title: Mono-(2-ethylhexyl) phthalate (MEHP) induces nuclear receptor 4A subfamily in NCI-H295R cells: a possible mechanism of aromatase suppression by MEHP.
abstract: Phthalate esters are widely used as plasticizers for polyvinylchloride and are suspected of functioning as endocrine disrupters. Di-(2-ethylhexyl) phthalate (DEHP), the most important phthalate ester in commercial use, has been reported to act as a rodent reproductive toxicant. In the present study, we investigated the effects of phthalate esters on aromatase (CYP19) activity and on its gene expression in a human adrenocortical carcinoma cell line, NCI-H295R. Mono-(2-ethylhexyl) phthalate (MEHP), a principle metabolite of DEHP, dose-dependently suppressed aromatase activity and its transcription level. Furthermore, MEHP rapidly and transiently induced transcription of the genes which encode nuclear receptor 4A subfamily members (Nur77, Nurr1 and NOR-1), and up-regulated Nur77 promoter activation and Nur77 protein expression in the cells. MEHP-induced Nur77 transcription was inhibited by bisindolylmaleimide I (protein kinase C inhibitor) and wortmannin (phosphoinositide 3-kinase inhibitor). Finally, ectopic expression of Nur77 markedly suppressed forskolin-induced transcriptional activation of promoters I.3 and II of the CYP19 gene. These results suggest that the suppression of aromatase activity and its transcription level by MEHP exposure to NCI-H295R cells was regulated through the rapid and transient expression of Nur77 gene.
authors.affiliation: Department of Biochemistry, Hoshi University School of Pharmacy and Pharmaceutical Sciences, 2-4-41 Ebara, Shinagawa, Tokyo 142-8501, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Noda
authors.forename: Shuji
authors.initials: S
authors.lastname: Ohno
authors.forename: Shizuo
authors.initials: S
authors.lastname: Nakajin
mesh_terms: D000818:Animals; D001141:Aromatase / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D004051:Diethylhexyl Phthalate / Q000494:pharmacology*; D052244:Endocrine Disruptors / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010968:Plasticizers / Q000494:pharmacology*; D011401:Promoter Regions, Genetic; D011493:Protein Kinase C / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004268:DNA-Binding Proteins; D052244:Endocrine Disruptors; C539821:NR4A1 protein, human; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D010968:Plasticizers; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D014157:Transcription Factors; D004051:Diethylhexyl Phthalate; D001141:Aromatase; D019869:Phosphatidylinositol 3-Kinases; D011493:Protein Kinase C