title: Heparin inhibits thrombin-induced mitogen-activated protein kinase signaling in arterial smooth muscle cells.
abstract: OBJECTIVE
  Smooth muscle cell proliferation is a key event in the development of intimal hyperplasia after arterial injury. Heparin can suppress smooth muscle cell proliferation in vitro and prevents intimal hyperplasia after arterial injury, but the mechanisms of action are poorly understood. Recently, we observed that heparin inhibited serum-induced activation of mitogen-activated protein kinase in smooth muscle cells, but heparin did not inhibit signaling induced by platelet-derived growth factor BB and basic fibroblast growth factor, both ligands of tyrosine kinase receptors. Here, we examined the possibility that heparin inhibits signaling by thrombin and other activators of heterotrimeric G-proteins.
  
  
  METHODS
  Baboon aortic smooth muscle cells were stimulated with thrombin, angiotensin II, endothelin-1, and lysophosphatidic acid in the presence or absence of heparin. After stimulation, mitogen-activated protein kinase activity was measured with an in-gel phosphorylation assay, mitogen-activated protein kinase kinase-1 was immunoprecipitated from the same samples, and activity was measured with recombinant mitogen-activated protein kinase as a substrate. DNA synthesis was measured by 3H-thymidine labeling and scintillation counting.
  
  
  RESULTS
  Heparin inhibited sustained activity of mitogen-activated protein kinase kinase-1 and mitogen-activated protein kinase and prevented DNA synthesis induced by thrombin, angiotensin II, endothelin-1, and lysophosphatidic acid.
  
  
  CONCLUSIONS
  Heparin inhibits growth of baboon smooth muscle cells by preventing prolonged mitogen-activated protein kinase activation elicited by ligands of seven transmembrane domain receptors and heterotrimeric G-proteins. The results indicate that heparin interferes with a specific pathway in smooth muscle cell growth, which could be a future target in attempts to inhibit lesion development after vascular surgery.
authors.affiliation: Department of Surgery, University of Washington, Seattle, USA.
authors.forename: U
authors.initials: U
authors.lastname: Hedin
authors.forename: G
authors.initials: G
authors.lastname: Daum
authors.forename: A W
authors.initials: AW
authors.lastname: Clowes
mesh_terms: D000818:Animals; D000933:Antifibrinolytic Agents / Q000494:pharmacology*; D001011:Aorta / Q000166:cytology / Q000293:injuries; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000187:drug effects*; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D004353:Drug Evaluation, Preclinical; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000254:growth & development*; D006493:Heparin / Q000494:pharmacology*; D006965:Hyperplasia / Q000209:etiology / Q000517:prevention & control; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D010215:Papio; D015398:Signal Transduction / Q000187:drug effects*; D013917:Thrombin / Q000502:physiology*; D017539:Tunica Intima / Q000473:pathology
chemical_list: D000933:Antifibrinolytic Agents; D006493:Heparin; D004247:DNA; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013917:Thrombin