Hashimoto T, Furuyashiki T, Sano T, Kihara K, Fukuda I, Ito W, Park P, Kanazawa K, Danno GI, Ashida H. Apoptosis in the thymus after intraperitoneal injection of rats with Trp-P-1.
ENVIRONMENTAL AND MOLECULAR MUTAGENESIS 2002;
40:175-183. [PMID:
12355551 DOI:
10.1002/em.10104]
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Abstract
3-Amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1), a contaminant in our daily diet, induces apoptosis in cultured immunocytes. In this study, Trp-P-1 (1 mg/kg) was injected intraperitoneally into male Wistar rats to investigate whether Trp-P-1 induces apoptosis in immune tissues in vivo. In the thymus, Trp-P-1 induced DNA fragmentation and morphological changes. Trp-P-1 also activated the initiator and executioner caspases, caspase-8 and -3, respectively, and activated caspase-3 in turn cleaved its intracellular substrate poly(ADP-ribose) polymerase 1 hr after injection. On the other hand, Trp-P-1 upregulated anti-apoptotic factors Bcl-2 and Bcl-XL and downregulated pro-apoptotic factor Bax in mitochondria 1 hr after injection, indicating that Trp-P-1 also stimulated anti-apoptotic signals. Trp-P-1 activated the serine-threonine protein kinase Akt, which is known to be an anti-apoptotic protein, and increased the DNA binding activities of apoptosis-associated transcription factors NF-kappaB and AP-1. In addition to the thymus, increases in the activities of these transcription factors were also observed in the spleen and in mononuclear cells from the blood. Therefore, Trp-P-1 activates both pro- and anti-apoptotic signals in vivo in the immune system, particularly in the thymus, and the former signal overcomes the latter.
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