ERK1/2参与自发性高血压大鼠离体血管环对apelin-13舒张反应性降低作用

研究自发性高血压大鼠(spontanously hypertensive rat,SHR)离体血管环对G蛋白偶联受体APJ的内源性配体apelin-13的血管收缩与舒张反应及其与一氧化氮(NO)和ERK1/2通路关系．采用离体血管环体外灌流方法用Power-Lab生物信息采集仪检测血管环的张力．实验分组如下：新福林(Phenylephrine,PE)组,乙酰胆碱(acetylcholine,Ach)组,apelin-13组,apelin-13 + PE组,apelin-13 + Ach组,PD98059(ERK1/2抑制剂) + PE组,PD98059 + Ach组,LNNA(L-nitro-arginine,硝基左旋精氨酸,一氧化氮合酶抑制剂) + PE组,LNNA+Ach组,apelin-13(预孵育) + PD98059 + PE组,apelin-13(预孵育)+PD98059+ Ach组,apelin-13(预孵育) + LNNA + PE组和apelin-13(预孵育) + LNNA + Ach组,以WKY大鼠血管环为对照组．培养大鼠血管平滑肌细胞,Western blot检测ERK1/2蛋白表达．结果显示：a．apelin-13对于有内皮的血管表现出浓度依赖性舒张作用,血管舒张百分比SHR < WKY大鼠,而对于去除内皮血管,apelin-13则表现出收缩血管的作用,且收缩张力SHR>WKY大鼠,apelin-13预孵育,能减少SHR和WKY大鼠血管对新福林的缩血管反应性,增加对乙酰胆碱的舒张反应性;b．NOS抑制剂LNNA阻断NO形成后,血管环对apelin-13的舒张反应明显抑制,且SHR组较WKY组对apelin的舒张反应减少更明显,提示apelin-13的舒血管效应至少部分依赖NO通路,而SHR高血压大鼠NO通路障碍减弱了apelin对血管的舒张作用;c．ERK1/2抑制剂PD98059预孵育后血管环对apelin-13表现出浓度依赖性的收缩,与去除内皮后apelin-13的收缩血管效应趋势一致,血管收缩张力SHR＞WKY大鼠,PD98059逆转了apelin-13引起的血管舒张效应;d．Apelin-13促大鼠VSMCs ERK1/2磷酸化增加并呈剂量依赖性和时间依赖性,ERK1/2抑制剂PD98059可以减少apelin-13诱导ERK1/2的磷酸化．结果表明,自发性高血压大鼠离体血管环对apelin-13舒张反应性降低, NO通路和ERK1/2通路介导了apelin-13的舒张血管作用．     

高血压大鼠心脏和血管MAPK磷酸酶-1表达的改变及对平滑肌细胞增殖的影响

目的和方法：比较自发性高血压大鼠（SHR）和对照（WKY）大鼠心脏和主动脉丝裂素活化蛋白激酶磷酸酶－1（MKP－1）及细胞外信号调节激酶（ERK－1）的表达,并观察用磷酸钙共沉淀方法转染MKP－1基因对血管紧张素Ⅱ（Ang Ⅱ）刺激平滑肌细胞（VSMC）^3H－胸腺叫啶（^3H-TdR)掺入的影响,以探讨MKP－1在细胞增殖中的调节作用。结果：①与WKY大鼠相比,SHR心脏和主动脉MKP－1呈低表达,分别降低53％和45％（P均＜0．01）;而SHR心脏和主动脉ERK－1呈明显高表达（P均＜0．01）,SHR心脏和主动脉ERK－1与MKP－1蛋白比值明显高于WKY。②AngⅡ 10^-7mol/L刺激VSMC增殖较对照组增加257％（P＜0．01）,转染野生型MKP－1基因细胞可使AngⅡ刺激的^3H-TdR掺入较未转染的细胞降低63％（P＜0．05）,转染突变型MKP－1基因和转染空载体的VSMC对AngⅡ的刺激与单纯AngⅡ组相比无明显抑制作用（P＞0．05）。结论：SHR心血管组织中促增殖肥大的ERK－1表达较其失活的MKP－1占优势,并且MKP－1可显著抑制AngⅡ的VSMC增殖。     

血管紧张素-(1-7)对大鼠血管平滑肌细胞PKC和ERK1/2的抑制作用

采用Westernblot、氚 胸腺嘧啶 ( 3H TdR)和氚 亮氨酸 ( 3H Leu )掺入等技术和方法 ,用血管紧张素Ⅱ(AngⅡ )和血管紧张素 ( 1 7) [Ang ( 1 7) ]刺激大鼠血管平滑肌细胞 (VSMCs) ,观察和分析Ang ( 1 7)对VSMCs增殖及蛋白激酶C (PKC)和胞外调节蛋白激酶 (ERK)表达的影响。Ang ( 1 7)能明显抑制基础和AngⅡ刺激下的VSMCsPKC ζ和ERK1/ 2蛋白表达 (P <0 0 1或P <0 0 5 ) ,减少3H TdR和3H Leu掺入量 (P <0 0 1或P <0 0 5 )。结果提示 ,Ang ( 1 7)对VSMCs增殖有抑制作用 ,这可能与影响PKC ζ和ERK1/ 2蛋白表达有关。     

自发性高血压大鼠心肌胶原与血管紧张素Ⅱ的关系

目的　观察成年 (16周龄 )自发性高血压大鼠 (spontaneouslyhypertensiverat,SHR)与同龄对照组 (WKY)大鼠之间细胞外基质成分的差异及血管紧张素Ⅱ (AngiotensinⅡ ,AngⅡ )在SHR大鼠左室肥厚形成过程的作用。方法　用尾袖法间接测定大鼠血压 ;检测左心室组织及血浆中的血管紧张素转化酶 (angiotensinconvertingenzyme ,ACE)活性 (紫外分光光度法 ) ;放免法测定左室心肌AngⅡ含量。免疫组化测定左室心肌胶原含量 ,用3H -Proline掺入量测定体外培养心肌成纤维细胞 (cardiacfibroblast,CFB)胶原的合成率。结果　 (1) 16周龄SHR大鼠血压明显高于对照组 (WKY)大鼠 ,分别为 (2 7.6 3± 2 .6 7)kPa和 (16 39± 0 54)kPa ,P <0 .0 5;(2 )SHR大鼠左室心肌AngⅡ含量明显高于WKY组 ,分别为 (2 6 6± 75)pg/ 10 0mg和 (134± 4 1)pg/ 10 0mg ,P <0 .0 5;(3)左室重量 (Leftventricalarmass,LVM)SHR明显高于WKY组 ,分别为 (10 14.3± 6 2 .1)mg和 (895.7± 86 .4 )mg ,P <0 .0 5;(4 )心体比 (Letventricrlarmass/bodyeight,LVM/BW )SHR明显高于WKY组 ,分别为 (3.4 4± 0 .15)mg/g和 (2 .17± 0 .11)mg/g ,P <0 .0 5;(5)体外细胞培养的心肌成纤维细胞3H -Proline掺入量随着AngⅡ浓度升高而增加 ,1μmol/L的AngⅡ使SH     

内皮素-1对大鼠血管平滑肌细胞产生MCP-1的影响及其机制

目的：观察内皮素-1（ET-1）对大鼠血管平滑肌细胞（VSMCs）产生单核细胞趋化蛋白-1（MCP-1）的影响及其机制。方法：培养大鼠血管平滑肌细胞（VSMCs）。细胞分为2组：ET-1刺激组：以不同浓度ET-1刺激VSMCs不同时间;阻断剂干预组：VSMCs分别与不同阻断剂[ET_AR、ET_BR阻断剂BQ123、BQ788,抗氧化剂N-乙酰半胱氨酸（NAC）,ERK、p38MAPK、JNK及NF-κB抑制剂PD98059、SB203580、SP600125及PDTC]预先孵育30 min,再加入ET-1刺激24 h。在预定时间,以酶联免疫吸附（ELISA）法、逆转录聚合酶链反应（RT-PCR）法分别测定不同因素下VSMCs MCP-1蛋白质及mRNA表达量。VSMCs分别与不同阻断剂（BQ123、BQ788、NAC、PD98059、SB203580及SP600125预先孵育20 min,再加入ET-1刺激5 min,免疫印迹（WB）法测定VSMCs胞浆中细胞外调节蛋白激酶（ERK）、p38丝裂原活化蛋白激酶（p38MAPK）、c-Jun氨基末端激酶（JNK）及其各自磷酸化蛋白质的水平。各项检测均重复3次。结果：ET-1能刺激VSMCs MCP-1蛋白质及mRNA表达,其表达量随ET-1浓度及刺激时间的增加呈升高趋势（P<0.05,P<0.01）;BQ123、NAC、PD98059、SB203580及PDTC能显著抑制ET-1诱导的大鼠VSMCs MCP-1蛋白质及mRNA表达（P<0.01）,而BQ788及SP600125对此作用无明显影响。BQ123、NAC与PD98059或SB203580能分别抑制ET-1刺激后VSMCs胞浆内ERK及p38MAPK的磷酸化（P<0.05,P<0.01）,而ET-1对JNK的磷酸化无明显激活作用。结论：ET-1通过ET_AR、ROS、ERK、p38MAPK及NF-κB诱导大鼠VSMCs产生MCP-1。     

血管紧张素—（1—7）对大鼠血管平滑肌细胞PKC和ERK1／2的抑制作用

采用Western blot,氘－胸腺嘧啶（3H－TdR)和氘－亮氨酸（3H－Leu)掺入等技术和方法,用血管紧张素Ⅱ（AngⅡ)和血管紧张素－（1－7）[Ang-(1-7)]刺激大鼠血管平滑肌细胞（VSMCs),观察和分析Ang-(1-7)对VSMCs增殖及蛋白激酶C（PKC）和胞外调节蛋白激酶（ERK）表达的影响,Ang-(1-7)能明显抑制基础和AngⅡ刺激下的VSMCs PKC-Ⅱ和ERK1／2蛋白表达（P＜0．01或P＜0．05）,减少3H－TdR和3H－Leu掺入量（P＜0．01或P＜0．05）,结果提示,Ang-(1-7)对VSMCs增殖有抑制作用,这可能与影响PKC－ζ和ERK1／2蛋白表达有关。     

锌指蛋白ZFP580在全反式维甲酸调节大鼠血管平滑肌细胞迁移中的作用及机制

目的:探讨锌指基因ZFP580在全反式维甲酸(ATRA)调节VSMCs迁移功能中的作用及其机制。方法:分离,培养并鉴定大鼠主动脉VSMCs;分别予以0、5、10、20 μmol/L ATRA刺激VSMCs 24h,以0 μmol/L ATRA组为对照组,观察不同溶度ATRA刺激不同时间对VSMCs迁移能力的影响或给予0、20 μmol/L ATRA刺激VSMCs 24、48、72h,观察ATRA刺激不同时间对VSMCs迁移能力的影响;QPCR及Western blot检测ATRA刺激VSMCs后ZFP580的mRNA和蛋白表达变化;应用ERK抑制剂PD98059抑制ERK的蛋白表达,观察ERK信号蛋白表达变化对ATRA刺激后ZFP580蛋白表达的影响;腺病毒转染技术获得过表达或低表达ZFP580的VSMCs,QPCR及Western blot检测MMP-2和MMP-9、ZFP580蛋白和mRNA表达水平。结果:分离的VSMCs在培养10d后,免疫荧光显示平滑肌细胞特异性标记物SM22α抗体阳性。与对照组相比,5、10、20 μmol/L ATRA预刺激分别降低了32%、43%和59%的VSMCs迁移能力;20 μmol/L ATRA刺激VSMCs与对照组相比,在24、48、72h分别降低49%、36%和22%细胞迁移能力。ZFP580的mRNA和蛋白表达随着ATRA刺激溶度的增加和刺激时间的延长而升高。ERK在ATRA刺激15min即显著升高,运用ERK抑制剂PD98059(20 μmol/L)预处理抑制ERK蛋白表达并降低了ATRA诱导ZFP580的蛋白表达。过表达ZFP580降低MMP-2和MMP-9的mRNA和蛋白表达,反之,低表达ZFP580则上调了MMP-2和MMP-9的mRNA和蛋白表达。结论:ATRA可通过ERK信号通路上调ZFP580的表达,而ZFP580通过调控MMP-2和MMP-9的表达参与ATRA对VSMCs迁移的抑制作用。     

耐力运动对大鼠骨骼肌ERK1/2活性的影响

目的:探讨耐力运动对大鼠骨骼肌蛋白总量(t-ERK1/2)及磷酸化ERK1/2(p-ERK1/2)及ERK2mRMA表达的影响。方法:SD大鼠随机分为对照组和运动组。运动组分为1h/d和1.5h/d组,共7周,运动结束后24h和48h取材,测定葡萄糖和胰岛素浓度;Westernblot法检测骨骼肌t-ERK1/2、p-ERK1/2蛋白表达;RT-PCR法分析ERK2mRNA表达。结果:与对照组比较,运动组胰岛素浓度降低;各运动组p-ERK1/2升高;1.5h/d-24h和-48h组t-ERK1/2增高;1h/d-24h组与1.5h/d-24h和-48hERK2mRNA表达增高。结论:耐力运动可能通过增加ERK1/2活性,提高大鼠骨骼肌对胰岛素的敏感性。     

CGRP抑制AngⅡ诱导HUVECs的损伤及其ERK1/2信号通路

目的:探索降钙素基因相关肽(CGRP)对经血管紧张素Ⅱ (AngⅡ)损伤的人脐静脉内皮细胞(HUVECs)的保护作用且CGRP与细胞外信号调节激酶(ERK1/2)的关系.方法:不同浓度的CGRP、AngⅡ处理体外培养的HUVECs,噻唑蓝比色法检测HUVECs活力;流式细胞仪分析HUVECs凋亡率及其增殖指数;显微镜观察HUVECs的形态学变化;Western blot检测p-ERK1/2的表达.结果:AngⅡ (0.1-100 nmol/L)浓度依赖性降低HUVECs的活力,而CGRP (0.1-1000 nmol/L)浓度依赖性增加HUVECs的活力;HUVECs增殖指数PI值受AngⅡ、CGRP及PD98059(ERK1/2抑制剂)影响;AngⅡ孵育HUVECs在第10min时ERK1/2磷酸化水平可达到最大;CGRP能抑制AngⅡ诱导的HUVECs内ERK1/2磷酸化水平;CGRP8-37(CGRP受体拮抗剂)可部分减弱CGRP抑制ERK1/2磷酸化水平作用;PD98059(ERK1/2抑制剂)作用下,ERK1/2磷酸化水平显著降低,但是对细胞内总ERK1/2水平表达无明显影响.结论:CGRP可抑制AngⅡ对HUVECs的损伤作用,可能与CGRP抑制信号通路ERK1/2有关.     

短期模拟失重可增强大鼠脑动脉平滑肌细胞L-型Ca~(2+)通道对血管紧张素Ⅱ的反应性

已有研究表明模拟失重可引起大鼠脑动脉发生区域特异性变化,其中Ca2+通道和肾素-血管紧张素系统(renin-angio-tensin system,RAS)可能发挥着重要的作用。本研究旨在探讨血管紧张素Ⅱ(angiotensin Ⅱ,Ang Ⅱ)对短期模拟失重大鼠脑基底动脉血管平滑肌细胞(vascular smooth muscle cells,VSMCs)L-型Ca2+通道(L-type calcium channel,CaL)功能的影响。模拟失重(尾部悬吊)3d后,用木瓜蛋白酶法分离大鼠脑基底动脉VSMCs。采用全细胞膜片钳技术,以Ba2+作为载流子,测定CaL电流密度,然后观察Ang Ⅱ对该电流的影响。结果显示,模拟失重3d对大鼠脑基底动脉VSMCs的膜电容和接入电阻无明显影响,但可致VSMCs的CaL电流密度显著增加。不过,模拟失重对CaL的电压激活特性和稳态激活曲线亦无明显影响。对照组和模拟失重组大鼠脑基底动脉VSMCs的CaL电流密度在给予Ang Ⅱ处理后均显著增加,且模拟失重组的增加幅度显著大于对照组。以上结果提示,3d短期模拟失重即可引起大鼠脑动脉VSMCs的CaL发生适应性改变,且可导致其对...     

LPS regulate ERK1/2-dependent signaling in cardiac fibroblasts via PKC-mediated MKP-1 induction

Activation of MAPK pathways by angiotensin II (Ang II) is important for cardiac fibroblast (CFB) proliferation and migration. Activity of MAP-kinases is closely controlled by a group of dual-specific MAP kinase phosphatases (MKPs). Lipopolysaccharides (LPS) and cytokines are elevated in patients with heart failure and may contribute to disease progression. In this study, we investigate the effect of LPS on Ang II-induced CFB function. Pretreatment of CFBs with LPS (1 microg/mL; 30 min) almost completely inhibited Ang II-induced DNA-synthesis and inhibited Ang II directed chemotaxis by more than 80%. Compared to controls, LPS pretreatment significantly reduced phosphorylation levels of ERK1/2- and p38 MAPK and induced MKP-1 levels. Silencing MKP-1 with antisense oligodesoxynucleotides reversed the antimitogenic effect of LPS on Ang II-induced CFB DNA-synthesis and migration. Induction of MKP-1 by LPS was inhibited by the protein kinase C (PKC)-inhibitor calphostin C, but not by the ERK1/2-pathway inhibitor PD98059, suggesting that PKC but not ERK1/2 is required for LPS-mediated MKP-1 induction in CFBs. Our data demonstrate that LPS have direct cellular effects in CFBs through an inhibition of Ang II-induced MAPK activity via PKC-mediated induction of MKP-1. This might be relevant with regard to the decreased MAPK activity and increased levels in MKPs reported during chronic heart failure in humans.     

Vascular smooth muscle cell growth and insulin regulation of mitogen-activated protein kinase in hypertension

Hyperinsulinemia (HI) and insulin resistance (IR) are frequentlyassociated with hypertension and atherosclerosis. However, the exactroles of HI and IR in the development of hypertension are unclear.Mitogen-activated protein kinases (MAPK) are well-characterized intracellular mediators of cell proliferation. In this study, weexamined the contribution of MAPK pathway in insulin-stimulated mitogenesis using primary vascular smooth muscle cells (VSMCs) isolatedfrom aortas of normotensive Wistar-Kyoto rats (WKY) and spontaneoushypertensive rats (SHR). VSMCs were grown to confluence in culture,serum starved, and examined for DNA synthesis {using [³H]thymidine (TDR),immunoprecipitated MAPK activity, and MAPK phosphatase (MKP-1)induction}. Basal rate of TDR incorporation into DNA was twofoldhigher in SHR compared with WKY (P < 0.005). Insulin caused a dose-dependent increase in TDR incorporation (150% over basal levels with 100 nM in 12 h). Stimulation was sustained for 24 h with a decline toward basal in 36 h. Pretreatment with insulin-like growth factor I (IGF-I) receptor antibody did notabolish mitogenesis mediated by 10-100 nM insulin, suggesting thatinsulin effect is mediated via its own receptors. Insulin had a smallmitogenic effect in WKY (33% over basal). Insulin-stimulated mitogenesis was accompanied by a dose-dependent increase in MAPK activity in SHR, with a peak activation (>2-fold over basal) between 5 and 10 min with 100 nM insulin. Insulin had very small effects onMAPK activity in WKY. In contrast, serum-stimulated MAPK activation wascomparable in WKY and SHR. Pretreatment with MEK inhibitor, PD-98059,completely blocked insulin's effect on MAPK activation andmitogenesis. Inhibition of phosphatidylinositol 3-kinase with wortmannin also prevented insulin's effects on MAPK activation andmitogenesis. In WKY, insulin and IGF-I treatment resulted in a rapidinduction of MKP-1, the dual-specificity MAPK phosphatase. Incontrast, VSMCs from SHR were resistant to insulin with respect toMPK-1 expression. We conclude that insulin is mitogenic in SHR, and theeffect appears to be mediated by sustained MAPK activation due toimpaired insulin-mediated MKP-1 mRNA expression, which may act asan inhibitory feedback loop in attenuating MAPK signaling.

     

Vascular smooth muscle cells direct extracellular dysregulation in aortic stiffening of hypertensive rats

Aortic stiffening is an independent risk factor that underlies cardiovascular morbidity in the elderly. We have previously shown that intrinsic mechanical properties of vascular smooth muscle cells (VSMCs) play a key role in aortic stiffening in both aging and hypertension. Here, we test the hypothesis that VSMCs also contribute to aortic stiffening through their extracellular effects. Aortic stiffening was confirmed in spontaneously hypertensive rats (SHRs) vs. Wistar‐Kyoto (WKY) rats in vivo by echocardiography and ex vivo by isometric force measurements in isolated de‐endothelized aortic vessel segments. Vascular smooth muscle cells were isolated from thoracic aorta and embedded in a collagen I matrix in an in vitro 3D model to form reconstituted vessels. Reconstituted vessel segments made with SHR VSMCs were significantly stiffer than vessels made with WKY VSMCs. SHR VSMCs in the reconstituted vessels exhibited different morphologies and diminished adaptability to stretch compared to WKY VSMCs, implying dual effects on both static and dynamic stiffness. SHR VSMCs increased the synthesis of collagen and induced collagen fibril disorganization in reconstituted vessels. Mechanistically, compared to WKY VSMCs, SHR VSMCs exhibited an increase in the levels of active integrin β1‐ and bone morphogenetic protein 1 (BMP1)‐mediated proteolytic cleavage of lysyl oxidase (LOX). These VSMC‐induced alterations in the SHR were attenuated by an inhibitor of serum response factor (SRF)/myocardin. Therefore, SHR VSMCs exhibit extracellular dysregulation through modulating integrin β1 and BMP1/LOX via SRF/myocardin signaling in aortic stiffening.     

自发性高血压大鼠心肌肥厚和心肌MAPK、AngⅡ的关系

放免法测定自发性高血压大鼠（ＳＨＲ）血浆及心肌血管紧张素Ⅱ（ＡｎｇⅡ）含量,凝胶内磷酸化法测定心肌丝裂素活化蛋白激酶活性（ＭＡＰＫ）,以心脏重／体重表示心肌肥厚程度。结果表明：与４个月的ＷＫＹ大鼠比较,４个月的ＳＨＲ血浆和心肌组织ＡｎｇⅡ及心肌ＭＡＰＫ活性分别增加了２１８．６％、１０１．２％和１０７．０％,心肌肥大程度严重,其中ＭＡＰＫ活性与心肌肥大程度呈明显正相关。提示４个月ＳＨＲ心肌肥厚可能是     

Increased reactivity in the mesenteric artery of spontaneously hypertensive rats to phorbol ester

The contraction responses of mesenteric artery from 10 week old spontaneously hypertensive rats (SHRs) and normotensive Wistar Kyoto controls (WKYs) to phorbol 12, 13 - dibutyrate (PDBu) and agents acting on the potential-operated calcium channels were compared. The vessels from the SHR were significantly more sensitive to PDBu than those from the WKY. The PDBu-induced contractions were inhibited by nifedipine. The vessels from the SHR were also more sensitive to Bay K 8644 and KCl than the WKY. Low concentrations of PDBu (1 nM) potentiated the KCl contraction significantly more in the SHR than the WKY. It is suggested that the increased reactivity to PDBu in the SHR may in part be related to changes in the activity of the potential-operated calcium channels.     

细胞外信号调节激酶活化在慢性支气管哮喘大鼠气道平滑肌细胞增殖中的作用

本文旨在探讨细胞外信号调节激酶（extracellular signal-regulated kinase,ERK）在慢性支气管哮喘大鼠气道平滑肌细胞（airway smooth muscle cells,ASMCs）增殖中的作用。建立慢性哮喘大鼠模型,用ERK激动剂表皮生长因子（epidermal growth factor,EGF）和抑制剂PD98059干预慢性哮喘大鼠ASMCs的培养。采用流式细胞仪、四甲基偶氮唑盐（MTT）法、^3H-thymidine（TdR）掺入法和增殖细胞核抗原（proliferating cell nuclear antigen,PCNA）免疫组织化学法检测ASMCs增殖情况,观察ERK信号通路对ASMCs增殖的影响。RT-PCR和Western blot检测ERK mRNA和ERK1／2、磷酸化ERK1／2（p-ERK1／2）蛋白的表达。与正常对照组ASMCs比较,慢性哮喘组ASMCs的G0/G1期细胞所占比例明显减少,S＋G2／M期细胞所占比例增高;吸光度（A490）值、细胞DNA合成量和PCNA阳性表达量均明显增加,ERK mRNA、ERK1／2蛋白、P-ERK1／2蛋白的表达量以及ERK活化率显著增高。经PD98059干预之后,慢性哮喘组ASMCs的S＋G2／M期细胞所占比例、A490值、细胞DNA合成量和PCNA阳性表达量明显降低,ERK mRNA、ERK1／2蛋白、p-ERK1／2蛋白的表达量以及ERK活化率显著降低。经EGF干预后,慢性哮喘组ASMCs的S＋G2／M期细胞所占比例、A490值、细胞DNA合成量和PCNA阳性表达量进一步增高,而这一作用可以被PD98059抑制。以上结果提示,慢性哮喘大鼠ASMCs内源性增殖活性增加,ERK1／2参与其增殖活性的调控,ERK信号通路在哮喘气道重建的ASMCs增殖调控中具有重要作用。     

ERK1/2 achieves sustained activation by stimulating MAPK phosphatase-1 degradation via the ubiquitin-proteasome pathway

Sustained extracellular signal-regulated kinase 1/2 (ERK1/2) activation does not always correlate with its upstream Ras-Raf-mitogen-activated protein kinase kinase 1/2 (MKK1/2) signal cascade in cancer cells, and the mechanism remains elusive. Here we report a novel mechanism by which sustained ERK1/2 activation is established. We demonstrate that Pb(II), a carcinogenic metal, persistently induces ERK1/2 activity in CL3 human lung cancer cells and that Ras-Raf-MKK1/2 signaling cannot fully account for such activation. It is intriguing that Pb(II) treatment reduces mitogen-activated protein kinase phosphatase 1 (MKP-1) protein levels in time- and dose-dependent manners, which correlates with sustained ERK1/2 activation, and that Pb(II) also induces mRNA and de novo protein synthesis of MKP-1. In Pb(II)-treated cells, MKP-1 is polyubiquitinated, and proteasome inhibitors markedly alleviate the ubiquitination and degradation of MKP-1. Inhibiting the Pb(II)-induced ERK1/2 activation by PD98059 greatly suppresses MKP-1 ubiquitination and degradation. It is remarkable that constitutive activation of MKK1/2 triggers endogenous MKP-1 ubiquitination and degradation in various mammalian cell lines. Furthermore, expression of functional MKP-1 decreases ERK1/2 activation and the c-Fos protein level and enhances cytotoxicity under Pb(II) exposure. Taken together, these results demonstrate that activated ERK1/2 can trigger MKP-1 degradation via the ubiquitin-proteasome pathway, thus facilitating long-term activation of ERK1/2 against cytotoxicity.     

Hypotonic stress upregulates β- and γ-ENaC expression through suppression of ERK by inducing MKP-1

We investigated a physiological role for ERK, a member of the MAPK family, in the hypotonic stimulation of epithelial Na(+) channel (ENaC)-mediated Na(+) reabsorption in renal epithelial A6 cells. We show that hypotonic stress causes a major dephosphorylation of ERK following a rapid transient phosphorylation. PD98059 (a MEK inhibitor) increases dephosphorylated ERK and enhances the hypotonic-stress-stimulated Na(+) reabsorption. ERK dephosphorylation is mediated by MAPK phosphatase (MKP). Hypotonic stress activates p38, which in turn induces MKP-1 and to a lesser extent MKP-3 mRNA expression. Inhibition of p38 suppresses MKP-1 induction, preventing hypotonic stress from dephosphorylating ERK. Inhibition of MKP-1 and -3 by the inhibitor NSC95397 also suppresses the hypotonicity-induced dephosphorylation of ERK. NSC95397 reduces both β- and γ-ENaC mRNA expression and ENaC-mediated Na(+) reabsorption stimulated by hypotonic stress. In contrast, pretreatment with PD98059 significantly enhances mRNA and protein expression of β- and γ-ENaC even under isotonic conditions. However, PD98059 only stimulates Na(+) reabsorption in response to hypotonic stress, suggesting that ERK inactivation by itself (i.e., under isotonic conditions) is not sufficient to stimulate Na(+) reabsorption, even though ERK inactivation enhances β- and γ-ENaC expression. Based on these results, we conclude that hypotonic stress stimulates Na(+) reabsorption through at least two signaling pathways: 1) induction of MKP-1 that suppresses ERK activity and induces β- and γ-ENaC expression, and 2) promotion of translocation of the newly synthesized ENaC to the apical membrane.     

A proteomic analysis of aorta from spontaneously hypertensive rat: RhoGDI alpha upregulation by angiotensin II via AT(1) receptor

Arteries undergo remodeling as a consequence of increased wall stress during hypertension. However, the molecular mechanisms of the vascular remodeling are largely unknown. Proteomics is a powerful tool to screen for differentially expressed proteins, but little effort was made on vascular disease research, especially on hypertension. In the present study, the differentially expressed proteins in aortas from 18-week-old spontaneously hypertensive rats (SHR) and their normotensive counterpart, Wistar Kyoto rats (WKY), were examined by two-dimensional electrophoresis (2-DE). We found 50 proteins to be differentially expressed, among which 27 were highly or only expressed in SHR and 23 in WKY. Using matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF-MS) and online data search, nine proteins, including Rho GDP dissociation inhibitor alpha (RhoGDIalpha), were identified with high confidence. Further, the upregulation of RhoGDIalpha was verified at both mRNA and protein level in SHR. In addition, when cultured vascular smooth muscle cells (VSMCs) from aortas of SHR and WKY were treated with angiotensin II (Ang II) and antagonist of angiotensin II type I (AT(1)) receptor, L158809, respectively, RhoGDIalpha was upregulated by Ang II and downregulated by L158809 in VSMCs of SHR. These results demonstrate that vascular remodeling results in significant alterations in the protein expression profile of the aorta during hypertension and suggest that the upregulation of RhoGDIalpha in hypertension is induced by Ang II via AT(1) receptor.