Abstract
Cell death following spinal cord injury (SCI) involves an inflammatory response that activates interleukin-1beta (IL-1beta). In the peripheral immune response, the inflammasome activates caspase-1 to process proinflammatory cytokines, but the regulation of inflammation in the nervous system is poorly understood. In this study, the cellular distribution, levels and protein association of inflammasome proteins were investigated in spinal cords of female Fischer (180-200g) rats subjected to moderated cervical (C5) injury and naive controls. Coimmunoprecipitation experiments revealed that Apoptosis-associated Speck-like protein containing a CARD (ASC) associates with caspase-1, -11, NAcht Leucine-Rich-Repeat Protein 1 (NALP1) and the inhibitor of apoptosis, XIAP, forming the NALP1 inflammasome. SCI resulted in increased levels of caspase-1, -11 and ASC, but levels of NALP1 were not significantly altered. After SCI, the composition of the inflammasome changed with increased association of caspase-1, -11 and NALP1 with ASC and cleavage of XIAP. Immunohistochemistry and confocal microscopy revealed that spinal cord neurons express NALP1 inflammasome proteins. Traumatized spinal cords showed alterations in the cellular distribution of these proteins. Therapeutic neutralization of ASC inhibited inflammasome activation, reduced caspase-1 activation, XIAP cleavage, and interleukin processing, resulting in significant tissue sparing and functional improvement. This thesis describes the first in vivo identification of the inflammasome. Furthermore, this work demonstrates that the NALP1 inflammasome is present and is activated in neurons after trauma to the spinal cord. Thus, the NALP1 inflammasome constitutes an important arm of the inflammatory response following SCI that can be used as a therapeutic target after trauma to the spinal cord.