title: Modulation of ADP-induced platelet activation by aspirin and pravastatin: role of lectin-like oxidized low-density lipoprotein receptor-1, nitric oxide, oxidative stress, and inside-out integrin signaling.
abstract: Lectin-like oxidized low-density lipoprotein (LDL) receptor-1 (LOX-1), a receptor for oxidized-LDL, is up-regulated in activated endothelial cells, and it plays a role in atherothrombosis. However, its role in platelet aggregation is unclear. Both aspirin and HMG CoA reductase inhibitors (statins) reduce LOX-1 expression in endothelial cells. In this study, we investigated the effect of aspirin and pravastatin on LOX-1 expression on plate-lets. After ADP stimulation, mean fluorescence intensity of LOX-1 expression on platelets increased 1.5- to 2.0-fold. Blocking LOX-1 inhibited ADP-induced platelet aggregation in a concentration- and time-dependent manner. We also established that LOX-1 is important for ADP-stimulated inside-out activation of platelet alpha(IIb)beta(3) and alpha(2)beta(1) integrins (fibrinogen receptors). The specificity of this interaction was determined by arginine-glycine-aspartate-peptide inhibition. Furthermore, we found that LOX-1 inhibition of integrin activation is mediated by inhibition of protein kinase C activity. In other experiments, treatment with aspirin (1-10 mM) and pravastatin (1-5 microM) reduced platelet LOX-1 expression, with a synergistic effect of the combination of aspirin and pravastatin. Aspirin and pravastatin both reduced reactive oxygen species (ROS) released by activated platelets measured as malonyldialdehyde (MDA) release and nitrate/nitrite ratio. Aspirin and pravastatin also enhanced nitric oxide (NO) release measured as nitrite/nitrite + nitrate (NOx) ratio in platelet supernates. Small concentrations of aspirin and pravastatin had a synergistic effect on the inhibition of MDA release and enhancement of nitrite/NOx. Thus, LOX-1 is important for ADP-mediated platelet integrin activation, possibly through protein kinase C activation. Furthermore, aspirin and pravastatin inhibit LOX-1 expression on platelets in part by favorably affecting ROS and NO release from activated platelets.
authors.affiliation: Division of Cardiovascular Medicine, University of Arkansas for Medical Sciences and Central Arkansas Veterans Healthcare System, Little Rock, AR 72205-7199, USA.
authors.forename: Muhammad R
authors.initials: MR
authors.lastname: Marwali
authors.forename: Chang-Ping
authors.initials: CP
authors.lastname: Hu
authors.forename: Bhavna
authors.initials: B
authors.lastname: Mohandas
authors.forename: Abhijit
authors.initials: A
authors.lastname: Dandapat
authors.forename: Prabhakar
authors.initials: P
authors.lastname: Deonikar
authors.forename: Jiawei
authors.initials: J
authors.lastname: Chen
authors.forename: Ian
authors.initials: I
authors.lastname: Cawich
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Sawamura
authors.forename: Mahendra
authors.initials: M
authors.lastname: Kavdia
authors.forename: Jawahar L
authors.initials: JL
authors.lastname: Mehta
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology*; D001241:Aspirin / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D004359:Drug Therapy, Combination; D005340:Fibrinogen / Q000378:metabolism; D006801:Humans; D038982:Integrin alpha2beta1 / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D015539:Platelet Activation / Q000187:drug effects*; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000187:drug effects / Q000378:metabolism; D017035:Pravastatin / Q000494:pharmacology*; D051127:Scavenger Receptors, Class E / Q000032:analysis / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D038982:Integrin alpha2beta1; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D051127:Scavenger Receptors, Class E; D009569:Nitric Oxide; D000244:Adenosine Diphosphate; D005340:Fibrinogen; D017035:Pravastatin; D001241:Aspirin