No evidence for oxidative stress in the cerebellar tissues or cells of juvenile male mice exposed via lactation to the 6 non-dioxin-like PCBs at levels below the regulatory safe limits for humans

The developing central nervous system is particularly vulnerable to environmental contaminants such as non-dioxin-like polychlorinated biphenyls (NDL-PCBs). This study investigated the potential oxidative effects in mice pups exposed via lactation to the sum of the six indicator NDL-PCBs (∑6 NDL-PCBs) at 0, 1, 10 and 100 ng/kg per 14 days, constituting levels below the guidance values fixed by French food safety agencies for humans at 10 ng/kg body weight per day. For this purpose, the oxidative status was assessed by flow cytometry via dichloro-dihydro-fluorescein diacetate in the cerebellum of juvenile male offspring mice during brain growth spurt [postnatal day (PND) 14]. No significant differences were found in the levels of reactive oxygen species in the cerebellar neurons or glial cells (astrocytes, oligodendrocytes and microglia) of lactationally exposed male mice at PND 14 (p> 0.05). Concordantly, oxidative-stress related gene expression was measured by qPCR for catalase, copper zinc superoxide dismutase 1, glyoxalase 1, glutathione peroxidase 1, and glutathione reductase 1, in the cerebellum at PND 14 appeared unaffected, as also verified at the protein level by immunoblots. Moreover, transcriptomic data from our previous work have not shown differences in the mRNA expressions of genes belonging to GO terms involved in oxidative stress in neurons of male mice exposed to ∑6 NDL-PCBs compared to controls; except for glyoxalase 1 which was downregulated in neurons isolated from exposed group compared to controls. Our findings suggest that lactational exposure to NDL-PCBs at environmental relevant concentrations may not cause significant oxidative effect on juvenile cerebellum.