Mitochondrial quality control mechanisms as molecular targets in cardiac ischemiareperfusion injury

Mitochondrial unfolded protein response in ischemia-reperfusion injury

Mitochondrial unfolded protein response (UPRmt) is a mitochondrial stress response that activates the transcriptional program of mitochondrial chaperone proteins and proteases to keep protein homeostasis in mitochondria. Ischemia-reperfusion injury results in multiple severe clinical issues linked to high morbidity and mortality in various disorders. The pathophysiology and pathogenesis of ischemia-reperfusion injury are complex and multifactorial. Emerging evidence showed the roles of UPRmt signaling in ischemia-reperfusion injury. Herein, we discuss the regulatory mechanisms underlying UPRmt signaling in C. elegans and mammals. Furthermore, we review the recent studies into the roles and mechanisms of UPRmt signaling in ischemia-reperfusion injury of the heart, brain, kidney, and liver. Further research of UPRmt signaling will potentially develop novel therapeutic strategies against ischemia-reperfusion injury.

ZNF281 drives hepatocyte senescence in alcoholic liver disease by reducing HK2-stabilized PINK1/Parkin-mediated mitophagy

We investigated the role of zinc-finger protein 281 (ZNF281), a novel molecule, in ethanol-induced hepatocyte senescence and uncovered the potential mechanism. Real-time PCR, Western blot, immunofluorescence staining, and enzyme-linked immunosorbent assay were performed to explore the role of ZNF281 in hepatocyte senescence. ZNF281 expression was upregulated in both alcohol-fed mice livers and ethanol-treated hepatocytes. Silence of ZNF281 in hepatocytes using siRNA mitigated ethanol-caused decrease in cell viability and increased release of aspartate aminotransferase, alanine transaminase, and lactate dehydrogenase. ZNF281 siRNA reduced senescence-associated β-galactosidase-positive cells under ethanol exposure, abolished cell cycle arrest at G0/G1 phase, and diminished senescence-associated secretory phenotype and proinflammatory cytokines (IL-1β and IL-6) release. At molecular level, ZNF281 deficiency altered the expression profile of senescence-associated proteins including p53, p21, p16, high mobility group AT-hook 1, and phospho-histone H2A.X and telomerase-associated regulatory factors including telomerase reverse transcriptase, telomeric repeat binding factor 1 (TRF1), and TRF2. ZNF281 knockdown promoted hepatocyte recovery from ethanol-induced mitochondrial dysfunction and ROS production, which was correlated with rescuing HK2-PINK1/Parkin signalling-mediated mitophagy. Mechanistically, ZNF281 directly bound to 5'-GGCGGCGGGCGG-3' motif within HK2 promoter region and transcriptionally repressed HK2 expression. Systematic ZNF281 knockdown by adeno-associated virus encoding ZNF281 shRNA protected mice from alcohol feeding-caused hepatocyte injury and senescence. This study provides a novel factor ZNF281 as a driver of hepatocyte senescence during alcoholic liver disease.

Design and Structural Optimization of Orally Bioavailable SOS1 Inhibitors for the Treatment of KRAS-Driven Carcinoma

KRAS mutations (G12C, G12D, etc.) are implicated in the oncogenesis and progression of many refractory cancers. Son of sevenless homolog 1 (SOS1) is a key regulator of KRAS to modulate KRAS from inactive to active states. Herein, we disclosed efficacy-improving tetra-cyclic quinazoline derivatives as an enhanced scaffold for inhibiting the SOS1-KRAS interaction. Compound 37, which conjugated 1-carbonitrile-cyclopropane to tetra-cyclic quinazoline, showed a twofold higher oral drug exposure and 2.5-fold longer half-life than BI-3406 in CD-1 mouse plasma. In a Mia-paca-2 xenograft model, 37 administrated alone inhibited tumor growth by 71%. Preclinical investigations demonstrated that 37 had a limited inhibition of CYP and hERG. Overall, our studies showed that 37 was a promising drug candidate for treatment of KRAS-driven cancer.

RPRM deletion preserves hematopoietic regeneration by promoting EGFR-dependent DNA repair and hematopoietic stem cell proliferation post ionizing radiation

Reprimo (RPRM), a target gene of p53, is a known tumor suppressor. DNA damage induces RPRM, which triggers p53-dependent G2 arrest by inhibiting cyclin B1/Cdc2 complex activation and promotes DNA damage-induced apoptosis. RPRM negatively regulates ataxia-telangiectasia mutated by promoting its nuclear-cytoplasmic translocation and degradation, thus inhibiting DNA damage. Therefore, RPRM plays a crucial role in DNA damage response. Moreover, the loss of RPRM confers radioresistance in mice, which enables longer survival and less severe intestinal injury after radiation exposure. However, the role of RPRM in radiation-induced hematopoietic system injury remains unknown. Herein, utilizing a RPRM-knockout mouse model, we found that RPRM deletion did not affect steady-state hematopoiesis in mice. However, RPRM knockout significantly alleviated radiation-induced hematopoietic system injury and preserved mouse hematopoietic regeneration in hematopoietic stem cells (HSCs) against radiation-induced DNA damage. Further mechanistic studies showed that RPRM loss significantly increased EGFR expression and phosphorylation in HSCs to activate STAT3 and DNA-PKcs, thus promoting HSC DNA repair and proliferation. These findings reveal the critical role of RPRM in radiation-induced hematopoietic system injury, confirming our hypothesis that RPRM may serve as a novel target for radiation protection.

Mitochondrial quality control mechanisms as molecular targets in diabetic heart

Mitochondrial dysfunction has been regarded as a hallmark of diabetic cardiomyopathy. In addition to their canonical metabolic actions, mitochondria influence various other aspects of cardiomyocyte function, including oxidative stress, iron regulation, metabolic reprogramming, intracellular signaling transduction and cell death. These effects depend on the mitochondrial quality control (MQC) system, which includes mitochondrial dynamics, mitophagy and mitochondrial biogenesis. Mitochondria are not static entities, but dynamic units that undergo fission and fusion cycles to maintain their structural integrity. Increased mitochondrial fission elevates the number of mitochondria within cardiomyocytes, a necessary step for cardiomyocyte metabolism. Enhanced mitochondrial fusion promotes communication and cooperation between pairs of mitochondria, thus facilitating mitochondrial genomic repair and maintenance. On the contrary, erroneous fission or reduced fusion promotes the formation of mitochondrial fragments that contain damaged mitochondrial DNA and exhibit impaired oxidative phosphorylation. Under normal/physiological conditions, injured mitochondria can undergo mitophagy, a degradative process that delivers poorly structured mitochondria to lysosomes. However, defective mitophagy promotes the accumulation of nonfunctional mitochondria, which may induce cardiomyocyte death. A decline in the mitochondrial population due to mitophagy can stimulate mitochondrial biogenesis), which generates new mitochondrial offspring to maintain an adequate mitochondrial number. Energy crises or ATP deficiency also increase mitochondrial biogenesis, because mitochondrial DNA encodes 13 subunits of the electron transport chain (ETC) complexes. Disrupted mitochondrial biogenesis diminishes the mitochondrial mass, accelerates mitochondrial senescence and promotes mitochondrial dysfunction. In this review, we describe the involvement of MQC in the pathogenesis of diabetic cardiomyopathy. Besides, the potential targeted therapies that could be applied to improve MQC during diabetic cardiomyopathy are also discussed and accelerate the development of cardioprotective drugs for diabetic patients.

Targeted Mitochondrial Drugs for Treatment of Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is a complex hemodynamic pathology that is a leading cause of death worldwide and occurs in many body organs. Numerous studies have shown that mitochondria play an important role in the occurrence mechanism of ischemia-reperfusion injury and that mitochondrial structural abnormalities and dysfunction lead to the disruption of the homeostasis of the whole mitochondria. At this time, mitochondria are not just sub-organelles to produce ATP but also important targets for regulating ischemia-reperfusion injury; therefore, drugs targeting mitochondria can serve as a new strategy to treat ischemia-reperfusion injury. Based on this view, in this review, we discuss potential therapeutic agents for both mitochondrial structural abnormalities and mitochondrial dysfunction, highlighting the application and prospects of targeted mitochondrial drugs in the treatment of ischemia-reperfusion injury, and try to provide new ideas for the clinical treatment of the ischemia-reperfusion injury.

Ozone protects cardiomyocytes from myocardial ischemia-reperfusion injury through miR-200c/FOXO3 axis

PURPOSE

Myocardial ischemia-reperfusion injury (I/R) is a detrimental process contributing to the pathological progression of coronary artery diseases. Studies indicate that miRNAs are implicated in ischemic heart disease, and ozone therapy could protect the heart from ischemic heart disease. In this study, we investigated the effect of ozone on miR-200c expression and the potential role of miR-200c in an I/R myocardial injury model.

METHODS

A myocardial cellular model of I/R was established to detect the expression of miR-200c. Cardiomyocytes with I/R induction were treated with ozone as a cellular model to detect miR-200 expression and investigate its functional roles. The downstream target of miR-200c was predicted with Starbase online tools and validated by dual luciferase reporter assay. The function of miR-200c/FOXO3 axis in I/R was examined by CCK-8 proliferation and apoptotic assays.

RESULTS

miR-200c was upregulated in primary cardiomyocytes of the I/R model. In cardiomyocyte cells, cell proliferation in the I/R group was significantly impaired, which could be partially rescued by miR-200c inhibitor or ozone treatment. Cell death detected by LDH release and apoptosis assay in the I/R model could also be inhibited by miR-200c inhibitor or ozone treatment. FOXO3 was identified as a downstream target of miR-200c, which was induced by ozone treatment and suppressed by miR-200c. Silencing FOXO3 abrogated the protective effect of ozone treatment on the I/R cell model.

CONCLUSION

Overall, our results suggest that ozone plays a cardio-protective role in I/R through regulating miR-200/FOXO3 axis, and indicate that targeting miR-200/FOXO3 axis could potentially alleviate I/R.

Mitochondrial citrate accumulation drives alveolar epithelial cell necroptosis in lipopolysaccharide-induced acute lung injury

Necroptosis is the major cause of death in alveolar epithelial cells (AECs) during acute lung injury (ALI). Here, we report a previously unrecognized mechanism for necroptosis. We found an accumulation of mitochondrial citrate (citrate^mt) in lipopolysaccharide (LPS)-treated AECs because of the downregulation of Idh3α and citrate carrier (CIC, also known as Slc25a1). shRNA- or inhibitor-mediated inhibition of Idh3α and Slc25a1 induced citrate^mt accumulation and necroptosis in vitro. Mice with AEC-specific Idh3α and Slc25a1 deficiency exhibited exacerbated lung injury and AEC necroptosis. Interestingly, the overexpression of Idh3α and Slc25a1 decreased citrate^mt levels and rescued AECs from necroptosis. Mechanistically, citrate^mt accumulation induced mitochondrial fission and excessive mitophagy in AECs. Furthermore, citrate^mt directly interacted with FUN14 domain-containing protein 1 (FUNDC1) and promoted the interaction of FUNDC1 with dynamin-related protein 1 (DRP1), leading to excessive mitophagy-mediated necroptosis and thereby initiating and promoting ALI. Importantly, necroptosis induced by citrate^mt accumulation was inhibited in FUNDC1-knockout AECs. We show that citrate^mt accumulation is a novel target for protection against ALI involving necroptosis.

Vaspin Attenuates Atrial Abnormalities by Promoting ULK1/FUNDC1-Mediated Mitophagy

The worldwide incidence and prevalence of atrial fibrillation (AF) are increasing, making it a life-threatening condition due to the higher numbers of people suffering from obesity. Vaspin, an adipokine derived from epicardial adipose tissue, has been reported to reduce inflammation, inhibit apoptosis, and induce autophagy; however, its role in the pathogenesis of AF is not known. In this study, we investigated the role of vaspin in patients with AF and explored the molecular mechanisms using atrial myocytes in vitro. Our data showed that vaspin levels were significantly reduced in the plasma of patients with AF. Lower plasma levels of vaspin were also associated with a higher risk of AF in patients with obesity. Vaspin treatment in vitro alleviated cardiomyocyte injury, atrial fibrosis, atrial myocyte apoptosis, and mitochondrial injury in atrial myocytes following Ang-II stress. Moreover, our results demonstrated that vaspin protected against Ang-II-induced atrial myocyte dysfunction by inducing mitophagy. We also observed that vaspin treatment enhanced the phosphorylation of Fun14 domain-containing protein 1 (FUNDC1) at Ser17 by unc-51 like autophagy activating kinase 1 (ULK1), resulting in the induction of mitophagy. These positive effects of vaspin were reversed by ULK1 silencing in Ang-II-stimulated HL-1 cells. Our study is the first to propose that vaspin plays a vital role in AF pathogenesis via ULK1/FUNDC1-regulated mitophagy and could be a novel therapeutic target for AF.

Disruption of histamine/H1R-STAT3-SLC7A11 axis exacerbates doxorubicin-induced cardiac ferroptosis

Doxorubicin (DOX) is widely used in the treatment of various cancers, increasing the great risk of adverse cardiovascular events, while the clinical intervention effect is not ideal. Histamine has been documented to participate in pathophysiological processes of cardiovascular diseases and inflammation-associated carcinogenesis. However, the potential roles of histamine in antitumor-related cardiotoxicity have not been fully elucidated. In this study, cardiomyocytes (hiPSC-CMs, HL-1 cells) and mice were treated with DOX to establish DOX-induced cardiotoxicity (DIC) models. Histidine decarboxylase knockout mice (HDC^-/-) mice and histamine 1 receptor (H₁R) antagonist were used to explore the effect of histamine/H₁R signaling on DIC. Our results demonstrated that histamine deficiency or pharmaceutical inhibition of H₁R accelerated myocardial ferroptosis, which is responsible for the aggravated DIC both in vivo and in vitro, while the supplementation of exogenous histamine reversed these changes. Our data revealed that the dysfunction of histamine/H₁R signaling repressed the activation of transducer and activator of transcription 3 (STAT3), accompanying with decreased expression of solute carrier family7member11 (SLC7A11), a major modulator of ferroptosis. Conclusively, the disruption of histamine/H₁R axis triggered ferroptosis and exacerbated DIC possibly by modulating STAT3-SLC7A11 pathway. Our findings point to a potential therapeutic target for DIC and provide more consideration on the usage of antihistamine drugs.

Pyroptosis is a drug target for prevention of adverse cardiac remodeling: The crosstalk between pyroptosis, apoptosis, and autophagy

Acute myocardial infarction (AMI) is one of the main reasons of cardiovascular disease-related death. The introduction of percutaneous coronary intervention to clinical practice dramatically decreased the mortality rate in AMI. Adverse cardiac remodeling is a serious problem in cardiology. An increase in the effectiveness of AMI treatment and prevention of adverse cardiac remodeling is difficult to achieve without understanding the mechanisms of reperfusion cardiac injury and cardiac remodeling. Inhibition of pyroptosis prevents the development of postinfarction and pressure overload-induced cardiac remodeling, and mitigates cardiomyopathy induced by diabetes and metabolic syndrome. Therefore, it is reasonable to hypothesize that the pyroptosis inhibitors may find a role in clinical practice for treatment of AMI and prevention of cardiac remodeling, diabetes and metabolic syndrome-triggered cardiomyopathy. It was demonstrated that pyroptosis interacts closely with apoptosis and autophagy. Pyroptosis could be inhibited by nucleotide-binding oligomerization domain-like receptor with a pyrin domain 3 inhibitors, caspase-1 inhibitors, microRNA, angiotensin-converting enzyme inhibitors, angiotensin Ⅱ receptor blockers, and traditional Chinese herbal medicines.

SGLT2i reduces renal injury by improving mitochondrial metabolism and biogenesis

OBJECTIVES

Despite advances in treatment, an effective therapeutic strategy for acute kidney injury (AKI) is still lacking. Considering the widely reported clinical benefits of canagliflozin in the kidneys, we assessed the effects of canagliflozin on AKI.

METHODS

Lipopolysaccharide was used to induce AKI in the presence of canagliflozin.

RESULTS

Canagliflozin treatment reduced blood urea nitrogen and serum creatinine levels and improved the renal tubular structure in mice with lipopolysaccharide-induced septic AKI. Canagliflozin also suppressed the inflammatory response, oxidative stress and tubular cell death in the kidneys during septic AKI. In vitro, canagliflozin supplementation maintained mitochondrial function in lipopolysaccharide-treated HK-2 cells by restoring the mitochondrial membrane potential, inhibiting mitochondrial reactive oxygen species production and normalizing mitochondrial respiratory complex activity. In HK-2 cells, canagliflozin stimulated the adenosine monophosphate-activated protein kinase catalytic subunit alpha 1 (AMPKα1)/peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC1α)/nuclear respiratory factor 1 (NRF1) pathway, thus elevating the number of live and healthy mitochondria following lipopolysaccharide treatment. Inhibition of the AMPKα1/PGC1α/NRF1/mitochondrial biogenesis pathway abolished the protective effects of canagliflozin on renal cell mitochondria and tubular viability. Similarly, the protective effects of canagliflozin on kidney function and tubular structure were abrogated in AMPKα1-knockout mice.

CONCLUSIONS

Canagliflozin could be used to treat septic AKI by activating the AMPKα1/PGC1α/NRF1/mitochondrial biogenesis pathway.

Mitochondrial transplantation as a promising therapy for mitochondrial diseases

Mitochondrial diseases are a group of inherited or acquired metabolic disorders caused by mitochondrial dysfunction which may affect almost all the organs in the body and present at any age. However, no satisfactory therapeutic strategies have been available for mitochondrial diseases so far. Mitochondrial transplantation is a burgeoning approach for treatment of mitochondrial diseases by recovery of dysfunctional mitochondria in defective cells using isolated functional mitochondria. Many models of mitochondrial transplantation in cells, animals, and patients have proved effective via various routes of mitochondrial delivery. This review presents different techniques used in mitochondrial isolation and delivery, mechanisms of mitochondrial internalization and consequences of mitochondrial transplantation, along with challenges for clinical application. Despite some unknowns and challenges, mitochondrial transplantation would provide an innovative approach for mitochondrial medicine.

Ischemic Preconditioning and Postconditioning Protect the Heart by Preserving the Mitochondrial Network

Background

Mitochondria fuse to form elongated networks which are more tolerable to stress and injury. Ischemic pre- and postconditioning (IPC and IPost, respectively) are established cardioprotective strategies in the preclinical setting. Whether IPC and IPost modulates mitochondrial morphology is unknown. We hypothesize that the protective effects of IPC and IPost may be conferred via preservation of mitochondrial network.

Methods

IPC and IPost were applied to the H9c2 rat myoblast cells, isolated adult primary murine cardiomyocytes, and the Langendorff-isolated perfused rat hearts. The effects of IPC and IPost on cardiac cell death following ischemia-reperfusion injury (IRI), mitochondrial morphology, and gene expression of mitochondrial-shaping proteins were investigated.

Results

IPC and IPost successfully reduced cardiac cell death and myocardial infarct size. IPC and IPost maintained the mitochondrial network in both H9c2 and isolated adult primary murine cardiomyocytes. 2D-length measurement of the 3 mitochondrial subpopulations showed that IPC and IPost significantly increased the length of interfibrillar mitochondria (IFM). Gene expression of the pro-fusion protein, Mfn1, was significantly increased by IPC, while the pro-fission protein, Drp1, was significantly reduced by IPost in the H9c2 cells. In the primary cardiomyocytes, gene expression of both Mfn1 and Mfn2 were significantly upregulated by IPC and IPost, while Drp1 was significantly downregulated by IPost. In the Langendorff-isolated perfused heart, gene expression of Drp1 was significantly downregulated by both IPC and IPost.

Conclusion

IPC and IPost-mediated upregulation of pro-fusion proteins (Mfn1 and Mfn2) and downregulation of pro-fission (Drp1) promote maintenance of the interconnected mitochondrial network, ultimately conferring cardioprotection against IRI.

Improving the ischemia-reperfusion injury in vascularized composite allotransplantation: Clinical experience and experimental implications

Long-time ischemia worsening transplant outcomes in vascularized composite allotransplantation (VCA) is often neglected. Ischemia-reperfusion injury (IRI) is an inevitable event that follows reperfusion after a period of cold static storage. The pathophysiological mechanism activates local inflammation, which is a barrier to allograft long-term immune tolerance. The previous publications have not clearly described the relationship between the tissue damage and ischemia time, nor the rejection grade. In this review, we found that the rejection episodes and rejection grade are usually related to the ischemia time, both in clinical and experimental aspects. Moreover, we summarized the potential therapeutic measures to mitigate the ischemia-reperfusion injury. Compare to static preservation, machine perfusion is a promising method that can keep VCA tissue viability and extend preservation time, which is especially beneficial for the expansion of the donor pool and better MHC-matching.

Coronary Microvascular Dysfunction in Diabetes Mellitus: Pathogenetic Mechanisms and Potential Therapeutic Options

Diabetic patients are frequently affected by coronary microvascular dysfunction (CMD), a condition consisting of a combination of altered vasomotion and long-term structural change to coronary arterioles leading to impaired regulation of blood flow in response to changing cardiomyocyte oxygen requirements. The pathogenesis of this microvascular complication is complex and not completely known, involving several alterations among which hyperglycemia and insulin resistance play particularly central roles leading to oxidative stress, inflammatory activation and altered barrier function of endothelium. CMD significantly contributes to cardiac events such as angina or infarction without obstructive coronary artery disease, as well as heart failure, especially the phenotype associated with preserved ejection fraction, which greatly impact cardiovascular (CV) prognosis. To date, no treatments specifically target this vascular damage, but recent experimental studies and some clinical investigations have produced data in favor of potential beneficial effects on coronary micro vessels caused by two classes of glucose-lowering drugs: glucagon-like peptide 1 (GLP-1)-based therapy and inhibitors of sodium-glucose cotransporter-2 (SGLT2). The purpose of this review is to describe pathophysiological mechanisms, clinical manifestations of CMD with particular reference to diabetes, and to summarize the protective effects of antidiabetic drugs on the myocardial microvascular compartment.

Activation of the Nrf2/ARE signaling pathway protects against palmitic acid-induced renal tubular epithelial cell injury by ameliorating mitochondrial reactive oxygen species-mediated mitochondrial dysfunction

Chronic kidney disease (CKD) is often accompanied by dyslipidemia, and abnormal lipid metabolism in proximal tubule cells is considered closely related to the dysfunction of proximal tubule cells and eventually leads to accelerated kidney damage. Nuclear factor E2-related factor 2 (Nrf2), known as a redox-sensitive transcription factor, is responsible for regulating cellular redox homeostasis. However, the exact role of Nrf2 in dyslipidemia-induced dysfunction of proximal tubule cells is still not fully elucidated. In the present study, we showed that palmitic acid (PA) induced mitochondrial damage, excessive mitochondrial reactive oxygen species (ROS) (mtROS) generation, and cell injury in HK-2 cells. We further found that mtROS generation was involved in PA-induced mitochondrial dysfunction, cytoskeletal damage, and cell apoptosis in HK-2 cells. In addition, we demonstrated that the Nrf2/ARE signaling pathway was activated in PA-induced HK-2 cells and that silencing Nrf2 dramatically aggravated PA-induced mtROS production, mitochondrial damage, cytoskeletal damage and cell apoptosis in HK-2 cells. However, the mitochondrial antioxidant MitoTEMPOL effectively eliminated these negative effects of Nrf2 silencing in HK-2 cells under PA stimulation. Moreover, activation of the Nrf2/ARE signaling pathway with tBHQ attenuated renal injury, significantly reduced mtROS generation, and improved mitochondrial function in rats with HFD-induced obesity. Taken together, these results suggest that the Nrf2/ARE-mediated antioxidant response plays a protective role in hyperlipidemia-induced renal injury by ameliorating mtROS-mediated mitochondrial dysfunction and that enhancing Nrf2 antioxidant signaling provides a potential therapeutic strategy for kidney injury in CKD with hyperlipidemia.

Effect of thymoquinone on sepsis-induced cardiac damage via anti-inflammatory and anti-apoptotic mechanisms

Objective

Sepsis is a systemic and deleterious host reaction to severe infection. Cardiac dysfunction is an established serious outcome of multiorgan failure associated with this condition. Therefore, it is important to develop drugs targeting sepsis-induced cardiac damage and inflammation. Thymoquinone (TQ) has anti-inflammatory, anti-oxidant, anti-fibrotic, anti-tumor, and anti-apoptotic effects. This study examined the effects of thymoquinone on sepsis-induced cardiac damage.

Methods

Male BALB/c mice were randomly segregated into four groups: control, TQ, cecal ligation and puncture (CLP), and CLP + TQ groups. CLP was performed after gavaging the mice with TQ for 2 weeks. After 48 hours, we estimated the histopathological changes in the cardiac tissue and the serum levels of cardiac troponin-T. We evaluated the expression of factors associated with inflammation, apoptosis, oxidative stress, and the PI3K/AKT pathway.

Results

TQ significantly reduced intestinal histological alterations and inhibited the upregulation of interleukin-6, tumor necrosis factor-α, Bax, NOX4, p-PI3K, and p-AKT. TQ also increased Bcl-2, HO-1, and NRF2 expression.

Conclusion

These results suggest that TQ effectively modulates pro-inflammatory, apoptotic, oxidative stress, and PI3K/AKT pathways, making it indispensable in the treatment of sepsis-induced cardiac damage.

Preclinical multi-target strategies for myocardial ischemia-reperfusion injury

Despite promising breakthroughs in diagnosing and treating acute coronary syndromes, cardiovascular disease’s high global mortality rate remains indisputable. Nearly half of these patients died of ischemic heart disease. Primary percutaneous coronary intervention (PCI) and coronary artery bypass grafting can rapidly restore interrupted blood flow and become the most effective method for salvaging viable myocardium. However, restoring blood flow could increase the risk of other complications and myocardial cell death attributed to myocardial ischemia-reperfusion injury (IRI). How to reduce the damage of blood reperfusion to ischemic myocardium has become an urgent problem to be solved. In preclinical experiments, many treatments have substantial cardioprotective effects against myocardial IRI. However, the transition from these cardioprotective therapies to clinically beneficial therapies for patients with acute myocardial infarction remains elusive. The reasons for the failure of the clinical translation may be multi-faceted, and three points are summarized here: (1) Our understanding of the complex pathophysiological mechanisms of myocardial IRI is far from enough, and the classification of specific therapeutic targets is not rigorous, and not clear enough; (2) Most of the clinical patients have comorbidities, and single cardioprotective strategies including ischemia regulation strategies cannot exert their due cardioprotective effects under conditions of hyperglycemia, hypertension, hyperlipidemia, and aging; (3) Most preclinical experimental results are based on adult, healthy animal models. However, most clinical patients had comorbidities and received multiple drug treatments before reperfusion therapy. In 2019, COST Action proposed a multi-target drug combination initiative for prospective myocardial IRI; the optimal cardioprotective strategy may be a combination of additive or synergistic multi-target therapy, which we support. By establishing more reasonable preclinical models, screening multi-target drug combinations more in line with clinical practice will benefit the translation of clinical treatment strategies.

Angiotensin II induces podocyte metabolic reprogramming from glycolysis to glycerol-3-phosphate biosynthesis

Recent studies have reported that Angiotensin II (Ang II) contributes to podocyte injury by interfering with metabolism. Glycolysis is essential for podocytes and glycolysis abnormality is associated with glomerular injury in chronic kidney disease (CKD). Glycerol-3-phosphate (G-3-P) biosynthesis is a shunt pathway of glycolysis, in which cytosolic glycerol-3-phosphate dehydrogenase 1 (GPD1) catalyzes dihydroxyacetone phosphate (DHAP) to generate G-3-P in the presence of the NADH. G-3-P is not only a substrate in glycerophospholipids and glyceride synthesis but also can be oxidated by mitochondrial glycerol-3-phosphate dehydrogenase (GPD2) to regenerate DHAP in mitochondria. Since G-3-P biosynthesis links to glycolysis, mitochondrial metabolism and lipid synthesis, we speculate G-3-P biosynthesis abnormality is probably involved in podocyte injury. In this study, we demonstrated that Ang II upregulated GPD1 expression and increased G-3-P and glycerophospholipid syntheses in podocytes. GPD1 knockdown protected podocytes from Ang II-induced lipid accumulation and mitochondrial dysfunction. GPD1 overexpression exacerbated Ang II-induced podocyte injury. In addition, we proved that lipid accumulation and mitochondrial dysfunction were correlated with G-3-P content in podocytes. These results suggest that Ang II upregulates GPD1 and promotes G-3-P biosynthesis in podocytes, which promote lipid accumulation and mitochondrial dysfunction in podocytes.

Ischemic preconditioning/ischemic postconditioning alleviates anoxia/reoxygenation injury via the Notch1/Hes1/VDAC1 axis

Ischemic preconditioning (IPC), and ischemic postconditioning (IPost) have a significant protective effect on myocardial ischemia/reperfusion (MI/R) injury by alleviating oxidative stress and mitochondrial disturbances, although the underlying molecular mechanisms are unclear. The study was to demonstrate that cardioprotection against anoxia/reoxygenation (A/R) injury is transduced via the Notch1/Hes1/VDAC1 signaling pathway. Using mass spectrometry and tandem affinity purification (TAP), to screen for differentially expressed proteins associated with Hes1, followed by standard bioinformatics analysis. The co-immunoprecipitation (Co-IP) assay confirmed an interaction between Hes1 and VDAC1 proteins. H9c2 cells were transfected with Hes1 adenoviral N-terminal TAP vector (AD-NTAP/Hes1) and Hes1-short hairpin RNA adenoviral vector (AD-Hes1-shRNA) to establish A/R injury, IPC, and IPost models, respectively. The expression of Hes1 and VDAC1 proteins were measured by western blot analysis, while the levels of reactive oxygen species (ROS), mitochondrial membrane potential (ΔΨm), and apoptosis were evaluated by flow cytometry. AD-NTAP/Hes1 can activate the exogenous protein expression of Hes1, thus decreasing creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) activity and promoting cell viability. The study found that VDAC1 was a potential target protein for Hes1 and the overexpression of Hes1 protein expression downregulated protein expression levels of VDAC1, reduced ROS production, stabilized ΔΨm, and inhibited apoptosis in H9c2 cells. Additionally, downregulation of Hes1 protein expression also upregulated VDAC1 protein expression, increased ROS production, imbalanced ΔΨm, promoted cell apoptosis, and attenuated the cardioprotection afforded by IPC and IPost. The Notch1/Hes1 signaling pathway activated by IPC/IPost can directly downregulate the protein expression of VDAC1 and consequently relieve A/R injury.

Proteomic analyses of mitochondrial damage in postmortem beef muscles

BACKGROUND

The objective of the study was to examine the expression profiles of mitochondrial proteins in at-death and 24 h postmortem (PM) using tandem mass tag (TMT) approach to characterize the mitochondria possible mechanisms that are affiliated with tenderization.

RESULTS

Results showed that the tender meat at 24 h PM emerged with more serious mitochondrial damage. Altogether 456 mitochondrial proteins were identified, including 442 down-regulated and 14 up-regulated proteins. These differentially-expressed proteins were primarily involved in the progress of PM energy metabolism, apoptosis, and the morphological alterations of mitochondrial. Among them, 47 subunits (such as NDUFA2, COX4I1, and ATP5PB) were annotated into the oxidative phosphorylation pathway. VDAC1, VDAC2, and VDAC3 involving in the damage of MPTP, and IMMT, CHCHD3, APOL and APOO modulating the morphology of mitochondria, and DIABLO and AIFM1 released from mitochondria affect caspase's activation. HSPD1 and HSPE1 involved in apoptosis, mitochondrial physiological and morphological alterations.

CONCLUSION

The earlier-mentioned proteins were validated as potential indicators of tenderness regulated by mitochondrial damage. These results highlighted that mitochondrial damage possibly participate in PM tenderization of beef muscles by energy metabolism and cell apoptosis status. © 2022 Society of Chemical Industry.

ALOX15-launched PUFA-phospholipids peroxidation increases the susceptibility of ferroptosis in ischemia-induced myocardial damage

Myocardial ischemia/reperfusion (I/R) injury is a classic type of cardiovascular disease characterized by injury to cardiomyocytes leading to various forms of cell death. It is believed that irreversible myocardial damage resulted from I/R occurs due to oxidative stress evoked during the reperfusion phase. Here we demonstrate that ischemia triggers a specific redox reaction of polyunsaturated fatty acids (PUFA)-phospholipids in myocardial cells, which acts as a priming signaling that initiates the outbreak of robust oxidative damage in the reperfusion phase. Using animal and in vitro models, the crucial lipid species in I/R injury were identified to be oxidized PUFAs enriched phosphatidylethanolamines. Using multi-omics, arachidonic acid 15-lipoxygenase-1 (ALOX15) was identified as the primary mediator of ischemia-provoked phospholipid peroxidation, which was further confirmed using chemogenetic approaches. Collectively, our results reveal that ALOX15 induction in the ischemia phase acts as a “burning point” to ignite phospholipid oxidization into ferroptotic signals. This finding characterizes a novel molecular mechanism for myocardial ischemia injury and offers a potential therapeutic target for early intervention of I/R injury.

Mitochondrial quality control in cardiac ischemia/reperfusion injury: new insights into mechanisms and implications

The current effective method for the treatment of myocardial infarction is timely restoration of the blood supply to the ischemic area of the heart. Although reperfusion is essential for reestablishing oxygen and nutrient supplies, it often leads to additional myocardial damage, creating an important clinical dilemma. Reports from long-term studies have confirmed that mitochondrial damage is the critical mechanism in cardiac ischemia/reperfusion (I/R) injury. Mitochondria are dynamic and possess a quality control system that targets mitochondrial quantity and quality by modifying mitochondrial fusion, fission, mitophagy, and biogenesis and protein homeostasis to maintain a healthy mitochondrial network. The system of mitochondrial quality control involves complex molecular machinery that is highly interconnected and associated with pathological changes such as oxidative stress, calcium overload, and endoplasmic reticulum (ER) stress. Because of the critical role of the mitochondrial quality control systems, many reports have suggested that defects in this system are among the molecular mechanisms underlying myocardial reperfusion injury. In this review, we briefly summarize the important role of the mitochondrial quality control in cardiomyocyte function and focus on the current understanding of the regulatory mechanisms and molecular pathways involved in mitochondrial quality control in cardiac I/R damage.

Investigating the role of DNMT1 gene expression on myocardial ischemia reperfusion injury in rat and associated changes in mitochondria

Altered DNA methylation and mitochondrial dysfunction are the two key features of myocardial ischemia reperfusion injury (I/R), but their association with I/R remains unknown. In the present study, the relationship between DNA methyl transferase1 (DNMT1), the key methylation gene, and the mitochondrial quality control genes in rat heart during I/R was explored. We used the Langendorff rat heart model with 30 min of ischemia followed by 60 min of reperfusion and subsequent inhibition of DNMT1 with 5-azacytidine to evaluate the role of DNA methylation in I/R. Reperfusion significantly increased the expression of the DNMT1 gene, enzyme activity, and global DNA methylation levels, along with decreased mitochondrial copy, electron transport chain (ETC) activities, and ATP level. This was in agreement with the significant downregulation of 11 mitochondrial genes PGC-1α, TFAM, POLG, MFN1 and MFN2, FIS1, PARKIN, OPTN, ND1, ND4L, Cyt B and COX1 in I/R induced rat hearts. The expression pattern of the mitochondrial genes PGC-1α, TFAM, ND1 and Cyt B showed a significant negative correlation with DNMT1 expression. Rate pressure product, index of cardiac performance negatively correlated with DNMT1 expression (r = -0.8231, p = 0.0456). However, DNMT1 inhibited rat hearts via 5-azacytidine significantly improved the heart from I/R injury and reversed the I/R associated changes in the gene expression of TFAM, POLG, PGC-1α, ND1, COX1 and Cyt B, and improved the overall mtDNA copies, with a subsequent improvement in the ETC enzyme activity and ATP levels. To conclude, I/R augmented the DNMT1 activity with a subsequent increase in cardiac injury via downregulating the mitochondrial functional genes.

Cellular and mitochondrial quality control mechanisms in maintaining homeostasis in ageing

Aging is a natural process in all living organisms defined as destruction of cell function as a result of long-term accumulation of damages. Autophagy is a cellular house safeguard pathway which responsible for degrading damaged cellular organelles. Moreover, it maintains cellular homeostasis, control lifetime, and longevity. Damaged mitochondrial accumulation is a characteristic of aging which associated with neurodegeneration. Mitochondria functions as a principal energy source via supplying ATP through oxidative phosphorylation which serves as fuel for neuronal function. Mitophagy and mitochondrial specific autophagy plays an important role in maintenance of neuronal health via the removal of dysfunctional and aged mitochondria. The mitochondrial QC system involves different strategies for protecting against mitochondrial dysfunction and maintaining healthy mitochondria in cells. Mitochondrial function protection could be a strategy for the promotion of neuroprotection. Mitophagy, could be an effective target for drug discovery. Therefore, further detailed studies for mechanism of mitophagy will advance our mitochondrial phenotype knowledge and understanding to disease pathogenesis. This review mainly focuses on ageing mediated mechanism of autophagy and mitophagy for maintaining the cellular homeostasis and longevity.

Empagliflozin activates Wnt/β-catenin to stimulate FUNDC1-dependent mitochondrial quality surveillance against type-3 cardiorenal syndrome

Objectives

Cardiorenal syndrome type-3 (CRS-3) is an abrupt worsening of cardiac function secondary to acute kidney injury. Mitochondrial dysfunction is a key pathological mechanism of CRS-3, and empagliflozin can improve mitochondrial biology by promoting mitophagy. Here, we assessed the effects of empagliflozin on mitochondrial quality surveillance in a mouse model of CRS-3.

Methods

Cardiomyocyte-specific FUNDC1-knockout (FUNDC1^CKO) mice were subjected to CRS-3 prior to assessment of mitochondrial homeostasis in the presence or absence of empagliflozin.

Results

CRS-3 model mice exhibited lower heart function, increased inflammatory responses and exacerbated myocardial oxidative stress than sham-operated controls; however, empagliflozin attenuated these alterations. Empagliflozin stabilized the mitochondrial membrane potential, suppressed mitochondrial reactive oxygen species production, increased mitochondrial respiratory complex activity and restored the oxygen consumption rate in cardiomyocytes from CRS-3 model mice. Empagliflozin also normalized the mitochondrial morphology, mitochondrial dynamics and mitochondrial permeability transition pore opening rate in cardiomyocytes. Cardiomyocyte-specific ablation of FUN14 domain-containing protein 1 (FUNDC1) in mice abolished the protective effects of empagliflozin on mitochondrial homeostasis and myocardial performance. Empagliflozin activated β-catenin and promoted its nuclear retention, thus increasing FUNDC1-induced mitophagy in heart tissues; however, a β-catenin inhibitor reversed these effects.

Conclusions

In summary, empagliflozin activated Wnt/β-catenin to stimulate FUNDC1-dependent mitochondrial quality surveillance, ultimately improving mitochondrial function and cardiac performance during CRS-3. Thus, empagliflozin could be considered for the clinical management of heart function following acute kidney injury.

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Empagliflozin reduces myocardial damage and improves myocardial function after CRS-3.

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Empagliflozin normalizes the mitochondrial structure in cardiomyocytes during CRS-3.

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Empagliflozin attenuates cardiomyocyte mitochondrial dysfunction during CRS-3.

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Empagliflozin activates FUNDC1-dependent mitophagy and preserves mitochondrial integrity in the heart during CRS-3.

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Loss of FUNDC1 abolishes the cardioprotective effects of empagliflozin during CRS-3.

Sirt6 deficiency contributes to mitochondrial fission and oxidative damage in podocytes via ROCK1‐Drp1 signalling pathway

Objectives

Materials and Methods

Results

Conclusion

Salidroside, a phenyl ethanol glycoside from Rhodiola crenulata, orchestrates hypoxic mitochondrial dynamics homeostasis by stimulating Sirt1/p53/Drp1 signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Rhodiola crenulata is clinically used to combat hypobaric hypoxia brain injury at high altitude with the function of invigorating Qi and promoting blood circulation in Tibetan medicine. Salidroside (Sal), an active compound identified from Rhodiola species, has been shown to exert neuroprotective effects against hypoxic brain injury. However, its mitochondrial protective mechanisms remain largely unknown.

AIM OF THE STUDY

The present study aimed to explore the mitochondrial protection of Sal and the involved mechanisms related to mitochondrial dynamics homeostasis on hypoxia-induced injury of HT22 cells.

MATERIALS AND METHODS

Hypoxic condition was performed as cells cultured in a tri-gas incubator with 1% O₂, 5% CO₂ and 94% N₂. We firstly investigated the effects of different concentrations of Sal on the viability of normal or hypoxic HT22 cells. Whereafter, the levels of lactate dehydrogenase (LDH), superoxide dismutase (SOD), malondialdehyde (MDA), adenosine triphosphate (ATP) and Na⁺-K⁺-ATPase were tested by commercial kits. Meanwhile, mitochondrial superoxide, intracellular reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) were determined by specific labeled probes. Mitochondrial morphology was detected by mito-tracker green with confocal microscopy. Additionally, the potential interactions of Sal with Sirt1/p53/Drp1 signaling pathway-related proteins were predicted and tested by molecular docking and localized surface plasmon resonance (LSPR) techniques, respectively. Furthermore, the protein levels of Sirt1, p53, ac-p53, Drp1, p-Drp1(s616), Fis1 and Mfn2 were estimated by western blot analysis.

RESULTS

Sal alleviated hypoxia-induced oxidative stress in HT22 cells as evidenced by increased cell viability and SOD activity, while decreased LDH release and MDA content. The protected mitochondrial function by Sal treatment was indicated by the increases of ATP level, Na⁺-K⁺-ATPase activity and MMP. Miraculously, Sal reduced hypoxia-induced mitochondrial fission, while increased mitochondrial tubular or linear morphology. The results of molecular docking and LSPR confirmed the potential binding of Sal to proteins Sirt1, p53, Fis1 and Mfn2 with affinity values 1.38 × 10^-2, 5.26 × 10^-3, 6.46 × 10^-3 and 7.26 × 10^-3 KD, respectively. And western blot analysis further demonstrated that Sal memorably raised the levels of Sirt1 and Mfn2, while decreased the levels of ac-p53, Drp1, p-Drp1 (s616) and Fis1.

CONCLUSION

Collectively, our data confirm that Sal can maintain mitochondrial dynamics homeostasis by activating the Sirt1/p53/Drp1 signaling pathway.

In vivo and in vitro impact of atorvastatin against myocardial ischaemia-reperfusion injury by upregulation of silent information regulator l and attenuation of endoplasmic reticulum stress-induced apoptosis

We aimed to investigate the effects and mechanism of Atorvastatin on Myocardial Ischaemia-Reperfusion Injury in vitro and in vivo. The effects of Atorvastatin on Silent information regulator l (SIRT1) and endoplasmic reticulum (ER) stress were investigated in Myocardial ischaemia-reperfusion (MI/R) injury rat model and hypoxia/reoxygenation (H/R)-treated H9c2 cells. Pathological changes, inflammatory and heart injury markers, cell apoptosis and cell death, SIRT1 and cleaved Caspase-12 expressions, and ER stress relative proteins were measured through HE, enzyme-linked immunosorbent assay, quantitative TUNEL and flow cytometry, immunofluorescence and Western blotting with the assistance of the SIRT1 specific inhibitor EX527 and ER stress pathway blocker treatment. The results of our study demonstrated that atorvastatin treatment attenuated MI/R and H/R mediated inflammatory and heart injury markers, cell apoptosis and cell death, SIRT1 and cleaved Caspase-12 expressions, and ER stress relative protein levels. Finally, we found that atorvastatin reversed SIRT1 expression and blockade the ER stress pathway and increase the cardiomyocytes survival rate in the presence of MI/R and H/R. Our findings provided a new rationale for subsequent academic and clinical research on MI/R injury.

Mitochondrial Dynamics and Mitophagy in Cardiometabolic Disease

Mitochondria play a key role in cellular metabolism. Mitochondrial dynamics (fusion and fission) and mitophagy, are critical to mitochondrial function. Fusion allows organelles to share metabolites, proteins, and mitochondrial DNA, promoting complementarity between damaged mitochondria. Fission increases the number of mitochondria to ensure that they are passed on to their offspring during mitosis. Mitophagy is a process of selective removal of excess or damaged mitochondria that helps improve energy metabolism. Cardiometabolic disease is characterized by mitochondrial dysfunction, high production of reactive oxygen species, increased inflammatory response, and low levels of ATP. Cardiometabolic disease is closely related to mitochondrial dynamics and mitophagy. This paper reviewed the mechanisms of mitochondrial dynamics and mitophagy (focus on MFN1, MFN2, OPA1, DRP1, and PINK1 proteins) and their roles in diabetic cardiomyopathy, myocardial infarction, cardiac hypertrophy, heart failure, atherosclerosis, and obesity.

Mitochondrial Quality Control in the Heart: The Balance between Physiological and Pathological Stress

Alterations in mitochondrial function and morphology are critical adaptations to cardiovascular stress, working in concert in an attempt to restore organelle-level and cellular-level homeostasis. Processes that alter mitochondrial morphology include fission, fusion, mitophagy, and biogenesis, and these interact to maintain mitochondrial quality control. Not all cardiovascular stress is pathologic (e.g., ischemia, pressure overload, cardiotoxins), despite a wealth of studies to this effect. Physiological stress, such as that induced by aerobic exercise, can induce morphologic adaptations that share many common pathways with pathological stress, but in this case result in improved mitochondrial health. Developing a better understanding of the mechanisms underlying alterations in mitochondrial quality control under diverse cardiovascular stressors will aid in the development of pharmacologic interventions aimed at restoring cellular homeostasis.

P53 regulates mitochondrial biogenesis via transcriptionally induction of mitochondrial ribosomal protein L12

The well-documented tumor suppressor p53 is also a major stress response factor for its diverse regulation on cellular energetics. However, the effect of p53 on mitochondrial biogenesis, which plays a predominant role in response to the elevated energy demands, appears to be pleiotropic in various conditions and has not reached agreement. Mitochondrial ribosomal protein L12 (MRPL12), reported as a bi-functional protein for its roles in both mitochondrial ribosomes and transcriptional complexes, is a core regulatory component in mitochondrial biogenesis. Here we proved that MRPL12 is transcriptionally regulated by p53. Furthermore, the p53/MRPL12 regulation of mitochondria is part of the signaling pathway that maintains the basal mitochondrial content and positively coordinates the mitochondrial biogenesis and oxidative phosphorylation (OXPHOS) in response to metabolic perturbation. Since p53 serves as the'Guardian of the Genome', our findings may revealed a new mechanism underlying the conditions when more ATP is warranted to maintain the genome integrity and cell survival. Therefore the pharmacological intervention or metabolic modulation (e.g., through fasting or exercise) of the p53/MRPL12 pathway promises to be a therapeutic approach that can safeguard health.

The Regulation and Characterization of Mitochondrial-Derived Methylmalonic Acid in Mitochondrial Dysfunction and Oxidative Stress: From Basic Research to Clinical Practice

Methylmalonic acid (MMA) can act as a diagnosis of hereditary methylmalonic acidemia and assess the status of vitamin B12. Moreover, as a new potential biomarker, it has been widely reported to be associated with the progression and prognosis of chronic diseases such as cardiovascular events, renal insufficiency, cognitive impairment, and cancer. MMA accumulation may cause oxidative stress and impair mitochondrial function, disrupt cellular energy metabolism, and trigger cell death. This review primarily focuses on the mechanisms and epidemiology or progression in the clinical study on MMA.

Targeted mitochondrial drugs for treatment of Myocardial ischemia-reperfusion injury

Myocardial ischemia-reperfusion injury (MI/RI) refers to the further damage done to ischemic cardiomyocytes when restoring blood flow. A large body of evidence shows that MI/RI is closely associated with excessive production of mitochondrial reactive oxygen species, mitochondrial calcium overload, disordered mitochondrial energy metabolism, mitophagy, mitochondrial fission, and mitochondrial fusion. According to the way it affects mitochondria, it can be divided into mitochondrial quality abnormalities and mitochondrial quantity abnormalities. Abnormal mitochondrial quality refers to the dysfunction caused by the severe destruction of mitochondria, which then affects the balance of mitochondrial density and number, causing an abnormal mitochondrial quantity. In the past, most of the reports were limited to the study of the mechanism of myocardial ischemia-reperfusion injury, some of which involved mitochondria, but no specific countermeasures were proposed. In this review, we outline the mechanisms for treating myocardial ischemia-reperfusion injury from the direction of mitochondria and focus on targeted interventions and drugs to restore mitochondrial health during abnormal mitochondrial quality control and abnormal mitochondrial quantity control. This is an update in the field of myocardial ischemia-reperfusion injury.

Empagliflozin attenuates cardiac microvascular ischemia/reperfusion through activating the AMPKα1/ULK1/FUNDC1/mitophagy pathway

Mitophagy preserves microvascular structure and function during myocardial ischemia/reperfusion (I/R) injury. Empagliflozin, an anti-diabetes drug, may also protect mitochondria. We explored whether empagliflozin could reduce cardiac microvascular I/R injury by enhancing mitophagy. In mice, I/R injury induced luminal stenosis, microvessel wall damage, erythrocyte accumulation and perfusion defects in the myocardial microcirculation. Additionally, I/R triggered endothelial hyperpermeability and myocardial neutrophil infiltration, which upregulated adhesive factors and endothelin-1 but downregulated vascular endothelial cadherin and endothelial nitric oxide synthase in heart tissue. In vitro, I/R impaired the endothelial barrier function and integrity of cardiac microvascular endothelial cells (CMECs), while empagliflozin preserved CMEC homeostasis and thus maintained cardiac microvascular structure and function. I/R activated mitochondrial fission, oxidative stress and apoptotic signaling in CMECs, whereas empagliflozin normalized mitochondrial fission and fusion, neutralized supraphysiologic reactive oxygen species concentrations and suppressed mitochondrial apoptosis. Empagliflozin exerted these protective effects by activating FUNDC1-dependent mitophagy through the AMPKα1/ULK1 pathway. Both in vitro and in vivo, genetic ablation of AMPKα1 or FUNDC1 abolished the beneficial effects of empagliflozin on the myocardial microvasculature and CMECs. Taken together, the preservation of mitochondrial function through an activation of the AMPKα1/ULK1/FUNDC1/mitophagy pathway is the working mechanism of empagliflozin in attenuating cardiac microvascular I/R injury.

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Empagliflozin reduces I/R-induced microvascular damage.

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Empagliflozin suppresses I/R-induced endothelial cell damage.

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Empagliflozin activates FUNDC1-dependent mitophagy through the AMPKα1/ULK1 pathway.

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Ablation of FUNDC1 or AMPKα1 abolishes the protective effects of empagliflozin against I/R-induced microvascular damage.

microRNA-301a-3p is a potential biomarker in venous ulcers vein and gets involved in endothelial cell dysfunction

Venous ulcer is a common contributor to chronic venous insufficiency (CVI) of lower limbs, which seriously affects the life quality of patients. In this study, we researched the expression characteristics of microRNA-301a-3p (miR-301a-3p) in patients with CVI and investigated the impact of miR-301a-3p on the dysfunction of human umbilical vein endothelial cells (HUVECs). The plasma level of miR-301a-3p in normal controls, patients with varicose great saphenous vein, and patients with the venous ulcer of lower limbs were measured. We adopted Interleukin-1β (IL-1β), H2O2, and oxygen and glucose deprivation (OGD) to induce endothelial cell injury in vitro. In this way, we evaluated the influence of miR-301a-3p on HUVEC viability, apoptosis, inflammatory response, and oxidative stress. Our data showed that miR-301a-3p was substantially overexpressed in patients with lower limb venous ulcers. The viability of HUVECs decreased, and miR-301a-3p was up-regulated after IL-1β, H2O2, and OGD treatment. miR-301a-3p inhibition greatly ameliorated the dysfunction and cell damage of HUVECs, promoted IGF1/PI3K/Akt/PPARγ, and down-regulated NF-κB/MMPs. The phosphatidylinositol 3-kinase (PI3K) inhibitor (LY294002) or the peroxisome proliferator-activated receptor-γ (PPARγ) inhibitor (GW9661) reversed the anti-inflammatory, antioxidant, and anti-apoptotic effects mediated by miR-301a-3p down-regulation. The nuclear factor-κB (NF-κB) inhibitor lessened cell injury mediated by miR-301a-3p overexpression. In terms of the mechanism, miR-301a-3p targeted the 3'UTR of Insulin-like growth factor-1 (IGF1) and repressed the profile of IGF1. Thus, miR-301a-3p mediates venous endothelial cell damage by targeting IGF1 and regulating the IGF1/PI3K/Akt/PPARγ/NF-κB/MMPs pathway.

Autophagy and beyond: Unraveling the complexity of UNC-51-like kinase 1 (ULK1) from biological functions to therapeutic implications

UNC-51-like kinase 1 (ULK1), as a serine/threonine kinase, is an autophagic initiator in mammals and a homologous protein of autophagy related protein (Atg) 1 in yeast and of UNC-51 in Caenorhabditis elegans. ULK1 is well-known for autophagy activation, which is evolutionarily conserved in protein transport and indispensable to maintain cell homeostasis. As the direct target of energy and nutrition-sensing kinase, ULK1 may contribute to the distribution and utilization of cellular resources in response to metabolism and is closely associated with multiple pathophysiological processes. Moreover, ULK1 has been widely reported to play a crucial role in human diseases, including cancer, neurodegenerative diseases, cardiovascular disease, and infections, and subsequently targeted small-molecule inhibitors or activators are also demonstrated. Interestingly, the non-autophagy function of ULK1 has been emerging, indicating that non-autophagy-relevant ULK1 signaling network is also linked with diseases under some specific contexts. Therefore, in this review, we summarized the structure and functions of ULK1 as an autophagic initiator, with a focus on some new approaches, and further elucidated the key roles of ULK1 in autophagy and non-autophagy. Additionally, we also discussed the relationships between ULK1 and human diseases, as well as illustrated a rapid progress for better understanding of the discovery of more candidate small-molecule drugs targeting ULK1, which will provide a clue on novel ULK1-targeted therapeutics in the future.

Drp1-mediated mitochondrial fission promotes carbon tetrachloride-induced hepatic fibrogenesis in mice

Background

Mitochondrial dynamics is essential for the maintenance of healthy mitochondrial network. Emerging evidence suggests that mitochondrial dysfunction is closely linked to the pathogenesis of hepatic fibrogenesis following chronic liver injury. However, the role of dynamin-related protein 1 (Drp1)-mediated mitochondrial fission in the context of liver fibrosis remains unclear.

Methods and Results

In this study, C57BL/6 mice were used to establish a model of liver fibrosis via oral gavage with CCl4 treatment for 8 weeks. Furthermore, mitochondrial fission intervention experiments were achieved by the mitochondrial division inhibitor 1 (Mdivi-1). The results demonstrated that chronic CCl4 exposure resulted in severe hepatic fibrogenesis and mitochondrial damage. By contrast, pharmacological inhibition of mitochondrial division by Mdivi-1 substantially reduced the changes of mitochondrial dynamics and finally prevented the deposition of extracellular matrix proteins. Mechanistically, excessive mitochondrial fission may activate hepatic stellate cells through RIPK1-MLKL-dependent hepatocyte death, which ultimately promotes liver fibrosis.

Conclusion

Our study imply that inhibiting Drp1-mediated mitochondrial fission attenuates CCl4-induced liver fibrosis and may serve as a therapeutic target for retarding progression of chronic liver disease.

Pigment epithelium-derived factor maintains tight junction stability after myocardial infarction in rats through inhibition of the Wnt/β-catenin signaling pathway

PURPOSE

The impairment of the coronary microcirculatory barrier caused by acute myocardial infarction (AMI) is closely related to poor prognosis. Recently, pigment epithelial-derived factor (PEDF) has been proven to be a promising cardiovascular protective drug. In this study, we demonstrated the protective role of PEDF in endothelial tight junctions (TJs) and the vascular barrier in AMI.

MATERIALS AND METHODS

2, 3, 5-triphenyltetrazolium chloride (TTC), echocardiography and immunofluorescence staining were used to observe the size of infarcted myocardium area and cardiac function in myocardial tissue, and the distribution of tight junction proteins in human coronary endothelial cells (HCAEC). Dextran leakage assay and Transwell were used to assess the extent of vascular and HCAEC leakage. PCR and Western blot were used to detect tight junction-related mRNA and protein, and signaling pathway protein expression.

RESULTS

PEDF effectively reduced the infarction area and improved cardiac function in AMI rats, and lowered the leakage in AMI rats' angiocarpy and oxygen-glucose deprivation (OGD)-treated HCAEC. Furthermore, PEDF upregulated the expression of TJ mRNA and proteins in vivo and vitro. Mechanistically, PEDF inhibited the expression of phosphorylated low-density lipoprotein receptor-related protein 6 (p-LRP6) and active β-catenin under OGD, thus suppressing the activation of the classical Wnt pathway.

CONCLUSIONS

These novel findings demonstrated that PEDF maintained the expression of TJ proteins and endothelial barrier integrity by inhibiting the classical Wnt pathway during AMI.

Therapeutic potential of a single-dose melatonin in the attenuation of cardiac ischemia/reperfusion injury in prediabetic obese rats

Although acute melatonin treatment effectively reduces cardiac ischemia/reperfusion (I/R) injury in lean rats by modulating melatonin receptor 2 (MT2), there is no information regarding the temporal effects of melatonin administration during cardiac I/R injury in prediabetic obese rats. Prediabetic obese rats induced by chronic consumption of a high-fat diet (HFD) were used. The rats underwent a cardiac I/R surgical procedure (30-min of ischemia, followed by 120-min of reperfusion) and were randomly assigned to receive either vehicle or melatonin treatment. In the melatonin group, rats were divided into 3 different subgroups: (1) pretreatment, (2) treatment during ischemic period, (3) treatment at the reperfusion onset. In the pretreatment subgroup either a nonspecific MT blocker (Luzindole) or specific MT2 blocker (4-PPDOT) was also given to the rats prior to melatonin treatment. Pretreatment with melatonin (10 mg/kg) effectively reduced cardiac I/R injury by reducing infarct size, arrhythmia, and LV dysfunction. Reduction in impaired mitochondrial function, mitochondrial dynamic balance, oxidative stress, defective autophagy, and apoptosis were observed in rats pretreated with melatonin. Unfortunately, the cardioprotective benefits were not observed when 10-mg/kg of melatonin was acutely administered to the rats after cardiac ischemia. Thus, we increased the dose of melatonin to 20 mg/kg, and it was administered to the rats during ischemia or at the onset of reperfusion. The results showed that 20-mg/kg of melatonin effectively reduced cardiac I/R injury to a similar extent to the 10-mg/kg pretreatment regimen. The MT2 blocker inhibited the protective effects of melatonin. Acute melatonin treatment during cardiac I/R injury exerted protective effects in prediabetic obese rats. However, a higher dose of melatonin is required when given after the onset of cardiac ischemia. These effects of melatonin were mainly mediated through activation of MT2.

Mitochondrial Damage in Myocardial Ischemia/Reperfusion Injury and Application of Natural Plant Products

Ischemic heart disease (IHD) is currently one of the leading causes of death among cardiovascular diseases worldwide. In addition, blood reflow and reperfusion paradoxically also lead to further death of cardiomyocytes and increase the infarct size. Multiple evidences indicated that mitochondrial function and structural disorders were the basic driving force of IHD. We summed up the latest evidence of the basic associations and underlying mechanisms of mitochondrial damage in the event of ischemia/reperfusion (I/R) injury. This review then reviewed natural plant products (NPPs) which have been demonstrated to mitochondria-targeted therapeutic effects during I/R injury and the potential pathways involved. We realized that NPPs mainly maintained the integrality of mitochondria membrane and ameliorated dysfunction, such as improving abnormal mitochondrial calcium handling and inhibiting oxidative stress, so as to protect cardiomyocytes during I/R injury. This information will improve our knowledge of mitochondrial biology and I/R-induced injury's pathogenesis and exhibit that NPPs hold promise for translation into potential therapies that target mitochondria.

FUN14 Domain Containing 1 (FUNDC1): A Promising Mitophagy Receptor Regulating Mitochondrial Homeostasis in Cardiovascular Diseases

Mitochondria, the intracellular organelles for cellular aerobic respiration and energy production, play an important role in the regulation of cell metabolism and cell fate. Mitophagy, a selective form of autophagy, maintains dynamic homeostasis of cells through targeting long-lived or defective mitochondria for timely clearance and recycling. Dysfunction in mitophagy is involved in the molecular mechanism responsible for the onset and development of human diseases. FUN14 domain containing 1 (FUNDC1) is a mitochondrial receptor located in the outer mitochondria membrane (OMM) to govern mitophagy process. Emerging evidence has demonstrated that levels and phosphorylation states of FUNDC1 are closely related to the occurrence, progression and prognosis of cardiovascular diseases, indicating a novel role for this mitophagy receptor in the regulation of mitochondrial homeostasis in cardiovascular system. Here we review mitophagy mediated by FUNDC1 in mitochondria and its role in various forms of cardiovascular diseases.

Isoliquiritigenin Ameliorates Ischemia-Induced Myocardial Injury via Modulating the Nrf2/HO-1 Pathway in Mice

Background

Oxidative stress and inflammatory reaction play critical roles in acute myocardial infarction (AMI). Isoliquiritigenin (ISL), a flavonoid monomer extracted from licorice, has been found to have antioxidant and anti-inflammatory effects in cancer studies. Here, we tested the effect and underlying mechanisms of ISL on ischemia-induced myocardial injury in a mouse AMI model.

Methods

Adult C57BL/6 mice were pre-treated by intraperitoneal injection of ISL and/or a specific nuclear factor E2-related factor 2 (Nrf2) inhibitor ML385 for 3 days, respectively. Then, the AMI model was established by ligating the anterior descending branch of the left coronary artery. Myocardial oxidative stress status, inflammatory response, cardiac function and infarction size were assessed after 7th day of surgery.

Results

Compared with sham group, the reactive oxygen species (ROS) and malondialdehyde (MDA) level in AMI group were significantly increased. However, the superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) level were dramatically decreased. ISL treatment significantly reduced the myocardial infarction area, improved cardiac function, inhibited the production of ROS and MDA and reduced the consumption of SOD and GSH-Px. Interestingly, ISL could significantly increase nuclear Nrf2 and cytosolic heme oxygenase 1 (HO-1) level in the infarcted myocardium and reduce the oxidative stress after AMI. Also, ISL treatment dramatically inhibited the activation of myocardial NF-κB pathway and reduced the expression of pro-inflammatory factors in the AMI group. However, the administration of ML385 not only suppressed the Nrf2/HO-1 activation, the anti-oxidant and anti-inflammatory effects induced by ISL, but also attenuated the beneficial role of ISL on reducing infarct size and improving cardiac function in the mouse with AMI.

Conclusion

The results suggested that activation of Nrf2/HO-1 pathway has an essential role in ISL-induced cardiac protection by alleviating myocardial oxidative stress and inflammation response in mice with AMI.

Mitochondria-actin cytoskeleton crosstalk in cell migration

Mitochondria perform diverse functions in the cell and their roles during processes such as cell survival, differentiation, and migration are increasingly being appreciated. Mitochondrial and actin cytoskeletal networks not only interact with each other, but this multifaceted interaction shapes their functional dynamics. The interrelation between mitochondria and the actin cytoskeleton extends far beyond the requirement of mitochondrial ATP generation to power actin dynamics, and impinges upon several major aspects of cellular physiology. Being situated at the hub of cell signaling pathways, mitochondrial function can alter the activity of actin regulatory proteins and therefore modulate the processes downstream of actin dynamics such as cellular migration. As we will discuss, this regulation is highly nuanced and operates at multiple levels allowing mitochondria to occupy a strategic position in the regulation of migration, as well as pathological events that rely on aberrant cell motility such as cancer metastasis. In this review, we summarize the crosstalk that exists between mitochondria and actin regulatory proteins, and further emphasize on how this interaction holds importance in cell migration in normal as well as dysregulated scenarios as in cancer.