Trichostatin A sensitises rheumatoid arthritis synovial fibroblasts for TRAIL-induced apoptosis

Abstract

Background: Histone acetylation/deacetylation has a critical role in the regulation of transcription by altering the chromatin structure. Objective: To analyse the effect of trichostatin A (TSA), a streptomyces metabolite which specifically inhibits mammalian histone deacetylases, on TRAIL-induced apoptosis of rheumatoid arthritis synovial fibroblasts (RASF). Methods: Apoptotic cells were detected after co-treatment of RASF with TRAIL (200 ng/ml) and TSA (0.5, 1, and 2 mmol/l) by flow cytometry using propidium iodide/annexin-V-FITC staining. Cell proliferation was assessed using the MTS proliferation test. Induction of the cell cycle inhibitor p21Waf/Cip1 by TSA was analysed by western blot. Expression of the TRAIL receptor-2 (DR5) on the cell surface of RASF was analysed by flow cytometry. Levels of soluble TRAIL were measured in synovial fluid of patients with RA and osteoarthritis (OA) by ELISA. Results: Co-treatment of the cells with TSA and TRAIL induced cell death in a synergistic and dose dependent manner, whereas TRAIL and TSA alone had no effect or only a modest effect. RASF express DR5 (TRAIL receptor 2), but treatment of the cells with TSA for 24 hours did not change the expression level of DR5, as it is shown for cancer cells. TSA induced cell cycle arrest in RASF through up regulation of p21 Waf1/Cip1 . Levels of soluble TRAIL were significantly higher in RA than in OA synovial fluids. Conclusion: Because TSA sensitises RASF for TRAIL-induced apoptosis, it is concluded that TSA discloses sensitive sites in the cascade of TRAIL signalling and may represent a new principle for the treatment of RA.

The pleiotropic effect of TRAIL on tumor-like synovial fibroblasts from rheumatoid arthritis patients is mediated by caspases

“…These authors found that upregulation of p21 induced by trichostatin A, an inhibitor of histone deacetylases, led to cell cycle arrest and decreased proliferation of RA FLS. 15 In line with this finding is our observation that nocodazole-induced cell cycle arrest sensitizes RA FLS for TRAIL-induced apoptosis (data not shown).…”

“…In fact, a recent report correlated the responses of RA FLS to TRAIL, with the expression levels of the cell cycle regulator p21. 15 We therefore analyzed the expression levels of p21 Waf1/Cip1 and of p27 Kip1 , another important cell cycle regulator, in TRAILtreated RA FLS. Expression levels of p21 and p27 were decreased in cells treated for 24 h with TRAIL compared with untreated cells.…”

Mechanisms and clinical relevance of TRAIL‐triggered responses in the synovial fibroblasts of patients with rheumatoid arthritis

“…Reports on the effect of TRAIL on RA FLS are controversial. According to some reports, TRAIL induces apoptosis of RA FLS (13,14), whereas other studies showed that RA FLS were not responsive to TRAIL when not sensitized (13,(18)(19)(20). We observed and patients with osteoarthritis (OA; n ϭ 4).…”

Apoptosis Resistance in Rheumatoid Arthritis Synovial Tissue

“…With regard to the role of histone acetylation in apoptosis, Jüngel et al [52] exploited trichostatin A (TSA), a Streptomyces metabolite and inhibitor of mammalian histone acetylases [53], to show that TSA when combined with TRAIL led to an induction of RASF apoptosis, whereas either TSA or TRAIL alone sparingly induced apoptosis in these cells. The mechanism of action of TSA on TRAIL-induced apoptosis was further explored.…”