Autophagy In Myocytes Research Articles

Photobiomodulation and Physical Exercise Modulate of Cell Survival Proteins in the Skeletal Muscle of Rats with Heart Failure and Diabetes Mellitus.

Introduction: Heart failure (HF) and type 2 diabetes mellitus (DM2) are global health problems that often lead to muscle atrophy. These conditions are associated with increased autophagy and apoptosis in the muscle cells, resulting in decreased muscle mass. Physical exercise associated with photobiomodulation (PBM) seems promising to attenuate the skeletal muscle changes caused by HF and DM2, due to its direct effects on mitochondria, which may result in an increase in antioxidant capacity. Objective: To verify the influence of physical exercise and the association with PBM on autophagy, apoptosis, and cell survival signaling pathways in myocytes from rats with HF and DM2. Materials and Methods: Male rats were assigned to one of four groups: control (CT), HF+DM (disease model), exercise+HF+DM (EX+HF+DM), and EX+HF+DM+PBM (EX+HF+DM+PBM). To induce DM2, we administered streptozotocin (STZ) (0.25 mL/kg, intraperitoneally). HF was induced by coronary ligation. One week post-induction, an 8-week aerobic exercise and PBM protocol was initiated. Western blot analysis was used to measure the expression of apoptosis-related proteins and autophagy. Results: The EX+HF+DM+PBM group showed a substantial increase in Nrf2, p-AKT, and LC3-I levels compared to the HF+DM group. Conclusions: These findings suggest that physical exercise combined with PBM can upregulate proteins that promote myocyte survival in rats with HF and DM2.

NADPH oxidase 2 mediates cardiac sympathetic denervation and myocyte autophagy, resulting in cardiac atrophy and dysfunction in doxorubicin-induced cardiomyopathy

Doxorubicin has been used extensively as a potent anticancer agent, but its clinical use is limited by its cardiotoxicity. However, the underlying mechanisms remain to be fully elucidated. In this study, we tested whether NADPH oxidase 2 (Nox2) mediates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, resulting in cardiac atrophy and dysfunction in doxorubicin-induced heart failure. Nox2 knockout (KO) and wild-type (WT) mice were randomly assigned to receive a single injection of doxorubicin (15 mg/kg, i.p.) or saline. WT doxorubicin mice exhibited the decreases in survival rate, left ventricular (LV) wall thickness and LV fractional shortening and the increase in the lung wet-to-dry weight ratio 1 week after the injections. These alterations were attenuated in Nox2 KO doxorubicin mice. In WT doxorubicin mice, myocardial oxidative stress was increased, myocardial noradrenergic nerve fibers were reduced, myocardial expression of PGP9.5, GAP43, tyrosine hydroxylase and norepinephrine transporter was decreased, and these changes were prevented in Nox2 KO doxorubicin mice. Myocyte autophagy was increased and myocyte size was decreased in WT doxorubicin mice, but not in Nox2 KO doxorubicin mice. Nox2 mediates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy—both of which contribute to cardiac atrophy and failure after doxorubicin treatment.

NADPH oxidase 2 inhibitor GSK2795039 prevents doxorubicin-induced cardiac atrophy by attenuating cardiac sympathetic nerve terminal abnormalities and myocyte autophagy

Doxorubicin is widely used for the treatment of human cancer, but its clinical use is limited by a cumulative dose-dependent cardiotoxicity. However, the mechanism of doxorubicin-induced cardiac atrophy and failure remains to be fully understood. In this study, we tested whether the specific NADPH oxidase 2 (Nox2) inhibitor GSK2795039 attenuates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, leading to the amelioration of cardiac atrophy and dysfunction in chronic doxorubicin-induced cardiomyopathy. Mice were randomized to receive saline, doxorubicin (2.5 mg/kg, every other day, 6 times) or doxorubicin plus GSK2795039 (2.5 mg/kg, twice a day, 9 weeks). Left ventricular (LV) total wall thickness and LV ejection fraction were decreased in doxorubicin-treated mice compared with saline-treated mice and the decreases were prevented by the treatment of the specific Nox2 inhibitor GSK2795039. The ratio of total heart weight to tibia length and myocyte cross-sectional area were decreased in doxorubicin-treated mice, and the decreases were attenuated by the GSK2795039 treatment. In doxorubicin-treated mice, myocardial Nox2 and 4-hydroxynonenal levels were increased, myocardial expression of GAP43, tyrosine hydroxylase and norepinephrine transporter, markers of sympathetic nerve terminals, was decreased, and these changes were prevented by the GSK2795039 treatment. The ratio of LC3 II/I, a marker of autophagy, and Atg5, Atg12 and Atg12-Atg5 conjugate proteins were increased in doxorubicin-treated mice, and the increases were attenuated by the GSK2795039 treatment. These findings suggest that inhibition of Nox2 by GSK2795039 attenuates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, thereby ameliorating cardiac atrophy and dysfunction after chronic doxorubicin treatment.

Retinoic acid-related orphan receptors regulate autophagy and cell survival in cardiac myocytes during hypoxic stress

Introduction: Autophagy is a highly conserved evolutionary process that regulates cell quality control through protein degradation, organelle turnover, and recycling of cellular components by fusing with lysosomes. Defects in autophagy can lead to increased reactive oxygen species (ROS) and oxidative stress from impaired mitochondrial clearance by mitophagy. These defects are commonly associated with chronic human diseases such as cancer, myocardial infarction, neurodegenerative diseases, and aging. Aim: Herein, we show that the gene Retinoic Acid-Related Orphan Receptors α (Rora ) is cardioprotective through modulation of autophagy and clearance of damaged ROS-producing mitochondria in cardiac myocytes. Methods and results: We show that RORα is downregulated during hypoxia, leading to increased death of cardiac cells and enhanced mitochondrial perturbations. We demonstrate that the small molecule Nobiletin, a polymethoxy flavonoid, can induce RORα activation and downregulate the aging-associated marker p16, coincident with reduced ROS-producing mitochondria. We further show that Nobiletin binds directly to the Rora gene promoter, leading to activation of autophagic function and increased cell survival of cardiac myocytes during hypoxia. Interestingly, loss of RORα activity during hypoxia resulted in the failure of Nobiletin to rescue autophagy and inhibits its capacity for cardiac protection. Furthermore, the inactivation of autophagy by ATG7 knockdown abrogated the cytoprotective effects of Nobiletin on autophagic activation. Conclusion: Collectively, these results demonstrate that RORα regulates autophagic processes linked to aging upon activation with Nobiletin. Interventions that activate RORα may prove beneficial in reducing hypoxia-induced mitochondrial ROS associated with cardiac aging.

The Role of Renin-Angiotensin System in Diabetic Cardiomyopathy: A Narrative Review.

Diabetic cardiomyopathy refers to myocardial dysfunction in type 2 diabetes, but without the traditional cardiovascular risk factors or overt clinical atherosclerosis and valvular disease. The activation of the renin-angiotensin system (RAS), oxidative stress, lipotoxicity, maladaptive immune responses, imbalanced mitochondrial dynamics, impaired myocyte autophagy, increased myocyte apoptosis, and fibrosis contribute to diabetic cardiomyopathy. This review summarizes the studies that address the link between cardiomyopathy and the RAS in humans and presents proposed pathophysiological mechanisms underlying this association. The RAS plays an important role in the development and progression of diabetic cardiomyopathy. The over-activation of the classical RAS axis in diabetes leads to the increased production of angiotensin (Ang) II, angiotensin type 1 receptor activation, and aldosterone release, contributing to increased oxidative stress, fibrosis, and cardiac remodeling. In contrast, Ang-(1-7) suppresses oxidative stress, inhibits tissue fibrosis, and prevents extensive cardiac remodeling. Angiotensin-converting-enzyme (ACE) inhibitors and angiotensin receptor blockers improve heart functioning and reduce the occurrence of diabetic cardiomyopathy. Experimental studies also show beneficial effects for Ang-(1-7) and angiotensin-converting enzyme 2 infusion in improving heart functioning and tissue injury. Further research is necessary to fully understand the pathophysiology of diabetic cardiomyopathy and to translate experimental findings into clinical practice.

Enhanced oxidative stress mediates pathological autophagy and necroptosis in cardiac myocytes in pressure overload induced heart failure in rats.

In cardiac myocytes in vitro, hydrogen peroxide induces autophagic cell death and necroptosis. Oxidative stress, myocyte autophagy and necroptosis coexist in heart failure (HF). In this study, we tested the hypothesis that excessive oxidative stress mediates pathological autophagy and necroptosis in myocytes in pressure overload-induced HF. HF was produced by chronic pressure overload induced by abdominal aortic constriction (AAC) in rats. Rats with AAC or sham operation were randomised to orally receive an antioxidant N-acetylcysteine (NAC) or placebo for 4weeks. Echocardiography was performed for the assessments of left ventricular (LV) structure and function. AAC rats exhibited decreased LV fractional shortening (FS) at 4weeks after surgery. NAC treatment attenuated decreased LV FS in AAC rats. In AAC rats, myocardial level of 8-hydroxydeoxyguanosine assessed by immunohistochemical staining, indicative of oxidative stress, was increased, LC3 II protein, a marker of autophagy, Beclin1 protein and Atg4b, Atg5, Atg7 and Atg12mRNA expression were markedly increased, RIP1, RIP3 and MLKL expression, indicative of necroptosis, was increased, and all of the alterations in AAC rats were prevented by the NAC treatment. NAC treatment also attenuated myocyte cross-sectional area and myocardial fibrosis in AAC rats. In conclusion, NAC treatment prevented the increases in oxidative stress, myocyte autophagy and necroptosis and the decrease in LV systolic function in pressure overload-induced HF. These findings suggest that enhanced oxidative stress mediates pathological autophagy and necroptosis in myocytes, leading to LV systolic dysfunction, and antioxidants may be of value to prevent HF through the inhibition of excessive autophagy and necroptosis.

Sphingosine-1-phosphate induces myocyte autophagy after myocardial infarction through mTOR inhibition

Sphingosine-1-phosphate (S1P)/S1P receptor 1 signaling exerts cardioprotective effects including inhibition of myocyte apoptosis. However, little is known about the effect of S1P treatment on myocyte autophagy after myocardial infarction (MI). In the present study, we tested the hypothesis that S1P induces myocyte autophagy through inhibition of the mammalian target of rapamycin (mTOR), leading to improvement of left ventricular (LV) function after MI. Sprague–Dawley rats underwent MI or sham operation. The animals were randomized to receive S1P (50 μg/kg/day, i.p.) or placebo for one week. H9C2 cardiomyocytes cultured in serum- and glucose-deficient medium were treated with or without S1P for 3 h. MI rats exhibited an increase in LV end-diastolic dimension (EDD) and decreases in LV fractional shortening (FS) and the maximal rate of LV pressure rise (+dP/dt). S1P treatment attenuated the increase in LV EDD and decreases in LV FS and +dP/dt. In the MI placebo group, the LC3 II/I ratio, a marker of autophagy, was increased, and increased further by S1P treatment. S1P also enhanced the autophagy-related proteins Atg4b and Atg5 after MI. Similarly, in cultured cardiomyocytes, autophagy was increased under glucose and serum deprivation, and increased further by S1P treatment. The effect of S1P on myocyte autophagy was associated with mTOR inhibition after MI or in cultured cardiomyocytes under glucose and serum deprivation. S1P treatment prevents LV remodeling, enhances myocyte autophagy and inhibits mTOR activity after MI. These findings suggest that S1P treatment induces myocyte autophagy through mTOR inhibition, leading to the attenuation of LV dysfunction after MI.

Inhibition of Autophagy Prevents Panax Notoginseng Saponins (PNS) Protection on Cardiac Myocytes Against Endoplasmic Reticulum (ER) Stress-Induced Mitochondrial Injury, Ca2+ Homeostasis and Associated Apoptosis

Endoplasmic reticulum (ER) stress is often closely linked to autophagy, hypoxia signaling, mitochondrial biogenesis and reactive oxygen species (ROS) responses. Understanding the interaction between ER stress, mitochondrial function and autophagy is of great importance to provide new mechanisms for the pathology, prevention and treatment of cardiovascular diseases. Our previous study has reported that Panax notoginseng saponins (PNS) protection against thapsigargin (TG)-induced ER stress response and associated cell apoptosis in cardiac myocytes is calcium dependent and mediated by ER Ca2+ release through RyR2. However, whether its protection upon ER stress and associated apoptosis is related to mitochondrial function and autophagy remains largely unknown. Here, we investigated the roles of PNS played in TG-induced mitochondrial function, ROS accumulation and autophagy. We also assessed its effects on Ca2+ homeostasis, ER stress response and associated cell death in the presence of autophagy inhibition. PNS-pretreated primary cultured neonatal rat cardiomyocytes were stimulated with TG to induce ER stress response. Mitochondrial potential (Δψm) was measured by JC-1. The general and mitochondrial ROS were measured by DCFH-DA and MitoSOX Red, respectively. Autophagy was evaluated by immunofluorescence of LC3, and immunoblots of LC3, p62, ATG7 and PINK1. In addition, mRFP-GFP-LC3 labeling was used to assess the autophagic influx. SiATG7 transfected H9c2 cells were generated to inhibit autophagy. Cytosolic and ER Ca2+ dynamics were investigated by calcium imaging. RyR2 oxidation was tested by oxyblot. Cell viability was examined by TUNEL assay. ER stress response and cell apoptosis were detected by immunoblots of BiP, CHOP, Cleaved Caspase-3 and Caspase-12. The results demonstrated that firstly, PNS protects against TG-induced mitochondrial injury and ROS accumulation. Secondly, PNS enhances autophagy in TG-induced cardiac myocytes. Thirdly, inhibition of autophagy diminishes PNS prevention of TG-induced mitochondrial injury, ROS accumulation and disruption of Ca2+ homeostasis. Last but not least, inhibition of autophagy abolishes PNS protection against TG-induced ER stress response and associated apoptosis. In summary, PNS protection against ER stress response and associated apoptosis is related to the regulation of mitochondrial injury and ROS overproduction via modulation of autophagy. These data provide new insights for molecular mechanisms of PNS as a potential preventive approach to the management of cardiovascular diseases.

Circular RNA circ_0010729 Knockdown Attenuates Oxygen-Glucose Deprivation-Induced Human Cardiac Myocytes Injury by miR-338-3p/CALM2 Axis.

Circular RNAs have pivotal roles in cardiovascular disease. The injury of cardiac myocytes is associated with occurrence of cardiovascular disease. Circular RNA hsa_circ_0010729 (circ_0010729) is associated with cardiac myocytes injury. However, the mechanism of circ_0010729 in cardiac myocytes injury remains largely unclear. In our study, cardiac myocytes were treated by oxygen-glucose deprivation (OGD). The abundances of circ_0010729, microRNA-338-3p (miR-338-3p), and calmodulin 2 (CALM2) were detected by quantitative reverse transcription polymerase chain reaction or Western blot. OGD-induced damage in AC16 cells was assessed by cell viability, apoptosis, and autophagy using Cell Counting Kit-8, flow cytometry, and Western blot analyses. The target relationship of miR-338-3p and circ_0010729 or CALM2 was explored by starBase and dual-luciferase reporter analysis. Our results showed that the circ_0010729 level was enhanced in OGD-treated AC16 cells and murine primary cardiac myocytes. circ_0010729 silence weakened OGD-induced viability inhibition and promotion of apoptosis and autophagy in AC16 cells and murine primary cardiac myocytes. miR-338-3p was sponged by circ_0010729 and miR-338-3p knockdown alleviated the effect of circ_0010729 silence on OGD-induced damage. miR-338-3p directly targeted CALM2 to inhibit OGD-induced damage in AC16 cells. circ_0010729 could regulate CALM2 expression by sponging miR-338-3p. Collectively, circ_0010729 interference mitigated OGD-induced damage in cardiac myocytes through increasing cell viability and inhibiting apoptosis and autophagy by regulating miR-338-3p/CALM2 axis. This study indicated circ_0010729 might act as a target for treatment of cardiovascular disease.

Induction of autophagy has protective roles in imatinib-induced cardiotoxicity.

Cardiotoxicity is one of the severe adverse effects of chemotherapeutic agents. Imatinib was previously reported to induce cardiotoxicity. Autophagy is an intracellular bulk protein and organelle degradation process, but its roles in cardiac diseases are unclear. We examined whether imatinib induces cardiomyocyte autophagy, and the role of autophagy in imatinib-induced cardiotoxicity using in vitro and in vivo experiments. In in vitro experiments, neonatal rat cardiomyocytes were treated with imatinib (1, 5, or 10 μM; 6 h). Myocyte autophagy was assessed by microtubule-associated protein light chain (LC) 3-II, beclin 1, mature cathepsin D, and acridine orange-stained mature autolysosome expression. Imatinib increased their expression, suggesting that it induced autophagy. Consequently, imatinib altered the production of mitochondria-derived reactive oxygen species (ROS) and loss of mitochondrial membrane potential, which were assessed by the fluorescent indicator MitoSOX and JC-1, respectively, leading to cardiomyocyte apoptosis. 3-methyl-adenine (3MA), an autophagic inhibitor, exacerbated imatinib-induced apoptosis by 30 %. In in vivo experiments, C57BL/6 mice were treated with imatinib (50 and 200 mg/kg/day) for 5 weeks in the presence or absence of 3MA. Echocardiographic measurement revealed that imatinib (200 mg) caused dilatation of the left ventricle (LV) and reduced LV fractional shortening. Apoptosis and LC3-II expression in cardiac tissue were increased by imatinib. Co-treatment with 3MA and imatinib further impaired imatinib-induced cardiac apoptosis and LV dysfunction. This study suggests that imatinib induces cardiomyocyte apoptosis, leading to cardiac dysfunction. Imatinib increases cardiomyocyte autophagy as a consequence of apoptosis and autophagy has a pro-survival role in imatinib-induced cardiac impairment.

Knockdown of lncRNA TTTY15 alleviates myocardial ischemia-reperfusion injury through the miR-374a-5p/FOXO1 axis.

Myocardial ischemia/reperfusion (I/R) injury greatly contributes to myocardial tissue damage in patients with coronary disease, which eventually leads to heart failure. Long noncoding RNAs (lncRNAs) have an emerging role in the process of myocardial I/R injury. Our previous work revealed the protective role of miR-374a-5p against myocardial I/R injury. In this study, we explored the role of lncRNA TTTY15 and its potential interaction mechanisms with miR-374a-5p in myocardial I/R injury. The expression of TTTY15 was increased both in vitro and in vivo after myocardial I/R injury models according to quantitative real-time polymerase chain reaction. Various assays were conducted to evaluate the regulatory relationship among TTTY15, miR-374a-5p, FOXO1, and autophagy in H9c2 and HL-1 cells. The results showed that TTTY15 suppresses autophagy and myocardial I/R injury by targeting miR-374a-5p. We found that TTTY15 regulates miR-374a-5p, thus affecting FOXO1 expression and autophagy in myocytes during I/R. Furthermore, in an in vivo mouse model of myocardial I/R injury, suppression of TTTY15 successfully alleviated myocardial I/R injury. Our results reveal a novel feedback mechanism in which TTTY15 regulates miRNA processing and a potential target in myocardial I/R injury. TTTY15 is a promising therapeutic target for treating myocardial I/R injury.

P6275Role of autophagy in imatinib-induced cardiotoxicity

Abstract Background Cardiotoxicity is one of the severe adverse effects of chemotherapeutic agents. Imatinib, a therapeutic agent for chronic myelogenous leukemia, has been reported to induce cardiotoxicity. Autophagy is an intracellular bulk protein and organelle degradation process, but it is unclear whether autophagy functions as pro-death or pro-survival program during disease conditions. We examined whether imatinib induces myocyte autophagy and the role of autophagy in imatinib-induced cardiotoxicity in in vitro and in vivo experiments. Methods In in vitro experiments, neonatal rat cardiac myocytes were treated with imatinib (1, 5, 10 μM; 1–6 hrs). Inhibition of autophagy was performed using 3-methyl-adenine (3MA), an autophagic inhibitor, and transfection with Atg5-targeted siRNA. Myocyte apoptosis was detected by morphological change in nuclei and caspase 3 activity. Mitochondria-derived reactive oxygen species production was detected using MitoSOX and mitochondrial membrane potential was assessed by TMRM staining. Expressions of cytochrome c in mitochondria and cytosole were examined by Werstern blotting. Myocyte autophagy was assessed by monodansylcadaverine staining and microtubule-associated protein light chain (LC) 3-II expression. In in vivo experiments, C57BL6 mice were treated with imatinib (50 and 200 mg/kg/day) for 5 weeks in the presence or absence of 3MA. Cardiac function was examined by echocardiography. In cardiac tissue, apoptotic myocytes were examined by TUNEL assay and autophagy was examined by LC3-II expression. Results In in vitro experiments, imatinib increased apoptotic nuclei and caspase 3 activity, in a dose-dependent manner. Consequently, imatinib augmented production of mitochondria-derived reactive oxygen species, loss of mitochondrial membrane potential, and the release of cytochrome c from mitochondria to cytosole, suggesting that imatinib induced mitochondrial-apoptotic pathway. On the other hand, imatinib significantly increased monodansylcadaverine stained dots and LC3-II expression, suggesting that imatinib increased autophagy. 3MA and Atg5 siRNA augmented imatinib-induced apoptosis by 60% and 30%, respectively. In in vivo experiments, imatinib (200 mg) exhibited the dilatation of left ventricle by 15% and the depression of left ventricular fractional shortening by 23%. Ratio of apoptotic myocytes was significantly increased and LC3-II expression in cardiac tissue was enhanced by imatinib in a dose-dependent fashion. Co-treatment with 3MA and imatinib further impaired imatinib-induced myocyte apoptosis by 3 fold and LV dysfunction by 20%. Conclusion These results indicate that imatinib induced myocyte apoptosis, leading to cardiac dysfunction. Imatinib enhanced myocyte autophagy as a consequence of apoptosis and autophagy was a beneficial phenomenon in this condition.

WIPI1 is a conserved mediator of right ventricular failure.

Right ventricular dysfunction is highly prevalent across cardiopulmonary diseases and independently predicts death in both heart failure (HF) and pulmonary hypertension (PH). Progression towards right ventricular failure (RVF) can occur in spite of optimal medical treatment of HF or PH, highlighting current insufficient understanding of RVF molecular pathophysiology. To identify molecular mechanisms that may distinctly underlie RVF, we investigated the cardiac ventricular transcriptome of advanced HF patients, with and without RVF. Using an integrated systems genomic and functional biology approach, we identified an RVF-specific gene module, for which WIPI1 served as a hub and HSPB6 and MAP4 as drivers, and confirmed the ventricular specificity of Wipi1, Hspb6, and Map4 transcriptional changes in adult murine models of pressure overload induced RV- versus LV- failure. We uncovered a shift towards non-canonical autophagy in the failing RV that correlated with RV-specific Wipi1 upregulation. In vitro siRNA silencing of Wipi1 in neonatal rat ventricular myocytes limited non-canonical autophagy and blunted aldosterone-induced mitochondrial superoxide levels. Our findings suggest that Wipi1 regulates mitochondrial oxidative signaling and non-canonical autophagy in cardiac myocytes. Together with our human transcriptomic analysis and corroborating studies in an RVF mouse model, these data render Wipi1 a potential target for RV-directed HF therapy.

P38β MAPK mediates ULK1-dependent induction of autophagy in skeletal muscle of tumor-bearing mice

Muscle wasting is the key manifestation of cancer-associated cachexia, a lethal metabolic disorder seen in over 50% of cancer patients. Autophagy is activated in cachectic muscle of cancer hosts along with the ubiquitin-proteasome pathway (UPP), contributing to accelerated protein degradation and muscle wasting. However, established signaling mechanism that activates autophagy in response to fasting or denervation does not seem to mediate cancer-provoked autophagy in skeletal myocytes. Here, we show that p38β MAPK mediates autophagy activation in cachectic muscle of tumor-bearing mice via novel mechanisms. Complementary genetic and pharmacological manipulations reveal that activation of p38β MAPK, but not p38α MAPK, is necessary and sufficient for Lewis lung carcinoma (LLC)-induced autophagy activation in skeletal muscle cells. Particularly, muscle-specific knockout of p38β MAPK abrogates LLC tumor-induced activation of autophagy and UPP, sparing tumor-bearing mice from muscle wasting. Mechanistically, p38β MAPK-mediated activation of transcription factor C/EBPβ is required for LLC-induced autophagy activation, and upregulation of autophagy-related genes LC3b and Gabarapl1. Surprisingly, ULK1 activation (phosphorylation at S555) by cancer requires p38β MAPK, rather than AMPK. Activated ULK1 forms a complex with p38β MAPK in myocytes, which is markedly increased by a tumor burden. Overexpression of a constitutively active p38Tbeta; MAPK in HEK293 cells increases phosphorylation at S555 and other amino acid residues of ULK1, but not several of AMPK-mediated sites. Finally, ULK1 activation is abrogated in tumor-bearing mice with muscle-specific knockout of p38β MAPK. Thus, p38β MAPK appears a key mediator of cancer-provoked autophagy activation, and a therapeutic target of cancer-induced muscle wasting.

GW29-e1773 Enhanced oxidative stress mediates pathological autophagy in cardiac myocytes in pressure overload induced heart failure in rats

In cardiac myocytes in vitro, a high concentration of hydrogen peroxide (1 mM) induces myocyte autophagy. Oxidative stress and myocyte autophagy coexist in pressure overload-induced heart failure. In this study, we tested the hypothesis that excessive oxidative stress mediates pathological autophagy

Antioxidant N-acetylcysteine inhibits maladaptive myocyte autophagy in pressure overload induced cardiac remodeling in rats

Increased oxidative stress and myocyte autophagy co-exist in cardiac remodeling. However, it is unclear whether oxidative stress mediates maladaptive myocyte autophagy in pathological ventricular remodeling. In this study, we tested the hypothesis that antioxidants prevent maladaptive myocyte autophagy in pressure overload-induced left ventricular (LV) remodeling. Sprague–Dawley rats underwent abdominal aortic constriction (AAC) or sham operation. The animals were randomized to receive an antioxidant N-acetylcysteine (NAC), an autophagy inhibitor 3-methyladenine (3-MA) or placebo treatment for 2 weeks. We measured LV structure and function by echocardiography and hemodynamics, myocyte autophagy and oxidative stress assessed by 8-hydroxy-2-deoxyguanosine (8-OHdG). AAC rats exhibited increased LV hypertrophy assessed by LV wall thickness and myocyte cross-sectional area. NAC prevented LV hypertrophy in AAC rats. There were no significant differences in LV fractional shortening, end-diastolic dimension and the maximal rate of LV pressure rise among the groups. AAC rats showed an increase in myocardial 8-OHdG that was prevented by NAC. The expression of LC3 II protein, a marker of autophagy, was increased at 2 weeks after AAC. Immunohistochemical scores further confirmed the increase in LC3 expression in AAC rats. The expression of autophagic proteins Beclin1 and Atg12 and ERK activity were also increased in AAC rats. NAC prevented the increases in LC3 II protein, LC3 scores, Beclin1, Atg12 and ERK activity in AAC rats. Inhibition of autophagy by 3-MA prevented LV hypertrophy after pressure overload. These findings suggest that antioxidants may be of value to prevent pressure overload-induced cardiac remodeling through inhibition of maladaptive myocyte autophagy.

In This Issue

HomeCirculation ResearchVol. 123, No. 5In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn This Issue Ruth Williams Ruth WilliamsRuth Williams Search for more papers by this author Originally published16 Aug 2018https://doi.org/10.1161/RES.0000000000000225Circulation Research. 2018;123:507is related toSafety and Efficacy of Intracoronary Infusion of Allogeneic Human Cardiac Stem Cells in Patients With ST-Segment Elevation Myocardial Infarction and Left Ventricular DysfunctionTransplanted Mesenchymal Stem Cells Reduce Autophagic Flux in Infarcted Hearts via the Exosomal Transfer of miR-125bThe Transcription Factor ETV1 Induces Atrial Remodeling and ArrhythmiaETV1 and Atrial Remodeling (p 550)Download figureDownload PowerPointIncreased ETVI levels drive arrhythmia in mice, report Rommel et al.Although advanced age, high blood pressure, and alcohol abuse have been recognized as important risk factors for developing atrial fibrillation (AF), the molecular pathology underlying the development of AF remains largely unknown. Rommel and colleagues have now discovered that the transcription factor ETV1 is upregulated in the atria of patients with permanent AF. To examine the potential role of this transcription factor in the development of AF, they created transgenic mice with cardiac myocyte-specific overexpression of ETV1. They found that at first the hearts of these animals appeared normal, but by 12 weeks of age, the mice had developed arrhythmias, and their atria were enlarged and dilated. Survival rates of these animals were significantly reduced. The team then created mice in which cardiac myocyte expression of ETV1 was ablated and found that these animals had survival rates comparable to wild-type controls and that they were protected against induced AF-like atrial remodeling. Transcriptome and chromatin analyses of the transgenic and control animals revealed 170 genes that were specifically targeted by ETV1. Further investigations of the ETV1 target genes could lead to novel insights and new treatments for AF.MSCs Protect MI Through Exosome-Mediated Autophagy (p 564)Download figureDownload PowerPointMesenchymal stem cell–derived exosomes protect infarcted hearts from excess autophagy, say Xiao et al.Autophagy—the intracellular process of degrading and recycling damaged organelles—is activated by mild ischemia and, under this condition, can preserve cell viability. During severe ischemia, however, autophagy can be activated chronically and lead to excessive cell death. It is thought that reduced cell death is one of the potential benefits of stem cell treatments for myocardial infarction. However, it is unclear whether stem cells treatments influence autophagy. Xiao and colleagues now report that treatment of mice with mesenchymal stem cells (MSCs), after myocardial infarction, leads to reduced cardiac myocyte autophagy compared with that seen in untreated animals. Furthermore, direct inhibition of autophagy prior to infarction resulted in mice with better cardiac performance and ventricular remodeling. In vitro, coculturing experiments confirmed the autophagy-suppressing effect of MSCs on cardiac myocytes. And the team went on to show that exosomes packed with the microRNA miR-125b-5p were the MSC-derived mediators of autophagy suppression. By identifying pathways and molecules that control autophagy, these results uncover new targets for postinfarction therapies that may bypass the need for cell therapy.Allogeneic Cardiac Cells for STEMI (p 579)Download figureDownload PowerPointFernandéz-Avilés et al find allogenic stem cells offer no clinical benefits to myocardial infarction patients.Stem cells of various types are under investigation as potential therapies for preventing heart failure following myocardial infarction. While the use of autologous stem cells avoids the possibility of immunorejection, these cells can be less effective if the patients are elderly or suffer from multiple comorbities. Allogenic cells from healthy donors avoid this problem, and can be readily produced in large quantities. To examine the safety and efficacy of allogenic human cardiac stem cells, Fernandéz-Avilés and colleagues conducted a phase I/II clinical trial (CAREMI). In this trial, donor-derived allogenic cardiac stem cells were administered via intracoronary infusions to 33 patients ≈1 week after myocardial infarction, while another 16 patients received a placebo. After a 12-month follow up, there were no deaths or major adverse cardiac events, indicating that the procedure was safe. However, there was no evidence that the stem cells reduced infarct size or improved left ventricle remodeling or the patients’ quality of life. These results could inform the design of future cell therapy trials. Previous Back to top Next FiguresReferencesRelatedDetailsRelated articlesSafety and Efficacy of Intracoronary Infusion of Allogeneic Human Cardiac Stem Cells in Patients With ST-Segment Elevation Myocardial Infarction and Left Ventricular DysfunctionFrancisco Fernández-Avilés, et al. Circulation Research. 2018;123:579-589Transplanted Mesenchymal Stem Cells Reduce Autophagic Flux in Infarcted Hearts via the Exosomal Transfer of miR-125bChangchen Xiao, et al. Circulation Research. 2018;123:564-578The Transcription Factor ETV1 Induces Atrial Remodeling and ArrhythmiaCarolin Rommel, et al. Circulation Research. 2018;123:550-563 August 17, 2018Vol 123, Issue 5 Advertisement Article InformationMetrics © 2018 American Heart Association, Inc.https://doi.org/10.1161/RES.0000000000000225PMID: 30355147 Originally publishedAugust 16, 2018 PDF download Advertisement

Treatment with crocin improves cardiac dysfunction by normalizing autophagy and inhibiting apoptosis in STZ-induced diabetic cardiomyopathy

Background and aimThe association of diabetes mellitus (DM) and poor metabolic control with high incidence of cardiovascular diseases is well established. The aim of this study was to investigate the potential cardioprotective effect of crocin (Crocus sativus L. extract) on diabetic heart dysfunction and to elucidate the mediating molecular mechanisms. Methods and resultsStreptozotocin (STZ)-induced diabetic rats were treated with two different concentrations of crocin (10 or 20 mg/kg), while isolated cardiac myocytes exposed to 25 mM glucose, were treated with 1 or 10 μM of crocin. Treatment of STZ-diabetic rats with crocin resulted in normalization of plasma glucose levels, inhibition of cardiac hypertrophy and fibrosis, and improvement of cardiac contractile function. Heat Shock Response was enhanced. Myocardial AMPK phosphorylation was increased after treatment with crocin, resulting in normalization of autophagy marker proteins (LC3BII/LC3BI ratio, SQSTM1/p62 and Beclin-1), while the diabetes-induced myocardial apoptosis was decreased. Similar results regarding the effect of crocin on autophagy and apoptosis pathways were obtained in isolated cardiac myocytes exposed to high concentration of glucose. ConclusionThe results suggest that crocin improves the deteriorated cardiac function in diabetic animals by enhancing the heat shock response, inhibiting apoptosis and normalizing autophagy in cardiac myocytes. Thus, treatment with crocin may represent a novel approach for treating diabetic cardiomyopathy.

Inflammation, Autophagy, and Apoptosis After Myocardial Infarction.

BackgroundThere is evidence for inflammation, autophagy, and apoptosis in the ischemic heart. Autophagy is a physiologic process for tissue survival. Apoptosis, on the other hand, is a mechanism that serves to clear the debris in the setting of tissue injury. The balance between autophagy and apoptosis may be important in cell survival and cardiac function.Methods and ResultsWe examined the interplay of inflammation and myocyte autophagy and apoptosis during the ischemic process. We subjected mice to total left coronary artery ligation and studied these animals for up to 4 weeks. The inflammatory (tumor necrosis factor [TNF]‐α, monocyte chemoattractant protein‐1, interleukin‐6, and interleukin‐1β) and autophagic signals (light chain‐3 and beclin‐1) were strongest during the first week and then began to decline. However, the apoptotic signals peaked at week 2 after left coronary artery ligation, and the elevated levels persisted until the end of the fourth week. To elucidate the role of inflammation in the regulation of myocyte autophagy and apoptosis, we administered TNF‐α inhibitor (CAS1049741‐03‐8, Millipore, Burlington, MA) to the mice daily during the first week of myocardial infarction. Anti‐TNF‐α therapy reduced the levels of inflammatory cytokines and the inflammatory cell infiltration in and around the infarct area. However, cardiac function measured by echocardiography (fractional shortening and ejection fraction) worsened with anti‐TNF‐α therapy. More importantly, application of TNF‐α inhibitor markedly inhibited autophagy and promoted myocyte apoptosis in the border zone.ConclusionsThese observations suggest that inflammatory response may be protective in the early stage of the myocardial infarction through stimulation of myocyte autophagy. Anti‐inflammatory treatment early after coronary occlusion may have an adverse effect.

Deficiency of aldose reductase exacerbates early pressure overload-induced cardiac dysfunction and autophagy in mice

Pathological cardiac hypertrophy is associated with the accumulation of lipid peroxidation-derived aldehydes such as 4-hydroxy-trans-2-nonenal (HNE) and acrolein in the heart. These aldehydes are metabolized via several pathways, of which aldose reductase (AR) represents a broad-specificity route for their elimination. We tested the hypothesis that by preventing aldehyde removal, AR deficiency accentuates the pathological effects of transverse aortic constriction (TAC). We found that the levels of AR in the heart were increased in mice subjected to TAC for 2 weeks. In comparison with wild-type (WT), AR-null mice showed lower ejection fraction, which was exacerbated 2 weeks after TAC. Levels of atrial natriuretic peptide and myosin heavy chain were higher in AR-null than in WT TAC hearts. Deficiency of AR decreased urinary levels of the acrolein metabolite, 3-hydroxypropylmercapturic acid. Deletion of AR did not affect the levels of the other aldehyde-metabolizing enzyme - aldehyde dehydrogenase 2 in the heart, or its urinary product - (N-Acetyl-S-(2-carboxyethyl)-l-cystiene). AR-null hearts subjected to TAC showed increased accumulation of HNE- and acrolein-modified proteins, as well as increased AMPK phosphorylation and autophagy. Superfusion with HNE led to a greater increase in p62, LC3II formation, and GFP-LC3-II punctae formation in AR-null than WT cardiac myocytes. Pharmacological inactivation of JNK decreased HNE-induced autophagy in AR-null cardiac myocytes. Collectively, these results suggest that during hypertrophy the accumulation of lipid peroxidation derived aldehydes promotes pathological remodeling via excessive autophagy, and that metabolic detoxification of these aldehydes by AR may be essential for maintaining cardiac function during early stages of pressure overload.