Panaxydol, a polyacetylenic compound derived from Panax ginseng roots, has been shown to inhibit the growth of
cancer cells. In this study, we demonstrated that
panaxydol induced apoptosis preferentially in transformed cells with a minimal effect on non-transformed cells. Furthermore,
panaxydol was shown to induce apoptosis through an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), activation of JNK and
p38 MAPK, and generation of
reactive oxygen species (ROS) initially by
NADPH oxidase and then by mitochondria.
Panaxydol-induced apoptosis was
caspase-dependent and occurred through a mitochondrial pathway. ROS generation by
NADPH oxidase was critical for
panaxydol-induced apoptosis. Mitochondrial ROS production was also required, however, it appeared to be secondary to the ROS generation by
NADPH oxidase. Activation of
NADPH oxidase was demonstrated by the membrane translocation of regulatory p47(
phox) and p67(
phox) subunits and shown to be necessary for ROS generation by
panaxydol treatment.
Panaxydol triggered a rapid and sustained increase of [Ca(2+)](i), which resulted in activation of JNK and
p38 MAPK. JNK and
p38 MAPK play a key role in activation of
NADPH oxidase, since inhibition of their expression or activity abrogated membrane translocation of p47(
phox) and p67(
phox) subunits and ROS generation. In summary, these data indicate that
panaxydol induces apoptosis preferentially in
cancer cells, and the signaling mechanisms involve a [Ca(2+)](i) increase, JNK and
p38 MAPK activation, and ROS generation through
NADPH oxidase and mitochondria.