Abstract
Ischemic preconditioning (IPC) has a strong renoprotective effect during renal ischemia/reperfusion (I/R) injury that is thought to relate to autophagy. However, the role of autophagy during IPC-afforded renoprotection and the precise mechanisms involved are unknown. In this study, an in vitro hypoxia/reoxygenation (H/R) model was established in which oxygen and glucose deprivation (OGD) was applied to renal cells for 15 h followed by reoxygenation under normal conditions for 30 min, 2 h or 6 h; transient OGD and subsequent reoxygenation were implemented before prolonged H/R injury to achieve hypoxic preconditioning (HPC). 3-Methyladenine (3-MA) was used to inhibit autophagy. In a renal I/R injury model, rats were subjected to 40 min of renal ischemia followed by 6 h, 12 h or 24 h of reperfusion. IPC was produced by four cycles of ischemia (8 min each) followed by 5 min of reperfusion prior to sustained ischemia. We found that IPC increased LC3II and Beclin-1 levels and decreased SQSTM/p62 and cleaved caspase-3 levels in a time-dependent manner during renal I/R injury, as well as increased the number of intracellular double-membrane vesicles in injured renal cells. IPC-induced renal protection was efficiently attenuated by pretreatment with 5 mM 3-MA. Pretreatment with IPC also dynamically affected the expression of SGK1/FOXO3a/HIF-1α signaling components. Moreover, knocking down SGK1 expression significantly downregulated phosphorylated-FOXO3a (p-FOXO3a)/FOXO3 and HIF-1α, suppressed LC3II and Beclin-1 levels, increased SQSTM/p62 and cleaved caspase-3 levels, and abolished the protective effect of IPC against I/R-induced renal damage. SGK1 overexpression efficiently increased p-FOXO3a/FOXO3 and HIF-1α levels, promoted the autophagy flux and enhanced the protective effect mediated by HPC. Furthermore, FOXO3a overexpression decreased HIF-1α protein levels, inhibited HIF-1α transcriptional activity and reduced the protective effect of IPC. Our study indicates that IPC can ameliorate renal I/R injury by promoting autophagy through the SGK1 pathway.
Highlights
Acute kidney injury (AKI) is a severe clinical syndrome and a major contributor to morbidity and mortality[1]
Increases in LC3II, Beclin-1 and decreases in SQSTM1/p62, cleaved caspase-3 were evident in the hypoxic preconditioning (HPC)+H/R group compared with the H/R group (P < 0.05 vs. H/R) whereas these changes were abolished by 3-MA (P < 0.05 vs. HPC+H/R)
CCK-8 and lactic dehydrogenase (LDH) assays showed that HPC increased HK2 cells viability after H/R injury (P < 0.05 vs. H/R) (Fig. 1c, d), but this protective effect was abolished by 3-MA (P < 0.05 vs. HPC + H/R), indicating that the inhibition of autophagy is correlated with increased apoptosis and cell injury
Summary
Acute kidney injury (AKI) is a severe clinical syndrome and a major contributor to morbidity and mortality[1]. Ischemia/reperfusion (I/R) injury is a common cause of AKI in patients experiencing acute stress, such as surgery, organ transplantation, trauma, sepsis, or shock[2]. IPC has been shown to have a strong renoprotection effect due to its anti-apoptosis/necrosis, anti-inflammatory and anti-oxidant properties[5]. Xie et al Cell Death and Disease (2018)9:338 damaged cytosolic proteins and organelles to facilitate cellular homeostasis and promote cell survival under stress conditions, such as nutrient deprivation and hypoxia[6]. The induction of autophagy was recently shown to attenuate renal I/R injury[1,2]. The role of autophagy during IPC-afforded renoprotection and the precise mechanisms involved are poorly understood
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
