Toxicity And Mechanism Of Nonylphenol On Oocyte Quality

At present,human infertility and reproductive obstacles in livestock production are quite serious problems,and environmental pollution is one of the important factors that cause this problem.Environmental endocrine disruptors,as a kind of emerging pollutants,have been widely detected in global sewage and sediment,which has brought serious threats to the environment.Endocrine disruptors,also known as environmental estrogens,can interfere with the synthesis,secretion,transport,combination,reaction and metabolism of hormones in human or animals through enrichment in the organism,and affect the health of the organism as an exogenous chemical substance.Endocrine disruptors can cause reproductive disorders in animals,and even induce obesity,diabetes,breast cancer,infertility and other diseases.As one of the environmental endocrine disruptors,nonylphenol is mainly used in the production of surfactants,lubricating oil additives and pesticide emulsifiers in daily life.It is widely found in sewage and sludge,and it is difficult to degrade naturally so that it can accumulate in the environment for a long time,causing harm to the health of animals and plants.Nonylphenol,with its estrogen-like properties,can bind to estrogen receptors,thus affecting hormone balance and interfering with the endocrine system,which has been proved to have negative effects on the health and reproductive development of many organisms.The purpose of this study was to study the toxicity of nonylphenol on the quality of mouse oocytes and its mechanism,so as to provide a theoretical basis for the effect of environmental endocrine disruptors on the maturation of oocytes.In this study,mice were used as experimental subjects to establish an in vivo model.Nonylphenol of different concentrations(0 μg /L,50 μg /L,500 μg /L)were added into the daily drinking water of mice.After feeding the mice for 4 weeks,we investigated the effects and mechanism of nonylphenol on the quality of mouse oocytes.We first observed the ovarian morphology and ovarian weight of the mice after exposuring nonylphenol,observed the development of follicles through histological sections,and then extracted the oocytes from the ovary for in vitro culture to observe their morphology and development ability.Then,the changes of mRNA expression in oocytes were detected by transcriptomics to explore the effect of nonylphenol on oocytes at the mRNA level.We used fluorescence staining to detect cytoskeleton,mitochondria,oxidative stress and early apoptosis in oocytes based on differentially gene-related biological pathways in transcriptomics.Our data suggest that nonylphenol exposure affects ovarian morphology and weight,including abnormal ovarian morphology and increased ovarian weight,as well as reduced the number of luminal follicles.The developmental ability of oocytes was decreased and the unequal division process was affected in vitro culture.Transcriptome analysis showed that nonylphenol altered the expression of more than 800 genes in oocytes,involving multiple biological pathways,such as ovarian steroidogenesis,cell cycle and p53 signaling pathway.Subcellular structural analysis showed that nonylphenol exposure disrupted meiotic spindle assembly,resulting in chromosomal disorder.In addition,the exposure to nonylphenol also led to abnormal mitochondrial distribution and decreased membrane potential,which proved that the mitochondrial dysfunction of oocytes.Further analysis showed that nonylphenol caused the accumulation of reactive oxygen species(ROS)and induced oxidative stress,leading to early apoptosis of oocytes.In conclusion,nonylphenol affects the developmental ability of mouse oocytes,induces oxidative stress and early apoptosis of oocytes by affecting cytoskeleton dynamics and mitochondrial function,and reduces the quality of oocytes.