High mobility group box chromosomal protein 1 in patients with renal diseases

Insight into the Interplay of Gd-IgA1, HMGB1, RAGE and PCDH1 in IgA Vasculitis (IgAV)

The pathogenesis of IgAV, the most common systemic vasculitis in childhood, appears to be complex and requires further elucidation. We aimed to investigate the potential role of galactose-deficient immunoglobulin A1 (Gd-IgA1), high-mobility group box 1 (HMGB1), receptor for advanced glycation end products (RAGE) and protocadherin 1 (PCDH1) in the pathogenesis of IgAV. Our prospective study enrolled 86 patients with IgAV and 70 controls. HMGB1, RAGE, Gd-IgA1 and PCDH1 in serum and urine were determined by the enzyme-linked immunosorbent assay (ELISA) method at the onset of the disease and after a six-month interval in patients and once in the control group. Serum concentrations of HMGB1, RAGE and PCDH1 and urinary concentrations of HMGB1, RAGE, Gd-IgA1 and PCDH1 were significantly higher in patients with IgAV than in the control group (p < 0.001). Concentrations of HMGB1 (5573 pg/mL vs. 3477 pg/mL vs. 1088 pg/mL, p < 0.001) and RAGE (309 pg/mL vs. 302.4 pg/mL vs. 201.3 pg/mL, p = 0.012) in the serum of patients remained significantly elevated when the disease onset was compared with the six-month follow-up interval, and thus could be a potential marker of disease activity. Urinary concentration of HMGB1 measured in the follow-up period was higher in patients with nephritis compared to IgAV without nephritis (270.9 (146.7-542.7) ng/mmol vs. 133.2 (85.9-318.6) ng/mmol, p = 0.049) and significantly positively correlated with the urine albumine to creatinine ratio (τ = 0.184, p < 0.05), the number of erythrocytes in urine samples (τ = 0.193, p < 0.05) and with the outcome of nephritis (τ = 0.287, p < 0.05); therefore, HMGB1 could be a potential tool for monitoring patients with IgAV who develop nephritis. Taken together, our results imply a possible interplay of Gd-IgA1, HMGB1, RAGE and PCDH1 in the development of IgAV. The identification of sensitive biomarkers in IgAV may provide disease prevention and future therapeutics.

HMGB1 in kidney diseases

High mobility group box 1 (HMGB1) is a highly conserved nucleoprotein involving in numerous biological processes, and well known to trigger immune responses as the damage-associated molecular pattern (DAMP) in the extracellular environment. The role of HMGB1 is distinct due to its multiple functions in different subcellular location. In the nucleus, HMGB1 acts as a chaperone to regulate DNA events including DNA replication, repair and nucleosome stability. While in the cytoplasm, it is engaged in regulating autophagy and apoptosis. A great deal of research has explored its function in the pathogenesis of renal diseases. This review mainly focuses on the role of HMGB1 and summarizes the pathway and treatment targeting HMGB1 in the various renal diseases which may open the windows of opportunities for the development of desirable therapeutic ends in these pathological conditions.

The role of high mobility group box 1 (HMGB1) in the pathogenesis of kidney diseases

High mobility group box 1 (HMGB1) is a nuclear protein that can bind to DNA and act as a co-factor for gene transcription. When released into extracellular fluid, it plays a proinflammatory role by acting as a damage-associated molecular pattern molecule (DAMP) (also known as an alarmin) to initiate innate immune responses by activating multiple cell surface receptors such as the receptor for advanced glycation end-products (RAGE) and toll-like receptors (TLRs), TLR2, TLR4 or TLR9. This proinflammatory role is now considered to be important in the pathogenesis of a wide range of kidney diseases whether they result from hemodynamic changes, renal tubular epithelial cell apoptosis, kidney tissue fibrosis or inflammation. This review summarizes our current understanding of the role of HMGB1 in kidney diseases and how the HMGB1-mediated signaling pathway may constitute a new strategy for the treatment of kidney diseases.

Increased serum HMGB1 levels in patients with Henoch-Schönlein purpura

High-mobility group box-1 (HMGB1) has been implicated as a pro-inflammatory cytokine in the pathogenesis of various inflammatory and autoimmune diseases. However, information about HMGB1 in Henoch-Schönlein purpura (HSP) is still unclear. Herein, we investigated the role of HMGB1 in patients with HSP and the pro-inflammatory effects of HMGB1 on human dermal microvascular endothelial cell line (HMEC-1). Serum HMGB1 levels in patients with HSP together with patients with allergic vasculitis (AV) and urticarial vasculitis (UV) were detected by enzyme-linked immunosorbent assay (ELISA). HMEC-1 cells were treated with HMGB1 at concentrations ranging from 4 ng/ml to 100 ng/ml. Serum HMGB1 levels were significantly increased in patients with HSP, AV and UV, when compared with those in control group. Moreover, abundant cytoplasmic expression of HMGB1 was observed in endothelial cells in lesional skin of HSP patients. Using membrane cytokine antibody array, we indicate that HMGB1 markedly induced TNF-α and IL-6 release in cultured supernatant. Furthermore, by real-time quantitative PCR and ELISA, the effects of HMGB1 on these cytokines production in HMEC-1 cells were established. Finally, Western blot data revealed that HMGB1 can induce phosphorylation of inhibitor of κB-α (IκBα) and the nuclear translocation of nuclear factor-κB (NF-κB) p65 in HMEC-1 cells. In conclusion, this study provides first observations on the association of HMGB1 with HSP. We suggest that HMGB1 may be an important mediator of endothelial inflammation through the induction of TNF-α and IL-6 production and may play a crucial role in the pathogenesis of HSP.

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.

Is serum HMGB1 a biomarker in ANCA-associated vasculitis?

Background

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitides (AAV) are systemic inflammatory disorders that include granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), Churg-Strauss syndrome and renal limited vasculitis (RLV). Extracellular high-mobility group box 1 (HMGB1) acts as an alarmin and has been shown to be a biomarker of disease activity as well as an autoantigen in systemic lupus erythematosus (SLE) and, possibly, in AAV. This study aims to assess antibodies against HMGB1 and HMGB1 levels as biomarkers for AAV disease activity and predictors of relapsing disease.

Methods

AAV patients with active disease and healthy controls (HC) were evaluated for anti-HMGB1 antibodies while serum HMGB1 levels were measured longitudinally in AAV patients at presentation, during remission, prior to and at relapses.

Results

HMGB1 levels were similar between AAV patients at presentation (n = 52) and HC (n = 35) (2.64 ± 1.80 ng/ml vs. 2.39 ± 1.09 ng/ml; P = 0.422) and no difference regarding HMGB1 levels could be found among AAV disease subsets (GPA: 2.66 ± 1.83 ng/ml vs. MPA: 3.11 ± 1.91 ng/ml vs. RLV: 1.92 ± 1.48 ng/ml; P = 0.369). AAV patients with renal involvement had lower HMGB1 levels than patients without renal involvement at presentation (2.35 ± 1.48 ng/ml vs. 3.52 ± 2.41 ng/ml; P = 0.042). A negative correlation was observed between HMGB1 levels and 24-hour proteinuria (ρ = -0.361, P = 0.028). Forty-nine AAV patients were evaluated for HMGB1 levels during follow-up and no differences were observed between relapsing and nonrelapsing patients (P = 0.350). No significant increase in HMGB1 levels was observed prior to a relapse compared with the remission period and changes in HMGB1 levels were not associated with an increased risk for relapse in AAV. Positivity for anti-HMGB1 antibodies was low in patients with active AAV (three out of 24 patients).

Conclusions

Serum HMGB1 levels at presentation are not increased and are lower in patients with renal involvement. Relapses are not preceded or accompanied by significant rises in HMGB1 levels and changes in HMGB1 levels are not related to ensuing relapses. Anti-HMGB1 antibodies are present in only a few patients in AAV. In contrast to SLE, HMGB1 is not a useful biomarker in AAV.

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.

The role of necrotic cell death in the pathogenesis of immune mediated nephropathies

Necrosis, an inflammatory form of cell death, has been considered to be an accidental death and/or cell death due to injury. However, the literature in the last decade has established that necrosis is a regulated form of cell death, and that inhibition of specific molecular pathways leading to necrosis can block it and reduce inflammation. Since necrotic lesions are observed in several immune mediated human pathologies, in this review we will discuss the impact that this form of programmed cellular demise has in the pathology of immune mediated nephropathies.

The alarmin functions of high-mobility group box-1 and IL-33 in the pathogenesis of systemic lupus erythematosus

'Alarmins' are a group of endogenous proteins or molecules that are released from cells during cellular demise to alert the host innate immune system. Two of them, high-mobility group box-1 (HMGB1) and IL-33 shared many similarities of cellular localization, functions and involvement in various inflammatory diseases including systemic lupus erythematosus (SLE). The expressions of HMGB1 and IL-33, and their corresponding receptors RAGE (receptor for advanced glycation end products) and ST2, respectively, are substantially upregulated in patients with lupus nephritis (LN). This review highlights the emerging roles of alarmin proteins in various pathologies of LN, by focusing on classical HMGB1 and a newly discovered alarmin IL-33.

Role of high mobility group box 1 and its signaling pathways in renal diseases

The high mobility group box 1 (HMGB1) protein, a member of the high mobility group nuclear protein family and an endogenous ligand for TLR2/4 and RAGE (receptor for advanced glycation end products), is one of the most evolutionarily conserved proteins and it has recently emerged as an extracellular signaling factor with key roles in cell differentiation, proliferation and disease pathogenesis. The present data indicate that HMGB1 is one of most important proinflammatory cytokines, and plays an important role in renal diseases. The literatures were searched extensively and this review was performed to sum up the role of HMGB1 in renal diseases.

The AGE-RAGE pathway and its relation to cardiovascular disease in patients with chronic kidney disease

Chronic kidney disease (CKD) carries an unequivocal high risk for cardiovascular disease (CVD) contributing to high morbimortality; however, the underlying reasons are not fully known. Among mechanisms involved in the pathophysiology of CVD, chronic overstimulation of the advanced glycation end-products (AGE)-receptor for AGE (RAGE) pathway is likely a major contributor in patients with CKD. This review describes briefly some of the components of this pathway, highlighting especially differences between circulating AGE and tissue AGE and how activation of the AGE-RAGE pathway may promote CVD in CKD.

Regulation of wound healing and organ fibrosis by toll-like receptors

Chronic injury often triggers maladaptive wound healing responses leading to the development of tissue fibrosis and subsequent organ malfunction. Inflammation is a key component of the wound healing process and promotes the development of organ fibrosis. Here, we review the contribution of Toll-like receptors (TLRs) to wound healing with a particular focus on their role in liver, lung, kidney, skin and myocardial fibrosis. We discuss the role of TLRs on distinct cell populations that participate in the repair process following tissue injury, and the contribution of exogenous and endogenous TLR ligands to the wound healing response. Systemic review of the literature shows that TLRs promote tissue repair and fibrosis in many settings, albeit with profound differences between organs. In particular, TLRs exert a pronounced effect on fibrosis in organs with higher exposure to bacterial TLR ligands, such as the liver. Targeting TLR signaling at the ligand or receptor level may represent a novel strategy for the prevention of maladaptive wound healing and fibrosis in chronically injured organs. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

High mobility group box 1 and kidney diseases (Review)

High mobility group box 1 (HMGB1), a non-histone DNA-binding protein, regulates nucleosome function and transcription in the nuclei of all metazoans and plants. However, extracellular HMGB1, which is actively or passively released under different conditions, can act as a key inflammatory mediator through MyD88/mitogen-activated protein kinase signaling by binding to its receptors including the receptor for advanced glycation end products or Toll-like receptors. A growing body of evidence indicates that HMGB1 plays an important role in kidney diseases, such as glomerulonephritis, lupus nephritis, antineutrophilic cytoplasmatic antibody-associated vaculitis, diabetic nephropathy, renal allograft rejection and acute kidney injury. In this review, we focus on the biology of HMGB1 and the association of HMGB1 with kidney diseases.

Urine levels of HMGB1 in Systemic Lupus Erythematosus patients with and without renal manifestations

INTRODUCTION

Lupus nephritis (LN) is a severe and frequent manifestation of systemic lupus erythematosus (SLE). Its pathogenesis has not been fully elucidated but immune complexes are considered to contribute to the inflammatory pathology in LN. High Mobility Group Box 1 (HMGB1) is a nuclear non-histone protein which is secreted from different types of cells during activation and/or cell death and may act as a pro-inflammatory mediator, alone or as part of DNA-containing immune complexes in SLE. Urinary excretion of HMGB1 might reflect renal inflammatory injury. To assess whether urinary HMGB1 reflects renal inflammation we determined serum levels of HMGB1 simultaneously with its urinary levels in SLE patients with and without LN in comparison to healthy controls (HC). We also analyzed urinary HMGB1 levels in relation with clinical and serological disease activity.

METHODS

The study population consisted of 69 SLE patients and 17 HC. Twenty-one patients had biopsy proven active LN, 15 patients had a history of LN without current activity, and 33 patients had non-renal SLE. Serum and urine levels of HMGB1 were both measured by western blotting. Clinical and serological parameters were assessed according to routine procedures. In 17 patients with active LN a parallel analysis was performed on the expression of HMGB1 in renal biopsies.

RESULTS

Serum and urinary levels of HMGB1 were significantly increased in patients with active LN compared to patients without active LN and HC. Similarly, renal tissue of active LN patients showed strong expression of HMGB1 at cytoplasmic and extracellular sites suggesting active release of HMGB1. Serum and urinary levels in patients without active LN were also significantly higher compared to HC. Urinary HMGB1 levels correlated with SLEDAI, and showed a negative correlation with complement C3 and C4.

CONCLUSION

Levels of HMGB1 in urine of SLE patients, in particular in those with active LN, are increased and correlate with SLEDAI scores. Renal tissue of LN patients shows increased release of nuclear HMGB1 compared to control renal tissue. HMGB1, although at lower levels, is, however, also present in the urine of patients without active LN. These data suggest that urinary HMGB1 might reflect both local renal inflammation as well as systemic inflammation.

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.

Dangers within: DAMP responses to damage and cell death in kidney disease

The response to exogenous pathogens leads to activation of innate immunity through the release of pathogen-associated molecular patterns (PAMPs) and their binding to pattern recognition receptors. A classic example is septic shock where Toll receptor 4 recognizes PAMPs. Although well accepted, this concept does not explain the activation of innate immunity and inflammation occurs with transplantation, autoimmunity, or trauma. Increasingly recognized is that endogenous molecules released by dying cells (damage-associated molecular patterns; DAMPs) activate cellular receptors leading to downstream inflammation. Thus endogenous danger signals and exogenous PAMPs elicit similar responses through seemingly similar mechanisms. Also emerging is our understanding that normal repair processes benefit from dampening the immune response to these endogenous danger molecules. Here we focus on the role of DAMPs and their putative receptors in the pathogenesis of acute and chronic kidney diseases.

Recent aspects of vasculitis and future direction

Vasculitis is pathologically identified as specific cellular inflammation, vessel destruction, and tissue necrosis. Current classifications of vasculitis such as the Chapel Hill Classification (CHCC) and American College of Rheumatology (ACR) guidelines are not sufficiently adequate for clinicians to diagnose vasculitis. The biomarkers that are currently in clinical use such as PR3-ANCA and MPO-ANCA, only help in diagnosing small vessel vasculitis and their sensitivity and specificity are not sufficient. However, recent developments related to the pathogenesis and etiopathogenesis of vasculitis have the potential to contribute to new and improved biomarkers. The determination of diverse roles of ANCA and synergistic effects of infection, genetic, environmental factors and drugs on pathogenesis is quite important. The demonstration of a new autoantibody directed to hLAMP-2 and the resemblance to some microbial structures, in addition to the determination of the possible roles of hepatitis B and C on vasculitis are important findings. These hints may lead to new biomarker developments, providing a better method to diagnose vasculitis. The evidence on T cell immunity as circulatory and lesional will likely contribute to the development of new drugs for vasculitis.

High-mobility group box-1 protein (HMGB1) is increased in antineutrophilic cytoplasmatic antibody (ANCA)-associated vasculitis with renal manifestations

High-mobility group box 1 (HMGB1) is a nuclear and cytosolic protein that is increasingly recognized as an important proinflammatory mediator actively secreted from monocytes and macrophages and passively released from necrotic cells. In antineutrophilic cytoplasmatic antibody (ANCA)-associated vasculitis (AAV), the kidneys are commonly affected vital organs, characterized by focal necrotizing and/or crescentic pauci-immune glomerulonephritis. The aim of the study was to determine whether HMGB1 serum levels are elevated in AAV with renal manifestations. A total of 30 AAV patients (16 female and 14 male; median age 59 years, range 17-82) with Wegener granulomatosis, microscopic polyangiitis and Churg-Strauss syndrome with available renal biopsies and serum samples were included. In seven cases, serum was also obtained at rebiopsy in remission. HMGB1 was analyzed with Western blot. Birmingham Vasculitis Activity Score (BVAS, version 2003), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), urinanalysis, creatinine, estimated glomerular filtration rate, sex and age were included in the analysis. Twenty-five episodes of biopsy-proven active disease with BVAS 17.9 ± 4.6 and 13 cases with inactive biopsies and BVAS 2.3 ± 3.7 (P = 0.0001) were identified. CRP, ESR, hematuria and proteinuria were significantly higher in active cases. HMGB1 was significantly elevated (P = 0.01) comparing active with inactive cases (120 ± 48 versus 78 ± 46 ng/mL) and significantly lower in the seven control patients (P = 0.03) at rebiopsy in remission. HMGB1 remained higher in inactive cases compared with historic healthy controls (10.9 ± 10.5 ng/mL). HMGB1 levels did not differ significantly between AAV subgroups. CRP and ESR did not correlate with HMGB1. HMGB1 is significantly increased in AAV with renal involvement. Residual HMGB1 elevation in remission could possibly reflect low-grade inflammatory activity or tissue damage. Future studies may further reveal whether HMGB1 is useful as a marker of disease activity and a predictor of outcome in AAV.

Comparative effects of benidipine and amlodipine on proteinuria, urinary 8-OHdG, urinary L-FABP, and inflammatory and atherosclerosis markers in early-stage chronic kidney disease

INTRODUCTION

We examined the effects of 2 calcium channel blockers, benidipine (T-, L-, and N-type) and amlodipine (L- and N-type), on renal, inflammatory, oxidative, and atherosclerosis markers in hypertensive patients with mild chronic kidney disease (CKD).

METHODS

Forty hypertensive patients with CKD were assigned randomly to either of the 2 treatments: 8 mg benidipine once daily (n = 20, group A) or 5 mg amlodipine once daily (n = 20, group B). Treatment was continued for 12 months. Blood pressure, serum creatinine, estimated glomerular filtration rate, urinary protein excretion, urinary liver-type fatty acid-binding protein, interleukin-6, high mobility group box-1 protein, urinary 8-hydroxy-2'-deoxyguanosine, pulse wave velocity, intima-media thickness, and blood asymmetric dimethylarginine were monitored.

RESULTS

Blood pressure decreased equally in both groups (P < 0.001, at 6 and 12 months versus before treatment). Serum creatinine and estimated glomerular filtration rate changed little during the experimental period in each group. However, urinary protein excretion (P < 0.001), urinary liver-type fatty acid-binding protein (P < 0.001), urinary 8-hydroxy-2'-deoxyguanosine (P < 0.001), blood interleukin-6 (P < 0.001), blood high mobility group box-1 (P < 0.05), and pulse wave velocity (P < 0.01) decreased more in group A than in group B with 12 months of treatment. The percent reductions in intima-media thickness and blood asymmetric dimethylarginine were significantly greater in group A than in group B (P < 0.001).

CONCLUSIONS

Benidipine is more effective than amlodipine for protecting renal function and potentially for ameliorating atherosclerosis in hypertensive patients with mild CKD. T-type calcium channel blockers may be effective in patients with CKD.

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.