High mobility group box 1 skews macrophage polarization and negatively influences phagocytosis of apoptotic cells.

OBJECTIVES: Decreased phagocytosis of apoptotic cells plays an important role in the pathogenesis of SLE. This can lead to secondary necrosis and release of nuclear proteins, such as high mobility group box 1 (HMGB1). We hypothesized that increased HMGB1 levels, as present in SLE, skew macrophage differentiation towards M1-like phenotypes and thereby diminish uptake of apoptotic cells. The aim of this study was to investigate the effect of HMGB1 on macrophage polarization and on phagocytic capacity of differentiated macrophages. METHODS: SLE patients with quiescent disease (SLEDAI ⩽4) and healthy controls (HCs) were included. Monocytes and differentiated M1 and M2 macrophages were assessed for expression of M1 and M2 markers and for phagocytic capacity. HMGB1 was added during differentiation and during phagocytosis. RESULTS: Expression of CD86 (M1) was not different, whereas CD163 (M2) was significantly lower on SLE monocytes. After differentiation, no differences regarding surface receptor expression and phagocytic capacity were observed between M1 and M2 macrophages from SLE patients and HCs. Addition of HMGB1 during M2 differentiation resulted in high IL-6 and TNF-α mRNA expression and reduced phagocytic capacity of apoptotic cells. Furthermore, adding HMGB1 to apoptotic Jurkat cells diminished phagocytosis of these cells. CONCLUSION: Circulating monocytes from SLE patients display an M1-like phenotype compared with HCs, but in vitro differentiation abolishes this difference. HMGB1 skews differentiation of M2-like macrophages towards an M1-like phenotype and, subsequently, reduces phagocytosis of apoptotic cells. These data imply that the phenotype of monocytes or macrophages is determined by their environment, such as the presence of cytokines and HMGB1.

Treatment with Anti-HMGB1 Monoclonal Antibody Does Not Affect Lupus Nephritis in MRL/lpr Mice.

High mobility group box 1 (HMGB1) is a nuclear DNA binding protein that acts as an alarmin when secreted. HMGB1 is increased in systemic lupus erythematosus and might represent a potential therapeutic target. We investigated whether treatment with an anti-HMGB1 antibody affects the development of lupus nephritis in MRL/lpr mice. Seven-week-old MRL/lpr mice were injected intraperitoneally twice weekly for 10 wks with 50 µg monoclonal anti-HMGB1 (2G7, mouse IgG2b) (n = 12) or control antibody (n = 11). Control MRL/MPJ mice (n = 10) were left untreated. Every 2 wks, blood was drawn and urine was collected at wk 7, 11 and 17. Mice were sacrificed at 17 wks for complete disease evaluation. Plasma HMGB1 and anti-HMGB1 levels were increased in MRL/lpr mice compared with control MRL/MPJ mice. There were no differences in albuminuria, urine HMGB1 and plasma levels of complement C3, anti-dsDNA and proinflammatory cytokines between untreated and treated mice at any time point. Lupus nephritis of mice treated with anti-HMGB1 monoclonal antibody (mAb) was classified as class III (n = 3) and class IV (n = 9), while mice treated with control mAb were classified as class II (n = 4), class III (n = 2) and class IV (n = 5). IgG and C3 deposits in kidneys were similar in mice treated with anti-HMGB1 mAb or control mAb. In conclusion, treatment with monoclonal anti-HMGB-1 antibody 2G7 does not affect development of lupus nephritis, disease progression or proinflammatory cytokine levels in MRL/lpr mice. This result indicates that blocking of HMGB1 by this neutralizing antibody does not affect lupus nephritis in MRL/lpr mice.

Impact of serum high mobility group box 1 and soluble receptor for advanced glycation end-products on subclinical atherosclerosis in patients with granulomatosis with polyangiitis.

The objective of this study was to evaluate whether levels of high mobility group box 1 (HMGB1) in granulomatosis with polyangiitis (GPA) patients are associated with carotid atherosclerosis, related to levels of soluble receptor for advanced glycation end-products (sRAGE) and influenced by immunosuppressive or lipid-lowering therapy. Twenty-three GPA patients and 20 controls were evaluated for HMGB1- and sRAGE levels and for carotid atherosclerosis using ultrasound to determine intima-media thickness (IMT). In vitro the effect of atorvastatin on the production of HMGB1 by lipopolysaccharide (LPS)-stimulated human umbilical vein endothelial cells (HUVEC) was assessed. Serum HMGB1 and sRAGE levels did not differ between patients and controls. A negative correlation was found between sRAGE and maximum IMT but HMGB1 and carotid IMT were not related. HMGB1 levels were reduced in GPA patients on statins and prednisolone. In vitro, atorvastatin reduced HMGB1 levels in supernatants of activated HUVEC. In conclusion, carotid IMT is inversely correlated with sRAGE levels but not with HMGB1 levels. Statins and prednisolone are associated with reduced serum HMGB1 levels and atorvastatin decreases HMGB1 release by activated HUVEC in vitro, indicating an additional anti-inflammatory effect of statins.

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.

Increased frequency of circulating IL-21 producing Th-cells in patients with granulomatosis with polyangiitis (GPA).

INTRODUCTION: The present study aimed to explore a possible role for IL-21 producing Th-cells in the immunopathogenesis of granulomatosis with polyangiitis (GPA). METHODS: Peripheral blood from 42 GPA patients in remission and 29 age-matched healthy controls (HCs) were stimulated in vitro, and the frequencies of IL-21 producing Th-cells were determined by flow cytometry. Since Th17-cells produce a low level of IL-21, IL-17 was also included in the analysis. Given that IL-21 is a hallmark cytokine for T follicular helper cells (T(FH)), we next evaluated the expression of their key transcription factor BCL-6 by RT-PCR and flow cytometry. To investigate the effect of IL-21 on autoantibody-production, PBMCs from GPA patients were stimulated in vitro with BAFF/IL-21 and total IgG and ANCA levels were measured in supernatants. In addition, the expression of IL-21-receptor on B-cells was analyzed. RESULTS: Percentages of IL-21 producing Th-cells were significantly elevated in GPA-patients compared to HCs, and were restricted to ANCA-positive patients. The expression of BCL-6 was significantly higher in ANCA-positive GPA-patients, as compared with ANCA-negative patients and HCs. IL-21 enhanced the production of IgG and ANCA in vitro in stimulated PBMCs from GPA patients. No difference was found in the expression of the IL-21-receptor on B-cells between ANCA-negative patients, ANCA-positive patients, and HCs. CONCLUSION: The increased frequency of circulating IL-21 producing Th-cells in ANCA-positive GPA patients and the stimulating capacity of IL-21 on ANCA-production suggest a role for these cells in the immunopathogenesis of GPA. Blockade of IL-21 could constitute a new therapeutic strategy for GPA.

Urinary CD8+ T-cell counts discriminate between active and inactive lupus nephritis.

INTRODUCTION: Lupus nephritis (LN) is a severe and frequent manifestation of systemic lupus erythematosus (SLE). Early detection of initial renal manifestations and relapses during follow-up is pivotal to prevent loss of renal function. Apart from renal biopsies, current urinary and serological diagnostic tests fail to accurately demonstrate the presence of active LN. Previously, we demonstrated that effector memory T-cells (CD45RO+CCR7-;TEM) migrate into the urine during active LN. The objective of this study was to assess the diagnostic value of urinary T-cells in comparison with traditional markers of active LN. METHODS: T-cells in the urine during active LN and remission were investigated. Twenty-two, in most cases biopsy-proven, active LN patients and 24 SLE patients without active LN were enrolled and serial measurements were performed in 16 patients. RESULTS: Analysis of the urinary sediment in active renal disease showed an increased number of CD8+ T-cells and absence of these cells during remission. Enumerating T-cell counts in LN patients with a history of renal involvement was a superior marker of active LN in comparison to traditional markers, such as proteinuria and s-creatinine. CONCLUSIONS: In conclusion, urinary T-cells, in particular CD8+ T cells, are a promising marker to assess renal activity in LN patients, in particular in those with prior renal involvement.

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.

Fluorescent cell barcoding as a tool to assess the age-related development of intracellular cytokine production in small amounts of blood from infants.

Fluorescent Cell Barcoding (FCB) is a flow cytometric technique which has been used for assessing signaling proteins. This FCB technique has the potential to be applied in other multiparameter analyses. Since data on antigen (Ag)-specific T-cell immune responses, like intracellular cytokine production, are still lacking in infants because limited blood volumes can be obtained for analysis, the FCB technique could be very useful for this purpose. The objectives of this study were to modify the FCB method to be able to measure multiple Ag-specific cytokine reponses in T-cells upon simultaneous stimulation by various antigens and mitogens in small amounts of blood and to investigate the cytokine pattern of T-cell subsets in healthy infants aged six and twelve months. Blood samples, collected from 20 healthy infants aged six and twelve months, were stimulated in vitro with the antigens: phorbol-myristate-acetate (PMA), purified-protein-derivative (PPD), Tetanus-toxoid (TT), Staphylococcal-enterotoxin-B (SEB), and phytohemagglutinin (PHA). Each stimulus was barcoded by labelling with different intensities of fluorescent cell barcoding (FCB) markers. Intracellular production of interleukin-2, interferon-gamma, and tumor necrosis factor-alpha was measured simultaneously in just one blood sample of 600 µl whole blood. Significant age-related differences in cytokine production were shown for PMA, PHA, and TT in CD4(+) T-cells, and for PMA, PHA, SEB, and TT in CD8(+) T-cells. The intracellular cytokine production by CD4(+) and CD8(+) T-cells was higher at twelve months compared to six months of age for all antigens, except for PMA, which was lower at the age of twelve months. Based on the consistency in both T-cell subsets, we conclude that the new FCB method is a promising tool to investigate the age-related development of intracellular cytokine production in infants.

Increase in IL-21 producing T-cells in patients with systemic lupus erythematosus.

INTRODUCTION: Systemic lupus erythematosus (SLE) is an autoimmune disease accompanied by a disturbed T-cell balance skewed towards effector T-cells, in particular Th17-cells. The novel cytokine interleukin-21 (IL-21) is suggested to be crucial for triggering T-cell responses towards IL-17 producing cells. Thus, we aimed to investigate the ability of T-cells to produce IL-21 and IL-17 in SLE patients. METHODS: Peripheral blood of 34 SLE patients and 18 healthy controls (HC) was stimulated with phorbol myristate acetate (PMA) and calcium ionophore (Ca-Io). Percentages of IL-21- and IL-17A expressing T-cells were analysed by flow cytometry. The expression levels of the transcription factors B-cell lymphoma-6 (BCL-6) and factors retinoid-related orphan receptor (ROR-γt) were assessed in T-cells by real-time RT-PCR and flow cytometry. Additionally, IL-21 receptor (IL-21R) expression on B- and T-cells of patients and HC was analyzed. RESULTS: Significantly increased percentages of IL-21 expressing CD4+ T-cells and CD8+ T-cells were found in SLE patients as compared to HC. The percentages of IL-21+ CD4+ T-cells and CD8+ T-cells correlated significantly with the percentages of IL-17A+ CD4+ T-cells and CD8+ T-cells, respectively. The relative expression of BCL-6 and ROR-γt did not differ between SLE patients and HC. IL-21R expression occurred mainly on B-cells and was not different comparing SLE patients and HC. CONCLUSIONS: This study demonstrates an increased proportion of IL-21+ T-cells in SLE patients correlating with the proportion of IL-17+ T-cells. This suggests a pivotal role of IL-21 in the pathogenesis of SLE.

Disturbed Th1, Th2, Th17 and T(reg) balance in patients with systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is an autoimmune disease accompanied by disturbed T-cell homeostasis. Dysbalance of T-helper-cell (Th) subsets (Th1/Th2/Th17) and regulatory T-cells (T(regs)) is suggested to contribute to the pathogenesis of SLE. Recent reports suggest functional deviation of T(regs) in terms of producing IL-17A, a process that may be aberrant in SLE. Therefore, we analyzed these T-cell subsets in SLE to test the hypothesis that aberrant T-cell subset skewing is present in SLE-patients. We investigated simultaneously the intracellular cytokines IFN-γ, IL-4 and IL-17A in CD4(+)T-cells as well as in T(regs). Skewing of T-cell subsets towards Th17 cells was observed in SLE-patients. Although the proportion of T(regs) was similar between SLE-patients and healthy controls, the ability of T(regs) to express IFN-γ and IL17A was impaired in SLE-patients. Even in quiescent SLE-patients T-cell homeostasis is aberrant in terms of skewing towards IL-17 producing T-cells.