Common ingredient in shampoo and personal care products impairs brain development

• An antimicrobial agent found in many shampoos and hand lotions and widely used in industrial settings inhibits the development of particular neuron structures that are essential for transmitting signals between cells, according to a University of Pittsburgh study presented today at Cell Biology 2004, the 44th annual meeting of the American Society for Cell Biology.
• Prolonged exposure to low levels of methylisothiazolinone (MIT) restricted growth of axons and dendrites of immature rat nerve cells in culture, apparently by disengaging the machinery of a key enzyme that is activated in response to cell-to-cell contact, and may have potentially damaging consequences to a developing nervous system, the researchers report.
• "While more research is needed to determine what effect MIT would have in rodent models, both at the cellular level and to a developing nervous system, our results thus far suggest there is potential that everyday exposure to the chemical could also be harmful to humans.
• I would be particularly concerned about occupational exposure in pregnant women and the possibility of risk to the fetus," said senior author Elias Aizenman, Ph.D., professor of neurobiology at the University of Pittsburgh School of Medicine.
• The first set of studies he and his team published in 2002 in The Journal of Neuroscience involved acute exposure to mature rat neurons.
• Additional studies revealed that MIT significantly hindered tyrosine phosphorylation, a process that initiates molecular events during cell-to-cell contact, and that a particular protein enzyme was its target.
• This enzyme, focal adhesion kinase (FAK), is known to be important for outgrowth of axons and dendrites as well as necessary for cell signaling.
• But to kick into action, FAK must undergo tyrosine phosphorylation, whereby collections of molecules called phosphate groups are added to FAK's sequence of amino acids.