Psoriasis is a common immune-mediated, chronic, inflammatory
skin disease characterized by hyperproliferation and abnormal differentiation of keratinocytes and infiltration of inflammatory cells. Although TNFα- and IL-17A-targeting drugs have recently proven to be highly effective, the molecular mechanism underlying the pathogenesis of
psoriasis remains poorly understood. We found that expression of the atypical IκB member IκB (inhibitor of NF-κB) ζ, a selective coactivator of particular NF-κB target genes, was strongly increased in skin of patients with
psoriasis. Moreover, in human keratinocytes IκBζ was identified as a direct transcriptional activator of TNFα/IL-17A-inducible
psoriasis-associated
proteins. Using genetically modified mice, we found that
imiquimod-induced
psoriasis-like skin
inflammation was completely absent in IκBζ-deficient mice, whereas skin
inflammation was still inducible in IL-17A- and TNFα-deficient mice. IκBζ deficiency also conferred resistance against IL-23-induced
psoriasis. In addition, local abrogation of IκBζ function by
intradermal injection of IκBζ
siRNA abolished
psoriasis-like skin
inflammation. Taken together, we identify IκBζ as a hitherto unknown key regulator of IL-17A-driven effects in
psoriasis. Thus, targeting IκBζ could be a future strategy for treatment of
psoriasis, and other inflammatory diseases for which
IL-17 antagonists are currently tested in clinical trials.