Karina Block, a marine oceanographer, had a hunch that the plane exhaust fumes that she and her fellow seafarers were regularly exposed to, along with the unavoidable stress of work, were leading to adverse health outcomes for their children. A new study in mice – funded in part by the NIEHS – backs up its suspicion, finding that air pollution and housing insecurity during pregnancy can lead to autism-like social behavior and different wired brains in males rather than females.
Find who was Published August 2 in Cell Reportsindicates that the immune system may be at fault.
“I was pregnant, exhausted, and working near airplanes,” Block recalls. “I used to walk by jet fuel exhaust every day. My child ended up developing a neurodevelopmental disorder, hydrocephalus.”
Block’s daughter is now thriving, as is Block, and is now Dr. Block after receiving her Ph.D. from Duke University in the Laboratories of Psychology and Neuroscience Professor Staci Bilbo, Ph.D., and Professor of Cell Biology Cagla Eroglu, Ph.D. . However, Block’s new post provides compelling evidence that if she had been pregnant with a son, he might have been born with autism.
missing link
Air pollution, such as exhaust from diesel engines in trucks, is associated with increased rates of neurodevelopmental disorders, such as 99% of people around the world Living in cities with unhealthy air only One in every 44 children has autism (And four times more boys than girls.)
So why doesn’t everyone have autism?
“Environmental toxins are worse for some people than others, and the most vulnerable populations are always affected,” Bilbo said. In the case of autism and air pollution, Bilbo believes the missing link is maternal stress caused by poverty and housing insecurity.
“It’s not that the rich aren’t nervous,” Bilbo said. “But it’s different when you have to worry about where you’re going to live and whether you’re safe in your home.”
Stressed moms
while there Persuasive data in humans In support of Bilbo’s claim, it is impossible (and unethical) to directly test these ideas on pregnant women in order to reveal the biological mechanism by which air pollution and stress may conspire to rewire the brains of developing children.
To fill this gap, Block and her team exposed pregnant mice to the poor housing and air quality conditions that many people tolerate every day, and investigated how their offspring live.
As evidence of air pollution, rat mothers were exposed to diesel exhaust particles, the invisible but harmful pollutants that semi-cars and construction machinery regularly exhale. Towards the end of pregnancy, the rat mothers were subjected to another stress: inadequate housing. Pregnant mice were allocated less building material than usual to build their nests for their young.
Despite all this, stressful mothers were still excellent fathers – they nurtured and groomed their pups just like those relieved of prenatal stress. But as their daughters grew up as expected, their sons misread social cues throughout life. As a teenager, males born out of stress and mothers exposed to smog preferred to hang out with a yellow rubber duck rather than a nearby mouse (rats usually prefer one’s own company rather than a bathing toy).
culling brain connections
Next, Block and her team looked at whether brains were reconnected earlier, resulting in more shy teenage boys. Specifically, the research team wondered whether male brains did not get their necessary refinement early in development. Early in life, all animals are born with an abundance of brain cell connections, called synapses, that need to shrink as we age. Synapses that lead to successful tasks, such as capturing and strengthening glass, are preserved, while connections that lead to failed attempts are removed.
Stressed mothers who inhaled diesel fumes resulted in males who, as young children, missed the scheduled shaving of the clip in the anterior cingulate cortex (ACC), a brain region important for perceiving and producing social cues. Males’ high synapses in this region seem to explain their shy social tendencies when they were teenagers, but it left open the question of how the double whammy of smog and stress during pregnancy halted typical brain sculpting.
To answer this question, Block and her team looked at the immune system, specifically immune cells in the brain called microglia. Aside from keeping an eye on bacteria and viruses, microglia are also on the alert for weak or dead synapses, which easily get stuck to help organize the brain. The block caused that if there were more synapses than normal, there might not be as many microglia in the affected males’ brains.
To her surprise, Block found that adolescent males from stressed mothers had the same number of microglia in the ACC as their peers from unstressed mothers. However, the smog and housing pressure cause the microglia to contain less protein that stimulates their appetite for synapses, which likely explains the observed overgrowth.
Understanding Autism
With the coming of age, everything turned upside down. Males from mothers exposed to smog now had fewer ACC synapses and were more clustered than their non-stressed peers. This atypical tendency to be more extroverted rather than conservative reflects Brain activity and behavior of mice with genes linked to autism It was recently described by Block’s collaborator and co-author, Duke professor of neurobiology and psychiatrist Kavoe Dzirasa, MD, PhD.
It is often mistakenly assumed that people with autism are less social, but Block shared that “if you meet someone with autism, you have met someone with autism.”
Dzirasa adds that many of his autistic patients may fail standard lab tests used to diagnose mice, which essentially make holes in rodents like autistics if they have less inclination to socialize. Instead, Dzirasa and Block say that for people with autism, it’s more about misunderstanding social cues and conventions rather than being inherently introverted.
Block and Bilbo suggest that this work provides a clear mechanism in mice that may explain why air pollution levels are so high Increased risk of a child having autism Only if they were born in a poor neighborhood. It may also lead to drugs to help prevent microglia from being tampered with by environmental stressors because diesel exhaust and housing stress trigger a similar immune response when pregnant women have influenza.
For now, Bilbo and her team hope that this compelling evidence about the impact of stress and air pollution during pregnancy will lead policymakers to support clean air and social service initiatives, such as improved and expanded public housing.
“You cannot ignore the mechanistic findings of this study,” Bilbo said. “It happens, and that’s how it is.”
the quote: Block CL, Eroglu O, Mague SD, Smith CJ, Ceasrine AM, Sriworarat C, Blount C, Beben KA, Malacon KE, Ndubuizu N, Talbot A, Gallagher NM, Chan Jo Y, Nyangacha T, Carlson DE, Dzirasa K, Eroglu C, Bilbo sed. 2022. Prenatal environmental stressors impair postnatal microglia function and adult male behavior. Cell Representative 40 (5): 111161.
(Editor’s note: This article was originally published on August 3 at Duke today. The author, Dan Vhaba, Ph.D., is director of communications at the Duke Institute for Brain Sciences.)
from San Jose News Bulletin https://sjnewsbulletin.com/environmental-factor-september-2022-smog-and-stress-alter-the-minds-and-social-behavior-of-male-mice/
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