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Neutral protease activation of peritoneal macrophage prostaglandin synthesis
Abstract:
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.
Insights
Proteolytic enzymes activate arachidonic acid (ARA) metabolism in macrophages, leading to prostaglandin E2 (PGE2) release. This suggests neutral proteases in inflammation influence prostaglandin production.
Area of Science:
- Immunology
- Biochemistry
- Cell Biology
Background:
- Macrophages play a crucial role in inflammatory responses.
- Arachidonic acid (ARA) metabolites, such as prostaglandins, are key mediators of inflammation.
- The role of proteolytic enzymes in regulating ARA metabolism in macrophages is not fully understood.
Purpose of the Study:
- To investigate the effect of neutral proteases on arachidonic acid (ARA) metabolism and prostaglandin E2 (PGE2) synthesis in murine macrophages.
- To determine if protease-activated ARA metabolism is linked to inflammatory processes.
Main Methods:
- Murine peritoneal macrophages were labeled with [14C]arachidonic acid (ARA).
- Cells were treated with various bacterial and mammalian neutral proteases, including thrombin and trypsin.
- Prostaglandin E2 (PGE2) synthesis and release were measured.
- Cell viability was assessed.
- The effect of protease inhibitors and 12-O-tetradecanoylphorbol 13-acetate (TPA) on PGE2 synthesis was evaluated.
Main Results:
- Specific neutral proteases activated the synthesis and release of PGE2 and other radiolabeled ARA metabolites from macrophages.
- Thrombin and trypsin did not induce significant PGE2 release.
- Protease treatment did not compromise macrophage viability.
- PGE2 synthesis was inhibited by protease inhibitors and synthetic substrates.
- TPA, an inflammatory agent, stimulated dose- and time-dependent PGE2 release, which was also blocked by protease inhibitors.
Conclusions:
- Neutral proteases can activate arachidonic acid (ARA) metabolism in macrophages.
- The findings imply that neutral proteases present during inflammation may modulate prostaglandin production.
- This provides a potential mechanism linking protease activity to inflammatory signaling pathways.