Sleep Deprivation Primes Synaptic Vulnerability Without Inducing Oxidative Damage: A Mechanistic Reappraisal
The question of whether sleep deprivation is inherently lethal has remained unresolved due to the inability to separate pure sleep loss from experimental stress. Historical studies dating back over a century have consistently reported that prolonged wakefulness leads to death, but these findings have been confounded by the stressful nature of the experimental interventions used to maintain wakefulness. Recent work has suggested that sleep deprivation-induced lethality may result from accumulation of reactive oxygen species (ROS) in the intestines, providing a potential molecular explanation for these long-standing observations. Here we address whether lethality stems from sleep loss itself or experimental stress using stress-controlled sleep deprivation in Drosophila and stress paradigms in both flies and mice. Using real-time feedback-controlled sleep deprivation in Drosophila--which only stimulates animals when they attempt to sleep--we found no lethality or intestinal ROS accumulation even after 240 hours of continuous wakefulness. In contrast, both physical perturbation and psychological challenges rapidly induced intestinal ROS accumulation independent of sleep loss, in flies and mice. Transcriptomic analysis revealed entirely distinct molecular signatures between sleep deprivation and oxidative stress, demonstrating these represent fundamentally different biological challenges. However, while sleep deprivation alone caused no lethality or intestinal oxidative stress, it increased susceptibility to traumatic brain injury through enhanced synaptic strength. Sleep-deprived flies showed increased mortality when subjected to violent physical challenges, an effect that correlated with synaptic excitability rather than sleep duration, and was rescued by restorative recovery sleep or prevented in mutants lacking synaptic potentiation mechanisms. Our findings demonstrate that experimental stress, not sleep loss, drives the oxidative damage and lethality historically attributed to sleep deprivation. Sleep deprivation, however, creates conditional vulnerability by transforming the brain into a hyperexcitable state susceptible to trauma, rather than causing cumulative damage.