In vitro models of xenobiotic metabolism in trout for use in environmental bioaccumulation studies.

1. In vitro screens are sought as informative, alternatives to the use of animals in vivo and to improve upon the current use of fish liver 9000 g supernatants (S9) in environmental risk assessment. 2. The rates of ethoxyresorufin-O-deethylation (relative to S9 protein) measured under different conditions of culture of rainbow trout hepatocytes were significantly higher than those detected in S9, in the order of freshly isolated hepatocytes > 10-day spheroid cultures > primary hepatocytes in culture > S9. The percentage of conjugated metabolites was also similar between freshly isolated and spheroid cultured hepatocytes (9.9 and 13.5%). 3. The rate of oxidation was enhanced (1.7 fold) when S9 was supplemented with cofactors for phase II conjugation but this was only approximately one tenth of the rate in freshly isolated hepatocytes (7.1 pmol/min/mg S9 protein equivalent). 4. Hepatocytes also hydroxylated ibuprofen, producing two metabolites, in contrast to only one (identified as the 1-hydroxy derivative) using hepatic S9 fractions. 5. Since the bioaccumulation potential of chemicals is often based on un-supplemented S9 in incubations ≥ 1 h when activity declines, it is recommended that predictability would be greatly improved through the use of hepatocyte spheroids, due to their maintenance of activity and longevity.

Towards a system level understanding of non-model organisms sampled from the environment: a network biology approach.

The acquisition and analysis of datasets including multi-level omics and physiology from non-model species, sampled from field populations, is a formidable challenge, which so far has prevented the application of systems biology approaches. If successful, these could contribute enormously to improving our understanding of how populations of living organisms adapt to environmental stressors relating to, for example, pollution and climate. Here we describe the first application of a network inference approach integrating transcriptional, metabolic and phenotypic information representative of wild populations of the European flounder fish, sampled at seven estuarine locations in northern Europe with different degrees and profiles of chemical contaminants. We identified network modules, whose activity was predictive of environmental exposure and represented a link between molecular and morphometric indices. These sub-networks represented both known and candidate novel adverse outcome pathways representative of several aspects of human liver pathophysiology such as liver hyperplasia, fibrosis, and hepatocellular carcinoma. At the molecular level these pathways were linked to TNF alpha, TGF beta, PDGF, AGT and VEGF signalling. More generally, this pioneering study has important implications as it can be applied to model molecular mechanisms of compensatory adaptation to a wide range of scenarios in wild populations.