A new study suggests nicotine exposure in males may cause cognitive deficits upon their descendants including children and grandchildren. In the study, researchers from Florida State University exposed male mice to nicotine, which was published in open-access journal PLOS Biology.
Impact of nicotine use by pregnant women have always received greater scrutiny; it is recognized as a potential risk factor for behavioral disorders such as attention deficit hyperactivity disorder (ADHD) in future generations. It is less clear whether the same applies to father and there has been a little focus on the effects of paternal nicotine use on the health of offspring. Further, it is difficult to separate the genetic factors such as ADHD from environmental factors including the use of nicotine.
To overcome the difficulty, the research team led by Pradeep Bhide, exposed male mice to low-dosed nicotine in drinking water at the stage of life where the mice produce sperm. These mice were then bred with females that have never been exposed to nicotine. The researchers discovered that although the father had normal behavior, both the sexes of offspring presented cognitive inflexibility, attention deficit, and hyperactivity. In the following experiment, female mice from this generation were bred with nicotine-naïve mates in which male offspring showed less but significant deficits in cognitive behavior.
DNA Analysis of spermatozoa from former nicotine exposure male mice suggested epigenetic modification in promoter region of multiple genes such as dopamine D2 gene. As the modification occurs in genes critical for brain development and learning, it is likely to contribute to cognitive deficits in the descendants.
Cigarette smoke contains over 1,000 chemical substances which may cause changes in DNA methylation and its effects on behavior and brain are mediated through direct action of the nicotine in developing or mature brain. Although nicotine and cigarette smoke have previously shown to cause various epigenetic changes, the studies were limited to females, particularly pregnant women.
According to the researchers, high prevalence of cigarette smoking over the years may have raised the possibilities that nicotine exposure in past generation could be contributing to growth in diagnosis of neurobehavioral disorders in the present generation. Bhide said that their findings emphasize the need for extensive research on the effects of nicotine caused by the father, rather than just the mother, on the multiple generations of descendants.