title: Activated platelets and leucocytes cooperatively stimulate smooth muscle cell proliferation and proto-oncogene expression via release of soluble growth factors.
abstract: BACKGROUND
  Previous studies indicate that platelets and leucocytes might contribute to the development of neointimal hyperplasia following arterial injury. The present study was aimed at further investigating the role of platelets and leucocytes, alone or in combination, in promoting vascular smooth muscle cell (SMC) proliferation in vitro, focusing on the relative contribution of different soluble growth factors released by these cells, and on the ability to induce proto-oncogene expression, such as c-fos.
  
  
  METHODS
  SMCs from rabbit aortas, made quiescent by serum deprivation, were stimulated with either activated platelets, leucocytes, or both, separated from SMCs by a membrane insert. SMC proliferation was evaluated by measuring the incorporation of 3H-thymidine. The relative contribution of different platelet-derived mediators to SMC growth was evaluated by adding either ketanserin, a 5-HT2 receptor antagonist, R68070, a TxA2 receptor antagonist, BN52021, a platelet activating factor (PAF) receptor antagonist, and trapidil, a platelet derived growth factor (PDGF) receptor antagonist. The role of different leucocyte sub-populations (neutrophils and monocytes + lymphocytes) was also determined in additional experiments.
  
  
  RESULTS
  SMC proliferation was significantly increased by activated platelets to 360 +/- 9% of control values (P < 0.05). This effect was reduced by ketanserin, R68070, BN 52021 or trapidil. Whole leucocytes, neutrophils or lymphocytes + monocytes also increased SMC proliferation with respect to control experiments. Simultaneous stimulation of SMCs by platelets and whole leucocytes was associated with a significant greater increase in SMC proliferation as compared to SMC stimulated with platelets or leucocytes alone. c-fos expression, almost undetectable in unstimulated SMCs, was markedly increased by activated platelets or leucocytes.
  
  
  CONCLUSIONS
  Activated platelets promote SMC proliferation in vitro via release of soluble mediators, including serotonin, thromboxane A2 PAF and PDGF; activated leucocytes also induce a significant SMC proliferation and exert an additive effect when activated together with platelets; SMCs stimulated with activated platelets and leucocytes show an early expression of the proto-oncogene c-fos.
authors.affiliation: Division of Cardiology, University of Naples Federico II, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Cirillo
authors.forename: P
authors.initials: P
authors.lastname: Golino
authors.forename: M
authors.initials: M
authors.lastname: Ragni
authors.forename: C
authors.initials: C
authors.lastname: Battaglia
authors.forename: F
authors.initials: F
authors.lastname: Pacifico
authors.forename: S
authors.initials: S
authors.lastname: Formisano
authors.forename: C
authors.initials: C
authors.lastname: Buono
authors.forename: M
authors.initials: M
authors.lastname: Condorelli
authors.forename: M
authors.initials: M
authors.lastname: Chiariello
mesh_terms: D000818:Animals; D002455:Cell Division / Q000187:drug effects; D018920:Coculture Techniques; D004224:Diterpenes; D005343:Fibrinolytic Agents / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects; D016762:Genes, fos; D046934:Ginkgolides; D006133:Growth Substances / Q000502:physiology*; D007650:Ketanserin / Q000494:pharmacology; D007783:Lactones / Q000494:pharmacology; D007962:Leukocytes / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000378:metabolism; D010421:Pentanoic Acids / Q000494:pharmacology; D015539:Platelet Activation; D011725:Pyridines / Q000494:pharmacology; D011817:Rabbits; D017479:Receptors, Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology; D014192:Trapidil / Q000494:pharmacology
chemical_list: D004224:Diterpenes; D005343:Fibrinolytic Agents; D046934:Ginkgolides; D006133:Growth Substances; D007650:Ketanserin; D007783:Lactones; D010421:Pentanoic Acids; D011725:Pyridines; D017479:Receptors, Platelet-Derived Growth Factor; D017482:Receptors, Thromboxane; D017367:Selective Serotonin Reuptake Inhibitors; D014192:Trapidil; C045856:ginkgolide B; C060219:ridogrel