NO inhibition of collagen in dermal SSc fibroblasts has been reported to be by cGMP-independent regulatory mechanisms and in part may be due to up-regulation of matrix metalloproteinase-1 (MMP-1, an essential collagenase involved in collagen degradation) protein and activity levels and/or inhibition of prolyl hydroxylase activity (an enzyme important in the posttranslational processing of collagen) [74]. The gene discussed is MMP1; the disease is systemic sclerosis.