Role of beclin 1-dependent autophagy in cardioprotection of ischemic preconditioning

Progress in the study of autophagy-related proteins affecting resistance to chemotherapeutic drugs in leukemia

Leukemia is a life-threatening malignant tumor of the hematopoietic system. Currently, the main treatment modalities are chemotherapy and hematopoietic stem cell transplantation. However, increased drug resistance due to decreased sensitivity of leukemia cells to chemotherapeutic drugs presents a major challenge in current treatments. Autophagy-associated proteins involved in autophagy initiation have now been shown to be involved in the development of various types of leukemia cells and are associated with drug resistance. Therefore, this review will explore the roles of autophagy-related proteins involved in four key autophagic processes: induction of autophagy and phagophore formation, phagophore extension, and autophagosome formation, on the development of various types of leukemias as well as drug resistance. Autophagy may become a promising therapeutic target for treating leukemia.

QishenYiqi dripping pill protects against myocardial ischemia/reperfusion injury via suppressing excessive autophagy and NLRP3 inflammasome based on network pharmacology and experimental pharmacology

Background: Myocardial ischemia/reperfusion (I/R) injury is associated with multiple serious clinical manifestations. Autophagy is upregulated in a short period of ischemia and further enhanced during reperfusion phase, which was considered as a “double-edged sword” in the pathological process of myocardial I/R injury. In addition, NLRP3 inflammasome triggers myocardial inflammatory response, which leads to cardiomyocyte death via pyroptosis and promotes subsequent myocardial remodelling. Qishen Yiqi Dripping Pill (QSYQ) has been recognized as a potential protective agent of cardiovascular diseases.

Objective: We predicted the bioactive compounds, targets and pathways of OSYQ intervening on myocardial I/R injury by network pharmacology. Furthermore, we investigated the effect of QSYQ on myocardial I/R injury and explored its underlying mechanism via autophagy and NLRP3 Inflammasome.

Methods: Bioactive compounds, targets of QSYQ and relevant targets of myocardial I/R injury were collected from public databases. The protein-protein interaction network, Gene ontology and KEGG pathway enrichment analysis were carried out to screen the key compounds, target genes, functional annotation and pivotal pathways. Molecular docking was used to validate the binding association between target genes and key bioactive ingredients. Furthermore, sixty SD rats were randomized into four groups: 1) sham, 2) model, 3) captopril and 4) QSYQ pretreatment (14 days before and after surgery). Each arm was subjected to ischemia/reperfusion surgery except sham arm (30 min coronary ligation, then reperfusion). Left ventricular (LV) function were evaluated and the hearts were used to evaluate size of myocardial infarction, cardiomyocyte fibrosis, and myocardial autophagosomes.

Results: The network pharmacology revealed the mechanism of QSYQ intervening on myocardial I/R injury might be related to NOD-like receptor signaling pathway, PI3K-Akt signaling pathway, autophagy-animal, etc., Molecular-docking suggested the core target proteins had good binding association with bioactive compounds of QSYQ. The experiment confirmed that QSYQ attenuated myocardial infarct size, decreased inflammatory infiltration and collagen fiber deposition and alleviated the autophagosome and myocardium ultrastructure injury, leading to LV systolic function improvement. The possible mechanism of cardioprotection was due to regulating autophagy-related proteins, activating PI3K/Akt-mTOR signaling pathway, and inhibiting activation and assembly of NLRP3 inflammasome.

Conclusion: QSYQ ameliorated myocardial I/R injury via suppressing excessive autophagy and NLRP3 Inflammasome.

Compositions and Functions of Mitochondria-Associated Endoplasmic Reticulum Membranes and Their Contribution to Cardioprotection by Exercise Preconditioning

Mitochondria-associated endoplasmic reticulum membranes (MAMs) are important components of intracellular signaling and contribute to the regulation of intracellular Ca²⁺/lipid homeostasis, mitochondrial dynamics, autophagy/mitophagy, apoptosis, and inflammation. Multiple studies have shown that proteins located on MAMs mediate cardioprotection. Exercise preconditioning (EP) has been shown to protect the myocardium from adverse stimuli, but these mechanisms are still being explored. Recently, a growing body of evidence points to MAMs, suggesting that exercise or EP may be involved in cardioprotection by modulating proteins on MAMs and subsequently affecting MAMs. In this review, we summarize the latest findings on MAMs, analyzing the structure and function of MAMs and the role of MAM-related proteins in cardioprotection. We focused on the possible mechanisms by which exercise or EP can modulate the involvement of MAMs in cardioprotection. We found that EP may affect MAMs by regulating changes in MFN2, MFN1, AMPK, FUNDC1, BECN1, VDAC1, GRP75, IP3R, CYPD, GSK3β, AKT, NLRP3, GRP78, and LC3, thus playing a cardioprotective role. We also provided direction for future studies that may be of interest so that more in-depth studies can be conducted to elucidate the relationship between EP and cardioprotection.

L-Borneol 7-O-[β-D-Apiofuranosyl-(1 → 6)]-β-D-Glucopyranoside Alleviates Myocardial Ischemia-Reperfusion Injury in Rats and Hypoxic/Reoxygenated Injured Myocardial Cells via Regulating the PI3K/AKT/mTOR Signaling Pathway

Ischemia/reperfusion (I/R) is a primary cause of morbidity and mortality in acute myocardial infarction (AMI). L-Borneol 7-O-[β-D-apiofuranosyl-(1→6)]-β-D-glucopyranoside (LBAG), extracted from the Radix Ophiopogonis, is the main bioactive component that may be exerting cardiovascular protection in AMI. The purpose was to examine the effects of LBAG on myocardial I/R injury (MIRI) in rats and H9c2 cells treated with hypoxia/reoxygenation (H/R). MIRI was induced through the combination of ischemia with reperfusion for 30 min and 24 h, respectively. LBAG was administered 7 days before vascular ligation. Myocardial function was detected by an electrocardiograph, histological, TTC, and TUNEL staining analyses. The influences of LBAG on the content concentration of cardiac enzymes in the serum were measured by ELISA. Moreover, H9c2 cells were exposed to LBAG or combined with AKT inhibitor (perifosine) and then exposed to H/R for simulating the cardiac injury process. Afterward, cell viability, LDH, CD-KM release, apoptosis, and autophagy were evaluated by CCK-8 and ELISA assays, flow cytometry, TUNEL, and immunofluorescence staining, respectively. Additionally, the proteins of apoptosis, autophagy, and PI3K/mTOR pathway were determined by western blotting. In I/R rats, LBAG pretreatment significantly ameliorated cardiac function, as illustrated by reducing the infarct size, myocardial autophagy, and apoptosis levels. In H/R-induced H9c2 cells, LBAG pretreatment significantly decreased cell apoptosis, LC3 II/I, and Beclin 1 levels, elevated the Bcl-2 levels, attenuated LDH, and CD-KM production. Moreover, LBAG pretreatment markedly increased the PI3K/mTOR pathway activation, and the protective influences of LBAG were partly abolished with the AKT inhibitor perifosine treatment. These findings demonstrated the protective functions of LBAG on I/R by regulating apoptosis and autophagy in vitro and in vivo by activating the PI3K/mTOR pathway.

Dehydrocostuslactone attenuated oxygen and glucose deprivation/reperfusion-induced PC12 cell injury through inhibition of apoptosis and autophagy by activating the PI3K/AKT/mTOR pathway

The purpose of this study is to investigate the protective effect of dehydrocostuslactone (DHL) on PC12 cells injury induced by oxygen and glucose deprivation/reperfusion (OGD/R) and its possible mechanism on the PI3K/AKT/mTOR pathway. The maestro 11.1 software was used to predict the binding sites of DHL with LC3, Beclin-1, PI3K, AKT, mTOR, Bax, Bcl-2, Caspase-3, Caspase-9, and Caspase-7. We used a cellular model of 2 h of OGD and 24 h of reperfusion to mimic cerebral ischemia-reperfusion injury. Cells were treated with DHL during the reperfusion phase. The docking results showed that DHL had binding sites with LC3, Beclin-1, PI3K, AKT, mTOR, Bax, Bcl-2, Caspase-3, Caspase-9, and Caspase-7. The expression levels of autophagy-related proteins, LC3 and Beclin-1 increased while P-PI3K, P-AKT, and P-mTOR decreased. Apoptosis-related proteins, namely, Bax, Cyto-c, Caspase-3, Caspase-7, Caspase-9 increased, but the anti-apoptosis Bcl-2 protein decreased. However, DHL effectively inhibited these undesirable changes induced by OGD/R in PC12 cells. Our results suggested that DHL attenuated OGD/R-induced neuronal injury by inhibiting apoptosis and autophagy by activating PI3K/AKT/mTOR signaling. This inhibition can improve cell survival and offer evidence for the beneficial effects of DHL on the nervous system.

Exercise Preconditioning Increases Beclin1 and Induces Autophagy to Promote Early Myocardial Protection via Intermittent Myocardial Ischemia-Hypoxia

Exercise preconditioning (EP) provides protective effects for acute cardiovascular stress; however, its mechanisms need to be further investigated. Autophagy is a degradation pathway essential for myocardium health. Therefore, we investigated whether intermittent myocardial ischemia-hypoxia affected Beclin1 and whether the changes in autophagy levels contribute to EP-induced early myocardial protective effects. Rats were trained on a treadmill using an EP model (four cycles of 10 minutes of running/10 minutes of rest). Exhaustive exercise (EE) was performed to induce myocardial injury. Cardiac troponin I (cTnI) and ischemia-hypoxia staining were used to evaluate myocardial injury and protection. Double-labeled immunofluorescence staining and western blot analysis were employed to examine related markers. EP attenuated the myocardial ischemic-hypoxic injury induced by EE. Compared with the control (C) group, the dissociations of Beclin1/Bcl-2 ratio and Beclin1 expression were both higher in all other groups. Compared with the C group, PI3KC3 and the LC3-II/LC3-I ratio were higher in all other groups, whereas LC3-II was higher in the EE and EEP + EE groups. p62 was higher in the EE group than in the C group but lower in the EEP + EE group than in the EE group. We concluded that EP increases Beclin1 via intermittent myocardial ischemia-hypoxia and induces autophagy, which exerts early myocardial protective effects and reduces the myocardial ischemic-hypoxic injury induced by exhaustive exercise.

Paeonol Protects Against Myocardial Ischemia/Reperfusion-Induced Injury by Mediating Apoptosis and Autophagy Crosstalk

Many studies have shown that crosstalk exists between apoptosis and autophagy, despite differences in mechanisms between these processes. Paeonol, a major phenolic compound isolated from Moutan Cortex Radicis, the root bark of Paeonia × suffruticosa Andrews (Paeoniaceae), is widely used in traditional Chinese medicine as an antipyretic, analgesic and anti-inflammatory agent. In this study, we investigated the detailed molecular mechanisms of the crosstalk between apoptosis and autophagy underlying the cardioprotective effects of paeonol in rats subjected to myocardial ischemia/reperfusion (I/R) injury. Myocardial I/R injury was induced by occlusion of the left anterior descending coronary artery (LAD) for 1 h followed by 3 h of reperfusion. Paeonol was intravenously administered 15 min before LAD ligation. We found that paeonol significantly improved cardiac function after myocardial I/R injury and significantly decreased myocardial I/R-induced arrhythmia and mortality. Paeonol also significantly decreased myocardial infarction and plasma LDH activity and Troponin-I levels in carotid blood after I/R. Compared with vehicle treatment, paeonol significantly upregulated Bcl-2 protein expression and significantly downregulated the cleaved forms of caspase-8, caspase-9, caspase-3 and PARP protein expression in the I/R injured myocardium. Myocardial I/R-induced autophagy, including the increase of Beclin-1, p62, LC3-I, and LC3-II protein expression in the myocardium was significantly reversed by paeonol treatment. Paeonol also significantly increased the Bcl-2/Bax and Bcl-2/Beclin-1 ratios in the myocardium after I/R injury. The cardioprotective role of paeonol during I/R injury may be due to its mediation of crosstalk between apoptotic and autophagic signaling pathways, which inhibits apoptosis and autophagic cell death.

MicroRNA-153-3p increases autophagy in sevoflurane-preconditioned mice to protect against ischaemic/reperfusion injury after knee arthroplasty

The use of tourniquet during total knee arthroplasty (TKA) can result in ischaemia/reperfusion injury (IRI). Of interest, microRNAs (miRs) are reported to be involved in various kinds of IRI due to their ability in modulating autophagy. Therefore, the study aimed to investigate the effect of miR‐153‐3p on autophagy in IRI in vitro and in vivo under sevoflurane preconditioning. In the in vitro model, chondrocytes from naive mice were treated with 0% FBS alone or in combination with sevoflurane. Additionally, in vivo assays were conducted in mouse models with tourniquet‐induced IRI after TKA under or without sevoflurane preconditioning. The pathological observation in vivo validated that sevoflurane preconditioning protected the knee joint against IRI. Moreover, miR‐153‐3p expression was diminished in chondrocytes of the in vitro model and in cartilage tissue of the in vivo model, but its expression was appreciably up‐regulated in the presence of sevoflurane preconditioning. Mechanistic study showed that miR‐153‐3p disrupted the interaction between Bcl‐2 and Beclin1 by targeting Bcl‐2, thereby facilitating autophagy in chondrocytes under sevoflurane preconditioning. Furthermore, the experiments in human chondrocytes also verified the protective effects of miR‐153‐3p against IRI were realized through inhibiting Bcl‐2. Collectively, miR‐153‐3p overexpression blocks the interaction between Bcl‐2 and Beclin1 via down‐regulation of Bcl‐2 to promote autophagy of chondrocytes, thus protecting knee joint against IRI after TKA under sevoflurane preconditioning.

Altered expression levels of autophagy-associated proteins during exercise preconditioning indicate the involvement of autophagy in cardioprotection against exercise-induced myocardial injury

Exercise has been reported to induce autophagy. We hypothesized that exercise preconditioning (EP)-related autophagy in cardiomyocytes could be attributed to intermittent ischemia-hypoxia, allowing the heart to be protected for subsequent high-intensity exercise (HE). We applied approaches, chromotrope-2R brilliant green (C-2R BG) staining and plasma cTnI levels measuring, to characterize two periods of cardioprotection after EP: early EP (EEP) and late EP (LEP). Further addressing the relationship between ischemia-hypoxia and autophagy, key proteins, Beclin1, LC3, Cathepsin D, and p62, were determined by immunohistochemical staining, western blotting, and by their adjacent slices with C-2R BG. Results indicated that exercise-induced ischemia-hypoxia is a key factor in Beclin1-dependent autophagy. High-intensity exercise was associated with the impairment of autophagy due to high levels of LC3II and unchanged levels of p62, intermittent ischemia-hypoxia by EP itself plays a key role in autophagy, which resulted in more favorable cellular effects during EEP-cardioprotection compared to LEP.

mTOR and Beclin1: Two key autophagy-related molecules and their roles in myocardial ischemia/reperfusion injury

Autophagy is the general term of lysosomal degradation of substances in cells, which is considered the key to maintaining the normal structure and function of the heart. It also has a correlation with several heart diseases, in particular, myocardial ischemia/reperfusion (I/R) injury. At the stage of myocardial ischemia, autophagy degrades nonfunctional cytoplasmic proteins providing the critical nutrients for the critical life activities, thereby suppressing cell apoptosis and necrosis. However, autophagy is likely to affect the heart negatively in the reperfusion stage. Mammalian target of rapamycin (mTOR) and Beclin1 are two vital autophagy-related molecules in myocardial I/R injury playing significant roles in different stages. In the ischemia stage, mTOR plays its roles through AMPK/mTOR and phosphoinositide 3-kinase/Akt/mTOR pathway, whereas Beclin1 plays its roles through its upregulation in the reperfusion stage. A possible interaction between mTOR and Beclin1 has been reported recently, and further studies need to be done to find the underlying interaction between the two molecules in myocardial I/R injury.

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.

3,3'‑Diindolylmethane attenuates cardiomyocyte hypoxia by modulating autophagy in H9c2 cells

Autophagy is activated in the ischemic heart and is a process that is essential for survival, differentiation, development and homeostasis. 3,3'‑Diindolylmethane (DIM) is a natural product of the acid‑catalyzed condensation of indole‑3‑carbinol in cruciferous vegetables. Numerous studies have suggested that DIM has various pharmacological effects, including antioxidant, antitumor, anti‑angiogenic and anti‑apoptotic properties. However, the function of DIM on hypoxia‑induced cardiac injury remains to be elucidated. In the present study, H9c2 cells were pretreated with DIM (1, 5 and 10 µM) for 12 h and exposed to hypoxia for 12 h. It was demonstrated that DIM markedly attenuated the increased transcription of interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α induced by hypoxia. In addition, the transcription of autophagy associated genes increased in the DIM pretreated group, compared with the hypoxia group. DIM additionally attenuated the increased apoptosis, as determined by terminal deoxynucleotidyl transferase dUTP nick end labeling staining, and regulated the relative protein expression level of B cell lymphoma (Bcl) 2 associated X protein, Bcl‑xL and cleaved caspase 3. Furthermore, the phosphorylation of the 5' AMP‑activated protein kinase a (AMPKa) was activated and the phosphorylation of c‑Jun N‑terminal kinase (JNK) was inhibited. The effect of DIM on hypoxia‑induced apoptosis was abolished following pretreatment with JNK activator (anisomycin, 40 ng/ml). The effect of DIM on autophagy was reversed following pretreatment with AMPKa inhibitor (CpC, 20 µM) following stimulation with hypoxia. The results demonstrated that DIM prevented hypoxia‑induced inflammation and apoptosis and activated cardiomyocyte autophagy, which may be mediated by activation of AMPKa and inhibition of JNK pathways.

Phellinus linteus Mycelium Alleviates Myocardial Ischemia-Reperfusion Injury through Autophagic Regulation

The incidence of myocardial ischemia-reperfusion (IR) injury is rapidly increasing around the world and this disease is a major contributor to global morbidity and mortality. It is known that regulation of programmed cell death including apoptosis and autophagy reduces the impact of myocardial IR injury. In this study, the cardioprotective effects and underlying mechanisms of Phellinus linteus (Berk. and Curt.) Teng, Hymenochaetaceae (PL), a type of medicinal mushroom, were examined in rats subjected to myocardial IR injury. The left main coronary artery of rats was ligated for 1 h and reperfused for 3 h. The arrhythmia levels were monitored during the entire process and the infarct size was evaluated after myocardial IR injury. Furthermore, the expression levels of proteins in apoptotic and autophagic pathways were observed. Pretreatment with PL mycelium (PLM) significantly reduced ventricular arrhythmia and mortality due to myocardial IR injury. PLM also significantly decreased myocardial infarct size and plasma lactate dehydrogenase level after myocardial IR injury. Moreover, PLM administration resulted in decreased caspase 3 and caspase 9 activation and increased Bcl-2/Bax ratio. Phosphorylation level of AMPK was elevated while mTOR level was reduced. Becline-1 and p62 levels decreased. These findings suggest that PLM is effective in protecting the myocardium against IR injury. The mechanism involves mediation through suppressed pro-apoptotic signaling and regulation of autophagic signaling, including stimulation of AMPK-dependent pathway and inhibition of beclin-1-dependent pathway, resulting in enhancement of protective autophagy and inhibition of excessive autophagy.

Conformational flexibility of BECN1: Essential to its key role in autophagy and beyond

BECN1 (Beclin 1), a highly conserved eukaryotic protein, is a key regulator of autophagy, a cellular homeostasis pathway, and also participates in vacuolar protein sorting, endocytic trafficking, and apoptosis. BECN1 is important for embryonic development, the innate immune response, tumor suppression, and protection against neurodegenerative disorders, diabetes, and heart disease. BECN1 mediates autophagy as a core component of the class III phosphatidylinositol 3-kinase complexes. However, the exact mechanism by which it regulates the activity of these complexes, or mediates its other diverse functions is unclear. BECN1 interacts with several diverse protein partners, perhaps serving as a scaffold or interaction hub for autophagy. Based on extensive structural, biophysical and bioinformatics analyses, BECN1 consists of an intrinsically disordered region (IDR), which includes a BH3 homology domain (BH3D); a flexible helical domain (FHD); a coiled-coil domain (CCD); and a β-α-repeated autophagy-specific domain (BARAD). Each of these BECN1 domains mediates multiple diverse interactions that involve concomitant conformational changes. Thus, BECN1 conformational flexibility likely plays a key role in facilitating diverse protein interactions. Further, BECN1 conformation and interactions are also modulated by numerous post-translational modifications. A better structure-based understanding of the interplay between different BECN1 conformational and binding states, and the impact of post-translational modifications will be essential to elucidating the mechanism of its multiple biological roles.

Acute consumption of a high-fat diet prior to ischemia-reperfusion results in cardioprotection through NF-κB-dependent regulation of autophagic pathways

Previous studies have demonstrated improvement of cardiac function occurs with acute consumption of a high-fat diet (HFD) after myocardial infarction (MI). However, no data exist addressing the effects of acute HFD upon the extent of injury after MI. This study investigates the hypothesis that short-term HFD, prior to infarction, protects the heart against ischemia-reperfusion (I/R) injury through NF-κB-dependent regulation of cell death pathways in the heart. Data show that an acute HFD initiates cardioprotection against MI (>50% reduction in infarct size normalized to risk region) after 24 h to 2 wk of HFD, but protection is completely absent after 6 wk of HFD, when mice are reported to develop pathophysiology related to the diet. Furthermore, cardioprotection after 24 h of HFD persists after an additional 24 h of normal chow feeding and was found to be dependent upon NF-κB activation in cardiomyocytes. This study also indicates that short-term HFD activates autophagic processes (beclin-1, LC-3) preischemia, as seen in other protective stimuli. Increases in beclin-1 and LC-3 were found to be NF-κB-dependent, and administration of chloroquine, an inhibitor of autophagy, abrogated cardioprotection. Our results support that acute high-fat feeding mediates cardioprotection against I/R injury associated with a NF-κB-dependent increase in autophagy and reduced apoptosis, as has been found for ischemic preconditioning.