HMGB1 contributes to glomerular endothelial cell injury in ANCA-associated vasculitis through enhancing endothelium-neutrophil interactions

Thrombosis in vasculitis: An updated review of etiology, pathophysiology, and treatment

Introduction

Thromboembolic disease is a complication of many vasculitides. A common observation is that thromboembolic events coincide with the period of vasculitic disease, but the mechanism by which this occurs remains unclear. Inflammatory thrombosis is now recognized as a symptom of arteritis rheumatic, and vasculitides such as Behçet's syndrome (BS), and anti-neutrophil cytoplasmic antibodies (ANCA)-associated vasculitis (AAV) or giant cell arteritis (GCA). This systematic review aimed to explain recent findings related to etiology, pathophysiology, and treatment methods for BS, AAV, and medium/large-vessel vasculitis.

Methods

A comprehensive literature search on English sources from PubMed, Scopus, MEDLINE, Science Direct, ProQuest, AIM, CINAHIL, and ELDIS databases was used to find the relevant articles and reports. The relevant papers (having full text) were obtained until June 2023. Two independent reviewers screened the titles and abstracts of the obtained articles, and a third arbitrator resolved disputes between the reviewers.

Results and conclusion

It is becoming increasingly clear that certain systemic inflammatory diseases, like vasculitis, are linked to a higher risk of both venous and arterial thrombosis. An increased incidence of thromboembolic disease in AAV has been noted, particularly during times of active disease. Growing evidence supports the use of immunosuppression in the management of venous thrombosis in vasculitis. These patients also have a higher risk of developing ischemic disease.

The role of toll-like receptors (TLRs) and their therapeutic applications in glomerulonephritis

One of the most important features of innate immunity is the presence of a special group of pattern recognition receptors (PRRs) called toll-like receptors (TLRs), which recognize pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs), resulting in a quick and effective immune response to them. Glomerulonephritis (GN) is one of the most important categories of renal disorders characterized by destructive responses of the immune system to the glomerulus. To date, the association of TLRs as important innate immune system members with GN has been one of the topics that attracted the attention of researchers in this field. However, the exact role of these receptors in the immunopathogenesis of GN has not yet been fully discussed. Therefore, this study aims to overview the role of TLRs in GN and the possibility of using them as a potential therapeutic target.

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.

Immunogenic cell death as driver of autoimmunity in granulomatosis with polyangiitis

Cell death and dysregulated clearance of dead cells play essential roles in the induction of chronic inflammatory processes and autoimmune diseases. Granulomatosis with polyangiitis (GPA), a neutrophil-driven autoimmune disorder, is characterized by necrotizing inflammation predominantly of the respiratory tract and an anti-neutrophil cytoplasmic autoantibody (ANCA)-associated systemic necrotizing vasculitis. Defective regulation of neutrophil homeostasis and cell death mechanisms have been demonstrated in GPA. Disturbed efferocytosis (i.e., phagocytosis of apoptotic neutrophils by macrophages) as well as cell death-related release of damage-associated molecular patterns (DAMP) such as high mobility group box 1 (HMGB1) contribute to chronic non-resolving inflammation in GPA. DAMP have been shown to induce innate as well as adaptive cellular responses thereby creating a prerequisite for the development of pathogenic autoimmunity. In this review, we discuss factors contributing to as well as the impact of regulated cell death (RCD) accompanied by DAMP-release as early drivers of the granulomatous tissue inflammation and autoimmune responses in GPA.

Neutrophils in ANCA-associated vasculitis: Mechanisms and implications for management

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is a group of systemic autoimmune diseases, which is typified by inflammatory necrosis predominantly affecting the small vessels and often accompanied by positive ANCA. Clinically, AAV primarily includes microscopic polyangiitis (MPA), granulomatosis with polyangiitis (GPA), and eosinophilic granulomatosis with polyangiitis (EGPA). It has been found that in AAV pathogenesis, both innate and adaptive immunity are related to neutrophil function mutually. Many proteins, such as myeloperoxidase (MPO) and proteinase 3 (PR3), in neutrophil cytoplasm lead to the production of proteins such as MPO-ANCA and PR3-ANCA by activating adaptive immunity. In addition, through the process of neutrophil extracellular trap (NET) formation, activation of an alternative complement pathway and the respiratory burst can stimulate the neutrophils close to vascular endothelial cells and will participate the vessel inflammation. This review aims to reveal the potential mechanisms regulating the association between the neutrophils and various types of AAVs and to emphasize the results of recent findings on these interactions. Moreover, multiple underlying signaling pathways involved in the regulation of neutrophils during AAV processes have also been discussed. The ultimate goal of this review is to identify novel biomarkers and therapeutic targets for AAV management in the future.

Alarmins in autoimmune diseases

Alarmins are endogenous, constitutively expressed, chemotacting and immune activating proteins or peptides released because of non-programmed cell death (i.e. infections, trauma, etc). They are considered endogenous damage-associated molecular patterns (DAMPs), able to induce a sterile inflammation. In the last years, several studies highlighted a possible role of different alarmins in the pathogenesis of various autoimmune and immune-mediated diseases. We reviewed the relevant literature about this topic, for about 160 articles. Particularly, we focused on systemic autoimmune diseases (systemic lupus erythematosus, rheumatoid arthritis, idiopathic inflammatory myopathies, ANCA-associated vasculitides, Behçet's disease) and cutaneous organ-specific autoimmune diseases (vitiligo, psoriasis, alopecia, pemphigo). Finally, we discussed about future perspectives and potential therapeutic implications of alarmins in autoimmune diseases. In fact, identification of receptors and downstream signal transducers of alarmins may lead to the identification of antagonistic inhibitors and agonists, with the capacity to modulate alarmins-related pathways and potential therapeutic applicability.

The Role of HMGB1 in Rheumatic Diseases

HMGB1, a highly conserved non-histone nuclear protein, is widely expressed in mammalian cells. HMGB1 in the nucleus binds to the deoxyribonucleic acid (DNA) to regulate the structure of chromosomes and maintain the transcription, replication, DNA repair, and nucleosome assembly. HMGB1 is actively or passively released into the extracellular region during cells activation or necrosis. Extracellular HMGB1 as an alarmin can initiate immune response alone or combined with other substances such as nucleic acid to participate in multiple biological processes. It has been reported that HMGB1 is involved in various inflammatory responses and autoimmunity. This review article summarizes the physiological function of HMGB1, the post-translational modification of HMGB1, its interaction with different receptors, and its recent advances in rheumatic diseases and strategies for targeted therapy.

Clinical significance and role of CXCL16 in anti-neutrophil cytoplasmic autoantibody-associated vasculitis

Anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is a group of potentially life-threatening autoimmune diseases. The kidney and lung are the most common and most severely affected organs. Previous studies have shown that the chemokine ligand CXCL16 and its receptor CXCR6 play an important role in kidney disease. However, whether CXCL16/CXCR6 is involved in the pathogenesis of AAV remains elusive. In this study, the levels of CXCL16 and its specific receptor CXCR6 were investigated. According to kidney outcome, patients were divided into two groups, specifically one with high CXCL16 levels and one with low CXCL16 levels, by cut-off values using receiver operating characteristic (ROC) curves. The clinical parameters and histological features were further compared between the two groups. The ability of CXCL16 to induce neutrophil chemotaxis was analysed using a Transwell migration assay in a coculture system of conditional immortalized human glomerular endothelial cells (ciGEnCs) and neutrophils. We observed that the levels of CXCL16 were significantly increased in the circulation, along with the expression in renal tissue of AAV patients compared to healthy controls (HCs). CXCR6 expression on neutrophils was significantly higher in patients with AAV than in HCs. There were positive correlations between the levels of CXCL16 and serum creatinine, IL-6, CRP, and TNF-α and negative correlations with eGFR. The serum levels of CXCL16 could act as a predictive biomarker of renal outcome in AAV. CXCL16 secretion was upregulated in ciGEnCs treated with AAV serum. CXCL16 released from ciGEnCs contributed to neutrophil migration. Furthermore, neutrophil migration was attenuated by silencing CXCL16 expression via transfection with short hairpin RNA (shRNA) sequences and lentivirus. Taken together, these data suggest that the inhibition of the CXCL16/CXCR6 axis may provide new therapeutic strategies targeting AAV.

Recent advances in Extracellular Vesicles and their involvements in vasculitis

Systemic vasculitis is a heterogeneous group of multisystem autoimmune disorders characterized by inflammation of blood vessels. Although many progresses in diagnosis and immunotherapies have been achieved over the past decades, there are still many unanswered questions about vasculitis from pathological understanding to more advanced therapies. Extracellular vesicles (EVs) are double-layer phospholipid membrane vesicles harboring various cargoes. EVs can be classified into exosomes, microvesicles (MVs), and apoptotic bodies depending on their size and origin of cellular compartment. EVs can be released by almost all cell types and may be involved in physical and pathological processes including inflammation and autoimmune responses. In systemic vasculitis, EVs may have pathogenic involvement in inflammation, autoimmune responses, thrombosis, endothelium injury, angiogenesis and intimal hyperplasia. EV-associated redox reaction may also be involved in vasculitis pathogenesis by inducing inflammation, endothelial injury and thrombosis. Additionally, EVs may serve as specific biomarkers for diagnosis or monitoring of disease activity and therapeutic efficacy, i.e. AAV-associated renal involvement. In this review, we have discussed the recent advances of EVs, especially their roles in pathogenesis and clinical involvements in vasculitis.

The Effect and Regulatory Mechanism of High Mobility Group Box-1 Protein on Immune Cells in Inflammatory Diseases

High mobility group box-1 protein (HMGB1), a member of the high mobility group protein superfamily, is an abundant and ubiquitously expressed nuclear protein. Intracellular HMGB1 is released by immune and necrotic cells and secreted HMGB1 activates a range of immune cells, contributing to the excessive release of inflammatory cytokines and promoting processes such as cell migration and adhesion. Moreover, HMGB1 is a typical damage-associated molecular pattern molecule that participates in various inflammatory and immune responses. In these ways, it plays a critical role in the pathophysiology of inflammatory diseases. Herein, we review the effects of HMGB1 on various immune cell types and describe the molecular mechanisms by which it contributes to the development of inflammatory disorders. Finally, we address the therapeutic potential of targeting HMGB1.

Extracellular Vesicles Tune the Immune System in Renal Disease: A Focus on Systemic Lupus Erythematosus, Antiphospholipid Syndrome, Thrombotic Microangiopathy and ANCA-Vasculitis

Extracellular vesicles (EV) are microparticles released in biological fluids by different cell types, both in physiological and pathological conditions. Owing to their ability to carry and transfer biomolecules, EV are mediators of cell-to-cell communication and are involved in the pathogenesis of several diseases. The ability of EV to modulate the immune system, the coagulation cascade, the angiogenetic process, and to drive endothelial dysfunction plays a crucial role in the pathophysiology of both autoimmune and renal diseases. Recent studies have demonstrated the involvement of EV in the control of renal homeostasis by acting as intercellular signaling molecules, mediators of inflammation and tissue regeneration. Moreover, circulating EV and urinary EV secreted by renal cells have been investigated as potential early biomarkers of renal injury. In the present review, we discuss the recent findings on the involvement of EV in autoimmunity and in renal intercellular communication. We focused on EV-mediated interaction between the immune system and the kidney in autoimmune diseases displaying common renal damage, such as antiphospholipid syndrome, systemic lupus erythematosus, thrombotic microangiopathy, and vasculitis. Although further studies are needed to extend our knowledge on EV in renal pathology, a deeper investigation of the impact of EV in kidney autoimmune diseases may also provide insight into renal biological processes. Furthermore, EV may represent promising biomarkers of renal diseases with potential future applications as diagnostic and therapeutic tools.

Toll-like Receptors as Potential Therapeutic Targets in Kidney Diseases

Toll-like Receptors (TLRs) are members of pattern recognition receptors and serve a pivotal role in host immunity. TLRs response to pathogen-associated molecular patterns encoded by pathogens or damage-associated molecular patterns released by dying cells, initiating an inflammatory cascade, where both beneficial and detrimental effects can be exerted. Accumulated evidence has revealed that TLRs are closely associated with various kidney diseases but their roles are still not well understood. This review updated evidence on the roles of TLRs in the pathogenesis of kidney diseases including urinary tract infection, glomerulonephritis, acute kidney injury, transplant allograft dysfunction and chronic kidney diseases.

Hirudin reduces nephropathy microangiopathy in STZ-induced diabetes rats by inhibiting endothelial cell migration and angiogenesis

OBJECTIVE

Kidney is the most common location of microangiopathy in diabetic patients, and we designed this study to investigate the effects of hirudin on renal microangiopathy in STZ-induced diabetes rats and in vitro.

METHODS

We established a diabetes model by intraperitoneal injection of STZ and administered hirudin daily by subcutaneous injection. HE staining was used to assess kidney pathological changes. Western blot and immunochemistry was used to detect the protein expression. Glomerular endothelial cells (GEC) in normal rats were assessed by cell scratch test for migration ability and tubule formation experiment for angiogenesis ability.

RESULTS

Compared with DN rats without any treatment, the serum creatinine, serum Cys C, 24-hour urine protein of DN rats with hirudin treatment were significantly decrease, the kidney/body weight and glomerular area of DN rats with hirudin treatment were all significantly decrease, and also significant improvement in renal pathology revealed by HE staining in DN rats after treating with hirudin. Moreover, we also found that hirudin coun not only significantly increase the prothrombin time and aivated partial thromboplastin time in DN rats, but also significantly decrease the expression of VEGF and TM-1 protein in kidney tissues of DN rats. In vitro, we found that high glucose could promote the migration and angiogensis of GEC, and significantly increased the expression of VEGF and Ang protein, but significantly decreased the expression of THBS1 and Arg1 protein. More importantly was that hirudin could inhibit the migration and angiogensis of GEC, and reversed HG-induced the expression of VEGF, Ang, THBS1 and Arg1 protein in GEC. In addition, we also found that hirudin could not only decrease HG-enhanced the activity of RhoA in GEC, but also decrease HG-enhanced the expression of p-MYPT1/MYPT1, p-p38/p38 protein in GEC.

CONCLUSION

Hirudin reduces nephropathy microangiopathy in STZ-induced diabetes, and might be related to hirudin inhibiting glomerular endothelial cell migration and angiogenesis through Rho-kinase and subsequent p38MAPK/NF-kB signaling pathway.

Association of serum high mobility group box 1 levels with disease activity and renal involvement in patients with systemic vasculitis

High mobility group box 1 (HMGB1) is a kind of proinflammatory mediator that acts as an alarmin when released by dying, injured or activated cells. Previous studies have reported that HMGB1 are closely linked to antineutrophil cytoplasmic antibody-associated vasculitis (AAV). The present study aimed to evaluate whether serum HMGB1 levels were associated with systemic vasculitis (VAs).The study population consisted of 51 patients with VAs, 46 patients with essential hypertension (EH) and 46 healthy controls (HC). Thirty-five patients with VAs had in active stage and 16 patients with VAs in an inactive stage. Furthermore, 31 patients with VAs had renal involvement, the other 20 patients were selected for without renal involvement. Serum HMGB1 levels were measured by enzyme-linked immunosorbent assay. Associations between serum HMGB1 levels with clinical and laboratory parameters were analyzed.Serum HMGB1 levels in patients with VAs were significantly higher than in EH and HC (all P < .05), and no difference regarding serum HMGB1 levels could be found between EH and HC (P = .208). Serum HMGB1 levels in VAs patients with active stage were significantly higher than those in HC and VAs patients with inactive stage (all P < .05). Patients with renal involvement and non-renal involvement had increased HMGB1 levels compared with HC (all P < .05). In addition, serum HMGB1 levels were significantly higher in patients with renal involvement compared with non-renal involvement patients (P = .001). Correlation analysis showed that serum HMGB1 levels were positive significant correlated with the Birmingham Vasculitis Activity Score, hypersensitive C reactive protein (Hs-CRP), serum creatinine (Scr) and 24-hour proteinuria (all P < .05). Among the subsets of VAs, serum HMGB1 levels were significantly higher in AAV, polyarteritis nodosa (PAN) and takayasu arteritis (TA) than in HC (all P < .05). More interestingly, serum HMGB1 were significantly higher in patients with PAN compared with AAV and TA patients (all P < .05). Furthermore, there was positive correlation between serum HMGB1 levels and Hs-CRP, Scr, and 24-hour proteinuria in patients with PAN (all P < .05).Serum HMGB1 levels are increased in patients with VAs compared with HC and EH and can reflect the disease activity and renal involvement.

Endothelial activation and injury by microparticles in patients with systemic lupus erythematosus and rheumatoid arthritis

BACKGROUND

Endothelial activation and damage is commonly observed in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) and is related to development of atherosclerosis and cardiovascular diseases. Different components of the immune system seem to participate in the endothelial injury, such as generation of autoantibodies and formation of immune complexes (ICs). Microparticles (MPs) and their immune complexes (MPs-ICs) are increased in the circulation of patients with SLE and RA; therefore, we propose these extracellular vesicles could interact and modulate the function of endothelial cells. Hence, the effect of MPs and MPs-ICs from patients with SLE and RA in endothelial cells was evaluated.

METHODS

Macrovascular and microvascular endothelial cells were exposed to MPs and MPs-ICs from healthy donors and patients with SLE and RA. Vesicles uptake/binding, expression of adhesion molecules, cytokine and chemokine production, monocyte adherence, and alterations of endothelial monolayer were evaluated by flow cytometry and fluorescence microscopy.

RESULTS

Endothelial cells internalized MPs and MPs-ICs and increased CD54 and CD102 expression and CCL2, CCL5, and IL-6 production after the treatment with these extracellular vesicles, which led to an increase in the adherence of classic monocytes. These vesicles also induced low expression of VE-cadherin in membrane, depolymerization of actin filaments, and formation of intercellular spaces, which led to endothelial death and increased permeability after MPs and MPs-ICs exposure.

CONCLUSIONS

MPs and MPs-ICs from patients with SLE and RA increase adhesion molecules expression, chemokine production, and structural alterations in macrovascular and microvascular endothelial cells. Therefore, high counts of these vesicles in patients would promote endothelial alterations and secondary tissue leukocyte infiltration.

Neutrophils and redox stress in the pathogenesis of autoimmune disease

Polymorphonuclear leukocytes, or neutrophils, are specialist phagocytic cells of the innate immune system. Their primary role is host defence against micro-organisms, which they kill via phagocytosis, followed by release of reactive oxygen species (ROS) and proteolytic enzymes within the phagosome. ROS are generated via the action of the NADPH oxidase (also known as NOX2), in a process termed the 'Respiratory Burst'. This process consumes large amounts of oxygen, which is converted into the highly-reactive superoxide radical O₂^- and H₂O₂. Subsequent activation of myeloperoxidase (MPO) generates secondary oxidants and chloroamines that are highly microbiocidal in nature, which together with proteases such as elastase and gelatinase provide a toxic intra-phagosomal environment able to kill a broad range of micro-organisms. However, under certain circumstances such as during an auto-immune response, neutrophils can be triggered to release ROS and proteases extracellularly causing damage to host tissues, modification of host proteins, lipids and DNA and dysregulation of oxidative homeostasis. This review describes the range of ROS species produced by human neutrophils with a focus on the implications of neutrophil redox products in autoimmune inflammation.

Towards precision medicine in ANCA-associated vasculitis

ANCA-associated vasculitis (AAV) is characterized by inflammation and destruction of small and medium-sized vessels. Current management strategies for AAV have been validated in large groups of patients. However, recent insights indicate that distinct patient subsets may actually exist within AAV, thereby justifying the development of more personalized treatment strategies. In this review, we discuss current evidence for a better classification of AAV based on ANCA type. We describe how thus defined categories of AAV patients may differ in genetic background, clinical presentation, immune pathology, response to treatment and disease outcome. We also explore how these insights may provide a rationale for targeted treatments in different categories of AAV patients. Finally, we provide recommendations on how to further establish precision medicine in AAV.

Glycyrrhizin ameliorates atopic dermatitis-like symptoms through inhibition of HMGB1

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease prevalent worldwide. This study investigated the effects of glycyrrhizin, an extract of licorice root, on the well-established model of 2,4-dinitrochlorobenzene-induced AD-like symptoms in mice. The severity of dermatitis, histopathological changes, serum IgE levels, changes in expression of high-mobility group box 1 (HMGB1), the receptor for advanced glycation end products (RAGE), nuclear factor (NF)-κB and inflammatory cytokines were evaluated. Treatment with glycyrrhizin inhibited the HMGB1 signaling cascade and ameliorated the symptoms of AD. Furthermore, in an in vitro study, the expression of RAGE was detected in a mouse mast cell line, P815 cells, and rmHMGB1 was found to be a potent inducer of mast cell activation by increasing Ca²⁺ influx, upregulating the CD117 and activating NF-κB signaling; these effects were also inhibited by glycyrrhizin. These findings implicate HMGB1 in the pathogenesis of AD and suggest that GL could be an effective therapeutic approach for cutaneous inflammation.

HMGB1 contributes to the irradiation-induced endothelial barrier injury through receptor for advanced glycation endproducts (RAGE)

This study aimed to investigate whether HMGB1 (high mobility group box-1 protein) and receptor for advanced glycation end products (RAGE) were involved in the irradiation-induced endothelial barrier damage and their mechanism. We constructed the damage model of endothelium barrier model with bEnd.3 cells. The permeability of endothelial barrier was detected by sodium fluorescein (Na-F) permeation test, and the irradiation dose which could induce permeability transition was determined by being exposed to different irradiation doses (5, 10, 15, 20 Gy). MTT assay was applied to detect cell viability under different concentrations of HMGB1, glycyrrhizic acid (GA, a specific inhibitor of HMGB1), and FPS-ZM1 (a blood-brain-barrier permeant blocker of RAGE V domain-mediated ligand binding). The expression of HMGB1, RAGE, and related molecules involved in MAPK signaling pathway, MMP-2, MMP-9, ZO-1, and claudin 5 of differently treated groups were measured by qRT-PCR, western blot, and immunofluorescence. Cells possessed stable endothelial barrier function on 4-7 days after seeded on transwell plates. The permeability of endothelial barrier would change under at least 10 Gy radiation. Both radiation and HMGB1 treatment alone could improve the permeability. After irradiation, the expressions of HMGB1 and RAGE increased and MAPK signal pathway was activated. Meanwhile, MMP-2 and MMP-9 were overexpressed, while the expression of tight junction proteins ZO-1 and claudin 5 was decreased. Radiation could activate MAPK signaling pathway through promoting the expression of HMGB1 and RAGE, which further led to endothelial barrier injury and changed its permeability.