AT1 Receptor Blocker Research Articles

Structural insights into angiotensin receptor signaling modulation by balanced and biased agonists.

The peptide hormone angiotensin II regulates blood pressure mainly through the type 1 angiotensin II receptor AT1 R and its downstream signaling proteins Gq and β-arrestin. AT1 R blockers, clinically used as antihypertensive drugs, inhibit both signaling pathways, whereas AT1 R β-arrestin-biased agonists have shown great potential for the treatment of acute heart failure. Here, we present a cryo-electron microscopy (cryo-EM) structure of the human AT1 R in complex with a balanced agonist, Sar1 -AngII, and Gq protein at 2.9 Å resolution. This structure, together with extensive functional assays and computational modeling, reveals the molecular mechanisms for AT1 R signaling modulation and suggests that a major hydrogen bond network (MHN) inside the receptor serves as a key regulator of AT1 R signal transduction from the ligand-binding pocket to both Gq and β-arrestin pathways. Specifically, we found that the MHN mutations N1113.35 A and N2947.45 A induce biased signaling to Gq and β-arrestin, respectively. These insights should facilitate AT1 R structure-based drug discovery for the treatment of cardiovascular diseases.

Telmisartan and losartan: The marked differences between their chemical and pharmacological properties may explain the difference in therapeutic efficacy in hospitalized patients with COVID‐19

Telmisartan and losartan: The marked differences between their chemical and pharmacological properties may explain the difference in therapeutic efficacy in hospitalized patients with COVID‐19

440 Role of angiotensin II in SARS-CoV-2 pathophysiology in a hamster model of COVID-19

OBJECTIVES/GOALS: Hamsters develop COVID-19 similarly to people because the SARS-CoV-2 spike protein binds with high affinity to hamster ACE2 resulting in host cell entry and replication. Our goal was to establish a hamster model that mirrors the lung and brain pathophysiology observed in COVID-19. METHODS/STUDY POPULATION: Hamsters infected with SARS CoV-2 are sacrificed on day 1 and day 6 postinfection. Lung histopathology scoring model was implemented for assessment all pathological relevant changes in the lungs of infected animals on tissue sections stained with hematoxylin and eosin. To quantify the extent and severity of lung pathology, two scoring systems were used: the first evaluated all relevant changes in the lungs of the infected animals and the second evaluated only the pathology associated with the pulmonary vasculature. Percentage of airway affected, airway severity, bronchiolar epithelial hyperplasia, alveoli affected, alveolar severity, type II pneumocyte hyperplasia and vessels affected were analyzed. Total airway score plus total lung alveolar score give lung histopathology score. RESULTS/ANTICIPATED RESULTS: Compared to the control hamster, the hamsters day 1 postinfection, exhibited a higher total airway score [9.00 ± 1.35 vs. 0.25 ± 0.1; p DISCUSSION/SIGNIFICANCE: Establishing this outstanding small animal model of COVID-19 will facilitate studies investigating diagnostics, prognosis and response to treatment in COVID-19 disease. These studies will provide insights that will complement on-going clinical trials on angiotensin type 1 receptor (AT1R) blockers (ARBs) in COVID-19.

A Low Concentration of Citreoviridin Prevents Both Intracellular Calcium Deposition in Vascular Smooth Muscle Cell and Osteoclast Activation In Vitro

Vascular calcification (VC) and osteoporosis are age-related diseases and significant risk factors for the mortality of elderly. VC and osteoporosis may share common risk factors such as renin-angiotensin system (RAS)-related hypertension. In fact, inhibitors of RAS pathway, such as angiotensin type 1 receptor blockers (ARBs), improved both vascular calcification and hip fracture in elderly. However, a sex-dependent discrepancy in the responsiveness to ARB treatment in hip fracture was observed, possibly due to the estrogen deficiency in older women, suggesting that blocking the angiotensin signaling pathway may not be effective to suppress bone resorption, especially if an individual has underlying osteoclast activating conditions such as estrogen deficiency. Therefore, it has its own significance to find alternative modality for inhibiting both vascular calcification and osteoporosis by directly targeting osteoclast activation to circumvent the shortcoming of ARBs in preventing bone resorption in estrogen deficient individuals. In the present study, a natural compound library was screened to find chemical agents that are effective in preventing both calcium deposition in vascular smooth muscle cells (vSMCs) and activation of osteoclast using experimental methods such as Alizarin red staining and Tartrate-resistant acid phosphatase staining. According to our data, citreoviridin (CIT) has both an anti-VC effect and anti-osteoclastic effect in vSMCs and in Raw 264.7 cells, respectively, suggesting its potential as an effective therapeutic agent for both VC and osteoporosis.

Neprilysin-dependent neuropeptide Y cleavage in the liver promotes fibrosis by blocking NPY-receptor 1.

Development of liver fibrosis is paralleled by contraction of hepatic stellate cells (HSCs), the main profibrotic hepatic cells. Yet, little is known about the interplay of neprilysin (NEP) and its substrate neuropeptide Y (NPY), a potent enhancer of contraction, in liver fibrosis. We demonstrate that HSCs are the source of NEP. Importantly, NPY originates majorly from the splanchnic region and is cleaved by NEP in order to terminate contraction. Interestingly, NEP deficiency (Nep-/-) showed less fibrosis but portal hypertension upon liver injury in two different fibrosis models in mice. We demonstrate the incremental benefit of Nep-/- in addition to AT1R blocker (ARB) or ACE inhibitors for fibrosis and portal hypertension. Finally, oral administration of Entresto, a combination of ARB and NEP inhibitor, decreased hepatic fibrosis and portal pressure in mice. These results provide a mechanistic rationale for translation of NEP-AT1R-blockade in human liver fibrosis and portal hypertension.

Evaluating the potential of tauroursodeoxycholic acid as add-on therapy in amelioration of streptozotocin-induced diabetic kidney disease

The bile acid tauroursodeoxycholic acid (TUDCA) is of natural origin and is used in traditional Chinese medicine for centuries. Earlier its use was limited to biliary disorders but owing to its pleiotropic effects dietary TUDCA supplementation is under clinical trials for diseases including type 1 and 2 diabetic complications.The current study aims to evaluate the potential and underlying molecular mechanism of the TUDCA as a monotherapy and as an add-on therapy to telmisartan, an angiotensin II type 1 receptor (AT1R) blocker against diabetic kidney disease (DKD). We employed both in-vitro and in-vivo approaches where NRK-52E cells were incubated with high glucose, and DKD was induced in Wistar rats using streptozotocin (55 mg/kg, i.p.). After 4 weeks, animals were administered with TUDCA (250 mg/kg, i.p.), telmisartan (10 mg/kg, p.o.), and their combination for 4 weeks. Plasma was collected for the biochemical estimation and kidneys were used for immunoblotting, PCR, and histopathological analysis. Similarly, for in-vitro experiments, cells were exposed to 1000 μM of TUDCA and 10 μM of telmisartan, and their combination, followed by cell lysate collection and immunoblotting analysis.We observed that the addition of TUDCA to conventional telmisartan treatment was more effective in restoring the renal function decline and suppressing the apoptotic and fibrotic signaling as compared to monotherapies of AT1R blocker and ER stress inhibitor.The results implicate the utility of traditionally used TUDCA as a potential renoprotective compound. Since, both TUDCA and telmisartan are approved for clinical usage, thus concomitant administration of them could be a novel therapeutic strategy against DKD.

Losartan impairs HTR-8/SVneo trophoblast migration through inhibition of angiotensin II-induced pro-inflammatory profile in human endometrial stromal cells

A deep interaction between the endometrium and the invading trophoblast occurs during implantation in humans, with the acquisition of uterine receptivity to the invading embryo promoted by an elevation of pro-inflammatory cytokines in the endometrium, and the invasiveness of decidualizing endometrial stromal cells, augmented by trophoblast-derived signals. Considering that usage of angiotensin II type 1 (AT1) receptor blockers, among other renin-angiotensin system (RAS) antagonists, is associated with adverse pregnancy outcomes, here we aim to analyse the involvement of AT1 receptor in the reciprocal dialogue occurring between endometrial stroma and trophoblast cells. In human endometrial stromal cells (T-HESC) pre-incubated with a decidualization cocktail, angiotensin (Ang) II increased protein expression of prolactin and FOXO1, markers of endometrial decidualization, while promoting nuclear translocation of FOXO1. In addition, Ang II treatment increased CXCL8, and matrix metalloprotease (MMP)-2 levels in T-HESC. Incubation with the AT1 receptor blocker losartan or with an NFAT signalling inhibitor, decreased Ang II-induced secretion of prolactin, CXCL8, and MMP-2 in T-HESC. In a wound healing assay, conditioned medium (CM) obtained from Ang II-treated T-HESC, but not CM from losartan-pre-incubated T-HESC, increased migration of HTR-8/SVneo trophoblasts, effect that was inhibited in the presence of a CXCL8-neutralizing antibody. An increased secretion of CXCL8 and MMP-2 was observed after treatment of T-HESC with CM obtained from HTR-8/SVneo cells, which was not observed in T-HESC pre-incubated with losartan or with the NFAT inhibitor. This study evidenced a reciprocal RAS-coded messaging between trophoblast and ESC which is affected by the AT1 receptor blocker losartan.

The Effect of Antioxidants and Cardiovascular Drugs in the Treatment of Cardiac Diseases

Abstract: Background: Reactive oxygen species mediate oxidative stress, is one of the major causes of the athero-thrombotic process involved in the etiology of peripheral arterial disease, ischemic strokes, and heart attack. Angiotensin-1 receptor blockers, betablockers, angiotensin-converting enzyme inhibitors, diuretics, calcium channel blockers are traditional cardio-protective drugs. But the problem associated with these medications is, a person diagnosed with high blood pressure in younger age, has to take these drugs for lifelong, which may lead to develop harmful drug-induced diseases on long-term use like Alzheimer’s disease, Raynaud’s phenomenon, decreased levels of plasma catecholamines, etc. Materials and Methods: Among all anti-hypertensive agents, angiotensin-1 receptor blockers are safer as they have minimal long-term health hazards. Many pieces of the literature suggest that, intake of foods rich in anti-oxidant reduces the chance of cardiovascular disease, as they consume free radicals formed by various endogenous systems, pathological states or exposure to different physiochemical conditions, and improper oxidation of lipids. We can focus on synergistic benefit of both anti-hypertensive drug and antioxidants. Conclusion: Hence, we can assume that, intake of antioxidant as an active pharmaceutical ingredient may positively benefit in the treatment of cardiovascular diseases. Co-administration of existing cardiovascular drug and a suitable antioxidant(s) may produce a better result. Keywords: Cardiovascular diseases, Oxidative stress, Reactive oxygen species, Antioxidants, AT1 receptor blocker.

PS-B02-6: CHANGES OF THE EXTRACELLULAR MATRIX AND INTERCELLULAR COMMUNICATION IN THE RAT HEARTS WITH VOLUME-PRESSURE OVERLOAD AND MODULATION BY CARDIOPROTECTIVE DRUGS

Objective: Pathogenesis of heart failure (HF) and hypertension with a focus on extracellular matrix (ECM) and communication in the heart is still a current scientific topic that calls for new findings. Design and method: We used as experimental model normotensive (HSD) and hypertensive (TGR) rats with aortocaval fistula (ACF) supplemented with an ACE inhibitor (ACEi)(15weeks, 6 mg/L) and an AT1 receptor blocker (ARB)(15weeks, 200 mg/L). At the end of the experiments, serum and myocardial tissue samples of the right and left ventricles were taken for biometric, biochemical, gene, protein and microscopic analyzes. Results: We observed an increase in the cardiac weight index after ACF, left and right ventricles in HSD and TGR rats. ACEi and ARB have normalized this condition to a greater extent. Due to ACF, serum concentrations of ANP and TBARS were increased in the blood serum of both strains. ACF increased hydroxyproline levels in right ventricular levels in HSD and TGR rats and left ventricular TBARS in TGR rats. In addition, ACF increased mRNA collagenI, and collagenI protein expression in the left and right ventricles of HSD rats. In contrast, ACF reduced Cx43 and pCx43 protein levels in the left and right ventricles of both strains, SMAD2 expression in the right ventricle in HSD and TGR rats. ACF also suppressed MMP-2 protein expression in both cardiac ventricles in HSD rats and PKCepsilon protein expression in both heart chambers of both strains. Hypertension caused a slight decrease in the protein expression of Cx43, pCx43 and PKCepsilon and an increase in the expression of PKCdelta in cardiac ventricles of both rat strain. Hypertension further increased and collagenI in TGR rats in the left and right ventricles of the heart. Microscopic analyzes showed that ACF induced cardiomyocyte hypertrophy as well as decreased activity of enzymes involved in ACF energy metabolism. An interesting finding was that the signaling pathways involved in cardiac remodeling were more normalized by the ARB, while proteins involved in intercellular communication by ACEi. Conclusions: Based on the results obtained from the experiment, it can be stated that the right ventricle is more significantly affected by ACF and the results of analyzes in TGR indicate adaptation, attenuated responses to the parameters we observed. Supported by: APVV-21-410, VEGA-2/0158/19.

PS-B12-8: ANGIOTENSIN II TYPE I RECEPTOR SIGNAL REGULATES MITOCHONDRIAL DYNAMICS, CAUSING MUSCULAR MITOCHONDRIAL DYSFUNCTION AND SARCOPENIA UNDER METABOLIC STRESS

Introduction: Metabolic stress, such as oxidized low density lipoprotein (ox-LDL) and advanced glycation end products (AGE) cause atherosclerotic cardiovascular diseases through dysfunction of mitochondria, which undergo quality control by mitochondrial dynamics, fission and fusion. Mitochondria also plays a crucial role in regulating muscular function, and its dysfunction leads to sarcopenia. This study aims to clarify whether and how mitochondrial dynamics are involved in the development of sarcopenia under metabolic stress. Methods: We used human skeletal muscle cells (HSMC) in in vitro experiments and C57BL6 (WT), apolipoprotein E (ApoE) deficient and the double knockout of ApoE and AT1R (DKO) mice in in vivo experiments. Results: Administration of either ox-LDL or AGE to HSMC induced mitochondrial fission through activation of fission factor, Drp1, decreased mitochondrial membrane potential assessed by JC-1 staining and increased reactive oxygen species assessed by Mito-sox Red staining and apoptosis, which were restored by Drp1-specific inhibitor, mdivi-1. Inhibition of angiotensin II type 1 receptor (AT1R) by AT1R blocker also ameliorated excessive mitochondrial fission, its function and oxidative stress induced by either ox-LDL or AGE in HSMC. These results suggest that metabolic stress induces mitochondrial fission and its dysfunction, which may cause sarcopenia. Muscular strength and the ratio of muscle weight to tibia length were lower in ApoE than those in WT. The number of fused mitochondria and mitochondrial function were lower and oxidative stress and the number of apoptotic cell were higher in ApoE KO than those of WT. Muscle strength, the ratio of muscle weight to tibia length, the number of fused mitochondria and its function were higher and the number of apoptotic cell were lower in DKO than those in ApoE KO mice. Taken together, these results suggest that either ox-LDL or AGE causes sarcopenia through AT1R signal-dependent mitochondrial fission and subsequent mitochondrial dysfunction. Conclusion: Either ox-LDL or AGE induces mitochondrial dysfunction through AT1R signal-regulating mitochondrial fission, which causes sarcopenia. Inhibition of AT1R signal may be a potential therapeutic strategy to avoid development of sarcopenia in patients with life style related diseases, such as dyslipidemia and diabetics.

AT1R blocker prevents mental stress induced retrograde blood flow in overweight/obese men.

The main goal was to determine the impact of mental stress (MS) on blood flow regulation in overweight/obese men. Fourteen overweight/obese men (27 ± 7 years; 29.8 ± 2.6kg/m2 ) participated in two randomized experimental sessions with oral administration of the AT1R blocker Olmesartan (40 mg; AT1RB) or placebo (PL). After 2 h, a 5-min acute MS session (Stroop Color Word Test) was administered. Blood flow was assessed at baseline and during the first 3 min of MS by vascular ultrasound in the brachial artery. Blood was collected before (baseline) and during mental stress (MS) for measurement of nitrite (chemiluminescence) and endothelin-1 (ELISA kit). The AT1R blocker was able to reverse the MS responses observed in the placebo session for retrograde flow (p < 0.01), retrograde SR (p < 0.01) and oscillatory shear index (p=0.01). Regarding vasoactive substances, no differences were observed in ET-1 (p > 0.05) responses to MS between experimental sessions. However, for nitrite responses, the administration of the AT1R blocker was able to increase circulating levels of NO (p=0.03) Blockade of AT1R appears to prevent the decrease in endothelial function by reducing low shear stress and maintaining the vasoactive substances balance after MS in overweight/obese men.

PS-BPB04-3: ENHANCEMENT EFFECTS OF GINSENOSIDE-RG2 ON SOME ANTIHYPERTENSIVE AGENTS-INDUCED SUPPRESSION OF ADRENAL CATECHOLAMINE RELEASE

Objective: The present study was aimed to investigate the effects of ginsenoside-Rg2 (Rg2), one of panaxadiol-type saponins, which is isolated from Korean Red ginseng, in some antihypertensive agents-induced reduction on the release of catecholamines (CA) from the perfused model of the rat adrenal medullae. Design and Methods: The adrenal gland was isolated and perfused with Krebs-bicarbonate. The CA amoiunt in the perfusate was measured directly by using the fluorospectrophotometer. Results: Ginsenoside-Rg2 (3∼30 μM) during perfusion into an adrenal vein for 90 min significantly inhibited the CA secretion evoked by acetylcholine (ACh) in a dose- and time-dependent fashion. Also, olmesartan (AT1 receptor blocker, 15 μM), simvastatin (an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, 60 μM), enalapril (an inhibitor of angiotensin converting enzyme, 150 μM), and cilnidipine (a voltage-dependent L-type Ca2+ channel blocker, 3 μM) significantly reduced the CA secretion evoked by ACh and angiotensin II (Ang II), respectively. In the simultaneous presence of ginsenoside-Rg2 (10 μM) along with four antihypertensive agents (olmesartan, enalapril, simvastatin or cilnidipine), the CA secretion evoked by ACh and Ang II was more strongly inhibited compared with that of each antihypertensive agent-treatment alone. Conclusion: Collectively, these results demonstrate that ginsenoside-Rg2 as well as antihypertensive agents can inhibit the CA secretion evoked by activation of both cholinergic and AT1 receptors from the perfused rat adrenal medulla. When this ginsenoside-Rg2 was used in combination with different antihypertensive agents, their effects of antihypertensive agents on reduction of adrenal CA secretion were significantly enhanced, which may also be clinically beneficial for the treatment of cardiovascular diseases.

PS-B03-5: HIGH-DOSES OF LOSARTAN RATHER ENHANCE CATECHOLAMINE SECRETION FROM THE PERFUSED ADRENAL GLAND

Objective: Previously, we have found that Losartan (5∼50 μM), an AT1 receptor blocker, dose-dependently inhibits secretion of catecholamines (CA) evoked by cholinergic and angiotensin II (Ang II) receptor stimulation from the perfused rat adrenal medulla. The aim of the present study was to examine the characteristic effects of high-dose losartan on the CA secretion from the isolated perfused rat adrenal gland, and also to establish its mechanism of action. Design and Methods: The adrenal gland was isolated and perfused with Krebs-bicarbonate. CA was measured directly by using the fluorospectrophotometer. Results: The perfusion of high-dose losartan (150 ∼ 600 μM) into an adrenal vein for 90 min resulted in great increases in CA secretions evoked by acetylcholine in a dose-dependent fashion. Also, losartan (300 μM) enhanced the CA release evoked by Ang II, high K+ and DMPP (a selective nicotinic receptor agonist), McN-A-343 (a selective muscarinic M1 receptor agonist). Also, in the presence of losartan (300 μM), the CA secretory responses to veratridine (a selective Na+ channel activator), Bay-K-8644 (a Ca2+ channel activator), and cyclopiazonic acid (a cytoplasmic Ca2+-ATPase inhibitor) were significantly potentiated, respectively. The facilitatory CA-releasing effect of Ach evoked by high-dose losartan (300 μM) was time-dependently depressed by pretreatment with nifedipine (Ca2+ channel blocker), while not by pretreatment with sodium nitroprusside (an NO donor). High-dose olmesartan (150 ∼ 600 μM), one of ARBs, also potentiated Ach-evoked CA release in time-dependent fashion. However, in the simultaneous presence of losartan (300 μM) and CGP42112 (an AT2 receptor agonist), the facilitatory responses of losartan on the CA secretion evoked by ACh were rather significantly reduced in comparison with that of losartan-treatment alone. Conclusion: Conclusively, these results demonstrate that high-dose losartan can potentiate the adrenomedullary CA secretion in a calcium-dependent fashion. It seems that this facilitatory effect of high-dose losartan may be mediated by activation of the Ca2+ influx through L-type Ca2+ channels into adrenomedullary cells without inhibition of NO synthesis, which seems to be relevant to AT2 receptor blockade. It also suggests that high-dose ARBs may be a risk factor in causing hypertensive response.

PS-BPC07-8: ARTERIAL HYPERTENSION AS PROGNOSTIC MARKER IN PATIENTS WITH ST-ELEVATION MYOCARDIAL INFARCTION AND EARLY PERCUTANEOUS CORONARY INTERVENTION

Objective: Strong evidence points to the prognostic value of renin angiotensin system (RAS)-inhibitors (ACE inhibitors or AT1-receptor blockers) and beta blockers (BB) in the secondary prevention after myocardial infarction (MI). However, adequate dosing of these drugs is often limited due to their blood pressure lowering effects, especially early after MI. The present study therefore sought to identify differences in rates of prescription, persistence and dosing of RAS-inhibitors and BB early after acute ST-elevation MI (STEMI) and its impact on survival in hypertensive and non-hypertensive patients. Design and method: 1003 consecutive patients with adjudicated STEMI treated by early percutaneous coronary intervention (PCI) between 2007 and 2011 in a single centre as part of the Cologne Infarction Model (KIM) were retrospectively dichotomized according to their history of arterial hypertension at the time of hospital admission. Comparisons were made using students T-test. Qualitative analyses were done using Chi square-test or given as odds ratio (OR (95% KI). Results: Mean age was 63 ± 13 years, body mass index 27 ± 5 kg/m2, 24% were women. 749 patients were diagnosed with hypertension. Mortality was 11.3% at 30 days and 17.2% at 1 year follow up. History of hypertension at time of hospital admission was significantly associated with lower mortality on follow up (OR, at 30 days: 0.41 (0.27–0.64), at 1 year 0.37 (0.26–0.53)). Long term persistence to RAS-inhibitors was significantly higher in hypertensive patients compared to non-hypertensives (84% vs. 70%, p = 0.004). However, persistence to BB did not differ between groups (88% vs 86%, n.s.). At discharge the rate of prescription of RAS-inhibitors and BB was significantly higher in hypertensive patients (RAS-inhibitors: 87.3% vs. 69.8%, p &lt; 0.001; BB: 92.8% vs. 84.3%, p &lt; 0.001). In addition, the defined daily dose (DDD) among patients receiving RAS-inhibitors at discharge was higher in hypertensive versus non-hypertensive patients (DDD: RAS-inhibitors, 0.40 vs. 0.30, p &lt; 0.001), whereas there was no difference for BB. At 30 days and at 1 year follow up survival was significantly associated with the prescription of RAS-inhibitors as well as BB at discharge. Conclusion: Patients with a history of hypertension show higher prescription rates at discharge, better long-term persistence as well as higher individual dosing of RAS-inhibitors after STEMI. This, as well as the higher prescription rates of BB, may contribute to the better survival that we observed in STEMI patients with history of hypertension compared to non-hypertensive controls.

Mental stress induces endothelial dysfunction by AT1R-mediated redox imbalance in overweight/obese men

The main goal of this study was to determine whether oxidative imbalance mediated by AT1 receptor (AT1R) is responsible for deleterious endothelial responses to mental stress (MS) in overweight/obese class I men. Fifteen overweight/obese men (27±7 years old; 29.8±2.6 kg/m2) participated in three randomized experimental sessions with oral administration of the AT1R blocker olmesartan (40 mg; AT1R blockade) or ascorbic acid (AA; 3g) infusion or placebo [both intravenously (0.9% NaCl) and orally]. After two hours, endothelial function was determined by flow-mediated dilation (FMD) before (baseline), 30 min (30MS), and 60 min (60MS) after a five-minute acute MS session (Stroop Color Word Test). Blood was collected before (baseline), during MS, and 60 min after MS for redox homeostasis profiling: lipid peroxidation (TBARS; thiobarbituric acid reactive species), protein carbonylation, and catalase activity by colorimetry and superoxide dismutase (SOD) activity by an ELISA kit. At the placebo session, FMD significantly decreased 30MS (P=0.05). When compared to baseline, TBARS (P<0.02), protein carbonylation (P<0.01), catalase (P<0.01), and SOD (P<0.01) increased during the placebo session. During AT1R blockade, FMD increased 30 min after MS (P=0.01 vs baseline; P<0.01 vs placebo), while AA infusion increased FMD only 60 min after MS. No differences were observed during MS with the AT1R blockade and AA regarding TBARS, protein carbonylation, catalase, and SOD. AT1R-mediated redox imbalances played an important role in endothelial dysfunction to mental stress.

Cardioprotective Mechanisms against Reperfusion Injury in Acute Myocardial Infarction: Targeting Angiotensin II Receptors.

Ischemia/reperfusion injury is a process associated with cardiologic interventions, such as percutaneous coronary angioplasty after an acute myocardial infarction. Blood flow restoration causes a quick burst of reactive oxygen species (ROS), which generates multiple organelle damage, leading to the activation of cell death pathways. Therefore, the intervention contributes to a greater necrotic zone, thus increasing the risk of cardiovascular complications. A major cardiovascular ROS source in this setting is the activation of multiple NADPH oxidases, which could result via the occupancy of type 1 angiotensin II receptors (AT1R); hence, the renin angiotensin system (RAS) is associated with the generation of ROS during reperfusion. In addition, ROS can promote the expression of NF-κΒ, a proinflammatory transcription factor. Recent studies have described an intracellular RAS pathway that is associated with increased intramitochondrial ROS through the action of isoform NOX4 of NADPH oxidase, thereby contributing to mitochondrial dysfunction. On the other hand, the angiotensin II/ angiotensin type 2 receptor (Ang II/AT2R) axis exerts its effects by counter-modulating the action of AT1R, by activating endothelial nitric oxide synthase (eNOS) and stimulating cardioprotective pathways such as akt. The aim of this review is to discuss the possible use of AT1R blockers to hamper both the Ang II/AT1R axis and the associated ROS burst. Moreover; we suggest that AT1R antagonist drugs should act synergistically with other cardioprotective agents, such as ascorbic acid, N-acetylcysteine and deferoxamine, leading to an enhanced reduction in the reperfusion injury. This therapy is currently being tested in our laboratory and has shown promising outcomes in experimental studies.

Heterogenous improvements in endothelial function by sub-blood pressure lowering doses of ARBs result in major anti-aortic root remodeling effects

Low basal nitric oxide (NO) production is associated with a dysfunctional endothelium and vascular diseases. We have shown that some angiotensin II (AngII) receptor type 1 (AT1R) blockers (ARBs), a group of clinic-approved blood pressure (BP)-lowering medications, are also capable of activating endothelial function acutely and chronically, both ex vivo and in vivo, in pleiotropic, AngII-independent fashions, which suggested that endothelial function enhancement with ARBs may be independent of their well-documented BP lowering properties. Herein, we attempt to identify the most potent ARB at activating endothelial function when administered at sub-BP-lowering doses and determine its anti-aortic root remodeling properties in a model of Marfan syndrome (MFS). Amongst the 8 clinically available ARBs tested, only telmisartan and azilsartan induced significant (70% and 49%, respectively) NO-dependent inhibition of aortic contractility when administered for 4 weeks at sub-BP lowering, EC5 doses. Low-dose telmisartan (0.47 mg/kg) attenuated MFS-associated aortic root widening, medial thickening, and elastic fiber fragmentation to the same degree as high-dose telmisartan (10 mg/kg) despite wide differences in BP lowering between the two doses. Our study suggests that telmisartan is the most potent ARB at promoting increased endothelial function at low sub-BP doses and that it retained major aortic root widening inhibition activities. ARBs may enhance endothelial function independently from BP-lowering pathways, which could lead to new therapeutic approaches.

MicroRNA profiles following telmisartan treatment in pancreatic ductal adenocarcinoma cells.

Pancreatic ductal adenocarcinoma (PDAC) is the most devastating of all cancers with an extremely poor prognosis. It has few effective and reliable therapeutic strategies. Telmisartan, a widely used antihypertensive drug, is an angiotensin II type 1 (AT1) receptor blocker (ARB). Telmisartan inhibits cancer cell proliferation, but the underlying mechanisms in PDAC, remain unknown. In the present study, we evaluated the effects of telmisartan on human PDAC cell proliferation in vitro. We assessed the effects of telmisartan on human PDAC cells using the cell lines PK-1 and PANC-1. Telmisartan inhibited the proliferation of these cells via blockade of the G0 to G1 cell cycle transition. This was accompanied by a strong decrease in cyclin D1. Telmisartan was also shown by receptor tyrosine kinase and angiogenesis arrays to reduce the phosphorylation of epidermal growth factor receptor (EGFR), and miRNA expression was markedly altered by telmisartan in PK-1 cells. In conclusion, telmisartan inhibits human PDAC cell proliferation by inducing cell cycle arrest. Furthermore, telmisartan significantly altered miRNA expression in vitro. Taken together, our study demonstrated the therapeutic potential of telmisartan and provides molecular mechanistic insights into its anti-tumor effect on PDAC cells.

Treatment with losartan, an AT1 receptor blocker, improves cognitive and cardiovascular function in a Dahl salt‐sensitive rat model of age‐associated vascular dementia.

AbstractBackgroundDementia is characterized by progressive cognitive impairment (CI), which is accompanied by decline in reasoning, planning and memory. Cardiovascular diseases are the major contributors to the pathogenesis of vascular dementia and affect mainly the aging population. Even on a normal salt diet, Dahl salt‐sensitive (DSS) rats exhibit age‐associated hypertension and CI. We hypothesized, that anti‐hypertensive treatment with the angiotensin II receptor blocker losartan (LOS) would improve cardiovascular and cognitive function in aged DSS rats.MethodMale DSS rats (n=30) were kept on a normal salt diet (0.5% NaCl) for the duration of the study. Baseline measurements were taken at 6‐mo of age. After that, treatment with 30mg/kg/day of LOS, added to the drinking water (n=14), or control (n=16) was started and continued for 6‐mo. Systolic blood pressure (SBP), aortic pulse wave velocity (aPWV), a measure of aortic stiffness, and behavioral testing in a visually cued reaction task to assess attention and inhibitory control were assessed every 3‐mo. Elevated plus maze (EPM) and Morris Water Maze (MWM) tests were performed at 12‐mo of age to measure anxiety‐like behavior and to evaluate spatial memory, respectively. Data were analyzed by 2‐way repeated measures ANOVA or t‐tests as applicable.ResultPrior to the treatment, LOS and control groups did not display differences in any parameter analyzed. Control rats exhibited gradual increase in SBP and aPWV from 6 to 12‐mo of age. Following 3‐ and 6‐mo of treatment, LOS rats exhibited lower SBP and aPWV vs. controls (Table 1). At 12‐mo of age, LOS rats had improved performance in the reaction task (Figure 1), and exhibited lower anxiety levels, spending less time on the closed arm in EPM and 1.5‐fold more time in the open arm vs. control rats. LOS rats also spent less time to find a hidden platform in the MWM vs. controls, indicating that LOS treatment improved spatial memory (Table 1).ConclusionImprovement of cardiovascular function and reduction in aortic stiffness by LOS were associated with better attentional control and memory and lower anxiety levels, demonstrating an association of CI with cardiovascular changes in the DSS rat model of vascular dementia.

Distinct Mechanisms of β-Arrestin-Biased Agonist and Blocker of AT1R in Preventing Aortic Aneurysm and Associated Mortality.

Aortic aneurysm (AA) is a "silent killer" human disease with no effective treatment. Although the therapeutic potential of various pharmacological agents have been evaluated, there are no reports of β-arrestin-biased AT1R (angiotensin-II type-1 receptor) agonist (TRV027) used to prevent the progression of AA. We tested the hypothesis that TRV027 infusion in AngII (angiotensin II)-induced mouse model of AA prevents AA. High-fat-diet-fed ApoE (apolipoprotein E gene)-null mice were infused with AngII to induce AA and co-infused with TRV027 and a clinically used AT1R blocker Olmesartan to prevent AA. Aortas explanted from different ligand infusion groups were compared with assess different grades of AA or lack of AA. AngII produced AA in ≈67% male mice with significant mortality associated with AA rupture. We observed ≈13% mortality due to aortic arch dissection without aneurysm in male mice. AngII-induced AA and mortality was prevented by co-infusion of TRV027 or Olmesartan, but through different mechanisms. In TRV027 co-infused mice aortic wall thickness, elastin content, new DNA, and protein synthesis were higher than untreated and Olmesartan co-infused mice. Co-infusion with both TRV027 and Olmesartan prevented endoplasmic reticulum stress, fibrosis, and vasomotor hyper responsiveness. TRV027-engaged AT1R prevented AA and associated mortality by distinct molecular mechanisms compared with the AT1R blocker, Olmesartan. Developing novel β-arrestin-biased AT1R ligands may yield promising drugs to combat AA.