The myeloic related protein MRP8/14 (27E10 antigen)--usefulness as a potential marker for disease activity in ulcerative colitis and putative biological function

Expression of S100A8 protein on B cells is associated with disease activity in patients with systemic lupus erythematosus

BACKGROUND

Systemic lupus erythematosus (SLE) is an intractable disease characterized by autoantibody production and autoreactive B and T cell proliferation. Although several studies have revealed multiple genetic and environmental associations, the underlying mechanisms remain unknown.

METHODS

We performed proteomics and transcriptomics using liquid chromatography-mass spectrometry and DNA microarray, using peripheral blood B cells from patients with SLE, and healthy controls (HC). We explored molecules associated with the pathophysiology of SLE by flow cytometry and B cell stimulation assay.

RESULTS

We identified for the first time that expression of both S100A8 protein and mRNA were markedly upregulated in SLE B cells. The results obtained using flow cytometry showed that S100A8 was highly expressed on the surface of B cells of patients with active SLE (MFI; HC 102.5 ± 5.97, stable SLE 111.4 ± 12.87, active SLE 586.9 ± 142.9), and S100A8 on the cell surface was decreased after treatment (MFI; pre-treat 1094.5 ± 355.38, post-treat 492.25 ± 247.39); therefore, it is suggested that S100A8 may be a marker for disease activity. The mRNA expression of S100A8 was particularly upregulated in memory B cells of SLE (56.68 fold higher than HC), suggesting that S100A8 may be mainly secreted by memory B cells in the pathogenesis of SLE.

CONCLUSIONS

Our results imply that the S100A8 proteins secreted from memory B cells may stimulate granulocytes and monocytes through pattern recognition receptors, activate the innate immune system, and are involved in the pathogenesis of SLE.

Preclinical Markers in Inflammatory Bowel Disease. A Nested Case-Control Study

Background

Our objective was to determine if patients who later develop inflammatory bowel disease (IBD) show signs of increased inflammatory activity in plasma measured with high sensitivity C-reactive protein (CRP), calprotectin, and albumin before the clinical onset of IBD.

Methods

We identified 96 subjects who later developed IBD (70 ulcerative colitis [UC] and 26 Crohn's disease [CD]). High sensitivity CRP, calprotectin, and albumin were analyzed in frozen plasma, donated from cases and sex-age matched controls 1-15 years before diagnosis.

Results

We found that subjects who later developed UC had lower albumin levels, and subjects who later developed CD had higher CRP levels than controls. Multivariable conditional logistic regression with albumin, calprotectin, and CRP showed a lower risk for developing IBD and UC with higher albumin levels (odds ratio [OR] 0.79, confidence interval [CI] 0.69-0.90; respective OR 0.77, CI 0.66-0.91). Higher CRP levels were associated with an increased risk of developing CD (OR 1.314, CI 1.060-1.630). When adjusting for body mass index or smoking in the logistic regression model, similar results were found. Plasma calprotectin levels in the preclinical period among patients with IBD did not differ from controls.

Conclusions

In this nested case-control study, subjects who later developed IBD had signs of low-grade systemic inflammation, indicated by significantly higher CRP plasma levels in CD and lower albumin plasma levels in UC, before the onset of clinical disease.

A Review of Selected IBD Biomarkers: From Animal Models to Bedside

Inflammatory bowel disease (IBD) is a dysregulated inflammatory condition induced by multiple factors. The etiology of IBD is largely unknown, and the disease progression and prognosis are variable and unpredictable with uncontrolled disease behavior. Monitoring the status of chronic colitis closely is challenging for physicians, because the assessment of disease activity and severity require invasive methods. Using laboratory biomarkers may provide a useful alternative to invasive methods in the diagnosis and management of IBD. Furthermore, patients with ulcerative colitis or Crohn’s disease are also at risk of developing cancer. Annual colonoscopies can help lower the risk for developing colorectal cancer. However, laboratory biomarkers may also be helpful as non-invasive indicators in predicting treatment responses, improving prognosis, and predicting possible tumors. This review addresses selected laboratory biomarkers (including ANCA, chitinase 3-like 1, S100A12/RAGE, calprotectin, and TNF/TNFR2), which are identified by utilizing two well-accepted animal models of colitis, dextran sodium sulfate-induced and T cell receptor alpha knockout colitis models. In addition to being useful for monitoring disease severity, these biomarkers are associated with therapeutic strategies. The factors may regulate the initiation and perpetuation of inflammatory factors in the gut.

Role of Calprotectin as a Biomarker in Periodontal Disease

Periodontal disease (PD) is a common infectious and inflammatory disease characterised by inflammation of tissues surrounding and supporting the teeth and destruction of the associated alveolar bone, eventually resulting in tooth loss. This disease is caused by periodontopathic bacteria in plaque biofilm and resultant innate and adaptive immune responses in periodontal tissues. Calprotectin (CLP) is a calcium-binding protein of the S-100 protein family and is found to be induced by activated granulocytes, monocytes, and epithelial cells. CLP has been shown to play an important role in numerous inflammatory diseases and disorders. Increasing evidence indicates that CLP is involved in the progression of PD, and its levels may be associated with disease severity and outcome of periodontal treatments. This review will summarise recent studies regarding the presence, regulation, and function of CLP in PD. The findings indicate that CLP may be an effective biomarker for diagnosis and treatment for the PD.

S100 proteins: An emerging cynosure in pregnancy & adverse reproductive outcome

S100 proteins are calcium (Ca²⁺)-binding proteins and these have an important function in progression, manifestation and therapeutic aspects of various inflammatory, metabolic and neurodegenerative disorders. Based on their involvement in intracellular or extracellular regulatory effects, S100 proteins are classified into three subgroups: one subgroup is specialized in exerting only intracellular effects, other performs both intracellular and extracellular functions and the third subgroup members only display extracellular regulatory effects. S100 proteins are expressed particularly in vertebrates and have cell-specific expression. Functionally, S100 proteins act through their surface receptors and regulate cell functions in autocrine or paracrine mode. Receptor for advanced glycation end products (RAGEs) and toll-like receptor 4 are the main surface receptors. S100 proteins participate in the regulation of cellular differentiation, proliferation, apoptosis and inflammation along with Ca²⁺ homeostasis, energy metabolism and cellular migration, and perform the respective functions through their interaction with transcription factors, nucleic acids, enzymes, receptors, cytoskeleton system, etc. Currently, their role in adverse pregnancy outcomes and compromised reproductive health is being explored. These proteins are present in amniotic fluid, endometrium tissue and foetal brain; therefore, it is quite likely that alterations in the expression levels of S100 family members will be affecting the particular function they are involved in and ultimately affecting the pregnancy in adverse manner. The current review discusses about an association of S100 proteins in pregnancy disorders such as endometriosis, intrauterine growth retardation and miscarriage.

The effect of calprotectin on TSLP and IL-25 production from airway epithelial cells

BACKGROUND

Calprotectin is a heterodimer complex of the S100A8 and S100A9 proteins, and has various functions as an innate mediator at the sites of inflammation. The aim of this study was to elucidate the roles of calprotectin in the eosinophilic chronic rhinosinusitis (ECRS).

METHODS

Allergen-induced production of calprotectin was evaluated in cultured normal human bronchial epithelial (NHBE) cells by ELISA and RT-PCR. We then examined the roles of calprotectin on Alternaria alternata (Alternaria)-induced production of thymic stromal lymphopoietin (TSLP) and IL-25 in NHBE cells. The extracellular concentration and allergen-induced secretion of calprotectin in cultured primary nasal epithelial (PNE) cells were examined and compared between patients with ECRS and non-eosinophilic chronic rhinosinusitis (NECRS).

RESULTS

Alternaria, house dust mites, protease from Staphylococcus aureus, papain, trypsin, polyinosinic:polycytidylic acid and lipopolysaccharide stimulated calprotectin production in the cultured NHBE cells. The combination of calprotectin and ATP stimulated the production of TSLP and IL-25 in NHBE cells, and calprotectin stimulated Alternaria-induced production of TSLP and IL-25, which was suppressed by blocking P2 purinergic receptors and by treatment with siRNA for S100A8, S100A9 or calprotectin receptors (Toll-like receptor 4 or receptor for advanced glycation end products). Allergen-induced calprotectin production was significantly stimulated in PNE cells from patients with ECRS.

CONCLUSIONS

These results indicate that calprotectin enhances the allergen-induced Th2-type inflammatory responses in airway epithelial cells via the secretion of TSLP and IL-25, and that calprotectin secreted by the epithelial cells may be involved in the pathogenesis of ECRS.

Fecal but not serum calprotectin is a potential marker of GVHD after stem cell transplantation

Gastrointestinal graft-versus-host disease (GvHD) represents a life-threatening complication after stem cell transplantation. Differential diagnosis between gut GvHD and other causes of diarrhea after HSCT is still subjected to endoscopy and histological findings. The research for a reliable biomarker for gut GvHD might allow an early diagnosis of this condition and a consequent prompt treatment that could reduce unfavorable outcomes. Recently, fecal calprotectin was reported as reliable marker of gut involvement. We would evaluate if serum instead of fecal calprotectin could be considered a possible biomarker of gut GvHD. Serum calprotectin was measured in a cohort of 54 patients submitted to allogeneic stem cell transplantation using ELISA assay. For a subset of 21 patients, calprotectin serum levels were compared with fecal calprotectin detection. Contrary to fecal calprotectin, we found only a trend to high level of serum calprotectin for GvHD development and gut involvement, but statistical difference was not reached. Fecal but not serum calprotectin could be considered as possible biomarker for gut GvHD.

S100A8/A9: From basic science to clinical application

Neutrophils and monocytes belong to the first line of immune defence cells and are recruited to sites of inflammation during infection or sterile injury. Both cells contain huge amounts of the heterodimeric protein S100A8/A9 in their cytoplasm. S100A8/A9 belongs to the Ca²⁺ binding S100 protein family and has recently gained a lot of interest as a critical alarmin modulating the inflammatory response after its release (extracellular S100A8/A9) from neutrophils and monocytes. Extracellular S100A8/A9 interacts with the pattern recognition receptors Toll-like receptor 4 (TLR4) and Receptor for Advanced Glycation Endproducts (RAGE) promoting cell activation and recruitment. Besides its biological function, S100A8/A9 (also known as myeloid related protein 8/14, MRP8/14) was identified as interesting biomarker to monitor disease activity in chronic inflammatory disorders including inflammatory bowel disease and rheumatoid arthritis. Furthermore, S100A8/A9 has been tested successfully in pre-clinical imaging studies to localize sites of infection or sterile injury. Finally, recent evidence using small molecule inhibitors for S100A8/A9 also suggests that blocking S100A8/A9 activity exerts beneficial effects on disease activity in animal models of autoimmune diseases including multiple sclerosis, systemic lupus erythematosus, rheumatoid arthritis and inflammatory bowel disease. This review will provide a comprehensive and detailed overview into the structure and biological function of S100A8/A9 and also will give an outlook in terms of diagnostic and therapeutic applications targeting S100A8/A9.

Myeloid-related protein 8 induces self-tolerance and cross-tolerance to bacterial infection via TLR4- and TLR2-mediated signal pathways

Myeloid-related protein 8 (Mrp8) is the active component of Mrp8/14 protein complex released by phagocytes at the site of infection and stimulates inflammatory responses. However, it is unclear whether Mrp8 could induce self-tolerance and cross-tolerance to bacterial infection. Here we report that Mrp8 triggered TNF-α and IL-6 release via a Toll-like receptor 4 (TLR4)-dependent manner. Pre-stimulation of murine macrophages and human monocytes with Mrp8 induced self-tolerance to Mrp8 re-stimulation and cross-tolerance to lipopolysaccharide (LPS), bacterial lipoprotein (BLP), gram-negative and gram-positive bacterial challenges, with substantially attenuated TNF-α and IL-6 release. Moreover, Mrp8 tolerisation significantly reduced serum TNF-α and IL-6, increased polymorphonuclear neutrophil (PMN) recruitment and accelerated bacterial clearance, thus protecting mice against LPS-induced lethality and cecal ligation and puncture (CLP)-induced polymicrobial sepsis. In addition to TLR4, TLR2 also contributed to Mrp8-induced inflammatory response and tolerance. Down-regulation of phosphorylated p38 by Mrp8 pre-stimulation was predominantly responsible for the intracellular mechanism of Mrp8-induced tolerance. Thus, our findings of Mrp8-induced self-tolerance and cross-tolerance may provide a potential strategy for attenuating an overwhelming proinflammatory cascade and enhancing antimicrobial responses during microbial sepsis.

Extracellular MRP8/14 is a regulator of β2 integrin-dependent neutrophil slow rolling and adhesion

Myeloid-related proteins (MRPs) 8 and 14 are cytosolic proteins secreted from myeloid cells as proinflammatory mediators. Currently, the functional role of circulating extracellular MRP8/14 is unclear. Our present study identifies extracellular MRP8/14 as an autocrine player in the leukocyte adhesion cascade. We show that E-selectin–PSGL-1 interaction during neutrophil rolling triggers Mrp8/14 secretion. Released MRP8/14 in turn activates a TLR4-mediated, Rap1-GTPase-dependent pathway of rapid β2 integrin activation in neutrophils. This extracellular activation loop reduces leukocyte rolling velocity and stimulates adhesion. Thus, we identify Mrp8/14 and TLR4 as important modulators of the leukocyte recruitment cascade during inflammation in vivo.

MRP8/14 are actively secreted by myeloid cells during inflammation. Here the authors show that MRP8/14 play an important role in leukocyte recruitment to the inflammatory site, triggering an autocrine cascade that promotes neutrophil adhesion to the endothelium.

Effect of Hangeshashinto on calprotectin expression in human oral epithelial cells

Oral epithelial cells produce antimicrobial peptides (AMPs) to prevent microbial infection. Calprotectin (S100A8/S100A9) is one of these AMPs in oral epithelial cells, the expression of which is up-regulated by interleukin-1α (IL-1α). Hangeshashinto (HST) is a traditional Japanese herbal medicine that has anti-inflammatory effects. The purpose of this study was to investigate the effect of HST on the expression of calprotectin through the regulation of IL-1α in oral epithelial cells. Human oral epithelial cells (TR146) were cultured with HST in the presence or absence of anti-IL-1α antibody or IL-1 receptor antagonist, or with six major components of HST (3,4-dihydroxybenzaldehyde, baicalin, ginsenoside Rb1, glycyrrhizin, oleanolic acid and berberine). The expression of S100A8, S100A9, other AMPs and cytokine mRNAs was examined by RT-PCR and quantitative real-time PCR. Calprotectin expression and IL-1α secretion were investigated by ELISA. HST (6 μg/ml) increased the expression of S100A8/S100A9 mRNAs and calprotectin protein, and also up-regulated β-defensin 2 (DEFB4) and S100A7 expression. The expression of IL-1α mRNA and its protein was slightly but significantly increased by HST. A neutralizing antibody against IL-1α and IL-1 receptor antagonist inhibited HST-up-regulated S100A8/S100A9 mRNA expression. Although 3,4-dihydroxybenzaldehyde, baicalin and ginsenoside Rb1 as HST components increased S100A8/S100A9 expression, oleanolic acid and berberine decreased their expression. These results suggest that HST increases the expression of calprotectin, DEFB4 and S100A7 in oral epithelial cells. In response to HST, up-regulation of calprotectin expression may be partially induced via IL-1α.

S100A8 and S100A9 induce cytokine expression and regulate the NLRP3 inflammasome via ROS-dependent activation of NF-κB(1.)

S100A8 and S100A9 are cytoplasmic proteins expressed by phagocytes. High concentrations of these proteins have been correlated with various inflammatory conditions, including autoimmune diseases such as rheumatoid arthritis and Crohn's disease, as well as autoinflammatory diseases. In the present study, we examined the effects of S100A8 and S100A9 on the secretion of cytokines and chemokines from PBMCs. S100A8 and S100A9 induced the secretion of cytokines such as IL-6, IL-8, and IL-1β. This secretion was associated with the activation and translocation of the transcription factor NF-κB. Inhibition studies using antisense RNA and the pharmacological agent BAY-117082 confirmed the involvement of NF-κB in IL-6, IL-8, and IL-1β secretion. S100A8- and S100A9-mediated activation of NF-κB, the NLR family, pyrin domain-containing 3 (NLRP3) protein, and pro-IL-1β expression was dependent on the generation of reactive oxygen species. This effect was synergistically enhanced by ATP, a known inflammasome activator. These results suggest that S100A8 and S100A9 enhance the inflammatory response by inducing cytokine secretion of PBMCs.

S100A8/A9 aggravates post-ischemic heart failure through activation of RAGE-dependent NF-κB signaling

The extracellular heterodimeric protein S100A8/A9 activates the innate immune system through activation of the receptor of advanced glycation end products (RAGE) and Toll-like receptors. As activation of RAGE has recently been associated with sustained myocardial inflammation and heart failure (HF) we studied the role of S100A8/A9 in the development of post-ischemic HF. Hypoxia led to sustained induction of S100A8/A9 accompanied by increased nuclear factor (NF-)κB binding activity and increased expression of pro-inflammatory cytokines in cardiac fibroblasts and macrophages. Knockdown of either S100A8/A9 or RAGE rescued the induction of pro-inflammatory cytokines and NF-κB activation after hypoxia. In a murine model of post-ischemic HF both cardiac RNA and protein levels of S100A8/A9 were elevated as soon as 30 min after hypoxia with sustained activation up to 28 days after ischemic injury. Treatment with recombinant S100A8/A9 resulted in reduced cardiac performance following ischemia/reperfusion. Chimera experiments after bone marrow transplantation demonstrated the importance of RAGE expression on immune cells for their recruitment to the injured myocardium aggravating post-ischemic heart failure. Signaling studies in isolated ventricles indicated that MAP kinases JNK, ERK1/2 as well as NF-κB mediate signals downstream of S100A8/A9-RAGE in post-ischemic heart failure. Interestingly, cardiac performance was not affected by administration of S100A8/A9 in RAGE(-/-)-mice, which demonstrated significantly improved cardiac recovery compared to WT-mice. Our study provides evidence that sustained activation of S100A8/A9 critically contributes to the development of post-ischemic HF driving the progressive course of HF through activation of RAGE.

Increased levels of calprotectin in obesity are related to macrophage content: impact on inflammation and effect of weight loss

Calprotectin has been recently described as a novel marker of obesity. The aim of this study was to determine the circulating concentrations and expression levels of calprotectin subunits (S100A8 and S100A9) in visceral adipose tissue (VAT), exploring its impact on insulin resistance and inflammation and the effect of weight loss. We included 53 subjects in the study. Gene expression levels of the S100A8/A9 complex were analyzed in VAT as well as in both adipocytes and stromovascular fraction cells (SVFCs). In addition, circulating calprotectin and soluble receptor for the advanced glycation end product (sRAGE) concentrations were measured before and after weight loss achieved by Roux-en-Y gastric bypass (RYGB) (n = 26). Circulating concentrations and VAT expression of S100A8/A9 complex were increased in normoglycemic and type 2 diabetic obese patients (P < 0.01) and associated with markers of inflammation (P < 0.01). Oppositely, concentrations of sRAGE were significantly lower (P < 0.001) in both obese groups compared to lean volunteers. Elevated calprotectin levels in obese patients decreased (P < 0.00001) after RYGB, whereas sRAGE concentrations tended to increase. Calprotectin was mainly expressed by SVFCs, and its expression was significantly correlated (P < 0.01) with mRNA levels of the monocyte-macrophage-related molecules macrophage-specific antigen CD68 (CD68), monocyte chemotactic protein 1 (MCP1), integrin α-M (CD11B), and NADPH oxidase 2 (NOX2). Tumor necrosis factor-α treatment significantly enhanced (P < 0.05) the mRNA levels of S100 calcium-binding protein A8 (S100A8) of human visceral adipocytes. The increased levels of calprotectin in obesity and obesity-associated type 2 diabetes, its positive association with inflammation as well as the higher expression levels in the SVFCs in VAT suggests a potential role of this protein as a chemotactic factor in the recruitment of macrophages to VAT, increasing inflammation and the development of obesity-associated comorbidities.

DAMPening inflammation by modulating TLR signalling

Damage-associated molecular patterns (DAMPs) include endogenous intracellular molecules released by activated or necrotic cells and extracellular matrix (ECM) molecules that are upregulated upon injury or degraded following tissue damage. DAMPs are vital danger signals that alert our immune system to tissue damage upon both infectious and sterile insult. DAMP activation of Toll-like receptors (TLRs) induces inflammatory gene expression to mediate tissue repair. However, DAMPs have also been implicated in diseases where excessive inflammation plays a key role in pathogenesis, including rheumatoid arthritis (RA), cancer, and atherosclerosis. TLR activation by DAMPs may initiate positive feedback loops where increasing tissue damage perpetuates pro-inflammatory responses leading to chronic inflammation. Here we explore the current knowledge about distinct signalling cascades resulting from self TLR activation. We also discuss the involvement of endogenous TLR activators in disease and highlight how specifically targeting DAMPs may yield therapies that do not globally suppress the immune system.

Transcript levels of different cytokines and chemokines correlate with clinical and endoscopic activity in ulcerative colitis

Background

A definition of disease activity in ulcerative colitis (UC) is difficult. The clinical activity index (CAI) is only an indirect assessment tool of bowel inflammation and the endoscopic activity index (EAI) sometimes cannot reflect the severity of disease to the full extent. Therefore, there is a need for an objective means to quantify inflammatory activity in mucosal biopsies. In our study, we wanted to examine the correlation between transcript levels of interleukin 8 (CXCL8), interferon γ inducible protein 10 (CXCL10), myeloid-related protein 14 (calgranulin B), macrophage inflammatory protein 2 α (CXCL2) with CAI and EAI in UC.

Methods

Cytokine and chemokine transcripts were quantified using real-time PCR in 49 mucosal biopsies from 27 different patients with UC. Cytokine transcript levels were correlated with CAI and EAI.

Results

There was a statistically significant positive correlation between CXCL8 (r = 0.30; p < 0.05), CXCL10 (r = 0.40; p < 0.02), calgranulin B (r = 0.36; p < 0.03), CXCL2 (r = 0.31; p < 0.05) and CAI. Concerning EAI significant positive correlations for CXCL8 (r = 0.37; p < 0.02), CXCL10 (r = 0.33; p < 0.04), calgranulin B (r = 0.31; p < 0.05) and CXCL2 (r = 0.44; p < 0.05) were found. Low clinical and endoscopic activity was accompanied by low cytokine levels whereas high CAI and EAI were associated with high cytokine levels.

Conclusion

From our data, we conclude that real-time PCR quantification of CXCL8, CXCL10, calgranulin B and CXCL2 in colonic biopsies is a simple and objective method for grading inflammation of intestinal mucosa in UC. CXCL8, CXCL10, calgranulin B and CXCL2 might be used as biomarkers and thus as an objective tool especially in clinical trials to evaluate anti-inflammatory and immunomodulatory regimens.

Binding of S100 proteins to RAGE: an update

The Receptor for Advanced Glycation Endproducts (RAGE) is a multi-ligand receptor of the immunoglobulin family. RAGE interacts with structurally different ligands probably through the oligomerization of the receptor on the cell surface. However, the exact mechanism is unknown. Among RAGE ligands are members of the S100 protein family. S100 proteins are small calcium binding proteins with high structural homology. Several members of the family have been shown to interact with RAGE in vitro or in cell-based assays. Interestingly, many RAGE ligands appear to interact with distinct domains of the extracellular portion of RAGE and to trigger various cellular effects. In this review, we summarize the modes of S100 protein-RAGE interaction with regard to their cellular functions.

S-nitrosylated S100A8: novel anti-inflammatory properties

S100A8 and S100A9, highly expressed by neutrophils, activated macrophages, and microvascular endothelial cells, are secreted during inflammatory processes. Our earlier studies showed S100A8 to be an avid scavenger of oxidants, and, together with its dependence on IL-10 for expression in macrophages, we postulated that this protein has a protective role. S-nitrosylation is an important posttranslational modification that regulates NO transport, cell signaling, and homeostasis. Relatively few proteins are targets of S-nitrosylation. To date, no inflammation-associated proteins with NO-shuttling capacity have been identified. We used HPLC and mass spectrometry to show that S100A8 and S100A9 were readily S-nitrosylated by NO donors. S-nitrosylated S100A8 (S100A8-SNO) was the preferred nitrosylated product. No S-nitrosylation occurred when the single Cys residue in S100A8 was mutated to Ala. S100A8-SNO in human neutrophils treated with NO donors was confirmed by the biotin switch assay. The stable adduct transnitrosylated hemoglobin, indicating a role in NO transport. S100A8-SNO suppressed mast cell activation by compound 48/80; intravital microscopy was used to demonstrate suppression of leukocyte adhesion and extravasation triggered by compound 48/80 in the rat mesenteric microcirculation. Although S100A8 is induced in macrophages by LPS or IFN-gamma, the combination, which activates inducible NO synthase, did not induce S100A8. Thus, the antimicrobial functions of NO generated under these circumstances would not be compromised by S100A8. Our results suggest that S100A8-SNO may regulate leukocyte-endothelial cell interactions in the microcirculation, and suppression of mast cell-mediated inflammation represents an additional anti-inflammatory property for S100A8.

Enhanced expression of myeloid-related protein complex (MRP8/14) in macrophages and multinucleated giant cells in granulomas of patients with active cardiac sarcoidosis

BACKGROUND

The myeloid-related protein complex (MRP8/14) is expressed in activated human macrophages and reported to be involved in the inflammatory process. The expression of MRP8/14 in patients with cardiac sarcoidosis and idiopathic dilated cardiomyopathy (DCM) was investigated.

METHODS AND RESULTS

Serum MRP8/14 levels were measured in 35 patients with sarcoidosis and 23 patients with DCM. Sera from 30 normal volunteers served as controls. Additionally, the expression profiles of MRP8/14 in the myocardium from 12 patients with active cardiac sarcoidosis and 10 DCM patients were examined immunohistochemically. Serum MRP8/14 levels were significantly higher in patients with sarcoidosis than in normal controls [515+/-549 (SD) ng/ml vs 230+/-115 ng/ml, p=0.0019]. In the sarcoidosis group, serum MRP8/14 levels in patients with definite cardiac involvement (n=10) were significantly higher than in those without (n=25) (974+/-878 ng/ml vs 332+/-204 ng/ml, p=0.0227) and they were also higher than in DCM patients (vs 252+/-108 ng/ml, p=0.0026). Immunohistochemically, MRP8/14 was specifically positive in the cytoplasm of macrophages and multinucleated giant cells in the myocardial granulomas.

CONCLUSIONS

MRP8/14 may be involved in the pathogenesis of sarcoid granulomas. The measurement of serum MRP8/14 levels is useful for the diagnosis of sarcoidosis, and their higher levels suggest the cardiac involvement.

Morphological characteristics of coronary atherosclerosis in diabetes mellitus

The incidence of diabetes is increasing in the general population because of increasing obesity, and is likely to result in a higher incidence of coronary artery disease. It was recently reported that diabetics (types I and II) dying suddenly from coronary artery disease have greater macrophage and T lymphocyte infiltration in atherosclerotic plaques, as well as larger necrotic cores compared with nondiabetics. The inflammatory cell infiltrates showed human leukocyte antigen-DR expression, which was greater in diabetics. The receptors for advanced glycosylation end-products expression, demonstrated by immunohistochemistry, was greater in diabetics than in nondiabetics in macrophages, smooth muscle cells and endothelial cells, and was associated with apoptosis of macrophages and smooth muscle cells, but not of endothelial cells. There is also a higher incidence of healed plaque ruptures and healed myocardial infarct in type II diabetics. Plaque burden is higher in diabetics than in nondiabetics; however, distal plaque burden was only significantly different in type II diabetics compared with nondiabetics. There was greater positive remodelling in diabetic coronary arteries than in nondiabetic ones, which correlated with the per cent necrotic core. Further studies are needed to better understand the mechanisms that govern greater inflammation and plaque burden in diabetics.

Proteomic analysis of human whole and parotid salivas following stimulation by different tastes

Whole and parotid salivas, collected after stimulation with tastants, were analyzed by 2D electrophoresis and mass spectrometry. In whole saliva, the number of proteins affected by taste stimulation increased in the order sweet < umami < bitter < acid. Annexin A1 and calgranulin A, involved in inflammation, were over-represented after umami, bitter, and sour stimulations. Their low abundance or absence in parotid saliva after bitter stimulation suggested that they originated from other oral glands or tissues.

MRP8/MRP14 impairs endothelial integrity and induces a caspase-dependent and -independent cell death program

Activated phagocytes express considerable amounts of MRP8 and MRP14, 2 calcium-binding S100 proteins forming stable heterodimers that are specifically secreted at inflammatory sites in many diseases. We previously reported that treatment of human microvascular endothelial cells with purified MRP8/MRP14 leads to loss of endothelial cell contacts. In this study, we demonstrate that MRP8/MRP14 complexes furthermore trigger cell death of endothelial cells after the onset of cell detachment. Morphologic analysis of dying endothelial cells revealed characteristic features of both apoptosis and necrosis. Furthermore, MRP8/MRP14 induced apoptotic caspase-9 and caspase-3 activation, DNA fragmentation, and membrane phosphatidylserine exposure in target cells. These events were independent of death receptor signaling and in part controlled by a mitochondrial pathway. Consistently, overexpression of antiapoptotic Bcl-2 abrogated caspase activation and externalization of phosphatidylserine; however, MRP8/MRP14 still induced plasma membrane damage and even DNA fragmentation. Thus, our results demonstrate that MRP8/MRP14 triggers cell death via caspase-dependent as well as -independent mechanisms. Excessive release of cytotoxic MRP8/MRP14 by activated phagocytes might therefore present an important molecular pathomechanism contributing to endothelial damage during vasculitis and other inflammatory diseases.

S100 proteins expressed in phagocytes: a novel group of damage-associated molecular pattern molecules

Damage-associated molecular pattern (DAMP) molecules have been introduced as important proinflammatory factors of innate immunity. One example known for many years to be expressed in cells of myeloid origin are phagocytic S100 proteins, which mediate inflammatory responses and recruit inflammatory cells to sites of tissue damage. An emerging concept of pattern recognition involves the multiligand receptor for advanced glycation end products (RAGE) and Toll-like receptors (TLRs) in sensing not only pathogen-associated molecular patterns (PAMPs) but also endogenous DAMPs, including S100 proteins. S100A8, S100A9, and S100A12 are found at high concentrations in inflamed tissue, where neutrophils and monocytes belong to the most abundant cell types. They exhibit proinflammatory effects in vitro at concentrations found at sites of inflammation in vivo. Although S100A12 binds to RAGE, at least part of the proinflammatory effects of the S100A8/S100A9 complex depend upon interaction with other receptors. Because of the divergent expression patterns, the absence of S100A12 in rodents, the different interaction partners described, and the specific intracellular and extracellular effects reported for these proteins, it is important to differentiate between distinct S100 proteins rather than subsuming them with the term "S100/calgranulins." Analyzing the molecular basis of the specific effects exhibited by these proteins in greater detail bears the potential to elucidate important mechanisms of innate immunity, to establish valid biomarkers of phagocytic inflammation, and eventually to reveal novel targets for innovative anti-inflammatory therapies.

Expression of S100A8 correlates with inflammatory lung disease in congenic mice deficient of the cystic fibrosis transmembrane conductance regulator

Background

Lung disease in cystic fibrosis (CF) patients is dominated by chronic inflammation with an early and inappropriate influx of neutrophils causing airway destruction. Congenic C57BL/6 CF mice develop lung inflammatory disease similar to that of patients. In contrast, lungs of congenic BALB/c CF mice remain unaffected. The basis of the neutrophil influx to the airways of CF patients and C57BL/6 mice, and its precipitating factor(s) (spontaneous or infection induced) remains unclear.

Methods

The lungs of 20-day old congenic C57BL/6 (before any overt signs of inflammation) and BALB/c CF mouse lines maintained in sterile environments were investigated for distinctions in the neutrophil chemokines S100A8 and S100A9 by quantitative RT-PCR and RNA in situ hybridization, that were then correlated to neutrophil numbers.

Results

The lungs of C57BL/6 CF mice had spontaneous and significant elevation of both neutrophil chemokines S100A8 and S100A9 and a corresponding increase in neutrophils, in the absence of detectable pathogens. In contrast, BALB/c CF mouse lungs maintained under identical conditions, had similar elevations of S100A9 expression and resident neutrophil numbers, but diverged in having normal levels of S100A8.

Conclusion

The results indicate early and spontaneous lung inflammation in CF mice, whose progression corresponds to increased expression of both S100A8 and S100A9, but not S100A9 alone. Moreover, since both C57BL/6 and BALB/c CF lungs were maintained under identical conditions and had similar elevations in S100A9 and neutrophils, the higher S100A8 expression in the former (or suppression in latter) is a result of secondary genetic influences rather than environment or differential infection.

S100A8 chemotactic protein is abundantly increased, but only a minor contributor to LPS-induced, steroid resistant neutrophilic lung inflammation in vivo

Neutrophilic lung inflammation is an essential component of host defense against diverse eukaryotic and prokaryotic pathogens, but in chronic inflammatory lung diseases, such as chronic obstructive lung disease (COPD), severe asthma, cystic fibrosis, and bronchiolitis, it may damage the host. Glucocorticosteroids are widely used in these conditions and in their infectious exacerbations; however, the clinical efficacy of steroids is disputed. In this study, we used a proteomic approach to identify molecules contributing to neutrophilic inflammation induced by transnasal administration of lipopolysaccharide (LPS) that were also resistant to the potent glucocorticosteroid dexamethasone (Dex). We confirmed that Dex was biologically active at both the transcript (suppression of GM-CSF and TNFalphatranscripts) and protein levels (induction of lipocortin) and used 2D-PAGE/MALDI-TOF to generate global expression profiles, identifying six LPS-induced proteins that were Dex resistant. Of these, S100A8, a candidate neutrophil chemotactic factor, was profiled in detail. Steroid refractory S100A8 expression was highly abundant, transcriptionally regulated, secreted into lung lavage fluid and immunohistochemically localized to tissue infiltrating neutrophils. However, in marked contrast to other vascular beds, neutralizing antibodies to S100A8 had only a weak anti-neutrophil recruitment effect and antibodies against the related S100A9 were ineffective. These data highlight the need for extensive in vivo profiling of proteomically identified candidate molecules and demonstrates that S100A8, despite its abundance, resistance to steroids and known chemotactic activity, is unlikely to be an important determinant of LPS-induced neutrophilic lung inflammation in vivo.

Phagocyte-specific calcium-binding S100 proteins as clinical laboratory markers of inflammation

The EF-hand homolog family of S100 proteins comprises the largest group of calcium-binding proteins. Within this S100 family, the phagocyte-specific calcium-binding proteins are pro-inflammatory molecules expressed and secreted by phagocytes, which play a pivotal role within the innate immune system. Although the exact biological functions of these proteins still remain to be defined in greater detail, there is evidence that they are involved in a pro-inflammatory axis associated with various inflammatory conditions. The three members of this group, S100A8, S100A9 and S100A12 are overexpressed at local sites of inflammation. High concentrations are found in synovial fluid, sputum, stool and blood plasma/serum during inflammation. Both the S100A8/S100A9 complex and S100A12 have been proven to be useful as diagnostic markers of inflammation especially in non-infectious inflammatory diseases such as arthritis, chronic inflammatory lung and bowel disease. They indicate phagocyte activation more sensitively than conventional parameters of inflammation. As a consequence, there is a strong correlation to the inflammation of various acute and chronic disorders, making these proteins sensitive parameters for the monitoring of disease activity and response to treatment in individual patients. The phagocyte-specific S100 proteins are able to indicate minimal residual inflammation, which is not detected by other diagnostic tests, and they may even be prospective markers for the outcome of patients. In this review, pro-inflammatory functions of S100 proteins and their usefulness as biomarkers of inflammation are presented.

Myeloid-related protein (MRP)8/14 (calprotectin) and its subunits MRP8 and MRP14 in plaque-induced early gingival inflammation

BACKGROUND

The inflammatory myeloid-related protein, MRP8/14, also called calprotectin, and its subunits MRP8 and MRP14 have been detected and identified recently in gingival crevicular fluid (GCF). It has been suggested that the type and phase of inflammation can be discriminated on the basis of differences in the expression of calprotectin and its subunits, released during activation and/or death of granulocytes and monocytes. The purpose of this study was to quantify calprotectin and its subunits (MRPs) simultaneously in the GCF during the initial phase of experimentally induced gingivitis, and to examine their inter- and intra-individual variations.

MATERIAL AND METHODS

Fifteen healthy non-smoking subjects, aged 18-30, were involved in this study. An initial hygiene phase (days -11 to 0) was followed by 10 days of undisturbed plaque accumulation. At days -11, -3, 0, 10, 11, clinical parameters were recorded and GCF samples collected with Durapore strips from 12 sites in each subject. Quantitative analyses of total proteins, MRP8/14, MRP14 and MRP8 were performed by ELISA procedures.

RESULTS

During the experimental phase with no oral hygiene (days 0-10), the clinical parameters Plaque Index, Gingival Index (GI) and bleeding on probing increased as expected, confirming that plaque accumulation leads to gingival inflammation. Levels of the MRPs were individually variable. They increased with plaque accumulation in one-half of the subjects, and decreased in the other subjects. The levels of MRP8/14 and MRP14 at subject recruitment (day -11) could predict a significant part of the GI at day 10. Only minute amounts of the subunits MRP8 and MRP14 were detected in comparison with the complex MRP8/14 throughout the experiment. Considerable variations were noted among sites within subjects.

CONCLUSION

The expression of calprotectin in the early phase of experimental gingivitis is variable between subjects, and two groups of subjects can be differentiated according to their response patterns. Clinical parameters at the very first visit (day -11) seemed to be different in the two response groups. The results of the present investigation indicate that the inflammatory response to plaque accumulation depends on the initial status of the subjects, which may not be leveled out by the introduction of perfect oral hygiene. Whether these patterns reflect a different susceptibility to periodontal diseases remains to be determined.

Cytokine/chemokine transcript profiles reflect mucosal inflammation in Crohn's disease

BACKGROUND AND AIMS

Immunoregulatory properties of cytokines may contribute to pathological immune reactions in inflammatory bowel disease. There is an urgent need for a simple and dependable means for quantitating inflammatory activity in mucosal biopsies and assessing relapse risk particularly in patients with active Crohn's disease (CD).

PATIENTS AND METHODS

Cytokine and chemokine transcripts were quantified using real-time PCR in mucosal biopsy specimens from 70 patients with active inflammatory bowel disease (CD, n=45; ulcerative colitis n=25) and 16 patients with specific colitis (ischemic colitis, infectious colitis). Controls were 12 patients with noninflammatory conditions. CD patients with steroid-induced remission (n=20) were followed for up to 12 months.

RESULTS

Compared to not-inflamed mucosa the vast majority of active CD tissue samples expressed significantly elevated transcript levels of IL-1beta, IL-8, IL-23, MRP-14, MIP2alpha, and MMP-1. Moreover, increased cytokine transcript levels were detected in both active ulcerative colitis and specific colitis. Importantly, TNF-alpha, IFN-gamma, CD40L, and IL-23 transcripts increased in active CD only. Transcript levels (MRP-14, IL-8, MMP-1, MIP2alpha) were correlated with clinical disease activity (CDAI) and endoscopic scoring indices. Medical treatment induced stable remission in 14 of 20 patients which was paralleled by a reduction in increased transcript levels. All six patients without normalization of MIP2alpha, MRP-14, TNF-alpha, and IL-1beta transcripts developed an early relapse (n=5) or chronic activity (n=1) during follow-up.

CONCLUSION

Elevated proinflammatory cytokine transcripts in active CD may underlie disease reactivation and chronicity. Real-time PCR quantification is a simple and objective method for grading inflammation of intestinal mucosa and may be useful in identifying patients who would benefit from anti-inflammatory remission maintenance.

Monocyte activation and disease activity in multiple sclerosis. A longitudinal analysis of serum MRP8/14 levels

In active multiple sclerosis (MS) lesions macrophages expressing myeloid related protein (MRP) 8/14 are present. The aim of this study was to determine whether serum levels of MRP8/14 complexes are related to disease activity in MS. In a longitudinal study of 16 relapsing remitting (RR) MS patients that underwent monthly gadolinium diethylentriaminepenta acid (Gd-DTPA) magnetic resonance imaging (MRI), the relation between serum MRP8/14 levels and disease activity was investigated. Patients were participating in a monoclonal antibody study targeting a specific T cell population (Vbeta5.2/5.3+ T-cells). In time, within patients large variations in serum MRP8/14 levels were observed. Serum MRP8/14 levels were not related to changes in clinical disease activity or increase in Gd-DTPA lesion enhancement. Neither did comparison of active (>1 relapse in follow-up period) with inactive (0-1 relapse) MS patients reveal any differences in MRP8/14 levels. Therefore, we conclude that although MRP8/14 expression is a good histopathological marker for monocyte activation, serum levels of these proteins do not correlate with disease activity in RR MS.

Blockade of S100A8 and S100A9 suppresses neutrophil migration in response to lipopolysaccharide

Recently, proinflammatory activities had been described for S100A8 and S100A9, two proteins found at inflammatory sites and within the neutrophil cytoplasm. In this study, we investigated the role of these proteins in neutrophil migration in vivo in response to LPS. LPS was injected into the murine air pouch, which led to the release of S100A8, S100A9, and S100A8/A9 in the pouch exudates that preceded accumulation of neutrophils. Passive immunization against S100A8 and S100A9 led to a 52% inhibition of neutrophil migration in response to LPS at 3 h postinjection. Injection of LPS was also associated with an increase in peripheral blood neutrophils and the presence in serum of S100A9 and S100A8/A9. Intravenous injection of S100A8, S100A9, or S100A8/A9 augmented the number of circulating neutrophils and diminished the number of neutrophils in the bone marrow, demonstrating that S100A8 and S100A9 induced the mobilization of neutrophils from the bone marrow to the blood. Finally, passive immunization with anti-S100A9 inhibited the neutrophilia associated with LPS injection in the air pouch. These results suggest that S100A8 and S100A9 play a role in the inflammatory response to LPS by inducing the release of neutrophils from the bone marrow and directing their migration to the inflammatory site.

Expression of S100A12 (EN-RAGE) in cystic fibrosis

BACKGROUND

Chronic airway inflammation and recurrent infections are a core phenomenon in cystic fibrosis (CF). Diagnosing acute infectious exacerbations is difficult in the presence of chronic inflammatory processes. S100A12 exhibits proinflammatory functions via interaction with the multiligand receptor for advanced glycation end products. Blocking this interaction inhibits inflammatory processes in mice.

METHODS

The expression of S100A12 in lung specimens of patients with end stage lung disease of CF was investigated, and S100A12 levels in the serum of patients with acute infectious exacerbations of CF were measured.

RESULTS

Immunohistochemical studies of CF lung biopsy specimens revealed a significant expression of S100A12 by infiltrating neutrophils. High S100A12 levels were found in the sputum of patients with CF, and serum levels of S100A12 during acute infectious exacerbations were significantly increased compared with healthy controls (median 225 ng/ml v 46 ng/ml). After treatment with intravenous antibiotics the mean S100A12 level decreased significantly. There was also a significant difference between S100A12 levels in patients with acute infectious exacerbations and 18 outpatients without exacerbations (median 225 ng/ml v 105 ng/ml).

CONCLUSIONS

S100A12 is extensively expressed at local sites of inflammation in CF. It is a serum marker for acute infectious exacerbations. High local expression of S100A12 suggests that this protein has a proinflammatory role during airway inflammation and may serve as a novel target for anti-inflammatory treatments.

Calgranulins S100A8 and S100A9 are negatively regulated by glucocorticoids in a c-Fos-dependent manner and overexpressed throughout skin carcinogenesis

The two calgranulins S100A8 and S100A9 were found to be differentially expressed at sites of acute and chronic inflammation. Here we have employed the phorbol ester-induced multistage skin carcinogenesis protocol in mice to determine the expression of both genes in inflamed skin and in skin tumors. We show that expression is coordinately induced by the phorbol ester TPA in epithelial cells as well as infiltrating leukocytes. By comparing S100A8 and S100A9 mRNA levels in wild type and c-Fos deficient mice (c-fos(-/-)) we found that expression is negatively regulated by c-Fos/AP-1. Glucocorticoids, which exhibit potent anti-inflammatory and anti-tumor promoting activities repressed TPA-mediated S100A8 and S100A9 induction in wild type, but not in c-fos(-/-) mice, thus identifying both genes as the first examples of AP-1 target genes whose repression of TPA-induced transcription by glucocorticoids depends on c-Fos. Finally, we show that enhanced expression is not restricted to the initial TPA-induced inflammatory response but is observed at all stages of skin carcinogenesis. These data identify S100A8 and S100A9 as novel, tumor-associated genes and may point to an as yet unrecognized function of both genes in the development of epithelial skin tumors.

RAGE and arthritis: the G82S polymorphism amplifies the inflammatory response

The receptor for advanced glycation end products (RAGE) and its proinflammatory S100/calgranulin ligands are enriched in joints of subjects with rheumatoid arthritis (RA) and amplify the immune/inflammatory response. In a model of inflammatory arthritis, blockade of RAGE in mice immunized and challenged with bovine type II collagen suppressed clinical and histologic evidence of arthritis, in parallel with diminished levels of TNF-alpha, IL-6, and matrix metalloproteinases (MMP) 3, 9 and 13 in affected tissues. Allelic variation within key domains of RAGE may influence these proinflammatory mechanisms, thereby predisposing individuals to heightened inflammatory responses. A polymorphism of the RAGE gene within the ligand-binding domain of the receptor has been identified, consisting of a glycine to serine change at position 82. Cells bearing the RAGE 82S allele displayed enhanced binding and cytokine/MMP generation following ligation by a prototypic S100/calgranulin compared with cells expressing the RAGE 82G allele. In human subjects, a case-control study demonstrated an increased prevalence of the 82S allele in patients with RA compared with control subjects. These data suggest that RAGE 82S upregulates the inflammatory response upon engagement of S100/calgranulins, and, thereby, may contribute to enhanced proinflammatory mechanisms in immune/inflammatory diseases.

Activation of NADPH oxidase by AGE links oxidant stress to altered gene expression via RAGE

Engagement of the receptor for advanced glycation end products (RAGE) by products of nonenzymatic glycation/oxidation triggers the generation of reactive oxygen species (ROS), thereby altering gene expression. Because dissection of the precise events by which ROS are generated via RAGE is relevant to the pathogenesis of complications in AGE-related disorders, such as diabetes and renal failure, we tested the hypothesis that activation of NADPH oxidase contributed, at least in part, to enhancing oxidant stress via RAGE. Here we show that incubation of human endothelial cells with AGEs on the surface of diabetic red blood cells, or specific AGEs, (carboxymethyl)lysine (CML)-modified adducts, prompted intracellular generation of hydrogen peroxide, cell surface expression of vascular cell adhesion molecule-1, and generation of tissue factor in a manner suppressed by treatment with diphenyliodonium, but not by inhibitors of nitric oxide. Consistent with an important role for NADPH oxidase, although macrophages derived from wild-type mice expressed enhanced levels of tissue factor upon stimulation with AGE, macrophages derived from mice deficient in a central subunit of NADPH oxidase, gp91phox, failed to display enhanced tissue factor in the presence of AGE. These findings underscore a central role of NADPH oxidase in AGE-RAGE-mediated generation of ROS and provide a mechanism for altered gene expression in AGE-related disorders.

Fecal calprotectin as a measure of disease activity in childhood inflammatory bowel disease

BACKGROUND

Calprotectin is an abundant neutrophil protein that is extremely stable in feces. The aim of this study was to assess the effectiveness of fecal calprotectin as a noninvasive measure of disease activity in childhood inflammatory bowel disease (IBD) by comparison to a modified Lloyd-Still and Green score and laboratory inflammatory indices.

METHODS

Spot fecal samples from 37 children with IBD and 31 control children were sent by ordinary mail to the laboratory. Fecal calprotectin concentration was measured by an in-house enzyme linked immunosorbent assay (ELISA). A modified Lloyd-Still & Green score (mLSS) was calculated for each child with IBD within 10 days of obtaining the fecal sample.

RESULTS

Compared with control values (median, range) (2.1, 0.5-6.3 mg/L), fecal calprotectin was increased in 16 children with ulcerative colitis, (11.5, 0.6-272.5 mg/L, P < 0.001) and in 21 children with Crohn disease, (14.0, 0.7-59.7 mg/L, P < 0.001). Twelve "moderately affected" children (mLSS of 35-65) had higher fecal calprotectin concentrations (22.2, 2.7-141.7 mg/L) than 25 "mildly affected" children (mLSS > 65), (10.3, 0.6-272.5 mg/L, P = 0.002). For the total IBD group, fecal calprotectin concentration correlated negatively with the mLSS (r = -0.61, P < 0.001). It also correlated negatively with serum albumin concentration (r = -0.49, P = 0.002) and positively with erythrocyte sedimentation rate (r = 0.40, P = 0.01).

CONCLUSIONS

Fecal calprotectin seems to reflect bowel inflammation in children with IBD. As a simple, safe, noninvasive test, it has the potential to reduce the number of invasive investigations performed in these children.

Total chemical synthesis and chemotactic activity of human S100A12 (EN-RAGE)

Human S100A12 (extracellular newly identified RAGE (receptor for advanced glycosylation end products)-binding protein), a new member of the S100 family of EF-hand calcium-binding proteins, was chemically synthesised using highly optimised 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate/tert-butoxycarbonyl in situ neutralisation solid-phase chemistry. Circular dichroism studies indicated that CaCl(2) decreased the helical content by 27% whereas helicity was marginally increased by ZnCl(2). The propensity of S100A12 to dimerise was examined by electrospray ionisation time-of-flight mass spectrometry which clearly demonstrated the prevalence of the non-covalent homodimer (20890 Da). Importantly, synthetic human S100A12 in the nanomolar range was chemotactic for neutrophils and macrophages in vitro.

The biology of the receptor for advanced glycation end products and its ligands

Receptor for advanced glycation end products (RAGE) is a multiligand member of the immunoglobulin superfamily of cell surface molecules whose repertoire of ligands includes advanced glycation end products (AGEs), amyloid fibrils, amphoterins and S100/calgranulins. The overlapping distribution of these ligands and cells overexpressing RAGE results in sustained receptor expression which is magnified via the apparent capacity of ligands to upregulate the receptor. We hypothesize that RAGE-ligand interaction is a propagation factor in a range of chronic disorders, based on the enhanced accumulation of the ligands in diseased tissues. For example, increased levels of AGEs in diabetes and renal insufficiency, amyloid fibrils in Alzheimer's disease brain, amphoterin in tumors and S100/calgranulins at sites of inflammation have been identified. The engagement of RAGE by its ligands can be considered the 'first hit' in a two-stage model, in which the second phase of cellular perturbation is mediated by superimposed accumulation of modified lipoproteins (in atherosclerosis), invading bacterial pathogens, ischemic stress and other factors. Taken together, these 'two hits' eventuate in a cellular response with a propensity towards tissue destruction rather than resolution of the offending pathogenic stimulus. Experimental data are cited regarding this hypothesis, though further studies will be required, especially with selective low molecular weight inhibitors of RAGE and RAGE knockout mice, to obtain additional proof in support of our concept.

Transendothelial migration of 27E10+ human monocytes

The myeloid-related proteins MRP8 (S100A8) and MRP14 (S100A9), two members of the S100 family of calcium-binding proteins, are co-expressed and form a cell-surface and cytoskeleton-associated heterodimer upon calcium mobilization which is recognized by the mAb 27E10. The heterodimer is abundantly expressed in the cytoplasm of granulocytes and a subpopulation of blood monocytes. Previously, we and others demonstrated endothelium-associated MRP8/14 in inflamed tissues in the vicinity of transmigrating leukocytes, suggesting a function of the proteins in this process. Here, we demonstrate that 27E10(+) cells represent a fast-migrating monocyte subpopulation which preferentially utilizes an ICAM-1-dependent mechanism. The following observations imply a function of MRP8/14 in the transmigration process: (i) higher secretion of MRP8/14 from 27E10(+) monocytes compared to 27E10(-) monocytes after interaction with activated endothelium, (ii) higher expression of CD11b on 27E10(+) compared to 27E10(-) monocytes, (iii) up-regulation of CD11b on 27E10(-) monocytes in the presence of MRP14 or MRP8/14 heterodimers but not MRP8 and (iv) active participation of MRP14 but not of MRP8 in transmigration as shown by blocking with respective antibodies. We show that the interaction of 27E10(+) monocytes with activated endothelium leads to MRP8/14 release which may account for the high MRP8/14 concentrations in body fluids of patients with acute or chronic inflammatory diseases. Released MRP8/14 may serve a function by enhancing CD11b expression and/or affinity in human monocytes and by participating in the transendothelial migration mechanism. Thus, MRP8/14 substantially contributes to the recruitment of monocytes to an inflammatory site.

MRP8/MRP14, CD11b and HLA-DR expression of alveolar macrophages in pneumonia

Activation of alveolar macrophages is characterised by specific alterations to the expression pattern of surface markers under certain pathological conditions. MRP8/MRP14 and CD11b are involved in the regulation of macrophage migration and adhesion. HLA-DR regulates the antigen presentation by alveolar macrophages. The aim of this study was to investigate the phenotype of alveolar macrophages in pneumonia particularly in relationship to the changes in concentrations of TGF-beta1 and IL-8. Using cytofluorimetry, we analysed the surface expression of MRP8/MRP14, CD11b, and HLA-DR on alveolar macrophages of 42 pneumonia (PN) patients, 14 patients with interstitial lung diseases (ILD), five patients with chronic obstructive lung disease (COPD), and 58 patients without lung disease. Phenotypic characteristics were correlated to the concentration of TGF-beta1 and IL-8 in the bronchoalveolar lavage fluid (BALF) of the same patients. The direct influence of TGF-beta1 and IL-8 on expression of MRP8/MRP14, CD11b and HLA-DR of cultured monocytes and MonoMac cells was analysed. Significantly more MRP8/MRP14 and CD11b positive macrophages and less HLA-DR-positive macrophages were found in PN but not in ILD or COPD. The percentage of CD11b-positive macrophages correlated with the TGF-beta1 as well as the IL-8 concentrations. The amount of HLA-DR-positive macrophages correlated negatively to the concentration of TGF-beta1 and IL-8. These findings document a significant activation of alveolar macrophages during pneumonia. TGF-beta1 led to a modulation of HLA-DR and MRP8/MRP14-antigen expression in vitro. In conclusion, it was shown that in pneumonia but not in ILD or COPD alveolar macrophages were characterised by an increased MRP8/MRP14 and CD11b expression and a diminished HLA-DR expression. The characterisation of subpopulations within the alveolar macrophages may be a useful tool for the monitoring of disease progression.

Human gingival crevicular fluid contains MRP8 (S100A8) and MRP14 (S100A9), two calcium-binding proteins of the S100 family

Human gingival crevicular fluid contains unidentified proteins which might play a role as markers in periodontal diseases. Therefore, low-molecular-weight proteins found in human gingival crevicular fluid (GCF), but absent from serum, were identified in the present study by means of two-dimensional electrophoresis (2-D PAGE) analysis. GCF, serum, and whole saliva were collected from periodontitis and healthy subjects, as well as from edentulous and newborn subjects. Protein samples were separated by two-dimensional polyacrylamide gel electrophoresis, stained with silver, and compared with reference protein maps in the SWISS-2D PAGE database. In GCF and saliva from periodontitis patients and healthy subjects, four dominant low-molecular-mass (from 8 to 14 kDa) acidic spots were observed. They were not found in serum and were less visible in saliva from edentulous and newborn subjects. From N-terminal amino acid sequencing, the two 2-D protein spots of 8 kDa and isoelectric points between 6.5 and 7.0 were both identified as protein MRP8 (SI00A8), a member of the S100 family of calcium-binding proteins. Using peptide mass fingerprinting and matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF-MS), we identified the other two protein spots, with mass of 14 kDa and isoelectric points between 5.5 and 6.0, as protein MRP14 (S100A9), also belonging to the S100 family. The presence of MRP8 and MRP14 in GCF was confirmed by Western blot, with monoclonal antibodies. The two polypeptides, MRP8 and MRP14, identified in GCF represent the major difference between the 2-D PAGE patterns of serum and GCF, and we hypothesize that they may play an important role in the gingival sulcus and could represent possible markers for periodontal diseases.

RAGE mediates a novel proinflammatory axis: a central cell surface receptor for S100/calgranulin polypeptides

S100/calgranulin polypeptides are present at sites of inflammation, likely released by inflammatory cells targeted to such loci by a range of environmental cues. We report here that receptor for AGE (RAGE) is a central cell surface receptor for EN-RAGE (extracellular newly identified RAGE-binding protein) and related members of the S100/calgranulin superfamily. Interaction of EN-RAGEs with cellular RAGE on endothelium, mononuclear phagocytes, and lymphocytes triggers cellular activation, with generation of key proinflammatory mediators. Blockade of EN-RAGE/RAGE quenches delayed-type hypersensitivity and inflammatory colitis in murine models by arresting activation of central signaling pathways and expression of inflammatory gene mediators. These data highlight a novel paradigm in inflammation and identify roles for EN-RAGEs and RAGE in chronic cellular activation and tissue injury.

CP-10, a chemotactic peptide, is expressed in lesions of experimental autoimmune encephalomyelitis, neuritis, uveitis and in C6 gliomas

CP-10 (chemotactic protein of m.w. 10,000) is a member of the S100 superfamily of Ca2+ binding peptides, which has potent chemotactic activity for murine and human myeloid cells. Here we report on the generation of monoclonal antibodies against CP-10 and accumulation of CP-10+ cells during experimental autoimmune encephalomyelitis (EAE), neuritis (EAN), uveitis (EAU) and in experimentally transplanted C6 gliomas. During acute inflammation, CP-10 is mainly expressed by large ED1+ monocytic perivascular cells that accumulate at days 11-14. CP-10+ cells are predominantly located in areas of cellular infiltration but are as well found in the meninges and infiltrating the brain parenchyma. In transplanted gliomas, CP-10+ cells are located exclusively within the tumor parenchyma. Using double labeling experiments, other cells participating in the inflammatory reaction were found to express CP-10, like few lymphoblastic W3/13+ cells in the vicinity of the inflammatory infiltrate.

The gene encoding the myeloid-related protein 14 (MRP14), a calcium-binding protein expressed in granulocytes and monocytes, contains a potent enhancer element in the first intron

Myeloid-related proteins 8 and 14 (MRP8 and MRP14) are two Ca2+-binding proteins of the S-100 family highly abundant in myelomonocytic cells. The expression is not only dependent on the developmental status of the cell but also on the inflammatory situation in the tissue. In order to identify regulatory elements responsible for the high expression of MRP14 in myeloid cells, reporter gene constructs have been transfected into HL-60 cells, Mono Mac 6 cells, and L132 cells. We demonstrated that a DNA element in the first intron (positions 153-361) enhances the transcriptional activity of the homologous promoter and of the heterologous herpes simplex virus thymidine kinase promoter up to 37-fold. To further identify the functional site, the region between positions 153 and 192 was analyzed functionally using the thymidine kinase promoter. The region increased the expression in the same magnitude as the complete intron. This enhancer is highly conserved in the human and murine MRP genes, indicative of its involvement in the transcription of MRPs. Protein binding to the region is demonstrated using EMSA, DNA cross-linking, Southwestern blotting, and affinity purification. Affinity purification confirms that four proteins bind to the enhancer element.

Elevated serum macrophage inhibitory factor-related protein (MRP) 8/14 levels in advanced HIV infection and during disease exacerbation

To assess the value of MRP 8, MRP 14, and MRP 8/14 serum concentrations as markers of disease progression in HIV infection and as markers of intercurrent infections.

DESIGN

We measured MRP 8, MRP 14, and MRP 8/14 serum concentrations in 184 HIV-infected patients in various stages of disease with or without disease exacerbation and in 50 healthy control subjects. In clinically stable HIV-infection correlations of MRP levels with stage of HIV disease, CD4 counts, p24 antigen, and beta-2 microglobulin levels were studied. In patients with intercurrent illnesses, correlations of MRP levels with type of disease exacerbation and with CRP were calculated and compared with those found in stable HIV infection.

RESULTS

MRP 8/14 levels were significantly elevated and MRP 8 levels slightly decreased in stable HIV infection compared with HIV-negative controls. The CD4 cell count and MRP 8/14 levels correlated significantly in patients with AIDS. Despite higher values of MRP 8/14 during advanced disease, these were not significant predictors of progression to death. In patients with acute infections, MRP 8/14 levels were significantly elevated, compared with patients with illnesses of noninfectious origin. Levels of MRP 8/14 associated with acute infections were significantly higher in patients with AIDS than in patients during earlier stages of HIV infection.

CONCLUSIONS

Both stable HIV infection and advanced immunedeficiency are associated with an elevation of the MRP 8/14 complex and probably with a decline of MRP 8 serum levels. MRP 8/14 is preserved as a marker of acute infection in immunecompromised patients.

Overexpression of calcium-binding protein calgranulin B in colonic mucosal diseases

Subtractive two-dimensional gel electrophoresis (2-DE) has been used for the study of the protein patterns of the normal colonic mucosa and the specimens collected from patients diagnosed for inflammatory bowel disease (IBD), colonic polyps and colorectal cancer. We found a 13 kDa protein that was detected in five of seven adenomas and in 13 of 15 colorectal carcinomas while it was absent or only slightly expressed in normal colonic mucosa. Furthermore, this protein occurred in all specimens collected from patients suffering from IBD and its quantity reflected the increased severity of inflammation. The combination of microsequencing and mass spectrometry led to the identification of the 13 kDa spot as calgranulin B. Our results indicate that the production of calgranulin B is unregulated in inflammatory, preneoplastic and neoplastic lesions of colonic mucosa.

Importance of combined treatment with IL-10 and IL-4, but not IL-13, for inhibition of monocyte release of the Ca(2+)-binding protein MRP8/14

Expression of the two myeloic related proteins MRP8 and MRP14 is restricted to distinct stages of monocytic differentiation. Heterodimeric MRP8/14 complexes (27E10 antigen) have been shown to represent their biologically active forms. In this study, we investigated the effects of Th2-cytokines on release of these proteins from freshly obtained blood monocytes and monocytes cultured for 7 days in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF). Monocytes were stimulated with pokeweed mitogen (PWM) in the presence or absence of interleukin-13 (IL-13), IL-4 and IL-10, and secretion of MRP8, MRP14 and MRP8/14 was assessed by using a sandwich enzyme-linked immunosorbent assay system. Peripheral monocytes secreted significantly increased amounts of MRP14 and MRP8/14 but not MRP8 under stimulation with PWM. IL-10 and IL-4, but not IL-13, down-regulated the PWM-stimulated MRP8/14 secretion in a dose-dependent manner. Maximal inhibition required that IL-10 and IL-4 be added up to 1 h before or simultaneous with PWM. A combination of IL-10 and IL-4 even at suboptimal concentrations significantly suppressed protein secretion much more than using IL-10 or IL-4 at a doubled concentration alone. Peripheral monocytes cultured for 7 days in the presence of GM-CSF showed two-to threefold higher protein levels compared with freshly obtained blood monocytes but responded inefficiently to either IL-4, IL-13, or IL-10 alone. However, treatment with IL-10 in combination with IL-4 but not IL-13 strongly suppressed MRP14 and MRP8/14 release by these cells. The unresponsiveness of 7-day-cultured blood macrophages suggests that more differentiated and activated cells may lose their ability to respond to anti-inflammatory cytokines. Combined cytokine treatment may therefore more effectively control the progression of chronic inflammatory processes.