Neutral protease activation of peritoneal macrophage prostaglandin synthesis.

We observed that the treatment of murine macrophages with proteolytic enzymes can activate the synthesis and release of arachidonic acid (ARA) metabolites. Murine peritoneal macrophage monolayers prelabeled with [14C]ARA were incubated with neutral proteases. Specific bacterial and mammalian proteases from various sources provoke the synthesis and release of prostaglandin E2 (PGE2) and other radiolabeled metabolites. However, cells treated with the neutral proteases thrombin and trypsin did not release significant amounts of PGE2. Neutral protease treatment did not decrease cell viability (> 90%) and boiled protease preparations did not activate prostaglandin synthesis. Protease-activated PGE2 synthesis was inhibited by a variety of protease inhibitors and synthetic substrates for neutral proteases. An inflammatory agent that induces macrophage neutral protease activity, 12-O-tetradecanoylphorbol 13-acetate (TPA) stimulated synthesis and release of PGE2 in a dose- and time-dependent manner. TPA-activated PGE2 synthesis was also blocked by a variety of protease inhibitors. These results suggest that neutral proteases have the capacity to activate ARA metabolism and imply that neutral proteases found in inflammatory reactions may infuence prostaglandin production.