title: Stimulation of tissue plasminogen activator production by retinoic acid: synergistic effect on protein kinase C-mediated activation.
abstract: Trans retinoic acid (t-RA) stimulated the production of tissue plasminogen activator (tPA) in HeLa-S3 and human umbilical vein endothelial cells (huvecs) in a dose-dependent manner with maximal release (four to five times control) at 40 nmol/L and 40 mumol/L, respectively. In endothelial cells, the stimulation of tPA production by phorbol 12-myristate 13-acetate (PMA) was potentiated 1.9-fold by 10 mumol/L t-RA, or 1.8 times the additive effect. In HeLa cells, total tPA secretion with 10 nmol/L PMA was increased from 43 ng/mL to 96 ng/mL by 40 nmol/L t-RA, which was two times the additive effect. Higher concentrations of t-RA (400 nmol/L) depressed tPA secretion by itself and also suppressed PMA-induced tPA production by 50%. Histamine and thrombin also synergized with t-RA. t-RA (40 nmol/L) and 10 micrograms/mL histamine or 10 U/mL thrombin combined to induce tPA production 3.4 and 1.3 times the additive effect in HeLa cells. Cyclic adenosine monophosphate (cAMP) levels were not significantly affected by 10 nmol/L to 10 mumol/L t-RA. Nor did 10 nmol/L PMA and 40 nmol/L t-RA together affect cAMP levels, suggesting that t-RA-mediated potentiation of PMA-induced tPA production occurred via a mechanism that was independent of cAMP levels. Downregulation of protein kinase C (PKC) by pretreatment of huvecs with 100 nmol/L PMA completely blocked a secondary response to PMA, but did not have a significant effect on t-RA induction. Pretreatment with 10 mumol/L t-RA, on the other hand, did not significantly affect a secondary stimulus by 100 nmol/L PMA, but completely suppressed a secondary stimulation by 10 mumol/L t-RA alone. These studies suggest that the mechanism mediating t-RA stimulation of tPA production interacts with the PKC pathway, resulting in synergism.
authors.affiliation: Department of Molecular and Experimental Medicine, Scripps Research Institute, La Jolla, CA 92037.
authors.forename: R D
authors.initials: RD
authors.lastname: Medh
authors.forename: L
authors.initials: L
authors.lastname: Santell
authors.forename: E G
authors.initials: EG
authors.lastname: Levin
mesh_terms: D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D006367:HeLa Cells / Q000378:metabolism; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D007700:Kinetics; D011493:Protein Kinase C / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D010959:Tissue Plasminogen Activator / Q000096:biosynthesis* / Q000378:metabolism; D014212:Tretinoin / Q000494:pharmacology*; D014471:Umbilical Veins
chemical_list: D014212:Tretinoin; D006632:Histamine; D000242:Cyclic AMP; D011493:Protein Kinase C; D013917:Thrombin; D010959:Tissue Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate