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Role of Phagocytosis in the Pro-Inflammatory Response in LDL-Induced Foam Cell Formation; a Transcriptome Analysis.
Orekhov, AN, Nikiforov, NG, Sukhorukov, VN, Kubekina, MV, Sobenin, IA, Wu, WK, Foxx, KK, Pintus, S, Stegmaier, P, Stelmashenko, D, et al
International journal of molecular sciences. 2020;(3)
Abstract
Excessive accumulation of lipid inclusions in the arterial wall cells (foam cell formation) caused by modified low-density lipoprotein (LDL) is the earliest and most noticeable manifestation of atherosclerosis. The mechanisms of foam cell formation are not fully understood and can involve altered lipid uptake, impaired lipid metabolism, or both. Recently, we have identified the top 10 master regulators that were involved in the accumulation of cholesterol in cultured macrophages induced by the incubation with modified LDL. It was found that most of the identified master regulators were related to the regulation of the inflammatory immune response, but not to lipid metabolism. A possible explanation for this unexpected result is a stimulation of the phagocytic activity of macrophages by modified LDL particle associates that have a relatively large size. In the current study, we investigated gene regulation in macrophages using transcriptome analysis to test the hypothesis that the primary event occurring upon the interaction of modified LDL and macrophages is the stimulation of phagocytosis, which subsequently triggers the pro-inflammatory immune response. We identified genes that were up- or downregulated following the exposure of cultured cells to modified LDL or latex beads (inert phagocytosis stimulators). Most of the identified master regulators were involved in the innate immune response, and some of them were encoding major pro-inflammatory proteins. The obtained results indicated that pro-inflammatory response to phagocytosis stimulation precedes the accumulation of intracellular lipids and possibly contributes to the formation of foam cells. In this way, the currently recognized hypothesis that the accumulation of lipids triggers the pro-inflammatory response was not confirmed. Comparative analysis of master regulators revealed similarities in the genetic regulation of the interaction of macrophages with naturally occurring LDL and desialylated LDL. Oxidized and desialylated LDL affected a different spectrum of genes than naturally occurring LDL. These observations suggest that desialylation is the most important modification of LDL occurring in vivo. Thus, modified LDL caused the gene regulation characteristic of the stimulation of phagocytosis. Additionally, the knock-down effect of five master regulators, such as IL15, EIF2AK3, F2RL1, TSPYL2, and ANXA1, on intracellular lipid accumulation was tested. We knocked down these genes in primary macrophages derived from human monocytes. The addition of atherogenic naturally occurring LDL caused a significant accumulation of cholesterol in the control cells. The knock-down of the EIF2AK3 and IL15 genes completely prevented cholesterol accumulation in cultured macrophages. The knock-down of the ANXA1 gene caused a further decrease in cholesterol content in cultured macrophages. At the same time, knock-down of F2RL1 and TSPYL2 did not cause an effect. The results obtained allowed us to explain in which way the inflammatory response and the accumulation of cholesterol are related confirming our hypothesis of atherogenesis development based on the following viewpoints: LDL particles undergo atherogenic modifications that, in turn, accompanied by the formation of self-associates; large LDL associates stimulate phagocytosis; as a result of phagocytosis stimulation, pro-inflammatory molecules are secreted; these molecules cause or at least contribute to the accumulation of intracellular cholesterol. Therefore, it became obvious that the primary event in this sequence is not the accumulation of cholesterol but an inflammatory response.
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2.
Immune Complexes and the Risk of CVD in Type 1 Diabetes.
Lopes-Virella, MF, Bebu, I, Hunt, KJ, Virella, G, Baker, NL, Braffett, B, Gao, X, Lachin, JM, ,
Diabetes. 2019;(9):1853-1860
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Abstract
We investigated whether the composition of modified forms of LDL in circulating immune complexes (LDL-ICs) was associated with cardiovascular disease (CVD) outcomes, including any CVD, major adverse cardiac and cerebrovascular events (MACCE), myocardial infarction (MI), and coronary artery disease, in type 1 diabetes (T1D). Our results demonstrate that the baseline levels of oxidized LDL (oxLDL), MDA-modified LDL (MDA-LDL), and advanced glycosylation-modified LDL (AGE-LDL) in circulating ICs were associated with the four CVD outcomes in unadjusted models, and adjustment by age and mean HbA1c only resulted in minimal reduction of these associations. After adjustments were made for other cardiovascular risk factors, particularly LDL cholesterol, oxLDL-IC and MDA-LDL-IC remained independently associated with the risk of CVD, and oxLDL-IC was independently associated with the risk of MACCE and MI. In the majority of cases, the baseline levels of modified LDL-IC (measured many years before the occurrence of any CVD event) were associated with the risk of CVD over a 25-year period even after adjustment for other risk factors (including LDL cholesterol). Therefore, modified LDL biomarkers may help identify patients with T1D at high risk for MACCE and CVD events very early in the evolution of the disease, before other signals of disease are apparent.
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Post-prandial effects of hazelnut-enriched high fat meal on LDL oxidative status, oxidative and inflammatory gene expression of healthy subjects: a randomized trial.
Di Renzo, L, Merra, G, Botta, R, Gualtieri, P, Manzo, A, Perrone, MA, Mazza, M, Cascapera, S, De Lorenzo, A
European review for medical and pharmacological sciences. 2017;(7):1610-1626
Abstract
OBJECTIVE Postprandial oxidative stress is characterized by an increased susceptibility of the organism towards oxidative damage after consumption of a meal rich in lipids and/or carbohydrates. Micronutrients modulate the immune system and exert a protective action by reducing low-density lipoproteins oxidation (ox-LDL) via induction of antioxidant enzymes. SUBJECTS AND METHODS The clinical study was a randomized and cross-over trial, conducted through the CONSORT flowchart. We evaluated the gene expression of 103 genes related to oxidative stress (HOSp) and human inflammasome pathways (HIp), and ox-LDL level at fasting and after 40 g raw "Tonda Gentile delle Langhe" hazelnut consumption, in association with a McDonald's® Meal (McDM) in 22 healthy human volunteers. RESULTS Ox-LDL levels significantly increased comparing no dietary treatment (NDT) vs. McDM, and decreased comparing McDM vs. McDM + H (p<0.05). Percentage of significant genes expressed after each dietary treatment were the follows: (A) NDT vs. McDM: 3.88% HIp and 17.48% HOSp; (B) NDT vs. McDM + H: 17.48% HIp and 23.30% HOSp; (C) McDM vs. McDM + H: 17.48% HIp and 33.98% HOSp. CONCLUSIONS Hazelnut consumption reduced post prandial risk factors of atherosclerosis, such as ox-LDL, and the expression of inflammation and oxidative stress related genes. Chronic studies on larger population are necessary before definitive conclusions.
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Early Transcriptomic Response to LDL and oxLDL in Human Vascular Smooth Muscle Cells.
Damián-Zamacona, S, Toledo-Ibelles, P, Ibarra-Abundis, MZ, Uribe-Figueroa, L, Hernández-Lemus, E, Macedo-Alcibia, KP, Delgado-Coello, B, Mas-Oliva, J, Reyes-Grajeda, JP
PloS one. 2016;(10):e0163924
Abstract
BACKGROUND Although nowadays it is well known that the human transcriptome can importantly vary according to external or environmental condition, the reflection of this concept when studying oxidative stress and its direct relationship with gene expression profiling during the process of atherogenesis has not been thoroughly achieved. OBJECTIVE The ability to analyze genome-wide gene expression through transcriptomics has shown that the genome responds dynamically to diverse stimuli. Here, we describe the transcriptome of human vascular smooth muscle cells (hVSMC) stimulated by native and oxidized low-density lipoprotein (nLDL and oxLDL respectively), with the aim of assessing the early molecular changes that induce a response in this cell type resulting in a transcriptomic transformation. This expression has been demonstrated in atherosclerotic plaques in vivo and in vitro, particularly in the light of the oxidative modification hypothesis of atherosclerosis. APPROACH AND RESULTS Total RNA was isolated with TRIzol reagent (Life Technologies) and quality estimated using an Agilent 2100 bioanalyzer. The transcriptome of hVSMC under different experimental conditions (1,5 and 24 hours for nLDL and oxLDL) was obtained using the GeneChip Human Gene 1.0 ST (Affymetrix) designed to measure gene expression of 28,869 well-annotated genes. A fixed fold-change cut-off corresponding to ± 2 was used to identify genes exhibiting the most significant variation and statistical significance (P< 0.05), and 8 genes validated by qPCR using Taqman probes. CONCLUSIONS 10 molecular processes were significantly affected in hVSMC: Apoptosis and cell cycle, extracellular matrix remodeling, DNA repair, cholesterol efflux, cGMP biosynthesis, endocytic mechanisms, calcium homeostasis, redox balance, membrane trafficking and finally, the immune response to inflammation. The evidence we present supporting the hypothesis for the involvement of oxidative modification of several processes and metabolic pathways in atherosclerosis is strengthen by the fact that gene expression patterns obtained when hVSMC are incubated for a long period of time in the presence of nLDL, correspond very much the same as when cells are incubated for a short period of time in the presence of chemically modified oxLDL. Our results indicate that under physiological conditions and directly related to specific environmental conditions, LDL particles most probably suffer chemical modifications that initially serve as an alert signal to overcome a harmful stimulus that with time might get transformed to a pathological pattern and therefore consolidate a pathological condition.
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HELP LDL apheresis reduces plasma pentraxin 3 in familial hypercholesterolemia.
Zanetti, M, Zenti, M, Barazzoni, R, Zardi, F, Semolic, A, Messa, MG, Mearelli, F, Russi, G, Fonda, M, Scarano, L, et al
PloS one. 2014;(7):e101290
Abstract
BACKGROUND Pentraxin 3 (PTX3), a key component of the humoral arm of innate immunity, is secreted by vascular cells in response to injury, possibly aiming at tuning arterial activation associated with vascular damage. Severe hypercholesterolemia as in familial hypercholesterolemia (FH) promotes vascular inflammation and atherosclerosis; low-density lipoprotein (LDL) apheresis is currently the treatment of choice to reduce plasma lipids in FH. HELP LDL apheresis affects pro- and antiinflammatory biomarkers, however its effects on PTX3 levels are unknown. We assessed the impact of FH and of LDL removal by HELP apheresis on PTX3. METHODS Plasma lipids, PTX3, and CRP were measured in 19 patients with FH undergoing chronic HELP LDL apheresis before and after treatment and in 20 control subjects. In the patients assessment of inflammation and oxidative stress markers included also plasma TNFα, fibrinogen and TBARS. RESULTS At baseline, FH patients had higher (p = 0.0002) plasma PTX3 than matched control subjects. In FH PTX3 correlated positively (p≤0.05) with age, gender and CRP and negatively (p = 0.01) with HELP LDL apheresis vintage. The latter association was confirmed after correction for age, gender and CRP. HELP LDL apheresis acutely reduced (p≤0.04) plasma PTX3, CRP, fibrinogen, TBARS and lipids, but not TNFα. No association was observed between mean decrease in PTX3 and in LDL cholesterol. PTX3 paralleled lipids, oxidative stress and inflammation markers in time-course study. CONCLUSION FH is associated with increased plasma PTX3, which is acutely reduced by HELP LDL apheresis independently of LDL cholesterol, as reflected by the lack of association between change in PTX3 and in LDL levels. These results, together with the finding of a negative relationship between PTX3 and duration of treatment suggest that HELP LDL apheresis may influence both acutely and chronically cardiovascular outcomes in FH by modulating PTX3.
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Pathogenic role of modified LDL antibodies and immune complexes in atherosclerosis.
Lopes-Virella, MF, Virella, G
Journal of atherosclerosis and thrombosis. 2013;(10):743-54
Abstract
There is strong evidence supporting a key role of the adaptive immune response in atherosclerosis, given that both activated Th cells producing predominantly interferon-γ and oxidized LDL (oxLDL) and the corresponding antibodies have been isolated from atheromatous plaques. Studies carried out using immune complexes (IC) prepared with human LDL and rabbit antibodies have demonstrated proatherogenic and pro-inflammatory properties, mostly dependent on the engagement of Fcγ receptors Ⅰ and Ⅱ in macrophages and macrophage-like cell lines. Following the development of a methodology for isolating modified LDL (mLDL) antibodies from serum and isolated IC, it was confirmed that antibodies reacting with oxLDL and advanced glycation end product-modified LDL are predominantly IgG of subtypes 1 and 3 and that mLDL IC prepared with human reagents possesses pro-inflammatory and proatherogenic properties. In previous studies, LDL separated from isolated IC has been analyzed for its modifications, and the reactivity of antibodies isolated from the same IC with different LDL modifications has been tested. Recently, we obtained strong evidence suggesting that the effects of mLDL IC on phagocytic cells are modulated by the composition of the mLDL. Clinical studies have shown that the level of mLDL in circulating IC is a strong predictor of cardiovascular disease (CVD) and, in diabetic patients, other significant complications, such as nephropathy and retinopathy. In conclusion, there is convincing ex vivo and clinical data supporting the hypothesis that, in humans, the humoral immune response to mLDL is pathogenic rather than protective.
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High concentrations of AGE-LDL and oxidized LDL in circulating immune complexes are associated with progression of retinopathy in type 1 diabetes.
Lopes-Virella, MF, Baker, NL, Hunt, KJ, Lyons, TJ, Jenkins, AJ, Virella, G, ,
Diabetes care. 2012;(6):1333-40
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Abstract
OBJECTIVE To determine whether immunocomplexes (ICs) containing advanced glycation end product (AGE)-LDL (AGE-LDL) and oxidized LDL (oxLDL) contribute to the development of retinopathy over a 16-year period in subjects with type 1 diabetes. RESEARCH DESIGN AND METHODS Levels of AGE-LDL and oxLDL in ICs were measured in 517 patients of the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) cohort. Retinopathy was assessed by stereoscopic fundus photography. Cox proportional hazards models were used to assess the effect of AGE-LDL-ICs and oxLDL-ICs on retinopathy progression. RESULTS In unadjusted models, higher baseline levels of AGE-LDL-ICs and oxLDL-ICs significantly predicted progression of diabetic retinopathy outcomes. After adjustment by study-design variables (treatment group, retinopathy cohort, duration of type 1 diabetes, and baseline albumin excretion rate [AER], hemoglobin A(1c) (HbA(1c)), and Early Treatment Diabetic Retinopathy Study [ETDRS] score), one SD increase in IC levels was associated with 47% (hazard ratio [HR] 1.47 [95% CI 1.19-1.81]; AGE-LDL-IC) and 45% (1.45 [1.17-1.80]; oxLDL-IC) increased risk of developing proliferative diabetic retinopathy (PDR) and 37% (1.37 [1.12-1.66]; to both ICs) increased risk of progressing to severe nonproliferative retinopathy. Analyses were stratified by retinopathy cohort because results differed between primary and secondary cohorts. For AGE-LDL-ICs, HR for progression to PDR was 2.38 (95% CI 1.30-4.34) in the primary cohort and attenuated in the secondary cohort (1.29 [1.03-1.62]). Similar results were observed for oxLDL-ICs. CONCLUSIONS Increased levels of AGE-LDL and oxLDL in ICs are associated with increased risk for progression to advanced retinopathy in patients with type 1 diabetes, indicating that the antibody response to modified LDL plays a significant role in retinopathy progression.
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A lipid-derived endogenous inducer of COX-2: a bridge between inflammation and oxidative stress.
Uchida, K
Molecules and cells. 2008;(3):347-51
Abstract
Several lines of evidence indicate that the oxidative modification of protein and the subsequent accumulation of the modified proteins have been found in cells during aging, oxidative stress, and in various pathological states including premature diseases, muscular dystrophy, rheumatoid arthritis, and atherosclerosis. The important agents that give rise to the modification of a protein may be represented by reactive aldehydic intermediates, such as ketoaldehydes, 2-alkenals and 4-hydroxy-2-alkenals. These reactive aldehydes are considered important mediators of cell damage due to their ability to covalently modify biomolecules, which can disrupt important cellular functions and can cause mutations. Furthermore, the adduction of aldehydes to apolipoprotein B in low-density lipoproteins (LDL) has been strongly implicated in the mechanism by which LDL is converted to an atherogenic form that is taken up by macrophages, leading to the formation of foam cells. During the search for an endogenous inducer of cyclooxygenase-2 (COX-2), an inducible isoform responsible for high levels of prostaglandin production during inflammation and immune responses, 4-hydroxy-2-noennal (HNE), one of the most representative lipid peroxidation product, has been identified as the potential inducer of COX-2. In addition, the following study on the molecular mechanism of the COX-2 induction by HNE has unequivocally established that a serum component, which is eventually identified to be denatured LDL, is essential for COX-2 induction. Here I review current understanding of the mechanisms by which HNE in cooperation with the serum component activates gene expression of COX-2.
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Reduction of oxidative stress and modulation of autoantibodies against modified low-density lipoprotein after rosuvastatin therapy.
Resch, U, Tatzber, F, Budinsky, A, Sinzinger, H
British journal of clinical pharmacology. 2006;(3):262-74
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Abstract
AIMS: To examine the effect of 24 weeks' rosuvastatin treatment on oxidative stress and changes in immune response to oxidized low-density lipoprotein (LDL). METHODS This was an open-label study of patients in Austria receiving 10 or 40 mg rosuvastatin daily alternately during 12 and 24 weeks. Circulating concentrations of antibodies to malondialdehyde-oxidized LDL (MDA-LDL), both IgG and IgM type, to copper-oxidized LDL (Cu-OxLDL-IgG), concentrations of oxidized LDL complexed to IgG (OxLDL-IC) and markers of oxidative stress and systemic inflammation in subjects with plasma LDL cholesterol concentrations between 130 mg dl-1 and 250 mg dl-1 and triglycerides RESULTS During statin therapy, plasma endogenous peroxides (POX-ACT) concentrations and peroxidase activity were significantly decreased, associated with a modest increase in total antioxidant capacity (TAC). Antibody titres to MDA-LDL-IgM, Cu-OxLDL-IgG and OxLDL-IC decreased, whereas MDA-LDL-IgG concentrations were increased after therapy. These changes were dose- and LDL-independent. POX-ACT concentrations were significantly positively correlated with inflammation markers before and after therapy and inversely with high-density lipoprotein-cholesterol concentrations after therapy. CONCLUSION This study provides in vivo evidence that rosuvastatin significantly reduces oxidative stress and has immunomodulatory properties in a dose- and LDL-independent manner.
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Oxidized low-density lipoprotein in children with familial hypercholesterolemia and unaffected siblings: effect of pravastatin.
Rodenburg, J, Vissers, MN, Wiegman, A, Miller, ER, Ridker, PM, Witztum, JL, Kastelein, JJ, Tsimikas, S
Journal of the American College of Cardiology. 2006;(9):1803-10
Abstract
OBJECTIVES To assess the role of oxidized phospholipids (OxPLs) in children with familial hypercholesterolemia (FH) and the effect of pravastatin. BACKGROUND Oxidized phospholipids are a major component of oxidized low-density lipoprotein (OxLDL) and are bound to lipoprotein (a) [Lp(a)]. The significance of OxPL markers in children is unknown. METHODS Children with FH were randomized to placebo (n = 88) or pravastatin (n = 90) after instruction on American Heart Association step II diet. Unaffected siblings (n = 78) served as controls. The OxPL content on apolipoprotein B-100 (apoB) detected by antibody E06 (OxPL/apoB ratio), immunoglobulin (Ig)G and IgM immune complexes per apoB (IC/apoB) and on all apoB particles (total apoB-IC = IC/apoB multiplied by plasma apoB levels), autoantibodies to malondialdehyde (MDA)-low-density lipoprotein (LDL), Lp(a), and apoB levels were measured at baseline and after two years of treatment. RESULTS Compared with unaffected siblings, children with FH had significantly lower levels of OxPL/apoB but higher levels of IgG and IgM total apoB-IC and IgM MDA-LDL autoantibodies. From baseline to two-year follow-up, compared with placebo pravastatin treatment resulted in a greater mean percentage change in apoB (-18.7% vs. 0.3%; p = 0.001), total IgG apoB-IC (-31.9% vs. -12.2%; p < 0.001), and total IgM apoB-IC (-25.5% vs. 13.2%; p = 0.001). Interestingly, pravastatin also resulted in higher OxPL/apoB (48.7% vs. 29.3%; p = 0.028) and Lp(a) levels (21.9% vs. 10.7%; p = 0.044). CONCLUSIONS Compared with unaffected siblings, children with FH are characterized by elevated levels of apoB-IC and IgM MDA-LDL autoantibodies. Compared with placebo, pravastatin led to a greater reduction in apoB-IC but also to a greater increase in OxPL/apoB and Lp(a), which may represent a novel mechanism of mobilization and clearance of OxPL.