皂苷类成分对血管内皮细胞功能的调节作用研究进展

血管内皮细胞在维持血管生理稳态中发挥了重要的作用,其功能障碍是动脉粥样硬化、冠心病、脑卒中、肿瘤等多种重大疾病发生发展的病理基础,调节血管内皮细胞功能是防治上述疾病的主要途径之一。大量研究表明,皂苷类成分可通过改善血管内皮功能达到治疗疾病的目的。综述了近年来报道的皂苷类成分调节血管内皮功能的研究进展,旨在为皂苷类成分作用机制的阐明和相关重大疾病的防治提供一定参考。     

Role of microRNAs in endothelial inflammation and senescence

The functionality of endothelial cells is fundamental for the homoeostasis of the vascular system. Increasing evidence shows that endothelial inflammation and senescence contribute greatly to multiple vascular diseases including atherosclerosis. However, little is known regarding the complex upstream regulators of gene expression and translation involved in these responses. MicroRNAs (miRNAs) have emerged as a novel class of endogenous, small, non-coding RNAs that negatively regulate over 30% of genes in a cell via degradation or translational inhibition of their target mRNAs. During the past few years, miRNAs have emerged as key regulators for endothelial biology and function. Endothelial inflammation is critically regulated by miRNAs such as miR-126 and miR-10a in vitro and in vivo. Endothelial aging is additionally controlled by miR-217 and miR-34a. In this review, we summarize the role of miRNAs and their target genes in endothelial inflammation and senescence, and discuss their applicability as drug targets.     

Human cytomegalovirus-specific CD4+-T-cell cytokine response induces fractalkine in endothelial cells

Cytomegalovirus (CMV) infection has been linked to inflammation-related disease processes in the human host, including vascular diseases and chronic transplant rejection. The mechanisms through which CMV affects the pathogenesis of these diseases are for the most part unknown. To study the contributing role of the host immune response to CMV in these chronic inflammatory processes, we examined endothelial cell interactions with peripheral blood mononuclear cells (PBMC). Endothelial cultures were monitored for levels of fractalkine induction as a marker for initiating the host inflammatory response. Our results demonstrate that in the presence of CMV antigen PBMC from normal healthy CMV-seropositive donors produce soluble factors that induce fractalkine in endothelial cells. This was not observed in parallel assays with PBMC from seronegative donors. Examination of subset populations within the PBMC further revealed that CMV antigen-stimulated CD4(+) T cells were the source of the factors, gamma interferon and tumor necrosis factor alpha, driving fractalkine induction. Direct contact between CD4(+) cells and the endothelial monolayers is required for this fractalkine induction, where the endothelial cells appear to provide antigen presentation functions. These findings indicate that CMV may represent one member of a class of persistent pathogens where the antigen-specific T-cell response can result in the induction of fractalkine, leading to chronic inflammation and endothelial cell injury.     

Endothelial cell functions

Endothelial cells play a wide variety of critical roles in the control of vascular function. Indeed, since the early 1980s, the accumulating knowledge of the endothelial cell structure as well as of the functional properties of the endothelial cells shifted their role from a passive membrane or barrier to a complex tissue with complex functions adaptable to needs specific in time and location. Hence, it participates to all aspects of the vascular homeostasis but also to physiological or pathological processes like thrombosis, inflammation, or vascular wall remodeling. Some of the most important endothelial functions will be described in the following review and more specifically, their role in blood vessel formation, in coagulation and fibribolysis, in the regulation of vascular tone as well as their participation in inflammatory reactions and in tumor neoangiogenesis.     

Endothelial mitochondria--a novel target for pharmacology of endothelial dysfunction

Vascular endothelium the inside layer of the cardiovascular system is presently looked upon as an important paracrine, autocrine and endocrine organ that determines the health of the cardiovascular system. In fact, healthy endothelium is essential for homeostasis of cardiovascular system, while endothelial dyfunction leads to cardiovascular diseases including atherosclerosis, diabetes and heart failure. Endothelial dysfunction is tightly linked to the overproduction of reactive oxygen species, development of oxidant stress and inflammatory response of endothelium. Mitochondria of the vascular endothelium seem to be an important player in these processes. In contrast to numerous cell types, synthesis of ATP in endothelium occurs in major part via a glycolytic pathway and endothelium seem to be relatively independent of the mitochondrial pathway of energy supply. However, as evident from recent studies, mitochondrial pathways of free radicals production tighly linked to mitochondrial and cytosol changes in the ion homeostasis play an important role in the regulation of endothelial inflammatory response, in the development of oxidative stress and apoptosis of vascular endothelium. Therefore, endothelial mitochondria appears critical in the regulation of endothelial functions and represent a novel target in pharmacology of endothelial dysfunction in cardiovascular diseases.     

Coplanar polychlorinated biphenyl-induced CYP1A1 is regulated through caveolae signaling in vascular endothelial cells

Polychlorinated biphenyls (PCBs) are persistent environmental contaminants that can induce inflammatory processes in the vascular endothelium. We hypothesize that the plasma membrane microdomains called caveolae are critical in endothelial activation and toxicity induced by PCBs. Caveolae are particularly abundant in endothelial cells and play a major role in endothelial trafficking and the regulation of signaling pathways associated with the pathology of vascular diseases. We focused on the role of caveolae and their major protein component, caveolin-1 (Cav-1), on aryl hydrocarbon receptor (AhR)-mediated induction of cytochrome P450 1A1 (CYP1A1) by coplanar PCBs. Endothelial cell exposure to PCB77 increased both caveolin-1 and CYP1A1 levels in a time-dependent manner in total cell lysates, with a maximum increase at 6h. Furthermore, PCB77 accumulated mainly in the caveolae-rich fraction, as determined by gas chromatograph-mass spectrometry. Immunoprecipitation analysis revealed that PCB77 increased AhR binding to caveolin-1. Silencing of caveolin-1 significantly attenuated PCB77-mediated induction of CYP1A1 and oxidative stress. Similar effects were observed in caveolin-1 null mice treated with PCB77. These data suggest that caveolae may play a role in regulating vascular toxicity induced by persistent environmental pollutants such as coplanar PCBs. This may have implications in understanding mechanisms of inflammatory diseases induced by environmental pollutants.     

Primary cultures of rat aortic endothelial and smooth muscle cells: I. An in vitro model to study xenobiotic-induced vascular cytotoxicity

Summary Primary cultures of rat vascular endothelial and smooth muscle cells were developed as models to study xenobiotic-induced cytotoxicity. Endothelial and smooth muscle cells were isolated by enzymatic digestion and mechanical dissociation of rat thoracic aortae. Optimal cell growth and minimal fibroblast contamination in cultures of both cell types were obtained in Medium 199 supplemented with 10% fetal bovine serum. Cultured cells were characterized by distinctive morphologic features and growth patterns. Intercellular endothelial cell junctions were selectively stained with silver nitrate. Endothelial cells also exhibited a nonthrombogenic surface, as reflected by platelet-binding studies. Confluent cultures of smooth muscle cells, but not endothelial cells, contracted in response to norepinephrine (10 μM). Cultures of both cell types were exposed to acrolein (2, 5 or 50 ppm), an environmental pollutant, for 4 24 h. Morphologic damage, lactate dehydrogenase release, and cellular thiol content were used as indices of cytotoxicity. Acrolein-induced enzyme leakage and morpholgic alterations were dose- and time-dependent and more pronounced in cultures of smooth muscle cells than in endothelial cells. The total thiol content of endothelial cells exposed to acrolein (50 ppm) for 24 h was not significantly different from that of respective controls. In contrast, the content of treated smooth muscle cells was higher than that of controls. These observations show that primary cultures of vascular cells provide a useful model to evaluate xenobiotic-induced cytotoxicity. The information obtained using a cell culture system may be complemented by the use of other in vivo and in vitro models to determine the mechanisms by which xenobiotics cause vascular cell injury.     

Phagocytosis of platelets enhances endothelial cell survival under serum deprivation

Platelets are key players in fundamental processes of vascular biology, such as angiogenesis, tissue regeneration, and tumor metastasis. However, the underlying mechanisms remain unclear. In this study, some tumor vascular endothelial cells were positively stained by antiplatelet antibodies. Further investigation revealed that platelets were taken up by endothelial cells in vitro and in vivo. Human umbilical vascular endothelial cells were rendered apoptotic under conditions of serum deprivation. However, endothelial apoptosis was suppressed and cell viability was enhanced when platelets were added to the cultures. Endothelial survival was paralleled by an upregulation of phosphorylated Akt and p70 S6K. In conclusion, this study demonstrated that platelets can be phagocytosed by endothelial cells, and the phagocytosed platelets could suppress endothelial apoptosis and promote cell viability level. The mechanism underlying this process involves the activation of Akt signaling.     

Neutrophil Elastase-Generated Fragment of Vascular Endothelial Growth Factor-A Stimulates Macrophage and Endothelial Progenitor Cell Migration

Elastase released from neutrophils as part of the innate immune system has been implicated in chronic diseases such as emphysema and cardiovascular disease. We have previously shown that neutrophil elastase targets vascular endothelial growth factor-A (VEGF) for partial degradation to generate a fragment of VEGF (VEGFf) that has distinct activities. Namely, VEGFf binds to VEGF receptor 1 but not to VEGF receptor 2 and shows altered signaling compared to intact VEGF. In the present study we investigated the chemotactic function of VEGF and VEGFf released from cells by neutrophil elastase. We found that endothelial cells migrated in response to intact VEGF but not VEGFf whereas RAW 264.7 macrophages/monocytes and embryonic endothelial progenitor cells were stimulated to migrate by either VEGF or VEGFf. To investigate the role of elastase-mediated release of VEGF from cells/extracellular matrices, a co-culture system was established. High or low VEGF producing cells were co-cultured with macrophages, endothelial or endothelial progenitor cells and treated with neutrophil elastase. Elastase treatment stimulated macrophage and endothelial progenitor cell migration with the response being greater with the high VEGF expressing cells. However, elastase treatment led to decreased endothelial cell migration due to VEGF cleavage to VEGF fragment. These findings suggest that the tissue response to NE-mediated injury might involve the generation of diffusible VEGF fragments that stimulate inflammatory cell recruitment.     

New uses for endothelial cell culture

Endothelial cells in culture have, in the past, been a valuable but capricious tool to test hypotheses on the role of components of the blood vessel wall in such functions as blood pressure homeostasis, hemostasis, permeability, transport of macromolecules and the processing of circulating biologically active substances. Now techniques are becoming available for raising long-term, large-scale cultures that can be maintained reproducibly and without loss of phenotypic characteristics. The outlook for establishing endothelial cell factories invites speculation on some far-reaching possibilities, such as endothelial cell banks that could be used for seeding autogenous cells on vascular prostheses, artificial kidney tubing, heart valves, or corneas, or for virus production, or for synthesis by endothelial cells of products at present beyond the reach of bacterial cells.     

Ang-Tie轴在血管和淋巴系统相关疾病中作用的研究进展

形成血管和淋巴管内层的内皮细胞是脉管系统的重要组成部分,并参与血管和淋巴系统疾病的发病机制。内皮细胞上的血管生成素(Angiopoietin,Ang)-具有免疫球蛋白和表皮生长因子同源性结构域的酪氨酸蛋白激酶(Tyrosine kinase receptors with immunoglobulin and EGF homology domains,Tie)轴是除了血管内皮生长因子受体途径外胚胎心血管和淋巴发育所必需的第二种内皮细胞特异性配体-受体信号传导系统。Ang-Tie轴参与调节产后血管生成与重塑、血管通透性和炎症,以维持血管平衡,因此,该系统在许多血管和淋巴系统疾病中发挥重要的作用。针对近年来Ang-Tie轴在血管和淋巴系统相关疾病中作用的研究进展,文中系统论述了Ang-Tie轴在炎症诱导的血管通透性、血管重塑、眼部新生脉管、剪切应力反应、动脉粥样硬化和肿瘤血管生成和转移中的作用,并总结了涉及Ang-Tie轴的相关治疗性抗体、重组蛋白和小分子药物。     

Phenotypic Alterations in Senescent Large-Vessel and Microvascular Endothelial Cells

Endothelial cell senescence likely plays a key role in age-associated vascular diseases. A close relationship between in vitro and in vivo senescence of endothelial cells has been established. Therefore, elucidating the structural and functional changes occurring during long-term cultures of endothelial cells would contribute to clarifying the pathogenesis of vascular disorders in the elderly. We investigated the effects of replicative senescence on the architecture of bovine aortic vs microvascular endothelial cells. A marked increase in cell area was observed in both cell types, whereas dramatic morphological alterations were detected in microvascular endothelial cells only. The latter also showed age-associated reorganization of the actin cytoskeleton. Finally, both aortic and microvascular endothelial cells lost their migratory response to basic fibroblast growth factor with age. Our results highlight dramatic structural and functional alterations in senescent endothelial cells. Such rearrangements might account for in vivo endothelial cell alterations involved in age-associated vascular dysfunction.     

肿瘤坏死因子alpha与子痫前期的关系

子痫前期是妊娠期特有疾病,是导致孕产妇及围生儿病死率的重要原因,其病因和发病机理仍未完全明确。目前,已被提出 和子痫前期的发生相关的因素包括遗传、氧化应激、异常滋养层细胞侵入、血管内皮细胞功能紊乱、营养缺乏、免疫缺陷等,其中 内皮细胞损伤导致的内皮细胞生理功能紊乱已经成为子痫前期病因学研究的热点。肿瘤坏死因子-alpha(tumor necrosis factor-alpha, TNF-alpha)在内皮细胞损害中发挥着重要作用,可能通过诱导炎性因子和血管内皮细胞黏附分子-1(VCAM-1)生成、抑制基质金属蛋 白酶(MMP)、影响血管活性物质、脂联素、瘦素和血管因子生成,介导子痫前期的发生。本文就TNF-琢与子痫前期发生的关系进行 综述。     

Rho GAPs and GEFs

Within blood vessels, endothelial cell–cell and cell–matrix adhesions are crucial to preserve barrier function, and these adhesions are tightly controlled during vascular development, angiogenesis, and transendothelial migration of inflammatory cells. Endothelial cellular signaling that occurs via the family of Rho GTPases coordinates these cell adhesion structures through cytoskeletal remodelling. In turn, Rho GTPases are regulated by GTPase-activating proteins (GAPs) and guanine nucleotide exchange factors (GEFs). To understand how endothelial cells initiate changes in the activity of Rho GTPases, and thereby regulate cell adhesion, we will discuss the role of Rho GAPs and GEFs in vascular biology. Many potentially important Rho regulators have not been studied in detail in endothelial cells. We therefore will first overview which GAPs and GEFs are highly expressed in endothelium, based on comparative gene expression analysis of human endothelial cells compared with other tissue cell types. Subsequently, we discuss the relevance of Rho GAPs and GEFs for endothelial cell adhesion in vascular homeostasis and disease.     

内皮祖细胞的生物学特性及其临床应用前景

内皮祖细胞（Endothelial Progenitor Cells,EPCs）是内皮细胞（endothelial cells,ECs）的前体细胞,即能分化为成熟ECs的祖细胞,它在血管内皮再生中发挥着重要作用。随着EPCs研究的深入,其在临床诊断、预后判断和各种缺血性疾病的治疗方面将会有广阔的应用前景。然而,关于EPCs的定义、来源、表面标记以及培养鉴定方法目前仍存在争议。     

Endothelial dysfunction as a cellular mechanism for vascular failure

The regulation of vascular tone, vascular permeability, and thromboresistance is essential to maintain blood circulation and therefore tissue environments under physiological conditions. Atherogenic stimuli, including diabetes, dyslipidemia, and oxidative stress, induce vascular dysfunction, leading to atherosclerosis, which is a key pathological basis for cardiovascular diseases such as ischemic heart disease and stroke. We have proposed a novel concept termed "vascular failure" to comprehensively recognize the vascular dysfunction that contributes to the development of cardiovascular diseases. Vascular endothelial cells form the vascular endothelium as a monolayer that covers the vascular lumen and serves as an interface between circulating blood and immune cells. Endothelial cells regulate vascular function in collaboration with smooth muscle cells. Endothelial dysfunction under pathophysiological conditions contributes to the development of vascular dysfunction. Here, we address the barrier function and microtubule function of endothelial cells. Endothelial barrier function, mediated by cell-to-cell junctions between endothelial cells, is regulated by small GTPases and kinases. Microtubule function, regulated by the acetylation of tubulin, a component of the microtubules, is a target of atherogenic stimuli. The elucidation of the molecular mechanisms of endothelial dysfunction as a cellular mechanism for vascular failure could provide novel therapeutic targets of cardiovascular diseases.     

The role of caveolin-1 in PCB77-induced eNOS phosphorylation in human-derived endothelial cells

Polychlorinated biphenyls (PCBs) may contribute to the pathology of atherosclerosis by activating inflammatory responses in vascular endothelial cells. Endothelial nitric oxide synthase (eNOS) is colocalized with caveolae and is a critical regulator of vascular homeostasis. PCBs may be proatherogenic by causing dysfunctional eNOS signaling. The objective of this study was to investigate the role of caveolin-1 in PCB-induced endothelial dysfunction with a focus on mechanisms associated with eNOS signaling. Cells derived from an immortalized human vascular endothelial cell line were treated with PCB77 to study nitrotyrosine formation through eNOS signaling. Phosphorylation studies of eNOS, caveolin-1, and kinases, such as Src, phosphatidylinositol 3-kinase (PI3K), and Akt, were conducted in cells containing either functional or small-interfering RNA-silenced caveolin-1 protein. We also investigated caveolin-1-regulated mechanisms associated with PCB-induced markers of peroxynitrite formation and DNA binding of NF-kappaB. Cellular exposure to PCB77 increased eNOS phosphorylation and nitric oxide production, as well as peroxynitrite levels. A subsequent PCB-induced increase in NF-kappaB DNA binding may have implications in oxidative stress-mediated inflammatory mechanisms. The activation of eNOS by PCB77 treatment was blocked by inhibitors of the Src/PI3K/Akt pathway. PCB77 also increased phosphorylation of caveolin-1, indicating caveolae-dependent endocytosis. Caveolin-1 silencing abolished both the PCB-stimulated Akt and eNOS phosphorylation, suggesting a regulatory role of caveolae in PCB-induced eNOS signaling. These findings suggest that PCB77 induces eNOS phosphorylation in endothelial cells through a Src/PI3K/Akt-dependent mechanism, events regulated by functional caveolin-1. Our data provide evidence that caveolae may play a critical role in regulating vascular endothelial cell activation and toxicity induced by persistent environmental pollutants such as coplanar PCBs.     

Proinflammatory Cytokines Induce Hyaluronan Synthesis and Monocyte Adhesion in Human Endothelial Cells through Hyaluronan Synthase 2 (HAS2) and the Nuclear Factor-κB (NF-κB) Pathway

Chronic inflammation is now accepted to have a critical role in the onset of several diseases as well as in vascular pathology, where macrophage transformation into foam cells contributes in atherosclerotic plaque formation. Endothelial cells (EC) have a critical function in recruitment of immune cells, and proinflammatory cytokines drive the specific expression of several adhesion proteins. During inflammatory responses several cells produce hyaluronan matrices that promote monocyte/macrophage adhesion through interactions with the hyaluronan receptor CD44 present on inflammatory cell surfaces. In this study, we used human umbilical chord vein endothelial cells (HUVECs) as a model to study the mechanism that regulates hyaluronan synthesis after treatment with proinflammatory cytokines. We found that interleukin 1β and tumor necrosis factors α and β, but not transforming growth factors α and β, strongly induced HA synthesis by NF-κB pathway. This signaling pathway mediated hyaluronan synthase 2 (HAS2) mRNA expression without altering other glycosaminoglycan metabolism. Moreover, we verified that U937 monocyte adhesion on stimulated HUVECs depends strongly on hyaluronan, and transfection with short interference RNA of HAS2 abrogates hyaluronan synthesis revealing the critical role of HAS2 in this process.