Angiotensin II-induced leukocyte adhesion on human coronary endothelial cells is mediated by E-selectin

Exploration of Toxins from a Marine Annelid: An Analysis of Phyllotoxins and Accompanying Bioactives

Proteinaceous toxins are peptides or proteins that hold great biotechnological value, evidenced by their ecological role, whether as defense or predation mechanisms. Bioprospecting using bioinformatics and omics may render screening for novel bioactives more expeditious, especially considering the immense diversity of toxin-secreting marine organisms. Eulalia sp. (Annelida: Phyllodocidae), a toxin bearing marine annelid, was recently shown to secrete cysteine-rich protein (Crisp) toxins (hitherto referred to as 'phyllotoxins') that can immobilize its prey. By analyzing and validating transcriptomic data, we narrowed the list of isolated full coding sequences of transcripts of the most abundant toxins or accompanying bioactives secreted by the species (the phyllotoxin Crisp, hyaluronidase, serine protease, and peptidases M12A, M13, and M12B). Through homology matching with human proteins, the biotechnological potential of the marine annelid's toxins and related proteins was tentatively associated with coagulative and anti-inflammatory responses for the peptidases PepM12A, SePr, PepM12B, and PepM13, and with the neurotoxic activity of Crisp, and finally, hyaluronidase was inferred to bear properties of an permeabilizing agent. The in silico analysis succeeded by validation by PCR and Sanger sequencing enabled us to retrieve cDNAs can may be used for the heterologous expression of these toxins.

B-cell lymphoma/leukaemia 10 and angiotensin II-induced kidney injury

AIMS

B-cell lymphoma/leukaemia 10 (Bcl10) is a member of the CARMA-Bcl10-MALT1 signalosome, linking angiotensin (Ang) II, and antigen-dependent immune-cell activation to nuclear factor kappa-B signalling. We showed earlier that Bcl10 plays a role in Ang II-induced cardiac fibrosis and remodelling, independent of blood pressure. We now investigated the role of Bcl10 in Ang II-induced renal damage.

METHODS AND RESULTS

Bcl10 knockout mice (Bcl10 KO) and wild-type (WT) controls were given 1% NaCl in the drinking water and Ang II (1.44 mg/kg/day) for 14 days. Additionally, Bcl10 KO or WT kidneys were transplanted onto WT mice that were challenged by the same protocol for 7 days. Kidneys of Ang II-treated Bcl10 KO mice developed less fibrosis and showed fewer infiltrating cells. Nevertheless, neutrophil gelatinase-associated lipocalin (Ngal) and kidney injury molecule (Kim)1 expression was higher in the kidneys of Ang II-treated Bcl10 KO mice, indicating exacerbated tubular damage. Furthermore, albuminuria was significantly higher in Ang II-treated Bcl10 KO mice accompanied by reduced glomerular nephrin expression and podocyte number. Ang II-treated WT mice transplanted with Bcl10 KO kidney showed more albuminuria and renal Ngal, compared to WT- > WT kidney-transplanted mice, as well as lower podocyte number but similar fibrosis and cell infiltration. Interestingly, mice lacking Bcl10 in the kidney exhibited less Ang II-induced cardiac hypertrophy than controls.

CONCLUSION

Bcl10 has multi-faceted actions in Ang II-induced renal damage. On the one hand, global Bcl10 deficiency ameliorates renal fibrosis and cell infiltration; on the other hand, lack of renal Bcl10 aggravates albuminuria and podocyte damage. These data suggest that Bcl10 maintains podocyte integrity and renal function.

Angiotensin II and leukocyte trafficking: New insights for an old vascular mediator. Role of redox-signaling pathways

Inflammation and activation of the immune system are key molecular and cellular events in the pathogenesis of cardiovascular diseases, including atherosclerosis, hypertension-induced target-organ damage, and abdominal aortic aneurysm. Angiotensin II (Ang-II) is the main effector peptide hormone of the renin-angiotensin system. Beyond its role as a potent vasoconstrictor and regulator of blood pressure and fluid homeostasis, Ang-II is intimately involved in the development of vascular lesions in cardiovascular diseases through the activation of different immune cells. The migration of leukocytes from circulation to the arterial subendothelial space is a crucial immune response in lesion development that is mediated through a sequential and coordinated cascade of leukocyte-endothelial cell adhesive interactions involving an array of cell adhesion molecules present on target leukocytes and endothelial cells and the generation and release of chemoattractants that activate and guide leukocytes to sites of emigration. In this review, we outline the key events of Ang-II participation in the leukocyte recruitment cascade, the underlying mechanisms implicated, and the corresponding redox-signaling pathways. We also address the use of inhibitor drugs targeting the effects of Ang-II in the context of leukocyte infiltration in these cardiovascular pathologies, and examine the clinical data supporting the relevance of blocking Ang-II-induced vascular inflammation.

Cellular and Molecular Differences between HFpEF and HFrEF: A Step Ahead in an Improved Pathological Understanding

Heart failure (HF) is the most rapidly growing cardiovascular health burden worldwide. HF can be classified into three groups based on the percentage of the ejection fraction (EF): heart failure with reduced EF (HFrEF), heart failure with mid-range-also called mildly reduced EF- (HFmrEF), and heart failure with preserved ejection fraction (HFpEF). HFmrEF can progress into either HFrEF or HFpEF, but its phenotype is dominated by coronary artery disease, as in HFrEF. HFrEF and HFpEF present with differences in both the development and progression of the disease secondary to changes at the cellular and molecular level. While recent medical advances have resulted in efficient and specific treatments for HFrEF, these treatments lack efficacy for HFpEF management. These differential response rates, coupled to increasing rates of HF, highlight the significant need to understand the unique pathogenesis of HFrEF and HFpEF. In this review, we summarize the differences in pathological development of HFrEF and HFpEF, focussing on disease-specific aspects of inflammation and endothelial function, cardiomyocyte hypertrophy and death, alterations in the giant spring titin, and fibrosis. We highlight the areas of difference between the two diseases with the aim of guiding research efforts for novel therapeutics in HFrEF and HFpEF.

Inflammation in Renal Diseases: New and Old Players

Inflammation, a process intimately linked to renal disease, can be defined as a complex network of interactions between renal parenchymal cells and resident immune cells, such as macrophages and dendritic cells, coupled with recruitment of circulating monocytes, lymphocytes, and neutrophils. Once stimulated, these cells activate specialized structures such as Toll-like receptor and Nod-like receptor (NLR). By detecting danger-associated molecules, these receptors can set in motion major innate immunity pathways such as nuclear factor ĸB (NF-ĸB) and NLRP3 inflammasome, causing metabolic reprogramming and phenotype changes of immune and parenchymal cells and triggering the secretion of a number of inflammatory mediators that can cause irreversible tissue damage and functional loss. Growing evidence suggests that this response can be deeply impacted by the crosstalk between the kidneys and other organs, such as the gut. Changes in the composition and/or metabolite production of the gut microbiota can influence inflammation, oxidative stress, and fibrosis, thus offering opportunities to positively manipulate the composition and/or functionality of gut microbiota and, consequentially, ameliorate deleterious consequences of renal diseases. In this review, we summarize the most recent evidence that renal inflammation can be ameliorated by interfering with the gut microbiota through the administration of probiotics, prebiotics, and postbiotics. In addition to these innovative approaches, we address the recent discovery of new targets for drugs long in use in clinical practice. Angiotensin II receptor antagonists, NF-ĸB inhibitors, thiazide diuretics, and antimetabolic drugs can reduce renal macrophage infiltration and slow down the progression of renal disease by mechanisms independent of those usually attributed to these compounds. Allopurinol, an inhibitor of uric acid production, has been shown to decrease renal inflammation by limiting activation of the NLRP3 inflammasome. So far, these protective effects have been shown in experimental studies only. Clinical studies will establish whether these novel strategies can be incorporated into the arsenal of treatments intended to prevent the progression of human disease.

Monocytes as immune targets in arterial hypertension

The role of myelomonocytic cells appears to be critical for the initiation, progression and manifestation of arterial hypertension. Monocytes can induce vascular inflammation as well as tissue remodelling and (mal)adaptation by secreting chemokines and cytokines, producing ROS, expressing coagulation factors and transforming into macrophages. A multitude of adhesion molecules promote the infiltration and accumulation of monocytes into the kidney, heart, brain and vasculature in hypertension. All these facets offer the possibility to pharmacologically target monocytes and may represent novel therapeutic ways to treat hypertension, attenuate hypertension-associated end organ damage or prevent the development or worsening of high blood pressure. LINKED ARTICLES: This article is part of a themed section on Immune Targets in Hypertension. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.12/issuetoc.

Phospholipid membranes drive abdominal aortic aneurysm development through stimulating coagulation factor activity

Abdominal aortic aneurysm (AAA) is a disease of the abdominal aorta where inflammation causes damage and can ultimately lead to rupture. When this happens, uncontrolled internal bleeding can lead to death within minutes. Many aneurysms are not detected until they rupture, and for those that are, treatments to stop them progressing are limited. Here we used biophysics and genetically modified mice to show that a new family of lipids (fats) made by circulating blood cells promote AAA formation in the vessel wall because they directly regulate blood clotting. An approach that prevents AAA development was identified, based on intravenous administration of lipids. The studies provide insights into how AAA develops and may lead to novel therapies for this disease.

Abdominal aortic aneurysm (AAA) is an inflammatory vascular disease with high mortality and limited treatment options. How blood lipids regulate AAA development is unknown. Here lipidomics and genetic models demonstrate a central role for procoagulant enzymatically oxidized phospholipids (eoxPL) in regulating AAA. Specifically, through activating coagulation, eoxPL either promoted or inhibited AAA depending on tissue localization. Ang II administration to ApoE^−/− mice increased intravascular coagulation during AAA development. Lipidomics revealed large numbers of eoxPL formed within mouse and human AAA lesions. Deletion of eoxPL-generating enzymes (Alox12 or Alox15) or administration of the factor Xa inhibitor rivaroxaban significantly reduced AAA. Alox-deficient mice displayed constitutively dysregulated hemostasis, including a consumptive coagulopathy, characterized by compensatory increase in prothrombotic aminophospholipids (aPL) in circulating cell membranes. Intravenously administered procoagulant PL caused clotting factor activation and depletion, induced a bleeding defect, and significantly reduced AAA development. These data suggest that Alox deletion reduces AAA through diverting coagulation away from the vessel wall due to eoxPL deficiency, instead activating clotting factor consumption and depletion in the circulation. In mouse whole blood, ∼44 eoxPL molecular species formed within minutes of clot initiation. These were significantly elevated with ApoE^−/− deletion, and many were absent in Alox^−/− mice, identifying specific eoxPL that modulate AAA. Correlation networks demonstrated eoxPL belonged to subfamilies defined by oxylipin composition. Thus, procoagulant PL regulate AAA development through complex interactions with clotting factors. Modulation of the delicate balance between bleeding and thrombosis within either the vessel wall or circulation was revealed that can either drive or prevent disease development.

Potential Protective Role of Blood Pressure-Lowering Drugs on the Balance between Hemostasis and Fibrinolysis in Hypertensive Patients at Rest and During Exercise

In patients with hypertension, the triad represented by endothelial dysfunction, platelet hyperactivity, and altered fibrinolytic function disturbs the equilibrium between hemostasis and fibrinolysis and translates into a hypercoagulable state, which underlies the risk of thrombotic complications. This article reviews the scientific evidence regarding some biological effects of antihypertensive drugs, which can protect patients from the adverse consequences of hypertensive disease, improving endothelial function, enhancing antioxidant activity, and restoring equilibrium between hemostatic and fibrinolytic factors. These protective effects appear not to be mediated through blood pressure reduction and are not shared by all molecules of the same pharmacological class.

Effects of Angiotensin-Converting Enzyme Inhibition and Alpha 1-Adrenergic Receptor Blockade on Inflammation and Hemostasis in Human Hypertension

Drugs blocking the renin-angiotensin-aldosterone system may offer benefit on endothelial function, inflammation, and hemostasis in addition to the effects of reducing blood pressure. We examined the contribution of the angiotensin-converting enzyme inhibitor ramipril and the alpha 1-adrenergic receptor blocker doxazosin on blood pressure and on markers of inflammation and hemostasis in 59 individuals with mild-to-moderate hypertension randomized to receive double-blind ramipril 10 mg od or doxazosin 8 mg od for 12 weeks. Inflammatory markers (interleukin-6, soluble interleukin-6 receptor, interleukin-8, tumor necrosis factor-α, monocyte chemoattractant protein-1, and C-reactive protein) and hemostasis (plasminogen activator inhibitor-1 activity, tissue plasminogen activator antigen, thrombin-antithrombin complex, and thrombin generation by calibrated automated thrombogram) were assessed. The treatment reduced blood pressure in both groups. Thrombin-antithrombin complex decreased by treatment, and this was dependent on a reduction in thrombin-antithrombin complex in the ramipril group alone. There were no changes in plasminogen activator inhibitor-1 activity, whereas tissue plasminogen activator antigen increased by ramipril and decreased by doxazosin. Only minor changes were observed in systemic inflammation by treatment. Treatment with ramipril seems to reduce thrombin generation beyond effects on reducing blood pressure. Drugs blocking the renin-angiotensin-aldosterone system may reduce atherothrombotic complications beyond their effects to reduce blood pressure.

Krüppel-like factor 14, a coronary artery disease associated transcription factor, inhibits endothelial inflammation via NF-κB signaling pathway

BACKGROUND AND AIMS

Human genetic studies indicated that variations near the transcription factor Krüppel-like factor 14 (KLF14) gene locus are highly associated with coronary artery disease. Activation of endothelial cells (ECs) by pro-inflammatory molecules and pathways is a primary step in atherosclerosis development. We aimed to investigate the effects and mechanism of KLF14 on inflammatory responses in ECs.

METHODS

Adenovirus-mediated overexpression of human KLF14 and EC specific Klf14 knockout mice were applied to study the role of KLF14 in EC inflammation. Intravital microscopy was used to examine leukocyte-endothelial cell interactions in vivo.

RESULTS

The expression of Klf14 was markedly decreased in mouse aortic ECs in both acute and chronic inflammatory conditions. Overexpression of KLF14 inhibited inflammatory activation of human ECs stimulated by interleukin 1β and tumor necrosis factor α. Primary pulmonary ECs from Klf14 knockout mice showed increased expression of adhesion molecules under IL-1β stimuli. Mechanistically, KLF14 inhibited NF-κB signaling pathway by transcriptionally suppressing the expression of p65, resulting in significantly decreased leukocyte adhesion to activated ECs. Using intravital microscopy, an increased leukocyte-endothelial cell interaction was observed in endothelial specific Klf14 knockout mice compared to wild type control mice. Additionally, perhexiline, a KLF14 activator, induces KLF14 expression in ECs and reduced leukocyte-endothelial cell interactions in vitro and in vivo.

CONCLUSIONS

The data revealed that KLF14 inhibited the inflammatory response in ECs and the protective effects were mediated by transcriptional inhibition of NF-κB signaling pathway. Endothelial KLF14 could be a potential therapeutic target for cardiovascular diseases.

Cucumis sativus Aqueous Fraction Inhibits Angiotensin II-Induced Inflammation and Oxidative Stress In Vitro

Inflammation and oxidative stress play major roles in endothelial dysfunction, and are key factors in the progression of cardiovascular diseases. The aim of this study was to evaluate in vitro the effect of three subfractions (SFs) from the Cucumis sativus aqueous fraction to reduce inflammatory factors and oxidative stress induced by angiotensin II (Ang II) in human microvascular endothelial cells-1 (HMEC-1) cells. The cells were cultured with different concentrations of Ang II and 0.08 or 10 μg/mL of SF1, SF2, or SF3, or 10 μmol of losartan as a control. IL-6 (Interleukin 6) concentration was quantified. To identify the most effective SF combinations, HMEC-1 cells were cultured as described above in the presence of four combinations of SF1 and SF3. Then, the effects of the most effective combination on the expression of adhesion molecules, the production of reactive oxygen species (ROS), and the bioavailability of nitric oxide (NO) were evaluated. Finally, a mass spectrometry analysis was performed. Both SF1 and SF3 subfractions decreased the induction of IL-6 by Ang II, and C4 (SF1 and SF3, 10 μg/mL each) was the most effective combination to inhibit the production of IL-6. Additionally, C4 prevented the expression of adhesion molecules, reduced the production of ROS, and increased the bioavailability of NO. Glycine, arginine, asparagine, lysine, and aspartic acid were the main components of both subfractions. These results demonstrate that C4 has anti-inflammatory and antioxidant effects.

Effect of asiatic acid on the Ang II-AT1R-NADPH oxidase-NF-κB pathway in renovascular hypertensive rats

Asiatic acid, a triterpenoid compound derived from Centella asiatica, has been demonstrated to have antioxidant and anti-inflammatory effects. The present study evaluated the effects of asiatic acid on hemodynamic alterations, renin-angiotensin system (RAS), oxidative stress, and inflammation in 2K-1C hypertensive rats. Renovascular hypertension was induced in male Sprague-Dawley rats and treated with vehicle, asiatic acid (30 mg/kg/day), or captopril (5 mg/kg/day) for 4 weeks. We observed that 2K-1C hypertensive rats exhibited hemodynamic alterations such as high blood pressure, heart rate, hindlimb vascular resistance, and low hindlimb blood flow. Signs of RAS activation, such as increased plasma angiotensin II and serum angiotensin-converting enzyme activity, enhanced AT₁R protein expression, and suppressed AT₂R expression was observed in 2K-1C hypertensive rats. Overproduction of vascular superoxide, high levels of plasma MDA, low levels of plasma nitric oxide metabolites (NOx), and upregulation of gp91^phox protein expression were observed in hypertensive rats. Furthermore, inflammation was observed in hypertensive rats, as evidenced by increased plasma TNF-α, NF-κB, and phospho-NF-κB protein expression. Asiatic acid or captopril alleviated hemodynamic alterations, RAS activation, oxidative stress, and inflammation in 2K-1C hypertensive rats. These findings indicate that asiatic acid is an antihypertensive agent that ameliorates hemodynamic alterations in 2K-1C hypertensive rats. This effect may involve one or both of the following mechanisms: the direct effect of asiatic acid on RAS activation, oxidative stress and inflammation, and/or asiatic acid acting as an ACE inhibitor agent to inhibit the Ang II-AT₁R-NADPH oxidase-NF-κB pathway.

Update on the role of angiotensin in the pathophysiology of coronary atherothrombosis

BACKGROUND

Coronary atherothrombosis due to atherosclerotic plaque rupture or erosion is frequently associated with acute coronary syndromes (ACS). Significant efforts have been made to elucidate the pathophysiological mechanisms underlying acute coronary events.

MATERIALS AND METHODS

This narrative review is based on the material searched for and obtained via PubMed up to August 2014. The search terms we used were as follows: 'angiotensin, acute coronary syndromes, acute myocardial infarction' in combination with 'atherosclerosis, vulnerability, clinical trial, ACE inhibitors, inflammation'.

RESULTS

Among several regulatory components, the renin-angiotensin system (RAS) was shown as a key pathway modulating coronary atherosclerotic plaque vulnerability. Indeed, these molecules are involved in all stages of atherogenesis. Classically, the RAS is composed by a series of enzymatic reactions leading to the angiotensin (Ang) II generation and activity. However, the knowledge of RAS has expanded and become more complex. The discovery of novel components and their functions has revealed additional pathways that contribute to or counterbalance the actions of Ang II. In this review, we discussed on recent findings concerning the role of different angiotensin peptides in the pathophysiology of ACS and coronary atherothrombosis, exploring the link between these molecules and atherosclerotic plaque vulnerability.

CONCLUSIONS

Treatments selectively targeting angiotensins (including Mas and AT2 agonists, ACE2 recombinant, or Ang-(1-7) and almandine in oral formulations) have been tested in animal studies or in small human subgroups, expanding the perspective in the ACS prevention. These novel strategies, especially in the counter-regulatory axis ACE2/Ang-(1-7)/Mas, might be promising to reduce plaque vulnerability and inflammation.

Inflammatory biomarkers for predicting cardiovascular disease

The pathology of cardiovascular disease (CVD) is complex; multiple biological pathways have been implicated, including, but not limited to, inflammation and oxidative stress. Biomarkers of inflammation and oxidative stress may serve to help identify patients at risk for CVD, to monitor the efficacy of treatments, and to develop new pharmacological tools. However, due to the complexities of CVD pathogenesis there is no single biomarker available to estimate absolute risk of future cardiovascular events. Furthermore, not all biomarkers are equal; the functions of many biomarkers overlap, some offer better prognostic information than others, and some are better suited to identify/predict the pathogenesis of particular cardiovascular events. The identification of the most appropriate set of biomarkers can provide a detailed picture of the specific nature of the cardiovascular event. The following review provides an overview of existing and emerging inflammatory biomarkers, pro-inflammatory cytokines, anti-inflammatory cytokines, chemokines, oxidative stress biomarkers, and antioxidant biomarkers. The functions of each biomarker are discussed, and prognostic data are provided where available.

Depletion of endothelial or smooth muscle cell-specific angiotensin II type 1a receptors does not influence aortic aneurysms or atherosclerosis in LDL receptor deficient mice

BACKGROUND

Whole body genetic deletion of AT1a receptors in mice uniformly reduces hypercholesterolemia and angiotensin II-(AngII) induced atherosclerosis and abdominal aortic aneurysms (AAAs). However, the role of AT1a receptor stimulation of principal cell types resident in the arterial wall remains undefined. Therefore, the aim of this study was to determine whether deletion of AT1a receptors in either endothelial cells or smooth muscle cells influences the development of atherosclerosis and AAAs.

METHODOLOGY/PRINCIPAL FINDINGS

AT1a receptor floxed mice were developed in an LDL receptor -/- background. To generate endothelial or smooth muscle cell specific deficiency, AT1a receptor floxed mice were bred with mice expressing Cre under the control of either Tie2 or SM22, respectively. Groups of males and females were fed a saturated fat-enriched diet for 3 months to determine effects on atherosclerosis. Deletion of AT1a receptors in either endothelial or smooth muscle cells had no discernible effect on the size of atherosclerotic lesions. We also determined the effect of cell-specific AT1a receptor deficiency on atherosclerosis and AAAs using male mice fed a saturated fat-enriched diet and infused with AngII (1,000 ng/kg/min). Again, deletion of AT1a receptors in either endothelial or smooth muscle cells had no discernible effects on either AngII-induced atherosclerotic lesions or AAAs.

CONCLUSIONS

Although previous studies have demonstrated whole body AT1a receptor deficiency diminishes atherosclerosis and AAAs, depletion of AT1a receptors in either endothelial or smooth muscle cells did not affect either of these vascular pathologies.

Contributions of ACE and mast cell chymase to endogenous angiotensin II generation and leucocyte recruitment in vivo

AIMS

In vitro studies suggest that mast cell chymase (MCP) is more important than angiotensin-converting enzyme (ACE) for generating angiotensin II (Ang II) within the cardiovascular system. We investigated in vivo the relative contributions of ACE and MCP to leucocyte recruitment induced by endogenously generated Ang II.

METHODS AND RESULTS

Exposure of the murine cremasteric microcirculation of C57BL/6 mice to Ang I (100 nM for 4 h) induced leucocyte-endothelium interactions. Either losartan (an Ang II receptor-1 antagonist, AT(1)) or enalapril (an ACE inhibitor), but not chymostatin (a chymase inhibitor), inhibited Ang I-induced responses. Mast cell degranulation with compound 48/80 (CMP48/80, 1 μg/mL) also induced leucocyte adhesion but this was only weakly affected by the inhibitors. When Ang I and CMP48/80 were co-administered, AT(1B) receptor expression was increased, MCP-4 was found surrounding the vessel wall, and ACE was detected in the endothelium. Ang I + CMP48/80 induced enhanced leucocyte adhesion that was attenuated by losartan, enalapril, enalapril + chymostatin, and cromolyn (a mast cell stabilizer). The use of male mast cell-deficient WBB6F1/J-Kit(w)/Kit(w-v) mice (C57BL/6 background) confirmed these findings.

CONCLUSION

In vivo, Ang II is primarily generated by ACE under basal conditions, but in inflammatory conditions, the release of MCP amplifies local Ang II concentrations and the associated inflammatory process. Thus, AT(1) receptor antagonists may be more effective than ACE inhibitors for treating ongoing Ang II-mediated vascular inflammation.

Effect of valsartan on monocyte/endothelial cell activation markers and adiponectin in hypertensive patients with type 2 diabetes mellitus

Angiotensin II receptor blockade has been shown to have a beneficial effect on the angiopathies of hypertension and hyperglycemia in patients with type 2 diabetes. However, the effect of angiotensin II receptor blockade on monocyte and endothelial cell adhesion markers in type 2 diabetes is poorly understood. We investigated the effects of valsartan on these markers in 53 hypertensive patients with and without type 2 diabetes mellitus. Levels of monocyte activation markers (soluble CD14: 2.1+/-0.9 vs. 3.3+/-1.4 microg/ml, p<0.01; monocyte chemotactic peptide: 392+/-94 vs. 489+/-114 pg/ml, p<0.05; and monocyte-derived microparticles: 264+/-98 vs. 511+/-128/microL, p<0.01) and endothelial cell activation markers (soluble E-selectin: 41+/-11 vs. 61+/-20 ng/ml, p<0.001; and soluble vascular cell adhesion molecule-1: 478+/-82 vs. 584+/-101 ng/ml, p<0.01) were significantly increased in hypertensive patients with type 2 diabetes compared to normotensive controls. In addition, the concentrations of adiponectin were significantly decreased in patients with type 2 diabetes (8.1+/-3.1 vs. 5.2+/-2.5 microg/ml, p<0.01). Regardless of the presence of diabetic complications, both systolic and diastolic blood pressures significantly decreased after valsartan administration (valsartan 80 mg/day for 8 weeks). Monocyte and endothelial cell activation markers were decreased significantly in patients with type 2 diabetes after valsartan treatment, but not in non-type 2 diabetic patients. In addition, valsartan alleviated hypoadiponectinemia in hypertensive patients with diabetes (before vs. after: 5.2+/-2.5 vs. 7.6+/-2.7 microg/ml, p<0.001) but did not increase adiponectin levels in the non-diabetic hypertensive group, for which the average adiponectin level was normal prior to treatment. These results suggest angiotensin II receptor blockade (valsartan) may be beneficial as an anti-atherosclerotic therapy in patients with type 2 diabetes in addition to its anti-hypertensive action.

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.

ACE inhibitors and angiotensin II receptor antagonists in Crohn's disease management

An increasing repertoire of therapeutic indications for the angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists has followed an explosion of research exploring the role of the proinflammatory and profibrotic renin-angiotensin-aldosterone system in numerous organ systems. This evidence also implicates the renin-angiotensin-aldosterone system in the pathogenesis of other chronic inflammatory and fibrotic disorders, such as Crohn's disease. While the research to date supports this hypothesis, further investigation of the renin-angiotensin-aldosterone system in human Crohn's disease is required before these agents can realistically be investigated in human trials.

Renin inhibition reduces hypercholesterolemia-induced atherosclerosis in mice

The role of the renin angiotensin system (RAS) in atherosclerosis is complex because of the involvement of multiple peptides and receptors. Renin is the rate-limiting enzyme in the production of all angiotensin peptides. To determine the effects of renin inhibition on atherosclerosis, we administered the novel renin inhibitor aliskiren over a broad dose range to fat-fed LDL receptor-deficient (Ldlr(-/-)) mice. Renin inhibition resulted in striking reductions of atherosclerotic lesion size in both the aortic arch and the root. Subsequent studies demonstrated that cultured macrophages expressed all components of the RAS. To determine the role of macrophage-derived angiotensin in the development of atherosclerosis, we transplanted renin-deficient bone marrow to irradiated Ldlr(-/-) mice and observed a profound decrease in the size of atherosclerotic lesions. In similar experiments, transplantation of bone marrow deficient for angiotensin II type 1a receptors failed to influence lesion development. We conclude that renin-dependent angiotensin production in macrophages does not act in an autocrine/paracrine manner. Furthermore, in vitro studies demonstrated that coculture with renin-expressing macrophages augmented monocyte adhesion to endothelial cells. Therefore, although previous work suggests that angiotensin peptides have conflicting effects on atherogenesis, we found that renin inhibition profoundly decreased lesion development in mice.

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

INTRODUCTION

Administration of the NO inhibitor N(wdelta)-nitro-L-arginine methyl ester (NAME) and a high-salt diet (HS) promotes severe albuminuria and renal injury, which regresses upon discontinuation of treatments.

OBJECTIVE

We investigated whether these changes reappear after reinstitution of HS, and whether they are prevented by treatment with the antilymphocyte agent mycophenolate mofetil (MMF) or the AT-1 receptor blocker losartan (L). Adult male Munich-Wistar rats received NAME and HS. A control Group (C) received only HS. After 20 days, rats receiving HS and NAME exhibited severe hypertension and albuminuria. After a 30-day recovery period, hypertension was attenuated and albuminuria had virtually disappeared.

MATERIAL AND METHODS

Rats were then distributed among the following groups: HS, receiving HS; NS, receiving a normal salt (NS) diet; HS-MMF, receiving HS and MMF; HS-LOS, receiving HS and L; HS-HDZ, receiving HS and hydralazine (HDZ). Sixty days later, NS rats showed only slight albuminuria and renal damage or inflammation. In contrast, HS rats developed severe hypertension, marked glomerulosclerosis with interstitial expansion and renal infiltration by macrophages and angiotensin II-positive cells. The group treated with losartan had lowered blood pressure and a lack of albuminuria or renal injury. MMF provided similar protection without altering blood pressure, suggesting a nonhemodynamic effect, a hypothesis reinforced by the finding that HDZ lowered blood pressure without preventing renal injury.

RESULTS

These results indicate that treatment with HS and NAME predisposes to the development of hypertension and renal injury upon salt overload, characterizing a new model of chronic nephropathy.

CONCLUSION

The response to MMF or L, but not HDZ, suggests a key role for inflammatory rather than hemodynamic factors.

Angiotensin AT1 receptor antagonists exert anti-inflammatory effects in spontaneously hypertensive rats

BACKGROUND AND PURPOSE

Although the main therapeutic effect of angiotensin AT1 receptor antagonists is to decrease blood pressure, they also exert anti-inflammatory effects in the cardiovascular system. However, the underlying mechanisms remain unclear. We investigated the inhibitory effect of AT1 antagonists on the chemokine monocyte chemoattractant protein 1 (MCP-1) and its receptor C-C chemokine receptor 2 (CCR2) in rat monocytes and aortas.

EXPERIMENTAL APPROACH

Spontaneous hypertensive rats (SHRs) were treated with the AT1 antagonists losartan or telmisartan for 4 weeks, and Wistar-Kyoto rats (WKYs) were used as normotensive controls. Systolic arterial pressure was measured, and the number of macrophages in the aortic vessel wall was assessed by anti-ED-1 antibody immunolabelling.

KEY RESULTS

Compared with WKYs, SHRs showed significantly increased ED-1 positive macrophages in the aortic wall, which were decreased after high doses of losartan or telmisartan. Low doses of losartan did not improve blood pressure significantly as did the high doses, but markedly decreased macrophage infiltration in the vessel wall. AT1 antagonists, particularly at high doses, improved aortic remodeling in SHR. At the molecular level, AT1 antagonists attenuated the expression of MCP-1 and CCR2 in the aorta and peripheral blood monocytes and lowered the serum level of MCP-1. In addition, Western blotting showed that AT1 antagonists inhibited the phosphorylation of Akt in mouse monocytes.

CONCLUSIONS AND IMPLICATIONS

AT1 antagonism inhibited vessel wall inflammation and inhibition of PI3K/Akt may be involved in the modulation of the MCP-1/CCR2 system by AT1 antagonists in SHRs.

A critical role for TNFα in the selective attachment of mononuclear leukocytes to angiotensin-II-stimulated arterioles

Angiotensin II (Ang-II) exerts inflammatory activity and is involved in different cardiovascular disorders. This study has evaluated the involvement of tumor necrosis factor alpha (TNFα) in the leukocyte accumulation elicited by Ang-II. Ang-II (1 nM intraperitoneally in rats) induced TNFα release at 1 hour followed by neutrophil and mononuclear cell recruitment. The administration of an antirat TNFα antiserum had no effect on Ang-IIinduced neutrophil accumulation but inhibited the infiltration of mononuclear cells and reduced CC chemokine content in the peritoneal exudate. Pretreatment with either an anti-TNFα or an anti-IL-4 antiserum decreased Ang-II-induced arteriolar mononuclear leukocyte adhesion by 68% and 60%, respectively, in the rat mesenteric microcirculation. While no expression of TNFα was found in the postcapillary venules of Ang-II-injected animals, this cytokine was clearly up-regulated in the arterioles. Stimulation of human umbilical arterial endothelial cells (HUAECs) or isolated human mononuclear cells with 1 μM Ang-II caused increased TNFα mRNA expression and protein. Neutralization of TNFα activity reduced Ang-II-induced MCP-1, MCP-3, and RANTES release from HUAECs and MIP-1α from blood cells. In conclusion, the selective mononuclear leukocyte adhesion to Ang-II-stimulated arterioles is largely mediated by TNFα in cooperation with constitutive IL-4. Therefore, neutralization of TNFα activity may help to prevent mononuclear cell infiltration and the progression of the atherogenic process.

Losartan attenuates ventilator-induced lung injury

BACKGROUND

Accumulating evidence shows that angiotensin II (ANG II) can be generated locally in the lung tissue and may have autocrine and/or paracrine actions on the cellular level. In addition, ANG II precursor, angiotensinogen, as well as ANG II type 1 receptor (AT(1)), are also expressed in the lung tissue. Recent studies revealed that ANG II promoted acute lung injury induced by acid aspiration or sepsis, and that ANG II receptor blockade had a protective effect against acute lung injury. Therefore, the authors hypothesized that ventilator-induced lung injury might also be exacerbated by local ANG II action, and that ANG II receptor blockade would protect the lung from ventilator-induced lung injury.

MATERIALS AND METHODS

Forty Sprague Dawley rats weighing 300-350 g were randomly divided into the following experimental groups (10 rats in each group): (1) control group: rats were unventilated; (2) LVT (low volume ventilation) group: rats were ventilated with 8 mL/kg tidal volume room air for 2 h; (3) HVT (high volume ventilation) group: rats were ventilated with 40 mL/kg tidal volume room air for 2 h; (4) HVT + Losartan group: rats were pretreated with Losartan (30 mg/kg, i.p.) prior to high volume ventilation. The samples of pulmonary tissue and lung lavage fluid were collected after experiments. The expression of angiotensinogen and AT(1) receptor mRNA in lung tissue was measured by reverse transcriptase-polymerase chain reaction. Apoptosis of the lung cells was assayed with terminal deoxynucleodityl transferase-mediated nick-end labeling method. Lung pathological changes were examined with optical microscopy. Total protein, wet/dry ratios (W/D), myeloperoxidase (MPO) activity, and neutrophil counts of the lung tissue or lavage fluid were measured with corresponding methods.

RESULTS

Compared with control or LVT, HVT caused significant ventilator-induced lung injury and increased the expression of angiotensinogen and AT(1) receptor mRNA in the lung. Total protein, the number of apoptotic cells, W/D ratio, MPO activity, and neutrophil counts were significantly higher in the HVT group than in the LVT or control group. Pretreatment with Losartan attenuated ventilator-induced lung injury and prevented the increase in total protein, the number of apoptotic cells, W/D ratio, MPO, and neutrophil counts caused by high volume ventilation.

CONCLUSION

Our study indicates that HVT causes remarkable lung injury and up-regulates angiotensinogen and AT(1) receptor expression of in the lung, and that Losartan, a selective inhibitor of subtype AT(1) receptors for angiotensin II, can relieve acute lung injury caused by high volume ventilation.

Vascular benefits of angiotensin receptor blockers

There is convincing evidence that angiotensin II, through activation of the angiotensin II type 1 (AT1) receptor, is involved in the atherosclerotic process. Similarly, angiotensin receptor blockers decrease vascular inflammation, hypertrophy and thrombosis, which are the key components of the progression of atherosclerosis. In addition, in several animal models, angiotensin receptor blockade was able to inhibit atherosclerosis. However, the effects of angiotensin receptor blockers on clinical outcome in cardiovascular patients remains to be established. Contradictory results have been found on the reduction of the risk on myocardial infarctions and in-stent restenosis, although there is solid evidence for cerebroprotective effects of these receptor blockers. These differences may be related to the role of the AT2 receptor. This review discusses the role of angiotensin II and angiotensin receptor blockers in the atherosclerotic process and its translation into clinical practice.

Angiotensin II mediates postischemic leukocyte-endothelial interactions: role of calcitonin gene-related peptide

Vascular inflammation and enhanced production of angiotensin II (ANG II) are involved in the pathogenesis of hypertension and diabetes, disease states that predispose the afflicted individuals to ischemic disorders. In light of these observations, we postulated that ANG II may play a role in promoting leukocyte rolling (LR) and adhesion (LA) in postcapillary venules after exposure of the small intestine to ischemia-reperfusion (I/R). Using an intravital microscopic approach in C57BL/6J mice, we showed that ANG II type I (AT1) or type II (AT2) receptor antagonism (with valsartan or PD-123319, respectively), inhibition of angiotensin-converting enzyme (ACE) with captopril, or calcitonin gene-related peptide (CGRP) receptor blockade (CGRP8-37) prevented postischemic LR but did not influence I/R-induced LA. However, both postischemic LR and LA were largely abolished by concomitant AT1 and AT2 receptor blockade or chymase inhibition (with Y-40079). Additionally, exogenously administered ANG II increased LR and LA, effects that were attenuated by pretreatment with a CGRP receptor antagonist or an NADPH oxidase inhibitor (apocynin). Our work suggests that ANG II, formed by the enzymatic activity of ACE and chymase, plays an important role in inducing postischemic LR and LA, effects that involve the engagement of both AT1 and AT2 receptors and may be mediated by CGRP and NADPH oxidase.

Angiotensin, bradykinin and the endothelium

Angiotensins and kinins are endogenous peptides with diverse biological actions; as such, they represent current and future targets of therapeutic intervention. The field of angiotensin biology has changed significantly over the last 50 years. Our original understanding of the crucial role of angiotensin II in the regulation of vascular tone and electrolyte homeostasis has been expanded to include the discovery of new angiotensins, their important role in cardiovascular inflammation and the development of clinically useful synthesis inhibitors and receptor antagonists. While less applied progress has been achieved in the kinin field, there are continuous discoveries in bradykinin physiology and in the complexity of kinin interactions with other proteins. The present review focuses on mechanisms and interactions of angiotensins and kinins that deal specifically with vascular endothelium.

Do valsartan and losartan have the same effects in the treatment of coronary artery disease?

BACKGROUND

Many angiotensin II type 1 receptor blockers (ARBs) are available for clinical use, but because they do not all have the same effects, the present study investigated whether all benefits conferred by ARBs are class effects.

METHODS AND RESULTS

Study 1 was a case-control study of patients with coronary artery disease, which showed that a non-depressor dose of valsartan significantly decreased the rate of target lesion revascularization at 6 months after stenting compared with the control group without ARB treatment. In Study 2, 44 patients with acute myocardial infarction who randomly received an initial lower dose of either valsartan or losartan after stenting were evaluated. The late loss and decrease in %diameter stenosis in the valsartan group were significantly lower than those in the losartan group as assessed by quantitative coronary angiography after 6 months. In addition, the valsartan group showed a significantly lower expression of intracellular adhesion molecule-1 and L-selectin.

CONCLUSION

A non-depressor dose of ARB may have beneficial effects on coronary restenosis that are associated with the regulation of adhesion molecules, and these effects might not be a class effect of ARBs.

Intracoronary enalaprilat during angioplasty for acute myocardial infarction: alleviation of postischaemic neurohumoral and inflammatory stress?

AIM

Reperfusion after myocardial ischaemia is associated with a distinct ischaemia/reperfusion injury. Since ACE-inhibition, beyond its influence on cardiac angiotensin II formation and kinin metabolism, has been shown to be cardioprotective by decreasing leucocyte adhesion and endothelin-1 (ET-1) release, we investigated the effects of intracoronary (i.c.) enalaprilat during primary angioplasty in acute myocardial infarction.

METHODS AND RESULTS

Twenty-two patients were randomized to receive i.c. enalaprilat (50 micro g) or placebo immediately after reopening of the infarct-related artery (IRA). Plasma concentrations of soluble L-selectin, P-selectin, intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), ET-1 and nitric oxide metabolite concentrations (NOx) were measured in pulmonary arterial blood. Coronary blood flow was assessed using corrected thrombolysis in myocardial infarction (TIMI) frame counts (CTFC). During reperfusion, there was a significant increase in sL-selectin, sP-selectin and ET-1 in the placebo group, which was greatly diminished by enalaprilat. Levels of sVCAM-1 and sICAM-1 were not affected in either group. CTFC in the placebo group remained higher than normal in both the IRA and nonculprit vessels, whereas myocardial blood flow improved with enalaprilat.

CONCLUSION

Enalaprilat as adjunct to primary angioplasty might be a protective approach to prevent leucocyte adhesion and the release of ET-1, thereby improving coronary blood flow.

Angiotensin II increases the cholesterol content of foam cells via down-regulating the expression of ATP-binding cassette transporter A1

ATP-binding cassette transporter A1 (ABCA1) as one kind of membrane protein was found recently to play a major role in cholesterol homeostasis. Angiotensin II (AngII) has been shown to possess several atherogenic properties. The aim of the study is to investigate the influence of AngII on the expression of ABCA1 and the content of cholesterol in THP-1 derived foam cells. Our study showed that: (1) reverse transcription-polymerase chain reaction (RT-PCR) and Western blotting demonstrated that AngII down-regulated the expression of ABCA1 in a dose-dependent manner. (2) The content of cholesterol was negatively correlated with ABCA1. The results suggest the promoting effects of AngII on the forming of foam cells are in a dose-dependent manner via down-regulating the expression of ABCA1.

Aldosterone synthesis and cytokine production in human peripheral blood mononuclear cells

Previously, we reported that spironolactone reduced cytokine production in cultured human peripheral blood mononuclear cells (PBMCs) with angiotensin (Ang) II stimulation. To address the mechanisms underlying this effect, we examined the contribution of aldosterone to cytokine production in cultured human PBMCs with Ang II stimulation. PBMCs expressed the messenger RNA (mRNA) of Ang II type 1 receptor (AT1R) and mineralocorticoid receptor (MR) both spontaneously and after Ang II stimulation, but expressed Ang II type 2 receptor (AT2R) under neither condition. After 24 h of incubation, exogenous Ang II induced the expression of CYP11B2 (a key enzyme of aldosterone synthesis) mRNA and caused aldosterone synthesis. CV-11974 (an AT1R antagonist) reduced Ang II-induced aldosterone synthesis, whereas PD-123319 (an AT2R antagonist) had no effect. The concentration of aldosterone peaked earlier than those of monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-alpha (TNF-alpha). After 48 h of incubation (under the influence of synthesized aldosterone), CV-11974 and spironolactone significantly reduced the Ang II-enhanced production of MCP-1 and TNF-alpha, whereas PD-123319 also had no effect. In conclusion, Ang II induces aldosterone synthesis through AT1R and enhances cytokine production through an AT1R-dependent mechanism and, at least partly, through a MR-dependent mechanism in human PBMCs.

Non-radioactive and colorimetric quantification of monocyte adhesion to endothelial cells in early atherogenesis

Monocyte adhesion to vascular endothelium is an initial step in atherogenesis. To quantify this, we incubated monocytes with cultured endothelial cells, and quantified the adhered live monocytes using a colorimetric assay. Endothelium activated with lipopolysaccharide attracted monocytes in a dose-dependent manner and the adhesion was attenuated with post-treatments with L-ascorbic acid (53%), alpha- (40%) and gamma-tocopherol (39%), resveratrol (39%), and Lithospermum erythrorhizon root extract (45%). This non-radioactive, colorimetric assay may be useful for screening anti-atherogenic compounds in early atherogenesis.

Microvascular responses to hypercholesterolemia: the interactions between innate and adaptive immune responses

Hypercholesterolemia is recognized as one of the major risk factors in cardiovascular disease. It promotes the development of a proinflammatory phenotype in large vessels, in particular arteries, with disease. Cells of the innate and adaptive immune system are localized within atherosclerotic plaques and participate in the initiation and progression of plaque formation. It is now recognized that each segment of the microvasculature also experiences inflammation due to hypercholesterolemia, and that this occurs long before events in the large vessels. More recently, it is has been established that the innate and adaptive immune systems participate in the responses of postcapillary venules, and possibly arterioles, to elevated cholesterol levels, and that T lymphocytes may be one of the early cell types activated by hypercholesterolemia. These cells initiate a series of steps that lead to leukocyte accumulation in postcapillary venules and endothelial dysfunction in the arterioles. This review discusses the microvascular alterations induced by hypercholesterolemia, with particular attention paid to the roles of the innate and adaptive immune responses, and how these two systems may communicate to induce the microvascular inflammation.

Angiotensin II type 1 receptors and the intestinal microvascular dysfunction induced by ischemia and reperfusion

The acute phase of intestinal ischemia-reperfusion (I/R) injury is mediated by leukocytes and is characterized by oxidative stress and blood cell recruitment. Upregulation of angiotensin II type 1 receptors (AT1-R) has been implicated in the pathogenesis of conditions associated with oxidative stress. The AT1-R-antagonist Losartan (Los) attenuates leukocyte recruitment following I/R. However, the role of AT1-R in intestinal I/R injury and the associated platelet-leukocyte interactions remains unclear. The objective of this study was to define the contribution of AT1-R to I/R-induced blood cell recruitment in intestinal venules. Leukocyte and platelet adhesion were quantified by intravital microscopy in the small bowel of C57Bl/6 [wild-type (WT)] mice exposed to sham operation or 45 min of ischemia and 4 h of reperfusion. A separate WT group received Los for 7 days before gut I/R (WT-I/R + Los). AT1-R bone marrow chimeras that express AT1-R on the vessel wall but not blood cells also underwent I/R. Platelet and leukocyte adhesion as well as AT1-R expression in the gut microvasculature were significantly elevated after I/R. All of these responses were attenuated in the WT-I/R + Los group, compared with untreated I/R mice. A comparable abrogation of I/R-induced blood cell adhesion was noted in AT1-R bone marrow chimeras. I/R-induced platelet adhesion was unaltered in mice overexpressing Cu,Zn-SOD or mice deficient in NAD(P)H oxidase. These data suggest that although gut I/R upregulates endothelial expression of AT1-R, engagement of these angiotensin II receptors on blood cells is more important in eliciting the prothrombogenic and proinflammatory state observed in postischemic gut venules, through a superoxide-independent pathway.

Losartan attenuates bleomycin induced lung fibrosis by increasing prostaglandin E2 synthesis

BACKGROUND

The angiotensin system has a role in the pathogenesis of pulmonary fibrosis. This study examines the antifibrotic effect of losartan, an angiotensin II type 1 receptor antagonist, in bleomycin induced lung fibrosis and its possible implication in the regulation of prostaglandin E(2) (PGE(2)) synthesis and cyclooxygenase-2 (COX-2) expression.

METHODS

Rats were given a single intratracheal instillation of bleomycin (2.5 U/kg). Losartan (50 mg/kg/day) was administrated orally starting one day before induction of lung fibrosis and continuing to the conclusion of each experiment.

RESULTS

Losartan reduced the inflammation induced by bleomycin, as indicated by lower myeloperoxidase activity and protein content in the bronchoalveolar lavage fluid. Collagen deposition induced by bleomycin was inhibited by losartan, as shown by a reduction in the hydroxyproline content and the amelioration of morphological changes. PGE(2) levels were lower in fibrotic lungs than in normal lungs. Losartan significantly increased PGE(2) levels at both 3 and 15 days. A reduction in COX-2 expression by bleomycin was seen at 3 days which was relieved by losartan.

CONCLUSIONS

The antifibrotic effect of losartan appears to be mediated by its ability to stimulate the production of PGE(2). Losartan, which is already widely used clinically, could be assessed as a new treatment in lung fibrosis.

Cytokines in Atherosclerosis: Pathogenic and Regulatory Pathways

Atherosclerosis is a chronic disease of the arterial wall where both innate and adaptive immunoinflammatory mechanisms are involved. Inflammation is central at all stages of atherosclerosis. It is implicated in the formation of early fatty streaks, when the endothelium is activated and expresses chemokines and adhesion molecules leading to monocyte/lymphocyte recruitment and infiltration into the subendothelium. It also acts at the onset of adverse clinical vascular events, when activated cells within the plaque secrete matrix proteases that degrade extracellular matrix proteins and weaken the fibrous cap, leading to rupture and thrombus formation. Cells involved in the atherosclerotic process secrete and are activated by soluble factors, known as cytokines. Important recent advances in the comprehension of the mechanisms of atherosclerosis provided evidence that the immunoinflammatory response in atherosclerosis is modulated by regulatory pathways, in which the two anti-inflammatory cytokines interleukin-10 and transforming growth factor-β play a critical role. The purpose of this review is to bring together the current information concerning the role of cytokines in the development, progression, and complications of atherosclerosis. Specific emphasis is placed on the contribution of pro- and anti-inflammatory cytokines to pathogenic (innate and adaptive) and regulatory immunity in the context of atherosclerosis. Based on our current knowledge of the role of cytokines in atherosclerosis, we propose some novel therapeutic strategies to combat this disease. In addition, we discuss the potential of circulating cytokine levels as biomarkers of coronary artery disease.

Cardiac fibrogenesis in magnesium deficiency: a role for circulating angiotensin II and aldosterone

Mechanisms underlying cardiac fibrogenesis in magnesium deficiency are unclear. It was reported earlier from this laboratory that serum from magnesium-deficient rats has a more pronounced stimulatory effect on cell proliferation, net collagen production, and superoxide generation in adult rat cardiac fibroblasts than serum from rats on the control diet. The profibrotic serum factors were, however, not identified. This study tested the hypothesis that circulating angiotensin II may modulate cardiac fibroblast activity in hypomagnesemic rats. Male Sprague-Dawley rats were pair-fed a magnesium-deficient (0.0008% Mg) or -sufficient (0.05%) diet for 6 days, and the effects of serum from these rats on [3H]thymidine and [3H]proline incorporation into cardiac fibroblasts from young adult rats were evaluated in the presence of losartan, an angiotensin II type 1 (AT1) receptor antagonist, and spironolactone, an aldosterone antagonist. Losartan and spironolactone markedly attenuated the stimulatory effects in vitro of serum from the magnesium-deficient and control groups, but the inhibitory effects were considerably higher in cells exposed to serum from magnesium-deficient animals. Circulating and cardiac tissue levels of angiotensin II were significantly elevated in magnesium-deficient animals (67.6% and 93.1%, respectively, vs. control). Plasma renin activity was 61.9% higher in magnesium-deficient rats, but serum angiotensin-converting enzyme activity was comparable in the two groups. Furthermore, preliminary experiments in vivo using enalapril supported a role for angiotensin II in magnesium deficiency. There was no significant difference between the groups in serum aldosterone levels. The findings suggest that circulating angiotensin II and aldosterone may stimulate fibroblast activity and contribute to a fibrogenic response in the heart in magnesium deficiency.

AT&sub1; Receptor Blockade Prevents Microvascular Dysfunction Induced by Ischemia/Reperfusion Injury

Ischemia/reperfusion (I/R) in post-arterior post-capillary venules induces an acute inflammatory response, characterized by increased adherence and emigration of leukocytes and vascular permeability, all of which play important roles in cardiovascular disease. The aim of this study was to determine the roles of angiotensin II and AT1 receptor blockade in microvascular I/R injury in rats. Rats were anesthetized and intubated, then the peritoneum was opened and the mesentery was revealed. Small post-capillary venules were examined by in vivo fluorescence microscopy. The flow of erythrocytes and leukocytes was observed under the microscope and video recorded for later dynamic analyses. The superior mesenteric artery (SMA) was ligated with polyethylene tubing and released to induce I/R (20 min of ischemia/60 min of reperfusion). Subsequently, leukocyte adhesion, emigration and albumin leakage were compared with those of non-I/R controls. I/R injury was significantly suppressed by superfusing tissues with the AT1 receptor antagonist losartan (LO; 10 microM). The beneficial effects of LO were inhibited by topical application of either the bradykinin B2 receptor antagonist HOE140 (10 nM) or nitric oxide (NO) synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME 10 microM). The effects of LO were lost in the presence of AT2 receptor blocker PD 123319 (PD). In conclusion, LO suppressed and protected against I/R injuries. The possible interaction between AT1 and AT2 receptors was also suggested.

ACE Inhibition Lowers Angiotensin-II-Induced Monocyte Adhesion to HUVEC by Reduction of p65 Translocation and AT1 Expression

Angiotensin-converting enzyme (ACE) inhibitors interfere with several key events of vascular inflammation resulting in impressive reductions in coronary vascular events. However, in human arteries ACE inhibitors block the production of angiotensin II (AngII) incompletely because of the involvement of alternative pathways in local AngII formation. Therefore, our study concentrated on the presumed modulation by ACE inhibition of local AngII-mediated inflammatory actions by a mechanism independent of blockage of AngII formation. We analyzed the effect of the ACE inhibitor ramiprilat on AngII-dependent cell adhesion molecule (CAM) expression and adhesion of monocytic THP-1 cells to endothelial cells. AngII induced upregulation of P-selectin, VCAM-1 and ICAM-1 on endothelial cells via activation of AT 1, which was correlated with enhanced THP-1 adhesion in flow chamber assays. Both enhanced adhesion and adhesion molecule expression were significantly reduced by pretreatment with ramiprilat. Ramiprilat reduced AT 1 expression on endothelial cells and decreased the AngII-induced p65 translocation into the nucleus. Diminished AT 1 expression and adhesion molecule expression in response to ramiprilat treatment were partially reversed after incubation with a bradykinin 2 receptor antagonist, suggesting that elevated bradykinin levels under ACE inhibition may be involved in the beneficial effect of ACE inhibitors. Thus, modulation of the local AngII system by ramiprilat may at least in part contribute to the benefits of ACE inhibition in the treatment of atherosclerotic diseases.

LPS induces permeability injury in lung microvascular endothelium via AT1 receptor

Lipopolysaccharide (LPS) is known to stimulate the circulation and local production of angiotensin II (Ang II). To assess whether Ang II plays a role in LPS-induced acute lung injury, rats were injected with LPS, the microvascular endothelial permeability injury was evaluated by histological changes, increased pulmonary wet/dry weight ratio, and pulmonary microvascular protein leak. Besides, increased rat pulmonary microvascular endothelial cell monolayer permeability coefficient (K(f)) was measured after treatment with LPS and/or Ang II, respectively. LPS/Ang II, treatment resulted in a significant increase in K(f). Ang II cooperates with LPS to further increase K(f). Hence, LPS increases pulmonary microvascular endothelial permeability both in vitro and in vivo. Local lung Ang II was increased in response to LPS challenge, and elevated Ang II ulteriorly exacerbates LPS-induced endothelium injury. [Sar(1),Ile(8)]Ang II, a selective block of Ang II type 1 (AT(1)) receptors, eliminated these changes significantly. Our conclusion is that the LPS-induced lung injury may be mediated by the AT(1) receptor.

An extremely high dose of losartan affords superior renoprotection in the remnant model

BACKGROUND

Rats subjected to 5/6 renal ablation (NX) exhibit large renal amounts of angiotensin II (Ang II) and of its main receptor, AT-1R. At previously used doses, AT-1R blockers (ARB) offer only partial renal protection. A possible explanation for this limited effect is that these doses are insufficient to block most of the abnormally expressed AT-1R. We investigated whether extremely high doses of the ARB, losartan (L), offer better protection than conventional doses in the NX model.

METHODS

Thirty days after NX, tail-cuff pressure (TCP), albuminuria (U(alb)V, mg/day), glomerulosclerosis index (GSI), fractional interstitial area (%INT), and macrophage infiltration (MO) were evaluated in a separate group (NX(pre)). The remaining rats were then subdivided among 4 groups: NX+V, receiving vehicle; NX+L50, treated with L, at the "conventional" dose of 50 mg/kg/day; NX+L500, receiving L, 500 mg/kg/day; and NX+HH, receiving hydrochlorothiazide and hydralazine to lower blood pressure to a similar extent as in group L500.

RESULTS

After a month of treatment, blood pressure and renal vascular resistance were lowest in group L500. Glomerular pressure was lowered by a similar extent by L50 and L500, while GFR was similar among groups. U(alb)V, TCP, and renal injury were only partially reduced by L50 120 days after renal ablation. By contrast, L500 arrested renal inflammation and glomerular/interstitial injury at pretreatment levels, and promoted regression of hypertension and U(alb)V, causing no apparent untoward effects.

CONCLUSION

The renal protection afforded by ARB in NX is dose dependent. Maximal protection may require doses several fold higher than those currently employed.

Anti-inflammatory strategies in hypertension: focus on COX-1 and COX-2

An increasing body of evidence suggests that elevated levels of blood pressure may induce a proinflammatory response. Indeed, both C-reactive protein and blood pressure are independent determinants of cardiovascular risk, and, in combination, each parameter has additional predictive value. Hence, strategies targeted to lower blood pressure and reduce vascular inflammation may potentially provide clinical benefit. In this review, we discuss the role of chronic low-grade inflammation in the context of cardiovascular disease with a focus on roles of cyclooxygenase-1 and -2 in potential anti-inflammatory treatment strategies.

The revised role of ACE-inhibition after myocardial infarction in the thrombolytic/primary PCI era

Many studies have investigated the process of left ventricular (LV) dilatation and the effects of angiotensin-converting enzyme (ACE) inhibitors after myocardial infarction (MI). It has been generally accepted that progression of LV dilatation is a major predictor of heart failure and death after MI. Also, attenuation of LV dilatation is thought to be one of the main mechanisms by which ACE inhibitors (ACE-Is) produce their beneficial effects. However, evidence for this hypothesis came from studies that were performed before thrombolytic therapy and primary percutaneous coronary intervention (PCI) were routinely used after acute MI. Nowadays, reperfusion is obtained much more frequently and LV dilatation after MI has become less prevalent. Nevertheless, ACE-Is proved effective in reducing cardiac morbidity and mortality. Therefore, mechanisms other than attenuation of LV dilatation, such as anti-atherosclerotic effects or plaque stabilisation, may explain the long-term beneficial effects of ACE-Is after MI. In the present overview, we evaluate the role of LV dilatation and the effects of ACE-Is after MI in the thrombolytic/primary PCI era and provide recommendations on ACE-I use in clinical practice.