Abstract: Objective To investigate the effect of recombinant Treponema pallidum protein Tp47 (rTpp47) on the expression of uPA in THP-1 macrophages and on the permeability of vascular endothelial cells. 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 THP-1 Cell culture supernatant was used to stimulate human umbilical vein endothelial cells (HUVEC) monolayers, FITC dextran was used to evaluate the permeability of HUVEC . Western blot method was used to observe the effect of uPA on the expression of tight junction protein claudin-5 in HUVEC cells and on the PKC signaling pathway in THP-1 cells stimulated by rTpp47.Results The synthesis and secretion of uPA in THP-1 cells stimulated by recombinant protein rTpp47 were significantly higher than those in the control group (P < 0.05). 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 < 0.0001 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) and significantly suppressed PKC phosphorylation (P < 0.05) in THP-1 cells induced by rTpp47. Conclusion Our data indicate that the recombinant protein rTpp47 can stimulate the synthesis and secretion of uPA in THP-1 cells by activating PKC signaling pathway and uPA may increase the permeability of vascular endothelial cells.

Key words: Treponema pallidum, recombinant protein TP47, Urokinase-type plasminogen activator, macrophages, human umbilical vein endothelial cells