Patulin (PAT) is a fungal secondarymetabolite that exhibits potential cellular and animal toxicities. In this
study, human promyelocytic leukemia (HL-60) cells were used to elucidate the mechanism and death
mode associated with PAT. Morphological evidence of apoptosis, including membrane blebbing, nuclei
fragmentation and DNA laddering formation was clearly observed 6 h after exposure to PAT. The results
ofWestern blotting indicated that PAT activated various processed caspases, and cleaved DFF45 and poly
(ADP-ribose) polymerase (PARP) in a dose-dependent manner; it also induced a time-dependent increase
in caspase 3 and 9 catalytic activities.
The apoptosis mediated by PAT in HL-60 was accompanied with cytochrome c release from mitochondria
and Bcl-2 expression decrease. The presence of thiol-containing compounds with PAT dramatically
reduced the caspase 3 activity thatwas triggered by PAT; the addition of antioxidants, including mannitol
and Tiron, had a similar effect. However, the suppression of p53 protein expression by RNA interference
(RNAi) in human embryonic kidney (HEK293) cells did not significantly modify PAT-elicited caspase 3
activity. These findings suggest that PAT-induced apoptosis is mediated through the mitochondrial pathway
without the involvement of p53; the interaction with sulfhydryl groups of macromolecules by PAT
and the subsequent generation of reactive oxygen species (ROS) plays a primary role in the apoptoticells