The role of α-, β-, and γ-ENaC subunits in distal lung epithelial fluid absorption induced by pulmonary edema fluid
The role of α-, β-, and γ-ENaC subunits in distal lung epithelial fluid absorption induced by pulmonary edema fluid
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DOI：
10.1152/ajplung.00373.2006
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发表时间：
2007-09-01
影响因子：
4.9
通讯作者：
O'Brodovich, Hugh
中科院分区：
文献类型：
--
作者：
Elias, Nael;Rafii, Bijan;O'Brodovich, Hugh
水肿液（EF）通过大鼠胎儿远端肺上皮（FDLE）增加上皮Na+转运，并诱导胎鼠肺外植体中的净肺液吸收[Rafii B，Gillie DJ，Sulowski C，Hannam V，Cheung T，Otulakowski G，Barker PM，O 'Brodovich H. J Physiol（Lond）544：537-548，2002]。我们现在表明，EF增加液体吸收在大鼠FDLE单层的剂量依赖性方式。为了研究上皮Na+通道（ENaC）亚基在该现象中的作用，我们培养了来自16天胎龄野生型（WT）或α-、β-或γ- ENaC敲除或杂合子（HT）小鼠的远端肺的外植体。由于净液体分泌，在培养基中培养的WT外植体随时间持续扩增。相反，当外植体暴露于EF 24小时，净液体吸收发生。EF暴露的外植体有正常的组织学，但显着的变化后，Triton X-100或星形孢菌素曝光。透射电镜显示EF促进了片层体的形成，并在外植体的管腔中形成了丰富的表面活性剂。EF诱导的外植体大小的变化在α- ENaC敲除、WT和HT同窝胎肺外植体中相似（P > 0.05）。相比之下，EF的作用在β-和γ- ENaC敲除（P < 0.05）中相对于WT和HT同窝胎仔肺外植体减弱。EF暴露对不同基因型小鼠中α- ENaC的mRNA水平略有降低或无影响，但在所有基因型组中均降低β-和γ- ENaC亚基mRNA的表达（P < 0.01）。我们的结论是，β-和γ-，而不是α-，ENaC亚基是必不可少的EF发挥其最大的净液体吸收远端肺上皮细胞的影响。
Edema fluid (EF) increases epithelial Na+ transport by rat fetal distal lung epithelia (FDLE) and induces net lung fluid absorption in fetal mouse lung explants [Rafii B, Gillie DJ, Sulowski C, Hannam V, Cheung T, Otulakowski G, Barker PM, O'Brodovich H. J Physiol (Lond) 544: 537-548, 2002]. We now show that EF increases fluid absorption across monolayers of rat FDLE in a dose-dependent manner. To study the role of subunits of the epithelial Na+ channel (ENaC) in the phenomena, we cultured explants from the distal lungs of 16-day gestational age wild-type (WT) or alpha-, beta-, or gamma- ENaC knockout or heterozygote (HT) mice. WT explants cultured in media continuously expanded over time as a result of net fluid secretion. In contrast, when explants were exposed to EF for 24 h, net fluid absorption occurred. EF-exposed explants had normal histology, but marked changes were seen after Triton X-100 or staurosporine exposure. Transmission electron microscopy showed EF promoted lamellar body formation and abundant surfactant in the explants' lumens. EF-induced changes in explant size were similar in alpha- ENaC knockout, WT, and HT littermate fetal lung explants (P > 0.05). In contrast, EF's effect was attenuated in beta- and gamma- ENaC knockouts (P < 0.05) vs. WT and HT littermate fetal lung explants. EF exposure slightly decreased or had no effect on mRNA levels for alpha- ENaC in various mouse genotypes but decreased expression of beta- and gamma- ENaC subunit mRNAs (P < 0.01) across all genotype groups. We conclude that beta- and gamma-, but not alpha-, ENaC subunits are essential for EF to exert its maximal effect on net fluid absorption by distal lung epithelia.