OSCAR is a receptor for surfactant protein D that activates TNF-α release from human CCR2+ inflammatory monocytes

Novel roles for cooperating collagen receptor families in fibrotic niches

Recent data indicate that integrin and non-integrin collagen receptors cooperate in the fibrosis-specific microenvironment (i.e., the fibrotic niche). In certain tumor types, DDR1 can regulate the interaction with collagen III to regulate dormancy and metastasis, whereas in other tumor types, DDR1 can be shed and used to reorganize collagen. DDR1 expressed on tumor cells, together with DDR2 and α11β1 integrin expressed on cancer-associated fibroblasts, can increase tumor tissue stiffness. Integrin α1β1 and α2β1 are present on immune cells where they together with the immunosuppressive collagen receptor LAIR-1 can mediate binding to intratumor collagens. In summary, collagen-binding integrins together with DDRs, can create fibrillar collagen niches that act as traps to hinder immune cell trafficking into the tumor cell mass. Binding of collagens via LAIR-1 on immune cells in turn results in CD8+T-cell exhaustion. Continued studies of these complex interactions are needed for successful new stroma-based therapeutic interventions. In the current review, we will summarize recent data on collagen receptors with a special focus on their potential role in tumor fibrosis and highlight their collaborative roles in tumor fibrotic niches.

Bioaerosol-induced in vitro activation of toll-like receptors and inflammatory biomarker expression in waste workers

PURPOSE

Occupational exposure to bioaerosols during waste handling remains a health concern for exposed workers. However, exposure-related health effects and underlying immunological mechanisms are still poorly described.

METHODS

The present study assessed the inflammatory potential of work-air samples (n = 56) in vitro and investigated biomarker expression in exposed workers (n = 69) compared to unexposed controls (n = 25). These quantitative results were compared to self-reported health conditions.

RESULTS

Personal air samples provoked an activation of TLR2 and TLR4 HEK reporter cells in one-third of all samples, indicating that the work environment contained ligands capable of inducing an immune response in vitro. Monocyte levels, as well as plasma biomarker levels, such as IL-1Ra, IL-18 and TNFα were significantly higher in exposed workers, compared to the control group when confounding factors such as BMI, sex, age and smoking habits were accounted for. Furthermore, a significant exposure-related increase in midweek IL-8 levels was measured among exposed workers. Tendencies of increased prevalence of health effects of the respiratory tract were identified in exposed workers.

CONCLUSION

Inhalable dust provoked TLR activation in vitro, indicating that an exposure-related immune response may be expected in susceptible workers. However, despite significant differences in inflammatory plasma biomarker levels between exposed and unexposed workers, prevalence of self-reported health effects did not differ between the groups. This may be due to the healthy worker effect, or other factors such as adequate use of personal protective respiratory devices or adaptation to the work environment with reduced activation of the immune system.

Surfactant protein A alters endosomal trafficking of influenza A virus in macrophages

Influenza A virus infection (IAV) often leads to acute lung injury that impairs breathing and can lead to death, with disproportionate mortality in children and the elderly. Surfactant Protein A (SP-A) is a calcium-dependent opsonin that binds a variety of pathogens to help control pulmonary infections by alveolar macrophages. Alveolar macrophages play critical roles in host resistance and susceptibility to IAV infection. The effect of SP-A on IAV infection and antiviral response of macrophages, however, is not understood. Here, we report that SP-A attenuates IAV infection in a dose-dependent manner at the level of endosomal trafficking, resulting in infection delay in a model macrophage cell line. The ability of SP-A to suppress infection was independent of its glycosylation status. Binding of SP-A to hemagglutinin did not rely on the glycosylation status or sugar binding properties of either protein. Incubation of either macrophages or IAV with SP-A slowed endocytic uptake rate of IAV. SP-A interfered with binding to cell membrane and endosomal exit of the viral genome as indicated by experiments using isolated cell membranes, an antibody recognizing a pH-sensitive conformational epitope on hemagglutinin, and microscopy. Lack of SP-A in mice enhanced IFNβ expression, viral clearance and reduced mortality from IAV infection. These findings support the idea that IAV is an opportunistic pathogen that co-opts SP-A to evade host defense by alveolar macrophages. Our study highlights novel aspects of host-pathogen interactions that may lead to better understanding of the local mechanisms that shape activation of antiviral and inflammatory responses to viral infection in the lung.

A 69 kb Deletion in chr19q13.42 including PRPF31 Gene in a Chinese Family Affected with Autosomal Dominant Retinitis Pigmentosa

We aimed to identify the genetic cause of autosomal dominant retinitis pigmentosa (adRP) and characterize the underlying molecular mechanisms of incomplete penetrance in a Chinese family affected with adRP. All enrolled family members underwent ophthalmic examinations. Whole-genome sequencing (WGS), multiplex ligation-dependent probe amplification (MLPA), linkage analysis and haplotype construction were performed in all participants. RNA-seq was performed to analyze the regulating mechanism of incomplete penetrance among affected patients, mutation carriers and healthy controls. In the studied family, 14 individuals carried a novel heterozygous large deletion of 69 kilobase (kb) in 19q13.42 encompassing exon 1 of the PRPF31 gene and five upstream genes: TFPT, OSCAR, NDUFA3, TARM1, and VSTM1. Three family members were sequenced and diagnosed as non-penetrant carriers (NPCs). RNA-seq showed significant differential expression of genes in deletion between mutation carriers and healthy control. The RP11 pedigree in this study was the largest pedigree compared to other reported RP11 pedigrees with large deletions. Early onset in all affected members in this pedigree was considered to be a special phenotype and was firstly reported in a RP11 family for the first time. Differential expression of PRPF31 between affected and unaffected subjects indicates a haploinsufficiency to cause the disease in the family. The other genes with significant differential expression might play a cooperative effect on the penetrance of RP11.

STAT1-mediated induction of Ly6c-expressing macrophages are involved in the pathogenesis of an acute colitis model

BACKGROUND

The development of inflammatory bowel diseases is thought to be multifactorial, but the exact steps in pathogenesis are poorly understood. In this study, we investigated involvement of the activation of STAT1 signal pathway in the pathogenesis of an acute colitis model.

METHODS

A dextran sulfate sodium-induced acute colitis model was established by using wild-type C57BL/6 mice and STAT1-deficient mice. Disease indicators such as body weight loss and clinical score, induction of cytokines, chemokines, and inflammatory cells were evaluated in the acute colitis model.

RESULTS

Disease state was significantly improved in the acute colitis model using STAT1-deficient mice compared with wild-type mice. The induction of Ly6c-highly expressing cells in colorectal tissues was attenuated in STAT1-deficient mice. IL-6, CCL2, and CCR2 gene expressions in Ly6c-highly expressing cells accumulated in the inflamed colon tissues and were significantly higher than in Ly6c-intermediate-expressing cells, whereas TNF-α and IFN-α/β gene expression was higher in Ly6c-intermediate-expressing cells. Blockade of CCR2-mediated signaling significantly reduced the disease state in the acute colitis model.

CONCLUSIONS

Two different types of Ly6c-expressing macrophages are induced in the inflamed tissues through the IFN-α/β-STAT1-mediated CCL2/CCR2 cascade and this is associated with the pathogenesis such as onset, exacerbation, and subsequent chronicity of acute colitis.

Complex Evaluation of Surfactant Protein A and D as Biomarkers for the Severity of COPD

Purpose

Pulmonary surfactant proteins A (SP-A) and D (SP-D) are lectins, involved in host defense and regulation of pulmonary inflammatory response. However, studies on the assessment of COPD progress are limited.

Patients and Methods

Pulmonary surfactant proteins were obtained from the COPD mouse model induced by cigarette and lipopolysaccharide, and the specimens of peripheral blood and bronchoalveolar lavage (BALF) in COPD populations. H&E staining and RT-PCR were performed to demonstrate the successfully established of the mouse model. The expression of SP-A and SP-D in mice was detected by Western Blot and immunohistochemistry, while the proteins in human samples were measured by ELISA. Pulmonary function test, inflammatory factors (CRP, WBC, NLR, PCT, EOS, PLT), dyspnea index score (mMRC and CAT), length of hospital stay, incidence of complications and ventilator use were collected to assess airway remodeling and progression of COPD.

Results

COPD model mice with emphysema and airway wall thickening were more prone to have decreased SP-A, SP-D and increased TNF-α, TGF-β, and NF-kb in lung tissue. In humans, SP-A and SP-D decreased in BALF, but increased in serum. The serum SP-A and SP-D were negatively correlated with FVC, FEV1, FEV1/FVC, and positively correlated with CRP, WBC, NLR, mMRC and CAT scores (P < 0.05, respectively). The lower the SP-A and SP-D in BALF, the worse the lung function and the increased probability of complications and ventilator use. Moreover, the same trend emerged in COPD patients grouped according to GOLD severity grade (Gold 1–2 group vs Gold 3–4 group). The worse the patient’s condition, the more pronounced the change.

Conclusion

This study suggests that SP-A and SP-D may be related to the progression and prognostic evaluation of COPD in terms of airway remodeling, inflammatory response and clinical symptoms, and emphasizes the necessity of future studies of surfactant protein markers in COPD.

Structural insights into collagen binding by platelet receptor glycoprotein VI

Glycoprotein VI (GPVI) mediates collagen-induced platelet activation after vascular damage and is an important contributor to the onset of thrombosis, heart attack, and stroke. Animal models of thrombosis have identified GPVI as a promising target for antithrombotic therapy. Although for many years the crystal structure of GPVI has been known, the essential details of its interaction with collagen have remained elusive. Here, we present crystal structures of the GPVI ectodomain bound to triple-helical collagen peptides, which reveal a collagen-binding site across the β-sheet of the D1 domain. Mutagenesis and binding studies confirm the observed binding site and identify Trp76, Arg38, and Glu40 as essential residues for binding to fibrillar collagens and collagen-related peptides (CRPs). GPVI binds a site on collagen comprising two collagen chains with the core formed by the sequence motif OGPOGP. Potent GPVI-binding peptides from Toolkit-III all contain OGPOGP; weaker binding peptides frequently contain a partial motif varying at either terminus. Alanine-scanning of peptide III-30 also identified two AGPOGP motifs that contribute to GPVI binding, but steric hindrance between GPVI molecules restricts the maximum binding capacity. We further show that no cooperative interactions could occur between two GPVI monomers binding to a stretch of (GPO)5 and that binding of ≥2 GPVI molecules to a fibril-embedded helix requires non-overlapping OGPOGP motifs. Our structure confirms the previously suggested similarity in collagen binding between GPVI and leukocyte-associated immunoglobulin-like receptor 1 (LAIR-1) but also indicates significant differences that may be exploited for the development of receptor-specific therapeutics.

Transcriptome-wide association study identified candidate genes associated with gut microbiota

Background

Gut microbiota is closely associated with host health and disease occurrence. Host genetic factor plays an important role in shaping gut microbial communities. The specific mechanism of host-regulated gene expression affecting gut microbiota has not been elucidated yet. Here we conducted a transcriptome-wide association study (TWAS) for gut microbiota by leveraging expression imputation from large-scale GWAS data sets.

Results

TWAS detected multiple tissue-specific candidate genes for gut microbiota, such as FUT2 for genus Bifidobacterium in transverse colon (P_PERM.ANL = 1.68 × 10^–3) and SFTPD for an unclassified genus of Proteobacteria in transverse colon (P_PERM.ANL = 5.69 × 10^–3). Fine mapping replicated 3 candidate genes in TWAS, such as HELLS for Streptococcus (PIP = 0.685) in sigmoid colon, ANO7 for Erysipelotrichaceae (PIP = 0.449) in sigmoid colon. Functional analyses detected 94 significant GO terms and 11 pathways for various taxa in total, such as GO_NUCLEOSIDE_DIPHOSPHATASE_ACTIVITY for Butyrivibrio (FDR P = 1.30 × 10^–4), KEGG_RENIN_ANGIOTENSIN_SYSTEM for Anaerostipes (FDR P = 3.16 × 10^–2). Literature search results showed 12 genes prioritized by TWAS were associated with 12 diseases. For instance, SFTPD for an unclassified genus of Proteobacteria was related to atherosclerosis, and FUT2 for Bifidobacterium was associated with Crohn’s disease.

Conclusions

Our study results provided novel insights for understanding the genetic mechanism of gut microbiota, and attempted to provide clues for revealing the influence of genetic factors on gut microbiota for the occurrence and development of diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13099-021-00474-w.

Pulmonary surfactant as a versatile biomaterial to fight COVID-19

The COVID-19 pandemic has wielded an enormous pressure on global health care systems, economics and politics. Ongoing vaccination campaigns effectively attenuate viral spreading, leading to a reduction of infected individuals, hospitalizations and mortality. Nevertheless, the development of safe and effective vaccines as well as their global deployment is time-consuming and challenging. In addition, such preventive measures have no effect on already infected individuals and can show reduced efficacy against SARS-CoV-2 variants that escape vaccine-induced host immune responses. Therefore, it is crucial to continue the development of specific COVID-19 targeting therapeutics, including small molecular drugs, antibodies and nucleic acids. However, despite clear advantages of local drug delivery to the lung, inhalation therapy of such antivirals remains difficult. This review aims to highlight the potential of pulmonary surfactant (PS) in the treatment of COVID-19. Since SARS-CoV-2 infection can progress to COVID-19-related acute respiratory distress syndrome (CARDS), which is associated with PS deficiency and inflammation, replacement therapy with exogenous surfactant can be considered to counter lung dysfunction. In addition, due to its surface-active properties and membrane-interaction potential, PS can be repurposed to enhance drug spreading along the respiratory epithelium and to promote intracellular drug delivery. By merging these beneficial features, PS can be regarded as a versatile biomaterial to combat respiratory infections, in particular COVID-19.

Pattern Recognition Proteins: First Line of Defense Against Coronaviruses

The rapid outbreak of COVID-19 caused by the novel coronavirus SARS-CoV-2 in Wuhan, China, has become a worldwide pandemic affecting almost 204 million people and causing more than 4.3 million deaths as of August 11 2021. This pandemic has placed a substantial burden on the global healthcare system and the global economy. Availability of novel prophylactic and therapeutic approaches are crucially needed to prevent development of severe disease leading to major complications both acutely and chronically. The success in fighting this virus results from three main achievements: (a) Direct killing of the SARS-CoV-2 virus; (b) Development of a specific vaccine, and (c) Enhancement of the host's immune system. A fundamental necessity to win the battle against the virus involves a better understanding of the host's innate and adaptive immune response to the virus. Although the role of the adaptive immune response is directly involved in the generation of a vaccine, the role of innate immunity on RNA viruses in general, and coronaviruses in particular, is mostly unknown. In this review, we will consider the structure of RNA viruses, mainly coronaviruses, and their capacity to affect the lungs and the cardiovascular system. We will also consider the effects of the pattern recognition protein (PRP) trident composed by (a) Surfactant proteins A and D, mannose-binding lectin (MBL) and complement component 1q (C1q), (b) C-reactive protein, and (c) Innate and adaptive IgM antibodies, upon clearance of viral particles and apoptotic cells in lungs and atherosclerotic lesions. We emphasize on the role of pattern recognition protein immune therapies as a combination treatment to prevent development of severe respiratory syndrome and to reduce pulmonary and cardiovascular complications in patients with SARS-CoV-2 and summarize the need of a combined therapeutic approach that takes into account all aspects of immunity against SARS-CoV-2 virus and COVID-19 disease to allow mankind to beat this pandemic killer.

OSCAR facilitates malignancy with enhanced metastasis correlating to inhibitory immune microenvironment in multiple cancer types

Cross talk between tumors and the immune microenvironment play a critical role in the malignant progression. The osteoclast-associated receptor (OSCAR) is a regulator of lymphocyte differentiation and maturation, but little is known about the role of OSCAR in multiple cancer types. We comprehensively analyzed OSCAR expression and explored its correlation with prognosis in multiple cancer types using Oncomine, TIMER, Gene GEPIA2 and CCLE. We examined OSCAR expression correlations with lymph node metastasis and pathological stage across tumor samples using UALCAN and GEPIA2. We analyzed the effects of OSCAR on survival using the Kaplan Meier plotter. We explored genes co-expressed with OSCAR using the LinkedOmics database and analyzed associated gene ontologies using Metascape. Further, we examined the correlation between OSCAR expression and immunocyte infiltration, markers of epithelial-mesenchymal transition, and lymphocyte subtypes using TIMER. OSCAR mRNA levels were upregulated in most cancer types compared with adjacent normal tissues. Higher expression of OSCAR correlated with lymph node metastasis or advanced stage subgroups. High expression of OSCAR was related to low tumor purity, with increased levels of M2 macrophage polarization, T cells exhaustion, and mesenchymal phenotype in most cancer types. We also showed that the strength of OSCAR expression influence in malignant progression and inhibitory immune microenvironment is mitigated by the infiltration of natural killer cells. These findings shed light on the pro-carcinogenic role of OSCAR in most cancer types and indicate OSCAR could be targeted in future therapeutics to reverse the inhibitory immune microenvironment.

Role of OSCAR Signaling in Osteoclastogenesis and Bone Disease

Formation of mature bone-resorbing cells through osteoclastogenesis is required for the continuous remodeling and repair of bone tissue. In aging and disease this process may become aberrant, resulting in excessive bone degradation and fragility fractures. Interaction of receptor-activator of nuclear factor-κB (RANK) with its ligand RANKL activates the main signaling pathway for osteoclastogenesis. However, compelling evidence indicates that this pathway may not be sufficient for the production of mature osteoclast cells and that co-stimulatory signals may be required for both the expression of osteoclast-specific genes and the activation of osteoclasts. Osteoclast-associated receptor (OSCAR), a regulator of osteoclast differentiation, provides one such co-stimulatory pathway. This review summarizes our present knowledge of osteoclastogenesis signaling and the role of OSCAR in the normal production of bone-resorbing cells and in bone disease. Understanding the signaling mechanism through this receptor and how it contributes to the production of mature osteoclasts may offer a more specific and targeted approach for pharmacological intervention against pathological bone resorption.

SP-A and SP-D: Dual Functioning Immune Molecules With Antiviral and Immunomodulatory Properties

Surfactant proteins A (SP-A) and D (SP-D) are soluble innate immune molecules which maintain lung homeostasis through their dual roles as anti-infectious and immunomodulatory agents. SP-A and SP-D bind numerous viruses including influenza A virus, respiratory syncytial virus (RSV) and human immunodeficiency virus (HIV), enhancing their clearance from mucosal points of entry and modulating the inflammatory response. They also have diverse roles in mediating innate and adaptive cell functions and in clearing apoptotic cells, allergens and other noxious particles. Here, we review how the properties of these first line defense molecules modulate inflammatory responses, as well as host-mediated immunopathology in response to viral infections. Since SP-A and SP-D are known to offer protection from viral and other infections, if their levels are decreased in some disease states as they are in severe asthma and chronic obstructive pulmonary disease (COPD), this may confer an increased risk of viral infection and exacerbations of disease. Recombinant molecules of SP-A and SP-D could be useful in both blocking respiratory viral infection while also modulating the immune system to prevent excessive inflammatory responses seen in, for example, RSV or coronavirus disease 2019 (COVID-19). Recombinant SP-A and SP-D could have therapeutic potential in neutralizing both current and future strains of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus as well as modulating the inflammation-mediated pathology associated with COVID-19. A recombinant fragment of human (rfh)SP-D has recently been shown to neutralize SARS-CoV-2. Further work investigating the potential therapeutic role of SP-A and SP-D in COVID-19 and other infectious and inflammatory diseases is indicated.

Cellular uptake of collagens and implications for immune cell regulation in disease

As the dominant constituent of the extracellular matrix (ECM), collagens of different types are critical for the structural properties of tissues and make up scaffolds for cellular adhesion and migration. Importantly, collagens also directly modulate the phenotypic state of cells by transmitting signals that influence proliferation, differentiation, polarization, survival, and more, to cells of mesenchymal, epithelial, or endothelial origin. Recently, the potential of collagens to provide immune regulatory signals has also been demonstrated, and it is believed that pathological changes in the ECM shape immune cell phenotype. Collagens are themselves heavily regulated by a multitude of structural modulations or by catabolic pathways. One of these pathways involves a cellular uptake of collagens or soluble collagen-like defense collagens of the innate immune system mediated by endocytic collagen receptors. This cellular uptake is followed by the degradation of collagens in lysosomes. The potential of this pathway to regulate collagens in pathological conditions is evident from the increased extracellular accumulation of both collagens and collagen-like defense collagens following endocytic collagen receptor ablation. Here, we review how endocytic collagen receptors regulate collagen turnover during physiological conditions and in pathological conditions, such as fibrosis and cancer. Furthermore, we highlight the potential of collagens to regulate immune cells and discuss how endocytic collagen receptors can directly regulate immune cell activity in pathological conditions or do it indirectly by altering the extracellular milieu. Finally, we discuss the potential collagen receptors utilized by immune cells to directly detect ECM-related changes in the tissues which they encounter.

Surfactant Protein D Recognizes Multiple Fungal Ligands: A Key Step to Initiate and Intensify the Anti-fungal Host Defense

With limited therapeutic options and associated severe adverse effects, fungal infections are a serious threat to human health. Innate immune response mediated by pattern recognition proteins is integral to host defense against fungi. A soluble pattern recognition protein, Surfactant protein D (SP-D), plays an important role in immune surveillance to detect and eliminate human pathogens. SP-D exerts its immunomodulatory activity via direct interaction with several receptors on the epithelial cells lining the mucosal tracts, as well as on innate and adaptive immune cells. Being a C-type lectin, SP-D shows calcium- and sugar-dependent interactions with several glycosylated ligands present on fungal cell walls. The interactome includes cell wall polysaccharides such as 1,3-β-D-glucan, 1,6-β-D-glucan, Galactosaminogalactan Galactomannan, Glucuronoxylomannan, Mannoprotein 1, and glycosylated proteins such as gp45, gp55, major surface glycoprotein complex (gpA). Recently, binding of a recombinant fragment of human SP-D to melanin on the dormant conidia of Aspergillus fumigatus was demonstrated that was not inhibited by sugars, suggesting a likely protein-protein interaction. Interactions of the ligands on the fungal spores with the oligomeric forms of full-length SP-D resulted in formation of spore-aggregates, increased uptake by phagocytes and rapid clearance besides a direct fungicidal effect against C. albicans. Exogenous administration of SP-D showed significant therapeutic potential in murine models of allergic and invasive mycoses. Altered susceptibility of SP-D gene-deficient mice to various fungal infections emphasized relevance of SP-D as an important sentinel of anti-fungal immunity. Levels of SP-D in the serum or lung lavage were significantly altered in the murine models and patients of fungal infections and allergies. Here, we review the cell wall ligands of clinically relevant fungal pathogens and allergens that are recognized by SP-D and their impact on the host defense. Elucidation of the molecular interactions between innate immune humoral such as SP-D and fungal pathogens would facilitate the development of novel therapeutic interventions.

Functional characterization of the different oligomeric forms of human surfactant protein SP-D

Surfactant Protein D (SP-D) is a collectin protein that participates in the innate immune defense of the lungs. SP-D mediates the clearance of invading microorganisms by opsonization, aggregation or direct killing, which are lately removed by macrophages. SP-D is found as a mixture of trimers, hexamers, dodecamers and higher order oligomers, "fuzzy balls". However, it is unknown whether there are differences between these oligomeric forms in functions, activity or potency. In the present work, we have obtained fractions enriched in trimers, hexamers and fuzzy balls of full-length recombinant human (rh) SP-D by size exclusion chromatography, in a sufficient amount to perform functional assays. We have evaluated the differences in protein lectin-dependent activity relative to aggregation and binding to E. coli, one of the ligands of SP-D in vivo. Fuzzy balls are the most active oligomeric form in terms of binding and aggregation of bacteria, achieving 2-fold binding higher than hexamers and 50% bacteria aggregation at very short times. Hexamers, recently described as a defined oligomeric form of the protein, have never been isolated or tested in terms of protein activity. rhSP-D hexamers efficiently bind and aggregate bacteria, achieving 50-60% aggregation at final time point and high protein concentrations. Nevertheless, trimers are not able to aggregate bacteria, although they bind to them. Therefore, SP-D potency, in functions that relay on the C-lectin activity of the protein, is proportional to the oligomeric state of the protein.

Sex-biased ceRNA networks reveal that OSCAR can promote proliferation and migration of lung adenocarcinoma in women

Lung adenocarcinoma (LUAD) is one of several malignant tumours with the highest incidence rates. Currently, there is an urgent need for effective diagnostic and therapeutic targets for LUAD in clinical practice. Numerous studies have shown that there may be differences in the development pattern of LUAD between male and female patients, leading to the need for differential treatment. At the same time, previous studies have shown that competitive endogenous (ce)RNA plays an important role in the development of LUAD, but there is no relevant research on whether there is a gender difference in the ceRNA network of LUAD. In this study, we constructed gender-independent, male-specific, and female-specific ceRNA networks using RNA sequencing results from TCGA database. Subsequently, through analysis of the core genes of the ceRNA network, we determined that the male and female ceRNA networks indeed display different features. In addition, we also found that the osteoclast-associated receptor (OSCAR) gene was a potential diagnostic target for detecting LUAD in females, and that increased expression of this gene promoted the proliferation and migration of A549 and H1975 LUAD cell lines; more specifically, A549 and H1975 are male and female LUAD cell lines, respectively. This suggests that the OSCAR gene has the potential to serve as target molecule for the diagnosis and treatment of female-specific LUADs.

Identification of Key Genes Involved in Diabetic Peripheral Neuropathy Progression and Associated with Pancreatic Cancer

INTRODUCTION

Diabetes mellitus (DM) patients suffer from high morbidity and premature mortality due to various diabetic complications and even cancers. Therefore, this study aimed to identify key genes involved in the pathogenesis of diabetic peripheral neuropathy (DPN) and pancreatic cancer (PC).

METHODS

We analyzed three gene expression profiles (GSE95849, GSE28735 and GSE59953) to obtain differentially expressed genes (DEGs). Then, Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed by using the Database for Annotation, Visualization, and Integrated Discovery (DAVID). The Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database was then used to establish a protein-protein interaction (PPI) network. The MCODE and cytoHubba plug-ins of Cytoscape were used to select hub genes. Finally, survival analysis of the hub genes was performed using the Kaplan-Meier plotter and GEPIA online tool.

RESULTS

We first analyzed GSE95849 to obtain DPN-related genes. DEGs were obtained from three groups in GSE95849. The DEGs were enriched in the Toll-like receptor signaling pathway, hematopoietic cell lineage and chemokine signaling pathway. Importantly, we identified three shared genes as hub genes, including TLR4, CCR2 and MMP9. We then analyzed and integrated GSE95849 and GSE28735 to obtain genes common in DM and PC. A total of 58 mutual DEGs were identified, and these DEGs were enriched in the ECM-receptor interaction, focal adhesion and pathways in cancer. Five hub genes (including PLAU, MET, CLU, APOL1 and MMP9) were associated with the overall survival of PC patients. However, the results from the analysis of GSE59953 showed that hyperglycemia or TGF-β1 treatment did not affect the expression level of these hub genes, but the DEGs based on hyperglycemia or TGF-β1 treatment were mostly enriched in the ECM-receptor interaction, focal adhesion and pathways in cancer. Finally, functional enrichment analysis of MMP9 showed that significant genes correlated with MMP9 were associated with the tumorigenicity of cancers, insulin resistance, development of DM and inflammation.

CONCLUSION

In summary, inflammation and immunity-related pathways may play an important role in DM and DPN, while the ECM-receptor interaction, focal adhesion and pathways in cancer pathways may play significant roles in DM and PC. MMP9 may be used as a prognostic marker for PC and may be helpful for the treatment of DM, DPN and PC.

The Dual Role of Surfactant Protein-D in Vascular Inflammation and Development of Cardiovascular Disease

Cardiovascular disease (CVD) is responsible for 31% of all global deaths. Atherosclerosis is the major cause of cardiovascular disease and is a chronic inflammatory disorder in the arteries. Atherosclerosis is characterized by the accumulation of cholesterol, extracellular matrix, and immune cells in the vascular wall. Recently, the collectin surfactant protein-D (SP-D), an important regulator of the pulmonary immune response, was found to be expressed in the vasculature. Several in vitro studies have examined the role of SP-D in the vascular inflammation leading to atherosclerosis. These studies show that SP-D plays a dual role in the development of atherosclerosis. In general, SP-D shows anti-inflammatory properties, and dampens local inflammation in the vessel, as well as systemic inflammation. However, SP-D can also exert a pro-inflammatory role, as it stimulates C-C chemokine receptor 2 inflammatory blood monocytes to secrete tumor necrosis-factor α and increases secretion of interferon-γ from natural killer cells. In vivo studies examining the role of SP-D in the development of atherosclerosis agree that SP-D plays a proatherogenic role, with SP-D knockout mice having smaller atherosclerotic plaque areas, which might be caused by a decreased systemic inflammation. Clinical studies examining the association between SP-D and cardiovascular disease have reported a positive association between circulatory SP-D level, carotid intima-media thickness, and coronary artery calcification. Other studies have found that circulatory SP-D is correlated with increased risk of both total and cardiovascular disease mortality. Both in vitro, in vivo, and clinical studies examining the relationship between SP-D and CVDs will be discussed in this review.

The Natural Cytotoxicity Receptors in Health and Disease

The Natural Cytotoxicity Receptors (NCRs), NKp46, NKp44, and NKp30, were some of the first human activating Natural Killer (NK) cell receptors involved in the non-MHC-restricted recognition of tumor cells to be cloned over 20 years ago. Since this time many host- and pathogen-encoded ligands have been proposed to bind the NCRs and regulate the cytotoxic and cytokine-secreting functions of tissue NK cells. This diverse set of NCR ligands can manifest on the surface of tumor or virus-infected cells or can be secreted extracellularly, suggesting a remarkable NCR polyfunctionality that regulates the activity of NK cells in different tissue compartments during steady state or inflammation. Moreover, the NCRs can also be expressed by other innate and adaptive immune cell subsets under certain tissue conditions potentially conferring NK recognition programs to these cells. Here we review NCR biology in health and disease with particular reference to how this important class of receptors regulates the functions of tissue NK cells as well as confer NK cell recognition patterns to other innate and adaptive lymphocyte subsets. Finally, we highlight how NCR biology is being harnessed for novel therapeutic interventions particularly for enhanced tumor surveillance.

Wound-Healing Markers Revealed by Proximity Extension Assay in Tears of Patients following Glaucoma Surgery

Tears are a constantly available and highly valuable body fluid collectable by non-invasive techniques. Although it can give information on ocular status and be used for follow-ups, tear analysis is challenging due to the low amount of sample that is available. Proximity extension assay (PEA) allows for a sensitive and scalable analysis of multiple proteins in a single run from a one-µL sample, so we applied this technique and examined the amount of 184 proteins in tears collected at different time points after trabeculectomy. The success rate of this surgical intervention highly depends on proper wound healing; therefore, information on the process is indispensable. We observed significantly higher levels of IL-6 and MMP1 at the early time points (day one, two, and four) following trabeculectomy, and the protein amounts went back to the level observed before the surgery three months after the intervention. Patients with or without complications were tested, and proteins that have roles in the immune response and wound healing could be observed with altered frequency and amounts in the cases of patients with complications. Our results highlight the importance of inflammation in wound-healing complications, and at the same time, indicate the utility of PEA in tear analysis.

Genome-wide DNA methylation profiling shows a distinct epigenetic signature associated with lung macrophages in cystic fibrosis

Background

Lung macrophages are major participants in the pulmonary innate immune response. In the cystic fibrosis (CF) lung, the inability of lung macrophages to successfully regulate the exaggerated inflammatory response suggests dysfunctional innate immune cell function. In this study, we aim to gain insight into innate immune cell dysfunction in CF by investigating alterations in DNA methylation in bronchoalveolar lavage (BAL) cells, composed primarily of lung macrophages of CF subjects compared with healthy controls. All analyses were performed using primary alveolar macrophages from human subjects collected via bronchoalveolar lavage. Epigenome-wide DNA methylation was examined via Illumina MethylationEPIC (850 K) array. Targeted next-generation bisulfite sequencing was used to validate selected differentially methylated CpGs. Methylation-based sample classification was performed using the recursively partitioned mixture model (RPMM) and was tested against sample case-control status. Differentially methylated loci were identified by fitting linear models with adjustment of age, sex, estimated cell type proportions, and repeat measurement.

Results

RPMM class membership was significantly associated with the CF disease status (P = 0.026). One hundred nine CpG loci were differentially methylated in CF BAL cells (all FDR ≤ 0.1). The majority of differentially methylated loci in CF were hypo-methylated and found within non-promoter CpG islands as well as in putative enhancer regions and DNase hyper-sensitive regions.

Conclusions

These results support a hypothesis that epigenetic changes, specifically DNA methylation at a multitude of gene loci in lung macrophages, may participate, at least in part, in driving dysfunctional innate immune cells in the CF lung.

Electronic supplementary material

The online version of this article (10.1186/s13148-018-0580-2) contains supplementary material, which is available to authorized users.

A Recombinant Fragment of Human Surfactant Protein D induces Apoptosis in Pancreatic Cancer Cell Lines via Fas-Mediated Pathway

Human surfactant protein D (SP-D) is a potent innate immune molecule, which is emerging as a key molecule in the recognition and clearance of altered and non-self targets. Previous studies have shown that a recombinant fragment of human SP-D (rfhSP-D) induced apoptosis via p53-mediated apoptosis pathway in an eosinophilic leukemic cell line, AML14.3D10. Here, we report the ability of rfhSP-D to induce apoptosis via TNF-α/Fas-mediated pathway regardless of the p53 status in human pancreatic adenocarcinoma using Panc-1 (p53mt), MiaPaCa-2 (p53mt), and Capan-2 (p53wt) cell lines. Treatment of these cell lines with rfhSP-D for 24 h caused growth arrest in G1 cell cycle phase and triggered transcriptional upregulation of pro-apoptotic factors such as TNF-α and NF-κB. Translocation of NF-κB from the cytoplasm into the nucleus of pancreatic cancer cell lines was observed via immunofluorescence microscopy following treatment with rfhSP-D as compared to the untreated cells. The rfhSP-D treatment caused upregulation of pro-apoptotic marker Fas, as analyzed via qPCR and western blot, which then triggered caspase cascade, as evident from cleavage of caspase 8 and 3 analyzed via western blot at 48 h. The cell number following the rfhSP-D treatment was reduced in the order of Panc-1 (~67%) > MiaPaCa-2 (~60%) > Capan-2 (~35%). This study appears to suggest that rfhSP-D can potentially be used to therapeutically target pancreatic cancer cells irrespective of their p53 phenotype.

Circulating Surfactant Protein-D Is Associated With Clinical Outcomes in Peripheral Artery Disease Patients Following Endovascular Therapy

BACKGROUND

Peripheral artery disease (PAD) is a risk factor for the development of cardiovascular disease and death. Surfactant protein-D (SP-D) is a 43-kDa protein secreted from type II pneumocytes in the lungs. Recent studies have demonstrated that circulating SP-D plays a key role in the development of atherosclerosis and is related to clinical outcomes in patients with ischemic heart disease. However, it remains unclear whether circulating SP-D is associated with clinical outcomes in patients with PAD.Methods and Results:We enrolled 364 patients with PAD who underwent endovascular therapy. We measured serum levels of SP-D and Krebs von den Lungen-6 (KL-6). During a median follow-up period of 974 days, there were 69 major adverse cardiovascular and leg events (MACLE), including 48 major adverse cardiovascular events (MACE). Kaplan-Meier analysis demonstrated that patients with high SP-D (≥110 ng/mL) had higher rates of MACE and MACLE than those with low SP-D. Multivariate Cox proportional hazard regression analysis demonstrated that SP-D, but not KL-6, was an independent predictor of MACE and MACLE. The addition of SP-D to known risk factors significantly improved the C index and net reclassification index. The circulating SP-D level was affected by sex, diabetes mellitus, and cilostazol prescription.

CONCLUSIONS

Circulating SP-D was associated with clinical outcomes in patients with PAD, suggesting that it may be a new therapeutic target in these patients.

Surfactant Protein D in Respiratory and Non-Respiratory Diseases

Surfactant protein D (SP-D) is a multimeric collectin that is involved in innate immune defense and expressed in pulmonary, as well as non-pulmonary, epithelia. SP-D exerts antimicrobial effects and dampens inflammation through direct microbial interactions and modulation of host cell responses via a series of cellular receptors. However, low protein concentrations, genetic variation, biochemical modification, and proteolytic breakdown can induce decomposition of multimeric SP-D into low-molecular weight forms, which may induce pro-inflammatory SP-D signaling. Multimeric SP-D can decompose into trimeric SP-D, and this process, and total SP-D levels, are partly determined by variation within the SP-D gene, SFTPD. SP-D has been implicated in the development of respiratory diseases including respiratory distress syndrome, bronchopulmonary dysplasia, allergic asthma, and chronic obstructive pulmonary disease. Disease-induced breakdown or modifications of SP-D facilitate its systemic leakage from the lung, and circulatory SP-D is a promising biomarker for lung injury. Moreover, studies in preclinical animal models have demonstrated that local pulmonary treatment with recombinant SP-D is beneficial in these diseases. In recent years, SP-D has been shown to exert antimicrobial and anti-inflammatory effects in various non-pulmonary organs and to have effects on lipid metabolism and pro-inflammatory effects in vessel walls, which enhance the risk of atherosclerosis. A common SFTPD polymorphism is associated with atherosclerosis and diabetes, and SP-D has been associated with metabolic disorders because of its effects in the endothelium and adipocytes and its obesity-dampening properties. This review summarizes and discusses the reported genetic associations of SP-D with disease and the clinical utility of circulating SP-D for respiratory disease prognosis. Moreover, basic research on the mechanistic links between SP-D and respiratory, cardiovascular, and metabolic diseases is summarized. Perspectives on the development of SP-D therapy are addressed.

Triggering Receptor Expressed on Myeloid Cells-2 Expression Tracks With M2-Like Macrophage Activity and Disease Severity in COPD

BACKGROUND

Cell and animal models show a key role for Triggering Receptor Expressed on Myeloid Cells (TREM)-2 in chronic airway disease after viral infection, but comparable evidence in humans still needs to be established.

METHODS

Lung tissue samples were obtained from lung transplant recipients with Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage IV COPD (n = 16), nontransplantable donor lung tissues (n = 7), and resected lung tissues from patients at risk or with GOLD stage I through IV (n = 55) and were assessed for TREM-2 and TREM-1 messenger RNA (mRNA), protein expression, and other markers of a type 2 immune response.

RESULTS

TREM2 (but not TREM1) mRNA levels were increased in GOLD stage IV COPD lung tissues compared with non-COPD lung tissues. TREM2 mRNA was coexpressed with its signaling molecule DAP12 and the macrophage marker CD68 and M2-macrophage markers CD206 and CHIT1. TREM-2 protein was also increased in COPD lung tissues and was localized to CD14+ macrophages by flow cytometry and CD68+ and CCR2+ macrophages by tissue immunostaining. In lung samples from patients at risk and with GOLD stage I through IV COPD, TREM2 but not TREM1 mRNA levels were also increased, and the ratio of TREM2/TREM1 mRNA levels was associated with increases in CHIT1 mRNA and decreases in FEV1 and FEV1/FVC.

CONCLUSIONS

TREM-2 expression is increased in lung macrophages in COPD, particularly in comparison with TREM-1. Therefore, TREM-2 levels and the ratio of TREM-2/TREM-1 signifies M2 activation in COPD lung tissues and may help to guide therapeutics directed against the type 2 immune response in patients with this disease.

Natural Killer Cells Control Tumor Growth by Sensing a Growth Factor

Many tumors produce platelet-derived growth factor (PDGF)-DD, which promotes cellular proliferation, epithelial-mesenchymal transition, stromal reaction, and angiogenesis through autocrine and paracrine PDGFRβ signaling. By screening a secretome library, we found that the human immunoreceptor NKp44, encoded by NCR2 and expressed on natural killer (NK) cells and innate lymphoid cells, recognizes PDGF-DD. PDGF-DD engagement of NKp44 triggered NK cell secretion of interferon gamma (IFN)-γ and tumor necrosis factor alpha (TNF-α) that induced tumor cell growth arrest. A distinctive transcriptional signature of PDGF-DD-induced cytokines and the downregulation of tumor cell-cycle genes correlated with NCR2 expression and greater survival in glioblastoma. NKp44 expression in mouse NK cells controlled the dissemination of tumors expressing PDGF-DD more effectively than control mice, an effect enhanced by blockade of the inhibitory receptor CD96 or CpG-oligonucleotide treatment. Thus, while cancer cell production of PDGF-DD supports tumor growth and stromal reaction, it concomitantly activates innate immune responses to tumor expansion.

Surfactant protein D regulates caspase-8-mediated cascade of the intrinsic pathway of apoptosis while promoting bleb formation

Surfactant-associated protein D (SP-D) is a soluble innate immune collectin present on many mucosal surfaces. We recently showed that SP-D suppresses the extrinsic pathway of apoptosis by downregulating caspase-8 activation. However, the effects of SP-D on the intrinsic pathway of apoptosis are not clearly understood. In the intrinsic pathway, cytochrome c is released by mitochondria into the cytoplasm. Oxidation of cytochrome c by cytochrome c oxidase activates the apoptosome and caspase-9 cascade. Both caspase-8- and caspase-9-mediated branches are activated in the intrinsic pathway of apoptosis; however, little is known about the relevance of the caspase-8 pathway in this context. Here we studied the effects of SP-D on different branches of the intrinsic pathway of apoptosis using UV-irradiated Jurkat T-cells. We found that SP-D does not inhibit the caspase-9 branch of apoptosis and the relevance of the caspase-8-related branch became apparent when the caspase-9 pathway was inhibited by blocking cytochrome c oxidase. Under these conditions, SP-D reduces the activation of caspase-8, executioner caspase-3 and exposure of phosphatidylserine (PS) on the membranes of dying cells. By contrast, SP-D increases the formation of nuclear and membrane blebs. Inhibition of caspase-8 confirms the effect of SP-D is unique to the caspase-8 pathway. Overall, SP-D suppresses certain aspects of the intrinsic pathway of apoptosis via reduction of caspase-8 activation and PS flipping while at the same time increasing membrane and nuclear bleb formation. This novel regulatory aspect of SP-D could help to regulate intrinsic pathway of apoptosis to promote effective blebbing and breakdown of dying cells.

Micron rhubarb charcoal plus Bletilla striata gelatin protects against gastric mucosal injury in rats

AIM

To investigate whether micron rhubarb charcoal plus Bletilla striata gelatin can protect against gastric mucosal injury by regulating the expression of focal adhesion kinase (FAK), vinculin, and kindlin-2.

METHODS

Eighty SD rats were randomly divided into four groups: control group, model group, micron rhubarb charcoal group, micron rhubarb charcoal plus Bletilla striata gelatin group. After treatment for 14 days, the area of mucosal lesions was detected. Radioimmunoassay was used to detect the contents of prostaglandin E₂ (PGE₂) and gastrin (GAS) in serum, and interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α) in the gastric mucosa. RT-PCR and Western blot were used to detect the mRNA and protein expression of FAK, vinculin and kindlin-2.

RESULTS

Compared with the control group, the injury area in the gastric mucosa was significantly increased (P < 0.01), the content of GAS in serum and the levels of TNF-α and IL-8 in the gastric mucosa (P < 0.01) were significantly increased, the content of PGE₂ in serum and the mRNA and protein expression of FAK, vinculin, and kindlin-2 were significantly decreased in the model group (P < 0.01). Compared with the model group, the area of gastric mucosal lesions was significantly decreased (P < 0.01), the content of GAS in serum and the levels of TNF-α and IL-8 in the gastric mucosa were significantly decreased (P < 0.01), the content of PGE₂ in serum and the mRNA and protein expression of FAK, vinculin, and kindlin-2 were significantly increased in the two treatment groups (P < 0.01). The changes in the above indexes were more significant in the micron rhubarb charcoal plus Bletilla striata gelatin group than in the micron rhubarb charcoal group.

CONCLUSION

Micron rhubarb charcoal plus Bletilla striata gelatin can significantly improve gastric mucosal injury in rats, and the protective effect may be related to un-regulating the expression of FAK, vinculin, and kindlin-2.

Structure, genetics and function of the pulmonary associated surfactant proteins A and D: The extra-pulmonary role of these C type lectins

The collectins family encompasses several collagenous Ca²⁺-dependent defense lectins that are described as pathogen recognition molecules. They play an important role in both adaptive and innate immunity. Surfactant proteins A and D are two of these proteins which were initially discovered in association with surfactant in the pulmonary system. The structure, immune and inflammatory functions, and genetic variations have been well described in relation to their roles, function and pathophysiology in the pulmonary system. Subsequently, these proteins have been discovered in a wide range of other organs and organ systems. The role of these proteins outside the pulmonary system is currently an active area of research. This review intends to provide a current overview of the genetics, structure and extra-pulmonary functions of the surfactant collectin proteins.

Paradigms in chronic obstructive pulmonary disease: phenotypes, immunobiology, and therapy with a focus on vascular disease

Chronic obstructive pulmonary disease (COPD) is a complex and heterogeneous syndrome that represents a major global health burden. COPD phenotypes have recently emerged based on large cohort studies addressing the need to better characterize the syndrome. Though comprehensive phenotyping is still at an early stage, factors such as ethnicity and radiographic, serum, and exhaled breath biomarkers have shown promise. COPD is also an immunological disease where innate and adaptive immune responses to the environment and tobacco smoke are altered. The frequent overlap between COPD and other systemic diseases, such as cardiovascular disease, has influenced COPD therapy, and treatments for both conditions may lead to improved patient outcomes. Here, we discuss current paradigms that center on improving the definition of COPD, understanding the immunological overlap between COPD and vascular inflammation, and the treatment of COPD-with a focus on comorbid cardiovascular disease.

A Comprehensive Review of Immunoreceptor Regulation of Osteoclasts

Osteoclasts require coordinated co-stimulation by several signaling pathways to initiate and regulate their cellular differentiation. Receptor activator for NF-κB ligand (RANKL or TNFSF11), a tumor necrosis factor (TNF) superfamily member, is the master cytokine required for osteoclastogenesis with essential co-stimulatory signals mediated by immunoreceptor tyrosine-based activation motif (ITAM)-signaling adaptors, DNAX-associated protein 12 kDa size (DAP12) and FcεRI gamma chain (FcRγ). The ITAM-signaling adaptors do not have an extracellular ligand-binding domain and, therefore, must pair with ligand-binding immunoreceptors to interact with their extracellular environment. DAP12 pairs with a number of different immunoreceptors including triggering receptor expressed on myeloid cells 2 (TREM2), myeloid DAP12-associated lectin (MDL-1), and sialic acid-binding immunoglobulin-type lectin 15 (Siglec-15); while FcRγ pairs with a different set of receptors including osteoclast-specific activating receptor (OSCAR), paired immunoglobulin receptor A (PIR-A), and Fc receptors. The ligands for many of these receptors in the bone microenvironment remain unknown. Here, we will review immunoreceptors known to pair with either DAP12 or FcRγ that have been shown to regulate osteoclastogenesis. Co-stimulation and the effects of ITAM-signaling have turned out to be complex, and now include paradoxical findings that ITAM-signaling adaptor-associated receptors can inhibit osteoclastogenesis and immunoreceptor tyrosine-based inhibitory motif (ITIM) receptors can promote osteoclastogenesis. Thus, co-stimulation of osteoclastogenesis continues to reveal additional complexities that are important in the regulatory mechanisms that seek to maintain bone homeostasis.

Calibrated kallikrein generation in human plasma

OBJECTIVES

The physiological role of the contact system remains inconclusive. No obvious clinical complications have been observed for factor XII (FXII), prekallikrein (PK), or high molecular weight kininogen deficiencies even though the contact system in vitro is associated with coagulation, fibrinolysis, and inflammation. A global generation assay measuring the initial phase of the contact system could be a valuable tool for studies of its physiological role.

DESIGN AND METHODS

We investigated whether such a method could be developed using the principle of the Calibrated Automated Thrombin generation method as a template.

RESULTS

A suitable kallikrein specific fluorogenic substrate was identified (K_M=0.91mM, k_cat=19s^-1), and kallikrein generation could be measured in undiluted plasma when silica was added as activator. Disturbing effects, including substrate depletion and the inner-filter effect, however, affected the signal. These problems were corrected for by external calibration with α₂-macroglobulin-kallikrein complexes. Selectivity studies of the substrate, experiments with FXII and PK depleted plasmas, and plasma with high or low complement C1-esterase inhibitor activity indicated that the obtained and calibrated signal predominantly was related to FXII-dependent kallikrein activity.

CONCLUSIONS

The findings described show that establishment of a kallikrein generation method is possible. Potentially, this setup could be used for clinical studies of the contact system.

Collagen binding to OSCAR: the odd couple

In this issue of Blood, Zhou et al reported the high-resolution structure of the collagen-activated osteoclast-associated receptor (OSCAR) bound to a collagen model peptide. Together with binding studies, the results confirm a novel recognition mechanism for collagen by immunoglobulin-like motifs.

Surveillance of cell and tissue perturbation by receptors in the LRC

The human leukocyte receptor complex (LRC) encompasses several sets of genes with a common evolutionary origin and which form a branch of the immunoglobulin superfamily (IgSF). Comparisons of LRC genes both within and between species calls for a high degree of plasticity. The drive for this unprecedented level of variation is not known, but it relates in part to interaction of several LRC products with polymorphic human leukocyte antigen (HLA) class I molecules. However, the range of other proposed ligands for LRC products indicates a dynamic set of receptors that have adapted to detect target molecules relating to numerous cellular pathways. Several receptors in the complex bind a molecular signature in collagenous ligands. Others detect a variety of motifs relating to pathogens in addition to cellular stress, attesting to the opportunistic versatility of LRC receptors.

Genetic Variants in IL6R and ADAM19 are Associated with COPD Severity in a Mexican Mestizo Population

Chronic obstructive pulmonary disease (COPD) is a complex and multifactorial disease with a strong genetic component. Our objective is to identify the genetic variants associated with COPD risk and its severity in Mexican Mestizo population. We evaluated 1285 single-nucleotide polymorphisms (SNPs) of candidate genes in 299 smokers with COPD (COPD-S) and 531 smokers without COPD (SWOC) using an Illumina GoldenGate genotyping microarray. In addition, 251 ancestry informative markers were included. Allele A of rs2545771 in CYP2F2P is associated with a lower risk of COPD (p = 4.02E-10, odds ratio [OR] = 0.104, confidence interval [CI] 95% 0.05-0.18). When the COPD group was stratified by severity according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD; levels III + IV vs. I + II), 3 SNPs (rs4329505 and rs4845626 in interleukin 6 receptor [IL6R] and rs1422794 in a disintegrin and metalloproteinase domain 19 [ADAM19]) were associated with a lower risk of suffering the most severe stages of the disease. rs2819096 in the surfactant protein D (SFTPD) gene was associated with a higher risk of COPD GOLD III + IV (p = 7.79E-03, OR = 1.80, CI 95% 1.16-2.79). Finally, the haplotype in IL6R was associated with a lower risk of suffering from more severe COPD, whereas the haplotype in ADAM19 was associated with a higher risk (p = 7.40E-03, OR = 2.83, CI 95% 1.20-6.86) of suffering from the severe stages of the disease. Our data suggest that there are alleles and haplotypes in the IL6R, ADAM19, and SFTPD genes associated with different severity stages of COPD; in CYP2F2P, rs25455771 is associated with a lower risk of COPD.

OSCAR-collagen signaling in monocytes plays a proinflammatory role and may contribute to the pathogenesis of rheumatoid arthritis

Osteoclast-associated receptor (OSCAR) is an activating receptor expressed by human myeloid cells. Collagen type I (ColI) and collagen type II (ColII) serve as ligands for OSCAR. OSCAR-collagen interaction stimulates RANK-dependent osteoclastogenesis. We have recently reported that OSCAR promotes functional maturation of monocyte-derived dendritic cells. OSCAR is upregulated on monocytes from rheumatoid arthritis (RA) patients with active disease, and these monocytes show an increased proosteoclastogenic potential. In the current study, we have addressed a functional role for an OSCAR-collagen interaction on monocytes. We show that OSCAR-ColII signaling promoted the survival of monocytes. Moreover, ColII stimulated the release of proinflammatory cytokines by monocytes from healthy donors, which could be completely blocked by an anti-OSCAR monoclonal antibody. Mononuclear cells from the synovial fluid of RA patients plated on ColII secreted TNF-α and IL-8 in an OSCAR-dependent manner. Global RNA profiling showed that components of multiple signaling pathways relevant to RA pathogenesis are regulated at the transcriptional level by OSCAR in monocytes. Thus, OSCAR can play a proinflammatory role in monocyte-derived cells and may contribute crucially on multiple levels to RA pathogenesis.

The integrin-collagen connection--a glue for tissue repair?

The α1β1, α2β1, α10β1 and α11β1 integrins constitute a subset of the integrin family with affinity for GFOGER-like sequences in collagens. Integrins α1β1 and α2β1 were originally identified on a subset of activated T-cells, and have since been found to be expressed on a number of cell types including platelets (α2β1), vascular cells (α1β1, α2β1), epithelial cells (α1β1, α2β1) and fibroblasts (α1β1, α2β1). Integrin α10β1 shows a distribution that is restricted to mesenchymal stem cells and chondrocytes, whereas integrin α11β1 appears restricted to mesenchymal stem cells and subsets of fibroblasts. The bulk of the current literature suggests that collagen-binding integrins only have a limited role in adult connective tissue homeostasis, partly due to a limited availability of cell-binding sites in the mature fibrillar collagen matrices. However, some recent data suggest that, instead, they are more crucial for dynamic connective tissue remodeling events--such as wound healing--where they might act specifically to remodel and restore the tissue architecture. This Commentary discusses the recent development in the field of collagen-binding integrins, their roles in physiological and pathological settings with special emphasis on wound healing, fibrosis and tumor-stroma interactions, and include a discussion of the most recently identified newcomers to this subfamily--integrins α10β1 and α11β1.

The role of serum surfactant protein D as a biomarker of exacerbation of chronic obstructive pulmonary disease

BACKGROUND

The exacerbation of chronic obstructive pulmonary disease (COPD) is a major factor for the high mortality associated with the disease. There is a paucity in the lung-specific biomarkers which diagnose these exacerbations. Surfactant protein D (SP-D) is a promising biomarker in predicting clinical outcomes for patients with COPD, is lung-specific and can be detected in serum. However, the profile in which serum concentrations of SP-D change during acute exacerbation is still unclear. This study aims to estimate and compare the concentrations of serum SP-D in patients with stable disease and during the exacerbation.

METHODS

A cross-sectional study was conducted which composed of apparently healthy individuals (n = 28), which included 14 smokers and 14 nonsmokers, patients with stable COPD (n = 28), and patients experiencing acute exacerbations (n = 28). Pulmonary functions were performed for all groups. Serum SP-D concentrations were measured using enzyme-linked immunosorbent assay (ELISA). These concentrations were compared by analysis of variance.

RESULTS

Serum SP-D levels were significantly elevated in patients with acute exacerbations (508.733 ± 102.813 ng/ml) compared to patients with stable COPD (337.916 ± 86.265 ng/ml) and healthy subjects (177.313 ± 46.998 ng/ml; p <  0.001). Serum SP-D levels correlated inversely with lung function parameters including FEV1%pred, FVC%pred and FEV1/FVC.

CONCLUSION

Serum SP-D levels are raised early on during acute exacerbations of COPD, which could be a potential early diagnostic biomarker for COPD exacerbations.

Structural basis of collagen recognition by human osteoclast-associated receptor and design of osteoclastogenesis inhibitors

Human osteoclast-associated receptor (OSCAR) is an immunoglobulin (Ig)-like collagen receptor that is up-regulated on osteoclasts during osteoclastogenesis and is expressed in a range of myeloid cells. As a member of the leukocyte receptor complex family of proteins, OSCAR shares a high degree of sequence and structural homology with other collagen receptors of this family, including glycoprotein VI, leukocyte-associated Ig-like receptor-1, and leukocyte Ig-like receptor B4, but recognizes a unique collagen sequence. Here, we present the crystal structures of OSCAR in its free form and in complex with a triple-helical collagen-like peptide (CLP). These structures reveal that the CLP peptide binds only one of the two Ig-like domains, the membrane-proximal domain (domain 2) of OSCAR, with the middle and trailing chain burying a total of 661 Å(2) of solvent-accessible collagen surface. This binding mode is facilitated by the unusual topography of the OSCAR protein, which displays an obtuse interdomain angle and a rotation of domain 2 relative to the membrane-distal domain 1. Moreover, the binding of the CLP to OSCAR appears to be mediated largely by tyrosine residues and conformational changes at a shallow Phe pocket. Furthermore, we investigated CLP peptides as inhibitors of osteoclastogenesis and found that a peptide length of 40 amino acids is required to ensure adequate inhibition of osteoclastogenesis in vitro. These findings provide valuable structural insights into the mode of collagen recognition by OSCAR and into the use of synthetic peptide matrikines for osteoclastogenesis inhibition.

Structural basis for collagen recognition by the immune receptor OSCAR

The osteoclast-associated receptor (OSCAR) is a collagen-binding immune receptor with important roles in dendritic cell maturation and activation of inflammatory monocytes as well as in osteoclastogenesis. The crystal structure of the OSCAR ectodomain is presented, both free and in complex with a consensus triple-helical peptide (THP). The structures revealed a collagen-binding site in each immunoglobulin-like domain (D1 and D2). The THP binds near a predicted collagen-binding groove in D1, but a more extensive interaction with D2 is facilitated by the unusually wide D1-D2 interdomain angle in OSCAR. Direct binding assays, combined with site-directed mutagenesis, confirm that the primary collagen-binding site in OSCAR resides in D2, in marked contrast to the related collagen receptors, glycoprotein VI (GPVI) and leukocyte-associated immunoglobulin-like receptor-1 (LAIR-1). Monomeric OSCAR D1D2 binds to the consensus THP with a KD of 28 µM measured in solution, but shows a higher affinity (KD 1.5 μM) when binding to a solid-phase THP, most likely due to an avidity effect. These data suggest a 2-stage model for the interaction of OSCAR with a collagen fibril, with transient, low-affinity interactions initiated by the membrane-distal D1, followed by firm adhesion to the primary binding site in D2.

TARM1 Is a Novel Leukocyte Receptor Complex-Encoded ITAM Receptor That Costimulates Proinflammatory Cytokine Secretion by Macrophages and Neutrophils

We identified a novel, evolutionarily conserved receptor encoded within the human leukocyte receptor complex and syntenic region of mouse chromosome 7, named T cell-interacting, activating receptor on myeloid cells-1 (TARM1). The transmembrane region of TARM1 contained a conserved arginine residue, consistent with association with a signaling adaptor. TARM1 associated with the ITAM adaptor FcRγ but not with DAP10 or DAP12. In healthy mice, TARM1 is constitutively expressed on the cell surface of mature and immature CD11b(+)Gr-1(+) neutrophils within the bone marrow. Following i.p. LPS treatment or systemic bacterial challenge, TARM1 expression was upregulated by neutrophils and inflammatory monocytes and TARM1(+) cells were rapidly recruited to sites of inflammation. TARM1 expression was also upregulated by bone marrow-derived macrophages and dendritic cells following stimulation with TLR agonists in vitro. Ligation of TARM1 receptor in the presence of TLR ligands, such as LPS, enhanced the secretion of proinflammatory cytokines by macrophages and primary mouse neutrophils, whereas TARM1 stimulation alone had no effect. Finally, an immobilized TARM1-Fc fusion protein suppressed CD4(+) T cell activation and proliferation in vitro. These results suggest that a putative T cell ligand can interact with TARM1 receptor, resulting in bidirectional signaling and raising the T cell activation threshold while costimulating the release of proinflammatory cytokines by macrophages and neutrophils.