Oxidative stress stimulates autophagic flux during ischemia/reperfusion

A Single, Acute Astragaloside IV Therapy Protects Cardiomyocyte Through Attenuating Superoxide Anion-Mediated Accumulation of Autophagosomes in Myocardial Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion (I/R) injury, characterized by myocardial cell death (e.g., apoptosis) and generation of reactive oxygen species (ROS) such as superoxide (O₂ ^·-) and hydrogen peroxide (H₂O₂), is a serious threat to human health and property. Saponin astragaloside IV (ASIV), extracted from Chinese herbal medicine astragalus, is effective in resolving multiple pathological issues including myocardial I/R injury. Recent studies have shown that autophagy is regulated by ROS and plays an important role in myocardial I/R injury. However, regulation of autophagy by ASIV during myocardial I/R injury and the role of specific ROS involved in the process have been rarely reported. In the present study, we found that SOD2 was downregulated and O₂ ^·- was upregulated in H₂O₂-induced H9C2 cardiac myocyte injury in vitro and myocardial I/R injury in vivo, while such alterations were reversed by ASIV. ASIV possessed the ability to alleviate myocardial I/R injury via attenuating I/R-caused autophagosome accumulation. Upregulate of O₂ ^·- by 2-methoxyestradiol (2-ME) reversed the effect of ASIV-mediated autophagy regulation, which suggested that O₂ ^·- was vital in this process. In conclusion, our results contribute to understanding the mechanism of ASIV-induced cardioprotective effect.

Circ-HIPK2 Accelerates Cell Apoptosis and Autophagy in Myocardial Oxidative Injury by Sponging miR-485-5p and Targeting ATG101

Myocardial injury has been deemed as a major cause of heart diseases including myocarditis and coronary heart disease, which have brought multiple mortalities globally. Long non-coding RNAs (lncRNAs) are widely recognized in diverse diseases. However, the role of circular RNA HIPK2 (circ-HIPK2) remains unclear in myocardial injury induced by H2O2. We attempted to investigate the probable role of circ-HIPK2 in myocardial injury induced by H2O2. This study discovered that the treatment of H2O2 inhibited cell proliferation but boosted cell apoptosis and autophagy. ATG101 was upregulated in primary mouse neonatal cardiomyocytes under H2O2 treatment. ATG101 knockdown promoted proliferation and limited apoptosis by attenuating autophagy in H2O2-injured mouse neonatal cardiomyocytes. Furthermore, miR-485-5p was validated to combine with ATG101 and circ-HIPK2, and circ-HIPK2 positively regulated ATG101 expression by sponging miR-485-5p. At last, silenced circ-HIPK2 mediated the promotion of cell proliferation, and repression of cell apoptosis was restored by ATG101 amplification. In a word, circ-HIPK2 facilitates autophagy to accelerate cell apoptosis and cell death in H2O2-caused myocardial oxidative injury through the miR-485-5p/ATG101 pathway, indicating a novel therapeutic target point for patients with myocardial injury.

PTH1-34 promotes osteoblast formation through Beclin1-dependent autophagic activation

INTRODUCTION

PTH1-34 can stimulate osteoblast formation, which contributes to the improvement of bone loss. PTH1-34 can activate autophagy, and autophagy plays a key role in osteoblast formation. This study aimed to explore the role of autophagy in PTH1-34-regulated osteoblastogenesis.

MATERIALS AND METHODS

In this study, the mice treated with ovariectomy (OVX mice) were used to observe the effect of PTH1-34 on the formation and autophagy of osteoblasts in trabecular bone in vivo. Osteoblast precursor cell line MC3T3-E1 was treated with PTH1-34, and then the autophagic parameters of osteoblast precursors (including autophagic proteins and autophagosome formation) were detected using Western Blotting and Transmission Electron Microscopy. Next, after using autophagic pharmacological inhibitor (3-MA) and silencing vectors of autophagic molecule Beclin1 to downregulate autophagic activity, the parameters related to osteogenesis (including ALP staining intensity, ALP activity, cell proliferation and osteoblastic protein expression) were evaluated using corresponding assays.

RESULTS

In vivo results showed that PTH1-34 not only improved bone loss caused by OVX but also restored Beclin1 expression and autophagic activity of immature osteoblasts in bone tissues. In vitro assays also showed that treatment of PTH1-34 enhanced the autophagy in osteoblast precursors. Moreover, under PTH1-34 intervention, the upregulated osteogenic parameters were reversed by autophagic inhibition with 3-MA. Of note, Beclin1 silencing can recover the osteogenic activity enhanced by PTH1-34.

CONCLUSION

PTH1-34 can enhance the autophagic activity of osteoblast precursors, which is involved in PTH1-34-regulated osteoblast formation. Furthermore, Beclin1, as a key autophagic regulator, plays a pivotal role in PTH1-34-regulated osteoblast precursor autophagy and osteoblastogenesis.

Age-related defects in autophagy alter the secretion of paracrine factors from bone marrow mononuclear cells

Bone marrow mononuclear cell therapy improves cardiac repair after myocardial infarction (MI), in-part through signaling to resident cardiac cells, such as fibroblasts, which regulate scar formation. The efficacy of cell therapy declines with age, as aging of both donor and recipient cells decreases repair responses. Autophagy regulates the microenvironment by both extracellular vesicle (EV)-dependent and independent secretion pathways. We hypothesized that age-related autophagy changes in bone marrow cells (BMCs) alter paracrine signaling, contributing to lower cell therapy efficacy. Here, we demonstrate that young Sca-1+ BMCs exhibited a higher LC3II/LC3I ratio compared to old Sca-1+ BMCs, which was accentuated when BMCs were cultured under hypoxia. To examine the effect on paracrine signaling, old cardiac fibroblasts were cultured with conditioned medium (CM) from young and old Sca-1+ BMCs. Young, but not old CM, enhanced fibroblast proliferation, migration, and differentiation, plus reduced senescence. These beneficial effects were lost when autophagy or EV secretion in BMCs was blocked pharmacologically, or by siRNA knockdown of Atg7. Therefore, both EV-dependent and -independent paracrine signaling from young BMCs is responsible for paracrine stimulation of old cardiac fibroblasts. In vivo, bone marrow chimerism of old mice with young BMCs increased the number of LC3b+ cells in the heart compared to old mice reconstituted with old BMCs. These data suggest that the deterioration of autophagy with aging negatively impacts the paracrine effects of BMCs, and provide mechanistic insight into the age-related decline in cell therapy efficacy that could be targeted to improve the function of old donor cells.

Role of Oxidative Stress in Reperfusion following Myocardial Ischemia and Its Treatments

Myocardial ischemia is a disease with high morbidity and mortality, for which reperfusion is currently the standard intervention. However, the reperfusion may lead to further myocardial damage, known as myocardial ischemia/reperfusion injury (MI/RI). Oxidative stress is one of the most important pathological mechanisms in reperfusion injury, which causes apoptosis, autophagy, inflammation, and some other damage in cardiomyocytes through multiple pathways, thus causing irreversible cardiomyocyte damage and cardiac dysfunction. This article reviews the pathological mechanisms of oxidative stress involved in reperfusion injury and the interventions for different pathways and targets, so as to form systematic treatments for oxidative stress-induced myocardial reperfusion injury and make up for the lack of monotherapy.

High glucose suppresses autophagy through the AMPK pathway while it induces autophagy via oxidative stress in chondrocytes

Diabetes (DB) is a risk factor for osteoarthritis progression. High glucose (HG) is one of the key pathological features of DB and has been demonstrated to induce apoptosis and senescence in chondrocytes. Autophagy is an endogenous mechanism that can protect cells against apoptosis and senescence. The effects of HG on autophagy in cells including chondrocytes have been studied; however, the results have been inconsistent. The current study aimed to elucidate the underlying mechanisms, which could be associated with the contrasting outcomes. The present study revealed that HG can induce apoptosis and senescence in chondrocytes, in addition to regulating autophagy dynamically. The present study demonstrated that HG can cause oxidative stress in chondrocytes and suppress the AMPK pathway in a dose-dependent manner. Elimination of oxidative stress by Acetylcysteine, also called N-acetyl cysteine (NAC), downregulated autophagy and alleviated HG-stimulated apoptosis and senescence, while activation of the AMPK signaling pathway by AICAR not only upregulated autophagy but also alleviated HG-stimulated apoptosis and senescence. A combined treatment of NAC and AICAR was superior to treatment with either NAC or AICAR. The study has demonstrated that HG can suppress autophagy through the AMPK pathway and induce autophagy via oxidative stress in chondrocytes.

Evidence Linking Protein Misfolding to Quality Control in Progressive Neurodegenerative Diseases

Several proteolytic systems including ubiquitin (Ub)-proteasome system (UPS), chaperonemediated autophagy (CMA), and macroautophagy are used by the mammalian cells to remove misfolded proteins (MPs). UPS mediates degradation of most of the MPs, where Ub-conjugated substrates are deubiquitinated, unfolded, and passed through the proteasome's narrow chamber, and eventually break into smaller peptides. It has been observed that the substrates that show a specific degradation signal, the KFERQ sequence motif, can be delivered to and go through CMA-mediated degradation in lysosomes. Macroautophagy can help in the degradation of substrates that are prone to aggregation and resistant to both the CMA and UPS. In the aforesaid case, cargoes are separated into autophagosomes before lysosomal hydrolase-mediated degradation. Even though the majority of the aggregated and MPs in the human proteome can be removed via cellular protein quality control (PQC), some mutant and native proteins tend to aggregate into β-sheet-rich oligomers that exhibit resistance to all identified proteolytic processes and can, therefore, grow into extracellular plaques or inclusion bodies. Indeed, the buildup of protease-resistant aggregated and MPs is a usual process underlying various protein misfolding disorders, including neurodegenerative diseases (NDs) for example Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, and prion diseases. In this article, we have focused on the contribution of PQC in the degradation of pathogenic proteins in NDs.

Exogenous Hydrogen Sulfide Plays an Important Role Through Regulating Autophagy in Ischemia/Reperfusion Injury

Ischemia/reperfusion (I/R) injury is characterized by limiting blood supply to organs, then restoring blood flow and reoxygenation. It leads to many diseases, including acute kidney injury, myocardial infarction, circulatory arrest, ischemic stroke, trauma, and sickle cell disease. Autophagy is an important and conserved cellular pathway, in which cells transfer the cytoplasmic contents to lysosomes for degradation. It plays an important role in maintaining the balance of cell synthesis, decomposition and reuse, and participates in a variety of physiological and pathological processes. Hydrogen sulfide (H₂S), along with carbon monoxide (CO) and nitric oxide (NO), is an important gas signal molecule and regulates various physiological and pathological processes. In recent years, there are many studies on the improvement of I/R injury by H₂S through regulating autophagy, but the related mechanisms are not completely clear. Therefore, we summarize the related research in the above aspects to provide theoretical reference for future in-depth research.

CREG1 improves the capacity of the skeletal muscle response to exercise endurance via modulation of mitophagy

CREG1 (cellular repressor of E1A-stimulated genes 1) is involved in tissue homeostasis and influences macroautophagy/autophagy to protect cardiovascular function. However, the physiological and pathological role of CREG1 in the skeletal muscle is not clear. Here, we established a skeletal muscle-specific creg1 knockout mouse model (creg1;Ckm-Cre) by crossing the Creg1-floxed mice (Creg1^fl/fl) with a transgenic line expressing Cre recombinase under the muscle-specific Ckm (creatine kinase, muscle) promoter. In creg1;Ckm-Cre mice, the exercise time to exhaustion and running distance were significantly reduced compared to Creg1^fl/fl mice at the age of 9 months. In addition, the administration of recombinant (re)CREG1 protein improved the motor function of 9-month-old creg1;Ckm-Cre mice. Moreover, electron microscopy images of 9-month-old creg1;Ckm-Cre mice showed that the mitochondrial quality and quantity were abnormal and associated with increased levels of PINK1 (PTEN induced putative kinase 1) and PRKN/PARKIN (parkin RBR E3 ubiquitin protein ligase) but reduced levels of the mitochondrial proteins PTGS2/COX2, COX4I1/COX4, and TOMM20. These results suggested that CREG1 deficiency accelerated the induction of mitophagy in the skeletal muscle. Mechanistically, gain-and loss-of-function mutations of Creg1 altered mitochondrial morphology and function, impairing mitophagy in C2C12 cells. Furthermore, HSPD1/HSP60 (heat shock protein 1) (401-573 aa) interacted with CREG1 (130-220 aa) to antagonize the degradation of CREG1 and was involved in the regulation of mitophagy. This was the first time to demonstrate that CREG1 localized to the mitochondria and played an important role in mitophagy modulation that determined skeletal muscle wasting during the growth process or disease conditions.Abbreviations: CCCP: carbonyl cyanide m-chlorophenylhydrazone; CKM: creatine kinase, muscle; COX4I1/COX4: cytochrome c oxidase subunit 4I1; CREG1: cellular repressor of E1A-stimulated genes 1; DMEM: dulbecco's modified eagle medium; DNM1L/DRP1: dynamin 1-like; FCCP: carbonyl cyanide p-trifluoro-methoxy phenyl-hydrazone; HSPD1/HSP60: heat shock protein 1 (chaperonin); IP: immunoprecipitation; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MFF: mitochondrial fission factor; MFN2: mitofusin 2; MYH1/MHC-I: myosin, heavy polypeptide 1, skeletal muscle, adult; OCR: oxygen consumption rate; OPA1: OPA1, mitochondrial dynamin like GTPase; PINK1: PTEN induced putative kinase 1; PPARGC1A/PGC-1α: peroxisome proliferative activated receptor, gamma, coactivator 1 alpha; PRKN/PARKIN: parkin RBR E3 ubiquitin protein ligase; PTGS2/COX2: prostaglandin-endoperoxide synthase 2; RFP: red fluorescent protein; RT-qPCR: real-time quantitative PCR; SQSTM1/p62: sequestosome 1; TFAM: transcription factor A, mitochondrial; TOMM20: translocase of outer mitochondrial membrane 20; VDAC: voltage-dependent anion channel.

Inhibiting miR-22 Alleviates Cardiac Dysfunction by Regulating Sirt1 in Septic Cardiomyopathy

High morbidity and mortality are the most typical characteristics of septic cardiomyopathy. We aimed to reveal the role of miR-22 in septic cardiomyopathy and to explore the underlying mechanisms. miR-22 cardiac-specific knockout (miR-22^cKO) mice and miR-22 cardiac-specific transgenic (miR-22^cOE) mice were subjected to a cecal ligation and puncture (CLP) operation, while a sham operation was used in the control group. The echocardiogram results suggested that miR-22^cKO CLP mice cardiac dysfunction was alleviated. The serum LDH and CK-MB were reduced in the miR-22^cKO CLP mice. As expected, there was reduced apoptosis, increased autophagy and alleviated mitochondrial dysfunction in the miR-22^cKO CLP mice, while it had contrary role in the miR-22^cOE group. Inhibiting miR-22 promoted autophagy by increasing the LC3II/GAPDH ratio and decreasing the p62 level. Additionally, culturing primary cardiomyocytes with lipopolysaccharide (LPS) simulated sepsis-induced cardiomyopathy in vitro. Inhibiting miR-22 promoted autophagic flux confirmed by an increased LC3II/GAPDH ratio and reduced p62 protein level under bafilomycin A1 conditions. Knocking out miR-22 may exert a cardioprotective effect on sepsis by increasing autophagy and decreasing apoptosis via sirt1. Our results revealed that targeting miR-22 may become a new strategy for septic cardiomyopathy treatment.

YAP plays a crucial role in the development of cardiomyopathy in lysosomal storage diseases

Lysosomal dysfunction caused by mutations in lysosomal genes results in lysosomal storage disorder (LSD), characterized by accumulation of damaged proteins and organelles in cells and functional abnormalities in major organs, including the heart, skeletal muscle, and liver. In LSD, autophagy is inhibited at the lysosomal degradation step and accumulation of autophagosomes is observed. Enlargement of the left ventricle (LV) and contractile dysfunction were observed in RagA/B cardiac-specific KO (cKO) mice, a mouse model of LSD in which lysosomal acidification is impaired irreversibly. YAP, a downstream effector of the Hippo pathway, was accumulated in RagA/B cKO mouse hearts. Inhibition of YAP ameliorated cardiac hypertrophy and contractile dysfunction and attenuated accumulation of autophagosomes without affecting lysosomal function, suggesting that YAP plays an important role in mediating cardiomyopathy in RagA/B cKO mice. Cardiomyopathy was also alleviated by downregulation of Atg7, an intervention to inhibit autophagy, whereas it was exacerbated by stimulation of autophagy. YAP physically interacted with transcription factor EB (TFEB), a master transcription factor that controls autophagic and lysosomal gene expression, thereby facilitating accumulation of autophagosomes without degradation. These results indicate that accumulation of YAP in the presence of LSD promotes cardiomyopathy by stimulating accumulation of autophagosomes through activation of TFEB.

SIRT1 attenuates sepsis-induced acute kidney injury via Beclin1 deacetylation-mediated autophagy activation

Our previous studies showed that silent mating-type information regulation 2 homologue-1 (SIRT1, a deacetylase) upregulation could attenuate sepsis-induced acute kidney injury (SAKI). Upregulated SIRT1 can deacetylate certain autophagy-related proteins (Beclin1, Atg5, Atg7 and LC3) in vitro. However, it remains unclear whether the beneficial effect of SIRT1 is related to autophagy induction and the underlying mechanism of this effect is also unknown. In the present study, caecal ligation and puncture (CLP)-induced mice, and an LPS-challenged HK-2 cell line were established to mimic a SAKI animal model and a SAKI cell model, respectively. Our results demonstrated that SIRT1 activation promoted autophagy and attenuated SAKI. SIRT1 deacetylated only Beclin1 but not the other autophagy-related proteins in SAKI. SIRT1-induced autophagy and its protective effect against SAKI were mediated by the deacetylation of Beclin1 at K430 and K437. Moreover, two SIRT1 activators, resveratrol and polydatin, attenuated SAKI in CLP-induced septic mice. Our study was the first to demonstrate the important role of SIRT1-induced Beclin1 deacetylation in autophagy and its protective effect against SAKI. These findings suggest that pharmacologic induction of autophagy via SIRT1-mediated Beclin1 deacetylation may be a promising therapeutic approach for future SAKI treatment.

Exosomal LINC00174 derived from vascular endothelial cells attenuates myocardial I/R injury via p53-mediated autophagy and apoptosis

In this study, we aim to investigate the regulation of specific long non-coding RNAs (lncRNAs) on the progression of ischemia/reperfusion (I/R) injury. We identified and characterized the exosomes derived from mouse primary aortic endothelial cells. Subsequently, we found that these exosomes expressed typical exosomal markers and high levels of LINC00174, which significantly ameliorated I/R-induced myocardial damage and suppressed the apoptosis, vacuolation, and autophagy of myocardial cells. Mechanistic approaches revealed that LINC00174 directly interacted with SRSF1 to suppress the expression of p53, thus restraining the transcription of myocardin and repressing the activation of the Akt/AMPK pathway that was crucial for autophagy initiation in I/R-induced myocardial damage. Moreover, this molecular mechanism was verified by in vivo study. In summary, exosomal LINC00174 generated from vascular endothelial cells repressed p53-mediated autophagy and apoptosis to mitigate I/R-induced myocardial damage, suggesting that targeting LINC00174 may be a novel strategy to treat I/R-induced myocardial infarction.

The Protective Effect of Cyanidin-3-Glucoside on Myocardial Ischemia-Reperfusion Injury through Ferroptosis

This study was conducted to estimate the protective effect of Cyanidin-3-glucoside (C3G) on myocardial ischemia-reperfusion (IR) injury and to explore its mechanism. The rats were subjected to left anterior descending ligation and perfusion surgery. In vitro experiments were performed on H9c2 cells using the oxygen-glucose deprivation/reoxygenation (OGD/R) model. The results showed the administration of C3G reduced the infarction area, mitigated pathological alterations, inhibited ST segment elevation, and attenuated oxidative stress and ferroptosis-related protein expression. C3G also suppressed the expressions of USP19, Beclin1, NCOA4, and LC3II/LC3I. In addition, treatment with C3G relieved oxidative stress, downregulated LC3II/LC3I, reduced autophagosome number, downregulated TfR1 expression, and upregulated the expressions of FTH1 and GPX4 in OGD/R-induced H9c2 cells. C3G could inhibit the protein levels of USP19 and LC3II. C3G promoted K11-linked ubiquitination of Beclin1. Further evidence that C3G reduced ferroptosis and ameliorated myocardial I/R injury was demonstrated with the ferroptosis promoter RSL3. Taken together, C3G could be a potential agent to protect myocardium from myocardial I/R injury.

Upregulation of Rubicon promotes autosis during myocardial ischemia/reperfusion injury

Although autophagy is generally protective, uncontrolled or excessive activation of autophagy can be detrimental. However, it is often difficult to distinguish death by autophagy from death with autophagy, and whether autophagy contributes to death in cardiomyocytes (CMs) is still controversial. Excessive activation of autophagy induces a morphologically and biochemically defined form of cell death termed autosis. Whether autosis is involved in tissue injury induced under pathologically relevant conditions is poorly understood. In the present study, myocardial ischemia/reperfusion (I/R) induced autosis in CMs, as evidenced by cell death with numerous vacuoles and perinuclear spaces, and depleted intracellular membranes. Autosis was observed frequently after 6 hours of reperfusion, accompanied by upregulation of Rubicon, attenuation of autophagic flux, and marked accumulation of autophagosomes. Genetic downregulation of Rubicon inhibited autosis and reduced I/R injury, whereas stimulation of autosis during the late phase of I/R with Tat-Beclin 1 exacerbated injury. Suppression of autosis by ouabain, a cardiac glycoside, in humanized Na+,K+-ATPase-knockin mice reduced I/R injury. Taken together, these results demonstrate that autosis is significantly involved in I/R injury in the heart and triggered by dysregulated accumulation of autophagosomes due to upregulation of Rubicon.

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

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

Protective effect of hydrogen sulfide on endothelial cells through Sirt1-FoxO1-mediated autophagy

Background

As a new member of the vasculoprotective gasotransmitter family, hydrogen sulfide (H₂S) functions similar to nitric oxide (NO) and carbon monoxide (CO). Endothelial cell (EC) death and autophagy enable cells to cope with the progression of cardiovascular diseases. However, the impacts and underlying mechanisms of H₂S in the autophagic process in ECs are not completely understood. Here, we investigated the effects of H₂S on autophagy in human vascular ECs.

Methods

Human umbilical vein endothelial cells (HUVECs) were exposed to different concentrations (0, 50, 100, 200, 500 and 1,000 µmol/L) GYY4137 (H₂S donor) for indicated times (0, 0.5, 1, 2, 4 and 8 h), with or without pre-treatment with the autophagy inhibitor 3-methyladenine (3-MA) or bafilomycin A1. HUVECs were transfected with sirtuin 1 (Sirt1) overexpression plasmids (PIRES-Sirt1), Sirt1-siRNAs or forkhead box O1 (FoxO1)-siRNA using Lipofectamine 2000. Cell autophagy was evaluated via Western blotting and fluorescence microscopy. Co-immunoprecipitation assay was used to measure acetylation level of FoxO1. The distribution of FoxO1 in the cytoplasm and nucleus was observed using Western blotting and immunofluorescence. Western blotting, flow cytometric analysis, and cell count kit-8 assay were conducted to evaluate the effect of H₂S on the oxidized low-density lipoprotein (Ox-LDL) induced apoptosis of HUVECs.

Results

Using both gain- and loss-of-function experiments, we showed that Sirt1-dependent activation of FoxO1, including its nuclear translocation and deacetylation, was critical for mediating H₂S-induced autophagy in ECs. Furthermore, H₂S-induced autophagy protected ECs from Ox-LDL-induced apoptosis by activating Sirt1.

Conclusions

These results suggest that Sirt1-mediated autophagy in ECs is a novel mechanism by which H₂S exerts vascular-protective actions.

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

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

Reproductive responses of the male Brandt’s vole, Lasiopodomys brandtii (Rodentia: Cricetidae) to tannic acid

Tannins are polyphenols that are present in various plants, and potentially contain antioxidant properties that promote reproduction in animals. This study investigated how tannic acid (TA) affects the reproductive parameters of male Brandt’s voles,Lasiopodomys brandtii(Radde, 1861). Specifically, the anti-oxidative level of serum, autophagy in the testis, and reproductive physiology were assessed in males treated with TA from the pubertal stage. Compared to the control, low dose TA enhanced relative testis and epididymis weight and sperm concentration in the epididymis, and significantly increased the level of serum superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). mRNA levels of autophagy related genes LC3 and Beclin1 decreased significantly with low dose TA compared to the control. However, compared to the control, high dose TA sharply reduced the levels of serum SOD, GSH-Px, CAT, serum testosterone (T), and mRNA level in steroidogenic acute regulatory protein (StAR) in the testis. Both sperm abnormality and mortality increased with high dose TA compared to the control and low dose TA. Collectively, this study demonstrated that TA treatment during puberty had a dose-dependent effect on the reproductive responses of male Brandt’s voles. TA might mediate autophagy in the testis, through both indirect and direct processes. TA mainly affected the reproductive function of male Brandt’s voles by regulating anti-oxidative levels. This study advances our understanding of the mechanisms by which tannins influence reproduction in herbivores.

The 14-3-3η/GSK-3β/β-catenin complex regulates EndMT induced by 27-hydroxycholesterol in HUVECs and promotes the migration of breast cancer cells

Endothelial-mesenchymal transition (EndMT) is the transformation of endothelial cell morphology to mesenchymal cell morphology, accompanied by decline of endothelial function and enhancement of mesenchymal function, which promotes tumor progression and tumor cell invasion and metastasis. 27-Hydroxycholesterol (27-HC) is a cholesterol metabolite, which has a high content in human blood. 27-HC promotes breast cancer cell proliferation, invasion, and migration. We previously showed that 27-HC promotes EndMT; however, the underlying mechanism still needs to be further explored. We studied the role of the 14-3-3η/GSK-3β/β-catenin complex in EndMT. Our results show that 27-HC induces oxidative stress in HUVECs and activates the p38 signaling pathway, thereby inhibiting the binding of 14-3-3η/GSK-3β/β-catenin, promoting the increase of free β-catenin and nuclear translocation, and finally inducing EndMT. Treatment with N-acetylcysteine (NAC) blocked 27-HC-induced ROS generation and p38 signaling pathway activation, prevented β-catenin from release from binding, and inhibited EndMT. Blocking ROS production or p38 signaling or knocking down 14-3-3η inhibited 27-HC-induced EndMT and inhibited breast cancer cell metastasis. These findings indicate 14-3-3η is necessary for interactions between the p38 kinase and the GSK-3β/β-catenin complex and serves as an adaptor to transmit the upstream kinase signal to the downstream signal, thereby promoting EndMT and breast cancer cell migration.

TXNIP/Redd1 signalling and excessive autophagy: a novel mechanism of myocardial ischaemia/reperfusion injury in mice

AIMS

Either insufficient or excessive autophagy causes cellular death and contributes to myocardial ischaemia/reperfusion (I/R) injury. However, mechanisms controlling the 'right-level' of autophagy in the heart remains unidentified. Thioredoxin-interacting protein (TXNIP) is a pro-oxidative molecule knowing to contribute to I/R injury. However, whether and how TXNIP may further inhibit suppressed autophagy or promote excessive cardiac autophagy in I/R heart has not been previously investigated.

METHODS AND RESULTS

Wild type or gene-manipulated adult male mice were subjected to myocardial I/R. TXNIP was increased in myocardium during I/R. Cardiac-specific TXNIP overexpression increased cardiomyocytes apoptosis and cardiac dysfunction, whereas cardiac-specific TXNIP knock-out significantly mitigated I/R-induced apoptosis and improved cardiac function. Importantly, TXNIP overexpression significantly promoted cardiac autophagy and TXNIP knock-out significantly inhibited cardiac autophagy. In vitro studies demonstrated that TXNIP increased autophagosome formation but inhibited autophagosome clearance during myocardial reperfusion. Atg5 siRNA significantly decreased hypoxia/reoxygenation induced apoptosis in cardiomyocytes with TXNIP overexpression. Mechanistically, TXNIP suppressed autophagosome clearance via increasing reactive oxygen species (ROS) level. However, TXNIP-increased autophagosome formation was not mediated by ROS as a ROS scavenger failed to block increased autophagosome formation in TXNIP overexpression heart. Finally, TXNIP directly interacted and stabilized Redd1 (an autophagy regulator), resulting in mTOR inhibition and autophagy activation. Redd1 knock-down significantly reduced autophagy formation and ameliorated I/R injury in TXNIP overexpression hearts.

CONCLUSIONS

Our results demonstrated that increased TXNIP-Redd1 expression is a novel signalling pathway that contributes to I/R injury by exaggerating excessive autophagy during reperfusion. These observations advance our understanding of the mechanisms of myocardial I/R injury.

Comprehensive autophagy evaluation in cardiac disease models

Autophagy is a highly conserved recycling mechanism essential for maintaining cellular homeostasis. The pathophysiological role of autophagy has been explored since its discovery 50 years ago, but interest in autophagy has grown exponentially over the last years. Many researchers around the globe have found that autophagy is a critical pathway involved in the pathogenesis of cardiac diseases. Several groups have created novel and powerful tools for gaining deeper insights into the role of autophagy in the aetiology and development of pathologies affecting the heart. Here, we discuss how established and emerging methods to study autophagy can be used to unravel the precise function of this central recycling mechanism in the cardiac system.

SMAD3 promotes autophagy dysregulation by triggering lysosome depletion in tubular epithelial cells in diabetic nephropathy

Macroautophagy/autophagy dysregulation has been noted in diabetic nephropathy; however, the regulatory mechanisms controlling this process remain unclear. In this study, we showed that SMAD3 (SMAD family member 3), the key effector of TGFB (transforming growth factor beta)-SMAD signaling, induces lysosome depletion via the inhibition of TFEB-dependent lysosome biogenesis. The pharmacological inhibition or genetic deletion of SMAD3 restored lysosome biogenesis activity by alleviating the suppression of TFEB, thereby protecting lysosomes from depletion and improving autophagic flux in renal tubular epithelial cells in diabetic nephropathy. Mechanistically, we found that SMAD3 directly binds to the 3'-UTR of TFEB and inhibits its transcription. Silencing TFEB suppressed lysosome biogenesis and resulted in a loss of the protective effects of SMAD3 inactivation on lysosome depletion under diabetic conditions. In conclusion, SMAD3 promotes lysosome depletion via the inhibition of TFEB-dependent lysosome biogenesis; this may be an important mechanism underlying autophagy dysregulation in the progression of diabetic nephropathy.Abbreviations: AGEs: advanced glycation end products; ATP6V1H: ATPase H+ transporting V1 subunit H; CTSB: cathepsin B; ChIP: chromatin immunoprecipitation; Co-BSA: control bovine serum albumin; DN: diabetic nephropathy; ELISA: enzyme-linked immunosorbent assay; FN1: fibronectin 1; HAVCR1/TIM1/KIM-1: hepatitis A virus cellular receptor 1; LAMP1: lysosomal associated membrane protein 1; LMP: lysosome membrane permeabilization; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; NC: negative control; SIS3: specific inhibitor of SMAD3; SMAD3: SMAD family member 3; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TECs: tubular epithelial cells; TFEB: transcription factor EB; TGFB1: transforming growth factor beta 1; TGFBR1: transforming growth factor beta receptor 1; UTR: untranslated region; VPS11: VPS11 core subunit of CORVET and HOPS complexes.

Interplay between reactive oxygen species and autophagy in the course of age-related macular degeneration

Pathological biomolecules such as lipofuscin, methylglyoxal-modified proteins (the major precursors of advanced glycationend products), misfolding protein deposits and dysfunctional mitochondria are source of oxidative stress and act as strong autophagic stimulators in age-related macular degeneration. Disturbed autophagy accelerates progression of the disease, since it leads to retinal cells' death and activates inflammation by the interplay with the NLRP3 inflammasome complex. Vascular dysfunction and hypoxia, as well as circulating autoantibodies against autophagy regulators (anti-S100A9, anti-ANXA5, and anti-HSPA8, A9 and B4) compromise an autophagy-mediated mechanism as well. Metformin, the autophagic stimulator, may act as a senostatic drug to inhibit the senescent phenotype in the age-related macular degeneration. PGC-1α , Sirt1 and AMPK represent new therapeutic targets for interventions in this disease.

Chloride channel 7 protects from redox status impairment-induced renal tubular epithelial cell apoptosis by activating autophagy

AIM

Chloride channel 7 (CLC-7), broadly expressed in kidney tissues, affects the lysosome degradation pathway. And redox status impairment contributes to cell apoptosis and activates autophagy flux. This study mainly investigates the role and molecular mechanism of CLC-7 in redox status impairment-induced autophagic flux and apoptosis.

MAIN METHODS

When NRK52E cells, rat renal tubular epithelial cells, were exposed to H₂O₂ treatment, apoptosis, autophagy flux, and CLC-7 expression were detected. Further investigation was done to observe the change of apoptosis and autophagy flux in renal cells under overexpression or knocking down of CLC-7. The lysosomes acidity, lysosome enzyme Cathepsin D activity and phosphorylation of Ampk/mTOR were also examined when CLC-7 was overexpressed or knocked down.

KEY FINDINGS

Redox status impairment induced apoptosis and autophagy flux in NRK52E cells and upregulated CLC-7. Overexpression of CLC-7 increased lysosome acidity and Cathepsin D activity. In cells with CLC-7 overexpression, we observed a significant increase of autophagy flux and decline of apoptosis, as well as an apparent increase of p-Ampk and decrease of p-mTOR. On the contrary, cells with knocking down CLC-7 led to opposite results.

SIGNIFICANCES

CLC-7 is essential to maintain and enhance acidity and enzyme activity in lysosome. Through activating autophagy flux, it exerts survival against renal tubular epithelial cell apoptosis induced by redox status impairment. Its function to modulate Ampk/mTOR pathway is the possible reason why CLC-7 can trigger autophagy flux.

Molecular adaptation to calsequestrin 2 (CASQ2) point mutations leading to catecholaminergic polymorphic ventricular tachycardia (CPVT): comparative analysis of R33Q and D307H mutants

Homozygous calsequestrin 2 (CASQ2) point mutations leads to catecholaminergic polymorphic ventricular tachycardia: a common pathogenetic feature appears to be the drastic reduction of mutant CASQ2 in spite of normal transcription. Comparative biochemical analysis of R33Q and D307H knock in mutant mice identifies different pathogenetic mechanisms for CASQ2 degradation and different molecular adaptive mechanisms. In particular, each CASQ2 point mutation evokes specific adaptive cellular and molecular processes in each of the four adaptive pathways investigated. Thus, similar clinical phenotypes and identical cellular mechanism for cardiac arrhythmia might imply different molecular adaptive mechanisms.

Hyperbaric oxygen protects against myocardial ischemia‑reperfusion injury through inhibiting mitochondria dysfunction and autophagy

Our previous study demonstrated that hyperbaric oxygen (HBO) improves heart function predominantly through reducing oxygen stress, modulating energy metabolism and inhibiting cell apoptosis. The present study aimed to investigate the protective effects of HBO on mitochondrial function and autophagy using rats with a ligated left anterior descending artery. The cardioprotective effects of HBO were mainly evaluated using ELISA, fluorescent probes, transmission electron microscopy and reverse transcription-quantitative PCR (RT-qPCR). HBO pretreatment for 14 days (once a day) using a 0.25 MPa chamber improved mitochondrial morphology and decreased the number of autophagic vesicles, as observed using a transmission electron microscope. HBO pretreatment significantly increased the levels of ATP, ADP, energy charge and the opening of the mitochondrial permeability transition pore, but decreased the levels of AMP, cytochrome c and reactive oxygen species. Moreover, HBO pretreatment significantly increased the gene or protein expression levels of eIF4E-binding protein 1, mammalian target of rapamycin (mTOR), mitochondrial DNA, NADH dehydrogenase subunit 1, mitofusin 1 and mitofusin 2, whereas it decreased the gene or protein expression levels of autophagy-related 5 (Atg5), cytochrome c, dynamin-related protein 1 and p53, as determined using RT-qPCR or immunohistochemistry. In conclusion, HBO treatment was observed to protect cardiomyocytes during myocardial ischemia-reperfusion injury (MIRI) by preventing mitochondrial dysfunction and inhibiting autophagy. Thus, these results provide novel evidence to support the use of HBO as a potential agent for the mitigation of MIRI.

CaMKIIδ inhibition protects against myocardial ischemia/reperfusion injury: Role of Beclin-1-dependent autophagy

Ca²⁺/calmodulin-dependent protein kinase II δ (CaMKIIδ) has been shown to play a vital role in pathological events in myocardial ischemia/reperfusion (IR) injury. Dysregulation of autophagy in cardiomyocytes is implicated in myocardial IR injury. Here, we examined whether CaMKIIδ inhibition could protect against myocardial IR injury through alleviating autophagy dysfunction and evaluated the potential role of CaMKIIδ in Beclin-1-dependent autophagy in ischemia/reperfused hearts. This study was performed using isolated perfused rat hearts and H9c2 cardiac myoblasts. KN-93, but not KN-92, inhibited the phosphorylation of CaMKIIδ at Thr286 and its substrate phospholamban at Thr17 besides the CaMKIIδ activity in myocardial IR. KN-93, but not KN-92 significantly improved post-ischemic cardiac function and reduced cell death. In cultured H9c2 cardiac myoblasts, KN-93 or CaMKIIδ siRNA, but not KN-92, attenuated simulated IR (SIR)-induced cell death. Moreover, CaMKIIδ inhibition could alleviate IR-induced autophagic dysfunction as evidenced in reduced levels of Atg5, p62, and LC3BII in isolated rat hearts and H9c2 cardiac myoblasts. Furthermore, co-treatment with bafilomycin A1, a lysosomal inhibitor, in CaMKII inhibition-treated cells suggested that CaMKII inhibition alleviated autophagic flux. CaMKIIδ inhibition mitigated the phosphorylation of Beclin-1 at Ser90. As expected, Beclin-1 siRNA significantly decreased the levels of Beclin-1 and Beclin-1 phosphorylation accompanied by partial reductions in Atg5, LC3BII, p62, cleaved caspase-3 and cytochrome c. However, Beclin-1 siRNA had little effect on CaMKIIδ phosphorylation. Taken together, these results demonstrated that CaMKIIδ inhibition reduced myocardial IR injury by improving autophagy dysfunction, and that CaMKIIδ-induced autophagy dysfunction partially depended on the phosphorylation of Beclin-1.

A Novel Cochlioquinone Derivative, CoB1, Regulates Autophagy in Pseudomonas aeruginosa Infection through the PAK1/Akt1/mTOR Signaling Pathway

Owing to multiple antibiotic resistance, Pseudomonas aeruginosa causes the most intractable infections to human beings worldwide, thus exploring novel drugs to defend against this bacterium remains of great importance. In this study, we purified a novel cochlioquinone B derivative (CoB1) from Salvia miltiorrhiza endophytic Bipolaris sorokiniana and reveal its role in host defense against P. aeruginosa infection by activating cytoprotective autophagy in alveolar macrophages (AMs) both in vivo and in vitro. Using a P. aeruginosa infection model, we observed that CoB1-treated mice manifest weakened lung injury, reduced bacterial systemic dissemination, decreased mortality, and dampened inflammatory responses, compared with the wild type littermates. We demonstrate that CoB1-induced autophagy in mouse AMs is associated with decreased PAK1 expression via the ubiquitination-mediated degradation pathway. The inhibition of PAK1 decreases the phosphorylation level of Akt, blocks the Akt/mTOR signaling pathway, and promotes the release of ULK1/2-Atg13-FIP200 complex from mTOR to initiate autophagosome formation, resulting in increased bacterial clearance capacity. Together, our results provide a molecular basis for the use of CoB1 to regulate host immune responses against P. aeruginosa infection and indicate that CoB1 is a potential option for the treatment of infection diseases.

O-GlcNAcylation Is Essential for Autophagy in Cardiomyocytes

Since both O-GlcNAcylation and autophagy sense intracellular nutrient level, the alteration of those two pathways plays substantial roles in the progression of heart failure. Hence, determining the relationship between O-GlcNAcylation and autophagy is imperative to understand, prevent, and treat heart failure. However, the mechanism on how O-GlcNAcylation regulates autophagy in the heart is poorly investigated. In this study, we demonstrated that O-GlcNAcylation is required for autophagy in cardiomyocytes by utilizing an O-linked β-N-acetylglucosamine transferase (OGT) cardiomyocyte-specific knockout mouse model for the first time. We also identified that OGT might regulate the initiation of autophagy in cardiomyocytes through promoting the activity of ULK1 by O-GlcNAcylation. In conclusion, our findings provide new insights into the molecular mechanisms underlying heart dysfunction and benefit the development of treatments for heart failure.

PKG1α Cysteine-42 Redox State Controls mTORC1 Activation in Pathological Cardiac Hypertrophy

RATIONALE

Stimulated PKG1α (protein kinase G-1α) phosphorylates TSC2 (tuberous sclerosis complex 2) at serine 1365, potently suppressing mTORC1 (mechanistic [mammalian] target of rapamycin complex 1) activation by neurohormonal and hemodynamic stress. This reduces pathological hypertrophy and dysfunction and increases autophagy. PKG1α oxidation at cysteine-42 is also induced by these stressors, which blunts its cardioprotective effects.

OBJECTIVE

We tested the dependence of mTORC1 activation on PKG1α C42 oxidation and its capacity to suppress such activation by soluble GC-1 (guanylyl cyclase 1) activation.

METHODS AND RESULTS

Cardiomyocytes expressing wild-type (WT) PKG1α (PKG1αWT) or cysteine-42 to serine mutation redox-dead (PKG1αCS/CS) were exposed to ET-1 (endothelin 1). Cells expressing PKG1αWT exhibited substantial mTORC1 activation (p70 S6K [p70 S6 kinase], 4EBP1 [elF4E binding protein-1], and Ulk1 [Unc-51-like kinase 1] phosphorylation), reduced autophagy/autophagic flux, and abnormal protein aggregation; all were markedly reversed by PKG1αCS/CS expression. Mice with global knock-in of PKG1αCS/CS subjected to pressure overload (PO) also displayed markedly reduced mTORC1 activation, protein aggregation, hypertrophy, and ventricular dysfunction versus PO in PKG1αWT mice. Cardioprotection against PO was equalized between groups by co-treatment with the mTORC1 inhibitor everolimus. TSC2-S1365 phosphorylation increased in PKG1αCS/CS more than PKG1αWT myocardium following PO. TSC2S1365A/S1365A (TSC2 S1365 phospho-null, created by a serine to alanine mutation) knock-in mice lack TSC2 phosphorylation by PKG1α, and when genetically crossed with PKG1αCS/CS mice, protection against PO-induced mTORC1 activation, cardiodepression, and mortality in PKG1αCS/CS mice was lost. Direct stimulation of GC-1 (BAY-602770) offset disparate mTORC1 activation between PKG1αWT and PKG1αCS/CS after PO and blocked ET-1 stimulated mTORC1 in TSC2S1365A-expressing myocytes.

CONCLUSIONS

Oxidation of PKG1α at C42 reduces its phosphorylation of TSC2, resulting in amplified PO-stimulated mTORC1 activity and associated hypertrophy, dysfunction, and depressed autophagy. This is ameliorated by direct GC-1 stimulation.

hUMSC transplantation restores ovarian function in POI rats by inhibiting autophagy of theca-interstitial cells via the AMPK/mTOR signaling pathway

Background

Previous studies of primary ovarian insufficiency (POI) have focused on granulosa cells (GCs) and ignored the role of theca-interstitial cells (TICs). This study aims to explore the mechanism of the protective effects of human umbilical cord-derived mesenchymal stem cells (hUMSCs) on ovarian function in POI rats by regulating autophagy of TICs.

Methods

The POI model was established in rats treated with cisplatin (CDDP). The hUMSCs were transplanted into POI rats by tail vein. Enzyme-linked immunosorbent assay (ELISA) analysis, hematoxylin and eosin (HE) staining, and immunohistochemistry were used to measure the protective effects of hUMSCs. The molecular mechanisms of injury and repairment of TICs were assessed by immunofluorescence, transmission electron microscope (TEM), flow cytometry (FCM), western blot, and quantitative real-time polymerase chain reaction (qRT-PCR).

Results

In vivo, hUMSC transplantation restored the ovarian function and alleviated the apoptosis of TICs in POI rats. In vitro, hUMSCs reduced the autophagy levels of TICs by reducing oxidative stress and regulating AMPK/mTOR signaling pathway, thereby alleviating the apoptosis of TICs.

Conclusion

This study indicates that hUMSCs protected ovarian function in POI by regulating autophagy signaling pathway AMPK/mTOR.

Reductive Stress Causes Pathological Cardiac Remodeling and Diastolic Dysfunction

Aims: Redox homeostasis is tightly controlled and regulates key cellular signaling pathways. The cell's antioxidant response provides a natural defense against oxidative stress, but excessive antioxidant generation leads to reductive stress (RS). This study elucidated how chronic RS, caused by constitutive activation of nuclear erythroid related factor-2 (caNrf2)-dependent antioxidant system, drives pathological myocardial remodeling. Results: Upregulation of antioxidant transcripts and proteins in caNrf2-TG hearts (TGL and TGH; transgenic-low and -high) dose dependently increased glutathione (GSH) redox potential and resulted in RS, which over time caused pathological cardiac remodeling identified as hypertrophic cardiomyopathy (HCM) with abnormally increased ejection fraction and diastolic dysfunction in TGH mice at 6 months of age. While the TGH mice exhibited 60% mortality at 18 months of age, the rate of survival in TGL was comparable with nontransgenic (NTG) littermates. Moreover, TGH mice had severe cardiac remodeling at ∼6 months of age, while TGL mice did not develop comparable phenotypes until 15 months, suggesting that even moderate RS may lead to irreversible damages of the heart over time. Pharmacologically blocking GSH biosynthesis using BSO (l-buthionine-SR-sulfoximine) at an early age (∼1.5 months) prevented RS and rescued the TGH mice from pathological cardiac remodeling. Here we demonstrate that chronic RS causes pathological cardiomyopathy with diastolic dysfunction in mice due to sustained activation of antioxidant signaling. Innovation and Conclusion: Our findings demonstrate that chronic RS is intolerable and adequate to induce heart failure (HF). Antioxidant-based therapeutic approaches for human HF should consider a thorough evaluation of redox state before the treatment.

Mitochondrial pyruvate and fatty acid flux modulate MICU1-dependent control of MCU activity

The tricarboxylic acid (TCA) cycle converts the end products of glycolysis and fatty acid β-oxidation into the reducing equivalents NADH and FADH2 Although mitochondrial matrix uptake of Ca2+ enhances ATP production, it remains unclear whether deprivation of mitochondrial TCA substrates alters mitochondrial Ca2+ flux. We investigated the effect of TCA cycle substrates on MCU-mediated mitochondrial matrix uptake of Ca2+, mitochondrial bioenergetics, and autophagic flux. Inhibition of glycolysis, mitochondrial pyruvate transport, or mitochondrial fatty acid transport triggered expression of the MCU gatekeeper MICU1 but not the MCU core subunit. Knockdown of mitochondrial pyruvate carrier (MPC) isoforms or expression of the dominant negative mutant MPC1R97W resulted in increased MICU1 protein abundance and inhibition of MCU-mediated mitochondrial matrix uptake of Ca2+ We also found that genetic ablation of MPC1 in hepatocytes and mouse embryonic fibroblasts resulted in reduced resting matrix Ca2+, likely because of increased MICU1 expression, but resulted in changes in mitochondrial morphology. TCA cycle substrate-dependent MICU1 expression was mediated by the transcription factor early growth response 1 (EGR1). Blocking mitochondrial pyruvate or fatty acid flux was linked to increased autophagy marker abundance. These studies reveal a mechanism that controls the MCU-mediated Ca2+ flux machinery and that depends on TCA cycle substrate availability. This mechanism generates a metabolic homeostatic circuit that protects cells from bioenergetic crisis and mitochondrial Ca2+ overload during periods of nutrient stress.

On the relevance of precision autophagy flux control in vivo - Points of departure for clinical translation

Macroautophagy (which we will call autophagy hereafter) is a critical intracellular bulk degradation system that is active at basal rates in eukaryotic cells. This process is embedded in the homeostasis of nutrient availability and cellular metabolic demands, degrading primarily long-lived proteins and specific organelles.. Autophagy is perturbed in many pathologies, and its manipulation to enhance or inhibit this pathway therapeutically has received considerable attention. Although better probes are being developed for a more precise readout of autophagic activity in vitro and increasingly in vivo, many questions remain. These center in particular around the accurate measurement of autophagic flux and its translation from the in vitro to the in vivo environment as well as its clinical application. In this review, we highlight key aspects that appear to contribute to stumbling blocks on the road toward clinical translation and discuss points of departure for reaching some of the desired goals. We discuss techniques that are well aligned with achieving desirable spatiotemporal resolution to gather data on autophagic flux in a multi-scale fashion, to better apply the existing tools that are based on single-cell analysis and to use them in the living organism. We assess how current techniques may be used for the establishment of autophagic flux standards or reference points and consider strategies for a conceptual approach on titrating autophagy inducers based on their effect on autophagic flux . Finally, we discuss potential solutions for inherent controls for autophagy analysis, so as to better discern systemic and tissue-specific autophagic flux in future clinical applications.Abbreviations: GFP: Green fluorescent protein; J: Flux; MAP1LC3/LC3: Microtubule-associated protein 1 light chain 3; nA: Number of autophagosomes; TEM: Transmission electron microscopy; τ: Transition time.

DNA Hypomethylation of miR-30a Mediated the Protection of Hypoxia Postconditioning Against Aged Cardiomyocytes Hypoxia/Reoxygenation Injury Through Inhibiting Autophagy

BACKGROUND

Ischemic postconditioning (IPostC) is an endogenous protective mechanism to reduce ischemia-reperfusion (I/R) injury. However, whether IPostC protects aged cardiomyocytes against I/R injury is not fully understood. Considering the protective function of microRNA 30a (miR-30a) against ischemia-induced injury in H9C2 cells, its role in the protective effects of IPostC on I/R injury of aged cardiomyocytes was investigated further.

METHODS AND RESULTS

To mimic I/R and IPostC in vitro, the aged cardiomyocyte model for hypoxia postconditioning (HPostC) treatment was established by 9 days of incubation with 8 mg/mL D-galactose and then followed by exposure to hypoxic environment. HPostC significantly alleviated hypoxia/reoxygenation (H/R) injury and reduced autophagy of aged cardiomyocytes, as evidenced by decreased LC3B-II expression and increased p62 by Western blot. Quantified by quantitative real-time polymerase chain reaction (qRT-PCR), miR-30a was increased in aged cardiomyocytes treated with HPostC compared with I/R injury group. Overexpression of miR-30a by LV3-rno-miR-30a mimic promoted cardioprotective effect of HPostC in aged cardiomyocytes by suppressing BECN1-mediated autophagy, all of which was abrogated by knockdown of miR-30a expression. Epigenetic analyses demonstrated that HPostC reduced DNA methyltransferase 3b-mediated DNA hypomethylation levels at miR-30a promoter, leading to upregulation of miR-30a.

CONCLUSIONS

HPostC protected aged cardiomyocytes survival against H/R injury via DNMT3b-dependent activation of miR-30a. miR-30a could be a potential therapeutic target for ischemic myocardial infarction.

Mitophagy Is Essential for Maintaining Cardiac Function During High Fat Diet-Induced Diabetic Cardiomyopathy

RATIONALE

Diabetic patients develop cardiomyopathy characterized by hypertrophy, diastolic dysfunction, and intracellular lipid accumulation, termed lipotoxicity. Diabetic hearts utilize fatty acids as a major energy source, which produces high levels of oxidative stress, thereby inducing mitochondrial dysfunction.

OBJECTIVE

To elucidate how mitochondrial function is regulated in diabetic cardiomyopathy.

METHODS AND RESULTS

Mice were fed either a normal diet or high-fat diet (HFD, 60 kcal % fat). Although autophagic flux was activated by HFD consumption, peaking at 6 weeks ( P<0.05), it was attenuated thereafter. Mitophagy, evaluated with Mito-Keima, was increased after 3 weeks of HFD feeding (mitophagy area: 8.3% per cell with normal diet and 12.4% with HFD) and continued to increase even after 2 months ( P<0.05). By isolating adult cardiomyocytes from GFP-LC3 mice fed HFD, we confirmed that mitochondria were sequestrated by LC3-positive autophagosomes during mitophagy. In wild-type mice, cardiac hypertrophy, diastolic dysfunction (end diastolic pressure-volume relationship =0.051±0.009 in normal diet and 0.11±0.004 in HFD) and lipid accumulation occurred within 2 months of HFD feeding ( P<0.05). Deletion of atg7 impaired mitophagy, increased lipid accumulation, exacerbated diastolic dysfunction (end diastolic pressure-volume relationship =0.11±0.004 in wild type and 0.152±0.019 in atg7 cKO; P<0.05) and induced systolic dysfunction (end systolic pressure-volume relationship =24.86±2.46 in wild type and 15.93±1.76 in atg7 cKO; P<0.05) during HFD feeding. Deletion of Parkin partially inhibited mitophagy, increased lipid accumulation and exacerbated diastolic dysfunction (end diastolic pressure-volume relationship =0.124±0.005 in wild type and 0.176±0.018 in Parkin KO, P<0.05) in response to HFD feeding. Injection of TB1 (Tat-Beclin1) activated mitophagy, attenuated mitochondrial dysfunction, decreased lipid accumulation, and protected against cardiac diastolic dysfunction (end diastolic pressure-volume relationship =0.110±0.009 in Control peptide and 0.078±0.015 in TB1, P<0.05) during HFD feeding.

CONCLUSIONS

Mitophagy serves as an essential quality control mechanism for mitochondria in the heart during HFD consumption. Impairment of mitophagy induces mitochondrial dysfunction and lipid accumulation, thereby exacerbating diabetic cardiomyopathy. Conversely, activation of mitophagy protects against HFD-induced diabetic cardiomyopathy.

Icariside II, a phosphodiesterase 5 inhibitor, attenuates cerebral ischaemia/reperfusion injury by inhibiting glycogen synthase kinase-3β-mediated activation of autophagy

Background and Purpose

Cerebral ischaemia/reperfusion causes exacerbated neuronal damage involving excessive autophagy and neuronal loss. The present study was designed to investigate the effect of icariside II, one of main active ingredients of Herba Epimedii on this loss and whether this is related to its PDE 5 inhibitory action.

Experimental Approach

Focal cerebral ischaemia was induced in the rat by transient middle cerebral artery occlusion over 2 hr, followed by reperfusion with icariside II, 3‐methylamphetamine or rapamycin. The effect of icariside II was determined measuring behaviour changes and the size of the infarction. The expressions of PDE 5, autophagy‐related proteins and the level of phosphorylation of glycogen synthase kinase‐3β (GSK‐3β) were determined. Cultured primary cortical neurons were subjected to oxygen and glucose deprivation followed by reoxygenation in the presence and absence of icariside II. A surface plasmon resonance assay and molecular docking were used to explore the interactions of icariside II with PDE 5 or GSK‐3β.

Key Results

Icariside II not only protected against induced ischaemic reperfusion injury in rats but also attenuated such injury in primary cortical neurons. The neuroprotective effects of icariside II on such injury were attributed to interfering with the PKG/GSK‐3β/autophagy axis by directly bounding to PDE 5 and GSK‐3β.

Conclusions and Implications

These findings indicate that icariside II attenuates cerebral I/R‐induced injury via interfering with PKG/GSK‐3β/autophagy axis. This study raises the possibility that icariside II and other PDE 5 inhibitors maybe effective in the treatment ischaemia stroke.

Cross-talk between autophagy and apoptosis regulates testicular injury/recovery induced by cadmium via PI3K with mTOR-independent pathway

Autophagy and apoptosis are two major modes of cell death. A balanced interplay between both is vital for phagocytic clearance of apoptotic testicular cells. Here, generating a SD rats model-treated with cadmium (Cd) to mimic environmental exposure on human, we show that autophagy and apoptosis present synchronous change trends in Cd-induced testicular injury/self-recovery. Further, the cross-talk of autophagy and apoptosis is investigated in four testicular cell lines (GC-1/GC-2/TM3/TM4 cells) respectively. Results reveal that Cd-exposure for five consecutive weeks induces reproductive toxicity in male rats. After one cycle of spermatogenesis within 8 weeks without Cd, toxic effects are ameliorated significantly. In vitro, we find that PI3K inhibitor 3-MA regulates apoptosis by inhibiting autophagy with mTOR-independent pathway in Cd-treated testicular cells. Conclusively, cross-talk between autophagy and apoptosis regulates testicular injury/recovery induced by Cd via PI3K with mTOR-independent pathway.

Mitochondrial Quality Control: Role in Cardiac Models of Lethal Ischemia-Reperfusion Injury

The current standard of care for acute myocardial infarction or 'heart attack' is timely restoration of blood flow to the ischemic region of the heart. While reperfusion is essential for the salvage of ischemic myocardium, re-introduction of blood flow paradoxically kills (rather than rescues) a population of previously ischemic cardiomyocytes-a phenomenon referred to as 'lethal myocardial ischemia-reperfusion (IR) injury'. There is long-standing and exhaustive evidence that mitochondria are at the nexus of lethal IR injury. However, during the past decade, the paradigm of mitochondria as mediators of IR-induced cardiomyocyte death has been expanded to include the highly orchestrated process of mitochondrial quality control. Our aims in this review are to: (1) briefly summarize the current understanding of the pathogenesis of IR injury, and (2) incorporating landmark data from a broad spectrum of models (including immortalized cells, primary cardiomyocytes and intact hearts), provide a critical discussion of the emerging concept that mitochondrial dynamics and mitophagy (the components of mitochondrial quality control) may contribute to the pathogenesis of cardiomyocyte death in the setting of ischemia-reperfusion.

Baicalein inhibits mitochondrial apoptosis induced by oxidative stress in cardiomyocytes by stabilizing MARCH5 expression

Abnormal mitochondrial fission and mitophagy participate in the pathogenesis of many cardiovascular diseases. Baicalein is a key active component in the roots of traditional Chinese medicinal herb Scutellaria baicalensis Georgi. It has been reported that baicalein can resist cardiotoxicity induced by several stress, but the mechanisms of baicalein operate in the protection of cardiomyocytes need to be researched further. Here we report that baicalein can promote cell survival under oxidative stress by up‐regulating the expression level of MARCH5 in cardiomyocytes. Pre‐treatment cells or mice with baicalein can stabilize the expression of MARCH5, which plays a crucial role in the regulation of mitochondrial network and mitophagy. Overexpressed MARCH5 is able to against H₂O₂ and ischaemia/reperfusion (I/R) stress by suppressing mitochondrial fission and enhancing mitophagy, and then attenuate cells apoptosis. Altogether, our present study investigated that baicalein exerts a protective effect through regulating KLF4‐MARCH5‐Drp1 pathway, our research also provided a novel theoretical basis for the clinical application of baicalein.

Low-dose nicotine promotes autophagy of cardiomyocytes by upregulating HO-1 expression

Nicotine as a major component of addiction in cigarettes has been reported to play protective roles in some pathological processes. It is reported that activation of the nicotinic acetylcholine receptor also has a cardioprotective effect. Thus, in our study, we investigated the effect and mechanism of nicotine on the autophagy of cardiomyocytes, and whether nicotine protects cardiomyocytes against palmitic acid (PA) injury. The results indicated that low-dose nicotine promoted neonatal mouse cardiac myocytes (NMCMs) autophagy and accelerated autophagic flux while inhibiting NMCMs apoptosis, but high-dose nicotine inhibited autophagy and promoted apoptosis. Moreover, low-dose nicotine upregulated heme oxygenase-1 (HO-1) expression and knocking down HO-1 abolished the effects of nicotine on the autophagy and apoptosis of NMCMs. Methyllycaconitine citrate (α7-nAChR blocker, MLA) inhibited HO-1 expression and the effects of nicotine on autophagy and apoptosis of NMCMs. Furthermore, low-dose nicotine improved the inhibited autophagy and increased apoptosis induced by palmitic acid (PA) in NMCMs and these effects were reversed by knocking down HO-1. In conclusion, our data suggested that low-dose nicotine promoted autophagy and inhibited apoptosis of cardiomyocytes by upregulating HO-1.

Inhibiting lysine 353 oxidation of GRP78 by a hypochlorous probe targeting endoplasmic reticulum promotes autophagy in cancer cells

The level of hypochlorous acid (HOCl) in cancer cells is higher than that in non-cancer cells. HOCl is an essential signal for the regulation of cell fate and works mainly through the protein post-translational modifications in cancer cells. However, the mechanism of HOCl regulating autophagy has not been clarified. Here we reported that a HOCl probe named ZBM-H targeted endoplasmic reticulum and induced an intact autophagy flux in lung cancer cells. Furthermore, ZBM-H promoted the binding of GRP78 to AMPK and increased the phosphorylation of AMPK in a dose- and time-dependent manner. GRP78 knockdown inhibited ZBM-H-induced AMPK phosphorylation and ZBM-H-stimulated autophagy. In addition, mass spectrometry combined with point mutation experiments revealed that ZBM-H increased GRP78 activity by inhibiting HOCl-induced lysine 353 oxidation of GRP78. Following ZBM-H treatment in vitro and in vivo, cell growth was significantly inhibited while apoptosis was induced. Nevertheless, exogenous HOCl partially reversed ZBM-H-inhibited cell growth and ZBM-H-induced GRP78 activation. In brief, we found that an endoplasmic reticulum-targeted HOCl probe named ZBM-H, acting through attenuating HOCl-induced GRP78 oxidation, inhibited tumor cell survival by promoting autophagy and apoptosis. Overall, these data demonstrated a novel mechanism of hypochlorous acid regulating autophagy by promoting the oxidation modification of GRP78.

TFEB activation in macrophages attenuates postmyocardial infarction ventricular dysfunction independently of ATG5-mediated autophagy

Lysosomes are at the epicenter of cellular processes critical for inflammasome activation in macrophages. Inflammasome activation and IL-1β secretion are implicated in myocardial infarction (MI) and resultant heart failure; however, little is known about how macrophage lysosomes regulate these processes. In mice subjected to cardiac ischemia/reperfusion (IR) injury and humans with ischemic cardiomyopathy, we observed evidence of lysosomal impairment in macrophages. Inducible macrophage-specific overexpression of transcription factor EB (TFEB), a master regulator of lysosome biogenesis (Mϕ-TFEB), attenuated postinfarction remodeling, decreased abundance of proinflammatory macrophages, and reduced levels of myocardial IL-1β compared with controls. Surprisingly, neither inflammasome suppression nor Mϕ-TFEB-mediated attenuation of postinfarction myocardial dysfunction required intact ATG5-dependent macroautophagy (hereafter termed "autophagy"). RNA-seq of flow-sorted macrophages postinfarction revealed that Mϕ-TFEB upregulated key targets involved in lysosomal lipid metabolism. Specifically, inhibition of the TFEB target, lysosomal acid lipase, in vivo abrogated the beneficial effect of Mϕ-TFEB on postinfarction ventricular function. Thus, TFEB reprograms macrophage lysosomal lipid metabolism to attenuate remodeling after IR, suggesting an alternative paradigm whereby lysosome function affects inflammation.