Beneficial Effects of Early mTORC1 Inhibition after Traumatic Brain Injury

The mammalian target of rapamycin complex 1 (mTORC1) signaling pathway mediates many aspects of cell growth and regeneration and is upregulated after moderate to severe traumatic brain injury (TBI). The significance of this increased signaling event for recovery of brain function is presently unclear. We analyzed the time course and cell specificity of mTORC1 signal activation in the mouse hippocampus after moderate controlled cortical impact (CCI) and identified an early neuronal peak of activity that occurs within a few hours after injury. We suppressed this peak activity by a single injection of the mTORC1 inhibitor rapamycin 1 h after CCI and showed that this acute treatment significantly diminishes the extent of neuronal death, astrogliosis, and cognitive impairment 1-3 days after injury. Our findings suggest that the early neuronal peak of mTORC1 activity after TBI is deleterious to brain function, and that acute, early intervention with mTORC1 inhibitors after injury may represent an effective form of treatment to improve recovery in human patients.