title: Regulation of biotransformation systems and ABC transporters by benznidazole in HepG2 cells: involvement of pregnane X-receptor.
abstract: BACKGROUND
  Benznidazole (BZL) is the only antichagasic drug available in most endemic countries. Its effect on the expression and activity of drug-metabolizing and transporter proteins has not been studied yet.
  
  
  RESULTS
  Expression and activity of P-glycoprotein (P-gp), Multidrug resistance-associated protein 2 (MRP2), Cytochrome P450 3A4 (CYP3A4), and Glutathione S-transferase (GST) were evaluated in HepG2 cells after treatment with BZL. Expression was estimated by immunoblotting and real time PCR. P-gp and MRP2 activities were estimated using model substrates rhodamine 123 and dinitrophenyl-S-glutathione (DNP-SG), respectively. CYP3A4 and GST activities were evaluated through their abilities to convert proluciferin into luciferin and 1-chloro-2,4-dinitrobenzene into DNP-SG, respectively. BZL (200 µM) increased the expression (protein and mRNA) of P-gp, MRP2, CYP3A4, and GSTπ class. A concomitant enhancement of activity was observed for all these proteins, except for CYP3A4, which exhibited a decreased activity. To elucidate if pregnane X receptor (PXR) mediates BZL response, its expression was knocked down with a specific siRNA. In this condition, the effect of BZL on P-gp, MRP2, CYP3A4, and GSTπ protein up-regulation was completely abolished. Consistent with this, BZL was able to activate PXR, as detected by reporter gene assay. Additional studies, using transporter inhibitors and P-gp-knock down cells, demonstrated that P-gp is involved in BZL extrusion. Pre-treatment of HepG2 cells with BZL increased its own efflux, as a consequence of P-gp up-regulation.
  
  
  CONCLUSIONS
  Modifications in the activity of biotransformation and transport systems by BZL may alter the pharmacokinetics and efficiency of drugs that are substrates of these systems, including BZL itself.
authors.affiliation: Institute of Experimental Physiology, School of Biochemical and Pharmaceutical Sciences, Rosario, Argentina.
authors.forename: Juan P
authors.initials: JP
authors.lastname: Rigalli
authors.forename: Virginia G
authors.initials: VG
authors.lastname: Perdomo
authors.forename: Marcelo G
authors.initials: MG
authors.lastname: Luquita
authors.forename: Silvina S M
authors.initials: SS
authors.lastname: Villanueva
authors.forename: Agostina
authors.initials: A
authors.lastname: Arias
authors.forename: Dirk
authors.initials: D
authors.lastname: Theile
authors.forename: Johanna
authors.initials: J
authors.lastname: Weiss
authors.forename: Aldo D
authors.initials: AD
authors.lastname: Mottino
authors.forename: María L
authors.initials: ML
authors.lastname: Ruiz
authors.forename: Viviana A
authors.initials: VA
authors.lastname: Catania
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000096:biosynthesis*; D000981:Antiprotozoal Agents / Q000378:metabolism*; D001711:Biotransformation; D015153:Blotting, Western; D020869:Gene Expression Profiling; D056945:Hep G2 Cells; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D053858:Metabolic Networks and Pathways / Q000235:genetics; D009593:Nitroimidazoles / Q000378:metabolism*; D000077297:Pregnane X Receptor; D060888:Real-Time Polymerase Chain Reaction; D011987:Receptors, Steroid / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000981:Antiprotozoal Agents; D009593:Nitroimidazoles; D000077297:Pregnane X Receptor; D011987:Receptors, Steroid; C009999:benzonidazole