Regulation of macrophage pyroptosis by SIRT1 during Pseudomonas aeruginosa-induced pneumonia

Abstract

Pseudomonas aeruginosa (PA), an opportunistic gram-negative bacterial pathogen, is the main cause of lung infections. Pulmonary infection induced by PA results in inflammatory lung injury characterized by macrophage pyroptosis. In our study, a mouse model of pulmonary infection was established by tracheal intubation with PA in vivo, and the MH-S macrophage line was stimulated with PA in vitro. HE staining was performed to observe changes in the lung tissue. The mechanism was further explored through various methods, including flow cytometry, LDH release assays, ELISA, real-time PCR, Western blotting (WB), and CCK8 assays. Additionally, the effect of MH-S cells on the proliferation of alveolar endothelial cells was observed by coculturing these two cell types. The results showed that PA-induced inflammatory injury in murine lung tissues increased the levels of inflammatory factors (IL-1β/6/12) and pyroptosis-related proteins (NLRP3, Caspase 1/11, and GSDMD-N) and promoted pulmonary macrophage pyroptosis. PA downregulated Sirt1 expression and increased p-NF-κB-p65 levels both in vitro and in vivo. Sirt1 activation or overexpression alleviated PA-induced lung tissue injury, inhibited macrophage pyroptosis, and decreased the expression of inflammatory factors and pyroptosis-related proteins. Sirt1 inhibition or knockdown critically strengthened the effect of PA on pulmonary macrophage pyroptosis. NF-κB inhibition suppressed the PA-induced increase in Sirt1-regulated pyroptosis in MH-S macrophages, decreased the levels of inflammatory factors and pyroptosis-related proteins, and weakened the inhibitory effect of MLE-12 cell proliferation on PA-infected MH-S cells. In conclusion, the Sirt1/NF-κB axis negatively regulates PA-induced inflammatory factor release and macrophage pyroptosis, promotes lung epithelial cell proliferation, and reduces inflammatory injury to the lung tissue.