Common phytochemicals are ecdysteroid agonists and antagonists: a possible evolutionary link between vertebrate and invertebrate steroid hormones

Ancestral lineages of dietary exposure to an endocrine disrupting chemical drive distinct forms of transgenerational subfertility in an insect model

Across the globe, many species of insects are facing population decline. This is largely driven by anthropogenic changes to the environment, including the widespread exposure of invertebrates to endocrine disrupting chemicals (EDCs), which impair fertility. To test whether generations of Drosophila melanogaster born from parents exposed to a common dietary EDC, equol, could recover reproductive function, we quantified the reproductive capacity of the two subsequent generations. Using a novel suite of flow cytometry assays to assess sperm functionality in real time, we find that sperm function is compromised across three generations, even after non-exposed in individuals contribute to the breeding population. Though the sex ratio alters in response to EDC exposure, favouring the survival of female offspring, most lineages with ancestral EDC exposure exhibit persistent subfertility in both the male and female. Male offspring with ancestral EDC exposure present with reduced fertility and dysfunctional spermatozoa, whereby spermatozoa are metabolically stressed, lack DNA integrity and present with permanent epigenetic alterations. Across generations, male and female offspring demonstrate distinct patterns of reproductive characteristics, depending upon the specific lineage of EDC exposure. Our results illustrate how dietary EDCs present in agricultural plants could promote transgenerational subfertility and contribute to declining insect populations.

Inhibitory effects of Serjania erecta on the development of Chrysodeixis includens

The soybean looper, Chrysodeixis includens, is a primary soybean pest that reduces crop productivity. This work examined control of C. includens populations with methanolic extract of Serjania erecta, a native Cerrado plant, while minimizing risks to pollinators, natural enemies and the environment. Serjania erecta specimens were collected, identified, and subjected to methanol extraction. Bioassays were performed using newly hatched and second-instar caterpillars and different extract concentrations on the diet surface to obtain IC₅₀ values. Two replicates, containing 10 caterpillars, were established in triplicate. The IC₅₀ values were 4.15 and 6.24 mg of extract mL⁻¹ for first-instar and second-instar caterpillars, respectively. These growth inhibition results informed the extract concentrations assessed in subsequent development inhibition assays, in which the pupal weight was higher under the control than under the treatments. Extract treatments increased the duration of the larval, pupal and total development. The potential of different concentrations of S. erecta extract to inhibit the enzymes carboxylesterases was also evaluated. Carboxylesterases activity decreased by 41.96 and 43.43% at 7.8 and 15.6 μg mL⁻¹ extract, respectively. At 31.3 μg mL⁻¹ extract, enzymatic activity was not detected. Overall, S. erecta leaf methanolic extract showed inhibitory potential against carboxylesterases.

Drosophila ecdysone receptor activity-based ex vivo assay to assess the endocrine disruption potential of environmental chemicals

Insect pollinators, critical for both agricultural output and the ecosystem, are declining at an alarming levels partly due to human-made chemicals. Majority of environmental chemicals hamper the endocrine function and studies on the same in insects remain neglected. Here, we report a Drosophila-based ex vivo assay system that employs a reproductive tissue from transgenic males carrying a reporter gene (lacZ) downstream of ecdysone receptor response element (EcRE) and permits the evaluation of chemical-mediated activity modulation of all three isoforms of ecdysone receptor, which are critical for male fertility. We show agonistic [plasticizers, cypermethrin, atrazine, methyl parathion, imidacloprid, cadmium chloride, mercuric chloride or 3-(4-methylbenzylidene) camphor] or antagonistic (apigenin, tributyltin chloride) effects or lack of effect thereof (rutin hydrate, dichlorvos, lead acetate, parabens) for seven different classes of environmental chemicals on ecdysone receptor activity reflecting the specificity and sensitivity of the developed ex vivo assay. Exposure to a few of these chemicals in vivo hampers the fertility of Drosophila males, thus linking the observed endocrine disruption to a quantifiable reproductive phenotype. The developed ex vivo assay offers a quick Drosophila-based screening tool for throughput monitoring of environmental chemicals for their ability to hamper the endocrine function of insect pollinators and other invertebrates.

Cascading Effects of Root Microbial Symbiosis on the Development and Metabolome of the Insect Herbivore Manduca sexta L

Root mutualistic microbes can modulate the production of plant secondary metabolites affecting plant-herbivore interactions. Still, the main mechanisms underlying the impact of root mutualists on herbivore performance remain ambiguous. In particular, little is known about how changes in the plant metabolome induced by root mutualists affect the insect metabolome and post-larval development. By using bioassays with tomato plants (Solanum lycopersicum), we analyzed the impact of the arbuscular mycorrhizal fungus Rhizophagus irregularis and the growth-promoting fungus Trichoderma harzianum on the plant interaction with the specialist insect herbivore Manduca sexta. We found that root colonization by the mutualistic microbes impaired insect development, including metamorphosis. By using untargeted metabolomics, we found that root colonization by the mutualistic microbes altered the secondary metabolism of tomato shoots, leading to enhanced levels of steroidal glycoalkaloids. Untargeted metabolomics further revealed that root colonization by the mutualists affected the metabolome of the herbivore, leading to an enhanced accumulation of steroidal glycoalkaloids and altered patterns of fatty acid amides and carnitine-derived metabolites. Our results indicate that the changes in the shoot metabolome triggered by root mutualistic microbes can cascade up altering the metabolome of the insects feeding on the colonized plants, thus affecting the insect development.

Discovery of Natural Products as Multitarget Inhibitors of Insect Chitinolytic Enzymes through High-Throughput Screening

Small-molecule inhibitors of insect chitinolytic enzymes are potential insecticides. However, the reported inhibitors that target one enzyme usually exhibit unsatisfactory bioactivity. On the basis of the multitarget strategy, we performed a high-throughput screening of a natural product library to find insecticide leads against four chitinolytic enzymes from the Asian corn borer Ostrinia furnacalis (OfChtI, OfChtII, OfChi-h, and OfHex1). Several phytochemicals were discovered to be multitarget inhibitors of these enzymes and were predicted to occupy the -1 substrate-binding subsite and engage in polar interactions with catalytically important residues. Shikonin and wogonin, which had good inhibitory activities toward all four enzymes, also exhibited significant insecticidal activities against lepidopteran agricultural pests. This study provides the first example of using a multitarget high-throughput screening strategy to exploit natural products as insecticide leads against chitin biodegradation during insect molting.

Reporter gene assays for screening and identification of novel molting hormone- and juvenile hormone-like chemicals

A reporter gene assay (RGA) is used to investigate the activity of synthetic chemicals mimicking the molting hormones (MHs) and juvenile hormones (JHs) of insects, so-called insect growth regulators (IGRs). The MH receptor, a heterodimer of the ecdysone receptor (EcR) and ultraspiracle (USP), and the JH receptor Methoprene-tolerant (Met) are ligand-dependent transcription factors. Ligand-bound EcR-USP and Met bind to specific cis-acting DNA elements, referred to as the ecdysone-responsive element (EcRE) and the JH-responsive element (JHRE), respectively, in order to transactivate target genes. Insect hormone-induced transactivation systems have been reconstituted by the introduction of reporter genes under the control of EcRE and JHRE, or two-hybrid reporter genes, into insect, mammalian, and yeast cells expressing receptor proteins. RGA is easy to use and convenient for examining the MH- and JH-like activities of synthetic chemicals and is suitable for the high-throughput screening of novel structural classes of chemicals targeting EcR-USP and Met.

The Multifunctional Roles of Polyphenols in Plant-Herbivore Interactions

There is no argument to the fact that insect herbivores cause significant losses to plant productivity in both natural and agricultural ecosystems. To counter this continuous onslaught, plants have evolved a suite of direct and indirect, constitutive and induced, chemical and physical defenses, and secondary metabolites are a key group that facilitates these defenses. Polyphenols—widely distributed in flowering plants—are the major group of such biologically active secondary metabolites. Recent advances in analytical chemistry and metabolomics have provided an opportunity to dig deep into extraction and quantification of plant-based natural products with insecticidal/insect deterrent activity, a potential sustainable pest management strategy. However, we currently lack an updated review of their multifunctional roles in insect-plant interactions, especially focusing on their insect deterrent or antifeedant properties. This review focuses on the role of polyphenols in plant-insect interactions and plant defenses including their structure, induction, regulation, and their anti-feeding and toxicity effects. Details on mechanisms underlying these interactions and localization of these compounds are discussed in the context of insect-plant interactions, current findings, and potential avenues for future research in this area.

Does estrogen regulate vitellogenin synthesis in corals?

Most broadcast spawner corals have a vitellogenic phase that lasts at least 6 months. It is established that estrogen regulates vitellogenin synthesis in vertebrates. Although some research have been conducted on the physiological role of sex steroids in corals, little is known about their involvement in oocyte development. This study aimed to detect steroid hormones - progesterone, testosterone, and estradiol-17β (E2) - in Acropora tenuis and study the relationships between vitellogenesis/vitellogenin synthesis and these steroids. This study also investigated the effect of E2 on vitellogenin synthesis in corals and identified steroidogenic enzymes in A. tenuis genome. Branches from tagged coral colonies were collected monthly from March to November. Histological observations showed that oocytes were vitellogenic from March to May (Stage IV and V), but not in June, and that gonads were occupied by immature oocytes in September (Stage I). Real-time qPCR revealed that vitellogenin (vg1 and vg2) transcript levels in coral branches were high in April and May, implying that corals actively underwent vitellogenesis during these months, and spawned before June. Liquid chromatography-mass spectrometry revealed that E2 could be detected in coral branches in March, April, and May, but not in June, whereas testosterone and progesterone did not fluctuate much in the same months. Immersing branches in E2-containing seawater failed to increase vitellogenin transcript levels. The results indicate that E2 is involved in oogenesis but does not positively regulate vitellogenin synthesis. Steroidogenic enzymes (except CYP19A) were identified in A. tenuis, suggesting that corals may endogenously synthesize progestogens and androgens from cholesterol.

Sirtuins transduce STACs signals through steroid hormone receptors

SIRT1 protects against several complex metabolic and ageing-related diseases (MARDs), and is therefore considered a polypill target to improve healthy ageing. Although dietary sirtuin-activating compounds (dSTACs) including resveratrol are promising drug candidates, their clinical application has been frustrated by an imprecise understanding of how their signals are transduced into increased healthspan. Recent work indicates that SIRT1 and orthologous sirtuins coactivate the oestrogen receptor/ER and the worm steroid receptor DAF-12. Here they are further shown to ligand-independently transduce dSTACs signals through these receptors. While some dSTACs elicit ER subtype-selectivity in the presence of hormone, most synergize with 17β-oestradiol and dafachronic acid respectively to increase ER and DAF-12 coactivation by the sirtuins. These data suggest that dSTACs functionally mimic gonadal steroid hormones, enabling sirtuins to transduce the cognate signals through a conserved endocrine pathway. Interestingly, resveratrol non-monotonically modulates sirtuin signalling, suggesting that it may induce hormesis, i.e. “less is more”. Together, the findings suggest that dSTACs may be informational molecules that use exploitative mimicry to modulate sirtuin signalling through steroid receptors. Hence dSTACs’ intrinsic oestrogenicity may underlie their proven ability to impart the health benefits of oestradiol, and also provides a mechanistic insight into how they extend healthspan or protect against MARDs.

Oestrogen-related receptor reduces vitellogenin expression by crosstalk with the ecdysone receptor pathway in female silkworm, Bombyx mori

Oestrogen-related receptor (ERR) is involved in oestrogen receptor (ER) signalling pathways owing to its similarity to ER in terms of domain structure and co-activator and response elements. Although insects lack ER, they harbour an ERR gene that is thought to modulate metabolism and energy conversion via an unknown mechanism. The present study investigated the function of ERR in insects using female silkworm (Bombyx mori, Bm). We found that the expression of B. mori vitellogenin (BmVg) and B. mori ERR (BmERR) in the fat bodies of female silkworms at different stages of development exhibited alternating patterns, and RNA interference of BmERR in females induced BmVg transcription, resulting in an increase in egg weight relative to the control. Furthermore, BmERR was found to be involved in regulating the transcription of BmVg through an oestrogen-related receptor response element (ERRE) in the promoter of the BmVg gene, as demonstrated by electrophoretic mobility shift assay, cell transfection assay and chromatin immunoprecipitation. In summary, our results indicate that BmERR bound to the ERRE motif in the BmVg promoter reducing the expression of BmVg in the fat body of the female silkworm. To our surprise, the ERRE also showed the ability to bind the ecdysone receptor (BmEcR) and ultraspiracle complex. Thus, we surmise that ERR participates in steroid hormone signalling by engaging in crosstalk with the ER pathway in vertebrates and with the EcR pathway in insects.

Nitrate: An Environmental Endocrine Disruptor? A Review of Evidence and Research Needs

Nitrate is heavily used as an agricultural fertilizer and is today a ubiquitous environmental pollutant. Environmental endocrine effects caused by nitrate have received increasing attention over the last 15 years. Nitrate is hypothesized to interfere with thyroid and steroid hormone homeostasis and developmental and reproductive end points. The current review focuses on aquatic ecotoxicology with emphasis on field and laboratory controlled in vitro and in vivo studies. Furthermore, nitrate is just one of several forms of nitrogen that is present in the environment and many of these are quickly interconvertible. Therefore, the focus is additionally confined to the oxidized nitrogen species (nitrate, nitrite and nitric oxide). We reviewed 26 environmental toxicology studies and our main findings are (1) nitrate has endocrine disrupting properties and hypotheses for mechanisms exist, which warrants for further investigations; (2) there are issues determining actual nitrate-speciation and abundance is not quantified in a number of studies, making links to speciation-specific effects difficult; and (3) more advanced analytical chemistry methodologies are needed both for exposure assessment and in the determination of endocrine biomarkers.

20-Hydroxyecdysone attenuates cardiac remodeling in spontaneously hypertensive rats

BACKGROUND

Ecdysteroids, a group of steroid hormones found in insects and many plants, have been shown to prevent various changes in mammalian tissues after female sex hormone deprivation.

PURPOSE

To examine whether an ecdysteroid, 20-hydroxyecdysone (20-HE), exhibits regulatory or protective roles in the cardiovascular system.

STUDY DESIGN/METHOD

Blood pressure and cardiac function were evaluated in spontaneously hypertensive rats (SHR) during and after daily treatment with 20-HE for six weeks.

RESULTS

The progressive increase in systolic blood pressure with age in SHR rats was significantly lower in animals treated with either 5 or 10mg/kg body weight of 20-HE. However, treatment with 20-HE did not diminish the increase in diastolic pressure. Echocardiography after six weeks of treatment demonstrated that the left ventricular chamber of SHR rats treated with 20-HE was smaller than that of SHR controls, while contractility was not affected by 20-HE. Histological images also demonstrated a decrease in cardiomyocyte cross-sectional area in 20-HE treated groups. Interestingly, treatment with 20-HE caused a shift in cardiac myosin heavy chain towards more β-isoforms. SHR rats treated with 20-HE also exhibited a decrease in seminal vesicular weight and an increase in testicular weight, especially at a dose of 10mg/kg body weight. This finding suggests a possible anti-androgenic effect of 20-HE.

CONCLUSION

Our finding reveal that 20-HE has a beneficial effect on reducing blood pressure and consequently preventing dilated cardiac hypertrophy in SHR rats.

Role of Elsholtzia communis in counteracting stress by modulating expression of hspa14, C/EBP homologous protein, nuclear factor (erythroid-derived 2)-like-2 factor, Caspase-3, and brain-derived neurotrophic factor in rat hippocampus

OBJECTIVE:

Elsholtzia communis (Collett and Hemsl.) Diels has been widely distributed and is reported for many therapeutic effects. The present study aims to investigate the antistress activity of the leaf extract and its possible molecular mechanism.

MATERIALS AND METHODS:

Hydroethanolic extract of leaves of E. communis (100 and 200 mg/kg, p.o.) were administered for 7 days to stress-induced male Wistar rats. The experimental animals were divided into five groups (n = 6). The mRNA/protein profile of few stress responsive chaperones (hspa14), endoplasmic reticulum stress markers (C/EBP homologous protein [CHOP]), antioxidant regulating genes (nuclear factor (erythroid-derived 2)-like-2 factor [Nrf2]), apoptotic factors (Caspase-3) in rat hippocampus were studied by polymerase chain reaction and immunoblotting.

RESULTS:

The stress-related genes such as hspa14, CHOP, antioxidant gene Nrf2, apoptotic gene Caspase-3 which were overexpressed in the stress control group were significantly suppressed following administration of the extract at both the doses and the standard drug Ginseng. Likewise, brain-derived neurotrophic factor which is closely related with stress, was downregulated in the stress control group, was found to be upregulated following treatment with the extract and the standard drug Ginseng.

CONCLUSION:

Our findings clearly indicate that E. communis was able to counteract stress. Hence, it has the potential to develop as adaptogen and also as a replacement/substitute of the popularly used drug, Ginseng or Ashwagandha, which is on the verge of extinction or becoming endemic due to overuse.

In vitro effects of caffeic acid, nortriptyline, precocene I and quercetin against Rhipicephalus annulatus (Acari: Ixodidae)

In the present study, the acaricidal effects of caffeic acid, nortriptyline, precocene I and quercetin against Rhipicephalus annulatus (syn. Boophilus annulatus) Say (Acari: Ixodidae) were evaluated. Adult immersion technique (24 ticks immersed for 2 min in one dilution of the compound) was used for the assessment of the effects of caffeic acid (0.39-100 mg/mL), nortriptyline (0.625-50 mg/L), precocene I (0.004488-5 mg/mL) and quercetin (6.25-100 mg/mL) against R. annulatus. Adult tick mortality, reproductive index, inhibition of fecundity and hatching were calculated. Caffeic acid, nortriptyline, precocene I and quercetin revealed very low adult mortality and inhibition of fecundity, even at the highest concentration tested. Quercetin (>50 mg/mL) caused blocking of hatching of eggs.

Differential Induction of Flavonoids in Groundnut in Response to Helicoverpa armigera and Aphis craccivora Infestation

Flavonoids are important plant secondary metabolites, which protect plants from various stresses, including herbivory. Plants differentially respond to insects with different modes of action. High performance liquid chromatography (HPLC) fingerprinting of phenols of groundnut (Arachis hypogaea) plants with differential levels of resistance was carried out in response to Helicoverpa armigera (chewing insect) and Aphis craccivora (sucking pest) infestation. The genotypes used were ICGV 86699, ICGV 86031, ICG 2271 (NCAc 343), ICG 1697 (NCAc 17090), and JL 24. Most of the identified compounds were present in H. armigera- and A. craccivora-infested plants of ICGV 86699. Syringic acid was observed in all the genotypes across the treatments, except in the uninfested control plants of ICG 2271 and aphid-infested plants of ICG 1697. Caffeic acid and umbelliferone were observed only in the H. armigera-infested plants of ICGV 86699. Similarly, dihydroxybenzoic acid and vanillic acid were observed in H. armigera- and aphid-infested plants of ICG 2271 and JL 24, respectively. The peak areas were transformed into the amounts of compounds by using internal standard peak areas and were expressed in nanograms. Quantities of the identified compounds varied across genotypes and treatments. The common compounds observed were chlorogenic, syringic, quercetin, and ferulic acids. These results suggest that depending on the mode of feeding, flavonoids are induced differentially in groundnut plants.

A Review of Bioinsecticidal Activity of Solanaceae Alkaloids

Only a small percentage of insect species are pests. However, pest species cause significant losses in agricultural and forest crops, and many are vectors of diseases. Currently, many scientists are focused on developing new tools to control insect populations, including secondary plant metabolites, e.g., alkaloids, glycoalkaloids, terpenoids, organic acids and alcohols, which show promise for use in plant protection. These compounds can affect insects at all levels of biological organization, but their action generally disturbs cellular and physiological processes, e.g., by altering redox balance, hormonal regulation, neuronal signalization or reproduction in exposed individuals. Secondary plant metabolites cause toxic effects that can be observed at both lethal and sublethal levels, but the most important effect is repellence. Plants from the Solanaceae family, which contains numerous economically and ecologically important species, produce various substances that affect insects belonging to most orders, particularly herbivorous insects and other pests. Many compounds possess insecticidal properties, but they are also classified as molluscides, acaricides, nematocides, fungicides and bactericides. In this paper, we present data on the sublethal and lethal toxicity caused by pure metabolites and crude extracts obtained from Solanaceae plants. Pure substances as well as water and/or alcohol extracts cause lethal and sublethal effects in insects, which is important from the economical point of view. We discuss the results of our study and their relevance to plant protection and management.

Aflatoxin Contamination Detected in Nutrient and Anti-Oxidant Rich Edible Stink Bug Stored in Recycled Grain Containers

Recently, there has been multi-agency promotion of entomophagy as an environmentally-friendly source of food for the ever increasing human population especially in the developing countries. However, food quality and safety concerns must first be addressed in this context. We addressed these concerns in the present study using the edible stink bug Encosternum delegorguei, which is widely consumed in southern Africa. We analysed for mycotoxins, and health beneficials including antioxidants, amino acids and essential fatty acids using liquid chromatography coupled to quadrupole time of flight mass spectrometry (LC-Qtof-MS) and coupled gas chromatography (GC)-MS. We also performed proximate analysis to determine nutritional components. We identified the human carcinogen mycotoxin (aflatoxin B₁) at low levels in edible stink bugs that were stored in traditonally woven wooden dung smeared baskets and gunny bags previously used to store cereals. However, it was absent in insects stored in clean zip lock bags. On the other hand, we identified 10 fatty acids, of which 7 are considered essential fatty acids for human nutrition and health; 4 flavonoids and 12 amino acids of which two are considered the most limiting amino acids in cereal based diets. The edible stink bug also contained high crude protein and fats but was a poor source of minerals, except for phosphorus which was found in relatively high levels. Our results show that the edible stink bug is a nutrient- and antioxidant-rich source of food and health benefits for human consumption. As such, use of better handling and storage methods can help eliminate contamination of the edible stink bug with the carcinogen aflatoxin and ensure its safety as human food.

Genistein administered as a once-daily oral supplement had no beneficial effect on the tibia in rat models for postmenopausal bone loss

OBJECTIVE

Estrogen deficiency after menopause results in rapid bone loss, predisposing women to osteoporotic fractures. Genistein, a phytoestrogen present in high concentrations in soy, is an ingredient in dietary supplements aggressively marketed for bone health. However, in a recent long-duration clinical trial in postmenopausal women, the efficacy of soy extracts in reducing bone loss was disappointing. To better understand the failure of soy extracts to consistently induce a robust skeletal response in women, we investigated the long-term (5 mo) efficacy of genistein, administered as a daily oral supplement, (1) in preventing cancellous bone loss in skeletally mature virgin Long-Evans rats ovariectomized at 7 months of age and (2) in improving cancellous bone mass and architecture in aged retired-breeder rats ovariectomized at 16 or 22 months of age.

METHODS

Rats within each age group were randomly assigned into one of three treatment groups (n = 7-12 rats/group): (1) vehicle control, (2) genistein 485 μg/day, or (3) genistein 970 μg/day, resulting in mean (SE) serum genistein levels of 0.18 (0.10), 0.76 (0.15), and 1.48 (0.31) μM, respectively. Total tibia bone mass and density were evaluated using dual-energy x-ray absorptiometry, whereas cancellous bone mass and architecture in the tibial metaphysis, as well as cortical bone mass and architecture in the tibial diaphysis, were evaluated by micro-CT.

RESULTS

Oral genistein administered as a dietary supplement did not influence the cumulative effects of ovariectomy, aging, and/or reproductive history on cancellous and cortical bone mass and architecture.

CONCLUSIONS

Serum levels of genistein similar to those in women consuming a high-soy diet are ineffective in preventing or treating bone loss in rat models for postmenopausal osteoporosis.

Are naringenin and quercetin useful chemicals in pest-management strategies?

The effects of two polyphenolic flavonoids (flavanone naringenin and flavonol quercetin) on development, fecundity, and mortality of the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae), were determined in vitro, on an artificial diets. Also determined in vitro (DC EPG method), on sucrose-agarose gels, were the effects of flavonoids on the probing and feeding behavior of adult apterae. When added to a liquid diet, higher concentrations of studied flavonoids increased the developmental time, the pre-reproductive period, and mortality and decreased fecundity and the intrinsic rate of natural increase of A. pisum. In most events associated with stylet activity (as indicated by EPG waveform g-C), differences in probing behavior did not statistically differ between the control gel and those with flavonoids; quercetin at 10, 100, and 1,000 µg cm^-3 prolonged the number of gel penetrations; and quercetin only at 10,000 μg cm^-3 prolonged the time the first g-C waveform was observed. Addition of flavonoids to the gels generally reduced passive ingestion from fluids of the gels (EPG waveform g-E2). At higher concentrations (>1,000 µg cm^-3) the flavonoids completely stopped salivation (EPG waveform g-E1) and passive ingestion from fluids of the gels (EPG waveform g-E2). In events associated with active ingestion (EPG waveform g-G), however, differences in feeding behavior did not statistically differ between the control gel and those with flavonoids. The present findings demonstrate detrimental effects of the flavanone naringenin and flavonol on the behavior of the pea aphid. This can be employed in a biotechnological projects for plant breeding resistant to herbivores, including aphids.

The Ecdysone receptor constrains wingless expression to pattern cell cycle across the Drosophila wing margin in a Cyclin B-dependent manner

Background

Ecdysone triggers transcriptional changes via the ecdysone receptor (EcR) to coordinate developmental programs of apoptosis, cell cycle and differentiation. Data suggests EcR affects cell cycle gene expression indirectly and here we identify Wingless as an intermediary factor linking EcR to cell cycle.

Results

We demonstrate EcR patterns cell cycle across the presumptive Drosophila wing margin by constraining wg transcription to modulate CycB expression, but not the previously identified Wg-targets dMyc or Stg. Furthermore co-knockdown of Wg restores CycB patterning in EcR knockdown clones. Wg is not a direct target of EcR, rather we demonstrate that repression of Wg by EcR is likely mediated by direct interaction between the EcR-responsive zinc finger transcription factor Crol and the wg promoter.

Conclusions

Thus we elucidate a critical mechanism potentially connecting ecdysone with patterning signals to ensure correct timing of cell cycle exit and differentiation during margin wing development.

Antifeedant activity of luteolin and genistein against the pea aphid, Acyrthosiphon pisum

Electrical penetration graphs (DC EPG) were used to monitor the feeding behavior of the pea aphid, Acyrthosiphon pisum Harris (Hemiptera: Aphididae) exposed to the flavonoids luteolin and genistein in artificial diets. The EPG patterns generated by aphids feeding on plants were used to interpret the patterns generated on the artificial diets. Addition of flavonoids to the diets generally prolonged the period of stylet probing (as indicated by EPG pattern d-C), reduced salivation (as indicated by pattern d-E1) and passive ingestion (as indicated by pattern d-E2), and also delayed the onset of salivation and passive ingestion. At higher concentrations (≥100 μg cm(-3) for luteolin, ≥1,000 μg cm(-3) for genistein), the flavonoids completely stopped salivation and passive ingestion. In most events associated with active ingestion (EPG pattern d-G), however, differences in feeding behavior did not statistically differ between the control diet and those with flavonoids; luteolin, and genistein only at 10 μg cm(-3) prolonged the time until the first d-G pattern was observed. The current findings demonstrate detrimental effects of the isoflavone genistein and the flavone luteolin on the feeding behavior of the pea aphid, A. pisum. This can be employed to create plants which are resistant to aphids and other herbivores.

Environmental signaling and reproduction: a comparative biological and chemical perspective

Reproduction is a critical element of life. Self-propagation in all living organisms ranging from bacteria to humans involves numerous common strategies. Underlying all reproductive strategies is the essential need for signaling molecules to initiate and maintain the process. In this paper we use comparative biological and chemical approaches to explore the origins and distribution of estrogen signaling as a pathway common to many life forms. In the process we illuminate the mechanisms whereby environmental agents alter reproduction and development. These mechanisms involve altered signaling pathways within cells and shifts in the targets of the signaling pathways to include regulators of gene transcription normally associated with other pathways. We also stress the role of signal cross talk in mediating hormone action.

Feeding rates of Balloniscus sellowii (Crustacea, Isopoda, Oniscidea): the effect of leaf litter decomposition and its relation to the phenolic and flavonoid content

The goal of this study was to compare the feeding rates of Balloniscus sellowii on leaves of different decomposition stages according to their phenolic and flavonoid content. Leaves from the visually most abundant plants were offered to isopods collected from the same source site. Schinus terebinthifolius,the plant species consumed at the highest rate, was used to verify feeding rates at different decomposition stages. Green leaves were left to decompose for one, two, or three months, and then were offered to isopods. The total phenolic and flavonoid contents were determined for all decomposition stages. Consumption and egestion rates increased throughout decomposition, were highest for two-month-old leaves, and decreased again in the third month. The assimilation rate was highest for green leaves. The mode time of passage through the gut was two hours for all treatments. Ingestion of leaves occurred after two or three days for green leaves, and on the same day for one-, two- and three-month-old leaves. The speed of passage of leaves with different decomposition stages through the gut does not differ significantly when animals are fed continuously. However, it is possible that the amount retained in the gut during starvation differs depending on food quality. The digestibility value was corrected using a second food source to empty the gut of previously ingested food, so that all of the food from the experiment was egested. The digestibility value was highest for green leaves, whereas it was approximately 20% for all other stages. This was expected given that digestibility declines during decomposition as the metabolite content of the leaves decreases. The phenolic content was highest in the green leaves and lowest in three-month-old leaves. The flavonoid content was highest in green leaves and lowest after two months of decomposition. Animals ingested more phenolics when consumption was highest. The estimated amount of ingested flavonoids followed the same trend as assimilation rate. Flavonoids accounted for a large portion of total phenolics, and the estimated amount of flavonoids consumed was similar for one-, two- and three-month-old leaves. Our results suggest that the high phenolic and flavonoid concentrations in green leaves are feeding deterrents. Isopods may discriminate among concentrations of flavonoids and modify their consumption rates to maintain their intake of flavonoids when ingesting leaves with lower flavonoid content.

Demasculinization of male fish by wastewater treatment plant effluent

Adult male fathead minnows (Pimephales promelas) were exposed to effluent from the City of Boulder, Colorado wastewater treatment plant (WWTP) under controlled conditions in the field to determine if the effluent induced reproductive disruption in fish. Gonadal intersex and other evidence of reproductive disruption were previously identified in white suckers (Catostomus commersoni) in Boulder Creek downstream from this WWTP effluent outfall. Fish were exposed within a mobile flow-through exposure laboratory in July 2005 and August 2006 to WWTP effluent (EFF), Boulder Creek water (REF), or mixtures of EFF and REF for up to 28 days. Primary (sperm abundance) and secondary (nuptial tubercles and dorsal fat pads) sex characteristics were demasculinized within 14 days of exposure to 50% and 100% EFF. Vitellogenin was maximally elevated in both 50% and 100% EFF treatments within 7 days and significantly elevated by 25% EFF within 14 days. The steroidal estrogens 17β-estradiol, estrone, estriol, and 17α-ethynylestradiol, as well as estrogenic alkylphenols and bisphenol A were identified within the EFF treatments and not in the REF treatment. These results support the hypothesis that the reproductive disruption observed in this watershed is due to endocrine-active chemicals in the WWTP effluent.

PTTH-stimulated ERK phosphorylation in prothoracic glands of the silkworm, Bombyx mori: role of Ca(2+)/calmodulin and receptor tyrosine kinase

Our previous studies showed that the prothoracicotropic hormone (PTTH) stimulated extracellular signal-regulated kinase (ERK) phosphorylation in prothoracic glands of Bombyx mori both in vitro and in vivo. In the present study, the signaling pathway by which PTTH activates ERK phosphorylation was further investigated using PTTH, second messenger analogs, and various inhibitors. ERK phosphorylation induced by PTTH was partially reduced in Ca(2+)-free medium. The calmodulin antagonist, calmidazolium, partially inhibited both PTTH-stimulated ERK phosphorylation and ecdysteroidogenesis, indicating the involvement of calmodulin. When the prothoracic glands were treated with agents that directly elevate the intracellular Ca(2+) concentration [either A23187, thapsigargin, or the protein kinase C (PKC) activator, phorbol 12-myristate acetate (PMA)], a great increase in ERK phosphorylation was observed. In addition, it was found that PTTH-stimulated ecdysteroidogenesis was greatly attenuated by treatment with PKC inhibitors (either calphostin C or chelerythrine C). However, PTTH-stimulated ERK phosphorylation was not attenuated by the above PKC inhibitors, indicating that PKC is not involved in PTTH-stimulated ERK phosphorylation. A potent and specific inhibitor of insulin receptor tyrosine kinase, HNMPA-(AM)(3), greatly inhibited the ability of PTTH to activate ERK phosphorylation and stimulate ecdysteroidogenesis. However, genistein, another tyrosine kinase inhibitor, did not inhibit PTTH-stimulated ERK phosphorylation, although it did markedly attenuate the ability of A23187 to activate ERK phosphorylation. From these results, it is suggested that PTTH-stimulated ERK phosphorylation is only partially Ca(2+)- and calmodulin-dependent and that HNMPA-(AM)(3)-sensitive receptor tyrosine kinase is involved in activation of ERK phosphorylation by PTTH.

Phenolic metabolites in leaves of the invasive shrub, Lonicera maackii, and their potential phytotoxic and anti-herbivore effects

Lonicera maackii is an invasive shrub in North America for which allelopathic effects toward other plants or herbivores have been suspected. We characterized the major phenolic metabolites present in methanol extracts of L. maackii leaves. In addition, we examined the effects of methanol-water extracts of L. maackii leaves on seed germination of a target plant species and on feeding preference and growth rate of a generalist insect herbivore. A total of 13 individual major and minor compounds were detected in crude leaf extracts by high-performance liquid chromatography coupled to electronspray ionization-tandem mass spectrometry (ESI-MS/MS). Extracts were dominated by two major flavones, apigenin and luteolin, and their glucoside derivatives, apigenin-7-glucoside and luteolin-7-glucoside. Quantities of these compounds, along with chlorogenic acid, varied between two sampling points. Leaf extracts that contained these compounds were inhibitory to seed germination of Arabidopsis thaliana. In addition, treatment of artificial diet with leaf extracts deterred feeding of the generalist herbivore, Spodoptera exigua, in choice experiments but had no effect on growth rate in short-term no-choice bioassays. Purified apigenin tended to deter feeding by S. exigua and inhibited seed germination of A. thaliana. We conclude that leaves of L. maackii contain phenolic compounds, including apigenin and chlorogenic acid, capable of having biological effects on other plants and insects.

Isovitexin-2'-O-beta-[6-O-E-p-coumaroylglucopyranoside] from UV-B irradiated leaves of rice, Oryza sativa L. inhibits fertility of Helicoverpa armigera

UV-B irradiated rice leaves (Oryza sativa L.) contained four closely related flavonoids, with either an isoorientin or isovitexin aglycone. These flavonoids have previously been purified and characterized, and were added to artificial diets of the African bollworm (Helicoverpa armigera Hübner) at 0.1x concentration found in irradiated rice leaves. Consumption of different diets had relatively small effects on laval, pupal and adult duration, weight and survival, indicating the insects lived near normal life cycles on all diets. However, one of the compounds, flavonoid IIa, isovitexin-2''-O-beta-[6-O-E-p-coumaroylglucopyranoside], dramatically reduced the number of fertile eggs laid to 7% of control insects (P<0.001) when added to insect diets at 18 nmol gFW(-1) (14 ppm). A similar antifertility effect was observed when only the male partner consumed diet containing flavonoid IIa, indicating that the reduced fertility may be male specific. In contrast, the fecundity and fertility of insects eating diets containing the closely related flavonoids, isoorientin-2''-O-beta-[6-O-E-p-coumaroylglucopyranoside] or isoorientin-2''-O-beta-[6-O-E-p-feruloylglucopyranoside], were not significantly different to control diets.

Effects of xenoestrogens on the differentiation of behaviorally-relevant neural circuits

It has become increasingly clear that environmental chemicals have the capability of impacting endocrine function. Moreover, these endocrine disrupting chemicals (EDCs) have long term consequences on adult reproductive function, especially if exposure occurs during embryonic development thereby affecting sexual differentiation. Of the EDCs, most of the research has been conducted on the effects of estrogen active compounds. Although androgen active compounds are also present in the environment, much less information is available about their action. However, in the case of xenoestrogens, there is mounting evidence for long-term consequences of early exposure at a range of doses. In this review, we present data relative to two widely used animal models: the mouse and the Japanese quail. These two species long have been used to understand neural, neuroendocrine, and behavioral components of reproduction and are therefore optimal models to understand how these components are altered by precocious exposure to EDCs. In particular we discuss effects of bisphenol A and methoxychlor on the dopaminergic and noradrenergic systems in rodents and the impact of these alterations. In addition, the effects of embryonic exposure to diethylstilbestrol, genistein or ethylene,1,1-dichloro-2,2-bis(p-chlorophenyl) is reviewed relative to behavioral impairment and associated alterations in the sexually dimorphic parvocellular vasotocin system in quail. We point out how sexually dimorphic behaviors are particularly useful to verify adverse developmental consequences produced by chemicals with endocrine disrupting properties, by examining either reproductive or non-reproductive behaviors.

Effects of early embryonic exposure to genistein on male copulatory behavior and vasotocin system of Japanese quail

Genistein is a phytoestrogen, particularly abundant in soybeans that can bind estrogen receptors and sex hormone binding proteins, exerting both estrogenic and antiestrogenic activity. In this study we used the Japanese quail embryo as a test end-point to investigate the effects of early embryonic exposure to genistein on male copulatory behavior and on vasotocin parvocellular system. Both differentiate by the organizational effects of estradiol during development and may therefore represent an optimal model to study the effects of xenoestrogens. We injected two doses of genistein (100 and 1000 microg) into the yolk of 3-day-old Japanese quail eggs. Other eggs were treated with either 25 microg of estradiol benzoate or sesame oil as positive and negative controls. At the age of 6 weeks, behavioral tests revealed a significant decrease of all aspects of copulatory behavior (in comparison to the control group) in estradiol-treated birds. In contrast, genistein-treated animals demonstrated various degrees of decrease in the mean frequencies of some aspects of the sexual behavior. The computerized analysis of vasotocin innervation in medial preoptic, stria terminalis and lateral septum nuclei revealed a statistically significant decreased immunoreactivity in treated animals compared to control ones. These results demonstrate that genistein, similarly to estradiol, has an organizational effect on quail parvocellular vasotocin system and on copulatory behavior. In conclusion, present results confirm, in this avian model, that embryonic exposure to phytoestrogens may have life-long effects on sexual differentiation of brain structures and behaviors.

Ligand-based approach to in silico pharmacology: nuclear receptor profiling

Bioactive ligands are a valuable and increasingly accessible source of information about protein targets. On the basis of this statement, a list of 25 nuclear receptors was described by a series of bioactive ligands extracted directly from bibliographical sources, stored properly in an annotated chemical library, and mathematically represented using the recently reported SHED molecular descriptors. Analysis of this ligand information allowed for derivation of a threshold of nuclear receptor concern. If the similarity of one molecule to any of the molecules annotated to one particular nuclear receptor is below that threshold, the molecule receives an alert on the probability of having affinity below 10 microM for that nuclear receptor. On this basis, a linkage map was constructed that reveals the interaction network of nuclear receptors from the perspective of their active ligands. This ligand-based approach to nuclear receptor profiling was subsequently applied to four external chemical libraries of 10,000 molecules targeted to proteases, kinases, ion channels, and G protein-coupled receptors. The percentage of each library that returned an alert on at least one nuclear receptor was reasonably low and varied between 4.4 and 9.7%. In addition, ligand-based nuclear receptor profiling of a set of 2944 drugs provided an alert for 153 drugs. For some of them, namely, acitretin, telmisartan, phenyltoloxamine, tazarotene, and flumazenil, bibliographical evidence could be found indicating that those drugs may indeed have some potential off-target residual affinity for the nuclear receptors annotated. Overall, the present findings suggest that ligand-based approaches to protein family profiling appear as a promising means toward the establishment of novel tools for in silico pharmacology.

Steroids in aquatic invertebrates

Steroid molecules are present in all invertebrates, and some of them have established hormonal roles: this is the case for ecdysteroids in arthropods and, to a lesser extent, for vertebrate-type steroids in molluscs. Steroids are not only hormones, they may also fulfill many other functions in chemical communication, chemical defense or even digestive physiology. The increasing occurrence of endocrine disruption problems caused by environmental pollutants, which interfere in particular with reproductive physiology of vertebrates but also of invertebrates has made necessary to better understand the endocrine physiology of the latter and the role of steroids in these processes. So many attempts are being made to better understand the endocrine roles of steroids in arthropods and molluscs, and to establish whether they also fulfill similar functions in other invertebrate phyla. At the moment, both the precise identification of these steroids, the determination of their origin (endogenous versus exogenous) and of their mechanism of action are under active investigation. This research takes profit of the development of genome sequencing programs on many invertebrate species, which allow the identification of receptors and/or biosynthetic enzymes, when related to their vertebrate counterparts, but the story is not so simple, as will be exemplified by estrogen receptors of molluscs.

Characterization of atrazine-induced gonadal malformations in African clawed frogs (Xenopus laevis) and comparisons with effects of an androgen antagonist (cyproterone acetate) and exogenous estrogen (17beta-estradiol): Support for the demasculinization/feminization hypothesis

Atrazine is a potent endocrine disruptor that both chemically castrates and feminizes male amphibians. It depletes androgens in adult frogs and reduces androgen-dependent growth of the larynx in developing male larvae. It also disrupts normal gonadal development and feminizes the gonads of developing males. Gonadal malformations induced by atrazine include hermaphrodites and males with multiple testes [single sex polygonadism (SSP)], and effects occur at concentrations as low as 0.1 ppb (microg/L). Here, we describe the frequencies at which these malformations occur and compare them with morphologies induced by the estrogen, 17beta-estradiol (E2) , and the antiandrogen cyproterone acetate, as a first step in testing the hypothesis that the effects of atrazine are a combination of demasculinization and feminization. The various forms of hermaphroditism did not occur in controls. Nonpigmented ovaries, which occurred at relatively high frequencies in atrazine-treated larvae, were found in four individuals out of more than 400 controls examined (1%). Further, we show that several types of gonadal malformations (SSP and three forms of hermaphroditism) are produced by E2 exposure during gonadal differentiation, whereas a final morphology (nonpigmented ovaries) appears to be the result of chemical castration (disruption of androgen synthesis and/or activity) by atrazine. These experimental findings suggest that atrazine-induced gonadal malformations result from the depletion of androgens and production of estrogens, perhaps subsequent to the induction of aromatase by atrazine, a mechanism established in fish, amphibians, reptiles, and mammals (rodents and humans).

DROSOPHILANUTRIGENOMICS CAN PROVIDE CLUES TO HUMAN GENE-NUTRIENT INTERACTIONS

Nutrigenomics refers to the complex effects of the nutritional environment on the genome, epigenome, and proteome of an organism. The diverse tissue- and organ-specific effects of diet include gene expression patterns, organization of the chromatin, and protein post-translational modifications. Long-term effects of diet range from obesity and associated diseases such as diabetes and cardiovascular disease to increased or decreased longevity. Furthermore, the diet of the mother can potentially have long-term health impacts on the children, possibly through inherited diet-induced chromatin alterations. Drosophila is a unique and ideal model organism for conducting nutrigenomics research for numerous reasons. Drosophila, yeast, and Caenorhabditis elegans all have sophisticated genetics as well as sequenced genomes, and researchers working with all three organisms have made valuable discoveries in nutrigenomics. However, unlike yeast and C. elegans, Drosophila has adipose-like tissues and a lipid transport system, making it a closer model to humans. This review summarizes what has already been learned in Drosophila nutrigenomics (with an emphasis on lipids and sterols), critically evaluates the data, and discusses fruitful areas for future research.

Naringenin-type flavonoids show different estrogenic effects in mammalian and teleost test systems

The estrogenic activity of several intermediary plant compounds has raised concern about possible risks of unwanted interference with endocrine regulation, but on the other hand there are potential medical benefits, in particular in treatment of menopausal symptoms or cancer. In the present study, we compare the estrogenic effects of phytoestrogens naringenin, 8-prenylnaringenin, 6-(1,1-dimethylallyl)naringenin, and the synthetic 4'-acetyl-7-prenyloxynaringenin. Two mammalian in vitro systems and a fish in vivo system were used to study the estrogenic properties with reference to genistein, 17-beta-estradiol or ethynylestradiol. Strong differences were observed between the mammalian in vitro and the fish in vivo test system. In the medaka sex reversal/vtg gene expression assay no estrogenic effects of the naringenin-type flavonoids were observed, while mammalian in vitro systems showed a similar and graded response to the test compounds.

Specific interactions of steroids, arylhydrocarbons and flavonoids with progesterone receptors from the cytosol of the fungus Rhizopus nigricans

Rhizopus nigricans (R. nigricans) transforms fungitoxic progesterone into the less toxic 11alpha-hydroxyprogesterone which is then able to exit the mycelia into the surrounding water. Hydroxylation of progesterone is an inducible process in which cytosolic progesterone receptors could be involved. In the present study, we characterised receptors with respect to ligand specificity and to their involvement in progesterone induction of hydroxylase. EC(50) values of different ligands (steroids, xenobiotic arylhydrocarbons and natural flavonoids) were determined by competition studies using 40nM ((3)H)progesterone. C21 and C19 3-oxo-4-ene steroids were good competitors (EC(50) of progesterone 2.3 +/- 0.1 x 10(-7)M, EC(50) of androsten-3,17-dione 24 +/- 2 x 10(-7)M). The presence of hydroxyl groups in steroids significantly decreased the affinity for receptors. The arylhydrocarbons alpha-naphthoflavone and ketoconazole exhibited EC(50) values of 0.3 +/- 0.01 x 10(-7)M and 27 +/- 5 x 10(-7)M, respectively, whereas beta-naphthoflavone and benzo(a)pyrene were not able to displace labelled progesterone completely. The competition curves obtained by natural flavonoids also did not reach the bottom level of non-labelled progesterone, indicating the interaction at some allosteric binding site(s) of progesterone receptors. All ligands were examined for their involvement in progesterone-hydroxylase induction. Steroid agonists induced the enzyme in a dose-dependent manner in accordance with their affinity for receptors, whereas arylhydrocarbons and natural flavonoids did not induce the enzyme. The agonistic action of steroids, together with the antagonistic action of alpha-naphthoflavone, strongly suggests the involvement of progesterone receptors in progesterone signalling resulting in the induction of progesterone-hydroxylase.

Estrogen-inducible uterine flavonoid binding sites: is it time to reconsider?

Epidemiological data support the beneficial effect of plant flavonoids on human health including anti-inflammatory and cancer preventing actions. The phytoestrogen flavonoids might interfere with estrogen action. The possible relations between the steroid- and the flavonoid-signalling in animal and plant cells have been addressed in numerous studies in the past decade. In search for possible sites of conjunction between these phenomena the post-receptor targets must not be disregarded. The estrogen-inducible type II estrogen binding sites of rat uteri have first been reported 25 years ago by Clark and coworkers [Biochem. Biophys. Res. Commun. 81 (1978) 1]. These sites are known to bind catecholic flavonoids with considerable affinity. Behaviour of the tyrosinase-like enzymatic activity associated with these sites appeared reminiscent to the recently described dopachrome oxidase or tautomerase activity exhibited by the cytokine macrophage migration inhibitory factor (MIF) inasmuch as it also accepts a broad range of catecholic melanogenic precursors. Therefore we assessed, whether the known type II ligand flavonoids interfere with the MIF tautomerase. We report here, that luteolin and quercetin have a biphasic effect on the enol-keto conversion of phenylpyruvate mediated by MIF tautomerase. We also demonstrate the presence of MIF immunoreactivity by Western blotting in rat uterine nuclear extracts prepared according to the method that yields high type II binding activity. These data support the possible participation of MIF in type II estrogen binding phenomena.

Effects of plant flavonoids on fecundity, survival, and feeding of the Formosan subterranean termite

Fecundity, mortality, and food consumption of the Formosan subterranean termite, Coptotermes formosanus Shiraki, were evaluated in response to five plant flavonoids (genistein, biochanin A, apigenin, quercetin, and glyceollin). Apigenin fed at 50 microg/primary reproductive pair proved to be the most toxic flavonoid. Biochanin A was most effective in reducing fecundity. Subsequently, these two flavonoids were tested through oral feeding and topical application at 100-microg dose. Significant reduction in the numbers of progeny was evident for biochanin A in both treatment methods. Choice feeding tests with termite workers showed that initially termites were attracted to filter paper treated with biochanin A, but over a period of 72 hr, consumed significantly less material when compared to controls. Biochanin A is a promising phytochemical with ability to reduce fecundity in primary reproductives of the Formosan subterranean termite, but it does not elicit phagostimulant activity.

Juvenile hormone potentiates ecdysone receptor-dependent transcription in a mammalian cell culture system

Insect development is guided by the combined actions of ecdysteroids and juvenile hormones (JHs). The transcriptional effects of ecdysteroids are mediated by a protein complex consisting of the ecdysone receptor (EcR) and its heterodimeric partner, Ultraspiracle (USP), but a corresponding JH receptor has not been defined conclusively. Given that the EcR ligand binding domain (LBD) is similar to that of the JH-responsive rat farnesoid-X-activated receptor (FXR), we sought to define experimental conditions under which EcR-dependent transcription could be promoted by JH. Chinese hamster ovary (CHO) cells were transfected with a plasmid carrying an ecdysteroid-inducible reporter gene, a second plasmid expressing one of the three amino-terminal variants of Drosophila EcR or an EcR chimera, and a third plasmid expressing either the mouse retinoid X receptor (RXR), or its insect orthologue, USP. Each of the EcR variants responded to the synthetic ecdysteroid, muristerone A (murA), but a maximal response to 20-hydroxyecdysone (20E) was achieved only for specific EcR combinations with its heterodimeric partner. Notably, the Drosophila EcR isoforms were responsive to 20E only when paired with USP, and only EcRB2 activity was further potentiated by JHIII in the presence of 20E. EcR chimeras that fuse the activator domains from VP16 or the glucocorticoid receptor to the Drosophila EcR DNA-binding and ligand-binding domains were responsive to ecdysteroids. Again, the effects of JHIII and 20E were associated with specific partners of the chimeric EcRs. In all experiments, the LBD of EcR proved to be the prerequisite component for potentiation by JHIII, and in this conformation may resemble the FXR LBD. Our results indicate that EcR responsiveness is influenced by the heterodimeric partner and that both the N-terminal domain of EcR and the particular ecdysteroid affect JHIII potentiation.

Allometric analysis of the induced flavonols on the leaf surface of wild tobacco (Nicotiana attenuata)

Trichomes excrete secondary metabolites that may alter the chemical composition of the leaf surface, reducing damage caused by herbivores, pathogens and abiotic stresses. We examined the surface exudates produced by Nicotiana attenuata Torr. Ex Wats., a plant known to contain and secrete a number of secondary metabolites that are toxic or a deterrent to herbivorous insects. Extractions specific to the leaf surface, the trichomes, and the laminar components demonstrated the localization of particular compounds. Diterpene glycosides occurred exclusively in leaf mesophyll, whereas nicotine was found in both the trichomes and mesophyll. Neither rutin nor nicotine was found on the leaf surface. Quercetin and 7 methylated derivatives were found in the glandular trichomes and appeared to be excreted onto the leaf surface. We examined the elicitation of these flavonols on the leaf surface with a surface-area allometric analysis, which measures changes in metabolites independent of the effects of leaf expansion. The flavonols responded differently to wounding, methyl jasmonate (MeJA), herbivore attack and UV-C radiation, and the response patterns corresponded to their compound-specific allometries. Finding greater amounts of quercetin on younger leaves and reduced amounts after herbivore feeding and MeJA treatment, we hypothesized that quercetin may function as an attractant, helping the insects locate a preferred feeding site. Consistent with this hypothesis, mirids (Tupiocoris notatus) were found more often on mature leaves sprayed with quercetin at a concentration typical of young leaves than on unsupplemented mature leaves. The composition of metabolites on the leaf surface of N. attenuata changes throughout leaf development and in response to herbivore attack or environmental stress, and these changes are mediated in part by responses of the glandular trichomes.

Tomato glycoalkaloids: role in the plant and in the diet

Tomatoes, a major food source for humans, accumulate a variety of secondary metabolites including phenolic compounds, phytoalexins, protease inhibitors, and glycoalkaloids. These metabolites protect against adverse effects of hosts of predators including fungi, bacteria, viruses, and insects. Because glycoalkaloids are reported to be involved in host-plant resistance, on the one hand, and to have a variety of pharmacological and nutritional properties in animals and humans, on the other, a need exists to develop a better understanding of the role of these compounds both in the plant and in the diet. To contribute to this effort, this integrated review presents data on the history, composition, and nutrition of tomatoes, with special focus on the assessment of the chemistry, analysis, composition, nutrition, microbiology, and pharmacology of the tomato glycoalkaloids comprising alpha-tomatine and dehydrotomatine; their content in different parts of the tomato plant, in processed tomato products, and in wild and transgenic tomatoes; their biosynthesis, inheritance, metabolism, and catabolism; plant-microbe relationships with fungi, bacteria, viruses, insects, and worms; interactions with ergosterol and cholesterol; disruption of cell membranes; tomatine-induced tomatinases, pantothenate synthetase, steroid hydroxylases, and cytokines; and inhibition of acetylcholinesterase. Also covered are tomato-human pathogen relationships and tomatine-induced lowering of plasma cholesterol and triglycerides and enhancement of the immune system. Further research needs in each of these areas are suggested. The overlapping aspects are discussed in terms of general concepts for a better understanding of the impact of tomato glycoalkaloids in the plant in general and in food in particular. Such an understanding can lead to the creation of improved tomatoes and to improved practices on the farm and in the consumption of tomatoes.

Putative effects of endocrine disrupters on pubertal development in the human

Pubertal development is regulated by gonadotrophins and sex hormones. There has been a clear secular trend in the timing of puberty during the last century, puberty becoming earlier. Although improved nutrition is assumed to be the cause, this could partly be associated with exposure to so-called endocrine disrupters. Precocious puberty has been described in several case reports of accidental exposure to oestrogenic compounds in cosmetic products, food and pharmaceuticals. Local epidemics of premature thelarche have also been suggested to be linked to endocrine disrupters. Children adopted from developing countries to industrialized countries often develop precocious puberty. Not only precocious puberty, but also delayed puberty can, theoretically, be associated with exposure to endocrine disrupters. While it is very plausible that endocrine disrupters may disturb pubertal development, there is very little research on this and, therefore, we do not yet have any clear cause-effect relationships in humans.