Involvement of oxidative stress and cytoskeletal disruption in microcystin-induced apoptosis in CIK cells

• MC-LR exhibited cytotoxicity to CIK (Ctenopharyngodon idellus kidney) cells.
• Apoptosis was induced with MC-LR treatment in CIK cells.
• Oxidative stress played an important role in MC-LR toxicity.
• Both transcriptional and morphological changes of cytoskeleton were detected.
• The interaction of cytoskeletal disruption and oxidative stress led to apoptosis.

The outbreak of cyanobacterial blooms induces the production and release of microcystins (MCs) into water, representing a health hazard to aquatic organisms and even humans. Some recent studies have suggested that kidney is another important target organ of MCs except liver, however, the potential toxicity mechanisms are still unclear. In this study, we first investigated the collaborative effect of oxidative stress and cytoskeletal disruption in microcystin-induced apoptosis in CIK (Ctenopharyngodon idellus kidney) cells in vitro. CIK cells were treated with 0, 1, 10, and 100 μg/L microcystin-LR (MC-LR) for 24 and 48 h. Cell viability was increased by MC-LR in 1 μg/L group, while decreased in 100 μg/L group at 48 h. Cell cycle assay showed that 1 and 10 μg/L MC-LR induced cell cycle through G1 into S and G2/M phases, while 100 μg/L MC–LR reduced G2/M phase population. MC-LR markedly induced apoptosis in 10 and 100 μg/L groups. Elevated reactive oxygen species (ROS) production, increased malondialdehyde (MDA) contents, decreased glutathione (GSH) levels, and modulated antioxidant enzymes including catalase (CAT) and superoxide dismutase (SOD) were observed in CIK cells exposed to MC-LR. These alterations were more pronounced at higher doses (10 and 100 μg/L), indicating that oxidative stress was induced by MC-LR. Laser scanning confocal microscope observation showed aggregation and collapse of microfilaments (MFs) and microtubules (MTs) in CIK cells, and even loss of some cytoskeleton structure. Moreover, transcriptional changes of cytoskeletal genes (β-actin, lc3a, and keratin) were also determined, which have a high probability with cytoskeleton structure damage. Our data suggest that oxidative stress and cytoskeletal disruption may interact with each other and jointly lead to apoptosis and renal toxicity induced by MCs.