Wosik K, Becher B, Ezman A, Nalbantoglu J, Antel J P
Neuroimmunology Unit, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Quebec, H3A 2B4, Canada.
Glia. 2001 Mar 1;33(3):217-24. doi: 10.1002/1098-1136(200103)33:3<217::aid-glia1020>3.0.co;2-w.
Fas (APO-1/CD95) is a cell surface receptor initially identified in lymphoid cells, but more recently detected in the central nervous system under pathological, usually inflammatory, conditions. In most Fas expressing cells, triggering of Fas by its ligand or by antagonistic antibodies leads to apoptosis. Human fetal astrocytes (HFA) constitutively express Fas yet are resistant to cell death following Fas ligation. In the current study, using dissociated cultures of human fetal central nervous system-derived cells, we attempted to identify a basis for HFA resistance to Fas-mediated injury. We compared the components of the Fas signaling pathway of HFA to those of two human cell lines susceptible to Fas-mediated injury, U251 glioma and Jurkat T-cells. We found that HFA did not express caspase 8 (FLICE), the caspase primarily activated on Fas signaling. Although we could induce caspase 8 in HFA with the inflammatory cytokines IFNgamma and TNFalpha, HFA remained resistant to Fas-mediated injury. Addition of inflammatory cytokines to the extracellular milieu also increased FLIP mRNA (FLICE inhibitory protein). Furthermore, upon triggering of cytokine-treated cells with FasL, we observed upregulation of the cleavage product of FLIP (p43-FLIP) previously shown to associate with the DISC and to block caspase 8 recruitment, thereby inhibiting Fas-mediated death. Our findings indicate that caspase 8 and its regulators play a central role in determining the response to Fas ligation of HFA and support a role for Fas signaling in the developing central nervous system other than related to cytotoxicity.
Fas（APO-1/CD95）是一种最初在淋巴细胞中发现的细胞表面受体，但最近在病理状态（通常为炎症状态）下的中枢神经系统中也被检测到。在大多数表达Fas的细胞中，其配体或拮抗抗体触发Fas会导致细胞凋亡。人胎儿星形胶质细胞（HFA）组成性表达Fas，但在Fas连接后对细胞死亡具有抗性。在本研究中，我们使用源自人胎儿中枢神经系统的解离细胞培养物，试图确定HFA对Fas介导的损伤具有抗性的基础。我们将HFA的Fas信号通路成分与两种易受Fas介导损伤的人细胞系（U251胶质瘤细胞和Jurkat T细胞）的成分进行了比较。我们发现HFA不表达caspase 8（FLICE），即主要在Fas信号传导时被激活的半胱天冬酶。尽管我们可以用炎性细胞因子IFNγ和TNFα在HFA中诱导caspase 8，但HFA对Fas介导的损伤仍具有抗性。向细胞外环境中添加炎性细胞因子也会增加FLIP mRNA（FLICE抑制蛋白）。此外，在用FasL触发细胞因子处理的细胞后，我们观察到FLIP的裂解产物（p43-FLIP）上调，先前已证明该产物与死亡诱导信号复合物（DISC）相关并阻止caspase 8募集，从而抑制Fas介导的死亡。我们的研究结果表明，caspase 8及其调节因子在决定HFA对Fas连接的反应中起核心作用，并支持Fas信号传导在发育中的中枢神经系统中除细胞毒性相关作用外的其他作用。
