Caspase-8 has an essential role in resveratrol-induced apoptosis of rheumatoid fibroblast-like synoviocytes

Objective. Resveratrol is a naturally occurring polyphenol,which possesses chemotherapeutic potential through its abilityto trigger apoptosis. The objective of this study was to investigatethe major determinant for the apoptotic cell death inductionby resveratrol in fibroblast-like synoviocytes (FLS) derivedfrom patients with RA. Methods. The effect of resveratrol on apoptotic cell death wasquantified in a population of subG1 in RA FLS by flow cytometry.The underlying signalling mechanism for apoptotic death wasexamined by analysing mitochondrial membrane potential, activationof the caspase cascade and translocation of Bid. Results. We show that activation of caspase-8 is essential fortriggering resveratrol-induced apoptotic signalling via theinvolvement of the mitochondrial pathway in RA FLS. Our findingsalso suggest that this enhanced apoptosis caused by resveratroloccurred in RA FLS irrespective of p53 status. Exposure to resveratrolcaused extensive apoptotic cell death, along with a caspase-dependent(activation of caspase-9 and -3, poly ADPribose polymerase (PARP)cleavage and mitochondrial cytochrome c release) or caspase-independent[translocation of apoptosis-inducing factor (AIF) to the nucleus]signalling pathway. Analysis of upstream signalling events affectedby resveratrol revealed that the activated caspase-8 triggeredmitochondrial apoptotic events by inducing Bid cleavage withoutany alteration in the levels of Bax, Bcl-xL or Bcl2. The caspase-8inhibitor or over-expression of crmA abrogated cell death inducedby resveratrol and prevented processing of the downstream cascade. Conclusion. The results suggest that resveratrol causes activationof caspase-8, which in turn results in modulation of mitochondrialapoptotic machinery to promote apoptosis of RA FLS. KEY WORDS: Resveratrol, Fibroblast-like synoviocytes, Apoptosis, Caspase-8, Mitochondria membrane potential