René Lafont

The Endocrinology of Invertebrates

Neuroendocrine controls exist already in lower invertebrates, and during evolution, endocrine glands have appeared in molluscs, although endocrine cells may have appeared earlier. The present review discusses at first the different strategies used in the past and nowadays to isolate hormones and to analyze their functions. Both peptidic and lipidic hormones have been found in invertebrates, just as in vertebrates. Some of these hormones are specific of invertebrates, whereas other ones may be very close to their vertebrate counterparts. However, hormonal functions are less conserved than structures, a fact that is also apparent within vertebrate hormones, depending on which tissues possess receptors and are therefore their targets. Some examples of hormone families (peptides, steroids, terpenes) are described. Xenobiotics disturb normal cell functions, and they may accordingly alter endocrine systems, either at the endocrine cells or at the target cell levels. This will be illustrated by a few characteristic examples. However, the rather fragmentary knowledge of invertebrate (except insect) endocrinology prevents in many cases an adequate understanding of the mechanisms involved in xenobiotic toxicity.

Chromatographic procedures for the isolation of plant steroids

In this review, we consider the general principles and specific methods for the purification of different classes of phytosteroids which have been isolated from plant sources: brassinosteroids, bufadienolides, cardenolides, cucurbitacins, ecdysteroids, steroidal saponins, steroidal alkaloids, vertebrate-type steroids and withanolides. For each class we give a brief summary of the characteristic structural features, their distribution in the plant world and their biological effects and applications. Most classes are associated with one or a few plant families, e.g., the withanolides with the Solanaceae, but others, e.g., the saponins, are very widespread. Where a compound class has been extensively studied, a large number of analogues are present across a range of species. We discuss the general principles for the isolation of plant steroids. The predominant methods for isolation are solvent extraction/partition followed by column chromatography and thin-layer chromatography/HPLC.

Mutations in the neverland Gene Turned Drosophila pachea into an Obligate Specialist Species

Limiting Your Options Many species are dependent on specific resources that may limit their range of hosts to that of a few or even a single species. The restriction of the fly Drosophila pachea to senita cactus is a classic case of an ecological specialization. Lang et al. (p. 1658) reveal how multiple amino acid substitutions in the neverland gene have rendered D. pachea dependent upon the lathosterol of the senita cactus. Thus, relatively few genetic changes can play a large role in determining a species ecological niche. A few changes made the fly Drosophila pachea reliant on the steroid precursors produced by the senita cactus. Most living species exploit a limited range of resources. However, little is known about how tight associations build up during evolution between such specialist species and the hosts they use. We examined the dependence of Drosophila pachea on its single host, the senita cactus. Several amino acid changes in the Neverland oxygenase rendered D. pachea unable to transform cholesterol into 7-dehydrocholesterol (the first reaction in the steroid hormone biosynthetic pathway in insects) and thus made D. pachea dependent on the uncommon sterols of its host plant. The neverland mutations increase survival on the cactus’s unusual sterols and are in a genomic region that faced recent positive selection. This study illustrates how relatively few genetic changes in a single gene may restrict the ecological niche of a species.

Phytoecdysteroids from the juice of Serratula coronata L. (Asteraceae)

Seven phytoecdysteroids have been isolated from Serratula coronata L. One of them is a new phytoecdysteroid, 3-epi-20-hydroxyecdysone. Two further ecdysteroids, 20-hydroxyecdysone 22-acetate and taxisterone, are isolated from this species for the first time in addition to the typical S. coronata ecdysteroids, 20-hydroxyecdysone, ecdysone, ajugasterone C and polypodine B. The juice squeezed from aerial parts of fresh plants of S. coronata was extracted with ethyl acetate. The ecdysteroids were isolated by a combination of chromatographic techniques (mainly HPLC) and identified by 1D and 2D (1)H and (13)C NMR experiments and mass-spectrometry. The biological activities of 3-epi-20-hydroxyecdysone (EC(50)=1.6 x 10(-7) M), taxisterone (EC(50)=9.5 x 10(-8) M) and ajugasterone C (EC(50)=6.2 x 10(-8) M) have been determined in the Drosophila melanogaster B(II) bioassay for ecdysteroid agonist activity.

Distribution of phytoecdysteroids in the Caryophyllaceae.

Certain genera within the Caryophyllaceae (especially Silene and Lychnis) have received a significant amount of attention with regard to the isolation and identification of ecdysteroids. However, the taxonomy of this family is difficult. Hence, the occurrence of phytoecdysteroids in members of the Caryophyllaceae is presented, and combined with new data on ecdysteroid agonist (phytoecdysteroid) and antagonist activities, in order to survey the distribution of phytoecdysteroid-containing species within this large family, and to assess the utility of phytoecdysteroids as chemotaxonomic markers. The new data presented (representing ca. 110 species) have been obtained by the application of sensitive biological/biochemical methods for the detection of ecdysteroid agonists and antagonists, using Drosophila melanogaster B(II) bioassay and ecdysteroid-specific immunoassays. In the antagonist version of the B(II) bioassay, only weak ecdysteroid antagonist activities were detected in a few of the extracts. From both new and previously available data, it was found that phytoecdysteroids were present predominantly in the Genera Lychnis, Petrocoptis, Sagina and Silene. Comparison of ecdysteroid occurrence with a molecular phylogeny for the tribe Sileneae [Taxon 44 (1995) 525] revealed close association of ecdysteroid occurrence with certain groups of this tribe. In 14 species of Silene examined, there is a reasonable, but not absolute, relationship between the presence of ecdysteroids in the seeds and in other plant parts. Where ecdysteroids are present in the plant, highest concentrations are generally present in the roots.

Dietary Effects of Four Phytoecdysteroids on Growth and Development of the Indian Meal Moth, Plodia interpunctella

Abstract Using pure phytoecdysteroids isolated from Ajuga iva (L.) Schreber (Lamiales: Lamiaceae) and Silene nutans L. (Caryophyllales: Caryophyllaceae), plants known for their high ecdysteroid content, a study was carried out on the effects of ingestion of four different phytoecdysteroids (20-hydroxyecdysone, polypodine B, ponasterone A and makisterone A) on the growth and development of the Indian meal moth, Plodia interpunctella Hübner (Lepidoptera: Pyralidae) larvae when added at a concentration of 200 ppm in their diet. The experiments clearly showed the susceptibility of P. interpunctella to phytoecdysteroid ingestion. The toxicity of phytoecdysteroids manifested itself by a decrease in larval weight, induction of cannibalism and an increase of mortality, together with disruption of development. The severity of the phytoecdysteroid effect on P. interpunctella depended on the structure of the molecule. The results demonstrate that the minimal structural differences existing between these four phytoecdysteroids significantly affected their toxicity toward P. interpunctella. Makisterone A was the most toxic of the four compounds towards P. interpunctella larvae. In conclusion, phytoecdysteroids ingestion evokes disruptive growth effects on P. interpunctella. This work supports a role for phytoecdysteroids in plant defence against phytophagous insects.

Diversity of Ecdysteroids in Animal Species

Arthropods contain a significant diversity of ecdysteroids which are used to control their development and reproduction. This diversity is for one part connected with the diversity of the sterol precursors used. Outside Arthropods, ecdysteroids or/and closely related molecules have been found in most other Invertebrates and also in Tunicates. Definite proof for their endogenous origin is however still lacking, and their physiological functions (if any) remain to be established. It is hoped that thanks to the availability of whole genome sequencing of an increasing species number, tools will become available for answering these questions.

The phytoecdysteroid profiles of 7 species of Silene (Caryophyllaceae)

The phytoecdysteroid profiles of extracts of aerial parts of flowering plants of 7 ecdysteroid-containing species in the genus Silene (Caryophyllaceae; S. fridvaldszkyana Hampe, S. gigantea L., S. graminifolia Otth, S. mellifera Boiss. & Reuter, S. repens Patr., S. schmuckeri Wettst., and S. sendtneri Boiss.) have been examined and identified by HPLC and, in the case of two new compounds, by mass spectrometry and NMR. S. frivaldszkyana was found to contain predominantly 20-hydroxyecdysone (20E), with smaller amounts of 2-deoxyecdysone (2dE), 2-deoxy-20-hydroxyecdysone (2d20E), polypodine B (polB), integristerone A (IntA), 26-hydroxypolypodine B (26polB), and 20,26-dihydroxyecdysone (20,26E). Additionally, a new minor ecdysteroid, 26-hydroxyintegristerone A, has been identified from this species. S. gigantea contains 3 major ecdysteroids (2dE, 2d20E, and 20E) and much smaller amounts of intA and 2-deoxy-20-hydroxyecdysone 25-beta-D-glucoside, which is a new ecdysteroid. Ecdysteroids in the other 5 species have been identified by co-chromatography with reference compounds on RP- and NP-HPLC systems. There is considerable variability with regard to ecdysteroid profiles within the genus Silene. The chemotaxonomic value of ecdysteroid profiles within the genus Silene is discussed.

Detection and identification of 20-hydroxyecdysone metabolites in calf urine by liquid chromatography-high resolution or tandem mass spectrometry measurements and establishment of their kinetics of elimination after 20-hydroxyecdysone administration

Ecdysteroids, which are steroid hormones in invertebrates, but are also present in plants, could be potentially used as anabolic agents in food-producing animals because of their growth-promoting properties. In this context, the metabolism of 20-hydroxyecdysone (20E) has been investigated in cattle in order to efficiently control its potential misuse. The analytical procedure involves purification on two solid-phase extraction cartridges (SPE octadecylsilyl and SPE silica) prior to detection based on liquid chromatography coupled to high resolution mass spectrometry in negative electrospray ionization mode (LC-(ESI-)-HRMS). Each new signal appearing on full-scan HRMS (30,000) during the analysis was investigated by tandem mass spectrometry (MS/MS). Comparison of the mass spectra pattern between 20E and potential metabolites has given informations on the chemical structures of the metabolites. This targeted approach, combining HRMS and MS(n) measurements on a linear trap in tandem with an orbital trap, allowed us to elucidate the structure of several 20E metabolites in calf urine: 14-deoxy-20-hydroxyecdysone, 20,26-dihydroxyecdysone and 14-deoxy-20,26-dihydroxyecdysone, the last of which had never previously been reported in bovine. The kinetics of elimination of these metabolites were investigated, and two of them were monitored by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) measurements over 6 days after 20E administration to calves, thus increasing the time-window for detection after 20E administration and thereby allowing for more efficient control of its misuse.

4 – Ecdysteroid Chemistry and Biochemistry

Publisher Summary This chapter focuses on the techniques used for ecdysteroid analysis and the biosynthesis and metabolism of these hormones. Ecdysteroids could be defined either by their biological activity (molting hormones) or their chemical structure. The huge chemical diversity of ecdysteroids results from variations in the number and position of OH groups, which can be either free or conjugated to various polar or apolar moieties, giving rise to the 70 different molecules. The greatest diversity has been found in the eggs/embryos of Orthoptera and Lepidoptera, probably because they contain very large amounts of these molecules. The nomenclature of insect ecdysteroids is generally derived from the ecdysone name, but this is not always the case, and the trivial name of many ecdysteroids is related to the name of the species from which they have been isolated; standardized abbreviations have been proposed for insect ecdysteroids and are used.