Mucosal tolerance to E-selectin provides cell-mediated protection against ischemic brain injury

We have demonstrated that induction of mucosal tolerance to E-selectin, a cytokine-inducible adhesion molecule restricted to activating blood vessels, prevents ischemic and hemorrhagic stroke in spontaneously hypertensive, genetically stroke-prone (SHR-SP) rats. We now examine whether mucosal tolerance to E-selectin has protective effects in ischemic brain damage after permanent middle cerebral artery occlusion (MCAO) in SHR-SP rats and whether these effects are related to generation of regulatory T cells. Rats were exposed to intranasal administration of E-selectin every other day for 10 days (single tolerization group) or on two tolerization schedules separated by 11 days (booster tolerization group). Control groups received PBS on corresponding schedules. MCAO was performed 48 h after the last dose of E-selectin or PBS. There were 45.8% and 37.9% (P < 0.05) decreases of infarction volume in the E-selectin booster group compared with the PBS group at 6 and 48 h, respectively. Single tolerization with E-selectin had only a slight trend toward a decrease in infarction volume (6.3%). CD8-positive cells were decreased in brains of E-selectin booster animals (46.6%, P < 0.01) compared with controls; splenocyte-culture supernatant levels of IL-10 were increased (59.3%, P < 0.05) in E-selectin booster animals. A decrease of infarction volume (34%, P < 0.05) was also observed in SHR-SP rats subjected to MCAO after adoptive transfer of splenocytes from E-selectin-tolerized compared with PBS-tolerized donors. The results indicate that, in addition to preventing stroke, mucosal tolerance to E-selectin is cytoprotective. Thus, immunomodulation targeted to activated blood vessel segments can both reduce stroke occurrence and attenuate brain damage if a stroke supervenes.