雷公藤红素与凋亡蛋白突变体通过强化Nur77诱发凋亡通路发挥协同抗肿瘤作用

雷公藤红素(Celastrol)和凋亡蛋白(Apoptin)均可通过Nur77信号通路介导肿瘤细胞凋亡,Celastrol与含有商陆皂苷甲(EsA)的Apoptin突变体tApoptin(简称为tApoptinE)联用是否具有高效的抗肿瘤活性及其协同作用的分子机制值得研究。通过MTT法检测药物联用后对肿瘤细胞增殖的抑制活性,流式细胞术和免疫印迹(Western blot)技术分析药物联用的分子机制。结果显示,Celastrol浓度≥300 nmol/L时可以显著提高tApoptinE对肝癌细胞SMMC-7721生长的抑制活性;上述联用条件下两种药物联合作用指数(Combined index)均小于1,其中,Celastrol(600 nmol/L)与tApoptinE联用的协同效果最显著;流式凋亡分析揭示联合用药强化了对细胞的凋亡效应;Western blot分析表明两种药物协同作用于共同的Nur77通路,促进更多的Nur77被磷酸化,磷酸化的Nur77显著调控Caspase和Bcl-2家族蛋白的表达,强化了细胞凋亡途径。上述两种药物联合使用后通过强化Nur77诱发的细胞凋亡通路,进一步诱导肿瘤细胞凋亡,从而发挥协同抗肿瘤作用。     

Nur77 在缺氧/ 复氧诱导的心肌细胞凋亡中的作用及其机制的研究

目的:观察Nur77通过线粒体转位对缺氧/复氧(H/R)诱导的心肌细胞凋亡的影响。方法:原代培养l-2天SD大鼠心肌细胞,建立H/R模型。随机分为正常对照组、H/R组、Nur77组,采用免疫荧光检测横纹肌肌动蛋白(α-actin)鉴定心肌细胞;采用TUNEL染色法及Caspase-3酶活性检测心肌细胞凋亡情况;采用Western blot检测细胞核及线粒体Nur77蛋白表达、线粒体及胞浆Omi/HtrA2蛋白表达。结果:H/R组细胞核中Nur77蛋白表达明显低于正常对照组;而在线粒体中则相反。Nur77组线粒体中的Omi/HtrA2蛋白表达明显低于正常对照组;而在胞浆中则相反。结论:在心肌细胞H/R损伤时,Nur77线粒体转位促使Omi/HtrA2蛋白从线粒体释放入胞浆,从而导致心肌细胞凋亡。     

血清对全反式视黄酸抑制肺癌细胞生长的影响

 研究不同浓度的血清对全反式视黄酸 (ATRA)抑制肺癌细胞生长的影响 .当细胞培养在 10 %血清中 ,ATRA不能抑制肺癌细胞生长 ,但是当细胞培养在 1%血清中 ,ATRA能够有效地抑制肺癌细胞生长 .视黄酸受体RARβ介导视黄酸的抗癌作用 .Northern印迹分析表明 ,在高浓度血清中AT RA不能诱导RARβ表达 ,但在低浓度血清中ATRA可以诱导RARβ表达 ,并且瞬时转染和CAT测定证实是通过激活RABβ启动子转录活性而诱导RARβ表达的 .孤生受体Nur77受到血清生长因子刺激后会大量表达 ,具有抗视黄酸活性的作用 .肺癌细胞培养在低浓度血清中 ,Nur77mRNA低水平表达和Nur77蛋白不表达 .然而在高浓度血清中 ,Nur77mRNA和蛋白高水平表达 .另外 ,在无血清条件下 ,EGF也可以诱导Nur77表达 .结果提示 ,血清中的生长因子可能拮抗ATRA抑制肺癌细胞生长的作用 ,其作用途径可能是通过刺激细胞中Nur77表达 ,或者通过下调RARβ启动子的转录活性而抑制RARβ的表达     

姜黄素通过MAPK信号通路诱导人肝癌SMMC-7721细胞凋亡

本文阐述了姜黄素(Curcumin)对体外培养的人肝癌SMMC-7721细胞增殖和凋亡的影响,并探讨了其诱导凋亡的信号转导机制。采用MTT法和细胞计数法检测不同浓度姜黄素对人肝癌细胞株SMMC-7721增殖的影响,利用流式细胞术检测姜黄素对人肝癌SMMC-7721细胞凋亡的影响,通过RT-PCR及Western blot检测姜黄素对人肝癌SMMC-7721细胞中凋亡相关蛋白Caspase-3、Survivin、Bcl-2和Bax表达的影响,最后通过检测MAPK的磷酸化水平分析姜黄素诱导SMMC-7721细胞凋亡的信号转导机制,通过MAPK抑制剂实验进一步证实诱导凋亡的分子机制。研究结果显示,姜黄素呈时间和剂量依赖性抑制人肝癌SMMC-7721细胞的增殖,其中40μmol/L姜黄素可明显诱导SMMC-7721细胞的凋亡,并呈时间依赖性上调促凋亡蛋白Caspase-3和Bax的表达、下调抗凋亡蛋白Survivin和Bcl-2的表达,姜黄素对凋亡相关蛋白表达的调节及诱导凋亡可以通过激活JNK、抑制ERK和p38 MAPK信号通路实现。表明姜黄素可诱导人肝癌SMMC-7721细胞凋亡,其机制与姜黄素激活JNK、抑制ERK和p38 MAPK信号通路从而上调Caspase-3和Bax的表达,下调Survivin和Bcl-2的表达有关。     

p38激酶在肌肉发生及运动中的作用

p38通路是真核细胞转导细胞外信号到细胞内引起细胞反应的一类重要信号通路,它能够调控多种细胞内分子事件。p38是p38通路发挥生物学作用的末端激酶,它能够通过调控MyoD、Myf-5活性或表达、组蛋白修饰、染色体重塑、某些细胞分化相关mRNA的更替等方式影响肌肉分化进程。运动能够激活p38,p38可能通过NF-κB/IL-6/成肌调节因子(myogenic regulatory factor,MRF)及肌细胞专一增强因子2(muscle-specific enhancement factor2,MEF2)、过氧化物增殖物活化受体γ辅激活因子1α(peroxisome proliferator activated receptor γ coactivator-1α,PGC-1α)、葡萄糖转运蛋白4(glucose transporter 4,GLUT4)在运动介导的肌肉发生、线粒体发生、血糖摄取能力提高等几方面发挥作用。     

Bcl-2家族蛋白调控线粒体膜通透性和细胞色素C释放的新机制

Bcl-2家族蛋白在调控线粒体功能和细胞色素C释放中起重要作用。最近发现Bcl-2分子通过与其他促凋亡分子相互作用调控线粒体外膜通透性,其具体分子机制尚不完全清楚。本课题组采用化学生物学方法,在研究Bax/Bak非依赖的细胞凋亡途径中,发现了一些小分子化合物能够诱导Bim表达量急剧升高,Bim能转位到线粒体上,与Bcl-2相互作用增强,并直接促进Bcl-2构象变化。有意义的是,Bim可以诱导Bcl-2功能发生转换并能够形成大的复合体通道来介导细胞色素C释放。研究结果提示Bcl-2分子可变成促凋亡分子,参与Bax/Bak非依赖的细胞色素C释放和细胞凋亡。     

MEF2C在湿性年龄相关性黄斑变性中的表达及其对脉络膜新生血管和巨噬细胞极化的影响

摘要 目的：揭示肌细胞增强因子2C（MEF2C）在湿性年龄相关性黄斑变性（AMD）中的表达及其对脉络膜新生血管（CNV）和巨噬细胞极化的影响。方法：通过qRT-PCR法检测30例湿性AMD患者（AMD组）和30例健康体检者（健康对照组）的血清MEF2C水平。将MEF2C过表达慢病毒（MEF2C-LV组）和阴性对照过表达慢病毒（NC-LV组）转染至恒河猴脉络膜血管内皮细胞系（RF/6A）。转染后,将RF/6A细胞分为常氧组（Normoxia组）、低氧组（Hypoxia组）、低氧+NC-LV组（Hypoxia+NC-LV组）、低氧+MEF2C-LV组（Hypoxia+MEF2C-LV组）。转染及缺氧处理后,分别测定各组细胞进行Matrigel小管。通过激光诱导CNV C57BL/6J小鼠模型,将建模成功的C57BL/6J小鼠随机分为模型组、NC-LV组和MEF2C-LV组,每组10只,未建模的小鼠作为对照组。然后对NC-LV组和MEF2C-LV组小鼠玻璃体腔注射NC-LV或MEF2C-LV,对照组和模型组小鼠不进行治疗。治疗7 d后进行眼底荧光血管造影（FFA）和眼球苏木精伊红（HE）染色。通过qRT-PCR和Western blot检测MEF2C、VEGFA、VEGFR2、IL-12p35、IL-12p40和IL-10的mRNA和蛋白表达。结果：与Healthy组相比,AMD组患者的血清MEF2C水平显著降低（1.00±0.23 vs 0.48±0.29,t=7.689,P<0.001）。与Normoxia组相比,Hypoxia组的闭合管腔数量增加（P<0.05）。与Hypoxia组相比,Hypoxia+MEF2C-LV组的闭合管腔数量减少（P<0.05）。与模型组相比,MEF2C-LV组视网膜和脉络膜病变程度减轻,结构基本恢复正常,脉络膜组织厚度降低,血管生成减少。与模型组相比,MEF2C-LV组的CNV相对荧光强度降低,脉络膜组织中MEF2C、VEGFA和VEGFR2的mRNA和蛋白表达水平均降低（P<0.05）。与模型组相比,MEF2C-LV组脉络膜组织中IL-12p35和IL-12p40的mRNA和蛋白表达水平均升高,IL-10均降低（P<0.05）。结论：MEF2C在湿性AMD患者血清中低表达,上调MEF2C可抑制脉络膜血管生成,并促进巨噬细胞从M2型向M1型的转换。     

MAPK磷酸酯酶-1通过抑制JNK和p38的磷酸化调节SH-SY5Y神经母细胞瘤的凋亡

目的研究MKP-1在SH-SY5Y神经母细胞瘤中的抗凋亡。方法建立稳定表达MKP-1的SH-SY5Y细胞,用H2O2诱导细胞凋亡,并通过Western blotting比较分析MKP-1的表达对JNK和p38磷酸化的调节。结果①H2O2诱导SH-SY5Y细胞表达MKP-1,同时导致JNK和p38的去磷酸化;②在稳定表达MKP-1的SH-SY5Y细胞中,MKP-1可以抑制JNK和p38的磷酸化。③稳定表达MKP-1的SH-SY5Y细胞抵抗H2O2诱导细胞凋亡的能力比对照细胞提高了1倍左右。结论MKP-1对神经细胞的凋亡具有重要的调节作用,提示MKP-1作为调节ERK、JNK和p38蛋白激酶信号途径的重要分子,可能对退行性神经系统疾病的发病机制和治疗有重要的作用。     

表没食子儿茶素没食子酸酯通过活化p38α诱导急性早幼粒细胞白血病NB4细胞凋亡

该文研究了表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)诱导NB4细胞凋亡的可能分子机制。不同浓度梯度EGCG处理NB4细胞,或预先用p38α抑制剂PD169316处理NB4细胞,再用EGCG处理。用CCK-8(cell counting kit-8)方法检测细胞增殖情况,用FITC-Annexin V/PI双染色法检测细胞凋亡情况,用Western blot检测p38α、P-p38α、Bcl-2和Bax蛋白质表达水平。结果显示,随着EGCG浓度的升高,NB4细胞增殖率逐渐降低,细胞凋亡率明显升高。P-p38α和Bax蛋白质表达水平升高,与EGCG浓度呈正相关;而Bcl-2蛋白质表达水平降低。p38α抑制剂处理后,NB4细胞增殖率升高,凋亡率降低,Bax蛋白质表达水平降低,而Bcl-2蛋白质表达水平无明显变化。以上结果表明,EGCG可能通过活化p38α诱导急性早幼粒细胞白血病NB4细胞凋亡。     

全反式维甲酸通过抑制ERK和激活p38 MAPK信号诱导KLF4基因表达

全反式维甲酸（all-trans retinoic acid, ATRA）诱导细胞分化与上调转录因子Krüppel样因子4 (KLF4)表达有关, 但目前对ATRA诱导KLF4表达的分子机制尚不清楚．为了研究ATRA在血管平滑肌细胞（VSMC）中诱导KLF4表达的分子机制,本 研究观察ATRA对视黄酸受体α (retinoic acid receptor α, RARα)和KLF4表达的影响及RARα介导ATRA诱导KLF4表达所依 赖的信号转导途径．实验结果显示,ATRA可显著诱导RARα和KLF4表达,用RARα拮抗剂Ro 41 5253阻断ATRA与受体相互作 用后,ATRA诱导的KLF4表达受到显著抑制．用p38 MAPK、ERK和Akt抑制剂阻断ATRA与RARα相互作用所激活的信号转导途径 后,发现阻断p38 MAPK信号途径显著抑制ATRA诱导的KLF4表达,抑制ERK信号途径使ATRA对KLF4表达的诱导作用明显增强, 抑制Akt信号途径不影响KLF4基因表达．表明RARα介导ATRA对KLF4表达的诱导作用,ATRA通过抑制ERK和激活p38 MAPK信号 途径发挥其对KLF4基因表达的诱导作用．     

Lactoferrin activates macrophages via TLR4-dependent and -independent signaling pathways

Lactoferrin (LF) is a component of innate immunity and is known to interact with accessory molecules involved in the TLR4 pathway, including CD14 and LPS binding protein, suggesting that LF may activate components of the TLR4 pathway. In the present study, we have asked whether bovine LF (bLF)-induced macrophage activation is TLR4-dependent. Both bLF and LPS stimulated IL-6 production and CD40 expression in RAW 264.7 macrophages and in BALB/cJ peritoneal exudate macrophages. However, in macrophages from congenic TLR4(-/-) C.C3-Tlr4(lps-d) mice, CD40 was not expressed while IL-6 secretion was increased relative to wild-type cells. The signaling components NF-kappaB, p38, ERK and JNK were activated in RAW 264.7 cells and BALB/cJ macrophages after bLF or LPS stimulation, demonstrating that the TLR4-dependent bLF activation pathway utilizes signaling components common to LPS activation. In TLR4 deficient macrophages, bLF-induced activation of NF-kappaB, p38, ERK and JNK whereas LPS-induced cell signaling was absent. We conclude from these studies that bLF induces limited and defined macrophage activation and cell signaling events via TLR4-dependent and -independent mechanisms. bLF-induced CD40 expression was TLR4-dependent whereas bLF-induced IL-6 secretion was TLR4-independent, indicating potentially separate pathways for bLF mediated macrophage activation events in innate immunity.     

Role of TLR2- and TLR4-mediated signaling in Mycobacterium tuberculosis-induced macrophage death

Infection of macrophages with Mycobacterium tuberculosis (Mtb) induces cell death by apoptosis or necrosis. TLRs 2 and 4 recognition of mycobacterial ligands has been independently associated to apoptosis induction. To try to understand the particular contribution of these receptors to apoptotic or necrotic signaling upon infection with live Mtb H37Rv, we used macrophage lines derived from wild-type or TLR2-, TLR4-, and MyD88-deficient mouse strains. Mtb-infection triggered apoptosis depending on a TLR2/TLR4/MyD88/p38/ERK/PI-3K/NF-kB pathway; however, necrosis was favored in absence of TLR4 signaling independently of p38, ERK1/2, PI-3K or NF-κB activity. In conclusion, our results indicate that cooperation between TLR2- and TLR4-dependent mediated signals play a critical role in macrophage apoptosis induced by Mtb and the TLR4-mediated signaling has important role in the maintenance of the balance between apoptotic vs. necrotic cell death induced by macrophage infection with Mtb.     

The extracellular signal-regulated kinase pathway is required for activation-induced cell death of T cells

T cells can undergo activation-induced cell death (AICD) upon stimulation of the T cell receptor-CD3 complex. We found that the extracellular signal-regulated kinase (ERK) pathway is activated during AICD. Transient transfection of a dominant interfering mutant of mitogen-activated/extracellular signal-regulated receptor protein kinase kinase (MEK1) demonstrated that down-regulation of the ERK pathway inhibited FasL expression during AICD, whereas activation of the ERK pathway with a constitutively active MEK1 resulted in increased expression of FasL. We also found that pretreatment with the specific MEK1 inhibitor PD98059 prevented the induction of FasL expression during AICD and inhibited AICD. However, PD98059 had no effect on other apoptotic stimuli. We found only very weak ERK activity during Fas-mediated apoptosis (induced by Fas cross-linking). Furthermore, preincubation with the MEK1 inhibitor did not inhibit Fas-mediated apoptosis. Finally, we also demonstrated that pretreatment with the MEK1 inhibitor could delay and decrease the expression of the orphan nuclear steroid receptor Nur77, which has been shown to be essential for AICD. In conclusion, this study demonstrates that the ERK pathway is required for AICD of T cells and appears to regulate the induction of Nur77 and FasL expression during AICD.     

Dioscorin isolated from Dioscorea alata activates TLR4-signaling pathways and induces cytokine expression in macrophages

The Toll-like receptor 4 (TLR4)-signaling pathway is crucial for activating both innate and adaptive immunity. TLR4 is a promising molecular target for immune-modulating drugs, and TLR4 agonists are of therapeutic potential for treating immune diseases and cancers. Several medicinal herb-derived components have recently been reported to act via TLR4-dependent pathways, suggesting that medicinal plants are potential resources for identifying TLR4 activators. We have applied a screening procedure to systematically identify herbal constituents that activate TLR4. To exclude possible LPS contamination in these plant-derived components, a LPS inhibitor, polymyxin B, was added during screening. One of the plant components we identified from the screening was dioscorin, the glycoprotein isolated from Dioscorea alata. It induced TLR4-downstream cytokine expression in bone marrow cells isolated from TLR4-functional C3H/HeN mice but not from TLR4-defective C3H/HeJ mice. Dioscorin also stimulated multiple signaling molecules (NF-kappaB, ERK, JNK, and p38) and induced the expression of cytokines (TNF-alpha, IL-1beta, and IL-6) in murine RAW 264.7 macrophages. Furthermore, the ERK, p38, JNK, and NF-kappaB-mediated pathways are all involved in dioscorin-mediated TNF-alpha production. In summary, our results demonstrate that dioscorin is a novel TLR4 activator and induces macrophage activation via typical TLR4-signaling pathways.     

Differential TLR2 downstream signaling regulates lipid metabolism and cytokine production triggered by Mycobacterium bovis BCG infection

The nuclear receptor PPARγ acts as a key modulator of lipid metabolism, inflammation and pathogenesis in BCG-infected macrophages. However, the molecular mechanisms involved in PPARγ expression and functions during infection are not completely understood. Here, we investigate signaling pathways triggered by TLR2, the involvement of co-receptors and lipid rafts in the mechanism of PPARγ expression, lipid body formation and cytokine synthesis in macrophages during BCG infection. BCG induces NF-κB activation and increased PPARγ expression in a TLR2-dependent manner. Furthermore, BCG-triggered increase of lipid body biogenesis was inhibited by the PPARγ antagonist GW9662, but not by the NF-κB inhibitor JSH-23. In contrast, KC/CXCL1 production was largely dependent on NF-κB but not on PPARγ. BCG infection induced increased expression of CD36 in macrophages in vitro. Moreover, CD36 co-immunoprecipitates with TLR2 in BCG-infected macrophages, suggesting its interaction with TLR2 in BCG signaling. Pretreatment with CD36 neutralizing antibodies significantly inhibited PPARγ expression, lipid body formation and PGE₂ production induced by BCG. Involvement of CD36 in lipid body formation was further confirmed by decreased BCG-induced lipid body formation in CD36 deficient macrophages. Similarly, CD14 and CD11b/CD18 blockage also inhibited BCG-induced lipid body formation, whereas TNF-α synthesis was not affected. Disruption of rafts recapitulates the latter result, inhibiting lipid body formation, but not TNF-α synthesis in BCG-infected macrophages. In conclusion, our results suggest that CD36-TLR2 cooperation and signaling compartmentalization within rafts, divert host response signaling through PPARγ-dependent and NF-κB-independent pathways, leading to increased macrophage lipid accumulation and down-modulation of macrophage response.