PB1300 - Intestinal Epithelial Protease-Activated Receptor-1 affects Gastrointestinal Motility and the Enteric Nervous System

Background: Protease-activated receptor-1 (PAR1), traditionally called the thrombin receptor (F2r), is expressed in several cell types in the gastrointestinal (GI) tract, where it mediates (patho)physiological functions.
The GI tract presents its own intrinsic nervous system, the enteric nervous system (ENS), controlling GI transit and composed by the submucosal and myenteric plexuses.
PAR1 modulates GI motility by affecting smooth muscle cell contraction/relaxation and sensory neurons. However, the underlying molecular pathways and the cell-specific contribution of PAR1 on the ENS remain elusive.

Aims: To analyze the cell type-specific role of PAR1 on GI motility and ENS morphology.

Methods: Two conditional PAR1-knockout mouse models were generated: flF2rxVil-Cre strain (F2rΔIEC) and flF2rxVE-Cdh-Cre strain (F2rΔEC), in which PAR1 is deleted in the intestinal epithelial or endothelial cells.
GI motility was analyzed by monitoring the ex vivo fecal transit time in the colon (cm/min).
The ENS was studied on the myenteric plexus isolated from the mid- and distal-small intestine. Longitudinal muscle-myenteric plexus (LMMP) layers were dissected and stained for β3-tubulin (Tuj1), a pan-marker for axons and dendrites. The status of the ENS was assessed by quantifying the Tuj1+ area on a region of interest.
For each strain, knockout mice were compared to wild type (WT) littermates. Results were presented as mean ± SEM and evaluated by independent samples Student’s t test.

Results: GI motility assay revealed that F2rΔIEC mice present an increased fecal speed compared to WT controls. Quantification of β3-tubulin highlighted a lower Tuj1+ area in the mid-small intestine of F2rΔIEC mice, while F2rΔEC mice showed an opposite, albeit not significant, trend. In both mouse models, distal-small intestine was unaffected.

Conclusion(s): Intestinal PAR1 mediates different effects on GI motility and ENS, depending on the cell type. In particular, PAR1-deletion in the epithelium leads to an impaired neuronal network in the jejunum, but increased GI motility in the colon.