Expression of PPAR γ in intestinal epithelial cells is dispensable for the prevention of colitis by dietary abscisic acid

Abstract

Dietary abscisic acid (ABA) has shown efficacy in ameliorating experimental IBD in mice through mechanisms requiring expression of peroxisome proliferator activated-receptor γ (PPAR γ) in immune cells. The goal of this study was to determine whether PPAR γ expression in colonic epithelial cells is required for the anti-inflammatory actions of ABA. Conditional knockout mice expressing a transgenic recombinase in intestinal epithelial cells under the control of a villin promoter (PPAR γ flfl; Villin Cre+ or VC+) with defective expression of PPAR γ in intestinal cells (IEC) and PPAR γ-expressing wild type (PPAR γ flfl; Villin Cre- or VC-) mice in a C57BL/6 background were fed diets with and without ABA (0.1 g/kg) for 35 days and challenged with 2.5% dextran sodium sulfate (DSS) in the drinking water for 7 days. Clinical disease severity was assessed daily and colonic lesions on day 7 through macroscopic and histopathological examination. Immune cell phenotypes were examined systemically and at the mesenteric lymph nodes (MLN). Epithelial gene expression was assayed in the colon. Dietary ABA-supplementation prevented colitis, reduced disease severity, improved colonic histopathology, and upregulated epithelial lanthionine synthetase C-like protein 2 (LANCL2) expression in VC+ mice. Dietary ABA significantly increased the percentages of MLN CD4+IL-10+ T cells, and blood CD4+CD25+FoxP3+ T cells and CD8+IL-10+ T cells. Expression of PPAR γ in IECs was not required for the anti-inflammatory efficacy of ABA in IBD. LANCL2 in IECs and T cell-derived IL-10 may be implicated in the mechanism underlying ABA's immune modulatory activity in IBD.