title: Allicin and disulfiram enhance platelet integrin alphaIIbbeta3-fibrinogen binding.
abstract: BACKGROUND
  Activation of the platelet receptor alphaIIbbeta3 (glycoprotein IIbIIIa) involves a change in the disulfide bonds pattern in the extra-cellular domain of the receptor. The disulfide-bond reducing agent, dithiothreitol (DTT), can increase integrin activity, and point mutations of specific cysteine residues of the integrin can cause its lockage at the high affinity state. The present study is aimed to support the hypothesis that prevention of specific alphaIIbbeta3 intra-molecular disulfide bond formation increases receptor-ligand binding activity.
  
  
  METHODS
  Platelet aggregation was induced by collagen or ADP and epinephrine. Integrin alphaIIbbeta3-fibrinogen binding was evaluated on prostaglandins E(1) (PGE(1))-treated washed platelets or baby hamster kidney (BHK) cells expressing human alphaIIbbeta3. Integrin was directly activated by an anti-ligand induced binding site (LIBS) PT25-2 antibody. The effect of sulfhydryl-reactive agents, such as allicin, glutathione, dithiobis nitrobenzoic acid (DTNB) and disulfiram, was tested on alphaIIbbeta3 activity.
  
  
  RESULTS
  Allicin (40 microM) completely inhibited washed platelets agonist-induced aggregation. Both allicin and disulfiram (40 microM) inhibited alphaIIbbeta3-fibrinogen binding and P-selectin expression in washed platelets. However, there was an increase in alphaIIbbeta3-fibrinogen binding but not P-selectin expression in PGE(1)-treated washed platelets activated by PT25-2 antibody. At a high concentration (400 microM) both inhibited alphaIIbbeta3-fibrinogen binding. Similarly, in BHK cells expressing alphaIIbbeta3 activated by PT25-2 antibody, allicin at a low concentration increased alphaIIbbeta3 activity.
  
  
  CONCLUSIONS
  Allicin and disulfiram inhibit agonist-induced washed platelet activation probably via inhibition of platelet signaling, but enhance PT25-2 antibody-induced alphaIIbbeta3 integrin activity most likely by preventing reformation of disulfide bridges thereby stabilizing the active conformation of the integrin.
authors.affiliation: Goldschleger Eye Research Institute and Department of Human Molecular Genetics and Biochemistry, Sackler Faculty of Medicine, Tel Aviv University, Israel.
authors.forename: Yoav
authors.initials: Y
authors.lastname: Manaster
authors.forename: Boris
authors.initials: B
authors.lastname: Shenkman
authors.forename: Nurit
authors.initials: N
authors.lastname: Rosenberg
authors.forename: Naphtali
authors.initials: N
authors.lastname: Savion
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D002460:Cell Line; D006224:Cricetinae; D004220:Disulfides; D004221:Disulfiram / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005340:Fibrinogen / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006801:Humans; D008024:Ligands; D019007:P-Selectin / Q000096:biosynthesis / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D013441:Sulfinic Acids / Q000494:pharmacology*
chemical_list: D004220:Disulfides; D008024:Ligands; D019007:P-Selectin; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D013441:Sulfinic Acids; C006452:allicin; D005340:Fibrinogen; D004221:Disulfiram