<scp>DUSP6</scp> Regulates Skin Inflammation, Parakeratosis and Disease Severity in a Murine Model of Psoriasis

Psoriasis is a chronic inflammatory skin disease characterised by keratinocyte hyperproliferation and immune cell infiltration driven by cytokines such as IL-17A. The dual-specificity phosphatase 6 (DUSP6) is a negative regulator of MAPK signalling and was previously reported to be a key mediator of arthritis severity. Here, we examine the role of DUSP6 in a mouse model of psoriasis. Psoriasis was studied in the imiquimod-induced model (IMQ). The skin of DUSP6+/+ and DUSP6-/- mice was treated with IMQ cream. Disease severity was assessed using well-established clinical and histologic systems. Skin inflammatory genes were quantified by qPCR.DUSP6-/- mice exhibited significantly reduced skin inflammation with lower PASI clinical scores (mean DUSP6-/- 1.8 and DUSP6+/+ 8.4; p < 0.0001). Histologic scores for epidermal thickening, parakeratosis and immune cell infiltration were decreased in the DUSP6-/- mice (p < 0.0005), and mRNA levels of IL1β, IL17A and STAT3 were lower in DUSP6-/- skin (p ≤ 0.05) compared with DUSP6+/+. In conclusion, DUSP6 is required for the development of psoriasis-like skin inflammation in mice. In the absence of DUSP6, mice were protected and had significantly lower levels of pathogenic genes, suggesting a new and central role for DUSP6 in skin inflammation and a potential therapeutic target in psoriasis.