title: Individual heterogeneity in platelet response to lysophosphatidic acid: evidence for a novel inhibitory pathway.
abstract: OBJECTIVE
  The bioactive lipid lysophosphatidic acid (LPA) stimulates platelet actin reorganization, adhesion, shape change, and aggregation. LPA is present in blood and exposure or release of LPA after atherosclerotic plaque rupture has been proposed to trigger platelet thrombus formation.
  
  
  RESULTS
  In this report, we characterize heterogeneity in LPA responses among individuals. Platelets isolated from approximately 20% of healthy donors consistently failed to aggregate in response to LPA. Our studies indicate that, rather than lacking stimulatory pathways, platelets from "nonresponsive" donors respond to LPA by triggering inhibitory pathway(s) to block platelet aggregation. Consistent with this observation, LPA-induced aggregation could be partially restored to "nonresponsive" platelets by pharmacological inhibition of cAMP generation. LPA "nonresponsiveness" may be related to heightened platelet expression of LPA receptor 4 and PPARgamma. Among 70 patients with stable coronary artery disease (CAD), only 1 (1.4%) was identified as an LPA nonresponder. Moreover, in 33 patients presenting for diagnostic catheterization, CAD was identified as having a bivariate association with platelet LPA responder/nonresponder status.
  
  
  CONCLUSIONS
  Platelet LPA signaling may involve stimulatory and inhibitory pathways, with the inhibitory pathway predominating in approximately 20% of individuals. Diseases such as CAD that affect platelet reactivity may attenuate this inhibitory pathway in platelets.
authors.affiliation: Division of Cardiovascular Medicine, The Gill Heart Institute, University of Kentucky, Lexington, KY 40536, USA.
authors.forename: Zehra
authors.initials: Z
authors.lastname: Pamuklar
authors.forename: Jin Sun
authors.initials: JS
authors.lastname: Lee
authors.forename: Hsin-Yuan
authors.initials: HY
authors.lastname: Cheng
authors.forename: Manikandan
authors.initials: M
authors.lastname: Panchatcharam
authors.forename: Steve
authors.initials: S
authors.lastname: Steinhubl
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Morris
authors.forename: Richard
authors.initials: R
authors.lastname: Charnigo
authors.forename: Susan S
authors.initials: SS
authors.lastname: Smyth
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001792:Blood Platelets / Q000166:cytology / Q000187:drug effects*; D003327:Coronary Disease / Q000097:blood* / Q000235:genetics / Q000503:physiopathology; D006801:Humans; D008246:Lysophospholipids / Q000494:pharmacology*; D008875:Middle Aged; D015539:Platelet Activation / Q000187:drug effects* / Q000502:physiology; D010974:Platelet Aggregation / Q000187:drug effects / Q000502:physiology; D016133:Polymerase Chain Reaction; D049368:Receptors, Lysophosphatidic Acid / Q000378:metabolism; D012016:Reference Values; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012737:Sex Factors; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology
chemical_list: D008246:Lysophospholipids; D049368:Receptors, Lysophosphatidic Acid; C032881:lysophosphatidic acid