Hydroxylated polychlorinated biphenyls may affect the thyroid hormone-induced brain development during metamorphosis of Xenopus laevis by disturbing the expression of matrix metalloproteinases

Thyroid hormones are primarily responsible for the brain development in perinatal mammals. However, this process can be inhibited by external factors such as environmental chemicals. Perinatal mammals are viviparous, which makes direct fetal examination difficult.

We used metamorphic amphibians, which exhibit many similarities to perinatal mammals, as an experimental system. Therefore, using metamorphic amphibians, we characterized the gene expression of matrix metalloproteinases, which play an important role in brain development.

The expression of many matrix metalloproteinases (mmps) was characteristically induced during metamorphosis. We also found that the expression of many mmps was induced by T₃ and markedly inhibited by hydroxylated polychlorinated biphenyls (PCBs).

Overall, our findings suggest that hydroxylated PCBs disrupt normal brain development by disturbing the gene expression of mmps.