New research shows how stress can weaken defenses

Dr. Mark Alkema's laboratory research, a professor of neurobiology, highlights how the "leak or leak" response harms the health of organisms in the long run. The study, conducted in the nematode worm, C. elegans, a common research model, has been published in Nature.

When humans perceive a dangerous or stressful situation, the body releases stress hormones such as adrenaline. Adrenaline accelerates the heart rate, increases blood flow to the brain and muscles and encourages the body to make sugar, which it uses as fuel. The adrenaline rush triggers the "fight or flight" reaction that gives the person the chance to escape a predator or react to a threat.

Dr. Alkema, in collaboration with the laboratory of Professor Diego Rayes of the Southern National University in Argentina, has studied the impact of the repeated activation of the "fight or flight" response on health nematode. C. elegans. This little worm is a popular model organism that has helped solve many fundamental questions in biology, from development to brain function and disease.

Animals are exposed to different forms of stress. These can be brutal, such as the appearance of a predator, or more progressive, such as a chronic food shortage, high temperatures or oxidation.

"Just like in humans, the repeated activation of the flight response C. elegans Jeremy Florman, doctoral candidate at the Alkema Laboratory, said: "The response to the theft is crucial for the worm to escape predators, but we find that there is a cost, the repeated activation of the Flight response reduces the worm's ability to cope with other challenges that it encounters in its environment. "

In the study, investigators found that the reaction of theft in C. elegans triggers the activation of a pair of neurons that release tyramine, the invertebrate analog of adrenaline. In contrast, exposure to environmental problems such as heat and oxidative stress reduces tyramine release. This stress hormone is therefore a switch that regulates the animal's response to acute or long-term stressors.

Alkema and Rayes then showed that tyramine stimulates the insulin pathway through the activation of an adrenergic type receptor in the intestine. The activation of the insulin pathway can satisfy the animal's energy needs for flight response. On the other hand, down-regulation of the insulin pathway is necessary to protect cells from environmental stress and prolong their life span.

"This shows how dynamic regulation of a stress neurohormone regulates the tradeoff between acute and long-term stress responses," Alkema said. "The worm never ceases to amaze me, it unceasingly reveals fundamental molecular and neural mechanisms that may underlie extremely complex human biology and disorders, the fight-or-flight response and stress neurohormones have a negative impact on health and aging by activating the insulin pathway. "