Phosphorylation and hypoxia-induced heme oxygenase-1 gene expression in cardiomyocytes.
BACKGROUND
Heme oxygenase-1 (HO-1) is a stress protein and the rate-limiting enzyme in heme degradation. We sought to examine the notion that protein kinases and phosphatases through phosphorylation and dephosphorylation modulate the HO-1 expression in cardiomyocytes under hypoxic conditions.


RESULTS
Exposure of neonatal rat cardiomyocytes to hypoxia markedly induced the HO-1 expression, as assessed by Northern blot, Western blot, and transfection assay. The hypoxia-induced HO-1 expression was blocked by the kinase inhibitors staurosporine and SB202190 in a dose-dependent manner. Hypoxia decreased the activity of phosphatase-1 (PP-1). To examine the effect of PP-1 inhibition on HO-1 expression we used the phosphatase inhibitor okadaic acid (OA) and an antisense vector. OA treatment or overexpression of the antisense PP-1 transcript markedly induced HO-1 expression. Furthermore, transfection assay using HO-1 promoter constructs revealed the involvement of the nuclear factor kB (NF-kB) and Activator protein-1 (AP-1) in the hypoxia-induced activation of the HO-1 gene. The HO-1 promoter activity was modulated by OA under normoxic conditions or staurosporine under hypoxia.


CONCLUSIONS
Our results suggest that activation of protein kinases and downregulation of PP-1 activity contribute to the hypoxia-induced HO-1 gene expression and that the proximal HO-1 promoter region containing NF-kB and AP-1 binding sites is likely to play a role in the transcriptional activation of the HO-1 gene in cardiomyocytes in response to hypoxic stress.
Wu
Guimei
G
The Molecular Cardiology and Neuromuscular Institute, 75 Raritan Avenue, Highland Park, NJ 08904, USA.
Marín-García
José
J
Rogers
Terry B
TB
Lakatta
Edward G
EG
Long
Xilin
X
D000818:Animals; D015536:Down-Regulation / Q000502:physiology; D015870:Gene Expression; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism*; D051547:Heme Oxygenase-1; D000860:Hypoxia / Q000378:metabolism*; D032383:Myocytes, Cardiac / Q000378:metabolism*; D016328:NF-kappa B / Q000502:physiology; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000502:physiology; D018808:Transcription Factor AP-1 / Q000502:physiology; D014162:Transfection
D016328:NF-kappa B; D018808:Transcription Factor AP-1; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1