Marine microalgae and their antiallergic properties

Microalgae are considered as the actual producers of some highly bioac-tive macromolecules in marine resources, including carotenoids, long-chain polyunsaturated fatty acids, proteins, chlorophylls, vitamins, and unique pigments (Kay, 1991). Thus, they have been used as additives in a variety of human foods and animal feeds. Ingestion of various edible microalgae not only supplies protein and other nutrients but also modulates both adaptive and innate aspects of immunity (Price et al., 2002). Indeed, Spirulina was determined to decrease IgE antibody level, and increased IgG1 and IgA antibody production in the serum of the mice immunized with crude shrimp extract as an antigen (Hayashi et al., 1998). In a clinical trial, Spirulina consumption resulted in the significant amelioration in symptoms and physical findings of allergic rhinitis patients compared with placebo (Cingi et al., 2008). The clinical effect of Spirulina on allergic rhinitis was determined due to inhibiting the production of IL-4 and thus may suppress the differentiation of Th2 cells (Mao et al., 2005). In addition, it has been documented that Spirulina had a great inhibition on allergic reaction via suppressing anaphylactic shock, PCA, and serum histamine levels in rats activated by compound 48/80 or anti-DNP IgE. Also, the in vitro experiment revealed that Spirulina inhibited histamine release and TNF-a production from rat peritoneal mast cells (Kim et al., 1998; Yang et al., 1997). As a result, Spirulina can be a rich source of potential anti-allergic components. Indeed, phycocyanin, a bili-protein of Spirulina, has been revealed to be an inhibitor of allergic responses (Remirez et al., 2002). Moreover, phycocyanin has been demonstrated to enhance biological defense activity against infectious diseases through sustaining functions of the mucosal immune system and reduce allergic inflammation by the suppression of antigen-specific IgE antibody (Nemoto-Kawamura et al., 2004).

Besides Spirulina, several other microalgae appeared as promising new candidates for antiallergic agents. Porphyridium purpureum and Dunaliella salina displayed their appreciable inhibition on the activation of hyaluronidase with IC50 values of 180 and 150 mg/ml, respectively, which were almost the same as that of disodium cromoglycate (IC50 = 140 mg/ml) (Fujitani et al., 2001). Further, oral administration of hot water extract of Chlorella vulgaris (CVE) in mice suppressed the production of IgE against casein antigen accompanied by increasing mRNA expression of Th1 cytokines, including IFN-g and IL-12 (Hasegawa et al., 1999). Likewise, Chlorella pyrenoidosa was found to inhibit the production of IL-5 and IgE-dependent cytokine GM-CSF from mast cells. In vivo, mice treated with C. pyrenoidosa during OVA sensitization process significantly reduced eosinophil and neutrophil infiltration in the airways (Kralovec et al., 2005). Collectively, the above studies suggested a potential beneficial role of microalgae against allergic responses and thus they may be used as functional food or medicinal food ingredient to prevent and treat allergic diseases.

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