OP0068 DISTINCT STROMAL AND IMMUNE CELL INTERACTIONS SHAPE THE PATHOGENESIS OF RHEUMATOID AND PSORIATIC ARTHRITIS

Background

Rheumatoid (RA) and psoriatic arthritis (PsA) are common autoimmune and autoinflammatory diseases of unknown aetiology characterised by complex synovial pathology with a detrimental effect on the patient’s quality of life. Significant differences in pathophysiology may explain distinct clinical manifestations and account for differential responses to specific therapeutics. Recent implementation of single cell transcriptomic analysis of sorted synovial cells has revealed the diverse cellular landscape of the RA synovial stromal and immune cell compartments, however, a complete analysis of immune and stromal cells in tandem, for RA and PsA patient synovial tissue has not been performed.

Objectives

To combine novel scRNA transcriptomic approaches and ex vivo assays in order to: identify differences in the cellular landscape of RA and PsA synovial tissue inflammation and immune – stromal cell interactions that drive pathology in RA and PsA.

Methods

Single cell transcriptomic profiling of 178,000 synovial tissue cells from 5 PsA and 4 RA patients, importantly, without prior sorting of immune and stromal cells. This approach enabled the generation of a unique cell atlas of intact synovial tissue identifying immune and stromal cell interactions. State of the art data integration and annotation techniques identified and characterised 18 stromal and 14 immune cell clusters. Bioinformatic examination of cell-cell communication via construction of receptor-ligand interaction networks with further in vitro validation of stromal and immune cell crosstalk through flow cytometric analysis, multiplex ELISA and mitochondrial and single cell metabolic profiling by multiphoton and florescent lifetime imaging microscopy, seahorse.

Results

Following quality control and data integration the PsA and RA cellular landscape was generated and nine mega clusters indicative of fibroblasts, endothelial cells, pericytes, macrophages, dendritic cells (DC), B cells, plasma cells, T cells and NKT consisting of several sub clusters were identified. Distinct points of transcriptomic deviation and convergence between RA and PsA were identified for each of the major cell types of the joint. Specifically, cell cycle and trajectory analysis revealed that only a fraction of synovial T cells are actively proliferating. Additionally, the differential usage of immunoglobulin light chains by memory and plasma cells indicates that plasma cells are potentially not derived from the local memory B cell pool of the synovial tissue. Importantly, we report distinct fibroblast and endothelial cell transcriptomes indicating differentially abundant subpopulations in RA and PsA characterised by distinct transcription factor usage and signalling pathway enrichment. Specifically transcriptomic imputation analysis revealed abundance of invasive FAPα+THY1+ regulated by transcription factor TEAD1 in RA compared to PsA synovial tissue. In order to identify potential cell-cell communication driving inflammation in RA and PsA, novel receptor–ligand interaction networks were generated and downstream of the receptor, target characterisation was performed. Herein we identify RA-specific synovial T cell-derived TGF-β and macrophage IL-1β synergy in driving the transcriptional profile of FAPα+THY1+ invasive synovial-fibroblasts, expanded in RA compared to PsA synovial tissue biopsies (Figure 1). Ex vivo treatment of RA patient synovial fibroblasts identified TGF-b and IL-1b synergy are a major driver of IL-6 production, fibroblast activation and adhesion molecule expression. Interestingly, the aforementioned proinflammatory changes of RA patient synovial fibroblasts were coupled with significant alterations in mitochondrial eccentricity and size and a marked metabolic adaptation towards a strongly glycolytic profile (Figure 1).

Figure 1.

Conclusion

Disrupting specific immune and stromal cell interactions offers novel opportunities for targeted therapeutic intervention in RA and PsA.

Disclosure of Interests

Achilleas Floudas: None declared, Conor Smith: None declared, Orla Tynan: None declared, Nuno Neto: None declared, Vinod Krishna Employee of: Janssen Pharmaceuticals, Sarah Wade: None declared, Megan Hanlon: None declared, Clare Cunningham: None declared, Viviana Marzaioli: None declared, Mary Canavan: None declared, Jean Fletcher: None declared, Suzanne Cole Employee of: Janssen Pharmaceuticals, Ling-Yang Hao Employee of: Janssen Pharmaceuticals, Sunil Nagpal Employee of: Janssen Pharmaceuticals, GSK, Michael Monaghan: None declared, Douglas Veale Consultant of: Janssen, Eli Lilly, Pfizer, Ursula Fearon Consultant of: Janssen, Eli Lilly, Pfizer.

POS0495 CYTOKINE SYNERGY ENHANCES SYNOVIAL FIBROBLAST ACTIVATION IN CHILDREN WITH DOWN’S SYNDROME-ASSOCIATED ARTHRITIS

Background

We have previously shown that children with Down’s syndrome-associated arthritis (DA) display a more aggressive form of inflammatory arthritis compared to that of Juvenile Idiopathic Arthritis (Shih et al., 2019). DA is associated with an increase in polyfunctional T-cells coexpressing TNF-α DA is associated with an increase in polyfunctional T-cells coexpressing TNF-fibroblasts (FLS) (Foley et al., 2019).

Objectives

In this study we examine the effect of cytokine synergy on primary DA FLS function.

Methods

Primary DA FLS were cultured and stimulated with TNF-α (0.1 and 1ng/ml), IL-17A (20 and 50ng/ml), IFN-ɣ (10 and 50ng/ml) and GM-CSF (20 and 100ng/ml) or a combination of these cytokines and the following functional experiments performed. Chemokine and adhesion molecule cell surface expression were quantified by flow cytometry, in addition to quantification of leukocyte-DA-FLS adhesion assays. Gene and protein expression of proinflammatory and metabolic mediators were quantified by ELISA and RT-PCR. Furthermore, real-time metabolic activity in response to cytokine stimulation was assessed by measuring the two major energy pathways: glycolysis (ECAR) and oxidative phosphorylation (OCR), by the Seahorse XFe96 Analyser.

Results

We examined the effects of T cell derived cytokines, TNF-α, IL-17A, IFN-γ and GM-CSF, alone and in combination on DA FLS function. TNF-α, IL-17A and IFN-γ induced IL-6, RANTES and MCP-1 production, with no effect observed for GM-CSF. Furthermore, TNF-α, IFN-ɣ and IL-17A increased leukocyte adhesion to DA FLS. TNF-α and IFN-ɣ induced cell surface expression of CXCR3, CXCR4, ICAM-1 and VCAM-1 on DA FLS. Next, we investigated the potential synergistic relationship that these cytokines could have on proinflammatory mediators. IL-17A and IFN-ɣ potentiated the effects TNF-α on IL-6 and MCP-1 secretion compared to stimulation alone. Furthermore, cytokine synergy significantly induced IL-6, IL-8, RANTES and LDHA mRNA expression compared to basal. IL-17A and IFN-αL-17A and IFN- eeased ts TNF-α on IL-6 and MCP-1 secretion compared to stimulation alone. Additionally, IFN the ECAR:OCR ratio demonstrating a shift in the metabolic profile of DA FLS to glycolysis. Overall DA FLS are transformed from a quiescent metabolic state to an energetic phenotype.

Conclusion

TNF-αNF-lusion:OCR ratio demonstrating a shift in the metabolhe aggressive phenotype of DA FLS through increased cytokine, adhesion molecule and chemokine expression, which is pathways for the treatment of DA.

References

[1]Foley, C. et al. (2019) ‘Increased T cell plasticity with dysregulation of T follicular helper, T peripheral helper and T regulatory cell responses in children with JIA and Down syndrome-associated arthritis’, Arthritis & Rheumatology, pp. 0–1. doi: 10.1002/art.41150.

[2]Shih, Y. J. et al. (2019) ‘Enthesitis-related arthritis is the most common category of juvenile idiopathic arthritis in Taiwan and presents persistent active disease’, Pediatric Rheumatology. Pediatric Rheumatology. doi: 10.1186/s12969-019-0363-0.

Disclosure of Interests

None declared.

POS0443 INSIDE THE JOINT OF INFLAMMATORY ARTHRITIS PATIENTS: HANDLING AND PROCESSING OF SYNOVIAL TISSUE BIOPSIES FOR HIGH THROUGHPUT ANALYSIS

Background

Inflammatory arthritis (IA) is a chronic systemic autoimmune disease of unknown aetiology, which affects the joints. While studies of immune cell populations in peripheral blood have been informative regarding potential immune cell dysfunction and possible patient stratification, there are considerable limitations in identifying the early events that lead to synovial inflammation. The joint, as the site of inflammation and the local microenvironment, exhibit unique characteristics that contribute to disease pathogenesis. The limited availability of synovial tissue (ST) biopsies is a key incentive for the utilisation of high-throughput techniques in order to maximise information gain.

Objectives

This work aims to provide an overview of key methods and novel techniques that are used in the handling, processing and analysis of ST biopsies and the potential synergy between these techniques.

Methods

We describe the utilisation of high dimensionality flow cytometric analysis, single cell RNA sequencing, ex vivo functional assays, including T cell activation, endocytosis and two-photon fluorescent lifetime imaging microscopy (FLIM).

Results

When comparing different methods for ST cell suspension generation we observed that the combination of mechanical and enzymatic digestion resulted in the release of considerably higher numbers of total viable cells when compared to mechanical digestion alone, although consideration should be taken in the cleaving of extracellular markers, like CD27. We next compared two different cryopreservation methods to that of freshly digested ST and observed similar viability and frequency of immune cells. Functional characterisation of ST cells can be challenging due to the high number of cells required for analysis, herein, we utilised the above protocols to establish ST viable cell suspensions and optimised different experimental approaches for phenotypical/functional characterisation. To investigate the functional consequence of OxPhos inhibition on ST T-cell polyfunctionality, ex-vivo ST cell suspensions from IA patients were stimulated with PMA/Ionomycin in the presence/absence of FCPP followed by metabolic profile characterisation via FLIM and high dimensionality flow-cytometric analysis for T cell-derived cytokines. Treatment with FCPP resulted in a decreased in T-cell polyfunctionality specifically in co-expression of TNF-α,-IL-2,-IFN-γ,IL-17A, -GM-CSF, an effect associated with a shift in their metabolic profile. In addition, freshly digested ST cell suspensions were subjected to an optimized assay to evaluate endocytosis in multiple populations simultaneously without the need for cell sorting. Briefly, digested cells were incubated in parallel at 4°C (passive endocytosis) and 37°C (active endocytosis) with DQ OVA(Ovalbumin). ST cells were then stained for multiple populations, demonstrating differential endocytosis capacity across pathotypes and disease controls.

Finally, utilisation of novel bioinformatics analysis of RNAseq a data showed differential gene expression and pathway enrichment involved in IA pathogenesis and allowed for the comparison of cell specific enrichment scores and transcription factor usage based on pathotype and gender.

Conclusion

The introduction of new powerful techniques in the study of ST inflammation, brings new challenges and significant opportunities. These approaches will accelerate our path towards understanding of the mechanisms involved in the pathogenesis of IA and lead to the identification of new avenues of therapeutic intervention.

Acknowledgements

We would like to thank all the patients who consented to be involved in this study.

Disclosure of Interests

None declared.

AB0018 ACCUMULATION OF FUNCTIONALLY MATURE CD1C+ DENDRITIC CELLS CONTRIBUTES TO SYNOVIAL INFLAMMATION IN INFLAMMATORY ARTHRITIS

Background:

Myeloid Dendritic Cells (DC) are potent antigen presenting cells that can be subdivided into CD141 and CD1c+ DC. We have previously reported an unacknowledged role for CD141+DC in the IA synovium. However, the identification and function of CD1c+ DC in the IA synovium has yet to be fully elucidated.

Objectives:

To investigate if CD1c+DC reside in the IA synovium and ascertain if they represent a unique population, distinct from peripheral CD1c+DC and if they contribute to synovial inflammation.

Methods:

Synovial tissue (ST) biopsies and synovial fluid mononuclear cells (SFMC) were obtained via arthroscopy and healthy control (HC) ST was obtained during ACL surgery. Synovial tissue single cells suspensions were generated following enzymatic and mechanical digestion. Single cell analysis of synovial tissue cell suspensions, along with PBMC and SFMC was performed by multicolour flow cytometry. CD1c+DC were sorted from IA synovial fluid and peripheral blood and bulk RNA sequencing was performed. CD1c+DC functionality and maturation was assessed using OVA DQ phagocytosis assays, multiplex ELISA and DC: T cell cocultures.

Results:

Within the circulation the frequency of CD1c+DC are significantly decreased in IA peripheral blood compared to HC (p<0.01) in addition to expressing significantly higher levels of the maturation markers CD80 (p<0.01) and CD40 (p=0.08). IA peripheral blood DC also express significantly higher levels of CXCR3 (p<0.01) and CCR7 (p<0.05) compared to HC - suggestive of DC migration from the periphery to the synovium. Following RNA-seq analysis, IPA and differentially expressed gene (DEG) analysis revealed an enrichment in genes involved in DC maturation, TLR signalling and chemokine signalling in IA peripheral blood compared to HC. In support of the hypothesis that DC migrate and accumulate in the IA synovium, CD1c+ DC were identified in IA ST and were significantly enriched compared to IA peripheral blood (p<0.01). IA ST CD1c+DC express significantly higher levels of the activation marker CD80 compared to IA peripheral blood (p<0.05) or HC ST (p<0.05). Upon examination of IA synovial fluid, we report similar findings to ST, whereby CD1c+DC are enriched in synovial fluid compared to PB (p<0.001). Moreover, RNA sequencing and PCA analysis of synovial versus blood CD1c+DC revealed distinct transcriptional variation between both sites. Functionally, synovial CD1c+DC express higher levels of the maturation markers CD80, CD83, CD40, PD-L1 and BTLA (all p<0.05) and have distinct coexpression of these maturation markers which is unique to the synovium. Synovial CD1c+DC are less phagocytic compared to peripheral blood DC, have decreased production of MMP1 and MMP9 and importantly are still capable of additional activation in-vitro. Finally, synovial CD1c+DC induce the proinflammatory cytokines TNFα, GMCSF, IL-17a and IFNγ from CD4+ T-cells in allogeneic DC: T cells cocultures.

Conclusion:

Mature circulatory CD1c+DC migrate and accumulate in the IA synovium. Synovial DC are present in the IA synovium in a mature state, have distinct tissue specific characteristics and can induce proinflammatory CD4+T cell responses.

Acknowledgements:

We would like to thank all the patients who contributed to this study

Disclosure of Interests:

Mary Canavan: None declared, Viviana Marzaioli: None declared, Vipul Bhargava Employee of: Janssen Research and Development, Sunil Nagpal Employee of: Janssen Research and Development, Phil Gallagher: None declared, Conor Hurson: None declared, Ronan Mullan: None declared, Douglas Veale Speakers bureau: Abbvie, Janssen, Novartis, Pfizer, MSD, UCB, Consultant of: Abbvie, Janssen, Novartis, Pfizer, MSD, UCB, Grant/research support from: Pfizer, Janssen, AbbVie, UCB, Ursula Fearon Speakers bureau: Abbvie, Grant/research support from: Pfizer, Janssen, Abbvie, UCB

AB0916-PARE KNOWLEDGE OF DISEASE, DIAGNOSIS, ADHERENCE AND IMPACT OF RESEARCH IN PATIENTS WITH INFLAMMATORY ARTHRITIS

Background:

The diagnosis and treatment of inflammatory arthritis has been transformed largely by the development of drugs that target specific molecules of the immune system. However, these changes have increased the complexity of the mechanisms of disease, its treatment and patients understanding. Patient education is needed in this area to facilitate decision making and to facilitate strong patient-partnerships in research.

Objectives:

The aim of this study was to examine the level of understanding of inflammatory arthritis patients and the need for strong patient-partnership in research.

Methods:

An online anonymous survey addressed questions about diagnosis, routine tests, medications and how they work, medication adherence, disease flare, heredity, pregnancy, and patient involvement in research.

Results:

There were 1,873 respondents, 1416 of which had inflammatory arthritis (IA)-RA (65.8%) and PsA (34.2%). They were predominantly female (RA 86%, PsA 85 %), aged 55±13 and 50±12. Less than 35% of patients had an understanding of diagnostic tests, what was measured and the implication for disease, with 75.5% also concerned about heredity. There was a high level of understanding of how specific medications treat inflammatory arthritis (72.9%). Adherence was also very high (>87%), with the main reasons for stopping medication without the advice of their clinician, ‘feeling better’ and ‘side effects’ however a significant proportion of patients (69.9%) reported a disease-flare following cessation of medication. Patients of childbearing age (69%) were also concerned that inflammatory arthritis reduced their chances of getting pregnant, with only 8% believing arthritis medications were safe to take during pregnancy. Finally, only 9% of patients had ever been asked to participate in a research study.

Conclusion:

This study demonstrates a need for the development of stronger patient-partnerships with clinicians and researchers in relation to patient education and engagement with research, to create a platform where patients can have meaningful input and involvement in future research studies.

Acknowledgements:

We wish to thank all the patients who contributed to this study

Disclosure of Interests:

Mary Canavan: None declared, Viviana Marzaioli: None declared, Alex Donnelly: None declared, Siobhan Wade: None declared, Alexander Fraser: None declared, Tim O’Sullivan: None declared, Sinead Harney: None declared, Arthritis Ireland: None declared, Douglas Veale Speakers bureau: Abbvie, Janssen, Novartis, MSD, Pfizer, UCB, Consultant of: Abbvie, Janssen, Novartis, MSD, Pfizer, UCB, Grant/research support from: Janssen, Abbvie, Pfizer, UCB, Ursula Fearon Speakers bureau: Abbvie, Grant/research support from: Janssen, Abbvie, Pfizer, UCB

POS0411 TARGETING JAK-STAT SIGNALLING ALTERS THE PHENOTYPIC CHARACTERISTICS OF PsA SYNOVIAL FIBROBLASTS IN RESPONSE TO THE JAK/STAT ACTIVATOR ONCOSTATIN M

Background:

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis. The JAK/STAT pathway has been linked to the pathogenesis of PsA. Recently, JAK/STAT inhibitors (JAKi) have emerged as an encouraging class of drugs for the treatment of PsA. Only a few of these inhibitors have been approved for use in PsA patients with others currently in clinical trials.

Objectives:

The aim of this study was to examine the effect of JAKi on primary PsA synovial fibroblasts (FLS) function.

Methods:

Primary PsA FLS were isolated and cultured with JAKi (Peficitinib, Filgotinib, Baricitinib and Upadacitinib) in the presence of the pro-inflammatory JAK/STAT activator - Oncostatin M (OSM). The effect of JAKi on these cells was determined by Migration and Invasion Assays, ELISA and rtPCR. PsA FLS bioenergetics was assessed using an XF24 analyser, which simultaneously quantifies two energetic pathways- glycolysis (ECAR) and Oxidative phosphorylation (OCR).

Results:

OSM-induced Migration and Invasion was supressed by all JAKi with Peficitinib, Filgotinib and Baracitinib showing the greatest effect. Analysis by ELISA and rtPCR showed reduction in MCP-1 and IL-6 expression in response to JAKi, in contrast, an increase in IL-8 was observed. These functional effects were accompanied by a change in the cellular bioenergetic profile of PsA FLS, where OSM significantly increased the ECAR:OCR ratio in favour of glycolysis where PsA FLS displayed a hypermetabolic phenotype. This effect was reversed in the presence of JAKi, which specifically targeted the glycolytic pathway with PsA FLS returning to a more quiescent phenotype.

Conclusion:

This study demonstrates that JAK/STAT signalling mediates the complex interplay between inflammation and cellular metabolism in PsA pathogenesis, inhibition of which shows effective suppression of the pathogenic phenotype of PsA FLS that drives joint destruction.

References:

[1]Chen M, Dai SM. A novel treatment for psoriatic arthritis: Janus kinase inhibitors. Chin Med J (Engl). 2020;133(8):959-967.

Disclosure of Interests:

Aisling O’ Brien: None declared, Megan Hanlon: None declared, Viviana Marzaioli: None declared, Keelin Flynn: None declared, Siobhan Wade: None declared, Douglas Veale Speakers bureau: Abbvie, Janssen, Novartis, MSD, Pfizer, UCB, Consultant of: Abbvie, Janssen, Novartis, MSD, Pfizer, UCB, Grant/research support from: Janssen, Abbvie, Pfizer, UCB, Ursula Fearon Speakers bureau: Abbvie, Grant/research support from: Janssen, Abbvie, Pfizer, UCB

OP0025 CD209+/CD14+ DENDRITIC CELLS ARE ENRICHED AND ACTIVATED AT THE SITE OF INFLAMMATION AND ARE MODULATED BY JAK/STAT SIGNALLING

Background:

Dendritic cells (DCs) are a heterogeneous population of professional antigen-presenting cells which are at the interface between innate and adaptive immunity. A specific subset of DCs is known to derive from monocyte and has a key role in inflammation and infection.

Objectives:

This study aimed to characterize the phenotype and function of a distinct CD209+/CD14+ DC subset in the periphery and at the site of inflammation in patients with rheumatoid (RA) and psoriatic arthritic (PsA), in addition to examining the effect Tofacitinib and TNF inhibitor on their development.

Methods:

Peripheral blood and synovial fluid mononuclear cells (PBMC and SFMC) were isolated by Ficoll density gradient from healthy subject (HC), and patients with RA and PsA. Single cell synovial tissue suspension (ST) from RA and PsA patients were also established using enzymatic/mechanical digestion. PBMC, SFMC and ST were analysed by flow cytometry to identify the CD209+/CD14+ DC subset, its frequency and the cell surface expression of chemokines receptors (CCR6, CCR7, CXCR3, CXCR4 and CXCR5) and activation markers (CD40 and CD80). In addition, PBMC were stimulated with different TLR (LPS, CPG, R848, Poly I:C) and intracellular staining for IL12, TNFα, IL1β and IL6 was performed by flow cytometry. Lineage negative cells (CD3/CD19/CD56-) were stimulate with GMCSF/IL4 in the presence or absence of the JAK/STAT inhibitor Tofacitinib or the TNF inhibitor Humira, and the CD209+/CD14+ DC development was evaluated by flow cytometry.

Results:

We identified, for the first time, a distinct CD209+/CD14+ DC population in PBMC of patients with RA and PsA, with similar frequency across the groups. However, when PBMC were stimulated with TLRs, an increase of IL12 and TNFα was observed in RA and PsA PBMC when compared to HC. Interestingly, this distinct DC population was significantly enriched at the site of inflammation, in both SFMC and ST, displaying a more mature phenotype, evident by the observed significant increase in CD40 and CD80 expression. SPICE analysis further identified differential expression and co-expression of chemokine receptors at the periphery of RA and PsA patients, when compared to the HC. Furthermore synovial tissue single cell analysis from RA/PsA demonstrated a unique chemokines receptors profile demonstrating increased single expression and co-expression of CXCR3 and CXCR5 compared to periphery. Finally, we have previously observed that JAK/STAT is involved in monocyte-derived dendritic cells population development (1,2), therefore we performed CD3, CD19 and CD56 depletion of RA/PsA PBMC followed by stimulation with GMCSF/IL4, to spike the Mo-DC population, in the presence of Tofacitinib or Humira. Interestingly, we observed that JAK/STAT inhibition, but not TNF inhibitor, reduced the generation and development of CD209+/CD14+ DC.

Conclusion:

We identify for the first time a distinct monocyte-derived DC population characterized as CD209+/CD14+ in the periphery of RA and PsA patients. This population was enriched at the site of inflammation and displayed a unique chemokine receptor profile and activation markers, suggesting that these cells are already activated in the periphery of IA patients, and are recruited and further activated in the inflamed joint. In addition, we showed that the CD209+/CD14+ DC development is regulated by JAK/STAT signalling, but not TNF inhibition.

References:

[1]Marzaioli V, Canavan M, Floudas A, et al. Monocyte-Derived Dendritic Cell Differentiation in Inflammatory Arthritis Is Regulated by the JAK/STAT Axis via NADPH Oxidase Regulation. Front. Immunol. 2020;11:1406.

[2]Marzaioli V, Hurtado-Nedelec M, Pintard C, et al. NOX5 and p22phox are 2 novel regulators of human monocytic differentiation into dendritic cells. Blood. 2017;130(15):1734–1745.

Acknowledgements:

The authors also wish to thank all the patients who volunteered to participate into this study and the funding

Disclosure of Interests:

Viviana Marzaioli: None declared, Achilleas Floudas: None declared, Mary Canavan: None declared, Siobhan Wade: None declared, Kieran Murray: None declared, Ronan Mullan: None declared, Douglas Veale Speakers bureau: Abbvie, Janssen, Novartis, MSD, Pfizer, UCB, Consultant of: Abbvie, Janssen, Novartis, MSD, Pfizer, UCB, Grant/research support from: Janssen, Abbvie, Pfizer, UCB, Ursula Fearon Speakers bureau: Abbvie, Grant/research support from: Janssen, Abbvie, Pfizer, UCB

Rheumatoid arthritis synovial microenvironment induces metabolic and functional adaptations in dendritic cells

Rheumatoid arthritis (RA) is a chronic autoimmune disease which causes degradation of cartilage and bone. It is well appreciated that the pathogenic hallmark of RA is the mass influx of inflammatory cells into the joint. However, the role that dendritic cells (DC) may play in this inflammatory milieu is still relatively unexplored. Moreover, the contribution this unique synovial microenvironment has on DC maturation is still unknown. Using monocyte-derived DC (MoDC), we established an in-vitro model to recapitulate the synovial microenvironment to explore DC maturation. MoDC treated with conditioned media from ex-vivo synovial tissue biopsy cultures [explant-conditioned media (ECM)] have increased expression of proinflammatory cytokines, chemokines and adhesion molecules. ECM DC have increased expression of CD83 and CC-chemokine receptor (CCR)7 and decreased expression of CCR5 and phagocytic capacity, suggestive of heightened DC maturation. ECM-induced maturation is concomitant with altered cellular bioenergetics, whereby increased expression of glycolytic genes and increased glucose uptake are observed in ECM DC. Collectively, this results in a metabolic shift in DC metabolism in favour of glycolysis. These adaptations are in-part mediated via signal transducer and activator of transcription-3 (STAT-3), as demonstrated by decreased expression of proinflammatory cytokines and glycolytic genes in ECM DC in response to STAT-3 inhibition. Finally, to translate these data to a more in-vivo clinically relevant setting, RNA-seq was performed on RA synovial fluid and peripheral blood. We identified enhanced expression of a number of glycolytic genes in synovial CD1c+ DC compared to CD1c+ DC in circulation. Collectively, our data suggest that the synovial microenvironment in RA contributes to DC maturation and metabolic reprogramming.

Vasoactive intestinal peptide dampens formyl-peptide-induced ROS production and inflammation by targeting a MAPK-p47phox phosphorylation pathway in monocytes

Reactive oxygen species (ROS) produced by the phagocyte NADPH oxidase (NOX2) are required for microbial clearance; however, when produced in excess they exacerbate inflammatory response and injure surrounding tissues. NOX2 is a multicomponent enzyme composed of membrane-associated cytochrome b588 and cytosolic components p47^phox, p67^phox, p40^phox, and rac1/2. We investigated whether vasoactive intestinal peptide (VIP), an endogenous immune-modulatory peptide, could affect ROS production by NOX2 in primary human phagocytes. VIP did not modulate basal ROS production by phagocytes, but it inhibited monocyte and not neutrophil ROS production in response to the bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLF). The action of VIP was essentially mediated by high-affinity G-protein coupled receptors VPAC1 as its specific agonist, [ALA^11,22,28]VIP, mimicked VIP-inhibitory effect, whereas the specific VPAC1 antagonist, PG97-269, blunted VIP action. Further, we showed that VIP inhibited fMLF-induced phosphorylation of ERK1/2 (extracellular signal-regulated kinase 1/2), p38MAPK (p38 mitogen-activated protein kinase) pathways, and phosphorylation of p47^phox on Ser345 residue. Also, VIP exerted an anti-inflammatory effect in a model of carrageenan-induced inflammation in rats. We thus found that VIP exerts anti-inflammatory effects by inhibiting the "MAPK-p47^phox phosphorylation-NOX2 activation" axis. These data suggest that VIP acts as a natural anti-inflammatory agent of the mucosal system and its analogs could be novel anti-inflammatory molecules.

Zn2+ Slows Down CaV3.3 Gating Kinetics: Implications for Thalamocortical Activity

We employed whole cell patch-clamp recordings to establish the effect of Zn2+ on the gating the brain specific, T-type channel isoform CaV3.3 expressed in HEK-293 cells. Zn2+ (300 μM) modified the gating kinetics of this channel without influencing its steady-state properties. When inward Ca2+ currents were elicited by step depolarizations at voltages above the threshold for channel opening, current inactivation was significantly slowed down while current activation was moderately affected. In addition, Zn2+ slowed down channel deactivation but channel recovery from inactivation was only modestly changed. Zn2+ also decreased whole cell Ca2+ permeability to 45% of control values. In the presence of Zn2+, Ca2+ currents evoked by mock action potentials were more persistent than in its absence. Furthermore, computer simulation of action potential generation in thalamic reticular cells performed to model the gating effect of Zn2+ on T-type channels (while leaving the kinetic parameters of voltage-gated Na+ and K+ unchanged) revealed that Zn2+ increased the frequency and the duration of burst firing, which is known to depend on T-type channel activity. In line with this finding, we discovered that chelation of endogenous Zn2+ decreased the frequency of occurrence of ictal-like epileptiform discharges in rat thalamocortical slices perfused with medium containing the convulsant 4-aminopyridine (50 μM). These data demonstrate that Zn2+ modulates CaV3.3 channel gating thus leading to increased neuronal excitability. We also propose that endogenous Zn2+ may have a role in controlling thalamocortical oscillations.