β2-Adrenergic receptor-dependent chemokine receptor 2 expression regulates leukocyte recruitment to the heart following acute injury

Abstract

Following cardiac injury, early immune cell responses are essential for initiating cardiac remodeling and tissue repair. We previously demonstrated the importance of β2-adrenergic receptors (β2ARs) in the regulation of immune cell localization following acute cardiac injury, with deficient leukocyte infiltration into the damaged heart. The purpose of this study was to investigate the mechanism by which immune cell-expressed β2ARs regulate leukocyte recruitment to the heart following acute cardiac injury. Chemokine receptor 2 (CCR2) expression and responsiveness to C-C motif chemokine ligand 2 (CCL2)-mediated migration were abolished in β2AR knockout (KO) bone marrow (BM), both of which were rescued by β2AR reexpression. Chimeric mice lacking immune cell-specific CCR2 expression, as well as wild-type mice administered a CCR2 antagonist, recapitulated the loss of monocyte/macrophage and neutrophil recruitment to the heart following myocardial infarction (MI) observed in mice with immune cell-specific β2AR deletion. Converse to β2AR ablation, β2AR stimulation increased CCR2 expression and migratory responsiveness to CCL2 in BM. Mechanistically, G proteindependent β2AR signaling was dispensable for these effects, whereas β-arrestin2-biased β2AR signaling was required for the regulation of CCR2 expression. Additionally, activator protein 1 (AP-1) was shown to be essential in mediating CCR2 expression in response to β2AR stimulation in both murine BM and human monocytes. Finally, reconstitution of β2ARKO BM with rescued expression of a β-arrestin-biased β2AR in vivo restored BM CCR2 expression as well as cardiac leukocyte infiltration following MI. These results demonstrate the critical role of β-arrestin2/AP-1-dependent β2AR signaling in the regulation of CCR2 expression and recruitment of leukocytes to the heart following injury.β2-adrenergic receptor | leukocyte | C-chemokine receptor 2 | cardiac injury | β-arrestin

An acute immune response underlies the benefit of cardiac adult stem cell therapy

“…Although initial infarct sizes post-I/R were not different among Ccr2 -/or Cx3cr1 -/mice or strain-matched wild-type controls (not shown), Ccr2 deficiency significantly improved cardiac function after I/R (Fig. 3h), consistent with previous reports 31,48,49 . Moreover, cell therapy by MNC injection in mice lacking Ccr2 imparted no further functional benefit, given the already enhanced state of cardiac healing after I/R (Fig.3h).…”

“…Moreover, cell therapy by MNC injection in mice lacking Ccr2 imparted no further functional benefit, given the already enhanced state of cardiac healing after I/R (Fig.3h). Loss of Ccr2 showed a reduction in overall CD68 + cell content in the post-I/R heart with or without cell therapy, consistent with prior studies demonstrating that targeting circulating CCR2 + monocytes/macrophages can reduce inflammation in the heart 31,49 . By comparison, Cx3cr1 null mice lacking tissue resident macrophage activity showed left ventricular dysfunction after I/R injury that was similar to wild-type controls, but these mice no longer benefitted from MNC therapy and showed a much greater total inflammatory response ( Fig.…”

Prior beta blocker treatment decreases leukocyte responsiveness to injury

“…Beta blocker infusion alters splenic leukocyte parameters over time in vivo. Our previous studies identified key molecular changes in leukocytes in response to hematopoietic cell-specific deletion of β 2 -AR, including increased splenic VCAM-1 expression and leukocyte retention, as well as decreased leukocyte CCR2 expression in BM-derived leukocytes (14,15). Therefore, we aimed to determine whether prior treatment with β 2 -ARselective or clinically used beta blockers would similarly alter these leukocyte parameters.…”

“…To this end, we previously developed chimeric mice lacking β 2 -AR expression in cells of hematopoietic origin via transplantation of β 2 -AR-knockout (β 2 -AR-KO) bone marrow (BM) into wild-type (WT, C57BL/6J) recipient mice and subjected them to MI. Strikingly, these chimeric mice displayed severe changes in several leukocyte parameters, including increased splenic vascular cell adhesion molecule 1 (VCAM-1) expression and leukocyte retention, as well as decreased bone marrow cell (BMC) expression of chemokine receptor 2 (CCR2) and leukocyte recruitment to the heart after injury (14,15). Collectively, these genetic studies suggested that because Following injury, leukocytes are released from hematopoietic organs and migrate to the site of damage to regulate tissue inflammation and repair; however, leukocytes lacking β 2 -adrenergic receptor (β 2 -AR) expression have marked impairments in these processes.…”

Anti‐inflammatory therapies in myocardial infarction: failures, hopes and challenges

“…It should be emphasized that some of the protective effects of certain established therapeutic approaches in patients with MI, such as angiotensin converting enzyme inhibition (Leuschner et al, ), angiotensin receptor blockade (Kohno et al, ), mineralocorticoid receptor (MR) inhibition (Fraccarollo et al, ), β‐adrenoceptor blockade (Garcia‐Prieto et al, ) and administration of statins (Zhang et al, ), may involve direct modulation of inflammation. For example, leukocyte‐specific β 2 ‐adrenoceptor signalling has been reported to mediate leukocyte recruitment in the infarcted heart (Grisanti et al, ), and a recent study suggested that the infarct‐limiting effects of β‐blockade with metoprolol in a mouse model of MI were lost following neutrophil depletion or through genetic knockdown of genes associated with platelet:neutrophil interactions (Garcia‐Prieto et al, ). However, considering the broad effects of neurohumoral pathways on both cardiomyocyte and non‐cardiomyocyte populations, the relative contribution of inflammatory cell modulation remains unclear.…”