1.25 Dihydroxyvitamin D3 Attenuates Hypertrophy Markers in Cardiomyoblast H9c2 Cells: Evaluation of Sirtuin3 mRNA and Protein Level.

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.

Sirtinol abrogates late phase of cardiac ischemia preconditioning in rats.

The aim of this study was to investigate the effect of sirtinol, as an inhibitor of sirtuin NAD-dependent histone deacetylases, on myocardial ischemia reperfusion injury following early and late ischemia preconditioning (IPC). Rats underwent sustained ischemia and reperfusion (IR) alone or proceeded by early or late IPC. Sirtinol (S) was administered before IPC. Arrhythmias were evaluated based on the Lambeth model. Infarct size (IS) was measured using triphenyltetrazolium chloride staining. The transcription level of antioxidant-coding genes was assessed by real-time PCR. In early and late IPC groups, IS and the number of arrhythmia were significantly decreased (P < 0.05 and P < 0.01 vs IR, respectively). In S + early IPC, incidences of arrhythmia and IS were not different compared with the early IPC group. However, in S + late IPC the IS was different from the late IPC group (P < 0.05). In late IPC but not early IPC, transcription levels of catalase (P < 0.01) and Mn-SOD (P < 0.05) increased, although this upregulation was not significant in the S + late IPC group. Our results are consistent with the notion that different mechanisms are responsible for early and late IPC. In addition, sirtuin NAD-dependent histone deacetylases may be implicated in late IPC-induced cardioprotection.