Anatoxin-a induces apoptosis of leukocytes and decreases the proliferative ability of lymphocytes of common carp (Cyprinus carpio L.) in vitro

Cyanobacteria (Cyanophyta, Cyanoprocaryota, Cyanobacteria) (blue-green algae) are procaryotic phototrophic microorganisms playing an important ecological role in the freshwater and marine environment as primary producers. However, as a consequence of water eutrophication observed in many reservoirs in different parts of the world, these microorganisms form massive scums, known as water blooms, releasing cyanotoxins hazardous to fish and other aquatic organisms. Cyanotoxins are cyanobacterial secondary metabolites of various chemical structures harmful to humans, terrestial and aquatic animals such as fish. The most abundant cyanotoxins are microcystins and hepatotoxins inducing toxic changes in fish liver, kidney, gills, digestive tract and immune system. Very little is known on the effects of alkaloid neurotoxic anatoxin-a on fish and their immunity. The aim of this study was to assess the in vitro influence of anatoxin-a on immune cells isolated from the common carp (Cyprinus carpio L.). The leukocyte intracellular level of ATP was reduced only at the highest concentration of anatoxin-a. Apoptotic and necrotic leukocytes were observed at the lower and the highest concentrations of anatoxin-a, respectively. Elevated activity of caspases 3/7 after 2 hours and a concentration-dependent decrease in the proliferative ability of T and B lymphocytes was also observed. The results suggest that anatoxin-a could be a possible immunotoxic agent in the aquatic environment and may increase the susceptibility of fish to infectious and neoplastic diseases. Therefore, constant monitoring of anatoxin-a and its producers in lakes and fish ponds should be performed.