Maternal exposure to flame retardants linked to behavioral traits relevant to ASD in offspring

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Polybrominated diphenyl ethers, or PBDEs, are a class of ubiquitous flame retardant chemicals. They are found on upholstery, rugs, curtains, electronics and even baby products. Flame retardants migrate products into dust that humans can ingest. Considered to be global environmental pollutants, they have been detected in water, soil, air, food, animals and human tissue. They are also found in the breast milk of women around the world.

A research team led by scientists at the University of California at Riverside has found that when female mice exposed to PBDEs pass these neuroendocrine disrupting chemicals to their developing offspring, the female offspring exhibit traits relevant to spectrum disorders. autistic, or ASD. Their capacity for short-term social recognition and their long-term social memory are considerably reduced and the offspring exhibit an exaggerated “marble burial” behavior -; repetitive behavior reminiscent of human compulsive behavior, a central symptom of ASD.

“Our data support a link between maternal exposures to toxic substances and abnormal social and repetitive behavior in the offspring of mice that is relevant for ASD,” said Margarita Curras-Collazo, professor of neuroscience, who led the study published in the journal. Toxicology Archives.

The research team also found that the olfactory of female offspring -; or smell -; social odor discrimination is greatly compromised.

Humans primarily rely on faces to recognize people, and most people with autism have deficits in facial identity processing. Mice, on the other hand, rely on smell for social recognition. The female offspring of mother mice exposed to PBDEs exhibited odor deficits which reduced their ability to recognize other mice. Indeed, these descendants do not distinguish the new mice from the familiar mice. Humans with ASD also exhibit abnormal olfactory ability. “

Margarita Curras-Collazo, professor of neuroscience

In their experiments, the researchers exposed the mother mice orally to flame retardants; their offspring acquired PBDEs in their brains through blood during gestation and breast milk during lactation. They then measured social and repetitive behavior and olfactory discrimination in female offspring in adulthood.

Next, the researchers looked at the offspring’s brains, specifically the expression of the gene for oxytocin, a neuropeptide involved in social recognition memory. They found that oxytocin and other prosocial genes had undergone changes, suggesting that PBDEs target distinct brain systems to promote neurodevelopmental abnormalities.

“This shows that developmental exposure to PBDEs produces neurochemical, olfactory and social behavioral traits relevant to ASD in adult female offspring that may result from early neurodevelopmental reprogramming within central social and memory neural networks,” said said Elena Kozlova, student at UCR Neuroscience Graduate Program working in the Curras-Collazo laboratory and first author of the research paper.

To the authors’ knowledge, their study is the first to show behavior and brain changes relevant to autism in female offspring due to maternal transfer of environmental pollutants. The behaviors were also tested in exposed mothers, but they were hardly affected.

“This indicates that PBDEs are particularly harmful if exposure occurs during development and the effects last for a long time, which is of concern given that children are disproportionately exposed to PBDEs,” Kozlova said.

While most biomedical research is done on rodents, these studies have implications for humans. Like humans, mice live in social groups and communicate their dominance and subordinate behavior while competing for access to resources. A mouse’s ability to recognize others is a key behavior with translational relevance to human social cognition.

“Consumers should be aware that they are exposed to chemicals such as PBDEs,” Curras-Collazo said. “You can’t avoid these chemicals because they are added to many interior products at home, at school, in the car, and on the plane. To avoid them, you can buy furniture without PBDEs or cover the foam on your furniture, choose less contaminated foods, and vacuum and mop frequently to remove dust contaminated with PBDEs. It is crucial that we understand that these chemicals are present in our body and what they do.

Curras-Collazo believes lawmakers should be aware that safe alternatives to toxic chemicals in production are possible, such as non-synthetic materials that serve as flame retardants.

“In addition, funding agencies need to support basic scientific toxicology studies so that flame retardant chemicals such as PBDEs can be examined in more detail before they are marketed,” she said. “Funding is also needed for longitudinal studies in humans to enable the study of the developmental effects of these chemicals throughout life.”

Source:

University of California – Riverside

Journal reference:

Kozlova, EV, et al. (2021) Persistent behavioral phenotype linked to autism and alterations of social neuropeptides in female mice of progeny induced by maternal transfer of PBDE congeners into the commercial mixture DE-71. Toxicology Archives. doi.org/10.1007/s00204-021-03163-4.


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