Impact of transgene expression on drug metabolism following systemic adenoviral vector administration.
BACKGROUND
Systemic administration of a first-generation adenovirus expressing E. coli beta-galactosidase (AdlacZ) alters expression and function of two hepatic drug-metabolizing enzymes, cytochrome P450 (CYP) 3A2 and 2C11, for 14 days. The objective of these studies was to determine how the transgene cassette influences CYP expression and function.


METHODS
Sprague-Dawley rats were given 5.7 x 10(12) viral particles (vp)/kg of either: AdlacZ, Ad expressing murine erythropoietin (Epo), Ad without a transgene (Null), or phosphate-buffered saline (Vehicle). Hepatic CYP protein expression, activity, mRNA and alanine aminotransferase (ALT) levels were analyzed 0.25, 1, 4, and 14 days following a single intravenous injection.


RESULTS
Administration of Epo did not alter CYP3A2 activity, but induced RNA levels by a factor of 2 at 4 and 14 days (P< or =0.01). This vector suppressed CYP2C11 activity levels by 45% at 1 day (P< or =0.05) and RNA levels throughout the study period (P< or =0.05). The Null vector suppressed CYP3A2 activity by 36, 63, 34, and 45% at 0.25, 1, 4 and 14 days, respectively (P< or =0.05). CYP2C11 activity was suppressed 1 day after administration (41%) and RNA levels were suppressed at 6 h (53%) and 1 day (36%, P< or =0.05). In contrast, AdlacZ suppressed both CYP3A2 and 2C11 at all time points.


CONCLUSIONS
The immunogenic and biological nature of the transgene cassette can influence changes in CYP3A2, but not the 2C11 isoform. The shift in transcription and translation of protein for maintenance of physiologic homeostasis to production of viral proteins and transgene product and their associated toxicity during viral infection may explain our observations.
Callahan
Shellie M
SM
College of Pharmacy, Division of Pharmaceutics, The University of Texas at Austin, Austin, TX 78712-1074, USA.
Boquet
Michael P
MP
Ming
Xin
X
Brunner
Lane J
LJ
Croyle
Maria A
MA
D000256:Adenoviridae / Q000235:genetics*; D000410:Alanine Transaminase / Q000097:blood; D000818:Animals; D030801:Animals, Genetically Modified; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D051544:Cytochrome P-450 CYP3A; D000072467:Cytochrome P450 Family 2; D004921:Erythropoietin / Q000235:genetics; D015870:Gene Expression; D005822:Genetic Vectors; D066298:In Vitro Techniques; D007763:Lac Operon; D008099:Liver / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D004364:Pharmaceutical Preparations / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins; D039181:Steroid 16-alpha-Hydroxylase / Q000235:genetics / Q000378:metabolism
D008565:Membrane Proteins; D004364:Pharmaceutical Preparations; D012333:RNA, Messenger; D011994:Recombinant Proteins; D004921:Erythropoietin; D001189:Aryl Hydrocarbon Hydroxylases; C450279:CYP2C11 protein, rat; C465260:Cyp3a2 protein, rat; D051544:Cytochrome P-450 CYP3A; D000072467:Cytochrome P450 Family 2; D039181:Steroid 16-alpha-Hydroxylase; D000410:Alanine Transaminase