title: Rifaximin Improves Clostridium difficile Toxin A-Induced Toxicity in Caco-2 Cells by the PXR-Dependent TLR4/MyD88/NF-κB Pathway.
abstract: BACKGROUND
  Clostridium difficile infections (CDIs) caused by Clostridium difficile toxin A (TcdA) lead to severe ulceration, inflammation and bleeding of the colon, and are difficult to treat.
  
  
  OBJECTIVE
  The study aimed to evaluate the effect of rifaximin on TcdA-induced apoptosis in intestinal epithelial cells and investigate the role of PXR in its mechanism of action.
  
  
  METHODS
  Caco-2 cells were incubated with TcdA and treated with rifaximin (0.1-10 μM) with or without ketoconazole (10 μM). The transepithelial electrical resistance (TEER) and viability of the treated cells was determined. Also, the expression of zona occludens-1 (ZO-1), toll-like receptor 4 (TLR4), Bcl-2-associated X protein (Bax), transforming growth factor-β-activated kinase-1 (TAK1), myeloid differentiation factor 88 (MyD88), and nuclear factor-kappaB (NF-κB) was determined.
  
  
  RESULTS
  Rifaximin treatment (0.1, 1.0, and 10 μM) caused a significant and concentration-dependent increase in the TEER of Caco-2 cells (360, 480, and 680% vs. TcdA treatment) 24 h after the treatment and improved their viability (61, 79, and 105%). Treatment also concentration-dependently decreased the expression of Bax protein (-29, -65, and -77%) and increased the expression of ZO-1 (25, 54, and 87%) and occludin (71, 114, and 262%) versus TcdA treatment. The expression of TLR4 (-33, -50, and -75%), MyD88 (-29, -60, and -81%) and TAK1 (-37, -63, and -79%) were also reduced with rifaximin versus TcdA treatment. Ketoconazole treatment inhibited these effects.
  
  
  CONCLUSIONS
  Rifaximin improved TcdA-induced toxicity in Caco-2 cells by the PXR-dependent TLR4/MyD88/NF-κB pathway mechanism, and may be useful in the treatment of CDIs.
authors.affiliation: Department of Physiology and Pharmacology "Vittorio Erspamer", Sapienza University of Rome Rome, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Esposito
authors.affiliation: Department of Physiology and Pharmacology "Vittorio Erspamer", Sapienza University of Rome Rome, Italy.
authors.forename: Nicola
authors.initials: N
authors.lastname: Nobile
authors.affiliation: Department of Physiology and Pharmacology "Vittorio Erspamer", Sapienza University of Rome Rome, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Gigli
authors.affiliation: Department of Physiology and Pharmacology "Vittorio Erspamer", Sapienza University of Rome Rome, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: Seguella
authors.affiliation: Department of Clinical Medicine and Surgery, University of Naples Federico II Naples, Italy.
authors.forename: Marcella
authors.initials: M
authors.lastname: Pesce
authors.affiliation: Department of Clinical Medicine and Surgery, University of Naples Federico II Naples, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: d'Alessandro
authors.affiliation: Department of Translational Medical Science, University of Naples Federico II Naples, Italy.
authors.forename: Eugenia
authors.initials: E
authors.lastname: Bruzzese
authors.affiliation: Department of Physiology and Pharmacology "Vittorio Erspamer", Sapienza University of Rome Rome, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Capoccia
authors.affiliation: Department of Physiology and Pharmacology "Vittorio Erspamer", Sapienza University of Rome Rome, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Steardo
authors.affiliation: Department of Clinical Medicine and Surgery, University of Naples Federico II Naples, Italy.
authors.forename: Rosario
authors.initials: R
authors.lastname: Cuomo
authors.affiliation: Department of Clinical Medicine and Surgery, University of Naples Federico II Naples, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Sarnelli
keywords: Caco-2 cells; Clostridium difficile toxin A; pregnane X receptor; pseudomembranous colitis; rifaximin