The effect of interleukin-1 on cytokine gene expression by human corneal epithelial cells

Abstract: The purpose of this study was to characterize the pattern of cytokine gene expression by human corneal epithelial cells (HCEC) in response to interleukin-1 (IL-1). Primary cultured HCEC (P-HCEC) or SV40 transformed HCEC (SV40-HCEC) were treated for 6 hr with serum-free growth-media alone or with recombinant human IL-1β or IL-1α (10 ng ml −1 ). 33 P labeled cDNA was generated from total RNA, then hybridized to a human cytokine expression array. An autoradiograph was generated for each experimental condition and results analysed semi-quantitatively. Reverse transcription polymerase chain reaction (RT-PCR) was performed to detect mRNA for IL-8, growth related oncogene-β (GRO-β), intercellular adhesion molecule (ICAM)-1 and Ephrin A5. P-HCEC and SV40-HCEC demonstrated comparable cytokine profiles. For P-HCEC ( n =2) the expression of 35 genes was upregulated or only detectable following IL-1β treatment whereas the expression of nine genes was downregulated or undetectable after IL-1β treatment. In SV40-HCEC ( n =3), the expression of 48 genes was upregulated or only detectable following IL-1β treatment and the expression of 10 genes was downregulated or undetectable after IL-1β treatment. Some genes that demonstrated increased expression included cadherin-5, ICAM-1, GRO-α, GRO-β, GRO-γ, Activin A (bA subunit), tumor necrosis factor-α, IL-6, and IL-8. Genes that showed decreased expression included the chemokine receptor—CXCR-4, ciliary neurotrophic factor (CNTF), c-kit ligand, Ephrin A5, G-protein coupled receptor RDC-1 and FGF family FGFR2. Bayesian analysis of the SV40-HCEC data ( n =3) revealed the expression of 15 genes that were significantly ( p n =1 P-HCEC; n =1 SV40-HCEC) produced results very similar to IL-1β treatment. RT-PCR revealed differential regulation of IL-8, GRO-β, ICAM-1 and ephrin A5 in accordance with gene array data. In conclusion, the data demonstrate that IL-1 treatment of HCEC differentially regulates the expression of other cytokine and related genes, thus adding to the body of evidence that IL-1 is a major mediator of ocular surface inflammatory reactions. Since the expression of a large number of genes can be studied simultaneously, gene array studies such as these offers the advantage of understanding global changes in response to a specific stimulus. Thus our study provides insight in to the ocular surface response in conditions of inflammation and corneal wound healing where the levels of IL-1 are known to be increased.