title: Advanced Glycation End Product 3 (AGE3) Increases Apoptosis and the Expression of Sclerostin by Stimulating TGF-β Expression and Secretion in Osteocyte-Like MLO-Y4-A2 Cells.
abstract: Advanced glycation end products (AGEs) cause bone fragility due to deterioration in bone quality. We previously reported that AGE3 induced apoptosis and inhibited differentiation via increased transforming growth factor (TGF)-β signaling in osteoblastic cells. Additionally, we demonstrated that AGE3 increased apoptosis and sclerostin expression and decreased receptor activator of nuclear factor-κB ligand (RANKL) expression in osteocyte-like cells. However, it remains unclear whether TGF-β signaling is involved in the effects of AGEs on apoptosis and the expression of sclerostin and RANKL in osteocytes. Effects of AGE3 on apoptosis of mouse osteocyte-like MLO-Y4-A2 cells were examined by DNA fragmentation ELISA. Expression of TGF-β, sclerostin, and RANKL was evaluated using real-time PCR, Western blotting, and ELISA kits. To block TGF-β signaling, we used SD208, a TGF-β type I receptor kinase inhibitor. AGE3 (200 µg/mL) significantly increased apoptosis and mRNA expression of Sost, the gene encoding sclerostin, and decreased Rankl mRNA expression in MLO-Y4-A2 cells. AGE3 significantly increased the expression of TGF-β. Co-incubation of SD208 with AGE3 significantly rescued AGE3-induced apoptosis in a dose-dependent manner. Moreover, SD208 restored AGE3-increased mRNA and protein expression of sclerostin. In contrast, SD208 did not affect AGE3-decreased mRNA and protein expression of RANKL. These findings suggest that AGE3 increases apoptosis and sclerostin expression through increasing TGF-β expression in osteocytes, and that AGE3 decreases RANKL expression independent of TGF-β signaling.
authors.affiliation: Internal Medicine 1, Shimane University Faculty of Medicine, 89-1, Enya-cho, Izumo, Shimane, 693-8501, Japan.
authors.forename: Masakazu
authors.initials: M
authors.lastname: Notsu
authors.affiliation: Internal Medicine 1, Shimane University Faculty of Medicine, 89-1, Enya-cho, Izumo, Shimane, 693-8501, Japan. ippei.k@med.shimane-u.ac.jp.
authors.forename: Ippei
authors.initials: I
authors.lastname: Kanazawa
authors.affiliation: Internal Medicine 1, Shimane University Faculty of Medicine, 89-1, Enya-cho, Izumo, Shimane, 693-8501, Japan.
authors.forename: Ayumu
authors.initials: A
authors.lastname: Takeno
authors.affiliation: Internal Medicine 1, Shimane University Faculty of Medicine, 89-1, Enya-cho, Izumo, Shimane, 693-8501, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Yokomoto-Umakoshi
authors.affiliation: Internal Medicine 1, Shimane University Faculty of Medicine, 89-1, Enya-cho, Izumo, Shimane, 693-8501, Japan.
authors.forename: Ken-Ichiro
authors.initials: KI
authors.lastname: Tanaka
authors.affiliation: Internal Medicine 1, Shimane University Faculty of Medicine, 89-1, Enya-cho, Izumo, Shimane, 693-8501, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Yamaguchi
authors.affiliation: Internal Medicine 1, Shimane University Faculty of Medicine, 89-1, Enya-cho, Izumo, Shimane, 693-8501, Japan.
authors.forename: Toshitsugu
authors.initials: T
authors.lastname: Sugimoto
mesh_terms: D000818:Animals; D017209:Apoptosis; D001842:Bone and Bones / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology; D002460:Cell Line; D017127:Glycation End Products, Advanced / Q000378:metabolism*; D006023:Glycoproteins / Q000378:metabolism; D051379:Mice; D010011:Osteocytes / Q000378:metabolism*; D053245:RANK Ligand / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*
chemical_list: D017127:Glycation End Products, Advanced; D006023:Glycoproteins; D053245:RANK Ligand; D016212:Transforming Growth Factor beta
keywords: Advanced Glycation End Products; Bone quality; Diabetes mellitus; Osteocyte; TGF-β