The occurrence of ecdysteroids in the cestode, Moniezia expansa

Origin of ecdysis: fossil evidence from 535-million-year-old scalidophoran worms

With millions of extant species, ecdysozoans (Scalidophora, Nematoida and Panarthropoda) constitute a major portion of present-day biodiversity. All ecdysozoans secrete an exoskeletal cuticle which must be moulted periodically and replaced by a larger one. Although moulting (ecdysis) has been recognized in early Palaeozoic panarthropods such as trilobites and basal groups such as anomalocaridids and lobopodians, the fossil record lacks clear evidence of ecdysis in early scalidophorans, largely because of difficulties in recognizing true exuviae. Here, we describe two types of exuviae in microscopic scalidophoran worms from the lowermost Cambrian Kuanchuanpu Formation ( ca 535 Ma) of China and reconstruct their moulting process. These basal scalidophorans moulted in a manner similar to that of extant priapulid worms, extricating themselves smoothly from their old tubular cuticle or turning their exuviae inside out like the finger of a glove. This is the oldest record of moulting in ecdysozoans. We also discuss the origin of ecdysis in the light of recent molecular analyses and the significance of moulting in the early evolution of animals.

Ancient origins of arthropod moulting pathway components

Ecdysis (moulting) is the defining character of Ecdysoza (arthropods, nematodes and related phyla). Despite superficial similarities, the signalling cascade underlying moulting differs between Panarthropoda and the remaining ecdysozoans. Here, we reconstruct the evolution of major components of the ecdysis pathway. Its key elements evolved much earlier than previously thought and are present in non-moulting lophotrochozoans and deuterostomes. Eclosion hormone (EH) and bursicon originated prior to the cnidarian-bilaterian split, whereas ecdysis-triggering hormone (ETH) and crustacean cardioactive peptide (CCAP) evolved in the bilaterian last common ancestor (LCA). Identification of EH, CCAP and bursicon in Onychophora and EH, ETH and CCAP in Tardigrada suggests that the pathway was present in the panarthropod LCA. Trunk, an ancient extracellular signalling molecule and a well-established paralog of the insect peptide prothoracicotropic hormone (PTTH), is present in the non-bilaterian ctenophore Mnemiopsis leidyi. This constitutes the first case of a ctenophore signalling peptide with homology to a neuropeptide.

Animals such as insects, crabs and spiders belong to one of the most species-rich animal groups, called the arthropods. These animals have exoskeletons, which are hard, external coverings that support their bodies. Arthropods shed their exoskeletons as they grow, a process called ecdysis or moulting, and this behaviour is controlled by a set of hormones and small protein-like molecules called neuropeptides that allow communication between neurons.

Other animals, such as roundworms, also moult; and together with arthropods they are classified into a group called the Ecdysozoa. Since moulting is a common behaviour in ecdysozoans, it was previously assumed that its signalling components had evolved in the common ancestor of roundworms and arthropods, although differences in the moulting machinery between both groups exist.

Here, De Oliveira et al. investigate the evolutionary origins of the arthropod moulting machinery and find that some of the hormones and neuropeptides involved appeared long before the arthropods themselves.

Database searches showed that important hormones and neuropeptides involved in arthropod moulting can be found in diverse animal groups, such as jellyfish, molluscs and starfish, confirming that these molecules evolved before the last common ancestor of roundworms and arthropods. These animals must therefore use the hormones and neuropeptides in many processes unrelated to moulting. De Oliveira et al. also found that roundworms have lost most of these molecules, and that moulting in these animals must be driven by a different complement of hormones and neuropeptides.

These results invite research into the role of moulting hormones and neuropeptides in animals outside the Ecdysozoa. They also show that signalling pathways and the processes they regulate are highly adaptable: two animals can use the same hormone in entirely different processes, but conversely, the same behaviour may be regulated by different molecules depending on the animal. This means that the evolution of a process and the evolution of its regulation can be decoupled, a finding that has important implications for the study of signalling pathways and their evolution.

Halloween genes in panarthropods and the evolution of the early moulting pathway in Ecdysozoa

Moulting is a characteristic feature of Ecdysozoa-the clade of moulting animals that includes the hyperdiverse arthropods and less speciose groups, such as onychophorans, tardigrades and nematodes. Moulting has been best analysed in arthropods, specifically in insects and crustaceans, in which a complex neuroendocrine system acts at the genomic level and initiates the transcription of genes responsible for moulting. The key moulting hormones, ecdysone and 20-hydroxyecdysone, are subsequently synthesized from cholesterol ingested with food. Their biosynthesis is regulated by the Rieske-domain protein Neverland and cytochrome P450 enzymes encoded by the so-called 'Halloween' genes. Ecdysone is then released into the haemolymph and modified into 20-hydroxyecdysone, which binds to the nuclear receptor EcR/USP and initiates transcription of the Early genes. As little is known about the moulting pathway of other ecdysozoans, we examined the occurrence of genes involved in ecdysteroid biosynthesis and the early moulting cascade across ecdysozoan subgroups. Genomic and transcriptomic searches revealed no Halloween genes in cycloneuralians, whereas only shadow (CYP315A1) is present in onychophorans and tardigrades, suggesting that the Halloween genes evolved stepwise in panarthropods. These findings imply that the genes which were responsible for the ecdysteroid biosynthesis in the last common ancestor of Ecdysozoa are currently unknown.

Cloning and characterization of an Echinococcus granulosus ecdysteroid hormone nuclear receptor HR3-like gene

Cystic echinococcosis is an important parasitic zoonosis caused by the dog tapeworm Echinococcus granulosus. Little is known about adult worm development at the molecular level. Transcription analysis showed that the E. granulosus hormone receptor 3-like (EgHR3) gene was expressed in protoscoleces and adult worms, indicating its role in early adult development. In this study, we cloned and characterized EgHR3 showing that its cDNA contains an open reading frame (ORF) of 1890 bp encoding a 629 amino acid protein, which has a DNA-binding domain (DBD) and a ligand-binding domain (LBD). Immunolocalization revealed the protein was localized in the parenchyma of protoscoleces and adult worms. Real-time PCR analysis showed that EgHR3 was expressed significantly more in adults than in other stages of development (p<0.01) and that its expression was especially high in the early stage of adult worm development induced by bile acids. EgHR3 siRNA silenced 69–78% of the level of transcription in protoscoleces, which resulted in killing 43.6–60.9% of protoscoleces after 10 days of cultivation in vitro. EgHR3 may play an essential role in early adult worm development and in maintaining adult biological processes and may represent a novel drug or vaccine target against echinococcosis.

Parasites and steroid hormones: corticosteroid and sex steroid synthesis, their role in the parasite physiology and development

In many cases parasites display highly complex life cycles that include the penetration and permanence of the larva or adults within host organs, but even in those that only have one host, reciprocal, intricate interactions occur. Evidence indicates that steroid hormones have an influence on the development and course of parasitic infections. The host gender's susceptibility to infection, and the related differences in the immune response are good examples of the host-parasite interplay. However, the capacity of these organisms to synthesize their own steroidogenic hormones still has more questions than answers. It is now well-known that many parasites synthesize ecdysteroids, but limited information is available on sex steroid and corticosteroid synthesis. This review intends to summarize some of the existing information in the field. In most, but not all parasitosis the host's hormonal environment determines the susceptibility, the course, and severity of parasite infections. In most cases the infection disturbs the host environment, and activates immune responses that end up affecting the endocrine system. Furthermore, sex steroids and corticosteroids may also directly modify the parasite reproduction and molting. Available information indicates that parasites synthesize some steroid hormones, such as ecdysteroids and sex steroids, and the presence and activity of related enzymes have been demonstrated. More recently, the synthesis of corticosteroid-like compounds has been shown in Taenia solium cysticerci and tapeworms, and in Taenia crassiceps WFU cysticerci. In-depth knowledge of the parasite's endocrine properties will contribute to understand their reproduction and reciprocal interactions with the host, and may also help designing tools to combat the infection in some clinical situations.

Internal chemical communication within flatworms

An understanding of reproductive function is important for control of parasitic helminths. In cestodes and trematodes virtually nothing is known about regulatory and coordinating mechanisms that control maturation, gamete formation, egg production, and related processes. Neurosecretory neurons have been reported in various species but specific modes of action of neurohormones have yet to be demonstrated. The role of ecdysone is being investigated.

Steroidogenic capacity of Trypanosoma cruzi trypomastigotes

American Trypanosomiasis is caused by the hemoflagellate Trypanosoma cruzi (T. cruzi) and affects millions of persons causing variable degrees of digestive and heart disturbances. As far as we concerned, T. cruzi capacity to synthesize steroid hormones has not been investigated. Therefore, the aim of this work was to investigate the capacity of T. cruzi trypomastigotes to transform tritiated steroid precursors into androgens and estrogens. The T. cruzi Tulahuén strain was obtained from mice blood. The trypomastigotes were cultured for 6 and 24h in Dulbbeco's modified Eagle's medium plus FCS and antibiotics. Tritiated dehydroepiandrosterone or androstendione were added to the culture media and parasites were incubated for 6 or 24h. The cultures were centrifuged and ether extracted. The steroids were analyzed by thin layer chromatography (TLC) in two solvent systems. After incubation with 3H-androstenedione, T. cruzi trypomastigotes synthesized 3H-testosterone (T), 3H-17beta-estradiol (E2) and 3H-estrone (E1). Metabolism of 3H-DHEA by the parasites yielded 3H-androstendione and 3H-androstendiol at 6h of incubation. The recrystallization procedure further demonstrated the 3H-androstendiol and 3H-17beta-estradiol syntheses. Results indicate for the first time that T. cruzi trypomastigotes produce androgens and estrogens when incubated in the presence of steroid precursors and suggest the presence of active parasite steroidogenic enzymes.

The key steroidogenic enzyme 3beta-hydroxysteroid dehydrogenase in Taenia solium and Taenia crassiceps (WFU)

Larval and adult stages of Taenia solium and Taenia crassiceps WFU strain were analyzed by histochemical and biochemical methods to determine the existence of steroid pathways. The presence of the key enzyme 3beta-hydroxisteroid-dehydrogenase (3beta-HSD) was examined in frozen sections of cysticerci obtained from mice and segments of tapeworms obtained from the intestine of hamsters. 3beta-HSD activity was detected by nitroblue-tetrazolium products after incubation with dehydroepiandrosterone, androstendiol, or pregnenolone. Tapeworm tissues exhibited 3beta-HSD activity in the subtegumentary areas of the neck and immature proglottids following incubation with androstendiol, as well as surrounding the testes in mature proglottids. T. solium cysticerci exhibited 3beta-HSD activity in the subtegumentary tissues. The synthesis of steroid hormones involving the activity of 3beta-HSD was studied in cysticerci or tapeworms incubated in the presence of tritiated steroid precursors. The culture media were analyzed by thin layer chromatography and showed synthesis of androstendiol, testosterone, and 17beta-estradiol by cysticerci, androstendiol, and 17beta-estradiol by tapeworms. The results strongly suggest the activity of 3beta-HSD in taeniid parasites that have at least a part of the enzymatic chain required for androgen and estrogen synthesis and that the enzymes are present in the larval stage and from the early strobilar stages to the mature proglottids.

Taenia solium cysticerci synthesize androgens and estrogens in vitro

Cysticerci from Taenia solium develop in the pig muscle and cause severe diseases in humans. Here we report on the capacity of T. solium cysticerci to synthesize sex steroid hormones. T. solium cysticerci were dissected from infected pork meat. Parasites were incubated for different periods in culture media plus antibiotics and tritiated steroid precursors. Blanks and parasite culture media were extracted and analyzed by thin-layer chromatography (TLC) in two different solvent systems. In some experiments, the scoleces were incubated separately. Results showed that T. solium cysticerci transform [(3)H]androstenedione to [(3)H]testosterone in a time-dependent manner. The production was confirmed in two different solvent systems. The incubation with [(3)H]testosterone yielded only small amounts of [(3)H]androstenedione. The recrystallization procedure further demonstrated that the metabolite identified by TLC was testosterone. The isolated scoleces incubated in the presence of [(3)H]androstenedione yielded [(3)H]testosterone and small quantities of [(3)H]17beta-estradiol. The results reported here demonstrate that T. solium cysticerci have the capacity to synthesize steroid hormones.

Immunohistochemical localisation of 3beta-hydroxysteroid dehydrogenase in Sarcocystis spp

3Beta-hydroxysteroid-dehydrogenase (3beta-HSD) is an isoenzyme that catalyses an essential step in the synthesis of all classes of active steroid hormones. The presence of steroid hormones of the vertebrate type in invertebrates is acknowledged in addition to a group of steroid-like hormones called ecdysteroids that were present in arthropods and helminths. In the present study, 3beta-HSD was detected in the bradyzoites enclosed in sarcocysts of Sarcocystis spp. with immunohistochemistry. The results suggest that self-originating steroid hormones may play important roles in the development of Sarcocystis spp., and possibly in the regulation of the reciprocal immune interaction between the host and these parasites.

Steroid hormone production by parasites: the case of Taenia crassiceps and Taenia solium cysticerci

Many examples of reciprocal endocrine interactions between parasites and hosts have been found in insects, arthropods and mammals. Cysticercosis produced by Taenia solium metacestodes is a widely distributed parasite infection that affects the human and the pig. Taenia crassiceps experimental murine cysticercosis has been used to explore the role of biological factors involved in host-parasite interactions. We had shown that T. crassiceps cysticercosis affects the serum concentration of steroid hormones and the reproduction behavior of the male mice host. In an effort to understand the biology of the parasite, we had investigated the parasite capacity to produce sex steroids. For this purpose, T. crassiceps cysticerci were incubated in the presence of different steroid precursors. TLC and recrystallization procedures showed that testosterone is produced from 3H-androstenedione in cysticerci. The conversion of 3H-testosterone to androstenedione, although present is much less significant. In addition, we had studied the production of testosterone by T. solium cysticerci. For this purpose, cysticerci were dissected from pork meat and incubated as above described. The results showed that T. solium cysticerci also produce testosterone. We have speculated about the importance of androgens in the growth of T. crassiceps cysticerci and found that the addition of the antiandrogen flutamide to the culture media of the parasites significantly decreased 3H-thymidine incorporation. We therefore hypothesized, that the ability of cysticerci to produce testosterone from steroid precursors might be important for the parasite growth and development.

Identification of free and conjugated ecdysteroids in cercariae of the schistosome Trichobilharzia ocellata

Extracts of cercariae of the avian schistosome Trichobilharzia ocellata were analysed for the presence of ecdysteroids by radioimmunoassay, high-performance liquid chromatography monitoring fractions by radioimmunoassay, and gas chromatography/mass spectrometry (selected ion monitoring). Both free ecdysteroids and polar conjugated ecdysteroids were detected in the cercarial extracts. The free ecdysteroid fraction, as well as the hydrolysed polar conjugated ecdysteroid fraction, contained both ecdysone and 20-hydroxyecdysone in approximately equal amounts. The amount of ecdysteroids detected is comparable to those found in other platyhelminths. A possible role for the ecdysteroids in the development of the parasite and/or the interactions between the parasite and its intermediate host, the freshwater snail Lymnaea stagnalis, is discussed.

Ecdysteroids in urine of African patients infected with helminths

The insect molting hormone and related compounds (ecdysteroids) have been found in patients infected with helminths. To investigate this phenomenon, we quantified and analyzed the urinary ecdysteroids in Malian subjects suffering from various helminthiases, as well as in Europeans. Very high titers (up to 100 nM) were found in some patients, whereas healthy persons had a basic level of 4 nM only. The high RIA activity was mainly due to two compounds. One of them was remarkable for being present in all the positive samples; it comigrated with the 20-hydroxyecdysone standard, both in HPLC and in TLC. The origin and the physiological significance of these compounds are questionable, since there was no clear relationship between their levels and the severity of the diseases. Numerous patients who were heavily infected had normal titers. Nevertheless, there is no doubt that high concentrations of ecdysteroid-like compounds in human urine indicate a pathological condition.

Effects of larval tapeworm (Taenia taeniaeformis) infection on reproductive functions in male and female host rats

This report examined the effects of larval tapeworm infection on the reproductive functions in both male and female host rats. Female rats were matched by age, then randomly assigned to control and treatment groups (infected with larval tapeworms). Estrous cycles were determined by vaginal smear with 95% of the control group exhibiting 4-day normal cyclicity and only 55% of the treated group exhibiting normal cycles. Female fertility was then evaluated for the normally cycling rats based on the percentage of successful matings on the evening of proestrus, number of implantation sites on Day 8 of pregnancy, and number of pups born at term. The normally cycling rats exhibited 96% successful mating, 12.95 +/- 1.80 implantation sites, and 11.20 +/- 1.80 pups born. Five months after larval tapeworm infection, the fertility parameters were decreased to 79%, 9.10 +/- 1.20, and 7.50 +/- 1.50, respectively. The control females were then used in a study of male fertility after larval tapeworm infection employing the same parameters used to test female fertility. At the onset of the study, control groups exhibited 95% successful mating, 12.50 +/- 1.50 implantation sites, and 11.60 +/- 1.60 pups born at full term. After the 5-month infection period, the parameters were substantially reduced to 29%, 6.20 +/- 0.80 implantation sites, and 5.10 +/- 0.80 pups, respectively. Average testosterone concentrations in serum and testis from control male rats were 8.80 +/- 0.95 ng/ml and 3.88 +/- 0.25 ng/mg protein, respectively. After the 5-month infection period, these levels were reduced to 2.47 +/- 0.31 ng/ml and 1.28 +/- 0.12 ng/mg protein, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Investigation of ecdysteroid excretion by adult Dirofilaria immitis and Brugia pahangi

The excretion of ecdysteroids by the filarial nematode species, Dirofilaria immitis and Brugia pahangi, was examined both in vitro, by the analysis of culture medium, and in vivo, through analysis of serum samples from experimentally infected hosts. There was no evidence of ecdysteroid excretion by intact parasites of either species in vitro. Free ecdysteroids were detected in the serum of ferrets and dogs infected with D. immitis, but concentrations would be at or below the limit of detection in sub-millilitre serum samples. The detection of ecdysteroids in the serum of potential hosts is unlikely to be of value in the diagnosis of filarial infections due to a combination of low titre in the presence of current infection and measurable titre in its absence. Ecdysteroids of dietary origin may contribute to the latter.

Ecdysteroid excretion by adult Hymenolepis diminuta in vitro

Both patent and prepatent adult Hymenolepis diminuta excreted 20-hydroxyecdysone into the culture medium when maintained in vitro. Patent worms also excreted ecdysone and comparatively large quantities of unidentified immunoreactive material of a relatively apolar nature. This latter material was shown to be depleted from the endogenous free ecdysteroids of patent adults during the culture period. Ecdysteroid excretion was affected both qualitatively and quantitatively when culturing conditions were varied.

Echinococcus granulosus: occurrence of ecdysteroids in protoscoleces and hydatid cyst fluid

Both free ecdysteroids and hydrolysable polar conjugated ecdysteroids were detected in protoscoleces of Echinococcus granulosus from the equine host, and in hydatid cyst fluid from the same source. Comparisons were made of hydatid cyst fluid from E. granulosus infections of three intermediate host species: horses, sheep and humans. Ecdysone and 20-hydroxyecdysone were identified in both protoscoleces and hydatid cyst fluids by high-performance liquid chromatography monitoring fractions by radioimmunoassay, and by capillary gas chromatography/mass spectrometry (selected ion monitoring). The free ecdysteroid fractions of hydatid cyst fluid from horses and sheep also contained several unidentified, chromatographically unique, immunoreactive compounds which were refractory to hydrolysis with a crude Helix pomatia aryl sulphatase enzyme preparation.

Capillary gas chromatography-mass spectrometry of ecdysteroids

Fully trimethylsilylated ecdysteroids have been analysed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) using flexible fused-silica capillary columns. Best results were obtained using columns coated with cross-bonded apolar (OV-1 type) stationary phases. By employing capillary GC-MS with selected-ion monitoring (SIM), very sensitive and selective analyses for ecdysteroids are possible. Detection limits of 10 and 100 pg have been determined for 20-hydroxyecdysone and ecdysone, respectively. At this level of sensitivity, capillary GC-SIM-MS constitutes a complementary means of ecdysteroid analysis to high-performance liquid chromatography (HPLC) with monitoring of the eluent fractions by radioimmunoassay (RIA), but with the advantage of enhanced selectivity. Examples are given of the application of capillary GC-SIM-MS and HPLC-RIA in combination to investigate the nature and concentration of ecdysteroids at the picogram level in three helminth species.

Ecdysteroids during embryonation of eggs of Ascaris suum

1. The optimal temperature for in vitro development of fertilized eggs of Ascaris suum was 24 degrees C. 2. Samples (2 X 10(7) eggs) were obtained from in vitro embryonating cultures every 3 days for 4 weeks; lipids were extracted, partially purified, fractionated with HPLC and analyzed for ecdysteroids by radioimmunoassay. 3. Free ecdysone and 20-hydroxyecdysone (20-HE) were at low levels (less than 20 pg) in freshly excised eggs and rose to maximal values on day 6 of embryonation. 4. Conjugated ecdysone and conjugated 20-HE rose to maximal values on day 9. 5. Both free and conjugated ecdysteroids were undetectable from days 15 to 27 of cultivation. 6. These profiles indicate that ecdysteroids might have a selective role in nematode embryonation and/or tanning of the egg shell.

Immunocytochemical localization of ecdysteroids in the life history stages of Schistosoma mansoni

Sporocysts, cercariae and adults of S. mansoni exhibit focal immunoreactivity against anti-ecdysone serum in an indirect immunofluorescence assay. In adult males immunoreactivity is limited to cell bodies and linear connections in the parenchyma surrounding the intestinal caeca. In both unisexual and paired mature females part of the lining of the ootype is reactive, especially near the entrance of the vitelline duct; this demonstrates that females can make ecdysteroids without mal contact. Adult worms cultured completely in vitro show a similar pattern of reactivity. Immunoreactivity is strong in cercariae, but is essentially absent in miracidia.