Myocardial Inflammation in Heart Failure With Reduced and Preserved Ejection Fraction.

Heart failure (HF) is characterized by a progressive decline in cardiac function and represents one of the largest health burdens worldwide. Clinically, 2 major types of HF are distinguished based on the left ventricular ejection fraction (EF): HF with reduced EF and HF with preserved EF. While both types share several risk factors and features of adverse cardiac remodeling, unique hallmarks beyond ejection fraction that distinguish these etiologies also exist. These differences may explain the fact that approved therapies for HF with reduced EF are largely ineffective in patients suffering from HF with preserved EF. Improving our understanding of the distinct cellular and molecular mechanisms is crucial for the development of better treatment strategies. This article reviews the knowledge of the immunologic mechanisms underlying HF with reduced and preserved EF and discusses how the different immune profiles elicited may identify attractive therapeutic targets for these conditions. We review the literature on the reported mechanisms of adverse cardiac remodeling in HF with reduced and preserved EF, as well as the immune mechanisms involved. We discuss how the knowledge gained from preclinical models of the complex syndrome of HF as well as from clinical data obtained from patients may translate to a better understanding of HF and result in specific treatments for these conditions in humans.

Ponatinib Drives Cardiotoxicity by S100A8/A9-NLRP3-IL-1ß Mediated Inflammation.

BACKGROUND: The tyrosine kinase inhibitor ponatinib is the only treatment option for chronic myelogenous leukemia patients with T315I (gatekeeper) mutation. Pharmacovigilance analysis of Food and Drug Administration and World Health Organization datasets has revealed that ponatinib is the most cardiotoxic agent among all Food and Drug Administration-approved tyrosine kinase inhibitors in a real-world scenario. However, the mechanism of ponatinib-induced cardiotoxicity is unknown. METHODS: The lack of well-optimized mouse models has hampered the in vivo cardio-oncology studies. Here, we show that cardiovascular comorbidity mouse models evidence a robust cardiac pathological phenotype upon ponatinib treatment. A combination of multiple in vitro and in vivo models was employed to delineate the underlying molecular mechanisms. RESULTS: An unbiased RNA sequencing analysis identified the enrichment of dysregulated inflammatory genes, including a multifold upregulation of alarmins S100A8/A9, as a top hit in ponatinib-treated hearts. Mechanistically, we demonstrate that ponatinib activates the S100A8/A9-TLR4 (Toll-like receptor 4)-NLRP3 (NLR family pyrin domain-containing 3)-IL (interleukin)-1ß signaling pathway in cardiac and systemic myeloid cells, in vitro and in vivo, thereby leading to excessive myocardial and systemic inflammation. Excessive inflammation was central to the cardiac pathology because interventions with broad-spectrum immunosuppressive glucocorticoid dexamethasone or specific inhibitors of NLRP3 (CY-09) or S100A9 (paquinimod) nearly abolished the ponatinib-induced cardiac dysfunction. CONCLUSIONS: Taken together, these findings uncover a novel mechanism of ponatinib-induced cardiac inflammation leading to cardiac dysfunction. From a translational perspective, our results provide critical preclinical data and rationale for a clinical investigation into immunosuppressive interventions for managing ponatinib-induced cardiotoxicity.

Neutrophils are indispensable for adverse cardiac remodeling in heart failure.

Persistent immune activation contributes significantly to left ventricular (LV) dysfunction and adverse remodeling in heart failure (HF). In contrast to their well-known essential role in acute myocardial infarction (MI) as first responders that clear dead cells and facilitate subsequent reparative macrophage polarization, the role of neutrophils in the pathobiology of chronic ischemic HF is poorly defined. To determine the importance of neutrophils in the progression of ischemic cardiomyopathy, we measured their production, levels, and activation in a mouse model of chronic HF 8 weeks after permanent coronary artery ligation and large MI. In HF mice, neutrophils were more abundant both locally in failing myocardium (more in the border zone) and systemically in the blood, spleen, and bone marrow, together with increased BM granulopoiesis. There were heightened stimuli for neutrophil recruitment and trafficking in HF, with increased myocardial expression of the neutrophil chemoattract chemokines CXCL1 and CXCL5, and increased neutrophil chemotactic factors in the circulation. HF neutrophil NETotic activity was increased in vitro with coordinate increases in circulating neutrophil extracellular traps (NETs) in vivo. Neutrophil depletion with either antibody-based or genetic approaches abrogated the progression of LV remodeling and fibrosis at both intermediate and late stages of HF. Moreover, analogous to murine HF, the plasma milieu in human acute decompensated HF strongly promoted neutrophil trafficking. Collectively, these results support a key tissue-injurious role for neutrophils and their associated cytotoxic products in ischemic cardiomyopathy and suggest that neutrophils are potential targets for therapeutic immunomodulation in this disease.

ß-hydroxybutyrate administered at reperfusion reduces infarct size and preserves cardiac function by improving mitochondrial function through autophagy in male mice.

Ischemia/reperfusion (I/R) injury after revascularization contributes ∼50% of infarct size and causes heart failure, for which no established clinical treatment exists. ß-hydroxybutyrate (ß-OHB), which serves as both an energy source and a signaling molecule, has recently been reported to be cardioprotective when administered immediately before I/R and continuously after reperfusion. This study aims to determine whether administering ß-OHB at the time of reperfusion with a single dose can alleviate I/R injury and, if so, to define the mechanisms involved. We found plasma ß-OHB levels were elevated during ischemia in STEMI patients, albeit not to myocardial protection level, and decreased after revascularization. In mice, compared with normal saline, ß-OHB administrated at reperfusion reduced infarct size (by 50%) and preserved cardiac function, as well as activated autophagy and preserved mtDNA levels in the border zone. Our treatment with one dose ß-OHB reached a level achievable with fasting and strenuous physical activity. In neonatal rat ventricular myocytes (NRVMs) subjected to I/R, ß-OHB at physiologic level reduced cell death, increased autophagy, preserved mitochondrial mass, function, and membrane potential, in addition to attenuating reactive oxygen species (ROS) levels. ATG7 knockdown/knockout abolished the protective effects of ß-OHB observed both in vitro and in vivo. Mechanistically, ß-OHB's cardioprotective effects were associated with inhibition of mTOR signaling. In conclusion, ß-OHB, when administered at reperfusion, reduces infarct size and maintains mitochondrial homeostasis by increasing autophagic flux (potentially through mTOR inhibition). Since ß-OHB has been safely tested in heart failure patients, it may be a viable therapeutic to reduce infarct size in STEMI patients.

Incident Heart Failure Risk Reclassification With Race-Independent Estimated Glomerular Filtration Rate: A National Heart, Lung, and Blood Institute Pooled Cohorts Analysis.

BACKGROUND: This study compared the predictive value of the race-independent creatinine- and cystatin C-based estimated glomerular filtration rate (eGFRcr-cys) and the race-dependent creatinine-based eGFR (eGFRcr) for incident heart failure (HF). METHODS: This study combined the participant-level data from ARIC (Atherosclerosis Risk in Communities) (visit 4) and MESA (Multi-Ethnic Study of Atherosclerosis) (visit 1) to calculate eGFRcr-cys and eGFRcr. The primary outcome of the study was adjudicated incident HF over a follow-up period of 10 years. Multivariable Cox models were used to assess the risk of incident HF with the quartiles of eGFRcr-cys and eGFRcr. RESULTS: Among 15,615 individuals (median age: 62 [57-68] years; 55.0% females; 23.9% Black), the median eGFRcr-cys and eGFRcr were 91.4 (79.4, 102.0) mL/min/1.73m2 and 84.7 (72.0, 94.7) mL/min/1.73m2, respectively. Compared with the fourth quartile of eGFRcr-cys, the hazard ratio for incident HF was 1.02 (95% CI:0.80-1.30) in the third quartile, 1.02 (95% CI:0.80-1.30) in the second quartile, and 1.47 (95% CI:1.16-1.86) in the first quartile. Compared with the 4th quartile of the eGFRcr, the risk of incident HF was similar in the 3rd (HRadj:0.90 [95% CI:0.73-1.12]), 2nd (HRadj: 0.96 [95% CI:0.77-1.20]), and 1st (HRadj:1.15 [95% CI:0.93-1.44]) quartiles. C-statistics were similar for the multivariable-adjusted Cox models for incident HF using eGFRcr (0.80 [0.79-0.81]) and eGFRcr-cys (0.80 [0.79-0.82]). CONCLUSION: The eGFRcr and eGFRcr-cys had comparable predictive values for incident HF.

Chronobiological Influence Over Cardiovascular Function: The Good, the Bad, and the Ugly.

Essentially all biological processes fluctuate over the course of the day, observed at cellular (eg, transcription, translation, and signaling), organ (eg, contractility and metabolism), and whole-body (eg, physical activity and appetite) levels. It is, therefore, not surprising that both cardiovascular physiology (eg, heart rate and blood pressure) and pathophysiology (eg, onset of adverse cardiovascular events) oscillate during the 24-hour day. Chronobiological influence over biological processes involves a complex interaction of factors that are extrinsic (eg, neurohumoral factors) and intrinsic (eg, circadian clocks) to cells. Here, we focus on circadian governance of 6 fundamentally important processes: metabolism, signaling, electrophysiology, extracellular matrix, clotting, and inflammation. In each case, we discuss (1) the physiological significance for circadian regulation of these processes (ie, the good); (2) the pathological consequence of circadian governance impairment (ie, the bad); and (3) whether persistence/augmentation of circadian influences contribute to pathogenesis during distinct disease states (ie, the ugly). Finally, the translational impact of chronobiology on cardiovascular disease is highlighted.

Coronary flow abnormalities in chronic kidney disease: A systematic review and meta-analysis.

BACKGROUND: Coronary vasomotion abnormalities have been described in small studies but not studied systematically. We aimed to review the present literature and analyze it to improve our understanding of chronic kidney disease (CKD) related-coronary microvascular dysfunction. OBJECTIVE: Coronary flow reserve (CFR) is a well-known measure of coronary vasomotion. We aimed to assess the difference in CFR among participants with and without CKD. METHODS: PubMed, Embase, and Cochrane CENTRAL were systematically reviewed to identify studies that compared CFR in participants with and without CKD. We estimated standardized mean differences in mean CFR reported in these studies. We performed subgroup analyses according to imaging modality, and the presence of significant epicardial coronary artery disease. RESULTS: In 14 observational studies with 5966 and 1410 patients with and without CKD, the mean estimated glomerular filtration rate (eGFR) was 29 ± 04 and 87 ± 25 ml/min/1.73 m2 , respectively. Mean CFR was consistently lower in patients with CKD in all studies and the cumulative mean difference was statistically significant (2.1 ± .3 vs. 2.7 ± .5, standardized mean difference -.8, 95% CI -1.1, -.6, p < .05). The lower mean CFR was driven by both significantly higher mean resting flow velocity (.58 cm/s, 95% CI .17, .98) and lower mean stress flow velocity (-.94 cm/s, 95% CI -1.75, -.13) in studies with CKD. This difference remained significant across diagnostic modalities and even in absence of epicardial coronary artery disease. In meta-regression, there was a significant positive relationship between mean eGFR and mean CFR (p < .05). CONCLUSION: Patients with CKD have a significantly lower CFR versus those without CKD, even in absence of epicardial coronary artery disease. There is a linear association between eGFR and CFR. Future studies are required to understand the mechanisms and therapeutic implications of these findings. KEY POINTS: In this meta-analysis of observational studies, there was a significant reduction in coronary flow reserve in studies with chronic kidney disease versus those without. This difference was seen even in absence of epicardial coronary artery disease. In meta-regression, a lower estimate glomerular filtration rate was a significant predictor of lower coronary flow reserve. Coronary microvascular dysfunction, rather than atherosclerosis-related epicardial disease may underly increase cardiovascular risk in a patient with chronic kidney disease.

Branched chain amino acids selectively promote cardiac growth at the end of the awake period.

Essentially all biological processes fluctuate over the course of the day, manifesting as time-of-day-dependent variations with regards to the way in which organ systems respond to normal behaviors. For example, basic, translational, and epidemiologic studies indicate that temporal partitioning of metabolic processes governs the fate of dietary nutrients, in a manner in which concentrating caloric intake towards the end of the day is detrimental to both cardiometabolic and cardiovascular parameters. Despite appreciation that branched chain amino acids impact risk for obesity, diabetes mellitus, and heart failure, it is currently unknown whether the time-of-day at which dietary BCAAs are consumed influence cardiometabolic/cardiovascular outcomes. Here, we report that feeding mice a BCAA-enriched meal at the end of the active period (i.e., last 4 h of the dark phase) rapidly increases cardiac protein synthesis and mass, as well as cardiomyocyte size; consumption of the same meal at the beginning of the active period (i.e., first 4 h of the dark phase) is without effect. This was associated with a greater BCAA-induced activation of mTOR signaling in the heart at the end of the active period; pharmacological inhibition of mTOR (through rapamycin) blocked BCAA-induced augmentation of cardiac mass and cardiomyocyte size. Moreover, genetic disruption of the cardiomyocyte circadian clock abolished time-of-day-dependent fluctuations in BCAA-responsiveness. Finally, we report that repetitive consumption of BCAA-enriched meals at the end of the active period accelerated adverse cardiac remodeling and contractile dysfunction in mice subjected to transverse aortic constriction. Thus, our data demonstrate that the timing of BCAA consumption has significant implications for cardiac health and disease.

Coronary Microvascular Dysfunction, Left Ventricular Remodeling, and Clinical Outcomes in Patients With Chronic Kidney Impairment.

BACKGROUND: Cardiac dysfunction and cardiovascular events are prevalent among patients with chronic kidney disease without overt obstructive coronary artery disease, but the mechanisms remain poorly understood. Coronary microvascular dysfunction has been proposed as a link between abnormal renal function and impairment of cardiac function and cardiovascular events. We aimed to investigate the relations between chronic kidney disease, coronary microvascular dysfunction, cardiac dysfunction, and adverse cardiovascular outcomes. METHODS: Patients undergoing cardiac stress positron emission tomography, echocardiogram, and renal function ascertainment at Brigham and Women's Hospital were studied longitudinally. Patients free of overt coronary (summed stress score <3 and without a history of ischemic heart disease), valvular, and end-organ disease were followed up for the adverse composite outcome of death or hospitalization for myocardial infarction or heart failure. Coronary flow reserve (CFR) was determined from positron emission tomography. Echocardiograms were used to measure cardiac mechanics: diastolic (lateral and septal E/e') and systolic (global longitudinal, radial, and circumferential strain). Image analyses and event adjudication were blinded. The associations between estimated glomerular filtration rate (eGFR), CFR, diastolic and systolic indices, and adverse cardiovascular outcomes were assessed in adjusted models and mediation analyses. RESULTS: Of the 352 patients (median age, 65 years; 63% female; 22% black) studied, 35% had an eGFR <60 mL·min-1·1.73 m-2, a median left ventricular ejection fraction of 62%, and a median CFR of 1.8. eGFR and CFR were associated with diastolic and systolic indices, as well as future cardiovascular events (all P<0.05). In multivariable models, CFR, but not eGFR, was independently associated with cardiac mechanics and cardiovascular events. The associations between eGFR, cardiac mechanics, and cardiovascular events were partly mediated via CFR. CONCLUSIONS: Coronary microvascular dysfunction, but not eGFR, was independently associated with abnormal cardiac mechanics and an increased risk of cardiovascular events. Coronary microvascular dysfunction may mediate the effect of chronic kidney disease on abnormal cardiac function and cardiovascular events in those without overt coronary artery disease.

Race, Natriuretic Peptides, and High-Carbohydrate Challenge: A Clinical Trial.

RATIONALE: Lower NP (natriuretic peptide) levels may contribute to the development of cardiometabolic diseases. Blacks have lower NP levels than middle-aged and older white adults. A high-carbohydrate challenge causes an upregulation of a negative ANP regulator microRNA-425 (miR-425), which reduces ANP (atrial-NP) levels in whites. OBJECTIVES: We designed a prospective trial to study racial differences in (1) NP levels among young adults, (2) NP response to a high-carbohydrate challenge, and (3) explore underlying mechanisms for race-based differences. METHODS AND RESULTS: Healthy self-identified blacks and whites received 3 days of study diet followed by a high-carbohydrate challenge. Gene expression from whole blood RNA was assessed in the trial participants. Additionally, atrial and ventricular tissue samples from the Myocardial Applied Genomics Network repository were examined for NP system gene expression. Among 72 healthy participants, we found that B-type-NP, NT-proBNP (N-terminal-pro-B-type NP), and MRproANP (midregional-pro-ANP) levels were 30%, 47%, and 18% lower in blacks compared with whites (P≤0.01), respectively. The decrease in MRproANP levels in response to a high-carbohydrate challenge differed by race (blacks 23% [95% CI, 19%-27%] versus whites 34% [95% CI, 31%-38]; Pinteraction<0.001), with no change in NT-proBNP levels. We did not observe any racial differences in expression of genes encoding for NPs (NPPA/NPPB) or NP signaling (NPR1) in atrial and ventricular tissues. NP processing (corin), clearance (NPR3), and regulation (miR-425) genes were ≈3.5-, ≈2.5-, and ≈2-fold higher in blacks than whites in atrial tissues, respectively. We also found a 2-and 8-fold higher whole blood RNA expression of gene encoding for Neprilysin (MME) and miR-425 among blacks than whites. CONCLUSIONS: Racial differences in NP levels are evident in young, healthy adults suggesting a state of NP deficiency exists in blacks. Impaired NP processing and clearance may contribute to race-based NP differences. Higher miR-425 levels in blacks motivate additional studies to understand differences in NP downregulation after physiological perturbations. CLINICAL TRIAL REGISTRATION: URL: https://clinicaltrials.gov/ct2/show/NCT03072602. Unique identifier: NCT03072602.

Convergences of Life Sciences and Engineering in Understanding and Treating Heart Failure.

On March 1 and 2, 2018, the National Institutes of Health 2018 Progenitor Cell Translational Consortium, Cardiovascular Bioengineering Symposium, was held at the University of Alabama at Birmingham. Convergence of life sciences and engineering to advance the understanding and treatment of heart failure was the theme of the meeting. Over 150 attendees were present, and >40 scientists presented their latest work on engineering human functional myocardium for disease modeling, drug development, and heart failure research. The scientists, engineers, and physicians in the field of cardiovascular sciences met and discussed the most recent advances in their work and proposed future strategies for overcoming the major roadblocks of cardiovascular bioengineering and therapy. Particular emphasis was given for manipulation and using of stem/progenitor cells, biomaterials, and methods to provide molecular, chemical, and mechanical cues to cells to influence their identity and fate in vitro and in vivo. Collectively, these works are profoundly impacting and progressing toward deciphering the mechanisms and developing novel treatments for left ventricular dysfunction of failing hearts. Here, we present some important perspectives that emerged from this meeting.

Perimyocarditis following first dose of the mRNA-1273 SARS-CoV-2 (Moderna) vaccine in a healthy young male: a case report.

BACKGROUND: Half of U.S. adults have received at least one dose of the COVID-19 vaccines produced by either Pfizer, Moderna, or Johnson and Johnson, which represents a major milestone in the ongoing pandemic. Given the emergency use authorizations for these vaccines, their side effects and safety were assessed over a compressed time period. Hence, ongoing monitoring for vaccine-related adverse events is imperative for a full understanding and delineation of their safety profile. CASE PRESENTATION: An 22-year-old Caucasian male presented to our hospital center complaining of pleuritic chest pain. Six months prior he had a mild case of COVID-19, but was otherwise healthy. He had received his first dose of the Moderna vaccine three days prior to developing symptoms. Laboratory analysis revealed a markedly elevated troponin and multiple imaging modalities during his hospitalization found evidence of wall motion abnormalities consistent with a diagnosis of perimyocarditis. He was started on aspirin and colchicine with marked improvement of his symptoms prior to discharge. CONCLUSIONS: We present a case of perimyocarditis that was temporally related to COVID-19 mRNA vaccination in an young male with prior COVID-19 infection but otherwise healthy. Our case report highlights an albeit rare but important adverse event for clinicians to be aware of. It also suggests a possible mechanism for the development of myocardial injury in our patient.

Echocardiographic diagnosis of left ventricular diastolic dysfunction: Impact of coronary artery disease.

BACKGROUND: In 2016, the American Society of Echocardiography (ASE) released guidelines for identifying left ventricular (LV) diastolic dysfunction (DD), but its ability to detect early hemodynamic abnormalities is not well established, especially in the setting of subclinical coronary artery disease (CAD). We hypothesize that the accuracy of ASE categorization of early LVDD is affected by knowledge of whether CAD history is present. METHODS: We studied 34 patients (age 62 ± 7 years) with NYHA class I to II symptoms and with transthoracic echocardiography without findings suggesting myocardial disease (all with preserved LV ejection fraction), who underwent cardiac catheterization with high-fidelity LV pressure measurement. Echocardiographic images were evaluated for LVDD using ASE algorithm without and with knowledge of CAD history and angiography findings. CAD was considered as having DD for the algorithm. RESULTS: CAD was identified in 22 patients at catheterization (65%). Using ASE guidelines without including history of CAD or angiographic results, 29 patients were DD-, 3 were DD+ (all grade II), and 2 were indeterminate. Inclusion of CAD history recategorized 59% (n = 20) patients to DD+ (all grade I) from DD- (P < .0001). Nineteen of the recategorized patients (95%) had increased isovolumetric relaxation time (IVRT). The addition of echocardiographic IVRT improved discrimination between DD- and DD+, when the presence of CAD is unknown. CONCLUSIONS: 2016-ASE algorithm reasonably accurately identifies early LVDD at rest as reflected by LV catheterization when CAD is disclosed, but without knowledge of the presence of CAD, it underdiagnoses DD+ grade I. The addition of IVRT may improve early LVDD diagnostics.

Dysfunctional and Proinflammatory Regulatory T-Lymphocytes Are Essential for Adverse Cardiac Remodeling in Ischemic Cardiomyopathy.

BACKGROUND: Heart failure (HF) is a state of inappropriately sustained inflammation, suggesting the loss of normal immunosuppressive mechanisms. Regulatory T-lymphocytes (Tregs) are considered key suppressors of immune responses; however, their role in HF is unknown. We hypothesized that Tregs are dysfunctional in ischemic cardiomyopathy and HF, and they promote immune activation and left ventricular (LV) remodeling. METHODS: Adult male wild-type C57BL/6 mice, Foxp3-diphtheria toxin receptor transgenic mice, and tumor necrosis factor (TNF) α receptor-1 (TNFR1)-/- mice underwent nonreperfused myocardial infarction to induce HF or sham operation. LV remodeling was assessed by echocardiography as well as histological and molecular phenotyping. Alterations in Treg profile and function were examined by flow cytometry, immunostaining, and in vitro cell assays. RESULTS: Compared with wild-type sham mice, CD4+Foxp3+ Tregs in wild-type HF mice robustly expanded in the heart, circulation, spleen, and lymph nodes in a phasic manner after myocardial infarction, beyond the early phase of wound healing, and exhibited proinflammatory T helper 1-type features with interferon-γ, TNFα, and TNFR1 expression, loss of immunomodulatory capacity, heightened proliferation, and potentiated antiangiogenic and profibrotic properties. Selective Treg ablation in Foxp3-diphtheria toxin receptor mice with ischemic cardiomyopathy reversed LV remodeling and dysfunction, alleviating hypertrophy and fibrosis, while suppressing circulating CD4+ T cells and systemic inflammation and enhancing tissue neovascularization. Tregs reconstituted after ablation exhibited restoration of immunosuppressive capacity and normalized TNFR1 expression. Treg dysfunction was also tightly coupled to Treg-endothelial cell contact- and TNFR1-dependent inhibition of angiogenesis and the mobilization and tissue infiltration of CD34+Flk1+ circulating angiogenic cells in a C-C chemokine ligand 5/C-C chemokine receptor 5-dependent manner. Anti-CD25-mediated Treg depletion in wild-type mice imparted similar benefits on LV remodeling, circulating angiogenic cells, and tissue neovascularization. CONCLUSIONS: Proinflammatory and antiangiogenic Tregs play an essential pathogenetic role in chronic ischemic HF to promote immune activation and pathological LV remodeling. The restoration of normal Treg function may be a viable approach to therapeutic immunomodulation in this disease.

MitoQ regulates redox-related noncoding RNAs to preserve mitochondrial network integrity in pressure-overload heart failure.

Evidence suggests that mitochondrial network integrity is impaired in cardiomyocytes from failing hearts. While oxidative stress has been implicated in heart failure (HF)-associated mitochondrial remodeling, the effect of mitochondrial-targeted antioxidants, such as mitoquinone (MitoQ), on the mitochondrial network in a model of HF (e.g., pressure overload) has not been demonstrated. Furthermore, the mechanism of this regulation is not completely understood with an emerging role for posttranscriptional regulation via long noncoding RNAs (lncRNAs). We hypothesized that MitoQ preserves mitochondrial fusion proteins (i.e., mitofusin), likely through redox-sensitive lncRNAs, leading to improved mitochondrial network integrity in failing hearts. To test this hypothesis, 8-wk-old C57BL/6J mice were subjected to ascending aortic constriction (AAC), which caused substantial left ventricular (LV) chamber remodeling and remarkable contractile dysfunction in 1 wk. Transmission electron microscopy and immunostaining revealed defective intermitochondrial and mitochondrial-sarcoplasmic reticulum ultrastructure in AAC mice compared with sham-operated animals, which was accompanied by elevated oxidative stress and suppressed mitofusin (i.e., Mfn1 and Mfn2) expression. MitoQ (1.36 mg·day-1·mouse-1, 7 consecutive days) significantly ameliorated LV dysfunction, attenuated Mfn2 downregulation, improved interorganellar contact, and increased metabolism-related gene expression. Moreover, our data revealed that MitoQ alleviated the dysregulation of an Mfn2-associated lncRNA (i.e., Plscr4). In summary, the present study supports a unique mechanism by which MitoQ improves myocardial intermitochondrial and mitochondrial-sarcoplasmic reticulum (SR) ultrastructural remodeling in HF by maintaining Mfn2 expression via regulation by an lncRNA. These findings underscore the important role of lncRNAs in the pathogenesis of HF and the potential of targeting them for effective HF treatment.NEW & NOTEWORTHY We have shown that MitoQ improves cardiac mitochondrial network integrity and mitochondrial-SR alignment in a pressure-overload mouse heart-failure model. This may be occurring partly through preventing the dysregulation of a redox-sensitive lncRNA-microRNA pair (i.e., Plscr4-miR-214) that results in an increase in mitofusin-2 expression.

The Apolipoprotein A-I Mimetic L-4F Attenuates Monocyte Activation and Adverse Cardiac Remodeling after Myocardial Infarction.

Excessive inflammation after myocardial infarction (MI) can promote infarct expansion and adverse left ventricular (LV) remodeling. L-4F, a mimetic peptide of apolipoprotein A-I (apoA-I), exhibits anti-inflammatory and anti-atherogenic properties; however, whether L-4F imparts beneficial effects after myocardial infarction (MI) is unknown. Here we demonstrate that L-4F suppresses the expansion of blood, splenic, and myocardial pro-inflammatory monocytes and macrophages in a mouse model of reperfused MI. Changes in immune cell profiles were accompanied by alleviation of post-MI LV remodeling and dysfunction. In vitro, L-4F also inhibited pro-inflammatory and glycolytic gene expression in macrophages. In summary, L-4F treatment prevents prolonged and excessive inflammation after MI, in part through modulation of pro-inflammatory monocytes and macrophages, and improves post-MI LV remodeling. These data suggest that L-4F could be a used as a therapeutic adjunct in humans with MI to limit inflammation and alleviate the progression to heart failure.

HDAC inhibition induces autophagy and mitochondrial biogenesis to maintain mitochondrial homeostasis during cardiac ischemia/reperfusion injury.

AIMS: The FDA-approved histone deacetylase (HDAC) inhibitor, suberoylanilide hydroxamic acid (SAHA, Vorinostat) has been shown to induce cardiomyocyte autophagy and blunt ischemia/reperfusion (I/R) injury when administered at the time of reperfusion. However, the precise mechanisms underlying the cardioprotective activity of SAHA are unknown. Mitochondrial dysfunction and oxidative damage are major contributors to myocardial apoptosis during I/R injury. We hypothesize that SAHA protects the myocardium by maintaining mitochondrial homeostasis and reducing reactive oxygen species (ROS) production during I/R injury. METHODS: Mouse and cultured cardiomyocytes (neonatal rat ventricular myocytes and human embryonic stem cell-derived cardiomyocytes) I/R models were used to investigate the effects of SAHA on mitochondria. ATG7 knockout mice, ATG7 knockdown by siRNA and PGC-1α knockdown by adenovirus in cardiomyocytes were used to test the dependency of autophagy and PGC-1α-mediated mitochondrial biogenesis respectively. RESULTS: Intact and total mitochondrial DNA (mtDNA) content and mitochondrial mass were significantly increased in cardiomyocytes by SAHA pretreatment before simulated I/R. In vivo, I/R induced >50% loss of mtDNA content in the border zones of mouse hearts, but SAHA pretreatment and reperfusion treatment alone reverted mtDNA content and mitochondrial mass to control levels. Moreover, pretreatment of cardiomyocytes with SAHA resulted in a 4-fold decrease in I/R-induced loss of mitochondrial membrane potential and a 25%-40% reduction in cytosolic ROS levels. However, loss-of-function of ATG7 in cardiomyocytes or mouse myocardium abolished the protective effects of SAHA on ROS levels, mitochondrial membrane potential, mtDNA levels, and mitochondrial mass. Lastly, PGC-1α gene expression was induced by SAHA in NRVMs and mouse heart subjected to I/R, and loss of PGC-1α abrogated SAHA's mitochondrial protective effects in cardiomyocytes. CONCLUSIONS: SAHA prevents I/R induced-mitochondrial dysfunction and loss, and reduces myocardial ROS production when given before or after the ischemia. The protective effects of SAHA on mitochondria are dependent on autophagy and PGC-1α-mediated mitochondrial biogenesis.

Optimized protocols for isolation, fixation, and flow cytometric characterization of leukocytes in ischemic hearts.

Immune activation post-myocardial infarction is an orchestrated sequence of cellular responses to effect tissue repair and healing. However, excessive and dysregulated inflammation can result in left ventricular remodeling and pathological alterations in the structural and mechanical attributes of the heart. Identification of key pathways and critical cellular mediators of inflammation is thus essential to design immunomodulatory therapies for myocardial infarction and ischemic heart failure. Despite this, the experimental approaches to isolate mononuclear cells from the heart are diverse, and detailed protocols to enable maximum yield of live cells in the shortest time possible are not readily available. Here, we describe optimized protocols for the isolation, fixation, and flow cytometric characterization of cardiac CD45+ leukocytes. These protocols circumvent time-consuming coronary perfusion and density-mediated cell-separation steps, resulting in high cellular yields from cardiac digests devoid of contaminating intravascular cells. Moreover, in contrast to methanol and acetone, we show that cell fixation using 1% paraformaldehyde is most optimal as it does not affect antibody binding or cellular morphology, thereby providing a considerable advantage to study activation/infiltration-associated changes in cellular granularity and size. These are highly versatile methods that can easily be streamlined for studies requiring simultaneous isolation of immune cells from different tissues or deployment in studies containing a large cohort of samples with time-sensitive constraints.NEW & NOTEWORTHY In this article, we describe optimized protocols for the isolation, fixation, and flow cytometric analysis of immune cells from the ischemic/nonischemic hearts. These protocols are optimized to process several samples/tissues, simultaneously enabling maximal yield of immune cells in the shortest time possible. We show that the low-speed centrifugation can be used as an effective alternative to lengthy coronary perfusion to remove intravascular cells, and sieving through 40-µm filter can replace density-mediated mononuclear cell separation which usually results in 50-70% cell loss in the sedimented pellets. We also show that cell fixation using 1% paraformaldehyde is better than the organic solvents such as methanol and acetone for flow cytometric analysis.

Role of left ventricle deformation analysis in stress echocardiography for significant coronary artery disease detection: A diagnostic study meta-analysis.

BACKGROUND: We compared the diagnostic accuracy of longitudinal strain (LS) imaging during stress echocardiography with visual assessment of wall motion (WM) for detecting significant coronary artery disease (CAD). METHODS: Our systematic search included studies reporting diagnostic measures for LS imaging and visual assessment of WM for detecting significant CAD during stress echocardiography. Summary diagnostic accuracy measures including area under the curve (AUC), sensitivity, specificity, diagnostic odds ratio (DOR), and likelihood ratios (LRs) were estimated. RESULTS: In thirteen studies with 978 patients, ten studies used invasive coronary angiography as the reference standard. Pooled AUC for diagnosing significant CAD was 0.92 (95% confidence interval [CI] 0.89-0.94) for LS imaging as compared to 0.83 (95% CI 0.80-0.86), P < 0.001 for visual assessment of WM. LS imaging had higher sensitivity (88% [95% CI 84-92] vs 74% [95% CI 68-80], P < 0.001) and comparable specificity to visual assessment of WM (80% [95% CI 72-87] vs 83% [95% CI 74-90], P = 0.592). The DOR for LS imaging and visual assessment of WM was 31 and 15, P = 0.254, respectively. The positive LR was 4.5 for both; negative LR was 0.14 and 0.31, P = 0.002 for LS imaging and visual assessment of WM, respectively. CONCLUSIONS: Longitudinal strain imaging during stress echocardiography has better diagnostic accuracy for detecting significant CAD as compared to visual assessment of WM. Studies using larger sample size and standardized techniques of strain measurement are required to further ascertain the added advantage of strain measurement over visual assessment alone.