rhodostomin and Thrombocytopenia

Septic shock is a major cause of morbidity and mortality in intensive care units, but there is still no effective therapy for the patients. We evaluated the effects of rhodostomin (Rn), an Arg-Gly-Asp-containing snake venom disintegrin, on lipopolysaccharide (LPS)-activated phagocytes in vitro and LPS-induced endotoxemia in vivo.. Rn inhibited adhesion, migration, cytokine production and mitogen-activated protein kinase (MAPK) activation of macrophage induced by LPS. Flow cytometric analysis revealed that Rn specifically blocked anti-αv mAb binding to RAW264.7. Besides inhibiting MAPK activation of THP-1, Rn bound to LPS-activated THP-1 and specifically blocked anti-αvβ3 mAb binding to THP-1. Binding assays proved that integrin αvβ3 was the binding site for rhodostomin on phagocytes. Rn reversed the enhancement of fibronectin and vitronectin on LPS-induced monocyte adhesion and cytokine release. Transfection of integrin αv siRNA also inhibited LPS-induced activation of monocyte, and Rn exerted no further inhibitory effect. Furthermore, Rn significantly decreased the production of tumor necrosis factor-α (TNF-a), interleukin (IL)-6, -1β and -10 and attenuated cardiovascular dysfunction, including blood pressure and heart pulse, and thrombocytopenia in LPS-induced endotoxemic mice. Rn also protected against tissue inflammation as evidenced by histological examination.. Rn may interact with αvβ3 integrin of monocytes/macrophages leading to interfere with the activation of phagocytes triggered by LPS. These results suggest that the protective function of Rn in LPS-induced endotoxemia may be attributed to its anti-inflammation activities in vivo.

Topics: Animals; Binding Sites; Cell Adhesion; Cell Line; Cell Movement; Cytokines; Disintegrins; Endotoxemia; Humans; Integrin alphaVbeta3; Lipopolysaccharides; Macrophage Activation; Male; MAP Kinase Signaling System; Mice; Mice, Inbred ICR; Peptides; Phagocytes; RNA Interference; RNA, Small Interfering; Thrombocytopenia

Thrombocytopenia as well as hemoconcentration and leukopenia followed by leukocytosis were induced after HoGG challenge on HoGG-sensitized mice. Thrombocytopenia was induced within 2 min and sustained for 1 day. HoGG-induced thrombocytopenia was not observed until day 10 after sensitization; mice challenged with HoGG dose > or = 10 micrograms developed thrombocytopenia. Two types of thrombocytopenia were observed in appropriately sensitized mice. HoGG induced thrombocytopenia at 2 min and 60 min, whereas, alpha-macroglobulin induced thrombocytopenia at 2 min, the platelet count of which returned to normal within 60 min. Poly (Glu60Ala30Tyr10) did not induce thrombocytopenia at 2 min or 60 min. The tracing study by 3H-serotonin labelled platelets demonstrated the 2 min-sequestration of platelets in lungs or livers. The HoGG-induced sequestration of platelets at 2 min was blocked by high dose heparin or Cobra Venom factor. Platelet activation at 60 min was partially inhibited by dexamethasone, rhodostomin synthetic peptide 45-59, or platelet activation factor antagonist (WEB 2086). Furthermore, the thrombocytopenia could be transferred by heat (56 degrees C, 4h) treated immune sera. This suggests that HoGG-induced, non-IgE-mediated thrombocytopenia in anaphylaxis involves sequestration and activation of platelets. The sequestion in lungs occurs within 2 min and can be inhibited by high dose heparin or Cobra Venom factor. The activation of platelets involves platelet activation factor, and fibrinogen receptor.

Topics: Amino Acid Sequence; Anaphylaxis; Animals; Blood Platelets; Elapid Venoms; gamma-Globulins; Heparin; Horses; Leukocytosis; Leukopenia; Liver; Lung; Mice; Mice, Inbred BALB C; Molecular Sequence Data; Peptides; Platelet Activation; Platelet Aggregation Inhibitors; Platelet Count; Thrombocytopenia