ABSTRACT
Acute myocardial infarction is a severe ischemic disease responsible for heart failure and sudden death. Here, we show that after acute myocardial infarction in mice, mature B lymphocytes selectively produce Ccl7 and induce Ly6C(hi) monocyte mobilization and recruitment to the heart, leading to enhanced tissue injury and deterioration of myocardial function. Genetic (Baff receptor deficiency) or antibody-mediated (CD20- or Baff-specific antibody) depletion of mature B lymphocytes impeded Ccl7 production and monocyte mobilization, limited myocardial injury and improved heart function. These effects were recapitulated in mice with B cell-selective Ccl7 deficiency. We also show that high circulating concentrations of CCL7 and BAFF in patients with acute myocardial infarction predict increased risk of death or recurrent myocardial infarction. This work identifies a crucial interaction between mature B lymphocytes and monocytes after acute myocardial ischemia and identifies new therapeutic targets for acute myocardial infarction.
Subject(s)
B-Lymphocytes/physiology , Heart/physiopathology , Monocytes/physiology , Myocardial Infarction/physiopathology , Animals , B-Cell Activating Factor/blood , B-Lymphocytes/metabolism , Chemokine CCL7/biosynthesis , Chemokine CCL7/blood , Humans , Lymphocyte Depletion , Mice , Myocardial Infarction/metabolism , Signal TransductionABSTRACT
OBJECTIVE: Leukocyte infiltration in ischemic areas is a hallmark of myocardial infarction, and overwhelming infiltration of innate immune cells has been shown to promote adverse remodeling and cardiac rupture. Recruitment of inflammatory cells in the ischemic heart depends highly on the family of CC-chemokines and their receptors. Here, we hypothesized that the chemokine decoy receptor D6, which specifically binds and scavenges inflammatory CC-chemokines, might limit inflammation and adverse cardiac remodeling after infarction. METHODS AND RESULTS: D6 was expressed in human and murine infarcted myocardium. In a murine model of myocardial infarction, D6 deficiency led to increased chemokine (C-C motif) ligand 2 and chemokine (C-C motif) ligand 3 levels in the ischemic heart. D6-deficient (D6(-/-)) infarcts displayed increased infiltration of pathogenic neutrophils and Ly6Chi monocytes, associated with strong matrix metalloproteinase-9 and matrix metalloproteinase-2 activities in the ischemic heart. D6(-/-) mice were cardiac rupture prone after myocardial infarction, and functional analysis revealed that D6(-/-) hearts had features of adverse remodeling with left ventricle dilation and reduced ejection fraction. Bone marrow chimera experiments showed that leukocyte-borne D6 had no role in this setting, and that leukocyte-specific chemokine (C-C motif) receptor 2 deficiency rescued the adverse phenotype observed in D6(-/-) mice. CONCLUSIONS: We show for the first time that the chemokine decoy receptor D6 limits CC-chemokine-dependent pathogenic inflammation and is required for adequate cardiac remodeling after myocardial infarction.
