Abstract
Peroxynitrite (ONOO
−) is a strong oxidant derived from nitric oxide (
NO) and superoxide (O
2
•−), reactive nitrogen (RNS) and oxygen species (ROS) present in inflamed tissue. Other oxidant stresses,
e.g., TNF-α and hyperoxia, induce mitochondrial, manganese-containing superoxide dismutase (MnSOD) gene expression. These experiments tested whether ONOO
− regulated MnSOD gene expression in human lung epithelial (A549) cells. 3-morpholinosydnonimine HCl (SIN-1) (10 or 1000 μM) increased MnSOD mRNA, but did not change hypoxanthine guanine phosphoribosyl transferase (HPRT) mRNA. Authentic peroxynitrite (ONOO
−) (100–500 μM) also increased MnSOD mRNA but did not change constitutive HPRT mRNA expression. ONOO
− stimulated luciferase gene expression driven by a 2.5 kb fragment of the rat MnSOD gene 5′ promoter region. MnSOD gene induction due to ONOO
− was inhibited effectively by L-cysteine (10 mM) and partially inhibited by N-acetyl cysteine (50 mM) or pyrrole dithiocarbamate (10 mM).
NO from 1-propanamine, 3-(2-hydroxy-2-nitroso-1-propylhydrazine) (PAPA NONOate) (100 or 1000 μM) did not change MnSOD or HPRT mRNA. Neither H
2O
2 nor NO
2
−, breakdown products of SIN-1 and ONOO
−, had any effect on MnSOD mRNA expression; however, ONOO
− and SIN-1 did not increase MnSOD protein content detectable by western blots, nor did they increase MnSOD enzymatic activity. Increased steady state [O
2
•−] in the presence of
NO yields ONOO
−, and ONOO
− has direct, stimulatory effects on MnSOD transcript expression.
