Unlocking microglia pyroptosis in a model of type I interferon-driven neuroinflammation: lessons from Rnaset2^-/- mice

RNaseT2-deficient cystic leukoencephalopathy (CLE) presents with severe psychomotor retardation, cystic brain lesions, white matter alterations, and cerebral atrophy. The Rnaset2^-/- mouse mirrors key features of this disease and represents the first murine model with a distinct neurological phenotype for type I interferonopathies. Rnaset2^-/- mice exhibit activated microglia, perivascular monocyte and CD8 + T cell infiltration, and hippocampal accentuated atrophy. However, the mechanisms linking interferon-driven neuroinflammation to neurodegeneration remain unclear, underscoring the need to clarify which molecular processes contribute to tissue injury in a time-dependent manner. We found a sustained upregulation of interferon-stimulated genes (IRF9, RIG-I) over three to 28 weeks of age in the brains of Rnaset2^-/- mice compared to controls. Expression of the chemokines Ccl2, Ccl5, and Cxcl10 peaked early but declined thereafter. Pyroptosis-related markers (ASC, CASP1, GSDMD) were significantly increased already at three to 6 weeks of age and decreased thereafter, whereas apoptotic markers such as Bax, Bad, Bid, CASP3, CASP8, and PARP were not differentially expressed compared to controls. Finally, Cd3e as well as Tnf peaked later (at 17 weeks of age) and declined at 28 weeks. Interestingly, double IHC confirmed the co-localization of the pyroptosis-related marker ASC with the microglia marker IBA-1. Taken together, these findings support the notion that pyroptosis is an early, disease-associated event restricted to microglia that likely contributes to establishing a proinflammatory milieu prior to T cell infiltration and brain atrophy. Targeting pyroptosis could therefore represent a potential strategy to attenuate neurodegeneration in type I interferon-driven neuroinflammatory disorders.