Autophagy and cardiovascular aging: lesson learned from rapamycin

The role of autophagy in the progression of HIV infected cardiomyopathy

Although highly active antiretroviral therapy (HAART) has changed infection with human immunodeficiency virus (HIV) from a diagnosis with imminent mortality to a chronic illness, HIV positive patients who do not develop acquired immunodeficiency syndrome (AIDs) still suffer from a high rate of cardiac dysfunction and fibrosis. Regardless of viral load and CD count, HIV-associated cardiomyopathy (HIVAC) still causes a high rate of mortality and morbidity amongst HIV patients. While this is a well characterized clinical phenomena, the molecular mechanism of HIVAC is not well understood. In this review, we consolidate, analyze, and discuss current research on the intersection between autophagy and HIVAC. Multiple studies have linked dysregulation in various regulators and functional components of autophagy to HIV infection regardless of mode of viral entry, i.e., coronary, cardiac chamber, or pericardial space. HIV proteins, including negative regulatory factor (Nef), glycoprotein 120 (gp120), and transactivator (Tat), have been shown to interact with type II microtubule-associated protein-1 β light chain (LC3-II), Rubiquitin, SQSTM1/p62, Rab7, autophagy-specific gene 7 (ATG7), and lysosomal-associated membrane protein 1 (LAMP1), all molecules critical to normal autophagy. HIV infection can also induce dysregulation of mitochondrial bioenergetics by altering production and equilibrium of adenosine triphosphate (ATP), mitochondrial reactive oxygen species (ROS), and calcium. These changes alter mitochondrial mass and morphology, which normally trigger autophagy to clear away dysfunctional organelles. However, with HIV infection also triggering autophagy dysfunction, these abnormal mitochondria accumulate and contribute to myocardial dysfunction. Likewise, use of HAART, azidothymidine and Abacavir, have been shown to induce cardiac dysfunction and fibrosis by inducing abnormal autophagy during antiretroviral therapy. Conversely, studies have shown that increasing autophagy can reduce the accumulation of dysfunctional mitochondria and restore cardiomyocyte function. Interestingly, Rapamycin, a mammalian target of rapamycin (mTOR) inhibitor, has also been shown to reduce HIV-induced cytotoxicity by regulating autophagy-related proteins, making it a non-antiviral agent with the potential to treat HIVAC. In this review, we synthesize these findings to provide a better understanding of the role autophagy plays in HIVAC and discuss the potential pharmacologic targets unveiled by this research.

Sex Differences in Molecular Mechanisms of Cardiovascular Aging

Cardiovascular disease (CVD) is still the leading cause of illness and death in the Western world. Cardiovascular aging is a progressive modification occurring in cardiac and vascular morphology and physiology where increased endothelial dysfunction and arterial stiffness are observed, generally accompanied by increased systolic blood pressure and augmented pulse pressure. The effects of biological sex on cardiovascular pathophysiology have long been known. The incidence of hypertension is higher in men, and it increases in postmenopausal women. Premenopausal women are protected from CVD compared with age-matched men and this protective effect is lost with menopause, suggesting that sex-hormones influence blood pressure regulation. In parallel, the heart progressively remodels over the course of life and the pattern of cardiac remodeling also differs between the sexes. Lower autonomic tone, reduced baroreceptor response, and greater vascular function are observed in premenopausal women than men of similar age. However, postmenopausal women have stiffer arteries than their male counterparts. The biological mechanisms responsible for sex-related differences observed in cardiovascular aging are being unraveled over the last several decades. This review focuses on molecular mechanisms underlying the sex-differences of CVD in aging.

Apatinib Through Activating the RhoA/ROCK Signaling Pathway to Cause Dysfunction of Vascular Smooth Muscle Cells

Vascular smooth muscle cells (VSMCs) are associated with differentiated, organized, and contractile phenotype under the effect of various types of physiological conditions those are associated with migratory, proliferative, and synthetic phenotype under the effect of various types of stimuli, which dysfunction drives many cardiovascular diseases. Abnormal cell proliferation and invasion of VSMCs are among the primary causes of hypertension. Apatinib is a small-molecule tyrosine kinase inhibitor (TKI) that highly selectively binds to and strongly inhibits VEGFR-2. Previous studies have confirmed that the TKIs can raise blood pressure through RhoA/ROCK pathway. LARG is a key gene in the RhoA/ROCK pathway and plays a critical role in the continuous vasoconstriction function because it regulates part of signal transduction in VSMCs. In this study, an in vitro experiment was conducted to observe that apatinib caused dysfunction of MOVAS cells through the RhoA/ROCK signalling pathway and Y27632, a nonspecific ROCK inhibitor, and knockout of LARG gene can improve the proliferation, antiapoptosis, oxidative stress, and mitochondrial autophagy of apatinib-induced MOVAS cells. These findings suggest that activation of the RhoA/ROCK signalling pathway could be the underlying mechanism of apatinib-induced dysfunction of MOVAS cells, while ROCK inhibitor and knockout of LARG gene have potential therapeutic value.

Mouse aortic biomechanics are affected by short-term defective autophagy in vascular smooth muscle cells

The physiology of vascular smooth muscle (VSMC) cells is affected by autophagy, a catabolic cellular mechanism responsible for nutrient recycling. Autophagy-inducing compounds may reverse arterial stiffening, whereas congenital VSMC-specific autophagy deficiency promotes arterial stiffening. The elevated aortic stiffness in 3.5-month-old C57Bl/6 mice, in which the essential autophagy-related gene Atg7 was specifically deleted in the VSMCs (Atg7F/F SM22α-Cre+ mice) was mainly due to passive aortic wall remodeling. The present study investigated whether aortic stiffness was also modulated by a shorter duration of autophagy deficiency. Therefore, aortic segments of 2-month-old Atg7F/F SM22α-Cre+ mice were studied. Similarly to the older mice, autophagy deficiency in VSMCs promoted aortic stiffening by elastin degradation and elastin breaks, and increased the expression of the calcium binding protein S100A4 (+ 157%), the aortic wall thickness (+ 27%), the sensitivity of the VSMCs to depolarization and the contribution of VGCC mediated Ca2+ influx to α1 adrenergic contractions. Hence, all these phenomena occurred before the age of 2 months. When compared to autophagy deficiency in VSMCs at 3.5 months, shorter term autophagy deficiency led to higher segment diameter at 80 mmHg (+ 7% versus - 2%), normal baseline tonus (versus increased), unchanged IP3-mediated phasic contractions (versus enhanced), and enhanced endothelial cell function (versus normal). Overall, and because in vivo cardiac parameters or aortic pulse wave velocity were not affected, these observations indicate that congenital autophagy deficiency in VSMCs of Atg7F/F SM22α-Cre+ mice initiates compensatory mechanisms to maintain circulatory homeostasis.

Irisin and Autophagy: First Update

Aging and sedentary life style are considered independent risk factors for many disorders. Under these conditions, accumulation of dysfunctional and damaged cellular proteins and organelles occurs, resulting in a cellular degeneration and cell death. Autophagy is a conserved recycling pathway responsible for the degradation, then turnover of cellular proteins and organelles. This process is a part of the molecular underpinnings by which exercise promotes healthy aging and mitigate age-related pathologies. Irisin is a myokine released during physical activity and acts as a link between muscles and other tissues and organs. Its main beneficial function is the change of subcutaneous and visceral adipose tissue into brown adipose tissue, with a consequential increase in thermogenesis. Irisin modulates metabolic processes, acting on glucose homeostasis, reduces systemic inflammation, maintains the balance between resorption and bone formation, and regulates the functioning of the nervous system. Recently, some of its pleiotropic and favorable properties have been attributed to autophagy induction, posing irisin as an important regulator of autophagy by exercise. This review article proposes to bring together for the first time the "state of the art" knowledge regarding the effects of irisin and autophagy. Furthermore, treatments on relation between exercise/myokines and autophagy have been also achieved.

Mitophagy Receptors and Mediators: Therapeutic Targets in the Management of Cardiovascular Ageing

Mitophagy serves as a cardinal regulator in the maintenance of mitochondrial integrity, function, and cardiovascular homeostasis, through the fine control and governance of cellular metabolism, ATP production, redox balance, and mitochondrial quality and quantity control. As a unique form of selective autophagy, mitophagy specifically recognizes and engulfs long-lived or damaged (depolarized) mitochondria through formation of the double-membraned intracellular organelles - mitophagosomes, ultimately resulting in lysosomal degradation. Levels of mitophagy are reported to be altered in pathological settings including cardiovascular diseases and biological ageing although the precise nature of mitophagy change in ageing and ageing-associated cardiovascular deterioration remains poorly defined. Ample clinical and experimental evidence has depicted a convincing tie between cardiovascular ageing and altered mitophagy. In particular, ageing perturbs multiple enigmatic various signal machineries governing mitophagy, mitochondrial quality, and mitochondrial function, contributing to ageing-elicited anomalies in the cardiovascular system. This review will update novel regulatory mechanisms of mitophagy especially in the perspective of advanced ageing, and discuss how mitophagy dysregulation may be linked to cardiovascular abnormalities in ageing. We hope to pave the way for development of new therapeutic strategies against the growing health and socieconomical issue of cardiovascular ageing through targeting mitophagy.

Enzyme-based autophagy in anti-neoplastic management: From molecular mechanisms to clinical therapeutics

Autophagy is an evolutionarily conserved self-cannibalization process commonly found in all eukaryotic cells. Through autophagy, long-lived or damaged organelles, superfluous proteins, and pathogens are sequestered and encapsulated into the double-membrane autophagosomes prior to fusion with lysosomes for ultimate degradation and recycling. Given that autophagy is deemed both protective and detrimental in malignancies, the clinical therapeutic utilization of autophagy modulators in cancer has attracted immense attentions over the past decades. Dependence of tumor cells on autophagy during amino acid insufficiency or deprivation has prompted us to explore the underlying autophagy regulatory mechanisms to inject amino acid degrading enzymes and enzyme-based strategies into therapeutic maneuvers of autophagy in cancer.

Autophagy as an emerging therapeutic target for age-related vascular pathologies

Introduction: The incidence of age-related vascular diseases such as arterial stiffness, hypertension and atherosclerosis, is rising dramatically and is substantially impacting healthcare systems. Mounting evidence suggests that there is an important role for autophagy in maintaining (cardio)vascular health. Impaired vascular autophagy has been linked to arterial aging and the initiation of vascular disease.Areas covered: The function and implications of autophagy in vascular smooth muscle cells and endothelial cells are discussed in healthy blood vessels and arterial disease. Furthermore, we discuss current treatment options for vascular disease and their links with autophagy. A literature search was conducted in PubMed up to October 2019.Expert opinion: Although the therapeutic potential of inducing autophagy in age-related vascular pathologies is considerable, several issues should be addressed before autophagy induction can be clinically used to treat vascular disease. These issues include uncertainty regarding the most effective drug target as well as the lack of potency and selectivity of autophagy inducing drugs. Moreover, drug tolerance or autophagy mediated cell death have been reported as possible adverse effects. Special attention is required for determining the cause of autophagy deficiency to optimize the treatment strategy.

Calorie Restriction Curbs Proinflammation That Accompanies Arterial Aging, Preserving a Youthful Phenotype

Background

Aging exponentially increases the incidence of morbidity and mortality of quintessential cardiovascular disease mainly due to arterial proinflammatory shifts at the molecular, cellular, and tissue levels within the arterial wall. Calorie restriction (CR) in rats improves arterial function and extends both health span and life span. How CR affects the proinflammatory landscape of molecular, cellular, and tissue phenotypic shifts within the arterial wall in rats, however, remains to be elucidated.

Methods and Results

Aortae were harvested from young (6‐month‐old) and old (24‐month‐old) Fischer 344 rats, fed ad libitum and a second group maintained on a 40% CR beginning at 1 month of age. Histopathologic and morphometric analysis of the arterial wall demonstrated that CR markedly reduced age‐associated intimal medial thickening, collagen deposition, and elastin fractionation/degradation within the arterial walls. Immunostaining/blotting showed that CR effectively prevented an age‐associated increase in the density of platelet‐derived growth factor, matrix metalloproteinase type II activity, and transforming growth factor beta 1 and its downstream signaling molecules, phospho‐mothers against decapentaplegic homolog‐2/3 (p‐SMAD‐2/3) in the arterial wall. In early passage cultured vascular smooth muscle cells isolated from AL and CR rat aortae, CR alleviated the age‐associated vascular smooth muscle cell phenotypic shifts, profibrogenic signaling, and migration/proliferation in response to platelet‐derived growth factor.

Conclusions

CR reduces matrix and cellular proinflammation associated with aging that occurs within the aortic wall and that are attributable to platelet‐derived growth factor signaling. Thus, CR reduces the platelet‐derived growth factor–associated signaling cascade, contributing to the postponement of biological aging and preservation of a more youthful aortic wall phenotype.

Microparticles and autophagy: a new frontier in the understanding of atherosclerosis in rheumatoid arthritis

Microparticles (MPs) are small membrane vesicles released by many cell types under physiological and pathological conditions. In the last years, these particles were considered as inert cell debris, but recently many studies have demonstrated they could have a role in intercellular communication. Increased levels of MPs have been reported in various pathological conditions including infections, malignancies, and autoimmune diseases, such as rheumatoid arthritis (RA). RA is an autoimmune systemic inflammatory disease characterized by chronic synovial inflammation, resulting in cartilage and bone damage with accelerated atherosclerosis increasing mortality. According to the literature data, also MPs could have a role in endothelial dysfunction, contributing to atherosclerosis in RA patients. Moreover many researchers have shown that a dysregulated autophagy seems to be involved in endothelial dysfunction. Autophagy is a reparative process by which cytoplasmic components are sequestered in double-membrane vesicles and degraded on fusion with lysosomal compartments. It has been shown in many works that basal autophagy is essential to proper vascular function. Taking into account these considerations, we hypothesized that in RA patients MPs could contribute to atherosclerosis process by dysregulation of endothelial autophagy process.

The correlation between mammalian target of rapamycin (mTOR) gene expression and sperm DNA damage among infertile patients with and without varicocele

This study aimed to assess the possible correlation between mammalian target of rapamycin (mTOR) gene expression and sperm DNA damage among infertile patients with and without varicocele. The study included sixty infertile males and fifty fertile males as controls. The infertile group was subdivided into the following subgroups: thirty males with varicocele and thirty males without varicocele. All subjects underwent medical history collection, clinical examination, semen analysis, sperm DNA integrity assessment, mTOR gene expression assessment and scrotal colour Doppler ultrasound. The mean mTOR gene expression in infertile patients with varicocele (23.52 ± 14.65) was significantly higher than that in infertile patients without varicocele (12.24 ± 12.44) and fertile control subjects (3.92 ± 3.26; p = 0.003 and p < 0.001 respectively). In the infertile varicocele-positive group, mTOR gene expression showed a significant negative correlation with sperm count (p = 0.028, r = -0.400) and progressive sperm motility (p = 0.038, r = -0.381), as well as a significant positive correlation with the sperm DNA fragmentation index (DFI; p = 0.001, r = 0.578). In the infertile varicocele-negative group, mTOR gene expression showed a significant negative correlation with progressive sperm motility (p = 0.018, r = -0.429) and a significant positive correlation with sperm DFI (p < 0.001, r = 0.673). In conclusion, according to these results, there is a significant positive correlation between mTOR gene expression and sperm DFI among infertile patients with and without varicocele.

Autophagy and aging: Maintaining the proteome through exercise and caloric restriction

Accumulation of dysfunctional and damaged cellular proteins and organelles occurs during aging, resulting in a disruption of cellular homeostasis and progressive degeneration and increases the risk of cell death. Moderating the accrual of these defunct components is likely a key in the promotion of longevity. While exercise is known to promote healthy aging and mitigate age‐related pathologies, the molecular underpinnings of this phenomenon remain largely unclear. However, recent evidences suggest that exercise modulates the proteome. Similarly, caloric restriction (CR), a known promoter of lifespan, is understood to augment intracellular protein quality. Autophagy is an evolutionary conserved recycling pathway responsible for the degradation, then turnover of cellular proteins and organelles. This housekeeping system has been reliably linked to the aging process. Moreover, autophagic activity declines during aging. The target of rapamycin complex 1 (TORC1), a central kinase involved in protein translation, is a negative regulator of autophagy, and inhibition of TORC1 enhances lifespan. Inhibition of TORC1 may reduce the production of cellular proteins which may otherwise contribute to the deleterious accumulation observed in aging. TORC1 may also exert its effects in an autophagy‐dependent manner. Exercise and CR result in a concomitant downregulation of TORC1 activity and upregulation of autophagy in a number of tissues. Moreover, exercise‐induced TORC1 and autophagy signaling share common pathways with that of CR. Therefore, the longevity effects of exercise and CR may stem from the maintenance of the proteome by balancing the synthesis and recycling of intracellular proteins and thus may represent practical means to promote longevity.

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.

Autophagy as an emerging target in cardiorenal metabolic disease: From pathophysiology to management

Although advances in medical technology and health care have improved the early diagnosis and management for cardiorenal metabolic disorders, the prevalence of obesity, insulin resistance, diabetes, hypertension, dyslipidemia, and kidney disease remains high. Findings from numerous population-based studies, clinical trials, and experimental evidence have consolidated a number of theories for the pathogenesis of cardiorenal metabolic anomalies including resistance to the metabolic action of insulin, abnormal glucose and lipid metabolism, oxidative and nitrosative stress, endoplasmic reticulum (ER) stress, apoptosis, mitochondrial damage, and inflammation. Accumulating evidence has recently suggested a pivotal role for proteotoxicity, the unfavorable effects of poor protein quality control, in the pathophysiology of metabolic dysregulation and related cardiovascular complications. The ubiquitin-proteasome system (UPS) and autophagy-lysosomal pathways, two major although distinct cellular clearance machineries, govern protein quality control by degradation and clearance of long-lived or damaged proteins and organelles. Ample evidence has depicted an important role for protein quality control, particularly autophagy, in the maintenance of metabolic homeostasis. To this end, autophagy offers promising targets for novel strategies to prevent and treat cardiorenal metabolic diseases. Targeting autophagy using pharmacological or natural agents exhibits exciting new strategies for the growing problem of cardiorenal metabolic disorders.

Targeting Autophagy in Aging and Aging-Related Cardiovascular Diseases

Aging, an irreversible biological process, serves as an independent risk factor for chronic disease including cancer, pulmonary, neurodegenerative, and cardiovascular diseases. In particular, high morbidity and mortality have been associated with cardiovascular aging, but effective clinical therapeutic remedies are suboptimal for the ever-rising aging population. Recent evidence suggests a unique role for aberrant aggregate clearance and the protein quality control machinery - the process of autophagy - in shortened lifespan, compromised healthspan, and the onset and development of aging-associated cardiovascular diseases. Autophagy degrades and removes long-lived or damaged cellular organelles and proteins, the functions of which decline with advanced aging. Induction of autophagy using rapamycin, resveratrol, nicotinamide derivatives, metformin, urolithin A, or spermidine delays aging, prolongs lifespan, and improves cardiovascular function in aging. Given the ever-rising human lifespan and aging population as well as the prevalence of cardiovascular disease provoked by increased age, it is pertinent to understand the contribution and underlying mechanisms of autophagy and organelle-selective autophagy (e.g., mitophagy) in the regulation of lifespan, healthspan, and cardiovascular aging. Here we dissect the mechanism of action for autophagy failure in aging and discuss the potential rationale of targeting autophagy using pharmacological agents as new avenues in the combating of biological and cardiovascular aging.

Transcriptome evidence reveals enhanced autophagy-lysosomal function in centenarians

Centenarians (CENs) are excellent subjects to study the mechanisms of human longevity and healthy aging. Here, we analyzed the transcriptomes of 76 centenarians, 54 centenarian-children, and 41 spouses of centenarian-children by RNA sequencing and found that, among the significantly differentially expressed genes (SDEGs) exhibited by CENs, the autophagy-lysosomal pathway is significantly up-regulated. Overexpression of several genes from this pathway, CTSB, ATP6V0C, ATG4D, and WIPI1, could promote autophagy and delay senescence in cultured IMR-90 cells, while overexpression of the Drosophila homolog of WIPI1, Atg18a, extended the life span in transgenic flies. Interestingly, the enhanced autophagy-lysosomal activity could be partially passed on to their offspring, as manifested by their higher levels of both autophagy-encoding genes and serum beclin 1 (BECN1). In light of the normal age-related decline of autophagy-lysosomal functions, these findings provide a compelling explanation for achieving longevity in, at least, female CENs, given the gender bias in our collected samples, and suggest that the enhanced waste-cleaning activity via autophagy may serve as a conserved mechanism to prolong the life span from Drosophila to humans.

HIF-1α/Beclin1-Mediated Autophagy Is Involved in Neuroprotection Induced by Hypoxic Preconditioning

Hypoxic preconditioning (HPC) exerts a protective effect against hypoxic/ischemic brain injury, and one mechanism explaining this effect may involve the upregulation of hypoxia-inducible factor-1 (HIF-1). Autophagy, an endogenous protective mechanism against hypoxic/ischemic injury, is correlated with the activation of the HIF-1α/Beclin1 signaling pathway. Based on previous studies, we hypothesize that the protective role of HPC may involve autophagy occurring via activation of the HIF-1α/Beclin1 signaling pathway. To test this hypothesis, we evaluated the effects of HPC on oxygen-glucose deprivation/reperfusion (OGD/R)-induced apoptosis and autophagy in SH-SY5Y cells. HPC significantly attenuated OGD/R-induced apoptosis, and this effect was suppressed by the autophagy inhibitor 3-methyladenine and mimicked by the autophagy agonist rapamycin. In control SH-SY5Y cells, HPC upregulated the expression of HIF-1α and downstream molecules such as BNIP3 and Beclin1. Additionally, HPC increased the LC3-II/LC3-I ratio and decreased p62 levels. The increase in the LC3-II/LC3-I ratio was inhibited by the HIF-1α inhibitor YC-1 or by Beclin1-short hairpin RNA (shRNA). In OGD/R-treated SH-SY5Y cells, HPC also upregulated the expression levels of HIF-1α, BNIP3, and Beclin1, as well as the LC3-II/LC3-I ratio. Furthermore, YC-1 or Beclin1-shRNA attenuated the HPC-mediated cell viability in OGD/R-treated cells. Taken together, our results demonstrate that HPC protects SH-SY5Y cells against OGD/R via HIF-1α/Beclin1-regulated autophagy.

Exendin-4 and Liraglutide Attenuate Glucose Toxicity-Induced Cardiac Injury through mTOR/ULK1-Dependent Autophagy

Mitochondrial injury and defective autophagy are common in diabetic cardiomyopathy. Recent evidence supports benefits of glucagon-like peptide-1 (GLP-1) agonists exendin-4 (Exe) and liraglutide (LIRA) against diabetic cardiomyopathy. This study was designed to examine the effect of Exe and LIRA on glucose-induced cardiomyocyte and mitochondrial injury, oxidative stress, apoptosis, and autophagy change. Cardiomyocytes isolated from adult mice and H9c2 myoblast cells were exposed to high glucose (HG, 33 mM) with or without Exe or LIRA. Cardiac contractile properties were assessed including peak shortening, maximal velocity of shortening/relengthening (±dL/dt), time to PS, and time-to-90% relengthening (TR₉₀). Superoxide levels, apoptotic proteins such as cleaved caspase-3, Bax, and Bcl-2, and autophagy proteins including Atg5, p62, Beclin-1, LC3B, and mTOR/ULK1 were evaluated using Western blot. Mitochondrial membrane potential (MMP) changes were assessed using JC-1, and autophagosomes were determined using GFP-LC3. Cardiomyocyte exposure to HG exhibited prolonged TR₉₀ associated with significantly decreased PS and ±dL/dt, the effects of which were partly restored by GLP-1 agonists, the effects of which were negated by the mTOR activator 3BDO. H9c2 cell exposure to HG showed increased intracellular ROS, apoptosis, MMP loss, dampened autophagy, and elevated p-mTOR and p-ULK1, the effects of which were nullified by the GLP-1 agonists. These results suggested that GLP-1 agonists rescued glucose toxicity likely through induction of mTOR-dependent autophagy.

Ablation of toll-like receptor 4 attenuates aging-induced myocardial remodeling and contractile dysfunction through NCoRI-HDAC1-mediated regulation of autophagy

Aging is usually accompanied with overt structural and functional changes as well as suppressed autophagy in the heart although the precise regulatory mechanisms are somewhat unknown. Here we evaluated the role of the innate proinflammatory mediator toll-like receptor 4 (TLR4) in cardiac aging and the underlying mechanism with a focus on autophagy. Cardiac geometry and function were monitored in young or old wild-type (WT) and TLR4 knockout (TLR4^-/-) mice using echocardiography, IonOptix® edge-detection and fura-2 techniques. Levels of autophagy and mitophagy, nuclear receptor corepressor 1 (NCoR1) and histone deacetylase I (HDAC1) were examined using western blot. Transmission electronic microscopy (TEM) was employed to monitor myocardial ultrastructure. Our results revealed that TLR4 ablation alleviated advanced aging (24 months)-induced changes in myocardial remodeling (increased heart weight, chamber size, cardiomyocyte cross-sectional area), contractile function and intracellular Ca²⁺ handling as well as autophagy and mitophagy [Beclin-1, Atg5, LC3B, PTEN-induced putative kinase 1 (PINK1), Parkin and p62]. Aging downregulated levels of NCoR1 and HDAC1 as well as their interaction, the effects were significantly attenuated or negated by TLR4 ablation. Advanced aging disturbed myocardial ultrastructure as evidenced by loss of myofilament alignment and swollen mitochondria, which was obliterated by TLR4 ablation. Moreover, aging suppressed autophagy (GFP-LC3B puncta) in neonatal mouse cardiomyocytes, the effect of which was negated by the TLR4 inhibitor CLI-095. Inhibition of HDCA1 using apicidin cancelled off CLI095-induced beneficial response of GFP-LC3B puncta against aging. Our data collectively indicate a role for TLR4-mediated autophagy in cardiac remodeling and contractile dysfunction in aging through a HDAC1-NCoR1-dependent mechanism.

Molecular Mechanisms Linking Exercise to Cancer Prevention and Treatment

The benefits of exercise training for cancer patients are becoming increasingly evident. Physical exercise has been shown to reduce cancer incidence and inhibit tumor growth. Here we provide the status of the current molecular understanding of the effect of exercise on cancer. We propose that exercise has a role in controlling cancer progression through a direct effect on tumor-intrinsic factors, interplay with whole-body exercise effects, alleviation of cancer-related adverse events, and improvement of anti-cancer treatment efficacy. These findings have wide-ranging societal implications, as this understanding may lead to changes in cancer treatment strategies.

Impact of resistance training on the autophagy-inflammation-apoptosis crosstalk in elderly subjects

Aging is associated with a decline in autophagy and a state of low-grade inflammation which further affects apoptosis and autophagy. Importantly, these alterations could reverse with regular physical activity. This study assessed the effects of a resistance exercise training program on autophagy, NLRP3 inflammasome, and apoptosis in peripheral blood mononuclear cells (PBMCs) from old subjects. Twenty-six healthy women and men (age, 69.6±1.5 yr) were randomized to a training (TG) or a control (CG) group. TG performed an 8-week resistance training program, while CG followed their daily routines. Protein expression of beclin-1, Atg12, Atg16 and LAMP-2 increased following the training program, while expression of p62/SQSTM1 and phosphorylation of ULK-1 at Ser757 were significantly lower. Resistance exercise also induced a decrease in NLRP3 expression and in the caspase-1/procaspase-1 ratio. Expression of Bcl-2 and Bcl-xL, as well as the Bad/BcL-2 ratio were reduced, and there was a significant decrease in the protein content of caspase-3. The results obtained seem to indicate that 8-week resistance training stimulates autophagy, prevents NLRP3 inflammasome activation, and reduces apoptosis in PBMCs from elderly subjects. These data could have a significant impact in prevention and rehabilitation programs currently employed in elderly population.

Akt2 ablation prolongs life span and improves myocardial contractile function with adaptive cardiac remodeling: role of Sirt1-mediated autophagy regulation

Aging is accompanied with unfavorable geometric and functional changes in the heart involving dysregulation of Akt and autophagy. This study examined the impact of Akt2 ablation on life span and cardiac aging as well as the mechanisms involved with a focus on autophagy and mitochondrial integrity. Cardiac geometry, contractile, and intracellular Ca2+ properties were evaluated using echocardiography, IonOptix® edge-detection and fura-2 techniques. Levels of Sirt1, mitochondrial integrity, autophagy, and mitophagy markers were evaluated using Western blot. Our results revealed that Akt2 ablation prolonged life span (by 9.1%) and alleviated aging (24 months)-induced unfavorable changes in myocardial function and intracellular Ca2+ handling (SERCA2a oxidation) albeit with more pronounced cardiac hypertrophy (58.1%, 47.8%, and 14.5% rises in heart weight, wall thickness, and cardiomyocyte cross-sectional area). Aging downregulated levels of Sirt1, increased phosphorylation of Akt, and the nuclear transcriptional factor Foxo1, as well as facilitated acetylation of Foxo1, the effects of which (except Sirt1 and Foxo1 acetylation) were significantly attenuated or negated by Akt2 ablation. Advanced aging disturbed autophagy, mitophagy, and mitochondrial integrity as evidenced by increased p62, decreased levels of beclin-1, Atg7, LC3B, BNIP3, PTEN-induced putative kinase 1 (PINK1), Parkin, UCP-2, PGC-1α, and aconitase activity, the effects of which were reversed by Akt2 ablation. Aging-induced cardiomyocyte contractile dysfunction and loss of mitophagy were improved by rapamycin and the Sirt1 activator SRT1720. Activation of Akt using insulin or Parkin deficiency prevented SRT1720-induced beneficial effects against aging. In conclusion, our data indicate that Akt2 ablation protects against cardiac aging through restored Foxo1-related autophagy and mitochondrial integrity.

The origin of the autophagosomal membrane in human atherosclerotic plaque: a preliminary ultrastructural study

Autophagy is an evolutionarily conserved process that occurs ubiquitously and functions as a primary route for the degradation of damaged organelles and proteins in response to starvation, oxidative stress, and other harmful conditions. The initial event upon autophagy induction is the formation of a membranous cistern called the phagophore or isolation membrane, a cup-shaped structure that elongates, engulfs cytoplasmic "cargo", and fuses at its rims to give rise to the autophagosome within which cytoplasmic material is enclosed. Although thoroughly studied in diverse cell culture systems, few attempts have been made to analyze the membrane dynamics during phagophore biogenesis in tissues. With respect to the cardiovascular system, no structural information is currently available regarding the sources that may contribute to the nucleation and growth of the phagophore membrane. The results presented here demonstrate that in the cells of human atherosclerotic plaque the phagophores are in contact with the endoplasmic reticulum (ER) membranes. Initially, the phagophore appears as a membrane sac that enwraps injured organelles and dysfunctional proteins and then matures into a double-membrane, closed structure often containing portions of the ER. These structural data indicate that the membrane source that elongates the phagophore might probably come from the ER. The topographical relationship between the ER tubules and the phagophore might also favor an efficient mechanism to transfer lipids from their site of synthesis to the nascent membrane, thus promoting its elongation and, ultimately, the formation of the autophagosome.

Small heat shock proteins in ageing and age-related diseases

Small heat shock proteins (sHSPs) are gatekeepers of cellular homeostasis across species, preserving proteome integrity under stressful conditions. Nonetheless, recent evidence suggests that sHSPs are more than molecular chaperones with merely auxiliary role. In contrast, sHSPs have emerged as central lifespan determinants, and their malfunction has been associated with the manifestation of neurological disorders, cardiovascular disease and cancer malignancies. In this review, we focus on the role of sHSPs in ageing and age-associated diseases and highlight the most prominent paradigms, where impairment of sHSP function has been implicated in human pathology.

Exercise restores bioavailability of hydrogen sulfide and promotes autophagy influx in livers of mice fed with high-fat diet

In the gold standard treatment for nonalcoholic fatty liver disease (NAFLD), exercise training has been shown to effectively improve nonalcoholic steatohepatitis (NASH). However, limited data are available about the underlying mechanisms involved. This work was undertaken to investigate the mechanisms underlying the beneficial effect of exercise training on high-fat diet (HFD)-induced NAFLD in mice. Male mice were fed with HFD and given moderate-intensity exercise for 24 weeks. Exercise training lowered mass gain, attenuated systemic insulin resistance and glucose intolerance, and mitigated hepatic steatosis and fibrosis in mice fed with HFD. Exercise training improved mitochondrial function and enhanced mitochondrial β-oxidation in livers of HFD-fed mice. Exercise training enhanced hydrogen sulfide (H2S) levels in plasma and livers, and mRNA expression of cystathionine β-synthase (CBS), cystathionine γ-lyase (CES), and 3-mercaptopyruvate sulfurtransferase (3-MST) in livers of HFD-fed mice. Exercise training had no significant effect on the ratio of LC3-II/LC3-I, but decreased p62 protein expression in livers of HFD-fed mice. Additionally, exercise training reduced formation of malondialdehyde, enhanced ratio of GSH/GSSG, and down-regulated expression of TNF-α and IL-6 in livers of HFD-fed mice. Exercise training restored bioavailability of H2S and promoted autophagy influx in livers, which might contribute to its benefit on HFD-induced NAFLD.

mTOR Regulates Gap Junction Alpha-1 Protein Trafficking in Sertoli Cells and Is Required for the Maintenance of Spermatogenesis in Mice

The mammalian target of rapamycin (Mtor) gene encodes a serine/threonine kinase that acts as a master regulator of processes as diverse as cell growth, protein synthesis, cytoskeleton reorganization, and cell survival. In the testis, physiological roles for Mtor have been proposed in perinatal Sertoli cell proliferation and blood-testis barrier (BTB) remodeling during spermatogenesis, but no in vivo studies of Mtor function have been reported. Here, we used a conditional knockout approach to target Mtor in Sertoli cells. The resulting Mtor(flox/flox); Amhr2(cre/+) mice were characterized by progressive, adult-onset testicular atrophy associated with disorganization of the seminiferous epithelium, loss of Sertoli cell polarity, increased germ cell apoptosis, premature release of germ cells, decreased epididymal sperm counts, increased sperm abnormalities, and infertility. Histopathologic analysis and quantification of the expression of stage-specific markers showed a specific loss of pachytene spermatocytes and spermatids. Although the BTB and the ectoplasmic specializations did not appear to be altered in Mtor(flox/flox);Amhr2(cre/+) mice, a dramatic redistribution of gap junction alpha-1 (GJA1) was detected in their Sertoli cells. Phosphorylation of GJA1 at Ser373, which is associated with its internalization, was increased in the testes of Mtor(flox/flox); Amhr2(cre/+) mice, as was the expression and phosphorylation of AKT, which phosphorylates GJA1 at this site. Together, these results indicate that Mtor expression in Sertoli cells is required for the maintenance of spermatogenesis and the progression of germ cell development through the pachytene spermatocyte stage. One mechanism of mTOR action may be to regulate gap junction dynamics by inhibiting AKT, thereby decreasing GJA1 phosphorylation and internalization. mTOR regulates gap junction alpha-1 protein distribution in Sertoli cells and is necessary for progression through the pachytene spermatocyte stage.

Intra-articular injection of Torin 1 reduces degeneration of articular cartilage in a rabbit osteoarthritis model

Objectives

Recent studies have shown that systemic injection of rapamycin can prevent the development of osteoarthritis (OA)-like changes in human chondrocytes and reduce the severity of experimental OA. However, the systemic injection of rapamycin leads to many side effects. The purpose of this study was to determine the effects of intra-articular injection of Torin 1, which as a specific inhibitor of mTOR which can cause induction of autophagy, is similar to rapamycin, on articular cartilage degeneration in a rabbit osteoarthritis model and to investigate the mechanism of Torin 1’s effects on experimental OA.

Methods

Collagenase (type II) was injected twice into both knees of three-month-old rabbits to induce OA, combined with two intra–articular injections of Torin 1 (400 nM). Degeneration of articular cartilage was evaluated by histology using the Mankin scoring system at eight weeks after injection. Chondrocyte degeneration and autophagosomes were observed by transmission electron microscopy. Matrix metallopeptidase-13 (MMP-13) and vascular endothelial growth factor (VEGF) expression were analysed by quantitative RT-PCR (qPCR).Beclin-1 and light chain 3 (LC3) expression were examined by Western blotting.

Results

Intra-articular injection of Torin 1 significantly reduced degeneration of the articular cartilage after induction of OA. Autophagosomes andBeclin-1 and LC3 expression were increased in the chondrocytes from Torin 1-treated rabbits. Torin 1 treatment also reduced MMP-13 and VEGF expression at eight weeks after collagenase injection.

Conclusion

Our results demonstrate that intra-articular injection of Torin 1 reduces degeneration of articular cartilage in collagenase-induced OA, at least partially by autophagy activation, suggesting a novel therapeutic approach for preventing cartilage degeneration and treating OA.

Cite this article: N-T. Cheng, A. Guo, Y-P. Cui. Intra-articular injection of Torin 1 reduces degeneration of articular cartilage in a rabbit osteoarthritis model. Bone Joint Res 2016;5:218–224. DOI: 10.1302/2046-3758.56.BJR-2015-0001.

Protective effect of autophagy on human retinal pigment epithelial cells against lipofuscin fluorophore A2E: implications for age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of central vision loss in the elderly. Degeneration of retinal pigment epithelial (RPE) cells is a crucial causative factor responsible for the onset and progression of AMD. A2E, a major component of toxic lipofuscin implicated in AMD, is deposited in RPE cells with age. However, the mechanism whereby A2E may contribute to the pathogenesis of AMD remains unclear. We demonstrated that A2E was a danger signal of RPE cells, which induced autophagy and decreased cell viability in a concentration- and time-dependent manner. Within 15 min after the treatment of RPE with 25 μM A2E, the induction of autophagosome was detected by transmission electron microscopy. After continuous incubating RPE cells with A2E, intense punctate staining of LC3 and increased expression of LC3-II and Beclin-1 were identified. Meanwhile, the levels of intercellular adhesion molecule (ICAM), interleukin (IL)1β, IL2, IL-6, IL-8, IL-17A, IL-22, macrophage cationic peptide (MCP)-1, stromal cell-derived factor (SDF)-1, and vascular endothelial growth factor A (VEGFA) were elevated. The autophagic inhibitor 3-methyladenine (3-MA) and activator rapamycin were also used to verify the effect of autophagy on RPE cells against A2E. Our results revealed that 3-MA decreased the autophagosomes and LC3 puncta induced by A2E, increased inflammation-associated protein expression including ICAM, IL1β, IL2, IL-6, IL-8, IL-17A, IL-22, and SDF-1, and upregulated VEGFA expression. Whereas rapamycin augmented the A2E-mediated autophagy, attenuated protein expression of inflammation-associated and angiogenic factors, and blocked the Akt/mTOR pathway. Taken together, A2E induces autophagy in RPE cells at the early stage of incubation, and this autophagic response can be inhibited by 3-MA or augmented by rapamycin via the mTOR pathway. The enhancement of autophagy has a protective role in RPE cells against the adverse effects of A2E by reducing the secretion of inflammatory cytokines and VEGFA.

Pharmacological Modulation of Photoreceptor Outer Segment Degradation in a Human iPS Cell Model of Inherited Macular Degeneration

Degradation of photoreceptor outer segments (POS) by retinal pigment epithelium (RPE) is essential for vision, and studies have implicated altered POS processing in the pathogenesis of some retinal degenerative diseases. Consistent with this concept, a recently established hiPSC-RPE model of inherited macular degeneration, Best disease (BD), displayed reduced rates of POS breakdown. Herein we utilized this model to determine (i) if disturbances in protein degradation pathways are associated with delayed POS digestion and (ii) whether such defect(s) can be pharmacologically targeted. We found that BD hiPSC-RPE cultures possessed increased protein oxidation, decreased free-ubiquitin levels, and altered rates of exosome secretion, consistent with altered POS processing. Application of valproic acid (VPA) with or without rapamycin increased rates of POS degradation in our model, whereas application of bafilomycin-A1 decreased such rates. Importantly, the negative effect of bafilomycin-A1 could be fully reversed by VPA. The utility of hiPSC-RPE for VPA testing was further evident following examination of its efficacy and metabolism in a complementary canine disease model. Our findings suggest that disturbances in protein degradation pathways contribute to the POS processing defect observed in BD hiPSC-RPE, which can be manipulated pharmacologically. These results have therapeutic implications for BD and perhaps other maculopathies.

The HIV proteins Tat and Nef promote human bone marrow mesenchymal stem cell senescence and alter osteoblastic differentiation

To maintain bone mass turnover and bone mineral density (BMD), bone marrow (BM) mesenchymal stem cells (MSCs) are constantly recruited and subsequently differentiated into osteoblasts. HIV-infected patients present lower BMD than non-HIV infected individuals and a higher prevalence of osteopenia/osteoporosis. In antiretroviral treatment (ART)-naive patients, encoded HIV proteins represent pathogenic candidates. They are released by infected cells within BM and can impact on neighbouring cells. In this study, we tested whether HIV proteins Tat and/or Nef could induce senescence of human BM-MSCs and reduce their capacity to differentiate into osteoblasts. When compared to nontreated cells, MSCs chronically treated with Tat and/or Nef up to 30 days reduced their proliferative activity and underwent early senescence, associated with increased oxidative stress and mitochondrial dysfunction. The antioxidant molecule N-acetyl- cysteine had no or minimal effects on Tat- or Nef-induced senescence. Tat but not Nef induced an early increase in NF-κB activity and cytokine/chemokine secretion. Tat-induced effects were prevented by the NF-κB inhibitor parthenolide, indicating that Tat triggered senescence via NF-κB activation leading to oxidative stress. Otherwise, Nef- but not Tat-treated cells displayed early inhibition of autophagy. Rapamycin, an autophagy inducer, reversed Nef-induced senescence and oxidative stress. Moreover, Tat+Nef had cumulative effects. Finally, Tat and/or Nef decreased the MSC potential of osteoblastic differentiation. In conclusion, our in vitro data show that Tat and Nef could reduce the number of available precursors by inducing MSC senescence, through either enhanced inflammation or reduced autophagy. These results offer new insights into the pathophysiological mechanisms of decreased BMD in HIV-infected patients.

Autophagy in Vascular Disease

Autophagy is a reparative, life-sustaining process by which cytoplasmic components are sequestered in double-membrane vesicles and degraded on fusion with lysosomal compartments. Growing evidence reveals that basal autophagy is an essential in vivo process mediating proper vascular function. Moreover, autophagy is stimulated by many stress-related stimuli in the arterial wall to protect endothelial cells and smooth muscle cells against cell death and the initiation of vascular disease, in particular atherosclerosis. Basal autophagy is atheroprotective during early atherosclerosis but becomes dysfunctional in advanced atherosclerotic plaques. Little is known about autophagy in other vascular disorders, such as aneurysm formation, arterial aging, vascular stiffness, and chronic venous disease, even though autophagy is often impaired. This finding highlights the need for pharmacological interventions with compounds that stimulate the prosurvival effects of autophagy in the vasculature. A large number of animal studies and clinical trials have indicated that oral or stent-based delivery of the autophagy inducer rapamycin or derivatives thereof, collectively known as rapalogs, effectively inhibit the basic mechanisms that control growth and destabilization of atherosclerotic plaques. Other autophagy-inducing drugs, such as spermidine or add-on therapy with widely used antiatherogenic compounds, including statins and metformin, are potentially useful to prevent vascular disease with minimal adverse effects.

Interplay of autophagy and apoptosis during murine cytomegalovirus infection of RPE cells

PURPOSE

Previous studies have demonstrated that autophagy is involved in the pathogenesis of human cytomegalovirus (HCMV) infection. However, whether autophagy is regulated by murine cytomegalovirus (MCMV) infection has not yet been investigated. The purpose of these studies was to determine how autophagy is affected by MCMV infection of the retinal pigment epithelial (RPE) cells and whether there is a functional relationship between autophagy and apoptosis; and if so, how regulation of autophagy impacts apoptosis.

METHODS

RPE cells were isolated from C57BL/6 mice and infected with MCMV K181. The cells were cultured in medium containing rapamycin, chloroquine, or ammonium chloride. Green fluorescent protein-light chain 3 (GFP-LC3) plasmid was transfected to RPE cells, and the GFP-LC3 positive puncta were counted. Electron microscopic (EM) images were taken to visualize the structure of the autophagic vacuoles. Western blot was performed to detect the expression of related proteins. Trypan blue exclusion assay was used to measure the percentage of viable cells.

RESULTS

Although the LC3B-II levels consistently increased during MCMV infection of RPE cells, administration of chloroquine or ammonium chloride increased LC3B-II expression only at the early stage of infection (6 h post-inoculation [p.i.] and 12 h p.i.), not at or after 24 h p.i. The punctate autophagic vacuoles in the GFP-LC3 transfected RPE cells were counted using light microscopy or by EM examination, the number of autophagic vacuoles was significantly increased in the MCMV-infected RPE cells compared to the uninfected controls. Compared to untreated MCMV-infected control cells, rapamycin treatment resulted in a significant decrease in the cleaved caspase 3 levels as well as a significant decrease in the ratio of phosphorylated mammalian target of rapamycin (mTOR) to total mTOR and in the ratio of phosphorylated P70S6K to total P70S6K. In contrast, chloroquine treatment resulted in a significant increase in the cleaved caspase 3 levels in the MCMV-infected RPE cells.

CONCLUSIONS

Autophagic vacuole accumulation was detected during MCMV infection of RPE cells. In contrast, autophagic flux was greatly decreased at or after 24 h p.i. The results suggest that MCMV might have a strategy for inhibiting or blocking autophagy activity by targeting a later autophagy process, such as the formation of autolysosomes or degradation of their content. Our data also suggest that there is a functional relationship between autophagy and apoptosis, which plays an important role during MCMV infection of the RPE.

The interplay between autophagy and the ubiquitin-proteasome system in cardiac proteotoxicity

Proteotoxicity refers to the detrimental effects of damaged/misfolded proteins on the cell. Cardiac muscle is particularly susceptible to proteotoxicity because sustained and severe proteotoxic stress leads to cell death and the cardiac muscle has very limited self-renewal capacity. The ubiquitin-proteasome system (UPS) and the autophagic-lysosomal pathway (ALP) are two major pathways responsible for degradation of most cellular proteins. Alterations of UPS and ALP functions are associated with the accumulation of proteotoxic species in the heart, a key pathological feature of common forms of heart disease including idiopathic, ischemic, and pressure-overloaded cardiomyopathies and a large subset of congestive heart failure. Emerging evidence suggests that proteasome inhibition or impairment activates autophagy and conversely, acute ALP inhibition may sometimes increase intrinsic proteasome peptidase activities but chronic ALP inhibition hinders UPS performance in ubiquitinated protein degradation. The exact molecular basis on which the two degradative pathways interact remains largely undefined. Here we review current understanding of the roles of the UPS and autophagy in the control of cardiac proteotoxicity, with a specific focus on the crosstalk between the two pathways. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

SIRT1 in cardiovascular aging

Cardiovascular disease (CVD) is the leading cause of death worldwide, with aging as the key independent risk factor. Effective interventions are necessary to delay aging. Sirtuin1 (SIRT1), a NAD(+)-dependent histone deacetylase, is closely related to lifespan extension. SIRT1 exerts beneficial effects on aging and age-related diseases, such as atherosclerosis. In this review, we summarize the current knowledge on the functions of SIRT1 in cardiovascular aging, focusing on the underlying molecular mechanisms, including inhibition of oxidative stress and inflammation, and induction of autophagy. We also demonstrate that moderate up-regulation or activation of SIRT1 in cardiovascular aging and age-related CVD may confer important application values.

RETRACTED: Akt2 knockout alleviates prolonged caloric restriction-induced change in cardiac contractile function through regulation of autophagy

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). At the request of the University of Wyoming, this article has been retracted. Although an investigation report from Air Force Medical University found no evidence of misconduct, the University of Wyoming’s institutional investigation of the work authored by Dr. Jun Ren found evidence of data irregularities in Figures 2, 3, and 4 that affect the reported results and conclusions. All authors have been notified of the retraction of this article.

Inhibition of AMPK accentuates prolonged caloric restriction-induced change in cardiac contractile function through disruption of compensatory autophagy

Prolonged caloric restriction often results in alteration in heart geometry and function although the underlying mechanism remains poorly defined. Autophagy, a conserved pathway for bulk degradation of intracellular proteins and organelles, preserves energy and nutrient in the face of caloric insufficiency. This study was designed to examine the role of AMPK in prolonged caloric restriction-induced change in cardiac homeostasis and the underlying mechanism(s) involved with a focus on autophagy. Wild-type (WT) and AMPK kinase dead (KD) mice were caloric restricted (by 40%) for 30 weeks. Echocardiographic, cardiomyocyte contractile and intracellular Ca²⁺ properties, autophagy and autophagy regulatory proteins were evaluated. Caloric restriction compromised echocardiographic indices (decreased ventricular mass, left ventricular diameters, and cardiac output), cardiomyocyte contractile and intracellular Ca²⁺ properties associated with upregulated autophagy (Beclin-1, Atg5 and LC3BII-to-LC3BI ratio), increased autophagy adaptor protein p62, elevated phosphorylation of AMPK and TSC1/2, depressed phosphorylation of mTOR and ULK1. Although AMPK inhibition did not affect cardiac mechanical function, autophagy and autophagy signaling proteins, it significantly accentuated caloric restriction-induced changes in myocardial contractile function and intracellular Ca²⁺ handling. Interestingly, AMPK inhibition reversed caloric restriction-induced changes in autophagy and autophagy signaling. AMPK inhibition led to dampened levels of Beclin-1, Atg 5 and LC3B ratio along with suppressed phosphorylation of AMPK and TSC1/2 as well as elevated phosphorylation of mTOR and ULK1. Taken together, these data suggest an indispensible role for AMPK in the maintenance of cardiac homeostasis under prolonged caloric restriction-induced pathological changes possibly through autophagy regulation. This article is part of a Special Issue entitled: Autophagy and protein quality control in cardiometabolic diseases.

Gender differences, aging and hormonal status in mucosal injury and repair

As the "baby boomers" age, the percentage of the population over sixty-five years of age is increasing rapidly. Chronic disease management is an important component in the care of the elderly. The effects of aging on different organ systems are also pertinent; such as the weakening homeostatic response to injury in the older individuals. Mucosal surfaces have the largest combined surface area in the body and are the site of important host microbe interactions, especially in the gut which is prone to injury, both from local and systemic insult. This susceptibility has been known to increase with age. Therefore it is important to understand the interplay between aging, injury and recovery at the mucosal surface. Sex hormones play an important role in the maintenance of the mucosal barrier function as well as the mucosa associated immune function in both genders. Menopause in women is a defined time period in which major hormonal changes occur such as a decline in systemic estradiol levels. The differential levels of sex hormones contribute to the sexual dimorphism seen in response to injury at the mucosal surface, prior to and following menopause. Thus the effect of sex hormone and aging on mucosal mechanisms in response to injury is an important area of investigation.

Apelin inhibits the proliferation and migration of rat PASMCs via the activation of PI3K/Akt/mTOR signal and the inhibition of autophagy under hypoxia

Apelin is highly expressed in the lungs, especially in the pulmonary vasculature, but the functional role of apelin under pathological conditions is still undefined. Hypoxic pulmonary hypertension is the most common cause of acute right heart failure, which may involve the remodeling of artery and regulation of autophagy. In this study, we determined whether treatment with apelin regulated the proliferation and migration of rat pulmonary arterial smooth muscle cells (SMCs) under hypoxia, and investigated the underlying mechanism and the relationship with autophagy. Our data showed that hypoxia activated autophagy significantly at 24 hrs. The addition of exogenous apelin decreased the level of autophagy and further inhibited pulmonary arterial SMC (PASMC) proliferation via activating downstream phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/the mammalian target of Rapamycin (mTOR) signal pathways. The inhibition of the apelin receptor (APJ) system by siRNA abolished the inhibitory effect of apelin in PASMCs under hypoxia. This study provides the evidence that exogenous apelin treatment contributes to inhibit the proliferation and migration of PASMCs by regulating the level of autophagy.

TOR-centric view on insulin resistance and diabetic complications: perspective for endocrinologists and gerontologists

This article is addressed to endocrinologists treating patients with diabetic complications as well as to basic scientists studying an elusive link between diseases and aging. It answers some challenging questions. What is the link between insulin resistance (IR), cellular aging and diseases? Why complications such as retinopathy may paradoxically precede the onset of type II diabetes. Why intensive insulin therapy may initially worsen retinopathy. How nutrient- and insulin-sensing mammalian target of rapamycin (mTOR) pathway can drive insulin resistance and diabetic complications. And how rapamycin, at rational doses and schedules, may prevent IR, retinopathy, nephropathy and beta-cell failure, without causing side effects.

Selective anti-cancer agents as anti-aging drugs

Recent groundbreaking discoveries have revealed that IGF-1, Ras, MEK, AMPK, TSC1/2, FOXO, PI3K, mTOR, S6K, and NFκB are involved in the aging process. This is remarkable because the same signaling molecules, oncoproteins and tumor suppressors, are well-known targets for cancer therapy. Furthermore, anti-cancer drugs aimed at some of these targets have been already developed. This arsenal could be potentially employed for anti-aging interventions (given that similar signaling molecules are involved in both cancer and aging). In cancer, intrinsic and acquired resistance, tumor heterogeneity, adaptation, and genetic instability of cancer cells all hinder cancer-directed therapy. But for anti-aging applications, these hurdles are irrelevant. For example, since anti-aging interventions should be aimed at normal postmitotic cells, no selection for resistance is expected. At low doses, certain agents may decelerate aging and age-related diseases. Importantly, deceleration of aging can in turn postpone cancer, which is an age-related disease.

M(o)TOR of aging: MTOR as a universal molecular hypothalamus

A recent ground-breaking publication described hypothalamus-driven programmatic aging. As a Russian proverb goes "everything new is well-forgotten old". In 1958, Dilman proposed that aging and its related diseases are programmed by the hypothalamus. This theory, supported by beautiful experiments, remained unnoticed just to be re-discovered recently. Yet, it does not explain all manifestations of aging. And would organism age without hypothalamus? Do sensing pathways such as MTOR (mechanistic Target of Rapamycin) and IKK-beta play a role of a "molecular hypothalamus" in every cell? Are hypothalamus-driven alterations simply a part of quasi-programmed aging manifested by hyperfunction and secondary signal-resistance? Here are some answers.

Regulation of blood-testis barrier (BTB) dynamics during spermatogenesis via the "Yin" and "Yang" effects of mammalian target of rapamycin complex 1 (mTORC1) and mTORC2

In mammalian testes, haploid spermatozoa are formed from diploid spermatogonia during spermatogenesis, which is a complicated cellular process. While these cellular events were reported in the 1960s and 1970s, the underlying molecular mechanism(s) that regulates these events remained unexplored until the past ∼10 years. For instance, adhesion proteins were shown to be integrated components at the Sertoli cell-cell interface and/or the Sertoli-spermatid interface in the late 1980s. But only until recently, studies have demonstrated that some of the adhesion proteins serve as the platform for signal transduction that regulates cell adhesion. In this chapter, a brief summary and critical discussion are provided on the latest findings regarding these cell-adhesion proteins in the testis and their relationship to spermatogenesis. Moreover, antagonistic effects of two mammalian target of rapamycin (mTOR) complexes, known as mTORC1 and mTORC2, on cell-adhesion function in the testis are discussed. Finally, a hypothetic model is presented to depict how these two mTOR-signaling complexes having the "yin" and "yang" antagonistic effects on the Sertoli cell tight junction (TJ)-permeability barrier can maintain the blood-testis barrier (BTB) integrity during the epithelial cycle while preleptotene spermatocytes are crossing the BTB.

CDK4/6-inhibiting drug substitutes for p21 and p16 in senescence: duration of cell cycle arrest and MTOR activity determine geroconversion

CDKN1A (p21) and CDKN2A (p16) inhibit CDK4/6, initiating senescence. According to our view on senescence, the role of p21 and p16 is to cause cell cycle arrest, whereas MTOR (mechanistic target of rapamycin) drives geroconversion to senescence. Recently we demonstrated that one of the markers of p21- and p16-initiated senescence is MEK-dependent hyper-elevation of cyclin D1. We noticed that a synthetic inhibitor of CDK 4/6 (PD0332991) also induced cyclin D1-positive senescence. We demonstrated that PD0332991 and p21 caused almost identical senescence phenotypes. p21, p16, and PD0332991 do not inhibit MTOR, and rapamycin decelerates geroconversion caused by all 3 molecules. Like p21, PD0332991 initiated senescence at any concentration that inhibited cell proliferation. This confirms the notion that a mere arrest in the presence of active MTOR may lead to senescence.

Thyroid hormone signaling and homeostasis during aging

Studies in humans and in animal models show negative correlations between thyroid hormone (TH) levels and longevity. TH signaling is implicated in maintaining and integrating metabolic homeostasis at multiple levels, notably centrally in the hypothalamus but also in peripheral tissues. The question is thus raised of how TH signaling is modulated during aging in different tissues. Classically, TH actions on mitochondria and heat production are obvious candidates to link negative effects of TH to aging. Mitochondrial effects of excess TH include reactive oxygen species and DNA damage, 2 factors often considered as aging accelerators. Inversely, caloric restriction, which can retard aging from nematodes to primates, causes a rapid reduction of circulating TH, reducing metabolism in birds and mammals. However, many other factors could link TH to aging, and it is these potentially subtler and less explored areas that are highlighted here. For example, effects of TH on membrane composition, inflammatory responses, stem cell renewal and synchronization of physiological responses to light could each contribute to TH regulation of maintenance of homeostasis during aging. We propose the hypothesis that constraints on TH signaling at certain life stages, notably during maturity, are advantageous for optimal aging.