text: Reticulated platelets and uninhibited COX-1 and COX-2 decrease the antiplatelet effects of aspirin.
  BACKGROUND: The mechanisms for the variability in antiplatelet effects of aspirin are unclear. Immature (reticulated) platelets may modulate the antiplatelet effects of aspirin through uninhibited cyclooxygenase (COX)-1 and COX-2. OBJECTIVES: To evaluate the role of reticulated platelets in the antiplatelet effects of aspirin. METHODS: Sixty healthy volunteers had platelet studies performed before and 24 h after a single 325-mg dose of aspirin. Platelet studies included light transmission aggregometry; P-selectin and integrin alpha(IIb)beta(3) expression, and serum thromboxane B(2) (TxB(2)) levels. Reticulated platelets and platelet COX-2 expression were measured using flow cytometry. RESULTS: Subjects were divided into tertiles based on the percentage of reticulated platelets in whole blood. Baseline platelet aggregation to 1 microg mL(-1) collagen, and postaspirin aggregations to 5 microm and 20 microm ADP and collagen, were greater in the upper than in the lower tertile of reticulated platelets. Stimulated P-selectin and integrin alpha(IIb)beta(3) expression were also higher in the upper tertile both before and after aspirin. Platelet COX-2 expression was detected in 12 +/- 7% (n = 10) of platelets in the upper tertile, and in 7 +/- 3% (n = 12) of platelets in the lower two tertiles (P = 0.03). Postaspirin serum TxB(2) levels were higher in the upper (5.5 +/- 4 ng mL(-1)) than in the lower tertile (3.2 +/- 2.5 ng mL(-1), P = 0.03), and decreased even further with ex vivo additional COX-1 and COX-2 inhibition. The incidence of aspirin resistance (>or= 70% platelet aggregation to 5 microm ADP) was significantly higher in the upper tertile (45%) than in the lower tertile (5%, P < 0.0001). CONCLUSIONS: Reticulated platelets are associated with diminished antiplatelet effects of aspirin and increased aspirin resistance, possibly because of increased reactivity, and uninhibited COX-1 and COX-2 activity.
entities.id: T10 T11 T12 T13 T14 T15 T16 T17 T18 T19 T1 T20 T21 T22 T23 T24 T25 T26 T27 T28 T2 T3 T4 T5 T6 T7 T8 T9
entities.type: CHEMICAL CHEMICAL GENE-Y GENE-N GENE-Y GENE-Y GENE-Y GENE-Y GENE-Y GENE-N CHEMICAL GENE-Y GENE-Y GENE-Y GENE-N GENE-Y GENE-N GENE-N GENE-Y GENE-Y CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL CHEMICAL
entities.text: ADP aspirin P-selectin integrin alpha(IIb)beta(3) COX-2 COX-1 COX-2 COX-1 COX-2 cyclooxygenase aspirin (COX)-1 COX-2 P-selectin integrin alpha(IIb)beta(3) COX-2 collagen collagen COX-1 COX-2 aspirin aspirin aspirin aspirin aspirin thromboxane B(2) TxB(2) aspirin