Two calcium-binding proteins in infiltrate macrophages of rheumatoid arthritis

Fc-gamma receptors and S100A8/A9 cause bone erosion during rheumatoid arthritis. Do they act as partners in crime?

Bone erosion is one of the central hallmarks of RA and is caused by excessive differentiation and activation of osteoclasts. Presence of autoantibodies in seropositive arthritis is associated with radiographic disease progression. ICs, formed by autoantibodies and their antigens, activate Fcγ-receptor signalling in immune cells, and as such stimulate inflammation-mediated bone erosion. Interestingly, ICs can also directly activate osteoclasts by binding to FcγRs on their surface. Next to autoantibodies, high levels of alarmins, among which is S100A8/A9, are typical for RA and they can further activate the immune system but also directly promote osteoclast function. Therefore, IC-activated FcγRs and S100A8/A9 might act as partners in crime to stimulate inflammation and osteoclasts differentiation and function, thereby stimulating bone erosion. This review discusses the separate roles of ICs, FcγRs and alarmins in bone erosion and sheds new light on the possible interplay between them, which could fuel bone erosion.

Circulating S100A8/A9 is potentially a biomarker that could reflect the severity of experimental colitis in rats

Aims

The clinical significance of circulating S100A8/A9 (calprotectin) in patients with ulcerative colitis (UC) is poorly understood. We examined whether serum S100A8/A9 is a good biomarker for UC, and whether the serum level is a useful index for the severity of the disease.

Main methods

Experimental animal (rats) were used to verify clinical significance of serum S100A8/A9 as a biomarker. Rats treated with 5% dextran sulfate sodium (DSS) alone (UCR) or with 5%DSS plus tacrolimus (TMR) were subjected to the experiment. The serum concentrations of rat S100A8/A9 (r-S100A8/A9) and other inflammatory biomarkers, such as C-reactive protein (CRP) and inflammatory cytokines, in the both groups were measured using enzyme-linked immunosorbent assays (ELISAs). The tissue damage in the large intestinal tract was visualized by hematoxylin-eosin staining. The relationship between the serum concetrations of these inflammatory biomarkers and the histological scores of the rectal tissue was statistically analyzed.

Principle findings

As determined by the ELISAs, the serum concentration of r-S100A8/A9 in the UCR hardly correlated with those of not only CRP but also some inflammatory cytokines. The deterioration of the rectal tissue, mainly epithelium structure of a large intestine, in the UCR was clearly observed, but was not so severe as that in the TMR. The histological scores of the rectal tissue in the UCR significantly correlated with the serum level of r-S100A8/A9, but not with other inflammatory biomarkers. Furthermore, macrophages actively produced r-S100A8/A9 in response to stimulation with lipopolysaccharide and quickly secreted it in circulation. Therefore, the serum level of r-S100A8/A9 suggestively changes in accordance with the severity of experimental UC.

Conclusion

Circulating r-S100A8/A9 is a useful biomarker for experimental UC, and its serum level correlates with the disease severity as judged by histological score.

Ablation of Myeloid Cell MRP8 Ameliorates Nephrotoxic Serum-induced Glomerulonephritis by Affecting Macrophage Characterization through Intraglomerular Crosstalk

Toll-like receptor 4 (TLR4) and one of its endogenous ligands myeloid-related protein 8 (MRP8 or S100A8), especially expressed in macrophages, play an important role in diabetic nephropathy and autoimmune disorders. However, detailed mechanisms and consequence of MRP8 expression remain unknown, partly due to embryonic lethality of MRP8 knockout mice. In this study, Myeloid lineage cell-specific MRP8 knockout mice were generated, and nephrotoxic serum-induced glomerulonephritis was developed. Mice with conditional ablation of MRP8 gene in myeloid cells exhibited less severe histological damage, proteinuria and inflammatory changes compared to control mice. Mechanism of MRP8 upregulation was investigated using cultured cells. Co-culture of macrophages with mesangial cells or mesangial cell-conditioned media, but not with proximal tubules, markedly upregulated MRP8 gene expression and inflammatory M1 phenotype in macrophages, which was attenuated in MRP8-deleted bone marrow-derived macrophages. Effects of MRP8 deletion was further studied in the context of macrophage-inducible C-type lectin (Mincle), which is critically involved in maintenance of M1 phenotype of macrophages. MRP8 ablation in myeloid cells suppressed the induction of Mincle expression on macrophages in glomerulonephritis. Thus, we propose that intraglomerular crosstalk between mesangial cells and macrophages plays a role in inflammatory changes in glomerulonephritis, and MRP8-dependent Mincle expression in macrophage may be involved in the process.

Inflammatory bowel disease and biomarkers of gut inflammation and permeability in a community with high exposure to perfluoroalkyl substances through drinking water

Perfluoroalkyl substances (PFAS) can act as surfactants and have been suggested to be capable of affecting gut mucosa integrity, a possible factor in the pathogenesis of inflammatory bowel disease (IBD). So far, only PFOA has been shown to have a positive association with ulcerative colitis. The present study aimed to investigate the association of PFAS and clinically diagnosed IBD in the Ronneby cohort, a population with high PFAS exposure (especially high PFOS and PFHxS) from Aqueous Film-Forming Foam through drinking water, using registry data. Additionally, to explore associations of PFAS with fecal zonulin and calprotectin, subclinical biomarkers of gut inflammation and permeability, in a sub-set of participants from Ronneby and Karlshamn (a nearby control municipality). The registry study included all people that ever resided in Ronneby municipality at least one year between 1980 and 2013. Yearly exposure to contaminated drinking water was assessed based on residential addresses and waterworks supply data, and the population classified by early, mid and late periods in ascending level of contamination. Diagnosed IBD cases were retrieved from the Swedish National Patient register and cause-of-death register. The Cox proportional hazards model was used to derive the hazard ratios (HRs) for diagnosed IBD. The biomarker study included 189 individuals who provided fecal samples. Serum PFAS were measured using LC-MS/MS. Fecal zonulin and calprotectin were measured using ELISA. Linear regression was used to assess the associations between measured PFAS and biomarker levels. In the registry study, no raised HRs for diagnosed IBD were found for cohort subjects with mid (1995-2004) or late period (2005-2013) exposure compared to never exposure. Early period exposure only (1985-1994) showed raised HRs for Crohn's disease (HR = 1.58, p = 0.048) and other non-specified IBD (HR = 1.38, p = 0.037). In the biomarker study, Karlshamn showed higher fecal calprotectin levels (median = 99.6 mg/kg in Karlshamn vs. 66.8 mg/kg in Ronneby, p = 0.04). A trend of decreased calprotectin with increased serum PFAS indicated higher PFAS was associated with lower degree of gut inflammation (p = 0.002). No association between serum PFAS and fecal zonulin was found. In conclusion, the present study found no consistent evidence to support PFAS exposure as a risk factor for IBD.

Serum S100A8/A9 as a Potentially Sensitive Biomarker for Inflammatory Bowel Disease

BACKGROUND

The clinical significance of human S100A8/A9 (h-S100A8/A9) in patients with inflammatory bowel disease (IBD) is poorly understood.

OBJECTIVE

To clarify whether serum S100A8/A9 is a sensitive biomarker for IBD.

METHODS

Serum specimens from outpatients with IBD (n = 101) and healthy volunteers (HVs) (n = 101) were used in this study. Enzyme-linked immunosorbent assays for h-S100A8/A9 and inflammatory cytokines were performed using these specimens. Further, correlation analysis was performed to investigate the significance of h-S100A8/A9 fluctuation in patients with IBD.

RESULTS

The average of serum h-S100A8/A9 concentration in outpatients with IBD was significantly higher than that in HVs. The concentration of h-S100A8/A9 in patients with IBD was barely correlated with that of CRP and inflammatory cytokines. Despite that finding, the serum level of h-S100A8/A9 in patients with ulcerative colitis (UC) was correlated with the severity of IBD, compared with other inflammatory proteins.

CONCLUSION

Serum h-S100A8/A9 is superior to CRP as a sensitive biomarker for IBD.

Pathological roles of MRP14 in anemia and splenomegaly during experimental visceral leishmaniasis

Myeloid-related protein 14 (MRP14) belongs to the S100 calcium-binding protein family and is expressed in neutrophils and inflammatory macrophages. Increase in the number of MRP14+ cells or serum level of MRP14 is associated with various diseases such as autoimmune diseases and infectious diseases, suggesting the involvement of the molecule in pathogenesis of those diseases. In this study, to examine the pathological involvement of MRP14 during cutaneous and visceral leishmaniasis, wild-type (WT) and MRP14 knockout (MRP14KO) mice were infected with Leishmania major and L. donovani. Increase in the number of MRP14+ cells at the infection sites in wild-type mice was commonly found in the skin during L. major infection as well as the spleen and liver during L. donovani infection. In contrast, the influence of MRP14 to the pathology seemed different between the two infections. MRP14 depletion exacerbated the lesion development and ulcer formation in L. major infection. On the other hand, the depletion improved anemia and splenomegaly but not hepatomegaly at 24 weeks of L. donovani infection. These results suggest that, distinct from its protective role in CL, MRP14 is involved in exacerbation of some symptoms during VL.

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.

Comparative proteomes change and possible role in different pathways of microRNA-21a-5p in a mouse model of spinal cord injury

Our previous study found that microRNA-21a-5p (miR-21a-5p) knockdown could improve the recovery of motor function after spinal cord injury in a mouse model, but the precise molecular mechanism remains poorly understood. In this study, a modified Allen's weight drop was used to establish a mouse model of spinal cord injury. A proteomics approach was used to understand the role of differential protein expression with miR-21a-5p knockdown, using a mouse model of spinal cord injury without gene knockout as a negative control group. We found that after introducing miR-21a-5p knockdown, proteins that played an essential role in the regulation of inflammatory processes, cell protection against oxidative stress, cell redox homeostasis, and cell maintenance were upregulated compared with the negative control group. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis identified enriched pathways in both groups, such as the oxidative phosphorylation pathway, which is relevant to Parkinson's disease, Huntington's disease, Alzheimer's disease, and cardiac muscle contraction. We also found that miR-21a-5p could be a potential biomarker for amyotrophic lateral sclerosis, as miR-21a-5p becomes deregulated in this pathway. These results indicate successful detection of some important proteins that play potential roles in spinal cord injury. Elucidating the relationship between these proteins and the recovery of spinal cord injury will provide a reference for future research of spinal cord injury biomarkers. All experimental procedures and protocols were approved by the Experimental Animal Ethics Committee of Shandong University of China on March 5, 2014.

Exploring Iron Withholding by the Innate Immune Protein Human Calprotectin

Calprotectin (CP) is a versatile player in the metal-withholding innate immune response, a process termed "nutritional immunity." CP is a heterooligomer of the polypeptides S100A8 and S100A9 and houses two transition-metal-binding sites at its S100A8/S100A9 heterodimer interface. During infection, CP is released from host cells and sequesters "bioavailable" transition metal ions in the extracellular space, thereby preventing microbial acquisition of these essential nutrients. For many years, the role of CP in nutritional immunity was interpreted in the contexts of Mn(II) and Zn(II) limitation, but recent work has broadened our understanding of its contributions to this process. We uncovered that CP provides a form of nutritional immunity that has previously received little attention: the battle between host and microbe for ferrous iron (Fe(II)). In this Account, we present our current understanding of Fe(II) coordination by CP and its role in Fe(II) withholding as well as considerations for future discovery. Nutritional immunity was first described in the context of host-microbe competition for ferric iron (Fe(III)). The battle for Fe(II) has received comparably little attention because the abundance of Fe(II) at infection sites and the importance of Fe(II) acquisition for microbial pathogenesis were recognized only recently. Several years ago, we discovered that human CP sequesters Fe(II) at its His6 site with subpicomolar affinity and thus hypothesized that it provides a means for Fe(II) limitation by the host during microbial infection. Fe(II) coordination by CP is unprecedented in biology because of its novel hexahistidine coordination sphere and its high-affinity binding, which surpasses that of other known Fe(II)-binding proteins. CP is also capable of shifting the Fe redox equilibrium by stabilizing Fe(II) in aerobic solution and can thereby sequester Fe in both reducing and nonreducing environments. These coordination chemistry studies allowed us to hypothesize that CP provides a means for Fe(II) limitation by the host during microbial infection. While investigating this putative Fe(II)-sequestering function, we discovered that CP withholds Fe from diverse bacterial pathogens. Recent studies by our lab and others of the bacterial pathogens Pseudomonas aeruginosa and Acinetobacter baumannii have shown that, by preventing sufficient Fe acquisition, CP induces Fe starvation responses in these organisms. As a result, CP affects bacterial virulence and metabolism. We also elucidated a complex interplay between CP and secondary metabolites produced by P. aeruginosa during the competition for Fe. Our work provides a foundation for understanding how CP affects Fe homeostasis during microbial infection. We believe that understanding how bacterial physiology is altered when challenged with Fe(II) withholding by CP will likely reveal crucial determinants of bacterial survival within the host.

XIST/miR-376c-5p/OPN axis modulates the influence of proinflammatory M1 macrophages on osteoarthritis chondrocyte apoptosis

The inflammatory microenvironment in the joints is one of the critical issues during osteoarthritis (OA) and also the main factor that may aggravate symptoms. Under inflammatory microenvironment, M1 macrophages are activated and produce large numbers of proinflammatory mediators, leading to the production of degradative enzymes, the disturbance of chondrocyte apoptosis and cartilage catabolic processes, and finally the deterioration of OA. In the present study, we reveal that the overexpression of osteopontin (OPN), a cytokine, and a matrix protein involved in arthritis and chondrocyte apoptosis in OA, could exacerbate the inflammatory microenvironment in OA via promoting the production of proinflammation cytokines and the levels of degradative enzymes in M1 macrophages, therefore, enhancing the cytotoxicity of M1 macrophage on chondrocytes. XIST expression significantly increases in OA tissue specimens. XIST serves as a competing endogenous RNA for miR-376c-5p to compete with OPN for miR-376c-5p binding, thus counteracting miR-376c-5p-mediated OPN suppression. XIST knockdown could improve the inflammatory microenvironment in OA via acting on M1 macrophages, subsequently affecting the apoptosis of cocultured chondrocytes. miR-376c-5p inhibition exerts an opposing effect on M1 macrophages and cocultured chondrocytes, as well as significantly reverses the effect of XIST knockdown. As a further confirmation, XIST and OPN mRNA expression significantly increased in OA tissues and was positively correlated in tissue samples. In summary, we provide a novel mechanism of macrophages and the inflammatory microenvironment affecting chondrocyte apoptosis. XIST and OPN might be potential targets for OA treatment, which needs further in vivo experimental confirmation.

A subset of calcium-binding S100 proteins show preferential heterodimerization

The assembly of proteins into dimers and oligomers is a necessary step for the proper function of transcription factors, muscle proteins, and proteases. In uncontrolled states, oligomerization can also contribute to illnesses such as Alzheimer's disease. The S100 protein family is a group of dimeric proteins that have important roles in enzyme regulation, cell membrane repair, and cell growth. Most S100 proteins have been examined in their homodimeric state, yet some of these important proteins are found in similar tissues implying that heterodimeric molecules can also be formed from the combination of two different S100 members. In this work, we have established co-expression methods in order to identify and quantify the distribution of homo- and heterodimers for four specific pairs of S100 proteins in their calcium-free states. The split GFP trap methodology was used in combination with other GFP variants to simultaneously quantify homo- and heterodimeric S100 proteins in vitro and in living cells. For the specific S100 proteins examined, NMR, mass spectrometry, and GFP trap experiments consistently show that S100A1:S100B, S100A1:S100P, and S100A11:S100B heterodimers are the predominant species formed compared to their corresponding homodimers. We expect the tools developed here will help establish the roles of S100 heterodimeric proteins and identify how heterodimerization might alter the specificity for S100 protein action in cells.

Alarmins of the S100-Family in Juvenile Autoimmune and Auto-Inflammatory Diseases

Autoimmune and auto-inflammatory diseases in children are causing chronic inflammation, organ damage, and pain. Although several options for treatment are nowadays available a significant number of patients does not respond sufficiently to current therapies. In these diseases inflammatory processes are triggered by numerous exogenous and endogenous factors. There is now increasing evidence that especially a novel family of pro-inflammatory molecules, named alarmins, play a significant role in inflammatory processes underlying these diseases. Alarmins are endogenous proteins released during stress reactions that confer inflammatory signaling via Pattern Recognition Receptors (PRRs), like the Toll-like receptor 4 (TLR4). The most abundant alarmins in juvenile rheumatic diseases belong to the family of pro-inflammatory calcium-binding S100-proteins. In this review we will give a general introduction in S100-biology. We will demonstrate the functional relevance of these proteins in animal models of autoimmune and auto-inflammatory diseases. We will show the expression patterns of S100-alarmins and correlation to disease activity in different forms of juvenile idiopathic arthritis, auto-inflammatory diseases, and systemic autoimmune disorders. Finally, we will discuss the clinical use of S100-alarmins as biomarkers for diagnosis and monitoring of rheumatic diseases in children and will point out potential future therapeutic approaches targeting inflammatory effects mediated by S100-alarmins.

Systemic calprotectin and chronic inflammatory rheumatic diseases

Calprotectin is a calcium binding protein produced by neutrophils and monocytes locally at the site of inflammation in order to trigger the innate immunity receptors. This unique characteristic makes it a good proxy for evaluation of local inflammation in chronic inflammatory rheumatic diseases. Complete data suggest, in inflammatory rheumatic diseases, a relevant role of calprotectin in the inflammatory process. The interest of serum or plasma calprotectin dosage has been studied intensively, in the current years, especially in rheumatoid arthritis, spondyloarthritis, juvenile idiopathic arthritis and ANCA associated vasculitis. Calprotectin seems to be a great candidate as biomarker to assess and monitor disease activity, to predict structural progression or response to the treatment. Calprotectin showed its ability to predict radiological progression in rheumatoid arthritis and ankylosing spondylitis. Serum calprotectin can predict the risk of relapse in ANCA associated vasculitis and the risk of inflammatory bowel disease in spondyloarthritis. Nevertheless, studies report controversial result requiring replication in other large cohort. The lack of assay standardization between studies is a problem to replicate and compare studies. In this review, we discuss on the interest of systemic calprotectin in chronic inflammatory rheumatic disease as a diagnostic, activity or prognostic biomarker.

S100A9 regulates cisplatin chemosensitivity of squamous cervical cancer cells and related mechanism

Objective

Our previous research has shown that the expression of S100 calcium-binding protein A9 (S100A9) in tumor cells was associated with neoadjuvant chemotherapy sensitivity in cervical squamous cell carcinoma. In the present study, we altered the expression of S100A9 through infecting lentivirus, investigated its effect on the chemosensitivity to cisplatin of cervical cancer cells and then made a primary exploration of the involved mechanism.

Materials and methods

Lentivirus was employed to upregulate and downregulate S100A9 expression in SiHa cells. The protein expression level of apoptotic-related proteins Bcl-2 and Bax, drug resistance-related proteins multiple drug resistance protein 1 (MRP1), P glycoprotein (P-gp), glutathione-S-transferase-π (GST-π), lung resistance-related protein (LRP), and FOXO1 signaling pathway related proteins was detected by Western blot. The CCK-8 assay was used to examine chemosensitivity to cisplatin, and the proportion of apoptosis cells was analyzed by the flow cytometry.

Results

S100A9 overexpression could obviously increase the IC50 value of SiHa cells to cisplatin and decrease the apoptosis rate induced by cisplatin. Downregulation of S100A9 led to the opposite results. In S100A9 overexpression SiHa cells, the expression level of Bcl-2, LRP, GST-π, p-AKT, p-ERK, p-FOXO1, and Nanog was significantly increased, while FOXO1 expression was decreased. The opposite results were observed in S100A9 knockdown SiHa cells.

Conclusion

Downregulation of S100A9 could significantly increase apoptosis rate, resulting in enhancing sensitivity of SiHa cells to cisplatin, which may be related to Bcl-2, GST-π, and LRP protein and by altering the AKT/ERK-FOXO1-Nanog signaling pathway.

The role of zinc in calprotectin expression in human myeloid cells

Elevated levels of calprotectin and other inflammatory mediators have been observed in inflammatory diseases paralleling serum hypozincemia. While a role of zinc in the regulation of tumor necrosis factor α, interleukin (IL)-1β and IL-6 expression has been established, the direct interrelation of zinc and calprotectin (S100A8/S100A9 heterodimer) expression is so far missing. In the present study, we analyzed mRNA and protein levels of S100A8 and S100A9 in monocytic Mono Mac (MM)1 and early myeloid THP-1 and U937 cells to elucidate the effect of zinc deficiency on their expression. We could depict that zinc deficiency alone enhances mRNA and protein expression of calprotectin in myeloid cells, independently from maturity stage. Moreover, pre-existing zinc deficiency augmented lipopolysaccharide (LPS)-induced calprotectin expression in CD14⁺ MM1, but not in CD14^- U937 or CD14^- THP-1 cells. Zinc deficiency and LPS seem therefore to activate different intracellular pathways. Our findings suggest that zinc does not only regulate the activity of calprotectin but also its expression by human myeloid cells.

Transcriptional profiling reveals monocyte-related macrophages phenotypically resembling DC in human intestine

The tissue dendritic cell (DC) compartment is heterogeneous, and the ontogeny and functional specialization of human tissue conventional DC (cDC) subsets and their relationship with monocytes is unresolved. Here we identify monocyte-related CSF1R⁺Flt3^- antigen presenting cells (APCs) that constitute about half of the cells classically defined as SIRPα⁺ DCs in the steady-state human small intestine. CSF1R⁺Flt3^- APCs express calprotectin and very low levels of CD14, are transcriptionally related to monocyte-derived cells, and accumulate during inflammation. CSF1R⁺Flt3^- APCs show typical macrophage characteristics functionally distinct from their Flt3⁺ cDC counterparts: under steady-state conditions they excel at antigen uptake, have a lower migratory potential, and are inefficient activators of naïve T cells. These results have important implications for the understanding of the ontogenetic and functional heterogeneity within human tissue DCs and their relation to the monocyte lineage.

Multifarious diagnostic possibilities of the S100 protein family: predominantly in pediatrics and neonatology

BACKGROUND

Numerous articles related to S100 proteins have been recently published. This review aims to introduce this large protein family and its importance in the diagnostics of many pathological conditions in children and adults.

DATA SOURCES

Based on original publications found in database systems, we summarize the current knowledge about the S100 protein group and highlight the most important proteins with focus on pediatric use.

RESULTS

The S100 family is composed of Ca²⁺ and Zn²⁺ binding proteins, which are present only in vertebrates. Some of these proteins can be used as diagnostic markers in cardiology (S100A1, S100A12), oncology (S100A2, S100A5, S100A6, S100A14, S100A16, S100P, S100B), neurology (S100B), rheumatology (S100A8/A9, S100A4, S100A6, and S100A12), nephrology and infections (S100A8, S100A9, S100A8/A9, S100A12). The most useful S100 proteins in pediatrics are S100A8, S100A9, heterodimers S100A8/A9, S100B and S100A12.

CONCLUSIONS

The S100 family members are promising biomarkers and provide numerous possibilities for implementation into clinical practice to optimize the differential diagnostic process.

Calcium-Binding Proteins S100A8 and S100A9: Investigation of Their Immune Regulatory Effect in Myeloid Cells

High expression levels of the calcium-binding proteins S100A8 and S100A9 in myeloid cells in kidney transplant rejections are associated with a favorable outcome. Here we investigated the myeloid cell subset expressing these molecules, and their function in inflammatory reactions. Different monocyte subsets were sorted from buffy coats of healthy donors and investigated for S100A8 and S100A9 expression. To characterize S100A9high and S100A9low subsets within the CD14+ classical monocyte subset, intracellular S100A9 staining was combined with flow cytometry (FACS) and qPCR profiling. Furthermore, S100A8 and S100A9 were overexpressed by transfection in primary monocyte-derived macrophages and the THP-1 macrophage cell line to investigate the functional relevance. Expression of S100A8 and S100A9 was primarily found in classical monocytes and to a much lower extent in intermediate and non-classical monocytes. All S100A9+ cells expressed human leukocyte antigen—antigen D related (HLA-DR) on their surface. A small population (<3%) of CD14+ CD11b+ CD33+ HLA-DR− cells, characterized as myeloid derived suppressor cells (MDSCs), also expressed S100A9 to high extent. Overexpression of S100A8 and S00A9 in macrophages led to enhanced extracellular reactive oxygen species (ROS) production, as well as elevated mRNA expression of anti-inflammatory IL-10. The results suggest that the calcium-binding proteins S100A8 and S100A9 in myeloid cells have an immune regulatory effect.

Transition Metal Sequestration by the Host-Defense Protein Calprotectin

In response to microbial infection, the human host deploys metal-sequestering host-defense proteins, which reduce nutrient availability and thereby inhibit microbial growth and virulence. Calprotectin (CP) is an abundant antimicrobial protein released from neutrophils and epithelial cells at sites of infection. CP sequesters divalent first-row transition metal ions to limit the availability of essential metal nutrients in the extracellular space. While functional and clinical studies of CP have been pursued for decades, advances in our understanding of its biological coordination chemistry, which is central to its role in the host-microbe interaction, have been made in more recent years. In this review, we focus on the coordination chemistry of CP and highlight studies of its metal-binding properties and contributions to the metal-withholding innate immune response. Taken together, these recent studies inform our current model of how CP participates in metal homeostasis and immunity, and they provide a foundation for further investigations of a remarkable metal-chelating protein at the host-microbe interface and beyond.

Blocking the interaction between S100A9 protein and RAGE V domain using S100A12 protein

The proteins S100A9 and S100A12 are associated with the human S100 calcium-binding protein family. These proteins promote interaction with target proteins and alter their conformation when they bind to calcium ions in EF-hand motifs. The V domain of RAGE (Receptor for Advanced Glycation End products) is crucial for S100A9 binding. The binding of RAGE with S100 family proteins aids in cell proliferation. In this report, we demonstrate that S100A12 protein hinders the binding of S100A9 with the RAGE V-domain. We used fluorescence and NMR spectroscopy to analyze the interaction of S100A9 with S100A12. The binary complex models of S100A9-S100A12 were developed using data obtained from 1H-15N HSQC NMR titrations and the HADDOCK program. We overlaid the complex models of S100A9-S100A12 with the same orientation of S100A9 and the RAGE V-domain. This complex showed that S100A12 protein blocks the interaction between S100A9 and the RAGE V-domain. It means S100A12 may be used as an antagonist for S100A9. The results could be favorable for developing anti-cancer drugs based on S100 family proteins.

Extracellular Matrix Metalloproteinase Inducer EMMPRIN (CD147) in Cardiovascular Disease

The receptor EMMPRIN is involved in the development and progression of cardiovascular diseases and in the pathogenesis of myocardial infarction. There are several binding partners of EMMPRIN mediating the effects of EMMPRIN in cardiovascular diseases. EMMPRIN interaction with most binding partners leads to disease progression by mediating cytokine or chemokine release, the activation of platelets and monocytes, as well as the formation of monocyte-platelet aggregates (MPAs). EMMPRIN is also involved in atherosclerosis by mediating the infiltration of pro-inflammatory cells. There is also evidence that EMMPRIN controls energy metabolism of cells and that EMMPRIN binding partners modulate intracellular glycosylation and trafficking of EMMPRIN towards the cell membrane. In this review, we systematically discuss these multifaceted roles of EMMPRIN and its interaction partners, such as Cyclophilins, in cardiovascular disease.

S100 Proteins As an Important Regulator of Macrophage Inflammation

The S100 proteins, a family of calcium-binding cytosolic proteins, have a broad range of intracellular and extracellular functions through regulating calcium balance, cell apoptosis, migration, proliferation, differentiation, energy metabolism, and inflammation. The intracellular functions of S100 proteins involve interaction with intracellular receptors, membrane protein recruitment/transportation, transcriptional regulation and integrating with enzymes or nucleic acids, and DNA repair. The S100 proteins could also be released from the cytoplasm, induced by tissue/cell damage and cellular stress. The extracellular S100 proteins, serving as a danger signal, are crucial in regulating immune homeostasis, post-traumatic injury, and inflammation. Extracellular S100 proteins are also considered biomarkers for some specific diseases. In this review, we will discuss the multi-functional roles of S100 proteins, especially their potential roles associated with cell migration, differentiation, tissue repair, and inflammation.

Role of Monocyte/Macrophages during HIV/SIV Infection in Adult and Pediatric Acquired Immune Deficiency Syndrome

Monocytes/macrophages are a diverse group of cells that act as first responders in innate immunity and then as mediators for adaptive immunity to help clear infections. In performing these functions, however, the macrophage inflammatory responses can also contribute to pathogenesis. Various monocyte and tissue macrophage subsets have been associated with inflammatory disorders and tissue pathogeneses such as occur during HIV infection. Non-human primate research of simian immunodeficiency virus (SIV) has been invaluable in better understanding the pathogenesis of HIV infection. The question of HIV/SIV-infected macrophages serving as a viral reservoir has become significant for achieving a cure. In the rhesus macaque model, SIV-infected macrophages have been shown to promote pathogenesis in several tissues resulting in cardiovascular, metabolic, and neurological diseases. Results from human studies illustrated that alveolar macrophages could be an important HIV reservoir and humanized myeloid-only mice supported productive HIV infection and viral persistence in macrophages during ART treatment. Depletion of CD4+ T cells is considered the primary cause for terminal progression, but it was reported that increasing monocyte turnover was a significantly better predictor in SIV-infected adult macaques. Notably, pediatric cases of HIV/SIV exhibit faster and more severe disease progression than adults, yet neonates have fewer target T cells and generally lack the hallmark CD4+ T cell depletion typical of adult infections. Current data show that the baseline blood monocyte turnover rate was significantly higher in neonatal macaques compared to adults and this remained high with disease progression. In this review, we discuss recent data exploring the contribution of monocytes and macrophages to HIV/SIV infection and progression. Furthermore, we highlight the need to further investigate their role in pediatric cases of infection.

Relationship between serum calprotectin (S100A8/9) and clinical, laboratory and ultrasound parameters of disease activity in rheumatoid arthritis: A large cohort study

Background

Calprotectin may be a sensitive biomarker of rheumatoid arthritis (RA) disease activity.

Objectives

In the current study, we investigated whether calprotectin is a better biomarker than CRP for predicting clinical activity and ultrasound parameters in patients with RA.

Methods

A total of 160 patients with RA underwent clinical (swollen joint count—SJC, tender joint count—TJC, Disease Activity Score—DAS28, Clinical Disease Activity Index—CDAI, and simplified Disease Activity Index—SDAI) and ultrasound (German US7) examination. Clinical and laboratory measures were correlated with ultrasound findings using Spearman´s correlation coefficient. Differences in serum calprotectin levels in patients with variable disease activity according to the DAS28-ESR and CDAI scores were assessed using ANOVA. Multivariate regression analysis was used to determine the predictive values of calprotectin, CRP and SJC for CDAI and PD US synovitis scores.

Results

Serum calprotectin was significantly associated with DAS28-ESR (r = 0.321, p<0.001), DAS28-CRP (r = 0.346, p<0.001), SDAI (r = 0.305, p<0.001), CDAI (r = 0.279, p<0.001) scores and CRP levels (r = 0.556, p<0.001). Moreover, calprotectin was significantly correlated with GS (r = 0.379, p<0.001) and PD synovitis scores (r = 0.419, p<0.001). The multivariate regression analysis showed that calprotectin is a better predictor of the CDAI score and PD US synovitis than CRP.

Conclusions

The results of this study support an additional role of calprotectin in assessing inflammatory activity in patients with RA.

Calprotectin as a marker of inflammation in patients with early rheumatoid arthritis

Objectives

Calprotectin is an inflammatory marker of interest in rheumatoid arthritis (RA). We evaluated whether the level of calprotectin was associated with disease activity, and if it was predictive of treatment response and radiographic progression in patients with early RA.

Methods

Plasma from disease-modifying antirheumatic drug (DMARD)-naïve patients with RA fulfilling 2010 American College of Rheumatology/European League Against Rheumatism classification criteria with symptom duration <2 years was analysed for calprotectin at baseline, and after 1, 3 and 12 months. All patients received treat-to-target therapy, as part of a randomised controlled strategy trial (ARCTIC). The association between calprotectin, erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) and measures of disease activity were assessed by correlations. We used likelihood ratios and logistic regression models to assess the predictive value of the baseline inflammatory markers for treatment response and radiographic damage.

Results

215 patients were included: 61% female, 82% anti-citrullinated peptide antibody positive, mean (SD) age 50.9 (13.7) years and median (25, 75 percentile) symptom duration 5.8 (2.8, 10.5) months. Calprotectin was significantly correlated with Clinical Disease Activity Index (r=0.32), ESR (r=0.50) and ultrasonography power Doppler (r=0.42) before treatment onset. After 12 months of treatment, calprotectin, but not ESR and CRP, was significantly correlated with power Doppler (r=0.27). Baseline levels of calprotectin, ESR and CRP were not predictive of treatment response, but high levels of calprotectin were associated with radiographic progression in multivariate models.

Conclusions

Calprotectin was correlated with inflammation assessed by ultrasound before and during DMARD treatment, and was also associated with radiographic progression. The data support that calprotectin may be of interest as an inflammatory marker when assessing disease activity in different stages of RA.

Trial registration number

NCT01205854; Post-results.

Elevated S100A8 protein expression in breast cancer cells and breast tumor stroma is prognostic of poor disease outcome

PURPOSE

Elevated S100A8 expression has been observed in cancers of the bladder, esophagus, colon, ovary, and breast. S100A8 is expressed by breast cancer cells as well as by infiltrating immune and myeloid cells. Here we investigate the association of elevated S100A8 protein expression in breast cancer cells and in breast tumor stroma with survival outcomes in a cohort of breast cancer patients.

PATIENTS AND METHODS

Tissue microarrays (TMA) were constructed from breast cancer specimens from 417 patients with stage I-III breast cancer treated at the University of Michigan Comprehensive Cancer Center between 2004 and 2006. Representative regions of non-necrotic tumor and distant normal tissue from each patient were used to construct the TMA. Automated quantitative immunofluorescence (AQUA) was used to measure S100A8 protein expression, and samples were scored for breast cancer cell and stromal S100A8 expression. S100A8 staining intensity was assessed as a continuous value and by exploratory dichotomous cutoffs. Associations between breast cancer cell and stromal S100A8 expression with disease-free survival and overall survival were determined using the Kaplan-Meier method and Cox proportional hazard models.

RESULTS

High breast cancer cell S100A8 protein expression (as indicated by AQUA scores), as a continuous measure, was a significant prognostic factor for OS [univariable hazard ratio (HR) 1.24, 95% confidence interval (CI) 1.00-1.55, p = 0.05] in this patient cohort. Exploratory analyses identified optimal S100A8 AQUA score cutoffs within the breast cancer cell and stromal compartments that significantly separated survival curves for the complete cohort. Elevated breast cancer cell and stromal S100A8 expression, indicated by higher S100A8 AQUA scores, significantly associates with poorer breast cancer outcomes, regardless of estrogen receptor status.

CONCLUSIONS

Elevated breast cancer cell and stromal S1008 protein expression are significant indicators of poorer outcomes in early stage breast cancer patients. Evaluation of S100A8 protein expression may provide additional prognostic information beyond traditional breast cancer prognostic biomarkers.

Association of Serum Calprotectin (S100A8/A9) Level With Disease Relapse in Proteinase 3-Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

OBJECTIVE

S100A8/A9 (calprotectin) has shown promise as a biomarker for predicting relapse in antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). This study was undertaken to investigate serum S100A8/A9 level as a biomarker for predicting future relapse in a large cohort of patients with severe AAV.

METHODS

Serum levels of S100A8/A9 were measured at baseline and months 1, 2, and 6 following treatment initiation in 144 patients in the Rituximab in ANCA-Associated Vasculitis trial (cyclophosphamide/azathioprine versus rituximab [RTX] for induction of remission) in whom complete remission was attained.

RESULTS

Patients were divided into 4 groups: proteinase 3 (PR3)-ANCA with relapse (n = 37), PR3-ANCA without relapse (n = 56), myeloperoxidase (MPO)-ANCA with relapse (n = 6), and MPO-ANCA without relapse (n = 45). Serum S100A8/A9 level decreased in all groups during the first 6 months of treatment. The percentage reduction from baseline to month 2 was significantly different between patients who experienced a relapse and those who did not in the PR3-ANCA group (P = 0.046). A significantly higher risk of relapse was associated with an increase in S100A8/A9 level between baseline and month 2 (P = 0.0043) and baseline and month 6 (P = 0.0029). Subgroup analysis demonstrated that patients treated with RTX who had increased levels of S100A8/A9 were at greatest risk of future relapse (P = 0.028).

CONCLUSION

An increase in serum S100A8/A9 level by month 2 or 6 compared to baseline identifies a subgroup of PR3-ANCA patients treated with RTX who are at higher risk of relapse by 18 months. Since RTX is increasingly used for remission induction in PR3-ANCA-positive patients experiencing a relapse, S100A8/A9 level may assist in identifying those patients requiring more intensive or prolonged treatment.

S100-alarmins: potential therapeutic targets for arthritis

INTRODUCTION

In arthritis, inflammatory processes are triggered by numerous factors that are released from joint tissues, promoting joint destruction and pathological progression. During inflammation, a novel family of pro-inflammatory molecules called alarmins is released, amplifying inflammation and joint damage. Areas covered: With regard to the role of the alarmins S100A8 and S100A9 in the pathogenesis of arthritis, recent advances and the future prospects in terms of therapeutic implications are considered. Expert opinion: There is still an urgent need for novel treatment strategies addressing the local mechanisms of joint inflammation and tissue destruction, offering promising therapeutic alternatives. S100A8 and S100A9, which are the most up-regulated alarmins during arthritis, are endogenous triggers of inflammation, defining these proteins as promising targets for local suppression of arthritis. In murine models, the blockade of S100A8/S100A9 ameliorates inflammatory processes, including arthritis, and there are several lines of evidence that S100-alarmins may already be targeted in therapeutic approaches in man.

Calprotectin in serum and zonulin in serum and feces are elevated after introduction of a diet with lower carbohydrate content and higher fiber, fat and protein contents

Calprotectin is a marker of inflammation and zonulin is a marker of intestinal permeability. Diets with lower carbohydrate content and higher contents of fat, fiber and protein, e.g., Okinawan-based diet, are considered to reduce inflammation and intestinal permeability. The aim of the present study was to evaluate calprotectin and zonulin levels in serum and feces after intervention with an Okinawan-based Nordic diet. Thirty patients (17 women) with type 2 diabetes, mean age 57.5±8.2 years, BMI 29.9±4.1 kg/m², were served the diet during 12 weeks, and were followed for another 16 weeks. Anthropometric and metabolic parameters were registered. Fasting levels of calprotectin and zonulin in serum and feces, and hormones in plasma, were measured by Luminex or ELISA before study start and after 12 and 28 weeks. Calprotectin in serum tended to be increased (P=0.074) after 12 weeks. Zonulin in serum and feces were elevated after 12 weeks (P=0.019 vs. P<0.001), and remained elevated in serum after 28 weeks (P=0.014). In contrast to baseline, there was a correlation between calprotectin and zonulin in serum and feces after dietary intervention (P=0.025 vs. P=0.079). Energy percentage of protein in breakfast correlated with serum calprotectin (P=0.008) and tended to correlate with serum zonulin (P=0.059). Calprotectin in serum tended to be elevated, and zonulin in serum and feces are elevated after introduction of an Okinawan-based Nordic diet. These biomarkers correlate with energy percentage of protein.

S100 Proteins As an Important Regulator of Macrophage Inflammation

The S100 proteins, a family of calcium-binding cytosolic proteins, have a broad range of intracellular and extracellular functions through regulating calcium balance, cell apoptosis, migration, proliferation, differentiation, energy metabolism, and inflammation. The intracellular functions of S100 proteins involve interaction with intracellular receptors, membrane protein recruitment/transportation, transcriptional regulation and integrating with enzymes or nucleic acids, and DNA repair. The S100 proteins could also be released from the cytoplasm, induced by tissue/cell damage and cellular stress. The extracellular S100 proteins, serving as a danger signal, are crucial in regulating immune homeostasis, post-traumatic injury, and inflammation. Extracellular S100 proteins are also considered biomarkers for some specific diseases. In this review, we will discuss the multi-functional roles of S100 proteins, especially their potential roles associated with cell migration, differentiation, tissue repair, and inflammation.

Serum Calprotectin Discriminates Subclinical Disease Activity from Ultrasound-Defined Remission in Patients with Rheumatoid Arthritis in Clinical Remission

OBJECTIVE

Clinical remission in some patients with rheumatoid arthritis (RA) may be associated with ongoing synovial inflammation that is not always detectable on clinical examination or reflected by laboratory tests but can be visualized by musculoskeletal ultrasound. The goal of our study was to determine the levels of serum calprotectin, a major leukocyte protein, in patients with RA in clinical remission and to investigate the ability of serum calprotectin levels to distinguish patients in ultrasound-defined remission from those with residual ultrasound subclinical inflammation.

METHODS

Seventy RA patients in clinical remission underwent clinical and ultrasound examination. Ultrasound examination was performed according to the German US7 score. Ultrasound remission was defined as grey scale (GS) range 0-1 and power Doppler (PD) range 0. The levels of serum calprotectin and C-reactive protein (CRP) were determined. The discriminatory capacity of calprotectin and CRP in detecting residual ultrasound inflammation was assessed using ROC curves.

RESULTS

The total number of patients fulfilling the DAS28-ESR, DAS28-CRP, SDAI and CDAI remission criteria was 58, 67, 32 and 31, respectively. Residual synovial inflammation was found in 58-67% of the patients who fulfilled at least one set of clinical remission criteria. Calprotectin levels were significantly higher in patients with residual synovial inflammation than in those with ultrasound-defined remission (mean 2.5±1.3 vs. 1.7±0.8 μg/mL, p<0.005). Using ultrasound-defined remission criteria, calprotectin had an AUC of 0.692, p<0.05 using DAS28-ESR remission criteria and an AUC of 0.712, p<0.005 using DAS28-CRP remission criteria. Calprotectin correctly distinguished ultrasound remission from subclinical activity in 70% of patients. CRP (AUC DAS28-ESR = 0.494, p = NS; AUC DAS28-CRP = 0.498, p = NS) had lower and insignificant discriminatory capacity.

CONCLUSION

The present study demonstrates the potential of calprotectin to distinguish RA patients in both clinical and ultrasound-defined remission from patients in clinical remission but with residual subclinical disease activity.

S100A8 promotes migration and infiltration of inflammatory cells in acute anterior uveitis

Uveitis, the pathologic condition of inflammation of the uvea, frequently leads to severe vision loss and blindness. S100A8 is a calcium-binding protein which mainly expresses in granulocytes and monocytes and plays a prominent role in the regulation of inflammatory processes and immune response. Here, we determined the role of S100A8-positive cells in acute anterior uveitis (AAU) and keratitis. In rat models of endotoxin (lipopolisaccharide, LPS) -induced uveitis (EIU) and keratitis, S100A8-positive granulocytes and monocytes increased significantly in the iris-ciliary body and cornea as well as in the blood. Interestingly, Glucocorticoids slightly increased S100A8 levels in leukocytes, but reduced its presence significantly in the iris-ciliary body after LPS injection. Moreover, inhibition of NF-kB activation remarkably suppressed both progression of AAU and total S100A8 levels in leukocytes and the iris-ciliary body after LPS administration. Additionally, S100A8 protein level was also found to be elevated in the serum of AAU patients parallel with the progression of AAU through the designated clinical stages. Thus, S100A8 plays a pivotal role in the processes of AAU through involvement in migration and infiltration of S100A8-positive cells. Our findings suggest that serum levels of S100A8 protein can be used to monitor inflammatory activity in AAU.

HMGB1, IL-1α, IL-33 and S100 proteins: dual-function alarmins

Our immune system is based on the close collaboration of the innate and adaptive immune systems for the rapid detection of any threats to the host. Recognition of pathogen-derived molecules is entrusted to specific germline-encoded signaling receptors. The same receptors have now also emerged as efficient detectors of misplaced or altered self-molecules that signal tissue damage and cell death following, for example, disruption of the blood supply and subsequent hypoxia. Many types of endogenous molecules have been shown to provoke such sterile inflammatory states when released from dying cells. However, a group of proteins referred to as alarmins have both intracellular and extracellular functions which have been the subject of intense research. Indeed, alarmins can either exert beneficial cell housekeeping functions, leading to tissue repair, or provoke deleterious uncontrolled inflammation. This group of proteins includes the high-mobility group box 1 protein (HMGB1), interleukin (IL)-1α, IL-33 and the Ca²⁺-binding S100 proteins. These dual-function proteins share conserved regulatory mechanisms, such as secretory routes, post-translational modifications and enzymatic processing, that govern their extracellular functions in time and space. Release of alarmins from mesenchymal cells is a highly relevant mechanism by which immune cells can be alerted of tissue damage, and alarmins play a key role in the development of acute or chronic inflammatory diseases and in cancer development.

Elevated S100A9 expression in tumor stroma functions as an early recurrence marker for early-stage oral cancer patients through increased tumor cell invasion, angiogenesis, macrophage recruitment and interleukin-6 production

S100A9 is a calcium-binding protein with two EF-hands and frequently deregulated in several cancer types, however, with no clear role in oral cancer. In this report, the expression of S100A9 in cancer and adjacent tissues from 79 early-stage oral cancer patients was detected by immunohistochemical staining. Although S100A9 protein was present in both tumor and stromal cells, only the early-stage oral cancer patients with high stromal expression had reduced recurrence-free survival. High stromal S100A9 expression was also significantly associated with non-well differentiation and recurrence. In addition to increasing cell migration and invasion, ectopic S100A9 expression in tumor cells promoted xenograft tumorigenesis as well as the dominant expression of myeloid cell markers and pro-inflammatory IL-6. The expression of S100A9 in one stromal component, monocytes, stimulated the aggressiveness of co-cultured oral cancer cells. We also detected the elevation of serum S100A9 levels in early-stage oral cancer patients of a separate cohort of 73 oral cancer patients. The release of S100A9 protein into extracellular milieu enhanced tumor cell invasion, transendothelial monocyte migration and angiogenic activity. S100A9-mediated release of IL-6 requires the crosstalk of tumor cells with monocytes through the activation of NF-κB and STAT-3. Early-stage oral cancer patients with both high S100A9 expression and high CD68+ immune infiltrates in stroma had shortest recurrence-free survival, suggesting the use of both S100A9 and CD68 as poor prognostic markers for oral cancer. Together, both intracellular and extracellular S100A9 exerts a tumor-promoting action through the activation of oral cancer cells and their associated stroma in oral carcinogenesis.

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.

Calprotectin: Clinical Applications in Pediatrics

As seen over the past 20 years, calprotectin has evolved as a novel, non-invasive biomarker of gastrointestinal (GI) inflammation. We present this review of calprotectin in pediatrics. This article will focus on studies using calprotectin concentrations from different body fluids to monitor inflammation in different disease states and conditions. The ultimate goal of our group is to lay down a foundation as we consider using calprotectin prospectively as a marker of intestinal inflammation that could lead to further testing and possibly a marker of preparedness for feeding. We surveyed all published studies in English of calprotectin in neonates, infants, children, and adolescents through February 2014. We will discuss calprotectin's basic properties and analysis such as characteristics, identification, presence in body fluids, and maturational development. In addition, calprotectin's use in inflammatory diseases exploring both GI and non-GI conditions will be evaluated and compared with other serum markers presently available. Finally, a summary of our findings and discussion of future work that could be undertaken in order to render calprotectin as a more useful monitoring tool to the medical research community will complete the review.

Expression of IL-1β in rhesus EAE and MS lesions is mainly induced in the CNS itself

Background

Interleukin (IL)-1β is a pro-inflammatory cytokine that plays a role in the pathogenesis of multiple sclerosis (MS) and experimental autoimmune encephalomyelitis (EAE), the animal model for MS. Yet, detailed studies on IL-1β expression in different stages of MS lesion development and a comparison of IL-1β expression in MS and EAE are lacking.

Methods

Here, we performed an extensive characterization of IL-1β expression in brain tissue of MS patients, which included different MS lesion types, and in brain tissue of rhesus macaques with EAE.

Results

In rhesus EAE brain tissue, we observed prominent IL-1β staining in MHC class II⁺ cells within perivascular infiltrates and at the edges of large demyelinating lesions. Surprisingly, staining was localized to resident microglia or differentiated macrophages rather than to infiltrating monocytes, suggesting that IL-1β expression is induced within the central nervous system (CNS). By contrast, IL-1β staining in MS brain tissue was much less pronounced. Staining was found in the parenchyma of active and chronic active MS lesions and in nodules of MHC class II⁺ microglia in otherwise normal appearing white matter. IL-1β expression was detected in a minority of the nodules only, which could not be distinguished by the expression of pro- and anti-inflammatory markers. These nodules were exclusively found in MS, and it remains to be determined whether IL-1β⁺ nodules are destined to progress into active lesions or whether they merely reflect a transient response to cellular stress.

Conclusions

Although the exact localization and relative intensity of IL-1β expression in EAE and MS is different, the staining pattern in both neuroinflammatory disorders is most consistent with the idea that the expression of IL-1β during lesion development is induced in the tissue rather than in the periphery.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0605-8) contains supplementary material, which is available to authorized users.

Urinary soluble CD163 level reflects glomerular inflammation in human lupus nephritis

BACKGROUND

In addition to classically activated macrophages that have effector roles in tissue injury, alternatively activated M2 macrophages are involved in the resolution of inflammation in animal models of kidney disease. To clarify the clinical relevance of macrophage phenotypes in human glomerular diseases, we evaluated the renal accumulation of macrophages and plasma and urine levels of CD163, an M2 marker, in lupus nephritis (LN) patients.

METHODS

Kidney biopsies and plasma and urine samples were obtained from LN patients who underwent renal biopsy between 2008 and 2012. CD163⁺, CD68⁺ and CD204⁺ cells were counted in paraffin-embedded and frozen sections. LN histological activity was evaluated semiquantitatively using the biopsy activity index. Plasma and urinary soluble CD163 (sCD163) concentrations were also measured and evaluated for their significance as potential LN biomarkers.

RESULTS

Immunohistological analysis of glomeruli from LN patients revealed that >60% of CD68⁺ macrophages had merged with CD163⁺ cells. The increased number of glomerular CD163⁺ macrophages was correlated with LN severity, as determined by the biopsy active index (r = 0.635). Urinary (u-) sCD163 level was strongly correlated with glomerular CD163⁺ cell counts and histological disease score as well as urinary monocyte chemoattractant protein 1 levels (r = 0.638 and 0.592, respectively). Furthermore, the u-sCD163 level was higher in patients with active LN than in those with other diseases.

CONCLUSIONS

Glomerular CD163⁺ macrophages are the predominant phenotype in the kidneys of lupus patients. These findings indicate that the u-sCD163 level can serve as a biomarker for macrophage-dependent glomerular inflammation in human LN.

α4-Integrin Antibody Treatment Blocks Monocyte/Macrophage Traffic to, Vascular Cell Adhesion Molecule-1 Expression in, and Pathology of the Dorsal Root Ganglia in an SIV Macaque Model of HIV-Peripheral Neuropathy

Traffic of activated monocytes into the dorsal root ganglia (DRG) is critical for pathology in HIV peripheral neuropathy. We have shown that accumulation of recently recruited (bromodeoxyuridine(+) MAC387(+)) monocytes is associated with severe DRG pathology and loss of intraepidermal nerve fibers in SIV-infected macaques. Herein, we blocked leukocyte traffic by treating animals with natalizumab, which binds to α4-integrins. SIV-infected CD8-depleted macaques treated with natalizumab either early (the day of infection) or late (28 days after infection) were compared with untreated SIV-infected animals sacrificed at similar times. Histopathology showed diminished DRG pathology with natalizumab treatment, including decreased inflammation, neuronophagia, and Nageotte nodules. Natalizumab treatment resulted in a decrease in the number of bromodeoxyuridine(+) (early), MAC387(+) (late), CD68(+) (early and late), and SIVp28(+) (late) macrophages in DRG tissues. The number of CD3(+) T lymphocytes in DRGs was not affected by natalizumab treatment. Vascular cell adhesion molecule 1, an adhesion molecule that mediates leukocyte traffic, was diminished in DRGs of all natalizumab-treated animals. These data show that blocking monocyte, but not T lymphocyte, traffic to the DRG results in decreased inflammation and pathology, supporting a role for monocyte traffic and activation in HIV peripheral neuropathy.

Beneficial Immune Effects of Myeloid-Related Proteins in Kidney Transplant Rejection

Acute rejection is a risk factor for inferior long-term kidney transplant survival. Although T cell immunity is considered the main effector in clinical acute rejection, the role of myeloid cells is less clear. Expression of S100 calcium-binding protein A8 (S100A8) and S100A9 was evaluated in 303 biopsies before and after transplantation from 190 patients. In two independent cohorts of patients with acute rejection (n = 98 and n = 11; mostly cellular rejections), high expression of S100 calcium-binding protein A8 (S100A8) and A9 (S100A9) was related to improved graft outcome. Mechanisms of action of the S100 molecules were investigated. In the graft and peripheral blood cells, S100A8 and S100A9 expression correlated with myeloid-derived suppressor markers. In line with this finding, recombinant S100A8 and S100A9 proteins inhibited maturation and the allogeneic T cell stimulatory capacity of dendritic cells. S100A9 enhanced the production of reactive oxygen species by macrophages, which suppressed T cell activity at low concentrations in the form of hydrogen peroxide. Intragraft S100A8 and S100A9 expression linked to reduced expression of T cell immunity and tissue injury markers and higher expression of immune regulatory molecules. This study sheds new light on the importance of myeloid cell subsets in directing the outcome of T cell-mediated acute rejection.

Histidine-rich glycoprotein promotes macrophage activation and inflammation in chronic liver disease

Pathogen- and injury-related danger signals as well as cytokines released by immune cells influence the functional differentiation of macrophages in chronic inflammation. Recently, the liver-derived plasma protein, histidine-rich glycoprotein (HRG), was demonstrated, in mouse tumor models, to mediate the transition of alternatively activated (M2) to proinflammatory (M1) macrophages, which limit tumor growth and metastasis. We hypothesized that liver-derived HRG is a critical endogenous modulator of hepatic macrophage functionality and investigated its implications for liver inflammation and fibrosis by comparing C57BL/6N wild-type (WT) and Hrg(-/-) mice. In homeostatic conditions, hepatic macrophages were overall reduced and preferentially polarized toward the anti-inflammatory M2 subtype in Hrg(-/-) mice. Upon chronic liver damage induced by CCl4 or methionine-choline-deficient (MCD) diet, liver injury and fibrosis were attenuated in Hrg(-/-) , compared to WT, mice. Macrophage populations were reduced and skewed toward M2 polarization in injured livers of Hrg(-/-) mice. Moreover, HRG-deficient mice showed significantly enhanced hepatic vascularization by micro-computed tomography and histology, corroborating proangiogenic activities of M2-polarized liver macrophages. Purified HRG protein induced, but HRG-deficient serum prevented, M1 macrophage differentiation in vitro. Accordingly, Hrg(-/-) mice transplanted with Hrg(+/+) bone marrow, but not Hrg(-/-) -transplanted Hrg(+/+) mice, remained protected from experimental steatohepatitis. Consistent with these findings, patients with chronic hepatitis C and nonalcoholic steatohepatitis significantly up-regulated hepatocytic HRG expression, which was associated with M1 polarization of adjacent macrophages.

CONCLUSIONS

Liver-derived HRG, similar to alarmins, appears to be an endogenous molecular factor promoting polarization of hepatic macrophages toward the M1 phenotype, thereby promoting chronic liver injury and fibrosis progression, but limiting angiogenesis. Therefore, controlling tissue levels of HRG or PGF might be a promising strategy in chronic inflammatory liver diseases.

Innate danger signals in acute injury: From bench to bedside

The description of the systemic inflammatory response syndrome (SIRS) as a reaction to numerous insults marked a turning point in the understanding of acute critical states, which are intensive care basic cases. This concept highlighted the final inflammatory response features whichever the injury mechanism is: infectious, or non-infectious such as extensive burns, traumas, major surgery or acute pancreatitis. In these cases of severe non-infectious insult, many endogenous mediators are released. Like infectious agents components, they can activate the immune system (via common signaling pathways) and initiate an inflammatory response. They are danger signals or alarmins. These molecules generally play an intracellular physiological role and acquire new functions when released in extracellular space. Many progresses brought new information on these molecules and on their function in infectious and non-infectious inflammation. These danger signals can be used as biomarkers and provide new pathophysiological and therapeutic approaches, particularly for immune dysfunctions occurring after an acute injury. We present herein the danger model, the main danger signals and the clinical consequences.

Myeloid-related Protein 8/14 Levels in Rheumatoid Arthritis: Marker of Disease Activity and Response to Methotrexate

Objective.

Myeloid-related proteins (MRP) 8/14 belong to a family of calcium-binding proteins produced by myeloid cells. Baseline serum levels of MRP8/14 have been shown to predict response to biologicals in rheumatoid arthritis (RA). Because methotrexate (MTX) is the first-line therapy in RA, we studied whether MRP8/14 levels can predict response to MTX.

Methods.

Patients with active RA disease who were naive to disease-modifying antirheumatic drugs were enrolled. All patients were treated with MTX only, to a maximum of 25 mg/week or the maximal tolerated dose. At 4 months, the European League Against Rheumatism response was assessed. All patients who needed rescue therapy after 2 months or who did not respond at 4 months were classified as nonresponders.

Results.

Ninety patients were enrolled, of whom 3 discontinued MTX within 4–6 weeks, so 87 patients were analyzed [74 women, median (interquartile range; IQR) for the Disease Activity Score at 28 joints (DAS28) was 4.43 (4.1–5.1)]. The median (IQR) serum MRP8/14 level at baseline was 19.95 µg/ml (11.49–39.06). The serum MRP8/14 had good correlation with DAS28-C-reactive protein (CRP; r = 0.35, p = 0.001). The MRP8/14 levels fell significantly after 4 months of treatment (10.28 µg/ml, 5.95–16.05, p < 0.001). Among 87 patients, 69 were responders. The median (IQR) baseline level of MRP8/14 was higher among responders compared with nonresponders: 23.99 µg/ml (15.39–42.75) versus 9.58 µg/ml (6.11–24.93, p = 0.00250). The levels declined in the responders, from 23.99 µg/ml (15.39–42.75) to 10.41 µg/ml (5.83–15.61, p < 0.001), but not in the nonresponders, from 9.58 µg/ml (6.11–24.93) to 9.19 µg/ml (7.74–21.96, p = 0.687). Receiver-operation characteristic analysis showed that MRP8/14 was a better predictor of response than CRP and erythrocyte sedimentation rate, especially with early disease onset (< 1-yr duration).

Conclusion.

MRP8/14 is a good marker of disease activity in RA, and higher levels predict response to MTX.