Project

Discipline

translation control; epigenetics; open reading frame; asthma; epigenetic; translation regualtion; airway smooth muscle; cell differentiation control; transcription factor interaction

Lead
Asthma, the most frequent chronic disease (> 350 million patients) is not curable. In human asthma we found faulty translation (mRNA-protein) of the cell differentiation factor C/EBP-alpha in airway smooth muscle cells, which explains the clinical well documented muscle hyperplasia. Here we investigate if the faulty translation affects only C/EBP-alpha mRNA or also other asthma relevant mRNAs. The faulty translation might be due to calreticulin overexpression a known C/EBP translation regulator.
Lay summary
The number of people suffering from asthma is increasing worldwide since 30 years and nobody knows why. Asthma affects over 300 million people and is the major cause of absence from school and work. Asthma cannot be treated, only the symptoms can be controlled by steroids, beta-agonists and other anti-inflammatory drugs. In the past decades asthma was thought to result from an activated over sensible immune system. However, the allergic reaction may indeed be a secondary pathology which develops after a change of the airway structure. The structure of asthmatic airway is changed and becomes stiffer, causing it unable to open up easily after an asthma attack where the airway muscle constricts. Interestingly, asthma was first defined as a disease of the airway muscle in 1922. New evidence suggests that this original hypothesis was correct. Inactivating airway smooth muscle by a novel therapy results a lasting improvement of symptoms and of overall life quality of asthma patients. However, this therapy is not used for treating most asthma patients as it is a major surgical procedure. Therefore, we are looking for alternatives to control the activity of airway smooth muscle in asthma. Together with our main collaborator (Prof. Black, Sydney, Australia), we have learned to isolate airway muscle cells from asthma patients and healthy volunteers with a minimal surgical methodology. With these human cells we described new pathologies which could be confirmed in patients. Here it should be noted that no asthma animal model shows the same pathologies as we know them in humans. Therefore, it is necessary and important to use human diseased cells to find out what is going wrong in the asthmatic lung. Our major findings in the past years was that human asthmatic airway muscle cells multiply faster and secrete more inflammatory proteins compared to healthy cells. We identified a missing protein (C/EBP-alpha) which controls cells maturation and this keeps the cell in a stage where they can multiply faster. This control protein is not correctly translated from its genetic information into a protein. In 2009 we described the mechanism which is responsible for not translating this particular protein. Furthermore, we found additional proteins and inflammation enhancing factors that are deregulated in asthma. In this study we aim to find out if the same mechanism that caused the down-regulation of C/EBP-alpha is responsible for the de-regulation of these other asthma related proteins. The expected results may open a new way on how to normalise the function of airway muscle cells and thereby curing asthma

Direct link to Lay Summary

Last update: 23.01.2013

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Over the past three decades, the prevalence of asthma dramatically increased, now affecting worldwide about 300 million people according to an analysis of the WHO. Although the cause of asthma is still unknown, it remains the major cause for absence from school and work; and thus is a significant health care cost factor. Today, asthma is regarded as a chronic inflammatory lung disease caused by an over-reactive im-mune response to a wide range of stimuli. Recently there is accumulating evidence this immune response may be accompanied or caused by an altered, disease specific behaviour of the airway smooth muscle cell (ASMC). In our studies on primary hu-man ASMC of asthma patients several disease-specific cellular and bio-molecular characteristics were maintained in vitro: increased secretion of pro-inflammatory cy-tokines, contracting properties, the disease-specific extracellular matrix composition, and a predisposition to proliferate faster. The latter was associated with diminished levels of the transcription/differentiation factor C/EBP-alpha. The diminished C/EBP-alpha level was due to a decreased mRNA translation initiation, and was induced by house dust mite allergen, cigarette smoke and oxidative stress by three independent mechanisms: (i) via direct interaction of calreticulin with C/EBP mRNA, (ii) indirect via PAR-2 activation, or (iii) by depletion of glutathione. Our observations provide a rationale for how several distinct environmental stimuli lead to the same pathological outcome, known as asthma. In addition to an impaired C/EBP-alpha mRNA transla-tion, we have data showing that the translation of IL-8 is also deregulated in asthma ASMC. Previously, we have proposed and provided evidence that asthma may be regarded a disease of the airways in which a deregulated translation control of gene expression in ASMC may play a pivotal role. Based on our earlier studies we now would like to as-sess to what extent the impaired regulation of mRNA translation into proteins is pre-sent in other cell types and at what molecular level it occurs. We will also link it to environmental triggers, including allergens, physical stress and oxygen radicals. In the proposed study, we will address the following questions: (i) What are the signalling pathways that lead to a de-regulated translation initiation and if this is a disease-specific defect?(ii) Is the increased expression of inflammatory cytokines (IL-4, IL-8, RANTES, and eoxtaxin) as observed in ASMC of astma patients due to the lack of C/EBP-alpha or due to more general defect related to faulty mRNA translation? (iii) Are house dust mite allergens, pollen and oxidative stress, (common asthma trig-gers) able to cause a general deregulation of mRNA translation? (iv) Is an impaired mRNA translation a specific pathology of the ASMC of asthma patients or do we also observe it in other lung cell types of the same asthma patients (fibroblasts, epithelial cells)?The expected results will not only improve the understanding of the molecular mechanism underlying asthma, it may also provide various new aspects how asthma is initiated. The data may become the basis to develop novel therapeutic curative con-cepts rather then the existing symptom controlling drugs.