Valproic acid-induced placental and teratogenic effects in rats

Animal Model of Autism Induced by Valproic Acid Combined with Maternal Deprivation: Sex-Specific Effects on Inflammation and Oxidative Stress

Autism spectrum disorder (ASD) etiology probably involves a complex interplay of both genetic and environmental risk factors, which includes pre- and perinatal exposure to environmental stressors. Thus, this study evaluated the effects of prenatal exposure to valproic acid (VPA) combined with maternal deprivation (MD) on behavior, oxidative stress parameters, and inflammatory state at a central and systemic level in male and female rats. Pregnant Wistar rats were exposed to VPA during gestation, and the offspring were submitted to MD. Offspring were tested for locomotor and social behavior; rats were euthanized, where the cerebellum, posterior cortex, prefrontal cortex, and peripheric blood were collected for oxidative stress and inflammatory analysis. It was observed that young rats (25-30 days old) exposed only to VPA presented a lower social approach when compared to the control group. VPA + MD rats did not present the same deficit. Female rats exposed to VPA + MD presented oxidative stress in all brain areas analyzed. Male rats in the VPA and VPA + MD groups presented oxidative stress only in the cerebellum. Regarding inflammatory parameters, male rats exposed only to MD exhibited an increase in pro-inflammatory cytokines in the blood and in the cortex total. The same was observed in females exposed only to VPA. Animals exposed to VPA + MD showed no alterations in the cytokines analyzed. In summary, gestational (VPA) and perinatal (MD) insults can affect molecular mechanisms such as oxidative stress and inflammation differently depending on the sex and brain area analyzed. Combined exposition to VPA and MD triggers oxidative stress especially in female brains without evoking an inflammatory response.

Exposure to Valproic acid (VPA) resulted in alterations in the expression of angiogenic genes (NRP-1, VEGFA, VEGFR-2 and sFlt1) and histological modifications in the placenta of mice (Mus musculus)

Valproic acid (VPA), an anti-epileptic drug (AED), has been reported to exhibit anti-angiogenic properties. This study aimed to examine the impact of VPA on the expression of NRP-1 and additional angiogenic factors, as well as angiogenesis, in mouse placenta. Pregnant mice were divided into four groups: control (K), solvent control (KP), VPA treatment at a dose of 400 mg/kg body weight (BW) (P1), and VPA treatment at a dose of 600 mg/kg BW (P2). The mice were subjected to daily treatment via gavage from embryonic day (E) 9 to E14 and E9 to E16. Histological analysis was performed to evaluate Microvascular Density (MVD) and percentage of the placental labyrinth area. In addition, a comparative analysis of Neuropilin-1 (NRP-1), vascular endothelial growth factor (VEGFA), vascular endothelial growth factor receptor (VEGFR-2), and soluble (sFlt1) expression was conducted in relation to glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The results of the MVD analysis and percentage of labyrinth area in the E14 and E16 placentas indicated that the treated groups were significantly lower than the control group. The relative expression levels of NRP-1, VEGFA, and VEGFR-2 in the treated groups were lower than those in the control group at E14 and E16. Meanwhile, the relative expression of sFlt1 in the treated groups at E16 was significantly higher than in the control group. Changes in the relative expression of these genes inhibit angiogenesis regulation in the mouse placenta, as evidenced by reduced MVD and a smaller percentage of the labyrinth area.

Transcriptomics and Other Omics Approaches to Investigate Effects of Xenobiotics on the Placenta

The conceptus is most vulnerable to developmental perturbation during its early stages when the events that create functional organ systems are being launched. As the placenta is in direct contact with maternal tissues, it readily encounters any xenobiotics in her bloodstream. Besides serving as a conduit for solutes and waste, the placenta possesses a tightly regulated endocrine system that is, of itself, vulnerable to pharmaceutical agents, endocrine disrupting chemicals (EDCs), and other environmental toxicants. To determine whether extrinsic factors affect placental function, transcriptomics and other omics approaches have become more widely used. In casting a wide net with such approaches, they have provided mechanistic insights into placental physiological and pathological responses and how placental responses may impact the fetus, especially the developing brain through the placenta-brain axis. This review will discuss how such omics technologies have been utilized to understand effects of EDCs, including the widely prevalent plasticizers bisphenol A (BPA), bisphenol S (BPS), and phthalates, other environmental toxicants, pharmaceutical agents, maternal smoking, and air pollution on placental gene expression, DNA methylation, and metabolomic profiles. It is also increasingly becoming clear that miRNA (miR) are important epigenetic regulators of placental function. Thus, the evidence to date that xenobiotics affect placental miR expression patterns will also be explored. Such omics approaches with mouse and human placenta will assuredly provide key biomarkers that may be used as barometers of exposure and can be targeted by early mitigation approaches to prevent later diseases, in particular neurobehavioral disorders, originating due to placental dysfunction.

Characterizing the effects of in utero valproic acid exposure on murine fetoplacental development

INTRODUCTION

Valproic acid (VPA) is an effective anti-epileptic drug clinically used to treat seizures, bipolar disorders and neuropathic pain in women of reproductive age. Current approval of VPA for psychiatric conditions and migraine has increased the number of VPA exposed pregnancies. VPA crosses the placental barrier and induces birth defects in about 10% of exposed pregnancies. In addition, VPA exposure results in neurodevelopmental disorders in children without any overt birth defects. The current study was designed to investigate the effects of in utero VPA exposure on fetoplacental growth in a mouse model.

METHODS

Pregnant CD-1 dams were exposed to a single teratogenic dose of 400 mg/kg VPA or saline via subcutaneous injection on gestational day (GD) 9 and fetuses were harvested on GD 13, 15, 17 and 19, respectively. Resorptions, gross malformations, fetal weight, fetal head weight, fetal crown-rump length, fetal head transverse and anteroposterior diameters, placental weight and placental diameter were noted.

RESULTS

VPA exposure led to multiple external deformities including exencephaly, open eye defect, subcutaneous hemorrhage and underdevelopment of tail. All fetoplacental growth parameters fetal weight, fetal head weight, fetal crown-rump length, placental weight and placental diameter were significantly reduced in VPA-exposed fetuses with and without congenital malformations such as exencephaly, compared to control fetuses.

DISCUSSION

In conclusion, the effects of in utero VPA exposure on fetal and placental growth persisted throughout pregnancy and our results suggest that the effects of VPA on placental growth may play a role in VPA-induced toxicity.

Gestational valproic acid exposure induces epigenetic modifications in murine decidua

INTRODUCTION

Valproic acid (VPA), a widely prescribed antiepileptic drug and an effective treatment for bipolar disorder and neuropathic pain, results in multiple developmental defects following in utero exposure. Uterine decidua provides nutritional and physical support during implantation and early embryonic development. Perturbations in the molecular mechanisms within decidual tissue during early pregnancy might affect early embryonic growth, result in early pregnancy loss or cause complications in the later gestational stage. VPA is a known histone deacetylase inhibitor and epigenetic changes such as histone hyperacetylation and methylation have been proposed as a mechanism of VPA-induced teratogenesis.

METHODS

This study investigated the effects of in utero VPA exposure on histone modifications in murine decidual tissue. Pregnant CD-1 mice were exposed to 400 mg/kg VPA or saline on GD9 via subcutaneous injection. Decidual tissue from each gestational sac was harvested at 1, 3 and 6 h following exposure. Levels of acetylated histones H3, H4 and H3K56, as well as methylated histones H3K9 and H3K27 were acid extracted and assessed by western blotting followed by acid histone extraction.

RESULTS

VPA exposure induced a significant increase (p < 0.05) in the levels of acetylated H3 at 1, 3 h; acetylated H4 at 1, 3 and 6 h and trimethylated H3K9 at 6 h. In contrast, no significant perturbations were noted in the levels of monomethylated H3K9, trimethylated H3K27 and acetylated H3K56.

DISCUSSION

The results from this study suggest that VPA-induced decidual histone modifications might play an important role as a mechanism of VPA-induced teratogenesis during early embryonic growth.

Effect of aspartame on the placenta of adult albino rat. A histological and immunohistochemical study

Aspartame is an artificial sweetener usually consumed by hundreds of millions of persons all over the world. Its metabolites can be toxic to many organs and there are only a few studies on the use of aspartame during gestation. The present study was designed to fully evaluate the effect of aspartame on the histological structure of the placenta in the adult albino rat. Twenty pregnant female rats were equally divided into group I that served as control, and group II that received aspartame at a dose 14 mg/kg by gavage on the 9th, 10th and 11th day of pregnancy. Placental specimens were processed for histological and immunohistochemical staining against vascular endothelial growth factor (VEGF). Aspartame induced a significant decrease in the mean placental weight and the mean thickness of both labyrinth and basal zones. Damage in the placenta was detected in the form of rupture of the interhemal membrane, lysis of glycogen trophoblast cells, spongiotrophoblast cells with vacuolated cytoplasm and darkly stained nuclei. A significant increase in vascular endothelial growth factor expression in both labyrinth and basal zones was detected. Ultrastructural examination showed fetal capillaries with condensed nuclei of endothelial cells, cytotrophoblasts with condensed fragmented nuclei and vacuolated cytoplasm, and syncytiotrophoblasts with irregular condensed fragmented nuclei. It could be concluded that aspartame has deeply impacted the normal structure and presumably the function of the placenta, therefore, restrictions are to be imposed on the consumption of aspartame especially during pregnancy.

Effect of in utero exposure to the atypical anti-psychotic risperidone on histopathological features of the rat placenta

For clinical management of different forms of psychosis, both classical and atypical anti-psychotic drugs (APDs) are available. These drugs are widely prescribed, even during pregnancy considering their minimal extra-pyramidal side effects and teratogenic potential compared to classical APDs. Among AAPDs, risperidone (RIS) is a first-line drug of choice by physicians. The molecular weight of RIS is 410.49 g/mol; hence, it can easily cross the placental barrier and enter the foetal bloodstream. It is not known whether or not AAPDs like RIS may affect the developing placenta and foetus adversely. Reports on this issue are limited and sketchy. Therefore, this study has evaluated the effects of maternal exposure to equivalent therapeutic doses of RIS on placental growth, histopathological and cytoarchitectural changes, and to establish a relationship between placental dysfunction and foetal outcomes. Pregnant rats (n = 24) were exposed to selected doses (0.8, 1.0 and 2.0 mg/kg) of RIS from gestation days 6-21. These dams were sacrificed; their placentas and foetuses were collected, morphometrically examined and further processed for histopathological examination. This study revealed that in utero exposure to equivalent therapeutic doses of RIS during organogenesis-induced placental dystrophy (size and weight), disturbed cytoarchitectural organization (thickness of different placental layers), histopathological lesions (necrosis in trophoblast with disruption of trophoblastic septa and rupturing of maternal-foetal interface) and intrauterine growth restriction of the foetuses. It may be concluded that multifactorial mechanisms might be involved in the dysregulation of structure and function of the placenta and of poor foetal growth and development.

Toxicological pathology in the rat placenta

The placenta grows rapidly for a short period with high blood flow during pregnancy and has multifaceted functions, such as its barrier function, nutritional transport, drug metabolizing activity and endocrine action. Consequently, the placenta is a highly susceptible target organ for drug- or chemical-induced adverse effects, and many placenta-toxic agents have been reported. However, histopathological examination of the placenta is not generally performed, and the placental toxicity index is only the placental weight change in rat reproductive toxicity studies. The placental cells originate from the trophectoderm of the embryo and the endometrium of the dam, proliferate and differentiate into a variety of tissues with interaction each other according to the development sequence, resulting in formation of a placenta. Therefore, drug- or chemical-induced placental lesions show various histopathological features depending on the toxicants and the exposure period, and the pathogenesis of placental toxicity is complicated. Placental weight assessment appears not to be enough to evaluate placental toxicity, and reproductive toxicity studies should pay more attention to histopathological evaluation of placental tissue. The detailed histopathological approaches to investigation of the pathogenesis of placental toxicity are considered to provide an important tool for understanding the mechanism of teratogenicity and developmental toxicity with embryo lethality, and could benefit reproductive toxicity studies.

Thrombophilic risk factors in epileptic children treated with valproic Acid

There are few reports on valproic acid related to thrombophilia. Thrombophilic risk factors were investigated in 21 children (age range, 1-13 years) diagnosed with epilepsy and newly treated with valproic acid monotherapy. None of the children had been previously treated with any anticonvulsant agent. Before starting valproic acid therapy, homocysteine, lipoprotein(a), factor VIII, factor IX, protein C, protein S, antithrombin III levels, and activated protein C resistance levels were evaluated in all patients, with repeat evaluation after 9 months or 1 year of the therapy. Thrombosis gene mutations (factor V Leiden and prothrombin G20210A) were also evaluated in all patients before therapy. There was statistically significant elevation in lipoprotein(a) levels and reduction in fibrinogen levels after treatment. Reduction in protein C levels and elevation in homocysteine levels were also observed, but without statistical significance. Before therapy, no thrombotic event had occurred, despite thrombotic risk factors in some patients. Valproic acid can increase lipoprotein(a) and decrease fibrinogen, which may increase the risk of stroke or other thrombotic events. No clinical adverse effects resulted from changes in the levels or activity of thrombophilic factors associated with valproic acid treatment. Thus, routine investigation of factors implicated in thrombosis prior to initiation of valproic acid is not warranted for all patients. Nonetheless, caution is advised when initiating valproic acid treatment in children who have had prior stroke or thrombotic events.

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

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

Valproate, thalidomide and ethyl alcohol alter the migration of HTR-8/SVneo cells

BACKGROUND

Valproate, thalidomide and alcohol (ethanol) exposure during the first trimester of pregnancy is known to cause several developmental disorders. All these teratogens are known to pass the placental barrier and interfere directly with the normal development of the fetus. However, these teratogens also alter the formation and function of the placenta itself which may in turn affect the proper nourishment and development of the fetus. Optimum development of the placenta requires adequate invasion of trophoblast into the maternal uterine tissues. Changes in the migratory behavior of trophoblast by maternal exposure to these teratogens during placentogenesis may therefore alter the structure and function of the placenta.

METHODS

In the present study, the effects of sodium valproate, thalidomide and alcohol on the migration of human first trimester trophoblast cell line (HTR-8/SVneo) were examined in vitro. Cells were cultured in the wells of 48-well culture plates as mono or multilayers. Circular patches of cells were removed from the center of the wells by suction, and the migration of cells into the wound was studied using microscopy. Effects of low and high concentrations of valproate, thalidomide and alcohol were examined on the healing of wounds and on the migration rate of cells by determining the wound areas at 0, 3, 6, 12, 24 and 48 h. Effects of drugs and alcohol on the proliferation and the expression levels of integrin subunits beta1 and alpha5 in cells were examined.

RESULTS

The migration rates of trophoblast differed between wounds created in mono and multilayers of cells. Exposure to teratogens altered the migration of trophoblast into mono and multilayer wounds. The effects of valproate, thalidomide and alcohol on the proliferation of cells during the rapid migratory phase were mild. Drug exposure caused significant changes in the expression levels of beta1 and alpha5 integrin subunits.

CONCLUSION

Results suggest that exposure to valproate, thalidomide or alcohol during the first trimester of pregnancy may change the ultrastructure of the placenta by altering the migration of trophoblast cells and this effect may be mediated by drug- or alcohol-induced changes in the expression levels of beta1 and alpha5 integrin subunits.

Cerebral vein thrombosis and prothrombin gene (G20210A) mutation

Recently, prothrombin gene mutation G20210A has been associated with elevated thrombosis risk and rarely with cerebral vein thrombosis (CVT). Three patients are described who had this genetic predisposition and who developed CVT in an unusual constellation with other factors. In the first patient, the intake of valproic acid (VPA) may have played an aggravating role in the development of CVT; in the second patient diagnosis of coagulation disorder was made during pregnancy consultation 6 years after CVT; in the third patient the CVT occurred at the age of 78 years. In patients with CVT, coagulation-examinations should include tests for the prothrombin gene (G20210A) mutation.

Placental effects of lead in mice

Although a number of studies in animal models have shown embryolethal and teratogenic lead effects when this element is administered by a parenteral route, the mechanism of the embryonary changes is well not established. In this study, the embryonic effects of parenteral lead exposure on day 9 of gestation were assessed in the Swiss mouse. Lead acetate trihydrate was injected intraperitoneally at 14, 28, 56 and 112 mg/kg. There was no maternal toxicity evidenced by death, reduced body weight gain or reduced food consumption. However, absolute placental weight at 112 mg/kg and relative placental weight at 14, 56 and 112 mg/kg were diminished significantly. The number of total implants, live and dead fetuses, sex ratio and fetal body weight were unaffected by lead exposure. Most sections of placenta showed vascular congestion, an increase of intracellular spaces and deposits of hyaline material of perivascular predominance. Trophoblast hyperplasia was also observed, whereas there was a reinforcement of the fibrovascular network in the labyrinth. It is concluded that the trophoblast hyperplasia observed in the placenta of pregnant mice after parenteral lead exposure at doses that are not toxic for the dam could act as a repairing mechanism of the extraembryonary tissues.

Morphological features of encephalopathy after chronic administration of the antiepileptic drug valproate to rats. A transmission electron microscopic study of capillaries in the cerebellar cortex

Long-term intragastric application of the antiepileptic drug sodium valproate (Vupral "Polfa") at the effective dose of 200 mg/kg b. w. once daily to rats for 1, 3, 6, 9 and 12 months revealed neurological disorders indicating cerebellum damage ("valproate encephalopathy"). The first ultrastructural changes in structural elements of the blood-brain-barrier (BBB) in the cerebellar cortex were detectable after 3 months of the experiment. They became more severe in the later months of the experiment, and were most severe after 12 months, located mainly in the molecular layer of the cerebellar cortex. Lesions of the capillary included necrosis of endothelial cells. Organelles of these cells, in particular the mitochondria (increased number and size, distinct degeneration of their matrix and cristae) and Golgi apparatus were altered. Reduced size of capillary lumen and occlusion were caused by swollen endothelial cells which had luminal protrusions and swollen microvilli. Pressure on the vessel wall was produced by enlarged perivascular astrocytic processes. Fragments of necrotic endothelial cells were in the vascular lumens and in these there was loosening and breaking of tight cellular junctions. Damage to the vascular basement lamina was also observed. Damage to the capillary was accompanied by marked damage to neuroglial cells, mainly to perivascular processes of astrocytes. The proliferation of astrocytes (Bergmann's in particular) and occasionally of oligodendrocytes was found. Alterations in the structural elements of the BBB coexisted with marked lesions of neurons of the cerebellum (Purkinje cells are earliest). In electron micrographs both luminal and antiluminal sides of the BBB of the cerebellar cortex had similar lesions. The possible influence of the hepatic damage, mainly hyperammonemia, upon the development of valproate encephalopathy is discussed.

Mouse placenta: hemodynamics in the main maternal vessel and histopathologic changes induced by 2-methoxyethanol and 2-methoxyacetic acid following maternal dosing

The two main maternal vessels that are a major, if not the entire, source of maternal blood for the mouse placenta are unique in possessing intraluminal valvular projections. The morphologic configuration of these projections suggests their potential to converge, diverge, and rotate blood currents flowing under systolic pressure. The intravascular occurrence of circular fibrin bodies composed of concentric fibrin strands coagulated from the plasma and almost no blood cellular elements in these strands lends credence to this concept. Histopathologic changes in the extraembryonic and embryonic tissues induced by an intraperitoneal injection of 250 or 500 mg/kg of 2-methoxyethanol, or its metabolite, 2-methoxyacetic acid, via oral gavage were determined 48 hr after dosing CD-1 mice on day 11 of pregnancy. Both compounds caused 1) marked congestion and dilatation, associated with or without fibrinous occlusions, of the main maternal vessel of the placenta, 2) serosanguinous exudation and maternal hemorrhages from the placental periphery, 3) necrosis and desquamation involving the mesometrial surface or peripheral edge of the placenta, 4) translabyrinthine embryonic hemorrhage into the maternal circulation, and 5) embryonic hemorrhages into the exocoelomic, amniotic, and pericardial cavities. These lesions signify a disordered maternal circulation in the placenta suggestive of potentially serious pathologic effects. These lesions may play a role in the resorption, reduction in fetal body weight, and syndactyly or oligodactyly attributed to 2-methoxyethanol and 2-methoxyacetic acid.

A morphologic basis postulated for valproic acid's embryotoxic action in rats

A tentative 3 phase sequence of pathogenesis is proposed for the embryotoxic action of valproic acid (800 mg/kg) administered orally to rats on day 13 of pregnancy. This is based on histopathological changes in the extraembryonic and embryonic tissues which occurred in the absence of any biologically significant effect on maternal homeostasis. Major events in the first, decidual (or maternal) phase are cells lining the maternal sinusoids in the decidua basalis are necrosed, desquamated, and washed away by the arterial circulation through the afferent channels. The necrosed cells, with their walls still intact, occlude the lumen of these arterial channels at the point of their entry into the giant cell-trophospongial zone. The channel occlusions cause ischemia and homeostasis of the maternal circulation in the labyrinth by reducing the rate of inflow of maternal blood. The embolic occlusion of maternal arterial channels apparently results in a long-term reduction in the number and size of maternal channels that supply arterial blood to the labyrinth. In the second or placental phase, the parenchyma of the labyrinth and connective tissue in the chorionic plate and umbilical cord, which have been deprived of nutrition and oxygen by the ischemia and stasis of maternal blood in the labyrinth, undergo degenerative changes. In the third or embryonic phase, a pleiotropic karyorrhexis in the embryo, initiated as early as 4 h postdosing, appeared aggravated, presumably by the preceding labyrinthine degeneration of the placental phase. The valproic acid-induced embryotoxicity thus seemed to result from a combination of maternal, placental, and embryonic changes.