Hasan Arshad

Tumour necrosis factor (TNFα) as a novel therapeutic target in symptomatic corticosteroid dependent asthma

Background: Tumour necrosis factor α (TNFα) is a major therapeutic target in a range of chronic inflammatory disorders characterised by a Th1 type immune response in which TNFα is generated in excess. By contrast, asthma is regarded as a Th2 type disorder, especially when associated with atopy. However, as asthma becomes more severe and chronic, it adopts additional characteristics including corticosteroid refractoriness and involvement of neutrophils suggestive of an altered inflammatory profile towards a Th1 type response, incriminating cytokines such as TNFα. Methods: TNFα levels in bronchoalveolar lavage (BAL) fluid of 26 healthy controls, 42 subjects with mild asthma and 20 with severe asthma were measured by immunoassay, and TNFα gene expression was determined in endobronchial biopsy specimens from 14 patients with mild asthma and 14 with severe asthma. The cellular localisation of TNFα was assessed by immunohistochemistry. An open label uncontrolled clinical study was then undertaken in 17 subjects with severe asthma to evaluate the effect of 12 weeks of treatment with the soluble TNFα receptor-IgG1Fc fusion protein, etanercept. Results: TNFα levels in BAL fluid, TNFα gene expression and TNFα immunoreative cells were increased in subjects with severe corticosteroid dependent asthma. Etanercept treatment was associated with improvement in asthma symptoms, lung function, and bronchial hyperresponsiveness. Conclusions: These findings may be of clinical significance in identifying TNFα as a new therapeutic target in subjects with severe asthma. The effects of anti-TNF treatment now require confirmation in placebo controlled studies.

The Role of the Airway Epithelium and its Interaction with Environmental Factors in Asthma Pathogenesis

Asthma is an inflammatory disorder of the airways dominated by a Th2-type pattern. Because of this, most research has focused on investigating the role of allergic pathways with the hope of discovering novel therapeutic targets. Unfortunately, this strategy (which has been extended to animal models) has failed to identify any therapeutic modalities other than anti-IgE and leukotriene modifiers directed to targets known about for many years. It seems that the problem lies in placing allergy at the center of disease pathogenesis, when in practice other environmental factors may be equally if not more important in the induction and then progression of asthma. An alternative view is that asthma is primarily a defect of epithelial barrier function that, as in atopic dermatitis, allows greater access of environmental allergens, microorganisms, and toxicants to the airway tissue. Evidence is provided to show that both the physical and functional barrier of the airway epithelium is defective in asthma with disrupted tight junctions, reduced antioxidant activity, and impaired innate immunity. This explains the remarkable susceptibility of asthmatic airways to respiratory viruses and the impact of air pollutants on asthma exacerbations. It also provides a mechanism for programming of dendritic cells to drive a Th2 response in the origins of asthma. Viewing asthma primarily as an epithelial disease with adoption of a chronic wound scenario also provides a route to airway wall remodeling and the varying asthma phenotypes over the life course.

A new look at the pathogenesis of asthma

Asthma is an inflammatory disorder of the conducting airways that has strong association with allergic sensitization. The disease is characterized by a polarized Th-2 (T-helper-2)-type T-cell response, but in general targeting this component of the disease with selective therapies has been disappointing and most therapy still relies on bronchodilators and corticosteroids rather than treating underlying disease mechanisms. With the disappointing outcomes of targeting individual Th-2 cytokines or manipulating T-cells, the time has come to re-evaluate the direction of research in this disease. A case is made that asthma has its origins in the airways themselves involving defective structural and functional behaviour of the epithelium in relation to environmental insults. Specifically, a defect in barrier function and an impaired innate immune response to viral infection may provide the substrate upon which allergic sensitization takes place. Once sensitized, the repeated allergen exposure will lead to disease persistence. These mechanisms could also be used to explain airway wall remodelling and the susceptibility of the asthmatic lung to exacerbations provoked by respiratory viruses, air pollution episodes and exposure to biologically active allergens. Variable activation of this epithelial–mesenchymal trophic unit could also lead to the emergence of different asthma phenotypes and a more targeted approach to the treatment of these. It also raises the possibility of developing treatments that increase the lungs resistance to the inhaled environment rather than concentrating all efforts on trying to suppress inflammation once it has become established.

Consensus Communication on Early Peanut Introduction and the Prevention of Peanut Allergy in High-risk Infants

The purpose of this brief communication is to highlight emerging evidence to existing guidelines regarding potential benefits of supporting early, rather than delayed, peanut introduction during the period of complementary food introduction in infants. This document should be considered as interim guidance based on consensus among the following organizations: American Academy of Allergy, Asthma & Immunology; American Academy of Pediatrics; American College of Allergy, Asthma & Immunology; Australasian Society of Clinical Immunology and Allergy; Canadian Society of Allergy and Clinical Immunology; European Academy of Allergy and Clinical Immunology; Israel Association of Allergy and Clinical Immunology; Japanese Society for Allergology; Society for Pediatric Dermatology; and World Allergy Organization. More formal guidelines regarding early-life, complementary feeding practices and the risk of allergy development will follow in the next year from the National Institute of Allergy and Infectious Diseases – sponsored Working Group and the European Academy of Allergy and Clinical Immunology.

Role of cysteinyl leukotrienes in adenosine 5`-monophosphate induced bronchoconstriction in asthma

Background: Adenosine induced bronchoconstriction in patients with asthma is thought to be mediated by the synthesis and release of autacoids from airway mast cells. In vitro, adenosine induced constriction of asthmatic bronchi is blocked by a combination of specific histamine and cysteinyl leukotriene receptor antagonists, but the relative contribution of these mediators in vivo is unclear. We hypothesised that adenosine induced bronchoconstriction in asthmatic patients may be blocked by pretreatment with the orally active selective cysteinyl leukotriene-1 (CysLT1) receptor antagonist, montelukast. Methods: In a randomised, double blind, crossover study, oral montelukast (10 mg) or placebo was administered once daily on two consecutive days to 18 patients with mild to moderate persistent atopic asthma. Incremental doses of adenosine 5`-monophosphate (AMP) from 0.39 to 400 mg/ml were inhaled by dosimeter and the dose producing a 20% fall in FEV1 (PC20AMP) after AMP inhalation was recorded. Leukotriene E4 (LTE4) urinary concentrations were measured by enzyme immunoassay 4 hours after AMP challenge. Results: Montelukast pretreatment provided highly significant protection against adenosine induced bronchoconstriction, with geometric mean PC20AMP values of 52.6 mg/ml (95% CI 35.2 to 78.7) after placebo and 123.9 mg/ml (95% CI 83.0 to 185.0) after montelukast (p=0.006). The geometric mean of the montelukast/placebo PC20AMP ratio was 2.4 (95% CI 1.3 to 4.2). Montelukast had no significant effect on 4 hour urinary excretion of LTE4 compared with placebo. Conclusions: Selective CysLT1 receptor antagonism with montelukast provides highly significant protection against AMP induced bronchoconstriction in patients with atopic asthma, implying that cysteinyl leukotrienes are generated from airway mast cells through preferential activation of their A2B receptors.

Genome-wide DNA methylation analysis of patients with imprinting disorders identifies differentially methylated regions associated with novel candidate imprinted genes

Background Genomic imprinting is allelic restriction of gene expression potential depending on parent of origin, maintained by epigenetic mechanisms including parent of origin-specific DNA methylation. Among approximately 70 known imprinted genes are some causing disorders affecting growth, metabolism and cancer predisposition. Some imprinting disorder patients have hypomethylation of several imprinted loci (HIL) throughout the genome and may have atypically severe clinical features. Here we used array analysis in HIL patients to define patterns of aberrant methylation throughout the genome. Design We developed a novel informatic pipeline capable of small sample number analysis, and profiled 10 HIL patients with two clinical presentations (Beckwith–Wiedemann syndrome and neonatal diabetes) using the Illumina Infinium Human Methylation450 BeadChip array to identify candidate imprinted regions. We used robust statistical criteria to quantify DNA methylation. Results We detected hypomethylation at known imprinted loci, and 25 further candidate imprinted regions (nine shared between patient groups) including one in the Down syndrome critical region (WRB) and another previously associated with bipolar disorder (PPIEL). Targeted analysis of three candidate regions (NHP2L1, WRB and PPIEL) showed allelic expression, methylation patterns consistent with allelic maternal methylation and frequent hypomethylation among an additional cohort of HIL patients, including six with Silver–Russell syndrome presentations and one with pseudohypoparathyroidism 1B. Conclusions This study identified novel candidate imprinted genes, revealed remarkable epigenetic convergence among clinically divergent patients, and highlights the potential of epigenomic profiling to expand our understanding of the normal methylome and its disruption in human disease.

The Study Team for Early Life Asthma Research (STELAR) consortium ‘Asthma e-lab’: team science bringing data, methods and investigators together

We created Asthma e-Lab, a secure web-based research environment to support consistent recording, description and sharing of data, computational/statistical methods and emerging findings across the five UK birth cohorts. The e-Lab serves as a data repository for our unified dataset and provides the computational resources and a scientific social network to support collaborative research. All activities are transparent, and emerging findings are shared via the e-Lab, linked to explanations of analytical methods, thus enabling knowledge transfer. eLab facilitates the iterative interdisciplinary dialogue between clinicians, statisticians, computer scientists, mathematicians, geneticists and basic scientists, capturing collective thought behind the interpretations of findings.

Tumor necrosis factor alpha (TNF-α) autoregulates its expression and induces adhesion molecule expression in asthma☆

Subjects with mild asthma underwent repeated low-dose allergen exposure and bronchial biopsies were examined for the expression of TNF-α and adhesion molecules. Bronchial biopsies from moderately severe asthmatics were then tested in an explant culture system to assess the effect of Der p and CDP-870, a TNF-α blocking pegylated-antibody Fab, on expression of TNF-α and adhesion molecules. Low-dose allergen challenge significantly upregulated sub-mucosal mast cells, TNF-α(+) cells, and VCAM. When bronchial explants were exposed to Der p and CDP 870 for 24h, CDP 870 caused a significant reduction in TNF-α release both at baseline and following stimulation with Der p allergen. The bronchial biopsies showed significant upregulation of TNF-α positive cells and ICAM-1 following exposure to Der p (p=0.03) and this was reduced in the presence of CDP-870. So, allergen exposure up-regulates TNF-α expression in asthma and down-stream targets, including adhesion molecules that contribute to airway inflammation.

Variable selection in semi-parametric models.

We propose Bayesian variable selection methods in semi-parametric models in the framework of partially linear Gaussian and problit regressions. Reproducing kernels are utilized to evaluate possibly non-linear joint effect of a set of variables. Indicator variables are introduced into the reproducing kernels for the inclusion or exclusion of a variable. Different scenarios based on posterior probabilities of including a variable are proposed to select important variables. Simulations are used to demonstrate and evaluate the methods. It was found that the proposed methods can efficiently select the correct variables regardless of the feature of the effects, linear or non-linear in an unknown form. The proposed methods are applied to two real data sets to identify cytosine phosphate guanine methylation sites associated with maternal smoking and cytosine phosphate guanine sites associated with cotinine levels with creatinine levels adjusted. The selected methylation sites have the potential to advance our understanding of the underlying mechanism for the impact of smoking exposure on health outcomes, and consequently benefit medical research in disease intervention.

Expression of the filaggrin gene in umbilical cord blood predicts eczema risk in infancy: A birth cohort study

Filaggrin gene (FLG) expression, particularly in the skin, has been linked to the development of the skin barrier and is associated with eczema risk. However, knowledge as to whether FLG expression in umbilical cord blood (UCB) is associated with eczema development and prediction is lacking.