Increased angiotensin II type 1 receptor expression in hypercholesterolemic atherosclerosis in rabbits

Vascular smooth muscle cell phenotypic switching in atherosclerosis

Atherosclerosis (AS) is a complex pathology process involving intricate interactions among various cells and biological processes. Vascular smooth muscle cells (VSMCs) are the predominant cell type in normal arteries, and under atherosclerotic stimuli, VSMCs respond to altered blood flow and microenvironment changes by downregulating contractile markers and switching their phenotype. This review overviews the diverse phenotypes of VSMCs, including the canonical contractile VSMCs, synthetic VSMCs, and phenotypes resembling macrophages, foam cells, myofibroblasts, osteoblasts/chondrocytes, and mesenchymal stem cells. We summarize their presumed protective and pro-atherosclerotic roles in AS development. Additionally, we underscore the molecular mechanisms and regulatory pathways governing VSMC phenotypic switching, encompassing transcriptional regulation, biochemical factors, plaque microenvironment, epigenetics, miRNAs, and the cytoskeleton, emphasizing their significance in AS development. Finally, we outline probable future research directions targeting VSMCs, offering insights into potential therapeutic strategies for AS management.

Lipotoxicity-Related Hematological Disorders in Obesity

Lipotoxicity can mediate endothelial dysfunction in obesity. Altered endothelial cell phenotype during the pathobiological course of the lipotoxicity may lead to hemostatic abnormalities, which is a hallmark of several hematological disorders. Impaired hemostasis could also be directly related to numerous metabolic diseases such as hypertension, diabetes, and atherosclerosis. On the other hand, the local hematopoietic bone marrow (BM) renin-angiotensin system (RAS) contributes to the development of atherosclerosis via acting on the lipotoxicity processes. Local BM RAS, principally an autocrine/paracrine/intracrine hematological system, is located at the crossroads of cellular regulation, molecular interactions, and lipotoxicity-mediated vascular endothelial dysfunction. The positive regulatory role of plasma LDL on AT1 receptor-mediated hematopoietic stem cell (HSC) differentiation and the production of pro-atherogenic monocytes have been described. LDL-regulated HSC function may explain in part hypercholesterolemia-induced inflammation as well as the anti-inflammatory and anti-atherosclerotic effects of AT1 receptor blockers. The role of local adipose tissue RAS is directly related to the pathogenesis of metabolic derangements in obesity. There may be a crosstalk between local BM RAS and local adipose tissue RAS at the genomics and transcriptomics levels. This chapter aims to review hematological alterations propagating the pathological influences of lipotoxicity on the vascular endothelium.

Squalene through Its Post-Squalene Metabolites Is a Modulator of Hepatic Transcriptome in Rabbits

Squalene is a natural bioactive triterpene and an important intermediate in the biosynthesis of sterols. To assess the effect of this compound on the hepatic transcriptome, RNA-sequencing was carried out in two groups of male New Zealand rabbits fed either a diet enriched with 1% sunflower oil or the same diet with 0.5% squalene for 4 weeks. Hepatic lipids, lipid droplet area, squalene, and sterols were also monitored. The Squalene administration downregulated 9 transcripts and upregulated 13 transcripts. The gene ontology of transcripts fitted into the following main categories: transporter of proteins and sterols, lipid metabolism, lipogenesis, anti-inflammatory and anti-cancer properties. When the results were confirmed by RT-qPCR, rabbits receiving squalene displayed significant hepatic expression changes of LOC100344884 (PNPLA3), GCK, TFCP2L1, ASCL1, ACSS2, OST4, FAM91A1, MYH6, LRRC39, LOC108176846, GLT1D1 and TREH. A squalene-enriched diet increased hepatic levels of squalene, lanosterol, dihydrolanosterol, lathosterol, zymostenol and desmosterol. Strong correlations were found among specific sterols and some squalene-changed transcripts. Incubation of the murine AML12 hepatic cell line in the presence of lanosterol, dihydrolanosterol, zymostenol and desmosterol reproduced the observed changes in the expressions of Acss2, Fam91a1 and Pnpla3. In conclusion, these findings indicate that the squalene and post-squalene metabolites play important roles in hepatic transcriptional changes required to protect the liver against malfunction.

Dietary squalene modifies plasma lipoproteins and hepatic cholesterol metabolism in rabbits

To evaluate the effects of squalene, the main unsaponifiable component of virgin olive oil, on lipid metabolism, two groups of male New Zealand rabbits were fed a 1% sunflower oil-enriched regular diet or the same diet containing 0.5% squalene for 4 weeks. Plasma triglycerides, total- and HDL-cholesterol and their lipoproteins were assayed. Analyses of hepatic lipid droplets, triglycerides, total- and non-esterified cholesterol, squalene, protein and gene expression, and cholesterol precursors were carried out. In the jejunum, the squalene content and mRNA and protein APOB expressions were measured. Finally, we studied the effect of cholesterol precursors in AML12 cells. Squalene administration significantly increased plasma total cholesterol, mainly carried as non-esterified cholesterol in IDL and large LDL, and corresponded to an increased number of APOB100-containing particles without accumulation of triglycerides and decreased reactive oxygen species. Despite no significant changes in the APOB content in the jejunum, the latter displayed increased APOB mRNA and squalene levels. Increases in the amounts of non-esterified cholesterol, squalene, lanosterol, dihydrolanosterol, lathosterol, cholestanol, zymostenol, desmosterol and caspase 1 were also observed in the liver. Incubation of AML12 cells in the presence of lanosterol increased caspase 1. In conclusion, squalene administration in rabbits increases the number of modified APOB-containing lipoproteins, and hepatic cholesterol biosynthesis is linked to caspase 1 probably through lanosterol.

Comparison of clinical outcomes between angiotensin-converting-enzyme inhibitors and ARBs in patients with acute myocardial infarction with dyslipidemia after a successful stent implantation

OBJECTIVE

Currently, there are limited comparative data concerning long-term major clinical outcomes following the angiotensin-converting-enzyme inhibitors (ACEIs) and angiotensin II type 1 (AT1) receptor blockers (ARBs) therapy in patients with acute myocardial infarction (AMI) with dyslipidemia after a successful stent implantation. Therefore, we investigated major clinical outcomes for 2 years following the ACEIs and ARBs therapy in these patients.

METHODS

A total of 3015 patients with AMI who underwent a successful stent implantation and were prescribed ACEIs (n=2175) or ARBs (n=840) were enrolled into the study from the Korea AMI Registry (KAMIR). The major clinical endpoint was the occurrence of major adverse cardiac events (MACEs) defined as all-cause death, recurrent myocardial infarction (Re-MI), and any repeat-revascularization-comprised target lesion revascularization (TLR), target vessel revascularization (TVR), and non-TVR.

RESULTS

After the adjustment, the cumulative incidence of all-cause death in the ARBs group was significantly higher than in the ACEIs group [adjusted hazard ratio (aHR), 2.277; 95% confidence interval (CI), 1.154-4.495; p=0.018]. The cumulative incidences of MACEs (aHR, 1.305; 95% CI, 0.911-1.869; p=0.146), cardiac death, Re-MI, any repeat revascularization, TLR, TVR, and non-TVR were similar between the two groups. In addition, an advanced age (≥65 years), decreased left ventricular ejection fraction (<50%), and cardiopulmonary resuscitation on admission were meaningful independent predictors for all-cause death in this study.

CONCLUSION

ACEIs were a preferred treatment modality when compared to ARBs for patients with AMI with dyslipidemia who underwent a successful stent implantation to reduce the incidences of all-cause death during a 2-year follow-up. However, additional research is required to determine the clinical implications of these results.

Angiotensin II, Hypercholesterolemia, and Vascular Smooth Muscle Cells: A Perfect Trio for Vascular Pathology

Cardiovascular disease is the leading cause of morbidity and mortality in the Western and developing world, and the incidence of cardiovascular disease is increasing with the longer lifespan afforded by our modern lifestyle. Vascular diseases including coronary heart disease, high blood pressure, and stroke comprise the majority of cardiovascular diseases, and therefore represent a significant medical and socioeconomic burden on our society. It may not be surprising that these conditions overlap and potentiate each other when we consider the many cellular and molecular similarities between them. These intersecting points are manifested in clinical studies in which lipid lowering therapies reduce blood pressure, and anti-hypertensive medications reduce atherosclerotic plaque. At the molecular level, the vascular smooth muscle cell (VSMC) is the target, integrator, and effector cell of both atherogenic and the major effector protein of the hypertensive signal Angiotensin II (Ang II). Together, these signals can potentiate each other and prime the artery and exacerbate hypertension and atherosclerosis. Therefore, VSMCs are the fulcrum in progression of these diseases and, therefore, understanding the effects of atherogenic stimuli and Ang II on the VSMC is key to understanding and treating atherosclerosis and hypertension. In this review, we will examine studies in which hypertension and atherosclerosis intersect on the VSMC, and illustrate common pathways between these two diseases and vascular aging.

Aspirin Improves Nonalcoholic Fatty Liver Disease and Atherosclerosis through Regulation of the PPARδ-AMPK-PGC-1α Pathway in Dyslipidemic Conditions

This study is aimed at elucidating how aspirin could systemically and simultaneously normalize nonalcoholic fatty liver disease (NAFLD) and atherosclerosis through both in vitro and in vivo studies in hyperlipidemic conditions. We evaluated the effects and mechanism of aspirin on the levels of various biomarkers related to NAFLD, atherosclerosis, and oxidative phosphorylation in cells and animals of hyperlipidemic conditions. The protein levels of biomarkers (PPARδ, AMPK, and PGC-1α) involved in oxidative phosphorylation in both the vascular endothelial and liver cells were elevated by the aspirin in hyperlipidemic condition. Also in the stimulation pathway of oxidative phosphorylation by aspirin, PPARδ was a superior regulator than AMPK and PGC-1α in HepG2 cells. In the vascular endothelial cells, the phosphorylated endothelial nitric oxide synthase level was increased by the treatment. The protein levels of biomarkers related to lipid synthesis were decreased by the treatment in the liver cells. In rabbits administered with cholesterol diet, the levels of triglyceride, HDL-cholesterol, and alanine amino transferase in serums were ameliorated by the aspirin treatment, the levels of ATP and TNFα were increased or decreased, respectively, by the aspirin in liver and aorta tissues, and mannose receptor and C-C chemokine receptor type 2 levels were increased or decreased by the aspirin in spleen, respectively. The elevated levels of macrophage antigen, angiotensin II type1 receptor, and lipid accumulation were decreased in both the liver and aorta tissues in the aspirin-treated group. In conclusion, aspirin can systemically and simultaneously ameliorate NAFLD and atherosclerosis by inhibiting lipid biosynthesis and inflammation and by elevating catabolic metabolism through the activation of the PPARδ-AMPK-PGC-1α pathway. Furthermore, aspirin may normalize atherosclerosis and NAFLD by modulating the mannose receptor and CCR2 in macrophages.

Hypertriglyceridemia and Atherosclerosis: Using Human Research to Guide Mechanistic Studies in Animal Models

Human studies support a strong association between hypertriglyceridemia and atherosclerotic cardiovascular disease (CVD). However, whether a causal relationship exists between hypertriglyceridemia and increased CVD risk is still unclear. One plausible explanation for the difficulty establishing a clear causal role for hypertriglyceridemia in CVD risk is that lipolysis products of triglyceride-rich lipoproteins (TRLs), rather than the TRLs themselves, are the likely mediators of increased CVD risk. This hypothesis is supported by studies of rare mutations in humans resulting in impaired clearance of such lipolysis products (remnant lipoprotein particles; RLPs). Several animal models of hypertriglyceridemia support this hypothesis and have provided additional mechanistic understanding. Mice deficient in lipoprotein lipase (LPL), the major vascular enzyme responsible for TRL lipolysis and generation of RLPs, or its endothelial anchor GPIHBP1, are severely hypertriglyceridemic but develop only minimal atherosclerosis as compared with animal models deficient in apolipoprotein (APO) E, which is required to clear TRLs and RLPs. Likewise, animal models convincingly show that increased clearance of TRLs and RLPs by LPL activation (achieved by inhibition of APOC3, ANGPTL3, or ANGPTL4 action, or increased APOA5) results in protection from atherosclerosis. Mechanistic studies suggest that RLPs are more atherogenic than large TRLs because they more readily enter the artery wall, and because they are enriched in cholesterol relative to triglycerides, which promotes pro-atherogenic effects in lesional cells. Other mechanistic studies show that hepatic receptors (LDLR and LRP1) and APOE are critical for RLP clearance. Thus, studies in animal models have provided additional mechanistic insight and generally agree with the hypothesis that RLPs derived from TRLs are highly atherogenic whereas hypertriglyceridemia due to accumulation of very large TRLs in plasma is not markedly atherogenic in the absence of TRL lipolysis products.

High Fib4 index in patients with suspected NASH is associated with elevation of chymase-dependent angiotensin II-forming activity in circulating mononuclear leucocytes

Fatal hepatic disease is closely related to non-alcoholic fatty liver disease, especially non-alcoholic steatohepatitis (NASH). NASH is associated with cardiovascular events because it develops on the background of lifestyle-related diseases. Chymase-dependent angiotensin II-forming activity (dAIIFA) in circulating mononuclear leucocytes (CML) is a marker of local angiotensin II production and inflammation. This study investigated the association between CML chymase dAIIFA and NASH. Cardiovascular outpatients were recruited and the Fib4 index (F4I) was calculated. Patients with an F4I > 2.67 were classified into the high F4I group and these patients were strongly suspected to have NASH, while patients with an F4I < 1.30 were classified into the low F4I group. Patient background factors were compared between these groups. CML chymase dAIIFA was measured by ELISA using Nma/Dnp-modified angiotensin I. Among 499 patients, 16% were classified into the high F4I group. Compared with the low F4I group, the high F4I group had a significantly higher age, pancytopenia, more frequent diabetes mellitus, lower diastolic blood pressure, lower estimated glomerular filtration rate, higher brain natriuretic peptide, lower plasma aldosterone concentration, higher total AIIFA, higher CML chymase dAIIFA, and higher pulse wave velocity. Contrary to expectations, the body mass index, triglycerides, and low-density lipoprotein cholesterol were relatively low in the high F4I group. Many cardiovascular outpatients have a high F4I and can probably be categorized as NASH. The high F4I patients had few features of metabolic syndrome and were suspected to have elevated tissue chymase dAIIFA contributing to inflammation in the liver as well as in cardiovascular organs.

Dose-Effect of Irbesartan on Cyclooxygenase-2 and Matrix Metalloproteinase-9 Expression in Rabbit Atherosclerosis

Irbesartan has previously shown antiatherosclerotic effects on human carotid atherosclerotic plaques. Our study aimed to assess the dose-effect of irbesartan on cyclooxygenase-2 (COX-2) and matrix metalloproteinase-9 (MMP-9) in rabbit atherosclerotic aorta. New Zealand rabbits were randomly divided into 6 groups: normal control (NC), high cholesterol (HC), low-dose (10 mg·kg·day), medium-dose (20 mg·kg·d), and high-dose (30 mg·kg·d) irbesartan and celecoxib (20 mg·kg·d). Except for the NCs, rabbits were fed a HC diet for 14 weeks to induce atherosclerosis. Aortic atherosclerotic lesions and messenger RNA and protein expression of COX-2, MMP-9, and nuclear factor-κB (NF-κB) were subsequently measured. The surface area of aortic atherosclerotic lesions was visibly larger in the HC group than in NCs (P < 0.01), but showed considerable reduction with medium- and high-dosage irbesartan and celecoxib treatments (P < 0.01). In medium- and high-dosage irbesartan and celecoxib groups, COX-2 and MMP-9 expression and NF-κB activity were significantly lower than in the high-cholesterol group (P < 0.01). No significant differences in treatment effects were observed between the high-dosage irbesartan and celecoxib groups (P > 0.05). Our results indicate that medium and high doses of irbesartan and celecoxib have antiatherosclerotic effects in aortic plaques via inhibition of COX-2 and MMP-9 by suppressing NF-κB activation. High-dose irbesartan has effects similar to celecoxib.

Increase of chymase-dependent angiotensin II-forming activity in circulating mononuclear leukocytes after acute myocardial infarction chymase activity after acute myocardial infarction

A previous clinical study revealed elevation of chymase- and cathepsin G-dependent angiotensin II-forming activity (AIIFA) in the myocardium after acute myocardial infarction (AMI). This study examined the time course of chymase- and cathepsin G-dependent AIIFA in circulating mononuclear leukocytes (CML) after AMI. Consecutive patients with AMI were recruited. Chymase- and cathepsin G-dependent AIIFA in CML were assayed using a modified angiotensin I substrate with Nma/Dnp fluorescence quenching. The changes of CML AIIFA were monitored over time in the patients. Fifteen consecutive AMI patients admitted to our hospital were recruited. At 1 day after the admission, CML chymase- and cathepsin G-dependent AIIFA were 2.9- and 1.7-fold higher than at discharge, respectively. The ratio of chymase-dependent AIIFA to total AIIFA was significantly increased. AIIFA gradually decreased over time after the admission. The peak value of chymase- and cathepsin G-dependent AIIFA was significantly correlated with the maximum levels of aspartate aminotransferase (r = 0.53, 0.64), lactate dehydrogenase (r = 0.57, 0.62), and creatine kinase (r = 0.60, 0.65). This is the first evidence that chymase- and cathepsin G-dependent AIIFA is elevated in CML after AMI. Our data suggested that chymase-dependent AIIFA is increased in CML as well as in the myocardium after AMI, and that the level of chymase-dependent AIIFA might reflect the severity of infarction.

Left ventricular metabolic remodeling and accompanied dysfunction in type 2 diabetic patients: A 3D speckle tracking analysis

PURPOSES

The purposes of our study were to determine the risk factors related to metabolic left ventricular remodeling (LVR) in type 2 diabetes mellitus (T2DM) patients and to assess the LV function with different geometry in such population.

METHODS

Seventy-eight T2DM patients with normal 2D-LVEF (≥55%) were enrolled and divided into two groups with LV normal geometry (LVN) and with LV remodeling (LVR). The control group was composed of forty age- and sex-matched healthy individuals with LVN. A multifactor logistic regression was used to determine the risk factors for LVR, and their diagnostic values were evaluated using the area under the ROC curves (AUC). Three-dimensional speckle tracking echocardiography (3DSTE) was used to measure LV global longitudinal strain (GLS), global circumferential strain (GCS), global area strain (GAS), and global radial strain (GRS).

RESULTS

Fasting plasma glucose (FPG), hyperlipidemia, and BMI were independently associated with LVR in T2DM patients, and the AUC values were 0.699, 0.697, and 0.732, respectively. The T2DM patients with LVN showed significantly lower GLS than the controls (P < 0.05), whereas the T2DM patients with LVR showed significantly lower GLS, GCS, GAS, and GRS than the T2DM patients with LVN (all P < 0.01). Additionally, GLS, GAS, and GRS values decreased significantly in the T2DM patients with LV hypertrophy than in those with LV concentric remodeling (all P < 0.05).

CONCLUSIONS

The routine echocardiography and 3DSTE could be used in combining way to detect the metabolic LV remodeling and accompanied dysfunction in T2DM patients.

LOX-1 receptor: A potential link in atherosclerosis and cancer

Altered production of reactive oxygen species (ROS), causing lipid peroxidation and DNA damage, contributes to the progression of atherosclerosis and cancer. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1) is a lectin-like receptor for oxidized low-density lipoproteins (ox-LDL) primarily expressed in endothelial cells and vasculature-rich organs. LOX-1 receptors is a marker for atherosclerosis, and once activated by ox-LDL or other ligands, stimulates the expression of adhesion molecules, pro-inflammatory signaling pathways and proangiogenic proteins, including NF-kB and VEGF, in vascular endothelial cells and macrophages. Several different types of cancer reported LOX-1 gene upregulation, and numerous interplays exist concerning LOX-1 in atherosclerosis, metabolic diseases and cancer. One of them involves NF-kB, an oncogenic protein that regulates the transcription of several inflammatory genes response. In a model of cellular transformation, the MCF10A ER-Src, inhibition of LOX-1 gene reduces NF-kB activation and the inflammatory and hypoxia pathways, suggesting a mechanistic connection between cellular transformation and atherosclerosis. The remodeling proteins MMP-2 and MMP-9 have been found increased in angiogenesis in atherosclerotic plaque and also in human prostate cancer cells. In this review, we outlined the role of LOX-1 in atherogenesis and tumorigenesis as a potential link in these diseases, suggesting that LOX-1 inhibition could represent a promising strategy in the treatment of atherosclerosis and tumors.

Antihypertensive effect of Ganjang (traditional Korean soy sauce) on Sprague-Dawley Rats

BACKGROUND/OBJECTIVES

Although Korean fermented foods contain large amounts of salt, which is known to exacerbate health problems, these foods still have beneficial effects such as anti-hypertension, anti-cancer, and anti-colitis properties. We hypothesized that ganjang may have different effects on blood pressure compared to same concentrations of salt.

MATERIALS/METHODS

Sprague-Dawley rats were divided into control (CT), NaCl (NC), and ganjang (GJ) groups and orally administered with 8% NaCl concentration for 9 weeks. The systolic blood pressure (SBP), serum chemistry, Na⁺ and K⁺ concentrations and renal gene expressions were measured.

RESULTS

The SBP was significantly increased in the NC group compared to the GJ and CT groups. In addition, the Na⁺ concentration in urine was higher in the GJ and NC groups than the CT group, but the urine volume was increased in the GJ group compared to the other groups. The serum renin levels were decreased in the GJ group compared to the CT group, while the serum aldosterone level was decreased in the GJ group relative to the NC group. The mRNA expression of the renin, angiotensin II type I receptor, and mineralocorticoid receptor were significantly lower in the GJ group compared to other groups. Furthermore, GJ group showed the lowest levels of genes for Na⁺ transporter in kidney cortex such as Na⁺/K⁺ ATPaseα1 (NKAα1), Na⁺/H⁺ exchanger 3 (NHE3), Na⁺/HCO₃^- co-exchanger (NBC), and carbonic anhydrases II (CAII).

CONCLUSIONS

The decreased SBP in the GJ could be due to decreased renin and aldosterone levels in serum and increased urinary volume and excretion of Na⁺ with its transporter gene alteration. Therefore, ganjang may have antihypertensive effect despite its high contents of salt.

Facilitative interaction between angiotensin II and oxidised LDL in cultured human coronary artery endothelial cells

Background Several studies have shown that angiotensin II (Ang II) and oxidised low-density lipoprotein (ox-LDL) are critical factors in atherosclerosis. In this study, we examined the molecular basis of mutually facilitative interactions between Ang II and ox-LDL in human coronary artery endothelial cells (HCAECs). Methods and results We observed that incubation of cultured HCAECs with Ang II (10-12 to 10-6 M) for 24 hours caused a concentration-dependent increase in the expression of mRNA and protein of a specialised receptor for ox-LDL (LOX-1). These effects of Ang II were completely blocked by pretreatment of HCAECs with candesartan (10-6 M), a specific AT1-receptor blocker, but not by PD 123319 (10-6 M), a specific AT2-receptor blocker. On the other hand, incubation of HCAECs with ox-LDL (10 and 40 µg/ml) for 24 hours progressively upregulated AT1-, but not AT 2-, receptor mRNA and protein. Pretreatment of cells with the anti-oxidant alpha-tocopherol (1-5 x 10-6 M) inhibited the upregulation of AT1-receptor expression induced by ox-LDL (p<0.05). To determine the significance of expression of AT1-receptors and LOX-1, we measured cell injury in response to Ang II and ox-LDL. Incubation of cells with both ox-LDL and Ang II synergistically increased cell injury, measured as cell viability and LDH release, compared with either ox-LDL or Ang II alone (both p<0.05). Alpha-tocopherol, as well as candesartan, attenuated cell injury in response to Ang II and ox-LDL (both p<0.05). Conclusions These observations show that Ang II upregulates a novel endothelial receptor for ox-LDL (LOX-1) gene expression and ox-LDL in turn upregulates Ang II AT 1receptor gene expression. This interaction between Ang II and ox-LDL further augments cell injury in HCAECs. These findings provide basis for the use of AT1-receptor blockers and anti-oxidants in designing therapy for atherosclerosis and myocardial ischaemia.

Renin-angiotensin system at the crossroad of hypertension and hypercholesterolemia

AIM

The aim of this study is to discuss the reliable scientific evidence of an interactive link between hypertension and hypercholesterolemia considering the metabolic pathways and the pathogenetic mechanisms connecting the two risk factors.

DATA SYNTHESIS

Hypertension and hypercholesterolemia are highly prevalent in the general population and their coexistence in the same subjects additively increases the risk of cardiovascular disease. Probably, hypercholesterolemia is also a risk factor for the development of hypertension. On the other side, it is also possible that lipid-lowering treatment could improve blood pressure control. Although the mechanisms of interaction between these two risk factors have not been completely elucidated thus far, there is rapidly growing evidence that the involvement of the renin-angiotensin system (RAS) can be considered as the common link between hypertension and hypercholesterolemia. In particular, hypercholesterolemia seems to promote the upregulation of type 1 angiotensin II (AT1) receptor genes because of an increase in the stability of mRNA followed by structural overexpression of vascular AT1 receptors for angiotensin II. The treatment of both risk factors greatly improves individual risk profile, especially when statins and RAS blockers are used together.

CONCLUSIONS

Hypertension and hypercholesterolemia are highly coprevalent and strongly related from a pathophysiological point of view. The RAS could be the main mediator of this link.

High Angiotensin II Responsiveness is Associated with Decreased Endothelium-Dependent Relaxation in Human Arteries

Introduction. Animal studies demonstrated an interaction between angiotensin II (Ang II) responsiveness and endothelium-dependent relaxation (EDR). However, this relation has not been well described in humans. Therefore, we investigated the relation between Ang II responsiveness and EDR in isolated human arteries.

Materials and Methods. Segments of the internal mammary artery (IMA) were harvested from 89 patients undergoing coronary bypass surgery. Rings of these segments were exposed in organ bath experiments to metacholine (ME; 10 nmol/L -0.1 mmol/L) after precontraction with phenylephrine (PE; 10 µmol/L), and secondly to increasing concentrations of Ang II (0.1 nmol/L —1 µmol/L).

Results. Patients with the highest contraction to Ang II showed the lowest ME relaxation (r=0.312; p=0.003). Angiotensin-converting enzyme (ACE)-inhibition significantly increased Ang II sensitivity (p=0.03). This increase was accompanied by a tendency toward decreased EDR (p=0.07). The inverse relation between Ang responsiveness and endotheliumdependent relaxation could not be explained by an increased tissue or serum ACE-inhibition in patients with a higher endothelium-dependent relaxation.

Conclusions. High Ang II responsiveness inversely correlates to EDR in IMA's of patients with established coronary artery disease. Short-term treatment with an ACE-inhibitor increased the response to Ang II, but had an adverse effect on EDR.

Atheroprotective effects of Cuphea carthagenensis (Jacq.) J. F. Macbr. in New Zealand rabbits fed with cholesterol-rich diet

ETHNOPHARMACOLOGICAL RELEVANCE

Although Cuphea carthagenensis (Jacq.) J. F. Macbr. is used in Brazilian folk medicine in the treatment of atherosclerosis and circulatory disorders, no study evaluating these effects has been conducted. The aim of this study was to evaluate the possible hypolipemiant and antiatherogenic activity of the ethanol soluble fraction obtained from C. carthagenensis (ES-CC) in an experimental atherosclerosis model using New Zealand (NZ) rabbits undergoing cholesterol-rich diet (CRD).

MATERIAL AND METHODS

Dyslipidemia and atherogenesis were induced by administration of standard commercial diet increased of 1% cholesterol (CRD) for 8 weeks. ES-CC was orally administered at doses of 10, 30 and 100mg/kg, once daily for four weeks, starting from the 4th week of CRD diet. Body weight measurements were weekly carried out from the beginning of experiments for 8 weeks. Serum levels of triglyceride (TG), total cholesterol (TC) and their fractions (LDL-C, VLDL-C and HDL-C) were measured at the beginning of experiments and at weeks four and eight. After euthanasia of rabbits, aorta segments (aortic arc, thoracic, abdominal and iliac segments) were macroscopically and microscopically evaluated and the intima and media layers of the arteries were measured. Additionally, the antioxidant activity of ES-CC and its influence on the functioning of hepatic antioxidant enzymes were also determined.

RESULTS

CRD induced dyslipidemia and major structural changes in the aortic wall. In addition, an increase in lipid peroxidation and a reduction of hepatic glutathione and serum nitrite levels were observed. Treatment with ES-CC was able to prevent the increase in TC, LDL-C, VLDL-C levels and triglycerides and promoted an increase in HDL-C levels in NZ rabbits. These effects were accompanied by a significant reduction in oxidative stress and modulation of the catalase and superoxide dismutase function. Moreover, the intima and media layers of the arterial segments were significantly reduced by ES-CC treatment.

CONCLUSIONS

This study demonstrated that ES-CC reduces serum lipids and hepatic oxidative stress when orally administered to NZ rabbits. In addition, it was able to prevent the development of CRD-induced atherosclerosis.

Hypercholesterolemia blunts the oxidative stress elicited by hypertension in venules through angiotensin II type-2 receptors

OBJECTIVE

Hypertension and hypercholesterolemia elicit inflammatory and thrombogenic responses in the microvasculature. However, little is known about whether and how risk factor combinations alter microvascular function. We examined how the actions of HTN+HCh on the microvasculature differ from the responses elicited by either risk factor alone.

METHODS

Intravital microscopy was used to monitor the adhesion and emigration of leukocytes and dihydrorhodamine oxidation in cremaster muscle venules of wild type mice that were infused with angiotensin II for 2 weeks (HTN), placed on a high cholesterol diet (HCD), or both.

RESULTS

Either HTN or HCh alone enhanced the production of reactive oxygen species and promoted the recruitment of leukocytes in venules. However, the combination of HTN and HCh produced changes in ROS production and leukocyte recruitment that were greatly attenuated compared to HTN alone. The inhibitory effects of HCh on the AngII mediated responses were also observed in genetically-induced HCh (ApoE-deficient mice). Treating HCh+HTN mice with an antagonist to AT2r reversed the HCh-dependent protection against oxidative stress and inflammation during HTN.

CONCLUSIONS

These findings indicate that HCh blunts the oxidative stress and inflammatory cell recruitment elicited by hypertension in venules through a mechanism that involves AT2 receptor activation.

International Union of Basic and Clinical Pharmacology. XCIX. Angiotensin Receptors: Interpreters of Pathophysiological Angiotensinergic Stimuli [corrected]

The renin angiotensin system (RAS) produced hormone peptides regulate many vital body functions. Dysfunctional signaling by receptors for RAS peptides leads to pathologic states. Nearly half of humanity today would likely benefit from modern drugs targeting these receptors. The receptors for RAS peptides consist of three G-protein-coupled receptors—the angiotensin II type 1 receptor (AT1 receptor), the angiotensin II type 2 receptor (AT2 receptor), the MAS receptor—and a type II trans-membrane zinc protein—the candidate angiotensin IV receptor (AngIV binding site). The prorenin receptor is a relatively new contender for consideration, but is not included here because the role of prorenin receptor as an independent endocrine mediator is presently unclear. The full spectrum of biologic characteristics of these receptors is still evolving, but there is evidence establishing unique roles of each receptor in cardiovascular, hemodynamic, neurologic, renal, and endothelial functions, as well as in cell proliferation, survival, matrix-cell interaction, and inflammation. Therapeutic agents targeted to these receptors are either in active use in clinical intervention of major common diseases or under evaluation for repurposing in many other disorders. Broad-spectrum influence these receptors produce in complex pathophysiological context in our body highlights their role as precise interpreters of distinctive angiotensinergic peptide cues. This review article summarizes findings published in the last 15 years on the structure, pharmacology, signaling, physiology, and disease states related to angiotensin receptors. We also discuss the challenges the pharmacologist presently faces in formally accepting newer members as established angiotensin receptors and emphasize necessary future developments.

Effect of dietary cholesterol and cholesterol oxides on blood cholesterol, lipids, and the development of atherosclerosis in rabbits

Two studies were conducted to determine the effects of dietary cholesterol (CHO) and cholesterol oxides (COPs) on the development of atherosclerosis and the changes in fatty acid and blood characteristics in rabbits. In the first study, forty male New Zealand white rabbits were divided into 5 groups and fed commercial rabbit chow with no added CHO or COPs, 1 g CHO, 0.9 g CHO + 0.1 g COPs, 0.8 g CHO + 0.2 g COPs, or 0.5 g CHO + 0.5 g COPs per kg diet. In the second study, 24 male New Zealand White rabbits were divided into 3 groups and fed a diet containing 2 g CHO, 1.6 g CHO + 0.4 g COPs, or 1.2 g CHO + 0.8 g COPs per kg diet. All diets induced atherosclerotic lesions in the rabbits' ascending thoracic aorta. The serum CHO and triglyceride levels (p < 0.05) increased significantly with the increased levels of CHO in the diets. Dietary CHO or COPs did not influence high-density lipoprotein CHO levels. The ratio of saturated fatty acid to unsaturated fatty acid increased as the level of dietary CHO and COPs increased.

Short-term hypercaloric diet induces blunted aortic vasoconstriction and enhanced vasorelaxation via increased nitric oxide synthase 3 activity and expression in Dahl salt-sensitive rats

AIM

To elucidate the role of the O(2)(-), H(2)O(2) or NO pathways in aortic angiotensin (Ang)II-induced vasoconstriction in Dahl salt-sensitive (SS) rats compared with control SS-13(BN) rats on a normal or hypercaloric diet.

METHODS

Aortic function was assessed using wire myography in 16-week-old rats maintained on a normal diet or a 4-week hypercaloric diet. Nitric oxide synthase (NOS) activity and expression was determined by the conversion of radio-labelled arginine to citrulline and Western blot analysis respectively.

RESULTS

On normal diet, AngII-induced vasoconstriction was greater in SS than SS-13(BN) rats. Polyethylene glycol superoxide dismutase (PEG-SOD) reduced the aortic AngII response similarly in both strains on normal diet. Catalase blunted, whereas N(ω)-Nitro-L-arginine methyl ester (L-NAME) did not affect the AngII response in SS rats. In SS-13(BN) rats, catalase had no effect and L-NAME enhanced AngII response. On hypercaloric diet, aortic AngII responsiveness was reduced in SS but unaltered in SS-13(BN) rats compared with their normal diet counterparts. PEG-SOD reduced the AngII response in both rats on hypercaloric diet. Catalase treatment did not alter aortic AngII response, while L-NAME increased the response in SS rats on hypercaloric diet. In SS-13(BN) rats on hypercaloric diet, catalase reduced and L-NAME did not alter the AngII response. Furthermore, aortic endothelial-dependent vasorelaxation was increased in SS rats on hypercaloric diet compared with normal diet and aortic NOS3 activity and expression was increased.

CONCLUSION

A short-term hypercaloric diet induces a blunted vasoconstrictive and enhanced vasodilatory phenotype in SS rats, but not in SS-13(BN) rats, via reduced H(2)O(2) and increased NOS3 function.

Plaque-stabilizing effect of angiotensin-converting enzyme inhibitor and/or angiotensin receptor blocker in a rabbit plaque model

AIM

Previous studies have revealed that blockade of the renin angiotensin system attenuates plaque vulnerability and reduces cardiovascular events; however, few studies have compared the effects of an angiotensin-converting enzyme inhibitor (ACEI) with an angiotensin receptor blocker (ARB) and evaluated combination therapy. The objective of this study was to compare the efficacy and mechanisms of plaque stabilization by ACEI or ARB and to determine the effects of combination therapy.

METHODS

Twenty-eight male Japanese white rabbits were fed a high-cholesterol diet after balloon injury of the carotid arteries, then separated into ACEI (n= 7; imidapril 0.5 mg/kg/day), ARB (n= 7; TA606 4.5 mg/kg/day), combination (n= 7; imidapril 0.5 mg/kg/day+TA606 4.5 mg/kg/day), and vehicle (n= 7) groups.

RESULTS

No difference in plaque volume was identified among the 4 groups. ACEI or ARB increased the thickness of the fibrous cap, collagen content and the number of smooth muscle cells in the intima (% smooth muscle cell in intima: ACEI, 36.3%; ARB, 36.4%; vehicle, 14.9%), and reduced the accumulation of macrophages (% macrophages in intima: ACEI, 20.1%; ARB, 24.0%; vehicle, 37.9%), suggesting the plaque-stabilizing effects of each drug. ACEI reduced matrix metalloproteinase (MMP)-9 expression and gelatinolytic activity in the intima. While ARB did not change gelatinolytic activity, accumulation ot T cell in the intima was suppressed. Combination therapy did not show additive effects.

CONCLUSION

These results suggest that ACEIs and ARBs have similar, but not additive, plaque-stabilizing effects. Each agent showed specific effects, with ACEIs decreasing gelatinolytic activity and ARBs suppressing T cell accumulation.

LOX-1 and angiotensin receptors, and their interplay

The renin-angiotensin system (RAS) plays an important role in regulating blood pressure, water-salt balance and the pathogenesis of cardiovascular diseases. Angiotensin II (Ang II) is the physiologically active mediator and mediates the main pathophysiological actions in RAS. Ang II exerts the effects by activating its receptors, primarily type 1 (AT1R) and type 2 (AT2R). Most of the known pathophysiological effects of Ang II are mediated by AT1R activation. The precise physiological function of AT2R is still not clear. Generally, AT2R is considered to oppose the effects of AT1R. Lectin-like oxidized low-density lipoprotein scavenger receptor-1 (LOX-1) is one of the major receptors responsible for binding, internalizing and degrading ox-LDL. The activation of LOX-1 has been known to be related to many pathophysiological events, including endothelial dysfunction and injury, fibroblast growth, and vascular smooth muscle cell hypertrophy. Many of these alterations are present in atherosclerosis, hypertension, and myocardial ischemia and remodeling. A growing body of evidence suggests the existence of a cross-talk between LOX-1 and Ang II receptors. Their interplays are embodied in the reciprocal regulation of their expression and activity. Their interplays are involved in a series of signals. Recent studies suggests that reactive oxygen species (ROS), nitric oxide (NO), protein kinase C (PKC) and mitogen activated protein kinases (MAPKs) are important signals responsible for their cross-talk. This paper reviews these aspects of dyslipidemia and RAS activation.

Relationship between angiotensin II receptor expression and cardiovascular risk factors in Mexican patients with coronary occlusive disease

The density of Angiotensin II (Ang) receptors on tissue surfaces is regulated by multiple hormones, cytokines and metabolic factors and is profoundly affected by various pathological conditions, such as age, diet and environmental conditions. The participation of several cardiovascular risk factors in the regulation of Angiotensin II receptor expression has been incompletely studied. We performed an ex-vivo study with human aortic postsurgical specimens to test the hypothesis that Ang AT1 and AT2 receptor expression in human aortic arteries is associated with the presence of cardiovascular risk factors. We included 31 Mexican patients with coronary artery disease. We evaluated Angiotensin II receptor expression by immunostaining and angiotensin converting enzyme insertion/deletion (ACE I/D) polymorphisms by polymerase chain reaction. AT1 and AT2 receptor expression was increased in the aortic segments from the cardiovascular patients compared with control arteries and in patients with the DD genotype. There was a correlation between increased AT1 receptor expression and the number of cardiovascular risk factors present in the patient. Furthermore, reduction of AT1 expression correlated with the number of drug combinations used in the patients. These correlations were not present with respect to AT2 receptor expression. We suggest that increased AT1 receptor expression is associated with the DD genotype. Thus the presence of several cardiovascular risk factors as well as DD genotype, induce AT1 expression increasing the probability to develop coronary occlusive disease.

Local bone marrow Renin-Angiotensin system and atherosclerosis

Local hematopoietic bone marrow (BM) renin-angiotensin system (RAS) affects the growth, production, proliferation differentiation, and function of hematopoietic cells. Angiotensin II (Ang II), the dominant effector peptide of the RAS, regulates cellular growth in a wide variety of tissues in pathobiological states. RAS, especially Ang II and Ang II type 1 receptor (AT1R), has considerable proinflammatory and proatherogenic effects on the vessel wall, causing progression of atherosclerosis. Recent investigations, by analyzing several BM chimeric mice whose BM cells were positive or negative for AT1R, disclosed that AT1R in BM cells participates in the pathogenesis of atherosclerosis. Therefore, AT1R blocking not only in vascular cells but also in the BM could be an important therapeutic approach to prevent atherosclerosis. The aim of this paper is to review the function of local BM RAS in the pathogenesis of atherosclerosis.

Angiotensin II induces afterdepolarizations via reactive oxygen species and calmodulin kinase II signaling

Renin-angiotensin system inhibitors significantly reduce the incidence of arrhythmias. However, the underlying mechanism(s) is not well understood. We aim to test the hypothesis that angiotensin II (Ang II) induces early afterdepolarizations (EADs) and triggered activities (TAs) via the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-ROS-calmodulin kinase II (CaMKII) pathway. ROS production was analyzed in the isolated rabbit myocytes loaded with ROS dye. Ang II (1-2 μM) increased ROS fluorescence in myocytes, which was abolished by Ang II type 1 receptor blocker losartan, NADPH oxidase inhibitor apocynin, and antioxidant MnTMPyP, respectively. Action potentials were recorded using the perforated patch-clamp technique. EADs emerged in 27 out of 41 (66%) cells at 15.8 ± 1.6 min after Ang II (1-2 μM) perfusion. Ang II-induced EADs were eliminated by losartan, apocynin, or trolox. The CaMKII inhibitor KN-93 (n=6) and inhibitory peptide (AIP) (n=4) also suppressed Ang II-induced EADs, whereas the inactive analogue KN-92 did not. Nifedipine, a blocker of L-type Ca current (I(Ca)(2+)(,L)), or ranolazine, an inhibitor of late Na current (I(Na)(+)), abolished Ang II-induced EADs. The effects of Ang II on major membrane currents were evaluated using voltage clamp. While Ang II at same concentrations had no significant effect on total outward K(+) current, it enhanced I(Ca.L) and late I(Na), which were attenuated by losartan, apocynin, trolox, or KN-93. We conclude that Ang II induces EADs via intracellular ROS production through NADPH oxidase, activation of CaMKII, and enhancement of I(Ca,L) and late I(Na). These results provide evidence supporting a link between renin-angiotensin system and cardiac arrhythmias.

Increased expression of endothelin ET(B) and angiotensin AT(1) receptors in peripheral resistance arteries of patients with suspected acute coronary syndrome

Patients who experience chest pain, in which ischemic heart disease has been ruled out, still have an increased risk of future ischemic cardiac events and premature death, possibly due to subclinical endothelial dysfunction. A feature of endothelial dysfunction is an increased expression of arterial vasoconstrictor endothelin (ET) and angiotensin (AT) receptors. Our aim was to investigate if the arterial expressions of these receptors are changed in patients with suspected but ruled out acute coronary syndrome (ACS). Small subcutaneous arteries (diameter of 100 microm) were surgically removed in an abdominal biopsy from 12 patients suspicious of ACS (susp ACS), admitted to the medical telemetry unit for chest pain. The vessels were analyzed for their receptor protein expression by quantitative immunohistochemistry using specific antibodies directed against ET(A), ET(B), AT(1), and AT(2) receptors. The control group (controls) consisted of eight healthy volunteers matched for age and sex with no previous cardiac illness or medication. The susp ACS group had an increased expression of ET(B) (by 94%) and AT(1) (by 34%) receptors in the smooth muscle cells of resistance arteries as compared to the control group. There were no significant differences in AT(2) and ET(A) receptor expression between the groups. The results indicate that the expression of arterial smooth muscle ET(B) and AT(1) receptors are increased in patients with suspected but ruled out ACS. These receptor changes could be important in the regulation of coronary tone and in the development of atherosclerosis, and may be related to increased cardiovascular risk.

Increased expression of vascular endothelin type B and angiotensin type 1 receptors in patients with ischemic heart disease

Background

Endothelin-1 and angiotensin II are strong vasoconstrictors. Patients with ischemic heart disease have elevated plasma levels of endothelin-1 and angiotensin II and show increased vascular tone. The aim of the present study was to examine the endothelin and angiotensin II receptor expression in subcutaneous arteries from patients with different degrees of ischemic heart disease.

Methods

Subcutaneous arteries were obtained, by biopsy from the abdomen, from patients undergoing coronary artery bypass graft (CABG) surgery because of ischemic heart disease (n = 15), patients with angina pectoris without established myocardial infarction (n = 15) and matched cardiovascular healthy controls (n = 15). Endothelin type A (ET_A) and type B (ET_B), and angiotensin type 1 (AT₁) and type 2 (AT₂) receptors expression and function were examined using immunohistochemistry, Western blot and in vitro pharmacology.

Results

ET_A and, to a lesser extent, ET_B receptor staining was observed in the healthy vascular smooth muscle cells. The level of ET_B receptor expression was higher in patients undergoing CABG surgery (250% ± 23%; P < 0.05) and in the patients with angina pectoris (199% ± 6%; P < 0.05), than in the healthy controls (100% ± 28%). The data was confirmed by Western blotting. Arteries from CABG patients showed increased vasoconstriction upon administration of the selective ET_B receptor agonist sarafotoxin S6c, compared to healthy controls (P < 0.05). No such difference was found for the ET_A receptors. AT₁ and, to a lesser extent, AT₂ receptor immunostaining was seen in the vascular smooth muscle cells. The level of AT₁ receptor expression was higher in both the angina pectoris (128% ± 25%; P < 0.05) and in the CABG patients (203% ± 41%; P < 0.05), as compared to the healthy controls (100% ± 25%). The increased AT₁ receptor expression was confirmed by Western blotting. Myograph experiment did however not show any change in vasoconstriction to angiotensin II in CABG patients compared to healthy controls (P = n.s).

Conclusion

The results demonstrate, for the first time, upregulation of ET_B and AT₁ receptors in vascular smooth muscle cells in ischemic heart disease. These receptors may play a role in the pathophysiology of ischemic heart disease and could provide important targets for pharmaceutical interventions.

Augmentation of the renin-angiotensin system by hypercholesterolemia promotes vascular diseases

Activation of the renin-angiotensin system (RAS) and aberrant cholesterol metabolism have generally been considered as independent mechanisms in the development of several vascular diseases. However, it is becoming increasingly apparent in both human and animal studies that many aspects of the RAS may be augmented by hypercholesterolemia, resulting in enhancement of the severity and occurrence of several vascular diseases, including hypertension, atherosclerosis and abdominal aortic aneurysms. Some potential hypercholesterolemia-induced mechanisms have been demonstrated to increase activity of specific components of the RAS. These include increased AT1-receptor expression, increased responsiveness to Ang II and increased synthesis of angiotensin peptides. Future studies need to validate mechanisms of hypercholesterolemia-induced RAS activation in different vascular diseases.

The M235T polymorphism of the AGT gene modifies the risk of coronary artery disease associated with the presence of hypercholesterolemia

OBJECTIVE

Atherosclerosis is an inflammatory disease resulting from interactions between various genetic and non-genetic factors. Angiotensinogen gene (AGT) belongs to polymorphic candidate genes. Recent evidence show that many traditional risk factors of coronary artery disease (CAD) influence synthesis of AGT. This report focuses on the interactions between M235T polymorphism of AGT gene and traditional risk factors of CAD.

MATERIAL AND METHODS

255 subjects, including 158 patients with angiographically confirmed CAD and 97 blood donors without history of cardiovascular diseases were studied. M235T polymorphism of the AGT gene was genotyped using PCR-RFLP method. To determine the possible interactions of AGT genotypes and traditional risk factors of CAD the attributable proportion due to interaction (AP) and synergy models were used.

RESULTS

The frequency of 235T allele carriers was significantly higher in patients than in controls (77.8 vs. 62.9, OR = 2.20, 95% CI; 1.10-4.40, P = 0.026, in multivariate logistic regression model). We found the existence of interaction between the 235T allele carrier-state and hypercholesterolemia (total cholesterol > or = 5 mmol/l) increasing the risk of CAD (SI = 3.39, 95% CI; 1.33-8.66, AP = 0.65, 95% CI; 0.39-0.91). The 235T allele also interacted with elevated LDL cholesterol levels (> or = 3 mmol/l) (AP = 0.49, 95% CI; 0.20-0.96), but not with the hypertension, overweight/ obesity and cigarette smoking.

CONCLUSION

The 235T allele increases the risk of CAD associated with the presence of hypercholesterolemia.

In-Stent Restenosis of the Renal Artery in a Single Kidney Patient: The Role of ACEI in the Therapeutic Choice

Renal artery stenosis (RAS) caused by atherosclerotic changes of the renal arteries has become a concern as a cause of end-stage renal failure. Percutaneous balloon angioplasty with or without endovascular stenting is an increasingly accepted procedure at the expense of classical approaches such as aortorenal bypass and other types of surgery. Renal percutaneous transluminal angioplasty and stenting (RPTAS) represent the first therapeutic choice; however, there is doubt regarding the satisfactory long-term outcome for primary RPTAS. Currently, there is no clear evidence whether or not RPTAS prevents further progressive renal function decline because comparisons between interventional randomized studies and medical therapy are still lacking. Despite the fact that the use of angiotensin-converting enzyme inhibitors (ACEIs) may be a potential cause of acute renal failure, clinical data suggest that ACEI therapy is associated with better survival in patient with RAS. In our case, the use of ACEIs has been fundamental for the indirect evaluation of restenosis degree and RPTAS.

The risk of coronary artery disease associated with cigarette smoking and hypercholesterolemia is additionally increased by the presence of the AT1R gene 1166C allele

Cigarette smoking and hypercholesterolemia influence the renin-angiotensin system (RAS) functions, including increased RAS-mediated vasoconstriction, mitogenic signaling, and angiotensin II type 1 receptor (AT1R) expression. We have explored the interactions of the AT1R gene 1166 A>C polymorphism and traditional risk factors using an epidemiological approach. The study cohort included 341 subjects; 172 were patients with angiographically confirmed coronary artery disease (CAD) and 169 were blood donors. The 1166 A>C polymorphism was genotyped using the PCR-RFLP method. We found a synergy of the 1166C allele with cigarette smoking (synergy indices: SI = 1.41, SIM = 1.33), LDL cholesterol levels > or = 3 mmol/l (SI = 1.25, SIM = 1.19), and elevated total cholesterol (> or =5 mmol/l) levels (SI = 1.15, SIM = 1.13). In each case, the estimated CAD risk was greater than that predicted by assuming the additivity and multiplication of effects. We conclude that the 1166C allele increases the risk of CAD associated with the presence of cigarette smoking and hypercholesterolemia.

Hypercholesterolaemia exacerbates ventricular remodelling after myocardial infarction in the rat: role of angiotensin II type 1 receptors

BACKGROUND AND PURPOSE

Diet-induced hypercholesterolaemia exacerbates post-myocardial infarction (MI) ventricular remodelling and heart failure, but the mechanism of this phenomenon remains unknown. This study examined whether worsening of post-MI ventricular remodelling induced by dietary hypercholesterolaemia was related to upregulation of angiotensin II type 1 (AT1) receptor in the rat heart.

EXPERIMENTAL APPROACH

MI was induced surgically in rats fed normal or high cholesterol diet. Both groups of rats were then assigned to control, atorvastatin, losartan or atorvastatin+losartan-treated subgroups and followed for 8 weeks. Left ventricular (LV) function was assessed with echocardiography. In isolated hearts, LV pressures were measured with a latex balloon and a tip catheter. AT1-receptor density was assessed in LV membranes with radioligand-binding assays.

KEY RESULTS

High cholesterol diet exacerbated LV dilation and dysfunction in post-MI hearts. Atorvastatin or losartan prevented these hypercholesterolaemia-induced effects, whereas their combination was not more effective than each drug alone. AT1 receptors were upregulated 8 weeks after MI, this was further increased by hypercholesterolaemia and restored to baseline levels by atorvastatin.

CONCLUSIONS AND IMPLICATIONS

Hypercholesterolaemia exacerbated LV remodelling and dysfunction in post-MI rat hearts and upregulated cardiac AT1 receptors. All these effects were effectively prevented by atorvastatin. Thus, the pleiotropic statin effects may include interference with the renin-angiotensin system through downregulation of AT1 receptors.

Modification of the coronary artery disease risk associated with the presence of traditional risk factors by insertion/deletion polymorphism of the ACE gene

Cigarette smoking, hypercholesterolemia, and obesity influence the renin-angiotensin system (RAS) functions including an increased synthesis of the angiotensin I converting enzyme (ACE). Thus in the present work we explore the interactions of the ACE gene insertion/deletion (I/D) polymorphism and traditional risk factors. The study cohort included 341 subjects composed of 172 patients with angiographically confirmed CAD and 169 blood donors without a history of cardiovascular diseases. The I/D polymorphism was genotyped using polymerase chain reaction (PCR) methodology. To determine the interactions between the ACE genotypes and traditional risk factors the epidemiologic approach was used (4 x 2 tables and the synergy measures). The frequency of the DD genotype was significantly higher in patients than in controls (33.7% versus 21.3%, odds ratio [OR] = 1.88, 95% CI; 1.13-3.15, p = 0.010), but greater differences were found in males (35.7% versus 20.5%, OR = 2.15, 95% CI: 1.14-4.04, p = 0.010). We found a synergy of the DD genotype with smoking (SI = 1.88, SIM = 1.22), total cholesterol > or =5 mmol/l (SI = 2.12, SIM = 1.31) and elevated low density lipoprotein (LDL) cholesterol level (> or =3 mmol/l) (SI = 1.78, SIM = 1.14). The presence of the D allele (DD + ID subjects) also increased the risk of coronary artery disease (CAD) associated with the presence of elevated total cholesterol and LDL cholesterol (SI = 1.69, SIM = 1.18, in both cases), elevated level (> or =1.7 mmol/l) of triacylglycerols (SI = 1.81, SIM = 1.18) and overweight/obesity (SI = 4.25, SIM = 2.36). In each case the estimated CAD risk was greater than that predicted by assuming the additivity of effects (the risk increased from 69% for the D allele - total cholesterol interaction to 325% for the D allele - overweight/obesity). The statistical significance was also confirmed by a multiplicative model of synergy. The DD genotype/D allele of the ACE gene increases the risk of CAD associated with the presence of traditional risk factors.

Endothelial dysfunction and improvement of the angiotensin II-reactivity in hypercholesterolemic rabbits: role of cyclooxygenase metabolites

The aim of this paper was to study the effect of high cholesterol diet on endothelial function and vascular reactivity to angiotensin II and to test the role of vasoconstrictor cyclooxygenase metabolites in this experimental condition. Rabbits were fed with either normal chow or a diet containing 1% cholesterol for 6-7-week. Isometric contractions were measured in rubbed or unrubbed aortic rings. Arteries were contracted with noradrenaline and then exposed to one cumulative dose-response curve to acetylcholine in absence (control) or in presence of indomethacin, (N-[2-cyvlohexyloxy)-4-nitrophenyl]-methanesulfonamide) (NS 398) or 4-hydroxy-2,2,6,6-tetraethylpiperidine-N-oxyl (tempol). After washing the arteries, one cumulative dose-response curve to angiotensin II was constructed in absence or presence of indomethacin, NS 398, [1S-[1 alpha,2 beta (5Z),3 beta,4 alpha]-7-[3-[[2-[(phenylamino) carbonyl]hydrazino]methyl]-7-oxabicyclo[2.2.1] hept-2-yl]-5-heptenoic acid (SQ29548) or 17-octadecynoic acid (17-ODYA). In other group, resting potential was recorded in basal and angiotensin II-stimulated conditions. Indomethacin, NS 398 or 17-ODYA were added to the bath before angiotensin II-stimulation. Rabbits fed on a diet enriched with cholesterol showed higher plasma levels of total cholesterol and LDL. Hypercholesterolemic diet impaired acetylcholine relaxation. Indomethacin normalized endothelium-dependent relaxation whereas NS 398 and tempol had no effect on this phenomenon. Angiotensin II-reactivity was increased in endothelium intact hypercholesterolemic aortic rings and indomethacin, SQ29548 or 17-ODYA blocked this effect. The resting potential of unrubbed hypercholesterolemic arteries was significantly less negative to control after angiotensin II-stimulation. 17-ODYA but not indomethacin prevented angiotensin II-depolarization. High cholesterol diet caused endothelial dysfunction and increased the angiotensin II-reactivity. Both effects were cyclooxygenase1-dependent. Deficit in the NO-production might improve 20-hydroxyeicosatrienoic acid availability, which induces depolarization and angiotensin II-sensitization. In addition, 20-hydroxyeicosatrienoic acid would be metabolized by cyclooxygenase1 to 20-endoperoxides which act through thromboxane A(2)/prostaglandin H(2) receptors contributing to angiotensin II-reactivity increase.

EP2306 [2-(4-Biphenyl)-4-methyl-octahydro-1,4-benzoxazin-2-ol, hydrobromide], A Novel Squalene Synthase Inhibitor, Reduces Atherosclerosis in the Cholesterol-Fed Rabbit

EP2306 [2-(4-biphenyl)-4-methyl-octahydro-1,4-benzoxazin-2-ol, hydrobromide] inhibits squalene synthase and lipid biosynthesis and possesses antioxidant properties. We hypothesized that EP2306 can effectively modify circulating lipids and reduce atherosclerosis in the cholesterol-fed rabbit. Animals were fed a high-cholesterol diet for 4 weeks followed by 4 (phase 1 and 2) or 12 weeks (phase 3) of drug treatment while on high-cholesterol diet. In phase 1, the dose-effect relationship of EP2306 on lipids and atherosclerosis was established, and its most effective dose was determined (2 mg/kg). This dose reduced significantly total cholesterol (512 +/- 96 mg/dl before versus 320 +/- 124 mg/dl after treatment, p < 0.05) and atherosclerotic lesions compared with control animals. In phase 2, the effects of 2 mg/kg EP2306, 2.5 mg/kg simvastatin, and their combination were assessed. Although no significant effect on lipid parameters was observed, there was a significant reduction (35 +/- 5%, p < 0.05) of atherosclerotic lesions in animals treated with EP2306, a similar reduction with simvastatin, and a further reduction (48 +/- 7%, p < 0.05) when the two agents were combined. In animals treated for 12 weeks with the drugs (phase 3), only EP2306 significantly reduced atherosclerotic lesions by more than 50%, whereas simvastatin alone or in combination with EP2306 had no effect. Treatment with EP2306 did not adversely affect liver transaminases or cause any histopathological changes on various organs of the animals. In conclusion, we have shown that EP2306 inhibits atherosclerosis in vivo, indicating potential as a novel therapeutic agent for coronary artery disease and other atherosclerosis-related disorders.

Late ventricular remodeling in non-reperfused acute myocardial infarction in humans is predicted by angiotensin II type 1 receptor density on blood platelets

BACKGROUND

Ventricular remodeling after myocardial infarction (MI) is largely dependent on renin-angiotensin system activity, which is determined by angiotensin II concentration and angiotensin II type 1 receptor (AT(1)R) density in target tissues. We have recently shown that AT(1)R density in the acute phase of MI determines post-MI ventricular remodeling at discharge (8 days). The aim of this study was to test whether this correlation is retained in a longer follow-up (6 months), in the same group of patients.

METHODS

In 48 patients with first acute MI who did not undergo reperfusion therapy, angiotensin AT(1)R density on blood platelets (a presumable marker of cardiovascular AT(1)R density) was assessed 13+/-5 h after the onset of MI, using radioligand binding assay. Echocardiographic indices of left ventricular function and dimensions were used as measures of ventricular remodeling.

RESULTS

6 months after the infarction patients who at baseline had AT(1)R density above median (N=17) as compared to those with AT(1)R density below median (N=20) had higher left ventricular end-systolic volume index (LVESVI, 41.3+/-2.7 vs. 33.2+/-2.3) and lower ejection fraction (LVEF 48.1+/-1.8 vs. 54.7+/-2.0). Moreover LVESVI positively and LVEF negatively correlated with AT(1)R density although the strength of these correlations was weaker than at discharge. Infarct size as reflected by a single troponin T measurement and post-MI therapy did not differ between high- and low-AT(1)R groups: over 85% patients received ACE-inhibitor, beta-blocker and statin.

CONCLUSIONS

High AT(1)R density on blood platelets (a presumable marker of cardiovascular AT(1)R density) drawn in the acute phase of MI predicts poorer left ventricular systolic function in 6-month follow up. This suggests that modern therapy offers suboptimal blockade of renin-angiotensin system activity in the setting of MI.

Renal artery stenosis and accelerated atherosclerosis: which comes first?

Renal artery stenosis (RAS) is usually observed in hypertensive patients with extensive atherosclerosis. There is some evidence that in these patients the atherosclerotic process and the consequent target-organ damage is more severe than in hypertensive patients without RAS. In this review we will entertain the hypothesis that some of the humoral factors that are activated by RAS may contribute to accelerate the progression of atherosclerosis. Several studies identified RAS as a predictor of cardiovascular events in high-risk patients, although in most cases the contribution of blood pressure per se to the progression of vascular lesions could not be determined. As a result of experimental RAS, hypertension and increased oxidative stress are stimuli for atherosclerosis as well as cardiac and renal damage. In the presence of RAS, the renin-angiotensin system is stimulated, and it has been shown that angiotensin II exerts proinflammatory, pro-oxidant and procoagulant activities in experimental models and humans. The potential contribution of reactive oxygen species to the prohypertensive and proatherosclerotic effects of RAS is supported by evidence that nicotinamide adenine dinucleotide phosphate, reduced form oxidase is specifically stimulated by angiotensin II, an activity not shared by epinephrine. Moreover, angiotensin II triggers the release of aldosterone, endothelin 1, thromboxane A2 and other derivatives of the arachidonic acid metabolism, all of which can further and independently aggravate cardiovascular damage. Epidemiological and experimental evidence so far available suggests that accelerated atherosclerosis can be both the cause and the consequence of RAS.

Angiotensin II and inflammation: the effect of angiotensin-converting enzyme inhibition and angiotensin II receptor blockade

Angiotensin II (Ang II) increases adhesion molecules, cytokines and chemokines and exerts a proinflammatory effect on leucocytes, endothelial cells and vascular smooth muscle cells. Acting via the type 1 receptor, Ang II initiates an inflammatory cascade of reduced nicotinamide-adenine dinucleotide phosphate oxidase, reactive oxygen species (ROS) and nuclear factor-kappaB, which mediates transcription and gene expression and increases adhesion molecules and chemokines. An excess of ROS decreases nitric oxide bioavailability, causes endothelial dysfunction, and promotes atherosclerosis. Moreover, Ang II interrupts the anti-inflammatory effects of insulin. Together, these effects promote a prothrombotic state as well as plaque rupture. Ang II receptor blockers suppress mediators of inflammation, including ROS and C-reactive protein, and they increase expression of inhibitory kappaB (an inhibitor of nuclear factor-kappaB). These anti-inflammatory and antioxidative effects, which are probably due in part to unopposed stimulation of the Ang II type 2 receptor, may be beneficial in acute coronary syndromes and may also contribute to the prevention of type II diabetes mellitus, as insulin resistance is mediated by inflammatory processes.

Angiotensin II cell signaling: physiological and pathological effects in the cardiovascular system

The renin-angiotensin system is a central component of the physiological and pathological responses of cardiovascular system. Its primary effector hormone, angiotensin II (ANG II), not only mediates immediate physiological effects of vasoconstriction and blood pressure regulation, but is also implicated in inflammation, endothelial dysfunction, atherosclerosis, hypertension, and congestive heart failure. The myriad effects of ANG II depend on time (acute vs. chronic) and on the cells/tissues upon which it acts. In addition to inducing G protein- and non-G protein-related signaling pathways, ANG II, via AT(1) receptors, carries out its functions via MAP kinases (ERK 1/2, JNK, p38MAPK), receptor tyrosine kinases [PDGF, EGFR, insulin receptor], and nonreceptor tyrosine kinases [Src, JAK/STAT, focal adhesion kinase (FAK)]. AT(1)R-mediated NAD(P)H oxidase activation leads to generation of reactive oxygen species, widely implicated in vascular inflammation and fibrosis. ANG II also promotes the association of scaffolding proteins, such as paxillin, talin, and p130Cas, leading to focal adhesion and extracellular matrix formation. These signaling cascades lead to contraction, smooth muscle cell growth, hypertrophy, and cell migration, events that contribute to normal vascular function, and to disease progression. This review focuses on the structure and function of AT(1) receptors and the major signaling mechanisms by which angiotensin influences cardiovascular physiology and pathology.

Interaction of oxidized low-density lipoprotein and the renin-angiotensin system in coronary artery disease

Hyperlipidemia and hypertension are frequently observed in patients with coronary artery disease. It has been proposed that an interaction between low-density lipoprotein, especially its oxidized form (ox-LDL), and renin-angiotensin system (RAS) activation is a major determinant of atherogenesis. Ox-LDL accumulation in the blood vessels enhances the expression and activation of RAS components; on the other hand, activation of RAS stimulates the accumulation of LDL and its oxidation into ox-LDL in the blood vessels. Individually ox-LDL and RAS activation induce oxidative stress and inflammatory cascade, whereas their combination exerts a synergistic effect. This concept of cross-talk between ox-LDL/hyperlipidemia and RAS activation has been proven in laboratory animals. Clinical trials also suggest that blockade of hyperlipidemia and RAS may have a synergistic salutary effect on the outcome of patients with hypertension and/or manifestations of atherosclerosis. This concept needs to be evaluated further in large clinical studies.