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Inhibition of cyclooxygenase-2 (cox-2) is considered to be anti-inflammatory, whereas inhibition of the constitutive isozyme cox-1 causes renal and gastrointestinal toxicity. Therefore, to achieve an optimal anti-inflammatory effect, an inhibitor should be cox-2 selective without inhibiting cox-1. For this purpose, 10 different cox-2-selective phosphorothioated oligonucleotides (S-oligos) were tested to inhibit the cox-2 enzyme selectively in vivo. An aqueous solution of these S-oligos (3 mg/kg body weight) was injected intraperitoneally (i.p.) into male Sprague-Dawley rats with colitis induced by trinitrobenzene sulfonic acid (TNBS). The colonic levels of cox-2 protein, mRNA, myeloperoxidase (MPO), and prostaglandin E2 (PGE2) were increased significantly on day 1 and remained significantly elevated until day 7 post-TNBS administration, whereas cox-1 remained unaltered. Two S-oligos were found to be effective in reducing the level of cox-2 protein selectively without any effect on the cox-1. The effective S-oligo, but not the mismatched control oligo, reduced the tissue levels of PGE2 and MPO activity significantly. The effective S-oligo reduced the level of cox-2 but not the cox-1 mRNA significantly, whereas a mismatched or a sense control oligo did not affect the levels of these isoforms. M-fold analysis demonstrated extensive secondary structure formation in the cox-2 mRNA. These findings demonstrate that only a few selected sites in the cox-2 target mRNA are accessible in vivo, probably because of the presence of secondary structures. Suppression of cox-2 protein, PGE2, and MPO activity by the S-oligo might prove to be an anti-inflammatory property.

The sodium hydrogen exchanger (NHE) plays an important role in the absorption of NaCl, the regulation of intracellular pH and cell growth. These functions are compromised in the inflammatory bowel diseases. The objective of this study was to examine the expression of the NHE-1 isoform during colitis induced by acetic acid or trinitrobenzenesulfonic acid in Sprague-Dawley male rats. We also examined the effect of dexamethasone on the expression of NHE-1. Levels of mRNA were estimated using the reverse transcription-polymerase chain reaction and slot blot analysis, and levels of protein were estimated by enhanced chemiluminescence light Western blot analysis. The levels of the NHE-1 mRNA and protein in colonic mucosa increased as assessed at 1, 2, 5 and 7 days post-acetic acid administration and 7 days post-trinitrobenzenesulphonic acid administration in the rats. The levels of mRNA were not suppressed by dexamethasone treatment in either case. These findings demonstrate that colitis-induced expression of the NHE-1 mRNA and protein is independent of the way colitis is induced. Although factor(s) responsible for the induction remain to be identified, our findings showing similar changes in the NHE-2 and NHE-3 mRNA isoforms, together with the lack of their suppression by dexamethasone, suggest that cytokines and intracellular pH are secondary factors.