Therapeutic potential of endothelin receptor antagonists and nitric oxide donors in pulmonary hypertension

Pulmonary hypertension can occur idiopathically as a primary disorder of the pulmonary circulation or more commonly, it can exist as a haemodynamic manifestation of a wide variety of pulmonary and cardiovascular diseases, including acute lung injury, chronic obstructive lung disease, congenital heart disease, mitral stenosis, chronic left-sided congestive heart failure and connective tissue diseases such as scleroderma. Pulmonary hypertension is associated with changes in vascular tone as well as vascular structure, with the relative contribution of each dependent upon the aetiology of the increased pulmonary vascular resistance. Most currently available treatments utilise anticoagulants as well as vasodilator drugs that only attenuate the vasoconstrictive component of the disease. The latter category includes oral calcium channel blockers, iv. and aerosolised prostacyclin analogues and inhaled nitric oxide but all three classes of vasodilators have disadvantages and limitations. Treatment with vasodilators is often ineffective in patients with longstanding pulmonary hypertension in which structural changes contribute significantly to the pulmonary hypertension, blood flow obstruction and right heart failure. In view of the immense clinical need, new therapies are being developed by pharmaceutical companies to treat pulmonary hypertension. This update will focus on the current development status of endothelin receptor antagonists and nitric oxide donors for the treatment of pulmonary hypertension.     

Dimensional prefernces in middle and old age

Dimensional preferences in 40 middle-aged (M = 41.62 years) and 40 elderly (M = 72.22 years) females were assessed using a dimensional choice task. Significant age differences in reaction times of choice but not in number of dimensional choices were obtained. There was a perfect rank-order correspondence between the two age groups in dimensional choices with form being the most preferred and color the least preferred perceptual dimension.     

Effect of Zataria multiflora Extract on Total and Differential White Blood Cell Count and Endothelin Level in Blood of Ovalbumin Sensitized Guinea Pigs

Objective: To investigate the effect of hydro-ethanolic extract of Zataria multiflora (Z. multiflora) on endothelin level, total and differential white blood cells (WBC) count of sensitized guinea pigs. Methods: Five groups of guinea pigs sensitized to ovalbumin (OA) were given drinking water alone (group S), drinking water containing three concentrations of Z. multiflora (0.2, 0.4 and 0.8 mg/mL as groups S+Z1, S+Z2 and S+Z3) and dexamethasone (group S+D), n=6 for each group. The endothelin levels as well as total and differential WBC count in blood of sensitized and control guinea pigs were evaluated using enzyme linked immunosorbent assay method, and hemocytometer and Wright-Giemsa''s staining of blood sample smear respectively. Results: Blood endothelin levels, total and most differential WBC count were increased but lymphocytes decreased in sensitized animals compared to controls (all P<0.01). In groups S+D, S+Z2 and S+Z3 endothelin level, total and differential WBC counts were significantly improved compared with group S (P<0.01). Although, all measured parameters in group S+Z1 was lower than group S+D (P<0.01), some parameters in group S+Z3 were greater than in group S+D (P<0.05 to P<0.01). Conclusion: The results showed an anti-inflammatory effect of Z. multiflora extract in sensitized guinea pigs, which may suggest a therapeutic potential for the plant on asthma.     

一氧化氮和内皮素在高血压左室肥厚形成中的作用

目的 探讨一氧化氮（NO）和内皮素（ET）在高血压左室肥厚（LVH）形成中的作用。方法 采用放射免疫分析法（RIA）和硝酸还原酶法检测30例单纯原发性高血压（EH，观察Ⅰ组）、30名健康体检者（对照组）及20例EH伴LVH（观察Ⅱ组）患者降压治疗前后血清ET、NO水平。并对结果进行相关分析。结果 观察Ⅰ组血清ET明显高于对照组、NO明显低于对照组（P均〈0．01）；观察Ⅱ组血清ET明显高于观察Ⅰ组、NO明显低于观察Ⅰ组（P均〈0．01），且ET与NO水平呈负相关（r=0．586，P〈0．01）；左心室重量指数（LVMI）与ET呈正相关（r=0．427，P〈0．05）、与NO呈负相关（r=0．653，P〈0．01）。观察Ⅱ组治疗后，血清ET水平明显低于治疗前、NO水平明显高于治疗前（p均〈0．01）。结论 ET和NO两者失衡可能参与了EH及LVH形成的病理生理过程。     

内皮素A型受体反义基因减弱内皮细胞条件培养液刺激的血管平滑肌细胞增殖

目的 :研究内皮素 （Endothelin,ET） A型受体 （ETA）反义寡核苷酸 （Oligonucleotide,OGN）对内皮细胞 （En-dothelial cells,ECs）条件培养液 （ECCM）刺激的人大隐静脉 （hum an saphenous vein,HSV）血管平滑肌细胞 （Vas-cular sm ooth m uscle cells,VSMCs）增殖的影响。方法 :分离、培养 HSV的 ECs和 VSMCs。收集 ECCM,分别用正常的 DMEM（Dulbecco’s Mod Ified Eagle medium ）、含 ET- 1的 DMEM、ECCM和加入 Phophoramidon（ET- 1转化酶抑制剂 ）的 ECCM培养 VSMCs。以放射免疫法测定 ECs培养基中 ET- 1水平 ;分别采用放射受体结合分析法和四唑盐 （MTT）比色实验检测 ETA 蛋白表达和细胞的增殖。结果 :ETA- OGN（15 μm ol/L）以时间依赖的方式抑制ETA 表达。 12～ 4 8h HSV的 ECs培养上清液 ET- 1水平呈现上升的趋势 ,4 8h达到高峰。 ECCM显著刺激 VSMCs增殖 （P<0 .0 1） ,ET- 1能够模拟 ECCM的促增殖作用。在 ECCM中加入 Phosphorimidon,不能使 ECCM的促增殖效应消失 （P<0 .0 5 ）。ETA- OGN（15 μm ol/L）对无血清正常的 DMEM培养基培养的 VSMCs增殖没有显著影响 ,但显著抑制 ECCM和 ET- 1的促增殖作用 （P<0 .0 1vs ECCM）。结论 :ECs通过分泌包括 ET- 1在内的多种因子促进 VSMCs增殖 ,其中 ET- 1发挥主要的作用。 E     

运动对大鼠胸主动脉损伤后内皮素和一氧化氮合成酶的影响

用2FFogarty球囊导管剥脱大鼠胸主动脉内皮，观察动脉一氧化氮合成酶（NOS）活性和内皮素（ET）水平的变化及运动对它们的影响。结果发现：动脉损伤4周后血浆和胸主动脉ET的含量较假手术组（SO）升高显著（P＜0．01），运动明显增强损伤动脉NOS活性，抑制ET的生成，较动脉损伤组明显低（P＜0．05）。提示运动增强NOS活性、抑制ET的合成是运动防治内皮损伤和平滑肌细胞异常增殖性疾病的重要机制。     

Hepatic effects of influxed endothelin-1 from portal vein: in situ portal vein infusion model using dogs

Background/Purpose

Endothelin-1 is a potent vasoconstrictor formed by vascular endothelium. This study was designed to investigate the hepatic effect of endothelin-1 produced by portal vascular endothelium.

Methods

Portal venous pressure, portal venous flow, hepatic arterial flow, tissue blood flow, and tissue oxygen pressure were measured during portal vein endothelin-1 infusion in dogs at rates of 1.0 to 5.0?ng/kg per minute. Sinusoidal width during maximal infusion was determined morphometrically. Serum concentrations of mitochondrial glutamic oxaloacetic transaminase and endothelin-1 in portal and hepatic venous blood were also measured.

Results

Intraportal endothelin-1 infusion dose-dependently increased portal venous pressure and reduced portal venous and hepatic arterial blood flow. Tissue blood flow and oxygen pressure also decreased. Endothelin-1 also significantly increased serum mitochondrial glutamic oxaloacetic transaminase and constricted hepatic sinusoids. These changes reversed after completion of infusion.

Conclusions

Intraportal endothelin-1 caused circulatory and histological changes in hepatic sinusoids that may suggest the role of endothelin-1 formed by portal venous bed epithelium.     

中国大陆人散发性先天性巨结肠症患者内皮素受体B基因的研究

目的 探讨中国大陆人散发性先天性巨结肠症（sHD）易患基因内皮素受体B（EDNRB）的突变与多态性特征。方法 以92例sHD及其中32例患儿双亲为研究对象，并以60例正常儿为对照。提取受检者外周静脉血DNA，采用聚合酶链反应-单链构象多态性技术（PCR-SSCP）对EDNRB基因外显子-2（exon-2）进行分析，并通过DNA测序检测阳性标本的核苷酸改变方式，与文献报道的其他种族sHD同一基因特征做比较。结果 全部标本EDNRB基因exon-2均未发现突变与多态性位点的存在。结论 中国大陆人sHD患者EDNRB基因的exon-2不存在突变与多态性位点。     

Influence of intercellular junctions on endothelin secretion of human umbilical vein endothelial cells in vitro

The endothelium plays a pivotal role in the theological regulation of blood flow by the secretion of vasoactive factors. The interaction between shear forces and the endothelium is determined by the mechanical properties of the endothelial cell layer which are associated with intercellular junctions. Cell-cell contacts could therefore modulate the secretion of vasocative factors in response to theological stimuli. We investigated the relationship between intercellular junctions and the secretion of the vasoconstrictor peptide endothelin and the coagulation co-factor von Willebrand factor (vWF). Human umbilical vein endothelial cells (HUVECs) were used as in vitro endothelial model system. Intercellular junctions were reversibly disrupted by calcium chelation or hypertonic stress; alternatively, the formation of intercellular junctions was inhibited by culturing the cells in suspension or by plating them in the presence of an inhibitory anti-VE-cadherin antibody. The opening of intercellular junctions was verified by assessing transmonolayer electrical resistance (TMR) and immunofluorescence morphology. The concentration of endothelin and vWF was measured in the cell culture supernatants using specific ELISAs. The secretion of endothelin was inhibited by EGTA (5 mM) and stimulated by incubation with tumor necrosis factor α (TNFα, 40 ng/ml). Treatment with hypertonic medium (glycerol, 1200 mosmol/l) for 10 minutes opened intercellular junctions and markedly reduced the secretion of endothelin. HUVECs in suspension culture did not secrete endothelin and failed to respond to TNFα, but readily resumed these functions upon forming a new monolayer on plastic. The reconstitution of intercellular junctions after suspension culture could be inhibited using a specific anti-VE-cadherin antibody. This antibody, but not a non-specific anti-humanIgG antibody reduced endothelin secretion. The secretion of von Willebrand Factor was less dependent on intercellular junctions. The opening of intercellular junctions did not induce cell death, since the cells continued to exclude trypan blue. The results of this study suggest a novel and potentially pathophysiologically/clinically relevant correlation between intercellular junctions and the secretion of endothelin in endothelial cells. Received: 17 December 1999, Returned for revision: 20 January 2000, Revision received: 14 February 2000, Accepted: 2 March 2000     

Cholangiocyte endothelin 1 and transforming growth factor beta1 production in rat experimental hepatopulmonary syndrome

BACKGROUND & AIMS: Hepatic production and release of endothelin 1 plays a central role in experimental hepatopulmonary syndrome after common bile duct ligation by stimulating pulmonary endothelial nitric oxide production. In thioacetamide-induced nonbiliary cirrhosis, hepatic endothelin 1 production and release do not occur, and hepatopulmonary syndrome does not develop. However, the source and regulation of hepatic endothelin 1 after common bile duct ligation are not fully characterized. We evaluated the sources of hepatic endothelin 1 production after common bile duct ligation in relation to thioacetamide cirrhosis and assessed whether transforming growth factor beta1 regulates endothelin 1 production. METHODS: Hepatopulmonary syndrome and hepatic and plasma endothelin 1 levels were evaluated after common bile duct ligation or thioacetamide administration. Cellular sources of endothelin 1 were assessed by immunohistochemistry and laser capture microdissection of cholangiocytes. Transforming growth factor beta1 expression and signaling were assessed by using immunohistochemistry and Western blotting and by evaluating normal rat cholangiocytes. RESULTS: Hepatic and plasma endothelin 1 levels increased and hepatopulmonary syndrome developed only after common bile duct ligation. Hepatic endothelin 1 and transforming growth factor beta1 levels increased over a similar time frame, and cholangiocytes were a major source of each peptide. Transforming growth factor beta1 signaling in cholangiocytes in vivo was evident by increased phosphorylation and nuclear localization of Smad2, and hepatic endothelin 1 levels correlated directly with liver transforming growth factor beta1 and phosphorylated Smad2 levels. Transforming growth factor beta1 also stimulated endothelin 1 promoter activity, expression, and production in normal rat cholangiocytes. CONCLUSIONS: Cholangiocytes are a major source of hepatic endothelin 1 production during the development of hepatopulmonary syndrome after common bile duct ligation, but not in thioacetamide-induced cirrhosis. Transforming growth factor beta1 stimulates cholangiocyte endothelin 1 expression and production. Cholangiocyte-derived endothelin 1 may be an important endocrine mediator of experimental hepatopulmonary syndrome.