Sesamin Induces Human Leukemic Cell Apoptosis via Mitochondrial and Endoplasmic Reticulum Stress Pathways

BACKGROUND: Sesamin is a purified compounds extracted from the seeds of Sesamum orientale Linn., which contains antioxidant and anticancer activities. The objective of this study was to identify the mechanistic effect of sesamin on human leukemic HL-60, U937 and Molt-4 cell apoptosis. METHODS: The cytotoxicity was performed by 3-(4,5-dimethyl)-2,5-diphenyl tetrazolium bromide (MTT) assay. Reactive oxygen species was measured by employing 2', 7'-dichlorodihydrofluorescein diacetate and flow cytometry. The mitochondrial transmembrane potential was determined by 3,3'-dihexyloxacarbocyanine iodide and flow cytometer. Caspase-3 and -8 activities were detected by using fluorogenic DEVD-AMC and IETD-AMC substrates, respectively. The protein expression of cytochrome c and GADD153, an endoplasmic reticulum (ER) stress protein, was illustrated by immunoblot. RESULTS: Sesamin was cytotoxic to HL-60 > U937 > Molt-4 > PBMCs and caused the three cell lines to die with the morphology of apoptotic character, i.e., condensed nuclei and apoptotic bodies. It produced reactive oxygen species in all cell lines, with a decrease in mitochondrial transmembrane potential. The caspase-3 activity was increased in sesamin-induced HL-60 cell apoptosis whereas casase-8 activity did not alter. Cytochrome c release was not increased. The expression of GADD153 was increased time dependently, indicating the involvement of ER stress pathway in HL-60 cells. CONCLUSIONS: Sesamin-induced human leukemic cell apoptosis was via oxidative stress, the mitochondrial and ER stress pathways.