Diet Modifies Colonic Microbiota and CD4+ T-Cell Repertoire to Induce Flares of Colitis in Mice With Myeloid-Cell Expression of Interleukin 23

Abstract

<div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d535822e258">Background &amp; Aims</h5> <p id="P2">Several studies have shown that signaling via the interleukin 23 (IL23) receptor is required for development of colitis. We studied the roles of IL23, dietary factors, alterations to the microbiota, and T cells in development and progression of colitis in mice. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d535822e263">Methods</h5> <p id="P3">All mice were maintained on lab diet 5053, unless otherwise noted. We generated mice that express IL23 in CX3CR1-positive myeloid cells ( <i>R23FR</i> mice) upon cyclic administration of tamoxifen dissolved in diet 2019. Diet 2019 and 5053 have minor differences in the overall composition of protein, fat, fiber, minerals, and vitamins. CX3CR1 ^CreER mice ( <i>FR</i> mice) were used as controls. Some mice were given antibiotics and others were raised in a germ-free environment. Intestinal tissues were collected and analyzed by histology and flow cytometry. Feces were collected and analyzed by 16S rDNA sequencing. Feces from C57/Bl6, <i>R23FR</i>, or <i>FR</i> mice were fed to <i>FR</i> and <i>R23FR</i> germ-free mice in microbiota transplant experiments. We also performed studies with <i>R23FR</i>/ <i>Rag</i> ^−/−, <i>R23FR</i>/ <i>Mu</i> ^−/−, and <i>R23FR</i>/ <i>Tcrd</i> ^−/− mice. <i>R23FR</i> mice were given injections of antibodies against CD4 or CD8 to deplete T cells. Mesenteric lymph nodes and large intestine CD4 ⁺ cells from <i>R23FR</i> or <i>FR</i> mice in remission from colitis were transferred into <i>Rag</i> ^−/− mice. CD4 ⁺ cells were isolated from donor <i>R23FR</i> mice and recipient <i>Rag</i> ^−/− mice, and T-cell receptor sequences were determined. </p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d535822e350">Results</h5> <p id="P4">Expression of IL23 led to development of a relapsing–remitting colitis that was dependent on the microbiota and CD4 ⁺ T cells. The relapses were caused by switching from the conventional diet used in our facility (diet 5053) to the diet 2019, and were not dependent on tamoxifen after the first cycle. The switch in the diet modified the microbiota, but did not alter levels of IL23 in intestinal tissues, compared to mice that remained on the conventional diet. Mesenteric lymph nodes and large intestine CD4 ⁺ cells from <i>R23FR</i> mice in remission, but not from <i>FR</i> mice, induced colitis after transfer into <i>Rag</i> ^−/− mice, but only when these mice were placed on the diet 2019. The CD4 ⁺ T-cell receptor repertoire of <i>Rag</i> ^−/− mice with colitis (fed the 2019 diet) was less diverse than that from donor mice and <i>Rag</i> ^−/− mice without colitis (fed the 5053 diet), due to expansion of dominant T-cell clones. </p> </div><div class="section"> <a class="named-anchor" id="S4"> <!-- named anchor --> </a> <h5 class="section-title" id="d535822e389">Conclusions</h5> <p id="P5">We developed mice that express IL23 in CX3CR1-positive myeloid cells ( <i>R23FR</i> mice) and found they are more susceptible to diet-induced colitis than mice that do not express IL23. The <i>R23FR</i> mice have a population of CD4 ⁺ T cells that becomes activated in response to dietary changes and alterations to the intestinal microbiota. The results indicate that alterations in the diet, intestinal microbiota, and IL23 signaling can contribute to pathogenesis of inflammatory bowel disease. </p> </div>