Intracellular Cholesterol Lowering as Novel Target for Anti‐Atherosclerotic Therapy

Atherosclerosis and disorders associated with cardiovascular system remain the major problem of modern medicine and the leading cause of mortality in developed countries. According to the current knowledge, atherosclerosis development can begin early in life. Clinically silent early‐stage lesions can be detected in a large population of young adults. Despite substantial progress in the recent years, therapy of atherosclerosis mostly remains limited to plasma lipid profile correction. Moreover, no therapy is currently available for the treatment of asymptomatic early stages of the disease. The existing synthetic drugs could not be used for this purpose, because of the unfavourable risk/benefit ratio and high cost of treatment, which has to be long‐lasting. In this regard, medications based on natural agents with anti‐atherosclerotic activity may offer interesting possibilities. Current research should focus on detection and evaluation of such agents. One of the important tools for anti‐atherosclerotic drug evaluation is a cell‐based model, which allows measurement of intracellular lipid accumulation. Anti‐atherosclerotic activity of various substances can therefore be evaluated by the decrease of intracellular lipid storage. In this chapter, we will discuss the development and application of cellular models based on primary culture of human arterial wall cells that are suitable for detection and measurement of anti‐atherosclerotic activity of various substances. Using these models, several natural agents have been successfully evaluated, which led to the development of pharmaceutical products with anti‐atherosclerotic activity based on botanicals

Cell Composition of the Subendothelial Aortic Intima and the Role of Alpha-Smooth Muscle Actin Expressing Pericyte-Like Cells and Smooth Muscle Cells in the Development of Atherosclerosis

The cell composition of the human arterial intima has been intensely studied but is still not well understood. The majority of cell population in normal and atherosclerotic intima is represented by cells expressing smooth muscle α-actin, which are thought to be smooth muscle cells. Some antigens, which are absent in medial smooth muscle cells, were detected in intimal smooth muscle cells. In particular, using 3G5 antipericyte antibody, presence of stellate-shaped pericyte-like resident cells in normal and atherosclerotic human aortic intima has been found. In all analyzed aortic tissue specimens, 3G5+ cells were found to account for more than 30% of the total intimal cell population of undiseased intima. In the atherosclerotic lesions, the number of 3G5+ cells becomes notably lower than that in undiseased intima. The use of 2A7 antibody that identifies activated pericytes revealed the presence of 2A7+ cells in atherosclerotic plaques, while no 2A7+ cells were detected in normal intima. The strongest correlation was established between the number of pericyte-like cells and the content of intimal lipids. The correlation coefficients between the number of pericyte-like cells and collagen content and intimal thickness were greater than the correlation coefficients for smooth muscle cells. On the basis of these findings, pericyte-like cells but not smooth muscle cells or other cell types have been declared to be the key cellular element driving the formation of atherosclerotic lesions. The present chapter aims to detail the abovementioned issues. The present chapter also aims to promote a view that α-smooth muscle actin+ pericyte-like cells represent the key players in the development of atherosclerotic lesions

Potential use of antioxidants for the treatment of chronic inflammatory diseases

The excessive production of various reactive oxidant species over endogenous antioxidant defense mechanisms leads to the development of a state of oxidative stress, with serious biological consequences. The consequences of oxidative stress depend on the balance between the generation of reactive oxidant species and the antioxidant defense and include oxidative damage of biomolecules, disruption of signal transduction, mutation, and cell apoptosis. Accumulating evidence suggests that oxidative stress is involved in the physiopathology of various debilitating illnesses associated with chronic inflammation, including cardiovascular diseases, diabetes, cancer, or neurodegenerative processes, that need continuous pharmacological treatment. Oxidative stress and chronic inflammation are tightly linked pathophysiological processes, one of which can be simply promoted by another. Although, many antioxidant trials have been unsuccessful (some of the trials showed either no effect or even harmful effects) in human patients as a preventive or curative measure, targeting oxidative stress remains an interesting therapeutic approach for the development of new agents to design novel anti-inflammatory drugs with a reliable safety profile. In this regard, several natural antioxidant compounds were explored as potential therapeutic options for the treatment of chronic inflammatory diseases. Several metalloenzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, are among the essential enzymes that maintain the low nanomolar physiological concentrations of superoxide (O2•−) and hydrogen peroxide (H2O2), the major redox signaling molecules, and thus play important roles in the alteration of the redox homeostasis. These enzymes have become a striking source of motivation to design catalytic drugs to enhance the action of these enzymes under pathological conditions related to chronic inflammation. This review is focused on several major representatives of natural and synthetic antioxidants as potential drug candidates for the treatment of chronic inflammatory diseases

Circulating Atherogenic Multiple-Modified Low-Density Lipoprotein: Pathophysiology and Clinical Applications

Low-density lipoprotein (LDL) circulating in human bloodstream is the source of lipids that accumulate in arterial intimal cells in atherosclerosis. In-vitro–modified LDL (acetylated, exposed to malondialdehyde, oxidized with transition metal ions, etc.) is atherogenic, that is, it causes accumulation of lipids in cultured cells. We have found that LDL circulating in the atherosclerosis patients’ blood is atherogenic, while LDL from healthy donors is not. Atherogenic LDL was found to be desialylated. Moreover, only the desialylated subfraction of human LDL was atherogenic. Desialylated LDL is generally denser, smaller, and more electronegative than native LDL. Consequently, these LDL types are multiply modified, and according to our observations, desialylation is probably the principal and foremost cause of lipoprotein atherogenicity. It was found that desialylated LDL of coronary atherosclerosis patients was also oxidized. Complex formation further increases LDL atherogenicity, with LDL associates, immune complexes with antibodies recognizing modified LDL and complexes with extracellular matrix components being most atherogenic. We hypothesized that a nonlipid factor might be extracted from the blood serum using a column with immobilized LDL. This treatment not only allowed revealing the nonlipid factor of blood atherogenicity but also opened the prospect for reducing atherogenicity in patients

The Interaction of Plasma Sialylated and Desialylated Lipoproteins with Collagen from the Intima and Media of Uninvolved and Atherosclerotic Human Aorta

We have evaluated the binding of sialylated and desialylated lipoproteins to collagen isolated from the proteoglycan and musculoelastic layers of intima and media of uninvolved human aorta and atherosclerotic lesions. Comparing various collagen preparations from the uninvolved intima-media, the binding of sialylated apoB-containing lipoproteins was best to collagen from the intimal PG-rich layer. Binding of sialylated apoB-containing lipoproteins to collagen from this layer of fatty streak and fibroatheroma was 1.4- and 3.1-fold lower, respectively, in comparison with normal intima. Desialylated VLDL versus sialylated one exhibited a greater binding (1.4- to 3.0-fold) to all the collagen preparations examined. Desialylated IDL and LDL showed a higher binding than sialylated ones when collagen from the intimal layers of fibroatheroma was used. Binding of desialylated HDL to collagen from the intimal PG-rich layer of normal tissue, initial lesion, and fatty streak was 1.2- to 2.0-fold higher compared with sialylated HDL

Use of Natural Products for Direct Anti-Atherosclerotic Therapy

Atherosclerosis and vascular disorders, which result from atherosclerosis, represent one of the major problems in the modern medicine and public health. Atherosclerosis is characterized by structural and functional changes of large arteries. The approaches for the treatment of atherosclerosis require at least the prevention of growth of atherosclerotic lesions and reduction in the lipid core mass, which would followed by plaque stabilization. Taken together, these approaches could theoretically result in the regression of arterial lesions. Atherosclerosis develops in the arterial wall and remains asymptomatic until ischemia of distal organs is evident. Therapy of clinical manifestations of atherosclerosis is largely aimed at reducing symptoms or affecting hemodynamic response and often does not affect the cause or course of disease, namely the atherosclerotic lesion itself. Of course, anti-atherosclerotic effects of statins revealed in many prospective clinical trials may be considered; however, statins have never been recognized as the drugs indicated just for direct treatment or prevention of atherosclerosis. They are used predominately in the course of hypolipidemic therapy, and the effects of treatment are estimated by success in reaching the target level of low density lipoprotein (LDL) cholesterol, but not the regression of atherosclerotic lesion or intimamedia thickness. The last should be considered as beneficial effect, which is mainly due to pleiotropic mechanisms of action. Atherosclerosis develops over many years, so anti-atherosclerotic therapy should be a long-term or even lifelong therapy. Tachyphylaxis, long-term toxicity and cost amongst other issues may present problems for the use of conventional medications in a long-term. Drugs based on natural products can be a good alternative

Small Dense Low-Density Lipoprotein as Biomarker for Atherosclerotic Diseases

Low-density lipoprotein (LDL) plays a key role in the development and progression of atherosclerosis and cardiovascular disease. LDL consists of several subclasses of particles with different sizes and densities, including large buoyant (lb) and intermediate and small dense (sd) LDLs. It has been well documented that sdLDL has a greater atherogenic potential than that of other LDL subfractions and that sdLDL cholesterol (sdLDL-C) proportion is a better marker for prediction of cardiovascular disease than that of total LDL-C. Circulating sdLDL readily undergoes multiple atherogenic modifications in blood plasma, such as desialylation, glycation, and oxidation, that further increase its atherogenicity. Modified sdLDL is a potent inductor of inflammatory processes associated with cardiovascular disease. Several laboratory methods have been developed for separation of LDL subclasses, and the results obtained by different methods can not be directly compared in most cases. Recently, the development of homogeneous assays facilitated the LDL subfraction analysis making possible large clinical studies evaluating the significance of sdLDL in the development of cardiovascular disease. Further studies are needed to establish guidelines for sdLDL evaluation and correction in clinical practice

The effect of maximal vs submaximal exertion on postprandial lipid levels in individuals with and without coronary heart disease

Background: Decisions about fat consumption and levels of physical activity are among the everyday choices we make in life and risk of coronary heart disease (CHD) can be affected by those choices. Objective: The purpose of this study was to investigate the influence of a standard fat load combined with physical exertion of different intensities on the plasma lipid profile of CHD patients and CHD-free individuals. Methods: This study looked at the influence of different intensities of physical exercise on postprandial lipid metabolism in 20 healthy men and 36 men with diagnosis of CHD. Venous blood samples were obtained after overnight fasting, 3 hours after standard fat load (before the physical load), and immediately after maximal or submaximal physical exercise on bicycle ergometer. Results: After fat load total cholesterol (TC) concentration did not change in either group. However, after the addition of maximal exercise, TC, triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and apolipoprotein (Apo) B increased significantly (P < .01) in both groups. After fat load and maximal exercise, there was no change in high-density lipoprotein cholesterol (HDL-C) in healthy men, but in men with CHD, HDL-C fell significantly (P < .01); and Apo AI rose in healthy men (P < .01) but dropped significantly (P < .01) in men with CHD. Submaximal physical exercise (60% of max VO2 load for 40 minutes) after fat load decreased TG level in CHD patients (P < .01) and improved other lipid parameters in both groups significantly (↓LDL-C, ↑HDL-C, ↑Apo AI, ↓Apo B, P < .01). We observed a worsening of physical work capacity in men with CHD (significant reduction of duration and total amount of work performed, maximal VO2, oxygen pulse), during maximal stress test performed 3 hours after fat load. There was a doubling of the number of abnormal stress test results (P < .01). Healthy persons showed an increase in respiratory parameters (ventilation, CO2 production, maximal VO2, and oxygen pulse), but no significant change was found in work capacity. Thus, maximal physical exercise produced atherogenic blood lipid changes (increased TC, increased LDL-C, increased TG, increased Apo B, P < .01) in men with CHD and in healthy men; however, individuals with CHD also demonstrated a significant decrease in HDL-C and Apo AI (P < .01). In contrast, the submaximal physical load improved postprandial lipid changes in both healthy men and men with CHD. Conclusions: This study demonstrates that moderate exercise is beneficial in improving postprandial lipid abnormalities in both CHD and CHD-free subjects after fatty meal preload. In addition, maximal exercise demonstrated evidence of increase of lipid abnormalities in both CHD and CHD-free individuals under similar conditions of fatty meal preload