Are urinary levels of high mobility group box 1 markers of active nephritis in anti-neutrophil cytoplasmic antibody-associated vasculitis?

Urinary T Cells Identify Renal ANCA-Associated Vasculitis and Predict Prognosis: a proof of concept study

Introduction

Necrotizing crescentic glomerulonephritis is a major contributor to morbidity and mortality in Antineutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV). Because therapy relies on immunosuppressive agents with potentially severe adverse effects, a reliable noninvasive biomarker of disease activity is needed to guide treatment.

Methods

We used flow cytometry to quantify T cell subsets in blood and urine samples from 95 patients with AAV and 8 controls to evaluate their biomarker characteristics. These were compared to soluble markers, monocyte chemoattractant protein-1 (MCP-1), soluble CD163 (sCD163), soluble CD25 (sCD25), and complement C5a (C5a), measured using multiplex analysis. Available kidney biopsies (n = 21) were classified according to Berden.

Results

Patients with active renal AAV (rAAV) showed significantly higher urinary cell counts than those in remission, or those with extrarenal manifestation, or healthy controls. Urinary T cells showed robust discrimination of disease activity with superior performance compared to MCP-1 and sCD163. Patients whose kidney biopsies had been classified as "crescentic" according to Berden classification showed higher urinary T cell counts. Discordant regulatory T cells (T_reg) proportions and CD4⁺/CD8⁺ ratio in blood and urine suggested that urinary cells reflect tissue migration rather than mere micro-bleeding. Furthermore, urinary T_reg and T helper cells (T_H17) patterns were associated with clinical response and risk of renal relapse.

Conclusion

Urinary T cells reflect the renal inflammatory milieu in AAV and provide further insights into the pathogenesis of this chronic condition. Their promising potential as noninvasive diagnostic and prognostic biomarkers deserves further exploitation.

Old known and possible new biomarkers of ANCA-associated vasculitis

Antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) comprises a group of multisystem disorders involving severe, systemic, small-vessel vasculitis with short- and long term serious and life-threating complications. Despite the simplification of treatment, fundamental aspects concerning assessment of its efficacy and its adaptation to encountered complications or to the relapsing/remitting/subclinical disease course remain still unknown. The pathogenesis of AAV is complex and unique, and despite the progress achieved in the last years, much has not to be learnt. Foremost, there is still no accurate marker enabling us to monitoring disease and guide therapy. Therefore, the disease management relays often on clinical judgment and follows a" trial and error approach". In the recent years, an increasing number of new molecules s have been explored and used for this purpose including genomics, B- and T-cell subpopulations, complement system factors, cytokines, metabolomics, biospectroscopy and components of our microbiome. The aim of this review is to discuss both the role of known historical and clinically established biomarkers of AAV, as well as to highlight potential new ones, which could be used for timely diagnosis and monitoring of this devastating disease, with the goal to improve the effectiveness and ameliorate the complications of its demanding therapy.

Monocytes and macrophages in ANCA-associated vasculitis

Anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitides (AAV) are characterized by inflammation of small-to-medium-sized blood vessels and the presence of autoantibodies against cytoplasmic proteases sited in neutrophils and monocytes. Increasing evidence indicates a substantial role of monocytes and macrophages in the pathogenesis of AAV. Activated monocytes and macrophages contribute to necroinflammation in peripheral vasculitic lesions as well as to central and peripheral mechanisms of autoimmunity. The intermediate monocyte subset (CD14⁺⁺CD16⁺) is increased and monocytes show elevated expression of CD14, Toll-like receptor 2/4, MHCII and integrins, likely reflecting activation and increased monocyte extravasation. Monocytes differentiate locally predominantly into alternatively activated (M2) macrophages, which are known for cell-clearance and phagocytosis, but may ultimately lead to fibrosis. Phagocytotic function of macrophages can be impaired by surface expression of cytoplasmic proteases on apoptotic neutrophils and causes release of inflammatory cytokines and immunogenic contents, presumably resulting in a vicious circle of increased neutrophil, T and B cell activation and consequent ANCA production. Considering their crucial role in initiating necroinflammation as well as fibrogenesis, monocytes and macrophages may represent a logic first-line target for new treatment options in AAV.

Sustained sterile inflammation is related to pulmonary morbidities in premature infants

OBJECTIVE

Sterile inflammation, initiated by endogenous molecules such as high-mobility group box-1 (HMGB1), has come to be recognized as a critical mechanism in a variety of chronic diseases. To elucidate the involvement of sterile inflammation in neonatal disease, the association between serum HMGB1 levels and the development of bronchopulmonary dysplasia (BPD) was evaluated.

STUDY DESIGN

Serum HMGB1 levels were measured in 25 premature infants born before 33 weeks of gestation, excluding any infection cases. Samples were collected at birth, two, and four weeks of age and compared according to BPD status.

RESULTS

The serum HMGB1 levels in infants with BPD were maintained up to 4 weeks of age, while those without BPD declined with time. Postnatal cardiopulmonary and nutritional transition was delayed in infants with BPD.

CONCLUSION

Sustained elevation of serum HMGB1 levels was associated with the development of BPD, suggesting that prolonged sterile inflammation may contribute to lung injury.

Granulomatous Inflammation in ANCA-Associated Vasculitis

ANCA-associated vasculitis (AAV) comprises granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA). While systemic vasculitis is a hallmark of all AAV, GPA is characterized by extravascular granulomatous inflammation, preferentially affecting the respiratory tract. The mechanisms underlying the emergence of neutrophilic microabscesses; the appearance of multinucleated giant cells; and subsequent granuloma formation, finally leading to scarred or destroyed tissue in GPA, are still incompletely understood. This review summarizes findings describing the presence and function of molecules and cells contributing to granulomatous inflammation in the respiratory tract and to renal inflammation observed in GPA. In addition, factors affecting or promoting the development of granulomatous inflammation such as microbial infections, the nasal microbiome, and the release of damage-associated molecular patterns (DAMP) are discussed. Further, on the basis of numerous results, we argue that, in situ, various ways of exposure linked with a high number of infiltrating proteinase 3 (PR3)- and myeloperoxidase (MPO)-expressing leukocytes lower the threshold for the presentation of an altered PR3 and possibly also of MPO, provoking the local development of ANCA autoimmune responses, aided by the formation of ectopic lymphoid structures. Although extravascular granulomatous inflammation is unique to GPA, similar molecular and cellular patterns can be found in both the respiratory tract and kidney tissue of GPA and MPA patients; for example, the antimicrobial peptide LL37, CD163⁺ macrophages, or regulatory T cells. Therefore, we postulate that granulomatous inflammation in GPA or PR3-AAV is intertwined with autoimmune and destructive mechanisms also seen at other sites.

Danger-associated molecular pattern molecules and the receptor for advanced glycation end products enhance ANCA-induced responses

Objectives

The pro-inflammatory activities of the calgranulins and HMGB1 can be counteracted by sRAGE, the soluble form of their shared receptor. To understand the role of these molecules in AAV and their potential as therapeutic targets we have studied (i) the relationship between these DAMPS and disease activity; (ii) the expression of RAGE and sRAGE in biopsy tissue and peripheral blood; and (iii) the effect of these molecules on ANCA-mediated cytokine production.

Methods

We examined circulating levels of calgranulins (S100A8/A9 and S100A12), HMGB1 and sRAGE by ELISA. RAGE was examined in AAV kidney and lung biopsies by immunohistochemistry and RAGE expression was monitored in peripheral blood by qPCR. In vitro, the effect of co-stimulating PBMC with ANCA and S100A8/A9 on cytokine production was studied by ELISA.

Results

We found significantly raised levels of calgranulins and HMGB1 in active AAV regardless of clinical phenotype (PR3+/MPO+ AAV). Levels of calgranulins showed significant correlations with each other. RAGE protein and message was raised in peripheral blood and in cells infiltrating kidney and lung biopsy tissue, while sRAGE was lowered. Furthermore, ANCA-mediated production of IL-8 from PBMC was significantly enhanced by the presence of S100A8/A9 in a RAGE/TLR4-dependent manner.

Conclusions

Raised circulating calgranulins provide a good marker of disease activity in AAV and are unlikely to be counteracted by sRAGE. Increased RAGE expression in AAV indicates receptor stimulation in active disease that may exacerbate ANCA-induced cytokine production. Targeting the RAGE pathway may provide a useful therapeutic approach in AAV.

HMGB-1 and TGFβ-1 highlight immuno-inflammatory and fibrotic processes before proteinuria onset in pediatric patients with Alport syndrome

INTRODUCTION

Alport syndrome (ALP) is a rare genetic condition characterized by progressive involvement of the basal membranes and renal dysfunction. The purpose of the study was to evaluate urinary (u) and serum (s) levels of tumor growth factor (TGF)-beta(β) and high mobility group box (HMGB)-1 in ALP patients with normal renal function, albuminuria and proteinuria.

METHODS

A prospective, single-center study was performed with a follow-up period of 12 months, enrolling 11 pediatric ALP patients and 10 healthy subjects (HS). Normal values of serum creatinine, albuminuria and proteinuria, as well as unaltered estimated glomerular filtration rate (eGFR) were required at enrollment.

RESULTS

ALP patients had significantly higher levels of serum and urinary HMGB1 compared to HS. The same trend was observed for TGF-β1, with higher values in ALP patients than in HS. HMGB1 and TGF-β1 correlated with each other and with markers of renal function and damage. Urinary biomarkers did not correlate with eGFR, whereas sHMGB1 and sTGF-β1 were negatively related to filtration rate (r: - 0.66; p = 0.02, r: - 0.96; p < 0.0001, respectively). Using proteinuria as a dependent variable in a multiple regression model, only the association with sTGF-β1 (β = 0.91, p < 0.0001) remained significant.

CONCLUSIONS

High levels of HMGB1 and TGF-β1 characterized ALP patients with normal renal function, highlighting the subclinical pro-fibrotic and inflammatory mechanisms triggered before the onset of proteinuria. Further studies are needed to evaluate the role of HMGB1 and TGFβ-1 in ALP patients.

Mechanism of HMGB1-RAGE in Kawasaki disease with coronary artery injury

Background

Kawasaki disease (KD) is a common, yet unknown etiology disease in Asian countries, which causes acquired heart disease in childhood. It is characterized by an inflammatory acute febrile vasculitis of medium-sized arteries, particularly the coronary arteries. High-mobility group box-1 protein (HMGB1) is a non-histone chromosomal-binding protein present in the nucleus of eukaryotic cells, which contains 215 amino acid residues. Although the cellular signal transduction mechanisms of HMGB1 are currently unclear, the important role of the receptor for advanced glycation end-products (RAGE), the main receptor for HMGB1 has been reported in detail. The purpose of our study was to verify the mechanism and clinical significance of HMGB1-RAGE in coronary artery injury of Kawasaki disease.

Methods

52 blood samples of patients in KD were collected, and the coronary artery Z score was calculated according to the echocardiographic results. The Z score ≥ 2.0 was classified as coronary artery lesions (CAL); otherwise, it was no-coronary artery lesions (NCAL). In addition, the fever group and control group were set. Among them, the fever group were children with fever due to respiratory tract infection at the same time period as KD (heat peak ≥ 38.5 ℃). The normal group were children at a routine physical examination in the outpatient clinic of Nantong University and the physical examination center of the child care insurance, and there were no infectious diseases and heart diseases. The serum levels of HMGB1, RAGE, and NF-κB in each group were detected by ELISA. The animal model of KD was established using the New Zealand young rabbits. We used RT-qPCR/H&E staining/immunohistochemistry/ELISA and western blot to detect the level of HMGB1/RAGE and NF-κB.

Results

In this study, we found that the HMGB1/RAGE/NF-κB axis was elevated in the serum of children with KD. In addition, an animal model of KD was subsequently prepared to examine the pathological changes of the coronary arteries. We found that the serum levels of HMGB1/RAGE/NF-κB in rabbits with KD were significantly higher than those of the control group. Moreover, the lumen diameter of the coronary artery was slightly enlarged, and the wall of the tube became thinner and deformed. In addition, the HMGB1/RAGE/NF-κB levels in the coronary artery were higher in the rabbits with KD in the acute phase.

Conclusions

On the whole, the findings of this study demonstrate that the expression of HMGB1/RAGE/NF-κB is altered at different stages of KD, suggesting that the HMGB1/RAGE/NF-κB signaling pathway plays an important role in vascular injury in KD. The results of this study may have important implications for the early warning of coronary artery lesions in KD.

Urinary and serum soluble CD25 complements urinary soluble CD163 to detect active renal anti-neutrophil cytoplasmic autoantibody-associated vasculitis: a cohort study

Background

Early detection of renal involvement in anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is of major clinical importance to allow prompt initiation of treatment and limit renal damage. Urinary soluble cluster of differentiation 163 (usCD163) has recently been identified as a potential biomarker for active renal vasculitis. However, a significant number of patients with active renal vasculitis test negative using usCD163. We therefore studied whether soluble CD25 (sCD25), a T cell activation marker, could improve the detection of renal flares in AAV.

Methods

sCD25 and sCD163 levels in serum and urine were measured by enzyme-linked immunosorbent assay in 72 patients with active renal AAV, 20 with active extrarenal disease, 62 patients in remission and 18 healthy controls. Urinary and blood CD4+ T and CD4+ T effector memory (TEM) cell counts were measured in 22 patients with active renal vasculitis. Receiver operating characteristics (ROC) curves were generated and recursive partitioning was used to calculate whether usCD25 and serum soluble CD25 (ssCD25) add utility to usCD163.

Results

usCD25, ssCD25 and usCD163 levels were significantly higher during active renal disease and significantly decreased after induction of remission. A combination of usCD25, usCD163 and ssCD25 outperformed all individual markers (sensitivity 84.7%, specificity 95.1%). Patients positive for sCD25 but negative for usCD163 (n = 10) had significantly higher C-reactive protein levels and significantly lower serum creatinine and proteinuria levels compared with the usCD163-positive patients. usCD25 correlated positively with urinary CD4+ T and CD4+ TEM cell numbers, whereas ssCD25 correlated negatively with circulating CD4+ T and CD4+ TEM cells.

Conclusion

Measurement of usCD25 and ssCD25 complements usCD163 in the detection of active renal vasculitis.

Relapse in Anti-Neutrophil Cytoplasm Antibody (ANCA)-Associated Vasculitis

Clinical relapses are common in anti-neutrophil cytoplasm antibody (ANCA)–associated vasculitis, necessitating repeated treatment with immunosuppressive therapy, and increasing the risks of severe adverse events. Better understanding the basis of relapse would help stratify patients, testing the notion that more treatment may prevent development of relapse, whereas in those at low risk of disease flares, treatment minimization may be appropriate, reducing risks of adverse events, most notably infectious complications and drug toxicity. However, relapse can only occur following remission, and although defining clinical remission may seem straightforward, there is evidence in many remission patients of persistent inflammatory and immunological activity, at levels above those found in healthy individuals. This suggests that we may not truly be achieving disease remission in many patients and these persistent responses may set the patient up for subsequent disease flares. Understanding the underlying pathophysiological basis of disease activity and remission is paramount to help define better biomarkers of relapse, which should positively affect adverse events and patient outcomes.

Disruption of a Regulatory Network Consisting of Neutrophils and Platelets Fosters Persisting Inflammation in Rheumatic Diseases

A network of cellular interactions that involve blood leukocytes and platelets maintains vessel homeostasis. It plays a critical role in the response to invading microbes by recruiting intravascular immunity and through the generation of neutrophil extracellular traps (NETs) and immunothrombosis. Moreover, it enables immune cells to respond to remote chemoattractants by crossing the endothelial barrier and reaching sites of infection. Once the network operating under physiological conditions is disrupted, the reciprocal activation of cells in the blood and the vessel walls determines the vascular remodeling via inflammatory signals delivered to stem/progenitor cells. A deregulated leukocyte/mural cell interaction is an early critical event in the natural history of systemic inflammation. Despite intense efforts, the signals that initiate and sustain the immune-mediated vessel injury, or those that enforce the often-prolonged phases of clinical quiescence in patients with vasculitis, have only been partially elucidated. Here, we discuss recent evidence that implicates the prototypic damage-associated molecular pattern/alarmin, the high mobility group box 1 (HMGB1) protein in systemic vasculitis and in the vascular inflammation associated with systemic sclerosis. HMGB1 could represent a player in the pathogenesis of rheumatic diseases and an attractive target for molecular interventions.

New insights on biomarkers in systemic vasculitis

The systemic vasculitis is a heterogeneous group of diseases characterized by the inflammation of blood vessels. The development of advanced diagnostic tests and genetic studies have resulted in greater improvement in our understanding of vasculitis pathogenesis and thus in the development of newer therapies. However, there is still an unmet need in the management of systemic vasculitis, focused on developing of new biomarkers that would enable distinction between active disease from damage or infection and predict treatment response and prognosis.

Involvement of high mobility group box 1 in the activation of C5a-primed neutrophils induced by ANCA

C5a plays a central role in antineutrophil cytoplasmic antibody (ANCA)-mediated neutrophil recruitment and activation. A previous study showed that C5a played a crucial role in the regulation of high mobility group box 1 (HMGB1) release from human neutrophils. The current study further investigated the interaction between C5a and HMGB1 in ANCA-induced neutrophil activation. The effects of HMGB1 inhibitors on the translocation of ANCA antigens, ANCA-induced respiratory burst and degranulation of C5a-primed neutrophils were tested. We found that blocking HMGB1 decreased C5a-mediated translocation of ANCA antigens, as well as ANCA-induced respiratory burst and degranulation of C5a-primed neutrophils. Further study showed that supernatant of C5a-primed neutrophils, which contained HMGB1, also caused translocation of ANCA antigens of primary neutrophils, whereas blocking HMGB1 decreased the translocation. In conclusion, blocking HMGB1 may attenuate ANCA-induced activation of C5a-primed neutrophils. The interaction between HMGB1 and C5a might play an important role in ANCA-induced neutrophil activation.

Urinary levels of high mobility group box-1 are associated with disease activity in antineutrophil cytoplasmic autoantibody-associated vasculitis

Background

High mobility group box-1 (HMGB1), a kind of pro-inflammatory mediator, is associated with inflammatory conditions and tissue damage. Our previous study demonstrated that the circulating levels of HMGB1 correlated with disease activity of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). In the current study, we aimed to measure urinary levels of HMGB1 in AAV patients, correlated them to clinical activity index and analysed the immunohistochemical HMGB1 staining in kidney specimens.

Methods

50 patients with AAV in active stage and 56 patients with AAV in remission were recruited. The urinary levels of HMGB1 were determined by enzyme-linked immunosorbent assay. Moreover, renal biopsy specimens from 27 patients with active AAV were randomly collected to evaluate the deposition of HMGB1.

Results

Urinary HMGB1 levels in AAV patients in active stage were significantly higher than those in AAV patients in remission and healthy controls (1.46 [0.56-3.43] versus 0.38 [0.10-1.35] mg/μmolCr, P=0.001; 1.46 [0.56-3.43] versus 0.48 [0.40-0.60] mg/μmolCr, P=0.000, respectively). Further analysis found that urinary levels of HMGB1 correlated with erythrocyte sedimentation rate (r=0.354, p=0.012), C-reactive protein (r=0.289, p=0.042), and Birmingham Vasculitis Activity Score (r=0.350, p=0.013). Renal tissue of active AAV patients showed HMGB1 was mainly expressed in the cytoplasm and the extracellular space. The percentage of HMGB1-negative nuclei in renal tissue of patients with active AAV was significantly higher than that in normal controls (60.6±20.2 % versus 2.7±0.6 %, p<0.01).

Conclusion

Urinary levels of HMGB1 may be associated with the disease activity in AAV patients.

High mobility group box 1 contributes to anti-neutrophil cytoplasmic antibody-induced neutrophils activation through receptor for advanced glycation end products (RAGE) and Toll-like receptor 4

Introduction

High mobility group box-1 (HMGB1), a typical damage-associated molecular pattern (DAMP) protein, is associated with inflammatory conditions and tissue damage. Our recent study found that circulating HMGB1 levels could reflect the disease activity of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). The current study aimed to investigate whether HMGB1 participated in ANCA-induced neutrophil activation, which is one of the most important pathogenic aspects in the development of AAV.

Methods

The various effects of HMGB1 in ANCA-induced neutrophil activation were measured. Antagonists for relevant receptors and signaling molecules were employed.

Results

ANCA antigens translocation on neutrophils primed with HMGB1 was significantly higher than non-primed neutrophils. The levels of respiratory burst and degranulation increased significantly in HMGB1-primed neutrophils activated with ANCA-positive IgG, as compared with non-primed neutrophils. Furthermore, blocking Toll-like receptor 4 (TLR4) and receptor for advanced glycation end products (RAGE), rather than TLR2, resulted in a significant decrease in HMGB1-induced ANCA antigens translocation, respiratory burst and degranulation. Similar effects were also found when blocking MyD88 and NF-κB.

Conclusions

HMGB1 could prime neutrophils by increasing ANCA antigens translocation, and the primed neutrophils could be further induced by ANCA, resulting in the respiratory burst and degranulation. This process is TLR4- and RAGE-dependent through the MyD88/NF-κB pathway.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-015-0587-4) contains supplementary material, which is available to authorized users.