Comprehensive Pneumology Center, University Hospital, Ludwig-Maximilians-University, Munich, Germany.
Am J Physiol Lung Cell Mol Physiol. 2012 Nov 1;303(9):L814-23. doi: 10.1152/ajplung.00128.2012. Epub 2012 Sep 7.
Cigarette smoke mediates DNA damage, lipid peroxidation, and modification and misfolding of proteins, thereby inducing severe cellular damage. The ubiquitin proteasome system serves as the major disposal system for modified and misfolded proteins and is thus essential for proper cellular function. Its role in cigarette smoke-induced cell damage, however, is largely unknown. We hypothesized that the ubiquitin-proteasome system is involved in the degradation of cigarette smoke-damaged proteins and that cigarette smoke exposure impairs the proteasome itself. Here, we show that treatment of human alveolar epithelial cells with cigarette smoke extract (CSE) induced time- and dose-dependent cell death, a rise in intracellular reactive oxygen species, and increased levels of carbonylated and polyubiquitinated proteins. While high doses of CSE severely impaired all three proteasomal activities, low CSE concentrations significantly inhibited only the trypsin-like activity of the proteasome in alveolar and bronchial epithelial cells. Moreover, acute exposure of mice to cigarette smoke significantly impaired the trypsin-like activity by 25% in the lungs. Reduced proteasome activity was not due to transcriptional regulation of the proteasome. Notably, cigarette smoke exposure induced accumulation of polyubiquitinated proteins in the soluble and insoluble protein fraction of the lung. We show for the first time that acute exposure to cigarette smoke directly impairs proteasome activity in the lungs of mice and in human epithelial cells at low doses without affecting proteasome expression. Our results indicate that defective proteasomal protein quality control may exacerbate the detrimental effects of cigarette smoke in the lung.
香烟烟雾会引发 DNA 损伤、脂质过氧化以及蛋白质的修饰和错误折叠，从而导致严重的细胞损伤。泛素蛋白酶体系统是修饰和错误折叠蛋白质的主要处理系统，因此对于细胞的正常功能至关重要。然而，其在香烟烟雾诱导的细胞损伤中的作用在很大程度上尚不清楚。我们假设泛素蛋白酶体系统参与了香烟烟雾损伤蛋白的降解，并且香烟烟雾暴露会损害蛋白酶体本身。在这里，我们表明，用香烟烟雾提取物（CSE）处理人肺泡上皮细胞会诱导时间和剂量依赖性的细胞死亡、细胞内活性氧的增加以及羰基化和多聚泛素化蛋白质水平的升高。虽然高剂量的 CSE 严重损害了三种蛋白酶体的活性，但低剂量的 CSE 仅显著抑制了肺泡和支气管上皮细胞中蛋白酶体的胰蛋白酶样活性。此外，急性暴露于香烟烟雾会使小鼠肺部的胰蛋白酶样活性显著降低 25%。蛋白酶体活性的降低不是由于蛋白酶体的转录调节。值得注意的是，香烟烟雾暴露会导致肺中多聚泛素化蛋白在可溶性和不溶性蛋白部分的积累。我们首次表明，急性暴露于香烟烟雾会直接损害小鼠肺部和人上皮细胞中低剂量的蛋白酶体活性，而不会影响蛋白酶体的表达。我们的结果表明，有缺陷的蛋白酶体蛋白质量控制可能会加剧香烟烟雾对肺部的有害影响。
