Apoptosis induced by the antigen receptor and Fas in a variant of the immature B cell line WEHI-231 and in splenic immature B cells

Signaling by the BCR causes proliferation and resistance to Fas-induced apoptosis in mature B cells, but growth arrest and apoptosis in immature B cells. We have identified a variant of the immature B cell line WEHI 231 that retains the apoptotic response to the BCR but has acquired susceptibility to Fas-induced apoptosis. The Fas susceptibility was associated with increased Fas expression on the cell surface and down-regulated IgD expression. These cells exhibited a distinctive functional relationship in response to signals from the BCR, Fas and CD40: BCR stimulation markedly promoted Fas-mediated apoptosis (and vice versa) and Fas-induced apoptosis was not subject to modulation by CD40 signaling. While BCR-induced apoptosis was effectively rescued by CD40, it was not affected by the expression of a dominant-negative FADD. The mechanistic distinctions between BCR- and Fas-induced apoptosis were further characterized by the differential effects of different caspase inhibitors on these two processes which imply the involvement of different subsets of caspases. For BCR-induced apoptosis, we provide evidence that the final apoptotic destruction phase can be inhibited by the pan-caspase inhibitor BOC-Asp-FMK (BD) and that, in the presence of BD, the BCR only induces growth arrest which is reversible. The striking enhancing effects of Fas on BCR-induced apoptosis seen in the variant cells prompted us to examine if a similar cooperation in induction of apoptosis occurs in the highly tolerizable immature B cells of the spleen. We found that the splenic immature B population contains a significant number of Fas-expressing cells, but neither Fas-induced apoptosis nor an enhancing effect of Fas on BCR-induced apoptosis of these cells was detected in vitro.     

穿心莲内酯对人皮肤基底细胞癌A431细胞生长、凋亡及增值细胞核抗原蛋白表达的影响

目的 探讨穿心莲内酯（AD）对人皮肤基底细胞癌A431细胞生长、凋亡及增殖细胞核抗原（PCNA）蛋白表达的影响。方法 应用酸性磷酸酶（APA）法检测细胞增殖抑制率,荧光显微镜观察细胞形态,Annexin V-FITC/PI双染法、流式细胞术（FCM）检测细胞凋亡率, Rh123染色FCM检测细胞线粒体膜电位,免疫细胞化学法检测细胞PCNA蛋白表达。结果AD呈时间、剂量依赖性抑制A431细胞生长增殖;且同一时间点50mg/L、100mg/L AD组与溶媒对照组相比差异显著（P＜0.05）。AD组作用A431细胞24h时,部分细胞核染色质出现典型凋亡形态学改变。不同浓度AD作用A431细胞24h,早期凋亡率、晚期凋亡及坏死率均随AD浓度升高而逐渐增加,且50mg/L、100mg/L AD组与溶媒对照组相比差异显著（P＜0.05）。AD作用A431 24h细胞内PCNA蛋白随AD浓度升高表达逐渐减少。AD作用A431细胞24h后,线粒体膜电位下降明显,与溶媒对照组相比较,50mg/L、100mg/L AD组差异有统计学意义（P＜0.05）。结论 AD可明显抑制A431细胞生长增殖,其抑制细胞增殖可能与下调PCNA蛋白表达有关。AD能诱导A431细胞凋亡,其凋亡机制可能与细胞线粒体膜电位下降有关。     

Morphological changes and patterns of ecdysone receptor B1 immunolocalization in the anterior silk gland undergoing programmed cell death in the silkworm, Bombyx mori

The silk gland is a specific larval tissue of Lepidopteran insects and begins to degenerate shortly before pupation. The steroid hormone ecdysone triggers the stage specific programmed cell death of the anterior silk glands during metamorphosis in the silkworm, Bombyx mori. The anterior silk gland expresses ecdysone receptors, which are involved in regulation processes in response to ecdysone. In this study, the morphological changes, immunohistochemical localization and protein levels of ecdysone receptor B1 (EcR-B1) in the anterior silk gland of B. mori were investigated during programmed cell death. Morphological changes observed during the degeneration process involve the appearance of large vacuoles, probably autophagic vacuoles, which increase in number in pupal anterior silk glands. No macrophages were found in the silk gland during the prepupal and pupal stage unlike in apoptosis, which strongly suggests that programmed cell death of the anterior silk gland is carried out by autophagy. Morphological changes of the silk glands were accompanied by changes in the immunolocalization and protein levels of EcR-B1. The differences in tissue distribution and protein levels of EcR-B1 during the programmed cell death indicate that the receptor plays a major role in the modulation and function of ecdysone activity in Bombyx anterior silk glands. Our results indicate that EcR-B1 expression may be important for the process of programmed cell death in the anterior silk glands.