TNF-alpha renders human peritoneal mesothelial cells sensitive to anti-Fas antibody-induced apoptosis.
BACKGROUND
Fas-mediated apoptosis is important in the regulation of immune response. Human peritoneal mesothelial cells (HPMCs) are able to regulate peritoneal inflammation, but the role of Fas in HPMCs is not clear. This study addresses the mechanisms of Fas-mediated apoptosis in HPMCs.


METHODS
Tumour necrosis factor-alpha (TNF-alpha) primed HPMCs were stimulated with agonistic anti-Fas antibody. The expression of Fas was evaluated by real-time reverse transcription polymerase chain reaction (TaqMan quantitative polymerase chain reaction) and flow cytometry. Apoptosis was assessed by nuclear morphology, TUNEL assay, fractional DNA content and cytokeratin 18 cleavage. Caspase activation and bcl-2 expression were analysed by western blotting. The phagocytosis of apoptotic HPMCs was demonstrated by immunofluorescence and transmission electron microscopy.


RESULTS
Cultured HPMCs constitutively expressed Fas, and the Fas expression was upregulated by TNF-alpha. TNF-alpha primed HPMCs underwent apoptosis after anti-Fas antibody treatment, and the apoptotic HPMCs could be phagocytosed by macrophages. TNF-alpha was able to downregulate bcl-2 expression. Activation of caspase-3 and caspase-8 was noted during the apoptotic process. The inhibitors of either caspase-3 or caspase-8 could prevent the Fas-induced apoptosis in HPMCs. We also detected increased HPMC apoptosis in dialysate effluent during the recovery phase of peritonitis in peritoneal dialysis patients.


CONCLUSIONS
TNF-alpha directs HPMCs to commit apoptosis via the Fas/Fas ligand pathway through a modulation of Fas and bcl-2. Our study shows that HPMCs undergo apoptosis during peritonitis and suggests that the apoptosis of HPMCs may be related to the resolution of peritoneal inflammation.
Chen
Jinn-Yang
JY
Division of Nephrology, Department of Medicine, Taipei Veterans General Hospital, Institute of Clinical Medicine, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
Chi
Chin-Wen
CW
Chen
Hui-Ling
HL
Wan
Chiung-Pei
CP
Yang
Wu-Chang
WC
Yang
An-Hang
AH
D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology; D002478:Cells, Cultured; D004848:Epithelium / Q000187:drug effects*; D006801:Humans; D010529:Peritoneal Cavity / Q000166:cytology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000494:pharmacology*; D019014:fas Receptor / Q000276:immunology* / Q000502:physiology
D014409:Tumor Necrosis Factor-alpha; D019014:fas Receptor