AT1 Receptor Modulator Attenuates the Hypercholesterolemia-Induced Impairment of the Myocardial Ischemic Post-Conditioning Benefits

BACKGROUND AND OBJECTIVES: Ischemic post-conditioning (PostC) has been demonstrated as a novel strategy to harness nature's protection against myocardial ischemia-reperfusion (I/R). Hypercholesterolemia (HC) has been reported to block the effect of PostC on the heart. Angiotensin II type-1 (AT1) modulators have shown benefits in myocardial ischemia. The present study investigates the effect of a novel inhibitor of AT1, azilsartan in PostC of the heart of normocholesterolemic (NC) and HC rats. MATERIALS AND METHODS: HC was induced by the administration of high-fat diet to the animals for eight weeks. Isolated Langendorff's perfused NC and HC rat hearts were exposed to global ischemia for 30 min and reperfusion for 120 min. I/R-injury had been assessed by cardiac hemodynamic parameters, myocardial infarct size, release of tumor necrosis factor-alpha troponin I, lactate dehydrogenase, creatine kinase, nitrite in coronary effluent, thiobarbituric acid reactive species, a reduced form of glutathione, superoxide anion, and left ventricle collagen content in normal and HC rat hearts. RESULTS: Azilsartan post-treatment and six episodes of PostC (10 sec each) afforded cardioprotection against I/R-injury in normal rat hearts. PostC protection against I/R-injury was abolished in HC rat hearts. Azilsartan prevented the HC-mediated impairment of the beneficial effects of PostC in I/R-induced myocardial injury, which was inhibited by L-N⁵-(1-Iminoethyl)ornithinehydrochloride, a potent inhibitor of endothelial nitric oxide synthase (eNOS). CONCLUSION: Azilsartan treatment has attenuated the HC-induced impairment of beneficial effects of PostC in I/R-injury of rat hearts, by specifically modulating eNOS. Azilsartan may be explored further in I/R-myocardial injury, both in NC and HC conditions, with or without PostC.

Effect of rosuvastatin combined with irbesartan on remodeling of myocar-dial hypertrophy in rats / 中国病理生理杂志

[ ABSTRACT] AIM:To evaluate the effect of rosuvastatin combined with irbesartan on the remodeling of myocar -dial hypertrophy in the rats.METHODS:Male SD rats (n=50) were randomly divided into control group, model group, rosuvastatin group , irbesartan group and combination group .The model of myocardial hypertrophy was established by sub-cutaneous injection of isoproterenol at dose of 2.5 mg/kg for 14 d.From the first day of modeling , the rats in control group and model group received intragastrical saline , and the rats in rosuvastatin group , irbesartan group and combination group were treated with rosuvastatin (4 mg· kg-1 · d-1 ), irbesartan (15 mg· kg-1 · d-1 ) and rosuvastatin (4 mg· kg -1 · d-1)+irbesartan (15 mg· kg-1· d-1), respectively.The interventions continued for 4 weeks.After the interventions, the cardiac mass index and left ventricular mass index of the SD rats were measured .Besides, the degree of myocardial hy-pertrophy was observed with HE staining .The mRNA expression of hypertrophy-related factors, such as ANF,β-MHC and AT1R was determined by RT-PCR, and the protein expression of AT1R was determined by Western blot .RESULTS:Compared with control group , the cardiac mass index , left ventricular mass index , as well as the mRNA expression of ANF andβ-MHC in model group were significantly increased (P<0.05).Compared with model group, the above factors in ro-suvastatin group and irbesartan group were decreased ( P<0.05 ) , and the factors in combination group were lower than those in rosuvastatin group and irbesartan group (P<0.05).In addition, the expression of AT1R at mRNA and protein levels in rosuvastatin group and irbesartan group was lower than that in model group ( P<0.05 ) , while the expression AT1R at mRNA and protein levels in combination group was lower than that in rosuvastatin group and irbesartan group (P<0.05).CONCLUSION:Rosuvastatin and irbesartan are equally effective drugs to resist the formation of myocardial hypertrophy by decreasing the expression of AT 1R.Moreover, combination of the 2 drugs is more effective to improve the degree of myocardial hypertrophy than the 2 drugs alone .

Role of AT1 receptor autoantibody in irbesartan-inhibited signaling of endoplasmic reticulum stress in rat kidney with diabetic nephropathy / 中华内分泌代谢杂志

Objective To investigate the role of AT1 receptor autoantibody (AT1-AA) in the inhibitory action of irbesartan on endoplasmic reticulum stress (ERS)-related apoptotic signals in rat kidney with diabetic nephropathy (DN).Methods DN model rats were induced by high-sugar and high-fat diet plus intraperitoneal injection of streptozotocin,and the serum level of AT1-AA was detected by ELISA.These DN rats with positive or negative AT1-AA were divided into DN group and irbesartan treated group.After 4 weeks of irbesartan treatment,TUNEL staining was used to detect renal cell apoptosis.The protein and mRNA expressions of ERS chaperone protein glucose-regulated protein 78 (GRP78) and ERS-associated apoptosis proteins were determined by Western blot and RT-PCR.Results Compared with NC group,the apoptosis rate of renal cells in DN group was obviously increased,along with the increased expressions of GRP78,C/EBP homology protein (CHOP),phosphorylated c-Jun N-terminal kinase (JNK),and Caspase12 protein and mRNA (all P＜0.01).The cell apoptosis and protein and mRNA levels of these genes were significantly decreased after irbesartan treatment (all P＜ 0.01),especially in AT1-AA positive DN rats(all P＜0.05).The renal cell apoptosis rate,and protein and mRNA levels of these four genes in AT1-AA positive DN group were much greater than those in AT1-AA negative DN group (all P＜0.05).Conclusions AT1-AA may be involved in ERS-related cell apoptosis in the kidney of DN rats,and play a role in irbesartan-improved renal function via inhibiting ERS-associated CHOP-JNK-Caspase12 apoptotic signals and renal cell apoptosis.

The Importance of the RAS Interacting with the HGF/C-Met Receptor System in Hypertensive Type 2 Diabetes Mellitus.

The classic renin-angiotensin system (RAS) is described as a circulating hormone system with primary roles in the regulation of blood pressure, body water balance and thirst and control over vasopressin and aldosterone release. Recently local tissue RASs have been identified with regulatory physiological functions and also with pathophysiological processes including fibrosis, inflammation and dysfunctional cell proliferation. There is a strong correlation between organs vulnerable to diabetic–induced hyperglycemic injury (eg. kidney and retina) and the over activation of local RASs. Increased angiotensin II concentrations in these tissues promotes hypertension and end-organ damage in at least two ways: 1) By activating AT1 receptor proteins thus inducing changes in local blood flow and tissue hydration and 2) Exacerbating hyperglycemic-induced oxidative stress, elevated polyol and hexosamine pathway variability and facilitating glycation end-products. Thus, inhibition of the RAS has become an important treatment approach to control diabetic related hypertension, nephropathy and to a lesser extent retinopathy. The present review emphasizes the recently established importance of the hepatocyte growth factor (HGF)/c-Met receptor system interacting with the RAS in Type 2 diabetes and their likely contribution to end-organ damage. A hypothesis is offered concerning how the pancreatic RAS may affect dimerization of HGF and in turn activation of the c-Met receptor to promote β cell proliferation and insulin synthesis. We conclude with details concerning the development of an AngIV-based small molecule HGF mimetic designed to act as an insulinotropic factor.

Effect of active immunization against angiotensin II type 1 (AT1) receptor on hypertension & arterial remodelling in spontaneously hypertensive rats (SHR).

Background & objectives: angiotensin II receptor type 1 (AaT1) is known to be involved in the pathogenesis of hypertension. tThis study was undertaken to explore the effect of active immunization against AaT1 receptor on blood pressure and small artery remodelling in spontaneously hypertensive rat (SHR). Methods: Male SHR and Wistar rats aged two months were actively immunized with different peptides (AaTR12185、AaTR10014 and AaTR12181) corresponding to particular sequences of rat receptor, while another SHR group was given losartan (10 mg/kg/day) orally once a day. Aanti-AaT1 receptor antibodies were detected by ELISAa and blood pressure was measured. The effect of the antibodies on the artery and vascular smooth muscle cells (VSMCs) proliferation was studied. Results: all immunized animals produced antibodies against the particular peptides. The systolic blood pressure was decreased in the SHR immunized with peptide-AaTR12181 compared with the control. However, no changes were observed in the SHR immunized with other two peptides. The Wistar rats immunized with the three peptides did not show any changes in blood pressure. The media/lumen area ratio of the mesenteric artery was reduced in SHR immunized with and similar to that of the SHR treated with losartan. The antibody from SHR immunized with AaTR12181 had no effect on the proliferation of VSMC. But it could inhibit the proliferation caused by angiotensin II and its effect at the titre of 1:40 was similar to that of 1μmol/l losartan. Interpretation & conclusions: Our findings demonstrated that the antibody from SHR immunized with AaTR12181 had the effect of reducing blood pressure and target organ protection similar to losartan. Aactive immunization against AaT1 receptor may be a promising strategy in future for the treatment of hypertension.

Cambios en la función ventricular sistólica y diastólica en un modelo de sobreexpresión cardíaca del receptor AT-1 de angiotensina / Changes in Systolic and Diastolic Function in a Mouse Model Overexpressing Cardiac Angiotensin II AT-1 Receptor

La angiotensina II (Ang II) está involucrada en diferentes procesos fisiopatológicos, particularmente actuando sobre los receptores AT-1 de Ang II (AT1R). El objetivo de este trabajo fue evaluar la función ventricular sistólica y diastólica in vivo e in vitro en ratones con sobreexpresión cardíaca específica del receptor AT-1 de Ang II (AT1R). Un segundo objetivo fue determinar si el bloqueo agudo y crónico del AT1R revierte los cambios en la función ventricular. Se estudiaron ratones divididos en cuatro grupos experimentales. El primer grupo incluyó animales no transgénicos (NTG, n = 10), el segundo grupo ratones transgénicos (TG, n = 7) que sobreexpresan el AT1R solo a nivel cardíaco y el tercero y el cuarto grupos, animales TG tratados con losartán (L) durante 7 días (TG L7, n = 9) y 30 días (TG L30, n = 7), respectivamente. Los ratones TG presentaron hipertrofia ventricular izquierda (HVI). El tratamiento con losartán por 7 días no revirtió la HVI, lo que sí sucede cuando se extiende por 30 días. Los animales TG presentan una disminución significativa de la fracción de acortamiento, desde un valor de 47,1% ± 2,3% hasta 32,3% ± 1,3% (p < 0,05), y de la +dP/dt máx, que se reduce desde un valor de 7.073 ± 674 mm Hg hasta 3.897,5 ± 209,7 mm Hg/seg (p < 0,05). El tratamiento con losartán por 7 y 30 días revierte esta disfunción sistólica. El tiempo de relajación isovolúmica y el t1/2 fueron de 24,1 ± 1,3 mseg y de 5,1 ± 0,5 mseg, respectivamente, en los NTG. Estos índices se incrementaron a 33,1 ± 2,2 mseg y a 8,4 ± 0,4 mseg, respectivamente, en los ratones TG (p < 0,05). Esta alteración de la función diastólica fue revertida por completo con el tratamiento con losartán por 7 y 30 días. El análisis de la función ventricular in vitro con control de variables corroboró los hallazgos realizados in vivo. La sobreexpresión cardíaca de los AT1R induce una disfunción ventricular sistólica y diastólica que es revertida completamente por el bloqueo del AT1R. Este efecto beneficioso es independiente de modificaciones en la masa ventricular izquierda.

Angiotensin II (Ang II) is involved in various patho-physiological processes through the activation of Ang II AT-1 receptors. The purpose of this study was to assess in vivo and in vitro systolic and diastolic ventricular function in mice overexpressing the cardiac-specific AT-1 receptor (AT1R). A second objective was to deter­mine whether acute and chronic ATIR blockade revert the changes in ventricular function. Mice were divided into four experimental groups. The first group included non-transgenic animals (NTG, n=10), the second group consisted of transgenic mice (TG, n=7) with cardiac-specific AT1R overexpression and the third and fourth groups were TG animals treated with losartan (L) for 7 (TG L7, n=9) and 30 days (TG L30, n=7), respectively. Transgenic animals exhibited left ventricular hypertrophy (LVH) which was only regressed with losartan treatment for 30 days. They also presented a significant decrease in shortening fraction from 47.1 ± 2.3% to 32.3 ± 1.3% (p max from 7073 ± 674 to 3897.5 ± 209.7 mm Hg/sec (p Isovolumic relaxation time and t1/2 were 24.1 ± 1.3 and 5.1 ± 0.5 ms, respectively, in the NTG group. These indexes increased to 33.1 ± 2.2 and 8.4 ± 0.4 ms, respectively, in TG mice (p In conclusion, cardiac-specific AT1R overexpression induces systolic and diastolic ventricular dysfunction which is completely reversed by AT1R blockade. This beneficial effect is independent of left ventricular mass changes.

Influence of Fimasartan (a Novel AT1 Receptor Blocker) on Catecholamine Release in the Adrenal Medulla of Spontaneously Hypertensive Rats

The aim of this study was to determine whether fimasartan, a newly developed AT1 receptor blocker, can affect the CA release in the isolated perfused model of the adrenal medulla of spontaneously hypertensive rats (SHRs). Fimasartan (5~50 microM) perfused into an adrenal vein for 90 min produced dose- and time-dependently inhibited the CA secretory responses evoked by ACh (5.32 mM), high K+ (56 mM, a direct membrane depolarizer), DMPP (100 microM) and McN-A-343 (100 microM). Fimasartan failed to affect basal CA output. Furthermore, in adrenal glands loaded with fimasartan (15 microM), the CA secretory responses evoked by Bay-K-8644 (10 microM, an activator of L-type Ca2+ channels), cyclopiazonic acid (10 microM, an inhibitor of cytoplasmic Ca(2+)-ATPase), and veratridine (100 microM, an activator of Na+ channels) as well as by angiotensin II (Ang II, 100 nM), were markedly inhibited. In simultaneous presence of fimasartan (15 microM) and L-NAME (30 microM, an inhibitor of NO synthase), the CA secretory responses evoked by ACh, high K+, DMPP, Ang II, Bay-K-8644, and veratridine was not affected in comparison of data obtained from treatment with fimasartan (15 microM) alone. Also there was no difference in NO release between before and after treatment with fimasartan (15 microM). Collectively, these experimental results suggest that fimasartan inhibits the CA secretion evoked by Ang II, and cholinergic stimulation (both nicotininc and muscarinic receptors) as well as by membrane depolarization from the rat adrenal medulla. It seems that this inhibitory effect of fimasartan may be mediated by blocking the influx of both Na+ and Ca2+ through their ion channels into the rat adrenomedullary chromaffin cells as well as by inhibiting the Ca2+ release from the cytoplasmic calcium store, which is relevant to AT1 receptor blockade without NO release.

Eccentric and concentric cardiac hypertrophy induced by exercise training: microRNAs and molecular determinants

Among the molecular, biochemical and cellular processes that orchestrate the development of the different phenotypes of cardiac hypertrophy in response to physiological stimuli or pathological insults, the specific contribution of exercise training has recently become appreciated. Physiological cardiac hypertrophy involves complex cardiac remodeling that occurs as an adaptive response to static or dynamic chronic exercise, but the stimuli and molecular mechanisms underlying transduction of the hemodynamic overload into myocardial growth are poorly understood. This review summarizes the physiological stimuli that induce concentric and eccentric physiological hypertrophy, and discusses the molecular mechanisms, sarcomeric organization, and signaling pathway involved, also showing that the cardiac markers of pathological hypertrophy (atrial natriuretic factor, β-myosin heavy chain and α-skeletal actin) are not increased. There is no fibrosis and no cardiac dysfunction in eccentric or concentric hypertrophy induced by exercise training. Therefore, the renin-angiotensin system has been implicated as one of the regulatory mechanisms for the control of cardiac function and structure. Here, we show that the angiotensin II type 1 (AT1) receptor is locally activated in pathological and physiological cardiac hypertrophy, although with exercise training it can be stimulated independently of the involvement of angiotensin II. Recently, microRNAs (miRs) have been investigated as a possible therapeutic approach since they regulate the translation of the target mRNAs involved in cardiac hypertrophy; however, miRs in relation to physiological hypertrophy have not been extensively investigated. We summarize here profiling studies that have examined miRs in pathological and physiological cardiac hypertrophy. An understanding of physiological cardiac remodeling may provide a strategy to improve ventricular function in cardiac dysfunction.

Exercício de força ativa a via AKT/mTor pelo receptor de angiotensina II tipo I no músculo cardíaco de ratos / Activation of AKT-mTor signaling pathways by angiotensin II receptor type 1 after a session of strength exercise in cardiac muscle of rats

O receptor de angiotensina II tipo I (AT1) tem uma importante participação no desenvolvimento da hipertrofia cardíaca. Em um trabalho publicado anteriormente, por nosso grupo, demonstramos que o bloqueio do receptor AT1 durante o treinamento de força inibiu a hipertrofia cardíaca em ratos. Por isso, o objetivo deste trabalho foi estudar a participação do receptor AT1 na ativação de vias de sinalização intracelular relacionadas com o aumento da síntese de proteína em ratos submetidos a uma sessão de exercício de força. Para isso, realizamos um experimento com seis grupos de animais (n = 6; cada): controle (Con), exercitado e sacrificado cinco minutos após o exercício (Exe 5), exercitado e sacrificado 30 minutos após o exercício (Exe 30), controle tratado com losartan (Con Los), tratado com losartan, exercitado e sacrificado cinco minutos após o exercício (Exe 5 Los), tratado com losartan, exercitado e sacrificado 30 minutos após o exercício (Exe 30 Los). Os resultados mostram que no grupo Exe 5 e Exe 30 ocorreu um aumento de 63 por cento (P < 0,05) e 62 por cento (P < 0,05), respectivamente, na fosforilação da proteína AKT comparado com o grupo controle. Enquanto a fosforilação da mTor foi aumentada 65 por cento (P < 0,05) somente no grupo Exe 30 comparado com o grupo controle, sendo estes efeitos bloqueados pelo uso do losartan nos grupos Exe 5 Los e Exe 30 Los. Portanto, esses resultados, juntamente com nossos resultados prévios, demonstram que o receptor AT1 tem participação na ativação da AKT e mTOR após uma sessão de exercício de força.

The angiotensin II type I (AT1) receptor has an important participation in the development of cardiac hypertrophy. Previously, we have shown that AT1 receptor participates in the cardiac hypertrophy induced by resistance training in rats. Here, we studied the involvement of AT1 receptor in the activation of intracellular signaling pathways related to the concentric HC in rats submitted to a session of strength exercise. Male Wistar rats were divided into 6 groups (n= 6 each): control (Con); exercised and killed 5 minutes after exercise (Exe 5); exercised and killed 30 minutes after exercise (Exe 30); control treated with Losartan (Con Los); treated with Losartan, exercised and killed 5 minutes after the exercise (Exe Los 5); treated with Losartan, exercised and killed 30 minutes after training (Exe Los 30). The results show that phosphorylation activity of AKT in group Exe 5 and Exe 30 increased 63 percent (P < 0.05) and 62 percent (P < 0.05), respectively, compared with Con. Whereas the phosphorylation of mTOR was increased 65 percent (P < 0.05), compared to Con, only in the group Exe 30. Furthermore, these effects were blocked by losartan treatment in groups Exe Los 5 and Exe Los 30. These results, together with ours previous data shows that the AT1 receptor has an role in the activation of AKT and mTOR pathway after a session of strength exercise.

Gadolinium increases the vascular reactivity of rat aortic rings

Gadolinium (Gd) blocks intra- and extracellular ATP hydrolysis. We determined whether Gd affects vascular reactivity to contractile responses to phenylephrine (PHE) by blocking aortic ectonucleoside triphosphate diphosphohydrolase (E-NTPDase). Wistar rats of both sexes (260-300 g, 23 females, 7 males) were used. Experiments were performed before and after incubation of aortic rings with 3 µM Gd. Concentration-response curves to PHE (0.1 nM to 0.1 mM) were obtained in the presence and absence of endothelium, after incubation with 100 µM L-NAME, 10 µM losartan, or 10 µM enalaprilat. Gd significantly increased the maximum response (control: 72.3 ± 3.5; Gd: 101.3 ± 6.4 percent) and sensitivity (control: 6.6 ± 0.1; Gd: 10.5 ± 2.8 percent) to PHE. To investigate the blockade of E-NTDase activity by Gd, we added 1 mM ATP to the bath. ATP reduced smooth muscle tension and Gd increased its relaxing effect (control: -33.5 ± 4.1; Gd: -47.4 ± 4.1 percent). Endothelial damage abolished the effect of Gd on the contractile responses to PHE (control: 132.6 ± 8.6; Gd: 122.4 ± 7.1 percent). L-NAME + Gd in the presence of endothelium reduced PHE contractile responses (control/L-NAME: 151.1 ± 28.8; L-NAME + Gd: 67.9 ± 19 percent AUC). ATP hydrolysis was reduced after Gd administration, which led to ATP accumulation in the nutrient solution and reduced ADP concentration, while adenosine levels remained the same. Incubation with Gd plus losartan and enalaprilat eliminated the pressor effects of Gd. Gd increased vascular reactivity to PHE regardless of the reduction of E-NTPDase activity and adenosine production. Moreover, the increased reactivity to PHE promoted by Gd was endothelium-dependent, reducing NO bioavailability and involving an increased stimulation of angiotensin-converting enzyme and angiotensin II AT1 receptors.

Influência do bloqueio de receptores do tipo 1 (AT1) sobre o perfil metabólico, endócrino e cardiovascular de ratos obesos / Influence of blocking receptor type 1 (AT1) profile metabolic, endocrine and cardiovascular obese mice

Variados agentes moleculares ativam mecanismos determinantes de alterações teciduais do coração, com frequente ocorrência de interação bioquímica entre estímulos distintos, como vigente entre angiotensina II (Ang-II) e insulina. A sinalização molecular principiada pela Ang-II é carreada a partir do acoplamento com receptores do tipo 1 (AT1) e culmina na ativação de proteínas quinases ativadas do mitógeno (MAPK), como extracellular signal-regulated (ERK) e c-Jun N-terminal (JNK). Em analogia, a ação da insulina sobre o receptor de insulina ( RI) determina a estimulação de respostas proliferativas e efeitos vinculados ao metabolismo de macro e micronutrientes. Por meio da ativação de receptores AT1, a Ang-II interfere na sinalização da insulina, regulando a fosforilação de tirosina e dessensibilizando três mensageiros de estímulos metabólicos: o receptor ( RI), o substrato receptor de insulina (IRS) e o peptídeo fosfatidil inositol 3 quinase (PI3K). Embora essas manifestações configurem importantes mecanismos de resistência à insulina na obesidade, não foram encontrados estudos abordando essa relação em modelos experimentais de obesidade exógena. O objetivo deste trabalho foi testar a hipótese de que a obesidade acarreta distúrbios metabólicos, endócrinos e cardiovasculares, incluindo remodelação e resistência insulínica cardíaca, decorrentes da ativação de receptores AT1. Ratos Wistar-Kyoto foram distribuídos em dois grupos: C e OB; ambos os grupos C e OB receberam, respectivamente, dietas padrão e hipercalórica durante 30 semanas...

Several molecular agents trigger cytosolic mechanisms of cardiac remodeling, with common occurrence of biochemical interaction between different stimuli, as observed between angiotensin II (Ang-II) and insulin. The molecular signaling from Ang-II is carried through the coupling of the receptor type 1 (AT1) and culminates in the activation of the mitogen activated protein kinases (MAPK), including extracellular signal-regulated (ERK) and c-Jun N-terminal (JNK). Similarly, the action of insulin on the insulin receptor ( RI) determines the stimulation of proliferative responses and multiple effects linked to metabolism of macro and micronutrients. Through activation of AT1 receptors, Ang-II interferes with insulin signaling by regulating the phosphorylation of three messengers of metabolic stimuli from insulin: the receptor ( IR), insulin receptor substrate (IRS) and phosphatidil inositol 3-kinase (PI3K). Although these events configure important mechanisms of insulin resistance in obesity, there are no studies addressing this relationship in experimental models of exogenous obesity. This study investigated whether obesity causes metabolic, endocrine and cardiovascular diseases, including insulin resistance and cardiac remodeling, due activation of AT1 receptors. Wistar-Kyoto rats (n=40) were subjected to control (C) or hypercaloric diet (OB) for 30 weeks and then assigned to four groups: C, C+Los, OB, and OB+Los. Los-groups received losartan (30mg/kg/day) during five weeks. Afterward, besides the nutritional and biometric analyzes, glycemia, lipids, insulin, leptin and activity of angiotensin-converting enzyme were also evaluated...

Inhibitory Effects of Olmesartan on Catecholamine Secretion from the Perfused Rat Adrenal Medulla

The present sutdy aimed to determine whether olmesartan, an angiotensin II (Ang II) type 1 (AT1) receptor blocker, can influence the CA release from the isolated perfused model of the rat adrenal medulla. Olmesartan (5~50 micrometer) perfused into an adrenal vein for 90 min produced dose- and time-dependent inhibition of the CA secretory responses evoked by ACh (5.32 mM), high K+ (56 mM, a direct membrane-depolarizer), DMPP (100 micrometer) and McN-A-343 (100 micrometer). Olmesartan did not affect basal CA secretion. Also, in adrenal glands loaded with olmesartan (15 micrometer), the CA secretory responses evoked by Bay-K-8644 (10 micrometer, an activator of voltage-dependent L-type Ca2+ channels), cyclopiazonic acid (10 micrometer, an inhibitor of cytoplasmic Ca2+ -ATPase), veratridine (100 micrometer, an activator of voltage-dependent Na+ channels), and Ang II (100 nM) were markedly inhibited. However, at high concentrations (150~300 micrometer), olmesartan rather enhanced the ACh-evoked CA secretion. Taken together, these results show that olmesartan at low concentrations inhibits the CA secretion evoked by cholinergic stimulation (both nicotininc and muscarinic receptors) as well as by direct membrane depolarization from the rat adrenal medulla, but at high concentrations it rather potentiates the ACh-evoked CA secretion. It seems that olmesartan has a dual action, acting as both agonist and antagonist at nicotinic receptors of the isolated perfused rat adrenal medulla, which might be dependent on the concentration. It is also thought that this inhibitory effect of olmesartan may be mediated by blocking the influx of both Na+ and Ca2+ into the rat adrenomedullary chromaffin cells as well as by inhibiting the Ca2+ release from the cytoplasmic calcium store, which is thought to be relevant to the AT1 receptor blockade, in addition to its enhancement on the CA secreton.

Losartan Inhibits Vascular Smooth Muscle Cell Proliferation through Activation of AMP-Activated Protein Kinase

Losartan is a selective angiotensin II (Ang II) type 1 (AT1) receptor antagonist which inhibits vascular smooth muscle cells (VSMCs) contraction and proliferation. We hypothesized that losartan may prevent cell proliferation by activating AMP-activated protein kinase (AMPK) in VSMCs. VSMCs were treated with various concentrations of losartan. AMPK activation was measured by Western blot analysis and cell proliferation was measured by MTT assay and flowcytometry. Losartan dose- and time-dependently increased the phosphorylation of AMPK and its downstream target, acetyl-CoA carboxylase (ACC) in VSMCs. Losartan also significantly decreased the Ang II- or 15% FBS-induced VSMC proliferation by inhibiting the expression of cell cycle associated proteins, such as p-Rb, cyclin D, and cyclin E. Compound C, a specific inhibitor of AMPK, or AMPK siRNA blocked the losartan-induced inhibition of cell proliferation and the G0/G1 cell cycle arrest. These data suggest that losartan-induced AMPK activation might attenuate Ang II-induced VSMC proliferation through the inhibition of cell cycle progression.

Angiotensin II stimulates MCP-1 production in rat glomerular endothelial cells via NAD(P)H oxidase-dependent nuclear factor-kappa B signaling

Angiotensin II (Ang II) plays a crucial role in the pathogenesis of renal diseases. The objective of the present study was to investigate the possible inflammatory effect of Ang II on glomerular endothelial cells and the underlying mechanism. We isolated and characterized primary cultures of rat glomerular endothelial cells (GECs) and observed that Ang II induced the synthesis of monocyte chemoattractant protein-1 (MCP-1) in GECs as demonstrated by Western blot. Ang II stimulation, at concentrations ranging from 0.1 to 10 µm, of rat GECs induced a rapid increase in the generation of reactive oxygen species as indicated by laser fluoroscopy. The level of p47phox protein, an NAD(P)H oxidase subunit, was also increased by Ang II treatment. These effects of Ang II on GECs were all reduced by diphenyleneiodonium (1.0 µm), an NAD(P)H oxidase inhibitor. Ang II stimulation also promoted the activation of nuclear factor-kappa B (NF-κB). Telmisartan (1.0 µm), an AT1 receptor blocker, blocked all the effects of Ang II on rat GECs. These data suggest that the inhibition of NAD(P)H oxidase-dependent NF-κB signaling reduces the increase in MCP-1 production by GECs induced by Ang II. This may provide a mechanistic basis for the benefits of selective AT1 blockade in dealing with chronic renal disease.

Effects of Losartan on Catecholamine Release in the Isolated Rat Adrenal Gland

The aim of this study was to determine whether losartan, an angiotensin II (Ang II) type 1 (AT1) receptor could influence the CA release from the isolated perfused model of the rat adrenal medulla. Losartan (5~50 micrometer) perfused into an adrenal vein for 90 min produced dose- and time-dependent inhibition of the CA secretory responses evoked by ACh (5.32 mM), high K+ (56 mM, a direct membrane depolarizer), DMPP (100 micrometer) and McN-A-343 (100 micrometer). Losartan failed to affect basal CA output. Furthermore, in adrenal glands loaded with losartan (15 micrometer) for 90 min, the CA secretory responses evoked by Bay-K-8644 (10 micrometer, an activator of L-type Ca2+ channels), cyclopiazonic acid (10 micrometer, an inhibitor of cytoplasmic Ca2+-ATPase), veratridine (100 micrometer, an activator of Na+ channels), and Ang II (100 nM) were markedly inhibited. However, at high concentrations (150~300 micrometer), losartan rather enhanced the CA secretion evoked by ACh. Collectively, these experimental results suggest that losartan at low concentrations inhibits the CA secretion evoked by cholinergic stimulation (both nicotininc and muscarinic receptors) as well as by membrane depolarization from the rat adrenal medulla, but at high concentration it rather inhibits ACh-evoked CA secretion. It seems that losartan has a dual action, acting as both agonist and antagonist to nicotinic receptors of the rat adrenal medulla, which might be dependent on the concentration. It is also thought that this inhibitory effect of losartan may be mediated by blocking the influx of both Na+ and Ca2+ into the rat adrenomedullary chromaffin cells as well as by inhibiting the Ca2+ release from the cytoplasmic calcium store, which is thought to be relevant to the AT1 receptor blockade, in addition to its enhancement of the CA release.

Puntos de vista sobre la prevención de la reestenosis dentro del stent después del implante de un stent de metal desnudo con valsartán más allá del ensayo VALVACE / Perspectives on prevention of in-stent-restenosis after baremetal stent implantation by valsartan beyond VALVACE trial

The VALVACE trial suggests that prevention of in-stent-restenosis after implantation of bare-metal stents is possible by administration of 80mg valsartan exclusively in those patients with initial acute coronary syndrome and diabetes. The hypothesis was tested whether higher dosage valsartan is able to reduce in-stent restenosis rate even in patients with initial stable angina. 450 consecutive «real-world¼ patients (241 males, mean age 62.7 ± 9.1 years) with matched demographic and angiographic characteristics to patients of the VALVACE trial were treated with high-dose valsartan (160 to 320 mg). Angiographic restenosis rate and MACE rate were analysed after 6 months. Angiographic restenosis rate in 368 patients with control angiography was 7.3%, 7.5% in patients with initial stable angina and 7.2% in patients with initial acute coronary syndrome. Mean lumen late loss was 0.42 ± 0.3 mm and mean residual stenosis 13.8 ± 13.3%. MACE rate was 4.3%. In males in-stent restenosis rate was 23.8% under 80 mg, 13.6% under 160 mg, 5.7% under 240 mg and 4.9% under 320 mg. In females restenosis rate was 12.2% under 80 mg and 4% under 160 mg; no restenosis appeared under higher doses. High-dose administration of valsartan is able to reduce angiographic in-stentrestenosis rate to about 7% in patients with initial stable angina and acute coronary syndrome with a MACE rate below 5%

El ensayo VALVACE sugiere que es posible la prevención de la reestenosis dentro de la prótesis después del implante de prótesis endovasculares de metal desnudo mediante la administración de 80 mg de valsartán, exclusivamente en aquellos pacientes con síndrome coronario agudo y diabetes inicial. Se evaluó la hipótesis acerca de si el valsartán en una dosificación más alta puede reducir la tasa de reestenosis dentro de la prótesis, aun en pacientes con angina estable inicial. Cuatrocientos cincuenta pacientes «del mundo real¼ consecutivos (241 hombres, edad promedio 62.7 ± 9.1 años) con características demográficas y angiográficas equiparables a los pacientes del ensayo VALVACE fueron tratados con valsartán en altas dosis (160 a 320 mg). Se analizaron las tasas de reestenosis angiográfica y la tasa MACE después de 6 meses. La tasa de reestenosis angiográfica en 368 pacientes con angiografía de control fue de 7.3%, 7.5% en pacientes con angina estable inicial y 7.2% en pacientes con síndrome coronario agudo inicial. La pérdida media tardía de la luz fue de 0.42 ± 0.3 mm y la estenosis residual media del 13.8% ± 13.3%. La tasa MACE fue de 4.3%. En los hombres, la tasa de reestenosis dentro de la prótesis fue de 23.8% con 80 mg, 13.6% con 160 mg, 5.7% con 240 mg y 4.9% con 320 mg. En las mujeres, la tasa de reestenosis fue de 12.2% con 80 mg y de 4% con 160 mg; no se observó reestenosis con dosis más altas. La administración de valsartán en altas dosis puede reducir la tasa de reestenosis angiográfica hasta alrededor del 7% en pacientes con angina de pecho inicial y síndrome coronario agudo con una tasa de MACE por debajo del 5%

Persistent hypertension and progressive renal injury induced by salt overload after short term nitric oxide inhibition

INTRODUCTION: Administration of the NO inhibitor Nwð-nitro-L-arginine methyl ester (NAME) and a high-salt diet (HS) promotes severe albuminuria and renal injury, which regresses upon discontinuation of treatments. OBJECTIVE: We investigated whether these changes reappear after reinstitution of HS, and whether they are prevented by treatment with the antilymphocyte agent mycophenolate mofetil (MMF) or the AT-1 receptor blocker losartan (L). Adult male Munich-Wistar rats received NAME and HS. A control Group (C) received only HS. After 20 days, rats receiving HS and NAME exhibited severe hypertension and albuminuria. After a 30-day recovery period, hypertension was attenuated and albuminuria had virtually disappeared. MATERIAL AND METHODS: Rats were then distributed among the following groups: HS, receiving HS; NS, receiving a normal salt (NS) diet; HS-MMF, receiving HS and MMF; HS-LOS, receiving HS and L; HS-HDZ, receiving HS and hydralazine (HDZ). Sixty days later, NS rats showed only slight albuminuria and renal damage or inflammation. In contrast, HS rats developed severe hypertension, marked glomerulosclerosis with interstitial expansion and renal infiltration by macrophages and angiotensin II-positive cells. The group treated with losartan had lowered blood pressure and a lack of albuminuria or renal injury. MMF provided similar protection without altering blood pressure, suggesting a nonhemodynamic effect, a hypothesis reinforced by the finding that HDZ lowered blood pressure without preventing renal injury. RESULTS: These results indicate that treatment with HS and NAME predisposes to the development of hypertension and renal injury upon salt overload, characterizing a new model of chronic nephropathy. CONCLUSION: The response to MMF or L, but not HDZ, suggests a key role for inflammatory rather than hemodynamic factors.

INTRODUÇÃO: A administração de Nômega-nitro-L-arginina metiléster (NAME), um inibidor da produção de NO, com dieta rica em sal (HS) promove albuminúria e dano renal graves, reversíveis ao interromperem-se os tratamentos. OBJETIVO: Investigamos se tais alterações recrudescem ao reinstituir-se a HS e se são prevenidas pelo micofenolato mofetil (MMF), um agente antilinfócito, ou losartan, um bloqueador do receptor AT-1. MATERIAL E MÉTODOS: Ratos Münich-Wistar machos adultos receberam NAME e HS. Um grupo controle (C) recebeu apenas HS. Após 20 dias, os ratos que receberam HS e NAME exibiam hipertensão e albuminúria graves. Após recuperação de 30 dias, a hipertensão atenuou-se e a albuminúria praticamente desapareceu. Formaram-se então os grupos: HS, recebendo HS; NS, recebendo dieta normal em sal (NS); HS-MMF, recebendo HS e MMF; HS-LOS, recebendo HS e losartan; HS-HDZ, recebendo HS e hidralazina. Após sessenta dias os ratos NS tinham albuminúria e dano/inflamação renal apenas discretos. Já os ratos HS desenvolveram hipertensão e glomerulosclerose acentuadas, expansão intersticial e infiltração renal por macrófagos e células positivas para angiotensina II. Losartan baixou a pressão arterial e preveniu albuminúria e lesão renal. MMF proporcionou proteção semelhante sem alteração pressórica, sugerindo a ação de mecanismos não hemodinâmicos, hipótese reforçada pelo achado de que a HDZ baixou a pressão arterial sem prevenir a nefropatia. RESULTADOS: Esses resultados indicam que o tratamento com HS e NAME predispõe ao desenvolvimento de hipertensão e lesão renal induzidos por excesso de sal, caracterizando um novo modelo de nefropatia crônica. CONCLUSÃO: A resposta ao MMF ou losartan, mas não à hidralazina, sugere o predomínio de fatores inflamatórios.

Effects of interleukin-1? on discharge of neurons in paraventricular nuclei of rat hypothalamus / 上海第二医科大学学报

Objective To observe the effects of interleukin-1 ?(IL-1?) on spontaneous electrical activity of neurons in paravenrticular nuclei,and discuss the possible mechanism.MethodsExtracellular recording technique was employed to observe the effects of IL-1? on spontaneous electrical activity of neurons in paravenricular nuclei in rat hypothalamic slices,and the influence of losartan on the electrical activity induced by IL-1? was examined.ResultsAfter exposure to IL-1?(1?10-7 mol/L),the discharge frequency was significantly increased in 46 of the 59 discharge units(78%) of neurons(P

Effects of Antihypertensive Protein from Pheretima on Angiotensin Ⅱ and Angiotensin Ⅱ AT_1 Receptor in Spontaneously Hypertensive Rats / 中国药房

OBJECTIVE:To investigate the effects of the antihypertensive protein from Pheretima on blood pressure, angiotensinⅡ and angiotensin Ⅱ AT1 receptor in spontaneously hypertensive rats (SHR).METHODS: The dynamic change of blood pressure in SHR after singel intravenous injection of antihypertensive protein from Pheretima was observed. After intervention with antihypertensive protein from earthworm for 28 d,the levels of blood pressure, angiotensinⅡ and expression of angiotensin Ⅱ AT1 receptor in SHR were detected. RESULTS: Either single intravenous injecion or multiple dosing of the antihypertensive protein from Pheretima could significantly reduce the blood pressure in SHR (P0.05).The expression of angiotensin Ⅱ AT1 receptor in kidney of SHR model increased significanlty compared the normal control (wistar rats), but decreased after the intervention of the antihypertensive protein from Pheretima.CONCLUSION: The antihypertensive protein from Pheretima has antihypertensive effect on SHR. The mechanism may be related to the reduction of angiotensinⅡ level and lowering of the expression of a angiotensin Ⅱ AT1 receptor in kidney.

The study of the relation between the AT_1 receptor gene polymorphism and some biochemical indices of essential hypertension patients / 医学研究生学报

Objective:To investigate the relation between the AT 1 receptor gene polymorphism and some biochemical indices of essential hypertension patients. Methods:Sixty-four patients of mild-moderate essential hypertension were not given any anti-hypertension drugs for 5 half lives,then used the PCR-RFLP to detect the AT 1 receptor gene type and measured the basic blood pressure at the same time. After that, fasting serum glucose , serum total cholesterol(TC) , triglyceride(TG) , high-density lipoprotein cholesterol(HDL-C) , low-density lipoprotein cholesterol(LDL-C) , blood urea nitrogen(BUN) , creatinine(Cr) were measured in all subjects. Results:①The frequency of AC gene type in these essential hypertension patients and the C1166 allete of AT 1 receptor gene was 23.4% and 11.7%. ②There was a remarkable difference on TG between two gene groups. ③There were obvious difference on Cr and UA between two gene groups .④There were no obvious difference on Glu, TC ,HDL-C ,LDL-C ,BUN between AC and AA gene type. Conclusion:①The concentration of TG of AC gene type is lower than that of AA , there may be relativity between two gene type. ② A1166/C gene polymorphism may be associated with renal function. AA gene type may have poorer renal function. ③A1166/C gene polymorphism may be not relative with Glu,TCH ,HDL-C ,LDL-C ,BUN.