Jing Xingzhi, Wang Wenchao, He Xining, Liu Xiaoyang, Yang Xiaoxia, Su Cheng, Shao Yuandong, Ge Zhongpeng, Wang Heran, Cui Xingang
Department of Spine Surgery, Shandong Provincial Hospital Affiliated to Shandong First Medical University, Jinan, 250000, China.
Department of Neurosurgery, Binzhou People's Hospital, Binzhou, 256600, China.
J Orthop Translat. 2024 May 21;46:65-78. doi: 10.1016/j.jot.2024.03.005. eCollection 2024 May.
Iron overload is a prevalent condition in the elderly, often associated with various degenerative diseases, including intervertebral disc degeneration (IDD). Nevertheless, the mechanisms responsible for iron ion accumulation in tissues and the mechanism that regulate iron homeostasis remain unclear. Transferrin receptor-1 (TFR1) serves as the primary cellular iron gate, playing a pivotal role in controlling intracellular iron levels, however its involvement in IDD pathogenesis and the underlying mechanism remains obscure.
Firstly, IDD mice model was established to determine the iron metabolism associated proteins changes during IDD progression. Then CEP chondrocytes were isolated and treated with TBHP or pro-inflammatory cytokines to mimic pathological environment, western blotting, immunofluorescence assay and tissue staining were employed to explore the underlying mechanisms. Lastly, TfR1 siRNA and Feristatin II were employed and the degeneration of IDD was examined using micro-CT and immunohistochemical analysis.
We found that the IDD pathological environment, characterized by oxidative stress and pro-inflammatory cytokines, could enhance iron influx by upregulating TFR1 expression in a HIF-2α dependent manner. Excessive iron accumulation not only induces chondrocytes ferroptosis and exacerbates oxidative stress, but also triggers the innate immune response mediated by c-GAS/STING, by promoting mitochondrial damage and the release of mtDNA. The inhibition of STING through siRNA or the reduction of mtDNA replication using ethidium bromide alleviated the degeneration of CEP chondrocytes induced by iron overload.
Our study systemically explored the role of TFR1 mediated iron homeostasis in IDD and its underlying mechanisms, implying that targeting TFR1 to maintain balanced iron homeostasis could offer a promising therapeutic approach for IDD management.
Our study demonstrated the close link between iron metabolism dysfunction and IDD, indicated that targeting TfR1 may be a novel therapeutic strategy for IDD.
铁过载在老年人中是一种普遍存在的情况，常与包括椎间盘退变（IDD）在内的各种退行性疾病相关。然而，负责铁离子在组织中积累的机制以及调节铁稳态的机制仍不清楚。转铁蛋白受体1（TFR1）作为主要的细胞铁通道，在控制细胞内铁水平方面发挥着关键作用，但其在IDD发病机制中的作用及潜在机制仍不清楚。
首先，建立IDD小鼠模型以确定IDD进展过程中与铁代谢相关蛋白的变化。然后分离CEP软骨细胞并用叔丁基过氧化氢（TBHP）或促炎细胞因子处理以模拟病理环境，采用蛋白质免疫印迹法、免疫荧光测定法和组织染色法来探究潜在机制。最后，使用TfR1小干扰RNA（siRNA）和铁抑素II，并通过显微CT和免疫组织化学分析检查IDD的退变情况。
我们发现，以氧化应激和促炎细胞因子为特征的IDD病理环境，可通过以低氧诱导因子-2α（HIF-2α）依赖的方式上调TFR1表达来增强铁流入。过量的铁积累不仅诱导软骨细胞铁死亡并加剧氧化应激，还通过促进线粒体损伤和线粒体DNA（mtDNA）释放来触发由环鸟苷酸-腺苷酸合成酶（c-GAS）/干扰素基因刺激蛋白（STING）介导的固有免疫反应。通过siRNA抑制STING或使用溴化乙锭减少mtDNA复制可减轻铁过载诱导的CEP软骨细胞退变。
我们的研究系统地探讨了TFR1介导的铁稳态在IDD中的作用及其潜在机制，这意味着靶向TFR1以维持铁稳态平衡可能为IDD的治疗提供一种有前景的治疗方法。
我们的研究证明了铁代谢功能障碍与IDD之间的密切联系，表明靶向TfR1可能是IDD的一种新的治疗策略。
