Resistance of CD-1 and ogg1 DNA Repair–Deficient Mice to Thalidomide and Hydrolysis Product Embryopathies in Embryo Culture

Abstract

Thalidomide (TD) displays remarkable species specificity, causing birth defects (teratogenesis) in humans and rabbits, but not rats or mice; yet, few determinants of species susceptibility have been identified. Also, certain mouse strains are susceptible to the embryopathic effects of some teratogens in embryo culture despite their resistance in vivo. Herein we show that CD-1 mouse embryos in culture are resistant to limb embryopathies caused by TD and two of its hydrolysis products, 2-phthalimidoglutaramic acid and 2-phthalimidoglutaric acid, although all three compounds cause these embryopathies in rabbit embryo culture. These results show that the resistance of CD-1 mice to TD teratogenesis is inherent to the embryo and is not dependent upon maternal factors, including differential in vivo exposure to the many hydrolysis products of TD. In utero TD exposure of rabbit but not mouse embryos elevates levels of the teratogenic oxidative DNA lesion 8-oxoguanine, which is repaired by oxoguanine glycosylase 1 (OGG1). However, DNA repair-deficient ogg1 knockout mice proved resistant to TD-initiated embryopathies in culture and teratogenesis in vivo, indicating that the resistance of mice is not due to a higher level of DNA repair.

Thalidomide Embryopathy: An Enigmatic Challenge

“…Many animal organisms have been used to study thalidomide's actions, including chicks, rabbits, zebrafish, marine fish, armadillos, marsupials, hydra, and nonhuman primates [1,2,44,54,121,123,159,[162][163][164][165]. One of the surprising aspects of thalidomide is that rodent embryos are less sensitive to thalidomide with varying results of activity as well as being mouse strain specific [166] and as such customarily are not seen as a primary tool to study thalidomide induced teratogenesis [165,[167][168][169][170][171][172][173][174]. In fact the thalidomide disaster of 1957-61 indicated, for the first time, that species differences exist in the reaction to drugs.…”

“…Embryo cultures of rabbit embryos indicate thalidomide and it's breakdown products teratogenic actions can be studied in vitro [175]. In addition, despite rodents being less sensitive to thalidomide, mouse embryo cultures following thalidomide exposure have been carried out and typically such embryos survive up to 2 days and exhibit thalidomide-like damage [116,166]. Although these embryo culture techniques are very useful and informative, it can be difficult to determine the precise range of damage to the limbs and other tissues as the cultures do not develop consistently further than around 2 days.…”

Embryopathic effects of thalidomide and its hydrolysis products in rabbit embryo culture: evidence for a prostaglandin H synthase (PHS)‐dependent, reactive oxygen species (ROS)‐mediated mechanism

“…By comparison, we could attain a maximal and nonembryolethal TD concentration of 117 M by dissolving TD in the organic solvent DMF (TD solubility of 1 mg/33 l, 117 mM), and then diluting this stock in ECM to 117 M, ensuring that no precipitation of TD occurred. This TD concentration also was nonembryolethal in mouse embryo culture (69). DMF at a final concentration of 0.1% (v/v) had no developmental effects compared to saline and baseline controls (Figs.…”

“…In summary, we have demonstrated for the first time that TD causes embryonic DNA oxidation and clinically relevant limb embryopathies in a mammalian rabbit (sensitive species) embryo culture system, but not in mouse embryo culture (resistant species) (69); and that two hydrolysis products of TD, PGMA and PGA, also cause embryonic DNA oxidation and clinically relevant embryopathies, and therefore likely contribute to TD teratogenesis. The underlying mechanism of TD teratogenesis might involve, at least in part, the bioactivation of TD and some of its hydrolysis products by embryonic PHSs to reactive intermediates that initiate the formation of embryopathic ROS.…”

“…In contrast to our results, that study did not detect any adverse developmental effects of TD in either rabbits or rats, but noted embryolethality in the insensitive rat species at a relatively low TD concentration of 50 M (Ͻ50% of the concentration used in the present study). This TD concentration also was nonembryolethal in mouse embryo culture (69). First, although TD has very poor water solubility (ϳ6 mg/100 ml water; ref.…”