Bruno Faivre
Centre national de la recherche scientifique
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Featured researches published by Bruno Faivre.
Proceedings of the Royal Society of London B: Biological Sciences | 2007
Carlos Alonso-Alvarez; Sophie Bertrand; Bruno Faivre; Olivier Chastel; Gabriele Sorci
Secondary sexual traits (SST) are usually thought to have evolved as honest signals of individual quality during mate choice. Honesty of SST is guaranteed by the cost of producing/maintaining them. In males, the expression of many SST is testosterone-dependent. The immunocompetence handicap hypothesis has been proposed as a possible mechanism ensuring honesty of SST on the basis that testosterone, in addition to its effect on sexual signals, also has an immunosuppressive effect. The immunocompetence handicap hypothesis has received mixed support. However, the cost of testosterone-based signalling is not limited to immunosuppression and might involve other physiological functions such as the antioxidant machinery. Here, we tested the hypothesis that testosterone depresses resistance to oxidative stress in a species with a testosterone-dependent sexual signal, the zebra finch. Male zebra finches received subcutaneous implants filled with flutamide (an anti-androgen) or testosterone, or kept empty (control). In agreement with the prediction, we found that red blood cell resistance to a free radical attack was the highest in males implanted with flutamide and the lowest in males implanted with testosterone. We also found that cell-mediated immune response was depressed in testosterone-treated birds, supporting the immunocompetence handicap hypothesis. The recent finding that red blood cell resistance to free radicals is negatively associated with mortality in this species suggests that benefits of sexual signalling might trade against the costs derived from oxidation.
Evolution | 2006
Carlos Alonso-Alvarez; Sophie Bertrand; Godefroy Devevey; Josiane Prost; Bruno Faivre; Olivier Chastel; Gabriele Sorci
Abstract Optimal investment into life‐history traits depends on the environmental conditions that organisms are likely to experience during their life. Evolutionary theory tells us that optimal investment in reproduction versus maintenance is likely to shape the pattern of age‐associated decline in performance, also known as aging. The currency that is traded against different vital functions is, however, still debated. Here, we took advantage of a phenotypic manipulation of individual quality in early life to explore (1) long‐term consequences on life‐history trajectories, and (2) the possible physiological mechanism underlying the life‐history adjustments. We manipulated phenotypic quality of a cohort of captive zebra finches (Taeniopygia guttata) by assigning breeding pairs to either an enlarged or a reduced brood. Nestlings raised in enlarged broods were in poorer condition than nestlings raised in reduced broods. Interestingly, the effect of environmental conditions experienced during early life extended to the age at first reproduction. Birds from enlarged broods delayed reproduction. Birds that delayed reproduction produced less offspring but lived longer, although neither fecundity nor longevity were directly affected by the experimental brood size. Using the framework of the life‐table response experiment modeling, we also explored the effect of early environmental condition on population growth rate and aging. Birds raised in reduced broods tended to have a higher population growth rate, and a steeper decrease of reproductive value with age than birds reared in enlarged broods. Metabolic resources necessary to fight off the damaging effect of reactive oxygen species (ROS) could be the mechanism underlying the observed results, as (1) birds that engaged in a higher number of breeding events had a weaker red blood cell resistance to oxidative stress, (2) red blood cell resistance to oxidative stress predicted short‐term mortality (but not longevity), and (3) was related with a parabolic function to age. Overall, these results highlight that early condition can have long‐term effects on life‐history trajectories by affecting key life‐history traits such as age at first reproduction, and suggest that the trade‐off between reproduction and self‐maintenance might be mediated by the cumulative deleterious effect of ROS.
Philosophical Transactions of the Royal Society B | 2009
Gabriele Sorci; Bruno Faivre
Innate, inflammation-based immunity is the first line of vertebrate defence against micro-organisms. Inflammation relies on a number of cellular and molecular effectors that can strike invading pathogens very shortly after the encounter between inflammatory cells and the intruder, but in a non-specific way. Owing to this non-specific response, inflammation can generate substantial costs for the host if the inflammatory response, and the associated oxygen-based damage, get out of control. This imposes strong selection pressure that acts to optimize two key features of the inflammatory response: the timing of activation and resolution (the process of downregulation of the response). In this paper, we review the benefits and costs of inflammation-driven immunity. Our aim is to emphasize the importance of resolution of inflammation as a way of maintaining homeostasis against oxidative stress and to prevent the ‘horror autotoxicus’ of chronic inflammation. Nevertheless, host immune regulation also opens the way to pathogens to subvert host defences. Therefore, quantifying inflammatory costs requires assessing (i) short-term negative effects, (ii) delayed inflammation-driven diseases, and (iii) parasitic strategies to subvert inflammation.
Proceedings of the National Academy of Sciences of the United States of America | 2010
Vincent Lecomte; Gabriele Sorci; Stéphane Cornet; Audrey Jaeger; Bruno Faivre; Emilie Arnoux; Maria Gaillard; Colette Trouvé; Dominique Besson; Olivier Chastel; Henri Weimerskirch
How does an animal age in natural conditions? Given the multifaceted nature of senescence, identifying the effects of age on physiology and behavior remains challenging. We investigated the effects of age on a broad array of phenotypic traits in a wild, long-lived animal, the wandering albatross. We studied foraging behavior using satellite tracking and activity loggers in males and females (age 6–48+ years), and monitored reproductive performance and nine markers of baseline physiology known to reflect senescence in vertebrates (humoral immunity, oxidative stress, antioxidant defenses, and hormone levels). Age strongly affected foraging behavior and reproductive performance, but not baseline physiology. Consistent with results of mammal and human studies, age affected males and females differently. Overall, our findings demonstrate that age, sex, and foraging ability interact in shaping aging patterns in natural conditions. Specifically, we found an unexpected pattern of spatial segregation by age; old males foraged in remote Antarctica waters, whereas young and middle-aged males never foraged south of the Polar Front. Old males traveled a greater distance but were less active at the sea surface, and returned from sea with elevated levels of stress hormone (corticosterone), mirroring a low foraging efficiency. In contrast to findings in captive animals and short-lived birds, and consistent with disposable soma theory, we found no detectable age-related deterioration of baseline physiology in albatrosses. We propose that foraging efficiency (i.e., the ability of individuals to extract energy from their environment) might play a central role in shaping aging patterns in natural conditions.
The Journal of Experimental Biology | 2006
Sophie Bertrand; Bruno Faivre; Gabriele Sorci
SUMMARY Carotenoid-based signals are thought to be indicators of male quality because they must be obtained from the diet and might thus indicate the ability of individuals to gather high-quality food. However, carotenoids are also known to have important physiological functions as immunoenhancers and antioxidants, and, as such, carotenoid-based sexual traits have also been suggested to reflect the health and antioxidant status of their bearers. This last idea is based on the hypothesis that carotenoids that are allocated to sexual signals are no longer available for the detoxification system. Recently, this hypothesis has been challenged on the grounds that the antioxidant activity is not the main biological role of carotenoids. Instead, carotenoid-based sexual traits might signal the availability of other non-pigmentary antioxidant molecules that might protect carotenoids from free radical attacks and make them available for sexual advertisements. We tested this hypothesis in the zebra finch, a passerine species with a carotenoid-based signal: the colour of the bill. We simultaneously manipulated the availability of carotenoids and of a non-pigmentary antioxidant (melatonin) in the drinking water. If the antioxidant properties of melatonin protect carotenoids from oxidation, we predict that birds supplemented with melatonin should have redder bills than birds not supplemented with melatonin, and that birds supplemented with carotenoids and melatonin should have redder bills than birds supplemented with carotenoids alone. Our findings are in agreement with these predictions since carotenoid and melatonin supplementation had an additive effect on bill colour. To our knowledge this is the first experimental evidence that a non-pigmentary antioxidant enhances the expression of a carotenoid-based sexual trait.
European Journal of Cell Biology | 2013
Corina Ciobanasu; Bruno Faivre; Christophe Le Clainche
Focal adhesions are clusters of integrin transmembrane receptors that mechanically couple the extracellular matrix to the actin cytoskeleton during cell migration. Focal adhesions sense and respond to variations in force transmission along a chain of protein-protein interactions linking successively actin filaments, actin binding proteins, integrins and the extracellular matrix to adapt cell-matrix adhesion to the composition and mechanical properties of the extracellular matrix. This review focuses on the molecular mechanisms by which actin binding proteins integrate actin dynamics, mechanotransduction and integrin activation to control force transmission in focal adhesions.
Nature Communications | 2014
Corina Ciobanasu; Bruno Faivre; Christophe Le Clainche
The force generated by the actomyosin cytoskeleton controls focal adhesion dynamics during cell migration. This process is thought to involve the mechanical unfolding of talin to expose cryptic vinculin-binding sites. However, the ability of the actomyosin cytoskeleton to directly control the formation of a talin–vinculin complex and the resulting activity of the complex are not known. Here we develop a microscopy assay with pure proteins in which the self-assembly of actomyosin cables controls the association of vinculin to a talin-micropatterned surface in a reversible manner. Quantifications indicate that talin refolding is limited by vinculin dissociation and modulated by the actomyosin network stability. Finally, we show that the activation of vinculin by stretched talin induces a positive feedback that reinforces the actin–talin–vinculin association. This in vitro reconstitution reveals the mechanism by which a key molecular switch senses and controls the connection between adhesion complexes and the actomyosin cytoskeleton.
The Journal of Experimental Biology | 2007
Cyril Eraud; Godefroy Devevey; Maria Gaillard; Josiane Prost; Gabriele Sorci; Bruno Faivre
SUMMARY Abiotic factors including thermal stress are suggested to exert constrains on sexual ornaments through trade-offs between sexual displays and physiological functions related to self-maintenance. Given the health properties of carotenoid pigments, carotenoid-based ornaments offer a relevant context in which to investigate the effect of environmental stress, such as ambient temperature, on the production and maintenance of secondary sexual traits and, also, to explore the proximate mechanisms shaping their expression. In this study, we exposed male zebra finches (Taeniopygia guttata) to environmental stress by exposing them to two temperature regimes (6 and 26°C) over a 4 week period. Simultaneously, half of the males in each temperature group were supplemented with carotenoids, whereas the other half were not. The expression of a carotenoid-based sexual trait (bill colour) and the amount of circulating carotenoids were assessed before and at the end of the experiment. Carotenoid-supplemented males developed a redder bill, but the effect of supplementation was reduced under cold exposure. However, we found evidence that birds facing a cold stress were carotenoid limited, since supplemented males developed redder bills than the non-supplemented ones. Interestingly, while cold-exposed and non-supplemented males developed duller bills, they circulated a higher amount of carotenoids at the end of the experiment compared to the pre-experimental values. Together, these results suggest that ambient temperature might contribute to the modulation of the expression of carotenoid-based ornaments. Our findings suggest that carotenoids are a limiting resource under cold exposure and that they might be prioritized for self-maintenance at the expense of the ornament. The physiological functions related to self-maintenance that might have benefited from carotenoid saving are discussed.
The Journal of Experimental Biology | 2010
Julien Cote; Emilie Arnoux; Gabriele Sorci; Maria Gaillard; Bruno Faivre
SUMMARY Aging is commonly attributed to age-related changes in oxidative damage due to an increased production of reactive oxygen species (ROS) and a weakened efficacy of enzymatic antioxidants. These age-related changes might therefore modify the use of dietary antioxidants, including carotenoids. As carotenoids are closely associated with the expression of secondary sexual signals, the allocation of carotenoids to sexual signal versus antioxidant defences may vary with age. In this study, we explored how carotenoid-based ornament and antioxidant activity varied with age and how an inflammatory-induced oxidative burst affected ornament and antioxidant activity across a range of ages. Using zebra finches (Taeniopygia guttata) as a model species, we assessed circulating carotenoids, beak coloration and the plasma antioxidant status of birds of different ages before and after an inflammatory challenge. Our results show that old individuals display similar carotenoid-based sexual signals regardless of the availability of circulating carotenoids, suggesting a terminal investment of old individuals in their last reproductive event. Additionally, we found that an inflammatory insult induced a decrease in the total antioxidant activity and in the expression of a carotenoid-based sexual signal in the oldest individuals. These results suggest that old individuals pay an extra cost of immune activation possibly because the efficiency of antioxidant machinery varies with age.
Journal of Ornithology | 2016
Juliette Bailly; Renaud Scheifler; Sarah Berthe; Valérie-Anne Clément-Demange; Matthieu Leblond; Baptiste Pasteur; Bruno Faivre
AbstractThe exploration of the effects of urbanization on bird demography has attracted much attention, and several studies found lower reproductive success in towns, which suggested strong environmental constraints. Here, we conducted a 3-year study to explore the consequences of urbanization on the breeding success of two species that originated in forests, the Blue Tit Cyanistes caeruleus and the Great Tit Parus major. In two replicates of urban and forest habitats, we studied the components of reproductive success. In one replicate of each habitat, we quantified nestling growth over the three breeding seasons, and we collected data on egg quality during one breeding season. The general picture that emerges from our finding is that in urban sites breeding success was lower with smaller clutch sizes, higher clutch, higher brood failure rates and lower survival rates. Our results also showed reduced growth in urban habitats, at the embryonic and nestling stages, with potential adverse consequences on fitness. Crucial ecological factors could explain the observed contrasts between the habitats, and food limitation is among the most likely. Overall, we demonstrated the negative effects of urbanization on the reproductive success of forest birds, and our results were consistent between species and geographic areas for these negative effects. Our results suggest a mismatch between urban environments and the habitat exploitation abilities that birds have evolved in their native forest ecosystems.ZusammenfassungVom Ei zum flüggen Jungvogel: negativer Einfluss von urbanem Lebensraum auf die Reproduktion bei zwei Meisenartenn Die Erforschung der Effekte von Urbanisierung auf Vogeldemografie hat viel Aufmerksamkeit auf sich gezogen und einige Studien haben einen niedrigeren Reproduktionserfolg innerhalb von Städten gefunden. Dies weist auf starke Umwelteinflüsse hin. In unserer dreijährigen Studie haben wir die Folgen der Urbanisierung auf den Bruterfolg von Blaumeisen C. caeruleus und Kohlmeisen P. major, welche beide ursprünglich in Wäldern vorkamen, erforscht. Auf je zwei Untersuchungsflächen je Lebensraum haben wir Komponenten des Reproduktionserfolgs untersucht. In einem Gebiet pro Brutsaison haben wir über je drei Jahre das Kükenwachstum aufgenommen, zudem in einem Jahr die Eiqualität untersucht. Das generelle Bild ist, dass in urbanem Gelände Bruterfolg und Gelegegröße geringer, Gelegeverluste und Brutverluste höher und die Überlebensraten geringer waren. Zudem war die Wachstumsrate in urbanen Lebensräumen während der embryonalen Phase und der Nestlingsphase geringer, was potentiell negative Auswirkungen auf die Fitness hat. Die beobachteten Unterschiede zwischen den Lebensräumen könnten von wichtigen ökologischen Faktoren erklärt werden, wobei Nahrungsbegrenzung vermutlich einer der wahrscheinlichsten ist. Wir haben den negativen Einfluss von Urbanisierung auf den Reproduktionserfolg von Waldvögeln gezeigt. Diese negativen Effekte stimmten zwischen den Arten und den geografischen Gebieten überein. Unsere Ergebnisse zeigen eine Diskrepanz zwischen urbaner Umwelt und den Fähigkeiten der Vögel, diesen Lebensraum zu nutzen, welche die welche Vögel in ihren ursprünglichen Lebensräumen evolviert haben.