Department of Biochemistry, Federal University of Santa Catarina, Florianopolis, SC, 88040-900, Brazil.
Cellular Neurobiology Laboratory, Salk Institute for Biological Studies, La Jolla, CA, 92037, USA.
Neurotox Res. 2017 Oct;32(3):340-350. doi: 10.1007/s12640-017-9738-5. Epub 2017 May 6.
Thioredoxin (Trx) and glyoxalase (Glo) systems have been suggested to be molecular targets of methylglyoxal (MGO). This highly reactive endogenous compound has been associated with the development of neurodegenerative pathologies and cell death. In the present study, the glutathione (GSH), Trx, and Glo systems were investigated to understand early events (0.5-3 h) that may determine cell fate. It is shown for the first time that MGO treatment induces an increase in glutathione reductase (GR) protein in hippocampal slices (1 h) and HT22 nerve cells (0.5 and 2.5 h). Thioredoxin interacting protein (Txnip), thioredoxin reductase (TrxR), Glo1, and Glo2 were markedly increased (2- to 4-fold) in hippocampal slices and 1.2- to 1.3-fold in HT22 cells. This increase in protein levels in hippocampal slices was followed by a corresponding increase in GR, TrxR, and Glo1 activities, but not in HT22 cells. In these cells, GR and TrxR activities were decreased by MGO. This result is in agreement with the idea that MGO can affect the Trx/TrxR reducing system, and now we show that GR and Txnip can also be affected by MGO. Impairment in the GR or TrxR reducing capacity can impair peroxide removal by glutathione peroxidase and peroxiredoxin, as both peroxidases depend on reduced GSH and Trx, respectively. In this regard, inhibition of GR and TrxR by 2-AAPA or auranofin, respectively, potentiated MGO toxicity in differentiated SH-SY5Y cells. Overall, MGO not only triggers a clear defense response in hippocampal slices and HT22 cells but also impairs the Trx/TrxR and GSH/GR reducing couples in HT22 cells. The increased MGO toxicity caused by inhibition of GR and TrxR with specific inhibitors, or their inhibition by MGO treatment, supports the notion that both reducing systems are relevant molecular targets of MGO.
硫氧还蛋白 (Trx) 和甘油醛-3-磷酸脱氢酶 (Glo) 系统被认为是甲基乙二醛 (MGO) 的分子靶标。这种具有高度反应性的内源性化合物与神经退行性病变和细胞死亡的发展有关。在本研究中，研究了谷胱甘肽 (GSH)、Trx 和 Glo 系统，以了解可能决定细胞命运的早期事件 (0.5-3 h)。这是首次表明 MGO 处理诱导海马切片 (1 h) 和 HT22 神经细胞 (0.5 和 2.5 h) 中谷胱甘肽还原酶 (GR) 蛋白增加。硫氧还蛋白相互作用蛋白 (Txnip)、硫氧还蛋白还原酶 (TrxR)、Glo1 和 Glo2 在海马切片中显著增加 (2-4 倍)，在 HT22 细胞中增加 1.2-1.3 倍。海马切片中蛋白质水平的增加伴随着 GR、TrxR 和 Glo1 活性的相应增加，但在 HT22 细胞中没有。在这些细胞中，GR 和 TrxR 活性被 MGO 降低。这一结果与 MGO 可以影响 Trx/TrxR 还原系统的观点一致，现在我们表明 GR 和 Txnip 也可以受到 MGO 的影响。GR 或 TrxR 还原能力的损害会损害谷胱甘肽过氧化物酶和过氧化物酶的过氧化物去除，因为这两种过氧化物酶分别依赖还原型 GSH 和 Trx。在这方面，用 2-AAPA 或金诺芬分别抑制 GR 和 TrxR，增强了分化的 SH-SY5Y 细胞中 MGO 的毒性。总的来说，MGO 不仅在海马切片和 HT22 细胞中引发了明显的防御反应，而且还损害了 HT22 细胞中的 Trx/TrxR 和 GSH/GR 还原对。用特异性抑制剂抑制 GR 和 TrxR 或用 MGO 处理抑制它们，会增加 MGO 毒性，这支持了这两种还原系统都是 MGO 的相关分子靶标的观点。
