On February 25, 2013 the journal Proceedings of the National Academy of Sciences published an article by Michele Yeo and colleagues on BPA and how it could cause neurodevelopmental disorders. BPA (bisphenol A) is a chemical that has hormone like qualities similar to estrogen. It can be found in the plastic materials in the environment, which can 'leak' into edible items (like water from a water bottle). This ingestion can lead to health problems like cancer and reproductive disorders.
In this paper, they found that BPA can impair central nervous system development. They did experiments to try to figure our how BPA exposure can lead to this using rodents and human nerve cells.
First of all, the development of neurons occurs with chloride presence. When the neurons are developing, there are high levels of chloride, and when the levels drop, the neurons are able to mature. KCC2 is a chloride transport protein that aids in removal of the chloride. It is known that if the level of chloride is not removed, damage can occur to the developing neurons by damaging neural circuits and "preventing" migration of the nerve cells to the appropriate position in the brain.
When BPA exposure is elevated the Kcc2 gene is shut down leading to altered altered levels of chloride in the neurons. This gene is responsible for making KCC2 protein. If that protein can not be made, then chloride regulation will be in trouble with a delay in removal. It was found that MECP2, which is a protein involved in normal brain function could be responsible for shutting down Kcc2 gene. MECP2's abundance increases during exposure of BPA. MECP2 binds to Kcc2 and shuts down the gene.
An interesting finding is that female's neurons were more sensitive to BPA exposure compared to males males. Further studies will be needed to give answers for this interesting finding, and if some sex hormone receptors, like estrogen, are involved with the relation of BPA and KCC2.
In summary, BPA exposure is involved with normal neuron development by effecting Kcc2 gene regulation.
Michele Yeo, Ken Berglund, Michael Hanna, Junjie U. Guo, Jaya Kittur, Maria D. Torres, Joel Abramowitz, Jorge Busciglio, Yuan Gao, Lutz Birnbaumer, and Wolfgang B. Liedtke. Bisphenol A delays the perinatal chloride shift in cortical neurons by epigenetic effects on the Kcc2 promoter. PNAS, February 25, 2013 DOI: 10.1073/pnas.1300959110