Reductive stress, which is due to a paradoxical excess of antioxidants such as reduced glutathione (GSH) and GSH-related enzymes associated with decreased oxidant levels, has emerged as a pathogenetic mechanism of myocardial damage in pathological conditions such as protein aggregation cardiomyopathy. Notably, in the aged heart a cardiomyopathy-like pathology occurs leading to myocardial dysfunction. Whether reductive stress, or instead its counterpart oxidative stress, is operative in the aged mammalian heart needs to be elucidated also for the different therapeutic implications of such redox stress conditions. In the present investigation, we assessed GSH and the specific enzymatic activities of γ-glutamylcysteine synthetase (γ-GCS), glutathione reductase (GSSG-Red) and selenium-dependent glutathione peroxidase (GSH-Px) as endogenous antioxidants, together with oxidized glutathione (GSSG) and the glutathione redox ratio (GSH/GSSG), in the aerobically perfused hearts of aged rabbits (about 4.5 years old) and young adult control rabbits (3-4 months old). We also assessed in the aged and control hearts H2O2 and catalytically active low molecular weight iron (LMWI) as oxidant forces, as well as fluorescent damage products of lipid peroxidation (FDPL) and protein carbonyls (PC) as biomarkers of lipid and protein oxidation. Moreover, the effects of 4.5 mM N-acetylcysteine (NAC) as reducing thiol antioxidant were studied on hemodynamic parameters and lipid peroxidation in the perfused hearts of the aged and control rabbits. The levels of GSH and of the GSH/GSSG ratio were lower, and those of GSSG higher, in the aged than in the control hearts. The aged hearts were also characterized by decreased activities of the antioxidant enzymes γ-GCS, GSSG-Red and GSH-Px, as well as by heightened levels of H2O2, LMWI, FDPL and PC, highlighting the occurrence of aging-dependent oxidative stress. Associated with such biochemical alterations, hemodynamic dysfunction occurred in the aged rabbit hearts, as evidenced by lowered developed pressure (DP) and enhanced end-diastolic pressure (EDP) with decreased coronary flow (CF). Remarkably, NAC administration significantly improved DP and EDP, and lowered lipid peroxidation, electively in the aged hearts. In conclusion, oxidative and not reductive stress is operative in the aged rabbit heart, whose hemodynamic dysfunction is improved by NAC together with reduction in myocardial lipid peroxidation.

中文翻译：

---

老年兔心脏氧化应激而非还原应激的证据。


还原应激是由于与氧化剂水平降低相关的还原型谷胱甘肽 (GSH) 和 GSH 相关酶等抗氧化剂的反常过量引起的，它已成为蛋白质聚集性心肌病等病理状况下心肌损伤的发病机制。值得注意的是，在衰老的心脏中，会发生类似心肌病的病理，导致心肌功能障碍。还原应激或其对应的氧化应激是否在老年哺乳动物心脏中起作用，还需要阐明这种氧化还原应激条件的不同治疗意义。在本研究中，我们评估了 GSH 以及作为内源抗氧化剂的 γ-谷氨酰半胱氨酸合成酶 (γ-GCS)、谷胱甘肽还原酶 (GSSG-Red) 和硒依赖性谷胱甘肽过氧化物酶 (GSH-Px) 以及氧化型谷胱甘肽的比酶活性(GSSG) 和谷胱甘肽氧化还原比 (GSH/GSSG)，在老年兔子（约 4.5 岁）和年轻成年对照兔子（3-4 个月大）的有氧灌注心脏中。我们还在老年心脏和对照心脏中评估了 H2O2 和催化活性低分子量铁 (LMWI) 作为氧化力，以及脂质过氧化 (FDPL) 和蛋白质羰基 (PC) 的荧光损伤产物作为脂质和蛋白质氧化的生物标志物。此外，还研究了 4.5 mM N-乙酰半胱氨酸（NAC）作为还原性硫醇抗氧化剂对老年兔和对照兔灌注心脏的血流动力学参数和脂质过氧化的影响。老年人心脏中的 GSH 水平和 GSH/GSSG 比值低于对照组心脏，而 GSSG 水平高于对照组心脏。 衰老心脏的特征还包括抗氧化酶 γ-GCS、GSSG-Red 和 GSH-Px 活性降低，以及 H2O2、LMWI、FDPL 和 PC 水平升高，突出了衰老依赖性氧化应激的发生。与这种生化改变相关，老年兔心脏出现血流动力学功能障碍，表现为发展压（DP）降低和舒张末期压力（EDP）增加，冠脉流量（CF）减少。值得注意的是，NAC 给药显着改善了老年心脏的 DP 和 EDP，并降低了脂质过氧化。总之，氧化应激而非还原应激在老年兔心脏中起作用，NAC 可改善其血流动力学功能障碍，并减少心肌脂质过氧化。