Oxidation of indole-3-acetic acid by horseradish peroxidase induces apoptosis in G361 human melanoma cells

• Published in: Cellular signalling Vol. 16; no. 1; pp. 81 - 88
• Main Authors: Kim, Dong-Seok, Jeon, Sang-Eun, Park, Kyoung-Chan
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 2004
• Subjects: Antioxidants - pharmacology; Apoptosis; Apoptosis - drug effects; Apoptosis - physiology; Ascorbic Acid - pharmacology; Caspases - drug effects; Caspases - metabolism; Catechin - analogs & derivatives; Catechin - pharmacology; Cell Line, Tumor; Dose-Response Relationship, Drug; Drug Screening Assays, Antitumor; Drug Synergism; Drug Therapy, Combination; Free radical; Free Radicals - metabolism; Horseradish peroxidase; Horseradish Peroxidase - metabolism; Horseradish Peroxidase - pharmacology; Humans; Indole-3-acetic acid; Indoleacetic Acids - metabolism; Indoleacetic Acids - pharmacology; JNK Mitogen-Activated Protein Kinases; Melanoma - drug therapy; Melanoma - metabolism; Melanoma - physiopathology; Mitochondria - drug effects; Mitochondria - metabolism; Mitogen-Activated Protein Kinases - drug effects; Mitogen-Activated Protein Kinases - metabolism; Oxidative Stress - drug effects; Oxidative Stress - physiology; p38 Mitogen-Activated Protein Kinases; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerases; Prodrugs - metabolism; Prodrugs - pharmacology; Proteins - drug effects; Proteins - metabolism; Indole-3-acetic acid; EGCG; JNK; HRP; Horseradish peroxidase; IAA; PARP; MTT; Free radical; DCFH-DA; NAC; ROS; PI; MAP; Apoptosis
• ISSN: 0898-6568; 1873-3913
• DOI: 10.1016/S0898-6568(03)00091-3

The combination of indole-3-acetic acid (IAA) and horseradish peroxidase (HRP) has recently been proposed as a novel cancer therapy. However, the mechanism underlying the cytotoxic effect involved is substantially unknown. Here, we show that IAA/HRP treatment induces apoptosis in G361 human melanoma cells, whereas IAA or HRP alone have no effect. It is known that IAA produces free radicals when oxidized by HRP. Because oxidative stress could induce apoptosis, we measured the production of free radicals at varying concentrations of IAA and HRP. Our results show that IAA/HRP produces free radicals in a dose-dependent manner, which are suppressed by ascorbic acid or (−)-epigallocatechin gallate (EGCG). Furthermore, antioxidants prevent IAA/HRP-induced apoptosis, indicating that the IAA/HRP-produced free radicals play an important role in the apoptotic process. In addition, IAA/HRP was observed to activate p38 mitogen-activated protein (MAP) kinase and c-Jun N-terminal kinase (JNK), which are almost completely blocked by antioxidants. We further investigated the IAA/HRP-mediated apoptotic pathways, and found that IAA/HRP activates caspase-8 and caspase-9, leading to caspase-3 activation and poly(ADP-ribose) polymerase (PARP) cleavage. These events were also blocked by antioxidants, such as ascorbic acid or EGCG. Thus, we propose that IAA/HRP-induced free radicals lead to the apoptosis of human melanoma cells via both death receptor-mediated and mitochondrial apoptotic pathways.