小檗碱对高糖高脂诱导的NIT-1胰岛β细胞凋亡的影响

目的：探讨小檗碱对高糖高脂诱导的NIT-1胰岛β细胞凋亡的影响。方法：采用四甲基偶氮唑蓝(MTT)比色法比较不同浓度的小檗碱对体外培养及高糖高脂诱导的NIT-1胰岛β细胞凋亡的作用，同时应用流式细胞术及原位末端核苷酸标记法(TUNEL)检测细胞凋亡。结果：不同浓度的小檗碱对NIT-1胰岛β细胞作用呈剂量依赖性：低浓度小檗碱（≤5 μmol/L） 对细胞无明显毒性，随浓度升高毒性作用明显。在培养基中加入高糖高脂及低浓度的小檗碱共同培养24 h, 小檗碱组细胞凋亡率低于高糖高脂组（P<0.01）。结论：小檗碱能抑制高糖高脂诱导的NIT-1胰岛β细胞凋亡。     

血小板衍化生长因子DD刺激大鼠肾成纤维细胞增殖及向肌成纤维细胞的转化

背景：血小板衍化生长因子可诱导肾小球系膜细胞及肾间质多种细胞增殖、迁移、转化及细胞外基质的过表达。目的：观察血小板衍化生长因子DD/血小板衍化生长因子βR信号通路激活对大鼠肾成纤维细胞细胞增殖及α-平滑肌肌动蛋白表达的影响。方法：体外培养正常大鼠肾成纤维细胞(NRK-49F),按照血小板衍化生长因子DD刺激质量浓度分为对照组、1 μg/L组、10 μg/L组、50 μg/L组、100 μg/L组,然后根据50 μg/L 血小板衍化生长因子DD刺激不同时间分为对照组、12 h组、24 h组、48 h组。CCK8检测不同血小板衍化生长因子DD质量浓度及血小板衍化生长因子DD作用不同时间对NRK-49F增殖的影响;Real-time PCR检测各质量浓度组血小板衍化生长因子βR、α-平滑肌肌动蛋白mRNA变化;Western blot检测各浓度组血小板衍化生长因子βR、α-平滑肌肌动蛋白蛋白表达变化。结果与结论：与对照组相比,血小板衍化生长因子DD可明显刺激NRK-49F细胞增殖,呈现剂量依赖性及时间依赖性。血小板衍化生长因子DD可剂量依赖性刺激其相应血小板衍化生长因子βR及α-平滑肌肌动蛋白在mRNA水平及蛋白水平上的表达增加。提示血小板衍化生长因子DD/血小板衍化生长因子βR信号通路的激活可显著刺激NRK-49F细胞的增殖及向肌成纤维细胞的转化。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：     

完全脾切除增加了小鼠胰岛对STZ的敏感性

目的: 探讨脾脏对链脲菌素(STZ)损伤胰岛β细胞是否具有保护作用。方法: 以外科手术切除小鼠全脾。60只脾切除小鼠随机分为3组,分别以80 mg/kg、160 mg/kg STZ给小鼠腹腔注射,另一组腹腔注射生理盐水。60只正常小鼠做同样分组及处理。1周后,测定各组小鼠空腹血糖、血清胰岛素水平,免疫组化分析各组胰岛β细胞总量,ELISA法分析胰岛细胞凋亡,Luminol化学发光法测定各组胰腺活性氧簇(ROS)水平。结果: 80 mg/kg STZ处理脾切除组空腹血糖浓度显著升高,血清胰岛素显著降低;同剂量STZ处理的正常小鼠血糖及胰岛素水平则正常;此外, 80 mg/kg STZ处理的脾切除小鼠β细胞总量、胰岛凋亡细胞核小体聚集值及胰腺组织ROS的产生与同剂量STZ处理的正常小鼠相比均有显著差异。结论: 脾可以阻止低剂量STZ对正常小鼠胰岛β细胞的破坏作用。完全脾切除增加了胰岛对STZ的敏感性,这一作用与胰腺组织ROS增加相关。     

5-氟尿嘧啶改变胰岛β细胞的超微结构并抑制胰岛素的释放

目的: 探讨5-氟尿嘧啶(5-FU)抑制小鼠胰岛β细胞(NIT-1细胞)胰岛素分泌的相关分子机制。方法: 不同剂量的5-FU作用于NIT-1细胞,放射免疫分析法检测细胞胰岛素分泌功能的变化;Annexin V/PI双染色流式细胞术检测细胞凋亡;透射电镜观察细胞超微结构的变化;RT-PCR及Western blotting 检测胰十二指肠同源盒蛋白-1(PDX-1)mRNA和蛋白的表达。结果: 5.0-40.0 mg/L的5-FU作用24 h后,低浓度葡萄糖(5.6 mmol/L)环境下,NIT-1细胞胰岛素分泌无明显下降(P>0.05);而高浓度葡萄糖(16.7 mmol/L)刺激下的胰岛素分泌量可被5.0-40.0 mg/L 5-FU以剂量依赖性的方式所抑制(P<0.01)。细胞凋亡率明显增高(P<0.05);透射电镜可见线粒体结构改变;经10.0-40.0 mg/L的5-FU作用24 h后,PDX-1 mRNA及蛋白表达的水平均有不同程度的下降(P<0.05)。结论: 5-FU可通过诱导细胞凋亡、导致β细胞超微结构改变及数量减少而抑制胰岛β细胞高糖刺激下的胰岛素释放。下调 PDX-1 基因表达可能是5-FU在高糖条件下诱导β细胞凋亡的机制之一。     

17β-雌二醇通过PI3K-Akt信号通路抑制丙泊酚诱导皮层神经元凋亡

 目的: 探讨17β-雌二醇对丙泊酚诱导原代培养皮层神经元凋亡的影响及机制。方法: 原代培养7 d的大鼠皮层神经元,给予不同浓度丙泊酚和或17β-雌二醇处理12 h,用MTT法检测神经元存活率变化,Hoechst 33258核染色法检测神经元调亡,Western blot法测定神经元p-Akt蛋白的变化。结果: 与溶剂对照组比较,丙泊酚呈剂量依赖性降低神经元存活率(P<0.05);与丙泊酚组比较,17β-雌二醇呈剂量依赖性提高神经元存活率(P<0.05),PI3K/Akt激动剂IGF组神经元存活率显著增加(P<0.01)。与溶剂对照组比较,丙泊酚组神经元凋亡率显著增加(P<0.01),丙泊酚+17β-雌二醇组神经元凋亡率较丙泊酚组显著下降(P<0.01),LY294002预处理可阻断17β-雌二醇的作用,使细胞凋亡率增加(P<0.01)。与溶剂对照组比较,丙泊酚呈剂量依赖性降低神经元p-Akt蛋白水平(P<0.05);与丙泊酚组比较,17β-雌二醇呈剂量依赖性提高神经元p-Akt蛋白水平(P<0.05);与丙泊酚+17β-雌二醇组比较,LY294002预处理组p-Akt蛋白水平显著下降(P<0.01)。结论: 17β-雌二醇可抑制丙泊酚诱导的原代培养皮层神经元凋亡,其机制可能与激活PI3K-Akt信号通路有关。     

3β，5α，6β-三羟基胆甾烷诱导恶性胶质瘤细胞的凋亡

 目的：研究3β,5α,6β-三羟基胆甾烷(Triol)诱导恶性胶质瘤细胞凋亡的作用及其机制。方法：以不同浓度的Triol作用于C6细胞和A172细胞不同时间。采用MTT法检测细胞存活率,Hoechst 33342染色和TUNEL法检测细胞凋亡,试剂盒检测caspase活性变化,蛋白免疫印记方法检测凋亡相关蛋白Bcl-2家族蛋白的变化。结果：Triol可呈剂量和时间依赖性降低C6细胞和A172细胞的存活率;Triol处理细胞48 h,C6细胞和A172细胞的IC50值分别为（17.8±0.6)μmol/L和(20.6±0.2)μmol/L。Hoechst 33342染色、TUNEL检测和凋亡执行酶caspase-3活性检测结果显示,给药组中2种细胞都出现明显凋亡核象、TUNEL阳性细胞数增多和caspase-3的激活。Triol作用于C6细胞12 h、24 h和48 h后,在凋亡外通路中激活的caspase-8和在凋亡内通路中激活的caspase-9活性均随时间升高,抗凋亡蛋白Bcl-2和Bcl-xL的表达量随时间降低,而促凋亡蛋白Bak的表达量随时间升高。结论：Triol通过激活内、外凋亡通路引起恶性胶质瘤细胞的凋亡,且 Bcl-2家族蛋白在此过程中起重要的调控作用。     

石杉碱甲的抗炎作用及其对大鼠神经干细胞的保护作用

 目的： 探讨石杉碱甲（HupA）的抗炎作用及其对大鼠神经干细胞的保护作用。方法：取新生SD大鼠海马组织,分离并培养神经干细胞和小胶质细胞,建立Transwell共培养体系。将细胞分成3组：空白对照组、淀粉样β肽（Aβ）组和HupA组。Aβ组小胶质细胞层中加入终浓度为10 μmol/L的Aβ1-42,HupA组于加入Aβ1-42前4 h用1 μmol/L HupA预处理小胶质细胞。液相芯片技术检测炎症因子白细胞介素6（IL-6）、肿瘤坏死因子α（TNF-α）和巨噬细胞炎症蛋白1α（MIP-1α）的表达,流式细胞术和Western blotting检测神经干细胞的凋亡。结果：小胶质细胞与神经干细胞共培养72 h后,与空白对照组相比,Aβ组IL-6、TNF-α和MIP-1α水平以及神经干细胞凋亡率（25.46%）均显著升高(P<0.01);HupA预处理小胶质细胞后,Aβ诱导的小胶质细胞炎症因子分泌显著减少,IL-6、TNF-α和MIP-1α的水平降低(P<0.01),同时神经干细胞凋亡率降低至8.05% (P<0.01)。Western blotting检测结果显示,HupA组Bcl-2/Bax值显著高于Aβ组(P<0.05)。结论：石杉碱甲可以抑制小胶质细胞分泌细胞因子和趋化因子,减弱Aβ诱导的炎症反应,降低神经干细胞凋亡率,从而发挥抗炎和神经保护作用。     

胰岛淀粉样多肽对高糖刺激下INS-1细胞凋亡及其相关基因表达的影响

目的探讨高糖刺激下转染过表达人胰岛淀粉样多肽基因的大鼠胰岛素瘤细胞(INS-1)细胞凋亡的影响及其相关基因表达。方法应用酶联免疫吸附法(ELISA)检测高糖刺激后INS-1及转染人胰岛淀粉样多肽的INS-1细胞(h IAPP/INS-1)上清液的胰岛素水平;利用Hoechst33258染色检测细胞凋亡百分率;采用RTPCR方法检测高糖刺激培养后的Bcl2、Bax m RNA的水平。结果高糖刺激下,与未转染人胰岛淀粉样多肽INS-1细胞相比较,h IAPP/INS-1细胞胰岛素分泌功能显著下降,凋亡细胞比例明显增加,抗凋亡基因Bcl2 m RNA表达水平下调,促凋亡基因Bax m RNA表达水平上调,Bcl2/Bax比例明显降低。结论人胰岛淀粉样多肽上调促凋亡基因表达和抑制抗凋亡基因表达可能与糖尿病的发生发展相关。     

α7nAChR参与生理浓度糖皮质激素的抗炎作用*

 目的： 探讨α7烟碱型乙酰胆碱受体（α7nAChR）在生理浓度糖皮质激素（GCs）抗炎过程中的作用。方法: MTT法检测不同浓度氢化可的松对小胶质细胞BV-2活性的影响;在建立LPS刺激的BV-2细胞炎症模型基础上,实验分组如下：(1) 空白对照组;(2) LPS组;(3) GCs＋LPS组;(4) α7nAChR阻断剂甲基牛扁亭碱（MLA）＋GCs＋LPS组,ELISA法测定细胞上清中TNF-α和IL-1β的含量。结果: 2 000 和1 000 nmol/L 氢化可的松可分别使细胞存活率降低至(76.9±5.5)%和(90.8±7.3)%,表现出超生理剂量GCs的细胞损伤作用。LPS明显刺激BV-2细胞释放TNF-α和IL-1β,并呈现时间和剂量依赖性。生理浓度（500和250 nmol/L）的氢化可的松均可减少LPS诱导BV-2细胞释放TNF-α和IL-1β,10 nmol/L MLA预处理BV-2细胞能拮抗GCs抑制炎症因子释放的作用。结论: α7nAChR参与了生理浓度GCs的抗炎作用。     

Akt信号通路在左归丸抑制左旋单钠谷氨酸大鼠神经细胞凋亡中的作用

目的:观察Akt信号通路在左旋单钠谷氨酸(MSG)和左归丸(ZGW)对成年大鼠神经细胞凋亡中的作用。方法:采用流式细胞仪和Westernblot方法检测细胞凋亡率和Akt信号通路变化。结果:MSG可增加细胞凋亡率,显著降低Akt(Ser473)和Akt(Thr308)水平;明显增加FKHR(Ser256)、GSK-3β(Ser9)和PTEN表达。ZGW可抑制MSG的部分效应。结论:左归丸能抑制MSG大鼠神经细胞凋亡,这一作用可能与Akt信号通路有关。     

Berberine Inhibits Inflammatory Response and Ameliorates Insulin Resistance in Hepatocytes

Berberine, a major isoquinoline alkaloid present in Chinese herb Rhizoma coptidis, is a potent inhibitor of inflammation and has anti-diabetic activity. This study aims to investigate effects of berberine on ameliorating insulin resistance and molecular mechanisms involved in HepG2 cells. Inflammatory responses and insulin resistance were induced by palmitate (PA) stimulation for 24 h. Treatment of berberine enhanced insulin-mediated glycogen synthesis and restored insulin inhibition of triglyceride secretion. Stimulation of PA resulted in IL-6 and TNF-α production in HepG2 cells, and antibody-neutralizing assay further confirmed that IL-6 and TNF-α were involved in the development of insulin resistance. Berberine effectively inhibited IL-6 and TNF-α production in a concentration-dependent manner, demonstrating its anti-inflammatory activity in hepatocytes. Meanwhile, PA-evoked inflammation impaired insulin signaling cascade and berberine improved insulin signaling cascade by modification of Ser/Thr phosphorylation of insulin receptor substrate-1(IRS-1) and downstream Akt (T308). Above results suggest that berberine improved insulin sensitivity in PA-stimulated hepatocytes and this regulation might relative with its anti-inflammatory activity.     

小檗碱干预2型糖尿病模型大鼠脑缺血再灌注损伤

文题释义： 小檗碱(berberine,BBR)：是从黄连中提取的一种异喹啉类生物碱,具有多种生化和药理作用,在临床上得到广泛应用。已有文献证明,小檗碱具有降低高血糖、减轻胰岛素抵抗和抑制脂质合成的作用。缺血再灌注损伤：遭受一定时间缺血的组织细胞恢复血流(再灌注)后,组织损伤程度迅速增剧的情况。再灌注后有大量钙内流,并生成大量氧自由基,是广泛组织细胞损伤的主要发病机制。临床上多种疾病如迟发性神经元坏死、不可逆性休克、心肌梗死、脑梗死及器官移植排斥反应等的发生、发展都与缺血、再灌注有关。 背景：既往研究提示小檗碱可减轻脑缺血再灌注损伤。 目的：探讨小檗碱对2型糖尿病大鼠脑缺血再灌注损伤的影响及其分子机制。 方法：实验方案经海南省中医院伦理委员会批准。用低剂量链脲佐菌素30 mg/kg每隔1 d大鼠腹腔注射2次,处理8周建立2型糖尿病模型,选取平均血糖≥11.1 mmol/L造模成功的雄性SD大鼠90只,随机分为对照组、缺血/再灌注组和缺血/再灌注+小檗碱组,每组30只。对照组和缺血/再灌注组大鼠经生理盐水灌胃,缺血/再灌注+小檗碱组用小檗碱 200 mg/(kg·d)灌胃,处理7 d后,后2组采用大脑中动脉阻断2 h,再灌注12 h建立大脑中动脉缺血再灌注模型。苏木精-伊红染色和透射电镜观察脑梗死体积;采用ELISA检测梗死区超氧化物歧化酶、丙二醛和一氧化氮水平;采用TUNEL法检测脑细胞凋亡情况;Westernblot检测PI3K、Akt和磷酸化Akt(p-Akt)蛋白的表达。 结果与结论：①与缺血/再灌注组比较,缺血/再灌注+小檗碱组脑梗死体积明显减少(P < 0.05),超氧化物歧化酶水平明显升高,丙二醛和一氧化氮的表达明显降低;②与缺血/再灌注组比较,缺血/再灌注+小檗碱组脑梗死区细胞凋亡减少,Bcl-2表达增加,cleaved-Caspase3和Bax表达降低;③与缺血/再灌注组相比,小檗碱可使缺血/再灌注+小檗碱组PI3K和p-Akt的表达水平明显上调;④结果说明,小檗碱可通过激活PI3K-Akt信号通路,在2型糖尿病大鼠脑缺血模型中发挥抗凋亡作用,减轻脑缺血/再灌注损伤。ORCID: 0000-0003-3326-2624(符芸瑜) 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程     

Presenilins regulate the cellular level of the tumor suppressor PTEN

Alzheimer's Disease (AD) is characterized by amyloid plaques consisting of beta-amyloid (Abeta) peptides and neurofibrillary tangles consisting of hyperphosphorylated tau protein. Abeta is proteolytically derived from its precursor protein through cleavages by beta-secretase and gamma-secretase complex comprising presenilins (PS, PS1/PS2), nicastrin, APH-1 and PEN-2. PS1 is also known to activate the PI3K/Akt cell survival pathway in a gamma-secretase-independent manner. The tumor suppressor PTEN, which antagonizes the PI3K/Akt pathway, has increasingly been recognized to play a key role in neural functions and its level found reduced in AD brains. Here, we demonstrate that the protein level of PTEN is dramatically reduced in cultured cells and embryonic tissues deficient in PS, and in the cortical neurons of PS1/PS2 conditional double knockout mice. Restoration of PS in PS-deficient cells reverses the reduction of PTEN. Regulation of PTEN by PS is independent of the PS/gamma-secretase activity since impaired gamma-secretase by the gamma-secretase inhibitor treatment or due to nicastrin deficiency has little effect on the protein level of PTEN. Our data suggest an important role for PS in signaling pathways involving PI3K/Akt and PTEN that are crucial for physiological functions and the pathogenesis of multiple diseases.     

小檗碱对人高转移肺癌系（PG）细胞增殖的影响及机制研究

目的：通过离体实验初探小檗碱对高转移性人肺癌细胞株（PG）增殖能力的影响，并探讨其作用机制。 方法： 用MTT法测定小檗碱对PG细胞增殖能力的影响。用流式细胞术测定小檗碱对PG细胞细胞周期及凋亡的影响。用激光共聚焦显微镜观察小檗碱诱导PG细胞氧自由基的产生。 结果： 小檗碱能够抑制PG细胞增殖，且随药物浓度增加抑制效应增强，呈浓度依赖性(P<0.05，P<0.01)。小檗碱对PG细胞细胞周期具有阻滞作用，40 mg/L的小檗碱能引起PG细胞的凋亡。小檗碱作用6 h、12 h只有在终浓度大于或等于10 mg/L时开始产生氧自由基，低浓度的小檗碱作用24h后就能诱导氧自由基的产生。 结论： 小檗碱对PG细胞增殖具有抑制作用，后者可能与调节细胞内活性氧自由基产生从而影响细胞周期进程有关。     

周络通提取物Z-6对高糖所致Schwann细胞损伤和PI3K/Akt/nNOS通路的影响

 目的:探讨磷酯酰肌醇3-激酶/蛋白激酶B/神经元型一氧化氮合酶（PI3K/Akt/nNOS）信号通路在周络通提取物抗糖尿病周围神经病变中的作用。方法:将体外培养的雪旺（Schwann）细胞分为正常组（D-葡萄糖25 mmol/L）、高糖模型组（D-葡萄糖100 mmol/L）、周络通提取物活性部位5（Z-5）+高糖组、周络通提取物活性部位6（Z-6）+高糖组、周络通+高糖组和甲钴胺+高糖组。采用CCK-8试剂盒检测各组细胞的生存活性,相关试剂盒分析培养上清中NO含量和细胞内Ca2+-ATPase活性的变化,流式细胞仪分析细胞的凋亡情况, Western blotting方法检测 Bcl-2、 Bcl-xL、 Bax、 Bak和caspase-3蛋白表达及nNOS和Akt的磷酸化情况。利用PI3K和Akt的显性负性突变体瞬时转染Schwann细胞,探讨PI3K/Akt信号通路在周络通提取物抗糖尿病周围神经病变中的作用。结果:与模型组比较,周络通提取物Z-6能显著提高高糖损伤后Schwann细胞的存活率,提高NO分泌量并明显上调Bcl-2、 Bcl-xL蛋白的表达及Akt、nNOS 的磷酸化水平,同时显著降低细胞凋亡率及Bax、 Bak、 caspase-3蛋白的水平,利用PI3K的显性负性突变体（δp85）阻断nNOS的上游信号通路PI3K/Akt后,NO分泌量减少,但未对Z-6上调nNOS 和Akt磷酸化的作用产生明显影响。结论: 在高糖损伤条件下,周络通提取物Z-6上调nNOS蛋白磷酸化水平,促进抗凋亡因子的表达,抑制促凋亡因子及caspase-3关键蛋白酶的表达,降低Schwann细胞凋亡率,从而提高高糖损伤细胞的存活率,这些作用与PI3K/Akt/nNOS通路的关系有待进一步研究。     

Akt-mediated activation of HIF-1 in pulmonary vascular endothelial cells by S-nitrosoglutathione

S-nitrosoglutathione (GSNO) stabilizes the alpha-subunit of hypoxia inducible factor-1 (HIF-1) in normoxic cells, but not in the presence of PI3K inhibitors. In this report, the biochemical pathway by which GSNO alters PI3K/Akt activity to modify HIF-1 expression was characterized in Cos cells and primary pulmonary vascular endothelial cells. GSNO increased Akt kinase activity--and downstream HIF-1alpha protein accumulation and DNA-binding activity--in a dose- and time-dependent manner. The PI3K inhibitors, wortmannin and LY294002, blocked these responses. Neither glutathione nor 8-bromo-cyclic GMP mimicked the GSNO-induced increases in Akt kinase activity. GSNO-induced Akt kinase activity and downstream HIF-1alpha stabilization were blocked by acivicin, an inhibitor of gamma-glutamyl transpeptidase (gammaGT), a transmembrane protein that can translate extracellular GSNO to intracellular S-nitrosocysteinylglycine. Dithiothreitol blocked GSNO-induced Akt kinase activity and HIF-1alpha stabilization. Moreover, the 3'-phosphatase of phosphoinositides, PTEN (phosphatase and tensin homolog deleted on chromosome ten) was S-nitrosylated by GSNO in pulmonary arterial endothelial cells, which was reversed by dithiothreitol and ultraviolet light. Interestingly, the abundance of S-nitrosylated PTEN also correlated inversely with PTEN activity. Taken together, these results suggest that GSNO induction of Akt appears to be mediated by S-nitrosylation chemistry rather than classic NO signaling through guanylate cyclase/cGMP. We speculate that gammaGT-dependent activation of Akt and subsequent activation of HIF-1 in vascular beds may be relevant to the regulation of HIF-1-dependent gene expression in conditions associated with oxyhemoglobin deoxygenation, as opposed to profoundly low Po(2), in the pulmonary vasculature.     

PTEN modulates hepatitis B virus-X protein induced survival signaling in Chang liver cells

PTEN gene, a novel tumor suppressor is frequently mutated or deleted in several malignancies including human hepatocellular carcinoma (HCC). We report previously that human hepatitis B virus-X (HBx) protein achieves protection from apoptotic cell death through-PI3K-Akt-Bad signaling that is p53-independent in liver cells (JBC; 276, 16969 (2000)). In this report, we demonstrated the PTEN effect on HBx induced anti-apoptotic signaling in Chang liver cells (CHL). Expression of PTEN in CHL cells downregulate HBx induced PI3K, Akt activities, Akt, Bad phosphorylations, decreased caspase 3 activity and protection from DNA fragmentations. PTEN suppression of CHL cell growth at G1 phase (JBC;278,4057(2003)) in cell cycle analysis, which is overcome by HBx activated Akt/PKB further confirmed that same PI3K/Akt pathway is involved in cell survival and apoptosis by HBx and PTEN. PTEN suppression of HBx-mediated cell survival through PI3K pathway is specific, since PTEN does not suppress the effect of HBx on the protection from Fas-mediated apoptosis. Taken together, these findings demonstrate that PTEN potently modulate HBx-mediated signaling and is a viable target in therapeutic approaches to inhibit the formation of HCC caused by HBV infections.     

PTEN induces apoptosis and cell cycle arrest through phosphoinositol-3-kinase/Akt-dependent and -independent pathways

The tumour suppressor PTEN inhibits cell growth through multiple mechanisms. We have previously demonstrated that overexpression of PTEN in MCF-7 breast cancer cells causes G(1) arrest followed by cell death, the latter of which is believed to be mediated by the phosphoinositol-3-kinase (PI3K) and Akt/PKB pro-apoptotic pathways. In this present study, we show that culture in the presence of low levels of growth factors increased PTEN-mediated growth suppression through the enhancement of PTEN-induced cell death. The caspase 9-specific inhibitor, ZVAD, blocked PTEN-induced cell death without altering the effect of PTEN on cell cycle distribution. Depending on the level of expression, overexpression of dominant-negative Akt induces more cell death and has less effect on the cell cycle or induces similar or decreased cell death without affecting the cell cycle compared with effects on cell death and the cell cycle when overexpressing PTEN. These observations in sum suggest that, in MCF-7 breast cancer cells, the apoptotic cells induced by the overexpression of PTEN did not derive from the G(1)-arrested cells. Further, the effect of PTEN on cell death is mediated through the PI3K/Akt pathway whereas PTEN-mediated cell cycle arrests are through PI3K/Akt-dependent and -independent pathways.