Widely used reagents in the peptide functionalization toolbox, Michael acceptors and N‐hydroxysuccinimide (NHS) activated esters, are combined in NHS‐activated acrylamides for efficient chemoselective amino‐sulfhydryl stapling on native peptides and proteins. NHS‐activated acrylamides allow for a fast functionalization of N‐terminal cysteines (k2=1.54±0.18×103 M−1 s−1) under dilute aqueous conditions, enabling selectivity over other nucleophilic amino acids. Additionally, the versatility of these new bioconjugation handles was demonstrated in the cross‐linking of in‐chain or C‐terminal cysteines with nearby lysine residues. NHS‐activated acrylamides are compatible with the use of other cysteine selective reagents, allowing for orthogonal dual‐modifications. This strategy was successfully applied to the late‐stage functionalization of peptides and proteins with a PEG unit, fluorescent probe, and cytotoxic agent. The level of molecular control offered by NHS‐activated acrylamides is expected to promote amino‐sulfhydryl stapling technology as a powerful strategy to design functional bioconjugates.

Multiple sclerosis (MS) is the most common autoimmune and demyelinating disease of the central nervous system (CNS), characterized, in the majority of cases, by initial relapses that later evolve into progressive neurodegeneration, severely impacting patients’ motor and cognitive functions. Despite the availability of immunomodulatory therapies effective to reduce relapse rate and slow disease progression, they all failed to restore CNS myelin that is necessary for MS full recovery. Microglia are the primary inflammatory cells present in MS lesions, therefore strongly contributing to demyelination and lesion extension. Thus, many microglial-based therapeutic strategies have been focused on the suppression of microglial pro-inflammatory phenotype and neurodegenerative state to reduce disease severity. On the other hand, the contribution of myelin phagocytosis advocating the neuroprotective role of microglia in MS has been less explored. Indeed, despite the presence of functional oligodendrocyte precursor cells (OPCs), within lesioned areas, MS plaques fail to remyelinate as a result of the over-accumulation of myelin-toxic debris that must be cleared away by microglia. Dysregulation of this process has been associated with the impaired neuronal recovery and deficient remyelination. In line with this, here we provide a comprehensive review of microglial myelin phagocytosis and its involvement in MS development and repair. Alongside, we discuss the potential of phagocytic-mediated therapeutic approaches and encourage their modulation as a novel and rational approach to ameliorate MS-associated pathology.

Boronic acid‐derived salicylidenehydrazone complex (BASHY) dyes with a polymethine backbone were designed to yield efficient red‐emitting and two‐photon absorbing fluorophores that can be used as markers for astrocytes. The dyes are chemically stable in aqueous solution and do not undergo photodecomposition. Their photophysical properties can be electronically fine‐tuned and thereby adapted to potentially different imaging situations and requirements.

No abstract

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system that is characterized by the presence of demyelinated regions with accumulated myelin lipid debris. Importantly, to allow effective remyelination, such debris must be cleared by microglia. Therefore, the study of microglial activity with sensitive tools is of great interest to better monitor the MS clinical course. Using a boronic acid-based (BASHY) fluorophore, specific for nonpolar lipid aggregates, we aimed to address BASHY’s ability to label nonpolar myelin debris and image myelin clearance in the context of demyelination. Demyelinated ex vivo organotypic cultures (OCSCs) and primary microglia cells were immunostained to evaluate BASHY’s co-localization with myelin debris and also to evaluate BASHY’s specificity for phagocytosing cells. Additionally, mice induced with experimental autoimmune encephalomyelitis (EAE) were injected with BASHY and posteriorly analyzed to evaluate BASHY+ microglia within demyelinated lesions. Indeed, in our in vitro and ex vivo studies, we showed a significant increase in BASHY labeling in demyelinated OCSCs, mostly co-localized with Iba1-expressing amoeboid/phagocytic microglia. Most importantly, BASHY’s presence was also found within demyelinated areas of EAE mice, essentially co-localizing with lesion-associated Iba1+ cells, evidencing BASHY’s potential for the in vivo bioimaging of myelin clearance and myelin-carrying microglia in regions of active demyelination.