Cyclic AMP potentiates phorbol ester stimulation of tissue plasminogen activator release and inhibits secretion of plasminogen activator inhibitor-1 from human endothelial cells.
We have examined the effect of phorbol esters and cAMP elevating compounds on tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) secretion. Phorbol esters induce a time- and dose-dependent increase in tPA release from endothelial cells, while forskolin, isobutylmethylxanthine, dibutyryl cAMP, and 8-bromo-cAMP had no significant stimulatory effect on tPA secretion. However, elevation of cAMP simultaneously with phorbol ester treatment potentiated the phorbol ester-induced release of tPA 6 times from 22.2 ng/ml with phorbol myristate acetate (PMA) alone to 122.1 ng/ml (PMA and forskolin). Potentiation was dose-dependent (half-maximal potentiation = 4 microM forskolin), and tPA release was enhanced at all stimulatory concentrations of PMA with no change in the PMA concentrations causing half-maximal or maximum tPA release. The kinetics of release was also similar in PMA versus PMA-forskolin-treated cells. A 4-h delay was observed, enhanced release was transient, and was followed by the onset of a refractory period. In contrast, elevation of cAMP reduced constitutive secretion of PAI-1 by 30-40% and prevented the increase in PAI-1 secretion stimulated by PMA. Elevated cAMP also decreased the rate of PAI-1 deposition into the endothelial substratum. These studies indicate that activation of a cAMP-dependent pathway(s) in coordination with phorbol ester-induced responses plays a central role in modifying the tPA and PAI-1 secretion from endothelial cells, leading to a profibrinolytic state in the endothelial environment.
Santell
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Department of Basic and Clinical Research, Research Institute of Scripps Clinic, La Jolla, California 92037.
Levin
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EG
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000378:metabolism; D006023:Glycoproteins / Q000378:metabolism*; D006801:Humans; D010703:Phorbol Esters / Q000494:pharmacology*; D015849:Plasminogen Inactivators; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010959:Tissue Plasminogen Activator / Q000378:metabolism*
D006023:Glycoproteins; D010703:Phorbol Esters; D015849:Plasminogen Inactivators; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003994:Bucladesine; D000242:Cyclic AMP; D010959:Tissue Plasminogen Activator; D013755:Tetradecanoylphorbol Acetate; D015056:1-Methyl-3-isobutylxanthine