Lectin-induced enhancement of superoxide anion production by red tide plankton, Chattonella marina

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Chattonella marina, a raphidophycean flagellate, is one of the most noxious red tide phytoplankton and is highly toxic to fish, especially to yellowtail Seriola quinqueradiata. Although the precise mechanism of the toxic action of Chattonella sp. remains unclear, it has been demonstrated that a decrease in oxygen partial pressure of arterial blood is the earliest physiological disturbance observed in fish after exposure to C. marina, Physiological and histological studies of fish exposed to C. marina also suggested that the blockade of respiratory water flow through the gill lamellae caused by excessive mucus interferes with O2 transfer, resulting in asphyxia. Recent studies have shown that Chattonella spp. Generate reactive oxygen species (ROS) such as O2-, H2O2, and hydroxyl radical (・OH). Furthermore, it has been reported that Heterosigma akashiwo, which is also classified in a raphidophycean, produces ROS, and showed an oxygen-radical-mediated toxic effect on rainbow trout, Oncorhy … More nchus mykiss. Thus, it is likely that the production of ROS is a common feature of raphidophycean flagellates. In the present study, we found that lectins such as concanavalin A (Con A), wheat germ agglutinin (WGA), and castor bean hemagglutinin (CBH) stimulated C. marina and H. akashiwo to generate enhanced amounts of O2- in a concentration dependent manner. The lectin-specific sugars potently inhibited the lectin-induced increase of O2-production, suggesting that the effects of lectins are mediated mainly through the interaction of these lectins with carbohydrate moiety present on the flagellate cell surface. In contrast to the potent ability of native Con A (tetravalent), succinylated Con A (divalent) showed only slight stimulative effect on these flagellates. O2- production was totally inhibited by treatment with proteinase K for 30 min, without affecting the viabilities of flagellates. These results suggest that cell-surface redox enzyme may be involved in O2- production, and such enzyme is responsible for the lectin-stimulation. Less