Water-soluble seaweed extracts modulate the respiratory burst activity of turbot phagocytes

In this study, we investigated the effects of water-soluble extracts (WSE) from seaweed species Ova rigida C. Agardh, Enteromorpha sp., Codium tomentosum (Huds) Stackh., Fucus vesiculosus L., Pelvetia canaliculata (L.) Decne et Thur, Dictyota dichotoma (Huds) Lamour, Chondrus crispus Stackh and Porphyra umbilicalis (L.) J. Agardh, on the respiratory burst of turbot phagocytes, in search of biologically active substances with immunostimulating capacities. The stimulatory capacities of the extracts varied greatly, depending on their origin, the concentrations used and the time of incubation. The best responses were induced by the extracts obtained from U. rigida, Enteromorpha sp. and C. crispus. Pre-incubation of the phagocyte cells with U. rigida and C crispus extracts and subsequent incubation with phorbol myristate acetate (PMA) showed that these cells responded to further stimulation by this substance and, at some concentrations, they showed higher respiratory burst activity than control cells stimulated by PMA alone, suggesting that the extracts had a priming effect. We also tested the effects of protein-free water-soluble extracts (PF-WSE) and of the polysaccharide fractions (PSF) obtained from the PF-WSE of U. rigida and C crispus. These extracts induced an increase in the respiratory burst activity of turbot phagocytes, suggesting that most of the stimulatory capacity of the water-soluble extracts was associated with polysaccharides. (C) 2004 Elsevier B.V. All rights reserved.