The Effects of Estrogen Receptors α- and β-Specific Agonists and Antagonists on Cell Proliferation and Energy Metabolism in Human Bone Cell line

In cultured human osteoblasts estradiol-17 beta (E2) modulated DNA synthesis, the specific activity of creatine kinase BB (CK), 12 and 15 lipoxygenase (LO) mRNA expression and formation of 12- and 15-hydroxyeicosatetraenoic acid (HETE). We now investigate the response of human bone cell line (SaOS2) to phytoestrogens and estrogen receptors (ER)-specific agonists and antagonists. Treatment of SaSO2 with E2, 2,3-bis (4-hydroxyphenyl)-propionitrile (DPN; ER beta-specific agonist), 4,4',4(4-propyl-(1H)-pyrazol-1,3,5-triyl] tris-phenol (PPT; ER alpha-specific agonist), biochainin A (BA), daidzein (D), genistein (G) and raloxifene (Ral) showed increased DNA synthesis and CK. Ral inhibited completely all stimulations except DPN and to sonic extent D. The ER alpha-specific antagonist methyl-piperidino-pyrazole (MPP) and the ER beta-specific antagonist 4-[2-phenyl-5,7-bis (tri-fluoro-methyl) pyrazolo [1,5-alpyrimidin-3-yl] phenol (PTHPP) inhibited DNA synthesis, CK and reactive oxygen species (ROS) formation induced by estrogens according to their receptors affinity. The LO inhibitor baicaleine inhibited only E2, DPN and G's effects. E2 and Ral unlike all other compounds had no effect on ER alpha mRNA expression, while ER beta mRNA expression was stimulated by all compounds. All compounds modulated the expression of 12LO and 15LO mRNA, except E2, PPT and Ral for 12LO, and 12- and 15-HETE productions and stimulated ROS formation which was inhibited by NADPH oxidase inhibitors diphenyleneiodonium chloride (DPI) and N-acetyl cysteine and the estrogen inhibitor ICI. DPI did not affect hormonal-induced DNA and CK. In conclusion, we provide evidence for the separation of mediation via ER alpha and ER beta pathways in the effects of estrogenic compounds on osteoblasts, but the role of LO/HETE/ROS is unclear. J. Cell. Biochem. 112: 625-632, 2011. (C) 2010 Wiley-Liss, Inc.