Transcriptome Profiling in Larval Fathead Minnow Exposed to Commercial Naphthenic Acids and Extracts from Fresh and Aged Oil Sands Process-Affected Water

Surface
mining and extraction of oil sands results in the generation of and
need for storage of large volumes of oil sands process-affected water
(OSPW). More structurally complex than classical naphthenic acids
(NAs), naphthenic acid fraction components (NAFCs) are key toxic constituents
of OSPW, and changes in the NAFC profile in OSPW over time have been
linked to mitigation of OSPW toxicity. Molecular studies targeting
individual genes have indicated that NAFC toxicity is likely mediated
via oxidative stress, altered cell cycles, ontogenetic differentiation,
endocrine disruption, and immunotoxicity. However, the individual-gene
approach results in a limited picture of molecular responses. This
study shows that NAFCs, from aged or fresh OSPW, have a unique effect
on the larval fathead minnow transcriptome and provides initial data
to construct adverse outcome pathways for skeletal deformities. All
three types of processed NAs (fresh, aged, and commercial) affected
the immunome of developing fish. These gene networks included immunity,
inflammatory response, B-cell response, platelet adhesion, and T-helper
lymphocyte activity. Larvae exposed to both NAFCs and commercial NA
developed cardiovascular and bone deformities, and transcriptomic
networks reflected these developmental abnormalities. Gene networks
found only in NAFC-exposed fish suggest NAFCs may alter fish cardiovascular
health through altered calcium ion regulation. This study improves
understanding regarding the molecular perturbations underlying developmental
deformities following exposure to NAFCs.