Na^＋／H^＋交换器-1抑制诱导大鼠肺动脉平滑肌细胞凋亡的可能机制

背景：肺动脉平滑肌细胞(pulmonary artery smooth muscle cells，PASMC)的增殖在缺氧肺动脉高压肺血管重构中起重要作用。解放军第三军医大学附属新桥医院全军呼吸研究所在前期实验中通过构建Na^+／H^+交换器-1(sodium／pmton exchanger isofom-1，Na^+／H^+exchanger isoflorm-1，Na^+／H^+ antiporter isoform-1，NHE-1)特异性核酶基因逆转录病毒载体，转染入体外培养的大鼠PASMC内表达，发现NHE-1抑制可诱导细胞内酸化而抑制PASMC增殖，并促进其凋亡。但这种促凋亡作用是通过什么途径来完成，尚不清楚。目的：探讨Bcl-2、Bax蛋白表达在NHE-1抑制而诱导大鼠PASMC凋亡中的作用。设计：分组对照实验。地点和材料：实验在解放军第三军医大学附属新桥医院全军呼吸内科研究所完成。转染表达NHE-1特异性核酶基因的体外培养大鼠PASMC(PRZ细胞)、转染PLXSN空载体的大鼠PASMC(PX细胞)、未处理大鼠PASMC细胞(PA细胞)为前期实验所制备。干预：已构建NHE-1特异性核酶基因逆转录病毒载体，转染入体外培养的大鼠PASMC内表达，同时转染pLXSN空载体入另一组大鼠PASMC内，后者与未转染的大鼠PASMC细胞为对照组。用荧光指示剂(Fura-2／AM)测定法检测转染NHE-1特异性核酶基因的大鼠PASMC内Ca^2+([Ca^2+]i)变化；RT-PCR方法检测细胞内Bcl-2和Bax mRNA表达变化，免疫组化法检测细胞内Bcl-2和Bax蛋白表达变化。主要观察指标：①转染NHE-1特异性核酶基因的大鼠PASMC内Ca^2+([Ca^2+]i)变化。②细胞内Bcl-2和Bax mRNA表达变化。③细胞内Bcl-2和Bax蛋白表达变化。结果：转染NHE-1特异性核酶基因后，大鼠PASMC内[Ca^2+]i显著升高，细胞内[Ca^2+]i在PA细胞[(95．94&;#177;6．39)nmol／L]与PX细胞[(98．08&;#177;7．37)nmol／L]之间差异无显著性意义(P&;gt;0．05)，而PRZ细胞[(198．08&;#177;16．59)nmol／L]显著高于PA细胞及PX细胞，差异有显著性意义(P&;lt;0．001)。Bcl-2 mRNA及蛋白表达显著降低(PA细胞、PX细胞、PRZ细胞的平均积分光密度分别为2．21&;#177;0．18，2．09&;#177;0．30。1．45&;#177;0．20)，Bax mRNA和蛋白表达显著增加(PA细胞、PX细胞、PRZ细胞的ABax／Aβ-actin分别为0．17&;#177;0．02，0．23&;#177;0．06，0．59&;#177;0．08)。结论：NHE-1抑制诱导的PASMC凋亡与[Ca^2+]i增加、Bcl-2表达降低及Bax表达增加有关。     

Fas和FasL在Na+/H+交换器-1抑制诱导缺氧大鼠肺动脉平滑肌细胞凋亡中的作用

目的探讨Fas、FasL在Na^＋／H^＋交换器-1（NHE-1）抑制所诱导的缺氧大鼠肺动脉平滑叽细胞（PASMCs）凋亡中的作用。方法将转染NHE-1特异性核酶基因的大鼠PASMCs置于缺氧条件下（O2的体积分数低下1％）培养。缺氧培养2、6、12、24和48h后用原位末端标记法（TUNEL）检测细胞凋亡情况；半定量逆转录-聚合酶链反应（sqRT—PCR）疗法检测细胞内fas和fasL mRNA表达变化；免疫细胞化学法检测细胞内Fas和FasL蛋白表达变化。结果转染NHE-1特异性核酶基因的大鼠PASMCs在缺氧培养时，其细胞凋亡率随缺氧时间的延长而逐渐升高，但细胞内fas、fasL mRNA及Fas、FasL蛋白表达与对照组细胞比较差异均无显著性。结论Fas／FasL死亡通路可能不参与NHE-1抑制而诱导缺氧大鼠PASMCs凋亡的调控。     

Na+/H+交换器-1反义RNA对大鼠肺动脉平滑肌细胞增殖的影响

目的 :探讨反义 RNA对大鼠肺动脉平滑肌细胞 Na / H 交换器 (NHE) 1表达和活性、细胞内 p H(p Hi)的影响 ,及其与细胞增殖的关系。方法 :构建含 NHE 1反义 RNA序列的 p L XSN反转录病毒重组载体 ,将其转染体外培养的大鼠肺动脉平滑肌细胞 ,G4 18筛选后获取含有重组载体的细胞克隆 ,检测细胞 NHE 1m RNA表达、2 2 Na摄取量、p Hi和 3H Td R掺入量。结果 :与转染 p L XSN空载体的细胞和正常对照组细胞比较 ,转染了重组载体的肺动脉平滑肌细胞中 NHE 1m RNA表达、2 2 Na摄取量明显减少 ,同时伴有 p Hi降低和 3H Td R掺入量减少 ,正常对照组和空载体组间无显著差异。结论 :NHE 1反义 RNA可以减少 NHE 1表达 ,从而诱导细胞酸化 ,抑制肺动脉平滑肌细胞增殖     

大鼠肺动脉平滑肌细胞钙池操纵的钙通道及其意义

【目的】通过对大鼠肺动脉平滑肌细胞钙库操纵性通道（SOC）的研究,阐述导致肺动脉平滑肌细胞内钙离子稳态失衡的信号途径,为治疗相关疾病提供新的思路。【方法】荧光探针Fura-2／AM标记细胞内Ca^2＋后。用荧光分光光度计检测EGTA耗竭胞内钙库后激活的SOC通道对急性酶分离的大鼠肺动脉平滑肌细胞（Ca^2＋）的影响。【结果】在无Ca^2＋缓冲液中,大鼠肺动脉平滑肌细胞静息Ca^2＋为（72．48±3．12）nmol／L,向细胞悬液中分别引入两种浓度的Ca^2＋（终浓度分别为1．5;3．0nmol／L）,此时静息Ca^2＋为（121．56±6．45）,（187．97±2．98）nmol／L,而预先用EAGA10mmol／L处理的大鼠肺动脉平滑肌细胞Ca^＋显著提高。上述升高效应对Verapamil（5μmol／L）不敏感,但可被2APB（20～100μmol／L）抑制。且抑制率随2-APB浓度的提高而增加。【结论】通过对急性酶分离的大鼠单个肺动脉平滑肌细胞上胞内钙库耗竭激活的SOC通道的研究,对于进一步深入研究钙通道活性改变在肺血管收缩（HPV）反应中所起的作用具有重要意义。     

超声联合微泡诱导血管平滑肌细胞凋亡的机制研究

目的 探讨低频超声联合脂质微泡诱导血管平滑肌细胞(VSMCs)凋亡的可能机制.方法 以低频连续波超声(频率1 MHz、声强0.3 W/cm2)联合脂质微泡(1 μl/ml)辐照VSMCs 120 s.分别用流式细胞仪Annexin V/PI染色、免疫细胞化学技术、荧光探针Fura-4/Am负载后激光共聚焦法检测细胞凋亡、凋亡相关蛋白表达和细胞内游离Ca2 浓度的变化情况.结果 与对照组和血小板衍生生长因子-BB刺激组(PDGF)比较,两组超声辐照联合微泡[(US MB)组和(PDGF US MB)组]的VSMCs凋亡率显著增加、Bax蛋白表达明显上调、而Bcl-2蛋白表达则显著减少(P<0.01);而且PDGF US MB组的细胞凋亡率明显高于US MB组,Bax蛋白表达上调和Bcl-2蛋白表达下调的程度较US MB组更为显著(P<0.01).各实验干预组VSMCs内Ca2 浓度均较对照组显著增高(P<0.01);PDGF US MB组和US MB组细胞内Ca2 浓度均明显低于PDGF组(P<0.01).结论 超声联合微泡诱导VSMCs凋亡的机制可能与细胞内游离Ca2 浓度增加、Bax蛋白表达增加和Bcl-2蛋白表达降低有关.     

急性缺氧对大鼠肺动脉平滑肌细胞Ca2＋及L型钙电流的影响

【目的】研究急性缺氧对大鼠肺动脉平滑肌细胞Ca2＋及ICa-L（L-型电压门控钙通道电流）的影响,以探讨钙通道活性改变在急性低氧性肺血管收缩（HPV）反应中所起的作用。【方法】应用全细胞膜片钳技术,于急性酶分离的大鼠单个肺动脉平滑肌细胞上,并用常氧和低氧的细胞浴液持续灌流肺动脉平滑肌细胞,以观察其对大鼠肺动脉平滑肌细胞Ca2＋及ICa-L的影响。【结果】用低氧的细胞浴液灌流肺动脉平滑肌细胞能显著增加肺动脉平滑肌细胞内Ca2＋荧光强度（P〈O．01）,降低相应电压下的ICa-L峰值（P〈0．01）,使电流一电压曲线相对上移。【结论】急性低氧可通过对ICa-L通道的抑制作用,使肺动脉平滑肌细胞膜发生去极化,肺动脉收缩而导致急性肺血管阻力增加,进而产生肺动脉高压。这可能在低氧性肺血管收缩反应中起着重要的作用。     

MiRNA-146a对血管平滑肌细胞凋亡的抑制作用

目的观察miRNA-146a对血管平滑肌细胞凋亡的作用并研究其机制。方法原代培养大鼠血管平滑肌细胞,分成inhibitor组、control组和normal组,采用脂质体2000分别转染miRNA-146ainhibitors（50μM）、错义链（50μM）、PBS,realtimePCR测定转染后miRNA-146a水平,流式细胞仪检测转染后血管平滑肌细胞凋亡,western blot检测转染后Bax蛋白水平。结果转染48h后,inhibitor组血管平滑肌细胞的miRNA-146a水平明显低于normal和control组（P〈O．01）,inhibitor组血管平滑肌细胞的凋亡显著高于normal、control组（P〈0．05）,且Bax蛋白表达水平增加（P〈O．05）。结论miRNA-146a可以抑制血管平滑肌细胞的凋亡,其机制与抑制Bax表达相关。     

血管平滑肌细胞凋亡与阿托伐他汀的干预效应

目的：观察阿托伐他汀对血管平滑肌细胞凋亡的影响,并探讨凋亡抑制因子Survivin蛋白表达的意义.方法：实验于2004-04/2005-03在医学遗传学国家重点实验室中南大学湘雅二医院中心实验室完成.①取培养五六代的5只1月龄健康雄性大鼠主动脉中层平滑肌细胞,进行干预前于六孔培养板中放置无菌盖玻片,细胞长满盖玻片的90%时开始干预,分为4组进行干预：正常对照组：培养的平滑肌细胞未用阿托伐他汀干预;阿托伐他汀0.1μmol/L组：用浓度为0.1μmol/L的阿托伐他汀干预培养的平滑肌细胞;阿托伐他汀1.0μmol/L组：用浓度为1.0 μmol/L的阿托伐他汀干预培养的平滑肌细胞;阿托伐他汀10.0 μmol/L组：用浓度为10.0μmol/L的阿托伐他汀干预培养的平滑肌细胞.②分别于干预后6,12,24,48,72 h采用Hoechst 33258荧光染色观察血管平滑肌细胞凋亡情况：用免疫组化法检测血管平滑肌细胞凋亡抑制因子Survivin蛋白表达情况.③组间差异比较采用t检验.结果：①荧光染色检测血管平滑肌细胞凋亡结果显示,阿托伐他汀干预培养的大鼠血管平平滑肌细胞后,随干预时间延长和用药浓度增加,平滑肌细胞凋亡增加.阿托伐他汀干预72 h后,血管平滑肌细胞凋亡率：阿托伐他汀0.1,1.0,10.0 μmol/L组明显高于正常对照组（11.1%,27.2%,50.5%,3.8%,P＜0.01）,各组间两两比较差异明显（P＜0.01）.②培养的血管平滑肌细胞Survivin因子表达情况：阿托伐他汀干预24 h,血管平滑肌细胞凋亡抑制因子Survivin蛋白表达下降,干预48 h～72 h,血管平滑肌细胞Survivin因子未见表达.结论：①阿托伐他汀可诱导血管平滑肌细胞凋亡,其凋亡率呈时间和剂量依赖性.②阿托伐他汀致血管平滑肌细胞凋亡的作用可能与其下调凋亡抑制因子Survivin蛋白的表达有关.     

淀粉样β蛋白（1-40）诱导血管平滑肌细胞损伤与利福平的保护效应

目的:采用淀粉样β蛋白诱导种植在人工基底胶上的血管平滑肌细胞损伤,观察利福平对血管平滑肌细胞的保护作用。方法:实验于2005-09/2006-09在武汉协和医院神经科实验室进行。①实验材料:100～150g清洁级SD大鼠;淀粉样β蛋白(1-40)(北京博奥森生物工程公司);利福平(华北制药厂)。②实验干预及分组:体外培养大鼠颈动脉平滑肌细胞;实验前所有的细胞培养板孔底经人工基底胶预处理。实验分为2组,实验组细胞培养板孔底沉积淀粉样β蛋白(1-40),对照组细胞培养板孔底无淀粉样β蛋白(1-40)沉积,实验组和对照组根据利福平终浓度不同分别分为7组(0,0.1,1,2,5,10,20g/L)。③实验评估:在显微镜下观察给药前后平滑肌细胞的形态学变化,用四甲基偶氮唑盐比色实验检测平滑肌细胞活性,依据乳酸脱氢酶漏出率检测平滑肌细胞膜的损伤程度。结果:①血管平滑肌细胞形态学变化:对照组内不同浓度利福平下细胞形态均基本正常,实验组细胞形态均异常,但经利福平处理后均有改善,并成剂量依赖关系。②细胞活性:对照组内四甲基偶氮唑盐染色吸光值无明显变化,实验组四甲基偶氮唑盐染色吸光值下降但经利福平处理也呈剂量依赖性上升。③乳酸脱氢酶漏出率:对照组中乳酸脱氢酶漏出率在利福平低浓度时无改变,高浓度时有所增加;实验组中乳酸脱氢酶漏出率均增加,在利福平浓度≤2g/L时,随利福平浓度增加,成剂量依赖关系的下降;在利福平浓度>2g/L时,乳酸脱氢酶漏出率又开始增加。结论:利福平在一定浓度范围内对淀粉样β蛋白(1-40)诱导的大鼠血管平滑肌细胞损伤有保护作用。     

糖尿病大鼠胃平滑肌细胞凋亡及相关基因蛋白表达的意义

目的:探讨糖尿病大鼠胃平滑肌细胞凋亡以及凋亡相关基因蛋白表达变化,为糖尿病胃轻瘫的发生研究提供理论基础。方法:Wistar大鼠70只,随机分为糖尿病组(链脲菌素STZ60mg/Kg,腹腔注射),对照组(腹腔注射等量的生理盐水)。2个月后大鼠色素胃排空和肠道传输速度测定,TUNEL法原位检测凋亡细胞,免疫组织化学方法和Westernblotting免疫印迹检测bcl-2/bax基因表达。结果:糖尿病组的胃内色素残留率显著增加,小肠传输速率减慢(t=4.26,4.18,P<0.01);糖尿病组平滑肌细胞凋亡细胞指数犤(9.63±2.47)%犦较正常对照组犤(3.23±1.28)%犦明显增高(t=4.02,P<0.01);bcl-2基因表达下调,bax基因表达上调。结论:糖尿病胃肠道动力改变与胃平滑肌细胞凋亡密切相关,bcl-2凋亡途径参与了胃轻瘫的发生。     

bcl-2、bax在NHE-1核酶基因转染所致缺氧大鼠肺动脉平滑肌细胞凋亡中的作用

目的　探讨 bcl 2、bax表达在 Na / H 交换器 1(NHE 1)抑制而诱导缺氧大鼠肺动脉平滑肌细胞 (PASMCs)凋亡中的作用。方法　将转染 NHE 1特异性核酶基因大鼠的 PASMCs置于缺氧条件下(O2 的体积分数 <1% )培养 ,分别在缺氧 0、2、6、12、2 4和 4 8h采用原位细胞凋亡检测法观察细胞凋亡情况 ,荧光指示剂 Fura 2 / AM测定法检测细胞内 Ca2 浓度 (〔 Ca2 〕i)变化 ,半定量逆转录聚合酶链反应方法检测细胞内 bcl 2 m RNA和 bax m RNA表达变化 ,免疫组化法检测细胞内 Bcl 2蛋白和 Bax蛋白表达的变化。结果　转染 NHE 1特异性核酶基因大鼠的 PASMCs在缺氧培养时 ,其细胞凋亡率随缺氧时间的延长而逐渐升高 ,但是〔 Ca2 〕i升高的幅度较小 ,从缺氧 6 h起就显著低于同时间点的对照组和转染逆转录病毒真核表达载体空载体组 (P均 <0 .0 1) ,bcl 2 m RNA及蛋白表达显著降低 ,bax m RNA和蛋白表达显著增加(P均 <0 .0 1)。结论　 NHE 1抑制可能通过阻止 PASMCs的〔 Ca2 〕i增加 ,并引起 bcl 2表达降低及 bax表达增加而诱导和促进缺氧培养的 PASMCs凋亡     

Spontaneously hypertensive rat vascular smooth muscle cells in culture exhibit increased growth and Na+/H+ exchange.

The cellular mechanisms responsible for abnormalities in spontaneously hypertensive rat (SHR) vascular smooth muscle cell (VSMC) growth and vasoreactivity are not defined. Because Na+/H+ exchange, which we have previously demonstrated in cultured VSMC, plays an essential role in mediating growth factor responses, we hypothesized that abnormalities in SHR growth regulation might be reflected in the activity of this transporter. To test this hypothesis, we studied DNA synthesis and Na+/H+ exchange (measured as the rate of amiloride-sensitive intracellular alkalinization or Na+ influx) in early subcultures (less than 6) of aortic VSMC from 12-wk-old SHR and Wistar Kyoto (WKY) animals. Serum-deprived SHR VSMC grew more rapidly in response to 10% serum with an increase in [3H]thymidine incorporation of 439% compared with 191% in WKY controls. Basal intracellular pH (pHi) values determined by fluorescent pH measurements were 7.37 +/- 0.04 and 7.27 +/- 0.03 (P less than 0.05) in early passage SHR and WKY, respectively. Acid recovery (initial pHi = 6.8) by SHR VSMC was faster than by WKY VSMC as measured by alkalinization (1.8 +/- 0.6 vs. 0.8 +/- 0.2 mmol H+/liter.min, P less than 0.05) or by amiloride-sensitive 22Na+ influx (14.5 +/- 1.2 vs. 4.0 +/- 0.5 nmol Na+/mg protein.min, P less than 0.05). In comparison to WKY cells early passage SHR VSMC exhibited 2.5-fold greater alkalinization and amiloride-sensitive 22Na+ influx in response to 100 nM angiotensin II. During serial passage, WKY cells acquired enhanced Na+/H+ exchange and growth rates so that by passage 6, these differences were no longer present. These findings in early cultures of SHR VSMC, removed from the in vivo neurohumoral milieu, suggest that increased Na+/H+ exchange in SHR may reflect alterations in Na+ homeostasis that might contribute to altered SHR VSMC function such as enhanced growth and vasoreactivity.     

Na+/H+交换抑制剂HMA抑制低氧刺激的大鼠肺动脉平滑肌细胞增殖

目的:观察低氧培养对大鼠肺动脉平滑肌细胞增殖的影响,以及Na /H 交换抑制剂HMA对此增殖效应的抑制作用。方法:实验于2004-12/2005-06在第四军医大学病理生理学教研室完成。健康SD大鼠2只,分离培养肺动脉平滑肌细胞,选择3～6代生长良好的细胞在常氧(O2的体积分数为0.21)或低氧(O2的体积分数为0.02)条件下培养,并分别给予0.3,1,3和10μmol/L等不同浓度的HMA(n=8),采用噻唑蓝比色实验和测定细胞总蛋白含量的方法观察细胞增殖情况,同时光镜观察细胞形态并测定培养液上清乳酸脱氢酶活力以反映药物的非特异性细胞毒作用。结果:实验所用细胞样本均进入结果分析。①体积分数为0.02氧浓度较体积分数为0.05氧浓度下培养的大鼠肺动脉平滑肌细胞生长曲线抬高,低氧刺激24h增殖达到高峰。②体积分数为0.05血清培养使此增殖效应更为显著[噻唑蓝光吸收值无血清常氧组(0.238±0.011),无血清低氧组(0.280±0.009),体积分数为0.05血清常氧组(0.313±0.013),体积分数为0.05血清低氧组(0.389±0.011)]。③HMA可以抑制增殖,显著降低噻唑蓝吸光度值[对照组(0.391±0.011),0.3μmol/L组(0.377±0.010),1μmol/L组(0.328±0.012),3μmol/L组(0.289±0.006),10μmol/L组(0.246±0.007)]。④细胞总蛋白含量也显著降低[对照组、0.3μmol/L组、1μmol/L组、3μmol/L组、10μmol/L组分别为(193.30±8.51),(177.63±8.71),(166.84±9.48),(155.72±10.46)和(135.13±10.30)μmol/L]。⑤各浓度处理组细胞形态无改变,培养液上清乳酸脱氢酶活力也无明显变化[对照组、0.3μmol/L组、1μmol/L组、3μmol/L组、10μmol/L组分别为(212.23±8.44),(208.80±6.37),(209.79±7.12),(208.77±7.33),(215.42±7.81)U/L],细胞无明显损伤。结论:0.3～10μmol/L浓度的Na /H 交换抑制剂HMA可以有效抑制低氧刺激的大鼠肺动脉平滑肌增殖,此作用不是非特异的细胞毒作用所致。     

Evidence for altered Na+/H+ antiport activity in cultured skeletal muscle cells and vascular smooth muscle cells from the spontaneously hypertensive rat.

1. Intracellular pH and Na+/H+ antiport activity were determined by a fluorimetric method in cultured skeletal muscle cells (myoblasts) and aortic vascular smooth muscle cells from spontaneously hypertensive and normotensive Wistar-Kyoto rats. 2. The intracellular pH was significantly more alkaline at three different extracellular pH values in both myoblasts and vascular smooth muscle cells from the spontaneously hypertensive rats than in those from the normotensive control rats. 3. A kinetic analysis of the Na+/H+ antiport activity in these cells showed that the raised activity in the spontaneously hypertensive rats was due to an increased maximal transport capacity in vascular smooth muscle cells and to an increase in the affinity of the antiport for internal H+ in the myoblasts. 4. When the extracellular pH was reduced in the skeletal muscle cells of both types of rat, the intracellular pH fell. However, in vascular smooth muscle cells, a reduction in the extracellular pH was not associated with a fall in the intracellular pH. This resistance of the intracellular pH to changes in the extracellular pH differentiates vascular smooth muscle cells from other cells that have been studied in this way.     

Effect of protein kinase C activation on platelet Na+/H+ exchanger]

Protein kinase C activation in human platelets has a modulatory role in maintaining intracellular pH (pHi), by adjusting pHi at a particular value (pH 7.22). Changes in pHi induced by protein kinase C appeared to depend upon differences between H+ efflux catalyzed by Na+/H+ exchanger and H+ production. The pHi recovery after acid loading was significantly facilitated by protein kinase C activation. Analysis of the rate constant for pHi recovery suggested that the turnover rate or the apparent affinity of the Na+/H+ exchanger for H+ was increased. Protein kinase C also decreased the Km value of the Na+/H+ exchanger for extracellular Na+. It is suggested that the role of protein kinase C in platelet pHi regulation is dual, adjusting the pHi value at a certain set-point, on the one hand, and increasing the rate constant of the Na+/H+, on the other.     

Inhibition of lipopolysaccharide-induced prostaglandin E2 production and inflammation by the Na+/H+ exchanger inhibitors

We analyzed the effects of the Na+/H+ exchanger (NHE) inhibitor 3,5-diamino-6-chloro-N-(diaminomethylidene)pyrazine-2-carboxamide hydrochloride (amiloride) and its analogs 5-(N,N-dimethyl)-amiloride (DMA) and 5-(N-ethyl-N-isopropyl)-amiloride (EIPA) on the lipopolysaccharide (LPS)-induced production of prostaglandin (PG) E2 in vitro and in vivo. In the mouse macrophage-like cell line RAW 264, these inhibitors suppressed the LPS (1 microg/ml)-induced production of PGE2 at 8 h in a concentration-dependent manner. They also reduced the LPS-induced release of arachidonic acid from membrane phospholipids at 4 h and the LPS-induced increase in the level of cyclooxygenase (COX)-2 protein at 6 h, but not the level of COX-2 mRNA at 3 h. The LPS-induced phosphorylation of mitogen-activated protein kinases and degradation of inhibitor of kappaB-alpha were not inhibited by these drugs. In an air pouch-type LPS-induced inflammation model in mice 30 mg/kg amiloride and 10 mg/kg EIPA as well as the COX inhibitor indomethacin (10 mg/kg), significantly reduced the level of PGE2 in the pouch fluid at 8 h and the vascular permeability from 4 to 8 h. The accumulation of pouch fluid and leukocytes in the pouch fluid at 8 h was significantly inhibited by amiloride and EIPA but not by indomethacin. These findings suggested that the NHE inhibitors suppress the production of PGE2 through inhibiting the release of arachidonic acid and the increase in COX-2 protein levels and thus induce anti-inflammatory activity.     

Halothane increases cytosolic Ca2+ and inhibits Na+/H+ exchange in L6 muscle cells

The effects of the general anesthetic halothane on the concentration of cytosolic free calcium ([Ca2+]i) and cytosolic pH (pHi), were investigated in L6 rat skeletal muscle cells. Basal [Ca2+]i was 169 +/- 8 nM, measured with the fluorescent Ca2(+)-indicator 1-[2-amino-5-(6-carboxyindol-2-yl)phenoxy]-2-(2'-amino-5- methylphenoxy)ethane-N,N,N',N'-tetra-acetate. Halothane (5.7 mM) increased [Ca2+]i to 225 +/- 15 nM in the presence of extracellular Ca2+, and from 137 +/- 6 nM to 179 +/- 9 nM in Ca2+ absence. This increase was dose-dependent. The anesthetic released about 50% of the releasable Ca2+ from intracellular stores. The resting pHi of L6 cells was 7.24 +/- 0.04, measured with the fluorescent pH indicator bis-carboxyethylcarboxyfluorescein. Halothane did not affect resting pHi, but inhibited cytoplasmic alkalinization by hypertonicity or cytoplasmic acidification: (1) The hypertonicity-induced alkalinization via activation of Na+/H+ exchange (to 7.50 +/- 0.08, initial rate 0.10 +/- 0.02 pH U/min) was inhibited with 5.7 mM halothane by 67%. (2) Acid-loaded cells (pHi 6.43 +/- 0.01 in cells) recovered towards neutrality via activation of Na+/H+ exchange (rate 0.47 pH U/min), and halothane inhibited the rate of pHi recovery by 50%. The halothane-mediated inhibition of alkalinizations after hypertonic exposure or acid-loading was also observed in bis-(o-amino-phenoxy)ethane-N,N,N',N'-tetra-acetate-loaded cells in Ca2(+)-free medium. Therefore, halothane increases [Ca2+]i and in parallel inhibits Na+/H+ exchange, compromising the ability of muscle cells to recover from imposed acidification.     

Activation of Na+/H+ exchanger is associated with hyperinsulinemia in borderline hypertensive rats

Activation of Na+/H+ exchanger (NHE) is known to be related to elevated blood pressure in hyperinsulinemia. To test whether there is the change in NHE activity in insulin resistance, we measured NHE activity of platelets in fructose-induced hyperinsulinemia in Wistar-Kyoto rats (WKY), in borderline hypertensive rats (BHR), and in spontaneously hypertensive rats (SHR). All rats were fed a 60% fructose diet for 4 weeks to induce hyperinsulinemia and hypertriglyceridemia. Intracellular pH (pHi) was measured with a pH-sensitive fluorescent dye 2'7'-bis (2-carboxyethyl)-5-carboxyfluorescein acetoxymethyl ester. NHE activity was evaluated by the recovery of pHi following addition of sodium propionate (Vmax). Measurement of intracellular calcium ([Ca2+]i) was performed using fura2/acetoxymethylester. Systolic blood pressure in fructose diet BHR elevated significantly greater than that in control diet BHR with the increase of both [Ca2+]i and Vmax. In WKY, there was no significant increase in systolic blood pressure and [Ca2+]i except Vmax in a fructose diet. Vmax in control diet SHR was greater than in control diet WKY and BHR, and we found no additional increase in Vmax with a fructose diet in SHR. In BHR, a high salt diet increased systolic blood pressure and Vmax to a similar degree as a fructose diet or a high salt combined with a fructose diet. Plasma insulin concentration correlated positively with Vmax in WKY and BHR, but not SHR. A fructose diet induces hyperinsulinemia and elevates blood pressure in BHR. Hyperinsulinemia appears to activate NHE in a different manner in SHR, and might be associated with an elevation in blood pressure in BHR.