Dithranol upregulates IL-10 receptors on the cultured human keratinocyte cell line HaCaT

Objective: Dithranol is highly effective in the treatment of psoriasis, how ever its mode of action is still not well known. Since interleukin-8 and in terleukin-10 are involved in the pathogenesis of psoriasis, the aim of our study was to investigate the effect of dithranol on interleukin-8, interleu kin-10 mRNA production and interleukin-10 receptor expression of the HaCaT keratinocyte cell line which is commonly used in experiments examining the effects of therapeutic drugs on keratinocytes. Materials and Methods: Cultured HaCaT cells were treated with 0.1-0.5 mug/m l dithranol for 30 minutes. After 2 and 4 h total cellular RNA isolated fro m HaCaT cells was reverse transcribed CRT to cDNA which was subjected to po lymerase chain reaction (PCR) with specific primer pairs for interleukin-8, interleukin-10 and interleukin-10 receptor. For immunohistochemistry cultu red HaCaT cells were stained with a monoclonal antibody against the human i nterleukin-10 receptor. Results: Our results showed that dithranol treatment did not change the hig hly elevated level of interleukin-8 mRNA of HaCaT cells. Interleukin-10 mRN A signal with RT-PCR could not be detected in HaCaT cells. Depending on the concentration dithranol increased the mRNA production of interleukin-10 re ceptors in HaCaT cells. This dithranol induced dose dependent upregulation of IL-10 receptors in HaCaT cells was also observed on the protein level us ing immunohistochemistry. Conclusions: Since the interleukin-10 receptor expression of keratinocytes in psoriatic lesional skin is downregulated, the dithranol induced upregula tion of the receptor in our model system might help to reveal the therapeut ic action of the drug.