Identification of the mouse calcium-binding proteins, MRP 8 and MRP 14, in Schistosoma mansoni-induced granulomas: biochemical and functional characterization

Neutrophils and the S100A9 protein critically regulate granuloma formation

Macrophages have the potential to undergo cellular transformation into epithelioid cells, and their concentric accumulation in tissues results in the development of granulomas. Although epithelioid cells are an essential and dominant component of granulomas, other cell types have also been detected, which may contribute to the establishment of well-organized granulomas, as observed in human granulomatous diseases. We herein demonstrated that neutrophils may mediate these functions. By taking advantage of the guinea pig pulmonary granuloma model, we obtained a rat monoclonal antibody with unique reactivity to granuloma cells. This antibody, termed G213, reacted with clusters of neutrophils located in the central area of granulomas, and a biochemical analysis identified the G213-reactive antigen as S100A9, a calcium-binding protein of the S100 family, which was expressed abundantly in neutrophils. Consistent with the multifaceted functions attributed to S100A9, including its role in neutrophil extravasation and macrophage activation, the blockade of S100A9 functions with the specific inhibitor, tasquinimod, impaired the formation of organized granulomas with neutrophil cores. These results demonstrate the critical role of neutrophils and the S100A9 protein in granuloma formation. Because intragranuloma S100A9⁺ neutrophils were also detected in humans, these results indicate the potential of tasquinimod, a new anticancer drug candidate, for manipulating human granulomatous diseases.

Phagocyte-specific S100 proteins in the local response to the Echinococcus granulosus larva

Infection by larval Echinococcus granulosus is usually characterized by tight inflammatory control. However, various degrees of chronic granulomatous inflammation are also observed, reaching a high point in infection of cattle by the most prevalent parasite strain worldwide, which is not well adapted to this host species. In this context, epithelioid and multinucleated giant macrophages surround the parasite, and the secreted products of these cells often associate with the larval wall. The phagocyte-specific S100 proteins, S100A8, S100A9 and S100A12, are important non-conventionally secreted amplifiers of inflammatory responses. We have analysed by proteomics and immunohistochemistry the presence of these proteins at the E. granulosus larva-host interface. We found that, in the context of inflammatory control as observed in human infections, the S100 proteins are not abundant, but S100A9 and S100A8 can be expressed by eosinophils distal to the parasite. In the granulomatous inflammation context as observed in cattle infections, we found that S100A12 is one of the most abundant host-derived, parasite-associated proteins, while S100A9 and S100A8 are not present at similarly high levels. As expected, S100A12 derives mostly from the epithelioid and multinucleated giant cells. S100A12, as well as cathepsin K and matrix metalloproteinase-9, also expressed by E. granulosus-elicited epithelioid cells, are connected to the Th17 arm of immunity, which may therefore be involved in this granulomatous response.

Intestinal schistosomiasis in mothers and young children in Uganda: investigation of field-applicable markers of bowel morbidity

To control intestinal schistosomiasis at a national level in sub-Saharan Africa, there is a need for field-applicable markers to measure morbidity associated with this disease. The purpose of this study was to determine whether fecal calprotectin or fecal occult blood assays could be used as morbidity indicators for intestinal schistosomiasis. The study was carried out in Uganda with a cohort of young children (n = 1,327) and their mothers (n = 726). The prevalence of egg-patent schistosomiasis was 27.2% in children and 47.6% in mothers. No association was found between schistosomiasis infection and fecal calprotectin in children (n = 83, odds ratio [OR] = 1.08, P = 0.881), although an inverse relationship (n = 58, OR = 0.17, P = 0.043) was found in mothers. Fecal occult blood was strongly associated with Schistosoma mansoni infection in children (n = 814, OR = 2.30, P < 0.0001) and mothers (n = 448, OR = 1.95, P = 0.004). Fecal occult blood appears to be useful for measuring morbidity associated with intestinal schistosomiasis and could be used in assessing the impact of control programs upon disease.

Expression and role of myeloid-related protein-14 in clinical and experimental sepsis

RATIONALE

Myeloid-related protein-8 (MRP8) and MRP14 can form heterodimers that elicit a variety of inflammatory responses. We showed that MRP8/14 is a ligand for Toll-like receptor-4, and that mice deficient in MRP8/14 are protected against endotoxic shock-induced lethality.

OBJECTIVES

To determine (1) the extent of MRP8/14 release in patients with sepsis and/or peritonitis and in healthy humans exposed to LPS and (2) the contribution of MRP8/14 to the host response in murine abdominal sepsis.

METHODS

MRP8/14 was measured in 51 patients with severe sepsis, 8 subjects after intravenous injection of LPS, and 17 patients with peritonitis. Host responses to sepsis were compared in mrp14 gene-deficient (and thereby MRP8/14-deficient) and wild-type mice intraperitoneally injected with Escherichia coli.

MEASUREMENTS AND MAIN RESULTS

Patients with sepsis displayed elevated circulating MRP8/14 concentrations on both Days 0 and 3, and LPS injection resulted in systemic MRP8/14 release in healthy humans. In patients with peritonitis, MRP8/14 levels in abdominal fluid were more than 15-fold higher than in plasma. MRP14-deficient mice displayed improved defense against E. coli abdominal sepsis in an early phase, as indicated by diminished dissemination of the bacteria at 6 hours. In addition, MRP14-deficient mice demonstrated decreased systemic inflammation, as reflected by lower cytokine plasma concentrations, and less severe liver damage.

CONCLUSIONS

Human sepsis and endotoxemia are associated with enhanced release of MRP8/14. In abdominal sepsis, MRP8/14 likely occurs primarily at the site of the infection, facilitating bacterial dissemination at an early phase and liver injury.

Characterisation of proteins differentially present in the plasma of Biomphalaria glabrata susceptible or resistant to Echinostoma caproni

Snail immune responses towards a trematode infection are known to rely on both plasmatic and cellular host factors. As an approach to further investigate the suspected involvement of plasmatic factors in Biomphalaria glabrata resistance/susceptibility to Echinostoma caproni, we compared protein patterns of plasma collected from susceptible and resistant snails. This proteomic approach revealed that 13 plasmatic proteins exhibited significant differences in their apparent representativity. The genes corresponding to five of them were characterised by a combination of mass spectrometry and molecular cloning. They encode two isoforms of a glycolytic enzyme, two isoforms of a calcium binding protein and an inhibitor of cysteine protease. Furthermore, we investigated gene expression in parasite-exposed or -unexposed snails as well as in various tissues by quantitative PCR. This study showed that: (i) differential representation of plasma proteins between the snail strains was correlated with a differential level of transcripts; (ii) expression of these genes after parasite exposure was differentially regulated in the two strains; and (iii) these genes were expressed predominantly in the albumen gland.

Migration inhibitory factor-related protein (MRP)8 and MRP14 are differentially expressed in free-electron laser and scalpel incisions

Incisions made in mouse skin by scalpel or the free-electron laser heal at different rates. To identify genes that are differentially expressed in free-electron laser or scalpel wounds, we isolated total RNA from free-electron laser- or scalpel-produced incisions and normal skin at day 7 postwounding. cDNA microarray analysis identified 89 of 15,000 genes in a mouse microarray as having significantly different expression levels. Migration inhibitory factor-related protein (MRP) 14 was almost 30 times more highly expressed in scalpel wounds than in free-electron laser wounds. This result was confirmed by Northern blot analysis, which also showed that scalpel wounds expressed higher levels of MRP8, a related S100 protein that can heterodimerize with MRP14, at days 2, 7, and 14 postwounding. Free-electron laser wounds also showed elevated expression of MRP8 and MRP14 relative to normal skin. In situ hybridization showed that the patterns of MRP14 and MRP8 expression in free-electron laser and scalpel wound tissues were similar. MRP14 and MRP8 were expressed in the dermal wound margin, while a very low level of MRP14 and MRP8 expression was seen in the migrating epidermis. Dual immunofluorescence staining for MRP14 or MRP8 and macrophage (F4/80) showed that most of the wound macrophages simultaneously expressed MRP14 and MRP8. Some expression was also found in neutrophils, while neither antigen accumulated to a significant degree in the epidermis. Relatively lower MRP8 and 14 expression in free-electron laser wounds was correlated with a higher level of matrix metalloproteinase-13 expression and a reduced rate of wound healing. While the regulation of MRP8 expression in mouse may be different from human skin, we suggest that elevated expression of MRP8 and MRP14 may have a relevant therapeutic effect against inflammation in wound healing.

Calprotectin (S100A8/S100A9), an inflammatory protein complex from neutrophils with a broad apoptosis-inducing activity

Calprotectin, a complex of two calcium-binding proteins that belong to the S100 protein family, is abundant in the cytosolic fraction of neutrophils. A high level of calprotectin reportedly exists in extracellular fluid during various inflammatory conditions, such as rheumatoid arthritis, cystic fibrosis and abscesses. However, the exact biological role(s) of the factor is now under investigation. We recently observed that neutrophils contain a factor that shows growth-inhibitory and apoptosis-inducing activities against various cell types including tumor cells and normal fibroblasts, and we identified that factor as calprotectin. The findings suggest that calprotectin exerts a regulatory activity in inflammatory processes through its effect on the survival or growth states of cells participating in the inflammatory reaction. It is also possible that calprotectin, at a high concentration, might have a deleterious effect on fibroblasts and influence the recovery of inflammatory tissue. Therefore, the protein factor may be a new drug target to control inflammatory reactions. We found that a few of the Amaryllidaceae alkaloids effectively inhibited the growth-inhibitory and apoptosis-inducing activities of calprotectin. In this article, we focus on the biological functions of calprotectin in extracellular fluids, focusing on its apoptosis-inducing activity.

IFN-gamma and TNF regulate macrophage expression of the chemotactic S100 protein S100A8

The murine calcium-binding protein S100A8 is a potent chemoattractant for neutrophils and monocytes in vivo and in vitro but may also play a protective role. We show that the kinetics of induction of S100A8 mRNA in elicited murine macrophages (Mac) by LPS, IFN-gamma, and TNF were distinct from the C-C chemokines monocyte chemoattractant protein-1 (MCP-1), macrophage-inflammatory protein-1alpha (MIP-1alpha), and RANTES. Monomeric S100A8 was predominantly secreted. IFN substantially increased S100A8 mRNA levels after 1 h with optimal induction after 12 h; induction by TNF was slower and more sustained. TNF did not up-regulate MCP-1 and MIP-1alpha mRNA in these cells. Luciferase reporter assays confirmed that LPS and IFN induce S100A8 gene transcription and mRNA in LPS-treated Mac showed little decay over 16 h, whereas transcripts induced by IFN and TNF were markedly less stable. Newly synthesized proteins may be required for mRNA transcription and stabilization in response to LPS. S100A9 associates with A8 in neutrophils, but was not coinduced with S100A8. S100A8 gene induction in Mac stimulated with LPS and IFN may be modulated by mobilization of intracellular Ca2+ concentration from distinct intracellular stores and/or the extracellular compartment and by distinct pathways involving protein kinase C and leading to activation of mitogen-activated protein kinase.

Functional roles of S100 proteins, calcium-binding proteins of the EF-hand type

A multigenic family of Ca2+-binding proteins of the EF-hand type known as S100 comprises 19 members that are differentially expressed in a large number of cell types. Members of this protein family have been implicated in the Ca2+-dependent (and, in some cases, Zn2+- or Cu2+-dependent) regulation of a variety of intracellular activities such as protein phosphorylation, enzyme activities, cell proliferation (including neoplastic transformation) and differentiation, the dynamics of cytoskeleton constituents, the structural organization of membranes, intracellular Ca2+ homeostasis, inflammation, and in protection from oxidative cell damage. Some S100 members are released or secreted into the extracellular space and exert trophic or toxic effects depending on their concentration, act as chemoattractants for leukocytes, modulate cell proliferation, or regulate macrophage activation. Structural data suggest that many S100 members exist within cells as dimers in which the two monomers are related by a two-fold axis of rotation and that Ca2+ binding induces in individual monomers the exposure of a binding surface with which S100 dimers are believed to interact with their target proteins. Thus, any S100 dimer is suggested to expose two binding surfaces on opposite sides, which renders homodimeric S100 proteins ideal for crossbridging two homologous or heterologous target proteins. Although in some cases different S100 proteins share their target proteins, in most cases a high degree of target specificity has been described, suggesting that individual S100 members might be implicated in the regulation of specific activities. On the other hand, the relatively large number of target proteins identified for a single S100 protein might depend on the specific role played by the individual regions that in an S100 molecule contribute to the formation of the binding surface. The pleiotropic roles played by S100 members, the identification of S100 target proteins, the analysis of functional correlates of S100-target protein interactions, and the elucidation of the three-dimensional structure of some S100 members have greatly increased the interest in S100 proteins and our knowledge of S100 protein biology in the last few years. S100 proteins probably are an example of calcium-modulated, regulatory proteins that intervene in the fine tuning of a relatively large number of specific intracellular and (in the case of some members) extracellular activities. Systems, including knock-out animal models, should be now used with the aim of defining the correspondence between the in vitro regulatory role(s) attributed to individual members of this protein family and the in vivo function(s) of each S100 protein.