Tacalcitol, an active vitamin D3, induces nerve growth factor production in human epidermal keratinocytes

The human epidermal keratinocyte cell line K-TL-1, developed from a benign epidermal tumor, was cultured in the presence of the synthetic vitamin D3 analogue tacalcitol [1alpha,24(R)-dihydroxyvitamin D3] to assess the effects on the production of nerve growth factor (NGF). Confluent K-TL-1 cells were cultured with 10(-8) M of tacalcitol. Supernatants and cell homogenates were collected and NGF concentrations were determined by enzyme-linked immunosorbent assay. The concentration of NGF in the supernatants of cultures treated with tacalcitol peaked within 24 h after the start of tacalcitol treatment and remained stable for 96 h. This NGF induction caused by tacalcitol was dose-dependent, showing an ED50 between 10(-10) and 10(-9) M. Induction of NGF mRNA expression by tacalcitol was also observed by RT-PCR, indicating that tacalcitol induced NGF expression through transcriptional activation. These results suggest that active vitamin D3 could treat peripheral neuropathy by inducing NGF production in the skin.