Oxidative stress regulates collagen synthesis and matrix metalloproteinaseactivity in cardiac fibroblasts

Oxidative stress has been implicated in the pathophysiology of myocardial f ailure. We tested the hypothesis that oxidative stress can regulate extrace llular matrix in cardiac fibroblasts. Neonatal and adult rat cardiac fibrob lasts in vitro were exposed to H2O2 (0.05-5 muM) or the superoxide-generati ng system xanthine (500 muM) plus xanthine oxidase (0.001-0.1 mU/ml) (XXO) for 24 h. In-gel zymography demonstrated that H2O2 and XXO each increased g elatinase activity corresponding to matrix metalloproteinases (MMP) MMP-13, MMP-2, and MMP-9. H2O2 and XXO decreased collagen synthesis (collagenase-s ensitive [H-3] proline incorporation) without affecting total protein synth esis ([H-3] leucine incorporation). H2O2 and XXO decreased the expression o f procollagen alpha (1)(I), alpha (2)(I), and alpha (1)(III) mRNA but incre ased the expression of fibronectin mRNA, suggesting a selective transcripti onal effect on collagen synthesis. H2O2, but not XXO, also decreased the ex pression of nonfibrillar procollagen alpha (1)(IV) and alpha (2)(IV) mRNA. To determine the role of endogenous antioxidant systems, cells were treated with the superoxide dismutase (SOD) inhibitor diethyldithiocarbamic acid ( DDC, 100 muM) to increase intracellular superoxide or with the glucose-6-ph osphate dehydrogenase inhibitor dehydroisoandrosterone 3-acetate (DHEA; 10 muM) to increase intracellular H2O2. DDC and DHEA decreased collagen synthe sis and increased MMP activity, and both effects were inhibited by an SOD/c atalase mimetic. Thus increased oxidative stress activates MMPs and decreas es fibrillar collagen synthesis in cardiac fibroblasts. Oxidative stress ma y play a role in the pathogenesis of myocardial remodeling by regulating th e quantity and quality of extracellular matrix.