Contribution of impaired mitochondrial autophagy to cardiac aging: mechanisms and therapeutic opportunities

Testosterone, myocardial function, and mortality

The cardiovascular system is particularly sensitive to androgens, but some controversies exist regarding the effect of testosterone on the heart. While among anabolic abusers, cases of sudden cardiac death have been described, recently it was reported that low serum level of testosterone was correlated with increased risk of cardiovascular diseases (CVD) and mortality rate. This review aims to evaluate the effect of testosterone on myocardial tissue function, coronary artery disease (CAD), and death. Low testosterone level is associated with increased incidence of CAD and mortality. Testosterone administration in hypogonadal elderly men and women has a positive effect on cardiovascular function and improved clinical outcomes and survival time. Although at supraphysiologic doses, androgen may have a toxic effect, and at physiological levels, testosterone is safe and exerts a beneficial effect on myocardial function including mechanisms at cellular and mitochondrial level. The interaction with free testosterone and estradiol should be considered. Further studies are necessary to better understand the interaction mechanisms for an optimal androgen therapy in CVD.

Oxidative stress assessment by glutathione peroxidase activity and glutathione levels in response to selenium supplementation in patients with Mucopolysaccharidosis I, II and VI

We assessed levels of plasma selenium (Se), selenoproteins and their change after Se supplementation in patients with mucopolysaccharidosis (MPS) types I, II and VI. This was done in a retrospective study of the medical records of 30 patients with MPS I (n=13), MPS II (n=9) and MPS VI (n=8) who were being treated with enzyme replacement therapy. As part of routine nutritional monitoring, Se levels were measured, revealing that 28 patients (93.3%) had values below the normal range. Therefore, they received supplementation for 12 months, and Se was measured after 6 and 12 months. Glutathione peroxidase (GPx) activity, total glutathione (GSHt), oxidized glutathione (GSSG) and reduced glutathione (GSH) were measured at baseline and 6 months after Se supplementation. The mean GSHt at baseline was 7.90 ± 2.36 μmol/g Hb, and after Se supplementation it was 5.76 ± 1.13 μmol/g Hb; GSH/GSSG was 2.3 ± 1.16 at baseline and 0.58 ± 0.38 after supplementation. GPx activity was 16.46 ± 3.31 U/g Hb at baseline and 4.53 ± 4.92 U/g Hb after Se supplementation. The difference was shown to be statistically significant by paired t-test. In conclusion, our study demonstrated that oxidative stress parameters were altered by Se supplementation in patients with MPS I, II and VI who were previously deficient in Se.

Autophagy and cardiac aging

Cardiovascular disease (CVD) is the leading cause of death and the prevalence of CVD dramatically increases with age. Cardiac aging is associated with hypertrophy, fibrosis, inflammation, and decreased contractility. Autophagy, a bulk degradation/recycling system, is essential to maintain cellular homeostasis. Cardiac autophagy is decreased with age, and misfolded proteins and dysfunctional mitochondria are accumulated in the aging heart. Inhibition of autophagy leads to exacerbated cardiac aging, while stimulation of autophagy improves cardiac function and also increases lifespan in many organisms. Thus autophagy represents a potential therapeutic target for aging-related cardiac dysfunction. This review discusses recent progress in our understanding of the role and regulation of autophagy in the aging heart.

Oxidative stress mediated by lipid metabolism contributes to high glucose-induced senescence in retinal pigment epithelium

Retinal pigment epithelium (RPE) dysfunction is thought to increase the risk of the development and progression of diabetic retinopathy (DR), the leading cause of blindness. However, the molecular mechanism behind high glucose-induced RPE cell damage is still blurred. We reported that ARPE-19 exposed to 25 mM glucose for 48 h did not induce apoptosis, but senescence validated by SA-β-Gal staining, p21 expression and cell cycle distribution. High glucose also increased oxidant species that exerted a pivotal role in senescence, which could be relieved by the treatment with antioxidant N-acetylcysteine (NAC). The accumulation of lipid droplets and the increase of lipid oxidation were also observed in ARPE-19 treated with high glucose. And the supplementation of free fatty acids (FFAs) indicated that lipid metabolism was associated with the generation of hydrogen peroxide (H₂O₂) and subsequent senescence in ARPE-19. PI3K/Akt/mTOR signaling pathway was shown to be responsible for the accumulation of intracellular lipids by regulating fatty acid synthesis, which in turn controlled senescence. Furthermore, high glucose induced autophagy in ARPE-19 with the treatment of glucose for 48 h, and autophagy inhibitor hydroxychloroquine (HCQ) or bafilomycin further aggravated the senescence, accompanying by an increase in oxidant species. Whereas, prolonged high glucose exposure inhibited autophagy and increased apoptotic cells. Experiments above provide evidence that lipid metabolism plays an important role in oxidative stressed senescence of RPE.

Therapeutic Potential and Effective Components of the Chinese Herb Gardeniae Fructus in the Treatment of Senile Disease

Gardeniae fructus (GF), an evergreen Rubiaceae shrub, is one of the most commonly used Chinese herbs in traditional Chinese medicine (TCM) and has been used for over a thousand years. It is usually prescribed for the treatment of brain aging, vascular aging, bone and joint aging, and other age-related diseases. It has been demonstrated that several effective compounds of GF, such as geniposide, genipin and crocin, have neuroprotective or related activities which are involved in senile disease treatment. These bioactivities include the mitochondrion dysfunction, antioxidative activity, apoptosis regulation and an anti-inflammatory activity, which related to multiple signaling pathways such as the nuclear factor-κB pathway, AMP-activated protein kinase signaling pathway, and the mitogen-activated protein kinase pathway. To lay the ground for fully elucidating the potential mechanisms of GF in treating age-related pathologies, we summarized the available research conducted in the last fifteen years about GF and its effective components, which have been studied in vivo and in vitro

Immunization with plasmids encoding M2 acetylcholine muscarinic receptor epitopes impairs cardiac function in mice and induces autophagy in the myocardium

Autoantibodies against the M2 subtype of muscarinic acetylcholine receptors with functional activities have been found in the sera of patients with dilated cardiomyopathy (DCM), and the second extracellular loop has been established as the predominant epitope. However, it has been shown that the third intracellular loop is recognized by Chagas disease patients with severe cardiac dysfunction. In this work, BALB/c mice were immunized with plasmids encoding these two epitopes, and a control group received the empty plasmid (pcDNA3 vector). Serum from these DNA-immunized animals had elevated and persistent titres of antibodies against respective antigens. Heart echocardiography indicated diminished left ventricular wall thickness and reduced ejection fraction for both epitope-immunized groups, and ergospirometry tests showed a significant decrease in the exercise time and oxygen consumption. Transfer of serum from these immunized mice into naïve recipients induced the same alterations in cardiac structure and function. Furthermore, electron microscopy analysis of donor-immunized animals revealed several ultrastructural alterations suggestive of autophagy and mitophagy, suggesting novel roles for these autoantibodies. Overall, greater functional and structural impairment was observed in the donor and recipient epitope groups, implicating the third intracellular loop epitope in the pathological effects for the first-time. Therefore, the corresponding peptides could be useful for autoimmune DCM diagnosis and targeted therapy.

Mitochondrial quality control in cardiac cells: Mechanisms and role in cardiac cell injury and disease

Mitochondria play an important role in maintaining cardiac homeostasis by supplying the major energy required for cardiac excitation-contraction coupling as well as controlling the key intracellular survival and death pathways. Healthy mitochondria generate ATP molecules through an aerobic process known as oxidative phosphorylation (OXPHOS). Mitochondrial injury during myocardial infarction (MI) impairs OXPHOS and results in the excessive production of reactive oxygen species (ROS), bioenergetic insufficiency, and contributes to the development of cardiovascular diseases. Therefore, mitochondrial biogenesis along with proper mitochondrial quality control machinery, which removes unhealthy mitochondria is pivotal for mitochondrial homeostasis and cardiac health. Upon damage to the mitochondrial network, mitochondrial quality control components are recruited to segregate the unhealthy mitochondria and target aberrant mitochondrial proteins for degradation and elimination. Impairment of mitochondrial quality control and accumulation of abnormal mitochondria have been reported in the pathogenesis of various cardiac disorders and heart failure. Here, we provide an overview of the recent studies describing various mechanistic pathways underlying mitochondrial homeostasis with the main focus on cardiac cells. In addition, this review demonstrates the potential effects of mitochondrial quality control dysregulation in the development of cardiovascular disease.

Postmitotic cell longevity-associated genes: a transcriptional signature of postmitotic maintenance in neural tissues

Different cell types have different postmitotic maintenance requirements. Nerve cells, however, are unique in this respect as they need to survive and preserve their functional complexity for the entire lifetime of the organism, and failure at any level of their supporting mechanisms leads to a wide range of neurodegenerative conditions. Whether these differences across tissues arise from the activation of distinct cell type-specific maintenance mechanisms or the differential activation of a common molecular repertoire is not known. To identify the transcriptional signature of postmitotic cellular longevity (PMCL), we compared whole-genome transcriptome data from human tissues ranging in longevity from 120 days to over 70 years and found a set of 81 genes whose expression levels are closely associated with increased cell longevity. Using expression data from 10 independent sources, we found that these genes are more highly coexpressed in longer-living tissues and are enriched in specific biological processes and transcription factor targets compared with randomly selected gene samples. Crucially, we found that PMCL-associated genes are downregulated in the cerebral cortex and substantia nigra of patients with Alzheimer's and Parkinson's disease, respectively, as well as Hutchinson-Gilford progeria-derived fibroblasts, and that this downregulation is specifically linked to their underlying association with cellular longevity. Moreover, we found that sexually dimorphic brain expression of PMCL-associated genes reflects sexual differences in lifespan in humans and macaques. Taken together, our results suggest that PMCL-associated genes are part of a generalized machinery of postmitotic maintenance and functional stability in both neural and non-neural cells and support the notion of a common molecular repertoire differentially engaged in different cell types with different survival requirements.

Conditioning-induced cardioprotection: Aging as a confounding factor

The aging process induces a plethora of changes in the body including alterations in hormonal regulation and metabolism in various organs including the heart. Aging is associated with marked increase in the vulnerability of the heart to ischemia-reperfusion injury. Furthermore, it significantly hampers the development of adaptive response to various forms of conditioning stimuli (pre/post/remote conditioning). Aging significantly impairs the activation of signaling pathways that mediate preconditioning-induced cardioprotection. It possibly impairs the uptake and release of adenosine, decreases the number of adenosine transporter sites and down-regulates the transcription of adenosine receptors in the myocardium to attenuate adenosine-mediated cardioprotection. Furthermore, aging decreases the expression of peroxisome proliferator-activated receptor gamma co-activator 1-alpha (PGC-1α) and subsequent transcription of catalase enzyme which subsequently increases the oxidative stress and decreases the responsiveness to preconditioning stimuli in the senescent diabetic hearts. In addition, in the aged rat hearts, the conditioning stimulus fails to phosphorylate Akt kinase that is required for mediating cardioprotective signaling in the heart. Moreover, aging increases the concentration of Na⁺ and K⁺, connexin expression and caveolin abundance in the myocardium and increases the susceptibility to ischemia-reperfusion injury. In addition, aging also reduces the responsiveness to conditioning stimuli possibly due to reduced kinase signaling and reduced STAT-3 phosphorylation. However, aging is associated with an increase in MKP-1 phosphorylation, which dephosphorylates (deactivates) mitogen activated protein kinase that is involved in cardioprotective signaling. The present review describes aging as one of the major confounding factors in attenuating remote ischemic preconditioning-induced cardioprotection along with the possible mechanisms.

Autophagy as a promoter of longevity: insights from model organisms

Autophagy is a conserved process that catabolizes intracellular components to maintain energy homeostasis and to protect cells against stress. Autophagy has crucial roles during development and disease, and evidence accumulated over the past decade indicates that autophagy also has a direct role in modulating ageing. In particular, elegant studies using yeasts, worms, flies and mice have demonstrated a broad requirement for autophagy-related genes in the lifespan extension observed in a number of conserved longevity paradigms. Moreover, several new and interesting concepts relevant to autophagy and its role in modulating longevity have emerged. First, select tissues may require or benefit from autophagy activation in longevity paradigms, as tissue-specific overexpression of single autophagy genes is sufficient to extend lifespan. Second, selective types of autophagy may be crucial for longevity by specifically targeting dysfunctional cellular components and preventing their accumulation. And third, autophagy can influence organismal health and ageing even non-cell autonomously, and thus, autophagy stimulation in select tissues can have beneficial, systemic effects on lifespan. Understanding these mechanisms will be important for the development of approaches to improve human healthspan that are based on the modulation of autophagy.

AMP-Activated Protein Kinase as a Reprogramming Strategy for Hypertension and Kidney Disease of Developmental Origin

Suboptimal early-life conditions affect the developing kidney, resulting in long-term programming effects, namely renal programming. Adverse renal programming increases the risk for developing hypertension and kidney disease in adulthood. Conversely, reprogramming is a strategy aimed at reversing the programming processes in early life. AMP-activated protein kinase (AMPK) plays a key role in normal renal physiology and the pathogenesis of hypertension and kidney disease. This review discusses the regulation of AMPK in the kidney and provides hypothetical mechanisms linking AMPK to renal programming. This will be followed by studies targeting AMPK activators like metformin, resveratrol, thiazolidinediones, and polyphenols as reprogramming strategies to prevent hypertension and kidney disease. Further studies that broaden our understanding of AMPK isoform- and tissue-specific effects on renal programming are needed to ultimately develop reprogramming strategies. Despite the fact that animal models have provided interesting results with regard to reprogramming strategies targeting AMPK signaling to protect against hypertension and kidney disease with developmental origins, these results await further clinical translation.

"Triple-Punch" Anticancer Strategy Mediated by Near-Infrared Photosensitizer/CpG Oligonucleotides Dual-Dressed and Mitochondria-Targeted Nanographene

Nanomedicine-based combination therapy has sparked a growing interest in clinical disease treatment and pharmaceutical industry. In this study, a mitochondria-targeted and near-infrared (NIR) light-activable multitasking nanographene (i.e., GT/IR820/DP-CpG) was engineered to in situ trigger highly efficient "triple-punch" strategy of cancer photodynamic therapy, photothermal therapy, and immunotherapy. Modification of triphenylphosphonium on graphene made the vehicle specifically guide the NIR dye IR820 home to mitochondria, followed by lysosomes escape in a time-dependent manner. The photoactive nanocomplex generated an abundant reactive oxygen species as well as photothermal heat to ultimately kill cancer cells by inducing mitochondrial collapse and irreversible cell apoptosis upon the NIR laser irradiation. Further introduction of an immunostimulatory conjugate DP-CpG significantly promoted the secretion of proinflammatory cytokines (i.e., interleukin-6, tumor necrosis factor-α, and interferon-γ) and thus improved the immunogenicity of tumors. In vivo studies demonstrated that GT/IR820/DP-CpG remarkably inhibited tumor growth (tumor inhibition rate, ∼88%) resulting from the combinational phototherapeutic effect of IR820 and immunostimulatory activity of DP-CpG, thereby causing negligible toxic effects on mice. Our work provides a new paradigm of architecting organelle-targeted and stimulative nanocomplex for highly efficient cancer photoimmunotherapy.

Mitochondrial oxidative stress and cardiac ageing

According with different international organizations, cardiovascular diseases are becoming the first cause of death in western countries. Although exposure to different risk factors, particularly those related to lifestyle, contribute to the etiopathogenesis of cardiac disorders, the increase in average lifespan and aging are considered major determinants of cardiac diseases events. Mitochondria and oxidative stress have been pointed out as relevant factors both in heart aging and in the development of cardiac diseases such as heart failure, cardiac hypertrophy and diabetic cardiomyopathy. During aging, cellular processes related with mitochondrial function, such as bioenergetics, apoptosis and inflammation are altered leading to cardiac dysfunction. Increasing our knowledge about the mitochondrial mechanisms related with the aging process, will provide new strategies in order to improve this process, particularly the cardiovascular ones.

NIPAAm-MMA nanoparticle-encapsulated visnagin ameliorates myocardial ischemia/reperfusion injury through the promotion of autophagy and the inhibition of apoptosis

The main method for the treatment of acute myocardial infarction (AMI) is percutaneous coronary intervention; however percutaneous coronary intervention will induce ischemia/reperfusion (IR) injury, resulting in the loss of cardiac function and cardiomyocyte death. An effective drug to target this condition is necessary. N-isopropylacrylamide and methacrylic acid were used to synthesize drug delivery nanoparticles (NP) containing the natural compound visnagin for IR injury treatment. It was demonstrated that NP containing fluorescein isothiocyanate localized to the site of myocardial IR, and that NP-visnagin treatment induced cardioprotection, reducing the size of the MI and ameliorating cardiac dysfunction through the induction of autophagy and the inhibition of apoptosis. In the future, visnagin may be suitable as a drug for IR injury treatment, and NP may be an effective drug delivery system.

Mitochondria as pharmacological targets in Down syndrome

Mitochondria play a pivotal role in cellular energy-generating processes and are considered master regulators of cell life and death fate. Mitochondrial function integrates signalling networks in several metabolic pathways controlling neurogenesis and neuroplasticity. Indeed, dysfunctional mitochondria and mitochondrial-dependent activation of intracellular stress cascades are critical initiating events in many human neurodegenerative or neurodevelopmental diseases including Down syndrome (DS). It is well established that trisomy of human chromosome 21 can cause DS. DS is associated with neurodevelopmental delay, intellectual disability and early neurodegeneration. Recently, molecular mechanisms responsible for mitochondrial damage and energy deficits have been identified and characterized in several DS-derived human cells and animal models of DS. Therefore, therapeutic strategies targeting mitochondria could have great potential for new treatment regimens in DS. The purpose of this review is to highlight recent studies concerning mitochondrial impairment in DS, focusing on alterations of the molecular pathways controlling mitochondrial function. We will also discuss the effects and molecular mechanisms of naturally occurring and chemically synthetized drugs that exert neuroprotective effects through modulation of mitochondrial function and attenuation of oxidative stress. These compounds might represent novel therapeutic tools for the modulation of energy deficits in DS.

Impact of age on the association between cardiac high-energy phosphate metabolism and cardiac power in women

OBJECTIVE

Diminished cardiac high-energy phosphate metabolism (phosphocreatine-to-ATP (PCr:ATP) ratio) and cardiac power with age may play an important roles in development of cardiac dysfunction and heart failure. The study defines the impact of age on PCr:ATP ratio and cardiac power and their relationship.

METHODS

Thirty-five healthy women (young≤50 years, n=20; and old≥60 years, n=15) underwent cardiac MRI with 31P spectroscopy to assess PCr:ATP ratio and performed maximal graded cardiopulmonary exercise testing with simultaneous gas-exchange and central haemodynamic measurements. Peak cardiac power output, as the best measure of pumping capability and performance of the heart, was calculated as the product of peak exercise cardiac output and mean arterial blood pressure.

RESULTS

PCr:ATP ratio was significantly lower in old compared with young age group (1.92±0.48 vs 2.29±0.55, p=0.03), as were peak cardiac power output (3.35±0.73 vs 4.14±0.81W, p=0.01), diastolic function (ie, early-to-late diastolic filling ratio, 1.33±0.54 vs 3.07±1.84, p<0.01) and peak exercise oxygen consumption (1382.9±255.0 vs 1940.3±434.4 mL/min, p<0.01). Further analysis revealed that PCr:ATP ratio shows a significant positive relationship with early-to-late diastolic filling ratio (r=0.46, p=0.02), peak cardiac power output (r=0.44, p=0.02) and peak oxygen consumption (r=0.51, p=0.01).

CONCLUSIONS

High-energy phosphate metabolism and peak power of the heart decline with age. Significant positive relationship between PCr:ATP ratio, early-to-late diastolic filling ratio and peak cardiac power output suggests that cardiac high-energy phosphate metabolism may be an important determinant of cardiac function and performance.

The spectrum of myocardial homeostasis mechanisms in the settings of cardiac surgery procedures (Review)

Classic cardiac surgery, determined through the function of cardiopulmonary bypass machine and myocardial cardioplegic arrest, represents the most controlled scenario for cardiomyocyte homeostatic disturbances due to systemic inflammatory response and myocardial reperfusion injury. An increasing number of studies have demonstrated that myocardial cell homeostasis in cardiac surgery procedures is a sequence of molecularly interrelated and overlapping mechanisms in the form of apoptosis, autophagy and necrosis, which are activated by a plethora of induced inflammatory mediators and gene-related signaling pathways. In this study, we outline the molecular mechanisms of the cardiomyocyte adaptive homeostatic process and the associated clinical implications, in the settings of classic cardiac surgery procedures.

Resveratrol Ameliorates Mitochondrial Elongation via Drp1/Parkin/PINK1 Signaling in Senescent-Like Cardiomyocytes

Resveratrol is widely known for its antiaging properties and exerts cardiovascular protective effects in different experimental models. The role of resveratrol in regulating mitochondrial functions and dynamics during the cardiac aging process remains poorly understood. In this study, the effects of resveratrol on mitochondrial morphology and mitochondrial depolarization and on expressions of Drp1, parkin, PINK1, and LC3 were investigated in H9c2 cells after D-galactose treatment that induced senescent-like cardiomyocytes. The results show that downregulation of Drp1 markedly increased mitochondrial elongation. Senescent-like cardiomyocytes were more resistant to CCCP-induced mitochondrial depolarization, which was accompanied by suppressed expression of parkin, PINK1, and LC3-II. Resveratrol treatment significantly increased Drp1 expression, ameliorated mitochondrial elongation, and increased the mitochondrial translocations of parkin and PINK1. In addition, resveratrol significantly enhanced LC3-II expression and decreased TOM20-labeled mitochondrial content. Resveratrol also suppressed the phosphorylation of parkin and PINK1, which may relate to its abilities to degrade the impaired mitochondria in senescent-like cardiomyocytes. These findings show that suppressing mitochondrial elongation in a Drp1-dependent manner is involved in the effect of resveratrol on attenuating the development of aging cardiomyocytes. Activation of parkin and PINK1 may be a potential mechanism of resveratrol for treating cardiovascular complications related to aging.

Florfenicol-induced Mitochondrial Dysfunction Suppresses Cell Proliferation and Autophagy in Fibroblasts

Florfenicol (FLO) is one of the most popular antibiotics used in veterinary clinic and aquaculture. FLO can inhibit both bacterial and mitochondrial protein synthesis. However, the effects of FLO on mitochondrial function and cellular homeostasis remain unclear. Here we show that FLO inhibits expression of mitochondrial DNA-encoded proteins, decreases mitochondrial membrane potential, and promotes generation of reactive oxygen species (ROS) in vitro. As a result, activities of mitochondrial respiratory chain complex I and IV and the cellular ATP level are decreased and mitochondrial morphology is damaged. FLO represses cell growth and proliferation by suppression of phosphorylation of p70S6K through AMPK/mTOR/p70S6K pathway. Furthermore, FLO also induces G0/G1 cell cycle arrest via increase of p21 levels through activating ROS/p53/p21 pathway. Moreover, the clearance of damaged mitochondria by autophagy is impaired, leading to cell proliferation inhibition and promotes cell senescence. In addition, FLO-induced upregulation of cytosolic p53 may contribute to mitophagy deficiency via regulation of Parkin recruitment. In summary, our data suggest that florfenicol is an inhibitor of mitochondrial protein synthesis that can induce noticeable cytotoxicity. Thus, these findings can be useful for guiding the proper use of FLO and the development of safe drugs.

Cardiac fibrosis in the ageing heart: Contributors and mechanisms

Cardiac fibrosis refers to an excessive deposition of extracellular matrix (ECM) in cardiac tissue. Fibrotic tissue is stiffer and less compliant, resulting in subsequent cardiac dysfunction and heart failure. Cardiac fibrosis in the ageing heart may involve activation of fibrogenic signalling and inhibition of anti-fibrotic signalling, leading to an imbalance of ECM turnover. Excessive accumulation of ECM such as collagen in older patients contributes to progressive ventricular dysfunction. Overexpression of collagen is derived from various sources, including higher levels of fibrogenic growth factors, proliferation of fibroblasts and cellular transdifferentiation. These may be triggered by factors, such as oxidative stress, inflammation, hypertension, cellular senescence and cell death, contributing to age-related fibrotic cardiac remodelling. In this review, we will discuss the fibrogenic contributors in age-related cardiac fibrosis, and the potential mechanisms by which fibrogenic processes can be interrupted for therapeutic intent.

Yoder M, Majluf-Cruz A, Alvarado-Moreno JA. Reduced proliferation of endothelial colony-forming cells in unprovoked venous thromboembolic disease as a consequence of endothelial dysfunction

BACKGROUND

Venous thromboembolic disease (VTD) is a public health problem. We recently reported that endothelial colony-forming cells (ECFCs) derived from endothelial cells (EC) (ECFC-ECs) from patients with VTD have a dysfunctional state. For this study, we proposed that a dysfunctional status of these cells generates a reduction of its proliferative ability, which is also associated with senescence and reactive oxygen species (ROS).

METHODS AND RESULTS

Human mononuclear cells (MNCs) were obtained from peripheral blood from 40 healthy human volunteers (controls) and 50 patients with VTD matched by age (20-50 years) and sex to obtain ECFCs. We assayed their proliferative ability with plasma of patients and controls and supernatants of cultures from ECFC-ECs, senescence-associated β-galactosidase (SA-β-gal), ROS, and expression of ephrin-B2/Eph-B4 receptor. Compared with cells from controls, cells from VTD patients showed an 8-fold increase of ECFCs that emerged 1 week earlier, reduced proliferation at long term (39%) and, in passages 4 and 10, a highly senescent rate (30±1.05% vs. 91.3±15.07%, respectively) with an increase of ROS and impaired expression of ephrin-B2/Eph-4 genes. Proliferation potential of cells from VTD patients was reduced in endothelial medium [1.4±0.22 doubling population (DP)], control plasma (1.18±0.31 DP), or plasma from VTD patients (1.65±0.27 DP).

CONCLUSIONS

As compared with controls, ECFC-ECs from individuals with VTD have higher oxidative stress, proliferation stress, cellular senescence, and low proliferative potential. These findings suggest that patients with a history of VTD are ECFC-ECs dysfunctional that could be associated to permanent risk for new thrombotic events.

Insulin-like growth factor-1 signaling in cardiac aging

Cardiovascular disease (CVD) is the leading cause of death in most developed countries. Aging is associated with enhanced risk of CVD. Insulin-like growth factor-1 (IGF-1) binds to its cognate receptor, IGF-1 receptor (IGF-1R), and exerts pleiotropic effects on cell growth, differentiation, development, and tissue repair. Importantly, IGF-1/IGF-1R signaling is implicated in cardiac aging and longevity. Cardiac aging is an intrinsic process that results in cardiac dysfunction, accompanied by molecular and cellular changes. In this review, we summarize the current state of knowledge regarding the link between the IGF-1/IGF-1R system and cardiac aging. The biological effects of IGF-1R and insulin receptor will be discussed and compared. Furthermore, we describe data regarding how deletion of IGF-1R in cardiomyocytes of aged knockout mice may delay the development of senescence-associated myocardial pathologies. This article is part of a Special issue entitled Cardiac adaptations to obesity, diabetes and insulin resistance, edited by Professors Jan F.C. Glatz, Jason R.B. Dyck and Christine Des Rosiers.

Berberine-induced cardioprotection and Sirt3 modulation in doxorubicin-treated H9c2 cardiomyoblasts

Doxorubicin (DOX) is one of the most widely used anti-neoplastic agents. However, treatment with DOX is associated with cumulative cardiotoxicity inducing progressive cardiomyocyte death. Sirtuin 3 (Sirt3), a mitochondrial deacetylase, regulates the activity of proteins involved in apoptosis, autophagy and metabolism. Our hypothesis is that pharmacological modulation by berberine (BER) pre-conditioning of Sirt3 protein levels decreases DOX-induced cardiotoxicity. Our results showed that DOX induces cell death in all experimental groups. Increase in Sirt3 content by transfection-mediated overexpression decreased DOX cytotoxicity, mostly by maintaining mitochondrial network integrity and reducing oxidative stress. p53 was upregulated by DOX, and appeared to be a direct target of Sirt3, suggesting that Sirt3-mediated protection against cell death could be related to this protein. BER pre-treatment increased Sirt3 and Sirt1 protein levels in the presence of DOX and inhibited DOX-induced caspase 9 and 3-like activation. Moreover, BER modulated autophagy in DOX-treated H9c2 cardiomyoblasts. Interestingly, mitochondrial biogenesis markers were upregulated in in BER/DOX-treated cells. Sirt3 over-expression contributes to decrease DOX cytotoxicity on H9c2 cardiomyoblasts, while BER can be used as a modulator of Sirtuin function and cell quality control pathways to decrease DOX toxicity.

[Myocardial fibrosis: Current aspects of the problem]

Fibrosis is one of the main components in the progression of most cardiovascular diseases, including coronary heart disease, by causing structural changes in the myocardium and vascular wall. The quantitative and qualitative characteristics of fibrosis of the myocardium are responsible for decreasing its elastic properties, developing diastolic dysfunction, impairing myocardial contractility, developing systolic dysfunction and cardiac arrhythmias, and worsening coronary blood flow in patients with heart failure of different etiologies. The important aspect of studying fibrosis is not only its interpretation as a model of the typical pathological process, but also its consideration as a systemic lesion of various organs and tissues. At the same time, the identification of myocardial fibrosis biomarkers that are available for their determination in circulating blood is of particular interest. Since there was evidence for the role of fibrosis in developing dysfunction of various organs and ensuring the systematicity of most diseases, especially at their development stages, the process of fibrosis came to be regarded as a promising therapeutic target. It is relevant to further investigate myocardial fibrosis, which is aimed at increasing the efficiency of its diagnosis and predicting its course and pathogenetically sound therapy.

Mitochondria and ageing: role in heart, skeletal muscle and adipose tissue

Age is the most important risk factor for most diseases. Mitochondria play a central role in bioenergetics and metabolism. In addition, several lines of evidence indicate the impact of mitochondria in lifespan determination and ageing. The best-known hypothesis to explain ageing is the free radical theory, which proposes that cells, organs, and organisms age because they accumulate reactive oxygen species (ROS) damage over time. Mitochondria play a central role as the principle source of intracellular ROS, which are mainly formed at the level of complex I and III of the respiratory chain. Dysfunctional mitochondria generating less ATP have been observed in various aged organs. Mitochondrial dysfunction comprises different features including reduced mitochondrial content, altered mitochondrial morphology, reduced activity of the complexes of the electron transport chain, opening of the mitochondrial permeability transition pore, and increased ROS formation. Furthermore, abnormalities in mitochondrial quality control or defects in mitochondrial dynamics have also been linked to senescence. Among the tissues affected by mitochondrial dysfunction are those with a high-energy demand and thus high mitochondrial content. Therefore, the present review focuses on the impact of mitochondria in the ageing process of heart and skeletal muscle. In this article, we review different aspects of mitochondrial dysfunction and discuss potential therapeutic strategies to improve mitochondrial function. Finally, novel aspects of adipose tissue biology and their involvement in the ageing process are discussed.

Pathophysiology of heart failure and frailty: a common inflammatory origin?

Frailty, a clinical syndrome that typically occurs in older adults, implies a reduced ability to tolerate biological stressors. Frailty accompanies many age‐related diseases but can also occur without overt evidence of end‐organ disease. The condition is associated with circulating inflammatory cytokines and sarcopenia, features that are shared with heart failure (HF). However, the biological underpinnings of frailty remain unclear and the interaction with HF is complex. Here, we describe the inflammatory pathophysiology that is associated with frailty and speculate that the inflammation that occurs with frailty shares common origins with HF. We discuss the limitations in investigating the pathophysiology of frailty due to few relevant experimental models. Leveraging current therapies for advanced HF and current known therapies to address frailty in humans may enable translational studies to better understand the inflammatory interactions between frailty and HF.

Evidence that a mitochondrial death spiral underlies antagonistic pleiotropy

The antagonistic pleiotropy (AP) theory posits that aging occurs because alleles that are detrimental in older organisms are beneficial to growth early in life and thus are maintained in populations. Although genes of the insulin signaling pathway likely participate in AP, the insulin‐regulated cellular correlates of AP have not been identified. The mitochondrial quality control process called mitochondrial autophagy (mitophagy), which is inhibited by insulin signaling, might represent a cellular correlate of AP. In this view, rapidly growing cells are limited by ATP production; these cells thus actively inhibit mitophagy to maximize mitochondrial ATP production and compete successfully for scarce nutrients. This process maximizes early growth and reproduction, but by permitting the persistence of damaged mitochondria with mitochondrial DNA mutations, becomes detrimental in the longer term. I suggest that as mitochondrial ATP output drops, cells respond by further inhibiting mitophagy, leading to a further decrease in ATP output in a classic death spiral. I suggest that this increasing ATP deficit is communicated by progressive increases in mitochondrial ROS generation, which signals inhibition of mitophagy via ROS‐dependent activation of insulin signaling. This hypothesis clarifies a role for ROS in aging, explains why insulin signaling inhibits autophagy, and why cells become progressively more oxidized during aging with increased levels of insulin signaling and decreased levels of autophagy. I suggest that the mitochondrial death spiral is not an error in cell physiology but rather a rational approach to the problem of enabling successful growth and reproduction in a competitive world of scarce nutrients.

Postnatal Hyperoxia Exposure Durably Impairs Right Ventricular Function and Mitochondrial Biogenesis

Prematurity complicates 12% of births, and young adults with a history of prematurity are at risk to develop right ventricular (RV) hypertrophy and impairment. The long-term risk for pulmonary vascular disease, as well as mechanisms of RV dysfunction and ventricular-vascular uncoupling after prematurity, remain poorly defined. Using an established model of prematurity-related lung disease, pups from timed-pregnant Sprague Dawley rats were randomized to normoxia or hyperoxia (fraction of inspired oxygen, 0.85) exposure for the first 14 days of life. After aging to 1 year in standard conditions, rats underwent hemodynamic assessment followed by tissue harvest for biochemical and histological evaluation. Aged hyperoxia-exposed rats developed significantly greater RV hypertrophy, associated with a 40% increase in RV systolic pressures. Although cardiac index was similar, hyperoxia-exposed rats demonstrated a reduced RV ejection fraction and significant RV-pulmonary vascular uncoupling. Hyperoxia-exposed RV cardiomyocytes demonstrated evidence of mitochondrial dysregulation and mitochondrial DNA damage, suggesting potential mitochondrial dysfunction as a cause of RV dysfunction. Aged rats exposed to postnatal hyperoxia recapitulate many features of young adults born prematurely, including increased RV hypertrophy and decreased RV ejection fraction. Our data suggest that postnatal hyperoxia exposure results in mitochondrial dysregulation that persists into adulthood with eventual RV dysfunction. Further evaluation of long-term mitochondrial function is warranted in both animal models of premature lung disease and in human adults who were born preterm.

Interplay between Oxidative Stress and Nutrient Sensing Signaling in the Developmental Origins of Cardiovascular Disease

Cardiovascular disease (CVD) presents a global health burden, despite recent advances in management. CVD can originate from early life by so-called “developmental origins of health and disease” (DOHaD). Epidemiological and experimental evidence supports that early-life insults can induce programming of later CVD. Underlying the DOHaD concept, early intervention may offset programming process to prevent the development of CVD, namely reprogramming. Oxidative stress and nutrient sensing signals have been considered to be major mechanisms of cardiovascular programming, while the interplay between these two mechanisms have not been examined in detail. This review summarizes current evidence that supports the link between oxidative stress and nutrient sensing signaling to cardiovascular programming, with an emphasis on the l-arginine–asymmetric dimethylarginine (ADMA)–nitric oxide (NO) pathway. This review provides an overview of evidence from human studies supporting fetal programming of CVD, insight from animal models of cardiovascular programming and oxidative stress, impact of the l-arginine–ADMA–NO pathway in cardiovascular programming, the crosstalk between l-arginine metabolism and nutrient sensing signals, and application of reprogramming interventions to prevent the programming of CVD. A greater understanding of the mechanisms underlying cardiovascular programming is essential to developing early reprogramming interventions to combat the globally growing epidemic of CVD.

MiRNA Deregulation in Cardiac Aging and Associated Disorders

The prevalence of age-related diseases is increasing dramatically, among which cardiac disease represents the leading cause of death. Aging of the heart is characterized by various molecular and cellular hallmarks impairing both cardiomyocytes and noncardiomyocytes, and resulting in functional deteriorations of the cardiac system. The aging process includes desensitization of β-adrenergic receptor (βAR)-signaling and decreased calcium handling, altered growth signaling and cardiac hypertrophy, mitochondrial dysfunction and impaired autophagy, increased programmed cell death, low-grade inflammation of noncanonical inflammatory cells, and increased ECM deposition. MiRNAs play a fundamental role in regulating the processes underlying these detrimental changes in the cardiac system, indicating that MiRNAs are crucially involved in aging. Among others, MiR-34, MiR-146a, and members of the MiR-17-92 cluster, are deregulated during senescence and drive cardiac aging processes. It is therefore suggested that MiRNAs form possible therapeutic targets to stabilize the aged failing myocardium.

[Autophagy in the cardiovascular system]

Cardiovascular diseases are the leading cause of mortality worldwide. Studies regarding the role of autophagy in cardiac and vascular tissues have opened new therapeutic avenues to treat cardiovascular disorders. Altogether, these studies point out that autophagic activity needs to be maintained at an optimal level to preserve cardiovascular function. Reaching this goal constitutes a challenge for future efficient therapeutic strategies. The present review therefore highlights recent advances in the understanding of the role of autophagy in cardiovascular pathologies.

Complex inhibition of autophagy by mitochondrial aldehyde dehydrogenase shortens lifespan and exacerbates cardiac aging

Autophagy, a conservative degradation process for long-lived and damaged proteins, participates in a cascade of biological processes including aging. A number of autophagy regulators have been identified. Here we demonstrated that mitochondrial aldehyde dehydrogenase (ALDH2), an enzyme with the most common single point mutation in humans, governs cardiac aging through regulation of autophagy. Myocardial mechanical and autophagy properties were examined in young (4months) and old (26-28months) wild-type (WT) and global ALDH2 transgenic mice. ALDH2 overexpression shortened lifespan by 7.7% without affecting aging-associated changes in plasma metabolic profiles. Myocardial function was compromised with aging associated with cardiac hypertrophy, the effects were accentuated by ALDH2. Aging overtly suppressed autophagy and compromised autophagy flux, the effects were exacerbated by ALDH2. Aging dampened phosphorylation of JNK, Bcl-2, IKKβ, AMPK and TSC2 while promoting phosphorylation of mTOR, the effects of which were exaggerated by ALDH2. Co-immunoprecipitation revealed increased dissociation between Bcl-2 and Beclin-1 (result of decreased Bcl-2 phosphorylation) in aging, the effect of which was exacerbated with ALDH2. Chronic treatment of the autophagy inducer rapamycin alleviated aging-induced cardiac dysfunction in both WT and ALDH2 mice. Moreover, activation of JNK and inhibition of either Bcl-2 or IKKβ overtly attenuated ALDH2 activation-induced accentuation of cardiomyocyte aging. Examination of the otherwise elderly individuals revealed a positive correlation between cardiac function/geometry and ALDH2 gene mutation. Taken together, our data revealed that ALDH2 enzyme may suppress myocardial autophagy possibly through a complex JNK-Bcl-2 and IKKβ-AMPK-dependent mechanism en route to accentuation of myocardial remodeling and contractile dysfunction in aging. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure - edited by Jun Ren & Megan Yingmei Zhang.

TLR4 knockout attenuated high fat diet-induced cardiac dysfunction via NF-κB/JNK-dependent activation of autophagy

Obesity is commonly associated with a low grade systemic inflammation, which may contribute to the onset and development of myocardial remodeling and contractile dysfunction. Toll-like receptor 4 (TLR4) plays an important role in innate immunity and inflammation although its role in high fat diet-induced obesity cardiac dysfunction remains elusive. This study was designed to examine the effect of TLR4 ablation on high fat diet intake-induced cardiac anomalies, if any, and underlying mechanism(s) involved. Wild-type (WT) and TLR4 knockout mice were fed normal or high fat (60% calorie from fat) diet for 12weeks prior to assessment of mechanical and intracellular Ca²⁺ properties. The inflammatory signaling proteins (TLR4, NF-κB, and JNK) and autophagic markers (Atg5, Atg12, LC3B and p62) were evaluated. Our results revealed that high fat diet intake promoted obesity, marked decrease in fractional shortening, and cardiomyocyte contractile capacity with dampened intracellular Ca²⁺ release and clearance, elevated ROS generation and oxidative stress as measured by aconitase activity, the effects of which were significantly attenuated by TLR4 knockout. In addition, high fat intake downregulated levels of Atg5, Atg12 and LC3B, while increasing p62 accumulation. TLR4 knockout itself did not affect Atg5, Atg12, LC3B and p62 levels while it reconciled high fat diet intake-induced changes in autophagy. In addition, TLR4 knockout alleviated high fat diet-induced phosphorylation of IKKβ, JNK and mTOR. In vitro study revealed that palmitic acid suppressed cardiomyocyte contractile function, the effect of which was inhibited the TLR4 inhibitor CLI-095, the JNK inhibitor AS601245 or the NF-κB inhibitor Celastrol. Taken together, these data showed that TLR4 knockout ameliorated high fat diet-induced cardiac contractile and intracellular Ca²⁺ anomalies through inhibition of inflammation and ROS, possibly through a NF-κB/JNK-dependent activation of autophagy. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure - edited by Jun Ren & Megan Yingmei Zhang.

High-Density Lipoprotein Regulation of Mitochondrial Function

Lipoproteins play a key role in regulating plasma and tissue levels of cholesterol. Apolipoprotein B (apoB)-containing lipoproteins, including chylomicrons, very-low density lipoprotein (VLDL) and low-density lipoprotein (LDL), serve as carriers of triglycerides and cholesterol and deliver these metabolites to peripheral tissues. In contrast, high-density lipoprotein (HDL) mediates Reverse Cholesterol Transport (RCT), a process by which excess cholesterol is removed from the periphery and taken up by hepatocytes where it is metabolized and excreted. Anti-atherogenic properties of HDL have been largely ascribed to apoA-I, the major protein component of the lipoprotein particle. The inflammatory response associated with atherosclerosis and ischemia-reperfusion (I-R) injury has been linked to the development of mitochondrial dysfunction. Under these conditions, an increase in reactive oxygen species (ROS) formation induces damage to mitochondrial structural elements, leading to a reduction in ATP synthesis and initiation of the apoptotic program. Recent studies suggest that HDL-associated apoA-I and lysosphingolipids attenuate mitochondrial injury by multiple mechanisms, including the suppression of ROS formation and induction of autophagy. Other apolipoproteins, however, present in lower abundance in HDL particles may exert opposing effects on mitochondrial function. This chapter examines the role of HDL-associated apolipoproteins and lipids in the regulation of mitochondrial function and bioenergetics.

Metabolomic Profiling of Pompe Disease-Induced Pluripotent Stem Cell-Derived Cardiomyocytes Reveals That Oxidative Stress Is Associated with Cardiac and Skeletal Muscle Pathology

Pompe disease (PD) is a lysosomal storage disease that is caused by a deficiency of the acid α‐glucosidase, which results in glycogen accumulation in the lysosome. The major clinical symptoms of PD include skeletal muscle weakness, respiratory failure, and cardiac hypertrophy. Based on its severity and symptom onset, PD is classified into infantile and late‐onset forms. Lysosomal accumulation of glycogen can promote many types of cellular dysfunction, such as autophagic dysfunction, endoplasmic reticulum stress, and abnormal calcium signaling within skeletal muscle. However, the disease mechanism underlying PD cardiomyopathy is not fully understood. Several researchers have shown that PD induced pluripotent stem cell (iPSC)‐derived cardiomyocytes successfully replicate the disease phenotype and are useful disease models. We have analyzed the metabolomic profile of late‐onset PD iPSC‐derived cardiomyocytes and found that oxidative stress and mitochondrial dysfunction are likely associated with cardiac complications. Furthermore, we have validated that these disease‐specific changes were also observed in the cardiomyocytes and skeletal muscle of a genetically engineered murine PD model. Oxidative stress may contribute to skeletal muscle and cardiomyocyte dysfunction in PD mice; however, NF‐E2‐related factor 2 was downregulated in cardiomyocytes and skeletal muscle, despite evidence of oxidative stress. We hypothesized that oxidative stress and an impaired antioxidative stress response mechanism may underlie the molecular pathology of late‐onset PD. Stem Cells Translational Medicine2017;6:31–39

Regulation of autophagy by mitochondrial phospholipids in health and diseases

Autophagy is an evolutionarily conserved mechanism that maintains nutrient homeostasis by degrading protein aggregates and damaged organelles. Autophagy is reduced in aging, which is implicated in the pathogenesis of aging-related diseases, including cancers, obesity, type 2 diabetes, cardiovascular diseases, and neurodegenerative diseases. Mitochondria-derived phospholipids cardiolipin, phosphatidylethanolamine, and phosphatidylglycerol are critical throughout the autophagic process, from initiation and phagophore formation to elongation and fusion with endolysosomal vesicles. Cardiolipin is also required for mitochondrial fusion and fission, an important step in isolating dysfunctional mitochondria for mitophagy. Furthermore, genetic screen in yeast has identified a surprising role for cardiolipin in regulating lysosomal function. Phosphatidylethanolamine plays a pivotal role in supporting the autophagic process, including autophagosome elongation as part of lipidated Atg8/LC3. An emerging role for phosphatidylglycerol in AMPK and mTORC1 signaling as well as mitochondrial fission may provide the first glimpse into the function of phosphatidylglycerol apart from being a precursor for cardiolipin. This review examines the effects of manipulating phospholipids on autophagy and mitophagy in health and diseases, as well as current limitations in the field. This article is part of a Special Issue entitled: Lipids of Mitochondria edited by Guenther Daum.

Age-associated vascular inflammation promotes monocytosis during atherogenesis

Aging leads to a proinflammatory state within the vasculature without disease, yet whether this inflammatory state occurs during atherogenesis remains unclear. Here, we examined how aging impacts atherosclerosis using Ldlr(-/-) mice, an established murine model of atherosclerosis. We found that aged atherosclerotic Ldlr(-/-) mice exhibited enhanced atherogenesis within the aorta. Aging also led to increased LDL levels, elevated blood pressure on a low-fat diet, and insulin resistance after a high-fat diet (HFD). On a HFD, aging increased a monocytosis in the peripheral blood and enhanced macrophage accumulation within the aorta. When we conducted bone marrow transplant experiments, we found that stromal factors contributed to age-enhanced atherosclerosis. To delineate these stromal factors, we determined that the vasculature exhibited an age-enhanced inflammatory response consisting of elevated production of CCL-2, osteopontin, and IL-6 during atherogenesis. In addition, in vitro cultures showed that aging enhanced the production of osteopontin by vascular smooth muscle cells. Functionally, aged atherosclerotic aortas displayed higher monocyte chemotaxis than young aortas. Hence, our study has revealed that aging induces metabolic dysfunction and enhances vascular inflammation to promote a peripheral monocytosis and macrophage accumulation within the atherosclerotic aorta.

Mitochondria and oxidative stress in heart aging

As average lifespan of humans increases in western countries, cardiac diseases become the first cause of death. Aging is among the most important risk factors that increase susceptibility for developing cardiovascular diseases. The heart has very aerobic metabolism, and is highly dependent on mitochondrial function, since mitochondria generate more than 90 % of the intracellular ATP consumed by cardiomyocytes. In the last few decades, several investigations have supported the relevance of mitochondria and oxidative stress both in heart aging and in the development of cardiac diseases such as heart failure, cardiac hypertrophy, and diabetic cardiomyopathy. In the current review, we compile different studies corroborating this role. Increased mitochondria DNA instability, impaired bioenergetic efficiency, enhanced apoptosis, and inflammation processes are some of the events related to mitochondria that occur in aging heart, leading to reduced cellular survival and cardiac dysfunction. Knowing the mitochondrial mechanisms involved in the aging process will provide a better understanding of them and allow finding approaches to more efficiently improve this process.

Bioenergetics of the aging heart and skeletal muscles: Modern concepts and controversies

Age-related alterations in the bioenergetics of the heart and oxidative skeletal muscle tissues are of crucial influence on their performance. Until now the prevailing concept of aging was the mitochondrial theory, the increased production of reactive oxygen species, mediated by deficiency in the activity of respiratory chain complexes. However, studies with mitochondria in situ have presented results which, to some extent, disagree with previous ones, indicating that the mitochondrial theory of aging may be overestimated. The studies reporting age-related decline in mitochondrial function were performed using mainly isolated mitochondria. Measurements on this level are not able to take into account the system level properties. The relevant information can be obtained only from appropriate studies using cells or tissue fibers. The functional interactions between the components of Intracellular Energetic Unit (ICEU) regulate the energy production and consumption in oxidative muscle cells. The alterations of these interactions in ICEU should be studied in order to find a more effective protocol to decelerate the age-related changes taking place in the energy metabolism. In this article, an overview is given of the present theories and controversies of causes of age-related alterations in bioenergetics. Also, branches of study, which need more emphasis, are indicated.

Aging and Autophagy in the Heart

The aging population is increasing in developed countries. Because the incidence of cardiac disease increases dramatically with age, it is important to understand the molecular mechanisms through which the heart becomes either more or less susceptible to stress. Cardiac aging is characterized by the presence of hypertrophy, fibrosis, and accumulation of misfolded proteins and dysfunctional mitochondria. Macroautophagy (hereafter referred to as autophagy) is a lysosome-dependent bulk degradation mechanism that is essential for intracellular protein and organelle quality control. Autophagy and autophagic flux are generally decreased in aging hearts, and murine autophagy loss-of-function models develop exacerbated cardiac dysfunction that is accompanied by the accumulation of misfolded proteins and dysfunctional organelles. On the contrary, stimulation of autophagy generally improves cardiac function in mouse models of protein aggregation by removing accumulated misfolded proteins, dysfunctional mitochondria, and damaged DNA, thereby improving the overall cellular environment and alleviating aging-associated pathology in the heart. Increasing lines of evidence suggest that autophagy is required for many mechanisms that mediate lifespan extension, such as caloric restriction, in various organisms. These results raise the exciting possibility that autophagy may play an important role in combating the adverse effects of aging in the heart. In this review, we discuss the role of autophagy in the heart during aging, how autophagy alleviates age-dependent changes in the heart, and how the level of autophagy in the aging heart can be restored.

Macromolecular Degradation Systems and Cardiovascular Aging

Aging-related cardiovascular diseases are a rapidly increasing problem worldwide. Cardiac aging demonstrates progressive decline of diastolic dysfunction of ventricle and increase in ventricular and arterial stiffness accompanied by increased fibrosis stimulated by angiotensin II and proinflammatory cytokines. Reactive oxygen species and multiple signaling pathways on cellular senescence play major roles in the process. Aging is also associated with an alteration in steady state of macromolecular dynamics including a dysfunction of protein synthesis and degradation. Currently, impaired macromolecular degradation is considered to be closely related to enhanced inflammation and be involved in the process and mechanism of cardiac aging. Herein, we review the role and mechanisms of the degradation system of intracellular macromolecules in the process and pathophysiology of cardiovascular aging.

Cardiac Senescence, Heart Failure, and Frailty: A Triangle in Elderly People

Cardiovascular disease (CVD) is a common problem in the elderly. In particular, the morbidity and mortality of patients with heart failure (HF) increase with age. The poor outcomes of elderly patients with HF can be explained partly by cardiac aging at the cellular and organ levels. Moreover, recent evidence has demonstrated that functional evaluation, which may reflect the status of individual aging, predicts mortality in patients with HF. Age-related changes occur throughout the body and in virtually all organ systems. Thus, we should pay more attention to geriatric conditions when treating patients with HF. Frailty represents a complex clinical syndrome that results from multiple impairments across different organs and is characterized by decreased physiological reserves and increased vulnerability to stressors. Frail patients with CVD have a worse prognosis than non-frail patients. Evidence demonstrates that frailty is an independent risk factor for incident HF among older people. The ways in which cellular senescence promotes age-related CVD and frailty remain an important issue in the biology of aging and clinical geriatrics. Senescent cells that have acquired a senescence-associated secretory phenotype (SASP) can cause local and potentially systemic inflammation. SASP might be a key phenomenon in the association between cellular senescence and the development of age-related CVD and frailty. Frailty is a dynamic and potentially reversible state; therefore, translational research efforts are focused on obtaining mechanistic insights into the pathobiology of frailty, the development of novel therapeutics, and the identification of biomarkers for frailty. This is particularly important in developed countries that are confronted with an aging society.

High-density lipoprotein, mitochondrial dysfunction and cell survival mechanisms

Ischemic injury is associated with acute myocardial infarction, percutaneous coronary intervention, coronary artery bypass grafting and open heart surgery. The timely re-establishment of blood flow is critical in order to minimize cardiac complications. Reperfusion after a prolonged ischemic period, however, can induce severe cardiomyocyte dysfunction with mitochondria serving as a major target of ischemia/reperfusion (I/R) injury. An increase in the formation of reactive oxygen species (ROS) induces damage to mitochondrial respiratory complexes leading to uncoupling of oxidative phosphorylation. Mitochondrial membrane perturbations also contribute to calcium overload, opening of the mitochondrial permeability transition pore (mPTP) and the release of apoptotic mediators into the cytoplasm. Clinical and experimental studies show that ischemic preconditioning (ICPRE) and postconditioning (ICPOST) attenuate mitochondrial injury and improve cardiac function in the context of I/R injury. This is achieved by the activation of two principal cell survival cascades: 1) the Reperfusion Injury Salvage Kinase (RISK) pathway; and 2) the Survivor Activating Factor Enhancement (SAFE) pathway. Recent data suggest that high density lipoprotein (HDL) mimics the effects of conditioning protocols and attenuates myocardial I/R injury via activation of the RISK and SAFE signaling cascades. In this review, we discuss the roles of apolipoproteinA-I (apoA-I), the major protein constituent of HDL, and sphingosine 1-phosphate (S1P), a lysosphingolipid associated with small, dense HDL particles as mediators of cardiomyocyte survival. Both apoA-I and S1P exert an infarct-sparing effect by preventing ROS-dependent injury and inhibiting the opening of the mPTP.

Dietary restriction: could it be considered as speed bump on tumor progression road?

Dietary restrictions, including fasting (or long-term starvation), calorie restriction (CR), and short-term starvation (STS), are considered a strong rationale that may protect against various diseases, including age-related diseases and cancer. Among dietary approaches, STS, in which food is not consumed during designed fasting periods but is typically not restricted during designated feeding periods, seems to be more suitable, because other dietary regimens involving prolonged fasting periods could worsen the health conditions of cancer patients, being they already naturally prone to weight loss. Until now, the limited amount of available data does not point to a single gene, pathway, or molecular mechanism underlying the benefits to the different dietary approaches. It is well known that the healthy effect is mediated in part by the reduction of nutrient-related pathways. The calorie restriction and starvation (long- and short-term) also suppress the inflammatory response reducing the expression, for example, of IL-10 and TNF-α, mitigating pro-inflammatory gene expression and increasing anti-inflammatory gene expression. The dietary restriction may regulate both genes involved in cellular proliferation and factors associated to apoptosis in normal and cancer cells. Finally, dietary restriction is an important tool that may influence the response to chemotherapy in preclinical models. However, further data are needed to correlate dietary approaches with chemotherapeutic treatments in human models. The aim of this review is to discuss the effects of various dietary approaches on the cancer progression and therapy response, mainly in preclinical models, describing some signaling pathways involved in these processes.

HSP27 Alleviates Cardiac Aging in Mice via a Mechanism Involving Antioxidation and Mitophagy Activation

Aging-induced cardiac dysfunction is a prominent feature of cardiac aging. Heat shock protein 27 (HSP27) protects cardiac function against ischemia or chemical challenge. We hypothesized that HSP27 attenuates cardiac aging. Transgenic (Tg) mice with cardiac-specific expression of the HSP27 gene and wild-type (WT) littermates were employed in the experiments. Echocardiography revealed a significant decline in the cardiac function of old WT mice compared with young WT mice. In striking contrast, the aging-induced impairment of cardiac function was attenuated in old Tg mice compared with old WT mice. Levels of cardiac aging markers were lower in old Tg mouse hearts than in old WT mouse hearts. Less interstitial fibrosis and lower contents of reactive oxygen species and ubiquitin-conjugated proteins were detected in old Tg hearts than in old WT hearts. Furthermore, old Tg hearts demonstrated lower accumulation of LC3-II and p62 than old WT hearts. Levels of Atg13, Vps34, and Rab7 were also higher in old Tg hearts than in old WT hearts. Additionally, old Tg hearts had higher levels of PINK1 and Parkin than old WT hearts, suggesting that mitophagy was activated in old Tg hearts. Taken together, HSP27 alleviated cardiac aging and this action involved antioxidation and mitophagy activation.

A graphene oxide based smart drug delivery system for tumor mitochondria-targeting photodynamic therapy

Subcellular organelles play critical roles in cell survival. In this work, a novel photodynamic therapy (PDT) drug delivery and phototoxicity on/off nano-system based on graphene oxide (NGO) as the carrier is developed to implement subcellular targeting and attacking. To construct the nanodrug (PPa-NGO-mAb), NGO is modified with the integrin αvβ3 monoclonal antibody (mAb) for tumor targeting. Pyropheophorbide-a (PPa) conjugated with polyethylene-glycol is used to cover the surface of the NGO to induce phototoxicity. Polyethylene-glycol phospholipid is loaded to enhance water solubility. The results show that the phototoxicity of PPa on NGO can be switched on and off in organic and aqueous environments, respectively. The PPa-NGO-mAb assembly is able to effectively target the αvβ3-positive tumor cells with surface ligand and receptor recognition; once endocytosized by the cells, they are observed escaping from lysosomes and subsequently transferring to the mitochondria. In the mitochondria, the 'on' state PPa-NGO-mAb performs its effective phototoxicity to kill cells. The biological and physical dual selections and on/off control of PPa-NGO-mAb significantly enhance mitochondria-mediated apoptosis of PDT. This smart system offers a potential alternative to drug delivery systems for cancer therapy.

Rapamycin transiently induces mitochondrial remodeling to reprogram energy metabolism in old hearts

Rapamycin, an inhibitor of mTOR signaling, has been shown to reverse diastolic dysfunction in old mice in 10 weeks, highlighting its therapeutic potential for a poorly treatable condition. However, the mechanisms and temporal regulation of its cardiac benefits remain unclear. We show that improved diastolic function in old mice begins at 2-4 weeks, progressing over the course of 10-week treatment. While TORC1-mediated S6 phosphorylation and TORC2 mediated AKT and PKCα phosphorylation are inhibited throughout the course of treatment, rapamycin inhibits ULK phosphorylation and induces autophagy during just the first week of treatment, returning to baseline at two weeks and after. Concordantly, markers of mitochondrial biogenesis increase over the first two weeks of treatment and return to control levels thereafter. This transient induction of autophagy and mitochondrial biogenesis suggests that damaged mitochondria are replaced by newly synthesized ones to rejuvenate mitochondrial homeostasis. This remodeling is shown to rapidly reverse the age-related reduction in fatty acid oxidation to restore a more youthful substrate utilization and energetic profile in old isolated perfused hearts, and modulates the myocardial metabolomein vivo. This study demonstrates the differential and dynamic mechanisms following rapamycin treatment and highlights the importance of understanding the temporal regulation of rapamycin effects.