Embryoprotective Role of Endogenous Catalase in Acatalasemic and Human Catalase-Expressing Mouse Embryos Exposed in Culture to Developmental and Phenytoin-Enhanced Oxidative Stress

Abstract

Reactive oxygen species (ROS) are implicated in spontaneous and xenobiotic-enhanced embryopathies, and protein therapy with exogenous catalase suggests an embryoprotective role, although embryonic catalase activity is only about 5% of adult activity. Using mutant catalase-deficient (acatalasemic, aCat) mice and transgenic mice expressing human catalase (hCat, enhanced catalase activity) compared with a confirmed outbred CD-1 mouse model, we investigated the protective importance of constitutive embryonic catalase against endogenous ROS and the ROS-initiating teratogen phenytoin in embryo culture. Vehicle-exposed aCat and hCat embryos, respectively, exhibited reduced and enhanced catalase activity compared with wild-type (WT) controls, with conversely enhanced and reduced spontaneous embryopathies. Phenytoin was embryopathic in all strains without altering catalase activity but less so in the WT embryos for the aCat and hCat strains, which exhibited about half the catalase activity of CD-1 embryos. Phenytoin, respectively, enhanced and reduced embryopathies in aCat and hCat embryos. Among aCat embryos exposed to phenytoin, embryopathies increased with decreasing catalase activity and were completely blocked by addition of exogenous catalase, which increased embryonic catalase activity to WT levels. These results provide the first direct evidence that (1) the low level of constitutive embryonic catalase protects the conceptus from developmental and xenobiotic-enhanced oxidative stress and (2) embryonic variations in activity of this enzyme affect development.

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.…”

“…Individual pups rather than litters were used as the experimental unit in the primary analysis because the teratogenicity of phenytoin depends at least in part on its bioactivation to a reactive intermediate, and risk depends upon fetal rather than maternal determinants of drug bioactivation and ROS formation, reactive intermediate and ROS detoxification, and possibly DNA repair [17]. We also have previously shown that the level of catalase in individual embryos correlates with their own developmental outcome, independent of the dam [23].…”

“…The embryo and fetus are particularly susceptible to ROS, as the embryonic activity of antioxidative enzymes like catalase, which detoxifies H 2 O 2, may amount to only about 5% of maternal activity [20][21][22][23]. 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].…”

“…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].…”

Valproic Acid Increases Formation of Reactive Oxygen Species and Induces Apoptosis in Postimplantation Embryos: A Role for Oxidative Stress in Valproic Acid-Induced Neural Tube Defects

“…at ASPET Journals on May 9, 2018 molpharm.aspetjournals.org ticularly susceptible to damage by hydrogen peroxide (Abramov and Wells, 2011). Of interest, the same study also demonstrated in embryos cultured with the ROS-initiating teratogen phenytoin that embryos with failed anterior neuropore closure and embryos that failed to turn have significantly decreased levels of catalase activity compared with those in embryos that developed normally.…”