Sebastiano Sciarretta

Mst1 inhibits autophagy by promoting the interaction between Beclin1 and Bcl-2

Yasuhiro Maejima1,4, Shiori Kyoi1, Peiyong Zhai1, Tong Liu2, Hong Li2, Andreas Ivessa1, Sebastiano Sciarretta1, Dominic P. Del Re1, Daniela K. Zablocki1, Chiao-Po Hsu3, Dae-Sik Lim5, Mitsuaki Isobe4, and Junichi Sadoshima1,6 1Cardiovascular Research Institute, Department of Cell Biology and Molecular Medicine, Rutgers, The State University of New Jersey, New Jersey Medical School, Newark, NJ 07103Here we show that Mst1, a proapoptotic kinase, impairs protein quality control mechanisms in the heart through inhibition of autophagy. Stress-induced activation of Mst1 in cardiomyocytes promoted accumulation of p62 and aggresome formation, accompanied by the disappearance of autophagosomes. Mst1 phosphorylated the Thr108 residue in the BH3 domain of Beclin1, which enhanced the interaction between Beclin1 and Bcl-2 and/or Bcl-xL, stabilized the Beclin1 homodimer, inhibited the phosphatidylinositide 3-kinase activity of the Atg14L-Beclin1-Vps34 complex and suppressed autophagy. Furthermore, Mst1-induced sequestration of Bcl-2 and Bcl-xL by Beclin1 allows Bax to become active, thereby stimulating apoptosis. Mst1 promoted cardiac dysfunction in mice subjected to myocardial infarction by inhibiting autophagy, associated with increased levels of Thr108-phosphorylated Beclin1. Moreover, dilated cardiomyopathy in humans was associated with increased levels of Thr108-phosphorylated Beclin1 and signs of autophagic suppression. These results suggest that Mst1 coordinately regulates autophagy and apoptosis by phosphorylating Beclin1 and consequently modulating a three-way interaction among Bcl-2 proteins, Beclin1 and Bax.

Natriuretic peptides: An update on bioactivity, potential therapeutic use, and implication in cardiovascular diseases

The natriuretic peptide system includes three known peptides: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP). They contribute to the regulation of cardiovascular homeostasis through diuretic, natriuretic, and vasodilatory properties. Among them, ANP has received particular attention because of its effects on blood pressure regulation and cardiac function. Although the potential for its therapeutic application in the treatment of hypertension and heart failure has been evaluated in several experimental and clinical investigations, no pharmacological approach directly targeted at modulation of ANP levels has ever reached the stage of being incorporated into clinical practice. Recently, ANP has also received attention as being a possible cardiovascular risk factor, particularly in the context of hypertension, stroke, obesity, and metabolic syndrome. Abnormalities in either peptide levels or peptide structure are thought to underlie its implied role in mediating cardiovascular diseases. Meanwhile, BNP has emerged as a relevant marker of left ventricular (LV) dysfunction and as a useful predictor of future outcome in patients with heart failure. This review deals with the major relevant findings related to the cardiovascular and metabolic effects of natriuretic peptides, to their potential therapeutic use, and to their role in mediating cardiovascular diseases.

Mammalian Target of Rapamycin Signaling in Cardiac Physiology and Disease

The protein kinase mammalian or mechanistic target of rapamycin (mTOR) is an atypical serine/threonine kinase that exerts its main cellular functions by interacting with specific adaptor proteins to form 2 different multiprotein complexes, mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2). mTORC1 regulates protein synthesis, cell growth and proliferation, autophagy, cell metabolism, and stress responses, whereas mTORC2 seems to regulate cell survival and polarity. The mTOR pathway plays a key regulatory function in cardiovascular physiology and pathology. However, the majority of information available about mTOR function in the cardiovascular system is related to the role of mTORC1 in the unstressed and stressed heart. mTORC1 is required for embryonic cardiovascular development and for postnatal maintenance of cardiac structure and function. In addition, mTORC1 is necessary for cardiac adaptation to pressure overload and development of compensatory hypertrophy. However, partial and selective pharmacological and genetic inhibition of mTORC1 was shown to extend life span in mammals, reduce pathological hypertrophy and heart failure caused by increased load or genetic cardiomyopathies, reduce myocardial damage after acute and chronic myocardial infarction, and reduce cardiac derangements caused by metabolic disorders. The optimal therapeutic strategy to target mTORC1 and increase cardioprotection is under intense investigation. This article reviews the information available regarding the effects exerted by mTOR signaling in cardiovascular physiology and pathological states.

Endogenous Drp1 mediates mitochondrial autophagy and protects the heart against energy stress

Rationale: Both fusion and fission contribute to mitochondrial quality control. How unopposed fusion affects survival of cardiomyocytes and left ventricular function in the heart is poorly understood. Objective: We investigated the role of dynamin-related protein 1 (Drp1), a GTPase that mediates mitochondrial fission, in mediating mitochondrial autophagy, ventricular function, and stress resistance in the heart. Methods and Results: Drp1 downregulation induced mitochondrial elongation, accumulation of damaged mitochondria, and increased apoptosis in cardiomyocytes at baseline. Drp1 downregulation also suppressed autophagosome formation and autophagic flux at baseline and in response to glucose deprivation in cardiomyocytes. The lack of lysosomal translocation of mitochondrially targeted Keima indicates that Drp1 downregulation suppressed mitochondrial autophagy. Mitochondrial elongation and accumulation of damaged mitochondria were also observed in tamoxifen-inducible cardiac-specific Drp1 knockout mice. After Drp1 downregulation, cardiac-specific Drp1 knockout mice developed left ventricular dysfunction, preceded by mitochondrial dysfunction, and died within 13 weeks. Autophagic flux is significantly suppressed in cardiac-specific Drp1 knockout mice. Although left ventricular function in cardiac-specific Drp1 heterozygous knockout mice was normal at 12 weeks of age, left ventricular function decreased more severely after 48 hours of fasting, and the infarct size/area at risk after ischemia/reperfusion was significantly greater in cardiac-specific Drp1 heterozygous knockout than in control mice. Conclusions: Disruption of Drp1 induces mitochondrial elongation, inhibits mitochondrial autophagy, and causes mitochondrial dysfunction, thereby promoting cardiac dysfunction and increased susceptibility to ischemia/reperfusion.

Rheb is a Critical Regulator of Autophagy During Myocardial Ischemia Pathophysiological Implications in Obesity and Metabolic Syndrome

Background— Rheb is a GTP-binding protein that promotes cell survival and mediates the cellular response to energy deprivation (ED). The role of Rheb in the regulation of cell survival during ED has not been investigated in the heart. Methods and Results— Rheb is inactivated during cardiomyocyte (CM) glucose deprivation (GD) in vitro, and during acute myocardial ischemia in vivo. Rheb inhibition causes mTORC1 inhibition, because forced activation of Rheb, through Rheb overexpression in vitro and through inducible cardiac-specific Rheb overexpression in vivo, restored mTORC1 activity. Restoration of mTORC1 activity reduced CM survival during GD and increased infarct size after ischemia, both of which were accompanied by inhibition of autophagy, whereas Rheb knockdown increased autophagy and CM survival. Rheb inhibits autophagy mostly through Atg7 depletion. Restoration of autophagy, through Atg7 reexpression and inhibition of mTORC1, increased cellular ATP content and reduced endoplasmic reticulum stress, thereby reducing CM death induced by Rheb activation. Mice with high-fat diet–induced obesity and metabolic syndrome (HFD mice) exhibited deregulated cardiac activation of Rheb and mTORC1, particularly during ischemia. HFD mice presented inhibition of cardiac autophagy and displayed increased ischemic injury. Pharmacological and genetic inhibition of mTORC1 restored autophagy and abrogated the increase in infarct size observed in HFD mice, but they failed to protect HFD mice in the presence of genetic disruption of autophagy. Conclusions— Inactivation of Rheb protects CMs during ED through activation of autophagy. Rheb and mTORC1 may represent therapeutic targets to reduce myocardial damage during ischemia, particularly in obese patients.

Differential Roles of GSK-3β During Myocardial Ischemia and Ischemia/Reperfusion

Rationale: Inhibition of glycogen synthase kinase-3 (GSK-3) protects the heart during ischemia/reperfusion (I/R), yet the underlying mechanisms of cardioprotection afforded by beta isoform-specific inhibition GSK-3 remain to be elucidated. Objective: We studied the molecular mechanism mediating the effect of GSK-3&bgr; activation/inhibition upon myocardial injury during prolonged ischemia and I/R. Methods and Results: Beta isoform–specific inhibition of GSK-3 by dominant negative GSK-3&bgr; in transgenic mice (Tg-DnGSK-3&bgr;) or in heterozygous GSK-3&bgr; knock-out mice (GSK-3&bgr;+/−) significantly increased, whereas activation of GSK-3&bgr; in constitutively active GSK-3&bgr; knock-in mice (&bgr;KI) significantly decreased, myocardial ischemic injury after prolonged ischemia. In contrast, inhibition of GSK-3&bgr; in Tg-DnGSK-3&bgr; or GSK-3&bgr;+/− significantly reduced, while activation of GSK-3&bgr; in &bgr;KI significantly enhanced, myocardial I/R injury. Inhibition of GSK-3&bgr; stimulated mTOR signaling and inhibited autophagy through a rapamycin-sensitive (mTOR dependent) mechanism. Rapamycin enhanced autophagy and, at the same time, abolished the effects of GSK-3&bgr; inhibition on both prolonged ischemic injury and I/R injury. Importantly, the influence of rapamycin over the effects of GSK-3&bgr; inhibition on myocardial injury was reversed by inhibition of autophagy. Conclusions: Our results suggest that beta isoform–specific inhibition of GSK-3 exacerbates ischemic injury but protects against I/R injury by modulating mTOR and autophagy.

Antihypertensive Treatment and Development of Heart Failure in Hypertension: A Bayesian Network Meta-analysis of Studies in Patients With Hypertension and High Cardiovascular Risk

BACKGROUND It is still debated whether there are differences among the various antihypertensive strategies in heart failure prevention. We performed a network meta-analysis of recent trials in hypertension aimed at investigating this issue. METHODS Randomized, controlled trials published from 1997 through 2009 in peer-reviewed journals indexed in the PubMed and EMBASE databases were selected. Selected trials included patients with hypertension or a high-risk population with a predominance of patients with hypertension. RESULTS A total of 223,313 patients were enrolled in the selected studies. Network meta-analysis showed that diuretics (odds ratio [OR], 0.59; 95% credibility interval [CrI], 0.47-0.73), angiotensin-converting enzyme (ACE) inhibitors (OR, 0.71; 95% CrI, 0.59-0.85) and angiotensin II receptor blockers (ARBs) (OR, 0.76; 95% CrI, 0.62-0.90) represented the most efficient classes of drugs to reduce the heart failure onset compared with placebo. On the one hand, a diuretic-based therapy represented the best treatment because it was significantly more efficient than that based on ACE inhibitors (OR, 0.83; 95% CrI, 0.69-0.99) and ARBs (OR, 0.78; 95% CrI, 0.63-0.97). On the other hand, diuretics (OR, 0.71; 95% CrI, 0.60-0.86), ARBs (OR, 0.91; 95% CrI, 0.78-1.07), and ACE inhibitors (OR, 0.86; 95% CrI, 0.75-1.00) were superior to calcium channel blockers, which were among the least effective first-line agents in heart failure prevention, together with β-blockers and α-blockers. CONCLUSIONS Diuretics represented the most effective class of drugs in preventing heart failure, followed by renin-angiotensin system inhibitors. Thus, our findings support the use of these agents as first-line antihypertensive strategy to prevent heart failure in patients with hypertension at risk to develop heart failure. Calcium channel blockers and β-blockers were found to be less effective in heart failure prevention.

Role of the renin-angiotensin-aldosterone system and inflammatory processes in the development and progression of diastolic dysfunction

Left ventricular diastolic dysfunction represents a frequent clinical condition and is associated with increased cardiovascular morbidity and mortality. Diastolic dysfunction is the most common cause of HF-PSF (heart failure with preserved ejection fraction). Therefore it becomes important to understand the pathophysiological mechanisms underlying diastolic dysfunction, as well as the effective therapeutic strategies able to antagonize its development and progression. Among the complex pathophysiological factors that may contribute to the development of diastolic dysfunction, the RAAS (renin-angiotensin-aldosterone system) has been shown to play a significant role. Paracrine and autocrine signals of the RAAS promote structural and functional changes in the heart largely linked to increased myocardial fibrosis. Enhanced and dysregulated activity of the RAAS also contributes to the development of volume overload and vasoconstriction with subsequent increases in left ventricular diastolic filling pressures and a higher susceptibility of developing CHF (congestive heart failure). More recently, it has also been suggested that the RAAS may play a role in triggering myocardial and vascular inflammation through the activation of different cell types and the secretion of cytokines and chemokines. RAAS-induced myocardial inflammation leads to perivascular myocardial fibrosis and to the development or progression of diastolic dysfunction. For these reasons pharmacological blockade of the RAAS has been proposed as a rational approach for the treatment of diastolic dysfunction. In fact, ACEIs (angiotensin-converting enzyme inhibitors), ARBs (angiotensin II receptor blockers) and AAs (aldosterone antagonists) have been demonstrated to delay the development and progression from pre-clinical diastolic dysfunction towards CHF, as well as to reduce the morbidity and mortality associated with this condition.

Is Autophagy in Response to Ischemia and Reperfusion Protective or Detrimental for the Heart

Autophagy is a catabolic process that degrades long-lived proteins and damaged organelles by sequestering them into double membrane structures termed “autophagosomes” and fusing them with lysosomes. Autophagy is active in the heart at baseline and further stimulated under stress conditions including starvation, ischemia/reperfusion, and heart failure. It plays an adaptive role in the heart at baseline, thereby maintaining cardiac structure and function and inhibiting age-related cardiac abnormalities. Autophagy is activated by ischemia and nutrient starvation in the heart through Sirt1-FoxO- and adenosine monophosphate (AMP)-activated protein kinase (AMPK)-dependent mechanisms, respectively. Activation of autophagy during ischemia is essential for cell survival and maintenance of cardiac function. Autophagy is strongly activated in the heart during reperfusion after ischemia. Activation of autophagy during reperfusion could be either protective or detrimental, depending on the experimental model. However, strong induction of autophagy accompanied by robust upregulation of Beclin1 could cause autophagic cell death, thereby proving to be detrimental. This review provides an overview regarding both protective and detrimental functions of autophagy in the heart and discusses possible applications of current knowledge to the treatment of heart disease.

Development of heart failure in recent hypertension trials.

Background Heart failure represents a major cause of disease burden worldwide and is expected to further rise in the coming decades. Hypertension is the clinical condition most frequently associated to heart failure. Objective To systematically review the incidence of heart failure compared to coronary heart diseases and stroke in recent hypertension trials. Methods We identified 23 trials concluded within the last decade including 193 424 patients with hypertension or at ‘high’ cardiovascular risk with a predominant presence of hypertensive patients, and reported incidence of major cardiovascular events, including heart failure, coronary heart disease and stroke. Results A total of 24 837 major cardiovascular events were recorded in trials performed between 1997 and 2007, of which 7171 (28.9%) were cases of heart failure, 10 223 (41.1%) of coronary heart disease and 7443 (30.0%) of stroke. The rate of heart failure was comparable with that of stroke, accounting for 8.5 and 9.1 events per 1000 patients (P = NS), respectively. Heart failure development was more prevalent in older subjects (>65 years) [odds ratio: 3.08, confidence interval 95% (2.88–3.31); P < 0.0001], in black versus nonblack individuals [odds ratio 1.90, (1.76–2.06); P < 0.0001], in diabetic versus nondiabetic patients [odds ratio 4.91, 95% confidence interval (4.40–5.43); P < 0.0001] and in patients with ‘very high’ risk versus those with a ‘high’ risk profile [odds ratio 1.29, 95% confidence interval (1.23–1.36); P < 0.0001]. Conclusion Our analysis shows that heart failure development remains a major problem in hypertension. In recent trials on hypertension, the development of heart failure was found comparable with that of stroke: it is more prevalent in older, black, diabetic and ‘very high’ risk individuals. These findings highlight the relevance of heart failure development in hypertension and support the need for optimizing antihypertensive strategies aimed at preventing the progression to overt heart failure, thus reducing the growing burden of disease associated with hypertension.