hirudin and Edema

Topics: Adult; Anticoagulants; Bandages; Edema; Female; Fibrinolytic Agents; Heparin; Hirudins; Humans; Meningioma; Neurosurgical Procedures; Optic Nerve Neoplasms; Thrombocytopenia; Thrombolytic Therapy; Thrombophlebitis

Besides its central role in coagulatory pathways, thrombin is known to be a key mediator of macrophage and granulocyte activation in vitro. During recent years the concept of thrombin inhibition by the specific thrombin inhibitor, hirudin, has been established to treat septic disorders. Since basic mechanisms of sepsis include leukocyte/endothelial cell interaction and deterioration of capillary perfusion, we hypothesized that hirudin modulates leukocyte activation and microvascular injury. Severe endotoxemia was induced in Syrian hamsters by intravenous administration of endotoxin (lipopolysaccharide [LPS], E. coli, 2mg/kg) at 0 h. Hirudin (0.25 mg/kg/h) was substituted intravenously during the 4 h after the induction of endotoxemia (n = 7, hirudin). In control animals (n = 6, control) LPS was given without hirudin substitution. In skinfold chamber preparations leukocyte/endothelial cell interaction and functional capillary density (FCD, measure of capillary perfusion) were analyzed during a 24-h period after LPS injection using intravital fluorescence microscopy. Hirudin effectively normalized thromboplastin time and antithrombin activity when compared to controls (P < 0.05, ANOVA). However, hirudin did not attenuate LPS-induced arteriolar and venular leukocyte adherence, and even tended to increase leukocyte adherence after 24 h (P > 0.05, MANOVA). In parallel, addition of hirudin led to a significant deterioration of FCD over time when compared to controls (hirudin: baseline = 171 +/- 19 cm(-1) versus 16 +/- 9 at 24 h; control: baseline = 150 +/- 20 cm(-1) versus 62 +/- 18 at 24 h; P < 0.05). The fall in FCD in hirudin animals was associated with a significant increase of wet-to-dry weight ratios in lung, kidney, muscle, and small intestine (P < 0.05 versus control, ANOVA). Thus our study does not indicate a protective effect of hirudin on microcirculation during endotoxemia, despite an improvement of coagulatory parameters. This result may at least in part explain the lack of efficacy of hirudin on lethality during endotoxemia and sepsis.

Topics: Animals; Antithrombins; Arterioles; Cricetinae; Edema; Endothelium, Vascular; Endotoxins; Escherichia coli; Hirudins; Intestine, Small; Leukocytes; Lipopolysaccharides; Liver; Lung; Mesocricetus; Microcirculation; Muscle, Skeletal; Organ Size; Venules

Coagulation proteases were tested in a rat model of acute inflammation. Subplantar injection of Factor Xa (10-30 microg) produced a time- and dose-dependent edema in the rat paw, and potentiated carrageenin-induced edema. In contrast, the homologous protease Factor IXa was ineffective. This inflammatory response was recapitulated by the Factor Xa sequence L83FTRKL88(G), which mediates ligand binding to effector cell protease receptor-1 (EPR-1), while a control scrambled peptide did not induce edema in vivo. Conversely, injection of the EPR-1-derived peptide S123PGKPGNQNSKNEPP137 (corresponding to the receptor binding site for Factor Xa) inhibited carrageenin-induced rat paw edema, while the adjacent EPR-1 sequence P136PKKRERERSSHCYP150 was without effect. EPR-1-Factor Xa-induced inflammation was characterized by fast onset and prominent perivascular accumulation of activated and degranulated mast cells, was inhibited by the histamine/serotonin antagonists cyproheptadine and methysergide, but was unaffected by the thrombin-specific inhibitor, Hirulog. These findings suggest that through its interaction with EPR-1, Factor Xa may function as a mediator of acute inflammation in vivo. This pathway may amplify both coagulation and inflammatory cascades, thus contributing to the pathogenesis of tissue injury in vivo.

Topics: Amino Acid Sequence; Analysis of Variance; Animals; Antithrombins; Blood Coagulation; Carrageenan; Cyproheptadine; Edema; Factor Xa; Hirudins; Histamine H1 Antagonists; Inflammation; Male; Mast Cells; Methysergide; Molecular Sequence Data; Peptide Fragments; Rats; Rats, Wistar; Recombinant Proteins; Serotonin Antagonists; Time Factors

A rat model of inflammation was used to investigate the biological effects of thrombin. The thrombin-specific inhibitor Hirulog markedly attentuated the carrageenin-induced edema of the paw of the rat. Injection of thrombin into the paw also produced edema. The effect of thrombin was due to activation of its receptor; a thrombin receptor activating peptide (TRAP) reproduced the effects of thrombin in causing edema. TRAP also increased vascular permeability as demonstrated by extravasation of Evans blue and 125I-labeled serum albumin. The release of bioactive amines played an important role in mediating the TRAP-induced edema; the serotonin/histamine antagonist cryproheptadine and the histamine H2 receptor antagonist cimetidine reduced significantly the edema caused by TRAP. Treatment of rats with the mast cell degranulator 48/80 to deplete these cells of their stores of histamine and serotonin abolished completely the ability of TRAP to produce edema. Histochemical examination confirmed that TRAP treatment led to mast cell degranulation. Thus, it has been possible to demonstrate that thrombin acts as an inflammatory mediator in vivo by activating its receptor, which in turn leads to release of vasoactive amines from mast cells.

Topics: Amino Acid Sequence; Animals; Antithrombins; Carrageenan; Cytoplasmic Granules; Edema; Hirudins; Histamine; Inflammation; Male; Mast Cells; Molecular Sequence Data; Peptide Fragments; Rats; Rats, Wistar; Receptors, Thrombin; Recombinant Proteins; Serotonin; Thrombin