Center for Pediatric Research Leipzig, Division of Neonatology, Department of Pediatrics, University of Leipzig, 04103 Leipzig, Germany.
Int J Mol Sci. 2022 Aug 8;23(15):8823. doi: 10.3390/ijms23158823.
Albumin is a major serum protein and is frequently used as a cell culture supplement. It is crucially involved in the regulation of osmotic pressure and distribution of fluid between different compartments. Alveolar epithelial Na transport drives alveolar fluid clearance (AFC), enabling air breathing. Whether or not albumin affects AFC and Na transport is yet unknown. We therefore determined the acute and chronic effects of albumin on Na transport in fetal distal lung epithelial (FDLE) cells and the involved kinase pathways. Chronic BSA treatment strongly increased epithelial Na transport and barrier integrity in Ussing chambers. BSA did not elevate mRNA expression of Na transporters in FDLE cells after 24 h. Moreover, acute BSA treatment for 45 min mimicked the chronic effects. The elevated Na transport was caused by an increased maximal ENaC activity, while Na,K-ATPase activity remained unchanged. Acute and chronic BSA treatment lowered membrane permeability, confirming the increased barrier integrity observed in Ussing chambers. Western blots demonstrated an increased phosphorylation of AKT and SGK1, and PI3K inhibition abolished the stimulating effect of BSA. BSA therefore enhanced epithelial Na transport and barrier integrity by activating the PI3K/AKT/SGK1 pathway.
白蛋白是一种主要的血清蛋白，常用于细胞培养的补充物。它在调节渗透压和不同隔室之间的液体分布方面起着至关重要的作用。肺泡上皮钠转运驱动肺泡液清除（AFC），从而实现空气呼吸。白蛋白是否影响 AFC 和钠转运仍不清楚。因此，我们确定了白蛋白对胎儿远端肺上皮（FDLE）细胞钠转运的急性和慢性影响及其涉及的激酶途径。慢性 BSA 处理强烈增加了 Ussing 室中上皮钠转运和屏障完整性。BSA 在 24 小时内未增加 FDLE 细胞中钠转运体的 mRNA 表达。此外，急性 BSA 处理 45 分钟即可模拟慢性作用。升高的钠转运是由 ENaC 最大活性增加引起的，而 Na，K-ATPase 活性保持不变。急性和慢性 BSA 处理降低了膜通透性，证实了在 Ussing 室中观察到的屏障完整性增加。Western blot 表明 AKT 和 SGK1 的磷酸化增加，PI3K 抑制消除了 BSA 的刺激作用。因此，BSA 通过激活 PI3K/AKT/SGK1 途径增强了上皮钠转运和屏障完整性。
