The course of inflammatory glomerular diseases is accompanied by changes in the expression of matrix-associated proteins, growth factors, and mediators in renal mesangial cells. Furthermore, the production of nitric oxide (NO) by the inducible isoform of nitric oxide synthase (iNOS) is enhanced after stimulation with pro-inflammatory cytokines. NO has been demonstrated to be a potent modulator of gene expression. To identify NO-regulated genes, we compared the expression patterns of mesangial cells treated for 24h with 500 microM (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (DETA-NO) with those of un-stimulated controls by applying a proteomics approach. One protein found to be NO-modulated by 2D gel electrophoresis is the manganese superoxide dismutase (Mn-SOD). Immunoblot and Northern blot analysis demonstrated a dose- and time-dependent induction of Mn-SOD expression by S-nitroso-N-acetyl-D, L-penicillamine (SNAP) and DETA-NO on both the protein and the mRNA levels. An upregulation of Mn-SOD expression by NO was accompanied by an increased Mn-SOD activity. Immunoblots of extracts of IL-1beta-treated cells cultivated with or without the iNOS inhibitor N(G)-monomethyl-L-arginine and the inhibitor of soluble guanylyl cyclase (sGC) 1H-[1,2,4]oxadiazole[4,3-a]quinoxalin-1-one (ODQ) demonstrated that the upregulation of the Mn-SOD by NO is due to a NO-dependent activation of sGC. The upregulation of Mn-SOD mRNA expression by NO was confirmed in vivo by Northern blot analysis in kidneys from rats treated with lipopolysaccharide (LPS) either in presence or absence of the iNOS inhibitor N(6)-(1-iminoethyl)-L-lysine (l-NIL).