Identification of a NFκB inhibition site on the proximal promoter region of human organic anion transporting polypeptide 1A2 coding gene SLCO1A2.

Organic anion transporting polypeptides (OATPs; gene symbol SLCO) are membrane transporters that mediate the transport of wide ranges of compounds. The expression of different OATP members has been reported in the kidney, liver, placenta, brain, and intestine. Because of their broad substrate spectra and wide distribution within the human body, these transporters have been proposed to play key roles in the influx transport of many oral drugs. Inflammation is known to regulate the expression and functions of many drug-metabolizing enzymes and drug transporters. As a proinflammatory cytokine, tumor necrosis factor-alpha (TNF alpha) has been shown to affect the expression of different drug transporters, including OATP family members. In the present study, a putative nuclear factor-kappa B (NF kappa B) binding site ranging from -1845 to -1836 was identified at the proximal promoter region of OATP1A2 coding gene SLCO1A2. Electrophoretic mobility shift assays and chromatin immunoprecipitation showed that nuclear extracts from both breast cancer cell MCF7 and liver cancer cell HepG2 interacted with an oligonucleotide probe containing the putative NF kappa B binding site and that the DNA-protein complexes contained both p65 and p50 subunits of NF kappa B. Further study revealed that the binding site may be responsible in part for the suppression effect of TNF alpha toward SLCO1A2 expression because the treatment of TNF alpha significantly increased. Treatment of TNF alpha significantly increased formation of the DNA-protein complexes and mutations at essential bases of the putative NF kappa B binding site abolished responsiveness to the TNF alpha neutralizing antibody, suggesting that the binding site may be responsible in part for the suppression effect of TNF alpha towars SLCO1A2 expression.