Size of platelet-leukocyte aggregates in patients with various degree of coronary atherosclerosis

An increased content of platelet-leukocyte aggregates suggests an elevated thrombogenic and inflammatory activity of peripheral blood cells. The aim of this study was to investigate the ratios and properties of platelet-monocyte and platelet-lymphocyte aggregates in patients with coronary atherosclerosis. The study included 19 patients with coronary artery disease and coronary atherosclerosis (15 men; 4 women; their mean age was 59.0 (55.0; 69.0) years old. The comparison group consisted of eight patients at high cardiovascular risk without coronary atherosclerosis. The atherosclerosis severity was assessed by coronary angiography and Gensini Score of ≥ 42.5 points. Platelet-leukocyte aggregates were analyzed by imaging flow cytometry. We assessed the percentage of platelet-monocyte and platelet-lymphocyte aggregates; the percentage of P-selectin (CD62P)⁺ aggregates; the number of platelets aggregated with each individual leukocyte (either monocyte or lymphocyte). In patients with coronary atherosclerosis, a significantly lower number of monocytes formed small aggregates of 1 monocyte and 1 platelet as compared to patients without atherosclerosis (Gensini Score > 0), i.e., 78.8% (68.1; 86.2) versus 84.7% (83.8; 87.1) (p = 0.039). At the same time, in patients with more severe atherosclerosis (Gensini Score ≥ 42.5), the percentage of lymphocyte aggregates with more than 3 platelets tended to increase to 0.6% (0.3; 1.6) compared to patients with Gensini Score < 42.5 with 0.1% (0; 0.8) (p = 0.075). The proportion of large platelet-lymphocyte aggregates (with 3 or more platelets) directly correlated with Gensini Score, IL-1b concentration, systemic inflammatory indices, as well as with ratios of triglycerides/glucose and triglycerides/high-density lipoprotein cholesterol (insulin resistance indices), and showed inverse correlation with high-density lipoprotein cholesterol concentration. The percentage of small aggregates (1 lymphocyte with 1 platelet) inversely correlated with severity of coronary atherosclerosis, IL-1b concentration, and insulin resistance index. Thus, the larger size of heterotypic aggregates but not the increased number of platelet-leukocyte aggregates seems to be a distinguishing feature between patients with coronary atherosclerosis. Formation of large aggregates with 3 or more platelets is an unfavorable sign which is also associated with intensity of systemic inflammation and metabolic imbalance.

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