Haem oxygenase-1 down-regulates high mobility group box 1 and matrix metalloproteinases in osteoarthritic synoviocytes.

OBJECTIVES

Activation of osteoarthritic synoviocytes by pro-inflammatory cytokines results in the release of biochemical mediators such as MMPs and high mobility group box 1 (HMGB1). Extracellular HMGB1 can play an important role in joint diseases as a mediator of synovitis. We have shown previously that haem oxygenase-1 (HO-1) exerts protective effects during inflammatory responses. In this study, we have examined whether HO-1 induction would be an effective strategy to control MMP and HMGB1 production in osteoarthritic synoviocytes.

METHODS

Osteoarthritic synoviocytes were obtained by digestion with collagenase and cultured until third passage. HO-1 was induced by cobalt protoporphyrin IX (CoPP). Lentiviral HO-1 vector (LV-HO-1) was also used for HO-1 overexpression. HO-1 gene silencing was achieved by using a specific small interfering RNA. Gene expression was analysed by quantitative PCR and protein expression by western blot, ELISA and IF. MMP activity was studied by fluorometric procedures.

RESULTS

Induction of HO-1 by CoPP in the presence of IL-1beta decreased the expression of MMP-1 and -3, and MMP activity. IL-1beta stimulation of synoviocytes increased HMGB1 expression, its translocation into the cytoplasm and secretion. HO-1 induction exerted inhibitory effects on these processes. The consequences of HO-1 induction were counteracted by HO-1 gene silencing, whereas transfection with LV-HO-1 confirmed the effects of pharmacological HO-1 induction.

CONCLUSIONS

We have provided direct evidence that HO-1 down-regulates MMP-1, -3 and HMGB1 in osteoarthritic synoviocytes. HO-1 may be a potential strategy to control inflammatory and degradative processes in the progression of OA.