The role of the NLRP3 inflammasome in a CLN2 mouse model of neuroinflammation

Abstract Neuronal ceroid lipofuscinoses, or Batten disease, comprises a group of inherited pediatric neurodegenerative disorders, and is characterized by the lysosomal accumulation of the fluorescent storage material lipofuscin. The human classical late-infantile form of the disorder (CLN2) is caused by mutations in the CLN2 / Tripeptidyl peptidase 1 ( TPP1 ) gene. Comparable to human CLN2, a knockout of the Tpp1 gene ( Tpp1 -/- ) in the mouse leads to progressive vision loss, ataxia, motor atrophy, seizures, and premature death. While we previously showed using bulk RNA-seq analysis that reactive gliosis develops between 3 and 4 months in this animal model, the role of the inflammasome in CLN2 remains unexplored. The inflammasome is a multiprotein complex formed through pattern recognition receptor engagement, which culminate in the cleavage and release of interleukin-1 beta. Here we report that while some inflammasome-associated genes are upregulated as early as 1-month in the Tpp1 -/- cerebellum, it is not until 3-months-old that all gene transcripts necessary for inflammasome assembly and function are upregulated, leading to IL1β release. In Tpp1 -/- slice cultures, we demonstrated that MCC950, an inhibitor of inflammasome assembly, downregulates transcriptional expression of genes associated with reactive microglia and inflammasome function. Furthermore, prophylactic administration of MCC950 in drinking water of Tpp1 -/- animals for two months is sufficient to lower the expression of these same genes in the forebrain and cerebellum, suggesting that inflammasome inhibitors are promising therapeutics for CLN2 and neurodegeneration broadly. Graphical Abstract The role of the NLRP3 inflammasome in a CLN2 model of neuroinflammation. The NLRP3 inflammasome is upregulated and assembled in Tpp1-/- microglia, leading to IL1β release. Treatment with an NLRP3 inflammasome inhibitor MCC950, in ex-vivo and in-vivo murine models of CLN2 neuroinflammation, results in the downregulation of inflammasome-associated genes.