Long-term leptin treatment exerts a pro-apoptotic effect on renal tubular cells via prostaglandin E2 augmentation

Adipokine leptin reportedly acts on the kidney in pathophysiological states. However, the influence of leptin on renal tubular epithelial cells is still unclear. Gentamicin, a widely used antibiotic for the treatment of bacterial infection, can cause nephrotoxicity. This study aims to investigate the influence of long-term leptin treatment on gentamicin-induced apoptosis in rat renal tubular cells (NRK-52E) and mice. We monitored apoptosis and molecular mechanisms using annexin V/ propidium iodide staining and small interfering RNA transfection. In NRK-52E cells, leptin reduced gentamicin-induced apoptosis at 24h, but significantly increased apoptosis at 48 h. Long-term treatment of leptin decreased Bcl-x(L) expression and increased caspase activity in gentamicin-treated NRK-52E cells. Leptin also increased the expression of cyclooxygenase-2 (COX-2) and its product, prostaglandin E(2) (PGE(2)), in a dose-dependent manner. The COX-2 inhibitor, NS398 (N-[2-(Cyclohexyloxy)-4- nitrophenyl]methanesulfonamide), blocked PGE(2) augmentation and the pro-apoptotic effects of leptin. The addition of PGE(2) recovered the pro-apoptotic effect of leptin in NS398-treated NRK-52E cells. In a mouse animal model, a 10 day leptin treatment significantly increased gentamicin-induced apoptotic cells in proximal tubules. NS398 treatment inhibited this in vivo pro-apoptotic effect of leptin. Results reveal that long-term elevation of leptin induces COX-2-mediated PGE(2) augmentation in renal tubular cells, and then increases these cells' susceptibility to gentamicin-induced apoptosis.     

Necroptosis contributes to the cyclosporin A-induced cytotoxicity in NRK-52E cells

Cyclosporin A (CsA) induces renal tubular epithelial cells apoptosis and necrosis following in vitro exposure. The mechanisms of CsA-induced apoptosis have been studied intensively, whereas the mechanisms of necrosis remain to be elucidated. Necroptosis has been described as programmed necrosis. This study investigated the ability of CsA to induce necroptosis in the rat tubular cell line NRK-52E. The NRK-52E cells were incubated with CsA for 24 hours with or without necrostatin-1 (Nec-1). The majority of the NRK-52E cells died of necrosis as indicated by LDH leakage, Hoechst 33342/PI staining, and flow cytometry analysis. Cell death was significantly reduced by Nec-1 pretreated before CsA exposure. CsA-induced apoptosis and necrosis were also compared in NRK-52E cells with or without knockdown of receptor interaction protein 3 (RIP3) expression using small interfering RNA. Moreover, the role of reactive oxygen species (ROS) in CsA-induced cell death was also attempted. The result suggests that necroptosis contributes to the CsA-induced cytotoxicity in NRK-52E cells. Meanwhile, RIP3 and ROS are involved in CsA-induced necroptosis. To our knowledge, this is the first report on necroptosis in CsA-induced renal tubular cell death pathways, which might offer a novel protective target for CsA nephrotoxicity.     

Berberine protects renal tubular cells against hypoxia/reoxygenation injury via the Sirt1/p53 pathway

Berberine (BBR) has been demonstrated to protect against renal ischemia/reperfusion injury; however, the underlying molecular mechanism is largely unknown. In the present study, we examined the role of silent information regulator 1 (Sirt1)/p53 in the protective effect of BBR on hypoxia/reoxygenation (H/R)-mediated mitochondrial dysfunction in rat renal tubular epithelial cells (NRK-52E cells). NRK-52E cells were preconditioned with small interfering RNA targeting Sirt1 (Sirt1-siRNA) and BBR before subjected to H/R. Cell damage was assessed by CCK8 assay and detection of oxidative parameters. The apoptotic rate was determined by flow cytometry and Hoechst 33258 staining. The expression of apoptotic markers, Sirt1, p53 and the translocation of p53 were examined by Western blotting assay. Nuclear p53 deacetylation by Sirt1 was detected using immunoprecipitation. Compared with the H/R group, BBR pretreatment increased cell viability and inhibited mitochondrial oxidative stress and apoptosis. Protein expression of Sirt1 was also enhanced along with a reduction of p53. Furthermore, both nuclear translocation of p53 and its acetylation were inhibited in NRK-52E cells pretreated with BBR. However, the knockdown of Sirt1 counteracted the renoprotection of BBR. BBR preconditioning protects rat renal tubular epithelial cells against H/R-induced mitochondrial dysfunction via regulating the Sirt1/p53 pathway.     

牛磺酸对肾NRK-52E细胞缺氧/复氧损伤的保护及初步机制

目的观察牛磺酸(Tau)对NRK-52E细胞缺氧/复氧(H/R)损伤的保护作用及初步机制。方法用NRK-52E细胞缺氧8 h复氧12 h培养建立了H/R模型,流式细胞仪检测凋亡率和胞内游离钙离子浓度,RT-PCR和Western blot检测GRP78、Caspase-12、Caspase-3 mRNA和蛋白表达。结果与对照组比较,H/R组细胞凋亡率上升,GRP78、Caspase-12及Caspase-3 mRNA和蛋白表达均明显增高(P<0.01),胞质游离钙离子浓度也升高(P<0.01);与H/R组比较,各浓度牛磺酸处理组的细胞Caspase-3活性和凋亡率明显下降,胞质游离钙和GRP78、Caspase-12及Caspase-3 mRNA和蛋白表达均有明显降低(P<0.01)。结论牛磺酸对NRK-52E细胞H/R损伤有较好的抑制作用,且呈一定的剂量依赖性,其机制可能是调节胞内钙稳态、抑制GRP78、Caspase-12及Caspase-3表达,减少了细胞凋亡。     

Omi/HtrA2短发夹RNA在大鼠肾小管上皮细胞凋亡中的作用及机制

目的探讨Omi/HtrA2短发夹RNA(shRNA)对缺氧/复氧诱导大鼠肾小管上皮细胞(NRK-52E)凋亡的作用及机制。方法细胞分为5组:正常组(常规培养),模型组(缺氧/复氧组)、HK组(转染重组质粒Pgenesil-1/HK)、shRNA1组(转染Pgenesil-1/Omi/HtrA2shRNA1)、shRNA2组(转染Pgenesil-1/Omi/HtrA2shRNA2)。用荧光显微镜观察荧光蛋白的表达,Westernblot检测各组Omi/HtrA2、半胱氨酰天冬氨酸特异性蛋白酶(caspase)-3/-9蛋白表达,比色法测定caspase-3/-9的活性。结果在荧光显微镜下,转染组细胞均可见绿色荧光,未转染组未见绿色荧光。与模型组相比,shRNA1组和shRNA2组Omi/HtrA2、caspase-3/-9蛋白表达明显减少(P<0.01)。模型组和HK组、shRNA1组和shRNA2组之间Omi/HtrA2、caspase-3/-9蛋白表达差异无统计学意义。与正常组相比,模型组Omi/HtrA2、caspase-3/-9蛋白表达明显增强(P<0.01)。结论Pgenesil-1/Omi/HtrA2shRNA1和Pgenesil-1/Omi/HtrA2shRNA2能明显减少缺氧/复氧诱导的NRK-52E中Omi/HtrA2蛋白的表达。通过抑制procaspase-9的活化,进而减少了下游procaspase-3的激活,最终减轻了缺氧/复氧诱导的NRK-52E的凋亡程度。     

Cadmium toxicity is caused by accumulation of p53 through the down-regulation of Ube2d family genes in vitro and in vivo

Cadmium (Cd) causes renal dysfunction with damage to kidney proximal tubule cells; however, the precise mechanisms of the toxicity remain unclear. Previously, we found that the expression of Ube2d4 gene, which is a member of the ubiquitin-conjugating enzyme Ube2d family, is suppressed by Cd in NRK-52E rat renal tubular epithelial cells. To investigate the mechanisms of Cd-induced renal toxicity, we examined the effects of Cd on the ubiquitin-proteasome system, particularly the expression and function of Ube2d family members in the NRK-52E cells and mice. Cd markedly decreased the expression of Ube2d1, Ube2d2, Ube2d3 and Ube2d4 prior to the appearance of cytotoxicity in the NRK-52E cells. Cd also dramatically increased p53 protein levels in the cells, without stimulation of p53 gene expression or inhibition of proteasome activity. In addition, Cd induced phosphorylation of p53 and caused apoptosis in the NRK-52E cells. In vivo, we examined the effect of orally administrated Cd for 12 months on the expression of Ube2d genes and accumulation of p53 in the mouse kidney. Chronic Cd exposure also caused suppression of Ube2d genes expression and accumulation of p53. Cd did not induce severe kidney injury, but caused apoptosis in the renal tubules. These results suggest that the Cd-induced accumulation of p53 may be due to inhibition of p53 degradation through the down-regulation of Ube2d family genes, and that Cd induces p53-dependent apoptosis in renal tubular cells. Moreover, Ube2d family members may be one of the critical targets of renal toxicity caused by Cd.     

Cellular energetics and glutathione status in NRK-52E cells: toxicological implications

Cellular energetics and redox status were evaluated in NRK-52E cells, a stable cell line derived from rat proximal tubules. To assess toxicological implications of these properties, susceptibility to apoptosis induced by S-(1,2-dichlorovinyl)-L-cysteine (DCVC), a well-known mitochondrial and renal cytotoxicant, was studied. Cells exhibited high activities of several glutathione (GSH)-dependent enzymes, including gamma-glutamylcysteine synthetase, GSH peroxidase, glutathione disulfide reductase, and GSH S-transferase, but very low activities of gamma-glutamyltransferase and alkaline phosphatase, consistent with a low content of brush-border microvilli. Uptake and total cellular accumulation of [14C]alpha-methylglucose was significantly higher when cells were exposed at the basolateral as compared to the brush-border membrane. Similarly, uptake of GSH was nearly 2-fold higher across the basolateral than the brush-border membrane. High activities of (Na(+)+K(+))-ATPase and malic dehydrogenase, but low activities of other mitochondrial enzymes, respiration, and transport of GSH and dicarboxylates into mitochondria were observed. Examination of mitochondrial density by confocal microscopy, using a fluorescent marker (MitoTracker Orange), indicated that NRK-52E cells contain a much lower content of mitochondria than rat renal proximal tubules in vivo. Incubation of cells with DCVC caused time- and concentration-dependent ATP depletion that was largely dependent on transport and bioactivation, as observed in the rat, on induction of apoptosis, and on morphological damage. Comparison with primary cultures of rat and human proximal tubular cells suggests that the NRK-52E cells are modestly less sensitive to DCVC. In most respects, however, NRK-52E cells exhibited functions similar to those of the rat renal proximal tubule in vivo.     

Pathways of proximal tubular cell death in bismuth nephrotoxicity

Colloidal bismuth subcitrate (CBS), a drug for treatment of peptic ulcers, has been reported in the literature to be nephrotoxic in humans when taken in high overdoses. To investigate the mechanism of bismuth nephropathy, we developed an animal model by feeding rats single doses of CBS containing 3.0 mmol Bi/kg body weight. Terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling assay, immunostaining for active caspase-3, and electron microscopy showed that proximal tubular epithelial cells die by necrosis and not by apoptosis within 3 h after CBS administration. Exposure of the renal epithelial cell lines NRK-52E and LLC-PK1 to Bi(3+) in citrate buffer served as an in vitro model of bismuth nephropathy. NRK-52E cells exposed to 100 microM Bi(3+) or more died by necrosis, as was demonstrated by nuclear staining with Hoechst 33258 and flow cytometry using Alexa(488)-labeled Annexin-V and the vital nuclear dye TOPRO-3. Bismuth-induced cell death of NRK-52E cells was not prevented by the caspase-3 inhibitor z-VAD-fmk, whereas this inhibitor did prevent cisplatinum-induced apoptosis. Mitochondrial dysfunction and induction of free radicals were shown not to be involved in bismuth nephrotoxicity. The early time point of damage induction in vitro as well as in vivo and the early displacement of N-cadherin, as found in previous studies, suggest that bismuth induces cell death by destabilizing the cell membrane. In conclusion, we showed that high overdose of bismuth induced cell death by necrosis in vivo as well as in vitro, possibly by destabilization of the cell membrane.     

激活素A及卵泡抑素对肾小管上皮细胞转分化的作用

目的探讨激活素A(ACTA)对大鼠肾小管上皮细胞(NRK-52E)转分化的影响及卵泡抑素(FS)的干预作用。方法 NRK-52E细胞生长于达氏修正伊氏培养基(DMEM)/F12培养基。实验A:将培养的NRK-52E细胞按rh-ACTA浓度不同分为4组:ACTA浓度分别为0,1,10,100ng/ml。实验B:分为4组:对照组;ACTA组(A组),rh-ACTA浓度10ng/ml;rh-FS组(F组),rh-FS浓度为100ng/ml;ACTA+FS组(A+F组):rh-ACTA浓度10ng/ml,rh-FS浓度为100ng/ml。24h后收集各组细胞及细胞上清液。蛋白印迹法检测各组细胞α-平滑肌肌动蛋白(α-SMA)和纤维连接蛋白(FN)的表达;酶联免疫吸附法(ELISA)检测各组细胞上清液转化生长因子-β(TGF-β)的含量。结果 ACTA能剂量依赖性刺激肾小管上皮细胞α-SMA及FN的表达(P<0.05),而对TGF-β的表达没有影响。FS能抑制ACTA的上述效应,而单纯FS对肾小管上皮细胞α-SMA及FN的表达无影响(P>0.05)。结论 ACTA能刺激NRK-52E细胞转分化及FN的合成;FS可通过阻断ACTA的上述效应产生有效的肾脏保护作用。     

Down-regulation of the JAK2/PI3K-mediated signaling activation is involved in Taiwan cobra cardiotoxin III-induced apoptosis of human breast MDA-MB-231 cancer cells

Cardiotoxin III (CTX III), a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom, has been reported to have anticancer activity. Exposure of MDA-MB-231 cells with 0.03, 0.09, and 0.15 μM of CTX III for 18 h, CTX III-induced cell apoptosis, as evidenced by accumulation of sub-G1 population, externalization of phosphatidylserine, loss of mitochondrial membrane potential (ΔΨm) with subsequent release of cytochrome c, and activation of both capases-9 and caspase-3. This correlated with up-regulation in Bax and Bad, and down-regulation of various anti-apoptotic proteins, including Bcl-2, Bcl-X_L, and survivin in CTX III-treated cells. Mechanistic studies showed that CTX III suppressed the phosphorylation of JAK2, STAT3, Akt, and activation of PI3K. Moreover, the PI3K inhibitor wortmannin blocked activation of STAT3 and Akt without affecting the JAK2 activation, whereas JAK2 inhibitor AG490 suppressed the levels of phospho-STAT3, phospho-Akt, and PI3K, suggesting that PI3K activation occurs after JAK2 phosphorylation, and both PI3K and JAK2 kinases cooperate to mediate STAT3 and Akt phosphorylation. Both AG490 and wortmannin also led to up-regulation in Bax and Bad, and down-regulation of Bcl-2, Bcl-X_L, and survivin in MDA-MB-231 cells. Taken together, these results indicate that CTX III induces apoptosis in MDA-MB-231 cells via concomitant inactivation of the JAK2, STAT3, PI3K, and Akt signaling pathways.     

Ginsenoside Rd prevents and rescues rat intestinal epithelial cells from irradiation-induced apoptosis

Panax ginseng has been shown to have a protective effect for irradiated animals or cells. Ginsenosides are the most active components isolated from ginseng, and ginsenoside Rd has been identified as one of the effective compounds responsible for the pharmaceutical actions of ginseng. In the present study, we studied the molecular mechanisms for the radio-protective action of ginsenoside Rd in rat intestinal epithelial IEC-6 cells. Cells were irradiated with gamma-ray, and apoptosis was examined using Hoechst staining and Western blot analysis. Treatment with ginsenoside Rd before gamma-irradiation inhibited irradiation-induced apoptosis in IEC-6 cells. Administration of Rd after irradiation also inhibited apoptosis in these cells. Irradiation of IEC-6 cells resulted in inactivation of Akt phosphorylation that was abrogated by Rd. On the other hand, irradiation activated phosphorylation of ERK1/2 but did not affect that of p38 MAPK. Inhibition of Akt phosphorylation prevented the reduction of apoptosis by Rd following irradiation. Pretreatment with an inhibitor of the MEK pathway further decreased the number of apoptotic cells. Rd decreased the ratios of Bax/Bcl-2 and Bax/Bcl-xL, the levels of cytochrome c, and the cleaved form of caspase-3 in irradiated IEC-6 cells. Our results suggest that ginsenoside Rd protects and rescues rat intestinal epithelial cells from irradiation-induced apoptosis through a pathway requiring activation of PI3K/Akt, inactivation of MEK, and also inhibition of a mitochondria/caspase pathway.     

Molecular mechanisms of ZD1839 （Iressa）-induced apoptosis in human leukemic U937 cells

Aim： To investigate the molecular mechanisms of ZD 1839-induced apoptosis in human leukemic U937 cells. Methods： The inhibition of human leukemic U937 cell growth was assessed by 3-（4,5-dimethyl-2-thiazolyl）-2,5-diphnyl-2H-tetrazolim bromide （MTT） assays, lactate dehydrogenase （LDH） release, and cell cycle distribution. The expression of anti- and pro-apoptotic proteins was detected by Western blot analysis. Results： This study demonstrated that ZD1839 induced apoptosis in leukemic U937 cells by the downregulation of Bcl-2, caspase activation and subsequent apoptotic features. Cotreatment with ZD 1839 and the caspase- 3 inhibitor z-DEVD-fmk blocked apoptosis, indicating that caspase-3 activation is at least partially responsible for ZD 1839-induced apoptosis. The ectopic expression of Bcl-2 attenuated caspase-3 activation, PARP cleavage, and subsequent indicators of apoptosis, including sub-G1 DNA content and LDH release. These results indicate that the downregulation of Bcl-2 plays a major role in the initiation of ZD1839-induced apoptosis, and that the activation of a caspase cascade is involved in the execution of apoptosis. Furthermore, ZD1839 treatment triggered the activation of p38 mitogen-activated protein kinase （MAPK） and the downregulation of c-Jun-N-terminal kinase （JNK）, extracellular signal-regulated kinase （ERK） and phosphatidyl inositol 3-kinase （PI3K）/Akt. The inhibition of the ERK and PI3K/Akt pathways also significantly increased cellular death. Conclusion： ZD 1839 activated caspase-3 and the inhibited Bcl-2 in human leukemic U937 cells through the downregulation of the ERK and PI3K/Akt pathways.     

Lonicera japonica THUNB. protects 6-hydroxydopamine-induced neurotoxicity by inhibiting activation of MAPKs, PI3K/Akt, and NF-κB in SH-SY5Y cells

In this study, we investigated the neuroprotective effects of Lonicera japonica THUNB. extract (LJ) on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in SH-SY5Y cells. We found that LJ significantly increased cell viability decrease, lactate dehydrogenase release (LDH), morphological changes, nuclear condensation, fragmentation, and reactive oxygen species (ROS) production induced by 6-OHDA in SH-SY5Y cells. The cytoprotection afforded by pretreatment with LJ was associated with increases of the glutathione (GSH) level, superoxide dismutase (SOD) activity, and catalase (CAT) activity in 6-OHDA-induced SH-SY5Y cells. In addition, LJ strikingly inhibited 6-OHDA-induced mitochondrial dysfunctions including reduction of mitochondria membrane potential (MMP) and activation of cleaved poly-ADP-ribose polymerase (PARP), cleaved caspase-3, cleaved caspase-9, increased Bax, as well as decreased Bcl-2 and Bcl-xL. Additionally, LJ dramatically attenuated 6-OHDA-induced phosphorylation of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase 1/2 (ERK 1/2), and phosphoinositide 3-kinase (PI3K)/Akt. Meanwhile, LJ counteracted nuclear factor-κB (NF-κB) activation by blocking its translocation to the nucleus. These findings suggest that LJ has a potent anti-parkinsonism; this effect was mediated, at least in part, by inhibition of neurotoxicity, apoptotic cascade events, and oxidative stress via activation of MAPKs, PI3K/Akt, and NF-κB.     

Effect of Sedum sarmentosum Bunge Extract on Aristolochic Acid– Induced Renal Tubular Epithelial Cell Injury

Aristolochic acid (AA) is known as a potent mutagen that induces significant cytotoxic and mutagenic effects on renal tubular epithelial cells. Clinically, the persistent injury of AA results in the infiltration of inflammatory cells, epithelial-to-mesenchymal transition (EMT), and renal tubulointerstitial fibrosis. There are no truly effective pharmaceuticals. In this study, we investigated the potential role of the extract of Sedum sarmentosum Bunge (SSB), a traditional Chinese herbal medicine, on rat tubuloepithelial (NRK-52E) cells after AA injury in vitro. Evidence revealed that AA induced mitochondrial-pathway–mediated cellular apoptosis, accompanied by cell proliferation in a feedback mechanism. Treatment with SSB also induced cells to enter early apoptosis, but inhibited cell proliferation. In cultured NRK-52E cells, AA induced the imbalance of MMP-2/TIMP-2 and promoted EMT and ECM accumulation. SSB treatment significantly alleviated AA-induced NRK-52E cells fibrosis-like appearance, inhibited the induction of EMT, and deposition of ECM. SSB also decreased the activity of the NF-κB signaling pathway, resulting in down-regulated expression of NF-κB–controlled chemokines and pro-inflammatory cytokines, including MCP-1, MIF, and M-CSF, which may regulate the macrophage-mediated inflammatory reaction during renal fibrosis in vivo. Therefore, these findings suggest that SSB exerts protective effects against AA-induced tubular epithelial cells injury through suppressing the synthesis of inflammatory factors, EMT, and ECM production.     

维生素D对过氧化氢诱导MIN6细胞凋亡的保护作用

目的探讨维生素D(vitamin D,VitD)对过氧化氢(hydrogen peroxide,H 2O 2)诱导小鼠胰岛β细胞株MIN6细胞凋亡的保护作用及机制。方法VitD预处理后,用H 2O 2处理MIN6细胞,分别运用CCK-8法、Hoechst 33258荧光染色法、流式细胞术检测MIN6细胞增殖、形态及凋亡百分率。Western blot检测增殖与凋亡相关基因Bax、Bcl-2、Caspase-3以及Cleaved caspase-3的表达。结果H 2O 2呈时间和剂量依赖性抑制MIN6细胞增殖,诱导细胞凋亡,降低Bcl-2表达、增加Bax及Cleaved caspase-3表达,Bcl-2/Bax比值降低,Cleaved caspase-3/caspase-3比值增加;当用VitD预处理后,Bcl-2表达增加,Bax、Cleaved caspase-3表达降低,Bcl-2/Bax比值增加,Cleaved caspase-3/caspase-3比值降低,MIN6细胞活力增加。结论VitD预处理后,通过增加抗凋亡Bcl-2表达,降低促凋亡Bax和Cleaved caspase-3表达,减少由H 2O 2诱导的小鼠胰岛β细胞株MIN6细胞凋亡。     

Neuroprotection by sodium ferulate against glutamate-induced apoptosis is mediated by ERK and PI3 kinase pathways

Aim： To investigate whether sodium ferulate （SF） can protect cortical neurons from glutamate-induced neurotoxicity and the mechanisms responsible for this protection. Methods： Cultured cortical neurons were incubated with 50 μmol/L glutamate for either 30 min or 24 h, with or without pre-incubation with SF （100, 200, and 500 pmol/L, respectively）. LY294002, wortmannin, PD98059, and U0126 were added respectively to the cells 1 h prior to SF treatment. After incubation with glutamate for 24 h, neuronal apoptosis was quantified by scoring the per- centage of cells with apoptotic nuclear morphology after Hoechst 33258 staining. After incubation with glutamate for either 30 rain or 24 h, cellular extracts were prepared for Western blotting of active caspase-3, poly （ADP-ribose） polymerase （PARP）, μ-calpain, Bcl-2, phospho-Akt, phosphorylated ribosomal protein S6 pro- tein kinase （p70S6K）, phospho-mitogen-activated protein kinase kinase （MEK1/2） and phosphorylated extracellular signal-regulated kinase （ERK） 1/2. Results： SF reduced glutamate-evoked apoptotic morphology, active caspase-3 protein expression, and PARP cleavage and inhibited the glutamate-induced upregulation of the ~-calpain protein level. The inhibition of the phosphatidylinositol 3-kinase （P13K） and the MEK/ERK1/2 pathways partly abrogated the protective effect of SF against glutamate-induced neuronal apoptosis. SF prevented the glutamate- induced decrease in the activity of the PI3K/Akt/p70S6K and the MEK/ERK1/2 pathways. Moreover, incubation of cortical neurons with SF for 30 min inhibited the reduction of the Bcl-2 expression induced by glutamate. Conclusion： The results indicate that PI3K/Akt/p70S6K and the MEK/ERK signaling pathways play important roles in the protective effect of SF against glutamate toxicity in cortical neurons.