Bazedoxifene Ameliorates Homocysteine-Induced Apoptosis via NADPH Oxidase-Interleukin 1β and 6 Pathway in Osteocyte-like Cells

• Published in: Calcified tissue international 2019-10, Vol.105 (4), p.446-457
• Main Authors: Notsu, Masakazu, Kanazawa, Ippei, Takeno, Ayumu, Tanaka, Ken-ichiro, Sugimoto, Toshitsugu
• Format: Article
• Language: English
• Subjects: 17β-Estradiol; Apoptosis; Biochemistry; Biomedical and Life Sciences; Cell Biology; Cell lines; CYBB protein; Cytokines; DNA fragmentation; Endocrinology; Enzyme-linked immunosorbent assay; Gene expression; Homocysteine; IL-1β; Inflammation; Interleukin 6; Interleukin 6 receptors; Life Sciences; Monoclonal antibodies; NAD(P)H oxidase; Original Research; Orthopedics; Osteocytes; Oxidative stress; Selective estrogen receptor modulators
• ISSN: 0171-967X; 1432-0827
• DOI: 10.1007/s00223-019-00580-7

Homocysteine (Hcy) increases oxidation and inflammation; however, the mechanism of Hcy-induced bone fragility remains unclear. Because selective estrogen modulators (SERMs) have an anti-oxidative effect, SERMs may rescue the Hcy-induced bone fragility. We aimed to examine whether oxidative stress and pro-inflammatory cytokines such as interleukin (IL)-1β and IL-6 are involved in the Hcy-induced apoptosis of osteocytes and whether bazedoxifene (BZA) inhibits the detrimental effects of Hcy. We used mouse osteocyte-like cell lines MLO-Y4-A2 and Ocy454. Apoptosis was examined by DNA fragmentation ELISA and TUNEL staining, and gene expression was evaluated by real-time PCR. Hcy 5 mM significantly increased expressions of NADPH oxidase (Nox)1, Nox2, IL-1β, and IL-6 as well as apoptosis in MLO-Y4-A2 cells. Nox inhibitors, diphenyleneiodonium chloride and apocynin, significantly suppressed Hcy-induced IL-1β and IL-6 expressions. In contrast, an IL-1β receptor antagonist and an IL-6 receptor monoclonal antibody had no effects on Hcy-induced Nox1 and Nox2 expressions, but significantly rescued Hcy-induced apoptosis. BZA (1 nM–1 μM) and 17β estradiol 100 nM significantly rescued Hcy-induced apoptosis, while an estrogen receptor blocker ICI 182,780 reversed the effects of BZA and 17β estradiol. BZA also rescued Hcy-induced apoptosis of Ocy454 cell, and ICI canceled the effect of BZD. Moreover, BZA significantly ameliorated Hcy-induced expressions of Nox1, Nox2, IL-1β, and IL-6, and ICI canceled the effects of BZA on their expressions. Hcy increases apoptosis through stimulating Nox 1 and Nox 2-IL-1β and IL-6 expressions in osteocyte-like cells. BZA inhibits the detrimental effects of Hcy on osteocytes via estrogen receptor.