Department of Pathology, Northwestern University, Chicago, IL.
Department of Pathology, Northwestern University, Chicago, IL
Diabetes. 2020 Jun;69(6):1248-1263. doi: 10.2337/db19-0935. Epub 2020 Mar 13.
Conceivably, upregulation of -inositol oxygenase (MIOX) is associated with altered cellular redox. Its promoter includes oxidant-response elements, and we also discovered binding sites for XBP1, a transcription factor of endoplasmic reticulum (ER) stress response. Previous studies indicate that MIOX's upregulation in acute tubular injury is mediated by oxidant and ER stress. Here, we investigated whether hyperglycemia leads to accentuation of oxidant and ER stress while these boost each other's activities, thereby augmenting tubulointerstitial injury/fibrosis. We generated MIOX-overexpressing transgenic (MIOX-TG) and MIOX knockout (MIOX-KO) mice. A diabetic state was induced by streptozotocin administration. Also, MIOX-KO were crossbred with to generate /KO mice. MIOX-TG mice had worsening renal functions with kidneys having increased oxidant/ER stress, as reflected by DCF/dihydroethidium staining, perturbed NAD-to-NADH and glutathione-to-glutathione disulfide ratios, increased NOX4 expression, apoptosis and its executionary molecules, accentuation of TGF-β signaling, Smads and XBP1 nuclear translocation, expression of GRP78 and XBP1 (ER stress markers), and accelerated tubulointerstitial fibrosis. These changes were not seen in MIOX-KO mice. Interestingly, such changes were remarkably reduced in /KO mice and, likewise, in vitro experiments with XBP1 siRNA. These findings suggest that MIOX expression accentuates, while its deficiency shields kidneys from, tubulointerstitial injury by dampening oxidant and ER stress, which mutually enhance each other's activity.
可以想象，肌醇氧化酶（MIOX）的上调与细胞氧化还原的改变有关。其启动子包括氧化剂反应元件，我们还发现了结合位点为 XBP1，内质网（ER）应激反应的转录因子。先前的研究表明，急性肾小管损伤中 MIOX 的上调是由氧化剂和 ER 应激介导的。在这里，我们研究了高血糖是否会导致氧化剂和 ER 应激的加剧，同时这些应激会增强彼此的活性，从而加重肾小管间质损伤/纤维化。我们生成了肌醇氧化酶过表达转基因（MIOX-TG）和肌醇氧化酶敲除（MIOX-KO）小鼠。通过链脲佐菌素给药诱导糖尿病状态。此外，MIOX-KO 与杂交生成 /KO 小鼠。MIOX-TG 小鼠肾功能恶化，肾脏氧化应激/内质网应激增加，反映在 DCF/二氢乙啶染色、NAD 到 NADH 和谷胱甘肽到谷胱甘肽二硫化物比例紊乱、NOX4 表达增加、细胞凋亡及其执行分子、TGF-β信号转导、Smads 和 XBP1 核易位、GRP78 和 XBP1（内质网应激标志物）的表达增加以及肾小管间质纤维化加速。这些变化在 MIOX-KO 小鼠中没有观察到。有趣的是，在 /KO 小鼠中，这些变化明显减少，同样，在 XBP1 siRNA 的体外实验中也是如此。这些发现表明，MIOX 的表达加重，而其缺乏通过抑制氧化剂和 ER 应激来保护肾脏免受肾小管间质损伤，这两种应激相互增强彼此的活性。
