Two calcium-binding proteins in infiltrate macrophages of rheumatoid arthritis

Identification of S100A8 and S100A9 as serological markers for colorectal cancer

In search of novel serological protein biomarkers for human colorectal cancer (CRC), we analyzed CRC tissues using two-dimensional difference in-gel electrophoresis (2D-DIGE) on a narrow range IPG strip (pH 5.5-6.7). By comparing tumor tissues with matched normal tissues in a pairwise manner (n = 6), we identified 34 up-regulated and 17 down-regulated spots with intensity changes greater than 2-fold (Student's t-test, p < 0.05). Expression of both mRNA and protein levels of four proteins, adenosylhomocysteinase, Nm23-H1, S100A8 and S100A9, in CRC tissues was further evaluated by semiquantitative RT-PCR and Western blot analysis. The results revealed that all four proteins were elevated in the tumor tissues. We also confirmed, by immunohistochemistry, that adenosylhomocysteinase and Nm23-H1 were overexpressed in tumor cell cytoplasm and that S100A8 and S100A9 proteins were strongly expressed in tumor infiltrating immune cells. Western blot analysis with fractionated plasma samples showed that S100A8 and S100A9 were significantly increased in the plasma of CRC patients (n = 77) and colorectal adenoma patients (n = 11), compared to healthy controls (n = 21). The area under a receiver operating characteristic (ROC) curve was 0.91 for S100A8 and 0.89 for S100A9, which was superior to the established tumor marker carcinoembryonic antigen with 0.78 for the area under the ROC curve. Some patients with inflammatory diseases such as pancreatitis also showed elevated levels of the proteins. Importantly, in comparison to the control group, both proteins showed a remarkable change at the early stage of cancer. Therefore, we suggest S100A8 and S100A9 as candidates for serological biomarkers in combination with other serum markers that aid CRC diagnosis.

Identification of human S100A9 as a novel target for treatment of autoimmune disease via binding to quinoline-3-carboxamides

Despite more than 25 years of research, the molecular targets of quinoline-3-carboxamides have been elusive although these compounds are currently in Phase II and III development for treatment of autoimmune/inflammatory diseases in humans. Using photoaffinity cross-linking of a radioactively labelled quinoline-3-carboxamide compound, we could determine a direct association between human S100A9 and quinoline-3-carboxamides. This interaction was strictly dependent on both Zn++ and Ca++. We also show that S100A9 in the presence of Zn++ and Ca++ is an efficient ligand of receptor for advanced glycation end products (RAGE) and also an endogenous Toll ligand in that it shows a highly specific interaction with TLR4/MD2. Both these interactions are inhibited by quinoline-3-carboxamides. A clear structure-activity relationship (SAR) emerged with regard to the binding of quinoline-3-carboxamides to S100A9, as well as these compounds potency to inhibit interactions with RAGE or TLR4/MD2. The same SAR was observed when the compound's ability to inhibit acute experimental autoimmune encephalomyelitis in mice in vivo was analysed. Quinoline-3-carboxamides would also inhibit TNFalpha release in a S100A9-dependent model in vivo, as would antibodies raised against the quinoline-3-carboxamide-binding domain of S100A9. Thus, S100A9 appears to be a focal molecule in the control of autoimmune disease via its interactions with proinflammatory mediators. The specific binding of quinoline-3-carboxamides to S100A9 explains the immunomodulatory activity of this class of compounds and defines S100A9 as a novel target for treatment of human autoimmune diseases.

Quantitative proteomic analysis of differential proteins in the stroma of nasopharyngeal carcinoma and normal nasopharyngeal epithelial tissue

The importance of stromal cells and the factors that they expressed during cancer initiation and progression have been highlighted by recent literature. To identify the stromal proteins involved in nasopharyngeal carcinoma (NPC) carcinogenesis, we assessed differences in protein expression of the stroma from NPC and normal nasopharyngeal epithelium tissues (NNET) using a quantitative proteomic approach combined with laser capture microdissection (LCM). LCM was performed to purify stromal cells from the NPC and NNET, respectively. The differential proteins between the pooled microdissected tumor and normal stroma were analyzed by two-dimensional difference gel electrophoresis (2D-DIGE) combined with mass spectrometry (MS). Twenty differential proteins were identified, and the expression and location of two differential proteins (L-plastin and S100A9) were further confirmed by Western blotting and immunohistochemical analysis. Our results will be helpful to study the role of stroma in the NPC carcinogenesis, as well as discover the interaction between NPC cells and their surrounding microenvironment.

Accumulation of macrophages expressing myeloid-related protein 8 associated with the progression of sclerotic changes in children with IgA nephropathy

Myeloid-related protein (MRP) 8 is a calcium-binding protein of the S100 family. The renal accumulation of macrophages expressing MRP8 is associated with the inflammatory activity of glomerulonephritis. We evaluated the renal accumulation of macrophages expressing MRP8 in children with IgA nephropathy (IgAN). We collected data on 25 IgAN children who had been treated with prednisolone and divided these patients into two groups: Favorable group, consisting of 11 patients with normal urine and 6 with minor urinary abnormalities at 4.3 +/- 1.3 years after initial treatment; and Unfavorable group, consisting of 8 patients with persistent nephropathy. The pathological renal findings were compared between both groups. The second biopsy was performed at two years after first biopsy at 5.5 +/- 4.9 months from onset. In Favorable group, the glomerular accumulation of macrophages expressing MRP8, and mesangial cells expressing alpha-smooth muscle actin (alpha-SMA) were lower in the second biopsy specimens than those of the first biopsy specimens. In Unfavorable group, the glomerular accumulation of macrophages expressing MRP8 detected in the second biopsy specimens was similar to that of the first biopsy, while the number of mesangial cells expressing alpha-SMA and the index of renal sclerosis were higher in the second biopsy than in the first biopsy. The indexes of renal sclerosis were higher in children with more macrophages expressing MRP8 than in children with less macrophages expressing MRP8. Our results suggest that renal macrophages expressing MRP8 may be involved in the progression of sclerotic changes in children with IgAN.

The endogenous Toll-like receptor 4 agonist S100A8/S100A9 (calprotectin) as innate amplifier of infection, autoimmunity, and cancer

The innate immune system is crucial for initiation and amplification of inflammatory responses. During this process, phagocytes are activated by PAMPs that are recognized by PRRs. Phagocytes are also activated by endogenous danger signals called alarmins or DAMPs via partly specific, partly common PRRs. Two members of the S100 protein family, S100A8 and S100A9, have been identified recently as important endogenous DAMPs. The complex of S100A8 and S100A9 (also called calprotectin) is actively secreted during the stress response of phagocytes. The association of inflammation and S100A8/S100A9 was discovered more than 20 years ago, but only now are the molecular mechanisms involved in danger signaling by extracellular S100A8/S100A9 beginning to emerge. Taking advantage of mice lacking the functional S100A8/S100A9 complex, these molecules have been identified as endogenous activators of TLR4 and have been shown to promote lethal, endotoxin-induced shock. Importantly, S100A8/S100A9 is not only involved in promoting the inflammatory response in infections but was also identified as a potent amplifier of inflammation in autoimmunity as well as in cancer development and tumor spread. This proinflammatory action of S100A8/S100A9 involves autocrine and paracrine mechanisms in phagocytes, endothelium, and other cells. As a net result, extravasation of leukocytes into inflamed tissues and their subsequent activation are increased. Thus, S100A8/S100A9 plays a pivotal role during amplification of inflammation and represents a promising new therapeutic target.

Analysis of the structure of human apo-S100B at low temperature indicates a unimodal conformational distribution is adopted by calcium-free S100 proteins

S100B is one of the best-characterized members of the calcium-signaling S100 protein family. Most S100 proteins are dimeric, with each monomer containing two EF-hand calcium-binding sites (EF1, EF2). S100B and other S100 proteins respond to calcium increases in the cell by coordinating calcium and undergoing a conformational change that allows them to interact with a variety of cellular targets. Although several three dimensional structures of S100 proteins are available in the calcium-free (apo-) state it has been observed that these structures appear to adopt a wide range of conformations in the EF2 site with respect to the positioning of helix III, the helix that undergoes the most dramatic calcium-induced conformational change. In this work, we have determined the structure of human apo-S100B at 10 degrees C to examine whether temperature might be responsible for these structural differences. Further, we have used this data, and other available apo-S100 structures, to show that despite the range of interhelical angles adopted in the apo-S100 structures, normal Gaussian distributions about the mean angles found in the structure of human apo-S100B are observed. This finding, only obvious from the analysis of all available apo-S100 proteins, provides direct structural evidence that helix III is a loosely packed helix. This is likely a necessary functional property of the S100 proteins that facilitates the calcium-induced conformational change of helix III. In contrast, the calcium-bound structures of the S100 proteins show significantly smaller variability in the interhelical angles. This shows that calcium binding to the S100 proteins causes not only a conformational change but results in a tighter distribution of helices within the EF2 calcium binding site required for target protein interactions.

Two chromogranin a-derived peptides induce calcium entry in human neutrophils by calmodulin-regulated calcium independent phospholipase A2

Background

Antimicrobial peptides derived from the natural processing of chromogranin A (CgA) are co-secreted with catecholamines upon stimulation of chromaffin cells. Since PMNs play a central role in innate immunity, we examine responses by PMNs following stimulation by two antimicrobial CgA-derived peptides.

Methodology/Principal Findings

PMNs were treated with different concentrations of CgA-derived peptides in presence of several drugs. Calcium mobilization was observed by using flow cytometry and calcium imaging experiments. Immunocytochemistry and confocal microscopy have shown the intracellular localization of the peptides. The calmodulin-binding and iPLA2 activating properties of the peptides were shown by Surface Plasmon Resonance and iPLA2 activity assays. Finally, a proteomic analysis of the material released after PMNs treatment with CgA-derived peptides was performed by using HPLC and Nano-LC MS-MS. By using flow cytometry we first observed that after 15 s, in presence of extracellular calcium, Chromofungin (CHR) or Catestatin (CAT) induce a concentration-dependent transient increase of intracellular calcium. In contrast, in absence of extra cellular calcium the peptides are unable to induce calcium depletion from the stores after 10 minutes exposure. Treatment with 2-APB (2-aminoethoxydiphenyl borate), a store operated channels (SOCs) blocker, inhibits completely the calcium entry, as shown by calcium imaging. We also showed that they activate iPLA2 as the two CaM-binding factors (W7 and CMZ) and that the two sequences can be aligned with the two CaM-binding domains reported for iPLA2. We finally analyzed by HPLC and Nano-LC MS-MS the material released by PMNs following stimulation by CHR and CAT. We characterized several factors important for inflammation and innate immunity.

Conclusions/Significance

For the first time, we demonstrate that CHR and CAT, penetrate into PMNs, inducing extracellular calcium entry by a CaM-regulated iPLA2 pathway. Our study highlights the role of two CgA-derived peptides in the active communication between neuroendocrine and immune systems.

Suppression of inflammation in rat autoimmune myocarditis by S100A8/A9 through modulation of the proinflammatory cytokine network

AIMS

S100A8/A9 is expressed in activated monocytes/macrophages and assumed to be heavily involved in the pathogenesis of acute inflammation. Although several studies have asserted that S100A8/A9 has a proinflammatory function, the exact biological function of S100A8/A9 is yet to be described. We examined the anti-inflammatory effects of S100A8/A9 on experimental autoimmune myocarditis (EAM) in rats.

METHODS AND RESULTS

Experimental autoimmune myocarditis was induced in Lewis rats by immunization with porcine cardiac myosin. The recombinant (R-) S100A8/A9 was injected intraperitoneally into EAM rats. R-S100A8/A9 attenuated the severity of myocarditis, as evidenced by echocardiographic and histological findings. In addition, we found that not only the mRNA expression of proinflammatory cytokines [interleukin (IL)-1beta, IL-6, and tumour necrosis factor (TNF)-alpha] in the myocardium, but also their serum concentrations were suppressed in EAM rats treated with R-S100A8/A9. Nuclear factor-kappa B expression in inflammatory cells was also suppressed in the treated rats. To elucidate the mechanistic function of S100A8/A9 on proinflammatory cytokines in vivo, we used an ELISA on the supernatant of homogenized heart tissue treated with R-S100A8/A9. The findings revealed high-affinity binding of R-S100A8/A9 with IL-1beta, IL-6, and TNF-alpha in the myocardium, suggesting the trapping of proinflammatory cytokines by R-S100A8/A9.

CONCLUSION

S100A8/A9 attenuates EAM through modulation of the proinflammatory cytokine network.

Calprotectin S100A9 calcium-binding loops I and II are essential for keratinocyte resistance to bacterial invasion

Epithelial cells expressing calprotectin, a heterodimer of S100A8 and S100A9 proteins, are more resistant to bacterial invasion. To determine structural motifs that affect resistance to bacterial invasion, mutations were constructed in S100A9 targeting the calcium-binding loops I and II (E36Q, E78Q, E36Q,E78Q) and the C terminus (S100A9(1-99) and S100A9(1-112)), which contains putative antimicrobial zinc-binding and phosphorylation sites. The S100A8 and mutated S100A9 encoding plasmids were transfected into calprotectin-negative KB carcinoma cells. All transfected cells (except KB-sham) expressed 27E10-reactive heterodimers. In bacterial invasion assays with Listeria monocytogenes and Salmonella enterica serovar Typhimurium (Salmonella typhimurium), cell lines expressing S100A8 in complex with S100A9E36Q, S100A9E78Q, S100A9(1-99), or S100A9(1-112) mutants or the S100A9(1-114) (full-length) calprotectin resisted bacterial invasion better than KB-sham. When compared with KB-S100A8/A9(1-114), cells expressing truncated S100A9(1-99) or S100A9(1-112) with S100A8 also showed increased resistance to bacterial invasion. In contrast, glutamic acid residues 36 and 78 in calcium-binding loops I and II promote resistance in epithelial cells, because cells expressing S100A9E36Q,E78Q with S100A8 were unable to resist bacterial invasion. Mutations in S100A9 E36Q, E78Q were predicted to cause loss of the calcium-induced positive face in calprotectin, reducing interactions with microtubules and appearing to be crucial for keratinocyte resistance to bacterial invasion.

Global gene expression profiling unveils S100A8/A9 as candidate markers in H-ras-mediated human breast epithelial cell invasion

The goal of the present study is to unveil the gene expression profile specific to the biological processes of human breast epithelial cell invasion and migration using an MCF10A model genetically engineered to constitutively activate the H-ras or N-ras signaling pathway. We previously showed that H-Ras, but not N-Ras, induces MCF10A cell invasion/migration, whereas both H-Ras and N-Ras induce cell proliferation and phenotypic transformation. Thus, these cell lines provide an experimental system to separate the gene expression profile associated with cell invasion apart from cell proliferation/transformation. Analysis of whole human genome microarray revealed that 412 genes were differentially expressed among MCF10A, N-Ras MCF10A, and H-Ras MCF10A cells and hierarchical clustering separated 412 genes into four clusters. We then tested whether S100A8 and S100A9, two of the genes which are most highly up-regulated in an H-Ras-specific manner, play a causative role for H-Ras-mediated MCF10A cell invasion and migration. Importantly, small interfering RNA-mediated knockdown of S100A8/A9 expression significantly reduced H-Ras-induced invasion/migration. Conversely, the induction of S100A8/A9 expression conferred the invasive/migratory phenotype to parental MCF10A cells. Furthermore, we provided evidence of signaling cross-talk between S100A8/A9 and the mitogen-activated protein kinase signaling pathways essential for H-Ras-mediated cell invasion and migration. Taken together, this study revealed S100A8/A9 genes as candidate markers for metastatic potential of breast epithelial cells. Our gene profile data provide useful information which may lead to the identification of additional potential targets for the prognosis and/or therapy of metastatic breast cancer.

Antinociceptive effect of the C-terminus of murine S100A9 protein on experimental neuropathic pain

The synthetic peptide identical to the C-terminus of murine S100A9 protein (mS100A9p) has antinociceptive effect on different acute inflammatory pain models. In this study, the effect of mS100A9p was investigated on neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve in rats. Hyperalgesia, allodynia, and spontaneous pain were assessed to evaluate nociception. These three signs were detected as early as 2 days after sciatic nerve constriction and lasted for over 14 days after CCI. Rats were treated with different doses of mS100A9p by intraplantar, oral, or intrathecal routes on day 14 after CCI, and nociception was evaluated 1h later. These three routes of administration blocked hyperalgesia, allodynia and spontaneous pain. The duration of the effect of mS100A9p depends on the route used and phenomenon analyzed. Moreover, intraplantar injection of mS100A9p in the contralateral paw inhibited the hyperalgesia on day 14 days after CCI. The results obtained herein demonstrate the antinociceptive effect of the C-terminus of murine S100A9 protein on experimental neuropathic pain, suggesting a potential therapeutic use for it in persistent pain syndromes, assuming that tolerance does not develop to mS100A9p.

Complement receptor 3 promotes severe ross river virus-induced disease

Alphaviruses such as Ross River virus (RRV) and chikungunya virus are mosquito-transmitted viruses that cause explosive epidemics of debilitating arthritis and myositis affecting millions of humans worldwide. Previous studies using a mouse model of RRV-induced disease demonstrated that viral infection results in a severe inflammatory arthritis and myositis and that complement component 3 (C3) contributes to the destructive phase of the inflammatory disease but not the recruitment of cellular infiltrates to the sites of RRV-induced inflammation. Here, we demonstrate that mice deficient in complement receptor 3 (CR3) (CD11b(-/-)), a signaling receptor activated by multiple ligands including the C3 cleavage fragment iC3b, develop less-severe disease signs and decreased tissue destruction compared to RRV-infected wild-type mice. CR3 deficiency had no effect on viral replication, nor did it diminish the magnitude, kinetics, and composition of the cellular infiltrates at the sites of inflammation. However, the genetic absence of CR3 diminished the expression of specific proinflammatory and cytotoxic effectors, including S100A9/S100A8 and interleukin-6, within the inflamed tissues, suggesting that CR3-dependent signaling at the sites of inflammation contributes to tissue damage and severe disease.

Immunopathogenesis of psoriatic arthritis: Recent advances

Psoriatic Arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis. The pathophysiology of PsA includes genetic, environmental and immunologic factors. Recent studies revealed the dynamic role of the immune system in the pathogenesis of the disease. Adhesion molecules, proinflammatory cytokines, angiogenic factors and metalloproteinases appear to orchestrate the inflammatory response in PsA. This article summarizes the current immunologic findings and suggests future therapeutic and researching approaches in the field of PsA.

RAGE, carboxylated glycans and S100A8/A9 play essential roles in colitis-associated carcinogenesis

Patients with inflammatory bowel diseases are at increased risk for colorectal cancer, but the molecular mechanisms linking inflammation and cancer are not well defined. We earlier showed that carboxylated N-glycans expressed on receptor for advanced glycation end products (RAGE) and other glycoproteins mediate colitis through activation of nuclear factor kappa B (NF-κB). Because NF-κB signaling plays a critical role in the molecular pathogenesis of colitis-associated cancer (CAC), we reasoned that carboxylated glycans, RAGE and its ligands might promote CAC. Carboxylated glycans are expressed on a subpopulation of RAGE on colon cancer cells and mediate S100A8/A9 binding to RAGE. Colon tumor cells express binding sites for S100A8/A9 and binding leads to activation of NF-κB and tumor cell proliferation. Binding, downstream signaling and tumor cell proliferation are blocked by mAbGB3.1, an anti-carboxylate glycan antibody, and by anti-RAGE. In human colon tumor tissues and in a mouse model of CAC, we found that myeloid progenitors expressing S100A8 and S100A9 infiltrate regions of dysplasia and adenoma. mAbGB3.1 administration markedly reduces chronic inflammation and tumorigenesis in the mouse model of CAC and RAGE-deficient mice are resistant to the onset of CAC. These findings show that RAGE, carboxylated glycans and S100A8/A9 play essential roles in tumor–stromal interactions, leading to inflammation-associated colon carcinogenesis.

S100A8/A9, a key mediator for positive feedback growth stimulation of normal human keratinocytes

S100A8 and S100A9 are known to be up-regulated in hyperproliferative and psoriatic epidermis, but their function in epidermal keratinocytes remains largely unknown. Here we show that (1) S100A8 and S100A9 are secreted by cultured normal human keratinocytes (NHK) in a cytokine-dependent manner, (2) when applied to NHK, recombinant S100A8/A9 (a 1:1 mixture of S100A8 and S100A9) induced expression of a number of cytokine genes such as IL-8/CXCL8, CXCL1, CXCL2, CXCL3, CCL20, IL-6, and TNFalpha that are known to be up-regulated in psoriatic epidermis, (3) the S100A8/A9-induced cytokines in turn enhanced production and secretion of S100A8 and S100A9 by NHK, and (4) S100A8 and S100A8/A9 stimulated the growth of NHK at a concentration as low as 1 ng/ml. These results indicate the presence of a positive feedback loop for growth stimulation involving S100A8/A9 and cytokines in human epidermal keratinocytes, implicating the relevance of the positive feedback loop to the etiology of hyperproliferative skin diseases, including psoriasis.

Circulating calprotectin in ovarian carcinomas and borderline tumors of the ovary

OBJECTIVE

Recent studies indicate that circulating calprotectin may serve as a biomarker in some cancers. We investigated whether this is the case for ovarian neoplasms.

STUDY DESIGN

Calprotectin was analyzed with an enzyme-linked immunosorbent assay in EDTA-plasma collected prior to surgery from women with ovarian carcinomas (n = 89), borderline ovarian tumors (BOT, n = 39), and benign ovarian tumors (n = 71). Serum CA 125 was analyzed in the same study population.

RESULTS

Median plasma calprotectin concentration was elevated in ovarian carcinoma, compared with controls, as well as compared with BOT (both P < .001). A positive correlation was found between CA 125 and calprotectin concentrations in ovarian carcinoma. Receiver operating characteristic curves demonstrated a larger area under the curve for CA 125 (0.85) as compared with calprotectin (0.70).

CONCLUSION

Plasma calprotectin is elevated in invasive ovarian cancer, but when used as a tumor marker, it is inferior to CA 125.

Structure of calcium-bound human S100A13 at pH 7.5 at 1.8 A resolution

S100A13 is a member of the S100 family of EF-hand-containing calcium-binding proteins. S100A13 plays an important role in the secretion of fibroblast growth factor-1 and interleukin 1 alpha, two pro-angiogenic factors released by the nonclassical endoplasmic reticulum/Golgi-independent secretory pathway. The X-ray crystal structure of human S100A13 at pH 7.5 was determined at 1.8 A resolution. The structure was solved by molecular replacement and was refined to a final R factor of 19.0%. The structure revealed that human S100A13 exists as a homodimer with two calcium ions bound to each protomer. The protomer is composed of four alpha-helices (alpha(1)-alpha(4)), which form a pair of EF-hand motifs. Dimerization occurs by hydrophobic interactions between helices alpha(1) and alpha(4) and by intermolecular hydrogen bonds between residues from helix alpha(1) and the residues between alpha(2) and alpha(3) of both chains. Despite the high similarity of the backbone conformation in each protomer, the crystal structures of human S100A13 at pH 7.5 (this study) and at pH 6.0 [Li et al. (2007), Biochem. Biophys. Res. Commun. 356, 616-621] exhibit recognizable differences in the relative orientation ( approximately 2.5 degrees) of the protomers within the dimer and also remarkable differences in the side-chain conformations of several amino-acid residues.

Neutrophil-selective CD18 silencing using RNA interference in vivo

Tissue-specific silencing of genes may be used for genetic engineering in mice and has possible therapeutic applications in humans. Current strategies in mice rely on Cre/loxP technology requiring the generation of multiple transgenic lines and breeding strategies. Here, we describe the selective silencing of CD18, a leukocyte-specific integrin in neutrophils using a micro RNA (miRNA) strategy that requires the generation of one transgenic line. CD18-specific miRNA hairpin driven by the myeloid specific human MRP8 promoter resulted in the generation of transgenic lines with 75% to 95% reduction in CD18 protein levels in neutrophils and monocytes. Minimal decreases in T cells and a partial diminution in macrophages were observed. Neutrophil CD18 silencing resulted in neutrophilia, splenomegaly, and significant defects in neutrophil trafficking with the degree of alterations correlating with the extent of CD18 silencing. Thus, our data demonstrate the utility of using miRNA approaches to silence genes in neutrophils, which are terminally differentiated cells with a short half-life that largely precludes their genetic manipulation in vitro. Furthermore, the mouse models provide a valuable tool to examine the contribution of CD18 on neutrophils to leukocyte adhesion deficiency type I (LAD-I), a complex inherited disorder in which reduced or absent CD18 expression in multiple leukocyte subsets leads to impaired innate and adaptive immune responses.

Localization of S100A8 and S100A9 expressing neutrophils to spinal cord during peripheral tissue inflammation

Investigation of hyperalgesia at the spinal transcriptome level indicated that carrageenan-induced inflammation of rat hind paws leads to a rapid but sustained increase in S100A8 and S100A9 expression, two genes implicated in the pathology of numerous inflammatory diseases including rheumatoid arthritis and gout. In situ hybridization revealed that the elevation occurred in neutrophils that migrate to the spinal cord vasculature during peripheral inflammation, not in spinal neurons or glial cells. Immunohistochemical analysis suggests, but does not prove, that these neutrophils abundantly release S100A8 and S100A9. Consistent with this, we detected an increase in ICAM and VCAM, both indicators of endothelial activation, a known trigger for secretion of S100A8 and S100A9. Migration of S100A8- and S100A9-expressing neutrophils to spinal cord is selective, since MCP-1- and CD68-expressing leukocytes do not increase in spinal cord vasculature during hind paw inflammation. Examination of many neutrophil granule mediators in spinal cord indicated that they are not regulated to the same degree as S100A8 and S100A9. Neutrophil migration also occurs in the vasculature of brain and pituitary gland during peripheral inflammation. Together, these findings suggest an interaction between a subpopulation of leukocytes and the CNS during peripheral tissue inflammation, as implied by an apparent release and possible diffusion of S100A8 and S100A9 through the endothelial blood-brain barrier. Although the present findings do not establish the neurophysiological or behavioral relevance of these observations to nociceptive processing, the data raise the possibility that selective populations of leukocytes may communicate the presence of disease or tissue damage from the periphery to cells in the central nervous system.

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

BACKGROUND

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

METHODS AND RESULTS

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

CONCLUSIONS

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

Mrp8 and Mrp14 are endogenous activators of Toll-like receptor 4, promoting lethal, endotoxin-induced shock

To identify new components that regulate the inflammatory cascade during sepsis, we characterized the functions of myeloid-related protein-8 (Mrp8, S100A8) and myeloid-related protein-14 (Mrp14, S100A9), two abundant cytoplasmic proteins of phagocytes. We now demonstrate that mice lacking Mrp8-Mrp14 complexes are protected from endotoxin-induced lethal shock and Escherichia coli-induced abdominal sepsis. Both proteins are released during activation of phagocytes, and Mrp8-Mrp14 complexes amplify the endotoxin-triggered inflammatory responses of phagocytes. Mrp8 is the active component that induces intracellular translocation of myeloid differentiation primary response protein 88 and activation of interleukin-1 receptor-associated kinase-1 and nuclear factor-kappaB, resulting in elevated expression of tumor necrosis factor-alpha (TNF-alpha). Using phagocytes expressing a nonfunctional Toll-like receptor 4 (TLR4), HEK293 cells transfected with TLR4, CD14 and MD2, and by surface plasmon resonance studies in vitro, we demonstrate that Mrp8 specifically interacts with the TLR4-MD2 complex, thus representing an endogenous ligand of TLR4. Therefore Mrp8-Mrp14 complexes are new inflammatory components that amplify phagocyte activation during sepsis upstream of TNFalpha-dependent effects.

Proteomic Analysis of Peritoneal Fluid in Women with Endometriosis

This study aims to evaluate differences in the expression of proteins present in the peritoneal fluid (PF) of women with and without endometriosis. PF samples were subjected to two-dimensional gel electrophoresis; protein spots of interest were identified by liquid chromatography tandem mass spectrometry. Several molecules had aberrant expression in PF of women with endometriosis; they may be useful for a better understanding of the pathogenesis of this disease.

The expression of S100A8 in pancreatic cancer-associated monocytes is associated with the Smad4 status of pancreatic cancer cells

The cross-talk between tumour cells and the surrounding supporting host cells (stroma) is a key regulator of cancer growth and progression. By undertaking 2-DE analysis of laser capture microdissected malignant and stromal components of pancreatic tumours and benign ductal elements, we have identified high levels of S100A8 and S100A9 in tumour-associated stroma but not in benign or malignant epithelia. Immunohistochemical analysis (n = 71 patients) revealed strong expression of both proteins in stromal myeloid cells, subsequently identified as CD14(+)/CD68(- )monocytes/macrophages. Co-immunofluorescence revealed that S100A8 was expressed in a subset of S100A9-positive cells. Correlation of the expression of S100A8 and S100A9 to patient parameters revealed that the microenvironments of tumours which lacked expression of the tumour suppressor protein, Smad4, had significantly reduced numbers of S100A8-immunoreactive (p = 0.023) but not S100A9-immunoreactive (p = 0.21) cells. The ratio of S100A8- to S100A9-positive cells within individual tumours was significantly lower in Smad4-negative tumours than in Smad4-positive tumours (p<0.003). Pancreatitic specimens also contained S100A8- and S100A9-expressing cells, although this was not observed in regions displaying extensive fibrosis. In conclusion, our study provides an extensive analysis of S100A8 and S100A9 in pancreatic disease and highlights a potentially important relationship between pancreatic cancer cells and their surrounding microenvironment.

Amide Exchange Shows Calcium-Induced Conformational Changes Are Transmitted to the Dimer Interface of S100B

S100B is a 21 kDa member of the S100 calcium-binding protein family. This protein comprises a symmetric homodimer with each subunit having two EF-hands arranged from four alpha-helices (I-IV). S100B binds calcium and undergoes a conformation change leading to the exposure of hydrophobic surface residues that enable the protein to interact with biological target molecules. The most significant structural change that occurs during calcium binding results in a change in the orientation of helix III with respect to helices II and IV. In this work, the calcium-sensitive conformational change has been studied by utilizing fast 1H-15N HSQC experiments and water-transfer methods to follow the amide exchange in apo-S100B and Ca-S100B at 35 degrees C. In apo-S100B, the protection factors are 2-3 orders of magnitude lower for helix III than for helix I, II, or IV. In addition, the exchange stability measured here for the dimer interface helices (I, I', IV, and IV'), in the absence of calcium, is similar to the stability obtained from chemical denaturation experiments. When calcium binds, significant decreases in the protection factors for helices I and IV indicate a modification in the stability of the dimer interface has occurred. In contrast, helix II protection factors increase slightly, which is consistent with a decreased level of surface exposure of this helix. These data have been compared with those of the monomeric S100 protein, calbindin D9k, to illustrate that upon calcium binding there is a balance maintained between the amide exchange rates in helices II and III, although largely the rates are dissimilar for each of these proteins. This distinguishing feature may be important for the calcium-induced conformational change in S100B, where calcium binding is transmitted to the dimer-forming helices.

Usefulness of S100A9 for diagnosis of intrathyroid epithelial thymoma (ITET)/carcinoma showing thymus-like differentiation (CASTLE)

AIMS

Intrathyroid epithelial tumour (ITET)/carcinoma showing thymus-like differentiation (CASTLE) is a rare malignant tumour, which is thought to originate from ectopic thymic tissue in the thyroid. The differential diagnosis between ITET/ CASTLE and squamous cell carcinoma (SCC) or undifferentiated carcinoma with squamoid component (UC-SCC) is very important, because ITET/CASTLE shows a far better prognosis than SCC or UC-SCC. In this study, we investigated the usefulness of S100A9, a marker of SCC and squamous cell epithelia, for diagnosis of ITET/CASTLE.

METHODS

We immunohistochemically investigated S100A9 expression in 23 ITET/CASTLEs, 26 SCCs, and 19 UC-SCCs, as well as eight thymomas and 12 normal thymic tissues.

RESULTS

All thymomas and thymic tissues showed a small number of S100A9-expressing cells in a scattered pattern in accordance with Hassall corpuscles. Twenty-one of 23 ITET/ CASTLEs showed the same pattern as thymomas or thymic tissues, while 14 SCCs and 15 UC-SCCs showed diffuse and laminated positivity of S100A9. The positive predictive value and specificity of S100A9 for diagnosis of ITET/CASTLE was 91.3 and 93.9%, respectively, and sensitivity was 75.0%.

CONCLUSIONS

These findings suggest that S100A9 is a useful marker for discriminating ITET/CASTLE from SCC or UC-SCC.

Neutrophilic cell-free exudate induces antinociception mediate by the protein S100A9

Calcium-binding protein S100A9 (MRP-14) induces antinociceptive effect in an experimental model of painful sensibility and participates of antinociception observed during neutrophilic peritonitis induced by glycogen or carrageenan in mice. In this study, the direct antinociceptive role of the protein S100A9 in neutrophilic cell-free exudates obtained of mice injected with glycogen was investigated. Mice were intraperitoneally injected with a glycogen solution, and after 4, 8, 24, and 48 hours, either the pattern of cell migration of the peritoneal exudate or the nociceptive response of animals was evaluated. The glycogen-induced neutrophilic peritonitis evoked antinociception 4 and 8 hours after inoculation of the irritant. Peritoneal cell-free exudates, collected in different times after the irritant injection, were transferred to naive animals which were submitted to the nociceptive test. The transference of exudates also induced antinociceptive effect, and neutralization of S100A9 activity by anti-S100A9 monoclonal antibody totally reverted this response. This effect was not observed when experiments were made 24 or 48 hours after glycogen injection. These results clearly indicate that S100A9 is secreted during glycogen-induced neutrophilic peritonitis, and that this protein is responsible by antinociception observed in the initial phase of inflammatory reaction. Thus, these data reinforce the hypothesis that the calcium-binding protein S100A9 participates of the endogenous control of inflammatory pain.

Diagnostic precision of fecal calprotectin for inflammatory bowel disease and colorectal malignancy

OBJECTIVES

Fecal calprotectin (FC) is a relatively new marker of intraluminal intestinal inflammation. Using meta-analytical techniques, the study aimed to evaluate the diagnostic precision of FC for inflammatory bowel disease (IBD) and colorectal cancer (CRC) in adults and children.

METHODS

Quantitative meta-analysis was performed on prospective studies, comparing FC levels against the histological diagnosis. Sensitivity, specificity, and diagnostic odds ratio (DOR) were calculated for each study. Summary receiver-operating characteristic (sROC) curves and subgroup analysis were undertaken. Study quality and heterogeneity were evaluated.

RESULTS

Thirty studies of 5,983 patients were included. FC levels in patients with IBD were higher by 219.2 micrograms per gram (microg/g) compared with normal patients (P < 0.001). sROC curve analysis showed a sensitivity of 0.95 (95% CI 0.93-0.97), specificity of 0.91 (95% CI 0.86-0.91), and an area under the curve (AUC) of 0.95 for the diagnosis of IBD. Patients with colorectal neoplasia had nonsignificantly higher FC levels by 132.2 microg/g compared with noncancer controls (P= 0.18). Sensitivity and specificity of FC for the diagnosis of CRC were 0.36 and 0.71, respectively, with an AUC of 0.66. The diagnostic precision of FC for IBD was higher in children than adults with better accuracy at a cutoff level of 100 microg/g versus 50 microg/g. Sensitivity analysis and metaregression analysis did not significantly alter the results.

CONCLUSIONS

FC cannot be recommended as a screening test for CRC in the general population. FC appeared to offer a good diagnostic precision in distinguishing IBD from non-IBD diagnoses, with higher precision at a cutoff of 100 microg/g.

Accumulation of macrophages expressing MRP8 and MRP14 in skin lesions during Leishmania major infection in BALB/c and RAG-2 knockout mice

Migration inhibitory factor-related protein 8 (MRP8) and MRP14 are expressed by myeloid cells and especially known as marker proteins of an immature and inflammatory subtype of macrophages. In this study, we immunohistochemically examined an accumulation of MRP8+ and MRP14+ macrophages in skin lesions during Leishmania major infection in susceptible BALB/c and RAG-2-/- mice. L. major infection caused the development of a nodular type of skin lesion at the infection site in mice and a massive accumulation of macrophages was observed in the lesions at four weeks after the infection. Immunohistochemical analyses showed MRP8+ and MRP14+ macrophages are predominant cell types in the skin lesions in both mouse strains. In contrast, F4/80+ cells, which correspond to mature macrophages, were rarely found in the skin lesions. These data suggest that the accumulation of inflammatory subtype of macrophages in BALB/c mice during L. major infection can be induced without acquired immune responses.

Culture and differentiation of preadipocytes in two-dimensional and three-dimensional in vitro systems

Adipogenesis is a complex process that involves the differentiation of preadipocytes into mature adipocytes. We have developed two-dimensional (2D) and three-dimensional (3D) cell culture systems for the purpose of culturing and differentiating primary preadipocytes in vitro. Differentiating preadipocytes show multiple lipid droplet accumulation and comparable protein expression patterns to mature adipocytes in vivo. We report that in both in vitro systems terminally differentiated adipocytes show characteristics similar to those of mature adipocytes in vivo, assessed by the expression of the S100alpha/beta protein, insulin receptor and caveolin-1, and receptors for inflammatory mediators, namely tumor necrosis factor-alpha receptors I and II (TNFRI and TNFRII) and chemokine receptor 5 (CCR5). Our results demonstrate that the S100 protein, caveolin-1, and insulin receptor are expressed and up-regulated in differentiating and terminally differentiated cells. In addition, the receptors for TNFalpha are not present in preadipocytes but are expressed in differentiating preadipocytes and in differentiated adipocytes. Similarly, CCR5 was exclusively expressed in differentiating preadipocytes and terminally differentiated adipocytes, but not in preadipocytes. Both 2D and 3D culture models are highly robust and reproducible and offer the potential to study adipogenesis and cellular interactions closely resembling and comparable to those in vivo. Our 3D collagen system offers a distinct advantage over the 2D system in that the adipocytes remain confined within the matrix and remain intact during biochemical analysis. Moreover, the collagen matrix allows adipocytes to closely simulate morphological characteristics and behavior as in vivo whilst permitting manipulation of the microenvironment in vitro to study adipogenesis.

Intrinsic function of S100A8/A9 complex as an anti-inflammatory protein in liver injury induced by lipopolysaccharide in rats

BACKGROUND

We hypothesized that the S100A8/A9 complex is effective in the suppression of acute inflammatory changes.

METHODS

To clarify such a functional role of the S100A8/A9 complex in acute inflammatory disorder, the complex purified from human leukocytes (approx. 1 mg) was intraperitoneally injected into rats 1.0 or 3.5 h after an injection of lipopolysaccharide (LPS).

RESULTS

The serum concentrations of interleukin-6 (IL-6) and nitric oxide (NOx) were significantly decreased in the treated rats. Conversely, when anti-S100A8/A9 complex IgG was injected into the tail blood vessel of a rat 1.0 h after the injection of LPS, the serum concentration of IL-6 increased slightly, indicating that the antibody immunoregulatorily blocked the activity of the complex as an anti-inflammatory protein in vivo. In addition, the S100A8/A9 complex bound non-specifically with interleukin-1beta (IL-1beta), IL-6 and TNF-alpha in vitro, suggesting that the complex could bind with these cytokines in vivo. A large number of endogenous S100A8/A9 complex-positive cells that accumulated in the inflamed region in the liver 6 h after the injection of LPS were microscopically observed, while apparent inflammatory changes were not found microscopically in other organs, such as the kidney, lung and spleen. In rats treated with the S100A8/A9 complex, neither acute inflammatory changes nor S100A8/A9 complex-positive cells were also observed microscopically in the liver tissue.

CONCLUSIONS

These findings suggest that the S100A8/A9 complex indirectly suppresses the overproduction of NOx from activated neutrophils and/or macrophages by neutralizing the activity of pro-inflammatory cytokines. Thus, the S100A8/A9 complex may play an important role in the suppression of acute inflammation by modulating the vital activity of pro-inflammatory cytokines in vivo.

Calprotectin (a major leucocyte protein) is strongly and independently correlated with joint inflammation and damage in rheumatoid arthritis

OBJECTIVE

Calprotectin is a major leucocyte protein, shown to correlate well with laboratory and clinical assessments in several inflammatory rheumatic diseases, and large concentrations of calprotectin have been found in synovial fluid from patients with rheumatoid arthritis (RA). The objective of the present study was to examine correlations between calprotectin and joint damage.

METHODS

145 patients with RA were analysed cross sectionally with laboratory (calprotectin, C reactive protein (CRP), and erythrocyte sedimentation rate (ESR)), clinical (28 joint counts (tender, swollen), physician global VAS, DAS28 and RA Articular Damage score (RAAD)), and radiographic (plain hand radiographs; modified Sharp's method) measurements, on the same day.

RESULTS

Calprotectin showed a highly significant correlation with measures of joint damage; modified Sharp score r = 0.43 (p<0.001) and RAAD r = 0.40 (p<0.001). The association with modified Sharp score and RAAD score was maintained after adjustment for CRP, ESR, rheumatoid factor, DAS28, sex, and age in a multiple regression analysis (p = 0.018 and p = 0.04, respectively), while neither CRP nor ESR showed any independent associations. Highly significant correlations (p<0.001) were also found between calprotectin and both laboratory and clinical markers of inflammation.

CONCLUSION

Calprotectin was found to significantly and independently explain the variation in the radiological and clinical assessments of joint damage. Longitudinal studies are required to examine whether calprotectin may predict the progression of joint damage in RA.

S100A9 mediates neutrophil adhesion to fibronectin through activation of beta2 integrins

Neutrophil migration from the blood to inflammatory sites follows a cascade of events, in which adhesion to endothelial cells and extracellular matrix proteins is essential. S100A8, S100A9, and S100A12 are small abundant proteins found in human neutrophil cytosol and presumed to be involved in leukocyte migration. Here we investigated the S100 proteins' activities in neutrophil tissue migration by evaluating their effects on neutrophil adhesion to certain extracellular matrix proteins. S100A9 induced adhesion only to fibronectin and was the only S100 protein that stimulated neutrophil adhesion to this extracellular matrix protein. Experiments with blocking antibodies revealed that neither beta1 nor beta3 integrins were strongly involved in neutrophil adhesion to fibronectin, contrary to what the literature predicted. In contrast, neutrophil adhesion to fibronectin was completely inhibited by anti-beta2 integrins, suggesting that S100A9-induced specific activation of beta2 integrin is essential to neutrophil adhesion.

S100A9-positive granulocytes and monocytes in lipopolysaccharide-induced anterior ocular inflammation

S100A9 is a pro-inflammatory protein expressed in infiltrating granulocytes and monocytes. We determined role of S100A9 in endotoxin (LPS)-induced uveitis (EIU) and keratitis in Wistar rats. Anti-S100A9 antibody decreased partially clinical scores, protein, and cells in the aqueous humor at 18-36 h, compared with the LPS group. S100A9-positive cells were expressed in the iris-ciliary body (ICB) and cornea at 24-48 h. Activated caspase-3 (related to apoptosis) and S100A9 co-expressed in ICB at 18-48 h after LPS injection. S100A9 was not expressed in ED2-positive cells in ICB. Dexamethasone (DEX) increased S100A9 mRNA and protein levels in the circulating blood leukocytes, but reduced S100A9 mRNA and protein levels in ICB after LPS injection. BAY 11-7085 (an inhibitor of I-kappaB phosphorylation) suppressed S100A9 mRNA in leukocytes (43.5%) and ICB (68.5%), respectively, after LPS injection. It is possible that S100A9-positive granulocytes and monocyte/macrophages may play a role in the late phase of EIU and keratitis that DEX may inhibit the migration of S100A9-positive granulocytes and monocytes from the blood into the extravascular tissues, and that nuclear factor (NF)-kappaB pathway may be involved in S100A9 expression. S100A9 could play a role in the clearance of inflammatory cells at the late phase of EIU.

Effect of the C-terminus of murine S100A9 protein on experimental nociception

Calcium-binding protein S100A9 induces antinociception in mice evaluated by the writhing test. Similarly, a peptide identical to the C-terminus of murine S100A9 (mS100A9p) inhibits the hyperalgesia induced by jararhagin, a metalloprotease. Thus, we investigated the effect of mS100A9p on different models used to evaluate nociception. mS100A9p induced a dose-dependent inhibitory effect on the writhing test, and on mechanical hyperalgesia induced by carrageenan. mS100A9p inhibited thermal hyperalgesia induced by carrageenan. mS100A9p did not modify the nociceptive response in hot plate or tail-flick tests. These data demonstrate that the C-terminus of S100A9 protein interferes with control mechanisms of inflammatory pain.

Elevated serum levels of calcium-binding S100 proteins A8 and A9 reflect disease activity and abnormal differentiation of keratinocytes in psoriasis

BACKGROUND

The expression of calcium-binding S100 molecules organized within the epidermal differentiation complex on chromosome 1q21 is disturbed in hyperproliferative skin diseases such as psoriasis.

OBJECTIVES

We studied whether serum levels of S100 proteins A8 (S100A8) and A9 (S100A9) are elevated in psoriasis, correlated their amounts with disease activity and identified potential cellular sources.

METHODS

Serum obtained from psoriasis patients or from healthy individuals was studied for S100A8 and S100A9 levels by enzyme-linked immunosorbent assay. Data were correlated to disease activity as reflected by the Psoriasis Area and Severity Index (PASI). Cellular sources of S100A8 and S100A9 were identified by in situ hybridization and immunohistochemistry of lesional psoriatic and nonlesional, nonpsoriatic skin.

RESULTS

A significant increase of S100A8/S100A9 serum levels was found in patients with psoriasis compared with healthy controls. Grading the patients into two groups of severity, individuals with a PASI of <15 showed serum levels of 705+/-120 ng mL-1 (mean+/-SEM, n=18), those with a PASI of >or=15 showed levels of 1315+/-150 ng mL-1 (n=32) while controls presented with 365+/-50 ng mL-1. Performing in situ hybridization of lesional psoriatic skin we detected a dramatic induction of both S100A8 and S100A9 mRNA and protein primarily in the suprabasal layers of the epidermis while expression was negligible in nonlesional, nonpsoriatic interfollicular epidermis.

CONCLUSIONS

Our data demonstrate that hyperproliferation and abnormal differentiation of psoriatic skin is associated with a massive upregulation and secretion of S100A8 and S100A9, suggesting not only a prominent role of these molecules during intracellular calcium-dependent signalling but also implying distinct extracellular functions.

Differential macrophage/microglia activation in neocortical EAE lesions in the marmoset monkey

Recent studies revealed an important involvement of the cerebral cortex in multiple sclerosis (MS) patients. Cortical lesions in MS were reported to be less inflammatory and to show less structural damage than white matter lesions. Animal models reflecting the histopathological hallmarks of cortical demyelinated lesions in MS are sparse. Induction of experimental autoimmune encephalomyelitis (EAE) in the common marmoset has turned out to be an attractive non-human-primate model for MS. In the present study we investigated the presence and detailed cellular composition of cortical inflammatory demyelinating pathology in the common marmoset upon immunization with myelin oligodendrocyte glycoprotein (MOG). Extensive cortical demyelination reflecting the topographically distinct cortical lesion types in MS patients was revealed by immunohistochemistry for myelin basic protein (MBP). We explored the density of T- and B-lymphocytes, MHC-II expressing macrophages/microglia cells and early activated macrophages (MRP14) at perivascular and parenchymal lesions sites in neocortex and subcortical white matter. Despite a similar density of perivascular inflammatory infiltrates in the demyelinated neocortex, a considerable lower fraction of macrophages was found to express MRP14 in the neocortex indicating a different activation pattern in cortical compared with white matter lesions. Furthermore, cortical EAE lesions in marmoset monkeys revealed immunoglobulin leakage and complement component C9 deposition in intracortical but not subpial demyelination. Our findings indicate that the inflammatory response, especially macrophage and microglia activation, may be regulated differently in gray matter areas in primate brain.

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

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

Proteomics, Part II: The Emerging Role of Proteomics Over Genomics in Spontaneous Preterm Labor/Birth

Conventional wisdom holds that complications of immature organ systems such as respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, and bronchopulmonary dysplasia are the primary causes of the high neonatal morbidity and mortality attendant preterm delivery. However, recent evidence suggests that a major cause of prematurity-associated neonatal pathology is the fetal and neonatal response to inflammation/infection. Although functional genomics offered the promise of providing answers to many of these questions, the identification of the genes intrinsic to human parturition proved to be a difficult task. Proteomic profiling of the amniotic fluid (AF) provides a precise means for detection of inflammation by revealing the presence of 4 biomarkers (defensins-2 and -1, calgranulin-C, and calgranulin-A) that are highly predictive of intrauterine inflammation (MR score). The MR score is especially useful as it presents a gradient of disease activity progressing from "absent" to "mild" to "severe" inflammation. Thus, it provides the ability to identify patients who may benefit from interventions in utero in a modern diagnostic-therapeutic framework.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians.

LEARNING OBJECTIVES

After completion of this article, the reader should be able to explain that the cause or causes of preterm delivery are still unknown, recall that functional genomics has not given the answer to these causes, and state that proteomic profiling of amniotic fluid, through mass-restricted (MR) scoring, may be predictive of intrauterine inflammation and allow for potential diagnosis and potential therapy.

S100A8 and S100A9 in inflammation and cancer

Calprotectin (S100A8/A9), a heterodimer of the two calcium-binding proteins S100A8 and S100A9, was originally discovered as immunogenic protein expressed and secreted by neutrophils. Subsequently, it has emerged as important pro-inflammatory mediator in acute and chronic inflammation. More recently, increased S100A8 and S100A9 levels were also detected in various human cancers, presenting abundant expression in neoplastic tumor cells as well as infiltrating immune cells. Although, many possible functions have been proposed for S100A8/A9, its biological role still remains to be defined. Altogether, its expression and potential cytokine-like function in inflammation and in cancer suggests that S100A8/A9 may play a key role in inflammation-associated cancer.

Myeloid-related protein-8/14 is associated with proinflammatory cytokines in cervical mucus

Myeloid-related protein-8 (MRP-8), MRP-14, and MRP-8/14 are found in a variety of inflammatory conditions and are involved in the host defense system. The objective of this study was to determine the concentrations of MRP-8, MRP-14, and MRP-8/14 in human cervical mucus and the associations between MRP-8/14 and proinflammatory cytokines. Samples of cervical mucus were obtained using a syringe from sexually active women (n=97) during the preovulatory phase. Samples from seven women were obtained using a swab placed in the cervical canal during the proliferative, preovulatory, and luteal phases. Concentrations of MRP-8, MRP-14, MRP-8/14, IL-1alpha, IL-6, IL-8, and granulocyte elastase were measured using an ELISA. The mean levels of MRP-8, MRP-14, and MRP-8/14 in cervical mucus were 1.87, 0.46, and 23.90microg/ml, respectively. The concentration of MRP-8/14 showed positive correlations with concentrations of IL-1alpha (p<0.0001), IL-8 (p<0.0001), and granulocyte elastase (p<0.0001). However, there were no significant differences in MRP-8/14 levels in the cervical mucus of each patient during the menstrual cycle. MRP-8/14 was mainly detected in human cervical mucus and showed a positive correlation with proinflammatory cytokines. The MRP-8/14 level in cervical mucus may be useful as a marker of inflammation of the uterine cervix.

Calcium-dependent and -independent interactions of the S100 protein family

The S100 proteins comprise at least 25 members, forming the largest group of EF-hand signalling proteins in humans. Although the proteins are expressed in many tissues, each S100 protein has generally been shown to have a preference for expression in one particular tissue or cell type. Three-dimensional structures of several S100 family members have shown that the proteins assume a dimeric structure consisting of two EF-hand motifs per monomer. Calcium binding to these S100 proteins, with the exception of S100A10, results in an approx. 40 degrees alteration in the position of helix III, exposing a broad hydrophobic surface that enables the S100 proteins to interact with a variety of target proteins. More than 90 potential target proteins have been documented for the S100 proteins, including the cytoskeletal proteins tubulin, glial fibrillary acidic protein and F-actin, which have been identified mostly from in vitro experiments. In the last 5 years, efforts have concentrated on quantifying the protein interactions of the S100 proteins, identifying in vivo protein partners and understanding the molecular specificity for target protein interactions. Furthermore, the S100 proteins are the only EF-hand proteins that are known to form both homo- and hetero-dimers, and efforts are underway to determine the stabilities of these complexes and structural rationales for their formation and potential differences in their biological roles. This review highlights both the calcium-dependent and -independent interactions of the S100 proteins, with a focus on the structures of the complexes, differences and similarities in the strengths of the interactions, and preferences for homo- compared with hetero-dimeric S100 protein assembly.

Calcium-dependent tetramer formation of S100A8 and S100A9 is essential for biological activity

S100 proteins comprise the largest family of calcium-binding proteins. Members of this family usually form homo- or heterodimers, which may associate to higher-order oligomers in a calcium-dependent manner. The heterodimers of S100A8 and S100A9 represent the major calcium-binding proteins in phagocytes. Both proteins regulate migration of these cells via modulation of tubulin polymerization. Calcium binding induces formation of (S100A8/S100A9)2 tetramers. The functional relevance of these higher-order oligomers of S100 proteins, however, is not yet clear. To investigate the importance of higher-order oligomerization for S100 proteins, we created a set of mutations within S100A9 (N69A, E78A, N69A+E78A) destroying the high-affinity C-terminal calcium-binding site (EF-hand II). Mutations in EF-hand II did not interfere with formation of the S100A8/S100A9 heterodimer as demonstrated by yeast two-hybrid experiments and pull-down assays. In contrast, mass spectrometric analysis and density gradient centrifugation revealed that calcium-induced association of (S100A8/S100A9)2 tetramers was strictly dependent on a functional EF-hand II in S100A9. Failure of tetramer formation was associated with a lack of functional activity of S100A8/S100A9 complexes in promoting the formation of microtubules. Thus, our data demonstrate that calcium-dependent formation of (S100A8/S100A9)2 tetramers is an essential prerequisite for biological function. This is the first report showing a functional relevance of calcium-induced higher-order oligomerization in the S100 family.

The S100A8/A9 heterodimer amplifies proinflammatory cytokine production by macrophages via activation of nuclear factor kappa B and p38 mitogen-activated protein kinase in rheumatoid arthritis

S100A8 and S100A9, two Ca²⁺-binding proteins of the S100 family, are secreted as a heterodimeric complex (S100A8/A9) from neutrophils and monocytes/macrophages. Serum and synovial fluid levels of S100A8, S100A9, and S100A8/A9 were all higher in patients with rheumatoid arthritis (RA) than in patients with osteoarthritis (OA), with the S100A8/A9 heterodimer being prevalent. By two-color immunofluorescence labeling, S100A8/A9 antigens were found to be expressed mainly by infiltrating CD68⁺ macrophages in RA synovial tissue (ST). Isolated ST cells from patients with RA spontaneously released larger amounts of S100A8/A9 protein than did the cells from patients with OA. S100A8/A9 complexes, as well as S100A9 homodimers, stimulated the production of proinflammatory cytokines, such as tumor necrosis factor alpha, by purified monocytes and in vitro-differentiated macrophages. S100A8/A9-mediated cytokine production was suppressed significantly by p38 mitogen-activated protein kinase (MAPK) inhibitors and almost completely by nuclear factor kappa B (NF-κB) inhibitors. NF-κB activation was induced in S100A8/A9-stimulated monocytes, but this activity was not inhibited by p38 MAPK inhibitors. These results indicate that the S100A8/A9 heterodimer, secreted extracellularly from activated tissue macrophages, may amplify proinflammatory cytokine responses through activation of NF-κB and p38 MAPK pathways in RA.