Placental toxicity in rats after administration of synthetic glucocorticoids. A morphological, histochemical and immunohistochemical investigation

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.

Rats Born to Mothers Treated with Dexamethasone 15 cH Present Changes in Modulation of Inflammatory Process

As little information about the effect of ultra high dilutions of glucocorticoid in reproduction is available in the literature, pregnant female Wistar rats (N = 12) were blindly subcutaneously treated during all gestational and lactation period with: dexamethasone 4 mg/kg diluted into dexamethasone 15 cH (mixed); or dexamethasone 4 mg/kg diluted in water; or dexamethasone 15 cH, or vehicle. Parental generation had body weight, food and water consumption monitored. The F1 generation was monitored regarding to newborn development. No birth occurred in both groups treated with dexamethasone 4 mg/kg. After 60 days from birth, 12 male F1 rats were randomly selected from each remaining group and inoculated subcutaneously with 1% carrageenan into the footpad, for evaluation of inflammatory performance. Edema and histopathology of the footpad were evaluated, using specific staining methods, immunohistochemistry and digital histomorphometry. Mothers treated with mixed dexamethasone presented reduced water consumption. F1 rats born to dexamethasone 15 cH treated females presented significant increase in mast cell degranulation, decrease in monocyte percentage, increase in CD18+ PMN cells, and early expression of ED2 protein, in relation to control. The results show that the exposure of parental generation to highly diluted dexamethasone interferes in inflammation modulation in the F1 generation.

Antenatal dexamethasone treatment in midgestation reduces system A-mediated transport in the late-gestation murine placenta

Clinically, approximately 30% of women who receive synthetic glucocorticoids (sGC) for risk of preterm labor carry to term. In vitro studies have shown that sGC acutely regulate the placental system A amino acid transporter, but there are no comparable data in vivo. Hence, the objective of our study was to examine the acute [embryonic day (E)15.5] and longer-term (E17.5 and E18.5) consequences of midgestation antenatal sGC [dexamethasone (DEX); 0.1 mg/kg on E13.5 and E14.5] on placental system A-mediated transfer in the mouse (measured in vivo as maternal-fetal unidirectional (14)C-methylaminoisobutyric acid transfer per gram of placenta). System A transfer and Slc38a mRNA expression significantly increased from E12.5 to E18.5 (P < 0.05), corresponding to increased fetal growth. DEX treatment had no acute effect at E15.5 or longer-term effect at E17.5 but significantly decreased system A-mediated transfer before term (E18.5; P < 0.05) in placentae of male and female fetuses. There was no effect of DEX on Slc38a gene expression. Administration of DEX in this regime had no effect on birth weight. We conclude that sGC treatment in midgestation leads to a substantial decrease in placental system A-mediated transport in late gestation, suggesting that prenatal sGC therapy may lead to a reduction in availability of neutral amino acids to the fetus if gestation persists to term.

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.

Endocrine regulation of human fetal growth: the role of the mother, placenta, and fetus

The environment in which the fetus develops is critical for its survival and long-term health. The regulation of normal human fetal growth involves many multidirectional interactions between the mother, placenta, and fetus. The mother supplies nutrients and oxygen to the fetus via the placenta. The fetus influences the provision of maternal nutrients via the placental production of hormones that regulate maternal metabolism. The placenta is the site of exchange between mother and fetus and regulates fetal growth via the production and metabolism of growth-regulating hormones such as IGFs and glucocorticoids. Adequate trophoblast invasion in early pregnancy and increased uteroplacental blood flow ensure sufficient growth of the uterus, placenta, and fetus. The placenta may respond to fetal endocrine signals to increase transport of maternal nutrients by growth of the placenta, by activation of transport systems, and by production of placental hormones to influence maternal physiology and even behavior. There are consequences of poor fetal growth both in the short term and long term, in the form of increased mortality and morbidity. Endocrine regulation of fetal growth involves interactions between the mother, placenta, and fetus, and these effects may program long-term physiology.

Antepartum glucocorticoid therapy suppresses human placental xenobiotic and steroid metabolizing enzymes

We investigated the effects of maternal gestational corticosteroid therapy on placental xenobiotic and steroid metabolizing enzymes at term in 20 glucocorticoid/betamethasone treated (with various doses) and control (n=10) women. A single dose of betamethasone (12 mg i.m. twice at a 24-h interval) was given to 15 mothers at risk of preterm delivery to prevent respiratory syndrome in their premature newborns. Five mothers were treated more than once. The gestation time in mothers receiving the glucocorticoid therapy varied from 22-38 gestational weeks. Compared with controls, a significant decrease in placental aromatase activity (53.6+/-18.0 pmol/mg/min versus 119+/-30 pmol/mg/min, P=0.0007) and placental CYP19 mRNA content (by 50 per cent ) was observed in mothers treated with glucocorticoids. Also the formation of androstenedione (13.2+/-8.1 pmol/mg/min, steroids versus 30.03+/-5.2 pmol/mg/min, controls, P< 0.001), using testosterone as the substrate, and 7-ethoxycoumarin O-deethylase (P< 0.05) and 7-ethoxyresorufin O-deethylase (P< 0.09) were slightly decreased in the glucocorticoid treated compared to control patients' values. The changes were not dependent on the number of treatments or the time between treatment and delivery. Our results demonstrate that even a single dose of glucocorticoid given to expectant mothers is associated with diminished placental steroid hormone and xenobiotic metabolizing enzymes at term. Further studies are needed to assess whether these changes affect the well-being of the fetus and its later development.

Effects of the synthetic glucocorticoid triamcinolone acetonide on vasoactive hydrolases of the human placenta in vitro

Therapy with glucocorticoids during pregnancy is still debated. Previously reported effects of glucocorticoid application in rats resemble certain symptoms of preeclampsia. Therefore, we studied in vitro the effects of the synthetic glucocorticoid triamcinolone acetonide soluble (0.1-10 mM) on placental alpha-glutamyl amino-peptidase, microsomal alanyl aminopeptidase, dipeptidyl peptidase IV, acetylcholinesterase and butyrylcholinesterase in purified trophoblast monolayers and villous explants from first trimester (n = 5) and term placentae (n = 9) using bio- and histochemical methods. In term placentae quantitative histochemistry (microdensitometry) of trophoblast monolayers revealed an increase of alpha-glutamyl aminopeptidase and microsomal alanyl aminopeptidase activity up to 149% and 126% respectively, after treatment with supraphysiological doses. In trophoblast monolayers from first trimester alpha-glutamyl aminopeptidase activity was not affected, whereas microsomal alanyl aminopeptidase activity increased by 25%. Dipeptidyl peptidase IV staining was reduced to 26%. Biochemical measurements of alpha-glutamyl aminopeptidase and microsomal alanyl aminopeptidase activity in homogenates of cultured villi revealed effects similar to those found by microdensitometry in trophoblast monolayers. In contrast, dipeptidyl peptidase IV activity increased in explants of term placentae by 47%. Acetyl- and butyrylcholinesterase activities were reduced in term placental villi by 38% and 40%, respectively. The data indicate that glucocorticoids may affect the activity of hydrolases which are thought to be involved in local placental blood pressure modulation.

Placental morphology and concentrations of glutathione (GSH and GSSG) and lipid peroxides (LPO) in two models of disturbed pregnancy of Uje:WIST rats

Treatment of pregnant rats with heat-denaturated bacterial material (endotoxin-model) or exposure to chronic restraint of prenatally lithium-treated pregnant dams (stress-model) were used as two models of disturbed pregnancy, both causing decreased fetal body mass. The quotient of fetal/placental mass was lowered in the endotoxin-group only. Placental mass and protein content were not changed significantly in both experimental groups, although a tendency to smaller placentae was noticed in the stress-group. Placental histology of the stress-group did not differ from untreated controls. In the endotoxin-group an altered structure of the placental barrier was observed. Small decreases of GSH and GSSG in the endotoxin-group and of GSSG in the stress-group without significant changes of the GSH/GSSG relationship were measured in homogenates of the placental labyrinth. Moderate enhancement of LPO concentration occurred in the endotoxin-group and more distinctly in two litters of the stress-group, the latter being connected with high GSSG concentrations and low fetal/placental mass-quotients.

Placental toxicity of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in mice

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a well-known model substance for inducing in humans and monkeys a severe extrapyramidal syndrome similar to Parkinson's disease. The neurotoxic action of MPTP can be exerted not only in adult animals but also during fetal development by diaplacental passage. Here we show that, during the gestation period of mice, the placenta is another important target organ of MPTP cytotoxicity. Pregnant NMRI mice on gestation day 15 received a single intraperitoneal dose of 20, 40, or 60 mg/kg MPTP. Developmental parameters of the fetuses and the placentas were determined on gestation day 18. Placental weight was consistently reduced in all experimental groups. Histology showed conspicuous alterations of the labyrinth layer; at 20 mg/kg MPTP there was already a significant reduction of the trabecular diameters and from 40 mg/kg onwards, severe necrosis of the syncytial trophoblast cells. In addition, there were necrotic alterations of the cells of the visceral yolk sac. The toxic effects are confined to the placenta at the doses used in the present experiments, leading at just 60 mg/kg to a marked placental insufficiency syndrome.