Study on the Effects of Transcutaneous Auricular Acupuncture Stimulation of the Vagus Nerve on Post-Traumatic Cerebral Oedema.

BACKGROUND

Secondary cerebral oedema following traumatic brain injury (TBI) is a major cause of poor prognosis, primarily driven by neuroinflammation. High-mobility group box 1 (HMGB1) is a key damage-associated molecular pattern that initiates a potent inflammatory cascade, yet targeted pharmacological interventions face clinical translation challenges. Non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) has shown anti-inflammatory potential, but its efficacy and specific mechanisms in treating traumatic cerebral oedema remain unclear.

METHODS

A controlled cortical impact (CCI) model was established in male C57BL/6 mice. The animals were randomly divided into five groups: sham, TBI, TBI + taVNS, TBI + HMGB1 agonist (high glucose), and TBI + HMGB1 antagonist (glycyrrhizic acid). taVNS was administered daily for 7 days. Cerebral oedema volume was quantified via magnetic resonance imaging (MRI) on days 3 and 10 post-injury. Neurological function was assessed using the open field test and modified neurological sign score (mNSS). Molecular mechanisms were investigated through transcriptomic sequencing, enzyme-linked immunosorbent assay (ELISA), western blotting, and immunofluorescence to analyze HMGB1 and downstream inflammatory factors (interleukin-1β (IL-1β), interleukin-6 (IL-6)).

RESULTS

Transcriptomic analysis revealed that taVNS reversed TBI-induced dysregulation of genes enriched in HMGB1-related pathways (e.g., Ras-associated protein-1 (Rap1), mitogen-activated protein kinase (MAPK)). Compared with the TBI group, taVNS significantly accelerated the resolution of cerebral oedema (reduction rate: 74.7 ± 12.1% vs 53.5 ± 16.2%, p < 0.05) and improved neurological function. Mechanistically, taVNS markedly suppressed the upregulation of HMGB1, IL-1β, and IL-6 in both serum and brain tissue. Crucially, the therapeutic effects of taVNS were abolished by HMGB1 agonism (high glucose), while HMGB1 antagonism (glycyrrhizic acid) alone mimicked the benefits of taVNS.

CONCLUSIONS

This study demonstrates that taVNS effectively promotes the resolution of post-traumatic cerebral oedema and facilitates neurological recovery by specifically inhibiting the HMGB1-mediated inflammatory pathway. These findings position taVNS as a promising, non-invasive therapeutic strategy for the early management of secondary brain injury.