胰腺癌细胞解离中occludin和MEK/ERK信号通路的作用

目的：明确occludin及MEK/ERK信号转导通路参与胰腺癌细胞解离的调节机制。方法：以免疫荧光法检测人及仓鼠胰腺癌细胞高转移株（Aspc-1、PC-1.0）和低转移株（Capan-2、PC-1）中occludin蛋白的表达变化,分析其与MEK/ERK信号转导通路的关系及相应细胞的形态学变化。结果：MEK抑制剂U0126可明显诱导细胞间连接处的occludin表达,并抑制仓鼠胰腺癌高转移株细胞中磷酸化MEK和ERK的表达,在光镜下可观察到高转移株细胞聚集成团,伪足消失。细胞解离因子（dissociation factor,DF）破坏occludin在细胞连接处的表达,同时诱导仓鼠胰腺癌低转移株细胞中磷酸化MEK和ERK的表达,光镜下可观察到低转移株细胞呈单个细胞、解离方式生长。而先经DF处理后,再加入U0126培养的低转移株细胞中,occludin表达较前恢复,磷酸化MEK和ERK的表达减少,光镜下观察到低转移株细胞从解离状态重新恢复为岛样细胞克隆方式生长。结论：MEK/ERK信号转导通路可能通过影响occludin的细胞内定位与表达,调控胰腺癌细胞的解离状态。     

通过抑制ERK1/2通路诱导肝癌细胞SMMC-7721凋亡的研究

目的应用细胞外信号调节激酶(ERK)1/2抑制剂U0126研究ERK1/2在肝癌细胞增殖、凋亡中的作用。方法以肝癌SMMC-7721细胞株为材料,分为空白对照组及不同浓度的U0126处理组。以MTT检测细胞增殖情况,流式细胞仪分析细胞周期及细胞凋亡情况。结果不同浓度的U0126处理后均可明显抑制肝癌SMMC-7721细胞的增殖(P<0.05,P<0.01),使处于G0/G1期的细胞明显增多(P<0.05)且呈剂量依赖性,并诱发细胞凋亡发生(P<0.05)。结论阻断ERK1/2通路有可能成为肝癌治疗的重要手段。     

结直肠癌中MEK2/ERK信号传导通路的研究

目的　研究丝裂原激活化蛋白激酶 (MAPK )中MEK2 /ERK信号传导通路在结直肠癌发生发展中的作用。方法　 ( 1)采用Westernblot检测 5 2例结直肠癌组织及其邻近肠黏膜中MEK 2蛋白的表达。 ( 2 )用丝裂原细胞外激酶 (MEK )抑制剂作用于结肠癌细胞系SW 480 ,然后以MTT法检测细胞增殖状态 ;用Westernblot检测MEK2 ,p ERK及其靶基因产物C myc的表达。结果　结直肠癌组织中MEK2蛋白表达水平明显高于邻近的肠黏膜 (P <0 .0 5 ) ,且与肿瘤的分化、Dukes分期及淋巴结转移有关 (P <0 .0 5 )。应用MEK的抑制剂后SW 480细胞中MEK2 ,p ERK ,C myc表达水平随作用时间延长而下降。结论　MEK2活性增高与结直肠癌细胞侵袭力有关 ,阻断MEK2 /ERK信号传导通路可以抑制结肠癌细胞的增殖 ,促进其凋亡。     

基于ERK/mTOR信号通路探讨六味地黄丸对氧化应激状态下成骨细胞自噬的影响

目的 从ERK/mTOR信号通路观察六味地黄丸对氧化应激状态下MC3T3-E1细胞自噬的影响,探讨其治疗绝经后骨质疏松症的作用机制。方法 用过氧化氢（H2O2）模拟氧化应激状态,六味地黄丸（LWDH）含药血清干预MC3T3-E1细胞,将细胞分为Model组（H2O2干预）、Blank组（空白血清）、LWDH组（LWDH含药血清）、Rap组（mTOR通路抑制剂）、U0126组（ERK通路抑制剂）、Rap+LWDH组（mTOR通路抑制剂、LWDH含药血清）、U0126+LWDH组（ERK通路抑制剂、LWDH含药血清）;以不做干预的Control组作为对照。通过细胞活性氧(reactive oxygen species,ROS)检测细胞ROS水平;检测自噬蛋白LC3B及ERK/mTOR信号通路相关蛋白mTOR、p-mTOR、ERK1/2和p-ERK1/2的表达。结果 ROS结果显示,与Model组相比,LWDH组、Rap组、U0126等各组细胞的ROS水平皆降低（P＜0.05）。Western blot结果显示,与Model组相比,LWDH组、Rap组、LWDH+Rap组蛋白LC3Ⅱ/Ⅰ增高（P＜0.05）;与Model组相比,LWDH组、Rap组与Rap+LWDH组的p-mTOR蛋白表达下调（P＜0.05）,LWDH组、U0126组的p-ERK1/2蛋白表达下调（P＜0.05）。结论 六味地黄丸治疗绝经后骨质疏松症的机制可能与抑制ERK/mTOR信号通路诱导氧化应激状态下成骨细胞自噬相关。     

应激激素肾上腺素激活ERK1/2促进人肝癌细胞生长

目的 探讨应激激素肾上腺素(EPI)对人肝癌细胞生长的影响及其作用机制.方法 采用噻唑蓝(MTT)、逆转录-聚合酶链反应(RT-PCR)和Western blot等方法,分析EPI对人肝癌HepG2和MHCC97H细胞生长的影响,与α1-/β2-肾上腺素受体(α1-/β2-ARs)、腺苷环化酶/蛋白激酶A(AC/PKA)、促分裂原活化蛋白激酶/细胞外信号调节激酶1/2(MAPK/ERK1/2)和磷脂酸激醇-3-激酶/蛋白激酶B(PI3K/AKT/PKB)的关系.结果癌细胞增殖与EPI的作用呈剂量和时间依赖关系(P<0.05),10μmol/L EPI作用24～48 h时其增殖能力最强[HepG2/(215±4)%和MHCC97H/(207±10)%],而正常肝细胞L-02的变化不明显(P>0.05).在HepG2和MHCC97H细胞中,α1-AR蛋白表达仅为L-02的30%和34%,而β2-AR蛋白表达上升至331%和309%.β2-AR阻滞剂ICI 118551可抑制EPI的促增殖作用.β-AR激动剂异丙肾上腺素(ISO,10μmol/L)具有类似EPI的促进增殖作用,其作用可分别被ICI118551和MEK抑制剂U0126显著抑制,被PKA抑制剂H-89和PI3K抑制剂LY294002部分抑制.ISO孵育15 min～8 h,在HepG2中p-ERK1/2蛋白水平上升3.49/3.02倍,在MHCC97H中上升3.15/2.73倍,该作用可被ICI 118551和U0126所阻断.结论 人肝癌HepG2和MHCC97H细胞过表达β2-AR,EPI通过β2-AR激活ERK1/2依赖性和非依赖性信号通路促进癌细胞的生长,其中MAPK/ERK1/2信号通路可能起主要作用.     

白蛋白诱导的肾小管细胞凋亡与丝裂素激活蛋白激酶信号通路

目的 探讨白蛋白诱导肾小管上皮细胞凋亡以及诱导凋亡的信号传导机制&#65377; 方法 将培养的大鼠肾小管细胞NRK-52E分别与不同浓度(10&#65380; 20&#65380; 30 mg/ml)的去脂无内毒素牛血清白蛋白(BSA)共同孵育6&#65380; 12&#65380; 18和24 h&#65377;透射电镜&#65380;共聚焦激光显微镜和流式细胞仪检测细胞凋亡&#65377;BSA 20 mg/ml刺激NRK-52E细胞15&#65380; 30&#65380; 60和120 min后, Westen印迹测定p38&#65380;氨基末端激酶(JNK)和细胞外信号调节激酶(ERK)活性&#65377;将SB202190(20 μmol/L, p38抑制剂)&#65380;SP600125(10 μmol/L, JNK抑制剂)和PD98059(20 μmol/L, ERK抑制剂)分别与白蛋白和NRK-52E细胞共同孵育24 h后检测细胞凋亡&#65377;结果 白蛋白以时间和剂量依赖方式诱导肾小管细胞凋亡&#65377;白蛋白与NRK-52E细胞共孵育后,p38和JNK活性明显升高,ERK活性显著降低&#65377;SB202190和SP600125可分别抑制白蛋白诱导NRK-52E细胞凋亡,而PD98059促进白蛋白诱导的NRK-52E细胞凋亡&#65377;结论 白蛋白以时间和剂量依赖方式诱导肾小管细胞凋亡,而p38和JNK激活与ERK抑制介导了白蛋白诱导的肾小管细胞凋亡&#65377;     

缓激肽对肾系膜细胞增殖与细胞外基质分泌的作用及有关机制的探讨

目的研究缓激肽(BK)对肾系膜细胞增殖与细胞外基质分泌的作用及探讨与血小板源生长因子BB(PDGF-BB)有关的ERK信号途径机制。方法BK单独或与PDGF-BB共同孵育系膜细胞后,以MTF法测细胞增殖情况;ELISA法测胶原(C01)Ⅰ、ColⅣ分泌;Western杂交测ERK蛋白表达。用BK受体特异阻断剂HOE-140、酪氨酸磷酸酶抑制剂(OV)和ERK途径阻断剂U0126预孵育,以BK和PDGF-BB共同刺激系膜细胞,Western杂交测ERK蛋白表达。结果BK(10-1000μg/L)可单独刺激系膜细胞增殖、ColⅠ和ColⅣ分泌及诱导ERK1/2磷酸化。20μg/L PDGF-BB预孵育也有类似作用,但可被BK呈剂量依赖性抑制。1μmol/L HOE-140和0.5 mmol/L OV能分别阻断BK对PDGF-BB-ERK1/2途径磷酸化的抑制作用,而U0126抑制了HOE-140和OV的作用。结论BK刺激系膜细胞增殖的作用主要是通过ERK途径介导的,与PDGF-BB共同作用时则呈拮抗作用,并且与ERK途径的受抑有关。缓激肽B2受体和酪氨酸磷酸酶参与了BK的双向调节作用。     

白蛋白诱导的鼠肾小管细胞凋亡与牛磺酸的抗凋亡作用

目的：观察白蛋白是否诱导鼠肾小管上皮细胞凋亡和牛磺酸对此过程的影响，探讨其信号传导机制。方法：将培养的大鼠肾小管细胞（NRK-52E）与不同浓度的去脂无内毒素牛血清白蛋白（BSA）共同孵育6、12、18、24h。然后用电镜、共聚焦激光显微系统和流式细胞仪检测细胞凋亡；将不同浓度的牛磺酸与NRK-52E细胞孵育1h后加入30mg／ml的白蛋白（BSA）再孵育12h，然后以流式细胞仪检测细胞凋亡，以Westenblot法测定p38、JNK和ERK磷酸化水平。结果：白蛋白以时间和剂量依赖方式导致肾小管细胞凋亡；牛磺酸使白蛋白诱导的NRK-52E细胞凋亡率减少，呈剂量依赖性；牛磺酸以剂量依赖方式降低p38和JNK磷酸化水平，增加ERK磷酸化水平。结论：白蛋白以时间和剂量依赖方式诱导肾小管细胞凋亡；牛磺酸通过抑制白p38和JNK磷酸化，促进ERK磷酸化拮抗白蛋白诱导的肾小管细胞凋亡。     

胰岛素经PI3K/Akt/p7056K1信号通路促进小鼠成肌细胞的增殖

目的:探讨在促小鼠成肌细胞增殖过程中,胰岛素对PI3K/Akt/p70S6K1信号传导通路的作用.方法:以小鼠成肌细胞C1C12为研究对象,利用蛋白免疫印迹(western blot)和MTT方法检测从t蛋白激酶的表达和细胞增殖变化.结果(1)胰岛素(100-200nM)浓度依赖性地促进C2C12细胞的增殖,胰岛素干预C2C12细胞,引起Akt/p70S6K1的磷酸化;(2)PI3K抑制剂LY294002能浓度依赖地抑制胰岛素引起的Akt磷酸化和细胞增殖;(3)p70S6K1抑制剂-雷帕霉素(rapamycin)浓度依赖地抑制胰岛素引起的p70S6K1磷酸化和细胞增殖.结论:胰岛素促进小鼠C2C12成肌细胞的增殖.胰岛素能激活C2C12细胞的Akt/p70S6K1信号通路,并且这种激活是胰岛素促进的C2C12细胞增殖所必需的.     

热休克蛋白72肽结合区对肾小管上皮间质转分化的影响

目的 探讨热休克蛋白72肽结合区在肾小管上皮间质转分化(EMT)过程中的作用和可能机制.方法 应用质粒转染方法分别诱导热休克蛋白72(HSP72)野生型、肽结合区缺失型(HSP72-△PBD)和肽结合区(PBD)的表达.用转化生长因子β1(TGF-β1)刺激大鼠肾小管上皮细胞(NRK-52E)48 h,Western印迹和免疫荧光染色检测细胞E-钙黏蛋白(cadherin),α-平滑肌肌动蛋白(SMA),HSP72和Smad3/磷酸化(p)-Smad3蛋白表达.结果 TGF-β1(10 μg/L)刺激NRK-52E细胞48 h后上调α-SMA和下调E-cadherin蛋白表达水平.Western印迹及细胞免疫荧光显示,过表达HSP72和PBD能明显减轻TGF-β1诱导的NRK-52E细胞E-cadherin蛋白表达下调和α-SMA蛋白表达上调,而过表达HSP72-△PBD不能改变上述蛋白的表达.此外,过表达HSP72和PBD显著抑制Smad3的磷酸化.结论 HSP72抑制Smad3活化和EMT的发生可能与PBD的功能有关.     

Differential sensitivity of chemoresistant neuroblastoma subtypes to MAPK-targeted treatment correlates with ERK, p53 expression, and signaling response to U0126

Purpose

Neuroblastoma tumors are comprised of neuroblastic (N), substrate-adherent (S), and intermediate (I) cells. Because cell growth and differentiation often involve p44/p42 mitogen-activated protein kinase (MAPK) pathway signaling, we explored MAPK signaling and growth response in three NB cell types after MAPK kinase (MEK) inhibition to evaluate the feasibility of MAPK-targeted treatment strategies.

Methods

Three human NB cell cultures, SH-SY5Y (N-type), BE(2)-C (I-type), and SK-N-AS (S-type), were treated in monolayer cultures with increasing concentrations of the MEK inhibitor U0126. MAPK pathway intermediates MEK and ERK, their activated (phosphorylated) forms p-MEK and p-ERK, and p53 expression were assessed by Western blot at 1 and 24 hours. At 72 hours, cell counts determined growth inhibition and DNA fragmentation ELISA assessed apoptosis.

Results

Among all three lines, total ERK and MEK expression were unaffected by U0126. However, constitutive total ERK and p53 expression were significantly greater in BE(2)-C (I-type) cells than in SH-SY5Y (N-type) and SK-N-AS (S-type). Active ERK (p-ERK) levels decreased in dose response to U0126 at 1 and 24 hours in all lines. Conversely, p-MEK levels increased with increasing U0126 concentrations at 1 hour in SH-SY5Y (N-type) and at 24 hours in all lines. BE(2)-C (I-type) cell counts decreased in concentration-dependent fashion with U0126, whereas SH-SY5Y (N-type) and SK-N-AS (S-type) showed a biphasic response with increased cell counts at 1 μmol/L U0126 and slightly decreased cell counts at 10 μmol/L U0126.

Conclusion

This study demonstrates that BE(2)-C (I-type) cells exhibit greater constitutive total ERK and p53 expression than SH-SY5Y (N-type) and SK-N-AS (S-type). Although all three lines exhibit p-ERK decreases with MEK inhibition, only BE(2)-C (I-type) cells significantly decrease their proliferation with U0126 treatment. Although MEK inhibition holds promise in targeting I-type NB cells, successfully treating this heterogeneous tumor may require combining agents against N- and S-type cells.     

Novel combination of cyclooxygenase-2 and MEK inhibitors in human hepatocellular carcinoma provides a synergistic increase in apoptosis

Cyclooxygenase-2 (COX-2) and ERK-MAPK mitogenic signaling pathways are important in human hepatocellular carcinoma. We investigated the effect of COX-2 inhibition on ERK-MAPK signaling and the effect of combining MEK (MAPK kinase) and COX-2 inhibitors in human hepatocellular carcinoma in vitro. COX and ERK expression were determined by immunoblot in HepG2 and Hep3B cells. COX-2 and MEK activity were determined by prostaglandin E2 assay and phosphospecific immunoblot, respectively. Cell growth was determined by cell proliferation and cell counts. Apoptosis was determined by DNA fragmentation enzyme-linked immunosorbent assay and flow cytometry. Cell cycle was determined by flow cytometry. HepG2 and Hep3B cells do not express COX-1 or COX-2. Correspondingly, basal and agonist (arachidonic acid, lipopolysaccharide)-stimulated COX-2 activity is undetectable. Treatment of HepG2 and Hep3B cells with NS398 resulted in an increase in ERK1/2 phosphorylation (MEK activity) in a concentration-dependent fashion (NS398, 1 to 100 μmol/L). Treatment with the COX-2 inhibitor NS398 in the presence of U0126 (MEK inhibitor) effectively suppressed ERK1/2 phosphorylation as determined by phosphospecific ERK1/2 immunoblot. Total ERK1/2 and COX-2 were unchanged with NS398 and U0126 treatments. In HepG2 cells, NS398 (1 to 100 μmol/L) decreased apoptosis as determined by DNA fragmentation enzyme-linked immunosorbent assay. Relative apoptosis was increased with U0126 alone or in combination with NS398 (9 to 10 times the control value), eliminating the anti-apoptotic effect of NS398. In Hep3B cells, apoptosis was unchanged with NS398 (1 to 50 μmol/L) or U0126 (1 to 10 μmol/L) alone. The combination of NS398 and U0126 in Hep3B cells resulted in a synergistic increase in apoptosis (10 times the control value). Relative apoptosis in both cell lines strongly correlated with changes in the expression of the antiapoptotic protein Bcl-xL. Cellular growth was assessed by colorimetric proliferation assay and cell counts. HepG2 and Hep3B cells had concentration-dependent inhibition of cell growth with NS398 or U0126 treatment alone. The combination of NS398 and U0126 resulted in complementary inhibitory effects on growth. Growth inhibitory effects in HepG2 and Hep3B cells with combination treatment appear to be, in part, secondary to the induction of G₀/G₁ and G₂/M cell cycle arrest, respectively, as determined by flow cytometry. Despite differential signaling in HepG2 and Hep3B cells, the sum effect of combining the COX-2 inhibitor NS398 and the MEK inhibitor U0126 results in enhanced antitumor actions. This novel combination may be useful for in vivo studies of hepatocellular carcinoma. Presented at the Forty-Fourth Annual Meeting of The Society for Surgery of the Alimentary Tract, Orlando, Florida, May 18–21, 2003. Supported by a grant from the Walther Oncology Center, Indianapolis, Indiana.     

Multiple anticancer effects of blocking MEK-ERK signaling in hepatocellular carcinoma

BACKGROUND: Human hepatocellular carcinoma (HCC) is associated with increased expression and activity of mitogen-activated protein kinase (MAPK) signaling intermediates (ie, MEK, ERK). STUDY DESIGN: We determined the effects of MEK-ERK signaling on proliferation, cell cycle, apoptosis, and tumorigenicity of HCC in vitro. HCC cell lines were treated with MEK enzyme-specific inhibitors, PD098059 and U0126, and ERK1,2 oligonucleotide antisense. RESULTS: In the HCC cells examined, MEK inhibitors blocked ERK1,2 phosphorylation without a change in total ERK expression. ERK1,2 oligonucleotide antisense inhibited ERK1,2 protein expression. PD098059, U0126, and ERK1,2 oligonucleotide antisense each inhibited HCC cellular proliferation in a concentration-dependent manner. Cell cycle, apoptosis, and tumorigenicity were examined in Hep3B and HepG2 cell lines. MEK enzyme inhibition resulted in anticancer effects through cell cycle arrest, increased apoptosis, and decreased tumorigenicity in these cell lines. U0126 exhibited more potent inhibition of ERK1,2 phosphorylation and had more pronounced anticancer effects in both cell lines. Correspondingly, HepG2 cells, the cell line more sensitive to ERK1,2 phosphorylation inhibition, sustained more pronounced anticancer effects with treatment. But Hep3B cells were more sensitive to ERK1,2 antisense-mediated decreases in ERK1,2 protein expression and correspondingly, their growth was inhibited to a greater degree than the HepG2 cells. MEK enzyme inhibition had downstream effects on the expression of the antiapoptotic protein survivin in both cell lines. CONCLUSIONS: These data suggest that there are multiple anticancer effects of blocking MEK-ERK signaling, and that these depend on both the susceptibility of the cells and the ability of the treatment to effect a selective block of MEK-ERK signaling in HCC cells.     

The map kinase ERK regulates renal activity of cyclin-dependent kinase 2 in experimental glomerulonephritis.

BACKGROUND: In vitro, the extracellular signal-regulated kinase (ERK) is an intracellular convergence point of multiple stimuli, which affect the cell cycle. However, the role of ERK in cell cycle regulation in vivo is unknown. METHODS: To address this issue, ERK activity was blocked both in vitro in mesangial cells (MC) and in vivo in experimental glomerulonephritis (GN) by a pharmacological inhibitor (U0126) of the ERK-activating kinase. RESULTS: In stimulated MC, inhibition of ERK reduced cyclin-dependent kinase 2 (CDK2) phosphorylation, CDK2 activity and cyclin E/A expression, whereas downregulation of CDK inhibitor p27(Kip1) expression was inhibited. In vivo, U0126 was given to rats in the acute phase of anti-Thy 1.1 GN. We previously showed that glomerular cell proliferation was reduced by 67% upon treatment with the inhibitor compared to nephritic controls. Now, we detected a significant increase in renal CDK2-activity/phosphorylation in the nephritic controls, that was significantly and dose-dependently reduced by ERK inhibition. CDK2 activation was accompanied by an increase in renal expression of cyclins E/A and the enhanced binding of these cyclins to CDK2 in the nephritic controls. These changes were blunted by U0126 treatment. Finally, we noted an increased expression and CDK2-binding of p27(KIP1) protein in the nephritic controls which was decreased in U0126 treated rats. CONCLUSIONS: Our observations provide the first evidence that ERK is an intracellular regulator of renal CDK2 activity in vivo in a glomerulonephritis model.     

A short pulse of mechanical force induces gene expression and growth in MC3T3-E1 osteoblasts via an ERK 1/2 pathway.

Physiological mechanical loading is crucial for maintenance of bone integrity and architecture. We have calculated the strain caused by gravity stress on osteoblasts and found that 4-30g corresponds to physiological levels of 40-300 microstrain. Short-term gravity loading (15 minutes) induced a 15-fold increase in expression of growth-related immediate early gene c-fos, a 5-fold increase in egr-1, and a 3-fold increase in autocrine bFGF. The non-growth-related genes EP-1, TGF-beta, and 18s were unaffected by gravity loading. Short-term physiological loading induced extracellular signal-regulated kinase (ERK 1/2) phosphorylation in a dose-dependent manner with maximum phosphorylation saturating at mechanical loading levels of 12g (p < 0.001) with no effect on total ERK. The phosphorylation of focal adhesion kinase (FAK) was unaffected by mechanical force. g-Loading did not activate P38 MAPK or c-jun N-terminal kinase (JNK). Additionally, a gravity pulse resulted in the localization of phosphorylated ERK 1/2 to the nucleus; this did not occur in unloaded cells. The induction of c-fos was inhibited 74% by the MEK1/2 inhibitor U0126 (p < 0.001) but was not affected by MEK1 or p38 MAPK-specific inhibitors. The long-term consequence of a single 15-minute gravity pulse was a 64% increase in cell growth (p < 0.001). U0126 significantly inhibited gravity-induced growth by 50% (p < 0.001). These studies suggest that short periods of physiological mechanical stress induce immediate early gene expression and growth in MC3T3-E1 osteoblasts primarily through an ERK 1/2-mediated pathway.     

尿酸活化ERK1/2信号通路刺激大鼠肾小球系膜细胞增殖

目的 探讨尿酸（UA）对大鼠肾小球系膜细胞（GMC）增殖的影响及其可能的机制。 方法 体外培养大鼠GMC,应用不同浓度的UA（50、100、300 μmol/L）刺激或应用细胞外信号调节激酶（ERK1/2）特异性抑制剂U0126（10 μmol/L）、NADPH氧化酶特异性抑制剂夹竹桃麻素（500 μmol/L）、线粒体复合体Ⅰ抑制剂鱼藤酮（10 μmol/L）预处理 30 min 后,再加入UA（300 μmol/L）。于实验终点收集细胞,应用3H-TdR掺入法、细胞计数及流式细胞术测定GMC增殖和细胞周期变化;应用实时定量PCR、Western印迹法检测细胞周期素cyclin D1和cyclin A2的表达及ERK1/2的磷酸化水平;应用荧光探针2,7-二氯二氢荧光素乙酰乙酸（DCFDA）检测细胞内活性氧（ROS）的变化。 结果 （1）与对照组相比,3H-TdR掺入法和细胞计数均显示,UA呈剂量依赖性促进GMC增殖,300 μmol/L UA刺激组其细胞数为对照组的1.5倍以上。（2）流式细胞术显示,UA呈剂量依赖性减少G1/G0期细胞数,增加S期细胞数,300 μmol/L UA刺激组其S期细胞数为对照组的2倍以上。（3）UA呈剂量依赖性促进系膜细胞周期蛋白cyclin D1和cyclin A2的表达。（4）UA呈剂量依赖性促进系膜细胞ERK1/2磷酸化且U0126能够抑制UA诱导的GMC增殖。细胞计数和3H-TdR掺入法分别显示,U0126的抑制率分别是UA 300 μmol/L刺激组的22%和31%（均P < 0.05）。（5）UA呈剂量依赖性促进ROS产生增加,夹竹桃麻素能够明显抑制UA诱导的ROS生成、ERK1/2的磷酸化和系膜细胞增殖（均P < 0.05）,而鱼藤酮对其无明显影响。 结论 UA可促进GMC增殖,其可能的机制为UA诱导NADPH 氧化酶来源的 ROS 产生增加,从而激活ERK1/2信号通路,引起周期蛋白表达增加,促进GMC增殖。     

High uric acid induces phenotypic transition of renal tubular cells via PI3K/Akt signaling pathway

Objective To investigate the effect and the mechanism of epithelial-mesenchymal transition (EMT) in renal tubular cells induced by uric acid. Methods Normal rat kidney tubular cell line (NRK-52E) were exposed to different concentrations of uric acid (100, 200, 400, 600, 800 μmol/L UA) for 48 hours to induce EMT. Morphological changes of the NRK-52E cells were examined under an inverted phase contrast microscope. The protein expression of E-cadherin, α-SMA, p-Akt and Akt were detected by Western blotting. The distribution of E-cadherin and α-SMA were detected by immunofluorescence. NRK-52E cells were pretreated by different concentrations of LY294002(0, 2.5, 5, 10, 15 μmol/L), the inhibitor of PI3K/p-Akt signaling pathway, and then processed by uric acid (400 μmol/L) for 48 hours. Western blotting was used to detect the protein expression of p-Akt and Akt. NRK-52E cells were then divided into four groups: normal group (N), uric acid group (UA), LY294002 group (LY), uric acid with LY294002 group (UA+LY). The protein expression of E-cadherin and α-SMA were detected by Western blotting, the distribution of E-cadherin, α-SMA and p-Akt were detected by immunofluorescence. Results There was abundant cellular expression of E-cadherin in unstimulated renal tubular cells whereas its expression was significantly decreased in uric acid-stimulated cells (P＜0.05). In addition, uric acid induced de novo expression of α-SMA in contrast to almost negative staining in untreated cells (P＜0.05). p-Akt were obviously increased in high uric acid group (P＜0.05) and Akt changed not significantly (P＞0.05). NRK-52E cells transformed into elongated fibroblast-like cells from cuboidal clustered epithelial cells. These indicated that uric acid has induced EMT and activated PI3K/p-Akt signaling pathway in NRK-52E cells. However, the above effects of uric acid were abolished when p-Akt was blocked by the PI3K inhibitor (10, 15 μmol/L LY294002), indicated that LY294002 has reversed the trend of EMT. Conclusions High uric acid induces phenotypic transition of renal tubular cells probably via activating PI3K/Akt signaling pathway.     

Extracellular signal-regulated kinase-dependent interstitial macrophage proliferation in the obstructed mouse kidney

Aim:   A number of growth factors have been shown to induce proliferation of renal cell types in animal models of kidney disease. In vitro studies suggest that many such growth factors induce renal cell proliferation through the extracellular signal-regulated kinase (ERK) pathway. The aim of this study was to determine the functional role of ERK signalling in cell proliferation in the obstructed kidney.
Methods:   Unilateral ureteric obstruction was induced in C57BL/6J mice which then received an ERK inhibitor drug (U0126 100 mg/kg t.i.d.), vehicle (DMSO) or no treatment, starting at day 2 after unilateral ureteric obstruction surgery and continuing until animals were killed on day 5. Cell proliferation was assessed by uptake of bromodeoxyuridine (BrdU).
Results:   In normal mice, phosphorylation (activation) of ERK (p-ERK) was restricted to collecting ducts. Western blotting identified a marked increase in p-ERK in the obstructed kidney in the no-treatment and vehicle-treated groups. Immunostaining showed strong p-ERK staining in many tubules and in interstitial cells. U0126 treatment inhibited ERK phosphorylation as assessed by western blot and immunostaining. The number of BrdU+ cortical tubular cells was reduced by vehicle treatment but was not further changed by U0126 treatment. In contrast, interstitial cell proliferation in the obstructed kidney was unaltered by vehicle treatment, but this was significantly inhibited by U0126. This was associated with a reduction in interstitial macrophage accumulation, but no effect was seen upon interstitial accumulation of α-SMA+ myofibroblasts. Renal fibrosis, as assessed by collagen deposition, was unaffected by U0126 or vehicle treatment.
Conclusion:   These studies show that accumulation of interstitial macrophages in the obstructed kidney is, in part, dependent upon the ERK signalling pathway.     

Extracellular signal-regulated kinases and calcium channels are involved in the proliferative effect of bisphosphonates on osteoblastic cells in vitro.

Bisphosphonates (BPs) are analogues of pyrophosphate, which are widely used for the treatment of different pathologies associated with imbalances in bone turnover. Recent evidence suggested that cells of the osteoblastic lineage might be targets of the action of BPs. The objective of this work was to determine whether BPs induce proliferation of osteoblasts and whether this action involves activation of the extracellular signal-regulated kinases (ERKs). We have shown that three different BPs (olpadronate, pamidronate, and etidronate) induce proliferation in calvaria-derived osteoblasts and ROS 17/2.8 as measured by cell count and by [3H]thymidine uptake. Osteoblast proliferation induced by all BPs diminished to control levels in the presence of U0126, a specific inhibitor of the upstream kinase MEK 1 responsible for ERK phosphorylation. Consistent with this, BPs induced ERK activation as assessed by in-gel kinase assays. Phosphorylation of ERK1/2 was induced by the BPs olpadronate and pamidronate within 30 s, followed by rapid dephosphorylation, whereas etidronate induced phosphorylation of ERKs only after 90 s of incubation and returned to basal levels within 15-30 minutes. In addition, both BP-induced cell proliferation and ERK phosphorylation were reduced to basal levels in the presence of nifedipine, an L-type voltage-sensitive calcium channel (VSCC) inhibitor. These results show that BP-induced proliferation of osteoblastic cells is mediated by activation of ERKs and suggest that this effect requires influx of Ca2+ from the extracellular space through calcium channels.