A38 EVALUATING GLYCOCAGED DEXAMETHASONE IN SHIP-DEFICIENT MICE

Abstract

Background

Corticosteroids systemically reduce immune system activity thereby limiting inflammation in the GI tract. Corticosteroid use is limited by deleterious systemic effects including immunosuppression and adverse effects on growth and development (Giles et al., 2018). The metabolism of dietary polysaccharides, such as plant cell wall xyloglucan, by gut symbionts has been demonstrated to be mediated by niche members of the human gut microbiota (Larsbrink et al., 2014). By caging corticosteroids like dexamethasone (DEX) with xyloglucans to be released by microbiota at the site of disease, there is potential to increase efficacy and limit adverse effects.

Mice deficient in Src homology 2 domain-containing inositol polyphosphate 5’-phosphatase (SHIP^-/-) develop spontaneous CD-like ileal inflammation (Ngoh et al., 2016). We have used SHIP^-/- mice to compare the efficacy of DEX versus caged DEX to reduce intestinal inflammation.

Aims

Caged DEX will reduce CD-like ileal inflammation in SHIP^-/- mice at a lower dose than uncaged DEX because it is released and acts at the site of inflammation.

To assess this hypothesis we propose 3 aims:

Measure decaging activity along the GI tract of SHIP^-/- mice ex vivo

Determine the minimum effective dose of DEX required to reduce ileal inflammation in SHIP^-/- mice

Determine if equimolar and lower concentrations of caged DEX can reduce ileal inflammation in SHIP^-/- mice

Methods

Intestinal contents and feces were harvested from SHIP^-/- mice. Decaging activity was measured ex vivo, using caged resorufin (a fluorescent reporter).

SHIP^-/- mice were orally gavaged with dexamethasone (or vehicle), or the molar equivalent of caged dexamethasone from 6–8 weeks of age. At 8 weeks of age, gross and histopathology were assessed and IL-1β concentrations were measured in full-thickness tissue homogenates.

Results

SHIP^-/- mice demonstrated decaging activity in the cecal, colon, and fecal contents assayed. DEX treatment (3 or 1 mg/kg) of SHIP^-/- mice eliminated CD-like gross pathology and histopathology, and reduced IL-1β concentrations in full-thickness ileal tissue homogenates from SHIP^-/- mice compared to untreated or vehicle-treated mice. DEX did not have any harmful effects on the intestines of SHIP^+/+ mice. 1 or 0.3 mg/kg molar equivalent of caged DEX (3-fold lower concentrations) eliminated CD-like gross pathology in SHIP^-/- mice compared to treatment with vehicle control. Additionally, the mean IL-1β concentration in tissue homogenates of mice treated with the molar equivalent of 1 mg/kg caged DEX was reduced

Conclusions

SHIP^-/- mice express decaging activity are effectively treated by DEX, and caged DEX shows similar efficacy at reducing SHIP^-/- ileal pathology at lower concentrations than uncaged DEX. In future experiments, we will examine caged DEX at a lower concentration, and in 2nd mouse model of intestinal inflammation.

Funding Agencies

GlycoNet