Department of Integrative Medical Sciences, Northeastern Ohio Universities-Colleges of Medicine and Pharmacy, Rootstown, OH 44272, USA.
Anat Rec (Hoboken). 2011 Sep;294(9):1461-71. doi: 10.1002/ar.21363. Epub 2011 Aug 1.
Near the end of gestation, the direction of ion and fluid flow across the alveolar epithelium rapidly changes from secretion to absorption. Thus, the relative cell membrane location of epithelial Na channels (ENaCs) and cystic fibrosis transmembrane regulator (CFTR) Cl channels during late fetal lung development and after maternal interleukin-1β (IL-1β) pretreatment was the focus of our study. Western blot analysis after sucrose gradient separation of caveolin-1-(Cav-1)-rich membrane regions (CRR) and Cav-1-poor membrane (non-CRR) revealed primary CRR ENaC localization at gestation day (GD) 61 in guinea pigs. Correlating with the natural induction of distal lung fluid absorption, ENaC appeared in the non-CRR cell membrane regions at GD68. Conversely, CFTR was present in the non-CRR cell membrane regions at GD61 and in the CRRs at GD68. IL-1β-induced conversion to distal lung fluid absorption at GD61 was associated with ENaC non-CRR presence and CFTR CRR presence, suggesting that relative ENaC and CFTR locations induced distal lung fluid absorption and decreased fluid secretion. Instilling fetal lungs with the CRR-disrupting agent methyl-β-cyclodextrin resulted in the conversion from lung fluid secretion to absorption and ENaC non-CRR presence at GD61. Coimmunoprecipitation of Cav-1 with α- and β-ENaC demonstrated reduced coimmunoprecipitation with increased GD and after IL-1β pretreatment. On the other hand, coimmunoprecipitation of Cav-1 with CFTR demonstrated increased coimmunoprecipitation with increasing GD and after IL-1β pretreatment. This concept may provide novel molecular mechanisms for the rapid transition from fetal distal lung fluid secretion to absorption in near-term lungs.
在妊娠末期，肺泡上皮细胞两侧的离子和液体流动方向迅速由分泌转为吸收。因此，我们的研究重点是在胎肺晚期发育和经母体白细胞介素-1β（IL-1β）预处理后上皮钠通道（ENaC）和囊性纤维化跨膜转导调节因子（CFTR）Cl 通道在相对细胞内膜的位置。蔗糖梯度分离窖蛋白-1（Cav-1）丰富膜区（CRR）和 Cav-1 贫膜（非-CRR）后进行 Western blot 分析显示，豚鼠在妊娠 61 天（GD）时主要在 CRR 定位 ENaC。与远端肺液吸收的自然诱导相一致，ENaC 出现在 GD68 时的非-CRR 细胞膜区。相反，CFTR 出现在 GD61 时的非-CRR 细胞膜区和 GD68 时的 CRR。IL-1β诱导的 GD61 远端肺液吸收的转变与 ENaC 非-CRR 的存在和 CFTR CRR 的存在相关，表明相对 ENaC 和 CFTR 位置诱导了远端肺液吸收和减少了液体分泌。向胎肺中注入 CRR 破坏剂甲基-β-环糊精导致从肺液分泌转变为吸收，并且在 GD61 时存在 ENaC 非-CRR。Cav-1 与 α-和 β-ENaC 的共免疫沉淀显示，随着 GD 的增加和 IL-1β 预处理，共免疫沉淀减少。另一方面，Cav-1 与 CFTR 的共免疫沉淀显示，随着 GD 的增加和 IL-1β 预处理，共免疫沉淀增加。这一概念可能为足月肺中从胎儿远端肺液分泌快速过渡到吸收提供新的分子机制。
