The anti-estrogenic activity of indole-3-carbinol in neonatal rat osteoblasts is associated with the estrogen receptor antagonist 2-hydroxyestradiol

• Published in: Journal of endocrinological investigation Vol. 39; no. 10; pp. 1149 - 1158
• Main Authors: Enríquez, J., Velázquez-Cruz, R., Parra‐Torres, A., Gutiérrez-Sagal, R., Larrea, F.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.10.2016; Springer Nature B.V
• Subjects: 17β-Estradiol; Alkaline phosphatase; Animals; Animals, Newborn; Anticarcinogenic Agents - pharmacology; Bioactive compounds; Cell Differentiation - drug effects; Cell growth; Cell proliferation; Cell Proliferation - drug effects; Cells, Cultured; Deoxyribonucleic acid; DNA; Endocrinology; Enzyme-Linked Immunosorbent Assay; Estradiol - analogs & derivatives; Estradiol - pharmacology; Estrogen Antagonists - pharmacology; Estrogen Receptor Antagonists - pharmacology; Estrogen receptors; Estrogenic activity; Estrogens; Estrone; Female; Hydroxylation; Indole-3-carbinol; Indoles - pharmacology; Medicine; Medicine & Public Health; Metabolic Diseases; Metabolites; Neonates; Original Article; Osteoblastogenesis; Osteoblasts; Osteoblasts - cytology; Osteoblasts - drug effects; Osteoblasts - metabolism; Osteocalcin; Rats; Rats, Wistar; Real-Time Polymerase Chain Reaction; Receptors, Estrogen - chemistry; Receptors, Estrogen - genetics; Receptors, Estrogen - metabolism; Reverse Transcriptase Polymerase Chain Reaction; Rodents; Studies; Vegetables; Xenoestrogens; Indole-3-carbinol; Osteoblast 2-hydroxylation; Osteoblasts differentiation; Estrogen metabolites; Osteoblasts proliferation
• ISSN: 1720-8386; 0391-4097; 1720-8386
• DOI: 10.1007/s40618-016-0494-9

Purpose To gain new insight into the roles of cruciferous vegetable-derived bioactive phytochemicals in bone cells, we investigated the effects of indole-3-carbinol (I3C) on cell proliferation and differentiation in estradiol (E 2 )-exposed calvarial osteoblasts that were obtained from neonatal rats. Methods Osteoblast activity was assessed by analyzing cellular DNA, cell-associated osteocalcin (OC) levels and alkaline phosphatase (AP) activity. We also examined [ 3 H]-estrone (E 1 ) metabolism and estrogen-agonistic and estrogen-antagonistic activities of 2-hydroxy (OH) E 1 and 2-OHE 2 and their capacity to displace [ 3 H]-E 2 at ER binding sites using competition studies. Results I3C did not affect on cellular DNA, OC levels or AP activity. However, I3C completely inhibited E 2 -induced increases in cell proliferation and differentiation in neonatal rat osteoblasts. Metabolic studies demonstrated that I3C promoted the conversion of [ 3 H]-E 1 to 2-OHE 1 and 2-OHE 2 and those higher rates of conversion (twofold–threefold) were archived when a higher dose of I3C was applied. Proliferation and differentiation studies showed that 2-OHE 2 but not 2-OHE 1 inhibited E 2 -induced increases in cell proliferation and differentiation via an ER-mediated mechanism. Likewise, Esr1 was expressed at high level than Esr2 . 2-OHE 1 showed no activity or affinity for ER. Conclusions This study is the first to show that a bioactive compound derived from cruciferous vegetables, I3C, abolishes the E 2 -mediated stimulation of cell activities including, proliferation and differentiation, in rat osteoblasts and increases the 2-hydroxylation of E 1 , resulting in the formation of inactive and anti-estrogenic metabolites. These results suggest that in neonatal rat osteoblasts, the anti-estrogenic effect of I3C is mediated by 2-OHE 2 through ER-α.