# MPO (Myeloperoxidase)

Myeloperoxidase (MPO) is an enzyme stored in granules of your neutrophils and monocytes. During inflammation, it makes hypochlorous acid (essentially bleach) and other reactive oxidants. It gets released into your blood at sites of vascular inflammation and plaque rupture. So MPO marks immune-cell activation, oxidative stress, and unstable artery plaque. Labs measure plasma MPO by ELISA or a chemiluminescent assay. Healthy values are commonly below 350 to 630 pmol/L (it depends on the assay). One key study makes the case (Brennan et al., NEJM 2003). Among 604 chest-pain patients with an initially negative troponin, baseline MPO independently predicted heart attacks and major events, at 30 days and 6 months. Watch the confounders. Any acute infection can raise it. So can a type of vasculitis (where MPO is the p-ANCA autoantigen). Heparin therapy falsely raises it, by releasing vessel-bound MPO. And so do smoking and pregnancy.

## Sources

- Brennan ML, Penn MS, Van Lente F, et al.. (2003). Prognostic value of myeloperoxidase in patients with chest pain. New England Journal of Medicine. https://doi.org/10.1056/NEJMoa035003
- Eiserich JP, Baldus S, Brennan ML, et al.. (2002). Myeloperoxidase, a leukocyte-derived vascular NO oxidase. Science. https://doi.org/10.1126/science.1106830

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_Canonical: https://longevity-switzerland.com/en/glossary/mpo-myeloperoxidase · Part of Longevity Cities · Updated 2026-06-22_