0155 Persistent Activation of TXNIP and NLRP3 Inflammasomes in Cortical Glia and Neurons after Mild Traumatic Brain Injury

Abstract

Abstract Introduction Mild traumatic brain injuries (TBI) induce persistent dysregulated sleep, reactive oxygen species (ROS), and inflammation. Nucleotide-binding domain leucine rich family pyrin containing 3 (NLRP3) inflammasomes are protein complexes that stimulate caspase-1 to activate the somnogenic pro-inflammatory cytokines IL-1β and IL-18. ROS induce thioredoxin interacting protein (TXNIP) to activate NLRP3 inflammasomes by inhibiting thioredoxin which inhibits ROS. We previously found that mice lacking NLRP3 have increased non-rapid-eye movement (NREM) sleep and slow-wave activity (SWA) 24 h after mild TBI, but at 2 months post-injury theses values are reduced. Following up on this, we sought to determine the activity of NLRP3 inflammasomes in glia and neurons after mild TBI. Methods Two-month-old mice lacking NLRP3, and wild-type mice received a craniectomy and mild TBI via controlled cortical impact or sham. Frontal and somatosensory cortices were collected without a TBI and at 24 h and 2 months post-TBI. Microglia, astrocytes, and neurons were isolated using fluorescent-activated cell sorting, and reactive oxygen species (ROS), RNA and protein were quantified using RT-PCR and ELISAs. Significance was set at p < 0.05. Results RNA, protein, and ROS control treatment values were similar for both genotypes in cortical microglia, astrocytes, and neurons. In wild-type mice, NLRP3, IL-1β, IL-18, caspase-1, and TXNIP expression along with ROS values were significantly greater and thioredoxin expression was significantly less in cortical microglia, astrocytes, and neurons 24 h and 2 months post-TBI. In wild-type cortical microglia, astrocytes, and neurons NLRP3, IL-1β, and TXNIP expression levels were significantly greater in these cell types 2 months vs. 24 h post-TBI. Wild-type mice caspase-1 activity and NLRP3, IL-18, IL-1β, and TXNIP protein levels, were significantly greater and thioredoxin protein levels were significantly less in both cortical areas 24 h and 2 months post-TBI. Mice lacking NLRP3 showed significant increased values of TXNIP but reduced thioredoxin expression and protein levels 24 and 2 months post-TBI but no significant differences in other measures. Conclusion Our findings suggest that TBI induces persistent oxidative stress, TXNIP, and NLRP3 inflammasome activation in cortical glia and neurons that likely contributes to sleep dysregulation. Support (if any) Merit Review Award (I01BX005379)(MRZ) and SPiRE Award (I21RX003722)(GBK) Department of Veterans Affairs