3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) induces caspase-dependent apoptosis in mononuclear cells.
3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), one of the tryptophan pyrolysates, is a dietary carcinogen and is formed in cooked meat and fish in our daily diet. Trp-P-1 will affect the cells in the blood circulation system before it causes carcinogenicity in target organs such as the liver. In this study, the cytotoxicity of Trp-P-1 was investigated in mononuclear cells (MNCs) from blood. Trp-P-1 (10-15 microM) decreased cell viability and induced apoptosis characterized both by morphological changes and by DNA fragmentation 4 h after treatment. DNA fragmentation was also observed following treatment at 1 nM after 24 h in culture. This result suggested that apoptosis would occur in the body following unexpected intake of foods containing Trp-P-1. To determine the mechanism of apoptosis, we investigated the activation of the caspase cascade in MNCs. Trp-P-1 (10-15 microM) activated the caspase cascade, i.e. the activity of caspase-3, -6, -7, -8 and -9 increased dose-dependently using peptide substrates, the active forms of caspase-3, -8 and -9 were detected by immunoblotting, and cleavage of poly(ADP-ribose) polymerase and protein kinase C-delta as the intracellular substrates for caspases was observed. A peptide inhibitor of caspase-8 completely suppressed activation of all other caspases, while an inhibitor of caspase-9 did not. These results indicated that caspase-8 may act as an apical caspase in the Trp-P-1-activated cascade.
Hashimoto
T
T
Division of Life Science, Graduaute School of Science and Technology, Kobe University, Japan.
Ashida
H
H
Sano
T
T
Furuyashiki
T
T
Hatanaka
Y
Y
Minato
K
K
Mizuno
M
M
Nomura
K
K
Kumatori
A
A
Kanazawa
K
K
Danno
G
G
D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002243:Carbolines / Q000633:toxicity*; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D053938:DNA Fragmentation; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D008297:Male; D009000:Monocytes / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D013997:Time Factors
D002243:Carbolines; D061945:Caspase Inhibitors; D017382:Reactive Oxygen Species; D020169:Caspases; C019132:3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole; D000111:Acetylcysteine