The impact of enzymatic treatments on red blood cell adhesion to the endothelium in plasma like suspensions

摘要

Red blood cells (RBC) experience many physico-chemical modifications on the membrane in physiological events as well as pathological complications, for example, the sialic acid loss on senescent RBC membrane. Abnormal RBC adhesion to the endothelium has been linked to the pathophysiology of various diseases associated with vascular disorders such as sickle cell anemia or diabetes mellilus. However, the correlation is still unclear between RBC membrane changes and abnormal RBC-EC adhesion, especially in plasma or plasma like suspensions. Multiple specific and non-specific forces govern cell-cell and cell-surface interactions. One nonspecific force that has only been found limited attention in cell adhesion is the depletion interaction, which occurs as a result of a lower localized protein or polymer concentration near the cell surface compared to the suspending medium (i.e., relative depletion near the cell surface). This exclusion of macromole-cules near the cell surface leads to an osmotic gradient, depletion interaction, and attractive forces. In order to elucidate the impact of physicochemical properties of the RBC membrane on RBC-EC adhesion induced by macromolecular depletion, we used various proteolytic enzymes to specifically cleave different components from RBC membrane. The dynamics of RBC-EC adhesion were then recorded using a flow chamber system and a stepwise shear profile. Our results indicate a dramatic increase of RBC adhesion to EC in the presence of high molecular mass (>40KDa) dextran with decreasing surface charge after sialic acid removal by neuraminidase. On the contrary, only minor alteration has been observed in RBC-EC adhesion and surface charge for the enzymatic cleavage by trypsin, α-chymotrypsin and pronase. In conclusion, this study demonstrates that polymer depletion can enhance RBC-EC adhesion under low shear stress and that it promotes adhesion of pathologic RBC. It thus provides new insight into potential mechanisms for enhanced RBC-EC adhesion and disturbed in vivo blood flow.