Centre for Kidney Disease Research, Faculty of Medicine, Translational Research Institute, University of Queensland , Brisbane , Australia.
Department of Biomedical Engineering, Cornell University , Ithaca, New York.
Am J Physiol Renal Physiol. 2018 May 1;314(5):F956-F968. doi: 10.1152/ajprenal.00057.2017. Epub 2018 Jan 10.
Oxidative stress and mitochondrial dysfunction exacerbate acute kidney injury (AKI), but their role in any associated progress to chronic kidney disease (CKD) remains unclear. Antioxidant therapies often benefit AKI, but their benefits in CKD are controversial since clinical and preclinical investigations often conflict. Here we examined the influence of the antioxidant N-acetyl-cysteine (NAC) on oxidative stress and mitochondrial function during AKI (20-min bilateral renal ischemia plus reperfusion/IR) and progression to chronic kidney pathologies in mice. NAC (5% in diet) was given to mice 7 days prior and up to 21 days post-IR (21d-IR). NAC treatment resulted in the following: prevented proximal tubular epithelial cell apoptosis at early IR (40-min postischemia), yet enhanced interstitial cell proliferation at 21d-IR; increased transforming growth factor-β1 expression independent of IR time; and significantly dampened nuclear factor-like 2-initiated cytoprotective signaling at early IR. In the long term, NAC enhanced cellular metabolic impairment demonstrated by increased peroxisome proliferator activator-γ serine-112 phosphorylation at 21d-IR. Intravital multiphoton microscopy revealed increased endogenous fluorescence of nicotinamide adenine dinucleotide (NADH) in cortical tubular epithelial cells during ischemia, and at 21d-IR that was not attenuated with NAC. Fluorescence lifetime imaging microscopy demonstrated persistent metabolic impairment by increased free/bound NADH in the cortex at 21d-IR that was enhanced by NAC. Increased mitochondrial dysfunction in remnant tubular cells was demonstrated at 21d-IR by tetramethylrhodamine methyl ester fluorimetry. In summary, NAC enhanced progression to CKD following AKI not only by dampening endogenous cellular antioxidant responses at time of injury but also by enhancing persistent kidney mitochondrial and metabolic dysfunction.
氧化应激和线粒体功能障碍加剧急性肾损伤 (AKI)，但其在任何相关慢性肾脏病 (CKD) 进展中的作用仍不清楚。抗氧化治疗通常对 AKI 有益，但在 CKD 中的益处存在争议，因为临床和临床前研究经常存在冲突。在这里，我们研究了抗氧化剂 N-乙酰半胱氨酸 (NAC) 在 AKI（20 分钟双侧肾缺血再灌注/IR）期间和向慢性肾脏病病理进展过程中对氧化应激和线粒体功能的影响。NAC（饮食中 5%）在 IR 前 7 天和 IR 后 21 天（21d-IR）给予小鼠。NAC 治疗导致以下结果：在早期 IR（缺血后 40 分钟）时预防近端肾小管上皮细胞凋亡，但在 21d-IR 时增强间质细胞增殖；增加转化生长因子-β1 的表达而不依赖于 IR 时间；并在早期 IR 时显著抑制核因子样 2 启动的细胞保护信号。从长远来看，NAC 增强了细胞代谢损伤，表现为 21d-IR 时过氧化物酶体增殖物激活受体-γ丝氨酸-112 磷酸化增加。活体多光子显微镜显示，在缺血过程中和 21d-IR 期间，皮质管状上皮细胞中的烟酰胺腺嘌呤二核苷酸 (NADH) 内源性荧光增加，而 NAC 并不能减轻这种增加。荧光寿命成像显微镜显示，在 21d-IR 时，皮质中的游离/结合 NADH 持续代谢损伤增加，NAC 增强了这种损伤。通过四甲基罗丹明甲酯荧光法在 21d-IR 时证明了残余管状细胞中的线粒体功能障碍增加。总之，NAC 不仅通过在损伤时抑制内源性细胞抗氧化反应，而且通过增强持续的肾脏线粒体和代谢功能障碍，增强了 AKI 后 CKD 的进展。
