The flight response impairs cytoprotective mechanisms by activating the insulin pathway

An animal’s stress response requires different adaptive strategies depending on the nature and duration of the stressor. While acute stressors, like predation, induce a rapid and energy-demanding fight or flight response, long-term environmental stressors induce the gradual and long-lasting activation of highly conserved cytoprotective processes(1–3). In animals across the evolutionary spectrum the continued activation of the fight-or-flight response weakens the animal’s resistance to environmental challenges(4,5). However, the molecular and cellular mechanisms that regulate the trade-off between flight response and long-term stressors are poorly understood. Here we show that repeated induction of the C. elegans flight response shortens lifespan and inhibits conserved cytoprotective mechanisms. The flight response activates neurons that release tyramine, the invertebrate analog of adrenaline/noradrenaline. Tyramine stimulates the DAF-2/Insulin/IGF-1 pathway and precludes the induction of stress response genes by activating an adrenergic-like receptor in the intestine. In contrast, long-term environmental stressors, such as heat or oxidative stress, reduce tyramine release allowing the induction of cytoprotective genes. These findings demonstrate that a neural stress-hormone supplies a state-dependent neural switch between acute flight and long-term environmental stress responses and provides mechanistic insights into how the flight response impairs cellular defense systems and accelerates aging.