Melatonin improves meiosis maturation against diazinon exposure in mouse oocytes

Updating the Role of JUNO and Factors Involved in Its Function during Fertilization

INTRODUCTION

The final step of the fertilization process involves gametes adhesion and fusion. JUNO is an essential folate receptor 4 protein present in the ooplasm of oocytes, which binds to IZUMO1, its receptor on the sperm surface. Both proteins are indispensable for the sperm-oocyte interaction, and their absence results in infertility. Despite the importance of JUNO in reproduction, there is still controversy about how different factors affect the functionality of JUNO. Therefore, the goal of this study was to provide a comprehensive overview of what we know so far about the presence and functionality of JUNO.

METHODS

In order to accomplish this, a total of 198 articles were identified. Based on both inclusion and exclusion criteria, 40 articles were finally included in this study.

RESULTS

The results showed that during oocyte maturation, the expression levels of JUNO undergo alterations and, in some instances, cross-species gamete fusion is possible. Additionally, it has been observed that exposure of oocytes to factors such as bisphenol A, 17α-ethynylestradiol, diazinon, benzo(a)pyrene, butylparaben, bis(2-ethylhexyl) phthalate, hydroxyurea, dichlorophenol, isoniazid, and para-phenylenediamine disrupt JUNO and decrease the fertilization process rates. Moreover, exposure to ionic radiation, vitrification, and synthetic materials as microplastics has the same effect. Nonetheless, other compounds such as melatonin, mogroside V, cholesterol-loaded methyl-β-cyclodextrin, methyl-β-cyclodextrin, protocatechuic acid, coenzyme Q10, resveratrol, and Shoutai pills have been shown to enhance female fertility in terms of JUNO functionality.

CONCLUSION

In summary, this update highlights the crucial role of JUNO during fertilization and reveals how different factors and experimental procedures affect its activity.

Effects of diazinon on the ovarian tissue of rats: a histochemical and ultrastructural study

Despite the negative environmental and biologic effects, organophosphates have currently been widely used. We aimed to examine the possible negative effects of diazinon, a type of organophosphate, on rat ovarian tissue. Wistar Albino rats were divided into four groups. No treatment was given to control, olive oil was applied to sham group. Experimental groups were injected intraperitoneally with 30 and 60 mg/kg/day diazinon, respectively. 24 h later, ovarian tissues were extracted, preparated, examined via light and electron microscope. In the experimental groups granulosa and corpus luteum showed degenerative changes. Dilatation of endoplasmic reticulum cisterns and morphological alterations of mitochondria in granulosa cells were detected utrastructurally. Also, accumulation of lipid droplets and autophagic vacuoles was observed in cells of corpus luteum. A statistically significant dose-dependent decrease in superoxide dismutase and catalase reactivity and a statistically significant increase in caspase-3 expression in cells of atretic follicles and corpus luteum were observed. Results show that exposure to a single dose of diazinon may disrupt antioxidant system, trigger atresia in follicles and negatively effect corpus luteum functions. It was concluded that studies applying possible antioxidant treatments should be carried out to reduce and prevent the negative effects of diazinon on the reproductive system.

Melatonin ameliorates the toxic effects of 2,6-Dichloro-1,4-benzoquinone on mouse oocytes by restoring subcellular structures

2,6-Dichloro-1,4-benzoquinone (2,6-DCBQ) is a disinfection by-product (DBP) formed during the disinfection of drinking water. Due to its frequent detection and high concentrations, it has garnered significant attention. However, the effects of 2,6-DCBQ on oocyte meiosis remain poorly understood. In this study, we demonstrate that 2,6-DCBQ exposure disrupts nuclear maturation in oocytes by damaging the spindle and chromosome structure. Additionally, exposure to 2,6-DCBQ impairs cytoplasmic maturation by altering actin dynamics, disrupting cortical granule distribution, and compromising the function of key organelles, including the mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes. Supplementing melatonin during meiotic maturation reverses these effects, enhancing organelle function, reducing reactive oxygen species (ROS) levels, alleviating DNA damage, and inhibiting apoptosis. Together, these findings show that 2,6-DCBQ causes organelle dysfunction and meiotic disruption in oocytes, while melatonin provides protective effects against these disruptions during meiotic maturation.

Gap junctions in polycystic ovary syndrome: Implications for follicular arrest

Gap junctions are specialized intercellular conduits that provide a direct pathway between neighboring cells, which are involved in numerous physiological processes, such as cellular differentiation, cell growth, and metabolic coordination. The effect of gap junctional hemichannels in folliculogenesis is particularly obvious, and the down-regulation of connexins is related to abnormal follicle growth. Polycystic ovary syndrome (PCOS) is a ubiquitous endocrine disorder of the reproductive system, affecting the fertility of adult women due to anovulation. Exciting evidence shows that gap junction is involved in the pathological process related to PCOS and affects the development of follicles in women with PCOS. In this review, we examine the expression of connexins in follicular cells of PCOS and figure out whether such communication could have consequences for PCOS women. While along with results from clinical and related animal studies, we summarize the mechanism of connexins involved in the pathogenesis of PCOS.

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.

Melatonin improves mouse oocyte quality from 2-ethylhexyl diphenyl phosphate-induced toxicity by enhancing mitochondrial function

2-Ethylhexyl diphenyl phosphate (EHDPP) is a representative organophosphorus flame retardant (OPFR) that has garnered attention due to its widespread use and potential adverse effects. EHDPP exhibits cytotoxicity, genotoxicity, developmental toxicity, and endocrine disruption. However, the toxicity of EHDPP in mammalian oocytes and the underlying mechanisms remain poorly understood. Melatonin is a natural free radical scavenger that has demonstrated cytoprotective properties. In this study, we investigated the effect of EHDPP on mouse oocytes in vitro culture system and evaluated the rescue effect of melatonin on oocytes exposed to EHDPP. Our results indicated that EHDPP disrupted oocyte maturation, resulting in the majority of oocytes arrested at the metaphase I (MI) stage, accompanied by cytoskeletal damage and elevated levels of reactive oxygen species (ROS). Nevertheless, melatonin supplementation partially rescued EHDPP-induced mouse oocyte maturation impairment. Results of single-cell RNA sequencing (scRNA-seq) analysis elucidated potential mechanisms underlying these protective effects. According to the results of scRNA-seq, we conducted further tests and found that EHDPP primarily disrupts mitochondrial distribution and function, kinetochore-microtubule (K-MT) attachment, DNA damage, apoptosis, and histone modification, which were rescued upon the supplementation of melatonin. This study reveals the mechanisms of EHDPP on female reproduction and indicates the efficacy of melatonin as a therapeutic intervention for EHDPP-induced defects in mouse oocytes.

C-Phycocyanin improves the quality of goat oocytes after in vitro maturation and vitrification

In vitro maturation (IVM) and cryopreservation of goat oocytes are important for establishing a valuable genetic bank for domesticated female animals and improving livestock reproductive efficiency. C-Phycocyanin (PC) is a Spirulina extract with antioxidant, antiinflammatory, and radical scavenging properties. However, whether PC has positive effect on goat oocytes IVM or developmental competence after vitrification is still unknown. In this study, we found that first polar body extrusion (n = 293), cumulus expansion index (n = 269), and parthenogenetic blastocyst formation (n = 281) were facilitated by adding 30 μg/mL PC to the oocyte maturation medium when compared with the control groups and that supplemented with 3, 10, 100 or 300 μg/mL PC (P < 0.05). Although PC supplementation did not affect spindle formation or chromosome alignment (n = 115), it facilitated or improved cortical granules migration (n = 46, P < 0.05), mitochondria distribution (n = 39, P < 0.05), and mitochondrial membrane potential (n = 46, P < 10-4). Meanwhile, supplementation with 30 μg/mL PC in the maturation medium could significantly inhibit the reactive oxygen species accumulation (n = 65, P < 10-4), and cell apoptosis (n = 42, P < 0.05). In addition, PC increased the oocyte mRNA levels of GPX4 (P < 0.01), and decreased the mRNA and protein levels of BAX (P < 0.01). Next, we investigated the effect of PC supplementation in the vitrification solution on oocyte cryopreservation. When compared with the those equilibrate in the vitrification solution without PC, recovered oocytes in the 30 μg/mL PC group showed higher ratios of normal morphology (n = 85, P < 0.05), survival (n = 85, P < 0.05), first polar body extrusion (n = 62, P < 0.05), and parthenogenetic blastocyst formation (n = 107, P < 0.05). Meanwhile, PC supplementation of the vitrification solution increased oocyte mitochondrial membrane potential (n = 53, P < 0.05), decreased the reactive oxygen species accumulation (n = 73, P < 0.05), promoted mitochondria distribution (n = 58, P < 0.05), and inhibited apoptosis (n = 46, P < 10-3). Collectively, our findings suggest that PC improves goat oocyte IVM and vitrification by reducing oxidative stress and early apoptosis, which providing a novel strategy for livestock gamete preservation and utilization.

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.

Epigallocatechin gallate improves meiosis maturation against Diazinon exposure in porcine oocytes

Diazinon (DZN) is a refractory organophosphorus pesticide (OP) in the surrounding environment due to its overuse in agriculture. The antioxidant activity of Epigallocatechin gallate (EGCG) from green tea is at least 100 times greater than that of vitamin C. This study aimed to study the effects of DZN on the meiotic maturation of porcine oocytes, as well as the protective roles of EGCG. Firstly, the effects of DZN and EGCG on meiotic nuclear maturation of porcine oocytes were detected, and then embryonic development was investigated by chemical parthenogenetic activation. Next, the spindle assembly, mitochondrial membrane potential (MMP), reactive oxygen species (ROS), DNA damage, and finally the early apoptosis of oocytes were examined by immunofluorescence staining. The results revealed that DZN exposure significantly reduced the quality of porcine oocytes, such as failure of nuclear and cytoplasmic maturation, evidenced by abnormal spindle assembly, disordered chromosome alignment, low MMP, observably increased ROS, severe DNA damage, and early apoptosis. Appropriate EGCG could significantly reduce all these defects caused by DZN. In conclusion, EGCG can help prevent the harm that DZN exposure can do. These findings offer convincing support for enhancing the oocyte quality from EGCG through daily ordinary beverages.