Trichlorfon induces apoptosis in SH-SY5Y neuroblastoma cells via the endoplasmic reticulum?

This study investigated the role of the endoplasmic reticulum pathway in apoptosis induced by trichlorfon in SH-SY5Y human neuroblastoma cells. Flow cytometric analysis demonstrated that trichlorfon and its degradation product dichlorvos-induced apoptosis in a dose-dependent manner and Hoechst 33342 staining experiments revealed trichlorfon/dichlorvos-induced nucleus condensation. Western blot analysis indicated decreased expression of caspase-12 and increased activated caspase-12 in trichlorfon-treated cells compared to a control, suggesting that trichlorfon may induce apoptosis in SH-SY5Y partly via the endoplasmic reticulum. Intracellular Ca2+ level ([Ca2+]i) in SH-SY5Y cells increased after treatment with trichlorfon but was significantly reduced by pre-treatment with a combination of a calcium channel blocker, an inositol trisphosphate receptor inhibitor, and a ryanodine receptor inhibitor. Percent apoptosis and activated caspase-3 and caspase-12 decreased in pre-treated cells compared to those treated with trichlorfon alone. Trichlorfon-induced apoptosis was also inhibited by the protein kinase C activator, phorbol 12-myristate 13-acetate (PMA). These results suggest that endoplasmic reticulum stress, which is related to calcium, may be involved in the cytotoxicity of trichlorfon.