CD69 Expression in Macrophages Regulates the Progression of Pulmonary Arterial Hypertension Via Modulation of Macrophage Polarization

Abstract RATIONALE: Various inflammatory cells are involved in the development of vascular remodeling in pulmonary arterial hypertension (PAH), and the involvement of macrophages in its progression has been particularly indicated. Although CD69, a cell surface marker known to be activation of inflammatory cells, has been implicated in various inflammatory diseases, the contribution of CD69-expressing macrophages in PAH pathogenesis is still unclear. This study aimed to identify the role of CD69-positive macrophage and contribution mechanism of that to the development of PAH. METHODS: PAH was induced in mice by VEGF-Zr inhibitor (Su5416) and chronically hypoxic exposure with wild type (SuHx-WT) and CD69 -/- (SuHx-CD69-/-). After the measurement of pulmonary hemodynamics, CD69 expression of inflammatory cells in the lung of SuHx-WT were evaluated, and the expression of M1 and M2 macrophages in lung tissue was compared between the groups by immunostaining and flowcytometry. Next, CD69 in PMA-treated THP-1, a human macrophage cell line, was knocked down using siRNA, and the response to M1 or M2 induction and the expression of inflammatory cytokines/growth factors related to each macrophage were compared with and without knocked down CD69. Additionally, the inhibitory effect of PAH progression by administering CD69 neutralizing antibodies was evaluated for SuHx-WT. RESULTS: Pulmonary hemodynamics and right ventricular hypertrophy of SuHx-CD69-/- were less severe than that of SuHx-WT. CD69-positive cell ratio of CD11b-positive macrophage in SuHx-WT was significantly higher than that in control WT, but not in the other inflammatory cells. CD69/CD11b-positive macrophages accumulated around the pulmonary arteries in SuHx-WT. The Mean Fluorescence Intensity (MFI) of M1/M2 macrophages and the expression of iNOS, Fizz1, IL-6, TNFα, TGF-β and PDGF-BB were significantly decreased in the lung tissue of SuHx-CD69-/-. Induction of M1 and M2 in PMA-treated THP-1 and expression of M1 macrophage related inflammatory cytokines in M1 induced PMA-treated THP-1 were suppressed under knocked down of CD69, significantly. Treatment with CD69 neutralizing antibodies suppressed the disease progression in SuHx-WT.CONCLUSIONS: Present results suggested that CD69 expression in macrophages regulates the progression of PAH via modulation of macrophage polarization.