Department of Cardiovascular Physiology, Heidelberg University, Heidelberg D-69120, Germany.
Molecular and Cellular Modeling Group, Heidelberg Institute for Theoretical Studies (HITS), Heidelberg D-69118, Germany; Heidelberg Graduate School of Mathematical and Computational Methods for the Sciences, Heidelberg D-69120, Germany.
Redox Biol. 2018 Jun;16:113-122. doi: 10.1016/j.redox.2018.02.018. Epub 2018 Mar 1.
High levels of glucose and reactive carbonyl intermediates of its degradation pathway such as methylglyoxal (MG) may contribute to diabetic complications partly via increased generation of reactive oxygen species (ROS). This study focused on glutathione peroxidase-1 (GPx1) expression and the impact of carbonylation as an oxidative protein modification on GPx1 abundance and activity in human umbilical vein endothelial cells (HUVEC) under conditions of mild to moderate oxidative stress.
High extracellular glucose and MG enhanced intracellular ROS formation in HUVECs. Protein carbonylation was only transiently augmented pointing to an effective antioxidant defense in these cells. Nitric oxide synthase expression was decreased under hyperglycemic conditions but increased upon exposure to MG, whereas superoxide dismutase expression was not significantly affected. Increased glutathione peroxidase (GPx) activity seemed to compensate for a decrease in GPx1 protein due to enhanced degradation via the proteasome. Mass spectrometry analysis identified Lys-114 as a possible carbonylation target which provides a vestibule for the substrate HO and thus enhances the enzymatic reaction.
Oxidative protein carbonylation has so far been associated with functional inactivation of modified target proteins mainly contributing to aging and age-related diseases. Here, we demonstrate that mild oxidative stress and subsequent carbonylation seem to activate protective cellular redox signaling pathways whereas severe oxidative stress overwhelms the cellular antioxidant defense leading to cell damage.
This study may contribute to a better understanding of redox homeostasis and its role in the development of diabetes and related vascular complications.
高浓度的葡萄糖和其降解途径中的反应性羰基中间产物（如甲基乙二醛[MG]）可能通过增加活性氧（ROS）的产生而部分导致糖尿病并发症。本研究聚焦于谷胱甘肽过氧化物酶 1（GPx1）的表达，并研究羰基化作为一种氧化蛋白修饰对人脐静脉内皮细胞（HUVEC）中 GPx1 丰度和活性的影响，实验条件为轻度至中度氧化应激。
高细胞外葡萄糖和 MG 增强了 HUVEC 内的细胞内 ROS 形成。蛋白羰基化只是短暂增加，表明这些细胞中存在有效的抗氧化防御机制。高糖条件下一氧化氮合酶表达减少，但暴露于 MG 时增加，而超氧化物歧化酶表达无明显变化。增加的谷胱甘肽过氧化物酶（GPx）活性似乎补偿了由于通过蛋白酶体增强降解而导致的 GPx1 蛋白减少。质谱分析鉴定出 Lys-114 可能是一个羰基化的靶标，它为底物 HO 提供了一个入口，从而增强了酶促反应。
氧化蛋白羰基化迄今为止与修饰靶蛋白的功能失活有关，主要导致衰老和与年龄相关的疾病。在这里，我们证明轻度氧化应激和随后的羰基化似乎激活了保护性的细胞氧化还原信号通路，而严重的氧化应激则使细胞抗氧化防御能力不堪重负，导致细胞损伤。
本研究可能有助于更好地理解氧化还原平衡及其在糖尿病和相关血管并发症发展中的作用。
