Regulation of rheumatoid synoviocyte proliferation by endogenous p53 induction

Abstract

SUMMARYThe p53 tumour suppressor protein protects cells from tumorigenic alterations by inducing either cell growth arrest or apoptosis. In the present study, we investigated the role of endogenous p53 expressed in rheumatoid arthritis synovial fibroblasts which show transformed-appearing phenotypes. Type B synovial cells (fibroblast-like synovial cells) were exposed to a proteasome inhibitor, carbobenzoxylleucinyl-leucinyl-leucinal (MG-132). During this process, the expressions of p53 and p21 were examined by Western blot. Cell cycle analysis of the synovial cells was determined by DNA staining using propidium iodide (PI). Inhibition of proteasome resulted in the accumulation of p53 which was followed by an increase in the amount of a cyclin-dependent kinase (CDK)-inhibitor, p21. As a consequence, the retinoblastoma gene product, Rb, remained in the hypophosphorylated state, thus preventing PDGF-stimulated synovial cells from progressing into S-phase. This study shows that endogenous p53, which is inducible in rheumatoid synovial cells, is functionally active based on the findings that its expression blocks the G1/S transition by inhibiting the CDK-mediated phosphorylation of Rb via p21 induction. Thus the induction of p53 using proteasome inhibitor may provide a new approach in the treatment of RA.

Taurine chloramine inhibits proliferation of rheumatoid arthritis synoviocytes by triggering a p53-dependent pathway

“…However, transduction of RA FLS with p53, followed by an elevation of p21 expression, failed to trigger RA FLS apoptosis [53], suggesting that in these cells p53 pathway is more critical for the cell cycle regulation. Consistently, data from in vitro studies indicate that it is possible to inhibit RA FLS proliferation by manipulation of the expression of either p53 or p53-dependent cell cycle regulators, e. g.: using proteasome inhibitor that results in accumulation of endogenous p53 and up-regulation of p21 CDKI [54], by transfer of p21 gene into the cells [51,54], or treatment with PCNA anti-sense oligodeoxynucleotides [19]. Importantly, present studies revealed that inhibition of RA FLS proliferation can easily be achieved by treatment of the cells with Tau-Cl that modifi es expression of all above proteins.…”

Novel tumor necrosis factor α–regulated genes in rheumatoid arthritis

“…Primary synovial cell lines were established as previously described (16). Synovial tissue was minced into small pieces (ϳ1 mm 3 ) in prewarmed Dulbecco's modified Eagle's medium (DMEM; Gibco Invitrogen, Carlsbad, CA). The small pieces of synovial tissue were incubated for 2 hours at 37°C in the presence of 1 mg/ml of type I collagenase (Sigma, St. Louis, MO).…”

The expression change of β-arrestins in fibroblast-like synoviocytes from rats with collagen-induced arthritis and the effect of total glucosides of paeony

“…After incubation at 37 • C for an additional 6 h, the cells were centrifuged at 1000 × g for 10 min and all the supernatants were aspirated without disturbing the pellet. The formazan crystals were dissolved by the addition of 120 l dimethylsulfoxide (DMSO) and oscillated for 30 s (Migita et al, 2001). The absorbance (A) was measured at 490 nm and the results were expressed as mean of triplicate wells.…”