Spatial Modulation of Immune Cell Distribution and Pro- and Anti-Inflammatory Cytokines by Transcutaneous Auricular...

Ulcerative colitis (UC) is characterized by reduced vagus nerve activity and colonic inflammation. This study examined region-specific effects of transcutaneous auricular vagus nerve stimulation (taVNS) on immune cells and cytokines in a UC-like mouse model, given its anti-inflammatory potential and differential innervation of the spleen, mesenteric lymph nodes (MLNs), and colon.

Male C57BL/6 mice received daily 10-minute taVNS or sham treatment (anesthesia only) beginning 24 hours before induction of colitis with 5% dextran sulfate sodium in drinking water for 120 hours; controls received regular water. taVNS continued until sacrifice (144 hours after initiation). Disease activity index (DAI), macroscopic, and histological scores were assessed. Immune cell frequencies in the cecum, proximal, mid, and distal colon, spleen, and MLNs were analyzed by flow cytometry, and colonic cytokine levels were measured by multiplex ELISA.

taVNS improved DAI, macroscopic scores, and histological damage throughout the cecum and colon. In colitic mice, taVNS reduced the total number of granulocytes and macrophages in the mid-colon but did not change granulocyte frequency in other colonic regions, MLNs, or spleen, nor did it affect macrophages in non-colitic mice. taVNS did not change M1/M2 macrophages, CD4⁺ and CD8⁺ T cells, B cells, or regulatory T cells. It reduced colonic IL-1β, TNF-α, and IL-6 in the cecum, proximal, and mid-colon; IFN-γ and IL-17A in the proximal and mid-colon; and IL-22 in the cecum and mid-colon of colitic mice. TGF-β1 was unchanged, whereas IL-10 increased in the proximal colon of colitic mice.

These findings show taVNS's local anti-inflammatory effects in colitic mice through modifying innate immune cells and inflammatory and anti-inflammatory cytokines regionally.