HYPOXIA INDUCES B-TYPE NATRIURETIC PEPTIDE RELEASE IN CELL LINES DERIVED FROM HUMAN CARDIOMYOCYTES.

Am J Physiol Heart Circ Physiol. 2009 Jun 19; Casals G, Ros J, Sionis A, Davidson MM, Morales-Ruiz M, Jimenez WB-type natriuretic peptide (BNP) is a peptide hormone of myocardial origin with significant cardioprotective properties. Patients with myocardial ischemia present with high levels of BNP in plasma and elevated expression in the myocardium. However, molecular mechanisms of BNP induction in the ischemic myocardium are not well understood. The aim of the investigation was to assess whether myocardial hypoxia induces the production of BNP in human ventricular myocytes. To test the hypothesis that reduced oxygen tension can directly stimulate BNP gene expression and release in the absence of hemodynamic or neurohormonal stimuli, we used an in vitro model system of cultured human ventricular myocytes (AC16 cells). Cells were cultured under normoxic (21% O2) or hypoxic (5% O2) conditions for up to 48 hours. Then, accumulation of BNP, Atrial Natriuretic Peptide (ANP) and Vascular Endothelial Growth Factor (VEGF) was measured. Hypoxia stimulated protein release of BNP and VEGF but not of ANP. In concordance, increased mRNA levels of BNP and VEGF but not of ANP were found on culturing AC16 cells under hypoxic conditions. The analysis of the transcriptional activity of the hypoxia inducible factor 1 (HIF-1) in nuclear extracts showed that HIF-1 activity was induced under hypoxic conditions. Finally, treatment of AC16 cells with the HIF-1 inhibitor rotenone in hypoxia inhibited BNP and VEGF release. In conclusion, these data indicate that hypoxia induces the synthesis and secretion of BNP in human ventricular myocytes, likely through HIF-1 enhanced transcriptional activity. Key words: natriuretic peptides, HIF-1, myocardial ischemia, heart failure.