Trichodimerol and sorbicillin induced apoptosis of HL-60 cells is mediated by reactive oxygen species

In this study, two secondary metabolite compounds, trichodimerol and sorbicillin were isolated from the mycelial mass of the marine fungus Trichothecium sp.. It was found that trichodimerol and sorbicillin exhibited strong cytotoxic activity with IC50 values from 6.55 μM to 28.55 μM on three cancer cell lines, HL-60, U937 and T47D. Then HL-60 cells were employed for apoptotic assay. The two compounds could significantly increase the levels of activated caspase-3/7 in a dose-dependent manner and remarkably increase sub-G1 fraction in the cell cycle using flow cytometry, indicating that trichodimerol and sorbicillin potently induced apoptosis in HL-60 cells. Trichodimerol or sorbicillin induced ROS levels also showed dose-dependent increases in HL-60 cells as measured by 2',7'-Dichlorodihydrofluorescein diacetate (DCFH-DA), while trichodimerol or sorbicillin induced apoptosis was effectively blocked by the ROS inhibitor N-acetyl-L-cysteine (NAC). Western blot results showed that trichodimerol or sorbicillin could increase phosphorylated p38 levels and decrease ERK and phosphorylated ERK levels in a concentration-dependent manner. Our findings suggest that the pro-apoptosis effects of trichodimerol and sorbicillin were mediated by ROS, while activation of p38 and inhibition of ERK may be involved in these effects.