p-Hydroxy benzaldehyde, a phenolic compound from Nostoc commune, ameliorates DSS-induced colitis against oxidative stress via the Nrf2/HO-1/NQO-1/NF-κB/AP-1 pathway.

Background: Ulcerative colitis (UC), a chronic idiopathic inflammatory bowel disease (IBD), presents with limited current drug treatment options. Consequently, the search for safe and effective drug for UC prevention and treatment is imperative. Our prior studies have demonstrated that the phenolic compound p-Hydroxybenzaldehyde (HD) from Nostoc commune, effectively mitigates intestinal inflammation. However, the mechanisms underlying HD's anti-inflammatory effects remain unclear.

Purpose: This study delved into the pharmacodynamics of HD and its underlying anti-inflammation mechanisms.

Methods: For in vivo experiments, dextran sodium sulfate (DSS)-induced colitis mouse model was established. In vitro inflammation model was established using lipopolysaccharide (LPS)-induced RAW264.7 and bone marrow-derived macrophages (BMDMs). The protective effect of HD against colitis was determined by monitoring clinical symptoms and histological morphology in mice. The levels of inflammatory factors and oxidative stress markers were subsequently analyzed with enzyme-linked immunosorbent assay (ELISA) and biochemical kits. Furthermore, western blotting (WB), immunofluorescence (IF), luciferase reporter gene, drug affinity reaction target stability (DARTS) assay, molecular docking, and molecular dynamics (MD) simulation were used to determine the potential target and molecular mechanism of HD.

Results: Our findings indicate that HD significantly alleviated the clinical symptoms and histological morphology of colitis in mice, and curtailed the production of pro-inflammatory cytokines, including TNF-α, IL-6, IFN-γ, COX-2, and iNOS. Furthermore, HD stimulated the production of SOD, CAT, and GSH-px, enhanced total antioxidant capacity (T-AOC), and reduced MDA levels. Mechanically, HD augmented the expression of Nrf2, HO-1, and NQO-1, while concurrently downregulating the phosphorylation of p65, IκBα, c-Jun, and c-Fos. ML385 and siNrf2 largely attenuated the protective effect of HD in enteritis mice and RAW 264.7 cells, as well as the promotion of HO-1 expression levels. ZnPP-mediated HO-1 knockdown reversed HD-induced inhibition of colonic inflammation. Luciferase reporter assay and IF assay confirmed the transcriptional activation of Nrf2 by HD. DARTS analysis, molecular docking, and MD results showed high binding strength, interaction efficiency and remarkable stability between Nrf2 and HD.

Conclusion: These outcomes extend our previous research results that HD can combat oxidative stress through the Nrf2/HO-1/NQO-1/NF-κB/AP-1 pathways, effectively alleviating colitis, and propose new targets for HD to protect against intestinal barrier damage.