412. Renal Pathophysiology after Systemic Administration of a Recombinant Adenovirus: Changes in Drug Metabolism Based upon Vector Dose

Abstract

In addition to its ability to maintain water and electrolyte balance and efficiently remove waste products from the circulation, the kidney actively metabolizes many drugs, hormones and xenobiotics through the cytochrome P450 (CYP) enzyme system. Considering that adenovirus (Ad) significantly alters the expression and function of specific CYP enzymes in the liver, and that slight changes in renal function can adversely affect hepatic CYP activity and expression, we investigated the effect of a model recombinant Ad on the expression of the renal CYP isoforms: 4A1, 4A2, 4F1, and 2E1. CYP4A and 4F convert arachidonic acid to active metabolites responsible for regulation of epithelial transport and vascular function. CYP2E1 oxidizes many small lipophilic compounds and metabolizes carcinogens and cytotoxic agents. Male Sprague-Dawley rats were given one of six doses (5.7 |[times]| 106 - 5.7 |[times]| 1012 virus particles/kilogram (vp/kg)) of Ad expressing E. coli beta-galactosidase or saline (vehicle control) intravenously and sacrificed 0.25, 1, 4, and 14 days after injection. CYP protein expression was measured by Western blot and gene expression by RT-PCR. Serum creatinine levels (SCr) were assessed to profile changes in kidney function. The CYP4A family of proteins were significantly induced within 24 hours of administration of 5.7 |[times]| 1011 vp/kg by 35% and by 47% after 5.7 |[times]| 1012 vp/kg (P|[le]|0.01). A similar increase was detected at the 4 day timepoint. RT-PCR revealed that CYP4A1 gene expression doubled 6 hours after administration of doses above 1010. Gene expression remained induced (70% above control) 1 day after administration of doses, which exceeded 106 vp/kg (P|[le]|0.001). Animals treated with 5.7 |[times]| 1012 vp/kg began to recover at 14 days. However, animals treated with 5.7 |[times]| 1010 and 5.7 |[times]| 1011 vp/kg remained elevated (41% and 67%, P|[le]|0.05). CYP4A2 gene expression was also significantly induced (18%, 24%, and 15%) above control at 1 day in animals treated with 5.7 |[times]| 1010 - 5.7 |[times]| 1012 vp/kg, respectively. This isoform was elevated throughout the duration of the study. CYP4F1 gene and protein expression was unaffected by any of the treatments (P|[ge]|0.05). CYP2E1 gene expression was significantly suppressed by all treatments throughout the study (P|[le]|0.05). In general, suppression peaked within 24 hours (approximately 50% of control) for all doses, but trended towards baseline at 14 days. SCr was significantly decreased at all time points for Ad doses at and below 5.7 |[times]| 1011 vp/kg. SCr was increased by a factor of 3 in animals treated with 5.7 |[times]| 1012 vp/kg 4 days after administration (P|[le]|0.01). This data indicates that systemic Ad treatment can alter renal CYP expression and function up to 14 days after injection. This is of particular importance as Ad genomes were only detected by quantitative real-time PCR in kidneys of animals given the 1011 and 1012 vp/kg doses. This suggests that the aberrations in renal CYPs may not be related to the physical presence of viral particles. This reduction in metabolism should be considered when evaluating the pharmacokinetics of drugs included in clinical protocols involving Ad gene transfer for any application.