Exogenous nitric oxide causes overexpression of TGF-β1 and overproduction of extracellular matrix in human coronary smooth muscle cells

Objective: Nitric oxide (NO) is a major signalling molecule in the vascular system enhancing vascular smooth muscle cell relaxation and vasodilation. NO donors are the most frequently and repeatedly used drugs for relief from angina pectoris. Methods: We investigated the effects of the synthetic NO donor DETA/NO on cultured human coronary smooth muscle cells. Results: Cells exposed to 100 μM DETA/NO for 48–72 h were channeled into a cell cycle-arrested hypertrophic growth status associated with overexpression of TGF-β1 on both the protein and mRNA levels. Increased TGF-β1 transcription and translation were associated with enhanced synthesis of extracellular matrix components including the collagen types I and III as shown by immunocytochemistry and enhanced incorporation of [3H]proline. Higher incorporation of [35S]sulfate into chondroitin/dermatan sulfate and heparan sulfate containing proteoglycans was observed in DETA/NO treated cells than in controls. The ratio of chondroitin/dermatan sulfate to heparan sulfate did not change significantly. Conclusions: Our results suggest a dual function of the overexpressed TGF-β1. Overexpressed TGF-β1 could stabilize the fibrous cap overlaying atherosclerotic plaques due to the accumulation of extracellular matrix components. However, the findings could also support a proatherogenic role of TGF-β1 resulting from the overexpression of LDL-binding proteoglycans.