Fig. 4

Celastrol activated ER stress through ROS. A Celastrol rapidly activates the ER stress pathway. H460, PC-9, and H520 cells were exposed to 4 µM celastrol for indicated times. Lysates were detected for p-eIF2α and ATF4. eIF2α and GAPDH was used as controls. B Effect of NAC on celastrol-induced ER stress. H460, PC-9, and H520 cells were pretreated with 5 mM NAC for 1 h and exposed to celastrol for 3 h. Western blot detected the lysates. Outcomes are representative of three independent experiments (*P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001)