A link between thimerosal and the brain: Can vaccines affect central nervous sys

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A link between thimerosal and the brain: Can vaccines affect central nervous

system function?

According to new research from Northeastern University pharmacy professor

Deth and colleagues from the University of Nebraska, Tufts, and s

Hopkins University, there is an apparent link between exposure to certain

neurodevelopmental toxins and an increased possibility of developing

neurological

disorders including autism and attention-deficit hyperactivity disorder. The

research – the first to offer an explanation for possible causes of two

increasingly common childhood neurological disorders – will be published in

the April

2004 issue of the journal Molecular Psychiatry, and earlier as advance online

publication.

Though some speculation exists regarding this link, Deth and his colleagues

found that exposure to toxins, such as ethanol and heavy metals (including

lead, aluminum and the ethylmercury-containing preservative thimerosal) potently

interrupt growth factor signaling, causing adverse effects on methylation

reactions (i.e. the transfer of carbon atoms). Methylation, in turn, plays a

significant role in regulating normal DNA function and gene expression, and is

critical to proper neurological development in infants and children. Scientists

and

practitioners have identified an increase in diagnoses of autism and ADHD in

particular, though the reasons why are largely unknown.

In their work, the scientists found that insulin-like growth factor-1 (IGF-1)

and the neurotransmitter dopamine both stimulated folate-dependent

methylation pathways in neuronal cells. At the same time they noted that

compounds like

thimerosal, ethanol and metals (like lead and mercury) effectively inhibited

these same biochemical pathways at concentrations that are typically found

following vaccination or other sources of exposure. By better understanding what

happens when infants and children are exposed to these materials, the work of

Deth and his colleagues helps to explain how environmental contact with metals

and administration of certain vaccines may lead to serious disorders that

manifest themselves during childhood, including autism and ADHD.

" Scientists certainly acknowledge that exposure to neurotoxins like ethanol

and heavy metals can cause developmental disorders, but until now, the precise

mechanisms underlying their toxicity have not been known. " said Deth. " The

recent increase in the incidence of autism led us to speculate that

environmental

exposures, including vaccine additives might contribute to the triggering of

this disorder. "

Thimerosal, which was largely phased out in the U.S. and in Europe starting

in 2000,was often used for its preservative abilities in multi-dose units of

vaccines for diseases like hepatitis, whooping cough, tetanus and diptheria.

Today, most vaccines carry only trace amounts of it, according to the CDC. But

in

larger, multi-dose vials of these vaccines, often shipped to and used in

third world countries, thimerosal is still very common. Multi-dose flu vaccines

still contain thimerosal.

Additionally, the scientists recently obtained more insight into the

mechanism by which thimerosal interferes with folate-dependent methylation. It

acts by

inhibiting the biosynthesis of the active form of vitamin B12

(methylcobalamin), which is of particular interest because doctors treating

autistic kids are

having good success with the administration of methycobalamin.

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Citation source: Molecular Psychiatry 2004 Volume 9, advance online

publication doi:10.1038/sj.mp.4001476

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