Abstract
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. TUNEL-positive cells began to increase at 3 hr, peaked at 12 hr, and rapidly decreased at 24 hr. Although the changes of p53 mRNA expression was not observed by RT-PCR, p53-positive reaction was detected immunohistochemically in the nuclei of neuroepithelial cells from 1 hr to 6 hr, and p53-protein expression was simultaneously identified by Western blot analysis. The expression of p53-target genes mRNAs and proteins was detected. The expression of apotosis-related(fas, fasL, and bax) and cell cycle-related genes mRNAs(p21) was sifnificantly elevated, and the degree and sequence of these target genes expression were similar with those of fas, fasL, mdm2 and p21 proteins expression. Flow-cytometric analysis and Western blot analysis on cell cycle-related proteins suggested that neuroepithelial cells might be arrested at S checkpoint from 3 to 6 hr and at G2/M checkpoint at 12 hr, respectively. From the above-mentioned results, it is suggested that HU-induced apoptosis was considered to be mediated by p53 in the fetal brain.
