EFFECTS OF IN UTERO AND LACTATIONAL EXPOSURE TO DI(2-ETHYL-HEXYL) PHTHALATE (DEHP) AND POLYCHLORINATED BIPHENYLS (PCBS) IN MICE: REPRODUCTIVE TOXICITY AND MULTIGENERATIONAL TRANSMISSION

Several studies indicate that in utero and peri-natal exposure to some classes of endocrine disruptors induces adverse reproductive effects, but it remains unclear whether such effects may be transmitted to subsequent generations. The present study examined the effects in mice of exposure to di(2-ethyl-hexyl) phthalate (DEHP) or to polychlorinated biphenyls (PCBs) throughout pregnancy and lactation on reproductive health in male and female offspring, at adult age, over three generations. Groups of two to three dams were exposed to increasing doses of contaminants with the diet from gestational day 0.5 until the end of lactation. The doses employed were within the range of environmental exposure levels in humans (DEHP: 0, 0.05, 5, and 500 mg/kg/day; PCBs 101+118: 0, 1, 10, 100 μg/kg/day). In DEHP experiments, treatment of pregnant F0 dams with the 500 mg dose caused complete pregnancy failure, while a slight reduction in litter size in the 5 mg was observed. Male and female F1 offspring born from dams treated with 0.05 and 5 DEHP doses showed, once they reach adult age, significant morphological and functional alterations of the reproductive system. Specifically: i) lower body weight; ii) altered gonad weight (i.e.: lighter testis and heavier ovary) and morphology; iii) reduced germ cells quality; iv) low expression of steroidogenesis and gonadotropin-receptor genes in the gonads; and v) up-regulated gonadotropin subunits gene expression in the pituitary. DEHP exposure altered morphological and reproductive indices in male offspring only in the first generation. Conversely, F2 and F3 female offspring exhibited altered gonad weight and morphology, concomitantly with poor embryo quality, similarly to what observed in F1, thus showing a transgenerational transmission of reproductive adverse effects. Interestingly, also disregulation of selected ovarian and embryonic genes was maintained up to the third generation. In PCBs experiments, treatment did not affect F0 dams’ reproductive outcome. Nevertheless, whole-body PCB burden increased in a dose-dependent manner confirming the effectiveness of the treatment. Furthermore, concentrations at all doses investigated were greater in the offspring than in the dams, confirming that the progeny were exposed as a result of maternal exposure. Pre- and peri-natal exposure to PCBs resulted in male and female offspring showing significant reproductive abnormalities, at adult age. Specifically, compared to controls, they showed reductions in: i) testis weight and seminiferous tubule diameter; ii) sperm viability and developmental capacity; iii) ovary weight; iv) oocyte developmental capacity. Furthermore, F1 ovaries showed a dose-dependent increase in follicular atresia, associated with down-regulation of cyp19a1 and pten mRNA levels. PCBs adverse reproductive effects in females were limited to F1 generation. In contrast, male offspring exhibited reduced sperm viability and altered seminiferous tubule distribution up to the third generation. These results evidence that maternal exposure to PCBs can affects reproductive health in multiple generations. In conclusion, our data indicate that exposure to the endocrine disruptors DEHP or PCBs, at the time of gonadal sex determination, perturbed significantly the reproductive indices of male and female adult offspring. Furthermore, some of the reproductive deficiencies observed upon direct exposure have been observed up to the third generation. These findings have significant implications for reproductive health and fertility of animals and humans.