Li Mirandy S, Adesina Sherry E, Ellis Carla L, Gooch Jennifer L, Hoover Robert S, Williams Clintoria R
School of Medicine, Emory University, Atlanta, Georgia.
Atlanta Veterans Affairs Medical Center, Atlanta, Georgia.
Am J Physiol Cell Physiol. 2017 Jan 1;312(1):C47-C55. doi: 10.1152/ajpcell.00208.2016. Epub 2016 Nov 2.
Zn deficiency (ZnD) is comorbid with chronic kidney disease and worsens kidney complications. Oxidative stress is implicated in the detrimental effects of ZnD. However, the sources of oxidative stress continue to be identified. Since NADPH oxidases (Nox) are the primary enzymes that contribute to renal reactive oxygen species generation, this study's objective was to determine the role of these enzymes in ZnD-induced oxidative stress. We hypothesized that ZnD promotes NADPH oxidase upregulation, resulting in oxidative stress and kidney damage. To test this hypothesis, wild-type mice were pair-fed a ZnD or Zn-adequate diet. To further investigate the effects of Zn bioavailability on NADPH oxidase regulation, mouse tubular epithelial cells were exposed to the Zn chelator N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) or vehicle followed by Zn supplementation. We found that ZnD diet-fed mice develop microalbuminuria, electrolyte imbalance, and whole kidney hypertrophy. These markers of kidney damage are accompanied by elevated Nox2 expression and HO levels. In mouse tubular epithelial cells, TPEN-induced ZnD stimulates HO generation. In this in vitro model of ZnD, enhanced HO generation is prevented by NADPH oxidase inhibition with diphenyleneiodonium. Specifically, TPEN promotes Nox2 expression and activation, which are reversed when intracellular Zn levels are restored following Zn supplementation. Finally, Nox2 knockdown by siRNA prevents TPEN-induced HO generation and cellular hypertrophy in vitro. Together, these findings reveal that Nox2 is a Zn-regulated enzyme that mediates ZnD-induced oxidative stress and kidney hypertrophy. Understanding the specific mechanisms by which ZnD contributes to kidney damage may have an important impact on the treatment of chronic kidney disease.
锌缺乏（ZnD）与慢性肾脏病合并存在，并会加重肾脏并发症。氧化应激与锌缺乏的有害影响有关。然而，氧化应激的来源仍有待确定。由于NADPH氧化酶（Nox）是导致肾脏活性氧生成的主要酶，本研究的目的是确定这些酶在锌缺乏诱导的氧化应激中的作用。我们假设锌缺乏会促进NADPH氧化酶上调，从而导致氧化应激和肾脏损伤。为了验证这一假设，对野生型小鼠进行配对喂养，分别给予锌缺乏或锌充足的饮食。为了进一步研究锌生物利用度对NADPH氧化酶调节的影响，将小鼠肾小管上皮细胞暴露于锌螯合剂N,N,N',N'-四（2-吡啶甲基）乙二胺（TPEN）或溶剂中，随后补充锌。我们发现，喂食锌缺乏饮食的小鼠出现微量白蛋白尿、电解质失衡和全肾肥大。这些肾脏损伤标志物伴随着Nox2表达和HO水平的升高。在小鼠肾小管上皮细胞中,TPEN诱导的锌缺乏刺激HO生成。在这个锌缺乏的体外模型中，用二苯基碘鎓抑制NADPH氧化酶可防止HO生成增加。具体而言，TPEN促进Nox2表达和激活，而在补充锌后细胞内锌水平恢复时，这种促进作用会逆转。最后，通过小干扰RNA敲低Nox2可防止TPEN在体外诱导的HO生成和细胞肥大。总之，这些发现表明Nox2是一种锌调节酶，介导锌缺乏诱导的氧化应激和肾脏肥大。了解锌缺乏导致肾脏损伤的具体机制可能对慢性肾脏病的治疗产生重要影响。
