A new study of its kind published in the journal PLOS One reports that the father’s exposure to nicotine may cause cognitive deficits in his descendants. The study suggests that the effect, which was not caused by direct secondhand exposure, may be due to epigenetic changes in key genes in the father’s sperm.
Previous studies have established that exposure of mothers to nicotine and other components of cigarette smoke is associated with increased for behavioral disorders, including attention deficit hyperactivity disorder, (or ADHD) in multiple generations of descendants. However the same applies to fathers has been less clear because in human studies it has been difficult to separate genetic factors (such as a genetic predisposition to ADHD) from environmental factors, such as direct exposure to cigarette smoke.
Pradeep Bhide and colleagues exposed male mice to low-dose nicotine in their drinking water during the stage of life in which the mice produce sperm. They then bred these mice with females that had never been exposed to nicotine.
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The investigators found that though the fathers were behaviorally normal, both sexes of offspring displayed hyperactivity, attention deficit, and cognitive inflexibility. When female (but not male) mice from this generation were bred with nicotine-naïve mates, male offspring displayed fewer, but still significant, deficits in cognitive flexibility.
Analysis of spermatozoa from the original nicotine-exposed males indicated that promoter regions of multiple genes had been epigenetically modified, including the dopamine D2 gene, critical for brain development and learning, suggesting that these modifications likely contributed to the cognitive deficits in the descendants.
“The fact that men smoke more than women makes the effects in males especially important from a public health perspective. Our findings underscore the need for more research on the effects of smoking by the father, rather than just the mother, on the health of their children,” writes the author.
For reference log on to https://doi.org/10.1371/journal.pbio.2006497