European heart journal 2017 04 18() doi 10.1093/eurheartj/ehx146
Hyperlipidaemia enhances susceptibility to thrombosis, while platelet oxidixed LDL (oxLDL) binding in acute coronary syndrome (ACS) correlates with activation status. This study explores the platelet lipidome in symptomatic coronary artery disease (CAD) patients and the functional consequences of the chemokine CXCL12 and its receptors CXCR-4/-7 on lipid uptake in platelets.
Methods and results
Platelet-oxLDL detected by flow cytometry was enhanced (P = 0.04) in CAD patients, moderately correlated with platelet CXCR7 surface expression (ρ = 0.39; P < 0.001), while inversely with CXCR4 (ρ = 0.35; P < 0.001). Platelet-oxLDL was elevated (P = 0.01) in ACS patients with angiographic evidence of intracoronary thrombi. Ex vivo analysis of intracoronary thrombi sections revealed oxLDL deposition in platelet-enriched areas verified by immunofluorescence confocal microscopy. LDL-oxLDL uptake enhanced reactive oxygen species, mitochondrial superoxide generation, intraplatelet LDL to oxLDL conversion, and lipid peroxidation, counteracted by SOD2-mimetic MnTMPyP. Lipidomic analysis revealed enhanced intraplatelet-oxidized phospholipids, cholesteryl esters, sphingomyelin, ceramides, di- and triacylglycerols, acylcarnitines in CAD patients compared with age-matched controls as ascertained by liquid chromatography hyphenated to high-resolution mass spectrometry. LDL-oxLDL induced degranulation, αIIbβ3-integrin activation, apoptosis, thrombin generation estimated by calibrated automated thrombinoscopy, and shape change verified by live imaging using scanning ion conductance microscopy. Further, LDL-oxLDL enhanced thrombus formation ex vivo and in vivo in mice (ferric chloride-induced carotid artery injury). LDL-oxLDL enhanced platelet CXCL12 release, differentially regulated CXCR4-CXCR7 surface exposure, while CXCL12 prompted LDL-oxLDL uptake and synergistically augmented the LDL-oxLDL-induced pro-oxidative, thrombogenic impact on platelet function. Conclusion
An altered platelet lipidome might be associated with thrombotic disposition in CAD, a mechanism potentially regulated by CXCL12-CXCR4-CXCR7 axis.