Division of Nephrology and Hypertension, Department of Medicine, University of California at Irvine, Irvine, CA 92868, USA.
Division of Nephrology and Hypertension, Department of Medicine, University of California at Irvine, Irvine, CA 92868, USA.
Free Radic Biol Med. 2015 Sep;86:374-81. doi: 10.1016/j.freeradbiomed.2015.04.022. Epub 2015 Apr 28.
Oxidative stress and inflammation play a central role in the progression and complications of chronic kidney disease (CKD) and are, in part, due to impairment of the Nrf2 system, which regulates the expression of antioxidant and detoxifying molecules. Natural Nrf2-inducing phytochemicals have been shown to ameliorate kidney disease in experimental animals. However, owing to adverse outcomes a clinical trial of a synthetic Nrf2 activator, bardoxolone methyl (BARD), in CKD patients was terminated. BARD activates Nrf2 via covalent modification of reactive cysteine residues in the Nrf2 repressor molecule, Keap1. In addition to Nrf2, Keap1 suppresses IKKB, the positive regulator of NF-κB. Treatment with a BARD analog, dh404, at 5-20mg/kg/day in diabetic obese Zucker rats exacerbates, whereas its use at 2mg/kg/day in 5/6 nephrectomized rats attenuates, CKD progression. We, therefore, hypothesized that deleterious effects of high-dose BARD are mediated by the activation of NF-κB. CKD (5/6 nephrectomized) rats were randomized to receive dh404 (2 or 10mg/kg/day) or vehicle for 12 weeks. The vehicle-treated group exhibited glomerulosclerosis; interstitial fibrosis and inflammation; activation of NF-κB; upregulation of oxidative, inflammatory, and fibrotic pathways; and suppression of Nrf2 activity and its key target gene products. Treatment with low-dose dh404 restored Nrf2 activity and expression of its target genes, attenuated activation of NF-κB and fibrotic pathways, and reduced glomerulosclerosis, interstitial fibrosis, and inflammation. In contrast, treatment with a high dh404 dosage intensified proteinuria, renal dysfunction, and histological abnormalities; amplified upregulation of NF-κB and fibrotic pathways; and suppressed the Nrf2 system. Thus therapy with BARD analogs exerts a dose-dependent dimorphic impact on CKD progression.
氧化应激和炎症在慢性肾脏病 (CKD) 的进展和并发症中起着核心作用,部分原因是 Nrf2 系统的损伤,该系统调节抗氧化和解毒分子的表达。已显示天然 Nrf2 诱导的植物化学物质可改善实验动物的肾脏疾病。然而,由于不良后果,一项针对 CKD 患者的合成 Nrf2 激活剂 bardoxolone 甲基 (BARD) 的临床试验被终止。BARD 通过共价修饰 Nrf2 抑制剂 Keap1 中的反应性半胱氨酸残基来激活 Nrf2。除了 Nrf2,Keap1 还抑制 NF-κB 的正调节剂 IKKB。在糖尿病肥胖 Zucker 大鼠中,每天用 5-20mg/kg 的 BARD 类似物 dh404 治疗会加重 CKD 进展,而每天用 2mg/kg 的 dh404 治疗则会减轻 CKD 进展。因此,我们假设高剂量 BARD 的有害影响是通过 NF-κB 的激活介导的。将 CKD(5/6 肾切除)大鼠随机分为 dh404(2 或 10mg/kg/天)或载体治疗 12 周。载体处理组表现出肾小球硬化;间质纤维化和炎症;NF-κB 的激活;氧化、炎症和纤维化途径的上调;以及 Nrf2 活性及其关键靶基因产物的下调。用低剂量 dh404 治疗可恢复 Nrf2 活性和靶基因的表达,减弱 NF-κB 和纤维化途径的激活,并减少肾小球硬化、间质纤维化和炎症。相比之下,用高 dh404 剂量治疗会加剧蛋白尿、肾功能障碍和组织学异常;放大 NF-κB 和纤维化途径的上调;并抑制 Nrf2 系统。因此,BARD 类似物的治疗对 CKD 进展具有剂量依赖性的双重影响。
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