Background: The production of reactive oxygen and nitrogen species contributes to the development of vascular injury and inflammation. The present study was focused on neutrophil adhesion to monolayers of primary endothelial cells in the presence of NO donors, a superoxide anion producing system (hypoxanthine-xanthine oxidase, HX-XO) and peroxynitrite under static conditions.
Material/methods: Phase contrast and scanning electron microscopy was used to study endothelial monolayer integrity. Neutrophil attachment to surfaces was quantified by myeloperoxidase assay in parallel with microscopic assessment of cell count.
Results: In the presence of HX-XO, the endothelial monolayer was destroyed and neutrophil adhesion to the endothelium and exposed subendothelial matrix was drastically increased. Neutrophil attachment was mainly CD18 integrins-mediated and depended on P-selectin, but not on the endothelial adhesion molecules E-selectin, ICAM-1 or PECAM-1. The endothelial monolayer damage caused by HX-XO was a result of superoxide-induced oxidative destruction, since tocopherol and superoxide dismutase protected the monolayer and reduced the number of attached PMNs. Together with the superoxide-producing system, nitric oxide donor diethylamine NONOate also protected the endothelium monolayer from disruption and reduced the number of PMNs attached. Additional exogenous peroxynitrite slightly enhanced neutrophil adhesion to endothelial cells, without monolayer injury.
Conclusions: Superoxide anions induced endothelium injury and neutrophil attachment, but nitric oxide played a protective role.