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

The beneficial effects of angiotensin-converting enzyme inhibitors on ameliorating cardiac fibrosis have been partially attributed to their ability to prevent the degradation of kinins. The potential role of bradykinin and the related signaling molecule nitric oxide (NO) in modulating extracellular matrix (ECM) production was examined in primary cultures of adult rat cardiac fibroblasts. Treatment of fibroblasts with 5 nM 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 Northern blot analysis. The NO synthase inhibitor L-NAME attenuated the reduction observed in fibronectin and collagen mRNA levels in response to bradykinin. The NO donor DETA NONOate (100 microM) mimicked the effects of bradykinin on ECM mRNA levels. Protein levels of soluble fibronectin, assessed in conditioned medium by ELISA, were decreased by 14 +/- 4% and 21 +/- 4% after 48 h treatment with 1 microM bradykinin and 100 microM DETA NONOate, respectively. 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 microM DETA NONOate. These data indicate that bradykinin downregulates ECM protein production in cardiac fibroblasts and suggest that NO and the related signaling molecule cGMP may play an important role in mediating this response.