Expression of ICAM-1 and E-selectin in irradiated cerebral microvasculature

The upregulation of cell adhesion molecules plays an important role in inflammatory response of normal tissue following radiation treatment, and also provides a potential avenue for targeting drugs to select tissues. The detailed time course of the expression of these molecules in vivo has not been well studied. To explore the dynamic consequences of radiation induced intracellular adhesion molecule-1 (ICAM-1) and E-selectin in vivo, a rat cranial window model was established. We coated microspheres with a mAb to ICAM-1 or E-selectin, and tested the adhesion of these microspheres to brain microvasculature following a single dose of 20 Gy radiation. IgG conjugated microspheres were used as negative control. The number of adherent anti-E-selectin microspheres was 6 and 4 times that of IgG microspheres at 3 hr and 6 hr post-irradiation, respectively. The number of adherent anti-ICAM-1 microspheres in irradiated cerebral tissue was 8 and 13 times that of IgG microspheres at 24 hr and 48 hr postirradiation, respectively, and returned to baseline 7 days postirradiation. The data indicate that ICAM-1 is upregulated over a prolonged period whereas E-selectin responds in a very early stage and acts transiently.