Fetal oxidative stress mechanisms of neurodevelopmental deficits and exacerbation by ethanol and methamphetamine.

In utero exposure of mouse progeny to alcohol (ethanol, EtOH) and methamphetamine (METH) causes substantial postnatal neurodevelopmental deficits. One emerging pathogenic mechanism underlying these deficits involves fetal brain production of reactive oxygen species (ROS) that alter signal transduction, and/or oxidatively damage cellular macromolecules like lipids, proteins, and DNA, the latter leading to altered gene expression, likely via non-mutagenic mechanisms. Even physiological levels of fetal ROS production can be pathogenic in biochemically predisposed progeny, and ROS formation can be enhanced by drugs like EtOH and METH, via activation/induction of ROS-producing NADPH oxidases (NOX), drug bioactivation to free radical intermediates by prostaglandin H synthases (PHS), and other mechanisms. Antioxidative enzymes, like catalase in the fetal brain, while low, provide critical protection. Oxidatively damaged DNA is normally rapidly repaired, and fetal deficiencies in several DNA repair proteins, including oxoguanine glycosylase 1 (OGG1) and breast cancer protein 1 (BRCA1), enhance the risk of drug-initiated postnatal neurodevelopmental deficits, and in some cases deficits in untreated progeny, the latter of which may be relevant to conditions like autism spectrum disorders (ASD). Risk is further regulated by fetal nuclear factor erythroid 2-related factor 2 (Nrf2), a ROS-sensing protein that upregulates an array of proteins, including antioxidative enzymes and DNA repair proteins. Imbalances between conceptal pathways for ROS formation, versus those for ROS detoxification and DNA repair, are important determinants of risk. Birth Defects Research (Part C) 108:108-130, 2016. © 2016 Wiley Periodicals, Inc.

Deficient DNA repair exacerbates ethanol-initiated DNA oxidation and embryopathies in ogg1 knockout mice: gender risk and protection by a free radical spin trapping agent.

Reactive oxygen species (ROS) have been implicated in the teratogenicity of alcohol (ethanol, EtOH). To determine the involvement of embryonic oxidative DNA damage, DNA repair-deficient oxoguanine glycosylase 1 (ogg1) knockout embryos were exposed in culture to EtOH (2 or 4 mg/ml), with or without pretreatment with the free radical spin trap phenylbutylnitrone (PBN) (0.125 mM). Visceral yolk sacs were used to genotype embryos for DNA repair status and gender. EtOH caused a concentration-dependent decrease in anterior neuropore closure (ANPC), somite development, turning, crown-rump length (CRL), yolk sac diameter (YSD) and head length (HL) (p < 0.001) in all 3 ogg1 genotypes. There was a further ogg1 gene dose-dependent decrease from +/+ to -/- embryos in ANPC, somite development, turning, CRL and HL (p < 0.05), and a gene-dependent correlation between HL and ANPC (p < 0.01). Female embryos exhibited lesser ANPC and turning than males (p < 0.05), suggesting underlying gender-dependent target-specific determinants. PBN pretreatment increased ANPC, somite development, turning, CRL, YSD and HL (p < 0.001), although this protection against EtOH was slightly less effective in -/- embryos. Oxidatively damaged DNA determined as 8-oxo-2'-deoxyguanosine (8-oxodGuo), which is repaired by OGG1, was measured in single embryos in vivo after maternal EtOH treatment (4 g/kg i.p). EtOH increased embryonic 8-oxodGuo in an ogg1 gene-dependent fashion, with the highest levels in -/- embryos. These results show that embryonic DNA repair status and gender are determinants of risk. ROS-initiated embryonic DNA oxidation is involved in EtOH embryopathies.

Enhanced NADPH oxidases and reactive oxygen species in the mechanism of methanol-initiated protein oxidation and embryopathies in vivo and in embryo culture.

Methanol (MeOH) teratogenicity in rodents may be mediated in part by reactive oxygen species (ROS), the source of which is unknown. To determine if MeOH enhances embryonic ROS-producing NADPH oxidases (NOXs), p22phox mRNA and protein and oxidatively damaged protein were measured in gestational day 12 MeOH-exposed CD-1 mouse embryos with or without pretreatment with the free radical spin trap phenylbutylnitrone (PBN) or the NOX inhibitor diphenyleneiodonium chloride (DPI). MeOH exposure upregulated p22phox mRNA and protein expression, and enhanced protein oxidation, within 3-6 h. Compared to embryos exposed to MeOH alone, PBN and DPI pretreatment decreased MeOH-enhanced p22phox mRNA expression, DPI but not PBN blocked p22phox protein expression, and both blocked protein oxidation. To assess developmental relevance, mouse embryos were exposed in culture for 24 h to MeOH or vehicle with or without pretreatment with PBN, DPI, or the prostaglandin H synthase (PHS) inhibitor eicosatetraynoic acid (ETYA), and evaluated for abnormalities. ETYA did not prevent MeOH embryopathies, despite blocking phenytoin embryopathies (ROS-initiating positive control), precluding bioactivation of MeOH or its metabolites by PHS. Concentration-dependent MeOH embryopathies were blocked by both DPI and PBN pretreatment, suggesting that enhanced embryonic NOX-catalyzed ROS formation and oxidative stress may contribute to the mechanism of MeOH embryopathies.

Embryonic catalase protects against ethanol embryopathies in acatalasemic mice and transgenic human catalase-expressing mice in embryo culture.

Reactive oxygen species (ROS) have been implicated in the mechanism of ethanol (EtOH) teratogenicity, but the protective role of the embryonic antioxidative enzyme catalase is unclear, as embryonic activity is only about 5% of maternal levels. We addressed this question in a whole embryo culture model. C57BL/6 mouse embryos expressing human catalase (hCat) or their wild-type (C57BL/6 WT) controls, and C3Ga.Cg-Cat(b)/J catalase-deficient, acatalasemic (aCat) mouse embryos or their wild-type C3HeB/FeJ (C3H WT) controls, were explanted on gestational day (GD) 9 (plug=GD 1), exposed for 24h to 2 or 4mg/mL EtOH or vehicle, and evaluated for functional and morphological changes. hCat and C57BL/6 WT vehicle-exposed embryos developed normally, while EtOH was embryopathic in C57BL/6 WT embryos, evidenced by decreases in anterior neuropore closure, somites developed, turning and head length, whereas hCat embryos were protected (p<0.001). Maternal pretreatment of C57BL/6 WT dams with 50kU/kg PEG-catalase (PEG-cat) 8h prior to embryo culture, which increases embryonic catalase activity, blocked all EtOH embryopathies (p<0.001). Vehicle-exposed aCat mouse embryos had lower yolk sac diameters compared to WT controls, suggesting that endogenous ROS are embryopathic. EtOH was more embryopathic in aCat embryos than WT controls, evidenced by reduced head length and somite development (p<0.01), and trends for reduced anterior neuropore closure, turning and crown-rump length. Maternal pretreatment of aCat dams with PEG-Cat blocked all EtOH embryopathies (p<0.05). These data suggest that embryonic catalase is a determinant of risk for EtOH embryopathies.

BRCA1 protein dose-dependent risk for embryonic oxidative DNA damage, embryopathies and neurodevelopmental disorders with and without ethanol exposure.

Although widely known as a tumor suppressor, the breast cancer 1 susceptibility protein (BRCA1) is also important in development, where it regulates fetal DNA repair pathways that protect against DNA damage caused by physiological and drug-enhanced levels of reactive oxygen species (ROS). We previously showed that conditional heterozygous (+/-) knockout (cKO) mouse embryos with a minor 28% BRCA1 deficiency developed normally in culture, but when exposed to the ROS-initiating drug, alcohol (ethanol, EtOH), exhibited embryopathies not evident in wild-type (+/+) littermates. Herein, we characterized a directBrca1 +/- knockout (KO) model with a 2-fold greater (58%) reduction in BRCA1 protein vs. the cKO model. We also characterized and compared learning & memory deficits in both the cKO and KO models. Even saline-exposed Brca1 +/- vs. +/+ KO progeny exhibited enhanced oxidative DNA damage and embryopathies in embryo culture and learning & memory deficits in females in vivo, which were not observed in the cKO model, revealing the potential pathogenicity of physiological ROS levels. The embryopathic EtOH concentration for cultured direct KO embryos was half that for cKO embryos, and EtOH affected Brca1 +/+ embryos only in the direct KO model. The spectrum and severity of EtOH embryopathies in culture were greater in both Brca1 +/- vs. +/+ embryos, and direct KO vs. cKO +/- embryos. Motor coordination deficits were evident in both male and female Brca1 +/- KO progeny exposed in utero to EtOH. The results in our direct KO model with a greater BRCA1 deficiency vs. cKO mice provide the first evidence for BRCA1 protein dose-dependent susceptibility to developmental disorders caused by physiological and drug-enhanced oxidative stress.

The UN Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection (GESAMP) - An ocean science-policy interface standing the test of time.

Addressing the wide range of marine pollution problems facing the global ocean requires a continual transfer of credible, relevant and timely scientific information to policy and decision makers in coastal and ocean management. The United Nations GESAMP (Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection) is a long-standing scientific advisory group providing such information on a wide range of marine topics and emerging issues of concern to ten UN Sponsoring Organizations. This paper presents an overview of GESAMPs operation and examples of its current work. The group's scientific output is often cited by national governments, inter-governmental groups, and a range of non-governmental groups. Given the growing concerns about ocean health and the impacts of many stressors in an era of climate change, the development of timely and effective ocean policy and decision making would benefit from wider recognition and application of GESAMPs work.

A role for glutathione, independent of oxidative stress, in the developmental toxicity of methanol.

Oxidative stress and reactive oxygen species (ROS) have been implicated in the teratogenicity of methanol (MeOH) in rodents, both in vivo and in embryo culture. We explored the ROS hypothesis further in vivo in pregnant C57BL/6J mice. Following maternal treatment with a teratogenic dose of MeOH, 4 g/kg via intraperitoneal (ip) injection on gestational day (GD) 12, there was no increase 6h later in embryonic ROS formation, measured by 2',7'-dichlorodihydrofluorescin diacetate (DCFH-DA) fluorescence, despite an increase observed with the positive control ethanol (EtOH), nor was there an increase in embryonic oxidatively damaged DNA, quantified as 8-oxo-2'-deoxyguanosine (8-oxodG) formation. MeOH teratogenicity (primarily ophthalmic anomalies, cleft palate) also was not altered by pre- and post-treatment with varying doses of the free radical spin trapping agent alpha-phenyl-N-tert-butylnitrone (PBN). In contrast, pretreatment with L-buthionine-(S,R)-sulfoximine (BSO), an inhibitor of glutathione (GSH) synthesis, depleted maternal hepatic and embryonic GSH, and enhanced some new anomalies (micrognathia, agnathia, short snout, fused digits, cleft lip, low set ears), but not the most common teratogenic effects of MeOH (ophthalmic anomalies, cleft palate) in this strain. These results suggest that ROS did not contribute to the teratogenic effects of MeOH in this in vivo mouse model, in contrast to results in embryo culture from our laboratory, and that the protective effect of GSH in this model may arise from its role as a cofactor for formaldehyde dehydrogenase in the detoxification of formaldehyde.

Sensitivity to methylmercury toxicity is enhanced in oxoguanine glycosylase 1 knockout murine embryonic fibroblasts and is dependent on cellular proliferation capacity.

Methylmercury (MeHg) is a persistent environmental contaminant with potent neurotoxic action for which the underlying molecular mechanisms remain to be conclusively delineated. Our objectives herein were twofold: first, to corroborate our previous findings of an increased sensitivity of spontaneously-immortalized oxoguanine glycosylase 1-null (Ogg1(-/-)) murine embryonic fibroblasts (MEFs) to MeHg through generation of Simian virus 40 (SV40) large T antigen-immortalized wild-type and Ogg1(-/-) MEFs; and second, to determine whether MeHg toxicity is proliferation-dependent. As with the spontaneously-immortalized cells used previously, the SV40 large T antigen-immortalized cells exhibited similar tendencies to undergo MeHg-initiated cell cycle arrest, with increased sensitivity in the Ogg1(-/-) MEFs as measured by clonogenic survival and DNA damage. Compared to exponentially growing cells, those seeded at a higher density exhibited compromised proliferation, which proved protective against MeHg-mediated cell cycle arrest and induction of DNA double strand breaks (DSBs), measured by phosphorylation of the core histone H2A variant (H2AX) on serine 139 (γH2AX), and by its functional confirmation by micronucleus assessment. This enhanced sensitivity of Ogg1(-/-) MEFs to MeHg toxicity using discrete SV40 immortalization corroborates our previous studies, and suggests a novel role for OGG1 in minimizing MeHg-initiated DNA lesions that trigger replication-associated DSBs. Furthermore, proliferative capacity may determine MeHg toxicity in vivo and in utero. Accordingly, variations in cellular proliferative capacity and interindividual variability in repair activity may modulate the risk of toxicological consequences following MeHg exposure.

Expression of human oxoguanine glycosylase 1 or formamidopyrimidine glycosylase in human embryonic kidney 293 cells exacerbates methylmercury toxicity in vitro.

Exposure to methylmercury (MeHg) acutely at high levels, or via chronic low-level dietary exposure from daily fish consumption, can lead to adverse neurological effects in both the adult and developing conceptus. To determine the impact of variable DNA repair capacity, and the role of reactive oxygen species (ROS) and oxidatively damaged DNA in the mechanism of toxicity, transgenic human embryonic kidney (HEK) 293 cells that stably express either human oxoguanine glycosylase 1 (hOgg1) or its bacterial homolog, formamidopyrimidine glycosylase (Fpg), which primarily repair the oxidative lesion 8-oxo-2'-deoxyguanosine (8-oxodG), were used to assess the in vitro effects of MeHg. Western blotting confirmed the expression of hOgg1 or Fpg in both the nuclear and mitochondrial compartments of their respective cell lines. Following acute (1-2h) incubations with 0-10µM MeHg, concentration-dependent decreases in clonogenic survival and cell growth accompanied concentration-dependent increases in lactate dehydrogenase (LDH) release, ROS formation, 8-oxodG levels and apurinic/apyrimidinic (AP) sites, consistent with the onset of cytotoxicity. Paradoxically, hOgg1- and Fpg-expressing HEK 293 cells were more sensitive than wild-type cells stably transfected with the empty vector control to MeHg across all cellular and biochemical parameters, exhibiting reduced clonogenic survival and cell growth, and increased LDH release and DNA damage. Accordingly, upregulation of specific components of the base excision repair (BER) pathway may prove deleterious potentially due to the absence of compensatory enhancement of downstream processes to repair toxic intermediary abasic sites. Thus, interindividual variability in DNA repair activity may constitute an important risk factor for environmentally-initiated, oxidatively damaged DNA and its pathological consequences.

Altered Epigenetic Marks and Gene Expression in Fetal Brain, and Postnatal Behavioural Disorders, Following Prenatal Exposure of Ogg1 Knockout Mice to Saline or Ethanol.

Oxoguanine glycosylase 1 (OGG1) is widely known to repair the reactive oxygen species (ROS)-initiated DNA lesion 8-oxoguanine (8-oxoG), and more recently was shown to act as an epigenetic modifier. We have previously shown that saline-exposed Ogg1 -/- knockout progeny exhibited learning and memory deficits, which were enhanced by in utero exposure to a single low dose of ethanol (EtOH) in both Ogg1 +/+ and -/- progeny, but more so in Ogg1 -/- progeny. Herein, OGG1-deficient progeny exposed in utero to a single low dose of EtOH or its saline vehicle exhibited OGG1- and/or EtOH-dependent alterations in global histone methylation and acetylation, DNA methylation and gene expression (Tet1 (Tet Methylcytosine Dioxygenase 1), Nlgn3 (Neuroligin 3), Hdac2 (Histone Deacetylase 2), Reln (Reelin) and Esr1 (Estrogen Receptor 1)) in fetal brains, and behavioural changes in open field activity, social interaction and ultrasonic vocalization, but not prepulse inhibition. OGG1- and EtOH-dependent changes in Esr1 and Esr2 mRNA and protein levels were sex-dependent, as was the association of Esr1 gene expression with gene activation mark histone H3 lysine 4 trimethylation (H3K4me3) and gene repression mark histone H3 lysine 27 trimethylation (H3K27me3) measured via ChIP-qPCR. The OGG1-dependent changes in global epigenetic marks and gene/protein expression in fetal brains, and postnatal behavioural changes, observed in both saline- and EtOH-exposed progeny, suggest the involvement of epigenetic mechanisms in developmental disorders mediated by 8-oxoG and/or OGG1. Epigenetic effects of OGG1 may be involved in ESR1-mediated gene regulation, which may be altered by physiological and EtOH-enhanced levels of ROS formation, possibly contributing to sex-dependent developmental disorders observed in Ogg1 knockout mice. The OGG1- and EtOH-dependent associations provide a basis for more comprehensive mechanistic studies to determine the causal involvement of oxidative DNA damage and epigenetic changes in ROS-mediated neurodevelopmental disorders.

Breast cancer 1 (BRCA1) protection in altered gene expression and neurodevelopmental disorders due to physiological and ethanol-enhanced reactive oxygen species formation.

The breast cancer 1 (Brca1) susceptibility gene regulates the repair of reactive oxygen species (ROS)-mediated DNA damage, which is implicated in neurodevelopmental disorders. Alcohol (ethanol, EtOH) exposure during pregnancy causes fetal alcohol spectrum disorders (FASD), including abnormal brain function, associated with enhanced ROS-initiated DNA damage. Herein, oxidative DNA damage in fetal brains and neurodevelopmental disorders were enhanced in saline-exposed +/- vs. +/+ Brca1 littermates. A single EtOH exposure during gestation further enhanced oxidative DNA damage, altered the expression of developmental/DNA damage response genes in fetal brains, and resulted in neurodevelopmental disorders, all of which were BRCA1-dependent. Pretreatment with the ROS inhibitor phenylbutylnitrone (PBN) blocked DNA damage and some neurodevelopmental disorders in both saline- and EtOH-exposed progeny, corroborating a ROS-dependent mechanism. Fetal BRCA1 protects against altered gene expression and neurodevelopmental disorders caused by both physiological and EtOH-enhanced levels of ROS formation. BRCA1 deficiencies may enhance the risk for FASD.

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

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.

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.

Thalidomide (TD) causes birth defects in humans and rabbits via several potential mechanisms, including bioactivation by embryonic prostaglandin H synthase (PHS) enzymes to a reactive intermediate that enhances reactive oxygen species (ROS) formation. We show herein that TD in rabbit embryo culture produces relevant embryopathies, including decreases in head/brain development by 28% and limb bud growth by 71% (P<0.05). Two TD hydrolysis products, 2-phthalimidoglutaramic acid (PGMA) and 2-phthalimidoglutaric acid (PGA), were similarly embryopathic, attenuating otic vesicle (ear) and limb bud formation by up to 36 and 77%, respectively (P<0.05). TD, PGMA, and PGA all increased embryonic DNA oxidation measured as 8-oxoguanine (8-oxoG) by up to 2-fold (P<0.05). Co- or pretreatment with the PHS inhibitors eicosatetraynoic acid (ETYA) or acetylsalicylic acid (ASA), or the free-radical spin trap phenylbutylnitrone (PBN), completely blocked embryonic 8-oxoG formation and/or embryopathies initiated by TD, PGMA, and PGA. This is the first demonstration of limb bud embryopathies initiated by TD, as well as its hydrolysis products, in a mammalian embryo culture model of a species susceptible to TD in vivo, indicating that all likely contribute to TD teratogenicity in vivo, in part through PHS-dependent, ROS-mediated mechanisms.

The leatherback turtle (Dermochelys coriacea) and plastics in the Northwest Atlantic ocean: A hazard assessment.

Atlantic leatherback turtles are faced with multiple threats, such as ship strikes, pollution and predation, throughout their annual migratory routes in the Northwest (NW) Atlantic. The risks associated with encounters with floating and submerged plastic debris are currently unknown. This study is a hazard assessment of plastics for this turtle's sub-population, using 2010-2019 data from the national Great Canadian Shoreline Cleanup (GSCS) program, therefore potential exposure, and published evidence on the interactions of plastics and leatherbacks, hence potential effects. The type of plastic items and their abundance along shorelines of three Atlantic Provinces - Nova Scotia (NS), Prince Edward Island (PEI), Newfoundland and Labrador (NL) - were evaluated and compared to plastic items known to interact with leatherbacks. During the 2010-2019 period, a total of 220,590 plastic items were collected from 578 sites, representing 1264 km of shoreline. Plastic bags and rope are in the top ten most common items found on shorelines of NS, PEI, and NL. Pot gear and trap nets are in the top ten for PEI and are the 14th most common plastic item found on all shorelines. Cigarette debris is also commonly found. From the literature, plastic bags, pot gear and trap nets, and rope are known to adversely affect leatherbacks. Assuming that a large proportion of the shoreline debris comes in from the sea, after being in coastal waters for unknown periods, the study shows that such items pose a hazard to leatherbacks through ingestion and entanglement, based on published studies. Evidence is now needed on actual exposure at sea to the most common items to establish the ecological risk of plastics to these turtles in NW Atlantic waters.

Sex- and OGG1-dependent reversal of in utero ethanol-initiated changes in postnatal behaviour by neonatal treatment with the histone deacetylase inhibitor trichostatin A (TSA) in oxoguanine glycosylase 1 (Ogg1) knockout mice.

Oxoguanine glycosylase 1 (OGG1) is both a DNA repair enzyme and an epigenetic modifier. We assessed behavioural abnormalities in OGG1-deficient progeny exposed once in utero to a low dose of ethanol (EtOH) and treated postnatally with a global histone deacetylase inhibitor, trichostatin A (TSA). The goal of this study was to determine if neurodevelopmental disorders initiated in the fetal brain by in utero exposure to EtOH could be mitigated by postnatal treatment with TSA. EtOH and TSA alone improved preference for novel location (short-term, 90 min) and novel object (long-term, 24 h) sex- and OGG1-dependently. Combined EtOH/TSA treatment reversed these effects in the short-term novel location test sex- and OGG1-dependently. In females but not males, the incidence of high shredders of nesting material was not altered by either TSA or EtOH alone, but was reduced by combined EtOH/TSA treatment in +/+ progeny. Similar but non-significant effects were observed in Ogg1 -/- females. Accelerated rotarod performance was enhanced by both EtOH and TSA alone in only male Ogg1 +/+ but not -/- progeny, and was not altered by combined EtOH/TSA exposure. The OGG1-dependent effects of EtOH and TSA particularly on novel location and the incidence of high shredders, and the reversal of EtOH effects on these parameters by combined EtOH/TSA treatment, suggests both xenobiotics may alter behaviour via a mechanism involving OGG1 acting as an epigenetic modifier, in addition to repairing DNA damage. These preliminary results suggest that the postnatal use of more selective epigenetic modifying agents may constitute a novel strategy for mitigating some components of ROS-initiated neurodevelopmental disorders.

DNA Damage and Repair and Epigenetic Modification in the Role of Oxoguanine Glycosylase 1 in Brain Development.

Oxoguanine glycosylase 1 (OGG1) repairs the predominant reactive oxygen species-initiated DNA lesion 8-oxoguanine. Human OGG1 polymorphisms resulting in reduced DNA repair associate with an increased risk for disorders like cancer and diabetes, but the role of OGG1 in brain development is unclear. Herein, we show that Ogg1 knockout mice at 2-3 months of age exhibit enhanced gene- and sex-dependent DNA damage (strand breaks) and decreased epigenetic DNA methylation marks (5-methylcytosine, 5-hydroxymethylcytosine), both of which were associated with increased cerebellar calbindin levels, reduced hippocampal postsynaptic function, altered body weight with age and disorders of brain function reflected in behavioral tests for goal-directed repetitive behavior, anxiety and fear, object recognition and spatial memory, motor coordination and startle response. These results suggest that OGG1 plays an important role in normal brain development, possibly via both its DNA repair activity and its role as an epigenetic modifier, with OGG1 deficiencies potentially contributing to neurodevelopmental disorders.

Methanol exposure does not lead to accumulation of oxidative DNA damage in bone marrow and spleen of mice, rabbits or primates.

Genotoxicity tests indicate methanol (MeOH) is not mutagenic, but a rodent study has suggested carcinogenic potential, which could result from free radical-initiated oxidative DNA damage. To investigate this possibility we treated male CD-1 mice, New Zealand white rabbits, and cynomolgus monkeys with MeOH (2.0 g/kg ip) and assessed tissue oxidative DNA damage 6 h post-dose, measured as 8-hydroxy-2'-deoxyguanosine (8-oxodG). We found no MeOH-dependent increases in 8-oxodG in bone marrow or spleen of any species. Chronic treatment of CD-1 mice with MeOH (2.0 g/kg ip) daily for 15 d also did not increase 8-oxodG levels in these organs. Further studies in the DNA repair deficient oxoguanine glycosylase 1 (Ogg1) knockout (KO) mice supported these findings. Fibroblasts from Ogg1 KO mice accumulated 8-oxodG following acute exposure to the renal carcinogen potassium bromate (KBrO(3) ; 2.0 mM) but did not accumulate 8-oxodG following exposure to 125 mM MeOH 6 h post-treatment. Ogg1 KO mice accumulated 8-oxodG in bone marrow and spleen with age but not following exposure to MeOH. In addition, free radical-mediated hydroxynonenal-histidine protein adducts were not enhanced by MeOH in primate bone marrow or spleen, or in rabbit bone marrow or mouse spleen, although modest increases were observed in rabbit spleen and mouse bone marrow. Taken together these observations suggest that MeOH exposure does not promote the accumulation of oxidative DNA damage in bone marrow and spleen, and it is unlikely that human environmental exposure to MeOH would lead to lymphomas via this mechanism.

Altered methanol embryopathies in embryo culture with mutant catalase-deficient mice and transgenic mice expressing human catalase.

The mechanisms underlying the teratogenicity of methanol (MeOH) in rodents, unlike its acute toxicity in humans, are unclear, but may involve reactive oxygen species (ROS). Embryonic catalase, although expressed at about 5% of maternal activity, may protect the embryo by detoxifying ROS. This hypothesis was investigated in whole embryo culture to remove confounding maternal factors, including metabolism of MeOH by maternal catalase. C57BL/6 (C57) mouse embryos expressing human catalase (hCat) or their wild-type (C57 WT) controls, and C3Ga.Cg-Catb/J acatalasemic (aCat) mouse embryos or their wild-type C3HeB/FeJ (C3H WT) controls, were explanted on gestational day (GD) 9 (plug=GD 1), exposed for 24 h to 4 mg/ml MeOH or vehicle, and evaluated for functional and morphological changes. hCat and C57 WT vehicle-exposed embryos developed normally. MeOH was embryopathic in C57 WT embryos, evidenced by decreases in anterior neuropore closure, somites developed and turning, whereas hCat embryos were protected. Vehicle-exposed aCat mouse embryos had lower yolk sac diameters compared to C3H WT controls, suggesting that endogenous ROS are embryopathic. MeOH was more embryopathic in aCat embryos than WT controls, with reduced anterior neuropore closure and head length only in catalase-deficient embryos. These data suggest that ROS may be involved in the embryopathic mechanism of methanol, and that embryonic catalase activity may be a determinant of teratological risk.

Methanol exposure does not produce oxidatively damaged DNA in lung, liver or kidney of adult mice, rabbits or primates.

In vitro and in vivo genotoxicity tests indicate methanol (MeOH) is not mutagenic, but carcinogenic potential has been claimed in one controversial long-term rodent cancer bioassay that has not been replicated. To determine whether MeOH could indirectly damage DNA via reactive oxygen species (ROS)-mediated mechanisms, we treated male CD-1 mice, New Zealand white rabbits and cynomolgus monkeys with MeOH (2.0 g/kg ip) and 6h later assessed oxidative damage to DNA, measured as 8-oxo-2'-deoxyguanosine (8-oxodG) by HPLC with electrochemical detection. We found no MeOH-dependent increases in 8-oxodG in lung, liver or kidney of any species. Chronic treatment of CD-1 mice with MeOH (2.0 g/kg ip) daily for 15 days also did not increase 8-oxodG levels in these organs. These results were corroborated in DNA repair-deficient oxoguanine glycosylase 1 (Ogg1) knockout (KO) mice, which accumulated 8-oxodG in lung, kidney and liver with age, but exhibited no increase following MeOH, despite a 2-fold increase in renal 8-oxodG in Ogg1 KO mice following treatment with a ROS-initiating positive control, the renal carcinogen potassium bromate (KBrO3; 100 mg/kg ip). These observations suggest that MeOH exposure does not promote the accumulation of oxidatively damaged DNA in lung, kidney or liver, and that environmental exposure to MeOH is unlikely to initiate carcinogenesis in these organs by DNA oxidation.