TNF-alpha induced NFκB signaling and p65 (RelA) overexpression repress Cldn5 promoter in mouse brain endothelial cells

Inflammatory cytokine TNF alpha enhances permeability of brain capillaries constituting blood brain barrier (BBB). In the monoculture endothelial models of BBB TNF alpha alters tight junction (TJ) structure and protein content. Claudin-5 (Cldn5) is a key TJ protein whose expression in the brain endothelial cells is critical to the function of BBB. TNF alpha reduces Cldn5 promoter activity and mRNA expression in mouse brain derived endothelial cells but the regulatory elements and signaling mechanism involved are not defined. Here we report that TNF alpha acts through NF kappa B signaling and requires a conserved promoter region for the down-regulation of Cldn5 expression. Overexpression of the NF kappa B subunit p65 (RelA) alone repressed Cldn5 promoter activity in mouse brain endothelial cells. We observed partial loss of Cldn5 protein expression after prolonged TNF alpha treatment in primary endothelial culture isolated from C56BL/6 mice brain. Taken together, our results confirm and extend previous observations of TNF alpha, induced down-regulation of Cldn5 expression in mouse brain endothelial cells. (C) 2011 Published by Elsevier Ltd.