Mannan induces ROS-regulated, IL-17A-dependent psoriasis arthritis-like disease in mice. Proc Natl Acad Sci U S A. 2014;111:E3669-E3678. [PMID: 25136095 DOI: 10.1073/pnas.1405798111]

The Role of Gamma Delta T Cells in Autoimmune Rheumatic Diseases

Autoimmune rheumatic diseases (ARDs), affecting ~1–1.5% of all humans, are associated with considerable life long morbidity and early mortality. Early studies in the 1990s showed numerical changes of the recently discovered γδ T cells in the peripheral blood and in affected tissues of patients with a variety of ARDs, kindling interest in their role in the immuno-pathogenesis of these chronic inflammatory conditions. Indeed, later studies applied rapid developments in the understanding of γδ T cell biology, including antigens recognized by γδ T cells, their developmental programs, states of activation, and cytokine production profiles, to analyze their contribution to the pathological immune response in these disorders. Here we review the published studies addressing the role of γδ T in the major autoimmune rheumatic diseases, including rheumatoid arthritis, juvenile idiopathic arthritis, ankylosing spondylitis, systemic lupus erythematosus and scleroderma, and animal models thereof. Due to their unique properties spanning adaptive and innate immune functions, the ever deeper understanding of this unique T cell population is shedding new light on the pathogenesis of, while potentially enabling new therapeutic approaches to, these diseases.

Pathophysiology, assessment and treatment of psoriatic dactylitis

Dactylitis is diffuse swelling of the digits that is usually related to an underlying inflammatory or infiltrative disorder. Psoriatic arthritis (PsA) is the most common severe disease thought to cause dactylitis. Our understanding of the pathogenesis of PsA-related dactylitis comes from experimental animal models of PsA-like disease, as well as advances in imaging and other clinical studies. Clinical trials in PsA have increasingly included dactylitis as an important secondary outcome measure. These studies indicate that cytokines drive multi-locus microanatomical pan-digital pathology. Given the importance of pro-inflammatory cytokines, the pathogenesis of dactylitis is best understood as an initial aberrant innate immune response to biomechanical stress or injury, with subsequent adaptive immune mechanisms amplifying the dactylitis inflammatory response. Regarding the treatment of dactylitis, no studies have been conducted using dactylitis as the primary outcome measure, and the current knowledge comes from analysis of dactylitis as a secondary outcome measure.

Interleukin-23 pathway at the enthesis: The emerging story of enthesitis in spondyloarthropathy

The inflammatory disorders collectively termed the seronegative spondyloarthropathies (SpA) include ankylosing spondylitis (AS), psoriatic arthritis (PsA), reactive arthritis, the arthritis associated with inflammatory bowel disease including Crohn's disease and ulcerative colitis, the arthritis related to anterior uveitis, and finally, somewhat controversially Behcet's disease. All of these diseases are associated with SNPs in the IL-23R or the interleukin-23 (IL-23) cytokine itself and related downstream signaling JAK pathway genes and the interleukin-17 (IL-17) pathway. In rheumatoid arthritis, the target of the immune response is the synovium but the SpA disorders target the tendon, ligament, and joint capsule skeletal anchorage points that are termed entheses. The discovery that IL-23R-expressing cells were ensconced in healthy murine enthesis, and other extraskeletal anchorage points including the aortic root and the ciliary body of the eye and that systemic overexpression of IL-23 resulted in a severe experimental SpA, confirmed a fundamentally different immunobiology to rheumatoid arthritis. Recently, IL-23R-expressing myeloid cells and various innate and adaptive T cells that produce IL-17 family cytokines have also been described in the human enthesis. Blockade of IL-23 pathway with either anti-p40 or anti-p19 subunits has resulted in some spectacular therapeutic successes in psoriasis and PsA including improvement in enthesitis in the peripheral skeleton but has failed to demonstrate efficacy in AS that is largely a spinal polyenthesitis. Herein, we discuss the known biology of IL-23 at the human enthesis and highlight the remarkable emerging story of this unique skeletal tissue.

Oncogenic role of Tc17 cells in cervical cancer development

BACKGROUND

As one of the subsets of CD8⁺ T cells, Tc17 cells have recently been identified and are characterized by the secretion of interleukin (IL)-17, which is related to inflammatory diseases.

AIM

To assess the status of Tc17 cells in cervical cancer and investigate the biological function of Tc17 cells in cervical cancer development.

METHODS

Flow cytometry assay, immunohistochemistry, and immunofluorescence were performed to detect the levels and phenotype of Tc17 cells in blood and tumor samples from patients with cervical cancer. Prior to cell suspension culture, ELISA was carried out to measure the production of IL-6, IL-1β, IL-23, CXCL12, and IL-17 in tumor tissue supernatant and co-cultured supernatant of patients with cervical cancer. In addition, multivariate analysis was performed to identify factors associated with overall survival using the Cox proportional hazards model.

RESULTS

Compared with normal tissues, Tc17 cells specifically accumulated in tumor tissues of cervical cancer patients. Cancer cells produced a greater amount of IL-6, IL-1β, and IL-23, which in turn promoted Tc17 cell polarization. Unlike the traditional cytotoxic CD8⁺ T cells, Tc17 cells secreted IL-17, which subsequently promoted CXCL12 expression in tumor cells, eventually enhancing the proliferation and migration of tumor cells. Thus, the ratio of tumor-infiltrating Tc17 cells was highly correlated with poor clinical outcome in patients with cervical cancer.

CONCLUSION

Our data identified the oncogenic role of Tc17 cells in the development of cervical cancer. We propose that the ratio of Tc17 cells may be a useful index in the prognosis of patients with cervical cancer.

Convallatoxin induces HaCaT cell necroptosis and ameliorates skin lesions in psoriasis-like mouse models

Psoriasis is considered an immune-mediated inflammatory skin disorder that affects the quality of life of nearly four percent of the world population. Considering the side effects of existing therapeutic drugs and the urgent need for new drug development, we screened more than 250 traditional Chinese medicine compounds to identify drugs that significantly reduced the viability of human HaCaT keratinocytes, a psoriasis-related model cell line. Convallatoxin (CNT) was found to be a highly effective inhibitor of HaCaT cell viability. Subsequent mechanistic studies revealed that CNT induced HaCaT cell death by necroptosis rather than by apoptosis. CNT destroyed the membrane integrity of HaCaT cells, as detected by nuclear propidium iodide (PI) staining and lactate dehydrogenase (LDH) release. Additionally, the intercellular levels of adenosine triphosphate (ATP) were lower in HaCaT cells treated with CNT than in control HaCaT cells, and typical necroptosis-associated characteristics were observed by electron microscopy in cells treated with CNT. Furthermore, compared with control HaCaT cells, CNT-treated HaCaT cells produced more reactive oxygen species (ROS), but this effect was inhibited by the antioxidants N-acetyl-cysteine (NAC), diphenyleneiodonium chloride (DPI), and apocynin and the necroptosis inhibitor Nec-1. In addition, antioxidant treatment attenuated necroptotic cell death, suggesting that CNT-induced HaCaT necroptosis is mediated by oxidative stress. More importantly, CNT ameliorated skin lesions and inflammation in imiquimod (IMQ)- and 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-induced psoriasis-like mouse models. In conclusion, our results demonstrate that CNT is cytotoxic against HaCaT cells in vitro and exerts antipsoriatic activities in two mouse models of psoriasis in vivo, making CNT a potential promising candidate drug for future research.

Mini Review: New Treatments in Psoriatic Arthritis. Focus on the IL-23/17 Axis

Psoriasis, an inflammatory skin disease, and psoriatic arthritis (PsA), an inflammatory arthritis, share clinical, genetic, and pathogenic factors and may be summed as one disease, the psoriatic disease. Interleukin (IL)-17 plays a major role in the development of both psoriasis and PsA. IL-23 is important in the proliferation and maintenance of IL-17, and therefore, cytokines of the IL-23/IL-17 axis attracted much interest as therapeutic targets in psoriasis and PsA. Therapeutic agents targeting the IL-23/IL-17 axis have been proven to be very effective in psoriasis and PsA, some are already in the therapeutic armamentarium and others are in the development. Some agents, target IL-23 and others IL-17 and include anti-IL-12/IL-23 p40 (ustekinumab, briankizumab), anti-IL-23p19 (guselkumab, tildrakizumab, risankizumab, brazikumab, mirikizumab), anti-IL-17A (secukinumab, ixekizumab), dual anti-IL-17A and anti-IL-17F (bimekizumab), or anti-IL-17 receptor (brodalumab) monoclonal antibodies. Janus tyrosine kinase(JAK) inhibitors also directly affect IL-23 and, thus, IL-17. After the first-generation pan-JAK inhibitors have been shown efficacy (tofacitinib, baricitinib), new-generation selective JAK inhibitors (filgotinib, upadacitinib) are under investigation in psoriasis and PsA.

The role of IL-17A in axial spondyloarthritis and psoriatic arthritis: recent advances and controversies

Although the pathogenic mechanisms underlying axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA) are not fully elucidated, several lines of evidence suggest that immune responses mediated by interleukin 17A (IL-17A) play a pivotal role in both diseases. This is best highlighted by the significant clinical efficacy shown with inhibitors of IL-17A in treating axSpA and PsA. Nevertheless, a number of knowledge gaps exist regarding the role of IL-17A in the pathophysiology of spondyloarthritis in man, including its cellular origin, its precise role in discrete disease processes such enthesitis, bone erosion, and bone formation, and the reasons for the discrepant responses to IL-17A inhibition observed in certain other spondyloarthritis manifestations. In this review, we focus on the latest data from studies investigating the role of IL-17A in ankylosing spondylitis (AS) and PsA that build on existing and emerging scientific knowledge in the field. Key remaining research questions are also highlighted to guide future research.

Glucan and Mannan-Two Peas in a Pod

In recent decades, various polysaccharides isolated from algae, mushrooms, yeast, and higher plants have attracted serious attention in the area of nutrition and medicine. The reasons include their low toxicity, rare negative side effects, relatively low price, and broad spectrum of therapeutic actions. The two most and best-studied polysaccharides are mannan and glucan. This review focused on their biological properties.

Hepatic serum amyloid A1 upregulates interleukin-17 (IL-17) in γδ T cells through Toll-like receptor 2 and is associated with psoriatic symptoms in transgenic mice

Serum amyloid A (SAA) is an acute phase protein with pro-inflammatory cytokine-like properties. Recent studies have revealed that SAA promoted interleukin-17 (IL-17) production by various cells, including γδ T cells. γδ T cells are innate immune cells and express Toll-like receptor 2 (TLR2) on their surface, which is one of the SAA receptors. In this study, we investigated the relationship between γδ T cells and SAA1 through TLR2, by using hepatic SAA1-overexpressing transgenic (TG) mice. By injecting CU-CPT22, which is a TLR2 inhibitor, into the mice, we confirmed that SAA1 induced IL-17 in γδ T cells through TLR2. In vitro studies have confirmed that SAA1 increased IL-17 secretion in γδ T cells in combination with IL-23. We also observed a thickened epidermis layer and granulocyte penetration into the skin similar to the pathology of psoriasis in TG mice. In addition, strongly expressed SAA1 and penetration of γδ T cells in the skin of TG mice were detected. The exacerbation of psoriasis is associated with an increase in IL-17 levels. Therefore, these symptoms were induced by IL-17-producing γδ T cells increased by SAA1. Our study confirmed that SAA1 was a prominent protein that increased IL-17 levels through TLR2 in γδ T cells, confirming the possibility that SAA1 may exacerbate inflammatory diseases through γδ T cells.

Rapid spread of mannan to the immune system, skin and joints within 6 hours after local exposure

Psoriasis (Ps), psoriatic arthritis (PsA) and rheumatoid arthritis (RA) are common diseases dependent on environmental factors that activate the immune system in unknown ways. Mannan is a group of polysaccharides common in the environment; they are potentially pathogenic, because at least some of them induce Ps-, PsA- and RA-like inflammation in mice. Here, we used positron emission tomography/computed tomography to examine in-vivo transport and spread of mannan labelled with fluorine-18 [¹⁸ F]. The results showed that mannan was transported to joints (knee) and bone marrow (tibia) of mice within 6 h after intraperitoneal injection. The time it took to transport mannan, and its presence in blood, indicated cellular transport of mannan within the circulatory system. In addition, mannan was filtered mainly through the spleen and liver. [¹⁸ F]fluoromannan was excreted via kidneys, small intestine and, to some extent, the mouth. In conclusion, mannan reaches joints rapidly after injection, which may explain why mannan-induced inflammatory disease is targeted to these tissues.

Cold atmospheric plasma ameliorates imiquimod-induced psoriasiform dermatitis in mice by mediating antiproliferative effects

Psoriasis is a chronic hyperproliferative skin disease characterised by excessive growth of keratinocytes. Indeed, inducing keratinocyte apoptosis is a key mechanism responsible for psoriatic plaques clearance following some important existing therapies, which display pro-oxidant activity. Cold atmospheric plasma (CAP), acting as a tuneable source of reactive oxygen and nitrogen species (RONS), can controllably transfer RONS to the cellular environment, deliver antiproliferative RONS concentrations and exert antiproliferative and proapoptotic effects. This study was undertaken to evaluate the therapeutic potential of CAP in psoriasis. We used cell models of psoriasis-like inflammation by adding lipopolysaccharide (LPS) or tumour necrosis factor alpha (TNF-α) to HaCaT keratinocytes. Indirect plasma, plasma-activated medium (PAM), was administered to HaCaT cells. Atmospheric pressure plasma jet (APPJ) was applied directly to imiquimod (IMQ)-induced psoriasiform dermatitis in mice. The results showed that PAM induced an increase in intracellular ROS and caused keratinocyte apoptosis. Moreover, cells under inflammation showed lesser viability and larger apoptosis rate. With repeated administration of APPJ, psoriasiform lesions showed ameliorated morphological manifestation and reduced epidermal proliferation. Overall, this study supports that CAP holds good potential in psoriasis treatment.

Redox imbalance and IL-17 responses in memory CD4+ T cells from patients with psoriasis

All stages of the inflammatory process involved in T cell-mediated chronic skin disorders like psoriasis are affected by redox imbalance. On the other hand, Th17 cells have a critical role in the pathogenesis of psoriasis. In this study, we evaluated redox status in memory CD4 + T cells and plasma of patients with psoriasis and its correlation with IL-17 response. To this end, memory T cells were isolated from 10 patients with psoriasis and 10 controls. Intracellular Glutathione (GSH), reactive oxygen species (ROS) and superoxide as well as IL-17 were measured using flow cytometry. Plasma total anti-oxidant capacity (TAC) was quantified by ferric reducing ability of plasma (FRAP) assay. The expression of catalase (CAT), superoxide dismutase 1(SOD1), superoxide dismutase 2 (SOD2), nuclear factor, erythroid 2 like 2 (NFE2L2) and cytochrome b-245 beta chain (CYBB) genes were analysed using real-time PCR. Our results showed an increased intracellular ROS production in memory CD4 + T cells of patients compared to controls, (P = 0.04). Furthermore, a significant decrease in expression of catalase gene was found in patients, (P = 0.02). However, no significant differences were observed for intracellular GSH, IL-17 and TAC levels between patients and controls. Also, no correlation was seen between the intracellular IL-17 level and intracellular ROS, GSH and catalase gene expression levels. Collectively, we found an increased ROS production in stimulated memory T cells of patients that could be due to reduced expression of catalase gene. However, it seems that these redox abnormalities have no relationship with IL-17 response in memory T cells.

MicroRNA‑146a inhibits the inflammatory responses induced by interleukin‑17A during the infection of Helicobacter pylori

Helicobacter pylori (H. pylori) infection is the major cause of chronic active gastritis and peptic ulcer disease. Upregulation of IL‑17A is associated with H. pylori infection in the gastric mucosa; however, the factors involved in the regulation of interleukin (IL)‑17A‑induced inflammatory responses in H. pylori‑associated gastritis remain unknown. MicroRNAs (miRNAs) serve as key post‑transcriptional regulators of gene expression and are associated with the H. pylori infection. The present study aimed to analyze the effects of IL‑17A on the expression of miR‑146a upon infection with H. pylori, as well as to identify the possible impact of miR‑146a dysregulation on the inflammatory response in vivo and in vitro. Reverse transcription‑quantitative polymerase chain reaction analysis was used to determine the expression levels of miR‑146a in gastric epithelial cells upon IL‑17A stimulation. The effects of miR‑146a mimics on IL‑17A‑induced inflammatory responses in SGC‑7901 cells were evaluated. The effects of miR‑146a mimics on the expression levels of IL‑1 receptor‑associated kinase 1 (IRAK1) and tumor necrosis factor receptor‑associated factor 6 (TRAF6) upon IL‑17A treatment were analyzed, and the IL‑17A‑stimulated inflammation following the silencing of IRAK1 and TRAF6 was observed. In addition, the correlation between miR‑146a and IL‑17A in human gastric mucosa with H. pylori was examined. The results indicated that IL‑17A‑induced miR‑146a may regulate the inflammatory response during the infection of H. pylori in a nuclear factor‑κB‑dependent manner. Furthermore, the expression of miR‑146a and IL‑17A are positively correlated in human gastric mucosa infected with H. pylori. These data suggested that miR‑146a may serve as a biomarker or therapeutic target in gastritis therapy.

LACC1 Regulates TNF and IL-17 in Mouse Models of Arthritis and Inflammation

Both common and rare genetic variants of laccase domain-containing 1 (LACC1, previously C13orf31) are associated with inflammatory bowel disease, leprosy, Behcet disease, and systemic juvenile idiopathic arthritis. However, the functional relevance of these variants is unclear. In this study, we use LACC1-deficient mice to gain insight into the role of LACC1 in regulating inflammation. Following oral administration of Citrobacter rodentium, LACC1 knockout (KO) mice had more severe colon lesions compared with wildtype (WT) controls. Immunization with collagen II, a collagen-induced arthritis (CIA) model, resulted in an accelerated onset of arthritis and significantly worse arthritis and inflammation in LACC1 KO mice. Similar results were obtained in a mannan-induced arthritis model. Serum and local TNF in CIA paws and C. rodentium colons were significantly increased in LACC1 KO mice compared with WT controls. The percentage of IL-17A-producing CD4⁺ T cells was elevated in LACC1 KO mice undergoing CIA as well as aged mice compared with WT controls. Neutralization of IL-17, but not TNF, prevented enhanced mannan-induced arthritis in LACC1 KO mice. These data provide new mechanistic insight into the function of LACC1 in regulating TNF and IL-17 during inflammatory responses. We hypothesize that these effects contribute to immune-driven pathologies observed in individuals carrying LACC1 variants.

Enthesitis and Dactylitis in Psoriatic Disease: A Guide for Dermatologists

Psoriatic arthritis (PsA) is an inflammatory arthritis that is estimated to affect approximately 30% of patients with psoriasis. Enthesitis and dactylitis, two hallmarks of PsA, are associated with radiographic peripheral/axial joint damage and severe disease. Clinical symptoms of enthesitis include tenderness, soreness, and pain at entheses on palpation, whereas dactylitis is recognized by swelling of an entire digit that is different from adjacent digits. Both ultrasound and magnetic resonance imaging can be used to diagnose enthesitis and dactylitis, especially in patients in whom symptoms may be difficult to discern. Delayed treatment of PsA can result in irreversible joint damage and reduced quality of life. Thus, it is recommended that dermatologists monitor patients with psoriasis for these two early and important manifestations of PsA.

Sulforaphane Inhibits Inflammatory Responses of Primary Human T-Cells by Increasing ROS and Depleting Glutathione

The activity and function of T-cells are influenced by the intra- and extracellular redox milieu. Oxidative stress induces hypo responsiveness of untransformed T-cells. Vice versa increased glutathione (GSH) levels or decreased levels of reactive oxygen species (ROS) prime T-cell metabolism for inflammation, e.g., in rheumatoid arthritis. Therefore, balancing the T-cell redox milieu may represent a promising new option for therapeutic immune modulation. Here we show that sulforaphane (SFN), a compound derived from plants of the Brassicaceae family, e.g., broccoli, induces a pro-oxidative state in untransformed human T-cells of healthy donors or RA patients. This manifested as an increase of intracellular ROS and a marked decrease of GSH. Consistently, increased global cysteine sulfenylation was detected. Importantly, a major target for SFN-mediated protein oxidation was STAT3, a transcription factor involved in the regulation of TH17-related genes. Accordingly, SFN significantly inhibited the activation of untransformed human T-cells derived from healthy donors or RA patients, and downregulated the expression of the transcription factor RORγt, and the TH17-related cytokines IL-17A, IL-17F, and IL-22, which play a major role within the pathophysiology of many chronic inflammatory/autoimmune diseases. The inhibitory effects of SFN could be abolished by exogenously supplied GSH and by the GSH replenishing antioxidant N-acetylcysteine (NAC). Together, our study provides mechanistic insights into the mode of action of the natural substance SFN. It specifically exerts TH17 prone immunosuppressive effects on untransformed human T-cells by decreasing GSH and accumulation of ROS. Thus, SFN may offer novel clinical options for the treatment of TH17 related chronic inflammatory/autoimmune diseases such as rheumatoid arthritis.

Metformin Promotes HaCaT Cell Apoptosis through Generation of Reactive Oxygen Species via Raf-1-ERK1/2-Nrf2 Inactivation

Although metformin (MET) may be useful for the treatment of psoriasis, the mechanisms underlying its method of action have yet to be fully elucidated. Here, the relationship between MET function and reactive oxygen species (ROS) levels and the underlying mechanism were explored in human immortalized keratinocyte cell line (HaCaT). HaCaT cells were incubated with MET at 0, 10, 20, 40, and 60 mM for 24 h. The cell viability was evaluated by the CCK-8 assay. The cell apoptosis rate and intracellular ROS levels were examined using flow cytometry. The protein expression and the phosphorylation levels of nuclear factor erythroid-derived 2 related factor 2 (Nrf2), Raf-1, and ERK1/2 were assessed by Western blot. The specific ROS scavenger N-acetyl-cysteine (NAC) and the specific Nrf2 agonist Oltipraz (OPZ) were used to analyze the effect of MET. MET decreased HaCaT cell proliferation and induced HaCaT cell apoptosis in a dose-dependent manner. MET was found to elevate intracellular ROS levels in a dose-dependent manner, while pretreatment with NAC attenuated these effects. MET inhibits the protein expression and the phosphorylation levels of Nrf2. The combination of OPZ and MET can significantly increase the cell viability, decrease the rate of apoptosis, and attenuate the intracellular ROS levels relative to MET alone. MET inhibits the protein expression and the phosphorylation levels of Raf-1 and ERK1/2. MET was found to attenuate Raf-1-ERK1/2 signaling in HaCaT cells to suppress the expression and phosphorylation levels of Nrf2, which contributed to the intracellular generation of ROS and the pro-apoptotic effects of MET.

The dual role of Reactive Oxygen Species in autoimmune and inflammatory diseases: evidence from preclinical models

Reactive oxygen species (ROS) are created in cells during oxidative phosphorylation by the respiratory chain in the mitochondria or by the family of NADPH oxidase (NOX) complexes. The first discovered and most studied of these complexes, NOX2, mediates the oxidative burst in phagocytes. ROS generated by NOX2 are dreadful weapons: while being essential to kill ingested pathogens they can also cause degenerative changes on tissue if production and release are not balanced by sufficient detoxification. In the last fifteen years evidence has been accumulating that ROS are also integral signaling molecules and are important for regulating autoimmunity and immune-mediated inflammatory diseases. It seems that an accurate redox balance is necessary to sustain an immune state that both prevents the development of overt autoimmunity (the bright side of ROS) and minimizes collateral tissue damage (the dark side of ROS). Herein, we review studies from rodent models of arthritis, lupus, and neurodegenerative diseases that show that low NOX2-derived ROS production is linked to disease and elaborate on the underlying cellular and molecular mechanisms and the translation of these results to disease in humans.

Association of NOX2 subunits genetic variants with autoimmune diseases

A single nucleotide polymorphism in Ncf1 has been found with a major effect on chronic inflammatory autoimmune diseases in the rat with the surprising observation that a lower reactive oxygen response led to more severe diseases. This finding was subsequently reproduced in the mouse and the effect operates in many different murine diseases through different pathogenic pathways; like models for rheumatoid arthritis, encephalomyelitis, lupus, gout, psoriasis and psoriatic arthritis. The human gene is located in an unstable region with many variable sequence repetitions, which means it has not been included in any genome wide associated screens so far. However, identification of copy number variations and single nucleotide polymorphisms has now clearly shown that major autoimmune diseases are strongly associated with the Ncf1 locus. In systemic lupus erythematosus the associated Ncf1 polymorphism (leading to an amino acid substitution at position 90) is the strongest locus and is associated with a lower reactive oxidative burst response. In addition, more precise mapping analysis of polymorphism of other NOX2 genes reveals that these are also associated with autoimmunity. The identified genetic association shows the importance of redox control and that ROS regulate chronic inflammation instead of promoting it. The genetic identification of Ncf1 polymorphisms now opens for relevant studies of the regulatory mechanisms involved, effects that will have severe consequences in many different pathogenic pathways and understanding of the origin of autoimmune diseases.

Chronic Active Arthritis Driven by Macrophages Without Involvement of T Cells: A Novel Experimental Model of Rheumatoid Arthritis

OBJECTIVE

To develop a new chronic rheumatoid arthritis model that is driven by the innate immune system.

METHODS

Injection of a cocktail of 4 monoclonal antibodies against type II collagen, followed on days 5 and 60 by intraperitoneal injections of mannan (from Saccharomyces cerevisiae), was used to induce development of chronic arthritis in B10.Q mice. The role of the innate immune system as compared to the adaptive immune system in this arthritis model was investigated using genetically modified mouse strains.

RESULTS

A new model of chronic relapsing arthritis was characterized in B10.Q mice, in which a persistently active, chronic disease was found. This relapsing disease was driven by macrophages lacking the ability to mount a reactive oxygen species response against pathogens, and was associated with the classical/alternative pathway, but not the lectin pathway, of complement activation. The disease was independent of Fcγ receptor type III, and also independent of the activity of adaptive immune cells (B and T cells), indicating that the innate immune system, involving complement activation, could be the sole driver of chronicity.

CONCLUSION

Chronic active arthritis can be driven innately by macrophages without the involvement of T and B cells in the adaptive immune system.

Augmented Th17 Differentiation Leads to Cutaneous and Synovio-Entheseal Inflammation in a Novel Model of Psoriatic Arthritis

OBJECTIVE

To introduce a novel preclinical animal model of psoriatic arthritis (PsA) in R26Stat3Cstopfl/fl CD4Cre mice, and to investigate the role of Th17 cytokines in the disease pathogenesis.

METHODS

We characterized a novel murine model of Th17-driven cutaneous and synovio-entheseal disease directed by T cell-specific expression of a hyperactive Stat3 allele. By crossing R26Stat3Cstopfl/fl CD4Cre mice onto an interleukin-22 (IL-22)-knockout background or treating the mice with a neutralizing antibody against IL-17, we interrogated how these Th17 cytokines could contribute to the pathogenesis of PsA.

RESULTS

R26Stat3Cstopfl/fl CD4Cre mice developed acanthosis, hyperkeratosis, and parakeratosis of the skin, as well as enthesitis/tendinitis and periarticular bone erosion in different joints, accompanied by osteopenia. T cell-specific expression of a hyperactive Stat3C allele was found to drive the augmented Th17 response in these animals. Careful characterization of the mouse bone marrow revealed an increase in osteoclast progenitor (OCP) and RANKL-producing cells, which contributed to the osteopenia phenotype observed in the mutant animals. Abrogation of the Th17 cytokines IL-17 or IL-22 improved both the skin and bone phenotype in R26Stat3Cstopfl/fl CD4Cre mice, revealing a central role of Th17 cells in the regulation of OCP and RANKL expression on stromal cells.

CONCLUSION

Perturbation of the IL-23/Th17 axis instigates Th17-mediated inflammation in R26Stat3Cstopfl/fl CD4Cre mice, leading to cutaneous and synovio-entheseal inflammation and bone pathologic features highly reminiscent of human PsA. Both IL-17A and IL-22 produced by Th17 cells appear to play critical roles in promoting the cutaneous and musculoskeletal inflammation that characterizes PsA.

Enthesitis: Much More Than Focal Insertion Point Inflammation

Purpose of Review

Recognition of the importance of enthesitis as the pivotal pathological process underpinning spondyloarthropathies (SpA) has increased in recent years. Thus, we summarized the current knowledge on the pathogenic role of enthesitis on SpA shown by both animal models and human studies in vivo.

Recent Findings

Experimental models have shown several SpA-like diseases that commence at entheses and are linked to nail disease as well as dactylitis, two important entheseal-associated conditions in humans. Frequently, enthesitis is not the primary outcome measure in studies of peripheral PsA and SpA although arguably it is the key parameter being indirectly assessed in spinal disease in ankylosing spondylitis. The use of different agents including JAK, IL-17, and IL-23 inhibitors contributes significantly to our understanding of enthesitis in terms of involved immune pathways.

Summary

Enthesitis and enthesis organ inflammation may be the primary pathological process underlying SpA associated skeletal inflammation. Emergent studies are beginning to elucidate the molecular basis for this type of joint inflammatory response.

Mannan-induced Nos2 in macrophages enhances IL-17-driven psoriatic arthritis by innate lymphocytes

Previous identification of the inducible nitric oxide synthase (NOS2) gene as a risk allele for psoriasis (Ps) and psoriatic arthritis (PsA) suggests a possible pathogenic role of nitric oxide (NO). Using a mouse model of mannan-induced Ps and PsA (MIP), where macrophages play a regulatory role by releasing reactive oxygen species (ROS), we found that NO was detectable before disease onset in mice, independent of a functional nicotinamide adenine dinucleotide phosphate oxidase 2 complex. MIP was suppressed by either deletion of Nos2 or inhibition of NO synthases with NG-nitro-l-arginine methyl ester, demonstrating that Nos2-derived NO is pathogenic. NOS2 expression was also up-regulated in lipopolysaccharide- and interferon-γ-stimulated monocyte subsets from patients with PsA compared to healthy controls. Nos2-dependent interleukin-1α (IL-1α) release from skin macrophages was essential for arthritis development by promoting IL-17 production of innate lymphoid cells. We conclude that Nos2-derived NO by tissue macrophages promotes MIP, in contrast to the protective effect by ROS.

Whodunit? The Contribution of Interleukin (IL)-17/IL-22-Producing γδ T Cells, αβ T Cells, and Innate Lymphoid Cells to the Pathogenesis of Spondyloarthritis

γδ T cells, αβ T cells, and innate lymphoid cells (ILCs) are capable of producing interleukin (IL)-17A, IL-17F, and IL-22. Among these three families of lymphocytes, it is emerging that γδ T cells are, at least in rodents, the main source of these key pro-inflammatory cytokines. γδ T cells were implicated in multiple inflammatory and autoimmune diseases, including psoriasis, experimental autoimmune encephalomyelitis and uveitis, colitis, and rheumatoid arthritis. Recent findings pointed toward a central role of γδ T cells in the pathogenesis of spondyloarthritis (SpA), a group of inflammatory rheumatic diseases affecting the axial skeleton. SpA primarily manifests as inflammation and new bone formation at the entheses, which are connecting tendons or ligaments with bone. In SpA patients, joint inflammation is frequently accompanied by extra-articular manifestations, such as inflammatory bowel disease or psoriasis. In humans, genome-wide association studies could link the IL-23/IL-17 cytokine axis to SpA. Accordingly, antibodies targeting IL-23/IL-17 for SpA treatment already showed promising results in clinical studies. However, the contribution of IL-17-producing γδ T cells to SpA pathogenesis is certainly not an open-and-shut case. Indeed, the cell types that are chiefly involved in local inflammation in human SpA still remain largely unclear. Some studies focusing on blood or synovium from SpA patients reported augmented IL-17-producing and IL-23 receptor-expressing γδ T cells, but other cell types might contribute as well. Here, we summarize the current understanding of how γδ T cells, αβ T cells, and ILCs contribute to the pathogenesis of human and experimental SpA.

The lymphoid cell network in the skin

Cutaneous immunity represents a crucial component of the mammalian immune response. The presence of a large array of commensal microorganisms along with a myriad of environmental stresses necessitates constant immuno-surveillance of the tissue. To achieve a perfect balance between immune-tolerance and immune-activation, the skin harbors strategically localized immune cell populations that modulate these responses. To maintain homeostasis, innate and adaptive immune cells assimilate microenvironmental cues and coordinate cellular and molecular functions in a spatiotemporal manner. The role of lymphoid cells in cutaneous immunity is gaining much appreciation due to their important roles in regulating skin health and pathology. In this review, we aim to highlight the recent advances in the field of cutaneous lymphoid biology.

The Macrophage Mannose Receptor Regulate Mannan-Induced Psoriasis, Psoriatic Arthritis, and Rheumatoid Arthritis-Like Disease Models

The injection of mannan into mice can result in the development of psoriasis (Ps) and psoriatic arthritis (PsA), whereas co-injection with antibodies toward collagen type II leads to a chronic rheumatoid-like arthritis. The critical event in all these diseases is mannan-mediated activation of macrophages, causing more severe disease if the macrophages are deficient in neutrophil cytosolic factor 1 (Ncf1), i.e., lack the capacity to make a reactive oxygen species (ROS) burst. In this study, we investigated the role of one of the receptors binding mannan; the macrophage mannose receptor (MR, CD206). MR is a C-type lectin present on myeloid cells and lymphatics. We found that mice deficient in MR expression had more severe mannan-induced Ps, PsA as well as rheumatoid-like arthritis. Interestingly, the MR-mediated protection was partly lost in Ncf1 mutated mice and was associated with an type 2 macrophage expansion. In conclusion, these results show that MR protects against a pathogenic inflammatory macrophage response induced by mannan and is associated with induction of ROS.

Reactive Oxygen Species Regulate Both Priming and Established Arthritis, but with Different Mechanisms

AIMS

Neutrophil cytosolic factor 1 (NCF1) is a key regulatory component of the phagocytic NOX2 complex, which produces reactive oxygen species (ROS). Polymorphism of the Ncf1 gene is associated with increased arthritis severity. In this study, we generated targeted Ncf1 knock-in mice with inducible Ncf1 expression and determined the critical time window during which the NOX2-derived ROS protect the mice from arthritis.

RESULTS

Targeted Ncf1 knock-in mice lacked NOX2-derived ROS, and in vivo allelic conversion of Ncf1 by the CreER^T2 recombinase led to full protein expression and ROS production within 10 days. Mice in which Ncf1 had been activated before immunization with type II collagen (CII) developed only mild clinical symptoms of collagen-induced arthritis (CIA), whereas the ROS-deficient littermates had severe arthritis. The functional Ncf1 restricted the expansion of IL-17A-producing T cells specific for the immunodominant CII peptide. When the Ncf1 gene was activated after the priming phase, Ncf1-dependent protection from autoimmune arthritis was still observed, together with a reduced number of splenic monocytes but it was not associated with alterations in peptide-specific T cell response. The Ncf1-deficient mice expressed pronounced interferon signature, which could be normalized by conditional expression of Ncf1 and was also present in the Ncf1-mutated mouse during arthritis. Innovation and Conclusion: Ncf1 deficiency has been known to predispose to autoimmunity in both humans and rodents. Our in vivo results point to a regulatory role of NOX2-derived ROS not only during priming but also during the effector phase of CIA, most likely via different mechanisms. Antioxid. Redox Signal. 27, 1473-1490.

Rheumatoid arthritis: identifying and characterising polymorphisms using rat models

Rheumatoid arthritis is a chronic inflammatory joint disorder characterised by erosive inflammation of the articular cartilage and by destruction of the synovial joints. It is regulated by both genetic and environmental factors, and, currently, there is no preventative treatment or cure for this disease. Genome-wide association studies have identified ∼100 new loci associated with rheumatoid arthritis, in addition to the already known locus within the major histocompatibility complex II region. However, together, these loci account for only a modest fraction of the genetic variance associated with this disease and very little is known about the pathogenic roles of most of the risk loci identified. Here, we discuss how rat models of rheumatoid arthritis are being used to detect quantitative trait loci that regulate different arthritic traits by genetic linkage analysis and to positionally clone the underlying causative genes using congenic strains. By isolating specific loci on a fixed genetic background, congenic strains overcome the challenges of genetic heterogeneity and environmental interactions associated with human studies. Most importantly, congenic strains allow functional experimental studies be performed to investigate the pathological consequences of natural genetic polymorphisms, as illustrated by the discovery of several major disease genes that contribute to arthritis in rats. We discuss how these advances have provided new biological insights into arthritis in humans.

Contribution of In Vivo and Organotypic 3D Models to Understanding the Role of Macrophages and Neutrophils in the Pathogenesis of Psoriasis

Psoriasis, a common chronic immune-mediated skin disease, is histologically characterized by a rapid keratinocyte turnover and differentiation defects. Key insights favor the idea that T cells are not the only key actors involved in the inflammatory process. Innate immune cells, more precisely neutrophils and macrophages, provide specific signals involved in the initiation and the maintenance of the pathogenesis. Current data from animal models and, to a lesser extent, three-dimensional in vitro models have confirmed the interest in leaning towards other immune cell types as a potential new cellular target for the treatment of the disease. Although these models do not mimic the complex phenotype nor all human features of psoriasis, their development is necessary and essential to better understand reciprocal interactions between skin cells and innate immune cells and to emphasize the crucial importance of the local lesional microenvironment. In this review, through the use of in vivo and 3D organotypic models, we aim to shed light on the crosstalk between epithelial and immune components and to discuss the role of secreted inflammatory molecules in the development of this chronic skin disease.

NADPH oxidases as drug targets and biomarkers in neurodegenerative diseases: What is the evidence?

Neurodegenerative disease are frequently characterized by microglia activation and/or leukocyte infiltration in the parenchyma of the central nervous system and at the molecular level by increased oxidative modifications of proteins, lipids and nucleic acids. NADPH oxidases (NOX) emerged as a novel promising class of pharmacological targets for the treatment of neurodegeneration due to their role in oxidant generation and presumably in regulating microglia activation. The unique function of NOX is the generation of superoxide anion (O₂^•-) and hydrogen peroxide (H₂O₂). However in the context of neuroinflammation, they present paradoxical features since O₂^•-/H₂O₂ generated by NOX and/or secondary reactive oxygen species (ROS) derived from O₂^•-/H₂O₂ can either lead to neuronal oxidative damage or resolution of inflammation. The role of NOX enzymes has been investigated in many models of neurodegenerative diseases by using either genetic or pharmacological approaches. In the present review we provide a critical assessment of recent findings related to the role of NOX in the CNS as well as how the field has advanced over the last 5 years. In particular, we focus on the data derived from the work of a consortium (Neurinox) funded by the European Commission's Programme 7 (FP7). We discuss the evidence gathered from animal models and human samples linking NOX expression/activity with neuroinflammation in neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and Creutzfeldt-Jakob disease as well as autoimmune demyelinating diseases like multiple sclerosis (MS) and chronic inflammatory demyelinating polyneuropathy (CIDP). We address the possibility to use measurement of the activity of the NOX2 isoform in blood samples as biomarker of disease severity and treatment efficacy in neurodegenerative disease. Finally we clarify key controversial aspects in the field of NOX, such as NOX cellular expression in the brain, measurement of NOX activity, impact of genetic deletion of NOX in animal models of neurodegeneration and specificity of NOX inhibitors.

Differential Role of B Cells and IL-17 Versus IFN-γ During Early and Late Rejection of Pig Islet Xenografts in Mice

BACKGROUND

Xenogeneic islet transplantation is an emerging therapeutic option for diabetic patients. However, immunological tolerance to xenogeneic islets remains a challenge.

METHODS

The current study used a pig-to-mouse discordant xenogeneic islet transplant model to examine antidonor xenogeneic immune responses during early and late rejection and to determine experimental therapeutic interventions that promote durable pig islet xenograft survival.

RESULTS

We found that during early acute rejection of pig islet xenografts, the rejecting hosts exhibited a heavy graft infiltration with B220 B cells and a robust antipig antibody production. In addition, early donor-stimulated IL-17 production, but not IFN-γ production, dominated during early acute rejection. Recipient treatment with donor apoptotic 1-ethyl-3-(3'-dimethylaminopropyl)-carbodiimide-treated splenocytes significantly inhibited antidonor IL-17 response, and when combined with B cell depletion and a short course of rapamycin led to survival of pig islet xenografts beyond 100 days in approximately 65% recipients. Interestingly, treated recipients in this model experienced late rejection between 100 and 200 days posttransplant, which coincided with B cell reconstitution and an ensuing emergence of a robust antidonor IFN-γ, but not IL-17, response.

CONCLUSIONS

These findings reveal that early and late rejection of pig islet xenografts may be dominated by different immune responses and that maintenance of long-term xenogeneic tolerance will require strategies that target the temporal sequence of antixenogeneic immune responses.

Therapeutic potential of carbohydrates as regulators of macrophage activation

It is well established for a broad range of disease states, including cancer and Mycobacterium tuberculosis infection, that pathogenesis is bolstered by polarisation of macrophages towards an anti-inflammatory phenotype, known as M2. As these innate immune cells are relatively long-lived, their re-polarisation to pro-inflammatory, phagocytic and bactericidal "classically activated" M1 macrophages is an attractive therapeutic approach. On the other hand, there are scenarios where the resolving inflammation, wound healing and tissue remodelling properties of M2 macrophages are beneficial - for example the successful introduction of biomedical implants. Although there are numerous endogenous and exogenous factors that have an impact on the macrophage polarisation spectrum, this review will focus specifically on prominent macrophage-modulating carbohydrate motifs with a view towards highlighting structure-function relationships and therapeutic potential.

Essential role for CCR6 in certain inflammatory diseases demonstrated using specific antagonist and knockin mice

The chemokine receptor CCR6 marks subsets of T cells and innate lymphoid cells that produce IL-17 and IL-22, and as such may play a role in the recruitment of these cells to certain inflammatory sites. However, the precise role of CCR6 has been controversial, in part because no effective monoclonal antibody (mAb) inhibitors against this receptor exist for use in mouse models of inflammation. We circumvented this problem using transgenic mice expressing human CCR6 (hCCR6) under control of its native promoter (hCCR6-Tg/mCCR6-/-). We also developed a fully humanized mAb against hCCR6 with antagonistic activity. The expression pattern of hCCR6 in hCCR6-Tg/mCCR6-/- mice was consistent with the pattern observed in humans. In mouse models of experimental autoimmune encephalomyelitis (EAE) and psoriasis, treatment with anti-hCCR6 mAb was remarkably effective in both preventive and therapeutic regimens. For instance, in the imiquimod model of psoriasis, anti-CCR6 completely abolished all signs of inflammation. Moreover, anti-hCCR6 attenuated clinical symptoms of myelin oligodendrocyte glycoprotein-induced (MOG-induced) EAE and reduced infiltration of inflammatory cells in the central nervous system. CCR6 plays a critical role in Th17 type inflammatory reactions, and CCR6 inhibition may offer an alternative approach for the treatment of these lesions.

Experimental lupus is aggravated in mouse strains with impaired induction of neutrophil extracellular traps

Many effector mechanisms of neutrophils have been implicated in the pathogenesis of systemic lupus erythematosus (SLE). Neutrophil extracellular traps (NETs) have been assigned a particularly detrimental role. Here we investigated the functional impact of neutrophils and NETs on a mouse model of lupus triggered by intraperitoneal injection of the cell death-inducing alkane pristane. Pristane-induced lupus (PIL) was aggravated in 2 mouse strains with impaired induction of NET formation, i.e., NOX2-deficient (Ncf1-mutated) and peptidyl arginine deiminase 4-deficient (PAD4-deficient) mice, as seen from elevated levels of antinuclear autoantibodies (ANAs) and exacerbated glomerulonephritis. We observed a dramatically reduced ability to form pristane-induced NETs in vivo in both Ncf1-mutated and PAD4-deficient mice, accompanied by higher levels of inflammatory mediators in the peritoneum. Similarly, neutropenic Mcl-1ΔMyelo mice exhibited higher levels of ANAs, which indicates a regulatory function in lupus of NETs and neutrophils. Blood neutrophils from Ncf1-mutated and human individuals with SLE exhibited exuberant spontaneous NET formation. Treatment with specific chemical NOX2 activators induced NET formation and ameliorated PIL. Our findings suggest that aberrant NET is one of the factors promoting experimental lupus-like autoimmunity by uncontrolled release of inflammatory mediators.

The kinase TPL2 activates ERK and p38 signaling to promote neutrophilic inflammation

Tumor progression locus 2 (TPL2; also known as MAP3K8) is a mitogen-activated protein kinase (MAPK) kinase kinase (MAP3K) that phosphorylates the MAPK kinases MEK1 and MEK2 (MEK1/2), which, in turn, activate the MAPKs extracellular signal-regulated kinase 1 (ERK1) and ERK2 (ERK1/2) in macrophages stimulated through the interleukin-1 receptor (IL-1R), Toll-like receptors (TLRs), or the tumor necrosis factor receptor (TNFR). We describe a conserved and critical role for TPL2 in mediating the effector functions of neutrophils through the activation of the p38 MAPK signaling pathway. Gene expression profiling and functional studies of neutrophils and monocytes revealed a MEK1/2-independent branch point downstream of TPL2 in neutrophils. Biochemical analyses identified the MAPK kinases MEK3 and MEK6 and the MAPKs p38α and p38δ as downstream effectors of TPL2 in these cells. Genetic ablation of the catalytic activity of TPL2 or therapeutic intervention with a TPL2-specific inhibitor reduced the production of inflammatory mediators by neutrophils in response to stimulation with the TLR4 agonist lipopolysaccharide (LPS) in vitro, as well as in rodent models of inflammatory disease. Together, these data suggest that TPL2 is a drug target that activates not only MEK1/2-dependent but also MEK3/6-dependent signaling to promote inflammatory responses.

Susceptibility to chronic inflammation: an update

Chronic inflammation is defined by the persistence of inflammatory processes beyond their physiological function, resulting in tissue destruction. Chronic inflammation is implicated in the progression of many chronic diseases and plays a central role in chronic inflammatory and autoimmune disease. As such, this review aims to collate some of the latest research in relation to genetic and environmental susceptibilities to chronic inflammation. In the genetic section, we discuss some of the updates in cytokine research and current treatments that are being developed. We also discuss newly identified canonical and non-canonical genes associated with chronic inflammation. In the environmental section, we highlight some of the latest updates and evidence in relation to the role that infection, diet and stress play in promoting inflammation. The aim of this review is to provide an overview of the latest research to build on our current understanding of chronic inflammation. It highlights the complexity associated with chronic inflammation, as well as provides insights into potential new targets for therapies that could be used to treat chronic inflammation and consequently prevent disease progression.

A Reduction in Intracellular Reactive Oxygen Species Due to a Mutation in NCF4 Promotes Autoimmune Arthritis in Mice

AIMS

The mechanisms linking deficits in the phagocytic NADPH oxidase 2 (NOX2) complex to autoimmunity are so far incompletely understood. Deficiency in neutrophil cytosolic factor 1 (NCF1) inactivates the NOX2 complex, leading to a dramatic reduction of intra- and extracellular reactive oxygen species (ROS) and enhanced susceptibility to autoimmune disease. The contribution of intracellular NOX2 activity to autoimmune regulation is, however, unknown. Another component of the NOX2 complex, NCF4, directs the NOX2 complex to phagosomal membranes via binding to phosphatidylinositol 3-phosphate (PtdIns3P) and has been proposed to regulate intracellular ROS levels. To address the impact of NCF4 and selective changes in intracellular ROS production on autoimmune inflammation, we studied collagen-induced arthritis (CIA) and mannan-induced psoriatic arthritis-like disease (MIP) in mice lacking NCF4 and mice with a mutation in the PtdIns3P-binding site of NCF4.

RESULTS

Targeted deletion of Ncf4 (Ncf4^-/-) led to severe defects in overall ROS production due to concomitant reduction of NCF2 and NCF1. These mice displayed delayed neutrophil apoptosis and enhanced innate immune responses, and they developed aggravated CIA and MIP. Disruption of the PtdIns3P-binding site by targeted mutation (Ncf4*^/*) resulted in selective defects in intracellular NOX2 activity, which entailed milder effects on innate immunity and MIP but clearly promoted susceptibility to CIA. Innovation and Conclusion: This is, to our knowledge, the first study addressing the development of autoimmunity in an organism with selectively compromised NOX2-dependent intracellular ROS levels. Our data reveal a specific role for NCF4-mediated intracellular ROS production in regulating autoimmunity and chronic inflammation. Antioxid. Redox Signal. 25, 983-996.

Interleukin (IL)-9/IL-9R axis drives γδ T cells activation in psoriatic arthritis patients

Cytokines such as tumour necrosis factor (TNF)-α, interleukin (IL)-12, interferon (IFN)-γ, IL-23 and, more recently, IL-9, have been implicated in the initiation/maintenance of inflammation in psoriasis and psoriatic arthritis (PsA). In the present study we aimed to characterize the role of γδ T cells in peripheral blood and synovial fluid of PsA patients and to investigate their response to in-vitro stimulation with antigen or cytokines (IL-9 and IL-23). γδ T cells isolated from peripheral blood mononuclear cells and synovial fluid were analysed by flow cytometry to evaluate the phenotype and cytokine production. IL-23R and IL-9R gene expression were also evaluated by reverse transcription-polymerase chain reaction (RT-PCR). Peripheral blood mononuclear cells (PBMC), sorted γδ T cells and γδ cell lines were also stimulated in vitro with isopentenyl pyrophosphate (IPP), recombinant IL-9 or recombinant IL-23. Our results show an expansion of γδ T cells with a predominant effector memory phenotype in peripheral blood and synovium of untreated PsA patients, which reverses significantly after treatment with anti-TNF-α or anti-IL-12/IL-23R monoclonal antibodies (mAbs). Moreover, in PsA patients γδ T cells activation is driven prevalently by IL-9/IL-9R interaction, and not only by IL-23/IL-23R. Together these findings indicate γδ T cells and IL-9 as new players in the pathogenesis of PsA.

Interleukin-23-Dependent γ/δ T Cells Produce Interleukin-17 and Accumulate in the Enthesis, Aortic Valve, and Ciliary Body in Mice

OBJECTIVE

The spondyloarthritides (SpA) are a group of rheumatic diseases characterized by ossification and inflammation of entheseal tissue, the region where tendon attaches to bone. Interleukin-23 (IL-23) is involved in the pathogenesis of SpA by acting on IL-23 receptor (IL-23R) expressed on enthesis-resident lymphocytes. Upon IL-23 binding, CD3+CD4-CD8- tissue-resident lymphocytes secrete IL-17A and IL-22, leading to inflammation, bone loss, and ossification. Knowledge about enthesis-resident lymphocytes remains fragmentary, and the contribution of entheseal γ/δ T cells in particular is not clear. This study was undertaken to investigate the presence of γ/δ T cells in the enthesis.

METHODS

We used 2-photon microscopy and flow cytometry to analyze entheseal lymphocytes from C57BL/6, Tcrd-H2BeGFP, Rorc-GFP, and IL-23R-eGFP mice. To analyze entheseal γ/δ T cells in IL-23-induced inflammation, Tcrd-H2BeGFP mice were crossed with mice of the susceptible B10.RIII background. Hydrodynamic injection of IL-23 minicircle DNA was performed for overexpression of IL-23 and induction of inflammation. Light-sheet fluorescence microscopy was used to visualize arthritic inflammation.

RESULTS

Activated Vγ6+CD27- γ/δ T cells were abundant in uninflamed entheseal tissue and constituted the large majority of retinoic acid receptor-related orphan nuclear receptor γt (RORγt)+IL-23R+ enthesis-resident lymphocytes. Fetal thymus-dependent γ/δ T cells were the main source of IL-17A at the enthesis. Under inflammatory conditions, γ/δ T cells increased in number at the Achilles tendon enthesis, aortic root, and adjacent to the ciliary body.

CONCLUSION

Entheseal γ/δ T cells are derived from fetal thymus and are maintained as self-renewing tissue-resident cells. As main IL-17A producers within tissues exposed to mechanical stress including enthesis, γ/δ T cells are key players in the pathogenesis of IL-23-induced local inflammation.

(18)F-Labeling of Mannan for Inflammation Research with Positron Emission Tomography

Recently mannan from Saccharomyces cerevisiae has been shown to be able to induce psoriasis and psoriatic arthritis in mice, and the phenotypes resemble the corresponding human diseases. To investigate the pathological processes, we set out to label mannan with fluorine-18 ((18)F) and study the (18)F-labeled mannan in vitro and in vivo with positron emission tomography (PET). Accordingly, mannan has been transformed into (18)F-fluoromannan with (18)F-bicyclo[6.1.0]nonyne. In mouse aorta, the binding of [(18)F]fluoromannan to the atherosclerotic lesions was clearly visualized and was significantly higher compared to blocking assays (P < 0.001) or healthy mouse aorta (P < 0.001). In healthy rats the [(18)F]fluoromannan radioactivity accumulated largely in the macrophage-rich organs such as liver, spleen, and bone marrow and the excess excreted in urine. Furthermore, the corresponding (19)F-labeled mannan has been used to induce psoriasis and psoriatic arthritis in mice, which indicates that the biological function of mannan is preserved after the chemical modifications.