Inhibition of Intestinal Bacterial Translocation with Rifaximin Modulates Lamina propria Monocytic Cells Reactivity and Protects against Inflammation in a Rodent Model of Colitis

Abstract

Background: A modification of the intestinal flora and an increased bacterial translocation is a common finding in patients with inflammatory bowel disease as well as in animal model of colitis. Rifaximin, a non-absorbable derivative of rifamycin, is an effective antibiotic that acts by inhibiting bacterial ribonucleic acid synthesis. Aims: In the present study, we investigated the effect of the administration of rifaximin (10, 30 and 50 mg/kg/day) or prednisolone (10 mg/kg/day) in 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis in mice. Methods: Colitis was induced in mice by intrarectal administration of TNBS (1.5 mg/mouse in 50% ethanol) and disease severity assessed clinically and by histologic scoring of colon damage, determination of interleukin (IL)-2, IL-12, interferon (IFN)-γ and tumor necrosis factor (TNF)-α (protein and mRNA and myeloperoxidase (MPO) activity in the colon. Cytokines production by the lamina propria mononuclear cells (LPMC) and luminal bacteria were also measured. Results: Rifaximin administration (30 or 50 mg/kg/day) increased survival rates of colitic mice and reduced colitis severity as demonstrated by improvement of wasting syndrome, histologic scores, decrease in colon IL-2, IL-12, IFN-γ and TNF-α (protein and mRNA) levels, and diminished colon MPO activity. Rifaximin administration caused a significant reduction of colon bacterial translocation towards mesenteric lymph nodes. LPMC obtained from rifaximin-treated mice released significantly lower amount of IFN-γ in response to ex vivo stimulation with agonistic anti-CD3 and anti-CD28 antibodies. Rifaximin (50 mg/kg/day) significantly accelerates recovery in mice with established colitis. Conclusions: Luminal bacterial microflora plays a role in the pathogenesis of TNBS-induced colitis in mice. Rifaximin administration reduces the development of colitis and accelerates healing of established disease by preventing bacterial translocation.