Calprotectin in patients with systemic lupus erythematosus: relation to clinical and laboratory parameters of disease activity

Serum Calprotectin in the Evaluation of Gastrointestinal Diseases: An Ace up Your Sleeve?

Background: Calprotectin (CP) is a calcium- and zinc-binding protein that plays a key role in innate immunity and in the recruitment of inflammatory cells. CP can be detected both in serum and in fecal samples. Serum CP (sCP) is more specific for autoimmune diseases, while fecal CP (fCP) has been well investigated for gastrointestinal diseases. Few studies have shown the clinical effectiveness of sCP as an acute-phase biomarker for gastrointestinal diseases. Aim: The aim of this narrative review is to discuss the role of sCP as a useful alternative biomarker of the acute-phase activity of gastrointestinal diseases and as a possible tool for screening and monitoring these diseases. Material and Methods: We searched original articles, abstracts, reviews, case reports, and clinical trials on PubMed®, Up-to-Date®, and Medscape® in the last ten years. Conclusion: We found that sCP could represent a useful biomarker in the evaluation of the inflammatory stage in patients with immune-mediated gastrointestinal diseases, but more studies are needed to promote its routine use in clinical practice as a diagnostic and prognostic biomarker as a replacement for fCP.

Possible Role of Dysbiosis of the Gut Microbiome in SLE

PURPOSE OF REVIEW

The resident gut microbiota serves as a double-edged sword that aids the host in multiple ways to preserve a healthy equilibrium and serve as early companions and boosters for the gradual evolution of our immune defensive layers; nevertheless, the perturbation of the symbiotic resident intestinal communities has a profound impact on autoimmunity induction, particularly in systemic lupus erythematosus (SLE). Herein, we seek to critically evaluate the microbiome research in SLE with a focus on intestinal dysbiosis.

RECENT FINDINGS

SLE is a complex and heterogeneous disorder with self-attack due to loss of tolerance, and there is aberrant excessive immune system activation. There is mounting evidence suggesting that intestinal flora disturbances may accelerate the formation and progression of SLE, presumably through a variety of mechanisms, including intestinal barrier dysfunction and leaky gut, molecular mimicry, bystander activation, epitope spreading, gender bias, and biofilms. Gut microbiome plays a critical role in SLE pathogenesis, and additional studies are warranted to properly define the impact of gut microbiome in SLE, which can eventually lead to new and potentially safer management approaches for this debilitating disease.

S-100 Proteins: Basics and Applications as Biomarkers in Animals with Special Focus on Calgranulins (S100A8, A9, and A12)

S100 proteins are a group of calcium-binding proteins which received this name because of their solubility in a 100% saturated solution of ammonium sulphate. They have a similar molecular mass of 10-12 KDa and share 25-65% similarity in their amino acid sequence. They are expressed in many tissues, and to date 25 different types of S100 proteins have been identified. This review aims to provide updated information about S100 proteins and their use as biomarkers in veterinary science, with special emphasis on the family of calgranulins that includes S100A8 (calgranulin A; myeloid-related protein 8, MRP8), S100A9 (calgranulin B; MRP14), and S100A12 (calgranulin C). The proteins SA100A8 and S100A9 can be linked, forming a heterodimer which is known as calprotectin. Calgranulins are related to the activation of inflammation and the immune system and increase in gastrointestinal diseases, inflammation and sepsis, immunomediated diseases, and obesity and endocrine disorders in different animal species. This review reflects the current knowledge about calgranulins in veterinary science, which should increase in the future to clarify their role in different diseases and potential as biomarkers and therapeutic targets, as well as the practical use of their measurement in non-invasive samples such as saliva or feces.

Circulating Calprotectin (cCLP) in autoimmune diseases

BACKGROUND AND AIM

Calprotectin (CLP) is a heterodimeric complex formed by two S100 proteins (S100A8/A9), which plays a pivotal role in innate immunity. Due to its intrinsic cytotoxic and proinflammatory properties, CLP controls cell differentiation, proliferation and NETosis and has been associated with a wide range of rheumatic diseases. Our review summarizes the widespread interest in circulating CLP (cCLP) as a biomarker of neutrophil-related inflammation, in autoimmune rheumatic disease (ARD) and non-ARD.

METHODS

A thorough literature review was performed using PubMed and EMBASE databases searching for circulating calprotectin and synonyms S100A8/A9, myeloid-related protein 8/14 (MRP8/MRP14), calgranulin A/B and L1 protein in addition to specific ARDs and autoimmune non-rheumatic diseases. We selected only English-language articles and excluded abstracts without the main text.

RESULTS

High cCLP serum levels are associated with worse structural outcomes in rheumatoid arthritis and to a lesser extent, in spondyloarthritis. In addition, cCLP can predict disease relapse in some autoimmune diseases including systemic lupus erythematosus (SLE), anti-neutrophil cytoplasmic antibodies-associated vasculitis (AAV) and some severe manifestations of connective tissue diseases, such as glomerulonephritis in SLE, AAV, juvenile idiopathic arthritis, adult-onset Still's disease and lung fibrosis in systemic sclerosis. Therefore, cCLP levels enable the identification of patients who need an accurate and tight follow-up. The clinical usefulness of cCLP as an inflammatory marker has been suggested for inflammatory/autoimmune non-rheumatic diseases, and especially for the monitoring of the inflammatory bowel diseases patients. Currently, there are only a few studies that evaluated the cCLP efficacy as a clinical biomarker in inflammatory/autoimmune non-rheumatic diseases with controversial results. Future studies are warranted to better clarify the role of cCLP in relation to the disease severity in myasthenia gravis, multiple sclerosis, chronic inflammatory demyelinating polyneuropathy, Graves' orbitopathy, autoimmune bullous diseases and uveitis.

CONCLUSION

Our literature review supports a relevant role of cCLP as potential prognostic biomarker mirroring local or systemic inflammation, especially in chronic inflammatory rheumatic diseases.

Linkage of calprotectin with inflammation, activity and treatment response of rheumatoid arthritis: a meta-analysis

Aim: This meta-analysis aimed to investigate the clinical value of calprotectin in rheumatoid arthritis (RA) patients. Methods: The data regarding blood calprotectin levels in RA patients were retrieved from PubMed, Embase, Web of Science and Cochrane databases. Results: Thirty-one eligible articles were included. Calprotectin was increased in RA patients compared with healthy controls (mean difference [MD] = 1.48, 95% CI: 1.16-1.79). Calprotectin was positively associated with C-reactive protein (correlation coefficient [CC] = 0.58, 95% CI: 0.53-0.63) and disease activity score (CC = 0.48, 95% CI: 0.38-0.58) in RA patients. Interestingly, calprotectin showed an increased trend in RA responders compared with nonresponders, but without statistical significance (MD = 0.38, 95% CI: -0.09-0.85). Conclusion: Blood calprotectin relates to disease risk, inflammation and activity in RA patients.

From bench to bedside: Calprotectin (S100A8/S100A9) as a biomarker in rheumatoid arthritis

S100A9/S100A8 (calprotectin), a member of the S100 protein family, has been shown to play a pivotal role in innate immunity activation. Calprotectin plays a critical role in the pathogenesis of rheumatoid arthritis (RA), as it triggers chemotaxis, phagocyte migration and modulation of neutrophils and macrophages. Higher calprotectin levels have been found in synovial fluid, plasma, and serum from RA patients. Recent studies have demonstrated better correlations between serum or plasma calprotectin and composite inflammatory disease activity indexes than c-reactive protein (CRP) or the erythrocyte sedimentation rate (ESR). Calprotectin serum levels decreased after treatment, independently of the DMARD type or strategy. Calprotectin has shown the strongest correlations with other sensitive techniques to detect inflammation, such as ultrasound. Calprotectin independently predicts radiographic progression. However, its value as a biomarker of treatment response and flare after tapering is unclear. This update reviews the current understanding of calprotectin in RA and discusses possible applications as a biomarker in clinical practice.

Serum calprotectin: a potential biomarker to diagnose chronic prosthetic joint infection after total hip or knee arthroplasty

The preoperative detection of prosthetic joint infection (PJI) prior to revision of total hip or knee arthroplasty is still a challenge. Serum Calprotectin (CP) is a heterodimer of two calcium-binding proteins present in the cytoplasm of neutrophils that is released in inflammatory processes and infections. The objective of this study is to determine the reliability of serum CP in the diagnosis of chronic PJI. 81 patients (40 women, 41 men) that presented a potential indication for revision arthroplasty of the hip (THA; n = 18) or knee (TKA, n = 63) at a single institution were prospectively evaluated. The joints were diagnosed as chronically infected or aseptic based on the musculoskeletal infection society (MSIS) criteria of 2018. Receiver operating characteristics and the Youden's index were used to define an ideal cutoff value. The median serum CP level was significantly higher in the group with chronic PJI (15,120 vs. 4980 ng/ml; p < 0.001) compared to the aseptic cases. The calculated optimal cut-off value was 9910 ng/ml (AUC 0.899, 95% CI 0.830-0.968) with a specificity of 91% and sensitivity of 81%. The present investigation suggests that serum CP has a high specificity and good sensitivity to diagnose chronic PJI after TJA of the knee or hip.

Inflammatory markers in saliva and urine reflect disease activity in patients with systemic lupus erythematosus

BACKGROUND

Laboratory tests of blood and sometimes urine are used to diagnose and to monitor disease activity (DA) in SLE. Clinical practice would be simplified if non-invasive urine and salivary tests could be introduced as alternatives to blood samples. We therefore explored the levels of innate immunity-related biomarkers in matched serum, urine and saliva samples from patients with SLE.

METHODS

A total of 84 patients with SLE selected to represent high and low general DA, and 21 controls were included. All participants underwent a thorough clinical examination. General DA and renal DA were measured. The levels of colony-stimulating factor (CSF)-1, interleukin (IL)-34, tumour necrosis factor (TNF)-α, interferon-γ-induced protein (IP)-10, monocyte chemoattractant protein (MCP)-1, calprotectin, macrophage inflammatory protein (MIP)-1α and MIP-1β were analysed by immunoassays and related to DA.

RESULTS

CSF-1, TNF-α, IP-10 and MCP-1 in saliva, serum and urine, as well as calprotectin in saliva and urine were increased in patients with SLE as compared with controls (p<0.05). TNF-α, IP-10 and MCP-1 in saliva, serum and urine, and CSF-1 in saliva and serum distinguished patients with SLE from controls (area under the curve >0.659; p<0.05 for all). CSF-1 in serum and urine, and calprotectin in saliva and urine, as well as TNF- α, IP-10 and MCP-1 in urine correlated positively with measures of general DA (p<0.05). Patients with SLE with active renal disease presented elevated levels of TNF-α, IP-10 and MCP-1 in urine and CSF-1 and IP-10 in serum as compared with patients with SLE with non-active renal disease.

CONCLUSIONS

Our investigation demonstrates that saliva is a novel alternative body fluid, with potential for surveillance of general DA in patients with SLE, but urine is more informative in patients with SLE with predominantly renal DA.

S100A8/A9 in COVID-19 pathogenesis: Impact on clinical outcomes

Coronavirus disease 2019 (COVID-19) has a broad range of clinical manifestations, highlighting the need for specific diagnostic tools to predict disease severity and improve patient prognosis. Recently, calprotectin (S100A8/A9) has been proposed as a potential biomarker for COVID-19, as elevated serum S100A8/A9 levels are associated with critical COVID-19 cases and can distinguish between mild and severe disease states. S100A8/A9 is an alarmin that mediates host proinflammatory responses during infection and it has been postulated that S100A8/A9 modulates the cytokine storm; the hallmark of fatal COVID-19 cases. However, it has yet to be determined if S100A8/A9 is a bona-fide biomarker for COVID-19. S100A8/A9 is widely implicated in a variety of inflammatory conditions, such as cystic fibrosis (CF) and chronic obstructive pulmonary disorder (COPD), as well as pulmonary infectious diseases, including tuberculosis and influenza. Therefore, understanding how S100A8/A9 levels correlate with immune responses during inflammatory diseases is necessary to evaluate its candidacy as a potential COVID-19 biomarker. This review will outline the protective and detrimental roles of S100A8/A9 during infection, summarize the recent findings detailing the contributions of S100A8/A9 to COVID-19 pathogenesis, and highlight its potential as diagnostic biomarker and a therapeutic target for pulmonary infectious diseases, including COVID-19.

Evaluation of Serum Calprotectin Levels in Patients with Inflammatory Bowel Disease

BACKGROUND

Fecal calprotectin has been proposed as a useful biomarker of disease activity in inflammatory bowel disease (IBD). However, the role of calprotectin in systemic circulation is not well established. Thus, this study aimed to quantify serum calprotectin levels to identify a potential inflammatory marker for IBD.

METHODS

Ninety-eight patients with ulcerative colitis (UC) and 105 patients with Crohn's disease (CD) were prospectively enrolled and clinically scored. Ninety-two healthy, age-matched subjects served as controls. Blood samples from UC and CD patients and controls were analyzed for serum calprotectin levels and routine laboratory parameters. Disease activity was assessed by partial Mayo score and Harvey-Bradshaw index for UC and CD, respectively.

RESULTS

Serum calprotectin levels were higher in CD and UC patients than in controls and were higher during active disease than during inactive disease in CD but not in UC. In UC, serum calprotectin levels were correlated with C-reactive protein (CRP) but not with other laboratory parameters or disease activity. In CD, serum calprotectin levels were positively correlated with disease activity, serum CRP, and platelet count. In UC and CD, serum calprotectin and CRP levels increased during the acute phase and decreased towards remission.

CONCLUSIONS

Serum calprotectin is an inflammatory marker in IBD but might be more effective in evaluating patients with CD than those with UC. Further studies are needed to confirm these findings and to better determine the specific uses of serum calprotectin in routine practice.

DSS-induced inflammation in the colon drives a proinflammatory signature in the brain that is ameliorated by prophylactic treatment with the S100A9 inhibitor paquinimod

Background

Inflammatory bowel disease (IBD) is established to drive pathological sequelae in organ systems outside the intestine, including the central nervous system (CNS). Many patients exhibit cognitive deficits, particularly during disease flare. The connection between colonic inflammation and neuroinflammation remains unclear and characterization of the neuroinflammatory phenotype in the brain during colitis is ill-defined.

Methods

Transgenic mice expressing a bioluminescent reporter of active caspase-1 were treated with 2% dextran sodium sulfate (DSS) for 7 days to induce acute colitis, and colonic, systemic and neuroinflammation were assessed. In some experiments, mice were prophylactically treated with paquinimod (ABR-215757) to inhibit S100A9 inflammatory signaling. As a positive control for peripheral-induced neuroinflammation, mice were injected with lipopolysaccharide (LPS). Colonic, systemic and brain inflammatory cytokines and chemokines were measured by cytokine bead array (CBA) and Proteome profiler mouse cytokine array. Bioluminescence was quantified in the brain and caspase activation was confirmed by immunoblot. Immune cell infiltration into the CNS was measured by flow cytometry, while light sheet microscopy was used to monitor changes in resident microglia localization in intact brains during DSS or LPS-induced neuroinflammation. RNA sequencing was performed to identify transcriptomic changes occurring in the CNS of DSS-treated mice. Expression of inflammatory biomarkers were quantified in the brain and serum by qRT-PCR, ELISA and WB.

Results

DSS-treated mice exhibited clinical hallmarks of colitis, including weight loss, colonic shortening and inflammation in the colon. We also detected a significant increase in inflammatory cytokines in the serum and brain, as well as caspase and microglia activation in the brain of mice with ongoing colitis. RNA sequencing of brains isolated from DSS-treated mice revealed differential expression of genes involved in the regulation of inflammatory responses. This inflammatory phenotype was similar to the signature detected in LPS-treated mice, albeit less robust and transient, as inflammatory gene expression returned to baseline following cessation of DSS. Pharmacological inhibition of S100A9, one of the transcripts identified by RNA sequencing, attenuated colitis severity and systemic and neuroinflammation.

Conclusions

Our findings suggest that local inflammation in the colon drives systemic inflammation and neuroinflammation, and this can be ameliorated by inhibition of the S100 alarmin, S100A9.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02317-6.

Circulating calprotectin as biomarker in neutrophil-related inflammation: Pre-analytical recommendations and reference values according to sample type

BACKGROUND

Calprotectin (CLP) is a promising biomarker for the evaluation of neutrophil-related inflammation. Our aim was to establish reference values for circulating CLP in different sample types and to study the effect of pre-analytical variables.

METHODS

Reference values were determined in 100 healthy individuals. Pre-analytical variables were evaluated in 10 healthy controls and four rheumatoid arthritis patients with active disease and covered sample type (serum with/without gel separator, heparin, EDTA and citrate plasma), pre-centrifugation time (<2 h, 6 h, 24 h), storage condition (2-8 °C, 18-25 °C, 30 °C) and storage time (24 h, 72 h, 7 days). CLP measurements were performed with the EliA™Calprotectin 2 assay on Phadia™200 (Thermo Fisher Scientific).

RESULTS

In healthy controls, baseline CLP concentrations in serum were more than double the concentration in EDTA and citrate plasma (0.909 µg/mL versus 0.259 µg/mL and 0.261 µg/mL respectively). Heparin, EDTA and citrate stabilized CLP concentrations for up to 6 h before centrifugation, whereas significant increases in CLP levels were observed when serum was left untreated during that time period.

CONCLUSION

Clinical studies on circulating CLP need to apply sample type-specific reference values and decision limits. To obtain reproducible CLP results in serum, more stringent pre-analytical sample handling instructions are needed.

Calprotectin, an Emerging Biomarker of Interest in COVID-19: A Systematic Review and Meta-Analysis

COVID-19 has been shown to present with varied clinical course, necessitating a need for more specific diagnostic tools that could identify severe cases and predict outcomes during COVID-19 infection. Recent evidence has shown an expanded potential role for calprotectin, both as a diagnostic tool and also as a tool in stratifying COVID-19 patients in terms of severity. Therefore, this systematic review and meta-analysis aims to evaluate the levels of calprotectin in severe and non-severe COVID-19 and also identify the implication of raised calprotectin levels. MEDLINE, EMBASE, The Cochrane Library, Web of science and MedRxiv were searched. Meta-analysis was done to compare the serum/fecal levels of calprotectin between severe and non-severe COVID-19 infections. A total of ten studies included in the review (eight had quantitative data while two were qualitative). A pooled analysis of the eight studies from 613 patients who were RT-PCR positive for COVID-19 (average age = 55 years; 52% males) showed an overall estimate as 1.34 (95%CI: 0.77, 1.91). In conclusion, calprotectin levels have been demonstrated to be significantly elevated in COVID-19 patients who develop the severe form of the disease, and it also has prognostic importance.

The Role of Plasma Calprotectin in Non-infectious Uveitis

PURPOSE

To investigate the role of plasma calprotectin in non-infectious uveitis.

METHODS

This is an observational both cross-sectional and prospective study. Patients with active non-infectious uveitis were recruited as well as nonuveitic controls. Plasma calprotectin was determined and an ophthalmological examination was performed for both patients and controls. Independent variables possibly influencing levels of plasma calprotectin were recorded and analyzed. Categorical variables were compared by chi-square test (applying correction by continuity if necessary). T-test (or Kruskal-Wallis when appropriate) was used to compare averages. Multiple linear regression analysis was used to assess relationship between plasma calprotectin levels and independent variables. Spearman coefficient was calculated in order to establish correlation between plasma calprotectin and anterior chamber cell grading. Changes in plasma calprotectin levels between the flare beginning and its resolution were determined with mixed model for repeated measures. R software (version 3.6.0) was used to perform the statistical analysis.

RESULTS

We included 74 patients and 40 controls in the cross-sectional study. Plasma calprotectin levels were higher in uveitis patients compared to those of controls (p = .003), being higher in younger patients and patients with posterior uveitis. No correlation between calprotectin and anterior chamber inflammation degree was found (p = .198). For the prospective study, we included 36 patients. We found no significant differences in calprotectin levels between active and inactive uveitis (p = .344).

CONCLUSIONS

Plasma calprotectin levels are elevated in uveitis patients and are influenced by age and anatomical location of uveitis. Further investigation is needed to assess the relationship between calprotectin and uveitis activity.

S100 family proteins in inflammation and beyond

The S100 family proteins possess a variety of intracellular and extracellular functions. They interact with multiple receptors and signal transducers to regulate pathways that govern inflammation, cell differentiation, proliferation, energy metabolism, apoptosis, calcium homeostasis, cell cytoskeleton and microbial resistance. S100 proteins are also emerging as novel diagnostic markers for identifying and monitoring various diseases. Strategies aimed at targeting S100-mediated signaling pathways hold a great potential in developing novel therapeutics for multiple diseases. In this chapter, we aim to summarize the current knowledge about the role of S100 family proteins in health and disease with a major focus on their role in inflammatory conditions.

The Role of Calprotectin in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease characterized by inflammatory cell infiltration, high levels of cytokines, and erosion of cartilage and bone in joints. Calprotectin (CLP), as a recently described member of S100 family proteins, is a heterodimeric complex of S100A8 and S100A9. Currently, plenty of studies have indicated significantly increased serum and synovial fluid levels of CLP in patients with RA. It was reported that CLP was related to cell differentiation, migration, apoptosis, and production of pro-inflammatory factors in RA. In addition, there are the positive relationships between serum, synovial CLP and traditional acute phase reactants, disease activity, ultrasound and radiographic progression of joints, and treatment response of RA. In this review, we mainly discuss the role of CLP in the pathogenesis of RA as well as its potential to estimate clinical disease progression of RA patients.

Hydroxychloroquine modulates elevated expression of S100 proteins in systemic lupus erythematosus

Objectives

We investigated the effect of hydroxychloroquine (HCQ) on S100A8 and S100A9 serum levels in systemic lupus erythematosus (SLE) patients with low disease activity receiving immunosuppressants.

Methods

SELENA-SLEDAI, Cutaneous Lupus Erythematous Disease Area and Severity Index (CLASI) and serum levels of complement factors, anti-dsDNA antibodies, and white blood cell, lymphocyte, and platelet counts were used to evaluate disease activity, cutaneous disease activity, and immunological activity, respectively. Serum S100A8 and S100A9 were measured at HCQ administration and after 3 or 6 months using ELISA.

Results

S100A8 and S100A9 serum levels were elevated at baseline and the magnitude of decrease from baseline at 3 and 6 months after HCQ administration was greater in patients with renal involvement than in those without (baseline: S100A8, p = 0.034; S100A9, p = 0.0084; decrease: S100A8, p = 0.049; S100A9, p = 0.023). S100 modulation was observed in patients with ( n = 17; S100A8, p = 0.0011; S100A9, p = 0.0002) and without renal involvement ( n = 20; S100A8, p = 0.0056; S100A9, p = 0.0012), and was more apparent in patients with improved CLASI activity scores (improved: S100A8, p = 0.013; S100A9, p = 0.0032; unimproved: S100A8, p = 0.055; S100A9, p = 0.055). No associations were observed for immunological biomarkers.

Conclusion

HCQ may improve organ involvement in SLE by modulating S100 protein levels, especially in patients with renal or skin involvement.

Insights from deconvolution of cell subtype proportions enhance the interpretation of functional genomic data

Cell subtype proportion variability between samples contributes significantly to the variation of functional genomic properties such as gene expression or DNA methylation. Although the impact of the variation of cell subtype composition on measured genomic quantities is recognized, and some innovative tools have been developed for the analysis of heterogeneous samples, most functional genomics studies using samples with mixed cell types still ignore the influence of cell subtype proportion variation, or just deal with it as a nuisance variable to be eliminated. Here we demonstrate how harvesting information about cell subtype proportions from functional genomics data can provide insights into cellular changes associated with phenotypes. We focused on two types of mixed cell populations, human blood and mouse kidney. Cell type prediction is well developed in the former, but not currently in the latter. Estimating the cellular repertoire is easier when a reference dataset from purified samples of all cell types in the tissue is available, as is the case for blood. However, reference datasets are not available for most other tissues, such as the kidney. In this study, we showed that the proportion of alterations attributable to changes in the cellular composition varies strikingly in the two disorders (asthma and systemic lupus erythematosus), suggesting that the contribution of cell subtype proportion changes to functional genomic properties can be disease-specific. We also showed that a reference dataset from a single-cell RNA-seq study successfully estimated the cell subtype proportions in mouse kidney and allowed us to distinguish altered cell subtype differences between two different knock-out mouse models, both of which had reported a reduced number of glomeruli compared to their wild-type counterparts. These findings demonstrate that testing for changes in cell subtype proportions between conditions can yield important insights in functional genomics studies.

Serum calprotectin and ischemia modified albumin levels as markers of disease activity in Behçet's disease

Introduction

Behçet’s disease (BD) is a complex multisystemic inflammatory disorder which is characterized by recurrent attacks of acute inflammation. As there is no universally recognized pathognomonic laboratory marker of BD, its diagnosis is still based on clinical findings.

Aim

To evaluate the role of calprotectin and ischemia modified albumin (IMA) as biomarkers in the assessment of disease activity of BD.

Material and methods

A total of 93 patients with BD and 62 age- and gender-matched healthy controls were included in the study. Disease activity was assessed with the BD Current Activity Form (BDCAF) score. Serum levels of calprotectin, high-sensitivity C-reactive protein (hsCRP) and IMA were measured in the patient and control groups.

Results

Serum levels of calprotectin, IMA and hsCRP in patients with BD were higher than those of the healthy control group (p < 0.001 for all). No correlations between calprotectin and IMA, hsCRP, erythrocyte sedimentation rate, CRP, or BDCAF score were found.

Conclusions

As the calprotectin level are increased in BD patients, it could be a candidate biomarker which plays a role in BD pathogenesis.

S100 Proteins in the Innate Immune Response to Pathogens

S100 proteins are distinct dimeric EF-hand Ca²⁺-binding proteins that can bind Zn²⁺, Mn²⁺, and other transition metals with high affinity at two sites in the dimer interface. Certain S100 proteins, including S100A7, S100A12, S100A8, and S100A9, play key roles in the innate immune response to pathogens. These proteins function via a "nutritional immunity" mechanism by depleting essential transition metals in the infection that are required for the invading organism to grow and thrive. They also act as damage-associated molecular pattern ligands, which activate pattern recognition receptors (e.g., Toll-like receptor 4, RAGE) that mediate inflammation. Here we present protocols for these S100 proteins for high-level production of recombinant protein, measurement of binding affinities using isothermal titration calorimetry, and an assay of antimicrobial activity.

Circulating S100 proteins effectively discriminate SLE patients from healthy controls: a cross-sectional study

S100 proteins are currently being investigated as potential diagnostic and prognostic biomarkers of several cancers and inflammatory diseases. The aims of this study were to analyse the plasma levels of S100A4, S100A8/9 and S100A12 in patients with incomplete systemic lupus erythematosus (iSLE), in patients with established SLE and in healthy controls (HCs) and to investigate the potential utility of the S100 proteins as diagnostic or activity-specific biomarkers in SLE. Plasma levels were measured by ELISA in a cross-sectional cohort study of 44 patients with SLE, 8 patients with iSLE and 43 HCs. Disease activity was assessed using the SLEDAI-2K. The mean levels of all S100 proteins were significantly higher in SLE patients compared to HCs. In iSLE patients, the levels of S100A4 and S100A12 but not S100A8/9 were also significantly higher compared to HCs. There were no significant differences in S100 levels between the iSLE and SLE patients. Plasma S100 proteins levels effectively discriminated between SLE patients and HCs. The area under the curve (AUC) for S100A4, S100A8/9 and S100A12 plasma levels was 0.989 (95% CI 0.976-1.000), 0.678 (95% CI 0.563-0.792) and 0.807 (95% CI 0.715-0.899), respectively. S100 levels did not differentiate between patients with high and low disease activity. Only the S100A12 levels were significantly associated with SLEDAI-2K and with cSLEDAI-2K. S100 proteins were significantly higher in SLE patients compared HCs and particularly S100A4 could be proposed as a potential diagnostic biomarker for SLE.

Calprotectin in patients with chronic rheumatoid arthritis correlates with disease activity and responsiveness to methotrexate

OBJECTIVE

Calprotectin (myeloid-related protein 8/14) is elevated in inflammatory diseases and a correlation of serum calprotectin and disease activity in rheumatoid arthritis (RA) has been shown. In this study, we investigated plasma calprotectin as a disease marker in patients with chronic RA treated with methotrexate (MTX) monotherapy and compared plasma calprotectin with C-reactive protein (CRP) in this matter.

METHODS

Seventy-six patients with chronic RA were included in this open prospective study and of these 40 were included prior to initiation of MTX therapy. The patients were followed with laboratory and clinical parameters for 52-56 weeks. Plasma calprotectin was analyzed at the start of study and at various intervals. Radiographic evaluation was performed at baseline and after 17.2 months and progression in joint destruction was measured with Larsen score. The response to MTX was evaluated according to the American College of Rheumatology criteria.

RESULTS

Patients starting MTX treatment had significantly higher levels of plasma calprotectin compared to patients well established on MTX therapy (p = .008). Among the 40 patients naive to MTX, 25 responded to MTX therapy and serum calprotectin decreased significantly in these patients (p = .0007). The radiographic damage showed no relation to calprotectin.

CONCLUSIONS

Plasma calprotectin is associated with disease activity in patients with chronic RA and is more strongly correlated to MTX response compared to CRP. The role of calprotectin as a disease marker is promising and the advantages compared to CRP needs to be further investigated.

Detection of calprotectin in inflammatory bowel disease: Fecal and serum levels and immunohistochemical localization

The aim of the present study was to quantify calprotectin levels using an enzyme-linked immunosorbent assay (ELISA) and a point-of-care test (POCT) in patients with inflammatory bowel disease. Overall, 113 patients with ulcerative colitis (UC; 51 men and 62 women) and 42 patients with Crohn's disease (CD; 29 men and 13 women), who were scheduled to undergo a colonoscopy, were prospectively enrolled and scored endoscopically and clinically. An additional 96 healthy, age-matched subjects served as the normal controls. Feces and blood samples from the patients with UC and CD, and the normal controls were analyzed. These patients had received adequate medical treatment. The tissue distribution of calprotectin was investigated using immunohistochemistry. The fecal calprotectin levels, as measured using an ELISA, were correlated with the endoscopic and clinical disease activities and laboratory parameters, including serum levels of hemoglobin (Hb), albumin and C-reactive protein, and erythrocyte sedimentation rate, particularly among the patients with UC. The fecal Hb level was close to that of the fecal calprotectin level (r=0.57; P<0.0001). The fecal calprotectin level measured using an ELISA was well-correlated with the fecal calprotectin level measured using the POCT (r=0.81; P<0.0001), but was not correlated with the serum calprotectin level (r=0.1013; P=0.47). An immunohistochemical investigation revealed that patients with both UC and CD had higher neutrophil and monocyte/macrophage calprotectin-positive cell expression levels, compared with those in the normal controls. Fecal calprotectin was considered a reliable marker for disease activity, and the assessment of fecal calprotectin via POCT showed potential as a rapid and simple measurement in clinical settings.

Urine S100 proteins as potential biomarkers of lupus nephritis activity

Background

Improved, noninvasive biomarkers are needed to accurately detect lupus nephritis (LN) activity. The purpose of this study was to evaluate five S100 proteins (S100A4, S100A6, S100A8/9, and S100A12) in both serum and urine as potential biomarkers of global and renal system-specific disease activity in childhood-onset systemic lupus erythematosus (cSLE).

Methods

In this multicenter study, S100 proteins were measured in the serum and urine of four cSLE cohorts and healthy control subjects using commercial enzyme-linked immunosorbent assays. Patients were divided into cohorts on the basis of biospecimen availability: (1) longitudinal serum, (2) longitudinal urine, (3) cross-sectional serum, and (4) cross-sectional urine. Global and renal disease activity were defined using the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) and the SLEDAI-2K renal domain score. Nonparametric testing was used for statistical analysis, including the Wilcoxon signed-rank test, Kruskal-Wallis test, Mann-Whitney U test, and Spearman’s rank correlation coefficient.

Results

All urine S100 proteins were elevated in patients with active LN compared with patients with active extrarenal disease and healthy control subjects. All urine S100 protein levels decreased with LN improvement, with S100A4 demonstrating the most significant decrease. Urine S100A4 levels were also higher with proliferative LN than with membranous LN. S100A4 staining in the kidney localized to mononuclear cells, podocytes, and distal tubular epithelial cells. Regardless of the S100 protein tested, serum levels did not change with cSLE improvement.

Conclusions

Higher urine S100 levels are associated with increased LN activity in cSLE, whereas serum S100 levels do not correlate with disease activity. Urine S100A4 shows the most promise as an LN activity biomarker, given its pronounced decrease with LN improvement, isolated elevation in urine, and positive staining in resident renal cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1444-4) contains supplementary material, which is available to authorized users.

Platelet-Derived S100A8/A9 and Cardiovascular Disease in Systemic Lupus Erythematosus

OBJECTIVE

Levels of S100A8/A9, a proinflammatory and prothrombotic protein complex, are increased in several diseases, and high levels predispose to cardiovascular disease (CVD). Recently, platelet S100A8/A9 synthesis was described in mice and humans in relation to CVD. The aim of this study was to investigate the role of platelet S100A8/A9 in systemic lupus erythematosus (SLE), a disease with markedly increased cardiovascular morbidity, as well as the exact platelet distribution of the S100A8/A9 proteins.

METHODS

The occurrence and distribution of platelet S100A8/A9 protein were detected by enzyme-linked immunosorbent assay, electron microscopy, Western blotting, and flow cytometry in healthy controls (n = 79) and in 2 individual cohorts of SLE patients (n = 148 and n = 318, respectively) and related to cardiovascular morbidity.

RESULTS

We observed that human platelets expressed S100A8/A9 proteins, and that these were localized in close proximity to intracellular membranes and granules as well as on the cell surface upon activation with physiologic and pathophysiologic stimuli. Interestingly, S100A8/A9 was enriched at sites of membrane interactions, indicating a role of S100A8/A9 in cell-cell communication. S100A8/A9 levels were highly regulated by interferon-α, both in vivo and in vitro. Patients with SLE had increased platelet S100A8/A9 content compared with healthy individuals. Increased levels of platelet S100A8/A9 were associated with CVD, particularly myocardial infarction (odds ratio 4.8, 95% confidence interval 1.5-14.9, P = 0.032 [adjusted for age, sex, and smoking]).

CONCLUSION

Platelets contain S100A8/A9 in membrane-enclosed vesicles, enabling rapid cell surface deposition upon activation. Furthermore, platelet S100A8/A9 protein levels were increased in SLE patients, particularly in those with CVD, and may be a future therapeutic target.

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.

Calprotectin in rheumatic diseases: a review

Calprotectin also known as MRP8/14 or S100A8/A9 is a heterodimeric complex of two S100 calcium-binding proteins: myeloid-related protein 8 (MRP-8 or S100A8) and MRP-14 (or S100A9). At present, according to many authors, it is considered that calprotectin MRP8/14 is a potentially more sensitive biomarker of disease activity in rheumatoid disease than conventional inflammatory indices such as the erythrocyte sedimentation rate, C-reactive protein and others. A review of the literature on concentration of calprotectin in patients with some rheumatic diseases (rheumatoid arthritis, juvenile idiopathic arthritis, adult-onset Still's disease, systemic vasculitis, polymyalgia rheumatica, ankylosis spondylitis, systemic lupus erythematosus, and primary Sjögren's syndrome) is presented.

Pro-inflammatory S100 proteins are associated with glomerulonephritis and anti-dsDNA antibodies in systemic lupus erythematosus

Objectives Systemic lupus erythematosus (SLE) is associated with elevated levels of S100A8/A9, pro-inflammatory proteins mainly secreted by activated polymorphonuclear neutrophils (PMNs). The underlying mechanisms for increased S100A8/A9 levels and their relation to the clinical phenotype have not been carefully investigated. We assessed S100A8/A9 and S100A12 levels in SLE patient sera in relation to disease activity, clinical phenotype, presence of anti-dsDNA antibodies and ability to promote phagocytosis of necrotic cells (NCs) by PMNs. Methods Serum levels of S100A8/A9 and S100A12 were measured by ELISA in paired samples of 100 SLE patients at time points of higher and lower disease activity. Serum-mediated phagocytosis of NCs by PMNs was analysed by flow cytometry. Clinical data were recorded at time points of blood sampling. Results Serum levels of S100A8/A9 and S100A12 were increased in SLE patients with high disease activity compared to paired samples at low disease activity ( p = 0.01 and p = 0.008, respectively). Elevated levels of S100A8/A9 were particularly seen in patients with anti-dsDNA antibodies ( p = 0.01) and glomerulonephritis before treatment ( p = 0.02). Immunosuppressive therapy was associated with a reduction of S100A8/A9 serum levels ( p = 0.002). The ability of serum to support phagocytosis of NCs by PMNs was related to increased S100A8/A9 levels ( p = 0.01). Conclusions Elevated serum levels of S100A8/A9 may be used to monitor disease activity and response to treatment in SLE patients, especially in patients with glomerulonephritis. S100A12 may be a marker of disease activity in SLE. Increased S100A8/A9 levels may reflect immune-pathological processes involving phagocytosis of immune complexes by PMNs.

Comparative Proteomic Analysis of Two Uveitis Models in Lewis Rats

PURPOSE

Inflammation generates changes in the protein constituents of the aqueous humor. Proteins that change in multiple models of uveitis may be good biomarkers of disease or targets for therapeutic intervention. The present study was conducted to identify differentially-expressed proteins in the inflamed aqueous humor.

METHODS

Two models of uveitis were induced in Lewis rats: experimental autoimmune uveitis (EAU) and primed mycobacterial uveitis (PMU). Differential gel electrophoresis was used to compare naïve and inflamed aqueous humor. Differentially-expressed proteins were separated by using 2-D gel electrophoresis and excised for identification with matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF). Expression of select proteins was verified by Western blot analysis in both the aqueous and vitreous.

RESULTS

The inflamed aqueous from both models demonstrated an increase in total protein concentration when compared to naïve aqueous. Calprotectin, a heterodimer of S100A8 and S100A9, was increased in the aqueous in both PMU and EAU. In the vitreous, S100A8 and S100A9 were preferentially elevated in PMU. Apolipoprotein E was elevated in the aqueous of both uveitis models but was preferentially elevated in EAU. Beta-B2-crystallin levels decreased in the aqueous and vitreous of EAU but not PMU.

CONCLUSIONS

The proinflammatory molecules S100A8 and S100A9 were elevated in both models of uveitis but may play a more significant role in PMU than EAU. The neuroprotective protein β-B2-crystallin was found to decline in EAU. Therapies to modulate these proteins in vivo may be good targets in the treatment of ocular inflammation.

Calprotectin (S100A8/A9) and S100A12 are associated with measures of disease activity in a longitudinal study of patients with rheumatoid arthritis treated with infliximab

OBJECTIVES

The pro-inflammatory proteins calprotectin (a heterocomplex of S100A8/A9) and S100A12 have been associated with disease activity in rheumatoid arthritis (RA). The aim of this study was to compare their potential as biomarkers in a prospective study of RA patients starting with infliximab as their first biological disease-modifying anti-rheumatic drug (DMARD).

METHOD

Thirty-nine RA patients were examined and serum samples collected when starting with infliximab and after 3, 6, and 12 months. Calprotectin and S100A12 were analysed by enzyme-linked immunosorbent assays (ELISAs) and, together with C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), measured at all time points. A disease activity score of 28 joints (DAS28) was calculated. Radiographs of the hands, wrists, and feet were taken at baseline and after 3 years, and assessed according to the modified Sharp/van der Heijde (SvH) score. Responsiveness was evaluated according to the European League of Associations for Rheumatology (EULAR) response criteria based on 28 joints.

RESULTS

Both S100 proteins were significantly higher in seropositive than in seronegative patients (p = 0.01). Calprotectin correlated significantly with CRP (ρ = 0.51-0.75), ESR (ρ = 0.32-0.52), and DAS28 (ρ = 0.32-0.62). S100A12 correlated with calprotectin (ρ = 0.62-0.77) and CRP (ρ = 0.32-0.63). The S100 proteins, and especially calprotectin (ρ = 0.23-0.39), showed weak associations with radiographic progression, unlike CRP/ESR. None of the S100 proteins could predict responsiveness.

CONCLUSIONS

Calprotectin showed the strongest correlation with measures of disease activity and may be better than S100A12 when evaluating disease activity in RA patients. More extensive studies are needed to further compare the predictive value of the S100 proteins relative to radiographic progression.

Calprotectin in rheumatic diseases

Calprotectin is a heterodimer formed by two proteins, S100A8 and S100A9, which are mainly produced by activated monocytes and neutrophils in the circulation and in inflamed tissues. The implication of calprotectin in the inflammatory process has already been demonstrated, but its role in the pathogenesis, diagnosis, and monitoring of rheumatic diseases has gained great attention in recent years. Calprotectin, being stable at room temperature, is a candidate biomarker for the follow-up of disease activity in many autoimmune disorders, where it can predict response to treatment or disease relapse. There is evidence that a number of immunomodulators, including TNF-α inhibitors, may reduce calprotectin expression. S100A8 and S100A9 have a potential role as a target of treatment in murine models of autoimmune disorders, since the direct or indirect blockade of these proteins results in amelioration of the disease process. In this review, we will go over the biologic functions of calprotectin which might be involved in the etiology of rheumatic disorders. We will also report evidence of its potential use as a disease biomarker. Impact statement Calprotectin is an acute-phase protein produced by monocytes and neutrophils in the circulation and inflamed tissues. Calprotectin seems to be more sensitive than CRP, being able to detect minimal residual inflammation and is a candidate biomarker in inflammatory diseases. High serum levels are associated with some severe manifestations of rheumatic diseases, such as glomerulonephritis and lung fibrosis. Calprotectin levels in other fluids, such as saliva and synovial fluid, might be helpful in the diagnosis of rheumatic diseases. Of interest is also the potential role of calprotectin as a target of treatment.

Myeloid-related proteins-8 and -14 are expressed but dispensable in the pathogenesis of experimental epidermolysis bullosa acquisita and bullous pemphigoid

BACKGROUND

Myeloid-related protein-8 (MRP-8) and its heterodimeric partner, MRP-14 belong to the group of danger-associated molecular patterns (DAMPs) and are associated with numerous chronic human disorders. However, their functional role in autoimmunity remains largely unclear.

OBJECTIVE

Here, we examined the involvement of MRP-8/-14 in two difficult-to-treat autoimmune blistering diseases, epidermolysis bullosa acquisita (EBA) and bullous pemphigoid (BP).

METHODS

MRP-8/-14 concentrations in the sera of EBA and BP patients were quantified by ELISA. Experimental EBA and BP in mice were induced by transfer of antibodies directed against type VII or XVII collagen, respectively. Expression of MRP-8/-14 was analyzed in skin samples of these experimental mouse models. The functional role of MRP-8/-14 proteins was evaluated by the induction of experimental EBA and BP in MRP-14-deficient mice.

RESULTS

We found serum levels of MRP-8/-14 to be elevated in both, EBA and BP patients. Furthermore, in the lesional skin of mice with experimental diseases expression of MRP-8/-14 was increased as compared to healthy controls. However, MRP-14-deficient mice were fully susceptible to experimental disease with a phenotype comparable to that of wild type controls.

CONCLUSION

Although MRP-8/-14 expression is highly increased in experimental as well as human disease, these proteins do not contribute to the pathogenesis in the effector phase of EBA and BP.

Correlation between myeloid-derived suppressor cells and S100A8/A9 in tumor and autoimmune diseases

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of cells that constitute an important component of immune regulatory system. Two calcium-binding proteins S100A8 and S100A9 act as important mediators in acute and chronic inflammation. In recent years, many researchers have found that MDSCs and S100A8/A9 operated with one another through a positive feedback loop to promote tumor development and metastasis. However, the correlation between MDSCs and S100A8/A9 in autoimmune diseases (AIDs) remains unknown. In this review, we discussed the co-operation of MDSCs and S100A8/A9 in tumor environment, and also, the role of these two components in AIDs.

Serum calprotectin--a promising diagnostic marker for adult-onset Still's disease

Calprotectin is a calcium-binding cytosolic protein, mainly expressed in immune cells, such as neutrophils, monocytes, and macrophages. Our study aimed to evaluate the diagnostic value of calprotectin for adult-onset Still’s disease (AOSD), by comparing serum calprotectin concentrations in patients with AOSD (n = 46), rheumatoid arthritis (RA, n = 34), primary Sjögren syndrome (pSS, n = 40), systemic lupus erythematosus (SLE, n = 39), osteoarthritis (OA, n = 20), and healthy controls (HCs, n = 49). Calprotectin concentrations were significantly higher in patients with AOSD (55.26 ± 18.00 ng/ml), compared to patients with RA (39.17 ± 18.90 ng/ml), pSS (35.31 ± 19.47 ng/ml), SLE (32.21 ± 25.01 ng/ml), OA (19.24 ± 10.67 ng/ml), and HCs (8.46 ± 5.17 ng/ml). All the differences were highly significant (p < 0.001). Using receiver-operating characteristic curve, the cut-off value of calprotectin was defined as 45.488 ng/ml, and its sensitivity and specificity for AOSD diagnosis were 63.0 and 80.1 %, respectively. The positive rate of calprotectin was significantly higher in AOSD cases compared to patients with other diseases and healthy controls (p < 0.001). Serum calprotectin was positively correlated with ferritin (r = 0.294, p < 0.05), and concentration of hemoglobin was significantly lower in calprotectin-positive patients compared to negative patients in AOSD (103.49 ± 20.21 g/l vs 115.71 ± 15.59 g/l, t = −2.142, p = 0.038). These findings suggest that serum calprotectin may serve as a promising marker for the diagnosis of AOSD and monitor disease activity to a certain extent.

Serum calprotectin (S100A8/9): an independent predictor of ultrasound synovitis in patients with rheumatoid arthritis

Introduction

Calprotectin, a heterodimeric complex of S100A8/9 (MRP8/14), has been proposed as an important serum biomarker that reflects disease activity and structural joint damage in rheumatoid arthritis (RA). The objective of this cross-sectional study was to test the hypothesis that calprotectin is associated with clinical and ultrasound-determined disease activity in patients with RA.

Methods

A total of 37 patients with RA (including 24 females, a mean disease duration of 20 months) underwent a clinical examination and 7-joint ultrasound score (German US-7) of the clinically dominant hand and foot to assess synovitis by grey-scale (GS) and synovial vascularity by power Doppler (PD) ultrasound using semiquantitative 0–3 grading. The levels of serum calprotectin and C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) were determined at the time of the ultrasound assessment. We analysed the relationship between serum calprotectin level, traditional inflammatory markers, and ultrasound-determined synovitis.

Results

The levels of serum calprotectin were significantly correlated with swollen joint count (r = 0.465, p < 0.005), DAS28-ESR (r = 0.430, p < 0.01), ESR (r = 0.370, p < 0.05) and, in particular, CRP (r = 0.629, p < 0.001). Calprotectin was significantly associated with GS (r = 0.359, p < 0.05) and PD synovitis scores (r = 0.497, p < 0.005). Using multivariate regression analysis, calprotectin, adjusted for age and sex, was a better predictor of PD synovitis score (R² = 0.765, p < 0.001) than CRP (R² = 0.496, p < 0.001).

Conclusions

The serum levels of calprotectin are significantly associated with clinical, laboratory and ultrasound assessments of RA disease activity. These results suggest that calprotectin might be superior to CRP for monitoring ultrasound-determined synovial inflammation in RA patients.

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.

The marker C-reactive protein is helpful in monitoring the integrity of anastomosis: plasma calprotectin

BACKGROUND

Despite improved surgical techniques and materials, anastomotic leakage is a big problem for surgeons. The most frequently used laboratory parameters is leukocyte (white blood cell) and C-reactive protein (CRP). Availability of plasma calprotectin with CRP to detect anastomotic leakage was studied.

METHODS

In this prospective study of 41 (male/female 18/23) patients in the anastomosis group, 30 (male/female 20/10) patients were included in the control group. The anastomosis groups viewed in preoperatively day and postoperatively 1st, 3rd, and 5th day of CRP, white blood cell, and plasma calprotectin values.

RESULTS

Anastomosis group with complications and without complications were studied. Statistically significant similarities between plasma calprotectin and CRP levels in the postoperative period were observed.

CONCLUSION

Plasma calprotectin in monitoring the integrity of the anastomosis can be used with a marker CRP.

Elevated expressions of myeloid-related proteins-8 and -14 are danger biomarkers for lupus nephritis

Myeloid-related proteins, MRP-8 and -14, which have been identified as molecules that mediate the danger signaling in innate immune response, are also known as the DAMPs (damage associated molecular pattern molecules). The proteins were found in infiltrating macrophages and neutrophils at inflammatory sites. Their expression was correlated with severe forms of glomerulonephritis. Therefore, this study examined whether or not MRP-8 and -14 can be used as biomarkers for identifying severely active lupus nephritis (LN). Total blood leukocyte samples and renal biopsy tissues from a prospective cohort of LN patients were used to determine mRNA and protein expression levels of MRP-8 and -14. The mRNA levels of MRP-8 and -14 in total blood leukocytes were significantly higher in active LN patients than quiescent LN patients and healthy controls. Moreover, the mRNA levels of MRP-8 and -14 in the total blood leukocytes and kidney tissues were significantly correlated with therapeutic response and the mRNA expression levels in the kidney were associated with an early loss of the kidney function. MRP-8 and -14 can be used as non-invasive prognostic biomarkers in patients with LN.

Nutritional Immunity: S100 Proteins at the Host-Pathogen Interface

The S100 family of EF-hand calcium (Ca(2+))-binding proteins is essential for a wide range of cellular functions. During infection, certain S100 proteins act as damage-associated molecular patterns (DAMPs) and interact with pattern recognition receptors to modulate inflammatory responses. In addition, these inflammatory S100 proteins have potent antimicrobial properties and are essential components of the immune response to invading pathogens. In this review, we focus on S100 proteins that exhibit antimicrobial properties through the process of metal limitation, termed nutritional immunity, and discuss several recent advances in our understanding of S100 protein-mediated metal sequestration at the site of infection.

Elevated serum levels of calprotectin (myeloid-related protein 8/14) in patients with ankylosing spondylitis and its association with disease activity and quality of life

BACKGROUND

Calprotectin is one of the major leukocyte S100 proteins showing both calcium binding and antimicrobial characteristics. The serum level of calprotectin is markedly elevated in patients with inflammatory bowel disease, rheumatoid arthritis, as well as systemic lupus erythematosus and has been suggested to play a prominent role in both progression and pathogenesis of these diseases.

AIM

The purpose of this study was to investigate the serum level of calprotectin in patients with ankylosing spondylitis (AS) and its association with disease activity and other clinical characteristics of AS.

MATERIALS AND METHODS

Thirty-one patients who met the modified New York criteria for AS and 45 healthy controls were included in this study. Both Bath AS disease activity index and AS disease activity score were applied on the patients with AS for the assessment of disease activity; Bath AS functional index, for the assessment of functional activity; Bath AS radiology index, for the assessment of radiological damage; and the AS quality of life questionnaire for the assessment of disease-related life status. Spinal and hip measurements were performed using Bath AS metrology index. The serum level of calprotectin was determined using enzyme-linked immunosorbent assay kit.

RESULTS

Mean serum level of calprotectin was significantly higher in the patients with AS compared with healthy controls (P = 0.003). Serum levels of calprotectin did not correlate with Bath AS disease activity index, AS disease activity score, Bath AS functional index, Bath AS radiology index, Bath AS metrology index, modified Schober, chest expansion, AS quality of life questionnaire, erythrocyte sedimentation rate, and C-reactive protein values (P > 0.05).

CONCLUSIONS

Our results suggest that calprotectin might play an important role in the pathogenetic mechanisms of AS; however, the calprotectin levels did not correlate with the measurements of disease activity, functional abilities, radiological damage, and the quality of life in these patients. Further insight into this area of research might provide opportunities to develop novel treatment strategies, which take into account the role of these peptides in the pathogenetic mechanisms of AS.

Identification of S100A9 as biomarker of responsiveness to the methotrexate/etanercept combination in rheumatoid arthritis using a proteomic approach

OBJECTIVES

One way to optimize the drug prescription in rheumatoid arthritis (RA) is to identify predictive biomarkers of drug responsiveness. Here, we investigated the potential "theranostic" value of proteins of the S100 family by monitoring levels of both S100A8 and S100A9 in blood samples from RA patients.

DESIGN

For proteomic analysis, peripheral blood mononuclear cells (PBMC) and serum samples were collected in patients prior to initiation of the methotrexate/etanercept (MTX/ETA) combination. Firstly, relative mass spectrometry (MS) quantification focusing on S100A8 and S100A9 proteins was carried out from PBMCs samples to identify potential biomarkers. The same approach was also performed from serum samples from responder (R) and non responder (NR) patients. Finally, to confirm these results, an absolute quantification of S100A8, S100A9 proteins and calprotectin (heterodimer of S100A8/S100A9) was carried out on the serum samples using ELISA.

RESULTS

MS analyses revealed that both S100A8 and S100A9 proteins were significantly accumulated in PBMC from responders. In contrast to PBMC, only the S100A9 protein was significantly overexpressed in the serum of R patients. Absolute quantification by ELISA confirmed this result and pointed out a similar expression level of S100A8 protein and calprotectin in sera from both R and NR groups. Thus, the S100A9 protein revealed to be predictive of MTX/ETA responsiveness, contrarily to parameters of inflammation and auto-antibodies which did not allow significant discrimination.

CONCLUSION

This is the first report of an overexpression of S100A9 protein in both PBMCs and serum of patients with subsequent response to the MTX/ETA combination. This protein thus represents an interesting biomarker candidate of therapeutic response in RA.

Elevated serum levels of calprotectin (MRP8/MRP14) in patients with Behçet's disease and its association with disease activity and quality of life

BACKGROUND

Behçet's disease (BD) is an inflammatory disease with multisystem chronic vasculitis. The disease is characterized by attacks of oral and genital ulcerations, skin lesions, arthritis, uveitis and deep vein thrombosis. The main histopathological feature is known to be vascular inflammatory change. Calprotectin (MRP8/MRP14) has been identified as an important alarmin that is expressed by activated phagocytes, granulocytes, monocytes and vascular endothelial cells, recognized by toll-like receptors, and induces a thrombogenic and inflammatory response in human microvascular endothelial cells.

AIM

We aimed to investigate the serum levels of calprotectin in patients with BD and its association with disease activity and quality of life.

MATERIALS AND METHODS

Forty-eight patients (25 males and 23 females) and 47 healthy controls (29 males and 18 females) were included to study. BD Current Activity Form (BDCAF) was used to assess the disease activity of patients with BD. Quality of life was assessed by using the Nottingham Health Profile (NHP). Depression and anxiety symptoms were assessed by using the Hospital Anxiety and Depression Scale (HADS). Serum level of calprotectin was determined using an ELISA kit. Results. Serum levels of calprotectin was significantly higher in patients with BD compared to healthy controls (p = 0.001). Serum levels of calprotectin did not correlate with the sores of BDCAF, NHP and HADS.

CONCLUSION

Calprotectin may play a significant role in the pathogenetic mechanisms of BD. Further insight into this area of research might provide opportunities to develop novel treatment strategies.

Increased serum levels of S100A8/A9 and S100A12 are associated with cardiovascular disease in patients with inactive systemic lupus erythematosus

OBJECTIVES

Patients with SLE have an increased morbidity and mortality from cardiovascular disease (CVD). The reason for this is not entirely understood, but is believed to be partly related to the long-lasting inflammatory process seen in SLE. The aim of the present study was to investigate whether there is an association between CVD and serum levels of the proinflammatory proteins S100A8/A9 and S100A12 in SLE.

METHODS

Serum levels of S100A8/A9 and S100A12 were measured with ELISA in 237 SLE patients with clinically inactive disease and without infections, as well as in 100 healthy individuals. Cardiovascular manifestations were defined according to the SLICC/ACR Damage Index (SLICC/ACR-DI).

RESULTS

Serum levels of S100A8/A9 were elevated in our inactive SLE patients as compared with healthy individuals (P < 0.0001), which was not seen for S100A12 (P = 0.12). SLE patients with a history of CVD had increased serum levels of both S100A8/A9 and S100A12 compared with patients with no CVD or venous thromboembolism (P = 0.003 and P = 0.006, respectively). The presence of organ damage according to SLICC/ACR-DI was associated with an increase in both S100A8/A9 and S100A12 serum levels (P = 0.001 and P = 0.006, respectively).

CONCLUSION

Elevated serum levels of S100A8/A9 and S100A12 may be used as an indicator of severe disease and CVD in SLE, suggesting that SLE patients with elevated serum S100A8/A9 and S100A12 concentrations may benefit from more intense cardiovascular primary preventive strategies and possibly also from more intense and early immunosuppressive treatment.

Calprotectin in rheumatoid arthritis : association with disease activity in a cross-sectional and a longitudinal cohort

BACKGROUND

Calprotectin is potentially a more sensitive biomarker of disease activity in rheumatoid arthritis (RA) than conventional acute-phase proteins such as the erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) because it directly reflects inflammation in the synovium and synovial fluid rather than systemic inflammatory activity.

OBJECTIVE

The aim of this study was to evaluate relationships between serum calprotectin levels, disease activity, and response to treatment. Calprotectin was also investigated as a predictive marker of clinical response.

METHODS

This observational study included selected cohorts of patients with RA treated at La Paz University Hospital, Madrid, Spain. Associations between serum calprotectin levels and clinical and laboratory parameters were analyzed in a cross-sectional cohort of 60 patients with varying disease activity, and changes in calprotectin levels in response to treatment with infliximab were analyzed at baseline and after 3 and 6 months of treatment in a longitudinal cohort of 20 patients with very active disease.

RESULTS

In the cross-sectional cohort, calprotectin levels correlated with rheumatoid factor levels (r = 0.25; p < 0.05) but not with titers of antibodies to cyclic citrullinated peptide. Significant correlations were also observed between calprotectin levels and the 28 swollen joint count (28-SJC), Disease Activity Score based on a 28-joint count (DAS28), Simplified Disease Activity Index (SDAI), ESR, and CRP levels. In the longitudinal cohort, calprotectin levels at baseline were not predictive of response to treatment but significantly decreased during treatment in responders (p < 0.0001).

CONCLUSION

Calprotectin levels strongly correlate with clinical and laboratory assessments of joint inflammation and also decrease in response to treatment, indicating that calprotectin is a promising marker for assessment and monitoring of disease activity in patients with RA. Investigations are required to further evaluate its diagnostic, prognostic, and therapeutic potential.

Leukocyte and serum S100A8/S100A9 expression reflects disease activity in ANCA-associated vasculitis and glomerulonephritis

Antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) commonly results in glomerulonephritis, in which neutrophils and monocytes have important roles. The heterodimer calprotectin (S100A8/S100A9, mrp8/14) is a Toll-like receptor-4 ligand found in neutrophils and monocytes and is elevated in inflammatory conditions. By immunohistochemistry of renal biopsies, patients with focal or crescentic glomerular lesions were found to have the highest expression of calprotectin and those with sclerotic the least. Serum levels of calprotectin as measured by ELISA were elevated in patients with active AAV and the levels decreased but did not normalize during remission, suggesting subclinical inflammation. Calprotectin levels in patients with limited systemic disease increased following treatment withdrawal and were significantly elevated in patients who relapsed compared with those who did not. As assessed by flow cytometry, patients with AAV had higher monocyte and neutrophil cell surface calprotectin expression than healthy controls, but this was not associated with augmented mRNA expression in CD14(+) monocytes or CD16(+) neutrophils. Thus, serum calprotectin is a potential disease biomarker in patients with AAV, and may have a role in disease pathogenesis.

Beneficial effects of quinoline-3-carboxamide (ABR-215757) on atherosclerotic plaque morphology in S100A12 transgenic ApoE null mice

OBJECTIVE

There is an emerging widespread interest in the role of damage-associated molecular pattern molecules (DAMP) S100A8, S100A9 and S100A12 in cardiovascular and other diseases. In this study we tested the efficacy of ABR-215757, a S100 protein binding immuno-modulatory compound to stabilize atherosclerosis in transgenic ApoE null mice that express the human pro-inflammatory S100A12 protein within the smooth muscle cell (SM22α-S100A12).

METHODS

Twelve-week old S100A12 transgenic/ApoE(-/-) and WT/ApoE(-/-) mice were treated with ABR-21575 for 5 weeks and were analyzed 4 month later.

RESULTS

Surface plasmon resonance analysis demonstrated that S100A12 interacts with ABR-215757 in a zinc dependent manner in vitro. In vivo, ABR-215757 administration reduced features of advanced plaque morphology resulting in smaller necrotic cores, diminished intimal and medial vascular calcification, and reduced amount of infiltrating inflammatory cells. ABR-215757 normalized aortic expression of RAGE protein and normalized experimentally-induced delayed hypersensitivity. The effect of ABR-215757 was more prominent in ApoE(-/-) mice expressing S100A12 than in ApoE(-/-) animals lacking expression of human S100A12 protein.

CONCLUSION

Our data suggest that S100A12 is important for progression of atherosclerosis and can be targeted by the small molecule ABR-215757. The specific binding of quinoline-3-carboxamides to S100A12 attenuates S100A12-mediated features of accelerated murine atherosclerosis.