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R. R. Sivaraj, R. K. Vijapurapu, P. Khosla, P. J. Tomlins, S. J. Curnow, M. S. Cooper, E. A. Walker, S. Rauz; 11-β Hydroxysteroid Dehydrogenase 1 and the Regulation of Cortisol Bioavailability in Human Ocular Fibroblasts. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4741.
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Fibroblasts play an important role in defining tissue-specific responses during the resolution of inflammation. The pre-receptor regulation of fibroblast derived glucocorticoids (GC) by 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) that activates cortisol from inactive cortisone, has been linked to the predilection of joint tissues to develop persistent inflammation. The eye is a key target for immune-mediated inflammatory disease. The aim of this study was to characterise tissue-specific GC responses in human ocular fibroblasts.
Primary cultures of human corneal and scleral fibroblasts were derived from donor corneal-scleral rims after trephination for corneal transplant surgery, and conjunctival fibroblasts from surgical conjunctival biopsies. Identity was confirmed with immunocytochemistry for the fibroblast marker ASO2 (CD90).. GC target genes (11β-HSD1, hexose-6-phosphate dehydrogenase (H6PD), glucocorticoid receptor-α (GRα)) were characterised by conventional and real-time RT-PCR analyses. Specific 11β-HSD1 enzyme assays were carried out following incubation with TNFα, IL-4, IL-6, IFNγ, and TGFβ. Culture supernatants were analysed for the production of IL-1β, IL-4, IL-6, IL-8, IL-10, IL-12, IL-13, TNFα and IFNα using multiplex bead immunoassays.
Conjunctival, corneal and scleral fibroblasts expressed 11β-HSD1, H6PD and GRα mRNA with the highest expression in corneal fibroblasts. 11β-HSD1 mRNA expression increased when cells were treated with TNFα. In addition, 11β-HSD1 oxo-reductase activity generating cortisol was seen in all ocular fibroblasts, and this was potently induced across all cell-lines when co-incubated with TNFα. Furthermore, induction of 11β-HSD1 also resulted in repression in the synthesis of pro-inflammatory cytokines (IL-6, IL-8, TNFα, and IFNγ).
Our data have shown increases in both expression and activity of 11β-HSD1 in response to pro-inflammatory cytokines which in turn abrogates pro-inflammatory cytokine synthesis. Differences in fibroblast-derived cortisol bioavailability may account for the susceptibility of certain ocular tissues to develop persistent ocular inflammation.
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