Background
Mycoplasma pneumoniae is a predominant cause of community-acquired respiratory infections. We recently discovered the clinical efficacy of Maxing shigan decoction (MXSG) in M. pneumoniae infection and designed a study to explore the mechanism of action.
Conclusion
MXSG mitigates M. pneumoniae-induced pyroptosis in A549 cells via the NLRP3 inflammasome.
Methods
Serum IL-1β, IL-18, and TNF-α, and transcript expression of the NLR Family, Pyrin Domain Containing Protein 3 (NLRP3) were measured in the peripheral blood mononuclear cells (PBMCs) of 30 children with M. pneumoniae infection and 30 healthy donors. An in vitro model of M. pneumoniae infection in A549 cell culture was used to explore the curative effects and mechanisms of MXSG. Pyroptosis was measured by flow cytometry with activated caspase-1 and propidium iodide staining. IL-1β, IL-18, and TNF-α, and NLRP3 transcript expression were measured by qRT-PCR. Protein expression of NLRP3, Caspase-1, pro-caspase-1, IL-1β, pro-IL-1β, and GSDMD-N was determined by Western blotting. Experimental confirmation was performed in NLRP3-overexpressing A549 cells and in the presence of an NLRP3 inhibitor, INF39.
Results
M. pneumoniae infection-induced IL-1β, IL-18, TNF-α, and mRNA expression of NLRP3 in PBMCs and promoted pyroptosis in A549 cells. It also induced IL-1β, IL-18, TNF-α, and up-regulated NLRP3, ro-IL-1β, Caspase-1, Pro-Caspase-1, and GSDMD-N in culture. Similar to the NLRP3 inhibitor INF39, MXSG (0.1, 0.2, and 0.4 mg/mL) suppressed pyroptosis induced by M. pneumoniae infection and decreased IL-1β (P < 0.001), IL-18, TNF-α in culture. MXSG down-regulated NLRP3, pro-IL-1β, Caspase-1, pro-Caspase-1, and GSDMD-N in infected cultures and mitigated NLRP3 overexpression-induced pyroptosis.