APOE4-promoted gliosis and degeneration in tauopathy are ameliorated by pharmacological inhibition of HMGB1 release

Apolipoprotein E4 (APOE4) is an important driver of Tau pathology, gliosis, and degeneration in Alzheimer’s disease (AD). Still, the mechanisms underlying these APOE4-driven pathological effects remain elusive. In this study, we demonstrated in a tauopathy mouse model that APOE4 promoted the nucleo-cytoplasmic translocation and release of high mobility group box 1 (HMGB1) from hippocampal neurons, which correlated with the severity of hippocampal microgliosis and degeneration. Injection of HMGB1 into the hippocampus of young APOE4-tauopathy mice induced considerable and persistent gliosis. Selective removal of neuronal APOE4 reduced the nucleo-cytoplasmic translocation and release of HMGB1. Therapeutic treatment of APOE4-tauopathy mice with HMGB1 inhibitors effectively blocked the intraneuronal translocation and release of HMGB1 and ameliorated the development of prominent APOE4-driven AD pathologies, including gliosis, Tau pathology, neurodegeneration, and myelin deficits. Single-nucleus RNA-sequencing revealed that treatment with HMGB1 inhibitors diminished disease-associated and enriched disease-protective subpopulations of neurons, microglia, and astrocytes in APOE4-tauopathy mice. Thus, HMGB1 inhibitors represent a promising approach for treating APOE4-related AD. Single-nucleus RNA sequencing on isolated hippocampi from 9.5-month-old PS19-E3 and PS19-E4 mice that underwent a 12-week treatment with either saline or the HMGB1 inhibitors.