Detection of novel CYP11A1-derived secosteroids in the human epidermis and serum and pig adrenal gland

Abstract

To investigate whether novel pathways of vitamin D3 (D3) and 7-dehydrocholesterol (7DHC) metabolism initiated by CYP11A1 and previously characterized in vitro, occur in vivo, we analyzed samples of human serum and epidermis, and pig adrenals for the presence of intermediates and products of these pathways. We extracted human epidermis from 13 individuals and sera from 13 individuals and analyzed them by LC/qTOF-MS alongside the corresponding standards. Pig adrenal glands were also analyzed for these steroids and secosteroids. Epidermal, serum and adrenal samples showed the presence of D3 hydroxy-derivatives corresponding to 20(OH)D3, 22(OH)D3, 25(OH)D3, 1,25(OH) ₂D3, 20,22(OH) ₂D3, 20,23(OH) ₂D3, 20,24(OH) ₂D3, 20,25(OH) ₂D3, 20,26(OH) ₂D3, 1,20,23(OH) ₃D3 and 17,20,23(OH) ₃D3, plus 1,20(OH) ₂D3 which was detectable only in the epidermis. Serum concentrations of 20(OH)D3 and 22(OH)D3 were only 30- and 15-fold lower than 25(OH)D3, respectively, and at levels above those required for biological activity as measured in vitro. We also detected 1,20,24(OH) ₃D3, 1,20,25(OH) ₃D3 and 1,20,26(OH) ₃D3 in the adrenals. Products of CYP11A1 action on 7DHC, namely 22(OH)7DHC, 20,22(OH) ₂7DHC and 7-dehydropregnenolone were also detected in serum, epidermis and the adrenal. Thus, we have detected novel CYP11A1-derived secosteroids in the skin, serum and adrenal gland and based on their concentrations and biological activity suggest that they act as hormones in vivo.