Biology subjects

Nicholas, R.

Publications and source records attributed to Nicholas, R..

7 recordsLinked to original sources

bioRxiv2026

Age-related loss of brain demyelinating and remyelinating potential is overcome by microglia renewal

Multiple sclerosis (MS) is an immune-mediated demyelinating disease, with progressive neurodegeneration that is refractory to current therapies. Here, we identify microglia aging as a major factor responsible for age-related loss of beneficial demyelinating and remyelinating brain functions. Brain transcriptomics and in situ spatial gene transcription analysis revealed significant oligodendrocyte loss in both young and aged mice during cuprizone-induced experimental demyelination, but impaired microglial activation in aged mice. Age-related defects in microglial activation were associated with reduced clearance of dead myelin and accumulation of lipid droplets, and impaired remyelination, implying exhaustion of microglial function in the aged mouse brain. Transcriptomic analysis of human brain samples from MS donors with matched disease course and severity and with chronic active and inactive lesions, validated that microglial activation is strongly reduced with increasing age. To investigate microglial responses after repeated demyelinating insults and their direct impact on myelin integrity, we established an experimental model of repeated demyelinating episodes in young and aged mice to recapitulate MS features. Notably, aged mice developed a progressive neuroinflammatory response following sequential demyelinating episodes, in contrast to the alternating cycles of demyelination and remyelination reminiscent of relapsing-remitting MS that were observed in young mice. Microglia depletion and repopulation using a CSF1R antagonist recovered demyelination-remyelination capacity in aged mice. The results indicate that microglia aging is a major determinant in the pathogenesis of progressive MS, and that microglia replacement represents a promising therapeutic approach.

immunology↗

bioRxiv2024

Sphingosine-1-phosphate signaling inhibition suppresses Th1-like Treg generation by reversing mitochondrial uncoupling

Inflammatory environments induce the generation of dysfunctional IFN{gamma}+T-bet+FOXP3+ Th1-like Tregs, which show defective function and are found in autoimmune conditions including multiple sclerosis (MS). The pathways that control the generation of Th1-like Tregs are not well understood. Sphingosine-1-phosphate (S1P) signaling molecules are upregulated in Th1-like Tregs, and in vivo S1P inhibition with Fingolimod (FTY720) inhibits the expression of genes responsible for Treg plasticity in MS patients. However, the underlying mechanisms are unknown. Here we show that S1P signaling inhibition by FTY720 inhibits the generation of Th1-like Tregs and rescues their suppressive function. These effects are mediated by a decrease in mTORC1 signaling and reversal of the mitochondrial uncoupling that Tregs undergo during their reprogramming into Th1-like Tregs in vitro. Finally, these results are validated in in vivo generated Th1-like Tregs, as the Tregs from MS patients treated with FTY720 display decreased Th1-like Treg frequency, increased suppressive function, and mitochondrial metabolism rebalance. These results highlight the involvement of mitochondrial uncoupling in Treg reprogramming and identify S1P signaling inhibition as a target to suppress the generation of dysfunctional Th1-like Tregs.

immunology↗

bioRxiv2023

Self-Assembly of a Repeatable DNA Nanohinge System Supporting Higher Order Structure Formation

DNA base pairs can both encode biological information and be used as a programmable material to build nanostructures with potential application in nanofabrication, data processing and storage, biosensing and drug delivery. Over several decades development of these DNA origami nanostructures has led to increasingly advanced self-assembling nanostructures and molecular machines actuated by various mechanisms such as toehold-mediated strand displacement (TMSD), magnetism and even light. However, scalability remains challenging as using larger scaffold strands can increase the likelihood of kinetic traps and misfolded conformations. Here we describe a repeatable DNA nanohinge system to increase the scalability of existing nanohinge designs for hierarchical assembly of more complex structures with greater degrees of mobility and functionality. The components of this system, comprising two distinct nanohinges, were designed in caDNAno. Structure conformation and stability were simulated using CanDo and MrDNA, and hinge assembly was validated by TEM. Electron micrographs revealed hinge-shaped nanostructures capable of self-assembly into more complex structures, as well as actuation using TMSD through a reversible locking mechanism incorporated into the design. Our work expands the existing utility of DNA nanohinges as building blocks for scalable DNA nanostructures and demonstrates the feasibility of polymerizing hinges in a novel manner for higher order assembly. The enhanced functionality of our dual hinge systems can be employed in future applications requiring greater control and mobility of DNA nanostructures.

bioengineering↗

bioRxiv2023

Long-range repression by ecdysone receptor on complex enhancers of the insulin receptor gene.

The insulin signaling pathway is evolutionarily conserved throughout metazoans, playing key roles in development, growth, and metabolism. Misregulation of this pathway is associated with a multitude of disease states including diabetes, cancer, and neurodegeneration. Genome-wide association studies indicate that natural variants in putative intronic regulatory elements of the human insulin receptor gene (INSR) are associated with metabolic conditions, however, this genes transcriptional regulation remains incompletely studied. INSR is widely expressed throughout development and was previously described as a housekeeping gene. Yet, there is abundant evidence that this gene is expressed in a cell-type specific manner, with dynamic regulation in response to environmental signals. The Drosophila insulin-like receptor gene (InR) is homologous to the human INSR gene and was previously shown to be regulated by multiple transcriptional elements located primarily within the introns of the gene. These elements were roughly defined in [~]1.5 kbp segments, but we lack an understanding of the potential detailed mechanisms of their regulation, as well as the integrative output of the battery of enhancers in the entire locus. Using luciferase assays, we characterized the substructure of these cis-regulatory elements in Drosophila S2 cells, focusing on regulation through the ecdysone receptor (EcR) and the dFOXO transcription factor. The direct action of EcR on Enhancer 2 reveals a bimodal form of regulation, with active repression in the absence of the ligand, and positive activation in the presence of 20E. By identifying the location of activators of this enhancer, we characterized a long-range of repression acting over at least 475 bp, similar to the action of long-range repressors found in the embryo. dFOXO and 20E have contrasting effects on some of the individual regulatory elements, and for the adjacent enhancers 2 and 3, their influence was/was not found to be additive, indicating that enhancer action on this locus can/cannot be characterized in part by additive models. Other characterized enhancers from within this locus exhibited "distributed" or "localized" modes of action, suggesting that predicting the joint functional output of multiple regulatory regions will require a deeper experimental characterization. The noncoding intronic regions of InR have demonstrated dynamic regulation of expression and cell type specificity. This complex transcriptional circuitry goes beyond the simple conception of a housekeeping gene. Further studies are aimed at identifying how these elements work together in vivo to generate finely tuned expression in tissue- and temporal-specific manners, to provide a guide to understanding the impact of natural variation in this genes regulation, applicable to human genetic studies.

molecular biology↗

bioRxiv2022

Commensal Neisseria species share immune suppressive mechanisms with Neisseria gonorrhoeae

Neisseria gonorrhoeae is a highly adapted human sexually transmitted pathogen that can cause symptomatic infections associated with localized inflammation as well as asymptomatic and subclinical infections, particularly in females. Gonococcal infection in humans does not generate an effective immune response in most cases, which contributes to both transmission of the pathogen and reinfection after treatment. Neisseria gonorrhoeae is known to evade and suppress human immune responses through a variety of mechanisms. Commensal Neisseria species that are closely related to N. gonorrhoeae, such as N. cinerea, N. lactamica, N. elongata, and N. mucosa, rarely cause disease and instead asymptomatically colonize mucosal sites for prolonged periods of time without evoking clearing immunologic responses. We have shown previously that N. gonorrhoeae inhibits the capacity of antigen-pulsed dendritic cells to induce CD4+ T cell proliferation in vitro. Much of the suppressive effects of N. gonorrhoeae on dendritic cells can be recapitulated either by outer-membrane vesicles released from the bacteria or by purified PorB, the most abundant outer-membrane protein in Neisseria gonorrhoeae. We show here that three commensal Neisseria species, N. cinerea, N. lactamica and N. mucosa, show a comparable capacity to suppress dendritic cell-induced T cell proliferation through mechanisms similar to those demonstrated previously for N. gonorrhoeae, including inhibition by purified PorB. Our findings suggest that some immune-evasive properties of pathogenic N. gonorrhoeae are shared with commensal Neisseria species and may contribute to the ability of both pathogens and commensals to cause prolonged mucosal colonization in humans.

microbiology↗

bioRxiv2019

Accelerated brain ageing and disability in multiple sclerosis

BackgroundBrain atrophy occurs in both normal ageing and in multiple sclerosis (MS), but it occurs at a faster rate in MS, where it is the major driver of disability progression. Here, we employed a neuroimaging biomarker of structural brain ageing to explore how MS influences the brain ageing process.\n\nMethodsIn a longitudinal, multi-centre sample of 3,565 MRI scans in 1,204 MS/clinically isolated syndrome (CIS) patients and 150 healthy controls (HCs) (mean follow-up time: patients 3*41 years, HCs 1*97 years) we measured brain-predicted age using T1-weighted MRI. Brain-predicted age difference (brain-PAD) was calculated as the difference between the brain-predicted age and chronological age. Positive brain-PAD indicates a brain appears older than its chronological age. We compared brain-PAD between MS/CIS patients and HCs, and between disease subtypes. In patients, the relationship between brain-PAD and Expanded Disability Status Scale (EDSS) at study entry and over time was explored.\n\nFindingsAdjusted for age, sex, intracranial volume, cohort and scanner effects MS/CIS patients had markedly older-appearing brains than HCs (mean brain-PAD 11*8 years [95% CI 9*1--14*5] versus -0*01 [-3*0--3*0], p<0*0001). All MS subtypes had greater brain-PAD scores than HCs, with the oldest-appearing brains in secondary-progressive MS (mean brain-PAD 18*0 years [15*4--20*5], p<0*05). At baseline, higher brain-PAD was associated with a higher EDSS, longer time since diagnosis and a younger age at diagnosis. Brain-PAD at study entry significantly predicted time-to-EDSS progression (hazard ratio 1*02 [1*01--1*03], p<0*0001): for every 5 years of additional brain-PAD, the risk of progression increased by 14*2%.\n\nInterpretationMS increases brain ageing across all MS subtypes. An older-appearing brain at baseline was associated with more rapid disability progression, suggesting brain-age could be an individualised prognostic biomarker from a single, cross-sectional assessment.\n\nFundingUK MS Society; National Institute for Health Research University College London Hospitals Biomedical Research Centre.

neuroscience↗

bioRxiv2018

Application of mechanistic methods to clinical trials in multiple sclerosis: the simvastatin case

The analysis of clinical trials is limited to pre-specified outcomes, thereby precluding a mechanistic understanding of the treatment response. Multivariate mechanistic models can elucidate the causal chain of events by simultaneous analysis of multimodal data that link intermediate variables to outcomes of interest. A double-blind, randomised, controlled, phase 2 clinical trial in secondary progressive multiple sclerosis (MS-STAT, NCT00647348) demonstrated that simvastatin (80mg/day) over two years reduced the brain atrophy rate and was associated with beneficial effects on cognitive and disability outcomes. Therefore, this trial offers an opportunity to apply mechanistic models to investigate the hypothesised pathways that link simvastatin to clinical outcome measures, either directly or indirectly via changes in serum total cholesterol levels and to determine which is the more likely.

neuroscience↗