Macrophage activation by polysaccharide fraction isolated from Salicornia herbacea

We demonstrate that polysaccharides isolated from Salicornia herbacea (Salicornia polysaccharides, SPS) significantly induces nitric oxide (NO) production and inducible NO synthase (iNOS) transcription through the activation of nuclear factor-κB/Rel (NF-κB/Rel). SPS dose-dependently induced the production of NO in isolated mouse peritoneal macrophages and RAW 264.7, a mouse macrophage-like cell line. Moreover, iNOS gene expression was strongly induced by SPS in RAW 264.7 cells. To further investigate the mechanism responsible for the induction of iNOS gene expression, we investigated the effect of SPS on the activation of transcription factors including NF-κB/Rel and Oct, whose binding sites were located in the promoter of iNOS gene. Treatment of RAW 264.7 cells with SPS produced strong induction of NF-κB/Rel-dependent reporter gene expression, whereas Oct-dependent gene expression was not affected by SPS. Nuclear translocation and DNA binding activity of NF-κB/Rel was significantly induced by SPS. The treatment with NF-κB SN50, an inhibitor of NF-κB/Rel nuclear translocation, effectively inhibited the activation of NF-κB/Rel binding complexes and NO production. In conclusion, we demonstrate that SPS stimulates macrophages to express iNOS gene through the activation of NF-κB/Rel.