Do microRNAs control inflammatory mediator production by airway epithelial cells from patients with asthma and COPD?

The airways of patients with asthma or chronic obstructive pulmonary disease
(COPD) are inflamed. Inflammation and inflammation-induced tissue remodelling
contribute to the clinic, and thus intervention is aimed at reducing
inflammation. Inflammation is directed by inflammatory mediators that are
produced amongst others by the airway epithelium. Earlier, studies have
indicated that airway epithelial cells from patients have an increased basal
expression and after stimulation an exaggerated production of inflammatory
mediators. It is assumed that the airway epithelium contributes to the chronic
airway inflammation in asthma and COPD.
The production of inflammatory mediators is strictly regulated. Previous
studies have shown that the post-transcriptional regulation of inflammatory
mediator expression is easily disturbed, which results in an exaggerated
prodcution of inflammatory mediators. Post-transcriptional regulation, in
particular mRNA degradation, is probably regulated by a family of RNA-binding
proteins and microRNAs. These microRNAs are recently recognized small RNAs that
do not encode for a protein but rather interact with mRNAs.

Besides more basic research into which RNA-binding proteins and microRNAs
regulate the expression of inflammatory mediators in airway epithelial cells,
we will also assess these proteins and microRNAs in airway epithelial cells
from patients with asthma and COPD as opposed to that of controls. We
hypothesize that differences in the expression of these proteins and/or of
these microRNAs provide an explanation for the exaggerated production of
inflammatory mediators by airway epithelial cells from patients. We expect to
reveal potential targets for intervention as well as why corticosteroids
downregulate the production of inflammatory mediators in asthma but not in
COPD.

Patients with mild asthma or mild COPD and healthy matched controls will be
subjected to three sequential brushes to remove epithelial cells from the
mucosal surface. These cells will be used in two approaches. On the one hand,
part of the epithelial cells will be processed immediately to collect protein
and RNA. On the other hand epithelial cells will be cultured for several weeks
afterwhich protein and RNA will be isolated. By directly processing the
epithelial cells we make a snapshot of RNA and protein expression in situ,
whereas the analyses on the cultured cells will reveal whether any differences
in protein and RNA expression are an intrinsic characteristic of the epithelial
cells or are caused by the local milieu (in situ). For this study we expect
that the analyses of material from 15 individuals per group suffices. In our
application, however, we mention 20 individuals per group, anticipating some
difficulties in culturing the cells from patients and healthy individuals.

After anamnesis and a physical examination, individuals will be subjected to a
lung function test and 10 mls of blood will be sampled, which are considered to
be a mild burden. Bronchoscopy is an invasive technique that, despite the use
of the anaesthetic lidocain, inflicts an unpleasant feeling and thus a
considerable burden to the individual. A bronchoscopy may give rise to a dry
cough and some distress at the nose, where the bronchsope is inserted. During
brushing a superficial bleeding may develop which normally stops rapidly. The
bronchoscopy will take about 5 minutes to complete.