ROS generation, lipid peroxidation and antioxidant enzyme activities in the aging brain

Summary. The objective of this study was to determine the specific relationship between brain aging and changes in the level of oxidative stress, lipid peroxidation (LPO) and in the activities of antioxidant enzymes. We used four different age groups (2–3 months, 10–11 months, 16–17 months and 20–21 months) which represented young adults, adults, beginning senescence and senescence, respectively. Basal levels of LPO products measured as malondialdehyde increased gradually with age in mouse brain homogenate. The extent of stimulated LPO products, however, was clearly decreased in the brain of adult mice compared to young mice but increased again in the brain of senescent mice. We could not detect any appreciable age-related changes in the basal as well as in stimulated levels of ROS measured with the fluorescent dyes dichlorofluorescein and dihydrorhodamine123. Nevertheless, there was a significant delay in the time course of ROS-generation in brain cells from old mice. The activities of the antioxidant enzymes CuZn-superoxide dismutase and glutathione reductase increased with age whereas glutathione peroxidase remained unchanged. On the basis of our present findings, we envisage a potential model that integrates several divergent findings described in the literature about the role of oxidative stress in brain aging. Received December 18, 2000; accepted March 12, 2001     

Estrogen inhibits lipid peroxidation after hypoxic-ischemic brain damage in neonatal rats

Sprague-Dawley neonatal rats within 7 days after birth were used in this study. The left common carotid artery was occluded and rats were housed in an 8% O2 environment for 2 hours to establish a hypoxic-ischemic brain damage model. 17β-estradiol (1 × 10-5 M) was injected into the rat abdominal cavity after the model was successfully established. The left hemisphere was obtained at 12, 24, 48, 72 hours after operation. Results showed that malondialdehyde content in the left brain of neonatal rats gradually increased as modeling time prolonged, while malondialdehyde content of 17β-estrodial-treated rats significantly declined by 24 hours, reached lowest levels at 48 hours, and then peaked at 72 hours after injury. Nicotinamide-adenine dinucleotide phosphate histochemical staining showed the nitric oxide synthase-positive cells and fibers dyed blue/violet and were mainly distributed in the cortex, hippocampus and medial septal nuclei. The number of nitric oxide synthase-positive cells peaked at 48 hours and significantly decreased after 17β-estrodial treatment. Our experimental findings indicate that estrogen plays a protective role following hypoxic-ischemic brain damage by alleviating lipid peroxidation through reducing the expression of nitric oxide synthase and the content of malondialdehyde.     

Effects of α-tocopherol on lipid peroxidation and mitochondrial reduction of tetraphenyl tetrazolium in the rat brain

The antioxidant effect of a-tocopherol was assessed in a model of ischemia-reperfusion in the rat brain. In this model, permanent ischemia of the cortical branches of the middle cerebral artery was combined with bilateral occlusion of the common carotid arteries for l h and restoration of circulation for a period of 2 h. Lipid peroxidation and mitochondrial reduction of tetraphenyl tetrazolium (TPT) were determined in both untreated and d-a-tocopherol treated rats. Ferrous sulfate and ascorbic acid (FeAs) were used to induce lipid peroxidation via the formation of hydroxyl anions. Malondialdehyde (MDA) increased in the ischemia-reperfusion areas (+101%), but FeAs-induced MDA did not vary in the area of permanent ischemia. Brain tissue undergoing ischemia-reperfusion was about 50% less sensitive to the antioxidant effect of ascorbic acid. The reduction of TPT showed 52% mitochondrial damage in the area of ischemia-reperfusion, whereas mitochondrial activity in the area of permanent ischemia was 177 times lower as compared to controls, d-a-tocopherol caused a 40% inhibition of MDA production and 16.5% and 21.5% decrease in mitochondrial activity in the areas of ischemia-reperfusion and permanent ischemia, respectively.     

Differential susceptibility of human skeletal muscle proteins to free radical induced oxidative damage: a histochemical,immunocytochemical and electron microscopical study in vitro

In this study we describe a novel experimental approach to quantify the relative susceptibility of (membrane-associated, contractile and mitochondrial) proteins in normal human muscle tissue sections to oxidative damage by the reactive oxygen species (ROS), hydroxyl (OH·) or superoxide (O₂.^–) radicals. The latter species were generated under controlled experimental conditions in vitro using a ⁶⁰Co gamma radiation source, with subsequent analysis of damage to target proteins (dystrophin, β-dystroglycan, β-spectrin, fast and slow myosin heavy chain, NADH tetrazolium reductase, succinate dehydrogenase and cytochrome oxidase) via standard histochemistry, immunocytochemistry and electron microscopy of muscle tissue sections. In general terms, each of the proteins listed above was more susceptible to oxidative damage by OH·, compared to O₂·^–. Different proteins (differing in structure, function or intracellular localisation) showed different susceptibility to oxidative damage, with certain mitochondrial proteins (succinate dehydrogenase, cytochrome oxidase) showing particular susceptibility. In addition, the use of monoclonal antibodies to four different regions of dystrophin showed the latter to contain both resistant and susceptible regions to ROS induced oxidative damage. At the ultrastructural level of subcellular organelle damage, mitochondria were identified as being particularly susceptible to ROS induced oxidative damage. We therefore speculate that oxidative damage to mitochondria and/or mitochondrial proteins may represent the principal initial route of free radical-induced damage within skeletal muscle tissue. Received:31 October 1995 / Revised, accepted: 19 February 1996