Alginate oligomer induces nitric oxide (NO) production in RAW264.7 cells: elucidation of the underlying intracellular signaling mechanism.

Alginate is an acidic linear polysaccharide with immune-modulating activities. In this study, we found that enzymatically digested alginate oligomer (AO) with various degrees of polymerization (DP; 2-5) induced a higher level of nitric oxide (NO) production in RAW264.7 cells than undigested alginate polymer (AP). Reverse transcription-polymerase chain reaction and western blot analyses revealed that the expression level of inducible NO synthase in AO-treated RAW264.7 cells was higher than that in AP-treated cells. AO induced nuclear translocation of nuclear factor (NF)-κB p65 subunit in RAW264.7 cells to a greater extent than AP. Although AO and AP induced similar extents of phosphorylation in three mitogen-activated protein (MAP) kinases, c-Jun N-terminal kinase inhibitor exhibited the most potent inhibitory effect on NO induction in AO- and AP-treated RAW264.7 cells, among three MAP kinase inhibitors that were tested.

Anti-metastatic effects of the sulfated polysaccharide ascophyllan isolated from Ascophyllum nodosum on B16 melanoma.

We previously found that ascophyllan, a sulfated polysaccharide isolated from brown seaweed Ascophyllum nodosum, exhibited antitumor activity in sarcoma-180 tumor-bearing mice. In this study, we found that ascophyllan inhibited the migration and adhesion of B16 melanoma cells by reducing the expression of N-cadherin and enhancing the expression of E-cadherin in a concentration-dependent manner. Transwell invasion assay revealed that ascophyllan suppressed the invasion ability of B16 cells. It also inhibited the expression of matrix metalloprotease-9 (MMP-9) mRNA and the secretion of MMP-9 protein in B16 cells, a process that may involve the extracellular signal-regulated kinase (ERK) signaling pathway. Furthermore, ascophyllan administered intraperitoneally at 25 mg/kg showed anti-metastatic activity in a mouse model of metastasis induced by intravenous injection of B16 cells, and the number of lung surface metastatic nodules in ascophyllan-treated mice was significantly reduced compared to that in the untreated control mice. Since splenic natural killer cell activity enhanced in the mice injected with ascophyllan intraperitoneally, we suggest that ascophyllan may exhibit in vivo anti-metastatic activity on B16 melanoma cells through activation of the host immune system in addition to a direct action on cancer cells.

Antioxidant and anti-inflammatory activities of porphyran isolated from discolored nori (Porphyra yezoensis).

We found that discolored waste nori with no commercial value, contains much higher level of porphyran than normal nori that is a sheeted food stuff prepared from P. yezoensis used in sushi. Chemical analyses revealed that mean molecular mass of the porphyran prepared from discolored nori (dc-porphyran) was much lower than that of the porphyran from normal nori (n-porphyran). Dc-porphyran showed slightly greater scavenging activity toward superoxide anion and hydroxyl radical than n-porphyran. Dc-porphyran inhibited nitric oxide (NO) production in LPS-stimulated RAW264.7 cells through preventing the expression of inducible NO synthase, whereas no such activity was observed in n-porphyran. Since acid-hydrolyzed n-porphyran showed the inhibitory activity on NO production from LPS-stimulated RAW264.7 cells, the molecular size of porphyran was suggested to be a critical factor for the activity. Dc-porphyran was separated into 4 fractions (F1-F4) on DEAE-chromatography, and F1 showed the highest inhibitory effect on NO production from LPS-stimulated RAW264.7 cells. Our results indicate that discolored waste nori is useful as a source of porphyran with even better bioactivities than porphyran from normal nori.

Inhibitory effect of orally-administered sulfated polysaccharide ascophyllan isolated from ascophyllum nodosum on the growth of sarcoma-180 solid tumor in mice.

We evaluated the antitumor activity of crude extract and ascophyllan prepared from Ascophyllum nodosum in sarcoma-180 solid tumor-bearing mice with continuous intraperitoneal (i.p.) administration at a dose of 50 mg/kg body weight/day or oral administration at a dose of 500 mg/kg body weight/day. Ascophyllan and crude extract administered via the oral route showed greater antitumor effects than via i.p. route, and the tumor sizes in mice treated with ascopyllan and crude extract were reduced by a mean of 68.7±6.8% and 42.4±24.8% by the oral route, and 41.4±16.1% and 13.6±20.6% by i.p. route compared to control mice. Splenic natural killer cell activity in the mice treated with ascophyllan and crude extract by i.p. route was significantly enhanced, while only a slight increase of this activity was observed in orally-treated mice. Furthermore, increase in spleen weight of tumor-bearing mice was slightly suppressed by oral administration of ascophyllan, whereas i.p. administration resulted in further enlargement. Analysis of serum cytokines revealed that oral treatment with ascophyllan resulted in significant increase of tumor necrosis factor-α and interleukin-12 levels. Since ascophyllan showed no direct cytotoxic effect on sarcoma-180 cells, orally-administered ascophyllan is suggested to exhibit its antitumor activity through the activation of the host immune system.