The goal of this proposal is to advance as a surgeon-scientist to become an independent investigator through
completion of the proposed research project and career development under the oversight of an outstanding
mentoring team of gastrointestinal and FXR signaling experts. The career development described will provide
foundational insight as I design experimental approaches and assess study outcomes. This award will also
support the protected time needed to establish a strong publication record in the field of intestinal physiology
and develop preliminary data for a competitive R level submission.
The farnesoid X receptor (FXR) is a key bile acid receptor that influences the intestinal epithelial barrier. While
activation of FXR seems to be beneficial in chronic injury models of the intestine, our preliminary data show
that in acute, inflammatory injury, FXR activation is deleterious. FXR knock-out (KO) animals, in contrast, are
protected from acute injury. In this proposal, we will define the role of FXR in intestinal barrier function during
acute injury. We hypothesize that FXR activation compromises intestinal barrier function by upregulating small
heterodimer protein (SHP), while interfering with EGFR signaling, leading to tight junction disruption. We will
test this hypothesis with the following specific aims: 1) Determine the mechanisms involved in FXR regulating
intestinal epithelial barrier function, and 2) Test the effect of tissue-specific FXR inhibition on the intestinal bar-
rier using acute injury models in vivo.
We will determine the role of FXR and its downstream effector SHP in intestinal barrier function in vitro and in
vivo. To explore this, we will use enteroid-derived monolayers from wild type, FXR KO, SHO KO, and EGFR
dominant-negative ‘Velvet’ mice to determine the effects on the intestinal barrier and tight junctional proteins
with and without injury. We will determine FXR and EGFR signal activation using qPCR and Western blot anal-
yses. We will determine the role of macrophages using bone marrow-derived culture from genetically-modified
animals. These in vitro findings will be tested in vivo using an LPS-injection model of acute injury, utilizing FXR
(whole body, intestinal-specific, and macrophage-specific) and SHP KO mice. Cecal ligation and puncture will
be used to test pharmacologic manipulation of the FXR pathway on disease progression.
This project will begin to establish the role of FXR regulation of the intestinal epithelial barrier in the setting of
acute injury. Long term, these findings will provide needed insight into the development of preventative and
therapeutic strategies in gut origin sepsis, inflammatory bowel disease, or other GI pathologies. This research
has the potential to improve the outcomes of patients with diseases that affect intestinal integrity through better
understanding of the mechanisms of FXR-mediated intestinal barrier function.