B-cell isotype control in atopy and asthma assessed with cDNA array technology

Host defense genes in asthma and sepsis and the role of the environment

PURPOSE OF REVIEW

There is growing evidence that innate immunity genes contribute to asthma pathogenesis. At the core of the innate immune response are ubiquitous, soluble fragments of bacterial lipopolysaccharide or endotoxin, and chronic exposure to domestic endotoxin has been shown to influence asthma severity. Asthmatic and atopic individuals are more sensitive to endotoxin than nonallergic individuals, suggesting a role for genetics in the innate immunity response, and the potential for gene-environment interactions. Variants in genes associated with classic innate immunity-related disorders, such as sepsis, may be unique candidates for asthma susceptibility.

RECENT FINDINGS

Candidate genes for asthma and allergic diseases co-associated with sepsis including innate immunity receptors and related molecules (CD14, TLR4 and AOAH) and novel genes such as MYLK provide good examples of pleitropic effects of innate immunity genes, where variants conferring risk to specific traits (i.e. sepsis) under one set of genetic and environmental circumstances confer a reduced risk in a different (but possibly related) clinical outcome (i.e. allergic asthma), and support the 'common variant/multiple disease' hypothesis.

SUMMARY

Collectively, these observations suggest a greater role for the innate immunity response in allergic asthma than previously assumed, and implicate host defense genes in disease pathology.

Gene expression profiling in human asthma

Asthma is a chronic inflammatory disease of the lungs, characterized by airway hyperreactivity, mucus hypersecretion, and airflow obstruction. Despite recent advances, the genetic regulation of asthma pathogenesis is still largely unknown. Gene expression profiling techniques are well suited to study complex diseases and hold substantial promise for identifying novel genes and pathways in asthma; however, relatively few studies have been completed in human asthma. The few studies that have been done have identified many novel candidate genes and pathways in asthma pathogenesis, including ALOX15 and serine proteinase inhibitors cathepsin C and G. The interpretation of results of these studies should be cautious, as limitations include small sample sizes and heterogeneity of study populations and tissues sampled. In the future, the promise of gene expression studies would be enhanced by the use of larger sample sizes and attempts to standardize phenotype, sample collection techniques, and analysis. As the field of expression profiling in asthma advances, we hope it will improve our understanding of critical questions about mechanisms involved in susceptibility to the disease, as well as help to personalize care by improving appropriate selection of patients for prevention and treatment strategies.

Development of a coral cDNA array to examine gene expression profiles in Montastraea faveolata exposed to environmental stress

The development of a cDNA array of coral genes and its application to investigate changes in coral gene expression associated with stressful conditions is described. The array includes both well-characterized and previously unidentified coral genes from Acropora cervicornis and Montastraea faveolata. Corals were exposed to either natural or anthropogenic stressors to elicit the expression of stress genes for isolation and incorporation onto the array. A total of 32 genes involved in protein synthesis, apoptosis, cell signaling, metabolism, cellular defense and inflammation were included on the array. Labeled cDNA from coral (Montastraea faveolata) exposed to elevated seawater temperature, salinity and ultraviolet light was tested against the microarray to determine patterns of gene expression associated with each stressor. Carbonic anhydrase, thioredoxin, a urokinase plasminogen activator receptor (uPAR) and three ribosomal genes demonstrated differential expression across all replicates on the array and between replicate colonies. Specific gene expression patterns produced in response to different stressors demonstrate the potential for gene expression profiling in characterizing the coral stress response.

Towards a proteomic analysis of atopic dermatitis: A two-dimensional-polyacrylamide gel electrophoresis/mass spectrometric analysis of cultured patient-derived fibroblasts

Atopic dermatitis (AD) is a chronic relapsing inflammatory skin disease typically characterized by a distribution of eczematous skin lesions with lichenification, pruritic excoriations, and dry skin with wide varieties of pathophysiologic aspects. Recently, AD was divided into extrinsic and intrinsic forms according to the presence or absence of an allergy. We investigated alterations in protein expression in primary cultured AD cells from the patient biopsy samples by two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization-time of flight. In the primary cultured fibroblasts, we obtained 31 candidate proteins from the two-dimensional gel image analysis in which 18 proteins were up-regulated, eight proteins were down-regulated and five proteins were post-translationally modified. From these 2-DE results, we found several candidate genes matched proteomic expression patterns by semiquantitative reverse transcription PCR. Since the exact mechanism of atopic alterations in fibroblasts remains unknown, our results may provide new clues to aid in understanding AD.

Functional classes of bronchial mucosa genes that are differentially expressed in asthma

BACKGROUND

Asthma pathogenesis and susceptibility involves a complex interplay between genetic and environmental factors. Their interaction modulates the airway inflammation and remodelling processes that are present even in mild asthma and governs the appearance and severity of symptoms of airway hyperresponsiveness. While asthma is felt to develop as the result of interaction among many different genes and signalling pathways, only a few genes have been linked to an increased risk of developing this condition.

RESULTS

We report the results of expression microarray studies using tissue obtained from bronchial biopsies of healthy controls and of subjects with allergic asthma, both before and following inhaled corticotherapy. We identified 79 genes that show significant differences in expression (following Bonferroni cutoff using p < 6.6 x 10(-6) to correct for multiple testing) in asthmatics compared to controls at significance levels. These included 21 genes previously implicated in asthma, such as NOS2A and GPX3, as well as new potential candidates, such as ALOX15, CTSC and CX3CR1. The expression levels of one third of these transcripts were partially or completely corrected following inhaled corticosteroid therapy.

CONCLUSION

The study shows that bronchial biopsies obtained from healthy and asthmatic subjects display distinct expression profiles. These differences provide a global view of physiopathologic processes active in the asthmatic lung and may provide invaluable help to clarify the natural history of asthma.

Genomics and proteomics of allergic disease

The world-wide effort to identify susceptibility genes for allergic diseases is motivated by the conviction that the identification of disease genes may permit the design of new classes of anti-inflammatory compounds. Molecules concerned with the allergic reaction, such as cytokines, chemokines, their receptors, major histocompatibility complex molecules, and transcription factors, could provide the candidate genes of the allergic diseases. On the basis of genetic studies, multiple research groups have attempted to identify a susceptibility gene for allergy using the candidate gene approach and/or genome-wide screening. Both of these approaches suggest genetic heterogeneity of allergic diseases. Many variants of candidate genes are or are not associated with particular diseases in different ethnic groups and the function of variants is now being investigated. Based on the information accumulated thus far and the information on the human genome sequence, future advances in research on genetic factors for allergic diseases will be likely lead to the establishment of more effective prophylaxis and therapy for these diseases.