CD1d1 intrinsic signaling in macrophages controls NLRP3 inflammasome expression during inflammation

Abstract

Dysregulation of immune responses in the gut often associates with inflammatory bowel diseases (IBD). Mouse CD1d1, an ortholog of human CD1d mainly participating in lipid-antigen presentation to NKT cells, is able to generate intrinsic signals upon stimulation. Mice with macrophage-specific <i>CD1d1</i> deficiency (<i>Lym^CD1d1-/-</i> ) acquire resistance to dextran sodium sulfate (DSS)-induced colitis, attributing to the transcriptional inhibition of NLRP3 inflammasome components. The hyperactivation of NLRP3 inflammasome accounts for gut epithelial proliferation and intestine-blood barrier integrity. Mechanistically, occupancy by the natural ligand glycosphingolipid iGb3, CD1d1 responds with intracellular Ser³³⁰ dephosphorylation thus to reduce the Peroxiredoxin 1 (PRDX1)-associated AKT-STAT1 phosphorylation and subsequent NF-κB activation, eventually causing transcriptional down-regulation of <i>Nlrp3</i> and its immediate substrates <i>Il1b</i> and <i>Il18</i> in macrophages. Therefore, the counterbalancing role of CD1d1 in macrophages appears to determine severity of DSS-mediated colitis in mice. These findings propose new intervention strategies for treating IBD and other inflammatory disorders.