Chronic CeACRH Activation Disrupts Colonic IL-22/Reg3g Signaling and Induces Depression-Associated Microbiome Shifts in Male Mice.

BACKGROUND: Psychological stress shapes brain-body interactions through bidirectionally signaling between central neural circuits and peripheral systems. Central amygdala corticotropin-releasing hormone (CeACRH) neurons are key regulators of stress response and immune function. However, their chronic impact on the brain-gut-immune axis and gut microbiota remains poorly understood. METHODS: We established a chronic stress model in mice by 14-day chemogenetic activating CRH neurons in the CeA. Behavioral assays were conducted to evaluate anxiety and depressive-like phenotypes. mRNA expression level of cytokines, tight junction proteins and antimicrobial peptide were compared in spleen or colon using qPCR between CeACRH activated group and control. In addition, 16S rRNA sequencing was performed to characterize changes in the microbial composition. RESULTS: Chronic activation of CeACRH neurons showed a tendency toward anxiety-like behavior and significantly disrupts splenic and colonic immune homeostasis. Notably, the colonic interleukin-22 (IL-22)/regenerating islet‑derived protein 3 gamma (Reg3g) mucosal defense axis was suppressed. Microbiota analysis revealed a shift toward a depression-associated profile, characterized by an increase in potentially pathogenic taxa (e.g., Eggerthella and Actinomycetota) and a reduction in short-chain fatty acid producers (e.g., Ruminococcaceae and Roseburia). These microbial alterations are consistent with clinical observations in patients with depression, supporting the translational relevance of mental disorders and gut microbiota. CONCLUSIONS: Chronic activation of CeACRH neurons drives coordinated immune, gut barrier, and microbiota alterations, including Claudin-2 upregulation and suppression of the IL-22/Reg3g axis, with IL-22 significantly reduced and Reg3g showing only a decreasing trend. These findings suggest a neuro-immune-microbiota pathway linking central stress circuits to peripheral dysfunction. Targeting IL-22 signaling, epithelial barrier integrity, or microbiota composition may represent promising therapeutic strategies for chronic stress-related disorders.