Fibroblast Growth Factors in the Management of Acute Kidney Injury Following Ischemia-Reperfusion

miR-208a-3p regulated by circUQCRC2 suppresses ischemia/reperfusion-induced acute kidney injury by inhibiting CELF2-mediated tubular epithelial cell apoptosis, inflammation and ferroptosis

ABSTRACT

Background : Acute kidney injury (AKI) is a prevalent clinical syndrome with persistent kidney dysfunction. Renal ischemia/reperfusion (I/R) injury is a major cause of AKI. miR-208a-3p overexpression attenuated myocardial I/R injury. This study aims to investigate the role and mechanism of miR-208a-3p in I/R-induced AKI. Methods : AKI models were established using hypoxia/reoxygenation (H/R)-exposed tubule epithelial cell HK-2 and I/R-induced mice. The function and mechanism of miR-208a-3p were investigated by gain- or loss-of-function methods using real-time PCR, CCK-8, flow cytometry, ELISA, western blot, hematoxylin-eosin staining, terminal deoxynucleotidyl transferase dUTP nick end labeling assay, detection of Fe 2+ , reactive oxygen species, blood urea nitrogen and creatinine, and luciferase reporter assay. Results : miR-208a-3p expression was suppressed, while the expression of CELF2 and circular RNA ubiquinol-cytochrome c reductase core protein 2 (circUQCRC2) was increased in both AKI models. miR-208a-3p upregulation or circUQCRC2 silencing increased the viability, decreased the levels of proinflammatory cytokines (TNF-α, IL-1β, and IL-6), reduced apoptosis and contents of Fe 2+ and reactive oxygen species, elevated expression of GPX4 and SLC7A11, and reduced ACSL4 expression in H/R-stimulated HK-2 cells. In addition, miR-208a-3p improved kidney function by alleviating renal injury, apoptosis, inflammation, and ferroptosis in AKI mouse model. CELF2 was a target gene of miR-208a-3p, which was negatively modulated by circUQCRC2. Overexpression of CELF2 blocked the function of miR-208a-3p upregulation or circUQCRC2 silencing on H/R-treated HK-2 cells. Moreover, the effects of circUQCRC2 downregulation on H/R-injured cells were also reversed by miR-208a-3p inhibitor. Conclusions : miR-208a-3p regulated by circUQCRC2 could attenuate I/R-induced AKI by inhibiting CELF2-mediated tubular epithelial cell apoptosis, inflammation and ferroptosis. This study provides potential therapeutic targets for I/R-induced AKI.

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.

Erythropoietin alleviates lung ischemia-reperfusion injury by activating the FGF23/FGFR4/ERK signaling pathway

Background

The purpose of the present study was to investigate the effect of erythropoietin (EPO) on lung ischemia-reperfusion injury (LIRI).

Methods

Sprague Dawley rats and BEAS-2B cells were employed to construct an ischemia-reperfusion (I/R)-induced model in vivo and in vitro, respectively. Afterward, I/R rats and tert-butyl hydroperoxide (TBHP)-induced cells were treated with different concentrations of EPO. Furthermore, 40 patients with LIRI and healthy controls were enrolled in the study.

Results

It was observed that lung tissue damage, cell apoptosis and the expression of BAX and caspase-3 were higher in the LIRI model in vivo and in vitro than in the control group, nevertheless, the Bcl-2, FGF23 and FGFR4 expression level was lower than in the control group. EPO administration significantly reduced lung tissue damage and cell apoptosis while also up-regulating the expression of FGF23 and FGFR4. Rescue experiments indicated that EPO exerted a protective role associated with the FGF23/FGFR4/p-ERK1/2 signal pathway. Notably, the expression of serum EPO, FGF23, FGFR4 and Bcl-2 was decreased in patients with LIRI, while the expression of caspase-3 and BAX was higher.

Conclusion

EPO could effectively improve LIRI, which might be related to the activation of the FGF23/FGFR4/p-ERK1/2 signaling pathway.

Impact of folic acid supplementation on ischemia‒reperfusion-induced kidney injury in rats: folic acid prophylactic role revisited

Folic acid (FA), with its anti-inflammatory and antioxidant properties, may offer protection against ischemia-reperfusion (IR) injury. This study investigated whether FA safeguards rat kidneys from IR by targeting high mobility group box-1 (HMGB1), a key inflammatory mediator. Fifty adult male Wistar rats were randomly allocated into four groups: control, IR, IR + FA pretreatment, and FA alone. Compared to controls, IR significantly impaired renal function and elevated levels of malondialdehyde, HMGB1, NF-κB, and caspase 3. FA pretreatment effectively reversed these detrimental changes, protecting renal function and minimizing tissue damage. The FA-alone group showed no significant differences compared to the control group, indicating no adverse effects of FA treatment. Mechanistically, FA inhibited HMGB1 expression and its downstream activation of NF-κB and caspase 3, thereby quelling inflammation and cell death. FA shields rat kidneys from IR-induced injury by suppressing HMGB1-mediated inflammation and apoptosis, suggesting a potential therapeutic avenue for IR-associated kidney damage.

Is there a role in acute kidney injury for FGF23 and Klotho?

Cardio-renal syndrome is a clinical condition that has recently been well defined. In acute kidney disease, this interaction might trigger chronic processes determining the onset of cardiovascular events and the progression of chronic kidney disease. Moreover, the high mortality rate of acute kidney injury (AKI) is also linked to the fact that this condition is often complicated by dysfunctions of other organs such as lungs or heart, or is associated with septic episodes. In this context the role and the potential link between bone, heart and kidney is becoming an important topic of research. The aim of this review is to describe the cardiac alterations in the presence of AKI (cardiorenal syndrome type 3) and explore how bone can interact with heart and kidney in determining and influencing the trend of AKI in the short and long term. The main anomalies of mineral metabolism in patients with AKI will be reported, with specific reference to the alterations of fibroblast growth factor 23 and Klotho as a link between the bone-kidney-heart axis.

Insights into Repeated Renal Injury Using RNA-Seq with Two New RPTEC Cell Lines

Renal proximal tubule epithelial cells (RPTECs) are a primary site for kidney injury. We created two RPTEC lines from CD-1 mice immortalized with hTERT (human telomerase reverse transcriptase) or SV40 LgT antigen (Simian Virus 40 Large T antigen). Our hypothesis was that low-level, repeated exposure to subcytotoxic levels of 0.25-2.5 μM cisplatin (CisPt) or 12.5-100 μM aflatoxin B1 (AFB1) would activate distinctive genes and pathways in these two differently immortalized cell lines. RNA-seq showed only LgT cells responded to AFB1 with 1139 differentially expressed genes (DEGs) at 72 h. The data suggested that AFB1 had direct nephrotoxic properties on the LgT cells. However, both the cell lines responded to 2.5 μM CisPt from 3 to 96 h expressing 2000-5000 total DEGs. For CisPt, the findings indicated a coordinated transcriptional program of injury signals and repair from the expression of immune receptors with cytokine and chemokine secretion for leukocyte recruitment; robust expression of synaptic and substrate adhesion molecules (SAMs) facilitating the expression of neural and hormonal receptors, ion channels/transporters, and trophic factors; and the expression of nephrogenesis transcription factors. Pathway analysis supported the concept of a renal repair transcriptome. In summary, these cell lines provide in vitro models for the improved understanding of repeated renal injury and repair mechanisms. High-throughput screening against toxicant libraries should provide a wider perspective of their capabilities in nephrotoxicity.

Mechanism study of Cordyceps sinensis alleviates renal ischemia–reperfusion injury

Cordyceps sinensis (C. sinensis) is a kind of traditional Chinese medicine commonly used to protect renal function and relieve kidney injury. This study aimed to reveal the renal protective mechanism of C. sinensis in renal ischemia–reperfusion injury (RIRI). First, we obtained 8 active components and 99 common targets of C. sinensis against RIRI from public databases. Second, we have retrieved 38 core targets through STRING database analysis. Third, Gene Ontology analysis of 38 core targets is indicated that C. sinensis treatment RIRI may related hormone regulation, oxidative stress, cell proliferation, and immune regulation. Kyoto Encyclopedia of Genes and Genomes enrichment analysis of 38 core targets is indicated that C. sinensis treatment RIRI may involve in PI3K–Akt, HIF-1, and MAPK signaling pathways, as well as advanced glycation end product (AGE)–receptor for AGE (RAGE) signaling pathway in diabetic complications. Lastly, molecular docking was used to detect the binding activity and properties of active components and core target using molecular docking. And the results showed that eight active components of C. sinensis had low affinity with core targets. In conclusion, C. sinensis may improve RIRI by regulating oxidative stress and immunity through PI3K–Akt, HIF-1, and MAPK pathways.

Fibroblast growth factor 7 alleviates myocardial infarction by improving oxidative stress via PI3Kα/AKT-mediated regulation of Nrf2 and HXK2

Acute myocardial infarction (MI) triggers oxidative stress, which worsen cardiac function, eventually leads to remodeling and heart failure. Unfortunately, effective therapeutic approaches are lacking. Fibroblast growth factor 7 (FGF7) is proved with respect to its proliferative effects and high expression level during embryonic heart development. However, the regulatory role of FGF7 in cardiovascular disease, especially MI, remains unclear. FGF7 expression was significantly decreased in a mouse model at 7 days after MI. Further experiments suggested that FGF7 alleviated MI-induced cell apoptosis and improved cardiac function. Mechanistic studies revealed that FGF7 attenuated MI by inhibiting oxidative stress. Overexpression of FGF7 actives nuclear factor erythroid 2-related factor 2 (Nrf2) and scavenging of reactive oxygen species (ROS), and thereby improved oxidative stress, mainly controlled by the phosphatidylinositol-3-kinase α (PI3Kα)/AKT signaling pathway. The effects of FGF7 were partly abrogated in Nrf2 deficiency mice. In addition, overexpression of FGF7 promoted hexokinase2 (HXK2) and mitochondrial membrane translocation and suppressed mitochondrial superoxide production to decrease oxidative stress. The role of HXK2 in FGF7-mediated improvement of mitochondrial superoxide production and protection against MI was verified using a HXK2 inhibitor (3-BrPA) and a HXKII VDAC binding domain (HXK2VBD) peptide, which competitively inhibits localization of HXK2 on mitochondria. Furthermore, inhibition of PI3Kα/AKT signaling abolished regulation of Nrf2 and HXK2 by FGF7 upon MI. Together, these results indicate that the cardio protection of FGF7 under MI injury is mostly attributable to its role in maintaining redox homeostasis via Nrf2 and HXK2, which is mediated by PI3Kα/AKT signaling.

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The expression of FGF7 in cardiomyocytes is decreased upon myocardial infarction (MI).

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Overexpression of FGF7 in the heart protects against cardiomyocytes apoptosis in a rodent model of MI.

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FGF7 attenuates MI-induced cardiac apoptosis via maintaining redox homeostasis.

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FGF7 maintains redox homeostasis by promoting mitochondrial HXK2 localization and Nrf2 nuclear translocation.

Clec7a expression in inflammatory macrophages orchestrates progression of acute kidney injury

Acute kidney injury (AKI) is associated with high risk of mortality, post-disease renal fibrosis, kidney dysfunction and renal failure. Renal macrophages play a key role in the pathogenesis (M1 subpopulation), healing and remodeling (M2 subpopulation) in AKI and, thus, have been a promising target for clinical treatment of AKI. Here, in a mouse renal ischemia/reperfusion injury (IRI) model for AKI, we showed that renal macrophages could be further classified into Clec7a+ M1 macrophages, Clec7a- M1 macrophages, Clec7a+ M2 macrophages and Clec7a- M2 macrophages, representing distinct macrophage populations with different functionality. Interestingly, Clec7a+ M1 macrophages exhibited potent pro-inflammatory and phagocytic effects compared to Clec7a- M1 macrophages, while Clec7a- M2 macrophages exhibited better proliferating and migrating potential, which is critical for their role in tissue repairing after injury. These data from mice were further strengthened by bioinformatics analyses using published database. In vivo, combined expression of Clec7a in M1 macrophages and depletion of Clec7a in M2 macrophages significantly improved the renal function after IRI-AKI. Together, our data suggest that Clec7a is crucial for the fine regulation of macrophage phenotype during AKI and could be a novel target for boosting clinical therapy.

New developments in the biology of fibroblast growth factors

The fibroblast growth factor (FGF) family is composed of 18 secreted signaling proteins consisting of canonical FGFs and endocrine FGFs that activate four receptor tyrosine kinases (FGFRs 1-4) and four intracellular proteins (intracellular FGFs or iFGFs) that primarily function to regulate the activity of voltage-gated sodium channels and other molecules. The canonical FGFs, endocrine FGFs, and iFGFs have been reviewed extensively by us and others. In this review, we briefly summarize past reviews and then focus on new developments in the FGF field since our last review in 2015. Some of the highlights in the past 6 years include the use of optogenetic tools, viral vectors, and inducible transgenes to experimentally modulate FGF signaling, the clinical use of small molecule FGFR inhibitors, an expanded understanding of endocrine FGF signaling, functions for FGF signaling in stem cell pluripotency and differentiation, roles for FGF signaling in tissue homeostasis and regeneration, a continuing elaboration of mechanisms of FGF signaling in development, and an expanding appreciation of roles for FGF signaling in neuropsychiatric diseases. This article is categorized under: Cardiovascular Diseases > Molecular and Cellular Physiology Neurological Diseases > Molecular and Cellular Physiology Congenital Diseases > Stem Cells and Development Cancer > Stem Cells and Development.

Tilianin Reduces Apoptosis via the ERK/EGR1/BCL2L1 Pathway in Ischemia/Reperfusion-Induced Acute Kidney Injury Mice

Background: Acute kidney injury (AKI) is a common syndrome impacting about 13.3 million patients per year. Tilianin has been reported to alleviate myocardial ischemia/reperfusion (I/R) injury, while its effect on AKI is unknown; thus, this study aimed to explore if tilianin protects I/R-induced AKI and the underlying mechanisms.

Methods: The microarray dataset GSE52004 was downloaded from GEO DataSets (Gene Expression Omnibus). Differential expression analysis and gene-set enrichment analysis (GSEA) were performed by R software to identify apoptosis pathway-related genes. Then, RcisTarget was applied to identify the transcription factor (TF) related to apoptosis. The STRING database was used to construct a protein–protein interaction (PPI) network. Cytoscape software visualized PPI networks, and hub TFs were selected via cytoHubba. AutoDock was used for molecular docking of tilianin and hub gene-encoded proteins. The expression levels of hub genes were assayed and visualized by quantitative real-time PCR, Western blotting, and immunohistochemistry by establishing I/R-induced AKI mouse models.

Results: Bioinformatics analysis showed that 34 genes, including FOS, ATF4, and Gadd45g, were involved in the apoptosis pathway. In total, seven hub TFs might play important roles in tilianin-regulating apoptosis pathways. In in vivo, tilianin improved kidney function and reduced the number of TUNEL-positive renal tubular epithelial cells (RTECs) after I/R-induced AKI. Tilianin reduced the activation of the ERK pathway and then downregulated the expression of EGR1. This further ameliorated the expression of anti-apoptotic genes such as BCL2L1 and BCL2, reduced pro-apoptotic genes such as BAD, BAX, and caspase-3, and reduced the release of cytochrome c.

Conclusion: Tilianin reduced apoptosis after I/R-induced AKI by the ERK/EGR1/BCL2L1 pathway. Our findings provided novel insights for the first time into the protective effect and underlying molecular mechanisms of tilianin on I/R-induced AKI.

MicroRNA-24 protects against myocardial ischemia-reperfusion injury via the NF-κB/TNF-α pathway

Acute myocardial infarction (AMI) is a form of cardiomyopathy in which a blocked coronary artery leads to an irreversible loss of cardiomyocytes due to inadequate blood and oxygen supply to the distal myocardium tissues, eventually leading to heart failure. Recently, studies have revealed that microRNA (miRNA/miR)-24 has diagnostic value in the pathogenesis of AMI by affecting multiple cell processes such as cell proliferation, differentiation and apoptosis. However, the specific mechanism of miR-24 in ischemia-reperfusion injury (IRI) after AMI remains to be fully elucidated. The present study aimed to investigate the effects and mechanisms of miR-24 in IRI. In vitro, the current study detected cellular apoptosis and apoptotic-related protein expression levels in the cardiomyocyte H9C2 cell line (negative control group, model group and miRNA group) via flow cytometry and western blot analysis. In the in vivo study, rats were randomly divided into sham, model and miRNA groups. The infarct area was observed using nitro blue tetrazolium staining, pathological changes of the myocardium were detected via hematoxylin and eosin staining and TUNEL staining was used to detect cardiomyocyte apoptosis. The expression levels of related proteins were evaluated via immunohistochemistry and western blot analysis. The in vitro and in vivo results demonstrated that miR-24 significantly inhibited cardiomyocyte apoptosis compared with the model group. Concurrently, the expression levels of proteins associated with the NF-κB/TNF-α pathway (NF-κB, caspase-3, Bax, Bcl-2, TNF-α, vascular cell adhesion molecule 1, intercellular adhesion molecule 1 and monocyte chemoattractant protein-1) in the miRNA group were significantly different from the model group (P<0.001). Compared with the model group, miR-24 significantly improved pathological damage and infarct size of rat myocardium. Overall, the present results suggested that miR-24 improves myocardial injury in rats by inhibiting the NF-κB/TNF-α pathway.

Role of HRTPT in kidney proximal epithelial cell regeneration: Integrative differential expression and pathway analyses using microarray and scRNA-seq

Damage to proximal tubules due to exposure to toxicants can lead to conditions such as acute kidney injury (AKI), chronic kidney disease (CKD) and ultimately end‐stage renal failure (ESRF). Studies have shown that kidney proximal epithelial cells can regenerate particularly after acute injury. In the previous study, we utilized an immortalized in vitro model of human renal proximal tubule epithelial cells, RPTEC/TERT1, to isolate HRTPT cell line that co‐expresses stem cell markers CD133 and CD24, and HREC24T cell line that expresses only CD24. HRTPT cells showed most of the key characteristics of stem/progenitor cells; however, HREC24T cells did not show any of these characteristics. The goal of this study was to further characterize and understand the global gene expression differences, upregulated pathways and gene interaction using scRNA‐seq in HRTPT cells. Affymetrix microarray analysis identified common gene sets and pathways specific to HRTPT and HREC24T cells analysed using DAVID, Reactome and Ingenuity software. Gene sets of HRTPT cells, in comparison with publicly available data set for CD133+ infant kidney, urine‐derived renal progenitor cells and human kidney‐derived epithelial proximal tubule cells showed substantial similarity in organization and interactions of the apical membrane. Single‐cell analysis of HRTPT cells identified unique gene clusters associated with CD133 and the 92 common gene sets from three data sets. In conclusion, the gene expression analysis identified a unique gene set for HRTPT cells and narrowed the co‐expressed gene set compared with other human renal–derived cell lines expressing CD133, which may provide deeper understanding in their role as progenitor/stem cells that participate in renal repair.

The endoplasmic reticulum stress and the unfolded protein response in kidney disease: Implications for vascular growth factors

Acute kidney injury (AKI) and chronic kidney disease (CKD) represent an important challenge for healthcare providers. The identification of new biomarkers/pharmacological targets for kidney disease is required for the development of more effective therapies. Several studies have shown the importance of the endoplasmic reticulum (ER) stress in the pathophysiology of AKI and CKD. ER is a cellular organelle devolved to protein biosynthesis and maturation, and cellular detoxification processes which are activated in response to an insult. This review aimed to dissect the cellular response to ER stress which manifests with activation of the unfolded protein response (UPR) with its major branches, namely PERK, IRE1α, ATF6 and the interplay between ER and mitochondria in the pathophysiology of kidney disease. Further, we will discuss the relationship between mediators of renal injury (with specific focus on vascular growth factors) and ER stress and UPR in the pathophysiology of both AKI and CKD with the aim to propose potential new targets for treatment for kidney disease.

miRNAs as Novel Biomarkers of Chronic Kidney Injury in Anabolic-Androgenic Steroid Users: An Experimental Study

miRNAs are a family of 20–22 non-coding nucleotides that control gene expression by inhibiting the translation of their target messenger RNAs (mRNAs). Two models have been proposed to elucidate the mechanism of action: they act either hindering mRNA translation or enhancing mRNA degradation. Anabolic-Androgenic Steroids (AASs) represent a class of drugs used to treat several diseases. In the last few years, AASs have frequently been used for aesthetic purposes, indeed, they form part of the larger group called image- and performance-enhancing drugs (IPEDs). Long-term AAS use can lead to serious health consequences. In this regard, the present study aimed to analyze the role of several microRNAs (miRNAs) in renal damage after AAS use, to better understand the underlying mechanisms. For this purpose, two miRNAs (miR-21 and miR-205) were tested in two groups: AAS group (seven males, mean age 33.28 ± 4.68 years; mean body mass index (BMI) 27.04 ± 1.07), and chronic kidney disease (CKD) group (seven males, mean age 66.2 ± 5.4 years; mean BMI 24.75 ± 1.35). Finally, the same miRNAs were tested in the “Control” group (seven males, mean age 44.85 ± 5.75 years; mean BMI 26.5 ± 1.88). Kolmogorov-Smirnov Test was used to determine the normality of data distribution. All variables were normally distributed. Student’s t-test was used for comparisons between two groups. Analyzing the results of the present study, the two tested miRNAs (miR-21 and miR-205) were significantly higher in the CKD group compared to the AAS group, with mir-21 being much more expressed than miR-205. This study represents a pilot study to define if these expression patterns could be studied in other biological samples (plasma, urine) in subjects with different kidney injury linked to chronic kidney diseases and AAS use, to identify reliable biomarkers that could be applied in clinical and forensic diagnostics, as well as a target for toxicological investigations or therapeutic treatments.