Recently, we reported that a combination of
indole-3-acetic acid (IAA) and
horseradish peroxidase (HRP) induces apoptosis in G361 human
melanoma cells. However, the apoptotic mechanism involved has been poorly studied. It is known that when IAA is oxidized by HRP,
free radicals are produced, and since oxidative stress can induce apoptosis, we investigated whether
reactive oxygen species (ROS) are involved in IAA/HRP-induced apoptosis. Our results show that IAA/HRP-induced
free radical production is inhibited by
catalase, but not by
superoxide dismutase or
sodium formate. Furthermore,
catalase was found to prevent IAA/HRP-induced apoptotic cell death, indicating that IAA/HRP-produced
hydrogen peroxide (H2O2) may be involved in the apoptotic process. Moreover, the antiapoptotic effect of
catalase is potentiated by
NADPH, which is known to protect
catalase. On further investigating the IAA/HRP-mediated apoptotic pathway, we found that the IAA/HRP reaction leads to
caspase-3 activation and
poly(ADP-ribose) polymerase (PARP) cleavage, which was also blocked by
catalase. Additionally, we found that IAA/HRP produces H2O2 and induces
peroxiredoxin (Prx) sulfonylation. Consequently, our results suggest that H2O2 plays a major role in IAA/HRP-induced apoptosis.