Renal Epithelial Cell Injury Research Articles

Burdock Fructooligosaccharide Attenuates High Glucose-Induced Apoptosis and Oxidative Stress Injury in Renal Tubular Epithelial Cells.

Hyperglycemia-induced apoptosis and oxidative stress injury are thought to play important roles in the pathogenesis of diabetic nephropathy (DN). Attenuating high glucose (HG)-induced renal tubular epithelial cell injury has become a potential approach to ameliorate DN. In recent years, burdock fructooligosaccharide (BFO), a water-soluble inulin-type fructooligosaccharide extracted from burdock root, has been shown to have a wide range of pharmacological activities, including antiviral, anti-inflammatory, and hypolipidemic activities. However, the role and mechanism of BFO in rat renal tubular epithelial cells (NRK-52E cells) have rarely been investigated. The present study investigated the protective effect of BFO on HG-induced damage in NRK-52E cells. BFO could protect NRK-52E cells against the reduced cell viability and significantly increased apoptosis rate induced by HG. These anti-oxidative stress effects of BFO were related to the significant inhibition of the production of reactive oxygen species, stabilization of mitochondrial membrane potential, and increased antioxidant (superoxide dismutase and catalase) activities. Furthermore, BFO increased the expression of Nrf2, HO-1, and Bcl-2 and decreased the expression of Bax. In conclusion, these findings suggest that BFO protects NRK-52E cells against HG-induced damage by inhibiting apoptosis and oxidative stress through the Nrf2/HO-1 signaling pathway.

Effect of methyl eugenol on hypoxia/reoxygenation injury of human renal tubular epithelial cells and its mechanism

This study aimed to investigate the effect of methyl eugenol(ME) on hypoxia/reoxygenation(H/R)-induced injury of human renal tubular epithelial HK-2 cells and its mechanism. The viability of HK-2 cells cultured with different concentrations of ME and exposed to H/R was detected by cell counting kit-8(CCK-8) assay. The effect of ME on the morphology of HK-2 cells was observed under an inverted microscope. The content of intracellular reactive oxygen species in different groups was detected after 2',7'-dichlorodihydrofluorescein diacetate(DCFH-DA) fluorescence staining. Cell apoptosis was determined by flow cytometry. Changes in mitochondrial membrane potential were monitored by JC-1 dye. The concentrations of nuclear factor erythroid 2 related factor 2(Nrf2), heme oxygenase-1(HO-1), and nicotinamide adenine dinucleotide phosphatase oxidase 4(Nox4) were measured by Western blot, followed by the assay of Nrf2 concentration changes in cytoplasm and nucleus by confocal fluorescence staining. The results showed that when the concentration of ME was 0-40 μmol·L~(-1), the activity of HK-2 cells was not affected. Compared with the model group, ME enhanced the activity of HK-2 cells and the cell morphology was normal. As revealed by further experiments, ME inhibited the release of reactive oxygen species and the decline in mitochondrial membrane potential of HK-2 cells after H/R injury, promoted Nrf2/HO-1 expression and Nrf2 translocation to the nucleus, and down-regulated the expression of Nox4, thereby significantly reducing apoptosis. This protective effect of ME could be reversed by the specific Nrf2 inhibitor ML385. These findings have preliminarily proved that ME effectively protected HK-2 cells against H/R injury, which might be related to its promotion of Nrf2/HO-1 signaling pathway and inhibition of Nox4. Such exploration on the possible mechanism of ME in the treatment of renal ischemia-reperfusion injury(IRI) and protection of organ function from the perspective of antioxidant stress has provided reference for related research on the treatment of acute kidney injury with traditional Chinese medicine.

MicroRNA-204 attenuates oxidative stress damage of renal tubular epithelial cells in calcium oxalate kidney-stone formation via MUC4-mediated ERK signaling pathway.

Oxalate-induced oxidative stress causes damage to cells, accompanied with renal deposition of calcium oxalate crystals. Recent studies have highlighted the extensive functions of microRNAs (miRNAs) in various processes, including cellular responses to oxidative stress. Hence, this study was intended to analyze the role of miR-204 in the calcium oxalate kidney-stone formation and the underlying mechanism. In silico analysis was performed to determine the miRNA/mRNA interaction involved in calculus, while dual-luciferase reporter assay was conducted for validation. A calcium oxalate kidney-stone model was established by H2O2 induction in RTEC HK-2 cells, in which the expression of miR-204 was examined. Gain- and loss-of-function approaches were employed to alter the expression of miR-204/MUC4 so as to assess the detailed role of miR-204 in oxidative stress injury in renal tubular epithelial cells (RTECs) and calcium oxalate kidney-stone formation. MUC4, an up-regulated gene in H2O2-induced HK-2 cells, was a target of MUC4. miR-204 functionally targeted MUC4 and blocked the ERK pathway activation. Furthermore, up-regulated miR-204 contributed to promotion of RTEC proliferation and suppression of ROS levels, RTEC apoptosis as well as formation of calcium oxalate crystal. Taken together, miR-204 impairs MUC4-dependent activation of the ERK signaling pathway and consequently ameliorates oxidative stress damage to RTECs and prevents calcium oxalate kidney-stone formation.

Angiotensin II type 2 receptor agonist, compound 21, prevents tubular epithelial cell damage caused by renal ischemia

During ischemic acute kidney injury (AKI), loss of cytoskeletal integrity and disruption of intercellular junctions are rapid events in response to ATP depletion. Angiotensin II type 2 receptor (AT2R) is overexpressed in injury situations and its stimulation by angiotensin II (AngII) is related to beneficial renal effects. Its role on ischemic AKI has not been deeply studied. The aim of the present study was to investigate whether pretreatment with the AT2R agonist, C21, prevents ischemic renal epithelial cell injury. Studies in a model of 40 min of renal ischemia followed by 24 h of reperfusion (IR) in rats demonstrated that C21 pretreatment attenuated renal dysfunction and induced better preservation of tubular architecture. In addition, we studied the expression of Rho GTPases, RhoA and Cdc42, since they are key proteins in the regulation of the actin cytoskeleton and the stability of epithelial intercellular junctions. IR downregulated RhoA and Cdc42 abundance in rat kidneys. C21 pretreatment prevented RhoA reduction and increased Cdc42 abundance compared to controls. We also used an in vitro model of ATP depletion in MDCK cells grown on filter support. Using immunofluorescence we observed that in MDCK cells, C21 pretreatment prevented the ATP depletion-induced reduction of actin in brush border microvilli and in stress fibers. Moreover, C21 prevented membrane E-cadherin reduction, and RhoA and Cdc42 downregulation. The present study describes for the first time a renoprotective effect of the AT2R agonist, C21, against AKI, and provides evidence supporting that stimulation of AT2R triggers cytoprotective mechanisms against an ischemic event.

Evaluation of In-vitro Cytoprotective, Wound Healing and Antioxidant Effects of Ocimum sanctum Leaf ExtractChetna

Exposure of renal epithelial cells to Calcium oxalate monohydrate crystals leads to cellular injury and play a significant role in the formation of kidney stones. Additionally, lipid peroxidation of polyunsaturated fatty acids further accelerates the generation and progression of the disease. Availability of safe and effective treatment of the disease is the need of hour. The objective of this research work was to evaluate the impact of hydro-alcoholic extract of Ocimum sanctum leaves on renal epithelial cell injury, oxidative stress and wound healing. Renal epithelial cells (Vero cells) were exposed to Calcium oxalate monohydrate crystals to cause injury and then injured cells were treated with Ocimum sanctum extract. Cell viability of the treated group was compared against control using MTT assay. Antioxidant potential was evaluated using malondialdehyde content as biomarker. Wound healing potential was evaluated using scratch assay. A significant increase in cell viability and wound closure rate was observed in the treated group compared to that in control group was observed. We observed reduced malondialdehyde content in the treated group as compared with control. It can be concluded that hydro-alcoholic extract of leaves of Ocimum sanctum possesses strong cytoprotective, antioxidant and wound healing potential and can be effective in the prevention and treatment of kidney stones.

LncRNA TUG1/miR-29c-3p/SIRT1 axis regulates endoplasmic reticulum stress-mediated renal epithelial cells injury in diabetic nephropathy model in vitro.

Long non-coding RNAs (lncRNAs) are important regulators in diabetic nephropathy. In this study, we investigated the potential role of lncRNA TUG1 in regulating endoplasmic reticulum stress (ERS)-mediated apoptosis in high glucose induced renal tubular epithelial cells. Human renal tubular epithelial cell line HK-2 was challenged with high glucose following transfection with lncRNA TUG1, miR-29c-3p mimics or inhibitor expression plasmid, either alone or in combination, for different experimental purposes. Potential binding effects between TUG1 and miR-29c-3p, as well as between miR-29c-3p and SIRT1 were verified. High glucose induced apoptosis and ERS in HK-2 cells, and significantly decreased TUG1 expression. Overexpressed TUG1 could prevent high glucose-induced apoptosis and alleviated ERS via negatively regulating miR-29c-3p. In contrast, miR-29c-3p increased HK-2 cells apoptosis and ERS upon high glucose-challenge. SIRT1 was a direct target gene of miR-29c-3p in HK-2 cells, which participated in the effects of miR-29c-3p on HK-2 cells. Mechanistically, TUG1 suppressed the expression of miR-29c-3p, thus counteracting its function in downregulating the level of SIRT1. TUG1 regulates miR-29c-3p/SIRT1 and subsequent ERS to relieve high glucose induced renal epithelial cells injury, and suggests a potential role for TUG1 as a promising diagnostic marker of diabetic nephropathy.

Mutation of Klotho rs3752472 protect the kidney from the renal epithelial cell injury caused by CaOx crystals through the Wnt/β-catenin signaling pathway.

Calcium oxalate (CaOx) is a major contributor to urolithiasis, one of the most common urological diseases. Our previous study has shown that Klotho rs3752472 polymorphism correlates with an increased risk of CaOx-related urolithiasis in human cohorts. This study aims to identify the effect of Klotho rs3752472 polymorphism on the renal epithelium injury caused by CaOx. A rat urolithiasis model was established and validated. Renal function was assessed, and histological examination was performed. The distribution and expression of Klotho in the rat model were detected by immunohistochemical staining and western blotting analysis. A renal epithelial cell line (HK2) was used and intervened by COM crystals with several concentrations and time points. Expression of Klotho and key mediators in Wnt/β-catenin pathway were assessed by Western blotting analysis. Wide-type and mutated plasmids of Klotho rs3752472 were added in the cell culture, and the activation of Wnt/β-catenin signaling was tested. Finally, Wide-type and mutated plasmids of Klotho rs3752472 were adoptively transferred to the rat model, and the expression of Klotho was verified. In the rat model, Klotho was mainly distributed in the renal tubular area, which significantly declined in the urolithiasis group. In vitro, COM crystals significantly inhibited the expression of Klotho and induced remarkable renal epithelial cell injury. The mutation of Klotho rs3752472 can notably enhance the expression of Klotho, as well as the protection from renal epithelial cell injury and the inhibition of Wnt/β-catenin signaling pathway. After adoptively transferred to the rat urolithiasis model, similar results were observed for the mutation of Klotho rs3752472. Klotho was significantly correlated with the renal epithelial cell injury induced by CaOx crystals. Furthermore, the mutation of Klotho rs3752472 can remarkably enhance the expression of Klotho in renal tissues and cells, and subsequently protect the renal epithelial cell from the formation of CaOx crystals through the inhibition of Wnt/β-catenin signaling pathway.

Galangin attenuates oxidative stress-mediated apoptosis in high glucose-induced renal tubular epithelial cells through modulating renin-angiotensin system and PI3K/AKT/mTOR pathway.

This study was to evaluate the regulatory network among Galangin (Gal), oxidative stress, and renin-angiotensin system (RAS) in diabetic nephropathy (DN) in vitro. A cell model of DN was set up by exposing HK-2 cells to high glucose (HG, 30mM) for 48h and Gal was applied at 10μM when needed. mRNA expression was analyzed by qPCR and protein level was detected by western blot. Malondialdehyde level and superoxide dismutase activity were evaluated by commercial kits. We analyzed cell viability by CCK8 assay and apoptosis by flow cytometry. DCFH-DA staining was conveyed for reactive oxygen species detection. HG induced RAS activation, oxidative stress, while inhibited cell viability. Gal suppressed oxidative stress-mediated apoptosis of HK-2 cells under the stimulation of HG via inhibiting RAS activation. Moreover, overexpression of AT1R, a RAS gene, could restrain the mitigative effect of Gal on cell injury. Furthermore, repression of RAS induced by AT1R knockdown partially reversed HG-induced PI3K/AKT/mTOR activation and oxidative stress in HK-2 cells. Also, AKT activation could antagonize Gal's functional roles in renal cell damage. Collectively, Gal alleviates HG-induced oxidative stress injury of renal tubular epithelial cells through PI3K/AKT/mTOR signal via modulating RAS activation. This finding would help to better understand mechanism of DN development and support future studies.

ROS-ERK Pathway as Dual Mediators of Cellular Injury and Autophagy-Associated Adaptive Response in Urinary Protein-Irritated Renal Tubular Epithelial Cells.

ERK, an extracellular signal-regulated protein kinase, is involved in various biological responses, such as cell proliferation and differentiation, cell morphology maintenance, cytoskeletal construction, apoptosis, and canceration of cells. In this study, we focused on ERK pathway on cellular injury and autophagy-associated adaptive response in urinary protein-irritated renal tubular epithelial cells and explored the potential mechanisms underlying it. By using antioxidants N-acetylcysteine and catalase, we found that ERK pathway was activated by a reactive oxygen species- (ROS-) dependent mechanism after exposure to urinary proteins. What is more, ERK inhibitor U0126 could decrease the release of neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), and the number of apoptotic cells induced by urinary proteins, indicating the damaging effects of ERK pathway in mediating cellular injury and apoptosis in HK-2 cells. Interestingly, we also found that the increased expression of microtubule-associated protein 1 light chain 3 (LC3)-II (a key marker of autophagy) and the decreased expression of p62 (autophagic substrate) induced by urinary proteins were reversed by U0126, suggesting autophagy was activated by ERK pathway. Furthermore, rapamycin reduced urinary protein-induced NGAL and KIM-1 secretion and cell growth inhibition, while chloroquine played the opposite effect, indicating that autophagy activation by ERK pathway was an adaptive response in the exposure to urinary proteins. Taken together, our results indicate that activated ROS-ERK pathway can induce cellular injury and in the meantime provide an autophagy-associated adaptive response in urinary protein-irritated renal tubular epithelial cells.

Resveratrol Attenuates Oxalate-Induced Renal Oxidative Injury and Calcium Oxalate Crystal Deposition by Regulating TFEB-Induced Autophagy Pathway.

The oxidative injury of renal tubular epithelial cells caused by inflammation and oxidative stress induced by hyperoxaluria is an important factor in the kidney calcium oxalate (CaOx) stone formation. Resveratrol (RSV) has been reported to reduce oxidative injury to renal tubular epithelial cells, and autophagy is critical for the protective effect of resveratrol. However, the protective mechanism of RSV in oxalate-induced oxidative injury of renal tubular cells and the role of autophagy in this process are still unclear. In our study, glyoxylic acid monohydrate-induced rats were treated with or without resveratrol, and it was detected that the overexpression of oxidant species, CaOx crystal deposition, apoptosis level, inflammatory cytokines and osteoblastic-associated protein expression were reversed by resveratrol. Additionally, Resveratrol pretreatment significantly reversed oxalate -induced decline in cell viability, cell damage, oxidant species overexpression, and osteogenic transformation in normal rat kidney epithelial-like (NRK-52E) cells. Furthermore, we found that RSV pretreatment promoted intracellular LC3II upregulation, p62 downregulation, and autophagosome formation, whereas 3-methyladenine treatment reduced this effect. Moreover, RSV induced the expression of transcription factor EB (TFEB) in the nucleus of NRK-52E cells in a concentration-dependent manner. After transfection of NRK-52E cells with TFEB siRNA, we showed that the RSV-induced increase in TFEB expression and autophagosome formation were inhibited. Simultaneously, RSV-induced NRK-52E cells protection was partially reversed. These results suggested that RSV regulates oxalate-induced renal inflammation, oxidative injury, and CaOx crystal deposition in vitro and in vivo through the activation of a TFEB-induced autophagy.

CREB1 protects against the renal injury in a rat model of kidney stone disease and calcium oxalate monohydrate crystals-induced injury in NRK-52E cells

Kidney stone disease (KSD) is a common urinary disease with increasing prevalence worldwide. In this study, we investigated the effect of cyclic AMP responsive element binding protein (CREB) 1 in a KSD model of rat and calcium oxalate monohydrate (COM) crystals-treated NRK-52E cells. Rats were pretreated with lentivirus (LV)-CREB1 vector or LV-control vector and administrated with ethylene glycol + ammonium chloride to induce KSD. It was found that CREB1 was activated in the renal tissue of non-treated KSD rats. Pretreating with LV-CREB1 vector significantly enhanced CREB1 expression in KSD rats. Biochemical analysis for serum and urine showed that upregulation of CREB1 could improve the renal function of KSD rats. Histological analysis confirmed that upregulation of CREB1 alleviated the renal injury in KSD rats. Moreover, the upregulation of CREB1 suppressed the apoptosis in renal tissue of KSD rats through regulating apoptosis-associated proteins. Further study showed that the upregulation of CREB1 could attenuate the oxidative stress in KSD rats as well. More interestingly, the upregulation of CREB1 enhanced the activity of complex I and complex III and the expression of mitochondrial cytochrome c, implicating the effect of CREB1 on improving mitochondrial function in KSD rats. In vitro study confirmed that upregulation of CREB1 inhibited the apoptosis and oxidative stress, while improved the mitochondrial function of NRK-52E cells treated with COM crystals, demonstrating the protective effect of CREB1 on COM crystals-induced renal epithelial cell injury. Therefore, CREB1 might be served as a promising target in the prophylaxis and treatment of KSD.

XBP1 modulates hypoxia/reoxygenation injury in mouse renal tubular epithelial cells through TXNIP-NLRP3 signaling pathway

Objective: To investigate the role and regulation mechanism of X box binding protein 1 (XBP1) for hypoxia/reoxygenation(H/R) injury in mouse renal tubular epithelial cells (TCMK-1) through thioredoxin interacting protein (TXNIP)-nucleotide-binding domain (NOD)-like receptor protein (TXNIP-NLRP3) signaling pathway. Methods: The cells were divided into 4 groups: si-NC group transfected with negative control siRNA (si-NC), si-XBP1 group transfected with siRNA targeting XBP1 (si-XBP1), si-NC+H/R group transfected with si-NC and exposed to H/R, and si-XBP1+H/R group transfected with si-XBP1 and exposed to H/R. The Annexin Ⅴ/PI double-staining method was used to detect cell apoptosis; The mitochondrial membrane potential (MMP) was determined by using JC-1 dye; The mitochondrial reactive oxygen species (mROS) was assessed by using MitoSOX™ dye. The interference efficiency of XBP1 was tested by Western blotting and quantitative real-time polymerase chain reaction. The expression levels of TXNIP, NLRP3 and IL-1β protein were detected by Western blotting. The colocalization of mitochondria and TXNIP was detected by double-labeling immunofluorescent staining. The intergroup difference was compared by using an independent samples t-test. Results: Compared with the si-NC group, more mROS, apoptosis and lower MMP were observed in si-NC+H/R group. Compared with the si-NC+H/R group, less apoptosis (12.08±0.51 vs 19.01±1.80, P<0.05), mROS (34.63±0.64 vs 48.17±1.84, P<0.01) and higher MMP (1.03±0.11 vs 0.45±0.08, P<0.05) were observed in si-XBP1+H/R group. Down-regulation of XBP1U (protein: 1.31±0.18 vs 0.23±0.02, P<0.01; mRNA: 1.12±0.07 vs 0.38±0.01, P<0.001) and XBP1S (protein: 1.13±0.17 vs 0.28±0.07, P<0.01; mRNA: 8.39±0.63 vs 2.45±0.22, P<0.001) inhibited expression of TXNIP (0.15±0.02 vs 0.04±0.01, P<0.01), NLRP3 (1.13±0.12 vs 0.51±0.12, P<0.05) and IL-1β (1.02±0.04 vs 0.19±0.06, P<0.001) during H/R. Meanwhile, TXNIP exhibited significantly much less colocalization with mitochondria in the si-XBP1+H/R group. Conclusion: Supression of XBP1 expression can effectively alleviate H/R-induced TCMK-1 cells injury, whose mechanism may be inhibition of TXNIP-induced NLRP3 inflammasome activation.

Integration of transcriptomic, proteomic and metabolomic data to reveal the biological mechanisms of AAI injury in renal epithelial cells

Overexposure to aristolochic acid I (AAI) can induce aristolochic acid nephropathy (AAN). However, the comprehensive mechanisms of AAI-induced nephrotoxicity have not been entirely explicated. To investigate the toxicological mechanisms by which AAI induces renal injury, human kidney cells (HK-2 cells) were subjected to comprehensive transcriptomic, proteomic and metabolomic analyses. The transcriptomic analysis identified a total of 7749 differentially expressed genes (DEGs) after AAI treatment, while the proteomic analysis found 598 differentially expressed proteins (DEPs) after AAI treatment. The metabolomic analysis revealed 49 and 42 differentially expressed metabolites (DEMs) in the positive and negative ion modes, respectively.Gene Ontology (GO) functional annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on these DEGs, DEPs and DEMs. The results of the comprehensive analyses of transcripts, proteins, and metabolites indicated that the DEGs, DEPs, and DEMs were jointly regulated in three ways. These genes, proteins and metabolites and their related dysregulated pathways may be promising targets for research on the mechanisms of AAI injury in human renal epithelial cells. This study provides large-scale omics data that can be used to formulate new strategies for the prevention, rapid diagnosis, and treatment of AAI injury.

Role of TLR4/MyD88/NF-κB signaling in the contrast-induced injury of renal tubular epithelial cells.

The aim of the present study was to explore the role of toll-like receptor 4 (TLR4)/myeloid differentiation primary response 88 (MyD88)/nuclear factor (NF)-κB signaling in the contrast-induced injury of renal tubular epithelial cells, and to investigate the potential mechanisms. HK-2 cells cultured in vitro were randomly divided into six groups as follows: i) The blank group; ii) the iohexol group; iii) the NF-κB RNAi group (NF-κB siRNA + iohexol); iv) the TLR4 RNAi group (TLR4 siRNA + iohexol); v) the NF-κB blocker group (PDTC + iohexol); and vi) the TLR4 blocker group (CLI-095 + iohexol). The expression of the TLR4/MyD88/NF-κB signaling pathway proteins was detected by reverse transcription-quantitative (RT-q)PCR and western blot analysis, and the cellular proliferation rate was determined using the Cell Counting Kit-8 assay. The mRNA expression levels of the inflammatory cytokines tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 were also detected using RT-qPCR, and apoptosis was assessed by flow cytometry and western blotting to detect apoptosis-associated proteins (caspase-3, caspase-9 and cleaved caspase-9). Compared with the blank group, the apoptotic rates and the expression levels of TLR4, MyD88, NF-κB, caspase-3, cleaved caspase-9, TNF-α, IL-1β and IL-6 were upregulated in the iohexol group (P<0.001). However, when TLR4 or NF-κB were blocked or silenced, these effects were reversed (P<0.001). Collectively, the results of the present study indicated that TLR4/MyD88/NF-κB signaling is involved in the contrast-induced injury of renal tubular epithelial cells by inducing inflammation and apoptosis.

HUWE1 promotes EGFR ubiquitination and degradation to protect against renal tubulointerstitial fibrosis.

Injury of renal tubular epithelial cells is a key feature of the pathogenicity associated with tubulointerstitial fibrosis and other kidney diseases. HUWE1, an E3 ubiquitin ligase, acts by participating in ubiquitination and degradation of its target proteins. However, the detailed mechanisms by which HUWE1 might regulate fibrosis in renal tubular epithelial cells have not been established. Here, the possible regulation of renal tubulointerstitial fibrosis by HUWE1 was investigated by examining the expression of HUWE1 and EGFR in unilateral ureteral obstruction (UUO) mice. Markedly consistent reciprocal changes in HUWE1 and EGFR expression were observed at the protein and mRNA levels in the kidney after UUO injury. Expression of HUWE1 inhibited TGF-β-induced injury to HK-2 cells, while HUWE1 overexpression decreased the expression of EGFR. Further analysis indicated that HUWE1 physically interacted with EGFR and promoted its ubiquitination and degradation. HUWE1 expression also showed clinical relevance in renal disease, as it notably decreased in multiple types of clinical nephropathy, while EGFR expression significantly increased when compared to the normal kidney. Therefore, this study demonstrated that HUWE1, which serves as an E3 ubiquitin ligase specific for EGFR, promotes EGFR ubiquitination and degradation, thereby regulating EGFR expression and providing protection against kidney injury.

Baicalin attenuates lipopolysaccharide-induced renal tubular epithelial cell injury by inhibiting the TXNIP/NLRP3 signalling pathway via increasing miR-223-3p expression.

Baicalin has been used in China to treat inflammation-related diseases, such as inflammation-induced acute kidney injury (AKI). However, the specific mechanism of baicalin remains unclear. To observe the protective effects of baicalin on lipopolysaccharide (LPS)-induced inflammatory injury of renal tubular epithelial cells (HK-2 cells) and to explore its protective mechanism. LPS (1 mg/L) was used to induce an HK-2 cell inflammatory injury model in vitro. The cells were divided into seven groups: the normal control group, LPS-induced group, LPS plus 5 μmol/L baicalin treatment group, LPS plus 15 μmol/L baicalin treatment group, LPS plus 25 μmol/L baicalin treatment group, LPS plus 50 μmol/L baicalin treatment group, and LPS plus 75 μmol/L baicalin treatment group. 3-(4,5-dimethyl-2-thiazolyl)-2,5- diphenyl-2-H-tetrazolium bromide (MTT) assay was employed for detecting the relative survival rate of HK-2 cells. Enzyme-linked immunosorbent assay was used for detecting the levels of inflammatory factors, including interleukin-6 (IL-6), IL-1β, and tumor necrosis factor-α (TNF-α). Moreover, the expression of inducible nitric oxide synthase (iNOS); cyclooxygenase-2 (COX-2); nuclear factor kB65 (NF-κB65); phosphorylated NF-κB inhibitory protein-α (p-IκB-α); NF-κB inhibitory protein (IκB); human thioredoxin interacting protein (TXNIP); and human NACHT, LRR, and PYD domain-containing protein 3 (NLRP3) were determined by Western blot analysis. The expression levels of NLRP3 and TXNIP mRNA and miR-223-3p were determined by RT-PCR. Results found that the relative survival rate of HK-2 cells treated with different baicalin concentrations was significantly increased (P<0.05) and the levels of the inflammatory factors IL-6, IL-1β, and TNF-α were significantly decreased (P<0.05) compared with those of the LPS-induced group. The expression levels of the inflammatory proteins inducible nitric oxide synthase and cyclooxygenase-2 and the genes expressions of TXNIP and NLRP3 were significantly decreased in the cells (P<0.05), while the expression level of miR-223- 3p was significantly increased (P<0.05). These changes were induced in a dose-dependent manner. The results suggest that baicalin significantly inhibited the expression of inflammation-related proteins and alleviated LPS-induced inflammatory injury in HK-2 cells. The mechanism may be associated with the inhibition of activation of the TXNIP/NLRP3 inflammatory pathway, which might be mediated by increased expression of miR-223-3p. Thus, NLRP3 is a regulatory target of miR-223-3p.

Pioglitazone Attenuates Reoxygenation Injury in Renal Tubular NRK-52E Cells Exposed to High Glucose via Inhibiting Oxidative Stress and Endoplasmic Reticulum Stress.

Renal ischemia-reperfusion injury is a major cause of acute kidney injury. In the present study, we investigated the effects of pioglitazone on hypoxia/reoxygenation (H/R) injury in rat renal tubular epithelial cells (RTECs) under normal- (NG) or high-glucose (HG) culture conditions via evaluating oxidative stress and endoplasmic reticulum stress (ERS). The RTECs (NRK-52E cells) were divided into six groups as follows: NG group, HG group, NG + H/R group, HG + H/R group, NG + Pio + H/R group, and HG + Pio + H/R group, among which cells in H/R groups were subjected to 4 h of hypoxia followed by 12 h of reoxygenation. After that, the cells were evaluated using the Cell Counting Kit-8 assay for the determination of their viability and flow cytometry assay for the detection of apoptosis. The levels of superoxide dismutase (SOD), glutathione reductase (GSH), catalase (CAT), and malondialdehyde (MDA) were determined via colorimetric chemical assays. In addition, the expression of ERS-associated proteins, i.e. ATF4, ATF6, GRP78, and CHOP, was determined via western blotting. A HG environment could reduce the viability and increase the apoptotic rate of NRK-52E cells with increased MDA levels and decreased SOD, CAT, and GSH levels, and upregulate the expression of ERS-associated proteins, i.e. ATF4, ATF6, and GRP78. H/R injury could further aggravate changes in the above indicators, but pioglitazone could significantly reverse such changes and alleviate cell injury. Thus, Pioglitazone exhibits a cytoprotective effect on RTECs against H/R injury under NG or HG culture conditions by inhibiting oxidative stress and ERS.

All-trans retinoic acid regulated prohibitin by retinoic acid receptor α in hypoxia-induced renal tubular epithelial cell injury

All-trans retinoic acid (ATRA) is a critical component in cell processes such as cell growth, differentiation and apoptosis, and it is also crucial in the regulation of extracellular matrix (ECM) deposition. Prohibitin (PHB) can regulate cell proliferation, apoptosis and differentiation. The current study investigated whether ATRA regulated PHB is induced by hypoxia/reoxygenation injury in renal tubular epithelial cells (RTEC), using gene interference treatments (knockdown or overexpression of RARα). Our results indicate that ATRA can augment the expression of RARα and PHB proteins and reduce the expression of TGF-β1, FN and Col-IV proteins. PHB expression was reduced in an ATRA treated RARα- group, and TGF-β1, FN and Col-IV were up-regulated compared to the ATRA treated RARα+ group. We postulate that ATRA can induce the PHB expression by RARα in hypoxia/reperfusion related RTEC injury.

Activation of vitamin D receptor attenuates high glucose-induced cellular injury partially dependent on CYP2J5 in murine renal tubule epithelial cell

AimsVitamin D and its receptor, vitamin D receptor (VDR), have renoprotection effect against diabetic nephropathy (DN). But the exact mechanism has not been fully elucidated. Epoxyeicosatrienoic acids (EETs) are cytochrome P450 (CYP) epoxygenase-derived metabolites of arachidonic acid, protecting against diabetes and DN. Herein, we hypothesized that activation of VDR attenuated high glucose-induced cellular injury in renal tubular epithelial cells partially through up-regulating CYP2J5 expression. Main methodsStreptozotocin (STZ) was injected to induce diabetic in wild type and Vdr−/− mice. The effects of VDR knockout and an activator of VDR, paricalcitol, on the renal injury were detected. In vitro, a murine kidney proximal tubule epithelial cell line BU.MPT induced by high glucose were treated with or without paricalcitol (30 mM) for 12 h or 24 h. Key findingsThe expression of CYP2J5 was significantly decreased both in wild type and Vdr−/− diabetic mice induced by STZ. The STZ-induced kidney architecture damage and apoptosis rate in Vdr−/− mice were more severe. In vitro, high glucose treatment strongly reduced the CYP2J5 expression and the synthesis of 14,15-EET in BU.MPT cells. Supplement of 14,15-EET significantly reduced the lactate dehydrogenase (LDH) release induced by high glucose in BU.MPT cells. Furthermore, treatment with paricalcitol attenuated cellular injury and restored the expression of CYP2J5 reduced by high glucose in BU.MPT cells. SignificanceWe conclude that activation of VDR attenuates high glucose-induced cellular injury partially dependent on CYP2J5 in murine renal tubule epithelial cells and paricalcitol may represent a potential therapy for DN.

Astragaloside IV protects rat renal ischemia-reperfusion injury by regulating Th1/Th2 imbalance

Objective To investigated the protective effect and immunology mechanism of Astragaloside Ⅳ(Ast) on rat renal ischemia-reperfusion injury model. Methods The SD rats were randomly divided into four group as the control, sham-operation, renal ischemia-reperfusion injury, and Ast treatment groups. Rat serum and urine were collected and detective for kidney function and interleukin cytokines. The kidney tissue was collected for histology exam. The rats in astragaloside group were intraperitoneally injected with 100 mg/kg astragaloside, and the other three groups were intraperitoneally injected with an equal volume of normal saline. The models of renal ischemia-reperfusion injury were prepared to generate in model and astragaloside groups, after 30 minutes of astragaloside injection. The rats with renal ischemia-reperfusion injury model were sacrificed after 24 hours, and the level of blood-urine creatinine, neutrophil gelatinase-associated lipocalin and Kidney damage molecule-1 were determined. The level of Th1 type cytokines (TNF-α, IFN-γ, IL-2) and Th2 type cytokines (IL-4, IL-5, IL-10) in serum were measured by using ELISA. The protein and gene expression of TNF-α, IFN-γ, IL-2, IL-4, IL-5, IL-10 in renal tissue were tested by western blot and PCR, respectively. The pathological changes and apoptosis of renal tissue in each group were detected by HE staining and TUNEL staining, respectively. The expression of CD20 protein in renal tissue was determined by immunohistochemistry. Results Compared with the model group, Ast treatment reduced serum creatinine (58.74 ± 9.44 μmol/L vs. 85.03 ± 23.48 μmol/L), increased creatinine clearance rate (0.81 ± 0.13 ml/min vs. 0.37 ± 0.08 ml/min), and reduce urine neutrophil gelatinase-associated lipocalin (NGAL) (579.34 ± 11.70 pg/ml vs. 827.60 ± 14.48 pg/ml), kidney injury molecule-1 (KIM-1) (105.06 ± 2.10 pg/ml vs. 151.67 ± 3.06 pg/ml) (P<0.05). Compared with the model group, Ast treatment alleviated renal tubular epithelial cell injury and significantly decreased the apoptosis (14.36 ± 1.36% vs. 28.63 ± 2.03%) (P < 0.05), and significantly decreased the serum TNF-α (361.44 ± 9.66 pg/ml vs. 515.93 ± 10.61 pg/ml), IFN-γ (64.11 ± 1.21 pg/ml vs. 93.51 ± 2.15 pg/ml), IL-2 (388.33 ± 1.21 pg/ml vs. 557.82 ± 15.29 pg/ml), IL-4 (60.89 ± 1.21 pg/ml vs. 95.56 ± 2.75 pg/ml), IL-5 (94.02 ± 2.81 pg/ml vs. 147.07 ± 3.50 pg/ml), and IL-10 (52.62 ± 2.51 pg/ml vs. 78.22 ± 3.24 pg/ml) (P<0.01). Compared with the model group, Ast treatment significantly decreased the kidney TNF-α mRNA (1.89 ± 0.59 vs. 2.87 ± 0.97), IFN-γ mRNA (3.11 ± 1.02 vs. 5.98 ± 1.52), IL-2 mRNA (1.68 ± 0.44 vs. 4.09 ± 1.65), IL-4 mRNA (2.41 ± 0.81 vs. 4.69 ± 1.62), IL-5 mRNA (1.56 ± 0.19 vs. 2.92 ± 0.55), IL-10 mRNA (1.45 ± 0.14 vs. 2.85 ± 0.32) (P<0.01). The ratio of IL-4 to IFN-γ was basically restored to the level of sham operation group (1.05 ± 0.02 vs. 1.02 ± 0.06) (P<0.01), and CD20 cells in renal tissue was reduced. Conclusions The Th1 and B lymphocytes play an important role in renal ischemia reperfusion injury, and Th2 cells play a protective role. Astragaloside can regulate the imbalance of Th1/Th2 in the early stage after acute renal injury, and alleviate renal tubular injury. Key words: Reperfusion injury; Astragaloside Ⅳ; Th1-Th2 balance; Antigens, CD20; Rats