Farnesoid X receptor (FXR) may be necessary for intestinal injury in experimental murine necrotizing enterocolitis

Author(s):
Michael Mallicote; Oswaldo Escobar; Christopher P. Gayer

Background:

FXR activation has been reported to decrease gut permeability in chronic injury models protecting against bacterial translocation from the intestinal lumen. However, FXR activation is also known to decrease intestinal cell proliferation, which possibly impedes barrier function following injury.

Hypothesis:

Given these inconsistencies, we hypothesize that FXR activation is detrimental to the intestinal barrier in an acute bacterially-induced injury model of necrotizing enterocolitis (NEC).

Methods:

Fourteen day-old wild-type (WT) and FXR knock-out (FXR‑KO) mice were injected with 75 mg/kg body weight of the zinc chelating agent dithizone or saline via intra-peritoneal route. Dithizone sensitizes the intestine to infectious injury by damaging Paneth cells. After 6 hours, the animals were gavage-fed 1×10^8 CFU Klebsiella pneumoniae per kg body weight. Animals were sacrificed at 16 hours. Terminal ileal sections were quantitatively graded in a blinded fashion on histology using a five-point scale (0-5) based on amount of sub-mucosal separation and edema. Additional small intestinal sections were stained to assess for phosphorylated ERK (pERK) expression with immunofluorescence (IF). Kruskal‑Wallis test was performed to compare multiple groups of non-parametric data.

Results:

Histological NEC scores in WT mice were significantly increased in dithizone/Klebsiella mice versus saline controls (p < 0.005). This effect, however, was attenuated in FXR‑KO mice, with histological scores similar to controls, suggesting that FXR is necessary for intestinal injury in this murine bacterial injury model of NEC. Expression of pERK measured by IF was lower in WT control mice compared to dithizone/Klebsiella treated WT mice. Interestingly, FXR-KO mice showed the opposite, with higher pERK levels in untreated versus treated animals, suggesting that FXR-KO mice may be primed to respond to this type of injury.

Conclusions:

Dithizone/Klebsiella-induced Intestinal injury was attenuated in FXR-KO mice compared to WT mice. FXR may be a valuable therapeutic target in NEC and intestinal injury in high-risk infants.