Reduced birth defects caused by maternal immune stimulation in methylnitrosourea-exposed mice: association with placental improvement

Reduction in valproic acid-induced neural tube defects by maternal immune stimulation: role of apoptosis

Teratogenic deregulation of apoptosis during development is a possible mechanism for birth defects. Administration of valproic acid (VA) during first trimester of pregnancy causes neural tube defects (NTDs). Nonspecific stimulation of the mother's immune system has been shown to reduce various teratogen-induced fetal malformations including NTDs in rodents. This present study investigated the role of reduced apoptosis by maternal immune stimulation in prevention of VA-induced NTDs in CD-1 mice. Prevention of VA-induced NTDs by nonspecific maternal immune stimulation using IFNγ was employed to evaluate the role of reduced apoptosis by IFNγ in this protective mechanism. Apoptosis was quantified using flow cytometry. Terminal Transferase dUTP Nick End Labeling assay was used to localize the apoptosis. Increased apoptosis, suggesting involvement in VA teratogenicity, was observed along the neural tube in both normal and abnormal embryos from VA-exposed dams. Increased apoptosis in normal VA-exposed embryos suggests that VA may alter other cellular processes such as cell proliferation and differentiation in addition to apoptosis. Apoptotic levels in embryos with closed neural tubes from IFNγ + VA dams were similar to controls indicating resistance to VA-induced apoptosis and protection against teratogenicity of VA. In IFNγ + VA exposed embryos with open neural tubes, maternal immune stimulation failed to regulate apoptosis resulting in an NTD. Overall, these results suggest that VA alters several biological processes including apoptosis in the developing embryos to induce fetal malformations. Resistance to VA-induced apoptosis in embryos resulting from maternal immune stimulation may be involved in protective mechanism.

Experimental gastric carcinogenesis in Cebus apella nonhuman primates

The evolution of gastric carcinogenesis remains largely unknown. We established two gastric carcinogenesis models in New-World nonhuman primates. In the first model, ACP03 gastric cancer cell line was inoculated in 18 animals. In the second model, we treated 6 animals with N-methyl-nitrosourea (MNU). Animals with gastric cancer were also treated with Canova immunomodulator. Clinical, hematologic, and biochemical, including C-reactive protein, folic acid, and homocysteine, analyses were performed in this study. MYC expression and copy number was also evaluated. We observed that all animals inoculated with ACP03 developed gastric cancer on the 9(th) day though on the 14(th) day presented total tumor remission. In the second model, all animals developed pre-neoplastic lesions and five died of drug intoxication before the development of cancer. The last surviving MNU-treated animal developed intestinal-type gastric adenocarcinoma observed by endoscopy on the 940(th) day. The level of C-reactive protein level and homocysteine concentration increased while the level of folic acid decreased with the presence of tumors in ACP03-inoculated animals and MNU treatment. ACP03 inoculation also led to anemia and leukocytosis. The hematologic and biochemical results corroborate those observed in patients with gastric cancer, supporting that our in vivo models are potentially useful to study this neoplasia. In cell line inoculated animals, we detected MYC immunoreactivity, mRNA overexpression, and amplification, as previously observed in vitro. In MNU-treated animals, mRNA expression and MYC copy number increased during the sequential steps of intestinal-type gastric carcinogenesis and immunoreactivity was only observed in intestinal metaplasia and gastric cancer. Thus, MYC deregulation supports the gastric carcinogenesis process. Canova immunomodulator restored several hematologic measurements and therefore, can be applied during/after chemotherapy to increase the tolerability and duration of anticancer treatments.

Effects of phenytoin and Echinacea purpurea extract on proliferation and apoptosis of mouse embryonic palatal mesenchymal cells

Cleft palate is one of the most common birth defects. Several environment factors are involved in the disorder, such as smoking, vitamin deficiency and teratogens. We investigated the teratogenic agent phenytoin and extract of the immunostimulant Echinacea purpurea in the etiology of cleft palate associated with the proliferation and apoptosis of mouse embryonic palatal mesenchymal (MEPM) cells. We measured the effects of phenytoin, E. purpurea extract, and the mixture of phenytoin and E. purpurea extract on the cell viability of MEPM cells by CCK-8 assay and on the proliferation and apoptosis of MEPM cells by BrdU labeling assay, flow cytometry, and TUNEL assay. Exposure to phenytoin for 24 h inhibited cell proliferation and increased cell apoptosis of MEPM cells, and E. purpurea extract had the reverse effect. Importantly, treatment with the mixture of phenytoin and E. purpurea extract increased the proliferation and decreased the apoptosis of MEPM cells as compared with treatment with phenytoin alone. The teratogenic effect of phenytoin on cleft palate is associated with the proliferation and apoptosis of MEPM cells, and E. purpurea extract may have a protective effect.

Methylnitrosourea induces neural progenitor cell apoptosis and microcephaly in mouse embryos

BACKGROUND

Prenatal exposure to methylnitrosourea (MNU), an alkylating agent, induces microcephaly in mice. However, its pathogenetic mechanism has not been clarified, especially that in the development of the cerebral cortex.

METHODS

ICR mice were treated with MNU at 10 mg/kg intraperitoneally on day 13.5 or 15.5 of gestation, and the embryos were observed histologically 24 hr after treatment with MNU or at term. To clarify the pathogenesis of microcephaly and histological changes, especially apoptosis, neurogenesis, and neural migration/positioning, we performed histological analysis employing a cell-specific labeling experiment using thymidine-like substances (BrdU, CldU, and IdU) and markers of neurons/neural stem cells.

RESULTS

Histological abnormalities of the dorsal telencephalon, and the excessive cell death of proliferative neural progenitor/stem cells were noted in the MNU-treated embryos. The highest frequencies of cell death occurred at 36 hr after MNU treatment, and little or no neurogenesis was observed in the ventricular zone of the dorsal telencephalon. Abnormality of the radial migration was caused by the reduction of radial fibers in the radial glias. Birth-date analysis revealed the abnormal positioning of neurons and aberrant lamination of the cerebral cortex.

CONCLUSIONS

Our data suggest that prenatal exposure to MNU induces the excessive cell death of neural precursor/stem cells, and the defective development of the cerebral cortex, resulting in microcephalic abnormalities.

Late-gestation ventricular myocardial reduction in fetuses of hyperglycemic CD1 mice is associated with increased apoptosis

BACKGROUND

Previous work in our laboratory showed reduced myocardium and dilated ventricular chambers in gestation day (GD) 17 hearts that were collected from hyperglycemic CD1 mouse dams. Pre-breeding maternal immune stimulation, using Freund's complete adjuvant (FCA), diminished the severity of these fetal heart lesions. The following experiments were performed to detect possible changes in fetal heart apoptotic cell death, under hyperglycemic conditions and with or without maternal immune stimulation.

METHODS

Female CD1 mice were injected with 200 mg/kg of streptozocin (STZ) to induce insulin-dependent diabetes mellitus. Half of these mice received prior FCA injection. Fetal hearts were collected on GD 17 and myocardial apoptotic cells were quantified using flow cytometry. A panel of apoptosis regulatory genes (Bcl2, p53, Casp3, Casp9, PkCe) was then examined in the fetal myocardium using RT-PCR.

RESULTS

Early apoptotic cells and late apoptotic/necrotic cells were significantly increased in fetal hearts from STZ or STZ+FCA dams. Pre-treatment with FCA reduced late apoptotic/necrotic cells to control level, suggesting some cell death protection was rendered by FCA. Paradoxically in the face of such increased cell death, the expression of pro-apoptotic genes Casp3 and Casp9 was decreased by diabetes, while the anti-apoptotic gene Bcl2 was increased.

CONCLUSIONS

Maternal hyperglycemia causes dys-regulated apoptosis of fetal myocardial cells. Such effect may be prevented by maternal immune stimulation.

Modulation of diabetes-induced palate defects by maternal immune stimulation

Maternal diabetes can induce a number of developmental abnormalities in both laboratory animals and humans, including deformities of the face and palate. The incidence of birth defects in newborns of women with diabetes is approximately 3 to 5 times higher than among nondiabetics. In mice, nonspecific activation of the maternal immune system can reduce fetal abnormalities caused by various etiologies including hyperglycemia. This study was conducted to determine whether nonspecific maternal immune stimulation could reduce diabetes-induced palate defects and orofacial clefts. Female ICR mice were immune stimulated before induction of hyperglycemia with Freund's complete adjuvant (FCA), granulocyte-macrophage colony-stimulating factor (GM-CSF), or interferon-gamma (IFNgamma). Streptozocin was used to induce hyperglycemia (26-35 mmol blood glucose) in females before breeding. Fetuses from 12 to 18 litters per treatment group were collected on Day 17 of gestation. Palate width and length were measured, and the incidence of orofacial clefts was determined. Palate length and width were both decreased by maternal hyperglycemia. Maternal immune stimulation with GM-CSF or FCA limited the degree of palate shortening from the hyperglycemia. Each of the three immune stimulants attenuated significant narrowing of the palate. Rates of orofacial clefts were not significantly different between treatment groups. Palatogenesis is a complex process driven by cellular signals, which regulate cell growth and apoptosis. Dysregulation of cellular signals by maternal hyperglycemia can result in fetal malformations. Maternal immune stimulation may prevent dysregulation of these signaling pathways thus reducing fetal malformations and normalizing palate growth.

Heart changes in 17-day-old fetuses of diabetic ICR (Institute of Cancer Research) mothers: improvement with maternal immune stimulation

Maternal diabetes mellitus is associated with increased fetal teratogenesis, including cardiovascular defects. Non-specific maternal immune stimulation with Freund's complete adjuvant (FCA) or interferon gamma (IFNgamma) has been associated with protection against birth malformations. Using a diabetic mouse model, late-gestation fetal heart and great vessel morphology were analyzed. Four groups of mice were used: non-diabetic females as a control group, hyperglycemic females induced by streptozotocin as a diabetic group, and diabetic females injected either with FCA or IFNgamma. At day 17 of gestation, females were euthanized and one fetus was arbitrarily selected per litter for fixation and sectioning. Treatment-induced changes in cardiac development were assessed from digital images of serial sections taken at standardized levels in the thorax. One-way parametric and non-parametric ANOVA and ordinal logistic regression were performed to compare the difference among groups (P<0.05). Maternal hyperglycemia altered morphology of the late-gestation fetal mouse heart by causing ventricular chamber dilation, sectional myocardial reduction, and an increase in transversal aortic area. FCA protected the fetal heart from cavitary dilation in diabetic mothers. FCA and IFNgamma protected the fetal heart against reduction of myocardial area, and ascending thoracic aorta dilation. Consequences of late gestation heart chamber dilation and myocardial reduction are not yet known. Maternal immune stimulation partially protected against these developmental defects by mechanisms that remain unclear.

Reduction in diabetes-induced craniofacial defects by maternal immune stimulation

BACKGROUND

Maternal diabetes can induce a number of developmental abnormalities in laboratory animals and humans, including facial deformities and defects in neural tube closure. The incidence of birth defects in newborns of diabetic women is approximately 3-5 times higher than among non-diabetics. In mice, non-specific activation of the maternal immune system can reduce fetal abnormalities caused by diverse etiologies, including diabetes induced neural tube defects. This study was conducted to determine whether non-specific maternal immune stimulation could reduce diabetes-induced craniofacial defects as well.

METHODS

Maternal immune function was stimulated before streptozocin (STZ) treatment by maternal footpad injection with Freund's complete adjuvant (FCA), maternal intraperitoneal (i.p.) injection with granulocyte-macrophage colony-stimulating factor (GM-CSF), or maternal i.p. injection with interferon-gamma (IFNgamma). Streptozocin (200 mg/kg i.p.) was used to induce hyperglycemia (26-35 mmol blood glucose) in female ICR mice before breeding. Fetuses from 12-18 litters per treatment group, were collected at Day 17 of gestation.

RESULTS

Craniofacial defects were observed in fetuses from all hyperglycemic groups. The incidence of defects was significantly decreased in fetuses from dams immune stimulated with IFNgamma or GM-CSF. The most common defects were reduced maxillary and mandibular lengths. Both were prevented by maternal stimulation with GM-CSF.

CONCLUSION

Maternal immune stimulation reduced the incidence of diabetic craniofacial embryopathy. The mechanisms for these protective effects are unknown but may involve maternal or fetal production of cytokines or growth factors that protect the fetus from the dysregulatory effects of hyperglycemia.

Valproic acid-induced fetal malformations are reduced by maternal immune stimulation with granulocyte-macrophage colony-stimulating factor or interferon-gamma

Valproic acid, a drug commonly used to treat seizures and other psychiatric disorders, causes neural tube defects (NTDs) in exposed fetuses at a rate 20 times higher than in the general population. Failure of the neural tube to close during development results in exencephaly or anencephaly, as well as spina bifida. In mice, nonspecific activation of the maternal immune system can reduce fetal abnormalities caused by diverse etiologies, including diabetes-induced NTDs. We hypothesized that nonspecific activation of the maternal immune system with interferon-gamma (IFN-gamma) and granulocyte-macrophage colony-stimulating factor (GM-CSF) could reduce valproic acid (VA)-induced defects as well. Female CD-1 mice were given immune stimulant prebreeding: either IFN-gamma or GM-CSF. Approximately half of the control and immune-stimulated pregnant females were then exposed to 500 mg/kg VA on the morning of gestational day 8. The incidence of developmental defects was determined on gestational day 17 from at least eight litters in each of the following treatment groups: control, VA only, IFN-gamma only, IFN-gamma+VA, GM-CSF only, and GM-CSF+VA. The incidence of NTDs was 18% in fetuses exposed to VA alone, compared to 3.7% and 2.9% in fetuses exposed to IFN-gamma+VA, or GM-CSF+VA respectively. Ocular defects were also significantly reduced from 28.0% in VA exposed groups to 9.8% in IFN-gamma+VA and 12.5% in GM-CSF+VA groups. The mechanisms by which maternal immune stimulation prevents birth defects remain unclear, but may involve maternal or fetal production of cytokines or growth factors which protect the fetus from the dysregulatory effects of teratogens.

Association of Ipomoea carnea and BCG reduces birth defects caused by cyclophosphamide in rats

Immunosuppressive drugs can induce the development of malformations in fetuses of mothers exposed to them, possibly affecting the placental function directly or by crossing the placenta to enter fetal circulation. However, activation of the maternal immune system with well-known immunomodulator substances has been shown to produce a significant decrease in morphological defects caused by diverse teratogenic agents. All of these studies were performed on mice only, whereas the rat is the chosen species for developing teratological studies. Thus, the purpose of the present study was to investigate the possible protective effect of Bacillus Calmette Guérin (BCG) and/or the aqueous fraction (AF) of the plant Ipomoea carnea on the decrease of the teratogenic effect resulting from cyclophosphamide (CP), an antineoplastic and immunosuppressive drug, exposure in pregnant rats. It was verified that both BCG and/or AF attenuated the embryotoxic effects of CP in rats. All immune stimulated dams demonstrated an increase in placenta and fetus body weight. In conclusion, the present work showed that the rat is a good model for performing studies which aim for a clearer understanding of the mechanism by which maternal stimulation reduces malformations and how the association of I. carnea AF and BCG provided improved immunostimulation compared to BCG alone; however, additional studies are required to determine the specific mechanisms by which immune stimulant substances decrease malformation.

A comparison study of effects of Echinacea extract and levamisole on phenytoin-induced cleft palate in mice

There are many reports that the teratogenic effects of phenytoin, especially cleft palate can be decreased by stimulation of maternal immune system. Also, there is some evidence that Echinacea extract and levamisole are immunomodulator drugs. So, in this study, we compared the prophylactic effects of levamisole and Echinacea extract on teratogenic effects of phenytoin. This study was performed on 32 pregnant mice that were divided into four groups. The first group (control group) received normal saline intraperitoneally and the other groups (test groups) received phenytoin (65 mg/kg intraperitoneally) at 10th day of gestation. Levamisole and extract of Echinacea purpurea were administrated at dose of 10 and 360 mg/kg intraperitoneally, respectively, in along with and 12h later after phenytoin injection, in two groups. Fetuses were carried out in 19th day of gestation and after determination of weight and length; they were stained by Alizarin red-Alcian blue method. Cleft palate incidence was 16, 5.3, and 3.2% in fetuses of mice that received only phenytoin, phenytoin with levamisole, and phenytoin with Echinacea extract, respectively. Mean weight and length of fetuses of animals that received levamisole and Echinacea extract were significantly greater than those received only phenytoin. It is concluded that Echinacea can stimulate immune system more than levamisole and has better prophylactic effect on incidence of phenytoin-induced cleft palate, but it is not significant.

Parental heat exposure and risk of childhood brain tumor: a Children's Oncology Group study

Medulloblastoma (MB) and primitive neuroectodermal tumor (PNET) are histologically similar brain tumors that occur mostly in children. As part of a comprehensive case-control study of MB/PNET, this study explored parental exposure to heat and electromagnetic fields as potential risk factors. Parents of 318 cases (<6 years of age at diagnosis in 1991-1997 and registered with the Children's Cancer Group) and 318 controls selected by random digit dialing were interviewed. In univariate analyses, moderately strong associations were observed for mother's sauna use close to conception (odds ratio = 3.8, 95% confidence interval (CI): 1.0, 13.7) or in the first trimester (odds ratio = 3.6, 95% CI: 0.7, 17.3) and for father's exposure in the 3 months before the pregnancy to sauna (odds ratio = 2.4, 95% CI: 1.3, 4.5), electric blanket (odds ratio = 2.0, 95% CI: 0.9, 4.3), or any heat source (for higher exposure: odds ratio = 2.5, 95% CI: 1.4, 4.6). In multivariate models, father's sauna use and father's exposure to any heat source were associated with MB/PNET in a dose-response fashion (for high exposure: odds ratio = 3.4, 95% CI: 1.2, 9.7, and odds ratio = 2.1, 95% CI: 1.1, 4.3, respectively). This new observation regarding paternal exposure to heat just prior to the index pregnancy deserves consideration in future animal and human studies of MB/PNET.

Role of Maternal Dietary Antioxidant Supplementation in Murine Placental and Fetal Limb Development

Methylnitrosourea (MNU) is a multisystem teratogen that damages proliferating cells through macromolecule alkylation and generation of reactive oxygen species (ROS). Murine dams exposed to MNU midgestation produce offspring with distal limb malformations, an outcome reduced by maternal immune stimulation. Immunostimulatory effects of antioxidant therapy may in part explain this improved birth outcome. The present study hypothesizes that placental, rather than fetal, damage from excessive ROS may contribute to MNU-induced embryopathy. Fetal limbs and placentas were examined in immunotolerant CD-1 and immunosensitive C57BL/6N mice exposed to MNU, dietary antioxidant butylated hydroxytoluene (BHT), or both. MNU increased fetal resorptions and incidence of syndactyly, oligodactyly, polydactyly, and interdigital webbing, and decreased fetal size in both mouse strains. BHT reduced syndactyly and oligodactyly in both strains, and reduced polydactyly in C57BL/6N mice. Increased webbing in MNU and MNU+BHT groups likely represented maturational delay. Placentas from CD-1 and C57BL/6N MNU-exposed dams demonstrated decreased trophoblasts and increased necrosis of endothelium. Similar to distal limb defects, placental damage was reduced in mice receiving MNU+BHT. These results suggest that placental damage and fetal defects caused by MNU are in part ROS-mediated, and reduced distal limb defects following MNU+BHT may be related to improved placental integrity and function.

Prebreeding Maternal Immunostimulation with Freund's Complete Adjuvant Reduces Placental Damage and Distal Limb Defects Caused by Methylnitrosourea

PROBLEM

Immunostimulation reduces murine teratogen-induced birth defects. It is unclear if placental improvement contributes to this outcome. The current study examined murine placental ultrastructure and fetal limb development following maternal methylnitrosourea (MNU) exposure, +/-Freund's complete adjuvant (FCA) immunostimulation.

METHOD OF STUDY

Two murine strains (CD-1, C57BL/6N) were administered MNU on gestation day 9 (GD9), FCA pre-breeding, or FCA + MNU. Fetal limb and placental development were examined on GD14.

RESULTS

MNU decreased placental weight and reduced placental cellular viability; FCA reversed these effects. MNU shortened fetal limbs and increased digital defects in both strains. Placentas were less damaged in C57BL/6N versus CD-1 mice, and distal limb malformations improved only in CD-1 mice. FCA immunostimulation also increased pregnancy rate.

CONCLUSION

Improved fetal outcome from immune-stimulated mice may not be dependent on improved placental morphology. However, placental function and morphology in immune-stimulated mice may not directly correlate, thus functional improvements should be examined for possible relationship to reduced birth defects.

Placental improvement and reduced distal limb defects by maternal interferon-γ injection in methylnitrosourea-exposed mice

BACKGROUND

Methylnitrosourea (MNU), an alkylating agent derived from creatinine metabolism, is cytotoxic, genotoxic, and mutagenic. Mid-gestational exposure to MNU leads to distal limb defects in mice. Previous studies have shown that nonspecific maternal immune stimulation protects against MNU-induced teratogenesis. A role for immune-mediated placental improvement in this effect remains uncertain.

METHODS

The immune system of timed-pregnant C57BL/6N and CD-1 mice was stimulated by GD 7 intraperitoneal (IP) injection with the cytokine interferon-gamma (IFN-gamma). A teratogenic dose of MNU was then administered by IP injection on the morning of GD 9 to disrupt distal limb formation. Fetal limb length, body length, digital deformities, and placental integrity were evaluated on GD 14.

RESULTS

The incidence of syndactyly, polydactyly, and interdigital webbing in MNU-exposed mice was decreased by maternal IFN-gamma treatment. In C57BL/6N mice, these defects were reduced by 47, 100, and 63%, respectively, as compared to previous reports on CD-1 mice, by 39, 71, and 20%, respectively. Administration of IFN-gamma significantly diminished MNU-induced endothelial and trophoblast placental damage in both strains of mice.

CONCLUSIONS

These findings support a possible link between maternal immunity, placental integrity, and fetal distal limb development. Further, these results suggest that IFN-gamma might act through placental improvement to indirectly protect against MNU-induced fetal limb malformations.