Adipose-derived mesenchymal stem cell-exosomes attenuate lipopolysaccharide-induced acute lung injury in mice by regulating the TGFBR2/Smad4 axis to suppress NLRP3-mediated macrophage M1 polarization and pyroptosis

Abstract

Objective This study investigated whether adipose-derived mesenchymal stem cells-exosomes (ADMSC-Exo) alleviate lipopolysaccharide (LPS)-induced acute lung injury (ALI) by regulating NLRP3 inflammasome-mediated macrophage M1 polarization and pyroptosis through the miR-19b-3p/TGFBR2/Smad4 signaling axis. Methods An LPS-induced mouse model of ALI was established and treated with ADMSC-Exo or adenoviral TGFBR2 overexpression (Ad-TGFBR2). Lung histopathology, lung wet-to-dry (W/D) weight ratio, macrophage polarization, and pyroptosis were evaluated. In vitro, macrophages with TGFBR2 knockdown or overexpression were stimulated with LPS and treated with ADMSC-Exo. Lung epithelial cells were subsequently cultured with macrophage-conditioned medium. The expression of miR-19b-3p, TGFBR2, mothers against decapentaplegic homolog 4 (Smad4), and NOD-like receptor protein 3 (NLRP3), together with macrophage polarization, pyroptosis, and epithelial cell apoptosis, was assessed. Predicted molecular interactions were validated using bioinformatic analyses and the JASPAR database. Results ADMSC-Exo alleviated LPS-induced lung injury by preserving alveolar architecture and reducing lung injury scores and the W/D ratio. They inhibited M1 macrophage polarization and pyroptosis both in vivo and in vitro, thereby decreasing apoptosis of lung epithelial cells. Mechanistically, ADMSC-Exo-delivered miR-19b-3p, which targeted TGFBR2 and inhibited TGFBR2/Smad4 signaling, resulting in transcriptional suppression of NLRP3 expression. Inhibition of miR-19b-3p or overexpression of Smad4/NLRP3 partially abolished the protective effects of ADMSC-Exo. Collectively, ADMSC-Exo attenuated LPS-induced ALI by suppressing NLRP3-mediated macrophage M1 polarization and pyroptosis through the miR-19b-3p/TGFBR2/Smad4 signaling axis. Conclusion ADMSC-derived exosomes alleviate LPS-induced acute lung injury by delivering miR-19b-3p to inhibit the TGFBR2/Smad4 signaling pathway, thereby suppressing NLRP3-mediated macrophage M1 polarization and pyroptosis and reducing lung epithelial cell apoptosis.