Kv1.2、Kv1.5、Kv2.1钾通道在缺氧性肺血管收缩中的作用

目的和方法:雄性Wistar大鼠随机分为两组:常氧对照组和低氧组。用酶消化的方法获得单个大鼠肺内动脉平滑肌细胞(PASMC)。采用全细胞膜片钳技术,记录PASMC静息膜电位(Em)和电压门控性钾通道电流(IKv),通过细胞内灌流Kv1.2/Kv1.5/Kv2.1抗体混合液(1∶125),探讨Kv1.2、Kv1.5、Kv2.1钾通道在缺氧性肺血管收缩(HPV)中的作用。结果:①低氧组膜电位明显去极化,由(-51.8±0.8) mV 去极到(-47.2± 0.7) mV,P<0.01,IKv与常氧组相比显著降低,在测试电压-30 mV时, IKv由(6.16±0.58) pA/pF 降为 (3.31±0.37) pA/pF (P<0.01)。②细胞内灌流Kv1.2/Kv1.5/Kv2.1抗体混合液可显著抑制常氧对照组PASMC 的IKv,使Em去极化,然而细胞内灌流Kir2.1/Kir2.3/Kir4.1(1∶125)抗体混合液对常氧对照组PASMC 的IKv和Em无显著影响。③细胞内灌流Kv1.2/Kv1.5/Kv2.1抗体混合液和Kir2.1/Kir2.3/Kir4.1抗体混合液对低氧组PASMC的IKv和Em均无显著影响。结论:Kv1.2、Kv1.5、Kv2.1可能是氧敏感型通道,并介导了低氧性肺血管收缩。     

慢性阻塞性肺疾病合并慢性缺氧患者肺动脉平滑肌细胞电压门控钾通道亚型基因表达的变化

目的：探讨人肺动脉平滑肌细胞（PASMCs）的几种Kv通道亚型：Kv1.2、 Kv1.3、Kv1.5、Kv2.1、Kv3.1等，在COPD合并慢性缺氧时基因表达的变化。旨在探索预防人类肺源性心脏病的发生和找到新的防治方法提供试验依据。 方法： 从手术室切取人正常肺组织、单纯COPD患者和COPD合并慢性缺氧患者肺组织，将标本分为：①正常对照的PASMCs、单纯COPD和COPD合并慢性缺氧患者的PASMCs；②正常对照的PASMCs和经过慢性缺氧培养的PASMCs。利用半定量RT-PCR技术，分析Kv1.2、Kv1.3、Kv1.5、Kv2.1、Kv3.1等的基因表达。 结果： ①Kv1.2、Kv1.3、Kv1.5、Kv2.1、Kv3.1等基因在正常PASMCs和单纯COPD患者PASMCs中均有表达，而且两者无显著差异；②Kv1.2、Kv1.5、Kv2.1在患者在体慢性缺氧和离体慢性缺氧时的表达均明显降低（P<0.05）；Kv1.3在患者在体慢性缺氧时表达明显降低（P<0.05），而离体慢性缺氧时无显著变化（P>0.05）；Kv3.1在患者在体慢性缺氧和离体慢性缺氧时的表达均无显著变化（P>0.05）；③Kv1.2、Kv1.5、Kv2.1、Kv3.1等基因在单纯COPD时表达显著上调（P<0.05）。 结论： 在慢性缺氧情况下，Kv1.2、Kv1.3、Kv1.5、Kv2.1 4种亚型基因表达明显下降，提示可能在促进人肺动脉高压的形成和发展中起重要作用。而慢性缺氧对Kv3.1基因表达无显著影响，提示它们可能对缺氧不敏感，在人肺动脉高压发生中处于次要地位。至于在单纯COPD时几种亚型的表达上调，原因不清楚，需进一步研究证实。     

BQ123对大鼠肺动脉平滑肌细胞电压门控钾通道表达的影响

目的：探讨内皮素-1受体拮抗剂BQ123 对大鼠肺动脉平滑肌细胞电压门控钾通道亚型基因表达的影响。 方法： 根据常氧 (PO2 152 mmHg ) 及慢性低氧（PO2 40±5 mmHg）的不同培养条件，将肺动脉平滑肌细胞分为常氧组和慢性低氧组，并用BQ123分别处理上述两组细胞，采用半定量RT-PCR技术检测大鼠肺动脉平滑肌细胞Kv2.1、Kv9.3基因表达的变化。 结果： 经过慢性低氧，大鼠肺动脉平滑肌细胞Kv2.1、Kv9.3的mRNA表达水平明显低于常氧组（P<0.01，n=5），BQ123对常氧组Kv2.1的mRNA表达无影响（P>0.05，n=5），但可明显增加慢性低氧组Kv2.1的表达（P<0.01，n=5）。无论在常氧还是慢性低氧时，BQ123对Kv9.3的mRNA表达均无影响（P>0.05，n=5）。 结论： 慢性低氧可降低大鼠肺动脉平滑肌细胞电压门控钾通道的表达，内皮素-1受体拮抗剂BQ123可能通过抑制PASMCs的增殖，改变了细胞内信号转导通路中某些因子的表达，从而间接促进Kv的表达。     

缺氧对肺动脉平滑肌细胞钾通道Kv1.2、Kv1.6基因表达的影响

目的:研究不同缺氧时间对大鼠肺动脉平滑肌细胞(PASMC)不同亚型钾通道(Kv)mRNA和蛋白质表达的影响。方法:采用半定量RT-PCR和Western-blot方法对常氧和不同缺氧时间后PASMC上Kv1.2、Kv1.6mRNA和蛋白质的表达进行测定。结果:(1)PASMC在常氧和缺氧时均有Kv1.2、Kv1.6mRNA和蛋白质表达;(2)缺氧18h使Kv1.2mRNA和蛋白质表达增强,缺氧48h则使其表达减弱且低于常氧时的表达;(3)缺氧18h、48h对Kv1.6的mRNA和蛋白质表达无影响。结论:Kv1.6不是氧敏感的钾通道;作为氧感受器的Kv1.2,其mRNA和蛋白质表达随缺氧时间而改变。     

慢性低氧对大鼠肺组织电压门控钾通道表达的影响

目的:探讨慢性低氧对大鼠肺组织电压门控钾通道亚型Kv1.5、Kv2.1、Kv9.3表达的影响。方法:将12只Wistar大鼠随机分为对照组和慢性低氧组,每组6只。采用RT-PCR和Westernblot对大鼠肺组织匀浆中Kv1.5、Kv2.1、Kv9.3mRNA和Kv1.5蛋白质的表达进行观察。结果:慢性低氧组大鼠肺组织匀浆中Kv1.5、Kv2.1、Kv9.3mRNA和Kv1.5蛋白质表达明显低于对照组(P<0.01)。结论:慢性低氧可以从转录、翻译两个水平抑制大鼠肺组织中Kv1.5、Kv2.1Kv9.3的表达,Kv1.5、Kv2.1、Kv9.3表达的减少必将导致Kv数目的减少和电流的降低。Kv1.5、Kv2.1、Kv9.3可能是氧敏感钾通道亚型。     

血栓烷A_2类似物对大鼠肺动脉血管平滑肌细胞钾离子通道表达的影响

目的:观察血栓烷A2(TXA2)类似物U46619对实验大鼠肺动脉血管平滑肌细胞(PASMCs)K+通道Kv1.2、Kv1.5、Kv2.1蛋白质和mRNA表达的影响。方法:采用酶法分离、培养Wistar大鼠PASMCs,通过Western-blot和RT-PCR方法分别从蛋白质水平和mRNA水平分析U46619对Kv1.2、Kv1.5、Kv2.1表达的抑制作用。结果:100nmol/LU46619对Kv1.2表达有明显抑制作用。结论:TXA2类似物U46619可能通过抑制Kv1.2表达而参与大鼠肺动脉血管的收缩。     

Hypoxia suppresses Kv 2.1 channel expression through endogenous 15-hydroxyeicosatetraenoic acid in rat pulmonary artery

We have previously reported that hypoxia activates lung 15-lipoxygenase (15-LOX), which catalyzes arachidonic acid to produce 15-HETE, leading to constriction of neonatal rabbit pulmonary arteries. Hypoxia suppresses Kv2.1 channel expression. Although the Kv channel inhibition by hypoxia is likely to be mediated through 15-HETE, direct evidence is still lacking. To explore whether 15-LOX/15-HETE pathway contributes to the hypoxia-induced down-regulation of Kv2.1 channel, we performed studies using 15-LOX blockers, semi-quantitative PCR and western blot analysis. We found that Kv2.1 channel expression at the mRNA and protein levels was greatly up-regulated in pulmonary arterial smooth muscle cells (PASMCs) and pulmonary artery (PA) after blockade of endogenous 15-HETE under hypoxic condition. 15-HETE further decreased Kv2.1 channel expression in comparison with 12-HETE and 5-HETE in cultured PASMCs and PA under normoxic conditions. These data indicate that hypoxia suppresses Kv2.1 channel expression through endogenous 15-HETE in PA.     

5-羟基癸酸盐对慢性低氧大鼠肺动脉Kv1.5通道表达的影响

目的: 以大鼠为研究对象,研究线粒体ATP敏感性钾通道(mitoK_ATP)的抑制剂5-羟基癸酸盐(5-HD)对慢性低氧肺动脉高压大鼠的影响及其潜在机制。方法: 24只SD雄性大鼠随机分成对照组、低氧组、低氧+5-羟基癸酸盐干预组,每组8只。将低氧组和5-HD干预组大鼠放入常压低氧舱内 以建立低氧肺动脉高压模型。 4周后测定平均肺动脉压(mPAP)及右心室与左心室及室间隔的重量比 ,并采用RT-PCR及Western blotting技术,分析各组肺动脉Kv1.5 mRNA及蛋白表达。结果: (1) 慢性低氧组大鼠的mPAP及RV/(LV+S)显著高于正常对照组(P<0.05),5-HD干预组mPAP及RV/(LV+S)显著低于低氧组,均P<0.05。(2) 低氧组Kv1.5通道mRNA及蛋白表达显著低于正常组,5-HD组Kv1.5通道表达显著高于低氧组, 均P<0.05。结论: mitoK_ATP通道的抑制剂5-HD通过降低mPAP及RV/(LV+S),在慢性低氧肺动脉高压中起保护作用。mitoK_ATP通道的抑制及Kv1.5通道表达的上调可能与该保护作用有关。     

Fluoxetine protects against big endothelin-1 induced anti-apoptosis by rescuing Kv1.5 channels in human pulmonary arterial smooth muscle cells

Purpose

Pulmonary Kv channels are thought to play a crucial role in the regulation of cell proliferation and apoptosis. Previous studies have shown that fluoxetine upregulated the expression of Kv1.5 and prevented pulmonary arterial hypertension in monocrotaline-induced or hypoxia-induced rats and mice. The current study was designed to test how fluoxetine regulates Kv1.5 channels, subsequently promoting apoptosis in human PASMCs cultured in vitro.

Materials and Methods

Human PASMCs were incubated with low-serum DMEM, ET-1, and fluoxetine with and without ET-1 separately for 72 h. Then the proliferation, apoptosis, and expression of TRPC1 and Kv1.5 were detected.

Results

In the ET-1 induced group, the upregulation of TRPC1 and down regulation of Kv1.5 enhanced proliferation and anti-apoptosis, which was reversed when treated with fluoxetine. The decreased expression of TRPC1 increased the expression of Kv1.5, subsequently inhibiting proliferation while promoting apoptosis.

Conclusion

The results from the present study suggested that fluoxetine protects against big endothelin-1 induced anti-apoptosis and rescues Kv1.5 channels in human pulmonary arterial smooth muscle cells, potentially by decreasing intracellular concentrations of Ca²⁺.     

Regulation of gadd153 mRNA expression by hypoxia in pulmonary artery smooth muscle cells.

Hypoxia causes pulmonary hypertension and induces oxygen radicals in pulmonary artery smooth muscle cells (PASMCs). Since oxidative stress regulates gaddl53 expression, we examined gaddl53 mRNA in PASMCs cultured in a hypoxic environment. Gadd153 mRNA content was increased in PASMCs cultured for 24 hours in 1% oxygen. This increase was not abrogated by inhibition of protein synthesis. To explore the signaling pathways mediating hypoxic regulation of gaddl53 mRNA, the impact of calcium channel blockade by verapamil, G protein inhibition by pertussis toxin, and protein kinase C (PKC) down-regulation, was examined. Although none of these interventions reduced basal expression of gaddl53 mRNA in PASMCs, all of them suppressed the induction by hypoxia. In contrast, antioxidants had no effect. These observations indicate hypoxia induces gaddl53 expression in PASMCs through common signaling pathways.     

Adaptative modifications of right coronary myocytes voltage-gated K+ currents in rat with hypoxic pulmonary hypertension

Chronic hypoxia (CH)-induced pulmonary hypertension (PHT) is well known to alter K+ channels in pulmonary myocytes. PHT induces right ventricle hypertrophy that increases oxygen demand; however, coronary blood flow and K+ channel adaptations of coronary myocytes during PHT remain unknown. We determined whether CH and PHT altered K+ currents and coronary reactivity and what impact they might have on right myocardial perfusion. Right ventricle perfusion, as attested by microspheres, was redistributed toward hypertrophied right ventricle [RV/LV (%)=0.59+/-0.07% in CH rats vs. 0.29+/-0.03 in control rats, P<0.05]. Whole-cell patch clamping showed a reduction of global outward current in hypoxic right coronary artery myocytes (H-RCA), whereas hypoxic left coronary artery myocytes exhibited an increase. K+ channel blockers revealed that a 4-aminopyridine (4AP)-sensitive current (Kv current) was decreased in H-RCA (14.3+/-1.1 vs. 23.4+/-2.5 pA/pF at 60 mV in control RCA, P<0.05) and increased in hypoxic left coronary artery myocytes (H-LCA; 26.4+/-3.8 vs. 11.8+/-1.6 pA/pF at 60 mV in control LCA, P<0.05). Constriction to 4AP was decreased in H-RCA when compared to normoxic control and increased in H-LCA when compared to LCA. Finally, we observed that the expression of Kv1.2 and Kv1.5 were lower in H-RCA than that in H-LCA. This study reveals that CH differentially regulates Kv channels in coronary myocytes. Hypoxia decreases Kv currents and therefore reduces vasoreactivity that contributes to an adaptative response leading to right hypertrophied ventricle perfusion enhancement at rest.     

慢性缺氧对大鼠肺内动脉平滑肌细胞Kv1.3、Kv2.1、Kv3.1钾通道基因在急性缺氧时表达的影响

目的与方法:用半定量RT-PCR方法,研究慢性连代缺氧对大鼠肺内动脉平滑肌细胞(PASMC)Kv13、Kv21、Kv31钾通道基因在急性缺氧时表达变化的影响。结果:①正常及慢性缺氧鼠PASMC中均有Kv13、Kv21、Kv31基因表达;②急性缺氧可使PASMC中Kv21、Kv31mRNA表达明显上调,其mRNA分别由0.646±0.092、0.782±0.104升高到1.059±0.134、0.985±0.116(P<0.01);③慢性缺氧后复氧12h再急性缺氧6h,PASMCKv21mRNA、Kv31mRNA水平均降低,其中Kv21mRNA由1.008±0.117下降到0.649±0.097,差异有极显著意义(P<0.01)。结论:Kv21、Kv31基因可能是缺氧反应基因,慢性缺氧可改变PASMC的Kv21、Kv31钾通道基因对急性缺氧的反应,使其由表达上调转变为下调,可能因而降低此钾通道在HPV中的作用。     

Kv1.5对大鼠低氧高二氧化碳性PASMCs增殖、凋亡的影响及与MAPK通路的关系

 目的：探讨电压依赖性钾离子通道Kv1.5对大鼠低氧高二氧化碳性肺动脉平滑肌细胞（PASMCs）增殖、凋亡的影响及其与丝裂原激活蛋白激酶（MAPK）信号通路的关系。方法：体外培养大鼠PASMCs,复制低氧高二氧化碳模型,随机分组如下：常氧组（N组）;低氧高二氧化碳组（HH组）;低氧高二氧化碳+溶剂DMSO对照组（HD组）;低氧高二氧化碳+ERK1/2通路抑制剂U0126组（HU组）;低氧高二氧化碳+p38 MAPK通路抑制剂SB203580组（HS组）;低氧高二氧化碳+MAPK通路激动剂茴香霉素（anisomycin）组（HA组）。采用CCK-8法检测细胞活性,蛋白免疫印迹法检测Kv1.5、增殖细胞核抗原（PCNA）及Bax蛋白的表达水平。结果：与N组相比,HH组和HD组细胞活性增加（P<0.01）,PCNA蛋白表达上调,Kv1.5及Bax蛋白表达均明显降低（P<0.01）,HH组和HD组间各指标变化均无显著差异（均P>0.05）;较之HD组,HU组、HS组及HA组细胞活性降低（P<0.05或P<0.01）,PCNA蛋白表达下调,Kv1.5及Bax蛋白表达均明显增加,差异均显著（P<0.01）,其中以HA组各指标变化最明显。结论：钾离子通道Kv1.5对低氧高二氧化碳性大鼠PASMCs增殖、凋亡的调节可能与MAPK通路的激活有关。     

肺动脉平滑肌细胞凋亡在大鼠低氧性肺动脉重构自然逆转中的作用及分子机制

目的:研究肺动脉平滑肌细胞(pulmonary arterial smooth muscle cells,PASMCs)凋亡在低氧性肺动脉重构自然逆转中的作用,并探讨其可能机制。方法:24只SD大鼠随机均分为常氧4周组、低氧4周组、低氧4周后复氧1周组及复氧6周组。分别检测右室收缩压(right ventricular systolic pressure,RVSP)、肺动脉中膜厚度(medial thickness,MT)和中膜面积(medial area,MA),以及肺动脉中膜自噬、凋亡等在低氧-复氧中的变化。大鼠原代PASMCs分为常氧48 h组、低氧48 h组、低氧48 h后复氧24 h组及常氧72 h组,观察PASMCs凋亡和自噬在低氧-复氧中的变化。再将PASMCs分为常氧72 h组、低氧48 h后复氧24 h组及低氧48 h+氯喹(自噬抑制剂)干预后复氧24 h组,观察PASMCs低氧阶段的自噬对其复氧阶段凋亡的影响。结果:(1)低氧使大鼠RVSP、右室肥厚指数、MT及MA显著升高(P0.05);复氧后上述指标逐渐降低。(2)低氧使肺动脉中膜LC3表达升高,P62表达降低,复氧后上述分子的表达逐步恢复正常。低氧显著降低了中膜cleaved caspase-3的表达,复氧1周其表达显著高于低氧组。(3)低氧期原代PASMCs cleaved caspase-3/PARP的表达显著低于常氧组,复氧后其表达明显升高(P0.05);PASMCs LC3和P62的表达在低氧期显著降低(P0.05)。(4)抑制了PASMCs低氧阶段的自噬后,其复氧阶段cleaved caspase-3/PARP表达显著降低(P0.05)。结论:PASMCs的凋亡参与了低氧性肺动脉重构的自然逆转;复氧期PASMCs凋亡的发生可能与其低氧期的自噬有关。     

α1-肾上腺素受体在缺氧性肺动脉平滑肌细胞增殖中的作用

目的: 探讨肾上腺素α₁受体(α₁AR)及β₂受体(β₂AR)在缺氧性肺动脉平滑肌细胞(PASMCs)增殖中的作用及分子机制。方法: 用贴块法培养新生牛肺动脉平滑肌细胞至第6代,并作免疫组化染色鉴定。细胞在6.6% O₂环境中常压缺氧6、12、24 h,用 -TdR掺入法反映DNA合成测定PASMCs的增殖,用Fura-2/AM测定胞内Ca²⁺浓度。用Northern blotting法观察PASMCs的c-fos、c-myc基因表达和α₁AR mRNA、β₂AR mRNA的变化。加用不同的受体激动剂和抑制剂,探讨α₁AR被激活和抑制后,以及β₂AR激活后对上述变化的影响。结果: 单纯缺氧,PASMCs DNA合成即明显增加,α₁AR激活后,增加更明显;而α₁AR抑制后,明显降低(P<0.01)。β₂AR激活时无明显变化。缺氧后胞内游离钙浓度也增高(P<0.01),PASMCs上c-fos和c-myc基因表达增强(P<0.05),α₁AR mRNA和β₂AR mRNA水平均显著增高(P<0.01)。结论: 结果提示缺氧刺激PASMCs,使胞内钙浓度增加,c-fos和c-myc基因表达增强,引起PASMCs增殖,这一增殖是通过α₁AR介导的,但β₂AR不起主要作用。缺氧时α₁AR增多,既促进肺血管收缩,又加强细胞增殖,在缺氧性肺血管收缩和肺血管重建导致的肺动脉高压中起一定的作用     

Altered expression of potassium channel subunit mRNA and alpha-dendrotoxin sensitivity of potassium currents in rat dorsal root ganglion neurons after axotomy

Previous studies have raised the possibility that a decrease in voltage-gated K+ currents may contribute to hyperexcitability of injured dorsal root ganglion (DRG) neurons and the emergence of neuropathic pain. We examined the effects of axotomy on mRNA levels for various Kv1 family subunits and voltage-gated K+ currents in L4-L5 DRG neurons from sham-operated and sciatic nerve-transected rats. RNase protection assay revealed that Kv1.1 and Kv 1.2 mRNAs are highly abundant while Kv1.3, Kv1.4, Kv1.5 and Kv1.6 mRNAs were detected at lower levels in L4-L5 DRGs from sham and intact rats. Axotomy significantly decreased Kv1.1, Kv1.2, Kv1.3 and Kv1.4 mRNA levels by approximately 35%, approximately 60%, approximately 40% and approximately 80%, respectively, but did not significantly change Kv1.5 or Kv1.6 mRNA levels. Patch clamp recordings revealed two types of K+ currents in small-sized L4-L5 DRG neurons: sustained delayed rectifier currents elicited from a -40 mV holding potential and slowly inactivating A-type currents that was additionally activated from a -120 mV holding potential. Axotomy decreased both types of K+ currents by 50-60% in injured DRG neurons. In addition, axotomy increased the alpha-dendrotoxin sensitivity of the delayed rectifier, but not slow A-type K+ currents in injured DRG neurons. These results suggest that Kv1.1 and Kv1.2 subunits are major components of voltage-gated K+ channels in L4-L5 DRG neurons and that the decreased expression of Kv1-family subunits significantly contributes to the reduction and altered kinetics of Kv current in axotomized neurons.     

缺氧对大鼠肺动脉平滑肌细胞 HO-1 基因表达和内源性一氧化碳生成的影响

目的:研究缺氧对体外培养的大鼠肺动脉平滑肌细胞诱导型血红素氧合酶(HO-1)基因表达及内源性一氧化碳(CO)产生的影响,探讨HO-CO系统在缺氧性肺动脉高压中的作用。方法:原代培养大鼠肺内动脉的平滑肌细胞(PASMC)并传代,选用第3-5代PASMC用于实验。在培养瓶内通缺氧气体(95%N₂,5%CO₂)12、24h和48h后,用逆转录-聚合酶链式反应(RT-PCR)检测PASMC中HO-1mRNA水平,用酶联免疫检测仪测定培养基中碳氧血红蛋白(COHb)含量,放免法测定培养基中环磷酸鸟苷(cGMP)含量。结果:缺氧12、24和48hHO-1mRNA分别较正常对照组高2.7%、5.7%和27.1%(P＜0.01),培养基中COHb的含量分别较正常对照组高13.8%、31.0%和93.1%(P＜0.01),PASMC中cGMP的含量分别为正常对照组的2.7、4.0和6.8倍(P＜0.01或P＜0.05)。结论:缺氧诱导PASMC中的HO-1基因表达上调,并使内源性CO产生增多,对PASMC内cGMP浓度有调节作用。     

三七皂苷单体R1 抑制低氧高二氧化碳诱导的肺动脉平滑肌细胞p38 MAPK信号通路的活化

目的: 探讨三七皂苷单体R₁(R₁)减轻低氧高二氧化碳(CO₂)性肺动脉收缩的作用及其与p38 MAPK信号通路的关系。方法: 原代培养雄性SD大鼠肺动脉平滑肌细胞(PASMCs),取第2至5代对数生长期细胞至低氧高CO₂(1% O₂, 6% CO₂)条件下继续培养,并分别用8、40、100 mg/L R₁ 孵育24 h后收集细胞,采用免疫印迹法测定p38 MAPK磷酸化蛋白表达,半定量RT-PCR检测p38 MAPK mRNA的表达。结果: Western blotting和RT-PCR结果显示,低氧高CO₂组p-p38 MAPK蛋白和p38 MAPK mRNA表达明显高于对照组(N)组(P<0.01)。与低氧高CO₂组相比,R₁(8、40、100 mg/L)不同程度抑制了p-p38 MAPK蛋白和p38 MAPK mRNA的表达(P<0.01),并呈剂量依赖关系。结论: 低氧高CO₂诱导PASMCs p38 MAPK活化,三七皂苷单体R₁可能通过抑制p38 MAPK通路减轻低氧高CO₂性肺动脉收缩。     

Effect of hypoxia and dexamethasone on inflammation and ion transporter function in pulmonary cells

Dexamethasone has been found to reduce the incidence of high-altitude pulmonary oedema. Mechanisms explaining this effect still remain unclear. We assessed the effect of dexamethasone using established cell lines, including rat alveolar epithelial cells (AEC), pulmonary artery endothelial cells (RPAEC) and alveolar macrophages (MAC), in an environment of low oxygen, simulating a condition of alveolar hypoxia as found at high altitude. Inflammatory mediators and ion transporter expression were quantified. Based on earlier results, we hypothesized that hypoxic conditions trigger inflammation. AEC, RPAEC and MAC, pre-incubated for 1 h with or without dexamethasone (10(-7) mol/l), were subsequently exposed to mild hypoxia (5% O(2), or normoxia as control) for 24 h. mRNA and protein levels of cytokine-induced neutrophil chemoattractant-1, monocyte chemoattractant protein-1 and interleukin-6 were analysed. mRNA expression and functional activity of the apical epithelial sodium channel and basolateral Na(+)/K(+)-ATPase were determined using radioactive marker ions. In all three types of pulmonary cells hypoxic conditions led to an attenuated secretion of inflammatory mediators, which was even more pronounced in dexamethasone pretreated samples. Function of Na(+)/K(+)-ATPase was not significantly influenced by hypoxia or dexamethasone, while activity of epithelial sodium channels was decreased under hypoxic conditions. When pre-incubated with dexamethasone, however, transporter activity was partially maintained. These findings illustrate that long-term hypoxia does not trigger an inflammatory response. The ion transport across apical epithelial sodium channels under hypoxic conditions is ameliorated in cells treated with dexamethasone.