Electronegative Low-density Lipoprotein Research Articles

Lipids and lipoproteins may play a role in the neuropathology of Alzheimer's disease.

Alzheimer's disease (AD) and other classes of dementia are important public health problems with overwhelming social, physical, and financial effects for patients, society, and their families and caregivers. The pathophysiology of AD is poorly understood despite the extensive number of clinical and experimental studies. The brain's lipid-rich composition is linked to disturbances in lipid homeostasis, often associated with glucose and lipid abnormalities in various neurodegenerative diseases, including AD. Moreover, elevated low-density lipoprotein (LDL) cholesterol levels may be related to a higher probability of AD. Here, we hypothesize that lipids, and electronegative LDL (L5) in particular, may be involved in the pathophysiology of AD. Although changes in cholesterol, triglyceride, LDL, and glucose levels are seen in AD, the cause remains unknown. We believe that L5-the most electronegative subfraction of LDL-may be a crucial factor in understanding the involvement of lipids in AD pathology. LDL and L5 are internalized by cells through different receptors and mechanisms that trigger separate intracellular pathways. One of the receptors involved in L5 internalization, LOX-1, triggers apoptotic pathways. Aging is associated with dysregulation of lipid homeostasis, and it is believed that alterations in lipid metabolism contribute to the pathogenesis of AD. Proposed mechanisms of lipid dysregulation in AD include mitochondrial dysfunction, blood-brain barrier disease, neuronal signaling, inflammation, and oxidative stress, all of which lead ultimately to memory loss through deficiency of synaptic integration. Several lipid species and their receptors have essential functions in AD pathogenesis and may be potential biomarkers.

LDL electronegativity and male predominance in early ventricular tachyarrhythmias following ST-elevation myocardial infarction: evidence of sexual dimorphism associated reduction of sodium currents

Abstract Background Early ventricular tachycardia/fibrillation (VT/VF) in patients with ST-elevation myocardial infarction (STEMI) was associated with a higher morbidity and mortality rate. We sought to investigate the gender-specific risk and explore the underlying mechanisms of early VT/VF in STEMI patients. Methods We analyzed the clinical and laboratory data among 2965 consecutive STEMI patients between Jan 1, 2008 and Dec 31, 2021. Early VT/VF was defined as occurrence of spontaneous VT/VF of ≥30 seconds or requirement of immediate cardioversion/defibrillation due to hemodynamic compromise within the first 48 hours after onset of symptoms. To explore the mechanisms underlying early VT/VF, ex vivo ischemic-reperfusion experiments were conducted in 8-week-old ApoE-/- mice fed a high-fat diet for 8 weeks to promote atherogenesis. Results Of the 2965 STEMI patients studied, 256 (8.6%) experienced early VT/VF. Patients who developed early VT/VF were younger (58±13 vs. 61±13 years old, P=0.012) and had a higher proportion of males (87% vs. 83%, P=0.043). Notably, some patients with early VT/VF had significantly higher plasma levels of L5, the most electronegative subclass of low-density lipoprotein (LDL), compared to those without early VT/VF (n=19, L5: 10.14±3.09% vs. n=43, L5: 2.11±0.23%, P=0.006). In animal study, we have previously showed that male mice have higher plasma L5 concentrations than female mice. In this study, all male mice (n=4) developed VT/VF following the sham operation, whereas none of the female mice (n=3) did. Moreover, male mice had significantly slower heart conduction velocity than female mice in whole heart preparations (13.37±3.81 cm/s vs. 40.70±4.97 cm/s, P<0.001), despite having similar action potential duration (61.00±7.07 vs. 50.33±4.16 ms, P=0.999). In addition, isolated ventricular myocytes from male mice exhibited markedly lower sodium current density (-29.20±3.04 pA/pF, n=6) compared to those from female mice (-114.05±6.41 pA/pF, n=6, P<0.001). The reduced sodium current density was accompanied by lower membranous Nav1.5 protein expression (0.38±0.06 vs. 0.89±0.09 A.U., P<0.001) and higher cytosolic Nav1.5 levels (0.59±0.06 vs. 0.29±0.04 A.U., P<0.01) in male mice. Conclusions Our study demonstrates that male STEMI patients with early VT/VF have higher levels of L5, the most electronegative LDL subclass. This gender disparity in the susceptibility of early VT/VF may be caused by compromised sodium channel trafficking, likely linked to increased LDL electronegativity.

28-LB: Role of Glycine N-methyltransferase in Electronegative Lipoproteins-Induced Vascular Dysfunction in a Diabetic Rodent Model

Several studies showed low-density lipoprotein (LDL) is associated with high risk of atherosclerosis in patients with diabetes. However, aggressively decreasing total LDL does not prevent all vascular complications. A novel culprit electronegative LDL (L5) was significantly increased in diabetic patients and could induce vascular damage according to our previous studies. However, the mechanism of L5 formation and how to reduce plasma L5 level are still unclear. In the present study, we found both aqueous and ethylacetate extracts of a traditional Chinese remedy Artemisia capillaris (AC) could decrease plasma L5 level in western diet-fed hamster (22.45 and 28.64 vs. 56.83%, respectively), while clinical remedies Simvastatin and Niacin could not. AC could also reverse western diet-induced vascular senescence (b-gal staining) and relaxation dysfunction in aortic rings (63.66±2.14 vs 40.13±1.48% of maximum contraction when compared to western diet hamsters; P<0.01). To further determine the underlying mechanism, we have found that AC reversed western diet-reduced Glycine N-methyltransferase (GNMT) protein abundance and altered several microRNA expression by analyzing the microarray heatmap in liver tissue. In conclusion, AC could significantly reverse western diet-induced vascular injury by lowering plasma L5 level through restore the liver enzyme GNMT activity. Disclosure A. Lee: None. Y. Chen: None. W. Chen: None.

The Oxidized Lipoproteins In Vivo: Its Diversity and Behavior in the Human Circulation

A high concentration of low-density lipoproteins (LDLs) in circulation has been well-known as a major risk factor for cardiovascular diseases. The presence of oxidized LDLs (oxLDLs) in atherosclerotic lesions and circulation was demonstrated using anti-oxLDL monoclonal antibodies. The so-called "oxLDL hypothesis", as a mechanism for atherosclerosis development, has been attracting attention for decades. However, the oxLDL has been considered a hypothetical particle since the oxLDL present in vivo has not been fully characterized. Several chemically modified LDLs have been proposed to mimic oxLDLs. Some of the subfractions of LDL, especially Lp(a) and electronegative LDL, have been characterized as oxLDL candidates as oxidized phospholipids that stimulate vascular cells. Oxidized high-density lipoprotein (oxHDL) and oxLDL were discovered immunologically in vivo. Recently, an oxLDL-oxHDL complex was found in human plasma, suggesting the involvement of HDLs in the oxidative modification of lipoproteins in vivo. In this review, we summarize our understanding of oxidized lipoproteins and propose a novel standpoint to understand the oxidized lipoproteins present in vivo.

The Association between Electronegative Low-Density Lipoprotein Cholesterol L5 and Cognitive Functions in Patients with Mild Cognitive Impairment

L5, the most electronegative subfraction of low-density lipoprotein cholesterol (LDL-C), may play a role in the pathogenesis of cerebrovascular dysfunction and neurodegeneration. We hypothesized that serum L5 is associated with cognitive impairment and investigated the association between serum L5 levels and cognitive performance in patients with mild cognitive impairment (MCI). This cross-sectional study conducted in Taiwan included 22 patients with MCI and 40 older people with normal cognition (healthy controls). All participants were assessed with the Cognitive Abilities Screening Instrument (CASI) and a CASI-estimated Mini-Mental State Examination (MMSE-CE). We compared the serum total cholesterol (TC), LDL-C, and L5 levels between the MCI and control groups and examined the association between lipid profiles and cognitive performance in these groups. The serum L5 concentration and total CASI scores were significantly negatively correlated in the MCI group. Serum L5% was negatively correlated with MMSE-CE and total CASI scores, particularly in the orientation and language subdomains. No significant correlation between the serum L5 level and cognitive performance was noted in the control group. Conclusions: Serum L5, instead of TC or total LDL-C, could be associated with cognitive impairment through a disease stage-dependent mode that occurs during neurodegeneration.

Presence of Ceramidase Activity in Electronegative LDL

Electronegative low-density lipoprotein (LDL(-)) is a minor modified fraction of human plasma LDL with several atherogenic properties. Among them is increased bioactive lipid mediator content, such as lysophosphatidylcholine (LPC), non-esterified fatty acids (NEFA), ceramide (Cer), and sphingosine (Sph), which are related to the presence of some phospholipolytic activities, including platelet-activating factor acetylhydrolase (PAF-AH), phospholipase C (PLC), and sphingomyelinase (SMase), in LDL(-). However, these enzymes' activities do not explain the increased Sph content, which typically derives from Cer degradation. In the present study, we analyzed the putative presence of ceramidase (CDase) activity, which could explain the increased Sph content. Thin layer chromatography (TLC) and lipidomic analysis showed that Cer, Sph, and NEFA spontaneously increased in LDL(-) incubated alone at 37 °C, in contrast with native LDL(+). An inhibitor of neutral CDase prevented the formation of Sph and, in turn, increased Cer content in LDL(-). In addition, LDL(-) efficiently degraded fluorescently labeled Cer (NBD-Cer) to form Sph and NEFA. These observations defend the existence of the CDase-like activity's association with LDL(-). However, neither the proteomic analysis nor the Western blot detected the presence of an enzyme with known CDase activity. Further studies are thus warranted to define the origin of the CDase-like activity detected in LDL(-).

Autoimmune Rheumatic Diseases: An Update on the Role of Atherogenic Electronegative LDL and Potential Therapeutic Strategies.

Atherosclerosis has been linked with an increased risk of atherosclerotic cardiovascular disease (ASCVD). Autoimmune rheumatic diseases (AIRDs) are associated with accelerated atherosclerosis and ASCVD. However, the mechanisms underlying the high ASCVD burden in patients with AIRDs cannot be explained only by conventional risk factors despite disease-specific factors and chronic inflammation. Nevertheless, the normal levels of plasma low-density lipoprotein (LDL) cholesterol observed in most patients with AIRDs do not exclude the possibility of increased LDL atherogenicity. By using anion-exchange chromatography, human LDL can be divided into five increasingly electronegative subfractions, L1 to L5, or into electropositive and electronegative counterparts, LDL (+) and LDL (−). Electronegative L5 and LDL (−) have similar chemical compositions and can induce adverse inflammatory reactions in vascular cells. Notably, the percentage of L5 or LDL (−) in total LDL is increased in normolipidemic patients with AIRDs. Electronegative L5 and LDL (−) are not recognized by the normal LDL receptor but instead signal through the lectin-like oxidized LDL receptor 1 (LOX-1) to activate inflammasomes involving interleukin 1β (IL-1β). Here, we describe the detailed mechanisms of AIRD-related ASCVD mediated by L5 or LDL (−) and discuss the potential targeting of LOX-1 or IL-1β signaling as new therapeutic modalities for these diseases.

Electronegative Low-density Lipoprotein (L5) may be Associated with the Severity of COVID-19

Electronegative Low-density Lipoprotein (L5) may be Associated with the Severity of COVID-19

Association of Electronegative LDL with Macrophage Foam Cell Formation and CD11c Expression in Rheumatoid Arthritis Patients.

L5, the most negatively charged subfraction of low-density lipoprotein (LDL), is implicated in atherogenesis, but the pathogenic association is relatively unexplored in patients with rheumatoid arthritis (RA). We examined the role of L5 LDL in macrophage foam cell formation and the association of L5 with CD11c expression in THP-1 cells and RA patients. Using quantitative real-time PCR, we determined mRNA expression levels of ITGAX, the gene for CD11c, a marker associated with vascular plaque formation and M1 macrophages in atherogenesis, in 93 RA patients. We also examined CD11c expression on THP-1 cells treated with L5 by flow cytometry analysis and the plasma levels of inflammatory mediators using a magnetic bead array. We found a dose-dependent upregulation of foam cell formation of macrophages after L5 treatment (mean ± SEM, 12.05 ± 2.35% in L5 (10 µg/mL); 50.13 ± 3.9% in L5 (25 µg/mL); 90.69 ± 1.82% in L5 (50 µg/mL), p < 0.01). Significantly higher levels of CD11c expression were observed in 30 patients with a high percentage of L5 in LDL (L5%) (0.0752 ± 0.0139-fold) compared to 63 patients with normal L5% (0.0446 ± 0.0054-fold, p < 0.05). CD11c expression levels were increased in the L5-treated group (30.00 ± 3.13% in L5 (10 µg/mL); 41.46 ± 2.77% in L5 (50 µg/mL), p < 0.05) and were positively correlated with plasma levels of interleukin (IL)-6 and IL-8. L5 augmented the expression of IL-6, IL-8, and tumor necrosis factor-α (TNF-α) on monocytes and macrophages. Our findings suggest that L5 may promote atherogenesis by augmenting macrophage foam cell formation, upregulating CD11c expression, and enhancing the expression levels of atherosclerosis-related mediators.

THU347 - The electronegative low-density lipoprotein in patients with chronic hepatitis C infection

THU347 - The electronegative low-density lipoprotein in patients with chronic hepatitis C infection

Clinical Significance of Electronegative Low-Density Lipoprotein Cholesterol in Atherothrombosis.

Despite the numerous risk factors for atherosclerotic cardiovascular diseases (ASCVD), cumulative evidence shows that electronegative low-density lipoprotein (L5 LDL) cholesterol is a promising biomarker. Its toxicity may contribute to atherothrombotic events. Notably, plasma L5 LDL levels positively correlate with the increasing severity of cardiovascular diseases. In contrast, traditional markers such as LDL-cholesterol and triglyceride are the therapeutic goals in secondary prevention for ASCVD, but that is controversial in primary prevention for patients with low risk. In this review, we point out the clinical significance and pathophysiological mechanisms of L5 LDL, and the clinical applications of L5 LDL levels in ASCVD can be confidently addressed. Based on the previously defined cut-off value by receiver operating characteristic curve, the acceptable physiological range of L5 concentration is proposed to be below 1.7 mg/dL. When L5 LDL level surpass this threshold, clinically relevant ASCVD might be present, and further exams such as carotid intima-media thickness, pulse wave velocity, exercise stress test, or multidetector computed tomography are required. Notably, the ultimate goal of L5 LDL concentration is lower than 1.7 mg/dL. Instead, with L5 LDL greater than 1.7 mg/dL, lipid-lowering treatment may be required, including statin, ezetimibe or PCSK9 inhibitor, regardless of the low-density lipoprotein cholesterol (LDL-C) level. Since L5 LDL could be a promising biomarker, we propose that a high throughput, clinically feasible methodology is urgently required not only for conducting a prospective, large population study but for developing therapeutics strategies to decrease L5 LDL in the blood.

Increased APOE glycosylation plays a key role in the atherogenicity of L5 low-density lipoprotein.

Low-density lipoprotein (LDL) is heterogeneous, composed of particles with variable atherogenicity. Electronegative L5 LDL exhibits atherogenic properties in vitro and in vivo, and its levels are elevated in patients with increased cardiovascular risk. Apolipoprotein E (APOE) content is increased in L5, but what role APOE plays in L5 function remains unclear. Here, we characterized the contributions of APOE posttranslational modification to L5's atherogenicity. Using two-dimensional electrophoresis and liquid chromatography-mass spectrometry, we studied APOE's posttranslational modification in L5 from human plasma. APOE structures with various glycan residues were predicted. Molecular docking and molecular dynamics simulation were performed to examine the functional changes of APOE resulting from glycosylation. We also examined the effects of L5 deglycosylation on endothelial cell apoptosis. The glycan sequence N-acetylgalactosamine, galactose, and sialic acid was consistently expressed on serine 94, threonine 194, and threonine 289 of APOE in L5 and was predicted to contribute to L5's negative surface charge and hydrophilicity. The electrostatic force between the negatively charged sialic acid-containing glycan residue of APOE and positively charged amino acids at the receptor-binding area suggested that glycosylation interferes with APOE's attraction to receptors, lipid-binding ability, and lipid transportation and metabolism functions. Importantly, L5 containing glycosylated APOE induced apoptosis in cultured endothelial cells through lectin-like oxidized LDL receptor-1 (LOX-1) signaling, and glycosylation removal from L5 attenuated L5-induced apoptosis. APOE glycosylation may contribute to the atherogenicity of L5 and be a useful biomarker for rapidly quantifying L5.

Electronegative LDL Induces M1 Polarization of Human Macrophages Through a LOX-1-Dependent Pathway.

In response to environmental stimuli, monocytes undergo polarization into classically activated (M1) or alternatively activated (M2) states. M1 and M2 macrophages exert opposing pro- and anti-inflammatory properties, respectively. Electronegative low-density lipoprotein (LDL) (LDL(-)) is a naturally occurring mildly oxidized LDL found in the plasma of patients with hypercholesterolemia, diabetes, and acute myocardial infarction, and has been shown to involve in the pathogenesis of atherosclerosis. In this study, we examined the effects of LDL(-) on macrophage polarization and the involvement of lectin-like oxidized LDL receptor-1 (LOX-1) in this process. THP-1 macrophages were treated with native LDL (nLDL) or LDL(-), and then the expression of M1/M2-related surface markers and cytokines were evaluated. The results show that treatment with LDL(-) resulted in profound increase in proinflammatory cytokines, IL-1β, IL-6, and TNF-α, and M1-surface marker CD86; however, M2-related cytokines, IL-10 and TGF-β, and M2-surface marker CD206 were not changed by LDL(-). Untreated or nLDL-treated cells were used as control. LDL(-)-induced M1 polarization and secretion of proinflammatory cytokines were diminished in LOX-1 knockdown cells. Taken together, the results show that LDL(-) promotes differentiation of human monocytes to M1 macrophages through a LOX-1-dependent pathway, and explore the contribution of LDL(-) and LOX-1 to the development of chronic inflammation in atherosclerosis.

Why are cardiovascular diseases more common among patients with severe mental illness? The potential involvement of electronegative low-density lipoprotein (LDL) L5

Despite tremendous efforts of experimental and clinical studies and knowledge, the pathophysiology of severe mental illness (SMI), including bipolar disorder (BD), unipolar depression (mood disorders, MD), and schizophrenia (SCZ), remains poorly understood. Besides their chronic course and high prevalence in society, mental and somatic comorbidities are really serious problems; patients with these disorders have increased risk of cardiovascular (CV) diseases (CVD) including coronary artery diseases (CAD, i.e. myocardial infarction and angina), stroke, sudden cardiac death, hypertension, cardiomyopathy, arrhythmia, and thromboembolic disease. Although it is determined that triglycerides, cholesterol, glucose, and low-density lipoprotein (LDL) levels are increased in MD and SCZ, the underlying reason remains unknown. Considering this, we propose that electronegative LDL (L5) is probably the main crucial element to understanding CVD induced by SMI and to discovering novel remedial approaches for these diseases. When it is hypothesized that L5 is greatly presupposed in CV system abnormalities, it follows that the anti-L5 therapies and even antioxidant treatment options may open new therapeutic opportunities to prevent CVD diseases secondary to SMI. In this review article, we tried to bring a very original subject to the attention of readers who are interested in lipoprotein metabolism in terms of experimental, clinical, and cell culture studies that corroborate the involvement of L5 in physiopathology of CVD secondary to SMI and also the new therapeutic approaches for these disorders.

Binding to heparin triggers deleterious structural and biochemical changes in human low-density lipoprotein, which are amplified in hyperglycemia

Low-density lipoprotein (LDL) binding to arterial proteoglycans initiates LDL retention and modification in the arterial wall, triggering atherosclerosis. The details of this binding, its effectors, and its ramifications are incompletely understood. We combined heparin affinity chromatography with biochemical, spectroscopic and electron microscopic techniques to show that brief binding to heparin initiates irreversible pro-atherogenic remodeling of human LDL. This involved decreased structural stability of LDL and increased susceptibility to hydrolysis, oxidation and fusion. Furthermore, phospholipid hydrolysis, mild oxidation and/or glycation of LDL in vitro increase the proteolytic susceptibility of apoB and its heparin binding affinity, perhaps by unmasking additional heparin-binding sites. For LDL from hyperglycemic type-2 diabetic patients, heparin binding was particularly destabilizing and caused apoB fragmentation and LDL fusion. However, for similar patients whose glycemic control was restored upon therapy, LDL-heparin binding affinity was rectified and LDL structural stability was partially restored. These results complement previous studies of LDL binding to arterial proteoglycans and suggest that such interactions may produce a particularly pro-atherogenic subclass of electronegative LDL. In summary, binding to heparin alters apoB conformation, perhaps by partially peeling it off the lipid, and triggers pro-atherogenic LDL modifications including hydrolysis, oxidation, and destabilization. Furthermore, phospholipid lipolysis, mild oxidation and glycation of LDL in vitro strengthen its binding to heparin, which helps explain stronger binding observed in hyperglycemic LDL. Combined effects of hyperglycemia and heparin binding are especially deleterious but are largely rectified upon diabetes therapy. These findings help establish a mechanistic link between diabetes and atherosclerosis.

Electronegative LDL Promotes Inflammation and Triglyceride Accumulation in Macrophages

Electronegative low-density lipoprotein (LDL) (LDL(−)), a modified LDL that is present in blood and exerts atherogenic effects on endothelial cells and monocytes. This study aimed to determine the action of LDL(−) on monocytes differentiated into macrophages. LDL(−) and in vitro-modified LDLs (oxidized, aggregated, and acetylated) were added to macrophages derived from THP1 monocytes over-expressing CD14 (THP1-CD14). Then, cytokine release, cell differentiation, lipid accumulation, and gene expression were measured by ELISA, flow cytometry, thin-layer chromatography, and real-time PCR, respectively. LDL(−) induced more cytokine release in THP1-CD14 macrophages than other modified LDLs. LDL(−) also promoted morphological changes ascribed to differentiated macrophages. The addition of high-density lipoprotein (HDL) and anti-TLR4 counteracted these effects. LDL(−) was highly internalized by macrophages, and it was the major inductor of intracellular lipid accumulation in triglyceride-enriched lipid droplets. In contrast to inflammation, the addition of anti-TLR4 had no effect on lipid accumulation, thus suggesting an uptake pathway alternative to TLR4. In this regard, LDL(−) upregulated the expression of the scavenger receptors CD36 and LOX-1, as well as several genes involved in triglyceride (TG) accumulation. The importance and novelty of the current study is that LDL(−), a physiologically modified LDL, exerted atherogenic effects in macrophages by promoting differentiation, inflammation, and triglyceride-enriched lipid droplets formation in THP1-CD14 macrophages, probably through different receptors.

Familial Combined Hyperlipidemia (FCH) Patients with High Triglyceride Levels Present with Worse Lipoprotein Function Than FCH Patients with Isolated Hypercholesterolemia.

Lipoprotein characteristics were analyzed in familial combined hyperlipidemia (FCH) patients before and after statin treatment. Twenty-six FCH patients were classified according to the presence (HTG group, n = 13) or absence (normotriglyceridemic (NTG) group, n = 13) of hypertriglyceridemia. Fifteen healthy subjects comprised the control group. Lipid profile, inflammation markers, and qualitative characteristics of lipoproteins were assessed. Both groups of FCH subjects showed high levels of plasma C-reactive protein (CRP), lipoprotein-associated phospholipase A2 (Lp-PLA2) activity and apolipoprotein J. Statins reverted the increased levels of Lp-PLA2 and CRP. Lipoprotein composition alterations detected in FCH subjects were much more frequent in the HTG group, leading to dysfunctional low-density lipoproteins (LDL) and high-density lipoproteins (HDL). In the HTG group, LDL was smaller, more susceptible to oxidation, and contained more electronegative LDL (LDL(-)) compared to the NTG and control groups. Regarding HDL, the HTG group had less Lp-PLA2 activity than the NTG and control groups. HDL from both FCH groups was less anti-inflammatory than HDL from the control group. Statins increased LDL size, decreased LDL(-), and lowered Lp-PLA2 in HDL from HTG. In summary, pro-atherogenic alterations were more frequent and severe in the HTG group. Statins improved some alterations, but many remained unchanged in HTG.

Inflammasome Activation in Human Macrophages Induced by a LDL (-) Mimetic Peptide.

The inflammasome is responsible for maturation of interleukin-1β (IL-1β) and interleukin-18 (IL-18) contributing to the inflammatory process in atherosclerosis. It is shown here that an electronegative low-density lipoprotein [LDL (-)] apoB-100 mimetic peptide can activate the transcriptional and posttranslational signs needed for complete inflammasome activation. This peptide, named p2C7, can activate the Toll-like receptor 4 (TLR4) that induces NF-κB activation and the transcription of inflammasome components. After blocking TLR4 with a neutralizing antibody, inflammasome component (NLRP3, CASP1, and ASC) and IL1b and IL18 gene downregulation occurred in human-derived macrophages stimulated with p2C7 or LDL (-). Moreover, the posttranslational signal was activated by the interaction between p2C7 and the lectin-type oxidized LDL receptor 1 (LOX-1), as demonstrated by the induction of caspase-1 cleavage in macrophages. The blockage of either TLR4 or LOX-1 decreased IL-1β and IL-18 secretion by human-derived macrophages as both pathways are necessary for complete inflammasome activation. These findings suggest a mechanism by which macrophages transduce the pro-inflammatory signal provided by LDL (-) ApoB-100 and its mimetic peptides to activate the inflammasome protein complex what may be relevant for the inflammatory process in atherosclerosis.

Electronegative low-density lipoprotein of patients with metabolic syndrome induces pathogenesis of aorta through disruption of the stimulated by retinoic acid6 cascade.

Aims/IntroductionElectronegative low‐density lipoprotein (L5) is the most atherogenic fraction of low‐density lipoprotein and is elevated in people with metabolic syndrome (MetS), whereas the retinol‐binding protein 4 receptor (stimulated by retinoic acid 6 [STRA6]) cascade is disrupted in various organs of patients with obesity‐related diseases. Our objective was to investigate whether L5 from MetS patients capably induces pathogenesis of aorta through disrupting the STRA6 cascade.Material and MethodsWe examined the in vivo and in vitro effects of L5 on the STRA6 cascade and aortic atherogenic markers. To investigate the role of this cascade on atherosclerotic formation, crbp1 transfection was carried out in vitro.ResultsThis study shows that L5 activates atherogenic markers (p38 mitogen‐activated protein kinases, pSmad2 and matrix metallopeptidase 9) and simultaneously suppresses STRA6 signals (STRA6, cellular retinol‐binding protein 1, lecithin‐retinol acyltransferase, retinoic acid receptor‐α and retinoid X receptor‐α) in aortas of L5‐injected mice and L5‐treated human aortic endothelial cell lines and human aortic smooth muscle cell lines. These L5‐induced changes of the STRA6 cascade and atherogenic markers were reversed in aortas of LOX1−/− mice and in LOX1 ribonucleic acid‐silenced human aortic endothelial cell lines and human aortic smooth muscle cell lines. Furthermore, crbp1 gene transfection reversed the disruption of the STRA6 cascade, the phosphorylation of p38 mitogen‐activated protein kinases and Smad2, and the elevation of matrix metallopeptidase 9 in L5‐treated human aortic endothelial cell lines.ConclusionsThis study shows that L5 from MetS patients induces atherogenic markers by disrupting STRA6 signaling. Suppression of STRA6 might be one novel pathogenesis of aorta in patients with MetS.

Electronegative LDL from Rabbits Fed with Atherogenic Diet Is Highly Proinflammatory.

Electronegative low-density lipoprotein (LDL(-)) has been found in the plasma of familial hypercholesterolemia and acute myocardial infarction and has been implicated in atherosclerosis and cardiovascular disease. However, less is known about the involvement of LDL(-) in atherosclerosis-related inflammation. This study aims at investigating the inducibility of LDL(-) by atherogenic diet in rabbits and at exploring the proinflammatory potential of the diet-induced LDL(-) in macrophages. Rabbits were fed with an atherogenic diet; LDL was isolated from plasma by NaBr density gradient ultracentrifugation and was then resolved into nLDL and LDL(-) by anion-exchange chromatography. Isolated nLDL and LDL(-) were directly used or incubated with 10 μM CuSO4 for 24 h to produce copper- (Cu-) ox-nLDL and Cu-ox-LDL(-). The effects of these LDLs on inflammation were evaluated in THP-1-derived macrophages. Macrophages were treated with nLDL, LDL(-), and extensively oxidized LDL (ox-LDL), then the levels of interleukin- (IL-) 1β, IL-6, and tumor necrosis factor- (TNF-) α in a culture medium were determined by ELISA, and the levels of total and phosphorylated IκB, p65, p38, JNK, and ERK in cell lysates were determined by Western blotting. The LDL(-) induced significantly higher levels of IL-1β, IL-6, and TNF-α in the medium. The levels of phosphorylated/total IκB, p65, p38, JNK, and ERK were also upregulated by LDL(-). In contrast, nLDL, Cu-ox-nLDL, and Cu-ox-LDL(-) exhibited much less effect. Knockdown of lectin-type oxidized LDL receptor- (LOX-) 1 resulted in significant reduction in LDL(-)-induced IL-1β, IL-6, and TNF-α. In addition, these LDL(-) effects were also markedly attenuated by inhibition of NF-κB and ERK1/2. The data suggested that LDL(-) induced inflammation through LOX-1-, NF-κB-, and ERK1/2-dependent pathways. Taken together, our results show that rabbits fed with atherogenic diet produce a highly proinflammatory LDL(-) that is more potent in inducing inflammation than nLDL and extensively oxidize LDL in macrophages. The results thus provide a novel link between diet-induced hypercholesterolemia and inflammation.