体外培养神经元内JNK/c-jun信号通路对nNOS表达的影响

目的:在中枢神经系统,损伤神经元内通常出现c-jun和nNOS基因的高表达,然而两者之间的关系还不清楚。本实验探讨PC12细胞JNK/c-jun信号通路对nNOS基因的调控作用。方法:体外培养分化的PC12细胞,免疫组化检测PC12细胞内JNK/c-jun,p-c-jun和nNOS的定位表达;应用SP600125抑制JNK/c-jun信号通路,MTT法检测不同浓度SP600125对分化的PC12细胞活力的影响,Western blot检测SP600125对JNK/c-jun,p-c-jun和nNOS基因表达的影响,验证c-jun和nNOS之间的关系。结果:全部分化的PC12的细胞核都表达c-jun基因,部分细胞表达p-c-jun,全部分化的PC12细胞均表达nNOS蛋白。与对照组相比,50μmol/L和100μmol/L的SP600125可明显降低细胞活力(P<0.05),50μmol/L的SP600125能有效抑制c-jun的磷酸化,即p-c-jun的表达(P<0.05),而对c-jun的表达无影响(P>0.05),同时引起nNOS蛋白表达的上调(P<0.05)。结论:c-jun,p-cjun和nNOS蛋白共表达于分化的PC12细胞中,SP600125有效抑制了c-jun的磷酸化激活,JNK/c-jun信号激活的抑制同时上调了nNOS的表达。这些结果表明在分化的PC12细胞内c-jun与nNOS之间的功能密切相关。     

葡萄糖通过mTORC1信号通路调控成纤维细胞增殖

目的 研究葡萄糖对小鼠皮肤成纤维细胞增殖的影响.方法 将小鼠皮肤成纤维细胞培养在含不同浓度葡萄糖的培养基里,用MTT法检测细胞增殖,7-MGTP pulldown实验检测细胞翻译起始情况,Western blot检测mTORC1信号通路分子的活化.结果 与培养基葡萄糖浓度为5.5 mmol/L相比较,当浓度为15 mmol/L时,促进细胞增殖,与7-MGTP结合的翻译起始复合物增加,mTORC1信号通路活化;当25 mmol/L时,抑制细胞增殖,与7-MGTP结合的翻译始复合物减少,mTORC1信号通路中与细胞增殖相关的4EBP1和与细胞生存相关的Akt的磷酸化减弱.结论 葡萄糖通过对mTORC1信号通路的双向调节作用调控成纤维细胞增殖.     

高糖上调大鼠主动脉平滑肌细胞骨桥蛋白表达

目的 探讨高糖对大鼠血管平滑肌细胞（VSMCs）骨桥蛋白（OPN）表达的影响及机制。方法 SD大鼠腹腔注射链脲佐菌素复制Ⅰ型糖尿病模型,免疫组化、RT-PCR和western blot检测大鼠主动脉OPN和PCNA的表达;大鼠主动脉VSMCs经含正常糖(5.5mmol/L)、高糖(25mmol/L)、甘露醇(25mmol/L)、高糖+GF109203X（蛋白激酶C抑制剂,10μmol/L),高糖+ NAC（N-acetyl-l-cysteine,NF-κB抑制剂,10μmol/L)的DMEM处理48 h,免疫荧光及western blot检测OPN的表达,western blot 分析PCNA、PKC和 p65的表达。结果 高糖血症大鼠主动脉VSMCs高表达OPN及PCNA。原代VSMCs经高糖刺激后OPN、PCNA、PKC及p65表达明显增加;GF109203X和NAC均可下调PCNA的高表达,但仅GF109203X抑制高糖诱导的OPN高表达。结论 高糖可能通过激活PKC信号诱导OPN表达并促进VSMCs增殖从而在糖尿病性血管并发症中起作用。     

Activin A通过JNK/ERK信号通路调控皮肤成纤维细胞肌动蛋白重组的研究

目的探讨Activin A对成纤维细胞微丝肌动蛋白的作用以及其信号机制。方法出生24 h内的C57BL/6乳鼠皮肤成纤维细胞分离培养。实验分为PBS组、Activin A组以及JNK特异性抑制剂SP600125组、ERK特异性抑制剂SL327组、p38特异性抑制剂SB202190组。3~5代成纤维细胞,提取细胞总蛋白,Western blot检测JNK、ERK、p38的磷酸化活性并且通过Phallotoxins染色观察成纤维细胞肌动蛋白变化。结果 Activin A可诱导成纤维细胞肌动蛋白聚集,给予JNK特异性抑制剂SP600125后,成纤维细胞肌动蛋白聚集现象完全被抑制;给予ERK特异性抑制剂SL327后,成纤维细胞肌动蛋白聚集现象减弱,但是尚未完全被抑制;而p38特异性抑制剂SB202190处理后,成纤维细胞肌动蛋白聚集未被抑制。结论 Activin A通过JNK和ERK信号通路诱导成纤维细胞肌动蛋白重组聚集。     

高糖毒性通过JNK信号通路对胰岛β细胞系INS-1细胞活性和凋亡的影响

目的:研究高糖毒性通过JNK信号分子对INS-1细胞功能影响的分子机制。方法:在5.6mmol/L(5.6G)、11.2mmol/L(11.2G)、33.3mmol/L(33.3G)葡萄糖浓度下加入或者不加IGF-1培养INS-1细胞,观察细胞的活性和凋亡,并通过添加或不添加JNK抑制剂后,观察JNK信号分子和IRS的丝氨酸磷酸化改变。结果:INS-1细胞活性随暴露高糖环境中的葡萄糖浓度和时间增加而下降,IGF-1有增加细胞活性的作用,但其作用随糖浓度增加而受抑制。流式细胞术检测3组细胞总的凋亡率分别为11.3%、12.7%、28.2%,33.3G组凋亡发生率是5.6G组的2.49倍(P0.01)。高糖激活JNK和IRS的丝氨酸磷酸化,在33.3G组2种蛋白的磷酸化水平分别是11.2G组的3.33倍(P0.01)和1.17倍(P0.01),加入IGF-1以后,进一步抑制它们的丝氨酸磷酸化水平。添加JNK抑制剂SP600125后,可以完全抑制JNK的激活,但仅部分抑制IRS的丝氨酸磷酸化水平,并且使33.3mmol/L葡萄糖培养下细胞活性增加8%(P0.05),凋亡减少49%(P0.01)。结论:高糖通过激活JNK信号分子抑制IRS信号系统,从而抑制胰岛β细胞活性,促进凋亡发生。阻断JNK信号分子可以通过抑制IRS的丝氨酸磷酸化而减少细胞凋亡,改善胰岛β细胞功能。     

儿茶素抑制兔晶状体上皮细胞增殖

目的：探讨在绿茶提取物表没食子儿茶素没食子酸酯（EGCG）抑制兔晶状体上皮细胞增殖过程中， MEK/ERK1/2(mitogen-activated protein kinase kinase, MAPKK, MEK; extracellular signal-regulated kinase，ERK)及c-jun氨基末端激酶（c-Jun NH2-terminal protein kinase， JNK）信号转导通路的作用。 方法： 实验按EGCG浓度分50、100和200 μmol/L 3组。预先分别加入25、50 μmol/L的ERK活性拮抗剂PD980059孵育1 h；用噻唑蓝比色法（MTT比色法）测定晶状体上皮细胞增殖；用蛋白质免疫沉淀法(Western blotting)法检测ERK及JNK的磷酸化水平。 结果： （1）PD980059能明显增强EGCG抑制晶状体上皮细胞增殖的作用，呈浓度依赖性。（2）晶状体上皮细胞内磷酸化的ERK基础水平高。加入EGCG后其活性升高，随后逐渐回降,但始终高于基础水平；ERK的活化水平也随EGCG浓度的增加而增高。（3）细胞内JNK的54 kD亚型磷酸化的基础水平较低而46 kD亚型的较高；呈剂量与时间依赖性。 结论： EGCG可能部分通过调节ERK和JNK的磷酸化水平而抑制晶状体上皮细胞的增殖。     

JNK抑制剂对D-氨基葡萄糖衍生物诱导人食管癌Eca-109细胞细胞周期阻滞和细胞凋亡的影响

目的 观察特异性c-Jun氨基末端激酶（JNK）抑制剂SP600125对D-氨基葡萄糖衍生物2-（3-羧基-1-丙酰氨基）-2-脱氧-D-葡萄糖（COPADG）诱导的Eca-109细胞凋亡和细胞周期阻滞的影响，并探讨COPADG诱导Eca-109细胞凋亡的潜在分子机制。方法 体外培养Eca-109细胞，以COPADG及SP600125与细胞作用；Western blot法检测P-JNK蛋白表达，MTT法检测细胞增殖，流式细胞术检测细胞周期。结果 COPADG显著增加Eca-109细胞P-JNK蛋白的表达和细胞凋亡率，且诱导Eca-109细胞发生G0/G1期细胞阻滞，SP600125明显减少Eca-109细胞凋亡，并使G0/G1期细胞阻滞向G2/M期细胞阻滞发展。 结论：COPADG可能通过激活JNK信号通路诱导Eca-109细胞凋亡。     

p38 MAPK- Pim-3通路可能介导预处理对抗心肌细胞缺氧/复氧损伤

目的： 研究MAPK通路在原癌基因Pim-3抗心肌急性缺氧复氧损伤中的作用。方法：采用原代培养新生大鼠的心肌细胞,随机分为4组：正常对照组（control）、缺氧复氧组(A/R)、缺氧预适应组(APC+A/R)、阻断剂组。在缺氧预处理前分别用终浓度为10 μmol/L SB203850(p38 MAPK阻断剂)、U0126（ERK1/2阻断剂）、SP600125（SAPK/JNK阻断剂）与细胞孵育30 min。实验结束后测定MAPKs通路中ERK1/2、JNK、p38 MAPK 磷酸化蛋白表达水平及Pim-3蛋白的表达水平,同时检测培养液中乳酸脱氢酶(LDH) 活性、四唑盐（MTT）比色试验测定细胞存活率、TUNEL法检测细胞凋亡。结果： SB203850、U0126、SP600125能分别取消由APC或A/R所诱导ERK1/2、JNK、p38 MAPK的磷酸化水平的升高;由APC所诱导的Pim-3表达的升高在p38 MAPK通路被阻断后明显下调(P<0.01),并且心肌细胞LDH值升高,细胞存活率则下降,心肌细胞的凋亡指数升高。结论： p38 MAPK的激活可上调原癌基因Pim-3的表达,从而可能对心肌细胞起到保护作用。     

氯沙坦通过ERK1/2 MAPK途径抑制高糖诱导小鼠系膜细胞CTGF表达

目的: 研究高糖环境下, 氯沙坦对CTGF的影响以及其作用机制.方法: 体外培养小鼠系膜细胞株(MMCs), 用高糖(25 mmol/L葡萄糖)刺激细胞分别作用24 h、 48 h、 72 h, 用Western blot方法检测磷酸化ERK1/2的表达.再将细胞分为低糖组(5.6 mmol/L葡萄糖), 山梨醇组(5.6 mmol/L葡萄糖+19.4 mmol/L山梨醇), 高糖组(25 mmol/L葡萄糖), 氯沙坦组(25 mmol/L葡萄糖+10-5 mol/L氯沙坦)以及 ERK抑制剂组(25 mmol/L葡萄糖+ 25 μmol/L PD98059), 48 h后采用Western blot方法检测磷酸化ERK1/2的表达, 72 h后采用Real-time PCR方法及Western blot分别检测 CTGF mRNA表达量以及蛋白的表达.结果: 高糖刺激小鼠系膜细胞后, ERK1/2磷酸化的蛋白表达逐渐增高, 呈现一定时间依赖性.与低糖组相比, 高糖组磷酸化ERK1/2、 CTGF的蛋白表达明显增加(P<0.01), 而与高糖组相比, 氯沙坦组以及ERK抑制剂组磷酸化ERK1/2的蛋白表达以及CTGF的蛋白均明显下降有统计学意义(P<0.05).与低糖组相比, 高糖组CTGF mRNA表达量明显增加(P<0.01), 而与高糖组相比, 氯沙坦组以及ERK抑制剂组CTGF mRNA表达量明显下降, 且有统计学意义(P<0.01).结论: 氯沙坦可抑制高糖对CTGF的诱导作用, 其机制可能与抑制ERK1/2 MAPK途径有关.     

肌肽对高糖诱导的心肌成纤维细胞增殖的影响

目的 研究肌肽(carnosine)对高糖环境下大鼠心脏成纤维细胞(cardiac flbroblasts,CFs)增殖的影响及机制.方法 以CFs为研究对象,使用Brdu-酶联免疫吸附试验(enzyme-linked immu-nosorbent assays,ELISA)检测法观察肌肽抑制高糖环境下心肌成纤维细胞DNA的合成;细胞周期的测定采用流式细胞仪法;Western blot法观察不同条件下CFs中CDK2、CyclinE、PCNA、ERK1/2、p-ERK1/2及p21和p27的蛋白表达情况.结果 肌肽能够抑制高糖环境下CFs的DNA合成,通过调节细胞周期和细胞周期的相关蛋白表达来实现这种作用.与高糖组比较,20 mmol/L肌肽组明显抑制了高糖刺激的大鼠CFs中CDK2、CyclinE、PCNA蛋白的表达增加(t CDK2=6.19、t CyclinE=5.7、t PCNA=8.56,P<0.05),差异具有统计学意义;与高糖组比较20 mmol/L肌肽则使p21、p27表达水平增加了(t p21=5.16、t p27=8.558,P<0.05),具有统计学意义;与高糖组比较20 mmol/L的肌肽或20 mol/L的PD-98059(ERK1/2抑制剂)明显抑制了高糖刺激的大CFs中p-ERK1/2的表达增加(t肌肽=5.64、t PD=8.68,P<0.05),差异具有统计学意义.结论 肌肽能够通过ERK1/2 MAPK信号通路抑制高糖环境下心肌成纤维细胞的DNA合成.     

高糖诱导人内皮细胞凋亡及其JNK、AKT信号途径的作用机制

目的探讨高糖诱导人脐静脉内皮细胞(humanumbilicalveinendothelialcells,HUVECs)凋亡的JNK及AKT信号途径作用机制。方法HUVECs细胞分别在生理浓度葡萄糖(5mmol/L) (NG)、高葡萄糖(30mmol/L) (HG)、高糖加JNK特异性阻断剂SP6 00 12 5 (10 μmol/L) (HG +I)条件下培养72h。Hoechst332 5 8染色,荧光显微镜观察细胞凋亡的形态学改变;annexinV FITC试剂盒染色,流式细胞仪进行细胞凋亡定量;Westernblot方法测定细胞p JNK、p- c- JUN、p AKT水平。结果高葡萄糖培养72h ,内皮细胞凋亡率为13 .31% ,显著高于对照组5 . 6 9% (P <0 . 0 1)。高糖条件下内皮细胞p JNK、p c JUN水平较对照组显著增加(P <0 . 0 5 ) ,而p AKT显著降低(P <0 . 0 1)。SP6 0 0 12 5应用后,与高糖组比较p JNK无显著变化、p c JUN含量降低(P <0 .0 5 ) ,而p AKT升高(P <0 . 0 1) ,高糖诱导的内皮细胞凋亡被抑制(8. 38% ,P <0 . 0 1)。结论高糖可诱导内皮细胞凋亡,其机制可能是激活JNK及其下游c- JUN ,而抑制AKT的活化,而JNK活化程度对AKT信号通路可能存在调节作用。     

Adiponectin exerts antiproliferative effect on human placenta via modulation of the JNK/c-Jun pathway

To determine the effects of adiponectin on human placenta during gestational diabetes mellitus (GDM) and on high glucose (HG)-induced BeWo cell proliferation. We examined the expression levels of adiponectin in control and GDM placenta using quantitative real-time PCR, Western blot, and immunohistochemistry (IHC). Cell proliferation and viability were assessed using a colorimetric assay (cell counting kit-8), PCNA immunocytochemical staining, and Western blot analysis of cyclin D1. Transfection of siRNA against c-jun was performed using Lipofectamine 2000. Cell cycle analysis was performed using propidium iodide staining and flow cytometry. Results show a decreased expression of adiponectin and an increased degree of trophoblast cell proliferation in GDM placenta compared to the normal placenta. Similarly, HG can promote BeWo cell proliferation that is associated with adiponectin down-regulation. This proliferation could be depressed by addition of exogenous adiponectin, i.e. adiponectin exerts antiproliferative effects on HG-induced trophoblast cells. Adiponectin suppresses the HG-induced BeWo cell proliferation by inhibiting the activation of JNK/c-jun. In conclusion, adiponectin inhibits HG-induced proliferation of BeWo cells through down-regulation of JNK/c-jun phosphorylation.     

柚皮苷在促大鼠骨髓间充质干细胞骨向分化过程中对MAPK信号通路的影响

目的: 研究中药单体柚皮苷(NG)对体外培养的大鼠骨髓间充质干细胞(MSCs)向成骨细胞分化过程中MAPK信号通路的影响。方法: 观察在正常、加入p38、ERK和JNK通路抑制剂SB203580、PD98059、SP600125及3种抑制剂全部加入的情况下,各组碱性磷酸酶(ALP)、骨钙素(BGP)、I型胶原(Col I)等骨向分化指标的差异。用Western blotting技术检测各组p38、ERK1/2和JNK蛋白的磷酸化水平,用荧光定量PCR技术检测细胞因子转化生长因子β₁(TGF-β₁)、骨形成蛋白2(BMP-2)和核心结合因子α1(Cbfα1) mRNA的表达。结果: (1)10^-7mol/L为本实验中NG的最佳促骨向分化浓度。(2) NG最佳浓度组的ALP和BGP含量比其它各组都高(P<0.05),Col I含量无明显差异(P>0.05);与NG组相比,加入不同抑制剂组的ALP、BGP和ColⅠ表达量出现不同程度的降低。(3)与空白组相比,NG组JNK蛋白的磷酸化水平升高(P<0.05),p38蛋白的磷酸化水平降低(P<0.01),ERK1/2蛋白的磷酸化水平无明显差异(P>0.05)。与NG组相比,加入不同抑制剂组的p38、ERK1/2和JNK蛋白的磷酸化水平有升高也有降低。(4) NG组上调BMP-2的表达(P<0.05),下调Cbfα1的表达(P<0.05),而对TGF-β₁的表达无明显影响(P>0.05)。与NG组相比,加入不同抑制剂组的TGF-β₁、BMP-2和Cbfα1 mRNA表达量出现不同程度的降低。结论: NG主要通过激活MAPK信号通路中ERK通路、JNK通路以及上调BMP-2的表达,促进MSCs的骨向分化。NG上调BMP-2的表达受MAPK通路中p38通路的影响较大。     

Growth suppression of human mast cells expressing constitutively active c-kit receptors by JNK inhibitor SP600125

Activation of c-jun N-terminal kinase (JNK) through c-kit-mediated phosphatidylinositol 3 (PI3) and Src kinase pathways plays an important role in cell proliferation and survival in mast cells. Gain-of-function mutations in c-kit are found in several human neoplasms. Constitutive activation of c-kit has been observed in human mastocytosis and gastrointestinal stromal tumor. In the present study, we demonstrate that an anthrapyrazole SP600125, a reversible ATP-competitive inhibitor of JNK inhibits proliferation of human HMC-1 showed constitutive activation of JNK/c-Jun, and the inhibitory effect of SP600125 on cell proliferation was associated with cell cycle arrest at the G1 phase and apoptosis accompanied by the cleavage of caspase-3 and PARP. Caspase-3 inhibitor Z-DEVD-FMK almost completely inhibited SP600125-induced apoptosis of HMC-1 cells. In contrast, caspase-9 inhibitor Z-LEHD-FMK failed to block SP600125-induced apoptosis. Following Sp600125 treatment, down-regulation of cyclin D3 protein expression, but not p53 was also observed. Thus, JNK/c-Jun is essential for proliferation and survival of HMC-1 cells. The results obtained from the present study suggest the possibility that JNK/c-Jun may be a therapeutic target in diseases associated with mutations in the catalytic domain of c-kit.     

胰岛素对高糖培养的人系膜细胞表达SGK1及合成细胞外基质的影响

目的：研究胰岛素对高糖培养的人系膜细胞（HMC）血清和糖皮质激素诱导的蛋白激酶1(SGK1)的表达及细胞外基质（ECM）合成的影响，初步探讨其主要作用环节。方法:用含有5.5 mmol/L、25 mmol/L葡萄糖和100 nmol/L胰岛素的DMEM培养基培养HMC细胞，即为对照组（NG）、高糖组（HG）、胰岛素干预对照组（NI）和胰岛素干预高糖组（HI）。4 h后检测SGK1的表达、胰岛素受体底物（IRS1和IRS2）蛋白的表达及磷酸化水平；24 h后检测结缔组织生长因子（CTGF）和纤连蛋白（FN）的表达。结果:HG组、NI组和HI组SGK1蛋白表达均显著高于NG组（P<0.01），高糖主要导致IRS2蛋白表达及磷酸化水平的增高（P<0.01）。胰岛素干预后，HI组IRS1蛋白表达及磷酸化水平明显高于HG组（P<0.05），而IRS2蛋白表达及磷酸化水平出现部分抑制（P<0.05）。高糖促进CTGF和FN的表达，胰岛素加强高糖此作用。结论:胰岛素和高糖能够通过不同的分子途径促进体外肾小球系膜细胞SGK1的表达，并最终促进ECM的合成；胰岛素的这种作用与IRS1信号转导通路密切相关。     

The c-Jun N-terminal kinase pathway is critical for cell transformation by the latent membrane protein 1 of Epstein-Barr virus

The latent membrane protein 1 (LMP1) of Epstein-Barr virus (EBV) transforms cells activating signal transduction pathways such as NF-kappaB, PI3-kinase, or c-Jun N-terminal kinase (JNK). Here, we investigated the functional role of the LMP1-induced JNK pathway in cell transformation. Expression of a novel dominant-negative JNK1 allele caused a block of proliferation in LMP1-transformed Rat1 fibroblasts. The JNK-specific inhibitor SP600125 reproduced this effect in Rat1-LMP1 cells and efficiently interfered with proliferation of EBV-transformed lymphoblastoid cells (LCLs). Inhibition of the LMP1-induced JNK pathway in LCLs caused the downregulation of c-Jun and Cdc2, the essential G2/M cell cycle kinase, which was accompanied by a cell cycle arrest of LCLs at G2/M phase transition. Moreover, SP600125 retarded tumor growth of LCLs in a xenograft model in SCID mice. Our data support a critical role of the LMP1-induced JNK pathway for proliferation of LMP1-transformed cells and characterize JNK as a potential target for intervention against EBV-induced malignancies.     

Effect of an inhibitor of Jun N-terminal protein kinase, SP600125, in single allergen challenge in sensitized rats

Jun N-terminal kinase (JNK) has been implicated in the pathogenesis of inflammatory diseases including asthma. We examined the effect of SP600125 (anthra [1,9-cd] pyrazol-6 (2H)-one), a novel inhibitor of JNK in a model of asthma. Brown-Norway rats were sensitized to ovalbumin and treated with SP600125 intraperitoneally (90 mg/kg in total). SP600125 inhibited allergen-induced, increased activity of phosphorylated c-jun but not of phosphorylated-MAPKAPK2, indicative of activation of p38 MAPK, in the lung. SP600125 inhibited macrophage (P < 0.04), lymphocyte (P < 0.05), eosinophil (P < 0.04) and neutrophil (P < 0.005) numbers in bronchoalveolar lavage. Eosinophil and T-cell accumulation in the airways, mRNA expression for interleukin-1beta, tumour necrosis factor-beta, interleukin-3, interleukin-4 and interleukin-5, serum levels of allergen-specific immunoglobulin E and bronchial hyperresponsiveness were not affected by SP600125. Selective inhibition of JNK reduced inflammatory cell egress into the airway lumen after single allergen exposure. The role of JNK mitogen-activated protein kinase activation may be limited in the pathogenesis of bronchial hyperresponsiveness after single allergen exposure.     

Neuroprotection by c-Jun NH2-terminal kinase inhibitor SP600125 against potassium deprivation–induced apoptosis involves the Akt pathway and inhibition of cell cycle reentry

Increasing evidence implicates the c-Jun NH₂-terminal kinase (JNK) pathway in the regulation of apoptosis in neurodegenerative diseases. In this study, we examined the neuroprotective effect of SP600125, a selective JNK inhibitor, in cerebellar granule cells (CGNs) deprived of serum and potassium (S/K withdrawal). S/K withdrawal-induced apoptosis occurs via activation of multiple pro-apoptotic pathways, including re-entry into the cell cycle, activation of glycogen synthase kinase-3 beta (GSK-3β), cyclin-dependent kinase 5 (cdk5/p35) breakdown, formation of cdk5/p25 and JNK activation. Here we demonstrate that SP600125 is able to inhibit all these pro-apoptotic pathways via the inhibition of JNK. Further, we found that JNK inhibition maintains the phosphorylation/activation of Akt after S/K withdrawal. For further confirmation of this result, we studied several targets downstream of Akt including GSK-3β, p-FOXO1, p-CREB and p35. In addition, the specific PI3K/Akt inhibitor LY294002 greatly diminished the antiapoptotic effects of SP600125 upon S/K withdrawal, confirming that Akt is involved in the neuroprotection achieved by SP600125. These results suggest that the maintenance of the PI3-kinase/Akt pathway by inhibition of JNK contributes to the prevention of apoptosis in rat cerebellar granule neurons mediated by S/K withdrawal. Furthermore, we propose that JNK may regulate the cell cycle re-entry by a novel mechanism that involves Akt, GSK-3β and Rb phosphorylation.