Cardiovascular Research Advance Access [Accepted Manuscript] published online on April 7, 2009
Cardiovascular Research, doi:10.1093/cvr/cvp107
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Nrf2-dependent upregulation of antioxidative enzymes – a novel pathway for proteasome inhibitor-mediated cardioprotection
Medizinische Klinik für Kardiologie und Angiologie, Campus Mitte, Charité – Universitätsmedizin Berlin, Germany
Correspondence to: Karl Stangl, MD, Medizinische Klinik für Kardiologie und Angiologie, Charité – Universitätsmedizin Berlin, Charitéplatz 1, D – 10117 Berlin, Germany, Phone: [+49] 30 450513075, Fax: [+49] 30 450513932, Email: Karl.stangl{at}charite.de
Aims: We have previously shown that non-toxic inhibition of the ubiquitin-proteasome system upregulates antioxidative defence mechanisms and protects endothelial cells from oxidative stress. Here, we addressed the question whether induction of antioxidative enzymes contributes to cardioprotection by non-toxic proteasome inhibition.
Results and Methods: Treatment with 0.5 µmol/L MG132 for 48 hours proved to be non-toxic and protected neonatal rat cardiac myocytes against H2O2-mediated oxidative stress in lactate dehydrogenase assays. This correlated with reduced levels of intracellular reactive oxygen species as determined by loading myocytes with dichlorofluorescein. Immunoblots showed significant upregulation of superoxide dismutase 1 (SOD1), heme oxygenase 1, and catalase upon proteasome inhibition. Luciferase assays using a reporter driven by the SOD1 promoter revealed proteasome inhibitor-mediated induction of luciferase activity. Deletion and mutation analyses identified an antioxidant response element (ARE) in the SOD1 promoter to be not only essential but also sufficient for transcriptional upregulation by proteasome inhibition. An essential role for the antioxidative transcription factor NF-E2-related factor 2 (Nrf2) – which was stabilised by proteasome inhibition – in ARE-mediated transcriptional activation was revealed in cardiac myocytes from Nrf2 wild-type and knockout mice: proteasome inhibition upregulated antioxidative enzymes and conferred protection against H2O2-mediated oxidative stress in Nrf2 wild-type cells. In contrast, induction of antioxidative enzymes and cytoprotection were completely abolished in cardiac myocytes from Nrf2 knockout mice.
Conclusion: Non-toxic proteasome inhibition upregulates antioxidative enzymes via an Nrf2-dependent transcriptional activation of antioxidant response elements and confers cardioprotection.
Time for primary review: 10 Days
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  H. Dreger, K. Westphal, N. Wilck, G. Baumann, V. Stangl, K. Stangl, and S. Meiners Protection of vascular cells from oxidative stress by proteasome inhibition depends on Nrf2 Cardiovasc Res, September 4, 2009; (2009) cvp279v2. [Abstract] [Full Text] [PDF]
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