Myeloperoxidase (MPO) is a heme peroxidase predominantly expressed in neutrophils and monocytes that serves dual roles in immunity and pathological inflammation. Functionally, MPO catalyzes the production of hypochlorous acid and other hypohalous acids from hydrogen peroxide, generating antimicrobial reactive oxygen species that enhance neutrophil killing of bacteria and fungi 1. Beyond microbicidal activity, MPO mediates proteolytic cleavage of alpha-1-microglobulin to form t-alpha-1-microglobulin, which inhibits low-density lipoprotein oxidation and limits vascular damage 2. MPO operates through oligomeric-dependent mechanisms: dimeric MPO disassembles nucleosomes to facilitate neutrophil extracellular trap (NET) formation, while monomeric MPO stably binds NETs to produce hypohalous acids extracellularly 3. Clinically, MPO is implicated in multiple diseases through oxidative mechanisms. In anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, anti-MPO antibodies drive necrotizing glomerulonephritis via complement pathway activation, with therapeutic benefit demonstrated through C5aR/CD88 blockade 4. MPO-generated oxidants contribute to atherosclerosis pathogenesis by oxidizing lipoproteins in arterial lesions 5 and mediates stroke pathogenesis through vascular injury, NET formation, oxidative stress, and blood-brain barrier disruption 6. In kidney disease, the MPO-hydrogen peroxide-chloride system generates chlorinated protein adducts causing cellular dysfunction 7. MPO expression is regulated by LXR and PPARalpha ligands, linking its expression to cholesterol homeostasis 8.