Abstract

NPY ATTENUATES ESTROGEN-INDUCED DIFFERENTIATION OF MC3T3-E1 THROUGH INHIBITING ER-? RECEPTOR

Xiaotong Lei, Haibin He, Ya Tian, Panpan Wang, Xiaofeng Zhu, Li Yang* and Ronghua Zhang*

ABSTRACT

Neuropeptide Y (NPY), a classic neuronal regulator of energy homeostasis, is recently known to be involved in the control of bone homeostatasis and metabolism. Estrogen is the major hormonal regulator of bone metabolism which bind to estrogen receptor α(ER-α) and ER-β in influencing the osteogenic differentiation ability. Earlier studies have found that NPY and estrogen exist an interaction in hypothalamic neurons. However, the possible interactions between NPY and estrogen signaling pathway in peripheral bone tissues have not been reported in detail. Here, we firstly found that NPY could attenuate the promotion of proliferation and differentiation in MC3T3-E1 cells induced by 17β-Estradiol (E2), which was proved by decreasing the proliferation rate and osteogenic mineral nudules Neuropeptide Y (NPY), a classic neuronal regulator of energy homeostasis, is recently known to be involved in the control of bone homeostatasis and metabolism. Estrogen is the major hormonal regulator of bone metabolism which bind to estrogen receptor α(ER-α) and ER-β in influencing the osteogenic differentiation ability. Earlier studies have found that NPY and estrogen exist an interaction in hypothalamic neurons. However, the possible interactions between NPY and estrogen signaling pathway in peripheral bone tissues have not been reported in detail. Here, we firstly found that NPY could attenuate the promotion of proliferation and differentiation in MC3T3-E1 cells induced by 17β-Estradiol (E2), which was proved by decreasing the proliferation rate and osteogenic mineral nudules osteogenic markers such as Runt-related transcription factor 2 (Runx2), Alkaline phosphatase (ALP), and Collagen type I (COL I) in MC3T3-E1. To further investigate the underlying mechanisms, we set up control group, E2 group, estrogen receptorICI 182780 group(ICIgroup), E2 + ICI group, NPY group, NPY receptor1 (NPY1R) antagonist BIBP 3226(BIBP group), NPY+ BIBP group, then examined the ER and NPY1R expression. As a result, NPY significantly down-regulated ER-α expression similar to the effect of ICI 182780, but failed to modulate ER-β. Additionally, BIBP 3226 could weaken the inhibitory effect of NPY. In contrast, E2 could not only increase the ER-α and ERβ expression, but also decrease the NPY1R expression significantly.And ICI 182780 could increase NPY1R expression compared with the treatment of E2 alone. This study indicates that there has a mutual antagonistic interaction between NPY and estrogen signaling pathway, which provides a new understanding of NPY and estrogen in regulating bone metabolism.

Keywords: NPY, Estrogen, NPY1R, ER-?, ER-?, MC3T3-E1, Osteogenic differentiation.