Sensitive apoptosis induced by microcystins in the crucian carp (Carassius auratus) lymphocytes in vitro

Microcystins including leucine–arginine l-amino acid (MCLR) and arginine–arginine l-amino acid (MCRR) can inhibit several serine/threonine protein phosphatases. In this study, we focused on the efficient biomarker for analyzing toxic cyanobacteria blooms using in vitro apoptosis bioassay. We explored the existence of sensitive apoptosis induced by MCLR and MCRR on isolated lymphocytes of the crucian carp (Carassius auratus) at a low exposure level. Apoptosis was detected in vitro and was clearly distinguished by condensation of nuclear chromatin and formation of apoptotic bodies, after 2 h exposure at 1, 5, 10 nM MCLR and MCRR, respectively. Agarose gel electrophoresis further revealed DNA fragmentation (DNA ladder) caused by apoptosis. We found that MCLR and MCRR can induce lymphocyte apoptosis in a dose- and time-dependent manner with flow cytometry analysis. Our study provides the first evidence that microcystins can induce fish lymphocytes apoptosis and may impair fish immune function.