Effect of streptavidin–biotin on endothelial vasoregulation and leukocyte adhesion

The current study examines whether the adhesion promoting arginine–glycine–aspartate–streptavidin mutant (RGD–SA) also affects two important endothelial cell (EC) functions in vitro: vasoregulation and leukocyte adhesion. EC adherent to surfaces via fibronectin (Fn) or Fn plus RGD–SA were subjected to laminar shear flow and media samples were collected over a period of 4 h to measure the concentration of nitric oxide (NO), prostacyclin (PGI2), and endothelin-1 (ET-1). Western blot analysis was used to quantify the levels of endothelial-derived nitric oxide synthase (eNOS) and cyclooxygenase II (COX II). In a separate set of experiments, fluorescent polymorphonuclear leukocyte (PMN) adhesion to EC was quantified for EC with and without exposure to flow preconditioning. When cell adhesion was supplemented with the SA–biotin system, flow-induced production of NO and PGI2 increased significantly relative to cells adherent on Fn alone. Previous exposure of EC to shear flow also significantly decreased PMN attachment to SA–biotin supplemented EC, but only after 2 h of exposure to shear flow. The observed decrease in PMN–EC adhesion was negated by NG-nitro- -arginine methyl ester ( -NAME), an antagonist of NO synthesis, but not by indomethacin, an inhibitor to PGI2 synthesis, indicating the induced effect of PMN–EC interaction is primarily NO-dependent. Results from this study suggest that the use of SA–biotin to supplement EC adhesion encourages vasodilation and PMN adhesion in vitro under physiological shear-stress conditions. We postulate that the presence of SA–biotin more efficiently transmits the shear-stress signal and amplifies the downstream events including the NO and PGI2 release and leukocyte–EC inhibition. These results may have ramifications for reducing thrombus-induced vascular graft failure.