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Effect of nitric oxide and peroxynitrite on type I collagen synthesis in normal and scleroderma dermal fibroblasts.

Posted Nov 12 2010 4:19am

Nitric oxide (()NO) is an important physiological signaling molecule and potent vasodilator. Recently, we have shown abnormal ()NO metabolism in the plasma of patients with systemic sclerosis (SSc), a disease that features excessive collagen overproduction as well as vascular dysfunction.

The current study investigates the effects of ()NO and peroxynitrite (ONOO(-)) on secretion of type I collagen by SSc dermal fibroblasts, compared with those from normal dermal fibroblasts (CON) and a dermal fibroblast cell line (AG). Dermal fibroblasts were incubated with ()NO donors (SNP, DETA-NONOate) with or without the antioxidant ascorbic acid, or ONOO(-) for 24-72 h. In CON and AG fibroblasts, type I collagen was dose dependently decreased by SNP or DETA-NONOate.

However, ()NO had no effect in SSc fibroblasts. Furthermore, the inhibition of collagen synthesis by ()NO was reversed by ascorbic acid and was not affected by 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one, an inhibitor of soluble guanyl cyclase, or 8-bromoguanosine cyclic 3',5'-monophosphate, a cGMP agonist.

SNP also showed a significant up-regulation of matrix metalloproteinase-1 (MMP-1) protein and activity levels, an essential collagenase involved in collagen degradation, in the AG fibroblasts. Additionally, ()NO-treated fibroblasts had lower prolyl hydroxylase activity, an enzyme important in the post-translational processing of collagen, while there was no effect on total protein levels.

There were no significant effects on type I collagen levels when dermal fibroblasts were treated with ONOO(-). Taken together, ()NO inhibits collagen secretion in normal dermal fibroblasts but regulation is lost in SSc fibroblasts, while ONOO(-) itself is ineffective. ()NO inhibition of collagen was by cGMP-independent regulatory mechanisms and in part may be due to up-regulation of MMP-1 and/or inhibition of prolyl hydroxylase. These differences may contribute to the observed pathology of SSc.

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