The mitochondrial superoxide/thioredoxin-2/Ask1 signaling pathway is critically involved in troglitazone-induced cell injury to human hepatocytes
The mitochondrial superoxide/thioredoxin-2/Ask1 signaling pathway is critically involved in troglitazone-induced cell injury to human hepatocytes
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DOI：
10.1093/toxsci/kfm273
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发表时间：
2008-02-01
影响因子：
3.8
通讯作者：
Boelsterli, Urs A.
中科院分区：
文献类型：
--
作者：
Lim, Priscilla L. K.;Liu, Jianchao;Boelsterli, Urs A.
尽管尚未阐明曲格列酮相关特异质肝损伤的机制和易感因素，但实验证据已将氧化应激和线粒体损伤确定为体外潜在危害。在寻找毒性的上游介质时，我们假设曲格列酮诱导的线粒体超氧化物生成增加可能会激活硫氧还蛋白-2（Trx 2）/细胞凋亡信号调节激酶1（Ask 1）信号途径，导致细胞死亡，因此，线粒体靶向自由基清除剂线粒体-羧基丙酰基（CP），将阻止超氧化物净水平的增加并抑制线粒体信号传导和细胞损伤。将永生化人肝细胞（HC-04）暴露于曲格列酮（0-100 μ M），12-24 h后（酮康唑不敏感）引起浓度和时间依赖性细胞凋亡。我们发现，曲格列酮迅速消散线粒体内跨膜电位（Δ Psi（m）），并独立地增加了5倍的线粒体超氧化物的净水平。随后是线粒体Trx 2的氧化还原比向氧化态和随后的Ask 1激活的转变。环孢菌素A（3 μ M）可防止细胞损伤，但不能防止Δ Psi（m）的降低，表明线粒体透化，但不能防止膜去极化，与细胞死亡有因果关系。Mito-CP不仅能降低曲格列酮诱导的超氧化物水平，还能阻止Trx 2氧化和Ask 1活化，保护细胞免受毒性损伤。这些数据表明，曲格列酮（而非其氧化代谢产物）产生线粒体内氧化应激，激活Trx 2/Ask 1途径，导致线粒体透化。此外，这些数据支持我们的概念，即向线粒体靶向递送抗氧化剂可以抑制上游信号传导并保护免受曲格列酮诱导的致死性细胞损伤。
Although the mechanisms and susceptibility factors of troglitazone-associated idiosyncratic liver injury have not been elucidated, experimental evidence has identified oxidant stress and mitochondrial injury as a potential hazard in vitro. In search of upstream mediators of toxicity, we hypothesized that troglitazone-induced increased mitochondrial generation of superoxide might activate the thioredoxin-2 (Trx2)/apoptosis signal-regulating kinase 1 (Ask1) signaling pathway, leading to cell death, and that, hence, the mitochondrially targeted radical scavenger, mito-carboxy proxyl (CP), would prevent the increase in superoxide net levels and inhibit mitochondrial signaling and cell injury. Immortalized human hepatocytes (HC-04) were exposed to troglitazone (0-100 mu M), which caused concentration and time-dependent apoptosis after 12-24 h (ketoconazole-insensitive). We found that troglitazone rapidly dissipated the mitochondrial inner transmembrane potential (Delta Psi(m)) and independently increased the net levels of mitochondrial superoxide by 5-fold. This was followed by a shift of the redox ratio of mitochondrial Trx2 toward the oxidized state and subsequent activation of Ask1. Cell injury, but not the decrease in Delta Psi(m), was prevented by cyclosporin A (3 mu M), indicating that mitochondrial permeabilization, but not membrane depolarization, was causally involved in cell death. Mito-CP not only decreased troglitazone-induced superoxide levels but also prevented Trx2 oxidation and activation of Ask1 and protected cells from toxic injury. These data indicate that troglitazone, but not its oxidative metabolite(s), produce intramitochondrial oxidant stress that activates the Trx2/Ask1 pathway, leading to mitochondrial permeabilization. Furthermore, the data support our concept that targeted delivery of an antioxidant to mitochondria can inhibit upstream signaling and protect from troglitazone-induced lethal cell injury.