Plants for Human Health Institute, Dept. of Animal Science, NC Research Campus, NC State University, Kannapolis, 28081, NC, USA; Dept. of Biotechnology, Chemistry and Pharmacy, University of Siena, Siena, Italy.
Plants for Human Health Institute, Dept. of Animal Science, NC Research Campus, NC State University, Kannapolis, 28081, NC, USA.
Arch Biochem Biophys. 2020 Sep 15;690:108416. doi: 10.1016/j.abb.2020.108416. Epub 2020 Jun 2.
Alkaptonuria (AKU) is a rare metabolic disease correlated with the deficiency of homogentisate 1,2-dioxygenase and leading to an accumulation of the metabolite homogentisic acid (HGA) which can be subjected to oxidation and polymerization reactions. These events are considered a trigger for the induction of oxidative stress in AKU but, despite the large description of an altered redox status, the underlying pathogenetic processes are still unstudied. In the present study, we investigated the molecular mechanisms responsible for the oxidative damage present in an osteoblast-based cellular model of AKU. Bone, in fact, is largely affected in AKU patients: severe osteoclastic resorption, osteoporosis, even for pediatric cases, and an altered rate of remodeling biomarkers have been reported. In our AKU osteoblast cell model, we found a clear altered redox homeostasis, determined by elevated hydrogen peroxide (HO) levels and 4HNE protein adducts formation. These findings were correlated with increased NADPH oxidase (NOX) activity and altered mitochondrial respiration. In addition, we observed a decreased activity of superoxide dismutase (SOD) and reduced levels of thioredoxin (TRX) that parallel the decreased Nrf2-DNA binding. Overall, our results reveal that HGA is able to alter the cellular redox homeostasis by modulating the endogenous ROS production via NOX activation and mitochondrial dysfunctions and impair the cellular response mechanism. These findings can be useful for understanding the pathophysiology of AKU, not yet well studied in bones, but which is an important source of comorbidities that affect the life quality of the patients.
尿黑酸尿症（AKU）是一种罕见的代谢疾病，与 4-羟基苯丙酮酸双加氧酶的缺乏有关，导致代谢物 4-羟基苯乙酸（HGA）的积累，HGA 可发生氧化和聚合反应。这些事件被认为是 AKU 中氧化应激诱导的一个触发因素，但是，尽管大量描述了氧化还原状态的改变，其潜在的发病机制仍未得到研究。在本研究中，我们研究了导致 AKU 基于成骨细胞的细胞模型中氧化损伤的分子机制。事实上，骨骼在 AKU 患者中受到严重影响：严重的破骨细胞吸收、骨质疏松症，甚至在儿科病例中，以及重塑生物标志物的改变率均有报道。在我们的 AKU 成骨细胞模型中，我们发现明显的氧化还原平衡失调，这是由过氧化氢（HO）水平升高和 4HNE 蛋白加合物形成所决定的。这些发现与 NADPH 氧化酶（NOX）活性增加和线粒体呼吸改变相关。此外，我们观察到超氧化物歧化酶（SOD）活性降低和硫氧还蛋白（TRX）水平降低，这与 Nrf2-DNA 结合减少平行。总的来说，我们的结果表明 HGA 能够通过激活 NOX 和线粒体功能障碍来调节内源性 ROS 产生，从而改变细胞的氧化还原平衡，并损害细胞的反应机制。这些发现对于理解 AKU 的病理生理学可能是有用的，尽管 AKU 在骨骼中的研究还不够深入，但它是影响患者生活质量的多种并发症的重要来源。
