Scoulerine promotes cell viability reduction and apoptosis by activating ROS-dependent endoplasmic reticulum stress in colorectal cancer cells

Scoulerine, an isoquinoline alkaloid isolated from Corydalis plants, has been reported to possess potent anti-proliferative and pro-apoptotic function in cancer cells. However, the effects and underlying mechanisms of scoulerine on colorectal cancer (CRC) progression remain elusive. CCK-8 and LDH assays were used to evaluate cell viability. Apoptosis was assessed by flow cytometry analysis, caspase-3/7 activity assay, and Western blot analysis of Bax, Bcl-2 and cytochrome c (Cyt C) expression. Oxidative stress level was examined by measuring reactive oxygen species (ROS) and glutathione (GSH) contents and superoxide dismutase (SOD) activity. Endoplasmic reticulum (ER) stress activation was detected by Western blot analysis of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) expression. Results showed that scoulerine dose-dependently suppressed CRC cell viability. Scoulerine induced apoptosis and increased caspase-3/7 activity in CRC cells. Bax and cytosolic Cyt C expression was enhanced while Bcl-2 and mitochondrial Cyt C expression was reduced in scoulerine-treated CRC cells. Additionally, scoulerine induced oxidative damage in CRC cells by increasing ROS generation and reducing GSH content and SOD activity. Scoulerine activated ER stress, as evidenced by the increased GRP78 and CHOP expression in CRC cells. Interestingly, blocking ROS production by ROS scavenger N-acetyl-cysteine (NAC) attenuated scoulerine-induced ER stress. Inhibition of ER stress by 4-phenyl butyric acid (4-PBA) abolished scoulerine-induced ROS generation in CRC cells. Blockage of ROS and ER stress attenuated scoulerine-induced cell viability reduction and apoptosis in CRC cells. In conclusion, scoulerine promoted cell viability reduction and apoptosis by activating ROS-dependent ER stress in CRC cells.

Keywords: Apoptosis; Colorectal cancer; Endoplasmic reticulum stress; Reactive oxygen species; Scoulerine.