title: MicroRNA-17-92a upregulation by estrogen leads to Bim targeting and inhibition of osteoblast apoptosis.
abstract: Anti-apoptotic effects of estrogen on osteoblasts are very important in the etiology of estrogen protection of the adult skeleton against bone loss. The mechanisms of this process are still not fully understood. Recent studies implicated an important role of microRNAs in estrogen-mediated responses in various cellular processes, including cell apoptosis and proliferation. Therefore, we hypothesized that these regulatory molecules might be involved with estrogen in protecting osteoblasts from apoptosis. Western blotting, quantitative real-time PCR, flow cytometry and luciferase assays were employed to investigate the role of microRNAs in this process. The microRNA cluster miR-17-92a, a post-transcriptional regulator, was significantly reduced during dexamethasone, etoposide and tumor necrosis factor alpha (TNF-α)-induced osteoblasts apoptosis. The repression of miR-17-92a was significantly attenuated by estrogen. To delineate the role of miR-17-92a in apoptosis, we silenced and overexpressed miR-17-92a in osteoblasts. We found that miR-17-92a depletion significantly enhanced dexamethasone-induced apoptosis and overexpressing miR-17-92a remarkably increased the anti-apoptotic effects of estrogen on osteoblasts. Mechanistic studies showed that miR-17-92a inhibited Bim expression through a microRNA-17-92a-binding site within the 3'-untranslated region of Bim. The post-transcriptional repression of Bim was further confirmed by a luciferase reporter assay. These results showed that miR-17-92a, plays a significant role in the process of estrogen protection of osteoblasts against apoptosis, by regulating Bim expression.
authors.affiliation: Shanghai Key Laboratory for Bone and Joint Diseases, Shanghai Institute of Orthopaedics and Traumatology, Shanghai Ruijin Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, 20025, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Guo
authors.forename: Jiping
authors.initials: J
authors.lastname: Xu
authors.forename: Jin
authors.initials: J
authors.lastname: Qi
authors.forename: Lianfang
authors.initials: L
authors.lastname: Zhang
authors.forename: Jinsheng
authors.initials: J
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Liang
authors.forename: Niandong
authors.initials: N
authors.lastname: Qian
authors.forename: Hanbing
authors.initials: H
authors.lastname: Zhou
authors.forename: Li
authors.initials: L
authors.lastname: Wei
authors.forename: Lianfu
authors.initials: L
authors.lastname: Deng
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D005047:Etoposide / Q000494:pharmacology; D005260:Female; D005434:Flow Cytometry; D007150:Immunohistochemistry; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D004967:Estrogens; C575895:MIRN17-92 microRNA, mouse; D008565:Membrane Proteins; D035683:MicroRNAs; D011518:Proto-Oncogene Proteins; D014409:Tumor Necrosis Factor-alpha; D005047:Etoposide; D003907:Dexamethasone