The efficacy and safety of topically applied indigo naturalis ointment in patients with plaque-type psoriasis

Background: It has been reported in the Chinese literature that indigo naturalis exhibits potential antipsoriatic effects in systemic therapy. Objective: To evaluate the efficacy and safety of topically applied indigo naturalis on treating plaque-type psoriasis and to analyze the histological change in skin tissues. Methods: Fourteen patients with chronic plaque psoriasis were enrolled. The patients were topically applied with either indigo naturalis ointment or vehicle ointment on contralateral skin lesions daily for 8 weeks. Efficacy was evaluated on the basis of the clinical scores, including induration, scaling, erythema and clearing percentage. At the end of treatment, skin punch biopsies were taken and prepared for the immunohistochemical analysis. Results: A significant reduction in clinical scores was achieved with topically applied indigo naturalis ointment. Analysis of biopsies showed a marked improvement of skin histology. The expressions of proliferating marker Ki-67 and inflammatory marker CD3 were decreased, but the differentiation marker such as filaggrin was increased in the epidermis after indigo naturalis ointment treatment. Conclusions: The results suggest that topical application of indigo naturalis ointment may be a novel, safe and effective therapy for psoriasis that is mediated, at least in part, by modulating the proliferation and differentiation of keratinocytes in epidermis, as well as by inhibiting the infiltration of T lymphocytes and therefore the subsequent inflammatory reactions in psoriatic lesions.