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Heme oxygenase‐1 is Transcriptionally Regulated by Akt in Human Vascular Smooth Muscle Cells (VSMC) in response to oxidative stress and inflammation
Author(s) -
Brunt Keith Russell,
Kiani Christopher Golam,
Melo Luis Gabriel
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a700-b
Subject(s) - heme oxygenase , protein kinase b , oxidative stress , pi3k/akt/mtor pathway , chemistry , gene knockdown , heme , biliverdin , vascular smooth muscle , inflammation , cytoprotection , microbiology and biotechnology , biology , signal transduction , endocrinology , biochemistry , immunology , apoptosis , enzyme , smooth muscle
Background Inflammation and oxidative stress play a key role in vascular injury in atherogenesis. Heme‐oxygenase 1 (HO‐1) is the rate limiting enzyme in the conversion of heme to carbon monoxide, biliverdin and iron and exerts anti‐inflammatory and anti‐oxidant effects in VSMC. However, the mechanisms underlying HO‐1 activation in response to these atherogenic stimuli are not known. Recent evidence from our work suggests that HO‐1‐mediated cytoprotection is dependent on Akt activity. Objective We investigated the role of Akt in transcriptional regulation of HO‐1 in response to oxidative stress. Methods Human aortic smooth muscle cells (HASMC) were transduced with a retroviral vector (MSCV) expressing Akt, rendered quiescent and exposed to 300 μM of H2O2. HO‐1 mRNA was quantified 6 hr after exposure to H2O2 using RT‐PCR. HO‐1 promoter activity was assessed in COS‐7 cells using a pGL3‐luc reporter construct containing the full length human HO‐1 promoter. Results H2O2 increase HO‐1 mRNA and protein levels in a time‐dependent fashion. Akt overexpression potentiated H2O2 induced HO‐1 mRNA synthesis and increased protein expression. The effect of H2O2 on HO‐1 transcription was abrogated by knockdown of Akt using siRNA. In parallel with induction of HO‐1 message, H2O2 increased HO‐1 promoter activity several fold in COS‐7 cells. Akt siRNA significantly reduced H2O2 induced HO‐1 promoter activity. Conclusion Akt upregulates oxidative stress‐induced HO‐1 activity at the transcriptional level. This mechanism of HO‐1 induction may underlie the dependence of HO‐1 on Akt for protection against oxidative stress‐induced injury in VSMC. Supported by grants from CIHR and HSFC to L.G. Melo