Nitric oxide stimulates heme oxygenase-1 gene transcription via the Nrf2/ARE complex to promote vascular smooth muscle cell survival.
OBJECTIVE
Previous studies from our laboratory and others found that NO is a potent inducer of heme oxygenase-1 (HO-1) gene transcription in vascular smooth muscle cells (SMC), however, the mechanism responsible for the induction of HO-1 gene expression has not been elucidated. In the present study, we determined the signaling pathway responsible for the induction of HO-1 and its biological significance.


METHODS
Cultured rat aortic SMC were exposed to nitrosative stress by treating cells with various NO donors or with inflammatory cytokines.


RESULTS
Nitrosative stress stimulated an increase in HO-1 mRNA expression and promoter activity in vascular SMC. However, mutation of the antioxidant response element (ARE) in the HO-1 promoter or overexpression of a dominant-negative mutant of NF-E2-related factor-2 (Nrf2) abrogated the activation by NO. Electromobility shift assays using an ARE probe detected a complex that was significantly increased in intensity by NO. In addition, the migration of this complex was retarded by using an antibody directed against Nrf2. NO also increased Nrf2 mRNA expression, total and nuclear Nrf2 levels, and the binding of Nrf2 to the HO-1 promoter. Finally, treatment of SMC with NO stimulated apoptosis that was increased by HO-1 inhibition.


CONCLUSIONS
These results demonstrate that nitrosative stress induces HO-1 gene transcription through the activation of the Nrf2/ARE complex to counteract NO-induced apoptosis of vascular SMC. The capacity of nitrosative stress to activate Nrf2 and stimulate HO-1 gene transcription may represent a critical adaptive response to maintain cell viability at sites of vascular inflammation and atherosclerosis.
Liu
Xiao-ming
XM
Department of Medical Pharmacology and Physiology, University of Missouri, Columbia, MO 65212, USA.
Peyton
Kelly J
KJ
Ensenat
Diana
D
Wang
Hong
H
Hannink
Mark
M
Alam
Jawed
J
Durante
William
W
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D024202:Electrophoretic Mobility Shift Assay; D015870:Gene Expression; D051547:Heme Oxygenase-1 / Q000235:genetics*; D009131:Muscle, Smooth, Vascular; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000378:metabolism*; D051267:NF-E2-Related Factor 2 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D015538:Nitrosation; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D020218:Response Elements; D014158:Transcription, Genetic
D000911:Antibodies, Monoclonal; D051267:NF-E2-Related Factor 2; D020030:Nitric Oxide Donors; D012333:RNA, Messenger; D009569:Nitric Oxide; D051547:Heme Oxygenase-1