The role of cyclic-3′,5′-adenosine monophosphate in prostaglandin-mediated inhibition of basic calcium phosphate crystal-induced mitogenesis and collagenase induction in cultured human fibroblasts

Abstract

Synovial fluid basic calcium phosphate (BCP) crystals are associated with severe destructive arthropathies characterised by synovial proliferation and non-inflammatory degradation of intra-articular collagenous structures. BCP crystals stimulate fibroblast and chondrocyte mitogenesis, metalloprotease secretion and prostaglandin production. As a tissue protective effect of prostaglandins has been suggested, we recently studied the effect of PGE 1 on BCP crystal-induced mitogenesis and collagenase mRNA accumulation in human fibroblasts (HF). We demonstrated a dose-dependent inhibition of BCP crystal-induced mitogenesis and collagenase mRNA accumulation. The mechanism of PGE 1 inhibition of BCP crystal-induced mitogenesis and collagenase mRNA accumulation was therefore explored. PGE 1 (100 ng/ml) increased HF intracellular cAMP 40-fold over control. BCP alone caused no such change but inhibited the PGE 1-induced increase in intracellular cAMP by at least 60%. The PGE 1-induced increase in intracellular cAMP was also blocked by the adenyl cyclase inhibitor, 2′,5′-dideoxyadenosine (ddA) (10 μM) and ddA reversed the PGE 1-mediated inhibition of BCP crystal-induced mitogenesis. Dibutyrul cAMP also inhibited BCP crystal-induced mitogenesis in a concentration-dependent manner. Agents which increase intracellular cAMP levels such as the adenyl cyclase activator forskolin and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) mimicked the effect of PGE 1 on HF collagenase mRNA levels. PGE 1 inhibits the biologic effects of BCP crystals through the cAMP signal transduction pathway and such inhibition may have significant therapeutic implications.