Biology subjects

Walsh, P. T.

Publications and source records attributed to Walsh, P. T..

4 recordsLinked to original sources

bioRxiv2026

Deficiency of IL-36 receptor antagonist (DITRA) is associated with decreased homoeostatic CCL27 expression leading to heightened dermal inflammation.

Deficiency of the Interleukin-36 Receptor antagonist (DITRA) is a rare autoinflammatory condition which commonly manifests as severe, recurrent episodes of Generalized Pustular Psoriasis (GPP). Loss-of-function mutations in the IL36RN gene result in unopposed IL-36 cytokine signalling leading to severe psoriatic inflammation, which can be successfully treated with Anti-IL-36 receptor (IL-36R) monoclonal antibodies. Despite such advances, there remain some key questions concerning how loss of a functional IL-36R antagonist predisposes to GPP, including identifying the potential impacts of IL36RN mutations on skin homeostasis. To address this question, we investigated the consequences of IL-36Ra deficiency using Il36rn-/- mice, which recapitulate the severe psoriatic inflammation observed in DITRA patients. Here, we demonstrate, that in overtly healthy Il36rn-/- mice, prior to disease onset, there is disrupted dermal immune homeostasis, characterised by decreased expression of the chemokine CCL27. Altered skin homeostasis occurred in association with dysbiosis of the skin microbiome, characterised by a significant outgrowth of the commensal bacteria, Cutibacterium acnes. Importantly, intradermal administration of recombinant CCL27, prior to disease induction, significantly reduced the enhanced severity of psoriasiform inflammation, demonstrating a central role for this chemokine in regulating predisposition to increased severity. Transcriptomic analysis of GPP patients skin also revealed decreased CCL27 expression in non-lesional, as well as lesional, compared to healthy skin, indicating that this chemokine may also play a key instructive role among DITRA patients. Together, these data identify a novel mechanism through which IL-36Ra deficiency alters dermal homeostasis and predisposes to increased severity of psoriatic disease observed in DITRA patients.

immunology↗

bioRxiv2026

Targeting redox imbalance through Nrf2 activation in the inflamed coeliac duodenum.

Coeliac Disease (CeD) is a chronic gastrointestinal inflammatory disease initiated by dietary gluten in genetically predisposed individuals. While the inflammatory processes which drive tissue destruction in the coeliac duodenum have been extensively characterised, an increased oxidative stress (OS) response has also been suggested to contribute to CeD pathogenesis. However, the precise mechanisms which regulate OS in the coeliac mucosa and whether they impact inflammation remain ill defined. The master anti-oxidant transcriptional regulator Nuclear factor erythroid 2-related factor 2 (Nrf2), and its inhibitor, Kelch like ECH-associated protein 1 (Keap1) have been implicated in chronic gastrointestinal inflammatory diseases, such as ulcerative colitis but have been largely unexplored in the context of CeD. To investigate redox balance in the CeD duodenum, we utilised single cell transcriptomics to assess overall OS and cytoprotective Nrf2 activation across cell subsets in duodenal biopsies from CeD patients. OS induced gene expression was broadly increased across multiple cell subsets in the CeD mucosa. Simultaneously, specific markers of Nrf2 activation were decreased in cell subtypes central to pathogenesis of CeD, including activated CD4+ T cells and intraepithelial T lymphocytes, indicating a distinct redox imbalance in these cells. Furthermore, pharmacological activation of Nrf2 significantly decreased gliadin induced IFNG expression in CeD duodenal biopsies. Taken together, our findings demonstrate that redox imbalance represents a therapeutic opportunity for the modulation of proinflammatory responses that drive the pathogenesis of CeD.

immunology↗

bioRxiv2024

Tissue factor-dependent colitogenic CD4+ T cell thrombogenicity is regulated by activated protein C signalling.

Inflammatory bowel disease (IBD) patients experience up to 6-fold increased risk of venous thromboembolism (VTE) compared to the general population, although the mechanistic basis for this increased risk remains poorly defined. We found that colitogenic CD4+ T cells express tissue factor (TF) and promote rapid TF-dependent plasma thrombin generation in T cell-dependent calibrated automated thrombinography assays. Furthermore, we identified the presence of TF+CD4+CD3+ T cells in the colons of both mice with colitis and paediatric IBD patients during active disease. TF is typically expressed in an encrypted state and requires decryption for optimal procoagulant activity. Notably, flow cytometric analysis demonstrated that activated CD4+ T cells express significantly increased acid sphingomyelinase and protein disulphide isomerase, critical mediators for TF decryption, on their cell membrane compared to naive T cells. The protein C (PC) pathway is an important regulator of TF-mediated thrombin generation. Pertinently, pre-clinical studies suggest an important role for diminished PC pathway activity in IBD pathophysiology. To understand how this process might be regulated, we performed meta-transcriptomic and gene expression analysis of IBD patient gut biopsy tissue, identifying dysregulated expression of genes involved in the regulation of coagulation, including PC (PROC) and its receptor (EPCR; PROCR). Subsequent functional studies revealed that activated protein C (APC) signalling reduced colitogenic T cell generation and activity, potently impaired TF decryption and significantly reduced T cell-mediated thrombin generation and clot formation. These data identify TF-mediated colitogenic T cell thrombogenicity and demonstrate a new role for APC signalling in regulating T cell thrombo-inflammatory activity.

immunology↗

bioRxiv2023

GLYCOLYTIC REPROGRAMMING FUELS MYELOID CELL-DRIVEN HYPERCOAGULABILITY

BackgroundMyeloid cell metabolic reprogramming is a hallmark of inflammatory disease, however, its role in inflammation-induced hypercoagulability is poorly understood. Objective/MethodsUsing novel myeloid cell-based global haemostasis assays and murine models of immunometabolic disease, we evaluated the role of inflammation-associated metabolic reprogramming in regulating blood coagulation. ResultsGlycolysis was essential for enhanced activated myeloid cell tissue factor expression and decryption, driving increased cell-dependent thrombin generation in response to inflammatory challenge. Similarly, inhibition of glycolysis enhanced activated macrophage fibrinolytic activity via reduced plasminogen activator inhibitor 1 (PAI-1)-activity. Macrophage polarisation or activation markedly increased endothelial protein C receptor (EPCR) expression on monocytes and macrophages, leading to increased myeloid cell-dependent protein C activation. Importantly, inflammation-dependent EPCR expression on tissue-resident macrophages was also observed in vivo. Adipose tissue macrophages from obese mice fed a high-fat diet exhibited significantly enhanced EPCR expression and APC generation compared to macrophages isolated from the adipose tissue of healthy mice. Similarly, the induction of colitis in mice prompted infiltration of EPCR+ innate myeloid cells within inflamed colonic tissue that were absent from the intestinal tissue of healthy mice. ConclusionCollectively, this study identifies immunometabolic regulation of myeloid cell hypercoagulability, opening new therapeutic possibilities for targeted mitigation of thrombo-inflammatory disease. ESSENTIALSO_LIInflammation-mediated glycolytic reprogramming enables myeloid cell-induced hypercoagulability and antifibrinolytic activity. C_LIO_LI2-Deoxy-D-glucose (2-DG) inhibits the expression of transcription factors necessary for inflammation-induced procoagulant gene expression. C_LIO_LIMyeloid cell membrane regulation of tissue factor procoagulant activity is glycolysis-dependent. C_LIO_LIActivation of myeloid innate immunity dysregulates activated protein C anticoagulant pathway activity. C_LI

immunology↗