Autophagy activation attenuates renal ischemia-reperfusion injury in rats

New insights into the potential cardioprotective effects of telmisartan and nanoformulated extract of Spirulina platensis via regulation of oxidative stress, apoptosis, and autophagy in an experimental model

Background

Cardiotoxicity is one of the limiting side effects of the commonly used anticancer agent cyclophosphamide (Cyclo).

Materials and methods

The possible protective effects of telmisartan and nanoformulated Spirulina platensis (Sp) methanolic extract against Cyclo-induced cardiotoxicity were examined in this study. Experimental groups of rats were randomly divided into nine groups as control vehicle, control polymer, telmisartan (TEL, 10 mg/kg), free Sp extract (300 mg/kg), nano Sp extract (100 mg/kg), Cyclo (200 mg/kg), TEL + Cyclo, free Sp + Cyclo, and nano Sp + Cyclo. The groups with Cyclo combinations were treated in the same manner as their corresponding ones without Cyclo, with a single dose of Cyclo on day 18.

Results

The results indicate that Cyclo causes significant cardiotoxicity, manifesting in the form of notable increases of 155.49%, 105.74%, 451.76%, and 826.07% in the serum levels of glutamic oxaloacetic transaminase (SGOT), lactate dehydrogenase (LDH), creatine kinase MB (CK-MB), and cardiac troponin I (cTnI) enzyme activities, respectively, as compared to the control. In addition, the cardiac glutathione (GSH) content and activity of glutathione peroxidase-1 (GPX-1) enzyme decreased by 65.94% and 73.85%, respectively. Treatment with nano Sp extract showed the most prominent restorations of the altered biochemical, histopathological, and immunohistochemical features as compared with those by TEL and free Sp; moreover, reductions of 30.64% and 43.02% in the p-AKT content as well as 60.43% and 75.30% of the endothelial nitric oxide synthase (eNOS) immunoreactivity were detected in the TEL and free Sp treatment groups, respectively. Interestingly, nano Sp boosted the autophagy signal via activation of beclin-1 (36.42% and 153.4%), activation of LC3II (69.13% and 195%), downregulation of p62 expressions (39.68% and 62.45%), and increased gene expressions of paraoxonase-1 (PON-1) (90.3% and 225.9%) compared to the TEL and free Sp treatment groups, respectively.

Conclusion

The findings suggest the protective efficiency of telmisartan and nano Sp extract against cardiotoxicity via activations of the antioxidant, antiapoptotic, and autophagy signaling pathways.

H2S alleviates renal ischemia and reperfusion injury by suppressing ERS-induced autophagy

BACKGROUND

Ischemia/reperfusion injury (IRI) can lead to acute kidney injury and result in high disability and mortality rates. Cystathionine γ-lyase (CSE)-produced hydrogen sulfide (H2S) has been confirmed to play a protective role in renal IRI. While autophagy is involved in renal IRI, its role in the regulation by endoplasmic reticulum stress (ERS) has not been considered. Our study explored the role of CSE/H2S in protecting against renal IRI by regulating ERS-induced autophagy.

METHODS

C57/BL6 mice were subjected to 30-min renal ischemia followed by .24-h reperfusion injury (IRI). The H2S donor sodium hydrosulfide hydrate (NaHS) or the CSE inhibitor D,L-propargylglycine (PAG) was injected intraperitoneally (i.p) into the mice. Serum creatinine and urea nitrogen levels were analyzed to evaluate renal function. Renal tubule epithelial cell damage was measured by HE and PAS staining. ERS and microtubule-associated protein light chain 3 (LC3) autophagy (LC3-I to LC3-II conversion) were analyzed by using western blotting.

RESULTS

In a C57/BL6 mouse model of acute renal IRI, the application of IRI impaired the renal function, which was accompanied by elevated serum creatinine (P < 0.001) and urea nitrogen levels (P < 0.001). While NaHS pretreatment dramatically attenuated renal IRI, PAG administration exacerbated renal IRI (P < 0.001). Furthermore, NaHS treatment inhibited the ERS-induced increased LC3II/I protein ratio (P < 0.001); increased Beclin-1 protein expression (P < 0.001); PAG pretreatment exacerbated the effects of ERS on both the LC3II/I ratio (P < 0.001) and the Beclin-1 protein expression (P < 0.001).

CONCLUSIONS

Our results suggest that the CSE/H2S system is an important therapeutic target for protecting against renal IRI, and it may protect renal tubule epithelial cells from IRI by suppressing ERS-induced autophagy.

STELLATE GANGLION BLOCK REVERSES PHSML-INDUCED VASCULAR HYPOREACTIVITY THROUGH INHIBITING AUTOPHAGY-MEDIATED PHENOTYPIC TRANSFORMATION OF VSMCs

ABSTRACT

Posthemorrhagic shock mesenteric lymph (PHSML) return-contributed excessive autophagy of vascular smooth muscle cells (VSMCs) is involved in vascular hyporeactivity, which is inhibited by stellate ganglion block (SGB) treatment. The contractile phenotype of VSMCs transforms into a synthetic phenotype after stimulation with excessive autophagy. Therefore, we hypothesized that SGB ameliorates PHSML-induced vascular hyporeactivity by inhibiting autophagy-mediated phenotypic transformation of VSMCs. To substantiate this hypothesis, a hemorrhagic shock model in conscious rats was used to observe the effects of SGB intervention or intravenous infusion of the autophagy inhibitor 3-methyladenine (3-MA) on intestinal blood flow and the expression of autophagy- and phenotype-defining proteins in mesenteric secondary artery tissues. We also investigated the effects of intraperitoneal administration of PHSML intravenous infusion and the autophagy agonist rapamycin (RAPA) on the beneficial effect of SGB. The results showed that hemorrhagic shock decreased intestinal blood flow and enhanced the expression of LC3 II/I, Beclin 1, and matrix metalloproteinase 2, which were reversed by SGB or 3-MA treatment. In contrast, RAPA and PHSML administration abolished the beneficial effects of SGB. Furthermore, the effects of PHSML or PHSML obtained from rats treated with SGB (PHSML-SGB) on cellular contractility, autophagy, and VSMC phenotype were explored. Meanwhile, the effects of 3-MA on PHSML and RAPA on PHSML-SGB were observed. The results showed that PHSML, but not PHSML-SGB, incubation decreased VSMC contractility and induced autophagy activation and phenotype transformation. Importantly, 3-MA administration reversed the adverse effects of PHSML, and RAPA treatment attenuated the effects of PHSML-SGB incubation on VSMCs. Taken together, the protective effect of SGB on vascular reactivity is achieved by inhibiting excessive autophagy-mediated phenotypic transformation of VSMCs to maintain their contractile phenotype.

Circ DENND4C inhibits pyroptosis and alleviates ischemia-reperfusion acute kidney injury by exosomes secreted from human urine-derived stem cells

Acute kidney injury (AKI) is a disease characterised by acute onset, high mortality, and poor prognosis, and is mainly caused by ischemia-reperfusion (I/R). Human urine-derived stem cells (USCs) exhibit antioxidant, anti-inflammatory, and anti-apoptotic cytoprotective effects. Previously, we found that exosomes from USCs had the ability to inhibit apoptosis and protect kidneys from I/R injury. This study aimed to investigate the role of USC-derived exosomes (USC-Exos) in reducing pyroptosis and alleviating I/R-AKI. Models of HK-2 cells hypoxia-reoxygenation (H/R) and I/R kidney injury was established in Sprague Dawley rats to simulate AKI in vitro and in vivo. USC-Exos were isolated using ultracentrifugation and identified via electron microscopy and western blotting. USC-Exos were co-cultured with HK-2 cells and injected into rats via the tail vein. The expression of pyroptosis-related molecules (GSDMD, caspase-1, and NLRP-3) was verified using PCR and western blotting. Changes in renal function were reflected in the serum creatinine, urea, and cystatin C levels. The degree of renal injury was determined using haematoxylin and eosin and immunohistochemical staining. The levels of IL-1β and IL-18 were detected using enzyme-linked immunosorbent assay (ELISA) to verify the role of USC-Exos in pyroptosis. Differentially expressed circRNAs in I/R rat kidneys were screened by transcriptome sequencing, and a dual-luciferase experiment was used to verify the interaction between upstream and downstream molecules. Ischemia-reperfusion resulted in significantly impaired renal function and expression of pyroptosis molecules, and significantly increased concentrations of inflammatory factors. These effects were reversed by injecting USC-Exos. Circ DENND4C was the most significantly decreased circRNA in I/R rat renal tissue, and knock-down of circ DENND4C can aggravate AKI in vivo and in vitro. DAVID(http://david.abcc.ncifcrf.gov) website showed that miR 138-5p/FOXO3a is a potential downstream target of circ DENND4C. Knock-down of circ DENND4C in HK-2 cells resulted in increased expression of miR 138-5p and increased miR 138-5p can reverse the regulation of FOXO3a. Dual-luciferase assay verified the reverse interaction between circ DENND4C, miR 138-5p, and FOXO3a. Exosomes promote cell proliferation and inhibit the activation of NLR family pyrin domain containing 3 through the circ DENND4C/miR 138-5p/FOXO3a pathway, thereby reducing pyroptosis and AKI. Circ DENND4C may be a potential therapeutic target for AKI.

Amlodipine alleviates renal ischemia/reperfusion injury in rats through Nrf2/Sestrin2/PGC-1α/TFAM Pathway

BACKGROUND

Previously, observational studies showed that amlodipine can mitigate calcineurin inhibitor- and contrast-induced acute kidney injury (AKI). Herein, we aimed to measure the effect of amlodipine on renal ischemia/reperfusion (I/R) injury and find the underlying mechanisms.

MATERIALS AND METHODS

Bilateral renal I/R was induced by clamping the hilum of both kidneys for 30 min. The first dose of amlodipine 10 mg/kg was gavaged before anesthesia. The second dose of amlodipine was administered 24 h after the first dose. Forty-eight hours after I/R, rats were anesthetized, and their blood and tissue specimens were collected.

RESULTS

Amlodipine significantly decreased the elevated serum levels of creatinine and blood urea nitrogen (BUN) and mitigated tissue damage in hematoxylin & eosin (H&E) staining. Amlodipine strongly reduced the tissue levels of malondialdehyde (MDA), interleukin 1β (IL1β), and tumor necrosis factor α (TNF-α). Amlodipine enhanced antioxidant defense by upregulating nuclear factor erythroid 2-related factor 2 (Nrf2) and Sestrin2. Furthermore, amlodipine significantly improved mitochondrial biogenesis by promoting Sestrin2/peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α)/mitochondrial transcription factor A (TFAM) pathway. It also enhanced autophagy and attenuated apoptosis, evidenced by increased LC3-II/LC3-I and bcl2/bax ratios after renal I/R.

CONCLUSION

These findings suggest that amlodipine protects against renal I/R through Nrf2/Sestrin2/PGC-1α/TFAM Pathway.

MicroRNA-192-5p downregulates Fat Mass and Obesity-associated Protein to aggravate renal ischemia/reperfusion injury

Acute kidney injury (AKI) is a common disorder without effective therapy yet. Renal ischemia/reperfusion (I/R) injury is a common cause of AKI. MicroRNA miR-192-5p has been previously reported to be upregulated in AKI models. However, its functional role in renal I/R injury is not fully understood. This study aimed to investigate the effects and the underlying mechanism of miR-192-5p in renal I/R progression. Hypoxia/reoxygenation (H/R)-induced cell injury model in HK-2 cells and I/R-induced renal injury model in mice were established in this study. Cell counting kit-8 assay was performed to determine cell viability. Quantitative real-time PCR and western blot analysis were performed to detect gene expressions. Hematoxylin-eosin and periodic acid-Schiff staining were performed to observe the histopathological changes. Enzyme-linked immunosorbent assay was performed to detect the kidney markers' expression. In vivo and in vitro results showed that miR-192-5p was up-regulated in the I/R-induced mice model and H/R-induced cell model, and miR-192-5p overexpression exacerbated I/R-induced renal damage. Then, the downstream target of miR-192-5p was analyzed by combining the differentially expressed mRNAs and the predicted genes and confirmed using a dual-luciferase reporter assay. It was found that miR-192-5p was found to regulate fat mass and obesity-associated (FTO) protein expression by directly targeting the 3' untranslated region of FTO mRNA. Moreover, in vivo and in vitro studies unveiled that FTO overexpression alleviated renal I/R injury and promoted HK-2 cell viability via stimulating autophagy flux. In conclusion, miR-192-5p aggravated I/R-induced renal injury by blocking autophagy flux via down-regulating FTO.

Astragaloside IV Blunts Epithelial-Mesenchymal Transition and G2/M Arrest to Alleviate Renal Fibrosis via Regulating ALDH2-Mediated Autophagy

Previous studies show that astragaloside IV (ASIV) has anti-renal fibrosis effects. However, its mechanism remains elusive. In this study, we investigated the anti-fibrosis mechanisms of ASIV on chronic kidney disease (CKD) in vivo and in vitro. A CKD model was induced in rats with adenine (200 mg/kg/d, i.g.), and an in vitro renal fibrosis model was induced in human kidney-2 (HK-2) cells treated with TGF-β1. We revealed that ASIV significantly alleviated renal fibrosis by suppressing the expressions of epithelial-mesenchymal transition (EMT)-related proteins, including fibronectin, vimentin, and alpha-smooth muscle actin (α-SMA), and G2/M arrest-related proteins, including phosphorylated p53 (p-p53), p21, phosphorylated histone H3 (p-H3), and Ki67 in both of the in vivo and in vitro models. Transcriptomic analysis and subsequent validation showed that ASIV rescued ALDH2 expression and inhibited AKT/mTOR-mediated autophagy. Furthermore, in ALDH2-knockdown HK-2 cells, ASIV failed to inhibit AKT/mTOR-mediated autophagy and could not blunt EMT and G2/M arrest. In addition, we further demonstrated that rapamycin, an autophagy inducer, reversed the treatment of ASIV by promoting autophagy in TGF-β1-treated HK-2 cells. A dual-luciferase report assay indicated that ASIV enhanced the transcriptional activity of the ALDH2 promoter. In addition, a further molecular docking analysis showed the potential interaction of ALDH2 and ASIV. Collectively, our data indicate that ALDH2-mediated autophagy may be a novel target in treating renal fibrosis in CKD models, and ASIV may be an effective targeted drug for ALDH2, which illuminate a new insight into the treatment of renal fibrosis and provide new evidence of pharmacology to elucidate the anti-fibrosis mechanism of ASIV in treating renal fibrosis.

Autophagy and mitophagy: physiological implications in kidney inflammation and diseases

Autophagy is a ubiquitous intracellular cytoprotective quality control program that maintains cellular homeostasis by recycling superfluous cytoplasmic components (lipid droplets, protein, or glycogen aggregates) and invading pathogens. Mitophagy is a selective form of autophagy that by recycling damaged mitochondrial material, which can extracellularly act as damage-associated molecular patterns, prevents their release. Autophagy and mitophagy are indispensable for the maintenance of kidney homeostasis and exert crucial functions during both physiological and disease conditions. Impaired autophagy and mitophagy can negatively impact the pathophysiological state and promote its progression. Autophagy helps in maintaining structural integrity of the kidney. Mitophagy-mediated mitochondrial quality control is explicitly critical for regulating cellular homeostasis in the kidney. Both autophagy and mitophagy attenuate inflammatory responses in the kidney. An accumulating body of evidence highlights that persistent kidney injury-induced oxidative stress can contribute to dysregulated autophagic and mitophagic responses and cell death. Autophagy and mitophagy also communicate with programmed cell death pathways (apoptosis and necroptosis) and play important roles in cell survival by preventing nutrient deprivation and regulating oxidative stress. Autophagy and mitophagy are activated in the kidney after acute injury. However, their aberrant hyperactivation can be deleterious and cause tissue damage. The findings on the functions of autophagy and mitophagy in various models of chronic kidney disease are heterogeneous and cell type- and context-specific dependent. In this review, we discuss the roles of autophagy and mitophagy in the kidney in regulating inflammatory responses and during various pathological manifestations.

Autophagy in acute kidney injury and maladaptive kidney repair

Acute kidney injury (AKI) is a major renal disease characterized by a sudden decrease in kidney function. After AKI, the kidney has the ability to repair, but if the initial injury is severe the repair may be incomplete or maladaptive and result in chronic kidney problems. Autophagy is a highly conserved pathway to deliver intracellular contents to lysosomes for degradation. Autophagy plays an important role in maintaining renal function and is involved in the pathogenesis of renal diseases. Autophagy is activated in various forms of AKI and acts as a defense mechanism against kidney cell injury and death. After AKI, autophagy is maintained at a relatively high level in kidney tubule cells during maladaptive kidney repair but the role of autophagy in maladaptive kidney repair has been controversial. Nonetheless, recent studies have demonstrated that autophagy may contribute to maladaptive kidney repair after AKI by inducing tubular degeneration and promoting a profibrotic phenotype in renal tubule cells. In this review, we analyze the role and regulation of autophagy in kidney injury and repair and discuss the therapeutic strategies by targeting autophagy.

Roles of NAD+ in Acute and Chronic Kidney Diseases

Nicotinamide adenine dinucleotide (oxidized form, NAD⁺) is a critical coenzyme, with functions ranging from redox reactions and energy metabolism in mitochondrial respiration and oxidative phosphorylation to being a central player in multiple cellular signaling pathways, organ resilience, health, and longevity. Many of its cellular functions are executed via serving as a co-substrate for sirtuins (SIRTs), poly (ADP-ribose) polymerases (PARPs), and CD38. Kidney damage and diseases are common in the general population, especially in elderly persons and diabetic patients. While NAD⁺ is reduced in acute kidney injury (AKI) and chronic kidney disease (CKD), mounting evidence indicates that NAD⁺ augmentation is beneficial to AKI, although conflicting results exist for cases of CKD. Here, we review recent progress in the field of NAD⁺, mainly focusing on compromised NAD⁺ levels in AKI and its effect on essential cellular pathways, such as mitochondrial dysfunction, compromised autophagy, and low expression of the aging biomarker αKlotho (Klotho) in the kidney. We also review the compromised NAD⁺ levels in renal fibrosis and senescence cells in the case of CKD. As there is an urgent need for more effective treatments for patients with injured kidneys, further studies on NAD⁺ in relation to AKI/CKD may shed light on novel therapeutics.

View of the Renin-Angiotensin System in Acute Kidney Injury Induced by Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion injury (RIRI) is a sequence of complicated events that is defined as a reduction of the blood supply followed by reperfusion. RIRI is the leading cause of acute kidney injury (AKI). Among the diverse mediators that take part in RIRI-induced AKI, the renin-angiotensin system (RAS) plays an important role via conventional (angiotensinogen, renin, angiotensin-converting enzyme (ACE), angiotensin (Ang) II, and Ang II type 1 receptor (AT1R)) and nonconventional (ACE2, Ang 1-7, Ang 1-9, AT2 receptor (AT2R), and Mas receptor (MasR)) axes. RIRI alters the balance of both axes so that RAS can affect RIRI-induced AKI. In overall, the alteration of Ang II/AT1R and AKI by RIRI is important to consider. This review has looked for the effects and interactions of RAS activities during RIRI conditions.

Pharmacological inhibitors of autophagy have opposite effects in acute and chronic cisplatin-induced kidney injury

The nephrotoxicity of cisplatin remains a major hurdle in the field of oncology. Thirty percent of patients treated with cisplatin develop acute kidney injury, and all patients are at risk for long-term impacts on kidney function. There are currently no Federal Drug Administration-approved agents to prevent or treat cisplatin-induced kidney injury. The dosing regimen used in preclinical models of nephrotoxicity may impact the success of therapeutic candidates in clinical trials. Here, we demonstrated that pharmacological inhibitors of autophagy have opposite effects when used as interventions in two different models of cisplatin-induced kidney injury. Eight-week-old male C57BL/6 mice were treated with either one dose of 20 mg/kg cisplatin or weekly doses of 9 mg/kg cisplatin for 4 wk or until body weight loss exceeded 30%. Concurrently, mice were administered multiple doses of 60 mg/kg chloroquine or 15 mg/kg 3-methyladenine attempting to globally inhibit autophagy. Mice that received a single high dose of cisplatin had worsened kidney function, inflammation, and cell death with the addition of chloroquine. 3-Methlyadenine did not impact the development of acute kidney injury in this model. In contrast, mice that received repeated low doses of cisplatin showed improved kidney function, reduced inflammation, and reduced fibrosis when treated with either chloroquine or 3-methyladenine. This study highlights how therapeutic candidates can have drastically different effects on the development of cisplatin-induced kidney injury depending on the dosing model used. This emphasizes the importance of choosing the appropriate model of injury for preclinical studies.NEW & NOTEWORTHY This study examined how inhibition of autophagy has opposite effects on the development of acute and chronic kidney injury. Autophagy inhibition exacerbated the development of acute kidney injury following a single high dose of cisplatin but prevented the development of injury and fibrosis following repeated low doses of cisplatin.

Anti-Fibrotic Effect of Synthetic Noncoding Decoy ODNs for TFEB in an Animal Model of Chronic Kidney Disease

Despite emerging evidence suggesting that autophagy occurs during renal interstitial fibrosis, the role of autophagy activation in fibrosis and the mechanism by which autophagy influences fibrosis remain controversial. Transcription factor EB (TFEB) is a master regulator of autophagy-related gene transcription, lysosomal biogenesis, and autophagosome formation. In this study, we examined the preventive effects of TFEB suppression on renal fibrosis. We injected synthesized TFEB decoy oligonucleotides (ODNs) into the tail veins of unilateral ureteral obstruction (UUO) mice to explore the regulation of autophagy in UUO-induced renal fibrosis. The expression of interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), and collagen was decreased by TFEB decoy ODN. Additionally, TEFB ODN administration inhibited the expression of microtubule-associated protein light chain 3 (LC3), Beclin1, and hypoxia-inducible factor-1α (HIF-1α). We confirmed that TFEB decoy ODN inhibited fibrosis and autophagy in a UUO mouse model. The TFEB decoy ODNs also showed anti-inflammatory effects. Collectively, these results suggest that TFEB may be involved in the regulation of autophagy and fibrosis and that regulating TFEB activity may be a promising therapeutic strategy against kidney diseases.

Autophagy and Renal Fibrosis

Renal fibrosis is a common process of almost all the chronic kidney diseases progressing to end-stage kidney disease. As a highly conserved lysosomal protein degradation pathway, autophagy is responsible for degrading protein aggregates, damaged organelles, or invading pathogens to maintain intracellular homeostasis. Growing evidence reveals that autophagy is involved in the progression of renal fibrosis, both in the tubulointerstitial compartment and in the glomeruli. Nevertheless, the specific role of autophagy in renal fibrosis has still not been fully understood. Therefore, in this review we will describe the characteristics of autophagy and summarize the recent advances in understanding the functions of autophagy in renal fibrosis. Moreover, the problem existing in this field and the possibility of autophagy as the potential therapeutic target for renal fibrosis have also been discussed.

Ebselen ameliorates renal ischemia-reperfusion injury via enhancing autophagy in rats

Renal ischemia-reperfusion (I/R) injury is one of the most common causes of chronic kidney disease (CKD). It brings unfavorable outcomes to the patients and leads to a considerable socioeconomic burden. The study of renal I/R injury is still one of the hot topics in the medical field. Ebselen is an organic selenide that attenuates I/R injury in various organs. However, its effect and related mechanism underlying renal I/R injury remains unclear. In this study, we established a rat model of renal I/R injury to study the preventive effect of ebselen on renal I/R injury and further explore the potential mechanism of its action. We found that ebselen pretreatment reduced renal dysfunction and tissue damage caused by renal I/R. In addition, ebselen enhanced autophagy and inhibited oxidative stress. Additionally, ebselen pretreatment activated the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway. The protective effect of ebselen was suppressed by autophagy inhibitor wortmannin. In conclusion, ebselen could ameliorate renal I/R injury, probably by enhancing autophagy, activating the Nrf2 signaling pathway, and reducing oxidative stress.

Autophagy and Oxidative Balance Mediate the Effect of Carvedilol and Glibenclamide in a Rat Model of Renal Ischemia-Reperfusion Injury

BACKGROUND: Reactive oxygen species and cytokines are the main players in the development of renal ischemia-reperfusion (I/R) injury. AIM: The current study aimed to evaluate the effects of carvedilol and/or glibenclamide and the interaction between autophagy and oxidative stress. METHODS: 50 male rats were divided into five groups: Control, IR injury (IRI), carvedilol pretreated, glibenclamide pretreated, and combined carvedilol and glibenclamide pretreated. Measurements of renal blood flow (RBF), creatinine clearance, serum blood urea nitrogen (BUN), histopathological, and immunohistochemical evaluation of autophagy marker Becl-1 in the rat kidney were performed. Beclin-1and light chain 3 (LC3) Mrna expression was detected by real time polymerase chain reaction. RESULTS: IRI was associated with significant increases in BUN, tumor necrosis factor-alpha, nuclear factor κB, and histo (H) score value of Becl-1. However, there was a significant decrease in RBF, creatinine clearance, and glutathione peroxidase compared to the control group. There was significant increase in Beclin-1 and LC3 mRNA gene expression in carvedilol, glibenclamide, and combined treatment groups as compared to IRI and control groups. Combination of carvedilol and glibenclamide significantly restored IRI changes when compared with the other pretreated groups. CONCLUSION: This study suggests that carvedilol and glibenclamide are promising reno-protective drugs to reduce renal injury induced by I/R through their antioxidant and autophagy stimulation.

Effect of Rho-Kinase and Autophagy on Remote Ischemic Conditioning-Induced Cardioprotection in Rat Myocardial Ischemia/Reperfusion Injury Model

Objective. Remote ischemic conditioning (RIC) is a cardioprotective method in ischemia/reperfusion (I/R) injury. This study investigated the mechanism of Rho-kinase-mediated autophagy in RIC. Methods. Sixty male Sprague–Dawley rats were randomly divided into six groups: sham, I/R, RIC, I/R+fasudil, RIC+wortmannin, and RIC+fasudil+wortmannin. Throughout the experiment, mean arterial pressure and heart rate were continuously monitored. Histopathology and ultrastructure and myocardial enzymes’ expression were evaluated to determine the degree of cardiac injury. The protein expression of the Rho-kinase substrates myosin light chain (MLC) and myosin phosphatase target subunit 1 (MYPT1), autophagy-related protein light chain 3-II (LC3-II) and Beclin 1, and protein kinase B (AKT) was measured in the myocardial tissue. Results. Compared with the sham group, the mean arterial pressure and heart rate were decreased, myocardial enzyme levels were increased, and myocardial damage was aggravated in the I/R group; however, RIC improved these alterations. The expression of phosphorylated MLC and MYPT1 was lower, while LC3-II, Beclin 1, and phospho-AKT expression levels were higher in the RIC group compared with the I/R group. Obviously, treatment of the I/R group rats with fasudil, a Rho-kinase inhibitor, significantly ameliorated the I/R effects, whereas treatment of the RIC group rats with wortmannin, a phosphatidylinositol-3 kinase (PI3K) inhibitor, inhibited the RIC protective effects. Moreover, the rats in the RIC+fasudil+wortmannin group showed similar changes to those in the RIC+wortmannin group. Conclusion. These results showed that RIC protected the myocardium from I/R injury by suppressing Rho-kinase and the underlying mechanism may be related to enhancing autophagy via the PI3K/AKT pathway.

SCM-198 Can Regulate Autophagy Through the Bax/Bcl-2/TLR4 Pathway to Alleviate Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion (I/R) injury is frequently observed in several clinical cases. In this study, we want to investigate that SCM-198 attenuates renal injury in the renal I/R model and find out the possible mechanisms. Wistar albino 40 male rats were classified into four groups (n=10): control, DMSO, I/R, and SCM-198 30 mg/kg. In the group 4, SCM-198 was administered intraperitoneally once at the doses of 30 mg/kg following the reperfusion. Glomerular associated proteins (PCX), tubular damage factors (NGAL, KIM-1), blood urea nitrogen (BUN), serum creatinine, inflammatory cytokines (IL-1β, IL-18, and TNF-α), Bax/Bcl-2, TLR4, LC3B, and Beclin-1 were evaluated. SCM-198 played an essential role in mitigating kidney damage. SCM-198 alleviated tubular damage and decreased IL-1β, IL-18, and TNF-α levels. SCM-198 reduced the apoptosis marker Bax/Bcl-2 ratio, immune system protein TLR4, and autophagy proteins LC3B and Beclin-1. In brief, our results support the notion that SCM-198 has protective effects on I/R-induced renal injury. SCM-198 therapy may be a new alternative for the prevention and treatment of renal I/R injury.

Autophagy Is Involved in Stellate Ganglion Block Reversing Posthemorrhagic Shock Mesenteric Lymph-Mediated Vascular Hyporeactivity

Objective: The aim of this study was to clarify the role of autophagy in stellate ganglion block (SGB) reversing posthemorrhagic shock mesenteric lymph (PHSML)-mediated vascular hyporeactivity.

Methods: Hemorrhagic shock model in conscious rats was employed to observe the effects of SGB (0.2 ml of 0.25% ropivacaine hydrochloride hydrate) and autophagy inhibitor 3-methyladenine (3-MA; 30 mg/kg) on the vascular reactivity of second-order rat mesenteric arteries in vitro, while the effects of PHSML (1 ml/kg) and autophagy agonist rapamycin (Rapa, 10 mg/kg) on the beneficial effect of SGB were investigated. The cellular viability, contractility, and autophagy-related protein expressions in vascular smooth muscle cells (VSMCs) were detected following treatments of PHSML, PHSML obtained from the rats that underwent hemorrhagic shock plus SGB (PHSML-SGB), and PHSML plus 3-MA (5 mM), respectively.

Results: Hemorrhagic shock significantly decreased the vascular reactivity to gradient norepinephrine (NE), which is reversed by the SGB treatment and 3-MA administration. On the contrary, PHSML intravenous infusion and Rapa administration inhibited the vascular contractile responses in rats that underwent hemorrhagic shock plus SGB treatment. PHSML treatment significantly inhibited the cellular viability and contractility in VSMCs, increased the expressions of LC3-II and Beclin 1, and decreased the expression of p62, along with opposite appearances in these indices following PHSML-SGB treatment. In addition, 3-MA counteracted the adverse roles of PHSML in these indices in VSMCs.

Conclusion: SGB inhibits PHSML-mediated vascular hyporeactivity by reducing the excessive autophagy in VSMCs.

α1-Antitrypsin alleviates inflammation and oxidative stress by suppressing autophagy in asthma

BACKGROUND

Asthma is considered an incurable disease, although many advances have been made in asthma treatments in recent years. Therefore, elucidating the pathological mechanisms and seeking novel and effective therapeutic strategies for asthma are urgently needed.

METHODS

Airway resistance was measured by whole-body plethysmography. H&E staining was used to observe the morphological changes in the lung. Oxidative stress was assessed by measuring the levels of MDA, CAT and SOD. Gene expression was analysed by western blotting and RT-qPCR. ELISA was used to analyse the concentrations of IL-4, IL-5 and IFN-γ.

RESULTS

In the present study, we successfully established in vivo and in vitro asthma models. OVA administration led to elevated lung resistance, cell counts in BALF, and cytokine secretion, impaired airway structure and enhanced oxidative stress and autophagy in a mouse model of asthma, while IL-13 induced inflammation, oxidative stress and autophagy in BEAS-2B cells. A1AT reduced lung resistance and cell counts in BALF and suppressed inflammation, oxidative stress and autophagy in a mouse model of asthma and IL-13-induced BEAS-2B cells. Mechanistic investigations revealed that autophagy activation compromised the protective effect of A1AT on IL-13-induced BEAS-2B cells. Further mechanistic studies revealed that A1AT alleviated inflammation and oxidative stress by inhibiting autophagy in the context of asthma.

CONCLUSION

We demonstrated that A1AT could alleviate inflammation and oxidative stress by suppressing autophagy in the context of asthma and thus ameliorate asthma. Our study revealed novel pathological mechanisms and provided novel potential therapeutic targets for asthma treatment.

Activation of the angiotensin II receptor promotes autophagy in renal proximal tubular cells and affords protection from ischemia/reperfusion injury

Roles of the renin-angiotensin system in autophagy and ischemia/reperfusion (I/R) injury in the kidney have not been fully characterized. Here we examined the hypothesis that modest activation of the angiotensin II (Ang II) receptor upregulates autophagy and increases renal tolerance to I/R injury. Sprague-Dawley rats were assigned to treatment with a vehicle or a non-pressor dose of Ang II (200 ng/kg/min) for 72 h before 30-min renal I/R. LC3-immunohistochemistry showed that Ang II treatment increased autophagosomes in proximal tubular cells by 2.7 fold. In Ang II-pretreated rats, autophagosomes were increased by 2.5 fold compared to those in vehicle-treated rats at 4 h after I/R, when phosphorylation of Akt and S6 was suppressed and ULK1-Ser555 phosphorylation was increased. Serum creatinine and urea nitrogen levels, incidence of oliguria, and histological score of tubular necrosis at 24 h after I/R were attenuated by Ang II-pretreatment. In NRK-52E cells, Ang II induced LC3-II upregulation, which was inhibited by losartan but not by A779. The results indicate that a non-pressor dose of Ang-II promotes autophagy via ULK1-mediated signaling in renal tubular cells and attenuates renal I/R injury. The AT1 receptor, but not the Mas receptor, contributes to Ang-II-induced autophagy and presumably also to the renoprotection.

Transfer of MicroRNA-216a-5p From Exosomes Secreted by Human Urine-Derived Stem Cells Reduces Renal Ischemia/Reperfusion Injury

Human urine-derived stem cells (USCs) protect rats against kidney ischemia/reperfusion (I/R) injury. Here we investigated the role of USCs exosomes (USCs-Exos) in protecting tubular endothelial cells and miRNA transfer in the kidney. Human USCs and USCs-Exos were isolated and verified by morphology and specific biomarkers. USC-Exos played a protective role in human proximal tubular epithelial cells (HK-2) exposed to hypoxia/reoxygenation (H/R). USCs-Exos were rich in miR-216a-5p, which targeted phosphatase and tensin homolog (PTEN) and regulated cell apoptosis through the Akt pathway. In HK-2 cells exposed to H/R, incubation with USC-Exos increased miR-216-5p, decreased PTEN levels, and stimulated Akt phosphorylation. Exposure of hypoxic HK-2 cells to USCs-Exos pretreated with anti-miR-216a-5p can prevent the increase of miR-216-5p and Akt phosphorylation levels, restore PTEN expression, and promote apoptosis. The dual-luciferase reported gene assay in HK-2 cells confirmed that miR-216a-5p targeted PTEN. In rats with I/R injury, intravenous infusion of USCs-Exos can effectively induce apoptosis suppression and functional protection, which is associated with decreased PTEN. Infusion of exosomes from anti-miR-216a-5p-transfected USCs weakened the protective effect in the I/R model. Therefore, USCs-Exos can reduce renal I/R injury by transferring miR-216a-5p targeting PTEN. Potentially, USCs-Exos rich in miR-216a-5p can serve as a promising therapeutic option for AKI.

miRNA-182/Deptor/mTOR axis regulates autophagy to reduce intestinal ischaemia/reperfusion injury

It had been reported miR‐182 was down‐regulated after intestinal ischaemia/reperfusion (I/R) damage. However, its role and potential mechanisms are still unknown. This study was aimed to elucidate the function of miR‐182 in intestinal I/R injury and the underlying mechanisms. The model of intestinal injury was constructed in wild‐type and Deptor knockout (KO) mice. Haematoxylin‐eosin staining, Chiu's score and diamine oxidase were utilized to detect intestinal damage. RT‐qPCR assay was used to detected miR‐182 expression. Electronic microscopy was used to detect autophagosome. Western blot was applied to detect the expression of Deptor, S6/pS6, LC3‐II/LC3‐I and p62. Dual‐luciferase reporter assay was used to verify the relationship between miR‐182 and Deptor. The results showed miR‐182 was down‐regulated following intestinal I/R. Up‐regulation of miR‐182 reduced intestinal damage, autophagy, Deptor expression and enhanced mTOR activity following intestinal I/R. Moreover, suppression of autophagy reduced intestinal damage and inhibition of mTOR by rapamycin aggravated intestinal damage following intestinal I/R. Besides, damage of intestine was reduced and mTOR activity was enhanced in Deptor KO mice. In addition, Deptor was the target gene of miR‐182 and was indispensable for the protection of miR‐182 on intestine under I/R condition. Together, our research implicated up‐regulation of miR‐182 inhibited autophagy to alleviate intestinal I/R injury via mTOR by targeting Deptor.

Protective effect of renal ischemic postconditioning in renal ischemic-reperfusion injury

Background

Renal ischemic postconditioning (RIPo) can protect the kidney from renal ischemia/reperfusion injury (RIRI). However, the underlying molecular mechanisms for RIPo in renal protection remained elusive. This study aimed to investigate the renoprotective effects of RIPo in an RIR rat model.

Method

The Sprague Dawley (SD) rats were randomly divided into three groups respectively: sham group, the RIRI group and the RIPo group. The levels of proteinuria, blood urea nitrogen (BUN), creatinine (Cr), malondialdehyde (MDA), superoxide dismutase (SOD), lactate dehydrogenase (LDH), reactive oxidative species (ROS), interleukins (IL)-6, IL-1β, and IL-18 were measured by ELISA. Apoptotic cells and caspase-3 positive cells were detected by TUNEL assay and immunohistochemistry, respectively. The protein expressive levels of caspase-3, caspase-9, ATG8, Beclin1, p62, LC3-II, P-P13K, P-AKT and P-mTOR were detected by western blot.

Results

Our results showed that pretreatment with RIPo significantly reduced ischemic pathological and morphological changes. The levels of proteinuria, BUN, and Cr were also significantly reduced by RIPo pretreatment. Besides, ATG8, LC3-II and Beclin-1 were upregulated in the RIPo group, but p62 was downregulated. Moreover, RIPo pretreatment resulted in higher levels of phosphorylated PI3K, Akt, and mTOR. These results showed that RIPo protects the kidneys of rats from IRI with suppressed apoptosis and activated autophagy. Mechanically, the activated PI3K/AKT/mTOR signaling pathway were activated.

Conclusions

Collectively, our data demonstrated that RIPo could suppress Inflammatory response, oxidative stress, apoptosis and induce autophagy as well as activate the PI3K/AKT/mTOR pathway, which may play an important role in renal protection against RIRI.

Protective effects of autophagy inhibitor 3-methyladenine on ischemia-reperfusion-induced retinal injury

OBJECTIVE

To investigate the protective effects of autophagy inhibitor 3-methyladenine (3-MA) in a rat model of ischemic-reperfusion injury (IRI).

METHODS

Forty Sprague-Dawley male rats (weight 220-250 g) were randomly divided into four groups: a control group (NC, n = 10), a Sham surgery group (n = 10), an IRI group (n = 10), and a 3-MA-treated IRI group [10 μL 3-MA (10 mmol/L) was injected in vitreous after the injury, n = 10]. The retinal IRI was induced by elevating the intraocular pressure to 110 mmHg for 60 min. Hematoxylin and eosin (HE) staining was used to calculate the number of retinal ganglion cells (RGCs). The level of microtubule-associated protein 1A/1B light chain 3 (LC3), Beclin-1, and Caspase-3 in the retina was detected using the immunofluorescence staining method. The LC3, Beclin-1, B-cell lymphoma/leukemia-2 (Bcl-2), and Caspase-3 protein levels were examined by Western blotting.

RESULTS

The number of RGCs in IRI group was significantly lower than that in NC group (P < 0.05), demonstrated by HE staining. Western blotting results indicated that the protein expression of LC3 and Beclin-1 in the IRI group was significantly elevated compared with those in the NC group (P < 0.05). However, with 3-MA treatment, the number of RCGs in 3-MA-treated IRI group was elevated and protein levels of LC3, Beclin-1 were down-regulated, compared with those in the IRI group (P < 0.05). Further immunohistochemistry staining and Western blot showed that 3-MA-treated IRI group presented down-regulated Caspase-3 and up-regulated Bcl-2 protein expression with comparison of IRI group (P < 0.05).

CONCLUSIONS

Retina IRI-caused RGCs loss involved activated autophagy pathway and apoptosis, which could be prevented by autophagy inhibitor 3-MA. Autophagy inhibitor 3-MA may act as a potent therapeutic tool in attenuating retina IRI.

Autophagy-deficiency in bone marrow mononuclear cells from patients with myasthenia gravis: a possible mechanism of pathogenesis

Myasthenia gravis (MG) is a chronic autoimmune disorder resulting from autoantibodies against neuromuscular junction components. Research shows that this disease might be a primary bone marrow (BM) stem cell disorder. Autophagy protects the dynamics and homeostasis of the host cells by removing damaged mitochondria, protein aggregates and other intercellular materials. Dysfunctional autophagy is associated with autoimmune diseases. However, the autophagy activity and mechanisms in BM stem cell from MG patients remain largely uncharacterized. We evaluated the autophagy activity in bone marrow mononuclear cells (BM-MNCs) and the effects of autophagy on cell survival from patients with MG and healthy controls. Our results revealed that autophagy was significantly decreased in patients with MG before immunomodulation treatment compared with that in age-/sex-matched controls, and was lower in generalized MG (GMG) patients than in ocular MG (OMG) patients. Immunomodulatory treatment partially increased autophagy activity of BM-MNCs in MG patients and improved the symptoms. Furthermore, defective BM-MNCs differentiation, proliferation and apoptosis were observed due to dysfunctional autophagy. These findings suggest for the first time that BM-MNCs autophagy is impaired in patients with MG before immunomodulation therapy, and that autophagy is indispensable for the survival of BM-MNCs, implicating autophagy might be a potential pathogenic mechanism of MG and a novel therapeutic strategy for MG treatment.

Remote Ischemic Preconditioning induces Cardioprotective Autophagy and Signals through the IL-6-Dependent JAK-STAT Pathway

Autophagy is a cellular process by which mammalian cells degrade and assist in recycling damaged organelles and proteins. This study aimed to ascertain the role of autophagy in remote ischemic preconditioning (RIPC)-induced cardioprotection. Sprague Dawley rats were subjected to RIPC at the hindlimb followed by a 30-min transient blockade of the left coronary artery to simulate ischemia reperfusion (I/R) injury. Hindlimb muscle and the heart were excised 24 h post reperfusion. RIPC prior to I/R upregulated autophagy in the rat heart at 24 h post reperfusion. In vitro, autophagy inhibition or stimulation prior to RIPC, respectively, either ameliorated or stimulated the cardioprotective effect, measured as improved cell viability to mimic the preconditioning effect. Recombinant interleukin-6 (IL-6) treatment prior to I/R increased in vitro autophagy in a dose-dependent manner, activating the Janus kinase/signal transducers and activators of transcription (JAK-STAT) pathway without affecting the other kinase pathways, such as p38 mitogen-activated protein kinases (MAPK), and glycogen synthase kinase 3 Beta (GSK-3β) pathways. Prior to I/R, in vitro inhibition of the JAK-STAT pathway reduced autophagy upregulation despite recombinant IL-6 pre-treatment. Autophagy is an essential component of RIPC-induced cardioprotection that may upregulate autophagy through an IL-6/JAK-STAT-dependent mechanism, thus identifying a potentially new therapeutic option for the treatment of ischemic heart disease.

Rapamycin Is Not Protective against Ischemic and Cisplatin-Induced Kidney Injury

Autophagy plays an important role in the pathogenesis of acute kidney injury (AKI). Although autophagy activation was shown to be associated with an increased lifespan and beneficial effects in various pathologies, the impact of autophagy activators, particularly, rapamycin and its analogues on AKI remains obscure. In our study, we explored the effects of rapamycin treatment in in vivo and in vitro models of ischemic and cisplatin-induced AKI. The impact of rapamycin on the kidney function after renal ischemia/reperfusion (I/R) or exposure to the nephrotoxic agent cisplatin was assessed by quantifying blood urea nitrogen and serum creatinine and evaluating the content of neutrophil gelatinase-associated lipocalin, a novel biomarker of AKI. In vitro experiments were performed on the primary culture of renal tubular cells (RTCs) that were subjected to oxygen-glucose deprivation (OGD) or incubated with cisplatin under various rapamycin treatment protocols. Cell viability and proliferation were estimated by the MTT assay and real-time cell analysis using an RTCA iCELLigence system. Although rapamycin inhibited mTOR (mammalian target of rapamycin) signaling, it failed to enhance the autophagy and to ameliorate the severity of AKI caused by ischemia or cisplatin-induced nephrotoxicity. Experiments with RTCs demonstrated that rapamycin exhibited the anti-proliferative effect in primary RTCs cultures but did not protect renal cells exposed to OGD or cisplatin. Our study revealed for the first time that the mTOR inhibitor rapamycin did not prevent AKI caused by renal I/R or cisplatin-induced nephrotoxicity and, therefore, cannot be considered as an ideal mimetic of the autophagy-associated nephroprotective mechanisms (e.g., those induced by caloric restriction), as it had been suggested earlier. The protective action of such approaches like caloric restriction might not be limited to mTOR inhibition and can proceed through more complex mechanisms involving alternative autophagy-related targets. Thus, the use of rapamycin and its analogues for the treatment of various AKI forms requires further studies in order to understand potential protective or adverse effects of these compounds in different contexts.

Autophagy in kidney disease: Advances and therapeutic potential

Autophagy is a highly conserved intracellular catabolic process for the degradation of cytoplasmic components that has recently gained increasing attention for its importance in kidney diseases. It is indispensable for the maintenance of kidney homeostasis both in physiological and pathological conditions. Investigations utilizing various kidney cell-specific conditional autophagy-related gene knockouts have facilitated the advancement in understanding of the role of autophagy in the kidney. Recent findings are raising the possibility that defective autophagy exerts a critical role in different pathological conditions of the kidney. An emerging body of evidence reveals that autophagy exhibits cytoprotective functions in both glomerular and tubular compartments of the kidney, suggesting the upregulation of autophagy as an attractive therapeutic strategy. However, there is also accumulating evidence that autophagy could be deleterious, which presents a formidable challenge in developing therapeutic strategies targeting autophagy. Here, we review the recent advances in research on the role of autophagy during different pathological conditions, including acute kidney injury (AKI), focusing on sepsis, ischemia-reperfusion injury, cisplatin, and heavy metal-induced AKI. We also discuss the role of autophagy in chronic kidney disease (CKD) focusing on the pathogenesis of tubulointerstitial fibrosis, podocytopathies including focal segmental glomerulosclerosis, diabetic nephropathy, IgA nephropathy, membranous nephropathy, HIV-associated nephropathy, and polycystic kidney disease.

Bacopa Monnieri Protects the Directly Affected Organ as Well as Distant Organs Against I/R Injury by Modulating Anti-Inflammatory and Anti-Nitrosative Pathways in A Rat Model for Infra-Renal Aortic Occlusion

OBJECTIVE

To investigate the protective effect and underlying mechanisms of B. monnieri, a medicinal plant, on kidney and skeletal muscle injury induced by infra-renal abdominal aorta clamping for 2-hours (ischemia) and following removal of the clamp (reperfusion, 2-hours).

METHODS

Rats were divided into four groups (n = 6): (I) animals given only saline (sham-control); (II) animals given B. monnieri extract for 10-days (300 mg/kg/day) (Bacopa-treated sham); (III) animals subjected to ischemia/reperfusion (I/R); (IV) animals given B. monnieri extract and then subjected to I/R. Kidneys and lower extremity muscles were examined for GPx, CAT, iNOS, 3-NT, IL-1β and TNF-α. Apoptosis and injury were evaluated by TUNEL and H&E staining, respectively.

RESULTS

I/R resulted in TUNEL positive cells, periarterial edema and glomerular capillary dilatation, decreased GPx activity, unchanged CAT, iNOS, 3-NT, IL-1β and TNF-α in kidney. B. monnieri minimized renal remote reperfusion injury, and Group IV showed a lower degree of renal histopathology score when compared to the others. B. monnieri mitigated muscle I/R injury, decreased muscle hypertrophy, myofibril abnormalities and apoptosis. Muscle 3-NT and cytokine levels were increased by I/R, and B. monnieri inhibited iNOS and 3-NT both in sham-control and I/R groups. Muscle GPx unaffected by I/R or B. monnieri, but CAT was inhibited only in B. monnieri-treated I/R group. Muscle iNOS, 3-NT, IL-1β, TNF-α levels and CAT activity of B. monnieri-treated I/R rats were lower than those in sham-control or Bacopa-treated sham.

CONCLUSIONS

B. monnieri can protect the directly affected organ as well as distant organs against I/R injury by modulating anti-inflammatory and anti-nitrosative pathways.

Inhibition of Disruptor of Telomeric Silencing 1-Like Alleviated Renal Ischemia and Reperfusion Injury-Induced Fibrosis by Blocking PI3K/AKT-Mediated Oxidative Stress

Background

Ischemia/reperfusion (I/R) injury is a major cause of acute kidney injury, usually occurs during renal surgeries, and may eventually lead to chronic kidney diseases. However, effective therapeutic targets for renal I/R injury remain limited.

Purpose

In the present study, we investigated whether inhibition of disruptor of telomeric silencing 1-like (Dot1l) could alleviate renal I/R in vivo and in vitro, as well as the potential mechanisms involved in this process.

Methods

Sprague–Dawley rats were subjected to right renal ischemia for 45 mins and reperfusion for 0, 7, or 14 days with and without the Dot1l inhibitor EPZ004777. In addition, human renal proximal tubular epithelial cell line human kidney-2 cells were subjected to the hypoxia/reoxygenation (H/R) process (ie, 3 hrs hypoxia, 12 hrs and 24 hrs reoxygenation), with or without Dot1l inhibitor or genetic knockdown.

Results

Inhibition of Dot1l through EPZ004777 or genetic knockdown reduced the expression of alpha-smooth muscle actin, vimentin, and fibronectin in I/R- and H/R-induced injury. Moreover, H/R-induced fibrosis depended on oxidative stress in vitro. In addition, I/R- and H/R-induced generation of reactive oxygen species (ROS) was attenuated by EPZ004777 or small interfering RNA for Dot1l. Furthermore, the elevation of ROS induced by Dot1l was regulated via phosphatidylinositol 3-kinase (PI3K) and serine-threonine protein kinase (AKT) phosphorylation in vivo and in vitro.

Conclusion

Inhibition of Dot1l alleviated renal fibrosis by preventing the generation of ROS via the PI3K/AKT pathway. These results indicate that inhibitor of Dot1l could be a potential therapeutic target for renal I/R injury.

Inhibition of PRMT5 Attenuates Oxidative Stress-Induced Pyroptosis via Activation of the Nrf2/HO-1 Signal Pathway in a Mouse Model of Renal Ischemia-Reperfusion Injury

Background

Extensive evidence has demonstrated that oxidative stress, pyroptosis, and proinflammatory programmed cell death are related to renal ischemia/reperfusion (I/R) injury. However, the underlying mechanism remains to be illustrated. Protein arginine methylation transferase 5 (PRMT5), which mediates arginine methylation involved in the regulation of epigenetics, exhibits a variety of biological functions and essential roles in diseases. The present study investigated the role of PRMT5 in oxidative stress and pyroptosis induced by I/R injury in a mouse model and in a hypoxia/reoxygenation (H/R) model of HK-2 cells.

Methods

C57 mice were used as an animal model. All mice underwent right nephrectomy, and the left renal pedicles were either clamped or not. Renal I/R injury was induced by ligating the left renal pedicle for 30 min followed by reperfusion for 24 h. HK-2 cells were exposed to normal conditions or stimulation through H/R. EPZ015666(EPZ)—a selective potent chemical inhibitor—and small interfering RNA (siRNA) were administered to suppress the function and expression of PRMT5. The levels of urea nitrogen and creatinine in the serum and renal tissue injury were assessed. Immunohistochemistry, western blotting, and reverse transcription-polymerase chain reaction were used to evaluate pyroptosis-related proteins including nod-like receptor protein-3, ASC, caspase-1, caspase-11, GSDMD-N, and interleukin-1β. Cell apoptosis and cell viability were detected through flow cytometry, and the levels of reactive oxygen species (ROS) and hydrogen peroxide (H₂O₂) were measured. Ki-67 was used to assess the proliferation of renal tubular epithelium. In addition, the activity of malondialdehyde and superoxide dismutase was determined.

Results

I/R or H/R induced an increase in the expression of PRMT5. Inhibition of PRMT5 by EPZ alleviated oxidative stress and I/R- or H/R-induced pyroptosis. In renal tissue, the application of EPZ promoted the proliferation of tubular epithelium. In addition, H/R-induced pyroptosis in HK-2 cells was dependent on oxidative stress in vitro. Administration of either EPZ or siRNA led to decreased expression of pyroptosis-related proteins. Inhibition of PRMT5 also attenuated the I/R- or H/R-induced oxidative stress in vivo and in HK-2 cells, respectively. It also resulted in a distinct decrease in the levels of malondialdehyde and H₂O₂, and an apparent increase in superoxide dismutase activity in mouse renal tissue. Moreover, it led to a significant decrease in the levels of ROS and H₂O₂ in HK-2 cells. When activated, NF-E2-related factor/heme oxygenase-1 (Nrf2/HO-1)—a key regulator of various cytoprotective proteins that withstand oxidative damage—can decrease the generation of ROS. Nrf2/HO-1 was downregulated during I/R in tissues and H/R in HK-2 cells, and this effect was reversed by the PRMT5 inhibitor. Furthermore, the expressions of Nrf2 and HO-1 proteins were markedly upregulated by EPZ or siRNA against PRMT5.

Conclusion

PRMT5 is involved in ischemia- and hypoxia-induced oxidative stress and pyroptosis in vitro and in vivo. Inhibition of PRMT5 may ameliorate renal I/R injury by suppressing oxidative stress and pyroptosis via the activation of the Nrf2/HO-1 pathway, as well as promoting the proliferation of tubular epithelium. Therefore, PRMT5 may be a promising therapeutic target.

Pioglitazone protects tubular cells against hypoxia/reoxygenation injury through enhancing autophagy via AMPK-mTOR signaling pathway

Pioglitazone (Pio), a peroxisome proliferators-activated receptor-γ (PPAR-γ) agonist, may protect against renal ischemia/reperfusion injury (IRI). Recent studies have shown that autophagy plays a protective role in IRI. We aimed to evaluate whether autophagy was involved in pioglitazone-induced protection during tubular cell hypoxia/reoxygenation (H/R). Normal rat kidney proximal tubular cells NRK-52E were subjected to H/R injury, and they were divided into 6 groups: control, control + Pio, H/R, H/R + Pio, H/R + MA, H/R + MA + Pio. Autophagy-related proteins were primarily assessed by Western blot and TUNEL was performed to assess cell apoptosis. Our results showed pioglitazone pretreatment had a cytoprotective effect against H/R injury. The H/R + Pio group had an increased ratio of LC3-II to LC3-I and increased Beclin-1, decreased p62. Pioglitazone also reduced apoptosis and enhanced cell survival while inducing autophagy. Correspondingly, autophagy inhibition with 3-MA alleviated this protective effect. Furthermore, pioglitazone-induced enhancement of autophagy could be related to increased AMP-activated protein kinase (AMPK) phosphorylation and decreased Mammalian target of rapamycin (mTOR) phosphorylation. Thus, pioglitazone pretreatment protects against H/R injury by enhancting autophagy through the AMPK-mTOR signaling pathway.

Advances on Cell Autophagy and Its Potential Regulatory Factors in Renal Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is a major reason for acute kidney injury and various kidney diseases. Autophagy plays an important role during renal ischemia-reperfusion injury (RIRI), but it remains controversial whether autophagy contributes to cell survival or ischemia-reperfusion-induced cell death. In the review, we summarized the function of autophagy in the progression of acute ischemic kidney injury, as well as its related molecular mechanisms. While analyzing the opposite roles of autophagy in RIRI, it was concluded that the protective or detrimental function of autophagy was depending on the timing and amount of the activation of cell autophagy. We also summarized the regulatory agents, including active compounds, proteins, or microRNAs (miRNAs), which regulated the cell autophagy during renal acute ischemic kidney injury process. This explained why the opposite conclusion occurred when cell autophagy was studied in the RIRI models from different researchers. Therefore, the article provided a hypothesis to control cell autophagy at the appropriate timing and intensity so as to alleviate renal injury and sustain cell survival of the renal cell.

Role of TFEB in autophagic modulation of ischemia reperfusion injury in mice kidney and protection by urolithin A

Kidney ischemia reperfusion injury (IRI) is an acute kidney injury associated with high number of mortality. We have examined the molecular mechanism and found that oxidative stress and hypoxia leads to induction of autophagy. In IRI induced autophagy, TFEB translocated to nucleus in response to IRI and induced a number of target genes of Coordinated Lysosomal Expression and Regulation (CLEAR) network. Real-time PCR analyses result showed IRI dependent increase in mRNA level to lysosomal hydrolases (Ctsa, Psap), lysosomal membranes (Lamp1), lysosomal acidification (Atp6ap1) non-lysosomal proteins involved in lysosomal biogenesis (M6pr, Nagpa) and autophagy (Becn1, VPS11). Overall, both lysosomal biogenesis and autophagy pathways were induced. Two key players of TFEB dependent proteins in autophagy, LAMP1 and BECN1 were verified by protein analyses. Pretreatment with urolithin A promoted autophagy and attenuated renal injury in kidney IRI and thus inverse relationship existed between TFEB-CLEAR pathway and kidney injury. Urolithin A also attenuated IRI induced pro-inflammatory cytokines TNFα, IL1β, MIP1α and MIP2 mRNA and associated kidney injury. Overall, our results explored the understanding of autophagy and CLEAR network to kidney IRI and those insights may help to develop new therapeutic strategies to protect against IRI.

Protective effect and mechanisms of exogenous neutrophil gelatinase-associated lipocalin on lipopolysaccharide-induced injury of renal tubular epithelial cell

PURPOSES

To investigate the protective effect of exogenous neutrophil gelatinase-associated lipocalin (NGAL) on the lipopolysaccharide-induced injury of renal tubular epithelial cells and its regulation of autophagy.

METHODS

Renal tubular epithelial cells were treated with lipopolysaccharide (LPS) at different concentrations (0-100 μg/mL) and at different times (0-24 h), the expression of NGAL was detected to determine the optimal time and concentration of LPS treatment. The NGAL gene knockdown lentivirus (NGAL-RNAi) was constructed and verified its knockdown rate and inhibition effect. Renal tubular epithelial cells were randomly divided into Control group, LPS group, LPS + NGAL group, NGAL-RNAi + LPS group, and NGAL-RNAi + LPS + NGAL group. Western blot and immunofluorescence tested the expression of autophagy-associated proteins, the changes in the number of autophagosomes were observed by electron microscopy, analyzed the role of exogenous NGAL.

RESULTS

The study showed the expression of autophagy-associated proteins (LC3-II and Beclin-1) in NGAL-RNAi + LPS group was significantly lower than the LPS group (P < 0.0100). The expression of LC3-II and Beclin-1 in the NGAL-RNAi + LPS + NGAL group was significantly higher than the NGAL-RNAi + LPS group (P < 0.0100). After the addition of exogenous NGAL, the autophagosomes in the LPS + NGAL group and the NGAL-RNAi + LPS + NGAL group were significantly increased under the electron microscope compared with the LPS group and the NGAL-RNAi + LPS group, and the cell proliferation rate and cell viability was significantly higher than unjoined groups (P < 0.0500).

CONCLUSION

NGAL knockdown can significantly reduce the level of autophagy and decrease the proliferation rate and viability of cells.The addition of exogenous NGAL can increase the level of autophagy. This suggests that NGAL may play a protective role in the LPS-induced injury of renal tubular epithelial cells by promoting autophagy.

Atg7 mediates renal tubular cell apoptosis in vancomycin nephrotoxicity through activation of PKC-δ

Recent studies have shown that autophagy exhibits a renoprotective role in various models of acute kidney injury (AKI). However, its role in vancomycin (Van)-induced AKI remains largely unclarified. This study was the first to indicate that autophagy was rapidly activated in both human kidney-2 cells and renal tissues, and mammalian target of rapamycin (mTOR) was inactivated via the suppression of ERK1/2 and mTOR during Van treatment. Interestingly, for both in vitro and in vivo experiments, the suppression of autophagy via chloroquine and PT-Atg7-KO significantly ameliorated Van-induced kidney injury and renal tubular cell apoptosis. Global gene expression analysis indicated that the expression levels of 6159 genes were induced by Van treatment in the kidney cortical tissues of PT-Atg7 wild-type mice, and 18 of them were notably suppressed in PT-Atg7-KO mice. These 18 genes were further classified as programmed cell death, protein binding, signal transduction, E3 ubiquitin ligase, nucleoside diphosphate kinase activity, and E1-like activating enzyme. Unexpectedly, following Van treatment, PKC-δ expression was found to be highest among the 4 genes related to cell death, which was remarkably suppressed in vitro and in PT-Atg7-KO mice. In addition, Atg7 could induce renal cell apoptosis during Van treatment via binding to PKC-δ. Likewise, the inhibition of PKCδ ameliorated Van-induced apoptosis in human kidney-2 cells and kidney tissues. Furthermore, the data showed that PT-Atg7-KO exerted a renoprotective effect against Van-induced nephrotoxicity, but this effect was lost after injection with myc-tagged PKCδ. Taken altogether, these results indicate that Van induces autophagy by suppressing the activation of the ERK1/2 and mTOR signaling pathway. In addition, Atg7 mediates Van-induced AKI through the activation of PKCδ. In sum, autophagy inhibition may serve as a novel therapeutic target for treating nephrotoxic AKI induced by Van.-Xu, X., Pan, J., Li, H., Li, X., Fang, F., Wu, D., Zhou, Y., Zheng, P., Xiong, L., Zhang, D. Atg7 mediates renal tubular cell apoptosis in vancomycin nephrotoxicity through activation of PKC-δ.

Aged kidneys are refractory to autophagy activation in a rat model of renal ischemia-reperfusion injury

Background

Ischemia-reperfusion (I/R) injury is the most common cause of acute kidney injury (AKI). Numerous therapeutic approaches for I/R injury have been studied, including autophagy, particularly in animal models of renal I/R injury derived from young or adult animals. However, the precise role of autophagy in renal ischemia-reperfusion in the aged animal model remains unclear. The purpose of this study was to demonstrate whether autophagy has similar effects on renal I/R injury in young and aged rats.

Materials and methods

All rats were divided into two age groups (3 months and 24 months) with each group being further divided into four subgroups (sham, I/R, I/R+Rap (rapamycin, an activator of autophagy), I/R+3-MA (3-methyladenine, an inhibitor of autophagy)). The I/R+Rap and I/R+3-MA groups were intraperitoneally injected with rapamycin and 3-MA prior to ischemia. We then measured serum levels of urea nitrogen, creatinine and assessed damage in the renal tissue. Immunohistochemistry was used to assess LC3-II and caspase-3, and Western blotting was used to evaluate the autophagy-related proteins LC3-II, Beclin-1 and P62. Apoptosis and autophagosomes were evaluated by TUNEL and transmission electron microscopy, respectively.

Results

Autophagy was activated in both young and aged rats by I/R and enhanced by rapamycin, although the level of autophagy was lower in the aged groups. In young rats, the activation of autophagy markedly improved renal function, reduced apoptosis in the renal tubular epithelial cells and the injury score in the renal tissue, thereby exerting protective effects on renal I/R injury. However, this level of protection was not present in aged rats.

Conclusion

Our data indicated that the activation of autophagy was ineffective in aged rat kidneys. These discoveries may have major implications in that severe apoptosis in aged kidneys might be refractory to antiapoptotic effect induced by the activation of autophagy.

Rapamycin induces autophagy to alleviate acute kidney injury following cerebral ischemia and reperfusion via the mTORC1/ATG13/ULK1 signaling pathway

Acute kidney injury (AKI) is a clinically common and severe complication of ischemia-reperfusion (I/R), associated with high morbidity and mortality rates, and prolonged hospitalization. Rapamycin is a type of macrolide, primarily used for anti-rejection therapy following organ transplantation and the treatment of autoimmune diseases. Rapamycin has been identified to exert a protective effect against AKI induced by renal I/R as an autophagy inducer. However, whether rapamycin preconditioning may relieve AKI following cerebral I/R (CIR) remains to be fully elucidated. The purpose of the present study was to investigate the effects of CIR on the renal system of rats and the role of rapamycin in AKI following CIR. In the present study, a CIR model was established in Sprague-Dawley rats via a 90-min period of middle cerebral artery occlusion and 24 h reperfusion, and pretreatment with an intraperitoneal injection of rapamycin (dosage: 1 mg/kg; 0.5 h) prior to CIR. The levels of serum creatinine and blood urea nitrogen (BUN), and the expression of inflammation-, apoptosis- and autophagy-associated markers were subsequently measured. In addition to certain histopathological alterations to the kidney, it was identified that CIR significantly increased the levels of serum creatinine, BUN, tumor necrosis factor-α and interleukin-1β, and significantly induced apoptosis and autophagy. It was observed that rapamycin induced autophagy through the mammalian target of rapamycin complex 1/autophagy-related 13/unc-51 like autophagy activating kinase 1 signaling pathway, and that rapamycin pre-treatment significantly improved renal function and alleviated renal tissue inflammation and cell apoptosis in rats following CIR. In conclusion, the results suggested that rapamycin may alleviate AKI following CIR via the induction of autophagy.

Aged kidney: can we protect it? Autophagy, mitochondria and mechanisms of ischemic preconditioning

The anti-aging strategy is one of the main challenges of the modern biomedical science. The term "aging" covers organisms, cells, cellular organelles and their constituents. In general term, aging system admits the existence of nonfunctional structures which by some reasons have not been removed by a clearing system, e.g., through autophagy/mitophagy marking and destroying unwanted cells or mitochondria. This directly relates to the old kidney which normal functioning is critical for the viability of the organism. One of the main problems in biomedical studies is that in their majority, young organisms serve as a standard with further extrapolation on the aged system. However, some protective systems, which demonstrate their efficiency in young systems, lose their beneficial effect in aged organisms. It is true for ischemic preconditioning of the kidney, which is almost useless for an old kidney. The pharmacological intervention could correct the defects of the senile system provided that the complete understanding of all elements involved in aging will be achieved. We discuss critical elements which determine the difference between young and old phenotypes and give directions to prevent or cure lesions occurring in aged organs including kidney.

ABBREVIATIONS

AKI: acute kidney injury; I/R: ischemia/reperfusion; CR: caloric restriction; ROS: reactive oxygen species; RC: respiratory chain.

Negative feedback loop of autophagy and endoplasmic reticulum stress in rapamycin protection against renal ischemia-reperfusion injury during initial reperfusion phase

Rapamycin, an immunosuppressant, is widely used in patients with kidney transplant. However, the therapeutic effects of rapamycin remain controversial. Additionally, previous studies have revealed deleterious effects of rapamycin predominantly when administered for ≥24 h. Few studies, however, have focused on the short-term effects of rapamycin administered only during the initial reperfusion phase. As such, we designed this study to explore the potential effects and mechanisms of rapamycin under a specific therapeutic regimen in which rapamycin is mixed in the perfusate during the initial reperfusion phase (within 24 h). Interestingly, we found that rapamycin maintained renal function and attenuated ischemia-reperfusion (I/R)-induced apoptosis in vivo and in vitro during the initial reperfusion phase, especially at 8 h after reperfusion. Simultaneously, rapamycin activated autophagy and inhibited endoplasmic reticulum (ER) stress and 3 pathways of unfolding protein response: ATF6, PERK, and IRE1α. Interestingly, we further found that the protective effects of rapamycin were suppressed when autophagy was inhibited by chloroquine and 3-methyladenine or when ER stress was induced by thapsigargin. Moreover, in terms of the regulatory effects of rapamycin, a negative-feedback loop between autophagy and ER stress occurred, with autophagy inhibiting ER stress and increased ER stress promoting autophagy during the initial reperfusion phase of renal I/R injury. Our study provides evidence that immediate reperfusion with rapamycin during the initial reperfusion phase repairs renal function and reduces apoptosis via activating autophagy, which could further inhibit ER stress. These results suggest a novel treatment modality for application during the initial reperfusion phase of renal I/R injury caused by kidney transplantation.-Li, X., Zhu, G., Gou, X., He, W., Yin, H., Yang, X., Li, J. Negative feedback loop of autophagy and endoplasmic reticulum stress in rapamycin protection against renal ischemia-reperfusion injury during initial reperfusion phase.

Rapamycin-induced autophagy protects proximal tubular renal cells against proteinuric damage through the transcriptional activation of the nerve growth factor receptor NGFR

Experimental evidence demonstrated that macroautophagy/autophagy exerts a crucial role in maintain renal cellular homeostasis and represents a protective mechanism against renal injuries. Interestingly, it has been demonstrated that in the human proximal tubular renal cell line, HK-2, the MTOR inhibitor rapamycin enhanced autophagy and mitigated the apoptosis damage induced by urinary protein overload. However, the underlying molecular mechanism has not yet been elucidated. In our study we demonstrated, for the first time, that in HK-2 cells, the exposure to low doses of rapamycin transactivated the NGFR promoter, leading to autophagic activation. Indeed, we observed that in HK-2 cells silenced for the NGFR gene, the rapamycin-induced autophagic process was prevented, as the upregulation of the proautophagic markers, BECN1, as well as LC3-II, and the autophagic vacuoles evaluated by transmission electron microscopy, were not found. Concomitantly, using a series of deletion constructs of the NGFR promoter we found that the EGR1 transcription factor was responsible for the rapamycin-mediated transactivation of the NGFR promoter. Finally, our results provided evidence that the cotreatment with rapamycin plus albumin further enhanced autophagy via NGFR activation, reducing the proapoptotic events promoted by albumin alone. This effect was prevented in HK-2 cells silenced for the NGFR gene or pretreated with the MTOR activator, MHY1485. Taken together, our results describe a novel molecular mechanism by which rapamycin-induced autophagy, mitigates the tubular renal damage caused by proteinuria, suggesting that the use of low doses of rapamycin could represent a new therapeutic strategy to counteract the tubule-interstitial injury observed in patients affected by proteinuric nephropathies, avoiding the side effects of high doses of rapamycin.

Neutrophil Gelatinase-Associated Lipocalin Attenuates Ischemia/Reperfusion Injury in an In Vitro Model via Autophagy Activation

Background

The aim of this study was to investigate the protective effects of neutrophil gelatinase-associated lipocalin (NGAL) on hypoxia/reoxygenation (H/R) induced acute kidney injury (AKI) in vitro.

Material/Methods

We used NRK-52E cells and H/R treatments to mimic ischemia/reperfusion injury (IRI) in vitro. Experimental groups were: the control group, the H/R group, the 3-methyladenine (3-MA)+H/R group, the NGAL (0.25, 0.5, and 1 ug/mL)+H/R group, and the NGAL (0.25, 0.5, 1 ug/mL)+3-MA+H/R group. After 24 hours of culture, cell proliferation was analyzed by CCK-8 assay. Expression of LC3-II was detected by immunoblot assay. Autophagy was detected by electron microscopy.

Results

The expression of LC3-II was increased in the H/R group compared with normoxic condition (p<0.05) and proliferation also improved. Autophagy was significantly inhibited by 3-MA, with downregulated of LC3-II, followed by decreased cell viability (p<0.05). We further detected the effect of different doses of NGAL in H/R induced injury, and found that low doses of NGAL alone slightly increased LC3-II protein accumulation, and autophagy was further induced with higher dose of NGAL treatment. Meanwhile, cell viability assays showed induced cell survival. We found that in the NGAL+3-MA group, cell viability assays revealed reduced cell damage, followed concomitantly with depressed autophagy. The formulation of autophagosomes were correlated with LC3-II protein expression in each group.

Conclusions

Autophagy plays a renoprotective role in H/R injury, as well in AKI. NGAL might be related to attenuated tubular epithelial cell damage via adjusting autophagy.

Autophagy: A new treatment strategy for MSC-based therapy in acute kidney injury (Review)

Acute kidney injury (AKI) is a common and serious medical condition associated with poor health outcomes. Autophagy is a conserved multistep pathway that serves a major role in many biological processes and diseases. Recent studies have demonstrated that autophagy is induced in proximal tubular cells during AKI. Autophagy serves a pro‑survival or pro‑death role under certain conditions. Furthermore, mesenchymal stem cells (MSCs) have therapeutic potential in the repair of renal injury. This review summarizes the recent progress on the role of autophagy in AKI and MSCs‑based therapy for AKI. Further research is expected to prevent and treat acute kidney injury.

Aggravation of acute kidney injury by mPGES-2 down regulation is associated with autophagy inhibition and enhanced apoptosis

The deletion of microsomal prostaglandin E synthase-2 (mPGES-2) does not affect in vivo PGE₂ production, and the function of this enzyme remains unknown until now. This study investigated the expression and roles of mPGES-2 in LPS induced acute kidney injury (AKI) both in vitro and in vivo. We found that mPGES-2 was up-regulated in kidney of mice with LPS induced AKI. Inhibition of mouse mpges2 gene expression exacerbated LPS-induced renal dysfunction, renal tubular cell damage and apoptosis, while inhibited kidney autophagy. Further cellular experiments showed that over-expression of mPGES-2 resulted in increased autophagy and decreased apoptosis rate of renal tubular epithelial cells. In addition, treatment with autophagy inhibitor 3-methyladenine could reverse the above-mentioned results. On the contrary, interference of mPGES-2 expression by siRNA decreased autophagy level but significantly increased apoptosis of tubular epithelial cells and treatment with autophagy inducer rapamycin can reverse these results. Overall, our study shows that mPGES-2 can protect renal tubular epithelial cells by regulating autophagy levels and aggravation of acute kidney injury by mPGES-2 down regulation is associated with autophagy inhibition and enhanced apoptosis.

Inhibition of HDAC6 protects against rhabdomyolysis-induced acute kidney injury

Histone deacetylase 6 (HDAC6) inhibition has been reported to protect against ischemic stroke and prolong survival after sepsis in animal models. However, it remains unknown whether HDAC6 inhibition offers a renoprotective effect after acute kidney injury (AKI). In this study, we examined the effect of tubastatin A (TA), a highly selective inhibitor of HDAC6, on AKI in a murine model of glycerol (GL) injection-induced rhabdomyolysis. Following GL injection, the mice developed severe acute tubular injury as indicated by renal dysfunction; expression of neutrophil gelatinase-associated lipocalin (NGAL), an injury marker of renal tubules; and an increase of TdT-mediated dUTP nick-end labeling (TUNEL)-positive tubular cells. These changes were companied by increased HDAC6 expression in the cytoplasm of renal tubular cells. Administration of TA significantly reduced serum creatinine and blood urea nitrogen levels as well as attenuated renal tubular damage in injured kidneys. HDAC6 inhibition also resulted in decreased expression of NGAL, reduced apoptotic cell, and inactivated caspase-3 in the kidney after acute injury. Moreover, injury to the kidney increased phosphorylation of nuclear factor (NF)-κB and expression of multiple cytokines/chemokines including tumor necrotic factor-α and interleukin-6 and monocyte chemoattractant protein-1, as well as macrophage infiltration. Treatment with TA attenuated all those responses. Finally, HDAC6 inhibition reduced the level of oxidative stress by suppressing malondialdehyde (MDA) and preserving expression of superoxide dismutase (SOD) in the injured kidney. Collectively, these data indicate that HDAC6 contributes to the pathogenesis of rhabdomyolysis-induced AKI and suggest that HDAC6 inhibitors have therapeutic potential for AKI treatment.

Autophagy and Tubular Cell Death in the Kidney

Many common renal insults such as ischemia and toxic injury primarily target the tubular epithelial cells, especially the highly metabolically active proximal tubular segment. Tubular epithelial cells are particularly dependent on autophagy to maintain homeostasis and respond to stressors. The pattern of autophagy in the kidney has a unique spatial and chronologic signature. Recent evidence has shown that there is complex cross-talk between autophagy and various cell death pathways. This review specifically discusses the interplay between autophagy and cell death in the renal tubular epithelia. It is imperative to review this topic because recent discoveries have improved our mechanistic understanding of the autophagic process and have highlighted its broad clinical applications, making autophagy a major target for drug development.

Autophagy in allografts rejection: A new direction?

Despite the introduction of new and effective immunosuppressive drugs, acute cellular graft rejection is still a major risk for graft survival. Modulating the dosage of immunosuppressive drugs is not a good choice for all patients, new rejection mechanisms discovery are crucial to limit the inflammatory process and preserve the function of the transplant. Autophagy, a fundamental cellular process, can be detected in all subsets of lymphocytes and freshly isolated naive T lymphocytes. It is required for the homeostasis and function of T lymphocytes, which lead to cell survival or cell death depending on the context. T cell receptor (TCR) stimulation and costimulator signals induce strong autophagy, and autophagy deficient T cells leads to rampant apoptosis upon TCR stimulation. Autophagy has been proved to be activated during ischemia-reperfusion (I/R) injury and associated with grafts dysfunction. Furthermore, Autophagy has also emerged as a key mechanism in orchestrating innate and adaptive immune response to self-antigens, which relates with negative selection and Foxp3(+) Treg induction. Although, the role of autophagy in allograft rejection is unknown, current data suggest that autophagy indeed sweeps across both in the graft organs and recipients lymphocytes after transplantation. This review presents the rationale for the hypothesis that targeting the autophagy pathway could be beneficial in promoting graft survival after transplantation.

Autophagy in acute kidney injury

Autophagy is a conserved multistep pathway that degrades and recycles damaged organelles and macromolecules to maintain intracellular homeostasis. The autophagy pathway is upregulated under stress conditions including cell starvation, hypoxia, nutrient and growth-factor deprivation, endoplasmic reticulum stress, and oxidant injury, most of which are involved in the pathogenesis of acute kidney injury (AKI). Recent studies demonstrate that basal autophagy in the kidney is vital for the normal homeostasis of the proximal tubules. Deletion of key autophagy proteins impaired renal function and increased p62 levels and oxidative stress. In models of AKI, autophagy deletion in proximal tubules worsened tubular injury and renal function, highlighting that autophagy is renoprotective in models of AKI. In addition to nonselective sequestration of autophagic cargo, autophagy can facilitate selective degradation of damaged organelles, particularly mitochondrial degradation through the process of mitophagy. Damaged mitochondria accumulate in autophagy-deficient kidneys of mice subjected to ischemia-reperfusion injury, but the precise mechanisms of regulation of mitophagy in AKI are not yet elucidated. Recent progress in identifying the interplay of autophagy, apoptosis, and regulated necrosis has revived interest in examining shared pathways/molecules in this crosstalk during the pathogenesis of AKI. Autophagy and its associated pathways pose potentially unique targets for therapeutic interventions in AKI.