In vivo inhibition of cyclooxygenase-2 by a selective phosphorothioated oligonucleotide

Inhibition of cyclooxygenase-2 (cox-2) is considered to be anti-inflammator y, whereas inhibition of the constitutive isozyme cox-1 causes renal and ga strointestinal toxicity. Therefore, to achieve an optimal anti-inflammatory effect, an inhibitor should be cox-2 selective without inhibiting cox-1. F or this purpose, 10 different cox-2-selective phosphorothioated oligonucleo tides (S-oligos) were tested to inhibit the cox-2 enzyme selectively in viv o. An aqueous solution of these S-oligos (3 mg/kg body weight) was injected intraperitoneally (i.p.) into male Sprague-Dawley rats with colitis induce d by trinitrobenzene sulfonic acid (TNBS). The colonic levels of cox-2 prot ein, mRNA, myeloperoxidase (MPO), and prostaglandin E-2 (PGE(2)) were incre ased significantly on day I and remained significantly elevated until day 7 post-TNBS administration, whereas cox-1 remained unaltered. Two S-oligos w ere found to be effective in reducing the level of cox-2 protein selectivel y without any effect on the cox-1. The effective S-oligo, but not the misma tched control oligo, reduced the tissue levels of PGE, and MPO activity sig nificantly. The effective S-oligo reduced the level of cox-2 but not the co x-1 mRNA significantly, whereas a mismatched or a sense control oligo did n ot affect the levels of these isoforms. M-fold analysis demonstrated extens ive secondary structure formation in the cox-2 mRNA. These findings demonst rate that only a few selected sites in the cox-2 target mRNA are accessible in vivo, probably because of the of secondary structures. Suppression of c ox-2 protein, PGE(2), and MPO activity by the S-oligo might prove to be an anti-inflammatory property.