Lipoprotein-associated Phospholipase A2 Activity

Lp-PLA₂ is a calcium-independent phospholipase A2 enzyme that is associated with both low-density lipoprotein (LDL) and, to a lesser extent, high-density lipoprotein (HDL) in human plasma and serum¹ and is distinct from other such phospholipases such as cPLA₂ and sPLA₂.^2,3 Lp-PLA₂ is produced by macrophages and other inflammatory cells and is expressed in greater concentrations in advanced atherosclerotic lesions than early-stage lesions.^4,5

Several lines of evidence suggest that oxidation of LDL plays a critical step in the development and progression of atherosclerosis.^6,7 Lp-PLA₂ participates in the breakdown of oxidized LDL in the vascular wall by hydrolyzing the oxidized phospholipid, producing lysophosphatidylcholine and oxidized free fatty acids, both of which are potent pro-inflammatory products that contribute to the formation of atherosclerotic plaques.^8-10

Lp-PLA₂ has demonstrated modest intra- and inter-individual variation, commensurate with other cardiovascular lipid markers and substantially less variability than high sensitivity C-reactive protein (hs-CRP). In addition, Lp-PLA₂ is not elevated in systemic inflammatory conditions, and may be a more specific marker of vascular inflammation. The relatively small biological variation of Lp-PLA₂ and its vascular specificity are of value in the detection and monitoring of cardiovascular risk.^11-13