Modulation of biotransformation systems and ABC transporters by benznidazole in rats

Abstract

The effect of antichagasic benznidazole (BZL; 100 mg/kg body weight/day, 3 consecutive days, intraperitoneally) on biotransformation systems and ABC transporters was evaluated in rats. Expression of cytochrome P-450 (CYP3A), UDP-glucuronosyltransferase (UGT1A), glutathione S-transferases (alpha glutathione S-transferase [GST-α], GST-μ, and GST-π), multidrug-resistance-associated protein 2 (Mrp2), and P glycoprotein (P-gp) in liver, small intestine, and kidney was estimated by Western blotting. Increases in hepatic CYP3A (30%) and GST-μ (40%) and in intestinal GST-α (72% in jejunum and 136% in ileum) were detected. Significant increases in Mrp2 (300%) and P-gp (500%) proteins in liver from BZL-treated rats were observed without changes in kidney. P-gp and Mrp2 were also increased by BZL in jejunum (170% and 120%, respectively). In ileum, only P-gp was increased by BZL (50%). The activities of GST, P-gp, and Mrp2 correlated well with the upregulation of proteins in liver and jejunum. Plasma decay of a test dose of BZL (5 mg/kg body weight) administered intraduodenally was faster (295%) and the area under the concentration-time curve (AUC) was lower (41%) for BZL-pretreated rats than for controls. The biliary excretion of BZL was higher (60%) in the BZL group, and urinary excretion of BZL did not show differences between groups. The amount of absorbed BZL in intestinal sacs was lower (25%) in pretreated rats than in controls. In conclusion, induction of biotransformation enzymes and/or transporters by BZL could increase the clearance and/or decrease the intestinal absorption of coadministered drugs that are substrates of these systems, including BZL itself.

Fig 1

Effect of BZL on CYP3A expression and GST expression and activity in hepatic and intestinal tissues. (A) Microsomal CYP3A was detected by Western blotting in liver from rats treated with BZL (100 mg/kg b.w./day, 3 consecutive days) or vehicle (control [C]). (B) Cytosolic GST-μ was detected by Western blotting in liver from rats treated with BZL (100 mg/kg b.w./day, 3 consecutive days) or vehicle. (C and D) Cytosolic GST-α was detected by Western blotting in jejunum and ileum, respectively, from rats treated with BZL (100 mg/kg b.w./day, 3 consecutive days) or vehicle. Equal amounts (15 μg) of total protein were loaded in the gels. The optical densities (ODs) of CYP3A and GST were related to the OD of β-actin. Uniformity of loading and transfer from gel to polyvinylidene difluoride (PVDF) membrane were controlled with Ponceau S. Data on densitometric analysis are presented as percentages relative to the value for the control, considered 100%, and were expressed as means ± SDs (n = 3). Typical Western blot detections from each group are shown at the bottom. *, significantly different from control; (P < 0.05).

Fig 2

Effect of BZL on apical transporter expression in hepatic and extrahepatic tissues. P-gp (A) and Mrp2 (B) were detected by Western blotting in liver, small intestine, and kidney from rats treated with BZL (100 mg/kg b.w./day, 3 consecutive days) or vehicle (control [C]). Equal amounts of total protein (30 μg) were loaded in the gels. The ODs of P-gp and Mrp2 were related to the OD for β-actin. Uniformity of loading and transfer from gel to PVDF membrane were controlled with Ponceau S. Data on densitometric analysis are presented as percentages relative to the value for the control, considered 100%, and were expressed as means ± SDs (n = 4). Typical Western blot detections from each group are shown at the bottom. *, significantly different from control; (P < 0.05).

Fig 3

Effect of BZL on P-gp and Mrp2 activities. (A) Excretion rate of Rh123, a prototypical substrate for P-gp, was measured in bile, intestinal perfusate, and urine at 10-, 15- and 30-min intervals, respectively, for 90 min. Insets depict cumulative excretion of Rh123 at 90 min. The data represent means ± SDs for 4 rats per group. *, significantly different from control (C); P < 0.05. (B) Excretion rate of DNP-SG, a classical substrate for Mrp2, and its derivative, DNP-CG, was assessed in bile, intestinal perfusate, and urine at 10-, 15- and 30-min intervals, respectively, for 90 min. Insets depict cumulative excretion of DNP-SG and DNP-CG at 90 min. The data represent means ± SDs for 4 rats per group. *, significantly different from control; P < 0.05.