The effect of broccoli in diet on the cytochrome P450 activities of tilapia fish (Oreochromis niloticus) during phenol exposure

Aquaculture is the fastest growing animal food-producing sector and represents around 40% of global fish production. Doubtless, aquaculture will be soon the main world source of marine and freshwater food, over the capture fishery. Water pollution is a main concern for production and represents a public health risk. Cruciferous vegetables, as broccoli, have been reported to have a chemoprotection capacity against the effect of pollutants on different organisms. Broccoli and its phytochemicals are able to modulate the cytochrome P450 enzymes (CYP) which are involved in the xenobiotic metabolism. In this work, the effect of a broccoli-rich diet on different cytochromes P450 activities in liver from tilapia juveniles exposed to phenol was determined. Activities on phenacetin, chlorzoxazone, tolbutamide, mephenytoin, dextromethorphan, and testosterone, were monitored in tilapia liver extracts from fish fed with and without enriched broccoli diets, before and after phenol exposure. Fish were fed with broccoli and control diets during 30 days prior to phenol exposure at two sub-lethal concentrations of phenol (2 and 20 mg L−1), then the profile of CYP activities was determined at 0, 12 and 24 h after phenol addition. Before phenol addition fish fed with broccoli-rich diet showed a significant induction of phenacetin and tolbutamide activities when compared with liver extracts from fish fed with control diet. After phenol exposure a clear and steady induction of the dextromethorphan and mephenytoin activities were detected. In spite of the fact that substrates are not specific for each CYP, the increase of activity on dextromethorphan could represent the first report of a hepatic CYP2D6 induction by the presence of a xenobiotic. In addition, phenol exposure through diet was evaluated. Consistently with the previous experiments, phenacetin and chlorzoxazone showed higher activities while dextromethorphan and testosterone activities were lower in the liver extract from fish fed with broccoli than in control fish. Interestingly, tolbutamide activity was significantly higher in fish fed with broccoli than these observed in the controls, while mephenytoin showed 8-times higher activity in fish fed with control diet than those fed with broccoli enriched diet. The role of cytochrome P450 enzymes in the xenobiotic metabolism and the potential use of designed diets, containing chemoprotectors, to contend against pollutant effects on cultivated fish are discussed.