Efectos subletales de la exposición al vertido tóxico de Aznalcóllar en aves de larga vida

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Ecología. Fecha de lectura: 05-02-201

Adrenocortical Response to Stress and Thyroid Hormone Status in Free-Living Nestling White Storks (Ciconia ciconia) Exposed to Heavy Metal and Arsenic Contamination

BACKGROUND/OBJECTIVE: Endocrine parameters have proven useful in the detection of early or low-level responses to pollutants. Although most of the studies on endocrine modulation have been focused on processes involving gonadal steroids, contaminants may target other parts of the endocrine system as well. In this study we examined the adrenocortical stress response and thyroid hormone status in free-living nestling white storks (Ciconia ciconia) in relation to heavy metals (zinc, lead, copper, cadmium) and arsenic levels in blood. METHODS: Fieldwork was conducted in an area polluted by the Aznalcóllar mine accident (southwestern Spain) and in a reference site. We used a standardized capture, handling, and restraint protocol to determine both baseline and maximum plasma corticosterone. Circulating levels of thyroxine (T(4)) and triiodothyronine (T(3)) were also measured. RESULTS: No effects of metals or As were found on baseline corticosterone, but maximum levels of corticosterone were positively related to Pb in both locations. This relationship was stronger in single nestlings than in birds from multiple-chick broods, which suggests a greater impact of Pb on more stressed individuals. Metal pollution did not affect plasma T(4) or T(3) levels, although thyroid status differed with location. CONCLUSIONS: Because a compromised hypothalamus–pituitary–adrenal (HPA) function can have far-reaching consequences in terms of altered behavioral and metabolic processes necessary for survival, our results suggest that birds exposed to sublethal Pb levels may be at risk through an altered adrenocortical stress response, and further support the idea that HPA axis-related end points might be useful indicators of metal exposure and potential toxicity in wild animals

Developmental Exposure to a Toxic Spill Compromises Long-Term Reproductive Performance in a Wild, Long-Lived Bird: The White Stork (Ciconia ciconia)

Background/Objective: Exposure to environmental contaminants may result in reduced reproductive success and long- lasting population declines in vertebrates. Emerging data from laboratory studies on model species suggest that certain life- stages, such as development, should be of special concern. However, detailed investigations of long-term consequences of developmental exposure to environmental chemicals on breeding performance are currently lacking in wild populations of long-lived vertebrates. Here, we studied how the developmental exposure to a mine spill (Aznalco´ llar, SW Spain, April 1998) may affect fitness under natural conditions in a long-lived bird, the White Stork (Ciconia ciconia). Methodology: The reproductive performance of individually-banded storks that were or not developmentally exposed to the spill (i.e. hatched before or after the spill) was compared when these individuals were simultaneously breeding during the seven years after the spill occurred (1999–2005). Principal Findings: Female storks developmentally exposed to the spill experienced a premature breeding senescence compared with their non-developmentally exposed counterparts, doing so after departing from an unusually higher productivity in their early reproductive life (non-developmentally exposed females: 0.560.33SE fledglings/year at 3-yr old vs. 1.3860.31SE at 6–7 yr old; developmentally exposed females: 1.560.30SE fledglings/year at 3-yr old vs. 0.8660.25SE at 6– 7 yr old). Conclusions/Significance: Following life-history theory, we propose that costly sub-lethal effects reported in stork nestlings after low-level exposure to the spill-derived contaminants might play an important role in shaping this pattern of reproduction, with a clear potential impact on population dynamics. Overall, our study provides evidence that environmental disasters can have long-term, multigenerational consequences on wildlife, particularly when affecting developing individuals, and warns about the risk of widespread low-level contamination in realistic scenarios.Peer reviewe

MSC therapy ameliorates experimental gouty arthritis hinting an early COX-2 induction

ObjectiveThe specific effect of Adipose-Derived Mesenchymal Stem Cells (Ad-MSC) on acute joint inflammation, where the response mostly depends on innate immunity activation, remains elusive. The pathogenesis of gouty arthritis, characterized by the deposition of monosodium urate (MSU) crystals in the joints, associated to acute flares, has been associated to NLRP3 inflammasome activation and subsequent amplification of the inflammatory response. Our aim was to study the effect of human Ad-MSC administration in the clinical inflammatory response of rabbits after MSU injection, and the molecular mechanisms involved.MethodsAd-MSC were administered by intraarterial route shortly after intraarticular MSU crystal injections. Joint and systemic inflammation was sequentially studied, and the mechanisms involved in NLRP3 inflammasome activation, and the synthesis of inflammatory mediators were assessed in the synovial membranes 72h after insult. Ad-MSC and THP-1-derived macrophages stimulated with MSU were co-cultured in transwell system.ResultsA single systemic dose of Ad-MSC accelerated the resolution of local and systemic inflammatory response. In the synovial membrane, Ad-MSC promoted alternatively M2 macrophage presence, inhibiting NLRP3 inflammasome and inducing the production of anti-inflammatory cytokines, such as IL-10 or TGF-β, and decreasing nuclear factor-κB activity. Ad-MSC induced a net anti-inflammatory balance in MSU-stimulated THP-1 cells, with a higher increase in IL-10 and IDO expression than that observed for IL-1β and TNF.ConclusionOur in vivo and in vitro results showed that a single systemic dose of Ad-MSC decrease the intensity and duration of the inflammatory response by an early local COX-2 upregulation and PGE2 release. Ad-MSCs suppressed NF-kB activity, NLRP3 inflammasome, and promoted the presence of M2 alternative macrophages in the synovium. Therefore, this therapeutic approach could be considered as a pharmacological alternative in patients with comorbidities that preclude conventional treatment

Adrenal Toxicology in Birds: Environmental Contaminants and the Avian Response to Stress

Peer reviewe

Efectos Subletales de la Exposición al Vertido Tóxico de Aznalcóllar en Aves de Larga Vida

Memoria presentada por Raquel Baos Sendarrubias para optar al Grado de Doctora en BiologíaPeer reviewe

Stress in the nest: Causes and consequences of adrenocortical secretion in developing birds

During the last decade, a vast number of studies have considerably increased our understanding of the interplay between the ecology and the endocrinology of the stress axis in wild avian populations. A theoretical framework known as the ‘Emergency Life History Stage’ has been developed to explore the ecological bases of stress and underlying endocrine mechanisms. Despite a growing body of literature on the role of hypothalamic-pituitary-adrenal (HPA) function in adult birds, little research has been performed in birds during development, possibly due to the wealth of variability in developmental strategies within the Class Aves, and the lack of evidence that non-precocial species have functional stress responses before parental independence. A series of investigations on HPA function in nestling white storks (Ciconia ciconia) under natural conditions have provided novel insights into the proximate causes and ultimate fitness consequences of adrenocortical responses to stress in developing birds. The aim of this review is to provide an integrated summary of recent research on endogenous and exogenous factors affecting adrenocortical function using stork chicks as a study model. Among the endogenous factors that explain differences in HPA function, nestling age constitutes a prime source of variability, which is discussed here within the context of the Developmental Hypothesis. Superimposed on this ontogenic pattern, exogenous factors of ecological origin such as food availability, habitat and parental quality generate interindividual differences in baseline corticosterone (cort) secretion. These findings support the notion that non- precocial nestlings can activate emergency responses to environmental perturbations despite their parental dependence for food and shelter, and suggest a role of environmental stressors in the preparation for fledging and independence. A second set of exogenous factors of concern for conservation biologists is the exposure of wild avian populations to environmental pollutants. Maximum levels of cort following capture and restraint were positively related to storks´ blood lead levels. This relationship was stronger in single nestlings than in birds from multiple-chick broods, suggesting a greater impact of pollutants on individuals additionally exposed to ecological stressors such as poor parental quality. With the aim of assessing the ultimate fitness consequences of individual variability in stress responses, the probability of survival and recruitment was modelled using information of a long-term study that accounted for all the factors described above. Survival and recruitment were negatively related to the magnitude of the adrenocortical response during development, providing the first empirical evidence for a link between stress- response early in life and subsequent fitness in a wild, long-lived vertebrate. In the light of these findings, here we review the published literature on this topic and discuss the current state of knowledge regarding adrenocortical function in developing birds, highlighting study gaps and suggesting future research directions.Peer reviewe

Evaluation of the antibody mediated immune response in nestling American kestrels (Falco sparverius)

Avian biologists and toxicologists use tests of immune function to evaluate health or quality in birds. Nestlings are widely studied members of the population because of the logistical ease of working with them, and because of their vulnerability to environmental contaminants. Current immunological techniques are designed for domestic poultry and are far from ideal, since poultry are precocial (developmentally mature at hatching), while many wild species are altricial (developmentally immature, i.e. blind, naked and totally dependent at hatching). The purpose of this study was to identify a sensitive means of evaluating in vivo antibody responsiveness in nestling American kestrels. Two antigens, sheep red blood cells (SRBC), and dinitrophenol– keyhole limpet hemocyanin (DNP–KLH), were used to stimulate a B cell mediated response. Antibody production was measured using a hemagglutination assay (SRBC), or an enzyme-linked immunosorbent assay (DNP–KLH). Two formulations of the antigen DNP–KLH were compared. DNP–KLH stimulated a stronger and more consistent antibody response in nestling kestrels than did SRBCsPeer reviewe

Eurasian otter (Lutra lutra) as sentinel species for the long-term biomonitoring of the Guadiamar River after the Aznalcóllar mine spill

Accidents at mines involving stored tailings have produced catastrophic environmental damage. In April 1998 the dam of the Aznalcóllar mine tailings pond in the surroundings of the Doñana National Park (southwestern Spain) broke, discharging into the Guadiamar River more than 6 million m3 of toxic mud and acidic water with high concentrations of heavy metals and arsenic. We used the Eurasian otter (Lutra lutra) as sentinel species to assess the potential impact of the toxic spill on the river ecosystems and their recovery with time by studying the spatial and temporal variation (1999-2003, 2006) of selected trace element (Cu, Zn, Cd, Pb and As) concentrations in feces. Throughout the sampling period, the highest heavy metal and As levels were found in the most spill-affected reaches of the Guadiamar River (i.e., the Middle and, to a lesser extent, the Lower reaches), pointing out the mining accident as the main origin of the contamination. Overall, levels of trace elements decreased with the time elapsed since the toxic spill, except for Cd (F1,352 = 0.29, P = 0.59). However, rebounds for some elements (Pb, As, and Cu) were also observed, especially in the Middle and Lower reaches of the river, which might be attributed to the residual contamination in abiotic compartments and/or new inputs from industrial and agricultural activities in the nearby areas. Concentrations were relatively high when compared to those reported for both our reference area (Guadalete River) and other metal-polluted zones. We found that the estimated amounts of Pb and As ingested during the first years after the spill in the Guadiamar Middle reach would be high enough to cause reproductive issues. This could affect the local population recovery, although evidence on distribution range and numbers suggests otherwise, with thriving populations at regional scale. Our results support the role of otters as sentinel species for biomonitoring contaminants and thus to evaluate fluvial ecosystem health.Peer reviewe