Metals are effectively used in biological systems under the strict regulation for exploiting their specific and broad reactivities. For example, manganese (Mn) can induce catecholamines-mediated oxidative biological damage in cooperation with iron (Fe) and/or copper (Cu). In children, the damage could induce developmental disorders such as attention deficit hyperactivity disorder (ADHD). We hypothesize that infant neurons are more labile to metals than adult ones due to the prematured protection systems and sensitive differentiating cells. An experimental system reconstituting neural differentiation is expected to assess the influences of endogenous/exogenous factors including metals. In this study, we investigated an impact of Mn together with Fe and dopamine (DA) on neural differentiation of mouse embryonic stem cells (mESCs). The differentiation of mESCs was initiated by embryoid bodies (EBs) formation in the presence of all-
trans retinoic acid, and then EBs were treated with Mn, Fe and/or DA. Then, the mRNA levels of neural differentiation marker genes (
Nestin,
Emx2,
Mtap2,
Th,
Olig2 and
Gfap) were examined using realtime RT-PCR analysis. Mn or DA alone reduced
Mtap2,
Th and
Olig2 expression levels and increased
Nestin. Moreover, combined treatment of Mn and DA also increased
Nestin expression level. On the other hand, Fe alone reduced
Mtap2,
Th and
Olig2 expression levels, and increased
Emx2. Combined treatments of Fe with Mn or DA also tended to increase
Emx2 expression level. These effects emerged at about 100 times less concentration than that inducing cytotoxicity in human neuroblastoma. The present study showed that Mn inhibits neural development, and that our mESCs system can be a useful tool to elucidate the toxicity mechanism as well as to evaluate the effects of metals and chemicals on differentiating cells.
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