Ethoxyquin and nordihydroguaiaretic acid reduce hydroxyurea developmental toxicity

Abstract

Hydroxyurea (HU) is a potent teratogen that causes a characteristic, rapidly occurring episode of embryonic cell death 2 to 4 h after subcutaneously injecting 650 mg/kg of HU into pregnant New Zealand White rabbits on gestational day 12. Previous studies documented the ability of the phenolic antioxidant, propyl gallate, to delay the onset of embryonic cell death and to decrease the number and severity of defects seen at term. The present study investigated the ability of the structurally different antioxidants, ethoxyquin (ETX) and nordihydroguaiaretic acid (NDGA), to also ameliorate HU developmental toxicity. Injection of pregnant rabbits with either ETX or NDGA at 950 mg/kg, 15 to 30 min prior to HU injection, resulted in reduced developmental toxicity seen at term. The reduction was manifested by fewer malformed fetuses with increased body weights compared with fetuses from HU-only treated litters, greatly reduced incidences of specific malformations, and diminished severity of some HU-induced defects. Microscopic analysis of HU, HU-ETX, and HU-NDGA embryos was performed at 4 or 8 h after treatment. HU caused cell death in the limb bud mesenchyme, clearly evident at 4 h. In contrast, HU-NDGA embryos exhibited no signs of cell death until 8 h after treatment. Although most HU-ETX embryos exhibited little or no cell death at 4 h after treatment, in about 20% the level of cell death was indistinguishable from that in HU-treated embryos. The amelioration of HU developmental toxicity in the present study is consistent with the results of previous studies utilizing propyl gallate. The results suggest that the antioxidant properties of these substances interfere with the rapidly occurring toxic effects of HU and that this may account for amelioration of HU developmental toxicity.