Induction of FGF-2 synthesis by IL-1β in aqueous Humor through P13-kinase and p38 in rabbit corneal endothelium

PURPOSE. To determine whether the elevated level of interleukin (IL)-1β in aqueous humor after transcorneal freezing upregulates FGF-2 synthesis in rabbit corneal endothelium through PI3-kinase and p38 pathways. METHODS. Transcorneal freezing was performed in New Zealand White rabbits to induce an injury-mediated inflammation. The concentration of IL-1β was measured, and the expression of FGF-2, p38, and Akt underwent Western blot analysis. Intracellular location of FGF-2 and actin cytoskeleton was determined by immunofluorescence staining. RESULTS. Massive infiltration of polymorphonuclear leukocytes (PMNs) to the corneal endothelium was observed after freezing, and IL-1β concentration in the aqueous humor was elevated in a time-dependent manner after freezing. Similarly, FGF-2 expression was increased in a time-dependent manner. When corneal endothelium was stained with anti-FGF-2 antibody, the nuclear location of FGF-2 was observed primarily in the cornea after cryotreatment, whereas FGF-2 in normal corneal endothelium was localized at the plasma membrane. Treatment of the ex vivo corneal tissue with IL-1β upregulated FGF-2 and facilitated its nuclear location in corneal endothelium. Transcorneal freezing disrupted the actin cytoskeleton at the cortex, and cell shapes were altered from cobblestone morphology to irregular shape. Topical treatment with LY294002 and SB203580 on the cornea after cryotreatment blocked the phosphorylation of Akt and p38, respectively, in the corneal endothelium. These inhibitors also reduced FGF-2 levels and partially blocked morphologic changes after freezing. CONCLUSIONS. These data suggest that after transcorneal freezing, IL-1β released by PMNs into the aqueous humor stimulates FGF-2 synthesis in corneal endothelium via PI3-kinase and p38.