Neural tube defects in mice exposed to tap water

In May of 2006 we suddenly began to observe neural tube defects (NTDs) in embryos of untreated control mice. We hypothesized the mice were being exposed unknowingly to a teratogenic agent and investigated the cause. Our results suggested that NTDs were not resulting from bedding material, feed, strain, or source of the mice. Additionally, mice were negative for routine and comprehensive screens of pathogens. To further test whether the NTDs resulted from infectious or genetic cause localized to our facility, we obtained three strains of timed pregnant mice from commercial suppliers located in four different states. All strains and sources of mice arrived in our laboratory with NTDs, implying that commercially available mice were possibly exposed to a teratogen prior to purchase. Our investigation eventually concluded that exposure to tap water was causing the NTDs. The incidence of NTDs was greatest in purchased mice provided tap water and lowest in purchased mice provided distilled deionized water (DDI). Providing mice DDI water for two generations (F2‐DDI) eliminated the NTDs. When F2‐DDI mice were provided tap water from three different urban areas prior to breeding, their offspring again developed NTDs. Increased length of exposure to tap water significantly increased the incidence of NTDs. These results indicate that a contaminant in municipal tap water is likely causing NTDs in mice. The unknown teratogen appears to have a wide geographic distribution but has not yet been identified. Water analysis is currently underway to identify candidate contaminants that might be responsible for the malformations. © 2010 Wiley Periodicals, Inc. Environ Toxicol, 2011.     

Myo-inositol soft gel capsules may prevent the risk of coffee-induced neural tube defects

Objective: Neural tube defects (NTDs) are classified as folate sensitive (about 70%) and folate resistant (about 30%); although folic acid is able to prevent the former, several data have shown that inositol may prevent the latter. It has recently been proposed that coffee intake might represent a risk factor for NTD, likely by interfering with the inositol signaling. In the present study, we tested the hypothesis that, beside affecting the inositol signaling pathway, coffee also interferes with inositol absorption.

Research design and methods: In order to evaluate coffee possible negative effects on inositol gastrointestinal absorption, a single-dose bioavailability trial was conducted. Pharmacokinetics (PK) parameters of myo-inositol (MI) powder and MI soft gelatin capsules swallowed with water and with a single ‘espresso' were compared. PK profiles were obtained by analysis of MI plasma concentration, and the respective MI bioavailability was compared.

Results: Myo-inositol powder administration was negatively affected by coffee intake, thus suggesting an additional explanation to the interference between inositol deficiency and coffee consumption. On the contrary, the concomitant single ‘espresso' consumption did not affect MI absorption following MI soft gelatin capsules administration. Furthermore, it was observed that MI soft gelatin capsule administration resulted in improved bioavailability compared to the MI powder form.

Conclusions: Myo-inositol soft gelatin capsules should be considered for the preventive treatment of NTDs in folate-resistant subjects due to their higher bioavailability and to the capability to reduce espresso interference.     

Folic acid supplementation during pregnancy protects against lipopolysaccharide-induced neural tube defects in mice

Folic acid is a water-soluble B-complex vitamin. Increasing evidence demonstrates that physiological supply of folic acid during pregnancy prevents folic acid deficiency-related neural tube defects (NTDs). Previous studies showed that maternal lipopolysaccharide (LPS) exposure caused NTDs in rodents. The aim of this study was to investigate the effects of high-dose folic acid supplementation during pregnancy on LPS-induced NTDs. Pregnant mice were intraperitoneally injected with LPS (20 μg/kg/d) from gestational day (GD) 8 to GD12. As expected, a five-day LPS injection resulted in 19.96% of fetuses with NTDs. Interestingly, supplementation with folic acid (3 mg/kg/d) during pregnancy significantly alleviated LPS-induced NTDs. Additionally, folic acid significantly attenuated LPS-induced fetal growth restriction and skeletal malformations. Additional experiment showed that folic acid attenuated LPS-induced glutathione (GSH) depletion in maternal liver and placentas. Moreover, folic acid significantly attenuated LPS-induced expression of placental MyD88. Additionally, folic acid inhibited LPS-induced c-Jun NH2-terminal kinase (JNK) phosphorylation and nuclear factor kappa B (NF-κB) activation in placentas. Correspondingly, folic acid significantly attenuated LPS-induced tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 in placentas, maternal serum and amniotic fluid. In conclusion, supplementation with high-dose folic acid during pregnancy protects against LPS-induced NTDs through its anti-inflammatory and anti-oxidative effects.     

Spontaneous neural tube defects in splotch mice supplemented with selected micronutrients

Splotch (Sp/Sp) mice homozygous for a mutation in the Pax3 gene inevitably present with neural tube defects (NTDs), along with other associated congenital anomalies. The affected mutant embryos usually die by gestation days (E) 12-13. In the present study, the effect of modifier genes from a new genetic background (CXL-Sp) and periconceptional supplementation with selected micronutrients (folic acid, 5-formyltetrahydrofolate, 5-methyltetrahydrofolate, methionine, myoinositol, thiamine, thymidine, and alpha-tocopherol) was determined with respect to the incidence of NTDs. In order to explore how different exposure parameters (time, dose, and route of compound administration) modulate the beneficial effects of micronutrient supplementation, female mice received either short- or long-term nutrient supplements via enteral or parenteral routes. Embryos were collected on E12.5 and examined for the presence of anterior or posterior NTDs. Additionally, whole mount in situ hybridization studies were conducted in order to reveal/confirm normal expression patterns of the Pax3 gene during neurulation in the wild-type and Sp/Sp homozygous mutant mouse embryos utilized in this study. A strong Pax3 signal was demonstrated in CXL-Sp embryos during neural tube closure (E9.5 to E10.5). The intensity and spatial pattern of expression were similar to other Splotch mutant mice. Of all the micronutrients tested, only supplementation with folic acid or 5-methyltetrahydrofolate rescued the normal phenotype in Sp/Sp embryos. When the folate supplementation dose was increased to 200 mg/kg in the diet, the incidence of rescued splotch homozygotes reached 30%; however, this was accompanied by six-fold increased resorption rate.     

Prevention of valproic acid-induced neural tube defects by sildenafil citrate

This study was undertaken to test the effects of sildenafil citrate (SC), a type 5 phosphodiesterase inhibitor, on valproic acid (VPA)-induced teratogenesis. On gestation day (GD) 8, ICR (CD-1) mice were treated by gastric intubation with SC at 0 (vehicle), 1.0, 2.5, 5.0 or 10 mg/kg. One hour later, animals received a teratogenic dose of VPA (600 mg/kg) or vehicle. Developmental endpoints were evaluated near the end of gestation. Twenty-eighth percent of fetuses exposed to VPA had neural tube defects (exencephaly). Pretreatment with SC at 2.5, 5.0 or 10 mg/kg significantly reduced the rate of VPA-induced exencephaly to 15.9%, 13.7%, and 10.0%, respectively. Axial skeletal defects were observed in 75.8% of VPA-exposed fetuses. Pre-treatment with SC at 10 mg/kg, but not at lower doses, significantly decreased the rate of skeletally affected fetuses to 61.6%. These results show that SC, which prolongs nitric oxide (NO) signaling action protects from VPA-induced teratogenesis.     

MTHFR基因C677T多态性与神经管缺陷相关性的Meta分析

摘要： 目的 探讨母亲 5,10-亚甲基四氢叶酸还原酶（MTHFR）基因 C677T 多态性与子代神经管缺陷（NTDs）发生的相关性。方法 计算机检索中国生物医学文献数据库、 重庆维普中文科技期刊全文数据库、 清华 CNKI 数据库、万方科技期刊数据库、 PubMed 和 Web of Science, 检索时间均为自建库至 2014 年 3 月。按照纳入与排除标准选择母亲 MTHFR 基因 C677T 位点多态性与子代 NTDs 发生相关的病例对照研究。提取相关数据并应用 RevMan5.0 软件进行 Meta 分析。结果 25 篇文献纳入分析, 包括病例组 2 282 例, 对照组 3 420 例。结果显示, 在共显性（TT 基因型 vs CC 基因型; CT 基因型 vs CC 基因型）及等位基因遗传模式下合并 OR（95%CI）分别为 2.28（1.60~3.24）、 1.25 （1.02~1.53）和 1.42（1.21~1.67）。亚组分析结果显示, 在亚洲人群中母亲 MTHFR 基因 C677T 位点多态性与子代 NTDs 发生间存在显著的相关性。结论 母亲 MTHFR 基因 C677T 位点多态性是子代发生 NTDs 的一个危险因素,尤以亚洲人群较为明显。     

Influence of the antifolate drug Methotrexate on the development of murine neural tube defects and genomic instability

Impaired folate metabolism is considered a risk factor for neural tube defects (NTDs). However, the relationship between folate deficiency and the risk of NTDs remains unclear, because experimentally induced dietary folate deficiency is insufficient to cause NTDs in non‐mutant mice. Methotrexate (MTX) is a specific folate antagonist that competitively inhibits dihydrofolate reductase (DHFR) activity. The objective of this study was to develop a folate dysmetabolism murine model, and study the development of NTDs and its mechanism. Pregnant mice were injected with different doses of MTX [0, 0.5, 1.0, 3.0, 4.5 and 6.0 mg kg^–1 body weight (b/w) intraperitoneally (i.p.)] on gestational day 7.5 and sacrificed on gestational day 11.5. DHFR activity in embryonic tissues was detected, and folate concentrations were analyzed using LC/MS/MS. Copy number variations (CNVs) in neural tube tissues were detected using array comparative genomic hybridization (aCGH). A dose of MTX 4.5 mg kg^–1 b/w, resulted in the highest incidence of NTDs (31.4%) compared with the other groups, and DHFR activities, 5‐MeTHF and 5‐FoTHF concentrations in embryonic tissues decreased significantly after MTX injection. Furthermore, we found three high‐confidence CNVs on chromosome X using aCGH, which was confirmed by RT‐PCR and MassARRAY. These results indicate that MTX could cause a folate‐associated dysmetabolism, which is similar to that of dietary folate deficiency in mice. The presence of CNVs in neural tube tissues was associated with the development of NTDs. Copyright © 2012 John Wiley & Sons, Ltd.     

All‐trans‐retinoic acid alters Smads expression in embryonic neural tissue of mice

Retinoic acid can cause malformations of the developing nervous system. Smad signaling is involved in embryonic development. The current study investigated all‐trans‐retinoic acid (ATRA)‐induced alteration of Smad expression in the developing neural tubes of mice. Pregnant mice were treated with a single dose of 50 mg/kg ATRA by oral gavage on embryonic day (E) 7. Western immunoblotting was used to examine Smads proteins, particularly phosphorylated (p‐) Smad1, total Smad1 and Smad6 in the neural tissue of the embryos on E8–E11 following treatment. Results showed that ATRA treatment significantly increased expression of both p‐Smad1 and total Smad1, while Smad6 was decreased in neural tissues of ATRA‐exposed embryos in utero from E8 to E11, a critical period for neural tube formation. Data suggest that disruption of Smad signaling may be involved in ATRA‐induced neural tube defects. Copyright © 2008 John Wiley & Sons, Ltd.     

Effects of choline on sodium arsenite-induced neural tube defects in chick embryos

Arsenic passes through the placenta and accumulates in the neuroepithelium of embryo, whereby inducing congenital malformations such as neural tube defects (NTDs) in animals. Choline (CHO), a methyl-rich nutrient, functions as a methyl donor to participate in methyl group metabolism. Arsenic methylation has been regarded as a detoxification process and choline (CHO) is the major source of methyl-groups. However, whether CHO intake reverses the abnormal embryo development induced by sodium arsenite (SA) and the relationship between CHO intake and arsenite-induced NTDs are still unclear. In this study, we used chick embryos as animal model to investigate the effects of SA and CHO supplementation on the early development of nervous system. Our results showed that the administration of SA led to reduction in embryo viability, embryo body weight and extraembryonic vascular area, accompanied by a significantly increased incidence of the failed closure of the caudal end of the neural tube. CHO, at low dose (25 μg/μL), reversed the decrease in embryo viability and the increase in the failed closure of the caudal end of the neural tube, which were induced by SA. In addition, CHO (25 μg/μL) inhibited not only the SA-induced cell apoptosis by up-regulating Bcl-2 level, but also the global DNA methylation by increasing the expressions of DNMT1 and DNMT3a. However, less significant difference was found between the embryos co-treated with SA and CHO (50 μg/μL) and the ones treated with SA alone. Taken together, these findings suggest that low dose CHO could protect chick embryos from arsenite-induced NTDs by a possible mechanism related to the methyl metabolism.     

BHMT和RFC1多态性与中国北方汉族儿童神经管缺陷的易感性研究

目的 研究中国北方汉族儿童中甜菜碱同型半胱氨酸甲基转移酶基因（BHMT）和还原叶酸载体1基因（RFC1,又称SLC19A1）的单核苷酸多态性（SNPs）与神经管缺陷（NTDs）易感性的关系。方法 以中国北方汉族152例NTDs患儿和169例正常对照为研究对象,采用Sequenom Mass-ARRAY分型技术对BHMT和RFC1两个基因的9个SNPs 位点进行基因分型,Haploview4.2 软件进行单体型分析。结果 BHMT 基因 rs3733890 位点等位基因频率与NTDs 的发病存在显著关联,且携带 A 等位基因儿童发生 NTDs 风险高于 G 等位基因的儿童（OR=1.408,95%CI： 1.013～1.956）;RFC1基因rs1051266位点等位基因和基因型频率分布与NTDs的发病存在显著关联,且携带G等位基因和 GG 基因型的儿童患 NTDs 风险分别高于 A 等位基因和 AA 基因型儿童（OR=1.492,95%CI：1.089～2.044;OR=2.020,95%CI：1.081～3.780）;RFC1基因rs3788200位点等位基因频率与NTDs发病存在显著关联,携带G等位基因的儿童患NTDs风险高于携带A等位基因儿童（OR=1.368,95%CI：1.002~1.868）。同时,单体型分析结果显示BHMT基因单体型C-A-A-A（rs567754-rs3733890-rs558133-rs585800）和RFC1基因单体型G-G-G-T（rs1051296-rs3788200-rs1051266-rs4819130）可使 NTDs 发病风险增加,而 BHMT 基因单体型 C-G-A-A 可使 NTDs 发病风险降低。结论BHMT基因rs3733890和RFC1基因rs1051266、rs3788200多态性与中国北方汉族儿童NTDs的易感性相关。     

Amniotic fluid cholinesterase of valproate-induced exencephaly in the mouse: an animal model for prenatal diagnosis of neural tube defects

After a single administration of the antiepileptic drug valproic acid (VPA; i.p.: 600 mg/kg) on day 8 of gestation in the mouse embryotoxicity and amniotic fluid (AF) cholinesterase (ChE) were evaluated on day 16 of gestation. VPA treatment induced an increase in embryolethality, neural tube defects (exencephaly), cleft palate, deformed vertebrae, open eyes, and a reduction in fetal weight. In VPA-exposed fetuses AF total ChE (TChE) activity of exencephalic fetuses was higher than that of normal fetuses. However, in 3 out of 110 normal fetuses of the control group TChE activity was found in the AF. There was no correlation between blood contamination of AF and its TChE activity, either in non-exencephalic control or treated embryos. Using ethopropazine as a pseudo-ChE inhibitor in vitro, the percentage of acetyl-ChE in blood-contaminated AF was similar to that of fetal rather than maternal serum, indicating that AF was contaminated with fetal and not with maternal blood. VPA-induced exencephaly in mice may provide an animal model to further investigate biochemical markers for prenatal diagnosis of neural tube defects.     

江门市新会区实施育龄妇女免费增补叶酸对神经管畸形与服药情况的影响

目的 探讨江门市新会区育龄妇女免费增补叶酸实施推广后围产儿病死及神经管畸形情况与孕产妇服用叶酸情况.方法 2011年4月至2013年4月向江门市新会区育龄妇女免费派放叶酸,通过统计分析并比较实施推广项目前后围产儿病死及神经管畸形情况,各年间孕产妇服用叶酸情况.结果 采用服药措施后,围产儿病死率也由采用服药措施前的0.65％下降到0.54％;神经管畸形由0.18％下降到0.04％,围产儿病死率与神经管畸形发生率改善情况显著优于采用服药措施前,差异有统计学意义（P＜0.05）; 2009年至2013年叶酸总服药率由23.5％上升至73.5％;叶酸全程服药依从率由12.7％上升至63.8％.2013年至4月叶酸总服药率与全程服药依从率显著高于2009年,差异有统计学意义（P＜0.05）.结论 实施推广育龄妇女免费增补叶酸措施后,明显降低围产儿病死率与神经管畸形发生率,叶酸总服用率与全程服药依从率均呈逐年上升趋势.     

Folic acid and pantothenic acid protection against valproic acid-induced neural tube defects in CD-1 mice

In utero exposure to valproic acid (VPA) during pregnancy is associated with an increased risk of neural tube defects (NTDs). Although the mechanism by which VPA mediates these effects is unknown, VPA-initiated changes in embryonic protein levels have been implicated. The objectives of this study were to investigate the effect of in utero VPA exposure on embryonic protein levels of p53, NF-kappaB, Pim-1, c-Myb, Bax, and Bcl-2 in the CD-1 mouse. We also evaluated the protective effects of folic acid and pantothenic acid on VPA-induced NTDs and VPA-induced embryonic protein changes in this model. Pregnant CD-1 mice were administered a teratogenic dose of VPA prior to neural tube closure and embryonic protein levels were analyzed. In our study, VPA (400 mg/kg)-induced NTDs (24%) and VPA-exposed embryos with an NTD showed a 2-fold increase in p53, and 4-fold decreases in NF-kappaB, Pim-1, and c-Myb protein levels compared to their phenotypically normal littermates (P<0.05). Additionally, VPA increased the ratio of embryonic Bax/Bcl-2 protein levels (P<0.05). Pretreatment of pregnant dams with either folic acid or pantothenic acid prior to VPA significantly protected against VPA-induced NTDs (P<0.05). Folic acid also reduced VPA-induced alterations in p53, NF-kappaB, Pim-1, c-Myb, and Bax/Bcl-2 protein levels, while pantothenic acid prevented VPA-induced alterations in NF-kappaB, Pim-1, and c-Myb. We hypothesize that folic acid and pantothenic acid protect CD-1 embryos from VPA-induced NTDs by independent, but not mutually exclusive mechanisms, both of which may be mediated by the prevention of VPA-induced alterations in proteins involved in neurulation.     

Essential trace elements in umbilical cord tissue and risk for neural tube defects

Deficient or excessive quantities of essential trace elements (ETEs)¹ in the fetal environment can compromise developmental processes. We investigated whether concentrations of zinc (Zn), manganese (Mn), selenium (Se), cobalt (Co), molybdenum (Mo), and nickel (Ni) in umbilical cord tissue are associated with risk for neural tube defects (NTDs). Umbilical cord tissues from 166 cases of NTD cases and 166 matched controls were collected and element concentrations were measured using inductively coupled plasma-mass spectrometry. Associations between ETE concentrations and the risk for NTDs were estimated using multivariate logistic regression while adjusting for potential confounders. Bayesian kernel machine regression (BKMR) was used to examine the joint effects of these ETEs. We found that median concentrations of Ni were higher but those of Mo and Co were lower in the NTD group than in the control group. Co was the only element that was associated with NTD risk after adjusting for confounders (OR 0.31, 95 % CI 0.12–0.79 for the second and OR 0.37, 95 % CI 0.15–0.91 for the top tertile relative to the lowest tertile). The association between Co and NTD risk was confirmed with the BKMR model. In addition, a joint effect of the six ETE mixture on NTD risk was observed: the risk decreased with the levels of the mixture from 25th percentile through 75th percentile. In conclusion, higher levels of Co were associated with lower risk for NTDs, and NTD risk decreased with the levels of the six ETEs as a co-exposure mixture, suggesting a protective effect.     

含叶酸的多种维生素制剂预防新生儿神经管畸形的进展

全世界每年约有 30万以上新生儿患神经管畸形 ,造成社会和病人家庭的巨大负担。本文综述了神经管畸形的临床特点 ,含叶酸的多种维生素制剂的代谢作用和预防神经管畸形发生的研究 ,特别介绍了中国妇女服用叶酸每日 4 0 0 μg预防新生儿神经管畸形的成功经验。作者认为 :计划受孕前后每日服用含 4 0 0 μg叶酸的多种维生素矿物质制剂 ,可以减少包括神经管畸形的多种新生儿畸形发生     

Arsenate-induced maternal glucose intolerance and neural tube defects in a mouse model

Background

Epidemiological studies have linked environmental arsenic (As) exposure to increased type 2 diabetes risk. Periconceptional hyperglycemia is a significant risk factor for neural tube defects (NTDs), the second most common structural birth defect. A suspected teratogen, arsenic (As) induces NTDs in laboratory animals.

Objectives

We investigated whether maternal glucose homeostasis disruption was responsible for arsenate-induced NTDs in a well-established dosing regimen used in studies of arsenic's teratogenicity in early neurodevelopment.

Methods

We evaluated maternal intraperitoneal (IP) exposure to As 9.6 mg/kg (as sodium arsenate) in LM/Bc/Fnn mice for teratogenicity and disruption of maternal plasma glucose and insulin levels. Selected compounds (insulin pellet, sodium selenate (SS), N-acetyl cysteine (NAC), l-methionine (L-Met), N-tert-Butyl-α-phenylnitrone (PBN)) were investigated for their potential to mitigate arsenate's effects.

Results

Arsenate caused significant glucose elevation during an IP glucose tolerance test (IPGTT). Insulin levels were not different between arsenate and control dams before (arsenate, 0.55 ng/dl; control, 0.48 ng/dl) or after glucose challenge (arsenate, 1.09 ng/dl; control, 0.81 ng/dl). HOMA-IR index was higher for arsenate (3.9) vs control (2.5) dams (p = 0.0260). Arsenate caused NTDs (100%, p < 0.0001). Insulin pellet and NAC were the most successful rescue agents, reducing NTD rates to 45% and 35%.

Conclusions

IPGTT, insulin assay, and HOMA-IR results suggest a modest failure of glucose stimulated insulin secretion and insulin resistance characteristic of glucose intolerance. Insulin's success in preventing arsenate-induced NTDs provides evidence that these arsenate-induced NTDs are secondary to elevated maternal glucose. The NAC rescue, which did not restore maternal glucose or insulin levels, suggests oxidative disruption plays a role.