College of Pharmacy, Pusan National University, Busan 46241, Republic of Korea.
Department of Chemistry, Center for Proteome Biophysics and Chemistry Institute for Functional Materials, Pusan National University, Busan 46241, Republic of Korea.
Int J Mol Med. 2017 Dec;40(6):2011-2017. doi: 10.3892/ijmm.2017.3184. Epub 2017 Oct 11.
Polycyclic aromatic hydrocarbons (PAHs) are widespread contaminants resulting from the incomplete combustion of organic materials in the environment. The primary concern for the hazardous effect of PAHs is their ability to activate the pathway linked to the aryl hydrocarbon receptor (AhR) and lead to carcinogenesis. While previous research has demonstrated that oxidative stress plays a key role in the AhR-dependent toxic response, the effect of PAHs on the biosynthesis of glutathione (GSH), which is a powerful endogenous antioxidant, has not been extensively investigated. In the present study, we utilized a global metabolomic approach, via high resolution magic angle spinning nuclear magnetic resonance spectroscopy, and identified significant metabolome differences between non-tumorigenic liver cells (BNL CL.2; CL2) and transformed liver cells (BNL 1MEA. 7R.1; 1MEA) chronically exposed to 3-methylcholanthrene (3MC), a well‑known carcinogenic PAH. A significant change that was observed, was a lower GSH level in 1MEA cells compared with that in CL2 cells. This was contrasted by increased levels of precursor metabolites for GSH synthesis, such as S-adenosylmethionine and cysteine. These changes were accompanied by a significantly reduced expression of γ-glutamylcysteine ligase (GCL), known to be the rate‑limiting step of GSH synthesis. Furthermore, the protein level of cysteine dioxygenase was downregulated; however, the concentration of taurine was unaltered. Therefore, the present study demonstrated that cells transformed by chronic exposure to 3MC exhibited inhibition of GSH biosynthesis by suppression of GCL protein expression and reduction of cysteine availability, which may subsequently render cells vulnerable to oxidative stress.
多环芳烃（PAHs）是广泛存在的污染物，它们是环境中有机物质不完全燃烧的产物。PAHs 的主要危害是其激活芳香烃受体（AhR）途径的能力，并导致致癌作用。虽然之前的研究表明氧化应激在 AhR 依赖性毒性反应中起着关键作用，但 PAHs 对谷胱甘肽（GSH）生物合成的影响，GSH 是一种强大的内源性抗氧化剂，尚未得到广泛研究。在本研究中，我们利用高分辨魔角旋转核磁共振波谱的全局代谢组学方法，鉴定出非致瘤性肝细胞（BNL CL.2；CL2）和转化肝细胞（BNL 1MEA.7R.1；1MEA）在慢性暴露于 3-甲基胆蒽（3MC）时的显著代谢组差异，3MC 是一种众所周知的致癌性 PAH。观察到的一个显著变化是，1MEA 细胞中的 GSH 水平明显低于 CL2 细胞。这与 GSH 合成前体代谢物如 S-腺苷甲硫氨酸和半胱氨酸的水平增加形成对比。这些变化伴随着 γ-谷氨酰半胱氨酸连接酶（GCL）的表达显著降低，GCL 是 GSH 合成的限速步骤。此外，胱氨酸双加氧酶的蛋白水平下调，但牛磺酸的浓度没有改变。因此，本研究表明，慢性暴露于 3MC 转化的细胞通过抑制 GCL 蛋白表达和降低半胱氨酸的可用性来抑制 GSH 生物合成，这可能使细胞容易受到氧化应激的影响。
