Improving the sexual activity and reproduction of female zebrafish with high testosterone levels

Cannabidiol exposure during embryonic period caused serious malformation in embryos and inhibited the development of reproductive system in adult zebrafish

Cannabidiol (CBD) is a non-psychoactive component of cannabis with potential applications in biomedicine, food, and cosmetics due to its analgesic, anti-inflammatory, and anticonvulsant properties. However, increasing reports of adverse CBD exposure events underscore the necessity of evaluating its toxicity. In this study, we investigated the developmental toxicity of CBD in zebrafish during the embryonic (0-4 dpf, days post fertilization) and early larval stages (5-7 dpf). The median lethal concentration of CBD in embryos/larvae is 793.28 μg/L. CBD exhibited concentration-dependent manner (ranging from 250 to 1500 μg/L) in inducing serious malformed somatotypes, like shorter body length, pericardial cysts, vitelline cysts, spinal curvature, and smaller eyes. However, no singular deformity predominates. The 5-month-old zebrafish treated with 100 and 200 μg/L of CBD during the embryonic and early larval stages produced fewer offspring with higher natural mortality and malformation rate. Gonadal growth and gamete development were inhibited. Transcriptomic and metabolomic analyses conducted with 400 μg/L CBD on embryos/larvae from 0 to 5 dpf suggested that CBD promoted the formation and transportation of extracellular matrix components on 1 dpf, promoting abnormal cell division and migration, probably resulting in random malformed somatotypes. It inhibited optical vesicle development and photoreceptors formation on 2 and 3 dpf, resulting in damaged sight and smaller eye size. CBD also induced an integrated stress response on 4 and 5 dpf, disrupting redox, protein, and cholesterol homeostasis, contributing to cellular damage, physiological dysfunction, embryonic death, and inhibited reproductive system and ability in adult zebrafish. At the tested concentrations, CBD exhibited developmental toxicity, lethal toxicity, and reproductive inhibition in zebrafish. These findings demonstrate that CBD threatens the model aquatic animal, highlighting the need for additional toxicological evaluations of CBD before its inclusion in dietary supplements, edible food, and other products.

Metabolomic-based analysis reveals bile acid-mediated ovarian failure induced by low temperature in zebrafish

As ectotherms, fish are highly sensitive to temperature fluctuations, which can profoundly impact their reproductive cycles. In this study, we investigated the fertility and histological characteristics of zebrafish ( Danio rerio) ovaries exposed to a temperature gradient ranging from the thermopreferendum temperature of the species, 27°C, to lower temperatures of 22°C, 20°C, and 13°C over a period of two weeks. Comparative metabolomic (six biological replicates for each temperature) and transcriptomic (four biological replicates for each temperature) analyses were conducted under the four temperature conditions. Results indicated that lower temperatures inhibited oocyte development and differential metabolites were involved in steroid hormone production, antioxidant function, and lipid and protein catabolism. Disrupted reproductive hormones, increased proteolysis, and lipid degradation significantly impeded oocyte development and egg maturation. Notably, a significant increase in bile acid content was noted in the ovaries of the cold-treated fish, indicating that bile acids play a critical role in ovarian failure. Overall, these findings provide valuable insights into the mechanisms governing the reproductive response of fish to cold stress.

Polystyrene nanoplastics cause reproductive toxicity in zebrafish: PPAR mediated lipid metabolism disorder

The ubiquitous presence of micro-and nanoplastics (MNPs) in the environment and everyday products has attracted attention due to their hazardous risks. However, the effects of MNPs on reproduction and the underlying mechanisms remain unclear. The present study investigated the impact of polystyrene (PS) nanoplastics of 80, 200 and 500 nm diameters on zebrafish reproduction at an environmentally relevant concentration of 0.5 mg/L. Exposure to PS delayed spermatogenesis and caused aberrant follicular growth, resulting in dysgenesis in F0 adults and impacting F1 embryo development. Notably, the reproductive toxicity exhibited size-dependency, with the 500 nm PS being the most detrimental. Combined analyses of transcriptomics and metabolomics in ovary tissue revealed that treatment with 500 nm PS affected the peroxisome proliferator-activated receptor (PPAR) signaling pathway, dysregulated lipid transport, binding and activity processes, and led to dysgenesis in zebrafish. Specifically, the ovulatory dysfunction induced by PS exposure resembled clinical manifestations of polycystic ovary syndrome (PCOS) and can be attributed to lipid metabolism disorder involving glycerophospholipid, sphingolipid, arachidonic acid, and alpha-linolenic acid. Collectively, our results provide new evidence revealing the molecular mechanisms of PS-induced reproductive toxicity, highlighting that MNPs may pose a risk to female reproductive health.

Letrozole induced a polycystic ovary syndrome model in zebrafish by interfering with the hypothalamic-pituitary-gonadal axis

Polycystic ovary syndrome (PCOS) is a common endocrine and metabolic disease in women of childbearing age, with an incidence of 5-10%. This study compared the traits of zebrafish with three diagnostic criteria for human PCOS, and the diagnostic criteria for zebrafish PCOS were proposed: decreased fecundity, elevated testosterone (T) or 11-ketotestosterone (11-KT) levels and increased cortical-alveolar oocyte (CO) ratio, enhancing the zebrafish PCOS model's accuracy. According to the mammalian PCOS classification, the type of zebrafsh PCOS is divided into four phenotypes (A, B, C and D), but the four phenotypes of zebrafish PCOS are not fully covered in the existing studies (A and D). In this study, we successfully induced phenotype B zebrafish PCOS model using the aromatase inhibitor, letrozole (LET). That is, wild-type female zebrafish were exposed to 1000 μg/L LET for 30 days. Reproductive tests showed decreased fecundity in female zebrafish exposed to LET (Control: 132.63, 146.00, 173.00; LET: 29.20, 90.00, 82.71). Hormone analysis showed that female zebrafish exposed to LET had significantly lower 17β-estradiol/testosterone (E2/T) ratios, indicating elevated T levels. Meanwhile, levels of 11-KT in the ovaries exposed to LET were significantly up-regulated (Control: 0.0076 pg/μg; LET: 0.0138 pg/μg). Pathological sections of the ovary showed fewer CO in the LET-exposed group (Control: 16.27%; LET: 8.38%). In summary, the zebrafish PCOS model summarized and studied in this study provide a reliable and economical tool for the screening of therapeutic drugs, as well as for the etiology research and treatment strategies of PCOS.

Evaluating the potential of daily intake of polystyrene microplastics via drinking water in inducing PCOS and its ovarian fibrosis progression using female zebrafish

Polystyrene microplastics, extensively considered endocrine disrupting chemicals, disturb the reproductive system of living organisms. Polycystic ovary syndrome (PCOS), the reproductive endocrinopathy, is longstanding concern due to its eternal impacts as reproductive disorder and infertility. Despite several reports in reproductive and endocrine toxicity, there is inadequate literature regarding the daily intake of polystyrene-microplastics via drinking water in causing PCOS and leading to ovarian fibrosis in long-term. The present study investigated whether daily consumption of polystyrene-microplastics at doses equivalent to human exposure can cause PCOS and progress to ovarian fibrosis, using female zebrafish as model. Resembling letrozole-PCOS zebrafish model, daily intake of polystyrene-microplastics displayed hallmark PCOS pathophysiology; like excess body weight and %Gonadosomatic index, decreased Follicle Stimulating Hormone and β-estradiol, increased Luteinising Hormone, brain and ovarian Testosterone (39.3% and 75% respectively). Correspondingly, ovarian histology revealed more developing (stage I and II) oocytes and less mature oocytes alongwith cystic lesions; like follicular membrane disorganization, zona pellucida invagination, theca hypertrophy, basophilic granular accumulation and oocyte buddings. Lipid deposition in intestinal and ovarian tissues was evidenced and increased fasting blood glucose manifesting insulin resistance. The expression of PCOS biomarkers (tox3, dennd1a, fem1a) was significantly disturbed. Polystyrene microplastics played vital role in inducing PCOS further enhancing oxidative stress, which positively influences inflammation and aggravate ovarian mitophagy, shedding light on its ability to harshen PCOS into ovarian fibrosis, which is characterized by collagen deposition and upregulation of pro-fibrogenic biomarker genes. These findings illustrate the potential of daily microplastics intake via drinking water in triggering PCOS and its progression to ovarian fibrosis.

Transgenerational effects of extracts containing Microcystin-LR exposure on reproductive toxicity and offspring growth inhibition in a model organism zebrafish

Cyanobacteria cell lysates release numerous toxic substances (e.g., cyanotoxins) into the water, posing a serious threat to human health and aquatic ecosystems. Microcystins (MCs) are among the most abundant cyanotoxins in the cell lysates, with microcystin-LR (MC-LR) being one of the most common and highly toxic congeners. In this study, zebrafish (Danio rerio) were exposed to different levels MC-LR that from extracts of Microcystis aeruginosa. Changes in the MC-LR accumulations, organ coefficients, and antioxidant enzyme activities in the zebrafish were analyzed. Transgenerational reproductive toxicity of MC-LR in the maternal and paternal generations was further investigated, as well as the influences of extracts containing MC-LR exposures of the F1 on the growth of zebrafish. The study found that high levels of MC-LR could be detected in the major organs of adult zebrafish, particularly in spleen. Notably, concentration of MC-LR in the spermary was significantly higher than that in the ovarium. MC-LR could induce oxidative damage by affecting the activities of catalase and superoxide dismutase. Inherited from F0, MC-LR led to impaired development in the F1 generation. Difference in offspring survival rates could be observed in the groups with different MC-LR levels of maternal and paternal exposures. This study reveals transgenerational effects of MC-LR on the reproductive toxicity and offspring growth inhibition to the aquatic organisms, which should be emphasized in the future ecological risk assessment.

Enhanced reproductive toxicity of photodegraded polylactic acid microplastics in zebrafish

Microplastics are widely used due to their numerous advantages. However, they can have detrimental effects on marine ecosystems. When microplastics enter the ocean, they can be absorbed by marine organisms, leading to toxic effects. Additionally, the transformation of microplastics during natural degradation can alter their toxicity, necessitating further investigation. Polylactic acid (PLA) biodegradable plastics are commonly used, yet research on their toxicity, particularly their reproductive effects on aquatic organisms, remains limited. In this study, we conducted photodegradation of PLA using potassium persulfate as a catalyst to simulate natural degradation conditions. Our objective was to assess the reproductive toxicity of photodegraded PLA microplastics on zebrafish. The results revealed that photodegraded PLA exhibited elevated reproductive toxicity, resulting in abnormal oocyte differentiation, disruption of sexual hormone levels, and alterations in ovarian tissue metabolism. Metabolomics analysis indicated that both unphotodegraded PLA (UPLA) and photodegraded PLA (DPLA) disrupted oxidative stress homeostasis in zebrafish ovarian tissue by influencing pathways such as purine metabolism, phenylalanine metabolism, glutathione metabolism, and riboflavin metabolism. Furthermore, the DPLA treatment induced abnormal biosynthesis of taurocholic acid, which was not observed in the UPLA treatment group. Importantly, the DPLA treatment group exhibited more pronounced effects on offspring development compared to the UPLA treatment group, characterized by higher mortality rates, inhibition of embryo hatching, accelerated heart rates, and reduced larval body length. These findings underscore the varying levels of toxicity to zebrafish ovaries before and after PLA photodegradation, along with evidence of intergenerational toxicity.

Mating behaviors in ovoviviparous black rockfish (Sebastes schlegelii): molecular function of prostaglandin E2 as both a hormone and pheromone

Prostaglandins (PGs) are profound hormones in teleost sexual behavior, especially in mating. PGs act as pheromones that affect the olfactory sensory neurons of males, inducing the initiation of a series of mating behaviors. However, the molecular mechanism by which PGs trigger mating behavior in ovoviviparous teleosts is still unclear. In the present study, we employed the ovoviviparous black rockfish (Sebastes schlegelii), an economically important marine species whose reproductive production is limited by incomplete fertilization, as a model species. The results showed that when the dose of PGE2 was higher than 10 nmol/L, a significant (P < 0.05) increase in mating behaviors was observed. Dual-fluorescence in situ hybridization indicated that PGE2 could fire specific neurons in different brain regions and receptor cells in the olfactory sac. After combining with specific neurons in the central nervous system (CNS), a series of genes related to reproduction are activated. The intracerebroventricular administration of PGE2 significantly increased lhb levels (P < 0.05) in both sexes. Moreover, steroidogenesis in gonads was also affected, inducing an increase (P < 0.05) in E2 levels in males and T levels in females. PGE2 levels were also increased significantly (P < 0.05) in both sexes. The present study revealed that PGE2 can activate mating behavior in black rockfish in both hormone and pheromone pathways, leading to variations in sex steroid levels and activation of reproductive behaviors. Our results provide not only novel insight into the onset of mating behaviors in ovoviviparous teleosts but also solutions for the incomplete fertilization caused by natural mating in cage aquaculture.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-023-00214-w.

Unraveling the complexity of polycystic ovary syndrome with animal models

Polycystic ovary syndrome (PCOS) is a highly familial and heritable endocrine disorder. Over half of the daughters born to women with PCOS may eventually develop their own PCOS-related symptoms. Progress in the treatment of PCOS is currently hindered by the complexity of its clinical manifestations and incomplete knowledge of its etiopathogenesis. Various animal models, including experimentally induced, naturally occurring, and spontaneously arising ones, have been established to emulate a wide range of phenotypical and pathological traits of human PCOS. These studies have led to a paradigm shift in understanding the genetic, developmental, and evolutionary origins of this disorder. Furthermore, emerging evidence suggests that animal models are useful in evaluating state-of-the-art drugs and treatments for PCOS. This review aims to provide a comprehensive summary of recent studies of PCOS in animal models, highlighting the power of these disease models in understanding the biology of PCOS and aiding high-throughput approaches.

Nimbin analog N2 alleviates high testosterone induced oxidative stress in CHO cells and alters the expression of Tox3 and Dennd1a signal transduction pathway involved in the PCOS zebrafish

Polycystic ovarian syndrome (PCOS) is a hormonal disorder that causes enlargement of ovaries and follicular maturation arrest, which lacks efficient treatment. N2, a semi-natural triterpenoid from the neem family, was already reported to have antioxidant and antiinflammatory properties in our previous report. This study investigated the anti-androgenic property of N2 on testosterone-induced oxidative stress in Chinese Hamster Ovarian cells (CHO) and PCOS zebrafish model. The testosterone exposure disrupted the antioxidant enzymes and ROS level and enhanced the apoptosis in both CHO cells and PCOS zebrafish. However, N2 significantly protected the CHO cells from ROS and apoptosis. N2 improved the Gonado somatic index (GSI) and upregulated the expression of the SOD enzyme in zebrafish ovaries. Moreover, the testosterone-induced follicular maturation arrest was normalized by N2 treatment in histopathology studies. In addition, the gene expression studies of Tox3 and Denndla in zebrafish demonstrated that N2 could impair PCOS condition. Furthermore, to confirm the N2 activity, the in-silico studies were performed against PCOS susceptible genes Tox3 and Dennd1a using molecular docking and molecular dynamic simulations. The results suggested that N2 alleviated the oxidative stress and apoptosis in-vitro and in-vivo and altered the expression of PCOS key genes.