Department of Molecular Biophysics, Division of Radiobiology, Faculty of Biology and Environmental Protection, University of Lodz, Lodz, Poland.
Adv Med Sci. 2013;58(1):134-42. doi: 10.2478/v10039-012-0067-x.
Melatonin (MEL) is an effective antioxidant in numerous experimental models, both in vitro and in vivo. However, it should be stressed that there are also papers reporting limited antioxidative activity of MEL or even giving evidence for its pro-oxidative properties. In the present paper we investigated the influence of MEL on the oxidative damage of human erythrocytes during prolonged incubation.
MATERIAL/METHODS: Human erythrocytes suspended in phosphate-buffered saline (PBS), pH 7.4 were incubated at 37ºC either in absence or presence of melatonin at concentration range 0.02 mM-3 mM for up to 96 hrs. The influence of MEL on erythrocyte damage was assessed on the basis of the intensity of intracellular oxidation processes (the oxidation of HbO₂, GSH, fluorescent label DCFH₂) as well as damage to the plasma membrane (lipid peroxidation, the potassium leakage) and the kinetics of hemolysis.
The prolonged incubation of erythrocytes induced a progressive destruction of erythrocytes. Melatonin prevented lipid peroxidation and hemolysis whereas the oxidation of HbO₂ and DCFH₂ was enhanced by melatonin at concentrations higher than 0.6 mM. In the case of erythrocytes incubated with 3 mM of MEL, the hemolysis rate constant (0.0498±0.0039 H%•h⁻¹) was 50% lower than that of the control while the HbO₂ oxidation rate constants were about 1.4 and 1.5 times higher for 1.5 and 3 mM of MEL, respectively. Melatonin had no influence on the oxidation of GSH and the potassium leakage.
Probably, MEL can stabilize the erythrocyte membrane due to interaction with lipids, thus prolonging the existence of cells. On the contrary, in the presence of MEL the accelerated oxidation of HbO₂ and generally, increased oxidative stress was observed in erythrocytes. Pro- and antioxidative properties of melatonin depend on the type of cells, redox state, as well as experimental conditions.
褪黑素（MEL）在体外和体内的许多实验模型中都是一种有效的抗氧化剂。然而，应该强调的是，也有一些论文报道 MEL 的抗氧化活性有限，甚至有证据表明它具有促氧化特性。在本文中，我们研究了 MEL 对人红细胞在长时间孵育过程中氧化损伤的影响。
材料/方法：将人红细胞悬浮在 pH 值为 7.4 的磷酸盐缓冲盐水（PBS）中，在 37°C 下孵育，无论是否存在褪黑素，浓度范围为 0.02 mM-3 mM，最长可达 96 小时。根据细胞内氧化过程的强度（HbO₂、GSH、荧光标记物 DCFH₂的氧化）以及对质膜的损伤（脂质过氧化、钾泄漏）和溶血动力学，评估 MEL 对红细胞损伤的影响。
红细胞的长时间孵育导致红细胞逐渐破坏。褪黑素可防止脂质过氧化和溶血，而当浓度高于 0.6 mM 时，HbO₂和 DCFH₂的氧化则被褪黑素增强。在孵育 3 mM MEL 的红细胞中，溶血速率常数（0.0498±0.0039 H%•h⁻¹）比对照低 50%，而 1.5 和 3 mM MEL 的 HbO₂氧化速率常数分别高约 1.4 和 1.5 倍。褪黑素对 GSH 的氧化和钾泄漏没有影响。
可能是由于与脂质相互作用，MEL 可以稳定红细胞膜，从而延长细胞的存在时间。相反，在 MEL 的存在下，观察到 HbO₂的加速氧化和红细胞中氧化应激的增加。褪黑素的促氧化和抗氧化特性取决于细胞类型、氧化还原状态以及实验条件。
