Immune Activation of RAW264.7 Macrophages by Low Molecular Weight Fucoidan Extracted from New Zealand Undaria pinnatifida

Fucoidan, a sulfated polysaccharide extracted from brown seaweeds, has been shown to possess various bioactivities. In particular, low molecular weight fucoidan (LMWF) has been shown to have better bioactivities. In this study, a LMWF (<10 kDa) was extracted from New Zealand Undaria pinnatifida and investigated for its immune modulation effects. LMWF at a concentration range from 1 to 50 μg/mL exerted an effective immune activation in RAW264.7 macrophages. LMWF treatment promoted significant NO release, iNOS expression, and TNF-α and IL-6 secretion in a concentration-dependent manner. It also significantly stimulated the activation of NF-κB and MAPK signaling pathways, and specific inhibitors of NF-κB and MAPK pathways diminished the stimulation, confirming the activation pathways. These results indicate that LMWF possesses potential health benefits through immune-stimulation, which may lead to future pharmaceutical development.