双孔钾通道TASK-1与缺氧性肺血管收缩的研究进展

缺氧性肺血管收缩是机体一项重要的代偿反应,K+通道在其发生中发挥重要作用,相关研究已成为当前热点.近期研究发现双孔钾通道亚型TASK-1在肺动脉平滑肌细胞上表达,并与缺氧性肺血管收缩存在一定相关性,此文拟从缺氧性肺血管收缩与TASK-1研究进展及其相关性研究作一综述.     

硝苯吡啶治疗慢性阻塞性肺疾病并发的肺动脉高压

慢性阻塞性肺疾病时肺动脉高压的程度是决定病人寿命的重要因素。肺动脉高压的发病机理主要是小的肺动脉和肺泡血管缺氧性收缩。最初,借血管收缩可维持正常的通气-灌注比例,但由于肺泡长期缺氧,肺血管持久狭窄,导致毛细血管阻力增大,肺动脉压明显升高;慢性缺氧尚可引起肺血管的器质性病变。肺血管收缩的主要机理是钙进入细胞内,如抑制钙的转运则可使缺氧性肺血管收缩减轻,故可以作为钙离子拮抗剂治疗缺氧性肺动脉高压的依据。作者观察慢性非特异性肺病13(男11,女2)例     

低体温增强缺氧性肺血管收缩反应

本文研究低体温对缺氧性肺血管收缩反应的影响。发现动物体温降低时肺动脉压上升,肺血管阻力加大,此时肺血管对缺氧刺激更敏感,缺氧性肺血管收缩反应(HPV)显著增强。α_1受体阻滞剂哌唑嗪明显抑制低温增强的HPV。血浆去甲肾上腺素含量在低温缺氧时显著增加,但同单纯缺氧刺激作用无差别,提示低温时HPV增强,可能主要与肺血管肾上腺素能受体功能在低体温时发生改变以及血管平滑肌膜兴奋性增加有关。     

急性吸烟使人的肺血管反应性增强——前列腺素、白三烯的介导作用

应用肺阻抗血流图测定肺血管收缩反应的方法,研究44名健康男性肺血管对缺氧有收缩反应性的自愿者,由急性吸烟引起的缺氧性肺血管收缩反应性的变化,并探讨前列腺素和白三烯在其中的作用。结果:急性吸烟(15分钟内吸完香烟3支)使缺氧性肺血管收缩反应明显增强,服环氧合酶抑制剂(消炎痛,25毫克日3次,共4天)或脂氧合酶抑制剂(乙胺嗪,200毫克日3次,共3天)均可使由急性吸烟所致的肺血管反应增强显著减弱。前列腺素和白三烯在急性吸烟引起人的缺氧性肺血管反应性的增强中起介导作用。     

吸入—氧化氮治疗肺部疾病的现状

体内生成的一氧化氮(NO)有广泛的生物学作用.吸入NO 对肺血管有选择性舒张作用,能对抗缺氧性肺血管收缩,已用于治疗新生儿肺动脉高压、与心脏病有关的肺动脉高压和成人呼吸窘迫综合征。吸入有效浓度时毒副作用不明显.     

Rho/Rho激酶信号通路与缺氧性肺动脉高压

缺氧性肺动脉高压（hypoxic pulmonary hypertension，HPH）是一些先天性心血管疾病和慢性肺部疾病最常见的并发症，以肺血管收缩反应性增强和肺血管结构重构为特征，其发生机制尚未完全清楚。近年来研究表明，Rho/Rho激酶信号通路在急性缺氧性肺血管收缩和慢性缺氧引起的肺动脉高压和肺血管结构重构过程中发挥重要作用。     

氧自由基与肺血管反应性

氧自由基能介导血管运动,是连接肺泡氧分压(P_AO_2)与肺血管紧张性的纽带。肺内适量的氧自由基对肺血管基础张力的调节有重要意义,并可能参与肺泡 V/Q 比例的调节。缺氧时,肺内氧自由基生成不足可能是引起缺氧性肺血管收缩反应的重要原因.     

氧自由基对肺血管的影响及其作用机制

氧自由基在某些肺疾病发生中的作用已不容置疑,但是否与缺氧性肺血管收缩和肺动脉高压的发生有关尚不十分清楚。本文介绍氧自由基对肺血管的影响及其作用机制。     

慢性缺氧性肺动脉高压大鼠内皮依赖性舒缩因子的变化

慢性缺氧性肺动脉高压大鼠内皮依赖性舒缩因子的变化李志斌邹霞英容中生缺氧性肺血管收缩反应（ＨＰＶ）和肺血管结构重建是缺氧性肺动脉高压（ＰＨ）形成和发展的主要因素。缺氧致肺血管内皮细胞（ＥＣ）损伤［１］，影响ＥＣ分泌内皮依赖性舒缩因子的平衡，增强ＨＰＶ和...     

吸入一氧化氮治疗肺部疾病的现状

体内生成的一氧化氮（ＮＯ）有广泛的生物学作用。吸入ＮＯ对肺血管有选择性舒张作用，能对抗缺氧性肺血管收缩，已用于治疗新生儿肺动高压、与心脏病有关的肺动脉高压和成人呼吸窘迫综合征。吸入有效浓度时毒副作用不明显。     

急性缺氧抑制大鼠肺动脉平滑肌细胞钙ATP钾通道

目的研究急性缺氧对大鼠肺动脉平滑肌细胞钾通道活性的影响，以探讨钾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。方法应用膜片钳单通道技术，在对称性高钾溶液中，于急性酶分离的大鼠单个肺动脉平滑肌细胞的内面向外式膜片（ｉｎｓｉｄｅｏｕｔｐａｔｃｈ）上，记录外向性钾通道电流，并用常氧和低氧的细胞浴液持续灌流肺动脉平滑肌细胞，以观察其对外向性钾通道电流的影响。结果在记录的外向性钾电流中，证实了一种电流为钙、ＡＴＰ激活性钾通道（Ｋ＋ＣａＡＴＰ）；用低氧的细胞浴液灌流肺动脉平滑肌细胞可明显抑制这种钙、ＡＴＰ激活性钾通道的活性（Ｐ＜０．０１）。而钾通道开放剂卡吗克啉（ｃｒｏｍａｋａｌｉｍ）对低氧所抑制的肺动脉平滑肌细胞钙、ＡＴＰ激活性钾通道具有明显的激活作用（Ｐ＜０．０１）。结论急性低氧可通过对钙、ＡＴＰ激活性钾通道的抑制作用，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。肺动脉平滑肌细胞钙、ＡＴＰ激活性钾通道活性的降低，可能在低氧性肺血管收缩反应中起着重要的作用。Ｃｒｏｍａｋａｌｉｍ可作为拮抗低氧性肺血管收缩的有效药物之一。     

钙库操纵性钙通道特性及其与低氧性肺血管收缩、重构的关系

肺动脉平滑肌细胞内Ca2+浓度增加是导致低氧性肺血管收缩与重构的重要分子基础.由瞬时受体电位蛋白构成的钙库操纵性钙通道(store-operated channels,SOC)是调节细胞内Ca2+浓度的重要机制,并参与了肺动脉高压时血管收缩和重构过程.充分了解SOC通道的特性,对深入认识肺动脉高压发病的病理生理学机制、指导临床治疗策略具有重要意义.     

YM155, a selective survivin inhibitor,reverses chronic hypoxic pulmonary hypertension in rats via upregulating voltage-gated potassium channels

Abstract

To test the hypothesis that chronic hypoxic pulmonary hypertension (CH-PH) is associated with increased survivin and decreased voltage-gated potassium (K_V) channels expression in pulmonary arteries, rats were randomized as: normoxia (N); normoxia?+?YM155, survivin suppressor (NY); hypoxia (H); hypoxia?+?YM155 (HY). HY group had significantly reduced pulmonary arterial pressure, right ventricular weight and right ventricular hypertrophy compared with H group. Survivin mRNA and protein were detected in pulmonary arteries of rats with CH-PH, but not rats without CH-PH. YM155 downregulated survivin protein and mRNA. K_V channel expression and activity were upregulated after YM155 treatment. Survivin may play a role in the pathogenesis of CH-PH.     

Effects of K+ channel blockers on vascular tone in the perfused rat lung

To learn more of the role of K+ channel activity in the regulation of pulmonary vascular tone, we compared the pressor effects of the differential blockers of numerous K+ channels, tetraethylammonium chloride and 4-aminopyridine, and the inhibitor of ATP-sensitive K+ channels glibenclamide in meclofenamate-treated salt solution-perfused rat lungs. Tetraethylammonium (1 to 20 mM) and 4-aminopyridine (1 to 10 mM), but not glibenclamide (1 to 20 microM) caused vasoconstriction in the normoxic lung. The Ca++ channel blocker nifedipine (0.1 microM) and the alpha adrenoceptor antagonist phentolamine (10 microM) inhibited the 4-aminopyridine response by about 50% and reduced slightly the smaller tetraethylammonium response. 4-Aminopyridine and, to a lesser extent, tetraethylammonium, but not glibenclamide, also potentiated peak vasoconstriction to angiotensin II and airway hypoxia. Nifedipine, but not phentolamine, inhibited hypoxic vasoconstriction and prevented the potentiation by 4-aminopyridine. These results suggest that Ca(++)- and/or voltage-activated (not ATP-sensitive) K+ channels may be important in maintaining low pulmonary vascular tone.     

Hypoxia Modulates Cyclic AMP Activation of BK<Subscript>Ca</Subscript> Channels in Rat Pulmonary Arterial Smooth Muscle

The signal transduction mechanisms defining the role of cyclic nucleotides in the regulation of potassium channel activity in pulmonary vascular smooth muscle are currently an area of great interest. Normally, signaling mechanisms that elevate cyclic AMP (cAMP) open potassium channels. Modulation of the large-conductance, calcium- and voltage-activated potassium (BK_Ca) channel is important in the regulation of pulmonary arterial pressure, and inhibition (closing) of the BK_Ca channel has been implicated in the development of pulmonary vasoconstriction. Accordingly, studies were done to determine the effect of cAMP-elevating agents on BK_Ca channel activity under normoxic and hypoxic conditions using patch-clamp studies in pulmonary arterial smooth muscle cells (PASMC) of the fawn-hooded rat (FHR). Forskolin (10 μM; n = 4), a stimulator of adenylate cyclase and an activator of cAMP-dependent protein kinase (PKA), and CPT-cAMP (100 μM; n = 3), a membrane-permeable derivative of cAMP, opened BK_Ca channels in single FHR PASMC under normoxic conditions. Exposure of FHRs to 4 weeks of 10% O₂ (hypoxia) significantly attenuated the effect of both forskolin (n = 7) and CPT-cAMP (n = 14) on BK_Ca channel activity in PASMC. These results suggest that this phenomenon may serve as a physiological mechanism to cause hypoxic vasoconstriction in the pulmonary circulation via modulation of BK_Ca channels.     

Ca2+ channels and chronic hypoxia

Many chronic lung diseases are associated with prolonged exposure to alveolar hypoxia, resulting in the development of pulmonary hypertension. While the exact mechanisms underlying the pathogenesis of hypoxic pulmonary hypertension remain poorly understood, a key role for changes in Ca2+ homeostasis has emerged. Intracellular Ca2+ concentration controls a variety of pulmonary vascular cell functions, including contraction, gene expression, growth, barrier function and synthesis of vasoactive substances. Several studies indicate that prolonged exposure to hypoxia causes alterations in the expression and activity of several Ca2+ handling pathways in pulmonary arterial smooth muscle cells. In contrast, the effect of chronic hypoxia on Ca2+ homeostasis in pulmonary arterial endothelial cells is relatively unexplored. In this review, we discuss data from our laboratory and others describing the effects of prolonged hypoxia on pulmonary vascular smooth muscle and endothelial cell Ca2+ homeostasis and the various Ca2+ channels and handling pathways involved in these responses. We will also highlight future directions of investigation that might improve our understanding of the response of pulmonary vascular cells to chronic hypoxia.     

O2 sensing is preserved in mice lacking the gp91 phox subunit of NADPH oxidase.

The rapid response to hypoxia in the pulmonary artery (PA), carotid body, and ductus arteriosus is partially mediated by O2-responsive K+ channels. K+ channels in PA smooth muscle cells (SMCs) are inhibited by hypoxia, causing membrane depolarization, increased cytosolic calcium, and hypoxic pulmonary vasoconstriction. We hypothesize that the K+ channels are not themselves "O2 sensors" but rather respond to the reduced redox state created by hypoxic inhibition of candidate O2 sensors (NADPH oxidase or the mitochondrial electron transport chain). Both pathways shuttle electrons from donors, down a redox gradient, to O2. Hypoxia inhibits these pathways, decreasing radical production and causing cytosolic accumulation of unused, reduced, freely diffusible electron donors. PASMC K+ channels are redox responsive, opening when oxidized and closing when reduced. Inhibitors of NADPH oxidase (diphenyleneiodonium) and mitochondrial complex 1 (rotenone) both inhibit PASMC whole-cell K+ current but lack the specificity to identify the O2-sensor pathway. We used mice lacking the gp91 subunit of NADPH oxidase [chronic granulomatous disease (CGD) mice] to assess the hypothesis that NADPH oxidase is a PA O2-sensor. In wild-type lungs, gp91 phox and p22 phox subunits are present (relative expression: macrophages > airways and veins > PASMCs). Deletion of gp91 phox did not alter p22 phox expression but severely inhibited activated O2 species production. Nonetheless, hypoxia caused identical inhibition of whole-cell K+ current (in PASMCs) and hypoxic pulmonary vasoconstriction (in isolated lungs) from CGD vs. wild-type mice. Rotenone vasoconstriction was preserved in CGD mice, consistent with a role for the mitochondrial electron transport chain in O2 sensing. NADPH oxidase, though a major source of lung radical production, is not the pulmonary vascular O2 sensor in mice.     

Cellular mechanisms that control pulmonary vascular tone during hypoxia and normoxia. Possible role of Ca2+ATPases.

We investigated cellular mechanisms that may be involved in controlling cytosol calcium and pulmonary artery pressure during hypoxia and normoxia in isolated blood-perfused ferret lungs. Alveolar hypoxia in ferret lungs causes an active increase in pulmonary vascular resistance. Hypoxic pulmonary vasoconstriction directly correlates with extracellular calcium ([Ca2+]o), and the absence of [Ca2+]o in the perfusate markedly attenuates the hypoxemia-induced pulmonary vasoconstriction. Alveolar hypoxia does not potentiate the production of thromboxane B2 (TxB2) or 6-keto-PGF1 alpha. Vanadate, a widely used inhibitor of Ca2+ATPases, increases pulmonary arterial pressure (Ppa) in the presence or absence of [Ca2+]o and without affecting the production of TxB2 or 6-keto-PGF1 alpha. Vanadate and ouabain, an inhibitor of Na+/K+ATPase, produce synergistic increases in Ppa. Amiloride, an inhibitor of Na+/Ca2+ exchange, reverses the increase in Ppa caused by ouabain, but not the increase caused by vanadate. The additional effect produced by ouabain on Ppa after near maximal vanadate effect and the ability of amiloride to reverse the pulmonary vasoconstriction caused by ouabain, but not vanadate, suggests that vanadate does not inhibit Na+/K+ATPase in ferret lungs. In addition, cyclic GMP (cGMP), which has been reported to increase the activity of Ca2+ATPases in vascular smooth muscle, was able to reverse and prevent the effect of vanadate on Ppa, but not the effect of ouabain. Inhibition of Ca2+ATPases with vanadate in ferret lungs increases pulmonary vascular resistance during both normoxia and hypoxia. The Ca2+ entry mediated by alveolar hypoxia appears to overpower the ability of Ca2+ATPases and other membrane Ca2+ transport proteins to translocate [Ca2+]i.(ABSTRACT TRUNCATED AT 250 WORDS)     

灯盏花素对低氧大鼠肺动脉压和肺小动脉Rho激酶的影响

目的 观察灯盏花素对低氧大鼠肺动脉压、肺小动脉Rho激酶ROCK Ⅰ和ROCK Ⅱ及Rho激酶mRNA的影响,探讨灯盏花素预防低氧性肺动脉高压的作用和机制.方法 将18只健康雄性SD大鼠分为健康组、低氧组和灯盏花素预防组.以常压低氧法复制肺动脉高压模型,以微导管法测定平均肺动脉压(mPAP).分离大鼠心脏,测量右心室(RV)及左心室加室间隔(LV+S)的重量,以RV/(LV+S)代表右心肥厚指数.应用图像分析技术测定肺小动脉管壁厚度占外径的百分比和管壁面积占总面积的百分比,反映肺血管重塑情况.应用免疫组化法测定肺小动脉Rho激酶蛋白的表达,原位杂交法测定肺小动脉Rho激酶mRNA的表达.结果 低氧组大鼠mPAP为(27.3±5.0)mm Hg(1 mm Hg=0.133 kPa),明显高于健康组的(16.0±0.6)mm Hg(t=6.74,P<0.05),灯盏花素预防组mPAP为(19.83±1.47)mm Hg,明显低于低氧组(t=4.28,P<0.05);低氧组RV/(LV+S)及肺小动脉厚度指数明显高于健康组(t=3.43,P<0.05),灯盏花素预防组低于低氧组(t=2.39,P<0.05);低氧组ROCK Ⅰ和ROCK Ⅱ免疫组织化学阳性染色(1.29±0.08和1.63±0.24)明显高于健康组(1.17±0.09和1.30±0.16),灯盏花素预防组(1.18±0.10和1.30±0.12)明显低于低氧组(t值分别为3.96,5.85,3.90,5.82,均P<0.05);低氧组ROCK Ⅰ mRNA和ROCK Ⅱ mRNA原位杂交阳性染色(分别为1.37±0.13和1.59±0.31)明显高于健康组(1.22±0.09和1.2±10.15),灯盏花素预防组(1.23±0.13和1.22±0.06)明显低于低氧组(t值分别为4.00,6.02,3.94,5.83,均P<0.05).结论 灯盏花素具有明显预防低氧性肺动脉高压和降低Rho激酶及Rho激酶mRNA的作用.