6-ketoprostaglandin-f1-alpha and thrombin-receptor-peptide-(42-55)

Antithrombin (AT), a natural anticoagulant, has been shown to exert anti-inflammatory activity by promoting the endothelial production of prostaglandin I2 (PGI2), thereby reducing tissue injury. To examine whether AT prevents post-traumatic spinal cord injury (SCI), a pathologic condition in which activated neutrophils are critically involved, we tested the effect of AT on SCI induced by compression trauma in rats. Intravenous administration of AT, either before or after the induction of SCI, significantly reduced SCI-related motor disturbances in these animals. AT also significantly inhibited both intramedullary hemorrhage and the decrease in the number of motor neurons following SCI, and inhibited the accumulation of neutrophils in the damaged segment of the spinal cord by inhibiting the increase in transcription of tumor necrosis factor-alpha (TNF-alpha). AT significantly enhanced the increase in the tissue level of 6-keto-PGF1alpha, a stable metabolite of PGI2, at the injured segment of the cord. These therapeutic effects of AT may not depend on its anticoagulant effect. AT did not show any effects in animals pretreated with indomethacin, a potent inhibitor of prostaglandin synthesis, and iloprost, a stable PGI2 analog, produced effects similar to those of AT. Furthermore, intravenously administered AT accumulated selectively at the injured segment of the spinal cord, where thrombin generation might be increased. These findings suggest that AT may reduce the effects of compression trauma-induced SCI by inhibiting neutrophil activation as a consequence of the AT-mediated inhibition of TNF-alpha production. Such therapeutic effects of AT might be mediated by its promoting the endothelial release of PGI2. These findings strongly suggest AT as a potential agent for treating SCI in the clinical setting.

Topics: 6-Ketoprostaglandin F1 alpha; Amino Acid Chloromethyl Ketones; Animals; Antithrombins; Endothelial Cells; Epoprostenol; Factor Xa; Indomethacin; Male; Motor Activity; Peptide Fragments; Peroxidase; Rats; Rats, Wistar; RNA, Messenger; Spinal Cord Compression; Thrombin; Tumor Necrosis Factor-alpha

Cleavage by thrombin of the platelet thrombin receptor exposes a new N-terminal segment SFLLRNPNDKYEPF (SFLL) which acts as a tethered ligand. The free peptide activates platelets and induces platelet aggregation. We now show that SFLL can also activate human umbilical vein endothelial cells (HUVEC) and induce rises in both cytosolic free calcium ([Ca2+]i) and prostacyclin (PGI2) production. These responses were time- and concentration-dependent and were similar to those for native thrombin except that they were not blocked by hirudin. Initial activation of HUVEC with thrombin desensitized the subsequent response to SFLL for both rises in [Ca2+]i and PGI2 production. Thus, SFLL alone can activate HUVEC and elevate [Ca2+]i and induce PGI2 production suggesting that the thrombin receptors on platelet and endothelial cells are functionally and structurally similar.

Topics: 6-Ketoprostaglandin F1 alpha; Amino Acid Sequence; Calcium; Cells, Cultured; Endothelium, Vascular; Epoprostenol; Hirudins; Humans; Kinetics; Molecular Sequence Data; Oligopeptides; Peptide Fragments; Receptors, Cell Surface; Receptors, Thrombin; Thrombin; Umbilical Veins