3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) induces apoptosis in rat splenocytes and thymocytes by different mechanisms.
3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) is a potent carcinogen present in cooked meat. Although the target of this carcinogen is mainly in the liver, Trp-P-1 is distributed in the thymus and spleen as well as in the liver after administration. However, the cytotoxic effect of Trp-P-1 on lymphocytes has not been examined in detail. In the present study, we investigated the cytotoxicity of Trp-P-1 against rat splenocytes and thymocytes. Trp-P-1 reduced viability of both types of cells in the same manner, the LD(50) at 6h in culture was 15 microM, and the time for the 50% decrease in cell viability (t(1/2)) at 20 microM was 3h. In both types of cells, Trp-P-1 caused the activation of caspase-3-like proteases and the cleavage of poly(ADP-ribose) polymerase, both of which are biochemical markers of apoptosis. On the other hand, DNA fragmentation occurred in splenocytes, but not in thymocytes although Trp-P-1 activated 32-34kDa nucleases that may not be able to degrade DNA into nucleosomal units. These results indicated that Trp-P-1 induces apoptosis in both splenocytes and thymocytes by different mechanisms in which distinct apoptotic pathways may exist downstream of the caspase cascade.
Hashimoto
T
T
Division of Life Science, Graduate School of Science and Technology, Kobe University, Rokkodai-cho 1, Nada-ku, 657-8501, Kobe, Japan.
Ashida
H
H
Sano
T
T
Furuyashiki
T
T
Shiotani
B
B
Kanazawa
K
K
Danno
G
G
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002243:Carbolines / Q000633:toxicity*; D002273:Carcinogens / Q000633:toxicity*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D053938:DNA Fragmentation / Q000187:drug effects; D003609:Dactinomycin / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009153:Mutagens / Q000633:toxicity*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013154:Spleen / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
D002243:Carbolines; D002273:Carcinogens; D009153:Mutagens; D011500:Protein Synthesis Inhibitors; D003609:Dactinomycin; D003513:Cycloheximide; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; C019132:3-amino-1,4-dimethyl-5H-pyrido(4,3-b)indole