Dose effect of shear stress on platelet complement activation in a cone and plate shearing device

Altered blood shear stress is one of the primary risk factors that can induce platelet activation, thrombosis, atherosclerosis, and many other cardiovascular diseases. Complement activation, an important contributor in inflammation, has also been reported to be related to blood flow-induced platelet activation. In this study, the dose effect of shear stress (magnitude and shear exposure time) on platelet surface complement activation was investigated using a dynamic cone and plate shearing device. Washed platelets were exposed to uniformly distributed shear stresses at 2.4 or 9 dyne/cm ² for 30 min. Timed samples at 0, 10, 20, and 30 min were taken and assayed for complement activation (C4d and C5b-9 deposition) using a solid-phase ELISA approach. In parallel, platelet activation was examined using flow cytometry for CD62P expression, and a modified prothrombinase assay for thrombin generation. Results indicated that activated platelets support complement activation to completion with the production of membrane attack complex C5b-9. The generation of complement activation products, C4d and C5b-9, increased significantly as shear stress magnitude and shear exposure time increased, correlating with the enhanced platelet activation levels. Therefore, platelet activation and its associated complement activation may interact and promote cardiovascular disease development under pathological shear conditions.