The methylation of m6A (N6-position of adenosine) has been found to be associated with inflammatory response. We hypothesize that m6A modification plays a role in the inflammation of airway epithelial cells during lung inflammation. However, the precise changes and functions of m6A modification in airway epithelial cells in acute lung injury (ALI) are not well understood. Here we report that METTL3 (methyltransferase-like 3)-mediated m6A of GATA6 (GATA-binding factor 6) mRNA inhibits ALI and the secretion of proinflammatory cytokines in airway epithelial cells. The expression of METTL3 and m6A levels decrease in lung tissues of mice with ALI. In cocultures, peripheral blood monocytes secreted TNF-α, which reduces METTL3 and m6A levels in the human bronchial epithelial cell line BEAS-2B. Knockdown of METTL3 promotes IL-6 and TNF-α release in BEAS-2B cells. Conversely, overexpression of METTL3 increases total RNA m6A level and reduces the levels of proinflammatory cytokines TNF-α, transforming growth factor-β, and thymic stromal lymphopoietin. Increasing METTL3 in mouse lungs prevented LPS-induced ALI and reduced the synthesis of proinflammatory cytokines. Mechanistically, sequencing and functional analysis show that METTL3 catalyzes m6A in the 3' untranslated region of GATA6 read by YTH N6-Methyladenosine RNA Binding Protein 2 and triggers mRNA degradation. GATA6 knockdown rescues TNF-α-induced inflammatory cytokine secretion of epithelial cells, indicating that GATA6 is a main substrate of METTL3 in airway epithelial cells. Overall, this study provides evidence of a novel role for METTL3 in the inflammatory cytokine release of epithelial cells and provides an innovative therapeutic target for ALI.
Keywords: ALI; GATA6; METTL3; YTHDF2; m6A modification.