Effects of endocrine disrupters on sex steroid synthesis and metabolism pathways in fish

The interactions of estrogenic (nonylphenol, dicofol, atrazine), androgenic (organotins, phthalates, fenarimol) and anti-androgenic compounds (vinclozolin, diuron, p,p'-DDE) with key enzymatic activities involved in both synthesis and metabolism of sex hormones was investigated. Carp testicular microsomes incubated in the presence of androstenedione and different xenobiotics evidenced higher sensitivity of 5alpha-reductase activity than 17beta-hydroxysteroid dehydrogenase activity towards those chemicals. Dicofol, organotins and phthalates were among the most effective inhibitors. In contrast, ovarian synthesis of maturation-inducing hormones (20alpha- and 20beta-hydroxysteroid dehydrogenase activities) were enhanced by nonylphenol, dicofol, fenarimol and p,p'-DDE. Metabolic clearance pathways of hormones were also affected. Fenarimol, nonylphenol and triphenyltin inhibited the glucuronidation of testosterone and estradiol at concentrations as low as 10, 50 and 100 microM, respectively. Triphenyltin, tributyltin and nonylphenol were also inhibitors of estradiol sulfation with IC(50) values of 17, 18 and 41 microM. Overall, the data indicates the interaction of selected chemicals with key enzymatic pathways involved in both synthesis and metabolism of sex hormones. This interference might be one of the underlying mechanisms for the reported hormonal disrupting properties of the tested compounds, and might finally affect physiological processes such as gamete growth and maturation.     

Esterification of vertebrate-type steroids in the Eastern oyster (Crassostrea virginica)

Characteristics of acyl-coenzyme A (acyl-CoA):steroid acyltransferase from the digestive gland of the oyster Crassostrea virginica were determined by using estradiol (E2) and dehydroepiandrosterone (DHEA) as substrates. The apparent Km and Vmax values for esterification of E2 with the six fatty acid acyl-CoAs tested (C20:4, C18:2, C18:1, C16:1, C18:0, and C16:0) were in the range of 9-17 microM E2 and 35-74 pmol/min/mg protein, respectively. Kinetic parameters for esterification of DHEA (Km: 45-120 microM; Vmax: 30-182 pmol/min/mg protein) showed a lower affinity of the enzyme for this steroid. Formation of endogenous fatty acid esters of steroids by microsomes of digestive gland and gonads incubated in the presence of ATP and CoA was assessed, and at least seven E2 fatty acid esters and five DHEA fatty acid esters were observed. Some peaks eluted at the same retention times as palmitoleoyl-, linoleoyl-, oleoyl/palmitoyl-, and stearoyl-E2; and palmitoleoyl-, oleoyl/palmitoyl-, and stearoyl-DHEA. The same endogenous esters, although in different proportions, were produced by gonadal microsomes. The kinetic parameters for both E2 (Km: 10 microM; Vmax: 38 pmol/min/mg protein) and DHEA (Km: 61 microM; Vmax: 60 pmol/min/mg protein) were similar to those obtained in the digestive gland. Kinetic parameters obtained are similar to those observed in mammals; thus, fatty acid esterification of sex steroids appears to be a well-conserved conjugation pathway during evolution.     

Oligomers of grape-seed procyanidin extract activate the insulin receptor and key targets of the insulin signaling pathway differently from insulin

Procyanidins are bioactive flavonoid compounds from fruits and vegetables that possess insulinomimetic properties, decreasing hyperglycaemia in streptozotocin-diabetic rats and stimulating glucose uptake in insulin-sensitive cell lines. Here we show that the oligomeric structures of a grape-seed procyanidin extract (GSPE) interact and induce the autophosphorylation of the insulin receptor in order to stimulate the uptake of glucose. However, their activation differs from insulin activation and results in differences in the downstream signaling. Oligomers of GSPE phosphorylate protein kinase B at Thr308 lower than insulin does, according to the lower insulin receptor activation by procyanidins. On the other hand, they phosphorylate Akt at Ser473 to the same extent as insulin. Moreover, we found that procyanidins phosphorylate p44/p42 and p38 MAPKs much more than insulin does. These results provide further insight into the molecular signaling mechanisms used by procyanidins, pointing to Akt and MAPK proteins as key points for GSPE-activated signaling pathways. Moreover, the differences between GSPE and insulin might help us to understand the wide range of biological effects that procyanidins have.     

Procyanidins protect Fao cells against hydrogen peroxide-induced oxidative stress

In this paper, we evaluate the extent to which flavonoids in red wine (catechin, epicatechin, quercetin and procyanidins) protect against hydrogen peroxide-induced oxidative stress in Fao cells. When cells were exposed to H(2)O(2), malondialdehyde (MDA) levels, oxidized glutathione (GSSG) levels and lactate dehydrogenase (LDH) release increased, indicating membrane damage and oxidative stress. All the flavonoids studied, and in particular epicatechin and quercetin, protected the plasma membrane. Only procyanidins lowered MDA levels and LDH leakage, maintained a higher reduced/oxidized glutathione ratio, and increased catalase/superoxide dismutase and glutathione peroxidase/superoxide dismutase ratios, and glutathione reductase and glutathione transferase activities. These results show that the procyanidin mixture has a greater antioxidant effect than the individual flavonoids studied, probably due to its oligomer content and/or the additive/synergistic effect of its compounds. This suggests that the mixture of flavonoids found in wine has a greater effect than individual phenols, which may explain many of the healthy effects attributed to wine.     

Biosynthesis and metabolism of steroids in molluscs

Molluscs are the second most diverse animal group, they are ecologically important and they are considered excellent indicators of ecosystem health. Some species have been widely used in pollution biomonitoring programs; however, their endocrinology is still poorly known. Despite some studies reporting the presence of (vertebrate-type) steroids in molluscs, information regarding enzymatic pathways involved in steroid synthesis and further catabolism of those steroids is still fragmentary. Regarding steroidogenesis, a number of excellent studies were performed in the 70s using different radio-labelled steroid precursors and detecting the formation of different metabolites. But, since then a long gap of research exist until the late 90s when the 'endocrine disruption' issue raised the need of a better knowledge of mollusc (and invertebrate) endocrinology in order to assess alterations caused by pollutants. Here we summarize past and recent studies dealing with steroid biosynthesis and metabolism in different mollusc species. Most of these studies suggest the involvement of steroids in mollusc reproduction. However, the knowledge is still fragmentary and many questions remain to be answered.     

Effects of the root-lesion nematode Pratylenchus vulnus and the mycorrhizal fungus Glomus mosseae on the growth of EMLA-26 apple rootstock

The interaction between Pratylenchus vulnus and the endomycorrhizal fungus Glomus mosseae on the growth of EMLA 26 apple rootstock was studied under shadehouse conditions in the field during the first 6 months of growth. Fresh top weights, fresh root weights, and shoot lengths of mycorrhizal plants with and without P. vulnus were significantly higher than those of nonmycorrhizal plants. Addition of P to non-mycorrhizal controls had little overall effect. Mycorrhizal treatments with the nematode showed a significantly lower amount of nematodes per gram of root than nonmycorrhizal treatments with P. vulnus. Root colonization by G. mosseae was not affected by the presence of the nematode. No nutrient deficiencies were detected in foliar analyses, although low levels of K, A1, and Fe were detected in nematode treatments. The highest levels of S, Mg, Mn and Zn were detected in P. vulnus inoculated plants. Mycorrhizal plants had the highest levels of N, Na, P, K, and Fe. The importance of early mycorrhizal infection of EMLA 26 apple root-stock in the presence of the nematode is discussed.     

Contrasting introduction scenarios among continents in the worldwide invasion of the banana fungal pathogen Mycosphaerella fijiensis

Reconstructing and characterizing introduction routes is a key step towards understanding the ecological and evolutionary factors underlying successful invasions and disease emergence. Here, we aimed to decipher scenarios of introduction and stochastic demographic events associated with the global spread of an emerging disease of bananas caused by the destructive fungal pathogen Mycosphaerella fijiensis. We analysed the worldwide population structure of this fungus using 21 microsatellites and 8 sequence‐based markers on 735 individuals from 37 countries. Our analyses designated South‐East Asia as the source of the global invasion and supported the location of the centre of origin of M. fijiensis within this area. We confirmed the occurrence of bottlenecks upon introduction into other continents followed by widespread founder events within continents. Furthermore, this study suggested contrasting introduction scenarios of the pathogen between the African and American continents. While potential signatures of admixture resulting from multiple introductions were detected in America, all the African samples examined seem to descend from a single successful founder event. In combination with historical information, our study reveals an original and unprecedented global scenario of invasion for this recently emerging disease caused by a wind‐dispersed pathogen.     

The role of age and exposure to Plasmodium falciparum in the rate of acquisition of naturally acquired immunity: a randomized controlled trial

Background

The rate of acquisition of naturally acquired immunity (NAI) against malaria predominantly depends on transmission intensity and age, although disentangling the effects of these is difficult. We used chemoprophylaxis to selectively control exposure to P. falciparum during different periods in infancy and explore the effect of age in the build-up of NAI, measured as risk of clinical malaria.

Methods and Findings

A three-arm double-blind randomized placebo-controlled trial was conducted in 349 infants born to Mozambican HIV-negative women. The late exposure group (LEG) received monthly Sulfadoxine-Pyrimethamine (SP) plus Artesunate (AS) from 2.5–4.5 months of age and monthly placebo from 5.5–9.5 months; the early exposure group (EEG) received placebo from 2.5–4.5 months and SP+AS from 5.5–9.5 months; and the control group (CG) received placebo from 2.5–9.5 months. Active and passive case detection (PCD) were conducted from birth to 10.5 and 24 months respectively. The primary endpoint was time to first or only episode of malaria in the second year detected by PCD. The incidence of malaria during the second year was of 0.50, 0.51 and 0.35 episodes/PYAR in the LEG, EEG and CG respectively (p = 0.379 for the adjusted comparison of the 3 groups). The hazard ratio of the adjusted comparison between the LEG and the CG was 1.38 (0.83–2.28, p = 0.642) and that between the EEG and the CG was 1.35 (0.81–2.24, p = 0.743).

Conclusions

After considerably interfering with exposure during the first year of life, there was a trend towards a higher risk of malaria in the second year in children who had received chemoprophylaxis, but there was no significant rebound. No evidence was found that the age of first exposure to malaria affects the rate of acquisition of NAI. Thus, the timing of administration of antimalarial interventions like malaria vaccines during infancy does not appear to be a critical determinant.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00231452","term_id":"NCT00231452"}}NCT00231452     

Contribution of arbuscular mycorrhizal symbiosis to the survival of psammophilic plants after sea water flooding

Aims

Plants on coastal sand dunes are subjected to strong environmental fluctuations which affect their growth and survival. Sea water invasion of the dunar zone caused by storms is an important factor that determines the persistence of a plant community. In the present study, the benefits of arbuscular mycorrhiza on psammophilic plant species subjected to sea water flooding episodes were evaluated under controlled conditions and the effect of sea water on in vitro spore production was determined.

Methods

In a greenhouse experiment, the growth response of nine plant species to inoculation with Glomus intraradices in beach sand was evaluated. A second experiment was designed in order to test if plant survival under sea water flooding was influenced by the symbiosis. A third experiment was conducted in vitro to quantify the effect of sea water on the production of G. intraradices spores.

Results

Glomus intraradices was effective in promoting plant growth and survival in beach sand and promoted the survival of some species subjected to flooding events. Spore production was inhibited by 50% of sea water in the growth media, but not by 10% sea water.

Conclusions

Results obtained under controlled conditions indicated that arbuscular mycorrhiza can improve the establishment of certain dune plant species in beach sand as the symbiosis contributes to enhanced plant tolerance against occasional sea water flooding.