Calcitriol Treatment Ameliorates Inflammation and Blistering in Mouse Models of Epidermolysis Bullosa Acquisita

A link between hypovitaminosis D and development of autoimmune bullous disorders has been suggested recently, but this association has not been elaborated experimentally. Here, the role of vitamin D was investigated in epidermolysis bullosa acquisita (EBA), an anti−type VII collagen autoantibody-induced blistering skin disease. Oral administration of the hormonally active vitamin D metabolite calcitriol ameliorated clinical disease severity and dermal neutrophil infiltration in both an antibody transfer- and immunization-induced EBA mouse model. Mechanistically, calcitriol hindered immune effector cell activation as evidenced by increased L-selectin expression on Gr-1⁺ cells in calcitriol-treated mice with antibody transfer-induced EBA, as well as suppressed in vitro immune complex−induced reactive oxygen species production in calcitriol-treated murine neutrophils. Additionally, calcitriol administration was associated with an increase of regulatory T (CD4⁺FoxP3⁺) and B (CD19⁺IL10⁺) cells as well as reduction of pro-inflammatory T helper 17 (CD4⁺IL-17⁺) cells in mice with immunization-induced EBA. In line, levels of circulating anti−type VII collagen autoantibodies were lower in mice that received calcitriol compared to solvent-treated animals. Together with the observed state of hypovitaminosis D in most cases of an analyzed EBA patient cohort, the results of this study support the use of vitamin D derivatives or analogs for patients with EBA and related diseases.