Acupuncture improves depression-like behaviors in rats through gut microbiota and TLR4/MyD88/NF-κB pathway modulation

Acupuncture (AP) is used for depression, but mechanisms remain unclear. We asked whether acupuncture attenuates chronic unpredictable mild stress (CUMS)-induced depressive-like behaviors in rats and, specifically, whether its efficacy is linked to remodeling gut microbiota and inhibiting TLR4/MyD88/NF-κB signaling along the gut-brain axis with concomitant rebalancing of hypothalamic-pituitary-adrenal (HPA) activity.

Male Sprague-Dawley rats underwent CUMS with or without acupuncture. Sucrose preference test (SPT) and forced swim test (FST) assessed behavior. Colonic injury was scored after H&E staining; microbiota were profiled by 16S rDNA sequencing. TLR4/MyD88/NF-κB expression in hypothalamus and colon was measured by Western blot/Real-time PCR; Iba1 + microglia were quantified by immunofluorescence. Serum cytokines and HPA hormones were assayed by ELISA.

Acupuncture increased sucrose preference (89.61 ± 2.551 % vs. 73.82 ± 5.711 %, P < 0.05) and reduced FST immobility (20.52 ± 3.784 s vs. 46.13 ± 7.391 s, P < 0.01) versus untreated CUMS. It lowered colonic injury (P < 0.05) and partly restored the Firmicutes/Bacteroidetes ratio. TLR4/MyD88/NF-κB signaling was suppressed in the hypothalamus and colon (TLR4 protein -37 %, P < 0.05), with fewer Iba1 + microglia (27.3 ± 3.2 % vs. 45.6 ± 4.8 %, P < 0.01). Serum IL-6, IL-1β, and TNF-α decreased, and HPA-axis activity normalized.

Acupuncture alleviates CUMS-induced depressive-like behaviors. The benefits are associated with gut microbiota remodeling, inhibition of TLR4/MyD88/NF-κB signaling, and stabilization of HPA-axis function, supporting an immune-microbiota-neuroendocrine mechanism.