Pharmacological Profiles of High‐Concentration (20 μg/g) Tacalcitol Ointment: Effects on Cutaneous Inflammation, Epidermal Proliferation, and Differentiation in Mice

This study focused on the effects of tacalcitol (1,24(R)(OH)2D3, TV‐02) ointment (20 μg/g) on cutaneous inflammation, epidermal proliferation, and differentiation and compared them with tacalcitol ointment (2 μg/g) and other anti‐psoriatic ointments using hairless mice. Tacalcitol ointment (0, 2 and 20 μg/g) significantly inhibited 12‐O‐tetradecanoylphorbol 13‐acetate (TPA)‐induced cutaneous inflammation, histopathologically. The effect of tacalcitol ointment (20 μg/g) on cutaneous inflammation was much stronger than that of tacalcitol ointment (0, 2 μg/g), and as effective as calcipotriol ointment (50 μg/g) or betamethasone valerate ointment (1.2 mg/g). Tacalcitol ointment (20 μg/g) also significantly inhibited TPA‐induced myeloperoxidase (MPO) activity, as effectively as calcipotriol ointment (50 μg/g) or betamethasone valerate ointment (1.2 mg/g). The effect of tacalcitol ointment on epidermal proliferation [ornithine decarboxylase (ODC) activity] and differentiation [transglutaminase (TGase) activity] was dose‐dependent from 0 μg/g to 20 μg/g. The effect of tacalcitol ointments on epidermal proliferation was significant at the doses of 2 μg/g and 20 μg/g, and that on epidermal differentiation was significant at the doses of 0.2 μg/g or more. The effect of tacalcitol ointment (20 μg/g) on epidermal differentiation was significantly stronger than tacalcitol ointment (2 μg/g). In this study, tacalcitol ointment (20 μg/g) was found to have a marked effect on cutaneous inflammation and improved effect on epidermal differentiation, although tacalcitol ointment (2 μg/g) also had significant effects on epidermal proliferation and differentiation. These findings support the clinical effectiveness of tacalcitol ointment (20 μg/g) against psoriasis.