Human Renal Tubular Epithelial Cells Research Articles

Quercetin Ameliorates Renal Injury and Pyroptosis in Lupus Nephritis through Inhibiting IL-33/ST2 Pathway In Vitro and In Vivo.

Lupus nephritis (LN) is a common and serious symptom in patients with systemic lupus erythematosus (SLE). Tubular interstitial fibrosis is a common underlying mechanism in the development of lupus nephritis to end-stage renal failure (ESRD). Quercetin is widely proven to prevent tissue fibrosis. Therefore, the purpose of this study is to investigate the beneficial effects of quercetin on the inhibition of fibrosis and inflammation pathways in in vitro and in vivo lupus nephritis models. In the current study, MRL/lpr mice as animal models, and HK-2 human renal tubular epithelial cells were stimulated by interleukin-33 (IL-33) to mimic the cellular model of lupus nephritis. Immunohistochemical staining, immunoblotting assay, immunofluorescence staining, and quantitative real-time polymerase chain reaction assay were used. The in vivo results showed that quercetin improved the renal function and inhibited both fibrosis- and inflammation-related markers in MRL/lpr mice animal models. The in vitro results indicated that quercetin ameliorated the accumulation of fibrosis- and inflammation-related proteins in IL-33-induced HK-2 cells and improved renal cell pyroptosis via the IL33/ST2 pathway. Overall, quercetin can improve LN-related renal fibrosis and inflammation, which may offer an effective potential therapeutic strategy for lupus nephritis.

MK-2206 Alleviates Renal Fibrosis by Suppressing the Akt/mTOR Signaling Pathway In Vivo and In Vitro.

Renal fibrosis is a common pathological feature of various kidney diseases, leading to irreversible renal failure and end-stage renal disease. However, there are still no effective treatments to reverse renal fibrosis. This study aimed to explore the potential mechanism of a targeted drug for fibrosis. Here, unilateral ureteral obstruction (UUO)-treated mice and a TGF-β1-treated human renal tubular epithelial cell line (HK-2 cells) were used as models of renal fibrosis. Based on the changes of mRNA in UUO kidneys detected by transcriptome sequencing, MK-2206, an Akt inhibitor, was predicted as a potential drug to alleviate renal fibrosis through bioinformatics. We dissolved UUO mice with MK-2206 by gastric gavage and cultured TGF-β-induced HK-2 cells with MK-2206. Histopathological examinations were performed after MK-2206 intervention, and the degree of renal fibrosis, as well as the expression of Akt/mTOR pathway-related proteins, were evaluated by immunohistochemical staining, immunofluorescence staining, and Western blot. The results showed that MK-2206 significantly improved the pathological structure of the kidney. Furthermore, MK-2206 intervention effectively inhibited UUO- and TGF-β1-induced epithelial-mesenchymal transition, fibroblast activation, and extracellular matrix deposition. Mechanistically, MK-2206 treatment attenuated the activation of the Akt/mTOR signaling pathway. Taken together, our study revealed for the first time that MK-2206 is a promising drug for the improvement of renal fibrosis.

The expression of apoptosis related genes in HK-2 cells overexpressing PPM1K was determined by RNA-seq analysis.

Chronic kidney disease (CKD) is a serious disease that endangers human health. It is reported that inhibiting renal cell apoptosis can delay the progress of CKD. Our previous study found that the mice with protein phosphatase Mg2+/Mn2+ dependent 1K (PPM1K) gene deletion had obvious symptoms of glomerular vascular and interstitial vascular dilatation, congestion and hemorrhage, glomerular hemorrhage and necrosis, interstitial fibrous tissue proliferation, decreased urinary creatinine clearance, and increased urinary protein level. In addition, studies have found that PPM1K is essential for cell survival, apoptosis and metabolism. However, no study has confirmed that PPM1K can inhibit renal cell apoptosis. In this study, PPM1K was overexpressed in human kidney-2 cells (HK-2), and the biological process of differentially expressed genes and its effect on apoptosis were comprehensively screened by RNA sequencing (RNA-seq). Through sequencing analysis, we found that there were 796 differentially expressed genes in human renal tubular epithelial cells transfected with PPM1K gene, of which 553 were down-regulated and 243 were up-regulated. Enrichment analysis found that differentially expressed genes may play an important role in amino acid metabolism and biosynthesis. In the GO analysis functional pathway list, we also found that multiple genes can be enriched in apoptosis related pathways, such as G0S2, GADD45A, TRIB3, VEGFA, NUPR1 and other up-regulated genes, and IL-6, MAGED1, CCL2, TP53INP1 and other down-regulated genes. Then we verified these differentially expressed genes by RT-PCR, and found that only the RT-PCR results of G0S2, VEGFA and NUPR1 were consistent with the transcriptome sequencing results. We believe that G0S2, VEGFA, NUPR1 and other genes may participate in the apoptosis process of HK-2 cells induced by PPM1K.In conclusion, these findings provide some data support for the study of HK-2 cell apoptosis mechanism, and also provide a scientific theoretical basis for further study of the effect of PPM1K on kidney disease.

Effect of Replicative Senescence on the Expression and Function of Transporters in Human Proximal Renal Tubular Epithelial Cells.

In the field of cosmetic research, there is a growing interest in alternatives to animal experiments, such as in vitro models using cultured cells. The trend is spreading to the field of food and drugs. Although various types of cells are used as in vitro models, the effect of cellular senescence on the expression and function of transporters in these models is unclear. In the present study, we examined the effect of replicative senescence (by passage culture) on the expression and function of transporters in renal proximal tubular epithelial cells (RPTECs). The increase in senescence-associated-β-galactosidase (SA-β-gal)-positive cells, cell cycle arrest markers, and senescence-associated secretory phenotype (SASP) markers was associated with an increase in passage numbers of RPTECs. Gene expression of various transporters in RPTEC was also altered. The mRNA level of organic cation transporter 2 decreased most rapidly with passage numbers among the transporters. The uptake of fluorescent cationic substrates in SA-β-gal-positive RPTECs was less than that in SA-β-gal-negative RPTECs. However, these changes in the expression of transporters seem to be significantly different from those observed in rodents and human kidneys in many aspects. As cellular senescence is observed in various situations, especially in RPTECs, it may be necessary to exclude it from toxicological and pharmacokinetic evaluations using in vitro models as much as possible. Additionally, when discussing cellular senescence, it is important to note the differences between aging in cells and aging and senescence in individuals.

NAG-1/GDF15 inhibits diabetic nephropathy via inhibiting AGE/RAGE-mediated inflammation signaling pathways in C57BL/6 mice and HK-2 cells

AimsOur previous studies showed that the nonsteroidal anti-inflammatory drug-activated gene-1, or growth differentiation factor-15 (NAG-1/GDF15) inhibits obesity and diabetes in mice. The current study aimed to examine the role and molecular mechanisms of NAG-1/GDF15 in diabetic nephropathy (DN), which is largely unknown. Main methodsBoth male and female wild-type (Wt) C57BL/6 mice and mice overexpressing human NAG-1/GDF15 (transgenic, Tg) were used, which were induced by high-fat diet (HFD)/streptozotocin (STZ) to establish the mouse model of DN. Transcriptome study was performed to identify the underlying molecular mechanisms of NAG-1/GDF15 against DN. In addition, human renal tubular epithelial cells (HK−2) were cultured with high glucose (HG) to establish a DN cellular model and were treated with NAG-1/GDF15 plasmid or the recombinant NAG-1/GDF15 protein for mechanism studies. Key findingsOverexpression of NAG-1/GDF15 in Tg mice significantly alleviated HFD/STZ-induced typical symptoms of DN, improved lipid homeostasis, glucose intolerance, and insulin sensitivity. Histopathology of renal tissues revealed that NAG-1/GDF15 mice had significantly reduced renal injury, glycogen deposition, and renal fibrosis. Transcriptome study uncovered inflammation, cell adhesion, and the inflammation-related signaling pathways as major pathways suppressed in the NAG-1/GDF15 mice. Further studies demonstrated that NAG-1/GDF15 overexpression inhibited renal and systematic inflammation, inhibited the AGE/RAGE axis and its associated downstream inflammatory molecules and adhesion molecules, and inhibited the upregulation of TLR4/MyD88/NF-κB signaling pathway in mice. These results were further confirmed in HG-induced HK-2 cells. SignificanceNAG-1/GDF15 plays an important role in the inhibition of the development and progression of DN via targeting AGE/RAGE-mediated inflammation pathways.

Prevention of LPS-Induced Acute Kidney Injury in Mice by Bavachin and Its Potential Mechanisms.

Acute kidney injury (AKI) is a serious complication of sepsis with a rapid onset and high mortality rate. Bavachin, an active component of Psoralea corylifolia L., reportedly has antioxidant, anti-apoptotic, and anti-inflammatory effects; however, its beneficial effects on AKI remain undetermined. We investigated the protective effect of bavachin on lipopolysaccharide (LPS)-induced AKI in mice and elucidated the underlying mechanism in human renal tubular epithelial HK-2 cells. Increased serum creatinine and blood urea nitrogen levels were observed in LPS-injected mice; however, bavachin pretreatment significantly inhibited this increase. Bavachin improved the kidney injury score and decreased the expression level of tubular injury markers, such as neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1), in both LPS-injected mice and LPS-treated HK-2 cells. LPS-induced oxidative stress via phosphorylated protein kinase C (PKC) β and upregulation of the NADPH oxidase (NOX) 4 pathway was also significantly decreased by treatment with bavachin. Moreover, bavachin treatment inhibited the phosphorylation of MAPKs (P38, ERK, and JNK) and nuclear factor (NF)-κB, as well as the increase in inflammatory cytokine levels in LPS-injected mice. Krüppel-like factor 5 (KLF5) expression was upregulated in the LPS-treated HK-2 cells and kidneys of LPS-injected mice. However, RNAi-mediated silencing of KLF5 inhibited the phosphorylation of NF-kB, consequently reversing LPS-induced KIM-1 and NGAL expression in HK-2 cells. Therefore, bavachin may ameliorate LPS-induced AKI by inhibiting oxidative stress and inflammation via the downregulation of the PKCβ/MAPK/KLF5 axis.

USP7 accelerates FMR1-mediated ferroptosis by facilitating TBK1 ubiquitination and DNMT1 deubiquitination after renal ischemia-reperfusion injury.

Renal ischemia/reperfusion (I/R) leads to acute kidney injury and is associated with cell ferroptosis, an oxidative programmed cell death. This study aims to explore whether USP7 regulates ferroptosis in rat kidneys suffered I/R and the underlying mechanisms. Human renal tubular epithelial cells HK-2 were treated with hypoxia/reoxygenation (H/R) to establish a cell model. The expression of ubiquitin specific peptidase 7 (USP7) in H/R-treated cells was determined. USP7 siRNA was transfected into H/R-treated cells, followed by the detection of cell proliferation, iron ion concentration, oxidative stress levels and glutathione peroxidase 4 (GPX4) and solute carrier family 7-member 11 (SLC7A11) protein levels. Western blotting and immunoprecipitation analyses were performed to detect the effects of USP7 on the ubiquitination of TANK-binding kinase 1 (TBK1) and DNA methyltransferase 1 (DNMT1). Then, H/R-treated cells were transfected with USP7 siRNA alone or together with TBK1 siRNA. Co-immunoprecipitation was used to detect binding relationship between TBK1 and FMRP translational regulator 1 (FMR1). The level of DNMT1 and methylation ratio of the FMR1 promoter region were determined with chromatin immunoprecipitation and methylation specific PCR assays, respectively. Furthermore, USP7 siRNA and FMR1 siRNA were transfected alone or together into H/R-treated cells, followed by the detection of cell functions. An I/R rat model was constructed to analyze the effects of USP7 on renal function in rats. USP7 was significantly upregulated in H/R-treated cells. USP7 interference markedly increased HK-2 cell proliferation and the protein levels of GPX4 and SLC7A11, restrained the iron ion concentration, and ameliorated oxidative stress. USP7 promoted TRIM27-mediated TBK1 ubiquitination and degradation. USP7 inhibition resulted in increased ubiquitination and decreased stability of DNMT1. USP7 was able to recruit DNMT1 to the FMR1 promoter region, which increased promoter methylation rates and suppressed FMR1 expression. TBK1 or FMR1 overexpression could reverse the effects of USP7 on cell functions. Inhibition of USP7 alleviated renal ischemia-reperfusion injury in rats. USP7 inhibition attenuated I/R-induced renal injury by inhibiting ferroptosis through decreasing ubiquitination of TBK1 and promoting DNMT1-mediated methylation of FMR1.

Retraction.

Guo, S , Sun, J , Zhuang, Y . Quercetin alleviates lipopolysaccharide-induced inflammatory responses by up-regulation miR-124 in human renal tubular epithelial cell line HK-2. BioFactors. 2020;46:402-410. https://doi.org/10.1002/biof.1596 The above article, published online on 5 December 2019 in Wiley Online Library (https://doi.org/10.1002/biof.1596), has been retracted by agreement between the International Union of Biochemistry and Molecular Biology, the Editor in Chief (Dr. Angelo Azzi), and Wiley Periodicals LLC. The retraction has been agreed following an investigation based on allegations raised by a third party. Evidence for image manipulation was found in figures 2 and 3. As a result, the conclusions of this article are considered to be invalid.

Calycosin attenuates renal ischemia/reperfusion injury by suppressing NF-κB mediated inflammation via PPARγ/EGR1 pathway.

Renal ischemia reperfusion injury (IRI) is a leading and common cause of acute kidney injury (AKI), and inflammation is a critical factor in ischemic AKI progression. Calycosin (CAL), a major active component of Radix astragali, has been reported to have anti-inflammatory effect in multiple organs. However, whether CAL can alleviate renal IRI and its mechanism remain uncertain. In the present study, a renal IRI model is established by bilateral renal pedicles occlusion for 35 min in male C57BL/6 mice, and the effect of CAL on renal IRI is measured by serum creatinine and pathohistological assay. Hypoxia/reoxygenation (H/R) stimulated human renal tubular epithelial cells HK-2 were applied to explore the regulatory mechanisms of CAL. Luciferase reporter assay and molecular docking were applied to identify the CAL’s target protein and pathway. In the mice with renal IRI, CAL dose dependently alleviated the renal injury and decreased nuclear factor kappa B (NF-κB) mediated inflammatory response. Bioinformatics analysis and experiments showed that early growth response 1 (EGR1) increased in mice with renal IRI and promoted NF-κB mediated inflammatory processes, and CAL dose-dependably reduced EGR1. Through JASPAR database and luciferase reporter assay, peroxisome proliferator-activated receptor γ (PPARγ) was predicted to be a transcription factor of EGR1 and repressed the expression of EGR1 in renal tubular epithelial cells. CAL could increase PPARγ in a dose dependent manner in mice with renal IRI and molecular docking predicted CAL could bind stably to PPARγ. In HK-2 cells after H/R, CAL increased PPARγ, decreased EGR1, and inhibited NF-κB mediated inflammatory response. However, PPARγ knockdown by siRNA transfection abrogated the anti-inflammation therapeutic effect of CAL. CAL produced a protective effect on renal IRI by attenuating NF-κB mediated inflammatory response via PPARγ/EGR1 pathway.

Bisphenol A impairs renal function by reducing Na+/K+-ATPase and F-actin expression, kidney tubule formation in vitro and in vivo

The kidney proximal tubule is responsible for reabsorbing water and NaCl to maintain the homeostasis of the body fluids, electrolytes, and nutrients. Thus, abnormal functioning of the renal proximal tubule can lead to life-threatening imbalances. Bisphenol A (BPA) has been used for decades as a representative chemical in household plastic products, but studies on its effects on the kidney proximal tubule are insufficient. In this study, immunocytochemical and cytotoxicity tests were performed using two- and three-dimensional human renal proximal tubular epithelial cell (hRPTEC) cultures to investigate the impact of low-dose BPA (1–10 μM) exposure. BPA was found to interfere with straight tubule formation as observed by low filamentous actin formation and reduced Na+/K+-ATPase expression in the tubules of hRPTEC 3D cultures. Similar results were observed in rat pup kidneys following oral administration of 250 mg/kg BPA. Moreover, the expression of HO-1 and 8-OHdG, key markers for oxidative stress, was increased in vitro and in vivo following BPA administration, whereas that of OAT1 and OAT, important transporters of the renal proximal tubules, was not altered. Overall, no-observed-adverse-effect-level (NOAEL)-dose BPA exposure can decrease renal function by promoting abnormal tubular formation both in vitro and in vivo. Therefore, we propose that although it does not exhibit life-threatening toxicity, exposure to low levels of BPA can negatively affect homeostasis in the body by means of long-term deterioration of renal proximal tubular function in humans.

Inhibition of Malate Dehydrogenase-2 Protects Renal Tubular Epithelial Cells from Anoxia-Reoxygenation-Induced Death or Senescence.

Ischemia-reperfusion injury is the leading cause of acute kidney injury. Reactive oxygen species (ROS) production causes cell death or senescence. In cultures of primary human renal tubular epithelial cells (RPTECs) subjected to anoxia-reoxygenation, inhibition of the Krebs cycle at the level of malate dehydrogenase-2 (MDH-2) decreases hypoxia-inducible factor-1α and oxidative stress and protects from apoptotic or ferroptotic cell death. Inhibition of MDH-2 decreased reoxygenation-induced upregulation of p53 and p21, restored the levels of the proliferation marker Ki-67, and prevented the upregulation of the senescence marker beta-galactosidase and interleukin-1β production. MDH-2 inhibition reduced the reoxygenation-induced upregulation of ATP, but the alterations of critical cell metabolism enzymes allowed enough ATP production to prevent cell energy collapse. Thus, inhibition of the Krebs cycle at the level of MDH-2 protects RPTECs from anoxia-reoxygenation-induced death or senescence. MDH-2 may be a promising pharmaceutical target against ischemia-reperfusion injury.

Fibroblast growth factor 21 attenuates the progression of hyperuricemic nephropathy through inhibiting inflammation, fibrosis and oxidative stress.

Elevated levels of circulating fibroblast growth factor 21 (FGF21) have been reported in patients with hyperuricemia. However, the effect of FGF21 in hyperuricemic nephropathy (HN) remains unexplored. Here, we investigated the effect and mechanism of action of FGF21 on HN. HN model was induced with adenine and potassium oxysalt in wild-type C57BL/6 mice and FGF21-/- mice. For in vitro studies, human renal tubular epithelial (HK-2) cells were exposed to uric acid with/without FGF21 or β-Klotho-siRNA. Here, we reported aggravated renal dysfunction and structural damage in the FGF21-/- mice compared to the wild-type mice. These were evident in the upsurge of inflammatory factors IL-1β, TNF-α, IL-6, and IL-18; fibrotic markers Collagen I and α-SMA; and oxidation products ROS and MDA. However, exogenous administration of FGF21 to wild-type HN mice significantly reversed these negative effects. In terms of mechanism, FGF21 significantly inhibited NF-κB/NLRP3 and TGF-β1/Smad3 pathways and promoted nuclear translocation of Nrf2 both in vivo and in vitro. Furthermore, the silencing of β-Klotho was marked by the attenuation of the improved effect of FGF21 on cell damage. In conclusion, our studies revealed that exogenous FGF21 treatment significantly improved HN, which was achieved by the inhibition of inflammation, fibrosis, and oxidative stress.

Mitochondria-Targeted Antioxidant Mitoquinone Maintains Mitochondrial Homeostasis through the Sirt3-Dependent Pathway to Mitigate Oxidative Damage Caused by Renal Ischemia/Reperfusion.

Mitochondrial dysfunction is a critical factor contributing to oxidative stress and apoptosis in ischemia-reperfusion (I/R) diseases. Mitoquinone (MitoQ) is a mitochondria-targeted antioxidant whose potent anti-I/R injury capacity has been demonstrated in organs such as the heart and the intestine. In the present study, we explored the role of MitoQ in maintaining mitochondrial homeostasis and attenuating oxidative damage in renal I/R injury. We discovered that the decreased renal function and pathological damage caused by renal I/R injury were significantly ameliorated by MitoQ. MitoQ markedly reversed mitochondrial damage after I/R injury and inhibited renal reactive oxygen species production. In vitro, hypoxia/reoxygenation resulted in increased mitochondrial fission and decreased mitochondrial fusion in human renal tubular epithelial cells (HK-2), which were partially prevented by MitoQ. MitoQ treatment inhibited oxidative stress and reduced apoptosis in HK-2 cells by restoring mitochondrial membrane potential, promoting ATP production, and facilitating mitochondrial fusion. Deeply, renal I/R injury led to a decreased expression of sirtuin-3 (Sirt3), which was recovered by MitoQ. Moreover, the inhibition of Sirt3 partially eliminated the protective effect of MitoQ on mitochondria and increased oxidative damage. Overall, our data demonstrate a mitochondrial protective effect of MitoQ, which raises the possibility of MitoQ as a novel therapy for renal I/R.

Baicalin Alleviates Contrast-Induced Acute Kidney Injury Through ROS/NLRP3/Caspase-1/GSDMD Pathway-Mediated Proptosis in vitro.

PurposeTo investigate the effect of baicalin on the reactive oxygen species (ROS)/ NOD-like receptor protein 3 (NLRP3)/Caspase-1/gasdermin-D (GSDMD) inflammasome pathway and its related mechanism in regulating pyroptosis of human renal tubular epithelial cells (HK-2) induced by contrast media.MethodsIohexol was used to act on HK-2 cells to establish a renal tubular cell pyroptosis model; and the signal pathway genes were silenced, cytokines were detected by enzyme-linked immunosorbent assay (ELISA), and cell viability, gene expression, and protein expression were evaluated by double fluorescence staining and flow cytometry. To assess the cytotoxicity caused by the contrast agent; cells were pretreated with different concentrations of baicalin; and then the cells were exposed to iohexol again, and the relevant indicators were tested again.ResultsAfter HK-2 cells were exposed to iohexol, the NLRP3 inflammasome pathway markers NLRP3, interleukin (IL)-1β, and IL-18 mRNA levels as well as the protein expression levels of NLRP3, ASC, Caspase-1, and GSDMD were up-regulated. In addition, the effect also significantly increased the IL-18, IL-1β, lactate dehydrogenase (LDH), superoxide dismutase (SOD), malondialdehyde (MDA) release, and cellular ROS levels. The results of Annexin V-FITC/PI flow cytometry showed that the level of apoptosis was increased. However, after the intervention of baicalin, the changes in the above indexes caused by iohexol stimulation of HK-2 cells were inhibited.ConclusionExposure to iohexol can induce pyroptosis of HK-2 cells through the ROS/NLRP3/Caspase-1/GSDMD signaling pathway. Baicalin ameliorated iohexol-induced pyroptosis in HK-2 cells by regulating the NLRP3 inflammasome pathway.

Transcriptomic signatures responding to PKM2 activator TEPP-46 in the hyperglycemic human renal proximal epithelial tubular cells.

Pyruvate kinase M2 (PKM2), as the terminal and last rate-limiting enzyme of the glycolytic pathway, is an ideal enzyme for regulating metabolic phenotype. PKM2 tetramer activation has shown a protective role against diabetic kidney disease (DKD). However, the molecular mechanisms involved in diabetic tubular have not been investigated so far. In this study, we performed transcriptome gene expression profiling in human renal proximal tubular epithelial cell line (HK-2 cells) treated with 25 mM high D-glucose (HG) for 7 days before the addition of 10 μM TEPP-46, an activator of PKM2 tetramerization, for a further 1 day in the presence of HG. Afterwards, we analyzed the differentially expressed (DE) genes and investigated gene relationships based on weighted gene co-expression network analysis. The results showed that 2,902 DE genes were identified (adjusted P-value ≤ 0.05), where 2,509 DE genes (86.46%) were co-expressed in the key module. Four extremely downregulated DE genes (HSPA8, HSPA2, HSPA1B, and ARRB1) and three extremely upregulated DE genes (GADD45A, IGFBP3, and SIAH1) enriched in the downregulated endocytosis (hsa04144) and upregulated p53 signaling pathway (hsa04115), respectively, were validated by qRT-PCR experiments. The qRT-PCR results showed that the relative expression levels of HSPA8 [adjusted P-value = 4.45 × 10-34 and log2(FC) = -1.12], HSPA2 [adjusted P-value = 6.09 × 10-14 and log2(FC) = -1.27], HSPA1B [adjusted P-value = 1.14 × 10-11 and log2(FC) = -1.02], and ARRB1 [adjusted P-value = 2.60 × 10-5 and log2(FC) = -1.13] were significantly different (P-value < 0.05) from the case group to the control group. Furthermore, the interactions and predicted microRNAs of the key genes (HSPA8, HSPA2, HSPA1B, and ARRB1) were visualized in networks. This study identified the key candidate transcriptomic biomarkers and biological pathways in hyperglycemic HK-2 cells responding to the PKM2 activator TEPP-46 that can highlight a possibility of PKM2 tetramerization reshaping the interplay among endocytic trafficking through the versatile networks of Hsp70s and rewiring the crosstalk between EGFR signal transduction circuits and metabolic stress to promote resilience, which will be valuable for further research on PKM2 in DKD.

Anthrahydroquinone-2,6-disulfonate alleviates paraquat-induced kidney injury via the apelin-APJ pathway in rats

Objective: To explore the protective effects of anthrahydroquinone- 2,6-disulfonate (AH2QDS) on the kidneys of paraquat (PQ) poisoned rats via the apelin-APJ pathway. Methods: Male Sprague Dawley rats were divided into four experimental groups: control, PQ, PQ+sivelestat, and PQ+AH2QDS. The PQ+sivelestat group served as the positive control group. The model of poisoning was established via intragastric treatment with a 20% PQ pesticide solution at 200 mg/kg. Two hours after poisoning, the PQ+sivelestat group was treated with sivelestat, while the PQ+AH2QDS group was given AH2QDS. Six rats were selected from each group on the first, third, and seventh days after poisoning and dissected after anesthesia. The PQ content of the kidneys was measured using the sodium disulfite method. Hematoxylin-eosin staining of renal tissues was performed to detect pathological changes. Apelin expression in the renal tissues was detected using immunofluorescence. Western blotting was used to detect the expression levels of the following proteins in the kidney tissues: IL- 6, TNF-α, apelin-APJ (the apelin-angiotensin receptor), NF-κB p65, caspase-1, caspase-8, glucose-regulated protein 78 (GRP78), and the C/EBP homologous protein (CHOP). In in vitro study, a PQ toxicity model was established using human tubular epithelial cells treated with standard PQ. Twenty-four hours after poisoning, sivelestat and AH2QDS were administered. The levels of oxidative stress in human renal tubular epithelial cells were assessed using a reactive oxygen species fluorescence probe. Results: The PQ content in the kidney tissues of the PQ group was higher than that of the PQ+AH2QDS group. Hematoxylin-eosin staining showed extensive hemorrhage and congestion in the renal parenchyma of the PQ group. Vacuolar degeneration of the renal tubule epithelial cells, deposition of crescent-like red staining material in renal follicles, infiltration by a few inflammatory cells, and a small number of cast formation were also observed. However, these pathological changes were less severe in the PQ+sivelestat group and the PQ+AH2QDS group (P&lt;0.05). On the third day after poisoning, immunofluorescence assay showed that the level of apelin in the renal tissues was significantly higher in the PQ+AH2QDS group than in the PQ group. Western blotting analysis results showed that IL-6, TNF-α, NF-κB p65, caspase-1, caspase-8, GRP78, and CHOP protein levels in the PQ group were higher than in the PQ+AH2QDS group (P&lt;0.05). The expression of apelin-APJ proteins in the PQ+AH2QDS group was higher than in the PQ+sivelestat and PQ groups (P&lt;0.05); this difference was significant on Day 3 and Day 7. The level of oxidative stress in the renal tubular epithelial cells of the PQ+AH2QDS group and the PQ+sivelestat group was significantly lower than in the PQ group (P&lt;0.05). Conclusions: This study confirms that AH2QDS has a protective effect on PQ-poisoned kidneys and its positive effect is superior to that of sivelestat. The mechanism of the protective effects of AH2QDS may be linked to reduction in cellular oxidative stress, PQ content of renal tissue, inflammatory injury, endoplasmic reticulum stress, and apoptosis. AH2QDS may play a role in the treatment of PQ poisoning by upregulating the expression of the apelin-APJ.

Human umbilical cord mesenchymal stem cell-derived exosomal miR-335-5p attenuates the inflammation and tubular epithelial–myofibroblast transdifferentiation of renal tubular epithelial cells by reducing ADAM19 protein levels

BackgroundRenal tubular epithelial–myofibroblast transdifferentiation (EMT) plays a key role in the regulation of renal fibrosis. Exosomes derived from human umbilical cord mesenchymal stem cells (hucMSCs) play a crucial role in alleviating renal fibrosis and injury. Additionally, hucMSC-derived exosomes contain numerous microRNAs (miRNAs). However, it is unclear whether mesenchymal stem cells can regulate the transforming growth factor (TGF)-β1-induced EMT of human renal tubular epithelial cells (RTECs) through exosomal miRNAs.MethodHK-2, a human RTEC line, was co-treated with TGF-β1 and hucMSC-derived exosomes. Additionally, TGF-β1-treated HK-2 cells were transfected with a miR-335-5p mimic and disintegrin and metalloproteinase domain-containing protein 19 (ADAM19)-overexpression plasmid. miR-335-5p expression and ADAM19 protein and inflammation levels were measured via quantitative reverse transcription polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assays, respectively.ResultsTGF-β1 treatment changed the shape of HK-2 cells from a cobblestone morphology to a long spindle shape, accompanied by an increase in interleukin (IL)-6, tumor necrosis factor-α, IL-1β, collagen I, collagen III, α-smooth muscle actin, vimentin, and N-cadherin protein levels, whereas E-cadherin protein levels were reduced in these HK-2 cells, suggesting that TGF-β1 treatment induced the inflammation and EMT of HK-2 cells. HucMSC-exosomes improved the inflammation and EMT phenotype of TGF-β1-induced HK-2 cells by transferring miR-335-5p. miR-335-5p was found to bind the ADAM19 3′-untranslated region to reduce ADAM19 protein levels. Additionally, miR-335-5p improved the inflammation and EMT phenotype of HK-2 cells by reducing ADAM19 protein levels with TGF-β1 induction.ConclusionsHucMSC-derived exosomal miR-335-5p attenuates the inflammation and EMT of HK-2 cells by reducing ADAM19 protein levels upon TGF-β1 induction. This study provides a potential therapeutic strategy and identifies targets for clinically treating renal fibrosis.

Renal Hypoxic Reperfusion Injury-on-Chip Model for Studying Combinational Vitamin Therapy.

Renal ischemic-reperfusion injury decreases the chances of long-term kidney graft survival and may lead to the loss of a transplanted kidney. During organ excision, the cycle of warm ischemia from the donor and cold ischemia is due to storage in a cold medium after revascularization following organ transplantation. The reperfusion of the kidney graft activates several pathways that generate reactive oxygen species, forming a hypoxic-reperfusion injury. Animal models are generally used to model and investigate renal hypoxic-reperfusion injury. However, these models face ethical concerns and present a lack of robustness and intraspecies genetic variations, among other limitations. We introduce a microfluidics-based renal hypoxic-reperfusion (RHR) injury-on-chip model to overcome current limitations. Primary human renal proximal tubular epithelial cells and primary human endothelial cells were cultured on the apical and basal sides of a porous membrane. Hypoxic and normoxic cell culture media were used to create the RHR injury-on-chip model. The disease model was validated by estimating various specific hypoxic biomarkers of RHR. Furthermore, retinol, ascorbic acid, and combinational doses were tested to devise a therapeutic solution for RHR. We found that combinational vitamin therapy can decrease the chances of RHR injury. The proposed RHR injury-on-chip model can serve as an alternative to animal testing for injury investigation and the identification of new therapies.

LncRNA MALAT1 Promotes Diabetic Nephropathy Progression via miR-15b-5p/TLR4 Signaling Axis.

Objective The long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) are closely associated with the pathogenesis of diabetic nephropathy (DN). But a complete mechanism for MALAT1 in DN has yet to be identified. This study investigated the effect of MALAT1 on DN through the regulation of miR-15b-5p/TLR4 signaling. Method Renal tissues were collected from DN patients. Human renal tubular epithelial cells (HK-2) were used as a model of DN induced by high glucose (HG). We then measured the viability, apoptosis, and inflammatory cytokine levels of HK-2 cells using the corresponding assays. Following transfections of si-MALAT1, si-MALAT1+miR-15b-5p inhibitor, or si-MALAT1+vector TLR4 into HG-stimulated HK-2 cells, cell viability, apoptosis, and inflammatory cytokines were again measured. Furthermore, dual-luciferase reporter assay validated the interactions of MALAT1/miR-15b-5p and miR-15b-5p/TLR4. In addition, the interaction between MALAT1 and miR-15b-5p was investigated by RNA immunoprecipitation (RIP). Results A significant upregulation of MALAT1 was observed in DN kidney tissues, as well as in HG-stimulated HK-2 cells. MALAT1 knockdown attenuates the inhibition of cell viability, apoptosis, and inflammatory response induced by HG in HK-2 cells. Moreover, a miR-15b-5p inhibitor or TLR4 overexpression reversed the above effects induced by MALAT1 knockdown. Conclusion These results indicate that reduced MALAT1 ameliorates HG-stimulated HK-2 cell damage through an inhibition of the miR-15b-5p/TLR4 axis. MALAT1 may serve as a biomarker and potential therapeutic target for DN.

Phosphoproteomic Analysis of FLCN Inactivation Highlights Differential Kinase Pathways and Regulatory TFEB Phosphoserines

In Birt–Hogg–Dubé (BHD) syndrome, germline loss-of-function mutations in the Folliculin (FLCN) gene lead to an increased risk of renal cancer. To address how FLCN inactivation affects cellular kinase signaling pathways, we analyzed comprehensive phosphoproteomic profiles of FLCNPOS and FLCNNEG human renal tubular epithelial cells (RPTEC/TERT1). In total, 15,744 phosphorylated peptides were identified from 4329 phosphorylated proteins. INKA analysis revealed that FLCN loss alters the activity of numerous kinases, including tyrosine kinases EGFR, MET, and the Ephrin receptor subfamily (EPHA2 and EPHB1), as well their downstream targets MAPK1/3. Validation experiments in the BHD renal tumor cell line UOK257 confirmed that FLCN loss contributes to enhanced MAPK1/3 and downstream RPS6K1/3 signaling. The clinically available MAPK inhibitor Ulixertinib showed enhanced toxicity in FLCNNEG cells. Interestingly, FLCN inactivation induced the phosphorylation of PIK3CD (Tyr524) without altering the phosphorylation of canonical Akt1/Akt2/mTOR/EIF4EBP1 phosphosites. Also, we identified that FLCN inactivation resulted in dephosphorylation of TFEB Ser109, Ser114, and Ser122, which may be linked to increased oxidative stress levels in FLCNNEG cells. Together, our study highlights differential phosphorylation of specific kinases and substrates in FLCNNEG renal cells. This provides insight into BHD-associated renal tumorigenesis and may point to several novel candidates for targeted therapies.