Gallic acid exerts therapeutic effects on sciatica by reducing inflammatory responses through the regulation of NOX4-mediated oxidative stress.

Background: Sciatica causes severe pain and impaired mobility. Neuroinflammation is involved in the development of sciatica. Purpose: This study aimed to explore whether Gallic acid (GA) reduces neuroinflammation to relieve sciatica by regulating NOX4-mediated oxidative stress. Methods: After scRNA-seq analysis was performed, 32 SD (Sprague-Dawley) rats were randomly divided into 4 groups: sham operation, chronic constriction injury (CCI), CCI+mecobalamin, and CCI+GA groups. We conducted behavioral tests, ELISA, western blotting, and immunofluorescence analysis. In cell experiments, we conducted ROS measurement, flow cytometry, PCR, and western blotting. Results: scRNA-seq analysis revealed that gene signatures related to the "inflammatory response" and "oxidative stress" were significantly enriched, with higher module scores observed specifically in M1 macrophages. In RAW264.7 cells, LPS stimulation significantly increased ROS generation and MDA levels and upregulated the expression of M1 macrophage markers, including IL-1β, iNOS, TNF-α, and CD32. In addition, LPS increased the protein expression of NOX4 and inflammatory mediators (TNF-α, IBA-1, IL-1β, COX-2, and iNOS) while reducing the levels of ATF4 and p-Nrf2. GA treatment reduced ROS generation and MDA levels; downregulated the mRNA expression of IL-1β, iNOS, TNF-α, and CD32; and increased CD206 mRNA expression. Similarly, GA decreased the protein levels of NOX4, TNF-α, IBA-1, IL-1β, COX-2, and iNOS but restored the expression of ATF4 and p-Nrf2. In CCI rats, GA significantly attenuated thermal hyperalgesia from Day 7 to Day 21, with thermal withdrawal thresholds recovering toward sham control levels. CCI markedly increased IL-8, COX-2, TNF-α, TGF-β, IL-6, and IL-1β levels in the sciatic nerve; increased IBA-1/CD32 coexpression; decreased IBA-1/CD206 coexpression; and markedly disrupted sciatic nerve architecture. These pathological changes were accompanied by elevated expression of IBA-1, NOX4, IL-1β, and iNOS, together with reduced ATF4 and p-Nrf2 levels. Notably, GA treatment largely reversed these CCI-induced alterations. Conclusion: GA alleviated sciatica in a rat model, possibly through its ability to promote the polarization of proinflammatory M1 macrophages toward anti-inflammatory M2 macrophages via the regulation of NOX4-mediated oxidative stress.