Saas P, Boucraut J, Quiquerez A L, Schnuriger V, Perrin G, Desplat-Jego S, Bernard D, Walker P R, Dietrich P Y
Laboratory of Tumor Immunology, Division of Oncology, University Hospital, Geneva, Switzerland.
J Immunol. 1999 Feb 15;162(4):2326-33.
Astrocytes are a major cellular component of the brain that are capable of intense proliferation and metabolic activity during diverse inflammatory brain diseases (such as multiple sclerosis, Alzheimer's dementia, tumor, HIV encephalitis, or prion disease). In this biological process, called reactive gliosis, astrocyte apoptosis is frequently observed and could be an important mechanism of regulation. However, the factors responsible for apoptosis in human astrocytes are poorly defined. Here, we report that short term cultured astrocytes derived from different brain regions express significant levels of CD95 at their surface. Only late passage astrocytes are sensitive to CD95 ligation using either CD95 mAb or recombinant CD95 ligand. Blocking experiments using caspase inhibitors with different specificities (DEVD-CHO, z-VAD-fmk, and YVAD-cmk), an enzymatic activity assay, and immunoblotting show that CPP32/caspase-3 play a prominent role in CD95-induced astrocyte death. In contrast, early passage astrocytes are totally resistant to death, but a significant increase in astrocytic IL-8 secretion (p < 0.001, by Wilcoxon's test for paired samples) is observed after CD95 triggering. Production of IL-8 contributes to the resistance of astrocytes to CD95 ligation. Furthermore, in the presence of IFN-gamma, resistant astrocytes became sensitive to CD95-mediated death. These data suggest that microenvironmental factors can influence the consequences of CD95 ligation on astrocytes. Therefore, we propose that CD95 expressed by human astrocytes plays a pivotal role in the regulation of astrocyte life and death and may be a key factor in inflammatory processes in the brain, such as reactive gliosis.
星形胶质细胞是大脑的主要细胞成分，在多种炎性脑疾病（如多发性硬化症、阿尔茨海默病性痴呆、肿瘤、HIV脑炎或朊病毒病）期间能够进行强烈增殖和代谢活动。在这个称为反应性胶质增生的生物学过程中，经常观察到星形胶质细胞凋亡，这可能是一种重要的调节机制。然而，人类星形胶质细胞凋亡的相关因素尚不清楚。在此，我们报告来自不同脑区的短期培养星形胶质细胞在其表面表达显著水平的CD95。只有传代后期的星形胶质细胞对使用CD95单克隆抗体或重组CD95配体的CD95连接敏感。使用具有不同特异性的半胱天冬酶抑制剂（DEVD-CHO、z-VAD-fmk和YVAD-cmk）进行的阻断实验、酶活性测定和免疫印迹表明，CPP32/半胱天冬酶-3在CD95诱导的星形胶质细胞死亡中起主要作用。相比之下，传代早期的星形胶质细胞对死亡完全具有抗性，但在CD95触发后观察到星形胶质细胞IL-8分泌显著增加（通过配对样本的Wilcoxon检验，p<0.001）。IL-8的产生有助于星形胶质细胞对CD95连接的抗性。此外，在干扰素-γ存在的情况下，抗性星形胶质细胞对CD95介导的死亡变得敏感。这些数据表明，微环境因素可影响CD95连接对星形胶质细胞的影响。因此，我们提出人类星形胶质细胞表达的CD95在星形胶质细胞生死调节中起关键作用，可能是大脑炎性过程（如反应性胶质增生）中的关键因素。
