Angiopoietin-1 and regulation of vascular permeability

Angiopoietin-1 (Ang-1) is a newly-found endothelium-specific proangiogenic factor and it had been proved essential roles in both vasculogenesis and angiogensis. Among them, its anti-leakage ability may have great potential applications in clinical treatment of vascular hyper-permeability in a variety of diseases such as cancer, diabetic retinopathy, rheumatoid arthritis, asthma. In this review, some research progresses focused on this aspect are discussed.     

Gene expressions of canine angiopoietin-1 and -2 in normal tissues and spontaneous tumours

The angiopoietin (Ang) family of proteins are central to the regulation of angiogenesis. The purposes of this study were to determine cDNA sequences of canine Ang-1 and Ang-2 and investigate their expressions in normal tissues and spontaneous tumours. The cDNA sequences of canine Ang-1 and Ang-2 were 1,494 and 1,488 bp, and the deduced amino acid sequences were 497 and 495 residues, respectively. The cDNA sequences of canine Ang-1 and Ang-2 showed high homology with those of the other mammalian species. Canine Ang-1 and Ang-2 mRNA were detectable in all 22 normal tissues and spontaneous tumours. Higher mRNA expression level of canine Ang-2 was demonstrated in mammary simple carcinomas, haemangiosarcoma and hepatocellular carcinoma in comparison with normal tissues.     

Histomorphological and immunohistochemical study of angiogenesis and angiogenic factors in the ovary of the mare

Cyclical ovaries of 18 mares were examined histologically and immunohistochemically for vascular endothelial growth factor A and B (VEGF A; VEGF B), angiopoietin1 and 2 (Ang1; Ang2), vascular endothelial growth factor receptor 1 and 2 (VEGF-R1; VEGF-R2), angiopoietin receptor (Tie2) and von Willebrand factor. The most intensive coexpression of the examined factors and receptors was detected in the periovulatory period, when a distinctive ovarian angiogenesis takes place, being essential for tertiary follicle maturation and for the endocrine function of the Corpus luteum. Based on the immunohistochemical results, VEGF A, Ang2, VEGF-R2 and Tie2 in particular seem to play a significant role on angiogenesis during follicular and luteal development in the mare, while Ang1 supports vessel stabilisation. The findings of luteal regression and follicular atresia showed that, in the absence of VEGF A, Ang2 and its receptor Tie2 contribute substantially to vessel regression and therefore to luteolysis and follicular atresia.     

大鼠血管生成素-2在脓毒症型急性肺损伤的变化及影响

目的 探讨血管生成素-2(angiopoietin-2,Ang-2)在脓毒症型急性肺损伤(Acute Lung Injury,ALI)中的变化及影响。方法 45只SD大鼠随机分为对照组10只,采用假手术处理;模型组35只,采用盲肠结扎穿孔术(cecal ligation and puncture,CLP)制作ALI模型(即盲肠结扎／脓毒症型);于假手术及CLP术后24h处死全部大鼠,取肺石蜡包埋,行苏木素-伊红(HE)染色观察肺组织变化及酶联免疫吸附试验(ELISA)检测血清Ang-2的水平。结果 对照组大鼠光镜下肺组织结构清楚,肺泡腔清晰,肺泡隔基本无水肿、炎症等特殊改变;模型组光镜下见部分肺泡萎陷,肺泡壁通透性增加,可见较多中性粒细胞及少许巨噬细胞浸润,肺泡间隔增宽等。S模型组血清Ang-2水平(10.72±1.49)ng/ml明显高于对照组(3.87±0.26)ng/ml(P<0.01);死亡鼠血清Ang-2水平(11.48±1.52)ng/ml亦显著高于存活鼠(7.69±1.83)ng/ml(P<0.05)。结论 Ang-2在脓毒症型ALI中具有重要病理作用,血清高Ang-2水平提示预后较差。     

天祝白牦牛ANGPTL4基因的单核苷酸多态性研究

[目的]本研究旨在对牛ANGPTL4基因进行SNPs检测,并研究其与天祝白牦牛部分经济性状的相关性。[方法]以36头天祝白牦牛为研究对象,采集其血样并提取基因组DNA,设计ANGPTL4基因的特异引物对P1和P2,对ANGPTL4基因的部分序列进行扩增,并利用PCR-SSCP结合测序的方法检测扩增产物序列的多态性。[结果]以自行设计的上述两对引物扩增分别获得长为260 bp（位于GenBank公布序列NC-007305.2的296~555 bp间）和170 bp（位于序列NC-007305.2的4 610~4 779 bp间）的天祝白牦牛ANGPTL4基因的两个片段。引物对P1的扩增产物经变性聚丙烯酰胺凝胶电泳,出现两种带型：AA和AB。AA和AB两种基因型频率分别为0.9444和0.0556。多态信息含量是0.1000,为低度多态。对具有不同带型的个体测序结果表明,引物对P1的扩增片段上有两处发生碱基突变,分别位于ANGPTL4基因的第466 bp处（T→C）和479 bp处（T→C）,导致相应的氨基酸改变Cys→Arg,Phe→Ser。在引物对P2的扩增片段上没有发现SNPs位点。[结论]引物对P1的扩增位点可以尝试作为天祝白牦牛品质改良的辅助选择标记。     

Current progress in structure and function of angiopoietin family

Angiopoietin family is a recently discovered type of cellular factors that specifically bind to the TIE-2 receptors located exclusively in endothelial cell membrane. The protein structures of this family members are similar. They can be structurally divided into three domains: an N-terminal region lacking homology to any known structures, an alpha-helical rich coiled-coil segment, and a fibrinogen-like domain. The distribution and biological activity of these factors are different in organism. Angiopoietin-1 as a agonist, mostly locates in close proximity with vascular endothelial cells, keeps the stability of blood vessels, enhances the affinity of vascular endothelial cells with surrounding cells and matrix, decreases the leakage of vessel. Ang-2 is a naturally occurring antagonist of Ang-1, exists in the angiogenic remodeling region and is related to the decrement of the stability of vessel. Ang-3 is widely distributed in multiple mouse tissues, while Ang-4 is expressed only in lung. Although Ang-3 and Ang-4 are structurally diverged from each other, they appear to represent the mouse and human counterparts of the same gene locus. Biological functions of Ang-3 and Ang-4 have not been elucidated yet. Angiopoietin family has potentially clinical applications for incurring illnesses which lead to vessel wound and vascular abnormal development.     

Neuregulin-1 induces expression of angiogenic factors in coronary artery smooth muscle cells

ATM: To investigate the effects of neuregulin-1 (NRG-1) on the expression of angiogenic factors in human coronary artery smooth muscle cells (HCASMCs). METHODS: HCASMCs were cultured in vitro, and the cells at the 3rd passage were collected to assess the expression and phosphorylation of ErbB by Western blot. After HCASMCs were cultured under normal condition, with hypoxia and serum deprivation, or with NRG-1 treatment, the expression of vascular endothelial growth factor (VEGF), angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) was determined by Western blot. RESULTS: The expression of ErbB2, ErbB3 and ErbB4 was observed in the HCASMCs, and the phosphorylation of these receptors was increased by NRG-1 treatment. Compared with control group, the expression of VEGF and Ang-1 in the HCASMCs was significantly increased in hypoxia and serum deprivation group (P<0.05﹚,while no difference in the expression of Ang-2 between the 2 groups was found.Compared with hypoxia and serum deprivation group,the expression of VEGF and Ang-1 in the H CASM Cs treated with NRG-1 was furtherincreased﹙P<0.05﹚,and no difference in the expression of Ang-2 between the 2 groups was observed.CONCLUSION: HCASMCs express ErbB2, ErbB3 and ErbB4, and the phosphorylation of the receptors is increased by NRG-1. Hypoxia, serum deprivation and NRG-1 treatment induce the increased expression of VEGF and Ang-1 significantly.     

Effects of angiopoietin 4 on lipopolysaccharide-induced injury of human umbilical vein endothelial cells

AIM:To observe the effects of angiopoietin 4 (Ang-4) on lipopolysaccharide (LPS)-induced injury of human umbilical vein endothelial cells (HUVECs). METHODS:The EnVision immunohistochemical method was used to identify the HUVECs. After pre-treated with different doses of Ang-4 for 0.5 h, HUVECs was exposed to LPS at concentration of 10 mg/L for 24 h. The cell viability was evaluated by MTT assay. The content of tumor necrosis factor-alpha (TNF-α) in the supernatant and the concentrations of intracellular and supernatant von Willebrand factor (vWF) were detected by ELISA. The mRNA levels of Toll-like receptor 4 (TLR4), NF-κB p65 and TNF-α were determined by real-time PCR. RESULTS:Factor Ⅷ in the cytoplasm was positive in the HUVECs.Compared with normal group, LPS reduced the cell viability (P<0.01), and significantly increased the secretion of TNF-α and vWF (P<0.01). The mRNA expression of TLR4, NF-κB p65 and TNF-α also increased (P<0.01). Ang-4 at concentration of 100 μg/L enhanced the cell viability (P<0.01), reduced the content of vWF and TNF-α, and inhibited the LPS-induced increases in the mRNA levels of TLR4, NF-κB p65 and TNF-α (P<0.01). CONCLUSION: Ang-4 antagonizes LPS-induced damage in HUVECs by inhibiting TLR4-NF-κB p65-TNF-α signaling pathways.