Mechanism of action of a new anti-inflammatory agent, naproxen (II). Effects of naproxen on activities of mucopolysaccharase, acid protease and collagenolytic enzymes in inflamed tissues.

In order to elucidate the biochemical anti-inflammatory properties of naproxen, the effects of this compound on activities of mucopolysaccharase [beta-glucuronidase (beta-Gase) and lysozyme (LZ)], acid protease (APase) and collagenolytic enzyme (CL) in inflamed tissues were investigated by means of a proliferative inflammatory model in filter-paper-implanted rats. In the preventive test, naproxen strongly inhibited granuloma formation and exudate accumulation as did indomethacin and prednisolone. Although the inhibitory effects of naproxen on all these enzymes were quite evident, indomethacin failed to inhibit APase activity. Prednisolone did not significantly inhibit LZ and APase activities in granuloma. In the curative test, prednisolone caused a marked decrease in the weight of the granuloma already formed and in the volume of the exudate, but with naproxen and indomethacin there was only a slight decrease. Naproxen and indomethacin induced slight but significant inhibition of LZ and CL activities, while prednisolone showing a weak inhibition of CL activity only. From these results, it may be concluded that anti-inflammatory and anti-rheumatic effects of naproxen are partly attributable to its inhibitory actions on these lysosomal enzymes.