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Disturbances in Endoplasmic Reticulum (ER) homeostasis induce ER stress, which has been involved in the development and progression of various heart diseases, including arrhythmias, cardiac hypertrophy, ischemic heart diseases, dilated cardiomyopathy, and heart failure. A mild-to-moderate ER stress is considered beneficial and adaptative for heart functioning by engaging the pro-survival unfolded protein response (UPR) to restore normal ER function. By contrast, a severe or prolonged ER stress is detrimental by promoting cardiomyocyte apoptosis through hyperactivation of the UPR pathways. Previously, we have demonstrated that the NAD+-dependent deacetylase SIRT1 is cardioprotective in response to severe ER stress by regulating the PERK pathway of the UPR, suggesting that activation of SIRT1 could protect against ER-stress-induced cardiac damage. The purpose of this study was to identify natural molecules able to alleviate ER stress and inhibit cardiomyocyte cell death through SIRT1 activation. Several phenolic compounds, abundant in vegetables, fruits, cereals, wine, and tea, were reported to stimulate the deacetylase activity of SIRT1. Here, we evaluated the cardioprotective effect of ten of these phenolic compounds against severe ER stress using cardiomyoblast cells and mice. Among the molecules tested, we showed that ferulic acid, pterostilbene, and tyrosol significantly protect cardiomyocytes and mice heart from cardiac alterations induced by severe ER stress. By studying the mechanisms involved, we showed that the activation of the PERK/eIF2α/ATF4/CHOP pathway of the UPR was reduced by ferulic acid, pterostilbene, and tyrosol under ER stress conditions, leading to a reduction in cardiomyocyte apoptosis. The protection afforded by these phenolic compounds was not directly related to their antioxidant activity but rather to their ability to increase SIRT1-mediated deacetylation of eIF2α. Taken together, our results suggest that ferulic acid, pterostilbene, and tyrosol are promising molecules to activate SIRT1 to protect the heart from the adverse effects of ER stress.

Many recent studies have demonstrated the involvement of endoplasmic reticulum (ER) stress in the development of cardiac diseases and have suggested that modulation of ER stress response could be cardioprotective. Previously, we demonstrated that the deacetylase Sirtuin 1 (SIRT1) attenuates ER stress response and promotes cardiomyocyte survival. Here, we investigated whether and how autophagy plays a role in SIRT1-afforded cardioprotection against ER stress. The results revealed that protective autophagy was initiated before cell death in response to tunicamycin (TN)-induced ER stress in cardiac cells. SIRT1 inhibition decreased ER stress-induced autophagy, whereas its activation enhanced autophagy. In response to TN- or isoproterenol-induced ER stress, mice deficient for SIRT1 exhibited suppressed autophagy along with exacerbated cardiac dysfunction. At the molecular level, we found that in response to ER stress (i) the extinction of eEF2 or its kinase eEF2K not only reduced autophagy but further activated cell death, (ii) inhibition of SIRT1 inhibited the phosphorylation of eEF2, (iii) eIF2&alpha, co-immunoprecipitated with eEF2K, and (iv) knockdown of eIF2&alpha, reduced the phosphorylation of eEF2. Our results indicate that in response to ER stress, SIRT1 activation promotes cardiomyocyte survival by enhancing autophagy at least through activation of the eEF2K/eEF2 pathway.

Heart failure is associated with profound alterations of energy metabolism thought to play a major role in the progression of this syndrome. SIRT1 is a metabolic sensor of cellular energy and exerts essential functions on energy metabolism, oxidative stress response, apoptosis, or aging. Importantly, SIRT1 deacetylates the peroxisome proliferator-activated receptor gamma co-activator 1&alpha, (PGC-1&alpha, ), the master regulator of energy metabolism involved in mitochondrial biogenesis and fatty acid utilization. However, the exact role of SIRT1 in controlling cardiac energy metabolism is still incompletely understood and conflicting results have been obtained. We generated a cardio-specific inducible model of Sirt1 gene deletion in mice (Sirt1ciKO) to decipher the role of SIRT1 in control conditions and following cardiac stress induced by pressure overload. SIRT1 deficiency induced a progressive cardiac dysfunction, without overt alteration in mitochondrial content or properties. Sixteen weeks after Sirt1 deletion an increase in mitochondrial reactive oxygen species (ROS) production and a higher rate of oxidative damage were observed, suggesting disruption of the ROS production/detoxification balance. Following pressure overload, cardiac dysfunction and alteration in mitochondrial properties were exacerbated in Sirt1ciKO mice. Overall the results demonstrate that SIRT1 plays a cardioprotective role on cardiac energy metabolism and thereby on cardiac function.