Impact of elevated lipoprotein(a) on coronary artery disease phenotype and severity

AIMS

A thorough characterization of the relationship between elevated lipoprotein(a) [Lp(a)] and coronary artery disease (CAD) is lacking. This study aimed to quantitatively assess the association of increasing Lp(a) levels and CAD severity in a real-world population.

METHODS AND RESULTS

This non-interventional, cross-sectional, LipidCardio study included patients aged ≥21 years undergoing angiography (October 2016-March 2018) at a tertiary cardiology centre, who have at least one Lp(a) measurement. The association between Lp(a) and CAD severity was determined by synergy between PCI with taxus and cardiac surgery (SYNTAX)-I and Gensini scores and angiographic characteristics. Overall, 975 patients (mean age: 69.5 years) were included; 70.1% were male, 97.5% had Caucasian ancestry, and 33.2% had a family history of premature atherosclerotic cardiovascular disease. Median baseline Lp(a) level was 19.3 nmol/L. Patients were stratified by baseline Lp(a): 72.9% had < 65 nmol/L, 21.0% had ≥100 nmol/L, 17.2% had ≥125 nmol/L, and 12.9% had ≥150 nmol/L. Compared with the normal (Lp(a) < 65 nmol/L) group, elevated Lp(a) groups (e.g. ≥ 150 nmol/L) had a higher proportion of patients with prior CAD (48.4% vs. 62.7%; P < 0.01), prior coronary revascularization (39.1% vs. 51.6%; P = 0.01), prior coronary artery bypass graft (6.0% vs. 15.1%; P < 0.01), vessel(s) with lesions (68.5% vs. 81.3%; P = 0.03), diffusely narrowed vessels (10.9% vs. 16.5%; P = 0.01) or chronic total occlusion lesions (14.3% vs. 25.2%; P < 0.01), and higher median SYNTAX-I (3.0 vs. 5.5; P = 0.01) and Gensini (10.0 vs. 16.0; P < 0.01) scores.

CONCLUSION

Elevated Lp(a) was associated with a more severe presentation of CAD. Awareness of Lp(a) levels in patients with CAD may have implications in their clinical management.

Omega-3 Polyunsaturated Fatty Acids Decrease Aortic Valve Disease Through the Resolvin E1 and ChemR23 Axis

Supplemental Digital Content is available in the text.

Background:

Aortic valve stenosis (AVS), which is the most common valvular heart disease, causes a progressive narrowing of the aortic valve as a consequence of thickening and calcification of the aortic valve leaflets. The beneficial effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) in cardiovascular prevention have recently been demonstrated in a large randomized, controlled trial. In addition, n-3 PUFAs serve as the substrate for the synthesis of specialized proresolving mediators, which are known by their potent beneficial anti-inflammatory, proresolving, and tissue-modifying properties in cardiovascular disease. However, the effects of n-3 PUFA and specialized proresolving mediators on AVS have not yet been determined. The aim of this study was to identify the role of n-3 PUFA–derived specialized proresolving mediators in relation to the development of AVS.

Methods:

Lipidomic and transcriptomic analyses were performed in human tricuspid aortic valves. Apoe^−/− mice and wire injury in C57BL/6J mice were used as models for mechanistic studies.

Results:

We found that n-3 PUFA incorporation into human stenotic aortic valves was higher in noncalcified regions compared with calcified regions. Liquid chromatography tandem mass spectrometry–based lipid mediator lipidomics identified that the n-3 PUFA–derived specialized proresolving mediator resolvin E1 was dysregulated in calcified regions and acted as a calcification inhibitor. Apoe^−/− mice expressing the Caenorhabditis elegans Fat-1 transgene (Fat-1^tg×Apoe^−/−), which enables the endogenous synthesis of n-3 PUFA and increased valvular n-3 PUFA content, exhibited reduced valve calcification, lower aortic valve leaflet area, increased M2 macrophage polarization, and improved echocardiographic parameters. Finally, abrogation of the resolvin E1 receptor ChemR23 enhanced disease progression, and the beneficial effects of Fat-1^tg were abolished in the absence of ChemR23.

Conclusions:

n-3 PUFA-derived resolvin E1 and its receptor ChemR23 emerge as a key axis in the inhibition of AVS progression and may represent a novel potential therapeutic opportunity to be evaluated in patients with AVS.

Proteoglycan 4 is Increased in Human Calcified Aortic Valves and Enhances Valvular Interstitial Cell Calcification

Aortic valve stenosis (AVS), a consequence of increased fibrosis and calcification of the aortic valve leaflets, causes progressive narrowing of the aortic valve. Proteoglycans, structural components of the aortic valve, accumulate in regions with fibrosis and moderate calcification. Particularly, proteoglycan 4 (PRG4) has been identified in fibrotic parts of aortic valves. However, the role of PRG4 in the context of AVS and aortic valve calcification has not yet been determined. Here, transcriptomics, histology, and immunohistochemistry were performed in human aortic valves from patients undergoing aortic valve replacement. Human valve interstitial cells (VICs) were used for calcification experiments and RNA expression analysis. PRG4 was significantly upregulated in thickened and calcified regions of aortic valves compared with healthy regions. In addition, mRNA levels of PRG4 positively associated with mRNA for proteins involved in cardiovascular calcification. Treatment of VICs with recombinant human PRG4 enhanced phosphate-induced calcification and increased the mRNA expression of bone morphogenetic protein 2 and the runt-related transcription factor 2. In summary, PRG4 was upregulated in the development of AVS and promoted VIC osteogenic differentiation and calcification. These results suggest that an altered valve leaflet proteoglycan composition may play a role in the progression of AVS.

Chemerin inhibits vascular calcification through ChemR23 and is associated with lower coronary calcium in chronic kidney disease

BACKGROUND

Chemerin is an adipokine that signals through the G protein-coupled receptor ChemR23 and is associated with inflammation, glucose homeostasis, lipid metabolism and renal function, all of which strongly influence cardiovascular risk. However, elevated chemerin provides a survival advantage in patients with chronic kidney disease (CKD), but how this relates to the cardiovascular phenotype is unknown.

OBJECTIVES

The aim of the present study was to establish the association of chemerin with coronary calcification and to determine the effects of chemerin signalling, through ChemR23, in vascular smooth muscle cell (VSMC) calcification.

METHODS

Plasma chemerin was measured in 113 patients with CKD and 50 healthy controls. All patients underwent computed tomography to determine coronary artery calcium (CAC) score. VSMCs were isolated from wild-type and ChemR23 knock-out mice and treated with chemerin.

RESULTS

Multivariate analyses established creatinine, cholesterol, body mass index and tumour necrosis factor as significant confounders for circulating chemerin levels. Despite these positive associations with renal function, cardiometabolic risk factors and inflammation, chemerin was inversely associated with CAC both in an age- and sex-adjusted analysis and in a multivariate analysis adjusting for the aforementioned confounders. In addition, circulating chemerin levels were associated with the calcification inhibitors matrix gla protein (MGP) and fetuin-A. Finally, chemerin significantly reduced phosphate-induced calcification and increased MGP expression in VSMCs, whereas chemerin was devoid of these effects in VSMCs lacking ChemR23.

CONCLUSION

In conclusion, these results suggest that chemerin signalling through ChemR23 in VSMCs protects against vascular calcification in CKD.

ERV1/ChemR23 Signaling Protects Against Atherosclerosis by Modifying Oxidized Low-Density Lipoprotein Uptake and Phagocytosis in Macrophages

Supplemental Digital Content is available in the text.

Background:

In addition to enhanced proinflammatory signaling, impaired resolution of vascular inflammation plays a key role in atherosclerosis. Proresolving lipid mediators formed through the 12/15 lipoxygenase pathways exert protective effects against murine atherosclerosis. n-3 Polyunsaturated fatty acids, including eicosapentaenoic acid (EPA), serve as the substrate for the formation of lipid mediators, which transduce potent anti-inflammatory and proresolving actions through their cognate G-protein–coupled receptors. The aim of this study was to identify signaling pathways associated with EPA supplementation and lipid mediator formation that mediate atherosclerotic disease progression.

Methods:

Lipidomic plasma analysis were performed after EPA supplementation in Apoe^−/− mice. Erv1/Chemr23^−/−xApoe^−/− mice were generated for the evaluation of atherosclerosis, phagocytosis, and oxidized low-density lipoprotein uptake. Histological and mRNA analyses were done on human atherosclerotic lesions.

Results:

Here, we show that EPA supplementation significantly attenuated atherosclerotic lesion growth induced by Western diet in Apoe^−/− mice and was associated with local cardiovascular n-3 enrichment and altered lipoprotein metabolism. Our systematic plasma lipidomic analysis identified the resolvin E1 precursor 18-monohydroxy EPA as a central molecule formed during EPA supplementation. Targeted deletion of the resolvin E1 receptor Erv1/Chemr23 in 2 independent hyperlipidemic murine models was associated with proatherogenic signaling in macrophages, increased oxidized low-density lipoprotein uptake, reduced phagocytosis, and increased atherosclerotic plaque size and necrotic core formation. We also demonstrate that in macrophages the resolvin E1–mediated effects in oxidized low-density lipoprotein uptake and phagocytosis were dependent on Erv1/Chemr23. When analyzing human atherosclerotic specimens, we identified ERV1/ChemR23 expression in a population of macrophages located in the proximity of the necrotic core and demonstrated augmented ERV1/ChemR23 mRNA levels in plaques derived from statin users.

Conclusions:

This study identifies 18-monohydroxy EPA as a major plasma marker after EPA supplementation and demonstrates that the ERV1/ChemR23 receptor for its downstream mediator resolvin E1 transduces protective effects in atherosclerosis. ERV1/ChemR23 signaling may represent a previously unrecognized therapeutic pathway to reduce atherosclerotic cardiovascular disease.

The G-protein coupled receptor ChemR23 determines smooth muscle cell phenotypic switching to enhance high phosphate-induced vascular calcification

Aims

Vascular calcification, a marker of increased cardiovascular risk, is an active process orchestrated by smooth muscle cells. Observational studies indicate that omega-3 fatty acids protect against vascular calcification, but the mechanisms are unknown. The G-protein coupled receptor ChemR23 transduces the resolution of inflammation induced by the omega-3-derived lipid mediator resolvin E1. ChemR23 also contributes to osteoblastic differentiation of stem cells and bone formation, but its role in vascular calcification is unknown. The aim of this study was to establish the role of ChemR23 in smooth muscle cell fate and calcification

Methods and results

Gene expression analysis in epigastric arteries derived from patients with chronic kidney disease and vascular calcification revealed that ChemR23 mRNA levels predicted a synthetic smooth muscle cell phenotype. Genetic deletion of ChemR23 in mice prevented smooth muscle cell de-differentiation. ChemR23-deficient smooth muscle cells maintained a non-synthetic phenotype and exhibited resistance to phosphate-induced calcification. Moreover, ChemR23-deficient mice were protected against vitamin D3-induced vascular calcification. Resolvin E1 inhibited smooth muscle cell calcification through ChemR23. Introduction of the Caenorhabditis elegans Fat1 transgene, leading to an endogenous omega-3 fatty acid synthesis and hence increased substrate for resolvin E1 formation, significantly diminished the differences in phosphate-induced calcification between ChemR23+/+ and ChemR23−/− mice.

Conclusion

This study identifies ChemR23 as a previously unrecognized determinant of synthetic and osteoblastic smooth muscle cell phenotype, favouring phosphate-induced vascular calcification. This effect may be of particular importance in the absence of ChemR23 ligands, such as resolvin E1, which acts as a calcification inhibitor under hyperphosphatic conditions.

Opposing Effects on Vascular Smooth Muscle Cell Proliferation and Macrophage-induced Inflammation Reveal a Protective Role for the Proresolving Lipid Mediator Receptor ChemR23 in Intimal Hyperplasia

Intimal hyperplasia remains a significant clinical problem in for example coronary artery bypass graft failure. Since omega-3 fatty acids reduce intimal hyperplasia, we hypothesized that the G protein-coupled receptor ChemR23 for the omega-3-derived pro-resolving lipid mediator resolvin E1 drives those effects. ChemR23+/+ and ChemR23-/- mice were generated with or without introduction of the Caenorhabditis elegans fat-1 transgene, which leads to an endogenous omega-3 fatty acid synthesis and thus increasing the substrate for resolvin E1 formation. ChemR23 deletion significantly increased intimal hyperplasia 28 days after ligation of the left common carotid artery. Mice expressing the fat-1 transgene showed reduced intimal hyperplasia independently of ChemR23 expression. ChemR23-/- Vascular smooth muscle cells (VSMCs) exhibited a significantly lower proliferation compared with VSMCs derived from ChemR23+/+ mice. In contrast, ChemR23-/- peritoneal macrophages had significantly higher mRNA levels of pro-inflammatory cytokines compared with ChemR23+/+ macrophages. Finally, conditioned media (CM) transfer from ChemR23-/- macrophages to VSMCs significantly increased VSMC proliferation compared with CM from ChemR23+/+ macrophages. Taken together, these results point to a dual effect of ChemR23 in resolution pharmacology by directly stimulating VSMC proliferation and at the same time suppressing macrophage-induced VSMC proliferation. In conclusion, these differential effects of ChemR23 signaling in VSMC and macrophages open up a novel notion for intimal hyperplasia pathophysiology, where ChemR23-transduced effects on the vascular wall may vary, and even be opposing, depending on the degrees of resolution of inflammation.

Iron alters valvular interstitial cell function and is associated with calcification in aortic stenosis

Aims

Aortic valve stenosis (AS) is the most common valvulopathy and is characterized by inflammation, extracellular matrix (ECM) remodelling and calcification, causing a narrowing of the valve and the consequential obstruction of the cardiac outflow. Although intraleaflet haemorrhage is associated with AS progression, the mechanisms involved are not known. The aims of this study were to identify valvular iron in relation to pathological changes associated with AS and the effects on valvular interstitial cells (VIC) in terms of iron uptake and iron-induced responses.

Methods and results

Valvular iron accumulation was detected by Perls' staining on aortic valve sections and shown to increase with the extent of calcification. Furthermore, qRT–PCR analysis revealed that iron-containing valve regions exhibited increased expression of genes involved in ECM remodelling and calcification. In addition, we demonstrate that iron transporters are regulated by pathways with major impact on AS and that VIC can take up and accumulate iron, which resulted in increased proliferation and decreased elastin production.

Conclusion

Iron, which may accumulate in the aortic valve by means of intraleaflet haemorrhages, can be taken up by VIC in a pro-inflammatory environment and actively contribute to VIC proliferation, ECM remodelling and calcification. These findings suggest a possible mechanism through which iron uptake by VIC may favour AS progression.

Inhibition of indoleamine 2,3-dioxygenase promotes vascular inflammation and increases atherosclerosis in Apoe-/- mice

AIMS

Atherosclerosis is a chronic inflammatory disease that is initiated by the retention and accumulation of low-density lipoprotein in the artery, leading to maladaptive response of cells from the immune system and vessel wall. Strong evidence implicates indoleamine 2,3-dioxygenase (IDO), the first and rate-limiting enzyme of the kynurenine pathway of tryptophan (Trp) degradation, with immune regulation and anti-inflammatory mechanisms in different diseases. However, the role of IDO and the endogenous degradation of Trp have never been directly examined in atherosclerosis development. We used the IDO inhibitor 1-methyl-Trp (1-MT) to determine the role of IDO-mediated Trp metabolism in vascular inflammation and atherosclerosis.

METHODS AND RESULTS

Apoe(-/-) mice were treated with 1-MT in drinking water for 8 weeks. Systemic IDO inhibition led to a significant increase in atherosclerotic lesions that were ∼58 and 54% larger in the aortic arch and root, respectively. 1-MT treatment enhanced vascular inflammation, up-regulated VCAM-1 and CCL2, and increased CD68 macrophage accumulation into the plaque. Notably, the rise in VCAM-1 expression was not limited to the plaque but also found in smooth muscle cells (SMCs) of the tunica media. Furthermore, we found that IDO-dependent Trp metabolism by SMCs regulates VCAM-1 expression, and that 1-MT-induced acceleration of atherosclerosis and vascular inflammation can be reversed by exogenous administration of the Trp metabolite 3-hydroxyanthranilic acid (3-HAA).

CONCLUSION

IDO-mediated Trp metabolism regulates vascular inflammation and plaque formation in hypercholesterolaemic Apoe(-/-) mice. Our data establish that this pathway plays a major role in the pathological process of atherogenesis.

Progestogens reduce thromboxane production by cultured human endothelial cells

OBJECTIVES

Progestogens have been poorly studied concerning their roles in endothelial physiology. Prostanoids are vasoactive compounds, such as thromboxane A2, a potent vasoconstrictor, and prostacyclin, a vasodilator. We examined the effects of two progestogens used clinically, progesterone and medroxyprogesterone acetate, on thromboxane A2 production by cultured human umbilical vein endothelial cells (HUVEC) and investigated the role of progesterone receptors and the enzymes involved in production of thromboxane A2 and prostacyclin.

METHODS

Cells were exposed to 1-100  nmol/l of either progesterone or medroxyprogesterone acetate, and thromboxane A2 production was measured in culture medium by enzyme immunoassay. Gene expression of prostacyclin synthase and thromboxane synthase was analyzed by quantitative real-time polymerase chain reaction. Expression of prostacyclin synthase protein was analyzed by Western blot.

RESULTS

Both progestogens decreased thromboxane A2 release after 24 h. Protein and gene expression of prostacyclin synthase were increased after exposure to both progestogens, without changes in thromboxane synthase expression. These effects induced by progestogens were mediated through progesterone receptors, since they were decreased in the presence of the progesterone receptor antagonist RU486. The cyclo-oxygenase-1 selective inhibitor reduced thromboxane release.

CONCLUSION

Progesterone and medroxyprogesterone acetate decreased HUVEC thromboxane release in a progesterone receptor-dependent manner, without changes in thromboxane synthase expression and enhanced prostacyclin synthase gene and protein expression.