Characterization of secondary structure and lipid binding behavior of N-terminal saposin like subdomain of human Wnt3a

Wnt signaling is essential for embryonic development and adult homeostasis in multicellular organisms. A conserved feature among Wnt family proteins is the presence of two structural domains. Within the N-terminal (NT) domain there exists a motif that is superimposable upon saposin-like protein (SAPLIP) family members. SAPLIPs are found in plants, microbes and animals and possess lipid surface seeking activity. To investigate the function of the Wnt3a saposin-like subdomain (SLD), recombinant SLD was studied in isolation. Bacterial expression of this Wnt fragment was achieved only when the core SLD included 82 NT residues of Wnt3a (NT-SLD). Unlike SAPLIPs, NT-SLD required the presence of detergent to achieve solubility at neutral pH. Deletion of two hairpin loop extensions present in NT-SLD, but not other SAPLIPs, had no effect on the solubility properties of NT-SLD. Far UV circular dichroism spectroscopy of NT-SLD yielded 50-60% α-helix secondary structure. Limited proteolysis of isolated NT-SLD in buffer and detergent micelles showed no differences in cleavage kinetics. Unlike prototypical saposins, NT-SLD exhibited weak membrane-binding affinity and lacked cell lytic activity. In cell-based canonical Wnt signaling assays, NT-SLD was unable to induce stabilization of β-catenin or modulate the extent of β-catenin stabilization induced by full-length Wnt3a. Taken together, the results indicate neighboring structural elements within full-length Wnt3a affect SLD conformational stability. Moreover, SLD function(s) in Wnt proteins appear to have evolved away from those commonly attributed to SAPLIP family members.

Visualization of the internal structure of Didymosphenia geminata frustules using nano X-ray tomography

For the first time, the three-dimensional (3D) internal structure of naturally produced Didymosphenia geminata frustules were nondestructively visualized at sub-100 nm resolution. The well-optimized hierarchical structures of these natural organisms provide insight that is needed to design novel, environmentally friendly functional materials. Diatoms, which are widely distributed in freshwater, seawater and wet soils, are well known for their intricate, siliceous cell walls called ‘frustules’. Each type of diatom has a specific morphology with various pores, ribs, minute spines, marginal ridges and elevations. In this paper, the visualization is performed using nondestructive nano X-ray computed tomography (nano-XCT). Arbitrary cross-sections through the frustules, which can be extracted from the nano-XCT 3D data set for each direction, are validated via the destructive focused ion beam (FIB) cross-sectioning of regions of interest (ROIs) and subsequent observation by scanning electron microscopy (SEM). These 3D data are essential for understanding the functionality and potential applications of diatom cells.

Nutlin-3a Nanodisks Induce p53 Stabilization and Apoptosis in a Subset of Cultured Glioblastoma Cells

Nanodisks (ND) are ternary complexes of phospholipid, one or more hydrophobic bioactive agents and an apolipoprotein scaffold. These nanoscale assemblies are organized as a disk-shaped lipid bilayer whose perimeter is stabilized by an apolipoprotein scaffold. Solubilization of hydrophobic bioactive agents is achieved by their integration into the ND lipid milieu. When the cis-imidazoline, nutlin-3a, was incubated with phosphatidylcholine and apolipoprotein A-I, it was conferred with aqueous solubility as judged by spectroscopic analysis. Nondenaturing polyacrylamide gel electrophoresis yielded evidence of a homogeneous population of ND particles ~9 nm in diameter. Gel filtration chromatography experiments revealed the association of nutlin-3a with ND is reversible. Biological activity of nutlin-3a ND was examined in three distinct glioblastoma cell lines, U87MG, SF763 and SF767. Incubation of U87MG cells with nutlin-3a ND induced concentration-dependent cell growth arrest and apoptosis. SF763 cells demonstrated modest cell growth arrest only at high concentrations of nutlin-3a ND and no apoptosis. SF767 cells were unaffected by nutlin-3a ND. Immunoblot analysis revealed nutlin-3a ND induced time-dependent stabilization of the master tumor suppressor, p53, and up regulation of the E3 ubiquitin ligase, murine double minute 2 in U87MG cells, but not the other glioma cell lines. The nanoscale size of the formulation particles, their facile assembly and nutlin-3a solubilization capability suggest ND represent a potentially useful vehicle for in vivo administration of this anti-tumor agent.

Abstract 16: Amyloidogenic Modifications of Apolipoprotein A-I Promote a Strong Pro-inflammatory Response in Macrophages, but Formation of Amyloid Fibrils Abrogates the Pro-inflammatory Effect

Inflammation is central to atherosclerosis, as inactivation of inflammation pathways strongly reduces atherosclerosis progression. Particulate matter, such as cholesterol crystals and amyloid materials, promotes release of the potent pro-inflammatory cytokine IL-1β in macrophages. Recently, it has been demonstrated that soluble substances that are precursors of particulate matter, such as free cholesterol, oxidized LDL and amyloidogenic peptides (i.e. amyloid-β, IAPP), can also induce an inflammatory response.

In this study, we investigated the interplay between oxidation of apolipoprotein A-I (apoA-I), amyloid formation, and the inflammatory response of macrophages. We previously reported that oxidation of apoA-I methionines (MetO-ApoA-I) promotes protein aggregation and formation of amyloid fibrils when MetO-ApoA-I is incubated at pH 6.0. In contrast, at physiological pH, MetO-ApoA-I remains soluble and perfectly functional, as it promotes cholesterol efflux from macrophages with the same efficiency of intact-ApoA-I. However, upon incubation of mouse bone marrow derived macrophages with soluble pre-fibrillar MetO-ApoA-I, levels of pro-IL-1β synthesis were more than 2-fold higher than those induced by intact-ApoA-I. In contrast, amyloid fibrils produced by MetO-ApoA-I did not increase the levels of pro-IL-1β synthesis compared to intact-ApoA-I. Furthermore, the pro-inflammatory effect was not observed in macrophages derived from MyD88/TRIF knock-out mice, indicating that the response is membrane TLR receptors-dependent. In contrast, the >2-fold increase (MetO-ApoA-I vs. intact-apoA-I) in pro-IL-1β synthesis was maintained in macrophages derived from CD36 knock-out mice. This observation suggests that the signaling pathway is not exclusively dependent on the TLR2/TLR6/CD36 membrane complex. Thus, in atherosclerotic lesions, oxidized apoA-I species that are amyloidogenic, but otherwise functional, may induce a pro-inflammatory response in macrophages. Amyloid fibril formation in contrast, could reduce, rather than exacerbate, the inflammatory burden produced by these pro-inflammatory apoA-I species by sequestering them in the form of inert amyloids.

Towards a multigene phylogeny of the Cymatosiraceae (Bacillariophyta, Mediophyceae) I: novel taxa within the subfamily cymatosiroideae based on molecular and morphological data

The family Cymatosiraceae, composed of two subfamilies (Cymatosiroideae and Extubocelluloideae), are elongate, non-pennate diatoms and are commonly reported in marine planktonic and benthic assemblages all over the world. The combination of the gross bilateral symmetry of the frustule and radial symmetry of the valve poration, distinct pore fields at the valve apices and DNA sequence data place this family in the controversial diatom class Mediophyceae, sister to the pennate diatoms. The relationships of the Cymatosiraceae within the Mediophyceae, and the monophyly of the two cymatosiroid subfamilies, have become less stable with the addition of new DNA sequence data. In this paper, we examined 24 cymatosiraceaen strains, including the new taxa Lambertocellus africana (Dąbek & Witkowski) Dąbek, Witkowski & Ashworth comb. nov., Leyanella probus Ashworth, Dąbek & Witkowski sp. nov., and Leyanella pauciporis Ashworth, Dąbek & Park sp. nov. to create the most complete molecular phylogeny of the Cymatosiraceae to date, using a three-gene (SSU, rbcL and psbC) data set. The results of the phylogenetic analysis supported the monophyly of the Cymatosiraceae, but not the monophyly of the subfamilies Cymatosiroideae and Extubocelluloideae. The phylogenetic analysis also suggested a close relationship of the Cymatosiraceae to the family Eupodiscaceae. The phylogenetic results have lead us to re-evaluate the taxonomy of L. africana, which is sister to Cymatosira lorenziana rather than Minutocellus as suggested in the original description.

Coexistence of bicuspid aortic valve, aberrant right subclavian artery and common origin of carotid arteries

BACKGROUND

Prevalence of bicuspid aortic valve (BAV) and right aberrant sub-clavian artery (ASA) separately is relatively common in general population, and much higher in some disorders. Surprisingly, coexistence of both valve and vessel anomalies has only been reported in single cases.

MATERIALS AND METHODS

From 2008 to 2016, in a single, high-volume tertiary cardiac centre, patients who underwent chest computed tomography (CT) for various reasons, were retrospectively screened for the presence of right ASA.

RESULTS

Seventy-two patients with either right or left ASA were identified by CT. Among them 7 cases of BAV and right ASA coexistence were identified. Additionally, 1 case with coexisting common origin of carotid arteries (COCA) was visualised in this subgroup.

CONCLUSIONS

Although coexistence of ASA and BAV has not been reported in paediatric population, it has been diagnosed in very few adults as well as in our series. Additional presence of COCA in this group seems to be very rare. From practical point of view, heart cannulation via the radial artery and subsequent ASA may be challenging. Similarly, COCA presence may have surgical implications during corrective procedures.

Platelet aggregation and risk of stent thrombosis or bleeding in interventionally treated diabetic patients with acute coronary syndrome

Background

Platelet aggregation monitoring in diabetic patients treated with coronary interventions (PCI) for an acute coronary syndrome (ACS) is a promising way of optimizing treatment and outcomes in this high risk group. The aim of the study was to verify whether clopidogrel response measured by Multiplate analyzer (ADPtest) in diabetic ACS patients treated with PCI predicts the risk of stent thrombosis or cardiovascular mortality and bleeding.

Methods

Into this prospective, observational study 206 elective PCI patients were enrolled. Two cutoff points of ADPtest were used in analysis to divide patients into groups. One (345 AU x min) was calculated based on ROC curve analysis; this cutoff provided the best ROC curve fit, although it did not reach statistical significance. The other (468 AU x min) was accepted based on the consensus of the Working Group on On-Treatment Platelet Reactivity. The risk of stent thrombosis and mortality was assessed using Cox regression analysis and Kaplan-Meier curves.

Results

The risk of stent thrombosis was higher in the group of patients with impaired clopidogrel response for either cutoff value (for >354 AU x min - HR 12.33; 95% CI 2.49–61.1; P = 0.002). Cardiovascular mortality was also higher in the impaired clopidogrel response group (for >354 AU x min - HR 10.58; 95% CI 2.05–54.58; P = 0.005). We did not find a clear relation of increased clopidogrel response to the risk of bleeding.

Conclusions

The results of this study show that in diabetic ACS patient group treated with PCI an impaired platelet response to clopidogrel measured by the Multiplate analyzer results in increased risk of stent thrombosis and cardiac death.

Ultrastructural and molecular characterization of diversity among small araphid diatoms all lacking rimoportulae. I. Five new genera, eight new species

Pennate diatoms are important contributors to primary production in freshwater and marine habitats. But the extent of their diversity, ecology, and evolution is still largely unknown. This is particularly evident among the clades of pennate diatoms without raphe slits, whose diversity is likely underestimated due to their small size and features that can be difficult to discern under light microscopy. In this study, we described five new araphid genera with eight new species based on morphological observations (light and electron microscopy) and molecular data (nuclear-encoded small subunit ribosomal RNA and chloroplast-encoded rbcL and psbC): Serratifera varisterna, Hendeyella rhombica, H. dimeregrammopsis, H. lineata, Psammotaenia lanceolata, Castoridens striata, C. hyalina, and Cratericulifera shandongensis. We also transferred Dimeregramma dubium to Hendeyella dubia. Phylogenetic analysis of the molecular data revealed that all the newly established taxa fell into a monophyletic group, with Fragilariforma virescens located at the base. The group was composed by two subclades: one comprising Castoridens, Cratericulifera, and Plagiostriata, and the larger including also the rest of the new genera plus some of the smallest known diatoms, such as Nanofrustulum, Opephora, Pseudostaurosira, Staurosirella, and Staurosira with a high level of support. This study enhances the general knowledge on the phylogeny and biodiversity of a group of small araphid diatoms that have been generally poorly described both by electron microscopy and DNA sequence data.

Wnt3a nanodisks promote ex vivo expansion of hematopoietic stem and progenitor cells

BACKGROUND

Wnt proteins modulate development, stem cell fate and cancer through interactions with cell surface receptors. Wnts are cysteine-rich, glycosylated, lipid modified, two domain proteins that are prone to aggregation. The culprit responsible for this behavior is a covalently bound palmitoleoyl moiety in the N-terminal domain.

RESULTS

By combining murine Wnt3a with phospholipid and apolipoprotein A-I, ternary complexes termed nanodisks (ND) were generated. ND-associated Wnt3a is soluble in the absence of detergent micelles and gel filtration chromatography revealed that Wnt3a co-elutes with ND. In signaling assays, Wnt3a ND induced β-catenin stabilization in mouse fibroblasts as well as hematopoietic stem and progenitor cells (HSPC). Prolonged exposure of HSPC to Wnt3a ND stimulated proliferation and expansion of Lin(-) Sca-1(+) c-Kit(+) cells. Surprisingly, ND lacking Wnt3a contributed to Lin(-) Sca-1(+) c-Kit(+) cell expansion, an effect that was not mediated through β-catenin.

CONCLUSIONS

The data indicate Wnt3a ND constitute a water-soluble transport vehicle capable of promoting ex vivo expansion of HSPC.

Abstract 539: Soluble Oxidized Apolipoprotein A-I, a Precursor of Amyloid Fibrils, Activates Secretion of Inflammatory Cytokines in Macrophages

Atherosclerosis is often described as an inflammatory disease of the arteries. One mechanism whereby apolipoprotein A-I (apoA-I) exerts its anti-atherosclerotic effect is by mitigating the inflammatory response of cells involved in atherosclerosis progression. However, oxidation transforms apoA-I from an anti-inflammatory to a pro-inflammatory protein. We previously reported that oxidation can also promote apoA-I aggregation and formation of amyloid fibrils. In this study, we investigated the mechanistic interplay between oxidation, amyloid formation and the inflammatory response of macrophages to apoA-I. We hypothesized that amyloid fibrils constituted of oxidized apoA-I activate production of inflammatory cytokines in macrophages. To test this hypothesis, amyloidogenic apoA-I was generated by oxidation with an excess of H 2 O 2 (H 2 O 2 -ApoA-I). Intracellular and secreted levels of IL-1β were determined upon incubation of mouse bone marrow derived macrophages (BMDM) with intact-apoA-I, soluble H 2 O 2 -ApoA-I and pre-formed H 2 O 2 -ApoA-I amyloid fibrils. Cellular cholesterol release from RAW264.7 cells was also measured. Soluble H 2 O 2 -ApoA-I (amyloid precursor) retained the cellular cholesterol release capacity of intact-ApoA-I. In BMDM incubated with soluble H 2 O 2 -ApoA-I however, levels of IL-1β synthesis and secretion were at least 2-fold higher than those induced by intact-ApoA-I. In contrast, incubation with H 2 O 2 -ApoA-I amyloid fibrils did not increase the levels of IL-1β synthesis and secretion, compared to intact-ApoA-I. Thus, soluble and functional oxidized apoA-I activates inflammatory cytokine synthesis and secretion in macrophages. Notably, this pro-inflammatory potential was completely neutralized when oxidized apoA-I was aggregated in amyloids. Therefore in atherosclerotic lesions, amyloid formation could reduce, rather than exacerbate, the inflammatory burden produced by pro-inflammatory soluble oxidized apoA-I species.

Cost-benefit of reflectance confocal microscopy in the diagnostic performance of melanoma

BACKGROUND

The sub-optimal diagnostic accuracy for melanoma leads to excise a high number of benign lesions, with consequent costs. Reflectance confocal microscopy (RCM) improves diagnostic specificity, thus possibly inducing a reduction in unnecessary excisions and related costs.

OBJECTIVE

To estimate the influence of RCM on number of benign lesions needed to excise (NNE) a melanoma, in term of clinical outcomes and costs per patient.

PATIENTS AND METHODS

Skin neoplasms excised by the dermatology public service in the Province of Modena were retrieved form centralized pathology database. Differences in NNE between the territorial service (using dermoscopy only) and the University Hospital (adding also RCM to the patients' workflow) were calculated and cost analysis was performed through a micro-costing approach.

RESULTS

A large reduction in benign lesions excised at University Hospital was evident, leading to NNE of 6.25 for University Hospital, compared to 19.41 for Territorial Dermatology. Since 4320 unnecessary excisions can be saved every million inhabitants, an overall yearly saving of over 280,000 Eur can be expected from the use of RCM.

CONCLUSIONS

The systematic use of RCM was dramatically affecting the number of benign lesions excised, and this can be translated in a significant cost-benefit advantage.

Changes in Quail Blastodermal Cell Status as a Result of Selection

Genetic selection over many years has significantly improved the growth rate of broilers and increased the number of eggs laid by egg laying chicken breeds. Selection has improved desired parameters, but has caused some negative effects as well. Adverse effects of selection may negatively affect embryonic development. The number of live and apoptotic blastodermal cells (BCs) at the X stage of embryogenesis may be a good indicator of changes in selected individuals. In this paper, a comparison of the number of live and apoptotic BCs was made for three lines of quail: Pharaoh (F33), meat-type line, selected for body weight; egg laying line (S33), selected for egg number; and laying line (S22), additionally selected (for 17 generations) for high yolk cholesterol content. Apoptotic BCs were separated by the magnetic activated cell sorting (MACS) method. The percentage of live and apoptotic BCs was different (P ≤ 0.01) for F33 (35.8% and 64.2%, respectively) and S33 (60.0% and 36.4%). The number of apoptotic BCs for F33 embryos (45,098) was higher (P ≤ 0.01) compared to the number of apoptotic BCs for S33 embryos (26,667). The selection for high yolk cholesterol content caused an increase (P ≤ 0.01) in the total number of BCs from 78,403 (S33) to 140,139 (S22). The percentage of apoptotic BCs was lower (P ≤ 0.01) in the S22 line (17.1%) compared to the S33 line (36.4%). The results showed that it is possible to evaluate the effects of selection in the early stage of embryonic development.

Total ischaemic time and 9-year outcomes in STEMI patients treated with pPCI

BACKGROUND

Prolonged total ischaemic time (TIT) has been shown to independently predict poor myocardial perfusion in STEMI patients and affect in-hospital mortality. We aim to evaluate the influence of TIT on long-term follow-up (F/U) and identify the factors associated with TIT in patients with STEMI treated with pPCI at a high volume centre.

METHODS

In a prospective "all-comer" registry, clinical, angiographic and procedural characteristics, TIT and 9-year mortality were determined in consecutive STEMI patients treated with pPCI. Patients were divided according to TIT into three groups: A) <3, B) 3-6 and C) >6h.

RESULTS

Among 1064 patients, TIT was known in 1002 patients, 5 patients were lost to F/U. For censored observations F/U was 7.2-8.8 years. There were 350, 461, and 186 patients in groups A, B, and C, respectively. Patients in group A compared to B and C were younger, more often males and smokers, less frequently had history of CAD, and more frequently had occluded infarct related artery. However, final TIMI3 was obtained more frequently. Overall 30-day mortality was 4%, one-year mortality 7% and nine-year mortality 27%. Multivariable logistic regression models indicated that longer TIT was associated with a higher risk of 9-year mortality (A-21%, B-28%, C-37%, p<0.0005). TIT>6h was independently associated with advanced age, diabetes mellitus, history of CAD and higher rate of initial TIMI grade flow 3.

CONCLUSIONS

TIT is strongly related with mortality in STEMI patients even after nine years of F/U. This finding reinforces the necessity of shortening the TIT in all STEMI patients.

Myeloperoxidase-mediated Methionine Oxidation Promotes an Amyloidogenic Outcome for Apolipoprotein A-I

High plasma levels of apolipoprotein A-I (apoA-I) correlate with cardiovascular health, whereas dysfunctional apoA-I is a cause of atherosclerosis. In the atherosclerotic plaques, amyloid deposition increases with aging. Notably, apoA-I is the main component of these amyloids. Recent studies identified high levels of oxidized lipid-free apoA-I in atherosclerotic plaques. Likely, myeloperoxidase (MPO) secreted by activated macrophages in atherosclerotic lesions is the promoter of such apoA-I oxidation. We hypothesized that apoA-I oxidation by MPO levels similar to those present in the artery walls in atherosclerosis can promote apoA-I structural changes and amyloid fibril formation. ApoA-I was exposed to exhaustive chemical (H2O2) oxidation or physiological levels of enzymatic (MPO) oxidation and incubated at 37 °C and pH 6.0 to induce fibril formation. Both chemically and enzymatically oxidized apoA-I produced fibrillar amyloids after a few hours of incubation. The amyloid fibrils were composed of full-length apoA-I with differential oxidation of the three methionines. Met to Leu apoA-I variants were used to establish the predominant role of oxidation of Met-86 and Met-148 in the fibril formation process. Importantly, a small amount of preformed apoA-I fibrils was able to seed amyloid formation in oxidized apoA-I at pH 7.0. In contrast to hereditary amyloidosis, wherein specific mutations of apoA-I cause protein destabilization and amyloid deposition, oxidative conditions similar to those promoted by local inflammation in atherosclerosis are sufficient to transform full-length wild-type apoA-I into an amyloidogenic protein. Thus, MPO-mediated oxidation may be implicated in the mechanism that leads to amyloid deposition in the atherosclerotic plaques in vivo.

A Description of Biremis panamae sp. nov., a New Diatom Species from the Marine Littoral, with an Account of the Phylogenetic Position of Biremis D.G. Mann et E.J. Cox (Bacillariophyceae)

Here we present a formal description of Biremis panamae Barka, Witkowski et Weisenborn sp. nov., which was isolated from the marine littoral environment of the Pacific Ocean coast of Panama. The description is based on morphology (light and electron microscopy) and the rbcL, psbC and SSU sequences of one clone of this species. The new species is included in Biremis due to its morphological features; i.e. two marginal rows of foramina, chambered striae, and girdle composed of numerous punctate copulae. The new species also possesses a striated valve face which is not seen in most known representatives of marine littoral Biremis species. In this study we also present the relationship of Biremis to other taxa using morphology, DNA sequence data and observations of auxosporulation. Our results based on these three sources point to an evolutionary relationship between Biremis, Neidium and Scoliopleura. The unusual silicified incunabular caps present in them are known otherwise only in Muelleria, which is probably related to the Neidiaceae and Scoliotropidaceae. We also discuss the relationship between Biremis and the recently described Labellicula and Olifantiella.

Isolation and characterization of recombinant murine Wnt3a

Wnt proteins are a family of morphogens that possess potent biological activity. Structure-function studies have been impeded by poor yield of biologically active recombinant Wnt as well as a propensity of isolated Wnt to self-associate in the absence of detergent. Using stably transfected Drosophila S2 cells, studies have been conducted to improve recovery of recombinant murine Wnt3a, establish conditions for a detergent-free Wnt preparation and examine the effects of limited proteolysis. S2 cell culture conditioned media was subjected to a 3-step protocol including dye-ligand chromatography, immobilized metal affinity chromatography and gel filtration chromatography. Through selective pooling of column fractions, homogeneous and purified Wnt3a preparations were obtained. Limited proteolysis of Wnt3a with thrombin resulted in site-specific cleavage within the N-terminal saposin-like motif. To generate detergent-free protein, Wnt3a was immobilized on Cu(2+)-charged, iminodiacetic acid-derivatized Sepharose beads, detergent-free buffer was applied and Wnt3a eluted from the beads with buffer containing imidazole plus 30mM methyl-ß-cyclodextrin (MßCD). Wnt3a recovered in MßCD-containing buffer was soluble and biologically active. Insofar as MßCD is a member of a family of non-toxic, low molecular weight compounds capable of binding and solubilizing small hydrophobic ligands, Wnt-cyclodextrin complexes may facilitate structure-activity studies in the absence of adverse detergent effects.