RBM15-mediated VEGFA m6A methylation drives M1 pro-inflammatory macrophage polarization and suppresses M2 anti-inflammatory polarization in acute lung injury.

Abstract

Background: Acute lung injury (ALI), recognized as a prevalent and severe respiratory disorder, represents a critical medical condition. During ALI, Vascular Endothelial Growth Factor A (VEGFA)-mediated M1/M2 macrophage polarization is crucial, yet its specific regulatory mechanisms remain unclear.

Methods: THP-1 cells were treated with lipopolysaccharide (LPS)/interferon-γ (IFN-γ). VEGFA expression in the serum of ALI patients was identified using enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qRT-PCR). Flow cytometry was employed to identify the expression of M1 and M2 polarization markers. Inflammatory cytokines were detected by ELISA. Bioinformatics was employed to predict the m6A sites on VEGFA mRNA, and Western blot was conducted to examine the protein levels. Methylated RNA immunoprecipitation (MeRIP), and RIP assays were used to verify the modification and binding between RBM15 and VEGFA. Actinomycin D assay was performed to evaluate the mRNA stability. An ALI mouse model was established to assess the in vivo role of the RBM15/VEGFA axis. HE staining was used to assess the lung tissue injury of mice. Meanwhile, myeloperoxidase (MPO) activity was measured using colorimetry.

Results: VEGFA exhibited elevated expression in the serum of ALI patients and LPS/IFN-γ-induced THP-1/M0 cells. Additionally, VEGFA inhibitor and silencing VEGFA restrained M1 polarization and contributed to M2 polarization of LPS/IFN-γ-induced THP-1/M0 cells accompanied by the reduction in the levels of pro-inflammatory cytokines (TNF-α, IL-12, IL-6, and IL-1β) and the relative increase in the anti-inflammatory cytokine (IL-10). Moreover, VEGFA expression was promoted by RBM15 through m6A modification. The RBM15/VEGFA axis promoted the M1 polarization while inhibiting the M2 polarization of LPS/IFN-γ-induced THP-1/M0 cells. ALI was alleviated by inhibiting the RBM15/VEGFA axis in vivo.

Conclusion: RBM15 enhanced VEGFA expression through m6A modification, thereby promoting M1 polarization, inhibiting M2 polarization of macrophages, and facilitating the progression of ALI.