Bisphenol A disrupts the temporal pattern of histofunctional changes in the female reproductive tract of Caiman latirostris

Exposure to atrazine and endosulfan alters oviductal adenogenesis in the broad-snouted caiman (Caiman latirostris)

The molecular pathways involved in oviductal adenogenesis are highly conserved among vertebrates. In this work, we study the histomorphological changes and molecular pathways involved in Caiman latirostris oviductal adenogenesis and the effects of in ovo exposure to environmentally relevant doses of endosulfan (END) and atrazine (ATZ) on these processes. To this end, the histomorphological changes at epithelial and subepithelial compartments, the protein expressions of β-catenin and Wnt-7a, and the gene expression of metalloproteinases (MMPs) and its inhibitors (TIMPs) were evaluated as biomarkers of oviductal adenogenesis in prepubertal juvenile C. latirostris. Exposure to END altered adenogenesis-related epithelium characteristics and mRNA expression of MMP2, MMP9, and TIMP1. Exposure to ATZ increased the width of the subepithelial stroma with loosely arranged collagen fibers and increased β-catenin expression in buds (invaginated structures that precede glands). The results demonstrate that in ovo exposure to ATZ and END alters oviductal adenogenesis at tissue, cellular, and molecular levels. An altered oviductal adenogenesis could impair fertility, raising concern on the effects of pesticide pollution in wildlife and domestic animals.

Bisphenol A contamination in aquatic environments: a review of sources, environmental concerns, and microbial remediation

The production of polycarbonate, a high-performance transparent plastic, employs bisphenol A, which is a prominent endocrine-disrupting compound. Polycarbonates are frequently used in the manufacturing of food, bottles, storage containers for newborns, and beverage packaging materials. Global production of BPA in 2022 was estimated to be in the region of 10 million tonnes. About 65-70% of all bisphenol A is used to make polycarbonate plastics. Bisphenol A leaches from improperly disposed plastic items and enters the environment through wastewater from plastic-producing industries, contaminating, sediments, surface water, and ground water. The concentration BPA in industrial and domestic wastewater ranges from 16 to 1465 ng/L while in surface water it has been detected 170-3113 ng/L. Wastewater treatment can be highly effective at removing BPA, giving reductions of 91-98%. Regardless, the remaining 2-9% of BPA will continue through to the environment, with low levels of BPA commonly observed in surface water and sediment in the USA and Europe. The health effects of BPA have been the subject of prolonged public and scientific debate, with PubMed listing more than 17,000 scientific papers as of 2023. Bisphenol A poses environmental and health hazards in aquatic systems, affecting ecosystems and human health. While several studies have revealed its presence in aqueous streams, environmentally sound technologies should be explored for its removal from the contaminated environment. Concern is mostly related to its estrogen-like activity, although it can interact with other receptor systems as an endocrine-disrupting chemical. Present review article encompasses the updated information on sources, environmental concerns, and sustainable remediation techniques for bisphenol A removal from aquatic ecosystems, discussing gaps, constraints, and future research requirements.

Sex Determination and Ovarian Development in Reptiles and Amphibians: From Genetic Pathways to Environmental Influences

BACKGROUND

Reptiles and amphibians provide untapped potential for discovering how a diversity of genetic pathways and environmental conditions are incorporated into developmental processes that can lead to similar functional outcomes. These groups display a multitude of reproductive strategies, and whereas many attributes are conserved within groups and even across vertebrates, several aspects of sexual development show considerable variation.

SUMMARY

In this review, we focus our attention on the development of the reptilian and amphibian ovary. First, we review and describe the events leading to ovarian development, including sex determination and ovarian maturation, through a comparative lens. We then describe how these events are influenced by environmental factors, focusing on temperature and exposure to anthropogenic chemicals. Lastly, we identify critical knowledge gaps and future research directions that will be crucial to moving forward in our understanding of ovarian development and the influences of the environment in reptiles and amphibians.

KEY MESSAGES

Reptiles and amphibians provide excellent models for understanding the diversity of sex determination strategies and reproductive development. However, a greater understanding of the basic biology of these systems is necessary for deciphering the adaptive and potentially disruptive implications of embryo-by-environment interactions in a rapidly changing world.

Systematic review of reptile reproductive toxicology to inform future research directions on endangered or threatened species, such as sea turtles

Threatened or endangered reptiles, such as sea turtles, are generally understudied within the field of wildlife toxicology, with even fewer studies on how contaminants affect threatened species reproduction. This paper aimed to better inform threatened species conservation by systematically and quantitatively reviewing available research on the reproductive toxicology of all reptiles, threatened and non-threatened. This review found 178 studies that matched our search criteria. These papers were categorized into location conducted, taxa studied, species studied, effects found, and chemicals investigated. The most studied taxa were turtles (n = 87 studies, 49%), alligators/crocodiles (n = 54, 30%), and lizards (n = 37, 21%). Maternal transfer, sex steroid alterations, sex reversal, altered sexual development, developmental abnormalities, and egg contamination were the most common effects found across all reptile taxa, providing guidance for avenues of research into threatened species. Maternal transfer of contaminants was found across all taxa, and taking into account the foraging behavior of sea turtles, could help elucidate differences in maternal transfer seen at nesting beaches. Sex steroid alterations were a common effect found with contaminant exposure, indicating the potential to use sex steroids as biomarkers along with traditional biomarkers such as vitellogenin. Sex reversal through chemical exposure was commonly found among species that exhibit temperature dependent sex determination, indicating the potential for both environmental pollution and climate change to disrupt population dynamics of many reptile species, including sea turtles. Few studies used in vitro, DNA, or molecular methodologies, indicating the need for more research using high-throughput, non-invasive, and cost-effective tools for threatened species research. The prevalence of developmental abnormalities and altered sexual development and function indicates the need to further study how anthropogenic pollutants affect reproductive output in threatened reptiles.

Exposure to xenoestrogens alters the expression of key morphoregulatory proteins of oviduct adenogenesis in the broad-snouted caiman (Caiman latirostris)

Endocrine disrupting compounds (EDCs) are contaminants ubiquitously found in the environment, which pose a potential threat to aquatic and wetland ecosystems. Caiman latirostris, a crocodilian species that inhabits South American wetlands, is highly sensitive to EDC exposure. Previously, we reported that early postnatal exposure to EDCs such as Bisphenol A (BPA) and 17β-Estradiol (E₂) alters C. latirostris oviduct differentiation. The aim of this work was to elucidate the molecular mechanisms behind this alteration. To accomplish this, we established the ontogenic changes in histological features and the expression of Wnt-7a, Wnt-5a, β-catenin, FoxA2, desmin, and alpha smooth muscle actin (α-SMA) in the oviduct of C. latirostris. Then, we evaluated the effects of BPA and E₂ exposure on these histological features and protein expressions. Our results showed that during the postnatal differentiation of the oviduct the presence of histological features related to adenogenesis is associated with the levels of expression of FoxA2, β-catenin, Wnt-5a and Wnt-7a. Early postnatal exposure to BPA and E₂ decreased the presence of histological features related to adenogenesis and altered the levels of expression of FoxA2, β-catenin, Wnt-5a and Wnt-7a, as well as the desmin/α-SMA ratio. These findings suggest that altered levels of Wnt-7a, Wnt-5a, β-catenin and FoxA2 could play a role in the BPA and E₂-induced alteration in oviduct differentiation in C. latirostris. Thus, impaired adenogenesis and, probably, impaired reproduction in wildlife naturally exposed to BPA and other estrogenic agonists cannot be completely ruled out.

Effects of agricultural pesticides on the reproductive system of aquatic wildlife species, with crocodilians as sentinel species

Agricultural pesticides represent a significant class of endocrine-disrupting chemicals (EDCs) to which non-target organisms around the world are constantly exposed. Laboratory studies have found strong evidence showing the endocrine-disruptive potential of these pesticides at environmentally relevant exposure levels. Since the field of endocrine disruption continues to grow in richness and complexity, this review aims to provide an update on the effects of two agricultural pesticides that act as EDCs: atrazine and endosulfan. We will focus mainly on the effects on crocodilians due to their worldwide occurrence in tropical and sub-tropical wetland ecosystems and their ecological and physiological features, which render them vulnerable to exposure to pesticides with endocrine-disrupting action at all life stages. The results here reviewed provide important insights into the effects of hormonally active agricultural pesticides at cellular, tissue, and organ levels in the reproductive system of crocodiles. A better understanding of the effects of exposure to environmentally relevant doses of EDCs on the reproductive system of crocodilians will contribute to protect and improve the health of both wildlife species and humans.

Androgen receptor and uterine histoarchitecture in a PCOS rat model

Polycystic ovary syndrome (PCOS) is associated with hyperandrogenemia and uterine abnormalities. Our aim was to investigate the uterine effects of PCOS that are mediated through the androgen receptor (AR). After weaning, female rats were treated with sesame oil (Control), dehydroepiandrosterone (DHEA), or DHEA + flutamide (FLU, an AR antagonist) for 20 consecutive days. On postnatal day 41, serum, ovarian and uterine tissues were collected. DHEA and DHEA + FLU rats showed increased testosterone levels. DHEA rats showed increased epithelial height, glandular density, subepithelial stroma and myometrial thickness, associated with decreased nuclei density. These rats also showed increased uterine water content, with decreased aquaporin (AQP) 3, 7 and 8 expression in the uterine epithelium and increased AQP8 expression in the myometrium. DHEA rats also showed decreased uterine collagen remodeling, decreased cell proliferation in the subepithelial stroma, and increased apoptosis in the luminal and glandular epithelium and in the myometrium. They also showed an increase in insulin-like growth factor-1 and a decrease in phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase. The uterine stroma of DHEA rats showed no changes in progesterone receptor or estrogen receptor alpha (ERα) and increased AR expression. DHEA + FLU rats showed a smaller increase in the myometrial thickness, an increase in the uterine water content without AQP8 induction and a smaller decrease in collagen remodeling. These rats also showed no apoptosis induction and decreased proliferation in the myometrium, decreased ERα in the subepithelial stroma and myometrium and no modifications in AR. Our results demonstrate that the uterine cell turnover and collagen remodeling in DHEA rats are regulated through AR, directly or indirectly associated with ERα expression.

Long-term effects of in ovo exposure to an environmentally relevant dose of atrazine on the thyroid gland of Caiman latirostris

The increased incidence of human thyroid disorders, particularly in women, suggests that the exposure to endocrine-disrupting compounds (EDCs) together with sex-related factors could play a role in thyroid dysregulation. Since the herbicide atrazine (ATZ) is an environmental EDC suspected to behave as a thyroid disruptor, and Caiman latirostris is a crocodilian species highly sensitive to endocrine disruption that can be exposed to ATZ, this study aimed to describe the histoarchitecture and sexually dimorphic features of the thyroid gland of C. latirostris, and to determine the long-term effects of in ovo exposure to an environmentally relevant dose of ATZ (0.2 ppm) on its thyroid gland and growth. Control caimans showed no sexual dimorphisms. In contrast, ATZ-exposed caimans showed altered embryo growth but an unaltered temporal pattern of development and a sexually dimorphic response in the body condition index growth curves postnatally, which suggests a female-related increase in fat storage. Besides, both male and female exposed caimans showed increases in the size of the thyroid stromal compartment, content of interstitial collagen, and follicular hyperplasia, and decreases in the expression of androgen receptor in the follicular epithelium. ATZ-exposed females, but not males, also showed evidences of thyroid enlargement, colloid depletion, increased follicular epithelial height and increased presence of microfollicular structures. Our results demonstrate that prenatal exposure of caimans to ATZ causes thyroid disruption and that females were more vulnerable to ATZ than males. The effects were organizational and observed long after exposure ended. These findings alert on ATZ side-effects on the growth, metabolism, reproduction and development of non-target exposed organisms, particularly females.

The external genitalia in juvenile Caiman latirostris differ in hormone sex determinate-female from temperature sex determinate-female

The broad-snouted caiman (Caiman latirostris) is a crocodilian species that inhabits South American wetlands. As in all other crocodilians, the egg incubation temperature during a critical thermo-sensitive window (TSW) determines the sex of the hatchlings, a phenomenon known as temperature-dependent sex determination (TSD). In C. latirostris, we have shown that administration of 17-β-estradiol (E₂) during the TSW overrides the effect of the male-producing temperature, producing phenotypic females (E₂SD-females). Moreover, the administration of E₂ during TSW has been proposed as an alternative way to improve the recovery of endangered reptile species, by skewing the population sex ratio to one that favors females. However, the ovaries of E₂SD-female caimans differ from those of TSD-females. In crocodilians, the external genitalia (i.e. clitero-penis structure or phallus) are sexually dimorphic and hormone-sensitive. Despite some morphological descriptions aimed to facilitate sexing, we found no available data on the C. latirostris phallus histoarchitecture or hormone dependence. Thus, the aims of this study were: (1) to establish the temporal growth pattern of the phallus in male and female caimans; (2) to evaluate histo-morphological features and the expression of estrogen receptor alpha (ERα) and androgen receptor (AR) in the phallus of male and female pre-pubertal juvenile caimans; and (3) to determine whether the phallus of TSD-females differs from the phallus of E₂SD-females. Our results demonstrated sexually dimorphic differences in the size and growth dynamics of the caiman external genitalia, similarities in the shape and spatial distribution of general histo-morphological compartments, and sexually dimorphic differences in innervation, smooth muscle fiber distribution, collagen organization, and ERα and AR expressions. The external genitalia of E₂SD-females differed from that of TSD-females in many histological features and in the expression of ERα and AR, resembling patterns described in males. Our results alert on the effects of estrogen agonist exposure during TSW and suggest that caution must be taken regarding the use of E₂SD as a procedure for wildlife population management.