Regulation of cardiac fibroblast extracellular matrix production by bradykinin and nitric oxide

The beneficial effects of angiotensin-converting enzyme inhibitors on ameli orating cardiac fibrosis have been partially attributed to their ability to prevent the degradation of kinins, The potential role of bradykinin and th e related signaling molecule nitric oxide (NO) in modulating extracellular matrix (ECM) production was examined in primary cultures of adult rat cardi ac fibroblasts, Treatment of fibroblasts with 5 nhl bradykinin for 24 h led to a reduction in steady-state mRNA levels for fibronectin (34 +/- 7%) and collagens type I (19 +/- 8%) and type III (48 +/- 4%), as determined by No rthern blot analysis. The NO synthase inhibitor L-NAME attenuated the reduc tion observed in fibronectin and collagen mRNA levels in response to bradyk inin. The NO donor DETA NONOate (100 mu M) mimicked the effects of bradykin in on ECM mRNA levels, Protein levels of soluble fibronectin, assessed in c onditioned medium by ELISA, were decreased by 14 +/- 4%, and 21 +/- 4% afte r 48 h treatment with 1 mu M bradykinin and 100 mu M DETA NONOate, respecti vely. Bradykinin stimulated intracellular cGMP accumulation 73.7 +/- 10.3% after 10 min of treatment, Cell proliferation rates at 48 h were unaffected by bradykinin, but were reduced by 26 +/- 12% by 100 mu M DETA NONOate. Th ese data indicate that bradykinin downregulates ECM protein production in c ardiac fibroblasts and suggest that NO and the related signaling molecule c GMP may play an important role in mediating this reponse. (C) 1999 Academic Press.