p38 MAPK Inhibition Prevents TACE-Mediated Receptor Shedding and Improves the Hemostatic Function of Stored Platelets.

Platelet transfusion is a lifesaving procedure widely used during surgery and chemotherapy. During storage platelets undergo several modifications that reduce their postransfusion survival and functionality. One important feature of this platelet storage lesion (PSL) is the shedding of surface glycoproteins such as GPIbα and GPV. We have recently demonstaretd that metalloproteinase inhibitors prevent storage-induced shedding of adhesion receptors, resulting in markedly improved postransfusion recovery and hemostatic function of platelets in mice. We now demonstrate that TNF-alpha converting enzyme (TACE/ADAM17) mediates receptor shedding from platelet stored for 18 hours at 37ºC or 22ºC. Using pharmacological inhibitors, we show that TACE -dependent shedding of GPIbα and GPV from both mouse and human platelets during storage required p38 MAP kinase signaling. In contrast, protein kinase C, Erk MAPK, and caspases were not involved. Inhibition of p38 MAPK during the storage of mouse platelets also markedly improved their posttransfusion recovery and hemostatic function in vivo. Moreover, p38 MAPK inhibition during storage of human platelets improved their adhesion to collagen under flow. Inhibition of p38 MAPK also prevented TACE-dependent shedding of GPIbα from platelets undergoing mitochondrial injury, a model for PSL. Phosphorylation of p38 MAPK was observed after platelet storage and mitochondrial injury. In summary, our data suggest that inhibition of p38 MAPK or TACE during storage may significantly improve the quality of stored platelets.