Apolipoprotein Signature of HDL and LDL from Atherosclerotic Patients in Relation with Carotid Plaque Typology: A Preliminary Report

Potential of low apolipoprotein A-I as a surrogate marker of vulnerable carotid artery plaques

OBJECTIVE

Recent studies suggested that the medical control of atherogenic lipoproteins is not sufficient for stroke prevention. A low apolipoprotein A-I (apoA-I) level may play a crucial role in the anti-atherogenic effects of high-density lipoprotein (HDL-C) and may also be associated with symptomatic vulnerable plaques in carotid artery stenosis. Therefore, the present study investigated the relationship between apoA-I levels and the status of carotid artery stenosis.

METHODS

Ninety-one patients with carotid artery stenosis were examined. The status of carotid artery plaques was divided into symptomatic (n = 47) and asymptomatic (n = 44). We examined patient profiles, including comorbidities, and laboratory lipid data, and plaque features visualized by ultrasonography, MRI, and digital subtraction angiography. The relationships between plaque instability and risk factors for carotid artery stenosis were investigated.

RESULTS

No significant differences were observed in the profiles of symptomatic and asymptomatic patients. Regarding plaque features, ulceration, low echo luminance, and a high signal intensity in plaques on T1-weighted images correlated with symptomatic plaques. ApoA-I, total cholesterol, and non-HDL-C levels were significantly lower in symptomatic patients than in asymptomatic patients. A multivariate logistic regression analysis identified low ApoA-I levels, ulceration, and low echo luminance as predictive factors for symptomatic carotid artery stenosis. Diagnostic accuracy for predicting symptomatic carotid stenosis was 0.84 when the following four factors were combined: ulceration, low echo luminance, a high signal intensity on T1-weighted images, and the level of apoA-I.

CONCLUSIONS

A low apoA-I level was associated with symptomatic carotid artery stenosis. Therefore, ApoA-I levels have potential as a surrogate marker to detect unstable carotid artery plaques.

Alterations in LDL and HDL after an ischemic stroke associated with carotid atherosclerosis are reversed after 1 year

Approximately, 20% of ischemic strokes are attributed to the presence of atherosclerosis. Lipoproteins play a crucial role in the development of atherosclerosis, with LDL promoting atherogenesis and HDL inhibiting it. Therefore, both their concentrations and their biological properties are decisive factors in atherosclerotic processes. In this study, we examined the qualitative properties of lipoproteins in ischemic stroke patients with carotid atherosclerosis. Lipoproteins were isolated from the blood of healthy controls (n = 27) and patients with carotid atherosclerosis (n = 64) at 7 days and 1 year postischemic stroke. Compared to controls, patients' LDL 7 days poststroke showed increased levels of apoC-III, triacylglycerol, and ceramide, along with decreased cholesterol and phospholipid content. LDL from patients induced more inflammation in macrophages than did LDL from controls. HDL isolated from patients 7 days after stroke showed alterations in the apolipoprotein cargo, with reduced levels of apoA-I and increased levels of apoA-II, and apoC-III compared to controls. Patients' HDL also showed a higher electronegative charge than that of controls and partially lost its ability to counteract the modification of LDL and the inflammatory effects of modified LDL. One year after stroke onset, the composition of patients' LDL and HDL resembled those of the controls. In parallel, LDL and HDL gained positive charge, LDL became less prone to oxidation and aggregation, and HDL regained protective properties. In conclusion, LDL and HDL in ischemic stroke patients with carotid atherosclerosis exhibited alterations in composition and function, which were partially reversed 1 year after stroke.

Identification of Protein Networks and Biological Pathways Driving the Progression of Atherosclerosis in Human Carotid Arteries Through Mass Spectrometry-Based Proteomics

Vulnerable atherosclerotic plaques, especially hemorrhaged lesions, are the major cause of mortalities related to vascular pathologies. The early identification of vulnerable plaques helps to stratify patients at risk of developing acute vascular events. In this study, proteomics analyses of human carotid artery samples collected from patients with atheromatous plaques and complicated lesions, respectively, as well as from healthy controls were performed. The proteins isolated from the carotid artery samples were analyzed by a bottom-up shotgun approach that relied on nanoflow liquid chromatography-tandem mass spectrometry analyses (LC-MS/MS) using both data-dependent (DDA) and data-independent (DIA) acquisitions. The data obtained by high-resolution DIA analyses displayed a stronger distinction among groups compared to DDA analyses. Differentially expressed proteins were further examined using Ingenuity Pathway Analysis® with focus on pathological and molecular processes driving atherosclerosis. From the more than 150 significantly regulated canonical pathways, atherosclerosis signaling and neutrophil extracellular trap signaling were verified by protein-targeted data extraction. The results of our study are expected to facilitate a better understanding of the disease progression's molecular drivers and provide inspiration for further multiomics and hypothesis-driven studies.

Atherogenic circulating lipoproteins in ischemic stroke

The fundamental role of qualitative alterations of lipoproteins in the early development of atherosclerosis has been widely demonstrated. Modified low-density lipoproteins (LDL), such as oxidized LDL (oxLDL), small dense LDL (sdLDL), and electronegative LDL [LDL(-)], are capable of triggering the atherogenic process, favoring the subendothelial accumulation of cholesterol and promoting inflammatory, proliferative, and apoptotic processes characteristic of atherosclerotic lesions. In contrast, high-density lipoprotein (HDL) prevents and/or reverses these atherogenic effects. However, LDL's atherogenic and HDL's anti-atherogenic actions may result altered in certain pathological conditions. The molecular mechanisms underlying the impaired effects of altered lipoproteins have been studied in numerous in vitro and in vivo studies, and have been extensively analyzed in coronary atherosclerosis, especially in the context of pathologies such as dyslipidemia, diabetes, obesity, and metabolic syndrome. However, the corresponding studies are scarcer in the field of ischemic stroke, despite carotid arteriosclerosis progression underlies at least 20% of ischemic strokes. The present review relates qualitative alterations of LDL and HDL with the development of carotid arteriosclerosis and the occurrence of ischemic stroke.

The Essence of Lipoproteins in Cardiovascular Health and Diseases Treated by Photodynamic Therapy

Lipids, together with lipoprotein particles, are the cause of atherosclerosis, which is a pathology of the cardiovascular system. In addition, it affects inflammatory processes and affects the vessels and heart. In pharmaceutical answer to this, statins are considered a first-stage treatment method to block cholesterol synthesis. Many times, additional drugs are also used with this method to lower lipid concentrations in order to achieve certain values of low-density lipoprotein (LDL) cholesterol. Recent advances in photodynamic therapy (PDT) as a new cancer treatment have gained the therapy much attention as a minimally invasive and highly selective method. Photodynamic therapy has been proven more effective than chemotherapy, radiotherapy, and immunotherapy alone in numerous studies. Consequently, photodynamic therapy research has expanded in many fields of medicine due to its increased therapeutic effects and reduced side effects. Currently, PDT is the most commonly used therapy for treating age-related macular degeneration, as well as inflammatory diseases, and skin infections. The effectiveness of photodynamic therapy against a number of pathogens has also been demonstrated in various studies. Also, PDT has been used in the treatment of cardiovascular diseases, such as atherosclerosis and hyperplasia of the arterial intima. This review evaluates the effectiveness and usefulness of photodynamic therapy in cardiovascular diseases. According to the analysis, photodynamic therapy is a promising approach for treating cardiovascular diseases and may lead to new clinical trials and management standards. Our review addresses the used therapeutic strategies and also describes new therapeutic strategies to reduce the cardiovascular burden that is induced by lipids.

Searching for Atherosclerosis Biomarkers by Proteomics: A Focus on Lesion Pathogenesis and Vulnerability

Plaque rupture and thrombosis are the most important clinical complications in the pathogenesis of stroke, coronary arteries, and peripheral vascular diseases. The identification of early biomarkers of plaque presence and susceptibility to ulceration could be of primary importance in preventing such life-threatening events. With the improvement of proteomic tools, large-scale technologies have been proven valuable in attempting to unravel pathways of atherosclerotic degeneration and identifying new circulating markers to be utilized either as early diagnostic traits or as targets for new drug therapies. To address these issues, different matrices of human origin, such as vascular cells, arterial tissues, plasma, and urine, have been investigated. Besides, proteomics was also applied to experimental atherosclerosis in order to unveil significant insights into the mechanisms influencing atherogenesis. This narrative review provides an overview of the last twenty years of omics applications to the study of atherogenesis and lesion vulnerability, with particular emphasis on lipoproteomics and vascular tissue proteomics. Major issues of tissue analyses, such as plaque complexity, sampling, availability, choice of proper controls, and lipoproteins purification, will be raised, and future directions will be addressed.

Molecular Characterization of Plasma HDL, LDL, and VLDL Lipids Cargos from Atherosclerotic Patients with Advanced Carotid Lesions: A Preliminary Report

Carotid atherosclerosis represents a relevant healthcare problem, since unstable plaques are responsible for approximately 15% of neurologic events, namely transient ischemic attack and stroke. Although statins treatment has proven effective in reducing LDL-cholesterol and the onset of acute clinical events, a residual risk may persist suggesting the need for the detection of reliable molecular markers useful for the identification of patients at higher risk regardless of optimal medical therapy. In this regard, several lines of evidence show a relationship among specific biologically active plasma lipids, atherosclerosis, and acute clinical events. We performed a Selected Reaction Monitoring-based High Performance Liquid Chromatography-tandem Mass Spectrometry (SRM-based HPLC-MS/MS) analysis on plasma HDL, LDL, and VLDL fractions purified, by isopycnic salt gradient ultracentrifugation, from twenty-eight patients undergoing carotid endarterectomy, having either a “hard” or a “soft” plaque, with the aim of characterizing the specific lipidomic patterns associated with features of carotid plaque instability. One hundred and thirty lipid species encompassing different lipid (sub)classes were monitored. Supervised multivariate analysis showed that lipids belonging to phosphatidylethanolamine (PE), sphingomyelin (SM), and diacylglycerol (DG) classes mostly contribute to discrimination within each lipoprotein fraction according to the plaque typology. Differential analysis evidenced a significant dysregulation of LDL PE (38:6), SM (32:1), and SM (32:2) between the two groups of patients (adj. p-value threshold = 0.05 and log₂FC ≥ |0.58|). Using this approach, some LDL-associated markers of plaque vulnerability have been identified, in line with the current knowledge of the key roles of these phospholipids in lipoprotein metabolism and cardiovascular disease. This proof-of-concept study reports promising results, showing that lipoprotein lipidomics may present a valuable approach for identifying new biomarkers of potential clinical relevance.