Egr-1 and Sp1 interact functionally with the 5-lipoxygenase promoter and its naturally occurring mutants

Role of arachidonic acid lipoxygenase pathway in Asthma

The arachidonic acid (AA) metabolism pathways play a key role in immunological response and inflammation diseases, such as asthma, etc. AA in cell membranes can be metabolized by lipoxygenases (LOXs) to a screen of bioactive substances that include leukotrienes (LTs), lipoxins (LXs), and eicosatetraenoic acids (ETEs), which are considered closely related to the pathophysiology of respiratory allergic disease. Studies also verified that drugs regulating AA LOXs pathway have better rehabilitative intervention for asthma. This review aims to summarize the physiological and pathophysiological importance of AA LOXs metabolism pathways in asthma and to discuss its prospects of therapeutic strategies.

Analysis of proximal ALOX5 promoter binding proteins by quantitative proteomics

5-Lipoxygenase (5-LO) is the initial enzyme in the biosynthesis of leukotrienes, which are mediators involved in pathophysiological conditions such as asthma and certain cancer types. Knowledge of proteins involved in 5-LO pathway regulation, including gene regulatory proteins, is needed to evaluate all options for therapeutic intervention in these diseases. Here, we present a mass spectrometric screening of ALOX5 promoter-interacting proteins, obtained by DNA pulldown and label-free quantitative mass spectrometry. Protein preparations from myeloid and B-lymphocytic cell lines were screened for promoter DNA interactors. Through statistical analysis, 66 proteins were identified as specific ALOX5 promotor binding proteins. Among those, the 15 most likely candidates for a prominent role in ALOX5 gene regulation are the known ALOX5 interactors Sp1 and Sp3, the related factor Sp2, two Krüppel-like factors (KLF13 and KLF16) and six other zinc finger proteins (MAZ, PRDM10, VEZF1, ZBTB7A, ZNF281 and ZNF579). Intriguingly, we also identified two helicases (BLM and DHX36) and the proteins hnRNPD and hnRNPK, which are, together with the protein MAZ, known to interact with DNA G-quadruplex structures. As G-quadruplexes are implicated in gene regulation, spectroscopic and antibody-based methods were used to confirm their presence within the GC-rich sequence of the ALOX5 promoter. In summary, we have systematically characterized the interactome of the ALOX5 promoter, identifying several zinc finger proteins as novel potential ALOX5 gene regulators. Further, we have shown that the ALOX5 promoter can form DNA G-quadruplex structures, which may play a functional role in ALOX5 gene regulation.

5-Lipoxygenase as a drug target: A review on trends in inhibitors structural design, SAR and mechanism based approach

The most common inflammatory disease of the airways is asthma among children affecting around 235 million people worldwide. 5-Lipoxygenase (5-LOX) is a crucial enzyme which helps in the conversion of arachidonic acid (AA) to leukotrienes (LTs), the lipid mediators. It is associated with several inflammation related disorders such as asthma, allergy, and atherosclerosis. Therefore, it is considered as a promising target against inflammation and asthma. Currently, the only drug against 5-LOX which is available is Zileuton, while a few inhibitors are in clinical trial stages such as Atreleuton and Setileuton. So, there is a dire requirement in the area of progress of novel 5-LOX inhibitors which necessitates an understanding of their structure activity relationship and mode of action. In this review, novel 5-LOX inhibitors reported so far, their structural design, SAR and developmental strategies along with clinical updates are discussed over the last two decades.

Biosynthesis of proresolving lipid mediators by vascular cells and tissues

Recent evidence suggests that specialized proresolving lipid mediators (SPMs) generated from docosahexaenoic acid (DHA) can modulate the vascular injury response. However, cellular sources for these autacoids within the vessel wall remain unclear. Here, we investigated whether isolated vascular cells and tissues can produce SPMs and assessed expression and subcellular localization of the key SPM biosynthetic enzyme 5-lipoxygenase (LOX) in vascular cells. Intact human arteries incubated with DHA ex vivo produced 17-hydroxy DHA (17-HDHA) and D-series resolvins, as assessed by liquid chromatography-tandem mass spectrometry. Addition of 17-HDHA to human arteries similarly increased resolvin production. Primary cultures of human saphenous vein endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) converted 17-HDHA to SPMs, including resolvin D1 (RvD1) and other D-series resolvins and protectins. This was accompanied by a rapid translocation of 5-LOX from nucleus to cytoplasm in both ECs and VSMCs, potentially facilitating SPM biosynthesis. Conditioned medium from cells exposed to 17-HDHA inhibited monocyte adhesion to TNF-α-stimulated EC monolayers. These downstream effects were partially reversed by antibodies against the RvD1 receptors ALX/FPR2 and GPR32. These results suggest that autocrine and/or paracrine signaling via locally generated SPMs in the vasculature may represent a novel homeostatic mechanism of relevance to vascular health and disease.-Chatterjee, A., Komshian, S., Sansbury, B. E., Wu, B., Mottola, G., Chen, M., Spite, M., Conte, M. S. Biosynthesis of proresolving lipid mediators by vascular cells and tissues.

Cysteinyl Leukotrienes Pathway Genes, Atopic Asthma and Drug Response: From Population Isolates to Large Genome-Wide Association Studies

Genetic variants associated with asthma pathogenesis and altered response to drug therapy are discussed. Many studies implicate polymorphisms in genes encoding the enzymes responsible for leukotriene synthesis and intracellular signaling through activation of seven transmembrane domain receptors, such as the cysteinyl leukotriene 1 (CYSLTR1) and 2 (CYSLTR2) receptors. The leukotrienes are polyunsaturated lipoxygenated eicosatetraenoic acids that exhibit a wide range of pharmacological and physiological actions. Of the three enzymes involved in the formation of the leukotrienes, arachidonate 5 lipoxygenase 5 (ALOX5), leukotriene C4 synthase (LTC4S), and leukotriene hydrolase (LTA4H) are all polymorphic. These polymorphisms often result in variable production of the CysLTs (LTC4, LTD4, and LTE4) and LTB4. Variable number tandem repeat sequences located in the Sp1-binding motif within the promotor region of the ALOX5 gene are associated with leukotriene burden and bronchoconstriction independent of asthma risk. A 444A > C SNP polymorphism in the LTC4S gene, encoding an enzyme required for the formation of a glutathione adduct at the C-6 position of the arachidonic acid backbone, is associated with severe asthma and altered response to the CYSLTR1 receptor antagonist zafirlukast. Genetic variability in the CysLT pathway may contribute additively or synergistically to altered drug responses. The 601 A > G variant of the CYSLTR2 gene, encoding the Met201Val CYSLTR2 receptor variant, is associated with atopic asthma in the general European population, where it is present at a frequency of ∼2.6%. The variant was originally found in the founder population of Tristan da Cunha, a remote island in the South Atlantic, in which the prevalence of atopy is approximately 45% and the prevalence of asthma is 36%. In vitro work showed that the atopy-associated Met201Val variant was inactivating with respect to ligand binding, Ca²⁺ flux and inositol phosphate generation. In addition, the CYSLTR1 gene, located at Xq13-21.1, has been associated with atopic asthma. The activating Gly300Ser CYSLTR1 variant is discussed. In addition to genetic loci, risk for asthma may be influenced by environmental factors such as smoking. The contribution of CysLT pathway gene sequence variants to atopic asthma is discussed in the context of other genes and environmental influences known to influence asthma.

Genetic variants in TNFα, TGFB1, PTGS1 and PTGS2 genes are associated with diisocyanate-induced asthma

Diisocyanates are the most common cause of occupational asthma, but risk factors are not well defined. A case-control study was conducted to investigate whether genetic variants in inflammatory response genes (TNFα, IL1α, IL1β, IL1RN, IL10, TGFB1, ADAM33, ALOX-5, PTGS1, PTGS2 and NAG-1/GDF15) are associated with increased susceptibility to diisocyanate asthma (DA). These genes were selected based on their role in asthmatic inflammatory processes and previously reported associations with asthma phenotypes. The main study population consisted of 237 Caucasian French Canadians from among a larger sample of 280 diisocyanate-exposed workers in two groups: workers with specific inhalation challenge (SIC) confirmed DA (DA(+), n = 95) and asymptomatic exposed workers (AW, n = 142). Genotyping was performed on genomic DNA, using a 5' nuclease PCR assay. After adjusting for potentially confounding variables of age, smoking status and duration of exposure, the PTGS1 rs5788 and TGFB1 rs1800469 single nucleotide polymorphisms (SNP) showed a protective effect under a dominant model (OR = 0.38; 95% CI = 0.17, 0.89 and OR = 0.38; 95% CI = 0.18, 0.74, respectively) while the TNFα rs1800629 SNP was associated with an increased risk of DA (OR = 2.08; 95% CI = 1.03, 4.17). Additionally, the PTGS2 rs20417 variant showed an association with increased risk of DA in a recessive genetic model (OR = 6.40; 95% CI = 1.06, 38.75). These results suggest that genetic variations in TNFα, TGFB1, PTGS1 and PTGS2 genes contribute to DA susceptibility.

Evolutionary aspects of lipoxygenases and genetic diversity of human leukotriene signaling

Leukotrienes are pro-inflammatory lipid mediators, which are biosynthesized via the lipoxygenase pathway of the arachidonic acid cascade. Lipoxygenases form a family of lipid peroxidizing enzymes and human lipoxygenase isoforms have been implicated in the pathogenesis of inflammatory, hyperproliferative (cancer) and neurodegenerative diseases. Lipoxygenases are not restricted to humans but also occur in a large number of pro- and eucaryotic organisms. Lipoxygenase-like sequences have been identified in the three domains of life (bacteria, archaea, eucarya) but because of lacking functional data the occurrence of catalytically active lipoxygenases in archaea still remains an open question. Although the physiological and/or pathophysiological functions of various lipoxygenase isoforms have been studied throughout the last three decades there is no unifying concept for the biological importance of these enzymes. In this review we are summarizing the current knowledge on the distribution of lipoxygenases in living single and multicellular organisms with particular emphasis to higher vertebrates and will also focus on the genetic diversity of enzymes and receptors involved in human leukotriene signaling.

Genomic perspectives in inter-individual adverse responses following nanomedicine administration: The way forward

The underlying mechanism of intravenous infusion-related adverse reactions inherent to regulatory-approved nanomedicines still remains elusive. There are substantial inter-individual differences in observed adverse reactions, which may include cardiovascular, broncho-pulmonary, muco-cutaneous, neuro-psychosomatic and autonomic manifestations. Although nanomedicine-mediated triggering of complement activation has been suggested to be a significant contributing factor to these adverse events, complement activation may still proceed in non-responders. Whether these reactions share similar immunological mechanisms and underpinning genetic factors with drug hypersensitivity syndrome remains to be investigated. Genetic association studies could be a powerful tool to dissect causative factors and reveal the multiple molecular pathways that induce infusion related adverse reactions. It is envisaged that such research may lead to the design of reliable in vitro profiling tests for risk assessment and treatment decisions, thereby revolutionizing the practice of medicine with nanopharmaceuticals. Such procedures may further improve regulatory approval processes for nanomedicines currently in the pipeline and decrease the overall cost of health care. Here we discuss some key innate immunity genes and their polymorphisms in relation to nanomedicine infusion-mediated symptomatic responses.

Arachidonate 5 lipoxygenase expression in papillary thyroid carcinoma promotes invasion via MMP-9 induction

Arachidonate 5-lipoxygenase (ALOX5) expression and activity has been implicated in tumor pathogenesis, yet its role in papillary thyroid carcinoma (PTC) has not been characterized. ALOX5 protein and mRNA were upregulated in PTC compared to matched, normal thyroid tissue, and ALOX5 expression correlated with invasive tumor histopathology. Evidence suggests that PTC invasion is mediated through the induction of matrix metalloproteinases (MMPs) that can degrade and remodel the extracellular matrix (ECM). A correlation between MMP-9 and ALOX5 protein expression was established by immunohistochemical analysis of PTC and normal thyroid tissues using a tissue array. Transfection of ALOX5 into a PTC cell line (BCPAP) increased MMP-9 secretion and cell invasion across an ECM barrier. The ALOX5 product, 5(S)-hydroxyeicosatetraenoic acid also increased MMP-9 protein expression by BCPAP in a dose-dependent manner. Inhibitors of MMP-9 and ALOX5 reversed ALOX5-enhanced invasion. Here we describe a new role for ALOX5 as a mediator of invasion via MMP-9 induction; this ALOX5/MMP9 pathway represents a new avenue in the search for functional biomarkers and/or potential therapeutic targets for aggressive PTC.

Association of Sp1 tandem repeat polymorphism of ALOX5 with coronary artery disease in Indian subjects

Lipoxygenases have been implicated in the pathogenesis of coronary artery disease (CAD) for its potent proinflammatory role. The Sp1 addition/deletion polymorphism in promoter region of the 5-lipoxygenase gene (ALOX5) has been associated with increased risk of carotid atherosclerosis and myocardial infarction. To determine the role of this polymorphism in our population we performed a case-control-genetic association study on 117 healthy controls and 119 angiographically verified CAD patients. Biochemical analysis was performed using standard automated assays. High-density lipoprotein cholesterol (HDL-C) and LDL-C subfraction levels were estimated using precipitation methods. Genotyping of polymorphism in the ALOX5 (Sp1 variants) was done using PCR-based heteroduplex analysis and automated sequencing. The Sp1 promoter repeat variants were found to be associated with CAD (p < 0.0001, OR = 4.47, 95% confidence interval = 2.58-7.74). Furthermore, the 5/5 genotype of the ALOX5 polymorphism in the healthy subjects was found to be associated with elevated HDL-C (p= 0.004), HDL(3) -C (p= 0.04), apo A1 (p= 0.011) and sdLDL (p= 0.001). We conclude that this polymorphism influences LDL and HDL subfraction levels and is a risk factor for CAD in our population. Clin Trans Sci 2012; Volume 5: 408-411.

Transcriptional regulation of the human FPR2/ALX gene: evidence of a heritable genetic variant that impairs promoter activity

Lipoxin (LX) A(4,) a main endogenous stop-signal of inflammation, activates the G-protein-coupled receptor FPR2/ALX, which triggers potent anti-inflammatory signaling in vivo. Thus, the regulation of FPR2/ALX expression may have pathophysiological and therapeutic relevance. Here, we mapped a nucleotide sequence with strong FPR2/ALX promoter activity. Chromatin immunoprecipitation revealed specificity protein 1 (Sp1) binding to the core promoter. Site-directed mutagenesis of the Sp1 cis-acting element and Sp1 overexpression established that this transcription factor is key for maximal promoter activity, which is instead suppressed by DNA methylation. LXA(4) enhanced FPR2/ALX promoter activity (+74%) and mRNA expression (+87.5%) in MDA-MB231 cells. A single nucleotide mutation (A/G) was detected in the core promoter of one subject with history of cardiovascular disease and of his two daughters. This mutation reduced by ∼35-90% the promoter activity in vitro. Moreover, neutrophils from individuals carrying the A/G variant displayed ∼10- and 3-fold reduction in FPR2/ALX mRNA and protein, respectively, compared with cells from their relatives or healthy volunteers expressing the wild-type allele. These results uncover FPR2/ALX transcriptional regulation and provide the first evidence of mutations that affect FPR2/ALX transcription, thus opening new opportunities for the understanding of the LXA(4)-FPR2/ALX axis in human disease.

Association of STR polymorphisms in CMA1 and IL-4 with asthma and atopy: the SAPALDIA cohort

Asthma is a chronic pulmonary disorder that is characterized by airway inflammation and bronchial hyperreactivity. Several genetic loci have been associated with asthma, and some of these associations have been replicated in independent studies. However, larger population-based replication studies for the association of short tandem repeat (STR) polymorphisms with asthma are limited. In this study, we investigated the association of STR polymorphisms in genes encoding mast cell chymase (CMA1), uteroglobin (UGB), tumor necrosis factor-α (TNF-α) and interleukin-4 (IL-4) with asthma and atopic phenotypes in the large population-based Swiss Cohort Study SAPALDIA. Our results show that the STR polymorphism in the CMA1 gene is associated with asthma and that this association is even stronger with atopic asthma. Similarly, we observed a weak association of the IL-4 2-allele with asthma that tended to be stronger for atopic asthma than for nonatopic asthma. This minor IL-4 2-allele was also associated with higher IgE levels, with a higher risk for a positive skin prick test and with a trend for a higher risk for bronchial hyperresponsiveness. These results support previous findings suggesting a role for CMA1 and IL-4 in atopic asthma and for IL-4 in atopy in general.

Placenta growth factor-induced early growth response 1 (Egr-1) regulates hypoxia-inducible factor-1alpha (HIF-1alpha) in endothelial cells

Leukotrienes, the lipid inflammatory products derived from arachidonic acid, are involved in the pathogenesis of respiratory and cardiovascular diseases and reactive airway disease in sickle cell disease. Placenta growth factor (PlGF), elaborated from erythroid cells, increased the mRNA expression of 5-lipoxygenase and 5-lipoxygenase-activating protein (FLAP) in human pulmonary microvascular endothelial cells. PlGF-induced both promoter activity and mRNA expression of hypoxia-inducible factor-1alpha (HIF-1alpha), which was abrogated by early growth response-1 (EGR-1) small interfering RNA. PlGF showed a temporal reciprocal relationship in the mRNA levels of EGR-1 and NAB2, the latter a repressor of Egr-1. Moreover, Nab2, but not mutant Nab2, significantly reduced promoter activity and mRNA expression of HIF-1alpha and also reduced expression of the HIF-1alpha target gene FLAP. Furthermore, overexpression of Egr-1 led to increased promoter activities for both HIF-1alpha and FLAP in the absence of PlGF. Additionally, the Egr-1-mediated induction of HIF-1alpha and FLAP promoters was reduced to basal levels by EGR-1 small interfering RNA. The binding of Egr-1 to HIF-1alpha promoter was corroborated by electrophoretic mobility shift assay and chromatin immunoprecipitation assay, which showed increased Egr-1 binding to the HIF-1alpha promoter in response to PlGF stimulation. These studies provide a novel mechanism for PlGF-mediated regulation of HIF-1alpha via Egr-1, which results in increased FLAP expression. This study provides a new therapeutic target, namely Egr-1, for attenuation of elevated leukotriene levels in patients with sickle cell disease and other inflammatory diseases.

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.

Pharmacogenetics and functional genomics in asthma

Asthma is a complex phenotype caused by a combination of genetic and environmental factors that remain poorly understood. The common variants involved in the pathogenesis of asthma have proved difficult to identify by candidate gene association studies. As a result, few genetic variants influencing clinical response to asthma and allergy medications have been uncovered. Recently, genome-wide association, which is more robust in identifying common predisposition variants, has been applied to disorders such as asthma. As genome-wide associations are hypothesis-free, they raise the possibility of identifying novel biological pathways that could be translated to the future benefit of patients through improved diagnostic and therapeutic measures in the form of personalized medicine. This review addresses both recent advances in the genetics of asthma and their potential in transforming the treatment of the disorder into more individualized care in the near future.

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.

Association of early growth response-1 gene polymorphisms with total IgE and atopy in asthmatic children

Early growth response-1 (Egr-1) is expressed in human airways and found to modulate tumor necrosis factor, immunoglobulin E (IgE), airway responsiveness, and interleukin-13-induced inflammation in mice. We investigated the effects of Chinese-tagging single nucleotide polymorphisms (SNPs) of Egr-1 on asthma traits in 298 Chinese asthmatic children and 175 controls, and a replication community cohort of 191 controls. Tag SNP (-4071 A-->G) and three additional SNPs (-1427 C-->T, -151 C-->T and IVS1 -42 C-->T) were genotyped by restriction fragment length polymorphism (RFLP). Significant associations were found between plasma total IgE concentration and -4071 A-->G (p = 0.008) and IVS1 -42 C-->T (p = 0.027) in asthmatic patients. After Bonferroni correction, only -4071 A-->G showed significant association. Multivariate regression analysis confirmed this significant association with a standardized coefficient beta of 0.156 (95% CI: 0.046-0.317; p = 0.009) in asthmatics among the three SNPs with age and gender-adjusted. In -4071 A-->G, IgE(log) was significantly higher in patients with the GG genotype than the AA genotype (p = 0.009). In addition, -4071 A-->G was significantly associated with atopy (p = 0.016) and high total IgE concentration (p = 0.030) among asthmatics. Patients with the G allele had a 3.5-fold risk of having atopy and a 2.0-fold risk of having high total IgE concentration than those homozygous for the A allele. This is the first report to show significant association of Egr-1 polymorphisms with plasma total IgE and atopy in asthmatics. It may help to explore the pharmacogenetics of Egr-1 inhibitors.

5-lipoxygenase and 5-lipoxygenase-activating protein gene polymorphisms, dietary linoleic acid, and risk for breast cancer

The n-6 polyunsaturated fatty acid 5-lipoxygenase pathway has been shown to play a role in the carcinogenesis of breast cancer. We conducted a population-based case-control study among Latina, African-American, and White women from the San Francisco Bay area to examine the association of the 5-lipoxygenase gene (ALOX5) and 5-lipoxygenase-activating protein gene (ALOX5AP) with breast cancer risk. Three ALOX5AP polymorphisms [poly(A) microsatellite, -4900 A>G (rs4076128), and -3472 A>G (rs4073259)] and three ALOX5 polymorphisms [Sp1-binding site (-GGGCGG-) variable number of tandem repeat polymorphism, -1279 G>T (rs6593482), and 760 G>A (rs2228065)] were genotyped in 802 cases and 888 controls. We did not find significant main effects of ALOX5 and ALOX5AP genotypes on breast cancer risk that were consistent across race or ethnicity; however, there was a significant interaction between the ALOX5AP -4900 A>G polymorphism and dietary linoleic acid intake (P=0.03). Among women consuming a diet high in linoleic acid (top quartile of intake, >17.4 g/d), carrying the AA genotype was associated with higher breast cancer risk (age- and race-adjusted odds ratio, 1.8; 95% confidence interval, 1.2-2.9) compared with carrying genotypes AG or GG. Among women consuming <or=17.4 g/d of linoleic acid, ALOX5AP -4900 genotype was not associated with breast cancer risk (age- and race-adjusted odds ratio, 0.9; 95% confidence interval, 0.7-1.2). These results support a role for n-6 polyunsaturated fatty acids in breast carcinogenesis and suggest that epidemiologic studies on dietary fat and breast cancer should take into account genetic predisposition related to n-6 polyunsaturated fatty acid metabolism.

Nutrigenetic association of the 5-lipoxygenase gene with myocardial infarction

BACKGROUND

5-Lipoxygenase (5-LO) catalyzes the rate-limiting step of the biosynthesis of proinflammatory leukotrienes from arachidonic acid (AA) and has been associated with atherosclerosis in animal models and humans. We previously reported that variants of a 5-LO promoter repeat polymorphism were associated with carotid atherosclerosis in humans, an effect that was exacerbated by high dietary AA but mitigated by high dietary n-3 fatty acids.

OBJECTIVE

We sought to confirm these initial observations with a more clinically relevant phenotype such as myocardial infarction (MI).

DESIGN

The 5-LO polymorphism was genotyped in 1885 Costa Rican case-control pairs and tested for association with MI. Functional experiments were carried out to determine whether the associated alleles had differences in mRNA expression.

RESULTS

The frequency of variant genotype groups did not differ significantly between cases and controls. However, a significant gene x diet interaction was observed, in which, relative to the common 5 repeat allele, the 3 and 4 alleles were associated with a higher MI risk in the high (> or = 0.25 g/d) dietary AA group (odds ratio: 1.31; 95% CI: 1.07, 1.61) and with a lower risk in the low (<0. 25 g/d) AA group (0.77; 0.63, 0.94) (P for interaction = 0.015). Using allele-specific quantitation, the short alleles had expression approximately twice that of the 5 allele (P < 0.0001).

CONCLUSIONS

The 3 and 4 variants lead to higher 5-LO expression and provide additional evidence that these alleles are associated with greater risks of atherosclerosis and MI in the context of a high-AA diet.

Proinflammatory role of leukocyte-derived Egr-1 in the development of murine postoperative ileus

BACKGROUND & AIMS

Early growth response gene-1 (Egr-1) is an important inflammatory transcription factor. We hypothesize that leukocyte-derived Egr-1 plays a key inflammatory role in causing postoperative ileus.

METHODS

Wild-type, Egr-1 knockout, and chimera mice (constructed by irradiation followed by injection with Egr-1(+/+) or Egr-1(-/-) bone marrow) were subjected to surgical manipulation of the gastrointestinal tract to induce ileus. Reverse-transcription polymerase chain reaction, Western blot, and immunohistochemistry quantified and localized Egr-1. Lumenal transit of nonabsorbable fluorescein isothiocyanate-labeled dextran and in vitro organ bath techniques measured functional gastrointestinal motility. Inflammatory mediator expressions were measured by Griess reaction, enzyme-linked immunosorbent assay, and multiplex Luminex assay.

RESULTS

Intestinal manipulation rapidly and significantly induced Egr-1 messenger RNA and protein within the inflamed muscularis externa. Egr-1 was colocalized early to smooth muscle and enteric neurons and later in extravasated monocytes after surgery when postoperative ileus was functionally prominent. The functional severity of postoperative ileus was significantly ameliorated in mice deficient in Egr-1(-/-) and chimera wild-type mice transplanted with Egr-1(-/-) bone marrow, whereas knockout mice with Egr-1(+/+) bone marrow again displayed significant ileus. Motility was mechanistically associated in Egr-1(-/-) gene deficiency with a down-regulation in the release of nitric oxide, prostanoids, monocyte chemoattractant protein-1, macrophage inflammatory protein-1alpha, interleukin-6, interleukin-1, and granulocyte colony-stimulating factor, as well as a decrease in the recruitment of leukocytes into the manipulated muscle wall of the intestine compared with wild-type mice.

CONCLUSIONS

Leukocyte-derived Egr-1 plays an early critical inflammatory role in the initiation of the postoperative inflammatory response, which leads to a prolonged decreased in gastrointestinal motility after intestinal surgery.

Recent development in pharmacogenomics: from candidate genes to genome-wide association studies

Genetic diversity, most notably through single nucleotide polymorphisms and copy-number variation, together with specific environmental exposures, contributes to both disease susceptibility and drug response variability. It has proved difficult to isolate disease genes that confer susceptibility to complex disorders, and as a consequence, even fewer genetic variants that influence clinical drug responsiveness have been uncovered. As such, the candidate gene approach has largely failed to deliver and, although the family-based linkage approach has certain theoretical advantages in dealing with common/complex disorders, progress has been slower than was hoped. More recently, genome-wide association studies have gained increasing popularity, as they enable scientists to robustly associate specific variants with the predisposition for complex disease, such as age-related macular degeneration, Type 2 diabetes, inflammatory bowel disease, obesity, autism and leukemia. This relatively new methodology has stirred new hope for the mapping of genes that regulate drug response related to these conditions. Collectively, these studies support the notion that modern high-throughput single nucleotide polymorphism genotyping technologies, when applied to large and comprehensively phenotyped patient cohorts, will readily reveal the most clinically relevant disease-modifying and drug response genes. This review addresses both recent advances in the genotyping field and highlights from genome-wide association studies, which have conclusively uncovered variants that underlie disease susceptibility and/or variability in drug response in common disorders.

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.

The histone deacetylase inhibitor trichostatin A mediates upregulation of 5-lipoxygenase promoter activity by recruitment of Sp1 to distinct GC-boxes

The histone deacetylase inhibitor trichostatin A (TsA) potently induces 5-lipoxygenase (5-LO) promoter activity in reporter gene assays as well as 5-LO mRNA expression. We identified two proximal Sp1/Sp3 binding sites in the 5-LO gene promoter mediating the TsA effect in both 5-LO-negative HeLa cells and in 5-LO expressing Mono Mac 6 (MM6) cells, the tandem GC-boxes, by contrast, were not important for the TsA effect. TsA neither altered the protein expression levels of Sp1/Sp3 nor of the histone deacetylases HDAC1/2, nor did it apparently change the protein complex formation by these factors. Also, treatment of cells with TsA did not change the binding affinity of Sp1/Sp3 in cell extracts, as tested by DAPA analysis using probes containing the proximal GC boxes. However, in the living cell TsA induced Sp1, Sp3 and RNA polymerase II recruitment to the 5-LO promoter without changing the acetylation status of histone protein H4. Cotransfection studies suggest that both Sp1 and Sp3 can mediate the TsA effect. This is the first report demonstrating that Sp3 is involved in the regulation of 5-LO promoter activity. In summary, we show that TsA increases 5-LO promoter activity by the enhanced recruitment of Sp1 and Sp3 to the 5-LO promoter.

5-Lipoxygenase: regulation of expression and enzyme activity

5-Lipoxygenase (5-LO) catalyzes the first two steps in the biosynthesis of leukotrienes, a group of pro-inflammatory lipid mediators derived from arachidonic acid. Leukotriene antagonists are used in the treatment of asthma, and the potential role of leukotrienes in atherosclerosis, another chronic inflammatory disease, has recently received considerable attention. In addition, some possible effects of 5-LO metabolites in tumorigenesis have emerged. Thus, knowledge of the biochemistry of this enzyme has potential implications for the treatment of various diseases. Recent advances have expanded our understanding of the regulatory mechanisms underlying the expression and control of 5-LO activity. With regard to the control of enzyme activity, many of these findings focus on the N-terminal domain of 5-LO.

5-Lipoxygenase: Regulation and possible involvement in atherosclerosis

This review article focuses on two aspects regarding 5-lipoxygenase. First, mechanisms for activation of the enzyme. Second, the involvement of 5-lipoxygenase and leukotrienes in atherosclerosis.

G-protein-coupled receptors and asthma endophenotypes: the cysteinyl leukotriene system in perspective

Genetic variation in specific G-protein coupled receptors (GPCRs) is associated with a spectrum of respiratory disease predispositions and drug response phenotypes. Although certain GPCR gene variants can be disease-causing through the expression of inactive, overactive, or constitutively active receptor proteins, many more GPCR gene variants confer risk for potentially deleterious endophenotypes. Endophenotypes are traits, such as bronchiole hyperactivity, atopy, and aspirin intolerant asthma, which have a strong genetic component and are risk factors for a variety of more complex outcomes that may include disease states. GPCR genes implicated in asthma endophenotypes include variants of the cysteinyl leukotriene receptors (CYSLTR1 and CYSLTR2), and prostaglandin D2 receptors (PTGDR and CRTH2), thromboxane A2 receptor (TBXA2R), beta2-adrenergic receptor (ADRB2), chemokine receptor 5 (CCR5), and the G protein-coupled receptor associated with asthma (GPRA). This review of the contribution of variability in these genes places the contribution of the cysteinyl leukotriene system to respiratory endophenotypes in perspective. The genetic variant(s) of receptors that are associated with endophenotypes are discussed in the context of the extent to which they contribute to a disease phenotype or altered drug efficacy.

Opposing actions of Stat1 and Stat6 on IL-13-induced up-regulation of early growth response-1 and platelet-derived growth factor ligands in pulmonary fibroblasts

IL-13 is a key cytokine involved in airway remodeling in asthma. We previously reported that IL-13 stimulated the mitogenesis of lung fibroblasts via platelet-derived growth factor (PDGF)-AA. In this report, we show that IL-13 increases PDGF-A and PDGF-C mRNA levels through a dual intracellular cascade that requires coactivation of Stat6 and Stat1 to impact transcriptional regulation of the early growth response (Egr)-1 gene, which then drives PDGF expression. Increased levels of PDGF-AA and PDGF-CC protein were observed in vivo in the airways of IL-13 transgenic mice. IL-13 up-regulated PDGF-A and PDGF-C mRNA levels in lung fibroblasts isolated from three different background strains of mice. However, IL-13-induced PDGF-A and PDGF-C mRNA levels were significantly reduced in Stat6-deficient (Stat6(-/-)) fibroblasts as compared with wild-type Stat6(+/+) fibroblasts. In contrast, IL-13-induced PDGF-A and PDGF-C mRNAs were enhanced in Stat1(-/-) fibroblasts as compared with Stat1(+/+) fibroblasts. IL-13 did not up-regulate PDGF-A or PDGF-C mRNA levels in Egr-1(-/-) fibroblasts. Moreover, IL-13 did not increase Egr-1 mRNA and protein levels in Stat6(-/-) fibroblasts and yet enhanced Egr-1 mRNA and protein levels in Stat1(-/-) fibroblasts. Our findings support the hypothesis that Stat6 and Stat1 exert stimulatory and inhibitory effects on Egr-1 and PDGF ligand mRNA transcription, respectively. This novel mechanism could aid in identifying molecular targets for the treatment of chronic airway remodeling and fibrosis in asthma.

Analysis of the 5-lipoxygenase promoter and characterization of a vitamin D receptor binding site

1,25-Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) and transforming growth factor beta (TGFbeta) potently induce 5-lipoxygenase (5-LO) in myeloid cells. We analyzed vitamin D receptor (VDR) binding to putative vitamin D response elements within the 5-LO promoter and analyzed its function by reporter gene analysis. Binding of VDR and retinoid X receptor to the promoter region was shown in DNase I footprinting, electrophoretic mobility shift and chromatin immunoprecipitation assays. However, the identified VDR binding region did not mediate induction of reporter gene activity by 1,25(OH)(2)D(3)/TGFbeta, neither in the 5-LO promoter context nor with the thymidine kinase (tk) promoter. Insertion of the rat atrial natriuretic factor VDRE in reporter plasmids containing the 5-LO promoter diminished induction by 1,25(OH)(2)D(3)/TGFbeta as compared with the tk promoter. Similarly, low inductions were obtained when cells were transiently or stably transfected with constructs containing various 5-LO promoter regions. Concerning basal promoter activity, we identified a positive regulatory region (-779 to -229), which includes the VDR binding region, in 5-LO-positive MonoMac6 cells. In summary, the VDR/RXR complex binds to putative VDREs in the 5-LO promoter, but other sequences outside the 5-LO promoter seem to be responsible or additionally required for the prominent induction of 5-LO mRNA expression by 1,25(OH)(2)D(3) and TGFbeta.

Overview of the pharmacogenetics of asthma treatment

Asthma affects approximately 300 million individuals worldwide. Medications comprise a substantial portion of asthma expenditures. Despite the availability of three primary therapeutic classes of medications, there are a significant number of nonresponders to therapy. Available data, as well as previous pharmacogenetic studies, suggest that genetics may contribute as much as 60-80% to the interindividual variability in treatment response. In this methodologic review, after providing a broad overview of the asthma pharmacogenetics literature to date, we describe the application of a novel family-based screening algorithm to the analysis of pharmacogenetic data and highlight our approach to identifying and verifying loci influencing asthma treatment response. This approach seeks to address issues related to multiple comparisons, statistical power, population stratification, and failure to replicate from which previous population-based or case-control pharmacogenetic association studies may suffer. Identification of such replicable loci is the next step towards the goal of 'individualized therapy' for asthma.

Early growth response-1 in cardiovascular pathobiology

The immediate-early gene product and zinc finger transcription factor early growth response (Egr)-1 plays a key master regulatory role in multiple cardiovascular pathological processes. This article reviews the amazing recent evidence implicating Egr-1 in atherosclerosis, intimal thickening after acute vascular injury, ischemic pathology, angiogenesis, allograft rejection, and cardiac hypertrophy.

Variable therapeutic response in asthma: a genetic perspective

Asthma is a complex clinical syndrome with multiple genetic and environmental factors contributing to its phenotypic expression. This etiological heterogeneity adds to the complexity when addressing variation in the response to antiasthma treatment. There is regular progress in the field of asthma pharmacogenetics in determining the efficacy and potential for adverse effects of the asthma medication from a patient's genetic background. This reveals that a clinically relevant variability in response to the asthma medications may be due to genetic determinants, and refers to the polymorphisms in the genes encoding either the drug targets, or the molecular component of the downstream signal transduction pathways responsible for drug actions. The major classes of asthma therapy, β-agonists, leukotriene antagonists and inhaled corticosteroids, demonstrate wide interindividual variability. The statistical issues, such as population stratification, sample size and statistical power, are crucial factors for the identification of significant biological marker(s) for patient's response. The aim of this review is to discuss the scientific rationale and outline the genetic impact on the variability in response to different asthma medications. In conclusion, despite of new developments and recent studies in asthma pharmacogenetics, significant gaps in knowledge still remain, and several replicate studies are needed in different populations to derive firm conclusions that may help to bring pharmacotyping into clinical practice.

Endogenous S-nitrosoglutathione modifies 5-lipoxygenase expression in airway epithelial cells

S-Nitrosoglutathione (GSNO) is an endogenous bronchodilator with several beneficial pulmonary effects. Levels are decreased in the asthmatic airway, and GSNO inhalation has been proposed as an asthma therapy. 5-lipoxygenase (5-LO) is the rate-limiting enzyme in the synthetic pathway for cysteinyl leukotrienes (CysLTs), bronchoconstricting agents that are overproduced in asthma. Here, we have studied the effect of GSNO on the expression of 5-LO in human airway A549 cell lines and in primary normal human tracheobronchial epithelial (NHBE) cells in vitro. GSNO at concentrations of 0.5-1 microM caused a 3- to 6-fold increase in 5-LO expression. However, GSNO at>5 microM significantly inhibited both 5-LO expression and LT production. We also found that airway epithelial cells had gamma-glutamyl transpeptidase (gamma-GT) activity. The effect of 1 microM GSNO on 5-LO expression was prevented by the gamma-GT inhibitor, acivicin, suggesting a convergence of GSNO and CysLT metabolic pathway that may be relevant to asthma. Our data demonstrate that GSNO levels<or=1 microM, likely recapitulating those in the asthmatic airway, increase 5-LO expression, an effect that may increase inflammation and bronchoconstriction. However, GSNO at concentrations>5microM suppresses 5-LO expression. These data suggest that GSNO might inhibit 5-LO expression in the clinical setting.

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.

Genetics of allergic disease

Currently, more than 20.3 million Americans report having asthma and an even greater number suffer from allergies. The cost for treatment of these dis-eases in the United States is greater than $8 billion with more than 40% of this total representing drug expenditure [59]. An intense effort has been made to understand the genetic components of asthma and allergies and how the identified genetic differences influence disease progression and response to drugs. In the future, it will be possible in the clinical setting to analyze a patient's genetic repertoire. From this information, the physician will gain in-sight into the genes involved in producing that subject's allergic and asthmatic phenotype; understand the natural history of that patient's disease;and predict responses (positive and negative) to pharmacologic agents. The end result will be the ability to tailor a specific treatment regime for each patient and reduce the overall cost of health care related to allergies and asthma.

Egr-1 Induces the Expression of Its Corepressor Nab2 by Activation of the Nab2 Promoter Thereby Establishing a Negative Feedback Loop

The transcription factor Egr-1 regulates the expression of numerous genes involved in differentiation, growth, and in response to environmental signals. Egr-1 activity is modulated in part through the binding of corepressors Nab1 and Nab2. Nab2 appears crucial for controlling Egr-1-mediated transactivation because it is a delayed early response gene, induced by the same stimuli that induce the immediate early gene Egr-1. To identify important elements regulating Nab2 expression, we cloned the human Nab2 gene and investigated the 5'-region. The TATA- and initiator-less Nab2 promoter, located from -679 to -74 bp, contains a total of 11 Egr binding sites, including a cluster of multiple overlapping Egr/Sp1 sites between -329 and -260 bp. This region is critical for basal promoter activity as well as for maximum induction by phorbol esters. Electromobility shifts show that Sp1 binds to this region in normal and stimulated cells, whereas stimulation induces binding of Egr-1. In addition Egr-1 activates the Nab2 promoter in a pattern similar to phorbol esters, suggesting that Egr-1 is a major inducer of protein kinase C-mediated Nab2 induction. Depletion of Egr-1 by each of two distinct Egr-1 short-interfering RNAs reduces Nab2 expression and inducibility, confirming that Egr-1 is an important regulator of Nab2 expression. Transfection experiments show that Egr-1-induced Nab2 promoter activity is itself repressed by Nab2. These results indicate that Egr-1 mediates the induction of its own repressor, thereby preventing a permanent transactivation of Egr-1 target genes and a damaging overreaction in response to environmental signals.

Zinc finger transcription factor Egr-1 is involved in stimulation of NHE2 gene expression by phorbol 12-myristate 13-acetate

The apical membrane Na(+)/H(+) exchanger isoforms NHE2 and NHE3 are involved in transepithelial Na(+) absorption in the intestine. However, they exhibit differences in their pattern of tissue expression and regulation of their activity by various molecular signals. To study the mechanisms involved in the transcriptional regulation of these genes, we characterized cis-acting elements within the human NHE2 promoter that regulate NHE2 promoter expression in C2BBe1 cells. A small DNA region (-85/+249) was involved in the regulation of basal transcriptional activity of the NHE2 promoter as determined by transient transfection assays. RT-PCR analysis showed that NHE2 mRNA was upregulated in response to phorbol 12-myristate 13-acetate (PMA). Results from actinomycin D-treated cells indicated that the regulation of the NHE2 gene by PMA occurs in part at the transcriptional level. Furthermore, PMA treatment led to a 100% increase in promoter activity through elements located on the -415/+249 DNA fragment. A PMA-induced nuclear factor that bound to the NHE2 promoter was identified as the transcription factor Egr-1. We identified two PMA response elements in the -415/+1 promoter region that bind to Sp1 and Sp3 in untreated nuclear extracts and to Egr-1 in PMA-treated nuclear extracts. In cotransfection experiments, Egr-1 was able to transactivate the NHE2 promoter. Our data indicate that Egr-1 may play a key role in regulated expression of the human NHE2 gene.

Leukotriene modifiers as potential therapeutics for cardiovascular disease

Owing to their anti-inflammatory properties, leukotriene modifiers have been the primary therapeutics in asthma management for several years. Although blocking the inflammatory component of human disease is a long-standing and established concept, the use of leukotriene modifiers in treating the inflammatory component of cardiovascular disease encompassing atherosclerosis, myocardial infarction, stroke and aortic aneurysm has, surprisingly, only been seriously contemplated in the past few years. As reviewed here, several exciting studies have recently contributed to this expanding area of interest, and so far one leukotriene modifier has entered Phase II clinical trials to assess its potential for reducing the risk of heart attacks.

Transcriptional events in a clinical model of oral mucosal tissue injury and repair

Tissue injury in the oral mucosa activates a cascade of transcriptional events important during the healing process that are not yet clearly defined. To characterize these events and identify potential gene targets for future studies, we used cDNA expression arrays in a clinical model of tissue injury. Mucosal biopsies were taken before third molar extraction, 2-4 hours postoperatively, or at 48 hours. Hybridization patterns were analyzed and validated using real-time polymerase chain reaction. Prior to extraction, the biopsied mucosal tissues were characterized by a panoply of genes that were constitutively expressed. After injury, analysis revealed differential expression of genes involved in transcription, inflammation, and remodeling. At 2-4 hours after injury, genes such as Fos, Jun, and early growth response protein were up-regulated, while genes responsible for intercellular adhesion were down-regulated. At 48 hours after injury, the gene profile had shifted toward tissue remodeling. Here we identify genes constitutively expressed in normal oral mucosa and transcriptional events following mucosal tissue injury, which may be useful in identifying new therapeutic targets.

Pharmacogenetic approaches in the treatment of asthma

A patient's response to asthma therapy is determined by both genetic and environmental factors. In the past 10 years, we have witnessed significant progress in the field of asthma pharmacogenetics--the study of how a patient's genetic background determines the efficacy and potential for adverse effects to current asthma medication. There are now clear examples of gene polymorphisms that can influence responses to beta(2)-agonists, glucocorticosteroids, and leukotriene modifier drugs, the three main classes of medication used clinically to treat asthma. Identification of genetic polymorphism that predicts drug responses has the potential to lead to the development of new therapeutics, improve asthma management, and reduce serious episodes and hospitalizations. In this review, we discuss the current understanding of asthma pharmacogenetics, focusing on the main three classes of drugs currently used clinically.

Co-factors p300 and CBP catch Egr1 in their network

p300 and CBP are large (300 kDa) nuclear scaffold proteins that act as co-activators of transcription in most cell types and are over-expressed in prostate cancer. Recently, the Egr1 transcription factor was shown to up- or down-regulate p300 and CBP transcription based on the nature of its post-translational modification. Notably, interactions of the three proteins provide fine tuning for Egr1-induced growth or cell death responses.

Potential genetic influences on the response to asthma treatment

Genetic factors play a key role in determining the widely heterogeneous response to pharmacological treatment detectable among asthmatics. In particular, polymorphisms of the genes encoding relevant anti-asthma drug targets contribute significantly to such a variability. Therefore, it is very important to characterize asthmatic patient's genotypes and the related phenotypic patterns, in order to predict the individual therapeutic outcome. This pharmacogenetic approach will eventually help clinicians to optimize and personalize anti-asthma treatment, and will also provide useful information with regard to pre- and post-marketing evaluation of both effectiveness and side effects of newly introduced drugs.

Role of prostanoid DP receptor variants in susceptibility to asthma

BACKGROUND

Previous genetic studies have associated the region of the human genome (14q22.1) containing the gene for the prostanoid DP receptor (PTGDR) with asthma. A study of a mouse model suggests that the receptor is required for the expression of the asthma phenotype. Our associations of asthma with functional genetic variants of PTGDR link these observations.

METHODS

We identified and evaluated combinations of genetic variants that influence PTGDR transcription for disease association in case-control studies of 518 white patients with asthma and 175 white controls and 80 black patients with asthma and 45 black controls.

RESULTS

We identified four novel and two previously reported single-nucleotide polymorphisms (SNPs) in PTGDR and its vicinity. These define four common three-SNP haplotypes, which vary in their ability to support transcription of PTGDR and have distinct DNA-binding-protein affinity profiles. Individual PTGDR SNPs were significantly associated with asthma in both populations. Specific PTGDR haplotypes were significantly associated with a diagnosis of asthma in a large case-control study of whites (P=0.002); we confirmed these findings in a second population of blacks (P=0.01). Multivariate analysis of the haplotype combinations (diplotypes) demonstrated that both whites (odds ratio, 0.55; 95 percent confidence interval, 0.38 to 0.80; P=0.002) and blacks (odds ratio, 0.32; 95 percent confidence interval, 0.12 to 0.89; P=0.03) who had at least one copy of the haplotype with a low transcriptional efficiency had a lower risk of asthma than subjects with no copies of the haplotype.

CONCLUSIONS

Our functional and genetic findings identify PTGDR as an asthma-susceptibility gene.

Therapeutic response to asthma medications: genotype predictors

Asthma is a major social and economic burden. Studies have shown that genetic polymorphisms can influence drug efficacy and/or toxicity. The understanding of the pharmacogenetics of asthma will allow therapeutic regimens to be tailored on an individual basis. It is hoped that linkage and association studies will define new therapeutic targets for asthma but until then, studies have focused on improving response to beta(2)-adrenoceptor agonist and leukotriene modifier therapy. Genetic polymorphism may account for interindividual differences in toxicity and efficacy of asthma medications. To date, single nucleotide polymorphism and limited haplotype analysis have provided inconclusive evidence as to how genotype predictors can be used to optimize current asthma therapies based on each patient's genetic profile.