CONTRIBUTION OF E-SELECTIN TO CELLULAR INFILTRATION DURING ENDOTOXIN-INDUCED UVEITIS

PURPOSE. The selectin family is a group of early-reactive adhesion mol ecules th:lt plays a role in the rolling phase of leukocytes in cellul ar infiltration. It has been reported that P-selectin is expressed on vascular endothelium in the iris-ciliary body 15 minutes after lipopol ysaccharide (LPS) treatment in endotoxin-induced uveitis (EIU) and may contribute to the initial phase of ocular inflammation. The objective of the present study was to identify the expression pattern of E-sele ctin, another member of the selectin family, and to investigate the ro le of E-selectin during the course of EIU. METHODS. Endotoxin-induced uveitis was induced in male Lewis rats by a footpad injection of 200 C LS LPS. The time-dependent expressions of E-selectin in EIU in the iri s- ciliary body auld the retina were studied by immunohistochemistry u sing wholemounts and paraffin-embedded sections and by monitoring the level of E-selectin mRNA expression. A monoclonal antibody to E-select in and a control antibody were each injected intravenously to evaluate the effects of E-selectin inhibition on ocular inflammation at the ti me of maximum uveitis. In the anterior uvea, the effect was evaluated by the number of infiltrated cells and by the protein concentration in the aqueous hunter 24 hours after LPS treatment; in the retina, the m yeloperoxidase (MPO) activity was measured 48 hours after LPS treatmen t. The effect of the combined injection of anti-P-selectin and;anti-E- selectin antibodies was also studied. It was then determined whether t he delayed inhibition of E-selectin (6, 12, or 24 hours after LPS inje ction) could contribute to the early resolution of the uveitis. RESULT S. E-selectin immunoreactivity was observed on the vessel walls of the iris and retina 7 hours after LPS treatment in wholemounts and paraff in-embedded sections and remained positive for 24 hours after LPS trea tment. The expression of E-selectin messenger RNA gene peaked at 6 hou rs and again at 18 hours after LPS treatment in the iris- ciliary body and retina. The expression returned to the basal level 24 hours after LPS treatment in the iris- ciliary body and 48 hours after LPS treatm ent in the retina. The selective inhibition of E-selectin significantl y blocked the cellular infiltration into the aqueous humor (P < 0.005) but had a milder effect on the protein concentration in die aqueous h umor (P = 0.0536). The inhibition of E-selectin and P-selectin almost abrogated cellular infiltration (P < 0.001). Myeloperoxidase activity in the retina 48 hours after LPS treatment was again significantly dec reased by the inhibition of E-selectin alone and by the inhibition of E-selectin and P-selectin (P < 0.0001). A single injection of anti-E-s electin antibody 6, 12, or 24 hours after LPS injection effectively bl ocked cellular infiltration in the aqueous humor 24 and 48 hours after LPS treatment. CONCLUSIONS. in EIU, E-selectin may be expressed on th e vascular endothelium and remain after the period of expression of P- selectin and until approximately the time of maximum uveitis. The pres ent results suggest that, in contrast to the role of P-selectin as an initiator of cellular infiltration, E-selectin may contribute to conti nuing cellular infiltration into the inflammatory site during inflamma tion, and its inhibition may contribute to the early resolution of the uveitis.