Trypsin as an inducer of platelet aggregation in an in vitro experiment and its putative mechanisms

Introduction. Serine proteases are the most numerous catalytic type of proteolytic enzymes and perform a variety of functions in the body. They participate in digestion, act as blood clotting factors, are components of complement and the kallikrein-kinin system, among others. Trypsin is the most studied serine protease. It is known that in certain pathological processes and conditions, such as pancreatitis and pancreatic necrosis, trypsin enters the systemic circulation. This can lead to the development of thrombosis and thromboembolism, but the mechanisms underlying these disorders remain poorly understood. One possible mechanism may be trypsin-mediated platelet activation followed by aggregation.

Aim. To investigate the ability of trypsin to induce platelet aggregation in vitro. Methods. Experiments were conducted on platelet-rich plasma obtained from 22 relatively healthy volunteers. Platelet aggregation by trypsin at final concentrations of 0.5, 1, 2.5, 5, and 10 μM was studied using optical aggregometry. Trypsin-induced platelet aggregation was then recorded in prothrombin-deficient plasma.

Results. Trypsin is capable of inducing platelet aggregation in vitro. The minimal effect was observed with the addition of 2.5 μM. Addition of 5 and 10 μM trypsin to platelet plasma induced pronounced and irreversible platelet aggregation. Trypsin-induced aggregation occurs in both heparinized plasma and plasma deficient in prothrombin complex factors.

Conclusion. The study revealed proaggregatory effects of trypsin that are thrombin-independent and can occur without its participation.

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