Immune Modulation with Combined Vitamin D Analogs and Corticosteroids in Psoriasis

Abstract

Psoriasis is characterized by excessive growth and aberrant differentiation of keratinocytes and by dysregulation of immune cells. Topical vitamin D analogs and corticosteroids are commonly used for the treatment of mild-to-moderate plaque psoriasis. The effects of corticosteroids are predominantly anti-inflammatory and immunosuppressive, while those of vitamin D analogs have long been considered antiproliferative. Recent evidence suggests an independent role of vitamin D analogs and corticosteroids in cytokine modulation, an important factor in treatment efficacy. In vitro and in vivo studies show that the combination of a vitamin D analog and a corticosteroid produces effects on T-cell subsets that are involved in psoriatic skin inflammation. Based on the respective mechanisms of action of vitamin D analogs and corticosteroids, there is a biologic rationale for the enhanced clinical effect observed with the combination therapy. This article reviews current understanding of the pathogenesis of psoriasis and recent evidence for immunomodulatory mechanisms of vitamin D analogs and corticosteroids.