IL-1β in the ischemic avascular retina induces Sema3A expression. (A) The inflammatory cytokines IL-6, TNF-α, and IL-1β are induced in OIR retinas, in particular IL-1β, which was up-regulated 6.8-fold compared with normoxia. n = 3; P < .01 compared with normoxia (Norm). (B) Microdissection of avascular (A) regions of the OIR retina reveals a marked induction in IL-1β (17 kDa) protein levels compared with the vascular regions (V) and the central (C) and peripheral (P) normoxic retina; higher molecular weight bands correspond to pro-IL-1β. n = 3; P < .01 compared with time 0. (C) RGC-5 stimulated with IL-1β (0.5 ng/mL) elicited a delayed (8 hours) but significant 4-fold increase in Sema3A (n = 3-4). (D) Confocal imaging of immunohistochemistry on retinal cross-sections (OIR P14) reveals a predominant expression of IL-1RI by RGCs, as confirmed by merging with RGC marker Thy1.1. (E) IL-1RI antagonist IL-1ra (Kineret) abrogated the OIR-dependent induction of Sema3A compared with vehicle-treated normoxia and OIR controls. Values are the fold increase of control ± SEM. n = 3; **P < .01 compared with normoxic vehicle (Veh). (D) Scale bar represents 25 μm.