Inverse regulation of the nuclear factor-kappaB binding to the p53 and interleukin-8 kappaB response elements in lesional psoriatic skin.

Nuclear factor-kappaB (NF-kappaB) is an inducible nuclear transcription factor regulating a range of cellular processes. An imbalance of the DNA binding activity of NF-kappaB may, therefore, be part of the pathophysiological mechanisms in psoriasis. The purpose of this study was to determine the NF-kappaB DNA binding activity in psoriatic skin using three different kappaB sites and to determine how DNA binding activity was modulated by the anti-psoriatic drug calcipotriol. By electrophoretic mobility shift assay, we demonstrated that the NF-kappaB DNA binding to the p53 kappaB site was decreased, whereas the NF-kappaB DNA binding to the interleukin-8 (IL-8) kappaB site was increased in lesional psoriatic skin compared with non-lesional psoriatic skin. No regulation was seen on the NF-kappaB DNA binding to the major histocompatibility complex class I kappaB site. These changes were paralleled by a similar decrease in p53 expression and an increase in IL-8 expression in involved psoriatic skin compared with uninvolved skin as determined by quantitative RT-PCR. The alteration in NF-kappaB DNA binding activity was neither accompanied by any change in the expression of the inhibitor kappaB (IkappaB) kinases, IKKalpha, IKKbeta, and IKKgamma nor in the expression of the NF-kappaB inhibitor proteins, IkappaBalpha and IkappaBbeta. Immunofluorescence analysis revealed that p65 was sequestered in the cytoplasm of keratinocytes, whereas p50 exhibited a cytoplasmic as well as a nuclear localization. Interestingly, this distribution of p50 and p65 was similar in lesional and non-lesional psoriatic skin. Topical application of calcipotriol to lesional psoriatic skin for 4 d resulted in increased NF-kappaB binding to the p53 kappaB site and decreased NF-kappaB binding to the IL-8 kappaB site. Taken together, our data demonstrate that the NF-kappaB DNA binding activity is regulated in a specific manner in psoriatic skin depending on the kappaB sites investigated, and that topical treatment of psoriatic skin normalizes the abnormal NF-kappaB binding activity seen in lesional psoriatic skin.