S. Silbiger et al., ESTRADIOL REVERSES TGF-BETA-1-STIMULATED TYPE-IV COLLAGEN GENE-TRANSCRIPTION IN MURINE MESANGIAL CELLS, American journal of physiology. Renal, fluid and electrolyte physiology, 43(6), 1998, pp. 1113-1118
We have previously shown that estradiol suppresses types I and IV coll
agen synthesis by mesangial cells grown in the presence of serum. In t
he present study, we examined the interaction between estradiol and tr
ansforming growth factor-beta (TGF-beta) on collagen IV synthesis. In
a luciferase reporter gene construct containing the type IV collagen p
romoter and alpha(1)-chain regulatory sequences, we found that TGF-bet
a 1 (2 ng/ml) stimulated alpha(1)-collagen IV gene transcription in se
rum-free media (140.5 +/- 6.2 relative luciferase units, expressed as
a percent of control untreated cells, P < 0.001). Estradiol reversed t
he stimulatory effects of TGF-beta 1 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-beta 1; for 10(-7) M, 89.5 +/- 4.0, P < 0.001 vs. TGF-beta 1
and P = not significant (NS) vs, control]. Using immunoprecipitation t
echniques, we found that estradiol (10(-7) M) reversed TGF-beta 1-stim
ulated type IV collagen synthesis (175.3 +/- 14.7 vs. 111.6 +/- 7.1, e
xpressed as a percent of control untreated cells, P < 0.001) but did n
ot affect TGF-pl-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-beta
1 showed increased binding to a Sp1 consensus binding sequence oligon
ucleotide and to an Sp1 binding site in the collagen IV promoter. Estr
adiol reversed this enhanced binding. These data suggest that estradio
l antagonizes TGF-beta 1-stimulated type IV collagen synthesis at a tr
anscriptional level and that this effect may be mediated by interactio
ns with the transcription factor Sp1.