Prenatal dexamethasone exposure-induced a gender-difference and sustainable multi-organ damage in offspring rats via serum metabolic profile analysis

Epigenetic programming mediates abnormal gut microbiota and disease susceptibility in offspring with prenatal dexamethasone exposure

Prenatal dexamethasone exposure (PDE) can lead to increased susceptibility to various diseases in adult offspring, but its effect on gut microbiota composition and the relationship with disease susceptibility remains unclear. In this study, we find sex-differential changes in the gut microbiota of 6-month-old infants with prenatal dexamethasone therapy (PDT) that persisted in female infants up to 2.5 years of age with altered bile acid metabolism. PDE female offspring rats show abnormal colonization and composition of gut microbiota and increased susceptibility to cholestatic liver injury. The aberrant gut microbiota colonization in the PDE offspring can be attributed to the inhibited Muc2 expression caused by decreased CDX2 expression before and after birth. Integrating animal and cell experiments, we further confirm that dexamethasone could inhibit Muc2 expression by activating GR/HDAC11 signaling and regulating CDX2 epigenetic modification. This study interprets abnormal gut microbiota and disease susceptibility in PDT offspring from intrauterine intestinal dysplasia.

Low H3K27 acetylation of SF1 in PBMC: a biomarker for prenatal dexamethasone exposure-caused adrenal insufficiency of steroid synthesis in male offspring

Dexamethasone is widely used to treat pregnancy disorders related to premature delivery. However, lots of researches have confirmed that prenatal dexamethasone exposure (PDE) could increase the risk of offspring multiple diseases. This study was designed to elucidate the epigenetic mechanism of adrenal developmental programming and explore its early warning marker in peripheral blood mononuclear cells (PBMC). We found the adrenal morphological and functional changes of PDE male offspring rats before and after birth, which were mainly performed as the decreased serum corticosterone concentration, steroidogenic acute regulatory (StAR) protein expression, and histone 3 lysine 27 acetylation (H3K27ac) level of steroidogenic factor 1 (SF1) promoter region and its expression. Simultaneously, the expressions of glucocorticoid receptor (GR) and histone acetylation enzyme 5 (HDAC5) in the PDE male fetal rats were increased. In vitro, dexamethasone reduced the expression of SF1, StAR, and cortisol production and still increased the expression of GR and HDAC5, the binding between GR and SF1 promoter region, and protein interaction between GR and HDAC5. GR siRNA or HDAC5 siRNA was able to reverse the above roles of dexamethasone. Furthermore, in vivo, we confirmed that H3K27ac levels of SF1 promoter region and its expression in PBMC of the PDE group were decreased before and after birth, showing a positive correlation with the same indexes in adrenal. Meanwhile, in clinical trials, we confirmed that prenatal dexamethasone application decreased H3K27ac of SF1 promoter region and its expression in neonatal PBMC. In conclusion, PDE-caused adrenal insufficiency of male offspring rats was related to adrenal GR activated by dexamethasone in uterus. The activated GR, on the one hand, increased its direct binding to SF1 promoter region to inhibit its expression, on the other hand, upregulated and recruited HDAC5 to decrease H3K27ac level of SF1 promoter region, and strengthened the inhibition of SF1 and subsequent StAR expression.

The molecular mechanisms in prenatal drug exposure-induced fetal programmed adult cardiovascular disease

The "developmental origins of health and disease" (DOHaD) hypothesis posits that early-life environmental exposures have a lasting impact on individual's health and permanently shape growth, structure, and metabolism. This reprogramming, which results from fetal stress, is believed to contribute to the development of adulthood cardiovascular diseases such as hypertension, coronary artery disease, heart failure, and increased susceptibility to ischemic injuries. Recent studies have shown that prenatal exposure to drugs, such as glucocorticoids, antibiotics, antidepressants, antiepileptics, and other toxins, increases the risk of adult-onset cardiovascular diseases. In addition, observational and animal experimental studies have demonstrated the association between prenatal drug exposure and the programming of cardiovascular disease in the offspring. The molecular mechanisms underlying these effects are still being explored but are thought to involve metabolism dysregulation. This review summarizes the current evidence on the relationship between prenatal drug exposure and the risk of adult cardiovascular disorders. Additionally, we present the latest insights into the molecular mechanisms that lead to programmed cardiovascular phenotypes after prenatal drug exposure.

MiR-133a-3p/Sirt1 epigenetic programming mediates hypercholesterolemia susceptibility in female offspring induced by prenatal dexamethasone exposure

Mounting evidence indicates that adverse intrauterine conditions increase offspring's hypercholesterolemia susceptibility in adulthood. This study aimed to confirm prenatal dexamethasone exposure (PDE)-induced hypercholesterolemia susceptibility in female adult offspring rats, and elucidate its intrauterine programming mechanism. Pregnant Wistar rats were injected with dexamethasone subcutaneously (0, 0.1 and 0.2 mg/kg·d) from gestational day (GD) 9 to 20. Serum and liver of the female offspring were collected at GD21 and postnatal week (PW) 12 and 28. PDE offspring showed elevated serum total cholesterol (TCH) levels and a cholesterol phenotype of high cardiovascular disease risk at PW12 and PW28. The histone acetylation levels of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (Hmgcr) and its expression were consistently increased in the PDE offspring both in utero and after birth. Moreover, PDE promoted glucocorticoid receptor (GR) nuclear translocation and miR-133a-3p expression and inhibited sirtuin-1 (Sirt1) expression in the fetal liver. In vitro, dexamethasone increased intracellular and supernatant TCH levels and miR-133a-3p expression, decreased SIRT1 expression, and promoted HMGCR histone acetylation and expression in bone marrow mesenchymal stem cells (BMSCs) hepatoid differentiated cells and HepG2 cell line. GR siRNA, miR-133a-3p inhibitor or SIRT1 overexpression reversed dexamethasone-induced downstream molecular and phenotypic changes. Furthermore, elevated TCH levels in umbilical cord blood and increased HMGCR expression in peripheral blood mononuclear cells (PBMCs) were observed in human female neonates who had received dexamethasone treatment during pregnancy. In conclusion, PDE can cause persistent enhancement of hepatic cholesterol synthesis function before and after birth through GR/miR-133a-3p/Sirt1 pathway, eventually leading to increased hypercholesterolemia susceptibility in female offspring rats.

Tryptophan-5-HT pathway disorder was uncovered in the olfactory bulb of a depression mice model by metabolomic analysis

Major depression (MD) is a severe mental illness that creates a heavy social burden, and the potential molecular mechanisms remain largely unknown. Lots of research demonstrate that the olfactory bulb is associated with MD. Recently, gas chromatography-mass spectrometry-based metabolomic studies on depressive rats indicated that metabolisms of purine and lipids were disordered in the olfactory bulb. With various physicochemical properties and extensive concentration ranges, a single analytical technique could not completely cover all metabolites, hence it is necessary to adopt another metabolomic technique to seek new biomarkers or molecular mechanisms for depression. Therefore, we adopted a liquid chromatography-mass spectrometry metabonomic technique in the chronic mild stress (CMS) model to investigate significant metabolic changes in the olfactory bulb of the mice. We discovered and identified 16 differential metabolites in the olfactory bulb of the CMS treatments. Metabolic pathway analysis by MetaboAnalyst 5.0 was generated according to the differential metabolites, which indicated that the tryptophan metabolism pathway was the core pathogenesis in the olfactory bulb of the CMS depression model. Further, the expressions of tryptophan hydroxylase (TpH) and aromatic amino acid decarboxylase (AAAD) were detected by western blotting and immunofluorescence staining. The expression of TpH was increased after CMS treatment, and the level of AAAD was unaltered. These results revealed that abnormal metabolism of the tryptophan pathway in the olfactory bulb mediated the occurrence of MD.

Low Birth Weight Intensifies Changes in Markers of Hepatocarcinogenesis Induced by Fructose Consumption in Rats

Intrauterine growth restriction (IUGR) due to fetal exposure to glucocorticoid excess results in metabolic inflexibility and hepatic steatosis upon nutritional stress during adulthood. We previously demonstrated that rats born to dexamethasone (DEX)-treated mothers developed hepatic steatosis when exposed to 10% fructose solution during adult life. Persistent triacylglyceride (TAG) accumulation in the liver, in turn, is a feature of non-alcoholic fatty liver disease (NAFLD), which serves as a risk factor for non-alcoholic steatohepatitis (NASH) and hepatocellular carcinoma (HCC). In the present study, we demonstrate that the combination of IUGR and fructose treatment during adulthood also results in increased hepatic myeloperoxidase (MPO) activity, AKT phosphorylation and serum aspartate transaminase. Growth-restricted rats also presented reduced hepatic TRIB3 and GADD45a after fructose treatment. Other markers of cell proliferation, such as Cyclin D, PCNA, Hgf and Hspa4/Hsp70 expression and the number of Ki-67 positive cells, were all increased in the liver of growth- restricted rats treated with fructose. On the other hand, the combination of IUGR and fructose treatment during adult life reduced the levels of IGF-1. In conclusion, our data indicate that after exposure to fructose, adult rats subjected to dexamethasone-induced IUGR display exacerbated molecular changes in markers of NASH and HCC.

Transforming growth factor-β receptor 1: An intervention target for genetic poor cartilage quality induced by prenatal dexamethasone exposure

INTRODUCTION

Fetal-originated osteoarthritis is relative to poor cartilage quality and may exhibit transgenerational genetic effects. Previous findings revealed prenatal dexamethasone exposure (PDE) induced poor cartilage quality in offspring.

OBJECTIVES

This study focused on further exploring molecular mechanism, heritability, and early intervention of fetal-originated osteoarthritis.

METHODS

Pregnant rats (F0) were segregated into control and PDE groups depending upon whether dexamethasone was administered on gestational days (GDs) 9-20. Some female offspring were bred with healthy males during postnatal week (PW) 8 to attain the F2 and F3 generations. The F3-generation rats were administrated with glucosamine intragastrically at PW12 for 6 weeks. The knee cartilages of male and female rats at different time points were harvested to assay their morphologies and functions. Furthermore, primary chondrocytes from the F3-generation rats were isolated to confirm the mechanism and intervention target of glucosamine.

RESULTS

Compared with the control, female and male rats in each generation of PDE group showed thinner cartilage thicknesses; shallower and uneven staining; fewer chondrocytes; higher Osteoarthritis Research Society International scores; and lower mRNA and protein expression of SP1, TGFβR1, Smad2, SOX9, ACAN and COL2A1. After F3-generation rats were treated with glucosamine, all of the above changes could be reversed. In primary chondrocytes isolated from the F3-generation rats of PDE group, glucosamine promoted SP1 expression and binding to TGFβR1 promoter to increase the expression of TGFβR1, p-Smad2, SOX9, ACAN and COL2A1, but these were prevented by SB431542 (a potent and selective inhibitor of TGFβR1).

CONCLUSIONS

PDE induced chondrodysplasia in offspring and stably inherited in F3-generation rats, which was related to decreased expression of SP1/TGFβR1/Smad2/SOX9 pathway to reduce the cartilage matrix synthesis, without major sex-based variations. Glucosamine could alleviate the poor genetic cartilage quality in offspring induced by PDE by up-regulating SP1/TGFβR1 signaling, which was prevented by a TGFβR1 inhibitor. This study elucidated the molecular mechanism and therapeutic target (TGFβR1) of genetic chondrodysplasia caused by PDE, which provides a research basis for precisely treating fetal-originated osteoarthritis.

Preparation and Taste Characteristics of Kokumi N-Lactoyl Phenylalanine in the Presence of Phenylalanine and Lactate

N-l-Lactoyl phenylalanine (N-l-lactoyl-Phe) has been identified as a taste-active contributor in many fermented foods. However, its preparation, taste property, and content in foodstuffs are little known to date. In the current study, two preparation technologies of N-l-lactoyl-Phe including heating and enzymatic methods were investigated. Other investigations include its taste property and quantification in several fermented foods. The results indicated that the heating preparation and enzymatic preparation only produced N-l-lactoyl-Phe instead of N-d-lactoyl-Phe in the presence of l-lactate/d-lactate and l-phenylalanine (Phe). A high yield (58.0% ± 0.7%) of N-l-lactoyl-Phe was achieved under the following conditions: Phe, lactate, CaO, and water at molar ratios of 1:8:0.3:9 kept at 100 °C for 3 h. With nine enzymes, a maximum yield of 21.2% ± 0.3% was achieved in the aqueous solution under mild operating conditions: 0.18 M Phe, 0.90 M lactate, 5 g/L Debitrase HYW 20, pH 8, and 55 °C for 24 h. The sensory evaluation revealed that N-l-lactoyl-Phe in water enhanced the salty and umami intensity. It also enhanced the thickness, mouthfulness, and continuity of salt solution, model broth, and chicken broth, revealing that N-l-lactoyl-Phe was a kokumi-active compound. The kokumi thresholds of N-l-lactoyl-Phe in these solutions were 50, 50, and 25 mg/L, respectively. N-l-Lactoyl-Phe was quantified in traditional Chinese fermented foods as 30.12 ± 0.28 mg/kg in preserved pickles, 14.11 ± 0.14 mg/kg in soybean paste, 4.87 ± 0.16 mg/kg in fermented bean, 0.71 ± 0.11 mg/kg in rice vinegar, and 20.34 ± 0.18 mg/kg in soy sauce. These results revealed the potential of N-l-lactoyl-Phe as a taste enhancer, presenting a new opportunity for the food industry.

p-Chloro-diphenyl diselenide modulates Nrf2/Keap1 signaling and counteracts renal oxidative stress in mice exposed to dexamethasone repeated administrations

Dexamethasone is a synthetic glucocorticoid that has been associated with oxidative stress in central and peripheral tissues. p-Chloro-diphenyl diselenide (p-ClPhSe)2 is an antioxidant organoselenium compound. The present study aimed to evaluate whether Nrf2/Keap-1 signaling contributes to the (p-ClPhSe)2 antioxidant effects in the kidney of mice exposed to dexamethasone. Adult Swiss mice received dexamethasone (i.p) at a dose of 2 mg/kg or its vehicle for 21 days. After, mice were treated with (p-ClPhSe)2 (i.g)(1, 5, or 10 mg/kg) for 7 days. Samples of kidneys were collected for biochemical assays. (p-ClPhSe)2 at dose of 1 mg/kg reversed the renal reactive oxygen species (ROS) and carbonyl protein (CP) levels increased by dexamethasone. (p-ClPhSe)2 at doses of 5 and 10 mg/kg was effective against the increase of TBARS (thiobarbituric acid reactive substances), ROS, and CP as well as the decrease of δ-aminolevulinic acid dehydratase (δ-ALA-D) activity and non-protein SH (NPSH) levels induced by dexamethasone. At 5 mg/kg, (p-ClPhSe)2 reduced the renal levels of 4-OH-2-HNE and HO-1 as well as modulated the Nrf2/Keap-1 signaling in mice exposed to dexamethasone. The present findings revealed that (p-ClPhSe)2 antioxidant effects were associated with the modulation of Nrf2/Keap-1 signaling pathway in the kidney of mice exposed to dexamethasone.

The miR-98-3p/JAG1/Notch1 axis mediates the multigenerational inheritance of osteopenia caused by maternal dexamethasone exposure in female rat offspring

As a synthetic glucocorticoid, dexamethasone is widely used to treat potential premature delivery and related diseases. Our previous studies have shown that prenatal dexamethasone exposure (PDE) can cause bone dysplasia and susceptibility to osteoporosis in female rat offspring. However, whether the effect of PDE on bone development can be extended to the third generation (F3 generation) and its multigenerational mechanism of inheritance have not been reported. In this study, we found that PDE delayed fetal bone development and reduced adult bone mass in female rat offspring of the F1 generation, and this effect of low bone mass caused by PDE even continued to the F2 and F3 generations. Furthermore, we found that PDE increases the expression of miR-98-3p but decreases JAG1/Notch1 signaling in the bone tissue of female fetal rats. Moreover, the expression changes of miR-98-3p/JAG1/Notch1 caused by PDE continued from the F1 to F3 adult offspring. Furthermore, the expression levels of miR-98-3p in oocytes of the F1 and F2 generations were increased. We also confirmed that dexamethasone upregulates the expression of miR-98-3p in vitro and shows targeted inhibition of JAG1/Notch1 signaling, leading to poor osteogenic differentiation of bone marrow mesenchymal stem cells. In conclusion, maternal dexamethasone exposure caused low bone mass in female rat offspring with a multigenerational inheritance effect, the mechanism of which is related to the inhibition of JAG1/Notch1 signaling caused by the continuous upregulation of miR-98-3p expression in bone tissues transmitted by F2 and F3 oocytes.

Sex difference in adrenal developmental toxicity induced by dexamethasone and its intrauterine programming mechanism

Dexamethasone is widely used to treat preterm labor and related diseases. However, prenatal dexamethasone treatment (PDT) can cause multiorgan developmental toxicities in offspring. Our previous study found that the occurrence of fetal-originated diseases was associated with adrenal developmental programming alterations in offspring. Here, we investigated the effects of PDT on adrenal function in offspring and its intrauterine programming mechanism. A rat model of PDT was established to observe the alterations of adrenal steroidogenesis in offspring. Furthermore, we confirmed the sex differences of adrenal steroidogenesis and its molecular mechanism combined with in vivo and in vitro experiments. PDT caused a decrease in adrenal steroidogenic function in fetal rats, but it was decreased in males and increased in females after birth. Meanwhile, the adrenal H3K14ac level and expression of 11β-hydroxysteroid dehydrogenase 2 (11β-HSD2) in PDT offspring were decreased in males and increased in females, suggesting that 11β-HSD2 might mediate sex differences in adrenal function. We further confirmed that dexamethasone inhibited the H3K14ac level and expression of 11β-HSD2 through the GR/SP1/p300 pathway. After bilateral testectomy or ovariectomy of adult PDT offspring rats, adrenal 11β-HSD2 expression and steroidogenic function were both reduced. Using rat primary fetal adrenal cells, the differential expression of AR and ERβ was proven to be involved in regulating the sex difference in 11β-HSD2 expression. This study demonstrated the sex difference in adrenal steroidogenic function of PDT offspring after birth and elucidated a sex hormone receptor-dependent epigenetically regulating mechanism for adrenal 11β-HSD2 programming alteration.

Maternally derived low glucocorticoid mediates adrenal developmental programming alteration in offspring induced by dexamethasone

Adverse environments during pregnancy can increase susceptibility to chronic diseases in adult offspring. The occurrence and development of fetal-originated diseases were associated with adrenal developmental programming and homeostasis alteration in offspring. Dexamethasone is widely used for preterm delivery-related pregnancy diseases, but the intrauterine programming alteration and its occurrence mechanism of prenatal dexamethasone exposure (PDE) on adrenal development in offspring have not been clarified. In this study, prenatal dexamethasone therapy could inhibit neonatal development and cause a low exposure of maternally derived glucocorticoid in clinic. Then, we established a rat model of PDE and observed a similar phenomenon. Further, the adrenal steroidogenic function was continuously inhibited in the PDE male offspring rats, accompanied by the decreased H3K27ac level of adrenal insulin-like growth factor 1 (IGF1) and its expression. Moreover, chronic stress in PDE adult offspring rats could reverse the changes of the above indicators through the high level of glucocorticoid. In combination with in vivo, in vitro and a series of interference experiments, we confirmed that the low level of endogenous glucocorticoids inhibited the adrenal IGF1 expression and steroidogenic function through the GRα/miR-370-3p/Sirt3 pathway. In summary, PDE could continuously inhibit the adrenal steroidogenic function in the male offspring, which is associated with the maternally derived low glucocorticoid-mediated the adrenal developmental programming alteration in offspring. This study provides a theoretical and experimental basis for explaining the adrenal development origin of PDE-induced adult chronic diseases.

Identification and validation of reference genes for RT-qPCR analysis in fetal rat pancreas

The choice of reference gene is crucial for quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) assay. To screen and determine the suitable reference genes in fetal rat pancreas, we selected eight candidate reference genes (Gapdh, Actb, Rn18 s, B2m, Rpl13a, Tbp, Ywhaz and Ubc), and evaluated the constancy of gene expression from fetal rat pancreases in non-pathological situation and prenatal dexamethasone exposure (PDE) model, using four algorithms: GeNorm, NormFinder, Bestkeeper and Comparative ΔCt method. In addition, the alteration of mRNA levels of pancreatic insulin was compared between control and PDE groups to validate the reliability of selected reference genes for data normalization of RT-qPCR. The comprehensive ranking of reference genes under physiological condition was as follow: Gapdh > Actb > Ywhaz > Ubc > Rn18s > Rpl13a > B2m > Tbp (female); Actb > Ywhaz > Gapdh > Ubc > B2m > Rpl13a > Rn18 s | Tbp (male). The top ranking reference genes were also stably expressed in PDE fetal pancreas. The best reference gene combinations are: Ywhaz+Actb for female and Ywhaz+Gapdh for male fetal rat pancreas, respectively. Compared with low ranking or single reference gene, the change trend of insulin mRNA normalized by the best reference gene combination between control and PDE groups was more significant and consistent with that of serum insulin level. In conclusion, our results provided the optimal combination of stable reference genes for RT-qPCR assay in pancreatic developmental toxicity study.

Maternal vitamin D administration attenuates metabolic disturbances induced by prenatal exposure to dexamethasone in a sex-dependent manner

PURPOSE

The overexposure to synthetic glucocorticoids (GC) during pregnancy can predispose to metabolic diseases during adulthood. Vitamin D is not only crucial for fetal development, but also exerts direct effects on the GC sensitivity and down-regulates GC receptors. Given the vitamin D effects on glucocorticoid-related parameters, we aimed to investigate a possible protective role of maternal vitamin D administration on the glucose homeostasis of rats exposed to dexamethasone in utero.

METHODS

Pregnant rats received dexamethasone (0.1 mg/kg, Dex) daily between the 14th and 19th days of pregnancy. A subgroup of dexamethasone-treated dams received oral administration of vitamin D (500UI, DexVD) during the whole gestation. The corresponding control groups of dams were included (CTL and VD groups, respectively). Male and female offspring were evaluated at 3, 6 and 12 months of age.

RESULTS

Prenatal exposure to dexamethasone caused metabolic disruption in an age and sex-dependent manner being the older male offspring more susceptible to insulin resistance, fatty liver and beta-cell mass expansion than females. Furthermore, we demonstrated that prenatal GC led to glucose intolerance in male and female offspring in an age-dependent manner. Maternal vitamin D administration did not influence glucose intolerance but attenuated the insulin resistance, liver lipid accumulation and prevented the beta-cell mass expansion caused by prenatal dexamethasone in the male offspring.

CONCLUSION

Maternal vitamin D administration mitigates metabolic disturbances that occur later in life in male rats exposed to GC in utero. Moreover, our data suggest vitamin D as an important nutritional supplement for pregnant overexposed to GC during gestation.

Dexamethasone induces an imbalanced fetal-placental-maternal bile acid circulation: involvement of placental transporters

BACKGROUND

The use of prenatal dexamethasone remains controversial. Our recent studies found that prenatal dexamethasone exposure can induce maternal intrahepatic cholestasis and have a lasting adverse influence on bile acid (BA) metabolism in the offspring. The purpose of this study was to investigate the effects of dexamethasone on fetal-placental-maternal BA circulation during the intrauterine period, as well as its placental mechanism.

METHODS

Clinical data and human placentas were collected and analyzed. Pregnant Wistar rats were injected subcutaneously with dexamethasone (0.2 mg/kg per day) from gestational day 9 to 20. The metabolomic spectra of BAs in maternal and fetal rat serum were determined by LC-MS. Human and rat placentas were collected for histological and gene expression analysis. BeWo human placental cell line was treated with dexamethasone (20-500 nM).

RESULTS

Human male neonates born after prenatal dexamethasone treatment showed an increased serum BA level while no significant change was observed in females. Moreover, the expression of organic anion transporter polypeptide-related protein 2B1 (OATP2B1) and breast cancer resistance protein (BCRP) in the male neonates' placenta was decreased, while multidrug resistance-associated protein 4 (MRP4) was upregulated. In experimental rats, dexamethasone increased male but decreased female fetal serum total bile acid (TBA) level. LC-MS revealed that primary BAs were the major component that increased in both male and female fetal serum, and all kinds of BAs were significantly increased in maternal serum. The expression of Oatp2b1 and Bcrp were reduced, while Mrp4 expression was increased in the dexamethasone-treated rat placentas. Moreover, dexamethasone increased glucocorticoid receptor (GR) expression and decreased farnesoid X receptor (FXR) expression in the rat placenta. In BeWo cells, dexamethasone induced GR translocation into the nucleus; decreased FXR, OATP2B1, and BCRP expression; and increased MRP4 expression. Furthermore, GR was verified to mediate the downregulation of OATP2B1, while FXR mediated dexamethasone-altered expression of BCRP and MRP4.

CONCLUSIONS

By affecting placental BA transporters, dexamethasone induces an imbalanced fetal-placental-maternal BA circulation, as showed by the increase of primary BA levels in the fetal serum. This study provides an important experimental and theoretical basis for elucidating the mechanism of dexamethasone-induced alteration of maternal and fetal BA metabolism and for exploring early prevention and treatment strategies.

Effects of contaminated surface water and groundwater from a rare earth mining area on the biology and the physiology of Sprague-Dawley rats

Previous studies have shown that an effective damage detection method for model rats from macro individual to micro cellular, was applied to assess the groundwater quality from rare earth metals tailings seepage. To determine whether it is universal method for measuring the toxicological damage caused by contaminated water around other mining areas to organisms at the organ-tissue-cell-chromosome-gene level. In this study, a rare earth mining area in North China was used as research base. Firstly, the core pollution factors in surface water and groundwater from five different sites were analyzed. Then, the degree of toxicological damage to Sprague-Dawley (SD) rats caused by contaminated water were systematically assessed using biological methods. Finally, the possible molecular mechanism of toxicological damage was further discussed. The synthesis results showed that the main pollution factors were some metal elements (Mn, Zn, Co, Ni) and rare earth elements (Sc, Nb, La, Ce, Pr, Dy and Y), which might cause significant DNA genetic damage to SD rats. Further, differential gene expression profile showed that DNA damage-inducible genes (Gadd45g and Ddit4), immunity-related genes (Mpo, Slpi and Elane) and two cancer-related genes (Mmp8 and Ltf) were used as a new prognostic and predictive biomarker for biosafety assessment. Therefore, this study provides a possible molecular mechanism for the toxicological damage, and also it provides a universal method to scientifically and effectively evaluate the water pollution risk for other mining areas.

Panel of suitable reference genes and its gender differences of fetal rat liver under physiological conditions and exposure to dexamethasone during pregnancy

The panel of suitable reference genes in the fetal liver have not been reported. In this study, five commonly used reference genes (GAPDH, β-actin, Rn18 s, Rpl13a, and Rps29) were firstly selected as candidates. Bestkeeper, GeNorm, and NormFinder software were then used to screen out the panel of suitable reference genes of male and female fetal rat liver under physiological and prenatal dexamethasone exposure (PDE) conditions. Finally, we verified the reliability of the screened panel of reference genes by standardizing sterol regulatory element binding protein 1c (SREBP1c) expression with different reference genes. The results showed that GAPDH + Rn18 s and GAPDH + Rpl13a were respectively the panel of suitable reference genes in male and female rat fetal liver under the physiological model, while Rn18 s + Rps29 and GAPDH + Rn18 s were respectively under the PDE model. The results showed that different reference genes affected the statistical results of SREBP1c expression, and the screened panel of suitable reference genes under the PDE model had smaller intragroup differences, when compared with other reference genes under physiological and PDE models. In conclusion, we screened and determined that the panel of suitable reference genes were GAPDH + Rn18 s and Rn18 s + Rps29 in the male rat fetal liver under physiological and PDE models, while they were GAPDH + Rpl13a and GAPDH + Rn18 s in the females, and confirmed that the selection of the panel of suitable reference genes in the fetal liver had gender differences and pathological model specificity.

Perinatal exposure to FireMaster® 550 (FM550), brominated or organophosphate flame retardants produces sex and compound specific effects on adult Wistar rat socioemotional behavior

Firemaster 550 (FM550) is a flame retardant (FR) mixture that has become one of the most commonly used FRs in household items such as foam-based furniture and baby products. Because this mixture readily leaches from products, contamination of the environment and human tissues is widespread. Prior work by us and others has reported sex-specific behavioral deficits in rodents and zebrafish following early life exposure. In an effort to understand the mechanisms by which these behavioral effects occur, here we explored the effects of its constituents on behavioral outcomes previously shown to be altered by developmental FM550 exposure. The FM550 commercial mixture is composed of two brominated compounds (BFR) and two organophosphate compounds (OPFRs) at almost equivalent proportions. Both the BFR and the OPFR components are differentially metabolized and structurally distinct, but similar to known neurotoxicants. Here we examined adult Wistar rat offspring socioemotional behaviors following perinatal exposure (oral, to the dam) to vehicle, 2000 μg/day FM550, 1000 μg/day BFR or 1000 μg/day OPFR from gestation day 0 to weaning. Beginning on postnatal day 65 offspring from all groups were subjected to a series of behavioral tasks including open field, elevated plus maze, marble burying, social interaction tests, and running wheel. Effects were exposure-, sex- and task-specific, with BFR exposure resulting in the most consistent behavioral deficits. Overall, exposed females showed more deficits compared to males across all dose groups and tasks. These findings help elucidate how different classes of flame retardants, independently and as a mixture, contribute to sex-specific behavioral effects of exposure.

Ryanodine receptor 1 mediated dexamethasone-induced chondrodysplasia in fetal rats

BACKGROUND

Osteoarthritis is caused by cartilage dysplasia and has fetal origin. Prenatal dexamethasone exposure (PDE) induced chondrodysplasia in fetal rats by inhibiting transforming growth factor β (TGFβ) signaling. This study aimed to determine the effect of dexamethasone on fetal cartilage development and illustrate the underlying molecular mechanism.

METHODS

Dexamethasone (0.2 mg/kg.d) was injected subcutaneously every morning in pregnant rats from gestational day (GD) 9 to GD21. Harvested fetal femurs and tibias at GD21 for immunofluorescence and gene expression analysis. Fetal chondrocytes were treated with dexamethasone (100, 250 and 500 nM), endoplasmic reticulum stress (ERS) inhibitor, and ryanodine receptor 1 (RYR1) antagonist for subsequent analyses.

RESULTS

In vivo, prenatal dexamethasone exposure (PDE) decreased the total length of the fetal cartilage, the proportion of the proliferation area and the cell density and matrix content in fetal articular cartilage. Moreover, PDE increased RYR1 expression and intracellular calcium levels and elevated the expression of ERS-related genes, while downregulated the TGFβ signaling pathway and extracellular matrix (ECM) synthesis in fetal chondrocytes. In vitro, we verified dexamethasone significantly decreased ECM synthesis through activating RYR 1 mediated-ERS.

CONCLUSIONS

PDE inhibited TGFβ signaling pathway and matrix synthesis through RYR1 / intracellular calcium mediated ERS, which ultimately led to fetal dysplasia. This study confirmed the molecular mechanism of ERS involved in the developmental toxicity of dexamethasone and suggested that RYR1 may be an early intervention target for fetal-derived adult osteoarthritis.

The effects, underlying mechanism and interactions of dexamethasone exposure during pregnancy on maternal bile acid metabolism

As important members in steroids related signal pathways, bile acids are very important in regulating substance metabolism and immune homeostasis. However, bile acids are highly cytotoxic, and the excessive accumulation can induce several abnormalities such as cholestatic liver injury. It is known that the bile acid metabolism alters during pregnancy and mostly will not result in pathologies. However, the effect of dexamethasone exposure during pregnancy on bile acid metabolism is still unknown. In this study, pregnant Wistar rats were subcutaneously administered dexamethasone (0.2 mg/kg.d) or saline from gestation day 9-21, while virgin rats were given the same treatment for 13 days. We found that, physiological pregnancy or dexamethasone exposure during non-pregnancy did not affect maternal serum TBA level and liver function. Nevertheless, dexamethasone exposure during pregnancy increased serum TBA level and accompanied with liver injury. Furthermore, we discovered that the conservation of bile acid homeostasis under pregnancy or dexamethasone exposure was maintained through compensatory pathways. However, dexamethasone exposure during pregnancy tipped the balance of liver bile acid homeostasis by increasing classical synthesis and decreasing efflux and uptake. In addition, dexamethasone exposure during pregnancy also increased serum estrogen level and nuclear receptors mRNA expression levels. Finally, two-way ANOVA analysis showed that dexamethasone exposure during pregnancy could induce or facilitate maternal cholestasis and liver injury by up-regulating ERα and CYP7A1 expression. This study confirmed that dexamethasone exposure during pregnancy was related to maternal intrahepatic cholestasis of pregnancy and should be carefully monitored in clinical settings.