Improving the meiotic competence of small antral follicle-derived porcine oocytes by using dibutyryl-cAMP and melatonin

OBJECTIVE

We increased the nuclear maturation rate of antral follicle derived oocytes by using a pre-in vitro maturation (IVM) culture system and improved the developmental potential of these porcine pathenotes by supplementing with melatonin. Furthermore, we investigated the expression patterns of genes involved in cumulus expansion (HAS2, PTGS2, TNFAIP6, and PTX3) derived from small and medium antral follicles before and after oocyte maturation.

METHODS

Only the cumulus oocyte-complexes (COCs) derived from small antral follicles were induced with [Pre-SF(+)hCG] or without [Pre-SF(-)hCG] the addition of human chorionic gonadotropin (hCG) during the last 7 h of the pre-IVM period before undergoing the regular culture system. The mature oocytes were investigated on embryonic development after parthenogenetic activation (PA). Melatonin (10-7 M) was supplemented during in vitro culture (IVC) to improve the developmental potential of these porcine pathenotes.

RESULTS

A pre-IVM culture system with hCG added during the last 7 h of the pre-IVM period [Pre-SF(+)hCG] effectively supported small antral follicle-derived oocytes and increased their nuclear maturation rate. The oocytes derived from medium antral follicles exhibited the highest nuclear maturation rate in a regular culture system. Compared with oocytes cultured in a regular culture system, those cultured in the pre-IVM culture system exhibited considerable overexpression of HAS2, PTGS2, and TNFAIP6. Porcine embryos treated with melatonin during IVC exhibited markedly improved quality and developmental competence after PA. Notably, melatonin supplementation during the IVM period can reduce and increase the levels of intracellular reactive oxygen species (ROS) and glutathione (GSH), respectively.

CONCLUSION

Our findings indicate that the Pre-SF(+)hCG culture system increases the nuclear maturation rate of small antral follicle-derived oocytes and the expression of genes involved in cumulus expansion. Melatonin supplementation during IVC may improve the quality and increase the blastocyst formation rate of porcine embryos. In addition, it can reduce and increase the levels of ROS and GSH, respectively, in mature oocytes, thus affecting subsequent embryos.

Forsythoside A protects against Zearalenone-induced cell damage in chicken embryonic fibroblasts via mitigation of endoplasmic reticulum stress

Zearalenone (ZEA) is a non-steroidal estrogenic mycotoxin that exerts its toxic effects through various damage mechanisms such as oxidative stress, endoplasmic reticulum stress (ERS), mitochondrial damage, cell cycle arrest, and apoptosis. At present, there are few studies on drugs that can rescue ZEA-induced chicken embryonic fibroblasts damage. Forsythoside A (FA) is one of effective ingredients of traditional Chinese medicine that plays a role in various biological functions, but its antitoxin research has not been investigated so far. In this study, in vitro experiments were carried out. Chicken embryo fibroblast (DF-1) cells was used as the research object to select the appropriate treatment concentration of ZEA and examined reactive oxygen species (ROS), mitochondrial membrane potential, ERS and apoptosis to investigate the effects and mechanisms of FA in alleviating ZEA-induced cytotoxicity in DF-1 cells. Our results showed that ZEA induced ERS and activated the unfolded protein response (UPR) leading to apoptosis, an apoptotic pathway characterized by overproduction of Lactate dehydrogenase (LDH), Caspase-3, and ROS and loss of mitochondrial membrane potential. We also demonstrated that FA help to prevent ERS and attenuated ZEA-induced apoptosis in DF-1 cells by reducing the level of ROS, downregulating GRP78, PERK, ATF4, ATF6, JNK, IRE1, ASK1, CHOP, BAX expression, and up-regulating Bcl-2 expression. Our results provide a basis for an in-depth study of the mechanism of toxic effects of ZEA on chicken cells and the means of detoxification, which has implications for the treatment of relevant avian diseases.

Reconsidering "low-dose"-Impacts of oral estrogen exposure during preimplantation embryo development

Perturbations of estrogen signaling during developmental stages of high plasticity may lead to adverse effects later in life. Endocrine-disrupting chemicals (EDC) are compounds that interfere with the endocrine system by particularly mimicking the action of endogenous estrogens as functional agonists or antagonists. EDCs compose synthetic and naturally occurring compounds discharged into the environment, which may be taken up via skin contact, inhalation, orally due to contaminated food or water, or via the placenta during in utero development. Although estrogens are efficiently metabolized by the liver, the role of circulating glucuro- and/or sulpho-conjugated estrogen metabolites in the body has not been fully addressed to date. Particularly, the role of intracellular cleavage to free functional estrogens could explain the hitherto unknown mode of action of adverse effects of EDC at very low concentrations currently considered safe. We summarize and discuss findings on estrogenic EDC with a focus on early embryonic development to highlight the need for reconsidering low dose effects of EDC.

Role of epigenetics in mycotoxin toxicity: a review

Mycotoxins can induce cell cycle disorders, cell proliferation, oxidative stress, and apoptosis through pathways such as those associated with MAPK, JAK2/STAT3, and Bcl-w/caspase-3, and cause reproductive toxicity, immunotoxicity, and genotoxicity. Previous studies have explored the toxicity mechanism of mycotoxins from the levels of DNA, RNA, and proteins, and proved that mycotoxins have epigenetic toxicity. To explore the toxic effects and mechanisms of these changes in mycotoxins, this paper summarizes the changes in DNA methylation, non-coding RNA, RNA and histone modification induced by several common mycotoxins (zearalenone, aflatoxin B1, ochratoxin A, deoxynivalenol, T-2 toxin, etc.) based on epigenetic studies. In addition, the roles of mycotoxin-induced epigenetic toxicity in germ cell maturation, embryonic development, and carcinogenesis are highlighted. In summary, this review provides theoretical support for a better understanding of the regulatory mechanism of mycotoxin epigenotoxicity and the diagnosis and treatment of diseases.

Resveratrol Protects against Zearalenone-Induced Mitochondrial Defects during Porcine Oocyte Maturation via PINK1/Parkin-Mediated Mitophagy

Mitochondria hold redox homeostasis and energy metabolism as a crucial factor during oocyte maturation, while the exposure of estrogenic mycotoxin zearalenone causes developmental incapacity in porcine oocyte. This study aimed to reveal a potential resistance of phytoalexin resveratrol against zearalenone during porcine oocyte maturation and whether its mechanism was related with PTEN-induced kinase 1 (PINK1)/Parkin-mediated mitophagy. Porcine oocytes were exposed to 20 μM zearalenone with or without 2 μM resveratrol during in vitro maturation. As for the results, zearalenone impaired ultrastructure of mitochondria, causing mitochondrial depolarization, oxidative stress, apoptosis and embryonic developmental incapacity, in which mitophagy was induced in response to mitochondrial dysfunction. Phytoalexin resveratrol enhanced mitophagy through PINK1/Parkin in zearalenone-exposed oocytes, manifesting as enhanced mitophagy flux, upregulated PINK1, Parkin, microtubule-associated protein light-chain 3 beta-II (LC3B-II) and downregulated substrates mitofusin 2 (MFN2), voltage-dependent anion channels 1 (VDAC1) and p62 expressions. Resveratrol redressed zearalenone-induced mitochondrial depolarization, oxidative stress and apoptosis, and accelerated mitochondrial DNA copy during maturation, which improved embryonic development. This study offered an antitoxin solution during porcine oocyte maturation and revealed the involvement of PINK1/Parkin-mediated mitophagy, in which resveratrol mitigated zearalenone-induced embryonic developmental incapacity.

Oxidative stress as a plausible mechanism for zearalenone to induce genome toxicity

Zearalenone (ZEN), a common non-steroidal estrogenic mycotoxin of the Fusarium genus, is one of the most frequent and powerful contaminant of grains and cereal products representing a serious threat for people and livestock health. In fact, ZEN causes cytotoxicity and genotoxicity in a variety of cell types at least in part through binding to estrogen receptors (ERs). The main pathways through which ZEN induces such effects remain, however, elusive. In particular, how the mycotoxin causes DNA damage, dysregulates DNA repair mechanisms, changes epigenome of targeted cells and, not least, affects chromatin conformation and non-coding RNA (ncRNA), is unclear. In the present paper, following extensive review of the literature about such ZEN effects and our own experience in studying the effects of this compound on reproductive processes, we propose that increased production of reactive oxygen species (ROS) and consequently oxidative stress (OS) are central in ZEN genotoxicity. Besides to shed light on the action mechanisms of the mycotoxin, this notion might help to develop effective strategies to counteract its deleterious biological effects.

Involvement of PINK1/Parkin-mediated mitophagy in mitochondrial functional disruption under oxidative stress in vitrified porcine oocytes

Vitrification is an effective technique for fertility preservation, but is known to lead to mitochondrial dysfunction in porcine oocytes. Mitophagy is induced to rebalance mitochondrial function, a process in which reactive oxygen species (ROS) plays a role. In this study, vitrified-warmed porcine oocytes were incubated for 4 h with the oxidant AAPH or antioxidant α-tocopherol to alter ROS levels. A series of tests suggested that vitrification damaged mitochondrial structure and caused dysfunction, including blurred mitochondrial cristae, decreased mitochondrial membrane potential, decreased mtDNA copy number and increased ROS generation. This dysfunction resulted in mitophagy and the loss of embryonic developmental potential. Incubation with AAPH or α-tocopherol altered mitochondrial function and mitophagy flux status in vitrified oocytes. The PINK1/Parkin pathway was involved in oxidative stress regulation in vitrified oocytes. Under AAPH-induced oxidative stress, increased fluorescence intensity of Parkin, increased expression of PINK1, Parkin, and LC3B-II, and decreased expression of MFN2 and p62 were observed, whereas the opposite effects were induced under α-tocopherol treatment. The inhibition of ROS by α-tocopherol benefitted mitochondrial homeostasis and alleviated PINK1/Parkin-mediated mitophagy, resulting in the recovery of embryonic developmental potential in vitrified porcine oocytes. Therefore, this study provides a new mechanism for the application of antioxidants to aid the cryopreservation of porcine oocytes.

Mitophagy is involved in the mitochondrial dysfunction of vitrified porcine oocytes

Mitochondrial dysfunction is considered a crucial factor aggravating oocyte viability after vitrification-warming. To clarify the role of mitophagy in mitochondrial extinction of vitrified porcine oocytes, mitochondrial function, ultrastructural characteristics, mitochondria-lysosomes colocalization, and mitophagic proteins were detected with or without chloroquine (CQ) treatment. The results showed that vitrification caused mitochondrial dysfunction, including increasing reactive oxygen species production, decreasing mitochondrial membrane potential, and mitochondrial DNA copy number. Damaged mitochondrial cristae and mitophagosomes were observed in vitrified oocytes. A highly fused fluorescence distribution of mitochondria and lysosomes was also observed. In the detection of mitophagic flux, mitophagy was demonstrated as increasing fluorescence aggregation of microtubule-associated protein light chain 3B (LC3B), enhanced colocalization between LC3B, and voltage-dependent anion channels 1 (VDAC1), and upregulated LC3B-II/I protein expression ratio. CQ inhibited the degradation of mitophagosomes in vitrified oocytes, manifested as decreased mitochondria-lysosomes colocalization, increased fluorescence fraction of VDAC1 overlapping LC3B, increased LC3B-II/I protein expression ratio, and p62 accumulation. The inhibition of mitophagosomes degradation by CQ aggravated mitochondrial dysfunction, including increased oxidative damage, reduced mitochondrial function, and further led to loss of oocyte viability and developmental potentiality. In conclusion, mitophagy is involved in the regulation of mitochondrial function during porcine oocyte vitrification.

Impact of Fusarium-Derived Mycoestrogens on Female Reproduction: A Systematic Review

Contamination of the world’s food supply and animal feed with mycotoxins is a growing concern as global temperatures rise and promote the growth of fungus. Zearalenone (ZEN), an estrogenic mycotoxin produced by Fusarium fungi, is a common contaminant of cereal grains and has also been detected at lower levels in meat, milk, and spices. ZEN’s synthetic derivative, zeranol, is used as a growth promoter in United States (US) and Canadian beef production. Experimental research suggests that ZEN and zeranol disrupt the endocrine and reproductive systems, leading to infertility, polycystic ovarian syndrome-like phenotypes, pregnancy loss, and low birth weight. With widespread human dietary exposure and growing experimental evidence of endocrine-disrupting properties, a comprehensive review of the impact of ZEN, zeranol, and their metabolites on the female reproductive system is warranted. The objective of this systematic review was to summarize the in vitro, in vivo, and epidemiological literature and evaluate the potential impact of ZEN, zeranol, and their metabolites (commonly referred to as mycoestrogens) on female reproductive outcomes. We conducted a systematic review (PROSPERO registration CRD42020166469) of the literature (2000–2020) following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The data sources were primary literature published in English obtained from searching PubMed, Web of Science, and Scopus. The ToxR tool was applied to assess risk of bias. In vitro and in vivo studies (n = 104) were identified and, overall, evidence consistently supported adverse effects of mycoestrogens on physiological processes, organs, and tissues associated with female reproduction. In non-pregnant animals, mycoestrogens alter follicular profiles in the ovary, disrupt estrus cycling, and increase myometrium thickness. Furthermore, during pregnancy, mycoestrogen exposure contributes to placental hemorrhage, stillbirth, and impaired fetal growth. No epidemiological studies fitting the inclusion criteria were identified.

Zearalenone Induces Apoptosis and Cytoprotective Autophagy in Chicken Granulosa Cells by PI3K-AKT-mTOR and MAPK Signaling Pathways

Zearalenone (ZEA) is a nonsteroidal estrogenic mycotoxin found in several food commodities worldwide. ZEA causes reproductive disorders, genotoxicity, and testicular toxicity in animals. However, little is known about the functions of apoptosis and autophagy after exposure to ZEA in granulosa cells. This study investigated the effects of ZEA on chicken granulosa cells. The results show that ZEA at different doses significantly inhibited the growth of chicken granulosa cells by inducing apoptosis. ZEA treatment up-regulated Bax and downregulated Bcl-2 expression, promoted cytochrome c release into the cytosol, and triggered mitochondria-mediated apoptosis. Consequently, caspase-9 and downstream effector caspase-3 were activated, resulting in chicken granulosa cells apoptosis. ZEA treatment also upregulated LC3-II and Beclin-1 expression, suggesting that ZEA induced a high level of autophagy. Pretreatment with chloroquine (an autophagy inhibitor) and rapamycin (an autophagy inducer) increased and decreased the rate of apoptosis, respectively, in contrast with other ZEA-treated groups. Autophagy delayed apoptosis in the ZEA-treated cells. Therefore, autophagy may prevent cells from undergoing apoptosis by reducing ZEA-induced cytotoxicity. In addition, our results further show that the autophagy was stimulated by ZEA through PI3K-AKT-mTOR and MAPK signaling pathways in chicken granulosa cells.

Modified hydrated sodium calcium aluminosilicate-supplemented diet protects porcine oocyte quality from zearalenone toxicity

Zearalenone (ZEN) is one of the most common mycotoxins produced by fungus in contaminated feed. ZEN has multiple toxicities, including reproductive toxicity of domestic animals, particularly pigs. However, studies on the effects of ZEN on ovary/oocytes have been primarily based on in vitro experiments, and there is still no evidence from porcine in vivo models due to multiple limitations. Moreover, no report has investigated the effect of hydrated sodium calcium aluminosilicate (HSCAS) as a supplement on pig oocyte quality. In the present study, we fed pigs a 1.0 mg/kg ZEN-contaminated diet for 10 days. The results showed that pigs fed ZEN presented reduced oocyte-cumulus cell interactions, an increase in the number of denuded oocytes in ovaries, a decrease in the number of oocytes in each ovary, and an increase in the oocyte death rate. Oocytes from ZEN-exposed pigs exhibited a delayed cell cycle and abnormal cytoskeletal dynamics during meiotic maturation, which could be due to oxidative stress-induced autophagy. Moreover, we also show that supplementing the ZEN-contaminated diet with modified HSCAS effectively protected porcine oocyte quality. Taken together, our study provides in vivo data demonstrating the protective effects of HSCAS against ZEN toxicity in porcine oocytes.

Differential susceptibility to endocrine disruptor-induced epimutagenesis

There is now considerable evidence indicating the potential for endocrine disrupting chemicals to alter the epigenome and for subsets of these epigenomic changes or "epimutations" to be heritably transmitted to offspring in subsequent generations. While there have been many studies indicating how exposure to endocrine disrupting chemicals can disrupt various organs associated with the body's endocrine systems, there is relatively limited information regarding the relative susceptibility of different specific organs, tissues, or cell types to endocrine disrupting chemical-induced epimutagenesis. Here we review available information about different organs, tissues, cell types, and/or cell lines which have been shown to be susceptible to specific endocrine disrupting chemical-induced epimutations. In addition, we discuss possible mechanisms that may be involved, or impacted by this tissue- or cell type-specific, differential susceptibility to different endocrine disrupting chemicals. Finally, we summarize available information indicating that certain periods of development display elevated susceptibility to endocrine disrupting chemical exposure and we describe how this may affect the extent to which germline epimutations can be transmitted inter- or transgenerationally. We conclude that cell type-specific differential susceptibility to endocrine disrupting chemical-induced epimutagenesis is likely to directly impact the extent to, or manner in, which endocrine disrupting chemical exposure initially induces epigenetic changes to DNA methylation and/or histone modifications, and how these endocrine disrupting chemical-induced epimutations can then subsequently impact gene expression, potentially leading to the development of heritable disease states.

Responses of oxidative stress and inflammatory cytokines after zearalenone exposure in human kidney cells

Zearalenone is a mycotoxin widely found worldwide that is produced by several fungal species. Due to its similarity to estradiol, it has been shown to have toxic effects on the reproductive system. Although various animal studies have been conducted to investigate the toxic effects of zearalenone, the mechanisms of toxicity have not been fully elucidated. The aim of the study was to investigate the dose-dependent toxic effects of zearalenone exposure in human kidney cells. The half-maximal inhibitory concentration values of zearalenone in HK-2 cells were found to be 133.42 and 101.74 µM in MTT- and NRU-tests, respectively. Zearalenone exposure at concentrations of 1, 10 and 50 µM decreased cell proliferation by 2.1, 11.07 and 24.34%, respectively. Reactive oxygen species levels increased significantly in a dose-dependent manner. A significant increase was observed in the expressions of MGMT, α-GST, Hsp70 and HO-1 genes, which are associated with oxidative damage, while a significant decrease in L-Fabp gene expression was observed. Moreover, zearalenone increased gene expression of inflammatory cytokines, such as IL-6, IL-8, TNFα and MAPK8. Significant increases were observed at the level of global DNA methylation and expression of DNMT1 in all exposure groups. These results indicate that changes in DNA methylation and oxidative damage may play an important role in the toxicity of zearalenone.

Autophagy in Female Fertility: A Role in Oxidative Stress and Aging

Significance: The precipitous age-related decline in female fertility is intimately associated with a reduction in both the quantity and quality of the germline (oocytes). Although complex etiologies undoubtedly contribute to the deterioration of oocyte quality, increasing attention has focused on the pervasive impact of oxidative stress. Indeed, the prolonged lifespan of the meiotically arrested oocyte places this cell at heightened risk of oxidative lesions, which commonly manifest in dysregulation of protein homeostasis (proteostasis). Although oocytes are able to mitigate this threat via the mobilization of a sophisticated network of surveillance, repair, and proteolytic pathways, these defenses are themselves prone to age-related defects, reducing their capacity to eliminate oxidatively damaged proteins. Recent Advances: Here, we give consideration to the quality control mechanisms identified within the ovary that afford protection to the female germline. Our primary focus is to review recent advances in our understanding of the autophagy pathway and its contribution to promoting oocyte longevity and modulating pathophysiological responses to oxidative stress. In addition, we explore the therapeutic potential of emerging strategies to fortify autophagic activity. Critical Issues: The complex interplay of oxidative stress and autophagy has yet to be fully elucidated within the context of the aging oocyte and surrounding ovarian environment. Future Directions: Emerging evidence provides a strong impetus to resolve the causal link between autophagy and oxidative stress-driven pathologies in the aging oocyte. Such research may ultimately inform novel therapeutic strategies to combat the age-related loss of female fertility via fortification of intrinsic autophagic activity.

Evaluation of the epigenetic alterations and gene expression levels of HepG2 cells exposed to zearalenone and α-zearalenol

Zearalenone, produced by various Fusarium species, is a non-steroidal estrogenic mycotoxin that contaminates cereals, resulting in adverse effects on human health. We investigated the effects of zearalenone and its metabolite alpha zearalenol on epigenetic modifications and its relationship with metabolic pathways in human hepatocellular carcinoma cells following 24 h of exposure. Zearalenone and alpha zearalenol at the concentrations of 1, 10 and 50 μM significantly increased global levels of DNA methylation and global histone modifications (H3K27me3, H3K9me3, H3K9ac). Expression levels of the chromatin modifying enzymes EHMT2, ESCO1, HAT1, KAT2B, PRMT6 and SETD8 were upregulated by 50 μM of zearalenone exposure using PCR arrays, consistent with the results of global histone modifications. Zearalenone and alpha zearalenol also changed expression levels of the AhR, LXRα, PPARα, PPARɣ, L-fabp, LDLR, Glut2, Akt1 and HK2 genes, which are related to nuclear receptors and metabolic pathways. PPARɣ, a key regulator of lipid metabolism, was selected from among these genes for further analysis. The PPARɣ promoter reduced methylation significantly following zearalenone exposure. Taken together, the epigenetic mechanisms of DNA methylation and histone modifications may be key mechanisms in zearalenone toxicity. Furthermore, effects of zearalenone in metabolic pathways could be mediated by epigenetic modifications.

Alterations in global DNA methylation and metabolism-related genes caused by zearalenone in MCF7 and MCF10F cells

Zearalenone (ZEN) is a non-steroidal estrogenic mycotoxin produced by Fusarium fungi. ZEN has endocrine disruptor effects and could impair the hormonal balance. Here, we aimed at investigating possible effects of ZEN on metabolism-related pathways and its relation to epigenetic mechanisms in breast adenocarcinoma (MCF7) and breast epithelial (MCF10F) cells. Using the MTT and neutral red uptake (NRU) cell viability tests, IC₅₀ values of ZEN after 24 h were found to be 191 μmol/L and 92.6 μmol/L in MCF7 cells and 67.4 μmol/L and 79.5 μmol/L in MCF10F cells. A significant increase on global levels of 5-methylcytosine (5-mC%) was observed for MCF7 cells, correlating with the increased expression of DNA methyltransferases. No alterations were observed on levels of 5-mC% and expression of DNA methyltransferases for MCF10F cells. Further, at least threefold upregulation compared to control was observed for several genes related to nuclear receptors and metabolism in MCF7 cells, while some of these genes were downregulated in MCF10F cells. The most notably altered genes were IGF1, HK2, PXR, and PPARγ. We suggested that ZEN could alter levels of global DNA methylation and impair metabolism-related pathways.

Protective Effects of Melatonin Against Zearalenone Toxicity on Porcine Embryos in vitro

Zearalenone (ZEA) is an estrogenic mycotoxin produced by Fusarium fungi commonly found in corn, wheat, and other cereals which can infect food and feed commodities, and ZEA mainly has reproductive toxicity which causes widely reproductive disorders in pigs and other animals. However, the toxicity and the functional ways of ZEA on early embryo development is still unclear. In present study we showed that exposure to ZEA (10 μM) significantly decreased the 2-cell and blastocyst developmental rate in porcine early embryos in vitro. ZEA treatment resulted in the occurrence of oxidative stress, showing with increased reactive oxygen species (ROS) level, following with aberrant mitochondrial distribution. Moreover, we found positive signals of γH2A.X in the ZEA-treated embryos, indicating that ZEA induced DNA damage, and the increased autophagy confirmed this. These results suggested that ZEA induced oxidative stress, which further caused mitochondria dysfunction and DNA damage on early embryonic development. We next investigated the effects of melatonin on the ZEA-treated embryo development, and we found that melatonin supplementation could significantly ameliorate ZEA-induced oxidative stress, aberrant mitochondria distribution and DNA damage. In all, our results showed that ZEA was toxic for porcine embryos cultured in vitro and melatonin supplementation could protect their development from the effects of ZEA.

Autophagy is required for proper meiosis of porcine oocytes maturing in vitro

Autophagy is an essential cellular mechanism that degrades cytoplasmic proteins and organelles to recycle their components; however, the contribution of autophagy during meiosis has not been studied in porcine oocytes maturing in vitro. In this study, we observed that the autophagy-related gene, LC3, was expressed in porcine oocytes during maturation for 44 h in vitro. Knockdown of the autophagy-related gene, BECN1, reduced both BECN1 and LC3 protein expression levels. Moreover, BECN1 knockdown and treatment with the autophagy inhibitor, LY294002, during maturation of porcine oocytes in vitro impaired polar body extrusion, disturbed mitochondrial function, triggered the DNA damage response, and induced early apoptosis in porcine oocytes. Autophagy inhibition during oocyte maturation also impaired the further developmental potential of porcine oocytes. These results indicate that autophagy is required for the in vitro maturation of porcine oocytes.

Sodium fluoride exposure exerts toxic effects on porcine oocyte maturation

Excessive long-term fluoride intake is associated with several health problems, including infertility. However, limited information is available on the toxic effects of fluoride exposure on the female reproductive system, especially oocyte maturation. In this study, we investigated the toxic effect of sodium fluoride (NaF) exposure on porcine oocyte maturation and its possible underlying mechanisms. Our results showed that NaF exposure during porcine oocyte maturation inhibited cumulus cell expansion and impaired polar body extrusion. Cell cycle analysis showed that NaF exposure blocked meiotic resumption, disturbed spindle dynamics, disrupted chromosome separation, and increased aneuploidy in porcine oocytes. Moreover, NaF exposure disturbed mitochondrial function, triggered DNA damage response, and induced early apoptosis in porcine oocytes. NaF exposure also induced oxidative stress, decreased GSH level, and increased cathepsin B activity in and impaired the further development potential of porcine oocytes, as indicated by a decrease in blastocyst formation rate, increase in apoptosis, and inhibition of cell proliferation. Together, these results indicate that NaF exposure impairs the maturation capacity of porcine oocytes by inhibiting cumulus cell expansion, disturbing cytoskeletal dynamics, and blocking nuclear and cytoplasmic maturation, thus decreasing the quality and affecting the subsequent embryonic development potential of porcine oocytes.

Trichothecenes: immunomodulatory effects, mechanisms, and anti-cancer potential

Paradoxically, trichothecenes have both immunosuppressive and immunostimulatory effects. The underlying mechanisms have not been fully explored. Early studies show that dose, exposure timing, and the time at which immune function is assessed influence whether trichothecenes act in an immunosuppressive or immunostimulatory fashion. Recent studies suggest that the immunomodulatory function of trichothecenes is also actively shaped by competing cell-survival and death-signaling pathways. Autophagy may also promote trichothecene immunosuppression, although the mechanism may be complicated. Moreover, trichothecenes may generate an "immune evasion" milieu that allows pathogens to escape host and vaccine immune defenses. Some trichothecenes, especially macrocyclic trichothecenes, also potently kill cancer cells. T-2 toxin conjugated with anti-cancer monoclonal antibodies significantly suppresses the growth of thymoma EL-4 cells and colon cancer cells. The type B trichothecene diacetoxyscirpenol specifically inhibits the tumor-promoting factor HIF-1 in cancer cells under hypoxic conditions. Trichothecin markedly inhibits the growth of multiple cancer cells with constitutively activated NF-κB. The type D macrocyclic toxin Verrucarin A is also a promising therapeutic candidate for leukemia, breast cancer, prostate cancer, and pancreatic cancer. The anti-cancer activities of trichothecenes have not been comprehensively summarized. Here, we first summarize the data on the immunomodulatory effects of trichothecenes and discuss recent studies that shed light on the underlying cellular and molecular mechanisms. These mechanisms include autophagy and major signaling pathways and their crosstalk. Second, the anti-cancer potential of trichothecenes and the underlying mechanisms will be discussed. We hope that this review will show how trichothecene bioactivities can be exploited to generate therapies against pathogens and cancer.

Melatonin enhances the developmental competence of porcine somatic cell nuclear transfer embryos by preventing DNA damage induced by oxidative stress

Melatonin has antioxidant and scavenger effects in the cellular antioxidant system. This research investigated the protective effects and underlying mechanisms of melatonin action in porcine somatic cell nuclear transfer (SCNT) embryos. The results suggested that the developmental competence of porcine SCNT embryos was considerably enhanced after melatonin treatment. In addition, melatonin attenuated the increase in reactive oxygen species levels induced by oxidative stress, the decrease in glutathione levels, and the mitochondrial dysfunction. Importantly, melatonin inhibited phospho-histone H2A.X (γH2A.X) expression and comet tail formation, suggesting that γH2A.X prevents oxidative stress-induced DNA damage. The expression of genes involved in homologous recombination and non-homologous end-joining pathways for the repair of double-stranded breaks (DSB) was reduced upon melatonin treatment in porcine SCNT embryos at day 5 of development under oxidative stress condition. These results indicated that melatonin promoted porcine SCNT embryo development by preventing oxidative stress-induced DNA damage via quenching of free radical formation. Our results revealed a previously unrecognized regulatory effect of melatonin in response to oxidative stress and DNA damage. This evidence provides a novel mechanism for the improvement in SCNT embryo development associated with exposure to melatonin.

The protective effect of resveratrol against cytotoxicity induced by mycotoxin, zearalenone

Zearalenone (ZEA), a non-steroidal estrogenic mycotoxin, is widely present in cereals and agricultural products.