Mercury in blood of free-ranging seals Phoca vitulina from the North Sea: Time-trend and association with environmental factors

Conference (2012, March 27)

The harbour seal (Phoca vitulina) population from the North Sea has experienced various fluctuations these last decades due to habitat loss, prey fluctuation and pollution of the marine environment ... [more ▼]

The harbour seal (Phoca vitulina) population from the North Sea has experienced various fluctuations these last decades due to habitat loss, prey fluctuation and pollution of the marine environment. Recently, development of monitoring programs and non-invasive sampling techniques, including seal catches allowed blood sampling on a regular basis together with measurements of blubber thickness, body mass, sex and body length. Concentrations of total mercury (T-Hg) and other trace elements (Cd, Pb, Zn, Cu, Fe) as well as ∂13C and ∂15N values were determined by mass spectrometry in blood of 75 wild harbour seals caught in the German Wadden Sea between 1997 and 2011. ∂13C and ∂15N mean values (-17.5‰ and 18.1 ‰ respectively) were strongly similar to that measured previously in the muscle of stranded harbour seals from the Wadden Sea. In contrast, ∂15N mean value was strikingly higher than that recorded in grey seals (Halichoerus grypus) from Scotland (14.1 ‰ respectively; Habran et al. submitted.) while ∂13C values remained similar between the two seal species. These values confirmed the high trophic position of the harbour seal in the North Sea. In contrast to Cd and Pb, T-Hg in blood harbour seals reached concentrations as high as 2.1 μg.g-1 dry weight (10 times higher than the 0.21 μg.g-1 dry weight recorded for grey seals from Scotland) but depended on several factors including ∂15N values, age group and the body mass. T-Hg was detected in juveniles confirming maternal transfer to offspring and time-trend revealed no decrease of T-Hg in blood of harbour seals these last 15 years. [less ▲]

STUDY OF SELENITE AND SELENOMETHIONINE EFFECT ON METHYLMERCURY IN VITRO TOXICITY

Conference (2011, May 16)

Methylmercury (MeHg) and selenium (Se) can be found at elevated concentrations in blood of marine mammals and both display modulatory effects on the immune system. Whereas mercury (Hg)-Se antagonism in ... [more ▼]

Methylmercury (MeHg) and selenium (Se) can be found at elevated concentrations in blood of marine mammals and both display modulatory effects on the immune system. Whereas mercury (Hg)-Se antagonism in liver of marine mammals is well known, the protective role of Se against Hg immunotoxicity in marine mammals has been poorly described. We propose here an in vitro approach using combined Hg and Se in vitro exposure of peripheral blood mononuclear cells (PBMCs) of the harbor seal (Phoca vitulina). PBMCs were isolated from the blood of 10 harbor seals and exposed to environmental concentrations of MeHg (1µM) and selenite or selenomethionine (5µM), respectively inorganic and organic forms of Se. MeHg leaded to a decrease of lymphocyte proliferation, to an increase of cells with compromised mitochondrial membrane potentials and cell death. Preliminary results evidenced that none of the two Se forms had a protective effect against MeHg toxicity, although cells were slightly stimulated by Se alone. Therefore MeHg expresses its toxicity among blood circulating lymphocytes in presence or absence of selenite or selenomethionine. [less ▲]

New insights in the toxicology and health status of marine marine mammals: Use of free-ranging harbour seals from the Wadden Sea

Conference (2011, March 20)

Methylmercury and selenium in vitro effects on harbor seal (Phoca vitulina) lymphocytes : a multidisciplinary approach

Poster (2010, May 26)

Methylmercury (MeHg) bioaccumulates along the food web, leading to the highest levels in tissues of predatory species. It constitutes the predominant form present in the blood of marine mammals. The blood ... [more ▼]

Methylmercury (MeHg) bioaccumulates along the food web, leading to the highest levels in tissues of predatory species. It constitutes the predominant form present in the blood of marine mammals. The blood cells, including the immune cells, are therefore exposed to the toxic properties of that chemical. Nevertheless, selenium (Se) is an essential element absorbed concomitantly to MeHg which seems to modulate this toxicity. The goal of this study is to evaluate the immunotoxicity of MeHg on the harbor seal (Phoca vitulina) T lymphocytes, highly important in the adaptive immune response, and to investigate the modulating effect of Se on that toxicity. In parallel, the concentrations of MeHg, total mercury (T-Hg) and Se are determined in free-ranging harbour seal blood in order to follow their contamination levels. The T lymphocytes were isolated from the whole blood, exposed to various MeHg and Se concentrations and the exposure effects were estimated by functional tests including the evaluation of viability, proliferation, metabolic activity, DNA and protein synthesis, and by morphological analysis by transmission electron microscopy. The mean T-Hg concentration was 172 ± 143 µg/l of whole blood. The T lymphocytes cultures in vitro displayed a decreasing number of viable cells with increasing concentrations of MeHg, and numerous ultrastructural defects. The cells exposed to MeHg notably displayed distortion of the plasmic membrane, nucleus fragmentations, chromatin compaction, swelling mitochondrias and cytoplasmic vacuolisations. Those results highlighted various immunotoxic effects of MeHg, both at the functional and ultrastructural levels. The antagonistic role of Se on MeHg immunotoxicity is discussed. [less ▲]

Etude in vitro de l’effet du méthylmercure et du sélénium sur les lymphocytes T de phoque commun (Phoca vitulina)

Speech (2009)

Methylmercury in vitro exposure of harbor seal (Phoca vitulina) lymphocytes: A multidisciplinary approach

Conference (2009, June 08)

Etude de l’effet du méthylmercure et du sélénium sur les lymphocytes de phoque commun (Phoca vitulina) par analyses fonctionnelles, morphologiques et protéomiques

Poster (2008, December 12)

Exposition et effets du méthylmercure chez le phoque commun (Phoca vitulina)

Speech (2008)

Mercury immune toxicity in harbour seals: Links to in vitro toxicity

in Environmental Health : A Global Access Science Source (2008), 7

Background Mercury is known to bioaccumulate and to magnify in marine mammals, which is a cause of great concern in terms of their general health. In particular, the immune system is known to be ... [more ▼]

Background Mercury is known to bioaccumulate and to magnify in marine mammals, which is a cause of great concern in terms of their general health. In particular, the immune system is known to be susceptible to long-term mercury exposure. The aims of the present study were (1) to determine the mercury level in the blood of free-ranging harbour seals from the North Sea and (2) to examine the link between methylmercury in vitro exposure and immune functions using seal and human mitogen-stimulated peripheral blood mononuclear cells (T-lymphocytes). Methods Total mercury was analysed in the blood of 22 harbour seals. Peripheral blood mononuclear cells were isolated from seals (n = 11) and from humans (n = 9). Stimulated lymphocytes of both species were exposed to functional tests (proliferation, metabolic activity, radioactive precursor incorporation) under increasing doses of methylmercury (0.1 to 10 µM). The expression of cytokines (IL-2; IL-4 and TGF-beta was investigated in seal lymphocytes by RT-PCR and by real time quantitative PCR (n = 5) at methylmercury concentrations of 0.2 and 1 µM. Finally, proteomics analysis was attempted on human lymphocytes (cytoplasmic fraction) in order to identify biochemical pathways of toxicity at concentration of 1 µM (n = 3). Results The results showed that the number of seal lymphocytes, viability, metabolic activity, DNA and RNA synthesis were reduced in vitro, suggesting deleterious effects of methylmercury concentrations naturally encountered in free-ranging seals. Similar results were found for human lymphocytes. Functional tests showed that a 1 µM concentration was the critical concentration above which lymphocyte activity, proliferation and survival were compromised. The expression of IL-2 and TGF-beta mRNA was weaker in exposed seal lymphocytes compared to control cells (0.2 and 1 µM). Proteomics showed some variation in the protein expression profile (e.g. vimentin). [less ▲]

Evaluation des niveaux de mercure dans le sang et mise au point d'un protocole d'exposition in vitro visant à comprendre l'effet du méthyl-mercure sur l'expression de cytokines chez le phoque commun (Phoca vitulina)

Master's dissertation (2005)

The objective of this work is to lay the bases of an in vitro experimental exposure model aiming to understand the immunotoxicological effect of methylmercury of harbour seal (Phoca vitulina) T ... [more ▼]

The objective of this work is to lay the bases of an in vitro experimental exposure model aiming to understand the immunotoxicological effect of methylmercury of harbour seal (Phoca vitulina) T lymphocytes by analysis of their expression of cytokines messenger RNA (mRNA). Cytokines are important mediators of the immune system and their disruption lead to dysfunction of immune responses. This pilot study is comprised of an analytical section consisting in the determination of whole blood mercury concentrations of alive and beached harbour seals from the North Sea, and an experimental section including in vitro lymphocyte cultures. The harbour seal blood sampling is a relatively easy and non-invasive method that enables lymphocyte isolation and controlled methylmercury in vitro exposure. The blood of marine mammal constitutes an interesting window as marine mammals, located in the highest levels of the trophic chain, accumulate high levels of trace metals in their tissues. They are thus good bioindicators of marine pollution. Optimal culture conditions and the most appropriate techniques were determined. T lymphocytes were exposed in vitro to two methylmercury concentrations comprised in the measured concentration range, and exposure effects were studied by analysis of the cytokine mRNA production. Results show an immunodepression at 0.2 and 1 µM in presence of mitogenic phytohemagglutinin (PHA) which specifically stimulates T lymphocytes. The interleukin-2 (IL-2) and transforming growth factor-β (TGF-β) mRNA quantities displayed a decrease, and interleukin-4 (IL-4) mRNA was in weak quantities in all culture conditions (with or without methylmercury). That could mean that methylmercury affects the cell-mediated immunity, but repetition of the experience with a larger sampling is needed to confirm those results. [less ▲]