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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.
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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Mediterranean meal versus Western meal effects on postprandial ox-LDL, oxidative and inflammatory gene expression in healthy subjects: a randomized controlled trial for nutrigenomic approach in cardiometabolic risk.
De Lorenzo, A, Bernardini, S, Gualtieri, P, Cabibbo, A, Perrone, MA, Giambini, I, Di Renzo, L
Acta diabetologica. 2017;(2):141-149
Abstract
AIMS: Inflammation and oxidative damage contribute significantly to the development of cardiovascular diseases (CVD). Postprandial oxidative stress and inflammation are characterized by an increased susceptibility of the organism toward oxidative damage after consumption of a meal rich in lipids and/or carbohydrates. Micronutrients modulate immune system and exert a protective action by reducing oxidized low-density lipoprotein (ox-LDL) level. The aim of the present study was to evaluate the postprandial plasma ox-LDL level and the gene expression of 13 genes related to oxidative stress (HOSp) and human inflammasome pathways (HIp), after a tocopherol-enriched Mediterranean meal (TEM), and a Western high-fat meal (HFM). Moreover, Mediterranean Adequacy Index was calculated to define the quality of both meals. METHODS We set up a randomized and crossover trial in healthy human volunteers. Ox-LDL level was measured by enzyme-linked immunosorbent assay and the gene expression of 13 genes related to HOSp and HIp by qRT-PCR. RESULTS Ox-LDL levels significantly decreased comparing HFM versus TEM (p < 0.05). Percentages of significantly overexpressed genes after each dietary treatment are as follows: (A) baseline versus HFM: 7.69 % HIp and 23.08 % HOSp; (B) baseline versus TEM: 7.69 % HIp and 7.69 % HOSp; (C) HFM versus TEM: 15.38 % HIp and 15.38 % HOSp. CONCLUSIONS TEM reduced postprandial risk factors of CVD, such as ox-LDL, and the expression of inflammation and oxidative stress-related genes. Chronic studies on larger population are necessary before definitive conclusions. TRIAL REGISTRATION ClinicalTrials.gov Id: NCT01890070.
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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.