Antiangiogenic effect by SU5416 is partly attributable to inhibition of Flt-1 receptor signaling

Interaction between vascular endothelial growth factor (VEGF) and its cognate receptors, KDR/Flk-1 and Flt-1, of vascular endothelial cells is expected to induce an angiogenesis "switch" in tumors and other angiogenesis-associated diseases. SU5416, a selective inhibitor of the KDR/Flk-1 tyrosine kinase, is known to be a potent inhibitor of tumor angiogenesis. In this study, we first observed that SU5416 inhibited Flt-1 tyrosine kinase activity at similar doses, in addition to inhibiting KDR/Flk-1 tyrosine kinase activity in response to VEGF. SU5416 inhibited cell migration of human vascular endothelial cells expressing both Flt-1 and KDR in response to VEGF and also inhibited the cell migration in response to placenta growth factor (PIGF), a specific ligand for Flt-1. Chemotaxis of monocytes expressing only Flt-1 was also inhibited by SU5416 in a dose-dependent manner. Moreover, SU5416 was found to inhibit tyrosine kinase of Flt-1 in response to PIGF in vitro. And angiogenesis induced by PIGF in a Matrigel plug assay was inhibited by administration of SU5416. The antiangiogenic effects by this VEGF receptor-targeting compound appeared to be mediated through interference not only with KDR/Flk-1 but also with Flt-1. Cell migration of vascular endothelial cells and monocytic cells through Flt-1, thus, might play a key role in VEGF-induced tumor angiogenesis in concert with KDR/Flk-1.     

Trimetazidine ameliorates hindlimb ischaemic damage in type 2 diabetic mice

BackgroundIschaemia caused by lower extremity artery stenosis is the main cause of peripheral artery disease (PAD) in patients with diabetes. Trimetazidine (TMZ) has traditionally been used as an anti-ischaemic drug for coronary artery disease. The effect of TMZ on PAD in a diabetic animal model and the underlying molecular mechanisms remain unclear.MethodsThe db/db mice were challenged with femoral artery ligation (FAL), followed by TMZ treatment for 2 weeks. Scores on hindlimb ischaemia and function were evaluated. Histological and capillary density analyses of gastrocnemius were performed. The expression of vascular endothelial growth factor (VEGF) and myogenic regulators was also confirmed by Western blotting. We also detected serum intercellular adhesion molecule 1 (ICAM-1) level through ELISA.ResultsDiabetic mice exhibited limb ulceration and motor dysfunction after FAL while TMZ-treated db/db mice exhibited milder ischaemic impairment. Furthermore, decreased capillary density in the gastrocnemius muscles of ischaemic hindlimb and reduced expressions of VEGF, myogenic markers, and serum ICAM-1 could be partially reversed by TMZ treatment.ConclusionTMZ may alleviate hindlimb ischaemic damage in db/db mice, at least partly, through enhancing angiogenesis and promoting myogenesis in ischaemia region.

Key messages

• TMZ intervention could alleviate hindlimb ischaemic damage in db/db mice.
• TMZ intervention could enhance angiogenesis and stimulate myogenesis in ischaemia region.

     

Acetylcholinesterase inhibitors attenuate angiogenesis

Donepezil {(RS)-2-[(1-benzyl-4-piperidyl)methyl]-5,6-dimethoxy-2,3-dihydroinden-1-one} is a reversible acetylcholinesterase inhibitor and used for treatment of patients with AD (Alzheimer's disease). Recent studies showed that treatment with donepezil reduced production of inflammatory cytokines in PBMCs (peripheral blood mononuclear cells). It was also reported that muscle-derived inflammatory cytokines play a critical role in neovascularization in a hindlimb ischaemia model. We sought to determine whether donepezil affects angiogenesis. A hindlimb ischaemia model was created by unilateral femoral artery ligation. Blood flow recovery examined by laser Doppler perfusion imaging and capillary density by immunohistochemical staining of CD31-positive cells in the ischaemic hindlimb were significantly decreased in donepezil- and physostigmine-treated mice compared with control mice after 2 weeks. Donepezil reduced expression of IL (interleukin)-1β and VEGF (vascular endothelial growth factor) in the ischaemic hindlimb. Intramuscular injections of IL-1β to the ischaemic hindlimb reversed the donepezil-induced VEGF down-regulation and the anti-angiogenic effect. Hypoxia induced IL-1β expression in C2C12 myoblast cells, which was inhibited by pre-incubation with ACh (acetylcholine) or LY294002, a PI3K (phosphoinositide 3-kinase) inhibitor. Donepezil inhibited phosphorylation of Akt [also known as PKB (protein kinase B)], a downstream kinase of PI3K, in the ischaemic hindlimb. These findings suggest that cholinergic stimulation by acetylcholinesterase inhibitors suppresses angiogenesis through inhibition of PI3K-mediated IL-1β induction, which is followed by reduction of VEGF expression. Acetylcholinesterase inhibitor may be a novel anti-angiogenic therapy.     

电刺激改善下肢缺血及促进骨骼肌血管生成的实验研究

目的　观察电刺激对后肢缺血大鼠VEGF及受体FLK/KDR的调节作用。方法　采用SD大鼠股浅动脉结扎法制备后肢缺血模型 ,应用RT PCR和免疫组化方法检测电刺激对后肢缺血大鼠VEGFmRNA和蛋白表达的影响 ,应用Westernblot和免疫荧光测定FLK 1表达。结果　刺激频率为 2 5Hz ,强度为 0 .3mA ,不引起肌肉收缩。缺血模型建立 7d后连续电刺激 7d ,VEGFmRNA的表达刺激组比非刺激组增加 3倍 (2 .5 8对 0 .93,P <0 .0 1) ,VEGF蛋白增加两倍 (0 .48对 0 .2 4,P <0 .0 1)。FLK 1也有明显增加。结论　电刺激可促进后肢缺血大鼠VEGF和FLK 1/KDR的表达 ,从而实现非分子的治疗性血管生成作用     

外阴白色病变组织中血管内皮生长因子受体1和2的表达

目的检测血管内皮生长因子受体1和2（VEGF受体Flt-1与KDR／Flk-1）在外阴白色病变组织中的表达水平,探讨其在外阴白色病变发病的意义。方法应用免疫组织化学方法对39例外阴白色病变组织中Fit-1和KDR／Flk-1的表达情况进行检测,并以11例正常外阴皮肤组织作为对照,了解其相关性。结果应用直线相关软件对Flt-1与KDR／Flk-1阳性表达情况进行统计分析发现,两者之间存在一定正相关（r=0．488,P=0．002）。结论外阴白色病变皮损中VEGF受体Flt-1与KDR／Flk-1的表达异常,可能是导致病变的原因之一。     

A synthetic small molecule, ONO-1301, enhances endogenous growth factor expression and augments angiogenesis in the ischaemic heart

It has been shown previously that administration of angiogenic growth factors as genes or proteins can augment collateral growth in ischaemic tissues. In the present study, we have investigated the effect of ONO-1301, a synthetic prostacyclin agonist with thromboxane-synthase-inhibitory activity, on expression of endogenous growth factors and angiogenesis. ONO-1301 induced secretion of HGF (hepatocyte growth factor) and VEGF (vascular endothelial growth factor) from cultured normal human dermal fibroblasts in a dose-dependent manner. Dibutyryl cAMP, an analogue of cAMP, and forskolin, an adenylate cyclase activator, mimicked the effect of ONO-1301. Conversely, Rp-cAMP (adenosine 3',5'-cyclic monophosphorothioate), an inhibitor of cAMP, partially inhibited the effect of ONO-1301, suggesting that cAMP mediated the effect of ONO-1301 in up-regulating the expression of HGF and VEGF, at least in part. ONO-1301 promoted tube-like formation by HUVECs (human umbilical vein endothelial cells) when co-cultured with fibroblasts, and the angiogenic effect of ONO-1301 was abrogated by administration of a neutralizing antibody against HGF or VEGF. To generate a slow-releasing form of ONO-1301, ONO-1301 was mixed with poly(DL-lactic-co-glycolic acid). The slow-releasing form of ONO-1301 was injected directly into the ischaemic myocardium of mice immediately after ligation of the left anterior descending artery. The slow-releasing form of ONO-1301 up-regulated HGF and VEGF expression and increased capillary density in the border zone (342.7+/-29.7 capillaries/mm(2) in controls compared with 557.2+/-26.7 capillaries/mm(2) in treated animals; P<0.01) at 7 days. The slow-releasing form of ONO-1301 ameliorated left ventricular enlargement after 28 days and improved survival rate. In conclusion, our results indicate that ONO-1301 up-regulated endogenous growth factors and promoted angiogenesis in response to acute ischaemia. Therefore ONO-1301 might have a therapeutic potential in treating ischaemic diseases.     

Extracorporeal shock wave therapy ameliorates hindlimb ischemia in rabbits

We have recently demonstrated that the low-energy extracorporeal cardiac shock wave (SW) therapy improves myocardial perfusion and cardiac function in a porcine model of chronic myocardial ischemia and also ameliorates myocardial ischemia in patients with severe coronary artery disease. The present study was designed to examine whether our SW therapy also is effective to ameliorate hindlimb ischemia in rabbits. Hindlimb ischemia was made by surgical excision of the entire unilateral rabbit femoral artery. One week after the operation, we performed the SW (n = 9) or sham-therapy (n = 9) to the ischemic region 3 times a week for 3 weeks. Three weeks after the SW therapy, the development of collateral arteries, the flow ratio of the ischemic/non-ischemic common iliac arteries, the blood pressure ratio of the ischemic/non-ischemic hindlimb, and the capillary density in the ischemic muscles were all significantly increased in the SW group compared with the control group, indicating that the SW therapy induced therapeutic angiogenesis. Importantly, no adverse effect, such as muscle damage, hemorrhage, or thrombosis, was noted with the therapy. Finally, we examined the role of endothelial nitric oxide synthesis (eNOS) and vascular endothelial growth factor (VEGF) in the mechanisms of SW-induced angiogenesis on day 28. The expression levels of eNOS and VEGF proteins in ischemic hindlimb muscles tended to be increased in the SW group compared with the control group. These results suggest that our low-energy SW therapy also is effective and safe for the treatment of peripheral artery disease.     

当归注射液对大鼠脑缺血再灌注损伤后VEGF表达的影响

目的观察大鼠局灶性脑缺血再灌注损伤后血管内皮生长因子(VEGF)在不同时间点的表达及当归注射液对其表达的影响.方法线栓法制作脑缺血再灌注损伤模型,雄性Wistar大鼠随机分为正常对照组、缺血损伤组和当归治疗组,采用免疫组织化学和RT-PCR方法观察VEGF表达变化.结果免疫组织化学显示缺血损伤组和当归治疗组大鼠VEGF蛋白表达均在24 h达到高峰后减弱;RT-PCR显示缺血损伤组VEGF mRNA在3 h开始表达增强,6 h达到高峰,后很快降低,至第7天恢复到基线水平;当归治疗组VEGF mRNA在3 d达到高峰后缓慢降低,至第7天仍有大量表达,且各时间点VEGF的表达比缺血损伤组明显增加.结论当归可促进局灶性脑缺血再灌注损伤后VEGF的表达.     

Vascular endothelial growth factor is an important determinant of sepsis morbidity and mortality

Sepsis, the systemic inflammatory response to infection, is a leading cause of morbidity and mortality. The mechanisms of sepsis pathophysiology remain obscure but are likely to involve a complex interplay between mediators of the inflammatory and coagulation pathways. An improved understanding of these mechanisms should provide an important foundation for developing novel therapies. In this study, we show that sepsis is associated with a time-dependent increase in circulating levels of vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) in animal and human models of sepsis. Adenovirus-mediated overexpression of soluble Flt-1 (sFlt-1) in a mouse model of endotoxemia attenuated the rise in VEGF and PlGF levels and blocked the effect of endotoxemia on cardiac function, vascular permeability, and mortality. Similarly, in a cecal ligation puncture (CLP) model, adenovirus-sFlt-1 protected against cardiac dysfunction and mortality. When administered in a therapeutic regimen beginning 1 h after the onset of endotoxemia or CLP, sFlt peptide resulted in marked improvement in cardiac physiology and survival. Systemic administration of antibodies against the transmembrane receptor Flk-1 but not Flt-1 protected against sepsis mortality. Adenovirus-mediated overexpression of VEGF but not PlGF exacerbated the lipopolysaccharide-mediated toxic effects. Together, these data support a pathophysiological role for VEGF in mediating the sepsis phenotype.     

Combined cord blood stem cells and gene therapy enhances angiogenesis and improves cardiac performance in mouse after acute myocardial infarction

BACKGROUND: Gene and stem cell therapies hold promise for the treatment of ischaemic cardiovascular disease. However, combined stem cell and angiogenic growth factor gene therapy for acute ischaemic myocardium has not been previously reported. This study hypothesized that combined stem cell and gene therapy would not only augment new vessels formation but also improve myocardial function in acute ischaemic myocardium. METHODS: Human angiopoietin-1 (Ang1) cDNA and VEGF(165) cDNA were ligated into AAV vector. The purified CD34(+) cells were obtained from human umbilical cord blood samples. Cord blood CD34(+) cells were transduced with AAV vector encoding either the human Ang1 (AAV-Ang1) or VEGF(165) (AAV-VEGF) cDNA alone, or both (AAV-Ang1 plus VEGF). Immediately after ligation of the left anterior descending coronary artery in male SCID mice, culture-expanded CD34(+) cells transduced with AAV-Ang1, AAV-VEGF or AAV-Ang1 plus VEGF were injected intramyocardially at the left anterior free wall. RESULTS: Western blot showed that Ang1 and VEGF protein expressions were enhanced in the CD34(+)cells transduced with AAV-Ang1 and AAV-VEGF, respectively. Infarct size significantly decreased and capillary density significantly increased after treatment with CD34(+)/AAV-Ang1 plus VEGF when compared with treatment by CD34(+) only. Combined therapy with CD34(+) and AAV-Ang1, CD34(+) and AAV-VEGF, CD34(+) and AAV-Ang1 plus VEGF, all showed significantly higher cardiac performance in echocardiography than the therapy with CD34(+) alone 4 weeks after myocardial infarction. CONCLUSIONS: Combined therapy with human umbilical cord blood CD34(+) cells and both Ang1 and VEGF genes reduced infarct size, attenuated the progression of cardiac dysfunction and increased capillary density in acute myocardial infarction in mice.     

Angiogenesis is confined to the transient period of VEGF expression that follows adenoviral gene delivery to ischemic muscle

Therapeutic angiogenesis involves the introduction of exogenous growth factor proteins and genes into ischemic tissues to augment endogenous factors and promote new vessel growth. Positive results from studies in animal models of peripheral arterial disease (PAD) and coronary artery disease over the past decade have supported the implementation of clinical trials testing vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) proteins and genes. Although several clinical trials reported positive results, others have been disappointing and results of a recent Phase II trial of VEGF delivered by adenovirus (the RAVE trial) were negative. It has been suggested that the duration of gene expression following delivery by adenovirus may be insufficient to produce stable vessels. Here we present direct evidence in support of this using the rabbit ischemic hindlimb model injected with adenovirus encoding VEGF165. Immunohistology indicated an activation of endothelial cell cycling and proliferation 2-3 days after VEGF delivery that coincided closely with transient VEGF expression. Ki-67-positive endothelial nuclei were evident at high levels in capillaries and large vessels in muscles from treated animals. Angiography indicated increased density of both large and small vessels in Ad-VEGF-treated muscle at 1 week, but no significant differences thereafter. The early burst of endothelial proliferation was accompanied by increased nuclear fragmentation and condensation in VEGF-treated muscles, suggesting coincident apoptosis. No further endothelial cell proliferation took place after 1 week although there was still evidence of apoptosis. The results suggest that angiogenesis is confined to the short period of VEGF expression produced by adenovirus and early gains in collateralization rapidly regress to control levels when VEGF production ceases.     

Aspirin inhibits endothelial nitric oxide synthase (eNOS) and Flk-1 (vascular endothelial growth factor receptor-2) prior to rat colon tumour development

Formation of blood vessels is a fundamental element in the control of tumour growth in which vascular endothelial growth factor (VEGF) and nitric oxide (NO) have been demonstrated to be involved. Our aim was to analyse whether changes in the expression of endothelial NO synthase (eNOS) and VEGF in colonic tissue could be detected early and even before the identification of colon tumour-associated morphological modifications in azoxymethane-treated rats. We studied further whether aspirin treatment changed these parameters. An increased expression of both eNOS and VEGF in colonic tissue from azoxymethane-treated rats compared with that from control rats was found. Aspirin treatment (10 mg/kg of body weight per day) reduced eNOS expression, but failed to modify the expression of VEGF in the colonic tissue of azoxymethane-treated rats. No evidence of aberrant crypt formation or changes in the number of blood vessels were observed in the colon of any of the animals studied. Expression of the VEGF receptor Flk-1, but not Flt-1, was increased in colonic tissue of azoxymethane-treated rats compared with control rats. The expression of Flk-1 was mainly localized in the epithelial cells, particularly in the lower part of the crypt. Aspirin treatment reduced Flk-1 expression in both control and azoxymethane-treated rats. Caspase-3 activity, which has been considered as an apoptotic index, was almost undetectable in azoxymethane-treated rats. Aspirin treatment stimulated caspase-3 activity. Overexpression of eNOS, VEGF and its receptor Flk-1 occurred early after azoxymethane administration in rat colonic tissue, even before morphological changes associated with tumour generation were observed, and aspirin prevented the overexpression of both eNOS and VEGF receptor Flk-1.     

Transgenic expression of human complement regulators reduces skeletal muscle ischaemia/reperfusion injury in mice

This study aimed to explore the hypothesis that activated complement components contribute significantly to I/R (ischaemia/reperfusion) injury in skeletal muscle. After 50, 70 and 90 min of tourniquet ischaemia and 24 h of reperfusion, viability of the medial gastrocnemius muscle in CBA-C57BL/6 wild-type mice, assessed histochemically by reduction of NBT (Nitro Blue Tetrazolium) dye, was 60, 21 and 8% respectively. Skeletal muscle viability after 70 min of ischaemia and 24 h of reperfusion in transgenic mice expressing a combination of human CD46, CD55 and CD59, all inhibitors of complement activation, was 45% compared with 24% in ischaemic reperfused wild-type mice (P=0.008; n=6 per group). Muscle from sham-treated transgenic mice and wild-type littermates had no significant loss of viability relative to normal contralateral gastrocnemius muscle. A significant reduction in myeloperoxidase activity (a measure of neutrophil infiltration), xanthine oxidase activity (a source of free radicals) and water content (a measure of oedema) was observed in ischaemic reperfused muscle from transgenic mice compared with ischaemic reperfused wild-type muscle (P<0.05). Haematoxylin and eosin-stained histological sections also showed less damage and less apparent leucocyte infiltration in muscles from ischaemic reperfused transgenic mice than those from wild-type animals given the same degree of injury. Muscles from sham-treated transgenic and wild-type controls were almost identical with normal muscle. It is concluded that complement activation contributes to the pathogenesis of I/R injury in murine skeletal muscle, resulting in increased neutrophil infiltration into the injured muscle, increased free radical production and vascular permeability during reperfusion, and a net detrimental effect on muscle viability.     

评估血管内皮细胞生长因子及其受体在大鼠大脑中动脉短暂闭塞再灌注后对缺血脑组织的保护作用

目的研究血管内皮细胞生长因子(VEGF)及其受体Flt-1在大鼠短暂大脑中动脉闭塞(MCAO)再灌注后不同时点表达的变化,探讨VEGF对缺血脑组织的保护作用。方法采用栓线法MCAO动物模型,通过免疫组化方法观察VEGF及Flt-1的表达情况。结果VEGF及FIt-1免疫阳性细胞主要在神经元、神经胶质细胞及内皮细胞中表达。结论这些发现表明短暂MCAO后VEGF及Flt-1的表达上调,提示可能VEGF及Flt-1表达的增加对促进缺血周边区血供的恢复有重要作用。     

Increased expression of VEGF following exercise training in patients with heart failure

BACKGROUND AND AIMS: During the last decades several angiogenic factors have been characterized but so far it is unknown whether local muscle exercise training increases the expression of these factors in patients with moderate heart failure. Expression of the major putative angiogenic factor vascular endothelial growth factor (VEGF) at the level of messenger RNA (mRNA) and/or protein was therefore studied before and after 8 weeks of training in patient with chronic heart failure. METHODS: VEGF mRNA and protein concentrations were determined in skeletal muscle biopsies before and after 8 weeks of one-legged knee extension training in patients with chronic heart failure (New York Heart Association II-III). RESULTS: Exercise training increased the citrate synthase activity and peripheral exercise capacity by 46% and 36%, respectively, in parallel with a two-fold increase in VEGF at both the mRNA (P = 0.03) and protein (P = 0.02) levels CONCLUSION: The increase in VEGF gene expression in response to exercise training indicates VEGF to be one possible mediator in exercise-induced angiogenesis and may therefore regulate an important and early step in adaptation to increased muscle activity in patient with chronic heart failure.     

运动训练对大鼠损伤远端脊髓及骨骼肌血管内皮生长因子表达的影响

目的:明确运动训练对大鼠损伤远端脊髓及骨骼肌血管内皮生长因子(VEGF)表达的影响,探讨运动促脊髓损伤功能恢复的机制。方法:成年雌性SD大鼠24只,采用改良Allen撞击法制作T9不完全性脊髓损伤模型。术后随机分为损伤后1d组、1周组、训练组(术后1周开始训练,共4周)、对照组(未行训练)。分别在损伤前、损伤后第1、2、3、4及5周时采用Basso-Beattie-Bresnahan(BBB)评分评定运动功能。取损伤后1d、1周,对照组及训练组大鼠L5—S1节段脊髓及腓肠肌新鲜组织,采用RT-PCR及Westernblot法测定VEGFmRNA及蛋白表达。结果:①对照组与训练组BBB评分均较损伤后1周、2周明显提高,但训练组较对照组增加更为显著(P<0.05);②训练组脊髓及腓肠肌VEGFmRNA及蛋白表达较对照组、损伤后1d、1周组显著增加(P<0.05);对照组与损伤1周组、1d组比较脊髓及腓肠肌内VEGF表达差异无显著性(P>0.05);但1周组脊髓内VEGF较1d组表达增加(P<0.05),而腓肠肌内VEGF表达较1d组降低(P<0.05)。结论:运动训练能有效诱导脊髓损伤大鼠远端脊髓及骨骼肌VEGF表达,促进运动功能恢复。     

VEGF antagonism reduces edema formation and tissue damage after ischemia/reperfusion injury in the mouse brain

VEGF is mitogenic, angiogenic, and a potent mediator of vascular permeability. VEGF causes extravasation of plasma protein in skin bioassays and increases hydraulic conductivity in isolated perfused microvessels. Reduced tissue oxygen tension triggers VEGF expression, and increased protein and mRNA levels for VEGF and its receptors (Flt-1, Flk-1/KDR) occur in the ischemic rat brain. Brain edema, provoked in part by enhanced cerebrovascular permeability, is a major complication in central nervous system pathologies, including head trauma and stroke. The role of VEGF in this pathology has remained elusive because of the lack of a suitable experimental antagonist. We used a novel fusion protein, mFlt(1-3)-IgG, which sequesters murine VEGF, to treat mice exposed to transient cortical ischemia followed by reperfusion. Using high-resolution magnetic resonance imaging, we found a significant reduction in volume of the edematous tissue 1 day after onset of ischemia in mice that received mFlt(1-3)-IgG. 8-12 weeks after treatment, measurements of the resultant infarct size revealed a significant sparing of cortical tissue. Regional cerebral blood flow was unaffected by the administration of mFlt(1-3)-IgG. These results demonstrate that antagonism of VEGF reduces ischemia/reperfusion-related brain edema and injury, implicating VEGF in the pathogenesis of stroke and related disorders.