METTL3 promotes infantile pneumonia-induced lung injury by the m6A-TBL1XR1-ACSL1 axis

Methyltransferase-like 3 (METTL3) is the catalytic subunit of methyltransferase complex that catalyzes mRNA methylation and has been identified to be involved in lipopolysaccharide (LPS)-induced lung cell injury. In this study, we investigated whether METTL3 is involved in the progression of infantile pneumonia (IP)-induced lung injury and its underlying mechanism.

WI-38 cells were exposed to LPS to induce in vitro proliferation, inflammation, apoptosis, and ferroptosis. The mRNA and protein levels of METTL3, TBL1XR1, IGF2BP1/2/3, and ACSL1 were measured by qRT-PCR and western blotting, respectively. The N6-methyladenosine (m6A) modification was analyzed using a methylated RNA immunoprecipitation assay. Protein interactions were determined using a Co-IP assay. LPS-induced pneumonia in mice was used for the in vivo analysis.

METTL3 was highly expressed in IP and LPS-induced WI-38 cells. Knockdown of METTL3 reversed LPS-induced apoptosis, inflammation, and ferroptosis in vitro and in vivo and improved LPS-induced lung injury and collagen deposition in lung tissues of IP mice. Mechanistically, METTL3 induces TBL1XR1 m6A modifications and stabilizes its expression in an m6A-IGF2BP1-dependent manner. Functionally, the protective effects mediated by METTL3 silencing in LPS-treated WI-38 cells were reversed by TBL1XR1 overexpression. In addition, TBL1XR1 interacts with ACSL1, and METTL3 regulates ACSL1 expression via TBL1XR1. Further functional analysis showed that TBL1XR1 deficiency suppressed LPS-induced apoptosis, inflammation, and ferroptosis, which were abolished by ACSL1 up-regulation.

METTL3 stabilized TBL1XR1 expression through IGF2BP1-m6A methylation, promoting LPS-induced IP lung injury by upregulating ACSL1 expression.