Cardioprotection by adaptation to ischaemia augments autophagy in association with BAG-1 protein

Identification of autophagy-related signatures in nonalcoholic fatty liver disease and correlation with non-parenchymal cells of the liver

Non-alcoholic fatty liver disease (NAFLD) is a chronic hepatic disease. The incidence and prevalence of NAFLD have increased greatly in recent years, and there is still a lack of effective drugs. Autophagy plays an important role in promoting liver metabolism and maintaining liver homeostasis, and defects in autophagy levels are considered to be related to the development of NAFLD. However, the molecular mechanisms of autophagy in NAFLD still remain unknown. In this study, we identified 6 autophagy-associated hub genes using gene expression profiles obtained from the GSE48452 and GSE89632 datasets. Biomarkers were screened according to gene significance (GS) and module membership (MM) using weighted gene co-expression network analysis (WGCNA), and the immune infiltration landscape of the liver in NAFLD patients was explored using the CIBERSORT algorithm. Subsequently, we analyzed the relationship between liver non-parenchymal cells and autophagy-related hub genes using scRNA-seq data (GSE129516). Finally, we separated the NAFLD patients into two groups based on 6 hub genes by consensus clustering and screened 10 potential autophagy-related small molecules based on the cMAP database.

Ginsenoside Rb2 improves heart failure by down-regulating miR-216a-5p to promote autophagy and inhibit apoptosis and oxidative stress

BACKGROUND

Ginsenoside Rb2 is beneficial in cardiovascular disease treatment, yet its role in heart failure (HF) is obscure. This study aimed to investigate the effect and mechanism of ginsenoside Rb2 on HF.

METHODS

The left anterior descending branch-ligated HF rat model and oxygen-glucose deprivation/reoxygenation (OGD/R) H9c2 cell model were constructed. Ginsenoside Rb2 were applied for intervention. Heart function indexes, miR-216a-5p expression, autophagy, oxidative stress, apoptosis, cell morphology, and proliferation were detected to explore the effect of ginsenoside Rb2 on HF. Overexpression of miR-216a-5p was employed to explore the specific mechanism of ginsenoside Rb2 on HF.

RESULTS

Ginsenoside Rb2 improved the heart function of HF rats, including the reduction of heart rate, LVEDP, and heart weight/body weight ratio, and the increase of LVSP, +dP/dtmax, -dP/dtmax, LVEF, and LVFS. It also down-regulated miR-216a-5p expression and enhanced OGD/R-induced cardiomyocyte viability. Ginsenoside Rb2 up-regulated Bcl2, LC3B II/I, and Beclin1, and down-regulated Bax, Caspase-3, and p62 in the myocardium of HF rats and OGD/R-induced H9c2 cells. Moreover, ginsenoside Rb2 increased the levels of SOD and CAT, but decreased the levels of MDA and ROS in the myocardium of HF rats and OGD/R-induced H9c2 cells. However, overexpression of miR-216a-5p promoted the apoptosis and oxidative stress of cardiomyocytes and inhibited autophagy, thus reversing the therapeutic effect of ginsenoside Rb2 on HF in vivo and in vitro.

CONCLUSION

Ginsenoside Rb2 demonstrated potential as a therapeutic intervention for HF by enhancing autophagy and reducing apoptosis and oxidative stress through miR-216a-5p downregulation. Further research could explore its application in clinical trials and investigate the complex mechanism networks underlying its effects.

Exercise preconditioning promotes myocardial GLUT4 translocation and induces autophagy to alleviate exhaustive exercise-induced myocardial injury in rats

Exercise preconditioning (EP) is a line of scientific inquiry into the short-term biochemical mediators of cardioprotection in the heart. This study examined the involvement of autophagy induced by energy metabolism in myocardial remodelling by EP and myocardial protection. A total of 120 healthy male Sprague Dawley (SD) rats were randomly divided into six groups. Plasma cTnI, HBFP staining and electrocardiographic indicators were examined in the context of myocardial ischemic/hypoxic injury and protection. Western blotting and fluorescence double labelling were used to investigate the relationship between energy metabolism and autophagy in EP-resistant myocardial injury caused by exhaustive exercise. Compared with those in the C group, the levels of myocardial ischemic/hypoxic injury were significantly increased in the EE group. Compared with those in the EE group, the levels of myocardial ischemic/hypoxic injury were significantly decreased in the EEP + EE and LEP + EE groups. Compared with that in the EE group, the level of GLUT4 in the sarcolemma was significantly increased, and the colocalization of GLUT4 with the sarcolemma was significantly increased in the EEP + EE and LEP + EE groups (P < 0.05). LC3-II and LC3-II/LC3-I levels of the EEP + EE group were significantly elevated compared with those in the EE group (P < 0.05). The levels of p62 were significantly decreased in the EEP + EE and LEP + EE groups compared with the EE group (P < 0.05). EP promotes GLUT4 translocation and induced autophagy to alleviate exhaustive exercise-induced myocardial ischemic/hypoxic injury.

Network pharmacology-based analysis of potential mechanisms of myocardial ischemia-reperfusion injury by total salvianolic acid injection

In this review, we investigated the potential mechanism of Total Salvianolic Acid Injection (TSI) in protecting against myocardial ischemia reperfusion injury (MI/RI). To achieve this, we predicted the component targets of TSI using Pharmmapper and identified the disease targets of MI/RI through GeneCards, DisGenNET, and OMIM databases. We constructed protein-protein interaction networks by analyzing the overlapping targets and performed functional enrichment analyses using Gene Ontology and Kyoto Encyclopedia of Genes and Genomes. Our analysis yielded 90 targets, which were implicated in the potential therapeutic effects of TSI on MI/RI. Seven critical signaling pathways significantly contributed to TSI's protective effects, namely, PI3K signaling, JAK-STAT signaling, Calcium signaling, HIF-1 signaling, Nuclear receptor signaling, Cell Cycle, and Apoptosis. Subsequently, we conducted a comprehensive literature review of these seven key signaling pathways to gain further insights into their role in the TSI-mediated treatment of MI/RI. By establishing these connections, our study lays a solid foundation for future research endeavours to elucidate the molecular mechanisms through which TSI exerts its beneficial effects on MI/RI.

Autophagy in Heart Failure: Insights into Mechanisms and Therapeutic Implications

Autophagy, a dynamic and complex process responsible for the clearance of damaged cellular components, plays a crucial role in maintaining myocardial homeostasis. In the context of heart failure, autophagy has been recognized as a response mechanism aimed at counteracting pathogenic processes and promoting cellular health. Its relevance has been underscored not only in various animal models, but also in the human heart. Extensive research efforts have been dedicated to understanding the significance of autophagy and unravelling its complex molecular mechanisms. This review aims to consolidate the current knowledge of the involvement of autophagy during the progression of heart failure. Specifically, we provide a comprehensive overview of published data on the impact of autophagy deregulation achieved by genetic modifications or by pharmacological interventions in ischemic and non-ischemic models of heart failure. Furthermore, we delve into the intricate molecular mechanisms through which autophagy regulates crucial cellular processes within the three predominant cell populations of the heart: cardiomyocytes, cardiac fibroblasts, and endothelial cells. Finally, we emphasize the need for future research to unravel the therapeutic potential associated with targeting autophagy in the management of heart failure.

Bacterial toxins and heart function: heat-labile Escherichia coli enterotoxin B promotes changes in cardiac function with possible relevance for sudden cardiac death

Bacterial toxins can cause cardiomyopathy, though it is not its most common cause. Some bacterial toxins can form pores in the membrane of cardiomyocytes, while others can bind to membrane receptors. Enterotoxigenic E. coli can secrete enterotoxins, including heat-resistant (ST) or labile (LT) enterotoxins. LT is an AB5-type toxin that can bind to specific cell receptors and disrupt essential host functions, causing several common conditions, such as certain diarrhea. The pentameric B subunit of LT, without A subunit (LTB), binds specifically to certain plasma membrane ganglioside receptors, found in lipid rafts of cardiomyocytes. Isolated guinea pig hearts and cardiomyocytes were exposed to different concentrations of purified LTB. In isolated hearts, mechanical and electrical alternans and an increment of heart rate variability, with an IC50 of ~0.2 μg/ml LTB, were observed. In isolated cardiomyocytes, LTB promoted significant decreases in the amplitude and the duration of action potentials. Na+ currents were inhibited whereas L-type Ca2+ currents were augmented at their peak and their fast inactivation was promoted. Delayed rectifier K+ currents decreased. Measurements of basal Ca2+ or Ca2+ release events in cells exposed to LTB suggest that LTB impairs Ca2+ homeostasis. Impaired calcium homeostasis is linked to sudden cardiac death. The results are consistent with the recent view that the B subunit is not merely a carrier of the A subunit, having a role explaining sudden cardiac death in children (SIDS) infected with enterotoxigenic E. coli, explaining several epidemiological findings that establish a strong relationship between SIDS and ETEC E. coli.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12551-023-01100-6.

Dysregulated autophagy: A key player in the pathophysiology of type 2 diabetes and its complications

Autophagy is essential in regulating the turnover of macromolecules via removing damaged organelles, misfolded proteins in various tissues, including liver, skeletal muscles, and adipose tissue to maintain the cellular homeostasis. In these tissues, a specific type of autophagy maintains the accumulation of lipid droplets which is directly related to obesity and the development of insulin resistance. It appears to play a protective role in a normal physiological environment by eliminating the invading pathogens, protein aggregates, and damaged organelles and generating energy and new building blocks by recycling the cellular components. Ageing is also a crucial modulator of autophagy process. During stress conditions involving nutrient deficiency, lipids excess, hypoxia etc., autophagy serves as a pro-survival mechanism by recycling the free amino acids to maintain the synthesis of proteins. The dysregulated autophagy has been found in several ageing associated diseases including type 2 diabetes (T2DM), cancer, and neurodegenerative disorders. So, targeting autophagy can be a promising therapeutic strategy against the progression to diabetes related complications. Our article provides a comprehensive outline of understanding of the autophagy process, including its types, mechanisms, regulation, and role in the pathophysiology of T2DM and related complications. We also explored the significance of autophagy in the homeostasis of β-cells, insulin resistance (IR), clearance of protein aggregates such as islet amyloid polypeptide, and various insulin-sensitive tissues. This will further pave the way for developing novel therapeutic strategies for diabetes-related complications.

Regulation of autophagy of the heart in ischemia and reperfusion

Ischemia/reperfusion (I/R) of the heart leads to increased autophagic flux. Preconditioning stimulates autophagic flux by AMPK and PI3-kinase activation and mTOR inhibition. The cardioprotective effect of postconditioning is associated with activation of autophagy and increased activity of NO-synthase and AMPK. Oxidative stress stimulates autophagy in the heart during I/R. Superoxide radicals generated by NADPH-oxidase acts as a trigger for autophagy, possibly due to AMPK activation. There is reason to believe that AMPK, GSK-3β, PINK1, JNK, hexokinase II, MEK, PKCα, and ERK kinases stimulate autophagy, while mTOR, PKCδ, Akt, and PI3-kinase can inhibit autophagy in the heart during I/R. However, there is evidence that PI3-kinase could stimulate autophagy in ischemic preconditioning of the heart. It was found that transcription factors FoxO1, FoxO3, NF-κB, HIF-1α, TFEB, and Nrf-2 enhance autophagy in the heart in I/R. Transcriptional factors STAT1, STAT3, and p53 inhibit autophagy in I/R. MicroRNAs could stimulate and inhibit autophagy in the heart in I/R. Long noncoding RNAs regulate the viability and autophagy of cardiomyocytes in hypoxia/reoxygenation (H/R). Nitric oxide (NO) donors and endogenous NO could activate autophagy of cardiomyocytes. Activation of heme oxygenase-1 promotes cardiomyocyte tolerance to H/R and enhances autophagy. Hydrogen sulfide increases cardiac tolerance to I/R and inhibits apoptosis and autophagy via mTOR and PI3-kinase activation.

Alpha-momorcharin preserves catalase activity to inhibit viral infection by disrupting the 2b-CAT interaction in Solanum lycopersicum

Many host factors of plants are used by viruses to facilitate viral infection. However, little is known about how alpha-momorcharin (αMMC) counters virus-mediated attack strategies in tomato. Our present research revealed that the 2b protein of cucumber mosaic virus (CMV) directly interacted with catalases (CATs) and inhibited their activities. Further analysis revealed that transcription levels of catalase were induced by CMV infection and that virus accumulation increased in CAT-silenced or 2b-overexpressing tomato plants compared with that in control plants, suggesting that the interaction between 2b and catalase facilitated the accumulation of CMV in hosts. However, both CMV accumulation and viral symptoms were reduced in αMMC transgenic tomato plants, indicating that αMMC engaged in an antiviral role in the plant response to CMV infection. Molecular experimental analysis demonstrated that αMMC interfered with the interactions between catalases and 2b in a competitive manner, with the expression of αMMC inhibited by CMV infection. We further demonstrated that the inhibition of catalase activity by 2b was weakened by αMMC. Accordingly, αMMC transgenic plants exhibited a greater ability to maintain redox homeostasis than wild-type plants when infected with CMV. Altogether, these results reveal that αMMC retains catalase activity to inhibit CMV infection by subverting the interaction between 2b and catalase in tomato.

Protective Role of miR-34c in Hypoxia by Activating Autophagy through BCL2 Repression

Hypoxia leads to significant cellular stress that has diverse pathological consequences such as cardiovascular diseases and cancers. MicroRNAs (miRNAs) are one of regulators of the adaptive pathway in hypoxia. We identified a hypoxia-induced miRNA, miR-34c, that was significantly upregulated in hypoxic human umbilical cord vein endothelial cells (HUVECs) and in murine blood vessels on day 3 of hindlimb ischemia (HLI). miR-34c directly inhibited BCL2 expression, acting as a toggle switch between apoptosis and autophagy in vitro and in vivo. BCL2 repression by miR-34c activated autophagy, which was evaluated by the expression of LC3-II. Overexpression of miR-34c inhibited apoptosis in HUVEC as well as in a murine model of HLI, and increased cell viability in HUVEC. Importantly, the number of viable cells in the blood vessels following HLI was increased by miR-34c overexpression. Collectively, our findings show that miR-34c plays a protective role in hypoxia, suggesting a novel therapeutic target for hypoxic and ischemic diseases in the blood vessels.

Genetic deletion of IL-6 increases CK-MB, a classic cardiac damage marker, and decreases UPRmt genes after exhaustive exercise

The intensity, duration, type of contraction, and muscle damage influence interleukin-6 (IL-6) response to acute exercise. However, in response to an exhaustive exercise session, the upregulation of IL-6 in the serum and heart is associated with an inflammatory condition and can inhibit autophagy. This study aimed to investigate the role of IL-6 in autophagy pathway responses and mitochondrial function in the heart of mice submitted to acute exhaustive physical exercise. The mice were allocated into three groups, five animals per group, for the wild type (WT) and the IL-6 knockout (IL-6 KO): Basal (sedentary; Basal), 1 h (after 1 h of the acute exercise; 1 h), and 3 h (after 3 h of the acute exercise; 3 h). After the specific time for each group, the blood was collected, each mouse heart was removed, and the left ventricle (LV) was isolated. In summary, under basal conditions, without the influence of the acute exercise, the IL-6 KO group showed lower number of nuclei in the cardiac tissue, but higher collagen deposition; lower messenger RNA (mRNA) levels of Prkaa1 and Mtco1, but higher mRNA levels of Ulk1; and higher protein levels of the ratio p-AMPK/AMPK in the heart when compared to WT at the same time point. After the acute exercise (1 and 3 h), the IL-6 KO group had lower mRNA levels of Tfam, Mtnd1, Mtco1, and Nampt in the heart when compared to WT after exercise; higher serum levels of creatine kinase (CK), CK-MB, and lactate dehydrogenase for the IL-6 group when compared to the WT group after the exercise. Specifically, the heat-shock protein 60 protein levels in the heart increased 3 h after exhaustive exercise in the WT group, but not in the IL-6 KO group. The study emphasizes that IL-6 may offer cardioprotective effects, including mitochondrial adaptations in response to acute exhaustive exercise.

BAG Family Members as Mitophagy Regulators in Mammals

The BCL-2-associated athanogene (BAG) family is a multifunctional group of co-chaperones that are evolutionarily conserved from yeast to mammals. In addition to their common BAG domain, these proteins contain, in their sequences, many specific domains/motifs required for their various functions in cellular quality control, such as autophagy, apoptosis, and proteasomal degradation of misfolded proteins. The BAG family includes six members (BAG1 to BAG6). Recent studies reported their roles in autophagy and/or mitophagy through interaction with the autophagic machinery (LC3, Beclin 1, P62) or with the PINK1/Parkin signaling pathway. This review describes the mechanisms underlying BAG family member functions in autophagy and mitophagy and the consequences in physiopathology.

The regulatory mechanism between lysosomes and mitochondria in the aetiology of cardiovascular diseases

Coordinated action among various organelles maintains cellular functions. For instance, mitochondria and lysosomes are the main organelles contributing to cellular metabolism and provide energy for cardiomyocyte contraction. They also provide essential signalling platforms in the cell that regulate many key processes such as autophagy, apoptosis, oxidative stress, inflammation and cell death. Often, abnormalities in mitochondrial or lysosomal structures and functions bring about cardiovascular diseases (CVDs). Although the communication between mitochondria and lysosomes throughout the cardiovascular system is intensely studied, the regulatory mechanisms have not been completely understood. Thus, we summarize the most recent studies related to mitochondria and lysosomes' role in CVDs and their potential connections and communications under cardiac pathophysiological conditions. Further, we discuss limitations and future perspectives regarding diagnosis, therapeutic strategies and drug discovery in CVDs.

Effect of Rho-Kinase and Autophagy on Remote Ischemic Conditioning-Induced Cardioprotection in Rat Myocardial Ischemia/Reperfusion Injury Model

Objective. Remote ischemic conditioning (RIC) is a cardioprotective method in ischemia/reperfusion (I/R) injury. This study investigated the mechanism of Rho-kinase-mediated autophagy in RIC. Methods. Sixty male Sprague–Dawley rats were randomly divided into six groups: sham, I/R, RIC, I/R+fasudil, RIC+wortmannin, and RIC+fasudil+wortmannin. Throughout the experiment, mean arterial pressure and heart rate were continuously monitored. Histopathology and ultrastructure and myocardial enzymes’ expression were evaluated to determine the degree of cardiac injury. The protein expression of the Rho-kinase substrates myosin light chain (MLC) and myosin phosphatase target subunit 1 (MYPT1), autophagy-related protein light chain 3-II (LC3-II) and Beclin 1, and protein kinase B (AKT) was measured in the myocardial tissue. Results. Compared with the sham group, the mean arterial pressure and heart rate were decreased, myocardial enzyme levels were increased, and myocardial damage was aggravated in the I/R group; however, RIC improved these alterations. The expression of phosphorylated MLC and MYPT1 was lower, while LC3-II, Beclin 1, and phospho-AKT expression levels were higher in the RIC group compared with the I/R group. Obviously, treatment of the I/R group rats with fasudil, a Rho-kinase inhibitor, significantly ameliorated the I/R effects, whereas treatment of the RIC group rats with wortmannin, a phosphatidylinositol-3 kinase (PI3K) inhibitor, inhibited the RIC protective effects. Moreover, the rats in the RIC+fasudil+wortmannin group showed similar changes to those in the RIC+wortmannin group. Conclusion. These results showed that RIC protected the myocardium from I/R injury by suppressing Rho-kinase and the underlying mechanism may be related to enhancing autophagy via the PI3K/AKT pathway.

Mitochondrial Quality Control in Cardiac-Conditioning Strategies against Ischemia-Reperfusion Injury

Mitochondria are the central target of ischemic preconditioning and postconditioning cardioprotective strategies, which consist of either the application of brief intermittent ischemia/reperfusion (I/R) cycles or the administration of pharmacological agents. Such strategies reduce cardiac I/R injury by activating protective signaling pathways that prevent the exacerbated production of reactive oxygen/nitrogen species, inhibit opening of mitochondrial permeability transition pore and reduce apoptosis, maintaining normal mitochondrial function. Cardioprotection also involves the activation of mitochondrial quality control (MQC) processes, which replace defective mitochondria or eliminate mitochondrial debris, preserving the structure and function of the network of these organelles, and consequently ensuring homeostasis and survival of cardiomyocytes. Such processes include mitochondrial biogenesis, fission, fusion, mitophagy and mitochondrial-controlled cell death. This review updates recent advances in MQC mechanisms that are activated in the protection conferred by different cardiac conditioning interventions. Furthermore, the role of extracellular vesicles in mitochondrial protection and turnover of these organelles will be discussed. It is concluded that modulation of MQC mechanisms and recognition of mitochondrial targets could provide a potential and selective therapeutic approach for I/R-induced mitochondrial dysfunction.

The potentials of distinct functions of autophagy to be targeted for attenuation of myocardial ischemia/reperfusion injury in preclinical studies: an up-to-date review

Despite remarkable advances in our knowledge about the function of autophagy in myocardial ischemia/reperfusion (I/R) injury, the debate continues over whether autophagy is protective or deleterious in cardiac I/R. Due to the complexity of autophagy signaling, autophagy can play a dual role in the pathological processes of myocardial I/R injury. Thus, more researches are needed to shed light on the complex roles of autophagy in cardioprotection for the future clinical development. Such researches can lead to the finding of new therapeutic strategies for improving cardiac I/R outcomes in patients. Several preclinical studies have targeted autophagy flux as a beneficial strategy against myocardial I/R injury. In this review, we aimed to discuss the complex contribution of autophagy in myocardial I/R injury, as well as the therapeutic agents that have been shown to be useful in reducing myocardial I/R injury by targeting autophagy. For this reason, we provided an updated summary of the data from in vivo, ex vivo, and in vitro experimental studies about the therapeutic agents that exert positive effects against myocardial I/R injury by modulating autophagy flux. By addressing these valuable studies, we try to provide a motivation for the promising hypothesis of "autophagy modulation as a therapeutic strategy against cardiac I/R" in the future clinical studies.

Ozone induces tolerance against cardiomyocytes oxygen-glucose deprivation/reperfusion through inhibition of autophagy pathway

Previous studies have reported that excess activation of autophagy in cardiomyocytes is associated with an increase in myocardial oxygen-glucose deprivation/reperfusion (OGD/R) injury. Ozone therapy affords significant cardio-protection against myocardial OGD/R injury. The present study was designed to determine whether ozone-induced tolerance to myocardial OGD/R injury was mediated by inhibiting autophagy. Subsequently, the rat cardio myoblast H9C2 cell line was used in the present study. A model of H9C2 cells under OGD/R was established. The cells were incubated with different concentrations of ozone (10-60 µg/ml) during reperfusion. Furthermore, to investigate the role of autophagy in OGD/R-induced injury, the autophagy inducer and inhibitor were applied. Cell viability was detected by Cell Counting kit-8 assay. Cell apoptosis was evaluated by flow cytometry. Oxidative stress was examined by superoxide dismutase, lactate dehydrogenase and malondialdehyde levels. The expressions of apoptosis regulator B-cell lymphoma-2 (Bcl-2), Bcl-2 associated X protein (BAX), cleaved caspase-3, markers of autophagy microtuble-associated protein 1 light chain 3 (LC3), autophagy-related protein 5 (Atg5) and Beclin-1 were measured by western blot analysis. As a result, OGD/R notably decreased cell viability and induced apoptosis in H9C2 cells, while ozone (10-40 µg/ml) reversed the noxious effects of OGD/R on H9C2 cells, and 20 µg/ml ozone was the most effective. Ozone inhibited the decrease in the ratio of Bcl-2/BAX and the expression of cleaved caspase-3, and inhibited the increase in the ratio of LC3-II/LC3-I and the expression of Atg5 and Beclin-1 elicited by OGD/R, as well as dose-dependently preventing OGD/R-induced oxidative stress. Furthermore, rapamycin markedly reversed the effects of ozone (20 µg/ml) on OGD/R-induced expression of autophagy marker proteins and 3-methyladenine further improved the effect of ozone. Taken together, the results of the present study provided a credible mechanism by which ozone treatment at low concentrations could protect the myocardium from OGD/R-induced injury by inhibiting autophagy.

Puerarin protects cardiomyocytes from ischemia-reperfusion injury by upregulating LncRNA ANRIL and inhibiting autophagy

This study analyzed the roles of puerarin and LncRNA ANRIL in myocardial ischemia-reperfusion injury. Hypoxia/reperfusion (H/R) model was established with H9C2 cells. Effects of puerarin of gradient concentrations on cardiomyocytes at different time points of hypoxia and reoxygenation were detected by quantitative real-time polymerase chain reaction (qRT-PCR), cell counting kit-8 (CCK-8), and microscope observation. Effects of puerarin on cardiomyocyte viability, ANRIL expression, contents of lactate dehydrogenase (LDH) and malondialdehyde (MDA), apoptosis, and expressions of autophagy-related genes after H/R injury were determined by CCK-8, quantitative real-time polymerase chain reaction (qRT-PCR), ELISA, flow cytometry, and Western blot, respectively. After cell transfection, the effects of overexpressed and knockdown of ANRIL on cardiomyocytes and H/R-injured cardiomyocytes were examined by rescue experiments. The ischemia-reperfusion (I/R)-injured rat model was established to examine the protective effect of puerarin in vivo. Prolonged hypoxia downregulated ANRIL expression in cardiomyocytes and reduced cardiomyocyte viability. Prolonged reoxygenation increased apoptosis. Both cardiomyocyte viability and ANRIL expression showed a dose-dependent relationship with puerarin. Puerarin reversed the effects of H/R injury on cardiomyocyte viability, ANRIL expression, contents of LDH and MDA, apoptosis, and expressions of autophagy-related genes. Overexpression and knockdown of ANRIL regulated the functions of cardiomyocytes and the expressions of autophagy-related genes. Puerarin reversed the effects of knockdown of ANRIL on H/R-injured cells. The results of In vivo experiments confirmed that puerarin protected myocardial tissues by up-regulating ANRIL and inhibiting autophagy.

Co-Chaperone Bag-1 Plays a Role in the Autophagy-Dependent Cell Survival through Beclin 1 Interaction

Expression levels of the major mammalian autophagy regulator Beclin 1 and its interaction with Bcl-2 regulate the switch between autophagic cell survival and apoptotic cell death pathways. However, some of the regulators and the precise mechanisms of these processes still remain elusive. Bag-1 (Bcl-2 associated athanogene-1), a member of BAG family proteins, is a multifunctional pro-survival molecule that possesses critical functions in vital cellular pathways. Herein, we report the role of Bag-1 on Bcl-2/Beclin 1 crosstalk through indirectly interacting with Beclin 1. Pull-down experiments suggested a molecular interaction between Bag-1 and Beclin 1 in breast cancer cell lines. On the other hand, in vitro binding assays showed that Bag-1/Beclin 1 interaction does not occur directly but occurs through a mediator molecule. Bag-1 interaction with p-Beclin 1 (T119), indicator of early autophagy, is increased during nutrient starvation suggesting involvement of Bag-1 in the autophagic regulation. Furthermore, CRISPR/Cas9-mediated Bag-1 knock-out in MCF-7 cells hampered cell survival and proliferation and resulted in decreased levels of total LC3 under starvation. Collectively, we suggest that Bag-1 modulates cell survival/death decision through maintaining macroautophagy as a component of Beclin 1-associated complexes.

Activation of Autophagy in Human Uterine Myometrium During Labor

OBJECTIVE

The purpose of this study was to analyze the autophagy of the human uterine myometrium during the labor.

METHODS

We collected uterine myometrium strips from term, singleton, nulliparous healthy women undergoing cesarean delivery before labor (nonlabor group, n = 10) or during normal labor (in-labor group, n = 10) without rupturing of membrane. The indications for cesarean delivery were breech presentation or maternal request. Transmission electron microscopy was used to observe autophagosomes. Reverse transcriptase polymerase chain reaction, immunofluorescence, and Western blot were used to quantify the messenger RNA (mRNA) and protein level of the autophagy markers LC3B, P62, and Beclin-1 in the uterine muscle strips.

RESULTS

There were no differences between both groups in maternal age, body mass index, gestational week, neonatal weight, operative bleeding, and postpartum bleeding. Transmission electron micrographs showed that autophagosomes existed in myometrial tissue in both groups. There were more autophagosomes in the in-labor group than in the nonlabor group, and the difference had significance. The in-labor group had significantly greater LC3B mRNA expression but significantly lower P62 mRNA expression compared with the nonlabor group. Semiquantitative immunofluorescence in uterine myometrial cells in the in-labor group showed increased LC3B puncta formation and greater Beclin-1 expression but reduced P62 puncta formation compared with the nonlabor group. The ratio of LC3BII/I proteins was significantly higher, but P62 protein was significantly lower in the in-labor group compared with the nonlabor group. The Beclin-1 mRNA and protein expressions were not significantly different between the 2 groups.

CONCLUSION

Autophagy was activated in human uterine myometrium during labor and might play an important role in maintaining uterine contraction function.

MMP9 inhibition increases autophagic flux in chronic heart failure

Increased matrix metalloprotease 9 (MMP9) after myocardial infarction (MI) exacerbates ischemia-induced chronic heart failure (CHF). Autophagy is cardioprotective during CHF; however, whether increased MMP9 suppresses autophagic activity in CHF is unknown. This study aimed to determine whether increased MMP9 suppressed autophagic flux and MMP9 inhibition increased autophagic flux in the heart of rats with post-MI CHF. Sprague-Dawley rats underwent either sham surgery or coronary artery ligation 6-8 wk before being treated with MMP9 inhibitor for 7 days, followed by cardiac autophagic flux measurement with lysosomal inhibitor bafilomycin A1. Furthermore, autophagic flux was measured in vitro by treating H9c2 cardiomyocytes with two independent pharmacological MMP9 inhibitors, salvianolic acid B (SalB) and MMP9 inhibitor-I, and CRISPR/cas9-mediated MMP9 genetic ablation. CHF rats showed cardiac infarct, significantly increased left ventricular end-diastolic pressure (LVEDP), and increased MMP9 activity and fibrosis in the peri-infarct areas of left ventricular myocardium. Measurement of the autophagic markers LC3B-II and p62 with lysosomal inhibition showed decreased autophagic flux in the peri-infarct myocardium. Treatment with SalB for 7 days in CHF rats decreased MMP9 activity and cardiac fibrosis but increased autophagic flux in the peri-infarct myocardium. As an in vitro corollary study, measurement of autophagic flux in H9c2 cardiomyocytes and fibroblasts showed that pharmacological inhibition or genetic ablation of MMP9 upregulates autophagic flux. These data are consistent with our observations that MMP9 inhibition upregulates autophagic flux in the heart of rats with CHF. In conclusion, the results in this study suggest that the beneficial outcome of MMP9 inhibition in pathological cardiac remodeling is in part mediated by improved autophagic flux.NEW & NOTEWORTHY This study elucidates that the improved cardiac extracellular matrix (ECM) remodeling and cardioprotective effect of matrix metalloprotease 9 (MMP9) inhibition in chronic heart failure (CHF) are via increased autophagic flux. Autophagy is cardioprotective; however, the mechanism of autophagy suppression in CHF is unknown. We for the first time demonstrated here that increased MMP9 suppressed cardiac autophagy and ablation of MMP9 increased cardiac autophagic flux in CHF rats. Restoring the physiological level of autophagy in the failing heart is a challenge, and our study addressed this challenge. The novelty and highlights of this report are as follows: 1) MMP9 regulates cardiomyocyte and fibroblast autophagy, 2) MMP9 inhibition protects CHF after myocardial infarction (MI) via increased cardiac autophagic flux, 3) MMP9 inhibition increased cardiac autophagy via activation of AMP-activated protein kinase (AMPK)α, Beclin-1, Atg7 pathway and suppressed mechanistic target of rapamycin (mTOR) pathway.

Hydrogen Sulfide Switch Phenomenon Regulating Autophagy in Cardiovascular Diseases

Hydrogen sulfide (H₂S), a novel gaseous signaling molecule, is a vital physiological signal in mammals. H₂S protects the cardiovascular system via modulation of vasodilation, vascular remodeling, and inhibition of vascular calcification, and also has anti-atherosclerosis properties. Autophagy is a lysosomal-mediated intracellular degradation mechanism for excessive or abnormal proteins and lipids. The contribution of autophagy to normal and disease-state cell physiology is extremely complicated. Autophagy acts as a double-edged sword in the cardiovascular system. It can defend against damage to cells caused by environmental changes and it can also induce active cell death under certain conditions. In recent years, accumulating evidence indicates that H₂S can up- or downregulate autophagy in many pathological processes, thereby switching from a harmful to a beneficial role. In this review, we summarize progress on understanding the mechanism by which H₂S regulates autophagy in cardiovascular disease. We also discuss a H₂S switch phenomenon that regulates autophagy and provides protection in cardiovascular diseases.

Blockade of HCN2 Channels Provides Neuroprotection Against Ischemic Injury via Accelerating Autophagic Degradation in Hippocampal Neurons

In the central nervous system, hyperpolarization-activated cyclic nucleotide-gated (HCN) channels are essential to maintain normal neuronal function. Recent studies have shown that HCN channels may be involved in the pathological process of ischemic brain injury, but the mechanisms remain unclear. Autophagy is activated in cerebral ischemia, but its role in cell death/survival remains controversial. In this study, our results showed that the HCN channel blocker ZD7288 remarkably decreased the percentage of apoptotic neurons and corrected the excessive autophagy induced by oxygen-glucose deprivation followed by reperfusion (OGD/R) in hippocampal HT22 neurons. Furthermore, in the OGD/R group, p-mTOR, p-ULK1 (Ser757), and p62 were significantly decreased, while p-ULK1 (Ser317), atg5, and beclin1 were remarkably increased. ZD7288 did not change the expression of p-ULK1 (Ser757), ULK1 (Ser317), p62, Beclin1, and atg5, which are involved in regulating autophagosome formation. Besides, we found that OGD/R induced a significant increase in Cathepsin D expression, but not LAMP-1. Treatment with ZD7288 at 10 μmol/L in the OGD/R group did not change the expression of cathepsin D and LAMP-1. However, chloroquine (CQ), which decreases autophagosome-lysosome fusion, eliminated the correction of excessive autophagy and neuroprotection by ZD7288. Besides, shRNA knockdown of HCN2 channels significantly reduced the accumulation of LC3-II and increased neuron survival in the OGD/R and transient global cerebral ischemia (TGCI) models, and CQ also eliminated the effects of HCN2-shRNA. Furthermore, we found that the percentage of LC3-positive puncta that co-localized with LAMP-1-positive lysosomes decreased in Con-shRNA-transfected HT22 neurons exposed to OGD/R or CQ. In HCN2-shRNA-transfected HT22 neurons, the percentage of LC3-positive puncta that co-localized with LAMP-1-positive lysosomes increased under OGD/R; however, the percentage was significantly decreased by the addition of CQ to HCN2-shRNA-transfected HT22 neurons. The present results demonstrated that blockade of HCN2 channels provides neuroprotection against OGD/R and TGCI by accelerating autophagic degradation attributable to the promotion of autophagosome and lysosome fusion.

Mitophagy in Cardiovascular Diseases

Cardiovascular diseases are one of the leading causes of death. Increasing evidence has shown that pharmacological or genetic targeting of mitochondria can ameliorate each stage of these pathologies, which are strongly associated with mitochondrial dysfunction. Removal of inefficient and dysfunctional mitochondria through the process of mitophagy has been reported to be essential for meeting the energetic requirements and maintaining the biochemical homeostasis of cells. This process is useful for counteracting the negative phenotypic changes that occur during cardiovascular diseases, and understanding the molecular players involved might be crucial for the development of potential therapies. Here, we summarize the current knowledge on mitophagy (and autophagy) mechanisms in the context of heart disease with an important focus on atherosclerosis, ischemic heart disease, cardiomyopathies, heart failure, hypertension, arrhythmia, congenital heart disease and peripheral vascular disease. We aim to provide a complete background on the mechanisms of action of this mitochondrial quality control process in cardiology and in cardiac surgery by also reviewing studies on the use of known compounds able to modulate mitophagy for cardioprotective purposes.

Remote Ischemic Preconditioning induces Cardioprotective Autophagy and Signals through the IL-6-Dependent JAK-STAT Pathway

Autophagy is a cellular process by which mammalian cells degrade and assist in recycling damaged organelles and proteins. This study aimed to ascertain the role of autophagy in remote ischemic preconditioning (RIPC)-induced cardioprotection. Sprague Dawley rats were subjected to RIPC at the hindlimb followed by a 30-min transient blockade of the left coronary artery to simulate ischemia reperfusion (I/R) injury. Hindlimb muscle and the heart were excised 24 h post reperfusion. RIPC prior to I/R upregulated autophagy in the rat heart at 24 h post reperfusion. In vitro, autophagy inhibition or stimulation prior to RIPC, respectively, either ameliorated or stimulated the cardioprotective effect, measured as improved cell viability to mimic the preconditioning effect. Recombinant interleukin-6 (IL-6) treatment prior to I/R increased in vitro autophagy in a dose-dependent manner, activating the Janus kinase/signal transducers and activators of transcription (JAK-STAT) pathway without affecting the other kinase pathways, such as p38 mitogen-activated protein kinases (MAPK), and glycogen synthase kinase 3 Beta (GSK-3β) pathways. Prior to I/R, in vitro inhibition of the JAK-STAT pathway reduced autophagy upregulation despite recombinant IL-6 pre-treatment. Autophagy is an essential component of RIPC-induced cardioprotection that may upregulate autophagy through an IL-6/JAK-STAT-dependent mechanism, thus identifying a potentially new therapeutic option for the treatment of ischemic heart disease.

Late Exercise Preconditioning Promotes Autophagy against Exhaustive Exercise-Induced Myocardial Injury through the Activation of the AMPK-mTOR-ULK1 Pathway

Accumulating evidence shows that the AMPK-mTOR pathway modulates autophagy via coordinated phosphorylation of ULK1. The aim of the present study was to investigate the relationship between AMPK, mTOR, and ULK1 during late exercise preconditioning (LEP), and to explore whether LEP-induced myocardial protection is related to the autophagy. The exercise preconditioning (EP) protocol was as follows: rats were instructed to for run four repeated in duration of 10 minutes (including 10 minutes rest between each period) on a treadmill. Exhaustive exercise (EE) after LEP pretreatment and administration of wortmannin (an autophagy inhibitor that suppresses Class III PI3K-kinase (PI3KC3) activity) were added to test the protective effect. Cardiac troponin I (cTnI), and transmission electron microscopy (TEM), along with hematoxylin-basic fuchsin-picric acid (HBFP) staining, were used to evaluate the myocardial ischemic-hypoxic injury and protection. Western blot was used to analyze the relationship of autophagy-associated proteins. Exhaustive exercise caused severe myocardial ischemic-hypoxic injury, which led to an increase in cTnI levels, changes of ischemia–hypoxia, and cells ultrastructure. Compared with the EE group, LEP significantly suppressed exhaustive exercise-induced myocardial injury. However, wortmannin attenuated LEP-induced myocardial protection by inhibiting autophagy. Compared with the C group, AMPK was increased in the LEP, EE, and LEP+EE groups, but phosphorylation of AMPK at Thr172 was not significantly changed. Exercise did not have any effect on mTOR expression. Compared with the C group, ULK1 was increased and the ULK1^ser757/ULK1 ratio was decreased in the LEP and LEP+EE groups. ULK1 was not significantly affected in the EE group, however, phosphorylation of ULK1 at Ser757 was remarkably decreased. To sum up, our results suggested that LEP promoted autophagy through the activation of AMPK-mTOR-ULK1 pathway, and that activated autophagy was partially involved in myocardial protection against EE-induced myocardial ischemic-hypoxic injury.

Rapamycin regulates the balance between cardiomyocyte apoptosis and autophagy in chronic heart failure by inhibiting mTOR signaling

The progressive loss of cardiomyocytes caused by cell death leads to cardiac dysfunction and heart failure (HF). Rapamycin has been shown to be cardioprotective in pressure-overloaded and ischemic heart diseases by regulating the mechanistic target of rapamycin (mTOR) signaling network. However, the impact of rapamycin on cardiomyocyte death in chronic HF remains undetermined. Therefore, in the current study we addressed this issue using a rat myocardial infarction (MI)-induced chronic HF model induced by ligating the coronary artery. Following surgery, rats were randomly divided into six groups, including the sham-, vehicle- and rapamycin-operated groups, at 8 or 12 weeks post-MI. A period of 4 weeks after MI induction, the rats were treated with rapamycin (1.4 mg-kg-day) or vehicle for 4 weeks. Cardiac function was determined using echocardiography, the rats were subsequently euthanized and myocardial tissues were harvested for histological and biochemical analyses. In the cell culture experiments with H9c2 rat cardiomyocytes, apoptosis was induced using angiotensin II (100 nM; 24 h). Cardiomyocyte apoptosis and autophagy were assessed via measuring apoptosis- and autophagy-associated proteins. The activities of mTOR complex 1 (mTORC1) and mTORC2 were evaluated using the phosphorylation states of ribosomal S6 protein and Akt, respectively. The activity of the endoplasmic reticulum (ER) stress pathway was determined using the levels of GRP78, caspase-12, phospho-JNK and DDIT3. Echocardiographic and histological measurements indicated that rapamycin treatment improved cardiac function and inhibited cardiac remodeling at 8 weeks post-MI. Additionally, rapamycin prevented cardiomyocyte apoptosis and promoted autophagy at 8 weeks post-MI. Rapamycin treatment for 4 weeks inhibited the mTOR and ER stress pathways. Furthermore, rapamycin prevented angiotensin II-induced H9c2 cell apoptosis and promoted autophagy by inhibiting the mTORC1 and ER stress pathways. These results demonstrated that rapamycin reduced cardiomyocyte apoptosis and promoted cardiomyocyte autophagy, by regulating the crosstalk between the mTOR and ER stress pathways in chronic HF.

Melatonin has profound effects on mitochondrial dynamics in myocardial ischaemia/reperfusion

Research focus recently shifted to mitochondrial dynamics and the role of fusion and fission in cardioprotection. The aim of this study was to evaluate (i) the function and dynamics of mitochondria isolated from hearts exposed to ischaemia/reperfusion (I/R) (ii) the effects of melatonin, a powerful cardioprotectant, on mitochondrial dynamics in I/R. Isolated perfused rat hearts were stabilized for 30 min, subjected to 20 min global ischaemia, followed by 30 min reperfusion. Tissue was collected, mitochondria isolated for measurement of mitochondrial oxidative function and lysates from mitochondrial and cytosolic fractions prepared for western blotting. Melatonin (0.3 or 50 μM) was administered for 10 min immediately before the onset of ischaemia and for 10 min at the onset of reperfusion. Infarct size was assessed after 35 min regional ischaemia/60 min reperfusion using triphenyltetrazolium staining. The results show that reperfusion significantly reduced mitochondrial QO2 (states 3 and 4), with minor effects by melatonin. Cytosolic Beclin 1 and the LC3 II/I ratio were reduced by ischaemia and increased by reperfusion. Both ischaemia and reperfusion reduced mitochondrial PINK1 and Parkin levels, while reperfusion increased p62. An alternative mitophagy pathway mediated by Rab9 is activated during myocardial ischaemia/reperfusion. Ischaemia reduced and reperfusion increased cytosolic ULK1 expression, associated with redistribution of Rab9 and Drp1 between the cytosol and mitochondria. Melatonin significantly reduced mitochondrial p62 expression upon reperfusion. Throughout the protocol, melatonin significantly (i) increased cytosolic total (t) and phospho (p) ULK1, and Rab9 levels (ii) increased the cytosolic and reduced the mitochondrial pDrp1 levels and p/t Drp1 ratio, suggesting inhibition of mitochondrial fission. Fusion was affected to a lesser extent. Cardioprotection by melatonin is associated with substantial effects on mitophagy, the significance thereof remains to be established.

iTRAQ-Based Proteomics Analysis of Autophagy-Mediated Responses against MeJA in Laticifers of Euphorbia kansui L

Autophagy is a well-defined catabolic mechanism whereby cytoplasmic materials are engulfed into a structure termed the autophagosome. Methyl jasmonate (MeJA), a plant hormone, mediates diverse developmental process and defense responses which induce a variety of metabolites. In plants, little is known about autophagy-mediated responses against MeJA. In this study, we used high-throughput comparative proteomics to identify proteins of latex in the laticifers. The isobaric tags for relative and absolute quantification (iTRAQ) MS/MS proteomics were performed, and 298 proteins among MeJA treated groups and the control group of Euphorbia kansui were identified. It is interesting to note that 29 significant differentially expressed proteins were identified and their associations with autophagy and ROS pathway were verified for several selected proteins as follows: α-L-fucosidase, β-galactosidase, cysteine proteinase, and Cu/Zn superoxide dismutase. Quantitative real-time PCR analysis of the selected genes confirmed the fact that MeJA might enhance the expression of some genes related to autophagy. The western blotting and immunofluorescence results of ATG8 and ATG18a which are two important proteins for the formation of autophagosomes also demonstrated that MeJA could promote autophagy at the protein level. Using the electron microscope, we observed an increase in autophagosomes after MeJA treatment. These results indicated that MeJA might promote autophagy in E. kansui laticifers; and it was speculated that MeJA mediated autophagy through two possible ways: the increase of ROS induces ATG8 accumulation and then aotophagosome formation, and MeJA promotes ATG18 accumulation and then autophagosome formation. Taken together, our results provide several novel insights for understanding the mechanism between autophagy and MeJA treatment. However, the specific mechanism remains to be further studied in the future.

Clearance of damaged mitochondria via mitophagy is important to the protective effect of ischemic preconditioning in kidneys

Ischemic preconditioning (IPC) affords tissue protection in organs including kidneys; however, the underlying mechanism remains unclear. Here we demonstrate an important role of macroautophagy/autophagy (especially mitophagy) in the protective effect of IPC in kidneys. IPC induced autophagy in renal tubular cells in mice and suppressed subsequent renal ischemia-reperfusion injury (IRI). The protective effect of IPC was abolished by pharmacological inhibitors of autophagy and by the ablation of Atg7 from kidney proximal tubules. Pretreatment with BECN1/Beclin1 peptide induced autophagy and protected against IRI. These results suggest the dependence of IPC protection on renal autophagy. During IPC, the mitophagy regulator PINK1 (PTEN induced putative kinase 1) was activated. Both IPC and BECN1 peptide enhanced mitolysosome formation during renal IRI in mitophagy reporter mice, suggesting that IPC may protect kidneys by activating mitophagy. We further established an in vitro model of IPC by inducing ‘chemical ischemia’ in kidney proximal tubular cells with carbonyl cyanide 3-chlorophenylhydrazone (CCCP). Brief treatment with CCCP protected against subsequent injury in these cells and the protective effect was abrogated by autophagy inhibition. In vitro IPC increased mitophagosome formation, enhanced the delivery of mitophagosomes to lysosomes, and promoted the clearance of damaged mitochondria during subsequent CCCP treatment. IPC also suppressed mitochondrial depolarization, improved ATP production, and inhibited the generation of reactive oxygen species. Knockdown of Pink1 suppressed mitophagy and reduced the cytoprotective effect of IPC. Together, these results suggest that autophagy, especially mitophagy, plays an important role in the protective effect of IPC.

Abbreviations: ACTB: actin, beta; ATG: autophagy related; BNIP3: BCL2 interacting protein 3; BNIP3L/NIX: BCL2 interacting protein 3 like; BUN: blood urea nitrogen; CASP3: caspase 3; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; COX4I1: cytochrome c oxidase subunit 4I1; COX8: cytochrome c oxidase subunit 8; DAPI: 4ʹ,6-diamidino-2-phenylindole; DNM1L: dynamin 1 like; EGFP: enhanced green fluorescent protein; EM: electron microscopy; ER: endoplasmic reticulum; FC: floxed control; FIS1: fission, mitochondrial 1; FUNDC1: FUN14 domain containing 1; H-E: hematoxylin-eosin; HIF1A: hypoxia inducible factor 1 subunit alpha; HSPD1: heat shock protein family D (Hsp60) member 1; IMMT/MIC60: inner membrane mitochondrial protein; IPC: ischemic preconditioning; I-R: ischemia-reperfusion; IRI: ischemia-reperfusion injury; JC-1: 5,5ʹ,6,6ʹ-tetrachloro-1,1ʹ,3,3ʹ-tetraethylbenzimidazolylcarbocyanine iodide; KO: knockout; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; mito-QC: mito-quality control; mRFP: monomeric red fluorescent protein; NAC: N-acetylcysteine; PINK1: PTEN induced putative kinase 1; PPIB: peptidylprolyl isomerase B; PRKN: parkin RBR E3 ubiquitin protein ligase; ROS: reactive oxygen species; RPTC: rat proximal tubular cells; SD: standard deviation; sIPC: simulated IPC; SQSTM1/p62: sequestosome 1; TOMM20: translocase of outer mitochondrial membrane 20; TUNEL: terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling

Modulating autophagy in mesenchymal stem cells effectively protects against hypoxia- or ischemia-induced injury

In mammals, a basal level of autophagy, a self-eating cellular process, degrades cytosolic proteins and subcellular organelles in lysosomes to provide energy, recycles the cytoplasmic components, and regenerates cellular building blocks; thus, autophagy maintains cellular and tissue homeostasis in all eukaryotic cells. In general, adaptive autophagy increases when cells confront stressful conditions to improve the survival rate of the cells, while destructive autophagy is activated when the cellular stress is not manageable and elicits the regenerative capacity. Hypoxia-reoxygenation (H/R) injury and ischemia-reperfusion (I/R) injury initiate excessive autophagy and endoplasmic reticulum (ER) stress and consequently induce a string of damage in mammalian tissues or organs. Mesenchymal stem cell (MSC)-based therapy has yielded promising results in repairing H/R- or I/R-induced injury in various tissues. However, MSC transplantation in vivo must overcome the barriers including the low survival rate of transplanted stem cells, limited targeting capacity, and low grafting potency; therefore, much effort is needed to increase the survival and activity of MSCs in vivo. Modulating autophagy regulates the stemness and the anti-oxidative stress, anti-apoptosis, and pro-survival capacity of MSCs and can be applied to MSC-based therapy for repairing H/R- or I/R-induced cellular or tissue injury.

Activation of Autophagy in Human Uterine Myometrium During Labor

OBJECTIVE:

The purpose of this study was to analyze the autophagy of the human uterine myometrium during the labor.

METHODS:

We collected uterine myometrium strips from term, singleton, nulliparous healthy women undergoing cesarean delivery before labor (nonlabor group, n = 10) or during normal labor (in-labor group, n = 10) without rupturing of membrane. The indications for cesarean delivery were breech presentation or maternal request. Transmission electron microscopy was used to observe autophagosomes. Reverse transcriptase polymerase chain reaction, immunofluorescence, and Western blot were used to quantify the messenger RNA (mRNA) and protein level of the autophagy markers LC3B, P62, and Beclin-1 in the uterine muscle strips.

RESULTS:

There were no differences between both groups in maternal age, body mass index, gestational week, neonatal weight, operative bleeding, and postpartum bleeding. Transmission electron micrographs showed that autophagosomes existed in myometrial tissue in both groups. There were more autophagosomes in the in-labor group than in the nonlabor group, and the difference had significance. The in-labor group had significantly greater LC3B mRNA expression but significantly lower P62 mRNA expression compared with the nonlabor group. Semiquantitative immunofluorescence in uterine myometrial cells in the in-labor group showed increased LC3B puncta formation and greater Beclin-1 expression but reduced P62 puncta formation compared with the nonlabor group. The ratio of LC3BII/I proteins was significantly higher, but P62 protein was significantly lower in the in-labor group compared with the nonlabor group. The Beclin-1 mRNA and protein expressions were not significantly different between the 2 groups.

CONCLUSION:

Autophagy was activated in human uterine myometrium during labor and might play an important role in maintaining uterine contraction function.

Effect of olprinone on ischemia-reperfusion induced myocardial injury in rats

AIMS

This study investigated the effect of olprinone on ischemia-reperfusion (I/R) induced cardiac injury, and the underlying mechanism.

MAIN METHODS

Male Sprague-Dawley rats were subjected to a 30-min coronary arterial occlusion followed by 24 h reperfusion. After the start of reperfusion, rats were respectively treated with olprinone in three different dosages (0.2, 0.6, 2 mg/kg, intraperitoneal injection, i.p./12 h). Twenty-four hours later, a mean arterial pressure (MAP) heart function analysis system was used to monitor hemodynamic parameters; TTC staining method was used to detect the myocardial infarct size; 24-hour mortality of rats was recorded; western blot was used to detect the protein expressions of Caspase-3, Bax, Bcl-2, Beclin-1 and LC3-II/LC3-I.

RESULTS

Cardiac function in I/R group was lower than that in sham group (dp/dt max: 1348.29 ± 266.01 vs. 3333.73 ± 1258.03, -dp/dt max: 1163.23 ± 588.18 vs. 3198.93 ± 1416.00, P <  0.05), which was significantly improved by treatment with high dosage of olprinone (dp/dt max: 1348.29±266.01 vs. 2022.43±493.39, -dp/dt max: 1163.23±588.18 vs. 1784.50±418.92, P <  0.05). The percentage of myocardial infarct size in medium and high dosages of olprinone group was lower than that in I/R group (42.67 ± 2.94, 22.33 ± 3.63 vs. 63.67 ± 5.86, P <  0.05). There was no significant difference in mortality among each group within 24 h. Compared with sham group, the expression of Caspase-3 was significantly up-regulated in I/R group (3.44±0.47-fold of sham, P <  0.05), which was inhibited by medium dosage of olprinone treatment (2.00±0.52-fold of sham, P <  0.05 vs. I/R group); also, expression of Bax was increased compared with sham group (4.06±0.25-fold of sham, P <  0.05), which was markedly inhibited by all dosages of olprinone treatment (low: 2.16±0.61-fold, medium: 2.74±0.66-fold, high 1.65±0.55-fold, P <  0.05 vs. I/R group). Expression of Bcl-2 was increased after I/R (1.17±0.06-fold, P < 0.05), which was further elevated in all dosages of olprinone treatment (low: 1.62 ± 0.13-fold, medium: 1.46 ± 0.13-fold, high: 1.82 ± 0.39-fold, P <  0.05 vs. I/R group). In addition, compared with sham group, the expression of Beclin-1 was up-regulated to 1.44±0.05-fold of sham in I/R group (P <  0.05), which was further increased in low and medium dosages of olprinone group (low: 2.46±0.44-fold, medium: 2.80±0.75-fold, P <  0.05 vs. I/R group). Moreover, expression of LC3-II was elevated in low dosage of olprinone treated group (low: 4.50±0.47-fold, P <  0.05 vs. I/R group).

CONCLUSIONS

Olprinone improves the cardiac function in response to myocardial I/R injury by regulation of anti-apoptotic, pro-apoptotic. In addition, autophagic signal pathways may also play a role in olprinone's therapeutic effect.

Sirt1 Activation by Post-ischemic Treatment With Lumbrokinase Protects Against Myocardial Ischemia-Reperfusion Injury

Lumbrokinase is used as an oral supplement to support and maintain healthy cardiovascular function, and to treat cardiovascular diseases in clinical for more than 10 years. Up until now, the mechanism of the cardioprotective effects of post-ischemic treatment with lumbrokinase has remained unclear. We therefore investigated the signaling pathways involved in the amelioration of myocardial ischemia-reperfusion (I-R) injury in rats treated with lumbrokinase 20 min after myocardial ischemia. Compared to vehicle-treated rats, post-ischemic treatment with lumbrokinase was associated with significant reductions in myocardial I-R-induced arrhythmias and myocardial damage, and an improvement in cardiac function. Moreover, lumbrokinase significantly upregulated levels of silent information regulator 1 (Sirt1). In addition, lumbrokinase significantly increased manganese-dependent superoxide dismutase expression, decreased Cleaved-Caspase-3 expression, and induced deacetylation of FoxO1. On the other hand, lumbrokinase also significantly downregulated levels of succinate dehydrogenase, cytochrome c oxidase, nuclear factor kappa B (NF-κB) and elevated levels of microtubule-associated protein light chain 3. Notably, the cardioprotective effects of lumbrokinase were abolished by administration of the specific Sirt1 inhibitor EX527. These findings demonstrate that post-ischemic treatment with lumbrokinase attenuates myocardial I-R injury through the activation of Sirt1 signaling, and thus enhances autophagic flux and reduces I-R-induced oxidative damage, inflammation and apoptosis.

Molecular mechanisms of autophagy in cardiac ischemia/reperfusion injury (Review)

Autophagy is a maintenance process for recycling long-lived proteins and cytoplasmic organelles. The level of this process is enhanced during ischemia/reperfusion (I/R) injury. Autophagy can trigger survival signaling in myocardial ischemia, whereas defective autophagy during reperfusion is detrimental. Autophagy can be regulated through multiple signaling pathways in I/R, including Beclin‑1/class III phosphatidylinositol‑3 kinase (PI‑3K), adenosine monophosphate activated protein kinase/mammalian target of rapamycin (mTOR), and PI‑3K/protein kinase B/mTOR pathways, which consequently lead to different functions. Thus, autophagy has both protective and detrimental functions, which are determined by different signaling pathways and conditions. Targeting the activation of autophagy can be a promising new therapeutic strategy for treating cardiovascular disease.

Inhibition of autophagy inhibits the conversion of cardiac fibroblasts to cardiac myofibroblasts

The incidence of heart failure with concomitant cardiac fibrosis is very high in developed countries. Fibroblast activation in heart is causal to cardiac fibrosis as they convert to hypersynthetic cardiac myofibroblasts. There is no known treatment for cardiac fibrosis. Myofibroblasts contribute to the inappropriate remodeling of the myocardial interstitium, which leads to reduced cardiac function and ultimately heart failure. Elevated levels of autophagy have been linked to stress-induced ventricular remodeling and other cardiac diseases. Previously, we had shown that TGF-β₁ treatment of human atrial fibroblasts both induced autophagy and enhanced the fibrogenic response supporting a linkage between the myofibroblast phenotype and autophagy. We now demonstrate that with in vitro culture of primary rat cardiac fibroblasts, inhibition of autophagy represses fibroblast to myofibroblast phenoconversion. Culturing unpassaged cardiac fibroblasts for 72 hours on plastic tissue culture plates is associated with elevated α-smooth muscle actin (α-SMA) expression. This activation parallels increased microtubule-associated protein 1A/1B-light chain 3 (LC-3β II) protein expression. Inhibition of autophagy with bafilomycin-A1 (Baf-A1) and chloroquine (CQ) in cardiac fibroblasts significantly reduces α-SMA and extracellular domain A fibronectin (ED-A FN) protein vs untreated controls. Myofibroblast cell migration and contractility were significantly reduced following inhibition of autophagy. These data support the possibility of a causal link between cardiac fibroblast-to-myofibroblast phenoconversion and autophagy.

Activation of calcium-sensing receptor-mediated autophagy in angiotensinII-induced cardiac fibrosis in vitro

Cardiac fibrosis is one of the primary mechanisms of ventricular remodeling, and there is no effective method for reversal. Activation of calcium sensing receptor (CaSR) has been reported to be involved in the development of myocardial fibrosis, but the molecular mechanism for CaSR activation has not yet been clarified and needs to be further explored. Here, we found that AngII induces cardiac fibroblast proliferation and phenotypic transformation in a dose-dependent manner with increased CaSR and autophagy related protein (Beclin1, LC3B) expression. CaSR activation results in intracellular calcium release, MEK1/2 pathway phosphorylation, autophagy activation and collagen formation induced by AngII in cardiac fibroblasts. However, pretreating the cells with Calhex₂₃₁, PD98059 or 3-MA partially blocked AngII-induced cardiac fibrosis. Our data indicate that the activation of CaSR-mediated MEK/ERK and autophagic pathways is involved in AngII-induced cardiac fibrosis in vitro.

Macroautophagy and Chaperone-Mediated Autophagy in Heart Failure: The Known and the Unknown

Cardiac diseases including hypertrophic and ischemic cardiomyopathies are increasingly being reported to accumulate misfolded proteins and damaged organelles. These findings have led to an increasing interest in protein degradation pathways, like autophagy, which are essential not only for normal protein turnover but also in the removal of misfolded and damaged proteins. Emerging evidence suggests a previously unprecedented role for autophagic processes in cardiac physiology and pathology. This review focuses on the major types of autophagic processes, the genes and protein complexes involved, and their regulation. It discusses the key similarities and differences between macroautophagy, chaperone-mediated autophagy, and selective mitophagy structures and functions. The genetic models available to study loss and gain of macroautophagy, mitophagy, and CMA are discussed. It defines the markers of autophagic processes, methods for measuring autophagic activities, and their interpretations. This review then summarizes the major studies of autophagy in the heart and their contribution to cardiac pathology. Some reports suggest macroautophagy imparts cardioprotection from heart failure pathology. Meanwhile, other studies find macroautophagy activation may be detrimental in cardiac pathology. An improved understanding of autophagic processes and their regulation may lead to a new genre of treatments for cardiac diseases.

Balancing Autophagy for a Healthy Heart

Autophagy is a well-known intracellular degradation process involved in clearing damaged or unnecessary components in cells. Functional autophagy is important for cardiac homeostasis. Given this, it is not surprising that dysregulation of autophagy has been implicated in the aging process and in various cardiovascular diseases. Therefore, understanding the functional role of autophagy in the heart under various conditions and whether manipulation of the pathway has therapeutic benefits have been a major focus of many investigations in recent years. Although consensus exists that autophagy is a critical cellular quality control pathway in the heart, its role in disease remains controversial. Whether altered autophagy is protective or detrimental in the heart seems to depend on the context and the disease. Here, we review the latest insights into autophagy in cardiovascular homeostasis and disease and its role in disease development.

The HMGB1‑IL‑17A axis contributes to hypoxia/reoxygenation injury via regulation of cardiomyocyte apoptosis and autophagy

Both the high‑mobility group box 1 protein (HMGB1) and interleukin (IL)‑17A serve important roles in myocardial ischemia and reperfusion injury. The purpose of the present study was to evaluate whether HMGB1 could induce IL‑17A secretion and lead to cardiomyocyte hypoxia/reoxygenation (H/R) injury. Neonatal rat cardiomyocytes were treated with HMGB1‑neutralizing antibody, IL‑17A‑neutralizing antibody, recombinant HMGB1 (rHMGB1) and recombinant IL‑17A (rIL‑17A), respectively. Cell viabilities, lactate dehydrogenase and creatine kinase levels were measured. Apoptotic cells were assessed by flow cytometry. The expression of HMGB1, IL‑17A, microtubule‑associated proteins 1A/1B light chain 3B (LC3), Beclin‑1, B‑cell lymphoma (Bcl)‑2 and Bcl‑2‑associated X protein were assessed by western blot analysis. The results demonstrated that HMGB1 significantly increased the expression of IL‑17A. HMGB1 or IL‑17A antibody significantly ameliorated H/R‑induced cell injury and improved the cell viability. In contrast, rHMGB1 or rIL‑17A aggravated cell injury and inhibited the cell viability. Furthermore, cardiomyocytes were treated with HMGB1 or IL‑17A antibody significantly increased Bcl‑2 protein expression and had fewer apoptotic cells, whereas rHMGB1 or rIL‑17A‑treated cardiomyocytes markedly decreased Bcl‑2 protein expression and had more apoptotic cells. Moreover, HMGB1 or IL‑17A antibodies significantly inhibited H/R induced autophagy dysfunction (as determined by the inhibition of Beclin‑1 expression, a lower ratio of LC3‑II to LC3‑I), whereas rHMGB1 or rIL‑17A may promote cardiomyocyte autophagy. Together, these results suggested that the HMGB1‑IL‑17A axis contributes to H/R injury via regulation of cardiomyocyte apoptosis and autophagy.

Restoring Pharmacologic Preconditioning in the Aging Heart: Role of Mitophagy/Autophagy

We previously reported that pretreatment with the potent antioxidant TEMPOL improves mitochondrial function and restores preconditioning in the aging heart. Because mitophagy is implicated in cardiac preconditioning and declines with age, this study was designed to investigate how age influences mitophagy in response to preconditioning and whether TEMPOL pretreatment improves it. Old (22-24 months) rats were pretreated with or without 4-week TEMPOL and compared with young (4-6 months) untreated rats. Cardioprotection induced by isoflurane (ISO) in vivo and in isolated cardiomyocytes in vitro was assessed following ischemia/reperfusion and simulated hypoxia/reoxygenation, respectively. Mitophagy was determined by comparing the levels/subcellular locations of key mitophagic markers using Western blotting and immunofluorescence techniques. ISO preconditioned the young but not old heart in vivo and in vitro. Aging impaired ISO-induced mitochondrial accumulation of PINK1 and Parkin, as well as mitochondrial ubiquitination, and baseline and ISO-induced autophagic flux assessed by LC3 puncta, membrane associated LC3-II and p62. Pretreatment with TEMPOL improved these processes and restored ISO preconditioning. Inhibition of autophagy abolished ISO-induced protection in cardiomyocytes from young and TEMPOL pretreated old rats. Thus, antioxidant pretreatment significantly improves mitophagic response to ISO in old myocardium, which may contribute to restoration of cardioprotection in senescent animals.

Efficacy and Mechanisms of Chinese Medicine on the Modulation of Myocardial Autophagy in Cardiovascular Disease

Autophagy refers to the process in which the cellular lysosome degrades the cell’s own damaged organelles and related macromolecule substances. It plays important roles in the homeostasis of organs, cell survival, and stable development. Previous studies indicate that the process of cardiopathology is closely associated with autophagy and some of Chinese medicines (active compounds and formulae) are found to have beneficial effects on injured cardiomyocytes via the modulation of autophagy. This review highlights the efficacy of the action of Chinese medicine on the regulation of myocardial autophagy and summarizes the related molecular and signal mechanisms. Our study discovers that some active compounds and formulae of Chinese medicines react on the specific targets of autophagy in related signal pathways to exert protective effects in the processes of ischemia and reperfusion, as well as, in other cardiopathological models. Parts of these compounds even have the characteristics of multiple targets in autophagic signal pathways and dual-directional regulated actions on autophagy, suggesting that Chinese medicines, which possess the ability to modulate autophagy, might improve effective cardio protection in the treatment of cardiovascular disease.

Autophagosome maturation mediated by Rab7 contributes to neuroprotection of hypoxic preconditioning against global cerebral ischemia in rats

Autophagy disruption leads to neuronal damage in hypoxic–ischemic brain injury. Rab7, a member of the Rab GTPase superfamily, has a unique role in the regulation of autophagy. Hypoxic preconditioning (HPC) provides neuroprotection against transient global cerebral ischemia (tGCI). However, the underlying mechanisms remain poorly understood. Thus, the current study explored the potential molecular mechanism of the neuroprotective effect of HPC by investigating how Rab7 mediates autophagosome (AP) maturation after tGCI in adult rats. We found that HPC attenuated AP accumulation in the hippocampal CA1 region after tGCI via restoration of autophagic flux. We also confirmed that this HPC-induced neuroprotection was not caused by the increase in lysosomes or the improvement of lysosomal function after tGCI. Electron microscopic analysis then revealed an increase in autolysosomes in CA1 neurons of HPC rats. Moreover, the inhibition of autophagosome-lysosome fusion by chloroquine significantly aggravated neuronal death in CA1, indicating that AP maturation contributes to HPC-induced neuroprotection against neuronal injury after tGCI. Furthermore, the activation of Rab7 was found to be involved in the neuroprotective effect of AP maturation after HPC. At last, the knockdown of ultraviolet radiation resistance-associated gene (UVRAG) in vivo disrupted the interaction between Vps16 and Rab7, attenuated the activation of Rab7, interrupted autophagic flux, and ultimately abrogated the HPC-induced neuroprotection against tGCI. Our results indicated that AP maturation was enhanced by the activation of Rab7 via UVRAG-Vps16 interaction, which further demonstrated the potential neuroprotective role of Rab7 in HPC against tGCI-induced neuronal injury in adult rats.