Macrophage-mediated myelin recycling fuels brain cancer malignancy.

Tumors growing in metabolically challenged environments, such as glioblastoma in the brain, are particularly reliant on crosstalk with their tumor microenvironment (TME) to satisfy their high energetic needs. To study the intricacies of this metabolic interplay, we interrogated the heterogeneity of the glioblastoma TME using single-cell and multi-omics analyses and identified metabolically rewired tumor-associated macrophage (TAM) subpopulations with pro-tumorigenic properties. These TAM subsets, termed lipid-laden macrophages (LLMs) to reflect their cholesterol accumulation, are epigenetically rewired, display immunosuppressive features, and are enriched in the aggressive mesenchymal glioblastoma subtype. Engulfment of cholesterol-rich myelin debris endows subsets of TAMs to acquire an LLM phenotype. Subsequently, LLMs directly transfer myelin-derived lipids to cancer cells in an LXR/Abca1-dependent manner, thereby fueling the heightened metabolic demands of mesenchymal glioblastoma. Our work provides an in-depth understanding of the immune-metabolic interplay during glioblastoma progression, thereby laying a framework to unveil targetable metabolic vulnerabilities in glioblastoma.

PD-1 Inhibitory Receptor Downregulates Asparaginyl Endopeptidase and Maintains Foxp3 Transcription Factor Stability in Induced Regulatory T Cells.

CD4+ T cell differentiation into multiple T helper (Th) cell lineages is critical for optimal adaptive immune responses. This report identifies an intrinsic mechanism by which programmed death-1 receptor (PD-1) signaling imparted regulatory phenotype to Foxp3+ Th1 cells (denoted as Tbet+iTregPDL1 cells) and inducible regulatory T (iTreg) cells. Tbet+iTregPDL1 cells prevented inflammation in murine models of experimental colitis and experimental graft versus host disease (GvHD). Programmed death ligand-1 (PDL-1) binding to PD-1 imparted regulatory function to Tbet+iTregPDL1 cells and iTreg cells by specifically downregulating endo-lysosomal protease asparaginyl endopeptidase (AEP). AEP regulated Foxp3 stability and blocking AEP imparted regulatory function in Tbet+iTreg cells. Also, Aep-/- iTreg cells significantly inhibited GvHD and maintained Foxp3 expression. PD-1-mediated Foxp3 maintenance in Tbet+ Th1 cells occurred both in tumor infiltrating lymphocytes (TILs) and during chronic viral infection. Collectively, this report has identified an intrinsic function for PD-1 in maintaining Foxp3 through proteolytic pathway.

Systemic sclerosis-associated pulmonary arterial hypertension is characterized by a distinct peripheral T helper cell profile.

OBJECTIVES: Systemic sclerosis (SSc) is characterized by multiple clinical manifestations. Vasculopathy is a main disease hallmark and ranges in severity from an exacerbated Raynaud phenomenon to pulmonary arterial hypertension (PAH). The potential involvement of immune system in SSc associated vascular abnormalities is not clear. Here, we set out to study SSc-related immune parameters and determine whether and which peripheral T cell subsets associate with vascular severity in SSc patients. METHODS: Peripheral blood and clinical data were collected from 30 SSc patients, 5 patients with idiopathic pulmonary arterial hypertension (IPAH) and 15 age and sex-matched healthy donors (HD). In this cross-sectional cohort SSc patients with PAH (n = 15) were matched for their age, sex and medication with SSc patients with no signs of PAH (n = 15). Lymphocyte subsets were quantified by multi-colour flow cytometry. RESULTS: SSc patients exhibited elevated percentages of T peripheral helper cells (Tph), CD4+GZMB+ T cells and decreased levels of Th1 cells compared with HD. Increased presence of both CD4+ and CD8+ exhausted-like (CD28-) T cells, characterized by raised cytokine and cytotoxic signature, was also observed in SSc compared with HD blood. Furthermore, IL-4 expressing CD4+CD8+ T cells were significantly increased in SSc peripheral blood. Interestingly, the presence of PAH in SSc was accompanied by a distinct T helper profile, characterized by raised percentages of Th17 and Tph cells. CONCLUSION: SSc patients with severe vasculopathy (presence of PAH) exhibited a distinct T cell profile, suggesting for a potential role of auto-immune inflammation in SSc vascular complications.

A Bioorthogonal Dual Fluorogenic Probe for the Live-Cell Monitoring of Nutrient Uptake by Mammalian Cells.

Cells rely heavily on the uptake of exogenous nutrients for survival, growth, and differentiation. Yet quantifying the uptake of small molecule nutrients at the single cell level is difficult. Here we present a new approach to studying the nutrient uptake in live single cells using Inverse Electron-Demand Diels Alder (IEDDA) chemistry. We have modified carboxyfluorescein-diacetate-succinimidyl esters (CFSE)-a quenched fluorophore that can covalently react with proteins and is only turned on in the cytosol of a cell following esterase activity-with a tetrazine. This tetrazine serves as a second quencher for the pendant fluorophore. Upon reaction with nutrients modified with an electron-rich or strained dienophile in an IEDDA reaction, this quenching group is destroyed, thereby enabling the probe to fluoresce. This has allowed us to monitor the uptake of a variety of dienophile-containing nutrients in live primary immune cell populations using flow cytometry and live-cell microscopy.

A Lysosome-Targeted Tetrazine for Organelle-Specific Click-to-Release Chemistry in Antigen Presenting Cells.

Bioorthogonal deprotections are readily used to control biological function in a cell-specific manner. To further improve the spatial resolution of these reactions, we here present a lysosome-targeted tetrazine for an organelle-specific deprotection reaction. We show that trans-cyclooctene deprotection with this reagent can be used to control the biological activity of ligands for invariant natural killer T cells in the lysosome to shed light on the processing pathway in antigen presenting cells. We then use the lysosome-targeted tetrazine to show that long peptide antigens used for CD8+ T cell activation do not pass through this organelle, suggesting a role for the earlier endosomal compartments for their processing.

Bioorthogonal Peptide Enrichment from Complex Samples Using a Rink-Amide-Based Catch-and-Release Strategy.

Uptake and processing of antigens by antigen presenting cells (APCs) is a key step in the initiation of the adaptive immune response. Studying these processes is complex as the identification of low abundant exogenous antigens from complex cell extracts is difficult. Mass-spectrometry based proteomics - the ideal analysis tool in this case - requires methods to retrieve such molecules with high efficiency and low background. Here, we present a method for the selective and sensitive enrichment of antigenic peptides from APCs using click-antigens; antigenic proteins expressed with azidohomoalanine (Aha) in place of methionine residues. We here describe the capture of such antigens using a new covalent method namely, alkynyl functionalized PEG-based Rink amide resin, that enables capture of click-antigens via copper-catalyzed azide-alkyne [2 + 3] cycloaddition (CuAAC). The covalent nature of the thus formed linkage allows stringent washing to remove a-specific background material, prior to retrieval peptides by acid-mediated release. We successfully identified peptides from a tryptic digest of the full APC proteome containing femtomole amounts of Aha-labelled antigen, making this a promising approach for clean and selective enrichment of rare bioorthogonally modified peptides from complex mixtures.

Evaluation of left cardiac chamber function with cardiac magnetic resonance and association with outcome in patients with systemic sclerosis.

OBJECTIVE: This study aimed to determine whether lower values of feature-tracking cardiovascular magnetic resonance (CMR)-derived left atrial reservoir strain (LARS) and impaired left ventricular (LV) global longitudinal strain (GLS) were associated with the presence of symptoms and long-term prognosis in patients with SSc. METHODS: A total of 100 patients {54 [interquartile range (IQR) 46-64] years, 42% male} with SSc who underwent CMR imaging at two tertiary referral centres were included. All patients underwent analysis of LARS and LV GLS using feature-tracking on CMR and were followed-up for the occurrence of all-cause mortality. RESULTS: The median LV GLS was -21.8% and the median LARS was 36%. On multivariable logistic regression, LARS [odds ratio (OR) 0.964 per %, 95% CI 0.929, 0.998, P = 0.049] was independently associated with New York Heart Association (NYHA) class II-IV heart failure symptoms. Over a median follow-up of 37 (21-62) months, a total of 24 (24%) patients died. Univariable Cox regression analysis demonstrated that LARS [hazard ratio (HR) 0.94 per 1%, 95% CI 0.91, 0.97, P < 0.0001) and LV GLS (HR 1.10 per %, 95% CI 1.03, 1.17, P = 0.005) were associated with all-cause mortality, while LV ejection fraction was not. Likelihood ratio tests demonstrated that LARS provided incremental value over prognostically important clinical and imaging parameters, including late gadolinium enhancement. CONCLUSION: In patients with SSc, LARS was independently associated with the presence of NYHA class II-IV heart failure symptoms. Although both LARS and LV GLS were associated with all-cause mortality, only LARS provided incremental value over all evaluated variables known to be prognostically important in patients with SSc.

Single-molecule imaging of glycan-lectin interactions on cells with Glyco-PAINT.

Most lectins bind carbohydrate ligands with relatively low affinity, making the identification of optimal ligands challenging. Here we introduce a point accumulation in nanoscale topography (PAINT) super-resolution microscopy method to capture weak glycan-lectin interactions at the single-molecule level in living cells (Glyco-PAINT). Glyco-PAINT exploits weak and reversible sugar binding to directly achieve single-molecule detection and quantification in cells and is used to establish the relative kon and koff rates of a synthesized library of carbohydrate-based probes, as well as the diffusion coefficient of the receptor-sugar complex. Uptake of ligands correlates with their binding affinity and residence time to establish structure-function relations for various synthetic glycans. We reveal how sugar multivalency and presentation geometry can be optimized for binding and internalization. Overall, Glyco-PAINT represents a powerful approach to study weak glycan-lectin interactions on the surface of living cells, one that can be potentially extended to a variety of lectin-sugar interactions.

Single-cell analysis of regions of interest (SCARI) using a photosensitive tag.

The functional activity and differentiation potential of cells are determined by their interactions with surrounding cells. Approaches that allow unbiased characterization of cell states while at the same time providing spatial information are of major value to assess this environmental influence. However, most current techniques are hampered by a tradeoff between spatial resolution and cell profiling depth. Here, we develop a photocage-based technology that allows isolation and in-depth analysis of live cells from regions of interest in complex ex vivo systems, including primary human tissues. The use of a highly sensitive 4-nitrophenyl(benzofuran) cage coupled to a set of nanobodies allows high-resolution photo-uncaging of different cell types in areas of interest. Single-cell RNA-sequencing of spatially defined CD8+ T cells is used to exemplify the feasibility of identifying location-dependent cell states. The technology described here provides a valuable tool for the analysis of spatially defined cells in diverse biological systems, including clinical samples.

Synthesis of glycopeptides and glycopeptide conjugates.

Protein glycosylation is a key post-translational modification important to many facets of biology. Glycosylation can have critical effects on protein conformation, uptake and intracellular routing. In immunology, glycosylation of antigens has been shown to play a role in self/non-self distinction and the effective uptake of antigens. Improperly glycosylated proteins and peptide fragments, for instance those produced by cancerous cells, are also prime candidates for vaccine design. To study these processes, access to peptides bearing well-defined glycans is of critical importance. In this review, the key approaches towards synthetic, well-defined glycopeptides, are described, with a focus on peptides useful for and used in immunological studies. Special attention is given to the glycoconjugation approaches that have been developed in recent years, as these enable rapid synthesis of various (unnatural) glycopeptides, enabling powerful carbohydrate structure/activity studies. These techniques, combined with more traditional total synthesis and chemoenzymatic methods for the production of glycopeptides, should help unravel some of the complexities of glycobiology in the near future.

A Prediction Model for Falls in Community-Dwelling Older Adults in Podiatry Practices.

INTRODUCTION: Falls are a worldwide health problem among community-dwelling older adults. Emerging evidence suggests that foot problems increase the risk of falling, so the podiatrist may be crucial in detecting foot-related fall risk. However, there is no screening tool available which can be used in podiatry practice. The predictive value of existing tools is limited, and the implementation is poor. The development of risk models for specific clinical populations might increase the prediction accuracy and implementation. Therefore, the aim of this study was to develop and internally validate an easily applicable clinical prediction model (CPM) that can be used in podiatry practice to predict falls in community-dwelling older adults with foot (-related) problems. METHODS: This was a prospective study including community-dwelling older adults (≥65 years) visiting podiatry practices. General fall-risk variables, and foot-related and function-related variables were considered as predictors for the occurrence of falls during the 12-month follow-up. Logistic regression analysis was used for model building, and internal validation was done by bootstrap resampling. RESULTS: 407 participants were analyzed; the event rate was 33.4%. The final model included fall history in the previous year, unsteady while standing and walking, plantarflexor strength of the lesser toes, and gait speed. The area under the receiver operating characteristic curve was 0.71 (95% CI: 0.66-0.76) in the sample and estimated as 0.65 after shrinkage. CONCLUSION: A CPM based on fall history in the previous year, feeling unsteady while standing and walking, decreased plantarflexor strength of the lesser toes, and reduced gait speed has acceptable accuracy to predict falls in our sample of podiatry community-dwelling older adults and is easily applicable in this setting. The accuracy of the model in clinical practice should be demonstrated through external validation of the model in a next study.

Decision-making regarding oral nutritional supplements for nursing home residents with advanced dementia: A cross-sectional pilot study.

BACKGROUND: Surrogate decision-making regarding oral nutritional supplements (ONS) for nursing home residents with advanced dementia is a complex process. In this cross-sectional study, we assessed whether Dutch dietitians, elderly care physicians (physicians) and surrogate decision-makers (SDMs) differ in the factors that they regard important when considering ONS. We also investigated differences in opinion regarding whether or not ONS is a life-prolonging measure. METHODS: Through an online survey, 90 dietitians, 53 physicians and 70 SDMs of nursing home residents (all aged ≥ 65 years old with advanced dementia) rated the level of perceived influence of 11 pre-defined factors on their decision-making, ranked factors in order of importance and stated whether they considered ONS a life-prolonging measure or not. By statistical analysis, we tested differences in the mean sum of ranks for perceived influence differing between groups. We also tested differences in proportions between groups of those who considered ONS a life-prolonging measure. RESULTS: Rating of perceived influence significantly differed for six factors. Quality of life was ranked as the most influential factor by all groups. Dietitians significantly differed in their opinion on the life-prolonging effect of ONS from physicians (odds ratio = 0.29, 95% confidence interval = 0.13-0.65), as well as from SDMs (odds ratio = 0.22, 95% confidence interval = 0.10-0.45). CONCLUSIONS: Although all groups proclaimed quality of life to be first priority in decision-making, we found that Dutch dietitians, physicians and SDMs differed in what they regarded important when considering ONS for nursing home residents with advanced dementia. Regarding the life-prolonging effect of ONS, dietitians differed in opinion from physicians, as well as from SDMs.

Live-Cell Imaging of Sterculic Acid-a Naturally Occurring 1,2-Cyclopropene Fatty Acid-by Bioorthogonal Reaction with Turn-On Tetrazine-Fluorophore Conjugates.

In the field of lipid research, bioorthogonal chemistry has made the study of lipid uptake and processing in living systems possible, whilst minimising biological properties arising from detectable pendant groups. To allow the study of unsaturated free fatty acids in live cells, we here report the use of sterculic acid, a 1,2-cyclopropene-containing oleic acid analogue, as a bioorthogonal probe. We show that this lipid can be readily taken up by dendritic cells without toxic side effects, and that it can subsequently be visualised using an inverse electron-demand Diels-Alder reaction with quenched tetrazine-fluorophore conjugates. In addition, the lipid can be used to identify changes in protein oleoylation after immune cell activation. Finally, this reaction can be integrated into a multiplexed bioorthogonal reaction workflow by combining it with two sequential copper-catalysed Huisgen ligation reactions. This allows for the study of multiple biomolecules in the cell simultaneously by multimodal confocal imaging.

Localization of active endogenous and exogenous ß-glucocerebrosidase by correlative light-electron microscopy in human fibroblasts.

ß-Glucocerebrosidase (GBA) is the enzyme that degrades glucosylceramide in lysosomes. Defects in GBA that result in overall loss of enzymatic activity give rise to the lysosomal storage disorder Gaucher disease, which is characterized by the accumulation of glucosylceramide in tissue macrophages. Gaucher disease is currently treated by infusion of mannose receptor-targeted recombinant GBA. The recombinant GBA is thought to reach the lysosomes of macrophages, based on the impressive clinical response that is observed in Gaucher patients (type 1) receiving this enzyme replacement therapy. In this study, we used cyclophellitol-derived activity-based probes (ABPs) with a fluorescent reporter that irreversibly bind to the catalytic pocket of GBA, to visualize the active enzymes in a correlative microscopy approach. The uptake of pre-labeled recombinant enzyme was monitored by fluorescence and electron microscopy in human fibroblasts that stably expressed the mannose receptor. The endogenous active enzyme was simultaneously visualized by in situ labeling with the ABP containing an orthogonal fluorophore. This method revealed the efficient delivery of recombinant GBA to lysosomal target compartments that contained endogenous active enzyme.

Feasibility of online home spirometry in systemic sclerosis-associated interstitial lung disease: a pilot study.

OBJECTIVES: Frequent monitoring of forced vital capacity at home may be of added value in patients with SSc-associated interstitial lung disease (SSc-ILD) to monitor disease progression and guide treatment decisions. The aim of this study was to evaluate the feasibility and optimal frequency of online home spirometry using a home monitoring application in patients with SSc-ILD. METHODS: This was a prospective, observational study in patients with SSc-ILD. Patients evaluated for 3 months the online home monitoring application ILD-online integrated with a Bluetooth-connected spirometer. Patients performed daily home spirometry for 6 weeks and weekly home spirometry for 6 weeks. In addition, patients completed an evaluation questionnaire after 3 months and online patient-reported outcomes at baseline and 3 months. RESULTS: Ten consecutive patients participated. Mean adherence to home spirometry was 98.8% (s.d. 1.5). Home and hospital spirometry were highly correlated. The mean coefficient of variation was lower for weekly [2.45% (s.d. 1.19)] than daily [3.86% (s.d. 1.45)] forced vital capacity measurements (P = 0.005). All patients considered the home monitoring application and spirometer easy to use and no patients considered home spirometry burdensome. All patients would recommend home monitoring to other patients with SSc. CONCLUSIONS: Home spirometry using an online home monitoring application is feasible in patients with SSc-ILD, with high adherence and patient satisfaction. Larger long-term studies are needed to assess whether home spirometry can detect the progression of ILD in patients with SSc.

Synthesis of Asparagine Derivatives Harboring a Lewis X Type DC-SIGN Ligand and Evaluation of their Impact on Immunomodulation in Multiple Sclerosis.

The protein myelin oligodendrocyte glycoprotein (MOG) is a key component of myelin and an autoantigen in the disease multiple sclerosis (MS). Post-translational N-glycosylation of Asn31 of MOG seems to play a key role in modulating the immune response towards myelin. This is mediated by the interaction of Lewis-type glycan structures in the N-glycan of MOG with the DC-SIGN receptor on dendritic cells (DCs). Here, we report the synthesis of an unnatural Lewis X (LeX )-containing Fmoc-SPPS-compatible asparagine building block (SPPS=solid-phase peptide synthesis), as well as asparagine building blocks containing two LeX -derived oligosaccharides: LacNAc and Fucα1-3GlcNAc. These building blocks were used for the glycosylation of the immunodominant portion of MOG (MOG31-55 ) and analyzed with respect to their ability to bind to DC-SIGN in different biological setups, as well as their ability to inhibit the citrullination-induced aggregation of MOG31-55 . Finally, a cytokine secretion assay was carried out on human monocyte-derived DCs, which showed the ability of the neoglycopeptide decorated with a single LeX to alter the balance of pro- and anti-inflammatory cytokines, inducing a tolerogenic response.

Metabolic labeling probes for interrogation of the host-pathogen interaction.

Bacterial infections are still one of the leading causes of death worldwide; despite the near-ubiquitous availability of antibiotics. With antibiotic resistance on the rise, there is an urgent need for novel classes of antibiotic drugs. One particularly troublesome class of bacteria are those that have evolved highly efficacious mechanisms for surviving inside the host. These contribute to their virulence by immune evasion, and make them harder to treat with antibiotics due to their residence inside intracellular membrane-limited compartments. This has sparked the development of new chemical reporter molecules and bioorthogonal probes that can be metabolically incorporated into bacteria to provide insights into their activity status. In this review, we provide an overview of several classes of metabolic labeling probes capable of targeting either the peptidoglycan cell wall, the mycomembrane of mycobacteria and corynebacteria, or specific bacterial proteins. In addition, we highlight several important insights that have been made using these metabolic labeling probes.

Immunoproteasome Inhibitor-Doxorubicin Conjugates Target Multiple Myeloma Cells and Release Doxorubicin upon Low-Dose Photon Irradiation.

Proteasome inhibitors are established therapeutic agents for the treatment of hematological cancers, as are anthracyclines such as doxorubicin. We here present a new drug targeting approach that combines both drug classes into a single molecule. Doxorubicin was conjugated to an immunoproteasome-selective inhibitor via light-cleavable linkers, yielding peptide epoxyketone-doxorubicin prodrugs that remained selective and active toward immunoproteasomes. Upon cellular uptake and immunoproteasome inhibition, doxorubicin is released from the immunoproteasome inhibitor through photoirradiation. Multiple myeloma cells in this way take a double hit: immunoproteasome inhibition and doxorubicin-induced toxicity. Our strategy, which entails targeting of a cytotoxic agent, through a covalent enzyme inhibitor that is detrimental to tumor tissue in its own right, may find use in the search for improved anticancer drugs.

Olaparib-Based Photoaffinity Probes for PARP-1 Detection in Living Cells.

The poly-ADP-ribose polymerase (PARP) is a protein from the family of ADP-ribosyltransferases that catalyzes polyadenosine diphosphate ribose (ADPR) formation in order to attract the DNA repair machinery to sites of DNA damage. The inhibition of PARP activity by olaparib can cause cell death, which is of clinical relevance in some tumor types. This demonstrates that quantification of PARP activity in the context of living cells is of great importance. In this work, we present the design, synthesis and biological evaluation of photo-activatable affinity probes inspired by the olaparib molecule that are equipped with a diazirine for covalent attachment upon activation by UV light and a ligation handle for the addition of a reporter group of choice. SDS-PAGE, western blotting and label-free LC-MS/MS quantification analysis show that the probes target the PARP-1 protein and are selectively outcompeted by olaparib; this suggests that they bind in the same enzymatic pocket. Proteomics data are available via ProteomeXchange with identifier PXD018661.

Conditionally Controlling Human TLR2 Activity via Trans-Cyclooctene Caged Ligands.

Toll-like receptors (TLRs) are key pathogen sensors of the immune system. Their activation results in the production of cytokines, chemokines, and costimulatory molecules that are crucial for innate and adaptive immune responses. In recent years, specific (sub)-cellular location and timing of TLR activation have emerged as parameters for defining the signaling outcome and magnitude. To study the subtlety of this signaling, we here report a new molecular tool to control the activation of TLR2 via "click-to-release"-chemistry. We conjugated a bioorthogonal trans-cyclooctene (TCO) protecting group via solid support to a critical position within a synthetic TLR2/6 ligand to render the compound unable to initiate signaling. The TCO-group could then be conditionally removed upon addition of a tetrazine, resulting in restored agonist activity and TLR2 activation. This approach was validated on RAW264.7 macrophages and various murine primary immune cells as well as human cell line systems, demonstrating that TCO-caging constitutes a versatile approach for generating chemically controllable TLR2 agonists.