Synthesis and biological properties of macrolactam analogs of the natural product macrolide (−)-A26771B

Promising synthetic derivatives of macrolactone natural product (−)-A26771B have been designed and synthesized both from semisynthesis and total synthesis. Further optimization led to the first synthesis of macrolactam analogs of (−)-A26771B with improved antibacterial activity and metabolic stability.     

Concentrations of Thirteen Trace Metals in Scales of Three Nototheniid Fishes from Antarctica (James Ross Island,Antarctic Peninsula)

In this study, we assessed concentrations of 13 trace metals in the scales of Notothenia coriiceps, Trematomus bernacchii and Gobionotothen gibberifrons caught off the coast of James Ross Island (Antarctic Peninsula). Overall, our results for scales broadly match those of previous studies using different fish and different organs, with most metals found at trace levels and manganese, aluminium, iron and zinc occurring at high levels in all species. This suggests that scales can serve as a useful, non-invasive bioindicator of long-term contamination in Antarctic fishes. High accumulation of manganese, aluminium, iron and zinc is largely due to high levels in sediments associated with nearby active volcanic sites. Manganese, vanadium and aluminium showed significant positive bioaccumulation in T. bernacchii (along with non-significant positive accumulation of iron, zinc, cobalt and chromium), most likely due to greater dietary specialisation on sediment feeding benthic prey and higher trophic species. Levels of significance in bioaccumulation regressions were strongly affected by large-scale variation in the data, driven largely by individual differences in diet and/or changes in habitat use and sex differences associated with life stage and reproductive status. Increased levels of both airborne deposition and precipitation and meltwater runoff associated with climate change may be further adding to the already high levels of manganese, aluminium, iron and zinc in Antarctic Peninsula sediments. Further long-term studies are encouraged to elucidate mechanisms of uptake (especially for aluminium and iron) and possible intra- and interspecific impacts of climate change on the delicate Antarctic food web.

     

Zinc-α2-Glycoprotein Modulates AKT-Dependent Insulin Signaling in Human Adipocytes by Activation of the PP2A Phosphatase

Objective

Evidence from mouse models suggests that zinc-α2-glycoprotein (ZAG) is a novel anti-obesity adipokine. In humans, however, data are controversial and its physiological role in adipose tissue (AT) remains unknown. Here we explored the molecular mechanisms by which ZAG regulates carbohydrate metabolism in human adipocytes.

Methods

ZAG action on glucose uptake and insulin action was analyzed. β1 and β2-adrenoreceptor (AR) antagonists and siRNA targeting PP2A phosphatase were used to examine the mechanisms by which ZAG modulates insulin sensitivity. Plasma levels of ZAG were measured in a lean patient cohort stratified for HOMA-IR.

Results

ZAG treatment increased basal glucose uptake, correlating with an increase in GLUT expression, but induced insulin resistance in adipocytes. Pretreatment of adipocytes with propranolol and a specific β1-AR antagonist demonstrated that ZAG effects on basal glucose uptake and GLUT4 expression are mediated via β1-AR, whereas inhibition of insulin action is dependent on β2-AR activation. ZAG treatment correlated with an increase in PP2A activity. Silencing of the PP2A catalytic subunit abrogated the negative effect of ZAG on insulin-stimulated AKT phosphorylation and glucose uptake but not on GLUT4 expression and basal glucose uptake. ZAG circulating levels were unchanged in a lean patient cohort stratified for HOMA-IR. Neither glucose nor insulin was associated with plasma ZAG.

Conclusions

ZAG inhibits insulin-induced glucose uptake in human adipocytes by impairing insulin signaling at the level of AKT in a β2-AR- and PP2A-dependent manner.     

Multicenter Experience with Boceprevir or Telaprevir to Treat Hepatitis C Recurrence after Liver Transplantation: When Present Becomes Past,What Lessons for Future?

Background and aims

First generation protease inhibitors (PI) with peg-interferon (PEG-IFN) and ribavirin (RBV) have been the only therapy available for hepatitis C virus (HCV) genotype 1 infection in most countries for 3 years. We have investigated the efficacy and tolerance of this triple therapy in transplanted patients experiencing a recurrence of HCV infection on the liver graft.

Patients

This cohort study enrolled 81 liver transplant patients (Male: 76%, mean age: 55.8±9.7 years) with severe HCV recurrence (F3 or F4: n = 34 (42%), treatment experienced: n = 44 (54%)), treated with boceprevir (n = 36; 44%) or telaprevir (n = 45; 56%). We assessed the percentages of patients with sustained virological responses 24 weeks after therapy (SVR24), and safety.

Results

The SVR24 rate was 47% (telaprevir: 42%; boceprevir: 53%, P = ns). At baseline, a normal bilirubin level (p = 0.0145) and albumin level >35g/L (p = 0.0372) and an initial RBV dosage of ≥800 mg/day (p = 0.0033) predicted SVR24. During treatment, achieving an early virological response after 12 weeks was the strongest independent factor to predict SVR24 (p<0.0001). A premature discontinuation of anti-HCV therapy due to a serious adverse event (SAE) was observed in 22 patients (27%). Hematological toxicity, infections and deaths were observed in 95%, 28% and 7% of patients, respectively. A history of post-LT antiviral therapy and thrombocytopenia (<50G/L) during treatment were both independent predictors of the occurrence of infections or SAE (p = 0.0169 and p = 0.011).

Conclusions

The use of first generation PI after liver transplantation enabled an SVR24 rate of 47% in genotype 1 patients, but induced a high rate of SAE. The identification of predictive factors for a response to treatment, and the occurrence of SAE, have enabled us to establish limits for the use of this anti-HCV therapy in the transplant setting.     

Paladin is a phosphoinositide phosphatase regulating endosomal VEGFR2 signalling and angiogenesis

Cell signalling governs cellular behaviour and is therefore subject to tight spatiotemporal regulation. Signalling output is modulated by specialized cell membranes and vesicles which contain unique combinations of lipids and proteins. The phosphatidylinositol 4,5‐bisphosphate (PI(4,5)P₂), an important component of the plasma membrane as well as other subcellular membranes, is involved in multiple processes, including signalling. However, which enzymes control the turnover of non‐plasma membrane PI(4,5)P₂, and their impact on cell signalling and function at the organismal level are unknown. Here, we identify Paladin as a vascular PI(4,5)P₂ phosphatase regulating VEGFR2 endosomal signalling and angiogenesis. Paladin is localized to endosomal and Golgi compartments and interacts with vascular endothelial growth factor receptor 2 (VEGFR2) in vitro and in vivo. Loss of Paladin results in increased internalization of VEGFR2, over‐activation of extracellular regulated kinase 1/2, and hypersprouting of endothelial cells in the developing retina of mice. These findings suggest that inhibition of Paladin, or other endosomal PI(4,5)P₂ phosphatases, could be exploited to modulate VEGFR2 signalling and angiogenesis, when direct and full inhibition of the receptor is undesirable.     

SNAP23 is selectively expressed in airway secretory cells and mediates baseline and stimulated mucin secretion

Airway mucin secretion is important pathophysiologically and as a model of polarized epithelial regulated exocytosis. We find the trafficking protein, SNAP23 (23-kDa paralogue of synaptosome-associated protein of 25 kDa), selectively expressed in secretory cells compared with ciliated and basal cells of airway epithelium by immunohistochemistry and FACS, suggesting that SNAP23 functions in regulated but not constitutive epithelial secretion. Heterozygous SNAP23 deletant mutant mice show spontaneous accumulation of intracellular mucin, indicating a defect in baseline secretion. However mucins are released from perfused tracheas of mutant and wild-type (WT) mice at the same rate, suggesting that increased intracellular stores balance reduced release efficiency to yield a fully compensated baseline steady state. In contrast, acute stimulated release of intracellular mucin from mutant mice is impaired whether measured by a static imaging assay 5 min after exposure to the secretagogue ATP or by kinetic analysis of mucins released from perfused tracheas during the first 10 min of ATP exposure. Together, these data indicate that increased intracellular stores cannot fully compensate for the defect in release efficiency during intense stimulation. The lungs of mutant mice develop normally and clear bacteria and instilled polystyrene beads comparable to WT mice, consistent with these functions depending on baseline secretion that is fully compensated.     

Pressure‐induced structural transition of mature HIV‐1 protease from a combined NMR/MD simulation approach

We investigate the pressure‐induced structural changes in the mature human immunodeficiency virus type 1 protease dimer, using residual dipolar coupling (RDC) measurements in a weakly oriented solution. ¹D_NH RDCs were measured under high‐pressure conditions for an inhibitor‐free PR and an inhibitor‐bound complex, as well as for an inhibitor‐free multidrug resistant protease bearing 20 mutations (PR20). While PR20 and the inhibitor‐bound PR were little affected by pressure, inhibitor‐free PR showed significant differences in the RDCs measured at 600 bar compared with 1 bar. The structural basis of such changes was investigated by MD simulations using the experimental RDC restraints, revealing substantial conformational perturbations, specifically a partial opening of the flaps and the penetration of water molecules into the hydrophobic core of the subunits at high pressure. This study highlights the exquisite sensitivity of RDCs to pressure‐induced conformational changes and illustrates how RDCs combined with MD simulations can be used to determine the structural properties of metastable intermediate states on the folding energy landscape. Proteins 2015; 83:2117–2123. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.     

Elucidating the spatio‐temporal dynamics of an emerging wildlife pathogen using approximate Bayesian computation

Emerging pathogens constitute a severe threat for human health and biodiversity. Determining the status (native or non‐native) of emerging pathogens, and tracing back their spatio‐temporal dynamics, is crucial to understand the eco‐evolutionary factors promoting their emergence, to control their spread and mitigate their impacts. However, tracing back the spatio‐temporal dynamics of emerging wildlife pathogens is challenging because (i) they are often neglected until they become sufficiently abundant and pose socio‐economical concerns and (ii) their geographical range is often little known. Here, we combined classical population genetics tools and approximate Bayesian computation (i.e. ABC) to retrace the dynamics of Tracheliastes polycolpus, a poorly documented pathogenic ectoparasite emerging in Western Europe that threatens several freshwater fish species. Our results strongly suggest that populations of T. polycolpus in France emerged from individuals originating from a unique genetic pool that were most likely introduced in the 1920s in central France. From this initial population, three waves of colonization occurred into peripheral watersheds within the next two decades. We further demonstrated that populations remained at low densities, and hence undetectable, during 10 years before a major demographic expansion occurred, and before its official detection in France. These findings corroborate and expand the few historical records available for this emerging pathogen. More generally, our study demonstrates how ABC can be used to determine the status, reconstruct the colonization history and infer key evolutionary parameters of emerging wildlife pathogens with low data availability, and for which samples from the putative native area are inaccessible.