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Inhibition of DNA Methylation Regulates Guanylyl Cyclase/Natriuretic Peptide Receptor‐A Gene Expression

Cardiac hormone atrial natriuretic peptide binds to guanylyl cyclase/natriuretic peptide receptor‐A (GC‐A/NPRA) and produces second messenger cGMP, which plays a pivotal role in maintaining blood pressure and cardiovascular homeostasis. The molecular and epigenetic mechanisms that contribute to the activation of Npr1 (coding for GC‐A/NPRA) gene expression are not well understood. The present study was aimed at understanding the mechanisms involved in DNA methylation inhibitor, 5‐Azacytidine (5‐aza)‐mediated Npr1 (coding for GC‐A/NPRA) gene transcription. The studies were carried out in rat thoracic aortic vascular smooth muscle cells (RTASMC), cultured in Dulbecco's modified Eagle's medium containing 10% fetal bovine serum and treated with 5‐aza for 24 h. The MethPrimer search result showed the presence of three cytosine‐phosphate‐guanine (CpG) islands on the Npr1 full length promoter, namely island 1 (−886 to −752, 134 bp), island 2 (−310 to −58, 152 bp), and island 3 (−514 to +310, 464 bp) from the transcription start site. 5‐azacytidine significantly induced mRNA levels of Npr1 gene by 4‐fold and NPRA protein expression by 3‐fold in RTASMCs in a dose‐dependent manner. Treatment of cells with 5‐aza significantly (p<0.05) attenuated DNA methyltransferase 1 (DNMT1) protein expression in a dose‐dependent manner. However, there was no noticeable change in the DNMT3a and DNMT3b protein levels. There was a significant reduction in the DNMT activity in 5‐aza‐treated RTASMCs compared with vehicle–treated cells as quantified by EpiQuik DNMT activity assay. The present findings provide a novel regulatory mechanism for Npr1 gene transcription, an important player in the control of hypertension and cardiovascular homeostasis.