Specific role of the tight junction proteins occludin and claudin-5 on the blood–brain barrier during Listeria monocytogenes infection

To investigate the blood-brain barrier (BBB) permeability of mice after Listeria monocytogenes infection for further study on the mechanism of L. monocytogenes crossing the BBB, a mouse model was established and Evans blue assay was performed to assess the BBB disruption. Using relative quantitative real-time PCR, the RNA expression of Zonula occludens-1 (ZO-1), occludin and claudin-5 were detected. In addition, the protein expression level of ZO-1, occludin and claudin-5 were detected by immunohistochemistry and western blot. The extravasation of Evans blue dye was significantly different between 24 h and 96 h (P < 0.05). The mRNA expression of occludin and claudin-5 were down-regulated than that of the control group at each sampling point (P < 0.05) and ZO-1 showed a significant change at 96 h (P < 0.05). In addition, the protein expression level of occludin and claudin-5 decreased significantly at 48 h and 96 h (P < 0.05) by immunohistochemistry and western blot, compared with the control, while ZO-1 was almost unchanged (P > 0.05). All results indicating that the tight junction integrity of endothelial cells was destroyed and BBB permeability was enhanced in the process of L. monocytogenes infection, and this change was related to the decrease of the expression occludin and claudin-5.