Effects of irradiation on endothelial cell-polymorphonuclear leukocyte interactions

Prominent early effects of irradiation include neutrophilic vasculitis and interstitial inflammation. To examine the role of the endothelium in these events, bovine aortic endothelial cells (EC) were irradiated (5 Gy) under ambient conditions followed by measurements of neutrophil chemotaxis toward conditioned media and adherence to EC. Neutrophil chemotactic activity increased at 4, 24, and 72 h in both the sham-treated (4.2 +/- 2.5, 15.2 +/- 4.8, and 20.0 +/- 2.7 microns, respectively) and irradiated EC-conditioned media (5.0 +/- 2.1, 18.7 +/- 4.5, and 24.1 +/- 3.4 microns, respectively), and the difference between them was significant at 72 h. The chemoattractant was trypsin sensitive, heat resistant, and chemotactic. It was not present in the EC sonicate. Adherence of neutrophils to EC that were irradiated 4 h earlier (19.3 +/- 4.2%) increased compared with controls (11.1 +/- 2.4%) and was similar to EC pretreated with zymosan-activated serum (22.0 +/- 4.0%), which is a potent inducer of adherence. Thus, following irradiation, bovine aortic EC have greater neutrophil chemotactic activity in their media and are more adherent to polymorphonuclear leukocytes.