Caspases‐2, ‐3, and ‐7 are involved in thapsigargin‐induced apoptosis of SH‐SY5Y neuroblastoma cells

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Abstract
Caspase‐2 has been reported to play a role in the cell death observed under a number of different conditions; however, it is unclear whether caspase‐2 plays a role in cell death triggered by endoplasmic reticulum (ER) stress. The purpose of this study was to determine whether caspase‐2 is involved in SH‐SY5Y neuroblastoma cell death caused by thapsigargin‐induced ER stress. Thapsigargin treatment (1 μM, 16 hr) stimulated the proteolytic processing of caspases‐2, ‐3, and ‐7, suggesting that these caspases are activated by ER stress. The role of these caspases in thapsigargin‐induced cell death was examined by using cell‐permeable caspase inhibitors. In the absence of pretreatment with caspase inhibitors, thapsigargin (0.1 μM, 20 hr) reduced the number of viable cells to 53.9% ± 3.3% of starting‐time control. Pretreatment for 90 min with either the pan‐caspase inhibitor Z‐VAD‐FMK or the caspase‐2‐selective inhibitor Z‐VDVAD‐FMK inhibited thapsigargin‐stimulated cell death, resulting in the number of viable cells being 115.6% ± 5.3% (P < 0.001) and 69.3% ± 2.9% (P < 0.01), respectively, of starting‐time control. Neither the caspase‐3‐ and ‐7‐selective inhibitor Z‐DEVD‐FMK nor the caspase‐9‐selective inhibitor Z‐LEHD‐FMK significantly affected thapsigargin‐stimulated cell death. An anticaspase‐12‐reactive protein was also identified in SH‐SY5Y cells, but thapsigargin had no effect on proteolysis of this protein. These data demonstrate that caspases‐2, ‐3, and ‐7 are involved in ER stress‐mediated death of SH‐SY5Y cells.