Retinoic acid signaling in ovarian folliculogenesis and steroidogenesis

EGFR-ERK1/2 signaling and mitochondrial dynamics in seasonal ovarian steroidogenesis of the muskrats (Ondatra zibethicus)

The dynamic systems of mitochondria, including mitochondrial fusion and fission, are essential for ovarian endocrine and follicular development. Meanwhile, ERK1/2 signaling is an important mechanism mediating altered mitochondrial dynamics and steroidogenesis. The purpose of this study was to investigate the seasonal changes in ovarian steroidogenesis concerning EGFR-ERK1/2 signaling and mitochondrial dynamics of the muskrats (Ondatra zibethicus). The results showed that follicular development in the muskrats remained in the tertiary follicular stage during the non-breeding season, accompanied by a significant decrease in serum and ovarian concentrations of 17β-estradiol and progesterone from the breeding season to the non-breeding season. EGF, EGFR, ERK1/2, p-ERK1/2, and mitochondrial dynamics regulators were mainly localized in granulosa cells and theca cells of muskrats during the breeding and non-breeding seasons. The mRNA levels of Egfr, Erk1/2, Mfn1/2, Opa1, Drp1, and steroidogenic enzymes in the ovaries were remarkably higher during the breeding season. The 17β-estradiol concentrations in the serum and ovaries as well as the relative levels of Mfn1/2, Opa1, and Drp1 were positively associated with each other. Furthermore, transcriptomic analysis of the ovaries revealed that differentially expressed genes might be linked to steroid biosynthesis, estrogen signaling pathway, and mitochondrial membrane-related pathways. In conclusion, these results suggest that the up-regulation of mitochondrial dynamics regulators during the breeding season is closely associated with enhanced ovarian steroidogenesis in the muskrats, which may be regulated by upstream EGFR-ERK1/2 signaling.

Granulosa cells provide transcriptomic information on ovarian follicle dynamics in southern white rhinoceros

Much remains unknown about the reproductive physiology of southern white rhinoceros (SWR) and the effect of ovarian stimulation prior to ovum pickup (OPU) have not been fully elucidated. Granulosa cells (GC) provide valuable insight into follicle growth and oocyte maturation status. The goals of this study were to evaluate transcriptomic changes in GC from three stages of follicle development and to identify biomarkers possibly associated with follicular growth and maturation as a result of ovarian stimulation. GC collected from SWRs following OPU were assigned stages based upon follicle size. Total RNA was isolated, and cDNA libraries were prepared and sequenced on a NovaSeq 6000. All bioinformatics analyses were performed utilizing the Galaxy web platform. Reads were aligned to CerSimCot1.0, and the manual curation was performed with EquCab3.0. Overall, 39,455 transcripts (21,612 genes) were identified across follicle stages, and manual curation yielded a 61% increase in gene identification from the original annotation. Granulosa cells from preovulatory follicles expressed the highest number of unique transcripts. The following seven biomarkers were determined based upon cluster analysis and patterns of expression: COL1A1, JMY, FBXW11, NRG1, TMPO, MACIR and COL4A1. These data can be used to potentially evaluate the effects of different ovarian stimulation protocols on follicle dynamics, improve OPU results, and support conservation efforts in this species.

Pet Wellness and Vitamin A: A Narrative Overview

The health of companion animals, particularly dogs and cats, is significantly influenced by nutrition, with vitamins playing a crucial role. Vitamin A, in particular, is indispensable, with diverse roles ranging from vision to immune modulation and reproduction. Despite its importance, the metabolism and dietary requirements of vitamin A in companion animals remain complex and not fully understood. This review provides a comprehensive overview of the historical perspective, the digestion, the metabolism, the physiological roles, the deficiency, the excess, and the interactions with other micronutrients of vitamin A in companion animals. Additionally, it highlights future research directions and gaps in our understanding. Insights into the metabolism of vitamin A in companion animals, personalized nutrition strategies based on genetic variability, longitudinal studies tracking the status of vitamin A, and investigations into its immunomodulatory effects are crucial for optimizing pet health and wellness. Furthermore, understanding the stability and bioavailability of vitamin A in pet food formulations is essential for ensuring the provision of adequate micronutrients. Overall, this review underscores the importance of vitamin A in companion animal nutrition and the need for further research to enhance our understanding and to optimize dietary recommendations for pet health and well-being.

CYP46A1-mediated cholesterol turnover induces sex-specific changes in cognition and counteracts memory loss in ovariectomized mice

The brain-specific enzyme CYP46A1 controls cholesterol turnover by converting cholesterol into 24S-hydroxycholesterol (24OH). Dysregulation of brain cholesterol turnover and reduced CYP46A1 levels are observed in Alzheimer's disease (AD). In this study, we report that CYP46A1 overexpression in aged female mice leads to enhanced estrogen signaling in the hippocampus and improved cognitive functions. In contrast, age-matched CYP46A1 overexpressing males show anxiety-like behavior, worsened memory, and elevated levels of 5α-dihydrotestosterone in the hippocampus. We report that, in neurons, 24OH contributes to these divergent effects by activating sex hormone signaling, including estrogen receptors. CYP46A1 overexpression in female mice protects from memory impairments induced by ovariectomy while having no effects in gonadectomized males. Last, we measured cerebrospinal fluid levels of 24OH in a clinical cohort of patients with AD and found that 24OH negatively correlates with neurodegeneration markers only in women. We suggest that CYP46A1 activation is a valuable pharmacological target for enhancing estrogen signaling in women at risk of developing neurodegenerative diseases.

Transcriptomic Analysis of the Aged Nulliparous Mouse Ovary Suggests a Stress State That Promotes Pro-Inflammatory Lipid Signaling and Epithelial Cell Enrichment

Ovarian cancer (OC) incidence and mortality peaks at post-menopause while OC risk is either reduced by parity or increased by nulliparity during fertile life. The long-term effect of nulliparity on ovarian gene expression is largely unknown. In this study, we describe a bioinformatic/data-mining analysis of 112 coding genes upregulated in the aged nulliparous (NP) mouse ovary compared to the aged multiparous one as reference. Canonical gene ontology and pathway analyses indicated a pro-oxidant, xenobiotic-like state accompanied by increased metabolism of inflammatory lipid mediators. Up-regulation of typical epithelial cell markers in the aged NP ovary was consistent with synchronized overexpression of Cldn3, Ezr, Krt7, Krt8 and Krt18 during the pre-neoplastic phase of mOSE cell cultures in a former transcriptome study. In addition, 61/112 genes were upregulated in knockout mice for Fshr and for three other tumor suppressor genes (Pten, Cdh1 and Smad3) known to regulate follicular homeostasis in the mammalian ovary. We conclude that the aged NP ovary displays a multifaceted stress state resulting from oxidative imbalance and pro-inflammatory lipid signaling. The enriched epithelial cell content might be linked to follicle depletion and is consistent with abundant clefts and cysts observed in aged human and mouse ovaries. It also suggests a mesenchymal-to-epithelial transition in the mOSE of the aged NP ovary. Our analysis suggests that in the long term, nulliparity worsens a variety of deleterious effects of aging and senescence thereby increasing susceptibility to cancer initiation in the ovary.

Seasonal changes in endoplasmic reticulum stress and steroidogenesis in the ovary of the wild ground squirrels (Citellus dauricus Brandt)

The development of the follicle is accompanied by steroidogenesis and secretion, the endoplasmic reticulum (ER) requires significant synthesis of relevant proteins to support changes in the follicular microenvironment. The aim of this study was to investigate whether seasonal changes in gonadotropins and ovarian steroid hormones in the wild ground squirrels induce endoplasmic reticulum stress (ERS) and changes in ERS-mediated unfolded protein response (UPR) signaling. There were significant seasonal differences in ovarian mass, with values higher in the breeding season and relatively low in the non-breeding season. Histological observations revealed that ovaries in the breeding season had germ cells including primordial follicles, primary follicles, secondary follicles, tertiary follicles, and the corpus luteal, whereas ovaries consisted mainly of primary and secondary follicles in the non-breeding season. Analysis of ovarian transcriptome data showed that 1298 genes were up-regulated in expression and 1432 genes were down-regulated in expression during both periods. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis indicated that these genes were mainly enriched in estrogen signaling pathways, ovarian steroidogenesis and endoplasmic reticulum protein processing pathways. The expression levels of steroidogenic enzymes (P450scc, P450c17, 3β-HSD, and P450arom) and gonadotropin receptor (FSHR and LHR) were significantly increased during the breeding season compared to the non-breeding season. GRP78 and UPR signaling factors (ATF4, ATF6, XBP1s) associated with ERS were expressed in both seasons. The mRNA expressions of Atf6 and Xbp1s were higher in the breeding season than those of the non-breeding season. Conversely, Atf4 and its downstream homologous protein (Chop) exhibited higher expression during the non-breeding season. In addition, follicle stimulating hormone (FSH), luteinizing hormone (LH), estradiol-17β, and progesterone of serum were significantly higher in the breeding season than those of the non-breeding season. These results suggested that UPR signaling, associated with seasonal changes in ovarian steroidogenesis, was activated during the breeding season and that ERS might be involved in regulating seasonal changes in ovarian steroidogenesis in the wild ground squirrels.

Molecular characterization and potential function of Rxrγ in gonadal differentiation of Chinese soft-shelled turtle (Pelodiscus sinensis)

Retinoid X receptor (RXR) is a member of the ligand-dependent nuclear receptor family. Previous studies revealed that RXRs are involved in reproduction in vertebrates. However, information on the function of RXRs in turtles is scarce. In this study, the Rxrγ cDNA sequence of Pelodiscus sinensis was cloned and analyzed, and a polyclonal antibody was constructed. RXRγ protein showed a positive signal in both mature and differentiated gonads of the turtle. Subsequently, the function of the Rxrγ gene in gonadal differentiation was confirmed using short interfering RNA (RNAi). The full-length cDNA sequence of the Rxrγ gene in P. sinensis was 2152 bp, encoding 407 amino acids and containing typical nuclear receptor family domains, including the DNA-binding domain (DBD), ligand-binding domain (LBD), and activation function 1 (AF1). Moreover, gonadal Ps-Rxrγ showed sexual dimorphism expression patterns in differentiated gonads. Real-time quantitative PCR results revealed that the Rxrγ gene was highly expressed in the turtle ovary. RNAi treatment increased the number of Sertoli cells in ZZ embryonic gonads. Furthermore, RNA interference upregulated Dmrt1 and Sox9 in ZZ and ZW embryonic gonads. However, Foxl2, Cyp19a1, Stra8, and Cyp26b1 were downregulated in embryonic gonads. The results indicated that Rxrγ participated in gonadal differentiation and development in P. sinensis.

The modulator role of Urtica dioica on deleterious effects of retinoic acid high doses on histological parameters and fertilization of rats

Aim

This study purposed to evaluate the modulator and protective role of Urtica dioica (UD) extract against deleterious effects of retinoic acid (RA) high doses on histological parameters and fertilization of rats.

Materials and methods

For the in-vivo phase, 60 female Wistar rats were divided into 6 identical groups as 1) control, 2) 25 mg/kg RA, 3) 25 mg/kg UD extract, 4) 50 mg/kg UD extract, 5) UD extract (25 mg/kg) + RA (25 mg/kg), and 6) UD extract (50 mg/kg) + RA (25 mg/kg). Biochemical parameters, including luteinizing hormone (LH), folliclestimulating hormone (FSH), malondialdehyde (MDA) levels, superoxide dismutase (SOD), and catalase (CAT) activities, were measured. In the in-vitro phase, oocytes were obtained from 10 female rats without injection. In addition to the mentioned parameters, histological parameters (oocytes in various stages) and the results of IVM, IVF, and embryo developments were assessed and compared among the groups with the use of one-way ANOVA and Tukey's post hoc tests.

Results

The high dosage of RA significantly reduced the LH and FSH levels; however, UD alone and with RA increased the hormone levels in rats. Regarding the reactive oxygen species (ROS) activity levels in rats' blood samples, RA increased the MDA and decreased the SOD and CAT levels. Treatment with UD extract (UD + RA groups) significantly improved the parameters mentioned, showing UD's antioxidant effect. The rate of oocyte maturation, 2-cell-4-cell and 4-cell-8-cell embryos, and blastocyst formation increased significantly in the groups in which UD extracts were administered compared to the control and RA groups. Furthermore, the increases were significant in the UD + RA groups compared to the RA group.

Conclusion

UD extract can significantly reduce RA high doses side effects on histological parameters and fertilization of rats and has the protective potential against RA deleterious effects.

Colitis-Mediated Dysbiosis of the Intestinal Flora and Impaired Vitamin A Absorption Reduce Ovarian Function in Mice

Changes in the composition and ratio of the flora during colitis have been found to potentially affect ovarian function through nutrient absorption. However, the mechanisms have not been fully explored. To investigate whether colitis-induced dysbacteriosis of the intestinal flora affects ovarian function, mice were given dextran sodium sulfate (DSS) through drinking water. High-throughput sequencing technology was used to clarify the composition and proportion of bacterial flora as well as gene expression changes in the colon. Changes in follicle type, number, and hormone secretion in the ovary were detected. The results showed that 2.5% DSS could induce severe colitis symptoms, including increased inflammatory cell infiltration, severe damage to the crypt, and high expression of inflammatory factors. Moreover, vitamin A synthesis metabolism-related genes Rdh10, Aldh1a1, Cyp26a1, Cyp26b1, and Rarβ were significantly decreased, as well as the levels of the steroid hormone synthase-related proteins STAR and CYP11A1. The levels of estradiol, progesterone, and Anti-Mullerian hormone as well as the quality of oocytes decreased significantly. The significantly changed abundances of Alistipes, Helicobacter, Bacteroides, and some other flora had potentially important roles. DSS-induced colitis and impaired vitamin A absorption reduced ovarian function.

RA-RAR signaling promotes mouse vaginal opening through increasing β-catenin expression and vaginal epithelial cell apoptosis

BACKGROUND

Retinoic acid (RA) plays important role in the maintenance and differentiation of the Müllerian ducts during the embryonic stage via RA receptors (RARs). However, the function and mechanism of RA-RAR signaling in the vaginal opening are unknown.

METHOD

We used the Rarα knockout mouse model and the wild-type ovariectomized mouse models with subcutaneous injection of RA (2.5 mg/kg) or E2 (0.1 µg/kg) to study the role and mechanism of RA-RAR signaling on the vaginal opening. The effects of Rarα deletion on Ctnnb1 mRNA levels and cell apoptosis in the vaginas were analyzed by real-time PCR and immunofluorescence, respectively. The effects of RA on the expression of β-catenin and apoptosis in the vaginas were analyzed by real-time PCR and western blotting. The effects of E2 on RA signaling molecules were analyzed by real-time PCR and western blotting.

RESULTS

RA signaling molecules were expressed in vaginal epithelial cells, and the mRNA and/or protein levels of RALDH2, RALDH3, RARα and RARγ reached a peak at the time of vaginal opening. The deletion of Rarα resulted in 25.0% of females infertility due to vaginal closure, in which the mRNA (Ctnnb1, Bak and Bax) and protein (Cleaved Caspase-3) levels were significantly decreased, and Bcl2 mRNA levels were significantly increased in the vaginas. The percentage of vaginal epithelium with TUNEL- and Cleaved Caspase-3-positive signals were also significantly decreased in Rarα^-/- females with vaginal closure. Furthermore, RA supplementation of ovariectomized wild-type (WT) females significantly increased the expression of β-catenin, active β-catenin, BAK and BAX, and significantly decreased BCL2 expression in the vaginas. Thus, the deletion of Rarα prevents vaginal opening by reducing the vaginal β-catenin expression and epithelial cell apoptosis. The deletion of Rarα also resulted in significant decreases in serum estradiol (E2) and vagina Raldh2/3 mRNA levels. E2 supplementation of ovariectomized WT females significantly increased the expression of RA signaling molecules in the vaginas, suggesting that the up-regulation of RA signaling molecules in the vaginas is dependent on E2 stimulation.

CONCLUSION

Taken together, we propose that RA-RAR signaling in the vaginas promotes vaginal opening through increasing β-catenin expression and vaginal epithelial cell apoptosis.

Synthesis, Regulatory Factors, and Signaling Pathways of Estrogen in the Ovary

New insights have been thrown for understanding the significant role of estrogen on various systems of humans. Increasing evidences have determined the significant roles of estrogen in female reproductive system. So, the normal synthesis and secretion of estrogen play important roles in maintaining the function of tissues and organs. The ovaries are the main synthetic organs of estrogen. In this review, we summarized the current knowledge of the estrogen synthesis in the ovaries. A series of factors and signaling pathways that regulate the synthesis of estrogen are expounded in detail. Understanding the regulating factors and potential mechanism related to estrogen synthesis will be beneficial for understanding estrogen disorder related diseases and may provide novel therapeutic targets.

LC-MS/MS-based metabolomic profiling identifies candidate biomarkers in follicular fluid of infertile women with chronic pelvic inflammatory disease

OBJECTIVES

How chronic pelvic inflammatory disease (CPID), the most common cause of infertility, affects metabolic profiles of follicular fluid (FF) remains unknown. This study aimed to identify candidate biomarkers in FF of infertile women with CPID.

METHOD

FF samples were collected from infertile women with CPID (n = 8) and healthy controls (n = 8) at the time of oocyte retrieval. Untargeted metabolomic profiling of FF samples was conducted using the liquid chromatography-tandem mass spectrometry (LC-MS/MS).

RESULTS

A total of 240 differential metabolites (104 named biochemicals and 136 unnamed biochemicals) were screened out and identified. Among them, pregnane-3,3-diol, pc(p-18:1(11z)/18:3(6z,9z,12z)), and 1-octadecanoyl-2-(4z,7z,10z,13z,16z,19z-docosahexaenoyl)-sn-glycero-3-phosphoethanolamine were markedly down-regulated, while 17,21-dihydroxypregnenolone was significantly up-regulated in infertile women with CPID. Furthermore, KEGG biological pathway analysis revealed that these metabolites were especially enriched in steroid hormone biosynthesis, glyoxylate and dicarboxylate metabolism, glucagon signaling pathway, and the tricarboxylic acid (TCA) cycle.

CONCLUSION

FF of infertile women with CPID showed unique metabolic changes that may be involved in the pathogenesis of infertility and serve as new therapeutic targets or diagnostic biomarkers.

Investigating the Effects of Hydro-alcoholic Urtica Dioica Extract and Retinoic Acid on Follicular Development: An Animal Study

Background: Urtica dioica (UD), as a natural antioxidant, has positive effects on oocyte maturation. This study aimed to investigate the effects of hydro-alcoholic UD extract and retinoic acid on follicular development in an in vitro fertilization (IVF) condition. Methods: A total of 40 female Wistar rats were randomly divided into 5 groups: group 1 received normal saline, group 2 was given 25 mg/kg retinoic acid, group 3 was administered with 100 mg/kg UD extract, group 4 was treated with retinoic acid plus UD extract, and group 5 received 10 mg/kg olive oil. The histomorphometric parameters were analyzed, including the number of follicles, follicular atrophy, fertilized oocytes, 2-cell embryos, dead embryos, and blastocysts. Results: Retinoic acid caused a significant increase in the primary, preantral, and atretic follicles and a substantial decrease in the corpus luteum compared with the control group (p<0.001). The number of preantral, antral follicles, and corpus luteum was significantly higher in group 3 compared with group 1 (p<0.001). Moreover, coadministration of UD plus retinoic acid (group 4) significantly reduced the atretic follicles (p<0.05). Conclusion: Based on the results, UD herbal extract, as a natural antioxidant agent, could reduce the adverse effects of retinoic acid on oocyte maturation in an IVF condition.

Carotenoids in female and male reproduction

Carotenoids are among the best-known pigments in nature, confer color to plants and animals, and are mainly derived from photosynthetic bacteria, fungi, algae, plants. Mammals cannot synthesize carotenoids. Carotenoids' source is only alimentary and after their assumption, they are mainly converted in retinal, retinol and retinoic acid, collectively known also as pro-vitamins and vitamin A, which play an essential role in tissue growth and regulate different aspects of the reproductive functions. However, their mechanisms of action and potential therapeutic effects are still unclear. This review aims to clarify the role of carotenoids in the male and female reproductive functions in species of veterinary interest. In female, carotenoids and their derivatives regulate not only folliculogenesis and oogenesis but also steroidogenesis. Moreover, they improve fertility by decreasing the risk of embryonic mortality. In male, retinol and retinoic acids activate molecular pathways related to spermatogenesis. Deficiencies of these vitamins have been correlated with degeneration of testis parenchyma with consequent absence of the mature sperm. Carotenoids have also been considered anti-antioxidants as they ameliorate the effect of free radicals. The mechanisms of action seem to be exerted by activating Kit and Stra8 pathways in both female and male. In conclusion, carotenoids have potentially beneficial effects for ameliorating ovarian and testes function.

Biochemical alterations in the follicular fluid of bovine peri-ovulatory follicles and association with final oocyte maturation

Follicular fluid (FF), a product of vascular transudate and granulosa and thecal cell secretions, is the milieu that has evolved to support oocyte growth and maturation which plays a central role in oocyte quality determination. Therefore, a suboptimal FF composition may be reflected in compromised oocyte progression through maturation, fertilization or embryo development. To date, the composition of bovine FF remains understudied. To address this, we comprehensively characterized the metabolomic constituency of bovine FF in the period during which the oocyte undergoes meiotic maturation. More specifically, FF from pre (-24 h) and peri (-2 h) -ovulatory follicles was profiled by high-throughput untargeted ultra-high-performance liquid chromatography tandem mass spectroscopy. A total of 634 metabolites were identified, comprising: lipids (37.1%), amino acids (30.0%), xenobiotics (11.5%), nucleotides (6.8%), carbohydrates (4.4%), cofactors and vitamins (4.4%), peptides (3.6%) and energy substrates (2.1%). The concentrations of 67 metabolites were significantly affected by stage of follicle development, 33.3% (n=21) were reduced (P≤0.05) by a mean of 9.0-fold, whereas 46 were elevated (P≤0.05) by a mean of 1.7-fold in peri vs. pre -ovulatory FF. The most pronounced individual metabolite concentration decreases were hypoxanthine (98.9-fold), xanthine (65.7-fold), 17β-oestradiol (12.4-fold), and inosine (4.6-fold). In contrast, the greatest increases were in retinal (4.9-fold), 1-methyl-5-imidazoleacetate (2.7-fold), and isovalerylcarnitine (2.7-fold). This global metabolomic analysis of bovine FF temporal dynamics provides new information for understanding the environment supporting oocyte maturation and facilitating ovulation, that has the potential for improving oocyte quality both in vivo and in vitro.

Seasonal Change in Adiponectin Associated with Ovarian Morphology and Function in Wild Ground Squirrels (Citellus dauricus Brandt)

The goal of this study is to explore the relationship between altered circulating adiponectin concentration, ovarian tissue morphology, ovarian steroidogenesis, and sex hormone production in ovaries of wild ground squirrels. The ovarian mass differed significantly during the breeding and non-breeding seasons, and the circulating estradiol and progesterone concentrations were significantly higher in the breeding season, while the circulating adiponectin level was significantly lower. The expression levels of gonadotropin receptors (FSHR and LHR) and steroidogenic enzymes (StAR, P450scc, P450arom, and 3β-HSD) were significantly higher during the breeding season. Comparing the ovarian transcriptome data of wild ground squirrels between the two periods, we found that some differentially expressed genes were enriched for ovarian steroidogenesis and the adipocytokine signaling pathway, which correlated with our present results. Notably, the MAPK signaling pathway was also enriched and its related genes (Erk1, p38 Mapk, Jnk) were up-regulated by qPCR during the non-breeding season. These findings suggested that adiponectin may be involved in the regulation of seasonal changes in the ovarian function of wild ground squirrels, possibly by acting on the MAPK signaling pathway to regulate sex steroidogenesis in the ovaries.

Identifying candidate reference chemicals for in vitro testing of the retinoid pathway for predictive developmental toxicity

Evaluating chemicals for potential in vivo toxicity based on their in vitro bioactivity profile is an important step toward animal- free testing. A compendium of reference chemicals and data describing their bioactivity on specific molecular targets, cellular pathways, and biological processes is needed to bolster confidence in the predictive value of in vitro hazard detection. Endogenous signaling by all-trans retinoic acid (ATRA) is an important pathway in developmental processes and toxicities. Employing data extraction methods and advanced literature extraction tools, we assembled a set of candidate reference chemicals with demonstrated activity on ten protein family targets in the retinoid system. The compendium was culled from Protein Data Bank, ChEMBL, ToxCast/Tox21, and the biomedical literature in PubMed. Finally, we performed a case study on one chemical in our collection, citral, an inhibitor of endogenous ATRA production, to determine whether the literature supports an adverse outcome pathway explaining the compound’s developmental toxicity initiated by disruption of the retinoid pathway. We also deliver an updated Abstract Sifter tool populated with these reference compounds and complex search terms designed to query the literature for the downstream consequences to support concordance with targeted retinoid pathway disruption.

Estrogen receptors and the aging brain

The female sex hormone estrogen has been ascribed potent neuroprotective properties. It signals by binding and activating estrogen receptors that, depending on receptor subtype and upstream or downstream effectors, can mediate gene transcription and rapid non-genomic actions. In this way, estrogen receptors in the brain participate in modulating neural differentiation, proliferation, neuroinflammation, cholesterol metabolism, synaptic plasticity, and behavior. Circulating sex hormones decrease in the course of aging, more rapidly at menopause in women, and slower in men. This review will discuss what this drop entails in terms of modulating neuroprotection and resilience in the aging brain downstream of spatiotemporal estrogen receptor alpha (ERα) and beta (ERβ) signaling, as well as in terms of the sex differences observed in Alzheimer's disease (AD) and Parkinson's disease (PD). In addition, controversies related to ER expression in the brain will be discussed. Understanding the spatiotemporal signaling of sex hormones in the brain can lead to more personalized prevention strategies or therapies combating neurodegenerative diseases.

Long-term treatment of Nicotinamide mononucleotide improved age-related diminished ovary reserve through enhancing the mitophagy level of granulosa cells in mice

Ovarian aging affects the reproductive health of elderly women due to decline in oocyte quality, which is closely related to mitochondrial dysfunction. Nicotinamide mononucleotide (NMN), as a precursor of NAD⁺, effectively regulate mitochondria metabolism in mice. However, roles of NMN in improving age-related diminished ovary reserve remain to be determined. In present study, 4, 8, 12, 24, 40-week old female ICR mice were collected and a 20-week-long administration of NMN was conducted to 40-week-old mice (60WN), meanwhile the control group is given water (60WC). First, we found that 20-week-long administration of NMN to 40-week-old mice exhibited anti-aging and anti-inflammatory effects on organ structures, along with the improvement of estrus cycle condition and endocrine function. The number of primordial, primary, secondary, antral follicles and corpora luteum of ovaries in 60WN group was significantly increased compared with those in 60WC group. Additionally, the protein and gene expressions of P16 of ovaries were significantly reduced in 60WN group than in 60WC group. the mitochondria biogenesis, autophagy level, and proteases activity enhanced in granulosa cells after 20-week-administration of NMN. Present results indicate that NMN has the potential to save diminished ovary reserve by long-term treatment, providing a basis for exploring the role of NMN in anti-ovarian aging by enhancing the mitophagy level of granulosa cells.

Role of Retinoid X Receptors (RXRs) and dietary vitamin A in Alzheimer's disease: Evidence from clinicopathological and preclinical studies

BACKGROUND

Vitamin A (VitA), via its active metabolite retinoic acid (RA), is critical for the maintenance of memory function with advancing age. Although its role in Alzheimer's disease (AD) is not well understood, data suggest that impaired brain VitA signaling is associated with the accumulation of β-amyloid peptides (Aβ), and could thus contribute to the onset of AD.

METHODS

We evaluated the protective action of a six-month-long dietary VitA-supplementation (20 IU/g), starting at 8 months of age, on the memory and the neuropathology of the 3xTg-AD mouse model of AD (n = 11-14/group; including 4-6 females and 7-8 males). We also measured protein levels of Retinoic Acid Receptor β (RARβ) and Retinoid X Receptor γ (RXRγ) in homogenates from the inferior parietal cortex of 60 participants of the Religious Orders study (ROS) divided in three groups: no cognitive impairment (NCI) (n = 20), mild cognitive impairment (MCI) (n = 20) and AD (n = 20).

RESULTS

The VitA-enriched diet preserved spatial memory of 3xTg-AD mice in the Y maze. VitA-supplementation affected hippocampal RXR expression in an opposite way according to sex by tending to increase in males and decrease in females their mRNA expression. VitA-enriched diet also reduced the amount of hippocampal Aβ₄₀ and Aβ₄₂, as well as the phosphorylation of tau protein at sites Ser396/Ser404 (PHF-1) in males. VitA-supplementation had no effect on tau phosphorylation in females but worsened their hippocampal Aβ load. However, the expression of Rxr-β in the hippocampus was negatively correlated with the amount of both soluble and insoluble Aβ in both males and females. Western immunoblotting in the human cortical samples of the ROS study did not reveal differences in RARβ levels. However, it evidenced a switch from a 60-kDa-RXRγ to a 55-kDa-RXRγ in AD, correlating with ante mortem cognitive decline and the accumulation of neuritic plaques in the brain cortex.

CONCLUSION

Our data suggest that (i) an altered expression of RXRs receptors is a contributor to β-amyloid pathology in both humans and 3xTg-AD mice, (ii) a chronic exposure of 3xTg-AD mice to a VitA-enriched diet may be protective in males, but not in females.

DEHP exposure to lactating mice affects ovarian hormone production and antral follicle development of offspring

Di (2-ethylhexyl) phthalate (DEHP) is widely used as a plastic additive and it could induce reproduction defects and fertility in mammals as environmental endocrine disruptor. However, the effects and potential mechanism of DEHP exposure during lactation stage on follicular development of offspring are still unclear. In this study, we found that the total primordial follicle number and antral follicles in the suckling of mice exposed to DEHP during lactation was significantly reduced. RNA-seq analysis results showed that the transcription levels of genes related to steroid production, ovarian hormone secretion and oxidative stress were significantly changed, which led to a decrease in 17β-estradiol and an increase in oxidative stress. The proportion of DNA damage marker γH2AX in the ovary of female suckling exposed to DEHP was significantly increased. We also found an increase in the level of ovarian apoptosis, and the proliferation of ovarian granulosa cells was inhibited. These alterations also lead to abnormal spindle and chromosome misalignment during oocyte maturation. Overall, our data indicate that lactation exposure to DEHP can affect the secretion of hormones and the development of antral follicles in suckling mice by affecting the secretion pathways of ovarian hormone enzymes and oxidative stress pathway.

The impact of isotretinoin on the pituitary-ovarian axis: An interpretative review of the literature

Isotretinoin (13-cis-retinoic acid), a derivative of vitamin A, is used in the treatment of severe acne resulting in sebum suppression induced by sebocyte apoptosis. Isotretinoin treatment is associated with several adverse effects including teratogenicity, hepatotoxicity, and dyslipidemia. Isotretinoin's effects on endocrine systems and its potential role as an endocrine disruptor are not yet adequately investigated. This review presents clinical, endocrine, and molecular evidence showing that isotretinoin treatment adversely affects the pituitary-ovarian axis and enhances the risk of granulosa cell apoptosis reducing follicular reserve. Isotretinoin is associated with pro-apoptotic signaling in sebaceous glands through upregulated expression of p53, forkhead box O transcription factors (FOXO1, FOXO3), and tumor necrosis factor-related apoptosis inducing ligand (TRAIL). Two literature searches including clinical and experimental studies respectively support the hypothesis that isotretinoin's toxicological mode of action on the pituitary-ovarian axis might be caused by over-expressed p53/FOXO1 signaling resulting in gonadotropin suppression and granulosa cell apoptosis. The reduction of follicular reserve by isotretinoin treatment should be especially considered when this drug will be administered for the treatment of acne in post-adolescent women, in whom fertility may be adversely affected. In contrast, isotretinoin treatment may exert beneficial effects in states of hyperandrogenism, especially in patients with polycystic ovary syndrome.

Endocrine, metabolic and apical effects of in utero and lactational exposure to non-dioxin-like 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB 180): A postnatal follow-up study in rats

PCB 180 is a persistent and abundant non-dioxin-like PCB (NDL-PCB). We determined the developmental toxicity profile of ultrapure PCB 180 in developing offspring following in utero and lactational exposure with the focus on endocrine, metabolic and retinoid system alterations. Pregnant rats were given total doses of 0, 10, 30, 100, 300 or 1000 mg PCB 180/kg bw on gestational days 7-10 by oral gavage, and the offspring were sampled on postnatal days (PND) 7, 35 and 84. Decreased serum testosterone and triiodothyronine concentrations on PND 84, altered liver retinoid levels, increased liver weights and induced 7-pentoxyresorufin O-dealkylase (PROD) activity were the sensitive effects used for margin of exposure (MoE) calculations. Liver weights were increased together with induction of the metabolizing enzymes cytochrome P450 (CYP) 2B1, CYP3A1, and CYP1A1. Less sensitive effects included decreased serum estradiol and increased luteinizing hormone levels in females, decreased prostate and seminal vesicle weight and increased pituitary weight in males, increased cortical bone area and thickness of tibial diaphysis in females and decreased cortical bone mineral density in males. Developmental toxicity profiles were partly different in male and female offspring, males being more sensitive to increased liver weight, PROD induction and decreased thyroxine concentrations. MoE assessment indicated that the 95^th percentile of current maternal PCB 180 concentrations do not exceed the estimated tolerable human lipid-based PCB 180 concentration. Although PCB 180 is much less potent than dioxin-like compounds, it shares several toxicological targets suggesting a potential for interactions.

The effects of plasticizers on the ovary

Endocrine disrupting chemicals pose a threat to health and reproduction. Plasticizers such as phthalates and bisphenols are particularly problematic because they are present in many consumer products and exposure can begin in utero and continue throughout the lifetime of the individual. Evidence suggests that these chemicals can have ancestral and transgenerational effects, making them a huge public health concern for the reproductive health of current and future generations. Studies performed in rodents or using rodent- or human-derived tissues have been critical for understanding the toxic effects of plasticizers on the ovary and their mechanisms of action. This review addresses current in vitro and rodent-based in vivo studies investigating the effects of bisphenols and phthalates on ovarian health, female reproduction, and correlations between human exposure and reproductive pathologies.

Clinical Application of Antioxidants to Improve Human Oocyte Mitochondrial Function: A Review

Mitochondria produce adenosine triphosphate (ATP) while also generating high amounts of reactive oxygen species (ROS) derived from oxygen metabolism. ROS are small but highly reactive molecules that can be detrimental if unregulated. While normally functioning mitochondria produce molecules that counteract ROS production, an imbalance between the amount of ROS produced in the mitochondria and the capacity of the cell to counteract them leads to oxidative stress and ultimately to mitochondrial dysfunction. This dysfunction impairs cellular functions through reduced ATP output and/or increased oxidative stress. Mitochondrial dysfunction may also lead to poor oocyte quality and embryo development, ultimately affecting pregnancy outcomes. Improving mitochondrial function through antioxidant supplementation may enhance reproductive performance. Recent studies suggest that antioxidants may treat infertility by restoring mitochondrial function and promoting mitochondrial biogenesis. However, further randomized, controlled trials are needed to determine their clinical efficacy. In this review, we discuss the use of resveratrol, coenzyme-Q10, melatonin, folic acid, and several vitamins as antioxidant treatments to improve human oocyte and embryo quality, focusing on the mitochondria as their main hypothetical target. However, this mechanism of action has not yet been demonstrated in the human oocyte, which highlights the need for further studies in this field.