Abstract: Objective To investigate the effects of suppressor of cytokine signaling 1(SOCS-1)on A549 cells infected with Klebsiella pneumoniae via the NOD-like receptor thermal protein domain-associated protein 3(NLRP3)/apoptosis-associated speck-like protein containing a CARD(ASC)/caspase-1 pathway. Methods Human type Ⅱ alveolar epithelial cells(A549 cells)were divided into four experimental groups:siRNA NC group,siRNA SOCS-1 group,pcDNA3.1 NC group,and pcDNA3.1 SOCS-1 group.Three hours after infection with Klebsiella pneumoniae,the corresponding A549 cells were treated with siRNA NC(50 nmol/L),siRNA SOCS-1(50 nmol/L),pcDNA3.1 NC(20 nmol/L),or pcDNA3.1 SOCS-1(20 nmol/L)for 48 h.MTT assays and BrdU staining were used to analyze the proliferative activity of A549 cells;flow cytometry was used to analyze the apoptosis rate of A549 cells;ELISA was used to determine the levels of inflammatory factors in the culture medium of A549 cells in each group;and Western blot analysis was used to detect the expression levels of SOCS-1,NLRP3,ASC,and caspase-1 proteins in A549 cells. Results Infection with Klebsiella pneumoniae led to increased SOCS-1 expression in A549 cells.Compared with the siRNA NC group,the siRNA SOCS-1 group exhibited increased A549 cell proliferation,reduced apoptosis rates and inflammatory cytokine levels,and decreased expression of NLRP3,ASC,and caspase-1.Compared with the pcDNA3.1 NC group,the pcDNA3.1 SOCS-1 group exhibited reduced A549 cell proliferation,increased apoptosis rates and levels of inflammatory factors,and elevated expression levels of NLRP3,ASC,and caspase-1. Conclusion SOCS-1 promotes apoptosis and the release of inflammatory factors in A549 cells infected with Klebsiella pneumoniae and inhibits A549 cell proliferation;this process is closely related to SOCS-1 regulation of the NLRP3/ASC/Caspase-1 signaling pathway.

Key words: suppressor of cytokine signaling 1, Klebsiella pneumoniae, NOD-like receptor protein 3, apoptosis-associated speck-like protein containing a CARD, caspase-1