Abstract: Objective To investigate the effect of recombinant Treponema pallidum protein Tp47 (rTpp47) on the expression of uPA by THP-1 macrophages and on the permeability of human umbilical vein/vascular endothelial cells(HUVECs). Methods THP-1 cells were stimulated with rTpp47 for 24 hours and then the culture supernatant and THP-1 cells were collected respectively. The expression of urokinase-type plasminogen activator (uPA) in THP-1 cells was detected by ELISA and Western blot. After stimulation of HUVECs monolayers by THP-1 cell culture supernatant, FITC-dextran was used to evaluate the permeability of HUVECs. Western blot method was used to observe the effect of uPA on the expression of tight junction protein claudin-5 of HUVECs and the protein kinase C(PKC) signaling pathway of THP-1 cells stimulated by rTpp47. Results The synthesis and secretion of uPA of THP-1 cells stimulated by rTpp47 were significantly higher than those in the control group(P＜0.05, P＜0.001). When HUVECs were stimulated by the THP-1 cell supernatant for 12 hours and 24 hours, the relative permeability of vascular endothelial cells in the experimental group was significantly higher than the control group (P＜0.05 for 12 hours and P＜0.000 1 for 24 hours). Amiloride, the synthetic inhibitor of uPA, significantly inhibited the uPA expression and secretion of THP-1 cells stimulated by rTpp47 (P＜0.0001), alleviated the inhibition effect of rTpp47 on claudin-5 expression of HUVECs (P＜0.05), and significantly suppressed PKC phosphorylation(P＜0.05) in THP-1 cells induced by rTpp47. Conclusions The rTpp47 can stimulate the synthesis and secretion of uPA in THP-1 cells through a potential mechanism of activating PKC signaling pathway and uPA may increase the permeability of vascular endothelial cells.

Key words: Treponema pallidum, recombinant Tp protein Tp47(rTpp47), urokinase-type plasminogen activator(uPA), macrophages, human umbilical vein/vascular endothelial cells(HUVECs)