Grandmother's cigarette smoking could be responsible for her grandchild's asthma, and the recent discovery of this multi-generational transmission of disease suggests the environmental factors experienced today could determine the health of family members for generations to come, two Los Angeles Biomedical Research Institute (LA BioMed) lead researchers write in the March edition of Review of Obstetrics & Gynecology.
The researchers, John S. Torday, PhD, and Virender K. Rehan, MD, wrote an editorial citing recent studies by Dr. Rehan that found pregnant rats given nicotine produced asthmatic pups that went on to produce their own asthmatic pups, despite the absence of nicotine exposure in the third generation.
The findings suggest nicotine can leave heritable epigenetic marks on the genome, which make future offspring more susceptible to respiratory conditions.
The researchers also cited the Children's Health Study from Southern California, which reported that grandmaternal smoking during pregnancy increases the risk of asthma in grandchildren regardless of whether the mother smoked or not.
Based on those findings, the researchers conclude that environmental factors experienced during pregnancy will affect not only the child in utero but also future generations of the same family. They say this multi-generational transmission could explain why 98% of inherited human diseases are unaccounted for by the prevailing view of genetic trait transmission, known as Mendelian genetics.
The researchers concluded that the cause of the second generation's asthma was epigenetic modification (an environmental factor causing a genetic change). Nicotine was affecting both the lung cells and the sex cells in ways that caused the lungs that developed from those cells to develop abnormally, causing asthma.