CGRP alleviates lipopolysaccharide-induced ARDS inflammation via the HIF-1α signalling pathway

Acute respiratory distress syndrome (ARDS) is an acute and severe disease with a high mortality rate. The outbreak of immune inflammation in the lung is an important pathogenic mechanism of ARDS. Notably, an imbalance in macrophage polarization is an important link in the occurrence and development of this inflammatory response. Recently, neuropeptides have been shown to regulate inflammation, but the role of neuropeptides in ARDS remains unclear. The aim of this study was to investigate the regulatory effect of calcitonin gene-related peptide (CGRP) on the inflammatory response in ARDS. We found that CGRP expression was increased in the serum of ARDS patients and in both in vitro and in vivo models of ARDS. CGRP can regulate the polarization of macrophages by targeting its receptor (receptor activity modifying protein 1 (RAMP1)), reduce the proportion of M1 macrophages, increase the proportion of M2 macrophages, and reduce pathological injury, inflammation, oxidative stress and apoptosis in lung tissue in LPS-induced ARDS both in vitro and in vivo. Additionally, we performed transcriptome sequencing and found that hypoxia-inducible factor-1α (HIF-1α) is involved in the above process and that CGRP can alleviate ARDS-related pathological damage, inflammation and oxidative stress by inhibiting the HIF-1α pathway to regulate macrophage polarization balance. These results indicate that CGRP has good potential for clinical translation in the treatment of pulmonary infection in ARDS. Furthermore, this study provides new ideas for the treatment of inflammatory bursts in ARDS.