title: Effect of cepharanthin and cytochalasin D on platelet internalization of anti-glycoprotein IIb/IIIa antibodies.
abstract: The effects of cepharanthin and cytochalasin D on the internalization of anti-glycoprotein IIb/IIIa antibodies by platelets were investigated in 13 patients with chronic immune thrombocytopenic purpura who had circulating anti-glycoprotein IIb/IIIa autoantibodies. Unfixed platelets were incubated with a monoclonal anti-glycoprotein IIb/IIIa antibody (NNKY1-32) or with platelet-binding IgG from the patients (which contained anti-glycoprotein IIb/IIIa antibodies). Flow cytometry showed that the binding of NNKY1-32 to platelets was markedly decreased after incubation for 120 min compared with incubation for 10 min. This decrease was inhibited by cepharanthin but not by cytochalasin D. Platelet-binding IgG also showed markedly reduced binding after incubation for 120 min compared with 10 min, and this decrease was inhibited by both cepharanthin and cytochalasin D. Cytochalasin D inhibits platelet cytoskeletal activity while cepharanthin does not. Therefore, our results suggest that the internalization of anti-glycoprotein IIb/IIIa antibodies from the plasma of patients with immune thrombocytopenic purpura is related to platelet cytoskeletal reorganization, while the cytoskeleton did not participate in internalization of the monoclonal anti-glycoprotein IIb/IIIa antibody (NNKY1-32). Cepharanthin may be useful for studying the internalization and cycling of glycoprotein IIb/IIIa in human platelets, and it may also be potentially useful for the treatment of immune thrombocytopenic purpura.
authors.affiliation: First Department of Internal Medicine, Kansai Medical University, Osaka, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Nomura
authors.forename: M
authors.initials: M
authors.lastname: Yanabu
authors.forename: T
authors.initials: T
authors.lastname: Miyake
authors.forename: Y
authors.initials: Y
authors.lastname: Miyazaki
authors.forename: T
authors.initials: T
authors.lastname: Kawakatsu
authors.forename: H
authors.initials: H
authors.lastname: Kido
authors.forename: K
authors.initials: K
authors.lastname: Yamaguchi
authors.forename: T
authors.initials: T
authors.lastname: Fukuroi
authors.forename: H
authors.initials: H
authors.lastname: Kagawa
authors.forename: M
authors.initials: M
authors.lastname: Suzuki
mesh_terms: D000470:Alkaloids / Q000494:pharmacology*; D001323:Autoantibodies / Q000097:blood*; D044182:Benzylisoquinolines; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D015638:Cytochalasin D / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D010980:Platelet Membrane Glycoproteins / Q000276:immunology*; D016553:Purpura, Thrombocytopenic, Idiopathic / Q000276:immunology*; D052117:Benzodioxoles
chemical_list: D000470:Alkaloids; D001323:Autoantibodies; D044182:Benzylisoquinolines; D015638:Cytochalasin D; D010980:Platelet Membrane Glycoproteins; C006947:cepharanthine; D052117:Benzodioxoles