Sulfation of Estradiol in Human Epidermal Keratinocyte

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Epidermis is one of the well-known estrogen target tissues. Information regarding estrogen metabolism in epidermis is still very limited compared to that of estrogen action. In the breast cancer tissue, 17β-estradiol (E2) is inactivated by sulfation and the expression level of estrogen sulfotransferase (SULT1E1) is inversely correlated with its malignancy. However, there is little datum about inactivation of estradiol in skin. In order to detect and measure E2 and its metabolites simultaneously, we established an assay method with radio HPLC. A majority of [3H] labeled E2 was converted to E2 sulfate in normal human epidermal keratinocyte (NHEK) cells. The estimated activity of sulfotransferase toward E2 at 20 nM was 0.11±0.01 (pmol/min/mg protein). Significant induction of estrogen sulfotransferase activity was observed in calcium-differentiated NHEK cells (0.58±0.07 (pmol/min/mg protein)). The gene expression of SULT1E1 was fifteen-fold higher in differentiated keratinocyte than in proliferating keratinocyte, whereas that of steroid sulfatase was reduced. These results suggest that E2 inactivation is primarily mediated by SULT1E1 in keratinocyte and E2 action is likely suppressed in epidermal differentiation.