title: 5-azacytidine, a chemotherapeutic drug, induces TRAIL-mediated apoptosis in mouse thymocytes in vivo.
abstract: 5-azacytidine (5AzC) is a cytidine analogue with two main effects on cellular conditions; DNA damage, resulting in apoptosis, and DNA hypomethylation, restoring normal growth control and differentiation. However, the molecular mechanism of 5AzC-induced apoptosis is not fully understood. The aim of the present study is to clarify this mechanism in mouse thymocytes in vivo. Ten-week-old, male C57BL/6J mice were injected with 5AzC (100 mg/kg) intraperitoneally, and thymuses were examined for apoptotic changes. In the 5AzC-treated thymus, increases of TUNEL-positive thymocytes and cleaved caspase-3 protein, both biochemical features of apoptosis, were detected. 5AzC-induced apoptosis was observed even in the thymuses of mice deficient in p53, a critical factor in the intrinsic apoptotic pathway, and mice with mutated Fas, a death receptor. Furthermore, levels of p53 and Fas proteins were unchanged in the thymus following 5AzC-treatment in wild-type mice. In the 5AzC-treated thymus, the level of cleaved caspase-8 protein, an initiator of the extrinsic apoptotic pathway, increased with the cleavage of its target protein, Bid. Moreover, the level of TRAIL protein, which induces apoptosis through the cleavage of caspase-8, robustly increased in the thymus treated with 5AzC. In conclusion, the 5AzC-induced apoptosis of thymocytes in vivo is implemented through the extrinsic pathway with the activation of TRAIL.
authors.affiliation: Department of Veterinary Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Tomoaki
authors.initials: T
authors.lastname: Tochitani
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kanemitsu
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yamauchi
authors.forename: Kazuyuki
authors.initials: K
authors.lastname: Uchida
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Nakayama
mesh_terms: D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D001374:Azacitidine / Q000494:pharmacology*; D051023:BH3 Interacting Domain Death Agonist Protein / Q000096:biosynthesis; D015153:Blotting, Western; D053181:Caspase 8 / Q000096:biosynthesis; D053453:Caspase 9 / Q000096:biosynthesis; D020287:In Situ Nick-End Labeling; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000096:biosynthesis* / Q000502:physiology; D013950:Thymus Gland / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology; D015854:Up-Regulation; D019014:fas Receptor / Q000235:genetics / Q000502:physiology
chemical_list: D000964:Antimetabolites, Antineoplastic; D051023:BH3 Interacting Domain Death Agonist Protein; C494815:Bid protein, mouse; C491899:Fas protein, mouse; D053221:TNF-Related Apoptosis-Inducing Ligand; C505654:Tnfsf10 protein, mouse; D016159:Tumor Suppressor Protein p53; D019014:fas Receptor; C505526:Casp8 protein, mouse; D053181:Caspase 8; D053453:Caspase 9; D001374:Azacitidine