Influence of NF kappa B inhibitors on IL-1 beta-induced chemokine CXCL8 and-10 expression levels in intestinal epithelial cell lines: glucocorticoid ineffectiveness and paradoxical effect of PDTC

Abstract

Activation of intestinal epithelial cell (IEC) nuclear factor kappa B (NF kappa B) and the consequent chemokine upregulation are crucial events in inflammatory bowel disease (IBD) pathogenesis. Not much is known about the consequences of NF kappa B inhibition in terms of chemokine expression in intestinal cells. Therefore, we aimed to evaluate the efficacy of compounds known to disrupt the NF kappa B pathway on NF kappa B transcriptional activity and CXCL8 and CXCL10 gene expression in intestinal cell lines. The influence of NF kappa B inhibitors (dexamethasone, pyrrolidine dithiocarbamate (PDTC) and BAY 11-7082) on IL-1 beta-induced NF kappa B transcriptional activity was investigated by transient transfection of Caco-2 cells with an NF kappa B-secreted alkaline phosphatase reporter plasmid. Il-1 beta stimulated CXCL8 and CXCL10 mRNA and protein expression and was studied in Caco-2 and HT29 cells in the presence and absence of the NF kappa B inhibitors by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent serologic assay, respectively. To reveal alternative signalling cascades, experiments were also performed in the presence of the p38MAPK inhibitor SB 203580 and the ERK inhibitor PD 98059. Dexamethasone did not downregulate chemokine expression sufficiently, probably due to a lack of glucocorticoid receptors in these cells. While BAY11-7082 inhibited chemokine expression, PDTC led to a paradoxical upregulation of CXCL8 in Caco-2 cells, which could be prevented by inhibition of p38MAPK. These data explain the frequent unresponsiveness of IBD to glucocorticoid treatment and suggest that alternative NF kappa B inhibition in IECs might be of use in IBD therapy. Drug development based on measuring anti-NF kappa B activity might be misleading and should therefore also include studies on relevant gene products.