Thrombospondin 1 Promotes Endoplasmic Reticulum Stress and Apoptosis in HK-2 Cells by Upregulating ATF6-CHOP

Objective The goal of this study is to investigate the role and mechanism of endoplasmic reticulum stress and apoptosis regulated by thrombospondin 1(TSP1)in human renal tubular epithelial cells(HK-2 cells).Methods HK-2 cells were exposed to high concentrations of glucose(HG).The endoplasmic reticulum stress inhibitor 4-phenylbutyric acid(4-PBA)was administered by transfecting TSP1 or an empty vector to explore the mechanism of the endoplasmic reticulum response regulated by TSP1 and stress in renal cell apoptosis.The effects of TSP1 and 4-PBA on the proliferation and apoptosis of HK-2 cells under HG conditions were assessed using Cell counting kit-8 and flow cytometry.Western blotting was used to detect the apoptosis-and endoplasmic reticulum stress-related protein expression regulated by TSP1 and 4-PBA.Results HG treatment induced high cell apoptosis,abundantly expressed TSP1 level and restrained viability in HK-2 cells.Overexpression of TSP1 significantly inhibited the proliferation of and facilitated apoptosis of HK-2 cells under HG conditions.Administration of endoplasmic reticulum stress inhibitor 4-PBA after overexpression of TSP1 antagonized the inhibitory proliferation and promoted apoptosis rate in HG-triggered HK-2 cells induced by TSP1 overexpression.4-PBA treatment significantly hindered the expression of endoplasmic reticulum stress markers,such as PERK,ATF4,ATF6,p-eIF2α,IRE1,CHOP and XBP1,suggesting that the administration of 4-PBA was successful.Conclusion Overexpression of TSP1 activated endoplasmic reticulum stress by regulating the ATF6-CHOP axis.TSP1 restrained cell proliferation,and promoted apoptosis and endoplasmic reticulum stress by activating the ATF6-CHOP axis.

USP19 Stabilizes TAK1 to Regulate High Glucose/Free Fatty Acid-induced Dysfunction in HK-2 Cells

Objective Obesity-induced kidney injury contributes to the development of diabetic nephropathy(DN).Here,we identified the functions of ubiquitin-specific peptidase 19(USP19)in HK-2 cells exposed to a combination of high glucose(HG)and free fatty acid(FFA)and determined its association with TGF-beta-activated kinase 1(TAK1).Methods HK-2 cells were exposed to a combination of HG and FFA.USP19 mRNA expression was detected by quantitative RT-PCR(qRT-PCR),and protein analysis was performed by immunoblotting(IB).Cell growth was assessed by Cell Counting Kit-8(CCK-8)viability and 5-ethynyl-2′-deoxyuridine(EdU)proliferation assays.Cell cycle distribution and apoptosis were detected by flow cytometry.The USP19/TAK1 interaction and ubiquitinated TAK1 levels were assayed by coimmunoprecipitation(Co-IP)assays and IB.Results In HG+FFA-challenged HK-2 cells,USP19 was highly expressed.USP19 knockdown attenuated HG+FFA-triggered growth inhibition and apoptosis promotion in HK-2 cells.Moreover,USP19 knockdown alleviated HG+FFA-mediated PTEN-induced putative kinase 1(PINK1)/Parkin pathway inactivation and increased mitochondrial reactive oxygen species(ROS)generation in HK-2 cells.Mechanistically,USP19 stabilized the TAK1 protein through deubiquitination.Importantly,increased TAK1 expression reversed the USP19 knockdown-mediated phenotypic changes and PINK1/Parkin pathway activation in HG+FFA-challenged HK-2 cells.Conclusion The findings revealed that USP19 plays a crucial role in promoting HK-2 cell dysfunction induced by combined stimulation with HG and FFAs by stabilizing TAK1,providing a potential therapeutic strategy for combating DN.

Dexmedetomidine Attenuates High Glucose-induced HK-2 Epithelial-mesenchymal Transition by Inhibiting AKT and ERK

Objective To explore the protective effects of dexmedetomidine(Dex)against high glucose-induced epithelial-mesenchymal transition in HK-2 cells and relevant mechanisms.Methods HK-2 cells were exposed to either glucose or glucose+Dex for 6 h.The production of ROS,morphology of HK-2 cells,and cell cycle were detected.Moreover,the expression of AKT,p-AKT,ERK,pERK,PI3 K,E-Cadherin,Claudin-1,andα-SMA were determined and compared between HK-2 cells exposed to glucose and those exposed to both glucose and Dex with or without PI3 K/AKT pathway inhibitor LY294002 and ERK pathway inhibitor U0126.Results Compared with HK-2 cells exposed to high level of glucose,the HK-2 cells exposed to both high level of glucose and Dex showed:(1)lower level of ROS production;(2)cell morphology was complete;(3)more cells in G1 phase;(4)lower expression of p-AKT,p-ERK andα-SMA,higher expression of ECadherin and Claudin-1.PI3 K/AKT inhibitor LY294002 and ERK inhibitor U0126 decreased the expression of p-AKT,p-ERK andα-SMA,and increased the expression of E-Cadherin and Claudin-1.Conclusion Dex can attenuate high glucose-induced HK-2 epithelial-mesenchymal transition by inhibiting AKT and ERK.

HG-Induced sEVs Mediate Biomechanics of HK-2 Cells

Small extracellular vesicles (sEVs) participate in the pathological progression of high glucose (HG)-induced kidney injury, which is closely related to diabetic nephropathy. How sEVs specifically mediate the cell biomechanics underlying HG injury is unclear. Herein, we utilized a versatile atomic force microscope to determine the contributions of sEVs in HG-induced cellular injury. The sEVs extracted from the culture medium of human proximal tubule kidney (HK-2) cells treated by HG for 72 h (HG-induced sEVs) were verified and analyzed by multiple techniques, and the results indicated the effective production and the effect of dehydration on the shape of HG-induced sEVs. Further investigation on the morphologies of HK-2 cells treated by HG-induced sEVs showed that the surface roughness of the HK-2 cells increased, and their pseudopodia transitioned from lamellipodia to filopodia, with almost doubled mean pseudopodia length. Quantitative analysis of the mechanical responses of the cells revealed that the mean Young’s modulus increased by 26.2%, and the mean adhesion decreased by 36.8%. The indirect mediation of cellular biomechanics guided by HG-induced sEVs was evaluated by comparing it with previously studied direct HG injury. The HG-induced sEVs caused a greater reduction in cell adhesion and an increase in Young’s modulus compared with direct HG stimulation. This work suggested the ability of HG-induced sEVs to elicit specific biomechanical responses during HG injury, advancing the understanding of the injury mechanism caused by HG. The comparison of the cellular biomechanics between direct and indirect HG stimulations through HG-induced sEVs can be beneficial for the diagnosis and treatment of kidney injury.

Lipopolysaccharide Stimulates Surfactant Protein-A in Human Renal Epithelial HK-2 Cells through Upregulating Toll-like Receptor 4 Dependent MEK1/2-ERK1/2-NF-KB Pathway

Background： Surfactant protein-A （SP-A） contributes to the regulation of sepsis-induced acute kidney injury. In a previous study, we demonstrated that the expression of SP-A in the human renal tubular epithelial （HK-2） cells can be stimulated by lipopolysaccharide （LPS）. The present study evaluated the possible signal-transducing mechanisms of LPS-induced SP-A biosynthesis in the HK-2 cells. Methods： Tetrazolium salt colorimetry （MTT） assay was used to detect cell viability of HK-2 cells after LPS stimulation on different time points. HK-2 cells were stimulated with 100 ng/ml of LPS for different durations to determine the effects of LPS on SP-A and toll-like receptor 4 （TLR4） messenger RNA （mRNA） expression, as well as phosphorylation of mitogen-activated/ extracellular signal-regulated kinase （MEK） 1, extracellular signal-regulated kinase 1/2 （ERK1/2）, p38 mitogen-activated protein kinase （p38MAPK）, and nuclear factor-kappa B （NF-KB） inhibitor-alpha （IkB-a）. Then, HK-2 cells were pretreated with CLI-095, a TLR4 inhibitor, to analyze mRNA and protein levels of SP-A and TLR4 and expression of NF-KB ill the cytoplasm and nucleus of HK-2 before LPS exposure. Results： HK-2 cells exposed to 100 ng/ml of LPS for 1,6, and 24 h did not affect cell viability which showed no toxic effect of 100 ng/ml LPS on cells （P = 0.16）; however, the biosynthesis of SP-A mRNA and protein in HK-2 cells was significantly increased （P = 0.02）. As to the mechanism, LPS enhanced transmembrane receptor TLR4 protein expression. Sequentially, LPS time dependently augmented phosphorylation of MEKI, ERKI/2, and p38MAPK. In addition, levels of phospborylatedand nuclear NF-KB were augmented with LPS exposure for 2 h. LPS-induced SP-A and TLR4 mRNA as well as NF-KB expression were significantly inhibited by pretreatment with CLI-095. Conclusions： The present study exhibited that LPS can increase SP-A synthesis in human renal epithelial cells through sequentially activating the TLR4-related MEK1 -ERK 1/2-NF-kB-dependent pathway.

Effects of P-glycoprotein expression induced by ulinastatin on HK-2 cells damage induced by paraquat

Objective To investigate the protective effect of Pglycoprotein up-regulated by ulinastatin(UTI)on HK-2cells during paraquat(PQ)-induced injury and its underlying mechanisms.Methods The research was divided into two parts.The first part of the research was divided into normal control group,PQ group,UTI+PQ group,UTI control group.The second part of the research was divided into negative virus group(including

Network pharmacology and verification experiment-based prediction of active components and potential targets of Alpiniae Oxyphyllae Fructus-Saposhnikoviae Radix(Yizhiren-Fangfeng)for treatment of diabetic kidney disease

Background:In this study,we analyzed the potential active components,related crucial targets and possible signaling pathway mechanisms of Alpiniae Oxyphyllae Fructus and Saposhnikoviae Radix(AOF-SR)herb pairs in the treatment of diabetic kidney disease(DKD)using network pharmacology and verification experiments.Methods:The active compounds and potential targets of AOF-SR were derived from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform,The Encyclopedia of Traditional Chinese Medicine,and PubChem databases,and the potential therapeutic targets of DKD were derived from the OMIM,Drugbank,and DisGeNET databases.The“compounds-diseases-targets”network was constructed using Cytoscape 3.6.0.ClusterMaker functionality in Cytoscape is being used to screen important targets for AOF-SR treatment of DKD.Gene Ontology and Kyoto Encyclopedia of Genes and Genomes enrichment analysis of important targets were performed using DAVID database.In addition,according to the predicted results of network pharmacology,HK-2 cells were used to construct DKD model for verification experiment.HK-2 cells were divided into control group,high glucose(HG)group and AOF-SR(HG+AOF-SR)group to detect survival rate and expression of key proteins in NF-κB and PI3K/Akt signaling pathways.Results:A total of 38 compounds were selected from AOF-SR,of which 23 were Alpiniae Oxyphyllae Fructus and 15 were Saposhnikoviae Radix.Through enrichment analysis of 82 important targets,88 signaling pathways were identified;some of these pathways,such as the NF-κB,PI3K-Akt,IL-17,and JAK/STAT signaling pathways,regulate the pathological process of DKD.In verification experiment,the HK-2 cells survival rate was higher in the HG+AOF-SR group than in the HG group(P<0.05).Moreover,western blotting results showed that the expression levels of NF-κB,p-PI3K,and p-Akt in HG+AOF-SR group were significantly lower than those in HG group(P<0.05).Conclusion:Overall,this study revealed the active compounds,important targets and possible mechanisms of AOF-SR treatment for DKD,and conducted preliminary verification experiments on its correctness,provided novel insights into the treatment of DKD by AOF-SR.

洛铂和顺铂对血管内皮细胞及肝、肾细胞损伤的体外实验研究

目的分析洛铂(LBP)和顺铂(DDP)对传代培养的人脐静脉内皮细胞株(HUVECs)、人肝细胞株(QSG-7701)和人近端肾小管上皮细胞(HK-2细胞)的抑制作用,并初步探讨其可能机制。方法采用MTT法检测LBP和DDP对HUVECs、QSG-7701和HK-2细胞抑制作用的差异,并测定HK-2细胞培养液中丙二醛(MDA)和超氧化物歧化酶(SOD)含量,观察LBP和DDP对HK-2细胞脂质过氧化过程的影响。结果在相同浓度、相同作用时间下,DDP组对HK-2细胞抑制率明显高于LBP组(P<0.05),而LBP组对HUVECs细胞的抑制率明显高于DDP组(P<0.05);LBP组和DDP组对QSG-7701抑制率的差异无统计学意义(P>0.05);此外,与空白对照组比较,LBP组和DDP组均使HK-2细胞培养液中MDA含量明显升高,SOD活性明显降低(P均<0.05),但LBP组和DDP组间差异无统计学意义(P>0.05)。结论 LBP和DDP均对肝、肾细胞有较强的抑制作用,LBP的肾细胞毒性较DDP低,LBP组对正常人脐静脉内皮细胞抑制作用明显强于DDP组,提示LBP可能具有更强的抑制血管形成的能力;氧化性损伤可能是两者造成肾毒性的机制。