Response to myocardial ischemia/reperfusion injury involves Bnip3 and autophagy

Ischemia-Reperfusion Injury in Peripheral Artery Disease and Traditional Chinese Medicine Treatment

Peripheral artery disease (PAD) is a serious public health issue, characterized by circulation disorder of the lower extreme that reduces the physical activity of the lower extremity muscle. The artery narrowed by atherosclerotic lesions initiates limb ischemia. In the progression of treatment, reperfusion injury is still inevitable. Ischemia-reperfusion injury induced by PAD is responsible for hypoxia and nutrient deficiency. PAD triggers hindlimb ischemia and reperfusion (I/R) cycles through various mechanisms, mainly including mitochondrial dysfunction and inflammation. Alternatively, mitochondrial dysfunction plays a central role. The I/R injury may cause cells' injury and even death. However, the mechanism of I/R injury and the way of cell damage or death are still unclear. We review the pathophysiology of I/R injury, which is majorly about mitochondrial dysfunction. Then, we focus on the cell damage and death during I/R injury. Further comprehension of the progress of I/R will help identify biomarkers for diagnosis and therapeutic targets to PAD. In addition, traditional Chinese medicine has played an important role in the treatment of I/R injury, and we will make a brief introduction.

Mitophagy in aging and longevity

The clearance of damaged or unwanted mitochondria by autophagy (also known as mitophagy) is a mitochondrial quality control mechanism postulated to play an essential role in cellular homeostasis, metabolism, and development and confers protection against a wide range of diseases. Proper removal of damaged or unwanted mitochondria is essential for organismal health. Defects in mitophagy are associated with Parkinson's, Alzheimer's disease, cancer, and other degenerative disorders. Mitochondria regulate organismal fitness and longevity via multiple pathways, including cellular senescence, stem cell function, inflammation, mitochondrial unfolded protein response (mtUPR), and bioenergetics. Thus, mitophagy is postulated to be pivotal for maintaining organismal healthspan and lifespan and the protection against aged-related degeneration. In this review, we will summarize recent understanding of the mechanism of mitophagy and aspects of mitochondrial functions. We will focus on mitochondria-related cellular processes that are linked to aging and examine current genetic evidence that supports the hypothesis that mitophagy is a pro-longevity mechanism.

Long Noncoding RNAs Involved in Cardiomyocyte Apoptosis Triggered by Different Stressors

Cardiomyocytes are essential to maintain the normal cardiac function. Ischemia, hypoxia, and drug stimulation can induce pathological apoptosis of cardiomyocytes which eventually leads to heart failure, arrhythmia, and other cardiovascular diseases. Understanding the molecular mechanisms that regulate cardiomyocyte apoptosis is of great significance for the prevention and treatment of cardiovascular diseases. In recent years, more and more evidences reveal that long noncoding RNAs (lncRNAs) play important regulatory roles in myocardial cell apoptosis. They can modulate the expression of apoptosis-related genes at post-transcriptional level by altering the translation efficacy of target mRNAs or functioning as a precursor for miRNAs or competing for miRNA-mediated inhibition. Moreover, reversing the abnormal expression of lncRNAs can attenuate and even reverse the pathological apoptosis of cardiomyocytes. Therefore, apoptosis-related lncRNAs may become a potential new field for studying cardiomyocyte apoptosis and provide new ideas for the treatment of cardiovascular diseases.

Molecular Signaling to Preserve Mitochondrial Integrity against Ischemic Stress in the Heart: Rescue or Remove Mitochondria in Danger

Cardiovascular diseases are one of the leading causes of death and global health problems worldwide, and ischemic heart disease is the most common cause of heart failure (HF). The heart is a high-energy demanding organ, and myocardial energy reserves are limited. Mitochondria are the powerhouses of the cell, but under stress conditions, they become damaged, release necrotic and apoptotic factors, and contribute to cell death. Loss of cardiomyocytes plays a significant role in ischemic heart disease. In response to stress, protective signaling pathways are activated to limit mitochondrial deterioration and protect the heart. To prevent mitochondrial death pathways, damaged mitochondria are removed by mitochondrial autophagy (mitophagy). Mitochondrial quality control mediated by mitophagy is functionally linked to mitochondrial dynamics. This review provides a current understanding of the signaling mechanisms by which the integrity of mitochondria is preserved in the heart against ischemic stress.

Ginsenoside Rb1 Inhibits Cardiomyocyte Autophagy via PI3K/Akt/mTOR Signaling Pathway and Reduces Myocardial Ischemia/Reperfusion Injury

Myocardial ischemia/reperfusion injury (MIRI) is the major cause of myocardial cell damage in acute myocardial infarction, and its treatment remains a clinical challenge. Ginsenoside Rb1 showed protective effects on the cardiovascular system; however, the underlying mechanism remains largely unclear. Effects of Ginsenoside Rb1 on rat MIRI-induced myocardial infarct size were evaluated through TTC staining. TUNEL assay and flow cytometry analysis were employed to estimate cell apoptosis. Apoptosis, autophagy and PI3K/Akt/mTOR pathway-related proteins were estimated via western blot. Expression of Beclin1 in myocardial tissues were examined by immunohistochemical analysis. Expression levels of IL-1[Formula: see text], TNF-[Formula: see text] and IL-6 were tested by enzyme-linked immunosorbent assay (ELISA). Here, we found that Ginsenoside Rb1 treatment not only alleviated MIRI in rats but also protected H9C2 cells against hypoxia/reoxygenation induced damage. Ginsenoside Rb1 abolished the MIRI-induced activation of autophagy. Meanwhile, we found that treatment of 3-MA (autophagy inhibitor) could enhance the protective effects of Ginsenoside Rb1 on H9C2 cells during H/R. Moreover, Ginsenoside Rb1 treatment resulted in the activation of the PI3K/Akt/mTOR pathway, and treatment of LY294002 (PI3K/Akt pathway repressor) abolished the protective effects of Ginsenoside Rb1 on myocardial in vitro and in vivo. Our results suggest that Ginsenoside Rb1 functions as a protector against MIRI by repressing cardiomyocyte autophagy through the PI3K/Akt/mTOR signaling pathway.

Shikonin regulates autophagy via the AMPK/mTOR pathway and reduces apoptosis of human umbilical cord mesenchymal stem cells to improve survival in tissues surrounding brain contusion

Shikonin has been reported to regulate autophagy via the AMP-activated protein kinase (AMPK)/mTOR signalling pathway and decrease apoptosis in transplanted human umbilical cord mesenchymal stem cells (HUMSCs). In the present study, HUMSCs were exposed to oxygen glucose deprivation (OGD) in vitro for 12 h, and TUNEL fluorescence staining was used to detect apoptosis. Differences in autophagy and AMPK/mTOR pathway-related protein expression following treatment with shikonin were quantitatively analyzed by western blotting. Green fluorescent protein-labelled stem cells were implanted into traumatic brain injury-model mice and the survival of HUMSCs was observed after 7 days. Shikonin increased the number of cells in brain tissue surrounding the contusion 7 days after transplantation. Furthermore, shikonin treatment decreased apoptosis, increased the expression of autophagy-related proteins, increased phosphorylated AMPK expression and downregulated phosphorylated mTOR expression. In addition, the autophagy inhibitor 3-methyladenine attenuated these effects and aggravated apoptosis. Subsequently, shikonin upregulated autophagy and protected HUMSCs in the area surrounding contused brain tissue. Shikonin may regulate autophagy via the AMPK/mTOR signalling pathway and protect transplanted HUMSCs from apoptosis induced by hypoxia/ischemia.

Propofol postconditioning ameliorates hypoxia/reoxygenation induced H9c2 cell apoptosis and autophagy via upregulating forkhead transcription factors under hyperglycemia

BACKGROUND

Administration of propofol, an intravenous anesthetic with antioxidant property, immediately at the onset of post-ischemic reperfusion (propofol postconditioning, P-PostC) has been shown to confer cardioprotection against ischemia-reperfusion injury, while the underlying mechanism remains incompletely understood. The FoxO transcription factors are reported to play critical roles in activating cardiomyocyte survival signaling throughout the process of cellular injuries induced by oxidative stress and are also involved in hypoxic postconditioning mediated neuroprotection, however, the role of FoxO in postconditioning mediated protection in the heart and in particular in high glucose condition is unknown.

METHODS

Rat heart-derived H9c2 cells were exposed to high glucose (HG) for 48 h (h), then subjected to hypoxia/reoxygenation (H/R, composed of 8 h of hypoxia followed by 12 h of reoxygenation) in the absence or presence of postconditioning with various concentrations of propofol (P-PostC) at the onset of reoxygenation. After having identified the optical concentration of propofol, H9c2 cells were subjected to H/R and P-PostC in the absence or presence of FoxO1 or FoxO3a gene silencing to explore their roles in P-PostC mediated protection against apoptotic and autophagic cell deaths under hyperglycemia.

RESULTS

The results showed that HG with or without H/R decreased cell viability, increased lactate dehydrogenase (LDH) leakage and the production of reactive oxygen species (ROS) in H9c2 cells, all of which were significantly reversed by propofol (P-PostC), especially at the concentration of 25 µmol/L (P25) (all P < 0.05, NC vs. HG; HG vs. HG + HR; HG + HR + P12.5 or HG + HR + P25 or HG + HR + P50 vs. HG + HR). Moreover, we found that propofol (P25) decreased H9c2 cells apoptosis and autophagy that were concomitant with increased FoxO1 and FoxO3a expression (all P < 0.05, HG + HR + P25 vs. HG + HR). The protective effects of propofol (P25) against H/R injury were reversed by silencing FoxO1 or FoxO3a (all P < 0.05, HG + HR + P25 vs. HG + HR + P25 + siRNA-1 or HG + HR + P25 + siRNA-5).

CONCLUSION

It is concluded that propofol postconditioning attenuated H9c2 cardiac cells apoptosis and autophagy induced by H/R injury through upregulating FoxO1 and FoxO3a under hyperglycemia.

miR-1 sustains muscle physiology by controlling V-ATPase complex assembly

Muscle function requires unique structural and metabolic adaptations that can render muscle cells selectively vulnerable, with mutations in some ubiquitously expressed genes causing myopathies but sparing other tissues. We uncovered a muscle cell vulnerability by studying miR-1, a deeply conserved, muscle-specific microRNA whose ablation causes various muscle defects. Using Caenorhabditis elegans, we found that miR-1 represses multiple subunits of the ubiquitous vacuolar adenosine triphosphatase (V-ATPase) complex, which is essential for internal compartment acidification and metabolic signaling. V-ATPase subunits are predicted miR-1 targets in animals ranging from C. elegans to humans, and we experimentally validated this in Drosophila. Unexpectedly, up-regulation of V-ATPase subunits upon miR-1 deletion causes reduced V-ATPase function due to defects in complex assembly. These results reveal V-ATPase assembly as a conserved muscle cell vulnerability and support a previously unknown role for microRNAs in the regulation of protein complexes.

Hypoxia-stimulated ATM activation regulates autophagy-associated exosome release from cancer-associated fibroblasts to promote cancer cell invasion

Cancer-associated fibroblasts (CAFs) as a predominant cell component in the tumour microenvironment (TME) play an essential role in tumour progression. Our earlier studies revealed oxidized ATM activation in breast CAFs, which is independent of DNA double-strand breaks (DSBs). Oxidized ATM has been found to serve as a redox sensor to maintain cellular redox homeostasis. However, whether and how oxidized ATM in breast CAFs regulates breast cancer progression remains poorly understood. In this study, we found that oxidized ATM phosphorylates BNIP3 to induce autophagosome accumulation and exosome release from hypoxic breast CAFs. Inhibition of oxidized ATM kinase by KU60019 (a small-molecule inhibitor of activated ATM) or shRNA-mediated knockdown of endogenous ATM or BNIP3 blocks autophagy and exosome release from hypoxic CAFs. We also show that oxidized ATM phosphorylates ATP6V1G1, a core proton pump in maintaining lysosomal acidification, leading to lysosomal dysfunction and autophagosome fusion with multi-vesicular bodies (MVB) but not lysosomes to facilitate exosome release. Furthermore, autophagy-associated GPR64 is enriched in hypoxic CAFs-derived exosomes, which stimulates the non-canonical NF-κB signalling to upregulate MMP9 and IL-8 in recipient breast cancer cells, enabling cancer cells to acquire enhanced invasive abilities. Collectively, these results provide novel insights into the role of stromal CAFs in promoting tumour progression and reveal a new function of oxidized ATM in regulating autophagy and exosome release.

Cardioprotective effect of MLN4924 on ameliorating autophagic flux impairment in myocardial ischemia-reperfusion injury by Sirt1

Neddylation is essential for cardiomyocyte survival in the presence of oxidative stress, and it participates in autophagy regulation. However, whether MLN4924-an inhibitor of neddylation-exerts cardioprotective effects against myocardial ischemia/reperfusion (MI/R) remains unknown. In the present study, MLN4924 exerted strong cardioprotective effects, demonstrated by significantly elevated cell viability, a decreased LDH leakage rate, and improved cell morphology following H₂O₂-induced injury in vitro. MLN4924 also markedly decreased the serum myocardial zymogram level, ameliorated cardiac histopathological alterations, and alleviated left ventricular contractile dysfunction, thus limiting the cardiac infarct size in vivo compared with those in MI/R mice. Amazingly, such action of MLN4924 was abrogated by a combined treatment with the autophagic flux inhibitor, chloroquine. The mRFP-GFP-LC3 assay illustrated that MLN4924 restored the defective autophagic flux via enhancing the autolysosome formation. Notably, the expression levels of Rab7 and Atg5 were markedly up-regulated in MLN4924 treated cells and mice subjected to H₂O₂ or MI/R, respectively, while knockdown of Sirt1 in cells and heart tissue largely blocked such effect and induced autophagosome accumulation by inhibiting its fusion with lysosomes. Transmission electron microscopic analysis, histopathological assay and TUNEL detection of the heart tissues showed that the absence of Sirt1 blocked the cardioprotective effect of MLN4924 by further exacerbating the impaired autophagic flux during MI/R injury in vivo. Taken together, MLN4924 exhibited the strong cardioprotective action via restoring the impaired autophagic flux in H₂O₂-induced injury in vitro and in MI/R mice. Our work implicated that Sirt1 played a critical role in autophagosome clearance, likely through up-regulating Rab7 in MI/R.

The Loss of Mitochondrial Quality Control in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the predominant complication of diabetes mellitus (DM) and the leading cause of chronic kidney disease and end-stage renal disease worldwide, which are major risk factors for death. The pathogenesis of DKD is very complicated, including inflammation, autophagy impairment, oxidative stress, and so on. Recently, accumulating evidence suggests that the loss of mitochondrial quality control exerts critical roles in the progression of DKD. Mitochondria are essential for eukaryotic cell viability but are extremely vulnerable to damage. The mechanisms of mitochondrial quality control act at the molecular level and the organelle level, including mitochondrial dynamics (fusion and fission), mitophagy, mitochondrial biogenesis, and mitochondrial protein quality control. In this review, we summarize current knowledge of the role of disturbances in mitochondrial quality control in the pathogenesis of DKD and provide potential insights to explore how to delay the onset and development of DKD.

Upregulation of hemeoxygenase enzymes HO-1 and HO-2 following ischemia-reperfusion injury in connection with experimental cardiac arrest and cardiopulmonary resuscitation: Neuroprotective effects of methylene blue

Oxidative stress plays an important role in neuronal injuries after cardiac arrest. Increased production of carbon monoxide (CO) by the enzyme hemeoxygenase (HO) in the brain is induced by the oxidative stress. HO is present in the CNS in two isoforms, namely the inducible HO-1 and the constitutive HO-2. Elevated levels of serum HO-1 occurs in cardiac arrest patients and upregulation of HO-1 in cardiac arrest is seen in the neurons. However, the role of HO-2 in cardiac arrest is not well known. In this review involvement of HO-1 and HO-2 enzymes in the porcine brain following cardiac arrest and resuscitation is discussed based on our own observations. In addition, neuroprotective role of methylene blue- an antioxidant dye on alterations in HO under in cardiac arrest is also presented. The biochemical findings of HO-1 and HO-2 enzymes using ELISA were further confirmed by immunocytochemical approach to localize selective regional alterations in cardiac arrest. Our observations are the first to show that cardiac arrest followed by successful cardiopulmonary resuscitation results in significant alteration in cerebral concentrations of HO-1 and HO-2 levels indicating a prominent role of CO in brain pathology and methylene blue during CPR followed by induced hypothermia leading to superior neuroprotection after return of spontaneous circulation (ROSC), not reported earlier.

Mitochondrial autophagy and cell survival is regulated by the circadian Clock gene in cardiac myocytes during ischemic stress

Cardiac function is highly reliant on mitochondrial oxidative metabolism and quality control. The circadian Clock gene is critically linked to vital physiological processes including mitochondrial fission, fusion and bioenergetics; however, little is known of how the Clock gene regulates these vital processes in the heart. Herein, we identified a putative circadian CLOCK-mitochondrial interactome that gates an adaptive survival response during myocardial ischemia. We show by transcriptome and gene ontology mapping in CLOCK Δ19/Δ19 mouse that Clock transcriptionally coordinates the efficient removal of damaged mitochondria during myocardial ischemia by directly controlling transcription of genes required for mitochondrial fission, fusion and macroautophagy/autophagy. Loss of Clock gene activity impaired mitochondrial turnover resulting in the accumulation of damaged reactive oxygen species (ROS)-producing mitochondria from impaired mitophagy. This coincided with ultrastructural defects to mitochondria and impaired cardiac function. Interestingly, wild type CLOCK but not mutations of CLOCK defective for E-Box binding or interaction with its cognate partner ARNTL/BMAL-1 suppressed mitochondrial damage and cell death during acute hypoxia. Interestingly, the autophagy defect and accumulation of damaged mitochondria in CLOCK-deficient cardiac myocytes were abrogated by restoring autophagy/mitophagy. Inhibition of autophagy by ATG7 knockdown abrogated the cytoprotective effects of CLOCK. Collectively, our results demonstrate that CLOCK regulates an adaptive stress response critical for cell survival by transcriptionally coordinating mitochondrial quality control mechanisms in cardiac myocytes. Interdictions that restore CLOCK activity may prove beneficial in reducing cardiac injury in individuals with disrupted circadian CLOCK.Abbreviations: ARNTL/BMAL1: aryl hydrocarbon receptor nuclear translocator-like; ATG14: autophagy related 14; ATG7: autophagy related 7; ATP: adenosine triphosphate; BCA: bovine serum albumin; BECN1: beclin 1, autophagy related; bHLH: basic helix- loop-helix; CLOCK: circadian locomotor output cycles kaput; CMV: cytomegalovirus; COQ5: coenzyme Q5 methyltransferase; CQ: chloroquine; CRY1: cryptochrome 1 (photolyase-like); DNM1L/DRP1: dynamin 1-like; EF: ejection fraction; EM: electron microscopy; FS: fractional shortening; GFP: green fluorescent protein; HPX: hypoxia; i.p.: intraperitoneal; I-R: ischemia-reperfusion; LAD: left anterior descending; LVIDd: left ventricular internal diameter diastolic; LVIDs: left ventricular internal diameter systolic; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MFN2: mitofusin 2; MI: myocardial infarction; mPTP: mitochondrial permeability transition pore; NDUFA4: Ndufa4, mitochondrial complex associated; NDUFA8: NADH: ubiquinone oxidoreductase subunit A8; NMX: normoxia; OCR: oxygen consumption rate; OPA1: OPA1, mitochondrial dynamin like GTPase; OXPHOS: oxidative phosphorylation; PBS: phosphate-buffered saline; PER1: period circadian clock 1; PPARGC1A/PGC-1α: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha; qPCR: quantitative real-time PCR; RAB7A: RAB7, member RAS oncogene family; ROS: reactive oxygen species; RT: room temperature; shRNA: short hairpin RNA; siRNA: small interfering RNA; TFAM: transcription factor A, mitochondrial; TFEB: transcription factor EB; TMRM: tetra-methylrhodamine methyl ester perchlorate; WT: wild -type; ZT: zeitgeber time.

Superiority of focused ion beam-scanning electron microscope tomography of cardiomyocytes over standard 2D analyses highlighted by unmasking mitochondrial heterogeneity

BACKGROUND

Cardioprotection by preventing or repairing mitochondrial damage is an unmet therapeutic need. To understand the role of cardiomyocyte mitochondria in physiopathology, the reliable characterization of the mitochondrial morphology and compartment is pivotal. Previous studies mostly relied on two-dimensional (2D) routine transmission electron microscopy (TEM), thereby neglecting the real three-dimensional (3D) mitochondrial organization. This study aimed to determine whether classical 2D TEM analysis of the cardiomyocyte ultrastructure is sufficient to comprehensively describe the mitochondrial compartment and to reflect mitochondrial number, size, dispersion, distribution, and morphology.

METHODS

Spatial distribution of the complex mitochondrial network and morphology, number, and size heterogeneity of cardiac mitochondria in isolated adult mouse cardiomyocytes and adult wild-type left ventricular tissues (C57BL/6) were assessed using a comparative 3D imaging system based on focused ion beam-scanning electron microscopy (FIB-SEM) nanotomography. For comparison of 2D vs. 3D data sets, analytical strategies and mathematical comparative approaches were performed. To confirm the value of 3D data for mitochondrial changes, we compared the obtained values for number, coverage area, size heterogeneity, and complexity of wild-type cardiomyocyte mitochondria with data sets from mice lacking the cytosolic and mitochondrial protein BNIP3 (BCL-2/adenovirus E1B 19-kDa interacting protein 3; Bnip3^-/- ) using FIB-SEM. Mitochondrial respiration was assessed on isolated mitochondria using the Seahorse XF analyser. A cardiac biopsy was obtained from a male patient (48 years) suffering from myocarditis.

RESULTS

The FIB-SEM nanotomographic analysis revealed that no linear relationship exists for mitochondrial number (r = 0.02; P = 0.9511), dispersion (r = -0.03; P = 0.9188), and shape (roundness: r = 0.15, P = 0.6397; elongation: r = -0.09, P = 0.7804) between 3D and 2D results. Cumulative frequency distribution analysis showed a diverse abundance of mitochondria with different sizes in 3D and 2D. Qualitatively, 2D data could not reflect mitochondrial distribution and dynamics existing in 3D tissue. 3D analyses enabled the discovery that BNIP3 deletion resulted in more smaller, less complex cardiomyocyte mitochondria (number: P < 0.01; heterogeneity: C.V. wild-type 89% vs. Bnip3^-/- 68%; complexity: P < 0.001) forming large myofibril-distorting clusters, as seen in human myocarditis with disturbed mitochondrial dynamics. Bnip3^-/- mice also show a higher respiration rate (P < 0.01).

CONCLUSIONS

Here, we demonstrate the need of 3D analyses for the characterization of mitochondrial features in cardiac tissue samples. Hence, we observed that BNIP3 deletion physiologically acts as a molecular brake on mitochondrial number, suggesting a role in mitochondrial fusion/fission processes and thereby regulating the homeostasis of cardiac bioenergetics.

MiR-23a Is Involved in Myocardial Ischemia/Reperfusion Injury by Directly Targeting CX43 and Regulating Mitophagy

Activation of CX43 signaling protects myocardial cells from myocardial ischemia/reperfusion (I/R) injury. However, the underlying mechanism remains unclear. MicroRNAs (miRNAs) are well known to play important roles in the progression of diverse diseases. Here, we first confirmed the expression profile of CX43 in rat heart tissues with I/R injury. Then, microRNAs (miRNAs) that target CX43 were predicted using miRDB, miRWalk, and TargetScan. The candidate miR-23a was selected, and its expression level in I/R samples was investigated. To determine the role of miR-23a, rat primary myocardial cells were transfected with miR-23a mimics after they were subjected to hypoxia-reoxygenation (H/R) injury. Transfection of miR-23a mimics stimulated mitophagy through the PINK1/Parkin pathway and downregulated the protein level of CX43. Treatment of miR-23a-transfected cells with NF-kB inhibitors completely abolished miR-23a-mediated mitophagy after H/R. Moreover, miR-23a transfection significantly suppressed CX43 expression and enhanced mitophagy in the model heart in vivo. Therefore, miR-23a plays a detrimental role in myocardial I/R injury by enhancing mitophagy and inhibiting CX43 mRNA.

Inhibition of Cardiac RIP3 Mitigates Early Reperfusion Injury and Calcium-Induced Mitochondrial Swelling without Altering Necroptotic Signalling

Receptor-interacting protein kinase 3 (RIP3) is a convergence point of multiple signalling pathways, including necroptosis, inflammation and oxidative stress; however, it is completely unknown whether it underlies acute myocardial ischemia/reperfusion (I/R) injury. Langendorff-perfused rat hearts subjected to 30 min ischemia followed by 10 min reperfusion exhibited compromised cardiac function which was not abrogated by pharmacological intervention of RIP3 inhibition. An immunoblotting analysis revealed that the detrimental effects of I/R were unlikely mediated by necroptotic cell death, since neither the canonical RIP3-MLKL pathway (mixed lineage kinase-like pseudokinase) nor the proposed non-canonical molecular axes involving CaMKIIδ-mPTP (calcium/calmodulin-dependent protein kinase IIδ-mitochondrial permeability transition pore), PGAM5-Drp1 (phosphoglycerate mutase 5-dynamin-related protein 1) and JNK-BNIP3 (c-Jun N-terminal kinase-BCL2-interacting protein 3) were activated. Similarly, we found no evidence of the involvement of NLRP3 inflammasome signalling (NOD-, LRR- and pyrin domain-containing protein 3) in such injury. RIP3 inhibition prevented the plasma membrane rupture and delayed mPTP opening which was associated with the modulation of xanthin oxidase (XO) and manganese superoxide dismutase (MnSOD). Taken together, this is the first study indicating that RIP3 regulates early reperfusion injury via oxidative stress- and mitochondrial activity-related effects, rather than cell loss due to necroptosis.

Mitochondrial Quality Control in Cerebral Ischemia-Reperfusion Injury

Ischemic stroke is one of the leading causes of death and also a major cause of adult disability worldwide. Revascularization via reperfusion therapy is currently a standard clinical procedure for patients with ischemic stroke. Although the restoration of blood flow (reperfusion) is critical for the salvage of ischemic tissue, reperfusion can also, paradoxically, exacerbate neuronal damage through a series of cellular alterations. Among the various theories postulated for ischemia/reperfusion (I/R) injury, including the burst generation of reactive oxygen species (ROS), activation of autophagy, and release of apoptotic factors, mitochondrial dysfunction has been proposed to play an essential role in mediating these pathophysiological processes. Therefore, strict regulation of the quality and quantity of mitochondria via mitochondrial quality control is of great importance to avoid the pathological effects of impaired mitochondria on neurons. Furthermore, timely elimination of dysfunctional mitochondria via mitophagy is also crucial to maintain a healthy mitochondrial network, whereas intensive or excessive mitophagy could exacerbate cerebral I/R injury. This review will provide a comprehensive overview of the effect of mitochondrial quality control on cerebral I/R injury and introduce recent advances in the understanding of the possible signaling pathways of mitophagy and potential factors responsible for the double-edged roles of mitophagy in the pathological processes of cerebral I/R injury.

The cardioprotective effect and mechanism of bioactive glass on myocardial reperfusion injury

Myocardial reperfusion treatment for ischemic infarction may cause lethal injury of cardiomyocytes, which is known as ischemia/reperfusion (I/R) injury. As a kind of prospective biomaterial with superior properties, the application of bioactive glasses (BGs) in myocardial tissue engineering have received great interests. In this study, the cardioprotective effect and relevant mechanism of BG on myocardial reperfusion injury were investigatedin vitro. H9c2 cardiomyocytes were pretreated with BG extracts and then cultured in hypoxic environment for 30 min followed by reoxygenation for 1 h. The activity of released lactate dehydrogenase (LDH) and the content of malondialdehyde (MDA) in H9c2 cells were tested by assay kits. Cell viability was analyzed by Live/Dead staining assay and the number of living cells was detected by Cell Counting Kit-8 (CCK-8) assay. The cytoskeletal protein F-actin was stained and observed under inverted fluorescence microscope. Mitochondrial membrane potential (MMP) level, reactive oxygen species (ROS) production and apoptosis ratio were evaluated by fluorescent observation and flow cytometry simultaneously. The gene expressions relevant to apoptosis were detected by quantitative real time polymerase chain reaction (qRT-PCR) analysis. The results showed that BG extracts effectively inhibited hypoxia/reoxygenation (H/R)-induced cell injury by suppressing oxidative stress and mitochondrial permeability transition (MPT) within H9c2 cells. Meanwhile, apoptosis caused by H/R injury was alleviated and three classic apoptotic signaling pathways were proved to be regulated by BG extracts. Further analysis showed that phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway was up-regulated in H/R-induced H9c2 cells by BG extracts, leading to relieved cellular apoptosis. These results indicated that BG might exert cardioprotective effect in reperfusion injury when applied in myocardial tissue regeneration and repair.

Mitochondrial Oxidative Phosphorylation Function and Mitophagy in Ischaemic/Reperfused Hearts from Control and High-Fat Diet Rats: Effects of Long-Term Melatonin Treatment

PURPOSE

Oxidative stress causes mitochondrial dysfunction in myocardial ischaemia/reperfusion (I/R) as well as in obesity. Mitochondrial depolarization triggers mitophagy to degrade damaged mitochondria, a process important for quality control. The aims of this study were to evaluate (i) the effect of I/R on mitochondrial oxidative phosphorylation and its temporal relationship with mitophagy in hearts from obese rats and their age-matched controls, and (ii) the role of oxidative stress in these processes using melatonin, a free radical scavenger.

METHODS

Male Wistar rats were divided into 4 groups: control (normal diet ± melatonin) and high-fat sucrose diet (HFSD ± melatonin). Rats received melatonin orally (10 mg/kg/day). After 16 weeks, hearts were removed and subjected to 40-min stabilization, and 25-min global ischaemia/10-min reperfusion for preparation of mitochondria. Mitochondrial oxidative phosphorylation was measured polarographically. Western blotting was used for evaluation of PINK1, Parkin, p62/SQSTM1 (p62) and TOM 70. Infarct size was measured using tetrazolium staining.

RESULTS

Ischaemia and reperfusion respectively reduced and increased mitochondrial QO2 (state 3) and the ox-phos rate in both control and HFSD mitochondria, showing no major changes between the groups, while melatonin pretreatment had little effect. p62 as indicator of mitophagic flux showed up- and downregulation of mitophagy by ischaemia and reperfusion respectively, with melatonin having no significant effect. Melatonin treatment caused a significant reduction in infarct size in hearts from both control and diet groups.

CONCLUSIONS

The results suggest that I/R (i) affects mitochondria from control and HFSD hearts similarly and (ii) melatonin-induced cardioprotection is not associated with reversal of mitochondrial dysfunction or changes in the PINK1/Parkin pathway.

Mitochondrial fission and mitophagy are independent mechanisms regulating ischemia/reperfusion injury in primary neurons

Mitochondrial dynamics and mitophagy are constitutive and complex systems that ensure a healthy mitochondrial network through the segregation and subsequent degradation of damaged mitochondria. Disruption of these systems can lead to mitochondrial dysfunction and has been established as a central mechanism of ischemia/reperfusion (I/R) injury. Emerging evidence suggests that mitochondrial dynamics and mitophagy are integrated systems; however, the role of this relationship in the context of I/R injury remains unclear. To investigate this concept, we utilized primary cortical neurons isolated from the novel dual-reporter mitochondrial quality control knockin mice (C57BL/6-Gt(ROSA)26Sortm1(CAG-mCherry/GFP)Ganl/J) with conditional knockout (KO) of Drp1 to investigate changes in mitochondrial dynamics and mitophagic flux during in vitro I/R injury. Mitochondrial dynamics was quantitatively measured in an unbiased manner using a machine learning mitochondrial morphology classification system, which consisted of four different classifications: network, unbranched, swollen, and punctate. Evaluation of mitochondrial morphology and mitophagic flux in primary neurons exposed to oxygen-glucose deprivation (OGD) and reoxygenation (OGD/R) revealed extensive mitochondrial fragmentation and swelling, together with a significant upregulation in mitophagic flux. Furthermore, the primary morphology of mitochondria undergoing mitophagy was classified as punctate. Colocalization using immunofluorescence as well as western blot analysis revealed that the PINK1/Parkin pathway of mitophagy was activated following OGD/R. Conditional KO of Drp1 prevented mitochondrial fragmentation and swelling following OGD/R but did not alter mitophagic flux. These data provide novel evidence that Drp1 plays a causal role in the progression of I/R injury, but mitophagy does not require Drp1-mediated mitochondrial fission.

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.

Manifestations of Age on Autophagy, Mitophagy and Lysosomes in Skeletal Muscle

Sarcopenia is the loss of both muscle mass and function with age. Although the molecular underpinnings of sarcopenia are not fully understood, numerous pathways are implicated, including autophagy, in which defective cargo is selectively identified and degraded at the lysosome. The specific tagging and degradation of mitochondria is termed mitophagy, a process important for the maintenance of an organelle pool that functions efficiently in energy production and with relatively low reactive oxygen species production. Emerging data, yet insufficient, have implicated various steps in this pathway as potential contributors to the aging muscle atrophy phenotype. Included in this is the lysosome, the end-stage organelle possessing a host of proteolytic and degradative enzymes, and a function devoted to the hydrolysis and breakdown of defective molecular complexes and organelles. This review provides a summary of our current understanding of how the autophagy-lysosome system is regulated in aging muscle, highlighting specific areas where knowledge gaps exist. Characterization of the autophagy pathway with a particular focus on the lysosome will undoubtedly pave the way for the development of novel therapeutic strategies to combat age-related muscle loss.

Capsaicin protects cardiomyocytes against lipopolysaccharide-induced damage via 14-3-3γ-mediated autophagy augmentation

Background: The myocardium is susceptible to lipopolysaccharide (LPS)-induced damage in sepsis, and cardiac dysfunction is a leading cause of mortality in patients with sepsis. The changes in cardiomyocyte autophagy in sepsis and the effects and mechanism of action of capsaicin (Cap) remain unclear.

Methods and Results: The potential pathway of 14-3-3γ-dependent autophagy and the effects and mechanisms of Cap were studied in LPS-induced injury to primary cultured neonatal rat cardiomyocytes. The results showed that cardiomyocyte viability decreased, lactate dehydrogenase and creatine kinase activities increased, 14-3-3γ expression was downregulated, and autophagy was inhibited after LPS challenge. Cap pretreatment augmented autophagy by upregulating 14-3-3γ expression and activating AMP-activated protein kinase (AMPK) and unc-51 like autophagy-activating kinase 1 (ULK1), suppressing mammalian target of rapamycin (mTOR), alleviating cardiac dysfunction and improving the inflammation response, whereas pAD/14-3-3γ-shRNA nullified the above effects. Cap pretreatment also decreased the levels of IL-1β, TNF-α, IL-6, and IL-10; suppressed intracellular oxidative stress; reduced the intracellular/mitochondrial reactive oxygen species (ROS); balanced GSH/GSSG; increased GSH-Px, catalase, and SOD activities; and decreased MDA contents. It also increased ATP content, activated complex Ⅰ and complex Ⅲ, stabilized the mitochondrial membrane potential, and decreased the mitochondrial permeability transition pore opening, thereby improving mitochondrial function.

Conclusion: Pretreatment with Cap can regulate autophagy by upregulating 14-3-3γ expression, inhibiting oxidative stress and inflammation, maintaining mitochondrial function, and protecting cardiomyocytes against LPS-induced injury.

Mitophagy in Human Diseases

Mitophagy is a selective autophagic process, essential for cellular homeostasis, that eliminates dysfunctional mitochondria. Activated by inner membrane depolarization, it plays an important role during development and is fundamental in highly differentiated post-mitotic cells that are highly dependent on aerobic metabolism, such as neurons, muscle cells, and hepatocytes. Both defective and excessive mitophagy have been proposed to contribute to age-related neurodegenerative diseases, such as Parkinson’s and Alzheimer’s diseases, metabolic diseases, vascular complications of diabetes, myocardial injury, muscle dystrophy, and liver disease, among others. Pharmacological or dietary interventions that restore mitophagy homeostasis and facilitate the elimination of irreversibly damaged mitochondria, thus, could serve as potential therapies in several chronic diseases. However, despite extraordinary advances in this field, mainly derived from in vitro and preclinical animal models, human applications based on the regulation of mitochondrial quality in patients have not yet been approved. In this review, we summarize the key selective mitochondrial autophagy pathways and their role in prevalent chronic human diseases and highlight the potential use of specific interventions.

Pharmacological Conditioning of the Heart: An Update on Experimental Developments and Clinical Implications

The aim of pharmacological conditioning is to protect the heart against myocardial ischemia-reperfusion (I/R) injury and its consequences. There is extensive literature that reports a multitude of different cardioprotective signaling molecules and mechanisms in diverse experimental protocols. Several pharmacological agents have been evaluated in terms of myocardial I/R injury. While results from experimental studies are immensely encouraging, translation into the clinical setting remains unsatisfactory. This narrative review wants to focus on two aspects: (1) give a comprehensive update on new developments of pharmacological conditioning in the experimental setting concentrating on recent literature of the last two years and (2) briefly summarize clinical evidence of these cardioprotective substances in the perioperative setting highlighting their clinical implications. By directly opposing each pharmacological agent regarding its recent experimental knowledge and most important available clinical data, a clear overview is given demonstrating the remaining gap between basic research and clinical practice. Finally, future perspectives are given on how we might overcome the limited translatability in the field of pharmacological conditioning.

Hongjingtian injection protects against myocardial ischemia reperfusion-induced apoptosis by blocking ROS induced autophagic- flux

BACKGROUND

Hongjingtian injection (HJT) has been widely used in the clinic to treat coronary heart disease in China. However, the underlying mechanisms of therapies still need to be illustrated. The present study aims to determine whether HJT protects against myocardial ischemia reperfusion injury via Reactive Oxygen Species (ROS)-induced autophagic flux and apoptosis and, if so, to explore the underlying mechanisms.

METHODS

In vivo myocardial protection and autophagy regulation of HJT in myocardial ischemia reperfusion injury in C57BL/6 J and CAG-RFP-EGFP-LC3 transgenic C57BL/6 J mice were investigated. In vitro, the effects of HJT on apoptosis, autophagic flux, oxidative stress and mitochondrial function were observed in H2O2-induced H9c2 cells. In addition, apoptosis-related proteins and autophagy-related proteins were assessed to explore the underlying mechanisms.

RESULTS

HJT significantly decreased the infarct area and cell apoptosis after myocardial ischemia reperfusion injury in C57BL/6 J mice. Autophagic flux was reduced by HJT treatment after myocardial ischemia reperfusion injury in CAG-RFP-EGFP-LC3 transgenic C57BL/6 J mice. HJT inhibited H2O2-induced cell apoptosis by significantly decreasing the levels of cleaved caspase 3 and increasing the Bcl-2/Bax ratio. HJT inhibited autophagic flux after H2O2 stimulation by significantly decreasing LC3-Ⅱ and p-AMPK expression and increasing p-mTOR. HJT inhibited ROS production and improved mitochondrial function in H2O2-induced cells by significantly increasing the mitochondrial membrane potential, intracellular ATP contents and oxygen consumption.

CONCLUSION

The beneficial effects of HJT in treating myocardial ischemia reperfusion are partially due to improved mitochondrial function and regulated autophagy to inhibit cell apoptosis through the AMPK/mTOR pathway.

Quantitative intravital imaging in zebrafish reveals in vivo dynamics of physiological-stress-induced mitophagy

Mitophagy, the selective recycling of mitochondria through autophagy, is a crucial metabolic process induced by cellular stress, and defects are linked to aging, sarcopenia and neurodegenerative diseases. To therapeutically target mitophagy, the fundamental in vivo dynamics and molecular mechanisms must be fully understood. Here, we generated mitophagy biosensor zebrafish lines expressing mitochondrially targeted, pH-sensitive fluorescent probes, mito-Keima and mito-EGFP-mCherry, and used quantitative intravital imaging to illuminate mitophagy during physiological stresses, namely, embryonic development, fasting and hypoxia. In fasted muscle, volumetric mitolysosome size analyses documented organelle stress response dynamics, and time-lapse imaging revealed that mitochondrial filaments undergo piecemeal fragmentation and recycling rather than the wholesale turnover observed in cultured cells. Hypoxia-inducible factor (Hif) pathway activation through physiological hypoxia or chemical or genetic modulation also provoked mitophagy. Intriguingly, mutation of a single mitophagy receptor (bnip3) prevented this effect, whereas disruption of other putative hypoxia-associated mitophagy genes [bnip3la (nix), fundc1, pink1 or prkn (Parkin)] had no effect. This in vivo imaging study establishes fundamental dynamics of fasting-induced mitophagy and identifies bnip3 as the master regulator of Hif-induced mitophagy in vertebrate muscle.

Dynamic properties of mitochondria during human corticogenesis

Mitochondria are signaling hubs responsible for the generation of energy through oxidative phosphorylation, the production of key metabolites that serve the bioenergetic and biosynthetic needs of the cell, calcium (Ca2+) buffering and the initiation/execution of apoptosis. The ability of mitochondria to coordinate this myriad of functions is achieved through the exquisite regulation of fundamental dynamic properties, including remodeling of the mitochondrial network via fission and fusion, motility and mitophagy. In this Review, we summarize the current understanding of the mechanisms by which these dynamic properties of the mitochondria support mitochondrial function, review their impact on human cortical development and highlight areas in need of further research.

Mitochondrial Homeostasis Mediates Lipotoxicity in the Failing Myocardium

Heart failure remains the most common cause of death in the industrialized world. In spite of new therapeutic interventions that are constantly being developed, it is still not possible to completely protect against heart failure development and progression. This shows how much more research is necessary to understand the underlying mechanisms of this process. In this review, we give a detailed overview of the contribution of impaired mitochondrial dynamics and energy homeostasis during heart failure progression. In particular, we focus on the regulation of fatty acid metabolism and the effects of fatty acid accumulation on mitochondrial structural and functional homeostasis.

Current status of cardiac regenerative medicine; An update on point of view to cell therapy application

Cardiovascular diseases (CVDs) are the leading cause of death globally. Because of the economic and social burden of acute myocardial infarction and its chronic consequences in surviving patients, understanding the pathophysiology of myocardial infarction injury is a major priority for cardiovascular research. MI is defined as cardiomyocytes death caused by an ischemic that resulted from the apoptosis, necrosis, necroptosis, and autophagy. The phases of normal repair following MI including inflammatory, proliferation, and maturation. Normal repair is slow and inefficient generally so that other treatments are required. Because of difficulties, outcomes, and backwashes of traditional therapies including coronary artery bypass grafting, balloon angioplasty, heart transplantation, and artificial heart operations, the novel strategy in the treatment of MI, cell therapy, was newly emerged. In cell therapy, a new population of cells has created that substitute with damaged cells. Different types of stem cell and progenitor cells have been shown to improve cardiac function through various mechanisms, including the formation of new myocytes, endothelial cells, and vascular smooth muscle cells. Bone marrow- and/or adipose tissue-derived mesenchymal stem cells, embryonic stem cells, autologous skeletal myoblasts, induced pluripotent stem cells, endothelial progenitor cells, cardiac progenitor cells and cardiac pericytes considered as a source for cell therapy. In this study, we focused on the point of view of the cell sources.

Roles of HDAC3-orchestrated circadian clock gene oscillations in diabetic rats following myocardial ischaemia/reperfusion injury

The circadian clock is closely related to the development of diabetes mellitus and cardiovascular disease, and disruption of the circadian clock exacerbates myocardial ischaemia/reperfusion injury (MI/RI). HDAC3 is a key component of the circadian negative feedback loop that controls the expression pattern of the circadian nuclear receptor Rev-erbα to maintain the stability of circadian genes such as BMAL1. However, the mechanism by which the HDAC3-orchestrated Rev-erbα/BMAL1 pathway increases MI/RI in diabetes and its relationship with mitophagy have yet to be elucidated. Here, we observed that the clock genes Rev-erbα, BMAL1, and C/EBPβ oscillations were altered in the hearts of rats with streptozotocin (STZ)-induced diabetes, with upregulated HDAC3 expression. Oscillations of Rev-erbα and BMAL1 were rapidly attenuated in diabetic MI/R hearts versus non-diabetic I/RI hearts, in accordance with impaired and rhythm-disordered circadian-dependent mitophagy that increased injury. Genetic knockdown of HDAC3 significantly attenuated diabetic MI/RI by mediating the Rev-erbα/BMAL1 circadian pathway to recover mitophagy. Primary cardiomyocytes with or without HDAC3 siRNA and Rev-erbα siRNA were exposed to hypoxia/reoxygenation (H/R) in vitro. The expression of HDAC3 and Rev-erbα in cardiomyocytes was increased under high-glucose conditions compared with low-glucose conditions, with decreased BMAL1 expression and mitophagy levels. After H/R stimulation, high glucose aggravated H/R injury, with upregulated HDAC3 and Rev-erbα expression and decreased BMAL1 and mitophagy levels. HDAC3 and Rev-erbα siRNA can alleviate high glucose-induced and H/R-induced injury by upregulating BMAL1 to increase mitophagy. Collectively, these findings suggest that disruption of HDAC3-mediated circadian gene expression oscillations induces mitophagy dysfunction, aggravating diabetic MI/RI. Cardiac-specific HDAC3 knockdown could alleviate diabetic MI/RI by regulating the Rev-erbα/BMAL1 pathway to restore the activation of mitophagy.

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)1

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field.

Perioperative Cardioprotection: General Mechanisms and Pharmacological Approaches

Cardioprotection encompasses a variety of strategies protecting the heart against myocardial injury that occurs during and after inadequate blood supply to the heart during myocardial infarction. While restoring reperfusion is crucial for salvaging myocardium from further damage, paradoxically, it itself accounts for additional cell death-a phenomenon named ischemia/reperfusion injury. Therefore, therapeutic strategies are necessary to render the heart protected against myocardial infarction. Ischemic pre- and postconditioning, by short periods of sublethal cardiac ischemia and reperfusion, are still the strongest mechanisms to achieve cardioprotection. However, it is highly impractical and far too invasive for clinical use. Fortunately, it can be mimicked pharmacologically, for example, by volatile anesthetics, noble gases, opioids, propofol, dexmedetomidine, and phosphodiesterase inhibitors. These substances are all routinely used in the clinical setting and seem promising candidates for successful translation of cardioprotection from experimental protocols to clinical trials. This review presents the fundamental mechanisms of conditioning strategies and provides an overview of the most recent and relevant findings on different concepts achieving cardioprotection in the experimental setting, specifically emphasizing pharmacological approaches in the perioperative context.

A novel danshensu/tetramethypyrazine derivative attenuates oxidative stress-induced autophagy injury via the AMPK-mTOR-Ulk1 signaling pathway in cardiomyocytes

Myocardial ischemia/reperfusion injury (MIRI) is an inevitable and unsolved clinical problem in the treatment of ischemic heart diseases. Compound DT-010 is a novel danshensu/tetramethylpyrazine derivative and was examined as a candidate for treating MIRI. In the present study, MTT, lactate dehydrogenase assay and Hoechst staining data indicated that DT-010 attenuated tert-butylhydroperoxide (t-BHP)-induced oxidative damage by increasing cell survival, reducing cell damage and decreasing apoptosis in H9c2 cardiomyocytes. Autophagy was assessed by western blotting for microtubule-associated protein 1A/1B-light chain 3 (LC3-II and LC3-I) expression, acridine orange and monodansylcadaverine staining for autophagosome formation and the monomeric red fluorescent protein-green fluorescent protein-LC3 assay for autophagic flow. t-BHP-induced cell damage was aggravated by the autophagy agonist rapamycin and alleviated by the autophagy blocker hydroxy-chloroquine, suggesting that autophagy was involved in t-BHP-induced cardiomyocyte injury. DT-010 pretreatment significantly prevented t-BHP-induced cell damage, which was partially but significantly abolished by rapamycin and significantly improved by hydroxy-chloroquine treatment. DT-010 treatment inhibited t-BHP-induced autophagy in H9c2 cells, reduced phosphorylation of 5'-AMP-activated protein kinase (AMPK) and promoted the phosphorylation of mTOR and unc-51 like autophagy activating kinase 1 (Ulk1). To conclude, DT-010 can serve as a potential candidate for myocardial ischemia-reperfusion injury therapy. The cardioprotective effects of DT-010 could be partially attributed to its inhibition of autophagy via the AMPK-mTOR-Ulk1 signaling pathway.

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

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

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.

It takes two to tango: coupling of Hippo pathway and redox signaling in biological process

Hippo pathway is a chain of kinases consists of a series of protein kinases and transcription factors. Meanwhile, oxidative stress is a condition of elevated concentrations of reactive oxygen species (ROS) that cause molecular damage to vital structures and functions. Both of them are key regulators in cell proliferation, survival, and development. These processes are strictly regulated by highly coordinated mechanisms, including c-Jun n-terminal kinase (JNK) pathway, mTOR pathway and a number of extrinsic and intrinsic factors. Recently, emerging evidence suggests that Hippo pathway is involved in the responses to cellular stresses, including mechanic stress, DNA damage, and oxidative stress, to mediate biological process, such as apoptosis, pyroptosis, and metastasis. But the exact mechanism remains to be further explored. Therefore, the purpose of this review is to summarize recent findings and discuss how Hippo pathway, oxidative stress, and the crosstalk between them regulate some biological process which determines cell fate.

Sulforaphane-cysteine inhibited migration and invasion via enhancing mitophagosome fusion to lysosome in human glioblastoma cells

Here we uncovered the involved subcellular mechanisms that sulforaphane-cysteine (SFN-Cys) inhibited invasion in human glioblastoma (GBM). SFN-Cys significantly upregulated 45 and downregulated 14 microtubule-, mitophagy-, and invasion-associated proteins in GBM cells via HPLC-MS/MS and GEO ontology analysis; SFN-Cys disrupted microtubule by ERK1/2 phosphorylation-mediated downregulation of α-tubulin and Stathmin-1 leading to the inhibition of cell migration and invasion; SFN-Cys downregulated invasion-associated Claudin-5 and S100A4, and decreased the interaction of α-tubulin to Claudin-5. Knockdown of Claudin-5 and S100A4 significantly reduced the migration and invasion. Besides, SFN-Cys lowered the expressions of α-tubulin-mediated mitophagy-associated proteins Bnip3 and Nix. Transmission electron microscopy showed more membrane-deficient mitochondria and accumulated mitophagosomes in GBM cells, and mitochondria fusion might be downregulated because that SFN-Cys downregulated mitochondrial fusion protein OPA1. SFN-Cys increased the colocalization and interplay of LC3 to lysosomal membrane-associated protein LAMP1, aggravating the fusion of mitophagosome to lysosome. Nevertheless, SFN-Cys inhibited the lysosomal proteolytic capacity causing LC3II/LC3I elevation but autophagy substrate SQSTM1/p62 was not changed, mitophagosome accumulation, and the inhibition of migration and invasion in GBM cells. These results will help us develop high-efficiency and low-toxicity anticancer drugs to inhibit migration and invasion in GBM.

LncRNA SNHG14 promotes OGD/R-induced neuron injury by inducing excessive mitophagy via miR-182-5p/BINP3 axis in HT22 mouse hippocampal neuronal cells

BACKGROUND

Long non-coding RNA (lncRNA) small nucleolar RNA host gene 14 (SNHG14) is associated with cerebral ischemia-reperfusion (CI/R) injury. This work aims to explore the role of SNHG14 in CI/R injury.

METHODS

HT22 (mouse hippocampal neuronal cells) cell model was established by oxygen-glucose deprivation/reoxygenation (OGD/R) treatment. The interaction among SNHG14, miR-182-5p and BNIP3 was verified by luciferase reporter assay. Flow cytometry, western blot and quantitative real-time PCR were performed to examine apoptosis, the expression of genes and proteins.

RESULTS

SNHG14 and BNIP3 were highly expressed, and miR-182-5p was down-regulated in the OGD/R-induced HT22 cells. OGD/R-induced HT22 cells exhibited an increase in apoptosis. SNHG14 overexpression promoted apoptosis and the expression of cleaved-caspase-3 and cleaved-caspase-9 in the OGD/R-induced HT22 cells. Moreover, SNHG14 up-regulation enhanced the expression of BNIP3, Beclin-1, and LC3II/LC3I in the OGD/R-induced HT22 cells. Furthermore, SNHG14 regulated BNIP3 expression by sponging miR-182-5p. MiR-182-5p overexpression or BNIP3 knockdown repressed apoptosis in OGD/R-induced HT22 cells, which was abolished by SNHG14 up-regulation.

CONCLUSION

Our study demonstrates that lncRNA SNHG14 promotes OGD/R-induced neuron injury by inducing excessive mitophagy via miR-182-5p/BINP3 axis in HT22 mouse hippocampal neuronal cells. Thus, SNHG14/miR-182-5p/BINP3 axis may be a valuable target for CI/R injury therapies.

A review of myocardial ischaemia/reperfusion injury: Pathophysiology, experimental models, biomarkers, genetics and pharmacological treatment

Cardiovascular diseases are known to be the most fatal diseases worldwide. Ischaemia/reperfusion (I/R) injury is at the centre of the pathology of the most common cardiovascular diseases. According to the World Health Organization estimates, ischaemic heart disease is the leading global cause of death, causing more than 9 million deaths in 2016. After cardiovascular events, thrombolysis, percutaneous transluminal coronary angioplasty or coronary bypass surgery are applied as treatment. However, after restoring coronary blood flow, myocardial I/R injury may occur. It is known that this damage occurs due to many pathophysiological mechanisms, especially increasing reactive oxygen types. Besides causing cardiomyocyte death through multiple mechanisms, it may be an important reason for affecting other cell types such as platelets, fibroblasts, endothelial and smooth muscle cells and immune cells. Also, polymorphonuclear leukocytes are associated with myocardial I/R damage during reperfusion. This damage may be insufficient in patients with co-morbidity, as it is demonstrated that it can be prevented by various endogenous antioxidant systems. In this context, the resulting data suggest that optimal cardioprotection may require a combination of additional or synergistic multi-target treatments. In this review, we discussed the pathophysiology, experimental models, biomarkers, treatment and its relationship with genetics in myocardial I/R injury. SIGNIFICANCE OF THE STUDY: This review summarized current information on myocardial ischaemia/reperfusion injury (pathophysiology, experimental models, biomarkers, genetics and pharmacological therapy) for researchers and reveals guiding data for researchers, especially in the field of cardiovascular system and pharmacology.

Metformin suppresses inflammation and apoptosis of myocardiocytes by inhibiting autophagy in a model of ischemia-reperfusion injury

Metformin (Met) is a major widely used oral glucose lowering drug for the treatment of type 2 diabetes. It is reported that metformin could regulate autophagy in various diseases of cardiovascular system including in I/R injury, diabetic cardiomyopathy and heart failure. Autophagy plays a controversial role in ischemia/reperfusion (I/R) injury, and this research was performed to explore the cardioprotective effect of Met on I/R injury and discuss the underlying mechanism of autophagy in it. In vivo and in vitro, Met exerted cardioprotection function of decreasing myocardial inflammation and apoptosis with a decrease in the level of autophagy. Moreover, Met significantly inhibited autophagosome formation and restore the impairment of autophagosome processing, which lead to cardioprotection effect of Met. Akt was up-regulated in Met-treated I/R hearts and miransertib, a pan-AKT inhibitor, was able to reverse the alleviating autophagy effect of Met. We demonstrate that Met protects cardiomyocytes from I/R-induced apoptosis and inflammation through down regulation of autophagy mediated by Akt signaling pathway.

Cystathionine beta synthase regulates mitochondrial dynamics and function in endothelial cells

Mutations in the human cystathionine beta synthase (CBS) gene are known to cause endothelial dysfunction responsible for cardiovascular and neurovascular diseases. CBS is the predominant hydrogen sulfide (H2 S)-producing enzyme in endothelial cells (ECs). Recently, H2 S was shown to attenuate ROS and improve mitochondrial function. Mitochondria are metabolic organelles that actively transform their ultrastructure to mediate their function. Therefore, we questioned whether perturbation of CBS/H2 S activity could drive mitochondrial dysfunction via mitochondrial dynamics in ECs. Here we demonstrate that silencing CBS induces mitochondria fragmentation, attenuates efficient oxidative phosphorylation, and decreases EC function. Mechanistically, CBS silencing significantly elevates ROS production, thereby leading to reduced mitofusin 2 (MFN2) expression, decouple endoplasmic reticulum-mitochondria contacts, increased mitochondria fission, enhanced receptor-mediated mitophagy, and increased EC death. These defects were significantly rescued by the treatment of H2 S donors. Taken together our data highlights a novel signaling axis that mechanistically links CBS with mitochondrial function and ER-mitochondrial tethering and could be considered as a new therapeutic approach for the intervention of EC dysfunction-related pathologies.

Targeting the MicroRNA-490-3p-ATG4B-Autophagy Axis Relieves Myocardial Injury in Ischemia Reperfusion

We investigated the potential role of miR-490-3p in ischemia reperfusion (IR) injury. We first determined the expression of miR-490-3p and autophagy-related 4B cysteine (ATG4B) in IR. Then, to explore whether miR-490-3p would affect autophagy, apoptosis, and IR injury, we evaluated apoptosis, autophagy, and infarct size via gain- and loss-of-function experiments. Furthermore, we used adenovirus to enhance or inhibit the expression of ATG4B, and then measured autophagy, apoptosis, and IR injury. miR-490-3p was downregulated in the hearts during the process of IR, while ATG4B was upregulated. The inhibition of miR-490-3p or overexpression of ATG4B could promote the expression of LC3II, increase the autolysosomes, inhibit the expression of p62, and reduce infarct size. On all accounts, the inhibition of miR-490-3p could promote autophagy to reduce myocardial IR injury by upregulating ATG4B, a finding that provides new insights for the protective mechanism of autophagy in IR. Graphical Abstract.

Exaggerated mitophagy: a weapon of striatal destruction in the brain?

Mechanisms responsible for neuronal vulnerability in the brain remain unclear. Striatal neurons are preferentially damaged by 3-nitropropionic acid (3-NP), a mitochondrial complex-II inhibitor, causing striatal damage reminiscent of Huntington's disease (HD), but the mechanisms of the selectivity are not as well understood. We have discovered that Rhes, a protein enriched in the striatum, removes mitochondria via the mitophagy process. The process becomes intensified in the presence of 3-NP, thereby eliminating most of the mitochondria from the striatum. We put forward the hypothesis that Rhes acts as a 'mitophagy ligand' in the brain and promotes mitophagy via NIX, a mitophagy receptor. Since Rhes interacts and promotes toxicity in association with mutant huntingtin (mHTT), the genetic cause of HD, it is tempting to speculate on whether the exaggerated mitophagy may be a contributing factor to the striatal lesion found in HD. Thus, Rhes-mediated exaggerated mitophagy may act as a weapon of striatal destruction in the brain.

The Dynein Adaptor RILP Controls Neuronal Autophagosome Biogenesis, Transport, and Clearance

Autophagy plays critical roles in neurodegeneration and development, but how this pathway is organized and regulated in neurons remains poorly understood. Here, we find that the dynein adaptor RILP is essential for retrograde transport of neuronal autophagosomes, and surprisingly, their biogenesis as well. We find that induction of autophagy by mTOR inhibition specifically upregulates RILP expression and its localization to autophagosomes. RILP depletion or mutations in its LC3-binding LIR motifs strongly decrease autophagosome numbers suggesting an unexpected RILP role in autophagosome biogenesis. We find that RILP also interacts with ATG5 on isolation membranes, precluding premature dynein recruitment and autophagosome transport. RILP inhibition impedes autophagic turnover and causes p62/sequestosome-1 aggregation. Together, our results identify an mTOR-responsive neuronal autophagy pathway, wherein RILP integrates the processes of autophagosome biogenesis and retrograde transport to control autophagic turnover. This pathway has important implications for understanding how autophagy contributes to neuronal function, development, and disease.

Oxidized LDL Modify the Human Adipocyte Phenotype to an Insulin Resistant, Proinflamatory and Proapoptotic Profile

Little information exists in humans on the regulation that oxidized low-density lipoprotein (oxLDL) exerts on adipocyte metabolism, which is associated with obesity and type 2 diabetes. The aim was to analyze the oxLDL effects on adipocytokine secretion and scavenger receptors (SRs) and cell death markers in human visceral adipocytes. Human differentiated adipocytes from visceral adipose tissue from non-obese and morbidly obese subjects were incubated with increasing oxLDL concentrations. mRNA expression of SRs, markers of apoptosis and autophagy, secretion of adipocytokines, and glucose uptake were analyzed. In non-obese and in morbidly obese subjects, oxLDL produced a decrease in insulin-induced glucose uptake, a significant dose-dependent increase in tumor necrosis factor-α (TNF-α), IL-6, and adiponectin secretion, and a decrease in leptin secretion. OxLDL produced a significant increase of Lox-1 and a decrease in Cxcl16 and Cl-p1 expression. The expression of Bnip3 (marker of apoptosis, necrosis and autophagy) was significantly increased and Bcl2 (antiapoptotic marker) was decreased. OxLDL could sensitize adipocytes to a lower insulin-induced glucose uptake, a more proinflammatory phenotype, and could modify the gene expression involved in apoptosis, autophagy, necrosis, and mitophagy. OxLDL can upregulate Lox-1, and this could lead to a possible amplification of proinflammatory and proapoptotic effects of oxLDL.

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

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

Mitophagy: An Emerging Role in Aging and Age-Associated Diseases

Mitochondrial dysfunction constitutes one of the hallmarks of aging and is characterized by irregular mitochondrial morphology, insufficient ATP production, accumulation of mitochondrial DNA (mtDNA) mutations, increased production of mitochondrial reactive oxygen species (ROS) and the consequent oxidative damage to nucleic acids, proteins and lipids. Mitophagy, a mitochondrial quality control mechanism enabling the degradation of damaged and superfluous mitochondria, prevents such detrimental effects and reinstates cellular homeostasis in response to stress. To date, there is increasing evidence that mitophagy is significantly impaired in several human pathologies including aging and age-related diseases such as neurodegenerative disorders, cardiovascular pathologies and cancer. Therapeutic interventions aiming at the induction of mitophagy may have the potency to ameliorate these dysfunctions. In this review, we summarize recent findings on mechanisms controlling mitophagy and its role in aging and the development of human pathologies.

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.