Prenatal exposure to triclosan induced brain telomere shortening in a wild bird species

Exposure to the antimicrobial agent Triclosan (TCS) induces oxidative stress in diverse organisms, including birds. However, whether TCS-induced oxidative stress effectively translates into detrimental effects is still unclear. The present study examined whether prenatal TCS exposure induces oxidative stress and telomere shortening in the brain and the liver of near-term embryos of the yellow-legged gull (Larus michahellis). Prenatal TCS exposure caused a significant overproduction of reactive oxygen species (ROS) in the brain, but no oxidative damage occurred. Telomeres of TCS-exposed embryos had brain telomeres 30 % shorter compared to controls, probably because the relatively modest antioxidant defenses of this organ during prenatal development cannot counteract the impact of the TCS-induced ROS. No telomere shortening was observed in the liver. Our results demonstrated that prenatal exposure to TCS in wild bird species can modulate the oxidative status and induce telomere shortening in the brain of the yellow-legged gull embryos.

Fluorescent Heme Degradation Products Are Biomarkers of Oxidative Stress and Linked to Impaired Membrane Integrity in Avian Red Blood Cells

Oxidative stress is generally understood to be an important mediator of life-history traits, yet the specific relationships between oxidative stress and life-history traits have been difficult to describe because there is often a lack of covariation among biomarkers of oxidative stress. For instance, although oxidative damage to red blood cell (RBC) membranes can lead to pathological conditions (i.e., anemia), in some cases there is not a clear relationship between lipid oxidation and RBC membrane resistance to pro-oxidants. Alternatively, oxidative damage to hemoglobin may be an indirect mechanism contributing to RBC membrane damage. To better understand the mechanisms contributing to oxidative damage and probe new approaches to measuring oxidative stress, we used a series of in vitro and in vivo procedures in zebra finches (Taeniopygia guttata) to explore (1) whether avian RBCs exposed to a pro-oxidant generate fluorescent heme degradation products (HDPs), (2) whether HDPs interact with RBC membranes, and (3) whether HDPs are linked to impaired RBC integrity. We found that finch RBCs exposed in vitro to hydrogen peroxide produced fluorescent HDPs and HDPs associated with RBC membranes. Exposure to hydrogen peroxide also caused a reduction in hemoglobin and an increase in percent methemoglobin (a hemoglobin oxidation product), further indicating hemoglobin degradation. Moreover, HDP fluorescence correlated with impaired membrane integrity and erythrocyte osmotic fragility in vivo. This study suggests that reactive oxygen species may indirectly impair RBC membrane integrity via hemoglobin degradation products that associate with RBC membranes and that HDPs may be an inexpensive and logistically simple tool for measuring oxidative stress.

Prenatal independent and combined effects of yolk vitamin E and corticosterone on embryo growth and oxidative status in the yellow-legged gull

Variation in the concentration of antioxidants and hormones of maternal origin in the eggs of birds can have a profound influence on offspring phenotype both prenatally and postnatally. Egg maternal substances can have interacting effects, but experimental studies of the consequences of the combined variation in the egg concentration of such molecules are extremely rare, particularly as far as prenatal stages are concerned. We manipulated the yolk concentration of vitamin E and corticosterone, which are, respectively, the main antioxidant and the main glucocorticoid hormone in bird eggs, both independently and simultaneously, and we tested their separate and combined effects on growth and oxidative status in the liver and in the brain of yellow-legged gull (Larus michahellis) embryos. Egg supplementation of relatively large physiological doses of corticosterone depressed embryo growth (total body mass, tarsus length and liver mass), whereas administration of vitamin E in association with corticosterone restored normal growth. Vitamin E did not affect embryo growth when administered alone. We further analysed the independent and combined effects of vitamin E and corticosterone on liver and brain total antioxidant capacity, the concentration of reactive oxygen molecules and lipid peroxidation. Vitamin E significantly reduced liver total antioxidant capacity, while corticosterone depressed brain lipid peroxidation. Prenatal exposure to vitamin E and corticosterone appears to have antagonistic effects on body growth, although vitamin E is not limiting in yellow-legged gull eggs. In combination with the results of previous experiments on the same species applying smaller experimental doses or focusing on the postnatal rather than prenatal life stages, our findings indicate that the effects of a physiological increase in the egg concentration of these substances can be life stage and dose specific, implying that generalizing prenatal effects of egg compounds may not be feasible.

Independent and combined effects of egg pro- and anti-oxidants on gull chick phenotype

Oviparous mothers transfer to their eggs components that have both independent and combined effects on offspring phenotype. The functional interaction between egg components, such as antioxidants and hormones, suggests that a change in the concentration of one component will have effects on offspring traits that depend on the concentration of other interacting components. However, the combined effects of variation in different egg components are virtually unknown. Bird eggs contain vitamin E, a major antioxidant, and also maternal corticosterone. The independent consequences of variation in the egg concentrations of these compounds for offspring phenotype are largely unknown and no study has investigated their combined effects. We manipulated the concentration of vitamin E and corticosterone in the eggs of the yellow-legged gull (Larus michahellis) by administering a physiological (2 s.d.) dose both independently and in combination. We tested for an effect on chick post-natal growth, plasma antioxidant capacity (TAC) and oxidative compounds (TOS). Separate administration of vitamin E or corticosterone caused a reduction in body mass relative to controls, whereas the combined administration of the two compounds reversed their negative effects. These results suggest that maternal egg components, such as antioxidants and steroid hormones, interact and mothers must balance their concentrations in order to achieve optimal offspring phenotype. The functional relationship between vitamin E and corticosterone is corroborated by the observation of positive covariation between these compounds.

Effects of egg weight and in ovo injection of <i>α</i>-tocopherol on chick development, hatching performance, and lipid-soluble antioxidant concentrations in quail chick tissues

Abstract. Lipid-soluble antioxidants can be more effective for chick development when provided via in ovo (IO) injection than when supplemented to the maternal diet. This study was conducted to evaluate the effects of egg weight (EW) and IO injection of α-tocopherol on chick development, hatching performance and lipid-soluble antioxidant concentrations in residual yolk sac (RYS), liver and brain tissues of quail chicks. Eggs were obtained from quail breeders at days 72 and 128 of age and incubated at 37.8 ∘C and 60 % relative humidity. Each egg was numbered and weighed prior to incubation, and the average EW of all eggs was 11.76 ± 0.05 g. The eggs were divided into light (< 11.76 EW; EWL) and heavy (> 11.76 EW; EWH) groups (148 eggs per EW). Each EW group was divided into two IO groups: the control (non-injection) group and α-tocopherol group, in which 3.75 mg of α-tocopherol per egg was injected into the yolk sac followed by a 120 h incubation period. There were 64 eggs for each EW–IO treatment combination (16 eggs per EW per tray). The chick and RYS weights were significantly lower in the EWL group than in the EWH group. A significant EW by IO interaction suggested that IO increased the eggshell temperature of light quail eggs. The non-injected light eggs had a shorter hatching time due to the interaction of EW with IO. Hatchability, embryonic mortalities, and the cumulative hatching rate were not affected by EW or IO. The chick and middle toe lengths increased following IO administration (P < 0.05), which indicated that IO administration had positive effects on chick quality. However, shank length decreased following IO administration with an unchanged relative asymmetry (RA). IO significantly affected the absolute weights of the liver and heart and the relative weight of the heart, which was lower in the α-tocopherol group than in the control group. IO administration had no effect on total retinol and carotenoid concentrations in the RYS, liver and brain. Vitamin E, α-tocopherol and δ-tocopherol concentrations in the RYS, liver and brain were significantly higher in the α-tocopherol-treated chicks than in the control chicks. The highest brain α-tocopherol concentration was found in the α-tocopherol-treated chicks of the EWH group, indicating a significant interaction between EW and IO. The highest total lipid-soluble antioxidant concentrations were obtained following IO α-tocopherol treatment (P < 0.05), in the order brain < liver < RYS, but this pattern was not observed with δ-tocopherol. In conclusion, IO injection of α-tocopherol into the yolk sac affected the concentrations of tissue-specific lipid-soluble antioxidants in the RYS and tissues of newly hatched quail chicks, and EW had effects on various parameters.