Calcipotriol and betamethasone dipropionate exhibit different immunomodulatory effects on imiquimod‐induced murine psoriasiform dermatitis

Psoriasis is a T-helper (Th)1/Th17-mediated, chronic inflammatory dermatitis that is commonly treated with topical corticosteroids and vitamin D3 analogs. The combination of a topical corticosteroid and vitamin D3 analog showed superior efficacy to each alone in clinical trials; however, the mechanisms by which the topical corticosteroid and vitamin D3 analog exert their effects on lesional skin in combination and each alone remain unknown. In this study, we examined the effects of combined calcipotriol (Cal)/betamethasone dipropionate (BD) ointment on psoriasis in vivo, utilizing imiquimod (IMQ)-induced murine psoriasiform skin inflammation, compared with each alone. Vehicle, Cal/BD, Cal or BD was applied on the shaved back skin for 3 consecutive days. Then, IMQ was applied for 6 consecutive days. Twenty-four hours after the last IMQ treatment, the murine skin was evaluated clinically and pathologically. mRNA expressions were examined by quantitative polymerase chain reaction. All ointments alleviated IMQ-induced psoriasiform skin inflammation clinically in comparison with vehicle application. Cal/BD suppressed mRNA expressions of cytokines involved in psoriasis pathogenesis such as interleukin (IL)-17A and IL-22 efficiently. Cal alone induced IL-10 expression, whereas BD alone reduced IL-6 mRNA expression and the number of phosphorylated signal transducer and activator of transcription 3-positive cells in lesional skin. Our study revealed that Cal and BD have different effects on IMQ-induced psoriasiform skin. Some of the immune effects of Cal and BD may be additive or synergistic, which may account for the superior clinical efficacy of their combination.