Association between increased CCL2 (MCP-1) expression in lesions and persistence of disease activity in giant-cell arteritis*

Decoding CD4+ T cell transcriptome in giant cell arteritis: Novel pathways and altered cross-talk with monocytes

BACKGROUND

Giant cell arteritis (GCA) is an immune-mediated large-vessels vasculitis with complex etiology. Although the pathogenic mechanisms remain poorly understood, a central role for CD4+ T cells has been demonstrated. In this context, understanding the transcriptome dysregulation in GCA CD4+ T cells will yield new insights into its pathogenesis.

METHODS

Transcriptome analysis was conducted on CD4+ T cells from 70 patients with GCA with different disease activity and treatment status (active patients before treatment and patients in remission with and without glucocorticoid treatment), and 28 healthy controls. The study also evaluated potential impacts of DNA methylation on gene expression alterations and assessed cross-talk with CD14+ monocytes.

RESULTS

This study has uncovered a substantial number of genes and pathways potentially contributing to the pathogenicity of CD4+ T cells in GCA. Specifically, CD4+ T cells from GCA patients with active disease exhibited altered expression levels of genes involved in multiple immune-related processes, including various interleukins (IL) signaling pathways. Notably, IL-2, a decisive interleukin for regulatory T cells homeostasis, was among the most significant. Additionally, impaired apoptotic pathways appear crucial in GCA development. Our findings also suggest that histone-related epigenetic pathways may be implicated in promoting an inflammatory phenotype in GCA active patients. Finally, our study observed altered signaling communication, such as the Jagged-Notch signaling, between CD4+ T cells and monocytes that could have pathogenic relevance in GCA.

CONCLUSIONS

Our study suggests the participation of novel cytokines and pathways and the occurrence of a disruption of monocyte-T cell crosstalk driving GCA pathogenesis.

Current Insights into Tissue Injury of Giant Cell Arteritis: From Acute Inflammatory Responses towards Inappropriate Tissue Remodeling

Giant cell arteritis (GCA) is an autoimmune disease affecting large vessels in patients over 50 years old. It is an exemplary model of a classic inflammatory disorder with IL-6 playing the leading role. The main comorbidities that may appear acutely or chronically are vascular occlusion leading to blindness and thoracic aorta aneurysm formation, respectively. The tissue inflammatory bulk is expressed as acute or chronic delayed-type hypersensitivity reactions, the latter being apparent by giant cell formation. The activated monocytes/macrophages are associated with pronounced Th1 and Th17 responses. B-cells and neutrophils also participate in the inflammatory lesion. However, the exact order of appearance and mechanistic interactions between cells are hindered by the lack of cellular and molecular information from early disease stages and accurate experimental models. Recently, senescent cells and neutrophil extracellular traps have been described in tissue lesions. These structures can remain in tissues for a prolonged period, potentially favoring inflammatory responses and tissue remodeling. In this review, current advances in GCA pathogenesis are discussed in different inflammatory phases. Through the description of these-often overlapping-phases, cells, molecules, and small lipid mediators with pathogenetic potential are described.

Exploring the causal role of gut microbiota in giant cell arteritis: a Mendelian randomization analysis with mediator insights

Background

Giant Cell Arteritis (GCA) is a complex autoimmune condition. With growing interest in the role of gut microbiota in autoimmune diseases, this research aimed to explore the potential causal relationship between gut microbiota and GCA, and the mediating effects of specific intermediaries.

Methods

Using a bidirectional two-sample Mendelian randomization (MR) design, we investigated associations between 191 microbial taxa and GCA. A two-step MR technique discerned the significant mediators on this relationship, followed by Multivariable MR analyses to quantify the direct influence of gut microbiota on GCA and mediation effect proportion, adjusting for these mediators.

Results

Nine taxa displayed significant associations with GCA. Among them, families like Bacteroidales and Clostridiaceae1 had Odds Ratios (OR) of 1.48 (p=0.043) and 0.52 (p=5.51e-3), respectively. Genera like Clostridium sensu stricto1 and Desulfovibrio showed ORs of 0.48 (p=5.39e-4) and 1.48 (p=0.037), respectively. Mediation analyses identified 25 hydroxyvitamin D level (mediation effect of 19.95%), CD14+ CD16- monocyte counts (mediation effect of 27.40%), and CD4+ T cell counts (mediation effect of 28.51%) as significant intermediaries.

Conclusion

Our findings provide invaluable insights into the complex interplay between specific gut microbiota taxa and GCA. By highlighting the central role of gut microbiota in influencing GCA risk and long-term recurrence, and their interactions with vital immune mediators, this research paves the way for potential therapeutic interventions in GCA management.

Disease stratification in GCA and PMR: state of the art and future perspectives

Giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are closely related conditions characterized by systemic inflammation, a predominant IL-6 signature, an excellent response to glucocorticoids, a tendency to a chronic and relapsing course, and older age of the affected population. This Review highlights the emerging view that these diseases should be approached as linked conditions, unified under the term GCA-PMR spectrum disease (GPSD). In addition, GCA and PMR should be seen as non-monolithic conditions, with different risks of developing acute ischaemic complications and chronic vascular and tissue damage, different responses to available therapies and disparate relapse rates. A comprehensive stratification strategy for GPSD, guided by clinical findings, imaging and laboratory data, facilitates appropriate therapy and cost-effective use of health-economic resources. Patients presenting with predominant cranial symptoms and vascular involvement, who usually have a borderline elevation of inflammatory markers, are at an increased risk of sight loss in early disease but have fewer relapses in the long term, whereas the opposite is observed in patients with predominant large-vessel vasculitis. How the involvement of peripheral joint structures affects disease outcomes remains uncertain and understudied. In the future, all cases of new-onset GPSD should undergo early disease stratification, with their management adapted accordingly.

The role of autoimmunity and autoinflammation in giant cell arteritis: A systematic literature review

Giant cell arteritis is the most common form of large vessel vasculitis and preferentially involves large and medium-sized arteries in patients over the age of 50. Aggressive wall inflammation, neoangiogenesis and consecutive remodeling processes are the hallmark of the disease. Though etiology is unknown, cellular and humoral immunopathological processes are well understood. Matrix metalloproteinase-9 mediated tissue infiltration occurs through lysis of basal membranes in adventitial vessels. CD4+ cells attain residency in immunoprotected niches, differentiate into vasculitogenic effector cells and enforce further leukotaxis. Signaling pathways involve the NOTCH1-Jagged1 pathway opening vessel infiltration, CD28 mediated T-cell overstimulation, lost PD-1/PD-L1 co-inhibition and JAK/STAT signaling in interferon dependent responses. From a humoral perspective, IL-6 represents a classical cytokine and potential Th-cell differentiator whereas interferon-γ (IFN- γ) has been shown to induce chemokine ligands. Current therapies involve glucocorticoids, tocilizumab and methotrexate application. However, new agents, most notably JAK/STAT inhibitors, PD-1 agonists and MMP-9 blocking substances, are being evaluated in ongoing clinical trials.

Changes in the molecular profiles of large-vessel vasculitis treated with biological disease-modifying anti-rheumatic drugs and Janus kinase inhibitors

Giant cell arteritis and Takayasu arteritis are two types of primary large-vessel vasculitis (LVV). Although glucocorticoids (GC) are the standard treatment for LVV, the disease relapse rates are high. Recent clinical trials on biological disease-modifying anti-rheumatic drugs (bDMARDs) and Janus kinase (JAK) inhibitors have demonstrated their efficacy in reducing LVV relapse rates and GC dosages. However, the control of residual inflammation and degenerative alterations in the vessel wall remains an outstanding requirement in the clinical management of LVV. The analysis of immune cell phenotypes in patients with LVV may predict their response to treatment with bDMARDs and JAK inhibitors and guide their optimal use. In this mini-review, we focused on molecular markers, including the immune cell proportions and gene expression, in patients with LVV and in mouse models of LVV treated with bDMARDs and JAK inhibitors.

Epidemiology and predictors of relapse in giant cell arteritis: A systematic review and meta-analysis

OBJECTIVES

The aim of this study was to estimate the timing of relapse, the prevalence of multiple relapses and the predictors of relapse in patients with giant cell arteritis (GCA).

METHODS

PubMed, Embase and Cochrane databases were searched from inception till November, 30 2021. Outcome measures include cumulative relapse rate (CRR) of first relapse at year 1, 2, and 5 after treatment initiation, CRR of second and third relapse and predictors of relapse.

RESULTS

Thirty studies (2595 patients) were included for timing of relapse, 16 studies (1947 patients) for prevalence of multiple relapses and 40 studies (4213 patients) for predictors of relapse. One-year, 2-year and 5-year CRRs were 32% [95% confidence interval (CI) 22-43%], 44% [95% CI 31-59%], and 47% [95% CI 27-67%], respectively. The duration of scheduled glucocorticoid therapy was negatively associated with the 1-year CRR (P=0.03). CRR of second and third relapse were 30% [95% CI 21-40] and 17% [95% CI 8-33%], respectively. Female sex (OR 1.43) and large vessel involvement (OR 2.04) were predictors of relapse.

CONCLUSION

Relapse occurred in almost half of GCA patients mainly during the first two years after diagnosis. One in three patients had multiple relapses. The optimal glucocorticoid tapering schedule, which seeks a balance between the lowest relapse risk and the shortest glucocorticoid duration, needs to be determined in future studies. Longer scheduled glucocorticoid therapy or early introduction of glucocorticoid-sparing agents may be warranted in female patients and patients with large vessel involvement.

Human monocyte-derived suppressive cells (HuMoSC) for cell therapy in giant cell arteritis

Introduction

The pathogenesis of Giant Cell Arteritis (GCA) relies on vascular inflammation and vascular remodeling, the latter being poorly controlled by current treatments.

Methods

This study aimed to evaluate the effect of a novel cell therapy, Human Monocyte-derived Suppressor Cells (HuMoSC), on inflammation and vascular remodeling to improve GCA treatment. Fragments of temporal arteries (TAs) from GCA patients were cultured alone or in the presence of HuMoSCs or their supernatant. After five days, mRNA expression was measured in the TAs and proteins were measured in culture supernatant. The proliferation and migration capacity of vascular smooth muscle cells (VSMCs) were also analyzed with or without HuMoSC supernatant.

Results

Transcripts of genes implicated in vascular inflammation (CCL2, CCR2, CXCR3, HLADR), vascular remodeling (PDGF, PDGFR), angiogenesis (VEGF) and extracellular matrix composition (COL1A1, COL3A1 and FN1) were decreased in arteries treated with HuMoSCs or their supernatant. Likewise, concentrations of collagen-1 and VEGF were lower in the supernatants of TAs cultivated with HuMoSCs. In the presence of PDGF, the proliferation and migration of VSMCs were both decreased after treatment with HuMoSC supernatant. Study of the PDGF pathway suggests that HuMoSCs act through inhibition of mTOR activity. Finally, we show that HuMoSCs could be recruited in the arterial wall through the implication of CCR5 and its ligands.

Conclusion

Altogether, our results suggest that HuMoSCs or their supernatant could be useful to decrease vascular in flammation and remodeling in GCA, the latter being an unmet need in GCA treatment.

Pathogenic role of monocytes/macrophages in large vessel vasculitis

Vasculitis is an autoimmune vascular inflammation with an unknown etiology and causes vessel wall destruction. Depending on the size of the blood vessels, it is classified as large, medium, and small vessel vasculitis. A wide variety of immune cells are involved in the pathogenesis of vasculitis. Among these immune cells, monocytes and macrophages are functionally characterized by their capacity for phagocytosis, antigen presentation, and cytokine/chemokine production. After a long debate, recent technological advances have revealed the cellular origin of tissue macrophages in the vessel wall. Tissue macrophages are mainly derived from embryonic progenitor cells under homeostatic conditions, whereas bone marrow-derived circulating monocytes are recruited under inflammatory conditions, and then differentiate into macrophages in the arterial wall. Such macrophages infiltrate into an otherwise immunoprotected vascular site, digest tissue matrix with abundant proteolytic enzymes, and further recruit inflammatory cells through cytokine/chemokine production. In this way, macrophages amplify the inflammatory cascade and eventually cause tissue destruction. Recent studies have also demonstrated that monocytes/macrophages can be divided into several subpopulations based on the cell surface markers and gene expression. In this review, the subpopulations of circulating monocytes and the ontogeny of tissue macrophages in the artery are discussed. We also update the immunopathology of large vessel vasculitis, with a special focus on giant cell arteritis, and outline how monocytes/macrophages participate in the disease process of vascular inflammation. Finally, we discuss limitations of the current research and provide future research perspectives, particularly in humans. Through these processes, we explore the possibility of therapeutic strategies targeting monocytes/macrophages in vasculitis.

New Insights into the Pathogenesis of Giant Cell Arteritis: Mechanisms Involved in Maintaining Vascular Inflammation

The giant cell arteritis (GCA) pathophysiology is complex and multifactorial, involving a predisposing genetic background, the role of immune aging and the activation of vascular dendritic cells by an unknown trigger. Once activated, dendritic cells recruit CD4 T cells and induce their activation, proliferation and polarization into Th1 and Th17, which produce interferon-gamma (IFN-γ) and interleukin-17 (IL-17), respectively. IFN-γ triggers the production of chemokines by vascular smooth muscle cells, which leads to the recruitment of additional CD4 and CD8 T cells and also monocytes that differentiate into macrophages. Recent data have shown that IL-17, IFN-γ and GM-CSF induce the differentiation of macrophage subpopulations, which play a role in the destruction of the arterial wall, in neoangiogenesis or intimal hyperplasia. Under the influence of different mediators, mainly endothelin-1 and PDGF, vascular smooth muscle cells migrate to the intima, proliferate and change their phenotype to become myofibroblasts that further proliferate and produce extracellular matrix proteins, increasing the vascular stenosis. In addition, several defects in the immune regulatory mechanisms probably contribute to chronic vascular inflammation in GCA: a defect in the PD-1/PD-L1 pathway, a quantitative and qualitative Treg deficiency, the implication of resident cells, the role of GM-CSF and IL-6, the implication of the NOTCH pathway and the role of mucosal‑associated invariant T cells and tissue‑resident memory T cells.

Functionally Heterogenous Macrophage Subsets in the Pathogenesis of Giant Cell Arteritis: Novel Targets for Disease Monitoring and Treatment

Giant cell arteritis (GCA) is a granulomatous large-vessel vasculitis that affects adults above 50 years of age. In GCA, circulating monocytes are recruited to the inflamed arteries. With cues from the vascular microenvironment, they differentiate into macrophages and play important roles in the pathogenesis of GCA via pro-inflammatory cytokine production and vascular remodeling. However, a deeper understanding of macrophage heterogeneity in GCA pathogenesis is needed to assist the development of novel diagnostic tools and targeted therapies. Here, we review the current knowledge on macrophage heterogeneity and diverse functions of macrophage subsets in the pathogenesis of GCA. We next discuss the possibility to exploit their heterogeneity as a source of novel biomarkers and as targets for nuclear imaging. Finally, we discuss novel macrophage-targeted therapies and future directions for targeting these cells in GCA.

High expression of pro-inflammatory cytokine genes IL-1β and IL-1R2 upon TLR4 activation in Takayasu arteritis

Toll-like receptors (TLR) 4 and its endogenous ligands are highly expressed in aorta. In the present study, we have explored the effect of TLR-4 activation by pro-inflammatory and angiogenic factors in PBMCs of patients with Takayasu Arteritis (TA). In the screening cohort, PBMCs of TA (n = 6) and healthy controls (n = 6) were stimulated with LPS and cultured. mRNA expression of 84 genes were quantitated by RT2 Profiler™ PCR Array kit in PBMCs. Validation set of additional PBMCs from TA (n = 7) and healthy controls [HC) (n = 7) were then stimulated with LPS to study expression of selected genes with delta Ct > 0.1 in the screening cohort. Significant gene expressions were correlated with Indian Takayasu arteritis activity scores (ITAS 2010). Increased expression of CCL2 was observed only in unstimulated PBMCs of patients with TA [median relative difference (RD) of 2.37] as compared to HC (RD 1.37, p < 0.03) in validation cohort, while stimulation with TLR4 ligand led to increased mRNA expression of IL-1β (RD 7.9, p < 0.028) and IL-1R2 (RD 0.08 p < 0.013) genes as compared to that of HC [RD of 5.32 for IL-1β and 0.01 for IL-1R2, respectively] in validation cohort. TLR4 activation also led to significantly higher expression of HPSE, TIMP1 and low expression of VEGFB, S1PR1, SERPINF1, ANGPLT4, ANGPT2, TIE1 and NOS3 genes in the screening cohort. But expression of VEGFB was not significant in validation cohort. The significant gene expressions, however, did not correlate with ITAS [ITAS2010 and ITAS-A (CRP)]. TLR4 activation leads to increased expression of IL-1β and IL-1R2 genes in PBMCs of patients with TA.

[Physiopathology of giant cell arteritis: From inflammation to vascular remodeling]

Giant cell arteritis (GCA) is a large-vessel vasculitis involving the aorta and its main branches, especially supra aortic branches. Although much progress has been made, the pathophysiology remains incompletely understood. An initial trigger, suspected of infectious origin, lead to the maturation and recruitment of dendritic cells (DC). The lack of migration of these DC allows the local recruitment of T-lymphocytes (LT). These LT- CD4⁺ polarize in Type 1 helper (Th1), Th17 but also Th9. A qualitative and quantitative deficit in regulatory T cells (Treg) is observed under the influence of IL-21 overproduction. In addition, an imbalance in the Th17/Treg balance is favored by IL-6. The secretion of IFN-γ, IL-17, IL-6, IL-33 is responsible for a sustained local inflammatory reaction that is organized around tertiary lymphoid follicles. Locally recruited macrophages secrete reactive forms of oxygen together with VEGF and PDGF. These growth factors, together with neurotrophins and endothelin contribute to increase the proliferation of vascular smooth muscle cells (VSMCs). The imbalance between matrix metalloproteases (MMP)-2, MMP-9 and MMP-14 and tissue inhibitors of metalloproteases (TIMP)-1 and TIMP-2 also contribute to the remodeling process occurring in the vessel wall. Finally, arterial neovascularization contribute to the perpetuation of lymphocyte recruitment. This persistent remodeling is sometimes complicated by ischemic events responsible for the initial severity of the disease.

Systematic literature review informing the 2018 update of the EULAR recommendation for the management of large vessel vasculitis: focus on giant cell arteritis

Objectives

To analyse the current evidence for the management of large vessel vasculitis (LVV) to inform the 2018 update of the EULAR recommendations.

Methods

Two systematic literature reviews (SLRs) dealing with diagnosis/monitoring and treatment strategies for LVV, respectively, were performed. Medline, Embase and Cochrane databases were searched from inception to 31 December 2017. Evidence on imaging was excluded as recently published in dedicated EULAR recommendations. This paper focuses on the data relevant to giant cell arteritis (GCA).

Results

We identified 287 eligible articles (122 studies focused on diagnosis/monitoring, 165 on treatment). The implementation of a fast-track approach to diagnosis significantly lowers the risk of permanent visual loss compared with historical cohorts (level of evidence, LoE 2b). Reliable diagnostic or prognostic biomarkers for GCA are still not available (LoE 3b).The SLR confirms the efficacy of prompt initiation of glucocorticoids (GC). There is no high-quality evidence on the most appropriate starting dose, route of administration, tapering and duration of GC (LoE 4). Patients with GCA are at increased risk of dose-dependent GC-related adverse events (LoE 3b). The addition of methotrexate or tocilizumab reduces relapse rates and GC requirements (LoE 1b). There is no consistent evidence that initiating antiplatelet agents at diagnosis would prevent future ischaemic events (LoE 2a). There is little evidence to guide monitoring of patients with GCA.

Conclusions

Results from two SLRs identified novel evidence on the management of GCA to guide the 2018 update of the EULAR recommendations on the management of LVV.

Genetic Predispositions of Glucocorticoid Resistance and Therapeutic Outcomes in Polymyalgia Rheumatica and Giant Cell Arteritis

Polymyalgia rheumatica (PMR) and giant cell arteritis (GCA) are closely related chronic inflammatory diseases. Glucocorticoids (GCs) are first-choice drugs for PMR and GCA, although some patients show poor responsiveness to the initial GC regimen or experience flares after GC tapering. To date, no valid biomarkers have been found to predict which patients are at most risk for developing GC resistance. In this review, we summarize PMR- and GCA-related gene polymorphisms and we associate these gene variants with GC resistance and therapeutic outcomes. A limited number of GC resistance associated-polymorphisms have been published so far, mostly related to HLA-DRB1*04 allele. Other genes such ICAM-1, TLR4 and 9, VEGF, and INFG may play a role, although discrepancies are often found among different populations. We conclude that more studies are required to identify reliable biomarkers of GC resistance. Such biomarkers could help distinguish non-responders from responders to GC treatment, with concomitant consequences for therapeutic strategy.

Review: What Is the Current Evidence for Disease Subsets in Giant Cell Arteritis?

Giant cell arteritis (GCA) is an autoimmune vasculitis affecting large and medium‐sized arteries. Ample evidence indicates that GCA is a heterogeneous disease in terms of symptoms, immune pathology, and response to treatment. In the current review, we discuss the evidence for disease subsets in GCA. We describe clinical and immunologic characteristics that may impact the risk of cranial ischemic symptoms, relapse rates, and long‐term glucocorticoid requirements in patients with GCA. In addition, we discuss both proven and putative immunologic targets for therapy in patients with GCA who have an unfavorable prognosis. Finally, we provide recommendations for further research on disease subsets in GCA.

Pathogenesis of giant-cell arteritis: how targeted therapies are influencing our understanding of the mechanisms involved

GCA is a chronic granulomatous vasculitis that affects large- and medium-sized vessels. Both the innate and the adaptive immune system are thought to play an important role in the initial events of the pathogenesis of GCA. Amplification cascades are involved in the subsequent development and progression of the disease, resulting in vascular inflammation, remodelling and occlusion. The development of large-vessel vasculitis in genetically modified mice has provided some evidence regarding potential mechanisms that lead to vascular inflammation. However, the participation of specific mechanistic pathways in GCA has not been fully established because of the paucity and limitations of functional models. Treatment of GCA is evolving, and novel therapies are being incorporated into the GCA treatment landscape. In addition, to improve the management of GCA, targeted therapies are providing functional proof of concept of the relevance of particular pathogenic mechanisms in the development of GCA and in sustaining vascular inflammation.

Expression and Function of IL12/23 Related Cytokine Subunits (p35, p40, and p19) in Giant-Cell Arteritis Lesions: Contribution of p40 to Th1- and Th17-Mediated Inflammatory Pathways

Background

Giant-cell arteritis (GCA) is considered a T helper (Th)1- and Th17-mediated disease. Interleukin (IL)-12 is a heterodimeric cytokine (p35/p40) involved in Th1 differentiation. When combining with p19 subunit, p40 compose IL-23, a powerful pro-inflammatory cytokine that maintains Th17 response.

Objectives

The aims of this study were to investigate p40, p35, and p19 subunit expression in GCA lesions and their combinations to conform different cytokines, to assess the effect of glucocorticoid treatment on subunit expression, and to explore functional roles of p40 by culturing temporal artery sections with a neutralizing anti-human IL-12/IL-23p40 antibody.

Methods and results

p40 and p19 mRNA concentrations measured by real-time RT-PCR were significantly higher in temporal arteries from 50 patients compared to 20 controls (4.35 ± 4.06 vs 0.51 ± 0.75; p < 0.0001 and 20.32 ± 21.78 vs 4.17 ± 4.43 relative units; p < 0.0001, respectively). No differences were found in constitutively expressed p35 mRNA. Contrarily, p40 and p19 mRNAs were decreased in temporal arteries from 16 treated GCA patients vs those from 34 treatment-naïve GCA patients. Accordingly, dexamethasone reduced p40 and p19 expression in cultured arteries. Subunit associations to conform IL-12 and IL-23 were confirmed by proximity-ligation assay in GCA lesions. Immunofluorescence revealed widespread p19 and p35 expression by inflammatory cells, independent from p40. Blocking IL-12/IL-23p40 tended to reduce IFNγ and IL-17 mRNA production by cultured GCA arteries and tended to increase Th17 inducers IL-1β and IL-6.

Conclusion

IL-12 and IL-23 heterodimers are increased in GCA lesions and decrease with glucocorticoid treatment. p19 and p35 subunits are much more abundant than p40, indicating an independent role for these subunits or their potential association with alternative subunits. The modest effect of IL-12/IL-23p40 neutralization may indicate compensation by redundant cytokines or cytokines resulting from alternative combinations.

Blocking interferon γ reduces expression of chemokines CXCL9, CXCL10 and CXCL11 and decreases macrophage infiltration in ex vivo cultured arteries from patients with giant cell arteritis

Background

Interferon γ (IFNγ) is considered a seminal cytokine in the pathogenesis of giant cell arteritis (GCA), but its functional role has not been investigated. We explored changes in infiltrating cells and biomarkers elicited by blocking IFNγ with a neutralising monoclonal antibody, A6, in temporal arteries from patients with GCA.

Methods

Temporal arteries from 34 patients with GCA (positive histology) and 21 controls were cultured on 3D matrix (Matrigel) and exposed to A6 or recombinant IFNγ. Changes in gene/protein expression were measured by qRT-PCR/western blot or immunoassay. Changes in infiltrating cells were assessed by immunohistochemistry/immunofluorescence. Chemotaxis/adhesion assays were performed with temporal artery-derived vascular smooth muscle cells (VSMCs) and peripheral blood mononuclear cells (PBMCs).

Results

Blocking endogenous IFNγ with A6 abrogated STAT-1 phosphorylation in cultured GCA arteries. Furthermore, selective reduction in CXCL9, CXCL10 and CXCL11 chemokine expression was observed along with reduction in infiltrating CD68 macrophages. Adding IFNγ elicited consistent opposite effects. IFNγ induced CXCL9, CXCL10, CXCL11, CCL2 and intracellular adhesion molecule-1 expression by cultured VSMC, resulting in increased PBMC chemotaxis/adhesion. Spontaneous expression of chemokines was higher in VSMC isolated from GCA-involved arteries than in those obtained from controls. Incubation of IFNγ-treated control arteries with PBMC resulted in adhesion/infiltration by CD68 macrophages, which did not occur in untreated arteries.

Conclusions

Our ex vivo system suggests that IFNγ may play an important role in the recruitment of macrophages in GCA by inducing production of specific chemokines and adhesion molecules. Vascular wall components (ie, VSMC) are mediators of these functions and may facilitate progression of inflammatory infiltrates through the vessel wall.

[Pathogenesis of large vessel vasculitis]

Giant cell arteritis (GCA) and Takayasu's arteritis (TA) are two granulomatous vasculitis affecting large arteries that present specific epidemiological and clinical features. Their pathogenesis is not fully understood but major advances have been obtained during the last years, thus allowing the emergence of new therapeutic strategies. GCA and TA develop on a specific genetic background but share some similarities regarding the immunological pathways involved in their pathogenesis. The trigger of these diseases is not clearly identified but it is thought that an infectious agent could activate and lead to the maturation of dendritic cells that are localized in the adventitia of arteries. Then, the cells of the adaptative immune response are recruited and activated: CD4 T cells that polarize into Th1 and Th17 cells, cytotoxic CD8 T cells and Natural Killer cells. Furthermore, the T regulatory cells (Treg) are decreased both in GCA and TA. Humoral immune response seems also to be involved, especially in TA. Then, the cytokines produced by T lymphocytes (especially IL-17 and IFN-γ) trigger the recruitment and activation of monocytes and their differentiation into macrophages and multinuclear giant cells that produce IL-1β and IL-6 that are responsible for general symptoms of GCA and TA, and cytotoxic mediators and growth factors that trigger the remodeling of the arterial wall leading to aneurysms and ischemic manifestations of GCA an TA.

Relapses in patients with giant cell arteritis: prevalence, characteristics, and associated clinical findings in a longitudinally followed cohort of 106 patients

Giant cell arteritis (GCA) is a relapsing disease. However, the nature, chronology, therapeutic impact, and clinical consequences of relapses have been scarcely addressed. We conducted the present study to investigate the prevalence, timing, and characteristics of relapses in patients with GCA and to analyze whether a relapsing course is associated with disease-related complications, increased glucocorticoid (GC) doses, and GC-related adverse effects. The study cohort included 106 patients, longitudinally followed by the authors for 7.8 ± 3.3 years. Relapses were defined as reappearance of disease-related symptoms requiring treatment adjustment. Relapses were classified into 4 categories: polymyalgia rheumatica (PMR), cranial symptoms (including ischemic complications), systemic disease, or symptomatic large vessel involvement. Cumulated GC dose during the first year of treatment, time required to achieve a maintenance prednisone dose <10 mg/d (T10), <5 mg/d (T5), or complete prednisone discontinuation (T0), and GC-related side effects were recorded. Sixty-eight patients (64%) experienced at least 1 relapse, and 38 (36%) experienced 2 or more. First relapse consisted of PMR in 51%, cranial symptoms in 31%, and systemic complaints in 18%. Relapses appeared predominantly, but not exclusively, within the first 2 years of treatment, and only 1 patient developed visual loss. T10, T5, and T0 were significantly longer in patients with relapses than in patients without relapse (median, 40 vs 27 wk, p  < 0.0001; 163 vs 89.5 wk, p = 0.004; and 340 vs 190 wk, p = 0.001, respectively). Cumulated prednisone dose during the first year was significantly higher in relapsing patients (6.2 ± 1.7 g vs 5.4 ± 0.78 g, p = 0.015). Osteoporosis was more common in patients with relapses compared to those without (65% vs 32%, p = 0.001). In conclusion, the results of the present study provide evidence that a relapsing course is associated with higher and prolonged GC requirements and a higher frequency of osteoporosis in GCA.

Changes in biomarkers after therapeutic intervention in temporal arteries cultured in Matrigel: a new model for preclinical studies in giant-cell arteritis

BACKGROUND

Search for therapeutic targets in giant-cell arteritis (GCA) is hampered by the scarcity of functional systems. We developed a new model consisting of temporal artery culture in tri-dimensional matrix and assessed changes in biomarkers induced by glucocorticoid treatment.

METHODS

Temporal artery sections from 28 patients with GCA and 22 controls were cultured in Matrigel for 5 days in the presence or the absence of dexamethasone. Tissue mRNA concentrations of pro-inflammatory mediators and vascular remodelling molecules was assessed by real-time RT-PCR. Soluble molecules were measured in the supernatant fluid by immunoassay.

RESULTS

Histopathological features were exquisitely preserved in cultured arteries. mRNA concentrations of pro-inflammatory cytokines (particularly IL-1β and IFNγ), chemokines (CCL3/MIP-1α, CCL4/MIP-1β, CCL5/RANTES) and MMP-9 as well as IL-1β and MMP-9 protein concentrations in the supernatants were significantly higher in cultured arteries from patients compared with control arteries. The culture system itself upregulated expression of cytokines and vascular remodelling factors in control arteries. This minimised differences between patients and controls but underlines the relevance of changes observed. Dexamethasone downregulated pro-inflammatory mediator (IL-1β, IL-6, TNFα, IFNγ, MMP-9, TIMP-1, CCL3 and CXCL8) mRNAs but did not modify expression of vascular remodelling factors (platelet derived growth factor, MMP-2 and collagens I and III).

CONCLUSIONS

Differences in gene expression in temporal arteries from patients and controls are preserved during temporal artery culture in tri-dimensional matrix. Changes in biomarkers elicited by glucocorticoid treatment satisfactorily parallel results obtained in vivo. This may be a suitable model to explore pathogenetic pathways and to perform preclinical studies with new therapeutic agents.

Increased IL-17A expression in temporal artery lesions is a predictor of sustained response to glucocorticoid treatment in patients with giant-cell arteritis

BACKGROUND

Interleukin 17A (IL-17A) exerts pivotal proinflammatory functions in chronic inflammatory and autoimmune diseases.

OBJECTIVE

To investigate IL-17A expression in temporal artery lesions from patients with giant-cell arteritis (GCA), and its relationship with disease outcome.

METHODS

Fifty-seven patients with biopsy-proven GCA were prospectively evaluated, treated and followed for 4.5 years (52-464 weeks). Relapses, time (weeks) required to achieve a maintenance prednisone dose <10 mg/day, and time (weeks) to complete prednisone withdrawal were prospectively recorded. IL-17A mRNA was measured by real-time quantitative RT-PCR in temporal arteries from all patients and 19 controls. IL-17 protein expression was assessed by immunohistochemistry/immunofluorescence.

RESULTS

IL-17A expression was significantly increased in temporal artery samples from GCA patients compared with controls (6.22±8.61 vs 2.50±3.9 relative units, p=0.016). Surprisingly, patients with strong IL-17A expression tended to experience less relapses, and required significantly shorter treatment periods (median 25 vs 44 weeks to achieve <10 mg prednisone/day, p=0.0079). There was no correlation between IL-17A and RORc or RORα expression suggesting that these transcription factors may not exclusively reflect Th17 differentiation, and that cells other than Th17 cells might contribute to IL-17 expression in active patients. Accordingly, FoxP3(+)IL-17A(+) cells were identified in lesions by confocal microscopy and were dramatically reduced in specimens from treated patients.

CONCLUSIONS

IL-17A expression is increased in GCA lesions, and is a predictor of response to glucocorticoid treatment. The contribution of FoxP3+ cells to IL-17A production in untreated patients suggests that induced-Tregs may facilitate disease remission when proinflammatory cytokine production is downregulated by glucocorticosteroids.

Association of NOS2 and potential effect of VEGF, IL6, CCL2 and IL1RN polymorphisms and haplotypes on susceptibility to GCA--a simultaneous study of 130 potentially functional SNPs in 14 candidate genes

OBJECTIVE

Frequent genetic variants may be associated with GCA. Existing studies have analysed a limited number of candidate genes and genetic variants. To expand this information, we performed a case-control study genotyping 130 single nucleotide polymorphisms (SNPs) in 82 biopsy-proven GCA patients and 166 healthy controls from the Spanish population.

METHODS

SNPs in coding and regulatory gene regions of 14 candidate genes (CCL2, CCR7, IL10, IL12A, IL1A, IL1B, IL1RN, IL6, IL8, INFG, LTA, NOS2, TNF and VEGF) were explored using the Illumina Bead Array System. Multivariate methods based on logistic regression were used for statistical analysis.

RESULTS

Nine SNPs located in five genes had significant association with GCA risk (P < 0.05). These SNPs were located in the NOS2 (rs2779251), VEGF (rs1885657, rs2010963, rs699946 and rs699947), IL1RN (rs17207494), IL6 (rs7805828 and rs1546766) and CCL2 (rs1860190) genes. The strongest associations were seen for rs2779251, rs1885657 and rs2010963 (P = 2.3 × 10(-5), P = 0.0078 and P = 0.0097, respectively). The presence of the minor allele of NOS2 variant rs2779251 had a protective effect on the risk for GCA [odds ratio (OR) = 0.27, 95% CI 0.14, 0.52]. Risk alleles for three of the four SNPs in the VEGF gene (rs2010963, rs699946 and rs699947) were associated in homozygosis with increased risk (OR = 4.22, 95% CI 1.38, 12.87; OR = 9.04, 95% CI 1.58, 51.81; and OR = 2.38, 95% CI 1.05, 5.38, respectively), whereas a minor allele for the other SNP (rs1885657) had a protective effect (OR = 0.46, 95% CI 0.26, 0.84).

CONCLUSION

Common genetic variants in NOS2, VEGF, IL6, ILRN1 and CCL2 genes are associated with GCA, indicating a polygenic influence on disease susceptibility.

Tissue and serum markers of inflammation during the follow-up of patients with giant-cell arteritis--a prospective longitudinal study

Objective. To evaluate the association between inflammatory markers and relapse in GCA patients longitudinally assessed in a clinical trial of infliximab and glucocorticosteroids.

Methods. Forty-four newly diagnosed GCA patients in glucocorticosteroid-induced remission were randomized to receive infliximab 5 mg/kg or placebo plus daily glucocorticosteroids, tapered using a standardized schedule. Sera were analysed for inflammatory markers at multiple, pre-defined time points. Temporal artery biopsies were performed in four patients before and after treatment to analyse changes in inflammatory and vascular remodelling marker expression.

Results. Thirteen of 44 patients relapsed. Similar proportions of relapsed patients were present in both treatment arms. ESR, CRP, intercellular adhesion molecule (ICAM)-1, TNF-α, and IL-12p40 were significantly elevated near relapse. In post-treatment biopsies, mRNA expression of pro-inflammatory cytokines decreased, while vascular remodelling factors increased relative to baseline biopsies. Tissue IL-12p40 and IFN-γ mRNA remained elevated in relapsing vs remitting patients.

Conclusion. Despite prior findings of high concentrations of TNF-α in temporal artery biopsies of GCA patients, infliximab plus glucocorticosteroids did not result in improved clinical outcomes. Increased measures of this biomarker did not provide useful insight into the relative importance of TNF-α in the pathogenesis of GCA. Gene expression analysis in paired temporal artery biopsies pre- and post-treatment revealed decreased inflammatory activity and active vascular remodelling following treatment. In relapsing patients, increased expression of IFN-γ and IL-12p40 in post-treatment biopsies suggests a role in sustaining disease and setting the stage for relapse during treatment withdrawal.

Trial registration. ClinicalTrials.gov; http://www.clinicaltrials.gov; NCT00076726.

Ischaemic manifestations in giant cell arteritis are associated with area level socio-economic deprivation, but not cardiovascular risk factors

OBJECTIVES

To determine whether ischaemic manifestations of GCA are associated with pre-existing hypertension, atherosclerosis or area-level socio-economic deprivation.

METHODS

We conducted an observational study of rheumatologist/ophthalmologist-diagnosed GCA in eight UK centres. The main outcome measure was ischaemic manifestations observed during active GCA: visual loss/blurring, aura, diplopia, jaw/tongue/limb claudication, cerebral/myocardial ischaemia or scalp necrosis.

RESULTS

Out of 271 patients, 222 had ischaemic manifestations. Adjusted odds ratios (ORs) for the influence of hypertension and atherosclerosis were 1.6 (95% CI 0.8, 3.1) and 1.5 (0.6, 3.5). The most striking finding was an association of ischaemic manifestations with increasing Index of Deprivation 2007 score: OR 4.2 (95% CI 1.3, 13.6) for the most-deprived quartile compared with the least-deprived quartile. Similar effect sizes were seen within each recruitment centre. Deprivation was associated with smoking and negatively associated with previous polymyalgia. However, neither of these variables, nor hypertension or atherosclerosis, appeared responsible for mediating the effect of deprivation on ischaemic complications. Smoking was not associated with ischaemic manifestations. Median symptom duration before treatment was 30 days; after adjusting for symptom duration, the OR for ischaemic complications was 3.2 (95% CI 1.0, 10.8) for the most-deprived quartile compared with the least-deprived quartile.

CONCLUSIONS

In GCA, area-level socio-economic deprivation was associated with ischaemic manifestations: this was not mediated by traditional cardiovascular risk factors. These findings are novel and require replication. Delay between first symptoms and treatment may play a role. Public awareness campaigns about GCA should aim especially to engage individuals living in more deprived areas to encourage early presentation and prompt treatment.

Functional effects of interleukin 31 in human primary keratinocytes

BACKGROUND

Interleukin (IL)-31 is a T-cell cytokine acting through a heterodimeric receptor composed of IL-31RA and OSMR which is expressed on epithelial cells including keratinocytes. A major function of IL-31 in atopic dermatitis (AD) is the induction of pruritus in the skin. Inflammatory effects of IL-31 in human primary keratinocytes (HPKs) still remain unclear. We investigated expression, regulation of the IL-31 receptor as well as functions of IL-31 in HPKs.

METHODS

Human primary keratinocytes were stimulated with TLR-2 ligands (Pam3Cys, lipoteichoic acid and peptidoglycan), or Th1 and Th2 associated cytokines (IFN-γ and IL-4), respectively. IL-31R expression and regulation as well as functional effects of IL-31 stimulation were then investigated at both the mRNA and protein level and compared with HPKs from patients with AD. The STAT signalling pathway and TLR-2 expression were investigated using Western blot and Immunohistochemical stainings, respectively.

RESULTS

Pam3Cys or IFN-γ significantly up-regulated IL-31RA and OSMR expression. IL-31 activated STAT-3 phosphorylation in HPKs which was augmented after preactivation with Pam3Cys or IFN-γ. IL-31 enhanced the secretion of CCL2 after up-regulation of the receptor with Pam3Cys or IFN-γ. However, this was not observed in keratinocytes from AD patients where an impaired TLR-2 expression was found.

CONCLUSIONS

Together, our findings show a functional role of IL-31 in HPKs and provide a new link between TLR-2 ligands and IL-31 which might be dysregulated in AD. Altered function of IL-31 may have implications for cutaneous inflammation in eczema where skin colonization with Staphylococcus aureus and dysregulation of TLR-2 have been described.

Current understanding and management of giant cell arteritis and polymyalgia rheumatica

Giant cell arteritis (GCA) and polymyalgia rheumatica (PMR) are linked conditions that occur in the elderly. GCA is a vasculitis of large- and medium-sized vessels causing critical ischemia. It is a medical emergency owing to the high incidence of neuro-ophthalmic complications. PMR is an inflammatory disease characterized by abrupt-onset pain and stiffness of the shoulder and pelvic girdle muscles. Both conditions are associated with a systemic inflammatory response and constitutional symptoms. The pathogeneses are unclear. The initiating step may be the recognition of an infectious agent by activated dendritic cells. The key cell type involved is CD4(+) T cells and the key cytokines are IFN-γ (implicated in granuloma formation) and IL-6 (key to the systemic response). The pathogenesis of PMR may be similar to that of GCA, however, PMR exhibits less clinical vascular involvement. The mainstay of therapy is corticosteroids, and disease-modifying therapy is indicated in relapsing disease. This article reviews recent guidelines on early recognition, investigations and management of these diseases, as well as advances in imaging.

Fatal subarachnoid hemorrhage due to ruptured vertebrobasilar aneurysm associated with giant cell arteritis in a child

A 3 ½-year-old previously healthy female experienced an episode of sudden unresponsiveness witnessed by her mother. Upon arrival to the local hospital, imaging studies of the still unresponsive child revealed severe bilateral "flash" pulmonary edema and diffuse anoxic brain injury. Aggressive resuscitative efforts were unsuccessful, and she was pronounced dead. External examination at autopsy was essentially unremarkable. Internal examination of the head revealed diffuse basilar subarachnoid blood originating from a collapsed, 2 cm irregular aneurysm arising from the junction of the vertebral and basilar arteries. Additionally, multiple calcified subpleural, parenchymal, and hilar nodal pulmonary granulomas were identified. The remaining internal examination, including that of the aorta and its major branches, was unremarkable. Histologic examination of the aneurysm revealed alternating mural attenuation and thickening, the latter resulting from prominent intimal proliferation with active fibroplasia. Most notably, numerous isolated and clustered multinucleated giant cells were seen, most prominently in areas of more intense inflammation. Specific immunolabeling and silver staining of the pulmonary granulomas revealed evidence of histoplasmosis, but both were negative for fungal elements in the aneurysm, as was ultrastructural examination. The cause of death is fatal subarachnoid hemorrhage due to rupture of a vertebrobasilar artery aneurysm caused by isolated intracranial giant cell arteritis.

Relevance of the CX3CL1/fractalkine-CX3CR1 pathway in vasculitis and vasculopathy

The clinical presentation of systemic vasculitis can vary widely and include skin disorders, neuropathy, eye symptoms, and systemic inflammation. The precise molecular mechanisms underlying this syndrome are not fully understood, but the importance of a chronic imbalance of the cytokines and chemokines involved in orchestrating inflammatory responses is now recognized. In similar fashion, atherosclerosis is now recognized to be a chronic inflammatory disease in which chemokines play important roles. In the current review, we discuss the involvement of CX3CL1, which is a unique member of the chemokine family, and its receptor, CX3CR1, in the pathogenesis of these vasculopathies.

Translational mini-review series on immunology of vascular disease: accelerated atherosclerosis in vasculitis

Premature atherosclerosis has been observed during the course of different systemic inflammatory diseases such as rheumatoid arthritis and sytemic lupus erythematosus. Remarkably, relatively few studies have been published on the occurrence of accelerated atherosclerosis in patients with vasculitis. In giant cell arteritis (GCA), mortality because of ischaemic heart disease is not increased. In addition, intima media thickness (IMT) is lower in patients with GCA than in age-matched controls. In contrast, IMT is increased significantly in Takayasu arteritis, another form of large vessel vasculitis occurring in younger patients. In Takayasu arteritis and in Kawasaki disease, a form of medium-sized vessel vasculitis, accelerated atherosclerosis has been well documented. In small vessel vasculitis because of anti-neutrophil cytoplasmic autoantibodies-associated vasculitis, cardiovascular diseases are a major cause of mortality. IMT measurements reveal conflicting results. During active disease these patients experience acceleration of the atherosclerotic process. However, when inflammation is controlled, these patients have atherosclerotic development as in healthy subjects. Several risk factors, such as diabetes and hypertension, are present more often in patients with vasculitis compared with healthy controls. In addition, steroids may be pro-atherogenic. Most importantly, many patients have impaired renal function, persistent proteinuria and increased levels of C-reactive protein, well-known risk factors for acceleration of atherosclerosis. Enhanced oxidation processes, persistently activated T cells and reduced numbers of regulatory T cells are among the many pathophysiological factors that play a role during acceleration of atherogenesis. Finally, autoantibodies that may be relevant for acceleration of atherosclerosis are found frequently in elevated titres in patients with vasculitis. Because patients have an increased risk for cardiovascular events, vasculitis should be treated with as much care as possible. In addition, treatment should be considered with angiotensin-converting-enzyme inhibitors and/or angiotensin receptor-1 blockers, statins and acetylsalicyl acid. Finally, classical risk factors for cardiovascular disease should be monitored and treated as much as possible.

[Pathogenesis of primary large vessel arteritis]

Giant cell arteritis (GCA) and Takayasu's arteritis (TA) are the two primary large-vessel arteritides. Recent advances in cellular immunology have allowed better understanding of pathogenesis of these diseases. In GCA and TA, resident adventitial dendritic cells are activated by unidentified stimuli. This activation induces chemokine synthesis which enhances recruitment of inflammatory cells. T-cells infiltrate the vascular wall and specifically recognize one or a few antigens presented by shared epitopes associated with specific HLA molecules on dendritic cells. Activated T-cells produce IFNgamma stimulating two distinct populations of macrophages. Macrophages located in the intima produce pro-inflammatory cytokines (IL-1, IL-6). Macrophages located in the media differentiate into giant cells and/or produce reactive oxygen species, nitric oxide and matrix metallo-proteinases. Macrophages of the media also produce VEGF, which leads to neovascularization and PDGF, which induces intimal hyperplasia and vascular occlusion. In TA, cytotoxic T cells infiltrate the vascular wall and induce apoptosis of the vascular cells. Better understanding of the pathogenesis of large-vessel arteritis may lead to development of immunosuppressive drugs specifically targeting the immunological mechanisms implicated in GCA and TA.

Five clinical conundrums in the management of giant cell arteritis

Clinicians who treat patients with giant cell arteritis (GCA) face many unresolved challenges. Visual loss still occurs in 15% to 20% of patients despite the availability of therapy for the disease that is generally effective. Aneurysm formation and large vessel stenosis are increasingly recognized complications. Substantial iatrogenic morbidity stems from glucocorticoid therapy, and recent trials have failed to identify an efficient steroid sparing agent. In this review, the authors address five major clinical conundrums in the management of GCA.