Asthma affects more than 350 million people from which the majority are children. Since thirty years, the prevalence of asthma is steadily increasing worldwide without known causes. Several studies published in 2011 and 2012 described that the available therapies for asthma are inadequate and over 50% of asthma patients are poorly controlled. All studies concluded that there is the need of better understanding the disease’s pathophysiology and to identify new therapeutic and diagnostic targets.
Beside chronic airway inflammation, airway wall remodelling is a major pathology of asthma. Recent studies in human and primates suggested that these structural changes of the airway wall can cause chronic inflammation. In 2009 we were the first to show that in asthma the protein synthesis (translation) of the cell differentiation factor C/EBP-α is disease and cell type specific in airway smooth muscle cells and is most probably the cause of airway wall muscle hypertrophy and hyperplasia. Furthermore, we reported that two well known triggers of asthma exacerbation (house dust mite allergen, cigarette smoke) reduce the translation of C/EBP-α in airway smooth muscle cells causing hyper-proliferation and secretion of inflammatory cytokines.
In total we can document the reduced expression of C/EBP-α in 63 smooth muscle samples of asthma patients suffering either from chronic or allergic asthma. In the healthy lung C/EBP-α directs lung development during embryogenesis, apoptosis and tissue repair and in other cell types it directs maturation (adipocytes, hematopoetic cells). The mechnaism how C/EBP-α controls cell differentiation is not fully understood and it is assumed that the four isoforms play a directive role. Furthermore, post-tranmslational modifications of the C/EBP-α proteins may regulate its interactionw with other transcription factors including CREB, AP-1, Oct-1, and hormone receptors. It was recently suggested that each of the four known C/EBP-α isoforms, executes specific functions which depend on the cellular compartment they are located.
In this project, we will investigate the asthma specific modified expression of C/EBP-α isoforms. In earlier experiments we used antibodies that recognised different epitopes of C/EBP-α which showed different expression ratios of the different isoforms. First, we aim to better define the cell compartmental accumulation of specific C/EBP-α isoform in isolated human diseased and healthy airway smooth muscle cells and in tissue sections of asthma patients.
Second, we will use different epitope specific antibodies to isolate the different C/EBP-α isoforms from asthmatic and non-asthmatic smooth muscle cells and then sequence the amino acids. The aim of this part is to identify possible sides for post-translational modifications including phosphorylation, sumoylation, ubiquitinylation and glutathionylation. Each of this modification can affect the cellular location and function of C/EBP-α.
Third, we aim to generate modified C/EBP-α isoform expression vectors to study their effect on smooth muscle cell differentiation by determining the expression of α-smooth muscle actin, desmin, calponin; on mitochondria activity, on proliferation and secretion of inflammatory cytokines.
The expected results will provide new understanding for the role of C/EBP-α isoforms in the physiology of the healthy lung as well as the contribution of specific isoforms to the pathology of asthma. We expect that the novel data will help to establish new concepts for therapy or even the cure for the disease.