76 What is Autism?
the mutations that occur as part of the normal development as it is clear from
the above discussion, but we have to look at how the normal branching of the
human brain tree is disturbed by elimination or reduction in certain cell types
that result in ASD. One approach is to utilize human fetal brain neurons that
arise from an anomaly in the development of a fetus, resulting in migration of
fetal brain‐progenitor neurons that settle somewhere in the body as nonmalig-
nant tumors. These progenitor bundles of neurons behave much like fetal brain
neurons but are disorganized. They also differentiate under specific neuronal
growth hormones, respond to mutagenic and neuromodifying agents, and
exhibit loss or gain of neuronal receptors similar to human fetal brain stem
cells. We decided to use these neuroblastoma tumor cell lines from male
and female origin and evaluate if there are unique or differential responses to
exposures of minuscule amounts of fragrances or testosterone levels that one
would expect to find in the amniotic environment during the early stages of
gestation.
Although no reliable neurophysiological network is associated with ASD,
low levels of plasma oxytocin and arginine vasopressin have been reported.
The “twin” nonapeptides oxytocin and arginine vasopressin are mainly pro-
duced in the brain of mammals, and dysregulation of these neuropeptides has
been associated with changes in behavior, especially social interactions.
Therefore, we analyzed the neuromodifications of three selected fragrances on
male and female human fetal brain neurons, utilizing immunohistochemistry.
We showed that exposure to even femtomolar concentrations of fragrances
resulted in morphological changes by light microscopy in the neuroblastoma
cell line (NBC). Importantly, these fragrances significantly reduced the oxy-
tocin‐ and arginine vasopressin‐receptor positive neurons in male NBC but
not in female NBC, possibly contributing to the development of male bias in
ASD. This study is the first to show a potential link between fragrance expo-
sure, depletion of oxytocin‐ and arginine vasopressin‐receptor positive neu-
rons, and a male bias in autism. We are also evaluating the exposure of
testosterone at the levels that are found in the amniotic fluids of normal as well
as in ASD children during 9–14 weeks of gestation. The results from these
lines of inquiry may show that ASD is the result of epigenetic factors, factors
that are not genetic in origin but are due to exposure to environmental factors.
Of note, we have identified over two dozen chemicals that show testosterone
and other sex hormone‐like properties in fragrances. For example, numerous
chemicals found to act like testosterone (i.e., oxybenzone, benzophenone‐1,
galaxolide, and tonalide) are found in fragrances [2–15,24,25]. Other chemicals
that have been shown to increase human estrogen receptor expression include
octinoxate, oxybenzone, benzophenone‐1, benzophenone‐2, benzyl salicylate,
benzyl benzoate, butylphenyl methylpropional, and synthetic musks (galaxo-
lide, tonalide, and musk ketone). Butylated hydroxy toluene, benzophenone‐2
and octinoxate have been linked to thyroid hormone disruption [reviewed in