Potentiation of the maternal immune system may modify the apoptotic process in embryos exposed to developmental toxicants.

Abstract

We have previously shown that teratogen-induced embryonic maldevelopment may result from excessive apoptosis in affected organs, but the mechanisms underlying this process are not well understood. Here we investigate the ability of maternal immunopotentiation to affect the apoptotic process and its regulatory genes p53 and bcl-2 in embryos exposed to a teratogenic insult. Potentiation of the immune system in pregnant females was performed with xenogeneic rat splenocytes or with granulocyte macrophage-colony stimulating factor (GM-CSF). The animals were exposed to cyclophosphamide (CP) and the reproductive performance in the various experimental groups was recorded. The level of apoptosis was assessed in the embryonic head and liver by TdT-mediated dUTP-biotin nick end labeling and fluorescence-activated cell sorter (FACS) analysis, while p53 and bcl-2 expression was evaluated by FACS and immunohistochemistry. In CP-treated females, a decrease in embryonic weight and an increase in the resorption rate and the percentage of embryos exhibiting head malformations were noted. These effects of CP were accompanied by the appearance of apoptotic cells in the head but not in the liver and an increased expression of p53 in embryonic organs, while bcl-2 expression was found to be decreased in the head and increased in the liver. Immunopotentiation with rat splenocytes or GM-CSF was shown to partially normalize the teratogenic effect of CP. It was also found to partially decrease the CP-induced apoptotic process and exhibited a tendency to normalize the expression of p53 and bcl-2 in the embryonic head and liver. Our results suggest a possible role for maternal immunopotentiation in protecting the embryo from teratogenic insults, possibly through regulation of the CP-induced apoptotic process and the expression of p53 and bcl-2.