Environmental exposures in early life can have immediate effects on health or accumulate over time to increase disease risk later. Exposure can start in the womb and can have effects throughout life.
Shedding light on this, a new study has tracked a lifetime of physiological changes experienced by mice given a liquid solution containing the stress hormone glucocorticoid while in the womb or soon after birth.
Scientists found when exposed to stress in the womb, and after birth, mice suffered a lifetime of immune system deficiencies that hinder the ability to ward off infections and cancer. Early-life exposure to the stress hormone can permanently alter many immune system responses, decreasing the body’s ability to ward off bacterial infections and fight tumors.
Glucocorticoids are normally occurring hormones that diminish inflammation and are instrumental in helping infants and adults the same adjust rapidly to environmental dangers, for example, starvation or violence. Physicians use them to treat asthma, and autoimmune diseases brought about by overactive immune systems, for instance.
Yale immunobiologist Ruslan Medzhitov, senior author of the study and Howard Hughes Medical Institute investigator, said, “Mice for rest of their lives are rewired and reprogrammed in ways fundamentally different from those not exposed to glucocorticoids.”
“The study helps explain why individuals vary so widely in their ability to ward off infections. It also explains a social phenomenon found throughout human history: an emphasis on shielding women from stress during pregnancy.”
Scientists also cataloged a host of physiological changes in mice. Adult mice were more likely to be prone to bacterial infections and tumors. One specific physiological change was decreased activity in a key T cell that responds to pathogens and other threats to the host.
First author Jun-Young Hun, also of Yale, said, “In all cultures, there are efforts to shelter women from stress during pregnancy. The effects of early life stress don’t just go away.”
“As more is learned about molecular changes caused by early exposure to stress, the more likely it is that medical science will find a way to minimize its damage.”
Medzhitov said, “We aren’t there yet.”
The study is published in the journal Cell.