Polymorphism of tandem repeat in promoter of 5-lipoxygenase in ASA-intolerant asthma: a positive association with airway hyperresponsiveness

Association between a single nucleotide polymorphism of the ALOX5 gene and susceptibility to multisystem tuberculosis in a Chinese Han population

BACKGROUND

Host genetic single nucleotide polymorphisms can exert an influence susceptibility to tuberculosis infection. Previous investigations have demonstrated an association between the polymorphism in the ALOX5 gene and a range of diseases, encompassing not only noninfectious conditions like asthma, acute myocardial infarction, and cerebral infarction but also infections caused by various pathogens. However, the relationship between ALOX5 gene polymorphism and susceptibility to tuberculosis has received limited research attention. The ALOX5 gene encodes arachidonic acid 5-lipoxygenase(5-LO), which serves as the initiating catalyst in the generation of the inflammatory mediator leukotriene. Leukotrienes, products derived from the 5-LO pathway, are potent proinflammatory lipid mediators that assume a pivotal role in tuberculosis infections.Consequently, ALOX5 gene variants may be intricately associated with the pathogenesis of tuberculosis. In instances where the host exhibits immunocompromisation, infection with Mycobacterium tuberculosis can impact multiple systems. The involvement of multiple systems significantly augments the complexity of treatment and escalates patient mortality rates. Regrettably, the underlying mechanisms driving multisystem tuberculosis pathogenesis remain enigmatic, with clinicians paying scant attention to this aspect. Although the protein encoded by the ALOX5 gene represents a pivotal enzyme that catalyzes the metabolism of arachidonic acid into LXA4, and thereby plays a significant role in the inflammatory response during tuberculosis infection, studies investigating ALOX5 gene polymorphism and its association with susceptibility to multisystem tuberculosis in the Chinese Han population are exceptionally scarce. Therefore, the primary objective of this study is to comprehensively examine the correlation between ALOX5 gene polymorphisms and susceptibility to tuberculosis within the Chinese Han population, with particular emphasis on multisystemic tuberculosis.

METHODS

A case‒control study design was employed, encompassing 382 individuals with pulmonary tuberculosis and 367 individuals with multisystemic tuberculosis as the case groups, along with 577 healthy controls.Whole blood DNA was extracted from all patients and healthy controls. Subsequently, three tag polymorphisms (rs2029253, rs7896431, rs2115819) within the ALOX5 gene were selectively identified and genotyped.

RESULTS

After adjusting for age and sex, the presence of allele A at rs2029253 exhibited a pronounced association with an elevated risk of TB susceptibility when compared to the tuberculosis group and healthy control group. (ORa: 2.174, 95% CI: 1.827-2.587; Pa<0.001, respectively). Notably, the rs2029253 AG genotype and AA genotype displayed a significantly increased susceptibility to tuberculosis (ORa: 2.236, 95% CI: 1.769-2.825; Pa <0.001 and ORa: 4.577, 95% CI: 2.950-7.100; Pa <0.001, respectively) compared to the GG genotype. Moreover, in the analysis utilizing genetic models, rs2029253 also exhibited a markedly heightened susceptibility to tuberculosis in additive models, dominant models, and recessive models (Pa <0.001). Conversely, no significant association was observed between rs7896431, rs2115819, and tuberculosis. In the subgroup analysis, when comparing the pulmonary tuberculosis group with the healthy control group, we observed no significant disparities in the distribution frequencies of alleles, genotypes, and gene models (additive model, dominant model, and recessive model) for the three tag SNPs, with P-values were >0.05 after adjusting for age and sex. Additionally, we noted that the presence of allele A at rs2029253 was linked to an increased susceptibility to tuberculosis in the multisystemic tuberculosis group relative to the healthy control group (ORa: 2.292, 95% CI: 1.870-2.810; Pa<0.001). Similarly, the rs2029253 AG genotype, AA genotype, and gene models, including the additive model, dominant model, and recessive model, demonstrated a significantly elevated risk of tuberculosis susceptibility.

CONCLUSIONS

The polymorphism in the ALOX5 gene is associated with susceptibility to multisystemic tuberculosis in the Chinese Han population.

Association between Sex-Related ALOX5 Gene Polymorphisms and Lung Atopy Risk

Atopy is an exaggerated IgE-mediated immune response to foreign antigens in which metabolic abnormalities of the leukotrienes (LTs) pathway play a crucial role. Recent studies have described sex as a key variable in LT biosynthesis, partly explaining why treatment with anti-LT drugs in atopic subjects leads to better control of symptoms in women. In addition, variability in LT production is often associated with single nucleotide polymorphisms (SNPs) in the arachidonate 5-lipoxygenase (ALOX5) gene, which encodes the leukotriene-synthesizing enzyme machinery, 5-lipoxygenase (5-LO). This study aimed to investigate whether two SNPs of ALOX5 are implicated in sex differences in allergic diseases in a prospective cohort of 150 age- and sex-matched atopic and healthy subjects. Rs2029253 and rs2115819 were genotyped using allele-specific RT-PCR, and serum levels of 5-LO and LTB4 were measured by ELISA. Both polymorphisms are significantly more common in women than in men, and their influences on LT production vary as a function of sex, leading to a decrease in men's and an increase in women's serum levels of 5-LO and LTB4. These data represent a new resource for understanding sex-related differences in lung inflammatory diseases, partly explaining why women are more likely to develop allergic disorders than men.

Complementary Participation of Genetics and Epigenetics in Development of NSAID-exacerbated Respiratory Disease

Nonsteroidal anti-inflammatory drug (NSAID)-exacerbated respiratory disease (NERD) has attracted a great deal of attention because of its association with severe asthma. However, it remains widely underdiagnosed in asthmatics as well as the general population. Upon pharmacological inhibition of cyclooxygenase 1 by NSAIDs, production of anti-inflammatory prostaglandin E2 and lipoxins ceases, while release of proinflammatory cysteinyl leukotrienes increases. To determine the underlying mechanisms, many studies have attempted to elucidate the genetic variants, such as single nucleotide polymorphisms, responsible for alterations of prostaglandins and leukotrienes, but the results of these genetic studies could not explain the whole genetic pathogenesis of NERD. Accordingly, the field of epigenetics has been introduced as an additional contributor to genomic alteration underlying the development of NERD. Recently, changes in CpG methylation, as one of the epigenetic components, have been identified in target tissues of NERD. This review discusses in silico analyses of both genetic and epigenetic components to gain a better understanding of their complementary roles in the development of NERD. Although the molecular mechanisms underlying NERD pathogenesis remain poorly understood, genetic and epigenetic variations play significant roles. Our results enhance the understanding of the genetic and epigenetic mechanisms involved in the development of NERD and suggest new approaches toward better diagnosis and management.

Genetic and Epigenetic Components of Aspirin-Exacerbated Respiratory Disease

Aspirin-exacerbated respiratory disease (AERD) severity and its clinical phenotypes are characterized by genetic variation within pathways for arachidonic acid metabolism, inflammation, and immune responses. Epigenetic effects, including DNA methylation and histone protein modification, contribute to regulation of many genes that contribute to inflammatory states in AERD. The development of noninvasive, predictive clinical tests using data from genetic, epigenetic, pharmacogenetic, and biomarker studies will improve precision medicine efforts for AERD and asthma treatment.

Physiopathology and genetics in aspirin-exacerbated respiratory disease

INTRODUCTION

Aspirin-exacerbated respiratory disease (AERD) is a clinical entity characterized by hypersensitivity to aspirin leading to asthma and chronic rhinosinusitis with nasosinusal polyposis. The pathophysiology of the disease involves disruption at the level of arachidonic acid metabolism. Therefore, genetic association studies have been focused on the genes coding this pathway. As other mechanisms involved in the genesis of the disease were elucidated, the corresponding genes were also explored.

AIM

To describe the association reported in the literature between gene polymorphisms involved in the pathophysiology or therapeutic processes of AERD.

RESULTS

There is a genetic association between polymorphisms of genes involved in the synthesis of proteins related to arachidonic acid metabolism (LTC4S, ALOX5), antigen presentation (HLA), inflammation (IL5, IL17), and aspirin metabolism (CYP2C19).

CONCLUSIONS

Genetic association research in AERD has evaluated studies of SNPs in metabolic pathways related to arachidonic acid. Recently, whole genome analysis strategies have allowed the detection of new genetic variants that were previously not considered. Furthermore, these studies have identified SNPs that are associated with inflammatory processes, which could serve as diagnostic markers or predictors of the therapeutic response.

Transcriptional regulation of the canine carbonyl reductase 1 gene (cbr1) by the specificity protein 1 (Sp1)

The clinical use of anthracyclines to treat various canine cancers is limited by the development of cardiotoxicity. The intra-cardiac synthesis of anthracycline C-13 alcohol metabolites (e.g. daunorubicinol) contributes to the development of cardiotoxicity. Canine carbonyl reductase 1 (cbr1) catalyzes the reduction of daunorubicin into daunorubicinol. Recent mapping of the cbr1 locus by sequencing DNA samples from dogs from various breeds revealed a cluster of conserved motifs for the transcription factor Sp1 in the putative promoter region of cbr1. We hypothesized that the variable number of Sp1 motifs could impact the transcription of canine cbr1. In this study, we report the functional characterization of the canine cbr1 promoter. Experiments with reporter constructs and chromatin immunoprecipitation show that cbr1 transcription depends on the binding of Sp1 to the proximal promoter. Site-directed mutagenesis experiments suggest that the variable number of Sp1 motifs impacts the transcription of canine cbr1. Inhibition of Sp1-DNA binding decreased canine cbr1 mRNA levels by 54% in comparison to controls, and also decreased enzymatic carbonyl reductase activity for the substrates daunorubicin (16%) and menadione (23%). The transactivation of Sp1 increased the expression of cbr1 mRNA (67%), and increased carbonyl reductase activity for daunorubicin (35%) and menadione (27%). These data suggest that the variable number of Sp1 motifs in the canine cbr1 promoter may impact the pharmacodynamics of anthracyclines in canine cancer patients.

The role of lipoxygenases in pathophysiology; new insights and future perspectives

Lipoxygenases (LOXs) are dioxygenases that catalyze the formation of corresponding hydroperoxides from polyunsaturated fatty acids such as linoleic acid and arachidonic acid. LOX enzymes are expressed in immune, epithelial, and tumor cells that display a variety of physiological functions, including inflammation, skin disorder, and tumorigenesis. In the humans and mice, six LOX isoforms have been known. 15-LOX, a prototypical enzyme originally found in reticulocytes shares the similarity of amino acid sequence as well as the biochemical property to plant LOX enzymes. 15-LOX-2, which is expressed in epithelial cells and leukocytes, has different substrate specificity in the humans and mice, therefore, the role of them in mammals has not been established. 12-LOX is an isoform expressed in epithelial cells and myeloid cells including platelets. Many mutations in this isoform are found in epithelial cancers, suggesting a potential link between 12-LOX and tumorigenesis. 12R-LOX can be found in the epithelial cells of the skin. Defects in this gene result in ichthyosis, a cutaneous disorder characterized by pathophysiologically dried skin due to abnormal loss of water from its epithelial cell layer. Similarly, eLOX-3, which is also expressed in the skin epithelial cells acting downstream 12R-LOX, is another causative factor for ichthyosis. 5-LOX is a distinct isoform playing an important role in asthma and inflammation. This isoform causes the constriction of bronchioles in response to cysteinyl leukotrienes such as LTC4, thus leading to asthma. It also induces neutrophilic inflammation by its recruitment in response to LTB4. Importantly, 5-LOX activity is strictly regulated by 5-LOX activating protein (FLAP) though the distribution of 5-LOX in the nucleus. Currently, pharmacological drugs targeting FLAP are actively developing. This review summarized these functions of LOX enzymes under pathophysiological conditions in mammals.

Recent advance in investigation of gene polymorphisms in Japanese patients with aspirin-exacerbated respiratory disease

Aspirin-exacerbated respiratory disease (AERD) is a complex clinical syndrome characterised by severe asthmatic attack upon treatment with aspirin and/or non-steroidal anti-inflammatory drugs (NSAIDs). Genetic predisposition has been considered as a crucial determinant and candidate genes have concentrated especially on cysteinyl leukotrienes (LTs)-related genes as the inhibitory action of aspirin and NSAIDs on cyclooxygenase activity may cause overproduction of cysteinyl LTs. However, conflicting results have been reported, in parallel with replication studies in different ethnic groups. Thus, future areas of investigations need to focus on comprehensive approaches towards the discovery of other genetic biomarkers. Unfortunately, few papers have been reported about gene polymorphisms in Japanese patients with AERD. Here, we described on our recent genetic investigations on B2ADR, IL-13, IL-17A, CYP2C19, TBXA2R, CRTH2 and HSP70. This review indicates potential genetic biomarkers contributing to the early diagnosis of AERD, which may include CYP2C19 and HSP70 gene polymorphisms, and future validation studies in independent population are required to provide reassurance about our findings.

ALOX5 polymorphism associates with increased leukotriene production and reduced lung function and asthma control in children with poorly controlled asthma

BACKGROUND

Identification of risk factors for reduced asthma control could improve the understanding and treatment of asthma. A promoter polymorphism in the 5-lipoxygenase gene affects gene expression and response to asthma therapy, but its impact on disease control remains unclear.

OBJECTIVE

We sought to determine if the ALOX5 promoter SP1 tandem repeat polymorphism was associated with changes in cysteinyl leukotriene production, lung function, airway inflammation and asthma control score.

METHODS

We analysed 270 children, 6- to 17-years old, with poorly controlled asthma enrolled in a 6-month clinical trial (NCT00604851). In secondary analysis, we associated the ALOX5 promoter SP1 tandem repeat polymorphism genotype (rs59439148) with asthma outcomes using both additive and recessive genetic models. We evaluated FEV1 percent predicted, symptom control, exhaled nitric oxide and urinary LTE4 levels.

RESULTS

Of all children, 14.8% (40/270) (and 28% (38/135) of African Americans) carried two non-5-repeat variant alleles of rs59439148. Children who were homozygous for variant alleles had significantly higher urinary LTE4 levels (38 vs. 30 nmol/mol creatinine, P = 0.0134), significantly worse FEV1% predicted (84 vs. 91, P = 0.017) and a trend towards worse asthma control. FEV1% predicted values were significantly negatively correlated with urinary LTE4 (r = -0.192, P = 0.009).

CONCLUSION AND CLINICAL RELEVANCE

Carrying two copies of a minor variant ALOX5 promoter SP1 tandem repeat allele contributes to increased cysLT exposure as determined by urinary LTE4 levels, reduced lung function and potentially worse asthma control. ALOX5 promoter SP1 tandem repeat genotype may be a risk factor for worse asthma outcomes.

Biochemical pathogenesis of aspirin exacerbated respiratory disease (AERD)

Aspirin exacerbated respiratory disease (AERD) is a distinct clinical entity characterized by eosinophilic rhinosinusitis, asthma and often nasal polyposis. Exposure to aspirin or other nonsteroid anti-inflammatory drugs (NSAIDs) exacerbates bronchospasms with asthma and rhinitis. Disease progression suggests a skewing towards TH2 type cellular response along with moderate to severe eosinophil and mast cell infiltration. Alterations in upper and lower airway cellular milieu with abnormalities in eicosanoid metabolism and altered eicosanoid receptor expression are the key features underlying AERD pathogenesis. Dysregulation of arachidonic acid (AA) metabolism, notably reduced prostaglandin E2 (PGE2) synthesis compared to their aspirin tolerant counterpart and relatively increased PGD2 production, a TH2/eosinophil chemoattractant are reported in AERD. Underproduced PGE2 is metabolized by overexpression of 15 prostaglandin dehydrogenase (15-PGDH) to inactive products further reducing PGE2 at real time. This relives the inhibitory effect of PGE2 on 5-lipoxygenase (5-LOX) resulting in overproduction of cysteinyl leukotrienes (CysLTs). Diminished formation of CysLT antagonists called lipoxins (LXs) also augments CysLTs responsiveness. Occasional intake of NSAIDs favors even more 5-LOX product formation, further narrowing the bronchoconstrictive bottle neck, resulting in acute asthmatic exacerbations along with increased mucus production. This review focuses on abnormalities in biochemical and molecular mechanisms in eicosanoid biosynthesis, eicosanoid receptor dysregulation and associated polymorphisms with special reference to arachidonic acid metabolism in AERD.

Potential association between ANXA4 polymorphisms and aspirin-exacerbated respiratory disease

Aspirin-exacerbated respiratory disease (AERD) is a clinical syndrome characterized by bronchoconstriction after ingestion of nonsteroidal anti-inflammatory drugs including aspirin. The Ca concentration in bronchial epithelial cells is an important factor for bronchoconstriction. Human annexin A4 (ANXA4) is predominantly expressed in the secretory epithelia in the lung, stomach, intestine, and kidney. Furthermore, translocation and induction of ANXA4 have been observed in human Ca-depleted neutrophils. To investigate the association between annexin A4 polymorphisms and the risk of AERD, we have genotyped 21 variants from 102 AERD subjects and 429 aspirin-tolerant asthma (ATA) controls. Logistic analyses controlling for sex, smoking status, and atopy as covariates were performed to estimate the association between the annexin A4 polymorphisms and AERD. Among these variants, 8 polymorphisms (rs2168116, rs4853017, rs6546547, rs13428251, rs7577864, rs7559354, rs7588022, and rs3816491) and 2 haplotypes (ANXA4-ht3 and ANXA4-ht5) were significantly associated with the risk of AERD. One common polymorphism in intron 11, rs3816491, showed the strongest association signal with susceptibility to aspirin-AERD even after multiple testing corrections (OR=0.57; 95% confidence interval 0.40-0.83; P=0.003; P=0.045 in the codominant model). Although further functional evaluations of replication studies in larger cohorts are required, our findings suggest that the annexin A4 could have susceptibility for AERD.

Genetics of hypersensitivity to aspirin and nonsteroidal anti-inflammatory drugs

Various hypersensitivity reactions have been reported with aspirin and nonsteroidal anti-inflammatory drugs. Hypersensitivity can occur regardless of a chemical drug structure or its therapeutic potency. Allergic conditions include aspirin-exacerbated respiratory disease (AERD or aspirin-induced asthma), aspirin-induced urticaria/angioedema (AIU), and anaphylaxis. Several genetic studies on aspirin hypersensitivity have been performed to discover the genetic predisposition to aspirin hypersensitivity and to gain insight into the phenotypic diversity. This article updates data on the genetic mechanisms that govern AERD and AIU and summarizes recent findings on the molecular genetic mechanism of aspirin hypersensitivity.

Association between arachidonate 5-lipoxygenase-activating protein (ALOX5AP) and lung function in a Korean population

Arachidonate 5-lipoxygenase-activating protein (ALOX5AP) plays a role in the 5-lipoxygenase (LO) pathway, which includes the LTC(4), LTD(4), LTE(4) and LTB(4). These leukotrienes are known causative factors of asthma, allergy, atopy and cardiovascular diseases. ALOX5AP lacks enzyme activity and acts by helping 5-LO function. In this study, healthy and general subjects who live in rural and urban areas of Korea were tested for the association of ALOX5AP polymorphisms with lung function. Lung function was also estimated by calculating the predicted values for forced expiratory volume in one second (FEV(1) _%PRED) and the proportion of the forced vital capacity exhaled in the first second (FEV(1) /FVC_PRED). The linear regression was adjusted for residence area, gender, age, height and smoking status. The analysis revealed associations between FEV(1) and the single-nucleotide polymorphism (SNP) rs9506352 and the haplotype TCAC (permuted P-value < 0.05). The linkage disequilibrium block that included the significant SNPs overlapped with SNPs that were revealed previously to associate with myocardial infarction and asthma and to affect lung function. This study is the first to demonstrate the association between lung function and ALOX5AP polymorphisms in a healthy and general population.

Association of the -1072G/A polymorphism in the LTC4S gene with asthma in an Indian population

BACKGROUND

Atopic asthma, the most common chronic disease affecting children and young adults, is a complex disorder with variable phenotypes. Cysteine leukotrienes (Cys-LTs) are powerful bronchoconstrictors and play a critical role in airway inflammation and remodeling that are characteristic of asthma.

OBJECTIVE

To investigate the association of ALOX5, LTC4S and CysLTR2 gene polymorphisms with atopic asthma in an Indian population.

METHODS

A total of 19 single nucleotide polymorphisms (SNPs) within these genes were genotyped in a family-based cohort (n = 239) and a case-control cohort (139 cases and 194 controls) followed by association analyses.

RESULTS

We found a significant association of the -1072G/A (rs3776944) SNP with atopic asthma in the family-based association analysis (p = 0.0004). These results were also replicated in the case-control cohort (p = 0.009). The allele A was negatively associated with atopic asthma. We also noted a significant association in the two-locus (rs3776944G/A and rs730012A/C) haplotypic analysis of this gene both in the family-based (p = 0.03) and the case-control (p = 0.02) analyses.

CONCLUSION

This study supports the role of the LTC4S gene polymorphism in genetic susceptibility to atopic asthma in an Indian population.

The clinical and environmental determinants of airway transcriptional profiles in allergic asthma

RATIONALE

Gene expression profiling of airway epithelial and inflammatory cells can be used to identify genes involved in environmental asthma.

METHODS

Airway epithelia and inflammatory cells were obtained via bronchial brush and bronchoalveolar lavage (BAL) from 39 subjects comprising three phenotypic groups (nonatopic nonasthmatic, atopic nonasthmatic, and atopic asthmatic) 4 hours after instillation of LPS, house dust mite antigen, and saline in three distinct subsegmental bronchi. RNA transcript levels were assessed using whole genome microarrays.

MEASUREMENTS AND MAIN RESULTS

Baseline (saline exposure) differences in gene expression were related to airflow obstruction in epithelial cells (C3, ALOX5AP, CCL18, and others), and to serum IgE (innate immune genes and focal adhesion pathway) and allergic-asthmatic phenotype (complement genes, histone deacetylases, and GATA1 transcription factor) in inflammatory cells. LPS stimulation resulted in pronounced transcriptional response across all subjects in both airway epithelia and BAL cells, with strong association to nuclear factor-κB and IFN-inducible genes as well as signatures of other transcription factors (NRF2, C/EBP, and E2F1) and histone proteins. No distinct transcriptional profile to LPS was observed in the asthma and atopy phenotype. Finally, although no consistent expression changes were observed across all subjects in response to house dust mite antigen stimulation, we observed subtle differences in gene expression (e.g., GATA1 and GATA2) in BAL cells related to the asthma and atopy phenotype.

CONCLUSIONS

Our results indicate that among individuals with allergic asthma, transcriptional changes in airway epithelia and inflammatory cells are influenced by phenotype as well as environmental exposures.

IL-13 and IL-17A gene polymorphisms in Japanese patients with aspirin-exacerbated respiratory disease

BACKGROUND

The role of interleukin (IL) 13 and IL-17A in aspirin-exacerbated respiratory disease (AERD) remains unknown.

OBJECTIVE

To analyze the IL-13 and IL-17A gene polymorphisms in Japanese patients with AERD.

METHODS

The single-nucleotide polymorphisms in each gene were examined in patients with AERD, patients with aspirin-tolerant asthma (ATA), and healthy controls.

RESULTS

Frequencies of the TT/CT genotype of the IL-13 -1111C>T gene were higher than frequencies of the CC genotype in AERD patients compared with ATA patients (P < .001). In female patients with AERD, frequencies of the TT/CT genotype were higher than those of the CC genotype compared with female patients with ATA (P < .001). However, genotype frequencies of IL-13 Arg110Gln did not differ between AERD and ATA patients. Frequencies of the CC genotype of the IL-17A -737C>T gene were higher than those of the TT/CT genotype in AERD patients compared with ATA patients (P = .02). In female patients with AERD, frequencies of the CC genotype were higher than those of the TT/CT genotype compared with female patients with ATA (P = .03). Forced expiratory volume in 1 second (percentage predicted) in AERD patients with the CC genotype of the IL-13 -1111C>T gene was lower than that in the patients with the TT/CT genotype. AERD patients with the TT/CT genotype of the IL-17A -737C>T gene had a higher peripheral total eosinophil count compared with the patients with the CC genotype. The comparison of the clinical characteristics according to the IL-13 Arg110Gln gene polymorphism showed no difference.

CONCLUSIONS

These findings suggest that the IL-13 -1111C>T and IL-17A -737C>T gene sequence variations might have a role in the development of AERD.

Arg16Gly β2-adrenergic receptor gene polymorphism in Japanese patients with aspirin-exacerbated respiratory disease

BACKGROUND

There has been no report that investigated β(2)-adrenergic receptor (ADRB2) gene polymorphism in patients with aspirin-exacerbated respiratory disease (AERD).

METHODS

DNA in the specimens in three groups of study subjects classified patients with AERD, patients with aspirin-tolerant asthma (ATA) and normal controls was extracted, and the target DNA sequence of the ADRB2 was amplified using a set of primers to generate an amplicon of 219 bp in length. Allelic discrimination assay for single nucleotide polymorphisms relating to the ADRB2 gene expression was carried out by using a previously described single nucleotide polymorphism detective system, sequence-specific thermal-elution chromatography.

RESULTS

The frequency of the Gly variant allele in patients with AERD was significantly lower than that in patients with ATA (p = 0.007), and the odds ratio (OR) of AERD to ATA associated with wild-type ArgArg homozygote was 3.300. Frequencies of wild-type ArgArg homozygote are significantly higher than those of variant-type ArgGly/GlyGly genotype in patients with AERD compared with those with ATA (p < 0.001, OR = 3.153). In patients with AERD, frequencies of wild-type ArgArg homozygote in both female and male patients are significantly higher than those of variant-type ArgGly/GlyGly genotype in male patients compared with those with ATA (p < 0.001, OR = 5.128 and p = 0.007, OR = 4.367, respectively). Also, in patients with AERD, frequencies of wild-type ArgArg homozygote in female patients are significantly higher than those of variant-type ArgGly/GlyGly genotype in female patients compared with those with ATA (p = 0.002, OR = 2.825).

CONCLUSIONS

We were the first to analyze Arg16Gly ADRB2 gene polymorphism in Japanese patients with AERD, and showed that Arg16Gly ADRB2 gene polymorphism in Japanese patients with AERD is different from that in the patients with ATA.

Genetics and phenotyping in chronic sinusitis

Chronic sinusitis with nasal polyposis historically has been treated as a single monolithic clinical disorder. Just as asthma is now accepted as numerous heterogeneous diseases, chronic sinusitis should also be viewed as comprising several diseases with varying causes, with each one characterized by distinct histologic and gene and protein expression patterns. This includes recognition of the need to define these diseases based on the presence or absence of an eosinophilic infiltrate but also on additional distinctions based on unique agents that drive their development and perpetuation. As a collection of heterogeneous diseases, proper differential diagnosis is required to delineate appropriate therapeutic intervention. This review will focus on recognized distinct presentations of chronic sinus disease, including distinguishing the clinical presentations, cellular and molecular characteristics, genetic differences, and current treatment options for each.

Novel allelic variants in the canine cyclooxgenase-2 (Cox-2) promoter are associated with renal dysplasia in dogs

Renal dysplasia (RD) in dogs is a complex disease with a highly variable phenotype and mode of inheritance that does not follow a simple Mendelian pattern. Cox-2 (Cyclooxgenase-2) deficient mice have renal abnormalities and a pathology that has striking similarities to RD in dogs suggesting to us that mutations in the Cox-2 gene could be the cause of RD in dogs. Our data supports this hypothesis. Sequencing of the canine Cox-2 gene was done from clinically affected and normal dogs. Although no changes were detected in the Cox-2 coding region, small insertions and deletions of GC boxes just upstream of the ATG translation start site were found. These sequences are putative SP1 transcription factor binding sites that may represent important cis-acting DNA regulatory elements that govern the expression of Cox-2. A pedigree study of a family of Lhasa apsos revealed an important statistical correlation of these mutant alleles with the disease. We examined an additional 22 clinical cases from various breeds. Regardless of the breed or severity of disease, all of these had one or two copies of the Cox-2 allelic variants. We suggest that the unusual inheritance pattern of RD is due to these alleles, either by changing the pattern of expression of Cox-2 or making Cox-2 levels susceptible to influences of other genes or environmental factors that play an unknown but important role in the development of RD in dogs.

Genome-wide and follow-up studies identify CEP68 gene variants associated with risk of aspirin-intolerant asthma

Aspirin-intolerant asthma (AIA) is a rare condition that is characterized by the development of bronchoconstriction in asthmatic patients after ingestion of non-steroidal anti-inflammatory drugs including aspirin. However, the underlying mechanisms of AIA occurrence are still not fully understood. To identify the genetic variations associated with aspirin intolerance in asthmatics, the first stage of genome-wide association study with 109,365 single nucleotide polymorphisms (SNPs) was undertaken in a Korean AIA (n = 80) cohort and aspirin-tolerant asthma (ATA, n = 100) subjects as controls. For the second stage of follow-up study, 150 common SNPs from 11 candidate genes were genotyped in 163 AIA patients including intermediate AIA (AIA-I) subjects and 429 ATA controls. Among 11 candidate genes, multivariate logistic analyses showed that SNPs of CEP68 gene showed the most significant association with aspirin intolerance (P values of co-dominant for CEP68, 6.0×10⁻⁵ to 4.0×10⁻⁵). All seven SNPs of the CEP68 gene showed linkage disequilibrium (LD), and the haplotype of CEP68_ht4 (T-G-A-A-A-C-G) showed a highly significant association with aspirin intolerance (OR  = 2.63; 95% CI  = 1.64–4.21; P = 6.0×10⁻⁵). Moreover, the nonsynonymous CEP68 rs7572857G>A variant that replaces glycine with serine showed a higher decline of forced expiratory volume in 1s (FEV₁) by aspirin provocation than other variants (P = 3.0×10⁻⁵). Our findings imply that CEP68 could be a susceptible gene for aspirin intolerance in asthmatics, suggesting that the nonsynonymous Gly74Ser could affect the polarity of the protein structure.

Update on recent advances in the management of aspirin exacerbated respiratory disease

Aspirin intolerant asthma (AIA) is frequently characterized as an aspirin (ASA)-exacerbated respiratory disease (AERD). It is a clinical syndrome associated with chronic severe inflammation in the upper and lower airways resulting in chronic rhinitis, sinusitis, recurrent polyposis, and asthma. AERD generally develops secondary to abnormalities in inflammatory mediators and arachidonic acid biosynthesis expression. Upper and lower airway eosinophil infiltration is a key feature of AERD; however, the exact mechanisms of such chronic eosinophilic inflammation are not fully understood. Cysteinyl leukotriene over-production may be a key factor in the induction of eosinophilic activation. Genetic studies have suggested a role for variability of genes in disease susceptibility and response to medication. Potential genetic biomarkers contributing to the AERD phenotype include HLA-DPB1*301, LTC4S, ALOX5, CYSLT, PGE2, TBXA2R, TBX21, MS4A2, IL10 -1082A > G, ACE -262A > T, and CRTH2 -466T > C; the four-locus SNP set was composed of B2ADR 46A > G, CCR3 -520T > G, CysLTR1 -634C > T, and FCER1B -109T > C. Management of AERD is an important issue. Aspirin ingestion may result in significant morbidity and mortality, and patients must be advised regarding aspirin risk. Leukotriene receptor antagonists (LTRA) that inhibit leukotriene pathways have an established role in long-term AERD management and rhinosinusitis. Aspirin desensitization may be required for the relief of upper and lower airway symptoms in AERD patients. Future research should focus on identification of biomarkers for a comprehensive diagnostic approach.

Association analysis of peroxisome proliferator-activated receptors gamma gene polymorphisms with asprin hypersensitivity in asthmatics

Purpose

Peroxisome proliferator-activated receptors (PPARs) are transcriptional factors activated by ligands of the nuclear hormone receptor superfamily. The activation of PPARγ regulates inflammation by downregulating the production of Th2 type cytokines and eosinophil function. In addition, a range of natural substances, including arachidonate pathway metabolites such as 15-hydroxyeicosatetranoic acid (15-HETE), strongly promote PPARG expression. Therefore, genetic variants of the PPARG gene may be associated with the development of aspirin-intolerant asthma (AIA). We investigated the relationship between single nucleotide polymorphism (SNP) of the PPARG gene and AIA.

Methods

Based on the results of an oral aspirin challenge, asthmatics (n=403) were categorized into two groups: those with a decrease in FEV₁ of 15% or greater (AIA) or less than 15% (aspirin-tolerant asthma, ATA). We genotyped two single nucleotide polymorphisms in the PPARG gene from Korean asthmatics and normal controls (n=449): +34C>G (Pro12Ala) and +82466C>T (His449His).

Results

Logistic regression analysis showed that +82466C>T and haplotype 1 (CC) were associated with the development of aspirin hypersensitivity in asthmatics (P=0.04). The frequency of the rare allele of +82466C>T was significantly higher in AIA patients than in ATA patients in the recessive model [P=0.04, OR=3.97 (1.08-14.53)]. In addition, the frequency of PPARG haplotype 1 was significantly lower in AIA patients than in ATA patients in the dominant model (OR=0.25, P=0.04).

Conclusions

The +82466C>T polymorphism and haplotype 1 of the PPARG gene may be linked to increased risk for aspirin hypersensitivity in asthma.

Functional analysis of 5-lipoxygenase promoter repeat variants

Variants of a hexanucleotide repeat polymorphism in the promoter of the 5-lipoxygenase (5-LO) gene have been associated with cardiovascular disease traits in humans, which may be due, at least in part, to differential expression of the at-risk alleles. To more fully characterize these variants, we carried out gene expression and DNA methylation studies in primary leukocytes from healthy individuals carrying various 5-LO promoter alleles. Regardless of genotype, 5-LO and 5-LO-activating protein (FLAP) gene expression was higher in granulocytes compared with monocytes and lymphocytes, whereas leukotriene A4 hydrolase (LTA4H) expression was higher in monocytes. In all three leukocyte populations, 5-LO mRNA levels were positively correlated with those of FLAP and LTA4H, with the highest correlation observed in granulocytes. In lymphocytes, individuals homozygous for the shorter 3 and 4 repeat alleles had between 20-35% higher 5-LO, FLAP and LTA4H expression compared with homozygous carriers of the wild-type 5 repeat allele (P = 0.03-0.0001). DNA methylation analysis of four CpG islands in a 1500 bp region encompassing the 5-LO promoter and the first approximately 100 bp of intron 1 revealed relatively low overall DNA methylation across all genotypes and leukocyte populations. However, analysis of the promoter repeats themselves demonstrated that, regardless of cell population, the 4 allele was methylated approximately twice as much as the 3 allele (P < 0.0001). Our results demonstrate that, in lymphocytes, the shorter repeat alleles of the 5-LO promoter lead to higher gene expression, which may be regulated through differential DNA methylation of the CpGs located within these repeats.

Genotyping the GGGCGG tandem repeat promoter polymorphism in the 5-lipoxygenase enzyme gene (ALOX5) by pyrosequencing assay

AIMS

Efficient genotyping methods for many biologically significant repeat genetic polymorphisms, particularly in GC-rich regions of the genome, are limited. In particular, a short tandem repeat polymorphism [GGCGGG] in the promoter region of ALOX5 has been implicated as an important marker for inflammatory diseases. We developed a pyrosequencing assay to genotype the ALOX5 short tandem repeat polymorphism using pyrosequencing technology that will make assessing this important genetic marker in large, diverse populations more accessible than using current methods.

MATERIALS AND METHODS

We used a nested polymerase chain reaction approach to amplify DNA for pyrosequencing. Population allele frequencies were assessed in two cohorts of previously collected human DNA samples with 188 and 1032 samples, respectively. Sixteen genetic samples with known genotypes were used to confirm the accuracy of the method.

RESULTS AND DISCUSSION

Genotypes were 100% concordant with samples of known genotype. Genotype frequencies in European American, Hispanic, and African American agreed with previously published results (wild-type homozygotes 66%, 64%, and 19%, respectively). The method presented here will facilitate both genetic association and pharmacogenomic research on this polymorphism in large samples that are ethnically and/or racially admixed.

Leukotriene pathway genetics and pharmacogenetics in allergy

Leukotrienes (LT) are biologically active lipid mediators known to be involved in allergic inflammation. Leukotrienes have been shown to mediate diverse features of allergic conditions including inflammatory cell chemotaxis/activation and smooth muscle contraction. Cysteinyl leukotrienes (LTC(4), LTD(4) and, LTE(4)) and the dihydroxy leukotriene LTB(4) are generated by a series of enzymes/proteins constituting the LT synthetic pathway or 5-lipoxygenase (5-LO) pathway. Their function is mediated by interacting with multiple receptors. Leukotriene receptor antagonists (LTRA) and LT synthesis inhibitors (LTSI) have shown clinical efficacy in asthma and more recently in allergic rhinitis. Despite growing knowledge of leukotriene biology, the molecular regulation of these inflammatory mediators remains to be fully understood. Genes encoding enzymes of the 5-LO pathway (i.e. ALOX5, LTC4S and LTA4H) and encoding for LT receptors (CYSLTR1/2 and LTB4R1/2) provide excellent candidates for disease susceptibility and severity; however, their role remains unclear. Preliminary data also suggest that 5-LO pathway/receptor gene polymorphism can predict patient responses to LTSI and LTRA; however, the exact mechanisms require elucidation. The aim of this review was to summarize the recent advances in the knowledge of these important mediators, focusing on genetic and pharmacogenetic aspects in the context of allergic phenotypes.

Functional variants of the human 5-lipoxygenase gene and their genetic diagnosis

Variants in the 5-lipoxygenase (ALOX5) gene are first-line candidate causes for interindividual differences in diseases where leukotrienes play a key role, e.g., inflammatory and immune diseases, atherosclerosis, asthma or the acute respiratory distress syndrome (ARDS). We developed and validated Pyrosequencing screening assays for single nucleotide polymorphism (dbSNP-IDs rs4986832, rs4987105, rs2115819, rs3740107, rs1565096, rs2291427, rs10571382, rs2242334, rs2229136, rs3802548), and a capillary electrophoresis assay for the ALOX5 Sp1/Egr1 promoter tandem repeat polymorphism. This selection spans the whole ALOX5 gene range and includes all variants with reported functional associations. A gene structure analysis in DNAs from 187 healthy unrelated Caucasians revealed two haploblocks, one in the promoter and one spanning six SNPs from rs3740107G>A in intron 6 to rs2229136A>G in exon 13. The five-repeat genotype was the most frequent Sp1/Egr1 promoter tandem repeat variant (allelic frequency 84%). These assays and analyses provide a solid basis for future assessments of the genetic modulation of leukotriene production.

What do we know about the genetics of aspirin intolerance?

Although acetylsalicylic acid is prescribed for a broad range of diseases, it can induce a wide array of clinically recognized hypersensitivity reactions, including aspirin-intolerant asthma (AIA) with rhinitis and aspirin-intolerant urticaria (AIU) with anaphylaxis. Altered eicosanoid metabolism is the generally accepted mechanism of aspirin intolerance; the overproduction of cysteinyl leucotrienes has been suggested to play a causative role in both AIA and AIU. Genetic markers suggested for AIA include HLA-DPBI*0301, leucotriene C4 synthase (LTC4S), ALOX5, CYSLT, PGE2, TBXA2R and TBX21. Similarly, HLA-DB1*0609, ALOX5, FCER1A and HNMT have been identified as possible genetic markers for AIU. An additional low-risk genetic marker for AIA is MS4A2, which encodes the beta-chain of FCER1. Other single and sets of two or more interacting genetic markers are currently being investigated. Analyses of the genetic backgrounds of patients with AIA and AIU will promote the development of early diagnostic and therapeutic interventions, which may reduce the incidence of AIA and AIU.

A network biology model of micronutrient related health

Micronutrients are involved in specific biochemical pathways and have dedicated functions in the body, but they are also interconnected in complex metabolic networks, such as oxidative-reductive and inflammatory pathways and hormonal regulation, in which the overarching function is to optimise health. Post-genomic technologies, in particular metabolomics and proteomics, both of which are appropriate for plasma samples, provide a new opportunity to study the metabolic effects of micronutrients in relation to optimal health. The study of micronutrient-related health status requires a combination of data on markers of dietary exposure, markers of target function and biological response, health status metabolites, and disease parameters. When these nutrient-centred and physiology/health-centred parameters are combined and studied using a systems biology approach with bioinformatics and multivariate statistical tools, it should be possible to generate a micronutrient phenotype database. From this we can explore external factors that define the phenotype, such as lifestage and lifestyle, and the impact of genotype, and the results can also be used to define micronutrient requirements and provide dietary advice. New mechanistic insights have already been developed using biological network models, for example genes and protein-protein interactions in the aetiology of type 2 diabetes mellitus. It is hoped that the challenge of applying this approach to micronutrients will, in time, result in a change from micronutrient oriented to a health oriented views and provide a more holistic understanding of the role played by multiple micronutrients in the maintenance of homeostasis and prevention of chronic disease, for example through their involvement in oxidation and inflammation.

Pharmacogenetics of asthma

Asthma is a common disease characterized by airway inflammation and bronchorestriction. There are several common categories of medications for treating asthma; however, not all asthmatics have the same response to these medications, some of which are adverse responses that are potentially life threatening. Because interindividual responses to asthma medications can vary considerably, the potential for genetic contributions to variable drug responses is significant. This chapter reviews the most common biological pathways targeted by asthma therapy and briefly discusses the genetic contribution to varied responses to asthma therapy for four common types of asthma medications: beta-agonists, anticholinergics, leukotriene modifiers, and corticosteroids.

CysLTR1 promoter polymorphism and requirement for leukotriene receptor antagonist in aspirin-intolerant asthma patients

OBJECTIVES

Leukotriene receptor antagonists (LTRA), such as montelukast, have been used as a first-line treatment for patients with aspirin-intolerant asthma (AIA). This study evaluated associations between the clinical requirement for LTRA and genetic polymorphisms of the ALOX5, LTC4S, COX-2, CysLTR1 and TBXA2R genes in the arachidonic acid cascade in the long-term management of 89 AIA patients from a Korean population.

METHODS

Asthma control status was monitored for 1 year with maintenance medications of inhaled corticosteroid and oral LTRA, and AIA patients were classified into three groups according to the mean montelukast dose required per month to maintain asthma control for 1 year: group I (> or = 200 mg montelukast/month; n = 37), group II (5-150 mg/month; n = 25) and group III (< 5 mg/month; n = 27). Genetic polymorphisms in the arachidonic acid cascade were determined using a single-base extension method.

RESULTS

We found that there was a significant difference in the genotype frequency of the CysLTR1 promoter polymorphism -634C > T among the three groups (p = 0.007 for group I vs group II, p = 0.017 for group I vs group III), while there were no significant associations between LTRA requirements and polymorphisms of the other genes. The patients with the variant genotype (CT or TT) of the -634C = T CysLTR1 promoter polymorphism showed a higher expression level than those with the common genotype (CC).

CONCLUSION

These findings indicate that the CysLTR1 promoter polymorphism is a useful genetic marker for predicting LTRA requirements in the long-term management of AIA patients.

Association of four-locus gene interaction with aspirin-intolerant asthma in Korean asthmatics

INTRODUCTION

Aspirin-intolerant asthma (AIA), a major clinical presentation of aspirin hypersensitivity, affects 10% of adult asthmatics. The genetic risk factors involved in the susceptibility to AIA have recently been investigated, but multilocus single-nucleotide polymorphisms (SNPs) associated with this susceptibility has not been evaluated.

METHODS

We examined 246 asthmatic patients: 94 having aspirin intolerance and 152 having aspirin tolerance. We selected 23 SNPs of 13 candidate genes and genotyped each SNP using a primer extension method. Multilocus genetic interactions were examined using multifactor dimensionality reduction (MDR) to test all multilocus SNP combinations to identify a useful SNP set for predicting the AIA phenotype.

RESULTS

We identified the best model using the MDR method, which consisted of a four-locus gene-gene interaction with 65.16% balanced accuracy and a cross-validation consistency of 70% in predicting AIA disease risk among asthmatic patients. This model included four SNPs such as B2ADR 46A>G, CCR3-520T>G, CysLTR1-634C>T, and FCER1B-109T>C.

DISCUSSION

These results suggest that a multilocus SNP acts in combination to influence the susceptibility to aspirin intolerance in asthmatics and could be a useful genetic marker for the diagnosis of AIA.

Pharmacogenetics of aspirin-intolerant asthma

Leukotriene overproduction is the major characteristic of aspirin-intolerant asthma (AIA). Most studies examining the molecular genetic mechanisms of AIA have focused on leukotriene-related genes, including ALOX5, LTC4S, TXA2R and prostanoid-receptor genes. One study suggested that the human leukocyte antigen (HLA) allele DPB1*0301 may be a genetic marker for the AIA phenotype in European and Asian populations, and HLA-DPB1*0301 has been suggested as a useful genetic marker for predicting more favorable responders to leukotriene-receptor antagonists for long-term management of AIA. Although several reports have indicated possible associations between genetic polymorphisms and variable responses to leukotriene modifiers in nonaspirin sensitive asthmatic patients, few have suggested relationships between such genetic polymorphisms and variable responses to asthma drugs in AIA patients.

Cysteinyl-leukotrienes and their receptors in asthma and other inflammatory diseases: critical update and emerging trends

Cysteinyl-leukotrienes (cysteinyl-LTs), that is, LTC4, LTD4, and LTE4, trigger contractile and inflammatory responses through the specific interaction with G protein-coupled receptors (GPCRs) belonging to the purine receptor cluster of the rhodopsin family, and identified as CysLT receptors (CysLTRs). Cysteinyl-LTs have a clear role in pathophysiological conditions such as asthma and allergic rhinitis (AR), and have been implicated in other inflammatory conditions including cardiovascular diseases, cancer, atopic dermatitis, and urticaria. Molecular cloning of human CysLT1R and CysLT2R subtypes has confirmed most of the previous pharmacological characterization and identified distinct expression patterns only partially overlapping. Interestingly, recent data provide evidence for the immunomodulation of CysLTR expression, the existence of additional receptor subtypes, and of an intracellular pool of CysLTRs that may have roles different from those of plasma membrane receptors. Furthermore, genetic variants have been identified for the CysLTRs that may interact to confer risk for atopy. Finally, a crosstalk between the cysteinyl-LT and the purine systems is being delineated. This review will summarize and attempt to integrate recent data derived from studies on the molecular pharmacology and pharmacogenetics of CysLTRs, and will consider the therapeutic opportunities arising from the new roles suggested for cysteinyl-LTs and their receptors.

Association between polymorphisms in prostanoid receptor genes and aspirin-intolerant asthma

BACKGROUND

Genetic predisposition is linked to the pathogenesis of aspirin-intolerant asthma. Most candidate gene approaches have focused on leukotriene-related pathways, whereas there have been relatively few studies evaluating the effects of polymorphisms in prostanoid receptor genes on the development of aspirin-intolerant asthma. Therefore, we investigated the potential association between prostanoid receptor gene polymorphisms and the aspirin-intolerant asthma phenotype.

METHODS

We screened for genetic variations in the prostanoid receptor genes PTGER1, PTGER2, PTGER3, PTGER4, PTGDR, PTGIR, PTGFR, and TBXA2R using direct sequencing, and selected 32 tagging single nucleotide polymorphisms among the 77 polymorphisms with frequencies >0.02 based on linkage disequilibrium for genotyping. We compared the genotype distributions and allele frequencies of three participant groups (108 patients with aspirin-intolerant asthma, 93 patients with aspirin-tolerant asthma, and 140 normal controls).

RESULTS

Through association analyses studies of the 32 single nucleotide polymorphisms, the following single nucleotide polymorphisms were found to have significant associations with the aspirin-intolerant asthma phenotype: -616C>G (P=0.038) and -166G>A (P=0.023) in PTGER2; -1709T>A (P=0.043) in PTGER3; -1254A>G (P=0.018) in PTGER4; 1915T>C (P=0.015) in PTGIR; and -4684C>T (P=0.027), and 795T>C (P=0.032) in TBXA2R. In the haplotype analysis of each gene, the frequency of PTGIR ht3[G-G-C-C], which includes 1915T>C, differed significantly between the aspirin-intolerant asthma patients and aspirin-tolerant asthma patients (P=0.015).

CONCLUSION

These findings suggest that genetic polymorphisms in PTGER2, PTGER3, PTGER4, PTGIR, and TBXA2R play important roles in the pathogenesis of aspirin-intolerant asthma.

Promoter polymorphism G-50T of a human CYP2J2 epoxygenase gene is associated with common susceptibility to asthma

BACKGROUND

Cytochrome P-450 2J2 (CYP2J2) has recently been shown to be an important enzyme in the metabolism of epoxygenase-derived eicosanoids that play important functional roles in pulmonary physiology and may contribute to the pathogenesis of asthma.

STUDY OBJECTIVE

The focus of our pilot study was to evaluate whether common polymorphism G-50T within the proximal promoter of human CYP2J2 gene is associated with the susceptibility to bronchial asthma.

DESIGN AND PARTICIPANTS

A total of 429 unrelated Russian subjects were recruited in this case-control study, including 215 sex-matched and age-matched patients with asthma and 214 healthy control subjects. The blood samples were analyzed for genetic polymorphism G-50T in the CYP2J2 gene by polymerase chain reaction followed by restriction fragment length polymorphism analysis.

RESULTS

The frequency of variant allele -50T of the CYP2J2 gene was significantly higher in asthmatic patients than in healthy subjects (odds ratio [OR], 5.04; 95% confidence interval [CI], 1.99 to 12.77; p = 0.0003). In addition, the heterozygous genotype -50GT of the CYP2J2 gene was found to be significantly associated with susceptibility to allergic asthma (OR, 5.40; 95% CI, 2.05 to 14.26; p = 0.0003) as well as nonallergic asthma (OR, 5.77; 95% CI, 1.84 to 18.10; p = 0.004). The associations of the CYP2J2 gene G-50T polymorphism with asthma remained significant after adjustment for age and gender using multiple logistic regression analysis.

CONCLUSIONS

Our data demonstrate for the first time that the CYP2J2 gene might be considered as a novel candidate gene for common susceptibility to asthma and highlight the importance of the P-450 epoxygenase pathway of metabolism of arachidonic acid in the pathogenesis of the disease.

Pathogenesis of nonsteroidal antiinflammatory drug-induced asthma

PURPOSE OF REVIEW

To summarize recent findings related to the pathogenic mechanisms of aspirin-induced asthma with emphasis on molecular genetic mechanisms.

RECENT FINDINGS

The overproduction of cysteinyl leukotrienes with the increased expression of cysteinyl leukotriene receptor 1 (CYSLTR1) is a consistent finding in aspirin-induced asthma patients. Recent data have suggested a dysregulation of cyclooxygenase-2 and prostaglandin E2, increased levels of 15-hydroxyeicosatetranoic acid, and decreased lipoxin generation as characteristics of the condition. The HLA allele DPB10301 was documented as a strong genetic marker for susceptibility in an Asian population. Leukotriene C4 synthase has been established as a key genetic determinant of aspirin-induced asthma, but recent studies have demonstrated that several single nucleotide polymorphisms in the promoters of prostaglandin E2 receptor subtype 2, CYSLTR1 and CYSLTR2 and T-box expressed in T cells (TBX21) could increase risk for the condition. Although cyclooxygenase-2 and thromboxane A2 receptor polymorphisms were not associated with aspirin-induced asthma phenotype, they may exert functional effects.

SUMMARY

The identification of genetic markers for aspirin-induced asthma susceptibility along with in-vitro functional studies would help to elucidate the pathogenesis of the condition. Further studies of the interactions among genes and between genes and the environment will be essential.

Determination of structure and transcriptional regulation of CYSLTR1 and an association study with asthma and rhinitis

Pharmacologic studies have revealed that cysteinyl leukotrienes (CYSLTs) act through two receptors, cysteinyl leukotriene receptor 1 (CYSLTR1) and CYSLTR2. CYSLTR1 antagonists are widely used to treat asthma and rhinitis. In this study, we characterized the genomic structure and transcriptional regulation of CYSLTR1 and examined associations between CYSLTR1 polymorphisms and asthma/rhinitis. The experiment of rapid amplification of cDNA end revealed that CYSLTR1 contains three exons and that the entire open reading frame is located in exon 3. Reverse transcriptase-polymerase chain reaction showed that there were multiple splice variants of CYSLTR1 and that the transcript expression patterns differed from tissues and cell types. The promoter region of CYSLTR1 is from -665 to -30 bp relative to the transcription start site. We identified four polymorphisms (c.-618-434T/C, c.-618-275C/A, c.-618-136G/A, and 927C/T), and transmission disequilibrium tests revealed that none of these polymorphisms was associated with the development of asthma/rhinitis. However, the TCG and CAA haplotypes in the promoter region caused different transcriptional activity. Our findings indicate that CYSLTR1 polymorphisms are not likely to be involved in the development of asthma/rhinitis, but it is possible that these polymorphisms could influence drug responses in individuals with atopic diseases.

Genetic markers for differentiating aspirin-hypersensitivity

Aspirin-induced asthma (AIA) and aspirin-induced urticaria/ angioedema (AIU) are two major aspirin-related allergies. We summarize recent findings related to their molecular genetic mechanisms in order to identify genetic susceptibility markers for differentiating AIU and AIA. The overproduction of cysteinyl leukotriene has been suggested as a mechanism in both AIU and AIA. Increased expression of CYSLTR1 with CYLSTR1 and CYSLTR2 polymorphisms are new findings in AIA, while the ALOX5 promoter polymorphism has been noted in AIU. An HLA study suggested that DPB1*0301 is a strong genetic marker for AIA, and that HLA DRB1*1302 and DQB1*0609 are markers for AIU susceptibility. Several single nucleotide polymorphisms (SNPs) in the promoters of EP2, TBX21, COX-2, Fc epsilon RIbeta, and TBXA2R were associated with AIA, while an Fc epsilon RIalpha promoter polymorphism was associated with AIU. The functional studies of the key genes involved in AIA and AIU are summarized. The identification and functional study of genetic markers for AIA and AIU susceptibility would further elucidate the pathogenic mechanisms and facilitate the development of early diagnostic markers to establish therapeutic targets.

Lack of an association between a newly identified promoter polymorphism (-1702G > A) of the leukotriene C4 synthase gene and aspirin-intolerant asthma in a Korean population

Aspirin-intolerant asthma (AIA) is a distinct clinical syndrome that refers to the development of bronchoconstriction in asthmatic individuals following the ingestion of aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs). It is widely recognized that increased cysteinyl leukotriene (cysLT) biosynthesis is associated with the development and progression of AIA. Leukotriene C4 synthase (LTC4S) is the terminal enzyme in cysLT production and is a strong candidate gene in the pathogenesis of aspirin-intolerant asthma (AIA). In this paper, we report a new single nucleotide polymorphism (SNP) of the LTC4S promoter, -1702G>A, in AIA patients and evaluate its genetic role in the association with the LTC4S-444 A>C polymorphism. We enrolled 110 AIA patients, 125 aspirin-tolerant asthma (ATA) patients, and 125 normal controls. SNP genotyping of the LTC4S-1702G>A and -444A>C polymorphisms was performed using SNP-IT assays. Haplotype analyses were performed using Haploview version 2.05, which is based on an estimation-maximization (EM) algorithm. There were no significant differences in the allele or genotype frequencies of the LTC4S-1702G>A and -444A>C polymorphisms among the three groups (p > 0.05), with no significant differences in the observed haplotype frequencies (p > 0.05). Moreover, no significant associations were found between the genotype of each SNP in AIA patients with the clinical characteristics, including a forced expiratory volume in one second (FEV1) %, a provocation concentration of methacholine to induce more than 20% decrease of FEV1 (PC20) to methacholine, and serum total IgE levels (p > 0.05). These results indicate that there is no association between these two promoter polymorphisms of LTC4S and the phenotype of AIA in a Korean population.

ALOX5 promoter genotype, asthma severity and LTC production by eosinophils

BACKGROUND

The number of Sp1-Egr1 binding tandem repeats at the ALOX5 promoter influences gene transcription and may modify the response to anti-leukotriene treatment. The relationship of ALOX5 variants to asthma severity and leukotriene production by eosinophils is unknown.

OBJECTIVE

To characterize ALOX5 mRNA expression and cysteinyl-leukotriene production by eosinophils from individuals bearing ALOX5 promoter deletional variants and their association with the severity of childhood asthma.

METHODS

Eosinophils from adult asthmatics bearing only variant alleles (with other than five tandem repeats on both chromosomes, non5/non5) or no variant alleles (5/5) were cultured in vitro and ALOX5 expression and leukotriene secretion were measured. A total of 621 children with mild or moderate-severe asthma were genotyped at the ALOX5 core promoter.

RESULTS

Asthmatics with non5/non5 genotype expressed less ALOX5 mRNA and produced less LTC4 into culture supernatants than 5/5 individuals (6.4 +/- 2.0 and 20.0 +/- 5.0 pg/ml, n = 5; P < 0.05). More asthmatic children bearing non5/non5 genotype had moderate-severe asthma than children with the 5/5 genotype (5.3% vs. 1.4%, P = 0.008). Multivariate logistic regression identified ALOX5 promoter genotype as a significant predictor of disease severity (OR = 3.647, 95% CI: 1.146-11.608, P = 0.03). Consistent with these findings, children bearing the non5/non5 genotype had greater bronchomotor response to exercise as measured by the maximum fall after exercise and the area under the exercise curve (P < 0.05 for both).

CONCLUSION

Our results suggest that children who express the asthma phenotype despite having a genetic variant that impairs their ability to express ALOX5 have more severe disease and thus are more likely to have asthma symptoms.

Influence of leukotriene pathway polymorphisms on response to montelukast in asthma

RATIONALE

Interpatient variability in montelukast response may be related to variation in leukotriene pathway candidate genes.

OBJECTIVE

To determine associations between polymorphisms in leukotriene pathway candidate genes with outcomes in patients with asthma receiving montelukast for 6 mo who participated in a clinical trial.

METHODS

Polymorphisms were typed using Sequenom matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass array spectrometry and published methods; haplotypes were imputed using single nucleotide polymorphism-expectation maximization (SNP-EM). Analysis of variance and logistic regression models were used to test for changes in outcomes by genotype. In addition, chi(2) and likelihood ratio tests were used to test for differences between groups. Case-control comparisons were analyzed using the SNP-EM Omnibus likelihood ratio test.

MEASUREMENTS

Outcomes were asthma exacerbation rate and changes in FEV(1) compared with baseline.

RESULTS

DNA was collected from 252 participants: 69% were white, 26% were African American. Twenty-eight SNPs in the ALOX5, LTA4H, LTC4S, MRP1, and cysLT1R genes, and an ALOX5 repeat polymorphism were successfully typed. There were racial disparities in allele frequencies in 17 SNPs and in the repeat polymorphism. Association analyses were performed in 61 whites. Associations were found between genotypes of SNPs in the ALOX5 (rs2115819) and MRP1 (rs119774) genes and changes in FEV(1) (p < 0.05), and between two SNPs in LTC4S (rs730012) and in LTA4H (rs2660845) genes for exacerbation rates. Mutant ALOX5 repeat polymorphism was associated with decreased exacerbation rates. There was strong linkage disequilibrium between ALOX5 SNPs. Associations between ALOX5 haplotypes and risk of exacerbations were found.

CONCLUSIONS

Genetic variation in leukotriene pathway candidate genes contributes to variability in montelukast response.