Carbon monoxide reduces the expression and activity of matrix metalloproteinases 1 and 2 in alveolar epithelial cells

Matrix metalloproteinases (MMPs), particularly MMP-1 and MMP-2, are involved in the pathophysiology of emphysema. MMPs contain zinc in the catalytic site and its expression is regulated transcriptionally via mitogen activated protein kinases (MAPKs). Carbon monoxide (CO), one of the end products of heme oxygenase activity, has anti-inflammatory properties, which are mediated, at least in part, by activation of p38 MAPK. Furthermore, CO has the unique ability to bind to metal centers in proteins and can affect their specific activity. Therefore, we hypothesized that CO could inhibit MMPs expression and/or activity. Here we show that a recently identified carbon monoxide-releasing molecule, [Ru(CO)(3)Cl-2](2) (or CORM-2) inhibits MMP-1 and MMP-2 mRNA expression in the human lung epithelial cell line A549. The MMPs mRNA expression was unaffected by the p38 MAPK inhibitor SB203580, but in the case of MMP-1 was reversed by the antioxidant N-acetylcysteine. In addition, CORM-2 inhibited both MMP-1 and MMP-2 activities. Interestingly, no effect was observed with (Ru( DMSO)(4)Cl-2), a negative control that does not contain CO groups. To the best of our knowledge this is the first evidence on the effect of CO on MMPs expression and activity. This effect could have important implications in the pathophysiology of emphysema and other diseases involving proteases/antiproteases imbalance.