Forred Benjamin J, Daugaard Darwin R, Titus Brianna K, Wood Ryan R, Floen Miranda J, Booze Michelle L, Vitiello Peter F
Children's Health Research Center, Sanford Research, Sioux Falls, South Dakota, United States of America.
Department of Pediatrics, University of South Dakota Sanford School of Medicine, Sioux Falls, South Dakota, United States of America.
PLoS One. 2017 Jan 3;12(1):e0168777. doi: 10.1371/journal.pone.0168777. eCollection 2017.
Mitochondria play a fundamental role in the regulation of cell death during accumulation of oxidants. High concentrations of atmospheric oxygen (hyperoxia), used clinically to treat tissue hypoxia in premature newborns, is known to elicit oxidative stress and mitochondrial injury to pulmonary epithelial cells. A consequence of oxidative stress in mitochondria is the accumulation of peroxides which are detoxified by the dedicated mitochondrial thioredoxin system. This system is comprised of the oxidoreductase activities of peroxiredoxin-3 (Prx3), thioredoxin-2 (Trx2), and thioredoxin reductase-2 (TrxR2). The goal of this study was to understand the role of the mitochondrial thioredoxin system and mitochondrial injuries during hyperoxic exposure. Flow analysis of the redox-sensitive, mitochondrial-specific fluorophore, MitoSOX, indicated increased levels of mitochondrial oxidant formation in human adenocarcinoma cells cultured in 95% oxygen. Increased expression of Trx2 and TrxR2 in response to hyperoxia were not attributable to changes in mitochondrial mass, suggesting that hyperoxic upregulation of mitochondrial thioredoxins prevents accumulation of oxidized Prx3. Mitochondrial oxidoreductase activities were modulated through pharmacological inhibition of TrxR2 with auranofin and genetically through shRNA knockdown of Trx2 and Prx3. Diminished Trx2 and Prx3 expression was associated with accumulation of mitochondrial superoxide; however, only shRNA knockdown of Trx2 increased susceptibility to hyperoxic cell death and increased phosphorylation of apoptosis signal-regulating kinase-1 (ASK1). In conclusion, the mitochondrial thioredoxin system regulates hyperoxic-mediated death of pulmonary epithelial cells through detoxification of oxidants and regulation of redox-dependent apoptotic signaling.
线粒体在氧化剂积累过程中对细胞死亡的调节起着至关重要的作用。临床上用于治疗早产儿组织缺氧的高浓度大气氧（高氧），已知会引发氧化应激和对肺上皮细胞的线粒体损伤。线粒体氧化应激的一个后果是过氧化物的积累，而专门的线粒体硫氧还蛋白系统可对其进行解毒。该系统由过氧化物酶3（Prx3）、硫氧还蛋白2（Trx2）和硫氧还蛋白还原酶2（TrxR2）的氧化还原酶活性组成。本研究的目的是了解线粒体硫氧还蛋白系统和高氧暴露期间线粒体损伤的作用。对氧化还原敏感的线粒体特异性荧光团MitoSOX的流式分析表明，在95%氧气中培养的人腺癌细胞中线粒体氧化剂形成水平增加。高氧反应中Trx2和TrxR2表达的增加并非归因于线粒体质量的变化，这表明线粒体硫氧还蛋白的高氧上调可防止氧化型Prx3的积累。通过金诺芬对TrxR2进行药理抑制以及通过Trx2和Prx3的短发夹RNA（shRNA）敲低在基因水平上调节线粒体氧化还原酶活性。Trx2和Prx3表达的减少与线粒体超氧化物的积累有关；然而，只有Trx2的shRNA敲低增加了对高氧细胞死亡的易感性，并增加了凋亡信号调节激酶1（ASK1）的磷酸化。总之，线粒体硫氧还蛋白系统通过氧化剂解毒和氧化还原依赖性凋亡信号调节来调节高氧介导的肺上皮细胞死亡。
