First Time Identification of Selenoneine in Seabirds and Its Potential Role in Mercury Detoxification

Abstract

Birds are principally exposed to selenium (Se) through their diet. In long-lived and top predator seabirds, such as the giant petrel, extremely high concentrations of Se are found.Selenium speciation in biota has aroused great interest in recent years, however there is a lack of information about the chemical form of Se in (sea)birds. The majority of publications focus on the growth performance and antioxidant status in broilers in relation to Se dietary supplementation. The present work combines elemental and molecular mass spectrometry for the characterization of Se species in wild (sea)birds. A set of 8 giant petrel (Macronectes sp.) individuals of a wide age range from the Southern Ocean was studied. Selenoneine (2-selenyl-N,N,N-trimethyl-L-histidine), a Se-analog of ergothioneine was identified for the first time in wild avian species. This novel Se-compound, previously reported in fish, constitutes the major Se species in the water-soluble fraction of all the internal tissues and blood samples analyzed.The levels of selenoneine found in giant petrels are the highest reported in animal tissues until now, supporting the trophic transfer in the marine food web. The characterization of selenoneine in brain, where it represents between 78 and 88% of the total Se, suggests a crucial role in the nervous system. The dramatic diminishment of selenoneine (from 70 to 5 %) with the increase of Hg concentrations in the liver strongly supports the hypothesis of its key role in Hg detoxification.

Emerging evidence on selenoneine and its public health relevance in coastal populations: a review and case study of dietary Se among Inuit populations in the Canadian Arctic

“…SeN has furthermore been shown to bind to myoglobin and hemoglobin to prevent auto-oxidation of iron (68) . SeN crosses the blood-brain barrier (78) and a recent study showed that the SeN can accumulate in the brains of giant petrels (69) . Authors suggest that SeN may play a role in the protection and function of the central nervous system.…”

“…SeN was identified in 2010 in the blood of bluefin tuna at concentrations in the range of 5-40 μg Se/g. Despite this, following more than a decade of subsequent research, SeN has also been reported in different biological matrices of marine animal origin, including beluga whale mattaaq (8) , dolphins (66) , sea turtles (67) , various fishes (e.g., swordfish, Pacific mackerel, sardines, and tilapia) (68) , and seabirds (69) , indicating trophic transfer through marine food webs. When found in animals, SeN is likely derived from the diet as only some fungi and bacteria synthesize ergothioneine and SeN (65,70,71) .…”

Impact of anthropogenous environmental factors on the marine ecosystem of trophically transmitted helminths and hosting seabirds: Focus on North Atlantic, North Sea, Baltic and the Arctic seas

“…The authors discussed different susceptibil-ity to Hg and/or parasites between males and females as well as the complexity of the antagonistic interactions of Hg and Se (Heinz & Hoffmann, 1998). When it comes to Hg detoxification in seabirds the potential role of selenoneine, the Se-analogue of ergothioneine should also be considered, because El Hanafi et al (2022) found a dramatic decrease of selenoneine with the increase of Hg concentration in the liver of giant petrels (Macronectes spec.). Sures et al (2017) reviewed a large number of studies which show that numerous species of digenea, cestoda, acanthocephala and nematoda accumulate organic pollutants and trace elements to a high extent.…”

Substrate binding and catalytic mechanism of the Se-glycosyltransferase SenB in the biosynthesis of selenoneine

“…Other organic forms of Se, including selenouridine (SeU), which is synthesized by SelU and used to modify microbial nucleic acids 8,9 , and cofactors for some redox enzymes, such as molybdenum dehydrogenase 10,11 , have been identified in bacteria. In addition, selenoneine (SEN), a Se analog of ergothioneine, was found in various sea-dwelling animals and in β-proteobacteria [12][13][14][15] . With the exception that SEN could protect against mercury toxicity and act as an effective antioxidant 14,16,17 , little was known about its other physiological roles.…”

“…In addition, selenoneine (SEN), a Se analog of ergothioneine, was found in various sea-dwelling animals and in β-proteobacteria [12][13][14][15] . With the exception that SEN could protect against mercury toxicity and act as an effective antioxidant 14,16,17 , little was known about its other physiological roles.…”