Inflammatory vs. Thrombotic States of Platelets: A Mini-review with a Focus on Functional Dichotomy

In addition to roles in hemostasis and thrombosis, the role of platelets in inflammation and immunity have been the focus of recent studies.Both proinflammatory and prothrombotic roles of platelets are considered important in the pathophysiology of sepsis as well as in the protection from severe infections.The facilitation of prothrombotic activity by the proinflammatory activity of platelets has been shown in many studies.Nonetheless, some studies have highlighted the dichotomy of platelet functionality.Within a limited time period and space, only proinflammatory or prothrombotic functionality is often present.In some cases, the activation of the proinflammatory function of platelets is not accompanied by prothrombotic activity.Recent analyses of pattern recognition receptors such as toll-like receptors (TLRs) in platelets motivate us to consider how pathways are activated in innate immunity compared with pathways for thrombogenesis and hemostasis.In this article, we mainly discuss recent studies showing the functional dichotomy of platelets and, in particular, the conditions and possible mechanisms that activate platelets in a biased manner, rather than the concordance between prothrombotic and proinflammatory pathways in platelets.