ω-Alkynyl arachidonic acid promotes anti-inflammatory M2 polarization of macrophages against acute myocardial infarction via attenuating the expression of iNOS and PKM2

Abstract

Delayed resolution of inflammation following acute myocardial infarction exacerbates heart injury and impairs cardiac repair. Macrophages exhibit either pro-inflammatory M1 or anti-inflammatory M2 phenotype, and thereby play key roles in acute myocardial infarction. The aim of the present study was to investigate whether ω-alkynyl arachidonic acid could regulate phenotypic and functional switch of macrophages in myocardial infarction. We initially discovered that ω-alkynyl arachidonic acid selectively suppressed the up-regulation of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in LPS-stimulated macrophages. We also found that ω-alkynyl arachidonic acid not only reduced the expression of M1 markers (TNF-α, CXCL10, iNOS and IL-6) but also increased the expression of M2 markers (IL-10 and arginase I) in LPS-stimulated macrophages. Moreover, ω-alkynyl arachidonic acid markedly enhanced the phagocytosis of fluorescently-labeled beads or apoptotic H9c2 cardiac cells. These results stimulated us to further investigate the cardioprotective activities of ω-alkynyl arachidonic acid in a mouse model of myocardial infarction. ω-Alkynyl arachidonic acid indeed reduced infarct size, cardiac damage and the release of myocardial enzymes CK-MB. To elucidate the underlying mechanisms, we intended to identify the covalent ω-alkynyl arachidonic acid-protein adducts. By performing biotinylation to the cellular proteins via “click chemistry” alkyne-azido cycloaddition, we isolated glycolytic enzyme pyruvate kinase M2 (PKM2) as a predominant ω-alkynyl arachidonic acid binding protein. ω-Alkynyl arachidonic acid could also attenuate PKM2 expression and suppress nuclear translocation of PKM2 in LPS-stimulated macrophages. Thus, ω-alkynyl arachidonic acid may promote anti-inflammatory M2 polarization of macrophages against acute myocardial infarction via regulating the expression of PKM2 and iNOS.