黄芪甲苷对高糖诱导的肾小管上皮细胞损伤的保护作用

目的:旨在探究黄芪甲苷(ASI)对高糖诱导的人肾小管上皮细胞损伤的抑制作用,并阐明其机制。方法:体外培养人肾小管上皮细胞,进行分组:正常对照组:低糖(葡萄糖浓度5.5mmol/L)环境下培养;高糖组:高糖(葡萄糖浓度25mmol/L)环境下培养;ASI各组:分别在高糖培养基内加入不同浓度ASI(包括25、50、100、200μg/ml),在处理后0、1、12、24、48、96h观察,采用TUNEL法和caspase3检测各组细胞凋亡情况,采用ELISA法检测TGF-β1和HGF蛋白含量,采用Western blot检测磷酸化p-38、磷酸化ERK和磷酸化JNK浓度。此外,另在同样高糖培养基内加入p38抑制剂SB202190,1、12、24h观察细胞凋亡情况。最后,取同样高糖环境培养细胞,依次加入HGF50、100、200μg/ml,24h后检测细胞内磷酸化p38蛋白水平。结果:ASI(25～200μg/ml)可抑制高糖诱导的人肾小管上皮细胞凋亡,其抑制作用呈现剂量依赖性与时间依赖性。ASI同样可抑制高糖诱导的TGF-β1蛋白表达和p38MAPK信号通路活性。此外ASI可提高肾小管上皮细胞内HGF浓度;HGF可对p38MAPK信号通路产生抑制作用。结论:ASI抑制高糖诱导的人肾小管上皮细胞凋亡,其机制可能与ASI促进HGF分泌,阻断p38MAPK信号通路,进而抑制细胞凋亡以及TGF-β1的表达有关。ASI可能有助于糖尿病肾病的治疗。     

白细胞介素6刺激人近端肾小管上皮细胞-α-平滑肌肌动蛋白的表达的机制研究

目的观察白细胞介素6（IL-6）在体外对人近曲肾小管上皮细胞株（HK-2）信号转导因子和转录活化因子1（STAT1）酪氨酸磷酸化的影响,探讨IL-6刺激人近端肾小管上皮细胞α-平滑肌肌动蛋白（α-SMA）表达的分子机制。方法采用流式细胞仪检测10、25、50 ng/mL浓度的IL-6刺激48 h后α-SMA阳性细胞表达百分数;采用Western blot方法检测0、5、10、25、50 ng/mL的IL-6刺激30 min以及IL-6（25 ng/mL）刺激0、15min、30min、60min、120min后P-STAT1蛋白的表达水平;同样方法检测,AG490预处理细胞4 h,IL-6（25 ng/mL）分别刺激30 min后及48 h后P-STAT1和α-SMA蛋白表达水平。结果与刺激前比较,IL-6以剂量依赖方式上调α-SMA阳性细胞表达百分数;与刺激前比较,IL-6以时间和剂量依赖方式上调HK-2细胞P-STAT1的表达,高峰发生在30 min;AG490部分抑制STAT1激活,下调α-SMA蛋白的表达。结论HK-2细胞中,信号蛋白STAT1酪氨酸磷酸化介导了IL-6诱导的α-SMA的表达,参与了肾间质纤维化的发病过程。     

p38有丝分裂素激活蛋白激酶在白蛋白刺激肾小管上皮细胞表达调节激活正常T细胞表达和分泌细胞因子中的作用

目的探讨p38有丝分裂素激活蛋白激酶（p38MAPK）对白蛋白诱导的大鼠肾小管上皮细胞表达调节激活正常T细胞表达和分泌细胞因子（RANTES）及核因子-κB（NF-κB）活性的影响。方法培养大鼠肾小管上皮细胞（NRK-52E），分别加入不同浓度白蛋白（5、15、30g／L）或／和SB203580（p38MAPK抑制剂），应用逆转录．聚合酶链反应（RT-PCR）和Western印迹法分别检测RANTESmRNA及蛋白表达水平；应用凝胶迁移率变动分析检测NF-κB的活性变化；p38MAPK的磷酸化水平分析采用Western印迹法。结果白蛋白呈浓度和时间依赖性上调RANTESmRNA及蛋白表达水平，呈时间依赖性激活NF-κB活性，白蛋白明显刺激了p38MAPK磷酸化水平增高，SB203580可抑制白蛋白刺激的RANTES表达与NF-κB活性。结论白蛋白通过p38MAPK信号通路刺激RANTES的表达和NF-κB的活性。     

青藤碱对白介素1β诱导的肾小管上皮细胞骨架变化和明胶酶活性的影响

目的 探讨青藤碱干预炎症介质诱导的肾小管上皮细胞表型转化的作用。 方法 用IL-1β(10 ng/ml)刺激小鼠肾小管上皮细胞株(MCT)和原代小鼠肾小管上皮细胞，并用青藤碱(10、100、500 μmol/L)进行干预。应用四唑盐(MTT)法测定青藤碱的细胞毒性。用免疫细胞化学法、Western印迹和RT-PCR分别测定细胞α-平滑肌肌动蛋白(α-SMA)、波形蛋白(Vim)蛋白和基因表达；明胶酶谱法测定明胶酶——基质金属蛋白酶类活性。 结果 IL-1β能够使肾小管上皮细胞α-SMA、Vim蛋白质合成和基因表达显著上调，明胶酶活性亦同时增强；各个浓度的青藤碱均可显著降低α-SMA、Vim蛋白质和基因的表达以及明胶酶活性。结论 青藤碱可抑制免疫炎症因子诱导的肾小管上皮细胞发生表型转化和降低明胶酶活性，可在一定程度上阻止肾小管上皮细胞迁移，防止肾小管萎缩，从而在防治肾小管间质纤维化中发挥其作用。     

萝卜硫素通过Traf6/TAK1通路调节肾小管上皮细胞间充质转分化

目的探讨萝卜硫素对脂多糖(LPS)诱导的肾小管上皮细胞(HK-2)间充质转分化的影响及其对Traf6/TAK1信号通路活化的作用。方法体外培养HK-2细胞,并将其分为正常组、LPS诱导组(100 ng/mL)、LPS+萝卜硫素低剂量组(10μmol/L)、LPS+萝卜硫素中剂量组(20μmol/L)、LPS+萝卜硫素高剂量组(40μmol/L)。培养12、24、48 h后,采用CCK8法检测细胞增殖情况,ELISA法检测细胞上清中IL-6、IL-1β及TNF-α含量,Western blot方法检测E-cadherin、α-SMA、Traf6、TAK1及p-TAK1蛋白的表达量。结果LPS诱导组相对于正常组HK-2细胞增殖能力、炎症因子(IL-6、IL-1β和TNF-α)水平、蛋白(α-SMA、Traf6及p-TAK1)表达量均升高,而E-cadherin蛋白表达水平降低;然而不同浓度萝卜硫素处理细胞后细胞增殖能力、炎症因子分泌量、蛋白(α-SMA、Traf6及p-TAK1)表达量均降低,E-cadherin蛋白表达水平升高,表现一定剂量依赖性,差异有统计学意义(P<0.05)。结论萝卜硫素能够抑制LPS诱导的HK-2细胞增殖能力及炎症因子的产生,发挥抑制肾小管上皮细胞-肌成纤维细胞转变的纤维化过程,其机制可能与抑制Traf6/TAK1信号通路活化有关。     

KB-R7943对造影剂诱导NRK52E细胞凋亡及p38MAPK信号通路的影响

目的 探讨经钠钙离子交换体介导的细胞内钙超载及p38MAPK信号通路是否参与了造影剂诱导的肾小管上皮细胞损伤及反向模式钠钙离子交换体抑制剂KB-R7943对造影剂诱导的肾小管上皮细胞凋亡及p38MAPK信号通路的影响.方法 鼠肾小管上皮细胞(NRK52E)被分成6组:A正常对照组;B造影剂组;C甘露醇组;D CCB(1×10-5mol/L);E KB-R7943(1×10-5mol/L);F KB-R7943(1×10-6mol/L).造影剂作用1 h后,细胞损伤采用LDH检测,细胞形态变化及细胞凋亡分别由倒置显微镜和流式细胞仪检测;细胞内钙通过Fluo-4染色共聚焦微镜测定;钠钙离子交换体mRNA表达采用RT-PCR测定;p38蛋白的表达采用Western blot测定.结果 造影剂作用1 h后,细胞损伤、细胞凋亡、细胞内钙明显增加,显著高于相同渗透压甘露醇组;p-p38表达30min时增加、60 min时下降.KB-R7943显著降低细胞损伤、细胞凋亡、细胞内钙水平、抑制p-p38的高表达述并显示出剂量效应;钠钙离子交换体mRNA表达没有变化.结论 经反向模式钠钙离子交换体导致的细胞内钙超载诱导了造影剂诱导的肾小管上皮细胞凋亡及p-p38蛋白的高表达;KB-R7943以呈剂量方式降低造影剂诱导的.肾小管上皮细胞凋亡及p-p38蛋白的表达.     

丝裂素激活蛋白激酶活化与肾小管上皮细胞生物学行为的关系

目的探讨丝裂素激活蛋白激酶(MAPK)信号通路对血小板源生长因子(PDGF)诱导肾小管上皮细胞表型转化的作用及其对细胞移行能力的影响.方法以PDGF(20 ng/ml)刺激培养的人近端肾小管上皮HK-2细胞,分别观察细胞形态、增殖和移行能力的变化.采用蛋白免疫印记法检测MAPK各亚类活性及α-平滑肌肌动蛋白(SMA)的表达,同时观察分别采用细胞外信号调节激酶(ERK)、c-Jun氨基末端激酶(JNK)和p38信号通路特异阻断剂PD98059、SP600125和SB203580后上述指标的变化.结果 PDGF刺激6～12 h使α-SMA表达上调近2倍,但刺激24～48 h反而使α-SMA表达低于基础水平.PDGF刺激24 h后HK-2细胞从立方形转变为梭形,细胞虽尚无增殖反应但移行能力增强至3倍(P＜0.01).PDGF诱导的ERK、JNK和p38活性均在2 min时迅速增高,分别在2～5 min达高峰,分别为基础水平的5.7倍、2.6倍和1.6倍(P＜0.05),ERK和JNK活性增高可持续至120 min,而p38活性则于60 min以后恢复至基础水平.在PDGF刺激24 h的情况下,PD98059和SP600125不影响基础状态及PDGF对α-SMA表达的作用,但SP600125可抑制PDGF上调的细胞移行能力(P＜0.01);而SB203580既可抑制α-SMA的基础表达(P＜0.01)及PDGF下调的α-SMA表达(P＜0.001),同时还可显著抑制PDGF诱导的细胞移行能力(P＜0.05).结论 PDGF可刺激MAPK的不同亚类信号通路磷酸化,并可诱导肾小管上皮细胞形态改变及其移行能力增强.在PDGF诱导的表型转化和移行功能改变中,ERK信号通路无介导作用,JNK通路主要与细胞移行能力变化相关,而p38可能是调控α-SMA表达和细胞移行改变的主要信号通路.     

阿司匹林诱生型脂氧素A4对脂多糖诱导小鼠急性肺损伤的影响

目的 评价阿司匹林诱生型脂氧素A4 (ATL)对脂多糖(LPS)诱导小鼠急性肺损伤的影响.方法 雄性SPF级BALB/C小鼠30只,体重25～30 g,10～ 12周龄,采用随机数字表法,将其分为3组(n=10):对照组(NS组)气管内滴定生理盐水(LPS溶媒)1.5 ml/kg,1h后尾静脉注射50％无水乙醇(ATL溶媒)0.1 ml; LPS组气管内滴定LPS 3 mg/kg,1h后尾静脉注射50％无水乙醇0.1 ml; ATL组气管内滴定LPS 3 mg/kg,1h后尾静脉注射ATL 0.2 mg/kg.气管内滴定药物后24h处死,采集支气管肺泡灌洗液(BALF),计数总细胞数、多形核粒细胞比例、单个核细胞比例及其总蛋白、TNF-α、IL-6、单核细胞趋化蛋白-1(MCP-1)、IL-10的浓度;取肺组织,测定髓过氧化物酶(MPO)活性、p38丝裂原活化蛋白激酶(p38 MAPK)、c-Jun氨基末端激酶(JNK)、细胞外调节蛋白激酶(ERK1/2)的磷酸化水平,并观察肺组织病理学结果,行肺损伤评分.结果 与NS组比较,LPS组和ATL组肺损伤评分、BALF中总细胞数、多形核粒细胞比例、TNF-α、IL-6、MCP-1浓度升高,单个核粒细胞比例降低,LPS组BALF中IL-10浓度降低,总蛋白浓度、肺组织MPO活性、p38 MAPK、JNK、ERK1/2的磷酸化水平升高(P＜0.05),ATL组BALF中总蛋白、IL-10浓度、肺组织MPO活性、p38 MAPK、JNK、ERK1/2的磷酸化水平差异无统计学意义(P＞0.05);与LPS组比较,ATL组肺损伤评分、BALF中总细胞数、多形核粒细胞比例和总蛋白、TNF-α、IL-6、MCP-1浓度降低,单个核粒细胞比例和IL-10浓度升高,肺组织MPO活性、p38MAPK和JNK的磷酸化水平降低(P＜0.05),ERK1/2的磷酸化水平差异无统计学意义(P＞0.05).结论 ATL可减轻LPS诱导的小鼠急性肺损伤,其机制与抑制p38 MAPK和JNK信号通路激活有关.     

青藤碱对肾小管上皮细胞转分化相关基因表达的影响

目的:探讨青藤碱干预炎症介质诱导的肾小管上皮细胞转分化及其相关基因的表达作用.方法:IL-1β(10 ng/ml)诱导体外培养的小鼠肾小管上皮细胞株(MCT),同时用青藤碱(10 μmol/L、100μmol/L、500μmol/L和1000μmol/L)进行干预.应用逆转录-聚合酶链反应(RT-PCR)分别测定细胞平滑肌肌动蛋白(α-SMA)、转化生长因子β(TGF-β)和纤连蛋白(Fn)的基因表达.结果:结果:IL-1β能够显著诱导肾小管上皮细胞α-SMA的基因表达上调,同时伴随着TGF β和Fn的基因表达显著上调;而青藤碱各个浓度均具有显著抑制肾小管上皮细胞转分化作用,TGF-β和Fn的基因表达也随之下调.结论:青藤碱可显著抑制IL-1β刺激下的肾小管上皮细胞转分化标志物和细胞外基质的基因表达,其机制可能与部分下调TGF-β的表达有关.     

戊糖多硫酸钠通过抑制P38MAPK通路的激活干预高糖刺激下肾小管上皮细胞的增殖

目的观察戊糖多硫酸钠是否通过调控P38MAPK干预糖尿病肾病肾小管上皮细胞的损伤。方法利用不同浓度(10 mmol/L~50 mmol/L)葡萄糖刺激人近端肾小管上皮细胞(human renal proximal tubular epithelial cells,HK-2)48 h,应用CCK-8比色法检测肾小管上皮细胞增殖的改变。利用不同时间段(0~48 h)葡萄糖刺激细胞,用Western blot法检测P38MAPK蛋白的表达水平,分为正常对照组(CON组)、高糖组(high glucose,HG组,葡萄糖30 mmol/L)、戊糖多硫酸钠(pentosan polysuflate,PPS)组(PPS 200μg/ml)、高糖+戊糖多硫酸钠组(HG+PPS组),P38抑制剂组(SB 202190,20μmol/L),p38抑制剂+高糖组(SB+HG组)、p38抑制剂+戊糖多硫酸钠组(SB+PPS),刺激48 h后检测HK-2细胞增殖的改变,刺激6 h后检测HK-2细胞P38MAPK蛋白的表达水平。结果高糖刺激下HK-2细胞增殖在30 mmol/L的浓度最高。与HG组相比,加用戊糖多硫酸钠干预能明显抑制HK-2的增殖,差异有统计学意义(P均0.01);与正常对照组相比,高糖刺激HK-2细胞6 h后磷酸化(p)p38MAPK蛋白表达水平明显增加(P均0.01);与HG组相比,HG加戊糖多硫酸钠干预6 h后HK-2细胞p-p38MAPK蛋白表达明显降低,差异有统计学意义(P均0.05)。应用p38MAPK抑制剂SB202190(20μmol/L)处理细胞,与HG组相比,HG加用SB202190干预能明显抑制p-p38MAPK蛋白表达及HK-2细胞的增殖(P均0.05);与PPS组相比,PPS加SB202190干预后p-p38MAPK蛋白表达降低及HK-2细胞数目减少(P均0.05)。结论戊糖多硫酸钠可能通过抑制p38MAPK的表达,减少肾小管上皮细胞的增殖而对糖尿病肾病起保护作用。     

Mediation of inflammatory activation of renal tubular epithelial cells by high mobility group protein box 1 interacting with Toll-like receptor 4

Objective To observe functional changes of renal tubular epithelial cells stimulated by high mobility group protein box 1 (HMGB1) and associated mechanism. Methods Renal tubular epithelial cells (NRK52E) were divided into control group, HMGB1 group and HMGB1+lipopolysaccharide from Rhodobactersphaeroides (LPS RS) group. Toll-like receptor 4 (TLR4) expression was detected by immunofluorescence and Western blotting. Apoptosis rate and cell cycle arrest were identified with flow cytometry. The activation of MAPK signaling pathway and NF-κB were detected by Western blotting. The IL-1, IL-6 and tissue inhibitor of metalloproteinases 2 (TIMP2) mRNA levels were measured by real-time PCR. The secretion levels of IL-1, IL-6 and TIMP2 were measured by protein chips assay. Results TLR4 was expressed by NRK52E cells. Compared with the control group, there were increased cell cycle G1 arrest, MAPK signaling pathway and NF-κB activation in HMGB1 group. Furthermore, IL-1, IL-6 and TIMP2 mRNA levels were increased and IL-1, IL-6 and TIMP2 were secreted by NRK52E when stimulated with HMGB1 (all P＜0.05). However, effects mediated by HMGB1 stimulation could be inhibited by LPS RS (all P＜0.05). Conclusions Inflammatory activation of NRK52E cells can be mediated by the interaction of HMGB1 and TLR4.     

Role of MAP kinase pathways in mediating IL-6 production in human primary mesangial and proximal tubular cells.

BACKGROUND: Both interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) are pleiotropic cytokines that have been implicated in the development of glomerular and tubular injury in various forms of immune-mediated renal disease, including glomerulonephritis. Although TNF-alpha has been shown to stimulate IL-6 production in renal cells in culture, the signaling mechanisms that regulate IL-6 production are not fully understood. The aim of this study was to examine the role of the p38 and extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathways in regulating TNF-alpha-mediated IL-6 production from both primary human mesangial cells (HMCs) and human proximal tubular (HPT) cells. METHODS: Primary mesangial and proximal tubular cells were prepared from nephrectomized human kidney tissue. Cells were treated for 24 hours with TNF-alpha in the presence and absence of the specific p38 and ERK1,2 MAPK inhibitors SB203580 and PD98059, respectively, either alone or in combination. IL-6 levels in the cell culture media were measured by enzyme-linked immunosorbent assay. MAPK activation was demonstrated by immunoblot for the active kinase (tyrosine/threonine phosphorylated) in whole cell extracts using phospho-specific antibodies. p38 MAPK activity in HPT cells was measured using an in vitro immunokinase assay using ATF2 as the substrate. RESULTS: TNF-alpha (0.1 to 100 ng/ml) stimulated a dose-dependent increase in IL-6 production in both renal cell types. The activation of the p38 and the ERK1,2 MAPKs occurred following TNF-alpha stimulation. The role of these activations in IL-6 production was confirmed by the ability of both inhibitors SB203580 (1 to 30 microM) and PD98059 (0.01 to 10 microM) to inhibit basal and TNF-alpha-stimulated IL-6 production in both cell types. The addition of both inhibitors in combination caused greater decreases in IL-6 production compared with either inhibitor alone. Pretreatment with SB203580 (10 microM) had no effect on basal or TNF-alpha-stimulated phosphorylation of p38 MAPK but completely abolished TNF-alpha-stimulated p38 MAPK activity. PD98059 decreased both basal and TNF-alpha-stimulated phosphorylation of ERK1,2. CONCLUSIONS: This study provides evidence that both the p38 and ERK MAPK pathways are important for the regulation of the production of IL-6 from the proximal tubular and glomerular mesangial regions of the nephron. In response to TNF-alpha, the activation of both pathways leads to IL-6 production. These findings could aid in an understanding of the cellular mechanisms that regulate IL-6 production and could provide insights into possible pharmacological strategies in inflammatory renal disease.     

Role of reactive oxygen species in TGF-beta1-induced mitogen-activated protein kinase activation and epithelial-mesenchymal transition in renal tubular epithelial cells

Epithelial-mesenchymal transition (EMT) plays an important role in renal tubulointerstitial fibrosis and TGF-beta1 is the key inducer of EMT. Phosphorylation of Smad proteins and/or mitogen-activated protein kinases (MAPK) is required for TGF-beta1-induced EMT. Because reactive oxygen species (ROS) are involved in TGF-beta1 signaling and are upstream signaling molecules to MAPK, this study examined the role of ROS in TGF-beta1-induced MAPK activation and EMT in rat proximal tubular epithelial cells. Growth-arrested and synchronized NRK-52E cells were stimulated with TGF-beta1 (0.2 to 20 ng/ml) or H(2)O(2) (1 to 500 microM) in the presence or absence of antioxidants (N-acetylcysteine or catalase), inhibitors of NADPH oxidase (diphenyleneiodonium and apocynin), mitochondrial electron transfer chain subunit I (rotenone), and MAPK (PD 98059, an MEK [MAP kinase/ERK kinase] inhibitor, or p38 MAPK inhibitor) for up to 96 h. TGF-beta1 increased dichlorofluorescein-sensitive cellular ROS, phosphorylated Smad 2, p38 MAPK, extracellular signal-regulated kinases (ERK)1/2, alpha-smooth muscle actin (alpha-SMA) expression, and fibronectin secretion and decreased E-cadherin expression. Antioxidants effectively inhibited TGF-beta1-induced cellular ROS, phosphorylation of Smad 2, p38 MAPK, and ERK, and EMT. H(2)O(2) reproduced all of the effects of TGF-beta1 with the exception of Smad 2 phosphorylation. Chemical inhibition of ERK but not p38 MAPK inhibited TGF-beta1-induced Smad 2 phosphorylation, and both MAPK inhibitors inhibited TGF-beta1- and H(2)O(2)-induced EMT. Diphenyleneiodonium, apocynin, and rotenone also significantly inhibited TGF-beta1-induced ROS. Thus, this data suggest that ROS play an important role in TGF-beta1-induced EMT primarily through activation of MAPK and subsequently through ERK-directed activation of Smad pathway in proximal tubular epithelial cells.     

表面活性蛋白A调节肾小管上皮细胞巨噬细胞炎症蛋白2的表达及其机制的探讨

目的 研究表面活性蛋白A(SP-A)对肾小管上皮细胞的巨噬细胞炎症蛋白2(MIP-2)表达和NF-κB活性的影响，探讨SP-A在肾组织炎症中的作用。方法 体外培养大鼠肾小管上皮细胞(NRK-52E)，经同步化后分别在低血清条件下经不同浓度的SP-A(0~80 μg/ml)共培养，用RT-PCR和ELISA法分别检测脂多糖(LPS，10 μg/ml)刺激的MIP-2 mRNA和蛋白的表达水平，并用电泳迁移率变动分析法(EMSA)检测NF-κB活性。结果 在LPS刺激下，NRK-52E细胞有明显的MIP-2表达。SP-A浓度达5 μg/ml以上时可显著降低上清液中的MIP-2的浓度；当达10 μg/ml以上时可显著下调MIP-2 mRNA的表达。LPS刺激使NRK-52E细胞的NF-κB活性升高，SP-A以剂量依赖方式降低LPS诱导的NF-κB活性。结论 SP-A可以下调趋化因子MIP-2在肾小管上皮细胞的表达，其作用可能与抑制NF-κB活性有关。SP-A可能在肾组织炎症反应时发挥重要的调节作用。     

Different roles of TiR8/Sigirr on toll-like receptor signaling in intrarenal antigen-presenting cells and tubular epithelial cells

Toll-like receptors (TLRs) exist on both myeloid and intrinsic renal cells contributing to the initiation of innate immunity during renal infection with uropathogenic Escherichia coli. Toll-interleukin 1 receptor (IL-1R) (TIR)8/SIGIRR is an orphan receptor of the TLR/IL-1R family, which suppresses TLR signaling of immune cells and is highly expressed in the kidney. Lack of TIR8/SIGIRR is associated with enhanced renal chemokine signaling upon exposure to lipopolysaccharide (LPS). This was because of TIR8/SIGIRR expression on resident intrarenal myeloid cells rather than tubular epithelial cells which express it on basolateral and luminal membranes. The lack of TIR8/SIGIRR does not enhance TLR/IL-1R signaling in tubular epithelial cells as was observed in monocytes. TIR8/SIGIRR is induced in monocytes treated with LPS or tumor necrosis factor and interferon-gamma in a dose-dependent manner but was downregulated in treated tubule epithelial cells. This cell type-specific regulation and function did not relate to mRNA splice variants but was associated with N- and O-glycosylation of the receptor in renal cells of myeloid and nonmyeloid origin. Our studies show that resident myeloid cells contribute to TLR-mediated antimicrobial immunity in the kidney and that this function is controlled by Tir8/sigirr. TIR8/SIGIRR does not suppress TLR signaling in tubular epithelial cells, which supports their role as sensors of microbial infection in the kidney.     

Effects of mycophenolic acid on IL-6 expression of human renal proximal and distal tubular cells in vitro.

BACKGROUND: Interleukin-6 (IL-6) is a multifunctional cytokine which regulates immune responses and host defence mechanisms. IL-6 has been found to be increased in certain inflammatory conditions of the kidney, in which tubular epithelial cells play a pivotal role. Human renal tubular cells express IL-6. Until now no data about the effect of the immunosuppressant drug mycophenolic acid (MPA) on IL-6 expression were available. METHODS: Proximal and distal tubular epithelial cells (PTC/DTC) have been isolated immunomagnetically. Confluent monolayers were stimulated with interleukin-1beta (IL-1beta; 25 U/ml), IL-1beta+ MPA (0.25-50 micro M) or MPA alone for 48 h. Release of IL-6 protein into the supernatant was evaluated with an enzyme immunoassay, IL-6 mRNA expression was evaluated using the Quantikine mRNA kit. RESULTS: After IL-1beta stimulation, a highly significant 2.6- (PTC) and 3.8-fold (DTC) upregulation of IL-6 expression was detectable. IL-6 mRNA was upregulated by IL-1beta [1.57- (PTC) and 2.03-fold (DTC)]. MPA inhibited this cytokine-induced IL-6 expression in a dose-dependent manner. Incubation with the lowest MPA concentration had no effect on the stimulated upregulation, whereas all higher doses significantly decreased IL-6 expression. Dexamethasone significantly inhibited the cytokine-induced IL-6 protein release in PTC, but not in DTC. CONCLUSIONS: In this study we demonstrated for the first time an inhibitory effect of MPA on the stimulated IL-6 expression of renal tubular epithelial cells. In contrast to older data, which showed a synergistic upregulation of the expression of a CC-chemokine by a combination of cytokines and MPA, in the present study we could demonstrate an immunosuppressive effect of MPA on the expression of an important cytokine.     

TNF-alpha and IL-1beta-mediated regulation of MMP-9 and TIMP-1 in renal proximal tubular cells

BACKGROUND: Tubulointerstitial fibrosis is a morphologic hallmark of chronic kidney disease and is a key factor in the prediction of progression to end-stage renal failure. Disruption of tubular basement membrane and interstitial extracellular matrix (ECM) via cytokine-induced alterations in matrix metalloproteinases (MMPs), and tissue inhibitors of metalloproteinases (TIMPs) may be an important mechanism in this process. The presence of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) and their effects on proximal tubular cells may be critical in this process. METHODS: Human proximal tubular cells were cultured in hormonally defined medium. Cells at 80% confluency were exposed to TNF-alpha (0.1 to 100 ng/mL) or IL-1beta (0.1 to 100 ng/mL) or a combination of both for 48 hours. Activity and expression of MMP-9 was examined by gelatin zymography and Western blot analysis. TIMP-1 expression was analyzed by Western blotting. Signaling through cytokine receptors, protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) pathways was investigated. RESULTS: TNF-alpha but not IL-1beta resulted in a dose-dependent increase in the latent form of MMP-9. TIMP-1 was decreased by treatment with either TNF-alpha or IL-1beta. Cotreatment with IL-1beta abolished the induction of MMP-9 but augmented the inhibition of TIMP-1 in the presence of TNF-alpha. Inhibition of PKC provided evidence of the importance of this pathway in mediating the cytokine-induced suppression of TIMP-1 in human kidney (HK-2) cells. Activation of the extracellular signal-regulated protein kinase (ERK1/2) MAPK mediated the up-regulation of MMP-9 by TNF-alpha whereas p38 was found to be involved in the IL-1beta-mediated inhibition of TNF-alpha-stimulated MMP-9. CONCLUSION: The differential effects of TNF-alpha and IL-1beta on proximal tubular MMP-9 and TIMP-1 expression are mediated through the TNF-RI, the IL-1-RI and the different signaling pathways of PKC, ERK1/2, and p38 MAPK. These findings may provide new insights into the role of proinflammatory cytokines TNF-alpha and IL-1beta in the development and possible therapeutic intervention in tubulointerstitial fibrosis.     

Astragaloside IV attenuates renal tubulointerstitial fibrosis by inhibiting p38 MAPK signaling

Objective To investigate the effect of astragaloside IV (AS-IV) on renal tubulointerstitial fibrosis and its regulation on p38 MAPK signaling. Methods In vivo, UUO model with renal tubulointerstitial injury was constructed. Mice in AS-IV group were orally administrated AS-IV 20 mg•kg-1•d-1 for 7 days after operation, and mice in other groups were administrated the equal volume vehicle. Bilateral kidneys were collected in 7 and 14 days after operation. Transverse kidney slices were stained with Masson trichrome to evaluate the severity of renal tubule injury. In vitro, normal human renal tubular epithelial cells (HK-2) were stimulated with recombinant TGF-β1 (10 ng/ml) and simultaneously treated with different concentrations of AS-IV (0, 50, 100, 200 μg/ml) for 24 h. SB203580 (10 μmol/L) was also ultilized to pre-treat HK-2 cells for 1 h to inhibit phosphorylation of p38 MAPK signaling. The expression of FN, Col IV, and α-SMA were investigated by western blotting and real-time PCR. The expression of p-p38 MAPKs were also observed by Western Blotting. Results Astragaloside IV morphologically ameliorated renal tubulointerstitial fibrosis. The proteins and mRNA expression of FN, Col IV, α-SMA, and TGF-β1 were also increased significantly in UUO kidney tissues (all P＜0.05), which could be reversed by AS-IV administration (all P＜0.05). In vitro, the expression of FN, Col IV, and α-SMA were up-regulated by TGF-β1 after stimulating for 24 h (all P＜0.05), which were decreased by AS-IV. The inhibition effect on FN and α-SMA were similar between AS-IV and MAPK inhibitor SB203580. AS-IV inhibited p-p38 MAPK signals both in vivo and in vitro. Conclusions AS-IV could attenuate renal tubulointerstitial fibrosis induced by UUO and TGF-β1 through reducing FN、Col IV、α-SMA expression in renal tubular cells. The mechanism of AS-IV protective effect might be associated with inhibition of p38 MAPK phosphorylation.     

Reactive oxygen species stimulate p44/42 mitogen-activated protein kinase and induce p27(Kip1): role in angiotensin II-mediated hypertrophy of proximal tubular cells

Angiotensin II (AngII) induces G(1) phase arrest and hypertrophy of cultured renal proximal tubular cells. In previous studies, it was shown that these effects depend on oxygen radical-mediated induction of p27(Kip1), an inhibitor of cyclin-dependent kinases. The present study was undertaken to investigate whether mitogen-activated protein (MAP) kinases serve as signaling intermediates between AngII-induced oxidative stress and induction of p27(Kip1). AngII (10(-7) M) induces a biphasic phosphorylation pattern of p44/42 MAP kinase with an early phosphorylation after 2 min and a later, second phosphorylation peak after prolong incubation (12 h) in cultured proximal tubular cells from two different species (MCT and LLC-PK(1) cells). Total protein expression of MAP kinase was not changed by AngII. These phosphorylation patterns of p44/42 MAP kinase caused activation of the enzyme, as detected by phosphorylated MAP substrate Elk-1 after immuno-precipitation of MAP kinase. Exogenous H(2)O(2) also stimulates a biphasic phosphorylation of p44/42 MAP kinase. The flavoprotein inhibitor diphenylene iodinium, as well as the antioxidant N-acetylcysteine, prevented AngII-induced p44/42 MAP kinase phosphorylation, indicating involvement of reactive oxygen species generated by membrane-bound NAD(P)H oxidase. The MAP kinase kinase inhibitor PD98059 completely inhibits AngII-induced p27(Kip1) expression and (3)[H]leucine incorporation into proteins as a previously established marker of cell hypertrophy. PD98059 did not attenuate AngII-stimulated intracellular synthesis of oxygen radicals. Transient transfection with p44/42 MAP kinase antisense, but not sense, phosphorothioate-modified oligonucleotides also prevented AngII-induced MAP kinase phosphorylation, p27(Kip1) expression, and cell hypertrophy. Furthermore, induction of p27(Kip1) by H(2)O(2) was also abolished in the presence of PD98059. Although AngII induces phosphorylation of the stress-activated p38 MAP kinase, inhibition of this enzyme with SB203580 failed to attenuate induced p27(Kip1) expression and hypertrophy. These data provide evidence that AngII- mediated oxygen stress leads to the phosphorylation of p44/42 MAP kinase in proximal tubular cells. Activation of this enzyme is essential for p27(Kip1) expression, G(1) phase arrest, and hypertrophy of proximal tubular cells. These findings may lead to new concepts concerning interference of the development of proximal tubular hypertrophy, which may eventually turn into a maladaptive process in vivo leading ultimately to tubular atrophy and tubulointerstitial fibrosis.