Ponasterone A: a new ecdysteroid from the embryos and serum of brachyuran crustaceans

Identification of Novel Environmental Substances Relevant to Pediatric Graves' Disease

Graves' disease (GD) is the most common cause of hyperthyroidism, yet a relatively rare disease in the pediatric population. GD is a complex disorder influenced by both genetic and environmental factors. In this study, we aimed to find new environmental factors influencing the pathogenesis of GD. We investigated serum substances in 30 newly diagnosed GD children and 30 age- and gender-matched healthy controls. We measured total iodine by inductively coupled plasma-mass spectrometry (ICP-MS), analyzed perfluorinated compounds via ultra-high-performance liquid chromatography coupled with multiple reaction monitoring mass spectrometry (UHPLC-MRM-MS), and explored other environmental substances using ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) analysis. Twenty-nine single-nucleotide polymorphisms (SNPs) in eight genes related to GD were analyzed by SNaPshot. The serum total iodine was significantly higher in GD group, but its association with GD onset was weak, only with Exp(B) value near 1. The perfluorinated compound levels were not different between the two groups. More importantly, we found 16 environmental substances significantly different between GD and control groups, among which ponasterone A is a risk factor (p = 0.007 and Exp(B) = 14.14), while confertifoline is a protective factor against GD onset (p = 0.002 and Exp(B) = 0.001). We also identified 10 substances correlated significantly with thyroid indices in GD patients, among which seven associated with levels of the thyroid autoantibody TPOAb. No known SNPs were found predisposing GD. In this study, we explored a broad variety of environmental substances and identified novel factors that are potentially involved in the pediatric GD pathogenesis.

Molecular toxicity identification evaluation (mTIE) approach predicts chemical exposure in Daphnia magna

Daphnia magna is a bioindicator organism accepted by several international water quality regulatory agencies. Current approaches for assessment of water quality rely on acute and chronic toxicity that provide no insight into the cause of toxicity. Recently, molecular approaches, such as genome wide gene expression responses, are enabling an alternative mechanism based approach to toxicity assessment. While these genomic methods are providing important mechanistic insight into toxicity, statistically robust prediction systems that allow the identification of chemical contaminants from the molecular response to exposure are needed. Here we apply advanced machine learning approaches to develop predictive models of contaminant exposure using a D. magna gene expression data set for 36 chemical exposures. We demonstrate here that we can discriminate between chemicals belonging to different chemical classes including endocrine disruptors and inorganic and organic chemicals based on gene expression. We also show that predictive models based on indices of whole pathway transcriptional activity can achieve comparable results while facilitating biological interpretability.

Endocrine interactions between plants and animals: Implications of exogenous hormone sources for the evolution of hormone signaling

Hormones are central to animal physiology, metabolism and development. Details on signal transduction systems and regulation of hormone synthesis, activation and release have only been studied for a small number of animal groups, notably arthropods and chordates. However, a significant body of literature suggests that hormonal signaling systems are not restricted to these phyla. For example, work on several echinoderm species shows that exogenous thyroid hormones (THs) affect larval development and metamorphosis and our new data provide strong evidence for endogenous synthesis of THs in sea urchin larvae. In addition to these endogenous sources, these larvae obtain THs when they consume phytoplankton. Another example of an exogenously acquired hormone or their precursors is in insect and arthropod signaling. Sterols from plants are essential for the synthesis of ecdysteroids, a crucial group of insect morphogenic steroids. The availability of a hormone or hormone precursor from food has implications for understanding hormone function and the evolution of hormonal signaling in animals. For hormone function, it creates an important link between the environment and the regulation of internal homeostatic systems. For the evolution of hormonal signaling it helps us to better understand how complex endocrine mechanisms may have evolved.

Hemolymph ecdysteroids during the last three molt cycles of the blue crab, Callinectes sapidus: quantitative and qualitative analyses and regulation

The profiles of circulating ecdysteroids during the three molt cycles prior to adulthood were monitored from the juvenile blue crab, Callinectes sapidus. Ecdysteroid patterns are remarkably similar in terms of peak concentrations ranging between 210-330 ng/ml hemolymph. Analysis of hemolymph at late premolt stage revealed six different types of ecdysteroids with ponasterone A (PoA) and 20-OH ecdysone (20-OH E) as the major forms. This ecdysteroid profile was consistent in all three molt cycles. Bilateral eyestalk ablation (EA) is a procedure that removes inhibitory neurohormones including crustacean hyperglycemic hormone (CHH) and molt-inhibiting hormone (MIH) and often results in precocious molting in crustaceans. However, the inhibitory roles of these neuropeptides in vivo have not yet been tested in C. sapidus. We determined the regulatory roles of CHH and MIH in the circulating ecdysteroid from ablated animals through daily injection. A daily administration of purified native CHH and MIH at physiological concentration maintained intermolt levels of ecdysteroids in the EA animals. This suggests that Y organs (YO) require a brief exposure to CHH and MIH in order to maintain the low level of ecdysteroids. Compared to intact animals, the EA crabs did not exhibit the level of peak ecdysteroids, and the major ecdysteroid turned out to be 20-OH E, not PoA. These results further underscore the important actions of MIH and CHH in ecdysteroidogenesis, as they not only inhibit, but also control the composition of output of the YO activity.

Interaction of PAHs and PCBs with ecdysone-dependent gene expression and cell proliferation

This study was done to determine whether PAHs and PCBs can interact with the arthropod steroid hormone system. Ecdysteroid molting hormones control growth, molting, and reproduction in arthropods. A spike in 20-OH ecdysone (20 HE) triggers the molt cycle in crustaceans, and earlier studies have shown that PAHs can affect this molt cycle in several crab species. However, the mechanism of this molt cycle interaction is unknown. Both PAHs and PCBs interact with other nuclear receptors; however, nothing is known about their ability to interact with the invertebrate ecdysone receptor (EcR). Four PAHs, benzo[a]pyrene, benzo[b]fluoranthene, pyrene, and chrysene, and the commercial PCB mixture, Aroclor 1254, were used to determine the ability of these classes of compounds to induce ecdysone-dependent reporter gene expression and to modify the proliferation and differentiation response of the ecdysteroid-responsive Cl.8+ cell line. The four PAHs were each able to enhance the ecdysteroid response in both the reporter gene and the cell proliferation assays only when given in conjunction with ecdysteroids. Aroclor 1254 had no effect in either system, either alone or in conjunction with ecdysteroids. These studies show that although the PAHs alone do not activate ecdysteroid-dependent gene expression or cell differentiation, they are able to enhance the effect of ecdysteroids, presumably through a non-receptor-mediated process. This mechanism may explain the effects on molting which have been reported after low-level crude oil exposures in crustaceans.

Ecdysteroids in the embryos and sera of the crabs, Cancer magister and C. anthonyi

Ecdysteroids in the embryos and sera of ovigerous brachyuran crabs, Cancer magister and C. anthonyi, were measured and characterized by radioimmunoassay (RIA) and high-performance liquid chromatography (HPLC). C. magister embryos displayed a biphasic pattern of ecdysteroid fluctuation during development; titers decreased until mid embryogenesis and then increased and peaked prior to hatching. HPLC-RIA analysis indicated increasing ecdysone concentrations from mid embryogenesis to hatching. Endogenous biosynthesis of ecdysone by the embryos is suggested. In contrast, ecdysteroid titers in the embryos of C. anthonyi showed a steady decrease from very high initial concentrations. The decrease in titers of ecdysone and 20-hydroxyecdysone is suggestive of utilization of maternally derived ecdysteroids rather than endogenous biosynthesis during the shorter embryogenic period for C. anthonyi. Ecdysteroid concentrations did not differ with respect to location of the embryo within the egg mass. Serum ecdysteroids in C. magister females generally showed a monotonic pattern during brooding. However, for C. anthonyi females, increasing and decreasing titers were observed during the brood and interbrood periods, respectively. These fluctuations suggest mobilization of the ecdysteroids to the ovaries for subsequent storage and utilization during embryogenesis. The evolutionary significance of these differing patterns of ecdysteroid metabolism in these congeners is discussed.

Studies on the biosynthesis of ecdysone by the Y-organs of Carcinus maenas

High specific activity tritiated ecdysone precursor, 2,22,25-trideoxyecdysone, was incubated with Y-organs from intermoult and premoult shore crabs. Several metabolites were identified among which ecdysone and 25-deoxyecdysone. The concomitant production of these 2 molecules by Y-organs and their subsequent hydroxylation at C-20 by peripheral tissues, provide an explanation for the presence of both 20-hydroxyecdysone and ponasterone A (25-deoxy-20-hydroxyecdysone) in the circulating haemolymph of crabs.

Ecdysteroid metabolism in a crab: Carcinus maenas L

Ponasterone A (25-deoxy-20-hydroxyecdysone) and 20-hydroxyecdysone were the major ecdysteroids detected in crab hemolymph, although some ecdysone was also present. The metabolism of ponasterone A was examined in intermolt and premolt crabs either by injecting the radiolabeled hormone or by incubating tissues in its presence. Metabolites were extracted from the surrounding seawater and from tissues and separated by high-performance liquid chromatography. Ponasterone A metabolism proceeds through (1) C-25 and C-26 hydroxylation, followed by formation of inactivation products via oxidation of the terminal alcoholic group to a carboxylic residue, (2) conjugation, (3) "binding" to very polar compounds and (4) side-chain scission. The conversion of ponasterone A into 20-hydroxyecdysone, inokosterone (25-deoxy-20, 26-dihydroxyecdysone), 20, 26-dihydroxyecdysone and ecdysonoic acids, as well as the formation of conjugates and of very polar compounds, occurs in various tissues. These metabolites were excreted by both intermolt and premolt crabs.

Structure of the egg funiculus and deposition of embryonic envelopes in a crab

The newly laid egg of Carcinus maenas is attached to a maternal ovigerous seta by a funiculus which consists of the two superimposed vitelline envelopes 1a + 1b, highly stretched and concurrently showing important structural alterations. The funiculus is glued to the specialized seta merely owing to the strong adhesiveness of its external face comprising the outermost vitelline envelope 1a, without any added adhesive. The subjacent envelope 2, originated from the cortical reaction, is not involved in such a funiculus elaboration. In the course of the embryonic development, four new coatings are successively secreted from the ectodermal embryonic cells, underneath the (1a + 1b + 2) fertilization envelope or embryonic capsule. They will remain until hatching in this concentric order, thus giving evidence of successive embryonic moulting cycles, with apolysis but without exuviation. In addition, the successive secretory phases, regarding to the embryonic envelope elaborations, happen in presence of high concentrations of the ecdysteroid ponasterone A which might be involved consequently in such secretory processes.