Su1193 Rifaximin Prevents Enteric Bacteria Alterations and Inflammation in a Rat Model of Diclofenac-Induced Enteropathy

Rifaximin Prevents Enteric Bacteria Alterations and Inflammation in a Rat Model of Diclofenac-Induced Enteropathy Inflammation in a Rat Model of Diclofenac-Induced Enteropathy Rocchina Colucci, Erika Tirotta, Emilia Ghelardi, Elena Piccoli, Luca Antonioli, Matteo Fornai, Cecilia Renzulli, Carolina Pellegrini, Corrado Blandizzi, Carmelo Scarpignato Introduction. Non-steroidal anti-inflammatory drugs (NSAIDs) can exert detrimental effects on the intestine. Although the underlying mechanisms remain unclear, enteric bacteria play a prominent role. In particular, NSAIDs increase mucosal permeability, thus facilitating the tissue entrance of bacteria, which then trigger inflammation via toll-like receptors (TLRs). This study examined the effects of rifaximin, a poorly absorbed antibiotic, on enteric bacteria and bowel inflammation in a rat model of diclofenac (DIC)-induced enteropathy. Methods. Enteropathy was induced in 40-week-old male rats by intragastric (i.g.) administration of DIC (4 mg/kg BID, 14 days). Controls received drug vehicle (1% methylcellulose). Coated microgranules of rifaximin (REIR, 50 mg/kg BID, i.g.) was administered twice daily 1 hour before DIC (n=6-7 per group). At end of treatments, feces were collected to quantify calprotectin by ELISA. Ileum was excised and processed for the evaluation of: microscopic damage (percent length of lesions over the length of ileal tissue examined), myeloperoxidase (MPO) levels (an index of neutrophil infiltration); bacterial total load and quantitative analysis of Bacterioidetes and Firmicutes phyla, via 16S real-time PCR; expression of TLR-2/4 and activation of downstream signaling as phosphorylated nuclear factor kB subunit p65 (NFkB p65) and myeloid-differentiation primary response-gene 88 (MyD88), by Western blot. Results. DIC treatment was associated with the development of ileal lesions, which were significantly reduced in animal receiving DIC+REIR. As compared with controls, tissue MPO and fecal calprotectin levels were significantly increased in DIC-treated animals. Coadministration of DIC with REIR counteracted these increments. Total bacterial load as well as Bacteroidetes and Firmicutes increased after treatment with DIC. The expression of TLR- 2/4, NF-kB p65 and MyD88 in DIC-treated animals were also higher, as compared with control animals (respectively: +104%,+23%,+147% and +71%). After co-administration of DIC with REIR, the bacterial total load decreased, with a significant reduction of Bacteroidetes and Firmicutes, and the increased expression levels of TLR-2/4, NF-kB p65 and MyD88 returned towards control values. The overall results are summarized in the enclosed table . Conclusion. In the small bowel, treatment with DIC leads to the occurrence of tissue lesions and inflammatory activation that are associated with quantitative and qualitative alterations of enteric bacteria, and an increased expression/activation of TLR-2/4 pathways. Under these conditions, REIR prevents the DIC-induced intestinal damage, this entero-protective effect being associated with a substantial decrease in tissue inflammation and modulation of the enteric bacterial population.