Amelioration of Clostridium difficile Infection in Mice by Dietary Supplementation With Indole-3-carbinol

Abstract

Objective To determine the therapeutic effects of dietary supplementation on C. difficile infection (CDI). Background With limited treatment options, the rise of Clostridium difficile-associated disease has spurred on the search for novel therapies. Recent data define a role for the aryl hydrocarbon receptor (AHR) and diet-derived AHR ligands in mucosal immunity. We investigated the efficacy of indole-3-carbinol (I3C), a dietary supplement and AHR precursor ligand, in a murine model of CDI. Methods C57BL/6 (B6), AHR−/− and AHR+/− mice were placed on either grain-based or semi-purified diets with or without I3C prior to and during CDI. Mice were followed clinically for a minimum of 6 days, or euthanized between days 0 and 4 of inoculation for analysis of the inflammatory response and microbiota. Results B6 mice fed an AHR ligand-deficient, semi-purified diet have significantly increased disease severity (p < 0.001) and mortality (p<0.001) compared to mice fed diet containing I3C. The addition of I3C to the diet of AHR null mice had less of an impact than in AHR heterozygous littermates, although some protection was seen. Mice on semi-purified I3C-diet had increased cecal Tregs, ILC3s, and γδ T cells as well as an increased neutrophilic response without increased inflammation or bacterial translocation compared to controls. Conclusions I3C is a powerful treatment to reduce impact of CDI in mice. The findings indicate I3C may be acting through both AHR-dependent and -independent mechanisms in this model. Dietary supplementation with I3C is a potential new therapy for prevention and amelioration of C. difficile disease.

Dietary broccoli impacts microbial community structure and attenuates chemically induced colitis in mice in an Ah receptor dependent manner

“…We found that the administration of the chemical mixture within broccoli does not mitigate AHR activation. Notably we observe the occurrence of broccoli mediated benefits and AHR activation at relatively low daily doses of I3C (4.64 mg/kg), which is 15–60 fold lower than that used in previous studies (Stoner, Casto et al 2002; Julliard, De Wolfe et al 2016). While heightened doses of I3C may promote intestinal health, they will lead to systemic circulation of AHR ligands that are associated with development of hepatocarcinoma (Stoner, Casto et al 2002; (NTP) 2014).…”

Aryl hydrocarbon receptor and intestinal immunity

“…Supplementation of a semipurified diet with I3C reduces the severity of C. difficile infection in WT and AhR -/mice, suggesting that the effects of I3C may be mediated by both AhR-dependent and independent mechanisms. 173 At least in WT mice, I3C diet-mediated protection against C. difficile infection was due to increased populations of cecal Treg, ILC3, γδ T cells, and neutrophils before infection. 173 In addition to its protective effect against intestinal pathogenic bacteria, AhR is also involved in resistance to fungi.…”

“…173 At least in WT mice, I3C diet-mediated protection against C. difficile infection was due to increased populations of cecal Treg, ILC3, γδ T cells, and neutrophils before infection. 173 In addition to its protective effect against intestinal pathogenic bacteria, AhR is also involved in resistance to fungi. Administration of IAld, a bacteria-derived AhR ligand, to Candida albicans-infected WT mice induced IL-22 production by colonic NKp46 + cells, which enhanced resistance to fungi.…”

Ligand activation of the Ah receptor contributes to gastrointestinal homeostasis

“…These studies, along with the general chemopreventive properties of AHR ligand treatment on gastrointestinal health would suggest that AHR ligands in the diet may protect against opportunistic bacterial infections. Indeed, a recent study demonstrated that dietary I3C can decrease the level of Clostridium difficile induced lethality in mice, in part through activation of the AHR [86]. It will be important to test other AHR ligands in this infection model.…”