Retinoids potentiate transforming growth factor-beta activity in bovine endothelial cells through up-regulating the expression of transforming growth factor-beta receptors.
Retinoic acid (RA) induces the activation of latent transforming growth factor-beta (TGF-beta) in bovine aortic endothelial cells (BAECs) via enhancement of cellular plasminogen activator (PA)/plasmin levels. The resultant TGF-beta suppresses the excessive fibrinolytic activity by decreasing PA expression and stimulating expression of the PA inhibitor, PA inhibitor-1 (PAI-1), and inhibits cell proliferation. Here, we report that, in this regulatory system, RA simultaneously up-regulates the expression of TGF-beta receptor types I and II, resulting in enhancement of TGF-beta activity in the cells. RA increased the numbers of high- and low-affinity binding sites for 125I-TGF-beta1 2.1-fold and 1.5-fold, respectively, without alteration of their Kd values. Affinity labeling and Western and Northern blotting studies showed that, following RA treatment, surface levels of both type I and type II receptors increased due to augmentation in their mRNA levels. The effect was dose- and time-dependent. Treatment with 1 microM RA for 15 hr increased mRNA levels of type I and II receptor threefold and eightfold, respectively. Pretreatment of BAECs with either RA or retinol lowered the concentration of TGF-beta1 required to suppress PA levels, to enhance PAI-1 levels, and to inhibit cell proliferation. Thus, retinoids may regulate cellular functions of BAECs not only by inducing the formation of active TGF-beta but also by stimulating TGF-beta receptor expression. This regulatory mechanism may sustain TGF-beta-mediated regulation of EC function at a focal site where RA is acting.
Yoshizawa
M
M
Institute of Applied Biochemistry, University of Tsukuba, Ibaraki, Japan.
Miyazaki
H
H
Kojima
S
S
D000199:Actins / Q000032:analysis; D030201:Activin Receptors, Type I; D000818:Animals; D001011:Aorta / Q000166:cytology; D002417:Cattle; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D005343:Fibrinolytic Agents / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000032:analysis; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics* / Q000378:metabolism; D012176:Retinoids / Q000494:pharmacology*; D016212:Transforming Growth Factor beta / Q000235:genetics* / Q000378:metabolism; D015854:Up-Regulation / Q000187:drug effects
D000199:Actins; D005343:Fibrinolytic Agents; D017395:Plasminogen Activator Inhibitor 1; D019408:Platelet Endothelial Cell Adhesion Molecule-1; D012333:RNA, Messenger; D018125:Receptors, Transforming Growth Factor beta; D012176:Retinoids; D016212:Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II