ABSTRACT
Objective: To evaluate the effect of meticillin-resistant Staphylococcus aureus(MRSA)on the pyroptosis of bone-marrow derived macrophages(BMDM)and investigate the mechanism of MRSA-induced pyroptosis in macrophages. Methods: The BMDM were triggered by the combination of lipopolysaccharide(LPS, 100 ng/ml)with adenosine-triphosphate(ATP, 3 mmol/L)or nigericin(Ng, 10 mmol/L)or treated with MRSA(multiplicity of infection 200, MOI 200)alone to induce pyroptosis in vitro. The cell morphology examination and lactate dehydrogenase(LDH)assay were applied to evaluate the cytotoxicity. The expression of pro- inflammatory cytokines, the interleukin(IL)- 1β, IL- 6 and tumor-necrosis factor(TNF)-α was detected by ELISA. The cleaved caspase-1 and mature IL-1β in the cells and released into the supernatant were detected by Western blotting. The signal pathway for the induction of pyroptosis by MRSA was investigated via the transfection of lentivirus- mediated short- hairpin RNA(shRNA)into the BMDM. Results: The treatment of BMDM with LPS/ATP, LPS/nigericin or MRSA alone caused cytotoxicity and up-regulated the expression of pro-inflammatory cytokines, IL-1β, IL-6 and TNF-α, as well as the caspase-1 activation and mature Zl-1β (P<0.01). After silencing NLRP3 or NLRC4, the expression of IL-1β induced by MRSA was significantly lessened(P< 0.01). Conclusion: MRSA could induce BMDM pyroptosis probably via activating NLRP3 inflammasome or NLRC4 inflammasome.