Relation of plasma selenium and lipid peroxidation end products in patients with Alzheimer's disease.

Increased oxidative stress in the brain during the course of Alzheimer's disease (AD) leads to an imbalance of antioxidants and formation of free radical reaction end-products which may be detected in blood as fluorescent lipofuscin-like pigments (LFPs). The aim of this study was to evaluate and compare LFPs with plasma selenium concentrations representing an integral part of the antioxidant system. Plasma samples from subjects with AD dementia (ADD; n=11), mild cognitive impairment (MCI; n=17) and controls (n=12), were collected. The concentration of selenium was measured using atomic absorption spectroscopy. LFPs were analyzed by fluorescence spectroscopy and quantified for different fluorescent maxima and then correlated with plasma selenium. Lower levels of selenium were detected in MCI and ADD patients than in controls (P=0.003 and P=0.049, respectively). Additionally, higher fluorescence intensities of LFPs were observed in MCI patients than in controls in four fluorescence maxima and higher fluorescence intensities were also observed in MCI patients than in ADD patients in three fluorescence maxima, respectively. A negative correlation between selenium concentrations and LFPs fluorescence was observed in the three fluorescence maxima. This is the first study focused on correlation of plasma selenium with specific lipofuscin-like products of oxidative stress in plasma of patients with Alzheimer´s disease and mild cognitive impairment.

[Some aspects of the immune system in the pathogenesis of Alzehimers disease]. / Nekteré aspekty imunitního systému v patogenezi Alzheimerovy choroby.

Alzheimers disease is a severe neurodegenerative disorder and the most common cause of dementia in the population above 60 years of age. Beta-amyloid accumulation and neurofibrillary tangles formation in the brain precedes the development of Alzheimer's dementia by many years. As beta-amyloid accumulation inhibition failed as a treatment option, the theories on the Alzheimers disease pathophysio-lo-gy are being revised. In this context, research targets the role of inflammation as the possible trigger mechanism and accompanying process of neurodegeneration. This article summarizes some knowledge of the immune function of brain cells and its potential relation to Alzheimers disease progression in the light of the immune reaction hypothesis.

Comparison of the effects of tert-butyl hydroperoxide and peroxynitrite on the oxidative damage to isolated beef heart mitochondria.

Isolated beef heart mitochondria have been exposed to tert-butyl hydroperoxide (tBHP) and peroxynitrite (PeN) in order to model the effects of reactive oxygen and nitrogen species on mitochondria in vivo. The formation of malondialdehyde (MDA), protein carbonyls, lipofuscin-like pigments (LFP), and nitrotyrosine was studied during incubations with various concentrations of oxidants for up to 24 h. The oxidants differed in their ability to oxidize particular substrates. Fatty acids were more sensitive to the low concentrations of tBHP, whereas higher concentrations of PeN consumed MDA. Oxidation of proteins producing carbonyls had different kinetics and also a probable mechanism with tBHP or PeN. Diverse proteins were affected by tBHP or PeN. In both cases, prolonged incubation led to the appearance of proteins with molecular weights lower than 29 kDa bearing carbonyl groups that might have been caused by protein fragmentation. PeN induced nitration of protein tyrosines that was more intensive in the soluble proteins than in the insoluble ones. LFP, the end products of lipid peroxidation, were formed more readily by PeN. On the other hand, fluorometric and chromatographic techniques have confirmed destruction of LFP by higher PeN concentrations. This is a unique feature that has not been described so far for any oxidant.

Short-term fasting reduces the extent of myocardial infarction and incidence of reperfusion arrhythmias in rats.

The effect of three-day fasting on cardiac ischemic tolerance was investigated in adult male Wistar rats. Anesthetized open-chest animals (pentobarbitone 60 mg/kg, i.p.) were subjected to 20-min left anterior descending coronary artery occlusion and 3-h reperfusion for infarct size determination. Ventricular arrhythmias were monitored during ischemia and at the beginning (3 min) of reperfusion. Myocardial concentrations of beta-hydroxybutyrate and acetoacetate were measured to assess mitochondrial redox state. Short-term fasting limited the infarct size (48.5+/-3.3 % of the area at risk) compared to controls (74.3+/-2.2 %) and reduced the total number of premature ventricular complexes (12.5+/-5.8) compared to controls (194.9+/-21.9) as well as the duration of ventricular tachycardia (0.6+/-0.4 s vs. 18.8+/-2.5 s) occurring at early reperfusion. Additionally, fasting increased the concentration of beta-hydroxybutyrate and beta-hydroxybutyrate/acetoacetate ratio (87.8+/-27.0) compared to controls (7.9+/-1.7), reflecting altered mitochondrial redox state. It is concluded that three-day fasting effectively protected rat hearts against major endpoints of acute I/R injury. Further studies are needed to find out whether these beneficial effects can be linked to altered mitochondrial redox state resulting from increased ketogenesis.

Reactive oxygen species production in the early and later stage of chronic ventilatory hypoxia.

Pulmonary hypertension resulting from chronic hypoxia is at least partly caused by the increased production of reactive oxygen species (ROS). The goal of the presented study was to investigate the dynamics and the site of production of ROS during chronic hypoxia. In our study Wistar rats were kept for 1, 4 and 21 days in an isobaric hypoxic chamber (F(iO2)=0.1), while controls stayed in normoxia. We compared NO production in expired air, plasma and perfusate drained from isolated rat lungs and measured superoxide concentration in the perfusate. We also detected the presence of superoxide products (hydrogen peroxide and peroxynitrite) and the level of ROS-induced damage expressed as the concentration of lipid peroxydation end products. We found that the production and release of ROS and NO during early phase of chronic hypoxia has specific timing and differs in various compartments, suggesting the crucial role of ROS interaction for development of hypoxic pulmonary hypertension.

The lipid peroxidation products as possible markers of Alzheimer's disease in blood.

Oxidative stress, which is present in Alzheimer's disease (AD), results in the formation of various end-products of free radical reactions with proteins and lipids. At present there are no reliable diagnostic biomarkers of AD in the blood. Therefore, specific products of lipid peroxidation in the blood of AD patients were investigated. Lipophilic extracts of erythrocytes in the group of patients with AD (n = 44) and age-matched controls (n = 16) were studied. The end-products of lipid peroxidation, so called lipofuscin-like pigments (LFP), were analysed by fluorescence spectroscopy. It was found that the level of these products is significantly increased in erythrocytes of AD patients compared to controls. LFP were further separated by means of HPLC into individual fractions to study their composition in AD and controls. The specific fraction of LFP in AD patients, which was isolated, might represent a disease-specific product in the blood.

Erythrocyte membranes inhibit respiratory burst and protein nitration during phagocytosis by macrophages.

Phagocytosis is associated with respiratory burst producing reactive oxygen and nitrogen species. Several studies imply that erythrocytes can inhibit the respiratory burst during erythrophagocytosis. In this work we studied the mechanisms of this effect using control and in vitro peroxidized erythrocyte membranes. We demonstrated that autofluorescence of peroxidation products can be used for visualization of phagocytozed membranes by fluorescence microscopy. We also found that respiratory burst induced by a phorbol ester was inhibited by control membranes (5 mg/ml) to 63 % (P < 0.001), and to 40 % by peroxidized membranes (P < 0.001). We proved that this effect is not caused by the direct interaction of membranes with free radicals or by the interference with luminol chemiluminescence used for the detection of respiratory burst. There are indications of the inhibitory effects of iron ions and free radical products. Macrophages containing ingested erythrocyte membranes do not contain protein-bound nitrotyrosine. These observations imply a specific mechanism of erythrocyte phagocytosis.

The role of free radicals in canine counterpart of senile dementia of the Alzheimer type.

The pathogenesis of Alzheimer's disease is still unknown. In recent time oxidative stress has been discussed as an important contributor. In the present study we investigated the role of free radicals in the spontaneous canine model of Alzheimer's disease. We analysed end-products of lipid peroxidation: lipofuscin-like pigments (LFP), protein carbonyls, and vitamin E to obtain data on oxidative damage in brain of demented dogs. When the generation of free radicals is intensive the toxic products of lipid peroxidation can diffuse from the site of the primary formation and merge with erythrocytes. Therefore we also determined the level of lipid peroxidation in red blood cells. In brain of demented animals the level of LFP increased (to 247%, P<0.05) as well as of protein carbonyls (to 438%, P<0.01) while the vitamin E concentration was lowered (to 34%, P<0.01) when compared to age-matched non-demented controls. The end-products of lipid peroxidation have been found increased also in erythrocytes of demented dogs (250%, P<0.05). These results indicate intensive production of free radicals in brain of animals with dementia which induces damage to erythrocytes. Detection of the specific products of free radical damage in blood samples could be used for diagnostic purposes.