Biology subjects

Elewaut, D.

Publications and source records attributed to Elewaut, D..

9 recordsLinked to original sources

bioRxiv2026

IL-23 licenses the transition from preclinical autoimmunity to inflammatory arthritis through IL-17A-dependent mechanisms

Objectives: The mechanisms driving transition from systemic autoimmunity to clinical rheumatoid arthritis (RA) remain poorly understood. We investigated the role of interleukin-23 (IL-23) in disease transition using a murine model of experimental arthritis, complemented by human transcriptomic analyses in individuals at risk of RA and RA synovial tissue. Methods: Collagen-induced arthritis (CIA) was induced in less susceptible C57BL/6 mice and combined with sustained systemic IL-23 overexpression. Disease severity, histopathology, immune responses, and tissue gene expression were evaluated. The contribution of IL-17A was assessed using a neutralizing anti-IL-17A antibody. Expression of IL-23 pathway-related genes was assessed in whole-blood transcriptomic data from a large cohort of first-degree relatives of patients with RA (n=1080) and in an independent synovial RNA-sequencing dataset (n=218). Results: In mice, sustained IL-23 overexpression converted a mild CIA phenotype into a highly penetrant arthritis characterized by increased expression of innate inflammatory mediators, and enhanced antigen-specific production of IL-17A and IFN-{gamma}, despite unchanged collagen-specific antibody responses. Neutralization of IL-17A prevented arthritis development. In human whole blood longitudinal analyses, lower RORC and KLRB1 expression was associated with a higher risk of RA onset. KLRB1 expression was persistently lower in progressors, whereas RORC expression showed a steeper decline before diagnosis, although this difference did not remain significant after correction for multiple testing. In RA synovium, IL23R, IL23A, and CCR2 expression was increased compared with controls, while IL23R expression was higher in early than established RA. Conclusions: IL-23 acts as a critical regulator of the transition from systemic autoimmunity to inflammatory arthritis by promoting IL-17A-dependent cellular and myeloid inflammatory pathways. The change in IL-23 pathway signatures in at-risk individuals and early RA supports the translational relevance of this pathway during disease initiation.

immunology↗

bioRxiv2025

Optimizing efficacy to safety ratio of glucocorticoids in rheumatoid arthritis models by leveraging PPARα agonism

ObjectivesGlucocorticoids remain essential therapies for several immune- and inflammatory diseases such as rheumatoid arthritis (RA) but are notorious for their (metabolic) side effects. Given the anti-inflammatory and metabolically favorable actions of peroxisome-proliferator activated nuclear receptor (PPAR) agonists, we investigated whether PPAR agonism could enhance the therapeutic efficacy and/or mitigate the (metabolic) side effects of glucocorticoids. MethodsWe evaluated the effects of the synthetic glucocorticoid dexamethasone and the PPAR agonist GW7647 (GW) across three RA model systems: L929sA fibroblasts, primary human fibroblast-like synoviocytes (FLS) and collagen-induced arthritis (CIA) mice. ResultsDexamethasone reduced the inflammatory TNF response in L929sA cells, which was further potentiated by GW. In vivo however, GW reduced the dexamethasone-induced adiposity and hypertriglyceridemia, but not arthritis severity. Curiously, GW alone induced several proinflammatory genes within arthritic synovium which were counteracted by glucocorticoids. Proteomic profiling of TNF-stimulated human FLS revealed that combined use of dexamethasone and GW selectively suppressed interferon-stimulated proteins. In line herewith, co-stimulation with TNF and IFN{beta} amplified the suppressive effect of combined dexamethasone and GW treatment on pro-inflammatory gene expression in L929sA versus TNF alone. ConclusionGW enhances the anti-inflammatory effects of glucocorticoids in human FLS and L929sA, and mitigates metabolic side effects of dexamethasone in vivo, without compromising their efficacy. In addition, PPAR agonism permits to broaden its anti-inflammatory profile to interferon driven pathways. Given that both synthetic glucocorticoids and PPAR agonists are already widely used in (general) clinical practice, these findings offer a promising strategy to optimize glucocorticoid-based therapies. KEY MESSAGESO_ST_ABSWhat is already known on this topicC_ST_ABSO_LISynthetic glucocorticoids such as dexamethasone are widely used as immunosuppressive drugs, but cause many (metabolic) side effects. C_LIO_LIPeroxisome-proliferator-activated nuclear receptor (PPAR) agonists are clinically primarily used to treat symptoms that resemble glucocorticoid-induced side effects, but they also exert (modest) immunosuppressive effects. C_LI What this study addsO_LIThis study explores the therapeutic potential of a combination treatment with dexamethasone and PPAR agonist GW7647 (GW) in cellular and murine models of rheumatoid arthritis C_LIO_LIWe reveal that GW attenuates dexamethasone-induced adiposity and hypertriglyceridemia in vivo, hereby improving glucocorticoid-related side effects. C_LIO_LIThe therapeutic efficacy of dexamethasone is maintained or even enhanced by GW in murine and cellular models of rheumatic arthritis, respectively. C_LIO_LIWe offer novel mechanistic insights in the proposed combination treatment by revealing the selective suppression of interferon signaling pathways in human FLS. C_LI How this study might affect research, practice or policyO_LIGiven that both synthetic glucocorticoids and PPAR agonists are already used in clinical practice, this study offers a promising, translatable strategy to optimize glucocorticoid-based therapies with an improved efficacy/safety ratio. C_LI

immunology↗

bioRxiv2025

A cell atlas of human and mouse synovium from early and advanced stages of knee osteoarthritis: BHLHE40 regulates fibroblast activation

Osteoarthritis (OA) is a destructive joint disease affecting multiple tissues, including synovium. Previous studies have identified some distinct fibroblast subtypes within synovium; however, the characterization of fibroblast subsets during distinct stages of knee (K)OA disease, and their contributions to the endogenous mechanisms that drive synovial fibrosis during KOA, are not well characterized. Here we profile synovium from early- (KL I) and advanced- (KL III/IV) stages of radiographic KOA. First, bulk-RNA sequencing of early- and advanced-staged KOA synovial tissue revealed transcriptomic differences between the two disease stages. Using single-nuclei RNA sequencing (snRNA-seq) and flow cytometry, we identified distinct fibroblast subsets and uncovered an endotypic shift in fibroblast subsets during KOA pathogenesis, transitioning from DPP4+ in early-stage to ITGB8+ in advanced-stages. SnRNA-seq of synovium from mice with experimental KOA revealed analogous populations of Dpp4+ and Itgb8+ fibroblasts in tissue from early and advanced model stages. Human advanced-stage KOA synovial tissue had stronger expression of matrisome-annotated genes compared to early-stage tissue. BHLHE40, a crucial transcriptional regulator of ECM related genes, was identified as upregulated in ITGB8+ fibroblasts compared to DPP4+ fibroblasts. Using primary human OA fibroblasts in vitro, and conditional knock out mice in vivo, we found that fibroblast-intrinsic loss of BHLHE40 increased fibrosis-related gene expression, enhanced fibroblast activation and induced severe synovial fibrosis in vivo. In contrast, overexpression of BHLHE40 in vitro was able to suppress TGF-{beta}-induced fibroblast activation. Overall, this study provides a comprehensive cellular atlas of KOA synovium and has identified BHLHE40 as a crucial regulator of fibroblast-mediated synovial fibrosis.

molecular biology↗

bioRxiv2025

Themis and Grb2 form a constitutive structural hub in T cell receptor signalling

Positive selection of thymocytes is essential for laying the foundations of the mammalian immune system that include the T cell repertoire, self-tolerance, and prevention of autoimmunity. Themis, the archetypal member of a metazoan protein family featuring distinctive CABIT domains, crucially regulates thymocyte positive selection by linking signalling by the T cell receptor (TCR) to the linker of activation of TCR (LAT). Intriguingly, Themis has been proposed to function via a constitutive complex with the multifunctional adaptor Grb2. Although poised to represent a paradigm shift in our understanding of TCR signalling, the structural and mechanistic basis of such an assembly has remained enigmatic. Here, we present the cryo-EM structure of Themis in complex with Grb2, which reveals how the tandem CABIT domains of Themis engulf the C-terminal SH3 domain of Grb2 (Grb2SH3C) to enable its latching onto the proline rich sequence of Themis. The remaining two domains of Grb2 adopt at least three conformational poses set to interact with other binding partners such as Sos1. Structural insights from unbound Themis unmask the pronounced flexibility of the CABIT domains of Themis, which becomes ordered upon binding to Grb2 to create a binding hotspot for their constitutive complex. Indeed, Themis variants that abrogate interactions with Grb2 also fail to activate the tyrosine phosphatase SHP-1 after TCR stimulation, analogous to the functional phenotype of Themis-deficient cells. Collectively, our study draws the blueprint of the Themis-Grb2 complex as a dynamic structural hub in T cell development.

immunology↗

bioRxiv2025

HIF1α gates tendon response to overload and drives tendinopathy independently of vascular recruitment

Tendons are mostly avascular dense connective tissues that link muscles to bones, withstanding some of the highest mechanical stresses in the body. Mechanical overload and tissue hypervascularity are implicated in tendinopathy, a common musculoskeletal disorder, but mechanistic understanding of their roles is largely lacking. Here, we identify HIF1 not only as a marker but as a driver of tendinopathy. Initial histological and multi-omics evaluation of human tendinopathic samples revealed extensive extracellular matrix remodeling, including pathological collagen crosslinking coinciding with active hypoxic signaling. Hypothesizing a causal contribution of hypoxia signaling, we generated mice with tenocyte-targeted deletions of the Von Hippel-Lindau (VHL) gene, which controls hypoxia signaling by regulating HIF degradation. We demonstrated that VHL inactivation suffices to induce pathological hallmarks of tendinopathy, such as collagen matrix disorganization, crosslinking, altered mechanics and neuro-vascular ingrowth. This phenotype was HIF1-dependent, since co-deleting HIF1 rescued tendon morphology and mechanics. Moreover, deleting vascular endothelial growth factor A (VEGFA) alongside VHL effectively decoupled the effects of vascular ingrowth from persistently aberrant extracellular matrix remodeling and mechanical dysfunction, emphasizing a direct role of HIF1 in driving tendon disease that is independent of angiogenesis. Mechanistically, we linked tendon mechanical overload to the onset of HIF1 signaling in primary cultured human tendon cells. Furthermore, genetically removing HIF1 from tenocytes prevented aberrant tendon remodeling in response to chronic overload. These findings position HIF1 signaling as a central driver of tendinopathy that acts through a maladaptive tissue response to chronic overload, providing mechanistic insights that could be leveraged for improved therapeutic approaches. One Sentence SummaryHIF1 activation promotes tendinopathy and its inhibition prevents overload-induced maladaptation, suggesting therapeutic potential.

cell biology↗

bioRxiv2023

GDF15 mediates inflammation-associated bone loss through a brain-bone axis

Metabolic mediators play an important role in regulating chronic inflammation in the body. Here we report an unexpected role for GDF15 (Growth Differentiation Factor 15), a central mediator of food intake, in inflammation-associated bone loss. GDF15 serum levels were found to be elevated in arthritis patients and inversely correlated with bone density. Despite being associated with inflammation, we found that GDF15 itself does not cause, nor contribute to, clinical or histopathological arthritis. Rather, under inflammatory conditions, GDF15 mediates trabecular bone loss through its receptor GFRAL, which is exclusively expressed in the hindbrain. GDF15-GFRAL binding results in {beta}-adrenergic activation of MALPs (Marrow Adipocytic Lineage Precursors) in the bone marrow, which stimulate osteoclasts and trigger bone loss. These data suggest a metabolic mediator-controlled brain-bone axis in inflammation, through which bone loss is induced in a contextual rather than general manner. These findings may lead to more specific therapeutic interventions to protect bone.

immunology↗

bioRxiv2023

Myeloid A20 is critical for type-2 immune mediated helminth resistance

Protective immunity against intestinal helminths requires induction of robust Type-2 immunity orchestrated by various cellular and soluble effectors which promote goblet cell hyperplasia, mucus production, epithelial proliferation and smooth muscle contractions to expel worms and reestablish immune homeostasis. Conversely, defects in type-2 immunity result in ineffective helminth clearance, persistent infection and chronic inflammation. We identify A20 as an essential myeloid factor for the induction of type-2 immune responses against the intestinal parasite Trichuris muris. Myeloid cell-specific loss of A20 in mice (A20myel-KO) results in chronic Trichuris muris infection and intestinal inflammation. Myeloid A20 deficient mice are not able to induce anti-helmith type-2 immune responses while instead mount detrimental Th1/Th17 polarized immune responses. Antibody-mediated neutralization of the type-1 cytokines IFN{gamma}, IL18 and IL12 prevents Th1/Th17 polarization and reestablishes Type-2 mediated protective immunity against Trichuris muris in A20myel-KO mice. In contrast, the strong Th1/Th17 biased immunity in A20myel-KO mice offers protection against Salmonella infection. We hereby identify A20 as an essential myeloid factor to initiate approriate adaptive immunity in response to infection, and to induce a balanced type-2 immune response against the intestinal parasite Trichuris muris. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/556360v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@632052org.highwire.dtl.DTLVardef@1def1f2org.highwire.dtl.DTLVardef@1de8459org.highwire.dtl.DTLVardef@1c316ff_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical abstractThe clearance of gastrointestinal helmiths depends on type-2 immunity. Helminths interact with and damage intestinal tissue, which leads to the release of intracellular DAMPs and cytokines such as TSLP and IL33, and IL25 produced by epithelial cells. These factors may activate myeloid cells and ILCs, which further activate T and B cells to mount effective Th2 responses and the secretion of IL4, IL5 and IL13 cytokines, as well as helminth-specific IgG1 immunoglobulins, leading to effective expulsion of the helminths. Deletion of A20 in the myeloid cells leads to enhanced secretion of type-1 cytokines, including IL12, IL18 and IFN{gamma}, which impede type-2 immune-mediated helminth clearance and promotes chronic intestinal inflammation.

immunology↗

bioRxiv2023

Sterile triggers drive joint inflammation in TNF and IL-1beta dependent mouse arthritis models

Arthritis is the most common extra-intestinal complication in inflammatory bowel disease (IBD). Conversely, arthritis patients are at risk for developing IBD and often display subclinical gut inflammation. These observations suggest a shared disease etiology, commonly termed the gut-joint-axis. The clinical association between gut and joint inflammation is further supported by the success of common therapeutic strategies and microbiota dysbiosis in both conditions. Most data however support a correlative relationship between gut & joint inflammation, while causative evidence is lacking. Using two independent transgenic mouse arthritis models, either TNF or IL1{beta} dependent, we demonstrate that arthritis develops independently of the microbiota and intestinal inflammation, since both lines develop full-blown articular inflammation under germ-free conditions. In contrast, TNF-driven gut inflammation is fully rescued in germ-free conditions indicating that the microbiota is driving TNF-induced gut inflammation. Together, our study demonstrates that, although common inflammatory pathways may drive both gut and joint inflammation, the molecular triggers initiating such pathways are distinct in these tissues.

immunology↗

bioRxiv2019

B cell tetherin: a flow-cytometric cell-specific assay for response to Type-I interferon predicts clinical features and flares in SLE

ObjectiveType I interferon (IFN-I) responses are broadly associated with autoimmune disease including SLE. Given the cardinal role of autoantibodies in SLE, we investigated whether a B lineage cell-specific IFN assay might correlate with SLE activity. MethodsB cells and PBMCs were stimulated with IFN-I and IFN-II. Gene expression was scrutinised for pathway-related membrane protein expression. A flow-cytometric assay for tetherin (CD317), an IFN-induced protein ubiquitously expressed on leucocytes, was validated in vitro then clinically against SLE diagnosis, plasmablast expansion, and BILAG-2004 score in a discovery cohort (156 SLE; 30 RA; 22 healthy controls). A second longitudinal validation cohort of 80 patients was also evaluated for SLE flare prediction. ResultsIn vitro, a close cell-specific and dose-responsive relationship between IFN-I responsive genes and cell surface tetherin in all immune subsets existed. Tetherin expression was selectively responsive to the IFN-I compared to IFN-II and -III. In the discovery cohort memory B-cell tetherin was best associated with diagnosis (SLE/HC: effect size=0.11, p=0.003;SLE/RA: effect size=0.17, p<0.001); plasmablast numbers in rituximab-treated patients (Rho=0.38, p=0.047) and BILAG-2004. Association were equivalent or stronger than interferon score or monocyte tetherin. The validation cohort confirmed this relationship with memory B-cell tetherin predictive of future clinical flares (Hazard Ratio=2.29 (1.01-4.64), p=0.022). ConclusionMemory B cell surface tetherin, a reflection of cell-specific IFN response in a convenient flow cytometric assay, was associated with SLE diagnosis, disease activity and predicted flares better than other cell subsets or whole blood assays in independent validation cohorts.

immunology↗