Promoter activity and regulation of human CYP4F2 LTB(4) omega-hydroxylase gene in HEPG2 cells

Leukotriene B4 (LTB4) is a potent pro-inflammatory mediator implicated in the pathogenesis of autoimmune inflammatory disease, liver injury and colon cancer. The human CYP4F2 gene encodes a LTB4 o-hydroxylase that metabolizes LTB4 to a biologically less active metabolite. Thus CYP4F2 has an important role in controlling inflammation. Understanding of CYP4F2 gene structure and regulation will provide information on the role of arachidonic acid and LTB4 metabolism in the mechanism underlying the inflammatory process, which may provide alternative avenues for the development of therapeutic drugs in treatment of inflammatory diseases.;The human CYP4F2 gene was isolated and a 6.7 kb (kilobases) 5'end fragment of the gene was sequenced. The CYP4F2 gene is about 20 kb long and contains 13 exons. Primer extension identified that the gene transcription starts at 49 bp (basepairs) upstream the 3' end of exon 1. The CYP4F2 gene has typical basic promoter elements such as TATA and CCAAT boxes, which have not been identified in other CYP4F gene family members. The region between -145bp and -84bp is critical for the promoter activity. An alternative promoter region may exist upstream the ATG codon in exon 2. Regulation studies show that the peroxisome proliferators Wy14,643 and PDFO inhibit CYP4F2 gene transcription. The nuclear receptor cotransfection studies show that hPPARalpha/RXRalpha can further enhance the inhibitory function of Wy14,643 Gene expression is stimulated by 10 muM 9-cis retinoic acid, and is further enhanced by hRXRalpha cotransfection while hRARalpha cotransfection can compromise the hRXRalpha enhancement. A putative Wy14,643 response element is found at the three hexamer repeat DR-1 element at -23 bp. A RARalpha element is identified at -717 bp of the gene, which may inhibit CYP4F2 gene activation mediated by hRXRalpha A 50% inhibition of gene expression is noted following addition of the pro-inflammatory cytokines TNFalpha, IL-6 and IFNgamma (100--200 ng/ml) in transfection assay. These data suggest a link between peroxisome proliferators, retinoic acids and inflammation control, and help us to further understand the role of CYP4F2 gene in inflammation, lipid homeostasis and carcinogenesis.