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Oestrogen-activated autophagy has a negative effect on the anti-osteoclastogenic function of oestrogen.

ABSTRACT: OBJECTIVES:Oestrogen is known to inhibit osteoclastogenesis, and numerous studies have identified it as an autophagic activator. To date, the role of oestrogen in the autophagy of osteoclast precursors (OCPs) during osteoclastogenesis remains unclear. This study aimed to determine the effect of autophagy regulated by the biologically active form of oestrogen (17?-estradiol) on osteoclastogenesis. MATERIALS AND METHODS:After treatment with 17?-estradiol in OCPs (from bone marrow-derived macrophages, BMMs) and ovariectomy (OVX) mice, we measured the effect of 17?-estradiol on the autophagy of OCPs in vitro and in vivo. In addition, we studied the role of autophagy in the OCP proliferation, osteoclast differentiation and bone loss regulated by 17?-estradiol using autophagic inhibitor or knock-down of autophagic genes. RESULTS:The results showed that direct administration of 17?-estradiol enhanced the autophagic response of OCPs. Interestingly, 17?-estradiol inhibited the stimulatory effect of receptor activator of nuclear factor-?B ligand (RANKL) on the autophagy and osteoclastogenesis of OCPs. Moreover, 17?-estradiol inhibited the downstream signalling of RANKL. Autophagic suppression by pharmacological inhibitors or gene silencing enhanced the inhibitory effect of 17?-estradiol on osteoclastogenesis. In vivo assays showed that the autophagic inhibitor 3-MA not only inhibited the autophagic activity of the OCPs in the trabecular bone of OVX mice but also enhanced the ability of 17?-estradiol to ameliorate bone loss. CONCLUSIONS:In conclusion, our study showed that oestrogen directly enhanced the autophagy of OCPs, which inhibited its anti-osteoclastogenic effect. Drugs based on autophagic inhibition may enhance the efficacy of oestrogen on osteoporosis.

SUBMITTER: Cheng L

PROVIDER: S-EPMC7162800 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Oestrogen-activated autophagy has a negative effect on the anti-osteoclastogenic function of oestrogen.

Cheng Liang L Zhu Yunrong Y Ke Dianshan D Xie Denghui D

Cell proliferation 20200311 4

<h4>Objectives</h4>Oestrogen is known to inhibit osteoclastogenesis, and numerous studies have identified it as an autophagic activator. To date, the role of oestrogen in the autophagy of osteoclast precursors (OCPs) during osteoclastogenesis remains unclear. This study aimed to determine the effect of autophagy regulated by the biologically active form of oestrogen (17β-estradiol) on osteoclastogenesis.<h4>Materials and methods</h4>After treatment with 17β-estradiol in OCPs (from bone marrow-de ...[more]

PMID: 32157750

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Project description:IntroductionOestrogens can mediate some of their cell survival properties through a nongenomic mechanism that involves the mitogen-activated protein kinase (MAPK) pathway. The mechanism of this rapid signalling and its dependence on a membrane bound oestrogen receptor (ER), however, remains controversial. The role of G-protein-coupled receptor and epidermal growth factor (EGF) receptor in an ER-independent signalling pathway modulated by oestrogen was investigated.MethodsER-positive and ER-negative breast cancer cell lines (MCF-7 and SKBR3) and primary breast cancer cell cultures were used in this study. Cell proliferation was assessed using standard MTT assays. Protein and cAMP levels were detected by Western blotting and ELISA, respectively. Antigen localization was performed by immunocytochemistry, immunohistochemistry and immunofluorescence. Protein knockdown was achieved using small interfering RNA technologies.ResultsEGF and oestrogen, alone and in combination, induced cell proliferation and phosphorylation of MAPK proteins Raf and ERK (extracellular signal regulated kinase)1/2 in both ER-negative SKBR3 and ER-positive MCF-7 human breast cancer cell lines. Increased Raf phosphorylation was also observed in primary human breast cultures derived from ER-positive and ER-negative breast tumours. Oestrogen induced an increase in intracellular cAMP in ER-negative SKBR3 human breast cancer cells. Oestrogen-mediated cell growth and phosphorylation of MAPK was modified by the EGF receptor antagonist AG1478, the G-protein antagonist pertussis toxin, and the angiotensin II receptor antagonist saralasin. Knockdown of angiotensin II type 1 receptor (AT1) protein expression with small interfering RNA attenuated oestrogen-induced Raf phosphorylation in ER-negative cells. AT1 receptor was found to be expressed in the cell membrane of breast tumour epithelial cells.ConclusionThese findings provide evidence that, in breast cancer cells, oestrogen can signal through AT1 to activate early cell survival mechanisms in an ER-independent manner.

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Oestrogen-activated autophagy has a negative effect on the anti-osteoclastogenic function of oestrogen.

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Oestrogen-activated autophagy has a negative effect on the anti-osteoclastogenic function of oestrogen.

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