Effects of Leptospira interrogans infection on the activation of NLRP3 in THP-1 and J774A.1 cells

Abstract

Objective To analyze the effects of Leptospira interrogans (L.interrogans) infection on the activation of NLRP3 in THP-1 and J774A.1 cells and to further understand the mechanism of inflammation caused by L. interrogans in different hosts. Methods Human mononuclear macrophage cell line (THP-1) and murine mononuclear macrophage cell line (J774A.1) were infected with L. interrogans strain 56601. The expression of NLRP3 at mRNA and protein levels were measured by using real-time RT-PCR and flow cytometry analysis, respectively. The NLRP3-mediated secretion of IL-1β, IL-18 and IL-33 was detected by ELISA combined with the NLRP3 inhibitory test. Results Compared with the normal cells, the expression of NLRP3 at mRNA level in L. interrogans-infected THP-1 cells was respectively increased by 4.05, 0.34, 0.33, 0.06 and 1.66 times at the time points of 1 h, 2 h, 4 h, 12 h and 24 h after infection (P 0.05). Results of the inhibitory test showed that the up-regulation of IL-1β , IL-18 and IL-33 in THP-1 and J774A.1 cells were effectively inhibited by the specific inhibitor of NLRP3. Conclusion NLRP3 inflammasome was activated and involved in the production of specific inflammatory cytokines IL-1β and IL-18 in both THP-1 and J774A.1 cells after L. interrogans infection, but the inflammatory cytokines induced by L. interrogans infection varied in different cells. L. interrogans induced earlier and higher level of IL-1β and IL-18 production in human macrophages than in murine macrophages. Key words: Leptospira interrogans; NLRP3 inflammasome; Macrophage; Inflammatory cytokine