Autophagy and the Kidney: Implications for Ischemia-Reperfusion Injury and Therapy

Icaritin attenuates ischemia-reperfusion injury by anti-inflammation, anti-oxidative stress, and anti-autophagy in mouse liver

BACKGROUND

Hepatic ischemia-reperfusion (IR) injury is a major complication of liver transplantation and gravely affects patient prognosis. Icaritin (ICT), the primary plasma metabolite of icariin (ICA), plays a critical role in anti-inflammatory and immunomodulatory processes. However, the role of ICT in hepatic IR injury remains largely undefined. In this study, we aimed to elucidate the role of ICT in hepatic IR injury.

METHODS

We established hepatic IR injury models in animals, as well as an oxygen-glucose deprivation/reperfusion (OGD/R) cell model. Liver injury in vivo was assessed by measuring serum alanine aminotransferase (ALT) levels, necrotic areas by liver histology and local hepatic inflammatory responses. For in vitro analyses, we implemented flow-cytometric and western blot analyses, transmission electron microscopy, and an mRFP-GFP-LC3 adenovirus reporter assay to assess the effects of ICT on OGD/R injury in AML12 and THLE-2 cell lines. Signaling pathways were explored in vitro and in vivo to identify possible mechanisms underlying ICT action in hepatic IR injury.

RESULTS

Compared to the mouse model group, ICT preconditioning considerably protected the liver against IR stress, and diminished the levels of necrosis/apoptosis and inflammation-related cytokines. In additional studies, ICT treatment dramatically boosted the expression ratios of p-PI3K/PI3K, p-AKT/AKT, and p-mTOR/mTOR proteins in hepatic cells following OGD/R damage. We also applied LY294002 (a PI3K inhibitor) and RAPA (rapamycin, an mTOR inhibitor), which blocked the protective effects of ICT in hepatocytes subjected to OGD/R.

CONCLUSION

This study indicates that ICT attenuates ischemia-reperfusion injury by exerting anti-inflammation, anti-oxidative stress, and anti-autophagy effects, as demonstrated in mouse livers. We thus posit that ICT could have therapeutic potential for the treatment of hepatic IR injury.

Protective Effect of CXCR7 Against Hypoxia/Reoxygenation Injury in Renal Tubular Epithelial Cells

Acute kidney injury (AKI) is a multifactorial syndrome with complex pathophysiology and prognosis. Ischaemia‒reperfusion injury (IRI) is a major cause of induced AKI. The aim of this study was to investigate the effect of upregulated CXCR7 expression on renal tubular epithelial cell apoptosis induced by hypoxia/reoxygenation (H/R). HK-2 cells were divided into three groups: control group (pcDNA3.1), hypoxia/reoxygenation + pcDNA3.1 group (H/R+pcDNA3.1) and CXCR7 overexpression + hypoxia/reoxygenation group (H/R+ Flag-CXCR7). Protein levels of renal tubular epithelial cell injury-, apoptosis- and autophagy-related markers were assessed by qRT‒PCR, Western blotting, flow cytometry (FCM), immunofluorescence and transmission electron microscopy (TEM). In addition, HK-2 cells were treated with the autophagy inhibitor 3-MA and divided into 3 groups: control group, 3-MA + pcDNA3.1 group, and 3-MA + Flag-CXCR7 group. Changes in autophagy and apoptosis in renal tubule epithelial cells were assessed by Western blotting and FCM. Compared with those in the control group, the protein and mRNA expression levels of CXCR7 in HK-2 cells were significantly lower under H/R conditions. Under H/R conditions, CXCR7 overexpression in HK-2 cells significantly downregulated the expression of NGAL. Moreover, CXCR7 overexpression significantly decreased H/R-induced cleaved PARP-1 and cleaved Caspase 3 levels, increased the level of the antiapoptotic protein BCL-2 and the autophagy-related molecules ATG5 and LC3B II, and significantly inhibited the expression of P62. Autophagy flow and TEM also showed that CXCR7 significantly promoted autophagy. CXCR7 significantly alleviated the 3-MA-induced inhibition of autophagy and increase in apoptosis. Upregulated CXCR7 expression can inhibit renal tubular epithelial cell apoptosis and damage by regulating autophagy. In conclusion, CXCR7 is a promising target for the prevention and/or treatment of AKI.

DUSP5 deficiency suppresses the progression of acute kidney injury by enhancing autophagy through AMPK/ULK1 pathway

Acute kidney injury (AKI) represents a critical clinical disease characterized by the rapid decline in renal function, carrying a substantial burden of morbidity and mortality. The treatment of AKI is frequently limited by its variable clinical presentations and intricate pathophysiology, highlighting the urgent need for a deeper understanding of its pathogenesis and potential therapeutic targets. Dual-specific protein phosphatase 5 (DUSP5), a member of the serine-threonine phosphatase family, possesses the capability to dephosphorylate extracellular regulated protein kinases (ERK). DUSP5 has emerged as a pivotal player in modulating metabolic signals, inflammatory responses, and cancer progression, while also being closely associated with various kidney diseases. This study systematically scrutinized the function and mechanism of DUSP5 in AKI for the first time, unveiling a substantial increase in DUSP5 expression during AKI. Moreover, DUSP5 knockdown was observed to attenuate the production of inflammatory factors and apoptotic cells in renal tubular epithelial cells by enhancing AMPK/ULK1-mediated autophagy, thus improving renal function. In a word, DUSP5 knockdown in AKI effectively impede disease progression by activating autophagy. This finding holds promise for introducing fresh perspectives and targets for AKI treatment.

Cell death induced by acute renal injury: a perspective on the contributions of accidental and programmed cell death

The involvement of cell death in acute kidney injury (AKI) is linked to multiple factors including energy depletion, electrolyte imbalance, reactive oxygen species, inflammation, mitochondrial dysfunction, and activation of several cell death pathway components. Since our review in 2003, discussing the relative contributions of apoptosis and necrosis, several other forms of cell death have been identified and are shown to contribute to AKI. Currently, these various forms of cell death can be fundamentally divided into accidental cell death and regulated or programmed cell death based on functional aspects. Several death initiator and effector molecules switch molecules that may act as signaling components triggering either death or protective mechanisms or alternate cell death pathways have been identified as part of the machinery. Intriguingly, several of these cell death pathways share components and signaling pathways suggesting complementary or compensatory functions. Thus, defining the cross talk between distinct cell death pathways and identifying the unique molecular effectors for each type of cell death may be required to develop novel strategies to prevent cell death. Furthermore, depending on the multiple forms of cell death simultaneously induced in different AKI settings, strategies for combination therapies that block multiple cell death pathways need to be developed to completely prevent injury, cell death, and renal function. This review highlights the various cell death pathways, cross talk, and interactions between different cell death modalities in AKI.

Autophagy: A Silent Protagonist in Kidney Transplantation

Autophagy is a lysosome-dependent regulated mechanism that recycles unnecessary cytoplasmic components. It is now known that autophagy dysfunction may have a pathogenic role in several human diseases and conditions, including kidney transplantation. Both defective and excessive autophagy may induce or aggravate several complications of kidney transplantation, such as ischemia-reperfusion injury, alloimmune response, and immunosuppressive treatment and side effects. Although it is still complicated to measure autophagy levels in clinical practice, more attention should be paid to the factors that may influence autophagy. In kidney transplantation, the association of low doses of a mammalian target of rapamycin inhibitor with low doses of a calcineurin inhibitor may be of benefit for autophagy modulation. However, further studies are needed to explore the role of other autophagy regulators.

An autophagy-associated diagnostic signature based on peripheral blood for antibody-mediated rejection in renal transplantation

BACKGROUND

Antibody-mediated rejection (ABMR) emerged as a major cause of graft loss in renal transplantation. Needle biopsy is the gold standard for diagnosis of ABMR in renal allografts. Thus, noninvasive diagnosis methods of ABMR with high accuracy are urgently needed to prevent unnecessary biopsies.

METHODS

We collected peripheral blood transcriptome data from two independent renal transplantation cohorts with patients with ABMR, stable well-functioning transplants (STA), and T-cell mediated rejection (TCMR). Differentially expressed genes (DEGs) were identified by comparing the ABMR group with the STA group. In addition, functional enrichment analysis and gene set enrichment analysis were performed to seek new key underlying mechanisms in ABMR. Subsequently, we utilized a Boruta algorithm and least absolute shrinkage and selection operator logistic algorithm to establish a diagnostic model which was then evaluated and validated in an independent cohort.

RESULTS

According to functional enrichment analysis, autophagy was found to be the primary upregulated biological process in ABMR. Based on algorithms, three autophagy-associated genes, ubiquitin specific peptidase 33 (USP33), Ras homolog mTORC1 binding (RHEB), and ABL proto-oncogene 2 (ABL2), were selected to establish the diagnostic model in the training cohort. This autophagy-related gene model possessed good diagnostic value in distinguishing ABMR from STA blood samples in the training cohort (AUC = 0.907) and in the validation cohort (AUC = 0.972). In addition, this model also showed good discernibility in distinguishing ABMR from TCMR in the training and validation cohorts (AUCs = 0.908 and 0.833).

CONCLUSION

We identified and validated an autophagy-associated diagnostic model with high accuracy for renal transplant patients with ABMR. Our study provided a new potential test for the non-invasive diagnosis of ABMR in clinical practice and highlighted the importance of autophagy in ABMR.

The protective role of vagus nerve stimulation in ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) encompasses the damage resulting from the restoration of blood supply following tissue ischemia. This phenomenon commonly occurs in clinical scenarios such as hemorrhagic shock, severe trauma, organ transplantation, and thrombolytic therapy. Despite its prevalence, existing treatments exhibit limited efficacy against IRI. Vagus nerve stimulation (VNS) is a widely utilized technique for modulating the autonomic nervous system. Numerous studies have demonstrated that VNS significantly reduces IRI in various organs, including the heart, brain, and liver. This article reviews the pathological processes during IRI and summarizes the role and possible mechanisms of VNS in IRI of different organs. Furthermore, this review addresses the current challenges of VNS clinical applications, providing a novel perspective on IRI treatment.

Albumin influences leucocyte FcRn expression in the early days of kidney transplantation

FcRn, a receptor originally known for its involvement in IgG and albumin transcytosis and recycling, is also important in the establishment of the innate and adaptive immune response. Dysregulation of the immune response has been associated with variations in FcRn expression, as observed in cancer. Recently, a link between autophagy and FcRn expression has been demonstrated. Knowing that autophagy is strongly involved in the development of reperfusion injury in kidney transplantation and that albuminemia is transiently decreased in the first 2 weeks after transplantation, we investigated variations in FcRn expression after kidney transplantation. We monitored FcRn levels by flow cytometry in leukocytes from 25 renal transplant patients and considered parameters such as albumin concentrations, estimated glomerular filtration rate, serum creatinine, serum IgG levels, and ischaemia/reperfusion time. Two groups of patients could be distinguished according to their increased or non-increased FcRn expression levels between days 2 and 6 (d2-d6) post-transplantation. Leukocyte FcRn expression at d2-d6 was correlated with albumin concentrations at d0-d2. These results suggest that albumin concentrations at d0-d2 influence FcRn expression at d2-d6, raising new questions about the mechanisms underlying these original observations.

GPX4, ferroptosis, and diseases

GPX4 (Glutathione peroxidase 4) serves as a crucial intracellular regulatory factor, participating in various physiological processes and playing a significant role in maintaining the redox homeostasis within the body. Ferroptosis, a form of iron-dependent non-apoptotic cell death, has gained considerable attention in recent years due to its involvement in multiple pathological processes. GPX4 is closely associated with ferroptosis and functions as the primary inhibitor of this process. Together, GPX4 and ferroptosis contribute to the pathophysiology of several diseases, including sepsis, nervous system diseases, ischemia reperfusion injury, cardiovascular diseases, and cancer. This review comprehensively explores the regulatory roles and impacts of GPX4 and ferroptosis in the development and progression of these diseases, with the aim of providing insights for identifying potential therapeutic strategies in the future.

Protection of Ndrg2 deficiency on renal ischemia-reperfusion injury via activating PINK1/Parkin-mediated mitophagy

BACKGROUND

Renal ischemia-reperfusion (R-I/R) injury is the most prevalent cause of acute kidney injury, with high mortality and poor prognosis. However, the underlying pathological mechanisms are not yet fully understood. Therefore, this study aimed to investigate the role of N-myc downstream-regulated gene 2 (Ndrg2) in R-I/R injury.

METHODS

We examined the expression of Ndrg2 in the kidney under normal physiological conditions and after R-I/R injury by immunofluorescence staining, real-time polymerase chain reaction, and western blotting. We then detected R-I/R injury in Ndrg2-deficient (Ndrg2-/-) mice and wild type (Ndrg2+/+) littermates in vivo, and detected oxygen and glucose deprivation and reperfusion injury (OGD-R) in HK-2 cells. We further conducted transcriptomic sequencing to investigate the role of Ndrg2 in R-I/R injury and detected levels of oxidative stress and mitochondrial damage by dihydroethidium staining, biochemical assays, and western blot. Finally, we measured the levels of mitophagy in Ndrg2+/+ and Ndrg2-/- mice after R-I/R injury or HK-2 cells in OGD-R injury.

RESULTS

We found that Ndrg2 was primarily expressed in renal proximal tubules and significantly decreased its expression 24 h after R-I/R injury. Ndrg2-/- mice exhibited significantly attenuated R-I/R injury compared to Ndrg2+/+ mice. Transcriptomics profiling showed that Ndrg2 deficiency induced perturbations of multiple signaling pathways, downregulated inflammatory responses and oxidative stress, and increased autophagy following R-I/R injury. Further studies revealed that Ndrg2 deficiency reduced oxidative stress and mitochondrial damage. Notably, Ndrg2 deficiency significantly activated phosphatase and tensin homologue on chromosome ten-induced putative kinase 1 (PINK1)/Parkin-mediated mitophagy. The downregulation of NDRG2 expression significantly increased cell viability after OGD-R injury, increased the expression of heme oxygenase-1, decreased the expression of nicotinamide adenine dinucleotide phosphate oxidase 4, and increased the expression of the PINK1/Parkin pathway.

CONCLUSION

Ndrg2 deficiency might become a therapy target for R-I/R injury by decreasing oxidative stress, maintaining mitochondrial homeostasis, and activating PINK1/Parkin-mediated mitophagy.

Inspiring Tactics with the Improvement of Mitophagy and Redox Balance for the Development of Innovative Treatment against Polycystic Kidney Disease

Polycystic kidney disease (PKD) is the most common genetic form of chronic kidney disease (CKD), and it involves the development of multiple kidney cysts. Not enough medical breakthroughs have been made against PKD, a condition which features regional hypoxia and activation of the hypoxia-inducible factor (HIF) pathway. The following pathology of CKD can severely instigate kidney damage and/or renal failure. Significant evidence verifies an imperative role for mitophagy in normal kidney physiology and the pathology of CKD and/or PKD. Mitophagy serves as important component of mitochondrial quality control by removing impaired/dysfunctional mitochondria from the cell to warrant redox homeostasis and sustain cell viability. Interestingly, treatment with the peroxisome proliferator-activated receptor-α (PPAR-α) agonist could reduce the pathology of PDK and might improve the renal function of the disease via the modulation of mitophagy, as well as the condition of gut microbiome. Suitable modulation of mitophagy might be a favorable tactic for the prevention and/or treatment of kidney diseases such as PKD and CKD.

Energy metabolic reprogramming regulates programmed cell death of renal tubular epithelial cells and might serve as a new therapeutic target for acute kidney injury

Acute kidney injury (AKI) induces significant energy metabolic reprogramming in renal tubular epithelial cells (TECs), thereby altering lipid, glucose, and amino acid metabolism. The changes in lipid metabolism encompass not only the downregulation of fatty acid oxidation (FAO) but also changes in cell membrane lipids and triglycerides metabolism. Regarding glucose metabolism, AKI leads to increased glycolysis, activation of the pentose phosphate pathway (PPP), inhibition of gluconeogenesis, and upregulation of the polyol pathway. Research indicates that inhibiting glycolysis, promoting the PPP, and blocking the polyol pathway exhibit a protective effect on AKI-affected kidneys. Additionally, changes in amino acid metabolism, including branched-chain amino acids, glutamine, arginine, and tryptophan, play an important role in AKI progression. These metabolic changes are closely related to the programmed cell death of renal TECs, involving autophagy, apoptosis, necroptosis, pyroptosis, and ferroptosis. Notably, abnormal intracellular lipid accumulation can impede autophagic clearance, further exacerbating lipid accumulation and compromising autophagic function, forming a vicious cycle. Recent studies have demonstrated the potential of ameliorating AKI-induced kidney damage through calorie and dietary restriction. Consequently, modifying the energy metabolism of renal TECs and dietary patterns may be an effective strategy for AKI treatment.

Protective Mechanism of Cordyceps sinensis Treatment on Acute Kidney Injury-Induced Acute Lung Injury through AMPK/mTOR Signaling Pathway

OBJECTIVE

To investigate protective effect of Cordyceps sinensis (CS) through autophagy-associated adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway in acute kidney injury (AKI)-induced acute lung injury (ALI).

METHODS

Forty-eight male Sprague-Dawley rats were divided into 4 groups according to a random number table, including the normal saline (NS)-treated sham group (sham group), NS-treated ischemia reperfusion injury (IRI) group (IRI group), and low- (5 g/kg·d) and high-dose (10 g/kg·d) CS-treated IRI groups (CS1 and CS2 groups), 12 rats in each group. Nephrectomy of the right kidney was performed on the IRI rat model that was subjected to 60 min of left renal pedicle occlusion followed by 12, 24, 48, and 72 h of reperfusion. The wet-to-dry (W/D) ratio of lung, levels of serum creatinine (Scr), blood urea nitrogen (BUN), inflammatory cytokines such as interleukin- β and tumor necrosis factor- α, and biomarkers of oxidative stress such as superoxide dismutase, malonaldehyde (MDA) and myeloperoxidase (MPO), were assayed. Histological examinations were conducted to determine damage of tissues in the kidney and lung. The protein expressions of light chain 3 II/light chain 3 I (LC3-II/LC3-I), uncoordinated-51-like kinase 1 (ULK1), P62, AMPK and mTOR were measured by Western blot and immunohistochemistry, respectively.

RESULTS

The renal IRI induced pulmonary injury following AKI, resulting in significant increases in W/D ratio of lung, and the levels of Scr, BUN, inflammatory cytokines, MDA and MPO (P<0.01); all of these were reduced in the CS groups (P<0.05 or P<0.01). Compared with the IRI groups, the expression levels of P62 and mTOR were significantly lower (P<0.05 or P<0.01), while those of LC3-II/LC3-I, ULK1, and AMPK were significantly higher in the CS2 group (P<0.05 or P<0.01).

CONCLUSION

CS had a potential in treating lung injury following renal IRI through activation of the autophagy-related AMPK/mTOR signaling pathway in AKI-induced ALI.

Autosomal Dominant Polycystic Kidney Disease: Is There a Role for Autophagy?

Autosomal-Dominant Polycystic Kidney Disease (ADPKD) is a monogenic disorder initiated by mutations in either PKD1 or PKD2 genes, responsible for encoding polycystin 1 and polycystin 2, respectively. These proteins are primarily located within the primary cilia. The disease follows an inexorable progression, leading most patients to severe renal failure around the age of 50, and extra-renal complications are frequent. A cure for ADPKD remains elusive, but some measures can be employed to manage symptoms and slow cyst growth. Tolvaptan, a vasopressin V2 receptor antagonist, is the only drug that has been proven to attenuate ADPKD progression. Recently, autophagy, a cellular recycling system that facilitates the breakdown and reuse of aged or damaged cellular components, has emerged as a potential contributor to the pathogenesis of ADPKD. However, the precise role of autophagy in ADPKD remains a subject of investigation, displaying a potentially twofold impact. On the one hand, impaired autophagy may promote cyst formation by inducing apoptosis, while on the other hand, excessive autophagy may lead to fibrosis through epithelial to mesenchymal transition. Promising results of autophagy inducers have been observed in preclinical studies. Clinical trials are warranted to thoroughly assess the long-term safety and efficacy of a combination of autophagy inducers with metabolic and/or aquaferetic drugs. This research aims to shed light on the complex involvement of autophagy in ADPKD, explore the regulation of autophagy in disease progression, and highlight the potential of combination therapies as a promising avenue for future investigations.

The role of LncRNA-regulated autophagy in AKI

Acute kidney injury (AKI) is a complex clinical syndrome involving a series of pathophysiological processes regulated by multiple pathways at the molecular and cellular level. Long noncoding RNAs (lncRNAs) play an important role in the regulation of epigenetics, and their regulation of autophagy-related genes in AKI has attracted increasing attention. However, the role of lncRNA-regulated autophagy in AKI has not been fully elucidated. Evidence indicated that lncRNAs play regulatory roles in most factors that induce AKI. LncRNAs can regulate autophagy in AKI via a complex network of regulatory pathways to affect the development and prognosis of AKI. This article reviewed and analyzed the pathways of lncRNA regulation of autophagy in AKI in recent years. The results provide new ideas for further study of the pathophysiological process and targeted therapy for AKI.

HYPERBILIRUBINEMIA AGGRAVATES RENAL ISCHEMIA REPERFUSION INJURY BY EXACERBATING PINK1-PARKIN-MEDIATED MITOPHAGY

ABSTRACT

Background: Hyperbilirubinemia is a common perioperative complication, which is associated with acute kidney injury. Bilirubin permeabilizes mitochondrial membranes leading to mitochondrial swelling and dysfunction. In this study, we aimed to determine the association between PINK1-PARKIN-mediated mitophagy and renal ischemia-reperfusion (IR) injury aggravated by hyperbilirubinemia. Methods: A C57BL/6 mouse hyperbilirubinemia model was induced via intraperitoneal injection of bilirubin solution. In addition, a hypoxia/reoxygenation (H/R) injury model of TCMK-1 cells was established. In these models, we determined the effects of hyperbilirubinemia on oxidative stress, apoptosis, mitochondrial damage, and fibrosis. Results:In vitro , colocalization of GFP-LC3 puncta and Mito-Tracker Red showed that the number of mitophagosomes increased in TCMK-1 cells under H/R and bilirubin condition. Silencing of PINK1 or inhibition of autophagy alleviated mitochondrial damage, oxidative stress, and apoptosis in H/R injury aggravated by bilirubin and decreased cell death detected by methyl-thiazolyl-tetrazolium. In vivo , hyperbilirubinemia increased serum creatinine level in the renal IR injury mice model. Hyperbilirubinemia enhanced apoptosis induced by renal IR. In addition, hyperbilirubinemia increased mitophagosomes and autophagosomes and disrupted mitochondrial cristae in the IR kidney. Inhibition of PINK1 or autophagy reduced histological damages by alleviating apoptosis in renal IR injury, aggravated by hyperbilirubinemia. 3-MA or PINK1-shRNA-AAV9 treatment decreased the area of collagen and proteins related to fibrosis in renal IR injury, aggravated by hyperbilirubinemia. Conclusions: We have demonstrated that hyperbilirubinemia aggravated oxidative stress, apoptosis, mitochondrial damage, and fibrosis in renal IR injury by exacerbating PINK1-PARKIN-mediated mitophagy.

Sulforaphane protects microvascular endothelial cells in lower limb ischemia/reperfusion injury mice

Background: Microvascular damage is a key pathological factor in acute lower limb ischemia/reperfusion (I/R) injury. Current evidence suggests that sulforaphane (SFN) protects tissue from I/R injury. However, the role of SFN in acute lower limb I/R injury remains elusive. This study aimed to investigate the role and potential mechanism of SFN in I/R-related microvascular damage in the limb. Methods: Limb viability was evaluated by laser Doppler imaging, tissue edema analysis and histological analysis. Western blotting and immunofluorescence were applied to analyze the levels of apoptosis, oxidative stress, autophagy, transcription factor EB (TFEB) activity and mucolipin 1 (MCOLN1)-calcineurin signaling pathway. Results: SFN administration significantly ameliorated I/R-induced hypoperfusion, tissue edema, skeletal muscle fiber injury and endothelial cell (EC) damage in the limb. Pharmacological inhibition of NFE2L2 (nuclear factor, erythroid 2 like 2) reversed the anti-oxidation and anti-apoptosis effects of SFN on ECs. Additionally, silencing of TFEB by interfering RNA abolished the SFN-induced autophagy restoration, anti-oxidant response and anti-apoptosis effects on ECs. Furthermore, silencing of MCOLN1 by interfering RNA and pharmacological inhibition of calcineurin inhibited the activity of TFEB induced by SFN, demonstrating that SFN regulates the activity of TFEB through the MCOLN1-calcineurin signaling pathway. Conclusion: SFN protects microvascular ECs against I/R injury by TFEB-mediated autophagy restoration and anti-oxidant response.

A protein encoded by circular ZNF609 RNA induces acute kidney injury by activating the AKT/mTOR-autophagy pathway

Autophagy plays a crucial role in the development and progression of ischemic acute kidney injury (AKI). However, the function and mechanism of circular RNAs (circRNAs) in the regulation of autophagy in ischemic AKI remain unexplored. Herein, we find that circ-ZNF609, originating from the ZNF609 locus, is highly expressed in the kidney after ischemia/reperfusion injury, and urinary circ-ZNF609 is a moderate predictor for AKI in heart disease patients. Overexpression of circ-ZNF609 can activate AKT3/mTOR signaling and induce autophagy flux impairment and cell apoptosis while inhibiting proliferation in HK-2 cells, which is blocked by silencing circ-ZNF609. Mechanistically, circ-ZNF609 encodes a functional protein consisting of 250 amino acids (aa), termed ZNF609-250aa, the overexpression of which can activate AKT3/mTOR signaling and induce autophagy flux impairment and cell apoptosis in HK-2 cells in vitro and in AKI kidneys in vivo. The blockade of AKT and mTOR signaling with pharmacological inhibitors is capable of reversing ZNF609-250aa-induced autophagy flux impairment and cell apoptosis in HK-2 cells. The present study demonstrates that highly expressed circ-ZNF609-encoded ZNF609-250aa induces cell apoptosis and AKI by impairing the autophagy flux via an AKT/mTOR-dependent mechanism. These findings imply that targeting circ-ZNF609 may be a novel therapy for ischemic AKI.

Overexpression of miR-92a attenuates kidney ischemia-reperfusion injury and improves kidney preservation by inhibiting MEK4/JNK1-related autophagy

BACKGROUND

Kidney ischemia-reperfusion injury is inevitable in kidney transplantation, and is essential for primary graft dysfunction and delayed graft function. Our previous study has proved that miR-92a could ameliorate kidney ischemia-reperfusion injury, but the mechanism has not been studied.

METHODS

This study conducted further research on the role of miR-92a in kidney ischemia-reperfusion injury and organ preservation. In vivo, mice models of bilateral kidney ischemia (30 min), cold preservation after ischemia (cold preservation time of 6, 12, and 24 h), and ischemia-reperfusion (reperfusion time of 24, 48, and 72 h) were established. Before or after modeling, the model mice were injected with miR-92a-agomir through the caudal vein. In vitro, the hypoxia-reoxygenation of HK-2 cells was used to simulate ischemia-reperfusion injury.

RESULTS

Kidney ischemia and ischemia-reperfusion significantly damaged kidney function, decreased the expression of miR-92a, and increased apoptosis and autophagy in kidneys. miR-92a agomir tail vein injection significantly increased the expression of miR-92a in kidneys, improved kidney function, and alleviated kidney injury, and the intervention before modeling achieved a better effect than after. Moreover, miR-92a agomir significantly reduced the apoptosis and autophagy in HK-2 cells induced by hypoxia, hypoxia-reoxygenation, and rapamycin, while miR-92a antagomir had opposite effects. Furthermore, mitogen-activated protein kinase, c-Jun NH (2) terminal kinase, caspase 3, Beclin 1, and microtubule-associated protein 1 light chain 3B were inhibited by overexpression of miR-92a both in vivo and in vitro, which in turn reduced apoptosis and autophagy.

CONCLUSIONS

Our results prove that overexpression of miR-92a attenuated kidney ischemia-reperfusion injury and improved kidney preservation, and intervention before ischemia-reperfusion provides better protection than after.

Inhibition of ALKBH5 attenuates I/R-induced renal injury in male mice by promoting Ccl28 m6A modification and increasing Treg recruitment

Ischemia reperfusion injury (IRI) is a common cause of acute kidney injury (AKI). The role of N^6-methyladenosine (m6A) modification in AKI remains unclear. Here, we characterize the role of AlkB homolog 5 (ALKBH5) and m6A modification in an I/R-induced renal injury model in male mice. Alkbh5-knockout mice exhibit milder pathological damage and better renal function than wild-type mice post-IRI, whereas Alkbh5-knockin mice show contrary results. Also conditional knockout of Alkbh5 in the tubular epithelial cells alleviates I/R-induced AKI and fibrosis. CCL28 is identified as a target of ALKBH5. Furthermore, Ccl28 mRNA stability increases with Alkbh5 deficiency, mediating by the binding of insulin-like growth factor 2 binding protein 2. Treg recruitment is upregulated and inflammatory cells are inhibited by the increased CCL28 level in IRI-Alkbh5^fl/flKsp^Cre mice. The ALKBH5 inhibitor IOX1 exhibits protective effects against I/R-induced AKI. In summary, inhibition of ALKBH5 promotes the m6A modifications of Ccl28 mRNA, enhancing its stability, and regulating the Treg/inflammatory cell axis. ALKBH5 and this axis is a potential AKI treatment target.

Ketogenic Diet and Ketone Bodies against Ischemic Injury: Targets, Mechanisms, and Therapeutic Potential

The ketogenic diet (KD) has been used as a treatment for epilepsy since the 1920s, and its role in the prevention of many other diseases is now being considered. In recent years, there has been an intensive investigation on using the KD as a therapeutic approach to treat acute pathologies, including ischemic ones. However, contradictory data are observed for the effects of the KD on various organs after ischemic injury. In this review, we provide the first systematic analysis of studies conducted from 1980 to 2022 investigating the effects and main mechanisms of the KD and its mimetics on ischemia-reperfusion injury of the brain, heart, kidneys, liver, gut, and eyes. Our analysis demonstrated a high diversity of both the composition of the used KD and the protocols for the treatment of animals, which could be the reason for contradictory effects in different studies. It can be concluded that a true KD or its mimetics, such as β-hydroxybutyrate, can be considered as positive exposure, protecting the organ from ischemia and its negative consequences, whereas the shift to a rather similar high-calorie or high-fat diet leads to the opposite effect.

The multifunctional roles of autophagy in the innate immune response: Implications for regulation of transplantation rejection

Organ transplantation is the main treatment for end-stage organ failure, which has rescued tens of thousands of lives. Immune rejection is the main factor affecting the survival of transplanted organs. How to suppress immune rejection is an important goal of transplantation research. A graft first triggers innate immune responses, leading to graft inflammation, tissue injury and cell death, followed by adaptive immune activation. At present, the importance of innate immunity in graft rejection is poorly understood. Autophagy, an evolutionarily conserved intracellular degradation system, is proven to be involved in regulating innate immune response following graft transplants. Moreover, there is evidence indicating that autophagy can regulate graft dysfunction. Although the specific mechanism by which autophagy affects graft rejection remains unclear, autophagy is involved in innate immune signal transduction, inflammatory response, and various forms of cell death after organ transplantation. This review summarizes how autophagy regulates these processes and proposes potential targets for alleviating immune rejection.

Targeted Mitochondrial Drugs for Treatment of Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is a complex hemodynamic pathology that is a leading cause of death worldwide and occurs in many body organs. Numerous studies have shown that mitochondria play an important role in the occurrence mechanism of ischemia-reperfusion injury and that mitochondrial structural abnormalities and dysfunction lead to the disruption of the homeostasis of the whole mitochondria. At this time, mitochondria are not just sub-organelles to produce ATP but also important targets for regulating ischemia-reperfusion injury; therefore, drugs targeting mitochondria can serve as a new strategy to treat ischemia-reperfusion injury. Based on this view, in this review, we discuss potential therapeutic agents for both mitochondrial structural abnormalities and mitochondrial dysfunction, highlighting the application and prospects of targeted mitochondrial drugs in the treatment of ischemia-reperfusion injury, and try to provide new ideas for the clinical treatment of the ischemia-reperfusion injury.

Regulation of the autophagy plays an important role in acute kidney injury induced acute lung injury

AIM

This study aimed to investigate the regulatory role of autophagy in acute kidney injury (AKI) induced acute lung injury (ALI).

METHODS

The male Sprague-Dawley rats were divided into four groups: normal saline-treated sham rats (sham group), normal saline-treated ischemia-reperfusion injury rats (IRI group), 3-methyladenine-treated IRI rats (3-MA group), and rapamycin-treated IRI rats (RA group). The rats in the IRI rat model received the nephrectomy of the right kidney and was subjected to 60 mins of left renal pedicle occlusion, followed by 12, 24, 48, and 72 h of reperfusion. The levels of Scr, BUN, wet-to-dry ratio of lung, inflammatory cytokines, and oxidative stress were determined. The damage to tissues was detected by histological examinations. The western blot and immunohistochemistry methods were conducted to determine the expression of indicated proteins.

RESULTS

Renal IRI could induce the pulmonary injury after AKI, which caused significant increases in the function index of pulmonary and renal, the levels of inflammatory cytokines, and biomarkers of oxidative stress. In comparison to the IRI group, the RA group showed significantly decreased P62 and Caspase-3 expression and increased LC-II/LC3-I, Beclin-1, Bcl-2, and unc-51-like autophagy activating kinase 1 expression. Meanwhile, by suppressing the inflammation and oxidative stress, as well as inhibiting the pathological lesions in kidney and lung tissues, the autophagy could effectively ameliorate IRI-induced AKI and ALI.

CONCLUSIONS

Autophagy plays an important role in AKI-induced ALI, which could be used as a new target for AKI therapy and reduce the mortality caused by the complication.

Ferroptosis-A New Dawn in the Treatment of Organ Ischemia-Reperfusion Injury

Ischemia-reperfusion (I/R) is a common pathological phenomenon that occurs in numerous organs and diseases. It generally results from secondary damage caused by the recovery of blood flow and reoxygenation, followed by ischemia of organ tissues, which is often accompanied by severe cellular damage and death. Currently, effective treatments for I/R injury (IRI) are limited. Ferroptosis, a new type of regulated cell death (RCD), is characterized by iron overload and iron-dependent lipid peroxidation. Mounting evidence has indicated a close relationship between ferroptosis and IRI. Ferroptosis plays a significantly detrimental role in the progression of IRI, and targeting ferroptosis may be a promising approach for treatment of IRI. Considering the substantial progress made in the study of ferroptosis in IRI, in this review, we summarize the pathological mechanisms and therapeutic targets of ferroptosis in IRI.

Ferroptosis: Shedding Light on Mechanisms and Therapeutic Opportunities in Liver Diseases

Cell death is a vital physiological or pathological phenomenon in the development process of the organism. Ferroptosis is a kind of newly-discovered regulated cell death (RCD), which is different from other RCD patterns, such as apoptosis, necrosis and autophagy at the morphological, biochemical and genetic levels. It is a kind of iron-dependent mode of death mediated by lipid peroxides and lipid reactive oxygen species aggregation. Noteworthily, the number of studies focused on ferroptosis has been increasing exponentially since ferroptosis was first found in 2012. The liver is the organ that stores the most iron in the human body. Recently, it was frequently found that there are different degrees of iron metabolism disorder and lipid peroxidation and other ferroptosis characteristics in various liver diseases. Numerous investigators have discovered that the progression of various liver diseases can be affected via the regulation of ferroptosis, which may provide a potential therapeutic strategy for clinical hepatic diseases. This review aims to summarize the mechanism and update research progress of ferroptosis, so as to provide novel promising directions for the treatment of liver diseases.

Synthetic Non-Coding RNA for Suppressing mTOR Translation to Prevent Renal Fibrosis Related to Autophagy in UUO Mouse Model

The global burden of chronic kidney disease is increasing, and the majority of these diseases are progressive. Special site-targeted drugs are emerging as alternatives to traditional drugs. Oligonucleotides (ODNs) have been proposed as effective therapeutic tools in specific molecular target therapies for several diseases. We designed ring-type non-coding RNAs (ncRNAs), also called mTOR ODNs to suppress mammalian target rapamycin (mTOR) translation. mTOR signaling is associated with excessive cell proliferation and fibrogenesis. In this study, we examined the effects of mTOR suppression on chronic renal injury. To explore the regulation of fibrosis and inflammation in unilateral ureteral obstruction (UUO)-induced injury, we injected synthesized ODNs via the tail vein of mice. The expression of inflammatory-related markers (interleukin-1β, tumor necrosis factor-α), and that of fibrosis (α-smooth muscle actin, fibronectin), was decreased by synthetic ODNs. Additionally, ODN administration inhibited the expression of autophagy-related markers, microtubule-associated protein light chain 3, Beclin1, and autophagy-related gene 5-12. We confirmed that ring-type ODNs inhibited fibrosis, inflammation, and autophagy in a UUO mouse model. These results suggest that mTOR may be involved in the regulation of autophagy and fibrosis and that regulating mTOR signaling may be a therapeutic strategy against chronic renal injury.

Mild Hypothermia Alleviates Complement C5a-Induced Neuronal Autophagy During Brain Ischemia-Reperfusion Injury After Cardiac Arrest

After restoration of spontaneous circulation (ROSC) following cardiac arrest, complements can be activated and excessive autophagy can contribute to the brain ischemia-reperfusion (I/R) injury. Mild hypothermia (HT) protects against brain I/R injury after ROSC, but the mechanisms have not been fully elucidated. Here, we found that HT significantly inhibited the increases in serum NSE, S100β, and C5a, as well as neurologic deficit scores, TUNEL-positive cells, and autophagic vacuoles in the pig brain cortex after ROSC. The C5a receptor 1 (C5aR1) mRNA and the C5a, C5aR1, Beclin 1, LC3-II, and cleaved caspase-3 proteins were significantly increased, but the P62 protein and the PI3K/Akt/mTOR pathway-related proteins were significantly reduced in pigs after ROSC or neuronal oxygen-glucose deprivation/reoxygenation. HT could significantly attenuate the above changes in NT-treated neurons. Furthermore, C5a treatment induced autophagy and apoptosis and reduced the PI3K/Akt/mTOR pathway-related proteins in cultured neurons, which could be reversed by C5aR1 antagonist PMX205. Our findings demonstrated that C5a could bind to C5aR1 to induce neuronal autophagy during the brain I/R injury, which was associated with the inhibited PI3K/Akt/mTOR pathway. HT could inhibit C5a-induced neuronal autophagy by regulating the C5a-C5aR1 interaction and the PI3K/Akt/mTOR pathway, which might be one of the neuroprotective mechanisms underlying I/R injury. The C5a receptor 1 (C5aR1) mRNA and the C5a, C5aR1, Beclin 1, LC3-II, and cleaved caspase-3 proteins were significantly increased, but the P62 protein and the PI3K/Akt/mTOR pathway-related proteins were significantly reduced in pigs after ROSC or neuronal oxygen-glucose deprivation/reoxygenation. Mild hypothermia (HT) could significantly attenuate the above changes in NT-treated neurons. Furthermore, C5a treatment induced autophagy and apoptosis and reduced the PI3K/Akt/mTOR pathway-related proteins in cultured neurons, which could be reversed by C5aR1 antagonist PMX205. Proposed mechanism by which HT protects against brain I/R injury by repressing C5a-C5aR1-induced excessive autophagy. Complement activation in response to brain I/R injury generates C5a that can interact with C5aR1 to inactivate mTOR, probably through the PI3K-AKT pathway, which can finally lead to autophagy activation. The excessively activated autophagy ultimately contributes to cell apoptosis and brain injury. HT may alleviate complement activation and then reduce C5a-induced autophagy to protect against brain I/R injury. HT, mild hypothermia; I/R, ischemia reperfusion.

The Effects of Rapamycin on the Intestinal Graft in a Rat Model of Cold Ischemia Perfusion and Preservation

Attenuating the rheological and structural consequences of intestinal ischemia-reperfusion-injury (IRI) is important in transplant proceedings. Preconditioning is an often-proposed remedy. This technique uses physical or pharmacological methods to manipulate key ischemia pathways, such as oxidation, inflammation, and autophagy, prior to ischemia. This study determined the time-dependent effects of Rapamycin preconditioning on small-bowel grafts undergoing cold ischemia perfusion and preservation. Our main parameters were mucosa and cell injury and autophagy. A total of 30 male Wistar rats were divided into 5 groups: sham, preservation-control, and 3 treated groups (Rapamycin administered either 0, 30, or 60 min prior to perfusion). After perfusion, the intestines were placed in chilled IGL-1 solution for 12 h. Thereafter, they were reperfused. Histology and bioanalysis (LDH and lactate) were used to ascertain intestinal injury while immunohistochemistry was used for measuring changes in autophagy markers (Beclin-1, LC3B, and p62 proteins). The results show no significant difference amongst the groups after vascular perfusion. However, intestinal injury findings and autophagy changes demonstrate that administering Rapamycin 30 min or 60 min prior was protective against adverse cold ischemia and reperfusion of the intestinal graft. These findings show that Rapamycin is protective against cold ischemia of the small intestine, especially when administered 30 min before the onset.

The pathological role of damaged organelles in renal tubular epithelial cells in the progression of acute kidney injury

Acute kidney injury (AKI) is a common clinical condition associated with high morbidity and mortality. The pathogenesis of AKI has not been fully elucidated, with a lack of effective treatment. Renal tubular epithelial cells (TECs) play an important role in AKI, and their damage and repair largely determine the progression and prognosis of AKI. In recent decades, it has been found that the mitochondria, endoplasmic reticulum (ER), lysosomes, and other organelles in TECs are damaged to varying degrees in AKI, and that they can influence each other through various signaling mechanisms that affect the recovery of TECs. However, the association between these multifaceted signaling platforms, particularly between mitochondria and lysosomes during AKI remains unclear. This review summarizes the specific pathophysiological mechanisms of the main TECs organelles in the context of AKI, particularly the potential interactions among them, in order to provide insights into possible novel treatment strategies.

Ischemic Preconditioning Alleviates Mouse Renal Ischemia/Reperfusion Injury by Enhancing Autophagy Activity of Proximal Tubular Cells

OBJECTIVES

Ischemia/reperfusion injury (IRI) is one of the most vital pathogenesis leading to kidney injury but lacks effective prevention and treatment strategies. This study was conducted to investigate the influences of ischemic preconditioning (IPC) on the pathological process of mouse renal IRI (RIRI) and to figure out the role of autophagy of proximal tubular cells (PTCs) in this process.

METHODS

C57BL/6J mice were randomized to three groups, i.e., sham-operated group, ischemia/reperfusion (I/R) group, and IPC + I/R group. Meanwhile, 3-methyladenine, an autophagy inhibitor, was administered when further verification was needed. Histological and functional severity of kidney injury, the autophagy and apoptosis activity of PTCs, as well as the characterization of the immune cell infiltration landscape in kidney tissues were investigated. Furthermore, HK-2 cells and primary cultured PTC were cultured to set up the hypoxic preconditioning and hypoxia/reoxygenation model for in vitro simulation and verification, and a microarray dataset derived from the Gene Expression Omnibus database was analyzed to explore the transcriptome profiles after IPC.

RESULTS

IPC could significantly attenuate I/R-induced kidney injury functionally and histologically both in the acute and recovery phase of RIRI by enhancing the autophagy activity of PTCs. Cell autophagy could regulate the release of monocyte chemoattractant protein-1, and sequentially decrease macrophages infiltration in kidney tissues in the acute phase of RIRI, thus mediating the reno-protective effect.

CONCLUSIONS

IPC could attenuate mouse RIRI-induced kidney injury. IPC-mediated activation of autophagy of PTCs plays a vital role in affording protection in RIRI-induced kidney injury.

Colchicine attenuates renal ischemia-reperfusion-induced liver damage: implication of TLR4/NF-κB, TGF-β, and BAX and Bcl-2 gene expression

Ischemia-reperfusion injury (IRI) is typically associated with a vigorous inflammatory and oxidative stress response to hypoxia and reperfusion that disturbs the function of the organ. The remote effects of renal IRI on the liver, however, require further study. Renal damage associated with liver disease is a common clinical problem. Colchicine, a polymerization inhibitor of microtubules, has been used as an anti-inflammatory and anti-fibrotic drug for liver diseases. The goal of the current study was to investigate the possible protective mechanisms of colchicine on liver injury following renal IRI. Forty rats were divided randomly into four groups: sham group, colchicine-treated group, IRI group, and colchicine-treated + IRI group. Treatment with colchicine significantly reduced hepatic toll-like receptor 4 (TLR4), nuclear factor kappa B (NF-κB) transcription factor, myeloid differentiation factor 88 (MyD88), and tumor necrosis factor-alpha (TNF-α) contents; downregulated BCL2 associated X apoptosis regulator (BAX) gene expression, transforming growth factor-β (TGF-β) content, and upregulated hepatic B cell lymphoma 2 (Bcl-2) gene expression as compared with the IRI group. Finally, hepatic histopathological examinations have confirmed the biochemical results. Renal IRI-induced liver damage in rats was alleviated by colchicine through its anti-inflammatory, anti-apoptotic, and anti-fibrotic actions.

The Protective Mechanism of Dexmedetomidine in Regulating Atg14L-Beclin1-Vps34 Complex Against Myocardial Ischemia-Reperfusion Injury

The blood flow restoration of ischemic tissues causes myocardial injury. Dexmedetomidine (Dex) protects multi-organs against ischemia/reperfusion (I/R) injury. This study investigated the protective mechanism of Dex post-treatment in myocardial I/R injury. The rat model of myocardial I/R was established. The effects of Dex post-treatment on cardiac function and autophagy flow were observed. Dex attenuated myocardial I/R injury and reduced I/R-induced autophagy in rats. Dex weakened the interactions between Beclin1 and Vps34 and Beclin1 and Atg14L, thus downregulating Vps34 kinase activity. In vitro, the cardiomyocytes subjected to oxygen glucose deprivation/reoxygenation were treated with Dex and PI3K inhibitor LY294002. LY294002 attenuated the myocardial protective effect of DEX, indicating that Dex protected against cardiac I/R by activating the PI3K/Akt pathway. In conclusion, Dex upregulated the phosphorylation of Beclin1 at S295 site by activating the PI3K/Akt pathway and reduced the interactions of Atg14L-Beclin1-Vps34 complex, thus inhibiting autophagy and protecting against myocardial I/R injury.

miR-17-5p attenuates kidney ischemia-reperfusion injury by inhibiting the PTEN and BIM pathways

Background

Kidney ischemia-reperfusion (I/R) injury is an independent risk factor for delayed graft function after kidney transplantation with long-term graft survival deterioration. Previously, we found that the upregulated expression of miR-17-5p exerts a protective effect in kidney I/R injury, but the mechanism has not been clearly studied.

Methods

A kidney I/R injury model was induced in adult C57BL/6 male mice (20–22 g) by clamping both kidney pedicles for 30 min. The miR-17-5p agomir complex was injected into mice 24 h before surgery via the tail vein at a total injection volume of 10 µL/g body weight. The mice were euthanized on post-I/R injury day 2, and kidney function, apoptosis, autophagy, and related molecules were then detected. Human kidney-2 (HK-2) cells, which underwent hypoxia/reoxygenation, were treated with the miR-17-5p agomir, miR-17-5p antagomir, and small interfering ribonucleic acids (siRNAs). Cell viability, apoptosis, autophagy, and molecules were also examined.

Results

Autophagy, miR-17-5p expression, and kidney function damage were significantly more increased in the I/R group than in the sham group. In the cultured HK-2 cells underwent hypoxia/reoxygenation, the miR-17-5p agomir directly inhibited the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and Bcl-2 like protein 11 (BIM), and attenuated apoptosis and autophagy. Further, miR-17-5p inhibited autophagy by activating the protein kinase B (Akt)/Beclin1 pathway, which was suppressed by siRNAs. Additionally, the administration of miR-17-5p agomir greatly improved kidney function in the I/R mice group by inhibiting autophagy and apoptosis.

Conclusions

These findings suggest a new possible therapeutic strategy for the prevention and treatment of kidney I/R injury. The upregulation of miR-17-5p expression appears to inhibit apoptosis and autophagy by suppressing PTEN and BIM expression, which in turn upregulates downstream Akt/Beclin1 expression.

Expression of the IL-2R in Human Podocytes and the Effect of Activation on Autophagy and Apoptosis

Interleukin 2 (IL-2) treatment is associated with proteinuria. Materials and Methods: A conditionally immortalized human podocyte cell line was used to investigate expression of the podocyte specific marker podocin, IL-2R alpha (IL-2Rα), apoptosis marker Bax, and autophagy markers LC3I AND LC3II, determined by quantitative immunoblotting, following 24, 48, and 72 hours of IL-2 stimulation, comparing them to unstimulated cells. Results: Podocin was expressed at all time points. IL-2Rα expression was increased after 24 and 72 hrs (p = 0.0014, p = 0.0139) and decreased after 48 hours (p = 0.0445). Bax, LC3I, and LC3II were increased after 24 hrs (p = 0.0094, p = 0.0016, p = 0.0004) and 48 hrs (p = 0.0072, p = 0.0024, p = 0.0087). Conclusion: Human podocytes express the IL-2R and activation results in increased autophagy and apoptosis.

GSK-3β inhibitor TDZD-8 prevents reduction of aquaporin-1 expression via activating autophagy under renal ischemia reperfusion injury

Renal ischemia/reperfusion (I/R) injury is a main cause of acute kidney injury (AKI). Aquaporin (AQP)-1 water channel in the kidney is critical for the maintenance of water homeostasis and the urinary concentrating ability. Increasing evidence supports an important role of autophagy in the pathogenesis of AKI induced by renal I/R. The purpose of the present study is to investigate whether activation of autophagy prevents downregulation of AQP1 protein induced by renal I/R and potential molecular mechanisms. Renal I/R induced consistently reduced protein expression of AQP1, 2, and 3, as well as sodium cotransporters Na⁺ -K⁺ -2Cl^- cotransporter and α-Na,K-ATPase, which was associated with increased urine output and decreased creatinine clearance in rats. Renal I/R also suppressed autophagy and increased inflammatory responses in the kidney. 4-Benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8), the glycogen synthase kinase-3β inhibitor, ameliorated renal injury under I/R, activated autophagy and markedly increased expression of AQPs and sodium transporters in the kidney, which was associated with improved urine output and creatinine clearance in rats. Hypoxia/reoxygenation (H/R) induced suppression of autophagy and downregulation of AQP1 in murine inner medullary collecting duct 3 (IMCD3) cells, which was fully prevented by TDZD-8 treatment. Inhibition of autophagy by 3-methyladenine or Atg5 gene knockdown attenuated recovery of AQP1 protein expression induced by TDZD-8 in IMCD3 cells with H/R. Interleukin-1 beta (IL-1β) decreased the abundance of AQP1 protein in IMCD3 cells. H/R induced increases in protein expression of nod-like receptor pyrin domain-containing 3 and IL-1β, which was reversed by TDZD-8. In conclusion, TDZD-8 treatment prevented downregulation of AQP1 expression under renal I/R injury, likely via activating autophagy and decreasing IL-1β production.

The Role of TRPC6 in Renal Ischemia/Reperfusion and Cellular Hypoxia/Reoxygenation Injuries

Renal ischemia/reperfusion (I/R), a major cause of acute kidney injury (AKI), is a serious clinical event in patients during post-renal transplantation. I/R is associated with renal dysfunction and tubular apoptosis, and calcium (Ca²⁺) overload has been reported to be a crucial factor on tubular apoptosis in I/R injury (IRI). The canonical transient receptor potential channel 6 (TRPC6), a type of non-selective Ca²⁺ channel, is involved in many renal diseases. Our earlier study identified that TRPC6-mediated Ca²⁺ influx plays a novel role in suppressing cytoprotective autophagy triggered by oxidative stress in primary tubular epithelial cells (TECs). This study explored the potential beneficial impact of TRPC6 knockout (TRPC6^−/−) and the relevant cellular mechanisms against I/R-induced AKI in mice. Measuring changes of renal function, apoptotic index, and autophagy in mouse kidneys that suffered 24 h reperfusion after 40 min ischemia and working in vitro with TECs that suffered 24 h reoxygenation after 24 h hypoxia, we found that 1) IRI tissues had increased TRPC6 expression and TRPC6 knockout significantly ameliorated renal damage induced by IRI; 2) TRPC6 knockout enhanced the level of autophagy and alleviated the depolarization of mitochondrial membrane potential (ψm, MMP) and apoptotic changes upon IRI; and 3) IRI tissues had increased p-AKT and p-ERK1/2 expressions, while TRPC6 knockout could markedly reduce the phosphorylation of AKT and ERK1/2. These discoveries suggest that, by reducing Ca²⁺ overload, the underlying protective mechanism of TRPC6^−/− may be involved in down-regulation of PI3K/AKT and ERK signaling, which is likely to provide a new avenue for future AKI therapies.

Characterizing Autophagy in the Cold Ischemic Injury of Small Bowel Grafts: Evidence from Rat Jejunum

Cold ischemic injury to the intestine during preservation remains an unresolved issue in transplantation medicine. Autophagy, a cytoplasmic protein degradation pathway, is essential for metabolic adaptation to starvation, hypoxia, and ischemia. It has been implicated in the cold ischemia (CI) of other transplantable organs. This study determines the changes in intestinal autophagy evoked by cold storage and explores the effects of autophagy on ischemic grafts. Cold preservation was simulated by placing the small intestines of Wistar rats in an IGL-1 (Institute George Lopez) solution at 4 °C for varying periods (3, 6, 9, and 12 h). The extent of graft preservation injury (mucosal and cellular injury) and changes in autophagy were measured after each CI time. Subsequently, we determined the differences in apoptosis and preservation injury after activating autophagy with rapamycin or inhibiting it with 3-methyladenine. The results revealed that ischemic injury and autophagy were induced by cold storage. Autophagy peaked at 3 h and subsequently declined. After 12 h of storage, autophagic expression was reduced significantly. Additionally, enhanced intestinal autophagy by rapamycin was associated with less tissue, cellular, and apoptotic damage during and after the 12-h long preservation. After reperfusion, grafts with enhanced autophagy still presented with less injury. Inhibiting autophagy exhibited the opposite trend. These findings demonstrate intestinal autophagy changes in cold preservation. Furthermore, enhanced autophagy was protective against cold ischemia-reperfusion damage of the small bowels.

Effect of NAD+ boosting on kidney ischemia-reperfusion injury

Acute kidney injury (AKI) is associated with a very high mortality and an increased risk for progression to chronic kidney disease (CKD). Ischemia-reperfusion injury (IRI) is a model for AKI, which results in tubular damage, dysfunction of the mitochondria and autophagy, and in decreased cellular nicotinamide adenine dinucleotide (NAD⁺) with progressing fibrosis resulting in CKD. NAD⁺ is a co-enzyme for several proteins, including the NAD⁺ dependent sirtuins. NAD⁺ augmentation, e.g. by use of its precursor nicotinamide riboside (NR), improves mitochondrial homeostasis and organismal metabolism in many species. In the present investigation the effects of prophylactic administration of NR on IRI-induced AKI were studied in the rat. Bilateral IRI reduced kidney tissue NAD⁺, caused tubular damage, reduced α-Klotho (klotho), and altered autophagy flux. AKI initiated progression to CKD, as shown by induced profibrotic Periostin (postn) and Inhibin subunit beta-A, (activin A / Inhba), both 24 hours and 14 days after surgery. NR restored tissue NAD⁺ to that of the sham group, increased autophagy (reduced p62) and sirtuin1 (Sirt1) but did not ameliorate renal tubular damage and profibrotic genes in the 24 hours and 14 days IRI models. AKI induced NAD⁺ depletion and impaired autophagy, while augmentation of NAD⁺ by NR restored tissue NAD⁺ and increased autophagy, possibly serving as a protective response. However, prophylactic administration of NR did not ameliorate tubular damage of the IRI rats nor rescued the initiation of fibrosis in the long-term AKI to CKD model, which is a pivotal event in CKD pathogenesis.

PPARγ in Ischemia-Reperfusion Injury: Overview of the Biology and Therapy

Ischemia-reperfusion injury (IRI) is a complex pathophysiological process that is often characterized as a blood circulation disorder caused due to various factors (such as traumatic shock, surgery, organ transplantation, burn, and thrombus). Severe metabolic dysregulation and tissue structure destruction are observed upon restoration of blood flow to the ischemic tissue. Theoretically, IRI can occur in various tissues and organs, including the kidney, liver, myocardium, and brain, among others. The advances made in research regarding restoring tissue perfusion in ischemic areas have been inadequate with regard to decreasing the mortality and infarct size associated with IRI. Hence, the clinical treatment of patients with severe IRI remains a thorny issue. Peroxisome proliferator-activated receptor γ (PPARγ) is a member of a superfamily of nuclear transcription factors activated by agonists and is a promising therapeutic target for ameliorating IRI. Therefore, this review focuses on the role of PPARγ in IRI. The protective effects of PPARγ, such as attenuating oxidative stress, inhibiting inflammatory responses, and antagonizing apoptosis, are described, envisaging certain therapeutic perspectives.

The critical role of FXR is associated with the regulation of autophagy and apoptosis in the progression of AKI to CKD

Autophagy is important for cells to break down and recycle cellular proteins, remove damaged organelles, and especially, for recovery from acute kidney injury (AKI). Despite research on the role and cellular mechanism of autophagy in AKI, the role of autophagy in the progression to chronic kidney disease (CKD) remains poorly understood. Here, using farnesoid X receptor (FXR) knockout (KO) mice, we determined whether FXR prevents the progression of AKI to CKD after renal ischemic-reperfusion (such as I/R) injury through the regulation of renal autophagy and apoptosis. FXR regulated genes that participate in renal autophagy under feeding and fasting conditions, such as hepatic autophagy, and the activation of FXR by agonists, such as GW4064 and INT-747, attenuated the increased autophagy and apoptosis of hypoxia-induced human renal proximal tubule epithelial (HK2) cells. The expression levels of autophagy-related and apoptosis-related proteins in FXR KO mice were increased compared with those in wild-type (WT) mice. We also showed that the increase in reactive oxidative species (ROS) in hypoxia-treated HK2 cells was attenuated by treatment with FXR agonist or by FXR overexpression, and that the level of ROS was elevated in FXR-deficient cells and mice. At 28 days after I/R injury, the autophagy levels were still elevated in FXR KO mice, and the expression levels of fibrosis-related proteins and ROS deposits were higher than those in WT mice. In conclusion, the regulation of renal autophagy and apoptosis by FXR may be a therapeutic target for the early stages of kidney damage, and the progression of AKI to CKD.

Inhibitory Effects of STAT3 Transcription Factor by Synthetic Decoy ODNs on Autophagy in Renal Fibrosis

Autophagy in the proximal tubules may promote fibrosis by activating tubular cell death, interstitial inflammation, and the production of pro-fibrotic factors. The signal transducer and activator of transcription 3 (STAT3) is activated as a potential transcription factor, which mediates the stimulation of renal fibrosis. We investigated the role of the STAT3 in autophagy and its effect on the prevention of interstitial renal fibrosis. In this study, we use synthesized STAT3 decoy oligonucleotides (ODN), which were injected 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-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and collagen were decreased by STAT3 decoy ODN. The autophagy markers microtubule-associated protein light chain 3 (LC3) and fibronectin, were identified through immunofluorescent staining, indicating that they were reduced in the group injected with ODN. The expressions of LC3, Beclin1, p62, and autophagy-related 5–12 (Atg5–12) and hypoxia inducible factor-1α (HIF-1α) were inhibited in the ODN injection group. We determined the inhibitory effect of autophagy in chronic kidney disease and confirmed that STAT3 decoy ODN effectively inhibited autophagy by inhibiting the expression of STAT3 transcription factors in the UUO group.

Overexpression of SP1 restores autophagy to alleviate acute renal injury induced by ischemia-reperfusion through the miR-205/PTEN/Akt pathway

Background

Acute kidney injury (AKI) is a major kidney disease with poor clinical outcome. SP1, a well-known transcription factor, plays a critical role in AKI and subsequent kidney repair through the regulation of various cell biologic processes. However, the underlying mechanism of SP1 in these pathological processes remain largely unknown.

Methods

An in vitro HK-2 cells with anoxia-reoxygenation injury model (In vitro simulated ischemic injury disease) and an in vivo rat renal ischemia-reperfusion injury model were used in this study. The expression levels of SP1, miR-205 and PTEN were detected by RT-qPCR, and the protein expression levels of SP1, p62, PTEN, AKT, p-AKT, LC3II, LC3I and Beclin-1 were assayed by western blot. Cell proliferation was assessed by MTT assay, and the cell apoptosis was detected by flow cytometry. The secretions of IL-6 and TNF-α were detected by ELISA. The targeted relationship between miR-205 and PTEN was confirmed by dual luciferase report assay. The expression and positioning of LC-3 were observed by immunofluorescence staining. TUNEL staining was used to detect cell apoptosis and immunohistochemical analysis was used to evaluate the expression of SP1 in renal tissue after ischemia-reperfusion injury in rats.

Results

The expression of PTEN was upregulated while SP1 and miR-205 were downregulated in renal ischemia-reperfusion injury. Overexpression of SP1 protected renal tubule cell against injury induced by ischemia-reperfusion via miR-205/PTEN/Akt pathway mediated autophagy. Overexpression of SP1 attenuated renal ischemia-reperfusion injury in rats.

Conclusions

SP1 overexpression restored autophagy to alleviate acute renal injury induced by ischemia-reperfusion through the miR-205/PTEN/Akt pathway.

Repurposing of metformin and colchicine reveals differential modulation of acute and chronic kidney injury

Acute kidney injury (AKI) is a major health problem affecting millions of patients globally. There is no effective treatment for AKI and new therapies are urgently needed. Novel drug development, testing and progression to clinical trials is overwhelmingly expensive. Drug repurposing is a more cost-effective measure. We identified 2 commonly used drugs (colchicine and metformin) that alter inflammatory cell function and signalling pathways characteristic of AKI, and tested them in models of acute and chronic kidney injury to assess therapeutic benefit. We assessed the renoprotective effects of colchicine or metformin in C57BL/6 mice challenged with renal ischemia reperfusion injury (IRI), treated before or after injury. All animals underwent analysis of renal function and biomolecular phenotyping at 24 h, 48 h and 4 weeks after injury. Murine renal tubular epithelial cells were studied in response to in vitro mimics of IRI. Pre-emptive treatment with colchicine or metformin protected against AKI, with lower serum creatinine, improved histological changes and decreased TUNEL staining. Pro-inflammatory cytokine profile and multiple markers of oxidative stress were not substantially different between groups. Metformin augmented expression of multiple autophagic proteins which was reversed by the addition of hydroxychloroquine. Colchicine led to an increase in inflammatory cells within the renal parenchyma. Chronic exposure after acute injury to either therapeutic agent in the context of reduced renal mass did not mitigate the development of fibrosis, with colchicine significantly worsening an ischemic phenotype. These data indicate that colchicine and metformin affect acute and chronic kidney injury differently. This has significant implications for potential drug repurposing, as baseline renal disease must be considered when selecting medication.

Penehyclidine hydrochloride alleviates lipopolysaccharide‑induced acute respiratory distress syndrome in cells via regulating autophagy‑related pathway

Acute progressive hypoxic respiratory failure caused by various predisposing factors is known as acute respiratory distress syndrome (ARDS). Although penehyclidine hydrochloride (PHC), an anticholinergic drug, is widely applied in clinical practice, the specific mechanisms underlying PHC in the treatment of ARDS are not completely understood. In the present study, BEAS-2B cells were treated with 10 ng/ml lipopolysaccharide (LPS) to establish an ARDS cell model and a rat model of acute lung injury (ALI). The influences of PHC and/or autophagy inhibitor (3-methyladenine (3-MA)) on the morphology, autophagy, proliferation and apoptosis of cells and tissues were evaluated using hematoxylin and eosin staining, Cell Counting Kit-8 assays, Hoechst staining, TUNEL staining, flow cytometry, immunofluorescence assays, ELISAs and scanning electron microscopy. The expression levels of apoptosis- and autophagy-related proteins were measured via western blotting. The results indicated that PHC enhanced proliferation and autophagy, and decreased apoptosis and the inflammatory response in LPS-induced BEAS-2B cells and ALI model rats. In addition, 3-MA reversed the effects of PHC on proliferation, inflammation, apoptosis and autophagy in LPS-induced BEAS-2B cells. Therefore, the present study suggested that PHC demonstrated a protective effect in LPS-induced ARDS by regulating an autophagy-related pathway.

Autophagy Dynamics and Modulation in a Rat Model of Renal Ischemia-Reperfusion Injury

Renal ischemia-reperfusion (IR) injury leading to cell death is a major cause of acute kidney injury, contributing to morbidity and mortality. Autophagy counteracts cell death by removing damaged macromolecules and organelles, making it an interesting anchor point for treatment strategies. However, autophagy is also suggested to enhance cell death when the ischemic burden is too strong. To investigate whether the role of autophagy depends on the severity of ischemic stress, we analyzed the dynamics of autophagy and apoptosis in an IR rat model with mild (45 min) or severe (60 min) renal ischemia. Following mild IR, renal injury was associated with reduced autophagy, enhanced mammalian target of rapamycin (mTOR) activity, and apoptosis. Severe IR, on the other hand, was associated with a higher autophagic activity, independent of mTOR, and without affecting apoptosis. Autophagy stimulation by trehalose injected 24 and 48 h prior to onset of severe ischemia did not reduce renal injury markers nor function, but reduced apoptosis and restored tubular dilation 7 days post reperfusion. This suggests that trehalose-dependent autophagy stimulation enhances tissue repair following an IR injury. Our data show that autophagy dynamics are strongly dependent on the severity of IR and that trehalose shows the potential to trigger autophagy-dependent repair processes following renal IR injury.

Sanqi Oral Solution Ameliorates Renal Ischemia/Reperfusion Injury via Reducing Apoptosis and Enhancing Autophagy: Involvement of ERK/mTOR Pathways

Ischemia-reperfusion (I/R) induced acute kidney injury (AKI) is a significant health problem with high morbidity and mortality, yet prophylaxis strategies and effective drugs are limited. Sanqi oral solution (SQ) is a formulated medicine widely used in clinical settings to treat various renal diseases via enriching qi and activating blood circulation while its role on I/R-AKI remains unclear. Herein, by establishing rat I/R-AKI models, we intended to investigate the effect of SQ on the prevention of I/R-AKI and explore its underlying mechanisms. We demonstrated that SQ treatment significantly attenuated renal dysfunction of I/R-AKI, alleviated histological damages, inhibited renal apoptosis, and enhanced autophagy. Further investigation proved that SQ could significantly inhibit the activation of ERK and mTOR signaling pathways. Moreover, its renoprotective effect can be abolished by autophagy inhibitor 3-methyladenine (3-MA). Collectively, our results suggest that SQ exerts renoprotective effects on renal I/R injury via reducing apoptosis and enhancing autophagy, which are associated with regulating ERK/mTOR pathways.

Ginsenoside Rb1 ameliorates autophagy via the AMPK/mTOR pathway in renal tubular epithelial cells in vitro and in vivo

Although ginsenoside Rb1 (G-Rb1) has exerted an inhibitory effect on renal fibrosis and progression of chronic kidney disease (CKD), its mechanism remains unknown. This study aims to explore the anti-fibrosis effect of G-Rb1 in unilateral ureter obstruction (UUO) mouse model and underlying mechanisms in HBSS-induced HK-2 cells. In vivo, renal function, kidney histological pathology, and autophagy-related protein molecules were assessed. Additionally, rapamycin, Deptor overexpression plasmid, Akt inhibitor, metformin, and a p38-MAPK inhibitor, as well as an ERK-MAPK inhibitor were used to evaluate the effect of AMPK/mTOR, Akt and MAPK signal pathways on the protective effect of G-Rb1 in HK-2 cells. Treatment with G-Rb1 significantly improved renal dysfunction. G-Rb1 reversed UUO-induced downregulation of p62, and upregulation of LC3 and the ratio of LC3 I/II, indicating that G-Rb1 restrained UUO-induced activation of autophagy. Furthermore, we found that treatment of HBSS-induced HK-2 cells with G-Rb1 resulted in AMPK/mTOR and ERK, p38 MAPKs signaling pathways regulated autophagy inhibition. These findings may explain, in part, the molecular mechanisms by which G-Rb1 could be applied in the treatment of patients with CKD, further suggesting that autophagy and its associated molecular signaling pathway may be new targets for the treatment of renal fibrosis and CKD.