Identification of an adverse outcome pathway (AOP) for chemical-induced craniofacial anomalies using the transgenic zebrafish model

Craniofacial anomalies are one of the most frequent birth defects worldwide and are often caused by genetic and environmental factors such as pharmaceuticals and chemical agents. Although identifying adverse outcome pathways (AOPs) is a central issue for evaluating the teratogenicity, the AOP causing craniofacial anomalies has not been identified. Recently, zebrafish has gained interest as an emerging model for predicting teratogenicity because of high throughput, cost-effectiveness and availability of various tools for examining teratogenic mechanisms. Here, we established zebrafish sox10-EGFP reporter lines to visualize cranial neural crest cells (CNCCs) and have identified the AOPs for craniofacial anomalies. When we exposed the transgenic embryos to teratogens that were reported to cause craniofacial anomalies in mammals, CNCC migration and subsequent morphogenesis of the first pharyngeal arch were impaired at 24 hours post-fertilization. We also found that cell proliferation and apoptosis of the migratory CNCCs were disturbed, which would be key events of the AOP. From these results, we propose that our sox10-EGFP reporter lines serve as a valuable model for detecting craniofacial skeletal abnormalities, from early to late developmental stages. Given that the developmental process of CNCCs around this stage is highly conserved between zebrafish and mammals, our findings can be extrapolated to mammalian craniofacial development and thus help in predicting craniofacial anomalies in human.

Developmental Toxicity Studies: The Path towards Humanized 3D Stem Cell-Based Models

Today, it is recognized that medicines will eventually be needed during pregnancy to help prevent to, ameliorate or treat an illness, either due to gestation-related medical conditions or pre-existing diseases. Adding to that, the rate of drug prescription to pregnant women has increased over the past few years, in accordance with the increasing trend to postpone childbirth to a later age. However, in spite of these trends, information regarding teratogenic risk in humans is often missing for most of the purchased drugs. So far, animal models have been the gold standard to obtain teratogenic data, but inter-species differences have limited the suitability of those models to predict human-specific outcomes, contributing to misidentified human teratogenicity. Therefore, the development of physiologically relevant in vitro humanized models can be the key to surpassing this limitation. In this context, this review describes the pathway towards the introduction of human pluripotent stem cell-derived models in developmental toxicity studies. Moreover, as an illustration of their relevance, a particular emphasis will be placed on those models that recapitulate two very important early developmental stages, namely gastrulation and cardiac specification.

Effects of Prenatal Cannabinoids Exposure upon Placenta and Development of Respiratory Neural Circuits

Cannabis use has risen dangerously during pregnancy in the face of incipient therapeutic use and a growing perception of safety. The main psychoactive compound of the Cannabis sativa plant is the phytocannabinoid delta-9-tetrahydrocannabinol (A-9 THC), and its status as a teratogen is controversial. THC and its endogenous analogues, anandamide (AEA) and 2-AG, exert their actions through specific receptors (eCBr) that activate intracellular signaling pathways. CB1r and CB2r, also called classic cannabinoid receptors, together with their endogenous ligands and the enzymes that synthesize and degrade them, constitute the endocannabinoid system. This system is distributed ubiquitously in various central and peripheral tissues. Although the endocannabinoid system's most studied role is controlling the release of neurotransmitters in the central nervous system, the study of long-term exposure to cannabinoids on fetal development is not well known and is vital for understanding environmental or pathological embryo-fetal or postnatal conditions. Prenatal exposure to cannabinoids in animal models has induced changes in placental and embryo-fetal organs. Particularly, cannabinoids could influence both neural and nonneural tissues and induce embryo-fetal pathological conditions in critical processes such as neural respiratory control. This review aims at the acute and chronic effects of prenatal exposure to cannabinoids on placental function and the embryo-fetal neurodevelopment of the respiratory pattern. The information provided here will serve as a theoretical framework to critically evaluate the teratogen effects of the consumption of cannabis during pregnancy.

Caffeic acid selectively eliminates teratogenic human-induced pluripotent stem cells via apoptotic cell death

BACKGROUND

Induced pluripotent stem cells (iPSCs) generated from reprogrammed adult somatic cells are considered as a promising cell source in cell-based regenerative medicine. To avoid teratoma formation, which is a safety issue in iPSC-based cell therapy, it is important to selectively remove undifferentiated iPSCs that remain in the differentiated cell product before in vivo transplantation. Caffeic acid (CAA, 3,4-dihydroxy-cinnamic acid) is a phenolic compound synthesized from various vegetables, fruits, and herbs; it has shown various pharmacological activities against inflammation, cancer, infection, diabetes, and neurodegenerative diseases. However, the beneficial effects of CAA in iPSC-based cell therapy, such as the selective elimination of iPSCs and anti-teratoma effects, have not yet been explored.

RESULTS

Here, we found that CAA induced apoptotic cell death in iPSCs; this process did not occur in iPSC-derived mesenchymal progenitor cells (MPCs) or human dermal fibroblast (hDFs). Under co-culture conditions with MPCs and hDFs, CAA treatment selectively removed iPSCs. In addition, CAA treatment in mixed cell culture with iPSCs and MPCs prior to grafting markedly suppressed iPSC-derived teratoma formation. Finally, CAA did not induce DNA damage in MPCs or hDFs.

CONCLUSION

Taken together, these results suggest that CAA is effective in preparing safe iPSC-based therapeutic cells without the risk of teratoma formation and DNA damage in normal cells and iPSC-derived differentiated cells.

Toxic effects of SiO2NPs in early embryogenesis of Xenopuslaevis

The exposure of organisms to the nanoparticulate is potentially hazardous, particularly when it occurs during embryogenesis. The effects of commercial SiO₂NPs in early development were studied, using Xenopus laevis as a model to investigate their possible future employment by means of the Frog Embryo Teratogenesis Assay-Xenopus test (FETAX). The SiO₂NPs did not change the survival but produced several abnormalities in developing embryos, in particular, the dorsal pigmentation, the cartilages of the head and branchial arches were modified; the encephalon, spinal cord and nerves are anomalous and the intestinal brush border show signs of suffering; these embryos are also bradycardic. In addition, the expression of genes involved in the early pathways of embryo development was modified. Treated embryos showed an increase of reactive oxygen species. This study suggests that SiO₂NPs are toxic but non-lethal and showed potential teratogenic effects in Xenopus. The latter may be due to their cellular accumulation and/or to the effect caused by the interaction of SiO₂NPs with cytoplasmic and/or nuclear components. ROS production could contribute to the observed effects. In conclusion, the data indicates that the use of SiO₂NPs requires close attention and further studies to better clarify their activity in animals, including humans.

Insights into Structural Modifications of Valproic Acid and Their Pharmacological Profile

Valproic acid (VPA) is a well-established anticonvulsant drug discovered serendipitously and marketed for the treatment of epilepsy, migraine, bipolar disorder and neuropathic pain. Apart from this, VPA has potential therapeutic applications in other central nervous system (CNS) disorders and in various cancer types. Since the discovery of its anticonvulsant activity, substantial efforts have been made to develop structural analogues and derivatives in an attempt to increase potency and decrease adverse side effects, the most significant being teratogenicity and hepatotoxicity. Most of these compounds have shown reduced toxicity with improved potency. The simple structure of VPA offers a great advantage to its modification. This review briefly discusses the pharmacology and molecular targets of VPA. The article then elaborates on the structural modifications in VPA including amide-derivatives, acid and cyclic analogues, urea derivatives and pro-drugs, and compares their pharmacological profile with that of the parent molecule. The current challenges for the clinical use of these derivatives are also discussed. The review is expected to provide necessary knowledgebase for the further development of VPA-derived compounds.

Pediatric Subspecialists' Practices and Attitudes Regarding Sexual and Reproductive Healthcare for Adolescent and Young Adult Women Prescribed Teratogenic Medications

OBJECTIVE

To evaluate pediatric subspecialists' practices and attitudes regarding sexual and reproductive healthcare for adolescent and young adult women for whom they prescribe teratogens.

STUDY DESIGN

We surveyed pediatric subspecialists at 1 tertiary care pediatric hospital. Items assessed attitudes and practices related to sexual and reproductive healthcare for adolescent and young adult women prescribed teratogens, and barriers and facilitators to sexual and reproductive healthcare provision. We used descriptive statistics, χ² tests, and logistic regression to analyze results.

RESULTS

There were 200 subspecialists from 17 subspecialties who completed the survey; 77% reported prescribing teratogens to adolescent and young adult women and 18% reported caring for a patient who became pregnant while taking a teratogen. Overall, 99% indicated that it is important to address sexual and reproductive healthcare. Respondents endorsed confidence in sexual and reproductive healthcare skills, including contraceptive counseling (71%), although 29% never or rarely discuss sexual and reproductive healthcare, and one-third never speak privately to this population. Of providers who discuss sexual and reproductive healthcare, 26% never assess reproductive intentions and 36% do so less often than annually. Nearly one-half never or rarely ask about sexual activity, and 68% never or rarely assess contraceptive knowledge. Barriers to sexual and reproductive healthcare provision included available time (80%) and the presence of family or partners at clinic visits (61%). Facilitators included a quick referral process to sexual and reproductive healthcare providers (92%) and access to lists of local sexual and reproductive healthcare providers (90%).

CONCLUSIONS

Pediatric subspecialists from a single institution report suboptimal sexual and reproductive healthcare provision for adolescent and young adult women prescribed teratogens. Identified barriers and facilitators may guide intervention development to improve sexual and reproductive healthcare for this population.

Prenatal MAM treatment altered fear conditioning following social isolation: Relevance to schizophrenia

Adolescent social isolation (SI) might change the trajectory of brain development. In the present study, we investigated the effect of short-term adolescent SI on fear memory, anxiety and protein levels in the adult medial prefrontal cortex of rats prenatally treated with methylazoxymethanol, MAM-E17 model of schizophrenia. The animals were maintained in standard housing (SH) or social isolation (P30-P40, SI) conditions. Behavioural tests (trace or delay fear conditioning, light/dark box) were performed in late adolescence and early adulthood. The results showed that MAM treatment did not alter fear memory, which was investigated with the use of either trace or delay fear conditioning, at any age, and SI decreased the fear response in adult control animals only under trace conditioning. Neither MAM nor SI influenced anxiety-related behaviour measured in the light/dark box. A proteomics study showed that both MAM and SI changed the protein levels related to synapse maturation and cytoskeletal organization, energy transfer and metabolic processes. Prenatal or adolescent environmental factors are able to change the expression of proteins that are correlated with behavioural impairments. Moreover, SI reversed some alterations in proteins induced by MAM. Thus, normally developing brains showed different responses to adolescent SI than those with altering courses of MAM administration.

Multifactorial Genetic and Environmental Hedgehog Pathway Disruption Sensitizes Embryos to Alcohol-Induced Craniofacial Defects

BACKGROUND

Prenatal alcohol exposure (PAE) is perhaps the most common environmental cause of human birth defects. These exposures cause a range of structural and neurological defects, including facial dysmorphologies, collectively known as fetal alcohol spectrum disorders (FASD). While PAE causes FASD, phenotypic outcomes vary widely. It is thought that multifactorial genetic and environmental interactions modify the effects of PAE. However, little is known of the nature of these modifiers. Disruption of the Hedgehog (Hh) signaling pathway has been suggested as a modifier of ethanol teratogenicity. In addition to regulating the morphogenesis of craniofacial tissues commonly disrupted in FASD, a core member of the Hh pathway, Smoothened, is susceptible to modulation by structurally diverse chemicals. These include environmentally prevalent teratogens like piperonyl butoxide (PBO), a synergist found in thousands of pesticide formulations.

METHODS

Here, we characterize multifactorial genetic and environmental interactions using a zebrafish model of craniofacial development.

RESULTS

We show that loss of a single allele of shha sensitized embryos to both alcohol- and PBO-induced facial defects. Co-exposure of PBO and alcohol synergized to cause more frequent and severe defects. The effects of this co-exposure were even more profound in the genetically susceptible shha heterozygotes.

CONCLUSIONS

Together, these findings shed light on the multifactorial basis of alcohol-induced craniofacial defects. In addition to further implicating genetic disruption of the Hh pathway in alcohol teratogenicity, our findings suggest that co-exposure to environmental chemicals that perturb Hh signaling may be important variables in FASD and related craniofacial disorders.

Embryotoxic and teratogenic profile of tretracycline at environmentally relevant concentrations on Cyprinus carpio

The objective of this work was to evaluate whether tetracycline (TC) in environmentally relevant concentrations was able to induce alterations to embryonic development and teratogenic effects in oocytes and embryos of Cyprinus carpio. For this purpose, an embryolethality study was conducted and the lethal concentration 50 (LC₅₀) and effective concentration 50 of malformations (EC₅₀) were calculated, and with these data the teratogenic index (TI) was determined. The main alterations to embryonic development and the teratogenic effects produced by TC on embryos of C. carpio were determined using the Kimmel and Hersem scale adapted for Cyprinus carpio. LC₅₀ and EC₅₀ were respectively 500.08 and 145.3 μg L^-1.TC was shown to be teratogenic with teratogenic index of 3.44, and the main malformations identified in concentrations of 90-900 μg L^-1 were malformation in tail, modified chorda structure, pericardical edema, scoliosis and malformations of the heart. A significant decrease in concentration-dependent in Kimmel and Hersem score was observed. The results allow us to conclude that TC at environmentally relevant concentrations is capable of inducing embryotoxic and teratogenic effects, generating risk in the integrity of the common carp C. Carpio.

The nuclear transporter SAD2 plays a role in calcium- and H2 O2 -mediated cell death in Arabidopsis

In response to pathogens, plant cells exhibit a rapid increase in the intracellular calcium concentration and a burst of reactive oxygen species (ROS). The cytosolic increase in Ca²⁺ and the accumulation of ROS are critical for inducing programmed cell death (PCD), but the molecular mechanism is not fully understood. We screened an Arabidopsis mutant, sad2-5, which harbours a T-DNA insertion in the 18^th exon of the importin beta-like gene, SAD2. The H₂ O₂ -induced increase in the [Ca²⁺ ]_cyt of the sad2-5 mutant was greater than that of the wild type, and the sad2-5 mutant showed clear cell death phenotypes and abnormal H₂ O₂ accumulation under fumonisin-B1 (FB1) treatment. CaCl₂ could enhance the FB1-induced cell death of the sad2-5 mutant, whereas lanthanum chloride (LaCl₃ ), a broad-spectrum calcium channel blocker, could restore the FB1-induced PCD phenotype of sad2-5. The sad2-5 fbr11-1 double mutant exhibited the same FB1-insensitive phenotype as fbr11-1, which plays a critical role in novo sphingolipid synthesis, indicating that SAD2 works downstream of FBR11. These results suggest the important role of nuclear transporters in calcium- and ROS-mediated PCD response as well as provide an important theoretical basis for further analysis of the molecular mechanism of SAD2 function in PCD and for improvement of the resistance of crops to adverse environments.

Thalidomide induces apoptosis during early mesodermal differentiation of human induced pluripotent stem cells

Thalidomide was once administered to pregnant women as a mild sedative; however, it was subsequently shown to be strongly teratogenic. Recently, there has been renewed interest in thalidomide because of its curative effects against intractable diseases. However, the teratogenicity of thalidomide is manifested in various ways and is still not fully understood. In the present study, we evaluated the effects of thalidomide on early mesodermal differentiation by examining the differentiation of human induced pluripotent stem cells (hiPSCs). The most common symptom of thalidomide teratogenicity is limb abnormality, which led us to hypothesize that thalidomide prevents early mesodermal differentiation. Therefore, mesodermal differentiation of hiPSCs was induced over a 6-d period. To induce early mesoderm differentiation, 1 d after seeding, the cells were incubated with the small molecule compound CHIR99021 for 3 d. Thalidomide exposure was initiated at the same time as CHIR99021 treatment. After 5 d of thalidomide exposure, the hiPSCs began expressing a mesodermal marker; however, the number of viable cells decreased significantly as compared to that of control cells. We observed that the proportion of apoptotic and dead cells increased on day 2; however, the proportion of dead cells on day 5 had decreased, suggesting that the cells were damaged by thalidomide during early mesodermal differentiation (days 0-2). Our findings may help elucidate the mechanism underlying thalidomide teratogenicity and bring us closer to the safe use of this drug.

Behavioral Profiling of Zebrafish (Danio rerio) Larvae Following Teratogen Exposure

Apart from morphological, biochemical, and genetic alterations induced by teratogen compounds, there is an increase interest in characterizing behavioral alterations. Behavior is a sensitive parameter that can provide information regarding developmental disruptions noninvasively, as it is the result of brain processes. Behavioral disturbances interfere with animals' capacity to cope with the environment, having an impact on the organism's life. Hereby, it is proposed behavioral assays consisting on recording larvae in multiwell plates and video analysis with a proper software, allowing for teratogen screening of behavior. How to evaluate locomotor, anxiety-like and avoidance-like behaviors, and the integrity of sensory-motor functions and learning are discussed in this chapter.

Quantitative volumetric analysis of a retinoic acid induced hypoplastic model of chick thymus, using Image-J

OBJECTIVE

To assess the total volume change in a retinoic acid-induced, hypoplastic model of a chick thymus using Image-J.

METHODS

This experimental study was carried out at the anatomy department of College of Physicians and Surgeons, Islamabad, Pakistan, from February 2009 to February 2010, and comprised fertilised chicken eggs. The eggs were divided into experimental group A and control group C. Group A was injected with 0.3µg of retinoic acid via yolk sac to induce a defective model of a thymus with hypoplasia. The chicks were sacrificed on embryonic day 15 and at hatching. The thymus of each animal was processed, serially sectioned and stained. The total area of each section of thymus was calculated using Image-J. This total area was summed and multiplied with the thickness of each section to obtain volume.

RESULTS

Of the 120 eggs, there were 60(50%) in each group. Image analysis revealed a highly significant decrease in the volume of the chick thymus in the experimental group A than its matched control at the time of hatching (p=0.001). Moreover, volumetric depletion progressed with time, being substantially pronounced at hatching compared to the embryonic stage.

CONCLUSIONS

The volume changes were significant and were effectively quantified using Image-J.

Teratogenic Effects of Topiramate in a Zebrafish Model

Topiramate is commonly used for treating epilepsy in both children and adults. Recent clinical data suggests that administration of topiramate to women during pregnancy increases the risk of oral clefts in their offspring. To better understand the potential effects of topiramate, we dosed adult female zebrafish with topiramate, and investigated the altered morphologies in adult females and their offspring. It showed that topiramate-treated female fish had reduced oocyte maturation, and the survival rates of their offspring were seriously decreased during embryogenesis. In addition, around 23% of offspring displayed cartilage malformation in the craniofacial area, such as loss of ceratobranchial cartilages as well as impaired ceratohyal, Meckel’s cartilage and ethmoid plate development. Moreover, mineralization of ceratohyal, Meckel’s cartilage, and vertebrae were downregulated during bone development. Taken together, we concluded that topiramate impaired oogenesis in the maternal reproductive system, and then caused offspring cartilage malformation or bone dysplasia.

Teratogenic responses of zebrafish embryos to decabromodiphenyl ether (BDE-209) in the presence of nano-SiO2 particles

This study investigated the influence of nano-SiO₂ particles (nSiO₂) on the teratogenic responses of zebrafish embryos to decabromodiphenyl ether (BDE-209). Zebrafish embryos were exposed to BDE-209 in the absence and presence of nSiO₂ for 96 h post fertilization (hpf). Results showed that formation of nSiO₂-BDE-209 associates promoted both extracellular and intracellular uptake of BDE-209 by zebrafish embryos, thereby increasing the bioconcentration of BDE-209 on the chorion surface and the embryos. Results also showed embryos delay hatching temporarily when co-exposure to BDE-209 and nSiO₂ at 60 hpf. Furthermore, there was heartbeat decline (28.3 beats/10s) and increase in irregular heartbeat (45.8%) in zebrafish larvae at 96 hpf, compared to the sole exposure to BDE-209 (32.7 beats/10s and 0%). Malformation in terms of spinal curvature (SC), pericardial edema (PE) and yolk sac edema (YSE) were observed on zebrafish larvae at 33.9, 23.4, and 18%, respectively. Overall, abnormal development of zebrafish was apparent when co-exposure to BDE-209 and nSiO₂. All relevant evidence considered, nSiO₂ could facilitate the transport of BDE-209 towards zebrafish embryos and negatively impact the development of zebrafish.

Does folinic acid ameliorates retinoic acid induced teratogenicity in chick embryo?

OBJECTIVE

To investigate the protective effect of folinic acid on the hatching ability and developmental defects in a retinoic acid-induced teratogenic model of chick embryo.

METHODS

The experimental study was conducted at the Department of Anatomy, Regional Centre of the College of Physicians and Surgeons Pakistan, Islamabad, from February 2009 to February 2010. Chicken eggs were divided into two experimental groups and a control group. The first experimental group was injected with retinoic acid to induce a defective model, while the second experimental group was concomitantly injected folinic acid to observe its protective effects on retinoic acid-induced defects in the development and hatching process. Both groups were compared with the age-matched control group.

RESULTS

A total of 90 fertilised eggs were divided into three groups. The experimental groups had significantly more delayed and assisted hatchings compared to the control group (p<0.05) but the difference between the experimental groups regarding the mode and day of hatching was insignificant (p>0.05).

CONCLUSIONS

Irrespective of the presence of folinic acid, prenatal retinoic acid exposure significantly altered the hatchability characteristics in the experimental groups compared to the control.

Hypermethylation of the Keap1 gene inactivates its function, promotes Nrf2 nuclear accumulation, and is involved in arsenite-induced human keratinocyte transformation

It is well known that long-term exposure to arsenite leads to human skin cancer, but the underlying mechanisms of carcinogenesis remain obscure. The transcription factor Nrf2-mediated antioxidant response represents a critical cellular defense mechanism; however, emerging data suggest that constitutive activation of Nrf2 is associated with cancer development and chemotherapy resistance. The reasons Nrf2 continuously accumulates in cancer cells remain to be fully understood. By establishing transformed human keratinocyte cells via chronic arsenite treatment, we observed a continuous reduction in reactive oxygen species levels and enhanced levels of Nrf2 and its target antioxidant enzymes in the later stage of arsenite-induced cell transformation. We also revealed that hypermethylation of the Keap1 gene promoter region induced by DNA methyltransferase-3 leading to inactivation of its function was responsible for constitutive activation of Nrf2 and its target enzymes. To validate these observations, the expression of Keap1 protein was restored in arsenite-transformed cells by treatment with a DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5-Aza-dC), and protein levels of Nrf2 and colony formation were then determined after these treatments. Results showed that enhancement of Keap1 expression by 5-Aza-dC significantly reduced Nrf2 and its target antioxidant enzyme levels, and that in turn suppressed cell proliferation and colony formation of the transformed cells. Taken together, the present study strongly suggests that loss of Keap1 function by hypermethylation of its promoter region leading to Nrf2 nuclear accumulation appears to play a role in arsenite-induced human keratinocyte transformation.

Histological changes induced by tamoxifen versus tamoxifen plus 13-cis-retinoic acid on rabbit uterine glands

OBJECTIVE

To study the effects of tamoxifen versus tamoxifen plus 13-cis-retinoic acid on the histology of uterine glands in rabbits.

METHODS

The experimental, randomised, controlled trial was conducted at the Army Medical College, Rawalpindi, from March 2009 to June 2009 and comprised rabbits acquired from the National Institute of Health, Islamabad. The animals were randomly divided into three equal groups: group A had controls, group B was treated with tamoxifen, and group C with tamoxifen plus retinoic acid. The uterine weight and cross-sectional diameter of uterine horns were measured after sacrifice. The uteri were processed for paraffin embedding. The sections were then assessed for stratification of glandular epithelium, changes in the glandular shape and glandular epithelial height. SPSS 13 was used for statistical analysis.

RESULTS

Tamoxifen administration resulted in variation of glandular shape and increase in glandular epithelial height in group B as compared to control group, p < 0.001 and 0.005 respectively. The adjuvant administration of 13-cis-retinoic acid showed a suppressive effect only on glandular epithelial height, when compared with Group B (p=0.01).

CONCLUSIONS

The 13-cis-retinoic acid has no significant inhibitory effect on uterine glandular proliferation induced by tamoxifen after a short-term administration of three months.

A novel post-translational modification of nucleolin, SUMOylation at Lys-294, mediates arsenite-induced cell death by regulating gadd45α mRNA stability

Nucleolin is a ubiquitously expressed protein and participates in many important biological processes, such as cell cycle regulation and ribosomal biogenesis. The activity of nucleolin is regulated by intracellular localization and post-translational modifications, including phosphorylation, methylation, and ADP-ribosylation. Small ubiquitin-like modifier (SUMO) is a category of recently verified forms of post-translational modifications and exerts various effects on the target proteins. In the studies reported here, we discovered SUMOylational modification of human nucleolin protein at Lys-294, which facilitated the mRNA binding property of nucleolin by maintaining its nuclear localization. In response to arsenic exposure, nucleolin-SUMO was induced and promoted its binding with gadd45α mRNA, which increased gadd45α mRNA stability and protein expression, subsequently causing GADD45α-mediated cell death. On the other hand, ectopic expression of Mn-SOD attenuated the arsenite-generated superoxide radical level, abrogated nucleolin-SUMO, and in turn inhibited arsenite-induced apoptosis by reducing GADD45α expression. Collectively, our results for the first time demonstrate that nucleolin-SUMO at K294R plays a critical role in its nucleus sequestration and gadd45α mRNA binding activity. This novel biological function of nucleolin is distinct from its conventional role as a proto-oncogene. Therefore, our findings here not only reveal a new modification of nucleolin protein and its novel functional paradigm in mRNA metabolism but also expand our understanding of the dichotomous roles of nucleolin in terms of cancer development, which are dependent on multiple intracellular conditions and consequently the appropriate regulations of its modifications, including SUMOylation.

Perinatal Domoic Acid as a Neuroteratogen

In mammals, the period shortly before and shortly after birth is a time of massive brain growth, plasticity and maturation. It is also a time when the developing brain is exquisitely sensitive to insult, often with long-lasting consequences. Many of society's most debilitating neurological diseases arise, at least in part, from trauma around the time of birth but go undetected until later in life. For the past 15 years, we have been studying the consequences of exposure to the AMPA/kainate agonist domoic acid (DOM) on brain development in the rat. Domoic acid is a naturally occurring excitotoxin that enters the food chain and is known to produce severe neurotoxicity in humans and other adult wildlife. Our work, and that of others, however, has demonstrated that DOM is also toxic to the perinatal brain and that toxicity occurs at doses much lower than those required in adults. This raises concern about the current regulatory limit for DOM contamination that is based on data in adult animals, but has also allowed creation of a novel model of neurological disease progression. Herein, we review briefly the toxicity of DOM in adults, including humans, and describe features of the developing nervous system relevant to enhanced risk. We then review the data on DOM as a prenatal neuroteratogen and describe in detail the work of our respective laboratories to characterize the long-term behavioural and neuropathological consequences of exposure to low-dose DOM in the newborn rat.

Accumulation of polyunsaturated aldehydes in the gonads of the copepod Acartia tonsa revealed by tailored fluorescent probes

Polyunsaturated aldehydes (PUAs) are released by several diatom species during predation. Besides other attributed activities, these oxylipins can interfere with the reproduction of copepods, important predators of diatoms. While intensive research has been carried out to document the effects of PUAs on copepod reproduction, little is known about the underlying mechanistic aspects of PUA action. Especially PUA uptake and accumulation in copepods has not been addressed to date. To investigate how PUAs are taken up and interfere with the reproduction in copepods we developed a fluorescent probe containing the α,β,γ,δ-unsaturated aldehyde structure element that is essential for the activity of PUAs as well as a set of control probes. We developed incubation and monitoring procedures for adult females of the calanoid copepod Acartia tonsa and show that the PUA derived fluorescent molecular probe selectively accumulates in the gonads of this copepod. In contrast, a saturated aldehyde derived probe of an inactive parent molecule was enriched in the lipid sac. This leads to a model for PUAs' teratogenic mode of action involving accumulation and covalent interaction with nucleophilic moieties in the copepod reproductive tissue. The teratogenic effect of PUAs can therefore be explained by a selective targeting of the molecules into the reproductive tissue of the herbivores, while more lipophilic but otherwise strongly related structures end up in lipid bodies.

Investigation of the teratogenic potential of VLA-4 antagonist derivatives in rats

Very late antigen-4 (VLA-4), which is concerned with cell-cell adhesion, plays important roles in development of the heart, and some VLA-4 antagonists cause cardiac anomalies. In this study, we evaluated the teratogenic potential of VLA-4 antagonist derivatives as screening, and investigated the conditions that induce cardiac anomalies. Seventeen compounds were orally administered to pregnant rats throughout the organogenesis period, and fetal examinations were performed. In addition, drug concentrations in the embryos were assayed. As a result, the incidence of ventricular septal defect (VSD) ranged from 0 to 100% depending on the compound. Plasma drug concentrations in the dams were related to increased incidence of VSD; however, these incidences were not increased when the concentration of the compound in the embryos at 24h after dosing was low. It is considered that continuous pharmacological activity in the embryo for more than 24h might disrupt closure of the ventricular septum.

Arsenite selectively inhibits mouse bone marrow lymphoid progenitor cell development in vivo and in vitro and suppresses humoral immunity in vivo

It is known that exposure to As⁺³ via drinking water causes a disruption of the immune system and significantly compromises the immune response to infection. The purpose of these studies was to assess the effects of As⁺³ on bone marrow progenitor cell colony formation and the humoral immune response to a T-dependent antigen response (TDAR) in vivo. In a 30 day drinking water study, mice were exposed to 19, 75, or 300 ppb As⁺³. There was a decrease in bone marrow cell recovery, but not spleen cell recovery at 300 ppb As⁺³. In the bone marrow, As⁺³ altered neither the expression of CD34+ and CD38+ cells, markers of early hematopoietic stem cells, nor CD45−/CD105+, markers of mesenchymal stem cells. Spleen cell surface marker CD45 expression on B cells (CD19+), T cells (CD3+), T helper cells (CD4+) and cytotoxic T cells (CD8+), natural killer (NK+), and macrophages (Mac 1+) were not altered by the 30 day in vivo As⁺³ exposure. Functional assays of CFU-B colony formation showed significant selective suppression (p<0.05) by 300 ppb As⁺³ exposure, whereas CFU-GM formation was not altered. The TDAR of the spleen cells was significantly suppressed at 75 and 300 ppb As⁺³. In vitro studies of the bone marrow revealed a selective suppression of CFU-B by 50 nM As⁺³ in the absence of apparent cytotoxicity. Monomethylarsonous acid (MMA⁺³) demonstrated a dose-dependent and selective suppression of CFU-B beginning at 5 nM (p<0.05). MMA⁺³ suppressed CFU-GM formation at 500 nM, a concentration that proved to be nonspecifically cytotoxic. As⁺⁵ did not suppress CFU-B and/or CFU-GM in vitro at concentrations up to 500 nM. Collectively, these results demonstrate that As⁺³ and likely its metabolite (MMA⁺³) target lymphoid progenitor cells in mouse bone marrow and mature B and T cell activity in the spleen.

Selection of reliable biomarkers from PCR array analyses using relative distance computational model: methodology and proof-of-concept study

It is increasingly evident about the difficulty to monitor chemical exposure through biomarkers as almost all the biomarkers so far proposed are not specific for any individual chemical. In this proof-of-concept study, adult male zebrafish (Danio rerio) were exposed to 5 or 25 µg/L 17β-estradiol (E2), 100 µg/L lindane, 5 nM 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or 15 mg/L arsenic for 96 h, and the expression profiles of 59 genes involved in 7 pathways plus 2 well characterized biomarker genes, vtg1 (vitellogenin1) and cyp1a1 (cytochrome P450 1A1), were examined. Relative distance (RD) computational model was developed to screen favorable genes and generate appropriate gene sets for the differentiation of chemicals/concentrations selected. Our results demonstrated that the known biomarker genes were not always good candidates for the differentiation of pair of chemicals/concentrations, and other genes had higher potentials in some cases. Furthermore, the differentiation of 5 chemicals/concentrations examined were attainable using expression data of various gene sets, and the best combination was the set consisting of 50 genes; however, as few as two genes (e.g. vtg1 and hspa5 [heat shock protein 5]) were sufficient to differentiate the five chemical/concentration groups in the present test. These observations suggest that multi-parameter arrays should be more reliable for biomonitoring of chemical exposure than traditional biomarkers, and the RD computational model provides an effective tool for the selection of parameters and generation of parameter sets.

Epigenetic drug 5-azacytidine impairs proliferation of rat limb buds in an organotypic model-system in vitro

AIM

To establish an organotypic in vitro model of limb bud development to verify whether epigenetic drug and teratogen 5-azacytidine (5azaC) has an effect on limb buds independent of its effects on the placenta.

METHODS

Fischer strain rat fore- and hindlimb buds were microsurgically isolated from 13 days old embryos and cultivated in vitro for two weeks at the air-liquid interface in Eagle's minimum essential medium (MEM) with 50% rat serum. 30 μmol of 5azaC was added to the fresh medium. Overall growth was measured by an ocular micrometer. Routine histology, immunohistochemical detection of the proliferating cell nuclear antigen (PCNA), and stereological quantification of PCNA expression were performed.

RESULTS

At four time points, significantly lower overall growth was detected for fore- and hindlimb bud explants cultivated with 5azaC in comparison to controls. After the culture period, numerical density of the PCNA signal for both types of limb buds was lower than for controls (P<0.001). Limb buds were initially covered by immature epithelium and contained mesenchyme, myotubes, single hemangioblasts, hemangioblast aggregates, blood islands, and capillaries. Regardless of the treatment, cartilage and epidermis differentiated, but cells and structures typical for vasculogenesis disappeared.

CONCLUSION

Our findings, obtained outside of the maternal organism, stress the importance of compromised cell proliferation for 5azaC impact on limb buds. This investigation points to the necessity to establish alternatives to in vivo research on animals using teratogenic agents.

Nuanced but significant: how ethanol perturbs avian cranial neural crest cell actin cytoskeleton, migration and proliferation

Children with fetal alcohol syndrome (FAS) display striking craniofacial abnormalities. These features are proposed to result from perturbations in the morphology and function of cranial neural crest cells (cNCCs), which contribute significantly to the craniofacial complex. While certain pathways by which this may occur have been suggested, precise teratogenic mechanisms remain intensely investigated, as does the question of the teratogenic dose. The present study focused on examining how avian cNCC actin cytoskeleton, migratory distance, and proliferation are affected ex vivo by exposure to ethanol concentrations that simulate maternal intoxication. Chick cNCCs were cultured in 0.2% and 0.4% v/v ethanol. Distances migrated by both ethanol-treated and control cells at 24 and 48 h were recorded. Following phalloidin immunocytochemistry, treated and control cNCCs were compared morphologically and quantitatively. Apoptosis and proliferation in control versus treated cNCCs were also studied. Chick cNCCs cultured in ethanol lost their spindle-like shapes and their ordered cytoskeleton. There was a significant stage-dependent effect on cNCC migration at 24 h (p = 0.035), which was greatest at stage 10 (HH). Ethanol treatment for 48 h revealed a significant main effect for ethanol, chiefly at the 0.4% level. There was also an interaction effect between ethanol dose and stage of development (stage 9 HH). Actin microfilament disruption was quantitatively increased by ethanol at the doses studied while cNCC proliferation was increased but not significantly. Ethanol had no effect on cNCC apoptosis. At ethanol levels likely to induce human FAS, avian cNCCs exhibit various subtle, potentially significant changes in morphology, migration, and proliferation, with possible consequences for fated structures.

Inhibition of nitric oxide synthesis enhances teratogenic effects induced by valproic Acid

BACKGROUND/AIM

The mechanism of valproic acid (VPA)-induced teratogenicity is poorly known. This study was carried out to probe into the potential consequences of nitric oxide (NO) deprivation on VPA teratogenicity.

MATERIALS AND METHODS

On gestation day 8, mice were injected with a non-teratogenic dose (20 mg/kg) of the nitric oxide synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl esther (L-NAME). Thirty minutes later, animals received a teratogenic dose of VPA (400 or 500 mg/kg). Developmental end-points were evaluated near the end of gestation.

RESULTS

After treatment with VPA at 400 mg/kg, 35.2% of fetuses exhibited skeletal teratogenesis. The rate of skeletally affected fetuses significantly increased to 53.7% after L-NAME co-administration. In the group treated with VPA at 500 mg/kg group, L-NAME pre-treatment increased the incidence of exencephaly from 5.4% to 22.2%.

CONCLUSION

Inhibition of NO synthesis can result in an enhancement of VPA-induced teratogenesis.

2,3,7,8-Tetrachlorodibenzo-p-dioxin promotes BHV-1 infection in mammalian cells by interfering with iron homeostasis regulation

Mammalian cells require iron to satisfy metabolic needs or to accomplish specialized functions, and DNA viruses, like bovine herpesvirus 1 (BHV-1), require an iron-replete host to efficiently replicate, so that iron bioavailability is an important component of viral virulence. Cellular iron metabolism is coordinately controlled by the Iron Regulatory Proteins (IRP1 and IRP2), whose activity is affected by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a current and persistent environmental contaminant. Considering that TCDD enhances BHV-1 replication, herein we analyzed the effects of TCDD on iron metabolism during BHV-1 infection in MDBK cells, and presented evidences of a divergent modulation of IRP1 and IRP2 RNA-binding capacity. Moreover, an up-regulation of transferrin receptor 1 (TfR1) and a concomitant down-regulation of ferritin were observed. This scenario led to an expansion of the labile iron pool (LIP) and induces a significant enhance of viral titer, as confirmed by increased levels of BHV-1 infected cell protein 0 (bICP0), the major transcriptional regulatory protein of BHV-1. Taken together, our data suggest that TCDD increases the free intracellular iron availability thereby promoting the onset of BHV-1 infection and rendering bovine cells more vulnerable to the virus.

Prochloraz effects on biomarkers activity in zebrafish early life stages and adults

Zebrafish early life stages (ELS) assays have been increasingly used to assess the toxicity of chemicals and waste waters, showing a great potential due to the wide variety of endpoints that can be incorporated in the test. Moreover, zebrafish ELS test have been proposed, mainly for ethical reasons, as a surrogate for tests with adults. In this work, the fungicide Prochloraz (PCZ) was used as a chemical model to compare sensitivities of embryos/larvae and adult zebrafish focusing on lethality and biomarkers as endpoints. Effects on embryo development were also assessed. Organization for economic cooperation and development (OECD) guidelines were followed and adapted to include the analyses of the biomarkers cholinesterase, glutathione S-transferase, and lactate dehydrogenase. The acute toxicity of PCZ for zebrafish ELS and adults seemed to be similar with 96 h-LC₅₀ values of 8.5 and 4.6 mg/L, respectively. However, biomarkers were only responsive in larvae indicating a higher sensitivity of this life stage at sublethal level. PCZ also proved to be teratogenic: at intermediate concentrations effects on embryo development could be noticed, including spine deformations, edemas, lack of pigmentation, slower heart rate, and complete hatching failure. At the lowest concentrations, the more relevant effects (edemas and abnormal absorption of the yolk sac) were observed after hatching. The measurement of biomarkers in the zebrafish ELS assay seems to a useful tool in the detection of chemical effects showing higher sensitivity than adults. Further research should focus on the link between biomarkers responses in larvae and effects at later life stages of zebrafish.

HAX-1 is a nucleocytoplasmic shuttling protein with a possible role in mRNA processing

HAX-1 is a multi-functional protein that is involved in the regulation of apoptosis, cell motility and calcium homeostasis. It is also reported to bind RNA: it associates with structural motifs present in the 3' untranslated regions of at least two transcripts, but the functional significance of this binding remains unknown. Although HAX-1 has been detected in various cellular compartments, it is predominantly cytoplasmic. Our detailed localization studies of HAX-1 isoforms revealed partial nuclear localization, the extent of which depends on the protein isoform. Further studies demonstrated that HAX-1 is in fact a nucleocytoplasmic shuttling protein, dependent on the exportin 1 nuclear export receptor. Systematic mutagenesis allowed identification of the two nuclear export signals in the HAX-1 sequence. HAX-1 nuclear accumulation was observed after inhibition of nuclear export by leptomycin B, but also after specific cellular stress. The biological role of HAX-1 nuclear localization and shuttling remains to be established, but the HAX-1 transcript-binding properties suggest that it may be connected to mRNA processing and surveillance. In this study, HAX-1 status was shown to influence mRNA levels of DNA polymerase β, one of the HAX-1 mRNA targets, although this effect becomes pronounced only after specific stress is applied. Moreover, HAX-1 tethering to the reporter transcript caused a significant decrease in its expression. Additionally, the HAX-1 co-localization with P-body markers, reported here, implies a role in mRNA processing. These results suggest that HAX-1 may be involved in the regulation of expression of bound transcripts, possibly as part of the stress response.

EMT and stem cell-like properties associated with HIF-2α are involved in arsenite-induced transformation of human bronchial epithelial cells

BACKGROUND

Arsenic is well-established as a human carcinogen, but the molecular mechanisms leading to arsenic-induced carcinogenesis are complex and elusive. It is not been determined if the epithelial-mesenchymal transition (EMT) and stem cell-like properties contribute in causing to carcinogen-induced malignant transformation and subsequent tumor formation.

METHODS

To investigate the molecular mechanisms underlying EMT and the emergence of cancer stem cell-like properties during neoplastic transformation of human bronchial epithelial (HBE) cells induced by chronic exposure to arsenite. HBE cells were continuously exposed to arsenite. Spheroid formation assays and analyses of side populations (SPs) were performed to confirm that arsenite induces the acquired EMT and cancer stem cell-like phenotype. Treated HBE cells were molecularly characterized by RT-PCR, Western blots, immunofluorescence, Southwestern assays, reporter assays, and chromatin immunoprecipitation.

RESULTS

With chronic exposure to arsenite, HBE cells undergo an EMT and then acquire a malignant cancer stem cell-like phenotype. Twist1 and Bmi1 are involved in arsenite-induced EMT. The process is directly regulated by HIF-2α. The self-renewal genes, Oct4, Bmi1, and ALDH1, are necessary for arsenite-mediated maintenance of stem cells.

CONCLUSIONS

EMT, regulated by HIF-2α, and the development of a cancer stem cell-like phenotype are associated with arsenite-induced transformation of HBE cells.

Caenorhabditis elegans as a model in developmental toxicology

A number of practical advantages have made the nematode Caenorhabditis elegans a useful model for genetic and developmental biological research. These same advantages, along with conservation of disease and stress response pathways, availability of mutant and transgenic strains, and wealth of biological information, have led to the increased use of C. elegans in toxicological studies. Although the potential to study the mechanisms of developmental toxicology in C. elegans is promising, embryonic and larval growth tests to identify compounds that affect the nematode have remained the primary use of C. elegans in developmental toxicology. Here, we describe a C. elegans larval growth and development assay for medium- and high-throughput screening using the COPAS Biosort flow cytometer and provide descriptions of the data and subsequent analysis.

Teratogenic effects of triphenyltin on embryos of amphibian (Xenopus tropicalis): a phenotypic comparison with the retinoid X and retinoic acid receptor ligands

Triphenyltin (TPT) has high binding affinity with the retinoid X receptor (RXR) in animals. The natural ligand of RXR, 9-cis-retinoic acid (RA), is known to induce featured malformations in vertebrate embryos by disrupting RA signal. Limited information is available on the TPT effects on amphibians. We exposed embryos of amphibian (Xenopus tropicalis) to TPT, 9-cis-RA, all-trans-RA (ligand of retinoic acid receptor, RAR), and LGD1069 (a selective ligand of RXR). The 72h LC50 of TPT was 5.25 μg Sn/L, and 72h EC50 was 0.96 μg Sn/L. TPT induced multiple malformations including enlarged proctodaeum and narrow fins. TPT at 5 μg Sn/L inhibited the differentiation of skins and muscles. The reduced brain, loss of external eyes and bent axis were observed in RXR and RAR ligands treatments. TPT and tributyltin (TBT) inhibited the mRNA expression of RXRα and increased that of TRβ. The phenotypes of malformations induced by TPT were similar to those by TBT and were much different from those by the RXR and RAR ligands. These results indicated that TPT was acute toxic and had high teratogenicity to amphibian embryos, and that TPT induced phenotypes of malformations. TPT and TBT might have a similar teratogenic mechanism, which seems not to be mainly mediated through RA signal.

Inhibition of hedgehog signaling decreases proliferation and clonogenicity of human mesenchymal stem cells

Human mesenchymal stem cells (hMSC) have the ability to differentiate into osteoblasts, adipocytes and chondrocytes. We have previously shown that hMSC were endowed with a basal level of Hedgehog signaling that decreased after differentiation of these cells. Since hMSC differentiation is associated with growth-arrest we investigated the function of Hh signaling on cell proliferation. Here, we show that inhibition of Hh signaling, using the classical inhibitor cyclopamine, or a siRNA directed against Gli-2, leads to a decrease in hMSC proliferation. This phenomenon is not linked to apoptosis but to a block of the cells in the G0/G1 phases of the cell cycle. At the molecular level, it is associated with an increase in the active form of pRB, and a decrease in cyclin A expression and MAP kinase phosphorylation. Inhibition of Hh signaling is also associated with a decrease in the ability of the cells to form clones. By contrast, inhibition of Hh signaling during hMSC proliferation does not affect their ability to differentiate. This study demonstrates that hMSC are endowed with a basal Hedgehog signaling activity that is necessary for efficient proliferation and clonogenicity of hMSC. This observation unravels an unexpected new function for Hedgehog signaling in the regulation of human mesenchymal stem cells and highlights the critical function of this morphogen in hMSC biology.

Arsenite stabilizes HIF-1α protein through p85α-mediated up-regulation of inducible Hsp70 protein expression

Hypoxia-inducible factor-1α (HIF-1α) has been reported to regulate over 100 gene expressions in response to hypoxia and other stress conditions. In the present study, we found that arsenite could induce HIF-1α protein accumulation in both mouse epidermal Cl41 cells and mouse embryonic fibroblasts (MEFs). Knockout of p85α, a regulatory subunit of PI-3K, in MEFs (p85α(-/-)) dramatically decreased the arsenite-induced HIF-1α accumulation, indicating that p85α is crucial for arsenite effects on the stabilization of HIF-1α protein. Our further studies suggest that arsenite could induce inducible Hsp70 expression, and transfection of inducible Hsp70 into p85α(-/-) MEFs could restore HIF-1α protein accumulation. Moreover, the results using EMSA and Supershift assays indicate that p85α is crucial for arsenite-induced activation of the heat-shock transcription factor 1 (HSF-1), which is responsible for transcription of inducible Hsp70. Taken together, p85α-mediated HIF-1α stabilization upon arsenite exposure is specifically through HSF-1 activation and subsequent up-regulation of the inducible Hsp70 expression.

Neuroplasticity of the central hypercapnic ventilatory response: teratogen-induced impairment and subsequent recovery during development

Neuroventilation is highly plastic and exposure to either of two distinct teratogens, nicotine or ethanol, during development results in a similar loss of the neuroventilatory response to hypercapnia in bullfrog tadpoles. Whether this functional deficit is permanent or transient following nicotine or ethanol exposure was unknown. Here, we tested the persistence of hypercapnic neuroventilatory response impairments in tadpoles exposed to either 30 microg/L nicotine or 0.12-0.06 g/dL ethanol for 10 weeks. Brainstem breathing-related neural activity was assessed in tadpoles allowed to develop teratogen-free after either nicotine or ethanol exposure. Nicotine-exposed animals responded normally to hypercapnia after a 3-week teratogen-free period but the hypercapnic response in ethanol-exposed tadpoles remained impaired. Tadpoles allowed to develop for only 1 week nicotine free after chronic exposure were unable to respond to hypercapnia. The hypercapnic response of ethanol-exposed tadpoles returned by 6 weeks following chronic ethanol exposure. These findings suggest that some nicotine- and ethanol-induced impairments can be resolved during early development. Understanding both the disruptive effects of nicotine and ethanol exposure and how impaired responses return when teratogen exposure stops may offer insight on the function and plasticity of respiratory control.

The effect of differentiating and apoptotic agents on notch signalling pathway in hepatoblastoma

BACKGROUND/AIMS

Notch expression is not yet determined in hepatoblastoma. In this study the effect of chemotherapeutics (cisplatin, doxorubicin, cytosin arabinoside); differentiating agent (13 cis-retinoic acid) and apoptotic agents (5-aza-2'-deoxycytidine, arsenic trioxide) on notch expression in hepatoblastoma were evaluated.

METHODOLOGY

After HepG2 cell line was cultured and the agents and their combinations were applied for 24 hour in pre-optimized 50% lethal doses, RNA isolation and cDNA converting, expression of 84 custom array genes of notch signaling pathway (SABiosciences, PAT059F-24) was determined by Real Time PCR. The methylation status of 6 genes that showed more than 5 fold changes compared with control group were explored by Methylation qPCR Assay. High expressed genes are HDAC1, NFKB1, CHUK, CDKN1A, and CBL. Low expressed genes are DLL1, CD44, FZD2, GLI1, IL17B, LMO2, NOTCH1, LOR, PAX5, PT-CRA, SH2D1A, and WISP1. The genes searched for methylation (DLL1, HEY1, DTX1, HDAC1, NOTCH2 and JAG1) were not found to be related with methylation.

RESULTS

The high expressed genes are related with cell proliferation. The main signaling genes that are closed to notch in signaling pathway are low expressed in hepatoblastoma. The agents do not show prominent effect of gene expression in many genes and methylation is not the reason of expression changes. The use of retinoic acid in the control of minimal residual disease of hepatoblastoma should be discussed. 5 aza "cytidin" the demethylating agent is not advised in treatment according to our results.

CONCLUSION

Cisplatin as main chemotherapeutic agent treatment is shown to change gene expression levels in notch signalling pathway in hepatoblastoma.

In vitro developmental toxicology assays: A review of the state of the science of rodent and zebrafish whole embryo culture and embryonic stem cell assays

In vitro developmental model systems have been an important tool for advancing basic research in the embryology and teratology fields. The rat and zebrafish embryo models have had broad utility in both fields for many decades. Furthermore embryonic stem cells, applied as a basic research tool, have broad applications across the development fields and many other fields including cancer, regeneration and epigenetic research. These models have historically been applied in mechanistic studies but were also considered promising for evaluating teratogenic potential of test substances. In recent years, in vitro teratogenicity assays have become an area of interest for supporting the 3 Rs (reduction, refinement, and replacement of animal use). Generation of such assays also provides a means to facilitate early assessment of test agents at a higher throughput without excessive use of animals. In this review, the three models are described with an emphasis of how they are being developed and/or refined to support teratogenicity assessment as screening tools. An overview of the state of the science and future directions are described.

Delayed ossification in Wistar rats induced by Morinda citrifolia L. exposure during pregnancy

Different products of plant Morinda citrifolia L. (noni) have been marketed and used around the world based on properties described by Polynesian people that use them for more than 2000 years. Marketing of these products is based on their presumptive phytotherapic properties. However there is little scientific evidence about their safety, especially when used during pregnancy.

AIM OF THE STUDY

Evaluate the possible developmental toxicity of the noni fruit aqueous extract and commercial product of TAHITIAN NONI juice in rats exposed during pregnancy.

MATERIALS AND METHODS

Pregnant Wistar rats were exposed by gavage to 7, 30 and 300 mg/kg bw (body weight) of noni aqueous extract or to 0.4, 2 and 20 mL/kg bw (body weight) of noni juice between day 7 and day 15 of pregnancy. Caesarean sections were performed on day 20 of pregnancy and reproductive parameters were evaluated. Implantations sites and postimplantation losses were recorded. Fetuses were weighted and examined for externally visible anomalies. After, the fetuses were cleared with KOH and the bones stained with alizarin red. Skeletal alterations of the skull, vertebral column, ribs, forelimbs, hindlimbs, sternum, sings of delayed ossification and variations were examined in accordance with pre-defined criteria and identified using harmonized and internationally accepted nomenclature recommended by the International Federation of Teratology Societies.

RESULTS

Exposure with extract and juice of Morinda citrifolia did not induce maternal toxicity at the tested doses, but induced delayed ossification in fetuses.

CONCLUSION

The exposure of pregnant rats to aqueous extract or juice Morinda citrifolia during organogenesis period may induce adverse effects on the normal development of fetuses. These findings indicate the need for further studies with noni derivates preceding their use in pregnant women.

Phosphoproteomic profiling of arsenite-treated human small airway epithelial cells

Arsenic is well documented as a chemotherapeutic agent capable of inducing cell death; however, it is also considered as a human carcinogen. Although it has recently been shown that arsenite exposure can potentiate genotoxicity, little is known about its global effects exerted in cells at the proteome level. Immortalized human small airway epithelial cells exposed to arsenite were used to identify phosphoproteins of two major signaling cascades, such as the human phospho-receptor tyrosine kinase (Phospho-RTK) and the mitogen-activated protein kinases (MAPKs). These two arrays included several phosphoproteins, such as EGFR, ErbB2, ErbB4, InsulinR, Flt-3, extracellular signal-regulated kinases (ERK1/2), intracellular kinases such as AKT, GSK-3, c-Jun N-terminal kinases (JNK1-3) and different p38 isoforms (alpha/beta/delta/gamma). In arsenite-treated cells, phosphorylation of EGFR, InsulinR and Flt3R showed an increase when compared to their non-arsenite treated counterparts. Inhibitors of these proteins further confirmed the involvement of such proteins in the neoplasm transformation of arsenite-treated human small airway epithelial cells as seen in changes in plating efficiency, anchorage-independent growth and proliferation rate. It can be concluded that analysis of phosphoprotein by using phosphoproteomic profiling can be very useful to understand the mechanism of arsenite-induced carcinogenesis.

Embryotoxicity of mirtazapine: a study using Chick Embryotoxicity Screening Test

OBJECTIVE

Mirtazapine is a new antidepressant used in last years, however experience with it during pregnancy is unsatisfactory on the present. Its wide therapeutic range and only little proved side effects may be an advantage for treatment during pregnancy. Aim of our study was to contribute to the knowledge on possible risks.

MATERIALS AND METHODS

For embryotoxicity testing we used an alternative method - CHEST, that used chicken embryos as experimental model. Fertilized eggs of outbred Grey Leghorn stock (AVČR farm Koleč) were treated on embryonic day (ED) 4 by Mirtazapine, incubated till 9ED, when they were weighed and examined. Summing the proportions of dead and malformed embryos, the beginning of the embryotoxicity dose range was estimated.

RESULTS

Mirtazapine solved in 15% DMSO in water revealed low embryotoxicity corresponding data from preclinical studies. If 100% DMSO was used as a solvent, the dose 0.05 μg/3 μL resulted in 57% mortality (LD50). Typical malformations were microphtalmia and malformation (shortening) of limbs on left side, which is a place of contact the embryonic body with maximal Mirtazapine concentration. Approximation of doses in chick embryos to mammals is complicated by low solubility of mirtazapine.

CONCLUSIONS

If the embryotoxic dose was close to LD50, risk at therapeutical doses will be probably low. Mirtazapine according to results of testing and cases published in literature is relatively safe for pregnant women, only higher rate of abortions was demonstrated, however more information is needed to exclude all potential risks.

Can iron be teratogenic?

Several kinds of evidence indicate that elevated iron during the 3-8 week embryonic (organogenesis) period of human gestation may be teratogenic. (1) In the embryonic period, the natural maternal absorption of food iron is 30% below the estimated daily iron loss. (2) As compared with maternal serum, embryonic fetal coelomic fluid contains only one-fourth as much iron but nearly six times the quantity of the iron withholding protein, ferritin. (3) In the embryonic period, intraplacental oxygen pressure is 2-3 times lower than in the subsequent fetal growth period. (4) Iron is a strong inducer of emesis which peaks in the embryonic period. (5) In a murine gestation model, iron was neurotoxic at a sharp peak of 8-9 days. Thus it would be prudent, in human pregnancy, to delay any needed iron supplementation until the embryonic period has been completed.

From teratogens to potential therapeutics: natural inhibitors of the Hedgehog signaling network come of age

Steroidal alkaloids from Veratrum californicum (Durand) are known to exert teratogenic effects (e.g., cyclopia, holoprosencephaly) by blocking the Hedgehog (Hh) signaling pathway, which plays a considerable role in embryonic development and organogenesis. Most surprisingly, recent studies demonstrate that this complex signaling network is active even in the healthy adult organism, where it seems to control important aspects of basic metabolism and interorgan homeostasis. Abnormal activation of Hh signaling, however, can lead to the development of different tumors, psoriasis, and other diseases. This review provides an overview of how the principle teratogenic and hazardous constituent of Veratrum californicum, cyclopamine, interferes with Hh signaling and can potentially serve as a beneficial therapeutic for different tumors and psoriasis.

Phosphate Increases Mitochondrial Reactive Oxygen Species Release

The effects of inorganic phosphate (Pi), the main intracellular membrane permeable anion capable of altering mitochondrial pH gradients (Delta pH), were measured on mitochondrial H2O2 release. As expected, Pi decreased Delta pH and increased the electric membrane potential (Delta Psi). Mitochondrial H2O2 release was stimulated by Pi and also by its structural analogue arsenate. However, acetate, another membrane-permeable anion, did not stimulate mitochondrial H2O2 release. The stimulatory effect promoted by Pi was prevented by CCCP, which decreases transport of Pi across the inner mitochondrial membrane, indicating that Pi must be in the mitochondrial matrix to stimulate H2O2 release. In conclusion, we found that Pi and arsenate stimulate mitochondrial reactive oxygen release, an effect that may contribute towards oxidative stress under conditions such as ischemia/reperfusion, in which high-energy phosphate bonds are hydrolyzed.

Radiosensitization by 6-aminonicotinamide and 2-deoxy-D-glucose in human cancer cells

The aim was to exploit simultaneous inhibition of glycolytic and pentose phosphate pathways of energy production for radiosensitization using 2-deoxy-D-glucose (2-DG) and 6-aminonicotinamide (6-AN) in transformed mammalian cells. Two human tumour cell lines (cerebral glioma, BMG-1 and squamous carcinoma cells 4197) were investigated. 2-DG and/or 6-AN added at the time of irradiation were present for 4 h after radiation. Radiation-induced cell death (macrocolony assay), cytogenetic damage (micronuclei formation), cell cycle delay (bromodeoxyuridne (BrdU) pulse chase), apoptosis (externalization of phosphotidylserine (PS) by annexin V), chromatin-bound proliferation cell nuclear antigen (PCNA) and cellular glutathione (GSH) levels were investigated as parameters of radiation response. The presence of 2-DG (5 mM) during and for 4 h after irradiation increased the radiation-induced micronuclei formation and cell death, and caused a time-dependent decrease in GSH levels in BMG-1 cells while no significant effects could be observed in 4197 cells. 6-AN (5 microM) enhanced the radiosensitivity of both cell lines and reduced the GSH content by nearly 50% in gamma-irradiated 4197 cells. Combining 2-DG and 6-AN caused a profound decrease in the GSH content and enhanced the radiation damage in both the cell lines by increasing mitotic and apoptotic cell death. Further, the combination (2-DG + 6-AN) enhanced the radiation-induced G2 block, besides arresting cells in S phase and inhibited the recruitment of PCNA. The combination of 2-DG and 6-AN enhances radiation damage by modifying damage response pathways and has the potential for improving radiotherapy of cancer.

Developmental consequences of prenatal tobacco exposure

PURPOSE OF REVIEW

This paper reviews results from published, in press, and conference proceedings from 2007 and 2008 that link in-utero tobacco exposure to neurodevelopmental outcomes in exposed offspring.

RECENT FINDINGS

Prenatal tobacco exposure (PTE) affected speech processing, levels of irritability and hypertonicity, attention levels, ability to self-regulate, need to be handled, and response to novelty preference in infants. In early childhood, PTE effects were mostly behavioral outcomes including activity and inattention and externalizing behaviors, including conduct disorder and antisocial behavior. In adolescents, PTE predicted increased attention deficit hyperactivity disorder, modulation of the cerebral cortex and white matter structure, and nicotine addiction. Several studies found moderating effects with PTE and genetic susceptibilities including dopamine transporter, serotonergic synaptic function, and monomine oxidase pathways. Other studies suggested that environmental and genetic factors might be more important than the direct teratological effects of PTE.

SUMMARY

The majority of studies reviewed were prospective and tobacco exposure was quantified biologically. Most demonstrated a direct association between PTE and neurodevelopmental outcomes. More work is needed to examine multifactorial influences. Effects of PTE on the offspring appear to be moderated by genetic variability, neurobehavioral disinhibition, and sex.

Dynein motor contributes to stress granule dynamics in primary neurons

Mobilization and translation of mRNAs, two important events believed to involve stress granules (SGs), in neurons are important for their survival and activities. However, the formation and disassembly of SGs in neurons remains unclear. By using an arsenite-induced neuronal stress model of rat primary spinal cord neuron cultures, we demonstrate the formation of SGs that contain common SG components and RNAs in both stressed neuronal cell bodies and their neurites. By employing small interfering RNA (siRNA) knockdown, we discovered that dynein motor subunit localizes in SG, and is important for SG assembly in neurons. Under stress, dynein motor subunit also facilitates translational repression and enhances the formation and integrity of SG in neurons. By blocking the energy source of dynein motor, both the formation and disassembly of SG are attenuated. These findings demonstrate, for the first time, that dynein motor complex plays a critical role in the dynamics of neuronal SGs, as well as translation of certain mRNAs.