Inactivation of alpha(2)-Macroglobulin by Activated Human Polymorphonuclear Leukocytes

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G Deby-Dupont1, J L Croisier, G Camus

  • 1Department of Anesthesiology Centre Hospitalier Universitaire, B35 Belgium.

Mediators of Inflammation
|January 1, 1994
PubMed

Insights

Alpha-2 macroglobulin normally inhibits trypsin. Activated human polymorphonuclear leukocytes inactivate alpha-2 macroglobulin, restoring trypsin activity. Myeloperoxidase activity is implicated in this inactivation process.

Area of Science:

  • Biochemistry
  • Immunology

Background:

  • Alpha-2 macroglobulin is a key protease inhibitor in plasma.
  • Human polymorphonuclear leukocytes (PMNs) play a role in inflammation and immune response.
  • Myeloperoxidase (MPO) is an enzyme released by PMNs.

Purpose of the Study:

  • To investigate the effect of activated PMNs on the inhibitory function of alpha-2 macroglobulin.
  • To identify the mechanism by which PMNs inactivate alpha-2 macroglobulin.

Main Methods:

  • Assay of trypsin proteolytic activity using Remazol Brilliant Blue substrate.
  • Incubation of alpha-2 macroglobulin with activated human PMNs.
  • Incubation of alpha-2 macroglobulin with granulocyte myeloperoxidase and hypochlorous acid.

Main Results:

  • Activated PMNs completely inactivated alpha-2 macroglobulin, leading to recovery of trypsin activity.
  • Incubation with myeloperoxidase also inactivated alpha-2 macroglobulin.
  • Hypochlorous acid, a product of myeloperoxidase, inactivated alpha-2 macroglobulin.

Conclusions:

  • Activated PMNs can neutralize the protease inhibitor alpha-2 macroglobulin.
  • Myeloperoxidase activity, specifically hypochlorous acid production, is a likely cause of alpha-2 macroglobulin inactivation by activated PMNs.

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