Susceptibility genes in asthma and allergy

Role of Transcription Factors in Pulmonary Artery Smooth Muscle Cells: An Important Link to Hypoxic Pulmonary Hypertension

Hypoxia, namely a lack of oxygen in the blood, induces pulmonary vasoconstriction and vasoremodeling, which serve as essential pathologic factors leading to pulmonary hypertension (PH). The underlying molecular mechanisms are uncertain; however, pulmonary artery smooth muscle cells (PASMCs) play an essential role in hypoxia-induced pulmonary vasoconstriction, vasoremodeling, and PH. Hypoxia causes oxidative damage to DNAs, proteins, and lipids. This damage (oxidative stress) modulates the activity of ion channels and elevates the intracellular calcium concentration ([Ca²⁺]_i, Ca²⁺ signaling) of PASMCs. The oxidative stress and increased Ca²⁺ signaling mutually interact with each other, and synergistically results in a variety of cellular responses. These responses include functional and structural abnormalities of mitochondria, sarcoplasmic reticulum, and nucleus; cell contraction, proliferation, migration, and apoptosis, as well as generation of vasoactive substances, inflammatory molecules, and growth factors that mediate the development of PH. A number of studies reveal that various transcription factors (TFs) play important roles in hypoxia-induced oxidative stress, disrupted PAMSC Ca²⁺ signaling and the development and progress of PH. It is believed that in the pathogenesis of PH, hypoxia facilitates these roles by mediating the expression of multiple genes. Therefore, the identification of specific genes and their transcription factors implicated in PH is necessary for the complete understanding of the underlying molecular mechanisms. Moreover, this identification may aid in the development of novel and effective therapeutic strategies for PH.

Roles of transcriptional factor 7 in production of inflammatory factors for lung diseases

Lung disease is the major cause of death and hospitalization worldwide. Transcription factors such as transcription factor 7 (TCF7) are involved in the pathogenesis of lung diseases. TCF7 is important for T cell development and differentiation, embryonic development, or tumorogenesis. Multiple TCF7 isoforms can be characterized by the full-length isoform (FL-TCF7) as a transcription activator, or dominant negative isoform (dn-TCF7) as a transcription repressor. TCF7 interacts with multiple proteins or target genes and participates in several signal pathways critical for lung diseases. TCF7 is involved in pulmonary infection, allergy or asthma through promoting T cells differentiating to Th2 or memory T cells. TCF7 also works in tissue repair and remodeling after acute lung injury. The dual roles of TCF7 in lung cancers were discussed and it is associated with the cellular proliferation, invasion or metastasis. Thus, TCF7 plays critical roles in lung diseases and should be considered as a new therapeutic target.

Allergic rhinitis

Allergic rhinitis is a costly disease associated with significant morbidity. It impacts the quality of life of millions of individuals, particularly in industrialized nations, and it is on the rise. Lost productivity and total healthcare expenditure exceeds several billion dollars annually in the United States, with an estimate of >$6 billion spent on prescription medications alone. It is also associated with asthma and other atopic conditions, sinusitis, otitis media, and sleep apnea. Primary care physicians should be well adept at recognizing and initiating empiric first-line therapy for chronic rhinitis. Allergen avoidance, topical nasal steroids, and antihistamines may be sufficient for some patients. In most cases, referral to a board-certified allergy specialist for skin testing and targeted management is indicated. It is essential to make sure that patients abstain from using antihistamines at least 1 week prior to reporting to the allergist for skin testing in order to avoid false-negative results. Traditional subcutaneous allergen immunotherapy, when performed by an experienced allergist, affords relief in >75% of cases. The growing armament of treatment options for refractory allergic rhinitis includes oral and sublingual immunotherapy, recombinant allergens, conjugated DNA vaccines, and anti-immunoglobulin E monoclonal antibody.

MicroRNA-21 expression in neonatal blood associated with antenatal immunoglobulin E production and development of allergic rhinitis

BACKGROUND

The prevalence of allergic diseases has increased in the past decades. It is unknown whether expression of certain microRNAs (miRNAs) in neonatal leucocytes is correlated to IgE production and/or allergic diseases.

OBJECTIVE

This study investigated the association of miRNA expression in neonatal leucocytes with cord blood IgE (CBIgE) elevation and development of allergic disease.

METHODS

We screened for the expression of a panel of 157 miRNAs in mononuclear leucocytes from human umbilical cord blood (CB) samples with elevated CBIgE and tracked the association of down-regulated miRNA expression to the miRNA-targeted gene expression and to children with allergic rhinitis (AR).

RESULTS

Among the initial screen of 10 CB samples with elevated CBIgE, expression of eight of the 157 miRNAs was low. Of these eight down-expressed miRNAs, three remained down-regulation in a validation with other 20 CB samples, and two of the three miRNAs, miR-21 and miR-126, were significantly lower in monocytes from AR children. Further analysis of mRNA expression of the miR-21-targeted genes identified that TGFBR2 expression on monocytes was significantly up-regulated in CB with elevated CBIgE, and in AR patients. Transfection of miR-21 precursor into monocytes from patients with AR increased miR-21 expression and decreased TGFBR2 expression.

CONCLUSION

This study demonstrated the first in the literature that lower miR-21 expression in CB and increased TGFBR2 expression is associated with antenatal IgE production and development of AR.

Genetics of allergic disease

Allergic diseases are complex genetic diseases resulting from the effect of multiple genetic and interacting environmental factors on their pathophysiology. Recent years have seen considerable progress in unraveling the contribution of these factors to an individual subject's susceptibility to, subsequent development of, and severity of disease. This has resulted in increasing insight into novel areas of allergic disease pathophysiology, for example the significant role played by locally acting tissue susceptibility factors like epithelial/epidermal barrier function and remodeling, such as filaggrin, ADAM33, and GSDML/ORMDL3, in patients with atopic dermatitis and asthma. Furthermore, studies of gene-environment interactions and Mendelian randomization approaches have led to increased insight into the importance of environmental triggers for allergic disease. Studies of the timing of action of genetic variants in determining disease susceptibility have highlighted the importance of in utero development and early life in determining susceptibility to allergic disease. In the future, genetic discoveries in allergic disease will potentially lead to better endophenotyping, prognostication, prediction of treatment response, and insights into molecular pathways to develop more targeted therapy for these conditions.

Asthma, genes, and air pollution

OBJECTIVE

The objective of this article is to evaluate genetic risks associated with the pulmonary response to air pollutants, including particulates and ozone.

METHODS

A comprehensive review of articles related to the genetics of asthma with particular attention to air pollution was conducted through a search of the National Library of Medicine's PubMed database.

RESULTS

Asthma, which affects over 15 million people in the United States, is characterized by inflammation leading to reversible airflow obstruction. Triggered by exposure to numerous occupational and environmental agents, asthma has long been considered to occur more frequently in families, with upwards of a 50% higher rate in the offspring of parents with asthma. Asthma genetic studies have used two major methods: mapping techniques that pinpoint gene loci and studies that identify genes and polymorphisms associated with various asthma mechanisms such as inflammatory mediators. The most consistently replicated chromosomal regions associated with asthma have been chromosomes 2q, 5q, 6p, 12 q, and 13q. Because the formation of reactive oxygen species is a major aspect of the inflammatory process of asthma, genetic aberrations associated with antioxidants such as glutathione S-transferase (GST) may shed light on reasons why some people with asthma seem more at risk of exacerbations as a result of air pollution. People with a polymorphism at the GSTP 1 locus, which codes for GST, one of a family of pulmonary antioxidants, have higher rates of asthma. Children in Mexico City with the GSTM1 null genotype demonstrated significant ozone-related decrements in lung function. Animal studies support the key role of antioxidants in reducing the inflammatory response associated with exposure to diesel exhaust particles.

CONCLUSIONS

Oxidative stress is a key mechanism underlying the toxic effects of exposure to some types of air pollution. Asthmatics with the null genotype for the antioxidant, GST, seem more at risk of the pulmonary effects of air pollution.

Allergic rhinitis: impact of the disease and considerations for management

AR is a common condition affecting individuals of all ages. Those afflicted with AR often suffer from associated inflammatory conditions of the mucosa,such as AC, rhinosinusitis, asthma, otitis media with effusion, and other atopic conditions, such as eczema and food allergies. Lack of treatment or treatment with suboptimal therapy may result in reduced quality of life and compromise productivity at work or school. Although environmental controls may prove difficult to implement, and not all controls appear adequately to mitigate symptoms of AR, they continue to represent a foundation for treatment. Many different classes of medications are now available, and they have been shown to be effective and safe in a large number of well-designed, double-blind, placebo-controlled clinical trials. Some of the over-the-counter medi-cations have been associated with increased sedation, potentially leading to accidents and fatalities at work or while operating complex machinery, such as automobiles. Only immunotherapy with increasing doses of individually targeted allergens results in sustained changes in the immune system. Although anti-IgE is probably only the first successful immunomodulator commercially available to treat AR, monoclonal antibodies will remain too costly, at least in the near future, to find their way into routine AR treatment.

Pharmacogenomic Discovery Approaches: Will the Real Genes Please Stand Up?

Genetic inheritance plays a significant role in the interindividual variability of drug response. The field of pharmacogenomics seeks to identify genetic factors that influence drug response, including both those that are inherited and those that arise within tumors, and use this information to improve drug therapy. Candidate gene approaches have led to clinical tests for toxicity avoidance (eg, TPMT, UGT1A1) and efficacy prediction (eg, epidermal growth factor receptor–activating mutations). However, the “right” genes are not known for most anticancer drugs. Strategies for uncovering pharmacogenomic associations vary widely from monogenic candidate gene approaches to polygenic genome-wide approaches. This review will place in context clinically relevant pharmacogenomic discovery approaches, including the relative strengths and weaknesses and the challenges inherent with achieving the goal of individualized therapy.

Adverse events diagnosed within three days of vaccine administration in dogs

OBJECTIVE

To determine incidence rates and potential risk factors for vaccine-associated adverse events (VAAEs) diagnosed within 3 days of administration in dogs.

DESIGN

Retrospective cohort study.

ANIMALS

1,226,159 dogs vaccinated at 360 veterinary hospitals.

PROCEDURE

Electronic records from January 1, 2002, through December 31, 2003, were searched for possible VAAEs (nonspecific vaccine reaction, allergic reaction, urticaria, or anaphylaxis) diagnosed within 3 days of vaccine administration. Information included age, weight, sex, neuter status, and breed. Specific clinical signs and treatments were reviewed in a random sample of 400 affected dogs. The association between potential risk factors and a VAAE was estimated by use of multivariate logistic regression.

RESULTS

4,678 adverse events (38.2/10,000 dogs vaccinated) were associated with administration of 3,439,576 doses of vaccine to 1,226,159 dogs. The VAAE rate decreased significantly as body weight increased. Risk was 27% to 38% greater for neutered versus sexually intact dogs and 35% to 64% greater for dogs approximately 1 to 3 years old versus 2 to 9 months old. The risk of a VAAE significantly increased as the number of vaccine doses administered per office visit increased; each additional vaccine significantly increased risk of an adverse event by 27% in dogs < or = 10 kg (22 lb) and 12% in dogs > 10 kg.

CONCLUSIONS AND CLINICAL RELEVANCE

Young adult small-breed neutered dogs that received multiple vaccines per office visit were at greatest risk of a VAAE within 72 hours after vaccination. These factors should be considered in risk assessment and risk communication with clients regarding vaccination.

Understanding the origin of asthma and its relationship to breastfeeding

Asthma is a chronic disease of the lung that has been increasing at an alarming rate in industrialized countries around the world over the last few decades. Although considerable progress has been made in our understanding of the underlying pathogenesis of the disease, the exact causes of the increasing prevalence are unknown. Studies suggest that most asthma develops in early childhood and that environmental factors present early in life may be crucial in the development of disease. One potential explanation for the recent epidemic referred to as the "hygiene hypothesis" postulates that factors that have resulted in a reduction in exposure to microbial products and/or infections in the western world may be contributing to this rise in disease prevalence. As early life influences are known to play an important role in establishment of asthma, studies have focused on the interface between mother and child that occurs during gestation and through breastfeeding. In this regard, the body of evidence regarding the relationship between breastfeeding and asthma indicates benefit but with the potential for risk. While providing population-level protection from infections and atopy in infancy and early childhood, breastfeeding might also pose an increased risk of atopic asthma among children with asthmatic mothers. In order to put this controversy in context, we discuss our current understanding of asthma pathogenesis, current theories on the factors driving the rising prevalence of asthma, and then discuss the potential influence of breastfeeding on asthma pathogenesis.

New strategies in the treatment and prevention of allergic diseases

Allergic diseases (AD) are more prevalent today than 30 years ago but over the same period, few novel efficacious drugs have been discovered to treat, control or even cure these disorders. Topical or systemic glucocorticosteroids combined with symptom-relieving medications, such as beta 2 -adrenoceptor agonists, leukotriene inhibitors or antihistamines, are still the mainstay of antiallergic treatment. Modified glucocorticosteroids with less adverse effects, better bronchodilators and new selective mediator inhibitors may improve symptom control in the future. Only specific immunotherapy has shown potential for long-lasting disease-modifying effects. Immunomodulation is a therapeutic goal, aiming to modify the dominant helper T cell Type 2 inflammation to a helper T cell Type 1 response using modified allergens, mycobacteria or CpG oligodeoxynucleotides. Humanised monoclonal anti-IgE antibodies are an exciting new immunomodulatory medication that are expected to reach the clinical practice and have recently been licensed in Australia and the US. Advances in molecular, cellular and genetic research of the immunopathophysiology of AD have led to the development of new antagonists for cytokines, chemokines, receptors, second messengers and transcription factors that may become available for clinical use in the next 10 years. Specific diets supplemented with antioxidants or probiotics need further study but offer promise as safe and cheap preventative medicine. The strong genetic component of AD and the Human Genome Project have opened a new field of research, and modification or replacement of target genes has a curative potential with exciting new therapeutic developments in the years ahead.

Susceptibility to neoplastic and non-neoplastic pulmonary diseases in mice: genetic similarities

Chronic inflammation predisposes toward many types of cancer. Chronic bronchitis and asthma, for example, heighten the risk of lung cancer. Exactly which inflammatory mediators (e.g., oxidant species and growth factors) and lung wound repair processes (e.g., proangiogenic factors) enhance pulmonary neoplastic development is not clear. One approach to uncover the most relevant biochemical and physiological pathways is to identify genes underlying susceptibilities to inflammation and to cancer development at the same anatomic site. Mice develop lung adenocarcinomas similar in histology, molecular characteristics, and histogenesis to this most common human lung cancer subtype. Over two dozen loci, called Pas or pulmonary adenoma susceptibility, Par or pulmonary adenoma resistance, and Sluc or susceptibility to lung cancer genes, regulate differential lung tumor susceptibility among inbred mouse strains as assigned by QTL (quantitative trait locus) mapping. Chromosomal sites that determine responsiveness to proinflammatory pneumotoxicants such as ozone (O3), particulates, and hyperoxia have also been mapped in mice. For example, susceptibility QTLs have been identified on chromosomes 17 and 11 for O3-induced inflammation (Inf1, Inf2), O3-induced acute lung injury (Aliq3, Aliq1), and sulfate-associated particulates. Sites within the human and mouse genomes for asthma and COPD phenotypes have also been delineated. It is of great interest that several susceptibility loci for mouse lung neoplasia also contain susceptibility genes for toxicant-induced lung injury and inflammation and are homologous to several human asthma loci. These QTLs are described herein, candidate genes are suggested within these sites, and experimental evidence that inflammation enhances lung tumor development is provided.

Novel genetic variation of human interleukin-21 receptor is associated with elevated IgE levels in females

The interleukin-21 receptor (IL21R) was recently discovered as a novel member of the class-I-cytokine-receptor family and is selectively expressed in lymphoid tissues. IL21R shows strong sequence homologies to the interleukin-4 receptor alpha chain gene (IL4RA). In addition, both genes are adjacent and share structural similarity. We analyzed all the exons of the human IL21R gene and its 5' flanking region for sequence variation. We identified four novel single nucleotide polymorphisms (SNPs) and genotyped 300 healthy blood donors. Total serum IgE levels were measured in all subjects and associated with IL21R SNPs. Results revealed a significant association of one IL21R polymorphism (T-83C) with elevated IgE levels (>100 kU/I) in females (OR=3.000, CI=[1.163;8.385], P=0.015, n=138). This was confirmed in a second prospectively collected group of female blood donors (OR=2.535, CI=[0.927;6.733], P=0.046, n=123). In contrast, no effects were observed in male subjects in either population. These findings identify IL21R as a possible novel target locus influencing IgE synthesis in female individuals.