Role of lipoxygenase products in platelet function: relation to fatty acid modified phospholipids

Acute coronary syndrome remodels the antiplatelet aggregation properties of HDL particle subclasses

Essentials HDL subclasses were studied in acute coronary syndrome (ACS). HDL2 from ACS patients have better antiplatelet potency than HDL from non ACS subjects. ACS remodels the antiplatelet properties of HDL subclasses. Oxidized polyunsaturated fatty acids content of HDL is modified by ACS.

SUMMARY

Background Although HDLs have antithrombotic effects by reducing platelet activation, the relationship between HDL levels and the risk of acute coronary syndrome (ACS) is unclear, as HDL particles are heterogeneous in composition and biological properties. Objective To characterize the effects of HDL2 and HDL3 subclasses from ACS patients and non-coronary artery disease (CAD) subjects on platelet activation. Methods We measured platelet aggregation and ex vivo thrombus formation, analyzed signaling pathways by flow cytometry, and performed a targeted lipidomics analysis on HDL subclasses. Results Analysis of human platelet aggregation in suspension, adhesion on von Willebrand factor and thrombus formation on collagen under arterial shear demonstrated that HDL2 from ACS patients had higher antiplatelet potency than HDL3 from ACS patients and HDL from non-CAD subjects. HDL binding to scavenger receptor class B type I was essential for this effect. A lipidomics analysis revealed that HDL2 from ACS patients had more oxidized polyunsaturated fatty acids (PUFAs). An inverse correlation between the concentrations of 9-hydroxyoctadecadienoic acid (9-HODE), 13-hydroxyoctadecadienoic acid (13-HODE), the eicosapentaenoic acid metabolite 18-hydroxyeicosapentaenoic acid (18-HEPE) and hydroxyeicosatetraenoic acid isomers in HDL2 and platelet aggregation was observed. This relationship was further demonstrated by the direct inhibitory effects of 18-HEPE, 9-HODE, 13-HODE, 17-hydroxydocosahexaenoic acid and 14-hydroxydocosahexaenoic acid on collagen-related peptide-induced platelet aggregation, indicating that oxidized PUFAs contribute to the antithrombotic effect of ACS HDL2. Conclusions Our data shed new light on the antiplatelet effects of HDL subclasses, and suggest physiological adaptation through the modulation of HDL properties in ACS patients that may limit their platelet-dependent thrombotic risk.

Novel 14,21-dihydroxy-docosahexaenoic acids: structures, formation pathways, and enhancement of wound healing

Chronic wounds remain a medical challenge, where well-coordinated cellular and molecular processes required by optimal healing are impaired by diabetes, aging, or other diseases. In determining mechanisms that regulate wound healing, we found that wounding induced formation of novel endogenous 14S,21S-dihydroxy-docosa-4Z,7Z,10Z,12E,16Z,19Z-hexaenoic acids (14S,21S-diHDHA);14R,21R-diHDHA; 14S,21R-diHDHA; and/or 14R,21S-diHDHA. 12-lipoxygenase and cytochrome P450 catalysis in tandem converted docosahexaenoic acid to 14S,21R-diHDHA and 14S,21S-diHDHA through the intermediacy of 14S-HDHA; P450 also converted 14R-HDHA to novel 14R,21R-diHDHA and 14R,21S-diHDHA. Macrophages function as the combination of 12-lipoxgenase and P450 to generate these 14,21-diHDHA stereoisomers, as well as their intermediates 14S-HDHA, 14R-HDHA, and 21-HDHA. The structure and formation pathways of 14,21-diHDHA stereoisomers were further confirmed by macrophage biosynthesis of 14,21-diHDHA-21,22,22,22-d(4) stereoisomers, 14S-HDHA-d(5), 14R-HDHA-d(5), and 21-HDHA-d(4) from DHA-21,21,22,22,22-d(5). We found that 14S,21-diHDHA and 14R,21-diHDHA enhanced wound closure, reepithelialization, granulation tissue growth, and capillary vasculature formation of murine wounds. 14S,21-diHDHA and 14R,21-diHDHA produced by macrophages may partially represent the molecular mechanisms for macrophage pro-healing function. Taken together, 14,21-dihydroxy-DHA stereoisomers and their formation pathways may represent a novel mechanism in the orchestration of wound healing processes, which may provide new insight for developing novel therapeutic modalities that counteract impairments to wound healing.

Maresins: novel macrophage mediators with potent antiinflammatory and proresolving actions

The endogenous cellular and molecular mechanisms that control acute inflammation and its resolution are of wide interest. Using self-resolving inflammatory exudates and lipidomics, we have identified a new pathway involving biosynthesis of potent antiinflammatory and proresolving mediators from the essential fatty acid docosahexaenoic acid (DHA) by macrophages (MΦs). During the resolution of mouse peritonitis, exudates accumulated both 17-hydroxydocosahexaenoic acid, a known marker of 17S-D series resolvin (Rv) and protectin biosynthesis, and 14S-hydroxydocosa-4Z,7Z,10Z,12E,16Z,19Z-hexaenoic acid from endogenous DHA. Addition of either DHA or 14S-hydroperoxydocosa-4Z,7Z,10Z,12E,16Z,19Z-hexaenoic acid to activated MΦs converted these substrates to novel dihydroxy-containing products that possessed potent antiinflammatory and proresolving activity with a potency similar to resolvin E1, 5S,12R,18R-trihydroxyeicosa-6Z,8E,10E,14Z,16E-pentaenoic acid, and protectin D1, 10R,17S-dihydroxydocosa-4Z,7Z,11E,13E,15Z,19Z-hexaenoic acid. Stable isotope incorporation, intermediate trapping, and characterization of physical and biological properties of the products demonstrated a novel 14-lipoxygenase pathway, generating bioactive 7,14-dihydroxydocosa-4Z,8,10,12,16Z,19Z-hexaenoic acid, coined MΦ mediator in resolving inflammation (maresin), which enhances resolution. These findings suggest that maresins and this new metabolome may be involved in some of the beneficial actions of DHA and MΦs in tissue homeostasis, inflammation resolution, wound healing, and host defense.