血管平滑肌细胞表型转换对动脉粥样硬化的作用研究进展

在动脉粥样硬化的进程中,血管中膜平滑肌细胞发生表型转换、迁移、增殖,进入血管内膜,参与动脉粥样硬化斑块纤维帽及新生血管的生成。本文就当前关于血管平滑肌细胞表型转换对动脉粥样硬化作用的研究进展作一综述。     

Gender-related differences in vascular smooth muscle cell proliferation: implications for prevention of atherosclerosis.

Premenopausal women have a significant reduction in coronary artery disease compared to age-matched males. Little is known about the mechanism underlying this cardioprotective effect of estrogen. Contradictory evidence has been published and our lack of basic understanding of hormone interactions and bioavailability of different estrogens prevents definitive interpretation of these data. We demonstrate gender-specific effects in the proliferation of coronary artery vascular smooth muscle cells obtained from a sexually mature animal model. Vascular smooth muscle cells are an integral component of the atherosclerotic plaque, and inhibition of cell proliferation by estrogen may be one mechanism by which estrogen exerts its cardioprotective effect. Various types of estrogen may also have different mechanistic actions on the vascular system. No differences are demonstrated in overall estradiol binding in vascular smooth muscle cells obtained from male or female animals: however, differences in c-jun, c-fos and TIEG gene expression were gender related. Inhibition of vascular smooth muscle cell proliferation may have important implications in the prevention of atherosclerotic disease and these studies may provide evidence for the cardioprotective effect of estrogen.     

Arterial smooth muscle cell heterogeneity: implications for atherosclerosis and restenosis development

During atheromatous plaque formation or restenosis after angioplasty, smooth muscle cells (SMCs) migrate from the media toward the intima, where they proliferate and undergo phenotypic changes. The mechanisms that regulate these phenomena and, in particular, the phenotypic modulation of intimal SMCs have been the subject of numerous studies and much debate during recent years. One view is that any SMCs present in the media could undergo phenotypic modulation. Alternatively, the seminal observation of Benditt and Benditt that human atheromatous plaques have the features of a monoclonal or an oligoclonal lesion has led to the hypothesis that a predisposed, medial SMC subpopulation could play a crucial role in the production of intimal thickening. The presence of a distinct SMC population in the arterial wall implies that under normal conditions, SMCs are phenotypically heterogeneous. The concept of SMC heterogeneity is gaining wider acceptance, as shown by the increasing number of publications on this subject. In this review, we discuss the in vitro studies that demonstrate the presence of distinct SMC subpopulations in arteries of various species, including humans. Their specific features and their regulation will be highlighted. Finally, the relevance of an atheroma-prone phenotype to intimal thickening formation will be discussed.     

The epigenetic phenotypic switch of vascular smooth muscle cells involved in atherosclerosis

Atherosclerosis is a progressive and chronic inflammatory response to pathological fatty deposits in the arterial wall. The resulting disease spectrum ranges from angina pectoris, myocardial infarction, and sudden cardiac death to peripheral vascular disease and stroke. Vascular smooth muscle cells (VSMCs) are one of the major cell types contributing to neointimal formation of the affected arteries leading to atherosclerosis and in-stent restenosis. The severity of this disease has been linked to the cellular plasticity of VSMCs. At least two phenotypic states have been described: a contractile state, in which cells have increased cytoplasmic myofilaments and are involved in maintaining vascular tone, and a synthetic state, in which cells have relatively few contractile elements but in contrast upregulate the machinery required for protein synthesis and extracellular matrix secretion. In healthy vessels, VSMC can switch between these states, but regulation of this switch is disrupted in atherosclerosis and thought to contribute to the progression of disease.Our aim was to characterise the epigenetic signature of these VSMC phenotypes to better understand the pathophysiology of atherosclerosis. We used primary mouse VSMC from aorta and characterised the phenotypic changes occurring in response to transforming growth factor β, which promote the contractile phenotype, and platelet-derived growth factor that is involved in VSMC proliferation and migration. First we showed that VSMC develop into a contractile or synthetic phenotype in response to growth factor stimulation. We then characterised the gene expression profile and pattern of epigenetic histone modifications of VSMC selective genes. This identified novel histone modification proteins which could be involved in promoting the atherosclerotic phenotype. We have also shown that key VSMC selective genes are regulated through different epigenetic gene regulation mechanisms. This cell model will be used to investigate the molecular pathways involved in VSMC phenotypic regulation and identify novel candidates for future therapeutic intervention.FundingUK National Health Service and British Heart Foundation.     

Angiotensin II-induced C-reactive protein generation: inflammatory role of vascular smooth muscle cells in atherosclerosis

BACKGROUND: As the major target of Angiotensin II (Ang II) in the vessel wall, vascular smooth muscle cells (VSMCs) are a tentative source to produce C-reactive protein (CRP). However, it is largely unknown if Ang II is capable of inducing CRP production in VSMCs. METHODS AND RESULTS: Ang II induced a concentration-dependent release of CRP in cultured rat VSMCs as measured by sandwich ELISA. Real-time PCR revealed that Ang II significantly upregulated CRP mRNA level in vitro. Ang II-induced CRP generation in aortic VSMCs was also investigated using double-labeled fluorescent immunohistochemistry and in situ hybridization in subchronic Ang II administration in rats. Losartan but not PD123319 markedly blocked the Ang II-induced CRP production in cultured VSMCs, suggesting that such effect was mediated via Ang II type 1 receptor. Further, Western blotting analysis showed that mitogen-activated protein kinase (MAPK) activation was obligatory in Ang II-induced CRP production, since specific MAPK inhibitor PD098059 almost abolished the action. CONCLUSIONS: We identified that Ang II is capable of inducing CRP generation in VSMCs, in which Ang II type 1 receptor followed by MAPK signal pathway is involved. It strengthened the role of Ang II-induced CRP production by VSMCs in the inflammatory process in atherosclerosis.     

The good smooth muscle cells in atherosclerosis

The formation of a fibrous cap made up of intimal smooth muscle cells and connective tissue is part of an attempt by the vessel wall to encapsulate the toxic products accumulating in the necrotic core of atherosclerotic lesions, and should be viewed as a beneficial healing response. In this review, we discuss the development of the intima and the potential origins of the intimal smooth muscle cell with a focus on the unique properties of these cells. We further discuss the role of intimal smooth muscle cells in plaque rupture and in wound healing, and the relationship of wound healing to the loss of lumen that occurs with development of advanced atherosclerotic lesions.     

Vascular smooth muscle cells and calcification in atherosclerosis

Vascular calcification is a prominent feature of atherosclerosis but the mechanisms underlying vascular calcification are still obscure. Since bone-associated proteins such as osteonectin, osteocalcin, and matrix Gla protein have been detected in calcified vascular tissues, calcification has been considered to be an organized, regulated process similar to mineralization in bone tissue. Vascular smooth muscle cells (VSMCs) are currently considered to be responsible for the formation of vascular calcifications. Apoptosis of VSMCs appears to be a key factor in this process, while other factors including cell-cell interactions (macrophages and VSMCs), lipids, and plasma inorganic phosphate levels modulate the calcification process. The focus of this review is on the role of VSMCs in the development of calcifications in atherosclerotic plaques.     

Monocyte prostaglandins inhibit procollagen secretion by human vascular smooth muscle cells: implications for plaque stability

Extracellular matrix remodelling occurs during atherosclerosis dictating the structure of the plaque and thus the resistance to rupture. Monocytes and macrophages are believed to play a role in this remodelling. In the present study, filter-separated co-culture has been used to study the effect of monocytes on procollagen turnover by human vascular smooth muscle cells (VSMC). In this system, freshly isolated human peripheral blood monocytes inhibited procollagen secretion from VSMC without affecting either degradation of procollagen, or DNA synthesis by the VSMC. Insertion of a 12 kDa dialysis membrane between the two cell types and treatment with indomethacin showed that the inhibitory factor was of low molecular weight and was cyclooxygenase-dependent. Pre-incubation of each cell type with indomethacin demonstrated that monocyte, but not VSMC cyclooxygenase was required. Thus, the inhibitory effect on procollagen secretion was due, most likely, to monocyte prostaglandins. Neither inhibition of thromboxane synthetase, nor blocking IL-1 activity, reduced the inhibitory activity. Addition of prostaglandins PGE1, PGE2 and PGF2alpha to VSMC cultures caused a reduction in procollagen secretion which was equivalent to, but was not additive with, the maximal effect achieved by monocytes. Monocytes and macrophages are a major source of prostaglandins and these molecules are likely to play an important role in collagen turnover within lesions.     

Chronic apoptosis of vascular smooth muscle cells accelerates atherosclerosis and promotes calcification and medial degeneration

Vascular smooth muscle cell (VSMC) accumulation is implicated in plaque development. In contrast, VSMC apoptosis is implicated in plaque rupture, coagulation, vessel remodeling, medial atrophy, aneurysm formation, and calcification. Although VSMC apoptosis accompanies multiple pathologies, there is little proof of direct causality, particularly with the low levels of VSMC apoptosis seen in vivo. Using a mouse model of inducible VSMC-specific apoptosis, we demonstrate that low-level VSMC apoptosis during either atherogenesis or within established plaques of apolipoprotein (Apo)E(-/-) mice accelerates plaque growth by two-fold, associated with features of plaque vulnerability including a thin fibrous cap and expanded necrotic core. Chronic VSMC apoptosis induced development of calcified plaques in younger animals and promoted calcification within established plaques. In addition, VSMC apoptosis induced medial expansion, associated with increased elastic lamina breaks, and abnormal matrix deposition reminiscent of cystic medial necrosis in humans. VSMC apoptosis prevented outward remodeling associated with atherosclerosis resulting in marked vessel stenosis. We conclude that VSMC apoptosis is sufficient to accelerate atherosclerosis, promote plaque calcification and medial degeneration, prevent expansive remodeling, and promote stenosis in atherosclerosis.     

Influence of atherosclerosis on vascular responsiveness in isolated rabbit vascular smooth muscle

Summary Coronary arteries and aortic rings were isolated from rabbits fed either a control diet or a high cholesterol (1 to 2%) diet for 8 to 11 weeks and studied for their vasoactive properties to a variety of vasoconstrictor and vasodilator agents. Perfused coronary arteries without intact endothelium constrict markedly to a thromboxane A₂ agonist (i.e., carbocyclic thromboxane A₂, CTA₂) and dilate markedly to iloprost, a prostacyclin analog. No differences occurred between the coronary arteries isolated from control or atherosclerotic rabbits. Additional studies were conducted on rabbit aortic vascular smooth muscle rings containing functionally intact endothelium and in rings denuded of their endothelium. Acetylcholine (20 to 2000 ng/ml) neither constricted nor dilated control aortic rings without endothelium, and markedly dilated aortic rings with intact endothelium in a concentration dependent manner. In atherosclerotic aortic rings, acetylcholine constricted preparations without endothelium, and dilated rings with endothelium to a much lesser extent than that observed in control rings. Similar reductions in responsiveness occurred with adenosine diphosphate (ADP), another endothelium-dependent vasodilator, but not with iloprost, a nonendothelium-dependent dilator. No differences were observed in constrictor responses to norepinephrine. Aortae from atherosclerotic rabbits produced less prostacyclin in response to arachidonic acid than control aortae. These data point to an important role of the endothelium in modulating the vascular response to vasodilators in atherosclerotic rabbit arterial vessels.This study was supported in part by Research Grant No. HL-25575 from the National Heart Lung and Blood Institute of the NIH.John A. Osborne is a Predoctoral Fellow of the Foerderer Foundation. Jian-zhong Sun is a WHO Postdoctoral Fellow.     

Smoothelin in vascular smooth muscle cells

Smoothelin-A and -B have only been found in fully differentiated contractile smooth muscle cells. They are increasingly used to monitor the smooth muscle cell differentiation process to a contractile or synthetic phenotype. Vascular-specific smoothelin-B is the first smooth muscle cell marker that disappears when vascular tissues are compromised, for example, in atherosclerosis or restenosis. Recently obtained data show that smoothelin deficiency results in a considerable loss of contractile potential and hence in impaired smooth muscle function and suggest that smoothelins are part of the contractile apparatus.     

Decreased caveolin-1 in atheroma: loss of antiproliferative control of vascular smooth muscle cells in atherosclerosis

OBJECTIVE: Proliferation of vascular smooth muscle cells (VSMC) is involved in the pathogenesis of primary atherosclerosis and restenosis after angioplasty. On the background of the antiproliferative activities of caveolin-1, the present study focused on the expression of caveolin-1 in proliferating VSMC of human atheroma. METHODS: VSMC were isolated from wild-type (Wt) and caveolin-1 knockout mice (Cav-/-). Proliferation of Wt-VSMC after supplementation of serum or Cav-/-VSMC after adenoviral overexpression of caveolin-1 was documented by either Western blot analysis of the cyclin-dependent kinase (Cdk) inhibitor p27kip1 and the proliferating cell nuclear antigen (PCNA) or BrdU incorporation. Using immunohistochemistry the proliferation of VSMC derived from atheroma of human carotid vessels as well as the expression of caveolin-1 in these cells were investigated ex vivo. RESULTS: Supplementation of serum to Wt-VSMC resulted in an augmented cell cycle entry and a concomitant decrease of caveolin-1 expression. Inversely, adenoviral overexpression of caveolin-1 in Cav-/-VSMC inhibited cellular proliferation. Corresponding to these in vitro data, the expression of caveolin-1 was significantly decreased in proliferating VSMC of human atheroma. CONCLUSION: The proliferation of VSMC in vitro and in human atheroma is associated with a decrease of caveolin-1 expression. These data suggest that the loss of antiproliferative control by caveolin-1 plays a pivotal role in VSMC proliferation in atherosclerosis.     

激活瞬时受体电位香草醛亚家族1改善平滑肌源性泡沫细胞形成机制研究

目的探讨瞬时受体电位香草醛亚家族1(TRPV1)在血管平滑肌细胞(VSMC)泡沫化过程中的作用及可能的机制。方法将野生型C57BL/6J雄性小鼠来源主动脉VSMC不加任何试剂刺激作为对照组,另将野生型C57BL/6J雄性小鼠和Toll样受体(TLR4)基因敲除(TLR4-/-)雄性小鼠来源主动脉VSMC使用氧化型低密度脂蛋白(oxLDL)80μg/ml刺激72h,建立oxLDL细胞模型,依次作为oxLDL组、辣椒素组(造模前预先用辣椒素50μmol/ml刺激VSMC 12h)和TLR4-/-组,每组5例。采用油红O染色观察VSMC内脂质聚积情况;检测VSMC内胆固醇、TRPV1、TLR4蛋白及炎性因子白细胞介素6(IL-6)和TNF-α表达。结果与对照组比较,oxLDL组VSMC泡沫化程度、胆固醇水平明显升高,TLR4及其介导的IL-6[(44.03±3.76)ng/L vs (25.64±4.84)ng/L]、TNF-α表达[(155.64±13.32)ng/L vs (89.86±9.18)ng/L]明显升高,差异有统计学意义(P<0.05),而TLR4-/-组和辣椒素组VSMC泡沫化程度、胆固醇水平、TLR4及其介导的IL-6、TNF-α表达与对照组比较,差异无统计学意义(P>0.05);与oxLDL组比较,辣椒素组VSMC中TRPV1蛋白表达明显上调,同时伴随VSMC泡沫化程度、胆固醇水平、TLR4及其介导的IL-6、TNF-α表达明显下调,差异有统计学意义(P<0.05)。结论激活TRPV1可通过干扰TLR4介导的炎性反应抑制VSMC泡沫化。