Association of eotaxin-2 gene polymorphisms with plasma eotaxin-2 concentration

Regulation of the Oligomeric Status of CCR3 with Binding Ligands Revealed by Single-Molecule Fluorescence Imaging

The relationship between the oligomeric status and functions of chemokine receptor CCR3 is still controversial. We use total internal reflection fluorescence microscopy at the single-molecule level to visualize the oligomeric status of CCR3 and its regulation of the membrane of stably transfected T-REx-293 cells. We find that the population of the dimers and oligomers of CCR3 can be modulated by the binding of ligands. Natural agonists can induce an increase in the level of dimers and oligomers at high concentrations, whereas antagonists do not have a significant influence on the oligomeric status. Moreover, monomeric CCR3 exhibits a stronger chemotactic response in the migration assay of stably transfected CCR3 cells. Together, these data support the notion that CCR3 exists as a mixture of monomers and dimers under nearly physiological conditions and the monomeric CCR3 receptor is the minimal functional unit in cellular signaling transduction. To the best of our knowledge, these results constitute the first report of the oligomeric status of CCR3 and its regulation.

Immune-related gene polymorphisms in pulmonary diseases

Between the DNA sequences of two randomly-selected human genomes, which consist of over 3 billion base pairs and twenty five thousand genes, there exists only 0.1% variation and 99.9% sequence identity. During the last couple of decades, extensive genome-wide studies have investigated the association between single-nucleotide polymorphisms (SNPs), the most common DNA variations, and susceptibility to various diseases. Because the immune system's primary function is to defend against myriad infectious agents and diseases, the large number of people who escape serious infectious diseases underscores the tremendous success of this system at this task. In fact, out of the third of the global human population infected with Mycobacterium tuberculosis during their lifetime, only a few people develop active disease, and a heavy chain smoker may inexplicably escape all symptoms of chronic obstructive pulmonary disease (COPD), lung cancer, and other smoke-associated lung diseases. This may be attributable to the genetic makeup of the individual(s), including their SNPs, which provide some resistance to the disease. Pattern recognition receptors (PRRs), transcription factors, cytokines and chemokines all play critical roles in orchestrating immune responses and their expression/activation is directly linked to human disease tolerance. Moreover, genetic variations present in the immune-response genes of various ethnicities may explain the huge differences in individual outcomes to various diseases and following exposure to infectious agents. The current review focuses on recent advances in our understanding of pulmonary diseases and the relationship of genetic variations in immune response genes to these conditions.

Association between inflammatory biomarkers in plasma, radiological severity, and duration of exposure in patients with silicosis

OBJECTIVE

To evaluate the plasma levels of CCL2, CCL3, CCL11, CCL24, tumor necrosis factor alpha, sTNFR1, and sTNFR2 in subjects exposed to silica (SES) with and without silicosis compared with unexposed reference control group, and their associations with the radiological severity and duration of exposure to silica.

METHODS

Fifty-seven SES; 36 with silicosis and 22 subjects in control group, were included in the study.

RESULTS

CCL3, CCL24, sTNFR1, and sTNFR2 were increased in SES and in SES with silicosis than in controls. There were no differences in the levels of CCL2, CCL11, or tumor necrosis factor alpha. The sTNFR2 level was greater in SES with silicosis than in SES without silicosis. There was a positive correlation between sTNFR1 and sTNFR2 and the radiological severity and time of exposure to silica. sTNFR2 was associated with all categories of radiological severity.

CONCLUSION

sTNFR2 is associated with silicosis severity and early exposure to silica.

Activation states of blood eosinophils in asthma

Asthma is characterized by airway inflammation rich in eosinophils. Airway eosinophilia is associated with exacerbations and has been suggested to play a role in airway remodelling. Recruitment of eosinophils from the circulation requires that blood eosinophils become activated, leading to their arrest on the endothelium and extravasation. Circulating eosinophils can be envisioned as potentially being in different activation states, including non-activated, pre-activated or 'primed', or fully activated. In addition, the circulation can potentially be deficient of pre-activated or activated eosinophils, because such cells have marginated on activated endothelium or extravasated into the tissue. A number of eosinophil surface proteins, including CD69, L-selectin, intercellular adhesion molecule-1 (ICAM-1, CD54), CD44, P-selectin glycoprotein ligand-1 (PSGL-1, CD162), cytokine receptors, Fc receptors, integrins including αM integrin (CD11b), and activated conformations of Fc receptors and integrins, have been proposed to report cell activation. Variation in eosinophil activation states may be associated with asthma activity. Eosinophil surface proteins proposed to be activation markers, with a particular focus on integrins, and evidence for associations between activation states of blood eosinophils and features of asthma are reviewed here. Partial activation of β1 and β2 integrins on blood eosinophils, reported by monoclonal antibodies (mAbs) N29 and KIM-127, is associated with impaired pulmonary function and airway eosinophilia, respectively, in non-severe asthma. The association with lung function does not occur in severe asthma, presumably due to greater eosinophil extravasation, specifically of activated or pre-activated cells, in severe disease.

Genetic polymorphisms and associated susceptibility to asthma

As complex common diseases, asthma and allergic diseases are caused by the interaction of multiple genetic variants with a variety of environmental factors. Candidate-gene studies have examined the involvement of a very large list of genes in asthma and allergy, demonstrating a role for more than 100 loci. These studies have elucidated several themes in the biology and pathogenesis of these diseases. A small number of genes have been associated with asthma or allergy through traditional linkage analyses. The publication of the first asthma-focused genome-wide association (GWA) study in 2007 has been followed by nearly 30 reports of GWA studies targeting asthma, allergy, or associated phenotypes and quantitative traits. GWA studies have confirmed several candidate genes and have identified new, unsuspected, and occasionally uncharacterized genes as asthma susceptibility loci. Issues of results replication persist, complicating interpretation and making conclusions difficult to draw, and much of the heritability of these diseases remains undiscovered. In the coming years studies of complex diseases like asthma and allergy will probably involve the use of high-throughput next-generation sequencing, which will bring a tremendous influx of new information as well as new problems in dealing with vast datasets.

Genome wide association identifies PPFIA1 as a candidate gene for acute lung injury risk following major trauma

Acute Lung Injury (ALI) is a syndrome with high associated mortality characterized by severe hypoxemia and pulmonary infiltrates in patients with critical illness. We conducted the first investigation to use the genome wide association (GWA) approach to identify putative risk variants for ALI. Genome wide genotyping was performed using the Illumina Human Quad 610 BeadChip. We performed a two-stage GWA study followed by a third stage of functional characterization. In the discovery phase (Phase 1), we compared 600 European American trauma-associated ALI cases with 2266 European American population-based controls. We carried forward the top 1% of single nucleotide polymorphisms (SNPs) at p<0.01 to a replication phase (Phase 2) comprised of a nested case-control design sample of 212 trauma-associated ALI cases and 283 at-risk trauma non-ALI controls from ongoing cohort studies. SNPs that replicated at the 0.05 level in Phase 2 were subject to functional validation (Phase 3) using expression quantitative trait loci (eQTL) analyses in stimulated B-lymphoblastoid cell lines (B-LCL) in family trios. 159 SNPs from the discovery phase replicated in Phase 2, including loci with prior evidence for a role in ALI pathogenesis. Functional evaluation of these replicated SNPs revealed rs471931 on 11q13.3 to exert a cis-regulatory effect on mRNA expression in the PPFIA1 gene (p = 0.0021). PPFIA1 encodes liprin alpha, a protein involved in cell adhesion, integrin expression, and cell-matrix interactions. This study supports the feasibility of future multi-center GWA investigations of ALI risk, and identifies PPFIA1 as a potential functional candidate ALI risk gene for future research.

Unraveling the complex genetic underpinnings of asthma and allergic disorders

PURPOSE OF REVIEW

Asthma and other allergic diseases are complex genetic disorders that result from interactions between multiple genes and environmental factors. In this review, we summarize findings from candidate gene analyses, discuss the recent success of genome-wide association (GWA) studies, and outline challenges facing the field.

RECENT FINDINGS

In the past year, five GWA studies have been reported for asthma, one for atopic dermatitis, and four for intermediate phenotypes using quantitative trait loci. These results have in general been more robust to replication than prior candidate gene studies, and have allowed the identification of novel loci for both asthma (i.e. 1q31, 9q21.31) and atopic dermatitis (11q13).

SUMMARY

The integration of results from recent GWA studies with careful analyses of candidate gene associations studies has confirmed the importance of immune detection and TH2-cell mediated immune responses in the pathogenesis of allergic disease, and has raised new interest in the role of epithelial barrier function and tissue-level responses. GWA studies appear to provide a robust way to identify novel gene loci contributing to disease susceptibility. Dissecting gene-gene and gene-environment interactions, and exploring the contribution of epigenetic phenomena to allergic disease susceptibility remain important challenges to understanding the complex nature of asthma and other allergic diseases.

Genetic interactions model among Eotaxin gene polymorphisms in asthma

Eotaxin family (Eotaxin 1,2 and 3) recruits and activates CCR3-bearing cells such as eosinophil, mast cells, and Th2 lymphocytes that play a major role in allergic disorders. We examined the polygenetic effects of the Eotaxin gene family in a Korean population. Gene-gene interactions were tested using a multistep approach with multifactor dimensionality reduction (MDR) method between asthmatics and normal controls. The overall best MDR model of the main effect single nucleotide polymorphisms (SNPs) included EOT2 + 1272A > G and EOT3 + 77C > T (model 1) [testing accuracy 0.597, cross-validation consistency (CVC) 10/10, P < 0.001]. The overall best MDR model of the SNPs with no main effects included EOT2 + 304C > A, EOT3 + 716A > G, and EOT3 + 1579G > A (model 2) (testing accuracy 0.616, CVC 10/10, P < 0.001). Model 3 was obtained by including the MDR variables for models 1 and 2. This new composite model predicted asthma with better accuracy than either model 1 or model 2 (testing accuracy 0.643, CVC 10/10, P < 0.001). The detection of statistical interaction models is one evidence of gene-gene interactions among Eotaxin genes, and this interaction is thought to influence the development of asthma. Although the models are limited to determining statistical interactions within a population, they may be useful for identifying groups at high risk of developing asthma.

The chemokine network. II. On how polymorphisms and alternative splicing increase the number of molecular species and configure intricate patterns of disease susceptibility

In this second review on chemokines, we focus on the polymorphisms and alternative splicings and on their consequences in disease. Because chemokines are key mediators in the pathogenesis of inflammatory, autoimmune, vascular and neoplastic disorders, a large number of studies attempting to relate particular polymorphisms of chemokines to given diseases have already been conducted, sometimes with contradictory results. Reviewing the published data, it becomes evident that some chemokine genes that are polymorphic have alleles that are found repeatedly, associated with disease of different aetiologies but sharing some aspects of pathogenesis. Among CXC chemokines, single nucleotide polymorphisms (SNPs) in the CXCL8 and CXCL12 genes stand out, as they have alleles associated with many diseases such as asthma and human immunodeficiency virus (HIV), respectively. Of CC chemokines, the stronger associations occur among alleles from SNPs in CCL2 and CCL5 genes and a number of inflammatory conditions. To understand how chemokines contribute to disease it is also necessary to take into account all the isoforms resulting from differential splicing. The first part of this review deals with polymorphisms and the second with the diversity of molecular species derived from each chemokine gene due to alternative splicing phenomena. The number of molecular species and the level of expression of each of them for every chemokine and for each functionally related group of chemokines reaches a complexity that requires new modelling algorithms akin to those proposed in systems biology approaches.

Effect and mechanism of lipopolysaccharide on allergen-induced interleukin-5 and eotaxins production by whole blood cultures of atopic asthmatics

Interleukin (IL)-5 and eotaxin families regulate the development of eosinophilic inflammation of asthma in a co-operative manner. The exposure to airborne lipopolysaccharide (LPS) induces varying degrees of airflow obstruction and neutrophilic airway inflammation. Production of IL-5 and eotaxin subfamily chemokines was analysed in response to Dermatophagoides pteronyssinus allergen (D.p.) according to the presence of specific IgE to D.p., and investigated the mechanism underlying their LPS-mediated regulation of these cytokines in response to the specific allergen. Peripheral blood cells (PBCs) from asthmatics with (group 1) or without (group 2) specific IgE to D.p. and from non-asthmatics with (group 3) or without (group 4) were stimulated with D.p. or LPS. For LPS-mediated inhibition of IL-5 and eotaxin-2 production, LPS-induced cytokines were added to the D.p.-stimulated PBCs. IL-5 and eotaxin-2, but not eotaxin-1 and 3, were significantly increased by D.p.-stimulated-PBCs from group 1, while only eotaxin-2 was elevated in group 3. Eotaxin-2 production was found in monocytes and correlated with the level of specific IgE to D.p. LPS treatment resulted in the decrease in eotaxin-2 and IL-5 production by the D.p.-stimulated PBCs. LPS-induced IL-10 completely inhibited D.p.-stimulated production of eotaxin-2 and IL-5. The differential responses of the eotaxin family to specific antigens suggest that the predominant role of eotaxin-2 and LPS may attenuate eosinophilic inflammation by inhibiting IL-5 and eotaxin-2 synthesis through IL-10 production.