Xiaoyaosan alleviates chronic psychological stress-induced TH17/Treg imbalance via modulation of the FKBP5/NF-κB axis

Ethnopharmacological relevance

Xiaoyaosan (XYS), a classical herbal formulation indicated for “depression syndrome”, can improve chronic stress-related mood disorders and immune disorders through multi-target modulation of inflammatory mediators, although its precise mechanism in regulating Th17/Treg balance remains to be clarified.

Aim of the study

This study aims to elucidate the regulatory impact of XYS on the peripheral Th17/Treg immunological imbalance generated by chronic psychological stress through modulation of the FKBP5/NF-κB signaling pathway, thereby establishing a mechanistic foundation for developing innovative interventions with dual stress-adaptogenic and immunoregulatory properties.

Materials and methods

FKBP5 knockout (FKBP5^−/−) and C57BL/6 mice underwent a 35-day chronic unpredictable mild stress (CUMS) paradigm. C57BL/6 mice were subsequently treated with XYS (1.61, 3.22, and 6.44 g/kg/d), fluoxetine (3 mg/kg/d). Behavioral phenotyping included the Open Field Test (OFT), Tail Suspension Test (TST), Forced Swimming Test (FST) and Sucrose preference test (SPT). Serum inflammatory cytokines (IL-17A, IL-23, IL-10, TNF-α) measured by enzyme-linked immunosorbent test (ELISA). Splenic Th17/Treg subset ratios were analyzed using multicolor flow cytometry. Western blotting evaluated FKBP5 expression and NF-κB pathway dynamics (IκB-α degradation, P65 nuclear translocation). UPLC-HRMS-based phytochemical profiling coupled with molecular docking elucidated XYS-FKBP5 interactions. FKBP5/IKKα/β complex formation was validated through confocal immunofluorescence (IF) colocalization and reciprocal co-immunoprecipitation (CO-IP) assays.

Results

CUMS mice exhibited significant depression-like behaviors and hippocampal neuronal damage, concomitant with elevated serum corticosterone levels and Th17/Treg immune dysregulation. Medium- and high-dose XYS interventions substantially ameliorated these behavioral abnormalities, reversed hippocampal pathological alterations, suppressed pro-inflammatory responses, and rectified Th17/Treg imbalance. Crucially, XYS exerted therapeutic effects through targeted suppression of FKBP5-IKK complex interaction, effectively blocking NF-κB nuclear translocation, thereby restoring Th17/Treg homeostasis.

Conclusion

XYS ameliorates chronic psychological stress-induced Th17/Treg immune imbalance through FKBP5-targeted suppression of NF-κB hyperactivation. This multicomponent synergistic mechanism establishes a novel therapeutic strategy for stress-associated inflammatory comorbidities, particularly depression with immune dysregulation.