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Toxicology and applied pharmacology

In vivo modulation of the rat cytochrome P450 1A1 by double-stranded phosphorothioate oligodeoxynucleotides.


PMID 8545825

Abstract

CYP1A1 gene expression is regulated by known cis- and transacting elements controlling inhibition and induction of CYP1A1 transcription. The influence of a double-stranded phosphorothioate oligonucleotide (dsODN) with sequence identical to the CYP1A1 negative regulatory element (NRE) was examined in Sprague-Dawley rats. Two strategies were employed: (i) two single-stranded complementary 25-mer ODNs that form a double-stranded ODN (ODN1) and (ii) a 54-base, self-complementary ODN which forms a dsODN hairpin (ODN2). A dsODN hairpin with scrambled NRE sequence was evaluated as a control (ODN3). Zoxazolamine paralysis times, an in vivo marker of CYP1A1 activity, were reduced from 184 +/- 18 min in saline-treated rats to 103 +/- 12.5 min 24 hr after a single 1.7-mg ODN1 iv injection. Liver microsomal EROD, an in vitro marker of CYP1A1/2 activity, was increased from 210 +/- 10 pmol in saline-treated animals to 703 +/- 73 and 623 +/- 89 pmol resorufin/mg protein/min after iv ODN1 and iv ODN2, respectively. ODN1's activity did not change PNP hydroxylation and PROD, markers of CYPs 2E1 and 2B1/2. ODN2 did not significantly change PNP but did significantly alter PROD. The ODN3 did not cause any significant changes in any assay measured. The ODN1-induced responses in ZX paralysis and EROD were observed post-iv injection, but not following ip injection of ODN1. Western blot analysis of ODN1- and HPO-treated rat liver microsomes also revealed increased in CYP1A1 protein. These data indicate double-stranded ODNs mimic the cis-acting NRE in vivo inducing CYP1A1 in the absence of other xenobiotics.

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