Reactive oxygen species are involved in FasL-induced caspase-independent cell death and inflammatory responses.
Fas-mediated caspase-dependent cell apoptosis has been well investigated. However, recent studies have shown that Fas can induce nonapoptotic caspase-independent cell death (CICD) when caspase activity is inhibited. Currently, the molecular mechanism of this alternative cell death mediated by Fas remains unclear. In this study, we investigated the signaling pathway of Fas-induced CICD in mouse embryonic fibroblasts (MEFs) whose caspase function was disrupted by the pan-caspase inhibitor Z-VAD-FMK and its coupling to inflammatory responses. Our results revealed that receptor-interacting protein 1 and tumor necrosis factor receptor-associated factor 2 play important roles in FasL-induced CICD. This death is associated with intracellular reactive oxygen species (ROS) production from mitochondria, as a ROS scavenger (BHA), antioxidants (trolox, NAC), and a mitochondrial respiratory chain uncoupler (rotenone) could prevent this event. Furthermore, delayed and sustained JNK activation, mitochondrial membrane potential breakdown, and loss of intracellular GSH were observed. In addition to CICD, FasL also induces cyclooxygenase-2 and MIP-2 gene upregulation, and both responses are attributed to ROS-dependent JNK activation. Taken together, these results demonstrate alternative signaling pathways of Fas upon caspase inhibition in MEFs that are unrelated to the classical apoptotic pathway, but steer cells toward necrosis and an inflammatory response through ROS production.
Chen
Tsai-Yu
TY
Department of Pharmacology, College of Medicine, National Taiwan University, Taipei.
Chi
Kwan-Hwa
KH
Wang
Jang-Shiun
JS
Chien
Chung-Liang
CL
Lin
Wan-Wan
WW
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology; D002460:Cell Line; D054426:Chemokine CXCL2 / Q000235:genetics / Q000378:metabolism; D002839:Chromans / Q000494:pharmacology; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D053222:Fas Ligand Protein / Q000378:metabolism*; D005347:Fibroblasts / Q000473:pathology / Q000502:physiology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D007249:Inflammation; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008928:Mitochondria / Q000502:physiology*; D017382:Reactive Oxygen Species; D015398:Signal Transduction; D019014:fas Receptor
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D054426:Chemokine CXCL2; D002839:Chromans; D053222:Fas Ligand Protein; C491899:Fas protein, mouse; D017382:Reactive Oxygen Species; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D019014:fas Receptor; D051546:Cyclooxygenase 2; D020169:Caspases; C010643:6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid