T6 PM Immune and Endocrine Disruption: Detection and Implication
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 324-326

(BRA-1117-846804) Increased disease susceptibility in Oncorhynchus mykiss associated with exposure to environmentally relevant concentrations of PAH.

Bravo, C.¹, Curtis, L.¹, Bayne, C.², Gerwick, L², Arkoosh, M.³, Lambertini, E.⁴, Loge, F.⁴, Collier, T.⁵, ¹ Department of Environmental and Molecular Toxicology , Oregon State University., Corvallis, OR, USA² Department of Zoology, Oregon State University., Corvallis, OR, USA³ Environmental Conservation Division, Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA., Newport, OR, USA⁴ Department of Civil and Environmental Engineering, University of California Davis., Davis, CA, USA⁵ Environmental Conservation Division, Northwest Fisheries Science Center, National Marine Fisheries Service, NOAA., Seattle, WA, USA

ABSTRACT- Polycyclic aromatic hydrocarbons (PAH) occur as complex mixtures in aquatic ecosystems. Rainbow trout (Oncorhynchus mykiss) were fed a mixture of ten, high molecular weight PAH at environmentally relevant concentrations (40 and 400 ppm) for 50 days. Fish were exposed to the PAH mixture at concentrations found in sediment samples and stomach contents of other salmonid species from PAH contaminated field sites in the Pacific Northwest. After 50 days of PAH feeding, fish were exposed to Aeromonas salmonicida. Bacterial concentrations that yielded LC₂₀ and LC₃₀ in healthy rainbow trout from the same stock as PAH treated fish were selected for disease challenges. Mortalities were monitored during challenge for 21 days. Diseased challenged fish treated with 400 ppm of the PAH mixture suffered about 40% cumulative mortality compared to 29% for controls. Microarray analysis was performed in kidney from fish collected on days 2, 4 10 and 20 during the disease challenge. We identified roughly 20 immunologically relevant genes differentially expressed under pathogen challenge. The genes were identified by comparing fish challenged with Aeromonas with fish not challenged with pathogen; both groups were not exposed to PAH. Interestingly, under pathogen challenge, roughly five additional genes were differentially expressed when the fish were exposed to PAH (these genes were identified by comparing fish exposed to PAH with fish not exposed to chemical, both groups were challenged with Aeromonas). These five genes were not differentially expressed with PAH exposure alone (no pathogen challenge); the genes have been associated with oxidative stress and immune function by other investigators. The expression profile of all genes statistically different from the control varied kinetically over time. Overall, the array results suggest that mechanisms other than aryl hydrocarbon receptor activation are potentially important in PAH-induced increased disease susceptibility in salmonids.

Key words: Disease Susceptibility, PAH, Rainbow trout array, Oxidative stress