title: Thrombin contraction of vascular smooth muscle: implications for vasospasm.
abstract: Thrombin contributes to hemostasis by activating platelets, the formation of fibrin, and contraction of the injured vessel. These effects are mediated through the proteolytic activity of thrombin. We hypothesized that thrombin may have a role in vasospasm after arterial injury and examined the physiologic and cellular signaling events of thrombin in intact vascular smooth muscles. Thrombin stimulation of strips of bovine carotid artery smooth muscle led to contractions which relaxed with the addition of the nitric oxide donor, sodium nitroprusside. However, washout of the thrombin and SNP resulted in the re-generation of force. This was not observed with other agonists such as endothelin, thromboxane analogues, or serotonin. Using two-dimensional immunoblotting we demonstrate that thrombin stimulation leads to increases in the tyrosine phosphorylation of 4 proteins, three different isoforms of P44 mitogen activated protein kinase (MAPK) and one isoform of P38 stress activated protein kinase (SAPK). Activation of P38 SAPK leads to activation of MAPKAP kinase-2 and a major substrate protein of MAPKAP kinase-2 is the small heat shock protein, HSP27. HSP27 has been implicated in mediating smooth muscle contraction. These data suggest that in the setting of arterial injury, thrombin-induced contraction may supercede over short acting vasorelaxants such as NO resulting in vasospasm. In addition to stress, physiologic substances such as thrombin, activate SAPKs leading to increases in the phosphorylation of HSP27. Thus, thrombin may play a central role in hemostasis after vascular injury and in the pathologic responses to plaque rupture and thrombosis in atherosclerosis.
authors.affiliation: Departments of Surgery, Medicine (Institute for Molecular Medicine and Genetics), and Cell Biology, Medical College of Georgia, Augusta VA Medical Center, Augusta, GA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Knoepp
authors.forename: C D
authors.initials: CD
authors.lastname: Bagwell
authors.forename: P
authors.initials: P
authors.lastname: Garlich
authors.forename: C M
authors.initials: CM
authors.lastname: Brophy
mesh_terms: D000818:Animals; D002417:Cattle; D015151:Immunoblotting; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*; D014443:Tyrosine / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D013917:Thrombin; D014443:Tyrosine; D048051:p38 Mitogen-Activated Protein Kinases; D000099190:MAP-Kinase-Activated Kinase 2