Inflammatory bowel disease (IBD) consists in two main clinical forms: ulcerative colitis and Crohn's disease. IBD is a complex and chronic disease with an increasing incidence in our country. Glucocorticoids are the first-line therapy in active ulcerative colitis, however, several studies have shown that up to 60% of patients do not respond adequately to steroid treatment. So the glucocorticoid treatment failure is an important complication in the treatment of IBD, with hight impact on patient evolution. Previous studies from our group have associated the presence of interleukin (IL)-10 in intestinal biopsies of patients with active Crohn's disease with a favourable response to glucocorticoid treatment. Moreover, the Il-10 deficiency in animal models has been associated with an increased intestinal permeability. Likewise,, IL-10 is capable of reducing TNF-α endoplasmic reticulum stress in intestinal epithelial cells. Our group and other groups suggest an important role of intestinal epithelium in ulcerative colitis. Taken together these last premises , it is been suggested that IL-10 plays a key role in intestinal epithelial promoting the lamina propria sealing and enabling steroid response in patients with active ulcerative colitis. The objectives of this thesis were: a) test in vitro, in Caco-2 epithelial monolayers cells, if the presence of IL-10 facilitates the glucocorticoid response acting on the barrier function, and b) determine whether these changes in vitro also are observed in the colonic mucosa of active ulcerative colitis patients with different response to glucocorticoid treatment. The results in Caco-2 monolayers cells showed that IL-10 in combination with glucocorticoids, influence the strengthening intestinal epithelium junctions through a mechanism involving the p38 MAPK phosphorylation. In these studies we found that the presence of IL-10 and glucocorticoids, increase positive nuclei p38 MAPK phosphorylation in epithelial cells. In this sense, the nuclear presence of phosphorylated p38 MAPK was higher in intestinal biopsies prior treatment in responders compared to non-responders patients, fact that may involve a higher sealing capacity of lamina propria in patients who were sensitive to treatment. Analysis by transmission electron microscopy in Caco-2 cells revealed that the main area of cell detachment occurred at desmosomes level, which was reversed getting IL-10 and glucocorticoids treatment. Moreover, in patients with active ulcerative colitis a differential pattern in the location and expression of IL-10 and glucocorticoid alpha receptor was observed depending of their steroid treatment response. In short, the synergistic action of IL-10 and glucocorticoids seems to favor the recovery of injured intestinal epithelium in active ulcerative colitis, strengthening the paracellular junctions. In this biological action p38 MAPK has a key role. Its activity is modulated mainly by IL-10 and favors the intestinal lamina propria sealing against luminal antigens. Thus the inflammatory cells activity may be diminished, thereby facilitating the apoptotic glucocorticoid response. Molecular changes that affect the glucocorticoid response can be detected in the intestinal epithelium of ulcerative colitis patients, suggesting their role as potential targets in the steroid treatment.
|Date of Award||11 Mar 2013|
|Supervisor||Josep Manyé (Director) & Rosa Miro Ametller (Tutor)|