Platelet activation patterns in platelet size sub-populations: differential responses to aspirin in vitro

Abstract

Circulating platelets are heterogeneous in size and structure. Whether this translates into differences in platelet function and efficacy of antiplatelet therapy is unclear. Hence, we decided to investigate the activation patterns among different platelet populations differentiated by size, and to compare the inhibitory effects of aspirin in these populations. Circulating platelets from 9 healthy volunteers were separated by size and stratified into the largest and smallest quintiles. Platelets were stimulated with 75 μM arachidonic acid (AA), 10 μM ADP or 25 μM TRAP. Alpha-granule protein secretion and expression (P-selectin, VWF, fibrinogen), surface-protein activation (activated integrin αIIbβ3) were assessed. Platelet thromboxane B(2) (TxB(2)) synthesis following AA stimulation was measured in vitro before and after incubation with 265 μM aspirin. Reticulated (juvenile) platelets were assessed using thiazole orange staining. A greater number of large platelets in the largest quintile were reticulated compared with the smallest quintile (6.1 ± 2.8% vs. 1.2 ± 1.5% respectively, p < 0.001). Larger platelets also synthesized more TxB(2) than small platelets both before (1348 ± 276 pg/mL vs. 1023 ± 214 pg/mL, respectively, p = 0.01) and after aspirin (1029 ± 190 pg/mL vs. 851 ± 159 pg/mL, respectively, p = 0.03). After stimulation with each agonist, a greater proportion of large platelets bound fibrinogen, VWF, P-selectin and activated integrin αIIbβ3 than small platelets both in the presence and in the absence of in vitro aspirin. In an in vitro setting, large platelets appear to be more active than small platelets and continue to be more active even after in vitro aspirin. Platelets exhibit heterogeneity in size and structure. Whether this translates into platelet function and efficacy of antiplatelet therapy is unclear. We evaluated platelet functional properties and the effects of aspirin on separated platelet subpopulations in an in vitro setting. Platelets were sorted into the largest and smallest size quintiles using flow cytometry forward scatter. Alpha-granule protein release, dense granule content, surface protein activation and thromboxane synthesis were significantly greater in large platelets compared with small platelets, before and after stimulation with arachidonic acid, ADP and TRAP. Even after incubation with aspirin, large platelets continued to be more active than small platelets. In conclusion, large platelets are more active than small platelets and aspirin fails to eliminate these differential activation properties.

Elevated Serum Neutrophil to Lymphocyte and Platelet to Lymphocyte Ratios Could be Useful in Lung Cancer Diagnosis

“…According to these pathways, PLR and MPV, which can be easily evaluated by hematological analyzers, were used in the current study both to determine platelet functions and activation. As previously mentioned, larger platelets are more metabolically and enzymatically active than smaller platelets (Mangalpally et al, 2010) and strong evidence indicates that MPV is an important biological variable and that larger platelets are more metabolically and enzymatically active than smaller platelets (Dvorak et al, 1995). Both MPV and PLR also alleviate the effect of many common conditions that can alter the intravascular water component of blood, and hence the platelet count.…”

“…It shows the average size of platelets and reflects the platelet production rate and stimulation (Kai et al, 2005). Larger platelets are more metabolically and enzymatically active than smaller platelets (Mangalpally et al, 2010). Recently, elevated preoperative or pretreatment NLR, PLR and MPV detected in peripheral blood have been identified in various cancers, including colon cancer, esophageal cancer, gastric cancer ovarian cancer and breast cancer (Walsh et al, 2005;Gwak et al, 2007;Smith et al, 2009;Sharaiha et al, 2011;Thavaramara et al, 2011;Azab et al, 2012;Kilincalp et al 2013).…”

Platelet Turnover and Atherothrombosis

“…Такие тромбоциты со-держат больше адгезивных молекул, больше гранул (поэтому они более плотные и секрети-руют больше биологически активных соедине-ний), синтезируют большие количества тром-боксана А2 и обладают повышенной способ-ностью к агрегации [1]. В более поздних рабо-тах аналогичные данные были получены при выявлении субпопуляций крупных и мелких тромбоцитов с помощью проточной цитофлу-ориметрии [21][22][23].…”

Antiplatelet agents: Is twice a day a better strategy?

“…The population of circulating platelets is not homogeneous [33], immature platelets comprise the youngest component of the circulating platelet pool, and appear to participate most actively in the thrombotic process [34]. They contain measurable amounts of cytosolic messenger ribonucleic acid (mRNA) that is translationally active [35].…”