SIRT3-mediated inhibition of FOS through histone H3 deacetylation prevents cardiac fibrosis and inflammation.

Sirtuin 3 (SIRT3) is a deacetylase that modulates proteins that control metabolism and protects against oxidative stress. Modulation of SIRT3 activity has been proposed as a promising therapeutic target for ameliorating metabolic diseases and associated cardiac disturbances. In this study, we investigated the role of SIRT3 in inflammation and fibrosis in the heart using male mice with constitutive and systemic deletion of SIRT3 and human cardiac AC16 cells. SIRT3 knockout mice showed cardiac fibrosis and inflammation that was characterized by augmented transcriptional activity of AP-1. Consistent with this, SIRT3 overexpression in human and neonatal rat cardiomyocytes partially prevented the inflammatory and profibrotic response induced by TNF-α. Notably, these effects were associated with a decrease in the mRNA and protein levels of FOS and the DNA-binding activity of AP-1. Finally, we demonstrated that SIRT3 inhibits FOS transcription through specific histone H3 lysine K27 deacetylation at its promoter. These findings highlight an important function of SIRT3 in mediating the often intricate profibrotic and proinflammatory responses of cardiac cells through the modulation of the FOS/AP-1 pathway. Since fibrosis and inflammation are crucial in the progression of cardiac hypertrophy, heart failure, and diabetic cardiomyopathy, our results point to SIRT3 as a potential target for treating these diseases.

Resveratrol induces nuclear factor-κB activity in human cardiac cells.

BACKGROUND: Resveratrol is a grape polyphenol that prevents cardiac hypertrophy and protects the heart from ischemic injury, metabolic dysregulation, and inflammatory processes in several murine models. METHODS AND RESULTS: The aim of this study was to investigate the effects of resveratrol on the inflammatory processes in human cardiac AC16 cells in order to gain a better understanding of its cardioprotective mechanisms in the human heart. Resveratrol induced the DNA-binding activity of the pro-inflammatory transcription factor NF-κB in AC16 cells, and exacerbated the increase caused by tumor necrosis factor-α (TNF-α). In accordance with this, resveratrol increased the expression of the pro-inflammatory genes ICAM-1 (intercellular adhesion molecule-1) and TNF-α. In contrast, resveratrol decreased the expression of pro-inflammatory genes IL-6 (interleukin-6) and MCP-1 (monocyte chemoattractant protein-1). Likewise, resveratrol also induced inflammation in rat neonatal cardiomyocytes, and in the heart of mice fed a standard chow diet supplemented with resveratrol (1g/kg diet) for four months. Western-blot analyses revealed that NF-κB p65 subunit levels were upregulated in an IκB-dependent manner in the nuclei of resveratrol-treated human cardiac cells. Finally, resveratrol activated the signal transducer and activator of transcription 3 (STAT3) signaling and induced the expression of its anti-apoptotic downstream effector Bcl-xL, both involved in the cardioprotective survival activating factor enhancement (SAFE) pathway. CONCLUSIONS: Resveratrol enhanced NF-κB activity in human and murine cardiac cells, in a process that coincided with the activation of STAT3 and anti-apoptotic downstream effectors. Therefore, activation of the SAFE pathway by resveratrol might be involved in the cardioprotective effects of this compound.