Early life corticosteroid overexposure: Epigenetic and fetal origins of adult diseases.

The relationship between events occurring during intrauterine development and later-life predisposition to long-term disease, has been described. The fetus responds to excess intrauterine exposure to high levels of corticosteroids, modifying their physiological development and stopping their growth. Fetal exposure to elevated levels of either endogenous (alterations in fetal hypothalamic-pituitary-adrenal axis) or synthetic corticosteroids, is one model of early-life adversity; to developing adult disease. At the molecular level, there are transcriptional changes in metabolic and growth pathways. Epigenetic mechanisms participate in transgenerational inheritance, not genomic. Exposures that change 11ß-hydroxysteroid dehydrogenase type 2 enzyme methylation status in the placenta can result in transcriptional repression of the gene, causing the fetus to be exposed to higher levels of cortisol. More precise diagnosis and management of antenatal corticosteroids for preterm birth, would potentially decrease the risk of long-term adverse outcomes. More studies are needed to understand the potential roles of factors to alter fetal corticosteroid exposure. Long-term infant follow-up is required to determine whether methylation changes in placenta may represent useful biomarkers of later disease risk. This review, summarize recent advances in the programming of fetal effects of corticosteroid exposure, the role of corticosteroids in epigenetic gene regulation of placental 11ß-hydroxysteroid dehydrogenase type 2 enzyme expression and transgenerational effects.

The effect of cold exposure on the levels of glucocorticoids, 11-hydroxysteroid dehydrogenase 2, and placental vascularization in a rat model.

OBJECTIVE: Cold exposure (CE) before birth is one of the initial stressors that may impact mammalian pregnancy, changing placental and fetal development and affecting the health of the offspring. While glucocorticoids (GCs) participate in the body's response to the stress of CE, the specific mechanisms of their action are unclear. This study aims to determine the effect of CE stress on the placenta and to test whether stress, caused by cold exposure in pregnancy impairs fetal development by changing placental angiogenesis via excessive GC expression. MATERIALS AND METHODS: CE rat model was created by exposing 30 SD rats to cold preconception, or during the first, second, and third weeks of pregnancy. Serum cortisol and soluble fms-like tyrosine kinase-1 (sFlt-1) expression levels, physiological index changes (food intake, body weight change and blood pressure), and pregnancy outcomes (fetal rat weight, number of live fetal rats, and placental weight) were collected at baseline and at different time points after the conception. Protein expression levels of 11 ß-hydroxysteroid dehydrogenase 2 (11ß-HSD2), glucocorticoid receptor, vascular endothelial growth factor A (VEGF-A), placental growth factor (PIGF), and sFlt-1 in placental tissues were measured by western blotting. Cytokeratin (CK) and laminin (LN) in trophoblasts, and α-actin in vascular smooth muscle of the spiral arteries of pregnant rats after the systemic cold treatment were assessed by immunofluorescence and visualized by fluorescent microscopy. To test the effect of 11ß-HSD2 levels on the placental recasting, human first-trimester extravillous trophoblast cells (HTR8/SVneo) underwent knockdown using specific 11ß-HSD2 siRNA constructs.  Expression levels of 11ß-HSD2 were analyzed by quantitative real-time PCR (qPCR) and into HTR8 cells, and the expression levels of the 11ß-HSD2 gene in each group were measured using qPCR. Cell migration and invasion was assessed by Transwell migration assay, and sFlt-1 levels in HTR8 cells were measured by ELISA. RESULTS: CE pre-conception led to consistently increasing serum corticosterone and sFlt-1 levels throughout pregnancy, and persistently increased diastolic blood pressure (DBP) in rat CE model compared to control animals. CE during the second week of gestation (Gp.3) was associated with significantly lower placental weight (p=0.0003). Cold exposure in the third week (Gp.4) was associated with significantly (p=0.001) lower fetal weight. CE pre-conception was associated with significantly decreased placental levels of 11ß-HSD2, glucocorticoid receptor, VEGF-A, PIGF, and sFlt-1 proteins and α-actin compared to the control group. Silencing 11ß-HSD2 by siRNA led to reduced cell migrations and invasion, and markedly increased expression levels of sFlt-1 in HTR8/SVneo cells (p<0.05). CONCLUSIONS: Pre-conception cold exposure and during early pregnancy leads to increased GCs levels and impaired placental 11ß-HSD2 activity. We suggest that the subsequent 11ß-HSD2-induced increase in the sFlt-1expression during early pregnancy may affect placental vascular remodeling and change placental morphological structure and function.

Selenium attenuates the cadmium-induced placenta glucocorticoid barrier damage by up-regulating the expression of specificity protein 1.

Cadmium (Cd) is an environmental pollutant and pregnant women are especially susceptible to the effects of exposure to Cd. Our previous study found Cd can be accumulated in the placenta and causes fetal growth restriction (FGR) through damage the placental glucocorticoid barrier. Selenium (Se), as an essential micronutrient, can allivate Cd-induced toxicity. In this study, we aim to explore the protective mechanism of Se against Cd-induced the placental glucocorticoid barrier damage and FGR. Pregnant Sprague Dawley (SD) rats were exposed to CdCl2 (1 mg/kg/day) and Na2 SeO3 (0.1-0.2-0.3 mg/kg/day) by gavage from gestational day (GD) 0 to GD 19. The results showed that reduced fetal weight, increased corticosterone concentrations in the maternal and fetal serum, and impaired placental labyrinth layer blood vessel development, appeared in pregnant rats after Cd exposure and improved after treated with Se. In cell experiments, we confirmed that Se reduces Cd-induced apoptosis. Moreover, Se can abolish Cd-induced 11ß-HSD2 and specificity protein 1 (Sp1) decreasing in vivo and vitro. In human JEG-3 cells, the knockdown of Sp1 expression by small interfering RNA can suppressed the protective effect of Se on Cd-induced 11ß-HSD2 decreasing. In general, our results demonstrated that Se is resistant to Cd-induced FGR through upregulating the placenta barrier via activation of the transcription factor Sp1.

Hypertrophy in the Distal Convoluted Tubule of an 11ß-Hydroxysteroid Dehydrogenase Type 2 Knockout Model.

Na(+) transport in the renal distal convoluted tubule (DCT) by the thiazide-sensitive NaCl cotransporter (NCC) is a major determinant of total body Na(+) and BP. NCC-mediated transport is stimulated by aldosterone, the dominant regulator of chronic Na(+) homeostasis, but the mechanism is controversial. Transport may also be affected by epithelial remodeling, which occurs in the DCT in response to chronic perturbations in electrolyte homeostasis. Hsd11b2(-/-) mice, which lack the enzyme 11ß-hydroxysteroid dehydrogenase type 2 (11ßHSD2) and thus exhibit the syndrome of apparent mineralocorticoid excess, provided an ideal model in which to investigate the potential for DCT hypertrophy to contribute to Na(+) retention in a hypertensive condition. The DCTs of Hsd11b2(-/-) mice exhibited hypertrophy and hyperplasia and the kidneys expressed higher levels of total and phosphorylated NCC compared with those of wild-type mice. However, the striking structural and molecular phenotypes were not associated with an increase in the natriuretic effect of thiazide. In wild-type mice, Hsd11b2 mRNA was detected in some tubule segments expressing Slc12a3, but 11ßHSD2 and NCC did not colocalize at the protein level. Thus, the phosphorylation status of NCC may not necessarily equate to its activity in vivo, and the structural remodeling of the DCT in the knockout mouse may not be a direct consequence of aberrant corticosteroid signaling in DCT cells. These observations suggest that the conventional concept of mineralocorticoid signaling in the DCT should be revised to recognize the complexity of NCC regulation by corticosteroids.

Glucocorticoids act directly on osteoblasts and osteocytes to induce their apoptosis and reduce bone formation and strength.

Whether the negative impact of excess glucocorticoids on the skeleton is due to direct effects on bone cells, indirect effects on extraskeletal tissues, or both is unknown. To determine the contribution of direct effects of glucocorticoids on osteoblastic/osteocytic cells in vivo, we blocked glucocorticoid action on these cells via transgenic expression of 11beta-hydroxysteroid dehydrogenase type 2, an enzyme that inactivates glucocorticoids. Osteoblast/osteocyte-specific expression was achieved by insertion of the 11beta-hydroxysteroid dehydrogenase type 2 cDNA downstream from the osteoblast-specific osteocalcin promoter. The transgene did not affect normal bone development or turnover as demonstrated by identical bone density, strength, and histomorphometry in adult transgenic and wild-type animals. Administration of excess glucocorticoids induced equivalent bone loss in wild-type and transgenic mice. As expected, cancellous osteoclasts were unaffected by the transgene. However, the increase in osteoblast apoptosis that occurred in wild-type mice was prevented in transgenic mice. Consistent with this, osteoblasts, osteoid area, and bone formation rate were significantly higher in glucocorticoid-treated transgenic mice compared with glucocorticoid-treated wild-type mice. Glucocorticoid-induced osteocyte apoptosis was also prevented in transgenic mice. Strikingly, the loss of vertebral compression strength observed in glucocorticoid-treated wild-type mice was prevented in the transgenic mice, despite equivalent bone loss. These results demonstrate for the first time that excess glucocorticoids directly affect bone forming cells in vivo. Furthermore, our results suggest that glucocorticoid-induced loss of bone strength results in part from increased death of osteocytes, independent of bone loss.