Pretreatment with Roxadustat (FG-4592) Attenuates Folic Acid-Induced Kidney Injury through Antiferroptosis via Akt/GSK-3β/Nrf2 Pathway.

Xue Li,Xiao-Yue Zhai,Jia Xing,Yuan-Yuan Fu,Yu Zou,Peng-Zhi Wan,Kai-Yue Wang

doi:10.1155/2020/6286984

Abstract

Folic acid- (FA-) induced kidney injury is characterized by the tubule damage due to the disturbance of the antioxidant system and subsequent interstitial fibrosis. FG-4592 is an inhibitor of prolyl hydroxylase of hypoxia-inducible factor (HIF), an antioxidant factor. The present study investigated the protective role of FG-4592 pretreatment at the early stage of the kidney injury and long-term impact on the progression of renal fibrosis. FG-4592 was administrated two days before FA injection in mice. On the second day after FA injection, the mice with FG-4592 pretreatment showed an improved renal function, compared with those without FG-4592 pretreatment, indicated by biochemical and histological parameters; meanwhile, the cellular content of iron, malondialdehyde, and 4-hydroxynonenal histologically decreased, implying the suppression of iron accumulation and lipid peroxidation. Simultaneously, upregulation of HIF-1α was found, along with Nrf2 activation, which was reflected by increased nuclear translocation and high-expression of downstream proteins, including heme-oxygenase1, glutathione peroxidase4, and cystine/glutamate transporter, as well as ferroportin. Correspondingly, the elevated levels of antioxidative enzymes and glutathione, as well as reduced iron accumulation, were observed, suggesting a lower risk of occurrence of ferroptosis with FG-4592 pretreatment. This was confirmed by reversed pathological parameters and improved renal function in FA-treated mice with the administration of ferrostatin-1, a specific ferroptosis inhibitor. Furthermore, a signal pathway study indicated that Nrf2 activation was associated with increased phosphorylation of Akt and GSK-3β, verified by the use of an inhibitor of the PI3K that phosphorylates Akt. Moreover, FG-4592 pretreatment also decreased macrophage infiltration and expression of inflammatory factors TNF-α and IL-1β. On the 14th day after FA injection, FG-4592 pretreatment decreased collagen deposition and expression of fibrosis biomarkers. These findings suggest that the protective role of FG-4592 pretreatment is achieved mainly by decreasing ferroptosis at the early stage of FA-induced kidney injury via Akt/GSK-3β-mediated Nrf2 activation, which retards the fibrosis progression.

Highlights

Acute kidney injury (AKI) is characterized by an acute and transient renal dysfunction and often progressively develops into chronic kidney disease (CKD) without adequate treatment [1,2,3,4]
Our present study indicated that the FA group showed increased serum levels of BUN, creatinine, and KIM-1, a marker of tubular damage, as compared to the control group on the second day after FA administration
FG-4592 is an inhibitor of prolyl hydroxylases (PHD) that degrades hypoxia-inducible factor (HIF) in normoxia and is a stabilizer of HIF

Summary

Introduction

Acute kidney injury (AKI) is characterized by an acute and transient renal dysfunction and often progressively develops into chronic kidney disease (CKD) without adequate treatment [1,2,3,4]. FA-induced AKI is a widely used model for studying the mechanisms underlying nephrotoxic tubule damage and gradual progression of renal fibrosis [6, 7]. Water and vacuole degeneration and cellular swelling are the initial pathological features of tubular damage [9, 10]. These pathological features in mice are comparable with those in human kidney injury, and the experimental model recapitulates all the major processes in human kidney injury [11]. The production of reactive oxygen species (ROS) and consequent disturbance of the antioxidation system followed by apoptosis, ferroptosis, or even necrosis are the generally accepted mechanisms for oxidative stressmediated kidney injury [12, 13]. The inflammatory responses caused by ferroptosis have been thought to be a driver for the occurrence of other cell death, such as apoptosis or necroptosis [16]

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