PEROXYNITRITE MODULATES MNSOD GENE-EXPRESSION IN LUNG EPITHELIAL-CELLS

Peroxynitrite (ONOO-) is a strong oxidant derived from nitric oxide (( NO)-N-.) and superoxide (O-2(.-)), reactive nitrogen (RNS) and oxygen species (ROS) present in inflamed tissue. Other oxidant stresses, e.g. , TNF-alpha and hyperoxia, induce mitochondrial, manganese-containing superoxide dismutase (MnSOD) gene expression. These experiments tested whether ONOO- regulated MnSOD gene expression in human lung epithelia l (A549) cells. 3-morpholinosydnonimine HCl (SIN-1) (10 or 1000 mu M) increased MnSOD mRNA, but did not change hypoxanthine guanine phosphor ibosyl transferase (HPRT) mRNA. Authentic peroxynitrite (ONOO-) (100-5 00 mu M) also increased MnSOD mRNA but did not change constitutive HPR T mRNA expression. ONOO- stimulated luciferase gene expression driven by a 2.5 kb fragment of the rat MnSOD gene 5' promoter region. MnSOD g ene induction due to ONOO- was inhibited effectively by L-cysteine (10 mM) and partially inhibited by N-acetyl cysteine (50 mM) or pyrrole d ithiocarbamate (10 mM). (NO)-N-. from 1-propanamine, 3-(2-hydroxy-2-ni troso-1-propylhydrazine) (PAPA NONOate) (100 or 1000 mu M) did not cha nge MnSOD or HPRT mRNA. Neither H2O2 nor NO2-, breakdown products of S IN-1 and ONOO-, had any effect on MnSOD mRNA expression; however, ONOO - and SIN-1 did not increase MnSOD protein content detectable by weste rn blots, nor did they increase MnSOD enzymatic activity. Increased st eady state [O-2(.-)] in the presence of (NO)-N-. yields ONOO-, and ONO O- has direct, stimulatory effects on MnSOD transcript expression. (C) 1998 Elsevier Science Inc.