Serum-stimulated α1 type IV collagen gene transcription is mediated by TGF-β and inhibited by estradiol

We examined the hypothesis that fetal calf serum (FCS) stimulates murine mesangial cell alpha(1) type IV collagen (COL4A1) gene transcription by increasing autocrine production of transforming growth factor-beta (TGF-beta) through a platelet-derived growth factor (PDGF)-dependent mechanism. PDGF-stimulated COL4A1 gene transcription was inhibited by neutralizing antibody to TGF-beta (119.3 +/- 3.6 vs. 106.0 +/- 6.2 relative luciferase units, expressed as a percentage of control untreated cells, P < 0.003). FCS-stimulated gene transcription was inhibited by neutralizing antibody to PDGF (145.3 +/- 4.1 vs. 136.7 +/- 0.3 relative luciferase units, P < 0.002) and by neutralizing antibody to TGF-beta (148.3 +/- 4.1 vs. 127.1 +/- 3.4 relative luciferase units, P < 0.036). The inhibitory effect of combined treatment with anti-PDGF and anti-TGF-beta antibody on gene transcription was no greater than that of anti-TGF-beta antibody alone [129.5 +/- 0.53 as, 127.1 +/- 3.4 relative luciferase units, P = not significant (NS)]. FCS-stimulated gene transcription was also inhibited by estradiol (10(-7) M) (148.4 +/- 3.1 vs. 119.4 +/- 8.1 relative luciferase units, P < 0.019). In the presence of estradiol, anti-TGF-beta antibody failed to further reduce serum-stimulated gene transcription (119.4 +/- 8.1 vs. 115.6 +/- 9.8, P = NS), suggesting that estradiol reverses FCS-stimulated COL4A1 gene transcription by antagonizing the actions of TGF-beta. Measurement of type IV collagen synthesis by Western blotting confirmed that the intact gene responded in a manner analogous to the promoter construct.