Up-regulated CD38 by daphnetin alleviates lipopolysaccharide-induced lung injury via inhibiting MAPK/NF-κB/NLRP3 pathway

Sepsis is a life-threatening organ dysfunction syndrome resulted from severe infection with high morbidity and mortality. Cluster of differentiation 38 (CD38) is a multifunctional type II transmembrane glycoprotein widely expressed on the surface of various immunocytes membranes that mediates host immune response to infection and plays an important role in many inflammatory diseases. Daphnetin (Daph), isolated from the daphne genus plant, is a natural coumarin derivative that possesses anti-inflammatory and anti-apoptotic effects. The current study aimed to investigate the role and mechanism of Daph in alleviating lipopolysaccharide (LPS)-induced septic lung injury, and to explore whether the protective effect of Daph in mice and cell models was related to CD38.Firstly, network pharmacology analysis of Daph was performed. Secondly, LPS-induced septic lung injury in mice were treated with Daph or vehicle control respectively and then assessed for survival, pulmonary inflammation and pathological changes. Lastly, Mouse lung epithelial cells (MLE-12 cells) were transfected with CD38 shRNA plasmid or CD38 overexpressed plasmid, followed by LPS and Daph treatment. Cells were assessed for viability and transfection efficiency, inflammatory and signaling.Our results indicated that Daph treatment improved survival rate and alleviated pulmonary pathological damage of the sepsis mice, as well as reduced the excessive release of pro-inflammatory cytokines IL-1β, IL-18, IL-6, iNOS and chemokines MCP-1 regulated by MAPK/NF-κB pathway in pulmonary injury. Daph treatment decreased Caspase-3 and Bax, increased Bcl-2, inhibited nucleotide-binding domain (NOD)-like receptor protein 3 (NLRP3) inflammasome-mediated pyroptosis in lung tissues of septic lung injury. Also, Daph treatment reduced the level of excessive inflammatory mediators, inhibited apoptosis and pyroptosis in MLE-12 cells. It is noteworthy that the protective effect of Daph on MLE-12 cells damage and death was assisted by the enhanced expression of CD38.Our results demonstrated that Daph offered a beneficial therapeutic effect for septic lung injury via the up-regulation of CD38 and inhibition of MAPK/NF-κB/NLRP3 pathway. Video Abstract.