MiR-223-3p inhibits rTp17-induced inflammasome activation and pyroptosis by targeting NLRP3.

The incidence of syphilis caused by Treponema pallidum subsp pallidum (T pallidum) infection is accompanied by inflammatory injuries of vascular endothelial cells. Studies have revealed that T pallidum infection could induce inflammasome activation and pyroptosis in macrophages. MicroRNA-223-3p (miR-223-3p) was reported to be a negative regulator in inflammatory diseases. The present study aimed to explore whether miR-223-3p regulates T pallidum-induced inflammasome activation and pyroptosis in vascular endothelial cells, and determine the mechanisms which underlie this process. MiR-223-3p levels in syphilis and control samples were determined. The biological function of miR-223-3p in the NLRP3 inflammasome and pyroptosis was evaluated in T pallidum-infected human umbilical vein endothelial cells (HUVECs). We observed a dramatic decrease in miR-223-3p levels in syphilis patients (n = 20) when compared to healthy controls (n = 20). Moreover, miR-223-3p showed a notable inhibitory effect on recombinant Tp17 (rTP17)-induced caspase-1 activation, resulting in decrease in IL-1β production and pyroptosis, which was accompanied by the release of lactate dehydrogenase (LDH) in HUVECs. Additionally, the dual-luciferase assay confirmed that NLRP3 is a direct target of miR-223-3p. Moreover, NLRP3 overexpression or knockdown largely blocked the effects of miR-223-3p on T pallidum-induced inflammasome activation and pyroptosis in HUVECs. Most importantly, a notable negative correlation was observed between miR-223-3p and NLRP3, caspase-1, and IL-1β, respectively, in the serum of syphilis patients and healthy controls. Taken together, our results reveal that miR-223-3p targets NLRP3 to suppress inflammasome activation and pyroptosis in T pallidum-infected endothelial cells, implying that miR-223-3p could be a potential target for syphilis patients.