Regional CNS immune fingerprint in chronic peripheral inflammation

Rheumatoid arthritis (RA) is linked to depression and dementia in later life by inflammatory involvement of the central nervous system (CNS). Regional heterogeneity of brain immunophenotypes was described under homeostasis, but a topographical resolution of CNS immune responses in chronic peripheral inflammatory diseases like RA is missing. We demonstrate regional heterogeneity of CNS susceptibility to chronic peripheral inflammation in the human tumor necrosis factor a transgenic (TNFtg) mouse model of RA. TNFtg mice showed myeloid cell infiltration, microglial activation, and a mutual transcriptomic fingerprint of neuroinflammation in the cortex, striatum, and thalamus. Immune responses were minimal in the hippocampus and cerebellum. We demonstrate regional CNS immune responses to chronic peripheral inflammation, sparing the hippocampus and cerebellum and reversible by peripheral anti-inflammatory treatment. Targeting microenvironmental susceptibility or resilience of brain regions will help to prevent and treat RA-related neuropsychiatric comorbidity. RNA-sequencing was performed from five brain regions (cortex, striatum, thalamus, hippocampus, and cerebellum) from C57Bl6/J wild type mice and TNFtg mice (strain Tg197; kindly provided by George Kollias (Fleming Institute, Vari, Greece).