DNA-PKcs promotes alcohol-related liver disease by activating Drp1-related mitochondrial fission and repressing FUNDC1-required mitophagy

Coronary microvascular injury in myocardial infarction: perception and knowledge for mitochondrial quality control

Endothelial cells (ECs) constitute the innermost layer in all blood vessels to maintain the structural integrity and microcirculation function for coronary microvasculature. Impaired endothelial function is demonstrated in various cardiovascular diseases including myocardial infarction (MI), which is featured by reduced myocardial blood flow as a result of epicardial coronary obstruction, thrombogenesis, and inflammation. In this context, understanding the cellular and molecular mechanisms governing the function of coronary ECs is essential for the early diagnosis and optimal treatment of MI. Although ECs contain relatively fewer mitochondria compared with cardiomyocytes, they function as key sensors of environmental and cellular stress, in the regulation of EC viability, structural integrity and function. Mitochondrial quality control (MQC) machineries respond to a broad array of stress stimuli to regulate fission, fusion, mitophagy and biogenesis in mitochondria. Impaired MQC is a cardinal feature of EC injury and dysfunction. Hence, medications modulating MQC mechanisms are considered as promising novel therapeutic options in MI. Here in this review, we provide updated insights into the key role of MQC mechanisms in coronary ECs and microvascular dysfunction in MI. We also discussed the option of MQC as a novel therapeutic target to delay, reverse or repair coronary microvascular damage in MI. Contemporary available MQC-targeted therapies with potential clinical benefits to alleviate coronary microvascular injury during MI are also summarized.

Acute Decompensation and Acute-on-Chronic Liver Failure

Liver cirrhosis is a major healthcare problem. Acute decompensation, and in particular its interplay with dysfunction of other organs, is responsible for the majority of deaths in patients with cirrhosis. Acute decompensation has different courses, from stable decompensated cirrhosis over unstable decompensated cirrhosis to pre-acute-on-chronic liver failure and finally acute-on-chronic liver failure, a syndrome with high short-term mortality. This review focuses on the recent developments in the field of acute decompensation and acute-on-chronic liver failure.

Mitochondrial dysfunction and mitochondrion-targeted therapeutics in liver diseases

The liver is a vital metabolic and detoxifying organ and suffers diverse endogenous or exogenous damage. Hepatocyte mitochondria experience various structural and functional defects from liver injury, bearing oxidative stress, metabolic dysregulation, and the disturbance of mitochondrial quality control (MQC) mechanisms. Mitochondrial malfunction initiates the mitochondria-mediated apoptotic pathways and the release of damage signals, aggravating liver damage and disease progression via inflammation and reparative fibrogenesis. Removal of mitochondrial impairment or the improvement of MQC mechanisms restore mitochondrial homeostasis and benefit liver health. This review discusses the association of mitochondrial disorders with hepatic pathophysiological processes and the resultant potential of mitochondrion-targeting therapeutics for hepatic disorders. The recent advances in the MQC mechanisms and the mitochondrial-derived damage-associated molecular patterns (DAMPs) in the pathology and treatment of liver disease are particularly focussed.

Mitochondrial dynamics and nonalcoholic fatty liver disease (NAFLD): new perspectives for a fairy-tale ending?

Nonalcoholic fatty liver disease (NAFLD) includes a broad spectrum of liver dysfunctions and it is predicted to become the primary cause of liver failure and hepatocellular carcinoma. Mitochondria are highly dynamic organelles involved in multiple metabolic/bioenergetic pathways in the liver. Emerging evidence outlined that hepatic mitochondria adapt in number and functionality in response to external cues, as high caloric intake and obesity, by modulating mitochondrial biogenesis, and maladaptive mitochondrial response has been described from the early stages of NAFLD. Indeed, mitochondrial plasticity is lost in progressive NAFLD and these organelles may assume an aberrant phenotype to drive or contribute to hepatocarcinogenesis. Severe alimentary regimen and physical exercise represent the cornerstone for NAFLD care, although the low patients' compliance is urging towards the discovery of novel pharmacological treatments. Mitochondrial-targeted drugs aimed to recover mitochondrial lifecycle and to modulate oxidative stress are becoming attractive molecules to be potentially introduced for NAFLD management. Although the path guiding the switch from bench to bedside remains tortuous, the study of mitochondrial dynamics is providing intriguing perspectives for future NAFLD healthcare.

Bevacizumab-Induced Mitochondrial Dysfunction, Endoplasmic Reticulum Stress, and ERK Inactivation Contribute to Cardiotoxicity

The molecular mechanisms underlying the cardiotoxicity associated with bevacizumab, a first-line immunotherapeutic agent used to treat lung cancer, are not fully understood. Here, we examined intracellular signal transduction in cardiomyocytes after exposure to different doses of bevacizumab in vitro. Our results demonstrated that bevacizumab significantly and dose-dependently reduces cardiomyocyte viability and increases cell apoptosis. Bevacizumab treatment also led to mitochondrial dysfunction in cardiomyocytes, as evidenced by the decreased ATP production, increased ROS production, attenuated antioxidative enzyme levels, and reduced respiratory complex function. In addition, bevacizumab induced intracellular calcium overload, ER stress, and caspase-12 activation. Finally, bevacizumab treatment inhibited the ERK signaling pathway, which, in turn, significantly reduced cardiomyocyte viability and contributed to mitochondrial dysfunction. Together, our results demonstrate that bevacizumab-mediated cardiotoxicity is associated with mitochondrial dysfunction, ER stress, and ERK pathway inactivation. These findings may provide potential treatment targets to attenuate myocardial injury during lung cancer immunotherapy.

Melatonin Attenuates ox-LDL-Induced Endothelial Dysfunction by Reducing ER Stress and Inhibiting JNK/Mff Signaling

Endothelial dysfunction, which is characterized by damage to the endoplasmic reticulum (ER) and mitochondria, is involved in a variety of cardiovascular disorders. Here, we explored whether mitochondrial damage and ER stress are associated with endothelial dysfunction. We also examined whether and how melatonin protects against oxidized low-density lipoprotein- (ox-LDL-) induced damage in endothelial cells. We found that CHOP, GRP78, and PERK expressions, which are indicative of ER stress, increased significantly in response to ox-LDL treatment. ox-LDL also induced mitochondrial dysfunction as evidenced by decreased mitochondrial membrane potential, increased mitochondrial ROS levels, and downregulation of mitochondrial protective factors. In addition, ox-LDL inhibited antioxidative processes, as evidenced by decreased antioxidative enzyme activity and reduced Nrf2/HO-1 expression. Melatonin clearly reduced ER stress and promoted mitochondrial function and antioxidative processes in the presence of ox-LDL. Molecular investigation revealed that ox-LDL activated the JNK/Mff signaling pathway, and melatonin blocked this effect. These results demonstrate that ox-LDL induces ER stress and mitochondrial dysfunction and activates the JNK/Mff signaling pathway, thereby contributing to endothelial dysfunction. Moreover, melatonin inhibited JNK/Mff signaling and sustained ER homeostasis and mitochondrial function, thereby protecting endothelial cells against ox-LDL-induced damage.

Mitochondrial quality surveillance as a therapeutic target in myocardial infarction

Myocardial infarction (MI) is a leading cause of morbidity and mortality worldwide. As mitochondrial dysfunction critically contributes to the pathogenesis of MI, intensive research is focused on the development of therapeutic strategies targeting mitochondrial homeostasis. Mitochondria possess a quality control system which maintains and restores their structure and function by regulating mitochondrial fission, fusion, biogenesis, degradation and death. In response to slight damage such as transient hypoxia or mild oxidative stress, mitochondrial metabolism shifts from oxidative phosphorylation to glycolysis, in order to reduce oxygen consumption and maintain ATP output. Mitochondrial dynamics are also activated to modify mitochondrial shape and structure, in order to meet cardiomyocyte energy requirements through augmenting or reducing mitochondrial mass. When damaged mitochondria cannot be repaired, poorly structured mitochondria will be degraded through mitophagy, a process which is often accompanied by mitochondrial biogenesis. Once the insult is severe enough to induce lethal damage in the mitochondria and the cell, mitochondrial death pathway activation is an inevitable consequence, and the cardiomyocyte apoptosis or necrosis program will be initiated to remove damaged cells. Mitochondrial quality surveillance is a hierarchical system preserving mitochondrial function and defending cardiomyocytes against stress. A failure of this system has been regarded as one of the potential pathologies underlying MI. In this review, we discuss the recent findings focusing on the role of mitochondrial quality surveillance in MI, and highlight the available therapeutic approaches targeting mitochondrial quality surveillance during MI.

Matrine Protects Cardiomyocytes Against Hyperglycemic Stress by Promoting Mitofusin 2-Induced Mitochondrial Fusion

Matrine, an active component of Sophora flavescens Ait root extracts, has been used in China for years to treat cancer and viral hepatitis. In the present study, we explored the effects of matrine on hyperglycemia-treated cardiomyocytes. Cardiomyocyte function, oxidative stress, cellular viability, and mitochondrial fusion were assessed through immunofluorescence, quantitative real-time PCR (qRT-PCR), enzyme-linked immunosorbent assays, and RNA interference. Matrine treatment suppressed hyperglycemia-induced oxidative stress in cardiomyocytes by upregulating transcription of nuclear factor erythroid 2-like 2 and heme oxygenase-1. Matrine also improved cardiomyocyte contractile and relaxation function during hyperglycemia, and it reduced hyperglycemia-induced cardiomyocyte death by inhibiting mitochondrial apoptosis. Matrine treatment increased the transcription of mitochondrial fusion-related genes and thus attenuated the proportion of fragmented mitochondria in cardiomyocytes. Inhibiting mitochondrial fusion by knocking down mitofusin 2 (Mfn2) abolished the cardioprotective effects of matrine during hyperglycemia. These results demonstrate that matrine could be an effective drug to alleviate hyperglycemia-induced cardiomyocyte damage by activating Mfn2-induced mitochondrial fusion.

Coronary Endothelium No-Reflow Injury Is Associated with ROS-Modified Mitochondrial Fission through the JNK-Drp1 Signaling Pathway

Coronary artery no-reflow is a complex problem in the area of reperfusion therapy, and the molecular mechanisms underlying coronary artery no-reflow injury have not been fully elucidated. In the present study, we explored whether oxidative stress caused damage to coronary endothelial cells by inducing mitochondrial fission and activating the JNK pathway. The hypoxia/reoxygenation (H/R) model was induced in vitro to mimic coronary endothelial no-reflow injury, and mitochondrial fission, mitochondrial function, and endothelial cell viability were analyzed using western blotting, quantitative polymerase chain reaction (qPCR), enzyme-linked immunosorbent assay (ELISA), and immunofluorescence. Our data indicated that reactive oxygen species (ROS) were significantly induced upon H/R injury, and this was followed by decreased endothelial cell viability. Mitochondrial fission was induced and mitochondrial bioenergetics were impaired in cardiac endothelial cells after H/R injury. Neutralization of ROS reduced mitochondrial fission and protected mitochondrial function against H/R injury. Our results also demonstrated that ROS stimulated mitochondrial fission via JNK-mediated Drp1 phosphorylation. These findings indicate that the ROS-JNK-Drp1 signaling pathway may be one of the molecular mechanisms underlying endothelial cell damage during H/R injury. Novel treatments for coronary no-reflow injury may involve targeting mitochondrial fission and the JNK-Drp1 signaling pathway.

Mitochondria: Novel Mechanisms and Therapeutic Targets for Secondary Brain Injury After Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a destructive form of stroke that often results in death or disability. However, the survivors usually experience sequelae of neurological impairments and psychiatric disorders, which affect their daily functionality and working capacity. The recent MISTIE III and STICH II trials have confirmed that early surgical clearance of hematomas does not improve the prognosis of survivors of ICH, so it is vital to find the intervention target of secondary brain injury (SBI) after ICH. Mitochondrial dysfunction, which may be induced by oxidative stress, neuroinflammation, and autophagy, among others, is considered to be a novel pathological mechanism of ICH. Moreover, mitochondria play an important role in promoting neuronal survival and improving neurological function after a hemorrhagic stroke. This review summarizes the mitochondrial mechanism involved in cell death, reactive oxygen species (ROS) production, inflammatory activation, blood–brain barrier (BBB) disruption, and brain edema underlying ICH. We emphasize the potential of mitochondrial protection as a potential therapeutic target for SBI after stroke and provide valuable insight into clinical strategies.

Autophagy in liver diseases

Autophagy is the liver cell energy recycling system regulating a variety of homeostatic mechanisms. Damaged organelles, lipids and proteins are degraded in the lysosomes and their elements are re-used by the cell. Investigations on autophagy have led to the award of two Nobel Prizes and a health of important reports. In this review we describe the fundamental functions of autophagy in the liver including new data on the regulation of autophagy. Moreover we emphasize the fact that autophagy acts like a two edge sword in many occasions with the most prominent paradigm being its involvement in the initiation and progress of hepatocellular carcinoma. We also focused to the implication of autophagy and its specialized forms of lipophagy and mitophagy in the pathogenesis of various liver diseases. We analyzed autophagy not only in well studied diseases, like alcoholic and nonalcoholic fatty liver and liver fibrosis but also in viral hepatitis, biliary diseases, autoimmune hepatitis and rare diseases including inherited metabolic diseases and also acetaminophene hepatotoxicity. We also stressed the different consequences that activation or impairment of autophagy may have in hepatocytes as opposed to Kupffer cells, sinusoidal endothelial cells or hepatic stellate cells. Finally, we analyzed the limited clinical data compared to the extensive experimental evidence and the possible future therapeutic interventions based on autophagy manipulation.

Mitochondrial Fission and Mitophagy Reciprocally Orchestrate Cardiac Fibroblasts Activation

Although mitochondrial fission has been reported to increase proliferative capacity and collagen production, it can also contribute to mitochondrial impairment, which is detrimental to cell survival. The aim of the present study was to investigate the role of mitochondrial fission in cardiac fibroblasts (CF) activation and explore the mechanisms involved in the maintenance of mitochondrial health under this condition. For this, changes in the levels of mitochondrial fission/fusion-related proteins were assessed in transforming growth factor beta 1 (TGF-β1)-activated CF, whereas the role of mitochondrial fission during this process was also elucidated, as were the underlying mechanisms. The interaction between mitochondrial fission and mitophagy, the main defense mechanism against mitochondrial impairment, was also explored. The results showed that the mitochondria in TGF-β1-treated CF were noticeably more fragmented than those of controls. The expression of several mitochondrial fission-related proteins was markedly upregulated, and the levels of fusion-related proteins were also altered, but to a lesser extent. Inhibiting mitochondrial fission resulted in a marked attenuation of TGF-β1-induced CF activation. The TGF-β1-induced increase in glycolysis was greatly suppressed in the presence of a mitochondrial inhibitor, whereas a glycolysis-specific antagonist exerted little additional antifibrotic effects. TGF-β1 treatment increased cellular levels of reactive oxygen species (ROS) and triggered mitophagy, but this effect was reversed following the application of ROS scavengers. For the signals mediating mitophagy, the expression of Pink1, but not Bnip3l/Nix or Fundc1, exhibited the most significant changes, which could be counteracted by treatment with a mitochondrial fission inhibitor. Pink1 knockdown suppressed CF activation and mitochondrial fission, which was accompanied by increased CF apoptosis. In conclusion, mitochondrial fission resulted in increased glycolysis and played a crucial role in CF activation. Moreover, mitochondrial fission promoted reactive oxygen species (ROS) production, leading to mitophagy and the consequent degradation of the impaired mitochondria, thus promoting CF survival and maintaining their activation.

Berberine Ameliorates Hepatic Insulin Resistance by Regulating microRNA-146b/SIRT1 Pathway

OBJECTIVE

Hepatic insulin resistance is a major initiating factor for type 2 diabetes mellitus. In previous study, Gegen Qinlian Decoction containing berberine could enhance hepatic insulin sensitivity by SIRT1-dependent deacetylation of FOXO1. However, it is not clear whether berberine also can improve hepatic insulin sensitivity by SIRT1/FOXO1 pathway. This study aimed to evaluate the efficacy of berberine for improving hepatic insulin resistance and the possible molecular mechanisms involved.

METHODS

In vitro, HepG2 cells were induced with palmitic acid, and glycogen synthesis was examined. In vivo, a high-fat diet (HFD)-fed mouse model was established, and metabolic parameters were assessed. The expressions of miR-146b and sirtuin 1 (SIRT1) in liver were also examined. The relationship between miR-146b and SIRT1 was examined by the dual-luciferase reporter gene assay.

RESULTS

Serum biochemical parameters, such as glucose and HOMA-IR index, were increased in HFD mice; miR-146b and SIRT1 were abnormally expressed in HFD mice and palmitic acid-treated HepG2 cells. Interestingly, berberine reduced body weight and caused a significant improvement in glucose tolerance and HOMA-IR index without altering food intake in mice. Overexpression of miR-146b abolished the protective effect of berberine on palmitic acid-induced impaired glycogen synthesis in HepG2 cells. Luciferase assay showed that miR-146b directly targeted SIRT1.

CONCLUSION

The present findings suggest that berberine could attenuate hepatic insulin resistance through the miR-146b/SIRT1 pathway, which may represent a potential therapeutic target for the prevention and treatment of metabolic diseases, particularly diabetes.

Total Glucosides of Peony Protect Cardiomyocytes against Oxidative Stress and Inflammation by Reversing Mitochondrial Dynamics and Bioenergetics

Total glucosides of peony (TGP) are used to treat rheumatoid arthritis and systemic lupus erythematosus. We explored the protective effects of TGP on cardiomyocyte oxidative stress and inflammation in the presence of hydrogen peroxide by focusing on mitochondrial dynamics and bioenergetics. Our study demonstrated that hydrogen peroxide significantly repressed cardiomyocyte viability and promoted cell apoptosis through induction of the mitochondrial death pathway. TGP treatment sustained cardiomyocyte viability, reduced cardiomyocyte apoptosis, and decreased inflammation and oxidative stress. Molecular investigation indicated that hydrogen peroxide caused mitochondrial dynamics disruption and bioenergetics reduction in cardiomyocytes, but this alteration could be normalized by TGP. We found that disruption of mitochondrial dynamics abolished the regulatory effects of TGP on mitochondrial bioenergetics; TGP modulated mitochondrial dynamics through the AMP-activated protein kinase (AMPK) pathway; and inhibition of AMPK alleviated the protective effects of TGP on mitochondria. Our results showed that TGP treatment reduces cardiomyocyte oxidative stress and inflammation in the presence of hydrogen peroxide by correcting mitochondrial dynamics and enhancing mitochondrial bioenergetics. Additionally, the regulatory effects of TGP on mitochondrial function seem to be mediated through the AMPK pathway. These findings are promising for myocardial injury in patients with rheumatoid arthritis and systemic lupus erythematosus.

A Potential Role for Mitochondrial DNA in the Activation of Oxidative Stress and Inflammation in Liver Disease

Mitochondria are organelles that are essential for cellular homeostasis including energy harvesting through oxidative phosphorylation. Mitochondrial dysfunction plays a vital role in liver diseases as it produces a large amount of reactive oxygen species (ROS), in turn leading to further oxidative damage to the structure and function of mitochondria and other cellular components. More severe oxidative damage occurred in mitochondrial DNA (mtDNA) than in nuclear DNA. mtDNA dysfunction results in further oxidative damage as it participates in encoding respiratory chain polypeptides. In addition, mtDNA can leave the mitochondria and enter the cytoplasm and extracellular environment. mtDNA is derived from ancient bacteria, contains many unmethylated CpG dinucleotide repeats similar to bacterial DNA, and thus can induce inflammation to exacerbate damage to liver cells and distal organs by activating toll-like receptor 9, inflammatory bodies, and stimulator of interferon genes (STING). In this review, we focus on the mechanism by which mtDNA alterations cause liver injuries, including nonalcoholic fatty liver, alcoholic liver disease, drug-induced liver injury, viral hepatitis, and liver cancer.

Oxidized LDL Disrupts Metabolism and Inhibits Macrophage Survival by Activating a miR-9/Drp1/Mitochondrial Fission Signaling Pathway

Mitochondrial dysfunction is associated with macrophage damage, but the role of mitochondrial fission in macrophage cholesterol metabolism is not fully understood. In this study, we explored the influences of miR-9 and mitochondrial fission on macrophage viability and cholesterol metabolism. Macrophages were incubated with oxidized low-density lipoprotein (ox-LDL) in vitro, after which mitochondrial fission, cell viability, and cholesterol metabolism were examined using qPCR, ELISAs, and immunofluorescence. ox-LDL treatment significantly increased Drp1-associated mitochondrial fission. Transfection of Drp1 siRNA significantly reduced cell death, attenuated oxidative stress, and inhibited inflammatory responses in ox-LDL-treated macrophages. Interestingly, inhibition of Drp1-related mitochondrial fission also improved cholesterol metabolism by balancing the transcription of cholesterol influx/efflux enzymes. We also found that miR-9 was downregulated in ox-LDL-treated macrophages, and administration of a miR-9 mimic decreased Drp1 transcription and mitochondrial fission, as well as its effects. These results indicate that signaling via the novel miR-9/Drp1/mitochondrial fission axis is a key determinant of macrophage viability and cholesterol metabolism.

Phosphoglycerate mutase 5 exacerbates cardiac ischemia-reperfusion injury through disrupting mitochondrial quality control

The death of cardiomyocytes either through apoptosis or necroptosis is the pathological feature of cardiac ischemia-reperfusion (I/R) injury. Phosphoglycerate mutase 5 (PGAM5), a mitochondrially-localized serine/threonine-protein phosphatase, functions as a novel inducer of necroptosis. However, intense debate exists regarding the effect of PGAM5 on I/R-related cardiomyocyte death. Using cardiac-specific PGAM5 knockout (PGAM5^CKO) mice, we comprehensively investigated the precise contribution and molecular mechanism of PGAM5 in cardiomyocyte death. Our data showed that both PGAM5 transcription and expression were upregulated in reperfused myocardium. Genetic ablation of PGAM5 suppressed I/R-mediated necroptosis but failed to prevent apoptosis activation, a result that went along with improved heart function and decreased inflammation response. Regardless of PGAM5 status, mitophagy-related cell death was not apparent following I/R. Under physiological conditions, PGAM5 overexpression in primary cardiomyocytes was sufficient to induce cardiomyocyte necroptosis rather than apoptosis. At the sub-cellular levels, PGAM5 deficiency increased mitochondrial DNA copy number and transcript levels, normalized mitochondrial respiration, repressed mitochondrial ROS production, and prevented abnormal mPTP opening upon I/R. Molecular investigation demonstrated that PGAM5 deletion interrupted I/R-mediated Drp^S637 dephosphorylation but failed to abolish I/R-induce Drp1^S616 phosphorylation, resulting in partial inhibition of mitochondrial fission. In addition, declining Mfn2 and OPA1 levels were restored in PGAM5^CKO cardiomyocytes following I/R. Nevertheless, PGAM5 depletion did not rescue suppressed mitophagy upon I/R injury. In conclusion, our results provide an insight into the specific role and working mechanism of PGAM5 in driving cardiomyocyte necroptosis through imposing mitochondrial quality control in cardiac I/R injury.

SERCA Overexpression Improves Mitochondrial Quality Control and Attenuates Cardiac Microvascular Ischemia-Reperfusion Injury

Despite significant advances in the treatment of myocardial ischemia-reperfusion (I/R) injury, coronary circulation is a so far neglected target of cardioprotection. In this study, we investigated the molecular mechanisms underlying I/R injury to cardiac microcirculation. Using gene delivery, we analyzed microvascular protective effects of sarcoplasmic/endoplasmic reticulum Ca²⁺-ATPase (SERCA) on the reperfused heart and examined the role of SERCA in regulating mitochondrial quality control in cardiac microvascular endothelial cells (CMECs). Our data showed that SERCA overexpression attenuates lumen stenosis, inhibits microthrombus formation, reduces inflammation response, and improves endothelium-dependent vascular relaxation. In vitro experiments demonstrated that SERCA overexpression improves endothelial viability, barrier integrity, and cytoskeleton assembly in CMECs. Mitochondrial quality control, including mitochondrial fusion, mitophagy, bioenergetics, and biogenesis, were disrupted by I/R injury but were restored by SERCA overexpression. SERCA overexpression also restored mitochondrial quality control by inhibiting calcium overload, inactivating xanthine oxidase (XO), and reducing intracellular/mitochondrial reactive oxygen species (ROS). Administration of exogenous XO or a calcium channel agonist abolished the protective effects of SERCA overexpression on mitochondrial quality control and offset the beneficial effects of SERCA overexpression after cardiac microvascular I/R injury. These findings indicate that SERCA overexpression may be an effective approach to targeting cardiac microvascular I/R injury by regulating calcium/XO/ROS signaling and preserving mitochondrial quality control.

Opa1 Reduces Hypoxia-Induced Cardiomyocyte Death by Improving Mitochondrial Quality Control

Mitochondrial dysfunction contributes to cardiovascular disorders, especially post-infarction cardiac injury, through incompletely characterized mechanisms. Among the latter, increasing evidence points to alterations in mitochondrial quality control, a range of adaptive responses regulating mitochondrial morphology and function. Optic atrophy 1 (Opa1) is a mitochondrial inner membrane GTPase known to promote mitochondrial fusion. In this study, hypoxia-mediated cardiomyocyte damage was induced to mimic post-infarction cardiac injury in vitro. Loss- and gain-of-function assays were then performed to evaluate the impact of Opa1 expression on mitochondrial quality control and cardiomyocyte survival and function. Hypoxic stress reduced cardiomyocyte viability, impaired contractile/relaxation functions, and augmented the synthesis of pro-inflammatory mediators. These effects were exacerbated by Opa1 knockdown, and significantly attenuated by Opa1 overexpression. Mitochondrial quality control was disturbed by hypoxia, as reflected by multiple mitochondrial deficits; i.e., increased fission, defective fusion, impaired mitophagy, decreased biogenesis, increased oxidative stress, and blunted respiration. By contrast, overexpression of Opa1 normalized mitochondrial quality control and sustained cardiomyocyte function. We also found that ERK, AMPK, and YAP signaling can regulate Opa1 expression. These results identify Opa1 as a novel regulator of mitochondrial quality control and highlight a key role for Opa1 in protecting cardiomyocytes against post-infarction cardiac injury.

Resveratrol Improves Bnip3-Related Mitophagy and Attenuates High-Fat-Induced Endothelial Dysfunction

Statin treatment reduces cardiovascular risk. However, individuals with well-controlled low-density lipoprotein (LDL) levels may remain at increased risk owing to persistent high triglycerides and low high-density lipoprotein cholesterol. Because resveratrol promotes glucose metabolism and mitigates cardiovascular disorders, we explored its mechanism of protective action on high-fat-induced endothelial dysfunction. Human umbilical venous endothelial cells were treated with oxidized LDL (ox-LDL) in vitro. Endothelial function, cell survival, proliferation, migration, and oxidative stress were analyzed through western blots, quantitative polymerase chain reaction, ELISA, and immunofluorescence. ox-LDL induced endothelial cell apoptosis, proliferation arrest, and mobilization inhibition, all of which resveratrol reduced. ox-LDL suppressed the activities of mitochondrial respiration complex I and III and reduced levels of intracellular antioxidative enzymes, resulting in reactive oxygen species overproduction and mitochondrial dysfunction. Resveratrol treatment upregulated Bnip3-related mitophagy and prevented ox-LDL-mediated mitochondrial respiration complexes inactivation, sustaining mitochondrial membrane potential and favoring endothelial cell survival. We found that resveratrol enhanced Bnip3 transcription through hypoxia-inducible factor 1 (HIF1) and 5' AMP-activated protein kinase (AMPK). Inhibition of AMPK and HIF1 abolished resveratrol-mediated protection of mitochondrial redox balance and endothelial viability. Together, these data demonstrate resveratrol reduces hyperlipemia-related endothelial damage by preserving mitochondrial homeostasis.

Mammalian STE20-Like Kinase 2 Promotes Lipopolysaccharides-Mediated Cardiomyocyte Inflammation and Apoptosis by Enhancing Mitochondrial Fission

In this study, we analyzed the role of mammalian STE20-like protein kinase 2 (Mst2), a serine-threonine protein kinase, in Lipopolysaccharides (LPS)-mediated inflammation and apoptosis in the H9C2 cardiomyocytes. Mst2 mRNA and protein levels were significantly upregulated in the LPS-treated H9C2 cardiomyocytes. LPS treatment induced expression of IL-2, IL-8, and MMP9 mRNA and proteins in the H9C2 cardiomyocytes, and this was accompanied by increased caspase-3/9 mediating H9C2 cardiomyocyte apoptosis. LPS treatment also increased mitochondrial reactive oxygen species (ROS) and the levels of antioxidant enzymes, such as GSH, SOD, and GPX, in the H9C2 cardiomyocytes. The LPS-treated H9C2 cardiomyocytes showed lower cellular ATP levels and mitochondrial state-3/4 respiration but increased mitochondrial fragmentation, including upregulation of the mitochondrial fission genes Drp1, Mff, and Fis1. LPS-induced inflammation, mitochondrial ROS, mitochondrial fission, and apoptosis were all significantly suppressed by pre-treating the H9C2 cardiomyocytes with the Mst2 inhibitor, XMU-MP1. However, the beneficial effects of Mst2 inhibition by XMU-MP1 were abolished by carbonyl cyanide-4-(trifluoromethoxy) phenylhydrazone (FCCP), a potent activator of mitochondrial fission. These findings demonstrate that Mst2 mediates LPS-induced cardiomyocyte inflammation and apoptosis by increasing mitochondrial fission.

Targeting Long Non-coding RNA to Therapeutically Regulate Gene Expression in Cancer

Long-chain non-coding RNAs (lncRNAs) are RNA molecules with a length greater than 200 nt and no function of encoding proteins. lncRNAs play a precise regulatory function at different levels of transcription and post-transcription, and they interact with various regulatory factors to regulate gene expression, and then participate in cell growth, differentiation, apoptosis, and other life processes. In recent years, studies have shown that the abnormal expression of lncRNAs is closely related to the occurrence and development of tumors, which is expected to become an effective biomarker in tumor diagnosis. The sequencing analysis of mutations in the whole tumor genome suggests that mutations in non-coding regions may play an important role in the occurrence and development of tumors. Therefore, in-depth study of lncRNAs is helpful to clarify the molecular mechanism of tumor occurrence and development and to provide new targets for tumor diagnosis and treatment. This review introduces the molecular mechanism and clinical application prospect of lncRNAs affecting tumor development from the perspective of gene expression and regulation.

Police Violence among Adults Diagnosed with Mental Disorders

Police violence is reportedly common among those diagnosed with mental disorders characterized by the presence of psychotic symptoms or pronounced emotional lability. Despite the perception that people with mental illness are disproportionately mistreated by the police, there is relatively little empirical research on this topic. A cross-sectional general population survey was administered online in 2017 to 1,000 adults in two eastern U.S. cities to examine the relationship between police violence exposure, mental disorders, and crime involvement. Results from hierarchical logistic regression and mediation analyses revealed that a range of mental health conditions are broadly associated with elevated risk for police violence exposure. Individuals with severe mental illness are more likely than the general population to be physically victimized by police, regardless of their involvement in criminal activities. Most of the excess risk of police violence exposure related to common psychiatric diagnoses was explained by confounding factors including crime involvement. However, crime involvement may necessitate more police contact, but does not necessarily justify victimization or excessive force (particularly sexual and psychological violence). Findings support the need for adequate training for police officers on how to safely interact with people with mental health conditions, particularly severe mental illness.

Role and Mechanisms of Mitophagy in Liver Diseases

The mitochondrion is an organelle that plays a vital role in the regulation of hepatic cellular redox, lipid metabolism, and cell death. Mitochondrial dysfunction is associated with both acute and chronic liver diseases with emerging evidence indicating that mitophagy, a selective form of autophagy for damaged/excessive mitochondria, plays a key role in the liver’s physiology and pathophysiology. This review will focus on mitochondrial dynamics, mitophagy regulation, and their roles in various liver diseases (alcoholic liver disease, non-alcoholic fatty liver disease, drug-induced liver injury, hepatic ischemia-reperfusion injury, viral hepatitis, and cancer) with the hope that a better understanding of the molecular events and signaling pathways in mitophagy regulation will help identify promising targets for the future treatment of liver diseases.

Mitophagy in the Pathogenesis of Liver Diseases

Autophagy is a catabolic process involving vacuolar sequestration of intracellular components and their targeting to lysosomes for degradation, thus supporting nutrient recycling and energy regeneration. Accumulating evidence indicates that in addition to being a bulk, nonselective degradation mechanism, autophagy may selectively eliminate damaged mitochondria to promote mitochondrial turnover, a process termed “mitophagy”. Mitophagy sequesters dysfunctional mitochondria via ubiquitination and cargo receptor recognition and has emerged as an important event in the regulation of liver physiology. Recent studies have shown that mitophagy may participate in the pathogenesis of various liver diseases, such as liver injury, liver steatosis/fatty liver disease, hepatocellular carcinoma, viral hepatitis, and hepatic fibrosis. This review summarizes the current knowledge on the molecular regulations and functions of mitophagy in liver physiology and the roles of mitophagy in the development of liver-related diseases. Furthermore, the therapeutic implications of targeting hepatic mitophagy to design a new strategy to cure liver diseases are discussed.

Role of mitochondrial quality control in the pathogenesis of nonalcoholic fatty liver disease

Nutrient oversupply and mitochondrial dysfunction play central roles in nonalcoholic fatty liver disease (NAFLD). The mitochondria are the major sites of β-oxidation, a catabolic process by which fatty acids are broken down. The mitochondrial quality control (MQC) system includes mitochondrial fission, fusion, mitophagy and mitochondrial redox regulation, and is essential for the maintenance of the functionality and structural integrity of the mitochondria. Excessive and uncontrolled production of reactive oxygen species (ROS) in the mitochondria damages mitochondrial components, including membranes, proteins and mitochondrial DNA (mtDNA), and triggers the mitochondrial pathway of apoptosis. The functionality of some damaged mitochondria can be restored by fusion with normally functioning mitochondria, but when severely damaged, mitochondria are segregated from the remaining functional mitochondrial network through fission and are eventually degraded via mitochondrial autophagy, also called as mitophagy. In this review, we describe the functions and mechanisms of mitochondrial fission, fusion, oxidative stress and mitophagy in the development and progression of NAFLD.

Liraglutide reduces hyperglycemia-induced cardiomyocyte death through activating glucagon-like peptide 1 receptor and targeting AMPK pathway

Objective: Hyperglycemia-mediated cardiomyocyte damage is associated with inflammation and AMPK inactivation.Aim: The aim of our study is to explore the protective effects exerted by liraglutide on AMPK pathway and glucagon-like peptide 1 receptor in diabetic cardiomyopathy.Methods: Cardiomyocytes were treated with high-glucose stress and cardiomyocyte viability was determined via (3-(4,5-dimethylthiazol-2-yl)-2,5diphenyltetrazolium bromide assay. Besides, LDH release, immunofluorescence, and qPCR were used to verify the influence of liraglutide on hyperglycemia-treated cardiomyocytes.Results: Hyperglycemia treatment caused inflammation response and oxidative stress were significantly elevated in cardiomyocytes. This alteration could be reversed by liraglutide. Besides, cell viability was reduced whereas apoptosis was increased after exposure to high glucose treatment. However, liraglutide treatment could attenuate apoptosis and reverse cell viability in cardiomyocyte. Further, we found that AMPK pathway was also activated and glucagon-like peptide 1 receptor expression was increased in response to liraglutide treatment.Conclusions: Liraglutide could attenuate hyperglycemia-mediated cardiomyocyte damage through reversing AMPK pathway and upregulating glucagon-like peptide 1 receptor.

Pathological Roles of Mitochondrial Oxidative Stress and Mitochondrial Dynamics in Cardiac Microvascular Ischemia/Reperfusion Injury

Mitochondria are key regulators of cell fate through controlling ATP generation and releasing pro-apoptotic factors. Cardiac ischemia/reperfusion (I/R) injury to the coronary microcirculation has manifestations ranging in severity from reversible edema to interstitial hemorrhage. A number of mechanisms have been proposed to explain the cardiac microvascular I/R injury including edema, impaired vasomotion, coronary microembolization, and capillary destruction. In contrast to their role in cell types with higher energy demands, mitochondria in endothelial cells primarily function in signaling cellular responses to environmental cues. It is clear that abnormal mitochondrial signatures, including mitochondrial oxidative stress, mitochondrial fission, mitochondrial fusion, and mitophagy, play a substantial role in endothelial cell function. While the pathogenic role of each of these mitochondrial alterations in the endothelial cells I/R injury remains complex, profiling of mitochondrial oxidative stress and mitochondrial dynamics in endothelial cell dysfunction may offer promising potential targets in the search for novel diagnostics and therapeutics in cardiac microvascular I/R injury. The objective of this review is to discuss the role of mitochondrial oxidative stress on cardiac microvascular endothelial cells dysfunction. Mitochondrial dynamics, including mitochondrial fission and fusion, are critically discussed to understand their roles in endothelial cell survival. Finally, mitophagy, as a degradative mechanism for damaged mitochondria, is summarized to figure out its contribution to the progression of microvascular I/R injury.