Caloric restriction ameliorates angiotensin II-induced mitochondrial remodeling and cardiac hypertrophy

Calorie restriction anti-hypertrophic effects are associated with improved mitochondrial content, blockage of Ca2+-induced mitochondrial damage, and lower reverse electron transport-mediated oxidative stress

Calorie restriction is a nutritional intervention that reproducibly protects against the maladaptive consequences of cardiovascular diseases. Pathological cardiac hypertrophy leads to cellular growth, dysfunction (with mitochondrial dysregulation), and oxidative stress. The mechanisms behind the cardiovascular protective effects of calorie restriction are still under investigation. In this study, we show that this dietetic intervention prevents cardiac protein elevation, avoids fetal gene reprogramming (atrial natriuretic peptide), and blocks the increase in heart weight per tibia length index (HW/TL) seen in isoproterenol-induced cardiac hypertrophy. Our findings suggest that calorie restriction inhibits cardiac pathological growth while also lowering mitochondrial reverse electron transport-induced hydrogen peroxide formation and improving mitochondrial content. Calorie restriction also attenuated the opening of the Ca2+-induced mitochondrial permeability transition pore. We also found that calorie restriction blocked the negative correlation of antioxidant enzymes (superoxide dimutase and glutatione peroxidase activity) and HW/TL, leading to the maintenance of protein sulphydryls and glutathione levels. Given the nature of isoproterenol-induced cardiac hypertrophy, we investigated whether calorie restriction could alter cardiac beta-adrenergic sensitivity. Using isolated rat hearts in a Langendorff system, we found that calorie restricted hearts have preserved beta-adrenergic signaling. In contrast, hypertrophic hearts (treated for seven days with isoproterenol) were insensitive to beta-adrenergic activation using isoproterenol (50 nM). Despite protecting against cardiac hypertrophy, calorie restriction did not alter the lack of responsiveness to isoproterenol in isolated hearts harvested from isoproterenol-treated rats. These results suggest (through a series of mitochondrial, oxidative stress, and cardiac hemodynamic studies) that calorie restriction possesses beneficial effects against hypertrophic cardiomyopathy.

Protective effects of calorie restriction and 17-β estradiol on cardiac hypertrophy in ovariectomized obese rats

Obesity and menopause lead to cardiovascular diseases. Calorie restriction (CR) can modulate estrogen deficiency and obesity-related cardiovascular diseases. The protective effects of CR and estradiol on cardiac hypertrophy in ovariectomized obese rats were explored in this study. The adult female Wistar rats were divided into sham and ovariectomized (OVX) groups that received a high-fat diet (60% HFD) or standard diet (SD) or 30% CR for 16 weeks, and then, 1mg/kg E2 (17-β estradiol) was injected intraperitoneally every 4 days for four weeks in OVX-rats. Hemodynamic parameters were evaluated before and after each diet. Heart tissues were collected for biochemical, histological, and molecular analysis. HFD consumption led to weight gain in sham and OVX rats. In contrast, CR and E2 led to body weight loss in these animals. Also, heart weight (HW), heart weight/body weight (HW/BW) ratio, and left ventricular weight (LVW) were enhanced in OVX rats that received SD and HFD. E2 reduced these indexes in both diet conditions but reduction effects of CR were seen only in HFD groups. HFD and SD feeding increased hemodynamic parameters, ANP (atrial natriuretic peptide) mRNA expression, and TGF-β1(transforming growth factor-beta 1) protein level in the OVX animals, while CR and E2 reduced these factors. Cardiomyocyte diameter and hydroxyproline content were increased in the OVX-HFD groups. Nevertheless, CR and E2 decreased these indicators. The results showed that CR and E2 treatment reduced obesity-induced-cardiac hypertrophy in ovariectomized groups (20% and 24% respectively). CR appears to have almost as reducing effects as estrogen therapy on cardiac hypertrophy. The findings suggest that CR can be considered a therapeutic candidate for postmenopausal cardiovascular disease.

Roles of autophagy in angiotensin II-induced cardiomyocyte apoptosis

Autophagy is a self-degradation process of cytoplasmic components and occurs in the failing heart. Angiotensin II plays a critical role in the progression of heart failure and induces autophagy. We investigated the mechanism underlying angiotensin II-enhanced autophagy and examined the role of autophagy in angiotensin II-induced cardiomyocyte injury. Neonatal rat cardiomyocytes were treated with angiotensin II (1-100 nmol/L). Angiotensin II dose-dependently increased autophagy indicators of microtubule-associated protein 1 light chain (LC) 3-II and monodansylcadaverine-labelled vesicles. It also enhanced the intracellular production of reactive oxygen species (ROS), assessed by H2DCFDA, an intracellular ROS indicator. NADPH oxidase- and mitochondria-derived ROS production was increased by angiotensin II, while angiotensin II-induced LC3-II expression was suppressed by inhibitors of these sources of ROS. Confocal microscopy revealed that superoxide-producing mitochondria colocalized with lysosomes after the angiotensin II stimulation. Myocyte apoptosis was assessed by nuclear staining with DAPI and caspase-3 activity. A 6-h stimulation with angiotensin II did not affect myocyte apoptosis, while a co-treatment with 3-methyl-adenine (3MA), an autophagy inhibitor, augmented apoptosis. These results indicate that autophagy suppressed apoptosis because it removed damaged mitochondria in the early stages of the angiotensin II stimulation. A longer angiotensin II stimulation for 24 h induced apoptosis and propidium iodide-positive lethal myocytes, while the co-treatment with 3MA did not lead to further increases. In conclusion, angiotensin II-induced autophagy removes ROS-producing mitochondria. Autophagy is a beneficial phenomenon against myocyte apoptosis in the early phase, but its benefit was limited in the late phase of angiotensin II stimulation.

Cyclic GMP and PKG Signaling in Heart Failure

Cyclic guanosine monophosphate (cGMP), produced by guanylate cyclase (GC), activates protein kinase G (PKG) and regulates cardiac remodeling. cGMP/PKG signal is activated by two intrinsic pathways: nitric oxide (NO)-soluble GC and natriuretic peptide (NP)-particulate GC (pGC) pathways. Activation of these pathways has emerged as a potent therapeutic strategy to treat patients with heart failure, given cGMP-PKG signaling is impaired in heart failure with reduced ejection fraction (HFrEF) and preserved ejection fraction (HFpEF). Large scale clinical trials in patients with HFrEF have shown positive results with agents that activate cGMP-PKG pathways. In patients with HFpEF, however, benefits were observed only in a subgroup of patients. Further investigation for cGMP-PKG pathway is needed to develop better targeting strategies for HFpEF. This review outlines cGMP-PKG pathway and its modulation in heart failure.

Calorie restriction changes lipidomic profiles and maintains mitochondrial function and redox balance during isoproterenol-induced cardiac hypertrophy

Typically, healthy cardiac tissue utilizes more fat than any other organ. Cardiac hypertrophy induces a metabolic shift leading to a preferential consumption of glucose over fatty acids to support the high energetic demand. Calorie restriction is a dietary procedure that induces health benefits and lifespan extension in many organisms. Given the beneficial effects of calorie restriction, we hypothesized that calorie restriction prevents cardiac hypertrophy, lipid content changes, mitochondrial and redox dysregulation. Strikingly, calorie restriction reversed isoproterenol-induced cardiac hypertrophy. Isolated mitochondria from hypertrophic hearts produced significantly higher levels of succinate-driven H₂O₂ production, which was blocked by calorie restriction. Cardiac hypertrophy lowered mitochondrial respiratory control ratios, and decreased superoxide dismutase and glutathione peroxidase levels. These effects were also prevented by calorie restriction. We performed lipidomic profiling to gain insights into how calorie restriction could interfere with the metabolic changes induced by cardiac hypertrophy. Calorie restriction protected against the consumption of several triglycerides (TGs) linked to unsaturated fatty acids. Also, this dietary procedure protected against the accumulation of TGs containing saturated fatty acids observed in hypertrophic samples. Cardiac hypertrophy induced an increase in ceramides, phosphoethanolamines, and acylcarnitines (12:0, 14:0, 16:0, and 18:0). These were all reversed by calorie restriction. Altogether, our data demonstrate that hypertrophy changes the cardiac lipidome, causes mitochondrial disturbances, and oxidative stress. These changes are prevented (at least partially) by calorie restriction intervention in vivo. This study uncovers the potential for calorie restriction to become a new therapeutic intervention against cardiac hypertrophy, and mechanisms in which it acts.

Impact of Dietary Restriction Regimens on Mitochondria, Heart, and Endothelial Function: A Brief Overview

Caloric restriction (CR) and intermittent fasting (IF) are strategies aimed to promote health beneficial effects by interfering with several mechanisms responsible for cardiovascular diseases. Both dietary approaches decrease body weight, insulin resistance, blood pressure, lipids, and inflammatory status. All these favorable effects are the result of several metabolic adjustments, which have been addressed in this review, i.e., the improvement of mitochondrial biogenesis, the reduction of reactive oxygen species (ROS) production, and the improvement of cardiac and vascular function. CR and IF are able to modulate mitochondrial function via interference with dynamics (i.e., fusion and fission), respiration, and related oxidative stress. In the cardiovascular system, both dietary interventions are able to improve endothelium-dependent relaxation, reduce cardiac hypertrophy, and activate antiapoptotic signaling cascades. Further clinical studies are required to assess the long-term safety in the clinical setting.

Understanding diabetes-induced cardiomyopathy from the perspective of renin angiotensin aldosterone system

Experimental and clinical evidence suggests that diabetic subjects are predisposed to a distinct cardiovascular dysfunction, known as diabetic cardiomyopathy (DCM), which could be an autonomous disease independent of concomitant micro and macrovascular disorders. DCM is one of the prominent causes of global morbidity and mortality and is on a rising trend with the increase in the prevalence of diabetes mellitus (DM). DCM is characterized by an early left ventricle diastolic dysfunction associated with the slow progression of cardiomyocyte hypertrophy leading to heart failure, which still has no effective therapy. Although the well-known "Renin Angiotensin Aldosterone System (RAAS)" inhibition is considered a gold-standard treatment in heart failure, its role in DCM is still unclear. At the cellular level of DCM, RAAS induces various secondary mechanisms, adding complications to poor prognosis and treatment of DCM. This review highlights the importance of RAAS signaling and its major secondary mechanisms involving inflammation, oxidative stress, mitochondrial dysfunction, and autophagy, their role in establishing DCM. In addition, studies lacking in the specific area of DCM are also highlighted. Therefore, understanding the complex role of RAAS in DCM may lead to the identification of better prognosis and therapeutic strategies in treating DCM.

Crosstalk between the renin-angiotensin system and the endoplasmic reticulum stress in the cardiovascular system: Lessons learned so far

The renin-angiotensin (Ang) system (RAS) is a complex hormonal system present locally in several tissues such as cardiovascular organs. RAS deregulation through overactivation of the classical arm [Ang-converting enzyme (ACE)/Ang-II/Ang type 1 receptor (AT1R)] has been linked to the development of cardiovascular diseases and activation of endoplasmic reticulum (ER) stress pathways. The ER stress is a condition that, if unresolved, might lead to heart failure, atherosclerosis, hypertension, and endothelial dysfunction. Accumulated evidence has shown that the RAS modulates the UPR activation. Several studies reported increased ER stress markers in response to Ang-II treatment, in both in vivo and in vitro models. Evidence has also pointed that targeting the RAS classical arm through RAS blockers, gene silencing or genetic models leads to lower levels of ER stress markers. Few studies demonstrated protective effects of the counter-regulatory arm (ACE-2/Ang-(1-7)/Mas receptor) over ER stress. However, the crosstalk mechanisms between the arms of the RAS and ER stress remain unclear. In this review, we sought to explore the classical arm of the RAS as a key mechanism in UPR activation and to suggest a possible protective role of the counter-regulatory arm in mitigating ER stress.

Preconditioning with Short-term Dietary Restriction Attenuates Cardiac Oxidative Stress and Hypertrophy Induced by Chronic Pressure Overload

Left ventricular (LV) hypertrophy and associated heart failure are becoming a more prevalent and critical public health issue with the aging of society, and are exacerbated by reactive oxygen species (ROS). Dietary restriction (DR) markedly inhibits senescent changes; however, prolonged DR is difficult. We herein investigated whether preconditioning with short-term DR attenuates chronic pressure overload-induced cardiac hypertrophy and associated oxidative stress. Male c57BL6 mice were randomly divided into an ad libitum (AL) diet or 40% restricted diet (DR preconditioning, DRPC) group for 2 weeks prior to ascending aortic constriction (AAC), and all mice were fed ad libitum after AAC surgery. Two weeks after surgery, pressure overload by AAC increased LV wall thickness in association with LV diastolic dysfunction and promoted myocyte hypertrophy and cardiac fibrosis in the AL+AAC group. Oxidative stress in cardiac tissue and mitochondria also increased in the AL+AAC group in association with increments in cardiac NADPH oxidase-derived and mitochondrial ROS production. LV hypertrophy and associated cardiac dysfunction and oxidative stress were significantly attenuated in the DRPC+AAC group. Moreover, less severe mitochondrial oxidative damage in the DRPC+AAC group was associated with the suppression of mitochondrial permeability transition and cardiac apoptosis. These results indicate that chronic pressure overload-induced cardiac hypertrophy in association with cardiac and mitochondrial oxidative damage were attenuated by preconditioning with short-term DR.

Pathological cardiac remodeling seen by the eyes of proteomics

Cardiac remodeling involves cellular and structural changes that occur as consequence of multifactorial events to maintain the homeostasis. The progression of pathological cardiac remodeling involves a transition from adaptive to maladaptive changes that eventually leads to impairment of ventricular function and heart failure. In this scenario, proteins are key elements that orchestrate molecular events as increased expression of fetal genes, neurohormonal and second messengers' activation, contractile dysfunction, rearrangement of the extracellular matrix and alterations in heart geometry. Mass spectrometry based-proteomics has emerged as a sound method to study protein dysregulation and identification of cardiac diseases biomarkers in plasma. In this review, we summarize the main findings related to large-scale proteome modulation of cardiac cells and extracellular matrix occurred during pathological cardiac remodeling. We describe the recent proteomic progresses in the selection of protein targets and introduce the renin-angiotensin system as an interesting target for the treatment of pathological cardiac remodeling.

Dietary Restriction and Oxidative Stress: Friends or Enemies?

Significance: It is well established that lifestyle and dietary habits have a tremendous impact on life span, the rate of aging, and the onset/progression of age-related diseases. Specifically, dietary restriction (DR) and other healthy dietary patterns are usually accompanied by physical activity and differ from Western diet that is rich in fat and sugars. Moreover, as the generation of reactive oxidative species is the major causative factor of aging, while DR could modify the level of oxidative stress, it has been proposed that DR increases both survival and longevity. Recent Advances: Despite the documented links between DR, aging, and oxidative stress, many issues remain to be addressed. For instance, the free radical theory of aging is under "re-evaluation," while DR as a golden standard for prolonging life span and ameliorating the effects of aging is also under debate. Critical Issues: This review article pays special attention to highlight the link between DR and oxidative stress in both aging and age-related diseases. We discuss in particular DR's capability to counteract the consequences of oxidative stress and the molecular mechanisms involved in these processes. Future Directions: Although DR is undoubtedly beneficial, several considerations must be taken into account when designing the best dietary intervention. Use of intermittent fasting, daily food reduction, or DR mimetics? Future research should unravel the pros and cons of all these processes. Antioxid. Redox Signal. 34, 421-438.

Cardiac Autophagy Deficiency Attenuates ANP Production and Disrupts Myocardial-Adipose Cross Talk, Leading to Increased Fat Accumulation and Metabolic Dysfunction

Increased myocardial autophagy has been established as an important stress-induced cardioprotective response. Three weeks after generating cardiomyocyte-specific autophagy deficiency, via inducible deletion of autophagy-related protein 7 (Atg7), we found that these mice (AKO) had increased body weight and fat mass without altered food intake. Glucose and insulin tolerance tests indicated reduced insulin sensitivity in AKO mice. Metabolic cage analysis showed reduced ambulatory activity and oxygen consumption with a trend of elevated respiratory exchange ratio in AKO mice. Direct analysis of metabolism in subcutaneous and visceral adipocytes showed increased glucose oxidation and reduced ATGL expression and HSL phosphorylation with no change in lipid synthesis or fatty acid oxidation. Importantly, we found AKO mice had reduced myocardial and circulating levels of atrial natriuretic peptide (ANP), an established mediator of myocardial-adipose cross talk. When normal ANP levels were restored to AKO mice with use of osmotic pump, the metabolic dysfunction evident in AKO mice was corrected. We conclude that cardiac autophagy deficiency alters myocardial-adipose cross talk via decreased ANP levels with adverse metabolic consequences.

Caloric restriction mimetics for the treatment of cardiovascular diseases

Caloric restriction mimetics (CRMs) are emerging as potential therapeutic agents for the treatment of cardiovascular diseases. CRMs include natural and synthetic compounds able to inhibit protein acetyltransferases, to interfere with acetyl coenzyme A biosynthesis, or to activate (de)acetyltransferase proteins. These modifications mimic the effects of caloric restriction, which is associated with the activation of autophagy. Previous evidence demonstrated the ability of CRMs to ameliorate cardiac function and reduce cardiac hypertrophy and maladaptive remodelling in animal models of ageing, mechanical overload, chronic myocardial ischaemia, and in genetic and metabolic cardiomyopathies. In addition, CRMs were found to reduce acute ischaemia-reperfusion injury. In many cases, these beneficial effects of CRMs appeared to be mediated by autophagy activation. In the present review, we discuss the relevant literature about the role of different CRMs in animal models of cardiac diseases, emphasizing the molecular mechanisms underlying the beneficial effects of these compounds and their potential future clinical application.

Mitochondrial Quality Control and Cellular Proteostasis: Two Sides of the Same Coin

Mitochondrial dysfunction is a hallmark of cardiac pathophysiology. Defects in mitochondrial performance disrupt contractile function, overwhelm myocytes with reactive oxygen species (ROS), and transform these cellular powerhouses into pro-death organelles. Thus, quality control (QC) pathways aimed at identifying and removing damaged mitochondrial proteins, components, or entire mitochondria are crucial processes in post-mitotic cells such as cardiac myocytes. Almost all of the mitochondrial proteins are encoded by the nuclear genome and the trafficking of these nuclear-encoded proteins necessitates significant cross-talk with the cytosolic protein QC machinery to ensure that only functional proteins are delivered to the mitochondria. Within the organelle, mitochondria contain their own protein QC system consisting of chaperones and proteases. This system represents another level of QC to promote mitochondrial protein folding and prevent aggregation. If this system is overwhelmed, a conserved transcriptional response known as the mitochondrial unfolded protein response is activated to increase the expression of proteins involved in restoring mitochondrial proteostasis. If the mitochondrion is beyond repair, the entire organelle must be removed before it becomes cytotoxic and causes cellular damage. Recent evidence has also uncovered mitochondria as participants in cytosolic protein QC where misfolded cytosolic proteins can be imported and degraded inside mitochondria. However, this process also places increased pressure on mitochondrial QC pathways to ensure that the imported proteins do not cause mitochondrial dysfunction. This review is focused on discussing the pathways involved in regulating mitochondrial QC and their relationship to cellular proteostasis and mitochondrial health in the heart.

Autophagy in metabolic syndrome: breaking the wheel by targeting the renin-angiotensin system

Metabolic syndrome (MetS) is a complex, emerging epidemic which disrupts the metabolic homeostasis of several organs, including liver, heart, pancreas, and adipose tissue. While studies have been conducted in these research areas, the pathogenesis and mechanisms of MetS remain debatable. Lines of evidence show that physiological systems, such as the renin-angiotensin system (RAS) and autophagy play vital regulatory roles in MetS. RAS is a pivotal system known for controlling blood pressure and fluid balance, whereas autophagy is involved in the degradation and recycling of cellular components, including proteins. Although RAS is activated in MetS, the interrelationship between RAS and autophagy varies in glucose homeostatic organs and their cross talk is poorly understood. Interestingly, autophagy is attenuated in the liver during MetS, whereas autophagic activity is induced in adipose tissue during MetS, indicating tissue-specific discordant roles. We discuss in vivo and in vitro studies conducted in metabolic tissues and dissect their tissue-specific effects. Moreover, our review will focus on the molecular mechanisms by which autophagy orchestrates MetS and the ways future treatments could target RAS in order to achieve metabolic homeostasis.

The microRNA in ventricular remodeling: the miR-30 family

Ventricular remodeling (VR) is a complex pathological process of cardiomyocyte apoptosis, cardiac hypertrophy, and myocardial fibrosis, which is often caused by various cardiovascular diseases (CVDs) such as hypertension, acute myocardial infarction, heart failure (HF), etc. It is also an independent risk factor for a variety of CVDs, which will eventually to damage the heart function, promote cardiovascular events, and lead to an increase in mortality. MicroRNAs (miRNAs) can participate in a variety of CVDs through post-transcriptional regulation of target gene proteins. Among them, microRNA-30 (miR-30) is one of the most abundant miRNAs in the heart. In recent years, the study found that the miR-30 family can participate in VR through a variety of mechanisms, including autophagy, apoptosis, oxidative stress, and inflammation. VR is commonly found in ischemic heart disease (IHD), hypertensive heart disease (HHD), diabetic cardiomyopathy (DCM), antineoplastic drug cardiotoxicity (CTX), and other CVDs. Therefore, we will review the relevant mechanisms of the miR-30 in VR induced by various diseases.

Mitochondrial Dysfunction and Diabetes: Is Mitochondrial Transfer a Friend or Foe?

Obesity, insulin resistance and type 2 diabetes are accompanied by a variety of systemic and tissue-specific metabolic defects, including inflammation, oxidative and endoplasmic reticulum stress, lipotoxicity, and mitochondrial dysfunction. Over the past 30 years, association studies and genetic manipulations, as well as lifestyle and pharmacological invention studies, have reported contrasting findings on the presence or physiological importance of mitochondrial dysfunction in the context of obesity and insulin resistance. It is still unclear if targeting mitochondrial function is a feasible therapeutic approach for the treatment of insulin resistance and glucose homeostasis. Interestingly, recent studies suggest that intact mitochondria, mitochondrial DNA, or other mitochondrial factors (proteins, lipids, miRNA) are found in the circulation, and that metabolic tissues secrete exosomes containing mitochondrial cargo. While this phenomenon has been investigated primarily in the context of cancer and a variety of inflammatory states, little is known about the importance of exosomal mitochondrial transfer in obesity and diabetes. We will discuss recent evidence suggesting that (1) tissues with mitochondrial dysfunction shed their mitochondria within exosomes, and that these exosomes impair the recipient's cell metabolic status, and that on the other hand, (2) physiologically healthy tissues can shed mitochondria to improve the metabolic status of recipient cells. In this context the determination of whether mitochondrial transfer in obesity and diabetes is a friend or foe requires further studies.

Mitochondrial complex I deficiency and cardiovascular diseases: current evidence and future directions

Compelling evidence demonstrates the emerging role of mitochondrial complex I deficiency in the onset and development of cardiovascular diseases (CVDs). In particular, defects in single subunits of mitochondrial complex I have been associated with cardiac hypertrophy, ischemia/reperfusion injury, as well as diabetic complications and stroke in pre-clinical studies. Moreover, data obtained in humans revealed that genes coding for complex I proteins were associated with different CVDs. In this review, we discuss recent experimental studies that underline the contributory role of mitochondrial complex I deficiency in the etiopathogenesis of several CVDs, with a particular focus on those involving loss of function models of mitochondrial complex I. We also discuss human studies and potential therapeutic strategies able to rescue mitochondrial function in CVDs.

Therapeutic Options Targeting Oxidative Stress, Mitochondrial Dysfunction and Inflammation to Hinder the Progression of Vascular Complications of Diabetes

Type 2 diabetes mellitus is a leading cause of morbidity and mortality worldwide, given its serious associated complications. Despite constant efforts and intensive research, an effective, ubiquitous treatment still eludes the scientific community. As such, the identification of novel avenues of research is key to the potential discovery of this evasive "silver bullet." We focus on this review on the matter of diabetic injury to endothelial tissue and some of the pivotal underlying mechanisms, including hyperglycemia and hyperlipidemia evoked oxidative stress and inflammation. In this sense, we revisited the most promising therapeutic interventions (both non-pharmacological and antidiabetic drugs) targeting oxidative stress and inflammation to hinder progression of vascular complications of diabetes. This review article gives particular attention to the relevance of mitochondrial function, an often ignored and understudied organelle in the vascular endothelium. We highlight the importance of mitochondrial function and number homeostasis in diabetic conditions and discuss the work conducted to address the aforementioned issue by the use of various therapeutic strategies. We explore here the functional, biochemical and bioenergetic alterations provoked by hyperglycemia in the endothelium, from elevated oxidative stress to inflammation and cell death, as well as loss of tissue function. Furthermore, we synthetize the literature regarding the current and promising approaches into dealing with these alterations. We discuss how known agents and therapeutic behaviors (as, for example, metformin, dietary restriction or antioxidants) can restore normality to mitochondrial and endothelial function, preserving the tissue's function and averting the aforementioned complications.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Utilizing proteomics to understand and define hypertension: where are we and where do we go?

INTRODUCTION

Hypertension is a complex and multifactorial cardiovascular disorder. With different mechanisms contributing to a different extent to an individual's blood pressure, the discovery of novel pathogenetic principles of hypertension is challenging. However, there is an urgent and unmet clinical need to improve prevention, detection, and therapy of hypertension in order to reduce the global burden associated with hypertension-related cardiovascular diseases. Areas covered: Proteomic techniques have been applied in reductionist experimental models including angiotensin II infusion models in rodents and the spontaneously hypertensive rat in order to unravel mechanisms involved in blood pressure control and end organ damage. In humans proteomic studies mainly focus on prediction and detection of organ damage, particularly of heart failure and renal disease. While there are only few proteomic studies specifically addressing human primary hypertension, there are more data available in hypertensive disorders in pregnancy, such as preeclampsia. We will review these studies and discuss implications of proteomics on precision medicine approaches. Expert commentary: Despite the potential of proteomic studies in hypertension there has been moderate progress in this area of research. Standardized large-scale studies are required in order to make best use of the potential that proteomics offers in hypertension and other cardiovascular diseases.

EndophilinA2 protects against angiotensin II-induced cardiac hypertrophy by inhibiting angiotensin II type 1 receptor trafficking in neonatal rat cardiomyocytes

Cardiac hypertrophy is one of the major risk factors for chronic heart failure. The role of endophilinA2 (EndoA2) in clathrin-mediated endocytosis and clathrin-independent endocytosis is well documented. In the present study, we tested the hypothesis that EndoA2 protects against angiotensin II (Ang II)-induced cardiac hypertrophy by mediating intracellular angiotensin II type 1 receptor (AT1-R) trafficking in neonatal rat cardiomyocytes (NRCMs). Cardiac hypertrophy was evaluated by using cell surface area and quantitative RT-PCR (qPCR) analyses. For the first time, we found that EndoA2 attenuated cardiac hypertrophy and fibrosis induced by Ang II. Moreover, EndoA2 inhibited apoptosis induced by excessive endoplasmic reticulum stress (ERS), which accounted for the beneficial effects of EndoA2 on cardiac hypertrophy. We further revealed that there was an interaction between EndoA2 and AT1-R.The expression levels of EndoA2, which inhibits AT1-R transport from the cytoplasm to the membrane, and the interaction between EndoA2 and AT1-R were obviously decreased after Ang II treatment. Furthermore, Ang II inhibited the co-localization of AT1-R with GRP-78, which was reversed by EndoA2 overexpression. In conclusion, our results suggested that EndoA2 plays a role in protecting against cardiac hypertrophy induced by Ang II, possibly by inhibiting AT1-R transport from the cytoplasm to the membrane to suppress signal transduction.

Nitric oxide-sensitive guanylyl cyclase stimulation improves experimental heart failure with preserved ejection fraction

Heart failure with preserved ejection fraction (HFpEF) can arise from cardiac and vascular remodeling processes following long-lasting hypertension. Efficacy of common HF therapeutics is unsatisfactory in HFpEF. Evidence suggests that stimulators of the nitric oxide-sensitive soluble guanylyl cyclase (NOsGC) could be of use here. We aimed to characterize the complex cardiovascular effects of NOsGC stimulation using NO-independent stimulator BAY 41-8543 in a double-transgenic rat (dTGR) model of HFpEF. We show a drastically improved survival rate of treated dTGR. We observed less cardiac fibrosis, macrophage infiltration, and gap junction remodeling in treated dTGR. Microarray analysis revealed that treatment of dTGR corrected the dysregulateion of cardiac genes associated with fibrosis, inflammation, apoptosis, oxidative stress, and ion channel function toward an expression profile similar to healthy controls. Treatment reduced systemic blood pressure levels and improved endothelium-dependent vasorelaxation of resistance vessels. Further comprehensive in vivo phenotyping showed an improved diastolic cardiac function, improved hemodynamics, and less susceptibility to ventricular arrhythmias. Short-term BAY 41-8543 application in isolated untreated transgenic hearts with structural remodeling significantly reduced the occurrence of ventricular arrhythmias, suggesting a direct nongenomic role of NOsGC stimulation on excitation. Thus, NOsGC stimulation was highly effective in improving several HFpEF facets in this animal model, underscoring its potential value for patients.

Loss of vascular smooth muscle cell autophagy exacerbates angiotensin II-associated aortic remodeling

OBJECTIVE

The pathophysiologic processes of abdominal aortic aneurysms (AAAs) and atherosclerosis often intersect. Given that anomalies in vascular smooth muscle cell (SMC) autophagy have been noted in models of atherosclerosis, we sought to evaluate the potential role that SMC autophagy may play in the initiation and progression of AAAs.

METHODS

Studies were conducted in ATG7^flx/flxSM22α-Cre^tg/+ (SMC ATG7 knockout [SMC-ATG7-KO]) and ATG7^WT/WT; SM22α-Cre^tg/+ (SMC ATG7 wild-type [SMC-ATG7-WT]) littermates that were continuously infused with angiotensin II (Ang II; 1.5 mg/kg/d) for up to 12 weeks. Mortality, morbidity, hemodynamics, and aortic remodeling were documented.

RESULTS

During the 12-week observation window, all of the Ang II-treated SMC-ATG-WT mice (n = 6) survived, whereas 10 of the 19 Ang II-treated SMC-ATG-KO mice had died by week 7 (log-rank test, P < .001). Mean arterial pressure (128.07 ± 3.4 mm Hg for Ang II-treated SMC-ATG-KO vs 138.5 ± 5.87 mm Hg for Ang II-treated SMC-ATG-WT mice) and diastolic arterial pressure (109.7 ± 2.55 mm Hg for Ang II-treated SMC-ATG7-KO vs 119.4 ± 2.12 mm Hg for Ang II-treated SMC-ATG7-WT mice) were significantly different between the two groups (P < .01). Cardiac rupture, myocardial infarct, end-organ damage, pleural effusion, and venous distention were noted in Ang II-treated SMC-ATG7-KO but not in Ang II-treated SMC-ATG7-WT mice. Although the suprarenal aortic diameters of the Ang II-treated SMC-ATG7-KO group demonstrated a trending increase (at week 4, 1.26 ± 0.06 mm [n = 14] for Ang II-treated SMC-ATG-KO mice vs 1.09 ± 0.02 mm [n = 5] for Ang II-treated SMC-ATG-WT mice; P < .05), only 2 of the 19 developed abdominal aortic dissections.

CONCLUSIONS

Mice with SMC ATG7 deficiency that are chronically infused with Ang II do not tend to develop dissecting AAA but do exhibit adverse aortic remodeling and appreciable cardiac failure-associated mortality.

Autophagy and Mitophagy in Cardiovascular Disease

Autophagy contributes to the maintenance of intracellular homeostasis in most cells of cardiovascular origin, including cardiomyocytes, endothelial cells, and arterial smooth muscle cells. Mitophagy is an autophagic response that specifically targets damaged, and hence potentially cytotoxic, mitochondria. As these organelles occupy a critical position in the bioenergetics of the cardiovascular system, mitophagy is particularly important for cardiovascular homeostasis in health and disease. Consistent with this notion, genetic defects in autophagy or mitophagy have been shown to exacerbate the propensity of laboratory animals to spontaneously develop cardiodegenerative disorders. Moreover, pharmacological or genetic maneuvers that alter the autophagic or mitophagic flux have been shown to influence disease outcome in rodent models of several cardiovascular conditions, such as myocardial infarction, various types of cardiomyopathy, and atherosclerosis. In this review, we discuss the intimate connection between autophagy, mitophagy, and cardiovascular disorders.

Pharmacological modulation of autophagy: therapeutic potential and persisting obstacles

Autophagy is central to the maintenance of organismal homeostasis in both physiological and pathological situations. Accordingly, alterations in autophagy have been linked to clinically relevant conditions as diverse as cancer, neurodegeneration and cardiac disorders. Throughout the past decade, autophagy has attracted considerable attention as a target for the development of novel therapeutics. However, such efforts have not yet generated clinically viable interventions. In this Review, we discuss the therapeutic potential of autophagy modulators, analyse the obstacles that have limited their development and propose strategies that may unlock the full therapeutic potential of autophagy modulation in the clinic.

Mild and Short-Term Caloric Restriction Prevents Obesity-Induced Cardiomyopathy in Young Zucker Rats without Changing in Metabolites and Fatty Acids Cardiac Profile

Caloric restriction (CR) ameliorates cardiac dysfunction associated with obesity. However, most of the studies have been performed under severe CR (30-65% caloric intake decrease) for several months or even years in aged animals. Here, we investigated whether mild (20% food intake reduction) and short-term (2-weeks) CR prevented the obese cardiomyopathy phenotype and improved the metabolic profile of young (14 weeks of age) genetically obese Zucker fa/fa rats. Heart weight (HW) and HW/tibia length ratio was significantly lower in fa/fa rats after 2 weeks of CR than in counterparts fed ad libitum. Invasive pressure measurements showed that systolic blood pressure, maximal rate of positive left ventricle (LV) pressure, LV systolic pressure and LV end-diastolic pressure were all significantly higher in obese fa/fa rats than in lean counterparts, which were prevented by CR. Magnetic resonance imaging revealed that the increase in LV end-systolic volume, stroke volume and LV wall thickness observed in fa/fa rats was significantly lower in animals on CR diet. Histological analysis also revealed that CR blocked the significant increase in cardiomyocyte diameter in obese fa/fa rats. High resolution magic angle spinning magnetic resonance spectroscopy analysis of the LV revealed a global decrease in metabolites such as taurine, creatine and phosphocreatine, glutamate, glutamine and glutathione, in obese fa/fa rats, whereas lactate concentration was increased. By contrast, fatty acid concentrations in LV tissue were significantly elevated in obese fa/fa rats. CR failed to restore the LV metabolomic profile of obese fa/fa rats. In conclusion, mild and short-term CR prevented an obesity-induced cardiomyopathy phenotype in young obese fa/fa rats independently of the cardiac metabolic profile.

Impaired Nrf2 regulation of mitochondrial biogenesis in rostral ventrolateral medulla on hypertension induced by systemic inflammation

Oxidative stress in rostral ventrolateral medulla (RVLM), where sympathetic premotor neurons reside, is involved in the development of hypertension under systemic inflammation. Mitochondrial dysfunction contributes to tissue oxidative stress. In this study, we sought to investigate whether hypertension developed under systemic inflammation is attributable to impaired mitochondrial biogenesis in RVLM. In normotensive Sprague-Dawley rats, intraperitoneal infusion of a low dose Escherichia coli lipopolysaccharide (LPS) for 7 days promoted a pressor response, alongside a decrease in mitochondrial DNA (mtDNA) copy number, reductions in protein expression of nuclear DNA-encoded transcription factors for mitochondrial biogenesis, including mitochondrial transcription factor A (TFAM) and nuclear factor erythroid-derived 2-like 2 (Nrf2), and suppression of nuclear translocation of the phosphorylated Nrf2 (p-Nrf2) in RVLM neurons; all of which were abrogated by treatment with intracisternal infusion of an interleukin-1β (IL-1β) blocker, IL-1Ra, or a mobile mitochondrial electron carrier, coenzyme Q10 (CoQ10). Microinjection into RVLM of IL-1β suppressed the expressions of p-Nrf2 and TFAM, and evoked a pressor response; conversely, the Nrf2 inducer, tert-butylhydroquinone, lessened the LPS-induced suppression of TFAM expression and pressor response. At cellular level, exposure of neuronal N2a cells to IL-1β decreased mtDNA copy number, increased protein interaction of Nrf2 to its negative regulator, kelch-like ECH-associated protein 1 (Keap1), and reduced DNA binding activity of p-Nrf2 to Tfam gene. Together these results indicate that defect mitochondrial biogenesis in RVLM neurons entailing redox-sensitive and IL-1β-dependent suppression of TFAM because of the increase in the formation of Keap1/Nrf2 complex, reductions in nuclear translocation of the activated Nrf2 and its binding to the Tfam gene promoter may underlie hypertension developed under the LPS-induced systemic inflammation.

Novel N-Substituted 2-(2-(Adamantan-1-yl)-1H-Indol-3-yl)-2-Oxoacetamide Derivatives: Synthesis and Biological Evaluation

In this study, a series of novel N-substituted 2-(2-(adamantan-1-yl)-1H-indol-3-yl)-2-oxoacetamide derivatives were synthesized, and evaluated for their cytotoxicity in human cell lines including Hela (cervical cancer), MCF7 (breast cancer ) and HepG2 (liver cancer). Several compounds were found to have potent anti-proliferative activity against those human cancer cell lines and compound 5r showed the most potent biological activity against HepG2 cells with an IC50 value of 10.56 ± 1.14 μΜ. In addition, bioassays showed that compound 5r induced time-dependent and dose-dependent cleavage of poly ADP-ribose polymerase (PARP), and also induced a dose-dependent increase in caspase-3 and caspase-8 activity, but had little effect on caspase-9 protease activity in HepG2 cells. These results provide evidence that 5r-induced apoptosis in HepG2 cell is caspase-8-dependent.

Assessing Cardiac Metabolism: A Scientific Statement From the American Heart Association

In a complex system of interrelated reactions, the heart converts chemical energy to mechanical energy. Energy transfer is achieved through coordinated activation of enzymes, ion channels, and contractile elements, as well as structural and membrane proteins. The heart's needs for energy are difficult to overestimate. At a time when the cardiovascular research community is discovering a plethora of new molecular methods to assess cardiac metabolism, the methods remain scattered in the literature. The present statement on "Assessing Cardiac Metabolism" seeks to provide a collective and curated resource on methods and models used to investigate established and emerging aspects of cardiac metabolism. Some of those methods are refinements of classic biochemical tools, whereas most others are recent additions from the powerful tools of molecular biology. The aim of this statement is to be useful to many and to do justice to a dynamic field of great complexity.

The renin-angiotensin system and its involvement in vascular disease

The renin-angiotensin system (RAS) plays a critical role in the pathogenesis of many types of cardiovascular diseases including cardiomyopathy, valvular heart disease, aneurysms, stroke, coronary artery disease and vascular injury. Besides the classical regulatory effects on blood pressure and sodium homoeostasis, the RAS is involved in the regulation of contractility and remodelling of the vessel wall. Numerous studies have shown beneficial effect of inhibition of this system in the pathogenesis of cardiovascular diseases. However, dysregulation and overexpression of the RAS, through different molecular mechanisms, also induces, the initiation of vascular damage. The key effector peptide of the RAS, angiotensin II (Ang II) promotes cell proliferation, apoptosis, fibrosis, oxidative stress and inflammation, processes known to contribute to remodelling of the vasculature. In this review, we focus on the components that are under the influence of the RAS and contribute to the development and progression of vascular disease; extracellular matrix defects, atherosclerosis and ageing. Furthermore, the beneficial therapeutic effects of inhibition of the RAS on the vasculature are discussed, as well as the need for additive effects on top of RAS inhibition.

Rcan1-1L overexpression induces mitochondrial autophagy and improves cell survival in angiotensin II-exposed cardiomyocytes

Mitochondrial autophagy is an important adaptive stress response and can be modulated by various key molecules. A previous study found that the regulator of calcineurin 1-1L (Rcan1-1L) may regulate mitochondrial autophagy and cause mitochondria degradation in neurocytes. However, the effect of Rcan1-1L on cardiomyocytes has not been determined. In the present study, we aimed to investigate the role of Rcan1-1L in angiotensin II (Ang II)-exposed human cardiomyocytes. Above all, Human adult cardiac myocytes (HACMs) were exposed to 200nmol/L Ang II for 4 days. Enhanced H2O2 production, cytochrome C release and mitochondrial permeability were observed in these cells, which were blocked by valsartan. Consistently, Ang II exposure significantly reduced cardiomyocyte viability. However, transfection of Rcan1-1L vector promoted cell viability and ameliorated the apoptosis caused by Ang II. Rcan1-1L clearly promoted mitochondrial autophagy in HACMs, with elevated autophagy protein (ATG) 5 and light chain 3 (LC3) expression. Transient mitochondrial biogenesis and reduced cytochrome C release was also induced by Rcan1-1L. Additionally, Rcan1-1L significantly inhibited calcineurin/nuclear factor of activated T cells (NFAT) signaling. We thus conclude that Rcan1-1L may play a protective role in Ang II-treated cardiomyocytes through the induction of mitochondrial autophagy, and may be an alternative method of cardiac protection.

Exacerbation of acute kidney injury by bone marrow stromal cells from rats with persistent renin–angiotensin system activation

Activation of the renin–angiotensin system (RAS) severely abated the therapeutic functionality of bone marrow stromal cells (BMSCs). Because BMSCs contribute to tissue repair and regeneration, end-organ damage associated with overtly active RAS and hypertension may be exacerbated by BMSC dysfunctionality.

Indispensable role of endothelial nitric oxide synthase in caloric restriction-induced cardioprotection against ischemia-reperfusion injury

Caloric restriction (CR) confers cardioprotection against ischemia-reperfusion injury (IRI). We previously found that treatment with N(G)-nitro-l-arginine methyl ester completely abrogates CR-induced cardioprotection and increases nuclear sirtuin 1 (Sirt1) expression. However, it remains unclear whether endothelial nitric oxide (NO) synthase (eNOS) plays a role in CR-induced cardioprotection and Sirt1 activation. We subjected eNOS-deficient (eNOS(-/-)) mice to either 3-mo ad libitum (AL) feeding or CR (-40%). Isolated perfused hearts were subjected to 25-min global ischemia followed by 60-min reperfusion. The degree of myocardial IRI in AL-fed eNOS(-/-) mice was more severe than that in AL-fed wild-type mice. Furthermore, CR did not exert cardioprotection in eNOS(-/-) mice. eNOS(-/-) mice exhibited elevated blood pressure and left ventricular hypertrophy compared with wild-type mice, although they underwent CR. Although nuclear Sir1 content was increased, the increases in cardiac Sirt1 activity with CR was absent in eNOS(-/-) mice. In eNOS(-/-) mice treated with hydralazine, blood pressure and left ventricular weight became comparable with CR-treated wild-type mice. However, CR-induced cardioprotection was not observed. Resveratrol enhanced cardiac Sirt1 activity but failed to mimic CR-induced cardioprotection in eNOS(-/-) mice. Finally, combination therapy with resveratrol and hydralazine attenuated myocardial IRI and reduced infarct size in eNOS(-/-) mice, and their effects were comparable with those observed in CR-treated wild-type mice. These results demonstrate the essential roles of eNOS in the development of CR-induced cardioprotection and Sirt1 activation during CR. The combination of a relatively low dose of resveratrol with an adequate vasodilator therapy might be useful for managing patients with endothelial dysfunction associated with impaired NO bioavailability.

Autophagy in cardiovascular biology

Cardiovascular disease is the leading cause of death worldwide. As such, there is great interest in identifying novel mechanisms that govern the cardiovascular response to disease-related stress. First described in failing hearts, autophagy within the cardiovascular system has been widely characterized in cardiomyocytes, cardiac fibroblasts, endothelial cells, vascular smooth muscle cells, and macrophages. In all cases, a window of optimal autophagic activity appears to be critical to the maintenance of cardiovascular homeostasis and function; excessive or insufficient levels of autophagic flux can each contribute to heart disease pathogenesis. In this Review, we discuss the potential for targeting autophagy therapeutically and our vision for where this exciting biology may lead in the future.

Pathogenesis of target organ damage in hypertension: role of mitochondrial oxidative stress

Hypertension causes target organ damage (TOD) that involves vasculature, heart, brain and kidneys. Complex biochemical, hormonal and hemodynamic mechanisms are involved in the pathogenesis of TOD. Common to all these processes is an increased bioavailability of reactive oxygen species (ROS). Both in vitro and in vivo studies explored the role of mitochondrial oxidative stress as a mechanism involved in the pathogenesis of TOD in hypertension, especially focusing on atherosclerosis, heart disease, renal failure, cerebrovascular disease. Both dysfunction of mitochondrial proteins, such as uncoupling protein-2 (UCP2), superoxide dismutase (SOD) 2, peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α), calcium channels, and the interaction between mitochondria and other sources of ROS, such as NADPH oxidase, play an important role in the development of endothelial dysfunction, cardiac hypertrophy, renal and cerebral damage in hypertension. Commonly used anti-hypertensive drugs have shown protective effects against mitochondrial-dependent oxidative stress. Notably, few mitochondrial proteins can be considered therapeutic targets on their own. In fact, antioxidant therapies specifically targeted at mitochondria represent promising strategies to reduce mitochondrial dysfunction and related hypertensive TOD. In the present article, we discuss the role of mitochondrial oxidative stress as a contributing factor to hypertensive TOD development. We also provide an overview of mitochondria-based treatment strategies that may reveal useful to prevent TOD and reduce its progression.

Mitochondria, endothelial cell function, and vascular diseases

Mitochondria are perhaps the most sophisticated and dynamic responsive sensing systems in eukaryotic cells. The role of mitochondria goes beyond their capacity to create molecular fuel and includes the generation of reactive oxygen species, the regulation of calcium, and the activation of cell death. In endothelial cells, mitochondria have a profound impact on cellular function under both healthy and diseased conditions. In this review, we summarize the basic functions of mitochondria in endothelial cells and discuss the roles of mitochondria in endothelial dysfunction and vascular diseases, including atherosclerosis, diabetic vascular dysfunction, pulmonary artery hypertension, and hypertension. Finally, the potential therapeutic strategies to improve mitochondrial function in endothelial cells and vascular diseases are also discussed, with a focus on mitochondrial-targeted antioxidants and calorie restriction.

Effects of hypertension and exercise on cardiac proteome remodelling

Left ventricle hypertrophy is a common outcome of pressure overload stimulus closely associated with hypertension. This process is triggered by adverse molecular signalling, gene expression, and proteome alteration. Proteomic research has revealed that several molecular targets are associated with pathologic cardiac hypertrophy, including angiotensin II, endothelin-1 and isoproterenol. Several metabolic, contractile, and stress-related proteins are shown to be altered in cardiac hypertrophy derived by hypertension. On the other hand, exercise is a nonpharmacologic agent used for hypertension treatment, where cardiac hypertrophy induced by exercise training is characterized by improvement in cardiac function and resistance against ischemic insult. Despite the scarcity of proteomic research performed with exercise, healthy and pathologic heart proteomes are shown to be modulated in a completely different way. Hence, the altered proteome induced by exercise is mostly associated with cardioprotective aspects such as contractile and metabolic improvement and physiologic cardiac hypertrophy. The present review, therefore, describes relevant studies involving the molecular characteristics and alterations from hypertensive-induced and exercise-induced hypertrophy, as well as the main proteomic research performed in this field. Furthermore, proteomic research into the effect of hypertension on other target-demerged organs is examined.

Mechanical stress triggers cardiomyocyte autophagy through angiotensin II type 1 receptor-mediated p38MAP kinase independently of angiotensin II

Angiotensin II (Ang II) type 1 (AT1) receptor is known to mediate a variety of physiological actions of Ang II including autophagy. However, the role of AT1 receptor in cardiomyocyte autophagy triggered by mechanical stress still remains elusive. The aim of this study was therefore to examine whether and how AT1 receptor participates in cardiomyocyte autophagy induced by mechanical stresses. A 48-hour mechanical stretch and a 4-week transverse aorta constriction (TAC) were imposed to cultured cardiomyocytes of neonatal rats and adult male C57B/L6 mice, respectively, to induce cardiomyocyte hypertrophy prior to the assessment of cardiomyocyte autophagy using LC3b-II. Losartan, an AT1 receptor blocker, but not PD123319, the AT2 inhibitor, was found to significantly reduce mechanical stretch-induced LC3b-II upregulation. Moreover, inhibition of p38MAP kinase attenuated not only mechanical stretch-induced cardiomyocyte hypertrophy but also autophagy. To the contrary, inhibition of ERK and JNK suppressed cardiac hypertrophy but not autophagy. Intriguingly, mechanical stretch-induced autophagy was significantly inhibited by Losartan in the absence of Ang II. Taken together, our results indicate that mechanical stress triggers cardiomyocyte autophagy through AT1 receptor-mediated activation of p38MAP kinase independently of Ang II.

The role of angiotensin II in nonalcoholic steatohepatitis

Nonalcoholic fatty liver disease (NAFLD) is now considered the most prevalent chronic liver disease, affecting over 30% of the US adult population. NAFLD is strongly linked to insulin resistance and is considered the hepatic manifestation of the metabolic syndrome. Activation of the renin-angiotensin-aldosterone system (RAAS) is known to play a role in the hypertension observed in the metabolic syndrome and also is thought to play a central role in insulin resistance and NAFLD. Angiotensin II (AngII) is considered the primary effector of the physiological outcomes of RAAS signaling, both at the systemic and local tissue level. Herein, we review data describing the potential involvement of AngII-mediated signaling at multiple levels in the development and progression of NAFLD, including increased steatosis, inflammation, insulin resistance, and fibrosis. Additionally, we present recent work on the potential therapeutic benefits of RAAS and angiotensin II signaling inhibition in rodent models and patients with NAFLD.

Caloric restriction ameliorates kidney ischaemia/reperfusion injury through PGC-1α-eNOS pathway and enhanced autophagy

AIM

We investigated whether preconditioning with caloric restriction (CR) ameliorates kidney ischaemia/reperfusion (I/R) injury and whether the salutary effects of CR are mediated through enhanced autophagy and/or activation of key metabolic sensors SIRT1, AMP-kinase and PGC-1α.

METHODS

Six- to seven-week-old Wistar rats were divided into three groups: (i) sham-operated group; (ii) I/R group (40-min ischaemia followed by 24 h of reperfusion); and (iii) I/R group kept under CR (energy intake 70%) for 2 weeks before surgery. In additional experiments, sirtinol and 3-methyladenine (3-MA) were used as inhibitors of SIRT1 and autophagy respectively. Renal function was measured, and acute tubular damage and nitrotyrosine expression were scored. Kidney adenosine monophosphate-activated kinase (AMPK), SIRT1, eNOS, PGC-1α and LC-3B expressions were measured.

RESULTS

Caloric restriction improved renal function, protected against the development of acute tubular necrosis and attenuated I/R-induced nitrosative stress. Kidney I/R injury decreased eNOS and PGC-1α expression, inhibit autophagy and increased SIRT1 and AMPK expressions by 2.6- and fourfold respectively. However, phosphorylation level of AMPK was decreased. As compared with I/R injury group, CR further increased kidney SIRT1 expression by 1.8-fold, promoted autophagy and counteracted I/R-induced decreases in the expression of eNOS and PGC-1α. 3-MA abolished the renoprotective effects of CR, whereas sirtinol did not influence renal function in CR rats with I/R injury.

CONCLUSIONS

Caloric restriction ameliorates acute kidney I/R injury through enhanced autophagy and counteraction of I/R-induced decreases in the renal expression of eNOS and PGC-1α.

Role of mitochondrial dysfunction and altered autophagy in cardiovascular aging and disease: from mechanisms to therapeutics

Advanced age is associated with a disproportionate prevalence of cardiovascular disease (CVD). Intrinsic alterations in the heart and the vasculature occurring over the life course render the cardiovascular system more vulnerable to various stressors in late life, ultimately favoring the development of CVD. Several lines of evidence indicate mitochondrial dysfunction as a major contributor to cardiovascular senescence. Besides being less bioenergetically efficient, damaged mitochondria also produce increased amounts of reactive oxygen species, with detrimental structural and functional consequences for the cardiovascular system. The age-related accumulation of dysfunctional mitochondrial likely results from the combination of impaired clearance of damaged organelles by autophagy and inadequate replenishment of the cellular mitochondrial pool by mitochondriogenesis. In this review, we summarize the current knowledge about relevant mechanisms and consequences of age-related mitochondrial decay and alterations in mitochondrial quality control in the cardiovascular system. The involvement of mitochondrial dysfunction in the pathogenesis of cardiovascular conditions especially prevalent in late life and the emerging connections with neurodegeneration are also illustrated. Special emphasis is placed on recent discoveries on the role played by alterations in mitochondrial dynamics (fusion and fission), mitophagy, and their interconnections in the context of age-related CVD and endothelial dysfunction. Finally, we discuss pharmacological interventions targeting mitochondrial dysfunction to delay cardiovascular aging and manage CVD.