Background: The cellular and molecular mechanisms of cardioprotective effects of Vitamin D are poorly understood. Given the essential role of sirtuin-3 (SIRT3) as an endogenous negative regulator of cardiac hypertrophy, this study was designed to investigate the effect of 1, 25-dihydroxyvitamin D3 (calcitriol) on hypertrophy markers and SIRT3 mRNA and protein levels following angiotensin II induced - hypertrophy in cardiomyoblast H9c2 cells. Methods: Rat cardiomyoblast H9c2 cells were treated for 48 hr with angiotensin II alone (Ang group) or in combination with 1, 10 and 100 nM of calcitriol (C + Ang groups). Intact cells served as control (Ctl). The cell area was measured using methylene blue staining. Atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and SIRT3 transcription levels were measured by real time RT-PCR. SIRT3 protein expression was evaluated using western blot technique. Results: The results showed that in Ang group cell size was increase by 128.4 ± 15% (P < 0.001 vs. Ctl) whereas in C100 + Ang group it was increased by 21.3 ± 6% (P < 0.001 vs. Ang group). Calcitriol pretreatment decreased ANP mRNA level significantly (P < 0.05) in comparison with Ang group (Ang: 75.5 ± 15%, C100 + Ang: 19.2 ± 9%). There were no significant differences between Ang group and cells pretreated with 1 and 10 nM of calcitriol. SIRT3 at mRNA and protein levels did not change significantly among the experimental groups. Conclusions: In conclusion, pretreatment with calcitriol (100 nM) prevents Ang II-induced hypertrophy in cardiomyoblast H9c2 cells. This probably occurs through other pathways except SIRT3 upregulation.
Keywords: 1,25-dihydroxyvitamin D3; ANP; Angiotensin II; BNP; Calcitriol; Hypertrophy; Sirtuin 3 (SIRT3).