REDD1 attenuates cardiac hypertrophy via enhancing autophagy

Cardiac hypertrophy is a major risk factor of cardiovascular morbidity and mortality. Autophagy is established to be involved in regulating cardiac hypertrophy. REDD1, a stress-responsive protein, is proved to contribute in autophagy induction. However, the role of REDD1 in cardiac hypertrophy remains unknown. Our study demonstrated that REDD1 knockdown by RNAi exacerbated phenylephrine (PE)-induced cardiac hypertrophy, manifested by increased hypertrophic markers such as ANP and cell surface area. In addition, we discovered that ERK1/2 signaling pathway was involved in the effect of REDD1 on hypertrophy. Moreover, our study showed that REDD1 knockdown impaired autophagy in hypertrophied cardiomyocytes. mTOR, a signaling molecule governing autophagy induction, was activated by the knockdown of REDD1 under PE stress. Importantly, the pro-hypertrophic effect of REDD1 knockdown was significantly reversed by the autophagy enhancer rapamycin. Taken together, we firstly prove that REDD1 is essential for inhibiting cardiac hypertrophy by enhancing autophagy.     

Sestrin 1 ameliorates cardiac hypertrophy via autophagy activation

Cardiac hypertrophy is one of the major risk factors of cardiovascular morbidity and mortality. Autophagy is acknowledged to be an important mechanism regulating cardiac hypertrophy. Sestrin 1, a downstream target gene of p53, has been proven to regulate autophagy. However, the role of Sestrin 1 in cardiac hypertrophy remains unknown. Our study showed that Sestrin 1 mRNA and protein expression declined in pressure overload cardiac hypertrophy and phenylephrine (PE)‐induced cardiac hypertrophy. Knockdown of Sestrin 1 by RNAi deteriorated PE‐induced cardiac hypertrophy, whereas the overexpression of Sestrin 1 by adenovirus transfection blunted hypertrophy. We discovered that knockdown of Sestrin 1 resulted in impaired autophagy while overexpression of Sestrin 1 resulted in increased autophagy without affecting lysosomal function. In addition, the antihypertrophic effect of Sestrin 1 overexpression was eliminated by autophagy blockade. Importantly, Sestrin 1 targets at the AMPK/mTORC1/autophagy pathway to inhibit cardiac hypertrophy by interaction with AMPK which is responsible for autophagy regulation. Taken together, our data indicate that Sestrin 1 regulates AMPK/mTORC1/autophagy axis to attenuate cardiac hypertrophy.     

Baicalein protects against cardiac hypertrophy through blocking MEK‐ERK1/2 signaling

Baicalein, a flavonoid present in the root of Scutellaria baicalensis, is well known for its antibacterial, antiviral, anti‐inflammatory, antithrombotic, and antioxidant effects. Here we show that baicalein also attenuates cardiac hypertrophy. Aortic banding (AB) was performed to induce cardiac hypertrophy secondary to pressure overload in mice. Mouse chow containing 0.05% baicalein (dose: 100 mg/kg/day baicalein) was begun 1 week prior to surgery and continued for 8 weeks after surgery. Our data demonstrated that baicalein prevented cardiac hypertrophy and fibrosis induced by AB, as assessed by echocardiographic and hemodynamic parameters and by pathological and molecular analysis. The inhibitory action of baicalein on cardiac hypertrophy was mediated by effects on mitogen‐activated protein kinase kinase (MEK)‐extracellular signal‐regulated kinases (ERK1/2) signaling and GATA‐4 activation. In vitro studies performed in rat cardiac H9c2 cells confirmed that baicalein attenuated cardiomyocyte hypertrophy induced by angiotensin II, which was associated with inhibiting MEK‐ERK1/2 signaling. In conclusion, our results suggest that baicalein has protective potential for targeting cardiac hypertrophy and fibrosis through suppression of MEK‐ERK1/2 signaling. Baicalein warrants further research as a potential antihypertrophic agent that might be clinically useful to treat cardiac hypertrophy and heart failure. J. Cell. Biochem. 114: 1058–1065, 2013. © 2012 Wiley Periodicals, Inc.     

Piceatannol attenuates cardiac hypertrophy in an animal model through regulation of the expression and binding of the transcription factor GATA binding factor 6

Piceatannol is found in grapes, passion fruit, and Japanese knotweed. Piceatannol pretreatment suppresses cardiac hypertrophy induced by isoproterenol as assessed by heart weight/body weight ratio, cross-sectional area, and expression of hypertrophic markers. The anti-hypertrophic effect of piceatannol in rat neonatal cardiomyocytes is the same as that in vivo. Piceatannol inhibits lentiviral-GATA6-induced cardiomyocyte hypertrophy. Furthermore, piceatannol reduces the interaction between GATA4 and GATA6 as well as the DNA-binding activity of endogenous GATA6 in the ANP promoter. Our results suggest that piceatannol may be a novel therapeutic agent for the prevention of cardiac hypertrophy.Structured summary of protein interactionsGATA6 physically interacts with GATA4 by anti V5 tag coimmunoprecipitation (View interaction)     

Deletion of ribosomal S6 kinases does not attenuate pathological, physiological, or insulin-like growth factor 1 receptor-phosphoinositide 3-kinase-induced cardiac hypertrophy

Ribosomal S6 kinases (S6Ks) have been depicted as critical effectors downstream of growth factor pathways, which play an important role in the regulation of protein synthesis by phosphorylating the ribosomal protein, S6. The goal of this study was to determine whether S6Ks regulate heart size, are critical for the induction of cardiac hypertrophy in response to a pathological or physiological stimulus, and whether S6Ks are critical downstream effectors of the insulin-like growth factor 1 (IGF1)-phosphoinositide 3-kinase (PI3K) pathway. For this purpose, we generated and characterized cardiac-specific S6K1 and S6K2 transgenic mice and subjected S6K1(-/-), S6K2(-/-), and S6K1(-/-) S6K2(-/-) mice to a pathological stress (aortic banding) or a physiological stress (exercise training). To determine the genetic relationship between S6Ks and the IGF1-PI3K pathway, S6K transgenic and knockout mice were crossed with cardiac-specific transgenic mice overexpressing the IGF1 receptor (IGF1R) or PI3K mutants. Here we show that overexpression of S6K1 induced a modest degree of hypertrophy, whereas overexpression of S6K2 resulted in no obvious cardiac phenotype. Unexpectedly, deletion of S6K1 and S6K2 had no impact on the development of pathological, physiological, or IGF1R-PI3K-induced cardiac hypertrophy. These studies suggest that S6Ks alone are not essential for the development of cardiac hypertrophy.