Department of Anesthesiology, School of Medicine, University of Alabama at Birmingham, BMR II 224, 901 19th St. South, Birmingham, AL 35205-3703, USA.
Am J Respir Cell Mol Biol. 2012 Mar;46(3):342-54. doi: 10.1165/rcmb.2011-0309OC. Epub 2011 Oct 13.
The mechanisms by which the exposure of mice to Cl(2) decreases vectorial Na(+) transport and fluid clearance across their distal lung spaces have not been elucidated. We examined the biophysical, biochemical, and physiological changes of rodent lung epithelial Na(+) channels (ENaCs) after exposure to Cl(2), and identified the mechanisms involved. We measured amiloride-sensitive short-circuit currents (I(amil)) across isolated alveolar Type II (ATII) cell monolayers and ENaC single-channel properties by patching ATII and ATI cells in situ. α-ENaC, γ-ENaC, total and phosphorylated extracellular signal-related kinase (ERK)1/2, and advanced products of lipid peroxidation in ATII cells were measured by Western blot analysis. Concentrations of reactive intermediates were assessed by electron spin resonance (ESR). Amiloride-sensitive Na(+) channels with conductances of 4.5 and 18 pS were evident in ATI and ATII cells in situ of air-breathing mice. At 1 hour and 24 hours after exposure to Cl(2), the open probabilities of these two channels decreased. This effect was prevented by incubating lung slices with inhibitors of ERK1/2 or of proteasomes and lysosomes. The exposure of ATII cell monolayers to Cl(2) increased concentrations of reactive intermediates, leading to ERK1/2 phosphorylation and decreased I(amil) and α-ENaC concentrations at 1 hour and 24 hours after exposure. The administration of antioxidants to ATII cells before and after exposure to Cl(2) decreased concentrations of reactive intermediates and ERK1/2 activation, which mitigated the decrease in I(amil) and ENaC concentrations. The reactive intermediates formed during and after exposure to Cl(2) activated ERK1/2 in ATII cells in vitro and in vivo, leading to decreased ENaC concentrations and activity.
氯气暴露降低小鼠远端肺空间中载体钠（Na+）转运和液体清除的机制尚未阐明。我们研究了 Cl(2) 暴露后啮齿动物肺上皮钠（ENaC）通道的生物物理、生化和生理变化，并确定了涉及的机制。我们通过在体分离肺泡 II 型（ATII）细胞单层和原位 ATI 和 ATII 细胞贴附测量阿米洛利敏感的短路电流（I(amil)），并测量 ENaC 单通道特性。Western blot 分析测量 ATII 细胞中的 α-ENaC、γ-ENaC、总和磷酸化细胞外信号调节激酶（ERK）1/2 以及脂质过氧化的高级产物。电子自旋共振（ESR）评估反应中间体的浓度。在呼吸空气的小鼠原位 ATI 和 ATII 细胞中，存在电导为 4.5 和 18 pS 的阿米洛利敏感的 Na+通道。暴露于 Cl(2) 1 小时和 24 小时后，这两个通道的开放概率降低。用 ERK1/2 或蛋白酶体和溶酶体抑制剂孵育肺切片可预防这种作用。Cl(2) 暴露增加了反应中间体的浓度，导致 ERK1/2 磷酸化，并且在暴露 1 小时和 24 小时后 I(amil)和α-ENaC 浓度降低。在 Cl(2)暴露前后向 ATII 细胞给予抗氧化剂可降低反应中间体和 ERK1/2 激活的浓度，从而减轻 I(amil)和 ENaC 浓度的降低。Cl(2) 暴露期间和之后形成的反应中间体激活了 ATII 细胞中的 ERK1/2，导致 ENaC 浓度和活性降低。
