Cloning and characterization of the murine claudin-5 promoter

Claudin-5, an integral tight junction protein component, plays a critical role in permeability of the endothelial cell barrier. Recently, we have shown that claudin-5 protein is down-regulated by the proinflammatory cytokine TNF alpha and its levels restored by dexamethasone treatment. In order to investigate the regulation of claudin-5 at the transcriptional level, we have cloned the murine claudin-5 promoter. The claudin-5 promoter sequence (1131 bp) showed no consensus TATA-box. We identified putative transcription factor binding sites, including six full and two half sites degenerated glucocorticoid-response elements (GREs), two NFkappaB, three Sp1, one Sp2, one Ap2, as well as three E-boxes. Serially deleted promoter constructs showed high basal activity. TNF alpha significantly reduced the promoter activity and mRNA levels of claudin-5 in brain cEND and myocardial MyEND endothelial cells. Dexamethasone treatment led to a significant increase of the murine claudin-5 promoter activity and mRNA levels in cEND cells. However, no claudin-5 induction could be observed in MyEND cells in response to dexamethasone. Our studies suggest tissue-specific regulation of the claudin-5 gene via glucocorticoids and a high vulnerability of claudin-5 to TNF alpha. This could be an important mechanism in diseases accompanied by the release of proinflammatory cytokines, for example in patients with chronic heart failure or multiple sclerosis. (c) 2008 Elsevier Ireland Ltd. All rights reserved.