Increase in cholesterol and cholesterol oxidation products,and role of cholesterol oxidation products in kainate-induced neuronal injury

Little is known about changes in sterols, in particular cholesterol, and cholesterol oxidation products (COPs) in oxidative injury in neural tissues. We have therefore examined changes in cholesterol and COPs using a model of excitotoxic injury. Intracerebroventricular injections of kainate in rats resulted in an increase in immunoreactivity to cholesterol in the affected CA fields of the hippocampus. The increase was confirmed by increased filipin staining of cholesterol in adjacent sections from the same animals, and in hippocampal slice or neuronal cultures after kainate treatment. In neuronal cultures, addition of lovastatin, an inhibitor of cholesterol synthesis, attenuated the increased filipin staining after kainate treatment, indicating that the increase in cholesterol could involve increased cholesterol synthesis. Furthermore, gas chromatographic mass spectrometric (GC/MS) analysis of cholesterol and COPs in kainate-injected rat brain showed a marked increase in cholesterol and COPs including 7-ketocholesterol, 3 days after kainate treatment. The addition of some COPs, including 7-ketocholesterol and cholesterol epoxides to hippocampal slices resulted in neuronal injury as reflected by decreased staining of a neuronal marker in the affected CA fields. The ability of these COPs to produce neuronal injury was attenuated by glutathione, suggesting that oxidative mechanisms are involved in neuronal injury induced by these products. These results, together with GC/MS results that showed significant increase in 7-ketocholesterol at 3 days post-kainate injury suggest that 7-ketocholesterol may be a factor in aggravating oxidative damage to neurons, after the initial stages of kainate-induced neuronal injury.     

纤维蛋白原在动脉粥样硬化发生中的作用

在家兔及培养的家兔主动脉平滑肌细胞上，观察了纤维蛋白原在动脉粥样硬化发生中的作用，Ｆｇ有其代谢产物对ＳＭＣ生长的影响，结果发现，高胆固醇饲料在诱发高胆固醇血症的同时，血浆中Ｆｇ含量也逐渐升高，二者在早期有明显的正相关。尸检病人冠脉ＡＳ病灶免疫组化分析发现，病灶内皮下及血管间质有大量Ｆｇ及其降解产物存在。     

The role of shear stress in the pathogenesis of atherosclerosis

Although the pathobiology of atherosclerosis is a complex multifactorial process, blood flow-induced shear stress has emerged as an essential feature of atherogenesis. This fluid drag force acting on the vessel wall is mechanotransduced into a biochemical signal that results in changes in vascular behavior. Maintenance of a physiologic, laminar shear stress is known to be crucial for normal vascular functioning, which includes the regulation of vascular caliber as well as inhibition of proliferation, thrombosis and inflammation of the vessel wall. Thus, shear stress is atheroprotective. It is also recognized that disturbed or oscillatory flows near arterial bifurcations, branch ostia and curvatures are associated with atheroma formation. Additionally, vascular endothelium has been shown to have different behavioral responses to altered flow patterns both at the molecular and cellular levels and these reactions are proposed to promote atherosclerosis in synergy with other well-defined systemic risk factors. Nonlaminar flow promotes changes to endothelial gene expression, cytoskeletal arrangement, wound repair, leukocyte adhesion as well as to the vasoreactive, oxidative and inflammatory states of the artery wall. Disturbed shear stress also influences the site selectivity of atherosclerotic plaque formation as well as its associated vessel wall remodeling, which can affect plaque vulnerability, stent restenosis and smooth muscle cell intimal hyperplasia in venous bypass grafts. Thus, shear stress is critically important in regulating the atheroprotective, normal physiology as well as the pathobiology and dysfunction of the vessel wall through complex molecular mechanisms that promote atherogenesis.     

Effects of cholesterol oxidation products on exocytosis

Increase in levels of oxysterols or cholesterol oxidation products have been detected in brain areas undergoing neuroinflammation after excitotoxic injury, and the present study was carried out to elucidate possible effects of these products on exocytosis in rat pheochromocytoma-12 (PC12) cells. An increase in vesicle fusion with the cell membrane indicating exocytosis was observed by total internal reflection microscopy (TIRFM), and confirmed by capacitance measurements, after addition of 7 ketocholesterol, 24 hydroxycholesterol or cholesterol 5, 6 beta epoxide. 7 ketocholesterol induced exocytosis was attenuated by pretreatment with a disruptor of cholesterol-rich domains or “lipid rafts”, methyl-β-cyclodextrin (MβCD) as demonstrated by capacitance and amperometry measurements of neurotransmitter release. Moreover, treatment of cells with thapsigargin to deplete intracellular calcium, or treatment of cells with lanthanum chloride to block calcium channels resulted in attenuation of 7 ketocholesterol induced exocytosis. Fura-2 imaging showed that 7 ketocholesterol induced rapid and sustained increases in intracellular calcium concentration, and that this effect was attenuated in cells that were pre-treated with MβCD, thapsigargin or lanthanum chloride. Together, the results suggest that neurotransmitter release triggered by 7 ketocholesterol is dependent on the integrity of cholesterol rich lipid domains on cellular membranes and a rise in intracellular calcium, either through release from internal stores or influx via calcium channels. Increased cholesterol oxidation product concentrations in brain areas undergoing neuroinflammation may enhance exocytosis and neurotransmitter release, thereby aggravating excitotoxicity.     

The role of vascular smooth muscle cells on the pathogenesis of atherosclerosis

Atherosclerosis is the leading cause of death and disability. The lesions of atherosclerosis represent a series of highly specific cellular and molecular responses. The earliest changes that precede the formation of lesions of atherosclerosis take place in the endothelium (EC), with resultant endothelial dysfunction. The EC-induced injury can result in increased lipid permeability, macrophage recruitment, formation of foam cells, and recruitment of T-lymphocytes and platelet. After intimal injury, different cell types,including ECs, platelets, and inflammatory cells release mediators, such as growth factors and cytokines that induce multiple effects including phenotype change of vascular smooth muscle cells (VSMC) from the quiescent "contractile" phenotype state to the active "synthetic" state, that can migrate and proliferate from media to the intima. The inflammatory response simulates migration and proliferation of VSMC that become intermixed with the area of inflammation to form an intermediate lesion. These responses continue uninhibited and is accompanied by accumulation of new extra cellular matrix (ECM). The migratory and proliferative activities of VSMC are regulated by growth promoters such as platelet derived growth factors (PGF), endothelin-1 (ET-1), thrombin, fibroblast growth factor (FGF), interleukin-1 (IL-1) and inhibitors such as, heparin sulfates , nitric oxide (NO), transforming growth factor (TGF)-beta. The matrix metallo proteinases (MMPs) could also participate in the process of VSMC migration. MMPs could catalyze and remove the basement membrane around VSMC and facilitate contacts with the interstitial matrix. This could promote a change from quiescent, contractile VSMC to cells capable of migrating and proliferating to mediate repair. The VSMC regulation is a very complex process, VSMC are stimulated to proliferate and migrate by some kind of cytokines, growth factors, angiotensin II (Ang-II). Together with apoptosis, proliferation and migration of VSMC are vital to the pathogenesis of atherosclerosis and plaque rupture. Rupture of the plaque is associated with increased fibrous cap macrophage, increased VSMC apoptosis, and reduced fibrous cap VSMC. VSMC are the only cells with plaques capable of synthesizing structurally important collagen isoforms, and the apoptosis of VSMC might promote plaque rupture.     

Reappraisal of the role of macrophages in the pathogenesis of atherosclerosis

New Zealand rabbits were fed an atherogenic diet, 8 with and 8 without twice weekly intravenous injections of GdCl2. The injections caused a reduction in the phagocytic activity of the reticuloendothelial system by one fourth to one half. No significant differences were found between the two groups in the planimetric extent of atheromata in the aortae. GdCl2 treatment inhibited the deposition of sudanophilic lipids in depth of the arterial wall. The findings indicate that macrophages are the primary foam cells and their uptake of lipoproteins is essential for the deposition of lipids in myocytes. Lipid-laden myocytes and ground substance mucopolysaccharides represent sinks in which lipids are removed from the flow and accumulate locally.     

The role of infection in the development of immune inflammation and pathogenesis of atherosclerosis

Pathogenesis of atherosclerosis from the point of view of immune inflammation in the vascular wall is discussed in this review. Potential role of adenoviruses and chlamydia in the development of immune inflammation and mechanisms and transport of infectious agents into the vascular wall and their influence on the cell kinetics are reviewed.     

The pathogenesis of atherosclerosis.

The pathogenesis of atherosclerosis is hypothesized to occur as a response to various forms of injury to the lining arterial endothelial cells. The resulting endothelial alterations could potentially lead to interactions between platelets in the circulation and the underlying subendothelial connective tissue or with the altered endothelial cells themselves. Such interactions provide an opportunity for platelet degranulation and release of a platelet-derived growth factor. This factor has been shown in cell culture to be an extremely potent mitogen and will induce DNA synthesis and cell multiplication of a number of cells including smooth muscle cells, fibroblasts, and other mesenchymally derived cells. Chronic endothelial injury and repeated interactions between platelet-derived mitogens, plasma components, and the underlying arterial smooth muslce cells would promote the progression of the intimal proliferative lesions of atherosclerosis that lead to the clinical sequelae associated with this disease process.     

The position of the liver in the pathogenesis of atherosclerosis

The review deals with two complexes: 1. Role of hepatocytes in the origin and course of general atherosclerosis. 2. The "Perisinusoidal Functional Unit" as pathogenetic factor in atherosclerosis. The central place of hepatocytes in the metabolism of lipoproteins of both exogenous and endogenous origins points to the fact that hepatocytes have a key function in the pathogenesis of atherosclerosis. In order to play their role in the metabolism, lipoproteins have to be capable of reaching the hepatocytes and of getting back from them into the circulation. The requisite for that is the passage of lipoproteins through the sinusoidal wall, i.e. the endothelial sieve. Its structuring is thought to be the cause for both distinct manifestation of atherosclerosis in different species, especially due to exogenous supply of lipids, and increasing risk of atherosclerosis, e.g., by nicotine or certain drugs. The following question might be derived from latest international research: "Is atherosclerosis a liver disease with secondary consequences for the vascular system?"     

Disease stage-dependent accumulation of lipid and protein oxidation products in human atherosclerosis

Oxidative modification of low-density lipoprotein is thought to promote arterial lipid accumulation and atherogenesis. Previous studies reported on the presence of certain lipid or protein oxidation products in lesions, although a systematic investigation measuring several oxidation parameters and the accumulation of nonoxidized lipids and antioxidants at various stages of atherosclerosis has not been performed in the same tissue. Using the intimal lipoprotein-containing fraction of human aortic lesions, we demonstrate here that cholesterol accumulated with lesion development and that this increase was already significant at the fatty streak stage. By comparison, cholesterylesters increased significantly only in fibro-fatty and more complex lesions that also contained significantly increased amounts of cholesterylester hydro(pero)xides and 27-hydroxycholesterol. Cholesterylester hydroxides were the major lipid oxidation product detected. Despite accumulation of oxidized lipid, alpha-tocopherol was also present and maintained at a comparable level over the disease process. Of the oxidized protein moieties measured only o,o-dityrosine increased with disease, although chlorotyrosines were present at relatively high levels in all lesions compared to healthy vessels. Our data show that accumulation of nonoxidized lipid precedes that of oxidized lipid in human aortic lesions.     

The involution of experimental cholesterol atherosclerosis in dogs

Summary Over a six-month period following the end of the cholesterol and 6-methylthiouracil feeding period, the ballistocardiographic changes in dogs went back more rapidly and more completely to the initial level than the electrocardiographic changes.Pathological and histological investigations of the cardiovascular system and internal organs of these animals showed involution of atherosclerotic lesions.High blood cholesterol 2 months after the administration of cholesterol was stopped points to important metabolic damage.(Presented by V. V. Parin, Active Member of the AMN SSSR) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 50, No. 10, pp. 58–61, October, 1960     

Autoantigens involved in the pathogenesis of atherosclerosis

Whether antigens are involved in the development of arterial atherosclerotic lesions is discussed. The complex of antigens determines the course of atherosclerotic lesion. By acting on the antigens, it is possible to prevent atherosclerosis and to induce its regression. The methodology for studying atherosclerosis and many other diseases is shown to be difficult and multifaceted and need the participation of specialists of diverse specialties in the solution of the problems associated with the treatment of atherosclerosis.     

The role of transferrin in atherosclerosis

Transferrin is a plasma protein with the primary role of transporting iron through the body and delivering it to the cells that utilize it. Because free ionic iron is very toxic by creating free radicals, the importance of transferrin lies in its antioxidant properties. Atherosclerosis, a pathological process affecting arterial walls, is a chronic inflammatory response in which oxidative stress caused by free radicals is a key factor in its pathogenesis. We postulate therefore that the plasma protein transferrin acts protectively in these events, by holding iron in containment and reducing oxidative stress. Furthermore, it is possible that a disturbance in transferrin function and homeostasis is a direct factor triggering and exacerbating atherosclerosis. Decreased transferrin levels, increased transferrin saturation, defective transferrin binding of iron, or other disorders may lead to increased oxidative stress and lipid peroxidation involved in the pathology of atherosclerosis. Some oxidative stress-related diseases have been linked to such systemic transferrin abnormalities, and we hypothesize that similar disruptions could account for an unfavorable microenviroment in the evolvement of atherosclerotic plaques. If confirmed, this proposed mechanism would significantly improve our understanding of the disease.     

Experimental cholesterol atherosclerosis in dogs

Summary No direct relationship existed (except in one case) between the weight gain, blood cholesterol content and the degree of morphological changes developing in the cardiovascular system of cholesterol and 6-methylthiourcil fed dogs. The localization and character of morphological changes in the cardiovascular system of dogs with experimentally induced atherosclerosis are similar to those in human atherosclerosis. The blood pressure in healthy dogs does not increase in response to moderate physical exertion; this is evidently due to reduction of the peripheral resistance as a result of adjustive dilation of the vessels.The blood pressure in atherosclerotic dogs showed a slight rise in response to moderate physical exertion with concurrent tachycardia.(Presented by Active member AMN SSSR V. V. Parin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 50, No. 11, pp. 37–41, November, 1960     

The effect of cholesterol oxidation products on the disruption of lipid metabolism and atherosclerotic damage of the aorta in rabbits

Feeding of rabbits with a cholesterol preparation containing 3-5% of cholesterol autooxidation products promotes elevation of plasma cholesterol and atherogenic low- and very-low-density lipoproteins as well as accumulation of neutral lipids (largely, of cholesterol ether) in hepatocytes and intramural arteries of the myocardium. The development of massive aortic lipoidosis can be also attributed to the intake of relevant products. The similar dose of non-oxidized cholesterol did not induce marked or any changes at all in rabbits lipid metabolism and aortic status. The evidence obtained indicates an essential role of food exogenic products of cholesterol oxidation in mechanisms of hypercholesterolemia development and atherosclerotic involvement of vascular walls.     

SLE患者抗载脂蛋白A-I抗体的检测及其对细胞内胆固醇外流的影响

研究系统性红斑狼疮(SLE)患者血中抗载脂蛋白A-I(Apo A-I)抗体的阳性率及其可能的致动脉粥样硬化的机制。采用酶联免疫吸附法(ELISA)检测175例SLE患者抗Apo A-I抗体,以64例正常人为对照;用抑制试验研究Apo A-I aa74- 105肽段能否抑制抗ApoA-I多抗和单抗IS4与Apo A-I的结合;并观察抗Apo A-I多抗和单抗对细胞内胆固醇流出的影响。结果显示,在SLE患者中存在抗Apo A-I抗体,阳性率为16.6%;肽段aa74-105能够抑制抗Apo A-I抗体与Apo A-I的结合;抗Apo A-I抗体在体外能抑制细胞内胆固醇的流出。实验表明,SLE患者的抗Apo A-I抗体可能通过和Apo A-I功能区中的部分氨基酸结合,影响Apo A-I的功能而抑制细胞胆固醇流出,促进SLE患者动脉粥样硬化的发生。