Embryonic catalase protects against endogenous and phenytoin‐enhanced DNA oxidation and embryopathies in acatalasemic and human catalase‐expressing mice

Abstract

Oxidative stress and reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)), which is detoxified by catalase, are implicated in fetal death and birth defects. However, embryonic levels of catalase are only ∼ 5% of adult activity, and its protective role is not understood completely. Herein, we used mutant catalase-deficient mice [acatalasemic (aCat)] and transgenic mice expressing human catalase (hCat), which, respectively, exhibited 40-50% reductions and 2-fold elevations in the activities of embryonic and fetal brain catalase, to show that embryonic catalase protects the embryo from both physiological oxidative stress and the ROS-initiating antiepileptic drug phenytoin. Compared to wild-type (WT) catalase-normal controls, both untreated and phenytoin-exposed aCat mice exhibited a 30% increase in embryonic DNA oxidation and a >2-fold increase in embryopathies, both of which were completely blocked by protein therapy with exogenous catalase. Conversely, compared to WT controls, untreated and, to a lesser extent, phenytoin-exposed hCat mice were protected, with untreated hCat embryos exhibiting a 40% decrease in embryonic DNA oxidation and up to a 67% decrease in embryopathies. Embryonic catalase accordingly plays an important protective role, and both physiological and phenytoin-enhanced oxidative stress can be embryopathic.

Protective role of endogenous catalase in baseline and phenytoin-enhanced neurodevelopmental and behavioral deficits initiated in utero and in aged mice

“…The results for fetal exposure extend the gestational range of importance covered in recent studies showing a protective role for endogenous catalase in the same genetically altered models during organogenesis in embryo culture [23] and in vivo [22], which revealed structural rather than functional consequences of in utero developmental and phenytoin-enhanced oxidative stress.…”

“…Similarly, surviving aCat pups continued to have a higher incidence of pre-weaning death, while hCat pups were relatively protected at the lower dose of phenytoin. Lower catalase activity in aCat embryos has been shown to result in increased levels of ROS leading to formation of oxidatively damaged DNA following phenytoin exposure [22].…”

“…The embryopathic importance of ROS and the potential protective role of catalase have been implicated by studies in embryo culture and in vivo, where the administration of exogenous enzyme reduced phenytoin-initiated DNA oxidation and embryopathies [20,24]. Similarly, a role for endogenous catalase in protecting the embryo from structural embryopathies caused by endogenous and drug-enhanced oxidative stress in culture and in vivo was found in genetically altered mice with deficient or enhanced levels of embryonic catalase [22,23]. Oxidative stress also has been implicated in neurodegeneration in the aging brain [25][26][27], where catalase activity is similarly low [28,29].…”

Biomarkers of teratogenesis: Suggestions from animal studies

“…It enhances embryonic and fetal levels of 7,8-dihydro-8-oxoguanine (commonly named 8-oxoguanine, 8-oxoG), one of the prevalent forms of oxidative DNA damage caused by hydroxyl radicals and also enhances the oxidation of GSH, proteins and lipids [33]. In an elegant series of experiments Abramov and Wells [34,35] were able to demonstrate the protective role of catalase against phenytoininduced DNA oxidation and embryopathies using both in vivo and in vitro approaches.…”

“…The use of specific biomarkers would also permit to avoid expensive in vivo tests which may usefully be substituted by in vitro tests as WEC or cell cultures. For example, hyperacetylation of histones has been observed in cell cultures [6,10,11], cholesterol unbalance has been observed in WEC [68], SOD and other oxidative stress biomarkers have been evaluated in WEC [34,38,47,51], WEC and Xenopus embryos have been used to demonstrate the increased expression of CRABP and Cyp26 after exposure to triazole fungicides [96,98]. These alternative methods, with the help of specific biomarkers, may be used to meet the three R (replacement, reduction, refinement) recommended by several regulatory agencies as a basis of a new approach of the animal welfare in the animal experiments.…”