Serum of Behçet's disease enhances superoxide production of normal neutrophils

The roles of immune cells in Behçet's disease

Behçet's disease (BD) is a systemic vasculitis that can affect multiple systems, including the skin, mucous membranes, joints, eyes, gastrointestinal and nervous. However, the pathogenesis of BD remains unclear, and it is believed that immune-inflammatory reactions play a crucial role in its development. Immune cells are a critical component of this process and contribute to the onset and progression of BD. By regulating the function of these immune cells, effective control over the occurrence and development of BD can be achieved, particularly with regards to monocyte activation and aggregation, macrophage differentiation and polarization, as well as T cell subset differentiation. This review provides a brief overview of immune cells and their role in regulating BD progression, which may serve as a theoretical foundation for preventing and treating this disease.

Neutrophil, NETs and Behçet's disease: A review

Behçet's disease (BD) is a chronic systemic vasculitis characterized by recurrent oral and genital ulcers, skin lesions, articular, neurological, vascular and sight-threatening ocular inflammation. BD is thought to share both autoimmune and autoinflammatory disease features. BD is triggered by environmental factors such as infectious agents in genetically predisposed subjects. Neutrophils seem to play an instrumental role in BD and recent works regarding the role of neutrophils extracellular traps (NETs) provides new insight in the pathophysiology of BD and the mechanisms involved in immune thrombosis. This review provides a recent overview on the role of neutrophils and NETs in the pathogenesis of BD.

Understanding Behçet's Disease in the Context of Innate Immunity Activation

Behçet´s disease (BD) is a heterogeneous condition consisting of idiopathic systemic vasculitis affecting large and small blood vessels of different types (i.e., arteries, veins, or capillaries). The disease frequently occurs in young adults without gender predilection, differently from several other autoimmune conditions. This challenging illness has recently been proposed by some authors as an example of complex autoinflammatory syndrome. Although much remains unanswered about BD pathogenesis, recent understanding of some aspects of innate immunity have clarified a few issues (and raised others). HLA-B*51 represents the strongest genetic risk factor for BD to date, albeit several other HLA-independent loci have also been associated with the disease. The consistent hyper-reactivity against Streptococcus sanguinis antigens and alterations in oral and gut microbioma suggests that infectious agents may play an important role. Moreover, functional abnormalities of pattern recognition receptors, especially Toll-like receptors in monocytes, have been demonstrated in patients with BD and can be associated with the development of the disease. Neutrophil hyperactivity is one of the most consistent findings in BD pathogenesis, as demonstrated by exacerbated constitutive oxidative burst, chemotaxis and NET formation. However, some studies suggest that the phagocyte-activated status in BD is not primary to the disease itself, but rather restricted to a fraction of patients with severe disease activity, and probably secondary to activating soluble factors carried by serum/plasma from BD patients. Herein we review the state of the art on BD etiopathogenesis with special emphasis on the participation of the innate immune system

Behçet disease (BD) and BD-like clinical phenotypes: NF-κB pathway in mucosal ulcerating diseases

Behçet's disease (BD) is a heterogeneous multi-organ disorder in search of a unified pathophysiological theory and classification. The disease frequently has overlapping features resembling other disease clusters, such as vasculitides, spondyloarthritides and thrombophilias with similar genetic risk variants, namely HLA-B*51, ERAP1, IL-10, IL-23R. Many of the BD manifestations, such as unprovoked recurrent episodes of inflammation and increased expression of IL-1, IL-6 and TNFα, overlap with those of the hereditary monogenic autoinflammatory syndromes, positioning BD at the crossroads between autoimmune and autoinflammatory syndromes. BD-like disease associates with various inborn errors of immunity, including familial Mediterranean fever, conditions related to dysregulated NF-κB activation (eg TNFAIP3, NFKB1, OTULIN, RELA, IKBKG) and either constitutional trisomy 8 or acquired trisomy 8 in myelodysplastic syndromes. We review here the recent advances in the immunopathology of BD, BD-like diseases and the NF-κB pathway suggesting new elements in the elusive BD etiopathogenesis.

Genetics and Epigenetics Mechanism in the Pathogenesis of Behçet's Disease

BACKGROUND

Behçet's Disease (BD) is characterized by numerous systemic manifestations and is known for its ability to affect both, arteries and the veins. However, the etiology of BD is only partially understood, and previous studies have demonstrated a role for genetic and epigenetic factors that contribute to disease pathophysiology. Several studies have implicated T cells and monocytes in the pathogenesis of BD especially when these cells are stimulated by heat shock proteins and streptococcal antigen. Furthermore, during disease exacerbations adenosine deaminase has an important role in activating lymphocyte proliferation, maturation, and differentiation in BD. This article presents a review of the published literature mainly from the last 20 years. The topics of main concern were the role of genetic and epigenetic factors as contributing factors in disease pathophysiology.

RESULT AND CONCLUSION

The authors used MeSH terms "Behçet's disease" with "pathophysiology," "pathogenesis," "genetic" or "epigenetic" to search the PubMed database. All the relevant studies identified were included and are described according to the aforementioned subheadings.

Soluble CD40L is associated with increased oxidative burst and neutrophil extracellular trap release in Behçet's disease

Background

Studies have suggested that soluble factors in plasma from patients with active (aBD) and inactive (iBD) Behçet’s disease (BD) stimulate neutrophil function. Soluble CD40 ligand (sCD40L) is an important mediator of inflammation in BD. Its expression and effect on neutrophil oxidative burst and neutrophil extracellular trap (NET) release have not been characterized. In this study, we sought to investigate the role of plasma and the CD40L pathway on NET release and the oxidative burst profile in patients with aBD and iBD.

Methods

Neutrophils and peripheral blood mononuclear cells (PBMCs) were obtained from patients with aBD (n = 30), patients with iBD (n = 31), and healthy control subjects (HCs; n = 30). sCD40L plasma concentration was determined in individual samples. A pool of plasma for each group was created. In some experiments, plasma pools were treated with recombinant CD40 (rhCD40-muIg) for sCD40L blockade. NET release and H₂O₂/O₂⁻ production were determined after stimulation with phorbol 12-myristate 13-acetate, sCD40L, or plasma pool. Flow cytometric analysis was performed to evaluate the expression of (1) CD40, Mac-1, and phosphorylated NF-κB p65 on neutrophils and monocytes and (2) CD40L on activated T cells and platelets. CD40L gene expression in PBMCs was determined by qRT-PCR.

Results

sCD40L plasma levels were significantly higher in patients with iBD (median 17,234, range 2346–19,279 pg/ml) and patients with aBD (median 18,289, range 413–19,883 pg/ml) than in HCs (median 47.5, range 33.7–26.7 pg/ml; p < 0.001). NET release was constitutively increased in BD compared with HC. NET release and H₂O₂/O₂⁻ were higher after stimulation with sCD40L or BD plasma and decreased after sCD40L blockade. Mac-1 expression was constitutively increased in neutrophils of patients with aBD (88.7 ± 13.2% of cells) and patients with iBD (89.2 ± 20.1% of cells) compared with HC (27.1 ± 18.8% of cells; p < 0.01). CD40 expression on phagocytes and CD40L expression on platelets were similar in the three groups. PBMCs as well as nonactivated and activated CD4⁺ T cells from patients with BD showed higher CD40L expression.

Conclusions

Plasma from patients with aBD exerts a stimulus on NET release and oxidative burst, probably induced by sCD40L.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1443-5) contains supplementary material, which is available to authorized users.

Ocular Behçet disease: current therapeutic approaches

PURPOSE OF REVIEW

To alert physician to timely recognition and current treatment of recurrent hypopyon iridocyclitis or panuveitis in ocular Behçet disease (OBD).

RECENT FINDINGS

Interferon-α, rituximab, intravitreal triamcinolone, and biological response modifiers by tumor necrosis factor inhibitors such as infliximab and adalimumab are being used increasingly for the treatment of severe sight-threatening ocular inflammation including retinal vasculitis and cystoid macular edema (CME).

SUMMARY

Biological agents offer tremendous potential in the treatment of OBD. Given that OBD predominantly afflicts the younger adults in their most productive years, dermatologist, rheumatologist, internist, or general practitioners supervising patients with oculo-articulo-oromucocutaneous syndromes should be aware of systemic Behçet disease. Early recognition of ocular involvement is important and such patients should strongly be instructed to visit immediately an ophthalmologist, as uveitis management differs from extraocular involvements with high ocular morbidity from sight-threatening complications due to relapsing inflammatory attacks in the posterior segment of the eye. A single infliximab infusion should be considered for the control of acute panuveitis, whereas repeated long-term infliximab infusions were proved to be more effective in reducing the number of episodes in refractory uveoretinitis with faster regression and complete remission of CME.

Pathophysiology of the Behçet's Disease

Behçet's disease (BD) is a multisystemic disease of unknown etiology characterized by chronic relapsing oral-genital ulcers and uveitis. Multiple systemic associations including articular, gastrointestinal, cardiopulmonary, neurologic, and vascular involvement are also observed in BD. Although the etiopathogenesis of the disease remains unknown, increased neutrophil functions such as chemotaxis, phagocytosis, and excessive production of reactive oxygen species (ROS), including superoxide anion, which may be responsible for oxidative tissue damage seen in BD, and also immunological alterations, T lymphocyte abnormalities in both subpopulation and function have been considered to be correlated with the etiopathogenesis of BD. There is some clinical evidence suggesting that emotional stress and hormonal alterations can influence the course and disease activity of BD.

Investigation of the association between Toll-like receptor 2 gene polymorphisms and Behçet's disease in Japanese patients

Behçet's disease (BD) is a chronic systemic inflammatory disorder characterized by recurrent ocular symptoms, oral and genital ulcers, and skin lesions. The etiology of BD is still uncertain, but genetic and environmental factors likely both play an important role in BD development. In the present study, we investigated whether polymorphisms of Toll-like receptor 2 (TLR2), previously reported to recognize BD candidate antigens, are associated with BD. Two hundred Japanese patients with BD and 128 Japanese healthy controls were recruited. We genotyped five single-nucleotide polymorphisms (SNPs) in the TLR2 gene and assessed the allele/genotype diversity between cases and controls for all SNPs. No significant differences in the frequency of TLR2 alleles, genotypes, and haplotypes in the BD cases were detected compared with the controls. These data indicate that TLR2 polymorphisms do not play an important role in the development of BD.

Circulating neutrophils in Behçet disease is resistant for apoptotic cell death in the remission phase of uveitis

BACKGROUND

Behçet disease (BD) is manifested by recurrent acute iridocyclitis with hypopyon in the active phase, which regresses spontaneously. Hypopyon consists of inflammatory cells infiltrating the eye, with polymorphonuclear cells (PMNs) as the main component. The present study was conducted to investigate the apoptosis property of PMNs in BD patients with uveitis.

METHODS

PMNs were purified from peripheral blood cells of BD patients with uveitis in the active or remission phase and were cultured for 12 hours. In some cultures, lipopolysaccharide (LPS), antagonistic anti-TNFalpha antibody, agonistic anti-Fas antibody, or Fas:Fc fusion protein was added. At the end of cultures, apoptotic cells were evaluated by Annexin V expression using flow cytometry.

RESULTS

Spontaneous apoptosis of PMNs showed lower levels in the remission phase of BD-related uveitis compared with the active phase or healthy controls. The lower level of PMN apoptosis in the remission phase of uveitis in BD remained even by stimulation with LPS, anti-TNFalpha antibody, or Fas:Fc fusion protein, which was abolished in the presence of agonistic anti-Fas antibody.

CONCLUSIONS

In BD patients, the apoptosis of PMNs was reduced in the remission phase of uveitis and restored in the active phase, which arose from the apoptotic cell death in part via Fas-Fas ligand interaction.

Nitric oxide levels in Behçet's disease

Behçet's disease (BD) is a chronic multisystemic disorder which is characterized by a relapsing systemic inflammatory process. In certain inflammatory conditions such as rheumatoid arthritis, over production of nitric oxide (NO) could damage host cells and tissues, either directly and/or following reaction with other free radicals, such as superoxide anion to form species including peroxynitrite or hydroxyl radicals. Excessive superoxide radical production and impaired antioxidant mechanism in both the neutrophils and plasma of patients with BD have been reported. Our study was designed to investigate the role of NO in BD. NO is an extremely unstable molecule and rapidly converted in vivo and in vitro to nitrate (NO3-) and nitrite (NO2-). For this reason serum NO2- and NO3- have been used as an index of NO generation. We measured serum nitrate + nitrite levels, by using an enzymatic one-step methodology based on the reduction of nitrate to nitrite by nitrate reductase from Aspergillus species, in the presence of beta-NADPH. When compared to healthy controls, serum nitrate + nitrite levels were found to be higher in active periods of BD patients (P < 0.01). It was concluded that increased NO production in patients with BD might have critical biological activities relevant to vasculitic events in the active period of disease.

The activities of serum adenosine deaminase and xanthine oxidase enzymes in Behcet's disease

BACKGROUND

Adenosine deaminase (AD) and xanthine oxidase (XO) are enzymes of purine catabolism that catalyze the conversion of adenosine to inosine, deoxyadenosine to deoxyinosine, hypoxanthine to xanthine and xanthine to uric acid, respectively. AD is known to be an important enzyme in the maturation and function of T lymphocytes. The aim of this prospective study was to evaluate whether there are changes in serum AD activity as an index of T lymphocyte function in Behcet's disease (BD) which is known as having T cell-mediated immune response.

METHODS

A total of 32 patients and 26 sex- and age-matched healthy control subjects were analysed for AD and XO activities. The patients with BD were divided into two subgroups: BD with and without eye lesions. Twelve patients with complete BD and four patients with incomplete BD had eye complications. AD and XO activities in serum were measured with spectrophotometric methods.

RESULTS

There was a remarkable increase in AD activity and moderate increase in XO in patients with BD compared to controls indicating T cell activation and increased maturation. Serum AD activity of complete BD was higher than that of incomplete BD. There was no difference in XO activity between the subgroups of BD. Significant positive correlation was found between AD and XO in BD, although there was no correlation in control group.

CONCLUSIONS

The results indicate that increased AD and XO activities may provide an additional benefit for the diagnosis of BD and subtyping of the disease as having eye complication or not and complete and incomplete BD. Further studies are needed to bring to light the exact mechanism of AD and XO activity elevation.

Immunoglobulin G induces microglial superoxide production

Activating microglias observed in the white matter after chronic cerebral hypoperfusion may play an important role in white matter changes (WMC). Microglial activation has been considered as a result of neuronal damage, however, recently it came to be recognized as a possible cause of the damage in various neurodegenerative diseases. The protective effect of an immunosuppressant on the WMC suggests that an immunologic reaction participates in the pathogenesis. Using a MCLA-dependent chemiluminescence method, we investigated the effect of immunoglobulin G (IgG) on microglial superoxide production. IgG stimulated microglias to produce superoxide. Microglial superoxide production by the Fab fragment of rat IgG was significantly less than that by the Fc fragment of rat IgG. The protective effect of an immunosuppressant on WMC may use the inhibiting effect on IgG. Our results suggest that if microglias come in contact with IgG in lesions, oxidative stress mediated by superoxide from microglial deteriorates WMC.

Increased corneal thickness in active Behçet's disease

PURPOSE

To measure central corneal thickness (CCT) in patients with Behçet's disease (BD), particularly in the active disease.

MATERIALS AND METHODS

We measured CCT by ultrasound pachymetry in 64 patients with Behçet's disease and in 20 healthy controls. Forty-one of the patients with BD had ocular involvement and 23 none; 19 of the 41 with ocular involvement were in an active period and 22 had inactive disease.

RESULTS

The mean CCT in the group with active ocular involvement was significantly higher (589+/-27 microm) than in the control group (553+/-21 microm) (p = 0.003), the group with inactive ocular involvement (560+/-26 microm) (p < 0.001), and the group with no ocular involvement (558+/-25 microm) (p < 0.001). After appropriate treatment of patients with active ocular involvement, the mean CCT returned nearly to normal (563+/-20 microm) and the difference from controls was not significant. There was no significant difference for the mean CCT between controls and the patients with no ocular involvement or with inactive ocular involvement.

CONCLUSIONS

Behçet's patients with active ocular involvement have a thicker CCT than patients with inactive ocular involvement. There was no difference in CCT between controls and patients with no ocular involvement. The CCT of patients with active ocular involvement returned to nearly normal after treatment. CCT must be taken into account when developing a managing and following approach for Behcet's patients with active ocular involvement.

Novel approaches to Behçet's disease

Behçet's disease is a systemic inflammatory disorder. The patients have repeated exacerbations and remissions of the symptoms. This disease may produce a wide variety of symptoms. In mild cases, mucocutaneous lesions are only the symptoms during the whole clinical course, whereas ocular lesions, which occur in about 70% of the patients, can cause blindness. Involvement of the gastrointestinal tract, CNS and large vessels is less frequent, but sometimes life-threatening. Colchicine, NSAIDs, corticosteroids and immunosuppressants are employed for the treatment of Behçet's disease with therapies tailored to individual patients depending on clinical manifestations. Cyclosporin A is the most effective drug for ocular lesions at the present, but its neurotoxicity, which occurs in 20-30% of patients receiving cyclosporin A, restricts usage of the agent. Many patients are still suffering from a severe form of uveitis and serious neurological symptoms, which are resistant to any conventional therapies. New drugs have been investigated for Behçet's disease. IFN-alpha therapy has shown significant efficacy for common symptoms including ocular lesions without any serious adverse effects. Thalidomide and its analogues also appear to be applicable to this disease. Monoclonal antibody to TNF-alpha is now in clinical trials. These novel therapeutic approaches may provide much needed treatment options for patients with Behçet's disease.