Enhancing 1 alpha-hydroxylase activity with the 25-hydroxyvitamin D-1 alpha-hydroxylase gene in cultured human keratinocytes and mouse skin

1 alpha ,25-Dihydroxyvitamin D-3 (1 alpha ,25(OH)(2)D-3) and its analogs ar e used to treat psoriasis because of their potent antiproliferative activit y. They have the potential for causing hypercalcemia, however, and patients often become resistant to the drug. We examined the feasibility of enhanci ng the cutaneous production of 1 alpha ,25(OH)(2)D-3 using a human 25-hydro xyvitamin D-1 alpha -hydroxylase (1 alpha -OHase) plasmid. The 1 alpha -OHa se gene was fused to the green fluorescent protein gene (1 alpha -OHase-GFP ) driven by the cytomegalovirus promoter. Transfection of cultured normal h uman keratinocytes with the 1 alpha -OHase-GFP plasmid resulted in a marked increase in the expression of 1 alpha -OHase-GFP in the mitochondria. Tran sfection of keratinocytes with 1 alpha -OHase-GFP or 1 alpha -OHase plasmid s in vitro enhanced the 1 alpha -OHase activity substantially and increased the sensitivity of the keratinocytes to the antiproliferative effect of 25 (OH)D-3. The 1 alpha -OHase-GFP plasmid was topically applied to shaved C57 /BL6 mice. Twenty-four hours after topical application, immunohistochemical analysis of the skin for 1 alpha -OHase-GFP revealed the presence of 1 alp ha -OHase-GFP in the epidermis and epidermal appendages including the hair follicles. The results from this study offer a unique new approach for the topical treatment of hyperproliferative disorders such as psoriasis and ski n cancer using the 1 alpha -OHase gene that could locally increase the prod uction of 1 alpha ,25(OH)(2)D-3 without causing hypercalcemia or resistance .