Repeated TLR7 Activation Increases Alcohol Consumption and Induces Cell Type-Specific Transcriptome Changes in Mice

Alcohol consumption triggers neuroinflammation, potentially creating a feed-forward loop that increases drinking. Previous studies have shown that activation of the toll-like receptor 7 (TLR7) leads to escalated drinking. In this study, we aim to identify cell type-specific transcriptomic patterns linking TLR7-induced neuroinflammation to drinking. Therefore, male C57BL/6J mice were treated with the selective TLR7 agonist R848 every-other day for 20 days in total. After 10 treatment-free days, brains were collected for single-nucleus RNA-Sequencing (snRNA-Seq) in the medial prefrontal cortex (mPFC) and central amygdala (AMG). The AMG showed a greater number of differentially expressed genes (DEGs), primarily in inhibitory and excitatory neurons. Among glial cells, AMG astrocytes exhibited the greatest number of DEGs, which were involved in blood-brain barrier (BBB) regulation (e.g., Cldn5, Mecom, Nrg1), a finding supported by secondary validation using Xenium in situ spatial transcriptomics on AMG-containing sections. BBB-regulatory genes, including those in the Wnt signaling pathway (e.g., Notch3, Top2a, Aldoc), were altered across multiple cell types in both regions. These findings suggest that repeated TLR7 activation induces persistent BBB dysfunction, which may contribute to escalated alcohol consumption.