S100A9: The Unusual Suspect Connecting Viral Infection and Inflammation

The study of S100A9 in viral infections has seen increased interest since the COVID-19 pandemic. S100A8/A9 levels were found to be correlated with the severity of COVID-19 disease, cytokine storm, and changes in myeloid cell subsets. These data led to the hypothesis that S100A8/A9 proteins might play an active role in COVID-19 pathogenesis. This review explores the structures and functions of S100A8/9 and the current knowledge on the involvement of S100A8/A9 and its constituents in viral infections. The potential roles of S100A9 in SARS-CoV-2 infections are also discussed.

Association Between Serum S100A8/S100A9 Heterodimer and Pulmonary Function in Patients with Acute Exacerbation of Chronic Obstructive Pulmonary Disease

BACKGROUND

Many studies have indicated that S100A8 and S100A9 may be involved in the development and progression of chronic obstructive pulmonary disease (COPD). However, there has been no clinical study analyzing the role of the serum S100A8/S100A9 heterodimer in COPD patients. The aim of this study was to analyze the correlation of the serum S100A8/S100A9 heterodimer with pulmonary function in COPD patients during acute exacerbation (AE-COPD) based on a cross-sectional study.

METHODS

A total of 131 AE-COPD patients and matched healthy subjects were recruited. Pulmonary function, arterial blood gas values, and serum inflammatory cytokines were measured.

RESULTS

Serum S100A8/S100A9 was increased in AE-COPD patients. AE-COPD patients were ranked into different grades based on FEV1%. Serum S100A8/S100A9 was higher in Grade 4 than in Grade 1-2 and Grade 3 patients with AE-COPD. Univariate regression analysis found that serum S100A8/S100A9 was negatively correlated with FEV1% in AE-COPD patients. Furthermore, serum S100A8/S100A9 was positively associated with MCP-1 in AE-COPD patients. Further stratified analysis revealed that serum S100A8/S100A9 was negatively associated with FEV1/FVC in Grade 3 (OR 0.629, P < 0.05) and in Grade 4 (OR 0.347, P < 0.05). In addition, there was a positive relationship between serum S100A8/S100A9 and PaCO2 in Grade 3 (OR 1.532, P < 0.05) and Grade 4 (OR 1.925, P < 0.01).

CONCLUSION

S100A8/S100A9 was negatively associated with pulmonary function in AE-COPD patients, indicating that the serum S100A8/S100A9 heterodimer may be involved in the progression of AE-COPD, and may be a relevant serum biomarker in the diagnosis for AE-COPD.

Toll-Like Receptor Signaling and Its Inducible Proteins

Studies that bridge innate immunity and various diseases are making rapid advances. Macrophages and dendritic cells play a leading role in innate immunity, using pattern recognition receptors (PRRs) to sense both pathogen invasion and danger signals. Among these PRRs, the Toll-like receptors (TLRs) play a central role in the immune response by recognizing not only pathogen-associated molecular patterns from bacteria and viruses but also damage-associated molecular patterns from dying or injured cells. These TLR family molecules facilitate not only the elimination of pathogens but also the development of various disorders, including arteriosclerosis, cancer, and metabolic syndrome. TLRs activate signaling pathways that result in the production of cytokines, chemokines, and various inducible molecules associated with the immune response. Although most components of the innate immune signaling pathways, such as the TLR family and its downstream signaling, have been identified, the physiological roles of many TLR signal-inducible proteins remain unclear. Recent studies have shown that some TLR-inducible proteins are critical in the immune response and the development of various disorders. In this review, we focus on the TLR signaling pathways and the roles of some TLR-inducible proteins.

Recombinant Phage Elicits Protective Immune Response against Systemic S. globosa Infection in Mouse Model

Sporothrix globosa is a type of fungus that typically infects immunocompromised patients. Its prevention continues to pose a challenge. A 70-KDa glycoprotein (Gp70) of Sporothrix has been previously reported to protect host against infection from this fungus. Here, we displayed an epitope peptide (kpvqhalltplgldr) of Gp70 on the major coat protein (pIII), and investigated its efficiency as a vaccine for preventing S. globosa infection. The recombinant phage and the heat-killed S. globosa were used to immunize mice separately. In this study, we evaluated the humoral and cellular immune responses in the mice and demonstrated that recombinant phage could induce mice to produce a stronger immune response and generate antibodies to inhibit S. globosa infection. Furthermore, immunization with recombinant phage could increase the survival rate of S. globosa infection in mice. All these results together indicated that recombinant phages displaying kpvqhalltplgldr are a potential vaccine candidate against S. globosa infection.

High-mobility group box 1 promotes extracellular matrix synthesis and wound repair in human bronchial epithelial cells

High mobility group box 1 (HMGB1) is a damage-associated molecular pattern (DAMP) protein that binds Toll-like receptors (e.g., TLR4) and the receptor for advanced glycated end products (RAGE). The direct effects of HMGB1 on airway structural cells are not fully known. As epithelial cell responses are fundamental drivers of asthma, including abnormal repair-restitution linked to changes in extracellular matrix (ECM) synthesis, we tested the hypothesis that HMGB1 promotes bronchial epithelial cell wound repair via TLR4 and/or RAGE signaling that regulates ECM (fibronectin and the γ2-chain of laminin-5) and integrin protein abundance. To assess impact of HMGB1 we used molecular and pharmacological inhibitors of RAGE or TLR4 signaling in scratch wound, immunofluorescence, and immunoblotting assays to assess wound repair, ECM synthesis, and phosphorylation of intracellular signaling. HMGB1 increased wound closure, and this effect was attenuated by blocking RAGE and TLR4 signaling. HMGB1-induced fibronectin and laminin-5 (γ2 chain) was diminished by blocking RAGE and/or blunting TLR4 signaling. Similarly, induction of α3-integrin receptor for fibronectin and laminin-5 was also diminished by blocking TLR4 signaling and RAGE. Lastly, rapid and/or sustained phosphorylation of SMAD2, ERK1/2, and JNK signaling modulated HMGB1-induced wound closure. Our findings suggest a role for HMGB1 in human airway epithelial cell repair and restitution via multiple pathways mediated by TLR4 and RAGE that underpin increased ECM synthesis and modulation of cell-matrix adhesion.

S100A9-induced release of interleukin (IL)-6 and IL-8 through toll-like receptor 4 (TLR4) in human periodontal ligament cells

S100A8, S100A9, and calprotectin (the S100A8/S100A9 complex) are calcium-binding proteins that promote extracellular pro-inflammatory functions and may play an important role in periodontal disease. Both toll-like receptor 4 (TLR4) and the receptor for advanced glycation end-products (RAGE) are thought to be important receptors for S100A8, S100A9, and calprotectin, but the specific pathways in periodontal ligament (PDL) cells are not yet clear. Our study was designed to identify the specific receptors for S100A9 in human PDL cells. Additionally, we investigated the specific pathways that activate the secretion of pro-inflammatory cytokines interleukins (IL)-6 and IL-8 in PDL cells. The role of nuclear factor (NF)-κB, mitogen-activated protein kinase (MAPK) and reactive oxygen species (ROS) in S100A9-induced pro-inflammatory cytokines were investigated through western blot analysis, dichlorodihydrofluorescein diacetate (H2DCFDA) probe and the application of specific pathway inhibitors. Our results suggest that the S100A9-induced release of IL-6 and IL-8 from human PDL cells is dependent on TLR4, but not RAGE. We provide evidence that S100A9 promotes the secretion of IL-6 and IL-8 through different pathways. Specifically, S100A9 up-regulates the secretion of IL-6 from human PDL cells through NF-κB and p38 pathways and up-regulates the release of IL-8 from human PDL cells through the NF-κB, extracellular-regulated kinase (ERK) 1/2, c-Jun amino-terminal kinase (JNK) 1/2, and p38 signaling pathways. In addition, the release of both cytokines depends on ROS production. The release of both cytokines depends on ROS production. These results suggest that S100A9 promotes pro-inflammatory responses in PDL cells through the TLR4-mediated NF-κB and MAPK signaling pathways.

Calprotectin induces cell death in human prostate cancer cell (LNCaP) through survivin protein alteration

Calprotectin (CP), an abundant heterodimeric cytosolic protein of neutrophils, conveys a variety of functions such as tumor cell growth arrest and antimicrobial activity. We investigated CP activity and its possible apoptosis-inducing mechanism of action against an antiandrogen therapy-resistance prostate cancer cell line LNCaP. Cell viability and Annexin V FITC assays were performed in order to investigate its cell death activity and apoptosis, respectively. In order to address cell death inducing mechanism(s), immunocytochemistry and immunobloting analysis, reactive oxygen species (ROS) and nitric oxide (NO) measurements were performed. The effective concentration of CP against LNCaP promoting LNCaP cell death was 200 µg/mL. ROS and NO levels of cells remarkably were enhanced following treatment with 50 and 100 µg/mL of CP, respectively. Protein expression of anti-apoptotic protein survivin was significantly decreased after administration of tumor cells with CP. Our data indicate that CP regulates the LNCaP cells viability via survivin-mediated pathway and ROS and NO enhancement. Thus, inhibition of survivin expression, enhancement of ROS and NO level by CP or other similar pharmaceutical agents might be effective in lowering the malignant proliferation of human prostate cancer cells.

Serum myeloid-related protein 8/14 complex is associated with microalbuminuria in patients with type 2 diabetes

OBJECTIVES

Microalbuminuria (MA) is associated independently with cardiovascular risk and progression of renal disease in patients with diabetes and the normal population. MA is an accepted factor for microvascular defects, in particular in patients with diabetes, and is associated with inflammation. Activated transmigrating macrophages are key cells in these inflammatory processes. Based on the theory that myeloid-related protein 8/14 complex (MRP8/14) is secreted by transmigrating macrophages, we hypothesized that MA was accompanied by elevated MRP8/14 and investigated whether MA predicts MRP8/14 in patients with type 2 diabetes.

METHODS

A total of 86 men with type 2 diabetes were grouped according to urinary albumin excretion in normoalbuminuria and MA. Serum MRP8/14 levels were measured by enzyme-linked immunosorbent assay. Established cardiovascular risk factors were quantified in both groups and compared with urinary albumin excretion.

RESULTS

Albuminuria (mg/day) was positively associated with MRP8/14 (r = 0.34) and systemic blood pressure (r = 0.33). Patients with type 2 diabetes and MA demonstrated significantly higher MRP8/14 levels than patients with normoalbuminuria [median (interquartile range), 1.24 (0.97-2.28) µg/ml versus 0.97 (0.67-1.35) µg/ml, p < 0.05]. Serum creatinine levels, systolic blood pressure (SBP), very low density lipoprotein levels and the incidence of hypertension and coronary artery disease were significantly higher in the group with MA. Both groups did not differ significantly in other cardiovascular risk factors. MA was an independent predictor of serum MRP8/14 levels (β = 0.454) as well as SBP (β = 0.625) and haemoglobin A1c (β = 0.322).

CONCLUSION

Our data demonstrate that albumin excretion is associated with the process of macrophage activation determined by MRP8/14 levels. These data not only suggest tissue inflammation as a factor for elevated cardiovascular risk in patients with type 2 diabetes, they further point to a role of macrophage activation in this process.

Transcriptional activation of hypoxia-inducible factor-1 (HIF-1) in myeloid cells promotes angiogenesis through VEGF and S100A8

Emerging evidence indicates that myeloid cells are essential for promoting new blood vessel formation by secreting various angiogenic factors. Given that hypoxia-inducible factor (HIF) is a critical regulator for angiogenesis, we questioned whether HIF in myeloid cells also plays a role in promoting angiogenesis. To address this question, we generated a unique strain of myeloid-specific knockout mice targeting HIF pathways using human S100A8 as a myeloid-specific promoter. We observed that mutant mice where HIF-1 is transcriptionally activated in myeloid cells (by deletion of the von Hippel-Lindau gene) resulted in erythema, enhanced neovascularization in matrigel plugs, and increased production of vascular endothelial growth factor (VEGF) in the bone marrow, all of which were completely abrogated by either genetic or pharmacological inactivation of HIF-1. We further found that monocytes were the major effector producing VEGF and S100A8 proteins driving neovascularization in matrigel. Moreover, by using a mouse model of hindlimb ischemia we observed significantly improved blood flow in mice intramuscularly injected with HIF-1-activated monocytes. This study therefore demonstrates that HIF-1 activation in myeloid cells promotes angiogenesis through VEGF and S100A8 and that this may become an attractive therapeutic strategy to treat diseases with vascular defects.

The effect of proatherogenic pathogens on adipose tissue transcriptome and fatty acid distribution in apolipoprotein E-deficient mice

Background

Chronic infections have been demonstrated to maintain low-grade systemic inflammation and associate with atherosclerosis. We studied the inflammation- and lipid homeostasis-related effects of Aggregatibacter actinomycetemcomitans (Aa) and Chlamydia pneumoniae (Cpn) infections on the epididymal and inguinal adipose tissue (AT) transcriptomes and fatty acid distribution in apolipoprotein (apo) E-deficient mice. Chow-fed apoE-deficient mice were exposed to 1) chronic intranasal infection with C. pneumoniae (Cpn group), 2) recurrent intravenous infection with A. actinomycetemcomitans (Aa group), 3) a combination of both types of infection (Cpn + Aa group), or 4) infection with the vehicle (control group). Epididymal and inguinal AT gene expression was analyzed using an Illumina Mouse WG-6 v2.0 platform and quantitative PCR (QPCR). Microarray data were analyzed using Gene Ontology enrichment analysis. AT fatty acid analysis was performed using gas–liquid chromatography.

Results

The transcriptomics data revealed significant enrichment in inflammation-associated biological pathways in both AT depots derived from the Aa and Cpn + Aa treated mice compared with the control group. The proportion of saturated fatty acids was higher in the inguinal AT in Aa (p = 0.027) and Cpn + Aa (p = 0.009) groups and in the epididymal AT in Aa group (p = 0.003). The proportion of polyunsaturated fatty acids was significantly lower among all Aa-infected groups in both depots. Chronic Cpn infection displayed only minor effects on transcriptomics and fatty acids of the AT depots.

Conclusions

Systemic infection with A. actinomycetemcomitans activates inflammation-related biological pathways and modulates cellular lipid homeostasis. The adverse changes in adipose tissues during chronic infection may promote atherosclerosis.

Impact of neutrophil-secreted myeloid related proteins 8 and 14 (MRP 8/14) on leishmaniasis progression

The myeloid-related proteins (MRPs) 8/14 are small proteins mainly produced by neutrophils, which have been reported to induce NO production in macrophages. On the other hand, Leishmania survives and multiplies within phagocytes by inactivating several of their microbicidal functions. Whereas MRPs are rapidly released during the innate immune response, their role in the regulation of Leishmaniasis is still unknown. In vitro experiments revealed that Leishmania infection alters MRP-induced signaling, leading to inhibition of macrophage functions (NO, TNF-α). In contrast, MRP-primed cells showed normal signaling activation and NO production in response to Leishmania infection. Using a murine air-pouch model, we observed that infection with L. major induced leukocyte recruitment and MRP secretion comparable to LPS-treated mice. Depletion of MRPs significantly reduced these inflammatory events and augmented both parasite load and footpad swelling during the first 8 weeks post-infection, as also observed in MRP KO mice. On the contrary, mouse treatment with recombinant MRPs (rMRPs) had the opposite effect. Collectively, our results suggest that rapid secretion of MRPs by neutrophils at the site of infection may protect uninfected macrophages and favor a more efficient innate inflammatory response against Leishmania infection. In summary, our study reveals the critical role played by MRPs in the regulation of Leishmania infection and how this pathogen can subvert its action.

Parasites of the Leishmania genus have developed multiple mechanisms to subvert the immune response. Among these mechanisms are the activation of host phosphatases and inactivation of cell signaling pathways, which in turn activate the immune response. On the other hand, it has been observed that the Myeloid Related Proteins (MRPs) 8 and 14 are potent activators of some components of the immune response. In this study, we evaluated the effect of MRPs 8 and 14 on the progression of cutaneous Leishmaniasis. To do so, we used immortalized macrophages and stimulated them with MRPs before or after infection with L. major. We observed that stimulating macrophages with MRPs prior to infection induced NO and TNF-α production, as well as phosphorylation of MAPKs and nuclear translocation of transcription factors NF-κB and AP-1. However, when MRP stimulation was performed after infection, these effects where subverted. Moreover, using a murine model of cutaneous infection, we observed that depletion of MRPs caused increased parasite burden and bigger lesions. On the contrary, injection of recombinant MRPs directly into the lesion, considerably reduced lesion size and parasite burden. Our study suggests that MRPs could have a potential therapeutic use in the control of Leishmania infection.

Functions of S100 proteins

The S100 protein family consists of 24 members functionally distributed into three main subgroups: those that only exert intracellular regulatory effects, those with intracellular and extracellular functions and those which mainly exert extracellular regulatory effects. S100 proteins are only expressed in vertebrates and show cell-specific expression patterns. In some instances, a particular S100 protein can be induced in pathological circumstances in a cell type that does not express it in normal physiological conditions. Within cells, S100 proteins are involved in aspects of regulation of proliferation, differentiation, apoptosis, Ca2+ homeostasis, energy metabolism, inflammation and migration/invasion through interactions with a variety of target proteins including enzymes, cytoskeletal subunits, receptors, transcription factors and nucleic acids. Some S100 proteins are secreted or released and regulate cell functions in an autocrine and paracrine manner via activation of surface receptors (e.g. the receptor for advanced glycation end-products and toll-like receptor 4), G-protein-coupled receptors, scavenger receptors, or heparan sulfate proteoglycans and N-glycans. Extracellular S100A4 and S100B also interact with epidermal growth factor and basic fibroblast growth factor, respectively, thereby enhancing the activity of the corresponding receptors. Thus, extracellular S100 proteins exert regulatory activities on monocytes/macrophages/microglia, neutrophils, lymphocytes, mast cells, articular chondrocytes, endothelial and vascular smooth muscle cells, neurons, astrocytes, Schwann cells, epithelial cells, myoblasts and cardiomyocytes, thereby participating in innate and adaptive immune responses, cell migration and chemotaxis, tissue development and repair, and leukocyte and tumor cell invasion.

MRP8/14 enhances corneal susceptibility to Pseudomonas aeruginosa Infection by amplifying inflammatory responses

PURPOSE

We explored the role of myeloid-related protein 8 and 14 (MRP8/14) in Pseudomonas aeruginosa (PA) keratitis.

METHODS

MRP8/14 mRNA levels in human corneal scrapes and mouse corneas infected by PA were tested using real-time PCR. MRP8/14 protein expression in C57BL/6 (B6) corneas was confirmed using Western blot assay and immunohistochemistry. B6 mice were injected subconjunctivally with siRNA for MRP8/14, and then infected with PA. Bacterial plate counts and myeloperoxidase assays were used to determine the bacterial load and polymorphonuclear neutrophil (PMN) infiltration in infected B6 corneas. Pro-inflammatory cytokine levels in vivo and in vitro were examined with PCR and ELISA. In murine macrophage-like RAW264.7 cells, phagocytosis and bacterial killing were assessed using plate count assays, and reactive oxygen species (ROS) and nitric oxide (NO) levels were tested with flow cytometry and Griess assay, respectively.

RESULTS

MRP8/14 expression levels were increased significantly in human corneal scrapes and B6 corneas after PA infection. Silencing of MRP8/14 in B6 corneas significantly reduced the severity of corneal disease, bacterial clearance, PMN infiltration, and pro-inflammatory cytokine expression after PA infection. In vitro studies demonstrated further that silencing of MRP8/14 suppressed pro-inflammatory cytokine production, bacterial killing, and ROS production, but not phagocytosis or NO production.

CONCLUSIONS

Our study demonstrated a dual role for MRP8/14 in bacterial keratitis. Although MRP8/14 promotes bacterial clearance by enhancing ROS production, it functions more importantly as an inflammatory amplifier at the ocular surface by enhancing pro-inflammatory cytokine expression, thus contributing to the corneal susceptibility.

MRP8/14 is associated with systemic inflammation in stable coronary atherosclerosis in men

BACKGROUND

MRP8/14, a secreted heterodimeric protein complex secreted upon phagocyte activation, plays an important role in atherogenesis and vascular injury. Phagocyte activation is crucially involved in the development of atherosclerotic processes, and MRP8/14 levels have also been linked to acute cardiovascular events. We investigated whether circulating MRP8/14 correlates to chronic coronary artery disease (CAD) stages in this observational, cross-sectional study.

METHODS AND RESULTS

A total of 240 male subjects undergoing elective coronary angiography were included in the study. CAD was present in 166 individuals, whereas 74 subjects were classified without prevalent CAD (control subjects). The atherosclerotic burden was obtained by three independent angiographic scores: the Severity, Gensini and Extent Score. Serum MRP8/14 levels were measured by ELISA. They were associated with hs-CRP, IL-6 and fibrinogen levels (r = 0·43, r = 0·40 and r = 0·44, respectively; all P < 0·001). However, MRP8/14 was neither associated with any other cardiovascular disease risk factor nor did serum levels differ between patients with stable CAD [0·82 (0·55-1·14) μg mL(-1) ] and control subjects [0·91 (0·63-1·30) μg mL(-1) ; P = 0·69]. Moreover, atherosclerotic wall irregularities did not demonstrate any association with circulating MRP8/14.

CONCLUSIONS

The phagocyte activation marker MRP8/14 is significantly associated with markers of systemic inflammation in male patients with CAD. However, we were unable to find a correlation between circulating MRP8/14 complex and stable CAD.

Oxidative modifications of DAMPs suppress inflammation: the case for S100A8 and S100A9

Several S100 Ca(2+)-binding proteins are considered damage-associated molecular pattern molecules (DAMPs). They are actively secreted or released from necrotic cells in response to tissue injury or stress and have various functions important in innate immunity. Here, we review several DAMPs, with particular focus on S100A8 and S100A9, which are susceptible to oxidative modifications by various forms of reactive oxygen species. We discuss the unique posttranslational modifications generated in S100A8 by hypochlorite and the likely structural consequences that alter function. We propose that some reversible modifications act as regulatory switches, representing a mechanism to arrest their novel antiinflammatory activities. These may be important in dampening mast cell activation and altering properties of the activated microcirculation to limit leukocyte adhesion, transmigration, and accumulation. S-nitrosylation of S100A8 in the vasculature could regulate nitric oxide transport and contribute to vessel reflow during resolution of inflammation.

Myeloid-related protein activity in rheumatoid arthritis

SA100A8, SA100A9, and SA100A12 are members of the myeloid-related protein class. SA100A8 and SA100A9, also known as MRP-8 and MRP-14, respectively, are intracellular Ca²⁺-binding proteins produced mainly by neutrophils and monocytes where they exist as a heterodimeric complex in the cytosol. The MRP-8/-14 complex has been shown to promote chronic inflammation associated with rheumatoid arthritis (RA). In that regard, MRP-8 and MRP-14 regulate the inflammatory response through their capacity to recruit neutrophils and monocytes to target tissues resulting in attachment to endothelium. MRPs also activate the signal transduction pathway principally involving the stress-activated/mitogen-activated protein kinases. MRP-8/MRP-14 also increased nitric oxide synthesis. Most recently, the MRP-8/MRP-14 complex was shown to be a novel ligand for the toll-like receptors (TLRs) and TLR-4, in particular. Engagement of TLRs by the MRP-8/-14 complex may be particularly important for activating antigen-presenting dendritic cells which regulate critical autoimmune responses that promote chronic synovitis characteristic of RA.

Proteome technologies in studying the pathogenesisof psoriasis

Psoriasis is one of the most prevalent inflammatory dermatoses. At the same time, its pathogenesis has not been studied in full. Proteome profiling is currently a promising method to study the biological mechanisms of developing different diseases. Proteome technologies make it possible to detect changes in the skin protein profile in psoriatic patients and identify the revealed proteins. The proteins serve as potential targets for drugs or biomarkers for assessing the patients individual drug response. The article describes the key achievements in the field of studying the pathogenesis of psoriasis using proteome technologies (two-dimensional electrophoresis and mass spectrometry) set out in the latest literature sources, and also analyzes the results of the authors studies aimed at detecting proteins being markers of the patients response to the infliximab therapy.

All-trans retinoic acid induces TLR-5 expression and cell differentiation and promotes flagellin-mediated cell functions in human THP-1 cells

Toll-like receptor 5 (TLR-5), which is expressed on macrophages and dendritic cells (DCs), is a crucial cell surface molecule that senses microbial-associated molecular patterns and initiates host innate immune responses upon infection with invaders that express flagellin. Little information is known about the induction factors and mechanisms of TLR-5 expression. In this study, we demonstrate that all-trans retinoic acid (ATRA) significantly up-regulated TLR-5 expression in human macrophage THP-1 cells by co-activating NF-κB and the RARα receptor and inducing the differentiation of CD11b(-)CD11c(-) THP-1 cells to CD11b(+)CD11c(low) cells. Furthermore, when stimulated with flagellin, ATRA-induced THP-1 cells expressed multiple cytokines, including TNF-α, IL-1beta, and IL-12p40, and several co-stimulatory molecules, such as CD40, CD80, CD86, and MHC class I and II. We also showed that when ATRA-induced THP-1 cells were stimulated with flagellin, the cells displayed an allostimulatory capacity rather than phagocytic activity. Taken together, our findings suggest that ATRA is a crucial immunostimulatory cofactor that induces the activation of macrophages and their subsequent differentiation into dendritic-like cells.

S100A8/A9 activate key genes and pathways in colon tumor progression

The tumor microenvironment plays an important role in modulating tumor progression. Earlier, we showed that S100A8/A9 proteins secreted by myeloid-derived suppressor cells (MDSC) present within tumors and metastatic sites promote an autocrine pathway for accumulation of MDSC. In a mouse model of colitis-associated colon cancer, we also showed that S100A8/A9-positive cells accumulate in all regions of dysplasia and adenoma. Here we present evidence that S100A8/A9 interact with RAGE and carboxylated glycans on colon tumor cells and promote activation of MAPK and NF-κB signaling pathways. Comparison of gene expression profiles of S100A8/A9-activated colon tumor cells versus unactivated cells led us to identify a small cohort of genes upregulated in activated cells, including Cxcl1, Ccl5 and Ccl7, Slc39a10, Lcn2, Zc3h12a, Enpp2, and other genes, whose products promote leukocyte recruitment, angiogenesis, tumor migration, wound healing, and formation of premetastatic niches in distal metastatic organs. Consistent with this observation, in murine colon tumor models we found that chemokines were upregulated in tumors, and elevated in sera of tumor-bearing wild-type mice. Mice lacking S100A9 showed significantly reduced tumor incidence, growth and metastasis, reduced chemokine levels, and reduced infiltration of CD11b(+)Gr1(+) cells within tumors and premetastatic organs. Studies using bone marrow chimeric mice revealed that S100A8/A9 expression on myeloid cells is essential for development of colon tumors. Our results thus reveal a novel role for myeloid-derived S100A8/A9 in activating specific downstream genes associated with tumorigenesis and in promoting tumor growth and metastasis.

In vitro characterization of the microglial inflammatory response to Streptococcus suis, an important emerging zoonotic agent of meningitis

Streptococcus suis is an important swine and human pathogen responsible for septicemia and meningitis. In vivo research in mice suggested that in the brain, microglia might be involved in activating the inflammatory response against S. suis. The aim of this study was to better understand the interactions between S. suis and microglia. Murine microglial cells were infected with a virulent wild-type strain of S. suis. Two isogenic mutants deficient at either capsular polysaccharide (CPS) or hemolysin production were also included. CPS contributed to S. suis resistance to phagocytosis and regulated the inflammatory response by hiding proinflammatory components from the bacterial cell wall, while the absence of hemolysin, a potential cytotoxic factor, did not have a major impact on S. suis interactions with microglia. Wild-type S. suis induced enhanced expression of Toll-like receptor 2 by microglial cells, as well as phosphotyrosine, protein kinase C, and different mitogen-activated protein kinase signaling events. However, cells infected with the CPS-deficient mutant showed overall stronger and more sustained phosphorylation profiles. CPS also modulated inducible nitric oxide synthase expression and further nitric oxide production from S. suis-infected microglia. Finally, S. suis-induced NF-κB translocation was faster for cells stimulated with the CPS-deficient mutant, suggesting that bacterial cell wall components are potent inducers of NF-κB. These results contribute to increase the knowledge of mechanisms underlying S. suis inflammation in the brain and will be useful in designing more efficient anti-inflammatory strategies for meningitis.

Premetastatic milieu explained by TLR4 agonist-mediated homeostatic inflammation

Accumulating evidence suggests that Toll-like receptor 4 (TLR4), a sensor for danger signals, is expressed not only in immune cells, but also in resident epithelial cells, and appears to participate in tissue homeostasis. To explain the premetastatic microenvironment created by the newly discovered endogenous TLR4 ligands, I propose a hypothesis of homeostatic inflammation that includes the classical danger hypothesis.

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.

Complicated urinary tract infection is associated with uroepithelial expression of proinflammatory protein S100A8

F344 rats chronically infected with Ureaplasma parvum develop two distinct profiles: asymptomatic urinary tract infection (UTI) and UTI complicated by struvite urolithiasis. To identify factors that affect disease outcome, we characterized the temporal host immune response during infection by histopathologic analysis and in situ localization of U. parvum. We also used differential quantitative proteomics to identify distinguishing host cellular responses associated with complicated UTI. In animals in which microbial colonization was limited to the mucosal surface, inflammation was indistinguishable from that which occurred in sham-inoculated controls, and the inflammation resolved by 72 h postinoculation (p.i.) in both groups. However, inflammation persisted in animals with microbial colonization that extended into the deeper layers of the submucosa. Proteome profiling showed that bladder tissues from animals with complicated UTIs had significant increases (P < 0.01) in proteins involved in apoptosis, oxidative stress, and inflammation. Animals with complicated UTIs (2 weeks p.i.) had the highest concentrations of the proinflammatory protein S100A8 (P Collapse

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MESH Headings

• Animals
• Calgranulin A/biosynthesis
• Cytokines/biosynthesis
• Histocytochemistry
• Humans
• Microscopy, Fluorescence
• Proteome/analysis
• Rats
• Ureaplasma/immunology
• Ureaplasma/pathogenicity
• Ureaplasma Infections/immunology
• Ureaplasma Infections/microbiology
• Ureaplasma Infections/pathology
• Urinary Bladder/immunology
• Urinary Bladder/microbiology
• Urinary Bladder/pathology
• Urinary Tract Infections/immunology
• Urinary Tract Infections/microbiology
• Urinary Tract Infections/pathology

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Grants

• K08 DK075651 NIDDK NIH HHS
• K08 DK075651-02 NIDDK NIH HHS
• R01 AI045875 NIAID NIH HHS
• K08DK075651 NIDDK NIH HHS

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Affiliation(s)

Leticia Reyes University of Florida, College of Veterinary Medicine, Department of Infectious Diseases & Pathology, P.O. Box 110880, Gainesville, FL 32611-0880, USA.
Sophie Alvarez
Ayman Allam
Mary Reinhard
Mary B Brown

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Endogenous damage-associated molecular pattern molecules at the crossroads of inflammation and cancer

Inflammatory mediators play important roles in the development and progression of cancer. Cellular stress, damage, inflammation, and necrotic cell death cause release of endogenous damage-associated molecular pattern (DAMP) molecules or alarmins, which alert the host of danger by triggering immune responses and activating repair mechanisms through their interaction with pattern recognition receptors. Recent studies show that abnormal persistence of these molecules in chronic inflammation and in tumor microenvironments underlies carcinogenesis and tumor progression, indicating that DAMP molecules and their receptors could provide novel targets for therapy. This review focuses on the role of DAMP molecules high-mobility group box 1 and S100 proteins in inflammation, tumor growth, and early metastatic events.

Comparison of the Expression Profile of JunB, c-Jun, and S100A8 (Calgranulin A) in Psoriasis Vulgaris and Guttate Psoriasis

BACKGROUND

Psoriasis is a chronic, inflammatory, immune-mediated skin disease. Recently, several psoriasis-linked genetic loci have been reported; PSORS4 contains S100A8 (calgranulin A), and PSOR6 (19p13) locus harbors JunB (19p13.2). S100A8 is considered to be a marker of inflammation in a variety of diseases. The expression of JunB and c-Jun have been reported to be reduced in psoriatic lesions.

OBJECTIVE

We attempted to assess the role and correlation of S100A8, JunB, and c-Jun in the pathogenesis of guttate psoriasis and psoriasis vulgaris by studying whether any difference of immunohistochemical expression existed.

METHODS

Skin biopsy specimens from patients with psoriasis vulgaris (n=37) and guttate psoriasis (n=17), and a normal skin controls (n=9) were utilized in the study. Formalin-fixed and paraffin-embedded tissue sections were prepared and JunB, c-Jun, and calgranulin A were immunohistochemically stained in order to compare the expression of those three proteins in each group.

RESULTS

Reduced JunB expression was observed in patients with psoriasis vulgaris and guttate psoriasis, as compared to patients in the control group; however, c-Jun expression was reduced only in the psoriasis vulgaris group. The expression of S100A8 increased in the psoriasis groups as compared to the control group. In addition, the expression of S100A8 was different between the psoriasis vulgaris and guttate psoriasis groups; S100A8 was expressed more profoundly in the guttate psoriasis group (p<0.05).

CONCLUSION

Our results indicate that S100A8 contributes to the pathogenesis of guttate psoriasis, and it may be a good target for therapy for guttate psoriasis provoked by microorganisms.