007 NLRP3 inflammasomes contribute to dysregulated sleep and electroencephalogram delta power after mild and moderate TBI in mice

Abstract

Abstract Introduction Most traumatic brain injuries (TBI) are mild to moderate and can cause persistent dysregulated sleep, although the mechanisms are not well understood. Interleukin-1 beta (IL-1β) is a pro-inflammatory molecule that is activated in the cortex after waking activity and pathogenic challenge and alters non-rapid eye movement (NREM) sleep and electroencephalogram (EEG) delta power. Nucleotide-binding domain leucine rich family pyrin containing 3 (NLRP3) inflammasomes sense changes in their local environment to stimulate caspase-1 to activate IL-1β into its mature form. We previously found that NLRP3 inflammasomes are increased in the cortex after acute sleep loss and contribute to increased NREM sleep and EEG delta power after sleep loss and toxin challenge. We aimed to determine if NLRP3 inflammasomes contribute to the persistent dysregulated sleep caused by TBI. Methods Using 2-3-month-old mice lacking NLRP3 and C57BL/6J wild-type control mice, we assessed sleep states and sleep state episode durations and frequencies prior to TBI, and 24 h, 2-weeks, and 2 months after mild or moderate TBI using polysomnography. TBI occurred in the frontal cortex from a controlled cortical impact device. Additional mice received identical treatments serving as a TBI procedural control but received a craniectomy without the TBI. Results Similar sleep findings were observed between the craniectomy control group and baseline measures. However, when compared to baseline values, mice lacking NLRP3 had attenuations in the significant increased amounts of NREM sleep and EEG delta power occurring 24 h after TBI and the significant reductions in NREM sleep and EEG delta power seen 2 months after TBI that were observed in wild-type mice. These effects were similar in moderate and mild TBI groups. Mice lacking NLRP3 were not found to exhibit the fragmented sleep after mild or moderate TBI that was found to persist from 24 h to 2 months post-TBI in the wild-type mice. These effects were evident by significant increased frequencies of waking episodes induced by the TBIs. Conclusion Our findings suggest that NLRP3 inflammasomes contribute to dysregulated sleep occurring acutely or more persistently after TBI. Support (if any) Career Development Award IBX002823 (MZ) and Merit Review Award I01RX001144 (GK) from the United States Department of Veterans Affairs