A comparison of human S100A12 with MRP-14 (S100A9)

The alarmin S100A12 causes sterile inflammation of the human chorioamniotic membranes as well as preterm birth and neonatal mortality in mice†

Sterile inflammation is triggered by danger signals, or alarmins, released upon cellular stress or necrosis. Sterile inflammation occurring in the amniotic cavity (i.e. sterile intra-amniotic inflammation) is frequently observed in women with spontaneous preterm labor resulting in preterm birth, the leading cause of neonatal morbidity and mortality worldwide; this condition is associated with increased amniotic fluid concentrations of alarmins. However, the mechanisms whereby alarmins induce sterile intra-amniotic inflammation are still under investigation. Herein, we investigated the mechanisms whereby the alarmin S100A12 induces inflammation of the human chorioamniotic membranes in vitro and used a mouse model to establish a causal link between this alarmin and adverse perinatal outcomes. We report that S100A12 initiates sterile inflammation in the chorioamniotic membranes by upregulating the expression of inflammatory mediators such as pro-inflammatory cytokines and pattern recognition receptors. Importantly, S100A12 induced the priming and activation of inflammasomes, resulting in caspase-1 cleavage and the subsequent release of mature IL-1β by the chorioamniotic membranes. This alarmin also caused the activation of the chorioamniotic membranes by promoting MMP-2 activity and collagen degradation. Lastly, the ultrasound-guided intra-amniotic injection of S100A12 at specific concentrations observed in the majority of women with sterile intra-amniotic inflammation induced preterm birth (rates: 17% at 200 ng/sac; 25% at 300 ng/sac; 25% at 400 ng/sac) and neonatal mortality (rates: 22% at 200 ng/sac; 44% at 300 ng/sac; 31% at 400 ng/sac), thus demonstrating a causal link between this alarmin and adverse perinatal outcomes. Collectively, our findings shed light on the inflammatory responses driven by alarmins in the chorioamniotic membranes, providing insight into the immune mechanisms leading to preterm birth in women with sterile intra-amniotic inflammation.

S100A12 is a promising biomarker in papillary thyroid cancer

S100A12 belongs to the S100 family and acts as a vital regulator in different types of tumors. However, the function of S100A12 in thyroid carcinoma has not yet been investigated. In this study, we analyzed the expression of S100A12 in human papillary thyroid cancer (PTC) samples and two PTC cell lines. In addition, we explored the effects of S100A12 on PTC cell progression in vitro and in vivo. Our results showed that S100A12 was significantly upregulated in PTC specimens. Moreover, silencing S100A12 markedly inhibited PTC cell proliferation, migration, invasion and cell cycle progression. In addition, knockdown of S100A12 significantly reduced the expression of CyclinD1, CDK4 and p-ERK in PTC cells. An in vivo study also showed that silencing S100A12 dramatically suppressed tumor cell growth and decreased Ki67 expression in a xenograft mouse model. This study provides novel evidence that S100A12 serves as an oncogene in PTC. Knockdown of S100A12 suppressed PTC cell proliferation, migration, and invasion and induced G0/G1 phase arrest via the inhibition of the ERK signaling pathway. Therefore, S100A12 may be a potent therapeutic target for PTC.

Plasma S100A8/A9 heterodimer is an early prognostic marker of acute kidney injury associated with cardiac surgery

AIM

We investigated whether plasma levels of the inflammation marker S100A8/A9, could predict acute kidney injury (AKI) onset in patients undergoing cardiac surgery necessitating cardiopulmonary bypass (CPB).

PATIENTS & METHODS

Plasma levels of S100A8/A9 and other neutrophil cytosolic proteins were measured in 39 patients pre- and immediately post-CPB.

RESULTS

All markers increased significantly post-CPB with S100A8/A9, S100A12 and myeloperoxidase levels significantly higher in patients who developed AKI within 7 days. S100A8/A9 had good prognostic utility for AKI, with an area under the receiver operating characteristic curve of 0.81 (95% CI: 0.676-0.949) and a cut-off value of 10.6 μg/ml (85.7% sensitivity and 75% specificity) irrespective of age.

CONCLUSION

Plasma S100A8/A9 levels immediately after cardiac surgery, can predict onset of AKI, irrespective of age.

Bioinorganic Explorations of Zn(II) Sequestration by Human S100 Host-Defense Proteins

The human innate immune system launches a metal-withholding response to starve invading microbial pathogens of essential metal nutrients. Zn(II)-sequestering proteins of the human S100 family contribute to this process and include calprotectin (CP, S100A8/S100A9 oligomer, calgranulin A/B oligomer), S100A12 (calgranulin C), and S100A7 (psoriasin). This Perspective highlights recent advances in the Zn(II) coordination chemistry of these three proteins, as well as select studies that evaluate Zn(II) sequestration as an antimicrobial mechanism.

An orthologue of the host-defense protein psoriasin (S100A7) is expressed in frog skin

Host-defense peptides and proteins are vital for first line protection against bacteria. Most host-defense peptides and proteins common in vertebrates have been studied primarily in mammals, while their orthologues in non-mammalian vertebrates received less attention. We found that the European Common Frog Rana temporaria expresses a protein in its skin that is evolutionarily related to the host-defense protein S100A7. This prompted us to test if the encoded protein, which is an important microbicidal protein in human skin, shows similar activity in frogs. The R. temporaria protein lacks the zinc-binding sites that are key to the antimicrobial activity of human S100A7 at neutral pH. However, despite being less potent, the R. temporaria protein does compromise bacterial membranes at low pH, similar to its human counterpart. We postulate that, while amphibian S100A7 likely serves other functions, the capacity to compromise bacterial cell membranes evolved early in tetrapod evolution.

Expression and clinical implication of S100A12 in gastric carcinoma

S100 protein family has been implicated in multiple stages of tumorigenesis and progression in which S100A12 is one of the subtypes. However, the role of S100A12 in gastric carcinoma (GC) has not been elucidated yet. This study was aimed to investigate the expression of S100A12 in GC tissues and evaluate the clinical significance of S100A12 in GC patients. S100A12 protein was detected in 207 GC and 52 paired non-cancerous mucosal tissues by immunohistochemistry, while messenger RNA (mRNA) was investigated by Oncomine database analysis. Moreover, survival analysis was performed and the correlation between S100A12 and ubiquitin-specific protease 10 (USP10) and p53 was determined. As for tumor cells, the expression of S100A12 protein and mRNA in GC was proved to be lower than that in non-cancerous mucosa tissues (p < 0.05). Clinicopathological analysis showed that S100A12 protein was negatively associated with tumor size (p = 0.004), depth of invasion (p = 0.022), tumor node metastasis (TNM) stage (p = 0.018), Lauren classification (p < 0.000), and cell differentiation (p < 0.000). In contrast, a positive correlation was found between S100A12 and USP10 protein (p < 0.000). However, no relationship was detected between S100A12 and p53. Moreover, the survival analysis indicated that S100A12 protein was a favorable factor of prognosis of GC (p < 0.05). Although the expression of S100A12 in the stromal cells was detected higher than that in the tumor cells, no relationship between S100A12 protein in stromal cells and the clinicopathological features described above was found (p > 0.05). Our findings suggested that low expression of S100A12 might be served as a new marker in the tumorigenesis and progression of GC.

The S100 proteins in epidermis: Topology and function

BACKGROUND

S100 proteins are small calcium binding proteins encoded by genes located in the epidermal differentiation complex (EDC). Differently to other proteins encoded by EDC genes, which are indispensable for normal epidermal differentiation, the role of S100 proteins in the epidermis remains largely unknown.

SCOPE OF REVIEW

Particular S100 proteins differ in their distribution in epidermal layers, skin appendages, melanocytes and Langerhans cells. Taking into account that each epidermal component consists of specialized cells with well-defined functions, such differential distribution may be indicative of the function of a given S100 protein. We used this criterion together with the survey of the current experimental data pertinent to epidermis to provide a fairly comprehensive view on the possible function of individual S100 proteins in this tissue.

MAJOR CONCLUSIONS

S100 proteins are differently expressed and, despite extensive structural homology, perform diverse functions in the epidermis. Certain S100 proteins probably ensure constant epidermal renewal and support wound healing while others act in epidermal differentiation or have a protective role. As their expression is differently affected in various skin pathologies, particular S100 proteins could be valuable diagnostic markers.

GENERAL SIGNIFICANCE

S100 proteins seem to be important although not yet fully recognized epidermal constituents. Better understanding of their role in the epidermis might be helpful in designing therapies to various skin diseases.

The neutrophil protein S100A12 is associated with a comprehensive ultrasonographic synovitis score in a longitudinal study of patients with rheumatoid arthritis treated with adalimumab

Background

The calcium-binding protein S100A12 correlates with measures of disease activity in patients with rheumatoid arthritis (RA). The protein reflects neutrophil activation and the present objective was to explore in a pilot study the associations between S100A12 and other inflammatory markers, clinical assessments as well as degree of synovitis detected by a comprehensive ultrasonography (US) examination in RA patients during biologic treatment.

Methods

Twenty patients with RA were examined clinically and by use of US as well as laboratory markers S100A12, calprotectin, C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) before starting adalimumab, with follow-up after 1, 3, 6 and 12 months. Ultrasonographic B-mode (BM) and power Doppler (PD) assessments of 78 joints, 36 tendons/tendon groups and 2 bursas were performed, and sum US scores calculated. Wilcoxon signed rank test assessed treatment response and Spearman rank correlation test was used to calculate correlations.

Results

The concentrations of S100A12 decreased after 3 months (p < 0.01) and significant correlations were found between S100A12 and the other laboratory markers during follow-up (0.50-0.62, p < 0.05). Of the clinical assessments, S100A12 had highest correlations with the assessor’s global VAS (0.46-0.85, p < 0.05). Compared with CRP and ESR, S100A12 showed higher correlations with the sum US scores (both BM and PD), with median (range) correlation coefficients of 0.55 (0.35-0.78 (NS-p < 0.001)) for sum BM scores and 0.45 (0.27-0.75 (NS-p < 0.001)) for sum PD scores.

Conclusions

The S100A12 protein was significantly associated with other inflammatory markers, clinical assessments as well as sum US scores, indicating that S100A12 is a potential marker of inflammation in RA patients.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2474-15-335) contains supplementary material, which is available to authorized users.

S100A8-S100A9 protein complex mediates psoriasis by regulating the expression of complement factor C3

Psoriasis is a common heterogeneous inflammatory skin disease with a complex pathophysiology and limited treatment options. Here we performed proteomic analyses of human psoriatic epidermis and found S100A8-S100A9, also called calprotectin, as the most upregulated proteins, followed by the complement component C3. Both S100A8-S100A9 and C3 are specifically expressed in lesional psoriatic skin. S100A9 is shown here to function as a chromatin component modulating C3 expression in mouse and human cells by binding to a region upstream of the C3 start site. When S100A9 was genetically deleted in mouse models of skin inflammation, the psoriasis-like skin disease and inflammation were strongly attenuated, with a mild immune infiltrate and decreased amounts of C3. In addition, inhibition of C3 in the mouse model strongly reduced the inflammatory skin disease. Thus, S100A8-S100A9 can regulate C3 at the nuclear level and present potential new therapeutic targets for psoriasis.

S100A9 has a protective role in inflammation-induced skin carcinogenesis

The S100A8/A9 heterodimer is expressed by myeloid cells where its function has been extensively investigated. Immune cell S100A8/A9 promotes proinflammatory effects, and its absence is often associated with lack of leukocyte recruitment resulting in protection in terms of disease progression. S100A8/A9 is also expressed by certain epithelia, either constitutively as in mucosal epithelia or following stimulation as in skin keratinocytes. The role of the heterodimer in this context has not been as frequently explored. In this study, the incidence of skin papillomas induced by 7,12-dimethylbenz(a)anthracene (DMBA)/12-O-tetradecanoylphorbol-13-acetate (TPA) in S100a9(-/-) mice has been investigated. Unlike the immune disorders and certain models of cancer, absence of S100A8/A9 caused an increased incidence in skin of papillomas and, subsequently, squamous cell carcinomas. Although associated in S100a9(-/-) mice with increased recruitment of neutrophils and T cells, a bone marrow chimera experiment revealed the major defect to be primarily due to the absence of S100A8/A9 in the skin keratinocytes. S100a9(-/-) skin displayed enhanced Ki-67 expression over the time period of appearance of the papillomas suggesting an effect of S100A8/A9 in regulating proliferation in the epidermal layer. Thus, despite immune cell recruitment in S100a9(-/-) mouse skin that might have been predicted to promote tumor growth, it was the absence of S100A8/A9 in skin keratinocytes that dominated in terms of papilloma formation. The study highlights the importance of the S100A8/A9-expressing skin epidermal layer in controlling skin tumor formation and suggests that the influence of the heterodimer is dependent on the tissue context in which it is expressed.

Transition metal ions at the crossroads of mucosal immunity and microbial pathogenesis

Transition metal ions are essential micronutrients for all living organisms. In mammals, these ions are often protein-bound and sequestered within cells, limiting their availability to microbes. Moreover, in response to infection, mammalian hosts further reduce the availability of metal nutrients by activating epithelial cells and recruiting neutrophils, both of which release metal-binding proteins with antimicrobial function. Microorganisms, in turn, have evolved sophisticated systems to overcome these limitations and acquire the metal ions essential for their growth. Here we review some of the mechanisms employed by the host and by pathogenic microorganisms to compete for transition metal ions, with a discussion of how evading “nutritional immunity” benefits pathogens. Furthermore, we provide new insights on the mechanisms of host-microbe competition for metal ions in the mucosa, particularly in the inflamed gut.

Regulation of antimicrobial peptide expression in human gingival keratinocytes by interleukin-1α

In the oral cavity, mucosal keratinocytes resist bacterial infection, in part, by producing broad-spectrum antimicrobial peptides (AMPs) including defensin, adrenomedullin and calprotectin. Epidermal keratinocyte expression of many AMPs increases in response to interleukin-1α (IL-1α). IL-1α is produced by epidermal keratinocytes and regulates cell differentiation. To better understand innate immunity in the oral cavity, we sought to determine how IL-1α might regulate expression of AMPs by human gingival keratinocytes (HGKs) using DNA microarray and Western blot analyses. HGKs from three subjects expressed eleven AMPs, including S100A7, S100A8, S100A9, S100A12, secretory leucocyte protease inhibitor, lipocalin 2 (LCN2), cystatin C and β-defensin 2. Of the expressed AMPs, S100A7, S100A12 and LCN2 were up-regulated by IL-1α (inducible AMPs); the other AMPs were considered to be constitutive. Human gingival keratinocytes, therefore, express constitutive and IL-1α-inducible AMPs to provide a rapid and robust innate response to microbial infection.

The tissue microlocalisation and cellular expression of CD163, VEGF, HLA-DR, iNOS, and MRP 8/14 is correlated to clinical outcome in NSCLC

Background

We have previously investigated the microlocalisation of M1 and M2 macrophages in NSCLC. This study investigated the non-macrophage (NM) expression of proteins associated with M1 and M2 macrophages in NSCLC.

Methods

Using immunohistochemistry, CD68⁺ macrophages and proteins associated with either a cytotoxic M1 phenotype (HLA-DR, iNOS, and MRP 8/14), or a non-cytotoxic M2 phenotype (CD163 and VEGF) were identified. NM expression of the markers was analysed in the islets and stroma of surgically resected tumours from 20 patients with extended survival (ES) (median 92.7 months) and 20 patients with poor survival (PS) (median 7.7 months).

Results

The NM expression of NM-HLA-DR (p<0.001), NM-iNOS (p = 0.02) and NM-MRP 8/14 (p = 0.02) was increased in ES compared to PS patients in the tumour islets. The tumour islet expression of NM-VEGF, was decreased in ES compared to PS patients (p<0.001). There was more NM-CD163 expression (p = 0.04) but less NM-iNOS (p = 0.002) and MRP 8/14 (p = 0.01) expression in the stroma of ES patients compared with PS patients. The 5-year survival for patients with above and below median NM expression of the markers in the islets was 74.9% versus 4.7% (NM-HLA-DR p<0.001), 65.0% versus 14.6% (NM-iNOS p = 0.003), and 54.3% versus 22.2% (NM-MRP 8/14 p = 0.04), as opposed to 34.1% versus 44.4% (NM-CD163 p = 0.41) and 19.4% versus 59.0% (NM-VEGF p = 0.001).

Conclusions

Cell proteins associated with M1 and M2 macrophages are also expressed by other cell types in the tumour islets and stroma of patients with NSCLC. Their tissue and cellular microlocalisation is associated with important differences in clinical outcome.

MRP14 is elevated in the bronchoalveolar lavage fluid of fibrosing interstitial lung diseases

Pulmonary fibrosis is defined by an overgrowth of fibroblasts and extracellular matrix deposition, and results in respiratory dysfunction that is often fatal. It is the end stage in many chronic inflammatory interstitial lung diseases (ILD) such as sarcoidosis and idiopathic pulmonary fibrosis (IPF). The myeloid-related proteins (MRPs) belong to the S100 family of calcium-binding proteins and are highly expressed by neutrophils, macrophages and epithelial cells during chronic inflammation. MRP14 stimulates fibroblast proliferation in vitro and is expressed in granulomas from sarcoidosis patients. We hypothesized that MRP14 may be a biomarker for fibrotic interstitial lung diseases. The objective of this study was to investigate whether levels of MRP14 in the bronchoalveolar lavage fluid (BALF) of patients with sarcoidosis and IPF correlate with clinical parameters. We used an enzyme-linked immunosorbent assay (ELISA) to measure MRP14 in BALF of 74 sarcoidosis patients, 54 IPF patients and 19 controls. Mean BALF levels of MRP14 were elevated significantly in IPF (P < 0.001) and sarcoidosis (P < 0.05) patients compared to controls. MRP14 levels were associated linearly with sarcoidosis disease severity based on chest radiographic stage. Moreover, BALF MRP14 levels were correlated inversely with diffusion capacity and forced vital capacity in sarcoidosis patients. In IPF patients, a correlation with BALF neutrophil percentage was found. In conclusion, BALF MRP14 levels are elevated in IPF and sarcoidosis and are associated with disease severity in sarcoidosis. The results support the need for further studies into the role of MRP14 in the pathogenesis of lung fibrosis.

Inflammation-associated S100 proteins: new mechanisms that regulate function

This review focuses on new aspects of extracellular roles of the calgranulins. S100A8, S100A9 and S100A12 are constitutively expressed in neutrophils and induced in several cell types. The S100A8 and S100A9 genes are regulated by pro- and anti-inflammatory mediators and their functions may depend on cell type, mediators within a particular inflammatory milieu, receptors involved in their recognition and their post-translational modification. The S100A8 gene induction in macrophages is dependent on IL-10 and potentiated by immunosuppressive agents. S100A8 and S100A9 are oxidized by peroxide, hypochlorite and nitric oxide (NO). HOCl generates intra-chain sulfinamide bonds; stronger oxidation promotes cross-linked forms that are seen in human atheroma. S100A8 is >200-fold more sensitive to oxidative cross-linking than low-density lipoprotein and may reduce oxidative damage. S100A8 and S100A9 can be S-nitrosylated. S100A8-SNO suppresses mast cell activation and inflammation in the microcirculation and may act as an NO transporter to regulate vessel tone in inflammatory lesions. S100A12 activates mast cells and is a monocyte and mast cell chemoattractant; a G-protein-coupled mechanism may be involved. Structure-function studies are discussed in relation to conservation and divergence of functions in S100A8. S100A12 induces cytokines in mast cells, but not monocytes/macrophages. It forms complexes with Zn(2+) and, by chelating Zn(2+), S100A12 significantly inhibits MMPs. Zn(2+) in S100A12 complexes co-localize with MMP-9 in foam cells in atheroma. In summary, S100A12 has pro-inflammatory properties that are likely to be stable in an oxidative environment, because it lacks Cys and Met residues. Conversely, S100A8 and S100A9 oxidation and S-nitrosylation may have important protective mechanisms in inflammation.

ANTI-INFECTIVE PROTECTIVE PROPERTIES OF S100 CALGRANULINS

The calgranulins are a subgroup of proteins in the S100 family (calgranulin A, S100A8; calgranulin B, S100A9 and calgranulin C, S100A12) that provide protective anti-infective and anti-inflammatory functions for the mammalian host. In this review, we discuss the structure-function relationships whereby S100A8 and S100A9, and for comparison, S100A12, provide intra- and extracellular protection during the complex interplay between infection and inflammation and how the calgranulins are regulated to optimally protect the host. Ideally located to support epithelial barrier function, calprotectin, a complex of S100A8/S100A9, is expressed in squamous mucosal keratinocytes and innate immune cells present at mucosal surfaces. The calgranulins are also abundantly produced in neutrophils and monocytes, whereas expression is induced in epidermal keratinocytes, gastrointestinal epithelial cells and fibroblasts during inflammation. The calgranulins show species-specific expression and function. For example, S100A8 is chemotactic in rodents but not in humans. In humans, S100A12 appears to serve as a functional chemotactic homolog to murine S100A8. Transition metal-binding and oxidation sites within calgranulins are able to create structural changes that may orchestrate new protective functions or binding targets. The calgranulins thus appear to adopt a variety of roles to protect the host. In addition to serving as a leukocyte chemoattractant, protective functions include oxidant scavenging, antimicrobial activity, and chemokine-like activities. Each function may reflect the concentration of the calgranulin, post-transcriptional modifications, oligomeric forms, and the proximal intracellular or extracellular environments. Calprotectin and the calgranulins are remarkable as multifunctional proteins dedicated to protecting the intra- and extracellular environments during infection and inflammation.

Proteomic profiling of growth hormone-responsive proteins in human peripheral blood leukocytes

CONTEXT

GH is a known modulator of the immune system, but the effect of exogenous GH administration on white blood cell proteins has not been investigated. Surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF MS) is a powerful platform for the study of GH effects on immune system proteins.

OBJECTIVE

Our objective was to explore a novel approach for the detection of GH-responsive proteins in human leukocytes by proteomic analysis using SELDI-TOF MS.

DESIGN

We conducted a randomized double-blind, placebo-controlled GH administration study of 8 wk treatment followed by 6 wk washout. Pre- and posttreatment samples from 30 subjects were used for biomarker discovery.

SETTING

The study was performed at a clinical research facility.

PARTICIPANTS

We studied 30 recreationally trained healthy athletes.

INTERVENTION

Subjects received either recombinant human GH (2 mg/d sc; n = 22) or placebo (n = 8) for 8 wk.

MAIN OUTCOME MEASURES

Proteomic profiles were determined using CM10 weak cation-exchange protein chips, and some GH-regulated proteins were purified and identified by mass spectrometry and/or immunoblotting.

RESULTS

SELDI-TOF analysis revealed a number of GH-regulated peptides/proteins in the 3- to 22-kDa range that are either up- or down-regulated by GH. Several of these may be useful as biomarkers of GH action. The calcium-binding, proinflammatory calgranulins S100A8, S100A9, and S100A12 were all significantly down-regulated in response to GH treatment.

CONCLUSION

This study illustrates the novel use of human leukocyte proteomic profiling by SELDI-TOF MS and reveals the negative regulation of proinflammatory S100 proteins by GH in human white blood cells.

Acute appendicitis is characterized by a uniform and highly selective pattern of inflammatory gene expression

Acute appendicitis (AA) is the most common life-threatening surgical emergency in pediatrics. To characterize the nature of the inflammatory response in AA, gene expression profiles were generated. We found remarkable uniformity in the genes that were differentially expressed between patients with appendicitis and control groups. Sixty-four probe sets were differentially expressed in samples from patients with both severe and mild appendicitis compared to control samples, and within this group we were able to identify four dominant clusters. Interestingly, expression levels of interleukin (IL)-8 significantly correlated with histologic score, and expression of IL-8 protein was observed within both neutrophils and mononuclear cells by immunohistochemistry, suggesting a possible role in the etiology of appendicitis. Although there was some overlap between genes reported to be differentially expressed in Crohn's disease (CD) and those observed in AA, differential expression of genes involved in interferon responses that characterize CD was not observed.

Mast cell and monocyte recruitment by S100A12 and its hinge domain

S100A12 is expressed at sites of acute, chronic, and allergic inflammation. S100 proteins have regions of high sequence homology, but the "hinge" region between the conserved calcium binding domains is structurally and functionally divergent. Because the murine S100A8 hinge domain (mS100A8(42-55)) is a monocyte chemoattractant whereas the human sequence (hS100A8(43-56)) is inactive, we postulated that common hydrophobic amino acids within the S100A12 hinge sequence may be functional. The hinge domain, S100A12(38-53), was chemotactic for human monocytes and murine mast cells in vitro. S100A12(38-53) provoked an acute inflammatory response similar to that elicited by S100A12 in vivo and caused edema and leukocyte and mast cell recruitment. Circular dichroism studies showed that S100A12(38-53) had increased helical structure in hydrophobic environments. Mutations in S100A12(38-53) produced using an alanine scan confirmed that specific hydrophobic residues (I44A, I47A, and I53A) on the same face of the helix were critical for monocyte chemotaxis in vitro and generation of edema in vivo. In a hydrophobic environment such as the cell membrane, these critical residues would likely align on one face of an alpha-helix to facilitate receptor interaction. Interaction is unlikely to occur via the receptor for advanced glycation end products but, rather, via a G-protein-coupled mechanism.

Proteomics of the amniotic fluid in assessment of the placenta. Relevance for preterm birth

Proteomics is the study of expressed proteins and has emerged as a complement to genomic research. The major advantage of proteomics over DNA-RNA based technologies is that it more closely relates to phenotypes and not the source code. Proteomics thus holds the promise of providing a direct insight into the true mechanisms of human diseases. Historically, examination of the placenta has been the first modality to subclassify pathogenetic entities responsible for preterm birth. Because placenta is a key pathophysiological participant in several major obstetrical syndromes (preterm birth, pre-eclampsia, intrauterine growth restriction) identification of relevant biomarkers of placental function can profoundly impact on the prediction of fetal outcome and treatment efficacy. Since proteomics is a young science and studies that associate proteomic patterns with long-term outcome require follow-up of children up to school age, using placental pathological footprints of cellular injury as intermediate outcomes can be useful in the interim. Furthermore, knowledge on the identity of the dysregulated proteins may provide the needed breakthrough insight into novel pathophysiological pathways and unravel possible targets for therapeutical intervention that could not have been envisioned through hypothesis-driven approaches.

The receptor for advanced glycation end products (RAGE) system in women with intraamniotic infection and inflammation

OBJECTIVE

Receptor for advanced glycation end products (RAGE) is a multiligand cell-surface receptor part of the immunoglobulin superfamily with crucial roles in inflammation. S100A12/ENRAGE, a biomarker of amniotic fluid (AF) inflammation, is a ligand for RAGE. sRAGE, a competitive soluble RAGE receptor, inhibits RAGE ligands. Here we aimed to investigate the presence and changes in components of the RAGE system in women with intra-amniotic infection and inflammation.

STUDY DESIGN

AF was retrieved by amniocentesis in 113 women stratified as follows: (1) positive AF culture (+AFC; GA = 27 [20-33] wk; n = 27); (2) negative AF culture (-AFC; GA = 30 [20-36] wk; n = 27); (3) second trimester control (2T-CRL; GA = 19 [15-25] wk; n = 31); (4) third trimester control (3T-CRL; GA = 36 [31-38] wk; n = 28). We used mass spectrometry (SELDI) to detect S100A12/ENRAGE in AF. sRAGE levels were measured using specific immunoassays. Placental pathology was interpreted in relationship to the presence or absence of histologic acute inflammation and immunoreactivity of S100A12/ENRAGE and RAGE. mRNA expression of S100A12/ENRAGE, sRAGE, and RAGE in amniochorion and placental villous tissue was investigated using quantitative real-time polymerase chain reaction (PCR).

RESULTS

Presence of the S100A12/ENRAGE biomarker SELDI peak was confirmed in 70% of the +AFC but in only 10% of the -AFC samples (P < .001). The inflammatory biomarker was absent in all control samples. We further determined that the competitive inhibitor sRAGE is temporally regulated during gestation and that its AF levels are not influenced by the presence of either intra-amniotic infection or inflammation. Histologic choriamnionitis associated with intense staining for S100A12/ENRAGE, particularly in inflammatory cells. The immunoreactivity for extracellular domain of RAGE was localized exclusively to amnion epithelial, decidual, and extravillous trophoblast cells. Yet, acute histologic chorioamnionitis was related to increased gene expression of S100A12/ENRAGE in fetal membranes and decreased sRAGE and RAGE in the placenta.

CONCLUSION

The S100A12/ENRAGE system is markedly upregulated in women with intra-amniotic infection and correlates with the degree of inflammation. Further studies remain to elucidate whether the gestational age dependence of the inhibitor molecule sRAGE may explain the higher incidence of infection-related preterm deliveries and especially rupture of the membranes at earlier gestational age.

The expression of RAGE and EN-RAGE in leprosy

BACKGROUND

Extracellular newly identified RAGE-binding protein (EN-RAGE) is a ligand of the receptor for advanced glycation endproducts (RAGE) and has been termed S100A12. The ligation of EN-RAGE with RAGE on the endothelium, mononuclear phagocytes and lymphocytes triggers cellular activation with the generation of the key proinflammatory mediators interleukin (IL)-1beta and tumour necrosis factor (TNF)-alpha.

OBJECTIVES

The aim of this study was to investigate the presence of RAGE and EN-RAGE, their spatial localization and their coexpression in leprosy lesions.

METHODS

Immunohistochemistry and confocal laser scanning microscopy were used to evaluate the expression of RAGE and EN-RAGE in leprosy. By enzyme-linked immunosorbent assay, RAGE and EN-RAGE were detected in the serum.

RESULTS

(1) In the multibacillary (MB) and paucibacillary (PB) groups, the level of RAGE production was significantly higher than in patients with atypical mycobacterial infection or sarcoidosis (P < 0.01). In the MB group, the production of RAGE was higher than in the PB group (P < 0.01), and it was higher in patients without the lepra reaction than in patients with the lepra reaction (P < 0.05). (2) In MB, PB and atypical mycobacterial infection, the level of EN-RAGE production was significantly higher than in sarcoidosis (P < 0.01). (3) In the confocal laser scanning microscopic examination, the RAGE and EN-RAGE proteins were detected in lepromatous leprosy. These proteins are spatially colocalized along the cell surface, which is in agreement with their receptor-ligand interaction. (4) A comparable amount of EN-RAGE was detected in the serum of the MB and PB groups. Patients with the reaction showed a higher level of EN-RAGE than patients without the reaction in leprosy.

CONCLUSIONS

Our data suggest that in leprosy, RAGE and EN-RAGE may be involved in the proinflammatory process rather than the antimycobacterial activity, especially during the lepra reaction. The blockade of the interaction of RAGE and EN-RAGE at the early stage of the inflammatory process may minimize the inflammatory response and consequent tissue damage or the sequelae of leprosy.

Investigation on the Surface Hydrophobicity and Aggregation Kinetics of Human Calprotectin in the Presence of Calcium

Calcium and zinc binding protein, calprotectin is a multifunctional protein with broad spectrum antimicrobial and antitumoural activity. It was purified from human neutrophil, using a two-step ion exchange chromatography. Since surface hydrophobicity of calprotectin may be important in membrane anchoring, membrane penetration, subunits oligomerization and some biological roles of protein, in this study attempted to explore the effect of calcium in physiological range on the calprotectin lipophilicity. Incubation of human calprotectin (50 microg/ml) with different calcium concentrations showed that 1-anilino-8-naphthalene sulfonic acid (ANS) fluorescence intensity of the protein significantly elevates with calcium in a dose dependent manner, suggesting an increase in calprotectin surface hydrophobicity upon calcium binding. Our study also indicates that calcium at higher concentrations (6, 8 and 10 mM) induces aggregation of human calprotectin. Our finding demonstrates that the starting time and the rate constant of calprotectin aggregation depend on the calcium concentration.

Computational searches for missing orthologs: the case of S100A12 in mice

The interaction of the Ca2+-binding protein S100A12 with RAGE (receptor of advanced glycation endproducts) has been considered as a novel proinflammatory axis, since blockage of RAGE/S100A12 ligation suppresses chronic cellular activation and tissue injury in mouse models. However, the existence of a murine S100A12 ortholog is unknown. Because experimental approaches failed to identify it, we started an analysis of gene locus evolution. Human S100A12 is localized in the S100 gene cluster between S100A8 and S100A9, which are neighbors in both mouse and human. Confirming identical gene order, we found a DNA region between the murine S100A8 and S100A9 genes that is 60.9% identical to a region of the human S100A12 gene, including the first exon. Instead of the second and third exon, we found homology to a region close to the human S100A9 locus. To exclude a murine S100A12 ortholog elsewhere in the genome, we used human S100A12 as query for TBlastN homology searches. The matches were either too short, or identity was too low, or they could clearly be identified as distinct S100 genes. Obviously, an S100A12 ortholog is neither present in mouse nor rat, indicating that S100A12 has been lost during rodent evolution, probably due to a deletion.

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

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

The regulation of EN-RAGE (S100A12) gene expression in human THP-1 macrophages

EN-RAGE is a ligand for the receptor for advanced glycation end products (RAGE) and may be involved in the development of diabetic macro- and micro-angiopathy. This study is designed to investigate the regulation of EN-RAGE gene expression in human macrophages. The amounts of EN-RAGE mRNA were measured in cultured human THP-1 macrophages after treatment with various stimuli known to modulate atherosclerosis. First, interleukin-6 (IL-6), a proinflammatory cytokine, increased the level of EN-RAGE mRNA by approximately 2-fold in a time- and a dose-dependent fashion. EN-RAGE protein was detected in the cultured medium and increased significantly by the addition of IL-6. The induction was abolished by pretreatment with the JAK kinase inhibitor and cycloheximide, but not with the MEK kinase inhibitor. Second, pioglitazone (PIO), a thiazolidinedione, decreased the level of EN-RAGE mRNA by approximately 25% of the basal in a time- and a dose-dependent fashion. Pioglitazone also inhibited the induction of EN-RAGE mRNA by IL-6. These results indicate the production of EN-RAGE is induced by IL-6 through de novo protein synthesis via the JAK-STAT kinase pathway and inhibited by the activation of peroxisome proliferator-activated receptor-gamma (PPARgamma) in human macrophages.

Expression of S100A12 (EN-RAGE) in cystic fibrosis

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

S100 protein subcellular localization during epidermal differentiation and psoriasis

S100 proteins are calcium-activated signaling proteins that interact with target proteins to modulate biological processes. Our present studies compare the level of expression, and cellular localization of S100A7, S100A8, S100A9, S100A10, and S100A11 in normal and psoriatic epidermis. S100A7 and S100A11 are present in the basal and spinous layers in normal epidermis. These proteins appear in the nucleus and cytoplasm in basal cells but are associated with the plasma membrane in spinous cells. S100A10 is present in basal and spinous cells, in the cytoplasm, and is associated with the plasma membrane. S100A8 and S100A9 are absent or are expressed at minimal levels in normal epidermis. In involved psoriatic tissue, S100A10 and S100A11 levels remain unchanged, whereas, S100A7, S100A8, and S100A9 are markedly overexpressed. The pattern of expression and subcellular localization of S100A7 is similar in normal and psoriatic tissue. S100A8 and S100A9 are strongly expressed in the basal and spinous layers in psoriasis-involved tissue. In addition, we demonstrate that S100A7, S100A10, and S100A11 are incorporated into detergent and reducing agent-resistant multimers, suggesting that they are in vivo transglutaminase substrates. S100A8 and S100A9 did not form these larger complexes. These results indicate that S100 proteins localize to the plasma membrane in differentiated keratinocytes, suggesting a role in regulating calcium-dependent, membrane-associated events. These studies also indicate, as reported previously, that S100A7, S100A8, and S100A9 expression is markedly altered in psoriasis, suggesting a role for these proteins in disease pathogenesis.

Multiple structural states of S100A12: A key to its functional diversity

S100A12 is a member of the S100 family of EF-hand calcium-binding proteins. Together with two other calgranulins, S100A8 and S100A9, it is mostly expressed in human granulocytes, although there is increasing evidence of expression in keratinocytes and psoriatic lesions. It is involved in host-parasite response, and linked to corneal autoimmune diseases connected with filarial parasite infestation. Interaction of S100A12 with a multiligand receptor for advanced glycation end products (RAGE) mediates inflammation. Human recombinant S100A12 was found to induce neuritogenesis of cultured hippocampal cells, similar to two other S100 proteins, S100B and S100A4. X-ray structure of S100A12 has been solved in two crystal forms: R3 and P2(1). In the R3 crystal form S100A12 is a dimer, and in the P2(1) crystal form the dimers are arranged as a hexamer. The hexameric form suggests its role in receptor oligomerisation. S100A12 binds copper at the predicted zinc/copper binding site, which is located close to the surface of the protein. We propose copper-mediated generation of reactive oxygen species by S100A12 as its function in host-parasite response.

Myeloid cell function in MRP-14 (S100A9) null mice

Myeloid-related protein 14 (MRP-14) and its heterodimeric partner, MRP-8, are cytosolic calcium-binding proteins, highly expressed in neutrophils and monocytes. To understand the function of MRP-14, we performed targeted disruption of the MRP-14 gene in mice. MRP-14(-/-) mice showed no obvious phenotype and were fertile. MRP-8 mRNA but not protein is present in the myeloid cells of these mice, suggesting that the stability of MRP-8 protein is dependent on MRP-14 expression. A compensatory increase in other proteins was not detected in cells lacking MRP-8 and MRP-14. Although the morphology of MRP-14(-/-) myeloid cells was not altered, they were significantly less dense. When Ca(2+) responses were investigated, there was no change in the maximal response to the chemokine MIP-2. At lower concentrations, however, there was reduced responsiveness in MRP-14(-/-) compared with MRP-14(+/+) neutrophils. This alteration in the ability to flux Ca(2+) did not impair the ability of the MRP-14(-/-) neutrophils to respond chemotactically to MIP-2. In addition, the myeloid cell functions of phagocytosis, superoxide burst, and apoptosis were unaffected in MRP-14(-/-) cells. In an in vivo model of peritonitis, MRP-14(-/-) mice showed no difference from wild-type mice in induced inflammatory response. The data indicate that MRP-14 and MRP-8 are dispensable for many myeloid cell functions.

Expression of myeloid-specific genes in childhood acute lymphoblastic leukemia - a cDNA array study

Several specific cytogenetic changes are known to be associated with childhood acute lymphoblastic leukemia (ALL), and many of them are important prognostic factors for the disease. Little is known, however, about the changes in gene expression in ALL. Recently, the development of cDNA array technology has enabled the study of expression of hundreds to thousands of genes in a single experiment. We used the cDNA array method to study the gene expression profiles of 17 children with precursor-B ALL. Normal B cells from adenoids were used as reference material. We discuss the 25 genes that were most over-expressed compared to the reference. These included four genes that are normally expressed only in the myeloid lineages of the hematopoietic cells: RNASE2, GCSFR, PRTN3 and CLC. We also detected over-expression of S100A12, expressed in nerve cells but also in myeloid cells. In addition to the myeloid-specific genes, other over-expressed genes included AML1, LCP2 and FGF6. In conclusion, our study revealed novel information about gene expression in childhood ALL. The data obtained may contribute to further studies of the pathogenesis and prognosis of childhood ALL.

The crystal structure of human MRP14 (S100A9), a Ca(2+)-dependent regulator protein in inflammatory process

Human MRP14 (hMRP14) is a Ca(2+)-binding protein from the S100 family of proteins. This protein is co-expressed with human MRP8 (hMRP8), a homologue protein in myeloid cells, and plays an indispensable role in Ca(2+)-dependent functions during inflammation. This role includes the activation of Mac-1, the beta(2) integrin which is involved in neutrophil adhesion to endothelial cells. The crystal structure of the holo form of hMRP14 was analyzed at 2.1 A resolution. hMRP14 is distinguished from other S100 member proteins by its long C-terminal region, and its structure shows that the region is extensively flexible. In this crystal structure of hMRP14, Chaps molecules bind to the hinge region that connects two EF-hand motifs, which suggests that this region is a target-binding site of this protein. Based on a structural comparison of hMRP14 with hMRP8 and human S100A12 (hS100A12) that is another homologue protein, the character of MRP8/14 hetero-complex and the functional significance of the flexibility of the C-terminal region of hMRP14 are discussed.

The S100 family heterodimer, MRP-8/14, binds with high affinity to heparin and heparan sulfate glycosaminoglycans on endothelial cells

The S100 family proteins MRP-8 (S100A8) and MRP-14 (S100A9) form a heterodimer that is abundantly expressed in neutrophils, monocytes, and some secretory epithelia. In inflamed tissues, the MRP-8/14 complex is deposited onto the endothelium of venules associated with extravasating leukocytes. To explore the receptor interactions of MRP-8/14, we use a model system in which the purified MRP-8/14 complex binds to the cell surface of an endothelial cell line, HMEC-1. This interaction is mediated by the MRP-14 subunit and is mirrored by recombinant MRP-14 alone. The cell surface binding of MRP-14 was blocked by heparin, heparan sulfate, and chondroitin sulfate B, and the binding sites were sensitive to heparinase I and trypsin treatment but not to chondroitinase ABC. Furthermore MRP-8/14 and MRP-14 did not bind to a glycosaminoglycan-minus cell line. MRP-14 has a high affinity for heparin (K(d) = 6.1 +/- 3.4 nm), and this interaction mimicked that with the endothelial cells. We therefore conclude that the MRP-8/14 complex binds to endothelial cells via the MRP-14 subunit interacting chiefly with heparan sulfate proteoglycans. CD36 and RAGE, two other putative receptors for MRP-8/14, were not expressed by HMEC-1 cells. This binding activity may explain the immobilization of the MRP-8/14 complex on endothelium that is observed in vivo.

Disease fingerprinting with cDNA microarrays reveals distinct gene expression profiles in lethal type 1 and type 2 cytokine-mediated inflammatory reactions

Development of polarized immune responses controls resistance and susceptibility to many microorganisms. However, studies of several infectious, allergic, and autoimmune diseases have shown that chronic type-1 and type-2 cytokine responses can also cause significant morbidity and mortality if left unchecked. We used mouse cDNA microarrays to molecularly phenotype the gene expression patterns that characterize two disparate but equally lethal forms of liver pathology that develop in Schistosoma mansoni infected mice polarized for type-1 and type-2 cytokine responses. Hierarchical clustering analysis identified at least three groups of genes associated with a polarized type-2 response and two linked with an extreme type-1 cytokine phenotype. Predictions about liver fibrosis, apoptosis, and granulocyte recruitment and activation generated by the microarray studies were confirmed later by traditional biological assays. The data show that cDNA microarrays are useful not only for determining coordinated gene expression profiles but are also highly effective for molecularly "fingerprinting" diseased tissues. Moreover, they illustrate the potential of genome-wide approaches for generating comprehensive views on the molecular and biochemical mechanisms regulating infectious disease pathogenesis.