Yankai Xia

Perfluorooctane sulfonate (PFOS) affects hormone receptor activity, steroidogenesis, and expression of endocrine‐related genes in vitro and in vivo

Perfluorooctane sulfonate (PFOS) is a widespread and persistent chemical in the environment. We investigated the endocrine-disrupting effects of PFOS using a combination of in vitro and in vivo assays. Reporter gene assays were used to detect receptor-mediated (anti-)estrogenic, (anti-)androgenic, and (anti-)thyroid hormone activities. The effect of PFOS on steroidogenesis was assessed both at hormone levels in the supernatant and at expression levels of hormone-induced genes in the H295R cell. A zebrafish-based short-term screening method was developed to detect the effect of PFOS on endocrine function in vivo. The results indicate that PFOS can act as an estrogen receptor agonist and thyroid hormone receptor antagonist. Exposure to PFOS decreased supernatant testosterone (T), increased estradiol (E2) concentrations in H295R cell medium and altered the expression of several genes involved in steroidogenesis. In addition, PFOS increased early thyroid development gene (hhex and pax8) expression in a concentration-dependent manner, decreased steroidogenic enzyme gene (CYP17, CYP19a, CYP19b) expression, and changed the expression pattern of estrogen receptor production genes (esr1, esr2b) after 500 µg/L PFOS treatment in zebrafish embryos. These results indicate that PFOS has the ability to act as an endocrine disruptor both in vitro and in vivo by disrupting the function of nuclear hormone receptors, interfering with steroidogenesis, and altering the expression of endocrine-related genes in zebrafish embryo.

Birth defects in children conceived by in vitro fertilization and intracytoplasmic sperm injection: a meta-analysis

OBJECTIVE To conduct a meta-analysis of studies assessing the effect of IVF and intracytoplasmic sperm injection (ICSI) on birth defects. DESIGN Meta-analysis. SETTING Centers for reproductive care. PATIENT(S) Patients treated by IVF and/or ICSI. INTERVENTION(S) We identified all studies published by September 2011 with data related to birth defects in children conceived by IVF and/or ICSI compared with spontaneously conceived children, or birth defects in the children conceived by IVF compared with those by ICSI. Risk ratios from individual studies were pooled with the fixed and random effect models. MAIN OUTCOME MEASURE(S) Risk of birth defects in children conceived by IVF and/or ICSI. RESULT(S) Of 925 studies reviewed for eligibility, 802 were excluded after screening titles and abstracts, 67 were excluded for duplicated data, data unavailable, or inappropriate control group, 56 were included in the final analysis. Among the 56 studies, 46 studies had data on birth defects in children conceived by IVF and/or ICSI (124,468) compared with spontaneously conceived children. These studies provided a pooled risk estimation of 1.37 (95% confidence interval [CI]: 1.26-1.48), which is also evident in subgroup analysis. In addition, 24 studies had data on birth defects in children conceived by IVF (46,890) compared with those by ICSI (27,754), which provided an overall no risk difference. CONCLUSION(S) Children conceived by IVF and/or ICSI are at significantly increased risk for birth defects, and there is no risk difference between children conceived by IVF and/or ICSI.

Study on the relation between occupational fenvalerate exposure and spermatozoa DNA damage of pesticide factory workers.

Aims: To determine sperm nuclear DNA integrity and to investigate the relation between fenvalerate (FE) exposure and spermatozoa DNA damage. Methods: Sperm DNA fragmentation was detected by a modified alkaline single cell gel electrophoresis (Comet) assay and a terminal deoxynucleotidyl transferase mediated dUTP nick end labelling (TUNEL) assay. The olive tail moment (OTM) and percentage tail DNA were measured by the Comet assay, and cell positive percentage was measured by the TUNEL assay for DNA damage evaluation. Results: The DNA integrity of spermatozoa of external and internal control groups were both significantly greater than that of the FE exposed group. The median value of tail DNA percentage in the exposure group was 11.30, which was significantly higher than 5.60 in the internal control group and 5.10 in the external control group. The median value of OTM was 3.80 in the exposure group, significantly higher than 1.50 in the internal control group and 2.00 in the external control group. Mean cell positive was 31.2% in the exposure group, significantly higher than 17.4% in the internal control and 19.6% in the external control groups. Cell positive (%) was significantly correlated with tail DNA percentage and with OTM of whole subjects (n = 63). Conclusions: Results showed that occupational FE exposure is associated with an increase in sperm DNA damage. A combination of the Comet and TUNEL assays would offer more comprehensive information for a better understanding of sperm DNA damage, and the biological significance of sperm DNA damage in sperm function and male infertility.

A genome-wide association study in Chinese men identifies three risk loci for non-obstructive azoospermia

Non-obstructive azoospermia (NOA) is one of the most severe forms of male infertility. Its pathophysiology is largely unknown, and few genetic influences have been defined. To identify common variants contributing to NOA in Han Chinese men, we performed a three-stage genome-wide association study of 2,927 individuals with NOA and 5,734 controls. The combined analyses identified significant (P < 5.0 × 10−8) associations between NOA risk and common variants near PRMT6 (rs12097821 at 1p13.3: odds ratio (OR) = 1.25, P = 5.7 × 10−10), PEX10 (rs2477686 at 1p36.32: OR = 1.39, P = 5.7 × 10−12) and SOX5 (rs10842262 at 12p12.1: OR = 1.23, P = 2.3 × 10−9). These findings implicate genetic variants at 1p13.3, 1p36.32 and 12p12.1 in the etiology of NOA in Han Chinese men.

Early second-trimester serum miRNA profiling predicts gestational diabetes mellitus.

Background Gestational diabetes mellitus (GDM) is one type of diabetes that presents during pregnancy and significantly increases the risk of a number of adverse consequences for the fetus and mother. The microRNAs (miRNA) have recently been demonstrated to abundantly and stably exist in serum and to be potentially disease-specific. However, no reported study investigates the associations between serum miRNA and GDM. Methodology/Principal Findings We systematically used the TaqMan Low Density Array followed by individual quantitative reverse transcription polymerase chain reaction assays to screen miRNAs in serum collected at 16–19 gestational weeks. The expression levels of three miRNAs (miR-132, miR-29a and miR-222) were significantly decreased in GDM women with respect to the controls in similar gestational weeks in our discovery evaluation and internal validation, and two miRNAs (miR-29a and miR-222) were also consistently validated in two-centric external validation sample sets. In addition, the knockdown of miR-29a could increase Insulin-induced gene 1 (Insig1) expression level and subsequently the level of Phosphoenolpyruvate Carboxy Kinase2 (PCK2) in HepG2 cell lines. Conclusions/Significance Serum miRNAs are differentially expressed between GDM women and controls and could be candidate biomarkers for predicting GDM. The utility of miR-29a, miR-222 and miR-132 as serum-based non-invasive biomarkers warrants further evaluation and optimization.

Assessing Hormone Receptor Activities of Pyrethroid Insecticides and Their Metabolites in Reporter Gene Assays

Pyrethroid insecticides, the most commonly used insecticides worldwide, are suspected endocrine-disrupting chemicals. But their interactions with hormone receptors are still unclear. The present study intended to evaluate and compare the hormone receptor (estrogen receptor [ER], androgen receptor [AR], and thyroid hormone receptor [TR]) activities of nine pyrethroids (cycloprothrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, etofenprox, fenvalerate, permethrin, and tetramethrin) and their metabolites (3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropne carboxylic acid [DCCA] and 3-phenoxybenzoic acid [3-PBA]) using receptor-mediated luciferase reporter gene assays. Of the 11 compounds tested, four showed very weak ER agonistic activities and six displayed antiestrogenic effects, among which cyhalothrin and DCCA possessed the most potent estrogenic and antiestrogenic activity respectively. Antagonistic effects to AR were found in 7 compounds, with cyfluthrin and deltamethrin exhibiting stronger AR antagonistic capacity. In the TR assay, all of tested chemicals except DCCA showed antagonistic effects. In this study, we provided evidence that a variety of pyrethroids and their metabolites might disrupt the function of multiple nuclear hormone receptors and thus have the potentials to affect the endocrine and the reproductive systems in humans.

Idiopathic Male Infertility Is Strongly Associated with Aberrant Promoter Methylation of Methylenetetrahydrofolate Reductase (MTHFR)

Background Abnormal germline DNA methylation in males has been proposed as a possible mechanism compromising spermatogenesis of some men currently diagnosed with idiopathic infertility. Previous studies have been focused on imprinted genes with DNA methylation in poor quality human sperms. However, recent but limited data have revealed that sperm methylation abnormalities may involve large numbers of genes or shown that genes that are not imprinted are also affected. Methodology/Principal Findings Using the methylation-specific polymerase chain reaction and bisulfite sequencing method, we examined methylation patterns of the promoter of methylenetetrahydrofolate reductase (MTHFR) gene (NG_013351: 1538–1719) in sperm DNA obtained from 94 idiopathic infertile men and 54 normal fertile controls. Subjects with idiopathic infertility were further divided into groups of normozoospermia and oligozoospermia. Overall, 45% (41/94) of idiopathic infertile males had MTHFR hypermethylation (both hemimethylation and full methylation), compared with 15% of fertile controls (P<0.05). Subjects with higher methylation level of MTHFR were more likely to have idiopathic male infertility (P-value for trend  = 0.0007). Comparing the two groups of idiopathic infertile subjects with different sperm concentrations, a higher methylation pattern was found in the group with oligozoospermia. Conclusions Hypermethylation of the promoter of MTHFR gene in sperms is associated with idiopathic male infertility. The functional relevance of hypermathylation of MTHFR to male fertility warrants further investigation.

Partial deletions are associated with an increased risk of complete deletion in AZFc: a new insight into the role of partial AZFc deletions in male infertility.

Background: The AZFc region on the human Y chromosome has been found to be functionally important in spermatogenesis. Complete AZFc deletion is one of the most frequent causes of male infertility and the roles of partial AZFc deletions (gr/gr and b2/b3 deletions) in spermatogenesis are controversial. Methods: To further study the roles of partial AZFc deletions in spermatogenic impairment and the relationship between complete and partial AZFc deletions, these deletions were typed and quantitative analysis of DAZ gene copies and Y chromosome haplogrouping were performed for seven pedigrees of complete AZFc deletion carriers, comprising 296 infertile and 280 healthy Chinese men. Results: Neither the gr/gr nor the b2/b3 deletion was found to be associated with spermatogenic failure. In one pedigree, a complete AZFc deletion was observed to result from the gr/gr deletion, suggesting that complete deletions of AZFc can be preceded by partial deletions. In addition, a new gr/gr-deleted Y haplogroup Q1 was identified and the reported fixation of the b2/b3 deletion in haplogroup N confirmed. The frequency of complete AZFc deletion in haplogroups Q1 and N was significantly higher than that in the other haplogroupsm with fewer partial deletions. Duplications of DAZ gene copies were also observed in this study. Conclusions: To date, these observations comprise the first evidence showing that partial AZFc deletions can increase the risk of complete AZFc deletion. The susceptibility of partial AZFc deletions to complete AZFc deletion deserves further examination, especially in the populations or Y haplogroups abundant in partial AZFc deletions.

The b2/b3 subdeletion shows higher risk of spermatogenic failure and higher frequency of complete AZFc deletion than the gr/gr subdeletion in a Chinese population

Microdeletions in the azoospermia factor (AZF) regions on the long arm of the human Y chromosome are known to be associated with spermatogenic failure. Although AZFc is recurrently deleted in azoospermic or oligozoospermic males, no definitive conclusion has been reached for the contribution of different partial AZFc deletions to spermatogenic failure. To further investigate the roles of partial deletions in spermatogenic failure and the relationship between the complete and partial AZFc deletions, we performed deletion typing and Y chromosome haplogrouping in 756 idiopathic infertile Han-Chinese and 391 healthy Han-Chinese. We found that both the b2/b3 partial deletion and the DAZ3/4+CDY1a deletion pattern were associated with spermatogenic failure. We also confirmed that two previously reported fixations, the b2/b3 deletion in haplogroup N1 and the gr/gr deletion in haplogroup Q1. Remarkably, the frequency of the complete AZFc deletion in haplogroup N1 was significantly higher than that in the haplogroup Q1. These results suggest that the b2/b3 partial deletion was associated with a higher risk of complete AZFc deletion compared with the gr/gr partial deletion. Compared with the gr/gr deletion, the b2/b3 deletion presents a shorter distance among recombination targets and longer recombination substrates, which may be responsible for the increased incidence of subsequent recombination events that can lead to the complete AZFc deletion in this Chinese study population. The susceptibility of the b2/b3 partial deletion to the complete AZFc deletion deserves further investigation in larger and diverse populations, especially those with a relatively high frequency of b2/b3 and gr/gr partial deletions.

Developmental toxicity of cypermethrin in embryo-larval stages of zebrafish

Cypermethrin, a type II pyrethroid insecticide, is widely used throughout the world in agriculture, forestry, horticulture and homes. Though the neurotoxicity of cypermethrin has been thoroughly studied in adult rodents, little is so far available regarding the developmental toxicity of cypermethrin to fish in early life stages. To explore the potential developmental toxicity of cypermethrin, 4-h post-fertilization (hpf) zebrafish embryos were exposed to various concentrations of cypermethrin (0, 25, 50, 100, 200 and 400 μg L⁻¹) until 96 h. Among a suite of morphological abnormalities, the unique phenotype curvature was observed at concentrations as low as 25 μg L⁻¹. Studies revealed that 400 μg L⁻¹ cypermethrin significantly increased malondialdehyde production. In addition, activity of antioxidative enzymes including superoxide dismutase and catalase were significantly induced in zebrafish larvae in a concentration-dependent manner. To further investigate the toxic effects of cypermethrin on fish, acridine orange (AO) staining was performed at 400 μg L⁻¹ cypermethrin and the result showed notable signs of apoptosis mainly in the nervous system. Cypermethrin also down-regulated ogg1 and increased p53 gene expression as well as the caspase-3 activity. Our results demonstrate that cypermethrin was able to induce oxidative stress and produce apoptosis through the involvement of caspases in zebrafish embryos. In this study, we investigated the developmental toxicity of cypermethrin using zebrafish embryos, which could be helpful in fully understanding the potential mechanisms of cypermethrin exposure during embryogenesis and also suggested that zebrafish could serve as an ideal model for studying developmental toxicity of environmental contaminants.