Publications

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2017
Nicklisch, SCT, Bonito LT, Sandin S, Hamdoun A.  2017.  Geographic differences in persistent organic pollutant levels of yellowfin tuna. Environ Health Perspect. 125:067014.   10.1289/ehp518   Abstract

BACKGROUND: Fish are a source of persistent organic pollutants (POPs) in the human diet. Although species, trophic level, and means of production are typically considered in predicting fish pollutant load, and thus recommendations of consumption, capture location is usually not accounted for. OBJECTIVES: Yellowfin tuna (Thunnus albacares) are harvested from across the world's oceans and are widely consumed. Here, we determined geographic variation in the overall mass, concentration, and composition of POPs in yellowfin and examined the differences in levels of several POP congeners of potential relevance to human health. METHODS: We sampled dorsal muscle of 117 yellowfin tuna from 12 locations worldwide, and measured POP levels using combined liquid or gas chromatography and mass spectrometry according to U.S. Environmental Protection Agency standard procedures. RESULTS: POP levels varied significantly among sites, more than 36-fold on a mass basis. Individual fish levels ranged from 0.16 to wet weight and lipid-normalized concentrations from . Levels of 10 congeners that interfere with the cellular defense protein P-glycoprotein, termed transporter interfering compounds (TICs), ranged from 0.05 to wet weight and from in tuna lipid. Levels of TICs, and their individual congeners, were strongly associated with the overall POP load. Risk-based analysis of several carcinogenic POPs indicated that the fish with the highest levels of these potentially harmful compounds were clustered at specific geographic locations. CONCLUSIONS: Capture location is an important consideration when assessing the level and risk of human exposure to POPs through ingestion of wild fish.

Nicklisch, SCT, Bonito LT, Sandin S, Hamdoun A.  2017.  Mercury levels of yellowfin tuna (Thunnus albacares) are associated with capture location. Environmental Pollution. 229:87-93.   10.1016/j.envpol.2017.05.070   AbstractWebsite

Mercury is a toxic compound to which humans are exposed by consumption of fish. Current fish consumption advisories focus on minimizing the risk posed by the species that are most likely to have high levels of mercury. Less accounted for is the variation within species, and the potential role of the geographic origin of a fish in determining its mercury level. Here we surveyed the mercury levels in 117 yellowfin tuna caught from 12 different locations worldwide. Our results indicated significant variation in yellowfin tuna methylmercury load, with levels that ranged from 0.03 to 0.82 mu g/g wet weight across individual fish. Mean mercury levels were only weakly associated with fish size (R-2 < 0.1461) or lipid content (R-2 < 0.00007) but varied significantly, by a factor of 8, between sites. The results indicate that the geographic origin of fish can govern mercury load, and argue for better traceability of fish to improve the accuracy of exposure risk predictions. (C)2017 Elsevier Ltd. All rights reserved.

2018
Mascuch, SJ, Boudreau PD, Carland TM, Pierce NT, Olson J, Hensler ME, Choi H, Campanale J, Hamdoun A, Nizet V, Gerwick WH, Gaasterland T, Gerwick L.  2018.  Marine natural product honaucin A attenuates inflammation by activating the Nrf2-ARE pathway. Journal of Natural Products. 81:506-514.   10.1021/acs.jnatprod.7b00734   AbstractWebsite

The cyanobacterial marine natural product honaucin A inhibits mammalian innate inflammation in vitro and in vivo. To decipher its mechanism of action, RNA sequencing was used to evaluate differences in gene expression of cultured macrophages following honaucin A treatment. This analysis led to the hypothesis that honaucin A exerts its anti-inflammatory activity through activation of the cytoprotective nuclear erythroid 2-related factor 2 (Nrf2)-antioxidant response element/electrophile response element (ARE/EpRE) signaling pathway. Activation of this pathway by honaucin A in cultured human MCF7 cells was confirmed using an Nrf2 luciferase reporter assay. In vitro alkylation experiments with the natural product and N-acetyl-L-cysteine suggest that honaucin A activates this pathway through covalent interaction with the sulfhydryl residues of the cytosolic repressor protein Keapl. Honaucin A presents a potential therapeutic lead for diseases with an inflammatory component modulated by Nrf2-ARE.

Barron, ME, Thies AB, Espinoza JA, Barott KL, Hamdoun A, Tresguerres M.  2018.  A vesicular Na+/Ca2+ exchanger in coral calcifying cells. PLOS ONE. 13: Public Library of Science   10.1371/journal.pone.0205367   Abstract

The calcium carbonate skeletons of corals provide the underlying structure of coral reefs; however, the cellular mechanisms responsible for coral calcification remain poorly understood. In osteoblasts from vertebrate animals, a Na+/Ca2+ exchanger (NCX) present in the plasma membrane transports Ca2+ to the site of bone formation. The aims of this study were to establish whether NCX exists in corals and its localization within coral cells, which are essential first steps to investigate its potential involvement in calcification. Data mining identified genes encoding for NCX proteins in multiple coral species, a subset of which were more closely related to NCXs from vertebrates (NCXA). We cloned NCXA from Acropora yongei (AyNCXA), which, unexpectedly, contained a peptide signal that targets proteins to vesicles from the secretory pathway. AyNCXA subcellular localization was confirmed by heterologous expression of fluorescently tagged AyNCXA protein in sea urchin embryos, which localized together with known markers of intracellular vesicles. Finally, immunolabeling of coral tissues with specific antibodies revealed AyNCXA was present throughout coral tissue. AyNCXA was especially abundant in calcifying cells, where it exhibited a subcellular localization pattern consistent with intracellular vesicles. Altogether, our results demonstrate AyNCXA is present in vesicles in coral calcifying cells, where potential functions include intracellular Ca2+ homeostasis and Ca2+ transport to the growing skeleton as part of an intracellular calcification mechanism.