The plasticizers contained in many everyday objects can impair important brain functions in humans. Biologists from the University of Bayreuth warn of this danger in an article in Communications Biology. Their study shows that even small amounts of the plasticizers bisphenol A and bisphenol S disrupt the transmission of signals between nerve cells in the brains of fish.
The researchers consider it
very likely that similar interference can also occur in the brains of adult
humans. They, therefore, call for the rapid development of alternative
plasticizers that do not pose a risk to the central nervous system.
Bisphenols are plasticisers
that are found in a large number of plastic products worldwide – for example,
in food packaging, plastic tableware, drinking bottles, toys, tooth fillings,
and babies’ dummies. In recent years, numerous health risks have already been
associated with them, especially with bisphenol A (BPA).
The Bayreuth research team
led by Dr. Peter Machnik at the Animal Physiology research group (led by Dr.
Stefan Schuster) has now for the first time investigated the effects of
plasticisers on signal transmission between nerve cells in the adult brain.
The study covers not only
BPA, but also bisphenol S (BPS), which is often considered less harmful to
health. Their findings: Both plasticisers impair communication between the
nerve cells of the brain.
Permanent
damage to the nervous system
The harmful effects on the
brain mainly affect the delicate balance between different neuronal functions.
While some brain cells transmit signals that trigger a state of excitation in
downstream cells, other brain cells have the function of inhibiting downstream
cells. However, the coordination of both excitation and inhibition is essential
for an intact central nervous system.
“It is well known that
numerous disorders in the nervous system of vertebrates are triggered by the
fact that excitatory signals and inhibitory signals are not or only
inadequately coordinated. So, it is all the more alarming that the plasticizers
BPA and BPS significantly impair precisely this coordination,” explains Dr.
Peter Machnik, lead author of the study.
“We were surprised how many
vital brain functions in fish are affected by the plasticizers used in numerous
industries. This damage, as we were able to show, does not occur immediately.
However, when the brain cells are exposed to small amounts of BPA or BPS for a
month, the damage is unmistakable,” says Elisabeth Schirmer, a doctoral student
from Bayreuth and first author of the study.
It turns out that the
plasticisers influence the action potential of brain cells. They alter the
chemical and electrical transmission of signals through the synapses. In
addition, they disrupt the circuits that are important for the perception and
processing of acoustic and visual stimuli.
Studies
on Mauthner cells in goldfish
The discovery of the damage
caused by plasticizers came from detailed studies on live goldfish. The focus
was on the two largest nerve cells in fish brain, the Mauthner cells. They
integrate all sensory stimuli, all of which must be processed quickly and in a
precisely coordinated manner when predators approach. In this case, the
Mauthner cells trigger life-saving escape reactions.Due to this function, which
is essential for survival, they have become particularly robust in the course
of evolution. Mauthner cells are able to ward off damaging influences to a
certain extent, or to compensate for damage afterwards. This makes it all the
more significant that plasticizers are able to cause considerable damage to
these cells.
Transferability of the results to humans
– Demand for alternative plasticisers
“The findings obtained
through studies on fish brains justify the assessment that BPA and BPS can also
seriously damage the brains of adult humans. Against this background, it is
essential that science and industry develop new plasticizers to replace these
bisphnols, while being safe for human health,” says Dr. Peter Machnik.
Prof. Dr. Stefan Schuster
adds: “The efficiency of the research techniques we used in our study could, in
addition, prove a valuable aid in the development of alternative plasticizers.
They make it possible to quickly and inexpensively test how a substance under
consideration affects brain cells.”
Source: https://www.uni-bayreuth.de/en/
Journal article: https://www.nature.com/articles/s42003-021-01966-w
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