Gene expression analysis to identify mechanisms underlying heart failure susceptibility in mice and humans

Cardioprotection by the adiponectin receptor agonist ALY688 in a preclinical mouse model of heart failure with reduced ejection fraction (HFrEF)

AIMS

Adiponectin has been shown to mediate cardioprotective effects and levels are typically reduced in patients with cardiometabolic disease. Hence, there has been intense interest in developing adiponectin-based therapeutics. The aim of this translational research study was to examine the functional significance of targeting adiponectin signaling with the adiponectin receptor agonist ALY688 in a mouse model of heart failure with reduced ejection fraction (HFrEF), and the mechanisms of cardiac remodeling leading to cardioprotection.

METHODS AND RESULTS

Wild-type mice were subjected to transverse aortic constriction (TAC) to induce left ventricular pressure overload (PO), or sham surgery, with or without daily subcutaneous ALY688-SR administration. Temporal analysis of cardiac function was conducted via weekly echocardiography for 5 weeks and we observed that ALY688 attenuated the PO-induced dysfunction. ALY688 also reduced cardiac hypertrophic remodeling, assessed via LV mass, heart weight to body weight ratio, cardiomyocyte cross sectional area, ANP and BNP levels. ALY688 also attenuated PO-induced changes in myosin light and heavy chain expression. Collagen content and myofibroblast profile indicated that fibrosis was attenuated by ALY688 with TIMP1 and scleraxis/periostin identified as potential mechanistic contributors. ALY688 reduced PO-induced elevation in circulating cytokines including IL-5, IL-13 and IL-17, and the chemoattractants MCP-1, MIP-1β, MIP-1alpha and MIP-3α. Assessment of myocardial transcript levels indicated that ALY688 suppressed PO-induced elevations in IL-6, TLR-4 and IL-1β, collectively indicating anti-inflammatory effects. Targeted metabolomic profiling indicated that ALY688 increased fatty acid mobilization and oxidation, increased betaine and putrescine plus decreased sphingomyelin and lysophospholipids, a profile indicative of improved insulin sensitivity.

CONCLUSION

These results indicate that the adiponectin mimetic peptide ALY688 reduced PO-induced fibrosis, hypertrophy, inflammation and metabolic dysfunction and represents a promising therapeutic approach for treating HFrEF in a clinical setting.

Modulation of miR-29 influences myocardial compliance likely through coordinated regulation of calcium handling and extracellular matrix

MicroRNAs (miRNAs) control the expression of diverse subsets of target mRNAs, and studies have found miRNA dysregulation in failing hearts. Expression of miR-29 is abundant in heart, increases with aging, and is altered in cardiomyopathies. Prior studies demonstrate that miR-29 reduction via genetic knockout or pharmacologic blockade can blunt cardiac hypertrophy and fibrosis in mice. Surprisingly, this depended on specifically blunting miR-29 actions in cardiomyocytes versus fibroblasts. To begin developing more translationally relevant vectors, we generated a novel transgene-encoded miR-29 inhibitor (TuD-29) that can be incorporated into a viral-mediated gene therapy for cardioprotection. Here, we corroborate that miR-29 expression and activity is higher in cardiomyocytes versus fibroblasts and demonstrate that TuD-29 effectively blunts hypertrophic responses in cultured cardiomyocytes and mouse hearts. Furthermore, we found that adeno-associated virus (AAV)-mediated miR-29 overexpression in mouse hearts induces early diastolic dysfunction, whereas AAV:TuD-29 treatment improves cardiac output by increasing end-diastolic and stroke volumes. The integration of RNA sequencing and miRNA-target interactomes reveals that miR-29 regulates genes involved in calcium handling, cell stress and hypertrophy, metabolism, ion transport, and extracellular matrix remodeling. These investigations support a likely versatile role for miR-29 in influencing myocardial compliance and relaxation, potentially providing a unique therapeutic avenue to improve diastolic function in heart failure patients.

New drug discovery of cardiac anti-arrhythmic drugs: insights in animal models

Cardiac rhythm regulated by micro-macroscopic structures of heart. Pacemaker abnormalities or disruptions in electrical conduction, lead to arrhythmic disorders may be benign, typical, threatening, ultimately fatal, occurs in clinical practice, patients on digitalis, anaesthesia or acute myocardial infarction. Both traditional and genetic animal models are: In-vitro: Isolated ventricular Myocytes, Guinea pig papillary muscles, Patch-Clamp Experiments, Porcine Atrial Myocytes, Guinea pig ventricular myocytes, Guinea pig papillary muscle: action potential and refractory period, Langendorff technique, Arrhythmia by acetylcholine or potassium. Acquired arrhythmia disorders: Transverse Aortic Constriction, Myocardial Ischemia, Complete Heart Block and AV Node Ablation, Chronic Tachypacing, Inflammation, Metabolic and Drug-Induced Arrhythmia. In-Vivo: Chemically induced arrhythmia: Aconitine antagonism, Digoxin-induced arrhythmia, Strophanthin/ouabain-induced arrhythmia, Adrenaline-induced arrhythmia, and Calcium-induced arrhythmia. Electrically induced arrhythmia: Ventricular fibrillation electrical threshold, Arrhythmia through programmed electrical stimulation, sudden coronary death in dogs, Exercise ventricular fibrillation. Genetic Arrhythmia: Channelopathies, Calcium Release Deficiency Syndrome, Long QT Syndrome, Short QT Syndrome, Brugada Syndrome. Genetic with Structural Heart Disease: Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia, Dilated Cardiomyopathy, Hypertrophic Cardiomyopathy, Atrial Fibrillation, Sick Sinus Syndrome, Atrioventricular Block, Preexcitation Syndrome. Arrhythmia in Pluripotent Stem Cell Cardiomyocytes. Conclusion: Both traditional and genetic, experimental models of cardiac arrhythmias' characteristics and significance help in development of new antiarrhythmic drugs.

Targeting gut microbiota-derived kynurenine to predict and protect the remodeling of the pressure-overloaded young heart

Pressure-overloaded left ventricular remodeling in young population is progressive and readily degenerate into heart failure. The aims of this study were to identify a plasma metabolite that predicts and is mechanistically linked to the disease. Untargeted metabolomics determined elevated plasma kynurenine (Kyn) in both the patient cohorts and the mice model, which was correlated with remodeling parameters. In vitro and in vivo evidence, combined with single-nucleus RNA sequencing (snRNA-seq), demonstrated that Kyn affected both cardiomyocytes and cardiac fibroblasts by activating aryl hydrocarbon receptors (AHR) to up-regulate hypertrophy- and fibrosis-related genes. Shotgun metagenomics and fecal microbiota transplantation revealed the existence of the altered gut microbiota-Kyn relationship. Supplementation of selected microbes reconstructed the gut microbiota, reduced plasma Kyn, and alleviated ventricular remodeling. Our data collectively discovered a gut microbiota-derived metabolite to activate AHR and its gene targets in remodeling young heart, a process that could be prevented by specific gut microbiota modulation.

Transcriptome studies of inherited dilated cardiomyopathies

Dilated cardiomyopathy (DCM) is a group of heart muscle diseases that often lead to heart failure, with more than 50 causative genes have being linked to DCM. The heterogenous nature of the inherited DCMs suggest the need of precision medicine. Consistent with this emerging concept, transcriptome studies in human patients with DCM indicated distinct molecular signature for DCMs of different genetic etiology. To facilitate this line of research, we reviewed the status of transcriptome studies of inherited DCMs by focusing on three predominant DCM causative genes, TTN, LMNA, and BAG3. Besides studies in human patients, we summarized transcriptomic analysis of these inherited DCMs in a variety of model systems ranging from iPSCs to rodents and zebrafish. We concluded that the RNA-seq technology is a powerful genomic tool that has already led to the discovery of new modifying genes, signaling pathways, and related therapeutic avenues. We also pointed out that both temporal (different pathological stages) and spatial (different cell types) information need to be considered for future transcriptome studies. While an important bottle neck is the low throughput in experimentally testing differentially expressed genes, new technologies in efficient animal models such as zebrafish starts to be developed. It is anticipated that the RNA-seq technology will continue to uncover both unique and common pathological events, aiding the development of precision medicine for inherited DCMs.

Animal Models to Study Cardiac Arrhythmias

Cardiac arrhythmias are a significant cause of morbidity and mortality worldwide, accounting for 10% to 15% of all deaths. Although most arrhythmias are due to acquired heart disease, inherited channelopathies and cardiomyopathies disproportionately affect children and young adults. Arrhythmogenesis is complex, involving anatomic structure, ion channels and regulatory proteins, and the interplay between cells in the conduction system, cardiomyocytes, fibroblasts, and the immune system. Animal models of arrhythmia are powerful tools for studying not only molecular and cellular mechanism of arrhythmogenesis but also more complex mechanisms at the whole heart level, and for testing therapeutic interventions. This review summarizes basic and clinical arrhythmia mechanisms followed by an in-depth review of published animal models of genetic and acquired arrhythmia disorders.

TECRL deficiency results in aberrant mitochondrial function in cardiomyocytes

Sudden cardiac death (SCD) caused by ventricular arrhythmias is the leading cause of mortality of cardiovascular disease. Mutation in TECRL, an endoplasmic reticulum protein, was first reported in catecholaminergic polymorphic ventricular tachycardia during which a patient succumbed to SCD. Using loss- and gain-of-function approaches, we investigated the role of TECRL in murine and human cardiomyocytes. Tecrl (knockout, KO) mouse shows significantly aggravated cardiac dysfunction, evidenced by the decrease of ejection fraction and fractional shortening. Mechanistically, TECRL deficiency impairs mitochondrial respiration, which is characterized by reduced adenosine triphosphate production, increased fatty acid synthase (FAS) and reactive oxygen species production, along with decreased MFN2, p-AKT (Ser473), and NRF2 expressions. Overexpression of TECRL induces mitochondrial respiration, in PI3K/AKT dependent manner. TECRL regulates mitochondrial function mainly through PI3K/AKT signaling and the mitochondrial fusion protein MFN2. Apoptosis inducing factor (AIF) and cytochrome C (Cyc) is released from the mitochondria into the cytoplasm after siTECRL infection, as demonstrated by immunofluorescent staining and western blotting. Herein, we propose a previously unrecognized TECRL mechanism in regulating CPVT and may provide possible support for therapeutic target in CPVT.

The endoplasmic reticulum protein TECRL promotes mitochondrial function in cardiomyocytes and its knockout in mice leads to cardiac dysfunction, decreased mitochondria function, and elevated levels of reactive oxygen species.

Effects of Short Term Adiponectin Receptor Agonism on Cardiac Function and Energetics in Diabetic db/db Mice

Objective

Impaired cardiac efficiency is a hallmark of diabetic cardiomyopathy in models of type 2 diabetes. Adiponectin receptor 1 (AdipoR1) deficiency impairs cardiac efficiency in non-diabetic mice, suggesting that hypoadiponectinemia in type 2 diabetes may contribute to impaired cardiac efficiency due to compromised AdipoR1 signaling. Thus, we investigated whether targeting cardiac adiponectin receptors may improve cardiac function and energetics, and attenuate diabetic cardiomyopathy in type 2 diabetic mice.

Methods

A non-selective adiponectin receptor agonist, AdipoRon, and vehicle were injected intraperitoneally into Eight-week-old db/db or C57BLKS/J mice for 10 days. Cardiac morphology and function were evaluated by echocardiography and working heart perfusions.

Results

Based on echocardiography, AdipoRon treatment did not alter ejection fraction, left ventricular diameters or left ventricular wall thickness in db/db mice compared to vehicle-treated mice. In isolated working hearts, an impairment in cardiac output and efficiency in db/db mice was not improved by AdipoRon. Mitochondrial respiratory capacity, respiration in the presence of oligomycin, and 4-hydroxynonenal levels were similar among all groups. However, AdipoRon induced a marked shift in the substrate oxidation pattern in db/db mice towards increased reliance on glucose utilization. In parallel, the diabetes-associated increase in serum triglyceride levels in vehicle-treated db/db mice was blunted by AdipoRon treatment, while an increase in myocardial triglycerides in vehicle-treated db/db mice was not altered by AdipoRon treatment.

Conclusion

AdipoRon treatment shifts myocardial substrate preference towards increased glucose utilization, likely by decreasing fatty acid delivery to the heart, but was not sufficient to improve cardiac output and efficiency in db/db mice.

Cardiomyocyte-specific miR-100 overexpression preserves heart function under pressure overload in mice and diminishes fatty acid uptake as well as ROS production by direct suppression of Nox4 and CD36

MicroRNAs are key regulators of the cardiac response to injury. MiR-100 has recently been suggested to be involved in different forms of heart failure, but functional studies are lacking. In the present study, we examined the impact of transgenic miR-100 overexpression on cardiac structure and function during physiological aging and pathological pressure-overload-induced heart failure in mice after transverse aortic constriction surgery. MiR-100 was moderately upregulated after induction of pressure overload in mice. While in our transgenic model the cardiomyocyte-specific overexpression of miR-100 did not result in an obvious cardiac phenotype in unchallenged mice, the transgenic mouse strain exhibited less left ventricular dilatation and a higher ejection fraction than wildtype animals, demonstrating an attenuation of maladaptive cardiac remodeling by miR-100. Cardiac transcriptome analysis identified a repression of several regulatory genes related to cardiac metabolism, lipid peroxidation, and production of reactive oxygen species (ROS) by miR-100 overexpression, possibly mediating the observed functional effects. While the modulation of ROS-production seemed to be indirectly affected by miR-100 via Alox5-and Nox4-downregulation, we demonstrated that miR-100 induced a direct repression of the scavenger protein CD36 in murine hearts resulting in a decreased uptake of long-chain fatty acids and an alteration of mitochondrial respiratory function with an enhanced glycolytic state. In summary, we identified miR-100 as a modulator of cardiac metabolism and ROS production without an apparent cardiac phenotype at baseline but a protective effect under conditions of pressure-overload-induced cardiac stress, providing new insight into the mechanisms of heart failure.

Gene expression profiling of hypertrophic cardiomyocytes identifies new players in pathological remodelling

AIMS

Pathological cardiac remodelling is characterized by cardiomyocyte (CM) hypertrophy and fibroblast activation, which can ultimately lead to maladaptive hypertrophy and heart failure (HF). Genome-wide expression analysis on heart tissue has been instrumental for the identification of molecular mechanisms at play. However, these data were based on signals derived from all cardiac cell types. Here, we aimed for a more detailed view on molecular changes driving maladaptive CM hypertrophy to aid in the development of therapies to reverse pathological remodelling.

METHODS AND RESULTS

Utilizing CM-specific reporter mice exposed to pressure overload by transverse aortic banding and CM isolation by flow cytometry, we obtained gene expression profiles of hypertrophic CMs in the more immediate phase after stress, and CMs showing pathological hypertrophy. We identified subsets of genes differentially regulated and specific for either stage. Among the genes specifically up-regulated in the CMs during the maladaptive phase we found known stress markers, such as Nppb and Myh7, but additionally identified a set of genes with unknown roles in pathological hypertrophy, including the platelet isoform of phosphofructokinase (PFKP). Norepinephrine-angiotensin II treatment of cultured human CMs induced the secretion of N-terminal-pro-B-type natriuretic peptide (NT-pro-BNP) and recapitulated the up-regulation of these genes, indicating conservation of the up-regulation in failing CMs. Moreover, several genes induced during pathological hypertrophy were also found to be increased in human HF, with their expression positively correlating to the known stress markers NPPB and MYH7. Mechanistically, suppression of Pfkp in primary CMs attenuated stress-induced gene expression and hypertrophy, indicating that Pfkp is an important novel player in pathological remodelling of CMs.

CONCLUSION

Using CM-specific transcriptomic analysis, we identified novel genes induced during pathological hypertrophy that are relevant for human HF, and we show that PFKP is a conserved failure-induced gene that can modulate the CM stress response.

GLP-1 receptor agonists (GLP-1RAs): cardiovascular actions and therapeutic potential

Type 2 diabetes mellitus (T2DM) is closely associated with cardiovascular diseases (CVD), including atherosclerosis, hypertension and heart failure. Some anti-diabetic medications are linked with an increased risk of weight gain or hypoglycemia which may reduce the efficacy of the intended anti-hyperglycemic effects of these therapies. The recently developed receptor agonists for glucagon-like peptide-1 (GLP-1RAs), stimulate insulin secretion and reduce glycated hemoglobin levels without having side effects such as weight gain and hypoglycemia. In addition, GLP1-RAs demonstrate numerous cardiovascular protective effects in subjects with or without diabetes. There have been several cardiovascular outcomes trials (CVOTs) involving GLP-1RAs, which have supported the overall cardiovascular benefits of these drugs. GLP1-RAs lower plasma lipid levels and lower blood pressure (BP), both of which contribute to a reduction of atherosclerosis and reduced CVD. GLP-1R is expressed in multiple cardiovascular cell types such as monocyte/macrophages, smooth muscle cells, endothelial cells, and cardiomyocytes. Recent studies have indicated that the protective properties against endothelial dysfunction, anti-inflammatory effects on macrophages and the anti-proliferative action on smooth muscle cells may contribute to atheroprotection through GLP-1R signaling. In the present review, we describe the cardiovascular effects and underlying molecular mechanisms of action of GLP-1RAs in CVOTs, animal models and cultured cells, and address how these findings have transformed our understanding of the pharmacotherapy of T2DM and the prevention of CVD.

Acetylation of muscle creatine kinase negatively impacts high-energy phosphotransfer in heart failure

A hallmark of impaired myocardial energetics in failing hearts is the downregulation of the creatine kinase (CK) system. In heart failure patients and animal models, myocardial phosphocreatine content and the flux of the CK reaction are negatively correlated with the outcome of heart failure. While decreased CK activity is highly reproducible in failing hearts, the underlying mechanisms remains elusive. Here, we report an inverse relationship between the activity and acetylation of CK muscle form (CKM) in human and mouse failing hearts. Hyperacetylation of recombinant CKM disrupted MM homodimer formation and reduced enzymatic activity, which could be reversed by sirtuin 2 treatment. Mass spectrometry analysis identified multiple lysine residues on the MM dimer interface, which were hyperacetylated in the failing hearts. Molecular modeling of CK MM homodimer suggested that hyperacetylation prevented dimer formation through interfering salt bridges within and between the 2 monomers. Deacetylation by sirtuin 2 reduced acetylation of the critical lysine residues, improved dimer formation, and restored CKM activity from failing heart tissue. These findings reveal a potentially novel mechanism in the regulation of CK activity and provide a potential target for improving high-energy phosphoryl transfer in heart failure.

Experimental model of congestive heart failure induced by transverse aortic constriction in BALB/c mice

INTRODUCTION

Murine transverse aortic constriction (TAC) is a frequently used model of pressure overload-induced left ventricular (LV) remodeling. However, there is considerable variability in disease progression to overt heart failure (HF) development in the most commonly used strain of mice (i.e., C57BL/6J). Studies have shown that C57BL/6J mice are more resistant than BALB/c mice to congestive HF development following myocardial infarction or angiotensin II-induced hypertension. Therefore, we tested the hypothesis that BALB/c mice may be a better research model to study TAC-induced progressive HF.

METHODS

Following sham or TAC surgery in both C57BL/6J (n = 29) and BALB/c (n = 32) mice, we evaluated cardiac dimensions and function by echocardiography at 2, 4, 8, and 12 weeks and monitored survival throughout the study. In a separate cohort of BALB/c mice, we repeated the study in the presence of the angiotensin converting enzyme inhibitor enalapril or a vehicle initiated 2 weeks post-TAC and administered for 6 weeks. At the end of the studies, we assessed the heart weight, lung weight, and plasma brain natriuretic peptide (BNP) concentration.

RESULTS

Following comparable TAC, both C57BL/6J and BALB/c mice showed significant LV remodeling compared with the sham control mice. BALB/c mice progressively developed systolic dysfunction, LV dilation, lung congestion, and significant mortality, whereas C57BL/6J mice did not. In the separate cohort of BALB/c TAC mice, enalapril significantly reduced the heart weight, lung weight, and plasma BNP concentration and improved survival compared with the vehicle control.

DISCUSSION

BALB/c mice uniformly developed congestive HF post-TAC. Enalapril was effective in improving survival and reducing lung congestion in this model. The data suggest that BALB/c mice may be a better research tool than C57BL/6J mice to study TAC-induced disease progression to HF and to evaluate novel therapies for the treatment of chronic HF with reduced ejection fraction.

Small animal models of heart failure

Heart disease is a major cause of death worldwide with increasing prevalence, which urges the development of new therapeutic strategies. Over the last few decades, numerous small animal models have been generated to mimic various pathomechanisms contributing to heart failure (HF). Despite some limitations, these animal models have greatly advanced our understanding of the pathogenesis of the different aetiologies of HF and paved the way to understanding the underlying mechanisms and development of successful treatments. These models utilize surgical techniques, genetic modifications, and pharmacological approaches. The present review discusses the strengths and limitations of commonly used small animal HF models, which continue to provide crucial insight and facilitate the development of new treatment strategies for patients with HF.

Cardioprotective Role of Melatonin in Acute Myocardial Infarction

Melatonin is a pleiotropic, indole secreted, and synthesized by the human pineal gland. Melatonin has biological effects including anti-apoptosis, protecting mitochondria, anti-oxidation, anti-inflammation, and stimulating target cells to secrete cytokines. Its protective effect on cardiomyocytes in acute myocardial infarction (AMI) has caused widespread interest in the actions of this molecule. The effects of melatonin against oxidative stress, promoting autophagic repair of cells, regulating immune and inflammatory responses, enhancing mitochondrial function, and relieving endoplasmic reticulum stress, play crucial roles in protecting cardiomyocytes from infarction. Mitochondrial apoptosis and dysfunction are common occurrence in cardiomyocyte injury after myocardial infarction. This review focuses on the targets of melatonin in protecting cardiomyocytes in AMI, the main molecular signaling pathways that melatonin influences in its endogenous protective role in myocardial infarction, and the developmental prospect of melatonin in myocardial infarction treatment.

Exendin-4 attenuates inflammation-mediated endothelial cell apoptosis in varicose veins through inhibiting the MAPK-JNK signaling pathway

Context: Inflammation response has been found to be associated with endothelial cell death in the progression of varicose veins. Exendin-4 is able to reduce inflammation and thus attenuate cell apoptosis.Aim: The aim of our study is to explore the influence of Exendin-4 on LPS-treated endothelial cells.Methods: Cells were treated with LPS. Exendin-4 was added into the medium of cells. Western blots, qPCR, and ELISA were used to analyze the role of Exendin-4 in LPS-mediated cell death.Results: We found that LPS treatment caused significantly cell death. Whereas this trend could be attenuated by Exendin-4. After treatment with Exendin-4, inflammation factors upregulation and oxidative stress activation were significantly repressed, an effect that was followed by a drop in the levels of glucose production and lactic acid generation. At the molecular levels, Exendin-4 treatment inhibited the activity of MAPK-JNK signaling pathway in the presence of LPS treatment.Conclusions: LPS causes cell apoptosis through inducing inflammation response, oxidative stress and energy stress. Exendin-4 treatment enhances cell survival, reduces inflammation, and improves energy stress through inhibiting the MAPK-JNK signaling pathway.

Sex-Specific Human Cardiomyocyte Gene Regulation in Left Ventricular Pressure Overload

OBJECTIVE

To assess gene expression in cardiomyocytes isolated from patients with aortic stenosis, hypothesizing that maladaptive remodeling and inflammation-related genes are higher in male vs female patients.

PATIENTS AND METHODS

In this study, 34 patients with aortic stenosis undergoing aortic valve replacement from March 20, 2016, through May 24, 2017, at the German Heart Centre in Berlin, Germany, were included. Isolated cardiomyocytes from interventricular septum samples were used for gene expression analysis. Clinical and echocardiographic data were collected preoperatively.

RESULTS

Age, body mass index, systolic and diastolic blood pressure, comorbidities, and medication were similar between the 17 male and 17 female patients. The mean ± SD left ventricular end-diastolic diameter (52±9 vs 45±4 mm; P=.007) and posterior wall thickness (14.2±2.5 vs 12.1±1.6 mm; P=.03) were higher in male vs female patients, while ejection fraction was lower in male patients (49%±14% vs 59%±5%; P=.01). Focusing on structural genes involved in the development of cardiac hypertrophy and remodeling, we found that most were expressed higher in male vs female patients. Our modeling analysis revealed that 2 inflammation-related genes, CCN2 and NFKB1, were negatively related to ejection fraction, with this effect being male specific (P=.03 and P=.02, respectively).

CONCLUSION

These findings provide novel insight into cardiomyocyte-specific molecular changes related to sex differences in pressure overload and a significant male-specific association between cardiac function and inflammation-related genes. Considering these sex differences may contribute toward a more accurate design of research and the development of more appropriate therapeutic approaches for both male and female patients.

Mitochondrial quality control in cardiac microvascular ischemia-reperfusion injury: New insights into the mechanisms and therapeutic potentials

Thrombolytic therapy and revascularization strategies create a complete recanalization of the occluded epicardial coronary artery in patients with myocardial infarction (MI). However, about 35 % of patients still experience an impaired myocardial reperfusion, which is termed a no-reflow phenomenon mainly caused by cardiac microvascular ischemia-reperfusion (I/R) injury. Mitochondria are essential for microvascular endothelial cells' survival, both because of their roles as metabolic energy producers and as regulators of programmed cell death. Mitochondrial structure and function are regulated by a mitochondrial quality control (MQC) system, a series of processes including mitochondrial biogenesis, mitochondrial dynamics/mitophagy, mitochondrial proteostasis, and mitochondria-mediated cell death. Our review discusses the MQC mechanisms and how they are linked to cardiac microvascular I/R injury. Additionally, we will summarize the molecular basis that results in defective MQC mechanisms and present potential therapeutic interventions for improving MQC in cardiac microvascular I/R injury.

Irisin activates Opa1-induced mitophagy to protect cardiomyocytes against apoptosis following myocardial infarction

Myocardial infarction is characterized by sudden ischemia and cardiomyocyte death. Mitochondria have critical roles in regulating cardiomyocyte viability and can sustain damage under ischemic conditions. Mitophagy is a mechanism by which damaged mitochondria are removed by autophagy to maintain mitochondrial structure and function. We investigated the role of the dynamin-like GTPase optic atrophy 1 (Opa1) in mitophagy following myocardial infarction. Opa1 expression was downregulated in infarcted hearts in vivo and in hypoxia-treated cardiomyocytes in vitro. We found that Opa1 overexpression protected cardiomyocytes against hypoxia-induced damage and enhanced cell viability by inducing mitophagy. Opa1-induced mitophagy was activated by treatment with irisin, which protected cardiomyocytes from further damage following myocardial infarction. Opa1 knockdown abolished the cardioprotective effects of irisin resulting in an enhanced inflammatory response, increased oxidative stress, and mitochondrial dysfunction in cardiomyocytes. Our data indicate that Opa1 plays an important role in maintaining cardiomyocyte viability and mitochondrial function following myocardial infarction by inducing mitophagy. Irisin can activate Opa1-induced mitophagy and protect against cardiomyocyte injury following myocardial infarction.

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.

Morphological and Functional Characteristics of Animal Models of Myocardial Fibrosis Induced by Pressure Overload

Myocardial fibrosis is characterized by excessive deposition of myocardial interstitial collagen, abnormal distribution, and excessive proliferation of fibroblasts. According to the researches in recent years, myocardial fibrosis, as the pathological basis of various cardiovascular diseases, has been proven to be a core determinant in ventricular remodeling. Pressure load is one of the causes of myocardial fibrosis. In experimental models of pressure-overload-induced myocardial fibrosis, significant increase in left ventricular parameters such as interventricular septal thickness and left ventricular posterior wall thickness and the decrease of ejection fraction are some of the manifestations of cardiac damage. These morphological and functional changes have a serious impact on the maintenance of physiological functions. Therefore, establishing a suitable myocardial fibrosis model is the basis of its pathogenesis research. This paper will discuss the methods of establishing myocardial fibrosis model and compare the advantages and disadvantages of the models in order to provide a strong basis for establishing a myocardial fibrosis model.

Periostin as a novel biomarker of cardiovascular disease: A systematic evidence landscape of preclinical and clinical studies

BACKGROUND

Periostin is a matricellular protein, expressed in various normal adult and fetal tissues. Recently, elevated periostin levels have been reported in heart failure, coronary artery disease, and stroke. However, there is lack of clinical studies to clarify the prognostic significance of systemic periostin levels in cardiovascular diseases (CVDs). The aim of the study was to perform a systematic review of published evidence on periostin and CVDs, and to clarify the diagnostic and prognostic significance of systemic periostin levels in CVDs.

METHODS

A systematic search on PubMed was performed to identify relevant articles from inception to December 2018. The eligible studies evaluating the periostin expression and periostin levels in animal and human studies.

RESULTS

A total of 24 relevant studies, including both animal and human data, were included. Periostin is significantly observed in myocardium tissue of failing hearts compared with control, and is also expressed in atherosclerotic plaques. Systemic periostin levels were significantly correlated with cardiac function and severity of CVD in several studies. A clinical study also observed positive correlation between periostin and N-terminal pro b-type natriuretic peptide (NT-proBNP), highly sensitive troponin (hsTnT), and ST2 cardiac biomarker. Studies reported limited adjustment for potential confounders.

CONCLUSIONS

The evidence of current review support potential role of periostin in the pathophysiology of CVD. However, scarcity of data regarding the clinical use of periostin levels in the current management of CVDs further creates room for the future investigation. Therefore, further studies warrant to clarify its potential role, if any, as a novel cardiac biomarker.

DNA methylation reprograms cardiac metabolic gene expression in end-stage human heart failure

Heart failure (HF) is a leading cause of morbidity and mortality in the United States and worldwide. As a multifactorial syndrome with unpredictable clinical outcomes, identifying the common molecular underpinnings that drive HF pathogenesis remains a major focus of investigation. Disruption of cardiac gene expression has been shown to mediate a common final cascade of pathological hallmarks wherein the heart reactivates numerous developmental pathways. Although the central regulatory mechanisms that drive this cardiac transcriptional reprogramming remain unknown, epigenetic contributions are likely. In the current study, we examined whether the epigenome, specifically DNA methylation, is reprogrammed in HF to potentiate a pathological shift in cardiac gene expression. To accomplish this, we used paired-end whole genome bisulfite sequencing and next-generation RNA sequencing of left ventricle tissue obtained from seven patients with end-stage HF and three nonfailing donor hearts. We found that differential methylation was localized to promoter-associated cytosine-phosphate-guanine islands, which are established regulatory regions of downstream genes. Hypermethylated promoters were associated with genes involved in oxidative metabolism, whereas promoter hypomethylation enriched glycolytic pathways. Overexpression of plasmid-derived DNA methyltransferase 3A in vitro was sufficient to lower the expression of numerous oxidative metabolic genes in H9c2 rat cardiomyoblasts, further supporting the importance of epigenetic factors in the regulation of cardiac metabolism. Last, we identified binding-site competition via hypermethylation of the nuclear respiratory factor 1 (NRF1) motif, an established upstream regulator of mitochondrial biogenesis. These preliminary observations are the first to uncover an etiology-independent shift in cardiac DNA methylation that corresponds with altered metabolic gene expression in HF.NEW & NOTEWORTHY The failing heart undergoes profound metabolic changes because of alterations in cardiac gene expression, reactivating glycolytic genes and suppressing oxidative metabolic genes. In the current study, we discover that alterations to cardiac DNA methylation encode this fetal-like metabolic gene reprogramming. We also identify novel epigenetic interference of nuclear respiratory factor 1 via hypermethylation of its downstream promoter targets, further supporting a novel contribution of DNA methylation in the metabolic remodeling of heart failure.

Suppression of Tafazzin promotes thyroid cancer apoptosis via activating the JNK signaling pathway and enhancing INF2-mediated mitochondrial fission

Tafazzin has been found to be associated with tumor progression. Mitochondrial homeostasis regulates cancer cell viability and metastasis. However, the roles of Tafazzin and mitochondrial homeostasis in thyroid cancer have not been explored. The aim of our study is to investigate the influences of Tafazzin on thyroid cancer apoptosis with a focus on mitochondrial fission. Our results indicated that Tafazzin deletion induced death in thyroid cancer via apoptosis. Biological analysis demonstrated that mitochondrial stress, including mitochondrial bioenergetics disorder, mitochondrial oxidative stress, and mitochondrial apoptosis, was activated by Tafazzin deletion. Furthermore, we found that Tafazzin affected mitochondrial stress by triggering inverted formin 2 (INF2)-related mitochondrial fission. The loss of INF2 sustained mitochondrial function and promoted cancer cell survival. Molecular investigation illustrated that Tafazzin regulated INF2 expression via the JNK signaling pathway; moreover, the blockade of JNK prevented Tafazzin-mediated INF2 expression and improved cancer cell survival. Taken together, our results highlight the key role of Tafazzin as a master regulator of thyroid cancer viability via the modulation of INF2-related mitochondrial fission and the JNK signaling pathway. These findings defined Tafazzin deletion and INF2-related mitochondrial fission as tumor suppressors that act by promoting cancer apoptosis via the JNK signaling pathway, with potential implications for new approaches to thyroid cancer therapy.

NADPH Oxidase 4 Regulates Inflammation in Ischemic Heart Failure: Role of Soluble Epoxide Hydrolase

Aims: Oxidative stress is implicated in cardiomyocyte cell death and cardiac remodeling in the failing heart. The role of NADPH oxidase 4 (NOX4) in cardiac adaptation to pressure overload is controversial, but its function in myocardial ischemic stress has not been thoroughly elucidated. This study examined the function of NOX4 in the pathogenesis of ischemic heart failure, utilizing mouse models, cell culture, and human heart samples. Results:Nox4^-/- mice showed a protective phenotype in response to permanent left anterior descending coronary artery ligation with smaller infarction area, lower cardiomyocyte cross-sectional area, higher capillary density, and less cell death versus wild-type (WT) mice. Nox4^-/- mice had lower activity of soluble epoxide hydrolase (sEH), a potent regulator of inflammation. Nox4^-/- mice also showed a 50% reduction in the number of infiltrating CD68⁺ macrophages in the peri-infarct zone versus WT mice. Adenoviral overexpression of NOX4 in cardiomyoblast cells increased sEH expression and activity and CCL4 and CCL5 levels; inhibition of sEH activity in NOX4 overexpressing cells attenuated the cytokine levels. Human hearts with ischemic cardiomyopathy showed adverse cardiac remodeling, increased NOX4 and sEH protein expression and CCL4 and CCL5 levels compared with control nonfailing hearts. Innovation and Conclusion: These data from the Nox4^-/- mouse model and human heart tissues show for the first time that oxidative stress from increased NOX4 expression has a functional role in ischemic heart failure. One mechanism by which NOX4 contributes to ischemic heart failure is by increasing inflammatory cytokine production via enhanced sEH activity.

Mammalian STE20-like Kinase 1 Knockdown Attenuates TNFα-Mediated Neurodegenerative Disease by Repressing the JNK Pathway and Mitochondrial Stress

Neuroinflammation has been acknowledged as a primary factor contributing to the pathogenesis of neurodegenerative disease. However, the molecular mechanism underlying inflammation stress-mediated neuronal dysfunction is not fully understood. The aim of our study was to explore the influence of mammalian STE20-like kinase 1 (Mst1) in neuroinflammation using TNFα and CATH.a cells in vitro. The results of our study demonstrated that the expression of Mst1 was dose-dependently increased after TNFα treatment. Interestingly, knockdown of Mst1 using siRNA transfection significantly repressed TNFα-induced neuronal death. We also found that TNFα treatment was associated with mitochondrial stress, including mitochondrial ROS overloading, mitochondrial permeability transition pore (mPTP) opening, mitochondrial membrane potential reduction, and mitochondrial pro-apoptotic factor release. Interestingly, loss of Mst1 attenuated TNFα-triggered mitochondrial stress and sustained mitochondrial function in CATH.a cells. We found that Mst1 modulated mitochondrial homeostasis and cell viability via the JNK pathway in a TNFα-induced inflammatory environment. Inhibition of the JNK pathway abolished TNFα-mediated CATH.a cell death and mitochondrial malfunction, similar to the results obtained via silencing of Mst1. Taken together, our results indicate that inflammation-mediated neuronal dysfunction is implicated in Mst1 upregulation, which promotes mitochondrial stress and neuronal death by activating the JNK pathway. Accordingly, our study identifies the Mst1-JNK-mitochondria axis as a novel signaling pathway involved in neuroinflammation.

Genetic ablation of TAZ induces HepG2 liver cancer cell apoptosis through activating the CaMKII/MIEF1 signaling pathway

Background and objective

Transcriptional coactivator with PDZ-binding motif (TAZ) has been found to be associated with tumor progression. Mitochondrial homeostasis regulates cancer cell viability and metastasis. However, the roles of TAZ and mitochondrial homeostasis in liver cancer viability have not been explored. The aim of our study was to investigate the influence of TAZ on HepG2 liver cancer cell apoptosis.

Materials and methods

HepG2 liver cancer cell was used in the present study, and shRNA against TAZ was transfected into HepG2 cell to knockdown TAZ expression. Mitochondrial function was analyzed using Western blotting, immunofluorescence assay, and flow cytometry. Pathway blocker was used to confirm the role of CaMKII pathway in TAZ-mediated cancer cell death.

Results

Our results indicated that TAZ deletion induced death in HepG2 cell via apoptosis. Biological analysis demonstrated that mitochondrial stress, including mitochondrial bioenergetics disorder, mitochondrial oxidative stress, and mitochondrial apoptosis, were activated by TAZ deletion. Furthermore, we found that TAZ affected mitochondrial stress by triggering mitochondrial elongation factor 1 (MIEF1)-related mitochondrial dysfunction. The loss of MIEF1 sustained mitochondrial function and promoted cancer cell survival. Molecular investigation illustrated that TAZ regulated MIEF1 expression via the CaMKII signaling pathway. Blockade of the CaMKII pathway prevented TAZ-mediated MIEF1 upregulation and improved cancer cell survival.

Conclusion

Taken together, our results highlight the key role of TAZ as a master regulator of HepG2 liver cancer cell viability via the modulation of MIEF1-related mitochondrial stress and the CaMKII signaling pathway. These findings define TAZ and MIEF1-related mitochondrial dysfunction as tumor suppressors that act by promoting cancer apoptosis via the CaMKII signaling pathway, with potential implications for new approaches to liver cancer therapy.

Melatonin enhances TNF-α-mediated cervical cancer HeLa cells death via suppressing CaMKII/Parkin/mitophagy axis

Background

Tumor necrosis factor-α (TNF-α) immunotherapy controls the progression of human cervical cancer. Here, we explored the detailed molecular mechanisms played by melatonin in human cervical cancer (HeLa cells) death in the presence of TNF-α injury, with a particular attention to the mitochondrial homeostasis.

Methods

HeLa cells were incubated with TNFα and then cell death was determined via MTT assay, TUNEL staining, caspase ELISA assay and western blotting. Mitochondrial function was detected via analyzing mitochondrial membrane potential using JC-1 staining, mitochondrial oxidative stress using flow cytometry and mitochondrial apoptosis using western blotting.

Results

Our data exhibited that treatment with HeLa cells using melatonin in the presence of TNF-α further triggered cancer cell cellular death. Molecular investigation demonstrated that melatonin enhanced the caspase-9 mitochondrion death, repressed mitochondrial potential, increased ROS production, augmented mPTP opening rate and elevated cyt-c expression in the nucleus. Moreover, melatonin application further suppressed mitochondrial ATP generation via reducing the expression of mitochondrial respiratory complex. Mechanistically, melatonin augmented the response of HeLa cells to TNF-α-mediated cancer death via repressing mitophagy. TNF-α treatment activated mitophagy via elevating Parkin expression and excessive mitophagy blocked mitochondrial apoptosis, ultimately alleviating the lethal action of TNF-α on HeLa cell. However, melatonin supplementation could prevent TNF-α-mediated mitophagy activation via inhibiting Parkin in a CaMKII-dependent manner. Interestingly, reactivation of CaMKII abolished the melatonin-mediated mitophagy arrest and HeLa cell death.

Conclusions

Overall, our data highlight that melatonin enhances TNF-α-induced human cervical cancer HeLa cells mitochondrial apoptosis via inactivating the CaMKII/Parkin/mitophagy axis.

Sirtuin 3 inhibition induces mitochondrial stress in tongue cancer by targeting mitochondrial fission and the JNK-Fis1 biological axis

Sirtuin 3 (Sirt3)-modified mitochondrial fission participates in the progression of several types of cancers. However, its role in tongue cancer requires investigation. The aim of our study is to determine whether Sirt3 knockdown regulates the viability of tongue cancer cells via modulating mitochondrial fission. Two types of tongue cancer cells were used in the present study, and siRNA was transfected into the cells to suppress Sirt3 expression. Mitochondrial function and cell apoptosis were determined via immunofluorescence, Western blotting, ELISA, and qPCR assays. A pathway blocker was applied to verify the role of the JNK-Fis1 signaling pathway in regulation of mitochondrial fission. The present study showed that loss of Sirt3 promoted tongue cancer cell death in a manner dependent on mitochondrial apoptosis. Mitochondrial oxidative stress, energy metabolism disorder, mitochondrial cyt-c liberation, and mitochondrial apoptosis activation were observed after Sirt3 silencing. Furthermore, we demonstrated that Sirt3 knockdown activated mitochondrial stress via triggering Fis1-related mitochondrial fission and that inhibition of Fis1-related mitochondrial fission abrogated the pro-apoptotic effect of Sirt3 knockdown on tongue cancer cells. To this end, we found that Sirt3 modulated Fis1 expression via the c-Jun N-terminal kinases (JNK) signaling pathway and that blockade of the JNK pathway attenuated mitochondrial stress and repressed apoptosis in Sirt3 knockdown cells. Altogether, our results identified a tumor-suppressive role for Sirt3 deficiency in tongue cancer via activation of the JNK-Fis1 axis and subsequent initiation of fatal mitochondrial fission. Given these findings, strategies to repress Sirt3 activity and enhance the JNK-Fis1-mitochondrial fission cascade have clinical benefits for patients with tongue cancer.

Dysregulation of the Mitochondrial Proteome Occurs in Mice Lacking Adiponectin Receptor 1

Decreased serum adiponectin levels in type 2 diabetes has been linked to the onset of mitochondrial dysfunction in diabetic complications by impairing AMPK-SIRT1-PGC-1α signaling via impaired adiponectin receptor 1 (AdipoR1) signaling. Here, we aimed to characterize the previously undefined role of disrupted AdipoR1 signaling on the mitochondrial protein composition of cardiac, renal, and hepatic tissues as three organs principally associated with diabetic complications. Comparative proteomics were performed in mitochondria isolated from the heart, kidneys and liver of Adipor1 ^-/- mice. A total of 790, 1,573, and 1,833 proteins were identified in cardiac, renal and hepatic mitochondria, respectively. While 121, 98, and 78 proteins were differentially regulated in cardiac, renal, and hepatic tissue of Adipor1^-/- mice, respectively; only 15 proteins were regulated in the same direction across all investigated tissues. Enrichment analysis of differentially expressed proteins revealed disproportionate representation of proteins involved in oxidative phosphorylation conserved across tissue types. Curated pathway analysis identified HNF4, NRF1, LONP, RICTOR, SURF1, insulin receptor, and PGC-1α as candidate upstream regulators. In high fat-fed non-transgenic mice with obesity and insulin resistance, AdipoR1 gene expression was markedly reduced in heart (-70%), kidney (-80%), and liver (-90%) (all P < 0.05) as compared to low fat-fed mice. NRF1 was the only upstream regulator downregulated both in Adipor1^-/- mice and in high fat-fed mice, suggesting common mechanisms of regulation. Thus, AdipoR1 signaling regulates mitochondrial protein composition across all investigated tissues in a functionally conserved, yet molecularly distinct, manner. The biological significance and potential implications of impaired AdipoR1 signaling are discussed.

Mst1 facilitates hyperglycemia-induced retinal pigmented epithelial cell apoptosis by evoking mitochondrial stress and activating the Smad2 signaling pathway

Hyperglycemia induces retinal pigmented epithelial cell apoptosis and mitochondrial stress via poorly understood mechanisms. The goal of our current study is to explore whether mammalian sterile 20-like kinase 1 (Mst1) is involved in the pathogenesis of hyperglycemia-mediated retinal pigmented epithelial cell apoptosis by triggering mitochondrial abnormalities and activating the Smad2 signaling pathway. Retinal pigmented epithelial ARPE-19 cells were presented with a high-glucose challenge in vitro. Cell viability and apoptosis were measured via western blotting, ELISAs, and immunofluorescence assays. Mitochondrial function was detected via JC-1 staining, mitochondrial ROS flow cytometry, western blotting, and ELISAs. Loss- and gain-of-function assays were performed via cell transfection and transduction with Mst1 siRNA and Smad2 adenovirus, respectively. The results indicated that hyperglycemia treatment upregulated the levels of Mst1, an effect that was accompanied by an increase in ARPE-19 cell apoptosis. Loss of Mst1 attenuated hyperglycemia-induced cell apoptosis, and this effect seemed to be associated with mitochondrial protection. In response to hyperglycemia stimulus, mitochondrial stress was noted in ARPE-19 cells, including mitochondrial ROS overproduction, mitochondrial respiratory metabolism dysfunction, mitochondrial fission/fusion imbalance, and mitochondrial apoptosis activation. Further, we provided evidence to support the crucial role played by Smad2 in promoting Mst1-mediated cell apoptosis and mitochondrial stress. Overexpression of Smad2 abrogated the beneficial effects of Mst1 deletion on ARPE-19 cell viability and mitochondrial protection. Altogether, our results identified Mst1 as a novel mediator controlling the fate of retinal pigmented epithelial cells and mitochondrial homeostasis via the Smad2 signaling pathway. Based on this finding, strategies to repress Mst1 upregulation and block Smad2 activation are vital to alleviate hyperglycemia-mediated retinal pigmented epithelial cell damage.

Genome-wide DNA methylation encodes cardiac transcriptional reprogramming in human ischemic heart failure

Ischemic cardiomyopathy (ICM) is the clinical endpoint of coronary heart disease and a leading cause of heart failure. Despite growing demands to develop personalized approaches to treat ICM, progress is limited by inadequate knowledge of its pathogenesis. Since epigenetics has been implicated in the development of other chronic diseases, the current study was designed to determine whether transcriptional and/or epigenetic changes are sufficient to distinguish ICM from other etiologies of heart failure. Specifically, we hypothesize that genome-wide DNA methylation encodes transcriptional reprogramming in ICM. RNA-sequencing analysis was performed on human ischemic left ventricular tissue obtained from patients with end-stage heart failure, which enriched known targets of the polycomb methyltransferase EZH2 compared to non-ischemic hearts. Combined RNA sequencing and genome-wide DNA methylation analysis revealed a robust gene expression pattern consistent with suppression of oxidative metabolism, induced anaerobic glycolysis, and altered cellular remodeling. Lastly, KLF15 was identified as a putative upstream regulator of metabolic gene expression that was itself regulated by EZH2 in a SET domain-dependent manner. Our observations therefore define a novel role of DNA methylation in the metabolic reprogramming of ICM. Furthermore, we identify EZH2 as an epigenetic regulator of KLF15 along with DNA hypermethylation, and we propose a novel mechanism through which coronary heart disease reprograms the expression of both intermediate enzymes and upstream regulators of cardiac metabolism such as KLF15.