TNFα up-regulates claudin-2 expression in epithelial HT-29/B6 cells via phosphatidylinositol-3-kinase signaling

• DOI: 10.1007/s00441-009-0751-8
• Publication Date: 2009-02-12T14:41:51Z
• Authors: J. Mankertz; M. Amasheh; S. M. Krug; A. Fromm; S. Amasheh; B. Hillenbrand; S. Tavalali; M. Fromm; J. D. Schulzke
• Keywords: Claudin

Our aim has been to characterize the molecular mechanisms regulating the expression of the channel-forming tight-junctional protein claudin-2 in response to the pro-inflammatory cytokine tumor necrosis factor-alpha (TNFalpha), which is elevated, for example, in active Crohn's disease. TNFalpha caused an 89% decrease of the paracellular resistance in colonic HT-29/B6 cells, whereas transcellular resistance was unaltered. The claudin-2 protein level was increased by TNFalpha without changes in subcellular tight-junctional protein localization as revealed by confocal laser scanning microscopy. Enhanced gene expression was identified as the source of this increase, since claudin-2-specific mRNA and promoter activity was elevated, whereas mRNA stability remained unaltered. Specific inhibitors and phospho-specific antibodies revealed that the increased gene expression of claudin-2 after TNFalpha treatment was mediated by the phosphatidylinositol-3-kinase pathway. Thus, the up-regulation of claudin-2 by TNFalpha is attributable to the regulation of the expression of the gene, as a result of which epithelial barrier function is disturbed, for example, during chronic intestinal inflammation.