The dynamics of gene expression of interleukin-19 and interleukin-20 and their receptors in psoriasis

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Abstract
Background Interleukin (IL)-20 and IL-19 are recently discovered members of the IL-10 family of cytokines. The skin of transgenic mice overexpressing IL-20 shows histological changes resembling some of those seen in psoriasis, i.e. thickened epidermis, hyperkeratosis and a compact stratum corneum. IL-19 and IL-20, as well as their receptor complexes, IL-20Rα/IL-20Rβ and IL-22Rα/IL-20Rβ, are expressed in human skin. Objectives To study the dynamics of IL-19 and IL-20 gene expression as well as the expression of their receptor subunits in psoriatic skin lesions. Methods Punch biopsies from patients with plaque-type psoriasis were collected before, during and after 28 days of treatment with either calcipotriol or ciclosporin (CsA). IL-20, IL-19, IL-20Rα, IL-20Rβ and IL-22Rα mRNA expression were determined by quantitative reverse transcriptase–polymerase chain reaction. Results We found IL-19 and IL-20 mRNA expression in lesional psoriatic skin to be strongly upregulated compared with nonlesional psoriatic skin by a factor of 65 and 22, respectively. In contrast to previous reports, IL-20Rα and IL-20Rβ mRNA levels showed a modest but statistically significant decrease in lesional psoriatic skin compared with nonlesional psoriatic skin. During treatment with calcipotriol or CsA, IL-19 and IL-20 mRNA levels decrease in accordance with the clinical improvement of psoriasis. Neither IL-19, IL-20, nor receptor subunit mRNA expression in lesional psoriatic skin reaches the levels of nonlesional skin during this short-term treatment. These findings are in line with the residual disease activity observed at the end of treatment. Conclusions The increased IL-19 and IL-20 mRNA expression levels in lesional psoriatic skin suggest that these two cytokines play a role in the pathogenesis of psoriasis. An imbalance in the receptor complexes for IL-19 and IL-20 might contribute to their suspected pathogenic effects.