It is inevitable to feel tender to see a pregnant woman, who longs for her child to arrive. This special and unique stage that women live, comes full of physical, hormonal and emotional changes, which prepare them for the development and arrival of the baby. In addition to the above, it is important that this process is always accompanied by prenatal care, such as feeding, avoiding drug use and a healthy environment. All this in order for the mother and child to enjoy a good state of health that allows a good development of the child, and decrease the likelihood of pathologies in both.
Even if the mother follows prenatal care to the letter, we cannot forget that it only contributes 50% of the child’s genetic burden, the other half is provided by the father at the time of conception. Just as good habits are conducive to good fetal development, there is also much evidence that the mother’s use of cigarettes, alcohol or other drugs, in pregnancy, will have a direct impact on the child. But what about the father’s vices and lifestyle? Will they have any direct effect on the fetus, too? Sounds hard to imagine. However, a group of researchers in charge of Deirdre McCarthy of the University of Florida made an important finding: exposure to nicotine in adult male mice causes cognitive and locomotion changes in their offspring. This means that dad rats exposed to nicotine, the most addictive compound in the cigar, generate changes in their children’s brains.
Currently, figures from the World Health Organization (WHO) indicate that globally men are older smokers than women and Chile is no exception, as it has the highest prevalence of tobacco in both young and adult people throughout Latin America. According to MINSAL figures, it kills 45 people a day. This reason prompted these scientists to investigate the effect that nicotine has from male heritage.
In their research, they exposed adult male mice daily to nicotine dissolved in the water they drank, and were crossed with healthy females. It is important to mention that in this study mothers were not exposed in any way to nicotine. Researchers conducted specific tests to determine whether animals had locomotor, learning or anxiety problems and found no difference in adults from males without nicotine exposure. However, to their surprise, the scientists noted that the offspring had different behaviors than offspring of parents not exposed to nicotine: they were hyperactive and had greater difficulty in learning; They also found that they had less dopamine, better known as the pleasure molecule, which is a neurotransmitter that transmits information between different neurons in our brain. And there’s more: not only was the amount of this molecule compromised, but it also decreased the amount of the dopamine receptor, which is a protein that is distributed in some specific neurons in the brain and binds with this neurotransmitter, generating a signal. The importance of dopamine and its receptors is that both are key to brain development pathways, memory, movement, behavior and cognition, among other important functions.
Changes in the behavior of the offspring led researchers to study the sperm of males exposed to nicotine. They specifically studied DNA, which contains the genetic information of the parent and, as they suspected, found methylations, which is a type of modification in DNA that does not alter the sequence, at specific gene sites. All these data were consistent with the results obtained in the young.
These modifications are explained by epigenetics, which comes from Greek and means «on genes», studies the changes that occur in DNA, specifically the expression or silencing of certain genes and how this information is influenced by the Environment. The interesting thing about this process is that it can be affected by both genetics and the environment, that is that our entire lifestyle, such as diet, physical activity, stress, among others, is able to influence at the DNA level.
What does this process resemble? Imagine a computer that has folders with information, each folder would correspond to a gene. In this way, we can hide the files so that they are not visible and we cannot access them, or else we can make this information again accessible, however, the information is still there. Epigenetic mechanisms work in the same way: each methylation hides gene information, there are also other mechanisms that allow them to be expressed again, however, the entire sequence remains unaltered.
More than a generation
The researchers did not just study only the first generation offspring, it also continued in a second generation and the finding is not surprising: the young of the latter also presented alterations in the behavior, indicating that in addition these modifications given by the father’s environment and lifestyle are inheritable for more than a generation. Therefore, nicotine consumption produces changes in the consumer’s DNA and can be passed on to future generations.
The study concludes that epigenetic changes, associated with nicotine consumption, transmitted by the father to offspring, produce changes in behavior and cognition, very similar to attention deficit hyperactivity disorders, the most common in Children. Figures estimate that 10% of school-age children in Chile have this disorder. Although the causes of this have not yet been fully worked out, the study shows us that our habits may be one of the factors.
Research shows that both men and women must be aware of our lifestyle, as it brings direct repercussions to ourselves and also to our offspring.
Original article: Nicotine exposure of male mice produces behavioral impairment in multiple generations of descendants, 2018. https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2006497
*This article is the result of the Agreement with the Interdisciplinary Center for Neuroscience in Valparaiso.