The potential contribution and role of a blood platelets in autoimmune thyroid diseases

Abstract

The blood platelets are multifunctional blood cells which are involved in the initiation of atheroma, endothelial dysfunction, and modulation of inflammatory and immune responses in the pathophysiology of many diseases. Because of their multifaceted pro-inflammatory activity, platelets may be involved in the pathogenesis of autoimmune thyroid diseases (AITDs), such as Hashimoto's thyroiditis and Graves' disease. The aim of this study was to assess the level of activation and response ability of platelets in AITDs. We used the flow cytometry technique and kinetic measurement of aggregation to analyse platelet function immediately after blood collection and to demonstrate their activation in the circulation of patients with AITDs. We noted reorganization of platelet subpopulations (normal platelets, microparticles and aggregates) in AITDs, dependent on the degree of cell activation. We proved the elevated expression of the active form of integrin receptor GPIIb/IIIa, responsible for platelet aggregation, and in the kinetic test we confirmed the increased aggregation of platelets in different intracellular signal pathways (dependent on ADP, collagen, arachidonic acid). Our study demonstrates the high platelet activation level found in AITDs.

Keywords: aggregation; autoimmune thyroid diseases; blood platelets; platelet-derived microparticles.

Figure 1

Cytometry analysis of nonstimulated and agonist‐stimulated platelets (ADP and collagen) in whole blood samples from GD and HT patients vs healthy controls. The data represents the median ± interquartile range Q1‐Q3 (box), and range—minimum and maximum (whisker) for each group. In each sample, 10 000 CD61‐positive objects (platelets) were measured. The subpopulations of platelets were distinguished based on their size and granularity on the forward light scatter (FSC) vs side light scatter (SSC) plots. CD61‐positive objects with FSC higher than 10⁴ were characterized as platelet aggregates (A), with FSC lower than 10^2.3 were characterized as PMPs (B). Expression of the active form of GPIIb/IIIa was determined based on fluorescence of PAC‐1‐FITC monoclonal antibody (C). Statistical analysis was performed using a Mann‐Whitney U test for GD and HT patients vs HC; ^∗ P < 0.01, ^∗∗ P < 0.001

Figure 2

Blood platelet aggregation measured in platelet‐rich‐plasma. The typical curves of platelet aggregation after stimulation of platelets by ADP (A), collagen (B), arachidonic acid (C), were recorded with the optical Chrono‐Log aggregometer. The data are also presented as means ± SD for HT and GD platelets vs HC, when the value of the control was taken as 100%;. ^∗ P < 0.05, ^∗∗ P < 0.005 (by Mann‐Whitney U test)