Neutrophil elastase activates near-silent epithelial Na+ channels and increases airway epithelial Na+ transport
Neutrophil elastase activates near-silent epithelial Na+ channels and increases airway epithelial Na+ transport
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DOI：
10.1152/ajplung.00435.2004
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发表时间：
2005-05-01
影响因子：
4.9
通讯作者：
Stutts, MJ
中科院分区：
文献类型：
--
作者：
Caldwell, RA;Boucher, RC;Stutts, MJ
中性粒细胞弹性蛋白酶是一种丝氨酸蛋白酶，在囊性纤维化患者的呼吸道中含量丰富，囊性纤维化是一种遗传性疾病，表现为呼吸道对Na+的过度吸收和由此导致的呼吸道表面液体层枯竭。尽管内源性上皮源性丝氨酸蛋白酶调节上皮细胞的Na+转运，但中性粒细胞弹性蛋白酶对上皮Na+转运和上皮Na+通道(ENaC)活性的影响尚不清楚。将微摩尔浓度的人中性粒细胞弹性蛋白酶(HNE)应用于人支气管细胞系(16HBE140-/β-γ)的顶端表面，可使Na+转运增加约两倍。同样是一种丝氨酸蛋白酶的胰酶也有类似的作用。HNE或胰酶的蛋白水解性抑制剂选择性地阻断了酶诱导的上皮Na+转运的增加。在单通道水平上，亚微摩尔浓度的HNE使表达大鼠α、β和γ-ENaC亚单位的NIH-3T3细胞斑块中近乎沉默的ENaC活性增加108倍。然而，在碱性活性的ENaCs上没有观察到酶的影响。HNE后的胰酶暴露没有显示对阿米洛利敏感的短路电流或ENaC活性的额外增加，这表明这些酶有共同的作用模式，可能是通过ENaC的蛋白水解性激活来增加Na+转运。HNE诱导的CF气道近静息ENaC活性增加可能是导致Na+高吸收、降低呼吸道表面液体高度和脱水粘液最终导致无效的粘液纤毛清除的原因之一。
Neutrophil elastase is a serine protease that is abundant in the airways of individuals with cystic fibrosis (CF), a genetic disease manifested by excessive airway Na+ absorption and consequent depletion of the airway surface liquid layer. Although endogenous epithelium-derived serine proteases regulate epithelial Na+ transport, the effects of neutrophil elastase on epithelial Na+ transport and epithelial Na+ channel (ENaC) activity are unknown. Low micromolar concentrations of human neutrophil elastase (hNE) applied to the apical surface of a human bronchial cell line (16HBE14o-/beta gamma) increased Na+ transport about twofold. Similar effects were observed with trypsin, also a serine protease. Proteolytic inhibitors of hNE or trypsin selectively abolished the enzyme-induced increase of epithelial Na+ transport. At the level of the single channel, submicromolar concentrations of hNE increased activity of near-silent ENaC similar to 108-fold in patches from NIH-3T3 cells expressing rat alpha-, beta-, and gamma-ENaC subunits. However, no enzyme effects were observed on basally active ENaCs. Trypsin exposure following hNE revealed no additional increase in amiloride-sensitive short-circuit current or in ENaC activity, suggesting these enzymes share a common mode of action for increasing Na+ transport, likely through proteolytic activation of ENaC. The hNE-induced increase of near-silent ENaC activity in CF airways could contribute to Na+ hyperabsorption, reduced airway surface liquid height, and dehydrated mucus culminating in inefficient mucociliary clearance.