Abstract：
Iron overload is a risk factor for osteoporosis due to its oxidative toxicity. Previous studies have demonstrated that an excessive amount of iron increases osteocyte apoptosis and receptor activator of nuclear factor κ-B ligand (RANKL) production, which stimulates osteoclast differentiation in vitro. However, the effects of exogenous iron supplementation-induced iron overload on osteocytes in vivo and its role in iron overload-induced bone loss are unknown. This work aimed to develop an iron overloaded murine model of C57BL/6 mice by intraperitoneal administration of iron dextran for two months. The iron levels in various organs, bone, and serum, as well as the microstructure and strength of bone, apoptosis of osteocytes, oxidative stress in bone tissue, and bone formation and resorption, were assessed. The results showed that 2 months of exogenous iron supplementation significantly increased iron levels in the liver, spleen, kidney, bone tissue, and serum. Iron overload negatively affected bone microstructure and strength. Osteocyte apoptosis and empty lacunae rate were elevated by exogenous iron. Iron overload upregulated RANKL expression but had no significant impact on osteoprotegerin (OPG) and sclerostin levels. Static and dynamic histologic analyses and serum biochemical assay showed that iron overload increased bone resorption without significantly affecting bone formation. Exogenous iron promoted oxidative stress in osteocytes in vivo and in vitro. Additional supplementation of iron chelator (deferoxamine) or N-acetyl-l-cysteine (NAC) partially alleviated bone loss, osteocyte apoptosis, osteoclast formation, and oxidative stress due to iron overload. These findings, in line with prior in vitro studies, suggest that exogenous iron supplementation induces osteoclastogenesis and osteoporosis by promoting osteocyte apoptosis and RANKL production via oxidative stress.
摘要：
铁过载是骨质疏松症的危险因素，因为它具有氧化毒性。以前的研究表明，过量的铁增加骨细胞凋亡和核因子κ-B受体活化因子配体（RANKL）的产生，在体外刺激破骨细胞分化。然而,外源性补铁诱导的铁过载对体内骨细胞的影响及其在铁过载诱导的骨丢失中的作用尚不清楚.这项工作旨在通过腹膜内施用右旋糖酐铁两个月来建立C57BL/6小鼠的铁过载鼠模型。各种器官中的铁水平，骨头,和血清，以及骨骼的微观结构和强度，骨细胞凋亡，骨组织中的氧化应激，骨的形成和吸收，被评估。结果表明,2个月的外源性补铁显著增加肝脏中的铁水平,脾,脾肾,骨组织,和血清。铁过载对骨骼微观结构和强度有负面影响。外源性铁可提高骨细胞凋亡和空腔率。铁过载上调RANKL表达，但对骨保护素（OPG）和硬化素水平没有显着影响。静态和动态组织学分析以及血清生化分析表明，铁过载会增加骨吸收，而不会显着影响骨形成。外源性铁在体内和体外促进骨细胞的氧化应激。补充铁螯合剂（去铁胺）或N-乙酰-L-半胱氨酸（NAC）部分缓解骨丢失，骨细胞凋亡,破骨细胞形成，和铁过载引起的氧化应激。这些发现,与先前的体外研究一致，提示外源性铁补充通过氧化应激促进骨细胞凋亡和RANKL的产生而诱导破骨细胞生成和骨质疏松。
