The first examples of iminosugar-type 2-deoxy(thio)glycoside mimetics are reported. The key step is the activation of a bicyclic iminoglycal carbamate to generate a highly reactive acyliminium ...cation. Cerium(IV) ammonium nitrate efficiently promoted the formation of 2-deoxy S-glycosides in the presence of thiols, probably by in situ generation of catalytic HNO3, with complete α-stereoselectivity. Cooperative phosphoric acid/Schreiner’s thiourea organocatalysis proved better suited for generating 2-deoxy O-glycosides, significantly broadening the scope of the approach.
Retinal diseases linked to inflammation are often accompanied by macrophage/microglial cells activation. However, the dynamics between M1 (pro-inflammatory) and M2 (anti-inflammatory) polarization of ...microglia during diabetic retinopathy (DR) has not been investigated and it might be therapeutically useful. We assessed microglia polarization in retinas from db/db mice and human diabetic donors and also the microglia-mediated anti-inflammatory effects of the bicyclic nojirimycin derivative (1R)-1-dodecylsulfinyl-5N,6O-oxomethylidenenojirimycin (R-DS-ONJ). Visual function in mice was evaluated by electroretinogram (ERG). Expression of pro- and anti-inflammatory markers in the retina was analyzed by immunofluorescence, Western-blot and quantitative real-time PCR. Lipopolysaccharide (LPS)-mediated polarization profile was studied in Bv.2 microglial cells in the absence or presence of anti-inflammatory cytokines (IL4/IL13) or R-DS-ONJ. At 5weeks of age, reduced ERG amplitude values of rod and mixed waves were detected in db/db compared to db/+ mice that correlated with elevated circulating endotoxemia and pro-inflammatory cytokines. At this early stage of DR, the marker of activated microglia Iba-1 co-localized with the M2 marker arginase-1 in the retina. Conversely, in retinas from 8weeks old db/db mice Iba-1-colocalized with active caspase-1, a key component of the inflammasome, reflecting an opposite pattern of microglia polarization. Markers of activated microglia were detected in retinas of diabetic donors. Treatment of Bv.2 cells with LPS and IL4/IL13 or R-DS-ONJ switched the M1 response towards M2. In retinal explants from db/db mice, R-DS-ONJ induced a M2 response. In conclusion, the modulation of microglia polarization dynamics towards a M2 status at early stages of DR offers novel therapeutic interventions.
•Neuroinflammation precedes neurodegeneration during DR progression.•During early stages of DR microglia displays a M2 phenotype.•Microglia-M2 phenotype switches towards M1 phenotype in advances stage of DR.•Modulation of microglia polarization is a new target against neuroinflammation in DR.
Lysosomal storage disorders (LSDs) are often caused by mutations that destabilize native folding and impair the trafficking of enzymes, leading to premature endoplasmic reticulum (ER)-associated ...degradation, deficiencies of specific hydrolytic functions and aberrant storage of metabolites in the lysosomes. Enzyme replacement therapy (ERT) and substrate reduction therapy (SRT) are available for a few of these conditions, but most remain orphan. A main difficulty is that virtually all LSDs involve neurological decline and neither proteins nor the current SRT drugs can cross the blood-brain barrier. Twenty years ago a new therapeutic paradigm better suited for neuropathic LSDs was launched, namely pharmacological chaperone (PC) therapy. PCs are small molecules capable of binding to the mutant protein at the ER, inducing proper folding, restoring trafficking and increasing enzyme activity and substrate processing in the lysosome. In many LSDs the mutated protein is a glycosidase and the accumulated substrate is an oligo- or polysaccharide or a glycoconjugate, e.g. a glycosphingolipid. Although it might appear counterintuitive, substrate analogues (glycomimetics) behaving as competitive glycosidase inhibitors are good candidates to perform PC tasks. The advancements in the knowledge of the molecular basis of LSDs, including enzyme structures, binding modes, trafficking pathways and substrate processing mechanisms, have been put forward to optimize PC selectivity and efficacy. Moreover, the chemical versatility of glycomimetics and the variety of structures at hand allow simultaneous optimization of chaperone and pharmacokinetic properties. In this Feature Article we review the advancements made in this field in the last few years and the future outlook through the lessons taught by three archetypical LSDs: Gaucher disease, GM1-gangliosidosis and Fabry disease.
High T_{c} superconductors show a rich variety of phases associated with their charge degrees of freedom. Valence charges can give rise to charge ordering or acoustic plasmons in these layered ...cuprate superconductors. While charge ordering has been observed for both hole- and electron-doped cuprates, acoustic plasmons have only been found in electron-doped materials. Here, we use resonant inelastic x-ray scattering to observe the presence of acoustic plasmons in two families of hole-doped cuprate superconductors (La_{1.84}Sr_{0.16}CuO_{4} and Bi_{2}Sr_{1.6}La_{0.4}CuO_{6+δ}), crucially completing the picture. Interestingly, in contrast to the quasistatic charge ordering which manifests at both Cu and O sites, the observed acoustic plasmons are predominantly associated with the O sites, revealing a unique dichotomy in the behavior of valence charges in hole-doped cuprates.
Extreme weight conditions (EWC) groups along a continuum may share some biological risk factors and intermediate neurocognitive phenotypes. A core cognitive trait in EWC appears to be executive ...dysfunction, with a focus on decision making, response inhibition and cognitive flexibility. Differences between individuals in these areas are likely to contribute to the differences in vulnerability to EWC. The aim of the study was to investigate whether there is a common pattern of executive dysfunction in EWC while comparing anorexia nervosa patients (AN), obese subjects (OB) and healthy eating/weight controls (HC).
Thirty five AN patients, fifty two OB and one hundred thirty seven HC were compared using the Wisconsin Card Sorting Test (WCST); Stroop Color and Word Test (SCWT); and Iowa Gambling Task (IGT). All participants were female, aged between 18 and 60 years.
There was a significant difference in IGT score (F(1.79); p<.001), with AN and OB groups showing the poorest performance compared to HC. On the WCST, AN and OB made significantly more errors than controls (F(25.73); p<.001), and had significantly fewer correct responses (F(2.71); p<.001). Post hoc analysis revealed that the two clinical groups were not significantly different from each other. Finally, OB showed a significant reduced performance in the inhibition response measured with the Stroop test (F(5.11); p<.001) compared with both AN and HC.
These findings suggest that EWC subjects (namely AN and OB) have similar dysfunctional executive profile that may play a role in the development and maintenance of such disorders.
Amphiphilic glycomimetics encompassing a rigid, undistortable nortropane skeleton based on 1,6-anhydro-l-idonojirimycin and a polyfluorinated antenna, when formulated as the corresponding inclusion ...complexes with β-cyclodextrin (βCD), have been shown to behave as pharmacological chaperones (PCs) that efficiently rescue lysosomal β-glucocerebrosidase mutants associated with the neuronopathic variants of Gaucher disease (GD), including the highly refractory L444P/L444P and L444P/P415R single nucleotide polymorphs, in patient fibroblasts. The body of work here presented includes the design criteria for the PC prototype, the synthesis of a series of candidates, the characterization of the PC:βCD complexes, the determination of the selectivity profiles toward a panel of commercial and human lysosomal glycosidases, the evaluation of the chaperoning activity in type 1 (non-neuronopathic), type 2 (acute neuronopathic), and type 3 (adult neuronopathic) GD fibroblasts, the confirmation of the rescuing mechanism by immunolabeling, and the analysis of the PC:GCase binding mode by docking experiments.
Antimicrobial fibers based on biodegradable polymers, poly(lactic acid) (PLA), and poly(butylene adipate‐co‐terephthalate) (PBAT) are prepared by electrospinning. For this purpose, a ...biodegradable/bio‐based polyitaconate containing azoles groups (PTTI) is incorporated at 10 wt.% into the electrospinning formulations. The resulting fibers functionalized with azole moieties are uniform and free of beads. Then, the accessible azole groups are subjected to N‐alkylation, treatment that provides cationic azolium groups with antibacterial activity at the surface of fibers. The positive charge density, roughness, and wettability of the cationic fibers are evaluated and compared with flat films. It is confirmed that these parameters exert an important effect on the antimicrobial properties, as well as the length of the alkylating agent and the hydrophobicity of the matrix. The quaternized PLA/PTTI fibers exhibit the highest efficiency against the tested bacteria, yielding a 4‐Log reduction against S. aureus and 1.7‐Log against MRSA. Then, biocompatibility and bioactivity of the fibers are evaluated in terms of adhesion, morphology and viability of fibroblasts. The results show no cytotoxic effect of the samples, however, a cytostatic effect is appreciated, which is ascribed to the strong electrostatic interactions between the positive charge at the fiber surface and the negative charge of the cell membranes.
Bio‐based and biodegradable fiber mats based on PLA and PBAT with antibacterial activity are prepared by incorporating a polyitaconate derivative with cationic azolium groups into the electrospinning process. The obtained fibers exhibit high antibacterial efficiency against Gram‐positive bacteria, non‐cytotoxicity, and cytostatic effect on human fibroblast cells.
The vision of multivalency as a strategy limited to achieve affinity enhancements between a protein receptor and its putative sugar ligand (glycotope) has proven too simplistic. On the one hand, ...binding of a glycotope in a dense glycocalix‐like construct to a lectin partner has been shown to be sensitive to the presence of a third sugar entity (heterocluster effect). On the other hand, several carbohydrate processing enzymes (glycosidases and glycosyltransferases) have been found to be also responsive to multivalent presentations of binding partners (multivalent enzyme inhibition), a phenomenon first discovered for iminosugar‐type inhibitory species (inhitopes) and recently demonstrated for multivalent carbohydrate constructs. By assessing a series of homo‐ and heteroclusters combining α‐d‐glucopyranosyl‐related glycotopes and inhitopes, it was shown that multivalency and heteromultivalency govern both kinds of events, allowing for activation, deactivation or enhancement of specific recognition phenomena towards a spectrum of lectin and glycosidase partners in a multimodal manner. This unified scenario originates from the ability of (hetero)multivalent architectures to trigger glycosidase binding modes that are reminiscent of those harnessed by lectins, which should be considered when profiling the biological activity of multivalent architectures.
Different selectivity patterns towards enzymes and lectins can be elicited by (hetero)multivalent displays of sugar and glycomimetic motifs. The binding modes at play reveal analogies between the (hetero)cluster effect and (hetero)multivalent enzyme inhibition that underline the need of a reformulation of the multivalent effect.
Background and Objective: Focused Ion Beam - Scanning Electron Microscopy (FIB-SEM) allows three-dimensional ultrastructural analysis of cells and tissues at the nanoscale. The technique iteratively ...removes a section of the sample with a FIB and takes an SEM image from the exposed surface. The section thickness is usually higher than the image pixel size to reduce acquisition time, thus resulting in anisotropic resolution. In this work, we explore novel interpolation methods along the sectioning direction to produce isotropic resolution and facilitate proper interpretation of the FIB-SEM 3D volumes.
Methods: Classical interpolation methods are usually applied in this context under the assumption that the changes through successive images are relatively smooth. However, the actual 3D arrangement of the structures in the sample may cause significant changes in the biological features between consecutive images of the FIB-SEM stacks. We have developed a novel interpolation strategy that accounts for this variation by using the Optical Flow (OF) to estimate it. As an intermediate stage, OF-compensated images are produced by aligning the spatial regions of the biological structures. Interpolated images are then generated from these OF-compensated images. The final isotropic stack is assembled by interleaving the interpolated images with the original images of the anisotropic stack.
Results: OF-driven and classical interpolation methods were compared using an objective assessment based on Pearson Correlation Coefficient (PCC) and a qualitative evaluation based on visual results, using public datasets and representative anisotropy conditions. The objective assessment demonstrated that the OF-driven interpolation always yields higher PCC values, with interpolated images closer to the ground truth. The qualitative evaluation corroborated those results and confirmed that classical interpolation may blur areas with substantial changes between consecutive images whereas OF-driven interpolation provides sharpness.
Conclusions: We have developed an OF-driven interpolation approach to generating FIB-SEM stacks with isotropic resolution from experimental anisotropic data. It adapts to the rapid variation of the biological structures observed through the images of the FIB-SEM stack. Our approach outperforms classical interpolation and manages to produce sharp interpolated views in cases where there are significant changes between consecutive experimental images.
It has been amply constated that sugar ligand multivalency increases lectin-binding avidities dramatically, thereby modulating the capacity of carbohydrates to participate in supramolecular ...recognition processes involving transfer of biological information. The importance of this concept, the multivalent or glycoside cluster effect, in cell biology in general and in the glycosciences in particular is reflected in the ever-growing number of papers in the field. An impressive range of glycoarchitectures has been conceived to imitate the glycan coating of cells (the glycocalyx) in order to target complementary lectin receptors. However, these models rarely address the heterogeneity and the fluidity of the densely glycosylated cell membrane. They also disregard the impact that high-density nanosized arrangements could have in their interactions with the whole spectrum of carbohydrate-interacting proteins, among which glycosidases are notable representatives. For many years it has been tacitly assumed that: (i) efficient recognition by lectins generally requires high densities of the putative primary ligand and (ii) the mechanisms governing binding of a carbohydrate motif by a lectin or a glycosidase are totally disparate. Notwithstanding, an increasing amount of evidence seriously questions this paradigm. First, it was shown that secondary "innocent" ligands can play important roles in the recognition of heteroglycocluster constructs by lectins through synergistic or antagonistic contributions, a phenomenon termed the heterocluster effect. Second, the existence of multivalent effects in the inhibition of certain glycosidases by glycomimetic- and, even more disturbing, glyco-coated architectures (multivalent enzyme inhibition) was demonstrated. These observations call for a generalized multivalent effect governing the supramolecular chemistry of carbohydrate or glycomimetic structures in a biological context, with (hetero)multivalency acting as a multimodal switcher to drive the encoded information through different pathways. In this Feature Article we review the advancements made in the last few years in our understanding of the mechanisms underpinning the generalized multivalent effect, with an emphasis on the potential risks and opportunities derived from (hetero)multivalency-elicited promiscuity.
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