Objectives: To observe the effect of electroacupuncture (EA) on neuroinflammatory response and glial scar formation Via regulating expression of neutrophil extracellular traps (NETs) in mice with spinal cord injury (SCI).

Methods: Sixty female C57BL/6 mice were randomized into sham operation, model, EA, DNase1 and EA+DNase1 groups, with 12 mice in each group. The SCI model was established by clamping the spinal cord with a serrefine after laminectomy at the 11th thoracic vertebra (T11). EA (1.5 Hz/7.5 Hz, 1 mA) was applied to bilateral "Jiaji" (EX-B2, T10, T12) for 10 min, once a day for 14 consecutive days, for mice of the EA and EA+DNasel groups. Mice of the DNase1 and EA+DNase1 groups were intraperitoneally injected with NETs inhibitor (DNase1, 50 μg/mice), twice daily for 14 days. The motor function was evaluated by BBB score. Histopathological changes of the injured area of the spinal cord were determined by H.E. staining. The positive expressions of citrullinated histone H3 (citH3) and glial fibrillary acidic protein (GFAP) in the spinal cord of mice were observed by immunofluorescence. Western blot was used to detect the expressions of citH3, elastase (NE), myeloperoxidase (Mpo), cyclic guanosine monophosphate-adenylate synthase (cGAS), interferon gene stimulator (STING), GFAP and Neurocan in spinal cord tissue. The contents of inflammatory factors interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) in spinal cord and serum were detected by ELISA .

Results: After SCI, the BBB scores were obviously decreased (P<0.05), while the protein relative expressions of citH3, NE, Mpo, cGAS, STING, GFAP, and Neurocan in spinal cord tissue, and the fluorescence intensities of citH3 and GFAP, as well as the contents of IL-1β and TNF-α in serum and spinal cord tissue were all increased in the model group relevant to the sham operation group (P<0.05, P<0.01). In the EA, DNase1 and EA+DNase1 groups, SCI-induced reduction of BBB scores, and increases of the protein relative expressions of citH3, NE, cGAS, STING, GFAP, and Neurocan, and the fluorescence intensities of citH3 and GFAP, as well as the contents of IL-1β and TNF-α were reversed relevant to the model group (P<0.05, P<0.01). The expression level of Mpo protein decreased (P<0.05, P<0.01) in spinal cord of rats in the EA and EA+DNasel groups relevant to the model group. The therapeutic effects of EA+DNase1 were better than EA or DNase1 (P<0.05, P<0.01). H.E. staining showed neuronal degeneration, nuclear pyknosis and inflammatory cell infiltration in the injured spinal cord tissue in the model group, which was relatively milder in the three intervention groups.

Conclusions: EA of EX-B2 can alleviate neuroinflammatory reactions and glial scar formation in SCI mice, and improve the recovery of neurological function after SCI, which maybe related to its function in down-regulating NETs expression.