Thrombogenic and atherogenic activities of lysophosphatidic acid

Abstract

Lysophosphatidic acid (LPA) has been identified as a biologically active lipid in mildly‐oxidized LDL, human atherosclerotic lesions, and the supernatant of activated platelets. The evidence that LPA has thrombogenic and atherogenic activities has increased substantially in recent years. Supporting the thrombogenic activity of LPA, analysis of the core region of human carotid plaques revealed recently the presence of alkyl‐ and acyl‐molecular species from LPA with high platelet‐activating potency (16:0 alkyl‐LPA, 20:4 acyl‐LPA). LPA, lipid extracts of atherosclerotic plaques, and the lipid‐rich core elicited shape change and, in synergy with other platelet stimuli, aggregation of isolated platelets. This effect was completely abrogated by prior incubation of platelets with LPA receptor antagonists. Furthermore, LPA at concentrations approaching those found in vivo, induced platelet shape change, aggregation, and platelet‐monocyte aggregate formation in blood. LPA‐stimulated platelet aggregation was mediated by the ADP‐stimulated activation of the P2Y₁ and P2Y₁₂ receptors. Supporting its atherogenic activity, LPA is a mitogen and motogen to vascular smooth muscle cells (VSMCs) and an activator of endothelial cells and macrophages. Recently, LPA has been identified as an agonist of the peroxisome proliferator activating receptor γ (PPARγ), which is a key regulator of atherogenesis. LPA elicits progressive neointima formation, which is fully abolished by GW9662, an antagonist of PPARγ. We propose that LPA plays a central role in eliciting vascular remodeling and atherogenesis. Furthermore, upon rupture of lipid‐rich atherosclerotic plaques, LPA may trigger platelet aggregation and intra‐arterial thrombus formation. Antagonists of LPA receptors might be useful in preventing LPA‐elicited thrombus formation and neointima formation in patients with cardiovascular diseases.