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Background: The murine myocardium contains distinct subsets of macrophages with disparate roles that can be defined by expression levels of CCR2 and MHC-II. The factors that modulate the composition of the myocardial macrophage pool in the naïve heart are not completely known. B cells have been recently shown to modulate the prevalence of T cells in the heart but the relationship between B cells and myocardial macrophage subsets remains unknown. Objective: To test the hypothesis that myocardial-associated B cells modulate the composition of the myocardial macrophage pool. Methods and Results: Hearts from B cell deficient (μMT) or B cell depleted (treated with Anti-CD20 antibody) mice and age/sex matched controls were analyzed via flow cytometry at post-natal day 14 and soon after weaning. Absence of B cells was consistently associated with a decrease in the prevalence of CCR2 - MHC-II high resident macrophages. Immunofluorescence analysis of the heart showed that the myocardial-associated B cells were frequently in close proximity of CD68+ myocardial macrophages. In vitro co-culture of myocardial-derived CD64+ macrophages with B cells or with B cell-conditioned media showed that B cells fostered an increase in the prevalence of CCR2 - MHC-II high macrophages through a direct paracrine effect. In vivo 10X single cells sequencing and flow cytometric analysis together with in vitro ELISA and antibody mediate blocking suggested that the paracrine effect of B cells on myocardial macrophages is mediated, at least in part, by IL-16 secretion. Conclusion: Myocardial-associated B cells modulate the phenotype of myocardial resident macrophages. This is likely the result of a direct paracrine effect mediated, at least in part, by IL-16. These findings describe for the first time a relationship between circulating naïve B cells and tissue resident macrophages and unveil a previously unappreciated relationship between lymphoid and myeloid myocardial cells.

High serum levels of aldosterone have been linked to the development of cardiac disease. In contrast, angiotensin (Ang)-(1-7) was extensively shown to possess cardioprotective effects, including the attenuation of cardiac dysfunction induced by excessive mineralocorticoid activation in vivo, suggesting possible interactions between these 2 molecules. Here, we investigated whether there is cross-talk between aldosterone and Ang-(1-7) and its functional consequences for calcium (Ca 2+ ) signaling in ventricular myocytes. Short-term effects of aldosterone on Ca 2+ transient were assessed in Fluo-4/AM-loaded myocytes. Confocal images showed that Ang-(1-7) had no effect on Ca 2+ transient parameters, whereas aldosterone increased the magnitude of the Ca 2+ transient. Quite unexpectedly, addition of Ang-(1-7) to aldosterone-treated myocytes further enhanced the amplitude of the Ca 2+ transient suggesting a synergistic effect of these molecules. Aldosterone action on Ca 2+ transient amplitude was mediated by protein kinase A, and was related to an increase in Ca 2+ current ( I Ca ) density. Both changes were not altered by Ang-(1-7). When cardiomyocytes were exposed to aldosterone, increased Ca 2+ spark rate was measured. Ang-(1-7) prevented this change. In addition, a NO synthase inhibitor restored the effect of aldosterone on Ca 2+ spark rate in Ang-(1-7)-treated myocytes and attenuated the synergistic effect of these 2 molecules on Ca 2+ transient. These results indicate that NO plays an important role in this cross-talk. Our results bring new perspectives in the understanding of how 2 prominent molecules with supposedly antagonist cardiac actions cross-talk to synergistically amplify Ca 2+ signals in cardiomyocytes.

The renin-angiotensin system (RAS) plays a key role inthe modulation of multiple functions in many organs. It has been demonstrated that the protective axis Ang-(1-7)/ACE2/Mas exerts anti-inflammatory effects in different disorders. Along this line, we have shown that Mas receptor deficiency exacerbates lipopolysaccharide(LPS)-induced cerebral and systemic inflammation in mice. In this study, we investigate the effects of LPS-induced shock in a mouse model for global increases in Mas receptor expression (UB8 mice). Mice were injected intraperitoneally (i.p.) with LPS, and experiments were performed 1h (RT-qPCR and ELISA) and 6 h (Echocardiography, NAG activity, and Lung histological analysis) after injection (except for the survival curve experiment). Cytokine gene expression was significantly attenuated in the left ventricle (LV) of UB8 vs. FVBN mice (p

Alamandine is a new component of the renin-angiotesin system generated from angiotensin A or angiotensin-(1[[Unable to Display Character: –]]7). Its biological actions include vasodilation, and antihypertensive effects. In the heart, the molecular pathways activated by alamandine have not been characterized. Our goal was to investigate the signaling pathways activated by alamandine in ventricular myocytes isolated from both healthy and hypertensive models. Cardiomyocytes isolated from C57BL/6 mice and from rats that overexpress renin (TGRmRen) were treated with 100nmol/L alamandine. Intracellular nitric oxide (NO) and Ca 2+ levels were recorded in cells loaded with DAF-FM and Fluo4-AM, respectively. Protein phosphorylation was assessed by western-blot. In cardiomyocytes, alamandine induced an increase in phosphorylation of PDK1 (arbitrary units (a.u.): control=0,20±0.06 versus alamandine=0,42±0.08 n=6, p2+ transient amplitude. Ventricular myocytes treated with alamandine showed decreased GSK3β phosphorylation (a.u.: control=0,62±0.19 versus alamandine=0,50±0.25 n=5 p2 ): control=447±23 n=58; angiotensin II= 609±26 n=70; angiotensin II+alamandine= 491±31 n=45 p