New roles for mitochondria in cell death in the reperfused myocardium

Effect of miR-206 on lower limb ischemia-reperfusion injury in rat and its mechanism

Lower limb ischemia-reperfusion is a common pathological process during clinical surgery. Because lower limb ischemia-reperfusion usually aggravates ischemia-induced skeletal muscle tissue injury after lower limb ischemia-reperfusion, it also causes remote organ heart, intestine, liver, lung and other injuries, and there is no effective clinical treatment for lower limb ischemia-reperfusion injury, so it is urgent to study its injury mechanism. In this study, the rat model of lower limb ischemia-reperfusion was established by clamping the femoral artery with microarterial clips, and the wall destruction such as intimal injury, cell edema, collagen degeneration, neutrophil infiltration, and elastic fiberboard injury of the femoral artery wall was detected. The expression of inflammatory factors was detected by immunohistochemistry. miR-206 preconditioning was used to observe the expression of inflammatory factors, redox status and apoptosis in the vascular wall of rats after acute limb ischemia-reperfusion. Our findings suggest that vascular endothelial cell edema increases, wall thickening, neutrophil infiltration, and elastic fiber layer damage during IRI. Inflammatory factor expression was increased in femoral artery tissue, and miR-206 expression levels were significantly down-regulated. Further studies have found that miR-206 attenuates lower limb IRI by regulating the effects of phase inflammatory factors. In this study, we investigated the effect of miR-206 on inflammatory factors and its possible role in the development of lower limb IRI, providing new research ideas for the regulatory mechanism of lower limb IRI, and providing a certain theoretical basis for the treatment of lower limb ischemia-reperfusion injury after surgery or endovascular intervention.

The protective effect of vagus nerve stimulation against myocardial ischemia/reperfusion injury: pooled review from preclinical studies

Aims: Myocardial ischemia-reperfusion (I/R) injury markedly undermines the protective benefits of revascularization, contributing to ventricular dysfunction and mortality. Due to complex mechanisms, no efficient ways exist to prevent cardiomyocyte reperfusion damage. Vagus nerve stimulation (VNS) appears as a potential therapeutic intervention to alleviate myocardial I/R injury. Hence, this meta-analysis intends to elucidate the potential cellular and molecular mechanisms underpinning the beneficial impact of VNS, along with its prospective clinical implications. Methods and Results: A literature search of MEDLINE, PubMed, Embase, and Cochrane Database yielded 10 articles that satisfied the inclusion criteria. VNS was significantly correlated with a reduced infarct size following myocardial I/R injury [Weighed mean difference (WMD): 25.24, 95% confidence interval (CI): 32.24 to 18.23, p < 0.001] when compared to the control group. Despite high heterogeneity (I2 = 95.3%, p < 0.001), sensitivity and subgroup analyses corroborated the robust efficacy of VNS in limiting infarct expansion. Moreover, meta-regression failed to identify significant influences of pre-specified covariates (i.e., stimulation type or site, VNS duration, condition, and species) on the primary estimates. Notably, VNS considerably impeded ventricular remodeling and cardiac dysfunction, as evidenced by improved left ventricular ejection fraction (LVEF) (WMD: 10.12, 95% CI: 4.28; 15.97, p = 0.001) and end-diastolic pressure (EDP) (WMD: 5.79, 95% CI: 9.84; -1.74, p = 0.005) during the reperfusion phase. Conclusion: VNS offers a protective role against myocardial I/R injury and emerges as a promising therapeutic strategy for future clinical application.

DIAPH1-MFN2 interaction regulates mitochondria-SR/ER contact and modulates ischemic/hypoxic stress

Inter-organelle contact and communication between mitochondria and sarco/endoplasmic reticulum (SR/ER) maintain cellular homeostasis and are profoundly disturbed during tissue ischemia. We tested the hypothesis that the formin Diaphanous-1 (DIAPH1), which regulates actin dynamics, signal transduction and metabolic functions, contributes to these processes. We demonstrate that DIAPH1 interacts directly with Mitofusin-2 (MFN2) to shorten mitochondria-SR/ER distance, thereby enhancing mitochondria-ER contact in cells including cardiomyocytes, endothelial cells and macrophages. Solution structure studies affirm the interaction between the Diaphanous Inhibitory Domain and the cytosolic GTPase domain of MFN2. In male rodent and human cardiomyocytes, DIAPH1-MFN2 interaction regulates mitochondrial turnover, mitophagy, and oxidative stress. Introduction of synthetic linker construct, which shorten the mitochondria-SR/ER distance, mitigated the molecular and functional benefits of DIAPH1 silencing in ischemia. This work establishes fundamental roles for DIAPH1-MFN2 interaction in the regulation of mitochondria-SR/ER contact networks. We propose that targeting pathways that regulate DIAPH1-MFN2 interactions may facilitate recovery from tissue ischemia.

Role of Mitochondrial Dynamics in Heart Diseases

Mitochondrial dynamics, including fission and fusion processes, are essential for heart health. Mitochondria, the powerhouses of cells, maintain their integrity through continuous cycles of biogenesis, fission, fusion, and degradation. Mitochondria are relatively immobile in the adult heart, but their morphological changes due to mitochondrial morphology factors are critical for cellular functions such as energy production, organelle integrity, and stress response. Mitochondrial fusion proteins, particularly Mfn1/2 and Opa1, play multiple roles beyond their pro-fusion effects, such as endoplasmic reticulum tethering, mitophagy, cristae remodeling, and apoptosis regulation. On the other hand, the fission process, regulated by proteins such as Drp1, Fis1, Mff and MiD49/51, is essential to eliminate damaged mitochondria via mitophagy and to ensure proper cell division. In the cardiac system, dysregulation of mitochondrial dynamics has been shown to cause cardiac hypertrophy, heart failure, ischemia/reperfusion injury, and various cardiac diseases, including metabolic and inherited cardiomyopathies. In addition, mitochondrial dysfunction associated with oxidative stress has been implicated in atherosclerosis, hypertension and pulmonary hypertension. Therefore, understanding and regulating mitochondrial dynamics is a promising therapeutic tool in cardiac diseases. This review summarizes the role of mitochondrial morphology in heart diseases for each mitochondrial morphology regulatory gene, and their potential as therapeutic targets to heart diseases.

Mitochondrial transfer from bone mesenchymal stem cells protects against tendinopathy both in vitro and in vivo

BACKGROUND

Although mesenchymal stem cells (MSCs) have been effective in tendinopathy, the mechanisms by which MSCs promote tendon healing have not been fully elucidated. In this study, we tested the hypothesis that MSCs transfer mitochondria to injured tenocytes in vitro and in vivo to protect against Achilles tendinopathy (AT).

METHODS

Bone marrow MSCs and H₂O₂-injured tenocytes were co-cultured, and mitochondrial transfer was visualized by MitoTracker dye staining. Mitochondrial function, including mitochondrial membrane potential, oxygen consumption rate, and adenosine triphosphate content, was quantified in sorted tenocytes. Tenocyte proliferation, apoptosis, oxidative stress, and inflammation were analyzed. Furthermore, a collagenase type I-induced rat AT model was used to detect mitochondrial transfer in tissues and evaluate Achilles tendon healing.

RESULTS

MSCs successfully donated healthy mitochondria to in vitro and in vivo damaged tenocytes. Interestingly, mitochondrial transfer was almost completely blocked by co-treatment with cytochalasin B. Transfer of MSC-derived mitochondria decreased apoptosis, promoted proliferation, and restored mitochondrial function in H₂O₂-induced tenocytes. A decrease in reactive oxygen species and pro-inflammatory cytokine levels (interleukin-6 and -1β) was observed. In vivo, mitochondrial transfer from MSCs improved the expression of tendon-specific markers (scleraxis, tenascin C, and tenomodulin) and decreased the infiltration of inflammatory cells into the tendon. In addition, the fibers of the tendon tissue were neatly arranged and the structure of the tendon was remodeled. Inhibition of mitochondrial transfer by cytochalasin B abrogated the therapeutic efficacy of MSCs in tenocytes and tendon tissues.

CONCLUSIONS

MSCs rescued distressed tenocytes from apoptosis by transferring mitochondria. This provides evidence that mitochondrial transfer is one mechanism by which MSCs exert their therapeutic effects on damaged tenocytes.

The Role of Genetic Mutations in Mitochondrial-Driven Cancer Growth in Selected Tumors: Breast and Gynecological Malignancies

There is an increasing understanding of the molecular and cytogenetic background of various tumors that helps us better conceptualize the pathogenesis of specific diseases. Additionally, in many cases, these molecular and cytogenetic alterations have diagnostic, prognostic, and/or therapeutic applications that are heavily used in clinical practice. Given that there is always room for improvement in cancer treatments and in cancer patient management, it is important to discover new therapeutic targets for affected individuals. In this review, we discuss mitochondrial changes in breast and gynecological (endometrial and ovarian) cancers. In addition, we review how the frequently altered genes in these diseases (BRCA1/2, HER2, PTEN, PIK3CA, CTNNB1, RAS, CTNNB1, FGFR, TP53, ARID1A, and TERT) affect the mitochondria, highlighting the possible associated individual therapeutic targets. With this approach, drugs targeting mitochondrial glucose or fatty acid metabolism, reactive oxygen species production, mitochondrial biogenesis, mtDNA transcription, mitophagy, or cell death pathways could provide further tailored treatment.

Disruption of mitochondrial bioenergetics, calcium retention capacity and cell viability caused by D-2-hydroxyglutaric acid in the heart

Accumulation of D-2-hydroxyglutaric acid (D-2-HG) is the biochemical hallmark of D-2-hydroxyglutaric aciduria type I and, particularly, of D-2-hydroxyglutaric aciduria type II (D2HGA2). D2HGA2 is a metabolic inherited disease caused by gain-of-function mutations in the gene isocitrate dehydrogenase 2. It is clinically characterized by neurological abnormalities and a severe cardiomyopathy whose pathogenesis is still poorly established. The present work investigated the potential cardiotoxicity D-2-HG, by studying its in vitro effects on a large spectrum of bioenergetics parameters in heart of young rats and in cultivated H9c2 cardiac myoblasts. D-2-HG impaired cellular respiration in purified mitochondrial preparations and crude homogenates from heart of young rats, as well as in digitonin-permeabilized H9c2 cells. ATP production and the activities of cytochrome c oxidase (complex IV), alpha-ketoglutarate dehydrogenase, citrate synthase and creatine kinase were also inhibited by D-2-HG, whereas the activities of complexes I, II and II-III of the respiratory chain, glutamate, succinate and malate dehydrogenases were not altered. We also found that this organic acid compromised mitochondrial Ca²⁺ retention capacity in heart mitochondrial preparations and H9c2 myoblasts. Finally, D-2-HG reduced the viability of H9c2 cardiac myoblasts, as determined by the MTT test and by propidium iodide incorporation. Noteworthy, L-2-hydroxyglutaric acid did not change some of these measurements (complex IV and creatine kinase activities) in heart preparations, indicating a selective inhibitory effect of the enantiomer D. In conclusion, it is presumed that D-2-HG-disrupts mitochondrial bioenergetics and Ca²⁺ retention capacity, which may be involved in the cardiomyopathy commonly observed in D2HGA2.

Knock-down of YME1L1 induces mitochondrial dysfunction during early porcine embryonic development

YME1L1, a mitochondrial metalloproteinase, is an Adenosine triphosphate (ATP)-dependent metalloproteinase and locates in the mitochondrial inner membrane. The protease domain of YME1L1 is oriented towards the mitochondrial intermembrane space, which modulates the mitochondrial GTPase optic atrophy type 1 (OPA1) processing. However, during embryonic development, there is no report yet about the role of YME1L1 on mitochondrial biogenesis and function in pigs. In the current study, the mRNA level of YME1L1 was knocked down by double strand RNA microinjection to the 1-cell stage embryos. The expression patterns of YME1L1 and its related proteins were performed by immunofluorescence and western blotting. To access the biological function of YME1L1, we first counted the preimplantation development rate, diameter, and total cell number of blastocyst on day-7. First, the localization of endogenous YME1L1 was found in the punctate structures of the mitochondria, and the expression level of YME1L1 is highly expressed from the 4-cell stage. Following significant knock-down of YME1L1, blastocyst rate and quality were decreased, and mitochondrial fragmentation was induced. YME1L1 knockdown induced excessive ROS production, lower mitochondrial membrane potential, and lower ATP levels. The OPA1 cleavage induced by YME1L1 knockdown was prevented by double knock-down of YME1L1 and OMA1. Moreover, cytochrome c, a pro-apoptotic signal, was released from the mitochondria after the knock-down of YME1L1. Taken together, these results indicate that YME1L1 is essential for regulating mitochondrial fission, function, and apoptosis during porcine embryo preimplantation development.

Perspectives on mitochondrial relevance in cardiac ischemia/reperfusion injury

Cardiovascular disease is the most common cause of death worldwide and in particular, ischemic heart disease holds the most considerable position. Even if it has been deeply studied, myocardial ischemia-reperfusion injury (IRI) is still a side-effect of the clinical treatment for several heart diseases: ischemia process itself leads to temporary damage to heart tissue and obviously the recovery of blood flow is promptly required even if it worsens the ischemic injury. There is no doubt that mitochondria play a key role in pathogenesis of IRI: dysfunctions of these important organelles alter cell homeostasis and survival. It has been demonstrated that during IRI the system of mitochondrial quality control undergoes alterations with the disruption of the complex balance between the processes of mitochondrial fusion, fission, biogenesis and mitophagy. The fundamental role of mitochondria is carried out thanks to the finely regulated connection to other organelles such as plasma membrane, endoplasmic reticulum and nucleus, therefore impairments of these inter-organelle communications exacerbate IRI. This review pointed to enhance the importance of the mitochondrial network in the pathogenesis of IRI with the aim to focus on potential mitochondria-targeting therapies as new approach to control heart tissue damage after ischemia and reperfusion process.

Light-Activated Gold-Selenium Core-Shell Nanocomposites with NIR-II Photoacoustic Imaging Performances for Heart-Targeted Repair

Mitochondrial dysfunction and oxidative damage represent important pathological mechanisms of myocardial ischemia-reperfusion injury (MI/RI). Searching for potential antioxidant agents to attenuate MI/RI is of great significance in clinic. Herein, gold-selenium core-shell nanostructures (AS-I/S NCs) with good near-infrared (NIR)-II photoacoustic imaging were designed for MI/RI treatment. The AS-I/S NCs after ischemic myocardium-targeted peptide (IMTP) and mitochondrial-targeted antioxidant peptide SS31 modification achieved cardiomyocytes-targeted cellular uptake and enhanced antioxidant ability and significantly inhibited oxygen-glucose deprivation-recovery (OGD/R)-induced cardiotoxicity of H9c2 cells by inhibiting the depletion of mitochondrial membrane potential (MMP) and restoring ATP synthase activity. Furthermore, the AS-I/S NCs after SS31 modification achieved mitochondria-targeted inhibition of reactive oxygen species (ROS) and subsequently attenuated oxidative damage in OGD/R-treated H9c2 cells by inhibition of apoptosis and oxidative damage, regulation of MAPKs and PI3K/AKT pathways. The in vivo AS-I/S NCs administration dramatically improved myocardial functions and angiogenesis and inhibited myocardial fibrosis through inhibiting myocardial apoptosis and oxidative damage in MI/RI of rats. Importantly, the AS-I/S NCs showed good safety and biocompatibility in vivo. Therefore, our findings validated the rational design that mitochondria-targeted selenium-gold nanocomposites could attenuate MI/RI of rats by inhibiting ROS-mediated oxidative damage and regulating MAPKs and PI3K/AKT pathways, which could be a potential therapy for the MI/RI treatment.

Connexin 43 hemichannels regulate mitochondrial ATP generation, mobilization, and mitochondrial homeostasis against oxidative stress

Oxidative stress is a major risk factor that causes osteocyte cell death and bone loss. Prior studies primarily focus on the function of cell surface expressed Cx43 channels. Here, we reported a new role of mitochondrial Cx43 (mtCx43) and hemichannels (HCs) in modulating mitochondria homeostasis and function in bone osteocytes under oxidative stress. In murine long bone osteocyte-Y4 cells, the translocation of Cx43 to mitochondria was increased under H2O2-induced oxidative stress. H2O2 increased the mtCx43 level accompanied by elevated mtCx43 HC activity, determined by dye uptake assay. Cx43 knockdown (KD) by the CRISPR-Cas9 lentivirus system resulted in impairment of mitochondrial function, primarily manifested as decreased ATP production. Cx43 KD had reduced intracellular reactive oxidative species levels and mitochondrial membrane potential. Additionally, live-cell imaging results demonstrated that the proton flux was dependent on mtCx43 HCs because its activity was specifically inhibited by an antibody targeting Cx43 C-terminus. The co-localization and interaction of mtCx43 and ATP synthase subunit F (ATP5J2) were confirmed by Förster resonance energy transfer and a protein pull-down assay. Together, our study suggests that mtCx43 HCs regulate mitochondrial ATP generation by mediating K+, H+, and ATP transfer across the mitochondrial inner membrane and the interaction with mitochondrial ATP synthase, contributing to the maintenance of mitochondrial redox levels in response to oxidative stress.

A Comprehensive Review on Beneficial Effects of Catechins on Secondary Mitochondrial Diseases

Mitochondria are the main sites for oxidative phosphorylation and synthesis of adenosine triphosphate in cells, and are known as cellular power factories. The phrase "secondary mitochondrial diseases" essentially refers to any abnormal mitochondrial function other than primary mitochondrial diseases, i.e., the process caused by the genes encoding the electron transport chain (ETC) proteins directly or impacting the production of the machinery needed for ETC. Mitochondrial diseases can cause adenosine triphosphate (ATP) synthesis disorder, an increase in oxygen free radicals, and intracellular redox imbalance. It can also induce apoptosis and, eventually, multi-system damage, which leads to neurodegenerative disease. The catechin compounds rich in tea have attracted much attention due to their effective antioxidant activity. Catechins, especially acetylated catechins such as epicatechin gallate (ECG) and epigallocatechin gallate (EGCG), are able to protect mitochondria from reactive oxygen species. This review focuses on the role of catechins in regulating cell homeostasis, in which catechins act as a free radical scavenger and metal ion chelator, their protective mechanism on mitochondria, and the protective effect of catechins on mitochondrial deoxyribonucleic acid (DNA). This review highlights catechins and their effects on mitochondrial functional metabolic networks: regulating mitochondrial function and biogenesis, improving insulin resistance, regulating intracellular calcium homeostasis, and regulating epigenetic processes. Finally, the indirect beneficial effects of catechins on mitochondrial diseases are also illustrated by the warburg and the apoptosis effect. Some possible mechanisms are shown graphically. In addition, the bioavailability of catechins and peracetylated-catechins, free radical scavenging activity, mitochondrial activation ability of the high-molecular-weight polyphenol, and the mitochondrial activation factor were also discussed.

Uncovering the Effect and Mechanism of Rhizoma Corydalis on Myocardial Infarction Through an Integrated Network Pharmacology Approach and Experimental Verification

Background: Myocardial infarction (MI), characterized by reduced blood flow to the heart, is a coronary artery disorder with the highest morbidity and mortality among cardiovascular diseases. Consequently, there is an urgent need to identify effective drugs to treat MI. Rhizoma Corydalis (RC) is the dry tuber of Corydalis yanhusuo W.T. Wang, and is extensively applied in treating MI clinically in China. Its underlying pharmacological mechanism remains unknown. This study aims to clarify the molecular mechanism of RC on MI by utilizing network pharmacology and experimental verification.

Methods: Based on network pharmacology, the potential targets of the RC ingredients and MI-related targets were collected from the databases. Furthermore, core targets of RC on MI were identified by the protein-protein interaction (PPI) network and analyzed with Gene Ontology (GO) analysis and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Molecular docking was used to validate the binding affinity between the core targets and the bioactive components. Oxygen-glucose deprivation (OGD) was performed on H9c2 cells to mimic MI in vitro. A Cell Counting Kit-8 assay was used to assess the cardioprotective effect of the active ingredient against OGD. Western blot analysis and RT-qPCR were used to measure the cell apoptosis and inflammation level of H9c2 cells.

Results: The network pharmacology obtained 60 bioactive components of RC, 431 potential targets, and 1131 MI-related targets. In total, 126 core targets were screened according to topological analysis. KEGG results showed that RC was closely related to the phosphatidylinositol 3-kinase (PI3K)/Protein kinase B (PKB, also called Akt) signaling pathway. The experimental validation data showed that tetrahydropalmatine (THP) pretreatment preserved cell viability after OGD exposure. THP suppressed cardiomyocyte apoptosis and inflammation induced by OGD, while LY294002 blocked the inhibition effect of THP on OGD-induced H9c2 cell injury. Moreover, the molecular docking results indicated that THP had the strongest binding affinity with Akt over berberine, coptisine, palmatine, and quercetin.

Conclusion: THP, the active ingredient of RC, can suppress OGD-induced H9c2 cell injury by activating the PI3K/Akt pathway, which in turn provides a scientific basis for a novel strategy for MI therapy and RC application.

NEU1 Regulates Mitochondrial Energy Metabolism and Oxidative Stress Post-myocardial Infarction in Mice via the SIRT1/PGC-1 Alpha Axis

Objective

Neuraminidase 1 (NEU1) participates in the response to multiple receptor signals and regulates various cellular metabolic behaviors. Importantly, it is closely related to the occurrence and progression of cardiovascular diseases. Because ischemic heart disease is often accompanied by impaired mitochondrial energy metabolism and oxidative stress. The purpose of this study was to investigate the functions and possible mechanisms of NEU1 in myocardial remodeling and mitochondrial metabolism induced by myocardial infarction (MI).

Methods

In this study, the MI-induced mouse mode, hypoxia-treated H9C2 cells model, and hypoxia-treated neonatal rat cardiomyocytes (NRCMs) model were constructed. Echocardiography and histological analysis were adopted to evaluate the morphology and function of the heart at the whole heart level. Western blot was adopted to determine the related expression level of signaling pathway proteins and mitochondria. Mitochondrial energy metabolism and oxidative stress were detected by various testing kits.

Results

Neuraminidase 1 was markedly upregulated in MI cardiac tissue. Cardiomyocyte-specific NEU1 deficiency restored cardiac function, cardiac hypertrophy, and myocardial interstitial fibrosis. What is more, cardiomyocyte-specific NEU1 deficiency inhibited mitochondrial dysfunction and oxidative stress induced by MI. Further experiments found that the sirtuin-1/peroxisome proliferator-activated receptor γ coactivator α (SIRT1/PGC-1α) protein level in MI myocardium was down-regulated, which was closely related to the above-mentioned mitochondrial changes. Cardiomyocyte-specific NEU1 deficiency increased the expression of SIRT1, PGC-1α, and mitochondrial transcription factor A (TFAM); which improved mitochondrial metabolism and oxidative stress. Inhibition of SIRT1 activity or PGC-1α activity eliminated the beneficial effects of cardiomyocyte-specific NEU1 deficiency. PGC-1α knockout mice experiments verified that NEU1 inhibition restored cardiac function induced by MI through SIRT1/PGC-1α signaling pathway.

Conclusion

Cardiomyocyte-specific NEU1 deficiency can alleviate MI-induced myocardial remodeling, oxidative stress, and mitochondrial energy metabolism disorder. In terms of mechanism, the specific deletion of NEU1 may play a role by enhancing the SIRT1/PGC-1α signaling pathway. Therefore, cardiomyocyte-specific NEU1 may provide an alternative treatment strategy for heart failure post-MI.

Mitochondrial DNA Release Contributes to Intestinal Ischemia/Reperfusion Injury

Mitochondria release many damage-associated molecular patterns (DAMPs) when cells are damaged or stressed, with mitochondrial DNA (mtDNA) being. MtDNA activates innate immune responses and induces inflammation through the TLR-9, NLRP3 inflammasome, and cGAS-STING signaling pathways. Released inflammatory factors cause damage to intestinal barrier function. Many bacteria and endotoxins migrate to the circulatory system and lymphatic system, leading to systemic inflammatory response syndrome (SIRS) and even damaging the function of multiple organs throughout the body. This process may ultimately lead to multiple organ dysfunction syndrome (MODS). Recent studies have shown that various factors, such as the release of mtDNA and the massive infiltration of inflammatory factors, can cause intestinal ischemia/reperfusion (I/R) injury. This destroys intestinal barrier function, induces an inflammatory storm, leads to SIRS, increases the vulnerability of organs, and develops into MODS. Mitophagy eliminates dysfunctional mitochondria to maintain cellular homeostasis. This review discusses mtDNA release during the pathogenesis of intestinal I/R and summarizes methods for the prevention or treatment of intestinal I/R. We also discuss the effects of inflammation and increased intestinal barrier permeability on drugs.

SOCS6 Promotes Mitochondrial Fission and Cardiomyocyte Apoptosis and Is Negatively Regulated by Quaking-Mediated miR-19b

Background. Mitochondrial dysfunction and abnormal mitochondrial fission have been implicated in the complications associated with I/R injury as cardiomyocytes are abundant in mitochondria. SOCS6 is known to participate in mitochondrial fragmentation, but its exact involvement and the pathways associated are uncertain. Methods and Results. The expression of SOCS6 was analyzed by western blot in cardiomyocytes under a hypoxia and reoxygenation (H/R) model. A dual-luciferase reporter assay was used to confirm the direct interaction between miR-19b and the 3 ${}^{\prime }$ -UTR of Socs6. In the present study, we found that Socs6 inhibition by RNA interference attenuated H/R-induced mitochondrial fission and apoptosis in cardiomyocytes. A luciferase assay indicated that Socs6 is a direct target of miR-19b. The overexpression of miR-19b decreased mitochondrial fission and apoptosis in vitro. Moreover, the presence of miR-19b reduced the level of SOCS6 and the injury caused by I/R in vivo. There were less apoptotic cells in the myocardium of mice injected with miR-19b. In addition, we found that the RNA-binding protein, Quaking (QK), participates in the regulation of miR-19b expression. Conclusions. Our results indicate that the inhibition of mitochondrial fission through downregulating Socs6 via the QK/miR-19b/Socs6 pathway attenuated the damage sustained by I/R. The QK/miR-19b/Socs6 axis plays a vital role in regulation of mitochondrial fission and cardiomyocyte apoptosis and could form the basis of future research in the development of therapies for the management of cardiac diseases.

Minimizing Ischemia Reperfusion Injury in Xenotransplantation

The recent dramatic advances in preventing "initial xenograft dysfunction" in pig-to-non-human primate heart transplantation achieved by minimizing ischemia suggests that ischemia reperfusion injury (IRI) plays an important role in cardiac xenotransplantation. Here we review the molecular, cellular, and immune mechanisms that characterize IRI and associated "primary graft dysfunction" in allotransplantation and consider how they correspond with "xeno-associated" injury mechanisms. Based on this analysis, we describe potential genetic modifications as well as novel technical strategies that may minimize IRI for heart and other organ xenografts and which could facilitate safe and effective clinical xenotransplantation.

Therapeutic potential and recent advances on targeting mitochondrial dynamics in cardiac hypertrophy: A concise review

Pathological cardiac hypertrophy begins as an adaptive response to increased workload; however, sustained hemodynamic stress will lead it to maladaptation and eventually cardiac failure. Mitochondria, being the powerhouse of the cells, can regulate cardiac hypertrophy in both adaptive and maladaptive phases; they are dynamic organelles that can adjust their number, size, and shape through a process called mitochondrial dynamics. Recently, several studies indicate that promoting mitochondrial fusion along with preventing mitochondrial fission could improve cardiac function during cardiac hypertrophy and avert its progression toward heart failure. However, some studies also indicate that either hyperfusion or hypo-fission could induce apoptosis and cardiac dysfunction. In this review, we summarize the recent knowledge regarding the effects of mitochondrial dynamics on the development and progression of cardiac hypertrophy with particular emphasis on the regulatory role of mitochondrial dynamics proteins through the genetic, epigenetic, and post-translational mechanisms, followed by discussing the novel therapeutic strategies targeting mitochondrial dynamic pathways.

Methylene blue and photobiomodulation recover cognitive impairment in hepatic encephalopathy through different effects on cytochrome c-oxidase

Mitochondrial dysfunction plays a central role in hepatic encephalopathy (HE), due to changes in enzyme cytochrome c-oxidase (CCO), causing a decline in brain metabolism. We used an HE animal model and applied intracranial administration of methylene blue (MB) and transcranial photobiomodulation (PBM), both targeting CCO, to determine their differential effects on recovering cognition. Five groups of rats were used: sham-operated group + saline (SHAM + SAL, n = 6), hepatic encephalopathy + SAL (HE + SAL, n = 7), SHAM + methylene blue (SHAM + MB, n = 7), HE + MB (n = 7), HE + PBM (n = 7). PBM animals were exposed transcranially to 670 +/- 10 nm LED light at a dose of 9 J/cm2 once a day for 7 days, and the MB and SAL groups were injected with 2.2 μg/0.5 μL in the accumbens. Cognitive dysfunction was evaluated on a striatal stimulus-response task using the Morris water maze. Our results showed cognitive improvement in the HE group when treated with MB. This improvement was accompanied by a decrease in CCO activity in the prefrontal cortex, dorsal striatum, and dorsal hippocampus. When comparing MB and PBM, we found that, although both treatments effectively improved the HE-memory deficit, there was a differential effect on CCO. A general decrease in CCO activity was found in the prefrontal and entorhinal cortices, dorsal striatum, and hippocampus when PBM, compared to MB, was applied. Our results suggest that mitochondrial dysfunction and brain metabolic decline in HE might involve CCO alteration and can be improved by administering MB and PBM.

Mitochondrial protective effects of PARP-inhibition in hypertension-induced myocardial remodeling and in stressed cardiomyocytes

AIMS

During oxidative stress mitochondria become the main source of endogenous reactive oxygen species (ROS) production. In the present study, we aimed to clarify the effects of pharmacological PARP-1 inhibition on mitochondrial function and quality control processes.

MAIN METHODS

L-2286, a quinazoline-derivative PARP inhibitor, protects against cardiovascular remodeling and heart failure by favorable modulation of signaling routes. We examined the effects of PARP-1 inhibition on mitochondrial quality control processes and function in vivo and in vitro. Spontaneously hypertensive rats (SHRs) were treated with L-2286 or placebo. In the in vitro model, 150 μM H2O2 stress was applied on neonatal rat cardiomyocytes (NRCM).

KEY FINDINGS

PARP-inhibition prevented the development of left ventricular hypertrophy in SHRs. The interfibrillar mitochondrial network were less fragmented, the average mitochondrial size was bigger and showed higher cristae density compared to untreated SHRs. Dynamin related protein 1 (Drp1) translocation and therefore the fission of mitochondria was inhibited by L-2286 treatment. Moreover, L-2286 treatment increased the amount of fusion proteins (Opa1, Mfn2), thus preserving structural stability. PARP-inhibition also preserved the mitochondrial genome integrity. In addition, the mitochondrial biogenesis was also enhanced due to L-2286 treatment, leading to an overall increase in the ATP production and improvement in survival of stressed cells.

SIGNIFICANCE

Our results suggest that the modulation of mitochondrial dynamics and biogenesis can be a promising therapeutical target in hypertension-induced myocardial remodeling and heart failure.

Involvement of Mitochondrial Dynamics and Mitophagy in Sevoflurane-Induced Cell Toxicity

General anesthesia is a powerful and indispensable tool to ensure the accomplishment of surgical procedures or clinical examinations. Sevoflurane as an inhalational anesthetic without unpleasant odor is commonly used in clinical practice, especially for pediatric surgery. However, the toxicity caused by sevoflurane has gained growing attention. Mitochondria play a key role in maintaining cellular metabolism and survival. To maintain the stability of mitochondrial homeostasis, they are constantly going through fusion and fission. Also, damaged mitochondria need to be degraded by autophagy, termed as mitophagy. Accumulating evidence proves that sevoflurane exposure in young age could lead to cell toxicity by triggering the mitochondrial pathway of apoptosis, inducing the abnormalities of mitochondrial dynamics and mitophagy. In the present review, we focus on the current understanding of mitochondrial apoptosis, dynamics and mitophagy in cell function, the implications for cell toxicity in response to sevoflurane, and their underlying potential mechanisms.

Lycopene Improves In Vitro Development of Porcine Embryos by Reducing Oxidative Stress and Apoptosis

In vitro culture (IVC) for porcine embryo development is inferior compared to in vivo development because oxidative stress can be induced by the production of excessive reactive oxygen species (ROS) under high oxygen tension in the in vitro environment. To overcome this problem, we investigated the effect of lycopene, an antioxidant carotenoid, on developmental competence and the mechanisms involved in mitochondria-dependent apoptosis pathways in porcine embryos. In vitro fertilized (IVF) embryos were cultured in IVC medium supplemented with 0, 0.02, 0.05, 0.1, or 0.2 μM lycopene. The results indicate that 0.1 μM lycopene significantly increased the rate of blastocyst formation and the total cell numbers, including trophectoderm cell numbers, on Day In terms of mitochondria-dependent apoptosis, IVF embryos treated with 0.1 μM lycopene exhibited significantly decreased levels of ROS, increased mitochondrial membrane potential, and decreased expression of cytochrome c on Days 2 and Furthermore, 0.1 μM lycopene significantly decreased the number and percentage of caspase 3-positive and apoptotic cells in Day-6 blastocysts. In addition, Day-2 embryos and Day-6 blastocysts treated with 0.1 μM lycopene showed significantly reduced mRNA expression related to antioxidant enzymes (SOD1, SOD2, CATALASE) and apoptosis (BAX/BCL2L1 ratio). These results indicate that lycopene supplementation during the entire period of IVC enhanced embryonic development in pigs by regulating oxidative stress and mitochondria-dependent apoptosis.

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

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

Prolylcarboxypeptidase Mitigates Myocardial Ischemia/Reperfusion Injury by Stabilizing Mitophagy

The role of prolylcarboxypeptidase (PRCP) in myocardial ischemia/reperfusion (I/R) injury is unclear. Herein, we aimed to evaluate the protective effect of the PRCP-angiotensin-(1-7) [Ang-(1-7)]/bradykinin-(1-9) [BK-(1-9)] axis on myocardial I/R injury and identify the mechanisms involved. Plasma PRCP level and activity, as well as Ang-(1-7) and BK-(1-9) levels, were compared in healthy subjects, patients with unstable angina, and those with ST-segment-elevated acute myocardial infarction (AMI). Thereafter, the effects of PRCP overexpression and knockdown on left ventricular function, mitophagy, and levels of Ang-(1-7) and BK-(1-9) were examined in rats during myocardial I/R. Finally, the effects of Ang-(1-7) and BK-(1-9) on I/R-induced mitophagy and the signaling pathways involved were investigated in vitro in rat cardiomyocytes. AMI patients showed increased plasma level and activity of PRCP and levels of Ang-(1-7) and BK-(1-9) as compared with healthy subjects and those with unstable angina. PRCP protected against myocardial I/R injury in rats by paradoxical regulation of cardiomyocyte mitophagy during the ischemia and reperfusion phases, which was mediated by downstream Ang-(1-7) and BK-(1-9). We further depicted a possible role of activation of AMPK in mitophagy induction during ischemia and activation of Akt in mitophagy inhibition during reperfusion in the beneficial effects of Ang-(1-7) and BK-(1-9). Thus, the PRCP-Ang-(1-7)/BK-(1-9) axis may protect against myocardial I/R injury by paradoxical regulation of cardiomyocyte mitophagy during ischemia and reperfusion phases.

Pharmacological inhibition of mitochondrial fission attenuates cardiac ischemia-reperfusion injury in pre-diabetic rats

An increase in the number of fragmented mitochondria contributes to the pathogenesis of ischemia-reperfusion (I/R) injury. Also, mitochondrial fission has shown an increase in obese condition. However, the cardioprotective roles of a mitochondrial fission inhibitor in obesity with cardiac I/R injury are unclear. We hypothesized that a fission inhibitor (Mdivi-1) reduces cardiac dysfunction during I/R injury in pre-diabetic rats. Male Wistar rats (n = 40) were received a high-fat diet for 12 weeks to induce prediabetes. Then, rats underwent a 30-min coronary artery ligation was performed followed by reperfusion for 120 min. These I/R rats were given either: (1) vehicle or Mdivi-1 treatment at 3 time points relative to onset of ischemia: (2) pre-ischemia; (3) during ischemia; and (4) at onset of reperfusion. Cardiac function, myocardial infarct size, mitochondrial function and dynamic balance were determined. Interestingly, Mdivi-1 given at any time points effectively attenuated mitochondrial reactive oxygen species production, depolarization, swelling, and dynamic imbalance, resulting in reduced arrhythmias, myocardial cell death, infarct size and enhanced cardiac performance during I/R injury in pre-diabetic rats. Taken together, inhibition of mitochondrial fission effectively protected the heart against cardiac I/R injury regardless of the time of administration in pre-diabetic rats.

Cardiac donation after circulatory death

PURPOSE OF REVIEW

Increasing number of patients with end-stage heart failure and those with improved survivorship from selective utilization of implantable mechanical circulatory support devices have added further burden and complexity to the transplant waitlist and on the rate-limiting availability of donor hearts from the standard pathway of donation after brain death. Unlike this conventional route, the increasing clinical use of donation after circulatory death (DCD) donor hearts necessitates a closer understanding of the logistics involved in the DCD process as well as of the risks associated with the unique pathophysiological consequences in this setting.

RECENT FINDINGS

Notwithstanding a higher incidence of delayed graft function, the clinical utilization of DCD hearts for cardiac transplantation over the past five years has demonstrated this to be a well-tolerated and strategic alternative with excellent medium-term clinical outcomes.

SUMMARY

The uptake of DCD heart transplantation remains selective and currently confined to Australia, the United Kingdom, Belgium, and more recently the USA. A more significant adoption will only come about through: a concerted effort to resolve the ethical and clinical controversies; a better understanding of postconditioning strategies; continued resolve to reduce the obligatory period of warm ischemia; and from better extracorporeal platforms that permit functional viability assessment of the DCD donor heart.

Exercise training protects the heart against ischemia-reperfusion injury: A central role for mitochondria?

Ischemic heart disease is one of the main causes of morbidity and mortality worldwide. Physical exercise is an effective lifestyle intervention to reduce the risk factors for cardiovascular disease and also to improve cardiac function and survival in patients with ischemic heart disease. Among the strategies that contribute to reduce heart damages during ischemia and reperfusion, regular physical exercise is efficient both in rodent experimental models and in humans. However, the cellular and molecular mechanisms of the cardioprotective effects of exercise remain unclear. During ischemia and reperfusion, mitochondria are crucial players in cell death, but also in cell survival. Although exercise training can influence mitochondrial function, the consequences on heart sensitivity to ischemic insults remain elusive. In this review, we describe the effects of physical activity on cardiac mitochondria and their potential key role in exercise-induced cardioprotection against ischemia-reperfusion damage. Based on recent scientific data, we discuss the role of different pathways that might help to explain why mitochondria are a key target of exercise-induced cardioprotection.

Gerontoxanthone I and Macluraxanthone Induce Mitophagy and Attenuate Ischemia/Reperfusion Injury

Mitophagy is a crucial process in controlling mitochondrial biogenesis. Balancing mitophagy and mitochondrial functions is required for maintaining cellular homeostasis. In this study, we found that Gerontoxanthone I (GeX1) and Macluraxanthone (McX), xanthone derivatives isolated from Garcinia bracteata C. Y. Wu ex Y. H. Li, induced Parkin puncta accumulation and promoted mitophagy. GeX1 and McX treatment induced the degradation of mitophagy-related proteins such as Tom20 and Tim23. GeX1 and McX directly stabilized PTEN-induced putative kinase 1 (PINK1) on the outer membrane of the mitochondria, and then recruited Parkin to mitochondria. This significantly induced phosphorylation and ubiquitination of Parkin, suggesting that GeX1 and McX mediate mitophagy through the PINK1-Parkin pathway. Transfecting ParkinS65A or pretreated MG132 abolished the induction effects of GeX1 and McX on mitophagy. Furthermore, GeX1 and McX treatment decreased cell death and the level of ROS in an ischemia/reperfusion (IR) injury model in H9c2 cells compared to a control group. Taken together, our data suggested that GeX1 and McX induce PINK1-Parkin–mediated mitophagy and attenuate myocardial IR injury in vitro.

Ferulic Acid Attenuates Hypoxia/Reoxygenation Injury by Suppressing Mitophagy Through the PINK1/Parkin Signaling Pathway in H9c2 Cells

Ferulic acid protects against cardiac injury by scavenging free radicals. However, the role of mitophagy in ferulic acid-induced cardioprotection remains obscure. In the present study, H9c2 cells were exposed to hypoxia/reoxygenation and ferulic acid treatment during hypoxia. We illustrated the impact of ferulic acid on oxidative damage in H9c2 cells. Our results showed that ferulic acid significantly attenuated apoptosis induced by hypoxia/reoxygenation injury and reduced mitochondrial dysfunction, evidenced by a decline in the overproduction of reactive oxygen species and ATP depletion and recovery of the membrane potential. We also found that mitophagy, a selective form of autophagy, was excessively activated in H9c2 cells subjected to hypoxia/reoxygenation. Ferulic acid reduced the binding of mitochondria to lysosomes, down-regulated the PINK1/Parkin pathway, and was accompanied by increased p62 and decreased LC3-II/LC3-I levels. Ferulic acid also antagonistically reduced the activation of mitophagy by rapamycin. These findings suggest that ferulic acid may protect H9c2 cells against ischemia/reperfusion injury by suppressing PINK1/Parkin-dependent mitophagy. Accordingly, our findings may provide a potential target and powerful reference for ferulic acid in clinical prevention and treatment of hypoxia/reoxygenation injury.

Shexiang Tongxin Dropping Pill () Reduces Coronary Microembolization in Rats via Regulation of Mitochondrial Permeability Transition Pore Opening and AKT-GSK3β Phosphorylation

OBJECTIVE

To investigate the protective effects of Shexiang Tongxin Dropping Pill (, STDP) following sodium laurate-induced coronary microembolization (CME) in rats.

METHODS

Forty rats were divided into 4 groups: the control (sham) group, CME group, low-dose STDP pretreatment group (20 mg·kg^-1·d^-1), and high-dose STDP pretreatment group (40 mg·kg^-1·d^-1). The rats were intragastric administrated with STDP 2 weeks before operation. Moreover, the histopathological alterations were observed using optical microscopy and transmission electron microscopy. Antioxidant biomarkers were analyzed by enzyme-linked immunosorbent assay. Mitochondrial functions including the mitochondrial permeability transition pore (mPTP) mtDNA copy number were determined and proteins of AKT/GSK3β were analyzed by Western blot.

RESULTS

The rats in the CME group showed a significant increase in the fibrinogen-like protein 2 expression level and mitochondrial dysfunction and a decrease in the expression level of antioxidant biomarkers (superoxide dismutase and catalase, P<0.01 for all). In contrast, the rats in the low- and high-dose STDP pretreatment groups showed a significant decrease in coronary microthrombi (P<0.05); moreover, STDP restored the antioxidant-related protein activities and mitochondrial function, inhibited mPTP opening, decreased AKT-Ser473 phosphorylation, and increased GSK3β-Ser9 phosphorylation (P<0.05 or P<0.01).

CONCLUSION

STDP may be useful for treatment of CME, possibly via regulation of mPTP opening and AKT/GSK3β phosphorylation.

Inhibition of the proteasome preserves Mitofusin-2 and mitochondrial integrity, protecting cardiomyocytes during ischemia-reperfusion injury

Cardiomyocyte loss is the main cause of myocardial dysfunction following an ischemia-reperfusion (IR) injury. Mitochondrial dysfunction and altered mitochondrial network dynamics play central roles in cardiomyocyte death. Proteasome inhibition is cardioprotective in the setting of IR; however, the mechanisms underlying this protection are not well-understood. Several proteins that regulate mitochondrial dynamics and energy metabolism, including Mitofusin-2 (Mfn2), are degraded by the proteasome. The aim of this study was to evaluate whether proteasome inhibition can protect cardiomyocytes from IR damage by maintaining Mfn2 levels and preserving mitochondrial network integrity. Using ex vivo Langendorff-perfused rat hearts and in vitro neonatal rat ventricular myocytes, we showed that the proteasome inhibitor MG132 reduced IR-induced cardiomyocyte death. Moreover, MG132 preserved mitochondrial mass, prevented mitochondrial network fragmentation, and abolished IR-induced reductions in Mfn2 levels in heart tissue and cultured cardiomyocytes. Interestingly, Mfn2 overexpression also prevented cardiomyocyte death. This effect was apparently specific to Mfn2, as overexpression of Miro1, another protein implicated in mitochondrial dynamics, did not confer the same protection. Our results suggest that proteasome inhibition protects cardiomyocytes from IR damage. This effect could be partly mediated by preservation of Mfn2 and therefore mitochondrial integrity.

Remote Ischemic Pre-Conditioning Attenuates Adverse Cardiac Remodeling and Mortality Following Doxorubicin Administration in Mice

Objectives

Because of its multifaceted cardioprotective effects, remote ischemic pre-conditioning (RIPC) was examined as a strategy to attenuate doxorubicin (DOX) cardiotoxicity.

Background

The use of DOX is limited by dose-dependent cardiotoxicity and heart failure. Oxidative stress, mitochondrial dysfunction, inflammation, and autophagy modulation have been proposed as mediators of DOX cardiotoxicity.

Methods

After baseline echocardiography, adult male CD1 mice were randomized to either sham or RIPC protocol (3 cycles of 5 min femoral artery occlusion followed by 5 min reperfusion) 1 h before receiving DOX (20 mg/kg, intraperitoneal). The mice were observed primarily for survival over 85 days (86 mice). An additional cohort of 50 mice was randomized to either sham or RIPC 1 h before DOX treatment and was followed for 25 days, at which time cardiac fibrosis, apoptosis, and mitochondrial oxidative phosphorylation were assessed, as well as the expression profiles of apoptosis and autophagy markers.

Results

Survival was significantly improved in the RIPC cohort compared with the sham cohort (p = 0.007). DOX-induced cardiac fibrosis and apoptosis were significantly attenuated with RIPC compared with sham (p < 0.05 and p < 0.001, respectively). Although no mitochondrial dysfunction was detected at 25 days, there was a significant increase in autophagy markers with DOX that was attenuated with RIPC. Moreover, DOX caused a 49% decline in cardiac BCL2/BAX expression, which was restored with RIPC (p < 0.05 vs. DOX). DOX also resulted in a 17% reduction in left ventricular mass at 25 days, which was prevented with RIPC (p < 0.01), despite the lack of significant changes in left ventricular ejection fraction.

Conclusions

Our preclinical results suggested that RIPC before DOX administration might be a promising approach for attenuating DOX cardiotoxicity.

Rosuvastatin Attenuates Myocardial Ischemia-Reperfusion Injury via Upregulating miR-17-3p-Mediated Autophagy

Myocardial diseases usually appear ischemic. Reperfusion therapy is one of the effective methods that can improve clinical therapeutic efficacy. However, reperfusion results in myocardial injury named I/R injury. Rosuvastatin (RS) is HMG-CoA reductase inhibitor. We investigated the role of RS in the myocardial I/R injury in vitro and its active mechanism. Oxygen-glucose deprivation/reoxygenation (OGD/R) model was applied to investigate I/R in vitro. OGD/R decreased cell viability and increased levels of miR-17-3p and lactate dehydrogenase (LDH) leakage. Besides, RS decreased cleaved caspase-3 level and LDH leakage, promoted the levels of miR-17-3p and LC3II/LC3I, and increased cell viability when H9C2 cell was treated by OGD/R. miR-17-3p inhibitor reduced the H9C2 cell viability and LC3II/LC3I level, whereas miR-17-3p mimics increased H9C2 cell viability and LC3II/LC3I level. RS promoted cell viability and increased LC3II/LC3I level while it lowered LDH leakage, apoptosis rate, and the levels of cleaved caspase-3 and Cyto c. Our study suggested that RS reduced I/R injury in cardiocyte via cleaved caspase-3/Cyto c apoptosis signaling pathway and autophagy. Moreover, the autophagy happens to cardiocyte by upregulating the expression of miR-17-3p.

Insight into long noncoding RNA-miRNA-mRNA axes in myocardial ischemia-reperfusion injury: the implications for mechanism and therapy

Emerging evidence has demonstrated that regulatory noncoding RNAs (ncRNAs), such as long noncoding RNAs (lncRNAs) and miRNAs, play crucial roles in the initiation and progress of myocardial ischemia-reperfusion injury (MIRI), which is associated with autophagy, apoptosis and necrosis of cardiomyocytes, as well as oxidative stress, inflammation and mitochondrial dysfunction. LncRNAs serve as a precursor or host of miRNAs and directly/indirectly affecting miRNAs via competitive binding or sponge effects. Simultaneously, miRNAs post-transcriptionally regulate the expression of genes by targeting various mRNA sequences due to their imperfect pairing with mRNAs. This review summarizes the potential regulatory role of lncRNA-miRNA-mRNA axes in MIRI and related molecular mechanisms of cardiac disorders, also provides insight into the potential therapies for MIRI-induced diseases.

Mitochondrial Peptide Humanin Protects Silver Nanoparticles-Induced Neurotoxicity in Human Neuroblastoma Cancer Cells (SH-SY5Y)

The extensive usage of silver nanoparticles (AgNPs) as medical products such as antimicrobial and anticancer agents has raised concerns about their harmful effects on human beings. AgNPs can potentially induce oxidative stress and apoptosis in cells. However, humanin (HN) is a small secreted peptide that has cytoprotective and neuroprotective cellular effects. The aim of this study was to assess the harmful effects of AgNPs on human neuroblastoma SH-SY5Y cells and also to investigate the protective effect of HN from AgNPs-induced cell death, mitochondrial dysfunctions, DNA damage, and apoptosis. AgNPs were prepared with an average size of 18 nm diameter to study their interaction with SH-SY5Y cells. AgNPs caused a dose-dependent decrease of cell viability and proliferation, induced loss of plasma-membrane integrity, oxidative stress, loss of mitochondrial membrane potential (MMP), and loss of ATP content, amongst other effects. Pretreatment or co-treatment of HN with AgNPs protected cells from several of these AgNPs induced adverse effects. Thus, this study demonstrated for the first time that HN protected neuroblastoma cells against AgNPs-induced neurotoxicity. The mechanisms of the HN-mediated protective effect on neuroblastoma cells may provide further insights for the development of novel therapeutic agents against neurodegenerative diseases.

Targeting Mitochondrial Fission Using Mdivi-1 in A Clinically Relevant Large Animal Model of Acute Myocardial Infarction: A Pilot Study

Background: New treatments are needed to reduce myocardial infarct size (MI) and prevent heart failure (HF) following acute myocardial infarction (AMI), which are the leading causes of death and disability worldwide. Studies in rodent AMI models showed that genetic and pharmacological inhibition of mitochondrial fission, induced by acute ischemia and reperfusion, reduced MI size. Whether targeting mitochondrial fission at the onset of reperfusion is also cardioprotective in a clinically-relevant large animal AMI model remains to be determined. Methods: Adult pigs (30-40 kg) were subjected to closed-chest 90-min left anterior descending artery ischemia followed by 72 h of reperfusion and were randomized to receive an intracoronary bolus of either mdivi-1 (1.2 mg/kg, a small molecule inhibitor of the mitochondrial fission protein, Drp1) or vehicle control, 10-min prior to reperfusion. The left ventricular (LV) size and function were both assessed by transthoracic echocardiography prior to AMI and after 72 h of reperfusion. MI size and the area-at-risk (AAR) were determined using dual staining with Tetrazolium and Evans blue. Heart samples were collected for histological determination of fibrosis and for electron microscopic analysis of mitochondrial morphology. Results: A total of 14 pigs underwent the treatment protocols (eight control and six mdivi-1). Administration of mdivi-1 immediately prior to the onset of reperfusion did not reduce MI size (MI size as % of AAR: Control 49.2 ± 8.6 vs. mdivi-1 50.5 ± 11.4; p = 0.815) or preserve LV systolic function (LV ejection fraction %: Control 67.5 ± 0.4 vs. mdivi-1 59.6 ± 0.6; p = 0.420), when compared to vehicle control. Similarly, there were no differences in mitochondrial morphology or myocardial fibrosis between mdivi-1 and vehicle control groups. Conclusion: Our pilot study has shown that treatment with mdivi-1 (1.2 mg/kg) at the onset of reperfusion did not reduce MI size or preserve LV function in the clinically-relevant closed-chest pig AMI model. A larger study, testing different doses of mdivi-1 or using a more specific Drp1 inhibitor are required to confirm these findings.

Epigallocatechin gallate prevents mitochondrial impairment and cell apoptosis by regulating miR-30a/p53 axis

PURPOSE

This study was designed to investigate whether EGCG prevents cardiac I/R mitochondrial impairment and cell apoptosis by regulating miR-30a/p53 axis.

METHODS

The H9c2 cardiomyocytes hypoxia/reoxygenation (H/R) model in vitro and myocardial ischemia /reperfusion (I/R) model in vivo were made, with or without EGCG treatment. The levels of I/R-induced creatine kinase-MB (CK-MB) and the release of lactate dehydrogenase (LDH), as well as the adenosine triphosphate (ATP) and cardiac functional impairment were examined. Stablely transfecting miR-30a mimic or inhibitor in H9c2 cardiomyocytes was built. The expression of miR-30a, p53 and related proteins in cells was measured by western blotting and qRT-PCR. Cell viability and apoptosis were examined using CCK-8 assay and flow cytometry. The content of reactive oxygen species (ROS), mitochondrial permeability transition pores (MPTP) opening and mitochondrial transmembrane potential (ΔΨm) in cells was measured by fluorescent probes. The levels of miR-30a and p53, some related proteins expression and apoptosis in the cardiac muscle tissues were determined by quantitative real-time PCR (qRT-PCR), H&E staining, western blotting and TUNEL assays.

RESULTS

We found that EGCG preconditioning significantly decreased the levels of CK-MB and LDH, increased the activity of ATP, reduced the apoptotic rate and partially preserved heart function. Furthermore, EGCG decreased ROS levels, MPTP opening and depolarization of ΔΨm, and improved the activity of post-I/R cardiomyocyte. The beneficial effect of EGCG was associated with restored levels of miR-30a expression in the I/R injury that correspond to p53 mRNA downregulation. The regulatory effect of EGCG was greatly enhanced by miR-30a mimic and suppressed by miR-30a inhibitor. More importantly, EGCG pretreatment inhibited the expression of mitochondrial apoptotic related proteins downstream of the miR-30a/p53 pathway.

CONCLUSION

This study demonstrated that EGCG pretreatment may attenuate mitochondrial impairment and myocardial apoptosis by regulation of miR-30a/p53 axis.

Mitochondrial dynamics modulation as a critical contribution for Shenmai injection in attenuating hypoxia/reoxygenation injury

ETHNOPHARMACOLOGICAL RELEVANCE

Shenmai injection (SMI) is a CFDA-approved and widely prescribed herbal medicine injection in China for treating cardiac dysfunction, especially myocardial ischemia and reperfusion (I/R) injury. However, despite of its known clinical efficacy, the cardioprotective mechanisms of SMI remain to be established.

AIM OF STUDY

The present study aimed to investigate the role of SMI on mitophagy and mitochondrial dynamics in cardiomyocytes with a hypoxia/reperfusion (H/R) injury setting.

MATERIALS AND METHODS

H9c2 cardiomyocytes were subjected to 12 h of hypoxia followed by 2 h of reoxygenation to induce cellular injury. Multi-parameter imaging analysis was performed using Operetta High Content Imaging System to detect changes in mitochondrial function and morphological texture. The mPTP opening was directly assessed by analyzing mitochondrial calcein release in H9c2 and by Ca²⁺-induced swelling of isolated cardiac mitochondria. Mitochondrial respiration was measured by XF 24 analyzer of Seahorse Bioscience. RT-PCR and Western blotting analyses were used to detect mitophagy, mitochondrial fusion and fission biomarkers at the gene and protein levels.

RESULTS

Pretreatment of SMI significantly improved myocardial cell survival and protected against H/R-induced deterioration of mitochondrial structure and function, as evidenced by decreased mitochondrial mass and cytosolic Ca²⁺, increased mitochondrial membrane potential (ΔΨ_m) and mitochondrial morphology by SER Texture analysis, inhibited mPTP opening in H9c2 cells and isolated cardiac mitochondria, and alleviated severely impaired mitochondrial respiration. Mechanistically, SMI attenuated H/R injury by inducing mitophagy and then modulated mitochondrial dynamics as indicated by a significantly increased expression of LC3, Beclin 1, Parkin and Pink, and the inhibition of excessive mitochondria fission and increased mitochondrial fusion. Finally, the cardioprotective effect of SMI was confirmed in a LAD-induced cardiac dysfunction model in vivo.

CONCLUSION

We found that alleviation of H/R injury by pretreatment with SMI may be attributable to inducing mitophagy and modulating mitochondrial dynamics in cardiomyocytes, thereby providing a rationale for future clinical applications and potential mitoprotective therapy for MI/R injury.

Mitochondrial protein 18 is a positive apoptotic regulator in cardiomyocytes under oxidative stress

Accumulation of reactive oxygen species is a common phenomenon in cardiac stress conditions, for instance, coronary artery disease, aging-related cardiovascular abnormalities, and exposure to cardiac stressors such as hydrogen peroxide (H2O2). Mitochondrial protein 18 (Mtp18) is a novel mitochondrial inner membrane protein, shown to involve in the regulation of mitochondrial dynamics. Although Mtp18 is abundant in cardiac muscles, its role in cardiac apoptosis remains elusive. The present study aimed to detect the role of Mtp18 in H2O2-induced mitochondrial fission and apoptosis in cardiomyocytes. We studied the effect of Mtp18 in cardiomyocytes by modulating its expression with lentiviral construct of Mtp18-shRNA and Mtp18 c-DNA, respectively. We then analyzed mitochondrial morphological dynamics with MitoTracker Red staining; apoptosis with terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling (TUNEL) and cell death detection assays; and protein expression with immunoblotting. Here, we observed that Mtp18 could regulate oxidative stress- mediated mitochondrial fission and apoptosis in cardiac myocytes. Mechanistically, we found that Mtp8 induced mitochondrial fission and apoptosis by enhancing dynamin-related protein 1 (Drp1) accumulation. Conversely, knockdown of Mtp18 interfered with Drp1-associated mitochondrial fission and subsequent activation of apoptosis in both HL-1 cells and primary cardiomyocytes. However, overexpression of Mtp18 alone was not sufficient to execute apoptosis when Drp1 was minimally expressed, suggesting that Mtp18 and Drp1 are interdependent in apoptotic cascade. Together, these data highlight the role of Mtp18 in cardiac apoptosis and provide a novel therapeutic insight to minimize cardiomyocyte loss via targetting mitochondrial dynamics.

CD47 deficiency protects cardiomyocytes against hypoxia/reoxygenation injury by rescuing autophagic clearance

To assess the effect of cluster of differentiation (CD47) downregulation on autophagy in hypoxia/reoxygenation (H/R)‑treated H9c2 cardiomyocytes. H9c2 cells were maintained in normoxic conditions (95% air, 5% CO2, 37˚C) without CD47 antibodies, Si‑CD47 or chloroquine (CQ) treatment; H9c2 cells in the H/R group were subjected to 24 h of hypoxia (1% O2, 94% N2, 5% CO2, 37˚C) followed by 12 h of reoxygenation (95% air, 5% CO2, 37˚C). All assays were controlled, triplicated and repeated on three separately initiated cultures. The biochemical parameters in the medium supernatant were measured to evaluate the oxidative stress in cardiomyocytes. The Annexin V‑fluorescein isothiocyanate assay was used to detect the apoptotic rate in the H9c2 cells. Transmission electron microscope, immunofluorescent staining and western blot analysis were performed to detect the effect of the CD47 antibody on autophagic flux in H/R‑treated H9c2 cardiomyocytes. The cardiomyocytic oxidative stress and apoptotic rate decreased and autophagic clearance increased after CD47 downregulation. H/R triggered cell autophagy, autophagosome accumulation and apoptosis in H9c2 cell lines. However, these effects can be attenuated by CD47 downregulation. This study demonstrates its clinical implications in ischemia/reperfusion injury treatment.

Knockout of dihydrofolate reductase in mice induces hypertension and abdominal aortic aneurysm via mitochondrial dysfunction

Hypertension and abdominal aortic aneurysm (AAA) are severe cardiovascular diseases with incompletely defined molecular mechanisms. In the current study we generated dihydrofolate reductase (DHFR) knockout mice for the first time to examine its potential contribution to the development of hypertension and AAA, as well as the underlying molecular mechanisms. Whereas the homozygote knockout mice were embryonically lethal, the heterozygote knockout mice had global reduction in DHFR protein expression and activity. Angiotensin II infusion into these animals resulted in substantially exaggerated elevation in blood pressure and development of AAA, which was accompanied by excessive eNOS uncoupling activity (featured by significantly impaired tetrahydrobiopterin and nitric oxide bioavailability), vascular remodeling (MMP2 activation, medial elastin breakdown and adventitial fibrosis) and inflammation (macrophage infiltration). Importantly, scavenging of mitochondrial reactive oxygen species with Mito-Tempo in vivo completely abrogated development of hypertension and AAA in DHFR knockout mice, indicating a novel role of mitochondria in mediating hypertension and AAA downstream of DHFR deficiency-dependent eNOS uncoupling. These data for the first time demonstrate that targeting DHFR-deficiency driven mitochondrial dysfunction may represent an innovative therapeutic option for the treatment of AAA and hypertension.

Calpain Inhibition Restores Autophagy and Prevents Mitochondrial Fragmentation in a Human iPSC Model of Diabetic Endotheliopathy

The relationship between diabetes and endothelial dysfunction remains unclear, particularly the association with pathological activation of calpain, an intracellular cysteine protease. Here, we used human induced pluripotent stem cells-derived endothelial cells (iPSC-ECs) to investigate the effects of diabetes on vascular health. Our results indicate that iPSC-ECs exposed to hyperglycemia had impaired autophagy, increased mitochondria fragmentation, and was associated with increased calpain activity. In addition, hyperglycemic iPSC-ECs had increased susceptibility to cell death when subjected to a secondary insult-simulated ischemia-reperfusion injury (sIRI). Importantly, calpain inhibition restored autophagy and reduced mitochondrial fragmentation, concurrent with maintenance of ATP production, normalized reactive oxygen species levels and reduced susceptibility to sIRI. Using a human iPSC model of diabetic endotheliopathy, we demonstrated that restoration of autophagy and prevention of mitochondrial fragmentation via calpain inhibition improves vascular integrity. Our human iPSC-EC model thus represents a valuable platform to explore biological mechanisms and new treatments for diabetes-induced endothelial dysfunction.

Balancing mitochondrial dynamics via increasing mitochondrial fusion attenuates infarct size and left ventricular dysfunction in rats with cardiac ischemia/reperfusion injury

An uncontrolled balance of mitochondrial dynamics has been shown to contribute to cardiac dysfunction during ischemia/reperfusion (I/R) injury. Although inhibition of mitochondrial fission could ameliorate cardiac dysfunction, modulation of mitochondrial fusion by giving a fusion promoter at different time-points during cardiac I/R injury has never been investigated. We hypothesized that giving of a mitochondrial fusion promoter at different time-points exerts cardioprotection with different levels of efficacy in rats with cardiac I/R injury. Forty male Wistar rats were subjected to a 30-min ischemia by coronary occlusion, followed by a 120-min reperfusion. The rats were then randomly divided into control and three treated groups: pre-ischemia, during-ischemia, and onset of reperfusion. A pharmacological mitochondrial fusion promoter-M1 (2 mg/kg) was used for intervention. Reduced mitochondrial fusion protein was observed after cardiac I/R injury. M1 administered prior to ischemia exerted the highest level of cardioprotection by improving both cardiac mitochondrial function and dynamics regulation, attenuating incidence of arrhythmia, reducing infarct size and cardiac apoptosis, which led to the preservation of cardiac function and decreased mortality. M1 given during ischemia and on the onset of reperfusion also exerted cardioprotection, but with a lower efficacy than when given at the pre-ischemia time-point. Attenuating a reduction in mitochondrial fusion proteins during myocardial ischemia and at the onset of reperfusion exerted cardioprotection by attenuating mitochondrial dysfunction and dynamic imbalance, thus reducing infarct size and improving cardiac function. These findings indicate that it could be a promising intervention with the potential to afford cardioprotection in the clinical setting of acute myocardial infarction.

Novel insights into the role of mitochondrial fusion and fission in cardiomyocyte apoptosis induced by ischemia/reperfusion

As the main source of energy in the body, mitochondria are highly dynamic organelles, which are constantly going through fusion and fission. The fine balance of mitochondrial fusion and fission plays an important role in maintaining the stability of cardiomyocyte homeostasis. The processes of mitochondrial fusion and fission are very complex, which is mediated by fusion and fission proteins. Disruptions in these processes through controlling fusion and fission proteins affect mitochondrial functions and cardiomyocyte survival. Ischemia/reperfusion (I/R) can regulate the expression and post-translational modifications of fusion and fission proteins thereby inducing the abnormality of mitochondrial fusion and fission and cardiomyocyte apoptosis. Furthermore, intervention with the expression and function of fusion and fission proteins influences on cardiomyocyte apoptosis under I/R conditions. In this review, we focus on the current developments in the effects of mitochondrial fusion and fission on cardiomyocyte functions, the implications for cardiomyocyte apoptosis in response to I/R, and possible mechanisms. And we review their roles as a potential therapeutic target for treating I/R-induced cardiomyocyte injury.