Antioxidant activity and inhibitory effects of hydralazine on inducible NOS/COX-2 gene and protein expression in rat peritoneal macrophages

This study investigated the effects of the peripheral vasodilator hydralazine on in vitro generation of reactive species of oxygen (ROS), nitrogen (RNS) and prostaglandin (PG) biosynthesis in elicited murine peritoneal macrophages, and on the gene expression and protein synthesis of two key enzymes in the inflammatory process, inducible NO(*) synthase (NOS-2) and inducible cyclooxygenase 2 (COX-2). Hydralazine at 0.1-10 mM inhibited both extracellular and intracellular ROS production by inflammatory macrophages, by a ROS-scavenging mechanism probably affecting superoxide radical (O(2)(*-))-generation by Xanthine Oxidase (XO) and nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase. Hydralazine at 0.1-10 mM significantly reduced NO(*) generation, and this effect was attributable to an inhibition of NOS-2 gene expression and protein synthesis. At 1-10 mM, hydralazine also effectively blocked COX-2 gene expression which perfectly correlated with a reduction of protein levels and PGE(2) synthesis. These data suggest that hydralazine, at the concentrations tested, show antioxidant properties and strongly attenuates the macrophage activation.