In vitro treatment with Treponema pallidum membrane protein Tpp17 increased the permeability of vascular endothelial barrier / 中华微生物学和免疫学杂志

ABSTRACT

Objective To investigate the in vitro effects of Treponema pallidum membrane protein Tpp17 on the permeability of endothelial barrier for further investigation on the immunopathogenesis of syphi-lis.Methods A cellular model of in vitro monolayer was established by using human umbilical vein endo-thelial cells ( HUVECs) .Cell-ELISA and a TMB kit were respectively used to measure the expression of VE-cadherin and the flux of horseradish peroxidase ( HRP) by monolayer HUVECs after stimulation with the re-combinant Tpp17 (rTpp17) protein.THP-1 cells stained with Calcein AM were added to the top of HUVEC monolayer in Transwell culture.Then, the numbers of THP-1 cells in the upper wells and beneath the HUVEC monolayer were counted by using a fluorescence microscope.The rTpp17 protein-treated HUVECs were fixed in 4%buffered paraformaldehyde and stained with rhodamine-phalloidin for observing the distri-bution of F-actin under a confocal laser scanning microscope.Results Compared with the control group, the expression of VE-cadherin in HUVECs was decreased, while the permeability of HUVEC monolayer was increased upon the stimulation with rTpp17 protein (P<0.05).Moreover, rTpp17 protein-induced F-actin redistribution and increased transendothelial migration of THP-1 cells were observed in rTpp17 protein-trea-ted HUVECs as compared with those of the control group (P<0.05).Conclusion Treponema pallidum membrane protein Tpp17 could suppress the expression of VE-cadherin and enhance the redistribution of F-actin, resulting in an enhanced transendothelial migration of THP-1 cells and an increased permeability of HUVEC monolayer.The Tpp17 protein might play an important role in the immunopathogenesis of syphilis.