BACKGROUND: Many studies have reported the important role of glucagon-like peptide-1 receptor (GLP-1R) in regulating glucose homeostasis. However, in addition to the pancreas, GLP-1R is distributed in organs such as the lungs. A few researches have reported the mechanism of action of GLP-1R in acute and chronic lung diseases. Nevertheless, its effect on lung development remains unclear. In this research, we aimed to explore the role of GLP-1R in regulating lung development and its potential mechanisms in in vivo and in vitro bronchopulmonary dysplasia (BPD) models.
METHODS: Neonatal Sprague-Dawley rats were divided into hyperoxia (FIO2 = 0.85) and control (FIO2 = 0.21) groups. Lung tissues were extracted at 3, 7, 10, and 14 postnatal days and subjected to hematoxylin and eosin staining for histopathological and morphological observation. Single-cell RNA sequencing was performed to explore the role of GLP-1R in lung development. Western blotting was conducted to assess the expression of GLP-1R, dynamin-related protein 1 (DRP1), and glycolysis-associated enzymes, including phosphofructokinase (PFKM), hexokinase 2 (HK2), and lactate dehydrogenase A (LDHA), in the lung tissues, primary alveolar type II (ATII) cells, and RLE-6TN cells. Double immunofluorescence staining was performed to confirm the co-localization of GLP-1R, DRP1, and ATII cells. A Seahorse XF96 metabolic extracellular flux analyzer was used to perform real-time analyses of extracellular acidification rate and oxygen consumption rate in ATII cells isolated from lung tissues and RLE-6TN cells. The adenosine triphosphate (ATP) concentrations in ATII and RLE-6TN cells were measured using an ATP kit. Mitochondria were stained with MitoTracker and observed using HiS-SIM. GLP-1R gene levels in lung tissues, primary ATII cells, and RLE-6TN cells were tested using RT-qPCR. We used MeRIP-qPCR to determine the m6A modification level of GLP-1R mRNA in RLE-6TN cells. A reporter gene was used to verify the modification site and key methyltransferases.
RESULTS: We observed that GLP-1R signaling regulates lung development and plays a key role in ATII cells, particularly after birth. Hyperoxia inhibits GLP-1R protein and gene expression in ATII cells and accelerates BPD development. ATP production decreased and glycolysis levels increased in ATII cells under hyperoxia. Activation of GLP-1R signaling promotes ATP production and downregulates glycolysis by regulating DRP1 induced mitochondria fission. In RLE-6TN cells, we verified that the m6A modification level of GLP-1R mRNA decreased; the modification site was tested by MeRIP-qPCR and was primarily induced by the methyltransferase-like 14 (METTL14).
CONCLUSION: GLP-1R is primarily expressed in ATII cells of neonatal rats and can promote lung development during the early postnatal period. The GLP-1R signaling pathway modulates mitochondrial fission and glucose metabolism in ATII cells under hyperoxia. Hyperoxia can inhibit the activation of GLP-1R by inhibiting m6A methylation during BPD pathogenesis.
