Oxidative stress in Perna perna and other bivalves as indicators of environmental stress in the Brazilian marine environment: antioxidants, lipid peroxidation and DNA damage.

Oxidative stress can take place in marine bivalves under a series of environmental adverse conditions. The study of different systems related to oxidative stress in these organisms can give important information about their physiological status and also about environmental health. Bivalves have been proposed as good sentinel organisms in pollution monitoring studies through the analysis of biochemical biomarkers, and most of the biomarkers analyzed are those related to oxidative stress. However, it is very important to know how other environmental factors not associated to the presence of pollutants might affect these parameters. We have studied a series of mechanisms related to oxidative stress in mussels which inhabit the Brazilian coast, especially in Perna perna species, subjected to different stress conditions, such as the exposure to different contaminants in the laboratory and in the field, the exposure of mussels to air and re-submersion, simulating the tidal oscillations, and in mussels collected at different seasons. Both oxidative damage levels and antioxidant defense systems were strongly affected by the different environmental stress. This review summarizes the data obtained in some studies carried out in bivalves from the Brazilian coast.

Expression of PXR, CYP3A and MDR1 genes in liver of zebrafish.

The Pregnane X Receptor (PXR) is a nuclear receptor involved in the transcriptional regulation of drug-metabolizing enzymes and transporters. In mammals, many xenobiotics induce the expression of cytochrome P4503A (CYP3A) and the multiple drug resistance 1 (MDR1) genes via the PXR pathway. Little attention has been given to studies about the identification and biological function of PXR homologues in non-mammalian species. Zebrafish is being widely used and accepted as model for toxicological and pharmacological studies to understand the mechanisms of human diseases and identify conserved signaling pathways. The aim of this study was to evaluate the in vivo expression of PXR, CYP3A and MDR1 genes in liver of zebrafish treated with the synthetic steroid pregnenolone 16alpha-carboninitrile (PCN), the antimycotic clotrimazole (CTZ) and the antianginal drug nifedipine (NIF). The liver of fish treated with PCN showed a 1.9-fold induction in the PXR followed by 1.8-fold induction in the CYP3A and 1.6-fold induction in the MDR1 mRNA. CTZ and NIF did not affect statistically the expression of PXR, CYP3A and MDR1. The similar pattern of mRNA expression of PXR, CYP3A and MDR1 genes found in fish treated with different PXR inducers suggests that the intrinsic association between these three genes is conserved in zebrafish.