Poly(ADP-ribose) polymerase suppression protects rheumatoid synovial fibroblasts from Fas-induced apoptosis.
OBJECTIVE
To investigate the effect of poly(ADP-ribose) polymerase 1 (PARP-1) suppression on CD95/Apo-1 (Fas)-induced apoptosis in fibroblast-like synoviocytes (FLS) from RA patients.


METHODS
Apoptosis, determined by Hoechst staining and quantification of nucleosomal release by ELISA, was induced by stimulation with anti-Fas antibody with or without pre-treatment with cycloheximide (CHX). PARP-1 and poly(ADP-ribose) glycohydrolase (PARG) were suppressed in RA FLS by small interfering RNA (siRNA) transfection. Fas-associated via death domain (FADD), pro-caspase-8, Fas, c-Fas-associated death domain-like IL-1b-converting enzyme-inhibitory protein (FLIP) expression, and AKT and GSK phosphorylation were analysed by western blot.


RESULTS
PARP-1-deficient FLS showed significantly lower apoptosis than non-transfected and control siRNA-transfected FLS. The expression of death-inducing signaling complex (DISC) components such as Fas, FADD and pro-caspase-8 was not modified by PARP-1 suppression; however, FLS lacking PARP-1 showed high activation of the Akt-GSK survival pathway and up-regulation of the c-FLIP-S isoform after Fas triggering. Inhibition of PI3K/Akt pathway did not modify the difference between PARP-1-competent or -deficient FLS in Fas-mediated apoptosis or c-FLIP-S expression. Poly(ADP-ribose) accumulation induced by PARG supression did not modify the apoptotic response.


CONCLUSIONS
PARP-1 deficiency increases the resistance of RA FLS to Fas-induced apoptosis through activation of the Akt-GSK survival pathway and up-regulation of c-FLIP-S isoform.
García
Samuel
S
Research Laboratory and Rheumatology Unit, Hospital Clínico Universitario de Santiago de Compostela, Spain.
Mera
Antonio
A
Gómez-Reino
Juan J
JJ
Conde
Carmen
C
D017209:Apoptosis; D001172:Arthritis, Rheumatoid / Q000201:enzymology* / Q000378:metabolism / Q000473:pathology; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D002478:Cells, Cultured; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology*; D038341:Glycogen Synthase Kinases / Q000378:metabolism; D006801:Humans; D010766:Phosphorylation; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013583:Synovial Membrane / Q000378:metabolism / Q000473:pathology*; D014162:Transfection; D019014:fas Receptor / Q000502:physiology*
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; C506386:CFLAR protein, human; C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D034741:RNA, Small Interfering; D019014:fas Receptor; C499320:PARP1 protein, human; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D038341:Glycogen Synthase Kinases; D051057:Proto-Oncogene Proteins c-akt; D053181:Caspase 8