Skewed Helper T-Cell Responses to IL-12 Family Cytokines Produced by Antigen-Presenting Cells and the Genetic Background in Behcet's Disease

Neutrophil extracellular traps and neutrophilic dermatosis: an update review

Neutrophils have both antimicrobial ability and pathogenic effect in the immune system, neutrophil extracellular traps (NETs) formation is one of the representative behaviors of their dual role. NETs formation was triggered by pathogen-related components and pathogen non-related proteins as cytokines to exert its effector functions. Recent studies indicate that the pathogenicity of NETs contributed to several skin diseases such as psoriasis, Stevens-Johnson syndrome, toxic epidermal necrolysis, and neutrophilic dermatosis. Especially in neutrophilic dermatosis, a heterogeneous group of inflammatory skin disorders characterized with sterile neutrophilic infiltrate on dermis, NETs formation was reported as the way of participation of neutrophils in the pathogenesis of these diseases. In this review, we describe the different processes of NETs formation, then summarized the most recent updates about the pathogenesis of neutrophilic dermatosis and the participation of NETs, including pyoderma gangrenosum and PAPA syndrome, Behçet syndrome, hidradenitis suppurativa, Sweet Syndrome, pustular dermatosis and other neutrophilic dermatosis. Furthermore, we discuss the link between NETs formation and the development of neutrophilic dermatosis.

Behçet syndrome

Behçet syndrome is a systemic vasculitis with an unknown aetiology affecting the small and large vessels of the venous and arterial systems. The presence of symptom clusters, regional differences in disease expression and similarities with, for example, Crohn's disease suggest that multiple pathological pathways are involved in Behçet syndrome. These disease features also make formulating disease criteria difficult. Genetic studies have identified HLA-B*51 as a genetic risk factor. However, the low prevalence of HLA-B*51 in many patients with bona fide disease, especially in non-endemic regions, suggests that other factors must also be operative in Behçet syndrome. Despite lacking a clear aetiological mechanism and definition, management of manifestations that include major vascular disease, eye disease and central nervous system involvement has improved with the help of new technology. Furthermore, even with our incomplete understanding of disease mechanisms, the prognoses of patients with Behçet syndrome, including those with eye disease, continue to improve. New treatment options and a better understanding of the underlying pathogenesis for various manifestations of this condition are required to further improve the management of the disease, which will improve patient quality of life.

Regulating the Polarization of Macrophages: A Promising Approach to Vascular Dermatosis

Macrophages, a kind of innate immune cells, derive from monocytes in circulation and play a crucial role in the innate and adaptive immunity. Under the stimulation of the signals from local microenvironment, macrophages generally tend to differentiate into two main functional phenotypes depending on their high plasticity and heterogeneity, namely, classically activated macrophage (M1) and alternatively activated macrophage (M2). This phenomenon is often called macrophage polarization. In pathological conditions, chronic persistent inflammation could induce an aberrant response of macrophage and cause a shift in their phenotypes. Moreover, this shift would result in the alteration of macrophage polarization in some vascular dermatoses; e.g., an increase in proinflammatory M1 emerges from Behcet's disease (BD), psoriasis, and systemic lupus erythematosus (SLE), whereas an enhancement in anti-inflammatory M2 appears in infantile hemangioma (IH). Individual polarized phenotypes and their complicated cytokine networks may crucially mediate in the pathological processes of some vascular diseases (vascular dermatosis in particular) by activation of T cell subsets (such as Th1, Th2, Th17, and Treg cells), deterioration of oxidative stress damage, and induction of angiogenesis, but the specific mechanism remains ambiguous. Therefore, in this review, we discuss the possible role of macrophage polarization in the pathological processes of vascular skin diseases. In addition, it is proposed that regulation of macrophage polarization may become a potential strategy for controlling these disorders.

Dysregulation of glycerophospholipid metabolism during Behçet's disease contributes to a pro-inflammatory phenotype of circulating monocytes

Behçet's disease (BD) is a relapsing, multisystem and inflammatory condition characterized by systemic vasculitis of small and large vessels. Although the etiopathogenesis of BD remains unknown, immune-mediated mechanisms play a major role in the development of the disease. BD patients present leukocyte infiltration in the mucocutaneous lesions as well as neutrophil hyperactivation. In contrast to neutrophils, whose involvement in the pathogenesis of BD has been extensively studied, the biology of monocytes during BD is less well known. In this study, we analyzed the phenotype and function of circulating monocytes of 38 BD patients from Hospital of Braga. In addition, we evaluated the impact of inflammatory and metabolomic plasma environment on monocyte biology. We observed a worsening of mitochondrial function, with lower mitochondrial mass and increased ROS production, on circulating monocytes of BD patients. Incubation of monocytes from healthy donors with the plasma of BD patients mimicked the observed phenotype, strongly suggesting the involvement of serum mediators. BD patients, regardless of their symptoms, had higher serum pro-inflammatory TNF-α and IP-10 levels and IL-1β/IL-1RA ratio. Untargeted metabolomic analysis identified a dysregulation of glycerophospholipid metabolism on BD patients, where a significant reduction of phospholipids was observed concomitantly with an increase of lysophospholipids and fatty acids. These observations converged to an enhanced phospholipase A2 (PLA2) activation. Indeed, inhibition of PLA2 with dexamethasone or the downstream cyclooxygenase (COX) enzyme with ibuprofen was able to significantly revert the mitochondrial dysfunction observed on monocytes of BD patients. Our results show that the plasma inflammatory environment coupled with a dysregulation of glycerophospholipid metabolism in BD patients contribute to a dysfunction of circulating monocytes.

Immunometabolic biomarkers of inflammation in Behçet's disease: relationship with epidemiological profile, disease activity and therapeutic regimens

Behcet's disease (BD) is a systemic inflammatory disease with a still unclear pathogenesis. Although several inflammatory molecules have been studied, current biomarkers are largely insensitive in BD and unable to predict disease progression and response to treatment. Our primary aim was to explore serum levels of soluble CD40 L (sCD40L), soluble intracellular adhesion molecule (sICAM-1), monocyte chemoattractant protein-1 (MCP-1), myeloperoxidase (MPO), leptin, resistin, osteoprotegerin (OPG), soluble type 1 tumour necrosis factor receptor (sTNFR), interleukin (IL)-6 and serum amyloid A (SAA) serum concentration in a cohort of 27 BD patients. The secondary aim was to evaluate potential correlations between the putative circulating biomarkers, demographic profile of patients, the status of disease activity, the specific organ involvement at the time of sample collection and different therapeutic regimens. Serum concentrations of sTNFR (P = 0·008), leptin (P = 0·0011), sCD40L (P < 0·0001) and IL-6 (P = 0·0154) were significantly higher in BD patients than in HC, while no difference was found in MCP-1, MPO and resistin serum levels. Moreover, we observed significantly higher sTNFR serum concentrations in BD patients presenting inactive disease than HC (P = 0·0108). A correlation between sTNFR and age was also found, with higher levels in patients over 40 years than HC (P = 0·0329). Although further research is warranted to elucidate the role of circulating biomarkers, some of that may contribute to the understanding of the physiopathology processes underlying BD activity and damage as well as to provide useful tools for prognostic purposes and a personalized treatment approach.

The exaggerated inflammatory response in Behçet's syndrome: identification of dysfunctional post-transcriptional regulation of the IFN-γ/CXCL10 IP-10 pathway

The mechanisms underlying the exaggerated inflammatory response in Behçet's syndrome (BS) remain poorly understood. We investigated the response of CD14(+) blood monocytes to interferon (IFN)-γ, focusing on the chemokine CXCL10. Chemokine synthesis and release were analysed at a protein and mRNA level following stimulation with IFN-γ. Findings in BS patients were compared with 25 healthy controls (HC), 15 rheumatoid arthritis (RA) and 15 systemic lupus erythematosus (SLE) disease control patients. BS monocytes produced significantly more CXCL10 protein than HC monocytes from 2 h following IFN-γ stimulation, despite equivalent quantities of mRNA, suggesting more efficient translation. This was significantly more pronounced in BS with high disease activity and in those with ocular and neurological clinical manifestations. The imbalance between CXCL10 protein and mRNA expression was not observed in either RA or SLE patients, and was not seen with other chemokines studied (CXCL9, CXCL11 and CCL2). Furthermore, BS monocytes treated with an alternative stimulant (LPS) did not show abnormal tumour necrosis factor (TNF)-α release. Sucrose density gradients to segregate monocyte CXCL10 mRNA into free RNA or polysome-associated RNA showed equal proportions in BS and HC samples, suggesting that the difference between BS and HC may be due to reduced negative control of CXCL10 translation in BS at a post-initiation level. We conclude that BS monocytes have dysfunctional post-transcriptional regulation of CXCL10 mRNA, resulting in over-expression of CXCL10 protein upon IFN-γ stimulation. As CXCL10 is a chemokine that recruits mononuclear cells, this abnormality may contribute to the exaggerated inflammatory responses that characterizes BS.

Comparative analysis of cytokine transcript profiles within mediastinal lymph node compartments of pigs after infection with porcine reproductive and respiratory syndrome genotype 1 strains differing in pathogenicity

Porcine reproductive and respiratory syndrome virus (PRRSV) induces a weak immune response enabling it to persist in different organs of infected pigs. This has been attributed to the ability of PRRSV to influence the induction of cytokine responses. In this study, we investigated the cytokine transcriptional profiles in different compartments of the mediastinal lymph node of pigs infected with three genotype 1 PRRSV strains of differing pathogenicity: the low virulence prototype Lelystad virus (LV), and UK field strain 215–06 and the highly virulent subtype 3 SU1-Bel isolate from Belarus. We have used a combination of laser capture micro-dissection (LCM) followed by real time quantitative PCR (RT-qPCR) and immunohistochemical (IHC) detection of immune cell markers (CD3, CD79a and MAC387) and RT-qPCR quantification of PRRSV and cytokine transcripts. Compared to mock infected pigs, we found a significant downregulation of TNF-α and IFN-α in follicular and interfollicular areas of the mediastinal lymph node from 3 days post-infection (dpi) in animals infected with all three strains. This was accompanied by a transient B cell depletion and T cell and macrophage infiltration in the follicles together with T cell depletion in the interfollicular areas. A delayed upregulation of IFN-γ and IL-23p19 was observed mainly in the follicles. The PRRSV load was higher in all areas and time-points studied in the animals infected with the SU1-Bel strain. This paper describes the first application of LCM to study the cytokine transcript profiles and virus distribution in different compartments of the lymph node of pigs.