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Murine prostaglandin endoperoxide (PGH) synthase-1 and PGH synthase-2 expressed in cos-1 cells were found to be differentially sensitive to inhibition by common nonsteroidal anti-inflammatory drugs (NSAIDs). Aspirin completely inhibited bis-oxygenation of arachidonate by PGH synthase-1; in contrast, aspirin-treated PGH synthase-2 metabolized arachidonate primarily to 15-hydroxyeicosatetraenoic acid (15-HETE) instead of PGH2. ID50 values were determined for a panel of common NSAIDs by measuring instantaneous inhibition of cyclooxygenase activity using an oxygen electrode. Among common NSAIDs tested, indomethacin, sulindac sulfide, and piroxicam preferentially inhibited PGH synthase-1; ibuprofen, flurbiprofen, and meclofenamate inhibited both enzymes with comparable potencies; and 6-methoxy-2-naphthylacetic acid preferentially inhibited PGH synthase-2. These results demonstrate that the two PGH synthases are pharmacologically distinct and indicate that it may be possible to develop isozyme-specific cyclooxygenase inhibitors useful both for anti-inflammatory therapy and for delineating between the biological roles of the PGH synthase isozymes.
Meade et al. (Mon,) studied this question.