Cardioprotective Effects of Angiotensin II Type 1 Receptor Blockade with Olmesartan on Reperfusion Injury in a Rat Myocardial Ischemia‐Reperfusion Model

We determined the effects of olmesartan on infarct size and cardiac function in a rat ischemia/reperfusion model. Rats underwent 30 min of left coronary artery (CA) occlusion followed by 2 h of reperfusion. In protocol 1, the rats received (by i.v.) 1 mL of vehicle at 10 min after CA occlusion (Group 1, n = 15); olmesartan (0.3 mg/kg) at 10 min after CA occlusion (Group 2, n = 15); 1 mL of vehicle at 5 min before CA reperfusion (Group 3, n = 15); or olmesartan (0.3 mg/kg) 5 min before CA reperfusion (Group 4, n = 15). In protocol 2, the rats received (by i.v.) 1 mL of vehicle at 5 min before CA reperfusion (Group 5, n = 21); or olmesartan (3 mg/kg) at 5 min before CA reperfusion (Group 6, n = 21). Systemic hemodynamics, left ventricular (LV) function, LV ischemic risk zone, no‐reflow zone, and infarct size were determined. In protocol 1, olmesartan (0.3 mg/kg) did not affect blood pressure (BP), heart rate, LV ± dp/dt or LV fractional shortening during the experimental procedure, and did not alter no‐reflow or infarct size. In protocol 2, olmesartan (3 mg/kg) significantly reduced infarct size to 21.7 ± 4.1% from 34.3 ± 4.1% of risk zone in the vehicle group (P= 0.035), but did not alter the no‐reflow size. Prior to CA reperfusion, olmesartan (3 mg/kg) significantly reduced mean BP by 22% and LV ±dp/dt, but did not affect heart rate. At 2 h after reperfusion, olmesartan significantly decreased heart rate by 21%, mean BP by 14%, and significantly increased LV fractional shortening from 54.1 ± 1.4% to 61.3 ± 1.6% (P= 0.0018). Olmesartan significantly reduced myocardial infarct size and improved LV contractility at a dose (3 mg/kg) with systemic vasodilating effects but not at a lower dose (0.3 mg/kg) without hemodynamic effects.     

ACE-Inhibition and Angiotensin II Receptor Blockers in Chronic Heart Failure: Pathophysiological Consideration of the Unresolved Battle

Reducing the effects of angiotensin II by blockade of AT1-receptors may be superior to inhibition of angiotensin II formation by angiotensin converting enzyme (ACE) inhibitors in chronic heart failure (CHF) patients. However, the results of several trials did not fulfil this expectation. In both ELITE II with symptomatic CHF patients and in OPTIMAAL involving high risk patients after acute myocardial infarction, angiotensin II type I (AT1) receptor blocker (ARB) losartan did not prove to be superior to captopril. There are several potential reasons, why ARBs did not fare better than ACE inhibitors. Although AT1-receptor blockade may block the effects of non-ACE pathways of tissue angiotensin II formation, no clinical evidence is available that a more powerful inhibition of the tissue renin-angiotensin system brings improved survival. The choice of patients for clinical trials of HF therapy is not based on the level of neurohumoral activation. Thus, the more effective attenuation of angiotensin II action with ARBs may not bring additional benefits. The potential antiremodeling effect of ARBs through the stimulation of AT2 receptors by angiotensin II could be counterbalanced by a failure of AT1-receptor blockers to enhance bradykinin, nitric oxide and prostacyclin formation with antigrowth properties. Although ACE-inhibitors seem to have slightly better results at present than AT1 blockers in the battle on heart failure patient, future trials will decide which is the definitive winner.     

Role of Angiotensin II in Coagulation and Fibrinolysis

Activation of the renin–angiotensin system increases the risk of atherohrombotic events in hypertensive patients. This relationship may be explained by multiple mechanisms, including effects on platelet function and on fibrinolysis. There is substantial evidence that angiotensin-converting enzyme (ACE) inhibitors may exert antithrombotic effects by enhancing the bradykinin-dependent release of tissue plasminogen activator (t-PA) while reducing the angiotensin-dependent production of its natural inhibitor PAI-1, thus improving vascular fibrinolytic balance. Recent studies suggest that angiotensin (II) type 1 (AT1) receptor antagonists inhibit the effects of prothrombotic prostanoids. The antithrombotic effects of agents that block the RAS may contribute to their vasculoprotective properties.     

Angiotensin II Type 1 Receptor Antagonist Suppress Angiogenesis and Growth of Gastric Cancer Xenografts

Angiotensin II (Ang II) has been reported to promote tumor progression, tumor growth and angiogenesis in many cancers. We previously observed that angiotensin II type1 receptors (AT1R) were upregulated in human gastric cancer and may be involved in the progression of gastric cancer. We studied the effects of AT1R antagonist on angiogenesis and growth in gastric cancer xenografts to observe the mechanism action of AT1R in the gastric cancer. The results showed that the growth of gastric cancer cells was significantly suppressed by treatment with AT1R antagonist. In vivo, TCV-116, at doses of both 2 and 5 mg/kg/day, significantly suppressed tumor growth in mice (47.3 and 70.2%). Microvessel density was significantly decreased by TCV-116 (3.4 ± 0.9 and 2.8 ± 0.5 per field) compared with the control group (12.9 ± 1.1 per field), and VEGF expression was significantly suppressed by AT1R antagonist. These results demonstrate that AT1R plays an important role in the progression of gastric cancer. Suppression tumor angiogenesis could be one of the mechanisms by which AT1R antagonist suppresses the growth of gastric cancer. These findings also provide a theoretical basis for the future clinical application of AT1R antagonist against gastric cancer.     

Angiotensin II Type 1 Receptor Expression in Human Gastric Cancer and Induces MMP2 and MMP9 Expression in MKN-28 Cells

Angiotensin II (Ang II), a main effector peptide in the renin–angiotensin system, acts as a growth-promoting and angiogenic factor via angiotensin II receptor1 (AT1R). In this study, we investigated the expression of angiotensin II type1 receptor (AT1R) in gastric cancer and the effects of Ang II on the expression of MMP2 and MMP9 in the human gastric cancer cell line MKN-28 cells. The expression of the Ang II type I receptor was examined by western and immunocytochemistry in gastric cancer cell lines and detected by real-time PCR and immunohistochemistry in normal and gastric cancer tissues. The expression of MMP2 and MMP9 were detected by real-time PCR and western after treatment with Ang II and/or AT1R antagonist. AT1R were expressed in all human gastric cancer lines and the expression of AT1R was significantly higher in cancer tissues than that in normal gastric tissues (P < 0.01). Furthermore, Ang II promoted the expression of MMP2 and MMP9 in MKN-28 cells, and the stimulatory effects of Ang II could be blocked by AT1R antagonist. These results suggest that AT1R is involved in the progression of gastric cancer and may promote the angiogenesis of gastric cancer cell line (MKN-28), and these effects may be associated with the upregulation of MMP2 and MMP9.     

胰腺癌细胞系血管紧张素Ⅱ1型受体蛋白表达的研究

目的：探讨血管紧张素Ⅱ1型受体（angiotensin Ⅱ type 1 receptor,AT1）在胰腺癌细胞中的表达。方法：用免疫细胞化学染色检测胰腺癌细胞系SW1990、PaTu8988s和PANC－1中AT1蛋白的表达。结果：胰腺癌细胞系SW1990、PaTu8988s和PANC－1中均有AT1蛋白的表达，结论：AT1在胰腺癌细胞生长中可能发挥重要作用，应用AT1拮抗剂对防治胰腺癌似乎有一定意义。     

Expression of angiotensin II type 1 receptor in human cirrhotic livers: Its relation to fibrosis and portal hypertension.

Angiotensin II (ANG-II) and its receptor (AT1) have been potential targets of therapy for liver cirrhosis. However, AT1 expression in human cirrhotic livers has not been clarified. We studied AT1 and ANG-II generating enzymes in human autopsy (20 cirrhotics and 20 normal controls) and biopsy (10 cirrhotics) livers. AT1 immunoreactivity in tissue sections was quantified by computer-aided morphometry. AT1 protein and mRNA levels were assessed by Western blotting and real-time polymerase chain reaction. Concerning ANG-II generating system, angiotensin-converting enzyme (ACE) and mast cell chymase were examined. AT1 expression was seen not only in vascular smooth muscle cells, but also in activated stellate cells/myofibroblasts and liver parenchymal cells. AT1-positive vessels and myofibroblasts were significantly increased in fibrous septa of cirrhosis, although overall hepatic AT1 expression was reduced in the cirrhotic livers compared with the controls. Augmentation of AT1-positive vessels was related to severity of portal hypertension. Expressions of ACE and chymase were enhanced in the cirrhotic livers. These results suggest that hepatic AT1 expression is shifted to and concentrated in vessels and myofibroblasts in cirrhotic settings, and increased ANG-II generation by ACE and chymase contributes to portal hypertension and liver fibrosis via binding to AT1 expressed on vessels and myofibroblasts.     

Effects of angiotensin II and angiotensin II type 1 receptor blockade on neointimal formation after stent implantation

The prevalence of chronic obstructive pulmonary disease (COPD) and chronic heart failure (CHF) increases substantially with age. The coexistence of COPD and CHF is common but often unrecognized in elderly patients. To avoid overlooking COPD in elderly patients with known CHF pulmonary function tests should be routinely obtained. Likewise, to avoid overlooking CHF in elderly patients with known COPD left ventricular (LV) function should be routinely assessed. Plasma brain natriuretic peptide levels are useful to differentiate COPD exacerbation from CHF decompensation in patients presenting with acute dyspnea. Aging exacerbates skeletal muscle alterations that occur in patients with CHF and COPD. Skeletal muscle metabolic alterations and atrophy and the resulting deterioration of functional capacity progress rapidly in elderly patients with COPD and CHF. Physical conditioning reverses rapidly progressing skeletal muscle metabolic alterations and atrophy and promotes independence and life quality in the elderly. Physical conditioning is clearly an essential component of the management of elderly patients with COPD and CHF. The pharmacological management of patients with coexistent COPD and CHF should focus on not depriving these patients from long-term beta adrenergic blockade. Long-term beta adrenergic blockade has been repeatedly shown to improve survival in elderly patients with CHF due to LV systolic dysfunction and, contrary to conventional belief, is well tolerated by patients with COPD.     

Cardioprotective Effect of Enalapril in Renovascular and Angiotensin II Hypertension

The influence of chronic treatment with enalapril or losartan (10 or 30mg/kg/24h, respectively) on cardiac mass was evaluated in one-kidney, one clip (1K-1C) hypertensive rats submitted to sodium restriction 3 weeks after clipping and in rats infused for 10 days with angiotensin II (ANGII: 200ng/kg/min). In 1K-1C hypertension, cardiac mass and arterial pressure were reduced to a similar extent by enalapril and losartan. In ANGII hypertension, enalapril and losartan blunted the increase in cardiac mass whereas losartan but not enalapril prevented the development of hypertension. The cardioprotective effect of enalapril was attenuated by concomitant blockade of bradykinin receptors (Hoe 140: 300pg/kg/24h) in both models. The beneficial influence of enalapril on cardiac mass appears to be independent of its effect on blood pressure and ANGII generation and seems partly mediated by endogenous bradykinin in these high ANGII models of hypertension.     

CV-11974, angiotensin II type I receptor antagonist, reduces the severity of indomethacin-induced rat enteritis

The aim of the present study was to examine the effect of angiotensin II type I receptor antagonist, CV-11974, on indomethacin-induced small intestinal injury in rats. Single administration of indomethacin provoked severe inflammatory lesions in the small intestine. The levels of thiobarbituric acid-reactive substances (TBARS), myeloperoxidase (MPO) activities and cytokine-induced neutrophil chemoattractant-1 (CINC-1) in the intestinal mucosa significantly increased in the indomethacin-treated group compared with the sham group. In addition, the angiotensin II type I receptor was increased in the small intestine after the administration of indomethacin. The development of intestinal lesions in response to indomethacin was prevented by pretreatment with CV-11974 together with significant suppression of the increased level of TBARS, MPO activities and CINC-1. These results indicate that CV-11974 protected against the small intestinal damage elicited by indomethacin, which suggests that angiotensin II/AT1 receptor interaction is involved in the pathogenesis of the intestinal inflammation associated with oxidative stress.     

Angiotensin II type 2 receptor gene polymorphisms and cardioprotective role in essential hypertension

Angiotensin II type 2 receptor (AT2R) has been proved to be involved in a cardioprotective role, but only a few studies have addressed the association of AT2R-genotype with this role. Whether the AT2R genotype is associated with hypertension is controversial. The aim of the study was to explore the information of single-nucleotide polymorphisms (SNPs) of the AT2R gene in Cantonese, an essential subpopulation of Chinese, and study the association of SNPs in the AT2R gene with hypertension, and to detect the genotypes that indicate a cardioprotective role. Two hundred and sixty-two patients with essential hypertension and 75 normotensive subjects were enrolled for a case-control study. All of the subjects were Cantonese. Sixteen individuals were chosen to sequence the AT2R gene and 16 SNPs were acquired. G/T rs5193 and G/A rs5194 were two SNPs in the 3′ untranslated region which were focused on the association of the AT2R-genotype and phonotype. Polymerase chain reaction was performed to amplify the fragment spanning the two SNPs. Genotype and haplotype were identified by dot blot hybridization. Four haplotypes in males (G-G, G-A, T-A, T-G) and eight haplotype combinations in females (G-G/G-G, G-A/G-A, G-G/G-A, G-G/T-A, G-G/T-G, T-A/T-A, T-G/T-G, and T-A/T-G) were detected. G-G and G-A haplotype were predominant, while T-A and T-G were rare in Cantonese. None of these was associated with hypertension. T-A carriers with essential hypertension indicated lower levels of left ventricular mass (LVM) and left ventricular hypertrophy index (LVHI). The levels of LVM and LVHI were still significantly lower in T-A carriers with hypertension adjusted for age or body mass index for men and women separately. No episodes of coronary heart disease and heart failure were detected in T-A carriers with hypertension. Haplotypes of G/T rs5193-G/A rs5194 are not associated with essential hypertension. Among these haplotypes, T-A may be implicated in a cardioprotective role to protect hypertense subjects from left ventricular hypertrophy.     

Angiotensin AT1 receptor upregulates expression of basic fibroblast growth factor,basic fibroblast growth factor receptor and coreceptor in human coronary smooth muscle cells

Abstract. Autocrine stimulation and paracrine interaction between coronary smooth muscle cells (cSMC) and endothelial cells (EC) act as regulators of the vascular angiogenesis. Basic fibroblast growth factor (bFGF), its receptor FGF-R1, and coreceptor heparansulfate proteoglycan (HSPG) are important components involved in this angiogenic process. We investigated the influence of angiotensin (Ang) II on this trimolecular bFGF complex, the underlying signaling and the proliferative process in human cSMC. Ang II induces an AT1 receptor-dependent expression of bFGF and also upregulates the FGF-R1 and HSPG expression which is suppressed by losartan, the AT1 receptor blocker. AT1 receptor signaling which is characterized by phosphorylation of p42-mitogen-activated protein kinase (MAPK) is involved in Ang II-induced bFGF, FGF-R1 and HSPG upregulation and DNA synthesis in human cSMC. In contrast, inhibition of the AT2 receptor by PD123,319 has no influence on these Ang II-stimulated and via the MAPK cascade-mediated proangiogenic effects. Finally, our data show that the Ang II-induced DNA synthesis in cSMC is mediated via the bFGF expression. In conclusion, our results suggest that the Ang II-induced angiogenic effects in the vessel wall are supported by the AT1 receptor-stimulated and MAPK pathway-mediated upregulation of the autocrine/paracrine trimolecular bFGF complex in cSMC.     

Local Inhibition of Angiotensin II Formation and Bradykinin Degradation in Isolated Hearts

ABSTRACT

The interaction of the converting enzyme (CE)-inhibitor ramipril and the bradykinin (BK)-antagonist D-Arg-[Hyp⁵,Thi^5,8,D-Phe⁷]BK with angiotensin I (ANG), ANG II and BK were studied in isolated hearts of rats and guinea pigs.

In isolated working rat hearts perfusion with ANG I and ANG II reduced cardiac function and coronary flow, increased the activities of lactate dehydrogenase (LDH) and creatine kinase (CK) in the perfusate, decreased high-energy rich phosphates and glycogen in the myocardium and increased duration and incidence of postischemic reperfusion arrhythmias. BK on the other hand reduced LDH and CK activities, improved metabolic parameters in the myocardium and reduced reperfusion arrhythmias.

In isolated rat hearts pretreatment with ramipril protected against reperfusion arrhythmias and reduced enzyme activities of LDH and CK in the coronary effluent. Cardiodynamic parameters and coronary flow improved and myocardial tissue levels of glycogen, ATP and creatine phosphate (CP) were elevated. Almost identical changes were seen during perfusion with BK. The cardioprotective effects produced by both, the CE-inhibitor and BK, were completely abolished when the BK-antagonist was added to the perfusate, while a smaller inhibition was obtained by indomethacin perfusion.

In isolated guinea pig hearts BK increased coronary flow. Single-dose oral pretreatment with ramipril potentiated, whereas perfusion with the BK-antagonist abolished this effect.

These data add support to the hypothesis that local inhibition of CE = kininase II contributes to the beneficial effects of CE-inhibitors in the heart.     

A Review on Telmisartan: A Novel,Long‐Acting Angiotensin II‐Receptor Antagonist

Telmisartan is a potent, long‐lasting, nonpeptide antagonist of the angiotensin II type‐1 (AT₁) receptor that is indicated for the treatment of essential hypertension. It selectively and insurmountably inhibits stimulation of the AT₁ receptor by angiotensin II without affecting other receptor systems involved in cardiovascular regulation. Very high lipophilicity, a unique feature of telmisartan, coupled with a high volume of distribution, indicate that the compound offers the clinically important advantage of good tissue penetration. Telmisartan is not a prodrug and has a longer terminal elimination half‐life than other commercially available sartans (～24 h), making it suitable for once‐daily dosing. The compound is not metabolized by cytochrome P450 isoenzymes and has a low risk for P450‐based drug interactions. In animal models, telmisartan exhibits pronounced cardio‐and renoprotective effects in animals with severe, essential hypertension. In clinical studies, telmisartan shows comparable antihypertensive activity to members of other major antihypertensive classes, such as ACE inhibitors, beta blockers and calcium antagonists. These trials have confirmed the placebo‐like safety and tolerability of telmisartan in hypertensive patients. Based on these data, telmisartan offers advantages over other sartans and represents an important new treatment option for hypertension.     

细胞间粘附因子-1在高血压致炎症和心脏纤维化中作用的研究

目的探讨细胞间粘附因子-1(Intercellular Adhesion Molecular-1,ICAM-1)在高血压致炎症与心脏纤维化中的作用。方法将12只野生小鼠和12只ICAM-1敲除小鼠随机分成四组:野生对照组,野生血管紧张素Ⅱ灌泵组,ICAM-1敲除对照组,ICAM-1敲除血管紧张素Ⅱ灌泵组,给予血管紧张素Ⅱ(1500ng/kg*min,7d)及乙酸溶液(对照组)微量泵灌注,在灌注后第7天通过小鼠尾动脉套法测定各组血压,超声心动图检查以观察小鼠心脏结构和功能改变,马松染色、天狼星红染色观察心脏纤维化,免疫组化α-SMA染色观察肌成纤维细胞的形成,HE染色和免疫组化Mac-2、IL-1β、TGF-β染色观察炎症细胞浸润及炎症因子分泌。结果血管紧张素Ⅱ灌注第7天,灌泵组较对照组血压升高,说明造模成功。ICAM-1敲除灌泵组较野生灌泵组炎症细胞浸润增多(p<0.05n=6),尤其是Mac-2+巨噬细胞(p<0.05n=6),炎症因子TGF-β、IL-1β分泌增多(p<0.05n=6),α-SMA+肌成纤维细胞增多(p<0.05n=6)。结论在高血压致心脏纤维化过程中,ICAM-1敲除后,加重以Mac-2+巨噬细胞为主的炎症细胞浸润、增加炎症因子(TGF-β、IL-1β)分泌,导致心脏组织中α-SMA+的肌成纤维细胞形成,最终加重心脏纤维化。