Thromboinflammatory Functions of Platelets in Ischemia-Reperfusion Injury and Its Dysregulation in Diabetes.

Ischemia-reperfusion (IR) injury is a common complication of a variety of cardiovascular diseases, including ischemic stroke and myocardial infarction (MI). While timely re-establishment of blood flow in a thrombosed artery is the primary goal of acute therapy in these diseases, paradoxically, reperfusion of ischemic tissue can cause widespread microvascular dysfunction that significantly exacerbates organ damage. Reperfusion injury is associated with activation of the humoral and cellular components of the hemostatic and innate immune systems and also with excessive reactive oxygen species production, endothelial dysfunction, thrombosis, and inflammation. Platelets are critical mediators of thromboinflammation during reperfusion injury and a hyperactive platelet phenotype may contribute to an exaggerated IR injury response. This is particularly relevant to diabetes which is characteristically associated with hyperactive platelets, significantly worse IR injury, increased organ damage, and increased risk of death. However, the mechanisms underlying vulnerability to IR injury in diabetic individuals is not well defined, nor the role of "diabetic platelets" in this process. This review summarizes recent progress in understanding the role of platelets in promoting microvascular dysfunction and inflammation in the context of IR injury. Furthermore, the authors discuss aspects of the thromboinflammatory function of platelets that are dysregulated in diabetes. They conclude that diabetes likely enhances the capacity of platelets to mediate microvascular thrombosis and inflammation during IR injury, which has potentially important implications for the future design of antiplatelet agents that can reduce microvascular dysfunction and inflammation.

Neutrophils--a key component of ischemia-reperfusion injury.

Ischemia-reperfusion injury (IRI) is a common occurrence following myocardial infarction, transplantation, stroke, and trauma that can lead to multiple organ failure, which remains the foremost cause of death in critically ill patients. Current therapeutic strategies for IRI are mainly palliative, and there is an urgent requirement for a therapeutic that could prevent or reverse tissue damage caused by IRI. Neutrophils are the primary responders following ischemia and reperfusion and represent important components in the protracted inflammatory response and severity associated with IRI. Experimental studies demonstrate neutrophil infiltration at the site of ischemia and show that inducing neutropenia can protect organs from IRI. In this review, we highlight the mechanisms involved in neutrophil recruitment, activation, and adherence and how this contributes to disease severity in IRI. Inhibiting neutrophil mobilization, tissue recruitment, and ultimately neutrophil-associated activation of local and systemic inflammatory responses may have therapeutic potential in the amelioration of local and remote tissue damage following IRI.