Inflammation-induced promoter hypermethylation of GLP-1R limits the protective effect of GLP-1R agonists against acute lung injury

Glucagon-like peptide 1 receptor (GLP-1R) agonists (GLP-1RAs) possess potent anti-inflammatory properties, whereas their therapeutic efficacy against acute lung injury (ALI) remains controversial. This study aimed to explore the potential molecular mechanisms underlying the heterogeneous therapeutic effects of GLP-1RAs in ALI. An ALI mouse model was established, and three cell lines, including vascular endothelial cells, human bronchial epithelial cells, and mouse alveolar epithelial cells, were utilized to characterize GLP-1R expression. In vivo results revealed transcriptional repression of GLP-1R in the lung tissues of ALI mice. Consistently, lipopolysaccharide (LPS) stimulation markedly reduced GLP-1R expression in all three cell lines. Mechanistically, integrated analyses involving assay for transposase-accessible chromatin sequencing, targeted bisulfite sequencing, and western blotting demonstrated that LPS upregulated DNA methyltransferase 3A/3B expression. This upregulation induced hypermethylation of the GLP-1R promoter, reduced chromatin accessibility, and ultimately triggered GLP-1R transcriptional silencing. Such inflammation-mediated epigenetic blockade contributed to therapeutic resistance of vascular endothelial cells to the anti-inflammatory effects of GLP-1RAs. Lentivirus-mediated GLP1R overexpression in vascular endothelial cells effectively restored the anti-inflammatory capacity of GLP-1RAs and ameliorated cellular energy metabolism disorders. Furthermore, in vivo experiments validated that adeno-associated virus-mediated Glp1r restoration in the lungs of ALI mice exerted superior protective effects compared with GLP-1RA monotherapy. Therefore, we identified inflammation-induced epigenetic silencing as a primary driver of therapeutic resistance to GLP-1RA in ALI. Our findings established that restoring GLP-1R expression was a prerequisite for acute respiratory distress syndrome effective therapy, shifting the strategy from simple receptor activation to receptor re-sensitization.