Soluble mediators, not cilia, determine airway surface liquid volume in normal and cystic fibrosis superficial airway epithelia.
Soluble mediators, not cilia, determine airway surface liquid volume in normal and cystic fibrosis superficial airway epithelia.
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DOI：
10.1085/jgp.200509468
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发表时间：
2006-05
影响因子：
3.8
通讯作者：
Boucher, Richard C
中科院分区：
文献类型：
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作者：
Tarran, Robert;Trout, Laura;Donaldson, Scott H;Boucher, Richard C
肺的天然防御系统的一个关键方面是表面上皮调节呼吸道表面液体(Asl)的能力，以维持7μm的纤毛周围液体层(Pcl)，这是纤毛跳动和产生粘液流动所必需的。呼吸道上皮细胞调节ASL高度至≥7μm的机制尚不清楚。使用布美他尼作为Cl-−分泌的抑制剂，制霉菌素作为Na+吸收的激活剂，我们发现，为了影响−的容量平衡，必须发生Cl-ASL分泌和Na+吸收的协同“混合”。然后，我们研究了ASL体积状态是如何由潜在的上皮细胞调节的。纤毛对这一过程并不关键，因为(A)原发纤毛运动障碍伴纤毛不动患者的培养物中ASL体积正常，(B)在尚未发生纤毛发生的正常培养物中。然而，我们发现，在粘液纤毛清除期间和腺体分泌之后，模仿过量ASL沉积到近端呼吸道的动作强烈地刺激了Na+的吸收，这表明容量调节对ASL中可溶性介质浓度的变化敏感，而不是纤毛搏动的变化。为了进一步研究这一假说，我们在ASL中加入了潜在的“可溶介质”。ASL容量调节对通道激活蛋白(CAP；胰酶)和CAP抑制剂(抑肽酶)敏感，后者通过改变正常和囊性纤维化培养细胞上皮Na+通道(ENaC)的活性来调节Na+的吸收。在正常和囊性纤维化(CF)培养中，ATP还通过诱导分泌而强烈地调节ASL的体积，而其代谢产物腺苷(ADO)在正常培养中刺激分泌，而在CF培养中刺激吸收。有趣的是，三磷酸腺苷/腺苷三磷酸腺苷诱导的−分泌量受CaP诱导的Na+吸收水平的影响，这表明调节AsL体积的可溶性调节剂之间存在重要的相互作用。
A key aspect of the lung's innate defense system is the ability of the superficial epithelium to regulate airway surface liquid (ASL) volume to maintain a 7-μm periciliary liquid layer (PCL), which is required for cilia to beat and produce mucus flow. The mechanisms whereby airway epithelia regulate ASL height to ≥7 μm are poorly understood. Using bumetanide as an inhibitor of Cl− secretion, and nystatin as an activator of Na+ absorption, we found that a coordinated “blending” of both Cl− secretion and Na+ absorption must occur to effect ASL volume homeostasis. We then investigated how ASL volume status is regulated by the underlying epithelia. Cilia were not critical to this process as (a) ASL volume was normal in cultures from patients with primary ciliary dyskinesia with immotile cilia, and (b) in normal cultures that had not yet undergone ciliogenesis. However, we found that maneuvers that mimic deposition of excess ASL onto the proximal airways, which occurs during mucociliary clearance and after glandular secretion, acutely stimulated Na+ absorption, suggesting that volume regulation was sensitive to changes in concentrations of soluble mediators in the ASL rather than alterations in ciliary beating. To investigate this hypothesis further, we added potential “soluble mediators” to the ASL. ASL volume regulation was sensitive to a channel-activating protein (CAP; trypsin) and a CAP inhibitor (aprotinin), which regulated Na+ absorption via changes in epithelial Na+ channel (ENaC) activity in both normal and cystic fibrosis cultures. ATP was also found to acutely regulate ASL volume by inducing secretion in normal and cystic fibrosis (CF) cultures, while its metabolite adenosine (ADO) evoked secretion in normal cultures but stimulated absorption in CF cultures. Interestingly, the amount of ASL/Cl− secretion elicited by ATP/ADO was influenced by the level of CAP-induced Na+ absorption, suggesting that there are important interactions between the soluble regulators which finely tune ASL volume.