Mercury-Modulated Immune Responses in Arctic Barnacle Goslings (Branta leucopsis) upon a Viral-Like Immune Challenge

Abstract

Historical mining activities in Svalbard (79°N/12°E) have caused local mercury (Hg) contamination. To address the potential immunomodulatory effects of environmental Hg on Arctic organisms, we collected newborn barnacle goslings (Branta leucopsis) and herded them in either a control or mining site, differing in Hg levels. An additional group at the mining site was exposed to extra inorganic Hg­(II) via supplementary feed. Hepatic total Hg concentrations differed significantly between the control (0.011 ± 0.002 mg/kg dw), mine (0.043 ± 0.011 mg/kg dw), and supplementary feed (0.713 ± 0.137 mg/kg dw) gosling groups (average ± standard deviation). Upon immune challenge with double-stranded RNA (dsRNA) injection, endpoints for immune responses and oxidative stress were measured after 24 h. Our results indicated that Hg exposure modulated the immune responses in Arctic barnacle goslings upon a viral-like immune challenge. Increased exposure to both environmental as well as supplemental Hg reduced the level of natural antibodies, suggesting impaired humoral immunity. Hg exposure upregulated the expression of proinflammatory genes in the spleen, including inducible nitric oxide synthase (iNOS) and interleukin 18 (IL18), suggesting Hg-induced inflammatory effects. Exposure to Hg also oxidized glutathione (GSH) to glutathione disulfide (GSSG); however, goslings were capable of maintaining the redox balance by de novo synthesis of GSH. These adverse effects on the immune responses indicated that even exposure to low, environmentally relevant levels of Hg might affect immune competence at the individual level and might even increase the susceptibility of the population to infections.

Interplay between pollution and avian influenza virus in shorebirds and waterfowl

“…The same effects have also been reported from air contaminants from oil sands (including ozone, sulphur dioxide, and polycyclic aromatic hydrocarbons) in wild tree swallows ( Tachycineta bicolor ) (Cruz-Martinez et al, 2015). Mercury pollution has been shown to cause a reduction in natural antibodies in barnacle goslings ( Branta leucopsis ) (Han, van den Berg, Loonen, Mateo, & van den Brink, 2022). Expression of different immune genes in embryonic chicken fibroblasts can be reduced by both polychlorinated biphenyls (PCBs: Badry, Jaspers, & Waugh, 2020) and per-/poly-fluoroalkyl substances (PFASs: Castaño-Ortiz et al, 2019).…”

“…Mercury pollution has been shown to cause a reduction in natural antibodies in barnacle goslings (Branta leucopsis) (Han, van den Berg, Loonen, Mateo, & van den Brink, 2022). Expression of different immune genes in embryonic chicken fibroblasts can be reduced by both polychlorinated biphenyls (PCBs: Badry, Jaspers, & Waugh, 2020) and per-/poly-fluoroalkyl substances (PFASs: Castaño-Ortiz et al, 2019).…”