Abstract
Fucoidan, a high-molecular weight sulfated polysaccharide in brown algae, has been reported to be effective in the enhancement of immune responses to tumors and infections. On the other hand, it is also known to have anti-inflammatory effects, and thought to help maintain immune homeostasis. In this study, the efficacy of CUA fucoidan which consists of fucoidan from Okinawamozuku, fucoidan from Mekabu and Agaricus mycelium extract in prevention of pneumonia caused by viral infection was evaluated. In this study, TLR ligands solution (TLR3-L: 62.5 µg poly(I:C), TLR4-L: 25 µg rSARS-CoV-2 spike protein, TLR7-L: 5.0 µg gardiquimod) was administered orally to C57BL/6J mice to create a mouse model of pneumonia. After 2 weeks of acclimatization, 30 mg CUA fucoidan was orally administered for 2 weeks, and pneumonia was induced by the above-mentioned infectious stimuli, and the pathological signs were analyzed and evaluated after 2 days. A remarkable inflammatory sign such as tissue thickening and monocyte infiltration was occurred in the control mice, whereas a remarkable alleviation of pulmonary inflammation was observed in the mice treated with CUA fucoidan. In this situation, the levels of IL-6, a key inflammatory cytokine, in alveolar lavage (BAL) fluid and plasma were significantly lower in the fucoidan group as compared with the control group. Interestingly, IFN-α and IFN-γ levels in BAL fluid were not reduced by CUA fucoidan treatment. In addition, the expression of class II MHC molecules in leukocytes was significantly reduced in the fucoidan-pretreated mice. These results suggest that continuous intake of CUA fucoidan may contribute to the prevention of inflammation caused by upper respiratory infections.
