Endothelial protein C receptor-dependent inhibition of human eosinophil chemotaxis by protein C.

Abstract

Eosinophil infiltration is a characteristic feature of allergic inflammation. Allergic responses are associated with local activation of the coagulation pathway and accumulation of fibrin. We tested whether protein C and activated protein C (APC), which are endogenous anti-inflammatory coagulation inhibitors, affect eosinophil function. Eosinophils were from venous blood of healthy donors. Cell migration and apoptosis were studied by using micropore filter assays and fluorometry, respectively. Receptor expression was investigated by means of RT-PCR and SDS-PAGE of immunoprecipitated protein. Protein C and APC had no significant chemotactic effects on eosinophils. Eosinophils pretreated with protein C or APC showed significantly reduced migration toward chemoattractants. No effect of either protein C preparation was seen in eosinophil apoptosis assays. The inhibiting effect on migration was reversed by an antibody against the endothelial protein C receptor (EPCR). Synthesis of EPCR by eosinophils is suggested by demonstration of receptor mRNA expression and detection of metabolically labeled receptor protein. Data suggest that an EPCR is expressed by eosinophils whose activation with protein C or APC arrests directed migration. Protein C-affected eosinophil chemotaxis is a novel thrombin-independent component of the protein C pathway.