Early-life lead exposure has been linked to long-term cognitive and behavioral problems in children, problems that can endure well into adulthood.
Researchers have looked at how lead exposure in early life affects a small number of genes involved in learning, memory, and brain development, but not enough research has been done to know the full extent of the toxicity.
The latest study from Thomas Jefferson University demonstrates that lead poisoning affects more than 3,500 genes in the hippocampus. This is a part of the brain that helps you learn and remember things.
The research also demonstrates that giving animals stimulating settings early in life can reverse the vast majority of these genetic alterations, highlighting the potential importance of early childhood education in preventing lead poisoning.
Children who live in homes built before 1978, when lead was outlawed as a paint ingredient, are at a high risk of lead exposure via lead dust or peeling and flaking paint, says senior author Jay Schneider.
Recent estimates indicate that at least half a million youngsters in the United States have blood lead levels that can severely damage cognitive performance. “Our work demonstrates,” adds the author, “that by providing an enriched early life environment, the adverse effects of lead on the brain may be minimized or potentially reversed, emphasizing how important early childhood interventions may be.”
The authors examined rats exposed to lead from birth to weaning, at 21 days of age, with main author Garima Singh, PhD, a research assistant professor in the department of Pathology, Anatomy, and Cell Biology, and colleagues.
“Our experiments aimed to replicate conditions of human lead exposure,” adds Dr. Singh. “21 days of age for rats is the equivalent to an age of about 2-3 years in humans, which is commonly when lead exposure occurs. That is because crawlers and toddlers are likely to put many things in their mouths including paint chips or toys covered in dust from deteriorating lead paint.”
From the age of 21 days, the lead-exposed animals were divided into two groups: those that were enriched and those that were not.
Six rats were housed in the so-called enriched cages, which also included chew toys, different objects to climb on and burrow through, and novelty-changing items that were swapped out twice a week. These cages promoted more social interaction.
The cages that were not enriched were smaller, could only house three animals, and had no extra stimulation.
“We now know that stimulating social environments are as important for rodents as they are for human children, in terms of cognitive and behavioral health and with effects on physical health as well,” adds the author.
Researchers studied gene expression variations in the hippocampus region of the brain, which is linked to memory.
They discovered that the lead exposure altered the expression levels of over 3,500 genes, causing some of them to produce abnormally more or less of their gene products.
Dr. Schneider says, “These data show for the first time that at a genome-wide level, a large number of hippocampal genes involved in various biological processes and functions are affected by lead exposure and further modified by an enriched environment.”
Genes important in brain development, neuronal signaling pathways, memory, and learning were among those impacted in lead-exposed rats.
However, in the group of animals that remained in the stimulating environment until day 55, which is roughly adolescence in humans, almost 80% of the gene expression changes brought on by the lead exposure were reversed.
In addition, animals in the non-enriched environment exhibited memory problems, whereas those in the enriched environment did not.
According to Dr. Schneider, there is no level of lead exposure that is safe for children. Lead exposure can harm the brain and impede healthy brain development.
“However, our work suggests that it may be possible to mitigate the wide-spread adverse effects of lead on the young brain by providing adequate access to stimulating, interesting environments and activities in early childhood and perhaps longer.”
Unfortunately, the population most at risk for lead poisoning—children growing up in low socioeconomic or disadvantaged environments—rarely has access to these kinds of programs.
Even though more research needs to be done in this area, both Drs. Schneider and Singh agree that early intervention programs with environmental enrichment are very important.
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