α-Ketoglutarate Improves Meiotic Maturation of Porcine Oocytes and Promotes the Development of PA Embryos, Potentially by Reducing Oxidative Stress through the Nrf2 Pathway.

α-Ketoglutarate (α-KG) is a metabolite in the tricarboxylic acid cycle. It has a strong antioxidant function and can effectively prevent oxidative damage. Previous studies have shown that α-KG exists in porcine follicles, and its content gradually increases as the follicles grow and mature. However, the potential mechanism of supplementation of α-KG on porcine oocytes during in vitro maturation (IVM) has not yet been reported. The purpose of this study was to explore the effect of α-KG on the early embryonic development of pigs and the mechanisms underlying these effects. We found that α-KG can enhance the development of early pig embryos. Adding 20 µM α-KG to the in vitro culture medium significantly increased the rate of blastocyst formation and the total cell number. Compared with to that of the control group, apoptosis in blastocysts of the supplement group was significantly reduced. α-KG reduced the production of reactive oxygen species and glutathione levels in cells. α-KG not only improved the activity of mitochondria but also inhibited the occurrence of apoptosis. After supplementation with α-KG, pig embryo pluripotency-related genes (OCT4, NANOG, and SOX2) and antiapoptotic genes (Bcl2) were upregulated. In terms of mechanism, α-KG activates the Nrf2/ARE signaling pathway to regulate the expression of antioxidant-related targets, thus combating oxidative stress during the in vitro culture of oocytes. Activated Nrf2 promotes the transcription of Bcl2 genes and inhibits cell apoptosis. These results indicate that α-KG supplements have a beneficial effect on IVM by regulating oxidative stress during the IVM of porcine oocytes and can be used as a potential antioxidant for IVM of porcine oocytes.

NAMPT reduction-induced NAD+ insufficiency contributes to the compromised oocyte quality from obese mice.

Maternal obesity is associated with multiple adverse reproductive outcomes, whereas the underlying molecular mechanisms are still not fully understood. Here, we found the reduced nicotinamide phosphoribosyl transferase (NAMPT) expression and lowered nicotinamide adenine dinucleotide (NAD+ ) content in oocytes from obese mice. Next, by performing morpholino knockdown assay and pharmacological inhibition, we revealed that NAMPT deficiency not only severely disrupts maturational progression and meiotic apparatus, but also induces the metabolic dysfunction in oocytes. Furthermore, overexpression analysis demonstrated that NAMPT insufficiency induced NAD+ loss contributes to the compromised developmental potential of oocytes and early embryos from obese mice. Importantly, in vitro supplement and in vivo administration of nicotinic acid (NA) was able to ameliorate the obesity-associated meiotic defects and oxidative stress in oocytes. Our results indicate a role of NAMPT in modulating oocyte meiosis and metabolism, and uncover the beneficial effects of NA treatment on oocyte quality from obese mice.

Dysfunction in Sertoli cells participates in glucocorticoid-induced impairment of spermatogenesis.

The effect of stress on male fertility is a widespread public health issue, but less is known about the related signaling pathway. To investigate this, we established a hypercortisolism mouse model by supplementing the drinking water with corticosterone for four weeks. In the hypercortisolism mice, the serum corticosterone was much higher than in the control, and serum testosterone was significantly decreased. Moreover, corticosterone treatment induced decrease of sperm counts and increase of teratozoospermia. Increased numbers of multinucleated giant cells and apoptotic germ cells as well as downregulated meiotic markers suggested that corticosterone induced impaired spermatogenesis. Further, upregulation of macrophage-specific marker antigen F4/80 as well as inflammation-related genes suggested that corticosterone induced inflammation in the testis. Lactate content was found to be decreased in the testis and Sertoli cells after corticosterone treatment, and lactate metabolism-related genes were downregulated. In vitro phagocytosis assays showed that the phagocytic activity in corticosterone-treated Sertoli cells was downregulated and accompanied by decreased mitochondrial membrane potential, while pyruvate dehydrogenase kinase-4 inhibitor supplementation restored this process. Taken together, our results demonstrated that dysfunctional phagocytosis capacity and lactate metabolism in Sertoli cells participates in corticosterone-induced impairment of spermatogenesis.

Nicotinamide Mononucleotide Supplementation Reverses the Declining Quality of Maternally Aged Oocytes.

Advanced maternal age is highly associated with a decline in oocyte quality, but effective approaches to improve it have still not been fully determined. Here, we report that in vivo supplementation of nicotinamide mononucleotide (NMN) efficaciously improves the quality of oocytes from naturally aged mice by recovering nicotinamide adenine dinucleotide (NAD+) levels. NMN supplementation not only increases ovulation of aged oocytes but also enhances their meiotic competency and fertilization ability by maintaining the normal spindle/chromosome structure and the dynamics of the cortical granule component ovastacin. Moreover, single-cell transcriptome analysis shows that the beneficial effect of NMN on aged oocytes is mediated by restoration of mitochondrial function, eliminating the accumulated ROS to suppress apoptosis. Collectively, our data reveal that NMN supplementation is a feasible approach to protect oocytes from advanced maternal age-related deterioration, contributing to the improvement of reproductive outcome of aged women and assisted reproductive technology.

Shoutai pills improve the quality of oocytes exposed to the chemotherapeutic drug Hydroxyurea.

Hydroxyurea (HU), a DNA synthesis inhibitor, is one of the most common chemotherapeutic drugs that have been widely applied to treat a variety of cancers. HU treatment exhibits severe side effects including renal toxicity, skin toxicity and embryo-toxicity. However, the influence of HU on the female gamete development has not yet fully clarified. Here, we found that HU exposure induced the degeneration of activated follicles after primordial follicle stage, resulting in the depletion of the ovarian reserve. HU exposure also led to the oocyte meiotic maturation arrest via disrupting normal spindle assembly, chromosome alignment and kinetochore-microtubule attachment. Furthermore, exposure to HU impaired the dynamics of ovastacin and Juno, two critical fertilization regulators. Notably, we illustrated that Shoutai pills (STP), a traditional Chinese medicine drug that has been commonly used for the treatment of miscarriage in China, partially restored all of the defects of oocyte development resulting from HU exposure through inhibiting the occurrence of oxidative stress-induced apoptosis. Taken together, our data not only reveal the adverse impact of HU exposure on the female gamete development, but also provide an effective strategy to prevent it, potentially contributing to the improvement of the quality of oocytes from patients treated with HU.

Zinc supports transcription and improves meiotic competence of growing bovine oocytes.

In the last years, many studies focused on the understanding of the possible role of zinc in the control of mammalian oogenesis, mainly on oocyte maturation and fertilization. However, little is known about the role of zinc at earlier stages, when the growing oocyte is actively transcribing molecules that will regulate and sustain subsequent stages of oocyte and embryonic development. In this study, we used the bovine model to gain insights into the possible involvement of zinc in oocyte development. We first mined the EmbryoGENE transcriptomic dataset, which revealed that several zinc transporters and methallothionein are impacted by physiological conditions throughout the final phase of oocyte growth and differentiation. We then observed that zinc supplementation during in vitro culture of growing oocytes is beneficial to the acquisition of meiotic competence when subsequently subjected to standard in vitro maturation. Furthermore, we tested the hypothesis that zinc supplementation might support transcription in growing oocytes. This hypothesis was indirectly confirmed by the experimental evidence that the content of labile zinc in the oocyte decreases when a major drop in transcription occurs in vivo. Accordingly, we observed that zinc sequestration with a zinc chelator rapidly reduced global transcription in growing oocytes, which was reversed by zinc supplementation in the culture medium. Finally, zinc supplementation impacted the chromatin state by reducing the level of global DNA methylation, which is consistent with the increased transcription. In conclusion, our study suggests that altering zinc availability by culture-medium supplementation supports global transcription, ultimately enhancing meiotic competence.

Melatonin ameliorates the advanced maternal age-associated meiotic defects in oocytes through the SIRT2-dependent H4K16 deacetylation pathway.

It has been widely reported that advanced maternal age impairs oocyte quality. To date, various molecules have been discovered to be involved in this process. However, prevention of fertility issues associated with maternal age is still a challenge. In the present study, we find that both in vitro supplement and in vivo administration of melatonin are capable of alleviating the meiotic phenotypes of aged oocytes, specifically the spindle/chromosome disorganization and aneuploidy generation. Furthermore, we identify SIRT2 as a critical effector mediating the effects of melatonin on meiotic structure in old oocytes. Candidate screening shows that SIRT2-controlled deacetylation of histone H4K16 is essential for maintaining the meiotic apparatus in oocytes. Importantly, non-acetylatable-mimetic mutant H4K16R partially rescues the meiotic deficits in oocytes from reproductive aged mice. In contrast, overexpression of acetylation-mimetic mutant H4K16Q abolishes the beneficial effects of melatonin on the meiotic phenotypes in aged oocytes. To sum up, our data uncover that melatonin alleviates advanced maternal aged-associated meiotic defects in oocytes through the SIRT2-depenendet H4K16 deacetylation pathway.

Insufficiency of melatonin in follicular fluid is a reversible cause for advanced maternal age-related aneuploidy in oocytes.

Age-related decline in female fertility is a common feature that occurs in the fourth decade of women as a result of a reduction in both oocyte quality and quantity [1]. However, strategies to prevent the deterioration of maternal aged oocytes and relevant mechanisms are still underexplored. Here, we find that the reduced abundance of melatonin in the follicular fluid highly correlates with the advanced maternal age-related aneuploidy. Of note, we show that exposure of oocytes from aged mice both in vitro and in vivo to exogenous melatonin not only eliminates the accumulated reactive oxygen species-induced DNA damage and apoptosis, but also suppresses the occurrence of aneuploidy caused by spindle/chromosome defect that is frequently observed in aged oocytes. Importantly, we reveal that melatonin supplementation reverses the defective phenotypes in aged oocytes through a Sirt1/Sod2-dependent mechanism. Inhibition of Sirt1 activity abolishes the melatonin-mediated improvement of aged oocyte quality. Together our findings provide evidence that supplementation of melatonin is a feasible way to protect oocytes from advanced maternal age-related meiotic defects and aneuploidy, demonstrating the potential for improving the quality of oocytes from aged women and the efficiency of assisted reproductive technology.

Melatonin protects against defects induced by malathion during porcine oocyte maturation.

Malathion (MAL) is a common organophosphorus pesticide and affects both animal and human reproduction. However, the mechanisms regarding how MAL affects the mammalian oocyte quality and how to prevent it have not been fully investigated. In this study, we used porcine oocyte as a model and proved that MAL impaired porcine oocyte quality in a dose-dependent manner during maturation. MAL decreased the first polar body extrusion, disrupted spindle assembly and chromosome alignment, impaired cortical granules (CGs) distribution, and increased reactive oxygen species (ROS) level in oocytes. RNA-seq analysis showed that MAL exposure altered the expression of 2,917 genes in the porcine maturated oocytes and most genes were related to ROS, the lipid droplet process, and the energy supplement. Nevertheless, these defects could be remarkably ameliorated by adding melatonin (MLT) into the oocyte maturation medium. MLT increased oocyte maturation rate and decreased the abnormities of spindle assembly, CGs distribution and ROS accumulation in MAL-exposed porcine oocytes. More important, MLT upregulated the expression of genes related to lipid droplet metabolism (PPARγ and PLIN2), decreased lipid droplet size and lipid peroxidation in MAL-exposed porcine oocytes. Finally, we found that MLT increased the blastocysts formation and the cell numbers of blastocysts in MAL-exposed porcine oocytes after parthenogenetic activation, which was mediated by reduction of ROS levels and maintaining lipid droplet metabolism. Taken together, our results revealed that MLT had a protective action against MAL-induced deterioration of porcine oocyte quality.

The autophagic inducer and inhibitor display different activities on the meiotic and developmental competencies of porcine oocytes derived from small and medium follicles.

This study aimed to examine the effect of rapamycin (autophagy inducer) and 3-methyladenine (3-MA, autophagy inhibitor) on the meiotic and developmental competencies of porcine oocytes derived from medium follicles (MF, 3-6 mm in diameter) and small follicles (SF, 1-2 mm in diameter) during in vitro maturation (IVM) process. The presence of 1 nM but not 10 nM rapamycin significantly increased the maturation rate of MF-derived oocytes (P < 0.05). However, the maturation rate of SF-derived oocytes was not affected by rapamycin at both concentrations (1 nM and 10 nM). The maturation rate of MF-derived oocytes decreased significantly (P < 0.05) in the presence of 0.2 mM but not 2 mM 3-MA than non-supplemented control. In contrast, in SF-derived oocytes, 3-MA at both 0.2 and 2 mM concentrations did not affect the maturation rates. The presence of 1 nM rapamycin significantly increased the blastocyst formation rate of MF-derived mature oocytes following parthenogenetic activation (P < 0.05). However, the blastocyst formation rate of SF-derived mature oocytes was not affected by the presence of rapamycin. The presence of 3-MA significantly reduced the blastocyst formation rate of MF-derived mature oocytes but did not change that of SF-derived oocytes. In conclusion, our study results show differences in activity of the autophagy inducer and inhibitor on the meiotic and developmental competencies of MF- and SF-derived porcine oocytes.

Vitamin C protects carboplatin-exposed oocytes from meiotic failure.

CBP (carboplatin) is a second-generation chemotherapeutic drug of platinum compound commonly applied in the treatment of sarcomas and germ cell tumours. Although it is developed to replace cisplatin, which has been proven to have a variety of side effects during cancer treatment, CBP still exhibits a certain degree of toxicity including neurotoxicity, nephrotoxicity, hematotoxicity and myelosuppression. However, the underlying mechanisms regarding how CBP influences the female reproductive system especially oocyte quality have not yet been fully determined. Here, we report that CBP exposure led to the oocyte meiotic defects by impairing the dynamics of the meiotic apparatus, leading to a remarkably aberrant spindle organisation, actin polymerisation and mitochondrial integrity. Additionally, CBP exposure caused compromised sperm binding and fertilisation potential of oocytes by due to an abnormal distribution of cortical granules and its component ovastacin. More importantly, we demonstrated that vitamin C supplementation prevented meiotic failure induced by CBP exposure and inhibited the increase in ROS levels, DNA damage accumulation and apoptotic incidence. Taken together, our findings demonstrate the toxic effects of CBP exposure on oocyte development and provide a potential effective way to improve the quality of CBP-exposed oocytes in vitro.

Tea polyphenol protects against cisplatin-induced meiotic defects in porcine oocytes.

DDP (cisplatin), a DNA cross-linking agent, is one of the most common chemotherapeutic drugs that have been widely used in the treatment of sarcomas and germ cell tumors. DDP treatment exhibits severe side effects including renal toxicity, ototoxicity and embryo-toxicity. Women of reproductive age treated with DDP may lead to loss of primordial follicles, resulting in the depletion of the ovarian reserve and consequent premature ovarian failure. However, the influence of DDP on the oocyte quality and the strategy to prevent it has not yet fully clarified. Here, we report that DDP exposure resulted in the oocyte meiotic failure via disrupting the meiotic organelle dynamics and arrangement, exhibiting a prominently impaired cytoskeleton assembly, including spindle formation and actin polymerization. In addition, exposure to DDP led to the abnormal distribution of mitochondrion and cortical granules, two indicators of cytoplasmic maturation of oocytes. Conversely, TP (tea polyphenols) supplementation partially restored all of the meiotic defects resulted from DDP exposure through suppressing the increase of ROS level and the occurrence of DNA damage as well as apoptosis.

Melatonin rescues the aneuploidy in mice vitrified oocytes by regulating mitochondrial heat product.

Vitrification of germinal vesicle (GV) stage oocytes has been shown to be closely associated with decreased rates of meiosis maturation and increased rates of aneuploidy. However, little is known about the effects of melatonin on these events in mice vitrified GV oocytes. In this study, the effects of melatonin on meiosis maturation potential and the incidence rate of aneuploidy in mouse vitrified oocytes were analyzed by supplementing in vitro maturation (IVM) solution with melatonin at different concentrations. This study, for the first time, showed that the mitochondrial heat production was markedly increased in vitrified oocytes (P < 0.05), which compromised the first polar body extrusion (PBE) of vitrified oocytes (73.3% vs. 85.1%, P < 0.05). However, 10-11 mol/L melatonin could significantly decrease mitochondrial heat production and ROS level (9.1 vs. 12.0 pixels, P < 0.05), meanwhile increase ATP level (1.1 vs. 0.88 pmol, P < 0.05) and mtDNA copies (107438 vs. 67869, P < 0.05), which rescued the abnormal chromosome alignment (32% vs. 69%, P < 0.05) and reduced the incidence of aneuploidy (15.6% vs. 38.5%, P < 0.05) in vitrified oocytes. The meiosis maturation ability of vitrified oocytes with melatonin supplementation was similar to that of fresh ones (83.4% vs. 85.1%, P > 0.05). Collectively, our data revealed that melatonin has a protective action against vitrification-induced injuries of oocytes meiosis maturation.

Vitamin C protects against defects induced by juglone during porcine oocyte maturation.

Juglone, a naphthoquinone isolated from many species of the Juglandaceae family, has been used in traditional Chinese medicine for centuries because of its antiviral, antibacterial, and antitumor activities. However, the toxicity of juglone has also been demonstrated. Here, we used porcine oocytes as a model to explore the effects of juglone on oocyte maturation and studied the impact of vitamin C (VC) administration on juglone exposure-induced meiosis defects. Exposure to juglone significantly restricted cumulus cell expansion and decreased the first polar body extrusion. In addition, juglone exposure disturbed spindle organization, actin assembly, and the distribution of mitochondria during oocyte meiosis, while the acetylation level of α-tubulin was also reduced. These defects were all ameliorated by VC administration. Our findings indicate that juglone exposure induced meiotic failure in porcine oocytes, while VC protected against these defects during porcine oocyte maturation by ameliorating the organization of the cytoskeleton and mitochondrial distribution.

Assessing effects of germline exposure to environmental toxicants by high-throughput screening in C. elegans.

Chemicals that are highly prevalent in our environment, such as phthalates and pesticides, have been linked to problems associated with reproductive health. However, rapid assessment of their impact on reproductive health and understanding how they cause such deleterious effects, remain challenging due to their fast-growing numbers and the limitations of various current toxicity assessment model systems. Here, we performed a high-throughput screen in C. elegans to identify chemicals inducing aneuploidy as a result of impaired germline function. We screened 46 chemicals that are widely present in our environment, but for which effects in the germline remain poorly understood. These included pesticides, phthalates, and chemicals used in hydraulic fracturing and crude oil processing. Of the 46 chemicals tested, 41% exhibited levels of aneuploidy higher than those detected for bisphenol A (BPA), an endocrine disruptor shown to affect meiosis, at concentrations correlating well with mammalian reproductive endpoints. We further examined three candidates eliciting aneuploidy: dibutyl phthalate (DBP), a likely endocrine disruptor and frequently used plasticizer, and the pesticides 2-(thiocyanomethylthio) benzothiazole (TCMTB) and permethrin. Exposure to these chemicals resulted in increased embryonic lethality, elevated DNA double-strand break (DSB) formation, activation of p53/CEP-1-dependent germ cell apoptosis, chromosomal abnormalities in oocytes at diakinesis, impaired chromosome segregation during early embryogenesis, and germline-specific alterations in gene expression. This study indicates that this high-throughput screening system is highly reliable for the identification of environmental chemicals inducing aneuploidy, and provides new insights into the impact of exposure to three widely used chemicals on meiosis and germline function.

Melatonin alleviates the deterioration of oocytes from mice subjected to repeated superovulation.

Induction of repeated superovulation with exogenous hormones is widely used in assisted reproductive technology (ART). Though it is generally safe, emerging evidence has indicated that repeated superovulation may compromise oocyte quality. However, few studies have explored how to ameliorate such impairment. Because melatonin has beneficial influences on oocytes in various detrimental environments, we aimed to explore whether melatonin could protect mouse oocytes after repeated superovulation. We found that repeated superovulation markedly reduced meiotic maturation and disrupted spindle organization and chromosome alignment. Furthermore, we observed reduced mitochondrial content and enhanced early apoptosis in oocytes from mice subjected to repeated superovulation. In addition, 5-methylcytosine (5mc) fluorescence intensity was lower in oocytes from experimental mice than in those from control mice, indicating that repeated superovulation disrupts genomic DNA methylation, and elevations in reactive oxygen species levels indicated that repeated superovulation also induces oxidative stress. Conversely, melatonin administration improved oocyte maturation and attenuated the observed defects. Interestingly, supplementation with melatonin during in vitro maturation had the same protective effects on oocytes as in vivo melatonin administration. In summary, our results show that melatonin can improve oocyte quality after repeated superovulation and thus provide a potential strategy to improve ART efficiency.

Effects of Heyan Kuntai Capsule () on Follicular Development and Oocyte Cohesin Levels in Aged Mice.

OBJECTIVE: To evaluate the effect of Heyan Kuntai Capsule (, HYKT) on the ovarian function of aged mice and expressions of cohesion complexes in oocytes. METHODS: Twenty-five 9-month-old female C57BL/6J mice were randomly divided into 5 groups by block randomization method (n=5 per group), including the control group (saline), 17ß-estradiol group [E2, 100 µg/(kg•d)], and low-, medium-, and highdose of HYKT groups [0.3, 0.9, 2.7 g/(kg•d), respectively]. All mice were treated by intragastric administration for 4 weeks. Hematoxylin and eosin staining and anti-VASA staining were used to detect the amounts of follicles. The apoptosis of follicles was measured by anti-gamma H2A histone family member X (γH2AX) staining and TdT-mediated dUTP Nick-End Labeling (TUNEL) assay. The density of cohesin subunits, REC8 meiotic recombination protein (REC8), structural maintenance of chromosome (SMC) 1ß and SMC3 in oocytes were evaluated by immunofluorescent staining. RESULTS: After administration of E2 and high-dose of HYKT, the total number of follicles as well as the number of primordial and primary follicles were significantly increased (P<0.05). Anti-γH2AX staining and TUNEL assay demonstrated that high-dose of HYKT and E2 partly suppressed the apoptosis of follicles (P<0.05). Furthermore, it showed an increased trend in the levels of REC8 and SMC1ß, after administration with E2 and HYKT, and no obvious change in the level of SMC3. CONCLUSION: HYKT could enhance the number of follicles, suppress apoptosis of oocytes and have a trend to elevate the meiotic-specific cohesin subunits (REC8 and SMC1ß) in oocytes of aged mice, indicating a beneficial effect on the ovarian function in terms of the quantity and quality of follicles.

In vitro mouse spermatogenesis with an organ culture method in chemically defined medium.

We previously reported the successful induction and completion of mouse spermatogenesis by culturing neonatal testis tissues. The culture medium consisted of α-minimum essential medium (α-MEM), supplemented with Knockout serum replacement (KSR) or AlbuMAX, neither of which were defined chemically. In this study, we formulated a chemically defined medium (CDM) that can induce mouse spermatogenesis under organ culture conditions. It was found that bovine serum albumin (BSA) purified through three different procedures had different effects on spermatogenesis. We also confirmed that retinoic acid (RA) played crucial roles in the onset of spermatogonial differentiation and meiotic initiation. The added lipids exhibited weak promoting effects on spermatogenesis. Lastly, luteinizing hormone (LH), follicle stimulating hormone (FSH), triiodothyronine (T3), and testosterone (T) combined together promoted spermatogenesis until round spermatid production. The CDM, however, was not able to produce elongated spermatids. It was also unable to induce spermatogenesis from the very early neonatal period, before 2 days postpartum, leaving certain factors necessary for spermatogenic induction in mice unidentified. Nonetheless, the present study provided important basic information on testis organ culture and spermatogenesis in vitro.

Involvement of CAT in the detoxification of HT-induced ROS burst in rice anther and its relation to pollen fertility.

KEY MESSAGE: HT-induced ROS burst in developing anther is closely related to the lowered CAT activity as the result of the markedly suppressed OsCATB transcript, thereby causing severe fertility injury for rice plants exposed to HT at meiosis stage. The reproductive stage of rice plants is highly sensitive to heat stress. In this paper, different rice cultivars were used to investigate the relationship of HT-induced floret sterility with reactive oxygen species (ROS) detoxification in rice anthers under well-controlled climatic conditions. Results showed that high temperature (HT) exposure significantly enhanced the ROS level and malondialdehyde (MDA) content in developing anther, and the increase in ROS amount in rice anther under HT exposure was closely associated with HT-induced decline in the activities of several antioxidant enzymes. For various antioxidant enzymes, SOD and CAT were more susceptible to the ROS burst in rice anther induced by HT exposure than APX and POD, in which SOD and CAT activity in developing anther decreased significantly by HT exposure, whereas APX activity was relatively stable among different temperature regimes. HT-induced decrease in CAT activity was attributable to the suppressed transcript of OsCATB. This occurrence was strongly responsible for HT-induced increase in ROS level and oxidative-damage in rice anther, thereby it finally caused significant reduction in pollen viability and floret fertility for the rice plants exposed to HT during meiosis. Exogenous application of 1000 µM salicylic acid (SA) may alleviate HT-induced reduction in pollen viability and floret fertility, concomitantly with the increased CAT activity and reduced ROS level in rice anther.

Melatonin protects oocytes from MEHP exposure-induced meiosis defects in porcine.

In 2011, DEHP (plasticizer) was reported to illegally be added in food and beverage products in Taiwan, which caused great concerns about food safety worldwide. DHEP has multiple toxic effects to human and animals such as endocrine disruption, cardiotoxicity, reproductive function, and development defects. However, the toxic effects of DEHP on mammalian oocyte quality are still unclear. Since MEHP is the active metabolite of DEHP in vivo, in this study we used porcine oocyte as model to explore the effects of MEHP on oocyte maturation and we also studied the effects of melatonin administration on MEHP exposure-induced meiosis defects. Our results showed that exposure to MEHP significantly decreased the polar body extrusion rate in porcine oocytes. Further study showed that cell cycle progression, meiotic spindle organization, and actin assembly were all disturbed after MEHP exposure. Moreover, the DNA and histone methylation levels were also affected, showing with altered 5mC and H3K4me2 levels. These results indicated that MEHP affected porcine oocyte maturation, while MEHP exposure-induced meiotic defects were all remarkably ameliorated by the administration of melatonin in porcine oocytes. We further tried to explore the causes of MEHP toxicity on oocytes, and we found that MEHP exposure resulted in significant elevations of oxidative stress and induced early apoptosis as well as elevated autophagy, while melatonin administration could reduce these. Taken together, our results indicated that MEHP exposure induced deterioration of oocyte quality, whereas melatonin supplement showed amelioration on oocyte maturation through its rescue effects on oocyte oxidative stress-mediated apoptosis and autophagy.