Zhuge Jian, Cederbaum Arthur I
Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, One Gustave L. Place, New York, NY 10029, USA.
Free Radic Biol Med. 2006 Oct 1;41(7):1100-12. doi: 10.1016/j.freeradbiomed.2006.06.017. Epub 2006 Jul 4.
Ethanol treatment causes an increase in expression of TGF-beta1 and CYP2E1 in the centrilobular area. Alcoholic liver disease is usually initiated in the centrilobular region of the liver. We hypothesized that the combination of TGF-beta1 and CYP2E1 produces increased oxidative stress and liver cell toxicity. To test this possibility, we studied the effects of TGF-beta1 on the viability of HepG2 E47 cells that express human CYP2E1, and C34 HepG2 cells, which do not express CYP2E1. E47 cells underwent greater growth inhibition and enhanced apoptosis after TGF-beta1 treatment, as compared to the C34 cells. There was an enhanced production of reactive oxygen species (ROS) and a decline in reduced glutathione (GSH) levels in the TGF-beta1-treated E47 cells and the enhanced cell death could be prevented by antioxidants. The CYP2E1 inhibitor diallyl sulfide prevented the potentiated cell death in E47 cells validating the role of CYP2E1. Mitochondrial membrane potential declined in the TGF-beta1-treated E47 cells, prior to developing toxicity, and cell death could be prevented by trifluoperazine, an inhibitor of the mitochondrial membrane permeability transition. TGF-beta1 also produced a loss of cell viability in hepatocytes from pyrazole-treated rats with elevated levels of CYP2E1, compared to control hepatocytes. In conclusion, increased toxic interactions by TGF-beta1 plus CYP2E1 can occur by a mechanism involving increased production of intracellular ROS and depletion of GSH, resulting in mitochondrial membrane damage and loss of membrane potential, followed by apoptosis. Potentiation of TGF-beta1-induced cell death by CYP2E1 may contribute to mechanisms of alcohol-induced liver disease.
乙醇处理会导致肝小叶中央区转化生长因子-β1（TGF-β1）和细胞色素P450 2E1（CYP2E1）表达增加。酒精性肝病通常始于肝脏的肝小叶中央区。我们推测TGF-β1和CYP2E1共同作用会增加氧化应激和肝细胞毒性。为了验证这一可能性，我们研究了TGF-β1对表达人CYP2E1的HepG2 E47细胞以及不表达CYP2E1的C34 HepG2细胞活力的影响。与C34细胞相比，TGF-β1处理后，E47细胞受到更强的生长抑制且凋亡增强。在TGF-β1处理的E47细胞中，活性氧（ROS）生成增加，还原型谷胱甘肽（GSH）水平下降，而抗氧化剂可预防细胞死亡增加。CYP2E1抑制剂二烯丙基硫醚可预防E47细胞中增强的细胞死亡，证实了CYP2E1的作用。在产生毒性之前，TGF-β1处理的E47细胞线粒体膜电位下降，而线粒体膜通透性转换抑制剂三氟拉嗪可预防细胞死亡。与对照肝细胞相比，TGF-β1也使吡唑处理的大鼠（CYP2E1水平升高）的肝细胞活力丧失。总之，TGF-β1加CYP2E1之间毒性相互作用增强可能通过细胞内ROS生成增加和GSH耗竭的机制发生，导致线粒体膜损伤和膜电位丧失，随后发生凋亡。CYP2E1增强TGF-β1诱导的细胞死亡可能有助于酒精性肝病的发病机制。
