Astrocytic aryl hydrocarbon receptor mediates chronic kidney disease-associated mental disorders involving GLT1 hypofunction and neuronal activity enhancement in the mouse brain

Chronic kidney disease (CKD)-associated mental disorders have been attributed to the excessive accumulation of hemodialysis-resistant indoxyl-3-sulfate (I3S) in the brain. I3S not only induces oxidative stress but is also a potent endogenous agonist of the aryl hydrocarbon receptor (AhR). Here, we investigated the role of AhR in CKD-induced brain disorders using a 5/6 nephrectomy-induced CKD mouse model, which showed increased I3S concentration in both blood and brain, anxiety and impaired novelty recognition, and AhR activation in the anterior cortex. GFAP⁺ reactive astrocytes were increased accompanied with the reduction of glutamate transporter 1 (GLT1) on perineuronal astrocytic processes (PAPs) in the anterior cingulate cortex (ACC) in CKD mice, and these alterations were attenuated in both neural lineage-specific and astrocyte-specific Ahr conditional knockout mice (nAhrCKO and aAhrCKO). By using chronic I3S treatment in primary astrocytes and glia-neuron (GN) mix cultures to mimic the CKD brain microenvironment, we also found significant reduction of GLT1 expression and activity in an AhR-dependent manner. Chronic I3S treatment induced AhR-dependent pro-oxidant Nox1 and AhR-independent anti-oxidant HO-1 expressions. Notably, AhR mediates chronic I3S-induced neuronal activity enhancement and synaptotoxicity in GN mix, not neuron-enriched cortical culture. In CKD mice, neuronal activity enhancement was observed in ACC and hippocampal CA1, and these responses were abrogated by both nAhrCKO and aAhrCKO. Finally, intranasal AhR antagonist CH-223191 administration significantly ameliorated the GLT1/PAPs reduction, increase in c-Fos⁺ neurons, and memory impairment in the CKD mice. Thus, astrocytic AhR plays a crucial role in the CKD-induced disturbance of neuron-astrocyte interaction and mental disorders.

The sex-specific association of prenatal phthalate exposure with low birth weight and small for gestational age: A nationwide survey by the Taiwan Maternal and Infant Cohort Study (TMICS)

The Taiwan Maternal and Infant Cohort Study (TMICS) was launched with the aim to assess the effects of prenatal exposure to phthalic acid esters (PAEs) on infant health. A total of 1102 pregnant women were enrolled in this study from 2012 to 2015. All participants completed a structured questionnaire, and provided urine specimens. The urinary concentrations of PAE metabolites in the third trimester were measured using liquid chromatography-electrospray ionization tandem mass spectrometry. Generalized additive model-penalized regression splines and logistic regression models were employed to determine the risk for low birth weight (LBW) or small for gestational age (SGA) among pregnant women exposed to PAEs. After adjustments for other covariates, each incremental unit of ln-transformed mono-n-butyl phthalate (MnBP) for pregnant women increased the odds of SGA in male neonates by 1.44 (95% CI: 0.92-2.23). An inverse association between SGA and maternal MnBP exposure level was observed in female neonates. An increase in one ln-transformed MnBP concentration unit decreased the risk of female SGA to 0.50 (95% CI: 0.24-0.97). In the penalized regression splines, increased risks of LBW/SGA in male neonates were presented while pregnant women exposed to increased MnBP levels. However, an association in the opposite direction was observed between maternal MnBP and LBW or SGA for male and female neonates. This study indicated that high maternal MnBP exposure in the third trimester was associated with LBW or SGA for male infants. Adverse effects on susceptible populations exposed to high levels of PAEs should be of concern.

Prenatal Bisphenol a Exposure, DNA Methylation, and Low Birth Weight: A Pilot Study in Taiwan

Prenatal exposure to bisphenol A (BPA) may increase the risk of abnormal birth outcomes, and DNA methylation might mediate these adverse effects. This study aimed to investigate the effects of maternal BPA exposure on maternal and fetal DNA methylation levels and explore whether epigenetic changes are related to the associations between BPA and low birth weight. We collected urine and blood samples originating from 162 mother-infant pairs in a Taiwanese cohort study. We measured DNA methylation using the Illumina Infinium HumanMethylation 450 BeadChip in 34 maternal blood samples with high and low BPA levels based on the 75th percentile level (9.5 μg/g creatinine). Eighty-seven CpGs with the most differentially methylated probes possibly interacting with BPA exposure or birth weight were selected using two multiple regression models. Ingenuity pathway analysis (IPA) was utilized to narrow down 18 candidate CpGs related to disease categories, including developmental disorders, skeletal and muscular disorders, skeletal and muscular system development, metabolic diseases, and lipid metabolism. We then validated these genes by pyrosequencing, and 8 CpGs met the primer design score requirements in 82 cord blood samples. The associations among low birth weight, BPA exposure, and DNA methylation were analyzed. Exposure to BPA was associated with low birth weight. Analysis of the epigenome-wide findings did not show significant associations between BPA and DNA methylation in cord blood of the 8 CpGs. However, the adjusted odds ratio for the dehydrogenase/reductase member 9 (DHRS9) gene, at the 2nd CG site, in the hypermethylated group was significantly associated with low birth weight. These results support a role of BPA, and possibly DHRS9 methylation, in fetal growth. However, additional studies with larger sample sizes are warranted.

The sex-specific association of phthalate exposure with DNA methylation and characteristics of body fat in children

The present study assessed the association between phthalate exposure and mitochondrial DNA (mtDNA) polymerase γ (POLG) methylation along with the potential effect on the characteristics of body fat in children. A total of 152 children were enrolled. The urinary concentrations of phthalate metabolites were measured using ultraperformance liquid chromatography-tandem mass spectrometry. Genomic DNA was extracted from the buffy coat, and bisulfite-treated DNA was subjected to a pyrosequencing assay. In total, 17 CpG sites in the exon 2 region of POLG were included in the analysis. A multivariable regression model was applied to determine whether characteristics of body fat were associated with phthalate exposure and methylation of POLG. After adjustment for covariates, male children with a ten-fold increase in mono-methyl phthalate (MMP) or mono-benzyl phthalate (MBzP) concentrations had significantly higher measurements for total body fat (MMP: β = 6.47%; MBzP: β = 3.54%), and trunk fat (MMP: β = 6.67%; MBzP: β = 3.90%). Male children who had hypermethylation at the 2nd CpG site in exon 2 of POLG also had high measurements for BMI (β = 1.66 kg/m2), waist (β = 4.49 cm) and hip (β = 4.81 cm) circumference, total body fat (β = 5.48%), and trunk fat (β = 6.21%). A dose-response relationship existed between methylation at the 2nd CpG site in exon 2 of POLG and characteristics of body fat (p for trend<0.01). This study suggested that male children who are exposed to phthalic acid esters have high body weight, BMI, and body and trunk fat percentages. Methylation of the exon 2 region of POLG is a possible mechanism behind the causal effect of endocrine-disrupting substances.

Evidence of high di(2-ethylhexyl) phthalate (DEHP) exposure due to tainted food intake in Taiwanese pregnant women and the health effects on birth outcomes

The contamination of a clouding agent with di(2-ethylhexyl) phthalate (DEHP), a substitute emulsifier-containing compound used in a variety of foods was announced on May 23, 2011. The aims of this study were as follows (1) compare the urine phthalates (PAE) metabolites concentration and estimate the daily intake (DI) of PAEs in pregnant women before and after the tainted food scandal and (2) examine the effect of relatively high PAEs exposure on birth outcome. One-hundred twelve pregnant women in Northern Taiwan participated in this study from March to December 2010, i.e., before the tainted food scandal. After the tainted food scandal, we collected 69, 73, and 180 urine specimens (January 2013 to August 2014) from women whom were in their first, second, and third trimesters of pregnancy, respectively. We measure urinary DEHP metabolite concentrations to estimate the DI of DEHP and the hazard quotient (HQ) of subjects. This was the first study to assess the effects of DEHP-tainted food scandal exposure in pregnant women across the three trimesters of pregnancy. After the tainted food report, the concentrations of urine PAE metabolite were significantly decreased, especially those of DEHP metabolites. Based on different reference limit values, the percentages of pregnant women whose HQ_DEHP value exceeded the limit ranged from 0.53% to 8.93%. Despite this low frequency, the higher ΣPAE exposure during the second trimester may significantly increase the risk of relatively low birth height compared to the lower exposure group (β=-0.63 (-1.20 to -0.06)). Our results support the hypothesis that exposure to relatively high concentrations of DEHP in pregnant Taiwanese women may have an adverse effect on birth outcomes. The percentage of subjects whose exposure level exceeded the exposure limit was low; however, high PAEs exposure appears to be significantly associated with birth outcomes. Therefore, we suggest that reference dose for PAEs should be revised.

Associations between urinary total arsenic levels, fetal development, and neonatal birth outcomes: A cohort study in Taiwan

BACKGROUND

Arsenic exposure is a global health concern. Several studies have focused on chronic arsenic exposure in adults; however, limited data are available regarding the potential adverse effects of prenatal exposure on fetuses and neonates.

OBJECTIVES

To assess which time point maternal arsenic exposure may influence the fetus during pregnancy and birth outcomes.

METHODS

In this study, total arsenic concentrations were analyzed in urine samples collected from 130 women with singleton pregnancies (22-45years old) in Taiwan from March to December of 2010. All fetal biometric measurements in each trimester period and birth outcomes at delivery were obtained. We applied a generalized estimating equation model and multivariate regression models to evaluate the associations between maternal urinary total arsenic (UtAs) exposure during pregnancy, fetal biometric measurements, and neonatal birth outcomes.

RESULTS

We observed statistically significant correlations between maternal UtAs levels and the fetal biparietal diameter over all three trimesters (β=-1.046mm, p<0.05). Multiple regression analyses showed a negative association between maternal UtAs levels and chest circumference in the first trimester (β=-0.721cm, p<0.05), and second-trimester UtAs exposure was associated with decreases in birth weight (β=-173.26g, p<0.01), head circumference (β=-0.611cm, p<0.05), and chest circumference (β=-0.654cm, p<0.05). Dose-response relationships were also observed for maternal UtAs exposure and birth outcomes.

CONCLUSIONS

We identified a negative relationship between maternal UtAs levels during pregnancy, fetal development, and neonatal birth outcomes. These findings should be confirmed in future studies with large sample sizes.

Concurrent exposures to nonylphenol, bisphenol A, phthalates, and organophosphate pesticides on birth outcomes: A cohort study in Taipei, Taiwan

Prenatal exposure to phenols, phthalates (PAEs), and organophosphate (OP) pesticides may increase the risk of abnormal birth outcomes. However, many previous studies have examined exposure to a limited number of chemical classes or exposure profiles limited to a specific stage of pregnancy. This study aims to characterize the concurrent exposure scenario throughout pregnancy by simultaneously monitoring internal doses of several endocrine-disrupting compounds (EDCs), including 2 phenols (nonylphenol (NP) and bisphenol A (BPA)), 9 PAEs, and 6 OP pesticide metabolites and to assess the relationships between concurrent exposure to EDCs and infant birth weight, length, and head and chest circumference. One hundred and sixty two women provided three spot urine samples at approximately 11 and 26weeks gestation and at delivery. We applied multivariable linear regression and ridge regression models to estimate the effects of separate and correlated exposures. Multivariable linear regression models revealed that women with short birth-length infants had significantly higher urinary second-trimester NP levels (50th percentile, 5.03μg/g creatinine) (β=-0.47cm; 95% CI=-0.93 to -0.01). Similarly significant relationships were observed between second-trimester mono-methyl phthalate (MMP) exposure and short birth length, second-trimester ΣPAEs and short birth length, second-trimester ΣPAEs exposure and reduced head and chest circumference, second-trimester diethylphosphate (DEP) exposure and reduced birth weight and length, and second-trimester ΣDEPs exposure and short birth length. Women with urinary BPA above the 75th percentile or ΣPAEs levels above the 50th percentile in the third trimester had infants with significantly reduced head circumference. These observations suggest that the second trimester may be the critical stage of susceptibility for fetal development. In ridge regression models, for which women with fewer measures for exposure to NP, BPA, MMP, ΣPAEs, DEP and ΣDEPs simultaneously were available, no relationships were found with infant size at birth. Additional studies with larger sample sizes are warranted.

Effects of high di(2-ethylhexyl) phthalate (DEHP) exposure due to tainted food intake on pre-pubertal growth characteristics in a Taiwanese population

On May 23, 2011, a major scandal involving the illegal use of phthalates as clouding agents in food products was reported. Specifically, di(2-ethylhexyl) phthalate (DEHP) was purposefully added to foods as a substitute emulsifier. The purpose of this study was to examine the effects of DEHP exposure on the growth characteristics of the child victims of this scandal. Eighty-eight victims, originating from northern, central, and southern Taiwan and ranging in age from 6.0 to 10.5 years, were invited to participate in this study during clinic visits. The participants underwent follow-up health examinations from August 2012 to February 2013. We collected information on each participant's history of exposure to tainted food products using a questionnaire, and we analyzed their urinary concentrations of DEHP metabolites using high-performance liquid chromatography/tandem mass spectrometry. These data were then used to estimate their daily DEHP intake (DIAll) during the scandal. We also measured physical development parameters (height, weight, and bone age) and hormone levels (thyroid, sex and growth hormones) to evaluate their overall growth characteristics. The average (SD) duration of DEHP intake from tainted nutrition supplements was 1.39 (1.01) years. The median DIAll values were 19.93 and 20.69μg/kg bw/day for boys and girls, respectively. Among the enrolled children, the DIAll values of 46.9% of boys and 51.3% of girls exceeded the reference dose (RfD) of 20μg/kg bw/day established by the US Environmental Protection Agency. Our results demonstrate that DIAll is negatively associated with the height percentile, weight percentile, bone age/chronological age, and insulin-like growth factor 1 (IGF-1) levels but not with IGF binding protein 3 (IGF-BP3) level, IGF-1/IGF-BP3, sex hormones, or thyroid hormone levels. The DEHP DIAll value exceeded the RfD at high rates among children of both genders. Our results suggest that high levels of DEHP exposure due to the consumption of tainted food products are negatively associated with body weight, height, bone age, and IGF-1 levels in children. The likelihood of delayed puberty among the affected children is therefore a reasonable concern, and further follow-up is required.

The critical fetal stage for maternal manganese exposure

Prenatal exposure and the health effects of that exposure have been intensively studied for a variety of environmental pollutants and trace elements. However, few studies have compared susceptibilities among the three trimesters of gestation. Manganese (Mn) is a naturally occurring and abundant trace element in the environment. Although the effects of Mn on animals are well documented, knowledge of the effects of Mn exposure on pregnant women and fetuses remains limited. A longitudinal study was conducted by collecting blood samples during all three trimesters, and Mn exposure was completely characterized during gestation. The aims of this study were to examine the effects of maternal Mn exposure on neonatal birth outcomes and to explore the critical stage of these effects. In total, 38, 76 and 76 samples were obtained from singleton pregnant women in their first, second and third trimesters, respectively. The cohort of pregnant women was selected at a medical center in northern Taiwan. Erythrocyte samples were collected during the first, second and third trimesters of gestation. Erythrocyte Mn concentrations were measured by inductively coupled plasma mass spectrometry. Neonatal birth outcomes were evaluated immediately after delivery. A multivariate regression model was used to determine the associations between maternal Mn levels in erythrocytes in each trimester and neonatal birth outcomes. The geometric mean concentrations of Mn were 2.93 μg/dL, 3.96 μg/dL and 4.41 μg/dL in the first, second and third trimesters, respectively. After adjusting for potential confounders, a consistently negative association was found between maternal Mn levels throughout the three trimesters and birth outcomes. Log-transformed Mn levels in maternal erythrocytes in the second trimester were significantly associated with neonatal birth weight, head and chest circumferences, respectively (β=-556.98 g, p=0.038; β=-1.87 cm, p=0.045; β=-2.74 cm, p=0.024). Despite the limited sample size in the first trimester, negative effects of maternal Mn levels on birth weight (β=-1108.95 g, p<0.01) and chest circumference (β=-4.40 cm, p=0.019) were also observed.

The association between nonylphenols and sexual hormones levels among pregnant women: a cohort study in Taiwan

Background

Nonylphenol (NP) has been proven as an endocrine disrupter and had the ability to interfere with the endocrine system. Though the health effects of NP on pregnant women and their fetuses are sustained, these negative associations related to the mechanisms of regulation for estrogen during pregnancy need to be further clarified. The objective of this study is to explore the association between maternal NP and hormonal levels, such as estradiol, testosterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH), and progesterone.

Methods

A pregnant women cohort was established in North Taiwan between March and December 2010. Maternal urine and blood samples from the first, second, and third trimesters of gestation were collected. Urinary NP concentration was measured by high-performance liquid chromatography coupled with fluorescent detection. A mixed-effects model using a generalised estimating equation (GEE) was applied to assess the associations between maternal NP concentration and plasma hormones throughout the three trimesters.

Results

In total, 162 singleton pregnant women completed this study through delivery. The geometric mean of creatinine-adjusted urinary NP concentrations were 4.27, 4.21, and 4.10 µg/g cre. in the first, second, and third trimesters respectively. A natural log-transformation of urinary NP concentrations were significantly associated with LH in the GEE model (β = −0.23 mIU/ml, p<0.01).

Conclusion

This perspective cohort study demonstrates that negative association occurs between maternal NP exposure and plasma LH levels. The estrogen-mimic effect of NP might influence the negative feedback on LH during pregnancy.

The association between maternal nonylphenol exposure and parity on neonatal birth weight: a cohort study in Taiwan

BACKGROUND

The aim of this study was to explore the association between NP exposure and parity and their effect on neonatal birth weight.

METHODS

A cohort of pregnant women was established in a medical center in North Taiwan. Urinary NP concentration was determined by high-performance liquid chromatography coupled with fluorescent detection and adjusted using creatinine. A multivariable regression model was fit to determine the association between the maternal NP level in each trimester and neonatal birth weight. The odds ratios (ORs) of infant birth weight below the 10th, 25th, and 50th percentiles, comparing pregnant women with the different NP exposure levels, was estimated using a logistic regression.

RESULTS

Of the 162 pregnant women in the study, 99 were multiparas and 63 were primiparas. After adjusting for other covariates, the NP level in the second trimester had a significant association with birth weight in the primiparas (β = -182.49 g, p value = 0.02). The OR of low infant birth weight, comparing pregnant women with different NP levels, was increased by decreasing the cutoff percentile for birth weight (OR = 1.18 for the 50th percentile, 2.12 for the 25th percentile, and 7.81 for the 10th percentile). The odds of primiparas with high NP level having a low neonatal birth weight increased to 3.87, 11.77, and 9.40 for the three different percentiles (p value < 0.05).

CONCLUSION

Maternal NP exposure level is associated with an increased risk of low neonatal weight. Primiparas are especially at risk, and the second trimester of pregnancy may be the critical stage of exposure.

Neonatal outcomes of intrauterine nonylphenol exposure--a longitudinal cohort study in Taiwan

BACKGROUND

Nonylphenol (NP) is an environmental hormone with proven estrogenic effects. Although its adverse effects on animals are well documented, the effects of NP exposure on humans remain unclear, and those on the human foetus are completely unknown. This study explores the effects of intrauterine NP exposure on neonates.

METHODS

A cohort of pregnant women was established in a medical centre in northern Taiwan. Urine samples from the first, second, and third trimesters of gestation were collected. Urinary NP concentration was measured by high-performance liquid chromatography coupled with fluorescent detection. Neonatal outcomes were evaluated immediately after delivery. A mixed-effects model using a generalised estimating equation was applied to assess the association between gestational age, maternal body weight, and maternal NP concentration throughout the three trimesters. A multivariable regression model was used to determine the association between maternal NP level in urine in each trimester and neonatal outcomes.

RESULTS

In total, 162 singleton pregnant women completed this study through delivery. The geometric mean of creatinine-adjusted urinary NP concentrations were 4.27 μg/g, 4.21 μg/g, and 4.10 μg/g in the first, second, and third trimesters, respectively. Pregnant women whose urinary NP concentrations were above the median in the second trimester had low maternal weight gain (β=-1.55 kg, p=0.02) and short neonatal body length (β=-0.47 cm, p=0.04). Women with an above-median urinary NP concentration had an odds ratio of having a small for gestational age (SGA) neonate of 7.81 (p<0.05).

CONCLUSIONS

This study indicates that maternal high NP exposure in the second trimester is associated with SGA, decreased foetal body length at birth, and low maternal weight gain. The effects of this endocrine-disrupting substance on pregnant women and foetuses should be a concern during gestation.

Trends in concentration of ground-level ozone and meteorological conditions during high ozone episodes in the Kao-Ping Airshed, Taiwan

This work analyzes the variations in daily maximum 1-hr ozone (O3) concentrations and the long-term trends in annual means of hourly ambient concentrations of O3, nitrogen oxides (nitrous oxide + nitrogen dioxide), and nonmethane hydrocarbons in the three administrative regions of Kao-Ping airshed in southern Taiwan over a recent 8-yr period. The annual or monthly means of all maxima, most 95th percentiles, and some 90th percentiles of the daily maximum 1-hr O3 concentrations exceed the daily limit of 120 parts per billion by volume in all three regions, namely, Kao-hsiung City, Kso-hsiung County, and P'ing-tung County. The monthly means of daily maximum 1-hr O3 concentrations exhibit distinct seasonal variations, with a bimodal form with the maxima in autumn and late winter to the middle of spring and a minimum in summer. The long-term variations in the annual means of hourly O3 concentrations in the three regions exhibit increasing trends. These increases in O3 are associated with the decline in ambient concentrations of nitrogen oxides and nonmethane hydrocarbons. High O3 episodes occur most often in autumn and most rarely in summer. The seasonal mean mixing heights in descending order follow the order of spring, summer, autumn, and winter. Meteorological parameters in autumn and winter indicate that the ground-level O3 tends to accumulate and trigger a high O3 episode on a warm day with sufficient sunlight and low wind in a high-pressure system, consistent with the low mixing heights in these two seasons.