Molecular mechanisms of hydroxyurea(HU)-induced apoptosis in the mouse fetal brain.
Hydroxyurea (HU), a potent mammalian teratogen, affects proliferating embryonic cells and inhibits DNA synthesis. The teratogenic potential of HU has been well known in experimental animals for several decades. In this study, we investigated molecular mechanisms of HU-induced apoptosis in the telencephalon of the fetal brain by exposing pregnant mice to HU on day 13 of gestation. The number of TUNEL-positive cells began to increase at 3 h, peaked at 12 h, and rapidly decreased at 24 h. Although changes of p53 mRNA expression were not observed by RT-PCR, a p53-positive reaction was detected immunohistochemically in the nuclei of neuroepithelial cells from 1 h to 6 h, and p53-protein expression was simultaneously identified by Western blot analysis. The expression of p53-target genes was detected at both the mRNA and protein. The mRNA levels of apotosis-related genes (fas, fasL, and bax) and cell cycle-related genes (mdm2 and p21) were significantly elevated, and the degree to and sequence in which these target genes expressed was similar to those for fas, fasL, mdm2 and p21. Flow-cytometric and Western blot analyses of cell cycle-related proteins suggested that neuroepithelial cells are arrested at the S checkpoint from 3 to 6 h and at the G2/M checkpoint at 12 h, respectively. HU-induced apoptosis is considered to be mediated by p53 in the fetal brain.
Woo
G H
GH
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.
Bak
E J
EJ
Nakayama
H
H
Doi
K
K
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001921:Brain / Q000002:abnormalities* / Q000187:drug effects* / Q000503:physiopathology; D018797:Cell Cycle Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects / Q000502:physiology; D018816:Genes, cdc / Q000187:drug effects / Q000502:physiology; D006918:Hydroxyurea / Q000633:toxicity*; D051379:Mice; D008813:Mice, Inbred ICR; D009421:Nervous System Malformations / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology; D019384:Nucleic Acid Synthesis Inhibitors / Q000633:toxicity; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000473:pathology* / Q000503:physiopathology; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D013234:Stem Cells / Q000187:drug effects / Q000473:pathology; D013687:Telencephalon / Q000002:abnormalities / Q000187:drug effects / Q000503:physiopathology; D013723:Teratogens / Q000633:toxicity; D016159:Tumor Suppressor Protein p53 / Q000187:drug effects / Q000378:metabolism; D019014:fas Receptor / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D012333:RNA, Messenger; D013723:Teratogens; D016159:Tumor Suppressor Protein p53; D019014:fas Receptor; D006918:Hydroxyurea