Miller Colin G, Kundert Jean A, Prigge Justin R, Amato Julie A, Perez Allison E, Coppo Lucia, Rizzo Gabrielle N, Kavanaugh Michael P, Orlicky David J, Shearn Colin T, Schmidt Edward E
Microbiology & Immunology, Montana State University, Bozeman, MT 59718, USA.
Chemistry & Biochemistry, Montana State University, Bozeman, MT 59718, USA.
Antioxidants (Basel). 2021 Feb 27;10(3):359. doi: 10.3390/antiox10030359.
Cellular oxidants are primarily managed by the thioredoxin reductase-1 (TrxR1)- and glutathione reductase (Gsr)-driven antioxidant systems. In mice having hepatocyte-specific co-disruption of TrxR1 and Gsr (TrxR1/Gsr-null livers), methionine catabolism sustains hepatic levels of reduced glutathione (GSH). Although most mice with TrxR1/Gsr-null livers exhibit long-term survival, ~25% die from spontaneous liver failure between 4- and 7-weeks of age. Here we tested whether liver failure was ameliorated by ascorbate supplementation. Following ascorbate, dehydroascorbate, or mock treatment, we assessed survival, liver histology, or hepatic redox markers including GSH and GSSG, redox enzyme activities, and oxidative damage markers. Unexpectedly, rather than providing protection, ascorbate (5 mg/mL, drinking water) increased the death-rate to 43%. In adults, ascorbate (4 mg/g × 3 days i.p.) caused hepatocyte necrosis and loss of hepatic GSH in TrxR1/Gsr-null livers but not in wildtype controls. Dehydroascorbate (0.3 mg/g i.p.) also depleted hepatic GSH in TrxR1/Gsr-null livers, whereas GSH levels were not significantly affected by either treatment in wildtype livers. Curiously, however, despite depleting GSH, ascorbate treatment diminished basal DNA damage and oxidative stress markers in TrxR1/Gsr-null livers. This suggests that, although ascorbate supplementation can prevent oxidative damage, it also can deplete GSH and compromise already stressed livers.
细胞内的氧化剂主要由硫氧还蛋白还原酶-1（TrxR1）和谷胱甘肽还原酶（Gsr）驱动的抗氧化系统进行调控。在肝细胞特异性共缺失TrxR1和Gsr的小鼠（TrxR1/Gsr基因敲除肝脏）中，甲硫氨酸分解代谢维持着肝脏中还原型谷胱甘肽（GSH）的水平。尽管大多数TrxR1/Gsr基因敲除肝脏的小鼠能长期存活，但约25%的小鼠在4至7周龄时死于自发性肝衰竭。在此，我们测试了补充抗坏血酸是否能改善肝衰竭。在给予抗坏血酸、脱氢抗坏血酸或模拟处理后，我们评估了小鼠的存活率、肝脏组织学或肝脏氧化还原标志物，包括GSH和GSSG、氧化还原酶活性以及氧化损伤标志物。出乎意料的是，抗坏血酸（5 mg/mL，饮用水）非但没有提供保护作用，反而将死亡率提高到了43%。在成年小鼠中，抗坏血酸（4 mg/g×3天，腹腔注射）在TrxR1/Gsr基因敲除肝脏中导致肝细胞坏死和肝脏GSH丢失，但在野生型对照中则没有。脱氢抗坏血酸（0.3 mg/g，腹腔注射）也会使TrxR1/Gsr基因敲除肝脏中的肝脏GSH耗竭，而野生型肝脏中的GSH水平在两种处理下均未受到显著影响。然而，奇怪的是，尽管抗坏血酸处理会耗竭GSH，但它却能降低TrxR1/Gsr基因敲除肝脏中的基础DNA损伤和氧化应激标志物。这表明，虽然补充抗坏血酸可以预防氧化损伤，但它也会耗竭GSH并损害本已处于应激状态的肝脏。
