Measurement of Rat Mitochondrial Hydroperoxides Using in Situ Liver Perfusion of 2′,7′-Dichlorodihydrofluorescein Diacetate

Determination of Intracellular Levels of Reactive Oxygen Species Using the 2,7-dichlorofluorescein Diacetate Assay by Kinetic Monte Carlo Simulation

Reactive oxygen species (ROS) are reactive molecules which are produced normally by metabolic reactions. 2,7-Dichlorofluorescein diacetate (DCHF-DA) assay is used to determine intracellular levels of ROS in cancer cells. In the present study, the mechanism and kinetic parameters of this determination are obtained by kinetic Monte Carlo simulation. The values of the rate constants for the suggested mechanism were obtained by simulation. Then, the effect of DCHF-DA concentration on the rate of reaction was studied. According to the results, the product concentration should increase on increasing the DCHF-DA concentration. In addition, the effect of ROS concentration on the rate of reaction was determined.

Noradrenaline activation of neurotrophic pathways protects against neuronal amyloid toxicity

Degeneration of locus coeruleus (LC) noradrenergic forebrain projection neurons is an early feature of Alzheimer's disease. The physiological consequences of this phenomenon are unclear, but observations correlating LC neuron loss with increased Alzheimer's disease pathology in LC projection sites suggest that noradrenaline (NA) is neuroprotective. To investigate this hypothesis, we determined that NA protected both hNT human neuronal cultures and rat primary hippocampal neurons from amyloid-beta (Abeta(1-42) and Abeta(25-35)) toxicity. The noradrenergic co-transmitter galanin was also effective at preventing Abeta-induced cell death. NA inhibited Abeta(25-35)-mediated increases in intracellular reactive oxygen species, mitochondrial membrane depolarization, and caspase activation in hNT neurons. NA exerted its neuroprotective effects in these cells by stimulating canonical beta(1) and beta(2) adrenergic receptor signaling pathways involving the activation of cAMP response element binding protein and the induction of endogenous nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF). Treatment with functional blocking antibodies for either NGF or BDNF blocked NA's protective actions against Abeta(1-42) and Abeta(25-35) toxicity in primary hippocampal and hNT neurons, respectively. Taken together, these data suggest that the neuroprotective effects of noradrenergic LC afferents result from stimulating neurotrophic NGF and BDNF autocrine or paracrine loops via beta adrenoceptor activation of the cAMP response element binding protein pathway.

Macrophages overexpressing tartrate-resistant acid phosphatase show altered profile of free radical production and enhanced capacity of bacterial killing

Activated macrophages and osteoclasts express high amounts of tartrate-resistant acid phosphatase (TRACP, acp5). TRACP has a binuclear iron center with a redox-active iron that has been shown to catalyze the formation of reactive oxygen species (ROS) by Fenton's reaction. Previous studies suggest that ROS generated by TRACP may participate in degradation of endocytosed bone matrix products in resorbing osteoclasts and degradation of foreign compounds during antigen presentation in activated macrophages. Here we have compared free radical production in macrophages of TRACP overexpressing (TRACP+) and wild-type (WT) mice. TRACP overexpression increased both ROS levels and superoxide production. Nitric oxide production was increased in activated macrophages of WT mice, but not in TRACP+ mice. Macrophages from TRACP+ mice showed increased capacity of bacterial killing. Recombinant TRACP enzyme was capable of bacterial killing in the presence of hydrogen peroxide. These results suggest that TRACP has an important biological function in immune defense system.

Oxidative damage of human skin lipids. Dependence of lipid peroxidation on sterol concentration

Photoprotection against sunburn and associated irradiation-induced damages of the human skin is mainly attributed to the darkening of the biochrome melanin by its oxidation. Human skin lipids were examined for an additional protection by sterols. Lipid vesicles prepared from extracted human skin lipids as well as from mixtures of typical lipids of the stratum corneum were irradiated by UV light in the presence and absence of oxygen. The oxidative degradation of various lipids was measured by quantitative HPTLC, by the dichlorofluorescein fluorescent assay, by the thiobarbituric acid assay and a novel luminol-based chemiluminescence technique. Electron spin resonance was used to look for certain radical intermediates. The results indicate, that sterols, mainly free cholesterol, with their high concentration in the lipid barrier of the stratum corneum (up to 50 mol%) effectively compete with the peroxidation of other human skin lipids (ceramides and free fatty acids).

Estimation of oxidative stress in Saccharomyces cerevisae with fluorescent probes

Oxidation of dichlorofluorescin and dihydrofluorescin and transport of their oxidation products were studied in Saccharomyces cerevisiae cells given diacetates of these compounds. It was found that addition of peroxidase significantly accelerates the formation of dichlorofluorescein and fluorescein, indicating that peroxidase activity may be a limiting factor in studies of cellular oxidation using these probes. A significant leakage of dichlorofluorescin and dihydrofluorescin, and of their oxidized forms from the yeast cells, was found, without any apparent lag period. This phenomenon complicates interpretation of data obtained with the fluorescent precursors used but, on the other hand, points to the possibility of using measurements of dichlorofluorescein or fluorescein in the extracellular medium for studies of cellular oxidation processes.