Sirt3 blocks the cardiac hypertrophic response by augmenting Foxo3a-dependent antioxidant defense mechanisms in mice
Nagalingam R. Sundaresan, … , Ayman Isbatan, Mahesh P. Gupta
Nagalingam R. Sundaresan, … , Ayman Isbatan, Mahesh P. Gupta
Published August 3, 2009
Citation Information: J Clin Invest. 2009;119(9):2758-2771. https://doi.org/10.1172/JCI39162.
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Research Article Aging

Sirt3 blocks the cardiac hypertrophic response by augmenting Foxo3a-dependent antioxidant defense mechanisms in mice

Abstract

Sirtuin 3 (SIRT3) is a member of the sirtuin family of proteins that promote longevity in many organisms. Increased expression of SIRT3 has been linked to an extended life span in humans. Here, we have shown that Sirt3 protects the mouse heart by blocking the cardiac hypertrophic response. Although Sirt3-deficient mice appeared to have normal activity, they showed signs of cardiac hypertrophy and interstitial fibrosis at 8 weeks of age. Application of hypertrophic stimuli to these mice produced a severe cardiac hypertrophic response, whereas Sirt3-expressing Tg mice were protected from similar stimuli. In primary cultures of cardiomyocytes, Sirt3 blocked cardiac hypertrophy by activating the forkhead box O3a–dependent (Foxo3a-dependent), antioxidant–encoding genes manganese superoxide dismutase (MnSOD) and catalase (Cat), thereby decreasing cellular levels of ROS. Reduced ROS levels suppressed Ras activation and downstream signaling through the MAPK/ERK and PI3K/Akt pathways. This resulted in repressed activity of transcription factors, specifically GATA4 and NFAT, and translation factors, specifically eukaryotic initiation factor 4E (elf4E) and S6 ribosomal protein (S6P), which are involved in the development of cardiac hypertrophy. These results demonstrate that SIRT3 is an endogenous negative regulator of cardiac hypertrophy, which protects hearts by suppressing cellular levels of ROS.

Authors

Nagalingam R. Sundaresan, Madhu Gupta, Gene Kim, Senthilkumar B. Rajamohan, Ayman Isbatan, Mahesh P. Gupta

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Figure 2

Sirt3 overexpression blocks cardiac hypertrophic response in vitro.

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Sirt3 overexpression blocks cardiac hypertrophic response in vitro. (A) ...
(A) Rat cardiomyocytes were overexpressed with Sirt3 WT (Ad.Sirt3) or mutant virus (Ad.Smut) and then treated with PE (20 μM) for 48 hours. Incorporation of [3H]-leucine into total cellular protein was determined and normalized to DNA content of the cells. Values are mean ± SEM (n = 5). (B and C) Cardiomyocytes expressing Ad.Sirt3 or Ad.Smut viruses were transfected with a CARP promoter/luciferase reporter vector (CARP-Luc) or β-MHC promoter/luciferase reporter vector (β-MHC–Luc). Cells were treated with vehicle (Veh) or PE (20 μM), and the luciferase activity was measured 48 hours after treatment. A β-gal/reporter plasmid was used as a reference control. Values are mean ± SEM (n = 3). (D) Cardiomyocytes were infected with the indicated adenoviruses and then stimulated with PE (20 μM), Ang II (2 μM), or vehicle for 48 hours. ANF release (green) was determined by staining cells with anti-ANF antibody. DAPI stain was used to mark the position of nuclei. (E) Reorganization of sarcomeres after PE treatment of cells. Cells were treated as in D and immunostained with α-actinin antibody for visualization of sarcomeres. Original magnification, ×630 (D); ×1,000 (E).