505
fish, immune organs such as the head, kidney, and spleen have the capacity to detoxify xenobiotics indicating a biotransformation system within the immune system
(Reynaud et al. 2008). In addition, in the liver, PAH activation of the AhR and PAH
metabolism by the CYP enzymes along with Ca
2+
mobilization can induce immunotoxicity (Reynaud and Deschaux 2006).
Three field studies of adult Gulf killifish collected in 2010 from DWH oilcontaminated sites of the northern GoM indicated modulations to both innate and
adaptive immunities had occurred. Modulation of the adaptive immune system
included notable decreases of circulating lymphocytes and enlargement of splenic
melano-macrophage centers (MMCs) in relation to increased activity of
ethoxyresorufin- O-deethylase (EROD), an established biomarker for PAH exposure
in the environment (Omar-Ali et al. 2014). In addition, RNA-seq analysis of liver
tissue indicated upregulation of adaptive immune genes, IgM, and tumor necrosis
factor receptors 14 and 21 (TNFr14 and 21), relative to upregulation of genes associated with hypoxia and the CYP/AhR pathway (Garcia et al. 2012). Whereas
microarray analysis of gill tissue demonstrated modulation of innate immunity with
enrichment of genes involved in wound healing, inflammation, and the acute phase
response, there was also a correlation with enrichment of CYP genes that have oilassociated expression (Dubansky et al. 2013).
RNA-seq and microarray analyses revealed immunosuppression in the livers of
GoM fish exposed to either oil or dispersed oil. In juvenile red drum exposed for
3 days to a CEWAF of 1.73 μg/L∑50PAH, differential gene expression analysis
indicated the majority of immune genes were significantly downregulated. These
included genes associated with granulocyte and macrophage function (23 genes), T
cell receptor (4 genes), and B cell receptor (2 genes). This downregulation of
immune genes further correlated to significant upregulation of CYP1A, GST, and
UDP-glucuronosyltransferase genes involved in metabolism of xenobiotics (Wetzel
DOI: 10.7266/NT8P5Z08). Altered immune processes were observed in adult
sheepshead minnow exposed for 7 or 14 days to environmentally relevant HEWAF
concentrations of 0.26–5.95 μg/L∑50PAH and CEWAF concentrations of 0.35–
1.10 μg/L∑50PAH, with the most affected responses related to macrophage and
granulocyte functions (Jones et al. 2017).
Following the DWH spill, offshore surveys of fish populations observed incidences of skin lesions in GoM fish especially in bottom-dwelling species near the
DWH site (Murawski et al. 2014). The lesions were hypothesized to be caused by
PAH suppression of the immune system allowing for opportunistic bacteria colonization. Bayhe et al. (2017) were able to demonstrate this phenomenon in juvenile
southern flounder exposed to weathered DWH oil-contaminated sediments at a concentration of 57.40 mg/kg∑50PAH for 7 days, followed by a 1-h bacterial challenge with V. anguillarum, resulting in body lesions similar to those reported in the
field. The observed lesions were most likely due to a reduction of IgM gene expression in the spleen and kidney of oil-exposed southern flounder. IgM is the main
immunoglobulin in fish that is essential for clearance of bacterial pathogens.
29 Digging Deeper than LC/EC50: Nontraditional Endpoints and Non-model Species…
fish, immune organs such as the head, kidney, and spleen have the capacity to detoxify xenobiotics indicating a biotransformation system within the immune system
(Reynaud et al. 2008). In addition, in the liver, PAH activation of the AhR and PAH
metabolism by the CYP enzymes along with Ca
2+
mobilization can induce immunotoxicity (Reynaud and Deschaux 2006).
Three field studies of adult Gulf killifish collected in 2010 from DWH oilcontaminated sites of the northern GoM indicated modulations to both innate and
adaptive immunities had occurred. Modulation of the adaptive immune system
included notable decreases of circulating lymphocytes and enlargement of splenic
melano-macrophage centers (MMCs) in relation to increased activity of
ethoxyresorufin- O-deethylase (EROD), an established biomarker for PAH exposure
in the environment (Omar-Ali et al. 2014). In addition, RNA-seq analysis of liver
tissue indicated upregulation of adaptive immune genes, IgM, and tumor necrosis
factor receptors 14 and 21 (TNFr14 and 21), relative to upregulation of genes associated with hypoxia and the CYP/AhR pathway (Garcia et al. 2012). Whereas
microarray analysis of gill tissue demonstrated modulation of innate immunity with
enrichment of genes involved in wound healing, inflammation, and the acute phase
response, there was also a correlation with enrichment of CYP genes that have oilassociated expression (Dubansky et al. 2013).
RNA-seq and microarray analyses revealed immunosuppression in the livers of
GoM fish exposed to either oil or dispersed oil. In juvenile red drum exposed for
3 days to a CEWAF of 1.73 μg/L∑50PAH, differential gene expression analysis
indicated the majority of immune genes were significantly downregulated. These
included genes associated with granulocyte and macrophage function (23 genes), T
cell receptor (4 genes), and B cell receptor (2 genes). This downregulation of
immune genes further correlated to significant upregulation of CYP1A, GST, and
UDP-glucuronosyltransferase genes involved in metabolism of xenobiotics (Wetzel
DOI: 10.7266/NT8P5Z08). Altered immune processes were observed in adult
sheepshead minnow exposed for 7 or 14 days to environmentally relevant HEWAF
concentrations of 0.26–5.95 μg/L∑50PAH and CEWAF concentrations of 0.35–
1.10 μg/L∑50PAH, with the most affected responses related to macrophage and
granulocyte functions (Jones et al. 2017).
Following the DWH spill, offshore surveys of fish populations observed incidences of skin lesions in GoM fish especially in bottom-dwelling species near the
DWH site (Murawski et al. 2014). The lesions were hypothesized to be caused by
PAH suppression of the immune system allowing for opportunistic bacteria colonization. Bayhe et al. (2017) were able to demonstrate this phenomenon in juvenile
southern flounder exposed to weathered DWH oil-contaminated sediments at a concentration of 57.40 mg/kg∑50PAH for 7 days, followed by a 1-h bacterial challenge with V. anguillarum, resulting in body lesions similar to those reported in the
field. The observed lesions were most likely due to a reduction of IgM gene expression in the spleen and kidney of oil-exposed southern flounder. IgM is the main
immunoglobulin in fish that is essential for clearance of bacterial pathogens.
29 Digging Deeper than LC/EC50: Nontraditional Endpoints and Non-model Species…