Association between genetic variations in prostaglandin E2 receptor subtype EP3 gene (Ptger3) and asthma in the Korean population

Polymorphisms rs2745557 in PTGS2 and rs2075797 in PTGER2 are associated with the risk of chronic obstructive pulmonary disease development in a Tunisian cohort

We hypothesized that polymorphisms of genes involved in the prostaglandin pathway could be associated with COPD. In this study we explored the involvement of genetic polymorphisms in PTGS2, PTGER2 and PTGER4 genes in the development and severity of COPD and their effects on plasma concentrations of inflammatory/oxidative stress markers. We identified genotypes of PTGS2, PTGER2 and PTGER4 SNPs in a Tunisian cohort including COPD patients (n = 138) and control subjects (n = 216) using PCR-RFLP and PCR TaqMan. Pulmonary function (FEV1 and FVC) were assessed by plethsmography. PGE₂, PGD₂ and cytokine plasma (IL-6, IL-18, TNF-α, TGF-β) concentrations were measured using ELISA and colorimetric standard methods were used to determine oxidative stress concentrations. Genotype frequencies of rs2745557 in PTGS2 and rs2075797 in PTGER2 were different between COPD cases and controls. There was no correlation between these polymorphisms and lung function parameters. For rs2745557, the A allele frequency was higher in COPD cases than in controls. For rs2075797, carriers of the GG genotype were more frequent in the COPD group than in controls. Only rs2745557 in PTGS2 had an effect on PGD₂ and cytokine plasma concentrations. PGD₂ was significantly decreased in COPD patients with the GA or AA genotypes. In contrast, IL-18 and NO plasma concentrations were increased in COPD rs2745557 A allele carriers as compared to homozygous GG subjects. Our findings suggest that rs2745557 in PTGS2 and rs2075797 in PTGER2 are associated with COPD development but not with its severity.

International Union of Basic and Clinical Pharmacology. CIX. Differences and Similarities between Human and Rodent Prostaglandin E2 Receptors (EP1-4) and Prostacyclin Receptor (IP): Specific Roles in Pathophysiologic Conditions

Prostaglandins are derived from arachidonic acid metabolism through cyclooxygenase activities. Among prostaglandins (PGs), prostacyclin (PGI2) and PGE2 are strongly involved in the regulation of homeostasis and main physiologic functions. In addition, the synthesis of these two prostaglandins is significantly increased during inflammation. PGI2 and PGE2 exert their biologic actions by binding to their respective receptors, namely prostacyclin receptor (IP) and prostaglandin E2 receptor (EP) 1-4, which belong to the family of G-protein-coupled receptors. IP and EP1-4 receptors are widely distributed in the body and thus play various physiologic and pathophysiologic roles. In this review, we discuss the recent advances in studies using pharmacological approaches, genetically modified animals, and genome-wide association studies regarding the roles of IP and EP1-4 receptors in the immune, cardiovascular, nervous, gastrointestinal, respiratory, genitourinary, and musculoskeletal systems. In particular, we highlight similarities and differences between human and rodents in terms of the specific roles of IP and EP1-4 receptors and their downstream signaling pathways, functions, and activities for each biologic system. We also highlight the potential novel therapeutic benefit of targeting IP and EP1-4 receptors in several diseases based on the scientific advances, animal models, and human studies. SIGNIFICANCE STATEMENT: In this review, we present an update of the pathophysiologic role of the prostacyclin receptor, prostaglandin E2 receptor (EP) 1, EP2, EP3, and EP4 receptors when activated by the two main prostaglandins, namely prostacyclin and prostaglandin E2, produced during inflammatory conditions in human and rodents. In addition, this comparison of the published results in each tissue and/or pathology should facilitate the choice of the most appropriate model for the future studies.

Pharmacogenomics of Prostaglandin and Leukotriene Receptors

Individual genetic background together with environmental effects are thought to be behind many human complex diseases. A number of genetic variants, mainly single nucleotide polymorphisms (SNPs), have been shown to be associated with various pathological and inflammatory conditions, representing potential therapeutic targets. Prostaglandins (PTGs) and leukotrienes (LTs) are eicosanoids derived from arachidonic acid and related polyunsaturated fatty acids that participate in both normal homeostasis and inflammatory conditions. These bioactive lipid mediators are synthesized through two major multistep enzymatic pathways: PTGs by cyclooxygenase and LTs by 5-lipoxygenase. The main physiological effects of PTGs include vasodilation and vascular leakage (PTGE2); mast cell maturation, eosinophil recruitment, and allergic responses (PTGD2); vascular and respiratory smooth muscle contraction (PTGF2), and inhibition of platelet aggregation (PTGI2). LTB4 is mainly involved in neutrophil recruitment, vascular leakage, and epithelial barrier function, whereas cysteinyl LTs (CysLTs) (LTC4, LTD4, and LTE4) induce bronchoconstriction and neutrophil extravasation, and also participate in vascular leakage. PTGs and LTs exert their biological functions by binding to cognate receptors, which belong to the seven transmembrane, G protein-coupled receptor superfamily. SNPs in genes encoding these receptors may influence their functionality and have a role in disease susceptibility and drug treatment response. In this review we summarize SNPs in PTGs and LTs receptors and their relevance in human diseases. We also provide information on gene expression. Finally, we speculate on future directions for this topic.

Myeloid-derived suppressor cell function is diminished in aspirin-triggered allergic airway hyperresponsiveness in mice

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) have recently been implicated in the pathogenesis of asthma, but their regulation in patients with aspirin-intolerant asthma (AIA) remains unclear.

OBJECTIVE

We sought to characterize MDSC accumulation and pathogenic functions in allergic airway inflammation mediated by COX-1 deficiency or aspirin treatment in mice.

METHODS

Allergic airway inflammation was induced in mice by means of ovalbumin challenge. The distribution and function of MDSCs in mice were analyzed by using flow cytometry and pharmacologic/gene manipulation approaches.

RESULTS

CD11b(+)Gr1(high)Ly6G(+)Ly6C(int) MDSCs (polymorphonuclear MDSCs [PMN-MDSCs]) recruited to the lungs are negatively correlated with airway inflammation in allergen-challenged mice. Aspirin-treated and COX-1 knockout (KO) mice showed significantly lower accumulation of PMN-MDSCs in the inflamed lung and immune organs accompanied by increased TH2 airway responses. The TH2-suppressive function of PMN-MDSCs was notably impaired by COX-1 deletion or inhibition, predominantly through downregulation of arginase-1. COX-1-derived prostaglandin E2 promoted PMN-MDSC generation in bone marrow through E prostanoid 2 and 4 receptors (EP2 and EP4), whereas the impaired arginase-1 expression in PMN-MDSCs in COX-1 KO mice was mediated by dysregulation of the prostaglandin E2/EP4/cyclic AMP/protein kinase A pathway. EP4 agonist administration alleviated allergy-induced airway hyperresponsiveness in COX-1 KO mice. Moreover, the immunosuppressive function of PMN-MDSCs from patients with AIA was dramatically decreased compared with that from patients with aspirin-tolerant asthma.

CONCLUSION

The immunosuppressive activity of PMN-MDSCs was diminished in both allergen-challenged COX-1 KO mice and patients with AIA, probably through an EP4-mediated signaling pathway, indicating that activation of PMN-MDSCs might be a promising therapeutic strategy for asthma, particularly AIA.

A polymorphism in the histone deacetylase 1 gene is associated with the response to corticosteroids in asthmatics

BACKGROUND/AIMS

Recent investigations suggest that histone deacetylase 1 (HDAC1) and HDAC2 may be target molecules to predict therapeutic responses to corticosteroids. We evaluated the effects of variation in HDAC1 and HDAC2 on the response to corticosteroids in asthmatics.

METHODS

Two single nucleotide polymorphisms (SNPs) were selected after resequencing HDAC1 and HDAC2. For the first analysis, we evaluated the association between those SNPs and asthma severity in 477 asthmatics. For the second analysis, we evaluated the effects of these SNPs on lung function improvements in response to corticosteroid treatment in 35 independent adult asthmatics and 70 childhood asthmatics.

RESULTS

We found that one SNP in HDAC1 (rs1741981) was significantly related to asthma severity in a recessive model (corrected p = 0.036). Adult asthmatics who were homozygous for the minor allele of rs1741981 showed significantly lower % forced expiratory volume in 1 second (%FEV1) increases in response to systemic corticosteroids treatment compared with the heterozygotes or those homozygous for the major allele (12.7% ± 7.2% vs. 37.4% ± 33.7%, p = 0.018). Similarly, childhood asthmatics who were homozygous for the minor allele of rs1741981 showed significantly lower %FEV1 increases in response to inhaled corticosteroid treatment compared with the heterozygotes or those homozygous for the major allele (14.1% ± 5.9% vs. 19.4% ± 8.9%, p = 0.035).

CONCLUSIONS

The present study demonstrated that rs1741981 in HDAC1 was significantly associated with the response to corticosteroid treatment in asthmatics.

Genetic variants of the arachidonic acid pathway in non-steroidal anti-inflammatory drug-induced acute urticaria

BACKGROUND

To date, genetic studies of hypersensitivity reactions to non-steroidal anti-inflammatory drugs (NSAIDs) have been carried out mainly in aspirin-induced asthma and to a lesser extent in chronic urticaria, with no studies in patients with acute urticaria (AU), the most common entity induced by these drugs.

OBJECTIVE

In this work, we analysed the association of common variants of 15 relevant genes encoding both enzymes and receptors from the arachidonic acid (AA) pathway with NSAID-induced AU.

METHODS

Patients were recruited in several Allergy Services that are integrated into the Spanish network RIRAAF, and diagnosed of AU induced by cross-intolerance (CRI) to NSAIDs. Genotyping was carried out by TaqMan allelic discrimination assays.

RESULTS

A total of 486 patients with AU induced by CRI to NSAIDs and 536 unrelated controls were included in this large Spanish case-control study. Seven variants from 31 tested in six genes were associated in a discovery study population from Malaga (0.0003 ≤ p-value ≤ 0.041). A follow-up analysis in an independent sample from Madrid replicated three of the SNPs from the ALOX15 (rs7220870), PTGDR (rs8004654) and CYSLTR1 (rs320095) genes (1.055x10(-6) ≤meta-analysis p-value ≤ 0.003).

CONCLUSIONS AND CLINICAL RELEVANCE

Genetic variants of the AA pathway may play an important role in NSAID-induced AU. These data may help understand the mechanism underlying this disease.

Genetic variability of prostaglandin E2 receptor subtype EP4 gene in aspirin-intolerant chronic urticaria

Prostaglandin E2 receptor subtype EP4 (PTGER4) is one of the four subtypes of receptors for prostaglandin E2 (PGE2). Overproduction of cysteinyl leukotriene in mast cells may be related with suppression of PGE2 in patients with aspirin hypersensitivity. Considering the association of PTGER4 in mast cells, urticaria- and aspirin-related disease, we hypothesized the genetic variability of PTGER4 may be associated with aspirin-intolerant chronic urticaria (AICU). The case-control study was performed in 141 with AICU, 153 with aspirin-tolerant chronic urticaria (ATCU) and 174 with normal controls (NCs). PTGER4 promoter single-nucleotide polymorphism was genotyped using a primer extension method with the SNAPshot ddNTP primer extension kit. The functional variability of PTGER4 promoter polymorphism was carried out by dual-luciferase system and electrophoretic mobility shift assay (EMSA) in human mast cells (HMC-1). Furthermore, the effect of aspirin was performed for PTGER4 mRNA expression using real-time PCR, and PGE2 production was checked in HMC-1 cells using ELISA. AICU patients carrying GG genotype at -1254 G>A showed significantly higher frequency compared with NC (P=0.032). Similarly, the minor allele frequency, G allele was significantly higher in AICU compared with NC (P=0.031). In vitro functional study demonstrated that the -1254 G allele had lower luciferase activity (P<0.001) in HMC-1 cells. EMSA finding showed that PTGER4 -1254 G produced a specific band. Significantly decreased PTGER4 expression (P=0.008) and PGE2 production by aspirin exposure was confirmed in in vitro HMC cell line model (P=0.001). The PTGER4 -1254 G allele demonstrated a higher frequency in AICU patients and lower promoter activity with decreased expression of PTGER4 and contributes to the development of AICU.

Evaluation of a partial genome screening of two asthma susceptibility regions using bayesian network based bayesian multilevel analysis of relevance

Genetic studies indicate high number of potential factors related to asthma. Based on earlier linkage analyses we selected the 11q13 and 14q22 asthma susceptibility regions, for which we designed a partial genome screening study using 145 SNPs in 1201 individuals (436 asthmatic children and 765 controls). The results were evaluated with traditional frequentist methods and we applied a new statistical method, called bayesian network based bayesian multilevel analysis of relevance (BN-BMLA). This method uses bayesian network representation to provide detailed characterization of the relevance of factors, such as joint significance, the type of dependency, and multi-target aspects. We estimated posteriors for these relations within the bayesian statistical framework, in order to estimate the posteriors whether a variable is directly relevant or its association is only mediated.With frequentist methods one SNP (rs3751464 in the FRMD6 gene) provided evidence for an association with asthma (OR = 1.43(1.2-1.8); p = 3×10(-4)). The possible role of the FRMD6 gene in asthma was also confirmed in an animal model and human asthmatics.In the BN-BMLA analysis altogether 5 SNPs in 4 genes were found relevant in connection with asthma phenotype: PRPF19 on chromosome 11, and FRMD6, PTGER2 and PTGDR on chromosome 14. In a subsequent step a partial dataset containing rhinitis and further clinical parameters was used, which allowed the analysis of relevance of SNPs for asthma and multiple targets. These analyses suggested that SNPs in the AHNAK and MS4A2 genes were indirectly associated with asthma. This paper indicates that BN-BMLA explores the relevant factors more comprehensively than traditional statistical methods and extends the scope of strong relevance based methods to include partial relevance, global characterization of relevance and multi-target relevance.

Association analysis of formyl peptide receptor 2 (FPR2) polymorphisms and aspirin exacerbated respiratory diseases

Aspirin-exacerbated respiratory diseases (AERD) are associated with the metabolism of arachidonic acid. FPR2 (formyl peptide receptor2) is a high-affinity ligand receptor for potent anti-inflammatory lipid metabolites: lipoxins. Thus, functional alterations of the FPR2 may contribute to AERD. We investigated the relationship between single-nucleotide polymorphisms (SNPs) in the FPR2 and AERD. Asthmatics were categorized into AERD <15% decreases in forced expiratory volume in one second (FEV(1)), and/or naso-ocular reactions after oral aspirin challenge (n=170) and aspirin-tolerant asthma (ATA, n=268). In all, 11 SNPs were genotyped. FPR2 protein expressions on CD14-positive monocytes in peripheral blood were measured using flow cytometric analysis. We performed RT-PCR of the FPR2 mRNA expressed by peripheral blood mononuclear cells. Logistic regression analysis showed that the minor allele frequency of FPR2 -4209T>G (rs1769490) in intron 2 was significantly lower in the AERD group (n=170) than in the ATA group (n=268) (P=0.006, P(corr)=0.04, recessive model). The decline of FEV(1) after aspirin challenge was significantly lower in the subjects with GG homozygotes of FPR2 -4209T>G than those with the other genotypes (P=0.0002). Asthmatic homozygotes for FPR2 -4209T>G minor allele exhibited significantly higher FPR2 protein expression in CD14-positive monocytes than did those with the common allele of FPR2 -4209T>G allele (P=0.01). There was no difference in the expression of the wild form and the exon 2 deleted variant form of FPR2 gene according to the genotypes of FPR2 -4209T>G. The minor allele at FPR2 -4209T>G may have a protective role against the development of AERD, via increase of FPR2 protein expression in inflammatory cells.

Genome-wide methylation profile of nasal polyps: relation to aspirin hypersensitivity in asthmatics

BACKGROUND

In addition to the dysregulation of arachidonic acid metabolism in aspirin-intolerant asthma (AIA), aspirin acetylsalicylic acid (ASA) exerts effects on inflammation and immunity; however, many of these effects are unknown.

OBJECTIVE

The aim of the study was to evaluate the methylation status of whole genome in blood and polyp tissues with and without aspirin hypersensitivity.

METHODS

Genome-wide DNA methylation levels in nasal polyps and peripheral blood cells were examined by microarray analysis using five subjects with AIA and four subjects with aspirin-tolerant asthma (ATA).

RESULTS

In the nasal polyps of the patients with AIA, hypermethylation was detected at 332 loci in 296 genes, while hypomethylation was detected at 158 loci in 141 genes. Gene ontologic and pathway enrichment analyses revealed that genes involved in lymphocyte proliferation, cell proliferation, leukocyte activation, cytokine biosynthesis, cytokine secretion, immune responses, inflammation, and immunoglobulin binding were hypomethylated, while genes involved in ectoderm development, hemostasis, wound healing, calcium ion binding, and oxidoreductase activity were hypermethylated. In the arachidonate pathway, PGDS, ALOX5AP, and LTB4R were hypomethylated, whereas PTGES was hypermethylated.

CONCLUSION

The nasal polyps of patients with AIA have characteristic methylation patterns affecting 337 genes. The genes and pathways identified in this study may be associated with the presence of aspirin hypersensitivity in asthmatics and are therefore attractive targets for future research.

Association of PTGER gene family polymorphisms with aspirin intolerant asthma in Korean asthmatics

Aspirin-intolerant asthma (AIA) is characterized by severe asthmatic attack after ingestion of aspirin and/or non-steroidal anti-inflammatory drugs. In this study, we investigated the relationship between Prostaglandin E2 receptor (PTGER) gene family polymorphisms and AIA in 243 AIA patients and 919 aspirin-tolerant asthma (ATA) controls of Korean ethnicity in two separate study cohorts. After genotyping 120 SNPs of the PTGER gene family for the 1(st) cohort study, four SNPs in PTGER1, ten in PTGER3, six in PTGER3, and a haplotype of PTGER2 showed association signals with decreased or increased risk of AIA. Among the positively associated SNPs, one in PTGER1 and four in PTGER3 were analyzed in the 2(nd) cohort study. The results show that rs7543182 and rs959 in PTGER3 retained their effect, although no statistical significance was retained in the 2(nd) cohort study. Our findings provide further evidence that polymorphisms in PTGER3 might play a significant role in aspirin hypersensitivity among Korean asthmatics.

Past, present, and future of allergy in Korea

Korean allergology has made great progress in keeping pace with global scientific advances in spite of a short history. Outstanding academic and scientific researches have been performed in a variety of allergy fields in Korea. Epidemiologic studies revealed increasing prevalence of asthma and allergic diseases and considerable morbidity and mortality in Korea. Novel inhalant allergens such as citrus red mite and two-spotted spider mite as causes of asthma and allergic rhinitis have been discovered and reported in Korea. Bidirectional translational researches have been performed and are underway to elucidate the pathogenesis of asthma and allergy, mechanisms of airway inflammation and remodeling, and new therapeutic modalities for asthma and allergic diseases. Experimental asthma models of different phenotypes according to exposed levels of lipopolysaccharide or double-stranded RNA suggested the crucial role of the innate immunity in the development of allergic airway inflammation and a new insight for asthma pathogenesis, in which both Th1 and Th2 inflammation are involved. In the field of genetic researches, numerous genetic associations with asthma and asthma-related phenotypes, such as atopy, IgE production, and airway hyperresponsiveness, have been demonstrated in Korean population. The Easy Asthma Management (EAM) program, a computer-assisted asthma management program, is anticipated to facilitate the achievement of more successful clinical outcomes by filling the gaps between guidelines and actual practices. The Integration of these multi-disciplinary allergy research resources and translation of scientific achievements to the bedside and society will lead to better allergy and asthma control in Korea.

Unraveling the genetic basis of asthma and allergic diseases

Asthma and allergic diseases are believed to be complex genetic diseases which may result from the interaction of multiple genetic factors and environmental stimuli. In past decades, great efforts have been exerted in unraveling their genetic basis. The strategies in discovering genes and genetic variants, confirming their importance in pathogenesis of asthma and allergic diseases, as well as their strengths and limitations are summarized comprehensively and concisely. The current consensus about the genetic basis of asthma and allergic diseases is briefly described as well.

Additive role of tiotropium in severe asthmatics and Arg16Gly in ADRB2 as a potential marker to predict response

BACKGROUND

Recent findings have raised new interests about the use of anticholinergics, especially tiotropium, for the treatment of asthma. This study was performed to determine whether an additional improvement in lung function is obtained when tiotropium is administrated in addition to conventional therapies in severe asthmatics, and to identify factors capable of predicting the response to tiotropium, using a pharmacogenetic approach.

METHODS

A total of 138 severe asthmatics on conventional medications and with decreased lung function were randomly recruited. Tiotropium 18 microg was added once a day and lung functions were measured every 4 weeks. Responders were defined as those with an improvement of > or = 15% (or 200 ml) in the forced expiratory volume in 1 s (FEV1) that was maintained for at least 8 successive weeks. Eleven single nucleotide polymorphisms (SNPs) in CHRM1-3 (coding muscarinic receptors one to three) which were identified by re-sequencing, and Arg16Gly and Gln27Glu in ADRB2 (coding beta(2) adrenoreceptor) were scored in 80 of the 138 asthmatics.

RESULTS

Forty-six of the 138 asthmatics (33.3%) responded to tiotropium treatment. Logistic regression analyses (controlled for age, gender, and smoking status) showed that Arg16Gly in ADRB2 [P = 0.003, OR (95% CI) = 0.21 (0.07-0.59) in a minor allele-dominant model] was significantly associated with response to tiotropium.

CONCLUSIONS

As many as 30% of severe asthmatics on conventional medications with reduced lung function were found to respond to adjuvant tiotropium. The presence of Arg16Gly in ADRB2 may predict response to tiotropium.

Gene-expression profiles in human nasal polyp tissues and identification of genetic susceptibility in aspirin-intolerant asthma

BACKGROUND

Aspirin-intolerant asthma (AIA) is a subtype of asthma induced by non-steroidal anti-inflammatory drugs and characterized by an aggressive mucosal inflammation of the lower airway (asthma) and the upper airways (rhinitis and nasal polyp). The lower airway lesion and the nasal polyp in AIA are postulated to have common pathogenic features involving aspirin sensitivity that would be reflected in the gene expression profile of AIA polyps.

OBJECTIVE

This study was conducted to clarify the pathogenesis of AIA using gene expression analysis in nasal polyps, and identify genetic susceptibilities underlying AIA in a case-control association study.

METHODS

Global gene expression of nasal polyps from nine AIA patients was examined using microarray technology in comparison with nasal polyps from five eosinophilic sinusitis (ES) patients, a related disease lacking aspirin sensitivity. Based on the AIA-specific gene expression profile of nasal polyp, candidate genes for AIA susceptibility were selected and screened by a case-control design of 219 AIA patients, 374 non-asthmatic control (CTR), and 282 aspirin-tolerant asthmatic (ATA) subjects.

RESULTS

One hundred and forty-three elevated and three decreased genes were identified as AIA-specific genes that were enriched in immune response according to Gene Ontology analysis. In addition, a k-means-based algorithm was applied to cluster the genes, and a subclass characteristic of AIA comprising 18 genes that were also enriched in immune response was identified. By examining the allelic associations of single nucleotide polymorphisms (SNPs) of AIA candidate genes relevant to an immune response with AIA, two SNPs, one each of INDO and IL1R2, showed significant associations with AIA (P=0.011 and 0.026 after Bonferroni's correction, respectively, in AIA vs. CTR). In AIA-ATA association analysis, modest associations of the two SNPs with AIA were observed.

CONCLUSION

These results indicate that INDO and IL1R2, which were identified from gene expression analyses of nasal polyps in AIA, represent susceptibility genes for AIA.

The Asian side of asthma and allergy

PURPOSE OF REVIEW

There is wide variation in the global epidemiology of allergic diseases, and the prevalence rates of asthma and allergy differ significantly among different Asian populations. The diversity of environment and ethnic background in Asia provide excellent opportunities for research into the environmental and genetic determinants of asthma and allergies. This review summarizes important lessons learnt from research findings from Asia on asthma and allergy.

RECENT FINDINGS

Recent epidemiologic studies revealed wide variation and increasing prevalence of asthma and allergy in many Asian countries. Comparative studies of population of the same ethnic background living in different environments revealed important environmental risk factors for asthma. Ambient air pollution plays an important role in the morbidity of patients with asthma but does not seem to affect the prevalence of asthma. There were many genetic association studies for allergic diseases from Asia. These studies identified novel gene targets, such as CD40, DCNP1 and PTGS2, for asthma and allergen sensitization whereas many others replicated the genetic associations on known candidate genes for asthma and atopic dermatitis.

SUMMARY

Epidemiologic and genetic researches in Asia advance our knowledge on the disease prevalence, healthcare burden and pathogenesis of asthma and allergy.