Efficiency Of Antioxidant System Research Articles

Complémentarité et équilibre de l’apport alimentaire en protéines et en lipides

The nature and level of dietary protein is liable to influence cholesterol and essential fatty acid (EFA) metabolism. Dietary vegetable protein, particularly the undigested fraction, decreases intestinal cholesterol absorption, increases the faecal excretion of steroids, and enhances the catabolism of cholesterol-carrying lipoproteins by increasing the activity or number of LDL receptors. However, the hypocholesterolemic effect of protein may be due to the presence of non-protein components and hence the purity degree of the selected protein, and the concomitant addition or not of cholesterol. Dietary proteins with different amino acid composition may modulate the secretion of hormones (e.g. glucagon and insulin), which in turn may modify the activity of enzymes responsible for cholesterol metabolism (e.g. HMG-CoA reductase, 7alpha-hydroxylase, lecithin: cholesterol acyl transferase) and polyunsaturated fatty acid synthesis (e.g. Delta5 and Delta6-desaturases). PUFA affect membrane fluidity and the synthesis of eicosanoids: prostaglandins and leukotrienes. Protein deficiency affects severely the PUFA amounts, particularly arachidonic and EPA acids which are precursors of prostaglandins, thromboxanes and leukotrienes, and the possible consequences of their diminution may be an underlying cause of some of the common clinical symptoms in protein malnutrition, such as hair loss, dry scaly dermatitis and increased water permeability. Protein deficiency may thus increase the EFA requirement and precipitate marginal EFA deficiency. The dietary protein level may also influence the efficiency of antioxidant system and/or the release of reactive oxygen species. Tissue lipid peroxidation could be markedly enhanced by feeding low-protein diets, probably due to a depressed efficiency of antioxidative enzyme activities.

Comparative Evaluation of Prooxidant/Antioxidant Balance in Seed Progeny of Plantago major L. from Radioactively and Chemically Contaminated Areas

There are many studies addressing plant responses to radioactive and chemical contamination of soils, but few works have been devoted to comparison of biological effects in the areas affected by these human-induced factors. Ionizing radiation and heavy metals have different mechanisms of interaction with biota. Both factors, however, are capable of increasing the generation of reactive oxygen species, which cause enzyme malfunction and cell structure damage. The efficiency of antioxidant systems plays an important role in plant resistance to these impacts. The present study offers a comparative evaluation of prooxidant/antioxidant balance in seed progeny of Plantago major L. growing in the East Ural Radioactive Trace (EURT), in the zone affected by operation of the Karabash Copper Smelter (KCS), and in the reference sites. Lipid peroxidation was assessed by determining malondialdehyde. Evaluation of the antioxidant system was based on the activities of superoxide dismutase, catalase, and total peroxidase, and on the content of low-molecular-weight antioxidants. The study showed that the prooxidant and antioxidant statuses of seed progeny of P. major from the contaminated sites were different from the reference samples and from each other. The pooled EURT sample exhibited a prooxidant shift relative to the reference samples, i. e. not only malondialdehyde but also activities of superoxide dismutase and catalase and the content of low-molecular-weight antioxidants were higher than in the reference samples. Malondialdehyde content in seedlings from the KCS zone did not differ from the reference values; superoxide dismutase and catalase activities were decreased whereas peroxidase activity was higher compared to the activities of these enzymes in the reference samples. Thus, the differences in the plant adaptive responses to ionizing radiation and heavy metals are caused by the dissimilarities in the induction of reactive oxygen species

Susceptibility to oxidative stress in Adélie and emperor penguin

The antioxidant defences in aerobic organisms represent the detoxification pathway against toxicity of reactive oxygen species (ROS). These highly reactive molecules are normally produced during the 4-electrons reduction of molecular oxygen to water coupled with oxidative phosphorylation, and during the activity of several enzymatic systems which produce ROS as intermediates. However, the endogenous generation of oxyradicals may be influenced by different environmental and biological factors, and the basal efficiency of antioxidant systems generally reflects the normal prooxidant pressure to which organisms are exposed. If the antioxidant capacity is exceeded (i.e. as a consequence of enhanced intracellular formation of ROS), a pathological condition, generally termed oxidative stress, may arise. In this preliminary work, susceptibility to oxidative stress has been compared in plasma of Adelie penguin (Pygoscelis adeliae), emperor penguin (Aptenodytes forsteri), south polar skua (Catharacta maccormicki) and snow petrel (Pagodroma nivea). Within the framework of the Italian Research Program in Antarctica, blood samples were collected during the austral summer 1998–1999 and the Total Oxyradical Scavenging Capacity (TOSC) analysed. The TOSC assay, measuring the capability of biological samples to neutralise different oxyradicals, has been recently standardised to provide a quantifiable value of biological resistance to toxicity of ROS. Penguins exhibited higher scavenging capacity towards peroxyl radicals than south polar skua and snow petrel. The greater resistance to toxicity of oxyradicals might suggest that penguins are naturally exposed to a higher basal prooxidant pressure in comparison to other analysed Antarctic birds.

Total oxyradical scavenging capacity (TOSC) in polluted and translocated mussels: a predictive biomarker of oxidative stress

Several classes of environmental pollutants are known to enhance the intracellular formation of reactive oxygen species in marine invertebrates with different consequences on their antioxidant system. Despite variations in the endogenous levels of antioxidants may reveal biological effects induced by pollutants, the overall efficiency of antioxidant system is not evaluated from such data. The total oxyradical scavenging capacity (TOSC) assay measures the biological resistance to various kinds of oxyradicals, thus providing useful indications to predict oxyradical-mediated adverse effects on the physiological condition of the organisms. In the present work, the capability to neutralize three potent cellular oxidants (peroxyl radicals, hydroxyl radicals and peroxynitrite) was compared in two natural populations of mussels from a clean and a metal polluted area, respectively, and in control organisms translocated for 8 weeks to the contaminated site. Within each group of mussels, the relative efficiency towards the various forms of oxyradicals, showed peroxyl radicals and hydroxyl radicals as the less and the most difficult species, respectively, to neutralize by cellular antioxidants. When the two populations were compared, polluted organisms revealed a significantly higher susceptibility to oxidative stress as indicated by their lower TOSC values. A significant reduction of antioxidant capacity was observed also in translocated organisms where only a moderate recovery was evident at the longer exposure time. Separation of soluble antioxidants from the protein fraction, suggested a greater depletion of low molecular weight molecules during the first phase of exposure to pollutants. The pollutant-induced impairment of antioxidant capability precludes the appearance of oxyradical toxicity. In the present study a high correlation was obtained between reduced TOSC values and lower Neutral Red retention time in lysosomal compartment of circulating haemocytes. The TOSC towards different forms of oxyradicals is confirmed an useful biomarker with predictive validity at the organism level.