Dectin-1 Contributes to Myocardial Ischemia-Reperfusion Injury by Regulating Macrophage Polarization and Neutrophil Infiltration.

Background: Macrophage-associated immune response plays an important role in myocardial ischemia/reperfusion (IR) injury. Dectin-1, expressed mainly on activated myeloid cells, is crucial for the regulation of immune homeostasis as a pattern recognition receptor. However, its effects and roles during the myocardial IR injury remain unknown. Methods: Genetic ablation, antibody blockade, or Dectin-1 activation, along with the adoptive bone marrow transfer chimeric model, was used to determine the functional significance of Dectin-1 in myocardial IR injury. Immune cell filtration and inflammation were examined by flow cytometry, quantitative real-time polymerase chain reaction, and immunohistochemistry. Moreover, Dectin-1(+) cells were analyzed by flow cytometry in the blood of patients with ST-segment-elevation myocardial infarction and stable patients with normal coronary artery (control). Results: We demonstrated that Dectin-1 expression observed on the bone marrow-derived macrophages is increased in the heart during the early phase after IR injury. Dectin-1 deficiency and antibody-mediated Dectin-1 inhibition led to a considerable improvement in cardiac function, accompanied by a reduction in cardiomyocyte apoptosis, which was associated with a decrease in M1 macrophage polarization and Ly-6C(+) monocyte and neutrophil infiltration. Activation of Dectin-1 with its agonist had the opposite effects. Furthermore, Dectin-1 contributed to neutrophil recruitment through the regulation of Cxcl1 and granulocyte colony-stimulating factor expression. In addition, Dectin-1-dependent interleukin-23/interleukin-1 production was shown to be essential for interleukin-17A expression by T cells, leading to neutrophil recruitment and myocardial IR injury. Furthermore, we demonstrated that circulating Dectin-1(+)CD14(++)CD16(-) and Dectin-1(+)CD14(++)CD16(+) monocyte levels were significantly higher in patients with ST-segment-elevation myocardial infarction than in controls and positively correlated with the severity of cardiac dysfunction. Conclusions: Our results reveal a crucial role of Dectin-1 in the process of mouse myocardial IR injury and provide a new, clinically significant therapeutic target.