459 Caspase-1 mediated inflammatory response - a critical player in concussive mild traumatic brain injury (mTBI) associated long term pain

Abstract

OBJECTIVES/GOALS: Patients who have experienced conjunctive mild traumatic brain injuries (mTBIs) suffer from a number of comorbidities, including chronic pain. Despite extensive studies investigating the underlying mechanisms of mTBI-associated chronic pain, the role of inflammation after mTBI and its contribution to long-term pain are still poorly understood. METHODS/STUDY POPULATION: Given the shifting dynamics of inflammation, it is important to understand the spatial-longitudinal changes and their effects on TBI-related pain. Utilizing a recently developed transgenic caspase-1 luciferase reporter mouse, we characterized the bioluminescence signal evident in both in vivo and ex vivo tissues following repetitive closed head mTBIs. This allowed us to reveal the spatiotemporal dynamics of caspase-1 activation in individual animals over time. Furthermore, we utilize various proteomic and behavioral assays to evaluate the role of caspase-1 mediated inflammation in the development and progression of injury-associated chronic pain. Lastly, by blocking inflammasome caspase-1 activation with a specific inhibitor, we assess its clinical potential as the next therapeutic approach to pain. RESULTS/ANTICIPATED RESULTS: We established that there were significant increases in bioluminescent signals upon protease cleavage in the brain, thorax, abdomen, and paws in vivo, which lasted for at least one week after each injury. Enhanced inflammation was also observed in ex vivo brain slice preparations following injury events that lasted for at least 3 days. Concurrent with the in vivo detection of the bioluminescent signal were persistent decreases in mouse hind paw withdrawal thresholds that lasted for more than two months postinjury. Using MCC950, a potent small molecule inhibitor of NLRP3 inflammasome-caspase 1 activity, we observed reductions in both caspase-1 bioluminescent signals in vivo and caspase-1 p45 expression by immunoblotting and an increase in hind paw withdrawal thresholds. DISCUSSION/SIGNIFICANCE: Overall, these findings suggest that neuroinflammation in the brain following repeated mTBIs is coincidental with a chronic nociplastic pain state, and repeated mTBI-associated events can be ameliorated by a highly specific small molecule inhibitor of NLRP3 inflammasome activation.