Myeloperoxidase deficiency preserves vasomotor function in humans.

Area of Science:

• Cardiovascular Biology
• Enzymology
• Human Physiology

Background:

• Observational studies suggest a link between myeloperoxidase (MPO) and vascular function.
• MPO is an enzyme derived from leukocytes with potential roles in vasomotor control.

Purpose of the Study:

• To investigate the systemic effects of MPO on vascular tone in humans.
• To determine if MPO directly influences blood vessel function.

Main Methods:

• Screening of 12,135 patients for leukocyte peroxidase activity to identify individuals with low MPO expression (MPO(low)).
• Comparing endothelial nitric oxide (NO) bioavailability in MPO(low) individuals versus controls after nicotine challenge.
• Administering MPO to anesthetized pigs to assess its impact on coronary blood flow and myocardial perfusion.
• Evaluating the relaxation response of isolated animal arterial rings to acetylcholine and nitroglycerine after MPO exposure.

Main Results:

• Nicotine-induced reduction in NO bioavailability was attenuated in MPO(low) individuals, with MPO levels correlating with vasomotor dysfunction.
• MPO injection in pigs led to decreased blood flow in major arteries and reduced myocardial perfusion.
• Isolated arterial rings exposed to MPO showed impaired relaxation responses to vasodilators.

Conclusions:

• Myeloperoxidase exerts significant effects on the vascular tone of both large conductance and small resistance vessels.
• Leukocytes function as systemic effectors of vascular tone, with MPO as a critical regulator.
• MPO represents a potential therapeutic target for conditions involving vasomotion dysfunction.