Early Cytokine Synthesis in the Excised Mouse Cornea

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Abstract
Corneas excised from normal BALB/c mice and incubated in vitro were analyzed for the production of "earlywarning" cytokines via reverse transcription-polymerase chain reaction and ELISA. It was found that the trauma of excision stimulated rapid IL-1α synthesis, with peak protein accumulation occurring at 6 h, whereas IL-6 synthesis was maximal at 18 h. Neither IL-1β protein nor message was detected at any point, and TNF-α synthesis never increased above constitutive levels. Antibody neutralization of endogenous IL-1α blocked IL-6 synthesis. Addition of exogenous IL-1α induced IL-1α and IL-6 synthesis in vitro. Inoculation of IL-1α into the cornea induced IL-6 synthesis in vivo. Addition of IL-1α could stimulate IL-1R, IL-1α, and IL-6 mRNA synthesis in the epithelial, stromal, and endothelial components of the cornea. However, protein production was readily detected only in the epithelial layer. We concluded that mechanical trauma to the mouse cornea triggers the enhanced synthesis of IL-1α and IL-1R, which in turn results in the production of IL-6 and more IL-1α. That corneal excision did not stimulate the synthesis of IL-1β or TNF-α indicates that there is a selective induction of early cytokine expression in this specialized tissue.