Stress-triggered abortion in mice prevented by alloimmunization

Evaluating possible maternal effect lethality and genetic background effects in Naa10 knockout mice

Amino-terminal (Nt-) acetylation (NTA) is a common protein modification, affecting approximately 80% of all human proteins. The human essential X-linked gene, NAA10, encodes for the enzyme NAA10, which is the catalytic subunit in the N-terminal acetyltransferase A (NatA) complex. There is extensive genetic variation in humans with missense, splice-site, and C-terminal frameshift variants in NAA10. In mice, Naa10 is not an essential gene, as there exists a paralogous gene, Naa12, that substantially rescues Naa10 knockout mice from embryonic lethality, whereas double knockouts (Naa10-/Y Naa12-/-) are embryonic lethal. However, the phenotypic variability in the mice is nonetheless quite extensive, including piebaldism, skeletal defects, small size, hydrocephaly, hydronephrosis, and neonatal lethality. Here we replicate these phenotypes with new genetic alleles in mice, but we demonstrate their modulation by genetic background and environmental effects. We cannot replicate a prior report of "maternal effect lethality" for heterozygous Naa10-/X female mice, but we do observe a small amount of embryonic lethality in the Naa10-/y male mice on the inbred genetic background in this different animal facility.

On use of animal models

Human pregnancy, critical for our species survival, is inefficient and prone to complications such as infertility, spontaneous miscarriages and preeclampsia (PE). Immunological factors may be important as the embryo is 50% paternal and foreign to the mother. Mouse pregnancy models, and in particular the murine CBA/J x DBA/2 mating combination, has been widely used to investigate mechanisms causing and preventing partner-specific recurrent miscarriages (RM) and PE. Occult losses can represent T cell-mediated rejection, and antigen-specific regulatory T cells (Tregs) with classical αβ T cell receptors (TcR) activated by semen antigens at the time of mating are protective. If there is no occult loss, an inadequate Treg response can also predispose to RM. In RM, proinflammatory cytokines from natural killer (NK)-type cells and macrophages of the innate immune system are responsible and cells with γδ TcR protect via release of TGF-β-type molecules. Immunization of abortion-prone female CBA/J mice or administration of cell-associated or soluble CD200, an immune check point inhibitor, can prevent abortions by augmenting uterine decidual suppressor cell activity. Human studies suggest that is also true in couples with RM. Environmental activators of the innate immune system, such as bacterial LPS and stress, can cause abortions as well as occult losses. The endogenous level of Tregs and activation of Tregs specific for the male H-Y antigen may determine success rates and alter the male:female birth ratio. Intralipid alters LPS clearance, prevents abortions in the CBAxDBA/2 model, and is effective in increasing live birth rates in couples undergoing IVF treatment.

Incidence and biomarkers of pregnancy, spontaneous abortion, and neonatal loss during an environmental stressor: Implications for female reproductive suppression in the cooperatively breeding meerkat

Meerkats are group-living, insectivorous herpestids in which subordinate members provide extensive care for the dominant female's young. In contrast to some cooperative breeders, subordinate female meerkats are physiologically able to reproduce and occasionally do so successfully; their attempts are more frequently 'suppressed' via eviction or infanticide by the dominant female. Spontaneous abortion and neonatal loss occur with some regularity, further negatively impacting reproductive success. Here, we compared the reproductive outcomes and endocrine profiles, including of serum progesterone (P₄), serum estradiol (E₂), and fecal glucocorticoid metabolites (fGCm), of dominant and subordinate dams residing within their clans in the Kalahari Desert of South Africa. Our study spanned years of drought, which reduced insect abundance and represented a substantial environmental stressor. Meerkat pregnancies were identified at mid-term and culminated either in spontaneous abortions or full-term deliveries, after which pups were either lost prior to emergence from the natal den (usually within 2days of birth) or emerged at 2-3weeks. Neonatal loss exceeded fetal loss for all females, and contributed to narrowing the status-related disparity in female reproductive output seen during less arid periods. Although E₂ concentrations were significantly lower in subordinate than dominant females, they were sufficient to support gestation. Absolute E₂ concentrations may owe to androgenic precursors that also attain highest concentrations in dominant dams and may mediate aggression underlying female reproductive skew. Pregnancies terminating in fetal loss were marked by significantly lower P₄ concentrations in mid-gestation and modestly lower E₂ concentrations overall. Consistently high fGCm concentrations further increased across trimesters, particularly (but not consistently) in subordinates and in aborted pregnancies. Environmental stressors may modulate reproductive outcomes in meerkats through their influence on sex steroids and their effects on intragroup competition. The social and eco-physiological factors affecting intraspecific variation in reproductive output, even in obligate cooperative breeders, may be most apparent during extreme conditions, reflecting the benefits of long-term studies for assessing the impact of climate change.

The Adverse Effects of Auditory Stress on Mouse Uterus Receptivity and Behaviour

Stress during gestation has harmful effects on pregnancy outcome and can lead to spontaneous abortion. Few studies, however, have addressed the impact of gestational stress, particularly auditory stress, on behavioural performance and pregnancy outcome in mice. This study aimed to examine the effect of two types of gestational stress on uterus receptivity and behavioural performance. Pregnant C57BL/6 mice were randomly assigned to either auditory or physical stress conditions or a control condition from gestational days 12-16. The auditory stress regimen used loud 3000 Hz tone, while the physical stressor consisted of restraint and exposure to an elevated platform. Three behavioural tests were performed in the dams after weaning. Uterine receptivity was investigated by counting the number of sites of implantation and fetal resorption. Also, the offspring survival rates during the early postnatal period were calculated. Auditory stress caused an increase in anxiety-like behaviour, reduced time spent exploring new object/environment, and reduced balance when compared to the physical stress and control groups. Auditory stress also caused higher rates of resorbed embryos and reduction of litter size. Our results suggest that the adverse effect of noise stress is stronger than physical stress for both uterus receptivity and behavioural performance of the dams.

Seasonally different reproductive investment in a medium-sized rodent (Cavia aperea)

Pronounced seasonal variations in day length, temperature, and resource availability characterize the temperate regions and strongly influence the animals living in these environments. To survive and reproduce successfully, animals must allocate resources among competing physiological systems, and they usually adjust their time of breeding to the most adequate season. Here, we examined whether reproductive investment in the wild guinea pig (Cavia aperea) differs across seasons. We kept animals in combined indoor-outdoor enclosures under natural light and temperature year-round. We measured littering probability, litter size, and birth weight, as well as maternal weight loss during lactation. In addition, we measured ovulation rate as a parameter to adjust reproductive investment prenatally. Our data reveal strong seasonal variations in reproductive traits despite the fact that the animals reproduced year-round. The results show a reduced reproductive investment in winter, indicated by a lower litter size and birth weight of pups, whereas investment was highest in warm seasons (summer and autumn) with higher litter size and birth weight. Maternal weight loss in lactation was highest in cold seasons even if the litter size was lower. Furthermore, we found the regulation on the proximate level of the reproductive investment, the ovulation rate, to differ significantly between the seasons.

Does pregnancy coloration reduce female conspecific aggression in the presence of maternal kin?

Colour signals arise in a variety of sexual contexts, including advertising reproductive status. Despite potentially attracting negative attention from unrelated competitors, bright pregnancy coloration may communicate gestation to kin and potential fathers, thereby garnering aid during agonistic encounters and reducing the overall amount of aggression received by pregnant females. To establish whether this 'pregnancy sign' influences rates of aggression in the presence versus absence of maternal kin, we conducted behavioural observations of wild olive baboons, Papio anubis, in Gombe National Park, Tanzania, in groups composed of maternal kin and nonkin, and of captive baboons at the Southwest National Primate Research Center (SNPRC, San Antonio, TX, U.S.A.), in group enclosures that were unlikely to include close kin. At SNPRC, we also experimentally obscured the coloration of the pregnancy sign, and we performed playback experiments to measure male responses to the distress calls of pregnant females. Free-ranging female baboons experienced significantly less aggression from nonkin females after the onset of the pregnancy sign compared to the pre-pregnancy sign. In contrast, captive pregnant females whose pregnancy coloration was obscured with paint experienced significantly lower aggression rates from female conspecifics compared to pre-painting. Male aggression towards females did not differ in the presence versus absence of the pregnancy sign in either the wild or the captive population, although captive fathers paid significantly more attention to distress calls of pregnant cage-mates than they did to those of cycling cage-mates, suggesting a willingness to aid mothers that were carrying their unborn offspring.

Physiological effects of polybrominated diphenyl ether (PBDE-47) on pregnant gartersnakes and resulting offspring

Polybrominated diphenyl ethers (PBDEs) are used as flame retardants and are persistent contaminants found in virtually every environment and organism sampled to date, including humans. There is growing evidence that PBDEs are the source of thyroid, neurodevelopmental, and reproductive toxicity. Yet little work has focused on how this pervasive contaminant may influence the reproduction and physiology of non-traditional model species. This is especially critical because in many cases non-model species, such as reptiles, are most likely to come into contact with PBDEs in nature. We tested how short-term, repeated exposure to the PBDE congener BDE-47 during pregnancy affected physiological processes in pregnant female gartersnakes (thyroid follicular height, bactericidal ability, stress responsiveness, reproductive output, and tendency to terminate pregnancy) and their resulting offspring (levels of corticosterone, bactericidal ability, and size differences). We found potential effects of BDE-47 on both the mother, such as increased size and higher thyroid follicular height, and her offspring (increased size), suggesting the effects on physiological function of PBDEs do indeed extend beyond the traditional rodent models.

Maternal CD4⁺ and CD8⁺ T cell tolerance towards a fetal minor histocompatibility antigen in T cell receptor transgenic mice

Tolerance of the maternal immune system in pregnancy is important for successful pregnancy because the semiallogeneic fetus may be subject to antifetal responses. We examined maternal tolerance to the fetus using a murine system in which a model paternally inherited antigen, ovalbumin (OVA), is expressed exclusively in the fetus and placenta. By employing T cell receptor (TCR) transgenic mice specific for major histocompatibility complex class I- or class II-restricted epitopes of OVA (OT-I and OT-II) as mothers, we investigated the fate of fetus-specific CD8⁺ and CD4⁺ T cells, respectively, during gestation. Both OVA-specific CD8⁺ and CD4⁺ T cells displayed an activated phenotype in the peripheral lymphoid tissues of OVA-bred OT-I and OT-II mice, consistent with their encounter of fetal antigen. Whereas a small percentage of OVA-specific CD4⁺ T cells were deleted in the periphery and thymus of OVA-bred OT-II mice, with evidence of TCR downregulation in the remaining T cells, deletion and TCR downregulation were not observed in OVA-bred OT-I mice. Both CD4⁺ and CD8⁺ T cells upregulated inducible costimulator expression in response to the fetal antigen, but only CD4⁺ T cells consistently upregulated the inhibitory receptors programmed cell death 1 and cytotoxic T lymphocyte antigen-4. More regulatory T cells (Tregs) were present in pregnant OVA-bred than in WT-bred OT-II mice, revealing that Tregs expanded specifically in response to the fetal antigen. These data indicate that several mechanisms tolerize fetal antigen-specific maternal CD4⁺ T cells, whereas tolerance of fetal antigen-specific CD8⁺ T cells is less effective. The importance of these mechanisms is underscored by the finding that fetal loss occurs in OVA-bred OT-I but not OT-II mice.

Profiling Lgals9 splice variant expression at the fetal-maternal interface: implications in normal and pathological human pregnancy

Disruption of fetal-maternal tolerance mechanisms can contribute to pregnancy complications, including spontaneous abortion. Galectin-9 (LGALS9), a tandem repeat lectin associated with immune modulation, is expressed in the endometrium during the mid and late secretory phases and in decidua during human early pregnancy. However, the role of LGALS9 during pregnancy remains poorly understood. We used real-time PCR and immunohistochemical staining to analyze the expression of Lgals9/LGALS9 during mouse gestation as well as in human tissues obtained from normal pregnancy and spontaneous abortions. In mice, three Lgals9 splice variants were detected, the expression of which was differentially regulated during gestation. Furthermore, decidual Lgals9 expression was deregulated in a mouse model of spontaneous abortion, whereas placental levels did not change. We further found that the LGALS9 D5 isoform suppresses interferon gamma production by decidual natural killer cells. In human patients, six Lgals9 splice variants were detected, and a decrease in Lgals9 D5/10 was associated with spontaneous abortion. Altogether, these results show a differential regulation of Lgals9 isoform expression during normal and pathological pregnancies and designate Lgals9 as a potential marker for adverse pregnancy outcomes.

Gene expression profiling of mouse aborted uterus induced by lipopolysac charide

To identify genes that participate in the abortion process, normal pregnant uteri were compared to lipopolysaccharide (LPS)-induced abortion uteri. At day 6 of pregnancy, mice were treated with LPS at various time points to induce an abortion. Total RNAs were applied to a cDNA microarray to analyze genes with altered expression. At the early stage (2 hours) of LPS-induced abortion, upregulated genes were mainly composed of immune responsive genes, including Ccl4, Ccl2, Cxcl13, Gbp3, Gbp2, Mx2, H2-Eb1, Irf1 and Ifi203. Genes related to toll-like receptor signaling were also overexpressed. At late stages of abortion (12-24 hours), many genes were suppressed rather than activated, and these were mainly related to the extracellular matrix, cytoskeleton, and anti-apoptosis. Altered expression of several selected genes was confirmed by real time reverse transcription-polymerase chain reaction. The results demonstrated that many known genes were altered in the LPS-treated pregnant uterus, implying that the molecular mechanisms of the genes involved in LPS-induced abortion are complicated. Further analysis of this expression profile will help our understanding of the pathophysiological basis for abortion.

Neutralization of LPS or blockage of TLR4 signaling prevents stress-triggered fetal loss in murine pregnancy

Maternal stress can cause loss of both histocompatible (syngeneic) and histoincompatible (semiallogeneic) embryos in pregnant mice. Stress increases abortogenic Th1 cytokines and reduces levels of anti-abortogenic Th2 cytokines, progesterone levels, and T regulatory cell activity. While physiological levels of interferon-γ promote vascular remodeling at the feto-maternal interface, an overshooting Th1 cytokine response requires a Toll-like receptor (TLR)-mediated "danger signal" such as lipopolysaccharide (LPS). Interestingly, stress can enhance permeability of mucosal membranes to entry of bacterial products and promote transmucosal migration of commensal bacteria. We hypothesized that bacterial component such as LPS may provide the danger signal through which stress triggers maternal immune activation, subsequently resulting in fetal rejection. Blocking the TLR4 receptor for LPS or neutralization of LPS using bactericidal permeability increasing protein abrogate fetal loss due to sonic stress challenge in DBA/2J-mated CBA/J mice. These treatments prevented stress-triggered immune responses in the decidua, upregulated Treg cells, and reduced the frequency of mature dendritic cells in uterine-draining lymph nodes but not in the uterus. Interestingly, anti-TLR4 treatment only partly ameliorated stress-induced endocrine responses, such as increased hypothalamic corticotropin releasing hormone and vasopressin mRNA expression but not decrease of serum progesterone. Galectin-1 knock-out mice were more susceptible to stress-triggered complete implantation failure rather than fetal loss, which was also abolished by LPS neutralization. Insights provided in this paper shed new light on the mechanisms by which stress affects pregnancy outcome and introduce microbial-derived LPS as a mediator within the cascade of stress-triggered immune and endocrine events during pregnancy.

Progesterone induces a switch in oligosaccharyltransferase isoform expression: consequences on IgG N-glycosylation

The presence of additional N-glycans in the Fab region of IgG has shown to dramatically modify the properties and functionality of these molecules including changes in antibody affinity and stability. However, the underlying molecular mechanism responsible for the presence or absence of these glycans remains unknown. Polypeptide N-linked glycosylation is catalyzed in the lumen of the endoplasmic reticulum by the oligosaccharyltransferase complex. Mammalian cells can express two isoforms of the oligosaccharyltransferase catalytic subunit (STT3-A and STT3-B), which are endowed with distinct enzymatic properties. In this work we employed a murine hybridoma cell culture to study whether the expression of STT3 isoforms could be modulated by progesterone, thus altering the pattern of IgG N-glycosylation. We found that progesterone induces a switch of STT3 isoform expression, increasing IgG N-glycosylation. These effects were dependent on the progesterone-induced blocking factor (PIBF), whose concentration was modulated by progesterone. PIBF was previously found to be an immunomodulatory molecule relevant for the maintenance of pregnancy. We concluded that the STT3-B/STT3-A ratio modulates the N-glycosylation level of IgG, in agreement with previous data showing that full N-glycosylation of polypeptides requires cooperation between both catalytic isoforms. This work provides the first evidence that STT3 isoforms can be hormonally modulated, with marked consequences on IgG N-glycosylation.

Natural Killer cells: keepers of pregnancy in the turnstile of the environment

During early pregnancy, an orchestrated endocrine-immunological scenario of maternal adaptation toward tolerance of the semiallogeneic fetus is required. Mechanisms preventing fetal loss by protecting the immune privilege of the gravid uterus, i.e. Galectin-1 or regulatory T cells, have recently been identified. Further, the presence of a unique population of Natural Killer (NK) cells, in humans identified by their CD56(+++)Galectin (Gal)-1(+)CD16(-) phenotype in the uterine lining (decidua), has been proposed to be a pivotal aspect of maternal adaptation to pregnancy. Decidual NK (dNK) cells comprise the largest population of immune cells during the first trimester in human decidua and control trophoblast invasion and vascular remodeling through their ability to secrete an array of angiogenesis-regulating molecules, chemokines and cytokines. A wealth of environmental factors, such as smoking, altered nutrition, pollution or stress has been proposed to peril not only pregnancy, but also fetal development. Further, published evidence supports that NK cells act as sentinel cells and environmental challenges can change their phenotype, e.g. via epigenetic pathways. We here review the effect of environmental factors, largely stress perception, on NK cells and its implication for pregnancy, fetal development and general health. As NK cells may not only be passive responders to the environment, but can also be 'educated and licensed', we propose novel strategies aiming to take advantage of the versatility of NK cells in maintaining immunosurveillance and tissue homeostasis.

Effect of stress on eotaxin and expression of adhesion molecules in a murine model of allergic airway inflammation

Recently we have shown that sound stress enhances allergic airway inflammation in a combined murine model. In the current study we investigated mediating factors and early kinetics of stress exacerbated allergic airway inflammation. Stress significantly increased allergen induced airway inflammation as identified by leukocyte numbers in BAL fluids. Eotaxin levels from stressed mice were significantly higher 24 h after stress. No differences were found for vascular or cellular adhesion molecule expression or cytokine levels. Our data indicate that the effect of stress on allergic airway inflammation might be mediated by the chemoattractant eotaxin, while Th2 cytokines and expression of adhesion molecules seem not to be differently regulated in stressed and non-stressed mice.

High expression of survivin and down-regulation of Stat-3 characterize the feto-maternal interface in failing murine pregnancies during the implantation period

The materno-fetal interface has for long been considered as an immune privileged biological site and thus understanding the mechanisms underlying fetal survival have been the focus of intense research. In adults, survivin and Stat-3 proteins are involved in tolerance as well as the induction of apoptosis. However, the role of these molecules in pregnancy and development has not been addressed. We have evaluated the expression of survivin and Stat-3 in allogeneic mouse models of low abortions (CBA/J x Balb/c), abortion prone (CBA/J x DBA/2J) and stress-triggered abortions from DBA/2J-mated CBA/J mice. We show that survivin is over-expressed in abortion-prone mating on gestation day 7.5. This effect was also found in stress-exposed mice, whereas expression was low in normal pregnancy mice. The phosphorylated Stat-3 (p-Stat-3) was down regulated in high abortion mating compared with low abortion mating, CBA/J x Balb/c. The level of apoptosis was similar in the three groups studied. Our results suggest that high expression of survivin and low expression of p-Stat-3 are involved in pregnancy loss in mice.

Reduced uterine indoleamine 2,3-dioxygenase versus increased Th1/Th2 cytokine ratios as a basis for occult and clinical pregnancy failure in mice and humans

PROBLEM

Indoleamine 2,3-dioxygenase (IDO) expression in fetal trophoblast and decidual antigen-presenting cells has been proposed to inactivate maternal T cells and thereby prevent rejection of the "fetal allograft" in early pregnancy. Psychic stress has been proposed to cause miscarriages as well as infertility, at the same time in pregnancy when blockade of IDO causes loss, but the suggested mechanism of stress-triggered loss has been an increased ratio of pro-rejection Th1-type cytokines to anti-rejection Th2/3 cytokines. Could stress act by reducing IDO expression?

METHODS

Using DBA/2-mated A/J mice where stress causes early pregnancy failure, we examined the role of stress in reducing IDO versus increasing Th1/Th2 ratio in deciduas. IDO loss was also examined in human decidua associated with pregnancy failure.

RESULTS

A post-implantation sonic stress increased the pregnancy failure rate, increased the Th1/Th2 ratio, but did not reduce IDO. IDO was reduced, and Th1/Th2 ratios increased in A/J mice pre-immunized against paternal DBA/2 antigens, and concomitant stress increased these effects. The rate of pregnancy failure was not further increased consistent with recent discoveries of factors that limit the impact of Th1 cytokines at the feto-maternal interface. In deciduas from spontaneous miscarriage patients, IDO(+) cell frequencies were low in only 30% of patients. CD3(+) T-cell numbers and percentage terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick end-labelling (TUNEL)(+) apoptotic T cells were increased, but the level of IDO did not correlate with likelihood of apoptosis.

CONCLUSIONS

Loss of an allogeneic embryo in early pregnancy is more likely to be due to a high Th1/Th2 ratio than loss of putative protection by IDO.

The endocrinology of pregnancy and fetal loss in wild baboons

An impressive body of research has focused on the mechanisms by which the steroid estrogens (E), progestins (P), and glucocorticoids (GC) ensure successful pregnancy. With the advance of non-invasive techniques to measure steroids in urine and feces, steroid hormones are routinely monitored to detect pregnancy in wild mammalian species, but hormone data on fetal loss have been sparse. Here, we examine fecal steroid hormones from five groups of wild yellow baboons (Papio cynocephalus) in the Amboseli basin of Kenya to compare the hormones of successful pregnancies to those ending in fetal loss or stillbirth. Using a combination of longitudinal and cross-sectional data, we analyzed three steroid hormones (E, P, GC) and related metabolites from 5 years of fecal samples across 188 pregnancies. Our results document the course of steroid hormone concentrations across successful baboon pregnancy in the wild and demonstrate that fecal estrogens predicted impending fetal loss starting 2 months before the externally observed loss. By also considering an additional 450 pregnancies for which we did not have hormonal data, we determined that the probability for fetal loss for Amboseli baboons was 13.9%, and that fetal mortality occurred throughout gestation (91 losses occurred in 656 pregnancies; rates were the same for pregnancies with and without hormonal data). These results demonstrate that our longstanding method for early detection of pregnancies based on observation of external indicators closely matches hormonal identification of pregnancy in wild baboons.

Stress and substance P but not the substance P-metabolite SP5-11 trigger murine abortion by augmenting TNF-alpha levels at the feto-maternal interface

In a well-established murine abortion model, stress is thought to trigger fetal rejection by inducing a proinflammatory immune response via substance P (SP), being tumour necrosis factor (TNF)-alpha-producing CD8+ T cells involved. Interestingly, the SP metabolite SP5-11 also binds to SP receptors and mediates SP-like effects on immune cells at sites of inflammation. No data were available regarding the effects of SP5-11 on pregnancy outcome in the CBA/J x DBA/2J abortion-prone combination. We investigated the influence of SP5-11 in contrast to stress or SP on the abortion rate and the cytokine production by lymphocytes as well as on the levels of CD8+ T cells. Stress and SP boosted the abortion rate and increased the percentage of type 1 [TNF-alpha, interferon-gamma, interleukin (IL)-12] and type 2 (IL-4 and IL-10) cytokine-producing lymphocytes in blood and decidua, predominantly CD8+ T cells. Interestingly, SP5-11 did not significantly affect the abortion rate or cytokine production in the decidua, while increasing the Th1 and Th2 cytokine production systemically. Our data suggest that stress and SP induce abortion by augmenting the local levels of TNF-alpha, which seems therefore to be a potent trigger of miscarriage. On the contrary, the SP metabolite SP5-11 only affects the systemic cytokine production without boosting the abortion rate in this experimental model.

Is intravenous immunoglobulins (IVIG) efficacious in early pregnancy failure? A critical review and meta-analysis for patients who fail in vitro fertilization and embryo transfer (IVF)

PROBLEM

Intravenous Immunoglobulins (IVIG) are widely used off label in the treatment of early reproductive failure. As IVIG is expensive, and may have side-effects, evidence of efficacy is needed. Previous results have suggested that the pre-conception treatment of primary recurrent abortion patients might be effective, but the data set has been too small for adequate statistical power. More recently it has been suggested that IVIG may improve the success rate of in vitro fertilization and embryo transfer (IVF) in patients with prior IVF failures, but clinical trials have given conflicting results that need explanation. Systematic reviews generating inconclusive results have focused on methodological rigor to the exclusion of biological plausibility.

METHODS

Review of current basic science of design, measurement, and evaluation of clinical trials and basic science mechanisms providing a rationale for treatment. Meta-analysis of published randomized controlled and cohort-controlled trials (updated with two unpublished data sets) evaluating IVIG treatment in IVF failure patients. Live birth rate was used as the most relevant endpoint. The ability of different sources of IVIG to suppress natural killer (NK) cell activity was determined using a standard (51)Cr-release assay in vitro.

RESULTS AND CONCLUSIONS

Meta-analysis of three published randomized controlled trials (RCTs) of IVIG in IVF failure patients shows a significant increase in the live birth rate per woman (p = 0.012; Number Needed to Treat for 1 additional live birth, NNT = 6.0 women). Using live birth rate per embryo transferred, and adding data from two cohort-controlled trials to the meta-analysis further supports this conclusion (overall p = 0.000015, NNT = 3.7 women). Relevant variables appear to include properties and scheduling of the IVIG, and selection of patients with abnormal immune test results. Different IVIG preparations vary significantly in their ability to suppress NK activity in vitro. A rationale for use of IVIG is provided by a review of mechanisms of IVIG action and mechanisms underlying failure of chromosomally normal embryos.

Maternal Immunopotentiation Affects Caspase Activation and NF-kappaB DNA-binding Activity in Embryos Responding to an Embryopathic Stress

PROBLEM

Increased embryonic resistance to teratogenic stresses as a result of maternal immunopotentiation is associated with a decrease in the intensity of teratogen-induced apoptosis in target embryonic structures. These findings suggest that this effect of maternal immunopotentiation might be realized through modification of the expression of molecules regulating the teratogen-induced apoptotic process. To examine this possibility, we evaluated caspases 3, 8 and 9 activation as well as nuclear factor (NF)-kappaB DNA-binding activity in the embryos of immunopotentiated mice exposed to cyclophosphamide (CP).

METHODS OF STUDY

The rate of resorptions and the proportion of malformed fetuses in CP-treated mice were recorded on day 19 of pregnancy. Activity of caspases was tested in cytoplasmic extracts collected from the embryonic brain 24 hr after CP treatment using appropriate fluorometric kits, whereas NF-kappaB DNA-binding activity was evaluated in nuclear extracts using the electrophoretic mobility shift assay.

RESULTS

As in our previous studies, immunopotentiated CP-treated females exhibited a lower rate of resorptions or fetuses with open eyes than their non-immunopotentiated counterparts. In parallel, we observed that maternal immunopotentiation normalized the CP-induced activation of the tested caspases as well as the CP-induced suppression of NF-kappaB DNA-binding activity.

CONCLUSIONS

As caspases act as inducers of apoptosis, and NF-kappaB acts in CP-treated embryos as an apoptosis suppressor, the above results suggest that maternal immunopotentiation might affect embryonic sensitivity to embryopathic stresses via NF-kappaB- and caspases-associated pathways.

Ecology of Danger-dependent Cytokine-boosted Spontaneous Abortion in the CBA × DBA/2 Mouse Model. I. Synergistic Effect of LPS and (TNF-α + IFN-γ) on Pregnancy Loss

PROBLEM

Previous data have shown "danger" signals, such as bacterial lipopolysaccharide (LPS) acting via toll-like (tlr) receptors are required for early pregnancy failure in several murine abortion models. Indeed, the abortion rate increased in the CBA x DBA/2 model after a gestation day (gd) 7.5 injection of tumour necrosis factor (TNF)-alpha + interferon (IFN)-gamma only if the LPS-tlr signalling pathway was intact. High rates of cytokine-boosted abortion >80% loss can be achieved in certain animal colonies, that have a high endogenous (spontaneous) rate of resorption (30-50%). A specific role for LPS has been postulated to determine both the endogenous and cytokine-boosted losses.

METHODS

To test the role of LPS in spontaneous and cytokine-boosted abortions, recombinant TNF-alpha + IFN-gamma, and LPS were injected in different doses and sequences intraperitoneally (i.p.) into CBA x DBA/2 mated mice in the Toronto General Research Institute animal facility where the endogenous abortion rate is <30%. The effects of poly IC, a tlr3 agonist that induces IFN-gamma that can reverse LPS-induced tolerance, and effects of anti-MD-1 on TNF-alpha induction by LPS, poly IC, CPG, or HSP in vitro were also examined.

RESULTS

A high endogenous rate of loss similar to that seen in Clamart could be achieved by increasing exposure to LPS on the morning after mating (gd 0.5). The magnitude by which the abortion rate could be increased by an i.p. injection of 2000 u TNF-alpha + 1000 u IFN-gamma on gd 7.5 was independent of the endogenous rate of loss, and could not be increased by doubling the dose. One microgram of LPS given on day 7.5 achieved a similar rate of loss, and if given with the cytokines, synergistically boosted the rate of loss to near Clamart rates. LPS given 1 day prior to the cytokines abrogated the cytokine effect, whereas LPS given day 0.5 had no significant effect on the response to day 7.5 cytokine injection. Blocking MD-1 inhibited TNF-alpha stimulation by poly IC, LPS, CPG, or HSP in vitro, and reduced abortion rates. Poly IC did not avert LPS-type tolerance effects in vivo.

CONCLUSIONS

High endogenous rates of abortion in the CBA x DBA/2 model may be explained by exposure to LPS at the time of mating. Increased rates of loss triggered by cytokines later in pregnancy may depend on increased absorption of LPS from intestinal flora.

Anesthesia and acoustic stress-induced intra-uterine growth retardation in mice

Stress interferes with reproduction, adversely influencing implantation and fetal growth, and sometimes even leading to abortion. Here, we attempted to evaluate the early gestational effects of uncomfortable sound on pregnant mice and their offspring. Ten-week-old pregnant Jcl:ICR mice were exposed to sound (100 dB, random frequency between 9-34 kHz) for 8 hours on the 3(rd), 5(th) and 7(th) gestational days (GD). The effects of general anesthesia were also investigated, with or without acoustic stress. All groups were examined on the 18(th) GD for fetal growth. Fetal weight, number of ossified sacrococcygeal vertebrae and placental weight were all significantly reduced (P<0.0001) when stress was induced on the 7(th) GD, but not on the 3(rd) or 5(th) GD. This intra-uterine growth retardation (IUGR) was significantly inhibited by general anesthesia (P<0.0001), although general anesthesia alone induced significant IUGR (P<0.0001) when compared with control mice. This suggests that acoustic exposure indirectly exerts an effect on fetal growth, possibly via a psycho-maternal pathway. We also found that analysis of the number of ossified sacrococcygeal vertebrae is the most sensitive tool for the study of IUGR.

Effects of restraint stress in gestation: implications for rodent developmental toxicology studies

Restraint has been used as a procedure to study the effects of stress on gestation outcome in rodents. The effects of restraint could potentially be used as a model for the impact of general stress produced by high doses of toxicants and other interventions. In mice, restraint in the peri-implantation period leads to implantation failure, and restraint at appropriate times in organogenesis produces cleft palate, supernumerary ribs, and resorption. In rats, there is some evidence for an association with restraint for implantation failure, but not for the morphological anomalies. Restraint in late gestation alters adult sexual behavior of male rat offspring, but consequences for their fertility are not known. Intrauterine growth retardation is not commonly associated with gestational restraint. In the few studies where they have been directly compared, different restraint procedures produced graded, qualitatively different, or no effects. Adrenocortical hormones have been implicated as mediating the effect of restraint on cleft palate, but not on supernumerary ribs, implantation failure, or sexual differentiation. Given the variety of restraint procedures and the varying species-dependent consequences, it is not possible to infer a generalizable pattern of developmental effects due to gestational stress from the restraint literature. As an alternative approach, contemporary methods in gene expression and developmental biology could profitably be applied to understanding different patterns of stress-mediated effects of toxicant exposures on intrauterine development.

Is there a place for immunomodulation in assisted reproduction techniques?

We briefly review the history of the concepts of the materno foetal relationship, and the (various) rationales which have been used to justify lymphocyte alloimmunisation (LA) as a treatment for recurrent spontaneous abortion of putative immune origins. The effectiveness of the treatment is at best dubious and limited to a small number of women for which there is no real positive selection rationale, at worst it is not efficient. The rationales themselves are rather "evolutive". The present one is to use the Th1:Th2 paradigm and, thus, to propose to "dampen NK activity" in abortion prone women and this concept has been extended by some to implantation failure. We briefly review why the Th1:Th2 paradigms is no longer fully valid, describe briefly why it is inappropriate for implantation, and conclude that alloimmunisation should no longer be proposed for RSA, hence, more for implantation failure. We, however, do not reject immunotherapy, but we believe that molecular and cellular defects specific approaches should be used, tailored for the specific pathway whose disruption cause the clinical symptom.

Topical minoxidil counteracts stress-induced hair growth inhibition in mice

Stress has long been suspected as a possible cause of hair loss in various species, even though convincing experimental evidence has not been available. Recently, we have shown in a murine model that sonic stress alters hair growth and cycling in vivo, and have postulated the existence of a 'brain-hair follicle axis' (BHA). In order to study whether a clinically available and widely used topically active hair growth stimulator mitigates stress-triggered hair growth inhibition in this stress model, we have applied a 5% minoxidil solution. Female CBA/J mice were depilated and randomized in to two groups: control (n = 20) and sonic stress (n = 20). These groups were further divided and either treated daily with 5% minoxidil solution or vehicle alone. The stress group was exposed to sonic stress for 24 h starting 14 days after anagen induction by depilation. All mice were sacrificed 16 days after the depilation and assessed by quantitative histomorphometry. Sonic stress significantly increased the number of hair follicles with apoptotic cells and inhibited intrafollicular keratinocyte proliferation. In addition, the number of clusters of perifollicular MHC class II+ cells and degranulated perifollicular mast cells was significantly enhanced in the stressed mice. In accordance with previous findings, all stressed mice showed an advanced hair cycle progression towards catagen. All of these stress-induced hair growth inhibitory changes along the BHA were down-regulated by topical minoxidil application. This encourages one to explore clinically whether topical minoxidil is a safe and effective pharmacologic tool for the management of stress-associated telogen effluvium in humans.

Shall We properly Re-examine the Status of Allogeneic Lymphocyte Therapy for Recurrent early Pregnancy Failure?

PROBLEM

How to evaluate immunological therapy advocated for recurrent spontaneous abortion and implantation failure. I was invited to comment on the opinion article of Chaouat (AJRI December 2003).

METHODS

A critical examination of key beliefs and application of the principles of evidence and logic utilizing current data.

RESULTS AND CONCLUSIONS

Although rationale has no bearing on efficacy of proposed treatments and is not sufficient justification for routine practice, insufficient attention to data concerning patient selection, insufficient attention to treatment methodology, and lack of full disclosure in some clinical trials needs to be corrected. A more systematic collection of follow-up data is needed.

Stress et implantation

Spontaneous abortion is the most common adverse pregnancy outcome, and stress has been suggested to be abortogenic in mice and humans. Stress-and/or pregnancy-related hormones (corticotropin releasing hormone, adrenocorticotropin, and progesterone) might interact with peripheral and local immunocompetent cells, such as certain T cell, mast cells or NK cells, and result in changes of cytokine production. In an established murine model, abortions can be triggered by exposing the mice to stress during early gestation. Recent data from this model indicated that increased levels of abortogenic Th1 cytokines, a decrease of progesterone and thus, PIBP were incongruous with successful pregnancy maintenance. Supplementation of progesterone exerts a pregnancy protective effect by induction of a pregnancy-protective Th2 biased immune response. Interestingly, data from a prospective study on human pregnancy revealed that women with a clinically normally progressing pregnancy but low levels of progesterone during the first trimester eventually suffered from a miscarriage. These data indicate that stress may lead to increase abortions by altering the endocrine system, which triggers an immune bias towards an abortogenic cytokine profile. Progesterone may be a good marker to identify a putative thread of a miscarriage in human and progesterone replacement therapy may abrogate this thread by inducing a Th2 biased immune response from the decidua.

Should We Re-Examine the Status of Lymphocyte Alloimmunization Therapy for Recurrent Spontaneous Abortion?

PROBLEM

In the human, lymphocyte alloimmunization immunotherapy (IT) has been proposed as a treatment for recurrent spontaneous abortion (RSA). This treatment has been the subject of debate for a long period of time. Recently, it has been proposed to extend such a treatment for implantation failure in humans, and I was asked to express my opinion on this topic.

METHODS

I reviewed the evolution and theories and current paradigms in Reproductive Immunology and rationales proposed for IT. New discoveries show the complexity of implantation as a step by step developmental event, in mice and humans, and as such led me to re-examine paradigms currently evoked for extension of IT to implantation. Such a re-examination obviously leads me to re-question the basis of IT for RSA itself.

CONCLUSIONS

I conclude that the Th1/Th2 paradigm, evoked as the current basis for IT, and as useful as it has been to explain pregnancy, is no longer sufficient. It is especially insufficient to explain the process of implantation, which involves inflammatory molecules and cannot fit in such a scheme. It ensues that alloimmunization has no scientific rationale for the treatment of human implantation as a whole, and should not be applied broadly at such a stage of pregnancy. Furthermore, its use in RSA should be re-examined.

The progesterone derivative dydrogesterone abrogates murine stress-triggered abortion by inducing a Th2 biased local immune response

Stress is known to induce abortions in mice and humans, putatively via increased levels of abortogenic Th1 cytokines and a decrease of progesterone. Adequate levels of progesterone exert an antiabortive response through binding to the progesterone-receptor, which induces the release of progesterone-induced blocking factor (PIBF) from lymphocytes. PIBF is highly pregnancy-protective by induction of a Th2 biased immune activity. The aim of this study was to investigate the effect of the progesterone derivative dydrogesterone (6-dehydro-retroprogesterone) in stress-triggered murine abortion. DBA/2J-mated CBA/J female mice were randomized in different groups: two groups were treated with different dydrogesterone dosages in a single injection before exposure to sound stress on Day 5 of pregnancy, one group was exposed to stress without dydrogesterone treatment, the fourth group received no stress and no dydrogesterone. On gestation Day 13, a highly elevated abortion rate was detected in stressed mice compared to control mice. Stressed animals presented lower levels of progesterone and PIBF in plasma and a reduced staining intensity of progesterone receptor at the feto-maternal interface. Injection of dydrogesterone abrogated the effect of stress on the abortion rate. Further, dydrogesterone increased levels of plasma PIBF in stressed mice, but did not affect progesterone levels. Interestingly, dydrogesterone dramatically increased the percentage of IL-4 positive decidual immune cells in stressed mice. Our data suggest that dydrogesterone abrogates stress-triggered abortion by inducing a Th2 biased local immune response.

Stress enhances airway reactivity and airway inflammation in an animal model of allergic bronchial asthma

OBJECTIVE

Despite the long-standing clinical assumption that stress and asthma morbidity are associated, convincing experimental evidence on mechanisms has been unavailable. A wide range of immunological, endocrinological, and neuronal pathways are known to mediate and modulate a systemic stress response. Interestingly, most of these mediators play a crucial role in initiating and perpetuating symptoms associated with bronchial asthma. To explore potential mechanisms linking stress to asthma exacerbation we developed an animal model that combines allergic airway inflammation and exposure to stress.

METHODS

CBA/J mice were sensitized by intraperitoneal injection of ovalbumin (OVA) and challenged with OVA aerosol via the airways. Additionally, some mice were stressed by exposure to an ultrasonic stressor. Airway hyperreactivity (AHR) was measured in vitro by electric field stimulation (EFS) of tracheal smooth muscle elements. Bronchoalveolar lavage fluid (BAL) was obtained and cell numbers determined. Cytokine levels of IL-4, IL-5, and IFN-gamma in BAL were determined by ELISA.

RESULTS

Our findings demonstrate that exogenously applied stress dramatically enhances airway reactivity in OVA-sensitized and challenged mice. Further, stress significantly increases allergen-induced airway inflammation identified by increased leukocyte (ie, eosinophil) numbers in bronchoalveolar lavage fluids.

CONCLUSIONS

We found further evidence that stress can indeed exacerbate airway hyperreactivity and airway inflammation in an animal model of allergic bronchial asthma and now introduce a novel murine model to identify stress-triggered pathways, including mediators as neurohormones, neuropeptides, and markers of inflammation.

L’impact du stress dans le dialogue materno-fœtal : une approche immunologique

Pregnancy is controlled primarily, though not exclusively, by a delicate equilibrium between locally acting growth factors and cytokines, some under steroid control. The hypothesis considered here is that stress is able to influence the equilibrium between cytokines and thus lead to abortions or implantation failure. We thus detailed the studies on that topic in order to explore the psycho-neuro-immunological mechanisms concerned. The duration of stress, the patient's strategy for coping with this and the social context might be able to produce some opposite immunological effects. Thus, the link between stress and the immunological events induced is complex, and much care is needed for such patients.

MD-1 is a critical part of the mechanism causing Th1-cytokine-triggered murine fetal loss syndrome

PROBLEM

Fetal loss syndrome (abortion/resorption) occurring on or after gestation day (gd) 9.5 in CBA/JxDBA/2 matings is dependent upon presence of TNF-alpha + IFN-gamma, which act by increasing expression of fg12 prothrombinase at the feto-maternal interface. The magnitude by which the abortion rate can be boosted by an injection of these cytokines on gd 7.5 depends on endogenous rate of loss, and appears to depend on microbial flora. Is cytokine-triggered abortion dependent upon a third signaling pathway that senses 'danger'?

METHODS

Female CBA/J were mated to DBA/2 males and, C57B1/6 and C57B1/6 TNFalphaR1-/-Mak were mated to C57B1/6 control or TNFalphaR1-/-Mak males. LPS from Escherichia coli and Salmonella enteritidis, or the combination of TNF-alpha + IFN-gamma, was injected to stimulate abortions. The effect of anti-MD-1, which interferes with expression of CD14 and, hence, with signaling by LPS via the CD14-tlr4 complex, on TNF-alpha + IFN-gamma was tested. The presence of MD-1 in the uterus was evaluated by in situ hybridization, and effect of lipopolysaccharide (LPS) on mice lacking TNF-alphaR1 was tested.

RESULTS

Anti-MD-1 completely abrogated TNF-alpha + IFN-gamma-induced abortions. MD-1 was expressed on trophoblast and in deciduas on gd 8.5 but LPS could not abort mice that lacked the type 1 receptor for TNF-alpha. Pregnant CBA/J females had classical resorptions (abortions) countable on gd 13.5-14.5 in response to LPS from E. coli or S. enteritidis, but C57B1/6 strain mice resorbed only in response to the latter, and E. coli LPS appeared to induce 'occult' losses. 'Occult' loss did not require TNF-alphaR1.

CONCLUSIONS

TNF-alpha + IFN-gamma could not induce murine abortions without co-presence of a 'danger' signal such as LPS acting via CD14 on toll receptors, and LPS could not act without co-signaling by TNF-alpha. Classical resorptions/abortions and 'occult' losses have a different mechanism in these models as reflected in type of endotoxin and requirement for TNF-alphaR1 signaling.

Th1 cytokines and the prothrombinase fgl2 in stress-triggered and inflammatory abortion

PROBLEM

The immune system contributes to the outcome of pregnancy by complex immunological interactions. Cytokines especially influence the immune milieu pro or contra pregnancy. T helper 1 (Th1) cytokines [tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma)] cause inflammation and together are thought to threaten the maintenance of pregnancy. It has been proposed that increased levels of these Th1 cytokines activate coagulation via up-regulating the novel prothrombinase, fgl2. This study further investigates the Th1 cytokine up-regulation of fgl2 expression in a pathophysiological, stress induced abortion model, and an inflammatory, interleukin-12 (IL-12) triggered abortion model.

METHOD

The DBA/2J-mated CBA/J female mice were exposed to sonic sound stress or were injected with IL-12 during early gestation. On day 13.5 of pregnancy the uteri were removed and the resorption rate was calculated. We evaluated TNF-alpha, IFN-gamma, fgl2 as well as IL-12 messenger RNA (mRNA) expression in decidual samples of all mice by quantitative, real-time polymerase chain reaction (PCR).

RESULTS

A similar resorption rate of 24% was detected in stressed mice, as well as in IL-12 injected mice compared with approximately 11% in non-stressed, non-injected control mice. In stressed mice compared with controls, we observed on day 13.5 up-regulated TNF-alpha, unchanged IFN-gamma down-regulated fgl2, and a slightly increased levels of IL-12. In the IL-12 triggered abortion model, we observed up-regulated levels of TNF-alpha, IFN-gamma and fgl2.

CONCLUSION

These novel data suggest two distinct cytokine patterns leading to similar abortion rates. A physiological cascade associated with up-regulation of TNF-alpha, and an IL-12-triggered cascade characterized by persistent up-regulation of TNF-alpha and IFN-gamma as well as a persistent increase in fgl2.

Stress inhibits hair growth in mice by induction of premature catagen development and deleterious perifollicular inflammatory events via neuropeptide substance P-dependent pathways

It has been much disputed whether or not stress can cause hair loss (telogen effluvium) in a clinically relevant manner. Despite the paramount psychosocial importance of hair in human society, this central, yet enigmatic and controversial problem of clinically applied stress research has not been systematically studied in appropriate animal models. We now show that psychoemotional stress indeed alters actual hair follicle (HF) cycling in vivo, ie, prematurely terminates the normal duration of active hair growth (anagen) in mice. Further, inflammatory events deleterious to the HF are present in the HF environment of stressed mice (perifollicular macrophage cluster, excessive mast cell activation). This provides the first solid pathophysiological mechanism for how stress may actually cause telogen effluvium, ie, by hair cycle manipulation and neuroimmunological events that combine to terminate anagen. Furthermore, we show that most of these hair growth-inhibitory effects of stress can be reproduced by the proteotypic stress-related neuropeptide substance P in nonstressed mice, and can be counteracted effectively by co-administration of a specific substance P receptor antagonist in stressed mice. This offers the first convincing rationale how stress-induced hair loss in men may be pharmacologically managed effectively.

Is there any evidence for immunologically mediated or immunologically modifiable early pregnancy failure?

PURPOSE

Human reproduction is an inefficient process. There is a high rate of loss of early pregnancies, often before the mother (or physician) knows she is pregnant. Genetic abnormalities can explain much of the wastage, but can it explain all of the failures? As embryos bear paternal and embryonic antigens foreign to the maternal immune system, could some otherwise normal embryos be "rejected"?

METHODS

Critical review of existing data.

RESULTS AND CONCLUSIONS

Otherwise normal embryos can fail prior to implantation, at implantation, in the periimplantation period as occult/chemical pregnancies, and as clinically evident miscarriages. The maternal immune system and its products (e.g., cytokines) can have innocent bystander effects, and a good case for direct recognition and "rejection" can also be made. The tools needed for accurate clinical diagnosis of such situations require further development and validation. Deliberate modification of the maternal host defence system can improve the chance of success, but the best evidence for efficacy of immunotherapeutic interventions is the situation of recurrent spontaneous abortions, which constitutes only a small percentage of losses. There is also evidence of clinical efficacy for several types of treatment to improve implantation and early pregnancy success.

The expression of T-cell surface antigens CTLA-4, CD26, and CD28 is modulated by inhibition of dipeptidylpeptidase IV (DPP IV, CD26) activity in murine stress-induced abortions

Inhibition of DPP IV has been shown to abrogate the stress-related increase in murine abortions and a concomitant increase in gamma-interferon. The aim of the present study was to investigate a potential impact of the DPP IV inhibitor Isoleucine Cyanopyrrolidide on the expression of surface antigens involved in T-cell responses. DBA/2-mated CBA mice were stressed on day 5.5 of pregnancy and received injections of a DPP IV inhibitor. On day 13 of gestation, the animals were sacrificed and the percentage of abortions was determined. As shown before, stress failed to boost the abortion rate in mice receiving the DPP IV inhibitor. In stressed animals, a lower surface density of CTLA-4 on decidual CD26-positive lymphocytes was observed than in non-stressed animals. Inhibition of DPP IV restored CTLA-4 surface density to normal and decreased surface expression of CD26 and CD28 on decidual lymphocytes irrespective of stress exposure. These observations suggest that a modulation of T-cell surface antigens expression due to inhibition of DPP IV activity may contribute to the potent anti-abortogenic effect observed here.

The role of pro- and anti-apoptotic molecular interactions in embryonic maldevelopment

PROBLEM

Pregnancy loss and the occurrence of inborn structural anomalies are often preceded by excessive apoptosis in targeted embryonic and extraembryonic tissues. Apoptogenic stimuli activate both death and survival, signaling cascades consisting of molecules acting as activators and effectors, or negative regulators of apoptosis. The interplay between these cascades determines whether the cell which is exposed to an apoptogenic stimulus dies or survives. This review summarizes the functioning of pro- and anti-apoptotic molecules in embryos responding to various teratogens. The effect of potentiation of the maternal immune system on these molecules is also discussed.

METHODS OF STUDY

The data on the functioning of various pro- and anti-apoptotic molecules in embryos exposed to various developmental toxicants, and embryos developing in a diabetic environment are reviewed. Techniques such as the TUNEL method, DNA fragmentation assay, electromobility shift assay (EMSA), fluorometric assay, immunohistochemistry, Western blot, In situ hybridization, have been used in our studies to detect apoptosis, and evaluate the functioning of molecules such as TNFalpha, caspases, NF-kappaB and IkappaB, p53, and bcl-2 in different embryonic and extraembryonic tissues.

RESULTS

Our and other data summarized in this review have demonstrated that the doses of developmental toxicants required to induce pregnancy loss and gross structural anomalies induce excessive apoptosis shortly after treatment. Depending on the intensity and type of targeted tissues, this apoptosis was accompanied by alterations in the activity of the molecules which act as activators and effectors (e.g. caspase 3, caspase 8, caspase 2, p53) or negative regulators (bcl-2, NF-kappaB) of apoptosis. Maternal immunopotentiation, which decreases the level of induced and spontaneous pregnancy loss and the incidence and severity of teratogen-induced structural anomalies has been shown to modulate the expression of these molecules both in embryonic tissues and at the feto-maternal interface.

CONCLUSIONS

The data presented in this review suggest that molecules such as TNFalpha, caspase 3, caspase 8, NF-kappaB, p53 and bcl-2, which are involved in the regulation of apoptosis, may also be involved in determining the sensitivity of the embryo to developmental toxicants. Maternal immunopotentiation may modulate the functioning of these molecules.

Thinking outside the box: mechanisms of environmental selective pressures on the outcome of the materno-fetal relationship

PROBLEM

Study of mechanisms causing spontaneous abortion of the vascularized placenta have focused primarily on the feto-maternal immunological relationship within the pregnant mother. The Th1 cytokines such as tumor necrosis factor (TNF)-alpha + interferon (IFN)-gamma derived in part from natural killer (NK) and NKgammadeltaT cells have been implicated in causing abortion via up-regulation of the novel prothrombinase fgl2 at the feto-maternal interface; Th2/3 cytokines such as interleukin (IL)-10, progesterone-induced blocking factor (PIBF), and TGF-beta2 derived from gammadeltaT cells stimulated by embryo antigens in the context of the OX-2 (CD200) tolerance signal have been viewed as counteracting the Th1 effect. These mechanisms are distinct from those causing and preventing occult pregnancy loss during the periimplantation phase of pregnancy prior to development of a vascularized placenta. Spontaneous abortions in the CBA/J x DBA/2 can be boosted by injecting TNF-alpha + IFN-gamma, but the boosted abortion rates can range from < or = 30 to > 80%, depending on the loss rate in uninjected mice, and this is not explainable by the endogenous level of these cytokines. Furthermore, there is a poor correlation between Th1/Th2.3 cytokine ratios and abortion rates. Could there be a third factor involved, and if so, what might this mean?

METHODS

Known precipitants of recurrent abortion in mice were reviewed with particular attention to stress and endotoxin absorption. The effect of antagonizing the response to bacterial lipopolysaccharide (LPS) (endotoxin) was tested. Data on environmental selective pressures were considered (i.e. thinking outside the 'box', which typifies the conventional approach to thinking about materno-fetal interactions).

RESULTS

Th1 cytokine-triggered abortions appear to depend on availability/presence of LPS.

CONCLUSIONS

Environmental selective pressures are implicated in eliminating 'genetically weaker' embryos in early pregnancy.

The role of apoptosis in normal and abnormal embryonic development

Programmed cell death or apoptosis is a widespread biological phenomenon. Apoptosis is characterized by typical cell features such as membrane blebbing, chromatin condensation, and DNA fragmentation. It involves a number of membrane receptors (e.g., Fas, TNFR) and a cascade of signal transduction steps resulting in the activation of a number of cysteine proteases known as caspases. Disordered apoptosis may lead to carcinogenesis and participates in the pathogenesis of Alzheimer disease, Parkinson disease, or AIDS. Programmed cell death plays an important role in the processes of gamete maturation as well as in embryo development, contributing to the appropriate formation of various organs and structures. Apoptosis is one of the mechanisms of action of various cytotoxic agents and teratogens. Teratogen-induced excessive death of embryonic cells is undoubtedly one of the most important events preceding the occurrence of structural abnormalities, regardless of their nature. Therefore understanding the mechanisms involved in physiological as well as in disturbed or dysregulated apoptosis may lead to the development of new methods of preventive treatment of various developmental abnormalities. The present review summarizes data on the mechanisms of programmed cell death and concentrates on apoptosis involved in normal or disturbed gametogenesis and in normal and abnormal embryonic development.

Maternal immunopotentiation affects the teratogenic response to hyperthermia

Immune responses occurring between the embryo and mother have been shown to influence the embryo's tolerance to teratogens, including chemical teratogens and diabetes-induced teratogenic insult. In this study, we tried to evaluate whether maternal immunostimulation alters the embryo's response to heat shock, one of few teratogens which directly affect the embryo. In order to induce structural anomalies, both intact ICR female mice and mice which had been immunostimulated with xenogeneic rat splenocytes before mating, were exposed to two consecutive exposures to heat (43.6 +/- 0.2 degrees C) for 10 min on day 9 of pregnancy. The number of malformed fetuses, resorptions, and fetal weight were assessed on day 19 of pregnancy. Heat shock-induced apoptosis, and the level of heat shock protein (HSP) 60 expression, were examined in embryonic cells at different time points within 24 h after heating. All these indices differed dramatically in immunized and non-immunized heat shocked females. Heat shocked non-immunized females demonstrated an increased level of resorptions (approximately, 21% versus 8.6% in controls) and the proportion of fetuses with such anomalies as encephalocele and open eyes reached 28% and 21%, respectively. Maternal immunostimulation was associated with a significant decrease in the proportion of fetuses with encephalocele (12.8%), open eyes (8.9%), and resorptions (8%). The maximum level of heat shock-induced apoptosis in cell populations from the embryos of non-immunized females, was approximately, 30% versus 7% in cells of embryos of immunized mice. Heat shock was also followed by a significant increase in HSP60 expression, but only in the cells of embryos of non-immunized females. Together, these findings suggest that the tolerance of mouse embryos to a heat shock-induced teratogenic insult may, to some extent, depend on the character of the maternal immune responses.