Background: Ghrelin, a novel endogenous ligand for the growth hormone secretagogue receptor (GHSR), has been demonstrated to possess multiple functions including antiinflammatory effects. The aim of this study was to investigate the expression of ghrelin and GHSR and the function of ghrelin in inflammatory bowel disease (IBD).
Methods: The expression of ghrelin and GHSR mRNA was quantified in mucosal biopsy specimens from 9 controls, 15 patients with Crohn's disease (CD), and 15 patients with ulcerative colitis (UC) using quantitative reverse-transcriptase polymerase chain reaction (RT-PCR). The locations of ghrelin and GHSR were investigated immunohistochemically in surgically resected specimens. We also evaluated the percentage of GHSR-positive peripheral blood mononuclear cells (PBMCs) in healthy controls and patients with CD by flow cytometry. In addition, we investigated the immunoregulatory function of ghrelin in peripheral blood T cells.
Results: Ghrelin mRNA levels in colonic mucosa of IBD were higher than control level. The GHSR-1a mRNA level in active CD was also significantly higher than the control level. Ghrelin and GHSR-1a were expressed on CD3- and CD68-positive cells. The percentage of GHSR-1a-positive peripheral blood T cells in patients with CD was significantly higher than the control level. Stimulation of human T cells with ghrelin increased levels of IL-4 and IL-13 proteins and decreased levels of IFN-gamma protein. Reactivity to ghrelin was low in CD compared with the control level.
Conclusions: Our findings demonstrate that ghrelin may play an important role in the immune system in CD. The dysregulation of reactivity of T cells induced by ghrelin suggests that ghrelin might participate in the pathogenesis of CD.