Abstract
How heparin inhibits vascular smooth muscle cell proliferation and migration has not been established. We have investigated the hypothesis that heparin inhibits vascular smooth muscle cell proliferation and migration by interfering with the expression and activity of proteases such as plasminogen activators. In an in vitro mitogenesis model, tissue-type plasminogen activator (tPA) mRNA and protein increase in baboon smooth muscle cells stimulated with fetal bovine serum or phorbol esters. Heparin inhibits smooth muscle cell proliferation and suppresses the induction of tPA mRNA and protein while it has little effect on the mRNA of urokinase-type plasminogen activator, plasminogen activator inhibitor type I, and a number of genes that are also modulated by serum and phorbol esters. The inhibitory effect on tPA mRNA is specific to heparin-like molecules and does not depend on the anticoagulation activity of heparin. The increase in tPA mRNA is due to increased transcription, which is suppressed by heparin. The induction of tPA by serum and phorbol esters is diminished by protein kinase C inhibitors such as H7 or staurosporine and by protein kinase C depletion. Since heparin suppresses the induction of the tPA gene by phorbol esters, these results suggest that heparin may interfere with the protein kinase C pathway.
Highlights
Attempts todefine a mechanism of action that accounts for all these effects of heparin have not as yet been successful
Since heparin suppresses the in- One way heparin might affect smooth muscle cell (SMC) proliferation, migraduction of the tissuetype plasminogen activator (tPA) gene byphorbol esters, these results suggest that heparin may interfere with the protein kinase C pathway
Heparin is a pharmacological inhibitor of vascular smooth muscle cell (SMC)’ proliferation and migration, and heparinlike glycosaminoglycanssecreted by vascular wall cellspossess SMC inhibitory activity and might be endogenous regulators of SMC growth i n uiuo [1, 2].How these molecules function has yet to be determined, anumber of physiological effects have been described
Summary
Materials-Heparin (isolated from porcine mucosa), dextran sulfate ( M , 500,000), chondroitin 6-sulfate, and phorbol 12-myristate 13-acetate (PMA) were purchased from Sigma. The isolated cDNA clone was subcloned in M13 vector and sequenced by the dideoxy method [45]. The tPA cDNA clone used for the nuclear runculture media were obtained from Sigma unless indicated otherwise. All reagents used for RNA isolation, nuclear run-on transcription assays, and dideoxy sequences were of molecular biology grade. Cells were plated at 20,000/cmZin Dulbecco-Vogt medium containing 5% calf serum and antibiotics. After the cells had been growth arrested inthe serum-free medium for 3 days, the experiments were started by the addition of fresh medium containing 10% FBS (GIBCO or Hyclone) or PMA with or without heparin. TPA ELZSA-To terminate an experiment, the mediumwas removed, centrifuged at 1,500 x g for 10 min and aliquots of the supernatant frozen at -20 "C. Heparin (5-50 pg/ml) had no significant effect (>go% recovery) on the assay of single chain tPA (0.03-1.2 ng).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
