Mitophagy modulation for the treatment of cardiovascular diseases.

BACKGROUND: Defects of mitophagy, the selective form of autophagy for mitochondria, are commonly observed in several cardiovascular diseases and represent the main cause of mitochondrial dysfunction. For this reason, mitophagy has emerged as a novel and potential therapeutic target. METHODS: In this review, we discuss current evidence about the biological significance of mitophagy in relevant preclinical models of cardiac and vascular diseases, such as heart failure, ischemia/reperfusion injury, metabolic cardiomyopathy and atherosclerosis. RESULTS: Multiple studies have shown that cardiac and vascular mitophagy is an adaptive mechanism in response to stress, contributing to cardiovascular homeostasis. Mitophagy defects lead to cell death, ultimately impairing cardiac and vascular function, whereas restoration of mitophagy by specific compounds delays disease progression. CONCLUSIONS: Despite previous efforts, the molecular mechanisms underlying mitophagy activation in response to stress are not fully characterized. A comprehensive understanding of different forms of mitophagy active in the cardiovascular system is extremely important for the development of new drugs targeting this process. Human studies evaluating mitophagy abnormalities in patients at high cardiovascular risk also represent a future challenge.

miR-93 and synaptotagmin-7: two novel players in the regulation of autophagy during cardiac hypertrophy.

The molecular mechanisms involved in the transition of cardiac hypertrophy to heart failure (HF) are not fully characterized. Autophagy is a catabolic, self-renewal intracellular mechanism, which protects the heart during HF. In the heart of a mouse model of angiotensin-II-induced hypertrophy, Sun and colleagues demonstrated that reduced levels of miR-93 lead to synaptotagmin-7 (Syt-7) upregulation and consequent inhibition of autophagy. miR-93 overexpression or syt-7 inhibition rescues autophagy and maladaptive hypertrophy. This research identifies new players in the pathophysiology of cardiac hypertrophy, opening innovative therapeutic perspectives. miR-93 may also be considered in the future as a novel circulating biomarker for patients at high risk to develop HF.

MST1 mediates doxorubicin-induced cardiomyopathy by SIRT3 downregulation.

Heart failure is a major side effect of doxorubicin (DOX) treatment in patients with cancer. However, the mechanisms underlying the development of DOX-induced heart failure need to be addressed. This study aims to test whether the serine/threonine kinase MST1, a major Hippo pathway component, contributes to the development of DOX-induced myocardial injury. C57BL/6J WT mice and mice with cardiomyocyte-specific dominant-negative MST1 (kinase-dead) overexpression received three weekly injections of DOX, reaching a final cumulative dose of 18 mg/kg. Echocardiographic, histological and biochemical analyses were performed six weeks after the first DOX administration. The effects of MST1 inhibition on DOX-induced cardiomyocyte injury were also tested in vitro. MST1 signaling was significantly activated in cardiomyocytes in response to DOX treatment in vitro and in vivo. Wild-type (WT) mice treated with DOX developed cardiac dysfunction and mitochondrial abnormalities. However, these detrimental effects were abolished in mice with cardiomyocyte-specific overexpression of dominant-negative MST1 (DN-MST1) or treated with XMU-MP-1, a specific MST1 inhibitor, indicating that MST1 inhibition attenuates DOX-induced cardiac dysfunction. DOX treatment led to a significant downregulation of cardiac levels of SIRT3, a deacetylase involved in mitochondrial protection, in WT mice, which was rescued by MST1 inhibition. Pharmacological inhibition of SIRT3 blunted the protective effects of MST1 inhibition, indicating that SIRT3 downregulation mediates the cytotoxic effects of MST1 activation in response to DOX treatment. Finally, we found a significant upregulation of MST1 and downregulation of SIRT3 levels in human myocardial tissue of cancer patients treated with DOX. In summary, MST1 contributes to DOX-induced cardiomyopathy through SIRT3 downregulation.

Effects of two-month treatment with a mixture of natural activators of autophagy on oxidative stress and arterial stiffness in patients with essential hypertension: A pilot study.

BACKGROUND AND AIMS: Trehalose, spermidine, nicotinamide, and polyphenols are natural substances that exert pro-autophagic and antioxidant properties. Their role in blood pressure (BP) regulation and preservation of vascular function in essential hypertension is unknown. The aim of this study was to evaluate the effect of a mixture of these agents on BP level, markers of oxidative stress, autophagy, endothelial function, and vascular stiffness in outpatients with grade 1 uncomplicated essential hypertension. METHODS AND RESULTS: A single-centre, open-label, case-control, pilot study was conducted in adult outpatients (aged ≥18 years) receiving or not the mixture for two months along with the standard therapies. Both at baseline and at the end of the treatment the following clinical parameters were evaluated: brachial seated office BP level, central aortic pressure, pulse wave velocity, augmentation index (AI@75). Both at baseline and at the end of the treatment, a blood sample was drawn for the measurement of: H2O2, HBA%, levels of sNOX2-dp, Atg 5, P62, endothelin 1, and NO bioavailability. The mixture of nutraceuticals did not influence BP levels. Patients receiving the mixture showed a significant decrease of oxidative stress, stimulation of autophagy, increased NO bioavailability and no increase of the AI@75, in contrast to what observed in hypertensive patients not receiving the mixture. CONCLUSIONS: The supplementation of the trehalose, spermidine, nicotinamide, and polyphenols mixture counteracted hypertension-related arterial stiffness through mechanisms likely dependent on oxidative stress downregulation and autophagy stimulation. These natural activators of autophagy may represent favourable adjuvants for prevention of the hypertensive cardiovascular damage.

An Overview of the Molecular Mechanisms Associated with Myocardial Ischemic Injury: State of the Art and Translational Perspectives.

Cardiovascular disease is the leading cause of death in western countries. Among cardiovascular diseases, myocardial infarction represents a life-threatening condition predisposing to the development of heart failure. In recent decades, much effort has been invested in studying the molecular mechanisms underlying the development and progression of ischemia/reperfusion (I/R) injury and post-ischemic cardiac remodeling. These mechanisms include metabolic alterations, ROS overproduction, inflammation, autophagy deregulation and mitochondrial dysfunction. This review article discusses the most recent evidence regarding the molecular basis of myocardial ischemic injury and the new potential therapeutic interventions for boosting cardioprotection and attenuating cardiac remodeling.

Trehalose, a natural disaccharide, reduces stroke occurrence in the stroke-prone spontaneously hypertensive rat.

Cerebrovascular disease, a frequent complication of hypertension, is a major public health issue for which novel therapeutic and preventive approaches are needed. Autophagy activation is emerging as a potential therapeutic and preventive strategy toward stroke. Among usual activators of autophagy, the natural disaccharide trehalose (TRE) has been reported to be beneficial in preclinical models of neurodegenerative diseases, atherosclerosis and myocardial infarction. In this study, we tested for the first time the effects of TRE in the stroke-prone spontaneously hypertensive rat (SHRSP) fed with a high-salt stroke permissive diet (JD). We found that TRE reduced stroke occurrence and renal damage in high salt-fed SHRSP. TRE was also able to decrease systolic blood pressure. Through ex-vivo studies, we assessed the beneficial effect of TRE on the vascular function of high salt-fed SHRSP. At the molecular level, TRE restored brain autophagy and reduced mitochondrial mass, along with the improvement of mitochondrial function. The beneficial effects of TRE were associated with increased nuclear translocation of TFEB, a transcriptional activator of autophagy. Our results suggest that TRE may be considered as a natural compound efficacious for the prevention of hypertension-related target organ damage, with particular regard to stroke and renal damage.

Screening young athletes for diseases at risk of sudden cardiac death: role of stress testing for ventricular arrhythmias.

AIMS: The athletic preparticipation evaluation (PPE) protocol proposed by the European Society of Cardiology includes history, physical examination and resting electrocardiogram (ECG). The aim of this study was to assess the results of adding constant-load ECG stress testing (EST) to the protocol for the evaluation of ventricular arrhythmias (VA) inducibility. METHODS: We evaluated a consecutive cohort of young athletes with history, physical examination, resting ECG and EST. Athletes with VA induced by EST underwent 24-hour 12-lead Holter monitoring and echocardiography. Cardiac magnetic resonance (CMR) was reserved for those with frequent, repetitive or exercise-worsened VA, and for athletes with echocardiographic abnormalities. RESULTS: Of 10,985 athletes (median age 15 years, 66% males), 451 (4.1%) had an abnormal history, physical examination or resting ECG and 31 (0.28%) were diagnosed with a cardiac disease and were at risk of sudden cardiac death. Among the remaining 10,534 athletes, VA at EST occurred in 524 (5.0%) and a previously missed at-risk condition was identified in 23 (0.22%); the most common (N = 10) was an echocardiographically silent non-ischaemic left-ventricular fibrosis evidenced by CMR. The addition of EST increased the diagnostic yield of PPE by 75% (from 0.28% to 0.49%) and decreased the positive predictive value by 20% (from 6.9% to 5.5%). During a 32 ± 21 months follow-up, no cardiac arrests occurred among either eligible athletes or non-eligible athletes with cardiovascular disease. CONCLUSIONS: The addition of exercise testing for the evaluation of VA inducibility to history, physical examination and ECG resulted in an increase of the diagnostic yield of PPE at the expense of an increase in false-positive findings.