Stress is never good for anyone, especially if it is ongoing. It affects various parts of our lives and can eventually become unhealthy. Signs of stress can include symptoms such as sweating, sleepless nights, and even nervous twitching, and can prevent us to from getting on with day-to-day tasks.
Typically, it is the health of mothers and the influence they have on their unborn child that's heavily studied. However, fathers have recently been going under the microscope too, as scientists find that their well-being also plays an important role.
Now, a new study led by Jennifer Chan, a neuroendocrinologist at the University of Pennsylvania, suggests that stress in male mice could have an affect on their sperm and thus their offspring. This effect was seen even after a considerable time had passed.
"Remarkably, studies in our mouse model reveal that males bred 3 months following stress exposure continue to produce offspring with altered stress reactivity, suggesting lasting effect," the team write.
Adrenaline, cortisol, and norepinephrine – the three hormones released when experiencing stress – are the reasons behind our “fight or flight” response. However, not all stress is actually bad, notes Daniela Kaufer, an associate professor of integrative biology from the University of California Berkeley, who was not involved with the study, to Berkeley News.
"Some amounts of stress are good to push you just to the level of optimal alertness, behavioral and cognitive performance," she shared.
On the flip side, "exposures to environmental insults such as stress, diet, drugs or toxins have been linked with increased risk of neuropsychiatric disease in subsequent generations," the team write.
To study this further, they looked at the caput epididymis, a region of a male's reproductive tract where sperm cells mature, and took away the glucocorticoid receptor, which is involved in the transmission of stress. Typically, stressed out fathers with the glucocorticoid receptor make too much corticosterone, a stress hormone. This is carried down to their offspring, who also overproduce corticosterone when exposed to a predator odor.
However, when the team got rid of the receptor, they effectively stopped the overproduction of corticosterone in the offspring and brought their hormonal response back to normal levels.
But why did this work? The team believe it's possible that the activation of the glucocorticoid receptor changes the RNA in epididymis vesicles, which deliver its altered contents to the sperm and, subsequently, the next generation of mice.
"These studies suggest that paternal experiences can have lasting changes on the germline and future offspring brain development, and offer an exciting novel mechanism by which the environment can dynamically regulate sperm epigenetic marks," the team conclude.
Their next step is to see if a similar process takes place in humans as well.
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