Decoding microglia responses to psychosocial stress reveals blood-brain barrier breakdown that may drive stress susceptibility. Decoding microglia responses to psychosocial stress reveals blood-brain barrier breakdown that may drive stress susceptibility

An animal’s ability to cope with or succumb to deleterious effects of chronic psychological stress may be rooted in the brain’s immune responses manifested in microglial activity. Mice subjected to chronic social defeat (CSD) were categorized as susceptible (CSD-S) or resilient (CSD-R) based on behavioral phenotyping, and their microglial RNAs were isolated and analyzed by global gene expression microarrays. Microglia transcriptome from CSD-S mice was enriched for pathways that describe phases of CNS healing to sterile injury including, inflammation, oxidative stress, debris clearance, and wound resolution. Histochemical experiments confirmed the array predictions: CSD-S microglia showed elevated phagocytosis and oxidative stress, and the brains of CSD-S but not CSD-R or HC mice showed vascular leakage of intravenously injected fluorescent tracers. The results suggest that the inflammatory profile of CSD-S microglia may be precipitated by leakage of blood-born substances into brain parenchyma. We hypothesize that these CNS-centric responses contribute to the stress-susceptible behavioral phenotype. Overall design: Microglia from mice that went through chronic social defeat were divided to either suceptible or resilient to stress and were compared to microglia from home caged animals.