Selenium (sodium selenite) causes cytotoxicity and apoptotic mediated cell death in PLHC-1 fish cell line through DNA and mitochondrial membrane potential damage

Elevated concentration of selenium poses a toxic threat to organisms inhabiting aquatic ecosystems influenced by excessive inputs from anthropogenic sources. Selenium is also an essential micronutrient in living things, particularly in fish, and provides antioxidant properties to tissues. Whole fish and hepatocytes in primary culture show selenite toxicity above threshold levels. The present study was designed to investigate the process by which selenite exposure causes cellular toxicity and apoptotic and necrotic cell death in fish hepatoma cell line PLHC-1. PLHC-1 cells were exposed to various selenite concentrations (1, 10, 50 and100 μM) for 10, 20 and 40 h intervals. The 24 h inhibitory concentration 50 (IC50) of selenite in PLHC-1 cell line was found to be 237 μM. Flow cytometery data showed that selenite exposed cells promote apoptotic and necrotic mediated cell death when selenite concentrations were ≥10 μM compared to control. Selenite exposure was associated with a significant increase of caspase-3 activities suggesting the induction of apoptosis. Selenite exposure at high levels (≥10 μM) and longer exposure times (≥20 h) induces mitochondrial membrane potential damage (ΔΨm), DNA damage and elevated production of ROS which could be associated with cell death.

► Selenite induces DNA damage as shown by comet assay. ► Apoptotic mediated cell death shown by TUNEL assay and flow cytometry assay. ► Selenite induced cell death is mediated by mitochondrial damage and elevated production of reactive oxygen species (ROS). ► Selenite also induces necrotic cell death based on LDH and flow cytometry. ► In vitro data’s relevance to environmental selenium exposure in whole fish is discussed.