Human Kidney Tubular Cells Research Articles

Palmitic acid complexed with control or advanced glycated albumin primes human kidney tubular cells to inflammation

Palmitic acid complexed with control or advanced glycated albumin primes human kidney tubular cells to inflammation

Marrow mesenchymal stem cell mediates diabetic nephropathy progression via modulation of Smad2/3/WTAP/m6A/ENO1 axis.

Diabetic nephropathy (DN) is one of the common microvascular complications in diabetic patients. Marrow mesenchymal stem cells (MSCs) have attracted attention in DN therapy but the underlying mechanism remains unclear. Here, we show that MSC administration alleviates high glucose (HG)-induced human kidney tubular epithelial cell (HK-2 cell) injury and ameliorates renal injury in DN mice. We identify that Smad2/3 is responsible for MSCs-regulated DN progression. The activity of Smad2/3 was predominantly upregulated in HG-induced HK-2 cell and DN mice and suppressed with MSC administration. Activation of Smad2/3 via transforming growth factor-β1 (TGF-β1) administration abrogates the protective effect of MSCs on HG-induced HK-2 cell injury and renal injury of DN mice. Smad2/3 has been reported to interact with methyltransferase of N6-methyladenosine (m6A) complex and we found a methyltransferase, Wilms' tumor 1-associating protein (WTAP), is involved in MSCs-Smad2/3-regulated DN development. Moreover, WTAP overexpression abrogates the improvement of MSCs on HG-induced HK-2 cell injury and renal injury of DN mice. Subsequently, α-enolase (ENO1)is the downstream target of WTAP-mediated m6A modification and contributes to the MSCs-mediated regulation. Collectively, these findings reveal a molecular mechanism in DN progression and indicate that Smad2/3/WTAP/ENO1 may present a target for MSCs-mediated DN therapy.

#1955 Ferroptotic proteins ACSL4 and ALOX15 as therapeutic targets in AKI

Abstract Background and Aims Ferroptosis is a regulated form of necrosis which is dependent on cellular iron and is characterized by the accumulation of lipid peroxides and failure of cellular antioxidant defences. We have previously described in vivo that ferroptosis is the primary cause of folic acid-induced acute kidney injury (FA-AKI) and that necroinflammation secondary to ferroptosis may further worsen kidney injury, since ferroptosis inhibition improved kidney function and decreased tubular cell death and oxidative stress. Acyl-CoA synthetase long-chain family member 4 (ACSL4) is involved in the incorporation of polyunsaturated fatty acid (PUFA) into membranes, while 15-Lipoxygenase (Alox15) catalyzes the regio- and enantioselective peroxidation of membrane-esterified PUFAs, forming the ultimate peroxidized species that induce ferroptosis. In the present work, we aim to explore the potential of both proteins as therapeutic targets in AKI, as well as the molecular characterization of kidney ferroptosis in cultured tubular cells. Method Animal model: Female 12- to 14-week-old C57BL/6J wild type mice received a single intraperitoneal (i.p) injection of folic acid or vehicle and were sacrificed 48 hours later. Troglitazone was intravenously administered for in vivo ACSL4 inhibition, and Compound 1 was i.p administered for in vivo ALOX15 inhibition. In vitro characterization of ferroptosis: HK2 human tubular kidney cells were incubated with arachidonic acid (AA) prior to sublethal RSL3 administration for sensitization to ferroptosis. We used Ferrostatin-1 (Fer-1) and Liproxstatin-1 (Lpx-1) as inhibitors of ferroptosis. The thiazolidinedione family members Rosiglitazone, Pioglitazone and Troglitazone were used as pharmacological inhibitors of ACSL4. We also performed transcriptional silencing of ACSL4 using a specific siRNA. Compound 1 and PD1646 were administered for in vitro Alox15 inhibition. Cellular lipid peroxidation was analyzed by flow cytometry with Bodipy 581/591 staining. To characterize the lipid signature of ferroptotic cells, supernatants were collected and 15-HETEs levels were measured by ELISA. Oxido-lipidomic analysis of ferroptotic cells was performed by LC-MS. Real Time PCR and Western Blot of whole kidneys and cultured cells were performed for the detection and quantification of ACSL4 and ALOX15. Cell death was assessed by measurement of cell viability (MTT assay) and cytotoxicity (LDH assay). Tissue cell death was assessed by TUNEL. Results Kidney transcriptomics identified Acsl4 as the most upregulated member of Acsl family during FA-AKI. This was validated at mRNA and protein levels. Supplementation with AA, the preferred ACSL4 substrate, sensitized HK2 tubular cells to ferroptosis under sublethal RSL3 conditions, and this was prevented with specific ferroptosis inhibitors Fer-1 and Lpx-1. Pharmacological inhibition of ACSL4 with Troglitazone and a specific siRNA protected from cell death and lipid peroxidation induced by co-stimulation of AA and RSL3 in HK2 cells. Likewise, ALOX15 proteins levels were also increased in FA-AKI at 48 hours. PD1646 and Compound 1, both used to inhibit ALOX15, protected from ferroptotic cell death and lipid peroxidation in HK2 cells. Lipidomic analysis on HK2 tubular cells stimulated with AA+RSL3 uncovered an increased content of key peroxidized lipid species involved in ferroptosis execution, which was alleviated by targeting ACSL4 or ALOX15. Additionally, renal function of FA-AKI in mice was improved by ACSL4 pharmacological inhibition with Troglitazone and with ALOX15 inhibition with Compound 1. Conclusion Our preliminary results suggest therapeutic potential of ACSL4 and ALOX15 as ferroptotic targes during AKI. High PUFA content sensitizes human tubular HK2 cells to cell death and lipid peroxidation in the presence of sublethal ferroptotic triggers, and this was prevented by targeting ACSL4 or ALOX15 both in vitro and in vivo in FA-AKI. Closely related lipid peroxide species were decreased by ACSL4 or ALOX15 inhibitors.

Network pharmacology and experimental validation to investigate the mechanism of Nao-Ling-Su capsule in the treatment of ischemia/reperfusion-induced acute kidney injury

Ethnopharmacological relevanceNao-Ling-Su Capsule (NLSC) is a traditional prescription, which is composed of fifteen herbs such as epimedium, Polygala tenuifolia, and Schisandra chinensis. It has the effect of strengthening the brain, calming nerves, and protecting the kidney, which has been used clinically for many years to strengthen the brain and kidney. However, the effect of NLSC in the treatment of acute kidney injury (AKI) is still unclear. Aim of the studyThe present study aims to elucidate the pharmacological actions of NLSC in the treatment of AKI. Materials and methodsMolecular targets for NLSC and AKI were obtained from various databases, and then we built networks of interactions between proteins (PPI) by employing string databases. Additionally, we employed the DAVID database to conduct gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses. Molecular docking was conducted to analyze the interaction between core components and their corresponding core targets. Next, the C57BL male mice model of ischemia/reperfusion damage (IRI) was developed, and the nephridial protective effect of NLSC was evaluated. The accuracy of the expected targets was confirmed using real-time quantitative polymerase chain reaction (RT-qPCR). The renal protective effect of NLSC was assessed using an immortalized human kidney tubular (HK-2) cell culture produced by oxygen-glucose deprivation (OGD). ResultsNetwork pharmacology analysis identified 199 common targets from NLSC and AKI. STAT3, HSP90AA1, TP53, MAPK3, JUN, JAK2, and VEGFA could serve as potential drug targets and were associated with JAK2/STAT3 signaling pathway, PI3K-Akt signaling pathway, etc. The molecular docking analysis confirmed significant docking activity between the main bioactive components and core targets, including STAT3 and KIM-1. Moreover, the AKI mice model was successfully established and NLSC pretreatment could improve renal function and alleviate renal damage. NLSC could alleviate renal inflammation and tubular cell apoptosis, and decrease the expression of STAT3 and KIM-1 in AKI mice. In vitro, both NLSC and drug-containing serum may protect HK-2 cells by inhibiting STAT3 signaling, especially STAT3-mediated apoptosis and KIM-1 expression. ConclusionNLSC could alleviate renal inflammation and apoptosis, exerting its beneficial effects by targeting the STAT3/KIM-1 pathway. NLSC is a promising candidate for AKI treatment and provides a new idea and method for the treatment of AKI.

Kidney tubular epithelial cells control interstitial fibroblast fate by releasing TNFAIP8-encapsulated exosomes

Kidney fibrosis, characterized by the activation and expansion of the matrix-producing fibroblasts, is the common outcome of chronic kidney disease (CKD). While fibroblast proliferation is well studied in CKD, little is known about the regulation and mechanism of fibroblast depletion. Here, we show that exosomes derived from stressed/injured tubules play a pivotal role in dictating fibroblast apoptosis and fate. When human kidney tubular cells (HK-2) were stimulated with TGF-β1, they produced and released increased amounts of exosomes (TGFβ-Exo), which prevented renal interstitial fibroblasts from apoptosis. In vivo, injections of TGFβ-Exo promoted renal fibroblast survival, whereas blockade of exosome secretion accelerated fibroblast apoptosis in obstructive nephropathy. Proteomics profiling identified the tumor necrosis factor-α-induced protein 8 (TNFAIP8) as a key component enriched in TGFβ-Exo. TNFAIP8 was induced in renal tubular epithelium and enriched in the exosomes from fibrotic kidneys. Knockdown of TNFAIP8 in tubular cells abolished the ability of TGFβ-Exo to prevent fibroblast apoptosis. In vivo, gain- or loss- of TNFAIP8 prevented or aggravated renal fibroblast apoptosis after obstructive injury. Mechanistically, exosomal-TNFAIP8 promoted p53 ubiquitination leading to its degradation, thereby inhibiting fibroblasts apoptosis and inducing their proliferation. Collectively, these results indicate that tubule-derived exosomes play a critical role in controlling the size of fibroblast population during renal fibrogenesis through shuttling TNFAIP8 to block p53 signaling. Strategies to target exosomes may be effective strategies for the therapy of fibrotic CKD.

Carnosine alleviates kidney tubular epithelial injury by targeting NRF2 mediated ferroptosis in diabetic nephropathy.

Diabetic nephropathy (DN) can promote the occurrence of end-stage renal disease (ESRD). The injury of renal tubular epithelial cells is a significant reason for the occurrence of ESRD. A recent research demonstrated that ferroptosis was associated with renal tubular injury in DN. Ferroptosis is a kind of cell death brought on by the buildup of iron ions and lipid peroxidation brought on by ROS. Because carnosine (CAR) is a scavenger of iron ions and reactive oxygen species, we investigated whether CAR can improve DN by regulating ferroptosis. The results show that both CAR and Fer-1 significantly reduced kidney damage and inhibited ferroptosis in STZ mice. In addition, ferroptosis caused by HG or erastin (an inducer of ferroptosis) in human kidney tubular epithelial cell (HK2) was also rescued by CAR treatment. It was discovered that the protective effect of CAR against HG-induced ferroptosis was abolished when NRF2 was specifically knocked down in HK2 cells.

Transcriptomic Responses to Polymyxin B and Analogues in Human Kidney Tubular Cells.

Polymyxins are last-line antibiotics for the treatment of Gram-negative 'superbugs'. However, nephrotoxicity can occur in up to 60% of patients administered intravenous polymyxins. The mechanisms underpinning nephrotoxicity remain unclear. To understand polymyxin-induced nephrotoxicity, human renal proximal tubule cells were treated for 24 h with 0.1 mM polymyxin B or two new analogues, FADDI-251 or FADDI-287. Transcriptomic analysis was performed, and differentially expressed genes (DEGs) were identified using ANOVA (FDR < 0.2). Cell viability following treatment with polymyxin B, FADDI-251 or FADDI-287 was 66.0 ± 5.33%, 89.3 ± 3.96% and 90.4 ± 1.18%, respectively. Transcriptomics identified 430, 193 and 150 DEGs with polymyxin B, FADDI-251 and FADDI-287, respectively. Genes involved with metallothioneins and Toll-like receptor pathways were significantly perturbed by all polymyxins. Only polymyxin B induced perturbations in signal transduction, including FGFR2 and MAPK signaling. SIGNOR network analysis showed all treatments affected essential regulators in the immune system, autophagy, cell cycle, oxidative stress and apoptosis. All polymyxins caused significant perturbations of metal homeostasis and TLR signaling, while polymyxin B caused the most dramatic perturbations of the transcriptome. This study reveals the impact of polymyxin structure modifications on transcriptomic responses in human renal tubular cells and provides important information for designing safer new-generation polymyxins.

Inwardly rectifying potassium channels mediate polymyxin-induced nephrotoxicity

Polymyxin antibiotics are often used as a last-line defense to treat life-threatening Gram-negative pathogens. However, polymyxin-induced kidney toxicity is a dose-limiting factor of paramount importance and can lead to suboptimal treatment. To elucidate the mechanism and develop effective strategies to overcome polymyxin toxicity, we employed a whole-genome CRISPR screen in human kidney tubular HK-2 cells and identified 86 significant genes that upon knock-out rescued polymyxin-induced toxicity. Specifically, we discovered that knockout of the inwardly rectifying potassium channels Kir4.2 and Kir5.1 (encoded by KCNJ15 and KCNJ16, respectively) rescued polymyxin-induced toxicity in HK-2 cells. Furthermore, we found that polymyxins induced cell depolarization via Kir4.2 and Kir5.1 and a significant cellular uptake of polymyxins was evident. All-atom molecular dynamics simulations revealed that polymyxin B1 spontaneously bound to Kir4.2, thereby increasing opening of the channel, resulting in a potassium influx, and changes of the membrane potential. Consistent with these findings, small molecule inhibitors (BaCl2 and VU0134992) of Kir potassium channels reduced polymyxin-induced toxicity in cell culture and mouse explant kidney tissue. Our findings provide critical mechanistic information that will help attenuate polymyxin-induced nephrotoxicity in patients and facilitate the design of novel, safer polymyxins.

Effects of preoperative high-oral protein loading on short- and long-term renal outcomes following cardiac surgery: a cohort study

BackgroundPost-cardiac surgery acute kidney injury (AKI) is associated with increased mortality. A high-protein meal enhances the renal blood flow and glomerular filtration rate (GFR) and might protect the kidneys from acute ischemic insults. Hence, we assessed the effect of a preoperative high-oral protein load on post-cardiac surgery renal function and used experimental models to elucidate mechanisms by which protein might stimulate kidney-protective effects.MethodsThe prospective “Preoperative Renal Functional Reserve Predicts Risk of AKI after Cardiac Operation” study follow-up was extended to postoperative 12 months for 109 patients. A 1:2 ratio propensity score matching method was used to identify a control group (n = 214) to comparatively evaluate the effects of a preoperative protein load and standard care. The primary endpoints were AKI development and postoperative estimated GFR (eGFR) loss at 3 and 12 months. We also assessed the secretion of tissue inhibitor of metalloproteases-2 (TIMP-2) and insulin-like growth factor–binding protein 7 (IGFBP7), biomarkers implicated in mediating kidney-protective mechanisms in human kidney tubular cells that we exposed to varying protein concentrations.ResultsThe AKI rate did not differ between the protein loading and control groups (13.6 vs. 12.3%; p = 0.5). However, the mean eGFR loss was lower in the former after 3 months (0.1 [95% CI − 1.4, − 1.7] vs. − 3.3 [95% CI − 4.4, − 2.2] ml/min/1.73 m2) and 12 months (− 2.7 [95% CI − 4.2, − 1.2] vs − 10.2 [95% CI − 11.3, − 9.1] ml/min/1.73 m2; p < 0.001 for both). On stratification based on AKI development, the eGFR loss after 12 months was also found to be lower in the former (− 8.0 [95% CI − 14.1, − 1.9] vs. − 18.6 [95% CI − 23.3, − 14.0] ml/min/1.73 m2; p = 0.008). A dose–response analysis of the protein treatment of the primary human proximal and distal tubule epithelial cells in culture showed significantly increased IGFBP7 and TIMP-2 expression.ConclusionsA preoperative high-oral protein load did not reduce AKI development but was associated with greater renal function preservation in patients with and without AKI at 12 months post-cardiac surgery. The potential mechanisms of action by which protein loading may induce a kidney-protective response might include cell cycle inhibition of renal tubular epithelial cells.Clinical trial registration ClinicalTrials.gov: NCT03102541 (retrospectively registered on April 5, 2017) and ClinicalTrials.gov: NCT03092947 (retrospectively registered on March 28, 2017).

Ochratoxin A induces human kidney tubular epithelial cell apoptosis through regulating lipid raft/PTEN/AKT signaling pathway.

Ochratoxin A (OTA) is a fungal toxin that causes serious threat to human health. OTA could lead to the injury of various tissues, especially kidney injury. However, the toxic effects of OTA on human kidney tubular epithelial cell (HK-2) and the possible mechanism remains poorly understood. This study was to investigate the toxic effects of OTA on HK-2 and elucidate the molecular mechanism. HK-2 cells were treated OTA to evaluate the effect of OTA on cell viability and apoptosis. OTA inhibited the growth of HK-2 in a concentration-dependent manner. With the concentration increased, OTA significantly lead to the apoptosis of HK-2. OTA could increase the levels of reactive oxygen species (ROS) and Malondialdehyde (MDA). Superoxide dismutase (SOD) and glutathione (GSH) activities were decreased by OTA. Furthermore, OTA increased Caspase-3 and Bax expression and decreased BCL2 expression. Compared to the control group, the expression of PTEN was increased and the expression of PI3K and AKT were decreased in OTA treated groups. In addition, we found OTA could disrupt the formation of lipid raft by attenuating sphingomyelin and cholesterol levels. In conclusion, our results indicated that OTA induces apoptosis in HK-2 through regulating PTEN/AKT signaling pathway via disrupting lipid raft formation.

MEG3 aggravates hypoxia/reoxygenation inducedapoptosis of renal tubular epithelial cells via the miR-129-5p/HMGB1 axis.

The apoptosis of renal tubular epithelial cells (TECs) during ischemia/reperfusion (I/R) facilitates the progression of acute kidney injury (AKI). This study aimed to probe the role of long noncoding RNA maternally expressed 3 (MEG3) in I/R-induced apoptosis of TECs. In this study, with CoCl2 and hypoxia/reoxygenation treatments, cell models were established to mimic I/R using the human kidney tubular cell line HK-2. In HK-2 cells, expression of MEG3 detected using quantitative real-time polymerase chain reaction (qRT-PCR), was significantly upregulated after CoCl2 treatment and hypoxia/reoxygenation treatment. The results of cell counting kit-8 assay and flow cytometry suggested that knockdown of MEG3 significantly increased the viability of HK-2 cells but inhibited its apoptosis, while overexpression of MEG3 exerted the reverse effects. Additionally, expression levels of interleukin 6 and tumor necrosis factor-α in the medium were elevated after MEG3 was overexpressed in HK-2 cells. Together with qRT-PCR and Western blot analysis, a dual-luciferase reporter gene assay was used to verify the interactions among MEG3, miR-129-5p, and HMGB1. The results demonstrated that in HK-2 cells, miR-129-5p was a target of MEG3, and HMGB1 served as a target gene of miR-129-5p. Besides this, compared with the control group, the expression levels of MEG3 and HMGB1 in samples derived from AKI patients were remarkably upregulated, and the expression of miR-129-5p was downregulated. Therefore, taken together, we conclude that the overexpression of MEG3 induced by I/R promotes apoptosis of TECs via regulating the miR-129-5p/HMGB1 axis.

Cell Polarity Protein Pals1-Associated Tight Junction Expression Is a Favorable Prognostic Marker in Clear Cell Renal Cell Carcinoma.

Introduction: The Pals1-associated tight junction (PATJ) is a Crumbs (CRB) complex component that regulates epithelial cell apico-basal polarity and directional migration. This study assessed PATJ expression in clear cell renal cell carcinoma (ccRCC) vs. normal tissues and associated with ccRCC progression and prognosis. Methods: The effects of PATJ knockdown were investigated on regulation of normal kidney epithelial cell viability and protein expression in vitro. The PATJ mRNA data in ccRCC were obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases and analyzed with UALCAN, LinkedOmics, Kaplan-Meier Plotter, GEPIA, and SurvExpress tools. Immunohistochemistry was performed for PATJ in tissue microarray sections (n = 150 ccRCC and 30 normal renal specimens). Normal human kidney tubular epithelial cell (HKC) cells were transfected with PATJ and negative control siRNA for cell viability CCK-8 assay, flow cytometry, and western blots. Results: The data showed that PATJ mRNA and protein were downregulated in ccRCC tissues and cell lines. Downregulation of PATJ mRNA was associated with male patients, advanced tumor stages, grades, and ccB subtypes as well as poorer overall and disease-free survival of patients. Furthermore, PATJ protein was also significantly downregulated in ccRCC tissues and associated with advanced tumor pathologic, TNM stages and poorer overall. In vitro, knockdown of PATJ expression promoted HKC proliferation and the activation of mitogen-activated protein kinases (MAPK) pathway proteins. Conclusions: This study revealed that a decrease of PATJ in ccRCC, which was associated with male patients, advanced tumor, and poorer survival, suggesting that PATJ may be a useful prognostic biomarker and therapeutic target for ccRCC.

Circ_WBSCR17 aggravates inflammatory responses and fibrosis by targeting miR-185-5p/SOX6 regulatory axis in high glucose-induced human kidney tubular cells

BackgroundDiabetic nephropathy (DN), a severe microvascular complication of diabetes, has complex pathogenesis. Circular RNAs (circRNAs) exert broad biological functions on human diseases. This study intended to explore the role and mechanism of circ_WBSCR17 in DN. MethodsDN mice models were constructed using streptozotocin injection, and DN cell models were assembled using high glucose (HG) treatment in human kidney 2 cells (HK-2). The expression of circ_WBSCR17, miR-185-5p and SRY-Box Transcription Factor 6 (SOX6) was detected by quantitative real-time polymerase chain reaction (qRT-PCR). The protein levels of SOX6 and fibrosis markers were examined by western blot. The release of inflammatory cytokines, cell proliferation and apoptosis, were assessed by enzyme-linked immunosorbent assay (ELISA), cell counting kit-8 (CCK-8) assay and flow cytometry assay, respectively. The predicted interaction between miR-185-5p and circ_WBSCR17 or SOX6 was verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. ResultCirc_WBSCR17 was highly expressed in DN mice models and HG-induced HK-2 cells. Circ_WBSCR17 knockdown or SOX6 knockdown promoted cell proliferation and blocked cell apoptosis, inflammatory responses and fibrosis, while circ_WBSCR17 overexpression or SOX6 overexpression conveyed the opposite effects. MiR-185-5p was a target of circ_WBSCR17 and directly bound to SOX6. MiR-185-5p could reverse the role of circ_WBSCR17 or SOX6. Moreover, the expression of SOX6 was modulated by circ_WBSCR17 through intermediating miR-185-5p. ConclusionCirc_WBSCR17 triggered the dysfunction of HG-induced HK-2 cells, including inflammatory responses and fibrosis, which was accomplished via the miR-185-5p/SOX6 regulatory axis.

Lactoferrin Contributes a Renoprotective Effect in Acute Kidney Injury and Early Renal Fibrosis.

Patients with acute kidney injury (AKI) who survive the acute stage are at notable risk for chronic kidney disease (CKD) progression. There is no single therapy that can effectively prevent the AKI to CKD transition. Autophagy is a cytoplasmic component degradation pathway and has complex functions in several diseases, such as renal fibrosis. Previous research has shown that lactoferrin has important functions in antioxidant defense and other defense systems, protecting kidneys against various injuries. The present study investigated the effect of lactoferrin in protecting against the AKI to CKD transition. We identified 62 consensus genes with two-fold changes in clinical kidney tissues from AKI and CKD patients. Among the 62 overlay genes, the mRNA levels of LTF were significantly upregulated in the kidney tissues of AKI and CKD patients. Lactoferrin induced autophagy via the activation of the AMPK and inhibition of Akt/mTOR pathway in human kidney proximal tubular cells. Lactoferrin suppressed oxidative stress-induced cell death and apoptosis by augmenting autophagy. Lactoferrin has an antifibrotic role in human kidney tubular cells. In a mouse model of folic acid-induced AKI to CKD transition, treatment with lactoferrin recovered renal function and further suppressed renal fibrosis through the inhibition of apoptosis and the induction of autophagy. These findings identify lactoferrin as a potential therapeutic target for the prevention of the AKI to CKD transition.

LncRNA NEAT1 promotes hypoxia-induced renal tubular epithelial apoptosis through downregulating miR-27a-3p.

Acute kidney injury (AKI) is a common kidney disorder that affects public health and the incidence of AKI. Sepsis, acute ischemia or hypoxia is the main reason for the occurrence of AKI. Recently, noncoding RNA that include microRNA and long noncoding RNA (lncRNAs) were reported to play important roles in AKI as well as have the potential to serve as a biomarker or therapeutic target for the development of the diagnostic and prognostic strategies of AKI. In the current study, we aimed to investigate the expression and biological function of lncRNA nuclear enriched abundant transcript 1 (NEAT1) in ischemia-induced AKI in patients' sample and in vitro. The expressions of NEAT1 and miR-27a-3p in ischemia/reperfusion-induced AKI patients were examined by quantitative reverse transcription polymerase chain reaction. Cell injury was induced by treatment of human kidney tubular cells (HK-2) with CoCl2 . After treatment, the influences of NEAT1 and miR-27a-3p on the cell apoptosis in the CoCl2 -stimulated HK-2 were tested by flow cytometry. The flow analysis results showed that the expression of NEAT1 was markedly higher in the ischemia-induced AKI patients compared with normal control. Moreover, repression the expression of NEAT1 decreased CoCl2 -induced injury in HK-2. The expression of miR-27a-3p was negatively regulated by NEAT1. Inhibition the expression of NEAT1 attenuated overexpression of miR-27a-3p enhanced CoCl2 -induced injury. In summary, an ischemia-induced injury may be enhanced by a high level of NEAT1 through targeting miR-27a-3p. Thus, NEAT1 has the potential to be explored as a biomarker for diagnosis and target for therapeutic strategies in ischemia-induced AKI.

Involvement of NADPH-oxidase enzyme in the nephroprotective effect of (−)-α-bisabolol on HK2 cells exposed to ischemia – Reoxygenation

Acute Kidney Injury (AKI) is associated with high morbidity and mortality. Ischemia and reperfusion (I/R) are events that lead to AKI through hypoxia, reactive oxygen species (ROS) production, oxidative stress and apoptosis. We aimed to evaluate the mechanism of nephroprotection mediated by Bisabolol in human tubular kidney cells after injury by I/R in vitro. HK2 cells were exposed to I/R and treated with Bisabolol. Cell viability was accessed by MTT assay. Cells were submitted to flow cytometry to evaluate necrotic/apoptotic cells, reactive oxygen species production and mitochondrial transmembrane depolarization. TBARS and GSH were used as parameters of redox balance. Also, KIM-1 supernatant levels were measured. In order to identify an interaction between bisabolol and NOX4, molecular docking and enzymatic assays were performed. Expression of isoform NOX4 on treated cells was examined by western-blot. Finally, cells were visualized by scanning electron microscopy. Bisabolol improved cell viability and prevented cell death by apoptosis, indicated also by the decreased levels of KIM-1. It was observed a decrease on reactive oxygen species production and mitochondrial depolarization, with antioxidant regulation by increased GSH and decreased lipid peroxidation. It was also demonstrated that bisabolol treatment can inhibit NOX4. Finally, SEM images showed that bisabolol reduced I/R-induced cell damage. Bisabolol treatment protects HK2 cells against oxidative damage occasioned by I/R. This effect is related to inhibition of apoptosis, decrease on KIM-1 release, reactive oxygen species accumulation and mitochondrial dysfunction. Bisabolol inhibited NOX4 activity in the tubular cells, impairing reactive oxygen species synthesis.

A High-Throughput Screen Identifies DYRK1A Inhibitor ID-8 that Stimulates Human Kidney Tubular Epithelial Cell Proliferation.

The death of epithelial cells in the proximal tubules is thought to be the primary cause of AKI, but epithelial cells that survive kidney injury have a remarkable ability to proliferate. Because proximal tubular epithelial cells play a predominant role in kidney regeneration after damage, a potential approach to treat AKI is to discover regenerative therapeutics capable of stimulating proliferation of these cells. We conducted a high-throughput phenotypic screen using 1902 biologically active compounds to identify new molecules that promote proliferation of primary human proximal tubular epithelial cells in vitro. The primary screen identified 129 compounds that stimulated tubular epithelial cell proliferation. A secondary screen against these compounds over a range of four doses confirmed that eight resulted in a significant increase in cell number and incorporation of the modified thymidine analog EdU (indicating actively proliferating cells), compared with control conditions. These eight compounds also stimulated tubular cell proliferation in vitro after damage induced by hypoxia, cadmium chloride, cyclosporin A, or polymyxin B. ID-8, an inhibitor of dual-specificity tyrosine-phosphorylation-regulated kinase 1A (DYRK1A), was the top candidate identified as having a robust proproliferative effect in two-dimensional culture models as well as a microphysiologic, three-dimensional cell culture system. Target engagement and genetic knockdown studies and RNA sequencing confirmed binding of ID-8 to DYRK1A and upregulation of cyclins and other cell cycle regulators, leading to epithelial cell proliferation. We have identified a potential first-in-class compound that stimulates human kidney tubular epithelial cell proliferation after acute damage in vitro.

Human extracellular microvesicles from renal tubules reverse kidney ischemia-reperfusion injury in rats.

Hypoxic acute kidney injury, a major unresolved problem, initiates, or aggravates, renal functional and structural decline. There is no treatment for hypoxic acute renal injury and its sequelae. We tested the hypothesis that human kidney tubular cells, or their extracellular vesicles (exosomes), prevent renal injury when infused intravenously 24 hours after 50 minutes of bilateral renal ischemia in Nude rats. Cells and their exosomes were from harvested human kidneys declined for transplantation. Injections of either cells or exosomes, given after 24 and 48 hours of reperfusion, preserved renal function and structure in both treatment groups. However, exosomes were superior to cells; and maintained renal vascular and epithelial networks, prevented renal oxidant stress, and apoptosis; and restrained activation of pro-inflammatory and pro-fibrogenic pathways. Exosomes worked in 24 hours, consistent with functional rather than regenerative activity. Comprehensive proteomic analysis identified 6152 renal proteins from all cellular compartments; and 628 were altered by ischemia at all cell levels, while 377 were significantly improved by exosome infusions. We conclude that renal damage from severe ischemia was broad, and human renal exosomes prevented most protein alterations. Thus, exosomes seem to acutely correct a critical and consequential abnormality during reperfusion. In their absence, renal structure and cells transition to a chronic state of fibrosis and extensive renal cell loss.

Renal tubular epithelial cells injury induced by mannitol and its potential mechanism

Administration of mannitol with high dose could induce extensive isometric renal proximal tubular vacuolization and acute renal failure in clinic. We previously demonstrated that mannitol-induced human kidney tubular epithelial cell (HK-2) injury. The objective of our present work was to further study the cytotoxicity of mannitol in HK-2 cells and its potential mechanism. Cell viability was assessed by an MTT method. Cell morphological changes were observed. Furthermore, levels of malondialdehyde (MDA) and glutathione (GSH) were measured. Flow cytometry was performed to determine cell apoptosis by using Annexin V-FITC and PI. In addition, the F-actin of cells was labeled by FITC-Phalloidin for observation of cytoskeleton. The MTT assay displayed that the cell viability decreased significantly in a dose- and time-dependent manner. The morphological changes were observed, including cell membrane rapture and cell detachment. The GSH concentration in HK-2 cells decreased dramatically in mannitol treatment group, while MDA content increased significantly. The results of flow cytometry indicated that apoptotic percentages of HK-2 cells increased in 250 mmol/L mannitol treatment group. After treatment with 250 mmol/L mannitol for 48 h, HK-2 cells showed disorganization of cytoskeleton and even exhibited a totally destroyed cytoskeleton. Therefore, high dose of mannitol has a toxic effect on renal tubular epithelial cells, which might be attributed to oxidative stress, destroyed cellular cytoskeleton and subsequent cell apoptosis.

TMBIM6 (transmembrane BAX inhibitor motif containing 6) enhances autophagy and reduces renal dysfunction in a cyclosporine A-induced nephrotoxicity model

Cyclosporine A (CsA) is widely used as an immunosuppressor in transplantation. Previous studies reported that CsA induces autophagy and that chronic treatment with CsA results in accumulation of autophagosomes and reduced autophagic clearance. Autophagy is a prosurvival process that promotes recovery from acute kidney injury by degrading misfolded proteins produced in the kidney. In the present study, we used TMBIM6-expressing HK-2, human kidney tubular cells (TMBIM6 cells) and Tmbim6 knockout (tmbim6−/−) mice. When exposed to CsA, the TMBIM6 cells maintained autophagy activity by preventing autophagosome accumulation. With regard to signaling, PRKKA/AMPK phosphorylation and mechanistic target of rapamycin (serine/threonine kinase) complex 1 (MTORC1) expression and its downstream target TFEB (transcription factor EB), a lysosome biogenesis factor, were regulated in the TMBIM6 cells. Lysosomal activity was highly increased or stably maintained in the presence of TMBIM6. In addition, treatment of tmbim6−/− mice with CsA resulted in increased autophagosome formation and decreased lysosome formation and activity. We also found that tmbim6−/− mice were susceptible to CsA-induced kidney injury. Taken together, these results indicate that TMBIM6 protects against CsA-induced nephrotoxicity both in vitro and in vivo by inducing autophagy and activating lysosomes.