Cadmium Exposure of Female Mice Impairs the Meiotic Maturation of Oocytes and Subsequent Embryonic Development

Epigenetic Modifications Are Involved in Transgenerational Inheritance of Cadmium Reproductive Toxicity in Mouse Oocytes

Maternal cadmium exposure during pregnancy has been demonstrated to have detrimental effects on offspring development. However, the impact of maternal cadmium exposure on offspring oocytes remains largely unknown, and the underlying mechanisms are not fully understood. In this study, we found that maternal cadmium exposure during pregnancy resulted in selective alteration in epigenetic modifications of mouse oocytes in offspring, including a decrease in H3K4me2 and H4K12ac, as well as an increase in DNA methylation of H19. Although ROS levels and mitochondrial activity remain at normal levels, the DNA damage marker γH2AX was significantly increased and the DNA repair marker DNA-PKcs was remarkably decreased in offspring oocytes from maternal cadmium exposure. These alterations are responsible for the decrease in the quality of mouse oocytes in offspring induced by maternal cadmium exposure. As a result, the meiotic maturation of oocytes and subsequent early embryonic development are influenced by maternal cadmium exposure. RNA-seq results showed that maternal cadmium exposure elicits modifications in the expression of genes associated with metabolism, signal transduction, and endocrine regulation in offspring ovaries, which also contribute to the disorders of oocyte maturation and failures in early embryonic development. Our research provides direct evidence of transgenerational epigenetic inheritance of cadmium reproductive toxicity in mouse germ cells.

Melatonin partially rescues defects induced by tranexamic acid exposure during oocyte maturation in mice

Tranexamic acid (TXA) is widely used among young women because of its ability to whiten skin and treat menorrhagia. Nevertheless, its potential effects on oocyte maturation and quality have not yet been clearly clarified. Melatonin (MT) is an endogenous hormone released by the pineal gland and believed to protect cells from oxidative stress injury. In the present study, we used an in vitro maturation model to investigate the toxicity of TXA and the protective role of MT in mouse oocytes. Compared with the control group, the TXA-exposed group had significantly lower nuclear maturation (57.72% vs. 94.08%, P < 0.001) and early embryo cleavage rates (38.18% vs. 87.66%, P < 0.001). Further study showed that spindle organization (52.56% vs. 18.77%, P < 0.01) and chromosome alignment (33.23% vs. 16.66%, P < 0.01) were also disrupted after TXA treatment. Mechanistically, we have demonstrated that TXA induced early apoptosis of oocytes (P < 0.001) by raising the level of reactive oxygen species (P < 0.001), which was consistent with an increase in mitochondrial damage (P < 0.01). Fortunately, all these effects except the spindle defect were successfully rescued by an appropriate level of MT. Collectively, our findings indicate that MT could partially reverse TXA-induced oocyte quality deterioration in mice by effectively improving mitochondrial function and reducing oxidative stress-mediated apoptosis.NEW & NOTEWORTHY Tranexamic acid is increasingly used to whiten skin, reverse dermal damages, and treat heavy menstrual bleeding in young women. However, its potential toxicity in mammalian oocytes is still unclear. Our study revealed that tranexamic acid exposure impaired the mouse oocyte quality and subsequent embryo development. Meanwhile, melatonin has been found to exert beneficial effects in reducing tranexamic acid-induced mitochondrial dysfunction and oxidative stress.

Low levels of Cd2+ combined with procymidone may cause ovarian damage in mice via unfolded protein response

As no study about the combined effect of low levels of Cd2+ with procymidone (PCM) on organs and organisms, we investigated their actions on mouse-ovary in vivo and in vitro. Four-week mice were treated with corn oil for the control group, corn oil + 0.0045 mg/L Cd2+ (CdCl2 was dissolved in ultrapure water and freely consumed by mice) for Cd2+ group, 50 mg/kg/d PCM (suspended in corn oil and administered orally to mice) for PCM group, and 50 mg/kg/d PCM + 0.0015 (0.0045 and 0.0135) mg/L Cd2+ for L+ (M+ and H+) PCM group for 21 days. For in vitro experiment, the cultured ovaries were treated with acetone for the control group, 0.1% acetone + 8.4 μg/L Cd2+ for the Cd2+ group, 0.63 mg/L PCM (dissolved in acetone) for the PCM-group, and 0.63 mg/L PCM + 2.8 (8.4 and 25.2) μg/L Cd2+ for L+ (M+ and H+) PCM group for 7 days. Mouse body weight in each treatment group, the weight and volume of ovaries in all PCM groups were lower than the control. Both in vivo and in vitro, all-stage follicle numbers were lower in M+PCM and H+PCM groups, whereas the atretic follicles and CASPASE3/8 were higher; meanwhile, lower estradiol and progesterone and higher unfolded protein response (UPR) members in all PCM groups. L+, M+, and H+PCM groups had further ovarian damage and stronger UPR than PCM groups, as did M+PCM groups over Cd2+ groups. It is hypothesized low-level PCM and Cd2+ may mutually promote each other's triggered UPR and exacerbate ovarian damage.

Endocrine disruptors in e-waste dismantling dust: In silico prediction of mixture-induced reproductive toxicity mechanisms

The constant exposure of humans to a mixture of low doses of toxic substances, emerging from the daily emission of toxic dust containing various metals and organic compounds in electrical and electronic waste (e-waste) recycling areas, poses potential harmful effects on health and the environment. While individually recognized as endocrine disruptors affecting hormonal balance, the combined impact of these toxic substances in a mixture remains insufficiently explored, particularly in relation to reproductive health. Thus, the aim of this in silico analysis was to: (i) assess the relationship between the exposure to a mixture of DBDE, DBDPE, TBBPA, Pb, Cd and Ni and development of male and female reproductive system disorders; and (ii) demonstrate the ability of in silico toxicogenomic tools in revealing the potential molecular mechanisms involved in the mixture toxicity. As the main data-mining tool, Comparative Toxicogenomics Database (CTD) was used, along with the ToppGene Suite portal and GeneMANIA online server. Our analysis identified 5 genes common to all the investigated substances and linked to reproductive system disorders. Notably, the most prominent interactions among these genes were physical interactions (77.64 %). Pathway enrichment analysis identified oxidative stress response as the central disrupted molecular pathway linked to reproductive pathology in the investigated mixture, while our chemical-phenotype CTD analysis uncovered additional affected pathways - apoptosis, hormonal regulation, and developmental functions. These findings highlight an increased risk of reproductive system disorders associated with the exposure to the investigated mixture of toxic substances in electronic waste recycling areas, emphasizing the urgent need for attention to address this environmental health concern. Hence, future laboratory studies should prioritize investigating the specific genes and common mechanisms identified in this study.

Cadmium as an ovarian toxicant: A review

Cadmium (Cd) is a ubiquitous heavy metal toxicant with no biological function in the human body. Considerably, because of its long biological half-life and very low excretion rate, Cd is inclined to accumulate and cause deleterious effects on various body organs (e.g., liver, kidney, and ovary) in humans and animals. Ovaries are the most vulnerable targets of Cd toxicity. Cd has been shown to induce oxidative stress, follicular atresia, hormonal imbalance, and impairment of oocyte growth and development. Moreover, Cd toxicity has been associated with increasing incidences of menstrual disorders, pregnancy loss, preterm births, delayed puberty, and female infertility. Therefore, it is crucial to understand how Cd poisoning impacts specific ovarian processes for the development of preventive interventions to enhance female fertility. The current review attempts to collate the recent findings on Cd-induced oxidative stress, follicular apoptosis, steroid synthesis inhibition, and teratogenic toxicity, along with their possible mechanisms in the ovarian tissue of different animal species. Additionally, the review also summarizes the studies related to the use of many antioxidants, medicinal herbs, and other compounds as remedial approaches for managing Cd-induced ovarian toxicity.

Heavy Metals in Follicular Fluid Affect the Ultrastructure of the Human Mature Cumulus-Oocyte Complex

It is known that exposure to heavy metal such as lead (Pb) and cadmium (Cd) has several adverse effects, particularly on the human reproductive system. Pb and Cd have been associated with infertility in both men and women. In pregnant women, they have been associated with spontaneous abortion, preterm birth, and impairment of the development of the fetus. Since these heavy metals come from both natural and anthropogenic activities and their harmful effects have been observed even at low levels of exposure, exposure to them remains a public health issue, especially for the reproductive system. Given this, the present study aimed to investigate the potential reproductive effects of Pb and Cd levels in the follicular fluid (FF) of infertile women and non-smokers exposed to heavy metals for professional reasons or as a result of living in rural areas near landfills and waste disposal areas in order to correlate the intrafollicular presence of these metals with possible alterations in the ultrastructure of human cumulus-oocyte complexes (COCs), which are probably responsible for infertility. Blood and FF metals were measured using atomic absorption spectrometry. COCs corresponding to each FF analyzed were subjected to ultrastructural analyses using transmission electron microscopy. We demonstrated for the first time that intrafollicular levels of Pb (0.66 µg/dL-0.85 µg/dL) and Cd (0.26 µg/L-0.41 µg/L) could be associated with morphological alterations of both the oocyte and cumulus cells' (CCs) ultrastructure. Since blood Cd levels (0.54 µg/L-1.87 µg/L) were above the current reference values established by the guidelines of the Agency for Toxic Substances and Disease Registry (ATSDR) and the Environmental Protection Agency (EPA) (0.4 µg/L), whereas blood Pb levels (1.28 µg/dL-3.98 µg/dL) were below the ATSDR reference values (≤5 µg/dL), we believe that these alterations could be due especially to Cd, even if we cannot exclude a possible additional effect of Pb. Our results highlighted that oocytes were affected in maturation and quality, whereas CCs showed scarcely active steroidogenic elements. Regressing CCs, with cytoplasmic alterations, were also numerous. According to Cd's endocrine-disrupting activity, the poor steroidogenic activity of CCs might correlate with delayed oocyte cytoplasmic maturation. So, we conclude that levels of heavy metals in the blood and the FF might negatively affect fertilization, embryo development, and pregnancy, compromising oocyte competence in fertilization both directly and indirectly, impairing CC steroidogenic activity, and inducing CC apoptosis.

Association of chromosomal abnormalities with prenatal exposure to heavy metals: A nested case-control study in high-risk pregnant women in China

Prenatal exposure to heavy metals causes multiple hazards to fetal growth and development. Epidemiological studies on the association between heavy metals and fetal chromosomal abnormalities (CAs) are lacking. We conducted a nested case-control study in a cohort of high-risk pregnant women in China from September 2018 to June 2021. A total of 387 participants were diagnosed with fetal CAs in the case group and 699 were diagnosed with a normal karyotype in the control group. Amniotic fluid concentrations of 10 metals (barium, cobalt, antimony, manganese, ferrum, copper, selenium, strontium, vanadium, and chromium) were measured using inductively coupled plasma-mass spectrometry. We applied quantile g-computation and weighted quantile sum regression to assess the overall effect of metal mixtures and identify metals with significant weight. Logistic and Poisson regression analyses were used to estimate the effects of metals on CAs and CAs subtypes. Our results showed that the metal mixture concentrations were positively associated with the risk of fetal CAs. In adjusted logistic models, Sb was associated with fetal CAs (OR=1.15, 95% CI: 1.02-1.30), and revealed a linear dose-response relationship between Sb level and the risk of fetal CAs. Additionally, the exploratory analysis revealed that Sb levels were associated with Klinefelter syndrome (OR=1.452, 95% CI: 1.063-1.984) and Turner syndrome (OR=1.698; 95% CI,1.048-2.751). Our study revealed that metal mixtures are associated with a higher risk of fetal CAs and that this association may be driven primarily by Sb. Moreover, we provide a genetic perspective on the effects of heavy metals on sexual development in humans.

Fertility loss: negative effects of environmental toxicants on oogenesis

There has been a global decline in fertility rates, with ovulatory disorders emerging as the leading cause, contributing to a global lifetime infertility prevalence of 17.5%. Formation of the primordial follicle pool during early and further development of oocytes after puberty is crucial in determining female fertility and reproductive quality. However, the increasing exposure to environmental toxins (through occupational exposure and ubiquitous chemicals) in daily life is a growing concern; these toxins have been identified as significant risk factors for oogenesis in women. In light of this concern, this review aims to enhance our understanding of female reproductive system diseases and their implications. Specifically, we summarized and categorized the environmental toxins that can affect oogenesis. Here, we provide an overview of oogenesis, highlighting specific stages that may be susceptible to the influence of environmental toxins. Furthermore, we discuss the genetic and molecular mechanisms by which various environmental toxins, including metals, cigarette smoke, and agricultural and industrial toxins, affect female oogenesis. Raising awareness about the potential risks associated with toxin exposure is crucial. However, further research is needed to fully comprehend the mechanisms underlying these effects, including the identification of biomarkers to assess exposure levels and predict reproductive outcomes. By providing a comprehensive overview, this review aims to contribute to a better understanding of the impact of environmental toxins on female oogenesis and guide future research in this field.

Cadmium exposure impairs oocyte meiotic maturation by inducing endoplasmic reticulum stress in vitro maturation of porcine oocytes

Cadmium (Cd) is toxic metal that can induce various diseases, such as cardiovascular, nervous, and reproductive systems. This study investigated the effect of Cd exposure on porcine oocyte maturation and the underlying mechanism. Porcine cumulus-oocyte complexes were exposed various Cd concentration and tauroursodeoxycholic acid (TUDCA), an inhibitor of endoplasmic reticulum (ER) stress during in vitro maturation (IVM). After IVM, we evaluated meiotic maturation, ER stress, and oocyte quality by Cd exposure. Cd exposure inhibited cumulus cell expansion and meiotic maturation, increased oocyte degeneration, and induced ER stress. The levels of spliced XBP1 and ER stress-associated transcripts, markers of ER stress, were elevated in Cd-treated cumulus-oocyte complexes and denuded oocytes during IVM. Moreover, Cd-induced ER stress impaired oocyte quality by disrupting mitochondrial function and elevating intracellular reactive oxygen species levels while decreasing ER function. Interestingly, TUDCA supplementation significantly decreased the expression of ER stress-related genes and increased the quantity of ER compared with the Cd treatment. Additionally, TUDCA was also able to rescue excessive levels of ROS and restore normal mitochondrial function. Moreover, the addition of TUDCA under Cd exposure greatly ameliorated Cd-mediated detrimental effects on meiotic maturation and oocyte quality, including cumulus cell expansion and MII rate. These findings suggest that Cd exposure during IVM impairs the meiotic maturation of oocytes by inducing of ER stress.

Applications of a powerful model organism Caenorhabditis elegans to study the neurotoxicity induced by heavy metals and pesticides

The expansion of industry and the use of pesticides in agriculture represent one of the major causes of environmental contamination. Unfortunately, individuals and animals are exposed to these foreign and often toxic substances on a daily basis. Therefore, it is crucial to monitor the impact of such chemicals on human health. Several in vitro studies have addressed this issue, but it is difficult to explore the impact of these compounds on living organisms. A nematode Caenorhabditis elegans has become a useful alternative to animal models mainly because of its transparent body, fast growth, short life cycle, and easy cultivation. Furthermore, at the molecular level, there are significant similarities between humans and C. elegans. These unique features make it an excellent model to complement mammalian models in toxicology research. Heavy metals and pesticides, which are considered environmental contaminants, are known to have affected the locomotion, feeding behavior, brood size, growth, life span, and cell death of C. elegans. Today, there are increasing numbers of research articles dedicated to this topic, of which we summarized the most recent findings dedicated to the effect of heavy metals, heavy metal mixtures, and pesticides on the well-characterized nervous system of this nematode.

Cumulus Cell Transcriptome after Cumulus-Oocyte Complex Exposure to Nanomolar Cadmium in an In Vitro Animal Model of Prepubertal and Adult Age

Cadmium (Cd), a highly toxic pollutant, impairs oocyte fertilization, through oxidative damage on cumulus cells (CCs). This study analysed the transcriptomic profile of CCs of cumulus-oocyte complexes (COCs) from adult and prepubertal sheep, exposed to Cd nanomolar concentration during in vitro maturation. In both age-groups, CCs of matured oocytes underwent RNA-seq, data analysis and validation. Differentially expressed genes (DEGs) were identified in adult (n = 99 DEGs) and prepubertal (n = 18 DEGs) CCs upon Cd exposure. Transcriptomes of adult CCs clustered separately between Cd-exposed and control samples, whereas prepubertal ones did not as observed by Principal Component Analysis. The transcriptomic signature of Cd-induced CC toxicity was identified by gene annotation and literature search. Genes associated with previous studies on ovarian functions and/or Cd effects were confirmed and new genes were identified, thus implementing the knowledge on their involvement in such processes. Enrichment and validation analysis showed that, in adult CCs, Cd acted as endocrine disruptor on DEGs involved in hormone biosynthesis, cumulus expansion, regulation of cell signalling, growth and differentiation and oocyte maturation, whereas in prepubertal CCs, Cd affected DEGs involved in CC development and viability and CC-oocyte communications. In conclusion, these DEGs could be used as valuable non-invasive biomarkers for oocyte competence.

Melatonin protects oocytes from cadmium exposure-induced meiosis defects by changing epigenetic modification and enhancing mitochondrial morphology in the mouse

Cadmium (Cd) is one major environmental pollutant that can cause detrimental impacts on human as well as animal reproductive systems as a result of oxidative stress. It is widely acknowledged that melatonin secreted principally by the pineal gland is not only a natural potent antioxidant but also a free radical scavenger, whereas concerning how to alleviate the toxic effects of Cd on oocyte maturation remains elusive. In this investigation, it was the first time to explore the protective effects and potential mechanism of melatonin on meiotic maturation of mouse oocytes exposed to Cd in vitro medium. We found that Cd exerts adverse effects on meiotic maturation progression by disrupting the normal function of mitochondrion combined with the aberrant mitochondrial distribution and decreased membrane potential and altering epigenetic modification, including H3K9me2 and H3K4me2. Additionally, it was observed that Cd exposure disrupted the morphology of spindle organization and caused chromosome misalignment, which might be through changing the level of acetylated tubulin, whereas melatonin administration alleviated the toxic impacts of Cd on oocytes. Furthermore, the mitochondrial morphology-related genes mRNA expression and protein expression of autophagy-related genes was also investigated. The results suggested that melatonin supplementation significantly altered the mRNA expression of mitochondrial dynamics-related genes, rather than the expression of mitophagy-related proteins. Taken together, our results validated that melatonin administration has a certain protective impact against oocytes meiosis maturation defects induced by cadmium through changing epigenetic modification and enhancing mitochondrial morphology rather than mitophagy.

Toxic Effects of Cadmium on the Female Reproductive Organs a Review

Cadmium (Cd) is a common environmental pollutant present in soil and associated with many modern industrial processes. Cadmium may adversely influence the health of experimental animals and humans and exert significant effects on the reproductive tract morphology and physiology. During embryonic development, cadmium suppresses the normal growth and development of the ovaries, and in adults it disrupts the morphology and function of the ovaries and uterus. The exposure to cadmium has adverse effects on the oocyte meiotic maturation affecting the structure of ovarian tissue. The distribution of follicles and corpus luteum in the ovarian tissues has been shown to be disrupted, affecting the normal growth and development of the follicles. In the ovarian cortex, the number of follicles at different stages of maturation decreased, and the number of atretic follicles increased. In the medulla, oedema and ovarian haemorrhage and necrosis appears at higher doses. Granulosa cells exposed to cadmium exhibited morphological alterations. Oocyte development was inhibited and the amount of oocyte apoptosis was higher. Cadmium exposure also caused changes in the structure of the ovarian blood vessels with reduction in the vascular area. Cadmium effects included increased uterine weight, hyperplasia and hypertrophy of the endometrial lining. Exposure to cadmium had specific effects on gonadal steroidogenesis by suppressing steroid biosynthesis of the ovarian granulosa cells and luteal cells. Progesterone, follicle stimulating hormone, and luteinizing hormone decreased significantly after CdCl2 administration. Cadmium can suppress the female’s ovulation process and cause temporary infertility.

Toxicity of cadmium salts on indicators of embryogenesis of rats

Cadmium is a toxic heavy metal which is considered a dangerous environmental pollutant and has a detrimental effect on the organs of the reproductive system, the period of implantation and the development of embryos. The experiment presented in this article established the effect of cadmium salts (chloride and citrate) on the general progress of embryogenesis. For this purpose, 60 rats were randomly divided into three groups: control, experimental group with cadmium chloride exposure and experimental group with cadmium citrate exposure. Cadmium chloride solvent, cadmium citrate solvent at a dose of 1.0 mg/kg and distilled intragastric water were injected from the first to the thirteenth (first subgroup) and from the first to the twentieth days of embryogenesis (second subgroup). When cadmium chloride was injected, total embryonic (by 4.24 and 3.67 times), pre-implantation (by 6.50 and 14.03 times) and post-implantation mortality (by 3.07 and 2.49 times) increased with a reduction of the number of surviving fetuses by 24.0% and 25.9% compared with the control group on the 13th and 20th days of embryogenesis respectively. At the same time, during exposure to cadmium citrate, indicators of total embryonic mortality increased by 4.02 and 3.52 times, pre-implantation mortality by 6.04 and 13.03 times, and post-implantation mortality by 3.09 and 2.26 times, and indicators of the number of live fetuses decreased by 18.3% and 22.2% in relation to the control group. When determining the accumulation of cadmium in embryos on the 20th day of gestation, polyelement analysis of biological materials using the atomic emission method with electric arc atomization revealed a 15.83-fold increase in cadmium chloride and 9.00 times in cadmium citrate relative to the control group. Embryolethality rates increased in animals of both experimental groups while the number of live fetuses per female decreased, which indicated an obvious embryotoxic effect of cadmium compounds. It is would be useful to conduct histological studies, which will help detect changes at the tissue level and possibly explain the level of embryonic mortality.

The environment and female reproduction: Potential mechanism of cadmium poisoning to the growth and development of ovarian follicle

Cadmium (Cd) is ubiquitous in our environment and can easily bioaccumulate into the organism after passage through the respiratory and digestive tracts. Long-term exposure to Cd can result in the significant bioaccumulation in organism because of its long biological high-life (10-30 years), which exerts irreversible damages on the health of animals and humans. Although there are increased evidence of impeding the normal function of female reproduction resulted from Cd exposure, the mechanism of the negative action of Cd on the growth and development of ovarian follicle remains enigmatic. Thus, the purpose of the presented study is to summarize available literature which describing Cd-related toxicity involved in the adverse effects on the growth and development of the ovarian follicle. In conclusion, it is suggested that Cd causes damage to the folliculogenesis of mammalians, which results in the decline in the number and quality of ovulated oocytes and the failure in the fertilization. The mechanism behinds that may be linked to the interference to the production of reproductive hormones and the augment of reactive oxygen species (ROS). Furthermore, the enhanced ROS, in turn, impairs various molecules including proteins, lipids and DNA, as well as the balance of the antioxidant defense system, mitochondrial homeostasis, endoplasmic reticulum, autophagy and epigenetic modification. This review is expected to elaborate the toxic mechanism of Cd exposure to the growth and development of ovarian follicles and provide essential remediation strategies to alleviate the damage of Cd to female reproductive health.

Maternal exposure to cadmium from puberty through lactation induces abnormal reproductive development in female offspring

Four-week-old female ICR mice were exposed to Cd through drinking water from puberty through lactation to investigate the effects of reproductive development in female offspring. Our results showed that maternal Cd exposure from puberty to lactation induced vaginal opening delay, and disturbed estrous cycle in the offspring on postnatal day (PND) 21, without affecting the body weight at vaginal opening. The histopathology results showed the increased primordial follicles and the decreased secondary follicles, and the mRNA level of Amh increased in the offspring's ovaries upon Cd exposure, suggesting the inhibition of ovarian follicular development on PND21. Moreover, the level of serum estradiol reduced and genes associated with steroidogenesis (3β-Hsd, P450scc and P450arom) were downregulated upon Cd exposure on PND 21. Thus, Cd may inhibit the follicular development via disturbing the mRNA level of genes associated with steroidogenesis and then the synthesis of estradiol in prepuberty. Taken together, despite the lack of attention to estrous cycle at termination, maternal Cd exposure from puberty to lactation induced the adverse effects on reproductive development of female offspring, including the delay of vaginal opening, irregular estrous cycle and inhibition of follicular development, via disturbing the mRNA level of genes associated with follicular development and steroidogenesis.

Protective effect of resveratrol against cadmium-induced toxicity on ovine oocyte in vitro maturation and fertilization

Background

Heavy metal cadmium (Cd) is a widespread environmental contaminant with a potential toxicity that might negatively affect female reproduction and fertility. It has been reported that Cd exposure impaired the quality of oocytes and led to a defective maturation and fertilization, through oxidative stress induction. Resveratrol (Res) is a natural polyphenol with strong antioxidant properties that exhibited protective role in preventing oocyte redox homeostasis disruption and quality decline. Here, we explored whether the addition of Res to in vitro maturation (IVM) medium might act as a protection against Cd-induced toxicity on ovine oocyte maturation and fertilization. Firstly, we evaluated the effect of supplementing IVM medium with two different Res concentrations (1 and 2 μmol/L) on nuclear maturation and fertilization of oocytes matured under CdCl₂ (2 μmol/L) exposure. Therefore, the concentration of 1 μmol/L Res was selected to analyse the effects of this compound on intracellular ROS levels, mitochondrial (mt) distribution and activity, chromatin configuration, cytoskeleton morphology, cortical granules (CGs) distribution and mRNA expression of genes associated with cellular response to oxidative stress (i.e. SIRT1, SOD 1, GPX1, GSR, CAT) in Cd-exposed in vitro matured oocytes.

Results

We found that 1 μmol/L Res restored the reduced oocyte meiotic competence induced by Cd exposure as well as, Res sustained oocyte ability to be normally fertilized and decreased polyspermic fertilization at both tested concentrations. Moreover, we demonstrated that 1 μmol/L Res mitigated Cd-induced alterations of oocyte cytoplasmic maturation by reducing reactive oxygen species (ROS) accumulation, preventing mt dysfunction, maintaining the correct meiotic spindle and cortical F-actin assembly and the normal cortical granule distribution as well as up-regulating SIRT1, SOD1 and GPX1 genes.

Conclusions

Taken together, our findings highlighted the beneficial influence exerted by Res in preventing Cd-induced disturbance of nuclear and cytoplasmic maturation and subsequent fertilization in ovine oocytes. Res treatment may help to establish defence strategies counteracting Cd-induced toxicity on the female gamete.

Aflatoxin B1 exposure disrupts organelle distribution in mouse oocytes

Aflatoxin B1 (AFB1) is a secondary metabolite produced by the fungus Aspergillus, which is ubiquitous in moldy grain products. Aflatoxin B1 has been reported to possess hepatotoxicity, renal toxicity, and reproductive toxicity. Previous studies have shown that AFB1 is toxic to mammalian oocytes. However, the potential toxicity of AFB1 on the organelles of mouse oocytes is unknown. In this study, we found that exposure to AFB1 significantly reduced mouse oocyte development capacity. Further analysis showed that the endoplasmic reticulum (ER) failed to accumulate around the spindle, and scattered in the cytoplasm under AFB1 exposure. Similar to the ER, the Golgi apparatus showed a uniform localization pattern following AFB1 treatment. In addition, we found that AFB1 exposure caused the condensation of lysosomes in the cytoplasm, presenting as a clustered or spindle peripheral-localization pattern, which indicated that protein modification, transport, and degradation were affected. Mitochondrial distribution was also altered by AFB1 treatment. In summary, our study showed that AFB1 exposure had toxic effects on the distribution of mouse oocyte organelles, which further led to a decline in oocyte quality.

Cyanidin-3-O-glucoside ameliorates cadmium induced uterine epithelium proliferation in mice

Cadmium (Cd) is an environmental pollutant and endocrine disrupter, abundantly present in water, food, and soil. Accumulation of Cd in the body can negatively affect female reproduction; especially the uterus is exceptionally sensitive to the toxic actions of Cd. The anthocyanin cyanidin-3-O-glucoside (C3G) is a naturally occurring phenolic compound in fruits and plants that can antagonize the toxic effects of Cd. This capacity makes C3G a possible candidate to prevent Cd-induced female infertility. The present study aimed to investigate: 1) whether C3G intake could prevent Cd-induced female reproductive toxicity, and 2) the underlying mechanisms responsible for this protective effect. The results of our study indicated that Cd exposure did not affect ovarian function, but induced hypertrophy of the uterine endometrium. Oral intake of C3G markedly reduced the effects of Cd exposure on the thickness of the uterine epithelium cells. Transcriptomic analysis of the endometrium revealed that C3G intake had anti-estrogenic effects, attenuating Cd-induced endometrial epithelial cell proliferation by inhibiting estrogen-responsive genes, enhancing epithelial progesterone receptor expression, and regulating Klf4 expression. The current findings implicate that C3G has the potential to be used as a dietary supplement based on its capacity to intervene in Cd-induced female reproductive toxicity.

CORO1A regulates lipoprotein uptake in Leydig cells exposed to cadmium

Cadmium (Cd) is one of the most common environmental pollutants, which has a long biological half-life. Maternal Cd-exposure in the natural environment causes steroidogenesis defects resulting in spermatogenesis disorder in male offspring. For better understanding its underlying mechanism, we have employed iTRAQ to screen the differentially expressed protein and found that the expression of CORO1A and Cofilin 1 was up-regulated approximately 2 fold in Leydig cells of maternal Cd-exposure offspring. As the major source of steroid hormone, cholesterol is transported to cells via receptor-mediated endocytosis which relies on the remodel of cytoskeleton, then stores in lipid droplets (LDs). However, few studies have focused on the role of cytoskeleton in abnormal steroidogenesis. This study was performed to explore the role of CORO1A in androgen deficiency caused by Cd exposure and its involvement of low-density lipoprotein (LDL) uptake and effects on LDs. We found that Cd resulted in the up-regulation of CORO1A and Cofilin 1, and down-regulation of Profilin 1 in the testis of male offspring with maternal exposure. The structure of filamentous actin was broken, disordered and even crumpled up in Cd-treated R2C cells. F-actin disassembly led to a low uptake of LDL with a reduced number of LDs, followed by decreased total cholesterol and low progesterone production. When CORO1A was silenced, the expression of Cofilin 1 was down-regulated and Profilin 1 was up-regulated in Cd-treated R2C cells. The filamentous actin was rescued and the integrated cytoskeleton prompted LDL uptake, which resulted in the increased total cholesterol and high progesterone production. These findings highlight the crucial role of CORO1A as a cytoskeleton regulatory protein in steroidogenesis, which may help to better understand Cd-induced steroid hormone deficiency in children.

Citrinin impairs pig oocyte maturation by inducing oxidative stress and apoptosis

Citrinin (CTN) is a polyketide mycotoxin produced by several strains of Penicillium, Monascus, and Aspergillus. While CTN poses various toxic effects on the female reproductive system in animals, its direct effects on germ cell development are unclear. This study aimed to evaluate the effects of increasing concentrations of CTN (0,20,40,80,100 μM) on porcine oocyte in vitro maturation. Our results indicate that CTN supplementation inhibited polar body extrusion in a dose-dependent manner. Actin and spindle assembly were also disrupted after treatment, indicating that CTN affects the cytoskeleton of porcine oocytes. Oxidative stress and apoptosis were observed under CTN treatment to explore the cause of meiotic maturation failure in porcine oocytes. The results showed that reactive oxygen species levels, cathepsin B activity, and caspase-3 activity were increased in the treated group, indicating that CTN induced oxidative stress and apoptosis. In conclusion, CTN exposure could reduce porcine oocyte maturation by affecting cytoskeletal dynamics, oxidative stress, and apoptosis.

Association between serum folate levels and blood concentrations of cadmium and lead in US adults

BACKGROUND

Folate may be involved in the detoxification of heavy metals. This has been demonstrated in animal studies, in in vivo and in vitro studies, and clinical evaluations. However, knowledge regarding the associations between serum folate and blood concentrations of cadmium and lead is limited.

OBJECTIVE

We aimed to investigate the relationship between serum folate levels and blood concentrations of cadmium and lead in US adults.

METHODS

Data on 15,501 adults were obtained from the 1999-2006 National Health and Nutrition Examination Survey (NHANES) and used for the analysis. Information on serum folate concentrations and blood levels of lead and cadmium was derived from laboratory measurements in the NHANES. Multivariable linear regression was used to examine the relationship between serum folate levels and blood concentrations of cadmium and lead in US adults, controlling for confounders.

RESULTS

The serum folate concentration was negatively correlated with blood levels of cadmium and lead (P-trends <0.01). When stratified by sex (male and female) and estimated glomerular filtration rate (eGFR ≤60 and >60 mL/min/1.73 m²), the association between serum folate concentrations and blood levels of cadmium and lead was found to be more stable in adults with eGFR > 60 mL/min/1.73 m², both in males and females.

SIGNIFICANCE

These findings warrant future studies to explore the mechanisms responsible for the beneficial role of folate in regulating cadmium and lead concentrations in the blood.

Toxic effects of methomyl on mouse oocytes and its possible mechanisms

Methomyl is a broad-spectrum carbamate insecticide that has a variety of toxic effects on humans and animals. However, there have been no studies on the toxicity of methomyl in female mammalian oocytes. This study investigated the toxic effects of environmental oestrogen methomyl exposure on mouse oocyte maturation and its possible mechanisms. Our results indicated that methomyl exposure inhibited polar body extrusion in mouse oocytes. Compared with that in the control group, in the methomyl treatment group, superoxide anion free radicals in oocytes were significantly increased. In addition, the mitochondrial membrane potential of metaphase II stage oocytes in the methomyl treatment group was significantly decreased, resulting in reduced mouse oocyte quality. After 8.5 h of exposure to methomyl, metaphase I stage mouse oocytes displayed an abnormal spindle morphology. mRNA expression of the pro-apoptotic genes Bax and Caspase-3 in methomyl-treated oocytes increased, which confirmed the apoptosis. Collectively, our results indicated that mouse oocyte maturation is defective after methomyl treatment at least through disruption of spindle morphology, mitochondrial function and by induction of oxidative stress.

Cadmium disturbs epigenetic modification and induces DNA damage in mouse preimplantation embryos

Cadmium is an environmental pollutant that has extensive deleterious effects on the reproductive system. However, the mechanisms underlying the effects of cadmium on preimplantation embryos are unclear. Here, we used a mouse model to investigate the effects of maternal cadmium (32 mg/l) exposure in drinking water for 2 days on early embryonic development, and studied the mechanisms associated with epigenetic modifications and DNA damage induced by oxidative stress. We observed that maternal cadmium exposure impaired preimplantation embryo development by inducing embryo death, fragmentation, or developmental blockade. After cadmium exposure, the most survived embryos were at the 8-cell stage, which were used for all measurements. Histone acetylation, not methylation, was disturbed by increasing histone deacetylase 1 (HDAC1) levels after cadmium exposure. Cadmium also disrupted DNA methylation of H19; however genomic DNA methylation can be normally reprogrammed in embryos. Furthermore, cadmium increased reactive oxygen species (ROS) levels and DNA damage, and partly inhibited gene expression related to DNA repair. The distribution and activity of mitochondria was increased; therefore, embryos maintain intracellular homeostasis for survival. Collectively, our findings revealed that maternal cadmium exposure impairs preimplantation embryo development by disturbing the epigenetic modification and inducing DNA damage.

Reducing the reproductive toxicity activity of Lactiplantibacillus plantarum: a review of mechanisms and prospects

Food pollution can cause a variety of negative effects on human health, especially reproductive toxicity. Common food contaminants include biological contaminants, chemical contaminants, and physical contaminants, among which endocrine disruptors, pesticides, and heavy metals have the greatest reproductive toxicity in chemical contaminants. Humans mainly solve food pollution through three aspects: decreasing the pollution of food raw materials, lowering the pollution in food processing, and reducing the harm to the human body after food pollutants enter the human body. With more and more research on probiotics, not only beneficial effects, but also the ability to reduce the toxicity of food contaminants is found. Thus, microbial treatment has been proved to be a more effective way to deal with food pollution. Recent research shows that several strains of Lactiplantibacillus plantarum can adsorb or degrade some chemical pollutants and relieve inflammation and oxidative stress caused by them. This review summarized the research to explore the possible role of Lactiplantibacillus plantarum in protecting human reproductive ability and maintaining food safety.

Epimutational effects of electronic cigarettes

Electronic cigarettes (e-cigarettes), since they do not require tobacco combustion, have traditionally been considered less harmful than conventional cigarettes (c-cigarettes). In recent years, however, researchers have found many toxic compounds in the aerosols of e-cigarettes, and numerous studies have shown that e-cigarettes can adversely affect the human epigenome. In this review, we provide an update on recent findings regarding epigenetic outcomes of e-cigarette aerosols. Moreover, we discussed the effects of several typical e-cigarette ingredients (nicotine, tobacco-specific nitrosamines, volatile organic compounds, carbonyl compounds, and toxic metals) on DNA methylation, histone modifications, and noncoding RNA expression. These epigenetic effects could explain some of the diseases caused by e-cigarettes. It also reminds the public that like c-cigarettes, inhaling e-cigarette aerosols could also be accompanied with potential epigenotoxicity on the human body.

Toxicant effects on mammalian oocyte mitochondria†

Oocyte mitochondria are unique organelles that establish a founder population in primordial germ cells (PGCs). As the oocyte matures in the postnatal mammalian ovary during folliculogenesis it increases exponentially in volume, and the oocyte mitochondria population proliferates to about 100 000 mitochondria per healthy, mature murine oocyte. The health of the mature oocyte and subsequent embryo is highly dependent on the oocyte mitochondria. Mitochondria are especially sensitive to toxic insults, as they are a major source of reactive oxygen species (ROS), they contain their own DNA (mtDNA) that is unprotected by histone proteins, they contain the electron transport chain that uses electron donors, including oxygen, to generate ATP, and they are important sensors for overall cellular stress. Here we review the effects that toxic insults including chemotherapeutics, toxic metals, plasticizers, pesticides, polycyclic aromatic hydrocarbons (PAHs), and ionizing radiation can have on oocyte mitochondria. This is very clearly a burgeoning field, as our understanding of oocyte mitochondria and metabolism is still relatively new, and we contend much more research is needed to understand the detrimental impacts of exposure to toxicants on oocyte mitochondria. Developing this field further can benefit our understanding of assisted reproductive technologies and the developmental origins of health and disease (DOHaD).

Parental exposure to cadmium chloride causes developmental toxicity and thyroid endocrine disruption in zebrafish offspring

Cadmium is a common heavy metal pollutant. Previous studies have found that long-term cadmium exposure can cause damage to multiple organs/systems in humans and experimental animals; however, there are few studies that elucidate its effects on offspring development, discuss whether it can be transmitted to offspring from the parent, and debate whether it affects the functional development of the thyroid hormone system in offsprings. In this study, sexually mature zebrafish were exposed to different concentrations of cadmium chloride (0.01 μmol/L, 0.1 μmol/L, and 1 μmol/L) to study reproductive toxicity. It was found that parental zebrafish exposed to 1 μmol/L of cadmium chloride produced offsprings with different degrees of malformation. At 5 days post-fertilization (dpf), the levels of 3,5,3'-triiododenosine (T3) and thyroxine (T4) in the zebrafish were decreased. At 10 dpf, the T4 and T3 levels in the zebrafish of the offspring were significantly reduced. At the same time, the expression of thyroid receptor (trα and trβ) genes in five dpf larvae was significantly up-regulated in the 1 μmol/L treatment group relative to the control group. The mRNAs of thyroid hormone synthesis and metabolism-related genes (tshβ, dio1, dio2, ugt1ab, and ttr) were significantly up-regulated in the 0.1 μmol/L and 1 μmol/L treatment groups. This study demonstrates that parental cadmium chloride exposure produces reproductive toxicity in zebrafish and that the effects can be transferred from the parent to the offspring, resulting in developmental toxicity in the thyroid endocrine system.

Chronic cadmium exposure causes oocyte meiotic arrest by disrupting spindle assembly checkpoint and maturation promoting factor

Cadmium (Cd) is a bioaccumulative heavy metal element with potential toxicity on the female reproductive system, but the exact molecular mechanisms have not yet been clearly defined. In this study, female mice were exposed to 0.5 mg/kg/day of CdCl₂ for 60 consecutive days. We found that chronic Cd exposure significantly decreased the fecundity of female mice by affecting oocyte meiotic progression as indicated by disrupted spindle assembly, chromosome alignment and kinetochore-microtubule attachments, consequently resulting in aneuploid oocytes. Further studies showed that the periodic fluctuations of MPF activity and cyclin B1 expression were disturbed in Cd-exposed oocytes probably by affecting the spindle assembly checkpoint protein Bub3. In addition, Cd exposure induced oxidative stress as indicated by an increased level of reactive oxygen species and apoptosis in oocytes, leading to oocyte quality deterioration. Taken together, these data suggest that Cd exposure causes disrupted molecular events of meiotic progression and deterioration of oocyte quality via oxidative stress, leading to decrease of female fertility.

Mul-tiomics analysis of cadmium stress on the ovarian function of the wolf spider Pardosa pseudoannulata

Cadmium (Cd) pollution is widespread in paddy filed soil in China. In this study, the toxicity of Cd with regard to the female reproductive system of paddy spider Pardosa pseudoannulata was investigated by means of multi-omics analyses (transcriptome, proteome, and miRNAs). Decreased activities of detoxifying enzymes including peroxidase (POD), Glutathione S-transferases (GST), and superoxide dismutase were detected in the ovary of P. pseudoannulata. Of these, GST and POD were consistently down-regulated at the transcriptional and translational levels. Vitellogenin content and fecundity of the spider were also reduced by Cd burden. Five vitellogenin encodes genes were down-regulated while only vitellogenin-6 protein was up-regulated. But protein lipovitellin-1, the main composition of vitellin, was down-regulated. In addition, the correlation between the mitogen-activated protein kinase (MAPK) signaling pathway and Cd stress was identified. A down-regulated gene that encoding connector of kinase to AP-1 in the MAPK signaling pathway was regulated by the up-regulated miRNA (miRNA id: miRNA dan-miR- 318>der-miR-318>dgr-miR-318>dme-miR-318-3p > dmo-miR-318>dpe-miR-318>dps-miR-318>dse-miR-318>dsi-miR-318>dvi-miR-318>dwi-miR-318>dya-miR-318). In conclusion, Cd stress possesses distinct female reproductive toxicity on P. pseudoannulata through impairing antioxidant system and synthesis of vitellin.

Embryonic cadmium exposure of male rats alters reproductive functions at adulthood, but without overt alterations in developmental and behavioral outcomes and metabolism

The effects of exposure of pregnant rats to cadmium (Cd) on the developmental and behavioral outcomes, reproductive functions, and metabolism of their male progeny were evaluated. Rats (Wistar) were injected intraperitoneally with either 0.5 or 5.0 µg Cd/kg body weight from day 12 to day 19 of pregnancy. The male offspring were evaluated for their developmental outcomes and behavioral changes. All developmental and behavioral parameters assessed were comparable among the different groups. All male pups were allowed to develop until 100 days of age and evaluated for reproductive end points. The results revealed that although the body weights and relative weights of liver, brain, kidney, testis, and epididymis were not altered, reproductive parameters, including daily sperm production, epididymal sperm numbers, and concentrations of motile, viable, and hypo-osmotic tail-swelled sperm declined significantly in rats exposed to 0.5 and 5.0 µg Cd during embryonic development. In addition, plasma testosterone levels and activity levels of testicular steroidogenic enzymes also decreased in these rats. In the fertility study, although each male in the 0.5, 5.0 µg, and control groups produced a copulatory plug and impregnated a female, the mean number of implantations and live fetuses was reduced significantly in females mated with rats exposed to 0.5 and 5.0 µg Cd during the prenatal period. The general metabolism of the animals exposed to Cd during embryonic development was comparable with the controls as evidenced by no significant changes in the activity levels of succinate dehydrogenase, lactate dehydrogenase, glucose-6-phosphate dehydrogenase, glutamate dehydrogenase, aspartate aminotransaminase, and alanine aminotransaminases in the liver, kidney, and testis. The results thus suggest that maternal Cd exposure during embryonic development markedly affected the spermatogenesis, steroidogenesis, and fertility potential, but without alterations in the development, behavior, and metabolism.

Melatonin ameliorates ochratoxin A-induced oxidative stress and apoptosis in porcine oocytes

Melatonin is a hormone which is generated from pineal gland, and it is responsible for the regulation of wake-sleep cycle. Melatonin is a well-known antioxidant and free radical scavenger to protect against multiple type of tissue damage. While ochratoxin A (OTA) is a mycotoxin found widely in contaminated food and foodstuffs, which causes nephrotoxicity, hepatotoxicity, immunotoxicity, and reproductive damage in humans and animals. In present study we report the toxicity of OTA on porcine oocyte quality and the protective effects of melatonin on OTA-exposed oocytes. Using transcriptome analysis our results show that OTA exposure alters the expression of multiple genes in oocytes, indicating its effect on oocyte maturation. The cellular changes following OTA treatment are examined, and the results show that OTA adversely affects oocyte polar body extrusion, which is confirmed by the delay of Cdc2-mediated cell cycle progression. OTA exposure also disrupts meiotic spindle formation, which is confirmed by altered phosphorylated MAPK expression. RNA-seq screening and further fluorescence staining results show that OTA induces aberrant mitochondria distribution and oxidative phosphorylation defects, which then causes oxidative stress, followed by early apoptosis and autophagy. Treatment with melatonin significantly ameliorates oxidative stress and apoptosis, which further protects cell cycle and spindle formation in OTA-exposed oocytes. Collectively, these results show the protective effects of melatonin against defects induced by OTA during porcine meiotic oocyte maturation.

The toxic effects and possible mechanisms of glyphosate on mouse oocytes

Glyphosate is a high-efficiency, low-toxicity, broad-spectrum herbicide. The residues of glyphosate-based herbicides are frequent pollutants in the environment. However, the effects of glyphosate on oocyte maturation, as well as its possible mechanisms, remain unclear. The present study revealed that mouse oocytes had reduced rates of germinal vesicle breakdown (GVBD) and first polar body extrusion (PBE) after treatment with 500 μM glyphosate. Reactive oxygen species (ROS) were found in mouse oocytes exposed to glyphosate, as shown by changes in the mRNA expression of related antioxidant enzyme genes (cat, sod2, gpx). After 14 h of exposure to glyphosate, metaphase II (MII) mouse oocytes displayed an abnormal spindle morphology and DNA double-strand breaks (DNA-DSBs). Simultaneously, mitochondria showed an aggregated distribution and decreased membrane potential in mouse oocytes exposed to glyphosate. The protein expression levels of apoptosis factors (Bax, Bcl-2) and the mRNA expression levels of apoptosis-related genes (bax, bcl-2, caspase3) were measured by Western blot and qRT-PCR, respectively. Meanwhile, the expression levels of autophagy-related genes (lc3, atg14, mtor) and proteins (LC3, Atg12) were significantly decreased in the glyphosate treatment group compared with the control group. Collectively, our results indicated that glyphosate exposure could interfere with mouse oocyte maturation by generating oxidative stress and early apoptosis.

Glutathione alleviates the cadmium exposure-caused porcine oocyte meiotic defects via eliminating the excessive ROS

Heavy metal cadmium (Cd) is a widespread environmental contaminant with a potential toxicity that might adversely influence the health of experimental animals and humans. It has been known that Cd might accumulate in vertebrates for many years and thus leads to the hepatic and renal toxicity. Additionally, Cd concentration in the ovary increases with age and is highly related to the reproductive hazard. However, the underlying mechanisms regarding how Cd affects the female reproductive system especially the oocyte quality have not yet fully defined. Here, we reported that Cd exposure led to the defective nuclear maturation of oocytes via the impairment of cytoskeleton assembly, displaying the aberrant spindle organization, chromosome alignment and actin polymerization. In the meantime, Cd exposure caused the impaired cytoplasmic maturation by showing the disrupted dynamics of mitochondrial integrity and cortical granules, and thereby resulting in the compromised sperm binding ability and fertilization capacity of oocytes. More importantly, we found that glutathione (GSH) supplementation was able to recover the meiotic failure induced by Cd exposure through suppressing the excessive ROS level, DNA damage accumulation and apoptotic incidence. Taken together, our findings demonstrate that Cd exposure has the adverse effects on the oocyte meiotic maturation as well as subsequent fertilization, and provide a potential effective strategy to improve the quality of Cd-exposed oocytes.

Ochratoxin A exposure causes meiotic failure and oocyte deterioration in mice

Ochratoxin A (OTA) is a mycotoxin produced by fungi and occurs naturally in various foodstuffs and some animal-derived products. This mycotoxin can cause deleterious effects on kidney, liver, central nervous, and immune system. However, potential mechanisms regarding how OTA disrupts the mammalian oocyte quality have not been clearly defined. In this study, we proved that OTA weakened oocyte quality by impairing oocyte meiotic maturation. We found that female mice treated with 1 mg/kg body weight OTA by intraperitoneal (IP) injection for 7 days displayed ovarian dysfunction and decreased offspring number. We also found that OTA treatment at 7.5 μM for 16 h decreased the rate of first polar body extrusion by disrupting spindle and chromosome alignment. In addition, OTA caused oxidative stress by inducing the accumulation of reactive oxygen species and consumption of antioxidants during meiosis, consequently resulting in oocytes apoptosis. Mitochondrial damage and insufficient energy supply were also observed in OTA-pretreated oocytes, which led to the meiotic failure of oocyte. Moreover, the epigenetic modifications were also affected, showing with altered 5 mC, 5hmC, H3K9ac, and H3K9me3 levels in mice oocytes. In summary, these results showed that OTA could decrease oocyte maturation and fertility by inducing oxidative stress and epigenetic changes.

Deltamethrin exposure induces oxidative stress and affects meiotic maturation in mouse oocyte

Pyrethroid insecticides are commonly used as insecticides and considered to be less toxic to mammals, but may still impair the reproduction of animals and humans. The aim of this research was to evaluate the tendency of deltamethrin induced oxidative stress and its effects on meiosis, apoptosis and autophagy of mouse oocytes in vitro maturation after deltamethrin exposure. Especially, the maturation rate of oocytes decreased significantly after 14 h exposure of deltamethrin in concentration-dependent manners, which was manifested as abnormal spindle morphology and DNA double strand breaks. Oxidative stress was found in mouse oocytes exposed to deltamethrin, as shown by changes in the expression of CAT and SOD2. Our results also show that deltamethrin affects the quality of oocytes by causing abnormal mitochondrial distribution and by decreasing mitochondrial membrane potential. The apoptosis of oocyte regulated by the expression of Bax and Bcl-2 protein was obviously affected by deltamethrin. Compared with the control group, the expression of key regulatory factors in the autophagy pathway, LC3, Atg12, Atg14, and Beclin, increased in the experimental group. In summary, these results revealed that deltamethrin might inhibit the maturation of mouse oocytes and adversely affect the survival of oocytes.

Impairment of learning and memory of mice offspring at puberty, young adulthood, and adulthood by low-dose Cd exposure during pregnancy and lactation via GABAAR α5 and δ subunits

Cadmium (Cd) is a pervasive carcinogen and environmental endocrine disruptor. We studied the changes in learning and memory of offspring mice, whose mothers were exposed to 10 mg Cd/L via the drinking water during pregnancy and lactation period, as well as the changes of testosterone and estrogen levels, serum Cd levels, the histopathological changes and the changes in the mRNA and protein levels of different subunits of γ-aminobutyric acid receptor subtype A subunits (G_ABA_ARs) in the hippocampus at the prepuberty, puberty, young adult, and adult stages. At birth, Cd had no obvious effect on mice offspring as statistically accessed based on their body weight, body length, and tail length (all p > 0.05). After grouped, the serum Cd levels increased in the three exposed groups more than in the normal control group at stages (all p < 0.05). Only serum estradiol of female offspring at age 7 weeks was significantly decreased compared with other groups (all p < 0.05). Histopathological results showed that the arrangement of the cells in hippocampal CA1 area of mice offspring was significantly sparse in the exposed groups compared with the control group. At 5 and 7 weeks, two Cd-exposed groups showed prolonged escape latency and exploring time for the platform compared with the normal group in the Morris water maze (all p < 0.05). Only increased protein expression of GABA_ARα5 was found in the Cd group at these two ages. At age 12 weeks, similar impaired learning and memory of female mice, and decreased protein expression of GABA_ARδ was found in Cd-exposed groups. Collectively, low-dose Cd had no effect on the growth of mice offspring but affected their learning and memory, especially female offspring, at puberty, young adulthood, and adulthood through changed structure in the hippocampal CA1 area and protein expression of GABA_ARα5 and GABA_ARδ.