Peli1 Deficiency in Macrophages Attenuates Pulmonary Hypertension by Enhancing Foxp1-Mediated Transcriptional Inhibition of IL-6

BACKGROUND: The infiltration of macrophages into the lungs is a common characteristic of perivascular inflammation, contributing to vascular remodeling in pulmonary hypertension (PH). Peli1 (pellino E3 ubiquitin-protein ligase 1) plays a critical role in regulating the production of proinflammatory cytokines and the polarization of macrophages in various diseases. However, the role of Peli1 in PH remains to be investigated. METHODS: The expression and biological function of Peli1 were investigated in both human and experimental models of PH. Peli1-deficient mice and bone marrow transplant mice were utilized to explore the roles of Peli1 in macrophages in vivo. Proteomic analysis and molecular biology techniques were used to uncover the underlying mechanisms. RESULTS: The upregulation of Peli1 in the lungs and alveolar macrophages was observed in hypoxia-treated mice. Peli1 knockout mice and myeloid Peli1-deficient mice significantly ameliorated hypoxia-induced right ventricular systolic pressure, right ventricular hypertrophy, and pulmonary vascular remodeling. Mechanistically, Peli1 facilitated the ubiquitination and subsequent proteasomal degradation of Foxp1 (forkhead box p1), thereby alleviating its suppression of IL (interleukin)-6 transcription and contributing to macrophage activation. Furthermore, myeloid Foxp1 deficiency partially eliminates the protective effect of myeloid Peli1 deficiency in hypoxia-induced PH mice. CONCLUSIONS: Our findings demonstrate that the Peli1-Foxp1-IL-6 pathway plays a crucial role in macrophage activation and recruitment during the development of PH, underscoring the potential of Peli1 as a therapeutic target for PH.