Abstract
Paternal environmental conditions can influence phenotypes in future generations, but it is unclear whether offspring phenotypes represent specific responses to particular aspects of the paternal exposure history, or a generic response to paternal ‘quality of life’. Here, we establish a paternal effect model based on nicotine exposure in mice, enabling pharmacological interrogation of the specificity of the offspring response. Paternal exposure to nicotine prior to reproduction induced a broad protective response to multiple xenobiotics in male offspring. This effect manifested as increased survival following injection of toxic levels of either nicotine or cocaine, accompanied by hepatic upregulation of xenobiotic processing genes, and enhanced drug clearance. Surprisingly, this protective effect could also be induced by a nicotinic receptor antagonist, suggesting that xenobiotic exposure, rather than nicotinic receptor signaling, is responsible for programming offspring drug resistance. Thus, paternal drug exposure induces a protective phenotype in offspring by enhancing metabolic tolerance to xenobiotics.
DOI:http://dx.doi.org/10.7554/eLife.24771.001
Until recently, it seemed impossible that the conditions a person or animal experiences during their lifetime might affect the health of their offspring and future generations. Research over the past decade, however, has shown that a parent’s environment can cause changes that can be passed to future generations. For example, studies in rodents have shown that a father’s diet influences the way their offspring metabolize food. Moreover, a male mouse exposed to stress or toxins fathers pups that often respond differently in stressful situations relative to other mice.
So, how do these traits get transferred to offspring via sperm and how specific is the next generation’s response to the environmental pressures faced by their fathers? Many studies so far have looked at environmental influences that may have broad biological effects, for example a high fat diet. Now, some scientists are trying to understand whether exposure to nicotine, which has a more targeted effect, causes drug-specific effects in offspring.
Vallaster et al. now show that mice whose fathers had been exposed to nicotine before mating are more able to withstand toxic levels of the chemical than mice whose fathers were never exposed to the drug. In the experiments, some male mice were given water with nicotine in it over the course of five weeks. Later, the offspring of these mice were exposed to nicotine to see whether they were more or less sensitive to it than offspring of unexposed males. It turns out the mice with nicotine-exposed fathers have a higher resistance to the toxic effects of nicotine and, unexpectedly, to toxic levels of cocaine as well. This suggests that the pups of nicotine-exposed fathers are not specifically programmed to respond to nicotine, but instead are more resistant to toxins in general.
Vallaster et al. found that the livers of the offspring of nicotine-exposed fathers appear to be better able to metabolize both drugs. Exposing the fathers to another drug called mecamylamine (which can prevent many of nicotine’s effects on the body) also made their offspring more resistant to nicotine, showing that multiple drugs may make offspring more toxin-resistant. Studies in humans will be needed to confirm whether a father’s nicotine use affects children the same way it does mice. Similar mice studies also may help scientists to study how other types of environmental exposure might affect a man’s future children.
DOI:http://dx.doi.org/10.7554/eLife.24771.002
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