Tubular Epithelial Cell Line HK-2 Research Articles

Gemigliptin mitigates TGF-β-induced renal fibrosis through FGF21-mediated inhibition of the TGF-β/Smad3 signaling pathway

Fibroblast growth factor 21 (FGF21), a well-known regulator of metabolic disorders, exhibits the potential to prevent renal fibrosis by negatively regulating the transforming growth factor β (TGF-β)/Smad3 signaling pathway. Gemigliptin and other dipeptidyl peptidase-4 inhibitors are frequently used for the management of patients with type 2 diabetes. However, the protective effect of gemigliptin against renal fibrosis, particularly its potential to upregulate the expression of FGF21, remains incompletely understood. This study assessed the renoprotective effects of gemigliptin against TGF-β-induced renal fibrosis by enhancing the expression of FGF21 in the cultured human proximal tubular epithelial cell line HK-2. Treatment with FGF21 effectively prevented TGF-β-induced renal fibrosis by attenuating the TGF-β/Smad3 signaling pathway. Similarly, gemigliptin exhibited protective effects against TGF-β-induced renal fibrosis by mitigating TGF-β/Smad3 signaling through the upregulation of FGF21 expression. However, the protective effects of gemigliptin were blocked when FGF21 expression was knocked down in TGF-β-treated HK-2 cells. These results indicate that gemegliptin has the potential to exhibit protective effects against TGF-β-induced renal fibrosis by elevating FGF21 expression levels in cultured human proximal tubular epithelial cells.

IFN-β Pretreatment Alleviates Allogeneic Renal Tubular Epithelial Cell-Induced NK Cell Responses via the IRF7/HLA-E/NKG2A Axis.

Immune checkpoint molecules are promising targets for suppressing the immune response but have received little attention in immune tolerance induction in organ transplantation. In this study, we found that IFN-β could induce the expression of HLA-E as well as PD-L1 on human renal tubular epithelial cell line HK-2 and renal tissue of the C57BL/6 mouse. The JAK/STAT2 pathway was necessary for this process. Upregulation of both HLA-E and PD-L1 was fully abrogated by the JAK1/2 inhibitor ruxolitinib. Signaling pathway molecules, including STAT1, STAT2, mTOR, Tyk2, and p38 MAPK, were involved in HLA-E and PD-L1 upregulation. IRF7 is the key transcription factor responsible for the activation of HLA-E and PD-L1 promoters. Through screening an epigenetic regulation library, we found a natural compound, bisdemethoxycurcumin, enhanced IFN-β-induced HLA-E and PD-L1 expression invitro and invivo. In PBMC-derived CD56+ NK cells, we found that NKG2A but not PD1 was constitutively expressed, indicating HLA-E/NKG2A as a more potent target to induce tolerance to innate immune cells. Pretreating HK-2 cells by IFN-β significantly attenuated the degranulation of their coincubated NK cells and protected cells from NK-mediated lysis. In conclusion, IFN-β pretreatment could activate HLA-E and PD-L1 transcription through the JAK/STAT/IRF7 pathway and then could protect renal tubular epithelial cells from allogeneic immune attack mediated by NK cells.

Ascorbate protects human kidney organoids from damage induced by cell-free hemoglobin.

Sepsis-associated acute kidney injury is associated with high morbidity and mortality in critically ill patients. Cell-free hemoglobin (CFH) is released into the circulation of patients with severe sepsis and the levels of CFH are independently associated with mortality. CFH treatment increased cytotoxicity in the human tubular epithelial cell line HK-2. To better model the intact kidney, we cultured human kidney organoids derived from induced pluripotent stem cells. We treated human kidney organoids grown using both three-dimensional and transwell protocols with CFH for 48 h. We found evidence for increased tubular toxicity, oxidative stress, mitochondrial fragmentation, endothelial cell injury and injury-associated transcripts compared to those of the untreated control group. To evaluate the protective effect of clinically available small molecules, we co-treated CFH-injured organoids with ascorbate (vitamin C) or acetaminophen for 48 h. We found significantly decreased toxicity, preservation of endothelial cells and reduced mitochondrial fragmentation in the group receiving ascorbate following CFH treatment. This study provides direct evidence that ascorbate or ascorbic acid protects human kidney cells from CFH-induced damage such as that in sepsis-associated acute kidney injury.

Role of myo-inositol in acute kidney injury induced by cisplatin

There is an increasing evidence suggesting that myo-inositol (MI) may be a renoprotective factor. Our previous study revealed that decreased MI concentrations and increased excretion are often observed in animal models of renal injury and in patients with nephropathy. However, the role of MI supplementation in renal injury remains unclear. In this study, we aimed to explore the role of MI in cisplatin-induced acute kidney injury (AKI). We established a model of acute kidney injury caused by cisplatin (CDDP). Male Kunming mice were randomly divided into six groups: Sham (normal saline), CDDP (15 mg/kg), + MI (150 mg/kg), + MI (300 mg/kg), + MI (600 mg/kg) and MI (600 mg/kg). Human renal tubular epithelial cell line HK-2 cells were likewise separated into six groups at random: Control (normal saline), CDDP (20 µM), + MI (200 µM), + MI (400 µM), + MI (800 µM) and MI (800 µM). After the model was established, renal function indexes were subsequently detected, and experiments such as pathological staining analysis and protein expression analysis were performed. Our results showed that cisplatin administration led to AKI and apoptosis in mice and HK-2 cells, accompanied by markedly increased levels of MIOX, kidney injury molecule-1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL), whereas exogenous MI significantly attenuated kidney injury and HK-2 cell damage induced by cisplatin both in vivo and in vitro by inhibiting excessive apoptosis. Overall, our findings demonstrate that exogenous MI can reduce excessive apoptosis, thus playing a protective role in cisplatin-induced AKI, indicating that exogenous MI may be used as an adjunctive treatment modality in cisplatin-induced AKI.

HK-2 cell response to TGF-β highly depends on cell culture medium formulations

The immortalized human renal proximal tubular epithelial cell line HK-2 is most commonly used to study renal cell physiology and human kidney diseases with tubulointerstitial fibrosis such as diabetic nephropathy, obstructive uropathy or allograft fibrosis. Epithelial-to-mesenchymal transition (EMT) is the main pathological process of tubulointerstitial fibrosis in vitro. Transforming growth factor-beta (TGF-β) is a key inducer of EMT. Several pro-fibrotic gene expression differences have been observed in a TGF-β-induced EMT model of HK-2 cells. However, growth conditions and medium formulations might greatly impact these differences. We investigated gene and protein expression of HK-2 cells cultured in six medium formulations. TGF-β1 increased the expression of ACTA2, TGFB1, COL4A1, EGR2, VIM and CTGF genes while reducing PPARG in all medium formulations. Interestingly, TGF-β1 treatment either increased or decreased EGR1, FN, IL6 and C3 gene expression, depending on medium formulations. The cell morphology was slightly affected, but immunoblots revealed TGFB1 and vimentin protein overexpression in all media. However, fibronectin expression as well as the nuclear translocation of EGR1 was medium dependent. In conclusion, our study demonstrates that, using the HK-2 in vitro model of EMT, the meticulous selection of appropriate cell culture medium formulation is essential to achieve reliable scientific results.

Dietary docosahexaenoic acid plays an opposed role in ferroptotic and non-ferroptotic acute kidney injury

Ferroptosis due to polyunsaturated fatty acid (PUFA) peroxidation has been implicated in the pathogenesis of acute kidney injury (AKI), suggesting the risk of dietary intake of PUFA for people susceptible to AKI. Clinically, however, in addition to ferroptosis, other mechanisms also contribute to different types of AKI such as inflammation associated necroptosis and pyroptosis. Therefore, the role of PUFA, especially ω3 PUFA which is a common food supplement, in various AKIs deserves further evaluation. In this study, rhabdomyolysis- and folic acid-induced AKI (Rha-AKI and FA-AKI) were established in mice fed with different fatty acids Histology of kidney, blood urea nitrogen and creatinine, lipid peroxidation, and inflammatory factors were examined. Results showed that these two types of AKIs had diametrically different pathogenesis indicated by that ferrostatin-1 (Fer-1), a lipid antioxidant, can attenuate FA-AKI rather than Rha-AKI. Further, dietary DHA (provided by fish oil) reduced tubular injury and renal lesion by inhibiting peroxidation and inflammation in mice with Rha-AKI while increasing cell death, tissue damage, peroxidation and inflammation in mice with FA-AKI. In human renal tubular epithelial cell line HK-2, MTT assay and DHE staining showed that both myoglobin and ferroptosis inducers can cause cell death and oxidative stress. Ferroptosis inducer-induced cell death was promoted by DHA, while such result was not observed in myoglobin-induced cell death when adding DHA. This study illustrates that the mechanisms of AKI might be either ferroptosis dependent or -independent and the deterioration effect of dietary DHA depends on whether ferroptosis is involved.

Exosomal microRNA-342-5p secreted from adipose-derived mesenchymal stem cells mitigates acute kidney injury in sepsis mice by inhibiting TLR9

BackgroundSepsis-related acute kidney injury (AKI) is an inflammatory disease associated with extremely high mortality and health burden. This study explored the possibility of exosomes secreted by adipose-derived mesenchymal stem cells (AMSCs) serving as a carrier for microRNA (miR)-342-5p to alleviate sepsis-related AKI and investigated the possible mechanism.MethodsSerum was obtained from 30 patients with sepsis-associated AKI and 30 healthy volunteers for the measurement of miR-342-5p, blood urea nitrogen (BUN), and serum creatinine (SCr) levels. For in vitro experiments, AMSCs were transfected with LV-miR-342-5p or LV-miR-67 to acquire miR-342-5p-modified AMSCs and miR-67-modified AMSCs, from which the exosomes (AMSC-Exo-342 and AMSC-Exo-67) were isolated. The human renal proximal tubular epithelial cell line HK-2 was induced by lipopolysaccharide (LPS) to construct a cellular model of sepsis. The expression of Toll-like receptor 9 (TLR9) was also detected in AKI cells and mouse models. The interaction between miR-342-5p and TLR9 was predicted by dual luciferase reporter gene assay.ResultsDetection on clinical serum samples showed that BUN, SCr, and TLR9 were elevated and miR-342-5p level was suppressed in the serum of patients with sepsis-associated AKI. Transfection with LV-miR-342-5p reinforced miR-342-5p expression in AMSCs and AMSC-secreted exosomes. miR-342-5p negatively targeted TLR9. LPS treatment enhanced TLR9 expression, reduced miR-342-5p levels, suppressed autophagy, and increased inflammation in HK-2 cells, while the opposite trends were observed in LPS-induced HK-2 cells exposed to AMSC-Exo-342, Rapa, miR-342-5p mimic, or si-TLR9. Additionally, the effects of AMSC-Exo-342 on autophagy and inflammation in LPS-induced cells could be weakened by 3-MA or pcDNA3.1-TLR9 treatment. Injection of AMSC-Exo-342 enhanced autophagy, mitigated kidney injury, suppressed inflammation, and reduced BUN and SCr levels in sepsis-related AKI mouse models.ConclusionmiR-342-5p transferred by exosomes from miR-342-5p-modified AMSCs ameliorated AKI by inhibiting TLR9 to accelerate autophagy.Graphical

Amelioration of Cyclosporine A-Induced Acute Nephrotoxicity by Cordyceps cicadae Mycelia via Mg+2 Reabsorption and the Inhibition of GRP78-IRE1-CHOP Pathway: In Vivo and In Vitro.

Fruiting bodies of Cordyceps cicadae (CC) have been reported to have a therapeutic effect in chronic kidney disease. Due to the rare and expensive resources from natural habitats, artificially cultivated mycelia using submerged liquid cultivation of CC (CCM) have been recently developed as an alternative to scarce sources of CC. However, little is known regarding potential protective effects of CCM against cyclosporine A (CsA)-induced acute nephrotoxicity in vivo and in vitro. In this study, male Sprague-Dawley rats were divided into six groups: control, CCM (40 mg and 400 mg/kg, orally), CsA (10 mg/kg, oral gavage), and CsA + CCM (40 mg and 400 mg/kg, orally). At the end of the study on day 8, all rats were sacrificed, and the blood and kidneys retrieved. CsA-induced acute nephrotoxicity was evident by increased levels of blood urea nitrogen (BUN). Levels of the endoplasmic reticulum (ER) resident chaperone glucose regulated protein 78 (GRP 78) were increased significantly in rats with acute nephrotoxicity. BUN and GRP 78 were significantly ameliorated in synchronous oral groups of CCM (40 or 400 mg/kg) plus CsA. Examination of hematoxylin and eosin stained kidney tissues revealed that the combined treatment of CCM slightly improved vacuolization in renal tubules upon CsA-induced damage. CsA-induced down-regulation of protein expression of magnesium ion channel proteins and transient receptor potential melastatin 6 and 7 were abolished by the combined treatment of CCM. CCM has the potential to protect the kidney against CsA-induced nephrotoxicity by reducing magnesium ion wasting, tubular cell damage, and ER stress demonstrated further by human renal proximal tubular epithelial cell line HK-2. Our results contribute to the in-depth understanding of the role of polysaccharides and nucleobases as the main secondary metabolites of CCM in the defense system of renal functions in CsA-induced acute nephrotoxicity.

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.

Gallic acid ameliorates calcium oxalate crystal-induced renal injury via upregulation of Nrf2/HO-1 in the mouse model of stone formation

BackgroundHigh prevalence and reoccurrence rate of nephrolithiasis bring about serious socioeconomic and healthcare burden, necessitating the need of effective therapeutic agents. Previous study revealed that gallic acid (GAL) alters the nucleation pathway of calcium oxalate (CaOx). On the other hand, it appears protective role against oxidative injury. Whether GAL could protect against crystal-induced lesion in vivo, and its underlying mechanism is yet unsolved. PurposeThis study aims to investigate the protective effects of GAL on the crystal-induced renal injury and its underlying mechanism in the mouse model of stone formation induced by glyoxylic acid. Study design and methodsThe mouse model of stone formation was established via successive intraperitoneal injection of glyoxylate. Proximal tubular epithelial cell line HK-2 treated with calcium oxalate monohydrate (COM) was used as in vitro model. The protective role of GAL on nephrolithiasis was tested by determination of tubular injury, crystal deposition and adhesion, levels of inflammatory cytokines, macrophage infiltration and the redox status of kidney. In vitro, effect of GAL on the ROS level and oxidative tubular injury induced by COM were detected, as well as major antioxidant pathway Nrf2/HO-1. ResultsAdministration of GAL alleviates the renal deposition and adhesion of CaOx stone. Meanwhile, GAL ameliorates the inflammation and renal tubular injury. Level of intracellular ROS, osteopontin and CD44 are reduced, either in the mouse model of stone formation or in the COM-treated HK-2 cells after treatment of GAL. Mechanistically, GAL activates Nrf2/HO-1 pathway in HK-2 cells. Silencing Nrf2 abrogates the protective effect of GAL on the oxidative injury and adhesion of COM in HK-2 cells. ConclusionTaken together, our study demonstrates the protective effect of GAL on the deposition of kidney stone and consequent tubular injury. Induction of the antioxidant pathway Nrf2/HO-1 was found to decrease the level of ROS and oxidative injury, thus implying that GAL could be a potential therapeutic agent for the treatment of nephrolithiasis.

FC 132: Deficiency of Proximal Tubular Cyclin-Dependent Kinase 12 Exacerbates Kidney Injury Through DNA-Damage Response

Abstract BACKGROUND AND AIMS Acute kidney injury (AKI) is a frequent, serious condition characterized by acute tubular necrosis involving the destruction of tubular epithelial cells. Recent studies have shown that DNA damage contributes to renal tubular cell death during kidney injury. Cyclin-dependent kinase 12 (CDK12) is a member of the cyclin-dependent kinase family that phosphorylates the carboxy-terminal domain of RNA polymerase II and selectively regulates transcription of DNA-damage response (DDR) genes. CDK12 inhibitor was reported to play an important role in a variety of cancers. So far, the functions of CDK12 deficiency in the pathogenesis of AKI have not been studied. METHOD Here, we established a cisplatin-induced AKI mouse model with CDK12 knockdown mice and created stable in vitro models with CDK12 knockdown tubular epithelial cells. Cisplatin nephrotoxicity was induced by intraperitoneal injection of cisplatin (20 mg/kg). After 2 days following cisplatin treatment, blood and kidney tissues were harvested. Renal function and histology were evaluated. DDR, tubular apoptosis, cell proliferation were evaluated by immunofluorescence assays, real-time PCR, flow cytometer and western blot analysis. RESULTS Here we found that CDK12 was downregulated in the renal tubular epithelial cells of AKI patients and murine AKI models and associated with kidney functions. RNA-sequencing of kidney cortex demonstrated increased transcripts involved in DDR and tubular apoptosis signaling pathways and decreased transcripts cell proliferation pathways, in knockout versus control mice. Moreover, more severe AKI occurred in tubular cell-specific knock-down of CDK12 mice (CDK12RTEC+/–) than age- and sex-matched wild type mice, as evidenced by increased levels of serum creatinine (Scr), blood urea nitrogen (BUN) and tubular injury score. Mechanistically, CDK12 deficiency accelerated cisplatin-induced DDR, mitochondrial apoptosis and abrogates cell proliferation of renal tubular cells in these mice. Similar results were observed after the human renal tubular epithelial cell line HK-2 cells exposure to CDK12 siRNA stimulation. In contrast, lentivirus-mediated CDK12 overexpression protected against DDR and mitochondrial apoptosis while attenuating renal dysfunction, morphological damage and renal tubular cell death in cisplatin-induced AKI models. Moreover, representative Integrative Genomics Viewer (IGV) profiles demonstrated a minimal impact of gene length-dependent elongation defects, a substantial proportion of which participate in the DDR and cell proliferation. CONCLUSION Thus, proximal tubule-specific deficiency of CDK12 exacerbates acute kidney injury and tubular apoptosis, likely due to affecting the expression of genes involved in the DDR and mRNA processing.

Scutellarin alleviates lipopolysaccharide-induced renal injury via mediating cysteine-rich protein 61-connective tissue growth factor-nephroblastoma overexpressed gene 1 expression to inhibit nuclear factor-κB signaling pathway

To explore the protective effect and mechanism of scutellarin (Scu) on sepsis associated-acute kidney injury (SA-AKI). (1) In vivo experiment: 36 male C57BL/6 mice were divided into normal saline (NS) control group, lipopolysaccharide (LPS) induced SA-AKI model group (LPS group), 20 mg/kg Scu control group (Scu 20 control group), and 5, 10, 20 mg/kg Scu pretreatment groups by random number table with 6 mice in each group. The SA-AKI model was reproduced by intraperitoneal injection of 10 mg/kg LPS. The NS control group was injected with NS intraperitoneally. The Scu pretreatment groups were intraperitoneally injected with different doses of Scu every day before LPS injection for 1 week. Scu 20 control group was injected with 20 mg/kg Scu for 1 week. After 24 hours of LPS treatment, mice in each group were sacrificed, kidney tissues were collected, and kidney injury was detected by hematoxylin-eosin (HE) staining. Western blotting was used to detect the protein expression levels of nuclear factor-κB (NF-κB) signaling pathway related molecules, apoptosis-related proteins and cysteine-rich protein 61-connective tissue growth factor-nephroblastoma overexpressed gene 1 (CCN1). (2) In vitro experiment: human renal tubular epithelial cell line HK-2 was cultured in vitro and used for experiment when the cells fused to 80%. In the cells without LPS treatment and after 100 g/L LPS treatment, pcDNA3.1-CCN1 and small interfering RNA (siRNA) CCN1 sequence were transfected to overexpress and inhibit CCN1 expression, respectively, to observe whether CCN1 was involved in NF-κB signaling pathway activation and apoptosis. In addition, 100g/L LPS and 20 μmol/L Scu were added into HK-2 cells transfected with and without CCN1 siRNA to investigate the mechanism of protective effect of Scu on LPS-induced HK-2 cells injury. (1) The results of in vivo experiment: the renal function of SA-AKI mice induced by LPS was significantly decreased, and had kidney histological damage and severely damaged renal tubules. Scu could alleviate renal function and histological damage in a dose-dependent manner. Western blotting results showed Scu could reduce the protein expression of NF-κB signaling pathway related molecules and CCN1 in the renal tissue, and had a significant alleviating effect on apoptosis, indicating that CCN1 was involved in NF-κB signaling pathway activation and apoptosis. (2) The results of in vitro experiment: in HK-2 cells not treated with LPS, CCN1 overexpression had no effect on apoptosis related protein and pro-inflammatory factors of NF-κB signaling pathway. In HK-2 cells treated with LPS, overexpression of CCN1 significantly inhibited the mRNA expressions of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1), with significant differences as compared with cells stimulated only by LPS [IL-1β mRNA (2-ΔΔCT): 3.20±0.57 vs. 4.88±0.69, TNF-α mRNA (2-ΔΔCT): 2.99±0.44 vs. 5.00±0.81, MCP-1 mRNA (2-ΔΔCT): 2.81±0.50 vs. 5.41±0.75, all P < 0.05], and the apoptosis-related protein was significantly down-regulated. However, when siRNA was used to inhibit the expression of CCN1, the mRNA expressions of pro-inflammatory factors were significantly increased as compared with cells stimulated only by LPS [IL-1β mRNA (2-ΔΔCT): 6.01±1.13 vs. 4.88±0.69, TNF-α mRNA (2-ΔΔCT): 5.15±0.86 vs. 5.00±0.81, all P < 0.05], and apoptosis-related protein was significantly up-regulated. In the LPS-induced HK-2 cells, the mRNA expressions of pro-inflammatory factors were significantly down-regulated after Scu treatment as compared with cells stimulated only by LPS [IL-1β mRNA(2-ΔΔCT): 2.55±0.50 vs. 6.15±1.04, TNF-α mRNA (2-ΔΔCT): 2.58±0.40 vs. 3.95±0.52, MCP-1 mRNA (2-ΔΔCT): 2.64±0.44 vs. 6.21±0.96, all P < 0.05], and apoptosis-related protein was also significantly reduced. When the expression of CCN1 was inhibited by siRNA, the protective effect of Scu on cells was weakened, which showed that the mRNA expressions of pro-inflammatory factors in cells was significantly up-regulated compared with the cells without inhibition of CCN1 expression [IL-1β mRNA (2-ΔΔCT): 5.34±0.76 vs. 2.55±0.50, TNF-α mRNA (2-ΔΔCT): 3.66±0.54 vs. 2.58±0.40, MCP-1 mRNA (2-ΔΔCT): 5.15±0.79 vs. 2.64±0.44, all P < 0.05], and the expression of apoptosis related protein was also significantly up-regulated. Scu could protect the renal function in SA-AKI mice, and the protective effect is associated with NF-κB signaling pathway and CCN1. Thus, Scu could alleviate LPS-induced kidney injury by regulating the NF-κB signaling pathway.

In vitro study on effect of bardoxolone methyl on cisplatin-induced cellular senescence in human proximal tubular cells

Bardoxolone methyl [methyl-2-cyano-3, 12-dioxooleana-1, 9(11)dien-28-oate (CDDO-Me)], an activator of the nuclear factor erythroid-derived 2-related factor2 pathway, is a potential therapeutic candidate for the treatment of kidney diseases. However, its effect against cellular senescence remains unclear. This study aimed to investigate whether CDDO-Me protects cells against cisplatin-induced cellular senescence using an in vitro model. The human renal proximal tubular epithelial cell line HK-2 was treated with cisplatin for 6 h, followed by treatment with or without CDDO-Me (0.1 or 0.2 μmol/L). Senescence markers were analyzed using western blotting and real-time PCR. Apoptosis was evaluated through TUNEL staining. Cisplatin induced changes in the levels of markers specific for proliferation, cell cycle, and senescence in a time- and dose-dependent manner. Furthermore, IL-6 and IL-8 levels in the culture medium increased markedly. These data suggested that cellular senescence-like alterations occurred in HK-2 cells exposed to cisplatin. CDDO-Me treatment reversed the cisplatin-mediated alterations in the levels of cellular senescence markers. The antioxidant enzymes, HO1, NQO1, GPX1, and CAT were upregulated by CDDO-Me treatment. Furthermore, CDDO-Me treatment induced apoptosis in cisplatin-exposed HK-2 cells. Pretreatment with Ac-DEVD-CHO, the caspase inhibitor, suppressed the reversal effect of CDDO-Me against cisplatin-induced cellular senescence-like alterations. This study showed that CDDO-Me attenuated cisplatin-induced premature senescence of HK-2 cells. This beneficial effect may be related to Nrf2 activation. Our findings also showed that CDDO-Me induced apoptosis in cisplatin-treated HK-2 cells, potentially protecting the kidneys from cellular senescence. CDDO-Me appears to be a candidate treatment for acute kidney injury.

Glaucocalyxin A Ameliorates Hypoxia/Reoxygenation-Induced Injury in Human Renal Proximal Tubular Epithelial Cell Line HK-2 Cells

Ischemia-reperfusion injury is one of the major causes of acute kidney injury (AKI), which is increasingly prevalent in clinical settings. Glaucocalxin A (GLA), a biologically ent-kauranoid diterpenoid, has various pharmacological effects like antioxidation, immune regulation, and antiatherosclerosis. In this study, the effect of GLA on AKI and its mechanism were studied in vitro. HK-2 human renal tubular epithelial cells were exposed to hypoxia/reoxygenation (H/R), which were established as an in vitro AKI model. Subsequently, the mRNA expressions of inflammatory and antioxidant factors were determined by quantitative reverse transcription polymerase chain reaction (RT-qPCR). Reactive oxygen species (ROS) production and cell death were detected by fluorescence-activated cell sorting. GLA pre-treatment improved the cell viability of HK-2 cells exposed to H/R. GLA suppressed the H/R-induced ROS production in HK-2 cells. GLA also elevated the activities of superoxide dismutase of HK-2 cells exposed to H/R. Moreover, GLA prevented H/R-induced cell death in HK-2 cells. Furthermore, GLA ameliorated the activation of the protein kinase B (Akt)/nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) signaling pathway in HK-2 cells exposed to H/R. Our findings suggested that GLA protected HK-2 cells from H/R-induced oxidative damage, which was mediated by the Akt/Nrf2/HO-1 signaling pathway. These results indicate that GLA may serve as a promising therapeutic drug for AKI.

Hirudin, a thrombin inhibitor, attenuates TGF-β-induced fibrosis in renal proximal tubular epithelial cells by inhibition of protease-activated receptor 1 expression via S1P/S1PR2/S1PR3 signaling.

Renal interstitial fibrosis (RIF) is the final common outcome of numerous chronic kidney diseases, contributing to end-stage renal disease. Hirudin, a thrombin inhibitor, has attracted increased attention as a potential treatment approach for renal fibrosis. The present study aimed to investigate the molecular mechanism underlying the effect of hirudin on fibrosis in renal proximal tubular epithelial cells. An in vivo mouse RIF model established using unilateral ureteral obstruction (UUO) and an in vitro of RIF using the renal tubular epithelial cell line HK-2 treated with TGF-β were used. Expressions of sphingosine-1-phosphate (S1P) receptors (S1PR)1-4 and protease-activated receptor 1 (PAR1) were measured by reverse transcription-quantitative PCR and western blotting in mice with UUO and TGF-β induced HK-2 cells. Western blotting was used to detect the expression of N-cadherin, Slug, E-cadherin, Collagen IV, fibronectin, MMP9 and monocyte chemoattractant protein-1. Immunofluorescence staining was conducted to measure α-SMA level expression. The results demonstrated that the expression levels of S1PR1, S1PR2, S1PR3, S1PR4 and PAR1 were upregulated in both TGF-β-induced HK-2 cells and renal tissues from mice with unilateral ureteral ligation. Notably, hirudin inhibited TGF-β-induced PAR1, S1PR2 and S1PR3 upregulation in both HK-2 cells and renal tissues. Additionally, the inhibition of S1PR2 and S1PR3 resulted in PAR1 downregulation. Furthermore, treatment with S1P and PAR1 agonists abolished the effect of hirudin on the expression of EMT, fibrosis-related proteins and monocyte chemoattractant protein 1. In conclusion, hirudin attenuated TGF-β-induced fibrosis in proximal renal tubular epithelial HK-2 cells by inhibiting PAR1 expression via the S1P/S1PR2/S1PR3 signaling pathway. Therefore, hirudin may be considered as a promising therapeutic agent for RIF.

Overexpression of TRIM3 protects against LPS-induced acute kidney injury via repressing IRF3 pathway and NLRP3 inflammasome.

The pathological process of sepsis involves multiple system organs, including kidney. Sepsis-induced acute kidney injury (AKI) has high morbidity and high mortality. Overproduced inflammatory factors contribute to the occurrence and evolvement of AKI. Here, the role and underlying mechanism of tripartite motif containing 3 (TRIM3) and in AKI was explored. Lipopolysaccharide (LPS) was used for constructing AKI model both in vitro and in vivo. RT-PCR and western blot were performed to detect TRIM3, Interferon regulatory factor 3 (IRF3) and NLRP3-ASC-Caspase1 inflammasome. Upon selectively regulating the TRIM3 or IRF3 expression, the proliferation, apoptosis and inflammatory response were detected. The interaction between TRIM3 and IRF3 was verified by Immunoprecipitation (IP). TRIM3 was down-regulated in mediated injury renal tubular epithelial cell line HK-2 treated with LPS. Overexpression of TRIM3 promoted cell viability and reduced apoptosis. In addition, overexpression of TRIM3 inhibited the expression of inflammatory factors (IL-1β, IL-6, TNF-α and IL-18), dampened the phosphorylation of IRF3 and repressed NLRP3 inflammasome activation. Furthermore, TRIM3 overexpression significantly eased the LPS-induced damage on AKI rat model and decreased the serum creatinine and urea nitrogen levels in rat kidney tissues. The results of immunohistochemistry (IHC) and Western blot manifested that TRIM3 was increased dramatically after TRIM3 was overexpressed in the rat kidney tissues, while IRF3 and NLRP3-ASC-Caspase1 inflammasome were significantly repressed following TRIM3 upregulation in the kidney tissues. Mechanistically, TRIM3 interacted with IRF3 and inhibited its phosphorylation. Overexpression of TRIM3 protected against LPS-induced AKI by inhibiting the IRF3 pathway and NLRP3 inflammasome activation.

Alamandine, a derivative of angiotensin-(1-7), alleviates sepsis-associated renal inflammation and apoptosis by inhibiting the PI3K/Ak and MAPK pathways

Sepsis is a frequent cause of kidney injury. The present study investigated whether Alamandine (Ala) could alleviate sepsis-associated renal injury by reducing inflammation and apoptosis. In addition, we investigated downstream signaling pathways modulated by Ala. Studies were performed in mice treated with lipopolysaccharide (LPS) and in the human proximal tubular epithelial cell line HK-2. The increase in serum creatinine, blood urea nitrogen, cystatin C and Fg, and neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 in the kidneys of mice treated with LPS were reduced after administration of Ala. Exposure to LPS increased interleukin-1 beta (IL-1β), IL-6, and tumor necrosis factor alpha (TNF-α) in mice and HK-2 cells, but were reduced after Ala treatment. Furthermore, increased levels of cleaved caspase 3, cleaved caspase 7, cleaved caspase 9, cleaved poly (ADP-ribose) polymerase (PARP) and Bax and reduced levels of Bcl2 in LPS-treated mice and HK-2 cells were reversed after Ala administration. In addition, LPS increased the levels of p-PI3K/PI3K, p-Akt/Akt, p-ERK/ERK, p-JNK/JNK, p-p38/p38 and p-FoxO1 in HK-2 cells, and all were reversed after Ala administration. These results indicate that Ala could improve renal function and inhibit inflammation and apoptosis in LPS induced sepsis mouse models. We demonstrated that Ala attenuated LPS induced sepsis by inhibiting the PI3K/Akt and MAPK signaling pathways.

MiR-150-5p protects against septic acute kidney injury via repressing the MEKK3/JNK pathway

BackgroundSeptic acute kidney injury (AKI) is associated with increased morbidity and mortality in critically ill patients. MicroRNA is reportedly involved in sepsis-induced organ dysfunction, while the role of miR-150 in septic AKI remains ambiguous. MethodsQuantitative real-time PCR (qRT-PCR) was carried out to examine miR-150-5p expression in both septic AKI patients and volunteers without septic AKI. Lipopolysaccharide (LPS) was used to treat renal tubular epithelial cell line HK-2 and C57/BL6 mice to establish in vitro and in vivo sepsis-induced AKI models. Cell apoptosis was determined using TdT-mediated dUTP nick end labeling (TUNEL) staining and flow cytometry. Cell viability was tested using a 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Renal pathological changes were examined via Hematoxylin-Eosin (H&E) staining, and renal function was measured via blood urea nitrogen (BUN) and creatinine (Cre) measurements. The MEKK3/JNK profile and oxidative stress markers (including COX2 and iNOS) were examined by immunoblot analysis, and the expression levels of inflammatory cytokines (TNF-α, IL-6, and IL-1β) and oxidative stress markers (MDA, SOD, and CAT) were evaluated by ELISA. ResultsMiR-150-5p was down-regulated in the serum of patients with septic AKI (compared to healthy volunteers). Moreover, miR-150-5p levels were lower in LPS-treated HK-2 cell lines and in the septic AKI mouse model. Additionally, Stat-3 activation mediated the decrease of miR-150-5p. Functionally, miR-150-5p agomir attenuated LPS-induced apoptosis in HK-2 cells, in addition to renal inflammatory responses and oxidative stress. In contrast, inhibition of miR-150-5p aggravated LPS-induced apoptosis, inflammatory reactions and oxidative stress. Furthermore, miR-150-5p agomir decreased BUN and Scr levels in the septic AKI mice model repressed TNF-α, IL-6 and IL-1β, and up-regulated SOD and CAT down-regulated MDA in the kidney tissues. Moreover, miR-150-5p was identified as a target gene for Stat3, and the overexpression of Stat3 partially promoted the effect of down-regulating miR-150-5p on LPS-induced HK2 cell injury. Mechanistically, the MEKK3/JNK pathway was identified as a functional target of miR-150-5p, and the knockdown of MEKK3 showed protective effects against LPS mediated HK-2 cell apoptosis. ConclusionStat3-mediated miR-150-5p exerted protective effects in sepsis-induced acute kidney injury by regulating the MEKK3/JNK pathway.

Pharmacologically Inhibiting Glycogen Synthase Kinase-3β Ameliorates Renal Inflammation and Nephrotoxicity in an Animal Model of Cisplatin-Induced Acute Kidney Injury.

The adverse effect of cisplatin administration causes acute kidney injury (AKI) following renal inflammation and nephrotoxicity, characterized by proximal tubular cell apoptosis and necrosis. Pro-apoptotic and pro-inflammatory roles of glycogen synthase kinase (GSK)-3β have been reported. This study investigated the therapeutic blockade of GSK-3β in cisplatin-induced AKI. A renal cisplatin nephrotoxicity model showed activation of GSK-3β in vivo, particularly in proximal tubular epithelial cells. Pharmacologically inhibiting GSK-3β abolished cisplatin nephrotoxicity, including proximal tubular injury, cell cytotoxicity, and biochemical dysfunction. Additionally, GSK-3β inhibitor treatment ameliorated renal inflammation by reducing immune cell infiltration, cell adhesion molecule expression, and pro-inflammatory cytokine/chemokine production. Cisplatin treatment caused GSK-3β activation in vitro in the human renal proximal tubular epithelial cell line HK-2, whereas either pharmacological administration of GSK-3β inhibitors or genetic transduction of GSK-3β short-hairpin RNA impeded cisplatin-induced cytotoxicity. These results indicate that cisplatin activates GSK-3β followed by GSK-3β-mediated renal inflammation and nephrotoxicity, contributing to AKI.

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.