Comparative studies on the cytotoxic effects induced by nodularin in primary carp leukocytes and the cells of the fish CLC line

Nodularin, one of the toxins produced by cyanobacteria commonly occurring in brackish waters, is a cyclic pentapeptide, that may exert adverse effects on animal and human health. The aim of the present study was to evaluate the cytotoxicity of nodularin on different fish cellular models. The leukocytes isolated from carp head kidney and common carp (Cyprinus carpio L.) leukocyte cell line (CLC) were incubated with the cyanotoxin at the concentrations of 0.001, 0.01, 0.05 or 0.1 μg/mL. Treatment of cells with the higher concentrations of the toxin resulted in a dramatic decrease in cell viability. Simultaneously, we observed an increase in the percentage of necrotic cells. Nodularin also induced apoptosis as demonstrated by increased caspase-3/7 activity, and DNA fragmentation. We found, that primary cell cultures were more sensitive to the toxin than CLC cells. Our study also demonstrated significant increases in intracellular ROS production and decreases in GSH levels, observed in both primary leukocytes and CLC cells exposed to nodularin at 0.01-0.1 μg/mL. These cells exhibited similar GSH/GSSG ratios and similar level of oxidized glutathione.