A System Out of Breath: How Hypoxia Possibly Contributes to the Pathogenesis of Systemic Sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by vascular alterations and immunological disturbances and fibrosis, the order of which remains to be fully determined. Clinically, patients show clear signs of hypoxia in skin and internal organs. The low oxygen tension is potentially caused by a yet to be indentified circuitry involving the three features that typify SSc. In addition, once present, the hypoxia creates a vicious circle of ongoing pathology. In this paper, we provide an overview of the evidence that points towards the mechanisms causing hypoxia in SSc. In addition, data that suggest how hypoxia itself may orchestrate worsening of symptoms is presented. Altogether, it is clear that hypoxia is an important hallmark in SSc patients. By providing an overview of the mechanisms at play and the possible therapeutic avenues that have emerged, we hope to stimulate researchers to provide novel clues into the conundrum in SSc patients

Serum miRNAs as potential biomarkers for the bronchiolitis obliterans syndrome after lung transplantation

Lung transplantation (LTx) is the last treatment for patients suffering from end-stage lung diseases. Survival post-LTx is hampered by the development of the bronchiolitis obliterans syndrome (BOS) and diagnosis is often late. Given the urgent clinical need to recognize BOS patients at an early stage, we analyzed circulating miRNAs to identify possible stratification markers for BOS development post-transplantation. Therefore, pro-fibrotic (miR-21, miR-155), anti-fibrotic (miR-29a) and fibrosis-unrelated (miR-103, miR-191) miRNAs were analyzed in serum of end-stage lung disease patients and during LTx follow-up.Significant elevated levels of serum miRNAs were observed for all investigated miRNAs in both chronic obstructive pulmonary disease and interstitial lung disease patients compared to healthy controls. The same miRNAs were also significantly increased in the serum of BOS + vs. BOS - patients. Most importantly, miR-21, miR-29a, miR-103, and miR-191 levels were significantly higher in BOS + patients prior to clinical BOS diagnosis.We demonstrated that a selected group of miRNAs investigated is elevated in end-stage lung disease and BOS + patients, prior to clinical BOS diagnosis. Even if further research is expedient on the prognostic value of circulating miRNAs in BOS and lung conditions in general, these results strongly suggest that circulating miRNAs could be used as potential biomarkers for BOS development

Promotion of macrophage activation by Tie2 in the context of the inflamed synovia of rheumatoid arthritis and psoriatic arthritis patients

OBJECTIVE: To examine the role of Tie2 signalling in macrophage activation within the context of the inflammatory synovial microenvironment present in patients with RA and PsA. METHODS: Clinical responses and macrophage function were examined in wild-type and Tie2-overexpressing (Tie2-TG) mice in the K/BxN serum transfer model of arthritis. Macrophages derived from peripheral blood monocytes from healthy donors, RA and PsA patients, and RA and PsA synovial tissue explants were stimulated with TNF (10 ng/ml), angiopoietin (Ang)-1 or Ang-2 (200 ng/ml), or incubated with an anti-Ang2 neutralizing antibody. mRNA and protein expression of inflammatory mediators was analysed by quantitative PCR, ELISA and Luminex. RESULTS: Tie2-TG mice displayed more clinically severe arthritis than wild-type mice, accompanied by enhanced joint expression of IL6, IL12B, NOS2, CCL2 and CXCL10, and activation of bone marrow-derived macrophages in response to Ang-2 stimulation. Ang-1 and Ang-2 significantly enhanced TNF-induced expression of pro-inflammatory cytokines and chemokines in macrophages from healthy donors differentiated with RA and PsA SF and peripheral blood-derived macrophages from RA and PsA patients. Both Ang-1 and Ang-2 induced the production of IL-6, IL-12p40, IL-8 and CCL-3 in synovial tissue explants of RA and PsA patients, and Ang-2 neutralization suppressed the production of IL-6 and IL-8 in the synovial tissue of RA patients. CONCLUSION: Tie2 signalling enhances TNF-dependent activation of macrophages within the context of ongoing synovial inflammation in RA and PsA, and neutralization of Tie2 ligands might be a promising therapeutic target in the treatment of these diseases

Polymorphisms in the interleukin 4, interleukin 13 and corresponding receptor genes are not associated with systemic sclerosis and do not influence gene expression

n/

Patients with gout have short telomeres compared with healthy participants: association of telomere length with flare frequency and cardiovascular disease in gout

Aim and background Chronic inflammation associates with increased senescence, which is a strong predictor for cardiovascular disease. We hypothesised that inflammation accelerates senescence and thereby enhances the risk of cardiovascular disease in gout.Methods We assessed replicative senescence by quantifying telomere length (TL) in a discovery cohort of 145 Dutch patients with gout and 273 healthy individuals and validated our results in 474 patients with gout and 293 healthy participants from New Zealand. Subsequently, we investigated the effect of cardiovascular disease on TL of all participants. Also, we measured TL of CD4(+) and CD8(+) T lymphocytes, B lymphocytes, monocytes, natural killer cells and plasmacytoid dendritic cells. Additionally, we assessed the potential temporal difference in TL and telomerase activity.Results TL in PBMCs of healthy donors decreased over time, reflecting normal ageing. Patients with gout demonstrated shorter telomeres (p=0.001, R-2=0.01873). In fact, the extent of telomere erosion in patients with gout was higher at any age compared with healthy counterparts at any age (p<0.0001, R-2=0.02847). Patients with gout with cardiovascular disease had the shortest telomeres and TL was an independent risk factor for cardiovascular disease in patients with gout (p=0.001). TL was inversely associated with the number of gouty flares (p=0.005).Conclusions Patients with gout have shorter telomeres than healthy participants, reflecting increased cellular senescence. Telomere shortening was associated with the number of flares and with cardiovascular disease in people with gout

Testing for the association of the KIAA1109/Tenr/IL2/IL21 gene region with rheumatoid arthritis in a European family-based study

INTRODUCTION: A candidate gene approach, in a large case-control association study in the Dutch population, has shown that a 480 kb block on chromosome 4q27 encompassing KIAA1109/Tenr/IL2/IL21 genes is associated with rheumatoid arthritis. Compared with case-control association studies, family-based studies have the added advantage of controlling potential differences in population structure. Therefore, our aim was to test this association in populations of European origin by using a family-based approach. METHODS: A total of 1,302 West European white individuals from 434 trio families were genotyped for the rs4505848, rs11732095, rs6822844, rs4492018 and rs1398553 polymorphisms using the TaqMan Allelic discrimination assay (Applied Biosystems). The genetic association analyses for each SNP and haplotype were performed using the Transmission Disequilibrium Test and the genotype relative risk. RESULTS: We observed evidence for association of the heterozygous rs4505848-AG genotype with rheumatoid arthritis (P = 0.04); however, no significance was found after Bonferroni correction. In concordance with previous findings in the Dutch population, we observed a trend of undertransmission for the rs6822844-T allele and rs6822844-GT genotype to rheumatoid arthritis patients. We further investigated the five SNP haplotypes of the KIAA1109/Tenr/IL2/IL21 gene region. We observed, as described in the Dutch population, a nonsignificant undertransmission of the AATGG haplotype to rheumatoid arthritis patients. CONCLUSIONS: Using a family-based study, we have provided a trend for the association of the KIAA1109/Tenr/IL2/IL21 gene region with rheumatoid arthritis in populations of European descent. Nevertheless, we failed to replicate a significant association of this region in our rheumatoid arthritis family sample. Further investigation of this region, including detection and testing of all variants, is required to confirm rheumatoid arthritis association

Comprehensive analysis of the major histocompatibility complex in systemic sclerosis identifies differential HLA associations by clinical and serological subtypes

Objective: The greatest genetic effect reported for systemic sclerosis (SSc) lies in the major histocompatibility complex (MHC) locus. Leveraging the largest SSc genome-wide association study, we aimed to fine-map this region to identify novel human leucocyte antigen (HLA) genetic variants associated with SSc susceptibility and its main clinical and serological subtypes. Methods: 9095 patients with SSc and 17 584 controls genome-wide genotyped were used to impute and test single-nucleotide polymorphisms (SNPs) across the MHC, classical HLA alleles and their composite amino acid residues. Additionally, patients were stratified according to their clinical and serological status, namely, limited cutaneous systemic sclerosis (lcSSc), diffuse cutaneous systemic sclerosis (dcSSc), anticentromere (ACA), antitopoisomerase (ATA) and anti-RNApolIII autoantibodies (ARA). Results: Sequential conditional analyses showed nine SNPs, nine classical alleles and seven amino acids that modelled the observed associations with SSc. This confirmed previously reported associations with HLA-DRB1*11:04 and HLA-DPB1*13:01, and revealed a novel association of HLA-B*08:01. Stratified analyses showed specific associations of HLA-DQA1*02:01 with lcSSc, and an exclusive association of HLA-DQA1*05:01 with dcSSc. Similarly, private associations were detected in HLA-DRB1*08:01 and confirmed the previously reported association of HLA-DRB1*07:01 with ACA-positive patients, as opposed to the HLA-DPA1*02:01 and HLA-DQB1*03:01 alleles associated with ATA presentation. Conclusions: This study confirms the contribution of HLA class II and reveals a novel association of HLA class I with SSc, suggesting novel pathways of disease pathogenesis. Furthermore, we describe specific HLA associations with SSc clinical and serological subtypes that could serve as biomarkers of disease severity and progression.Funding: This work was supported by the Spanish Ministry of Science and Innovation (grant ref. SAF2015-66761-P and RTI20181013 (32-B-100)), Red de Investigación en Inflamación y Enfermedades Reumáticas from Instituto de Salud Carlos III (RD16/0012/0013) and grants from National Institutes of Health (R01AR073284) and DoD (W81XWH-16-1-0296). MAH was funded by the Spanish Ministry of Science and Innovation through the Juan de la Cierva Incorporacion program (ref. IJC2018-035131-I). GO, AB and ALH were supported by the NIHR Manchester Biomedical Research Centre and Versus Arthritis (grant ref 21754)

Toll-Like Receptor 2 Induced Angiogenesis and Invasion Is Mediated through the Tie2 Signalling Pathway in Rheumatoid Arthritis

BACKGROUND: Angiogenesis is a critical early event in inflammatory arthritis, facilitating leukocyte migration into the synovium resulting in invasion and destruction of articular cartilage and bone. This study investigates the effect of TLR2 on angiogenesis, EC adhesion and invasion using microvascular endothelial cells and RA whole tissue synovial explants ex-vivo. METHODS: Microvascular endothelial cells (HMVEC) and RA synovial explants ex vivo were cultured with the TLR2 ligand, Pam3CSK4 (1 µg/ml). Angiopoietin 2 (Ang2), Tie2 and TLR2 expression in RA synovial tissue was assessed by immunohistology. HMVEC tube formation was assessed using Matrigel matrix assays. Ang2 was measured by ELISA. ICAM-1 cell surface expression was assessed by flow cytometry. Cell migration was assessed by wound repair scratch assays. ECM invasion, MMP-2 and -9 expression were assessed using transwell invasion chambers and zymography. To examine if the angiopoietin/Tie2 signalling pathway mediates TLR2 induced EC tube formation, invasion and migration assays were performed in the presence of a specific neutralising anti-Tie2mAb (10 ug/ml) and matched IgG isotype control Ab (10 ug/ml). RESULTS: Ang2 and Tie2 were localised to RA synovial blood vessels, and TLR2 was localised to RA synovial blood vessels, sub-lining infiltrates and the lining layer. Pam3CSK4 significantly increased angiogenic tube formation (p<0.05), and upregulated Ang2 production in HMVEC (p<0.05) and RA synovial explants (p<0.05). Pam3CSK4 induced cell surface expression of ICAM-1, from basal level of 149±54 (MFI) to 617±103 (p<0.01). TLR-2 activation induced an 8.8±2.8 fold increase in cell invasion compared to control (p<0.05). Pam3CSK4 also induced HMVEC cell migration and induced MMP-2 and -9 from RA synovial explants. Neutralisation of the Ang2 receptor, Tie2 significantly inhibited Pam3CSK4-induced EC tube formation and invasion (p<0.05). CONCLUSION: TLR2 activation promotes angiogenesis, cell adhesion and invasion, effects that are in part mediated through the Tie2 signalling pathway, key mechanisms involved in the pathogenesis of RA