Dual-backbone pectic polysaccharide activates NOD1/RIPK2/NF-κB and mitochondrial metabolism to enhance the immune activity of macrophages

A novel pectic polysaccharide with dual backbones (SHP-A, 15,866 Da) was isolated from Sinopodophyllum hexandrum fruits. This polysaccharide is a heteropolymer composed of six monosaccharides. Structural characterization based on nuclear magnetic resonance spectroscopy, methylation analysis, and other methods demonstrated that SHP-A features a unique architecture consisting of a rhamnogalacturonan-I backbone (alternating α-GalpA and α-Rha molecules with β-Galp/α-Araf side chains) and a β-glucomannan backbone (alternating β-Manp and β-Glcp molecules), interconnected via β-Galp bridges. Bioactivity assays showed that SHP-A exerts potent immunomodulatory effects by enhancing macrophage phagocytosis and nitric oxide release. Transcriptomics analyses and NOD1 inhibitor interventions confirmed that SHP-A can activate the NOD1/RIPK2/NF-κB axis and induce M1 polarization in RAW264.7 macrophages, thereby upregulating various cytokines and chemokines. Furthermore, SHP-A also appeared to enhance immune function through mitochondrial metabolism, which indicated its potential as an immunomodulatory agent that can be used in the development of immune-enhancing health foods in the future.