Isobutylparaben Negatively Affects Porcine Oocyte Maturation Through Increasing Oxidative Stress and Cytoskeletal Abnormalities

Propylparaben exposure impairs G2/M and metaphase-anaphase transition during mouse oocyte maturation

Propylparaben (PrPB) is a known endocrine disrupting chemicals that is widely applied as preservative in pharmaceuticals, food and cosmetics. PrPB has been detected in human urine samples and human serum and has been proven to cause functional decline in reproduction. However, the direct effects of PrPB on mammalian oocyte are still unknown. Here, we demonstrationed that exposure to PrPB disturbed mouse oocyte maturation in vitro, causing meiotic resumption arrest and first polar body extrusion failure. Our results indicated that 600 μM PrPB reduced the rate of oocyte germinal vesicle breakdown (GVBD). Further research revealed that PrPB caused mitochondrial dysfunction and oxidative stress, which led to oocyte DNA damage. This damage further disturbed the activity of the maturation promoting factor (MPF) complex Cyclin B1/ Cyclin-dependent kinase 1 (CDK1) and induced G2/M arrest. Subsequent experiments revealed that PrPB exposure can lead to spindle morphology disorder and chromosome misalignment due to unstable microtubules. In addition, PrPB adversely affected the attachment between microtubules and kinetochore, resulting in persistent activation of BUB3 amd BubR1, which are two spindle-assembly checkpoint (SAC) protein. Taken together, our studies indicated that PrPB damaged mouse oocyte maturation via disrupting MPF related G2/M transition and SAC depended metaphase-anaphase transition.

Isorhamnetin Improves Oocyte Maturation by Activating the Pi3k/Akt Signaling Pathway

SCOPE

Isorhamnetin is a natural flavonoid with various pharmacological activities, which can be widely and continuously ingested by humans and animals through their daily diet. The aim of this study is to explore the benefits and molecular mechanisms of isorhamnetin on oocyte maturation.

METHODS AND RESULTS

Oocytes are incubated with isorhamnetin (5, 10, 20, and 30 µM) for 44 h. Isorhamnetin (10 µM) increases the polar body extrusion rate of oocytes. Furthermore, isorhamnetin alleviates oxidative stress by inhibiting reactive oxygen species levels and stimulating SOD2 protein expression. The changes in intracellular mitochondrial autophagy and apoptosis-related proteins (Bcl-2, Bax/Bcl-2, and C-Casp3) indicate that isorhamnetin inhibits oocyte apoptosis. Isorhamnetin inhibits endoplasmic reticulum stress by reducing the protein expression of CHOP and GRP78 and improving the normal distribution rate of endoplasmic reticulum. Mechanistic studies show that isorhamnetin activates the PI3K/Akt signaling pathway.

CONCLUSION

Isorhamnetin promotes oocyte maturation by inhibiting oxidative stress, mitochondrial dysregulation, apoptosis, and endoplasmic reticulum stress, which have important potential for improving oocyte quality and treating female infertility.

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.

Rhus tripartite methanolic extract alleviates propylparaben-induced reproductive toxicity via anti-inflammatory, antioxidant, 5-α reductase in male rats

Evidence showed that herbal medicine could be beneficial for protection against diseases that may be exist in consequence of exposure to environmental toxicants. Propylparaben (PrP) is used as preservative in food, pharmaceuticals, and cosmetics. It is classified as one of endocrine disruptive chemicals (EDCs). This study evaluated the protective effect of Rhus tripartita methanolic extract (RTME) against reproductive toxicity induced by PrP in male rats. A total of 60 Wister albino rats were divided into four groups (15 rats for each group). Group I (control): rats received the vehicle (DMSO), group II: normal rats received RTME (10 mg/kg/day), group III: rats received PrP (10 mg/kg/day), and group IV: rats received PrP (10 mg/kg/day) and RTME (10 mg/kg/day) for 4 weeks. At the end of experiment, levels of testosterone, dihydrotestosterone (DHT), and 5α-reductase were analyzed in sera. Data obtained showed a significant reduction in the levels of testosterone, dihydrotestosterone (DHT), and 5α- reductase in rats given PrP versus control (p < 0.001) and RTME treatment improved these parameters but not returned to normal. Data obtained showed a significant elevation in levels of IL-6 and TNF-α in the testis of rats given PrP versus control (p < 0.001), these inflammatory mediators were significant reduced in rats treated with RTME compared with untreated rats (p < 0.001). There was a positive correlation between level of DHT and antioxidant enzymes activities (r = 0.56). A significant elevation in the levels of MDA with reduction in the activities of GST, GSPx, SOD, and catalase (p < 0.001) in rat testicular tissues of PrP group versus control (p < 0.001) was found. Treatment with RTME significantly reduced the levels of MDA and enhanced activities of GST, GSPx, SOD, and catalase (p < 0.001) compared to untreated group (p < 0.001). In conclusion, the active ingredient components of RTME abrogate the toxicity of PrP by exhibiting antioxidative and anti-inflammatory effects, enhancing 5-α reductase with improved hormonal status against PrP- induced testicular damage. Toxicity of propylparaben, and effect of Rhus tripartita methanolic extract.

Paraben exposure and couple fecundity: a preconception cohort study

STUDY QUESTION

Is pre-conception exposure to parabens associated with fecundity in couples of childbearing age?

SUMMARY ANSWER

Paraben exposure in female partners was associated with reduced couple fecundity and anti-Müllerian hormone (AMH) might be one of the possible mediators.

WHAT IS KNOWN ALREADY

The reproductive toxicity of parabens, a class of widely used preservatives, has been suggested but evidence regarding their effects on couple fecundity is scarce.

STUDY DESIGN, SIZE, DURATION

In this couple-based prospective cohort study, a total of 884 pre-conception couples who participated in the Shanghai Birth Cohort between 2013 and 2015 were included.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Concentrations of six parabens were measured in urine samples collected from couples. Malondialdehyde, C-reactive protein, and AMH were assessed in female partners. The outcomes included couple fecundability (time-to-pregnancy, TTP) and infertility (TTP > 12 menstrual cycles). Partner-specific and couple-based models were applied to estimate the associations. The joint effect of paraben mixture on couple fecundity was estimated by quantile-based g-computation (q-gcomp). Mediation analysis was used to assess the mediating roles of oxidative stress, inflammation and ovarian reserve.

MAIN RESULTS AND THE ROLE OF CHANCE

A total of 525 couples (59.4%) conceived spontaneously. In the partner-specific model, propyl paraben (PrP), butyl paraben (BuP), and heptyl paraben (HeP) in female partners were associated with reduced fecundability (fecundability odds ratio (95% CI): 0.96 (0.94-0.98) for PrP; 0.90 (0.87-0.94) for BuP; 0.42 (0.28-0.65) for HeP) and increased risk of infertility (rate ratio (95% CI): 1.06 (1.03-1.10) for PrP; 1.14 (1.08-1.21) for BuP; 1.89 (1.26-2.83) for HeP). Similar associations were observed in the couple-based model. AMH played a significant mediation role in the association (average causal mediation effect (95% CI): 0.001 (0.0001-0.003)). Paraben exposure in male partners was not associated with couple fecundity. The joint effect of paraben mixture on couple fecundity was non-significant.

LIMITATIONS, REASONS FOR CAUTION

Self-reported pregnancy and single urine sample may lead to misclassification. The mediation analysis is limited in that levels of sex hormones were not measured. The inclusion of women with irregular menstrual cycles might affect the results. It is possible that the observed association was due to reverse causation.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first study to assess the effects of paraben exposure on couple fecundity in Asians. Given the widespread exposure to parabens in couples of childbearing age, the present findings may have important public health implications.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported in part by the National Natural Science Foundation of China (41991314), the Shanghai Science and Technology Development Foundation (22YF1426700), the Science and Technology Commission of Shanghai Municipality (21410713500), and the Shanghai Municipal Health Commission (2020CXJQ01). All authors declare no conflict of interest.

TRIAL REGISTRATION NUMBER

N/A.

Chronic exposure to propylparaben at the humanly relevant dose triggers ovarian aging in adult mice

Parabens, a type of endocrine-disrupting chemicals, are widely used as antibacterial preservatives in food and cosmetics in daily life. Paraben exposure has gained particular attention in the past decades, owing to its harmful effects on reproductive function. Whether low-dose paraben exposure may cause ovarian damage has been ignored recently. Here, we investigated the effects of chronic low-dose propylparaben (PrPB) exposure on ovarian function. Female C57BL/6J mice were exposed to PrPB at a humanly relevant dose for 8 months. Our results showed that chronic exposure to PrPB at a humanly relevant dose significantly altered the estrus cycle, hormone levels, and ovarian reserve, accelerating ovarian aging in adult mice. These effects are accompanied by oxidative stress enrichment, leading to steroidogenesis dysfunction and acceleration of primordial follicle recruitment. Notably, melatonin supplementation has been shown to protect against PrPB-induced steroidogenesis dysfunction in granulosa cells. Here, we report that daily chronic PrPB exposure may contribute to ovarian aging by altering oxidative stress-mediated JNK and PI3K-AKT signaling regulation, and that melatonin may serve as a pharmaceutical candidate for PrPB-associated ovarian dysfunction.

Epigenetic Regulation in Exposome-Induced Tumorigenesis: Emerging Roles of ncRNAs

Environmental factors, including pollutants and lifestyle, constitute a significant role in severe, chronic pathologies with an essential societal, economic burden. The measurement of all environmental exposures and assessing their correlation with effects on individual health is defined as the exposome, which interacts with our unique characteristics such as genetics, physiology, and epigenetics. Epigenetics investigates modifications in the expression of genes that do not depend on the underlying DNA sequence. Some studies have confirmed that environmental factors may promote disease in individuals or subsequent progeny through epigenetic alterations. Variations in the epigenetic machinery cause a spectrum of different disorders since these mechanisms are more sensitive to the environment than the genome, due to the inherent reversible nature of the epigenetic landscape. Several epigenetic mechanisms, including modifications in DNA (e.g., methylation), histones, and noncoding RNAs can change genome expression under the exogenous influence. Notably, the role of long noncoding RNAs in epigenetic processes has not been well explored in the context of exposome-induced tumorigenesis. In the present review, our scope is to provide relevant evidence indicating that epigenetic alterations mediate those detrimental effects caused by exposure to environmental toxicants, focusing mainly on a multi-step regulation by diverse noncoding RNAs subtypes.

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.

Effect of exogenous glutathione supplementation on the in vitro developmental competence of ovine oocytes

The beneficial effect of glutathione (GSH) on the in vitro maturation (IVM) of bovine/porcine oocytes has been confirmed; however, the antioxidant effect of exogenous GSH supplementation on the IVM of ovine oocytes has not been determined. In this study, ovine cumulus oocyte complexes (COCs) were classified into three groups according to the layer number of cumulus cells (the Grade A group has more than five layers, the Grade B group has three to four layers and the Grade C group has less than three layers). After in vitro culture of COCs in the presence of exogenous GSH, the meiotic competence of ovine oocytes was assessed by analyzing nuclear maturation to metaphase II (MII) stage, cortical granules (CGs) dynamics, astacin like metalloendopeptidase (ASTL) distribution, histone methylation pattern, reactive oxygen species (ROS) production, mitochondrial activities and genes expression. After in vitro fertilization (IVF), assessments of embryonic development were conducted to confirm the effects of exogenous GSH supplementation. The results showed that exogenous GSH not only enhanced the maturation rates of the Grade B and Grade C groups but also promoted CGs dynamics and ASTL distribution of the Grade A, B and C groups (p < 0.05). Exogenous GSH increased the mitochondrial activities of the Grade A, B and C groups and decreased the ROS production levels of oocytes (p < 0.05), regardless of the layer number of cumulus cells. Moreover, exogenous GSH promoted the expression levels of genes related with oocyte maturation, antioxidant activity and antiapoptotic effects in the Grade B and Grade C groups (p < 0.05). The expression levels of H3K4me3 and H3K9me3 in the Grade B and Grade C groups were promoted after exogenous GSH supplementation (p < 0.05), consistent with the expression levels of genes related with histone methylation (p < 0.05). In addition, exogenous GSH strongly promoted the embryonic developmental competence of Grade B and Grade C groups (p < 0.05). Taken together, our findings provide foundational evidence for the free radical scavenging potential of exogenous GSH in the in vitro developmental competence of ovine oocytes, especially oocytes from COCs lacking cumulus cells. These findings, which demonstrated the potential for improving the quality of ovine oocytes during IVM, will contribute to researches on GSH applications and the efficiency of assisted reproductive technology for ovine breeding.

Scanning Ion Conductance Microscopy Study Reveals the Disruption of the Integrity of the Human Cell Membrane Structure by Oxidative DNA Damage

Oxidative stress can damage organs, tissues, and cells through reactive oxygen species (ROS) by oxidizing DNA, proteins, and lipids, thereby resulting in diseases. However, the underlying molecular mechanisms remain to be elucidated. In this study, employing scanning ion conductance microscopy (SICM), we explored the early responses of human embryonic kidney (HEK293H) cells to oxidative DNA damage induced by potassium chromate (K₂CrO₄). We found that the short term (1-2 h) exposure to a low concentration (10 μM) of K₂CrO₄ damaged the lipid membrane of HEK293H cells, resulting in structural defects and depolarization of the cell membrane and reducing cellular secretion activity shortly after the treatment. We further demonstrated that the K₂CrO₄ treatment decreased the expression of the cytoskeleton protein, β-actin, by inducing oxidative DNA damage in the exon 4 of the β-actin gene. These results suggest that K₂CrO₄ caused oxidative DNA damage in cytoskeleton genes such as β-actin and reduced their expression, thereby disrupting the organization of the cytoskeleton beneath the cell membrane and inducing cell membrane damages. Our study provides direct evidence that oxidative DNA damage disrupted human cell membrane integrity by deregulating cytoskeleton gene expression.

CoQ10 improves meiotic maturation of pig oocytes through enhancing mitochondrial function and suppressing oxidative stress

Coenzyme Q10 (CoQ10) is essential to many fundamental biological processes. However, the effect of CoQ10 on meiotic maturation of pig oocytes still remains elusive. In the present study we aimed to understand the effects of CoQ10 on porcine oocyte maturation, by supplementing different concentrations of CoQ10 (25, 50 and 100 μM) into the maturation medium. We showed that CoQ10 at 50 μM had better capacity to promote the nuclear maturation of pig oocytes derived from both small and large antral follicles. Though the cleavage and blastocyst rates of parthenotes stayed stable, 50 μM CoQ10 treatment could accelerate the development of parthenotes to blastocyst stage, and increase the average cell number of blastocyst. For cumulus-oocyte complexes from large antral follicles categorized by the brilliant cresyl blue (BCB) test, 50 μM CoQ10 treatment could specifically promote the nuclear maturation of poor-quality oocytes in the BCB-negative group. Mitochondrial function of oocytes treated by 50 μM CoQ10 could be boosted, through increasing the levels of mitochondrial membrane potential, ATP production and CoQ6, and changing the pattern of mitochondrial distribution as well. Moreover, 50 μM CoQ10 treatment suppressed the level of reactive oxygen species and reduced the percentage of oocytes with early apoptosis signal. Taken together, CoQ10 could improve the meiotic maturation of pig oocytes, especially for poor-quality oocytes, mainly through enhancing mitochondrial function and suppressing oxidative stress to reduce apoptosis.

Effects of methylparaben on in vitro maturation of porcine oocytes

Parabens (PBs) are compounds widely used in industry for food and personal care products as antimicrobials and preservatives. Their indiscriminate use has resulted in their detection in different ecosystems so that humans and other organisms are highly exposed. Methylparaben (MePB), compared with other PBs, is mostly detected in food, personal care and baby care products. PBs could be linked to the generation of hormonal disorders and fertility impairment since their recent classification as endocrine disruptors. The knowledge of the effects that MePB can exert is of great importance as, in terms of reproduction, information is limited. Therefore, the objective of the present study was to evaluate the effect of MePB on porcine oocyte viability and in vitro maturation (IVM), as well as to determine the lethal concentration at 50% (LC₅₀ ) and the maturation inhibition concentration at 50% (MIC₅₀ ). Oocytes were exposed to different MePB concentrations 0 (control), 50, 100, 500, 750 and 1000 μm during 44 h of IVM. Cytoplasmic alterations and reduced cumulus cell expansion were observed in oocytes exposed to MePB; however, viability was not affected. In addition, oocyte maturation decreased in a concentration-dependent manner after exposure to MePB. The estimated LC₅₀ was 2028.38 μm, whereas MIC₅₀ was 780.31 μm. To our knowledge, this is the first study that demonstrates that MePB altered porcine oocyte morphology, and caused a reduction in cumulus cell expansion, both of which resulted in decreased oocyte maturation. Therefore, MePB exposure may be one of the factors involved in fertility impairment in mammals, including that of humans.

Butylparaben Is Toxic to Porcine Oocyte Maturation and Subsequent Embryonic Development Following In Vitro Fertilization

Parabens are widely used in personal care products due to their antimicrobial effects. Although the toxicity of parabens has been reported, little information is available on the toxicity of butylparaben (BP) on oocyte maturation. Therefore, we investigated the effects of various concentrations of BP (0 μM, 100 μM, 200 μM, 300 μM, 400 μM, and 500 μM) on the in vitro maturation of porcine oocytes. BP supplementation at a concentration greater than 300 μM significantly reduced the proportion of complete cumulus cell expansion and metaphase II oocytes compared to the control. The 300 μM BP significantly decreased fertilization, cleavage, and blastocyst formation rates with lower total cell numbers and a higher rate of apoptosis in blastocysts compared to the control. The BP-treated oocytes showed significantly higher reactive oxygen species (ROS) levels, and lower glutathione (GSH) levels than the control. BP significantly increased the aberrant mitochondrial distribution and decreased mitochondrial function compared to the control. BP-treated oocytes exhibited significantly higher percentage of γ-H2AX, annexin V-positive oocytes and expression of LC3 than the control. In conclusion, we demonstrated that BP impaired oocyte maturation and subsequent embryonic development, by inducing ROS generation and reducing GSH levels. Furthermore, BP disrupted mitochondrial function and triggered DNA damage, early apoptosis, and autophagy in oocytes.