Understanding diversity in oxidative status and oxidative stress: the opportunities and challenges ahead

Sexual selection may support phenotypic plasticity in male coloration of an African cichlid fish

The expression of sexually selected traits, such as ornaments or body coloration, is often influenced by environmental conditions. While such phenotypic plasticity is often thought to precede evolutionary change, plasticity itself can also be a target of selection. However, the selective forces supporting the evolution and persistence of plasticity in sexual traits are often unclear. Using the cichlid fish Astatotilapia burtoni, we show that variation in the level of mate competition may promote plasticity in body coloration. In this species, males can change between yellow and blue colour. We found that experimentally increased competition over mating territories led to a higher proportion of males expressing the yellow phenotype. The expression of yellow coloration was found to be beneficial because yellow males won more staged dyadic contests and exhibited a lower level of oxidative stress than blue males. However, females were more likely to spawn with blue males in mate choice experiments, suggesting that expression of blue coloration is sexually more attractive. The ability to adjust colour phenotype according to the local competitive environment could therefore promote the persistence of plasticity in coloration.

Short communication: The boring sponge (Pione vastifica, Hancock, 1849) induces oxidative stress in the Pacific oyster (Magallana gigas, Thunberg, 1793)

Boring sponge infection affects growth, development and reduces the soft tissue weight of oysters. In this study, we investigated the effects of boring sponge on the activity of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GP)) in the mantle, and the production of reactive oxygen species (ROS) and potential genotoxicity in hemocytes of the Pacific oyster Magallana gigas. Our results showed a significant increase in ROS production and DNA damage in hemocytes. Notably, the activity of SOD, CAT, and GP in the mantle was not significantly affected by boring sponge infection. Collectively, these results suggest that sponge invasion may cause oxidative stress in Pacific oyster hemocytes through ROS overproduction.

Oxidative stress across multiple tissues in house sparrows (Passer domesticus) acclimated to warm, stable cold, and unpredictable cold thermal treatments

With climate change increasing not just mean temperatures but the frequency of cold snaps and heat waves, animals occupying thermally variable areas may be faced with thermal conditions for which they are not prepared. Studies of physiological adaptations of temperate resident birds to such thermal variability are largely lacking in the literature. To address this gap, we acclimated winter-phenotype house sparrows (Passer domesticus) to stable warm, stable cold, and fluctuating cold temperatures. We then measured several metrics of the oxidative stress (OS) system, including enzymatic and non-enzymatic antioxidants and lipid oxidative damage, in brain (post-mitotic), kidney (mitotic), liver (mitotic) and pectoralis muscle (post-mitotic). We predicted that high metabolic flexibility could be linked to increases in reactive oxygen damage. Alternatively, if variation in ROS production is not associated with metabolic flexibility, then we predict no antioxidant compensation with thermal variation. Our data suggest that ROS production is not associated with metabolic flexibility, as we found no differences across thermal treatment groups. However, we did find differences across tissues. Brain catalase activity demonstrated the lowest values compared with kidney, liver and muscle. In contrast, brain glutathione peroxidase (GPx) activities were higher than those in kidney and liver. Muscle GPx activities were intermediate to brain and kidney/liver. Lipid peroxidation damage was lowest in the kidney and highest in muscle tissue.

Impairment on fillet fatty acid profile and oxidative damage in pirarucu, Arapaima gigas, acutely exposed to extreme ambient temperature

Climatic events are affecting the Amazon basin and according to projections it is predicted the intensification of climate changes through increases in temperature and carbon dioxide (CO2). Recent evidence has revealed that exposure to an extreme climate scenario elicits oxidative damage in some fish species, impairing their metabolism and physiology, contributing to their susceptibility. Thus, the comprehension of physiological alterations in Arapaima gigas (pirarucu) to the climatic changes forecasted for the next 100 years is important to evaluate its capability to deal with oxidative stress. The objective of this work was to determine whether antioxidant defense system is able to prevent muscle oxidative damage of pirarucu exposed 96 h to extreme climate scenario, as well as the effects of this exposition on muscle fatty acid levels. Lipid peroxidation and reactive oxygen species significantly increase in the muscle of pirarucus exposed to an extreme climate scenario compared to control, while muscle superoxide dismutase, catalase, and glutathione peroxidase were significantly lower. Total amount of saturated fatty acids (SFAs) was significantly higher in pirarucu exposed to an extreme climate scenario compared to control, while total content of monounsaturated (MUFAs) and polyunsaturated fatty acids (PUFAs) was significantly lower. Exposure to an extreme climate scenario causes muscular oxidative stress and that the antioxidant systems are inefficient to avoid oxidative damage. In addition, the increase of total SFAs and the decrease of MUFAs and PUFAs probably intend to maintain membrane fluidity while facing high temperature and CO2 levels.

REVIEW: Evidence supporting the 'preparation for oxidative stress' (POS) strategy in animals in their natural environment

Hypometabolism is a common strategy employed by resilient species to withstand environmental stressors that would be life-threatening for other organisms. Under conditions such as hypoxia/anoxia, temperature and salinity stress, or seasonal changes (e.g. hibernation, estivation), stress-tolerant species down-regulate pathways to decrease energy expenditures until the return of less challenging conditions. However, it is with the return of these more favorable conditions and the reactivation of basal metabolic rates that a strong increase of reactive oxygen and nitrogen species (RONS) occurs, leading to oxidative stress. Over the last few decades, cases of species capable of enhancing antioxidant defenses during hypometabolic states have been reported across taxa and in response to a variety of stressors. Interpreted as an adaptive mechanism to counteract RONS formation during tissue hypometabolism and reactivation, this strategy was coined "Preparation for Oxidative Stress" (POS). Laboratory experiments have confirmed that over 100 species, spanning 9 animal phyla, apply this strategy to endure harsh environments. However, the challenge remains to confirm its occurrence in the natural environment and its wide applicability as a key survival element, through controlled experimentation in field and in natural conditions. Under such conditions, numerous confounding factors may complicate data interpretation, but this remains the only approach to provide an integrative look at the evolutionary aspects of ecophysiological adaptations. In this review, we provide an overview of representative cases where the POS strategy has been demonstrated among diverse species in natural environmental conditions, discussing the strengths and weaknesses of these results and conclusions.

Life-history stage influences immune investment and oxidative stress in response to environmental heterogeneity in Antarctic fur seals

Immune defenses are crucial for survival but costly to develop and maintain. Increased immune investment is therefore hypothesized to trade-off with other life-history traits. Here, we examined innate and adaptive immune responses to environmental heterogeneity in wild Antarctic fur seals. In a fully crossed, repeated measures design, we sampled 100 pups and their mothers from colonies of contrasting density during seasons of contrasting food availability. Biometric and cortisol data as well as blood for the analysis of 13 immune and oxidative status markers were collected at two key life-history stages. We show that immune responses of pups are more responsive than adults to variation in food availability, but not population density, and are modulated by cortisol and condition. Immune investment is associated with different oxidative status markers in pups and mothers. Our results suggest that early life stages show greater sensitivity to extrinsic and intrinsic effectors, and that immunity may be a strong target for natural selection even in low-pathogen environments such as Antarctica.

Exploring the Antiproliferative and Modulatory Effects of 1-Methoxyisobrassinin on Ovarian Cancer Cells: Insights into Cell Cycle Regulation, Apoptosis, Autophagy, and Its Interactions with NAC

Ovarian cancer, a highly lethal malignancy among reproductive organ cancers, poses a significant challenge with its high mortality rate, particularly in advanced-stage cases resistant to platinum-based chemotherapy. This study explores the potential therapeutic efficacy of 1-methoxyisobrassinin (MB-591), a derivative of indole phytoalexins found in Cruciferae family plants, on both cisplatin-sensitive (A2780) and cisplatin-resistant ovarian cancer cells (A2780 cis). The findings reveal that MB-591 exhibits an antiproliferative effect on both cell lines, with significantly increased potency against cisplatin-sensitive cells. The substance induces alterations in the distribution of the cell cycle, particularly in the S and G2/M phases, accompanied by changes in key regulatory proteins. Moreover, MB-591 triggers apoptosis in both cell lines, involving caspase-9 cleavage, PARP cleavage induction, and DNA damage, accompanied by the generation of reactive oxygen species (ROS) and mitochondrial dysfunction. Notably, the substance selectively induces autophagy in cisplatin-resistant cells, suggesting potential targeted therapeutic applications. The study further explores the interplay between MB-591 and antioxidant N-acetylcysteine (NAC), in modulating cellular processes. NAC demonstrates a protective effect against MB-591-induced cytotoxicity, affecting cell cycle distribution and apoptosis-related proteins. Additionally, NAC exhibits inhibitory effects on autophagy initiation in cisplatin-resistant cells, suggesting its potential role in overcoming resistance mechanisms.

Are reactive oxygen species always bad? Lessons from hypoxic ectotherms

Oxygen (O2) is required for aerobic energy metabolism but can produce reactive oxygen species (ROS), which are a wide variety of oxidant molecules with a range of biological functions from causing cell damage (oxidative distress) to cell signalling (oxidative eustress). The balance between the rate and amount of ROS generated and the capacity for scavenging systems to remove them is affected by several biological and environmental factors, including oxygen availability. Ectotherms, and in particular hypoxia-tolerant ectotherms, are hypothesized to avoid oxidative damage caused by hypoxia, although it is unclear whether this translates to an increase in ecological fitness. In this Review, we highlight the differences between oxidative distress and eustress, the current mechanistic understanding of the two and how they may affect ectothermic physiology. We discuss the evidence of occurrence of oxidative damage with hypoxia in ectotherms, and that ectotherms may avoid oxidative damage through (1) high levels of antioxidant and scavenging systems and/or (2) low(ering) levels of ROS generation. We argue that the disagreements in the literature as to how hypoxia affects antioxidant enzyme activity and the variable metabolism of ectotherms makes the latter strategy more amenable to ectotherm physiology. Finally, we argue that observed changes in ROS production and oxidative status with hypoxia may be a signalling mechanism and an adaptive strategy for ectotherms encountering hypoxia.

Natural products for the treatment of chemotherapy-related cognitive impairment and prospects of nose-to-brain drug delivery

Chemotherapy-related cognitive deficits (CRCI) as one of the common adverse drug reactions during chemotherapy that manifest as memory, attention, and executive function impairments. However, there are still no effective pharmacological therapies for the treatment of CRCI. Natural compounds have always inspired drug development and numerous natural products have shown potential therapeutic effects on CRCI. Nevertheless, improving the brain targeting of natural compounds in the treatment of CRCI is still a problem to be overcome at present and in the future. Accumulated evidence shows that nose-to-brain drug delivery may be an excellent carrier for natural compounds. Therefore, we reviewed natural products with potential anti-CRCI, focusing on the signaling pathway of these drugs' anti-CRCI effects, as well as the possibility and prospect of treating CRCI with natural compounds based on nose-to-brain drug delivery in the future. In conclusion, this review provides new insights to further explore natural products in the treatment of CRCI.

Pesticide concentrations in a threatened freshwater turtle (Emys orbicularis): Seasonal and annual variation in the Camargue wetland, France

Wetlands are among the most threatened ecosystems on the planet and pollution is a major factor causing the decline of wetland biodiversity. Despite the increasing use of pesticides, their fate and effects on freshwater reptiles remain largely unknown. We studied the European pond turtle (Emys orbicularis), a long-lived species at risk with a high exposure potential to pesticides. Between 2018 and 2020, we measured 29 pesticides and metabolites in 408 blood samples of turtles from two populations in the Camargue wetland (France). We were able to quantify 24 compounds and at least one pesticide or one degradation product in 62.5% of samples. Pesticide occurrences and concentrations were low, except for a herbicide widely used in rice cultivation and locally detected in water: bentazone that reached high blood concentrations in E. orbicularis. The occurrence and the concentration of pesticides in E. orbicularis blood depended mainly on the site and the sampling date in relation to pesticide application. Individual characteristics (sex, age, body condition) did not explain the occurrence or the concentration of pesticides found in turtle blood. Assessing the exposure of aquatic wildlife to a cocktail of currently-used pesticides is a first and crucial step before studying their effects at the individual and population levels.

The effect of alpha-lipoic acid supplementation on anthropometric, glycemic, lipid, oxidative stress, and hormonal parameters in individuals with polycystic ovary syndrome: a systematic review and meta-analysis of randomized clinical trials

This systematic review and meta-analysis aimed to examine the effect of the antioxidant alpha-lipoic acid (ALA) on various cardiometabolic risk factors and hormonal parameters in patients with polycystic ovary syndrome (PCOS). We searched PubMed, EMBASE, SCOPUS, Cochrane Library, and Web of Science databases without language restrictions until May 2023 to find randomized controlled trials (RCTs) that assessed the impact of ALA supplementation on anthropometric, glycemic, lipid, oxidative stress, and hormonal parameters in women with PCOS. Outcomes were summarized using the standardized mean difference (SMD) and 95% confidence interval (CI) in a random-effects model. An I2 statistic of >60% established significant between-study heterogeneity. The overall certainty of the evidence for each outcome was determined using the grading of recommendations, assessment, development, and evaluations system. Seven RCTs met the inclusion criteria. The ALA group had significant reductions in fasting blood sugar (fasting blood sugar (FBS), n=7 RCTs, SMD, -0.60; 95% CI, -1.10 to -0.10; I2=63.54%, moderate certainty of evidence) and homeostatic model assessment for insulin resistance (homeostatic model assessment of insulin resistance (HOMA-IR), n=4 RCTs, SMD, -2.03; 95% CI, -3.85 to -0.20; I2=96.32%, low certainty of evidence) compared with the control group. However, significant differences were observed between the groups in body mass index, insulin, estrogen, follicle-stimulating hormone, luteinizing hormone, testosterone, low-density lipoprotein, highdensity lipoprotein, triglyceride, total cholesterol, malondialdehyde, or total antioxidant capacity profiles. ALA supplementation improves FBS and HOMA-IR levels in women with PCOS. ALA consumption is an effective complementary therapy for the management of women with PCOS.

Seasonal changes in diet, immune function, and oxidative stress in three passerines inhabiting a Mediterranean climate

Oxidative status and immune function are energy-demanding traits closely linked to diet composition, particularly resource availability and nutritional value. In seasonal environments, nutrient availability and diet quality fluctuate, potentially influencing these traits. However, limited evidence exists regarding these dietary effects on immune function in seasonal environments. In this study, we employed stable isotope analysis to assess the impact of seasonal changes in niche width and trophic level (i.e., δ15N) on two immune variables (hemolysis and hemagglutination scores) and two oxidative status parameters (lipid peroxidation and total antioxidant capacity) in three passerine species: Zonotrichia capensis (omnivorous), Troglodytes aedon (insectivorous), and Spinus barbatus (granivorous). We found that hemolysis scores varied seasonally in Z. capensis, with higher values in winter compared to summer. Total antioxidant capacity (TAC) also increased during the winter in Z. capensis and S. barbatus. The isotopic niche width for Z. capensis and S. barbatus was smaller in winter than in summer, with the omnivorous species exhibiting a decrease in δ15N. Despite the seasonal shifts in ecological and physiological traits in Z. capensis, we identified no correlation between immune response and TAC with trophic level. In contrast, in the granivorous S. barbatus, the lower trophic level resulted in an increase in TAC without affecting immunity. Our findings revealed that dietary shifts do not uniformly impact oxidative status and immune function across bird species, highlighting species-specific responses to seasonal changes. This underscores the importance of integrating ecological and evolutionary perspectives when examining how diet shapes avian immunity and oxidative balance.

In-vivo exposure of a plant model organism for the assessment of the ability of PM samples to induce oxidative stress

This study aims to propose an innovative, simple, rapid, and cost-effective method to study oxidative stress induced by PM through in-vivo exposure of the plant model organism Arabidopsis thaliana. A. thaliana seedlings were exposed to urban dust certified for its elemental content and to PM2.5 samples collected in an urban-industrial area of Northern Italy. An innovative technique for the detachment and suspension in water of the whole intact dust from membrane filters was applied to expose the model organism to both the soluble and insoluble fractions of PM2.5, which were analyzed for 34 elements by ICP-MS. Oxidative stress induced by PM on A. thaliana was assessed by light microscopic localization and UV-Vis spectrophotometric determination of superoxide anion (O2-) content on the exposed seedlings by using the nitro blue tetrazole (NBT) assay. The results showed a good efficiency and sensitivity of the method for PM mass concentrations >20 μg m-3 and an increase in O2- content in all exposed seedlings, which mainly depends on the concentration, chemical composition, and sources of the PM administered to the model organism. Particles released by biomass burning appeared to contribute more to the overall toxicity of PM. This method was found to be cost-effective and easy to apply to PM collected on membrane filters in intensive monitoring campaigns in order to obtain valuable information on the ability of PM to generate oxidative stress in living organisms.

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.

Oxidatively stressed extracellular microenvironment drives fibroblast activation and kidney fibrosis

Kidney fibrosis is associated with tubular injury, oxidative stress and activation of interstitial fibroblasts. However, whether these events are somehow connected is poorly understood. In this study, we show that glutathione peroxidase-3 (GPX3) depletion in renal tubular epithelium after kidney injury plays a central role in orchestrating an oxidatively stressed extracellular microenvironment, which drives interstitial fibroblast activation and proliferation. Through transcriptional profiling by RNA-sequencing, we found that the expression of GPX3 was down-regulated in various models of chronic kidney disease (CKD), which was correlated with induction of nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase-4 (NOX4). By using decellularized extracellular matrix (ECM) scaffold, we demonstrated that GPX3-depleted extracellular microenvironment spontaneously induced NOX4 expression and reactive oxygen species (ROS) production in renal fibroblasts and triggered their activation and proliferation. Activation of NOX4 by advanced oxidation protein products (AOPPs) mimicked the loss of GPX3, increased the production of ROS, stimulated fibroblast activation and proliferation, and activated protein kinase C-α (PKCα)/mitogen-activated protein kinase (MAPK)/signal transducer and activator of transcription 3 (STAT3) signaling. Silencing NOX4 or inhibition of MAPK with small molecule inhibitors hampered fibroblast activation and proliferation. In mouse model of CKD, knockdown of NOX4 repressed renal fibroblast activation and proliferation and alleviated kidney fibrosis. These results indicate that loss of GPX3 orchestrates an oxidatively stressed extracellular microenvironment, which promotes fibroblast activation and proliferation through a cascade of signal transduction. Our studies underscore the crucial role of extracellular microenvironment in driving fibroblast activation and kidney fibrosis.

Early-life environmental effects on mitochondrial aerobic metabolism: a brood size manipulation in wild great tits

In avian species, the number of chicks in the nest and subsequent sibling competition for food are major components of the offspring's early-life environment. A large brood size is known to affect chick growth, leading in some cases to long-lasting effects for the offspring, such as a decrease in size at fledgling and in survival after fledging. An important pathway underlying different growth patterns could be the variation in offspring mitochondrial metabolism through its central role in converting energy. Here, we performed a brood size manipulation in great tits (Parus major) to unravel its impact on offspring mitochondrial metabolism and reactive oxygen species (ROS) production in red blood cells. We investigated the effects of brood size on chick growth and survival, and tested for long-lasting effects on juvenile mitochondrial metabolism and phenotype. As expected, chicks raised in reduced broods had a higher body mass compared with enlarged and control groups. However, mitochondrial metabolism and ROS production were not significantly affected by the treatment at either chick or juvenile stages. Interestingly, chicks raised in very small broods were smaller in size and had higher mitochondrial metabolic rates. The nest of rearing had a significant effect on nestling mitochondrial metabolism. The contribution of the rearing environment in determining offspring mitochondrial metabolism emphasizes the plasticity of mitochondrial metabolism in relation to the nest environment. This study opens new avenues regarding the effect of postnatal environmental conditions in shaping offspring early-life mitochondrial metabolism.

Long-term exposure to small-sized silica nanoparticles (SiO2-NPs) induces oxidative stress and impairs reproductive performance in adult zebrafish (Danio rerio)

The widespread use of silica nanoparticles (SiO2-NPs) in various industries, including chemical polishing, cosmetics, varnishes, medical, and food products, has increased the risk of their release into aquatic ecosystems. The toxic effects of small-size SiO2-NPs on the reproductive performance of zebrafish (Danio rerio) have yet to be widely studied. This study aimed to investigate the impact of chronic exposure to small-sized (35 ± 6 nm) SiO2-NPs on adult zebrafish through waterborne exposure to concentrations of 5 (SNP5), 10 (SNP10), 15 (SNP15), and 20 (SNP20) μg/L of SiO2-NPs for 28 days. Our results showed that SiO2-NPs significantly impacted several biochemical parameters, including cholesterol, triglycerides, LDL, HDL, total protein, albumin, urea levels, and alkaline phosphatase and aspartate aminotransferase activity. Cortisol and glucose levels in the SNP20 group significantly differed from the control group. All the exposed groups, apart from SNP5, experienced a significant increase in their total immunoglobulin levels and lysozyme activity. While there was a considerable increase in the activity of catalase and superoxide dismutase in all exposed groups, the expression of antioxidant genes did not appear to be affected. Furthermore, the expression level of il8 was significantly higher in SNP5 and SNP10 than in other treatments. Exposure to SiO2-NPs caused a decrease in gonad weight, absolute fecundity, and larval survival rate, particularly in the SNP20 group. The present study indicates that SiO2-NPs can harm zebrafish and thus further research is necessary to assess their health and environmental risks.

The evolution of selective autophagy as a mechanism of oxidative stress response: The evolutionarily acquired ability of selective autophagy receptors to respond to oxidative stress is beneficial for human longevity

Ageing is associated with a decline in autophagy and elevated reactive oxygen species (ROS), which can breach the capacity of antioxidant systems. Resulting oxidative stress can cause further cellular damage, including DNA breaks and protein misfolding. This poses a challenge for longevous organisms, including humans. In this review, we hypothesise that in the course of human evolution selective autophagy receptors (SARs) acquired the ability to sense and respond to localised oxidative stress. We posit that in the vicinity of protein aggregates and dysfunctional mitochondria oxidation of key cysteine residues in SARs induces their oligomerisation which initiates autophagy. The degradation of damaged cellular components thus could reduce ROS production and restore redox homeostasis. This evolutionarily acquired function of SARs may represent one of the biological adaptations that contributed to longer lifespan. Inversely, loss of this mechanism can lead to age-related diseases associated with impaired autophagy and oxidative stress.

Upstream migrant sea lamprey (Petromyzon marinus) show signs of increasing oxidative stress but maintain aerobic capacity with age

Following the parasitic juvenile phase of their life cycle, sea lamprey (Petromyzon marinus) mature into a reproductive but rapidly aging and deteriorating adult, and typically die shortly after spawning in May or June. However, pre-spawning upstream migrant sea lamprey can be maintained for several months beyond their natural lifespan when held in cold water (∼4-8 °C) under laboratory conditions. We exploited this feature to investigate the interactions between senescence, oxidative stress, and metabolic function in this phylogenetically ancient fish. We investigated how life history traits and mitochondria condition, as indicated by markers of oxidative stress (catalase activity, lipid peroxidation) and aerobic capacity (citrate synthase activity), changed in adult sea lamprey from June to December after capture during their upstream spawning migration. Body mass but not liver mass declined with age, resulting in an increase in hepatosomatic index. Both effects were most pronounced in males, which also tended to have larger livers than females. Lamprey experienced greater oxidative stress with age, as reflected by increasing activity of the antioxidant enzyme catalase and increasing levels of lipid peroxidation in liver mitochondrial isolates over time. Surprisingly, the activity of citrate synthase also increased with age in both sexes. These observations implicate mitochondrial dysfunction and oxidative stress in the senescence of sea lamprey. Due to their unique evolutionary position and the technical advantage of easily delaying the onset of senescence in lampreys using cold water, these animals could represent an evolutionary unique and tractable model to investigate senescence in vertebrates.

Oxidative damage varies in response to bacterial, fungal and viral antigen challenges in bats

The immune system plays an important role in defending against pathogens and regulating physiological homeostasis, but the strength of the immune responses depends on the type of pathogen. The immune system of bats shows a high variability in responsiveness towards various pathogens; they can safely harbor certain pathogens that are highly lethal to other mammals. Oxidative stress may act as a pathophysiological cellular mechanism mediating the immunological function of bats because of its potentially detrimental effects on physiological homeostasis, fertility and longevity. By experimentally exposing greater mouse-eared bats (Myotis myotis) to three antigens, it was previously shown that animals reacted immunologically most strongly to bacterial and viral antigens, but not to fungal ones. As a follow up, in this study we observed that both bacterial and fungal antigens induced a significant increase of plasma oxidative damage, whereas viral antigens did not cause any increase of plasma oxidative damage at all albeit the mild immune response. Thus, experimental bats were able to avoid oxidative stress only in the face of a viral antigen, possibly by dampening inflammatory signalling. Bats may be able to handle viral infections and live well beyond expectations by reducing the detrimental effects of molecular oxidation.

Metabolic stress as a driver of life-history plasticity: flight promotes longevity and antioxidant production in monarch butterflies

Life-history theory predicts that increased investment in traits related to reproduction will be associated with a reduced ability to invest in survival or longevity. One mechanistic explanation for this trade-off is that metabolic stress generated from current fitness activities (e.g. reproduction or locomotion) will increase somatic damage, leading to reduced longevity. Yet, there has been limited support for this damage-based hypothesis. A possible explanation is that individuals can respond to increases in metabolic stress by plastically inducing cellular maintenance responses, which may increase, rather than decrease, longevity. We tested this possibility by experimentally manipulating investment in flight activity (a metabolic stressor) in the migratory monarch butterfly (Danaus plexippus), a species whose reproductive fitness is dependent on survival through a period of metabolically intensive migratory flight. Consistent with the idea that metabolic stress stimulated investment in self-maintenance, increased flight activity enhanced monarch butterfly longevity and somatic tissue antioxidant capacity, likely at a cost to reproductive investment. Our study implicates a role for metabolic stress as a driver of life-history plasticity and supports a model where current engagement in metabolically stressful activities promotes somatic survival by stimulating investment in self-maintenance processes.

Oxidative physiology of two small and highly migratory Arctic seabirds: Arctic terns (Sterna paradisaea) and long-tailed jaegers (Stercorarius longicaudus)

Arctic ecosystems are changing rapidly. The tundra supports nesting migratory seabirds that spend most of their year over the ocean. Migrations are demanding, but it is unclear how physiological capability may equip organisms to respond to their changing environments. For two migratory seabird species nesting in Alaska, USA, the Arctic tern (n = 10) and the long-tailed jaeger (n = 8), we compared oxidative physiology and aerobic capacity measured during incubation and we recorded individual movement paths using electronic tracking tags. Within species, we hypothesized that individuals with longer-distance migrations would show higher oxidative stress and display better aerobic capacity than shorter-distance migrants. We examined blood parameters relative to subsequent fall migration in jaegers and relative to previous spring migration in terns. We present the first measurements of oxidative stress in these species and the first migratory movements of long-tailed jaegers in the Pacific Ocean. Arctic terns displayed positive correlation of oxidative variables, or better integration than jaegers. Relative to physiological sampling, pre-breeding northward migration data were available for terns and post-breeding southward data were available for jaegers. Terns reached a farther maximum distance from the colony than jaegers (16 199 ± 275 km versus 10 947 ± 950 km) and rate of travel northward (447 ± 41.8 km/day) was positively correlated with hematocrit, but we found no other relationships. In jaegers, there were no relationships between individuals' physiology and southward rate of travel (193 ± 52.3 km/day) or migratory distance. While it is not clear whether the much longer migrations of the terns is related to their better integration, or to another factor, our results spark hypotheses that could be evaluated through a controlled phylogenetic study. Species with better integration may be less susceptible to environmental factors that increase oxidative stress, including thermal challenges or changes in prey distribution as the Arctic climate changes rapidly.

Future shock: Ocean acidification and seasonal water temperatures alter the physiology of competing temperate and coral reef fishes

Climate change can directly (physiology) and indirectly (novel species interactions) modify species responses to novel environmental conditions during the initial stages of range shifts. Whilst the effects of climate warming on tropical species at their cold-water leading ranges are well-established, it remains unclear how future seasonal temperature changes, ocean acidification, and novel species interactions will alter the physiology of range-shifting tropical and competing temperate fish in recipient ecosystems. Here we used a laboratory experiment to examine how ocean acidification, future summer vs winter temperatures, and novel species interactions could affect the physiology of competing temperate and range-extending coral reef fish to determine potential range extension outcomes. In future winters (20 °C + elevated pCO₂) coral reef fish at their cold-water leading edges showed reduced physiological performance (lower body condition and cellular defence, and higher oxidative damage) compared to present-day summer (23 °C + control pCO₂) and future summer conditions (26 °C + elevated pCO₂). However, they showed a compensatory effect in future winters through increased long-term energy storage. Contrastingly, co-shoaling temperate fish showed higher oxidative damage, and reduced short-term energy storage and cellular defence in future summer than in future winter conditions at their warm-trailing edges. However, temperate fish benefitted from novel shoaling interactions and showed higher body condition and short-term energy storage when shoaling with coral reef fish compared to same-species shoaling. We conclude that whilst during future summers, ocean warming will likely benefit coral reef fishes extending their ranges, future winter conditions may still reduce coral reef fish physiological functioning, and may therefore slow their establishment at higher latitudes. In contrast, temperate fish species benefit from co-shoaling with smaller-sized tropical fishes, but this benefit may dissipate due to their reduced physiological functioning under future summer temperatures and increasing body sizes of co-shoaling tropical species.

Changes of oxidative status in yellowfin seabream larvae (Acanthopagrus latus) during development

Dynamic changes of tissues, organs and growth that occur in fish larvae during the transition to the juvenile stage are accompanied by differences in metabolic, locomotor and feeding activities that can reflect on fish's oxidative status. In this study, we examine how body growth, antioxidant system (superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and total antioxidant capacity (TAC) and oxidative damage (malondialdehyde-MDA) parameters change in larvae of yellowfin seabream larvae (Acanthopagrus latus) during early development (0, 7, 15, 22 and 30 day after hatching-DAH). Body growth (length and weight) starts to intensify from 15 DAH. We observed general increase in the antioxidant system (AOS) with the age of larvae from newly hatched and 7 DAH up to 15 and 22 DAH individuals. 15 and 22 DAH larvae had the greatest levels of TAC, SOD and GR activity, while 30 DAH larvae had higher CAT activity from 0, 7 and 15 DAH and MDA concentration in comparison to 15 DAH individuals. Several developmental events can be linked with observed results: lower AOS in 0 and 7 DAH individuals with low locomotor activity, growth, endo-exogenous feeding phase and cell differentiation; 15 and 22 DAH larvae are under pressure of fast growth, enhanced swimming and foraging capacity; while higher MDA production in 30 DAH larvae can be a result of shifts in muscle metabolism, changes in both quality and quantity of food and a significant increase in weight. The present study provides insight into the changes in redox status during the ontogeny of A. latus, fish species about which physiology is still little known but with a potential for use in marine culture. Ability to lower oxidative stress during critical developmental periods can enhance that potential.

Impacts of rising temperatures and water acidification on the oxidative status and immune system of aquatic ectothermic vertebrates: A meta-analysis

Species persistence in the Anthropocene is dramatically threatened by global climate change. Large emissions of carbon dioxide (CO₂) from human activities are driving increases in mean temperature, intensity of heatwaves, and acidification of oceans and freshwater bodies. Ectotherms are particularly sensitive to CO₂-induced stressors, because the rate of their metabolic reactions, as well as their immunological performance, are affected by environmental temperatures and water pH. We reviewed and performed a meta-analysis of 56 studies, involving 1259 effect sizes, that compared oxidative status or immune function metrics between 42 species of ectothermic vertebrates exposed to long-term increased temperatures or water acidification (≥48 h), and those exposed to control parameters resembling natural conditions. We found that CO₂-induced stressors enhance levels of molecular oxidative damages in ectotherms, while the activity of antioxidant enzymes was upregulated only at higher temperatures, possibly due to an increased rate of biochemical reactions dependent on the higher ambient temperature. Differently, both temperature and water acidification showed weak impacts on immune function, indicating different direction (increase or decrease) of responses among immune traits. Further, we found that the intensity of temperature treatments (Δ°C) and their duration, enhance the physiological response of ectotherms, pointing to stronger effects of prolonged extreme warming events (i.e., heatwaves) on the oxidative status. Finally, adult individuals showed weaker antioxidant enzymatic responses to an increase in water temperature compared to early life stages, suggesting lower acclimation capacity. Antarctic species showed weaker antioxidant response compared to temperate and tropical species, but level of uncertainty in the antioxidant enzymatic response of Antarctic species was high, thus pairwise comparisons were statistically non-significant. Overall, the results of this meta-analysis indicate that the regulation of oxidative status might be one key mechanism underlying thermal plasticity in aquatic ectothermic vertebrates.

Ammonium effects on oxidative stress, telomere length, and locomotion across life stages of an anuran from habitats with contrasting land-use histories

Understanding the mechanistic implications behind wildlife responses to global changes is a central topic in eco-evolutionary research. In particular, anthropic pollution is known to impact wild populations across the globe, which may have even stronger consequences for species with complex life cycles. Among vertebrates, amphibians represent a paradigmatic example of metamorphosis, and their characteristics make them highly vulnerable to pollution. Here, we tested for differences in the redox status, telomere length, and locomotor performance across life stages of green frogs (Pelophylax perezi) from agrosystem and natural habitats, both constitutively and in response to an experimental ammonium exposure (10 mg/L). We found that larvae from the agrosystem constitutively showed an enhanced redox status (better antioxidant balance against H₂O₂, lower lipid peroxidation) but shorter telomeres as compared to larvae from the natural environment. The larval redox response to ammonium was, overall, similar in both habitats. In contrast, after metamorphosis, the redox status of individuals from the natural habitat seemed to cope better with ammonium exposure (denoted by lower lipid peroxidation), and differences between habitats in telomere length were no longer present. Intriguingly, while the swimming performance of larvae did not correlate with individual's physiology, metamorphs with lower glutathione reductase activity and longer telomeres had a better jumping performance. This may suggest that locomotor performance is both traded off with the production of reactive oxygen species and potentiated directly by longer telomeres or indirectly by the mechanisms that buffer their shortening. Overall, our study suggests that contrasting land-use histories can drive divergence in physiological pathways linked to individual health and lifespan. Since this pattern was life-stage dependent, divergent habitat conditions can have contrasting implications across the ontogenetic development of species with complex life cycles.

FoxO3 and oxidative stress: a multifaceted role in cellular adaptation

Oxidative stress is a major cause of morbidity and mortality in human health and disease. In this review, we focus on the Forkhead Box (Fox) subclass O3 (FoxO3), an extensively studied transcription factor that plays a pleiotropic role in a wide range of physiological and pathological processes by regulating multiple gene regulatory networks involved in the modulation of numerous aspects of cellular metabolism, including fuel metabolism, cell death, and stress resistance. This review will also focus on regulatory mechanisms of FoxO3 expression and activity, such as crucial post-translational modifications and non-coding RNAs. Moreover, this work discusses and evidences some pathways to how this transcription factor and reactive oxygen species regulate each other, which may lead to the pathogenesis of various types of diseases. Therefore, in addition to being a promising therapeutic target, the FoxO3-regulated signaling pathways can also be used as reliable diagnostic and prognostic biomarkers and indicators for drug responsiveness.

Higher temperature induces oxidative stress in hybrids but not in parental species: A case study of crested newts

Ectotherms are particularly sensitive to global warming due to their limited capacity to thermoregulate, which can impact their performance and fitness. From a physiological standpoint, higher temperatures often enhance biological processes that can induce the production of reactive oxygen species and result in a state of cellular oxidative stress. Temperature alters interspecific interactions, including species hybridization. Hybridization under different thermal conditions could amplify parental (genetic) incompatibilities, thus affecting a hybrid's development and distribution. Understanding the impact of global warming on the physiology of hybrids and particularly their oxidative status could help in predicting future scenarios in ecosystems and in hybrids. In the present study, we investigated the effect of water temperature on the development, growth and oxidative stress of two crested newt species and their reciprocal hybrids. Larvae of Triturus macedonicus and T. ivanbureschi, and their T. macedonicus-mothered and T. ivanbureschi-mothered hybrids were exposed for 30 days to temperatures of 19°C and 24°C. Under the higher temperature, the hybrids experienced increases in both growth and developmental rates, while parental species exhibited accelerated growth (T. macedonicus) or development (T. ivanbureschi). Warm conditions also had different effects on the oxidative status of hybrid and parental species. Parental species had enhanced antioxidant responses (catalase, glutathione peroxidase, glutathione S-transferase and SH groups), which allowed them to alleviate temperature-induced stress (revealed by the absence of oxidative damage). However, warming induced an antioxidant response in the hybrids, including oxidative damage in the form of lipid peroxidation. These findings point to a greater disruption of redox regulation and metabolic machinery in hybrid newts, which can be interpreted as the cost of hybridization that is likely linked to parental incompatibilities expressed under a higher temperature. Our study aims to improve mechanistic understanding of the resilience and distribution of hybrid species that cope with climate-driven changes.

Prognostic Role of Vascular Endothelial Growth Factor and Correlation with Oxidative Stress Markers in Locally Advanced and Metastatic Ovarian Cancer Patients

BACKGROUND

Vascular endothelial growth factor (VEGF) plays an important role in tumor progression in ovarian cancer, but the complex mechanism and interaction with oxidative stress are not fully understood.

METHODS

A prospective study included 52 patients with ovarian adenocarcinoma stage IIIA-IV. Serum VEGF and reactive oxygen species (ROS) such as malondialdehyde and ceruloplasmin were measured.

RESULTS

VEGF levels were elevated (mean 1014.7 ± 165 pg/mL), especially in patients with macroscopic residual disease (1058 vs. 810 pg/mL, p = 0.0001). Median progression-free survival (PFS) and overall survival (OS) were 6 and 40 months in patients with a very high VEGF (over 1200 pg/mL), 11 and 48 months in patients with VEGF between 1000-1200 pg/mL, 18 and 84 months in patients with VEGF between 800-1000 pg/mL, and not reached in patients with normal VEGF. Increased VEGF values were associated with a 2.6-fold increased risk of disease progression (HR = 2.60, 95% CI 1.69-3.99), and a 1.4-fold increased risk of death (HR = 1.4, 95% CI 1.15-1.91, p = 0.002). Receiver operator characteristic (ROC) curves were used to validate VEGF as a prognostic factor and the area under the curve (AUC) was 0.814, p = 0.036 for PFS and 0.729, p = 0.043, for OS. There was a positive correlation between VEGF and malondialdehyde, Pearson coefficient of 0.35, p = 0.0001.

CONCLUSIONS

VEGF and malondialdehyde are important prognostic markers in ovarian cancer, especially in macroscopic residual disease, and there is a positive correlation between angiogenesis and oxidative stress.

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.

Of telomeres and temperature: Measuring thermal effects on telomeres in ectothermic animals

Ectotherms are classic models for understanding life-history tradeoffs, including the reproduction-somatic maintenance tradeoffs that may be reflected in telomere length and their dynamics. Importantly, life-history traits of ectotherms are tightly linked to their thermal environment, with diverse or synergistic mechanistic explanations underpinning the variation. Telomere dynamics potentially provide a mechanistic link that can be used to monitor thermal effects on individuals in response to climatic perturbations. Growth rate, age and developmental stage are all affected by temperature, which interacts with telomere dynamics in complex and intriguing ways. The physiological processes underpinning telomere dynamics can be visualized and understood using thermal performance curves (TPCs). TPCs reflect the evolutionary history and the thermal environment during an individual's ontogeny. Telomere maintenance should be enhanced at or near the thermal performance optimum of a species, population and individual. The thermal sensitivity of telomere dynamics should reflect the interacting TPCs of the processes underlying them. The key processes directly underpinning telomere dynamics are mitochondrial function (reactive oxygen production), antioxidant activity, telomerase activity and telomere endcap protein status. We argue that identifying TPCs for these processes will significantly help design robust, repeatable experiments and field studies of telomere dynamics in ectotherms. Conceptually, TPCs are a valuable framework to predict and interpret taxon- and population-specific telomere dynamics across thermal regimes. The literature of thermal effects on telomeres in ectotherms is sparse and mostly limited to vertebrates, but our conclusions and recommendations are relevant across ectothermic animals.

Implications of Salinity and Acidic Environments on Fitness and Oxidative Stress Parameters in Early Developing Seahorses Hippocampus reidi

Water acidification affects aquatic species, both in natural environmental conditions and in ex situ rearing production systems. The chronic effects of acidic conditions (pH 6.5 vs. pH 8.0) in seahorses (Hippocampus spp.) are not well known, especially when coupled with salinity interaction. This study investigated the implications of pH on the growth and oxidative stress in the seahorse Hippocampus reidi (Ginsburg, 1933), one of the most important seahorse species in the ornamental trade. Two trials were carried out in juveniles (0-21 and 21-50 DAR-days after the male's pouch release) reared under acid (6.5) and control (8.0) pH, both in brackish water (BW-salinity 11) and seawater (SW-salinity 33). In the first trial (0-21 DAR), there was no effect of pH on the growth of seahorses reared in SW, but the survival rate was higher for juveniles raised in SW at pH 6.5. However, the growth and survival of juveniles reared in BW were impaired at pH 6.5. Compared to SW conditions, the levels of superoxide dismutase and DT-diaphorase, as well as the oxidative stress index, increased for juveniles reared in BW. In the second trial, seahorse juveniles were reared in SW at pH 8.0, and subsequently kept for four weeks (from 21 to 50 DAR) at pH 6.5 and 8.0. The final survival rates and condition index were similar in both treatments. However, the growth under acidic conditions was higher than at pH 8.0. In conclusion, this study highlights that survival, growth, and oxidative status condition was enhanced in seahorse juveniles reared in SW under acidic conditions (pH = 6.5). The concurrent conditions of acidic pH (6.5) and BW should be avoided due to harmful effects on the fitness and development of seahorse juveniles.

Mothers modify the cost of reproduction by dynamic changes in antioxidant function and filial cannibalism

Investment in current reproduction may negatively influence subsequent fitness. Oxidative stress has been proposed as a potential mediator of this trade-off between current and future reproductive success. However, evidence of reproduction causing oxidative stress is limited, possibly owing to compensatory mechanisms that counteract oxidative insults. Here we test the idea that organisms protect against oxidative challenges through a dynamic interaction between behavioural and physiological adjustments at different stages of reproduction. To test this idea, we manipulated maternal care in the mouthbrooding cichlid fish Astatotilapia burtoni by allowing females to continue care (brooders) or by preventing care (non-brooders). We found that brooders depleted the pool of antioxidants as brood care progressed; however, we only observed increased oxidative DNA damage at the early stage of care relative to non-brooders, possibly owing to upregulated antioxidant protection during later stages of care. Most brooders adjusted parental investment by consuming some of their offspring during mouthbrooding. Intriguingly, the level of filial cannibalism was positively related to liver antioxidant function. These changes in antioxidant function and filial cannibalism allow parents to manage the cost of reproduction and are important for our understanding of how oxidative stress mediates life-history trade-offs.

Early life parameters and personality affect oxidative status during adulthood in an altricial rodent

It is increasingly recognized that alterations of the cellular oxidative status might be an important cost underlying challenging early life conditions. For example, an increased litter size can impose challenges as the offspring will face increased competition for maternal resources. Within a litter, individuals with relatively higher starting mass typically show higher growth rates, which can lead to increased oxidative damage. We investigated the long-term consequences of these early life parameters on the oxidative status in mature mound-building mice (Mus spicilegus). Individual differences in the animals' exploration tendency were assessed by repeated open field and novel object tests. We predicted less exploratory phenotypes, which typically show a higher stress responsiveness, to be particularly susceptible to possible effects of these early life parameters on oxidative status. We quantified oxidative damage of DNA (8-hydroxy-2'-deoxyguanosine levels, 8-OHdG) and proteins (protein carbonyl content, PCC), and activities of the antioxidants catalase (CAT), glutathione peroxidase (GPx), and superoxide dismutase (SOD) in liver and skeletal muscle tissue. 8-OHdG levels were positively associated with CAT and SOD in both tissues, indicating that increased oxidative DNA damage was associated with an upregulation of antioxidant production. Hepatic DNA damage after maturity was increased in animals from larger litters. In less exploratory animals, DNA damage and the activity of CAT and SOD in the muscle were increased, but only in individuals with higher relative starting mass (measured on postnatal day 9). This interaction may be explained by the typically higher adrenocortical activity in less exploratory phenotypes and by the higher growth in relatively heavier pups, two factors known to increase oxidative stress. These findings contribute to enlightening the complex interplay between early life conditions, personality, and oxidative status.

Defining the link between oxidative stress, behavioural reproductive suppression and heterothermy in the Natal mole-rat (Cryptomys hottentotus natalensis)

Sub-lethal effects, such as oxidative stress, can be linked to various breeding and thermophysiological strategies, which themselves can be linked to seasonal variability in abiotic factors. In this study, we investigated the subterranean, social living Natal mole-rat (Cryptomys hottentotus natalensis), which, unlike other social mole-rat species, implements heterothermy seasonally in an attempt to avoid exercise-induced hyperthermia and relies solely on behavioural reproductive suppression to maintain reproductive skew in colonies. Subsequently, we investigated how oxidative stress varied between season, sex and breeding status in Natal mole-rats. Oxidative markers included total oxidant status (TOS measure of total peroxides present), total antioxidant capacity (TAC), OSI (oxidative stress index) and malondialdehyde (MDA) to measure oxidative stress. Breeding and non-breeding mole-rats of both sexes were captured during the summer (wet season) and winter (dry season). Seasonal environmental variables (air temperature, soil temperature and soil moisture) had a significant effect on TOS, OSI and MDA, where season affected each sex differently. Unlike other social mole-rat species that use both physiological and behavioural means of reproductive suppression, no oxidative costs to reproduction were present in the Natal mole-rats. Males had significantly higher MDA than females, which was most apparent in summer (wet season). We conclude that the significant oxidative damage in males is a consequence of exercise-induced oxidative stress, exacerbated by increased burrow humidities and poorer heat dissipation abilities as a function of body mass. This study highlights the importance of both breeding and thermophysiological strategies in affecting oxidative stress.

Markers of Oxidative Stress in Obstetrics and Gynaecology-A Systematic Literature Review

Oxidative stress has been implicated in many diseases, including reproductive and pregnancy disorders, from subfertility to maternal vascular disease or preterm labour. There is, however, discrepancy within the standardized markers of oxidative stress in obstetrics and gynaecology in clinical studies. This review aims to present the scope of markers used between 2012 and 2022 to describe oxidative stress with regard to reproduction, pregnancy, and pregnancy-related issues. Despite the abundance of evidence, there is no consensus on the set of standardised markers of oxidative stress which poses a challenge to achieve universal consensus in order to appropriately triangulate the results.

Activities of Antioxidant and Proteolytic Systems and Biomarkers in the Fat Body and Hemolymph of Young Apis mellifera Females

Simple Summary

The proteolytic system consists of compounds that, similar to “scissors”, cut proteins found in bee cells (e.g., to activate these proteins) or released by pathogens. During these reactions, reactive oxygen species are created and then removed by antioxidants. The actions of the proteolytic and antioxidant systems are enhanced by biomarkers. These compounds are produced mainly in the fat body and then released into the hemolymph. We determined the activities of these compounds in various localizations/segments of the fat body and in the hemolymph in females with increased reproductive potential, i.e., queens and rebels, and in normal (sterile non-rebel) workers. Rebels are workers who resemble the queen in terms of anatomical, behavioural, and physiological features. It was revealed that the activities of these compounds in the rebels were between those of queens and normal workers. Normal workers had higher activities of the proteolytic and antioxidant systems in the fat body and hemolymph than the other females. These results are important for understanding the functioning of the fat body, the stress ecology, and the formation of the different castes of Apis mellifera females.

Abstract

The proteolytic and antioxidant systems are important components of humoral immunity, and these biomarkers indicate the immune status. These compounds are synthesized in the bees’ fat body and released into the hemolymph. Their functions maintain the organism’s homeostasis and protect it against adverse environmental factors (including pathogens). We determined the activities of acidic, neutral, and alkaline proteases and their inhibitors, as well as superoxide dismutase (SOD), catalase (CAT), aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), and the level of total antioxidant potential (TAC). These compounds were investigated in the fat body and hemolymph in the females with increased reproductive potential, i.e., queens and rebels, and in normal (non-reproductive sterile non-rebel) workers. The phenoloxidase (PO) activities were determined in the hemolymph. The normal workers had higher activities of proteases and their inhibitors, SOD and CAT, in the fat body and hemolymph, compared to the queens and rebels. The protease inhibitors were not usually active in the queens. As we predicted, the rebels revealed values between those of the queens and normal workers. The highest activities of proteases and antioxidants were identified in the fat body from the third tergite in comparison with the sternite and the fifth tergite. These results are important for oxidative stress ecology and give a better understanding of the functioning of the fat body and the division of labor in social insects.

A meta-analysis of impacts of immune response and infection on oxidative status in vertebrates

Inferring from patterns observed in biomedical research, ecoimmunological theory predicts that oxidative stress is a ubiquitous physiological cost that contributes to generating variation in immune function between individuals or species. This prediction is, however, often challenged by empirical studies testing the relationship between immune response or infection and oxidative status markers. This points out the importance of combining ecological immunology and oxidative stress ecology to further our understanding of the proximate causes and fitness consequences of individual variation in health, and adaptability to natural and anthropogenic environmental changes. I reviewed evidence and performed phylogenetic meta-analyses of changes in oxidative status markers owing to either injection of an antigen or infection in captive and free-living vertebrates (141 studies, 1262 effect sizes, 97 species). The dataset was dominated by studies on fish, birds and mammals, which provided 95.8% of effect sizes. Both antigen injection and parasite exposure were associated with changes of oxidative status. There were significant effects of taxonomic class and experimental environment (captivity vs. wild). In contrast with my predictions, age category (young vs. adult), study design (correlational vs. experimental) and proxies of pace of life (clutch size, litter size, and body mass; for birds and mammals only) were negligible in this dataset. Several methodological aspects (type of immunostimulant, laboratory assay, tissue analysed) showed significant effects on both strength and direction of effect. My results suggest that alterations of oxidative status are a widespread consequence of immune function across vertebrates. However, this work also identified heterogeneity in strength and direction of effect sizes, which suggests that immune function does not necessarily result in oxidative stress. Finally, this work identifies methodological caveats that might be relevant for the interpretation and comparability of results and for the application in conservation programs.

Changes in antioxidant enzyme levels following capture in juvenile American Alligators (Alligator mississippiensis) are tissue dependent

Many parameters used to investigate stress in vertebrates are temporally sensitive. The act of capture and sampling can influence them, hindering their functionality for evaluating the effects of stressors. Consequently, the investigation and subsequent incorporation of less time sensitive parameters are necessary to better evaluate stressors affecting vertebrates. In this study, we investigated how capture stress and handling associated with sampling influences antioxidant status in American Alligators (Alligator mississippiensis, Daudin, 1802; hereafter Alligator), long-lived, top-trophic carnivores found in the southeastern United States, by measuring levels of two antioxidant enzymes in destructive (brain and pancreas) and nondestructive (tail scutes) tissues: superoxide-dismutase-1 (SOD1) and glutathione peroxidase-1 (GPX1). Capture stress had no effect on pancreatic SOD1 and no effect on brain and pancreatic GPX1 (all p > 0.05). However, brain SOD1, scute SOD1, and scute GPX1 were all impacted by capture stress. These disparate results illustrate that the influence of capture stress on antioxidant enzymes in Alligators is tissue and marker dependent, necessitating further investigation. Our results provide a firm foundation to further investigate oxidative status in crocodilians.

Two stressors are worse than one: combined heatwave and drought affect hydration state and glucocorticoid levels in a temperate ectotherm

Heatwaves and droughts are becoming more intense and frequent with climate change. These extreme weather events often occur simultaneously and may alter organismal physiology, yet their combined impacts remain largely unknown. Here, we experimentally investigated physiological responses of a temperate ectotherm, the asp viper (Vipera aspis), to a simulated heatwave and drought. We applied a two-by-two factorial design by manipulating the daily temperature cycle (control vs. heatwave) and the water availability (water available vs. water-deprived) over a month followed by exposure to standard thermal conditions with ad libium access to water. Simulated heatwave and water deprivation additively increased mass loss, while water deprivation led to greater plasma osmolality (dehydration). Mass gain from drinking after the treatment period was higher in vipers from the heatwave and water-deprived group suggesting that thirst was synergistically influenced by thermal and water constraints. Heatwave conditions and water deprivation also additively increased baseline corticosterone levels but did not influence basal metabolic rates and plasma markers of oxidative stress. Our results demonstrate that a short-term exposure to combined heatwave and drought can exacerbate physiological stress through additive effects, and interactively impact behavioral responses to dehydration. Considering combined effects of temperature and water availability is thus crucial to assess organismal responses to climate change.

Chronic stress and captivity alter the cloacal microbiome of a wild songbird

There are complex interactions between an organism's microbiome and its response to stressors, often referred to as the “gut-brain axis;” however, the ecological relevance of this axis in wild animals remains poorly understood. Here, we used a chronic mild stress protocol to induce stress in wild-caught house sparrows (Passer domesticus), and compared microbial communities among stressed animals, those recovering from stress, captive controls (unstressed), and a group not brought into captivity. We assessed changes in microbial communities and abundance of shed microbes by culturing cloacal samples on multiple media to select for aerobic and anaerobic bacteria and fungi. We complemented this with cultivation-independent 16S and ITS rRNA gene amplification and sequencing, pairing these results with host physiological and immune metrics, including body mass change, relative spleen mass, and plasma corticosterone concentrations. We found significant effects of stress and captivity on the house sparrow microbiomes, with stress leading to an increased relative abundance of endotoxin-producing bacteria— a possible mechanism for the hyperinflammatory response observed in captive avians. While we found evidence that the microbiome community partially recovers after stress cessation, animals may lose key taxa, and the abundance of endotoxin-producing bacteria persists. Our results suggest an overall link between chronic stress, host immune system, and the microbiome, with the loss of potentially beneficial taxa (e.g., lactic acid bacteria), and an increase in endotoxin-producing bacteria due to stress and captivity. Ultimately, consideration of the host's microbiome may be useful when evaluating the impact of stressors on individual and population health.

Positive Aspects of Oxidative Stress at Different Levels of the Human Body: A Review

Oxidative stress is the subject of numerous studies, most of them focusing on the negative effects exerted at both molecular and cellular levels, ignoring the possible benefits of free radicals. More and more people admit to having heard of the term "oxidative stress", but few of them understand the meaning of it. We summarized and analyzed the published literature data in order to emphasize the importance and adaptation mechanisms of basal oxidative stress. This review aims to provide an overview of the mechanisms underlying the positive effects of oxidative stress, highlighting these effects, as well as the risks for the population consuming higher doses than the recommended daily intake of antioxidants. The biological dose-response curve in oxidative stress is unpredictable as reactive species are clearly responsible for cellular degradation, whereas antioxidant therapies can alleviate senescence by maintaining redox balance; nevertheless, excessive doses of the latter can modify the redox balance of the cell, leading to a negative outcome. It can be stated that the presence of oxidative status or oxidative stress is a physiological condition with well-defined roles, yet these have been insufficiently researched and explored. The involvement of reactive oxygen species in the pathophysiology of some associated diseases is well-known and the involvement of antioxidant therapies in the processes of senescence, apoptosis, autophagy, and the maintenance of cellular homeostasis cannot be denied. All data in this review support the idea that oxidative stress is an undesirable phenomenon in high and long-term concentrations, but regular exposure is consistent with the hormetic theory.

Fat Stores and Antioxidant Capacity Affect Stopover Decisions in Three of Four Species of Migratory Passerines With Different Migration Strategies: An Experimental Approach

During migratory stopovers, birds must make decisions about when and where to travel and these decisions are likely contingent on their fuel stores, food availability, and antioxidant capacity as well as seasonal changes in key environmental factors. We conducted a field experiment on an offshore stopover site (Block Island, Rhode Island, United States: 41°130N, 71°330W) during autumn migration to test the hypothesis that birds with greater fuel stores and non-enzymatic antioxidant capacity have shorter stopovers than lean birds with low antioxidant capacity, and to determine the extent to which this depends on migration strategy. We used a 2 × 2 factorial field experiment (two levels each of available food and dietary polyphenols) with four species of songbirds kept in captivity for 3–5 days to produce experimental groups with different fuel stores and antioxidant capacity. We attached digital VHF transmitters to assess stopover duration and departure direction using automated telemetry. Non-enzymatic antioxidant capacity increased during refueling for Red-eyed Vireos (Vireo olivaceus) and Blackpoll Warblers (Setophaga striata) fed ad lib diets, and for ad lib fed Hermit Thrushes (Catharus guttatus) supplemented with polyphenols, but not for Yellow-rumped Warblers (Setophaga coronata coronata). Glutathione peroxidase (GPx) decreased during captivity and was influenced by dietary treatment only in Red-eyed Vireos. Oxidative damage decreased during captivity for all species except Yellow-rumped Warblers. Stopover duration was shorter for Vireos and Blackpolls fed ad lib as compared to those fed maintenance. Ad lib fed Hermit Thrushes supplemented with polyphenols had shorter stopovers than those fed ad lib, as did thrushes fed at maintenance and supplemented with polyphenols compared with those fed at maintenance alone. There was no influence of condition on stopover duration for Yellow-rumped Warblers. Departure direction was not strongly related to condition, and birds primarily reoriented north when departing Block Island. Thus, fat stores and oxidative status interacted to influence the time passerines spent on stopover, and condition-dependent departure decisions were related to a bird’s migration strategy. Therefore, seasonal variation in macro- and micro-nutrient resources available for refueling at stopover sites can affect body condition and antioxidant capacity and in turn influence the timing and success of migration.

Rates of warming impact oxidative stress in zebrafish (Danio rerio)

Potentially negative effects of thermal variation on physiological functions may be modulated by compensatory responses, but their efficacy depends on the timescale of phenotypic adjustment relative to the rate of temperature change. Increasing temperatures in particular can affect mitochondrial bioenergetics and rates of reactive oxygen species (ROS) production. Our aim was to test whether different rates of temperature increase impact mitochondrial bioenergetics and modulate oxidative stress. We exposed zebrafish (Danio rerio) to warming from 20 to 28°C over 3, 6, 24, or 48 h, and compared these to a control group that was kept at constant 20°C. Fish exposed to the fastest (3 h) and slowest (48 h) rates of warming had significantly higher rates of H2O2 production relative to the control treatment, and the proportion of O2 converted to H2O2 (H2O2/O2 ratio) was significantly greater in these groups. However, ROS production was not paralleled by differences in mitochondrial substrate oxidation rates, leak respiration rates, or coupling (respiratory control ratios). Increased rates of ROS production did not lead to damage of proteins or membranes, which may be explained by a moderate increase in catalase activity at the fastest, but not the slowest rate of warming. The increase in ROS production at the slowest rate of heating indicates that even seemingly benign environments may be stressful. Understanding how animals respond to different rates of temperature change is important, because the rate determines the time period for phenotypic adjustments and it also alters the environmental thermal signal that triggers compensatory pathways.

Aminomethylphosphonic acid (AMPA) alters oxidative status during embryonic development in an amphibian species

Glyphosate's primary metabolite (aminomethylphosphonic acid, AMPA) is known to alter embryonic development at environmentally relevant concentrations in amphibians. However, we have limited understanding of the physiological mechanisms through which AMPA affects organisms. In this study, we tested whether alteration of the oxidative status is one mechanism through which AMPA affects organism performance. To this end, we analysed several oxidative status markers in hatchling tadpoles that were exposed to sublethal concentrations of AMPA during embryonic development (~16 days). We compared the influence of environmentally relevant concentrations of AMPA (from 0.07 to 3.57 μg l^-1) on the relation between developmental traits (i.e, embryonic development duration, embryonic mortality and hatchling size) and oxidative status markers known to alter homeostasis when unbalanced (superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), thiols and ratios thereof). We included measures of telomere length as an indicator of physiological state. We found that AMPA concentrations induce non-monotonic effects on some oxidative status markers with hatchlings displaying elevated antioxidant responses (elevated thiols and unbalanced SOD/(GPx + CAT) ratio). The lack of effect of AMPA on the relation between developmental traits, oxidative status and telomere length suggests that selective mortality of embryos susceptible to oxidative stress may have occurred prior to hatching in individuals less resistant to AMPA which display lower hatching success. Future studies are required to disentangle whether oxidative unbalance is a cause or a consequence of AMPA exposition. This study highlights the need to investigate effects of the metabolites of contaminants at environmental concentrations to comprehensively assess impacts of anthropogenic contamination on wildlife.

Flight and dietary antioxidants influence antioxidant expression and activity in a migratory bird

Ecologically relevant factors such as exercise and diet quality can directly influence how physiological systems work including those involved in maintaining oxidative balance; however, to our knowledge, no studies to date have focused on how such factors directly affect expression of key components of the endogenous antioxidant system (i.e., transcription factors, select antioxidant genes, and corresponding antioxidant enzymes) in several metabolically active tissues of a migratory songbird. We conducted a three-factor experiment that tested the following hypotheses: (H1) Daily flying over several weeks increases the expression of transcription factors NRF2 and PPARs as well as endogenous antioxidant genes (i.e., CAT, SOD1, SOD2, GPX1, GPX4), and upregulates endogenous antioxidant enzyme activities (i.e., CAT, SOD, GPx). (H2) Songbirds fed diets composed of more 18:2n-6 PUFA are more susceptible to oxidative damage and thus upregulate their endogenous antioxidant system compared with when fed diets with less PUFA. (H3) Songbirds fed dietary anthocyanins gain additional antioxidant protection and thus upregulate their endogenous antioxidant system less compared with songbirds not fed anthocyanins. Flight training increased the expression of 3 of the 6 antioxidant genes and transcription factors measured in the liver, consistent with H1, but for only one gene (SOD2) in the pectoralis. Dietary fat quality had no effect on antioxidant pathways (H2), whereas dietary anthocyanins increased the expression of select antioxidant enzymes in the pectoralis, but not in the liver (H3). These tissue-specific differences in response to flying and dietary antioxidants are likely explained by functional differences between tissues as well as fundamental differences in their turnover rates. The consumption of dietary antioxidants along with regular flying enables birds during migration to stimulate the expression of genes involved in antioxidant protection likely through increasing the transcriptional activity of NRF2 and PPARs, and thereby demonstrates for the first time that these relevant ecological factors affect the regulation of key antioxidant pathways in wild birds. What remains to be demonstrated is how the extent of these ecological factors (i.e., intensity or duration of flight, amounts of dietary antioxidants) influences the regulation of these antioxidant pathways and thus oxidative balance.

Do low molecular weight antioxidants contribute to the Protection against oxidative damage? The interrelation between oxidative stress and low molecular weight antioxidants based on data from the MARK-AGE study

A redox steady state is important in maintaining vital cellular functions and is therefore homeostatically controlled by a number of antioxidative agents, the most important of which are enzymes. Oxidative Stress (OS) is associated with (or/and caused by) excessive production of damaging reactive oxygen and/or nitrogen species (ROS, RNS), which play a role in many pathologies. Because OS is a risk factor for many diseases, much effort (and money) is devoted to early diagnosis and treatment of OS. The desired benefit of the "identify (OS) and treat (by low molecular weight antioxidants, LMWA)" approach is to enable selective treatment of patients under OS. The present work aims at gaining understanding of the benefit of the antioxidants based on interrelationship between the concentration of different OS biomarkers and LMWA. Both the concentrations of a variety of biomarkers and of LMWA were previously determined and some analyses have been published by the MARK-AGE team. For the sake of simplicity, we assume that the concentration of an OS biomarker is a linear function of the concentration of a LMWA (if the association is due to causal relationship). A negative slope of this dependence (and sign of the correlation coefficient) can be intuitively expected for an antioxidant, a positive slope indicates that the LMWA is pro-oxidative, whereas extrapolation of the OS biomarker to [LMWA] = 0 is an approximation of the concentration of the OS biomarker in the absence of the LMWA. Using this strategy, we studied the effects of 12 LMWA (including tocopherols, carotenoids and ascorbic acid) on the OS status, as observed with 8 biomarkers of oxidative damage (including malondialdehyde, protein carbonyls, 3-nitrotyrosine). The results of this communication show that in a cross-sectional study the LMWA contribute little to the redox state and that different "antioxidants" are very different, so that single LMWA treatment of OS is not scientifically justified assuming our simple model. In view of the difficulty of quantitating the OS and the very different effects of various LMWA, the use of the "identify and treat" approach is questionable.

The Cost of Reproduction in a Cooperatively Breeding Mammal: Consequences of Seasonal Variation in Rainfall, Reproduction, and Reproductive Suppression

Biological investments, such as reproduction, are influenced by both biotic and abiotic factors and their interactions. The trade-off between reproduction and survival has been well established. Seasonally breeding species, therefore, may exhibit variations in these trade-offs, but there is a dearth of knowledge concerning this. This study investigated the physiological cost of reproduction (measured through oxidative stress) across seasons in the cooperatively breeding highveld mole-rat (Cryptomys hottentotus pretoriae), one of the few seasonal breeding mole-rats. Oxidative stress indicates elevated reactive oxygen species (ROS) levels, which can overwhelm antioxidant defences resulting in damaged proteins, lipids and DNA, which overall can reduce longevity and compromise reproduction. Oxidative markers such as total oxidant status (TOS-measure of total peroxides present), total antioxidant capacity (TAC), oxidative stress index (OSI), and malondialdehyde (MDA) are utilised to measure oxidative stress. In this study, breeding and non-breeding male (NBM) and female mole-rats were captured during the dry season (breeding period) and wet season (non-breeding period). There was an apparent cost of reproduction in the highveld mole-rat; however, the seasonality pattern to the cost of reproduction varied between the sexes. Breeding females (BFs) had significantly higher MDA during the breeding period/dry season in comparison to the non-breeding period/wet season; this is possibly a consequence of bearing and nursing offspring. Contrastingly, breeding males (BMs) showed increased oxidative damage in the non-breeding/wet season compared to the breeding/dry season, possibly due to increased activities of protecting their mating rights for the next breeding/dry season, but this was not significant. Interestingly, during the non-breeding period/wet season, non-breeding females (NBFs) are released from their reproductive suppression, which resulted in increases in TOS and OSI, which again indicated that just the mere ability to be able to breed results in a cost (oxidative stress). Therefore we can speculate that highveld mole-rats exhibited seasonal variation in redox balance brought about by variation in abiotic variables (e.g., rainfall), physiology and behaviour. We conclude that physiological changes associated with reproduction are sufficient to induce significant acute oxidative stress in the plasma of female highveld mole-rats, which become alleviated following transition to the non-breeding season/wet period suggesting a possible hormetic effect.

The dinoflagellate Alexandrium affine acutely induces significant modulations on innate immunity, hepatic function, and antioxidant defense system in the gill and liver tissues of red seabream

Alexandrium affine is a global harmful algal bloom (HAB)-forming dinoflagellate. In this study, the effect of non-toxin-producing A. affine on the gill and liver tissues of red seabream, Pagrus major, was analyzed over 24 h exposure and 2 h depuration phases. After exposure to three concentrations of A. affine (4,000, 6,000, and 7,000 cells mL^-1), survival rates, respiration rates, immunities (lysozyme, total Ig), hepatic biomarkers (alanine aminotransferase, ALT; aspartate aminotransferase, AST; and alkaline phosphatase, ALP), lipid peroxidation (malondialdehyde, MDA), and antioxidant defense systems (glutathione, GSH; catalase, CAT; superoxide dismutase, SOD; glutathione peroxidases, GPx; and glutathione reductase, GR) were analyzed in gill and liver tissues. Dose-dependent decreases in survival and respiration rates were detected in red seabream. A. affine levels of to 6,000 and 7,000 cells mL^-1 induced immunosuppression and hepatic impairment in both tissues, as measured by significant decreases in lysozyme activity, total Ig level, ALT, AST, and ALP content. The levels of GSH, CAT, SOD, GPx, and GR were significantly decreased in the gills and liver in response to 7,000 cells mL^-1 of A. affine at 24 h, and MDA was elevated. However, different response patterns were observed between tissues in response to 4,000 cells mL^-1. Activity of antioxidant defense enzymes was significantly elevated in the liver but decreased in the gills. This suggests that the gills were more vulnerable than the liver. In the case of 6,000 and 7,000 cells mL^-1 treatments, higher susceptibility was also detected at 3 h in the gill compared to the overall responses of each parameter measured in liver. Taken together, direct attachment of A. affine to the gill tissue strongly affects immunity and antioxidant capacity of red seabream even after a short exposure period. These results could be helpful for understanding HAB-mediated effects in marine fish.

How Birds During Migration Maintain (Oxidative) Balance

Animals dynamically adjust their physiology and behavior to survive in changing environments, and seasonal migration is one life stage that demonstrates these dynamic adjustments. As birds migrate between breeding and wintering areas, they incur physiological demands that challenge their antioxidant system. Migrating birds presumably respond to these oxidative challenges by up-regulating protective endogenous systems or accumulating dietary antioxidants at stopover sites, although our understanding of the pre-migration preparations and mid-migration responses of birds to such oxidative challenges is as yet incomplete. Here we review evidence from field and captive-bird studies that address the following questions: (1) Do migratory birds build antioxidant capacity as they build fat stores in preparation for long flights? (2) Is oxidative damage an inevitable consequence of oxidative challenges such as flight, and, if so, how is the extent of damage affected by factors such as the response of the antioxidant system, the level of energetic challenge, and the availability of dietary antioxidants? (3) Do migratory birds ‘recover’ from the oxidative damage accrued during long-duration flights, and, if so, does the pace of this rebalancing of oxidative status depend on the quality of the stopover site? The answer to all these questions is a qualified ‘yes’ although ecological factors (e.g., diet and habitat quality, geographic barriers to migration, and weather) affect how the antioxidant system responds. Furthermore, the pace of this dynamic physiological response remains an open question, despite its potential importance for shaping outcomes on timescales ranging from single flights to migratory journeys. In sum, the antioxidant system of birds during migration is impressively dynamic and responsive to environmental conditions, and thus provides ample opportunities to study how the physiology of migratory birds responds to a changing and challenging world.