The role of autophagy in the heart

lncRNA C2dat2 facilitates autophagy and apoptosis via the miR-30d-5p/DDIT4/mTOR axis in cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion injury (CIRI) is an important pathophysiological process of ischemic stroke associated with various physiological and pathological processes, including autophagy and apoptosis. In this study, we examined the role and mechanism of long noncoding RNA CAMK2D-associated transcript 2 (C2dat2) in regulating CIRI in vivo and in vitro. C2dat2 up-regulation facilitated neuronal autophagy and apoptosis induced by CIRI. Mechanistically, C2dat2 acts as a competing endogenous RNA (ceRNA) to negatively regulate miR-30d-5p expression. More specifically, miR-30d-5p targeted the 3′-untranslated region of DNA damage-inducible transcript 4 (DDIT4) and silenced its target mRNA DDIT4. Additionally, C2dat2 binding with heat shock cognate 70/heat shock protein 90 blocked RNA-induced silencing complex assembly to abolish the miR-30d-5p targeting of DDIT4 and inhibited miR-30d-5p to silence its target mRNA DDIT4. Further analysis showed that C2dat2 knockdown conspicuously inhibited the up-regulation of DDIT4 and Beclin-1 levels and LC3B II/I ratio and the down-regulation of P62 and phosphorylated mammalian target of rapamycin (mTOR)/mTOR and phosphorylated-P70S6K/P70S6K ratio in Neuro-2a cells after oxygen-glucose deprivation/reoxygenation. This study first revealed that C2dat2/miR-30d-5p/DDIT4/mTOR forms a novel signaling pathway to facilitate autophagy and apoptosis induced by CIRI, contributing to the better understanding of the mechanisms of CIRI and enriching the ceRNA hypothesis in CIRI.

Ataxia Telangiectasia Mutated Protein Kinase: A Potential Master Puppeteer of Oxidative Stress-Induced Metabolic Recycling

Ataxia Telangiectasia Mutated protein kinase (ATM) has recently come to the fore as a regulatory protein fulfilling many roles in the fine balancing act of metabolic homeostasis. Best known for its role as a transducer of DNA damage repair, the activity of ATM in the cytosol is enjoying increasing attention, where it plays a central role in general cellular recycling (macroautophagy) as well as the targeted clearance (selective autophagy) of damaged mitochondria and peroxisomes in response to oxidative stress, independently of the DNA damage response. The importance of ATM activation by oxidative stress has also recently been highlighted in the clearance of protein aggregates, where the expression of a functional ATM construct that cannot be activated by oxidative stress resulted in widespread accumulation of protein aggregates. This review will discuss the role of ATM in general autophagy, mitophagy, and pexophagy as well as aggrephagy and crosstalk between oxidative stress as an activator of ATM and its potential role as a master regulator of these processes.

Diminished substrate-mediated cardiac mitochondrial respiration and elevated autophagy in adult male offspring of gestational diabetic rats

Heart diseases are common in the offspring of diabetic mother (ODM). Defects in mitochondrial metabolism and autophagy may, in part, be responsible for the adverse structural and functional alterations in the heart. The principal objective of this study was to investigate cardiac mitochondrial respiration and autophagy in male and female offspring of diabetic pregnancy at two different developmental stages of life, weaning and adult. Male and female offspring of rats with streptozotocin-induced gestational diabetes were used for the study and compared with offspring of control (non-diabetic) mother (OCM) rats. High-resolution respirometry was used to measure substrate-mediated respiration in mitochondria isolated from ventricular tissues of ODM and OCM. Expression of proteins associated with autophagy and oxidative stress was examined by western blot analysis. Mitochondrial complex I and complex II respiration was significantly reduced in adult male ODM while it was unaltered or less affected in weaning male, adult and weaning female ODM. Elevated autophagy was observed in adult male but not in adult female ODM. Expression of oxidative stress markers was observed to be similar in all the groups. Altered cardiac mitochondrial respiration and autophagy were observed in adult male ODM compared to OCM, while the male and female offspring at weaning stage were less affected. The results of the study show that maternal hyperglycemia affects mitochondrial respiration and autophagy in the ODM heart, which may potentially be responsible for the cardiovascular complications observed in adult life.

The Role of Autophagy in Eye Diseases

Autophagy is a catabolic process that ensures homeostasis in the cells of our organism. It plays a crucial role in protecting eye cells against oxidative damage and external stress factors. Ocular pathologies of high incidence, such as age-related macular degeneration, cataracts, glaucoma, and diabetic retinopathy are of multifactorial origin and are associated with genetic, environmental factors, age, and oxidative stress, among others; the latter factor is one of the most influential in ocular diseases, directly affecting the processes of autophagy activity. Alteration of the normal functioning of autophagy processes can interrupt organelle turnover, leading to the accumulation of cellular debris and causing physiological dysfunction of the eye. The aim of this study is to review research on the role of autophagy processes in the main ocular pathologies, which have a high incidence and result in high costs for the health system. Considering the role of autophagy processes in cell homeostasis and cell viability, the control and modulation of autophagy processes in ocular pathologies could constitute a new therapeutic approach.

Pretreatment of Huoxue Jiedu Formula Ameliorates Myocardial Ischaemia/Reperfusion Injury by Decreasing Autophagy via Activation of the PI3K/AKT/mTOR Pathway

Background: Myocardial ischaemia/reperfusion (I/R) results in myocardial injury via excessive autophagy. Huoxue Jiedu Formula (HJF) has been widely applied in China for the treatment of ischaemic heart disease. However, the mechanisms of HJF are still poorly understood. Thus, the present experiment was designed to observe the effects of HJF on myocardial I/R injury and explore the possible mechanism.

Methods: Myocardial injury in rats subjected to myocardial I/R was reflected by nitrotetrazolium blue chloride staining, thioflavin S staining, serum creatine kinase-MB (CK-MB) and cardiac troponin T (cTnT). Autophagy was determined by electron microscopy, laser confocal microscopy, Q-PCR and western blot. The possible pathway was predicted by network pharmacology and validated in vivo and in vitro.

Results: Pretreatment of HJF decreased the no-reflow area, infarcted area, serum CK-MB levels and serum cTnT levels in I/R rat model. In addition, pretreatment of HJF decreased autophagy in heart tissues (decrease in Beclin-1 and LC3-II, and increase in Bcl-2, p62 and ratio of LC3-I/LC3-II). In the vivo study, pretreatment of HJF significantly decreased hypoxia/reoxygenation (H/R)-induced autophagy in H9C2 cells. Network pharmacology was applied to predict the possible mechanism by which HJF affects cardiac autophagy, and the PI3K/AKT/mTOR signalling pathway was the most significantly enriched pathway. And experimental studies demonstrated that pretreatment of HJF increased the phosphorylation of AKT and mTOR, and the effects of HJF on autophagy would be offset by PI3K inhibitor LY294002.

Conclusion: Pretreatment of HJF ameliorates myocardial I/R injury by decreasing autophagy through activating PI3K/AKT/mTOR pathway.

Ubiquitin-like protein FAT10 suppresses SIRT1-mediated autophagy to protect against ischemic myocardial injury

Autophagy plays a deleterious role in ischemic myocardial injury. The deacetylase SIRT1 is a well-established regulator of autophagy that can be modified by the ubiquitin-like protein SUMO1. Our previous work demonstrated that another ubiquitin-like protein, FAT10, exerts cardioprotective effects against myocardial ischemia by stabilizing the caveolin-3 protein; however, the effects of FAT10 on autophagy through SIRT1 are unclear. Here, we constructed a Fat10-knockout rat model to evaluate the role of FAT10 in autophagy. In vivo and in vitro assays confirmed that FAT10 suppressed autophagy to protect the heart from ischemic myocardial injury. Mechanistically, FAT10 was mainly involved in the regulation of the autophagosome formation process. FAT10 affected autophagy through modulating SIRT1 degradation, which resulted in reduced SIRT1 nuclear translocation and inhibited SIRT1 activity via its C-terminal glycine residues. Notably, FAT10 competed with SUMO1 at the K734 modification site of SIRT1, which further reduced LC3 deacetylation and suppressed autophagy. Our findings suggest that FAT10 inhibits autophagy by antagonizing SIRT1 SUMOylation to protect the heart from ischemic myocardial injury. This is a novel mechanism through which FAT10 regulates autophagy as a cardiac protector.

High Expression of miR-204 in Chicken Atrophic Ovaries Promotes Granulosa Cell Apoptosis and Inhibits Autophagy

Chicken atrophic ovaries have decreased volume and are indicative of ovarian failure, presence of a tumor, or interrupted ovarian blood supply. Ovarian tumor is accompanied by an increase in follicular atresia, granulosa cell (GC) apoptosis, and autophagy. In a previous study, we found using high throughput sequencing that miR-204 is highly expressed in chicken atrophic ovaries. Thus, in the present study, we further investigated its function in GC apoptosis and autophagy. We found that overexpression of miR-204 reduced mRNA and protein levels of proliferation-related genes and increased apoptosis-related genes. Cell counting kit-8 (CCK-8), 5-ethynyl-2-deoxyuridine (EdU), and flow cytometry assays revealed that miR-204 inhibited GC proliferation and promoted apoptosis. Furthermore, we confirmed with reporter gene assays that Forkhead box K2 (FOXK2) was directly targeted by miR-204. FOXK2, as a downstream regulator of phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signal pathways, promoted GC proliferation and inhibited apoptosis. Subsequently, we observed that miR-204 was involved in GC autophagy by targeting Transient Receptor Potential Melastatin 3 (TRPM3). The luciferase activities of the two binding sites of TRPM3 were decreased in response to treatment with a miR-204 mimic, and the autophagic flux was increased after miR-204 inhibition. However, overexpression of miR-204 had opposite results in autophagosomes and autolysosomes. miR-204 inhibits GC autophagy by suppressing the protein expression of TRPM3/AMP-activated protein kinase (AMPK)/ULK signaling pathway components. Inhibition of miR-204 enhanced autophagy by accumulating and degrading the protein levels of LC3-II (Microtubule Associated Protein Light Chain 3B) and p62 (Protein of 62 kDa), respectively, whereas miR-204 overexpression was associated with contrary results. Immunofluorescence staining showed that there was a significant reduction in the fluorescent intensity of LC3B, whereas p62 protein was increased after TRPM3 silencing. Collectively, our results indicate that miR-204 is highly expressed in chicken atrophic ovaries, which promotes GC apoptosis via repressing FOXK2 through the PI3K/AKT/mTOR pathway and inhibits autophagy by impeding the TRPM3/AMPK/ULK pathway.

Protection against Doxorubicin-Induced Cardiac Dysfunction Is Not Maintained Following Prolonged Autophagy Inhibition

Doxorubicin (DOX) is a highly effective chemotherapeutic agent used in the treatment of various cancer types. Nevertheless, it is well known that DOX promotes the development of severe cardiovascular complications. Therefore, investigation into the underlying mechanisms that drive DOX-induced cardiotoxicity is necessary to develop therapeutic countermeasures. In this regard, autophagy is a complex catabolic process that is increased in the heart following DOX exposure. However, conflicting evidence exists regarding the role of autophagy dysregulation in the etiology of DOX-induced cardiac dysfunction. This study aimed to clarify the contribution of autophagy to DOX-induced cardiotoxicity by specifically inhibiting autophagosome formation using a dominant negative autophagy gene 5 (ATG5) adeno-associated virus construct (rAAV-dnATG5). Acute (2-day) and delayed (9-day) effects of DOX (20 mg/kg intraperitoneal injection (i.p.)) on the hearts of female Sprague–Dawley rats were assessed. Our data confirm established detrimental effects of DOX on left ventricular function, redox balance and mitochondrial function. Interestingly, targeted inhibition of autophagy in the heart via rAAV-dnATG5 in DOX-treated rats ameliorated the increase in mitochondrial reactive oxygen species emission and the attenuation of cardiac and mitochondrial function, but only at the acute timepoint. Deviation in the effects of autophagy inhibition at the 2- and 9-day timepoints appeared related to differences in ATG5–ATG12 conjugation, as this marker of autophagosome formation was significantly elevated 2 days following DOX exposure but returned to baseline at day 9. DOX exposure may transiently upregulate autophagy signaling in the rat heart; thus, long-term inhibition of autophagy may result in pathological consequences.

Programmed Cell Death in the Left and Right Ventricle of the Late Phase of Post-Infarction Heart Failure

While necroptosis has been shown to contribute to the pathogenesis of post-infarction heart failure (HF), the role of autophagy remains unclear. Likewise, linkage between these two cell death modalities has not been sufficiently investigated. HF was induced by 60-min left coronary occlusion in adult Wistar rats and heart function was assessed 6 weeks later followed by immunoblotting analysis of necroptotic and autophagic proteins in both the left (LV) and right ventricle (RV). HF had no effect on RIP1 and RIP3 expression. PhosphoSer229-RIP3, acting as a pro-necroptotic signal, was increased in LV while deceased in RV of failing hearts. Total MLKL was elevated in RV only. Decrease in pSer555-ULK1, increase in pSer473-Akt and no significant elevation in beclin-1 and LC3-II/I ratio indicated rather a lowered rate of autophagy in LV. No beclin-1 upregulation and decreased LC3 processing also suggested the inhibition of both autophagosome formation and maturation in RV of failing hearts. In contrast, p89 PARP1 fragment, a marker of executed apoptosis, was increased in RV only. This is the first study showing a different signaling in ventricles of the late phase of post-infarction HF, highlighting necroptosis itself rather than its linkage with autophagy in LV, and apoptosis in RV.

THRIL mediates endothelial progenitor cells autophagy via AKT pathway and FUS

Background

This study focused on the roles of lncRNA THRIL in coronary atherosclerotic heart disease (CAD) through regulating AKT signaling pathway and directly interacting with FUS.

Methods

QRT-PCR was conducted to detect the expression of THRIL in CAD blood samples and endothelial progenitor cells (EPCs). Cell autophagy of EPCs was examined through Cyto-ID Autophagy Detection Kit. CCK-8 assay and flow cytometry were carried out to assess cell viability and apoptosis under various interference conditions. Western blotting was conducted to detect the expression of interest proteins. The expression levels of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) were measured by qRT-PCR. The direct interactions between HCG18 and FUS was confirmed through RNA electrophoretic mobility shift assay (RNA EMSA) and RNA immunoprecipitation (RIP) assay.

Results

THRIL was upregulated in CAD blood samples and EPCs. Knockdown of THRIL in EPCs promoted cell viability, inhibited cell autophagy and further suppressed the development of CAD. Over-expression of THRIL induced inactivation of AKT pathway, while knockdown of THRIL played reversed effects. THRIL directly interacted with FUS protein and knockdown of FUS reversed the over-expressing effect of THRIL on cell proliferation, autophagy and the status of AKT pathway.

Conclusion

THRIL inhibits the proliferation and mediates autophagy of endothelial progenitor cells via AKT pathway and FUS.

MD1 deletion exaggerates cardiomyocyte autophagy induced by heart failure with preserved ejection fraction through ROS/MAPK signalling pathway

In our previous studies, we reported that myeloid differentiation protein 1 (MD1) serves as a negative regulator in several cardiovascular diseases. However, the role of MD1 in heart failure with preserved ejection fraction (HFpEF) and the underlying mechanisms of its action remain unclear. Eight‐week‐old MD1‐knockout (MD1‐KO) and wild‐type (WT) mice served as models of HFpEF induced by uninephrectomy, continuous saline or d‐aldosterone infusion and a 1.0% sodium chloride treatment in drinking water for 4 weeks to investigate the effect of MD1 on HFpEF in vivo. H9C2 cells were treated with aldosterone to evaluate the role of MD1 KO in vitro. MD1 expression was down‐regulated in the HFpEF mice; HFpEF significantly increased the levels of intracellular reactive oxygen species (ROS) and promoted autophagy; and in the MD1‐KO mice, the HFpEF‐induced intracellular ROS and autophagy effects were significantly exacerbated. Moreover, MD1 loss activated the p38‐MAPK pathway both in vivo and in vitro. Aldosterone‐mediated cardiomyocyte autophagy was significantly inhibited in cells pre‐treated with the ROS scavenger N‐acetylcysteine (NAC) or p38 inhibitor SB203580. Furthermore, inhibition with the autophagy inhibitor 3‐methyladenine (3‐MA) offset the aggravating effect of aldosterone‐induced autophagy in the MD1‐KO mice and cells both in vivo and in vitro. Our results validate a critical role of MD1 in the pathogenesis of HFpEF. MD1 deletion exaggerates cardiomyocyte autophagy in HFpEF via the activation of the ROS‐mediated MAPK signalling pathway.

Cardiac effects and toxicity of chloroquine: a short update

There is currently increased interest in the use of the antimalarial drugs chloroquine and hydroxychloroquine for the treatment of other diseases, including cancer and viral infections such as coronavirus disease 2019 (COVID-19). However, the risk of cardiotoxic effects tends to limit their use. In this review, the effects of these drugs on the electrical and mechanical activities of the heart as well as on remodelling of cardiac tissue are presented and the underlying molecular and cellular mechanisms are discussed. The drugs can have proarrhythmic as well as antiarrhythmic actions resulting from their inhibition of ion channels, including voltage-dependent Na⁺ and Ca²⁺ channels, background and voltage-dependent K⁺ channels, and pacemaker channels. The drugs also exert a vagolytic effect due at least in part to a muscarinic receptor antagonist action. They also interfere with normal autophagy flux, an effect that could aggravate ischaemia/reperfusion injury or post-infarct remodelling. Most of the toxic effects occur at high concentrations, following prolonged drug administration or in the context of drug associations.

Dilated cardiomyopathy-linked heat shock protein family D member 1 mutations cause up-regulation of reactive oxygen species and autophagy through mitochondrial dysfunction

AIMS

During heart failure, the levels of circulatory heat shock protein family D member 1 (HSP60) increase. However, its underlying mechanism is still unknown. The apical domain of heat shock protein family D member 1 (HSPD1) is conserved throughout evolution. We found a point mutation in HSPD1 in a familial dilated cardiomyopathy (DCM) patient. A similar point mutation in HSPD1 in the zebrafish mutant, nbl, led to loss of its regenerative capacity and development of pericardial oedema under heat stress condition. In this study, we aimed to determine the direct involvement of HSPD1 in the development of DCM.

METHODS AND RESULTS

By Sanger method, we found a point mutation (Thr320Ala) in the apical domain of HSPD1, in one familial DCM patient, which was four amino acids away from the point mutation (Val324Glu) in the nbl mutant zebrafish. The nbl mutants showed atrio-ventricular block and sudden death at 8-month post-fertilization. Histological and microscopic analysis of the nbl mutant hearts showed decreased ventricular wall thickness, elevated level of reactive oxygen species (ROS), increased fibrosis, mitochondrial damage, and increased autophagosomes. mRNA and protein expression of autophagy-related genes significantly increased in nbl mutants. We established HEK293 stable cell lines of wild-type, nbl-type, and DCM-type HSPD1, with tetracycline-dependent expression. Compared to wild-type, both nbl- and DCM-type cells showed decreased cell growth, increased expression of ROS and autophagy-related genes, inhibition of the activity of mitochondrial electron transport chain complexes III and IV, and decreased mitochondrial fission and fusion.

CONCLUSION

Mutations in HSPD1 caused mitochondrial dysfunction and induced mitophagy. Mitochondrial dysfunction caused increased ROS and cardiac atrophy.

Ulinastatin attenuates lipopolysaccharide-induced cardiac dysfunction by inhibiting inflammation and regulating autophagy

Ulinastatin exerts protective effects against lipopolysaccharide (LPS)-induced cardiac dysfunction. Autophagy has been demonstrated to serve an important role in sepsis-induced cardiomyopathy; however, whether ulinastatin has an anti-autophagic effect in sepsis requires further investigation. The present study aimed to determine the protective effects of ulinastatin on cardiac dysfunction and its role in autophagy during sepsis. C57BL/6J mice were randomly divided into a control, LPS and LPS + ulinastatin group, the survival status of the mice was observed every 6 h and the survival rate at each time point was calculated for 7 days. Furthermore, JC-1 dye and ELISAs were used to analyze the mitochondrial membrane potential (MMP) and serum cardiac troponin I (cTnI) levels, respectively. Western blotting and ELISAs were used to measure the levels of tumor necrosis factor (TNF)-α and interleukin (IL)-6. In addition, the cardiac ultrastructure and the number of autophagosomes formed were visualized using transmission electron microscopy, and the pathological changes in the myocardial tissues were analyzed using hematoxylin & eosin staining. Finally, the expression levels of autophagy-related proteins were analyzed using western blotting and immunofluorescence staining. The current study indicated that ulinastatin significantly improved the survival rate of septic mice. It was suggested that ulinastatin may protect against LPS-induced myocardium injury through its anti-inflammatory activity, as decreased cTnI levels, increased MMP and decreased expression levels of TNF-α and IL-6 were all observed following ulinastatin treatment. Furthermore, the number of autophagosomes formed, and the expression levels of microtubule-associated protein light chain 3 and Beclin 1 were significantly decreased following ulinastatin treatment. It was further observed that ulinastatin suppressed LPS-induced autophagosome formation, as indicated by the accumulation of sequestosome 1/p62, and the elimination of lysosome-associated membrane glycoprotein 1. In conclusion, the results of the present study suggested that ulinastatin treatment may improve survival and exert a protective effect over LPS-induced cardiac dysfunction. Furthermore, this protective effect may be associated with its anti-inflammatory and anti-autophagic activity.

Cardiomyocyte Contractility and Autophagy in a Premature Senescence Model of Cardiac Aging

Globally, cardiovascular diseases are the leading cause of death in the aging population. While the clinical pathology of the aging heart is thoroughly characterized, underlying molecular mechanisms are still insufficiently clarified. The aim of the present study was to establish an in vitro model system of cardiomyocyte premature senescence, culturing heart muscle cells derived from neonatal C57Bl/6J mice for 21 days. Premature senescence of neonatal cardiac myocytes was induced by prolonged culture time in an oxygen-rich postnatal environment. Age-related changes in cellular function were determined by senescence-associated β-galactosidase activity, increasing presence of cell cycle regulators, such as p16, p53, and p21, accumulation of protein aggregates, and restricted proteolysis in terms of decreasing (macro-)autophagy. Furthermore, the culture system was functionally characterized for alterations in cell morphology and contractility. An increase in cellular size associated with induced expression of atrial natriuretic peptides demonstrated a stress-induced hypertrophic phenotype in neonatal cardiomyocytes. Using the recently developed analytical software tool Myocyter, we were able to show a spatiotemporal constraint in spontaneous contraction behavior during cultivation. Within the present study, the 21-day culture of neonatal cardiomyocytes was defined as a functional model system of premature cardiac senescence to study age-related changes in cardiomyocyte contractility and autophagy.

Autophagy is involved in the sclerotic phase of systemic sclerosis

Autophagy is an essential intracellular self-degradation system, and is known to maintain the homeostatic balance between the synthesis, degradation, and recycling of cellular proteins and organelles. Recent studies have suggested a possible role of autophagy in systemic sclerosis (SSc);however, differences in autophagy among pathological phases of SSc have not yet been examined. Therefore, in the current study we investigated the expression pattern of an autophagosome marker protein, microtubule-associated protein 1 light chain 3 (LC3) in the lesional skin of a murine model and human SSc. In bleomycin-induced mouse scleroderma skin, the number of LC3-positive puncta was significantly higher than that in phosphate buffered salts-injected control skin after 4 weeks of treatment. Such an increase, however, was not observed in the skin after 2 weeks of bleomycin treatment, in which few myofibroblasts were detected. In the sclerotic phase of SSc patients, the number of LC3-positive puncta in the lower dermis was significantly higher than in the upper dermis. It was also significantly higher than in the lower dermis of the control patients. No increase in LC3-positive puncta was observed in the skin from SSc patients in edematous phase, in which myofibroblasts were hardly detected. These results suggest that changes in the autophagic degradation system reflect a skin remodeling process that leads to fibrosis.

Berberine Protects Against Simulated Ischemia/Reperfusion Injury-Induced H9C2 Cardiomyocytes Apoptosis In Vitro and Myocardial Ischemia/Reperfusion-Induced Apoptosis In Vivo by Regulating the Mitophagy-Mediated HIF-1α/BNIP3 Pathway

Berberine (BBR) has a variety of pharmacological activities and is widely used in Asian countries. However, the clinical application of BBR still lacks scientific basis, what protective mechanism of BBR against myocardial ischemia-reperfusion injury (MIRI). In vitro experiments, BBR pretreatment regulated autophagy-related protein expression, induced cell proliferation and autophagosome formation, and reduced the mitochondrial membrane potential (ΔΨm) increase in H9C2 cells. In vivo experiments, BBR reduced the myocardial infarct size, decreased cardiomyocyte apoptosis, and markedly decreased myocardial enzyme (CK-MB, LDH, and AST) activity-induced I/R. In addition, upon BNIP3 knockdown, the regulatory effects of BBR on the above indicators were weakened both in H9C2 cells and in vivo. Luciferase reporter and ChIP assays indicated that BBR mediated BNIP3 expression by enhancing the binding of HIF-1α to the BNIP3 promoter. BBR protects against myocardial I/R injury by inducing cardiomyocytes proliferation, inhibiting cardiomyocytes apoptosis, and inducing the mitophagy-mediated HIF-1α/BNIP3 pathway. Thus, BBR may serve as a novel therapeutic drug for myocardial I/R injury.

How autophagy can restore proteostasis defects in multiple diseases?

Cellular evolution develops several conserved mechanisms by which cells can tolerate various difficult conditions and overall maintain homeostasis. Autophagy is a well-developed and evolutionarily conserved mechanism of catabolism, which endorses the degradation of foreign and endogenous materials via autolysosome. To decrease the burden of the ubiquitin-proteasome system (UPS), autophagy also promotes the selective degradation of proteins in a tightly regulated way to improve the physiological balance of cellular proteostasis that may get perturbed due to the accumulation of misfolded proteins. However, the diverse as well as selective clearance of unwanted materials and regulations of several cellular mechanisms via autophagy is still a critical mystery. Also, the failure of autophagy causes an increase in the accumulation of harmful protein aggregates that may lead to neurodegeneration. Therefore, it is necessary to address this multifactorial threat for in-depth research and develop more effective therapeutic strategies against lethal autophagy alterations. In this paper, we discuss the most relevant and recent reports on autophagy modulations and their impact on neurodegeneration and other complex disorders. We have summarized various pharmacological findings linked with the induction and suppression of autophagy mechanism and their promising preclinical and clinical applications to provide therapeutic solutions against neurodegeneration. The conclusion, key questions, and future prospectives sections summarize fundamental challenges and their possible feasible solutions linked with autophagy mechanism to potentially design an impactful therapeutic niche to treat neurodegenerative diseases and imperfect aging.

CD5L-induced activation of autophagy is associated with hepatoprotection in ischemic reperfusion injury via the CD36/ATG7 axis

Hepatic ischemia/reperfusion (I/R) injury is a side effect of major liver surgery that is difficult to prevent. I/R injury induces metabolic strain on hepatocytes and limits the tolerable ischemia during liver resection, as well as preservation times during transplantation. Additionally, I/R injury induces apoptosis in hepatocytes. CD5-like (CD5L), an inducer of autophagy, is a soluble scavenger cysteine-rich protein that modulates hepatocyte apoptosis. The aim of the present study was to determine if pharmacologic CD5L was protective against hepatic ischemia-reperfusion injury. Hepatocytes were subjected to I/R culture conditions, and apoptosis and caspase family activity were measured after I/R to model hepatic injury. Treatment with recombinant CD5L significantly suppressed apoptosis and caspase activity through modulating cellular autophagy to maintain activation of the cluster of differentiation 36 (CD36)-dependent autophagy-related 7 (ATG7) signaling pathway. The regulation loop between CD5L and the autophagy signaling pathway was identified to be associated with the inhibition of oxidative stress. Treatment with CD5L significantly inhibited cellular oxidative stress, which was confirmed by silencing the CD36 receptor or the autophagy related protein ATG7 using small interfering RNA, which reversed the antiapoptotic and antioxidative effects of CD5L on hepatocytes under I/R conditions. The results of the present study suggested that CD5L-mediated attenuation of hepatic I/R injury occurs through the CD36-dependent ATG7 pathway, accompanied by the inhibition of oxidative stress, which is associated with enhanced autophagy. In conclusion, the present study identifies CD5L as a novel therapeutic agent for hepatic I/R injury.

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

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

Downregulation of P300/CBP-Associated Factor Attenuates Myocardial Ischemia-Reperfusion Injury Via Inhibiting Autophagy

Cardiomyocyte autophagy plays an important role in myocardial ischemia-reperfusion injury (MIRI). P300/CBP-associated factor (PCAF) was involved in the regulation of autophagy. However, the role of PCAF in MIRI is currently unknown. This study was to investigate whether downregulation of PCAF attenuate MIRI. The results showed that the expression of PCAF was significantly increased in MIRI in vivo and in vitro. Downregulation of PCAF not only inhibited autophagy and damage of H9c2 cells induced by hypoxia-reoxygenation, but also reduced autophagy and myocardial infarct size during myocardial ischemia-reperfusion in rats. In addition, downregulation of PCAF promoted activation of PI3K/Akt/mTOR signaling pathway in cardiomyocytes during hypoxia-reoxygenation. Wortmannin, a PI3K/Akt inhibitor, could abrogate the effects of downregulation of PCAF on cardiomyocytes autophagy. These results demonstrated that downregulation of PCAF alleviated MIRI by inhibiting cardiomyocyte autophagy through PI3K/Akt/mTOR signaling pathway. Thus, PCAF may be a potential target for prevention and treatment of MIRI.

Regulation of cell death in the cardiovascular system

The adult heart is a post-mitotic terminally differentiated organ; therefore, beyond development, cardiomyocyte cell death is maladaptive. Heart disease is the leading cause of death in the world and aberrant cardiomyocyte cell death is the underlying problem for most cardiovascular-related diseases and fatalities. In this chapter, we will discuss the different cell death mechanisms that engage during normal cardiac development, aging, and disease states. The most abundant loss of cardiomyocytes occurs during a myocardial infarction, when the blood supply to the heart is obstructed, and the affected myocardium succumbs to cell death. Originally, this form of cell death was considered to be unregulated; however, research from the last half a century clearly demonstrates that this form of cell death is multifaceted and employees various degrees of regulation. We will explore all of the cell death pathways that have been implicated in this disease state and the potential interplay between them. Beyond myocardial infarction, we also explore the role and mechanisms of cardiomyocyte cell death in heart failure, myocarditis, and chemotherapeutic-induced cardiotoxicity. Inhibition of cardiomyocyte cell death has extensive therapeutic potential that will increase the longevity and health of the human heart.

Rapamycin Treatment Reduces Acute Myocarditis Induced by Trypanosoma cruzi Infection

Chagas disease affects millions of people mainly in Latin America and is a protozoan illness caused by the parasite Trypanosoma cruzi. Chagasic cardiomyopathy is the leading cause of mortality of infected patients, due to compromised electrical and mechanical cardiac function induced by tissue remodeling, especially fibrosis, and lymphocytic infiltration. Some cellular biochemical pathways can be protective to the heart, and we tested if the in vivo activation of the autophagic machinery by rapamycin could reduce parasite-induced myocarditis. Regarding the expression of LC3, an autophagy marker, we observed its upregulation in the cardiac tissue of infected untreated mice. However, after rapamycin treatment, an autophagy inducer, infected mice showed reduced electrical cardiac dysfunctions, myocarditis, cardiac damage, and reduced production of pro-inflammatory cytokines by the heart. On the other hand, the parasite's life cycle was not affected, and we observed no modulations in cardiac tissue or blood parasitemia. Our data indicate that, at least partially, autophagy induction controls inflammation in the heart¸ illustrating the complexity of the pathways that concur to the development of the infection.

Role of Autophagy Biomarkers In Burn-Age Estimation and Progression

BACKGROUND

Determination of time passed since burn injury in the living is critical in forensic science. Autophagy biomarkers and vitronectin can play an important role in determination of the age of burn injuries through their levels in the tissue.

OBJECTIVE

The aim of this study was to investigate the role of autophagy biomarkers in dating burn injury and to correlate them with the histopathological effects of deep second-degree thermal burn.

METHOD

Fifty-four male rats were used in this study after infliction of second-degree thermal burns to their skin. Samples were taken from them after 30 minutes and one, four, 24, 48, and 72 hours following burn to be examined histologically and also for autophagy biomarkers and vitronectin.

RESULTS

Significant reduction in the autophagy biomarkers (p < 0.001) over the first 24 hours then began to increase but still not reach the normal level up to 72 hours after burn. Vitronectin level increased after burn infliction 1.5-fold after first hour, then up to four-fold after four hours and after that began to decline but still did not reach the normal level up to 72 hours.

CONCLUSION

Autophagy biomarkers can be used as a forensic tool in determination of the time passed since burn infliction in living.

Cardioprotective roles of sestrin 1 and sestrin 2 against doxorubicin cardiotoxicity

Doxorubicin is a chemotherapy medication widely used to treat a variety of cancers. Even though it offers one of the most effective anti-cancer treatments, its clinical use is limited because of its strong cardiotoxicity that can lead to fatal conditions. Here, we show that sestrin 1 and sestrin 2, members of the sestrin family of proteins that are stress-inducible regulators of metabolism, are critical for suppressing doxorubicin cardiotoxicity and coordinating the AMPK-mammalian target of rapamycin complex 1 (mTORC1) autophagy signaling network for cardioprotection. Expression of both sestrin 1 and sestrin 2 was highly increased in the mouse heart after doxorubicin injection. Genetic ablation of sestrin 1 and sestrin 2 rendered mice more vulnerable to doxorubicin and exacerbated doxorubicin-induced cardiac pathologies including cardiomyocyte apoptosis and cardiac dysfunction. These pathologies were associated with strong dysregulation of the cardiac signaling network, including suppression of the AMPK pathway and activation of the mTORC1 pathway. Consistent with AMPK downregulation and mTORC1 upregulation, autophagic activity of heart tissue was diminished, leading to prominent accumulation of autophagy substrate, p62/SQSTM1. Taken together, our results indicate that sestrin 1 and sestrin 2 are important cardioprotective proteins that coordinate metabolic signaling pathways and autophagy to minimize cardiac damage in response to doxorubicin insult. Augmenting this protective mechanism could provide a novel therapeutic rationale for prevention and treatment of doxorubicin cardiotoxicity. NEW & NOTEWORTHY Doxorubicin is a highly efficient chemotherapeutic medicine; however, its use is limited because of its strong cardiotoxicity. Here, we show that sestrin 1 and sestrin 2 are critical protectors of cardiomyocytes from doxorubicin damage. By upregulating AMPK and autophagic activities and suppressing mammalian target of rapamycin complex 1 and oxidative stress, sestrins counteract detrimental effects of doxorubicin on cardiomyocytes. Correspondingly, loss of sestrin 1 and sestrin 2 produced remarkable dysregulation of these pathways, leading to prominent cardiac cell death and deterioration of heart function.

miR-27a-5p Attenuates Hypoxia-induced Rat Cardiomyocyte Injury by Inhibiting Atg7

Acute myocardial infarction (AMI) is an ischemic heart disease with high mortality worldwide. AMI triggers a hypoxic microenvironment and induces extensive myocardial injury, including autophagy and apoptosis. MiRNAs, which are a class of posttranscriptional regulators, have been shown to be involved in the development of ischemic heart diseases. We have previously reported that hypoxia significantly alters the miRNA transcriptome in rat cardiomyoblast cells (H9c2), including miR-27a-5p. In the present study, we further investigated the potential function of miR-27a-5p in the cardiomyocyte response to hypoxia, and showed that miR-27a-5p expression was downregulated in the H9c2 cells at different hypoxia-exposed timepoints and the myocardium of a rat AMI model. Follow-up experiments revealed that miR-27a-5p attenuated hypoxia-induced cardiomyocyte injury by regulating autophagy and apoptosis via Atg7, which partly elucidated the anti-hypoxic injury effects of miR-27a-5p. Taken together, this study shows that miR-27a-5p has a cardioprotective effect on hypoxia-induced H9c2 cell injury, suggesting it may be a novel target for the treatment of hypoxia-related heart diseases.

TEEG Induced A549 Cell Autophagy by Regulating the PI3K/AKT/mTOR Signaling Pathway

TEEG (3β,16β,23-trihydroxy-13,28-epoxyurs-11-ene-3-O-β-D-glucopyranoside) is derived from the chloroform extract of the Chinese medicine formula Shenqi San (CE-SS). In the present study, we aimed to elucidate the anticancer effect and possible molecular mechanism underlying the action of TEEG against the human non-small cell lung cancer (NSCLC) cell line A549 in vitro. A549 cells were incubated with different concentrations of TEEG. Cell proliferation was assessed by MTT assay. Autophagy was evaluated by immunofluorescence staining. Autophagy-associated proteins were examined by Western blot analysis. TEEG markedly inhibited A549 cell proliferation in a concentration-dependent manner. Immunofluorescence staining showed that TEEG induced autophagy in A549 cells. The LC3-II : LC3-I conversion ratio and the expression of Beclin-1, Atg5, Atg7, and Atg12 increased with the concentration of TEEG. In addition, increased TEEG concentration enhanced the expression of Class III p-PI3K and reduced the expression of Class I p-PI3K, p-AKT, p-mTOR, and p-P70S6K. These results indicate that TEEG induces autophagy of A549 cells through regulation of the PI3K/AKT/mTOR signaling pathway.

Effects of miR‑103a‑3p on the autophagy and apoptosis of cardiomyocytes by regulating Atg5

Autophagy and apoptosis are associated with cardiovascular diseases. Emerging evidence shows that microRNAs (miRs) are critical in the development of pathological processes underlying cardiovascular diseases by regulating the induction of apoptosis and autophagy. The present study aimed to investigate the role of miR-103a-3p in cardiomyocyte injury through autophagy and apoptosis. H9c2 cells were cultured under hypoxia and reoxygenation (H/R) conditions and were used to mimic cells under ischemia. The transfection of cells with miR-103a-3p (mimics and inhibitors) was performed to examine its function in cardiomyocytes. The expression levels of miR-103a-3p were evaluated by reverse transcription-quantitative polymerase chain reaction analysis. Cell viability was determined using an MTT assay, and the lactate dehydrogenase assay (LDH) was used to investigate cell injury. The expression levels of B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein, Beclin-1, autophagy-related 5 (Atg5), cleaved caspase-3 and cleaved caspase-9 were detected using western blotting. Immunofluorescence assays were performed to detect the expression of LC3 as a marker of autophagy. The target gene of miR-103a-3p was identified using dual-luciferase reporter assays. The results revealed that the expression levels of miR-103a-3p were significantly downregulated in cardiomyocytes under H/R conditions. Injury of the cardiomyocytes was evaluated under H/R conditions. Following transfection of the cells with miR-103a-3p inhibitors, cell injury was increased, as determined by LDH and MTT assays. The expression levels of apoptotic proteins were consistent with the results obtained in the LDH and cell viability assays. The induction of autophagy was increased in cells under H/R conditions and cells with miR-103a-3p inhibitor transfection, whereas the induction of autophagy was decreased in cells transfected with miR-103a-3p mimics. In addition, the data indicated that miR-103a-3p directly targeted Atg5, which regulated the induction of autophagy and apoptosis. Taken together, these findings indicate that, following the inhibition of miR-103a-3p, Atg5 promotes autophagy and apoptosis in cardiomyocytes by directly targeting Atg5. Therefore, miR-103a-3p can be considered a potential therapeutic target for myocardial ischemia.

Autophagy in the Heart

The autophagic machinery is a well-conserved degradation system in eukaryotes from yeast to mammals. Autophagy has been thought of as a nonselective degradation process in which cytoplasmic proteins and organelles are degraded by fusion with lysosome. Recent studies have revealed selective forms of autophagy, such as mitochondria-specific autophagy, termed "mitophagy". Research over the past decade has revealed that autophagy in cardiomyocytes plays a protective role, not only during hemodynamic stress but in homeostasis during aging. Hemodynamic stress and aging induce mitochondrial damage, leading to increased oxidative stress and decreased ATP production. Damaged mitochondria are generally degraded through mitophagy, which might be the main protective function of autophagy in the heart. Complete digestion of mitochondrial DNA through mitophagy is important to avoid inflammatory responses that can induce heart failure. A polyamine, spermidine, is reported to bring about an extension of lifespan and to protect the heart from age-related cardiac dysfunction, both of which are mediated through induction of autophagy. Therefore, appropriate induction of autophagy could be a novel therapeutic target for cardiovascular diseases, including heart failure. However, precise evaluation of autophagic activity in the human heart is difficult at this time, but exploitation of the novel technique of autophagy evaluation is expected for both drug discovery and clinical application.

Role of Autophagy in Proteostasis: Friend and Foe in Cardiac Diseases

Due to ageing of the population, the incidence of cardiovascular diseases will increase in the coming years, constituting a substantial burden on health care systems. In particular, atrial fibrillation (AF) is approaching epidemic proportions. It has been identified that the derailment of proteostasis, which is characterized by the loss of homeostasis in protein biosynthesis, folding, trafficking, and clearance by protein degradation systems such as autophagy, underlies the development of common cardiac diseases. Among various safeguards within the proteostasis system, autophagy is a vital cellular process that modulates clearance of misfolded and proteotoxic proteins from cardiomyocytes. On the other hand, excessive autophagy may result in derailment of proteostasis and therefore cardiac dysfunction. Here, we review the interplay between autophagy and proteostasis in the healthy heart, discuss the imbalance between autophagy and proteostasis during cardiac diseases, including AF, and finally explore new druggable targets which may limit cardiac disease initiation and progression.

Silencing H19 regulated proliferation, invasion, and autophagy in the placenta by targeting miR-18a-5p

Fetal growth restriction (FGR) is a serious pregnancy complication associated with increased perinatal mortality and morbidity. It may lead to neurodevelopmental impairment and adulthood onset disorders. Recently, long noncoding RNAs (lncRNAs) were found to be associated with the pathogenesis of FGR. Here we report that the lncRNAH19 is significantly decreased in placentae from pregnancies with FGR. Downregulation of H19 leads to reduced proliferation and invasion of extravillous trophoblast cells. This is identified with reduced trophoblast invasion, which has been discovered in FGR. Autophagy is exaggerated in FGR. Downregulation of H19 promotes autophagy via the PI3K/AKT/mTOR and MAPK/ERK/mTOR pathways of extravillous trophoblast cells in FGR. We also found that the expression level of microRNAs miR-18a-5p was negatively correlated with that of H19. H19 can act as an endogenous sponge by directly binding to miR-18a-5p, which targets IRF2. The expression of miR-18a-5p was upregulated, but IRF2 expression was downregulated after the H19 knockdown. In conclusion, our study revealed that H19 downexpressed could inhibit proliferation and invasion, and promote autophagy by targeting miR-18a-5pin HTR8 and JEG3 cells. We propose that aberrant regulation of H19/miR-18a-5p-mediated regulatory pathway may contribute to the molecular mechanism of FGR. We indicated that H19 may be a potential predictive, diagnostic, and therapeutic modality for FGR.

The effect of fasting or calorie restriction on autophagy induction: A review of the literature

Autophagy is a lysosomal degradation process and protective housekeeping mechanism to eliminate damaged organelles, long-lived misfolded proteins and invading pathogens. Autophagy functions to recycle building blocks and energy for cellular renovation and homeostasis, allowing cells to adapt to stress. Modulation of autophagy is a potential therapeutic target for a diverse range of diseases, including metabolic conditions, neurodegenerative diseases, cancers and infectious diseases. Traditionally, food deprivation and calorie restriction (CR) have been considered to slow aging and increase longevity. Since autophagy inhibition attenuates the anti-aging effects of CR, it has been proposed that autophagy plays a substantive role in CR-mediated longevity. Among several stress stimuli inducers of autophagy, fasting and CR are the most potent non-genetic autophagy stimulators, and lack the undesirable side effects associated with alternative interventions. Despite the importance of autophagy, the evidence connecting fasting or CR with autophagy promotion has not previously been reviewed. Therefore, our objective was to weigh the evidence relating the effect of CR or fasting on autophagy promotion. We conclude that both fasting and CR have a role in the upregulation of autophagy, the evidence overwhelmingly suggesting that autophagy is induced in a wide variety of tissues and organs in response to food deprivation.

Long non-coding RNAs in the failing heart and vasculature

Following completion of the human genome, it became evident that the majority of our DNA is transcribed into non-coding RNAs (ncRNAs) instead of protein-coding messenger RNA. Deciphering the function of these ncRNAs, including both small- and long ncRNAs (lncRNAs), is an emerging field of research. LncRNAs have been associated with many disorders and a number have been identified as key regulators in the development and progression of disease, including cardiovascular disease (CVD). CVD causes millions of deaths worldwide, annually. Risk factors include coronary artery disease, high blood pressure and ageing. In this review, we will focus on the roles of lncRNAs in the cellular and molecular processes that underlie the development of CVD: cardiomyocyte hypertrophy, fibrosis, inflammation, vascular disease and ageing. Finally, we discuss the biomarker and therapeutic potential of lncRNAs.

Effects of farnesoid-X-receptor SUMOylation mutation on myocardial ischemia/reperfusion injury in mice

Myocardial ischemia/reperfusion (MI/R) injury induces excessive cellular apoptosis and contributes significantly to final infarct size. We previously demonstrated that a nuclear receptor, Farnesoid X receptor (FXR), plays a crucial role in mediating myocardial apoptosis. The FXR functions are regulated by post translational modifications (PTM). However, whether the proapoptotic effect of FXR in MI/R injury is regulated by PTM remains unclear. Here, we aimed to study the effect of SUMOylation, a PTM involved in the pathogenesis of MI/R injury per se, on the proapoptotic effect of FXR in MI/R injury. We observed that FXR could be SUMOylated in heart tissues, and FXR SUMOylation levels were downregulated in ischemia reperfused myocardium. By overexpression of SUMOylation-defective FXR mutant, it was demonstrated that decreased SUMOylation augmented the detrimental effect of FXR, via activation of mitochondrial apoptosis pathway and autophagy dysfunction in MI/R injury. Further mechanistic studies suggested that decreased SUMOylation levels increased the transcription activity of FXR, and the subsequently upregulated FXR target gene SHP mediated the proapoptotic effects of FXR. Taken together, we provided the first evidence that the cardiac effects of FXR could be regulated by SUMOylation, and that manipulating FXR SUMOylation levels may hold therapeutic promise for constraining MI/R injury.

Electroacupuncture Preconditioning Improves Myocardial Infarction Injury via Enhancing AMPK-Dependent Autophagy in Rats

Background

Electroacupuncture (EA) pretreatment plays a protective role in myocardial infarction injury. However, the mechanism of electroacupuncture remains unknown. The aim of this study was to confirm the protective effects of electroacupuncture (EA) on myocardial infarction injury and the possible mechanism.

Methods

Sprague-Dawley (SD) rats, used to serve as acute myocardial infarction (AMI) model, were divided into sham group, model (M) group, M+EA group, AMPK inhibitor Compound C (M+EA+CC), and AMPK inhibitor solvent control (M+EA+DMSO) group, respectively. Rats in EA group were pretreated with EA and those in M+EA+CC group with intravenous AMPK inhibitor Compound C. The myocardial morphological changes and infarct size were observed through HE staining and TTC staining, and the concentrations of CK-MB and LDH were detected using ELISA kits. Transmission electron microscopy was employed to observe the autophagosome formation, and the AMPK-dependent autophagy-related protein expression was detected by immunohistochemistry and western blot.

Results

EA could alleviate myocardial infarction injury and decrease the concentrations of CK-MB and LDH. Transmission electron microscopy showed that EA could also regulate the AMPK-dependent autophagosome formation and the AMPK-dependent autophagy-related protein expression. AMPK inhibitor Compound C could impair the effect of EA through regulating the concentrations of CK-MB and LDH, autophagosome formation, and autophagy-related protein expression.

Conclusion

These results indicated that electroacupuncture could improve myocardial infarction injury and induce autophagy, and AMPK-dependent autophagy might be involved in this process.

Internalization of Titanium Dioxide Nanoparticles Is Cytotoxic for H9c2 Rat Cardiomyoblasts

Titanium dioxide nanoparticles (TiO₂ NPs) are widely used in industry and daily life. TiO₂ NPs can penetrate into the body, translocate from the lungs into the circulation and come into contact with cardiac cells. In this work, we evaluated the toxicity of TiO₂ NPs on H9c2 rat cardiomyoblasts. Internalization of TiO₂ NPs and their effect on cell proliferation, viability, oxidative stress and cell death were assessed, as well as cell cycle alterations. Cellular uptake of TiO₂ NPs reduced metabolic activity and cell proliferation and increased oxidative stress by 19-fold measured as H₂DCFDA oxidation. TiO₂ NPs disrupted the plasmatic membrane integrity and decreased the mitochondrial membrane potential. These cytotoxic effects were related with changes in the distribution of cell cycle phases resulting in necrotic death and autophagy. These findings suggest that TiO₂ NPs exposure represents a potential health risk, particularly in the development of cardiovascular diseases via oxidative stress and cell death.

Immunity, Inflammation, and Oxidative Stress in Heart Failure: Emerging Molecular Targets

PURPOSE

Heart failure (HF) remains a major cause of morbidity and mortality worldwide. Although various therapies developed over the last two decades have shown improved long term outcomes in patients with established HF, there has been little progress in preventing the adverse cardiac remodeling that initiates HF. To fill the gap in treatment, current research efforts are focused on understanding novel mechanisms and signaling pathways. Immune activation, inflammation, oxidative stress, alterations in mitochondrial bioenergetics, and autophagy have been postulated as important pathophysiological events in this process. An improved understanding of these complex processes could facilitate a therapeutic shift toward molecular targets that can potentially alter the course of HF.

METHODS

In this review, we address the role of immunity, inflammation, and oxidative stress as well as other novel emerging concepts in the pathophysiology of HF that may have therapeutic implications.

CONCLUSION

Based on the experimental and clinical studies presented here, we anticipate that a better understanding of the pathophysiology of HF will open the door for new therapeutic targets. A one-size-fits-all approach may not be appropriate for all patients with HF, and further clinical trials utilizing molecular targeting in HF may result in improved outcomes.

Effect of varying hypoxia reoxygenation times on autophagy of cardiomyocytes

PURPOSE

To investigate the impact of different hypoxia reoxygenation (HR) times on autophagy of rat cardiomyocytes (H9C2).

METHODS

Rat cardiomyocytes were randomly divided into normal control group (group A), hypoxia group (group B), 2 h HR group (group C), 12 h HR group (group D), and 24 h HR group (group E). LC3 II/LC3 I was determined via western blotting, and cell viabilities of cardiomyocytes were measured using methyl thiazolyl tetrazolium (MTT) assay.

RESULTS

Cell viabilities in HR model groups were significantly lower than those of group A (P<0.05). LC3 II/LC3 I levels in groups B to D were significantly higher than those of group A (P<0.05), and group D showed the highest LC3 II/LC3 I levels. Cell viabilities in groups B to D were significantly lower than those of group A (P<0.05), with group D showing the lowest cell viabilities (P<0.05).

CONCLUSIONS

Hypoxia can induce autophagy in rat cardiomyocytes, which can be further activated by reoxygenation; most notable after 12 h. Hypoxia-induced cell injury can be aggravated by reoxygenation. The lowest cell viability was observed at 12 h after reoxygenation; however, cell viability can be recovered after 24 h.

Negative feedback loop of autophagy and endoplasmic reticulum stress in rapamycin protection against renal ischemia-reperfusion injury during initial reperfusion phase

Rapamycin, an immunosuppressant, is widely used in patients with kidney transplant. However, the therapeutic effects of rapamycin remain controversial. Additionally, previous studies have revealed deleterious effects of rapamycin predominantly when administered for ≥24 h. Few studies, however, have focused on the short-term effects of rapamycin administered only during the initial reperfusion phase. As such, we designed this study to explore the potential effects and mechanisms of rapamycin under a specific therapeutic regimen in which rapamycin is mixed in the perfusate during the initial reperfusion phase (within 24 h). Interestingly, we found that rapamycin maintained renal function and attenuated ischemia-reperfusion (I/R)-induced apoptosis in vivo and in vitro during the initial reperfusion phase, especially at 8 h after reperfusion. Simultaneously, rapamycin activated autophagy and inhibited endoplasmic reticulum (ER) stress and 3 pathways of unfolding protein response: ATF6, PERK, and IRE1α. Interestingly, we further found that the protective effects of rapamycin were suppressed when autophagy was inhibited by chloroquine and 3-methyladenine or when ER stress was induced by thapsigargin. Moreover, in terms of the regulatory effects of rapamycin, a negative-feedback loop between autophagy and ER stress occurred, with autophagy inhibiting ER stress and increased ER stress promoting autophagy during the initial reperfusion phase of renal I/R injury. Our study provides evidence that immediate reperfusion with rapamycin during the initial reperfusion phase repairs renal function and reduces apoptosis via activating autophagy, which could further inhibit ER stress. These results suggest a novel treatment modality for application during the initial reperfusion phase of renal I/R injury caused by kidney transplantation.-Li, X., Zhu, G., Gou, X., He, W., Yin, H., Yang, X., Li, J. Negative feedback loop of autophagy and endoplasmic reticulum stress in rapamycin protection against renal ischemia-reperfusion injury during initial reperfusion phase.

Chronic intermittent hypobaric hypoxia protects vascular endothelium by ameliorating autophagy in metabolic syndrome rats

AIMS

The study aimed to investigate the protective effect of chronic intermittent hypobaric hypoxia (CIHH) on endothelium function and relaxation of mesenteric artery in metabolism syndrome (MS) rats.

MAIN METHODS

Male adult Sprague-Dawley rats were randomly divided into control (CON), CIHH (treated with 28-days hypobaric hypoxia simulating an altitude of 5000 m, 6 h daily), MS (induced by high fat diet and 10% fructose water feeding), and MS + CIHH groups. Body weight, systolic arterial pressure, blood biochemical and the endothelium dependent relaxation (EDR) of mesenteric arteries were measured. The expression of phosphor-endothelial nitric oxide synthase (p-eNOS), endoplasmic reticulum (ER) stress-related proteins and autophagy-related proteins in mesenteric arteries was assayed.

KEY FINDINGS

The MS rats displayed hypertension, obesity, metabolic abnormity and insulin resistance, EDR was attenuated, p-eNOS expression was down-regulated, the expressions of ER stress-related proteins were up-regulated, and autophagy dysfunction occurred. All aforementioned abnormalities in MS rats were ameliorated in MS + CIHH rats. Furthermore, the improvement of CIHH on EDR and p-eNOS was cancelled by the ER stress inducer, and the autophagy inhibitor.

SIGNIFICANCE

In conclusion CIHH protects endothelium function and enhances relaxation in mesenteric arteries of MS rats through improving autophagy function, reducing ER stress and up-regulating p-eNOS.

Melatonin reduces oxidative damage in mouse granulosa cells via restraining JNK-dependent autophagy

Oxidative stress-induced granulosa cell (GCs) injury is believed to be a common trigger for follicular atresia. Emerging evidence indicates that excessive autophagy occurs in mammalian cells with oxidative damage. N-acetyl-5-methoxytrypamine (melatonin) has been shown to prevent GCs from oxidative injury, although the exact mechanism remains to be elucidated. Here, we first demonstrated that the suppression of autophagy through the JNK/BCL-2/BECN1 signaling is engaged in melatonin-mediated GCs protection against oxidative damage. Melatonin inhibited the loss of GCs viability, formation of GFP-MAP1LC3B puncta, accumulation of MAP1LC3B-II blots, degradation of SQSTM1 and the expression of BECN1, which was correlated with impaired activation of JNK during oxidative stress. On the other hand, blocking of autophagy and/or JNK also reduced the level of H2O2-induced GCs death, but failed to further restore GCs viability in the presence of melatonin. Particularly, the suppression of autophagy provided no additional protective effects when GCs were pretreated with JNK inhibitor and/or melatonin. Importantly, we found that the enhanced interaction between BCL-2 and BECN1 might be a responsive mechanism for autophagy suppression via the melatonin/JNK pathway. Moreover, blocking the downstream antioxidant system of melatonin using specific inhibitors further confirmed a direct role of melatonin/JNK/autophagy axis in preserving GCs survival without scavenging reactive oxygen species (ROS). Taken together, our findings uncover a novel function of melatonin in preventing GCs from oxidative damage by targeting JNK-mediated autophagy, which might contribute to develop therapeutic strategies for patients with ovulation failure-related disorders.