Structural Identification of Oxidized Acyl-Phosphatidylcholines That Induce Platelet Activation

Abstract

Oxidation of low-density lipoprotein (LDL) generates proinflammatory and prothrombotic mediators that may play a crucial role in cardiovascular and inflammatory diseases. In order to study platelet-activating components of oxidized LDL 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, a representative of the major phospholipid species in LDL, the 1-acyl-phosphatidylcholines (PC), was oxidized by CuCl₂ and H₂O₂. After separation by high-performance liquid chromatography, three compounds were detected which induced platelet shape change at low micromolar concentrations. Platelet activation by these compounds was distinct from the pathways stimulated by platelet-activating factor, lyso-phosphatidic acid, lyso-PC and thromboxane A₂, as evidenced by the use of specific receptor antagonists. Further analyses of the oxidized phospholipids by electrospray ionization mass spectrometry structurally identified them as 1-stearoyl-2-azelaoyl-sn-glycero-3-phosphocholine (m/z 694; SAzPC), 1-stearoyl-2-glutaroyl-sn- glycero-3-phosphocholine (m/z 638; SGPC), and 1-stearoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphocholine (m/z 622; SOVPC). These observations demonstrate that novel 1-acyl-PC which had previously been found to stimulate interaction of monocytes with endothelial cells also induce platelet activation, a central step in acute thrombogenic and atherogenic processes.

Type 2 scavenger receptor CD36 in platelet activation: the role of hyperlipemia and oxidative stress

“…These agents did not induce activation of platelets from cd36 -null mice or from human CD36-null donors. These observations are consistent with pharmacologic studies from Göpfert et al demonstrating that platelet activation by specific oxidized phospholipids was not mediated by platelet-activating factor receptor, thromboxane receptor or LPA receptors [109]. At lower concentrations (e.g., observed in individuals with atherosclerosis), we demonstrated that oxLDL augmented platelet aggregation responses to low doses of ‘classic’ platelet agonists, such as ADP and collagen (Figure 3) [16,110].…”

Platelet Interaction with Bioactive Lipids Formed by Mild Oxidation of Low-Density Lipoprotein

“…Very recently, three biologically active oxidative products of acyl-PC (1-stearoyl-2-arachidonoyl-snglycero-3-phosphocholine) were identifi ed by electrospray ionization mass spectrometry which induced shape change of human platelets at low micromolar concentrations: 1-stearoyl-2-azelaoyl-sn -glycero-3-phosphocholine, 1-stearoyl-2-glutaroyl-sn -glycero-3-phosphocholine, and 1-stearoyl-2-(5-oxovaleroyl)-sn -glycero-3-phosphocholine. All these compounds activated platelets independently of the PAF receptor and LPA receptors [54] . The concentrations of these platelet-stimulating alkyl-PC and acyl-PC products in mm-LDL and mox-LDL are not known.…”

Lipid peroxidation generates biologically active phospholipids including oxidatively N-modified phospholipids

“…This result raised that possibility that AZ-PAF might also be a PAF receptor agonist, because octanoyl-PAF, the other major fragmentation product of linoleoyl-PAF, does not agonize the PAF receptor. Subsequently, Gopfert et al showed that 10 μM OV-PC, glutaryl-PC, and AZ-PC could all stimulate shape-change in platelets, but that they reported that these effects were not blocked by the PAF receptor antagonist WEB2086 (Gopfert et al, 2005). However, when Chen et al examined the effects of submicromolar concentrations of AZ-PAF on platelet activation, they found that 200 nM AZ-PAF activated calcium in platelets and that 100 nM AZ-PAF synergistically activated platelets induced with suboptimal concentrations of thrombin, ADP, or collagen (Chen et al, 2009a).…”