The P2X7 receptor mediates NLRP3-dependent IL-1ß secretion and promotes phagocytosis in the macrophage response to Treponema pallidum.

ABSTRACT

It is unclear whether P2X7 receptor (P2X7R) mediates NOD-like receptor family protein 3 (NLRP3)-dependent IL-1ß secretion and spirochete phagocytosis in syphilis. This study was conducted to investigate the role of P2X7R in modifying NLRP3-dependent IL-1ß secretion and regulating phagocytosis by Treponema pallidum (T. pallidum)-induced macrophages. Macrophages derived from a human acute monocytic leukemia cell line were cultured with T. pallidum. The activation of P2X7R in T. pallidum-treated macrophages occurred in a dose- and time-dependent manner. The P2X7R silencing group showed significantly decreased NLRP3 mRNA and protein levels (vs. the Tp group, P < 0.001). Similar results were observed for IL-1ß secretion using ELISA (vs. the Tp group, P < 0.001). Furthermore, P2X7R siRNA transfection significantly decreased the percentage of spirochete-positive macrophages (29.73% vs. 70.83%, P < 0.001) and spirochete internalization (mean fluorescence intensity (MFI), 9.20 vs. 19.39, P < 0.001). This finding revealed that P2X7R played a role in the induction of NLRP3-dependent IL-1ß secretion by T. pallidum-induced macrophages. Furthermore, we found that P2X7R plays an important role in IL-1ß secretion and in the promotion of T. pallidum phagocytosis by macrophages. These results may not only contribute to our understanding of the immune mechanism that is active during T. pallidum infection but may also lay the groundwork for strategies to combat syphilis.