Bicarbonate disruption of the pulmonary endothelial barrier via activation of endogenous soluble adenylyl cyclase, isoform 10.
Bicarbonate disruption of the pulmonary endothelial barrier via activation of endogenous soluble adenylyl cyclase, isoform 10.
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碳酸氢盐通过激活内源性可溶性腺苷酸环化酶（亚型 10）破坏肺内皮屏障。
DOI：
10.1152/ajplung.00392.2012
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Sayner,SarahL
中科院分区：
文献类型：
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作者：
Obiako,Boniface;Calchary,Wendy;Xu,Ningyong;Kunstadt,Ryan;Richardson,Bianca;Nix,Jessica;Sayner,SarahL
越来越明显的是，肺内皮内的cAMP信号是高度区室化的，并且这种区室化对于维持内皮屏障完整性至关重要。研究表明，外源性可溶性细菌毒素ExoY和毛喉素刺激的可溶性哺乳动物腺苷酸环化酶（AC）嵌合体sACI/II的异源表达可升高细胞溶质cAMP并破坏肺微血管内皮屏障。由外源性可溶性AC产生的胞质cAMP的屏障破坏作用与由跨膜AC产生的质膜下cAMP的屏障保护作用相反，跨膜AC增强了内皮屏障的完整性。内源性可溶性AC同种型10（AC 10或通常称为sAC）缺乏跨膜结构域并且定位在胞质区室内。AC 10被碳酸氢盐独特地激活以产生胞质cAMP，但其在调节内皮屏障完整性中的作用尚未得到解决。在这里，我们证明，在肺循环中，AC 10在肺微血管内皮细胞（PMVEC）和肺动脉内皮细胞（PAEC）中表达，但在PAEC中的表达较低。此外，肺内皮细胞选择性表达碳酸氢盐协同转运蛋白。虽然细胞外碳酸氢盐在PMVEC中产生磷酸二酯酶4敏感性cAMP池，但在PAEC中未检测到此类cAMP反应。最后，加入细胞外碳酸氢盐降低了PMVEC单层的阻力，并增加了渗透压对照组以上的分离灌注肺的过滤系数。总的来说，这些研究结果表明，PMVEC有一个碳酸氢盐敏感的胞质cAMP池，破坏内皮屏障的完整性。这些研究可能为碳酸氢盐纠正急性呼吸窘迫综合征患者酸中毒的争议性作用提供替代机制。
It is becoming increasingly apparent that cAMP signals within the pulmonary endothelium are highly compartmentalized, and this compartmentalization is critical to maintaining endothelial barrier integrity. Studies demonstrate that the exogenous soluble bacterial toxin, ExoY, and heterologous expression of the forskolin-stimulated soluble mammalian adenylyl cyclase (AC) chimera, sACI/II, elevate cytosolic cAMP and disrupt the pulmonary microvascular endothelial barrier. The barrier-disruptive effects of cytosolic cAMP generated by exogenous soluble ACs are in contrast to the barrier-protective effects of subplasma membrane cAMP generated by transmembrane AC, which strengthens endothelial barrier integrity. Endogenous soluble AC isoform 10 (AC10 or commonly known as sAC) lacks transmembrane domains and localizes within the cytosolic compartment. AC10 is uniquely activated by bicarbonate to generate cytosolic cAMP, yet its role in regulation of endothelial barrier integrity has not been addressed. Here we demonstrate that, within the pulmonary circulation, AC10 is expressed in pulmonary microvascular endothelial cells (PMVECs) and pulmonary artery endothelial cells (PAECs), yet expression in PAECs is lower. Furthermore, pulmonary endothelial cells selectively express bicarbonate cotransporters. While extracellular bicarbonate generates a phosphodiesterase 4-sensitive cAMP pool in PMVECs, no such cAMP response is detected in PAECs. Finally, addition of extracellular bicarbonate decreases resistance across the PMVEC monolayer and increases the filtration coefficient in the isolated perfused lung above osmolality controls. Collectively, these findings suggest that PMVECs have a bicarbonate-sensitive cytosolic cAMP pool that disrupts endothelial barrier integrity. These studies could provide an alternative mechanism for the controversial effects of bicarbonate correction of acidosis of acute respiratory distress syndrome patients.