Selective Regulation of Osteoblastic OPG and RANKL by Dehydroepiandrosterone Through Activation of the Estrogen Receptor β-mediated MAPK Signaling Pathway

The aim of the work was to investigate the differential regulation by dehydroepiandrosterone (DHEA) of the osteoblastic production via the estrogen receptor beta (ER beta)-mediated signaling pathway. Having developed hMG63-ER beta cells and hMG63-shER beta cells, we analyzed the regulation by DHEA of human osteoblastic viability, the receptor activator of nuclear factor kappa-B ligand (RANKL), osteoprotegerin (OPG), and the differential expression of ER beta, ER alpha, or p-ERK1/2 (extracellular signal-regulated kinase) in hMG63, hMG63-shER beta, and hMG63-ER beta cells pre-treated with or without U0126, flutamide, and ICI 182780, followed by DHEA culture. When the level of ER beta was high, DHEA (10(-7) mol/l) could effectively amplify the proliferation and inhibit the etoposide-induced apoptosis of hMG63 cells (p < 0.01 and p < 0.05, respectively), which was blocked by U0126. When the expression of ER beta was silenced, DHEA could not significantly improve the viability of hMG63. In the presence of ER beta, DHEA activated the pERK1/2-MAPK signaling pathway but not p38 and JNK. Besides, the regulation of p-ERK1/2 upon DHEA treatment was mainly modulated by ER beta instead of androgen receptor and ER alpha. The secretion of OPG was declined following the silence of ER beta (p < 0.05). RANKL and ER alpha, however, were unaffected by culture with or without DHEA and U0126, regardless of the ER beta level. DHEA seems to act selectively on osteoblasts via the dominant ER beta receptor, which mediates amplified cell viability through the MAPK signaling pathway involving pERK1/2 and upregulates the production of OPG rather than RANKL.