Long Term Effects of Men’s Phthalate Exposure

Article Author: Brooke Linnehan, Molecular and Cellular Biology, M.S. student, POB Science Translator

What makes you, you? Maybe you have your mother’s nose, or your father’s eyes. Maybe people tell you, “You look just like your great grandfather did at your age!” Whether you are a spitting image of your parents, or see yourself as a random mixture of traits, the truth is that your genes were passed down to you in a unique combination that makes you precisely who you are.

Your DNA is a library that contains all of your genes, which are the instructions needed for making different proteins. Proteins are the worker bees that carry out specific functions like forming the traits we see and giving our bodies the ability to grow, fight disease, and respond to our environment. When a cell needs to turn on a gene, a special protein will come and start reading the DNA instructions to create the new protein.

Epigenetic changes sometimes interfere with this process. “Epigenetics” means on top of the genes, indicating that these changes don’t alter the genes themselves. They act on a different level; much like a traffic light can either grant or deny access to the road ahead, epigenetic tags are placed directly onto the DNA to either allow the DNA to be accessed more easily or make it more difficult to access the DNA. The chemical properties of an epigenetic tag determine which effect it may have on this access. Methyl groups are one of the most studied epigenetic tags. Methyl groups, comprising a carbon and three hydrogen, can obstruct DNA access and act as a way to block or suppress genes. 

Epigenetic changes are often caused by exposure to chemicals, lifestyle habits, and some epigenetic changes can be inherited if they are made to a sperm or egg cell. A recent study from the Pilsner Lab at the University of Massachusetts Amherst, now at Wayne State University, studied the effects of phthalates, a group of chemicals commonly found in plastics and personal care products, on methylation patterns in sperm of male mice (Oluwayiose et al., 2021). The researchers exposed the male mice to low and high doses of phthalates (specifically DEHP) and measured methylation patterns on their sperm cells compared to sperm of non-exposed male mice. They then mated those mice with unexposed female mice and measured methylation in the embryos of their offspring to see if the effects of phthalate exposure would be passed on to the next generation. 

Pilsner et al. measured the methyl groups on the sperm DNA from mice exposed to DEHP. Interestingly, they found over 700 differences when compared to the sperm DNA of unexposed mice. They then wondered how this exposure affects the developing mice embryos. The embryo stage is the earliest stage of development where organs and tissues are made while still in the mother’s uterus. The researchers found that mice embryos had over 1,700 differences in methyl groups when their fathers were exposed to DEHP. Even further, they explored the effects of father DEHP exposure on the tissues that surround the embryo that eventually makes the placenta, where they found over 3,100 differences in methyl groups on the DNA. 

To figure out how these epigenetic changes affect the embryo, they analyzed gene expression levels. In the mouse embryos from fathers exposed to DEHP, the researchers found that many of the affected genes are important and involved in processes like embryo development, cellular regulation of gene expression, and proper physical growth. Together, these findings point to the danger of males’ exposure to phthalates, as the resulting epigenetic changes can be passed onto the offspring and potentially affect the trajectory of development. Since humans are also susceptible to the harmful effects of phthalates, these results are concerning for men’s reproductive health.

Phthalates such as DEHP are often hiding in pliable plastics such as PVC and found in products such as vinyl shower curtains and other home furnishings, packaging, toys, etc. Other types of phthalates, linked but not studied in this research specifically, are found in men’s personal care products under the guise of “fragrance” or “parfum” in the ingredients list. The best way to avoid exposure to phthalates is by choosing safer packaging and products that get their nice scent from essential oils or other organic ingredients. By limiting exposure to phthalates we can invest in the health of our children and grandchildren, and reduce their chances of negative health outcomes like cancer in the future.

To learn more about the Pilsner Lab visit: www.pilsnerlab.com

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Source:

Oluwayiose, O. A., Marcho, C., Wu, H., Houle, E., Krawetz, S. A., Suvorov, A., … & Pilsner, J. R. (2021). Paternal preconception phthalate exposure alters sperm methylome and embryonic programming. Environment International, 155, 106693.

https://pubmed.ncbi.nlm.nih.gov/34120004/

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