title: Inhibition of glutamate receptors reduces the homocysteine-induced whole blood platelet aggregation but does not affect superoxide anion generation or platelet membrane fluidization.
abstract: Homocysteine (Hcy) is an excitotoxic amino acid. It is potentially possible to prevent Hcy-induced toxicity, including haemostatic impairments, by antagonizing glutaminergic receptors. Using impedance aggregometry with arachidonate and collagen as platelet agonists, we tested whether the blockade of platelet NMDA (N-methyl-D-aspartate), AMPA (α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid) and kainate receptors with their inhibitors: MK-801 (dizocilpine hydrogen maleate, [5R,10S]-[+]-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine), CNQX (7-nitro-2,3-dioxo-1,4-dihydroquinoxaline-6-carbonitrile) and UBP-302 (2-{[3-[(2S)-2-amino-2-carboxyethyl]-2,6-dioxo-3,6-dihydropyrimidin 1(2H)-yl]methyl}benzoic acid) may hamper Hcy-dependent platelet aggregation. All the tested compounds significantly inhibited Hcy-augmented aggregation of blood platelets stimulated either with arachidonate or collagen. Hcy stimulated the generation of superoxide anion in whole blood samples in a concentration-dependent manner; however, this process appeared as independent on ionotropic glutamate receptors, as well as on NADPH oxidase and protein kinase C, and was not apparently associated with the extent of either arachidonate- or collagen-dependent platelet aggregation. Moreover, Hcy acted as a significant fluidizer of surface (more hydrophilic) and inner (more hydrophobic) regions of platelet membrane lipid bilayer, when used at the concentration range from 10 to 50 µmol/l. However, this effect was independent on the Hcy action through glutamate ionotropic receptors, since there was no effects of MK-801, CNQX or UBP-302 on Hcy-mediated membrane fluidization. In conclusion, Hcy-induced changes in whole blood platelet aggregation are mediated through the ionotopic excitotoxic receptors, although the detailed mechanisms underlying such interactions remain to be elucidated.
authors: a Department of Haemostatic Disorders, Chair of Biomedical Sciences , Medical University of Lodz , Lodz , Poland.
authors: Kamil
authors: K
authors: Karolczak
authors: b Department of Medical Biophysics, Faculty of Biology and Environmental Protection , University of Lodz , Lodz , Poland.
authors: Anna
authors: A
authors: Pieniazek
authors: a Department of Haemostatic Disorders, Chair of Biomedical Sciences , Medical University of Lodz , Lodz , Poland.
authors: Cezary
authors: C
authors: Watala
mesh_terms: D000328:Adult; D016718:Arachidonic Acid / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism*; D003094:Collagen / Q000378:metabolism; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D006710:Homocysteine / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects*; D010084:Oxidation-Reduction / Q000187:drug effects; D010974:Platelet Aggregation / Q000187:drug effects*; D017382:Reactive Oxygen Species / Q000378:metabolism; D017470:Receptors, Glutamate / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*; D055815:Young Adult
chemical_list: D018691:Excitatory Amino Acid Antagonists; D017382:Reactive Oxygen Species; D017470:Receptors, Glutamate; D006710:Homocysteine; D013481:Superoxides; D016718:Arachidonic Acid; D003094:Collagen
keywords: Excitotoxicity; glutamate receptors; homocysteine; platelet aggregation