Effects of Polar Bear and Killer Whale Derived Contaminant Cocktails on Marine Mammal Immunity

Abstract

Most controlled toxicity studies use single chemical exposures that do not represent the real world situation of complex mixtures of known and unknown natural and anthropogenic substances. In the present study, complex contaminant cocktails derived from the blubber of polar bears (PB; Ursus maritimus) and killer whales (KW; Orcinus orca) were used for in vitro concentration-response experiments with PB, cetacean and seal spp. immune cells to evaluate the effect of realistic contaminant mixtures on various immune functions. Cytotoxic effects of the PB cocktail occurred at lower concentrations than the KW cocktail (1 vs 16 μg/mL), likely due to differences in contaminant profiles in the mixtures derived from the adipose of each species. Similarly, significant reduction of lymphocyte proliferation occurred at much lower exposures in the PB cocktail (EC: 0.94 vs 6.06 μg/mL; P < 0.01), whereas the KW cocktail caused a much faster decline in proliferation (slope: 2.9 vs 1.7; P = 0.04). Only the KW cocktail modulated natural killer (NK) cell activity and neutrophil and monocyte phagocytosis in a concentration- and species-dependent manner. No clear sensitivity differences emerged when comparing cetaceans, seals and PB. Our results showing lower effect levels for complex mixtures relative to single compounds suggest that previous risk assessments underestimate the effects of real world contaminant exposure on immunity. Our results using blubber-derived contaminant cocktails add realism to in vitro exposure experiments and confirm the immunotoxic risk marine mammals face from exposure to complex mixtures of environmental contaminants.

Predicting global killer whale population collapse from PCB pollution

“…Our finding that a single chemical class (PCBs) may represent a substantial conservation threat to killer whales around the world raises concerns about the potential for other persistent contaminants to generate additional toxic injury in long-lived, high-trophic level aquatic species. Indeed, a long list of additional http://science.sciencemag.org/ known and as yet unmeasured contaminants are present in killer whale tissues, including biologically active compounds like perfluoroalkyl acids, brominated and organophosphate flame retardants, and polychlorinated naphthalenes (25), and although these are less well characterized, they may contribute to reproductive and immune failure or other health endpoints not included here.…”

Apex marine predators and ocean health: Proactive screening of halogenated organic contaminants reveals ecosystem indicator species

“…A comprehensive assessment of contaminant load is required to evaluate the toxicological risk associated with contaminant exposure in wildlife, which may vary depending on the complexity of the contaminant mixture (Desforges et al, 2017). Marine mammals serve as effective indicators of marine pollution due to their high trophic position, large stores of lipid-rich blubber, and relatively long lifespans (Bossart, 2011;Ross, 2000).…”

Persistent Organic Pollutant Burden, Experimental POP Exposure, and Tissue Properties Affect Metabolic Profiles of Blubber from Gray Seal Pups

“…Experimental studies have demonstrated that POPs can alter adipocyte function in rodents and human cell lines25,104 . POPs are associated with altered adipose and liver expression of metabolic pathway genes in adult polar bears55,66 and ringed seals (Pusa hispida)63,64 , but the functional consequences of such changes for fat tissue have not been identified.Recent experimental studies that replicate environmental or physiological POP concentrations and congener mixtures provide causal evidence of their immunological105 and adipogenic effects91 . Our work builds on these findings by showing that existing POP concentrations in blubber tissue, generated in utero and through lactational transfer, can alter metabolic properties of adipose tissue in young, developing seals.Our data are consistent with experimental studies showing PCB 77, 153 and dioxin reduce glucose and insulin tolerance in mice, guinea pigs (Cavia porcellus),…”