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

Summary 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.