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Background and aimsLipoprotein(a) [Lp(a)] is causally associated with aortic valve stenosis (AS) but Lp(a) testing among AS patients is not broadly incorporated into clinical practice. We evaluated trends in Lp(a) testing in an academic medical center.MethodsEducational efforts and adding Lp(a) to the lipid panel on the electronic medical record (EMR) and pre-procedure order sets were used to increase awareness of Lp(a) as a risk factor in AS. Medical records at University of California San Diego Health (UCSDH) were analyzed from 2010 to 2020 to define the yearly frequency of first time Lp(a) testing in patients with diagnosis codes for AS or undergoing transcatheter aortic valve replacement (TAVR).ResultsLp(a) testing for any indication increased over 5-fold from 2010 to 2020. A total of 3808 patients had a diagnosis of AS and 417 patients had TAVR. Lp(a) levels >30mg/dL were present in 37% of AS and 35% of TAVR patients. The rates of Lp(a) testing in AS and TAVR were 14.0% and 65.7%, respectively. In AS, Lp(a) testing increased over time from 8.5% in 2010, peaking at 24.2% in 2017, and declining to 13.9% in 2020 (p&nbsp

Background: Lipoproteins are important regulators of hematopoietic stem and progenitor cell (HSPC) biology, predominantly affecting myelopoiesis. Since myeloid cells, including monocytes and macrophages, promote the inflammatory response that propagates atherosclerosis, it is of interest whether the atherogenic low-density lipoprotein (LDL)-like particle lipoprotein(a) [Lp(a)] contributes to atherogenesis via stimulating myelopoiesis. Methods & results: To assess the effects of Lp(a)-priming on long-term HSPC behavior we transplanted BM of Lp(a) transgenic mice, that had been exposed to elevated levels of Lp(a), into lethally-irradiated C57Bl6 mice and hematopoietic reconstitution was analyzed. No differences in HSPC populations or circulating myeloid cells were detected ten weeks after transplantation. Likewise, in vitro stimulation of C57Bl6 BM cells for 24 h with Lp(a) did not affect colony formation, total cell numbers or myeloid populations 7 days later. To assess the effects of elevated levels of Lp(a) on myelopoiesis, C57Bl6 bone marrow (BM) cells were stimulated with lp(a) for 24 h, and a marked increase in granulocyte-monocyte progenitors, pro-inflammatory Ly6high monocytes and macrophages was observed. Seven days of continuous exposure to Lp(a) increased colony formation and enhanced the formation of pro-inflammatory monocytes and macrophages. Antibody-mediated neutralization of oxidized phospholipids abolished the Lp(a)-induced effects on myelopoiesis. Conclusion: Lp(a) enhances the production of inflammatory monocytes at the bone marrow level but does not induce cell-intrinsic long-term priming of HSPCs. Given the short-term and direct nature of this effect, we postulate that Lp(a)-lowering treatment has the capacity to rapidly revert this multi-level inflammatory response.

Lipoprotein (a) [Lp(a)] is a risk factor for CVD and a target of therapy, but Lp(a) measurements are not globally standardized. Commercially available assays generally use polyclonal antibodies that detect multiple sites within the kringle (K)IV(2) repeat region of Lp(a) and may lead to inaccurate assessments of plasma levels. With increasing awareness of Lp(a) as a cardiovascular risk factor and the active clinical development of new potential therapeutic approaches, the broad availability of reagents capable of providing isoform independence of Lp(a) measurements is paramount. To address this issue, we generated a murine monoclonal antibody that binds to only one site on apo(a). A BALB/C mouse was immunized with a truncated version of apo(a) that contained eight total KIV repeats, including only one copy of KIV(2). We generated hybridomas, screened them, and successfully produced a KIV(2)-independent monoclonal antibody, named LPA-KIV9. Using a variety of truncated apo(a) constructs to map its binding site, we found that LPA-KIV9 binds to KIV(9) without binding to plasminogen. Fine peptide mapping revealed that LPA-KIV9 bound to the sequence (4076)LETPTVV(4082) on KIV(9). In conclusion, the generation of monoclonal antibody LPA-KIV9 may be a useful reagent in basic research studies and in the clinical application of Lp(a) measurements.

Rationale: Patients with elevated levels of lipoprotein(a) [Lp(a)] are hallmarked by increased metabolic activity in the arterial wall on positron emission tomography/computed tomography, indicative of a proinflammatory state. Objective: We hypothesized that Lp(a) induces endothelial cell inflammation by rewiring endothelial metabolism. Methods and Results: We evaluated the impact of Lp(a) on the endothelium and describe that Lp(a), through its oxidized phospholipid content, activates arterial endothelial cells, facilitating increased transendothelial migration of monocytes. Transcriptome analysis of Lp(a)-stimulated human arterial endothelial cells revealed upregulation of inflammatory pathways comprising monocyte adhesion and migration, coinciding with increased 6-phophofructo-2-kinase/fructose-2,6-biphosphatase (PFKFB)-3–mediated glycolysis. ICAM (intercellular adhesion molecule)-1 and PFKFB3 were also found to be upregulated in carotid plaques of patients with elevated levels of Lp(a). Inhibition of PFKFB3 abolished the inflammatory signature with concomitant attenuation of transendothelial migration. Conclusions: Collectively, our findings show that Lp(a) activates the endothelium by enhancing PFKFB3-mediated glycolysis, leading to a proadhesive state, which can be reversed by inhibition of glycolysis. These findings pave the way for therapeutic agents targeting metabolism aimed at reducing inflammation in patients with cardiovascular disease.

It is postulated that lipoprotein (a) [Lp(a)] inhibits fibrinolysis, but this hypothesis has not been tested in humans due to the lack of specific Lp(a) lowering agents. Patients with elevated Lp(a) were randomized to antisense oligonucleotide [IONIS-APO(a)(Rx)] directed to apo(a) (n = 7) or placebo (n = 10). Ex vivo plasma lysis times and antigen concentrations of plasminogen, factor XI, plasminogen activator inhibitor 1, thrombin activatable fibrinolysis inhibitor, and fibrinogen at baseline, day 85/92/99 (peak drug effect), and day 190 (3 months off drug) were measured. The mean ± SD baseline Lp(a) levels were 477.3 ± 55.9 nmol/l in IONIS-APO(a)(Rx) and 362.1 ± 89.9 nmol/l in placebo. The mean± SD percentage change in Lp(a) for IONIS-APO(a)(Rx) was −69.3 ± 12.2% versus −5.4 ± 6.9% placebo (P < 0.0010) at day 85/92/99 and −15.6 ± 8.9% versus 3.2 ± 12.2% (P = 0.003) at day 190. Clot lysis times and coagulation/fibrinolysis-related biomarkers showed no significant differences between IONIS-APO(a)(Rx) and placebo at all time points. Clot lysis times were not affected by exogenously added Lp(a) at concentrations up to 200 nmol/l to plasma with very low (12.5 nmol/l) Lp(a) levels, whereas recombinant apo(a) had a potent antifibrinolytic effect. In conclusion, potent reductions of Lp(a) in patients with highly elevated Lp(a) levels do not affect ex vivo measures of fibrinolysis; the relevance of any putative antifibrinolytic effects of Lp(a) in vivo needs further study.

High levels of lipoprotein(a) [Lp(a)], an apoB100-containing lipoprotein, are an independent and causal risk factor for atherosclerotic cardiovascular diseases through mechanisms associated with increased atherogenesis, inflammation, and thrombosis. Lp(a) is predominantly a monogenic cardiovascular risk determinant, with ≈70% to ≥90% of interindividual heterogeneity in levels being genetically determined. The 2 major protein components of Lp(a) particles are apoB100 and apolipoprotein(a). Lp(a) remains a risk factor for cardiovascular disease development even in the setting of effective reduction of plasma low-density lipoprotein cholesterol and apoB100. Despite its demonstrated contribution to atherosclerotic cardiovascular disease burden, we presently lack standardization and harmonization of assays, universal guidelines for diagnosing and providing risk assessment, and targeted treatments to lower Lp(a). There is a clinical need to understand the genetic and biological basis for variation in Lp(a) levels and its relationship to disease in different ancestry groups. This scientific statement capitalizes on the expertise of a diverse basic science and clinical workgroup to highlight the history, biology, pathophysiology, and emerging clinical evidence in the Lp(a) field. Herein, we address key knowledge gaps and future directions required to mitigate the atherosclerotic cardiovascular disease risk attributable to elevated Lp(a) levels.

This study sought to investigate whether reactive oxygen species (ROS)-generating reduced nicotinamide adenine dinucleotide phosphate oxidase 2 (Nox2) contributes to calcific aortic valve disease (CAVD) or whether celastrol, a natural Nox2 inhibitor, may provide potential therapeutic target for CAVD. CAVD is an active and cellular-driven fibrocalcific process characterized by differentiation of aortic valvular interstitial cells (AVICs) toward an osteogenic-like phenotype. ROS levels increase in calcified aortic valves, while the sources of ROS and their roles in the pathogenesis of CAVD are elusive. The roles of Nox2 and the effects of celastrol were studied using cultured porcine AVICs in vitro and a rabbit CAVD model in vivo. Nox2 proteins were significantly upregulated in human aortic valves with CAVD. In vitro, Nox2 was markedly induced upon stimulation of AVICs with osteogenic medium, along with the increases in ROS production and calcium nodule formation. Celastrol significantly decreased calcium deposition of AVICs by 35%, with a reduction of ROS generation. Knockdown of endogenous Nox2 substantially suppressed AVIC calcification by 39%, the inhibitory effect being similar to celastrol treatment. Mechanistically, either celastrol treatment or knockdown of Nox2 significantly inhibited glycogen synthase kinase 3 beta/β-catenin signaling, leading to attenuation of fibrogenic and osteogenic responses of AVICs. In a rabbit CAVD model, administration of celastrol significantly reduced aortic valve ROS production, fibrosis, calcification, and severity of aortic stenosis, with less left ventricular dilatation and better preserved contractile function. Upregulation of Nox2 is critically involved in CAVD. Celastrol is effective to alleviate CAVD, likely through the inhibition of Nox2-mediated glycogen synthase kinase 3 beta/β-catenin pathway in AVICs.

Aims Lipoprotein(a) [Lp(a)] is elevated in 20–30% of people. This study aimed to assess the effect of statins on Lp(a) levels. Methods and results This subject-level meta-analysis includes 5256 patients (1371 on placebo and 3885 on statin) from six randomized trials, three statin-vs.-placebo trials, and three statin-vs.-statin trials, with pre- and on-treatment (4–104 weeks) Lp(a) levels. Statins included atorvastatin 10 mg/day and 80 mg/day, pravastatin 40 mg/day, rosuvastatin 40 mg/day, and pitavastatin 2 mg/day. Lipoprotein(a) levels were measured with the same validated assay. The primary analysis of Lp(a) is based on the log-transformed data. In the statin-vs.-placebo pooled analysis, the ratio of geometric means [95% confidence interval (CI)] for statin to placebo is 1.11 (1.07–1.14) (P 1 indicating a higher increase in Lp(a) from baseline in statin vs. placebo. The mean percent change from baseline ranged from 8.5% to 19.6% in the statin groups and −0.4% to −2.3% in the placebo groups. In the statin-vs.-statin pooled analysis, the ratio of geometric means (95% CI) for atorvastatin to pravastatin is 1.09 (1.05–1.14) (P Conclusion This meta-analysis reveals that statins significantly increase plasma Lp(a) levels. Elevations of Lp(a) post-statin therapy should be studied for effects on residual cardiovascular risk.

Lipoprotein(a) [Lp(a)] is a genetically determined risk factor for calcific aortic valve stenosis (CAVS) for which transcatheter aortic valve replacement (TAVR) is increasingly utilized as treatment. We evaluated the effect of a program to increase testing of and define the prevalence of elevated Lp(a) among patients undergoing TAVR. Educational efforts and incorporation of a “check-box” Lp(a) order to the preoperative TAVR order set were instituted. Retrospective chart review was performed in 229 patients requiring TAVR between May 2013 and September 2018. Of these patients, 57% had an Lp(a) level measured; testing rates increased from 0% in 2013 to 96% in 2018. Lipoprotein(a) testing occurred in 11% of patients before and in 80% of patients after the “check-box” order set ( P < .001). The prevalence of elevated Lp(a) (≥30 mg/dL) was 35%; these patients had a higher incidence of coronary artery disease requiring revascularization compared with patients with normal Lp(a) (65% vs 47%; P = .047). Patients with Lp(a) ≥30 mg/dL also had higher incidence of paravalvular leak compared with those with normal Lp(a) (13% vs 4%; P = .04). This study defines the prevalence of elevated Lp(a) in advanced stages of CAVS and provides a practice pathway to assess procedural complications and long-term outcomes of TAVR in patients with elevated Lp(a) levels.

Deleterious somatic mutations in DNA methyltransferase 3 alpha (DNMT3A) and TET mehtylcytosine dioxygenase 2 (TET2) are associated with clonal expansion of hematopoietic cells and higher risk of cardiovascular disease (CVD). Here, we investigated roles of DNMT3A and TET2 in normal human monocyte-derived macrophages (MDM), in MDM isolated from individuals with DNMT3A or TET2 mutations, and in macrophages isolated from human atherosclerotic plaques. We found that loss of function of DNMT3A or TET2 resulted in a type I interferon response due to impaired mitochondrial DNA integrity and activation of cGAS signaling. DNMT3A and TET2 normally maintained mitochondrial DNA integrity by regulating the expression of transcription factor A mitochondria (TFAM) dependent on their interactions with RBPJ and ZNF143 at regulatory regions of the TFAM gene. These findings suggest that targeting the cGAS-type I IFN pathway may have therapeutic value in reducing risk of CVD in patients with DNMT3A or TET2 mutations.

The mechanisms leading to oxidative stress and cellular dysfunction during stroke are not well understood. To test the hypothesis that transient cerebral artery occlusion (MCAo) in mice results in the generation of oxidized phospholipids (oxPLs) that contribute to neuronal cell death and glial activation. Both in vitro and in vivo cerebral ischemia and reperfusion injury (IRI) resulted in the elevation of specific oxPLs. Neuronal cell death was determined in the presence of oxPLs and the natural oxPL E06 antibody protected the cells from the toxic effects. IRI in mice gave rise to increased immunoreactivity of oxPLs in the brain. E06 reduced inflammatory markers in the brain following IRI, including iba-1, GFAP and inflammatory cytokines. In addition, oxPLs gave rise to M1 and Mox microglial phenotypes which was reversed in the presence of E06 and elicited a more M2 phenotype. Nrf2 deficient mice show increased infarct volumes and microglia from Nrf2 -/- mice show a reduction in Mox gene expression, and E06 protects both mice and cells from the Nrf2 deficit. Cerebral IRI generates oxPLs which triggers neuronal cell loss and inflammation and inactivation of oxPLs in vivo reduces infarct volume and improves outcomes.

Background Conventional "low‐density lipoprotein cholesterol (LDL‐C)" assays measure cholesterol content in both low‐density lipoprotein and lipoprotein(a) particles. To clarify the consequences of this methodological limitation for clinical care, our study aimed to compare associations of “LDL‐C” and corrected LDL‐C with risk of cardiovascular disease and to assess the impact of this correction on the classification of patients into guideline‐recommended LDL‐C categories. Methods and Results Lipoprotein(a) cholesterol content was estimated as 30% of lipoprotein(a) mass and subtracted from “LDL‐C” to obtain corrected LDL‐C values (LDL‐C corr30 ). Hazard ratios for cardiovascular disease (defined as coronary heart disease, stroke, or coronary revascularization) were quantified by individual‐patient‐data meta‐analysis of 5 statin landmark trials from the Lipoprotein(a) Studies Collaboration (18 043 patients; 5390 events; 4.7 years median follow‐up). When comparing top versus bottom quartiles, the multivariable‐adjusted hazard ratio for cardiovascular disease was significant for “LDL‐C” (1.17; 95% CI, 1.05–1.31; P =0.005) but not for LDL‐C corr30 (1.07; 95% CI, 0.93–1.22; P =0.362). In a routine laboratory database involving 531 144 patients, reclassification of patients across guideline‐recommended LDL‐C categories when using LDL‐C corr30 was assessed. In “LDL‐C” categories of 70 to corr30 was used: 30.2% (30.0%–30.4%), 35.1% (34.9%–35.4%), 32.9% (32.6%–33.1%), and 41.1% (40.0%–42.2%), respectively. Conclusions “ LDL‐C” was associated with incident cardiovascular disease only when lipoprotein(a) cholesterol content was included in its measurement. Refinement in techniques to accurately measure LDL‐C, particularly in patients with elevated lipoprotein(a) levels, is warranted to assign risk to the responsible lipoproteins.

Purpose of review Elevated levels of lipoprotein(a) [Lp(a)] are present in 30-50% of patients with familial hypercholesterolemia. The contribution of Lp(a) towards risk stratification of patients with familial hypercholesterolemia has been recently recognized, with studies showing a significantly worse prognosis if Lp(a) is elevated. However, the role of elevated Lp(a) in diagnosis of familial hypercholesterolemia is less well defined or accepted. Recent findings An important confounder in the diagnosis of familial hypercholesterolemia is the significant contribution of the cholesterol content on Lp(a) (Lp(a)-C) in individuals with elevated Lp(a). Because Lp(a)-C is incorporated into all clinical LDL-C measurements, it can contribute significantly to the cholesterol threshold diagnostic criteria for familial hypercholesterolemia used in most clinical algorithms. Summary In this review, we discuss the interrelationship of Lp(a), Lp(a)-C and correct LDL-C in the diagnosis and prognosis of familial hypercholesterolemia. Future studies of accurately measuring correct LDL-C or in using apoB-100 and Lp(a) criteria may overcome the limitations of using estimated LDL-C in the diagnosis of familial hypercholesterolemia in individuals with concomitant elevation of Lp(a).

Summary: The LPA gene is the only monogenetic risk factor for calcific aortic valve stenosis (CAVS). Oxidized phospholipids (OxPL) and lysophosphatidic acid generated by autotaxin (ATX) from OxPL are pro-inflammatory. Aortic valve leaflets categorized pathologically from both ATXâapolipoprotein B and ATXâapolipoprotein(a) were measureable in plasma. Lipoprotein(a) (Lp[a]), ATX, OxPL, and malondialdehyde epitopes progressively increased in immunostaining (p < 0.001 for all). Six species of OxPL and lysophosphatidic acid were identified after extraction from valve leaflets. The presence of a constellation of pathologically linked, Lp(a)-associated molecules in plasma and in aortic valve leaflets of patients with CAVS suggest that Lp(a) is a key etiologic factor in CAVS. Key Words: aortic valve stenosis, autotaxin, inflammation, Lp(a), oxidation-specific epitopes

Lipoprotein(a; Lp[a]) and its associated oxidized phospholipids are causal, genetic risk factors for calcific aortic valve stenosis (CAVS). We determined the prevalence of Lp(a) measurement among 2710 patients with CAVS and 1369 control patients (∼50% of study group) without CAVS with an echocardiogram between January 2010 and February 2016 in an academic echocardiography laboratory. Lipoprotein(a) measurements were performed at a referral laboratory using an isoform-independent assay. The prevalence of any Lp(a) measurement was 4.6% (124 of the 2710) in patients with CAVS and 3.1% (42 of the 1369) in the control group ( P = .021). In patients with CAVS, mean (standard deviation) Lp(a) levels were 38 (54) mg/dL and median (interquartile range) Lp(a) levels were 14 (6-48) mg/dL. Of the 124 patients with CAVS having Lp(a) measurements, 83 (66.9%) had Lp(a)

ObjectiveThis study assessed whether apolipoprotein CIII-lipoprotein(a) complexes (ApoCIII-Lp(a)) associate with progression of calcific aortic valve stenosis (AS).MethodsImmunostaining for ApoC-III was performed in explanted aortic valve leaflets in 68 patients with leaflet pathological grades of 1–4. Assays measuring circulating levels of ApoCIII-Lp(a) complexes were measured in 218 patients with mild–moderate AS from the AS Progression Observation: Measuring Effects of Rosuvastatin (ASTRONOMER) trial. The progression rate of AS, measured as annualised changes in peak aortic jet velocity (Vpeak), and combined rates of aortic valve replacement (AVR) and cardiac death were determined. For further confirmation of the assay data, a proteomic analysis of purified Lp(a) was performed to confirm the presence of apoC-III on Lp(a).ResultsImmunohistochemically detected ApoC-III was prominent in all grades of leaflet lesion severity. Significant interactions were present between ApoCIII-Lp(a) and Lp(a), oxidised phospholipids on apolipoprotein B-100 (OxPL-apoB) or on apolipoprotein (a) (OxPL-apo(a)) with annualised Vpeak(all ppeak(pConclusionApoC-III is present on Lp(a) and in aortic valve leaflets. Elevated levels of ApoCIII-Lp(a) complexes in conjunction with Lp(a), OxPL-apoB or OxPL-apo(a) identify patients with pre-existing mild–moderate AS who display rapid progression of AS and higher rates of AVR/cardiac death.Trial registrationNCT00800800.

BACKGROUND: Lipoprotein(a) [Lp(a)] is generally measured as total mass of the entire particle or as apolipoprotein(a) particle number. OBJECTIVE: The cholesterol content of Lp(a) [Lp(a)-C)] can be estimated by the vertical auto profile (VAP) method. We assessed whether this is an accurate surrogate measurement of Lp(a) mass. METHODS: VAP-Lp(a)-C and VAP-high density lipoprotein cholesterol (HDL-C) estimated by the VAP technique, Lp(a) mass, oxidized phospholipids on apolipoprotein B-100 (OxPL-apoB) that primarily reflect OxPL on Lp(a), and HDL-C measured by enzymatic methods were measured in 552 hypercholesterolemic patients at baseline and 24 weeks after therapy with niacin monotherapy (N = 118), ezetimibe/simvastatin monotherapy (n = 155), or ezetimibe/simvastatin (10/20 mg) + niacin (to 2 g) (N = 279) in a randomized, double-blind trial. RESULTS: VAP-Lp(a)-C correlated only modestly with Lp(a) mass at baseline (r = 0.56, P 100, which is not possible. CONCLUSIONS: VAP-Lp(a)-C is a poor estimate for Lp(a) mass and likely reflects the content of HDL-C in the overlapping density spectrum of Lp(a) and HDL. These data suggest that patients with prior VAP-Lp(a)-C measurements may have misclassification of Lp(a)-related risk.

As the incidence of calcific aortic valve stenosis increases with the aging of the population, improved understanding and novel therapies to reduce its progression and need for aortic valve replacement are urgently needed.Lipoprotein(a) is the only monogenetic risk factor for calcific aortic stenosis. Elevated levels are a strong, causal, independent risk factor, as demonstrated in epidemiological, genome-wide association studies and Mendelian randomization studies. Lipoprotein(a) is the major lipoprotein carrier of oxidized phospholipids, which are proinflammatory and promote calcification of vascular cells, two key pathophysiological drivers of aortic stenosis. Elevated plasma lipoprotein(a) and oxidized phospholipids predict progression of pre-existing aortic stenosis and need for aortic valve replacement. The failure of statin trials in pre-existing aortic stenosis may be partially due to an increase in lipoprotein(a) and oxidized phospholipid levels caused by statins. Antisense oligonucleotides targeted to apo(a) are in Phase 2 clinical development and shown to lower both lipoprotein(a) and oxidized phospholipids.Lipoprotein(a) and oxidized phospholipids are key therapeutic targets in calcific aortic stenosis. Strategies aimed at potent lipoprotein(a) lowering to normalize levels and/or to suppress the proinflammatory effects of oxidized phospholipids may prevent progression of this disease.

Since its first description in 1963, significant advances in lipoprotein(a) [Lp(a)] biology have taken place. Lp(a) is composed of a low-density lipoprotein (LDL)–like particle where apolipoprotein B-100 (apoB) is covalently attached to the hydrophilic, glycosylated apolipoprotein(a) [apo(a)]. Our understanding of Lp(a)’s pathophysiology has been enhanced by epidemiology studies, meta-analyses, and genetic instrumental variable analyses that suggest Lp(a) is a causal mediator, and not merely a risk marker, of cardiovascular disease and calcific aortic valve stenosis.1 Elevated plasma Lp(a) levels, >30 to 50 mg/dL or >≈75 to 125 nmol/L, are present in 20% to 30% of the general population and in even higher percentages in patients with established cardiovascular disease and calcific aortic valve stenosis. However, one area of Lp(a) biology that remains incompletely understood and in need of further clarification is defining the mechanisms regulating its catabolism. Article, see p 1091 In this issue of the Circulation Research , Sharma et al2 elegantly extend our understanding of hepatic Lp(a) catabolism. Using confocal microscopy to study exogenously added Lp(a) to cultured hepatocytes and fibroblasts, the authors describe different intracellular fates of the lipid components of Lp(a) and of the protein apo(a). After initial binding and uptake, the lipid components leave the Rab5+ early endosomes and undergo lysosomal degradation. In contrast, apo(a) dissociates from apoB and traffics to the Golgi network and ultimately traffics to Rab11+ endosomes and is secreted back into the media (Figure). Via this process, the authors suggest that ≈30% of apo(a) recycles back to the extracellular space over a 24-hour period. The fate of any such free apo(a) is unknown, but it could bind to LDL in the extracellular space or circulate free until it binds LDL to generate Lp(a) (Figure), be cleared by other receptors, enter the vessel wall or kidney, or be …

Oxidized phospholipids (OxPL) are ubiquitous, are formed in many inflammatory tissues, including atherosclerotic lesions, and frequently mediate proinflammatory changes 1 . Because OxPL are mostly the products of non-enzymatic lipid peroxidation, mechanisms to specifically neutralize them are unavailable and their roles in vivo are largely unknown. We previously cloned the IgM natural antibody E06, which binds to the phosphocholine headgroup of OxPL, and blocks the uptake of oxidized low-density lipoprotein (OxLDL) by macrophages and inhibits the proinflammatory properties of OxPL2-4. Here, to determine the role of OxPL in vivo in the context of atherogenesis, we generated transgenic mice in the Ldlr-/- background that expressed a single-chain variable fragment of E06 (E06-scFv) using the Apoe promoter. E06-scFv was secreted into the plasma from the liver and macrophages, and achieved sufficient plasma levels to inhibit in vivo macrophage uptake of OxLDL and to prevent OxPL-induced inflammatory signalling. Compared to Ldlr-/- mice, Ldlr -/- E06-scFv mice had 57-28% less atherosclerosis after 4, 7 and even 12 months of 1% high-cholesterol diet. Echocardiographic and histologic evaluation of the aortic valves demonstrated that E06-scFv ameliorated the development of aortic valve gradients and decreased aortic valve calcification. Both cholesterol accumulation and in vivo uptake of OxLDL were decreased in peritoneal macrophages, and both peritoneal and aortic macrophages had a decreased inflammatory phenotype. Serum amyloid A was decreased by 32%, indicating decreased systemic inflammation, and hepatic steatosis and inflammation were also decreased. Finally, the E06-scFv prolonged life as measured over 15 months. Because the E06-scFv lacks the functional effects of an intact antibody other than the ability to bind OxPL and inhibit OxLDL uptake in macrophages, these data support a major proatherogenic role of OxLDL and demonstrate that OxPL are proinflammatory and proatherogenic, which E06 counteracts in vivo. These studies suggest that therapies inactivating OxPL may be beneficial for reducing generalized inflammation, including the progression of atherosclerosis, aortic stenosis and hepatic steatosis.

Aims Myocardial ischaemia followed by reperfusion (IR) causes an oxidative burst resulting in cellular dysfunction. Little is known about the impact of oxidative stress on cardiomyocyte lipids and their role in cardiac cell death. Our goal was to identify oxidized phosphatidylcholine-containing phospholipids (OxPL) generated during IR, and to determine their impact on cell viability and myocardial infarct size. Methods and results OxPL were quantitated in isolated rat cardiomyocytes using mass spectrophotometry following 24 h of IR. Cardiomyocyte cell death was quantitated following exogenously added OxPL and in the absence or presence of E06, a ‘natural’ murine monoclonal antibody that binds to the PC headgroup of OxPL. The impact of OxPL on mitochondria in cardiomyocytes was also determined using cell fractionation and Bnip expression. Transgenic Ldlr−/− mice, overexpressing a single-chain variable fragment of E06 (Ldlr−/−-E06-scFv-Tg) were used to assess the effect of inactivating endogenously generated OxPL in vivo on myocardial infarct size. Following IR in vitro, isolated rat cardiomyocytes showed a significant increase in the specific OxPLs PONPC, POVPC, PAzPC, and PGPC (P Conclusions OxPL are generated within cardiomyocytes during IR and have detrimental effects on cardiomyocyte viability. Inactivation of OxPL in vivo results in a reduction of infarct size.

Background The laboratory measurement of "low-density lipoprotein cholesterol (LDL-C)" includes the cholesterol content of lipoprotein(a) (Lp(a)-C). Objective To estimate the "true" LDL-C in relation to changes in apolipoprotein B-100 (apoB-100) and assess changes in proprotein convertase subtilisin/kexin 9 (PCSK9) levels in patients with elevated Lp(a) treated with IONIS-APO(a) Rx. Methods A pooled placebo group (n = 29), and cohort A (n = 24, baseline Lp(a) 50–175 mg/dL) and cohort B (n = 8, baseline Lp(a) > 175 mg/dL) treated with IONIS-APO(a) Rx were studied. Lp(a) particle number, ultracentrifugation-measured "LDL-C", apoB-100, total PCSK9, and lipoprotein-associated PCSK9 (PCSK9-Lp(a), PCSK9-apoB, PCSK9-apoAI) were measured. Lp(a)-cholesterol (Lp(a)-C) and LDL-C corrected for Lp(a)-C (LDL-C corr ) were calculated. Results Baseline mean (standard deviation) "LDL-C" was 120 (42), 128 (45), and 112 (39) mg/dL in placebo, cohorts A and B, respectively, whereas LDL-C corr was 86 (48), 96 (43), and 57 (37) mg/dL ( P Rx treatment at day 85/99, Lp(a) particle number and Lp(a)-C decreased –66.8% and –71.6%, apoB-100 –10.3% and –17.5%, "LDL-C" –11.8% and –22.7%, ( P corr increased +10.4% ( P = .66) and +49.9% ( P Rx vs placebo (–39.0% vs +8.4%, P Conclusion LDL-C corr is lower than laboratory "LDL-C" in patients with elevated Lp(a). Following apolipoprotein(a) inhibition and decline in Lp(a) and Lp(a)-C, the decline in apoB-100 is consistent with the notion that LDL devoid of apo(a) is cleared faster than Lp(a). These types of analyses may provide insights into the mechanisms of drugs affecting Lp(a) levels in clinical trials.

BACKGROUND Oxidation-specific epitopes (OSEs) are proinflammatory, and elevated levels in plasma predict cardiovascular events. OBJECTIVES The purpose of this study was to develop novel positron emission tomography (PET) probes to noninvasively image OSE-rich lesions. METHODS An antigen-binding fragment (Fab) antibody library was constructed from human fetal cord blood. After multiple rounds of screening against malondialdehyde-acetaldehyde (MAA) epitopes, the Fab LA25 containing minimal nontemplated insertions in the CDR3 region was identified and characterized. In mice, pharmacokinetics, biodistribution, and plaque specificity studies were performed with Zirconium-89 (Zr-89)-labeled LA25. In rabbits, Zr-89-LA25 was used in combination with an integrated clinical PET/magnetic resonance (MR) system. F-18-fluorodeoxyglucose PET and dynamic contrast-enhanced MR imaging were used to evaluate vessel wall inflammation and plaque neovascularization, respectively. Extensive ex vivo validation was carried out through a combination of gamma counting, near infrared fluorescence, autoradiography, immunohistochemistry, and immunofluorescence. RESULTS LA25 bound specifically to MAA epitopes in advanced and ruptured human atherosclerotic plaques with accompanying thrombi and in debris from distal protection devices. PET/MR imaging 24 h after injection of Zr-89-LA25 showed increased uptake in the abdominal aorta of atherosclerotic rabbits compared with nonatherosclerotic control rabbits, confirmed by ex vivo gamma counting and autoradiography. F-18-fluorodeoxyglucose PET, dynamic contrastenhanced MR imaging, and near-infrared fluorescence signals were also significantly higher in atherosclerotic rabbit aortas compared with control aortas. Enhanced liver uptake was also noted in atherosclerotic animals, confirmed by the presence of MAA epitopes by immunostaining. CONCLUSIONS Zr-89-LA25 is a novel PET radiotracer that may allow noninvasive phenotyping of high-risk OSE-rich lesions. (c) 2018 by the American College of Cardiology Foundation

Background Elevated lipoprotein(a) (Lp[a]) is associated with aortic stenosis (AS). Oxidized phospholipids (OxPL) are key mediators of calcification in valvular cells and are carried by Lp(a). Objectives This study sought to determine whether Lp(a) and OxPL are associated with hemodynamic progression of AS and AS-related events. Methods OxPL on apolipoprotein B-100 (OxPL-apoB), which reflects the biological activity of Lp(a), and Lp(a) levels were measured in 220 patients with mild-to-moderate AS. The primary endpoint was the progression rate of AS, measured by the annualized increase in peak aortic jet velocity in m/s/year by Doppler echocardiography; the secondary endpoint was need for aortic valve replacement and cardiac death during 3.5 ± 1.2 years of follow-up. Results AS progression was faster in patients in the top tertiles of Lp(a) (peak aortic jet velocity: +0.26 ± 0.26 vs. +0.17 ± 0.21 m/s/year; p = 0.005) and OxPL-apoB (+0.26 ± 0.26 m/s/year vs. +0.17 ± 0.21 m/s/year; p = 0.01). After multivariable adjustment, elevated Lp(a) or OxPL-apoB levels remained independent predictors of faster AS progression. After adjustment for age, sex, and baseline AS severity, patients in the top tertile of Lp(a) or OxPL-apoB had increased risk of aortic valve replacement and cardiac death. Conclusions Elevated Lp(a) and OxPL-apoB levels are associated with faster AS progression and need for aortic valve replacement. These findings support the hypothesis that Lp(a) mediates AS progression through its associated OxPL and provide a rationale for randomized trials of Lp(a)-lowering and OxPL-apoB-lowering therapies in AS. (Aortic Stenosis Progression Observation: Measuring Effects of Rosuvastatin [ASTRONOMER]; NCT00800800)

The measurement that is termed 'LDL-cholesterol' (LDL-C) includes the cholesterol content of lipoprotein(a) [Lp(a)-C], which can contribute approximately 30-45% to measured LDL-C levels as a percentage of its mass. We review the implications of achieved very low LDL-C levels in patients treated with potent LDL-C-lowering agents in the context of varying Lp(a) levels.Combination therapy with statins, ezetimibe, and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors can lower LDL-C to unprecedentedly low levels. Recent PCSK9 trials have shown that routine achievement of mean LDL-C less than 50 mg/dl is feasible, along with the modest reductions in Lp(a). Many patients will achieve LDL-C less than 25 mg/dl with concomitantly elevated Lp(a) levels that contribute substantially to the measured 'LDL-C'. Therefore, it is possible that some of these patients may have little to no circulating LDL-C.As the new era of ultralow LDL-C levels ensues, it is imperative to understand the contribution of Lp(a)-C to measured LDL-C and the consequences of achieving ultralow or potentially absent LDL-C in the setting of elevated Lp(a) levels and possibly free apo(a). We review this concept and suggest avenues of research, including analyses of existing datasets in current clinical trials and new research studies, to understand its pathophysiological and clinical significance.

Oxidation-specific epitopes (OSE) within developing atherosclerotic lesions are key antigens that drive innate and adaptive immune responses in atherosclerosis, leading to chronic inflammation. Oxidized phospholipids and malondialdehyde-lysine epitopes are well-characterized OSE present in human atherosclerotic lesions, particularly in pathologically defined vulnerable plaques. Using murine and human OSE-specific antibodies as targeting agents, we have developed radionuclide and magnetic resonance based nanoparticles, containing gadolinium, manganese or lipid-coated ultrasmall superparamagnetic iron oxide, to non-invasively image OSE within experimental atherosclerotic lesions. These methods quantitate plaque burden, allow detection of lesion progression and regression, plaque stabilization, and accumulation of OSE within macrophage-rich areas of the artery wall, suggesting they detect the most active lesions. Future studies will focus on using "natural" antibodies, lipopeptides, and mimotopes for imaging applications. These approaches should enhance the clinical translation of this technique to image, monitor, evaluate efficacy of novel therapeutic agents, and guide optimal therapy of high-risk atherosclerotic lesions.

IMPORTANCE: Several studies have reported an association of levels of lipoprotein(a) (Lp[a]) and the content of oxidized phospholipids on apolipoprotein B (OxPL-apoB) and apolipoprotein(a) (OxPL-apo[a]) with faster calcific aortic valve stenosis (CAVS) progression. However, whether this association is threshold or linear remains unclear. OBJECTIVE: To determine whether the plasma levels of Lp(a), OxPL-apoB, and OxPL-apo(a) have a linear association with a faster rate of CAVS progression. DESIGN, SETTING, AND PARTICIPANTS: This secondary analysis of a randomized clinical trial tested the association of baseline plasma levels of Lp(a), OxPL-apoB, and OxPL-apo(a) with the rate of CAVS progression. Participants were included from the ASTRONOMER (Effects of Rosuvastatin on Aortic Stenosis Progression) trial, a multicenter study conducted in 23 Canadian sites designed to test the effect of statin therapy (median follow-up, 3.5 years [interquartile range, 2.9-4.5 years]). Patients with mild to moderate CAVS defined by peak aortic jet velocity ranging from 2.5 to 4.0 m/s were recruited; those with peak aortic jet velocity of less than 2.5 m/s or with an indication for statin therapy were excluded. Data were collected from January 1, 2002, through December 31, 2005, and underwent ad hoc analysis from April 1 through September 1, 2018. INTERVENTIONS: After the randomization process, patients were followed up by means of echocardiography for 3 to 5 years. MAIN OUTCOMES AND MEASURES: Progression rate of CAVS as assessed by annualized progression of peak aortic jet velocity. RESULTS: In this cohort of 220 patients (60.0% male; mean [SD] age, 58 [13] years), a linear association was found between plasma levels of Lp(a) (odds ratio [OR] per 10-mg/dL increase, 1.10; 95% CI, 1.03-1.19; P = .006), OxPL-apoB (OR per 1-nM increase, 1.06; 95% CI, 1.01-1.12; P = .02), and OxPL-apo(a) (OR per 10-nM increase, 1.16; 95% CI, 1.05-1.27; P = .002) and faster CAVS progression, which is marked in younger patients (OR for Lp[a] level per 10-mg/dL increase, 1.19 [95% CI, 1.07-1.33; P = .002]; OR for OxPL-apoB level per 1-nM increase, 1.06 [95% CI, 1.02-1.17; P = .01]; and OR for OxPL-apo[a] level per 10-nM increase, 1.26 [95% CI, 1.10-1.45; P = .001]) and remained statistically significant after comprehensive multivariable adjustment (β coefficient, ≥ 0.25; SE, ≤ 0.004 [P ≤ .005]; OR, ≥1.10 [P ≤ .007]). CONCLUSIONS AND RELEVANCE: This study demonstrates that the association of Lp(a) levels and its content in OxPL with faster CAVS progression is linear, reinforcing the concept that Lp(a) levels should be measured in patients with mild to moderate CAVS to enhance management and risk stratification. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT00800800

Oxidized phospholipids (OxPL) are ubiquitously generated during inflammation, and found on apoptotic cells, OxLDL, and Lp(a). They facilitate uptake of OxLDL by macrophages (Mac) and mediate cellular inflammatory responses. The E06 natural IgM binds to the PC of OxPL, neutralizing biological effects and inhibiting OxLDL uptake by Mac. To determine the role of OxPL in atherogenesis, we generated transgenic mice expressing a single chain variant (scFv) of E06 in Ldlr background (E06-Tg). E06-scFv was secreted into plasma, bound to OxLDL and had sufficient titer to inhibit OxLDL uptake into Mac. E06-Tg or Ldlr mice were fed 1% Chol diet for 4, 7 or 12 months (n=12-15 mice/group). Plasma Chol was ~ 1600 mg/dL in all mice. Atherosclerosis decreased in E06-Tg mice: En face lesions decreased 57%, 34% and 28%, and aortic root lesions decreased 55%, 41% and 26% at 4, 7 and 12-months, respectively. OxLDL uptake by Macs was decreased: Thus, in E06-Tg mice, the uptake by peritoneal Mac of fluorescently-labeled OxLDL injected ip was decreased ~ 50%, as was peritoneal Mac Chol content. As Macs secrete E06-scFv, we performed BMT from E06-Tg donors into irradiated Ldlr recipients (n=10-12): This also decreased lesions 31% compared to BMT from control donors, even though plasma titers of E06-scFv were ~10% of Tg mice. Overexpression of E06-scFv was anti-inflammatory: Thus, in E06-Tg mice, both peritoneal and aortic wall resident macrophages exhibited decreased inflammatory gene expression, and phenotypic switches from M1 to M2 analyzed by RNAseq and FACS. Further, in E06-Tg mice, plasma SAA levels were reduced 32%, and hepatic steatosis was also decreased (-50% in both TG and Chol), as was hepatic inflammatory gene expression. Finally, E06-scFv attenuated both a progressive increase in aortic valve gradient (via echocardiography) and calcification in aged Ldlr mice. The E06-scFv lacks functional effects of an intact antibody other than the ability to “neutralize” OxPL. Thus, these data demonstrate that OxPL are profoundly proatherogenic and proinflammatory, which E06 counteracts in vivo . Neutralizing OxPL may therefore reduce the progression of atherosclerosis and cardiovascular events and more generally, represents a novel strategy to safely attenuate inflammation.

Background: The LPA gene causes elevated lipoprotein(a) (Lp(a)) levels and causally mediates calcific aortic valve stenosis (AS). Elevated Lp(a) and its associated oxidized phospholipids (OxPL-apoB) predict the progression of pre-existing AS and need for aortic valve replacement and are targets of therapy. Methods: We determined the prevalence and the extent of Lp(a) elevation in patients with AS diagnosed by echocardiography performed at the University of California San Diego between 2010-2015. Severity of AS was classified as critical, severe, moderate, mild, or trace. Lp(a) levels were organized as Lp(a) 100 mg/dL. Results: 2,266 patients with AS were found, with 130 critical, 333 severe, 477 moderate, 1318 mild, and 8 cases of trace AS. Mean age was 75.0 and range 18-106 years. 51% of patients were male. Prevalence of any Lp(a) measurement was 159/2,266 patients (7.02%). The number (%) of patients with an Lp(a) level was: 1) critical (n=4, 3.1%), 2) severe (n=28, 8.4%), 3) moderate (n=56, 11.7%), 4) mild (n=71, 5.4%), and 5) trace (n=0). The extent of Lp(a) elevation within each AS category is in Table 1: 55/159 (34%), 35/159 (22%) and 19/159 (12%) of patients had Lp(a) >30 mg/dL, >50 mg/dL and >100 mg/dL, respectively. Conclusion: Lp(a) was measured in only 7.0% of patients with AS in an academic setting. Given the ongoing development of therapies to lower Lp(a) in patients with AS, educational efforts are needed to raise awareness of Lp(a) as a causal risk factor for AS.

Rationale: Lipoprotein(a) [Lp(a)] is a highly atherogenic low-density lipoprotein–like particle characterized by the presence of apoprotein(a) [apo(a)] bound to apolipoprotein B. Proprotein convertase subtilisin/kexin type 9 (PCSK9) selectively binds low-density lipoprotein; we hypothesized that it can also be associated with Lp(a) in plasma. Objective: Characterize the association of PCSK9 and Lp(a) in 39 subjects with high Lp(a) levels (range 39–320 mg/dL) and in transgenic mice expressing either human apo(a) only or human Lp(a) (via coexpression of human apo(a) and human apolipoprotein B). Methods and Results: We show that PCSK9 is physically associated with Lp(a) in vivo using 3 different approaches: (1) analysis of Lp(a) fractions isolated by ultracentrifugation; (2) immunoprecipitation of plasma using antibodies to PCSK9 and immunodetection of apo(a); (3) ELISA quantification of Lp(a)-associated PCSK9. Plasma PCSK9 levels correlated with Lp(a) levels, but not with the number of kringle IV-2 repeats. PCSK9 did not bind to apo(a) only, and the association of PCSK9 with Lp(a) was not affected by the loss of the apo(a) region responsible for binding oxidized phospholipids. Preferential association of PCSK9 with Lp(a) versus low-density lipoprotein (1.7-fold increase) was seen in subjects with high Lp(a) and normal low-density lipoprotein. Finally, Lp(a)-associated PCSK9 levels directly correlated with plasma Lp(a) levels but not with total plasma PCSK9 levels. Conclusions: Our results show, for the first time, that plasma PCSK9 is found in association with Lp(a) particles in humans with high Lp(a) levels and in mice carrying human Lp(a). Lp(a)-bound PCSK9 may be pursued as a biomarker for cardiovascular risk.

Lipoprotein(a) [Lp(a)], comprised of apolipoprotein(a) [apo(a)] and a low-density lipoprotein-like particle, is a genetically determined, causal risk factor for cardiovascular disease and calcific aortic valve stenosis. Lp(a) is the major plasma lipoprotein carrier of oxidized phospholipids, is pro-inflammatory, inhibits plasminogen activation, and promotes smooth muscle cell proliferation, as defined mostly through in vitro studies. Although Lp(a) is not expressed in commonly studied laboratory animals, mouse and rabbit models transgenic for Lp(a) and apo(a) have been developed to address their pathogenicity in vivo. These models have provided significant insights into the pathophysiology of Lp(a), particularly in understanding the mechanisms of Lp(a) in mediating atherosclerosis. Studies in Lp(a)-transgenic mouse models have demonstrated that apo(a) is retained in atheromas and suggest that it promotes fatty streak formation. Furthermore, rabbit models have shown that Lp(a) promotes atherosclerosis and vascular calcification. However, many of these models have limitations. Mouse models need to be transgenic for both apo(a) and human apolipoprotein B-100 since apo(a) does not covalently associated with mouse apoB to form Lp(a). In established mouse and rabbit models of atherosclerosis, Lp(a) levels are low, generally < 20 mg/dL, which is considered to be within the normal range in humans. Furthermore, only one apo(a) isoform can be expressed in a given model whereas over 40 isoforms exist in humans. Mouse models should also ideally be studied in an LDL receptor negative background for atherosclerosis studies, as mice don't develop sufficiently elevated plasma cholesterol to study atherosclerosis in detail. With recent data that cardiovascular disease and calcific aortic valve stenosis is causally mediated by the LPA gene, development of optimized Lp(a)-transgenic animal models will provide an opportunity to further understand the mechanistic role of Lp(a) in atherosclerosis and aortic stenosis and provide a platform to test novel therapies for cardiovascular disease.