic cascades and the points where anti-apoptotic agents act.     

The prevention of the staurosporine-induced apoptosis by Bcl-XL, but not by Bcl-2 or caspase inhibitors, allows the extensive differentiation of human neuroblastoma cells

Staurosporine is one of the best apoptotic inducers in different cell types including neuroblastomas. In this study we have compared the efficiency and final outcome of three different anti-apoptotic strategies in staurosporine-treated SH-SY5Y human neuroblastoma cells. At staurosporine concentrations up to 500 nm, z-VAD.fmk a broad-spectrum, noncompetitive inhibitor of caspases, reduced apoptosis in SH-SY5Y cells. At higher concentrations, z-VAD.fmk continued to inhibit caspases and the apoptotic phenotype but not cell death which seems to result from oxidative damage. Stable over-expression of Bcl-2 in SH-SY5Y protected cells from death at doses of staurosporine up to 1 microm. At higher doses, cytochrome c release from mitochondria occurred, caspases were activated and cells died by apoptosis. Therefore, we conclude that Bcl-2 increased the threshold for apoptotic cell death commitment. Over-expression of Bcl-X(L) was far more effective than Bcl-2. Bcl-X(L) transfected cells showed a remarkable resistance staurosporine-induced cytochrome c release and associated apoptotic changes and survived for up to 15 days in 1 microm staurosporine. In these conditions, SH-SY5Y displayed a remarkable phenotype of neuronal differentiation as assessed by neurite outgrowth and expression of neurofilament, Tau and MAP-2 neuronal specific proteins.     

Adenovirus-mediated transfer of Bcl-X(L) protects neuronal cells from Bax-induced apoptosis

Bax-mediated apoptosis in neurons is involved in many pathologic conditions affecting the central nervous system, including degenerative diseases, stroke, and trauma. Two molecules belonging to the Bcl-2 family, Bcl-2 and Bcl-X(L), protect cells from Bax-induced apoptosis and show distinct expression patterns in adult neurons, with downregulated Bcl-2 and highly upregulated Bcl-X(L) expression. To investigate the biological functions of these two molecules in Bax-mediated apoptosis in neurons, we transduced various levels of Bcl-X(L) or Bcl-2 via adenoviral vectors into nerve growth factor (NGF)-treated PC12 cells. Overexpression of Bax induced drastic apoptosis in NGF-treated PC12 cells. Bcl-X(L) expressed at a wide range of levels conferred a high level of protection against Bax-mediated apoptosis. In contrast, Bcl-2 at various levels conferred far less protection against apoptosis. Moreover, Bcl-X(L) protected PC12 cells from apoptosis induced by NGF withdrawal. These data indicate that Bcl-X(L)-mediated protection is the major pathway that suppresses apoptosis in NGF-treated PC12 cells and that Bcl-X(L) would be a more relevant target of manipulation in future treatment strategies, including gene therapies.     

Streptozotocin-induced diabetes increases the interaction of Bad/Bcl-XL and decreases the binding of pBad/14-3-3 in rat testis

Sexual dysfunction is frequently associated with diabetes in males. The present study was designed to evaluate whether streptozotocin-induced diabetes increases apoptotic cell death in rat testis through the regulation of Bcl-2 family proteins. Diabetes was induced by a single intravenous injection of streptozotocin (40 mg/kg body weight) and testis samples were collected after 3 months. The number of positive cells for TUNEL histochemistry was significantly increased in the testicular germ cells of the diabetic group, compared to those of control. The levels of Bcl-2 and Bcl-X(L), anti-apoptotic proteins, were decreased in the diabetic group. In contrast, the levels of Bax and Bad, pro-apoptotic factors, were increased in the diabetic group, compared with the control group. Moreover, the diabetic condition increased the interaction of Bad and Bcl-X(L), and decreased the binding of pBad and 14-3-3. 14-3-3 acts as an anti-apoptotic factor through interaction with Bad. Our findings suggest that streptozotocin-induced diabetes increases apoptotic cell death in testis tissue through the up-and down-regulation of Bcl-2 family proteins and the interaction of Bad and Bcl-X(L).     

PUMA inactivation protects against oxidative stress through p21/Bcl-XL inhibition of bax death

The tumor suppressor protein p53 activates growth arrest and proapoptotic genes in response to DNA damage. It is known that negative feedback by p21(Cip1/Waf1/Sdi1) represses p53-dependent transactivation of PUMA. The current study investigates PUMA feedback on p53 during oxidative stress from hyperoxia and the subsequent effects on cell survival mediated through p21 and Bcl-X(L). Deletion of PUMA in HCT116 colon carcinoma cells increased levels of p53 and p21, resulting in a larger G(1) population during hyperoxia. P21-dependent increase in Bcl-X(L) levels protected PUMA-deficient cells against hyperoxic cell death. Bax and Bak were both able to promote hyperoxic cell death. Bcl-X(L) protection against hyperoxic death was lost in cells lacking Bax, not PUMA, suggesting that Bcl-X(L) acts to inhibit Bax-dependent death. These results indicate that PUMA exerts a negative feedback on p53 and p21, leading to p21-dependent growth suppressive and survival changes. Enhanced survival was associated with increased Bcl-X(L) to block Bax activated cell death during oxidative stress.     

Eriodictyol protects against H(2)O(2)-induced neuron-like PC12 cell death through activation of Nrf2/ARE signaling pathway

Eriodictyol, a flavonoid isolated from the Chinese herb Dracocephalum rupestre has long been established as an antioxidant. The present study was designed to explore the protective effects of eriodictyol against hydrogen peroxide (H(2)O(2))-induced neurotoxicity with cultured rat pheochromocytoma cells (PC12 cells) and the possible mechanisms involved. For this purpose, differentiated PC12 cells were cultured and exposed to 200 μM H(2)O(2) in the absence or presence of eriodictyol (20, 40 and 80 μM). In addition, the potential contribution of the Nrf2/ARE neuroprotective pathway in eriodictyol-mediated protection against H(2)O(2)-induced neurotoxicity was also investigated. The results showed that H(2)O(2)-induced cell death can be inhibited in the presence of eriodictyol as measured by assays for MTT and apoptosis. Further study revealed that eriodictyol induced the nuclear translocation of Nrf2, enhanced the expression of heme oxygenase (HO-1) and γ-glutamylcysteine synthetase (γ-GCS), and increased the levels of intracellular glutathione. Treatment of PC12 cells with Nrf2 small interference RNA abolished eriodictyol-induced HO-1 and γ-GCS expression and its protective effects. In conclusion, these results suggest that eriodictyol upregulates HO-1 and γ-GCS expression through the activation of Nrf2/ARE pathway and protects PC12 cells against H(2)O(2)-induced oxidative stress.     

Peroxide mediates ethanol-induced cytotoxicity in PC12 cells

Pheochromocytoma (PC12) cell cultures exhibited a loss of cells and increase in intracellular oxidative stress when exposed to ethanol (EtOH) for 24 h. Catalase, an enzyme that hydrolyzes hydrogen peroxide (H(2)O(2)) to O(2) and H(2)O can attenuate EtOH-induced cell loss and oxidative stress in PC12 cells. This study provides the first clear evidence that oxidative stress in the form of elevated intracellular H(2)O(2) is a primary mechanism of EtOH neurotoxicity in PC12 cells.     

Carbon monoxide protects PC12 cells from peroxynitrite-induced apoptotic death by preventing the depolarization of mitochondrial transmembrane potential

Heme oxygenase-1 (HO-1), the rate-limiting enzyme in catalyzing heme degradation into biliverdin, free iron, and carbon monoxide (CO), serves as a protective enzyme against oxidative and nitrosative stresses. In the present study, we investigated the cytoprotective effects of HO-1 upregulation and its product CO against the peroxynitrite-induced PC12 cell death. PC12 cells treated with 3-morphoinosydonimine (SIN-1), a generator of peroxynitrite (ONOO-), underwent apoptotic cell death as evidenced by dissipation of mitochondrial transmembrane potential (DeltaPsim), release of mitochondrial cytochrome c into cytoplasm, cleavage of poly(ADP-ribose)polymerase and fragmentation of internucleosomal DNA. Pretreatment of PC12 cells with a low non-toxic concentration of SIN-1 (0.5 mM) induced HO-1 expression and abrogated the cell death caused by subsequent challenge with high dose SIN-1 (2.5 mM). Furthermore, pretreatment of PC12 cells with SnCl2, a potent inducer of HO-1 expression, increased endogenous production of CO (HO activity) and rescued the PC12 cells from peroxynitrite-induced apoptosis. The cytoprotective effect of SnCl2 was abolished when the HO activity was inhibited by zinc protoporphyrin IX (ZnPP IX). PC12 cells treated directly with the CO-releasing molecule, tricarbonyldichlororuthenium (II) dimer ([Ru(CO)3Cl2]2) became tolerant to the depolarization of DeltaPsim and apoptosis induced by high dose peroxynitrite. Taken together, these data demonstrate that the adaptive protection against peroxynitrite-induced apoptotic death in PC12 cells is mediated by CO formed as a consequence of HO-1 induction.     

Sequential Cleavage of Poly(ADP-Ribose)polymerase and Appearance of a Small Bax-Immunoreactive Protein Are Blocked by Bcl-XL and Caspase Inhibitors During Staurosporine-Induced Dopaminergic Neuronal Apoptosis

To assess the role of Bcl-X(L) and its splice derivative, Bcl-X(S), in staurosporine-induced cell death, we used a dopaminergic cell line, MN9D, transfected with bcl-xL (MN9D/Bcl-X(L)), bcl-xS (MN9D/Bcl-X(S)), or control vector (MN9D/Neo). Only 8.6% of MN9D/Neo cells survived after 24 h of 1 microM staurosporine treatment. Caspase activity was implicated because a caspase inhibitor, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-fmk), attenuated staurosporine-induced cell death. Bcl-X(L) rescued MN9D cells from death (89.4% viable cells), whereas Bcl-X(S) had little or no effect. Bcl-X(L) prevented morphologically apoptotic changes as well as cleavage of poly(ADP-ribose)polymerase (PARP) induced by staurosporine. It is interesting that a small Bax-immunoreactive protein appeared 4-8 h after PARP cleavage in MN9D/Neo cells. The appearance of the small Bax-immunoreactive protein, however, may be cell type-specific as it was not observed in PC12 cells after staurosporine treatment. The sequential cleavage of PARP and the appearance of the small Bax-immunoreactive protein in MN9D cells were blocked either by Z-VAD-fmk or by Bcl-X(L). Thus, our present study suggests that Bcl-X(L) but not Bcl-X(S) prevents staurosporine-induced apoptosis by inhibiting the caspase activation that may be directly or indirectly responsible for the appearance of the small Bax-immunoreactive protein in some types of neurons.     

Crocin suppresses tumor necrosis factor-alpha-induced cell death of neuronally differentiated PC-12 cells.

Crocus sativus L. is used in Chinese traditional medicine to treat some disorders of the central nervous system. Crocin is an ethanol-extractable component of Crocus sativus L.; it is reported to prevent ethanol-induced impairment of learning and memory in mice. In this study, we demonstrate that crocin suppresses the effect of tumor necrosis factor (TNF)-alpha on neuronally differentiated PC-12 cells. PC-12 cells dead from exposure to TNF-alpha show apoptotic morphological changes and DNA fragmentation. These hallmark features of cell death did not appear in cells treated in the co-presence of 10 microM crocin. Moreover, crocin suppressed the TNF-alpha-induced expression of Bcl-Xs and LICE mRNAs and simultaneously restored the cytokine-induced reduction of Bcl-X(L) mRNA expression. The modulating effects of crocin on the expression of Bcl-2 family proteins led to a marked reduction of a TNF-alpha-induced release of cytochrome c from the mitochondria. Crocin also blocked the cytochrome c-induced activation of caspase-3. To learn how crocin exhibits these anti-apoptotic actions in PC-12 cells, we tested the effect of crocin on PC-12 cell death induced by daunorubicin. We found that crocin inhibited the effect of daunorubicin as well. Our findings suggest that crocin inhibits neuronal cell death induced by both internal and external apoptotic stimuli.     

The intrinsic apoptotic pathway is required for lipopolysaccharide-induced lung endothelial cell death

LPS has been implicated in the pathogenesis of endothelial cell death associated with Gram-negative bacterial sepsis. The binding of LPS to the TLR-4 on the surface of endothelial cells initiates the formation of a death-inducing signaling complex at the cell surface. The subsequent signaling pathways that result in apoptotic cell death remain unclear and may differ among endothelial cells in different organs. We sought to determine whether LPS and cycloheximide-induced cell death in human lung microvascular endothelial cells (HmVECs) was dependent upon activation of the intrinsic apoptotic pathway and the generation of reactive oxygen species. We found that cells overexpressing the anti-apoptotic protein Bcl-X(L) were resistant to LPS and cycloheximide-induced death and that the proapoptotic Bcl-2 protein Bid was cleaved following treatment with LPS. The importance of Bid was confirmed by protection of Bid-deficient (bid(-/-)) mice from LPS-induced lung injury. Neither HmVECs treated with the combined superoxide dismutase/catalase mimetic EUK-134 nor HmVECs depleted of mitochondrial DNA (rho(0) cells) were protected against LPS and cycloheximide-induced death. We conclude that LPS and cycloheximide-induced death in HmVECs requires the intrinsic cell death pathway, but not the generation of reactive oxygen species.     

Mature dendritic cells are protected from Fas/CD95-mediated apoptosis by upregulation of Bcl-XL

The clinical use of dendritic cells (DC) as tumor vaccines is very much dependent on their survival potential. Members of the tumor necrosis factor (TNF) receptor superfamily and their ligands are involved in the regulation of cell death. Fas (CD95) is a representative protein that promotes apoptosis. The Bcl-2 family of proteins functions as an integrator of diverse pro- and anti-apoptotic signals. It has been found that DC maturation facilitates their survival, and thus has an anti-apoptotic function. However, little is known about the underlying mechanisms. We investigated the effects of TNF-alpha and lipopolysaccharide (LPS) on the expression of apoptotic molecules during differentiation and maturation of DC under serum-free conditions, and correlated this to the sensitivity to apoptosis by the Fas-mediated pathway. Indeed, DC activation effectively inhibited DC apoptosis, which was predominantly accompanied by the upregulation of Bcl-X(L) and to a lesser extent Bcl-2, while Bax and FLICE inhibitory protein (FLIP) remained unchanged. In contrast, in the presence of serum FLIP was also upregulated. We conclude that under serum-free conditions, Bcl-X(L) rather than FLIP plays the main role in protection against DC apoptosis.     

Ginsenoside Rg1 protects against hydrogen peroxide-induced cell death in PC12 cells via inhibiting NF-κB activation

Oxidative stress is a major cause in neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease (PD), and cerebral ischemia. Ginsenoside Rg1, a natural product extracted from Panax ginseng C.A. Meyer, has been reported to exert notable neuroprotective activities, which partly ascribed to its antioxidative activity. However, its molecular mechanism against oxidative stress induced by exogenous hydrogen peroxide (H(2)O(2)) remained unclear. In this study, we investigated its effect on H(2)O(2)-induced cell death and explored possible signaling pathway in PC12 cells. We proved that pretreatment with Rg1 at concentrations of 0.1-10 μM remarkably reduced the cytotoxicity induced by 400 μM of H(2)O(2) in PC12 cells by MTT and Hoechst and PI double staining assay. Of note, we demonstrated the activation of NF-κB signaling pathway induced by H(2)O(2) thoroughly in PC12 cells, and Rg1 suppressed phosphorylation and nuclear translocation of NF-κB/p65, phosphorylation and degradation of inhibitor protein of κB (IκB) as well as the phosphorylation of IκB-kinase complex (IKK) by western blotting or indirect immunofluorescence assay. Besides, Rg1 also inhibited the activation of Akt and the extracellular signal-regulated kinase 1/2 (ERK1/2). Furthermore, the protection of Rg1 on H(2)O(2)-injured PC12 cells was attenuated by pretreatment with two NF-κB pathway inhibitors (JSH-23 or BOT-64). In conclusion, our results suggest that Rg1 could rescue the cell injury by H(2)O(2) via down-regulation NF-κB signaling pathway as well as Akt and ERK1/2 activation, which put new evidence on the neuroprotective mechanism of Rg1 against the oxidative stress and the regulatory role of H(2)O(2) in NF-κB pathway in PC12 cells.