Cardiac-specific inducible overexpression of human plasma membrane Ca2+ ATPase 4b is cardioprotective and improves survival in mice following ischemic injury

Genetic Screening of Haploid Neural Stem Cells Reveals that Nfkbia and Atp2b4 are Key Regulators of Oxidative Stress in Neural Precursors

Neurological diseases are expected to become the leading cause of death in the next decade. Although little is known about it, the interaction between oxidative stress and inflammation is harmful to the nervous system. To find an advanced tool for neural genetics, mouse haploid neural stem cells (haNSCs) from the somite of chimeric mouse embryos at E8.5 is established. The haNSCs present a haploid neural progenitor identity for long-term culture, promising to robustly differentiate into neural subtypes and being able to form cerebral organoids efficiently. Thereafter, haNSC mutants via a high-throughput approach and screened targets of oxidative stress is generated using the specific mutant library. Deletion of Nfkbia (the top hit among the insertion mutants) reduces damage from reactive oxygen species (ROS) in NSCs exposed to H2O2. Transcriptome analysis revealed that Atp2b4 is upregulated significantly in Nfkbia-null NSCs and is probably responsible for the observed resistance. Additionally, overexpression of Atp2b4 itself can increase the survival of NSCs in the presence of H2O2, suggesting that Atp2b4 is closely involved in this resistance. Herein, a powerful haploid system is presented to study functional genetics in neural lineages, shedding light on the screening of critical genes and drugs for neurological diseases.

Neuronal nitric oxide synthase required for erythropoietin modulation of heart function in mice

Introduction: Erythropoietin (EPO) acts primarily in regulating red blood cell production mediated by high EPO receptor (EPOR) expression in erythroid progenitor cells. EPO activity in non-erythroid tissue is evident in mice with EPOR restricted to erythroid tissues (ΔEPORE) that become obese, glucose-intolerant, and insulin-resistant. In animal models, nitric oxide synthase (NOS) contributes to EPO activities including erythropoiesis, neuroprotection, and cardioprotection against ischemia-reperfusion injury. However, we found that extended EPO treatment to increase hematocrit compromised heart function, while the loss of neuronal NOS (nNOS) was protective against the deleterious activity of EPO to promote heart failure. Methods: Wild-type (WT) mice, ΔEPORE mice, and nNOS-knockout mice (nNOS-/-) were placed on a high-fat diet to match the ΔEPORE obese phenotype and were treated with EPO for 3 weeks. Hematocrit and metabolic response to EPO treatment were monitored. Cardiac function was assessed by echocardiography and ultrasonography. Results: ΔEPORE mice showed a decrease in the left ventricular outflow tract (LVOT) peak velocity, ejection fraction, and fractional shortening, showing that endogenous non-erythroid EPO response is protective for heart function. EPO treatment increased hematocrit in all mice and decreased fat mass in male WT, demonstrating that EPO regulation of fat mass requires non-erythroid EPOR. EPO treatment also compromised heart function in WT mice, and decreased the pulmonary artery peak velocity (PA peak velocity), LVOT peak velocity, ejection fraction, and fractional shortening, but it had minimal effect in further reducing the heart function in ΔEPORE mice, indicating that the adverse effect of EPO on heart function is not related to EPO-stimulated erythropoiesis. ΔEPORE mice had increased expression of heart failure-associated genes, hypertrophic cardiomyopathy-related genes, and sarcomeric genes that were also elevated with EPO treatment in WT mice. Male and female nNOS-/- mice were protected against diet-induced obesity. EPO treatment in nNOS-/- mice increased the hematocrit that tended to be lower than WT mice and decreased the PA peak velocity but did not affect the LVOT peak velocity, ejection fraction, and fractional shortening, suggesting that nNOS is required for the adverse effect of EPO treatment on heart function in WT mice. EPO treatment did not change expression of heart failure-associated gene expression in nNOS-/- mice. Discussion: Endogenous EPO has a protective effect on heart function. With EPO administration, in contrast to the protective effect to the cardiac injury of acute EPO treatment, extended EPO treatment to increase hematocrit in WT mice adversely affected the heart function with a corresponding increase in expression of heart failure-associated genes. This EPO activity was independent of EPO-stimulated erythropoiesis and required EPOR in non-erythroid tissue and nNOS activity, while nNOS-/- mice were protected from the EPO-associated adverse effect on heart function. These data provide evidence that nNOS contributes to the negative impact on the heart function of high-dose EPO treatment for anemia.

Calcium dysregulation in heart diseases: Targeting calcium channels to achieve a correct calcium homeostasis

Intracellular calcium signaling is a universal language source shared by the most part of biological entities inside cells that, all together, give rise to physiological and functional anatomical units, the organ. Although preferentially recognized as signaling between cell life and death processes, in the heart it assumes additional relevance considered the importance of calcium cycling coupled to ATP consumption in excitation-contraction coupling. The concerted action of a plethora of exchangers, channels and pumps inward and outward calcium fluxes where needed, to convert energy and electric impulses in muscle contraction. All this without realizing it, thousands of times, every day. An improper function of those proteins (i.e., variation in expression, mutations onset, dysregulated channeling, differential protein-protein interactions) being part of this signaling network triggers a short circuit with severe acute and chronic pathological consequences reported as arrhythmias, cardiac remodeling, heart failure, reperfusion injury and cardiomyopathies. By acting with chemical, peptide-based and pharmacological modulators of these players, a correction of calcium homeostasis can be achieved accompanied by an amelioration of clinical symptoms. This review will focus on all those defects in calcium homeostasis which occur in the most common cardiac diseases, including myocardial infarction, arrhythmia, hypertrophy, heart failure and cardiomyopathies. This part will be introduced by the state of the art on the proteins involved in calcium homeostasis in cardiomyocytes and followed by the therapeutic treatments that to date, are able to target them and to revert the pathological phenotype.

Identification of critical molecular pathways involved in exosome-mediated improvement of cardiac function in a mouse model of muscular dystrophy

Duchenne muscular dystrophy (DMD) is a progressive disease characterized by skeletal muscle atrophy, respiratory failure, and cardiomyopathy. Our previous studies have shown that transplantation with allogeneic myogenic progenitor-derived exosomes (MPC-Exo) can improve cardiac function in X-linked muscular dystrophy (Mdx) mice. In the present study we explored the molecular mechanisms underlying this beneficial effect. We quantified gene expression in the hearts of two strains of Mdx mice (D2.B10-DmdMdx/J and Utrntm1Ked-DmdMdx/J). Two days after MPC-Exo or control treatment, we performed unbiased next-generation RNA-sequencing to identify differentially expressed genes (DEGs) in treated Mdx hearts. Venn diagrams show a set of 780 genes that were ≥2-fold upregulated, and a set of 878 genes that were ≥2-fold downregulated, in both Mdx strains following MPC-Exo treatment as compared with control. Gene ontology (GO) and protein-protein interaction (PPI) network analysis showed that these DEGs were involved in a variety of physiological processes and pathways with a complex connection. qRT-PCR was performed to verify the upregulated ATP2B4 and Bcl-2 expression, and downregulated IL-6, MAPK8 and Wnt5a expression in MPC-Exo-treated Mdx hearts. Western blot analysis verified the increased level of Bcl-2 and decreased level of IL-6 protein in MPC-Exo-treated Mdx hearts compared with control treatment, suggesting that anti-apoptotic and anti-inflammatory effects might be responsible for heart function improvement by MPC-Exo. Based on these findings, we believed that these DEGs might be therapeutic targets that can be explored to develop new strategies for treating DMD.

PMCA4 inhibition does not affect cardiac remodelling following myocardial infarction, but may reduce susceptibility to arrhythmia

Ischaemic heart disease is the world's leading cause of mortality. Survival rates from acute myocardial infarction (MI) have improved in recent years; however, this has led to an increase in the prevalence of heart failure (HF) due to chronic remodelling of the infarcted myocardium, for which treatment options remain poor. We have previously shown that inhibition of isoform 4 of the plasma membrane calcium ATPase (PMCA4) prevents chronic remodelling and HF development during pressure overload, through fibroblast mediated Wnt signalling modulation. Given that Wnt signalling also plays a prominent role during remodelling of the infarcted heart, this study investigated the effect of genetic and functional loss of PMCA4 on cardiac outcomes following MI. Neither genetic deletion nor pharmacological inhibition of PMCA4 affected chronic remodelling of the post-MI myocardium. This was the case when PMCA4 was deleted globally, or specifically from cardiomyocytes or fibroblasts. PMCA4-ablated hearts were however less prone to acute arrhythmic events, which may offer a slight survival benefit. Overall, this study demonstrates that PMCA4 inhibition does not affect chronic outcomes following MI.

Reciprocality Between Estrogen Biology and Calcium Signaling in the Cardiovascular System

17β-Estradiol (E₂) is the main estrogenic hormone in the body and exerts many cardiovascular protective effects. Via three receptors known to date, including estrogen receptors α (ERα) and β (ERβ) and the G protein-coupled estrogen receptor 1 (GPER, aka GPR30), E₂ regulates numerous calcium-dependent activities in cardiovascular tissues. Nevertheless, effects of E₂ and its receptors on components of the calcium signaling machinery (CSM), the underlying mechanisms, and the linked functional impact are only beginning to be elucidated. A picture is emerging of the reciprocality between estrogen biology and Ca²⁺ signaling. Therein, E₂ and GPER, via both E₂-dependent and E₂-independent actions, moderate Ca²⁺-dependent activities; in turn, ERα and GPER are regulated by Ca²⁺ at the receptor level and downstream signaling via a feedforward loop. This article reviews current understanding of the effects of E₂ and its receptors on the cardiovascular CSM and vice versa with a focus on mechanisms and combined functional impact. An overview of the main CSM components in cardiovascular tissues will be first provided, followed by a brief review of estrogen receptors and their Ca²⁺-dependent regulation. The effects of estrogenic agonists to stimulate acute Ca²⁺ signals will then be reviewed. Subsequently, E₂-dependent and E₂-independent effects of GPER on components of the Ca²⁺ signals triggered by other stimuli will be discussed. Finally, a case study will illustrate how the many mechanisms are coordinated to moderate Ca²⁺-dependent activities in the cardiovascular system.

Extracorporeal membrane oxygenation mitigates myocardial injury and improves survival in porcine model of ventricular fibrillation cardiac arrest

INTRODUCTION

Despite decades of improved strategy in conventional cardiopulmonary resuscitation (CCPR), survival rates of favorable neurological outcome after cardiac arrest (CA) remains poor. It is indicated that the survival rate of successful resuscitation of extracorporeal membrane oxygenation (ECMO) is superior to that of CCPR. But the effect of ECMO in heart is unclear. We aimed to investigate whether ECMO produces cardiac protection by ameliorating post-ischemia reperfusion myocardial injury and myocardial apoptosis.

METHODS

After undergoing 8-min untreated ventricle fibrillation (VF) and 6-min basic life support, 20 male pigs were ultimately used in this study and randomly divided into two groups: CCPR group (n = 10) and extracorporeal CPR (ECPR) group (n = 10). Hemodynamics and blood samples were obtained at baseline and 1, 2, 4, and 6 h during resuscitation. The successfully resuscitated pigs were sacrificed at 6 h after return of spontaneous circulation (ROSC), and the hearts were removed and analyzed under electron microscopy, and immunohistochemistry, quantitative real-time polymerase chain reaction, and immunofluorescence staining assay were performed to evaluate myocardial injury and myocardial apoptosis.

RESULTS

There were no significant differences at basic hemodynamic status between the two groups. The survival rate of ECPR was significantly higher than CCPR group (10/10 [100%] vs. 4/10 [40%], P = 0.04). Compared to CCPR group, ECPR group exhibited a better outcome in hemodynamic function. Cardiac function was significantly impaired after ROSC in both groups, but left ventricular ejection fraction (LVEF) was significantly elevated in ECPR group than CCPR group. The expression of myocardial injury biomarkers (CK-MB, cTNI, H-FABP), endothelial injury biomarker (sP-selectin), and cardiac function biomarker (BNP) were remarkably increased after ROSC in both groups, but low levels in ECPR group than in CCPR group. Cardiomyocytes injury was attenuated in ECPR group under transmission electron microscopy (TEM). Typical apoptotic nuclei of cardiomyocytes were significantly reduced and oxidative damage were attenuated in ECPR group.

CONCLUSIONS

During prolonged VF-induced CA, ECPR contributes to improving hemodynamics, attenuating myocardial ischemia-reperfusion injury, ameliorating myocardial ultra structure, improving cardiac function, and elevating survival rate by preventing oxidative damage, regulating energy metabolism, inhibiting cardiomyocyte apoptosis.

Brg1 deficiency in vascular endothelial cells blocks neutrophil recruitment and ameliorates cardiac ischemia-reperfusion injury in mice

BACKGROUND

Increased neutrophil infiltration and the ensuing inflammatory response represent a hallmark event in cardiac ischemia-reperfusion injury (IRI). It remains poorly defined how the epigenetic machinery contributes to this process.

METHODS AND RESULTS

Here we report that mice with endothelial specific deletion of brahma related gene 1 (BRG1), a chromatin remodeling protein, exhibited amelioration when subjected to cardiac ischemia-reperfusion as evidenced by a reduction in infarct size as well as better recovery of heart function. Endothelial BRG1 deficiency also attenuated cardiac fibrosis following IRI when compared to wild type littermates. Interestingly, ablation of BRG1 in the endothelium suppressed neutrophil infiltration and down-regulated the levels of pro-inflammatory mediators in the heart following IRI. Further studies revealed that BRG1 activated the transcription of PODOCALYXIN (PODXL), an L-SELECTIN ligand crucial for neutrophil adhesion, in vascular endothelial cells in response to hypoxia-reoxygenation (HR). BRG1 knockdown by small interfering RNA abrogated HR-induced PODXL expression and blocked the adhesion of neutrophils to endothelial cells. Mechanistically, BRG1 alters the chromatin structure surrounding the PODXL promoter by interacting with JMJD2B, a histone H3K9 demethylase. Depletion of JMJD2B abrogated PODXL induction by HR and inhibited the adhesion of neutrophils to endothelial cells.

CONCLUSION

Our data suggest that trans-activation of PODXL by the BRG1-JMJD2B complex in endothelial cells may promote neutrophil infiltration and consequently the pathogenesis of cardiac ischemia-reperfusion injury.