Influence of a decontamination protocol on the blood redox status of dioxin-like PCB naturally contaminated heifers

Introduction Exposure to dioxin-like (DL) compounds promotes reactive oxygen species (ROS) production and depression of several ROS quenching systems, leading to oxidative stress. We previously reported that dioxins impair the plasma antioxidant defence system (ADS) of lactating buffalos (1), and that the extent of damage to plasma proteins and lipids in dairy cows is correlated with the concentration of DL-PCBs in bulk milk (2). Aim of the study was to evaluate in naturally exposed heifers the effect of a decontamination procedure, based on the removal of animals from the polluted area and the feeding of a controlled diet, on specific markers of blood redox homeostasis. Materials and Methods Eight one-year old DL-PCB exposed heifers were removed from a contaminated area to be reared in an experimental facility under controlled conditions and diet. From each animal perirenal fat biopsies and blood samples were collected bimonthly 4 times (A-B-C-D). Fat PCB content was measured by GC-HR-MS with a validated method. Serum Retinol (Ret), alpha-Tocopherol (Toc), Ascorbate (Asc), the total antioxidant capacity (TAC), and the glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were used as indices of the ADS. Protein and lipid damage were assayed by serum Nitro-tyrosine (N-Tyr), protein-bound carbonyls (PC), and lipid hydroperoxides (LPO) measurement. Values were expressed as mean ± SEM and statistically analyzed by one-way ANOVA followed by Tukey's test. Correlation was calculated through the Pearson's coefficient. Results and Conclusions Initial DL-PCB TEQ values of each animal was higher than 20 pg/g fat, and decreased rapidly in sampling B (7.71± 0.32 pg/g fat), complying with legal limits in samplings C and D (below 5 pg/g fat) (3). According to previous data (2), sampling A displayed significantly lower (P<0.001) Ret, Toc and Asc concentrations, as well as the TAC and the SOD and GPx activities, and significantly higher (P<0.001) N-Tyr, PC and LPO levels, compared to the decontaminated samples. A correlation between TEQ values and TAC, N-Tyr, and PC was also observed in sampling A. Our results confirm the DL-PCB mediated impairment of the ADS, associated with a higher extent of oxidative protein and lipid modifications, and demonstrate the restoration of the redox homeostasis by a decontamination procedure. Finally, TAC, N-Tyr and PC could be suitable monitoring biomarkers, as their levels are strongly affected by the extent of contamination.