Physiology and fertility of two gull species in relation to plastic additives' exposure

Understanding the impact of plastic and its additives on wild species is crucial as their presence in the environment increases. Polybrominated diphenyl ethers (PBDEs), once used as flame retardants, were restricted due to known toxic effects, but are still detected in the environment. Naturally occurring methoxylated PBDEs (MeO-BDEs) can result from PBDE transformation and may cause similar hazardous effects. Yellow-legged gulls (Larus michahellis, YLG) and Audouin's gulls (Ichthyaetus audouinii, AG) are highly susceptible to plastic additives, due to their distribution, trophic position, and behaviour. In this study, we assessed PBDEs and MeO-BDEs uptake in different tissues and their effects on physiological and reproductive parameters. Findings indicate that, apart from annual differences, adult AG accumulated more MeO-BDEs than YLG in a natural breeding habitat (Deserta), while the latter had lower PBDE levels than YLG breeding in the city of Porto. In relation to chicks, only YLG from Deserta showed higher PBDE concentrations than AG chicks. Individual analysis of each physiological parameter revealed impacts only for adult YLG from Deserta, with neurofunction and immune system inhibition at higher MeO-BDE concentrations. For chicks, AG showed impaired neurofunction, while YLG chicks from Porto exhibited potential genotoxicity effects triggered by higher MeO-BDE levels. Overall health analysis showed activation of antioxidant defences and compromised immune system in YLG adults from Porto due to high values of PBDEs, while chicks from Deserta exhibited inflammation and oxidative stress with high concentrations of MeO-BDEs in the same species. Fertility parameters showed significant differences for sperm counts though suggesting individuals may be able to compensate any exposure effects. This study confirms the widespread presence of plastic-associated compounds and their harmful effects on gulls, particularly on neurofunction, immune system, oxidative balance and fertility, especially due to the presence of MeO-BDEs.

CRP and IHF act as host regulators in Royal Jelly's antibacterial activity

Royal Jelly (RJ) is a natural substance produced by honeybees, serving not only as nutrition for bee brood and queens but also as a functional food due to its health-promoting properties. Despite its well-known broad-spectrum antibacterial activity, the precise molecular mechanism underlying its antibacterial action has remained elusive. In this study, we investigated the impact of RJ on the bacteria model MG1655 at its half-maximal inhibitory concentration, employing LC-MS/MS to analyze proteomic changes. The differentially expressed proteins were found to primarily contribute to the suppression of gene expression processes, specifically transcription and translation, disrupting nutrition and energy metabolism, and inducing oxidative stress. Notably, RJ treatment led to a marked inhibition of superoxide dismutase and catalase activities, resulting in heightened oxidative damage and lipid peroxidation. Furthermore, through a protein-protein interaction network analysis using the STRING database, we identified CRP and IHF as crucial host regulators responsive to RJ. These regulators were found to play a pivotal role in suppressing essential hub genes associated with energy production and antioxidant capabilities. Our findings significantly contribute to the understanding of RJ's antibacterial mechanism, highlighting its potential as a natural alternative to conventional antibiotics. The identification of CRP and IHF as central players highlights the intricate regulatory networks involved in RJ's action, offering new targets for developing innovative antimicrobial strategies.

Correlated evolution of oxidative physiology and MHC-based immunosurveillance in birds

Maintenance and activation of the immune system incur costs, not only in terms of substrates and energy but also via collateral oxidative damage to host cells or tissues during immune response. So far, associations between immune function and oxidative damage have been primarily investigated at intra-specific scales. Here, we hypothesized that pathogen-driven selection should favour the evolution of effective immunosurveillance mechanisms (e.g. major histocompatibility complex, MHC) and antioxidant defences to mitigate oxidative damage resulting from immune function. Using phylogenetically informed comparative approaches, we provided evidence for the correlated evolution of host oxidative physiology and MHC-based immunosurveillance in birds. Species selected for more robust MHC-based immunosurveillance (higher gene copy numbers and allele diversity) showed stronger antioxidant defences, although selection for MHC diversity still showed a positive evolutionary association with oxidative damage to lipids. Our results indicate that historical pathogen-driven selection for highly duplicated and diverse MHC could have promoted the evolution of efficient antioxidant mechanisms, but these evolutionary solutions may be insufficient to keep oxidative stress at bounds. Although the precise nature of mechanistic links between the MHC and oxidative stress remains unclear, our study suggests that a general evolutionary investment in immune function may require co-adaptations at the level of host oxidative metabolism.

Invading nonnative frogs use different microhabitats and change physiology along an elevation gradient

The coqui frog (Eleutherodactylus coqui) was introduced to the island of Hawai'i in the 1980s, and has spread across much of the island. There is concern they will invade higher elevation areas where negative impacts on native species are expected. It is not known if coqui change behavior and baseline physiology in ways that allow them to invade higher elevations. We investigated where coqui are found across the island and whether that includes recent invasion into higher elevations. We also investigated whether elevation is related to coqui's microhabitat use, including substrate use and height off the forest floor, and physiological metrics, including plasma osmolality, oxidative status, glucose, free glycerol, and triglycerides, that might be associated with invading higher elevations. We found coqui have increased the area they occupy along roads from 31% to 50% and have moved into more high-elevation locations (16% vs. 1%) compared to where they were found 14 years ago. We also found frogs at high elevation on different substrates and closer to the forest floor than frogs at lower elevations-perhaps in response to air temperatures which tended to be warmer close to the forest floor. We observed that blood glucose and triglycerides increase in frogs with elevation. An increase in glucose is likely an acclimation response to cold temperatures while triglycerides may also help frogs cope with the energetic demands of suboptimal temperatures. Finally, we found that female coqui have higher plasma osmolality, reactive oxygen metabolites (dROMs), free glycerol, and triglycerides than males. Our study suggests coqui behavior and physiology in Hawai'i may be influenced by elevation in ways that allow them to cope with lower temperatures and invade higher elevations.

Songbirds avoid the oxidative stress costs of high blood glucose levels: a comparative study

Chronically high blood glucose levels (hyperglycaemia) can compromise healthy ageing and lifespan at the individual level. Elevated oxidative stress can play a central role in hyperglycaemia-induced pathologies. Nevertheless, the lifespan of birds shows no species-level association with blood glucose. This suggests that the potential pathologies of high blood glucose levels can be avoided by adaptations in oxidative physiology at the macroevolutionary scale. However, this hypothesis remains unexplored. Here, we examined this hypothesis using comparative analyses controlled for phylogeny, allometry and fecundity based on data from 51 songbird species (681 individuals with blood glucose data and 1021 individuals with oxidative state data). We measured blood glucose at baseline and after stress stimulus and computed glucose stress reactivity as the magnitude of change between the two time points. We also measured three parameters of non-enzymatic antioxidants (uric acid, total antioxidants and glutathione) and a marker of oxidative lipid damage (malondialdehyde). We found no clear evidence for blood glucose concentration being correlated with either antioxidant or lipid damage levels at the macroevolutionary scale, as opposed to the hypothesis postulating that high blood glucose levels entail oxidative costs. The only exception was the moderate evidence for species with a stronger stress-induced increase in blood glucose concentration evolving moderately lower investment into antioxidant defence (uric acid and glutathione). Neither baseline nor stress-induced glucose levels were associated with oxidative physiology. Our findings support the hypothesis that birds evolved adaptations preventing the (glyc)oxidative costs of high blood glucose observed at the within-species level. Such adaptations may explain the decoupled evolution of glycaemia and lifespan in birds and possibly the paradoxical combination of long lifespan and high blood glucose levels relative to mammals.

Under pressure-exploring partner changes, physiological responses and telomere dynamics in northern gannets across varying breeding conditions

Background

Life history theory predicts trade-offs between reproduction and survival in species like the northern gannet (Morus bassanus). During breeding, demanding foraging conditions lead them to expand their foraging range and diversify their diet, increasing the risk of reproductive failure. Changing partners may enhance breeding success but lead to more physiological costs.

Methods

To investigate the physiological costs of reproduction upon partner changes, we measured and compared 21 biomarkers related to telomere dynamics, oxidative stress, inflammation, hematology, nutritional status, and muscle damage. We used a longitudinal approach with gannets (n = 38) over three contrasting years (2017, 2018 and 2019).

Results

Our results suggest that annual breeding conditions exert a greater influence on physiological changes than partnership status. Individuals that changed partner experienced greater short-term stress than retained partners. This transient increase in stress was marked by short-term increases in oxidative lipid damage, lower antioxidant capacity, signs of inflammation, and greater weight loss than individuals that retained partners. During favorable conditions, individuals that changed mates had stabilized telomere length, decreased antioxidant capacity, glucose concentration, and muscle damage, along with increased oxygen transport capacity. Conversely, unfavorable breeding conditions led to increased telomere attrition, stabilized antioxidant capacity, decreased inflammation susceptibility, diminished oxygen transport capacity, and increased muscle damage. In the cases where partners were retained, distinct physiological changes were observed depending on the year's conditions, yet the telomere dynamics remained consistent across both partnership status categories. During the favorable year, there was an increase in unsaturated fatty acids and oxygen transport capacity in the blood, coupled with a reduction in inflammation potential and protein catabolism. In contrast, during the unfavorable year in the retained mates, we observed an increase in oxidative DNA damage, antioxidant capacity, weight loss, but a decrease in inflammation susceptibility as observed in changed mates.

Discussion

Our study shows that behavioral flexibility such as mate switching can help seabirds cope with the challenges of food scarcity during reproduction, but these coping strategies may have a negative impact on physiological status at the individual level. In addition, the marked reduction in telomere length observed during harsh conditions, coupled with the stabilization of telomere length in favorable conditions, highlights the long-term physiological impact of annual breeding conditions on seabirds. These findings underscore the effect on their potential survival and fitness, emphasizing that the influence of annual breeding conditions is greater than that of partnership status.

Eating in the city: Experimental effect of anthropogenic food resources on the body condition, nutritional status, and oxidative stress of an urban bioindicator passerine

Urban areas provide a constant and predictable supply of anthropogenic processed food. The House Sparrow (Passer domesticus Linnaeus, 1758), a declining urban bioindicator species, has recently been reported to have a high level of oxidative stress, with urban diet or pollutants proposed as the potential cause. In this study, we aimed to experimentally determine the effects of two urban trophic resource types (bar snack food leftovers and pet food) on sparrows' physical condition, plasma biochemical nutritional parameters, and blood oxidative status in captivity. To exclude the potential previous effect of urban pollutants, 75 House Sparrows were captured from a rural area in SE Spain and kept in outdoor aviaries. Individuals were exposed to one of three diet treatments: control diet (fruit, vegetables, poultry grain mixture), bar snack diet (ultra-processed snacks), or cat food diet (dry pellets) for 20 days. Blood samples were collected before and after diet treatments to analyze the relative change rates of 12 variables, including physical condition, nutritional status, and oxidant-antioxidant status. A principal component analysis was run to identify gradients of variables covariation, and Generalized Linear Mixed Models were used to determine the effect of diets on each selected PC and on raw variables. The bar snack diet led to signs of anemia and malnutrition, and females tended to lose body condition. The cat food diet increased oxidative stress indicators and protein catabolism. Unbalanced urban diets can affect the body condition and nutritional physiology of House Sparrows and may also induce oxidative stress despite the absence of environmental pollution.

Oxidative stress mediates the impact of heatwaves on survival, growth and immune status in a lizard

Climate change often includes increases in the occurrence of extreme environmental events. Among these, heatwaves affect the pace of life and performance of wildlife, particularly ectothermic animals, owing to their low thermoregulatory abilities. However, the underlying mechanisms by which this occurs remain unclear. Evidence shows that heatwaves alter the redox balance of ectotherms, and oxidative stress is a major mediator of life-history trade-offs. Therefore, oxidative stress may mediate the effect of extreme thermal conditions on the life histories of ectotherms. To test this hypothesis, a 2 × 2 experiment was conducted to manipulate the redox balance (through a mitochondrial uncoupler that alleviates oxidative stress) of the desert toad-headed agama (Phrynocephalus przewalskii) exposed to heatwave conditions. We recorded lizard growth and survival rates and quantified their redox and immune statuses. In control lizards (unmanipulated redox balance), heatwave conditions decreased growth and survival and induced oxidative damage and immune responses. By contrast, lizards with alleviated oxidative stress showed close-to-normal growth, survival, and immune status when challenged with heatwaves. These results provide mechanistic insight into the role of oxidative stress in mediating the effects of extreme temperatures on ectothermic vertebrates, which may have major eco-evolutionary implications.

Stopovers Serve Physiological Recovery in Migratory Songbirds

AbstractMigrating birds perform extreme endurance exercise when flying. This shifts the balance between the production of reactive oxygen species and the antioxidant defense system toward the former, potentially generating oxidative damages. In between migratory flights, birds make stopovers, where besides accumulating fuel (mainly fats), they are assumed to rest and recover from the strenuous flight. We performed a series of studies on both temporarily caged (northern wheatears) and free-flying (northern wheatears and European robins) migrants to investigate whether migrants recover during stopover by decreasing the amount of oxidative lipid damage (malondialdehyde [MDA]) and/or increasing the total nonenzymatic antioxidant capacity (AOX). In caged wheatears, MDA decreased within a single day. These birds were able to simultaneously accumulate considerable amounts of fuel. Also, in the free-flying wheatears, there was a decrease in MDA during stopover; however, this process seemed incompatible with refueling. The reason for this difference could relate to constraints in the wild that are absent in caged birds, such as food limitation/composition and locomotor activity. In the robins, there was a near significant decrease in MDA concentration in relation to how long the birds were already at stopover, suggesting that this species also physiologically recovers during stopover. AOX did not change during stopover in either of the wheatear studies. For the robins, however, uric acid-corrected AOX declined during stopover. Our results show that during stopover, migrating birds rapidly reduce oxidative lipid damage, thereby likely recovering their physiological state. In addition to the commonly accepted function of refueling, stopovers thus probably serve physiological recovery.

Fitness correlates of blubber oxidative stress and cellular defences in grey seals (Halichoerus grypus): support for the life-history-oxidative stress theory from an animal model of simultaneous lactation and fasting

Life-history-oxidative stress theory predicts that elevated energy costs during reproduction reduce allocation to defences and increase cellular stress, with fitness consequences, particularly when resources are limited. As capital breeders, grey seals are a natural system in which to test this theory. We investigated oxidative damage (malondialdehyde (MDA) concentration) and cellular defences (relative mRNA abundance of heat shock proteins (Hsps) and redox enzymes (REs)) in blubber of wild female grey seals during the lactation fast (n = 17) and summer foraging (n = 13). Transcript abundance of Hsc70 increased, and Nox4, a pro-oxidant enzyme, decreased throughout lactation. Foraging females had higher mRNA abundance of some Hsps and lower RE transcript abundance and MDA concentrations, suggesting they experienced lower oxidative stress than lactating mothers, which diverted resources into pup rearing at the expense of blubber tissue damage. Lactation duration and maternal mass loss rate were both positively related to pup weaning mass. Pups whose mothers had higher blubber glutathione-S-transferase (GST) expression at early lactation gained mass more slowly. Higher glutathione peroxidase (GPx) and lower catalase (CAT) were associated with longer lactation but reduced maternal transfer efficiency and lower pup weaning mass. Cellular stress, and the ability to mount effective cellular defences, could proscribe lactation strategy in grey seal mothers and thus affect pup survival probability. These data support the life-history-oxidative stress hypothesis in a capital breeding mammal and suggest lactation is a period of heightened vulnerability to environmental factors that exacerbate cellular stress. Fitness consequences of stress may thus be accentuated during periods of rapid environmental change.

Inter-annual variation of physiological traits between urban and forest great tits

Urbanization is characterized by rapid environmental changes such as an increase in building surface, in pollution, or a decrease in invertebrate abundance. For many bird species, morphological and physiological differences have been observed between urban and rural individuals that seem to reflect a negative impact of urban life on the health and fitness of individuals. Studies on passerine birds also showed important differences between populations and species in their responses to the urban environment. We propose to test physiological differences between urban and forest individuals over 3 years to understand whether the observed patterns are constant or subject to variations across years. For this purpose, we assessed the health parameters of adults and fledgling of great tits, Parus major, living in an urban and in a forest site in the Eurometropole of Strasbourg, for three years. Bird health was estimated with morphological parameters (body condition and size) and also with physiological parameters (oxidative status and telomere length). Our results showed lower body condition of urban fledglings regardless of the year, but no site effects on telomere length. On the contrary, for adult breeders, urban individuals had longer telomeres than forest ones except for one year which coincide with bad weather conditions during reproduction where no difference was detected. Urban birds also had higher antioxidant capacity whatever the years. These results suggest that cities act as a filter in which only good quality individuals survive and achieve successful reproduction regardless of year, whereas in the forest the selection occurs only during harsh weather years.

Oxidative status in relation to blood parasite infections in house sparrows living along an urbanization gradient

Living organisms are exposed to a wide range of substances - internal and external - which act like reactive oxygen species (ROS). Oxidative damage accurs when the balance between ROS and antioxidant defenses is altered. Urbanization and parasite infection are both important sources of ROS with different harmful effects on wildlife health, but the potential synergies between both factors are poorly known. Here, we analyse the oxidative stress of wild juvenile male house sparrows (Passer domesticus) along an urbanization gradient in relation to the infection status by three common blood parasites (Plasmodium, Haemoproteus and Leucocytozoon) and bird body condition. We analysed samples from 688 birds captured at 45 localities from southern Spain grouped into triplets including an urban, a rural and a natural habitat, with 15 localities per habitat type. We measured i) thiobarbituric acid reactive substances (TBARS) levels as indicator of the oxidative damage to lipids, and the activity of three antioxidant enzymes ii) glutathione peroxidase (GPx), iii) superoxide dismutase (SOD) and iv) glutathione reductase (GR) as indicators of bird's antioxidant capacity. Birds infected with Haemoproteus and urban birds showed significantly and marginally higher levels of TBARS than uninfected and rural birds, respectively. The relationship between TBARS and body condition is different regarding the infection status (significative) and habitat (marginally significant) being negative for Haemoproteus infected and urban birds but positive for uninfected and non-urban birds. The antioxidant activity was significantly lower in Plasmodium infected birds but marginally higher in Leucocytozoon infected birds than in uninfected ones. Individuals with higher body condition had higher GPx and SOD activity in relation to a lower GR activity. Overall, these results suggest that blood parasites infections and urbanization affect the oxidative status of wild birds and highlight the role of bird's body condition on the regulation of the oxidative stress status.

Perinatal stress exposure induced oxidative stress, metabolism disorder, and reduced GLUT-2 in adult offspring of rats

PURPOSE

Growing evidence has demonstrated that adversity in early life, especially in the prenatal and postnatal period, may change the programming of numerous body systems and cause the incidence of various disorders in later life. Accordingly, this experimental animal study aimed to investigate the effect of stress exposure during perinatal (prenatal and/or postnatal) on the induction of oxidative stress in the pancreas and its effect on glucose metabolism in adult rat offspring.

METHODS

In this experimental study based on maternal exposure to variable stress throughout the perinatal period, the pups were divided into eight groups, as follows: control group (C); prepregnancy, pregnancy, lactation stress group (PPPLS); prepregnancy stress group (PPS); pregnancy stress group (PS); lactation stress group (LS); prepregnancy, pregnancy stress group (PPPS); pregnancy, lactation stress group (PLS); and prepregnancy, lactation stress group (PPLS). Following an overnight fast on postnatal day (PND) 64, plasma glucose, insulin, leptin levels, and lipid profiles were evaluated in the offspring groups. GLUT-2 protein levels, lipid peroxidation, antioxidant status, and number of beta-cells in the pancreatic islets of Langerhans as well as the weights of intra-abdominal fat and adrenal glands were assessed. Levels of plasma corticosterone were determined in the different groups of mothers and offspring.

RESULTS

The levels of plasma corticosterone, insulin, and HOMA-B index increased, whereas glucose level and QUICKI index were reduced in the perinatal stress groups compared to C group (p < 0.001 to p < 0.05). Plasma triglyceride, LDL, and cholesterol level rose significantly, but HDL level decreased in the perinatal stress groups compared to C group (p < 0.001 to p < 0.05). Perinatal stress raised MDA concentrations and reduced the activities of antioxidant enzymes in plasma and pancreas compared to C group (p < 0.001 to p < 0.05). GLUT-2 protein levels and number of beta-cells in the stress groups declined compared to C group (p < 0.001 to p < 0.05). Intra-abdominal fat weight decreased in the PPS, PS, and LS groups compared to C group (p < 0.001 to p < 0.01), but adrenal gland weight remained unchanged.

CONCLUSION

Our results showed that long-term exposure to elevated levels of corticosterone during critical development induces metabolic syndrome in adult male rats.

Dietary Intake of Polyphenols Enhances Executive/Attentional Functioning and Memory with an Improvement of the Milk Lipid Profile of Postpartum Women from Argentina

Puerperium may lead to memory and executive/attentional complaints that interfere with women’s daily life. This might be prevented by dietary compounds, such as neuroprotective polyphenols. Their bioactivity depends on their effects on lipid metabolism in different tissues, such as the brain, fat, and breast. Thus, a polyphenol-related cognitive improvement may be associated with changes of lipids in human milk, which are key for infant neurodevelopment. A cross-sectional study was conducted on 75 postpartum women from Córdoba (Argentina), involving several neuropsychological tests. Diet was registered to identify polyphenol intake and food pattern adherence, with sociodemographic and other psychological variables (insomnia, stress, subjective cognitive complaints) being also studied. Triacylglycerols, cholesterol, and their oxidative forms were analyzed as milk biomarkers. Multivariate statistical methods were applied. Results confirmed that women who consumed polyphenols presented better executive/attentional performance (i.e., higher correct responses, conceptual level responses, complete categories, verbal fluency; lower attentional interferences, and perseverative errors) and word retention with lower interference. Polyphenols were positively associated with milk lipids, which were higher in women with better cognition. Furthermore, they had lower oxidized triacylglycerols. In conclusion, polyphenolic intake during postpartum may improve executive/attentional functioning, memory, and milk lipid profile.

Intergenerational Costs of Oxidative Stress: Reduced Fitness in Daughters of Mothers That Experienced High Levels of Oxidative Damage during Reproduction

AbstractParental condition transfer effects occur when the parents' physiological state during reproduction affects offspring performance. Oxidative damage may mediate such effects, yet evidence that oxidative damage experienced by parents during reproduction negatively affects offspring fitness is scarce and limited to early life stages. We show in Japanese quail (Coturnix japonica) that maternal levels of oxidative damage, measured during reproduction, negatively predict the number of offspring produced by daughters. This maternal effect on daughters' reproductive success was mediated by an effect on hatching success rather than on the number of eggs laid by daughters. We also observed a negative association between fathers' oxidative damage levels and the number of eggs laid by daughters but a positive association between fathers' oxidative damage levels and the hatching success of those eggs. These opposing paternal effects canceled each other out, resulting in no overall effect on the number of offspring produced by daughters. No significant association between a female's own level of oxidative damage during reproduction and her reproductive success was observed. Our results suggest that oxidative damage experienced by parents is a better predictor of an individual's reproductive performance than oxidative damage experienced by the individual itself. Although the mechanisms underlying these parental condition transfer effects are currently unknown, changes in egg composition or (epi)genetic alterations of gametes may play a role. These findings highlight the importance of an intergenerational perspective when quantifying costs of physiological stress.

Oxidative damage increases with degree of simulated bacterial infection, but not ectoparasitism, in tree swallow nestlings

The purpose of mounting an immune response is to destroy pathogens, but this response comes at a physiological cost, including the generation of oxidative damage. However, many studies on the effects of immune challenges employ a single high dose of a simulated infection, meaning that the consequences of more mild immune challenges are poorly understood. We tested whether the degree of immunological challenge in tree swallows (Tachycineta bicolor) affects oxidative physiology and body mass, and whether these metrics correlate with parasitic nest mite load. We injected 14 day old nestlings with 0, 0.01, 0.1 or 1 mg lipopolysaccharide (LPS) per kg body mass, then collected a blood sample 24 h later to quantify multiple physiological metrics, including oxidative damage (i.e. d-ROMs), circulating amounts of triglyceride and glycerol, and levels of the acute phase protein haptoglobin. After birds had fledged, we identified and counted parasitic nest mites (Dermanyssus spp. and Ornithonyssus spp.). We found that only nestlings injected with 1 mg LPS kg-1 body mass, which is a common dosage in ecoimmunological studies, lost more body mass than individuals from other treatment groups. However, every dose of LPS resulted in a commensurate increase in oxidative damage. Parasitic mite abundance had no effect on oxidative damage across treatments. The amount of oxidative damage correlated with haptoglobin levels, suggesting compensatory mechanisms to limit self-damage during an immune response. We conclude that while only the highest-intensity immune challenges resulted in costs related to body mass, even low-intensity immune challenges result in detectable increases in oxidative damage.

Repeated stimulation of the HPA axis alters white blood cell count without increasing oxidative stress or inflammatory cytokines in fasting elephant seal pups

The hypothalamic-pituitary-adrenal (HPA) axis controls the release of glucocorticoids, which regulate immune and inflammatory function by modulating cytokines, white blood cells and oxidative stress via glucocorticoid receptor (GR) signaling. Although the response to HPA activation is well characterized in many species, little is known about the impacts of HPA activation during extreme physiological conditions. Hence, we challenged 18 simultaneously fasting and developing elephant seal pups with daily intramuscular injections of adrenocorticotropin (ACTH), a GR antagonist (RU486), or a combination of the two (ACTH+RU486) for 4 days. We collected blood at baseline, 2 h and 4 days after the beginning of treatment. ACTH and ACTH+RU486 elevated serum aldosterone and cortisol at 2 h, with effects diminishing at 4 days. RU486 alone induced a compensatory increase in aldosterone, but not cortisol, at 4 days. ACTH decreased neutrophils at 2 h, while decreasing lymphocytes and increasing the neutrophil:lymphocyte ratio at 4 days. These effects were abolished by RU486. Despite alterations in white blood cells, there was no effect of ACTH or RU486 on transforming growth factor-β or interleukin-6 levels; however, both cytokines decreased with the 4 day fasting progression. Similarly, ACTH did not impact protein oxidation, lipid peroxidation or antioxidant enzymes, but plasma isoprostanes and catalase activity decreased while glutathione peroxidase increased with fasting progression. These data demonstrate differential acute (2 h) and chronic (4 days) modulatory effects of HPA activation on white blood cells and that the chronic effect is mediated, at least in part, by GR. These results also underscore elephant seals' extraordinary resistance to oxidative stress derived from repeated HPA activation.

Impacts of selective logging on haemosporidian infection and physiological correlates in tropical birds

Tropical forest degradation affects host-parasite interactions, determining the probability of animals acquiring an infection. The activation of an immune response to fight off infections requires energy and other resources such as antioxidants which may be redirected from growth and reproduction. A key question is how selective logging-the most common form of tropical forest degradation-impacts the prevalence of avian haemosporidian infection and its correlated physiological responses (nutritional and oxidative status markers). We investigated the prevalence of Plasmodium, Haemoproteus, and Leucocytozoon parasites in 14 understorey bird species in lowland, logged and unlogged, old-growth forests of Borneo. Prevalences of infections were similar between selectively logged and unlogged forests. To explore nutritional and oxidative status effects of haemosporidian infections, we examined associations between infections and plasma proteins, plasma triglycerides, and multiple blood-based markers of oxidative status, testing for an impact of selective logging on those markers. Birds infected with Plasmodium showed higher levels of plasma proteins and non-enzymatic antioxidant capacity, and lower levels of plasma triglycerides and glutathione, compared with haemosporidian-free individuals. Conversely, birds infected with Haemoproteus showed no changes in nutritional or physiological markers compared with uninfected individuals. These results indicate higher metabolic and physiological costs of controlling Plasmodium infection, compared with Haemoproteus, possibly due to higher pathogenicity of Plasmodium. Selectively logged forests had no effect on the responses of birds to infection, suggesting that the environmental conditions of degraded forests do not appear to induce any appreciable physiological demands in parasitised birds.

Influence of growing up in the city or near an airport on the physiological stress of tree sparrow nestlings (Passer montanus)

Urbanization constitutes one of the major transformations of natural habitats, creating new areas characterized by multiple potential wildlife stressors. Birds that live in highly anthropized zones are confronted with physiological and behavioural challenges caused by these stressors. Here, we investigated if several health parameters differed between three subpopulations of tree sparrow nestlings subjected to different levels of anthropogenic pollution, and particularly noise pollution: a quiet rural area, a noisy rural area adjacent to an airport and a heavily urbanized area. We compared body condition, oxidative stress markers and baseline corticosterone levels, expecting urban nestlings to be in overall worse condition as compared to rural (rural and rural airport) birds. In addition, we expected nestlings exposed to aircraft noise to show intermediate stress levels. We found that rural-airport nestlings had the highest levels of antioxidant capacity of plasma and did not differ from rural counterparts in the rest of the parameters. By contrast, urban nestlings were in slightly worse body condition and had lower antioxidant capacity than rural and rural-airport individuals. Our results suggest that aircraft noise does not constitute a significant stressor for nestlings. In contrast, urban conditions constitute a more challenging situation, negatively impacting different physiological systems. Although nestlings seem able to buffer these challenges in the short-term, further research should explore the long-term potential consequences of early exposure to these conditions.

Fasting ameliorates oxidative stress: A review of physiological strategies across life history events in wild vertebrates

Fasting is a component of many species' life history due to environmental factors or behavioral patterns that limit access to food. Despite metabolic and physiological challenges associated with these life history stages, fasting-adapted wild vertebrates exhibit few if any signs of oxidative stress, suggesting that fasting promotes redox homeostasis. Here we review mammalian, avian, reptilian, amphibian, and piscine examples of animals undergoing fasting during prolonged metabolic suppression (e.g. hibernation and estivation) or energetically demanding processes (e.g. migration and breeding) to better understand the mechanisms underlying fasting tolerance in wild vertebrates. These studies largely show beneficial effects of fasting on redox balance via limited oxidative damage. Though some species exhibit signs of oxidative stress due to energetically or metabolically extreme processes, fasting wild vertebrates largely buffer themselves from the negative consequences of oxidative damage through specific strategies such as elevating antioxidants, selectively maintaining redox balance in critical tissues, or modifying behavioral patterns. We conclude with suggestions for future research to better elucidate the protective effects of fasting on oxidative stress as well as disentangle the impacts from other life history stages. Further research in these areas will facilitate our understanding of the mechanisms wild vertebrates use to mitigate the negative impacts associated with metabolically-extreme life history stages as well as potential translation into therapeutic interventions in non-fasting-adapted species including humans.

The Relationship between Hormones, Glucose, and Oxidative Damage Is Condition and Stress Dependent in a Free-Living Passerine Bird

AbstractPhysiological state is an emergent property of the interactions among physiological systems within an intricate network. Understanding the connections within this network is one of the goals in physiological ecology. Here, we studied the relationship between body condition, two neuroendocrine hormones (corticosterone and insulin-like growth factor 1 [IGF-1]) as physiological regulators, and two physiological systems related to resource metabolism (glucose) and oxidative balance (malondialdehyde). We measured these traits under baseline and stress-induced conditions in free-living house sparrows (Passer domesticus). We used path analysis to analyze different scenarios about the structure of the physiological network. Our data were most consistent with a model in which corticosterone was the major regulator under baseline conditions. This model shows that individuals in better condition have lower corticosterone levels; corticosterone and IGF-1 levels are positively associated; and oxidative damage is higher when levels of corticosterone, IGF-1, and glucose are elevated. After exposure to acute stress, these relationships were considerably reorganized. In response to acute stress, birds increased their corticosterone and glucose levels and decreased their IGF-1 levels. However, individuals in better condition increased their corticosterone levels more and better maintained their IGF-1 levels in response to acute stress. The acute stress-induced changes in corticosterone and IGF-1 levels were associated with an increase in glucose levels, which in turn was associated with a decrease in oxidative damage. We urge ecophysiologists to focus more on physiological networks, as the relationships between physiological traits are complex and dynamic during the organismal stress response.

DNA Integrity Estimated via the Comet Assay Reflects Oxidative Stress and Competitive Disadvantage in Developing Birds

AbstractIncreases in DNA degradation have been detected in numerous situations in which organisms are exposed to pollutants. However, outside of the ecotoxicological literature, few studies have investigated whether there exists important variation in DNA integrity in free-living, healthy animals. Using the alkaline version of the comet assay to estimate DNA integrity in blood samples, we aimed to evaluate whether DNA integrity during early life is associated with nestlings' age, body mass, within-brood status, and oxidative stress using nestlings from a wild population of spotless starlings (Sturnus unicolor) as a model. We found important levels of variation in DNA integrity, suggesting the possibility that DNA integrity may have implications for offspring fitness. DNA integrity was dependent on the developmental stage, being lower at hatching than at the end of the nestling period. DNA integrity was also negatively related to the levels of oxidative damage at hatching and positively associated with wing length at fledging. In addition, position within the size hierarchy of the brood at fledging explained differences in DNA integrity, with higher levels in core than in marginal nestlings. Finally, despite extensive within-individual variation along nestling's age, we found DNA integrity during early life to be moderately repeatable within broods. Hence, DNA integrity in early life appears to be mainly affected by environmental factors, such as natural stressors. Our results suggest that measuring the variation in DNA integrity may be a fruitful approach for the assessment of individual fitness in natural populations and can be applied to studies in developmental biology and ecology.

Timescale and colony-dependent relationships between environmental conditions and plasma oxidative markers in a long-lived bat species

To increase the applicability and success of physiological approaches in conservation plans, conservation physiology should be based on ecologically relevant relationships between physiological markers and environmental variation that can only be obtained from wild populations. Given their integrative and multifaceted aspects, markers of oxidative status have recently been considered in conservation physiology, but still need to be validated across environmental conditions and locations. Here, we examined whether inter-annual variation in two oxidative markers, plasma antioxidant capacity and plasma hydroperoxides, followed inter-annual variation in temperature anomalies and associated vegetation changes in four colonies of long-lived greater mouse-eared bats (Myotis myotis) monitored over five consecutive years. We found that the plasma antioxidant capacity of bats decreased while plasma hydroperoxide concentrations increased with increasing temperature anomalies occurring in the two weeks before blood sampling. Moreover, the antioxidant defences of these bats reflected vegetation indices, which themselves reflected the thermal conditions experienced by bats in their foraging habitat. Variation in oxidative markers therefore appears to be due to variation in thermoregulatory costs and to indirect changes in foraging costs. Overall, these results validate the use of markers of oxidative status in conservation physiology to monitor thermal perturbations recently experienced by animals in their natural habitat. However, even though oxidative markers varied in the same direction in all four bat colonies across years, the amplitude of their response differed. If these different physiological responses reflect different performances (e.g. productivity, survival rate) between colonies, this implies that, if necessary, conservation measures may need to be applied at the local scale.

Impacts of selective logging on the oxidative status of tropical understorey birds

Selective logging is the dominant form of human disturbance in tropical forests, driving changes in the abundance of vertebrate and invertebrate populations relative to undisturbed old-growth forests. A key unresolved question is understanding which physiological mechanisms underlie different responses of species and functional groups to selective logging. Regulation of oxidative status is thought to be one major physiological mechanism underlying the capability of species to cope with environmental changes. Using a correlational cross-sectional approach, we compared a number of oxidative status markers among 15 understorey bird species in unlogged and selectively logged forest in Borneo in relation to their feeding guild. We then tested how variation of markers between forest types was associated with that in population abundance. Birds living in logged forests had a higher activity of the antioxidant enzyme superoxide dismutase and a different regulation of the glutathione cycle compared to conspecific birds in unlogged forest. However, neither oxidative damage nor oxidized glutathione differed between forest types. We also found that omnivores and insectivores differed significantly in all markers related to the key cellular antioxidant glutathione irrespective of the forest type. Species with higher levels of certain antioxidant markers in a given type of forest were less abundant in that forest type compared to the other. Our results suggest that there was little long-term effect of logging (last logging rotation occurred ~15 years prior to the study) on the oxidative status of understorey bird species. However, it is unclear if this was owing to plasticity or evolutionary change. Our correlative results also point to a potential negative association between some antioxidants and population abundance irrespective of the forest type.

Low-dose immune challenges result in detectable levels of oxidative damage

Infection can result in substantial costs to animals, so they frequently respond by removing infectious agents with an immune response. However, immune responses entail their own costs, including upregulation of processes that destroy pathogens (e.g. the production of reactive oxygen species) and processes that limit the extent of self-damage during the immune response (e.g. production of anti-inflammatory proteins such as haptoglobin). Here, we simulated bacterial infection across a 1000-fold range using lipopolysaccharide (LPS) administered to northern bobwhite quail (Colinus virginianus), and quantified metrics related to pro-inflammatory conditions [i.e. generation of oxidative damage (d-ROMs), depletion of antioxidant capacity], anti-inflammatory mechanisms (i.e. production of haptoglobin, expression of the enzyme heme oxygenase, production of the organic molecule biliverdin) and nutritional physiology (e.g. circulating triglyceride levels, maintenance of body mass). We detected increases in levels of haptoglobin and d-ROMs even at LPS doses that are 1/1000th the concentration of doses frequently used in ecoimmunological studies, while loss of body mass and decreases in circulating triglycerides manifested only in individuals receiving the highest dose of LPS (1 mg LPS kg-1 body mass), highlighting variation among dose-dependent responses. Additionally, individuals that lost body mass during the course of the experiment had lower levels of circulating triglycerides, and those with more oxidative damage had greater levels of heme oxygenase expression, which highlights the complex interplay between pro- and anti-inflammatory processes. Because low doses of LPS may simulate natural infection levels, variation in dose-dependent physiological responses may be particularly important in modeling how free-living animals navigate immune challenges.

N-Oleoyl-Phosphatidyl-Ethanolamine and Epigallo Catechin-3-Gallate Mitigate Oxidative Stress in Overweight and Class I Obese People on a Low-Calorie Diet

Oxidative stress and lipid peroxidation are considered key factors linking obesity with its associated complications. Epigallo catechin-3-gallate (EGCG) and oleoylethanolamide, together with its phospholipid precursor N-oleoyl-phosphatidylethanolamine (NOPE), are nutritional compounds that might improve the oxidative stress status of obese people. Unfortunately, the bioavailability of these compounds is low; however, the coadministration of NOPE with EGCG has been shown to ameliorate both the plasma availability of EGCG and the intestinal levels of NOPE in rats. This double-blind placebo-controlled study investigated the effects of 2 months' supplementation with EGCG complexed with NOPE, combined with moderate energy restriction, on plasma oxidative status of overweight and class I obese subjects. A total of 138 subjects (body mass index: 25-35 kg/m²) were recruited and randomized into two groups: the first (n = 67) received caps of placebo and the second (n = 71) caps of an oily dispersion of EGCG complexed with NOPE for 2 months. Subjects' supplementation was combined with moderate energy restriction (-800 kcal/day). Plasma oxidative status was determined by measuring the levels of oxidized low-density lipoprotein (Ox-LDL), malondialdehyde and reactive oxygen metabolites, and by calculating the lag time and the slope of Cu-induced lipid peroxidation kinetics. In total 116 subjects (27 M/89 F) completed the supplementation period, 49 in the placebo group and 67 in the treated group. Treatment induced a similar significant weight reduction in the two groups. Moreover, we found the mean changes of Ox-LDL significantly lower and the mean changes of antioxidant capacity (lag time) significantly higher in NOPE-EGCG group than in placebo group (treatment effect mean difference: -3.15 UL, P < .044 and +5.37 min, P < .0347, respectively). EGCG plasma levels were detectable only after 2 months of NOPE-EGCG diet. The NOPE-EGCG integration to a low-energy diet seems, therefore, useful for ameliorating oxidative stress-related markers, which are concomitant causes of obesity-induced disorders.

Lipidome alterations in human prefrontal cortex during development, aging, and cognitive disorders

Lipids are essential to brain functions, yet they remain largely unexplored. Here we investigated the lipidome composition of prefrontal cortex gray matter in 396 cognitively healthy individuals with ages spanning 100 years, as well as 67 adult individuals diagnosed with autism (ASD), schizophrenia (SZ), and Down syndrome (DS). Of the 5024 detected lipids, 95% showed significant age-dependent concentration differences clustering into four temporal stages, and resulting in a gradual increase in membrane fluidity in individuals ranging from newborn to nonagenarian. Aging affects 14% of the brain lipidome with late-life changes starting predominantly at 50-55 years of age-a period of general metabolic transition. All three diseases alter the brain lipidome composition, leading-among other things-to a concentration decrease in glycerophospholipid metabolism and endocannabinoid signaling pathways. Lipid concentration decreases in SZ were further linked to genetic variants associated with disease, indicating the relevance of the lipidome changes to disease progression.

Ghrelin ameliorates A549 cell apoptosis caused by paraquat via p38-MAPK regulated mitochondrial apoptotic pathway

Paraquat has relatively strong detrimental effects on humans and animals and can cause acute lung injury with high mortality. Ghrelin is a brain-gut peptide which plays important roles in regulating various physiological processes. This study investigated whether ghrelin could inhibit paraquat-induced lung injuries and attempted to elucidate the possible molecular mechanisms. A549 cells were preincubated with different concentrations of ghrelin and then treated with 200 μM of PQ for 24 h. Then cell survival, apoptosis, cellular oxidative stress and lipid peroxidation of A549 cells were detected after different treatments. Subsequently, we analyzed the mitochondrial membrane potential (ΔΨm) and measured caspase-3 activation in A549 cells. In addition, we investigated the activation of the MAPKs pathway and the function of p38-MAPK within mitochondrial apoptosis. Our study indicated that ghrelin administration improved cell viability and reduced apoptosis of PQ-treated A549 cells dose-dependently. Ghrelin treatment reduced the elevation of ROS and MDA, while improved GSH content in A549 cells after paraquat exposure. Moreover, we found that ghrelin dose-dependently increased ΔΨm and decreased caspase-3 activity. The phosphorylated p38 MAPK and JNK levels elevated following PQ exposure, while the phosphorylation of p38 MAPK decreased following ghrelin pretreatment. p38 MAPK siRNA or SB203580 pretreatment ameliorated PQ-caused cell injury and apoptosis related signals, however, the intracellular ROS production was not affected. N-Acetylcysteine (NAC), a classic antioxidant pretreatment decreased the phosphorylated p38 MAPK level and intracellular ROS production, alleviated cell injury, and inhibited apoptosis. The results showed that p38-MAPK pathway plays an important role in PQ-caused alveolar epithelial cell insult, and ghrelin might attenuate PQ-induced cell injury by inhibiting ROS-induced p38-MAPK modulated mitochondrial apoptotic pathway.

Immune challenge-induced oxidative damage may be mitigated by biliverdin

An effective immune response results in the elimination of pathogens, but this immunological benefit may be accompanied by increased levels of oxidative damage. However, organisms have evolved mechanisms to mitigate the extent of such oxidative damage, including the production and mobilization of antioxidants. One potential mechanism of mitigating immune challenge-induced changes in oxidative physiology is increasing biliverdin production. Biliverdin is chemically an antioxidant, but within-tissue correlations between biliverdin concentration and oxidative damage have never been directly examined. To test how biliverdin tissue concentrations are associated with physiological responses to an immune challenge, we exposed northern bobwhite quail (Colinus virginianus) to one of four treatments: injection of a non-pathogenic antigen - either lipopolysaccharide or phytohemagglutinin, control injection of phosphate-buffered saline or a sham procedure with no injection. Twenty-four hours later, we quantified oxidative damage and triglyceride concentration in the plasma, and biliverdin concentration in the plasma, liver and spleen. We found that both types of immune challenge increased oxidative damage relative to both non-injected and vehicle-injected controls, but treatment had no effects on any other metric. However, across all birds, oxidative damage and biliverdin concentration in the plasma were negatively correlated, which is consistent with a localized antioxidant function of biliverdin. Additionally, we uncovered multiple links between biliverdin concentration, change in mass during the immune challenges and triglyceride levels, suggesting that pathways associated with biliverdin production may also be associated with aspects of nutrient mobilization. Future experiments that manipulate biliverdin levels or oxidative damage directly could establish a systemic antioxidant function or elucidate important physiological impacts on body mass maintenance and triglyceride storage, mobilization or transport.

Varied effects of dietary carotenoid supplementation on oxidative damage in tissues of two waterfowl species

Carotenoids are regarded as a cornerstone of avian vitality and coloration. Currently, the antioxidant potential of dietary carotenoids is debated for birds. Although some studies support a protective role, others report either no effect or pro-oxidant effects. However, the majority of research on this topic has not analyzed the oxidative status of a series of tissues in animals nor considered a range of carotenoid dosages. We investigated the effects of three levels of carotenoid supplementation on plasma, liver, adipose, heart and breast muscle oxidative damage in two congeneric species of waterfowl that exhibit marked differences in carotenoid coloration. After a 6-week depletion period, captive adult northern pintail (Anas acuta) and mallard (A. platyrhynchos) ducks of both sexes were fed either a carotenoid-depleted diet (<3 μg/g xanthophylls, lutein and zeaxanthin), a carotenoid-supplemented diet (50 μg/g) within physiological range, or a carotenoid-rich diet (100 μg/g) within pharmacological range for 22 to 32 weeks. We hypothesized that these dosages of dietary carotenoids would differentially affect oxidative damage between species and sexes and among the tissues examined. We found that dietary xanthophyll supplementation had no significant effect on tissue pro-oxidation in males and females from both species. Moreover, sex or species differences in oxidative stress were only observed in two tissues (plasma and heart). Significant correlations in the levels of oxidative damage were not observed among the tissues examined. In conclusion, the current study does not support a consistent antioxidant role for dietary carotenoids in the tissues of these two waterfowl species. Instead, our results align with the notion that carotenoids play complex, tissue- and species-specific roles in oxidative status in birds.

Eucalypt leaf litter impairs growth and development of amphibian larvae, inhibits their antipredator responses and alters their physiology

Consequences of human actions like global warming, spread of exotic species or resource consumption are pushing species to extinction. Even species considered to be at low extinction risk often show signs of local declines. Here, we evaluate the impact of eucalypt plantations, the best-known exotic tree species worldwide and its interaction with temperature and predators on amphibian development, growth, antipredator responses and physiology. For this purpose, we applied a fully factorial experiment crossing two types of leaf litter (native oak or eucalypt), two temperatures (15 and 20°C) and presence/absence of native predators. We found that leachates of eucalypt leaf litter reduced amphibian development and growth, compromised their antipredator responses and altered their metabolic rate. Increased temperature itself also posed serious alterations on development, growth, antioxidant ability and the immune status of tadpoles. However, the combined effects of eucalypt leaf litter and increased temperature were additive, not synergistic. Therefore, we show that non-lethal levels of a globally spread disruptor such as leachates from eucalypt leaf litter can seriously impact the life history and physiology of native amphibian populations. This study highlights the need to evaluate the status of wild populations exposed to human activities even if not at an obvious immediate risk of extinction, based on reliable stress markers, in order to anticipate demographic declines that may be hard to reverse once started. Replacing eucalypt plantations with native trees in protected areas would help improving the health of local amphibian larvae. In zones of economic interest, we would recommend providing patches of native vegetation around ponds and removing eucalypt leaf litter from pond basins during their dry phase.

Harsh conditions during early development influence telomere length in an altricial passerine: Links with oxidative stress and corticosteroids

Stress during early development can induce substantial long-term effects in organisms. In the case of birds, despite growth compensations, nestlings reared under harsh conditions typically show reduced survival chances in adulthood. It has been proposed that environmental early-life stressors could affect longevity via effects on telomere length, possibly mediated through oxidative stress. However, the link between these processes is not clear. In this study, we experimentally manipulated brood size in spotless starlings (Sturnus unicolor) to test the causal relationship between early stress, oxidative and corticosterone-mediated stress and telomere shortening. Our results show that experimentally enlarged brood sizes led to a reduction in morphometric development on nestlings, the effect being stronger for females than males. Additionally, basal corticosterone levels increased with increasing brood size in female nestlings. Neither plasma antioxidant status nor malondialdehyde levels (a marker of lipid peroxidation) were affected by experimental brood size, although the levels of a key intracellular antioxidant (glutathione) decreased with increasing brood size. We found that the treatment showed a quadratic effect on nestling telomere lengths: these were shortened either by increases or by decreases in the original brood size. Our study provides experimental evidence for a link between developmental stress and telomere length, but does not support a direct causal link of this reduction with corticosterone or oxidative stress. We suggest that future studies should focus on how telomere length responds to additional markers of allostatic load.

Dietary canthaxanthin reduces xanthophyll uptake and red coloration in adult red-legged partridges

Carotenoids give color to conspicuous animal signals that are often the product of sexual selection. Knowledge of the mechanisms involved in carotenoid-based signaling is critical to understanding how these traits evolve. However, these mechanisms remain only partially understood. Carotenoids are usually viewed as scarce dietary antioxidants whose allocation to ornaments may trade off against health. This trade-off would ensure its reliability as a signal of individual quality. In the case of red (keto)carotenoids, the literature suggests that some species may show constraints in their uptake. Canthaxanthin is one of the most common ketocarotenoids in red ornaments of animals. It is often commercially used as a dietary supplement to obtain redder birds (e.g. poultry). We increased the dietary canthaxanthin levels in captive red-legged partridges (Alectoris rufa). This species shows red non-feathered parts mostly pigmented by another common ketocarotenoid: astaxanthin. We studied the impact on the uptake of carotenoids and vitamins and, finally, on coloration. We also tested the potential protective effect of canthaxanthin when exposing birds to a free radical generator (diquat). Canthaxanthin did not apparently protect birds from oxidative stress, but interfered with the absorption of yellow carotenoids (lutein and zeaxanthin). Zeaxanthin is a precursor of astaxanthin in enzymatic pathways, and their levels in tissues and eggs were lower in canthaxanthin-supplied birds. This led to lower astaxanthin levels in ornaments and paler coloration. As far as we know, this is the first report of a carotenoid supplementation decreasing animal coloration. The results have implications for understanding carotenoid-based signaling evolution, but also for improving husbandry/experimental procedures.

Experimental increase in baseline corticosterone level reduces oxidative damage and enhances innate immune response

Glucocorticoid (GC) hormones are significant regulators of homeostasis. The physiological effects of GCs critically depend on the time of exposure (short vs. long) as well as on their circulating levels (baseline vs. stress-induced). Previous experiments, in which chronic and high elevation of GC levels was induced, indicate that GCs impair both the activity of the immune system and the oxidative balance. Nonetheless, our knowledge on how mildly elevated GC levels, a situation much more common in nature, might influence homeostasis is limited. Therefore, we studied whether an increase in GC level within the baseline range suppresses or enhances condition (body mass, hematocrit and coccidian infestation) and physiological state (humoral innate immune system activity and oxidative balance). We implanted captive house sparrows Passer domesticus with either 60 days release corticosterone (CORT) or control pellets. CORT-treated birds had elevated baseline CORT levels one week after the implantation, but following this CORT returned to its pre-treatment level and the experimental groups had similar CORT levels one and two months following the implantation. The mass of tail feathers grown during the initial phase of treatment was smaller in treated than in control birds. CORT implantation had a transient negative effect on body mass and hematocrit, but both of these traits resumed the pre-treatment values by one month post-treatment. CORT treatment lowered oxidative damage to lipids (malondialdehyde) and enhanced constitutive innate immunity at one week and one month post-implantation. Our findings suggest that a relatively short-term (i.e. few days) elevation of baseline CORT might have a positive and stimulatory effect on animal physiology.

A hidden cost of migration? Innate immune function versus antioxidant defense

Migration is energetically demanding and physiologically challenging. Migrating birds, for example, need to boost their antioxidant defenses to defeat the pro‐oxidants produced during high energetic activity. The enhanced antioxidant defense possibly withdraws limited resources (e.g., energy or micronutrients) from other physiological functions, such as immune defense. Such a trade‐off might not occur outside the migration seasons or in resident individuals. Here, we investigate whether there is a negative relationship between innate immune function and antioxidant defense by sampling both migrating and resident blackbirds (Turdus merula) at the same location during the same period of the annual cycle. We show that in migrating blackbirds microbial killing capacity (BKA), an integrative measure of baseline innate immune function was negatively correlated with total nonenzymatic antioxidant capacity. In contrast, in resident conspecifics, sampled at the same time and location, these two physiological measures were not correlated. This suggests that migrating birds trade off innate immune function and antioxidant defense. Furthermore, and likely a consequence of this trade‐off, in migrant blackbirds BKA was positively correlated with oxidative damage to lipids. In resident blackbirds BKA and degree of lipid oxidation were uncorrelated. The mechanism and currencies of the supposed trade‐off are currently unknown, but energetic investments or micronutrients are likely candidates. Future experimental studies could provide more conclusive evidence for this trade‐off; yet, our results open up a new level of thinking about the physiological costs of migration.

An in vivo test of the biologically relevant roles of carotenoids as antioxidants in animals

Carotenoids are well known for their contribution to the vibrant coloration of many animals and have been hypothesized to be important antioxidants. Surprisingly few examples of carotenoids acting as biologically relevant antioxidants in vivo exist, in part because experimental designs often employ dosing animals with carotenoids at levels that are rarely observed in nature. Here we use an approach that reduces carotenoid content from wild-type levels to test for the effect of carotenoids as protectants against an oxidative challenge. We used the marine copepod, Tigriopus californicus reared on a carotenoid-free or a carotenoid-restored diet of nutritional yeast and then exposed them to a prooxidant. We found that carotenoid-deficient copepods not only accumulated more damage, but also were more likely to die during an oxidative challenge than carotenoid-restored copepods. We suggest that carotenoid reduction, and not supplementation, better tests the proposed roles of carotenoids in other physiological functions in animals.

Marker-dependent associations among oxidative stress, growth and survival during early life in a wild mammal

Oxidative stress (OS) is hypothesized to be a key physiological mechanism mediating life-history trade-offs, but evidence from wild populations experiencing natural environmental variation is limited. We tested the hypotheses that increased early life growth rate increases OS, and that increased OS reduces first-winter survival, in wild Soay sheep (Ovis aries) lambs. We measured growth rate and first-winter survival for four consecutive cohorts, and measured two markers of oxidative damage (malondialdehyde (MDA), protein carbonyls (PC)) and two markers of antioxidant (AOX) protection (total AOX capacity (TAC), superoxide dismutase (SOD)) from blood samples. Faster lamb growth was weakly associated with increased MDA, but not associated with variation in the other three markers. Lambs with higher SOD activity were more likely to survive their first winter, as were male but not female lambs with lower PC concentrations. Survival did not vary with MDA or total TAC. Key predictions relating OS to growth and survival were therefore supported in some OS markers, but not others. This suggests that different markers capture different aspects of the complex relationships between individual oxidative state, physiology and fitness, and that overarching hypotheses relating OS to life-history variation cannot be supported or refuted by studying individual markers.

Sensitive and selective quantification of free and total malondialdehyde in plasma using UHPLC-HRMS

Quantification of malondialdehyde (MDA) as a marker of lipid peroxidation is relevant for many research fields. We describe a new sensitive and selective method to measure free and total plasmatic MDA using derivatization with 2,4-dinitrophenylhydrazine (DNPH) and ultra-HPLC-high-resolution MS. Free and total MDA were extracted from minute sample amounts (10 μl) using acidic precipitation and alkaline hydrolysis followed by acidic precipitation, respectively. Derivatization was completed within 10 min at room temperature, and the excess DNPH discarded by liquid-liquid extraction. Quantification was achieved by internal standardization using dideuterated MDA as internal standard. The method's lowest limit of quantification was 100 nM and linearity spanned greater than three orders of magnitude. Intra- and inter-day precisions for total MDA were 2.9% and 3.0%, respectively, and those for free MDA were 12.8% and 24.9%, respectively. Accuracy was 101% and 107% at low and high concentrations, respectively. In human plasma, free MDA levels were 120 nM (SD 36.26) and total MDA levels were 6.7 μM (SD 0.46). In addition, we show the applicability of this method to measure MDA plasma levels from a variety of animal species, making it invaluable to scientists in various fields.

Family-transmitted stress in a wild bird

Recent data suggest that, in animals living in social groups, stress-induced changes in behavior have the potential to act as a source of information, so that stressed individuals could themselves act as stressful stimuli for other individuals with whom they interact repeatedly. Such form of cross-over of stress may be beneficial if it enhances adaptive responses to ecological stressors in the shared environment. However, whether stress can be transferred among individuals during early life in natural populations remains unknown. Here we tested the effect of living with stressed siblings in a gull species where, as in many vertebrates, family represents the basic social unit during development. By experimentally modifying the level of stress hormones (corticosterone) in brood mates, we demonstrate that the social transfer of stress level triggers similar stress responses (corticosterone secretion) in brood bystanders. Corticosterone-implanted chicks and their siblings were faster in responding to a potential predator attack than control chicks. In gulls, fast and coordinated reactions to predators may increase the chances of survival of the whole brood, suggesting a beneficial fitness value of cross-over of stress. However, our data also indicate that living with stressed brood mates early in life entails some long-term costs. Near independence, fledglings that grew up with stressed siblings showed reduced body size, high levels of oxidative damage in lipids and proteins, and a fragile juvenile plumage. Overall, our results indicate that stress cross-over occurs in animal populations and may have important fitness consequences.