Cardiac Contractile Dysfunction Research Articles

Roles of cMyBP-C phosphorylation on cardiac contractile dysfunction in db/db mice

Type 2 diabetes mellitus (T2DM) is a metabolic disease and comorbidity associated with several conditions, including cardiac dysfunction leading to heart failure with preserved ejection fraction (HFpEF), in turn resulting in T2DM-induced cardiomyopathy (T2DM-CM). However, the molecular mechanisms underlying the development of T2DM-CM are poorly understood. It is hypothesized that molecular alterations in myopathic genes induced by diabetes promote the development of HFpEF, whereas cardiac myosin inhibitors can rescue the resultant T2DM-mediated cardiomyopathy. To test this hypothesis, a Leptin receptor-deficient db/db homozygous (Lepr db/db) mouse model was used to define the pathogenesis of T2DM-CM. Echocardiographic studies at 4 and 6 months revealed that Lepr db/db hearts started developing cardiac dysfunction by four months, and left ventricular hypertrophy with diastolic dysfunction was evident at 6 months. RNA-seq data analysis, followed by functional enrichment, revealed the differential regulation of genes related to cardiac dysfunction in Lepr db/db heart tissues. Strikingly, the level of cardiac myosin binding protein-C phosphorylation was significantly increased in Lepr db/db mouse hearts. Finally, using isolated skinned papillary muscles and freshly isolated cardiomyocytes, CAMZYOS® (mavacamten, MYK-461), a prescription heart medicine used for symptomatic obstructive hypertrophic cardiomyopathy treatment, was tested for its ability to rescue T2DM-CM. Compared with controls, MYK-461 significantly reduced force generation in papillary muscle fibers and cardiomyocyte contractility in the db/db group. This line of evidence shows that 1) T2DM-CM is associated with hyperphosphorylation of cardiac myosin binding protein-C and 2) MYK-461 significantly lessened disease progression in vitro, suggesting its promise as a treatment for HFpEF.

[Cardiotoxicity risk assessment of anti-cancer drugs and future perspectives].

Cardiotoxicity is a serious adverse effect of anti-cancer drugs. Anti-cancer drug-induced cardiotoxicity are arrhythmia, cardiac contractile dysfunction, coronary artery disease, and hypertension, which affect to the quality of life in patients with cancer. In particular, cardiac contractile dysfunction is a life-threatening symptom leading to heart failure, suggesting that it is very important to predict the risk of developing the contractile dysfunction by anti-cancer drugs. Recently, human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) can be used to assess the risk of drug-induced arrhythmias. This prompts us to evaluate other cardiotoxic effects such as contractility dysfunction and structural toxicity with hiPSC-CMs. Since anti-cancer drug-induced contractility dysfunction are considered to be induced by chronic exposure, we have developed a method to assess chronic contractility dysfunction by imaging analysis of hiPSC-CMs. BMS-986094, which failed in clinical trials due to the occurrence of heart failure, was used as a positive compound. We found that chronic exposure to BMS-986094 decreased the contraction and relaxation velocity in hiPSC-CMs. Doxorubicin was observed to decrease cytotoxicity and both contraction and relaxation velocities in hiPSC-CMs. We are currently further evaluating other anti-cancer drugs with different mode-of-actions using hiPSC-CMs and assess the predictivity and utility of contractile assessment using hiPSC-CMs by comparing with real-world data. Here, we introduce our novel method to assess the chronic contractility of hiPSC-CMs by imaging analysis and discuss the future perspectives for assessing the anti-cancer drug-induced cardiotoxicity.

Cardiac function may be compromised in patients with elevated blood cobalt levels secondary to metal-on-metal hip implants.

Elevated blood cobalt levels secondary to metal-on-metal (MoM) hip arthroplasties are a suggested risk factor for developing cardiovascular complications including cardiomyopathy. Clinical studies assessing patients with MoM hips using left ventricular ejection fraction (LVEF) have found conflicting evidence of cobalt-induced cardiomyopathy. Global longitudinal strain (GLS) is an echocardiography measurement known to be more sensitive than LVEF when diagnosing early cardiomyopathies. The extent of cardiovascular injury, as measured by GLS, in patients with elevated blood cobalt levels has not previously been examined. A total of 16 patients with documented blood cobalt ion levels above 13 µg/l (13 ppb, 221 nmol/l) were identified from a regional arthroplasty database. They were matched with eight patients awaiting hip arthroplasty. All patients underwent echocardiography, including GLS, investigating potential signs of cardiomyopathy. Patients with MoM hip arthroplasties had a mean blood cobalt level of 29 µg/l (495 nmol/l) compared to 0.01 µg/l (0.2 nmol/l) in the control group. GLS readings were available for seven of the MoM cohort, and were significantly lower when compared with controls (-15.5% vs -18% (MoM vs control); p = 0.025)). Pearson correlation demonstrated that GLS significantly correlated with blood cobalt level (r = 0.8521; p < 0.001). However, there were no differences or correlations for other echocardiography measurements, including LVEF (64.3% vs 63.7% (MoM vs control); p = 0.845). This study supports the hypothesis that patients with elevated blood cobalt levels above 13 µg/l in the presence of a MoM hip implant may have impaired cardiac function compared to a control group of patients awaiting hip arthroplasty. It is the first study to use the more sensitive parameter of GLS to assess for any cardiac contractile dysfunction in patients with a MoM hip implant and a normal LVEF. Larger studies should be performed to determine the potential of GLS as a predictor of cardiac complications in patients with MoM arthroplasties.

Role of AMP deaminase in diabetic cardiomyopathy.

Diabetes mellitus is one of the major causes of ischemic and nonischemic heart failure. While hypertension and coronary artery disease are frequent comorbidities in patients with diabetes, cardiac contractile dysfunction and remodeling occur in diabetic patients even without comorbidities, which is referred to as diabetic cardiomyopathy. Investigations in recent decades have demonstrated that the production of reactive oxygen species (ROS), impaired handling of intracellular Ca2+, and alterations in energy metabolism are involved in the development of diabetic cardiomyopathy. AMP deaminase (AMPD) directly regulates adenine nucleotide metabolism and energy transfer by adenylate kinase and indirectly modulates xanthine oxidoreductase-mediated pathways and AMP-activated protein kinase-mediated signaling. Upregulation of AMPD in diabetic hearts was first reported more than 30years ago, and subsequent studies showed similar upregulation in the liver and skeletal muscle. Evidence for the roles of AMPD in diabetes-induced fatty liver, sarcopenia, and heart failure has been accumulating. A series of our recent studies showed that AMPD localizes in the mitochondria-associated endoplasmic reticulum membrane as well as the sarcoplasmic reticulum and cytosol and participates in the regulation of mitochondrial Ca2+ and suggested that upregulated AMPD contributes to contractile dysfunction in diabetic cardiomyopathy via increased generation of ROS, adenine nucleotide depletion, and impaired mitochondrial respiration. The detrimental effects of AMPD were manifested at times of increased cardiac workload by pressure loading. In this review, we briefly summarize the expression and functions of AMPD in the heart and discuss the roles of AMPD in diabetic cardiomyopathy, mainly focusing on contractile dysfunction caused by this disorder.

Activation of the cannabinoid type 2 (CB2) receptor improves cardiac contractile performance in fish, Brycon amazonicus

In addition to their well-known classical effects, cannabinoid CB1 and CB2 receptors have also been involvement in both deleterious and protective actions on the heart under various pathological conditions. While the potential therapeutic applications of the endocannabinoid system in the context of cardiovascular function are indeed a viable prospect, significant debate exists within the literature regarding whether CB1, CB2, or a combination of both receptors exert a favorable influence on cardiac function. Hence, the aim of this study was to investigate the effects of CB1 + CB2 or CB2 agonists on cardiac excitation-contraction (E-C) coupling, utilizing fish (Brycon amazonicus) as an experimental model. The CB2 agonist elicited marked positive inotropic and lusitropic responses in isolated ventricular myocardium, induced cyclic adenosine 3′,5′-monophosphate (cAMP) production, and upregulated critical Ca2+ handling proteins, such as sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) and Na+/Ca2+ exchanger (NCX). Our current study demonstrated, for the first time, that CB2 receptor activation-induced effects improved the efficiency of Ca2+ cycling, excitation-contraction coupling (E-C coupling), and cardiac performance in under physiological conditions. Hence, CB2 receptors could be considered a potential therapeutic target for modulating cardiac contractile dysfunctions.

Evaluation of Atrial Fibrillation Risk and Outcome after Allogeneic Transplantation Using an Artificial Intelligence ECG Algorithm and Echocardiographic Parameters in an MDS Cohort

Introduction Atrial fibrillation/flutter (Afib) contributes independently to the hematopoietic cell transplant comorbidity index (HCTCI) and is a known complication of allogeneic hematopoietic transplantation (AlloHCT) which has been linked to inferior outcomes, particularly in older patients. An electrocardiogram (ECG)-based artificial intelligence (AI) algorithm to predict Afib and cardiac contractile dysfunction risk has been validated (Lancet 394:861, 2019). We hypothesized that assessment of pre-transplant Afib risk using the AI algorithm may predict future development of Afib and help identify patients at higher risk for this complication. Methods 191 consecutive MDS patients undergoing AlloHCT with curative intent using myeloablative (28.3%) or reduced intensity conditioning (62.3%) in the Mayo Clinic Comprehensive Cancer Center (Rochester, Jacksonville, Phoenix) between November 2015 and January 2022 were included in this retrospective analysis. Primary outcome was Afib within 100 days and 365 days of transplantation, and we also assessed the outcomes of Death and Relapse. Revised IPSS (IPSS-R) and HCTCI scores were included for all patients. Elevated Afib risk score using the AI algorithm was calculated from pre-transplant ECG, performed during vital organ testing at AlloHCT clearance. In addition to left ventricular (LV) ejection fraction (EF) we evaluated detailed echocardiographic (Echo) parameters including LV volume and mass indices, left atrial volume index (LAVI), maximum trans mitral flow velocities during LV filling (E velocity) and during the diastolic phase due to atrial contraction (A velocity), the velocity of the annulus away from the apex during the protodiastolic phase (e' velocity), E/A and E/e' ratios, the presence of valvular disease, and right ventricular systolic pressure (RVSP). We performed an analysis using a Cox proportional hazards regression models (adjusting for age and sex) to evaluate associations with Afib risk, Relapse, and Overall Survival. Results The median age was 64 years (18-75), 58.6% were male, 6.9% non-white race, and 3.7% Hispanic/Latino ethnicity. Most patients had an HCTCI score of 0-3 (76.3%). GVHD prophylaxis was predominantly with calcineurin inhibitor-based regimes plus/minus methotrexate or mycophenolate mofetil (83.8%). 5.2% of patients had a history of Afib before transplant. Non-relapse mortality was 7.9% at 100 days, and 18.3% at 365 days. N=25 patients (13.1%) developed Afib within 100 days, and n=28 (14.7%) within 1-year after AlloHCT. On multivariable analysis, Age [Hazard Ratio (HR) 2.83, 95% Confidence Interval (CI) 1.36-5.89, p=0.0055] and Echo parameters [including LAVI (HR 2.10, CI 1.23-3.58, p=0.0067), E velocity (HR 3.28, CI 1.29-8.80, p=0.013), E/A ratio (HR 3.74, CI 1.75-7.97, p=0.0006), E/e ' ratio (HR 1.81, CI 1.07-3.07, p=0.026) and RVSP (HR 1.68, CI 1.04-2.70, p=0.032)] were significantly associated with Afib risk; elevated AI risk score was significant in the univariate model (HR 2.74, CI 1.15-6.53, p=0.023) but was borderline in the multivariate model (HR 2.34, CI 0.98-5.60, p=0.056) ( Table 1). Based on previous observations we evaluated the association of AI and Echo parameters with Relapse and Death after AlloHCT ( Table 1). Age (HR 1.32, CI 1.01-1.71, p=0.041) and IPSS-R (HR 1.20, CI 1.08-1.33, p=0.0009) were significantly associated with Death after AlloHCT, while HCTCI (HR 1.10, CI 1.00-1.22, p=0.052) and higher LV EF (HR 0.63, CI 0.38-1.06, p=0.084) were borderline. For Relapse, only IPSS-R (HR 1.52, CI 1.31-1.75, p=1.22E-08) was significant, while increase Echo E velocity was of borderline significance (HR 0.45, CI 0.20-1.02, p=0.057). Conclusions Afib is a common post-AlloHCT complication and is more frequent with increasing Age. Echo parameters (specifically E/A ratio) predict significantly higher Afib risk, while the baseline ECG AI algorithm was of borderline significance. The selection of patients with lower HCTCI scores, and the low background prevalence of Afib in this cohort (i.e., selection of patients with lower baseline cardiac morbidity) are possible explanations for non-significance of the AI algorithm. As anticipated Age and IPSS-R are the greatest predictors of Death after AlloHCT, although the suggestion of an association with baseline Echo parameters highlights the importance of identifying those who may benefit from preemptive Cardiology intervention.

Cardiomyocyte-specific deletion of endothelin receptor A (ETA) obliterates cardiac aging through regulation of mitophagy and ferroptosis

Advanced aging evokes unfavorable changes in the heart including cardiac remodeling and contractile dysfunction although the underlying mechanism remains elusive. This study was conducted to evaluate the role of endothelin-1 (ET-1) in the pathogenesis of cardiac aging and mechanism involved. Echocardiographic and cardiomyocyte mechanical properties were determined in young (5–6 mo) and aged (26–28 mo) wild-type (WT) and cardiomyocyte-specific ETA receptor knockout (ETAKO) mice. GSEA enrichment identified differentially expressed genes associated with mitochondrial respiration, mitochondrial protein processing and mitochondrial depolarization in cardiac aging. Aging elevated plasma levels of ET-1, Ang II and suppressed serum Fe2+, evoked cardiac remodeling (hypertrophy and interstitial fibrosis), contractile defects (fractional shortening, ejection fraction, cardiomyocyte peak shortening, maximal velocity of shortening/relengthening and prolonged relengthening) and intracellular Ca2+ mishandling (dampened intracellular Ca2+ release and prolonged decay), the effects with the exception of plasma AngII, ET-1 and Fe2+ were mitigated by ETAKO. Advanced age facilitated O2− production, carbonyl protein damage, cardiac hypertrophy (GATA4, ANP, NFATc3), ER stress, ferroptosis, compromised autophagy (LC3B, Beclin-1, Atg7, Atg5 and p62) and mitophagy (parkin and FUNDC1), and deranged intracellular Ca2+ proteins (SERCA2a and phospholamban), the effects of which were reversed by ETA ablation. ET-1 provoked ferroptosis in vitro, the response was nullified by the ETA receptor antagonist BQ123 and mitophagy inducer CsA. ETA but not ETB receptor antagonism reconciled cardiac aging, which was abrogated by inhibition of mitophagy and ferroptosis. These findings collectively denote promises of targeting ETA, mitophagy and ferroptosis in the management of aging-associated cardiac remodeling and contractile defect.

Abstract 14505: BSCL2/Seipin Deletion Rescues ATGL-Deficiency-Induced Lethal Lipotoxic Cardiomyopathy

Imbalances in triglyceride (TG) catabolism are associated with cardiac lipid deposition and contractile dysfunction, as manifested in patients with primary triglyceride deposit cardiomyovasculopathy (TGCV) caused by adipose triglyceride lipase (ATGL) deficiency. BSCL2/Seipin is a highly conserved endoplasmic reticulum protein widely implicated in lipid droplet biogenesis and TG metabolism. We previously reported that global Bscl2 –/– mice and mice with cardiac-specific deletion of Bscl2 manifest higher myocardial ATGL expression and develop mild cardiomyopathy with reduced cardiac steatosis. However, the interplay between BSCL2 and ATGL in hearts remains to be further interrogated. In this study, we surprisingly discovered that global BSCL2 deletion completely rescued the lethal lipotoxic cardiomyopathy in the genetic ATGL-deficient TGCV model ( Atgl –/– mice) by drastically reducing cardiac TG deposits, abolishing cardiac hypertrophy, and restoring cardiac contractility. Transcriptomic analyses identified the elevated inflammatory, oxidative stress, and extracellular matrix pathways in Atgl –/– hearts, which were dramatically ameliorated by BSCL2 deletion. Conversely, the severely suppressed cardiac metabolic functions, muscle contraction, and ion transport pathways in Atgl –/– hearts were also normalized by BSCL2 deletion. Heatmap data further revealed that the mRNA levels of Pgc1/Ppara and fatty acid oxidation (FAO) genes were not altered in Bscl2 –/– hearts but were severely repressed in Atgl –/– hearts due to defective TG lipolysis. However, their expressions in Atgl –/– Bscl2 –/– hearts were restored to similar levels as wild-type and Bscl2 –/– hearts. RT-PCR analyses further confirmed such changes. Notably, cardiac-specific deletion of BSCL2 rescues lethal cardiomyopathy in mice with cardiac-specific deletion of ATGL. These data suggest that cardiac BSCL2 cell-autonomously regulates ATGL-independent TG hydrolysis and FAO pathways essential for cardiac function. Our study highlights the presence of BSCL2-mediated ATGL-independent pathways that regulate cardiac TG metabolism and provide novel therapeutic approaches to treat ATGL-deficiency-associated lethal cardiomyopathy.

Exploring the mechanisms underlying stroke volume variability reduction in a murine model of heart failure with reduced ejection fraction.

Heart failure with reduced ejection fraction (HFrEF) is accompanied by disregulation of cardiovascular function. Heart rate variability (HRV) is commonly used to assess autonomic dysfunction in HFrEF. However, analysis of stroke volume variability (SVV) may provide additional insights. We examined HRV and SVV in a mouse model of HFrEF. HFrEF mice exhibited reduced stroke volume and ejection fraction versus controls, confirming cardiac contractile dysfunction. HRV was preserved in HFrEF mice. However, SVV was markedly diminished, indicating dissociation between HRV and SVV regulation. Using a mathematical model, we propose that Frank-Starling mechanism abnormalities in HFrEF disrupt SVV independent of HRV. Assessing SVV could thus provide unique insights beyond HRV into cardiovascular control deficits in HFrEF.

TBC1D15 deficiency protects against doxorubicin cardiotoxicity via inhibiting DNA-PKcs cytosolic retention and DNA damage

Clinical application of doxorubicin (DOX) is heavily hindered by DOX cardiotoxicity. Several theories were postulated for DOX cardiotoxicity including DNA damage and DNA damage response (DDR), although the mechanism(s) involved remains to be elucidated. This study evaluated the potential role of TBC domain family member 15 (TBC1D15) in DOX cardiotoxicity. Tamoxifen-induced cardiac-specific Tbc1d15 knockout (Tbc1d15CKO) or Tbc1d15 knockin (Tbc1d15CKI) male mice were challenged with a single dose of DOX prior to cardiac assessment 1 week or 4 weeks following DOX challenge. Adenoviruses encoding TBC1D15 or containing shRNA targeting Tbc1d15 were used for Tbc1d15 overexpression or knockdown in isolated primary mouse cardiomyocytes. Our results revealed that DOX evoked upregulation of TBC1D15 with compromised myocardial function and overt mortality, the effects of which were ameliorated and accentuated by Tbc1d15 deletion and Tbc1d15 overexpression, respectively. DOX overtly evoked apoptotic cell death, the effect of which was alleviated and exacerbated by Tbc1d15 knockout and overexpression, respectively. Meanwhile, DOX provoked mitochondrial membrane potential collapse, oxidative stress and DNA damage, the effects of which were mitigated and exacerbated by Tbc1d15 knockdown and overexpression, respectively. Further scrutiny revealed that TBC1D15 fostered cytosolic accumulation of the cardinal DDR element DNA-dependent protein kinase catalytic subunit (DNA-PKcs). Liquid chromatography–tandem mass spectrometry and co-immunoprecipitation denoted an interaction between TBC1D15 and DNA-PKcs at the segment 594–624 of TBC1D15. Moreover, overexpression of TBC1D15 mutant (∆594–624, deletion of segment 594–624) failed to elicit accentuation of DOX-induced cytosolic retention of DNA-PKcs, DNA damage and cardiomyocyte apoptosis by TBC1D15 wild type. However, Tbc1d15 deletion ameliorated DOX-induced cardiomyocyte contractile anomalies, apoptosis, mitochondrial anomalies, DNA damage and cytosolic DNA-PKcs accumulation, which were canceled off by DNA-PKcs inhibition or ATM activation. Taken together, our findings denoted a pivotal role for TBC1D15 in DOX-induced DNA damage, mitochondrial injury, and apoptosis possibly through binding with DNA-PKcs and thus gate-keeping its cytosolic retention, a route to accentuation of cardiac contractile dysfunction in DOX-induced cardiotoxicity.

Alpha-lipoic Acid Protects Against Chronic Alcohol Consumption-induced Cardiac Damage by the Aldehyde Dehydrogenase 2-associated PINK/Parkin Pathway.

Chronic alcohol intake contributes to high mortality rates due to ethanol-induced cardiac hypertrophy and contractile dysfunction, which are accompanied by increased oxidative stress and disrupted mitophagy. Alpha-lipoic acid (α-LA), a well-known antioxidant, has been shown to protect against cardiac hypertrophy and inflammation. However, little is known about its role and mechanism in the treatment of alcoholic cardiomyopathy. Here, we evaluated the role of α-LA in alcohol-induced cardiac damage by feeding mice a 4.8% (v/v) alcohol diet with or without α-LA for 6 w. Our results suggested that chronic alcohol consumption increased mortality, blood alcohol concentrations, and serum aldehyde levels, but a-LA attenuated the elevations in mortality and aldehydes. Chronic alcohol intake also induced cardiac dysfunction, including enlarged left ventricles, reduced left ventricular ejection fraction, enhanced cardiomyocyte size, and increased serum levels of brain natriuretic peptide, lactate dehydrogenase, and creatine kinase myocardial isoenzyme. Moreover, alcohol intake led to the accumulation of collagen fiber and mitochondrial dysfunction, the effects of which were alleviated by α-LA. In addition, α-LA intake also prevented the increase in reactive oxygen species production and the decrease in mitochondrial number that were observed after alcohol consumption. Chronic alcohol exposure activated PINK1/Parkin-mediated mitophagy. These effects were diminished by α-LA intake by the activation of aldehyde dehydrogenase 2. Our data indicated that α-LA helps protect cardiac cells against the effects of chronic alcohol intake, likely by inhibiting PINK1/Parkin-related mitophagy through the activation of aldehyde dehydrogenase 2.

Matrix metalloproteinase-2 proteolyzes mitofusin-2 and impairs mitochondrial function during myocardial ischemia-reperfusion injury.

During myocardial ischemia and reperfusion (IR) injury matrix metalloproteinase-2 (MMP-2) is rapidly activated in response to oxidative stress. MMP-2 is a multifunctional protease that cleaves both extracellular and intracellular proteins. Oxidative stress also impairs mitochondrial function which is regulated by different proteins, including mitofusin-2 (Mfn-2), which is lost in IR injury. Oxidative stress and mitochondrial dysfunction trigger the NLRP3 inflammasome and the innate immune response which invokes the de novo expression of an N-terminal truncated isoform of MMP-2 (NTT-MMP-2) at or near mitochondria. We hypothesized that MMP-2 proteolyzes Mfn-2 during myocardial IR injury, impairing mitochondrial function and enhancing the inflammasome response. Isolated hearts from mice subjected to IR injury (30min ischemia/40min reperfusion) showed a significant reduction in left ventricular developed pressure (LVDP) compared to aerobically perfused hearts. IR injury increased MMP-2 activity as observed by gelatin zymography and increased degradation of troponin I, an intracellular MMP-2 target. MMP-2 preferring inhibitors, ARP-100 or ONO-4817, improved post-ischemic recovery of LVDP compared to vehicle perfused IR hearts. In muscle fibers isolated from IR hearts the rates of mitochondrial oxygen consumption and ATP production were impaired compared to those from aerobic hearts, whereas ARP-100 or ONO-4817 attenuated these reductions. IR hearts showed higher levels of NLRP3, cleaved caspase-1 and interleukin-1β in the cytosolic fraction, while the mitochondria-enriched fraction showed reduced levels of Mfn-2, compared to aerobic hearts. ARP-100 or ONO-4817 attenuated these changes. Co-immunoprecipitation showed that MMP-2 is associated with Mfn-2 in aerobic and IR hearts. ARP-100 or ONO-4817 also reduced infarct size and cell death in hearts subjected to 45min ischemia/120min reperfusion. Following myocardial IR injury, impaired contractile function and mitochondrial respiration and elevated inflammasome response could be attributed, at least in part, to MMP-2 activation, which targets and cleaves mitochondrial Mfn-2. Inhibition of MMP-2 activity protects against cardiac contractile dysfunction in IR injury in part by preserving Mfn-2 and suppressing inflammation.

Mettl13 protects against cardiac contractile dysfunction by negatively regulating C-Cbl-mediated ubiquitination of SERCA2a in ischemic heart failure.

Ischemic heart failure (HF) remains a leading cause of morbidity and mortality. Maintaining homeostasis of cardiac function and preventing cardiac remodeling deterioration are critical to halting HF progression. Methyltransferase-like protein 13 (Mettl13) has been shown to regulate protein translation efficiency by acting as a protein lysine methyltransferase, but its role in cardiac pathology remains unexplored. This study aims to characterize the roles and mechanisms of Mettl13 in cardiac contractile function and HF. We found that Mettl13 was downregulated in the failing hearts of mice post-myocardial infarction (MI) and in a cellular model of oxidative stress. Cardiomyocyte-specific overexpression of Mettl13 mediated by AAV9-Mettl13 attenuated cardiac contractile dysfunction and fibrosis in response to MI, while silencing of Mettl13 impaired cardiac function in normal mice. Moreover, Mettl13 overexpression abrogated the reduction in cell shortening, Ca2+ transient amplitude and SERCA2a protein levels in the cardiomyocytes of adult mice with MI. Conversely, knockdown of Mettl13 impaired the contractility of cardiomyocytes, and decreased Ca2+ transient amplitude and SERCA2a protein expression in vivo and in vitro. Mechanistically, Mettl13 impaired the stability of c-Cbl by inducing lysine methylation of c-Cbl, which in turn inhibited ubiquitination-dependent degradation of SERCA2a. Furthermore, the inhibitory effects of knocking down Mettl13 on SERCA2a protein expression and Ca2+ transients were partially rescued by silencing c-Cbl in H2O2-treated cardiomyocytes. In conclusion, our study uncovers a novel mechanism that involves the Mettl13/c-Cbl/SERCA2a axis in regulating cardiac contractile function and remodeling, and identifies Mettl13 as a novel therapeutic target for ischemic HF.

Ribonucleicacid interference or small molecule inhibition of Runx1 in the border zone prevents cardiac contractile dysfunction following myocardial infarction.

Myocardial infarction (MI) is a major cause of death worldwide. Effective treatments are required to improve recovery of cardiac function following MI, with the aim of improving patient outcomes and preventing progression to heart failure. The perfused but hypocontractile region bordering an infarct is functionally distinct from the remote surviving myocardium and is a determinant of adverse remodelling and cardiac contractility. Expression of the transcription factor RUNX1 is increased in the border zone 1-day after MI, suggesting potential for targeted therapeutic intervention. This study sought to investigate whether an increase in RUNX1 in the border zone can be therapeutically targeted to preserve contractility following MI. In this work we demonstrate that Runx1 drives reductions in cardiomyocyte contractility, calcium handling, mitochondrial density, and expression of genes important for oxidative phosphorylation. Both tamoxifen-inducible Runx1-deficient and essential co-factor common β subunit (Cbfβ)-deficient cardiomyocyte-specific mouse models demonstrated that antagonizing RUNX1 function preserves the expression of genes important for oxidative phosphorylation following MI. Antagonizing RUNX1 expression via short-hairpin RNA interference preserved contractile function following MI. Equivalent effects were obtained with a small molecule inhibitor (Ro5-3335) that reduces RUNX1 function by blocking its interaction with CBFβ. Our results confirm the translational potential of RUNX1 as a novel therapeutic target in MI, with wider opportunities for use across a range of cardiac diseases where RUNX1 drives adverse cardiac remodelling.

Cannabidiol treatment changes myocardial lipid profile in spontaneously hypertensive rats

Background and aimsHypertension is a potent risk factor for cardiovascular diseases, which are the leading worldwide cause of death. Within time increased blood pressure (BP) induces cardiac contractile dysfunction, metabolic alternations, and eventually, heart failure, which makes hypertension an area for seeking safe therapies such as phytocannabinoids. Methods and resultsIn the present study spontaneously hypertensive rats (SHRs) were used as an experimental model of genetically induced hypertension, where cannabidiol (CBD) was applied as a potential treatment (intraperitoneally administered for 2 weeks, 10 mg/kg) for elevated BP and related metabolic disturbances. Langendorff working heart system, Western blotting as well as gas-liquid chromatography were applied to determine radiolabeled 3H-palmitate uptake, incorporation, and oxidation, protein expression, as well as the content and fatty acid composition of different lipid fractions in the left ventricle and plasma, respectively. Most importantly, we noticed that 2-week CBD treatment was effective in upregulating ex vivo3H-palmitate uptake, oxidation, and its incorporation into triacylglycerol and cholesterol fractions with concomitant lowering free fatty acid, diacylglycerol, and phospholipid fractions, which was in agreement with in vivo studies and alternations in protein expressions of lipoprotein lipase, carnitine palmitoyltransferase I, 3-hydroxyacyl-CoA dehydrogenase, diacylglycerol acyltransferase 1, and adipose triglyceride lipase as well as proteins associated with eicosanoid signaling pathways and extracellular matrix remodeling in the heart of hypertensive rats. ConclusionOur study reveals that 2-week CBD administration substantially affects the energetic substrate milieu in cardiac muscle regarding fatty acids uptake and their further utilization without parallel significant alternations in cardiovascular parameters.

Machine learning for spatial stratification of progressive cardiovascular dysfunction in a murine model of type 2 diabetes mellitus.

Speckle tracking echocardiography (STE) has been utilized to evaluate independent spatial alterations in the diabetic heart, but the progressive manifestation of regional and segmental cardiac dysfunction in the type 2 diabetic (T2DM) heart remains understudied. Therefore, the objective of this study was to elucidate if machine learning could be utilized to reliably describe patterns of the progressive regional and segmental dysfunction that are associated with the development of cardiac contractile dysfunction in the T2DM heart. Non-invasive conventional echocardiography and STE datasets were utilized to segregate mice into two pre-determined groups, wild-type and Db/Db, at 5, 12, 20, and 25 weeks. A support vector machine model, which classifies data using a single line, or hyperplane, that best separates each class, and a ReliefF algorithm, which ranks features by how well each feature lends to the classification of data, were used to identify and rank cardiac regions, segments, and features by their ability to identify cardiac dysfunction. STE features more accurately segregated animals as diabetic or non-diabetic when compared with conventional echocardiography, and the ReliefF algorithm efficiently ranked STE features by their ability to identify cardiac dysfunction. The Septal region, and the AntSeptum segment, best identified cardiac dysfunction at 5, 20, and 25 weeks, with the AntSeptum also containing the greatest number of features which differed between diabetic and non-diabetic mice. Cardiac dysfunction manifests in a spatial and temporal fashion, and is defined by patterns of regional and segmental dysfunction in the T2DM heart which are identifiable using machine learning methodologies. Further, machine learning identified the Septal region and AntSeptum segment as locales of interest for therapeutic interventions aimed at ameliorating cardiac dysfunction in T2DM, suggesting that machine learning may provide a more thorough approach to managing contractile data with the intention of identifying experimental and therapeutic targets.

RIP140 deficiency enhances cardiac fuel metabolism and protects mice from heart failure.

During the development of heart failure (HF), the capacity for cardiomyocyte (CM) fatty acid oxidation (FAO) and ATP production is progressively diminished, contributing to pathologic cardiac hypertrophy and contractile dysfunction. Receptor-interacting protein 140 (RIP140, encoded by Nrip1) has been shown to function as a transcriptional corepressor of oxidative metabolism. We found that mice with striated muscle deficiency of RIP140 (strNrip1-/-) exhibited increased expression of a broad array of genes involved in mitochondrial energy metabolism and contractile function in heart and skeletal muscle. strNrip1-/- mice were resistant to the development of pressure overload-induced cardiac hypertrophy, and CM-specific RIP140-deficient (csNrip1-/-) mice were protected against the development of HF caused by pressure overload combined with myocardial infarction. Genomic enhancers activated by RIP140 deficiency in CMs were enriched in binding motifs for transcriptional regulators of mitochondrial function (estrogen-related receptor) and cardiac contractile proteins (myocyte enhancer factor 2). Consistent with a role in the control of cardiac fatty acid oxidation, loss of RIP140 in heart resulted in augmented triacylglyceride turnover and fatty acid utilization. We conclude that RIP140 functions as a suppressor of a transcriptional regulatory network that controls cardiac fuel metabolism and contractile function, representing a potential therapeutic target for the treatment of HF.

Impact of IH-induced sympathetic hyperactivity and metabolic dysfunctions on ischemic cardiomyopathy progression

Patients with obstructive sleep apnea (OSA) exhibit poor prognosis after myocardial infarction (MI). Intermittent hypoxia (IH), the hallmark feature of OSA, promotes sympathetic hyperactivity and systemic insulin resistance, and has been identified as a major contributor to post-MI cardiac remodeling and contractile dysfunction. We hypothesize that sympathetic hyperactivity and metabolic alterations induced by IH promote desensitization of cardiac adrenergic and insulin pathways via activation of G protein-coupled receptors (GRK2), and subsequently participate in the aggravation of ischemic cardiomyopathy. MI is induced in C57bl6 mice by permanent ligation of the left coronary artery (MI). Mice are then randomized to IH (21–5% FiO2, 60 s cycle, 8 h/day) or normoxia for up to 6 weeks. After two weeks, mice are treated with a GRK2 inhibitor, Paroxetine (5 mg/kg/d), or 25% DMSO (Alzet® pumps). Longitudinal follow-up of mice includes evaluation of sympathetic activity (spectral analysis of heart rate variability (HRV), systemic insulin sensitivity (dynamic insulin tolerance test) and determination of cardiac function/remodeling (echocardiography). At the end of the protocol, cardiac interstitial fibrosis and hypertrophy are evaluated by RT-qPCR and histology (Sirius Red and WGA staining, respectively). Assessment of insulin signaling pathway is performed by Western blot. IH induces sympathetic hyperactivity in MI mice, demonstrated by a modification of the sympathovagal balance (LF increase). Paroxetine treatment abolishes the increase in LF in MI-IH condition and restores mRNA expression of β1 and β2 adrenergic receptors. MI-IH induces systemic insulin resistance compared to MI-N condition, which is prevented by Paroxetine treatment. In addition, Paroxetine treatment improves insulin signaling in the liver of MI-IH mice (pIRβ and pAKT). IH exacerbates cardiac interstitial fibrosis and worsens contractile dysfunction in MI mice, resulting in a significant decrease in ejection fraction (19.4 ± 2.1% vs. 29.9 ± 3.6% in IH vs. N respectively, P < 0.05). The effect of paroxetine on cardiac remodeling and function is currently being analyzed. These findings demonstrate that IH induces cardiac sympathetic hyperactivity and insulin resistance, which could contribute to the worsening of ischemic heart disease via GRK2.

MK-886 protects against cardiac ischaemia/reperfusion injury by activating proteasome-Keap1-NRF2 signalling

Oxidative stress is considered a key factor contributing to the initiation and development of cardiac injury following ischaemia‒reperfusion (I/R). Arachidonate 5-lipoxygenase (ALOX5) is a rate-limiting enzyme for leukotriene biosynthesis. MK-886 is an inhibitor of ALOX5 that exhibits anti-inflammatory and antioxidant activities. However, the significance of MK-886 in preventing I/R-mediated cardiac injury and the underlying mechanism remain unclear. Cardiac I/R model was produced by ligation/release of the left anterior descending artery. MK-886 (20 mg/kg) was administered intraperitoneally into mice at 1 and 24 h before I/R. Our results indicated that MK-886 treatment significantly attenuated I/R-mediated cardiac contractile dysfunction and decreased the infarct area, myocyte apoptosis, and oxidative stress accompanied with reduction of Kelch-like ECH-associated protein 1 (keap1) and upregulation of nuclear factor erythroid 2-related factor 2 (NRF2). Conversely, administration of the proteasome inhibitor epoxomicin and NRF2 inhibitor ML385 greatly abrogated MK-886-mediated cardioprotection after I/R injury. Mechanistically, MK-886 enhanced the expression of the immunoproteasome subunit β5i, which interacted with keap1 and enhanced its degradation, leading to activation of the NRF2-dependent antioxidant response and improvement of mitochondrial fusion-fission balance in the I/R-treated heart. In summary, our present findings indicated that MK-886 could protect the heart against I/R injury and highlight that MK-886 may represent a promising therapeutic candidate for preventing ischaemic disease.

Expression of Concern: Toll-like receptor 4 knockout protects against anthrax lethal toxin-induced cardiac contractile dysfunction: role of autophagy.

Expression of Concern: Toll-like receptor 4 knockout protects against anthrax lethal toxin-induced cardiac contractile dysfunction: role of autophagy.