Arterial wall production of cytokines in giant cell arteritis: results of a pilot study using human temporal artery cultures

IL-25 exacerbates autoimmune aortitis in IL-1 receptor antagonist-deficient mice

IL-25, a member of the IL-17 family of cytokines, is known to enhance type 2 immune responses, but suppress type 3 (IL-17A)-mediated immune responses. Mice deficient in IL-1 receptor antagonist (Il1rn^−/− mice) have excessive IL-1 signaling, resulting in spontaneous development of IL-1–, TNF– and IL-17A–dependent aortitis. We found that expression of II25 mRNA was increased in the aortae of Il1rn^−/− mice, suggesting that IL-25 may suppress development of IL-1–, TNF– and IL-17A–dependent aortitis in Il1rn^−/− mice by inhibiting type 3-mediated immune responses. However, we unexpectedly found that Il25^−/−Il1rn^−/− mice showed attenuated development of aortitis, accompanied by reduced accumulation of inflammatory cells such as dendritic cells, macrophages and neutrophils and reduced mRNA expression of Il17a and Tnfa—but not Il4 or Il13—in local lesions compared with Il1rn^−/− mice. Tissue–, but not immune cell–, derived IL-25 was crucial for development of aortitis. IL-25 enhanced IL-1β and TNF production by IL-25 receptor–expressing dendritic cells and macrophages, respectively, at inflammatory sites of aortae of Il1rn^−/− mice, contributing to exacerbation of development of IL-1–, TNF– and IL-17A–dependent aortitis in those mice. Our findings suggest that neutralization of IL-25 may be a potential therapeutic target for aortitis.

The association of gout with incident giant cell arteritis in older adults

OBJECTIVES

To assess whether gout is associated with a higher or lower risk of a new diagnosis of giant cell arteritis (GCA) in older adults, adjusting for known risk factors of GCA.

METHODS

We used the 5% Medicare claims to conduct a multivariable Cox regression analyses to assess the association of gout with incident GCA in adults 65 years or older adjusting for age, gender, race (known risk factors for GCA) and Charlson-Romano comorbidity score, the use of medications for cardiovascular diseases (statins, beta-blockers, diuretics, ACE-inhibitors) and gout (allopurinol, febuxostat). Hazard ratios (HR) and 95% confidence intervals (CI) were calculated.

RESULTS

There were 3004 incident cases (new diagnosis) of GCA with crude incidence rates of GCA of 28.0/100,000 person-years in patients without gout and 63.8/100,000 person-years in patients with gout. Multivariable-adjusted analyses showed that preexisting gout was associated with a higher risk of incident/new GCA diagnosis with a hazard ratio of 2.05 (95% CI: 1.76, 2.40), confirmed in sensitivity analyses that substituted continuous Charlson-Romano comorbidity score with categorized score or individual comorbidities (plus hypertension, hyperlipidemia, and coronary artery disease). Older age, female gender, white race and higher comorbidity index, were also associated with a higher hazard of GCA. Subgroup analyses did not show any significant variation of the association of preexisting gout with incident GCA by age, race or sex.

CONCLUSIONS

Gout was associated with more than 2-fold higher risk of incident GCA in older adults, independent of known risk factors of GCA. Future studies should explore the underlying mechanisms for this association.

The Inflammasomes in Cardiovascular Disease

Cardiovascular disease (CVD) is the number one cause of death worldwide. The pathogenesis of various disease entities that comprise the area of CVD is complex and multifactorial. Inflammation serves a central role in these complex aetiologies. The inflammasomes are intracellular protein complexes activated by danger-associated molecular patterns (DAMPs) present in CVD such as atherosclerosis and myocardial infarction (MI). After a two-step process of priming and activation, inflammasomes are responsible for the formation of pro-inflammatory cytokines interleukin-1β and interleukin-18, inducing a signal transduction cascade resulting in a strong immune response that culminates in disease progression. In the past few years, increased interest has been raised regarding the inflammasomes in CVD. Inflammasome activation is thought to be involved in the pathogenesis of various disease entities such as atherosclerosis, MI and heart failure (HF). Interference with inflammasome-mediated signalling could reduce inflammation and attenuate the severity of disease. In this chapter we provide an overview of the current literature available on the role of inflammasome inhibition as a therapeutic intervention and the possible clinical implications for CVD.

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.

Lack of nitric oxide synthases increases lipoprotein immune complex deposition in the aorta and elevates plasma sphingolipid levels in lupus

Systemic lupus erythematosus (SLE) patients display impaired endothelial nitric oxide synthase (eNOS) function required for normal vasodilatation. SLE patients express increased compensatory activity of inducible nitric oxide synthase (iNOS) generating excess nitric oxide that may result in inflammation. We examined the effects of genetic deletion of NOS2 and NOS3, encoding iNOS and eNOS respectively, on accelerated vascular disease in MRL/lpr lupus mouse model. NOS2 and NOS3 knockout (KO) MRL/lpr mice had higher plasma levels of triglycerides (23% and 35%, respectively), ceramide (45% and 21%, respectively), and sphingosine 1-phosphate (S1P) (21%) compared to counterpart MRL/lpr controls. Plasma levels of the anti-inflammatory cytokine interleukin 10 (IL-10) in NOS2 and NOS3 KO MRL/lpr mice were lower (53% and 80%, respectively) than counterpart controls. Nodule-like lesions in the adventitia were detected in aortas from both NOS2 and NOS3 KO MRL/lpr mice. Immunohistochemical evaluation of the lesions revealed activated endothelial cells and lipid-laden macrophages (foam cells), elevated sphingosine kinase 1 expression, and oxidized low-density lipoprotein immune complexes (oxLDL-IC). The findings suggest that advanced vascular disease in NOS2 and NOS3 KO MRL/lpr mice maybe mediated by increased plasma triglycerides, ceramide and S1P; decreased plasma IL-10; and accumulation of oxLDL-IC in the vessel wall. The results expose possible new targets to mitigate lupus-associated complications.

Vascular dendritic cells in giant cell arteritis

Giant cell arteritis (GCA) is a granulomatous vasculitis that selectively targets medium-sized and large arteries, especially the cranial branches of the aorta. The inflammatory activity of vascular lesions is driven by adaptive immune responses, with CD4 T cells undergoing clonal expansion in the vessel wall and releasing interferon gamma. Recent studies have described a distinctive population of dendritic cells (DCs) localized at the adventitia-media border of normal medium-sized arteries that appear to play a critical role in the initiation of vasculitis. Immune effector functions of this DC population are being examined in human artery-severe combined immunodeficient (SCID) mouse chimeras. In their constitutive form, CD11c+ fascin+ adventitial DCs are not recognized by alloreactive T cells. Triggering with Toll-like receptor (TLR) ligands is sufficient to break this state of tolerance and initiate DC activation, T-cell recruitment, T-cell activation, and T-cell retention in the arterial wall. Systemic administration of ligands for TLR2 or -4 in human artery-SCID chimeras drives differentiation of adventitial DCs into chemokine-producing effector cells with high-level expression of both CD83 and CD86 and mediates T-cell regulatory function through release of interleukin 18. In established vasculitis, fully matured DCs retain antigen-presenting function; antibody-mediated DC depletion disrupts T-cell and macrophage activation and has marked anti-inflammatory effects. We conclude that adventitial DCs, an indigenous cell population of the arterial wall, are responsive to pathogen-derived macromolecules and have gatekeeper function in regulating T-cell recruitment and retention to the arterial adventitia. A switch of adventitial DCs from being nonstimulatory to T-cell activating emerges as a critical event in the initiation of vasculitis.

Are steroids alone sufficient for the treatment of giant cell arteritis?

Glucocorticosteroids are the cornerstone of treatment of giant cell arteritis. An initial dose of prednisone or its equivalent of at least 40-60mg per day as single or divided dose is usually adequate. Glucocorticosteroids may prevent, but usually do not reverse, visual loss. A treatment course of 1-2 years is often required. Some patients, however, have a more chronic-relapsing course and may require low doses of glucocorticosteroids for several years. Glucocorticosteroid-related adverse events are common. In studies on immunosuppressant agents, methotrexate has been used as a glucocorticosteroid-sparing drug with conflicting results. This drug may, however, be given to patients who need high doses of glucocorticosteroids to control active disease and who have serious side effects. A recent pilot study found that infliximab was efficacious in patients with glucocorticosteroid-resistant giant cell arteritis. However, randomized controlled trials are required to define the role of anti-tumor necrosis factor-alpha agents in the treatment of giant cell arteritis. Finally, low-dose aspirin has been shown in a recent retrospective study to decrease the rate of cranial ischemic complications secondary to giant cell arteritis. It is conceivable that the definition of different patterns of inflammation in giant cell arteritis in the future might facilitate the design of differentiated therapeutic approaches.

Bilateral scalp necrosis with giant cell arteritis

We present a patient with bilateral scalp necrosis caused by giant cell arteritis (temporal arteritis). A 67-year-old woman, who had been treated with 5 mg of oral prednisolone every other day for polymyalgia rheumatica, developed painful egg-sized regions of necrosis on both of her temples. Doppler pulsemetory revealed bilateral obstruction of the temporal arteries. Biopsy revealed ischemic necrosis of the skin and necrotic angiitis of the temporal arteries with giant cell infiltration. Bilateral stenosis of the internal carotid arteries and moderate retinal bleeding were revealed by angiography. Daily administration of prednisolone (20 mg/day) with intravenous and topical limaprost alphadex markedly improved her condition. The ulcers reepithelized without surgical treatment. There are few reports of bilateral scalp necrosis. Rapid and complete obstruction of the temporal artery may result in this condition. Simultaneous development of two ulcerative lesions in the ventro-parietal cranial regions is thought to correspond to systemic arterial involvement, including involvement of the internal carotid arteries.