Moesin becomes linked to the plasma membrane in attached neutrophil granulocytes

The role of anti-HMGB1 antibody and anti-moesin antibody in ANCA-associated vasculitis

OBJECTIVE

The study aims to evaluate the role of anti-high mobility group box 1 (HMGB1) antibody and anti-moesin antibody in the diagnosis of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and its possible relationship with the different clinical manifestations.

METHODS

The study involved 60 AAV patients, 58 patients with autoimmune disease other than AAV and 50 healthy subjects. The serum levels of anti-HMGB1 and anti-moesin antibodies were determined by enzyme-linked immunosorbent assay (ELISA), and the second determination was made 3 months after treatment of AAV patients.

RESULTS

Serum levels of anti-HMGB1 and anti-moesin antibodies in AAV group were significantly higher than those in non-AAV group and HC group. The area under the curve (AUC) of anti-HMGB1 and anti-moesin in diagnosing AAV were 0.977 and 0.670, respectively. Anti-HMGB1 levels were significantly elevated in AAV patients with pulmonary involvement, while the concentrations of anti-moesin were significantly increased in patients with renal damage. Anti-moesin were positively correlated with BVAS (r=0.261, P=0.044), creatinine (r=0.296, P=0.024) and negatively correlated with complement C3 (r=-0.363, P=0.013). Besides, anti-moesin levels of active AAV patients were significantly higher than those in inactive patients. The concentrations of serum anti-HMGB1 could be significantly decreased after induction remission treatment (P<0.05).

CONCLUSION

Anti-HMGB1 and anti-moesin antibodies play important roles in the diagnosis and prognosis of AAV, which may act as potential disease markers for AAV.

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.

Moesin Is a Novel Biomarker of Endothelial Injury in Sepsis

Objective

Increased vascular permeability and inflammation are principal hallmark of sepsis. Moesin (MSN) is a membrane-associated cytoskeleton protein and crucial for the vascular endothelial function. This study is aimed at evaluating the role of MSN in endothelial injury during the process of sepsis.

Methods

Serum MSN in septic patients was measured by ELISA. BALB/c mice were injected with different doses of lipopolysaccharide (LPS) or underwent cecal ligation and single or double puncture (CLP) to mimic sublethal and lethal sepsis. After treatment, their serum MSN and PCT levels, wet to dry lung weights (W/D ratio), bronchoalveolar lavage fluid (BALF) protein concentrations, and lung injury scores were measured. The impact of MSN silencing on LPS-altered Rock1/myosin light chain (MLC), NF-κB, and inflammatory factors in human microvascular endothelial cells (HMECs), as well as monolayer HMEC permeability, was tested in vitro.

Results

Compared with healthy controls, serum MSN increased in septic patients and was positively correlated with SOFA scores and serum PCT levels in septic patients. LPS injection significantly increased serum the MSN and PCT expression, BALF protein levels, and W/D ratio, and the serum MSN levels were positively correlated with serum PCT, lung W/D ratio, and lung injury scores in mice. Similar results were obtained in the way of CLP modelling. LPS enhanced MSN, MLC, NF-κB phosphorylation, increased Rock1 expression, and inflammatory factors release in the cultured HMECs, while MSN silencing significantly mitigated the LPS-induced Rock1 and inflammatory factor expression, NF-κB, and MLC phosphorylation as well as the monolayer hyperpermeability in HMECs.

Conclusions

Increased serum MSN contributes to the sepsis-related endothelium damages by activating the Rock1/MLC and NF-κB signaling and may be a potential biomarker for evaluating the severity of sepsis.

Moesin expression in fibrosis in the mouse cornea after sterile mechanical trauma or infection

PURPOSE

The aim of this study was to compare the expression patterns of 3 important biochemical characteristics of fibrosis-moesin, transforming growth factor (TGF)-β1, and α-smooth muscle actin (SMA) in the mouse cornea with fibrosis induced by common etiologies-sterile mechanical injury and infection.

METHODS

Corneas of 8-week-old C57BL6 mice were either wounded after an anterior keratectomy or were infected by Pseudomonas aeruginosa, and the animals were killed on days 2 and 7, and on weeks 2 and 4 after the procedure. Western blot and immunofluorescence were used to analyze the expression of moesin and phospho-moesin, and the presence of myofibroblasts identified by the expression of α-SMA in the corneal stroma. The expression of TGF-β1 was analyzed by immunofluorescence.

RESULTS

By immunofluorescent analysis, TGF-β1, α-SMA, and phospho-moesin were not detected in the normal corneal stroma. However, after either treatment, TGF-β1 expression increased, along with phospho-moesin in the wounded corneal stroma until day 7, and decreased after week 2. No expression of TGF-β1 and phospho-moesin was found at postoperative week 4. Moesin expression increased until week 2. Myofibroblasts positive for α-SMA were detected on day 2 until week 4 and peaked at week 2. Western blot analysis confirmed the immunofluorescent data for moesin, phospho-moesin, and α-SMA.

CONCLUSIONS

The similar expression pattern of moesin, phospho-moesin, TGF-β1, and α-SMA in the mouse cornea with fibrosis caused by sterile mechanical injury or infection indicated a role for moesin signaling in corneal fibrosis. Interference with the action of moesin may be a potential approach for intervention strategies to avert fibrosis after infection or mechanical injury.

A novel autoantibody against moesin in the serum of patients with MPO-ANCA-associated vasculitis

BACKGROUND

Antineutrophil cytoplasmic autoantibody (ANCA) directed against myeloperoxidase (MPO), a diagnostic criterion in MPO-ANCA-associated vasculitis (MPO-AAV), does not always correlate with disease activity. Here, we detected autoantibodies against moesin, which was located on the surface of stimulated endothelial cells, in the serum of patients.

METHODS

The anti-moesin autoantibody titer was evaluated by ELISA. Seventeen kinds of cytokines/chemokines were measured by a Bio-Plex system.

RESULTS

Serum creatinine in the anti-moesin autoantibody-positive group was higher than that in the negative group. Additionally, interferon (IFN)-γ, macrophage chemotactic peptide-1 (MCP-1), interleukin (IL)-2, IL-7, IL-12p70, IL-13, granulocyte/macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor were significantly higher in the positive group. Furthermore, IL-7 and IL-12p70 levels correlated with the anti-moesin autoantibody titer. Based on these findings and the binding of anti-moesin IgG to neutrophils and monocytes, we detected the secretion of cytokines/chemokines such as IFN-γ, MCP-1 and GM-CSF from these cells.

CONCLUSIONS

The anti-moesin autoantibody existed in the serum of patients with MPO-AAV and was associated with the production of inflammatory cytokines/chemokines targeting neutrophils with a cytoplasmic profile, which suggests that the anti-moesin autoantibody has the possibility to be a novel autoantibody developing vasculitis via neutrophil and endothelial cell activation.

Proposal of anti-moesin as a novel biomarker for ANCA-associated vasculitis

Myeloperoxidase (MPO)-specific antineutrophil cytoplasmic antibody (ANCA) is associated with rapidly progressive glomerulonephritis (RPGN) in microscopic polyangiitis (MPA). MPO-ANCA activates neutrophils by binding to cell surface MPO expressed on tumor necrosis factor-α (TNF-α)-primed neutrophils and induces neutrophil degranulation and production of reactive oxygen species, consequently resulting in glomerular endothelial damage. Recently, anti-MPO antibody has been found to activate glomerular endothelial cells, leading to an upregulation of adhesion molecules. MPO-ANCA, however, is not always correlated with disease activity in MPA. Accordingly, the molecule(s) responsible for the anti-MPO antibody have been explored on mouse glomerular endothelial cells. The molecule was identified as moesin, which is a heparin-binding protein and belongs to the ezrin/radixin/moesin family of proteins distributed in the plasma membrane in the cellular cortex. Interestingly, anti-moesin is observed in sera of SCG/Kj mice, which spontaneously develop MPO-ANCA-associated RPGN, and of patients with MPO-AAV. The activation of glomerular endothelial cells by the anti-MPO antibody appears to be associated with signaling through moesin.

Moesin-induced signaling in response to lipopolysaccharide in macrophages

BACKGROUND AND OBJECTIVE

Many physiological and pathophysiological conditions are attributable in part to cytoskeletal regulation of cellular responses to signals. Moesin (membrane-organizing extension spike protein), an ERM (ezrin, radixin and moesin) family member, is involved in lipopolysaccharide (LPS)-mediated events in mononuclear phagocytes; however, its role in signaling is not fully understood. The aim of this study was to investigate the LPS-induced moesin signaling pathways in macrophages.

MATERIAL AND METHODS

Macrophages were stimulated with 500 ng/mL LPS in macrophage serum-free medium. For blocking experiments, cells were pre-incubated with anti-moesin antibody. Moesin total protein and phosphorylation were studied with western blotting. Moesin mRNA was assessed using quantitative real-time PCR. To explore binding of moesin to LPS, native polyacrylamide gel electrophoresis (PAGE) gel shift assay was performed. Moesin immunoprecipitation with CD14, MD-2 and Toll-like receptor 4 (TLR4) and co-immunoprecipitation of MyD88-interleukin-1 receptor-associated kinase (IRAK) and IRAK-tumor necrosis factor receptor-activated factor 6 (TRAF6) were analyzed. Phosphorylation of IRAK and activities of MAPK, nuclear factor kappaB (NF-kappaB) and IkappaBalpha were studied. Tumor necrosis factor alpha, interleukin-1beta and interferon beta were measured by ELISA.

RESULTS

Moesin was identified as part of a protein cluster that facilitates LPS recognition and results in the expression of proinflammatory cytokines. Lipopolysaccharide stimulates moesin expression and phosphorylation by binding directly to the moesin carboxyl-terminus. Moesin is temporally associated with TLR4 and MD-2 after LPS stimulation, while CD14 is continuously bound to moesin. Lipopolysaccharide-induced signaling is transferred downstream to p38, p44/42 MAPK and NF-kappaB activation. Blockage of moesin function interrupts the LPS response through an inhibition of MyD88, IRAK and TRAF6, negatively affecting subsequent activation of the MAP kinases (p38 and ERK), NF-kappaB activation and translocation to the nucleus.

CONCLUSION

These results suggest an important role for moesin in the innate immune response and TLR4-mediated pattern recognition in periodontal disease.

p40phox: The last NADPH oxidase subunit

The phagocytic NADPH-oxidase is a multiprotein system activated during the inflammatory response to produce superoxide anion (O2-), which is the substrate for formation of additional reactive oxygen species (ROS). The importance of this system for innate immunity is established by chronic granulomatous disease (CGD), a primary immunodeficiency caused by defects in the NADPH oxidase. In this review, we present and discuss recent knowledge about p40phox, the last NADPH oxidase component to be identified. Furthermore, its interaction with cellular pathways outside of the NADPH oxidase is discussed. Described in this review is evidence that p40phox participates in NADPH oxidase dynamics within cells, what is known about its role in the oxidase, the possibility that p40phox participates in non-NADPH oxidase processes in phagocytic and non-phagocytic cells and whether p40phox could mediate a similar function in other NADPH oxidases. An improved understanding of p40phox should provide new insights about NADPH oxidase, the physiology of phagocytic cells and the innate immune system.

Lipid Rafts Regulate Lipopolysaccharide-induced Activation of Cdc42 and Inflammatory Functions of the Human Neutrophil

Lipid rafts are cholesterol-rich membrane microdomains that are thought to act as coordinated signaling platforms by regulating dynamic, agonist-induced translocation of signaling proteins. They have been described to play a role in multiple prototypical cascades, among them the lipopolysaccharide pathway, and to host multiple signaling proteins, including kinases and low molecular weight G-proteins. Here we report lipopolysaccharide-induced activation of the Rho family GTPase Cdc42, and we show its activation in the human neutrophil to be mediated by a p38 mitogen-activated protein kinase-dependent mechanism. Subcellular fractionation reveals that lipopolysaccharide induces translocation of Cdc42 to lipid rafts, where it and p38 are both found to be activated. By contrast, lipopolysaccharide causes translocation of Rac from the polymorphonuclear leukocyte (PMN) rafts and does not induce its activation. With the use of methyl-beta-cyclodextrin, a cholesterol-depleting agent that reversibly disrupts rafts, we confirm an important regulatory role for rafts in the activation state of p38 and Cdc42 and in the Rho GTPase-dependent functions superoxide anion production and actin polymerization. Methyl-beta-cyclodextrin induces activation of p38 and Cdc42, but not Rac, in the nonstimulated PMN, yet inhibits subsequent lipopolysaccharide-induced activation of p38 and Cdc42. In parallel, methyl-beta-cyclodextrin primes the human PMN for subsequent superoxide release triggered by the formylated bacterial tripeptide formyl-Met-Leu-Phe, and induces actin polymerization in a subcellular distribution distinct from that induced by lipopolysaccharide. In sum, these findings provide evidence for an important regulatory role of cholesterol in both transmission of the lipopolysaccharide signal and the inflammatory phenotype of the human neutrophil.

Role for moesin in lipopolysaccharide-stimulated signal transduction

Moesin is a 78-kDa protein with diverse functions in linking the cytoskeleton to the membrane while controlling cell shape, adhesion, locomotion, and signaling. The aim of this study was to characterize the expression and localization of moesin in mononuclear phagocytes by using confocal microscopy, flow cytometry, immunoprecipitation, and Western blotting and to analyze the function of moesin as a lipopolysaccharide receptor, utilizing an antisense oligonucleotide approach to knock down the moesin gene. Results revealed that moesin is expressed on the surface of monocytes/macrophages and surface expression is increased after lipopolysaccharide stimulation. The total protein mass of moesin is increased in monocytes after lipopolysaccharide stimulation. Immunoprecipitation showed that moesin coprecipitates with TLR4, a well-known lipopolysaccharide receptor, suggesting an early role of moesin in the formation of the initiation complex for lipopolysaccharide signaling. Two antisense and two control sense oligonucleotides were synthesized and introduced every 4 h for 48 h in adherent macrophage-like cells. Cells were then stimulated with lipopolysaccharide for 4 h, and the supernatants were assayed for tumor necrosis factor alpha (TNF-alpha) production. Cell lysates were assayed for moesin expression by Western blotting immediately after the 48-h treatment period and also after 116 h of recovery to assess the return of moesin expression and function. Moesin gene expression was completely suppressed after 48 h of incubation with antisense oligonucleotides. The antisense elimination of moesin gene expression led to a significant reduction of lipopolysaccharide-induced TNF-alpha secretion. Restoration of moesin gene expression led to restoration of TNF-alpha production. These data suggest an important role for moesin in lipopolysaccharide-induced TNF-alpha production, highlighting its importance in lipopolysaccharide-mediated signal transduction.

The NADPH oxidase components p47(phox) and p40(phox) bind to moesin through their PX domain

The NADPH oxidase of phagocytes is a membrane-bound heterodimeric flavocytochrome which catalyses the transfer of electrons from NADPH in the cytoplasm to oxygen in the phagosome. A number of cytosolic proteins are involved in its activation/deactivation: p47phox, p67phox, p40phox and the small GTP-binding protein, rac. The cytosolic phox proteins interact with the cytoskeleton in human neutrophils and, in particular, an interaction with coronin has been reported (Grogan A., Reeves, E., Keep, N. H., Wientjes, F., Totty, N., Burlingame, N. L., Hsuan, J., and Segal, A. W. (1997) J. Cell Sci. 110, 3071-3081). Here, we report on the interaction of another cytoskeletal protein, moesin, with the phox proteins. Moesin belongs to the ezrin-radixin-moesin family of F-actin-binding proteins and we show that it binds to p47phox and p40phox in a phosphoinositide-dependent manner. Furthermore, we show that its N-terminal part binds to the PX domain of p47phox and p40phox.