Coated‐platelet levels are influenced by smoking, aspirin, and selective serotonin reuptake inhibitors

Coated-platelets are a subpopulation of platelets observed upon dual-agonist stimulation with collagen and thrombin [1]. Unlike single-agonist activated platelets, coated-platelets support a robust prothrombinase activity and express high levels of several procoagulant proteins on their surface including factor V, fibrinogen, fibronectin, thrombospondin and von Willebrand factor [1]. Procoagulant proteins on coated-platelets are conjugated with serotonin via a transglutaminase-mediated reaction, and fibrinogen and thrombospondin bound to the platelet surface provide binding sites to stabilize serotonin-conjugated proteins [1]. The ability to produce coated-platelets varies dramatically among normal blood donors, ranging from 15% to 55% [1], although the basis for this wide variability is unknown. Prompted by the procoagulant potential of coated-platelets [1] and our previous unpublished observations, we have examined the effect of cigarette smoking,HMG-CoA reductase inhibitors (statins), selective serotonin reuptake inhibitors (SSRI) and antiplatelet agents on coated-platelet production in adults. Seventy subjects from the University of Oklahoma Health Sciences Center and Oklahoma City Veterans Administration Medical Center were enrolled in the study. The study was approved by the Institutional Review Board, and informed consent was obtained for all study subjects. The study population consisted of hospital volunteers, visitors and employees. Exclusion criteria included: concurrent diagnosis of dementia, stroke, transient ischemic attack (TIA), acute coronary syndrome (ACS), active infectious disease, bleeding diathesis or previous history of stroke, TIA or ACS within one year of enrollment. Smoking status, medications, gender and age were recorded at the time of enrollment. All individuals on antiplatelet medication reported daily use of aspirin ranging between 81.5 and 325 mg. Race was recorded through selfidentification for all study subjects. The subjects mean age was 64.8 ± 8.15 years (mean ± SD). The clinical characteristics of this study population including demographics, smoking status and use of aspirin, SSRI and statin medications are listed in Table 1. Blood was drawn, platelet-rich plasma was prepared, and coated-platelets were assayed as described [1,2]. Briefly, platelets were activated concurrently with thrombin and convulxin, a ligand for the collagen receptor glycoprotein VI, and the coated-platelet population was identified by its ability to bind biotinylated-fibrinogen [2]. Analysis was performed by flow cytometry, and coated-platelets were expressed as a percentage of all platelets [2]. Statistical analyses were performed using SAS (SAS System forWindows, version 8.2, SAS Institute Inc., Cary, NC, USA). Multiple-way ANOVAs were conducted to evaluate the effect of smoking, gender, race and use of aspirin, SSRIs and statins on coated-platelet synthesis. Regression analyses were used to evaluate relationships between coated-platelets levels and other independent variables (e.g. age). A P-value of < 0.05 was considered to be statistically significant. The subjects coated-platelet levels were 31.6% ± 13.2% (mean ± SD), with a range from 6.7% to 58.9%, consistent with previous published findings [1]. A six-way ANOVA was conducted to evaluate the effects of gender, race, smoking status, aspirin, statins and SSRIs on coated-platelets levels. All main effects and two-way interactions were considered. Nonsignificant interactions were excluded from the final model. Significant main effects were detected for smoking status [F(1, 62) = 6.3, P = 0.015], use of aspirin [F(1, 62) = 5.6, P = 0.022] and use of SSRIs [F(1, 62) = 4.2, P = 0.046]. Specifically, coated-platelet levels were significantly higher in individuals currently smoking when compared to individuals not smoking (32.6% ± 4.1%, n = 14 vs. 23.2% ± 3.1%, n = 56; adjusted mean ± 1SEM). Subjects taking aspirin had significantly lower coated-platelet levels than those not on aspirin (23.8% ± 4.0%, n = 22 vs. 32.0 ± 3.1, n = 48). Individuals using SSRIs had significantly lower coated-platelet levels when compared with persons not taking SSRIs (21.9% ± 5.6%, n = 5 vs. 33.9 ± 2.3, n = 65). The main effects for gender, race and statin use were not statistically significant for coated-platelet synthesis (P-values > 0.19). However, a significant interaction for coated-platelet potential was detected between race and statin use [F(1, 62) = 6.0, P = 0.018]. Specifically, coated-platelet Correspondence: Calin I. Prodan, 711 S.L. Young Blvd, PPOB Suite 215, Oklahoma City, OK 73104, USA. Tel. : +1 405 271 4113; fax: +1 405 271 5723; e-mail: calinprodan@ouhsc.edu