title: Estradiol reverses TGF-beta1-stimulated type IV collagen gene transcription in murine mesangial cells.
abstract: We have previously shown that estradiol suppresses types I and IV collagen synthesis by mesangial cells grown in the presence of serum. In the present study, we examined the interaction between estradiol and transforming growth factor-beta (TGF-beta) on collagen IV synthesis. In a luciferase reporter gene construct containing the type IV collagen promoter and 1-chain regulatory sequences, we found that TGF-beta1 (2 ng/ml) stimulated alpha1-collagen IV gene transcription in serum-free media (140.5 +/- 6.2 relative luciferase units, expressed as a percent of control untreated cells, P < 0.001). Estradiol reversed the stimulatory effects of TGF-beta1 on reporter gene transcription in a dose-dependent manner [for 2.5 x 10(-9) M, 114.2 +/- 0.2, P < 0.002 vs. TGF-beta1; for 10(-7) M, 89.5 +/- 4.0, P < 0.001 vs. TGF-beta1 and P = not significant (NS) vs. control]. Using immunoprecipitation techniques, we found that estradiol (10(-7) M) reversed TGF-beta1-stimulated type IV collagen synthesis (175.3 +/- 14.7 vs. 111.6 +/- 7.1, expressed as a percent of control untreated cells, P < 0.001) but did not affect TGF-beta1-stimulated type I collagen synthesis (166.9 +/- 18.8 vs. 162.2 +/- 16.2, P = NS). These results were confirmed with Western blotting. Nuclear extracts from mesangial cells treated with TGF-beta1 showed increased binding to a Sp1 consensus binding sequence oligonucleotide and to an Sp1 binding site in the collagen IV promoter. Estradiol reversed this enhanced binding. These data suggest that estradiol antagonizes TGF-beta1-stimulated type IV collagen synthesis at a transcriptional level and that this effect may be mediated by interactions with the transcription factor Sp1.
authors.affiliation: Department of Medicine, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, New York 10467, USA.
authors.forename: S
authors.initials: S
authors.lastname: Silbiger
authors.forename: J
authors.initials: J
authors.lastname: Lei
authors.forename: F N
authors.initials: FN
authors.lastname: Ziyadeh
authors.forename: J
authors.initials: J
authors.lastname: Neugarten
mesh_terms: D000818:Animals; D002461:Cell Line, Transformed; D003094:Collagen / Q000096:biosynthesis* / Q000235:genetics; D004958:Estradiol / Q000494:pharmacology*; D017930:Genes, Reporter; D005920:Glomerular Mesangium / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D014158:Transcription, Genetic / Q000187:drug effects*; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors* / Q000494:pharmacology
chemical_list: D016212:Transforming Growth Factor beta; D004958:Estradiol; D003094:Collagen