Anticancer drugs are synergistic with freezing in induction of apoptosis in HCC cells

Cryotherapy has been shown to be an important therapeutic alternative to surgery in the treatment of hepatocellular carcinoma (HCC). Here, the influence of cryo-chemotherapy on HCC was examined in vitro using the human HCC cell line Bel-7402, a drug-resistant HCC cell line originating from Bel-7402 cells (Bel-7402/R), as well as two control cell lines, the HCC cell line SMMC-7721 and a colorectal tumor cell line HIC-251. Cells were treated with either exposure to different freezing temperatures (ranging from −15 to −80 °C for 20 min), exposure to sub-lethal concentrations of anticancer chemotherapy drugs or a combination of cryotherapy and chemotherapy. Cell viability and apoptosis under each condition were investigated. We found that the combined treatment resulted in increases in both cell death and apoptosis compared to either treatment alone. The increased level of apoptosis observed in Bel-7402 cells after cryo-chemotherapy was inhibited in the presence of caspase inhibitors. Furthermore, Bax expression was increased 2- to 3-fold in cells exposed to the combination treatment compared with cells treated by freezing or drugs alone. In contrast, Bcl-2 levels remained constant. Although Bel-7402/R cells originated from the Bel-7402 cell line, they were more sensitive to the freezing procedure than the parental cell line. The level of Bax expression in Bel-7402/R cells was also higher than that observed in the parental cell line. In addition, we found that Bel-7402/R cells had lower levels of survivin mRNA than the parental Bel-7402 cells, in both untreated and treated cells. In conclusion, our data show that in HCC cells, apoptosis induced by cryotherapy can be synergistically enhanced using anticancer drugs.     

Bax/Bcl-2 mRNA在恒河猴药物流产胎盘中的表达

目的：通过检测重要的细胞凋亡调节因子Bax和Bcl-2的表达,探讨恒河猴胎盘细胞凋亡与药物流产的关系。方法：利用RT-PCR和原位杂交的方法检测恒河猴对照组和药物流产组(RU-486与AG诱导)胎盘中Bax和Bcl-2mRNA的表达。结果：Bax mRNA在流产胎盘中的表达量明显高于对照组胎盘。在胎盘绒毛滋养层细胞可见明显表达,基底层蜕膜细胞也有表达。Bcl-2mRNA在流产胎盘中的表达量明显低于对照组胎盘,表达部位与Bax类似。结论：RU-486和AG可能通过上调Bax mRNA和下调Bcl-2mRNA的表达,导致胎盘组织凋亡细胞的数量明显增加,从而影响胎盘的正常结构和功能,增加了流产的危险性。     

Interplay between bax, reactive oxygen species production, and cardiolipin oxidation during apoptosis

Bax/Bak activation and cardiolipin peroxidation are essential for cytochrome c release during apoptosis, yet, the link between them remains elusive. We report that sequence of events after exposure of mouse embryonic fibroblast (MEF) cells to actinomycin D followed the order: Bax translocation → superoxide production → cardiolipin peroxidation. Genetic ablation of Bax/Bak inhibited actinomycin D induced superoxide production and cardiolipin peroxidation. Rotenone caused robust superoxide generation but did not trigger cardiolipin peroxidation in Bax/Bak double knockout MEF cells. This suggests that, in addition to participating in ROS generation, Bax/Bak play another specific role in cardiolipin oxidation. In isolated mitochondria, recombinant Bax enhanced succinate induced cardiolipin oxidation and cytochrome c release. Mitochondrial peroxidase activity, likely involved in cardiolipin peroxidation, was enhanced upon incubation with recombinant Bax. Thus, cardiolipin peroxidation may be causatively and time-dependently related to Bax/Bak effects on ROS generation and peroxidase activation of cytochrome c.     

Cleavage of Bax is mediated by caspase-dependent or -independent calpain activation in dopaminergic neuronal cells: protective role of Bcl-2.

Two cysteine protease families, caspase and calpain, are known to participate in cell death. We investigated whether a stress-specific protease activation pathway exists, and to what extent Bcl-2 plays a role in preventing drug-induced protease activity and cell death in a dopaminergic neuronal cell line, MN9D. Staurosporine (STS) induced caspase-dependent apoptosis while a dopaminergic neurotoxin, MPP(+) largely induced caspase-independent necrotic cell death as determined by morphological and biochemical criteria including cytochrome c release and fluorogenic caspase cleavage assay. At the late stage of both STS- and MPP(+)-induced cell death, Bax was cleaved into an 18-kDa fragment. This 18-kDa fragment appeared only in the mitochondria-enriched heavy membrane fraction of STS-treated cells, whereas it was detected exclusively in the cytosolic fraction of MPP(+)-treated cells. This proteolytic cleavage of Bax appeared to be mediated by calpain as determined by incubation with [(35)S]methionine-labelled Bax. Thus, cotreatment of cells with calpain inhibitor blocked both MPP(+)- and STS-induced Bax cleavage. Intriguingly, overexpression of baculovirus-derived inhibiting protein of caspase, p35 or cotreatment of cells with caspase inhibitor blocked STS- but not MPP(+)-induced Bax cleavage. This appears to indicate that calpain activation may be either dependent or independent of caspase activation within the same cells. However, cotreatment with calpain inhibitor rescued cells from MPP(+)-induced but not from STS-induced neuronal cell death. In these paradigms of dopaminergic cell death, overexpression of Bcl-2 prevented both STS- and MPP(+)-induced cell death and its associated cleavage of Bax. Thus, our results suggest that Bcl-2 may play a protective role by primarily blocking drug-induced caspase or calpain activity in dopaminergic neuronal cells.     

Bax κ, a novel Bax splice variant from ischemic rat brain lacking an ART domain, promotes neuronal cell death

Bax is a pro-apoptotic Bcl-2 family protein that regulates programmed cell death through homodimerization and through heterodimerization with Bcl-2. Bax alpha is encoded by six exons and undergoes alternative splicing. Bax kappa, a splice variant of Bax with conserved BH1, BH2 and BH3 binding domains and a C-terminal transmembrane domain (TM), but with an extra 446-bp insert between exons 1 and 2 leading to loss of an N-terminal ART domain, was identified from an ischemic rat brain cDNA library. Expression of Bax kappa mRNA and protein was up-regulated in hippocampus after cerebral ischemic injury. The increased Bax kappa mRNA was distributed mainly in selectively vulnerable hippocampal CA1 neurons that are destined to die after global ischemia. Overexpression of Bax kappa protein in HN33 mouse hippocampal neuronal cells induced cell death, which was partially abrogated by co-overexpression of Bcl-2. Moreover, co-overexpression of Bax kappa and Bax alpha increased HN33 cell death. The results suggest that the Bax kappa may have a role in ischemic neuronal death.     

吐温80合并温热诱导BGC-823胃癌细胞凋亡及对Hsp70,Bcl-2和Bax表达的影响

目的　观察膜活化剂吐温 80合并温热作用对BGC 82 3人胃癌细胞生长、凋亡及对Hsp70、Bcl 2、Bax表达的影响。方法　应用MTT法、荧光染色及DNA琼脂糖凝胶电泳 ,测定 0 1%吐温 80与 4 2℃ 10 0min合并作用对BGC 82 3细胞的抑制效应和诱导细胞凋亡的影响 ;应用免疫细胞化学染色 ,观察合并作用后不同时间 (0h、 8h、 16h、 2 4h)BGC 82 3细胞Hsp70、Bcl 2、Bax的表达改变。结果　①吐温 80合并 4 2℃温热作用对细胞具有明显的抑制效应 (P <0 0 0 1)。②合并作用后 2 4h ,可见大量肿瘤细胞凋亡。③合并作用可明显抑制BGC 82 3细胞Hsp70的表达 ;Bcl 2、Bax的表达均增加 ,且Bax的表达强于Bcl 2 ,并全部分布在胞浆。结论　吐温 80合并 4 2℃温热可通过诱导细胞凋亡来抑制肿瘤细胞生长 ,其对细胞Hsp70表达的抑制和对Bcl 2、Bax表达及分布的影响可能与凋亡的发生有关     

Expression of a Highly Toxic Protein, Bax, in Escherichia coli by Attachment of a Leader Peptide Derived from the GroES Cochaperone

Expression of the human apoptosis modulator protein Bax in Escherichia coli is highly toxic, resulting in cell lysis at very low concentrations (Asoh, S., et al., J. Biol. Chem. 273, 11384–11391, 1998). Attempts to express a truncated form of murine Bax in the periplasm by using an expression vector that attached the OmpA signal sequence to the protein failed to alleviate this toxicity. In contrast, attachment of a peptide based on a portion of the E. coli cochaperone GroES reduced Bax's toxicity significantly and allowed good expression. The peptide, which was attached to the N-terminus, included the amino acid sequence of the mobile loop of GroES that has been demonstrated to interact with the chaperonin, GroEL. Under normal growth conditions, expression of this construct was still toxic, but generated a small amount of detectable recombinant Bax. However, when cells were grown in the presence of 2% ethanol, which stimulated overproduction of the molecular chaperones GroEL and DnaK, toxicity was reduced and good overexpression occurred. Two-dimensional gel electrophoresis analysis showed that approximately 15-fold more GroES-loop-Bax was produced under these conditions than under standard conditions and that GroEL and DnaK were elevated approximately 3-fold.     

Endoplasmic reticulum stress in insulin resistance and diabetes

The endoplasmic reticulum is the main intracellular Ca²⁺ store for Ca²⁺ release during cell signaling. There are different strategies to avoid ER Ca²⁺ depletion. Release channels utilize first Ca²⁺-bound to proteins and this minimizes the reduction of the free luminal [Ca²⁺]. However, if release channels stay open after exhaustion of Ca²⁺-bound to proteins, then the reduction of the free luminal ER [Ca²⁺] (via STIM proteins) activates Ca²⁺ entry at the plasma membrane to restore the ER Ca²⁺ load, which will work provided that SERCA pump is active. Nevertheless, there are several noxious conditions that result in decreased activity of the SERCA pump such as oxidative stress, inflammatory cytokines, and saturated fatty acids, among others. These conditions result in a deficient restoration of the ER [Ca²⁺] and lead to the ER stress response that should facilitate recovery of the ER. However, if the stressful condition persists then ER stress ends up triggering cell death and the ensuing degenerative process leads to diverse pathologies; particularly insulin resistance, diabetes and several of the complications associated with diabetes. This scenario suggests that limiting ER stress should decrease the incidence of diabetes and the mobility and mortality associated with this illness.