Nitric oxide induces heme oxygenase-1 gene expression in mesangial cells.
BACKGROUND
Nitric oxide (NO) release as a result of activation of inducible NO synthase (iNOS) can be sustained and reach cytotoxic concentrations. It is unknown whether cells possess intrinsic systems to attenuate NO-mediated cytotoxicity. One potential system is the heme oxygenase-1 (HO-1) enzyme because it catabolizes heme and therefore may limit synthesis or availability of iNOS. These studies were undertaken to explore whether NO derived from NO donors or from activation of iNOS induces HO-1 in mesangial cells.


METHODS
The expression of the HO-1 gene was evaluated at the mRNA (Northern blot analysis) and protein (Western blot analysis) levels in mesangial cells treated with two NO donors, sodium nitroprusside (SNP) and S-nitroso-N-acetyl-DL-penicillamine (SNAP), or was stimulated by the combination of lipopolysaccharide (LPS) and interferon-gamma (IFN-gamma) to induce iNOS in the presence and absence of NOS inhibitor NG-Monomethyl-L-arginine (L-NMMA).


RESULTS
HO-1 was constitutively expressed in mesangial cells. Both SNP and SNAP induced HO-1 mRNA in a dose-dependent manner. The increase in mRNA was associated with an increase in HO-1 protein in SNP-treated cells. The combination of the LPS/IFN-gamma mixture induced iNOS expression and NO production in murine mesangial cells, as assessed by Western blot analysis and measurement of nitrite levels. HO-1 expression was also increased in response to LPS/IFN-gamma. L-NMMA dose dependently attenuated HO-1 mRNA and protein levels. In contrast, iNOS expression was dose dependently enhanced.


CONCLUSIONS
Our studies demonstrate that both exogenously or iNOS-derived NO enhance HO-1 expression in mesangial cells and point to regulatory interactions between the iNOS and HO pathways. HO-1 activation may defend against NO-mediated toxicity.
Datta
P K
PK
Department of Medicine, Medical College of Wisconsin, Milwaukee, USA.
Lianos
E A
EA
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology; D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D003603:Cytotoxins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects / Q000502:physiology*; D005920:Glomerular Mesangium / Q000201:enzymology* / Q000473:pathology; D006419:Heme Oxygenase (Decyclizing) / Q000032:analysis / Q000235:genetics*; D051547:Heme Oxygenase-1; D007371:Interferon-gamma / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology; D008565:Membrane Proteins; D051379:Mice; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000032:analysis / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D019323:omega-N-Methylarginine / Q000494:pharmacology
D000970:Antineoplastic Agents; D003603:Cytotoxins; D004791:Enzyme Inhibitors; D008070:Lipopolysaccharides; D008565:Membrane Proteins; D012333:RNA, Messenger; D019323:omega-N-Methylarginine; D009569:Nitric Oxide; D007371:Interferon-gamma; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C496318:Nos2 protein, rat; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse