Abstract
Objective To evaluate the effects of Treponema pallidum (T. pallidum) on the expression of chemokine ligands (CXCL) in human brain microvascular endothelial cells (HBMECs) . Methods HBMECs were randomly divided into 4 groups, which were treated with viable T. pallidum suspension (T. pallidum group) , heat-inactivated T. pallidum suspension (inactivated T. pallidum group) , 200 μg/L lipopolysaccharide (LPS group) and cell culture medium (blank control group) , respectively, for 6, 12 and 24 hours. Fluorescence-based quantitative PCR and enzyme-linked immunosorbent assay (ELISA) were performed to determine the mRNA and protein expression of CXCL6, CXCL8 and CXCL10 in HBMECs in the above groups respectively. Transwell migration assay was conducted to evaluate the effects of T. pallidum-stimulated HBMECs on the chemotaxis of human promyelocytic HL-60 leukemia cells (HL-60 cells) . Results At 6, 12 and 24 hours, the T. pallidum group showed significantly higher mRNA expression of CXCL6, CXCL8 and CXCL10 in HBMECs compared with the blank control group and inactivated T. pallidum group (all P 0.05) . Compared with the LPS group, theT. pallidum group showed significantly decreased mRNA expression of CXCL6 and CXCL8 (P 0.05) at 6, 12 and 24 hours. At these time points, the levels of CXCL6 and CXCL8 in the culture supernatant of HBMECs were significantly higher in the T. pallidum group than in the blank control group and the inactivated T. pallidum group (all P 0.05) . Moreover, there were no significant differences in the level of CXCL10 in the culture supernatant of HBMECs among the T. pallidum group, the inactivated T. pallidum group and the blank control group (all P > 0.05) . The number of migratory HL-60 cells in the lower Transwell chambers was significantly higher in the T. pallidum group than in the inactivated T. pallidum group and the blank control group (both P < 0.05) . Conclusion Viable T. pallidum can up-regulate the gene expression of CXCL6, CXCL8 and CXCL10 in HBMECs, promote the secretion of CXCL6 and CXCL8, and enhance the chemotactic effect of HBMECs on HL-60 cells, which may play a certain role in the occurrence of neurosyphilis. Key words: Neurosyphilis; Treponema pallidum; Chemotactic factors; Cell migration assays, leukocyte; Human brain microvascular endothelial cells; HL-60 cells
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