Myeloperoxidase TechNotes

Myeloperoxidase(MPO) is a peroxi-dase enzyme that is abundantly expressed in polymorphonuclear leukocytes (neutrophils) and secreted during their activation.

MPO plays an important role in neutrophil micro-bicidal action through catalyzing chloride ionoxidation to hypochlor-ous acid, which is a potent antimicrobial agent. On the other hand, it has been demonstrated that MPO causes oxidative modification of low density lipoprotein (LDL) to a high uptake form that is considered to be a key event in the promotion of atherogenesis (1). For this reason, MPO is believed to participate in the initiation and progression of cardiovascular diseases. MPO possesses potent proinflammatory properties and may directly contribute to tissue injury. In addition, MPO has been suggested to be involved in pathogenesis of lung cancer (2), Alzheimer’s disease (3) and multiple sclerosis (4).

Native MPO is a covalently bound tetrameric complex consisting of two glycosylated heavy chains (MW 59 – 64 kDa) and two unglycosylated light chains (MW 14 kDa) with total MW approximately 150 kDa and theoretical pI 9.2 (5).

MPO as a diagnostic marker

MPO is an inflammation marker that can serve as a cardiac marker. It has been shown that an increased MPO level in patient’s blood serves as a risk marker for atherosclerosis (6) and coronary artery disease (7). It predicts the early risk of myocardial infarction, as well as the risk of other major adverse cardiac events in patients with chest pain in the ensuing 30-day and 6-month periods (8, 9). The value of MPO as a marker is that MPO predicts these outcomes independently of other known laboratory tested risk factors, including troponins, creatine kinase MB isoform (CK-MB), C-reactive protein (CRP) and lipid profile. Moreover, unlike troponins I and T, CK-MB, and CRP, MPO makes it possible to identify patients at risk for cardiac events in the absence of myocardial necrosis (8). All of these factors make MPO measurements in patients an indispensable procedure to reveal patients with chest pain that are at an increased risk of cardiovascular complications.

There are some autoimmune diseases connected with the development of autoantibodies against MPO. MPO is a main target of anti-neutrophil cytoplasm antibodies (ANCA) -serological markers for certain systemic vasculitides, microscopic polyarteritis and pulmonary eosinophilic granulomatosis (Churg-Strauss syndrome) (10). Low to moderate anti-MPO autoantibody levels are also reported in rheumatoid arthritis.

Reagents for assay development

At HyTest, we provide several monoclonal antibodies that can be used for the development of quantitative immunoassays enabling the detection of human MPO. We also provide purified native MPO and MPO depleted human serum.

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