Increased serum high mobility group box-1 level in Churg-Strauss syndrome

HMGB1 Promotes Systemic Lupus Erythematosus by Enhancing Macrophage Inflammatory Response

Background/Purpose. HMGB1, which may act as a proinflammatory mediator, has been proposed to contribute to the pathogenesis of multiple chronic inflammatory and autoimmune diseases including systemic lupus erythematosus (SLE); however, the precise mechanism of HMGB1 in the pathogenic process of SLE remains obscure. Method. The expression of HMGB1 was measured by ELISA and western blot. The ELISA was also applied to detect proinflammatory cytokines levels. Furthermore, nephritic pathology was evaluated by H&E staining of renal tissues. Results. In this study, we found that HMGB1 levels were significantly increased and correlated with SLE disease activity in both clinical patients and murine model. Furthermore, gain- and loss-of-function analysis showed that HMGB1 exacerbated the severity of SLE. Of note, the HMGB1 levels were found to be associated with the levels of proinflammatory cytokines such as TNF-α and IL-6 in SLE patients. Further study demonstrated that increased HMGB1 expression deteriorated the severity of SLE via enhancing macrophage inflammatory response. Moreover, we found that receptor of advanced glycation end products played a critical role in HMGB1-mediated macrophage inflammatory response. Conclusion. These findings suggested that HMGB1 might be a risk factor for SLE, and manipulation of HMGB1 signaling might provide a therapeutic strategy for SLE.

HMGB1 in health and disease

Complex genetic and physiological variations as well as environmental factors that drive emergence of chromosomal instability, development of unscheduled cell death, skewed differentiation, and altered metabolism are central to the pathogenesis of human diseases and disorders. Understanding the molecular bases for these processes is important for the development of new diagnostic biomarkers, and for identifying new therapeutic targets. In 1973, a group of non-histone nuclear proteins with high electrophoretic mobility was discovered and termed high-mobility group (HMG) proteins. The HMG proteins include three superfamilies termed HMGB, HMGN, and HMGA. High-mobility group box 1 (HMGB1), the most abundant and well-studied HMG protein, senses and coordinates the cellular stress response and plays a critical role not only inside of the cell as a DNA chaperone, chromosome guardian, autophagy sustainer, and protector from apoptotic cell death, but also outside the cell as the prototypic damage associated molecular pattern molecule (DAMP). This DAMP, in conjunction with other factors, thus has cytokine, chemokine, and growth factor activity, orchestrating the inflammatory and immune response. All of these characteristics make HMGB1 a critical molecular target in multiple human diseases including infectious diseases, ischemia, immune disorders, neurodegenerative diseases, metabolic disorders, and cancer. Indeed, a number of emergent strategies have been used to inhibit HMGB1 expression, release, and activity in vitro and in vivo. These include antibodies, peptide inhibitors, RNAi, anti-coagulants, endogenous hormones, various chemical compounds, HMGB1-receptor and signaling pathway inhibition, artificial DNAs, physical strategies including vagus nerve stimulation and other surgical approaches. Future work further investigating the details of HMGB1 localization, structure, post-translational modification, and identification of additional partners will undoubtedly uncover additional secrets regarding HMGB1's multiple functions.

High-mobility group box 1 (HMGB1) in childhood: from bench to bedside

High-mobility group box protein 1 (HMGB1) is a nonhistone nuclear protein that has a dual function. Inside the cell, HMGB1 binds DNA, regulating transcription and determining chromosomal architecture. Outside the cell, HMGB1 activates the innate system and mediates a wide range of physiological and pathological responses. HMGB1 exerts these actions through differential engagement of multiple surface receptors, including Toll-like receptor (TLR)2, TLR4, and receptor for advanced glycation end products (RAGE). HMGB1 is implicated as a late mediator of sepsis and is also involved in inflammatory and autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. Interestingly, HMGB1 was associated with tumor progression, becoming a potential therapeutic target, due to its involvement in the resistance to chemotherapy. Its implication on the pathogenesis of systemic vasculitis and inflammatory bowel diseases has also been evaluated. Moreover, it regulates neuroinflammation after traumatic brain injuries or cerebral infectious diseases. The aim of this review is to analyze these different roles of HMGB1, both in physiological and pathological conditions, discussing clinical and scientific implications in the field of pediatrics.

CONCLUSION

HMGB1 plays a key role in several pediatric diseases, opening new scenarios for diagnostic biomarkers and therapeutic strategies development.

Intravascular immunity as a key to systemic vasculitis: a work in progress, gaining momentum

Vascular inflammation contributes to the defence against invading microbes and to the repair of injured tissues. In most cases it resolves before becoming apparent. Vasculitis comprises heterogeneous clinical entities that are characterized by the persistence of vascular inflammation after it has served its homeostatic function. Most underlying mechanisms have so far remained elusive. Intravascular immunity refers to the surveillance of the vasculature by leucocytes that sense microbial or sterile threats to vessel integrity and initiate protective responses that entail most events that determine the clinical manifestations of vasculitis, such as end-organ ischaemia, neutrophil extracellular traps generation and thrombosis, leucocyte extravasation and degranulation. Understanding how the resolution of vascular inflammation goes awry in patients with systemic vasculitis will facilitate the identification of novel pharmacological targets and bring us a step closer in each patient to the selection of more effective and less toxic treatments.

Anti-high mobility group box 1 monoclonal antibody ameliorates experimental autoimmune encephalomyelitis

High mobility group box 1 (HMGB1) is an established inflammatory mediator when released from cells. Recent studies have implicated extracellular HMGB1 in the pathogenesis of various autoimmune diseases. The objective of this study was to determine whether HMGB1 could be a therapeutic target for experimental autoimmune encephalomyelitis (EAE). In this study, an anti-HMGB1 monoclonal antibody was injected intraperitoneally into a mouse model of EAE. We also measured serum cytokines levels in EAE and anti-HMGB1 monoclonal antibody-treated EAE. As a result, intraperitoneal injection of an anti-HMGB1 monoclonal antibody ameliorated the clinical and pathological severity of EAE and attenuated interleukin-17 up-regulation in serum. In conclusion, HMGB1 is involved in EAE pathogenesis and could trigger inflammation in the central nervous system. The novel aspect of this study is the demonstration that anti-HMGB1 ameliorates EAE. HMGB1 may be a novel therapeutic strategy for multiple sclerosis.

Serum biomarkers are similar in Churg-Strauss syndrome and hypereosinophilic syndrome

RATIONALE

Churg-Strauss syndrome (CSS) and hypereosinophilic syndrome (HES) overlap considerably in clinical presentation. A reliable means of distinguishing between these groups of patients is needed, especially in the setting of glucocorticoid therapy.

METHODS

A retrospective chart review of 276 adult subjects referred for evaluation of eosinophilia > 1500/μl was performed, and subjects with a documented secondary cause of eosinophilia or a PDGFR -positive myeloproliferative neoplasm were excluded. The remaining subjects were assessed for the presence of American College of Rheumatology (ACR) criteria. Laboratory and clinical parameters were compared between subjects with biopsy-proven vasculitis (CSS; n = 8), ≥4 ACR criteria (probable CSS; n = 21), HES with asthma and/or sinusitis without other CSS-defining criteria (HESwAS; n = 20), HES without asthma or sinusitis (HES; n = 18), and normal controls (n = 8). Serum biomarkers reported to be associated with CSS were measured using standard techniques.

RESULTS

There were no differences between the subjects with definite or probable CSS or HES with respect to age, gender, or maintenance steroid dose. Serum CCL17, IL-8, and eotaxin levels were significantly increased in eosinophilic subjects as compared to normal controls, but were similar between the eosinophilic groups. Serum CCL17 correlated with eosinophil count (P < 0.0001, r = 0.73), but not with prednisone dose.

CONCLUSIONS

In patients with a history of asthma and sinusitis, distinguishing between ANCA-negative CSS and PDGFR-negative HES is difficult because of significant overlap in clinical presentation and biomarker profiles.

HMGB1: a multifunctional alarmin driving autoimmune and inflammatory disease

HMGB1 is a non-histone nuclear protein that can serve as an alarmin to drive the pathogenesis of inflammatory and autoimmune disease. Although primarily located in the cell nucleus, HMGB1 can translocate to the cytoplasm, as well as the extracellular space, during cell activation and cell death; during activation, HMGB1 can undergo post-translational modifications. The activity of HMGB1 varies with the redox states of the cysteine residues, which are required for binding to TLR4. In addition to stimulating cells directly, HMGB1 can form immunostimulatory complexes with cytokines and other endogenous and exogenous factors. In the synovia of patients with rheumatoid arthritis, as well as animal models of this disease, extranuclear expression of HMGB1 is increased and blockade of HMGB1 expression attenuates disease in animal models. In systemic lupus erythematosus, HMGB1 can be a component of immune complexes containing anti-DNA because of its interaction with DNA. In myositis, expression of HMGB1 is enhanced in inflamed muscle and can perturb muscle function. Together, these findings indicate that HMGB1 might be an important mediator and biomarker in rheumatic diseases as well as a target of new therapy.

High mobility group box 1 (HMGB1) and anti-HMGB1 antibodies and their relation to disease characteristics in systemic lupus erythematosus

Introduction

High Mobility Group Box 1 (HMGB1) is a nuclear non-histone protein. HMGB1, which is secreted by inflammatory cells and passively released from apoptotic and necrotic cells, may act as a pro-inflammatory mediator. As apoptotic cells accumulate in systemic lupus erythematosus (SLE), HMGB1 levels might be increased in SLE. HMGB1 may also serve as an autoantigen, leading to the production of anti-HMGB1 antibodies. In this study we determined levels of HMGB1 and anti-HMGB1 in SLE patients in comparison to healthy controls (HC) and analysed their relation with disease activity.

Methods

The study population consisted of 70 SLE patients and 35 age- and sex-matched HC. Thirty-three SLE patients had quiescent disease, the other 37 patients were selected for having active disease. Nineteen of these had lupus nephritis. HMGB1 levels were measured with both Western blot and ELISA. Anti-HMGB1 levels were measured by ELISA. Clinical and serological parameters were assessed according to routine procedures.

Results

HMGB1 levels in SLE patients could be measured reliably by Western blotting only, and were significantly increased compared to HC. During active disease HMGB1 levels increased, in particular in patients with renal involvement. Serum HMGB1 levels correlated with SLEDAI, proteinuria, and anti-dsDNA levels, and showed a negative correlation with complement C3. Anti-HMGB1 levels were significantly increased in SLE patients compared to HC, and positively correlated with HMGB1 levels.

Conclusions

Levels of HMGB1 in the sera of SLE patients, in particular in those with active renal disease, are increased. Serum HMGB1 levels are related to SLEDAI scores and proteinuria, as well as to levels of anti-HMGB1 antibodies. These findings suggest that besides HMGB1, HMGB1-anti-HMGB1 immune complexes play a role in the pathogenesis of SLE, in particular in patients with renal involvement.

Increased levels of HMGB-1 and endogenous secretory RAGE in induced sputum from asthmatic patients

BACKGROUND

High mobility group box 1 (HMGB-1), a ligand of the receptor for advanced glycation end products (RAGE), is an inflammatory mediator in various disorders. Its endogenous decoy inhibitor, endogenous secretory RAGE (esRAGE), prevents the activation of RAGE signaling, and imbalance between HMGB-1 and esRAGE is known to be a factor determining progression of chronic inflammatory diseases.

METHODS

We measured HMGB-1 and esRAGE levels in induced sputum from 44 asthmatic patients and 15 normal controls, and examined their correlations with asthma indices including pulmonary function test values and induced sputum indices.

RESULTS

HMGB-1 levels in induced sputum were significantly higher in asthmatic patients than in normal controls (p < 0.001). Similarly, esRAGE levels were significantly higher in asthmatic patients than in normal controls (p < 0.001). In asthmatic patients, HMGB-1 levels were inversely correlated with percentage of predicted forced expiratory volume in 1 s (%FEV(1)) and FEV(1)/forced vital capacity (FEV(1)/FVC). There was a significant increase in HMGB-1 level associated with severity of asthma (p < 0.001). However, there was no significant increase in esRAGE level associated with severity of asthma. In asthmatic patients, HMGB-1 levels were significantly correlated with percentage of neutrophils in induced sputum.

CONCLUSIONS

Our findings suggest that the HMGB-1 is a mediator of neutrophilic airway inflammation in asthma and that imbalance between HMGB-1 and esRAGE is related to the severity of asthma. Combined measurement of HMGB-1 and esRAGE may be novel biomarkers in asthma with severe airflow limitation.

Translational mini-review series on immunology of vascular disease: mechanisms of vascular inflammation and remodelling in systemic vasculitis

Vessel walls are the primary inflammatory sites in systemic vasculitides. In most cases the initiating event is unknown, and a self-sustaining circuit attracts and activates inflammatory leucocytes in the wall of vessels of various size and anatomical characteristics. Recent studies have revealed homeostatic roles of vascular inflammation and have identified the action of humoral innate immunity, in particular injury-associated signals and acute phase proteins, on the activation of circulating leucocytes, platelets and endothelial cells. These advances have provided clues to the molecular mechanisms underlying the vicious circle that maintains and amplifies vessel and tissue injury.

Lupus antibodies to the HMGB1 chromosomal protein: epitope mapping and association with disease activity

The high mobility group box 1 (HMGB1) protein is a non-histone chromosomal protein that acts as a potent proinflammatory cytokine when actively secreted from LPS- or TNF-activated macrophages, monocytes, and other cells. Anti-HMGB1/2 antibodies have been previously identified in sera from a high proportion of patients with autoimmune diseases. In this study, we examined anti-HMGB1 antibody titers in sera of patients with systemic rheumatic diseases and the correlations between the presence of anti-HMGB1 antibodies and disease activity in systemic lupus erythematosus (SLE) patients by enzyme-linked immunosorbent assay and western blotting. We detected increases in both the levels and the frequency of anti-HMGB1 antibodies in sera from SLE and polymyositis/dermatomyositis (PM/DM) patients, and observed that the presence of anti-HMGB1 antibodies positively correlates with SLE disease activity index. Through epitope mapping, we found that multiple HMGB1 epitopes were recognised in SLE sera, with the major epitope mapping to box A. Another epitope, the joiner region of HMGB1, was preferentially recognized by SLE sera, but not by PM/DM sera. Collectively, these observations suggest that the presence of anti-HMGB1 antibodies correlates with disease activity in SLE patients.

Churg-Strauss syndrome: 2005-2008 update

Churg-Strauss syndrome (CSS) is a rare necrotizing small-vessel vasculitis associated with eosinophil-rich granulomatous inflammation of tissues and vessels and is also associated with asthma and eosinophilia. Epidemiologic studies continue to show that CSS is the rarest of the necrotizing small-vessel vasculitides. However, it is not possible to know with any certainty if there has been an increase in incidence. There has been an attempt to divide the patients with CSS into an antineutrophil cytoplasmic antibody-positive and cytoplasmic antibody-negative group. The former group has an increased frequency of renal involvement, parenchymal pulmonary disease, constitutional symptoms, and peripheral and central nervous system involvement, whereas the latter group has more frequent cardiac disease. The role of eosinophils and antineutrophil cytoplasmic antibodies remains poorly defined but provocative. Leukotriene receptor antagonists do not appear to induce CSS but facilitate the tapering of glucocorticoids, which unmasks the condition. Glucocorticoids and cyclophosphamide remain the foundation of treatment for vasculitis, but there are other promising and less toxic alternatives on the horizon.

Clonal CD8+ TCR-Vbeta expanded populations with effector memory phenotype in Churg Strauss syndrome

Churg Strauss Syndrome (CSS) is a systemic vasculitis in which oligoclonal T cell expansions might be involved in the pathogenesis. Combined analysis of TCR-Vbeta expression profile by flow cytometry and of TCR gene rearrangement by heteroduplex PCR was used to detect and characterize T cell expansions in 8 CSS patients, 10 asthmatics and 42 healthy subjects. In all CSS patients one or two Vbeta families were expanded among CD8+ cells, with an effector memory phenotype apt to populate tissues and inflammatory sites. Heteroduplex PCR showed the presence of one or more clonal TCR rearrangements, which reveals monoclonal or oligoclonal T cells subpopulations. After purification with a Vbeta specific monoclonal antibody, each CD8+/Vbeta+ expanded family showed a single TCR rearrangement, clearly suggestive of monoclonality. All CD8+ expansions were detectable throughout the disease course. TCR-Vbeta expanded or deleted populations were not observed in asthmatic patients. Clonal CD8+/Vbeta+ T cell expansions might be useful as a disease marker.

The role of cell death in the pathogenesis of autoimmune disease: HMGB1 and microparticles as intercellular mediators of inflammation

Cell death is critical to normal homeostasis, although this process, when increased aberrantly, can lead to the production of pro-inflammatory mediators promoting autoimmunity. Two novel intercellular mediators of inflammation generated during cell death are high mobility group box 1 (HMGB1) protein and microparticles (MPs). HMGB1 is a nuclear protein that functions in transcription when inside the nucleus but takes on pro-inflammatory properties when released during cell death. Microparticles are small, membrane-bound structures that extrude from cells when they die and contain cell surface proteins and nuclear material from their parent cells. MPs circulate widely throughout the vasculature and mediate long-distance communication between cells. Both MPs and HMGB1 have been implicated in the pathogenesis of a broad spectrum of inflammatory diseases, including the prototypic autoimmune conditions systemic lupus erythematosus and rheumatoid arthritis. Given their range of activity and association with active disease, both structures may prove to be targets for effective therapy in these and other disorders.