Pharmacological basis of different targets for the treatment of atherosclerosis

The development of atherosclerotic plaque is a highly regulated and complex process which occurs as a result of structural and functional alterations in endothelial cells, smooth muscle cells (SMCs), monocytes/macrophages, T-lymphocytes and platelets. The plaque formation in the coronary arteries or rupture of the plaque in the peripheral vasculature in latter stages of atherosclerosis triggers the onset of acute ischemic events involving myocardium. Although lipid lowering with statins has been established as an important therapy for the treatment of atherosclerosis, partially beneficial effects of statins beyond decreasing lipid levels has shifted the focus to develop newer drugs that can affect directly the process of atherosclerosis. Blockade of renin angiotensin system, augmentation of nitric oxide availability, reduction of Ca(2+) influx, prevention of oxidative stress as well as attenuation of inflammation, platelet activation and SMC proliferation have been recognized as targets for drug treatment to control the development, progression and management of atherosclerosis. A major challenge for future drug development is to formulate a combination therapy affecting different targets to improve the treatment of atherosclerosis.     

Bromodomain-containing protein 7 deficiency augments atherosclerotic lesions in ApoE−/− mice

Atherosclerotic plaque formation is characterized by the persistence of lipid-laden macrophages on the inner walls of arteries. Chronic inflammation and imbalanced macrophage function are likely to play a critical role. Herein, we investigated whether bromodomain-containing protein 7 (Brd7), a member of the bromodomain-containing protein family, regulates atherosclerosis, and if so, which mechanisms are responsible for the process. We found that Brd7 is expressed in mouse atherosclerotic plaques, and mostly in macrophages. Inhibition of Brd7 accelerates atherosclerotic lesion formation in ApoE^?/? mice by promoting NF-κB–mediated inflammation. Furthermore, Brd7 inhibition alters the phenotype of macrophages and promotes plaque instability, at least partly via STAT6 signaling. Our data define a previously undescribed role of Brd7 in the development of atherosclerosis.     

How radiation influences atherosclerotic plaque development: a biophysical approach in ApoE ¯/¯ mice

Atherosclerosis is the development of lipid-laden plaques in arteries and is nowadays considered as an inflammatory disease. It has been shown that high doses of ionizing radiation, as used in radiotherapy, can increase the risk of development or progression of atherosclerosis. To elucidate the effects of radiation on atherosclerosis, we propose a mathematical model to describe radiation-promoted plaque development. This model distinguishes itself from other models by combining plaque initiation and plaque growth, and by incorporating information from biological experiments. It is based on two consecutive processes: a probabilistic dose-dependent plaque initiation process, followed by deterministic plaque growth. As a proof of principle, experimental plaque size data from carotid arteries from irradiated ApoE\(^{{-/-}}\) mice was used to illustrate how this model can provide insight into the underlying biological processes. This analysis supports the promoting role for radiation in plaque initiation, but the model can easily be extended to include dose-related effects on plaque growth if available experimental data would point in that direction. Moreover, the model could assist in designing future biological experiments on this research topic. Additional biological data such as plaque size data from chronically-irradiated mice or experimental data sets with a larger variety in biological parameters can help to further unravel the influence of radiation on plaque development. To the authors’ knowledge, this is the first biophysical model that combines probabilistic and mechanistic modeling which uses experimental data to investigate the influence of radiation on plaque development.     

Maturation-dependent neointima formation in fowl aorta.

Fowl show spontaneous elevation of blood pressure (BP) and neointimal plaque formation in the abdominal aorta at young ages. Maturation/age-dependent modulation of vascular lesions and a causal relationship between elevated BP and neointima formation, however, have not been clarified. We therefore intended to characterize, first, maturation/age-dependent neointimal plaque formation and vascular lesions and, second, their relationship to BP elevation. The BP measured in conscious domestic fowl, Gallus gallus, White Leghorn breed, DeKalb strain, via an indwelling catheter inserted into the ischiadic artery, increased with maturation in males; and at plateau level, BP (mmHg) was significantly (P<0.01) higher in males (194.0+/-4.6, n=11) than in females (169.3+/-3.1, n=10). Neointimal plaques consisting of neointimal cells and abundant extracellular matrix appeared initially in the distal segment of the abdominal aorta (lesion-prone area) of chicks as early as 6 weeks old. The area (size) of neointimal plaques right above the ischiadic bifurcation increased with maturation, whereas the plaque area became smaller with some degenerative changes in adult birds. In some birds, diffuse subendothelial hyperplasia and more extensive plaque formation at the branching points of the aorta were observed. The plaque area appears to be larger in birds, particularly in males that have higher BP (r=0.68). The width of aortic smooth muscle (SM) layers, measured in regions with no plaque, increased with age, whereas the number of cells per unit of area decreased, suggesting that hypertrophy of vascular SM occurs in response to exposure of the vascular wall to high BP. The number of cells was significantly (P<0.01) higher in the plaque than in underlying aortic SM layers or in layers with no plaque formation. Both neointimal plaques and underlying SM layers are immunohistochemically positive for alpha SM actin, suggesting that neointimal cells are modulated SM cells, whereas the staining with SM myosin heavy chain antibody is low in neointimal plaques. Furthermore, plasma arginine levels dropped in accordance with the time of neointimal plaque formation, whereas plasma cholesterol levels showed an age-dependent increase. The results suggest that spontaneous development of neointimal plaques may be a consequence of exposure to high BP and associated local hemodynamic changes.     

Arterial wall damage by X-rays and fast neutrons.

Radiation-induced atheromatosis has been studied for 200 kVp X-rays and 15 MeV neutrons. From the results of two earlier experiments, a r.b.e. less than 1 was expected for neutrons. (1) Irradiation of blood-vessels causes depolymerization of the mucopolysaccharides in the vessel wall, resulting in atheromatosis, and (2) in two other mucopolysaccharide systems a r.b.e. less than 1 is observed for fast neutrons. Irradiation of the carotid arteries of a total number of 120 hypercholesterolaemic rabbits, divided over several groups, with 500 and 1000 rad of X-rays or neutrons results, however, in atheromatous plaques which are more pronounced for neutrons than for X-rays at the 500 rad dose-level; for a dose of 1000 rad the effect of neutrons is less extensive than the effect of X-rays. These results lead to the assumption that the origin of the atheromatosis seems not only to be the mucopolysaccharide depolymerization, but that radiation induced damage at the cellular level must be taken into account.     

Inflammation in atherosclerosis: a cause or a result of vascular disorders?

Sound data support the concept that in atherosclerosis, inflammation and dyslipidemia intersect each other and that irrespective of the initiator, both participate from the early stages to the ultimate fate of the atheromatous plaque. The two partakers manoeuvre a vicious circle in atheroma formation: dyslipidaemia triggers an inflammatory process and inflammation elicits dyslipidaemia. Independent of the initial cause, the atherosclerotic lesions occur focally, in particular arterial-susceptible sites, by a process that, although continuous, can be arbitrarily divided into a sequence of consecutive stages that lead from fatty streak to the fibro-lipid plaque and ultimately to plaque rupture and thrombosis. In the process, the initial event is a change in endothelial cells (EC) constitutive properties. Then, the molecular alarm signals send by dysfunctional EC are decoded by specific blood immune cells (monocytes, T lymphocytes, neutrophils, mast cells) and by the resident vascular cells, that respond by initiating a robust inflammatory process, in which the cells and the factors they secrete hasten the atheroma development. Direct and indirect crosstalk between the cells housed within the nascent plaque, complemented by the increase in risk factors of atherosclerosis lead to atheroma development and outcome. The initial inflammatory response can be regarded as a defense/protective reaction mechanism, but its further amplification, speeds up atherosclerosis. In this review, we provide an overview on the role of inflammation and dyslipidaemia and their intersection in atherogenesis. The data may add to the foundation of a novel attitude in the diagnosis and treatment of atherosclerosis.     

A critical function of Th17 proinflammatory cells in the development of atherosclerotic plaque in mice

Considerable evidence supports that the CD4(+) T cell-mediated immune response contributes to the development of atherosclerotic plaque. However, the effects of Th17 cells on atherosclerosis are not thoroughly understood. In this study, we evaluated the production and function of Th17 and Th1 cells in atherosclerotic-susceptible ApoE(-/-) mice. We observed that the proportion of Th17 cells, as well as Th1, increased in atherosclerotic ApoE(-/-) mice compared with nonatherosclerotic wild-type littermates. In ApoE(-/-) mice with atherosclerosis, the expression of IL-17 and retinoic acid-related orphan receptor γt was substantially higher in the arterial wall with plaque than in the arterial wall without plaque. Increased Th17 cells were associated with the magnitude of atherosclerotic plaque in ApoE(-/-) mice. Importantly, treatment of ApoE(-/-) mice with neutralizing anti-IL-17 Ab dramatically inhibited the development of atherosclerotic plaque, whereas rIL-17 application significantly promoted the formation of atherosclerotic plaque. These data demonstrate that Th17 cells play a critical role in atherosclerotic plaque formation in mice, which may have implications in patients with atherosclerosis.     

Role of Cell Adhesion Molecules and Immune-Cell Migration in the Initiation,Onset and Development of Atherosclerosis

Atherosclerosis is currently the leading factor of death in developed countries. It is now recognized as a chronic immune-inflammatory disease, whose initial stages involve the interaction of leukocytes with the endothelial monolayer. The initial stage of atherosclerosis requires the interplay of various cell adhesion molecules and immune cells to trigger leukocyte and lymphocyte migration from the circulating blood into the arterial intima. Studies have unveiled the role of inflammatory mediators in the initiation, onset and progression of the disease. During the last few years we have gained a greater understanding of the mechanism that modulates monocyte, macrophage and T cell infiltration, the role these cells play in the atherosclerotic lesion, in the formation of the fibrous plaque formation with the consequent narrowing of the arteries, and the mechanisms that lead to plaque rupture and the formation of thrombi and emboli. This review talks about the leukocyte recruitment in early atherosclerosis, the formation of the plaque and the mechanisms that lead to thrombosis in advanced atherosclerosis. Finally, we discuss the potential for novel therapies to treat this disease.     

Immunosuppressive properties of sera and urine dialysates from kidney-graft recipients treated with azathioprine,prednisolone, and niridazole

Niridazole, an antischistosomal agent, was given to renal transplant recipients in addition to azathioprine and prednisolone, as there is experimental evidence that this combination of drugs is highly immunosuppressive. Sera obtained from kidney-graft recipients during the first two weeks after transplantation were examined for their ability to inhibit the one-way mixed lymphocyte reaction (MLR). Sera from seven patients receiving azathioprine, prednisolone, and niridazole (triple-drug treatment), five patients receiving azathioprine and prednisolone, and two other patients treated with niridazole alone for schistosomiasis produced MLR inhibition by comparison with pretreatment (control) sera.A mean of 78% inhibition was observed with sera taken after one day''s treatment with the three-drug combination, whereas this level of in-vitro immunosuppression occurred only after eight days of treatment with azathioprine and prednisolone. Niridazole alone produced an effect similar to azathioprine and prednisolone. Concentrated dialysate of urine from a patient receiving triple-drug treatment not only inhibited the MLR but also significantly prolonged the survival of heterotopic heart allografts in rats, whereas dialysate from the same patient after niridazole had been stopped gave less MLR inhibition and failed to prolong heart allograft survival.Since niridazole thus increased the in-vitro and in-vivo immunosuppressive action of azathioprine and prednisolone, we suggest that this triple-drug combination might be useful for preventing early acute kidney graft rejection.     

胆固醇结晶激活动脉粥样硬化斑块巨噬细胞NLRP3炎症体的途径

动脉粥样硬化既是胆固醇在血管壁聚集的疾病,也是发生在动脉壁的一种低强度慢性炎症形式。近年来有研究证实胆固醇结晶在动脉粥样硬化发生发展中具有重要作用。新的显微技术证实,胆固醇结晶在动脉粥样硬化斑块形成的早期即已出现,并与早期炎症有关。胆固醇结晶通过诱发局部炎症,促进大的脂质核心形成;刺破纤维帽,导致斑块破裂进而促进动脉粥样硬化斑块的进展。在影响斑块进程中,NLRP3炎症体的激活对此发挥了重要的作用。NLRP3炎症体是研究最多最明确的炎症体,其与非炎症性疾病的发生发展密切相关。以胆固醇结晶激活NLRP3炎症体的途径作为研究靶点,为动脉粥样硬化的诊断和治疗提供了新的思路和方法。该文就胆固醇结晶在动脉粥样硬化斑块中激活巨噬细胞NLRP3炎症体的两种途径做一综述。     

Shear strain in the adventitial layer of the arterial wall facilitates development of vulnerable plaques

Myocardial infarction and stroke are two of the leading causes of death and primarily triggered by destabilization of atherosclerotic plaques. Fatty streaks are known to develop at sites in the arterial wall where shear stress is low. These fatty streaks can develop into more advanced plaques that are prone to rupture. Rupture leads to thrombus formation, which may subsequently result in a myocardial infarction or stroke. The relation between shear stress on the inner (endothelial) layer of the arterial wall in relation to plaque development has been studied extensively. However, a causal relation between adventitial shear forces and atherosclerosis development has never been considered.Arterial stiffening increases with age and may facilitate an increase in shear strain in the adventitial layer, an axial shear between artery and surrounding tissue. In the adventitial layer, a large number of inflammatory cells and perivascular structures are present that are subjected to shear strain. Cyclic strain applied to endothelial cells stimulates neovascularisation via different pathways. The conduit arteries in the human body (e.g. coronary and carotid artery) have their own nutrition supply: the vasa vasorum, which is located in the adventitial layer and sprouts into the intimal layer when atherosclerotic plaque develops. Increased plaque neovascularisation makes the plaques more prone to rupture. Therefore we hypothesize that increased shear strain facilitates the development of vulnerable plaques by stimulation of atherosclerotic plaque neovascularisation that sprouts from the adventitial vasa vasorum. Validation of this hypothesis paves the road to the use of adventitial shear strain (measured using a noninvasive ultrasound technique) as risk assessment in plaque.     

Inhibition of c-Jun N-terminal kinase attenuates low shear stress-induced atherogenesis in apolipoprotein E-deficient mice

Atherosclerosis begins as local inflammation of arterial walls at sites of disturbed flow, such as vessel curvatures and bifurcations with low shear stress. c-Jun NH?-terminal kinase (JNK) is a major regulator of flow-dependent gene expression in endothelial cells in atherosclerosis. However, little is known about the in vivo role of JNK in low shear stress in atherosclerosis. We aimed to observe the effect of JNK on low shear stress-induced atherogenesis in apolipoprotein E-deficient (ApoE(-/-)) mice and investigate the potential mechanism in human umbilical vein endothelial cells (HUVECs). We divided 84 male ApoE(-/-) mice into two groups for treatment with normal saline (NS) (n = 42) and JNK inhibitor SP600125 (JNK-I) (n = 42). Perivascular shear stress modifiers were placed around the right carotid arteries, and plaque formation was studied at low shear stress regions. The left carotid arteries without modifiers represented undisturbed shear stress as a control. The NS group showed atherosclerotic lesions in arterial regions with low shear stress, whereas the JNK-I group showed almost no atherosclerotic lesions. Corresponding to the expression of proatherogenic vascular cell adhesion molecule 1 (VCAM-1), phospho-JNK (p-JNK) level was higher in low shear stress regions with NS than with JNK-I inhibitor. In HUVECs under low shear stress, siRNA knockdown and SP600125 inhibition of JNK attenuated nuclear factor (NF)-κB activity and VCAM-1 expression. Furthermore, siRNA knockdown of platelet endothelial cell adhesion molecule 1 (PECAM-1) (CD31) reduced p-JNK and VCAM-1 levels after low shear stress stimulation. JNK may play a critical role in low shear stress-induced atherogenesis by a PECAM-1-dependent mechanosensory pathway and modulating NF-κB activity and VCAM-1 expression.     

一个日益重要的冠心病标志物———新蝶呤

动脉粥样硬化是一种慢性炎症过程,炎症反应在动脉粥样斑块的形成、发展、稳定性丧失和斑块破裂过程中都起着非常重要的作用,贯穿于动脉粥样硬化的各个环节。从早期的脂质条纹到进一步的动脉粥样病变及血栓性并发症都能见到炎症细胞的浸润,其中又以激活的巨噬细胞尤为重要。新蝶呤是巨噬细胞激活后的代谢产物,它不仅是巨噬细胞激活的炎症标志物,还参与多种调节氧化平衡的生化途径,增加氧化应激水平,促进动脉粥样硬化的进展,是斑块不稳定性及不良性心血管事件的独立预测因子。在临床上,降低血清新蝶呤水平可以降低冠心病患者发生危险事件的风险。因此,新蝶呤对冠心病的诊断和治疗都有重要意义。本文将对新蝶呤在冠心病中的角色做一综述。     

Experimental determination of circumferential properties of fresh carotid artery plaques

Carotid endarterectomy (CEA) is currently accepted as the gold standard for interventional revascularisation of diseased arteries belonging to the carotid bifurcation. Despite the proven efficacy of CEA, great interest has been generated in carotid angioplasty and stenting (CAS) as an alternative to open surgical therapy. CAS is less invasive compared with CEA, and has the potential to successfully treat lesions close to the aortic arch or distal internal carotid artery (ICA). Following promising results from two recent trials (CREST; Carotid revascularisation endarterectomy versus stenting trial, and ICSS; International carotid stenting study) it is envisaged that there will be a greater uptake in carotid stenting, especially amongst the group who do not qualify for open surgical repair, thus creating pressure to develop computational models that describe a multitude of plaque models in the carotid arteries and their reaction to the deployment of such interventional devices. Pertinent analyses will require fresh human atherosclerotic plaque material characteristics for different disease types. This study analysed atherosclerotic plaque characteristics from 18 patients tested on site, post-surgical revascularisation through endarterectomy, with 4 tissue samples being excluded from tensile testing based on large width-length ratios. According to their mechanical behaviour, atherosclerotic plaques were separated into 3 grades of stiffness. Individual and group material coefficients were then generated analytically using the Yeoh strain energy function. The ultimate tensile strength (UTS) of each sample was also recorded, showing large variation across the 14 atherosclerotic samples tested. Experimental Green strains at rupture varied from 0.299 to 0.588 and the Cauchy stress observed in the experiments was between 0.131 and 0.779 MPa. It is expected that this data may be used in future design optimisation of next generation interventional medical devices for the treatment and revascularisation of diseased arteries of the carotid bifurcation.     

Computed high concentrations of low-density lipoprotein correlate with plaque locations in human coronary arteries

Subendothelial accumulation of low-density lipoprotein (LDL) in arterial walls is an initiator of atherosclerotic plaque formation. We report here on the correlation between healthy state subendothelial LDL concentration distribution and sites of subsequent plaque formation in coronary arteries of patients with coronary artery disease (CAD). We acquired left (LCA) and right coronary artery (RCA) and atherosclerotic plaque geometries of 60 patients with CAD using dual-source computed tomography angiography. After virtually removing all plaques to obtain an approximation of the arteries' healthy state, we calculated LDL concentration in the artery walls as a function of local lumen-side shear stress. We found that maximum subendothelial LDL concentrations at plaque locations were, on average, 45% (RCA) and 187% (LCA) higher than the respective average subendothelial concentration. Our results demonstrate that locally elevated subendothelial LDL concentration correlates with subsequent plaque formation at the same location.     

Matrix metalloproteinases at key junctions in the pathomechanism of stroke

Matrix metalloproteinases play a crucial role in the remodelling of the extracellular matrix through direct degradation of its structural proteins and control of extracellular signalling. The most common cause of ischemic brain damage is an atherothrombotic lesion in the supplying arteries. The progress of the atherosclerotic plaque development and the related thrombotic complications are mediated in part by matrix metalloproteinases. In addition to their role in the underlying disease, various members of this protease family are upregulated in the acute phase of ischemic brain damage as well as in the post-ischemic brain recovery following stroke. This review summarizes the current understanding of the matrix metalloproteinase-related molecular events at three stages of the ischemic cerebrovascular disease (in the atherosclerotic plaque, in the neurovascular unit of the brain and in the regenerating brain tissue).     

Role of Cell Adhesion Molecules and Immune-Cell Migration in the Initiation,Onset and Development of Atherosclerosis

Atherosclerosis is currently the leading factor of death in developed countries. It is now recognized as a chronic immune-inflammatory disease, whose initial stages involve the interaction of leukocytes with the endothelial monolayer. The initial stage of atherosclerosis requires the interplay of various cell adhesion molecules and immune cells to trigger leukocyte and lymphocyte migration from the circulating blood into the arterial intima. Studies have unveiled the role of inflammatory mediators in the initiation, onset and progression of the disease. During the last few years we have gained a greater understanding of the mechanism that modulates monocyte, macrophage and T cell infiltration, the role these cells play in the atherosclerotic lesion, in the formation of the fibrous plaque formation with the consequent narrowing of the arteries and the mechanisms that lead to plaque rupture and the formation of thrombi and emboli. This review talks about the leukocyte recruitment in early atherosclerosis, the formation of the plaque, and the mechanisms that lead to thrombosis in advanced atherosclerosis. Finally, we discuss the potential for novel therapies to treat this disease.Key Words: CAMs, leukocyte, lymphocyte, migration, atherosclerosis, extravasation     

Bovine herpesvirus 1 attachment to permissive cells is mediated by its major glycoproteins gI, gIII, and gIV.

A bovine herpesvirus 1 (BHV-1) gIII deletion mutant (gIII-) was produced by means of recombinant DNA that retained the ability to replicate in cell culture. However, the gIII- mutant was functionally defective, showing impaired attachment to permissive cells, a delay in virus replication, and reduced extracellular virus production. The attachment defect exhibited by the gIII- mutant is an indication of the role played by gIII in the normal infection process. This was shown by dramatically decreased binding of radiolabelled gIII- virus to permissive cells and a slower adsorption rate, as measured by plaque formation, than the wild-type (wt) virus. Furthermore, treatment of the gIII- virus with neomycin increased virus adsorption and plaque formation by severalfold, whereas neomycin treatment had no effect on the wt virus. This observation showed that the gIII- mutant was strictly defective in adsorption but fully competent to produce productive infections once induced to attach. The gIII- mutant showed greater sensitivities than did the wt virus to anti-gI and anti-gIV antibody-mediated neutralization. Analyses with panels of monoclonal antibodies to gI and gIV revealed that the epitopes gI-IV and gIV-III were the main targets for enhanced neutralization. This provided evidence that gI and gIV may also participate in virus attachment. Finally, when affinity-purified gI, gIII, and gIV were tested for their ability to inhibit virus adsorption, gIII had the most pronounced inhibitory effect, followed by gI and then gIV. gIII was able to completely inhibit wt virus adsorption, and at a high concentration, it also partially inhibited the gIII- mutant. gI and gIV inhibited wt and gIII- mutant adsorption to a comparable extent. Our results collectively indicate that gIII plays a predominant role in virus attachment, but gI and gIV also contribute to this process. In addition, a potential cooperative mechanism for virus attachment with these three proteins is presented.     

Noninvasive detection of macrophages using a nanoparticulate contrast agent for computed tomography

Sudden fibrous cap disruption of 'high-risk' atherosclerotic plaques can trigger the formation of an occlusive thrombus in coronary arteries, causing acute coronary syndromes. High-risk atherosclerotic plaques are characterized by their specific cellular and biological content (in particular, a high density of macrophages), rather than by their impact on the vessel lumen. Early identification of high-risk plaques may be useful for preventing ischemic events. One major hurdle in detecting high-risk atherosclerotic plaques in coronary arteries is the lack of an imaging modality that allows for the identification of atherosclerotic plaque composition with high spatial and temporal resolutions. Here we show that macrophages in atherosclerotic plaques of rabbits can be detected with a clinical X-ray computed tomography (CT) scanner after the intravenous injection of a contrast agent formed of iodinated nanoparticles dispersed with surfactant. This contrast agent may become an important adjunct to the clinical evaluation of coronary arteries with CT.