The human IL-17A/F heterodimer regulates psoriasis-associated genes through IBζ

Antagonists of IL-17A and its receptor have proven to be highly effective in the treatment of psoriasis. However, many of the underlying molecular mechanisms involved in the pathogenesis of psoriasis are still to be determined. IB (encoded by the NFKBIZ gene) plays a key role in the development of psoriasis by mediating IL-17A- and IL-17F-driven effects. Both IL-17A and IL-17F expression are increased in lesional psoriatic skin. IL-17A/A and IL-17F/F homodimers as well as the IL-17A/F heterodimer signal through the same receptors. The aim of this study was to characterize the role of the IL-17A/F heterodimer in the regulation of NFKBIZ expression and in the regulation of selected psoriasis-associated genes. We demonstrated that IL-17A/F stimulation of human keratinocytes significantly induced NFKBIZ expression. Moreover, silencing IB by siRNA revealed that IB is a key regulator of IL-17A/F-inducible psoriasis-associated genes, including CCL20, DEFB4, IL-8, CHI3L1 and S100A7. In addition, IL-17A/F-induced NFKBIZ expression was mediated by a mechanism involving the p38 MAPK and NF-B signalling pathways. In conclusion, we present IB as a novel key regulator of IL-17A/F-driven effects in psoriasis. Thus, antagonists to IL-17A/F or IB may present a targeted approach for treating psoriasis.