Effects of Ochratoxin A exposure on DNA damage in porcine granulosa cells in vitro

Circular RNA WRNIP1 activates the PI3K-AKT and ERK1/2 signaling pathways by binding to miR-129-5p/IGF2 axis and facilitates ovarian follicle development in chickens

The healthy and orderly development of ovarian follicles is the basic premise to maintain normal and continuous egg production of chickens. Emerging researches continue to reveal the crucial functions of circular RNAs (circRNAs) involved in follicle development. In the present study, a novel circular RNA WRNIP1 (circWRNIP1) with higher abundance in healthy follicles than in atretic follicles was identified, suggesting its important regulatory role in follicle selection and maturation. In this study, we demonstrate that circWRNIP1 promotes chicken ovarian follicle development by enhancing granulosa cell proliferation and inhibiting apoptosis. Furthermore, we validated the targeting relationships between circWRNIP1 and miR-129-5p, as well as between miR-129-5p and IGF2. Mechanistically, through co-transfection experiments, we show that circWRNIP1 activates the PI3K-AKT and ERK1/2 signaling pathways via the miR-129-5p/IGF2 axis. The present study provides new insights into the downstream molecular mechanism of circRNAs regulating follicle development, and is expected to provide reliable targets for the subsequent establishment of new molecular breeding strategies.

Mycotoxin toxicity and its alleviation strategy on female mammalian reproduction and fertility

BACKGROUND

Mycotoxin, a secondary metabolite of fungus, found worldwide and concerning in crops and food, causes multiple acute and chronic toxicities. Its toxic profile includes hepatotoxicity, carcinogenicity, teratogenicity, estrogenicity, immunotoxicity, and neurotoxicity, leading to deleterious impact on human and animal health. Emerging evidence suggests that it adversely affects perinatal health and progeny by its ability to cross placental barriers.

AIM OF REVIEW

Due to its wide occurrence and potential toxicity on reproductive health, it is essential to understand the mechanisms of mycotoxin-related reproductive toxicity. This review summarizes the toxicities and mechanisms of mycotoxin on maternal and offspring reproduction among mammalian species. Approaches for effective mycotoxin alleviation are also discussed, providing strategies against mycotoxin contamination.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The profound mycotoxin toxicities in female mammalian reproduction affect follicle assembly, embryo development, and fetus growth, thereby decreasing offspring fertility. Factors from endocrine system such as hypothalamic-pituitary-gonadal axis and gut-ovarian axis, placenta ABC transporters, organelle and cytoskeleton dynamics, cell cycle control, genomic stability, and redox homeostasis are found to be closely related to mycotoxin toxicities. Approaches from physical, chemical, biological, and supplementation of natural antioxidants are discussed for the mycotoxin elimination, while their applications are not widespread. Available ways for mycotoxin and its toxicities alleviation need further study. Since a species-, time-, and dose-specific response might exist in mycotoxin toxicities, more consideration should be given to the protocols for mycotoxin toxicity studies, such as experimental animal models, exposure duration, and dosage. Specific mechanism for mycotoxin, especially form a molecular biology perspective, could be investigated with multi-omics technologies and advanced imaging techniques. Mass spectrometry with algorithms may provide more accurate exposure assessments, and it may be further helpful to identify the high-risk individuals in the future.

Detoxification of Selenium Yeast on Mycotoxins and Heavy Metals: a Review

Mycotoxins are secondary metabolites produced by specific fungi. More than 400 different mycotoxins are known in the world, and the concentration of these toxins in food and feed often exceeds the acceptable limit, thus causing serious harm to animals and human body. At the same time, modern industrial agriculture will also bring a lot of environmental pollution in the development process, including the increase of heavy metal content, and often the clinical symptoms of low/medium level chronic heavy metal poisoning are not obvious, thus delaying the best treatment opportunity. However, the traditional ways of detoxification cannot completely eliminate the adverse effects of these toxins on the body, and sometimes bring some side effects, so it is essential to find a new type of safe antidote. Trace element selenium is among the essential mineral nutrient elements of human and animal bodies, which can effectively remove excessive free radicals and reactive oxygen species in the body, and has the effects of antioxidant, resisting stress, and improving body immunity. Selenium is common in nature in inorganic selenium and organic selenium. In previous studies, it was found that the use of inorganic selenium (sodium selenite) can play a certain protective role against mycotoxins and heavy metal poisoning. However, while it plays the role of antioxidant, it will also have adverse effects on the body. Therefore, it was found in the latest study that selenium yeast could not only replace the protective effect of sodium selenite on mycotoxins and heavy metal poisoning, but also improve the immunity of the body. Selenium yeast is an organic selenium source with high activity and low toxicity, which is produced by selenium relying on the cell protein structure of growing yeast. It not only has high absorption rate, but also can be stored in the body after meeting the physiological needs of the body for selenium, so as to avoid selenium deficiency again in the short term. However, few of these studies can clearly reveal the protective mechanism of yeast selenium. In this paper, the detoxification mechanism of selenium yeast on mycotoxins and heavy metal poisoning was reviewed, which provided some theoretical support for further understanding of the biological function of selenium yeast and its replacement for inorganic selenium. The conclusions suggest that selenium yeast can effectively alleviate the oxidative damage by regulating different signaling pathways, improving the activity of antioxidant enzymes, reversing the content of inflammatory factors, regulating the protein expression of apoptosis-related genes, and reducing the accumulation of mycotoxins and heavy metals in the body.

Mycotoxins Have a Potential of Inducing Cell Senescence: A New Understanding of Mycotoxin Immunotoxicity

Mycotoxins result in immune dysfunction and cause immune diseases in animals and humans. However, the mechanisms of immunotoxicity involved in mycotoxins have not been fully explored, and emerging evidence suggests that these toxins may promote their immunotoxicity via cellular senescence. Mycotoxins induce cell senescence after DNA damage, and activate signaling via the NF-κB and JNK pathways to promote the secretion of senescence-associated secretory phenotype (SASP) cytokines including IL-6, IL-8, and TNF-α. DNA damage can also over-activate or cleave poly (ADP-ribose) polymerase-1 (PARP-1), increase the expression of cell cycle inhibitory proteins p21, and p53, and induce cell cycle arrest and then senescence. These senescent cells further down-regulate proliferation-related genes and overexpress inflammatory factors resulting in chronic inflammation and eventual immune exhaustion. Here we review the underlying mechanisms by which mycotoxins trigger cell senescence and the potential roles of SASP and PARP in these pathways. This work will help to further understand the mechanisms of immunotoxicity involved in mycotoxins.

Mycotoxins and cellular senescence: the impact of oxidative stress, hypoxia, and immunosuppression

Mycotoxins induce oxidative stress, hypoxia, and cause immunosuppressive effects. Moreover, emerging evidence show that mycotoxins have a potential of inducing cellular senescence, which are involved in their immunomodulatory effects. Mycotoxins upregulate the expression of senescence markers γ-H2AX, senescence-associated β-galactosidase, p53, p16, and senescence-associated secretory phenotype (SASP) inflammatory factors. Moreover, mycotoxins cause senescence-associated cell cycle arrest by diminishing cyclin D₁ and Cdk4 pathways, as well as increasing the expression of p53, p21, and CDK6. Mycotoxins may induce cellular senescence by activating reactive oxygen species (ROS)-induced oxidative stress. In addition, hypoxia acts as a double-edged sword on cell senescence; it could both act as the stress-induced senescence and also hinder the onset of cellular senescence. The SASP inflammatory factors have the ability to induce an immunosuppressive environment, while mycotoxins directly cause immunosuppression. Therefore, there is a potential relationship between mycotoxins and cellular senescence that synergistically cause immunosuppression. However, most of the current studies have involved the effect of mycotoxins on cell cycle arrest, but only limited in-depth research has been carried out to link the occurrence of this condition (cell cycle arrest) with cellular senescence.

Antioxidant and antiapoptotic effects of quercetin against ochratoxin A-induced nephrotoxicity in broiler chickens

The mycotoxin ochratoxin A (OTA) is produced by the fungi Aspergillus and Penicillium. The flavonoid quercetin (QUE) is distinguished by its antioxidant, anti-inflammatory, and antiapoptotic properties. This study was designed to determine whether QUE can protect broiler chickens against OTA-induced nephrotoxicity. Forty broiler chicks were randomly divided into four equal groups: control, OTA, QUE, and OTA + QUE. For 6 weeks, OTA (0.5 mg/kg) and/or QUE (0.5 g/kg) were added to the diet of chickens. The results demonstrated that OTA exposure increased serum levels of creatinine, uric acid, and blood urea nitrogen. OTA exposure also increased renal malondialdehyde content but decreased renal antioxidants. OTA-exposed chickens exhibited multiple pathological kidney lesions. Moreover, OTA exposure induced apoptosis in renal tissue, which was manifested by the up-regulation of proapoptotic genes and down-regulation of antiapoptotic genes via the suppression of the PI3K/AKT pathway. In addition, coadministration of QUE and OTA mitigated most of these nephrotoxic effects.

Maternal ochratoxin A exposure impairs meiosis progression and primordial follicle formation of F1 offspring

Ochratoxin A (OTA), a mycotoxin produced by Aspergillus and Penicillium fungi, widely contaminates feed, food and their raw materials. OTA has been proved to have hepatotoxicity and nephrotoxicity. Its reproductive toxicity needs to be further explored. We found that OTA inhibited the progression of meiosis, keeping more germ cells at leptotene and zygotene. Furthermore, OTA impaired primordial follicle formation, keeping more germ cells in cysts. Increased γH2AX suggested that DNA damage occurred both at the stages of meiosis and primordial follicle formation. The expression of RAD51 increased with the concentration of OTA at the stage of meiosis, while decreased later, suggesting the activated DNA repair induced by DNA damage then inhibited by persistent and excessive stress of DNA damage, which further induced apoptosis. DEGs caused by OTA were also mainly enriched in DNA damage and repair through RNA-seq analysis. Higher level of reactive oxygen species (ROS) and increased degree of oxidative damage marker 8-OHdG were both found in the ovaries exposed to OTA. We concluded that maternal OTA exposure affected meiosis progression and primordial follicle formation via oxidative damage and DNA repair. Clarification of the mechanism of OTA will contribute to the development of more effective detoxification strategies.

N-3 polyunsaturated fatty acids prevent the D-galactose-induced cognitive impairment by up-regulating the levels of 5-hydroxymethylcytosine in the mouse brain

Decreased 5-hydroxymethylcytosine (5hmC) levels caused by mitochondrial dysfunction in the brain are closely associated with the development of neurodegenerative disease. It has been reported that n-3 polyunsaturated fatty acids (PUFAs) prevent cognitive dysfunction by improving mitochondrial function in the brain. However, whether n-3 PUFA prevents cognitive dysfunction by increasing the levels of 5hmC in the brain is undisclosed. Mice were randomly divided into six groups (n = 10), injected with D-galactose (200 mg kg-1 day-1) for the model group and given different oils [0.1 mL per 10 g body weight per day, fish oil (FO), peony seed oil (PSO), corn oil (CO) and olive oil (OO)] for the prevention groups, and injected with the same dose of saline for the normal control group (NC) for 10 weeks, respectively. Peony seed oil and fish oil have shown preventive effects on D-galactose-induced cognitive dysfunction in behavioral tests. The content of docosahexaenoic acid (C22:6n-3, DHA content) in the brain was significantly higher in FO and PSO groups than in the other groups. Brain oxidative stress and neuronal apoptosis were significantly lower in PSO and FO groups than in the other groups. RNA-seq results showed that the different genes between PSO and FO compared with the model group were involved in the DNA demethylation process and the 5-methylcytosine metabolic process. The brain levels of 5hmC and the ten-eleven translocation family of dioxygenases (TETs) were significantly higher in FO and PSO groups compared with the model group, as analyzed by dot-blot and western blot. In conclusion, peony seed oil and fish oil increased the C22:6n-3 content, which activated the TET activity, led to up-regulation of the 5hmc level, resulted in inhibition of neuronal apoptosis, and then improved the cognitive function in D-gal-induced mice.

Ochratoxin A induces human kidney tubular epithelial cell apoptosis through regulating lipid raft/PTEN/AKT signaling pathway

Ochratoxin A (OTA) is a fungal toxin that causes serious threat to human health. OTA could lead to the injury of various tissues, especially kidney injury. However, the toxic effects of OTA on human kidney tubular epithelial cell (HK-2) and the possible mechanism remains poorly understood. This study was to investigate the toxic effects of OTA on HK-2 and elucidate the molecular mechanism. HK-2 cells were treated OTA to evaluate the effect of OTA on cell viability and apoptosis. OTA inhibited the growth of HK-2 in a concentration-dependent manner. With the concentration increased, OTA significantly lead to the apoptosis of HK-2. OTA could increase the levels of reactive oxygen species (ROS) and Malondialdehyde (MDA). Superoxide dismutase (SOD) and glutathione (GSH) activities were decreased by OTA. Furthermore, OTA increased Caspase-3 and Bax expression and decreased BCL2 expression. Compared to the control group, the expression of PTEN was increased and the expression of PI3K and AKT were decreased in OTA treated groups. In addition, we found OTA could disrupt the formation of lipid raft by attenuating sphingomyelin and cholesterol levels. In conclusion, our results indicated that OTA induces apoptosis in HK-2 through regulating PTEN/AKT signaling pathway via disrupting lipid raft formation.

Reactive oxygen species-evoked genotoxic stress mediates arsenic-induced suppression of male germ cell proliferation and decline in sperm quality

This study aimed to investigate whether genotoxic stress mediates arsenic (As)-induced decline in sperm quality. Mice drank ultrapure water containing NaAsO₂ (15 mg/L) for 70 days. The mature seminiferous tubules and epididymal sperm count were reduced in As-exposed mice. Cell proliferation, determined by immunostaining with Ki67, was suppressed in As-exposed seminiferous tubules and GC-1 cells. PCNA, a proliferation marker, was reduced in As-exposed mouse testes. Cell growth index was decreased in As-exposed GC-1 cells. Flow analysis showed that As-exposed GC-1 cells were retarded at G2/M phase. CDK1 and cyclin B1 were reduced in As-exposed GC-1 cells and mouse testes. Additional experiment revealed that p-ATR, a marker of genotoxic stress, was elevated in As-exposed mouse testes and GC-1 cells. Accordingly, p-p53 and p21, two downstream molecules of ATR, were increased in As-exposed GC-1 cells. Excess reactive oxygen species (ROS), measured by immunofluorescence, and DNA-strand break, determined by Comet assay, were observed in As-exposed GC-1 cells. γH2AX, a marker of DNA-strand break, was elevated in As-exposed seminiferous tubules and GC-1 cells. NAC alleviated As-evoked DNA damage, genotoxic stress, cell proliferation inhibition and sperm count reduction. In conclusion, ROS-evoked genotoxic stress mediates As-induced germ cell proliferation inhibition and decline in sperm quality.