title: Molecular mechanism of suppression of testicular steroidogenesis by proinflammatory cytokine tumor necrosis factor alpha.
abstract: Tumor necrosis factor alpha (TNF-alpha) has been demonstrated to inhibit steroidogenesis in Leydig cells at the transcriptional level of steroidogenic enzymes. However, the molecular mechanism of this observed gene repression is not well understood. We now demonstrate that nuclear factor kappaB (NF-kappaB) activated by TNF-alpha inhibits the transactivation of orphan nuclear receptors, which regulate the expression of steroidogenic-enzyme genes. TNF-alpha treatment suppressed the luteinizing-hormone-induced or Nur77/SF-1-stimulated promoter activity of steroidogenic-enzyme genes in Leydig cells. The TNF-alpha-mediated gene suppression was blocked by treatment with an inhibitor of NF-kappaB. In addition, overexpression of the p65 (RelA) subunit of NF-kappaB showed the same effect as TNF-alpha and inhibited Nur77 transactivation, suggesting the involvement of NF-kappaB activation in the observed gene repression. Physical association of Nur77 with p65 was revealed by mammalian two-hybrid, GST pull-down, and coimmunoprecipitation analyses. The NF-kappaB inhibition of Nur77 transactivation was likely due to the competition of p65 for Nur77 binding with coactivators. Finally, chromatin immunoprecipitation assays revealed that TNF-alpha treatment caused the recruitment of NF-kappaB to the promoter of the steroidogenic-enzyme p450c17 gene, supporting the hypothesis that the TNF-alpha-mediated gene repression involves NF-kappaB inhibition of the transcriptional activity of Nur77 and other orphan nuclear receptors. These findings provide a molecular mechanism underlying the inhibition of testicular steroidogenesis by proinflammatory cytokines.
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Department of Biology, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors.forename: Cheol Yi
authors.initials: CY
authors.lastname: Hong
authors.forename: Jin Hee
authors.initials: JH
authors.lastname: Park
authors.forename: Ryun Seop
authors.initials: RS
authors.lastname: Ahn
authors.forename: Suhn Young
authors.initials: SY
authors.lastname: Im
authors.forename: Hueng-Sik
authors.initials: HS
authors.lastname: Choi
authors.forename: Jaemog
authors.initials: J
authors.lastname: Soh
authors.forename: Synthia H
authors.initials: SH
authors.lastname: Mellon
authors.forename: Keesook
authors.initials: K
authors.lastname: Lee
mesh_terms: D015096:3-Hydroxysteroid Dehydrogenases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D051548:Histone Acetyltransferases; D006655:Histone Deacetylases / Q000378:metabolism; D006801:Humans; D007985:Leydig Cells / Q000166:cytology / Q000378:metabolism*; D008297:Male; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D056920:Nuclear Receptor Coactivator 1; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism; D013256:Steroids / Q000378:metabolism*; D013739:Testosterone / Q000378:metabolism; D051996:Transcription Factor RelA; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D000098682:Steroidogenic Acute Regulatory Protein
chemical_list: D004268:DNA-Binding Proteins; D016328:NF-kappa B; C539821:NR4A1 protein, human; C539818:Nr4a1 protein, mouse; C539820:Nr4a1 protein, rat; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D010750:Phosphoproteins; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D013256:Steroids; D051996:Transcription Factor RelA; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; D000098682:Steroidogenic Acute Regulatory Protein; D013739:Testosterone; D011374:Progesterone; D003577:Cytochrome P-450 Enzyme System; D015096:3-Hydroxysteroid Dehydrogenases; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1; D006655:Histone Deacetylases