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Cholesteryl-conjugated phosphorothioate oligodeoxynucleotides modulate CYP2B1 expression in vivo
J Desjardins1, J Mata, T Brown
1Department of Pharmacology, University of Nebraska Medical Center, Omaha 68198-6260, USA.
Journal of Drug Targeting
|January 1, 1995
Summary
Cholesteryl-conjugated oligodeoxynucleotides effectively reduced rat CYP2B1 gene expression in vivo. This modification enhanced potency for modulating gene expression, despite lower bioavailability and some liver toxicity.
Area of Science:
- Pharmacology
- Molecular Biology
- Toxicology
Background:
- Cytochrome P450 enzymes, particularly CYP2B1, play crucial roles in drug metabolism.
- Oligodeoxynucleotides (ODNs) offer a potential strategy for sequence-specific gene modulation.
- Investigating the in vivo properties of modified ODNs is essential for therapeutic development.
Purpose of the Study:
- To evaluate the pharmacokinetic properties, toxicity, and gene modulation capabilities of 5' cholesteryl-conjugated phosphorothioate oligodeoxynucleotides targeting rat CYP2B1 mRNA in vivo.
- To compare the efficacy and safety of cholesteryl-modified ODNs versus unmodified ODNs.
- To assess the impact of cholesteryl conjugation on ODN potency and bioavailability.
Main Methods:
- Administration of 35S-labelled oligodeoxynucleotides (cholesteryl-conjugated and unmodified) via intraperitoneal injection in adult male Sprague-Dawley rats.
- Pharmacokinetic analysis including volume of distribution and elimination half-life determination.
- Toxicity assessment, including liver histopathology and RNA content.
- Evaluation of CYP2B1 enzyme activity using hexobarbital sleep times and specific liver microsomal enzyme assays (pentoxyresorufin O-dealkylase and p-nitrophenol hydroxylase).
Main Results:
- Cholesteryl-conjugated ODNs exhibited a lower volume of distribution (0.12 l/kg) and a shorter elimination half-life (23.2 hrs) compared to unmodified ODNs (0.33 l/kg and 55.4 hrs, respectively).
- Toxicity, including liver cell enlargement and increased total RNA, was observed at 1.0 mg/kg for cholesteryl-conjugated ODNs.
- Hexobarbital sleep times increased significantly in animals treated with cholesteryl-conjugated ODNs, indicating increased CYP2B1 activity, while pentoxyresorufin O-dealkylase activity decreased, confirming CYP2B1/2 inhibition.
- No significant change in CYP2E1 activity was observed.
Conclusions:
- Synthetic phosphorothioate oligodeoxynucleotides can effectively modulate CYP2B1 gene expression in vivo in a sequence-specific manner.
- Cholesteryl conjugation enhances the potency of oligodeoxynucleotides for gene modulation, even with reduced bioavailability.
- Further research is warranted to optimize the therapeutic window by balancing potency and toxicity.