Given the worldwide popularity of hair dyeing, there is an urgent need to understand the toxicities and risks associated with exposure to chemicals found in hair dye formulations. Hair dyes are categorized as oxidative and nonoxidative in terms of their chemical composition and ingredients. For several decades, the expert panel's Cosmetic Ingredient Review (CIR) has assessed the safety of many of the chemicals used in hair dyes; however, a comprehensive review of hair dye ingredients and the risk of exposure to hair dyeing has not been documented. Herein, we review the safety of the various chemicals in oxidative and nonoxidative hair dyes, toxicities associated with hair dyeing, and the carcinogenic risks related to hair dyeing. While many compounds are considered safe for users at the concentrations in hair dyes, there are conflicting data about a large number of hair dye formulations. The CIR expert panel has ratified a number of coloring ingredients for hair dyes and banned a series of chemicals as carcinogenic to animals and unsafe for this application. The use of these chemicals as raw materials for producing hair dyes may result in the synthesis of other contaminants with potential toxicities and increased risk of carcinogenesis. It is an open question whether personal or occupational hair dyeing increases the risk of cancer; however, in specific subpopulations, a positive association between hair dye use and cancer occurrence has been reported. To address this question, a better understanding of the chemical and mechanistic basis of the reported toxicities of hair dye mixtures and individual hair dye ingredients is needed. It is anticipated that in-depth chemical and systems toxicology studies harnessing modern and emerging techniques can shed light on this public health concern in the future.

Antral follicle size is a useful predictive marker of the competency of enclosed oocytes for yielding an embryo following in vitro maturation and fertilization. However, the molecular mechanisms underpinning oocyte developmental potential during bovine antral follicle growth are still unclear. Here, we used a modified single-cell multi-omics approach to analyze the transcriptome, DNA methylome and chromatin accessibility in parallel for oocytes and cumulus cells collected from bovine antral follicles of different sizes. Transcriptome profiling identified three types of oocytes (Small, Medium and Large) that underwent different developmental trajectories, with Large oocytes exhibiting the largest average follicle size and characteristics resembling metaphase-II oocytes. Differential expression analysis and real-time PCR assay showed that most replication-dependent histone genes were highly expressed in Large oocytes. The joint analysis of multi-omics data revealed that the transcription of 20 differentially expressed genes in Large oocytes was associated with both DNA methylation and chromatin accessibility. In addition, oocyte-cumulus interaction analysis showed that inflammation, DNA damage, and p53 signaling pathways were active in Small oocytes, which had the smallest average follicle sizes. We further confirmed that p53 pathway inhibition in in vitro maturation experiments using oocytes obtained from small antral follicles could improve the quality of oocytes and increased the blastocyte rate after in vitro fertilization and culture. Our work provides new insights into the intricate orchestration of bovine oocyte fate determination during antral folliculogenesis, which is instrumental for optimizing in vitro maturation techniques to optimize oocyte quality.

Cryopreserved semen is extensively utilized in the artificial insemination (AI) of domestic animals; however, suboptimal conception rates due to oxidative damage following AI continue to pose a challenge. The present study investigated the effects of Pyrroroquinoline Quinone (PQQ), a novel antioxidant, on the semen quality of Holstein bulls during cryopreservation, as well as its potential molecular mechanisms. Semen samples were diluted with varying concentrations of PQQ (0, 50 μmol/L, 100 μmol/L, 150 μmol/L) prior to cryopreservation. Following the freeze–thaw process, a comprehensive evaluation was conducted to assess sperm motility, plasma membrane integrity, acrosome integrity, and the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and adenosine triphosphate (ATP). Western blot analysis was employed to examine the levels of proteins including PGAM2, CAPZB, CAT, SOD1, and GPX1. Notably, the inclusion of 100 μmol/L PQQ significantly enhanced sperm motility, membrane integrity, and acrosome integrity post freeze–thawing (p < 0.05). Furthermore, the group treated with 100 μmol/L PQQ exhibited reduced levels of MDA and ROS (p < 0.05), while ATP levels were significantly elevated (p < 0.05). Interestingly, treatment with 100 μmol/L PQQ resulted in decreased consumption of PGAM2, CAPZB, CAT, SOD1, and GPX1 proteins in sperm after freeze–thawing, compared to the control group (p < 0.05). These findings indicate that PQQ treatment enhances the quality of bull semen, mitigates oxidative stress damage, and ultimately improves the efficacy of sperm cryopreservation.

Chlorogenic acid (CGA) has strong antioxidant properties. In order to improve the low maturation rate and poor vitrification freezing effect of sheep oocytes caused by oxidative stress. In this study, oocytes from 200 2–3-year-old Kazakh sheep were collected, and different concentrations of CGA were added to the maturation medium and vitrification freezing solution to study the effects of CGA on the maturation rate, cleavage rate, blastocyst rate, reactive oxygen species (ROS) and glutathione (GSH) levels, mitochondrial membrane potential, and the expression levels of oxidation and apoptosis-related genes in sheep oocytes. The results showed that adding 40 μmol/L CGA to the oocyte in vitro maturation solution significantly increased the maturation rate of oocytes, adding 50 μmol/L CGA to the vitrification cryopreservative solution significantly increased the cleavage and blastocyst rates of mature oocytes activated by parthenogenetic activation after freezing. During in vitro maturation and vitrification freezing in sheep oocytes, CGA significantly reduced the level of ROS and the expression of apoptosis-related genes (Caspase-3 and Bax/Bcl-2), and significantly increased the level of glutathione (GSH), mitochondrial membrane potential, and the expression of antioxidant and anti-apoptosis-related genes (SOD-2 and GPX-3). In addition, CGA significantly increased the expression of the anti-apoptotic gene (AKT) and anti-stress gene (FOXO) during vitrification freezing of sheep oocytes. In conclusion, 40 μmol/L CGA improves the maturation rate of sheep oocytes, and 50 μmol/L CGA improves the quality of parthenogenetic activation embryos after vitrification freezing of mature oocytes in sheep. These results provide a basis for the production of sheep in vitro embryos and the establishment of a germplasm resource bank.

Lactating oocytes consume a lot of energy during maturation, a large part of which comes from lipid metabolism. PPARγ is a key regulator of lipid metabolism. In this study, rosiglitazone (RSG), an activator of PPARγ, was added to a mature medium to investigate its effects on the levels of spindle and the chromosome arrangement, lipid deposition, reactive oxygen species (ROS), and glutathione (GSH) levels, oocyte secretion factors, apoptosis and lipid metabolism-related gene expression, and subsequent embryonic development during the maturation of sheep oocytes. The oocyte secretion factor affects gene expression related to apoptosis and lipid metabolism and subsequent embryonic development. The results showed that the proportion of spindle and normal chromosome arrangements increased in the 5 μM RSG treatment group, the lipid content increased after cell maturation, the ROS level decreased, and the GSH level increased. The expressions of oocyte secretion factor (GDF9 and BMP15), anti-apoptosis gene (BCL2), and lipid metabolism-related genes (ACAA1, CPT1A, PLIN2) were increased in the 5 μM treatment group. Finally, the development of blastocysts was examined. After the oocytes were treated with 5 μM RSG, the blastocyst rate and the gene expression of the totipotency gene (OCT4) were increased. It was concluded that increasing PPARγ activity during ovine oocyte maturation could promote lipid metabolism, reduce oxidative stress, and improve the ovine oocyte maturation rate and subsequent embryo development.