Role of peroxynitrite in the protein oxidation and apoptotic DNA fragmentation in vascular smooth muscle cells stimulated with bacterial lipopolysaccharide and interferon-γ

In the present study, we investigated the role of endogenous and exogenous peroxynitrite in the process of DNA fragmentation and protein oxidation in cultured rat aortic smooth muscle cells. Peroxynitrite induced DNA fragmentation over a 24 hr period. The effect of peroxynitrite was unaffected by pretreatment with 3-aminobenzamide, an inhibitor of the nuclear enzyme poly (ADP-ribose) synthetase (PARS). Stimulation of the smooth muscle cells with bacterial lipopolysaccharide and interferon-γ produced nitric oxide and peroxynitrite, and resulted in a significant degree of apoptotic DNA fragmentation. The nitric oxide synthase inhibitor N^G-methyl-L-arginine (3 mM), but not the PARS inhibitor 3-aminobenzamide (1 mM), reduced the DNA fragmentation. Stimulation with bacterial lipopolysaccharide and interferon-γ also caused a marked oxidation of proteins in the smooth muscle cells, which was inhibited by N^G-methyl-L- arginine, as well as by the superoxide dismutase mimetic Mn(lll)tetrakis (4-benzoic acid) porphyrin. Based on these data, we propose a role for peroxynitrite-mediated, PARS-independent pathways in the apoptotic process and in the protein oxidation in bacterial lipopolysaccharide and interferon-γ-stimulated smooth muscle cells.