Biology subjects

Robinson, D. A.

Publications and source records attributed to Robinson, D. A..

9 recordsLinked to original sources

bioRxiv2025

Mitochondrial Dysfunction in Endothelial Cells Drives Greater Vascular Impairment in Females with Diabetes-Associated Peripheral Artery Disease

BackgroundWomen with peripheral artery disease (PAD) experience poorer clinical outcomes than men, particularly in the setting of diabetes. However, the mechanistic basis for these sex- specific disparities remains unclear. MethodsHere, we investigated endothelial cell (EC) function(s) in diabetes-associated PAD, with a focus on sex differences. Limb tissues from patients with diabetes and chronic limb-threatening ischemia (CLTI) undergoing amputation, and a diabetes mouse model of hindlimb ischemia (HLI), were assessed for vasodilatory capacity, angiogenesis, oxidative stress and changes to expression of mitochondrial complex genes. ECs exposed to a hyperglycemic environment in vitro were assessed for mitochondrial function. The therapeutic potential of the mitochondrial-targeted antioxidant MitoQ was investigated. ResultsECs from females with diabetes-associated PAD have altered responses compared to males. Specifically, limb vessels and skeletal muscle from females exhibit reduced arterial relaxation, angiogenesis and increased oxidative stress in response to HLI in mice, and in tissues from patients. Single-cell RNA sequencing of murine limbs revealed marked suppression of EC mitochondrial complex genes in females with diabetes. Female human ECs exposed to high glucose had reduced respiration, reduced expression of mitochondrial genes and increased oxidative stress. Remarkably, MitoQ restored arterial relaxation and the angiogenic response in female diabetes- associated PAD. ConclusionOur findings uncover a striking sex-specific vulnerability involving oxidative stress and mitochondrial dysfunction in EC health in diabetes-associated PAD. These results highlight the need for sex-specific therapeutic strategies in diabetic PAD, which might include mitochondrial targeted antioxidant strategies.

pathology↗

bioRxiv2024

Impact of variants and vaccination on nasal immunity across three waves of SARS-CoV-2

SARS-CoV-2 infection and COVID-19 disease vary with respect to viral variant and host vaccination status. However, how vaccines, emergent variants, and their intersection shift host responses in the human nasal mucosa remains uncharacterized. We and others have shown during the first SARS-CoV-2 wave that a muted nasal epithelial interferon response at the site of infection underlies severe COVID-19. We sought to further understand how upper airway cell subsets and states associate with COVID-19 phenotypes across viral variants and vaccination. Here, we integrated new single-cell RNA-sequencing (scRNA-seq) data from nasopharyngeal swabs collected from 67 adult participants during the Delta and Omicron waves with data from 45 participants collected during the original (Ancestral) wave in our prior study. By characterizing detailed cellular states during infection, we identified changes in epithelial and immune cells that are both unique and shared across variants and vaccination status. By defining SARS-CoV-2 RNA+ cells for each variant, we found that Delta samples had a marked increase in the abundance of viral RNA+ cells. Despite this dramatic increase in viral RNA+ cells in Delta cases, the nasal cellular compositions of Delta and Omicron exhibit greater similarity, driven partly by myeloid subsets, than the Ancestral landscapes associated with specialized epithelial subsets. We found that vaccination prior to infection was surprisingly associated with nasal macrophage recruitment and activation rather than adaptive immune cell signatures. While patients with severe disease caused by Ancestral or Delta variants had muted interferon responses, Omicron-infected patients had equivalent interferon responses regardless of disease severity. Our study defines the evolution of cellular targets and signatures of disease severity in the upper respiratory tract across SARS-CoV-2 variants, and suggests that intramuscular vaccines shape myeloid responses in the nasal mucosa upon SARS-CoV-2 infection.

immunology↗

bioRxiv2023

Ultrastructural, metabolic and genetic determinants of the acquisition of macrolide resistance by Streptococcus pneumoniae

AimStreptococcus pneumoniae (Spn) acquires genes for macrolide resistance, MEGA or ermB, in the human host. These genes are carried either in the chromosome, or on integrative conjugative elements (ICEs). Here, we investigated molecular determinants of the acquisition of macrolide resistance. Methods and ResultsWhole genome analysis was conducted for 128 macrolide-resistant pneumococcal isolates to identify the presence of MEGA (44.5%, 57/128) or ermB (100%), and recombination events in Tn916-related elements or in the locus comCDE encoding competence genes. Confocal and electron microscopy studies demonstrated that, during the acquisition of macrolide resistance, pneumococcal strains formed clusters of varying size, with the largest aggregates having a median size of [~]1600 {micro}m2. Remarkably, these pneumococcal aggregates comprise both encapsulated and nonencapsulated pneumococci, exhibited physical interaction, and spanned extracellular and intracellular compartments. We assessed the recombination frequency (rF) for the acquisition of macrolide resistance by a recipient D39 strain, from pneumococcal strains carrying MEGA ([~]5.4 kb) in the chromone, or in large ICEs (>23 kb). Notably, the rF for the acquisition of MEGA, whether in the chromosome or carried on an ICE was similar. However, the rF adjusted to the acquisition of the full-length ICE ([~]52 kb), compared to that of the capsule locus ([~]23 kb) that is acquired by transformation, was three orders of magnitude higher. Finally, metabolomics studies revealed a link between the acquisition of ICE and the metabolic pathways involving nicotinic acid and sucrose. ConclusionsExtracellular and intracellular pneumococcal clusters facilitate the acquisition of full-length ICE at a rF higher than that of typical transformation events, involving distinct metabolic changes that present potential targets for interventions.

microbiology↗

bioRxiv2023

Staphylococcus aureus skin colonization is mediated by SasG lectin variation

Staphylococcus aureus causes the majority of skin and soft tissue infections, but this pathogen only transiently colonizes healthy skin. However, this transient skin exposure enables S. aureus to transition to infection. Initial adhesion of S. aureus to skin corneocytes is mediated by surface protein G (SasG). Here, phylogenetic analyses reveal the presence of two major divergent SasG alleles in S. aureus, SasG-I and SasG-II. Structural analyses of SasG-II identified a unique non-aromatic arginine in the binding pocket of the lectin subdomain that mediates adhesion to corneocytes. Atomic force microscopy and corneocyte adhesion assays indicated SasG-II can bind to a broader variety of ligands than SasG-I. Glycosidase treatment resulted in different binding profiles between SasG-I and SasG-II on skin cells. Additionally, SasG-mediated adhesion was recapitulated using differentiated N/TERT keratinocytes. Our findings indicate that SasG-II has evolved to adhere to multiple ligands, conferring a distinct advantage to S. aureus during skin colonization.

microbiology↗

bioRxiv2023

A diversity of diversities: evaluating the relationships between below and aboveground biodiversity

O_LITo predict how biodiversity will respond to global change, it is crucial to understand the relative roles of abiotic drivers and biotic interactions in driving associations between the biodiversity of disparate taxa. It is particularly challenging to understand diversity-diversity links across domains and habitats, because data are rarely available for multiple above- and below-ground taxa across multiple sites. C_LIO_LIHere we analyse data from a unique biodiversity dataset gathered across a variety of oceanic temperate terrestrial habitats in Wales, comprising 300 sites with co-located soil microbial, plant, bird, and pollinator surveys along with climate and soil physicochemical information. Soil groups are analysed using metabarcoding of the 16S, ITS1 and 18S DNA regions, allowing in depth characterisation of microbial and soil animal biodiversity. C_LIO_LIWe explore biodiversity relationships along three aspects of community composition: First, we assess correlation between the alpha diversity of different groups. Second, we assess whether biotic turnover between sites is correlated across different groups. Finally, we investigate the co-occurrence of individual taxa across sites. In each analysis, we assess the contribution of linear or non-linear environmental effects. C_LIO_LIWe find that a positive correlation between alpha diversity of plants, soil bacteria, soil fungi, soil heterotrophic protists, bees and butterflies is in fact driven by complex non-linear responses to abiotic drivers. In contrast, environmental variation did not account for positive associations between the diversity of plants and both birds and AM fungi, suggesting a role for biotic interactions. C_LIO_LIBoth the diversity and taxon-level associations between the differing soil groups remained even after accounting for non-linear environmental gradients. Aboveground, spatial factors played larger roles in driving biotic communities, while linear environmental gradients were sufficient to explain many group- and taxon-level relationships. C_LIO_LISynthesis. Our results show how non-linear responses to environmental gradients drive many of the relationships between plant biodiversity and the biodiversity of above- and belowground biological communities. Our work shows how different aspects of biodiversity might respond non-linearly to changing environments and identifies cases where management-induced changes in one community could either influence other taxa or lead to loss of apparent biological associations. C_LI

ecology↗

bioRxiv2022

Fifty years of reduction in sulphur deposition drives recovery in soil pH and plant communities

O_LISulphur deposition through rainfall has led to species loss and ecosystem degradation globally, and across Europe huge reductions in sulphur emissions since the 1970s were expected to promote the recovery of acidified ecosystem. However, the rate and ecological impact of recovery from acidification in terrestrial ecosystems is still unclear as is the influence of management and climate, as to date there has been no long-term spatially extensive evaluation of these changes. C_LIO_LIHere we present data from thousands of sites across Great Britain surveyed repeatedly from 1978-2019 and assess change in soil pH and plant acidity preference (Ellenberg R) in response to atmospheric deposition of sulphur and nitrogen. We analyse change in grasslands managed for pasture, referred to as high-intensity habitats, and compare to semi-natural habitats comprising rough grassland, broadleaved woodland, bog and heathland, referred to as low-intensity habitats. C_LIO_LISoil pH increased from 1978 to 2007 but then decreased between 2007 and 2019, resulting in a net increase of ~0.2 pH units in low-intensity habitats but no change in high-intensity habitats. The community average Ellenberg R increased in semi-natural habitats by ~0.2 units but remained stable in intensive grasslands. C_LIO_LIIn semi-natural habitats, but not intensive grasslands, these changes in plant community composition were associated with the soil pH changes which were in turn linked to decreasing sulphur deposition and differences in rainfall. C_LIO_LINitrogen deposition, which was relatively stable over the survey period, showed no additional effect upon soil acidity once sulphur deposition was accounted for. C_LIO_LISynthesis: Our results provide conclusive evidence that reductions in acid emissions are stimulating the gradual recovery of chronically acidified terrestrial ecosystems at a whole-country scale, while also suggesting this recovery is being compromised by changing climate and land management. C_LI

ecology↗

bioRxiv2020

Targeting a critical step in fungal hexosamine biosynthesis

Aspergillus fumigatus is a human opportunistic fungal pathogen with a cell wall that protects it from the extracellular environment. Chitin, an essential cell wall component, is synthesised from UDP-GlcNAc that is produced by the hexosamine biosynthetic pathway. Here, we provide genetic and chemical evidence that glucosamine 6-phosphate N-acetyltransferase (Gna1), a key enzyme in this pathway, is an exploitable antifungal drug target. Deletion of GNA1 results in loss of viability and disruption of the cell wall, phenotypes that can be rescued by the product of the enzyme. In a murine model of aspergillosis, the{Delta} gna1 mutant strain attenuates virulence. Using a fragment-based approach, we discovered a small heterocyclic scaffold that binds proximal to the active site and can be optimised to a selective sub-micromolar binder. Taken together, we have provided genetic, structural and chemical evidence for Gna1 as an antifungal target in Aspergillus fumigatus.

microbiology↗

bioRxiv2019

Characterization of Peripheral Blood Mononuclear Cells Gene Expression Profiles of Pediatric Staphylococcus aureus Persistent and Non-Carriers Using a Targeted Assay

Defects in innate immunity affect many different physiologic systems and several studies of patients with primary immunodeficiency disorders demonstrated the importance of innate immune system components in disease prevention or colonization of bacterial pathogens. To assess the role of the innate immune system on nasal colonization with Staphylococcus aureus, innate immune responses in pediatric S. aureus nasal persistent carriers (n=15) and non-carriers (n=15) were profiled by analyzing co-clustered gene sets (modules) identified through large-scale transcriptome data analysis as the basis for the development of a targeted assay. We stimulated previously frozen peripheral blood mononuclear cells (PBMCs) from these subjects with i) a panel of TLR ligands, ii) live S. aureus (either a mixture of strains or stimulation with respective carriage isolates), or iii) heat-killed S. aureus. We found no difference in responses between carriers and non-carriers when PBMCs were stimulated with a panel of TLR ligands. However, PBMCs stimulated with live S. aureus elicited a significantly different response that also differed from the response elicited following stimulation with dead S. aureus. Furthermore, we observed a distinct stimulation profile for PBMCs isolated from persistent carriers stimulated with their respective live or dead carriage strains compared to responses observed for PBMCs isolated from non-carriers that were similar regardless of whether or not the bacteria were alive or not. These data suggested that innate pathway signaling is different between persistent and non-carriers of S. aureus.

immunology↗

bioRxiv2017

Global phylogenomics of multidrug-resistant Staphylococcus aureus sequence type 772: the Bengal Bay clone

The global spread of antimicrobial resistance has been well documented in Gram-negative bacteria and healthcare-associated epidemic pathogens, often emerging from regions with heavy antimicrobial use. However, the degree to which similar processes occur with Gram-positive bacteria in the community setting is less well understood. Here we demonstrate the recent origin and global spread from the Indian subcontinent of a multidrug resistant Staphylococcus aureus lineage, sequence type 772 (Bengal Bay clone). Short-term outbreaks occurred following intercontinental transmission, typically associated with travel and family contacts, but ongoing endemic transmission was uncommon. Instrumental in the emergence of a single dominant clade in the early 1990s was the acquisition of a multidrug resistance integrated plasmid that did not appear to incur a significant fitness cost. The Bengal Bay clone therefore combines the multidrug resistance of traditional healthcare-associated clones with the epidemiological and virulence potential of community-associated clones.

genomics↗