Fat soluble antioxidants in brood‐rearing great tits Parus major: relations to health and appearance

The concept of parasite‐mediated sexual selection assumes that females may improve offspring fitness by selecting mates on the basis of sexual ornaments that honestly reveal the health state of a partner. Expression of such signals may be particularly sensitive to oxidative damage caused by excess production of oxidative metabolites and free radicals. To control and neutralise free radicals, animals rely heavily on dietary fat‐soluble antioxidants such as vitamin E and A, and carotenoids. However, the organism's need for free radical scavenging may interfere with the opposite need to generate oxidative stress for fighting parasitic infections. We investigated plasma concentrations of carotenoids and vitamin A and E in brood‐rearing great tits Parus major in relation to carotenoid‐based plumage coloration, sex, habitat, leukocyte hemoconcentrations and infection status with Haemoproteus blood parasites. Rural great tits differed from urban ones and males from females with respect to the hue of the yellow ventral feathers. However, plasma antioxidant concentrations were not related to sex, habitat or plumage coloration. Plasma carotenoid concentration correlated positively with indices of immune system activation as measured by blood counts of lymphocytes and eosinophils. Birds with gametocytes of Haemoproteus in their blood had higher plasma concentrations of carotenoids and vitamin E than unparasitized individuals. These results are consistent with the idea that maintenance of high blood antioxidant levels might conflict with individual needs to rely on oxidative stress for fighting infections.     

Biologically Active Polymers from Spontaneous Carotenoid Oxidation: A New Frontier in Carotenoid Activity

In animals carotenoids show biological activity unrelated to vitamin A that has been considered to arise directly from the behavior of the parent compound, particularly as an antioxidant. However, the very property that confers antioxidant activity on some carotenoids in plants also confers susceptibility to oxidative transformation. As an alternative, it has been suggested that carotenoid oxidative breakdown or metabolic products could be the actual agents of activity in animals. However, an important and neglected aspect of the behavior of the highly unsaturated carotenoids is their potential to undergo addition of oxygen to form copolymers. Recently we reported that spontaneous oxidation of ß-carotene transforms it into a product dominated by ß-carotene-oxygen copolymers. We now report that the polymeric product is biologically active. Results suggest an overall ability to prime innate immune function to more rapidly respond to subsequent microbial challenges. An underlying structural resemblance to sporopollenin, found in the outer shell of spores and pollen, may allow the polymer to modulate innate immune responses through interactions with the pattern recognition receptor system. Oxygen copolymer formation appears common to all carotenoids, is anticipated to be widespread, and the products may contribute to the health benefits of carotenoid-rich fruits and vegetables.     

Biomarkers of antioxidant capacity in the hydrophilic and lipophilic compartments of human plasma

Antioxidants located in both the hydrophilic and lipophilic compartments of plasma are actively involved as a defense system against reactive oxygen species (ROS), which are continuously generated in the body due to both normal metabolism and disease. However, when the production of ROS is not controlled, it leads to cellular lipid, protein, and DNA damage in biological systems. Several assays to measure 'total' antioxidant capacity of plasma have been developed to study the involvement of oxidative stress in pathological conditions and to evaluate the functional bioavailability of dietary antioxidants. Conventional assays to determine antioxidant capacity primarily measure the antioxidant capacity in the aqueous compartment of plasma. Consequently, water-soluble antioxidants such as ascorbic acid, uric acid and protein thiols mainly influence these assays, whereas fat-soluble antioxidants such as tocopherols and carotenoids play only a minor role. However, there are active interactions among antioxidants located in the hydrophilic and lipophilic compartments of plasma. Therefore, new approaches to define the 'true' total antioxidant capacity of plasma should reflect the antioxidant network between water- and fat-soluble antioxidants in plasma. Revelation of the mechanism of action of antioxidants and their true antioxidant potential will help us to optimize the antioxidant defenses in the body.     

Correlates of oxidative stress in wild kestrel nestlings (Falco tinnunculus)

The fitness of an organism can be affected by conditions experienced during early development. In light of the impact that oxidative stress can have on the health and ageing of a bird species, this study evaluated factors accounting for the variation in oxidative stress levels in nestlings of the Eurasian kestrel (Falco tinnunculus) by measuring the serum concentration of reactive oxygen metabolites and the serum antioxidant barrier against hypochlorite-induced oxidation. The ratio between these two variables was considered as an index of oxidative stress, with higher values meaning higher oxidative damage. Six-chick broods showed the highest level of oxidative stress, while no effect of sex was found. Age showed an inverse relationship with the oxidants and the levels of oxidative stress, with younger birds having higher levels. Hatching date, body condition, body mass and carotenoid concentration did not show any relationship with oxidants, antioxidants or degree of oxidative stress. These findings suggest that intrabrood sibling competition could play a role in determining oxidative stress, and that in carnivorous birds other antioxidant molecules could be more important than carotenoids to reduce oxidative stress.     

Knockout of crtB or crtI gene blocks the carotenoid biosynthetic pathway in Deinococcus radiodurans R1 and influences its resistance to oxidative DNA-damaging agents due to change of free radicals scavenging ability

Deinococcus radiodurans R1, a red-pigmented strain of the extremely radioresistant genus Deinococcus, contains a major carotenoid namely deinoxanthin. The high resistance of this organism against the lethal actions of DNA-damaging agents including ionizing radiation and ultraviolet light (UV) has been widely reported. However, the possible antioxidant role of carotenoids in this strain has not been completely elucidated. In this study, we constructed two colorless mutants by knockout of crtB and crtI genes, respectively. Comparative analysis of the two colorless mutants and the wild type showed that the two colorless mutants were more sensitive to ionizing radiation, UV, and hydrogen peroxide, but not to mitomycin-C (MMC). With electron spin resonance (ESR) and spin trapping techniques, we observed that hydroxyl radical signals occurred in the suspensions of UV irradiated Deinococcus radiodurans cells and the intensity of signals was influenced by carotenoids levels. We further showed that the carotenoid extract from the wild type could obviously scavenge superoxide anions generated by the irradiated riboflavin/EDTA system. These results suggest that carotenoids in D. radiodurans R1 function as free radical scavengers to protect this organism against the deleterious effects of oxidative DNA-damaging agents.     

Antioxidant defense system in the apple snail eggs, the role of ovorubin

A novel role of ovorubin as a protection system against oxidative damage in eggs from Pomacea canaliculata was investigated. Carotenoid composition, and their antioxidant capacity, as well as the carotenoid-apoprotein interaction, were studied for this lipoglycocarotenoprotein. Carotenoid extracts from ovorubin were analysed by TLC and spectrophotometry. The major carotenoid was astaxanthin in its free (40%), monoester (24%), and diester (35%) forms, mainly esterified with 16:0 fatty acid. The antioxidant capacity of ovorubin carotenoids was studied by the inhibition of microsomal oxidation in a non-enzymatic system, showing strong protection against oxidative damage (IC50=3.9 nmol/mg protein). The carotenoid-apoprotein interaction was studied by spectrophotometry and electrophoresis using reconstituted ovorubin. Astaxanthin does not seem to affect the structural characteristics of ovorubin, however the carotenoid-protein association significantly protected astaxanthin against oxidation. Ovorubin therefore, besides its role in providing energy and structural precursors during embryogenesis, would be an antioxidant carrier, protecting at the same time this pigment from oxidation in the perivitellin fluid environment of the egg.     

Carotenoids modulate the trade-off between egg production and resistance to oxidative stress in zebra finches

The allocation of resources to reproduction and survival is a central question of studies of life history evolution. Usually, increased allocation to current reproduction is paid in terms of reduced future reproduction and/or decreased survival. However, the proximal mechanisms underlying the cost of reproduction are poorly understood. Recently, it has been shown that increased susceptibility to oxidative stress might be one of such proximate links between reproduction and self-maintenance. Organisms possess a range of antioxidant defenses, including endogenously produced molecules (e.g., enzymes) and compounds ingested with food (e.g., carotenoids). If reproductive effort increases the production of reactive oxygen species, the availability of antioxidant defenses may partly or fully counteract the free-radical damages. One could, therefore, expect that the trade-off between reproduction and oxidative stress is modulated by the availability of antioxidant defenses. We tested this hypothesis in zebra finches. We manipulated reproductive effort by either allowing or preventing pairs to breed. Within each breeding or non-breeding group, the availability of antioxidant compounds was manipulated by supplementing or not supplementing the drinking water with carotenoids. We found that although birds in the breeding and non-breeding groups did not differ in their resistance to oxidative stress (the breakdown of red blood cells submitted to a controlled free-radical attack), one aspect of breeding effort (i.e., the number of eggs laid by birds in both breeding and non-breeding groups) was negatively correlated with resistance to oxidative stress only in birds that did not benefit from a carotenoid-supplemented diet. This result therefore suggests that carotenoid availability can modulate the trade-off between reproduction and resistance to oxidative stress.     

Fat soluble antioxidants in brood-rearing great tits Parus major: relations to health and appearance

The concept of parasite-mediated sexual selection assumes that females may improve offspring fitness by selecting mates on the basis of sexual ornaments that honestly reveal the health state of a partner. Expression of such signals may be particularly sensitive to oxidative damage caused by excess production of oxidative metabolites and free radicals. To control and neutralise free radicals, animals rely heavily on dietary fat-soluble antioxidants such as vitamin E and A, and carotenoids. However, the organism's need for free radical scavenging may interfere with the opposite need to generate oxidative stress for fighting parasitic infections. We investigated plasma concentrations of carotenoids and vitamin A and E in brood-rearing great tits Parus major in relation to carotenoid-based plumage coloration, sex, habitat, leukocyte hemoconcentrations and infection status with Haemoproteus blood parasites. Rural great tits differed from urban ones and males from females with respect to the hue of the yellow ventral feathers. However, plasma antioxidant concentrations were not related to sex, habitat or plumage coloration. Plasma carotenoid concentration correlated positively with indices of immune system activation as measured by blood counts of lymphocytes and eosinophils. Birds with gametocytes of Haemoproteus in their blood had higher plasma concentrations of carotenoids and vitamin E than unparasitized individuals. These results are consistent with the idea that maintenance of high blood antioxidant levels might conflict with individual needs to rely on oxidative stress for fighting infections.     

Antioxidant actions of plant foods: Use of oxidative DNA damage as a tool for studying antioxidant efficacy

Plant-food-derived antioxidants and active principles such as flavonoids, hydroxycinnamates (ferulic acid, chlorogenic acids, vanillin etc.), β-carotene and other carotenoids, vitamin E, vitamin C, or rosemary, sage, tea and numerous extracts are increasingly proposed as important dietary antioxidant factors. In this endeavor, assays involving oxidative DNA damage for characterizing the potential antioxidant actions are suggested as in vitro screens of antioxidant efficacy. The critical question is the bioavailability of the plant-derived antioxidants.     

Oxidative stress does not influence carotenoid mobilization and plumage pigmentation

Oxidative stress has been suggested to create a link between 'good genes' and carotenoid coloration via an allocation conflict between external pigmentation and internal antioxidant functions. However, although carotenoid displays have been extensively investigated, there are no experimental tests of the antioxidant efficiency of carotenoids in vivo. We induced oxidative stress in a small passerine (the great tit, Parus major) under both carotenoid deprivation and supplementation, and investigated the effect on carotenoid mobilization (i.e. plasma) and allocation (i.e. deposition in feather incorporation and liver storage). We found no effects of the stressor on either mobilization or allocation of carotenoids. These results reject the previously suggested superior role of carotenoid's function as antioxidant in vivo with important implications for signal content and honesty.     

Effect of copper-induced oxidative stress on sclerotial differentiation and antioxidant properties of Penicillium thomii PT95 strain

Penicillium thomii PT95 strain was able to form abundant orange, sand-shaped sclerotia in which carotenoids were accumulated. The aim of this work was to determine the effects of copper-induced oxidative stress on the sclerotial differentiation and antioxidant properties of PT95 strain. The results showed that the time of exudates initiation, sclerotial initiation and sclerotial maturation of PT95 strain were advanced in 1–2 days under the copper-induced oxidative stress growth conditions. The analytical results of sclerotial biomass, carotenoids content in sclerotia showed that copper-induced oxidative stress favored the sclerotial differentiation and biosynthesis of carotenoids. Under the copper-induced oxidative stress growth conditions, the total phenolics content and DPPH free radical scavenging activity of sclerotia of this fungus were decreased as compared with the control. However, the oxidative stress induced by a lower amount of CuSO₄ in media could enhance significantly the reducing power of sclerotia.     

Is there a potential therapeutic role for vitamin E or other antioxidants in atherosclerosis?

In-vitro studies and animal model studies provide an ever-growing body of evidence, direct and indirect, that oxidation of low-density lipoprotein and/or related oxidative mechanisms play a role in atherogenesis. However, two recent, very large, carefully conducted clinical intervention trials using adequate doses of vitamin E demonstrated no effect on a composite end-point of non-fatal infarction, stroke or death from cardiovascular causes. Why the unexpected negative results? Possibly because the animal intervention evidence on which these trials were based deals primarily with very early lesions (fatty streaks). That evidence does not necessarily provide a basis for predicting what antioxidant intervention will do in patients with advanced lesions, particularly when the end-points used relate to unstable plaques and fatal thrombosis, events for which we have no adequate animal models. Nor does it necessarily follow that the same antioxidants used successfully in animals will be effective in humans. The strength of the evidence for the oxidative modification hypothesis is such that negative clinical trials with one particular antioxidant, in patients with very advanced coronary heart disease and lasting only 3-5 years, should not be taken as refutation of the hypothesis. Perhaps different kinds of human trials are needed, trials in which the development of new lesions is measured, in order to test whether antioxidants can decrease the rate of initiation and early progression of atherosclerosis as they do in animals. The answer to the title query is 'Probably, but it is too soon to say'.     

Effects of carotenoid supplementation on colour expression,oxidative stress and body mass in rehabilitated captive adult kestrels (<Emphasis Type="Italic">Falco tinnunculus</Emphasis>)

Carotenoids are considered a limited resource for animals because they are not synthesised by the body. Birds use carotenoids, mainly xanthophylls, for physiological functions, such as anti-oxidant activity, and for colour expression; hence, they need to shunt carotenoids between competitive demands. Recent studies suggest that the anti-oxidant role of xanthophylls might not be as important as previously thought and that at high concentrations they may, in fact, acquire pro-oxidant properties. In this work, we studied the effects of a moderate xanthophyll supplementation (115 mg of carotenoids/kg diet/day; 4 weeks) on serum carotenoids, serum concentration of reactive oxygen metabolites (ROMs), serum anti-oxidant capacity (OXY), the degree of oxidative stress (OS; ROMs/OXY × 1,000), body mass, and skin colour, in rehabilitated captive adult Eurasian kestrels (Falco tinnunculus). The supplementation caused increased levels of serum carotenoids (∼90%), ROMs (∼82%), OS (∼115%) and an immediate loss of body mass (∼6.2%), but it did not affect OXY and tarsi skin hue. The red (∼16%) and yellow (∼15%) colorimetric components were increased after the first week of supplementation and the effect persisted during the rest of the experiment. Two months after the end of supplementation, serum carotenoids, OS and ROMs returned to baseline levels, however the body mass did not. Our findings suggest that, above a certain physiological threshold, carotenoids can cause detrimental effects. This is relevant for the trade-off between expression of sexual signals and the costs of maintaining/producing them.     

Oxidative stress in microorganisms—I

Oxidative stress in microbial cells shares many similarities with other cell types but it has its specific features which may differe in prokaryotic and eukaryotic cells. We survey here the properties and actions of primary sources of oxidative stress, the role of transition metals in oxidative stress and cell protective machinery of microbial cells, and compare them with analogous features of other cell types. Other features to be compared are the action of reactive oxygen species (ROS) on cell constituents, secondary lipid-or protein-based radicals and other stress products. Repair of oxidative injury by microorganisms and proteolytic removal of irreparable cell constituents are briefly described. Oxidative damage of aerobically growing microbial cells by endogenously formed ROS mostly does not induce changes similar to the aging of multiplying mammalian cells. Rapid growth of bacteria and yeast prevents accumulation of impaired macromolecules which are repaired, diluted or eliminated. During growth some simple fungi, such as yeast orPodospora spp., exhibit aging whose primary cause seems to be fragmentation of the nucleolus or impairment of mitochondrial DNA integrity. Yeast cell aging seems to be accelerated by endogenous oxidative stress. Unlike most growing microbial cells, stationaryphase cells gradually lose their viability because of a continuous oxidative stress, in spite of an increased synthesis of antioxidant enzymes. Unlike in most microorganisms, in plant and animal cells a severe oxidative stress induces a specific programmed death pathway-apoptosis. The scant data on the microbial death mechanisms induced by oxidative stress indicate that in bacteria cell death can result from activation of autolytic enzymes (similarly to the programmed mother-cell death at the end of bacillar sporulation). Yeast and other simple eukaryotes contain components of a proapoptotic pathway which are silent under normal conditions but can be activated by oxidative stress or by manifestation of mammalian death genes, such asbak orbax. Other aspects, such as regulation of oxidative-stress response, role of defense enzymes and their control, acquisition of stress tolerance, stress signaling and its role in stress response, as well as cross-talk between different stress factors, will be the subject of a subsequent review.     

Prooxidant effects of beta-carotene in cultured cells

There is a growing body of interest on the role of β-carotene and other carotenoids in human chronic diseases, including cancer. While epidemiological evidence shows that people who ingest more dietary carotenoids exhibit a reduced risk for cancer, results from intervention trials indicate that supplemental β-carotene enhances lung cancer incidence and mortality among smokers. A possible mechanism which can explain the dual role of β-carotene as both a beneficial and a harmful agent in cancer as well as in other chronic diseases is its ability in modulating intracellular redox status. β-Carotene may serve as an antioxidant or as a prooxidant, depending on its intrinsic properties as well as on the redox potential of the biological environment in which it acts. This review summarizes the available evidence for a prooxidant activity of β-carotene in cultured cells, focusing on biochemical and molecular markers of oxidative stress, which have been reported to be enhanced by the carotenoid.     

Carotenoids from mamey (Pouteria sapota) and carrot (Daucus carota) increase the oxidative stress resistance of Caenorhabditis elegans

Carotenoids are natural pigments and antioxidants found in fruits and vegetables such as carrot, tomato, orange, mango, yellow corn, pumpkin, and mamey. In this study, we evaluated the antioxidant potential of mamey (Pouteria sapota) carotenoids and compared them to carrot (Daucus carota) carotenoids. The carotenoids were extracted from mamey and carrot, and their antioxidant capacity were determined via in vitro (ABTS method) and in vivo assays (resistance against oxidative stress in Caenorhabditis elegans). The carotenoid contents in mamey and carrot were 4.42 ± 0.12 and 5.47 ± 0.04 mg β-carotene/100 g, respectively. Despite the differences between the carotenoid contents in both products (p < 0.05), the in vitro antioxidant capacity results showed no significant differences between the extracts (p > 0.05). The mamey and carrot carotenoid extracts decreased the oxidative damage in C. elegans by 20–30% and 30–40%, respectively. Both extracts increased the resistance and enhanced the survival of the nematodes, and showed better effects than pure β-carotene, probably owing to the complex mixture in the carotenoid extracts. These results suggest that mamey is a good alternative source of carotenoids and that it protects against oxidative stress in C. elegans. The protective effect of mamey carotenoids was similar to the effect of carrot carotenoids.     

Variation of a carotenoid-based trait in relation to oxidative stress and endocrine status during the breeding season in the Eurasian kestrel: a multi-factorial study

Carotenoid-based skin colorations vary seasonally in many bird species and are thought to be honest sexually selected signals. In order to provide more insight in the potential signal function and underlying mechanisms of such colorations we here quantified patterns of variation of leg coloration in adult male and female Eurasian kestrels (Falco tinnunculus tinnunculus) over the breeding season, and evaluated the relationship between coloration and levels of carotenoids, androgens and estrogens, oxidative damage and plasma non-enzymatic antioxidant capacity. We studied both reproducing wild and non-reproducing captive birds to test for the effect of diet and breeding effort. Males were more colored than females only during mating, and independently of diet, suggesting that leg-color is a sexually selected trait. Seasonal variation in leg color was associated with circulating carotenoids, but concentrations of these molecules were not related to antioxidant capacity, body condition or oxidative damage. These results indicate that carotenoid-based colorations may not be an honest signal of health status in this species. Production of carotenoid rich eggs coincided with low levels of circulating carotenoids in females, indicating that carotenoids might be a limited resource for laying female kestrels. Finally, young rearing males had higher levels of oxidative damage than females, and wild birds of both sexes had higher levels of these parameters than captive birds. These results may indicate that parental effort and physical activity are costly, independently from hormonal status. Since androgens did not explain carotenoid variation we suggest that multiple interacting factors can regulate carotenoid levels along the season.     

Bilirubin and oxidative stress in term and preterm infants

Hyperbilirubinemia is the most frequent clinical problem neonatologists must deal with during the newborn period. It has been suggested that bilirubin is involved in the balance between antioxidant and pro-oxidant agents due to its antioxidant properties. However, the relevance of these effects in vivo in term and preterm infants is still debated. We performed a literature review of studies that investigated the association between total serum bilirubin (TSB) and oxidative stress in newborn infants. We found that studies in term infants give contradictory results, while studies in preterm infants suggest that the TSB increase is associated with an oxidative stress increase due to concurrent factors other than bilirubin level, such as heme oxygenase (HO) activity. Moreover, it could be speculated that low physiologic TSB values are associated with antioxidant effects, while high pathologic TSB values are associated with pro-oxidant effects. Literature data do not allow the establishment of whether if the antioxidant properties of bilirubin are important from a clinical point of view and can affect the outcome in ill infants.     

The role of oxidative stress in an equine model of human asthma

Abstract

Equine recurrent airway obstruction (RAO) is a naturally occurring respiratory disease in horses with many similarities to human asthma and, as a result, has been used as an animal model of this disease. Oxidative stress has been demonstrated to occur in a range of respiratory diseases in human beings including asthma. Quantitatively, horses have a greater non-enzymatic antioxidant capacity in the pulmonary epithelial lining fluid compared to human beings due to high ascorbic acid concentrations, which reflects their ability to synthesise ascorbic acid. Consequently, a greater oxidative load is likely to be required to induce oxidative stress in horses compared to human beings. Induction of acute neutrophilic airway inflammation in RAO horses by exposure to organic dust does not result in marked pulmonary oxidative stress. However, with a more prolonged inflammatory response, the antioxidant capacity is depleted and oxidative stress occurs. Despite the clear evidence of oxidative stress in RAO, there is currently limited data linking oxidative stress with a causal role in the development of the pathophysiological features of RAO, namely airway obstruction, airway hyper-responsiveness, airway inflammation and mucus accumulation. However, pathways do exist whereby oxidants could potentially augment the production of important mediators in RAO. Further work is required to ascertain the benefits of antioxidant supplementation in RAO and to determine the role of oxidative stress in the pathogenesis of the disease. Given the similarities with human asthma, results from RAO horses could enhance the understanding of the role of oxidative stress in human asthma.