Oridonin induces a caspase-independent but mitochondria- and MAPK-dependent cell death in the murine fibrosarcoma cell line L929

Oridonin, an active component isolated from Rabdosia rubescences, has been reported to exhibit antitumor effects, but little is known about its molecular mechanisms of action. In this study, the growth-inhibitory activity of oridonin for L929 cells is in time- and dose-dependent manner. After treatment with various concentrations of oridonin for 12 h, the majority of L929 cells underwent apoptosis as measured by an LDH activity-based assay. Although apoptotic bodies were observed in oridonin-treated L929 cells, DNA fragmentation as a hallmark of apoptosis was not found. The pan-caspase inhibitor, z-VAD, and caspase-3 inhibitor, z-DEVD, sensitized L929 cells to oridonin, however, a PARP inhibitor (DPQ) effectively blocked oridonin-induced cell death. After 12 h treatment, PARP proenzyme was significantly cleaved. This result indicated that oridonin-induced L929 cell death required PARP degradation in a caspase-independent manner. In addition, an MEK/ERK inhibitor (PD98059) markedly blocked oridonin-induced cell death, whereas a p38 inhibitor (SB203580) and JNK inhibitor (SP600125) weakly protected the cells against death. Treatment with 41.2 microM oridonin for 12 h induced significant and persistent ERK activation and p38 inactivation in L929 cells without evident changes in the protein levels. The responsiveness of ERK and p38 to oridonin suggests the involvement of these kinases in this apoptotic process. Moreover, oridonin increased the ratio of Bax/Bcl-2 protein expression, whereas it had no effect on the expression of Bcl-xL. These results indicate that regulation of the Bcl-2 and MAPK families maybe the effector mechanisms of oridonin-induced L929 cell death, independent of the caspase pathway.     

Fas/FasL signaling allows extracelluar-signal regulated kinase to regulate cytochrome c release in oridonin-induced apoptotic U937 cells

Previously, we found that human histocytic lymphoma U937 cells possessed high susceptibility to oridonin-induced cell death, but the molecular mechanisms in response to oridonin remain unclear. In this study, U937 cells showed susceptible to apoptosis induced by 27 microM oridonin and an agonistic anti-Fas IgM mAb (CH-11) (500 ng/ml) as a Fas-sensitized positive control. Caspase 8 inhibitor z-IETD, but neither caspase 1 inhibitor Ac-YVAD nor caspase 10 inhibitor z-AEVD, effectively blocked oridonin-induced cell death as well as DNA fragmentation. Western blot analysis showed the up-regulated expression of Fas, FasL, and FADD, and down-regulated expression of procaspase 8, suggesting that Fas/FasL pathway was activated in oridonin-induced cell apoptosis. Further, stimulation of U937 cells with oridonin and CH11 resulted in significant ERK MAPK activation. However, inhibition of ERK by PD98059 reversed oridonin-induced cell death as well as the activation of caspase 8, indicating that ERK-mediated control occured upstream of caspase 8. Simultaneously, ERK activation accounted for the release of cytochrome c, but failed to influence decreased Bcl-2 expression induced by oridonin. Taken together, these results suggest that Fas/FasL signaling pathway-mediated ERK activation sensitized U937 cells to mitochondrial pathway-mediated apoptosis induced by oridonin.     

Intracellular regulation of evodiamine-induced A375-S2 cell death

We have reported that in A375-S2 cells, evodiamine isolated from Evodia rutaecarpa induces cell death of human melanoma, A375-S2, through two distinct pathways: apoptosis and necrosis. In the present study, we further demonstrate two different mechanisms by which evodiamine induces apoptosis and necrosis. Although caspase-1 and -10 inhibitors failed to block cell death, pan-caspase inhibitor and caspase-3, -8, and -9 inhibitors had marked inhibitory effects on apoptosis induced by 15 microM evodiamine. Furthermore, evodiamine-induced activation of caspase-3 resulted in the down-regulation of anti-apoptotic Bcl-2 expression and up-regulation of proapoptotic Bax expression. After 24 h incubation with evodiamine, no caspase inhibitor had any influence on cell death, but p38 mitogen-activated protein kinase (MAPK) inhibitor (SB203580) attenuated cell death; in contrast, extracellular signal-regulated protein kinase (ERK) MAPK inhibitor (PD98059) augmented cell death, as was further confirmed by cotreatment with SB203580 or PD98059 and pan-caspase inhibitor. Moreover, evodiamine increased the phosphorylation of p38 and decreased the expression and phosphorylation of ERK in caspase-independent necrosis. Consequently, evodiamine induced the caspase- and Bax-mediated apoptosis at an early stage, but, initiated MAPKs-dependent necrosis at a later stage.     

The roles of Akt and MAPK family members in silymarin's protection against UV-induced A375-S2 cell apoptosis

Silymarin is a polyphenolic flavonoid derived from milk thistle (Silybum marianum) and has anti-inflammatory, cytoprotective as well as anticarcinogenic effects [Manna, S.K., Mukhopadlhyay, A., Van, N.T., Aggarwal, B., Silymarin suppresses TNF-induced activation of NF-kappaB, c-Jun N-terminal kinase, and apoptosis. J. Immunol. 1999; 163, 6800-6809.]. In this study, we assessed the effect of silymarin on ultraviolet light (UV)-induced cell apoptosis in human malignant melanoma, A375-S2 cells. Silymarin pre-treatment reversed the effect of UV irradiation on the expression of phosphorylated Akt and phosphorylated p53 (regulated by Akt activation), followed by down-regulation of Bax and up-regulated expressions of Bcl-2 and Bcl-xL proteins in UV-irradiated A375-S2 cells. Akt inhibitor decreased the viability of UV-irradiated cells which was treated with silymarin. In addition, the effect of UV irradiation on the phosphorylation of mitogen-activated protein kinase (MAPK) family members [extracellular signal-regulated kinase (ERK), p38 and c-Jun N-terminal kinase (JNK)] was also reversed by silymarin. Moreover, ERK inhibitor (PD98059) and p38 inhibitor (SB203580) augmented UV-induced apoptosis in silymarin treated A375-S2 cells. Consequently, silymarin partially reduced UV-induced apoptosis by activating the Akt pathway, and silymarin's protective effect was also exerted by MAPK family members.     

Dracorhodin perchlorate induces A375-S2 cell apoptosis via accumulation of p53 and activation of caspases

Dracorhodin perchlorate, an anthocyanin red pigment, induces human melanoma A375-S2 cell death through the apoptotic pathway. Caspase-3, -8, -9, and -10 inhibitors partially reversed the cell death induced by dracorhodin perchlorate. Caspase-3 and -8 were activated, followed by the degradation of caspase-3 substrates, the inhibitor of caspase-activated DNase, and poly-(ADP-ribose) polymerase. Dracorhodin perchlorate upregulated the expression ratio of Bax/Bcl-2 and significantly increased the expression of p53 and p21(WAF1) proteins. The cell death was partially reduced by the mitogen-activated protein kinase c-JUN NH2-terminal protein kinase (JNK MAPK) inhibitor (SP600125) and p38 MAPK inhibitor (SB 203580), while the MEK inhibitor (PD98059) augmented cell death; the drug induced sustained phosphorylation of JNK and p38 MAPK. Moreover, the Fas agonistic antibody CH-11 has a synergistic effect with dracorhodin perchlorate. The phoshatidylinositol 3-kinase (PI3-K) family inhibitor wortmanin and tyrosine kinase inhibitor genistein rescued the viability loss induced by dracohodin perchlorate. Taken together, dracorhodin perchlorate induces apoptosis in A375-S2 cells via accumulation of p53, alters the Bax/Bcl-2 ratio, and activates caspases and p38/JNK MAPKs.     

蛋白激酶C在吴茱萸碱诱导A375-S2细胞死亡中的作用

目的研究蛋白激酶C(protein kinase C，PKC)在吴茱萸碱(evodiamine)诱导的A375-S2细胞死亡过程中的作用。方法TUNEL法检测吴茱萸碱诱导细胞凋亡的比例。MTT法测定药物对A375-S2细胞的细胞毒作用。Western blotting法分析药物作用后对ERK及其磷酸化蛋白和Bcl-2家族蛋白的影响。结果吴茱萸碱诱导A375-S2细胞的死亡在24 h以前以凋亡为主。PKC抑制剂staurosporine和ERK抑制剂PD98059均能促进吴茱萸碱诱导的A375-S2细胞死亡。吴茱萸碱能够抑制PKC的活力，下调ERK及其磷酸化蛋白的表达水平，并使Bax/Bcl-2表达比例上升。而staurosporine对吴茱萸碱抑制PKC活力，降低ERK及其磷酸化蛋白和Bcl-2的表达有进一步增强的作用。结论在吴茱萸碱诱导的A375-S2细胞死亡中，PKC位于ERK和Bcl-2的上游发挥其调节作用。     

Dracorhodin perchlorate induces apoptosis in HL-60 cells

Dracorhodin perchlorate, an anthocyanin red pigment, induces human premyelocytic leukemia HL-60 cell death through apoptotic pathway. Caspase -1, -3, -8, -9, and -10 inhibitors partially reversed the cell death induced by dracorhodin perchlorate. Caspase-3 and -8 were activated followed to the degradation of caspase-3 substrates, inhibitor of caspase-activated DNase (ICAD) and poly-(ADP-ribose) polymerase (PARP). Dracorhodin perchlorate up-regulated the expression ratio of mitochondrial proteins, Bax/Bcl-X_L. The cell death was accompanied with phosphorylation of ERK, JNK and p38 MAPK and partially reduced by MEK inhibitor (PD98059), JNK MAPK inhibitor (SP600125) and p38 MAPK inhibitor (SB 203580). Taken together, dracorhodin perchlorate-induced apoptosis in HL-60 cells via up-regulation of Bax, activation of caspases and ERK/p38/JNK MAPKs.     

The course of uncarinic acid E-induced apoptosis of HepG2 cells from damage to DNA and p53 activation to mitochondrial release of cytochrome c

Uncarinic acid E, an active component isolated from Gelsemium elegans BENTH, has been reported to exhibit antitumor effects, but little is known about its molecular mechanisms of action. In this study, the growth-inhibitory activity of uncarinic acid E for HepG2 cells is in time- and dose-dependent manner. HepG2 cells treated with uncarinic acid E exhibited several typical characteristics of apoptosis through photomicroscopical observation, DNA agarose gel electrophoresis. The inhibitory effect of uncarinic acid E on HepG2 cells was partially reversed by the inhibitors of pan-caspase, caspase-3 and caspase-6. The protein expression ratio of Bcl-xL/Bax and Bcl-2/Bax was down-regulated and uncarinic acid E-induced apoptosis involves the initial phase mediated by the balance among Bcl-xL, Bcl-2 and Bax proteins, resulting in cytochrome c release from the mitochondria. Uncarinic acid E significantly increased the expression of p53 proteins indicates that p53 plays a pivotal role in the initiation phase of uncarinic acid E-induced HepG2 cell apoptosis. The phoshatidylinositol 3-kinase (PI3-K) family inhibitor wortmanin and the MEK inhibitor (PD98059) rescued the viability loss induced by uncarinic acid E through the expression of p53. Taken together, uncarinic acid E induces apoptosis in HepG2 cells via accumulation of p53, alters the Bax/Bcl-2 ratio, and activates caspases, resulting in cytochrome c release from the mitochondria.     

Activation of phosphoinositide 3-kinase, protein kinase C, and extracellular signal-regulated kinase is required for oridonin-enhanced phagocytosis of apoptotic bodies in human macrophage-like U937 cells

Our previous study showed that oridonin isolated from Rabdosia rubescens enhanced phagocytosis of apoptotic cells by macrophage-like U937 cells through tumor necrosis factor (TNF) alpha and interleukin (IL)-1beta release. In this study, we further investigated signaling events involved in oridonin-augmented phagocytosis. Phagocytic stimulation was significantly suppressed by inhibitors, including a phosphoinositide 3-kinases (PI3K) inhibitor (wortmannin), a protein kinase C (PKC) inhibitor (stauroporine), and a phospholipase C (PLC) inhibitor (U73122). Exposure of U937 cells to oridonin caused an increase in PKC activity time- dependently, which was prevented by pretreatment with inhibitors of PI3K and PLC. Simultaneously, the activation of protein kinase B (PKB/Akt) and the increased expression of PLCgamma2 were also blocked by wortmannin. In addition, an extracellular signal-regulated kinase (ERK) MAPK inhibitor, PD98059, suppressed oridonin-augmented phagocytosis, whereas the p38 MAPK inhibitor (SB203580) and c-Jun N-terminal kinase (JNK) MAPK inhibitor (SP98059) had no inhibitory effect. Furthermore, pretreatment of U937 cells with anti-TNFalpha and anti-IL-1beta antibodies blocked oridonin-induced phagocytic stimulation as well as phosphorylation of ERK, but did not block the activation of PKC, indicating that these signaling events are triggered by oridonin, whereas secreted TNFalpha or IL-1beta only activate the ERK-dependent pathway. Taken together, oridonin is suggested to enhance phagocytosis of apoptotic bodies by activating PI3K, PKC, and ERK-dependent pathways.     

冬凌草甲素通过改变Bax/Bcl-xL表达激活caspase-3诱导A375-S2细胞凋亡

目的　研究冬凌草甲素诱导人黑色素瘤A375 S2细胞凋亡的作用原理。方法　形态学观察 ,DNA凝胶电泳法及WesternBlot法。结果　冬凌草甲素能明显诱导A375 S2细胞发生凋亡 ,其作用呈明显的量效关系和时间依赖性。形态学观察可见凋亡小体的形成 ,琼脂糖凝胶电泳可见凋亡典型的DNA梯带 ;caspase 3的抑制剂能阻止caspase 3的活力升高 ;免疫印迹结果显示冬凌草甲素作用A375 S2细胞 12h改变Bax与Bcl xL蛋白的表达 ;且发现caspase 3的底物PARP蛋白在 12h时被降解。结论　冬凌草甲素 (34 3μmol·L-1)诱导A375 S2细胞凋亡 ,这种作用是通过改变了Bax/Bcl xL的表达比率 ,激活caspase 3而实现的。     

Sequence-dependent potentiation of paclitaxel-mediated apoptosis in human leukemia cells by inhibitors of the mitogen-activated protein kinase kinase/mitogen-activated protein kinase pathway.

Effects of inhibitors of the mitogen-activated protein kinase kinase/mitogen-activated protein kinase (MEK/MAPK) cascade have been examined in relation to paclitaxel-induced apoptosis in human monocytic leukemia cells (U937). Cells treated with paclitaxel (250 nm; 6 h) followed by PD98059 [corrected] exhibited a significant increase in mitochondrial dysfunction (e.g., cytochrome c release), caspase activation, poly ADP-ribose polymerase cleavage, and apoptosis, whereas pretreatment of cells with PD98059 reduced lethality. Similar results were obtained with other MEK/MAPK inhibitors (e.g., U0126 and PD184352). Subsequent exposure of paclitaxel-treated cells to PD98059 did not enhance dephosphorylation/activation of p34(cdc2) but diminished expression of the antiapoptotic protein Mcl-1. The caspase inhibitor ZVAD-fmk opposed potentiation of paclitaxel-induced loss of mitochondrial membrane potential (Deltapsi(m)) and apoptosis by PD98059, but not cytochrome c release. Paclitaxel treatment induced sustained phosphorylation/activation of MAPK, an effect prevented by subsequent, but not prior, exposure to PD98059. Paclitaxel treatment also induced c-Jun N-terminal kinase phosphorylation, but this effect was enhanced only slightly by subsequent PD98059 administration. Although paclitaxel alone failed to induce p38 MAPK activation, subsequent (but not prior) exposure to PD98059 induced a dramatic increase in p38 MAPK phosphorylation. Moreover, coadministration of the p38 MAPK inhibitors SB203580 and SB202190 abrogated the increase in paclitaxel-mediated apoptosis induced by PD98059. Finally, subsequent PD98059 exposure increased, whereas prior exposure decreased inhibition of clonogenicity by paclitaxel. Together, these findings suggest that subsequent exposure of paclitaxel-treated U937 cells to MEK/MAPK inhibitors induces perturbations in signaling pathways, particularly the p42/44 MAPK and p38 MAPK cascades, that lower the threshold for mitochondrial injury and induction of cell death.     

Melatonin Induces Apoptotic Cell Death via p53 in LNCaP Cells

In this study, we examined whether melatonin promotes apoptotic cell death via p53 in prostate LNCaP cells. Melatonin treatment significantly curtailed the growth of LNCaP cells in a dose- and time-dependent manner. Melatonin treatment (0 to 3 mM) induced the fragmentation of poly(ADP-ribose) polymerase (PARP) and activation of caspase-3, caspase-8, and caspase-9. Moreover, melatonin markedly activated Bax expression and decreased Bcl-2 expression in dose increments. To investigate p53 and p21 expression, LNCaP cells were treated with 0 to 3 mM melatonin. Melatonin increased the expressions of p53, p21, and p27. Treatment with mitogen-activated protein kinase (MAPK) inhibitors, PD98059 (ERK inhibitor), SP600125 (JNK inhibitor) and SB202190 (p38 inhibitor), confirmed that the melatonin-induced apoptosis was p21-dependent, but ERK-independent. With the co-treatment of PD98059 and melatonin, the expression of p-p53, p21, and MDM2 did not decrease. These effects were opposite to the expression of p-p53, p21, and MDM2 observed with SP600125 and SB202190 treatments. Together, these results suggest that p53-dependent induction of JNK/p38 MAPK directly participates in apoptosis induced by melatonin.     

Activation of peroxisome proliferator-activated receptor-gamma (PPARgamma) induces cell death through MAPK-dependent mechanism in osteoblastic cells

The present study was undertaken to determine the role of the mitogen-activated protein kinase (MAPK) subfamilies in cell death induced by PPARgamma agonists in osteoblastic cells. Ciglitazone and troglitazone, PPARgamma agonists, resulted in a concentration- and time-dependent cell death, which was largely attributed to apoptosis. But a PPARalpha agonist ciprofibrate did not affect the cell death. Ciglitazone caused reactive oxygen species (ROS) generation and ciglitazone-induced cell death was prevented by antioxidants, suggesting an important role of ROS generation in the ciglitazone-induced cell death. ROS generation and cell death induced by ciglitazone were inhibited by the PPARgamma antagonist GW9662. Ciglitazone treatment caused activation of extracellular signal-regulated kinase (ERK) and p38. Activation of ERK was dependent on epidermal growth factor receptor (EGFR) and that of p38 was independent. Ciglitazone-induced cell death was significantly prevented by PD98059, an inhibitor of ERK upstream kinase MEK1/2, and SB203580, a p38 inhibitor. Ciglitazone treatment increased Bax expression and caused a loss of mitochondrial membrane potential, and its effect was prevented by N-acetylcysteine, PD98059, and SB203580. Ciglitazone induced caspase activation, which was prevented by PD98059 and SB203580. The general caspase inhibitor z-DEVD-FMK and the specific inhibitor of caspases-3 DEVD-CHO exerted the protective effect against the ciglitazone-induced cell death. The EGFR inhibitors AG1478 and suramin protected against the ciglitazone-induced cell death. Taken together, these findings suggest that the MAPK signaling pathways play an active role in mediating the ciglitazone-induced cell death of osteoblasts and function upstream of a mitochondria-dependent mechanism. These data may provide a novel insight into potential therapeutic strategies for treatment of osteoporosis.     

Inactivation of ras and changes of mitochondrial membrane potential contribute to oridonin-induced autophagy in a431 cells

We have previously shown that oridonin isolated from Rabdosia rubescens augmented apoptosis while inhibiting autophagy within 24 h in HeLa cells. However, the mechanisms between apoptosis and autophagy induced by oridonin in A431 cells are largely unknown. Here, it was found that autophagic level is significantly upregulated when A431 cells are pretreated with manumycin A (Ras specific inhibitor) compared with oridonin alone treatment, whereas cells precultured with GW5074 (Raf inhibitor) or PD98059 (ERK inhibitor) did not exhibit such an effect. Ras, but not Raf or ERK, was engaged in the control of oridonin-induced autophagy. At the same time, manumycin A contributes to oridonin-induced downregulation of Ras protein expression. Treatment with the combination of oridonin and manumycin A downregulated phosphorylation of Akt, downstream of phosphatidylinositol 3-OH kinase (PI3-K). Preincubation with the PI3-K inhibitor wortmannin and Akt inhibitor KP372-1 enhanced oridonin-induced apoptosis, whereas it inhibited oridonin-induced autophagy. However, under oridonin treatment, the expression of Beclin-1, which has autophagy-inducing activity, was reduced, suggesting that Beclin-1 did not participate in the oridonin-induced autophagy. Morphologic observations, DNA fragmentation analysis, and LDH activity-based assay showed that 3-methyladenine (3-MA), an inhibitor of autophagy, increased the apoptotic sensitivity of A431 cells to oridonin. In addition, manumycin A contributed to oridonin-induced decrease of mitochondrial membrane potential (Deltapsim), consistent with the upregulation of Bax/Bcl-2 ratio. In conclusion, Ras negatively regulated autophagy in oridonin-treated A431 cells, which might be associated with activation of class I PI3-K. Downregulation of Deltapsim and increasing of the ratio of Bax/Bcl-2 might also be partially responsible for the initiation of the autophagic process.     

Oridonin induced A375-S2 cell apoptosis via bax-regulated caspase pathway activation, dependent on the cytochrome c/caspase-9 apoptosome

Two diterpenoids, oridonin (1) and ponicidin (2), were isolated from the 95% ethanol extract of Rabdosia rubescens and were evaluated for antiproliferative activity on cancer cells and human peripheral blood mononuclear cells (PBMC) in vitro. Oridonin has much more potent cytotoxic effects on four tumor cells (human melanoma A375-S2, human cervical cancer HeLa, human breast adenocarcinoma MCF-7, murine fibrosarcoma L929) than does ponicidin. The growth-inhibitory activity of oridonin for A375-S2 cells was more potent than that for the other cell lines, with an IC₅₀ of 15.1±1.2 μmol L^-1. Treatment with oridonin (34.3 μmol L_-1) for 12 h significantly inhibited A375-S2 cell growth, and showed weaker cytotoxicity against PBMC. By contrast, ponicidin markedly inhibited the growth of PBMC under the same conditions. When caspases-3 and -8 were activated at early stages after treatment of A375-S2 cells with oridonin (34.3 μmol L_-1), apoptotic bodies were formed, nuclear damage was observed by Hoechst 33258 staining and DNA fragmentation was exhibited. In addition, oridonin increased the expression of the apoptosis inducer, Bax, promoted the release of cytochrome c without affecting Bcl-2 expression, and activated down-stream caspase-9 in the mitochondrial pathway. These observations indicated that an appropriate dose of oridonin gave an initial premitochondrial phase that involved the Bcl-2 family of the pro-apoptotic protein Bax that required the participation of caspase-9 and caspase-3. However, on treatment with oridonin (137.4 μmol L_-1) for 12 h, the majority of A375-S2 cells underwent necrosis as measured by an LDH activity-based assay. Our results suggest that oridonin induces A375-S2 cell death on the balance of apoptosis and necrosis.     

Norcantharidin induces apoptosis in HeLa cells through caspase, MAPK, and mitochondrial pathways

AIM: To investigate the mechanism of norcantharidin (NCTD)-induced HeLa cell apoptosis. METHODS: HeLa cell growth inhibition was measured by MTT method. Apoptosis was detected by Hoechst 33258 staining and agarose gel electrophoresis. Caspase activities were assayed using caspase apoptosis detection kit. Western blot analysis was used to evaluate the level of ICAD, ERK/p-ERK, JNK/p-JNK, and Bcl-XL/Bax expression. RESULTS: Norcantharidin inhibited HeLa cell growth in a time- and dose-dependent manner. HeLa cells treated with norcantharidin showed typical characteristics of apoptosis including the morphological changes and DNA fragmentation. Caspase family inhibitor (z-VAD-fmk), caspase-8, -9 inhibitor (z-IETD-fmk, Ac-LEHD-CHO, respectively) and caspase-3 inhibitor (z-DEVD-fmk) partially prevent norcantharidin-induced apoptosis, but initiator caspase-1 inhibitor (Ac-YVAD-fmk) did not. The activities of caspase-3, -8, and -9 were up-regulated after norcantharidin treatment. Furthermore, NCTD-induced activat     

紫草素诱导A375-S2细胞凋亡的分子机制研究

目的　研究紫草素诱导人黑色素瘤A375 S2细胞凋亡的分子机制。方法　MTT法、Hoechst33258荧光染色、DNA片段化分析、Westernblot、流式细胞分析以及caspase活力分析等。结果　10μmol·L-1紫草素可明显地抑制A375 S2细胞的生长,其半数有效抑制浓度IC50为 (10 9±1 8)μmol·L-1。10μmol·L-1紫草素可诱导A375 S2细胞凋亡,并经历了caspase 9和caspase 3的激活。紫草素促进p53蛋白的积聚,Bax蛋白表达的上调和Bcl xL蛋白表达的下调,进而导致细胞色素C的释放,致使细胞凋亡。紫草素可使细胞周期停止在G1 期。结论　紫草素可诱导A375 S2细胞周期停止在G1 期,其诱导细胞凋亡的途径经过p53介导的Bax和caspase 9的激活。     

oridonin部分通过TNFα信号转导途径诱导小鼠成纤维L929细胞凋亡

目的比较冬凌草甲素(oridonin)和TNFα诱导小鼠成纤维L929细胞凋亡的分子机制。方法MTT法、Hoechst33258荧光染色、DNA片断化分析和Western blot分析法。结果Oridonin和TNFα均能诱导L929细胞发生凋亡,其半数有效抑制浓度IC50分别为(24·8±1·2)μmol·L-1和(20·9±1·9)μg·L-1。Oridonin和TNFα均能引起L929细胞凋亡形态学变化,TNFα处理过的细胞在琼脂糖凝胶电泳上可见典型的凋亡DNA梯状条带,但是oridonin处理的细胞却不能,称之为非典型凋亡;caspase-3,-8抑制剂和caspase家族抑制剂能明显得促进25μmol·L-1oridonin和20μg·L-1TNFα诱导的L929细胞凋亡,caspase-9抑制剂只能促进oridonin诱导的L929细胞凋亡;ERK的抑制剂PD98059能明显的抑制oridonin和TNFα诱导的L929细胞凋亡,但是p38的抑制剂SB203580只能抑制TNFα诱导的L929细胞凋亡;在L929细胞中oridonin能促进内源性pro-TNFα的表达和其上游蛋白IκB的磷酸化。结论Oridonin通过激活转录因子NF-κB而促进内源性pro-TNFα的表达,并且部分通过细胞因子TNFα信号转到途径诱导L929细胞凋亡。     

Oridonin-induced A431 cell apoptosis partially through blockage of the Ras/Raf/ERK signal pathway

We have reported that oridonin, a diterpenoid isolated from the plant Rabdosia rubescens, had apoptosis-inducing activities in many cell lines (e.g., human melanoma A375-S2, human cervical cancer HeLa, human breast adenocarcinoma MCF-7, and murine fibrosarcoma L929). In this study, we further investigated signaling events involved in oridonin-induced apoptosis in human epidermoid carcinoma A431 cells. It was found that the total tyrosine kinase activity was inhibited and the protein expressions of epidermal growth factor receptor (EGFR) and phosphorylated EGFR were decreased in oridonin-induced A431 cell apoptosis. Expression of EGFR downstream effector proteins, Grb2, Ras, Raf-1, and extracellular signal-regulated kinase (ERK), was also downregulated by oridonin. Moreover, the oridonin-induced apoptosis was augmented by the Ras inhibitor manumycin A, Raf-1 inhibitor GW5074, or ERK inhibitor PD98059, suggesting that inactivation of Ras, Raf, or ERK participates in oridonin-induced apoptosis. Taken together, oridonin-induced apoptosis in A431 cells might be through blocking EGFR and its downstream Ras/Raf/ERK signal pathway.     

Nanoparticle realgar powders induce apoptosis in u937 cells through caspase mapk and mitochondrial pathways

Nanoparticle realgar powders (NRP) inhibited U937 cell growth in a time and dose-dependent manner. U937 cells treated with NRP showed typical characteristics of apoptosis including the morphological changes and DNA fragmentation. Caspase family inhibitor (z-VAD-fmk), caspase-8, -9 inhibitor (z-IETD-fmk, Ac-LEHD-CHO, respectively) and caspase-3 inhibitor (z-DEVD-fmk) partially prevented NRP -induced apoptosis. Moreover, the classical substrates of caspase-3, poly-ADP ribose polymerase (PARP) was degraded after U937 cells treatment with NRP. In addition, NRP increased the ratio of Bax/Bcl-2 protein expression. Although p38 inhibitor (SB203580) and ERK inhibitor (PD98059) failed to block cell death, JNK inhibitor (SP600125) had marked inhibitory effects on NRP -induced apoptosis. Furthermore, the phosphorylation of JNK was up-regulated, suggesting that JNK was responsible for NRP -induced apoptosis in U937 cells. These results suggested that the caspase, mitochondria and MAPK signal pathways were involved in NRP-induced U937 apoptosis.