ABSTRACT
BACKGROUND AND PURPOSE: Erythropoietin (EPO) is used to treat anaemia associated with chronic kidney disease (CKD). Hypoxia is associated with anaemia and is known to cause a decrease in cytochrome P450 (P450) expression. As EPO production is regulated by hypoxia, we investigated the role of EPO on P450 expression and function. EXPERIMENTAL APPROACH: Male Wistar rats were subjected to a 0.7% adenine diet for 4 weeks to induce CKD. The diet continued for an additional 2 weeks while rats received EPO by i.p. injection every other day. Following euthanasia, hepatic P450 mRNA and protein expression were determined. Hepatic enzyme activity of selected P450s was determined and chromatin immunoprecipitation was used to characterize binding of nuclear receptors involved in the transcriptional regulation of CYP2C and CYP3A. KEY RESULTS: EPO administration decreased hepatic mRNA and protein expression of CYP3A2 (P < 0.05), but not CYP2C11. Similarly, EPO administration decreased CYP3A2 protein expression by 81% (P < 0.001). A 32% decrease (P < 0.05) in hepatic CYP3A enzymatic activity (Vmax ) was observed for the formation of 6ßOH-testosterone in the EPO-treated group. Decreases in RNA pol II recruitment (P < 0.01), hepatocyte nuclear factor 4α binding (P < 0.05) and pregnane X receptor binding (P < 0.01) to the promoter region of CYP3A were also observed in EPO-treated rats. CONCLUSIONS AND IMPLICATIONS: Our data show that EPO decreases the expression and function of CYP3A, but not CYP2C in rat liver.
Subject(s)
Cytochrome P-450 Enzyme System/metabolism , Erythropoietin/pharmacology , Liver/drug effects , Renal Insufficiency, Chronic/metabolism , Adenine , Animals , Constitutive Androstane Receptor , Cytochrome P-450 Enzyme System/genetics , Diet , Disease Models, Animal , Hepatocyte Nuclear Factor 4/genetics , Hepatocyte Nuclear Factor 4/metabolism , Kidney/pathology , Liver/metabolism , Male , Microsomes, Liver/drug effects , Microsomes, Liver/enzymology , Pregnane X Receptor , RNA Polymerase II/genetics , RNA Polymerase II/metabolism , RNA, Messenger/metabolism , Rats, Wistar , Receptors, Cytoplasmic and Nuclear/metabolism , Receptors, Steroid/genetics , Receptors, Steroid/metabolism , Recombinant Proteins/pharmacology , Renal Insufficiency, Chronic/pathologyABSTRACT
Mesna and its dimer, dimesna, are coadministered for mitigation of ifosfamide- and cisplatin-induced toxicities, respectively. Dimesna is selectively reduced to mesna in the kidney, producing its protective effects. In vitro screens of uptake and efflux transporters revealed saturable uptake by renal organic anion transporters OAT1, OAT3, and OAT4. Efflux transporters breast cancer resistance protein; multidrug and toxin extrusion 1 (MATE1); multidrug resistance proteins MRP1, MRP2, MRP4, and MRP5; and P-glycoprotein (Pgp) significantly reduced dimesna accumulation. Further investigation demonstrated that renal apical efflux transporters MATE1, MRP2, and Pgp were also capable of mesna efflux. Administration of OAT inhibitor probenecid to healthy subjects significantly increased combined mesna and dimesna plasma exposure (91% ± 34%) while decreasing the renal clearance due to net secretion (67.0% ± 12.7%) and steady-state volume of distribution (45.2% ± 13.4%). Thus, the kidney represents a significant sink of total mesna, whereas function of renal drug transporters facilitates clearance in excess of glomerular filtration rate and likely the presence of active mesna in the urine. Loss of renal transporter function due to genetic variability or drug-drug interactions may decrease the efficacy of chemoprotectants, increasing the risk of ifosfamide- and cisplatin-induced toxicities.
