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Background: Advances in congestive heart failure (CHF) management depend on biomarkers for monitoring disease progression and therapeutic response. During systole, intracellular Ca 2+ is released from the sarcoplasmic reticulum into the cytoplasm through type-2 ryanodine receptor/Ca 2+ release channels. In CHF, chronically elevated circulating catecholamine levels cause pathological remodeling of type-2 ryanodine receptor/Ca 2+ release channels resulting in diastolic sarcoplasmic reticulum Ca 2+ leak and decreased myocardial contractility. Similarly, skeletal muscle contraction requires sarcoplasmic reticulum Ca 2+ release through type-1 ryanodine receptors (RyR1), and chronically elevated catecholamine levels in CHF cause RyR1-mediated sarcoplasmic reticulum Ca 2+ leak, contributing to myopathy and weakness. Circulating B-lymphocytes express RyR1 and catecholamine-responsive signaling cascades, making them a potential surrogate for defects in intracellular Ca 2+ handling because of leaky RyR channels in CHF., Methods: Whole blood was collected from patients with CHF, CHF following left-ventricular assist device implant, and controls. Blood was also collected from mice with ischemic CHF, ischemic CHF+S107 (a drug that specifically reduces RyR channel Ca 2+ leak), and wild-type controls. Channel macromolecular complex was assessed by immunostaining RyR1 immunoprecipitated from lymphocyte-enriched preparations. RyR1 Ca 2+ leak was assessed using flow cytometry to measure Ca 2+ fluorescence in B-lymphocytes in the absence and presence of RyR1 agonists that empty RyR1 Ca 2+ stores within the endoplasmic reticulum., Results: Circulating B-lymphocytes from humans and mice with CHF exhibited remodeled RyR1 and decreased endoplasmic reticulum Ca 2+ stores, consistent with chronic intracellular Ca 2+ leak. This Ca 2+ leak correlated with circulating catecholamine levels. The intracellular Ca 2+ leak was significantly reduced in mice treated with the Rycal S107. Patients with CHF treated with left-ventricular assist devices exhibited a heterogeneous response., Conclusions: In CHF, B-lymphocytes exhibit remodeled leaky RyR1 channels and decreased endoplasmic reticulum Ca 2+ stores consistent with chronic intracellular Ca 2+ leak. RyR1-mediated Ca 2+ leak in B-lymphocytes assessed using flow cytometry provides a surrogate measure of intracellular Ca 2+ handling and systemic sympathetic burden, presenting a novel biomarker for monitoring response to pharmacological and mechanical CHF therapy.

The t-SNARE protein SNAP23 conventionally functions as a component of the cellular machinery required for intracellular transport vesicle fusion with target membranes and has been implicated in the regulation of fasting glucose levels, BMI, and type 2 diabetes. Surprisingly, we observed that adipocyte-specific KO of SNAP23 in mice resulted in a temporal development of severe generalized lipodystrophy associated with adipose tissue inflammation, insulin resistance, hyperglycemia, liver steatosis, and early death. This resulted from adipocyte cell death associated with an inhibition of macroautophagy and lysosomal degradation of the proapoptotic regulator BAX, with increased BAX activation. BAX colocalized with LC3-positive autophagic vacuoles and was increased upon treatment with lysosome inhibitors. Moreover, BAX deficiency suppressed the lipodystrophic phenotype in the adipocyte-specific SNAP23-KO mice and prevented cell death. In addition, ATG9 deficiency phenocopied SNAP23 deficiency, whereas ATG7 deficiency had no effect on BAX protein levels, BAX activation, or apoptotic cell death. These data demonstrate a role for SNAP23 in the control of macroautophagy and programmed cell death through an ATG9-dependent, but ATG7-independent, pathway regulating BAX protein levels and BAX activation.

Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field.

Coronary artery anomalies may cause life-threatening cardiac complications; however, developmental mechanisms underpinning coronary artery formation remain ill-defined. Here we identify an angiogenic cell population for coronary artery formation in mice. Regulated by a DLL4/NOTCH1/VEGFA/VEGFR2 signaling axis, these angiogenic cells generate mature coronary arteries. The NOTCH modulator POFUT1 critically regulates this signaling axis. POFUT1 inactivation disrupts signaling events and results in excessive angiogenic cell proliferation and plexus formation, leading to anomalous coronary arteries, myocardial infarction and heart failure. Simultaneous VEGFR2 inactivation fully rescues these defects. These findings show that dysregulated angiogenic precursors link coronary anomalies to ischemic heart disease.Though coronary arteries are crucial for heart function, the mechanisms guiding their formation are largely unknown. Here, Wang et al. identify a unique, endocardially-derived angiogenic precursor cell population for coronary artery formation in mice and show that a DLL4/NOTCH1/VEGFA/VEGFR2 signaling axis is key for coronary artery development.

Mitochondria are dynamic organelles that exchange contents and undergo remodelling during cyclic fusion and fission. Genetic mutations in MFN2 (the gene encoding mitofusin 2) interrupt mitochondrial fusion and cause the untreatable neurodegenerative condition Charcot-Marie-Tooth disease type 2A (CMT2A). It has not yet been possible to directly modulate mitochondrial fusion, in part because the structural basis of mitofusin function is not completely understood. Here we show that mitofusins adopt either a fusion-constrained or a fusion-permissive molecular conformation, directed by specific intramolecular binding interactions, and demonstrate that mitofusin-dependent mitochondrial fusion can be regulated in mouse cells by targeting these conformational transitions. On the basis of this model, we engineered a cell-permeant minipeptide to destabilize the fusion-constrained conformation of mitofusin and promote the fusion-permissive conformation, reversing mitochondrial abnormalities in cultured fibroblasts and neurons that harbour CMT2A-associated genetic defects. The relationship between the conformational plasticity of mitofusin 2 and mitochondrial dynamism reveals a central mechanism that regulates mitochondrial fusion, the manipulation of which can correct mitochondrial pathology triggered by defective or imbalanced mitochondrial dynamics.

Circulating levels of undercarboxylated and bioactive osteocalcin double during aerobic exercise at the time levels of insulin decrease. In contrast, circulating levels of osteocalcin plummet early during adulthood in mice, monkeys, and humans of both genders. Exploring these observations revealed that osteocalcin signaling in myofibers is necessary for adaptation to exercise by favoring uptake and catabolism of glucose and fatty acids, the main nutrients of myofibers. Osteocalcin signaling in myofibers also accounts for most of the exercise-induced release of interleukin-6, a myokine that promotes adaptation to exercise in part by driving the generation of bioactive osteocalcin. We further show that exogenous osteocalcin is sufficient to enhance the exercise capacity of young mice and to restore to 15-month-old mice the exercise capacity of 3-month-old mice. This study uncovers a bone-to-muscle feedforward endocrine axis that favors adaptation to exercise and can reverse the age-induced decline in exercise capacity., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Cardiovascular disease is a major leading cause of morbidity and mortality in the United States and elsewhere. Alterations in mitochondrial function are increasingly being recognized as a contributing factor in myocardial infarction and in patients presenting with cardiomyopathy. Recent understanding of the complex interaction of the mitochondria in regulating metabolism and cell death can provide novel insight and therapeutic targets. The purpose of this statement is to better define the potential role of mitochondria in the genesis of cardiovascular disease such as ischemia and heart failure. To accomplish this, we will define the key mitochondrial processes that play a role in cardiovascular disease that are potential targets for novel therapeutic interventions. This is an exciting time in mitochondrial research. The past decade has provided novel insight into the role of mitochondria function and their importance in complex diseases. This statement will define the key roles that mitochondria play in cardiovascular physiology and disease and provide insight into how mitochondrial defects can contribute to cardiovascular disease; it will also discuss potential biomarkers of mitochondrial disease and suggest potential novel therapeutic approaches., (© 2016 American Heart Association, Inc.)

For decades, peripartum cardiomyopathy has remained an enigma. Despite extensive research, our understanding of how a previously healthy woman can develop lethal heart failure in the context of pregnancy remains vague. Recent work suggests that inadequacy of the cardiac microvasculature may be the primary abnormality and has implicated an antiangiogenic fragment of the nursing hormone prolactin as playing an important role. In this issue of the JCI, Halkein et al. explore signaling downstream of this prolactin fragment and demonstrate that miR-146a is a critical mediator of the antiangiogenic effects in endothelial cells. In addition, the study uncovers unexpected exosomal transfer of this microRNA to cardiomyocytes that may affect myocardial metabolism.

Myocyte apoptosis is considered a major mechanism in the pathogenesis of heart failure. Accordingly, manipulations that inhibit apoptosis are assumed to preserve cardiac function by maintaining myocyte numbers. We tested this assumption by examining the effects of caspase inhibition (CI) on cardiac structure and function in C57BL/6 mouse with pressure overload model induced by transverse aortic constriction (TAC). CI preserved left ventricular (LV) function following TAC compared with the vehicle. TAC increased apoptosis in non-myocytes more than in myocytes and these increases were blunted more in non-myocytes by CI. Total myocyte number, however, did not differ significantly among control and TAC groups and there was no correlation between myocyte number and apoptosis, but there was a strong correlation between myocyte number and an index of myocyte proliferation, Ki67-positive myocytes. Despite comparable pressure gradients, LV hypertrophy was less in the CI group, likely attributable to decreased wall stress. Since changes in myocyte numbers did not account for protection from TAC, several other CI-mediated mechanisms were identified including: (a) lessening of TAC-induced fibrosis, (b) augmentation of isolated myocyte contractility, and (c) increased angiogenesis and Ki67-positive myocytes, which were due almost entirely to the non-myocyte apoptosis, but not myocyte apoptosis, with CI. CI maintained LV function following TAC not by protecting against myocyte loss, but rather by augmenting myocyte contractile function, myocyte proliferation, and angiogenesis resulting in reduced LV wall stress, hypertrophy, and fibrosis.

The goal of this investigation was to determine the distribution of myocardial apoptosis in myocytes and nonmyocytes in primates and patients with heart failure (HF). Almost all clinical cardiologists and cardiovascular investigators believe that myocyte apoptosis is considered to be a cardinal sign of HF and a major factor in its pathogenesis. However, with the knowledge that 75% of the number of cells in the heart are nonmyocytes, it is important to determine whether the apoptosis in HF is occurring in myocytes or in nonmyocytes. We studied both a nonhuman primate model of chronic HF, induced by rapid pacing 2-6 mo after myocardial infarction (MI), and biopsies from patients with ischemic cardiomyopathy. Dual labeling with a cardiac muscle marker was used to discriminate apoptosis in myocytes versus nonmyocytes. Left ventricular ejection fraction decreased following MI (from 78% to 60%) and further with HF (35%, P < 0.05). As expected, total apoptosis was increased in the myocardium following recovery from MI (0.62 cells/mm(2)) and increased further with the development of HF (1.91 cells/mm(2)). Surprisingly, the majority of apoptotic cells in MI and MI + HF, and in both the adjacent and remote areas, were nonmyocytes. This was also observed in myocardial biopsies from patients with ischemic cardiomyopathy. We found that macrophages contributed the largest fraction of apoptotic nonmyocytes (41% vs. 18% neutrophils, 16% fibroblast, and 25% endothelial and other cells). Although HF in the failing human and monkey heart is characterized by significant apoptosis, in contrast to current concepts, the apoptosis in nonmyocytes was eight- to ninefold greater than in myocytes.

Fas is a widely expressed cell surface receptor that can initiate apoptosis when activated by its ligand (FasL). Whereas Fas abundance on cardiac myocytes increases in response to multiple pathological stimuli, direct evidence supporting its role in the pathogenesis of heart disease is lacking. Moreover, controversy exists even as to whether Fas activation induces apoptosis in cardiac myocytes. In this study, we show that adenoviral overexpression of FasL, but not beta-galactosidase, results in marked apoptosis both in cultures of primary neonatal cardiac myocytes and in the myocardium of intact adult rats. Myocyte killing by FasL is a specific event, because it does not occur in lpr (lymphoproliferative) mice that lack functional Fas. To assess the contribution of the Fas pathway to myocardial infarction (MI) in vivo, lpr mice were subjected to 30 min of ischemia followed by 24 h of reperfusion. Compared with wild-type mice, lpr mice exhibited infarcts that were 62.3% smaller with 63.8% less myocyte apoptosis. These data provide direct evidence that activation of Fas can induce apoptosis in cardiac myocytes and that Fas is a critical mediator of MI due to ischemia-reperfusion in vivo.