CHOLESTERYL-CONJUGATED PHOSPHOROTHIOATE OLIGODEOXYNUCLEOTIDES MODULATE CYP2B1 EXPRESSION IN-VIVO

5' cholesteryl-conjugated phosphorothioate oligodeoxynucleotides with sequence complementary to the rat CYP2B1 mRNA were evaluated in adult male Sprague-Dawley rats for their pharmacokinetic properties, toxicit y, and ability to modulate CYP2B1 expression in vivo. Following intrap eritoneal administration of S-35-labelled oligodeoxynucleotides, volum e of distribution for the phosphorothioate was 0.33 1/kg while the 5' cholesteryl-conjugate oligodeoxynucleotide was 0.12 1/kg. The eliminat ion half-life was 23.2 and 55.4 hrs for cholesteryl modified and unmod ified oligodeoxynucleotides, respectively. Cholesteryl-conjugate oligo deoxynucleotide toxicity was detected at a dose of 1.0 mg/kg and consi sted primarily of midzonal liver cell enlargement and increased total RNA. Hexobarbital sleep times, a measure of CYP2B1 enzyme activity in vivo, increased from 21.9 minutes in saline-treated animals to 29.5 mi nutes in cholesterol oligodeoxynucleotide-treated animals. A significa nt decrease in liver microsomal pentoxyresorufin O-dealkylase enzyme a ctivity, a CYP2B1/2 specific assay, was observed but not a change in p -nitrophenol hydroxylase activity, a specific CYP2E1 assay. These data indicate that in vivo modulation of the CYP2B1 gene can be accomplish ed with synthetic phosphorothioate oligodeoxynucleotides in a sequence -specific manner. Further, cholesteryl conjugation to the 5' end of th e oligodeoxynucleotide enhanced potency despite lesser bioavailability .