Modulation of human polymorphonuclear leukocyte adherence by cyanopeptide toxins

The oligopeptides microcystins and nodularins are the most common and abund ant cyanotoxins present in diverse water systems. They cause different illn esses in animal and humans, sometimes leading to death, and are responsible for severe environmental problems. Here we demonstrate that both microcyst in-LR and N. spumigena nodularin (Nod) significantly enhance the early spon taneous adherence of peripheral polymorphonuclear leukocytes (PMNs) over th e concentration range 10(-11)-10(-9) M. However, neither of them affect sig nificantly the late spontaneous adherence or the early or late PMN-stimulat ed adherence (when cells are treated with formyl-methionyl-leucyl-phenylala nine). Since PMN adherence is a key step in the immune response, our data c learly indicate for the first time the immunomodulatory capacity of cyanope ptide toxins. The low concentrations at which the adherence modulation occu rs are similar to the physiological concentrations for natural mammalian pe ptide hormones. Such concentrations are well below those recommended by oth er authors and World Health Organization in terms of risk assessment as saf e for drinking water (8 x 10(-10) to 10(-9) M). (C) 2000 Academic Press.