• Prof. H.G. Gooszen, Dept. of Surgery, University Medical Centre Utrecht. Prof.
• Dr. J-P.Timmermans, Dept. of Biomedical Sciences, University of Antwerp, Belgium.

The main objective of the project is the determination of the role of mucosal mast cells in the impairment of the intestinal mucosal barrier during pathological conditions such as acute pancreatitis (AP).

Functional and morphological properties of the intestinal barrier of mice with induced AP will be characterized in vitro with the aim to quantify its impairment. With the aim to obtain direct evidence for a role of the mast cells in the impairment of the intestinal barrier, the barrier properties will be measured also on tissues from (KO) mice that lack mucosal mast cells or mast cell protease-1. The applicability of this approach on existing models of food allergies will also be tested. The possibility to suppress the barrier impairment will be investigated by application of probiotics to these models.

Further, the pathways involved in mast cell activation by physiological signalling molecules (neurotransmitters and neuropeptides) will be characterized in a cultured mucosal mast cell model. This will, apart from providing detailed insight in the mechanisms associated with the activation of mast cells, allow for the development of verifiable hypotheses for the (presumably neural) origin of the activating substances and for the neuro-immune interactions involved in impairment of the barrier.

Mucosal barrier:

To characterize the mucosal barrier condition, electrical resistance and permeability of isolated mouse ileum and colon will be measured in vitro in a Ussing chamber. The Ussing chamber experiments will be performed on an AP mice model (using cerulein).

The degree of intactness of the mucosal barrier will be determined morphologically by immunohistochemical labelling of functionally relevant proteins in the tight junctions between the epithelial cells.

Mast cells in vitro:

Using electrophysiological techniques for characterization of membrane ion channels and optical recordings of the intracellular Ca2+ concentration, in vitro mast cell responses to activating substances will be obtained to characterize membrane receptors, cellular responses and intracellular signalling pathways. Also, the vesicular release of serotonin during degranulation will be quantified using amperometry with single vesicle resolution.

Mechanisms relevant to early events in the development of immune responses will be investigated in two models, i.e. the AP mouse model and the peanut allergy model. AP is a disease with high mortality rates because small bowel bacteria overgrowth and increased intestinal permeability facilitate translocation of gastrointestinal bacteria. Study of the effects of probiotics on AP will provide knowledge of the bacterial risk factor in the intestinal system. Additionally, this research will provide information on the intestinal barrier mechanisms involved in development of food allergies, which is a major societal concern.

Recent publications (for reprint requests mail to a.kroese@uu.nl):

Rychter JW, van Minnen LP, Verheem A, Timmerman HM, Rijkers GT, Schipper MEI, Gooszen HG, Akkermans LMA, Kroese ABA. (2009) Pretreatment but not treatment with probiotics abolishes mouse intestinal barrier dysfunction in acute pancreatitis. Surgery, 145, 157-167.