Effect of bosentan on NF-kappaB, inflammation, and tissue factor in angiotensin II-induced end-organ damage

Dual blockade of endothelin A and angiotensin II type 1 receptors with sparsentan as a novel treatment strategy to alleviate IgA nephropathy

INTRODUCTION

Although immunoglobulin A nephropathy (IgAN) had been discovered more than 50 years ago, 30-40% of IgAN patients still have primary glomerular disease that progresses to end-stage renal disease. However, various treatment strategies for IgAN have rapidly expanded in recent years to include endothelin (ET) receptor antagonists.

AREAS COVERED

In this review, we discuss the role of the ET-1/ETA receptor axis in the development of IgAN, especially focusing on the potential of sparsentan, a dual ET and angiotensin receptor antagonist as a novel therapy for IgAN.

EXPERT OPINION

Evaluation of the MEST-C score at the time of renal biopsy in IgAN is important in determining treatment strategies. If lesions are mainly in the acute phase, such as crescents, steroid therapy should be continued. However, if lesions are mainly in the chronic phase, such as glomerulosclerosis, sparsentan rather than steroid or angiotensin II receptor blocker alone may improve renal outcomes. Although further clinical studies are needed to back up these assumptions, appropriate combination of new drugs containing sparsentan and conventional drugs for IgAN treatment at the appropriate disease stage is expected to further inhibit the progression of renal damage.

Immune and inflammatory mechanisms in hypertension

Hypertension is a global health problem, with >1.3 billion individuals with high blood pressure worldwide. In this Review, we present an inflammatory paradigm for hypertension, emphasizing the crucial roles of immune cells, cytokines and chemokines in disease initiation and progression. T cells, monocytes, macrophages, dendritic cells, B cells and natural killer cells are all implicated in hypertension. Neoantigens, the NLRP3 inflammasome and increased sympathetic outflow, as well as cytokines (including IL-6, IL-7, IL-15, IL-18 and IL-21) and a high-salt environment, can contribute to immune activation in hypertension. The activated immune cells migrate to target organs such as arteries (especially the perivascular fat and adventitia), kidneys, the heart and the brain, where they release effector cytokines that elevate blood pressure and cause vascular remodelling, renal damage, cardiac hypertrophy, cognitive impairment and dementia. IL-17 secreted by CD4+ T helper 17 cells and γδ T cells, and interferon-γ and tumour necrosis factor secreted by immunosenescent CD8+ T cells, exert crucial effector roles in hypertension, whereas IL-10 and regulatory T cells are protective. Effector mediators impair nitric oxide bioavailability, leading to endothelial dysfunction and increased vascular contractility. Inflammatory effector mediators also alter renal sodium and water balance and promote renal fibrosis. These mechanisms link hypertension with obesity, autoimmunity, periodontitis and COVID-19. A comprehensive understanding of the immune and inflammatory mechanisms of hypertension is crucial for safely and effectively translating the findings to clinical practice.

Endothelin System in Hypertension and Chronic Kidney Disease

ET (endothelin) is a powerful vasoconstrictor 21-amino acid peptide present in many tissues, which exerts many physiological functions across the body and participates as a mediator in many pathological conditions. ETs exert their effects through ETA and ETB receptors, which can be blocked by selective receptor antagonists. ETs were shown to play important roles among others, in systemic hypertension, particularly when resistant or difficult to control, and in pulmonary hypertension, atherosclerosis, cardiac hypertrophy, subarachnoid hemorrhage, chronic kidney disease, diabetic cardiovascular disease, scleroderma, some cancers, etc. To date, ET antagonists are only approved for the treatment of primary pulmonary hypertension and recently for IgA nephropathy and used in the treatment of digital ulcers in scleroderma. However, they may soon be approved for the treatment of patients with resistant hypertension and different types of nephropathy. Here, the role of ETs is reviewed with a special emphasis on participation in and treatment of hypertension and chronic kidney disease.

The Brain-Heart Axis: Neuroinflammatory Interactions in Cardiovascular Disease

PURPOSE OF REVIEW

The role of neuroimmune modulation and inflammation in cardiovascular disease has been historically underappreciated. Physiological connections between the heart and brain, termed the heart-brain axis (HBA), are bidirectional, occur through a complex network of autonomic nerves/hormones and cytokines, and play important roles in common disorders.

RECENT FINDINGS

At the molecular level, advances in the past two decades reveal complex crosstalk mediated by the sympathetic and parasympathetic nervous systems, the renin-angiotensin aldosterone and hypothalamus-pituitary axes, microRNA, and cytokines. Afferent pathways amplify proinflammatory signals via the hypothalamus and brainstem to the periphery, promoting neurogenic inflammation. At the organ level, while stress-mediated cardiomyopathy is the prototypical disorder of the HBA, cardiac dysfunction can result from a myriad of neurologic insults including stroke and spinal injury. Atrial fibrillation is not necessarily a causative factor for cardioembolic stroke, but a manifestation of an abnormal atrial substrate, which can lead to the development of stroke independent of AF. Central and peripheral neurogenic proinflammatory factors have major roles in the HBA, manifesting as complex bi-directional relationships in common conditions such as stroke, arrhythmia, and cardiomyopathy.

Exploring the pivotal role of endothelin in rheumatoid arthritis

A chronic inflammatory disorder, rheumatoid arthritis (RA) is an autoimmune and systemic disease characterized by progressive and prolonged destruction of joints. This results in increased mortality, physical disability and destruction. Cardiovascular disorders are one of the primary causes of mortality in patients with RA. It is multifactorial in nature and includes genetic, environmental and demographic factors which contribute to the severity of disease. Endothelin-1 (ET-1) is a peptide which acts as a potent vasoconstrictor and is generated through vascular smooth muscle and endothelial cells. Endothelins may be responsible for RA, as under certain circumstances they produce reactive oxygen species which further promote the production of pro-inflammatory cytokines. This enhances the production of superoxide anion, which activates pro-inflammatory cytokines, resulting in RA. The aim of this review is to elucidate the role of endothelin in the progression of RA. This review also summarizes the natural and synthetic anti-inflammatory drugs which have provided remarkable insights in targeting endothelin.

Evidence for a Role of CCR6+ T Cells in Chronic Thromboembolic Pulmonary Hypertension

Introduction

Previous studies have shown an increase of T cells and chemokines in vascular lesions of patients with chronic thromboembolic pulmonary hypertension (CTEPH). However, detailed characterization of these T cells is still lacking, nor have treatment effects been evaluated.

Methods

We included 41 treatment-naive CTEPH patients at diagnosis, 22 patients at 1-year follow-up, and 17 healthy controls (HCs). Peripheral blood T cells were characterized by flow cytometry for subset distribution, cytokine expression and activation marker profile. We used multiplex immunofluorescence to identify CCR6⁺ T cells in endarterectomy tissue from 25 patients.

Results

At diagnosis, proportions of CCR6⁺ CD4⁺ T cells were increased in CTEPH patients compared with HCs. Patients displayed a significantly reduced production capacity of several cytokines including TNFα, IFNγ, GM-CSF and IL-4 in CD4⁺ T cells, and TNFα and IFNγ in CD8⁺ T cells. CD4⁺ and CD8⁺ T cells showed increased expression of the immune checkpoint protein CTLA4. Multivariate analysis separated CTEPH patients from HCs, based on CCR6 and CTLA4 expression. At 1-year follow-up, proportions of CCR6⁺CD4⁺ T cells were further increased, IFNγ and IL-17 production capacity of CD4⁺ T cells was restored. In nearly all vascular lesions we found substantial numbers of CCR6⁺ T cells.

Conclusion

The observed increase of CCR6⁺ T cells and modulation of the IFNγ and IL-17 production capacity of circulating CD4⁺ T cells at diagnosis and 1-year follow-up – together with the presence of CCR6⁺ T cells in vascular lesions - support the involvement of the Th17-associated CCR6⁺ T cell subset in CTEPH.

The Targeting of Nuclear Factor Kappa B by Drugs Adopted for the Prevention and Treatment of Preeclampsia

Preeclampsia (PE) is characterised by high levels and activity of the transcription factor Nuclear Factor kappa B (NFĸB) in the maternal blood and placental cells. This factor is responsible for the regulation of over 400 genes known to influence processes related to inflammation, apoptosis and angiogenesis, and cellular responses to oxidative stress and hypoxia. Although high NFĸB activity induces hypoxia and inflammation, which are beneficial for the process of implantation, NFĸB level should be reduced in the later stages of physiological pregnancy to favour maternal immunosuppression and maintain gestation. It is believed that the downregulation of NFĸB activity by pharmacotherapy might be a promising way to treat preeclampsia. Interestingly, many of the drugs adopted for the prevention and treatment of preeclampsia have been found to regulate NFĸB activity. Despite this, further innovation is urgently needed to ensure treatment safety and efficacy. The present article summarizes the current state of knowledge about the drugs recommended by cardiology, obstetrics, and gynaecology societies for the prevention and treatment of preeclampsia with regard to their impact on the cellular regulation of NFĸB pathways.

"The possible implication of endothelin in the pathology of COVID-19-induced pulmonary hypertension"

COVID-19 pandemic has changed the world dramatically since was first reported in Wuhan city, China [1]. Not only as a respiratory illness that could lead to fatal respiratory failure, but also some evidences suggest that it can propagate as a chronic disease associated with a variety of persistent post COVID-19 pathologies that affect patients' life [2,3]. Pulmonary hypertension (PH) is one of the challenging diseases that may develop as a consequence of SARS-COV-2 infection in some COVID-19 survivors [4,5]. The vasopressor, proliferative, proinflammatory, and prothrombotic actions of endothelin [6] may be encountered in the COVID-19-induced PH pathology. And so, endothelin blockers may have an important role to restrict the development of serious PH outcomes with special precautions considering patients with significant hypoxemia.

Obesity, kidney dysfunction, and inflammation: interactions in hypertension

Obesity contributes 65-75% of the risk for human primary (essential) hypertension (HT) which is a major driver of cardiovascular and kidney diseases. Kidney dysfunction, associated with increased renal sodium reabsorption and compensatory glomerular hyperfiltration, plays a key role in initiating obesity-HT and target organ injury. Mediators of kidney dysfunction and increased blood pressure include (i) elevated renal sympathetic nerve activity (RSNA); (ii) increased antinatriuretic hormones such as angiotensin II and aldosterone; (iii) relative deficiency of natriuretic hormones; (iv) renal compression by fat in and around the kidneys; and (v) activation of innate and adaptive immune cells that invade tissues throughout the body, producing inflammatory cytokines/chemokines that contribute to vascular and target organ injury, and exacerbate HT. These neurohormonal, renal, and inflammatory mechanisms of obesity-HT are interdependent. For example, excess adiposity increases the adipocyte-derived cytokine leptin which increases RSNA by stimulating the central nervous system proopiomelanocortin-melanocortin 4 receptor pathway. Excess visceral, perirenal and renal sinus fat compress the kidneys which, along with increased RSNA, contribute to renin-angiotensin-aldosterone system activation, although obesity may also activate mineralocorticoid receptors independent of aldosterone. Prolonged obesity, HT, metabolic abnormalities, and inflammation cause progressive renal injury, making HT more resistant to therapy and often requiring multiple antihypertensive drugs and concurrent treatment of dyslipidaemia, insulin resistance, diabetes, and inflammation. More effective anti-obesity drugs are needed to prevent the cascade of cardiorenal, metabolic, and immune disorders that threaten to overwhelm health care systems as obesity prevalence continues to increase.

Inhibition of IL-1β by Aliskiren Improved Renal AQP2 Expression and Urinary Concentration Defect in Ureteral Obstruction and Release

We previously demonstrated that ureteral obstruction is associated with a urinary concentrating defect and reduced expression of renal aquaporins (AQPs), in which the renin–angiotensin system (RAS) may play an important role. The aims of the present study were to examine whether the renin inhibitor aliskiren could prevent the reduction in AQP expression and improve the urinary concentrating capacity in mice with bilateral ureteral obstruction (BUO) and BUO release. BUO was performed for 24 h, and BUO release was performed for 1 (B-R1D) or 3 days (B-R3D) with or without aliskiren treatment. Aliskiren prevented polyuria and decreased urine osmolality induced by B-R3D. In mice with BUO and BUO release, aliskiren attenuated the reduction in AQP2 protein and mRNA expression in the obstructed kidneys. B-R3D increased the protein expression of NLRP3 inflammasome components ASC, caspase-1, and interleukin-1β in the obstructed kidneys, which was markedly prevented by aliskiren. Moreover, the NF-κB inhibitor Bay 11-7082 blocked NLRP3 inflammasome activation and attenuated the decrease in AQP2 protein expression in primary cultured rat inner medullary collecting duct cells treated with angiotensin II. These results indicate that the renin inhibitor aliskiren increases water channel AQP2 expression at least partially by suppressing NLRP3 inflammasome activation in the obstructed kidneys of mice with BUO and BUO release.

Distinct effects of bosentan on NO-dependent vasodilation and calcium influx in heterozygous Ren-2 transgenic rats on high-salt diet

Our studies in hypertensive Ren-2 transgenic rats (TGR) demonstrated that chronic administration of atrasentan (ETA receptor antagonist) decreased blood pressure by reduced Ca2+ influx through L-type voltage-dependent calcium channels (L-VDCC) and attenuated angiotensin II-dependent vasoconstriction. We were interested whether bosentan (nonselective ET(A)/ET(B) receptor antagonist) would have similar effects. Young 4-week-old (preventive study) and adult 8-week-old (therapeutic study) heterozygous TGR and their normotensive Hannover Sprague-Dawley (HanSD) controls were fed normal-salt (NS, 0.6 % NaCl) or high-salt (HS, 2 % NaCl) diet for 8 weeks. An additional group of TGR fed HS was treated with bosentan (100 mg/kg/day). Bosentan had no effect on BP of TGR fed high-salt diet in both the preventive and therapeutic studies. There was no difference in the contribution of angiotensin II-dependent and sympathetic vasoconstriction in bosentan-treated TGR compared to untreated TGR under the condition of high-salt intake. However, bosentan significantly reduced NO-dependent vasodilation and nifedipine-sensitive BP component in TGR on HS diet. A highly important correlation of nifedipine-induced BP change and the BP after L-NAME administration was demonstrated. Although bosentan did not result in any blood pressure lowering effects, it substantially influenced NO-dependent vasodilation and calcium influx through L-VDCC in the heterozygous TGR fed HS diet. A significant correlation of nifedipine-induced BP change and the BP after L-NAME administration suggests an important role of nitric oxide in the closure of L-type voltage dependent calcium channels.

MicroRNAs as markers to monitor endothelin-1 signalling and potential treatment in renal disease: Carcinoma - proteinuric damage - toxicity

This review highlights new developments in miRNA as diagnostic and surveillance tools in diseases damaging the renal proximal tubule mediated by endothelin in the field of renal carcinoma, proteinuric kidney disease and tubulotoxicity. A new mechanism in the miRNA regulation of proteins leads to the binding of the miRNA directly to the DNA with premature transcriptional termination and hence the formation of truncated protein isoforms (Mxi2, Vim3). These isoforms are mediated through miRNA15a or miRNA 498, respectively. ET-1 can activate a cytoplasmic complex consisting of NF-κB p65, MAPK p38α, and PKCα. Consequently, PKCα does not transmigrate into the nucleus, which leads to the loss of suppression of a primiRNA15a, maturation of this miRNA in the cytoplasm, tubular secretion and detectability in the urine. This mechanism has been shown in renal cell carcinoma and in proteinuric disease as a biomarker for the activation of the signalling pathway. Similarly, ET-1 induced miRNA 498 transmigrates into the nucleus to form the truncated protein Vim3, which is a biomarker for the benign renal cell tumour, oncocytoma. In tubulotoxicity, ET-1 induced miRNa133a down-regulating multiple-drug-resistant related protein-2, relevant for proteinuric and cisplatin/cyclosporine A toxicity. Current advantages and limitations of miRNAs as urinary biomarkers are discussed.

Renoprotective effects of ET(A) receptor antagonists therapy in experimental non-diabetic chronic kidney disease: Is there still hope for the future?

Chronic kidney disease (CKD) is a life-threatening disease arising as a frequent complication of diabetes, obesity and hypertension. Since it is typically undetected for long periods, it often progresses to end-stage renal disease. CKD is characterized by the development of progressive glomerulosclerosis, interstitial fibrosis and tubular atrophy along with a decreased glomerular filtration rate. This is associated with podocyte injury and a progressive rise in proteinuria. As endothelin-1 (ET-1) through the activation of endothelin receptor type A (ET(A)) promotes renal cell injury, inflammation, and fibrosis which finally lead to proteinuria, it is not surprising that ET(A) receptors antagonists have been proven to have beneficial renoprotective effects in both experimental and clinical studies in diabetic and non-diabetic CKD. Unfortunately, fluid retention encountered in large clinical trials in diabetic CKD led to the termination of these studies. Therefore, several advances, including the synthesis of new antagonists with enhanced pharmacological activity, the use of lower doses of ET antagonists, the addition of diuretics, plus simply searching for distinct pathological states to be treated, are promising targets for future experimental studies. In support of these approaches, our group demonstrated in adult subtotally nephrectomized Ren-2 transgenic rats that the addition of a diuretic on top of renin-angiotensin and ET(A) blockade led to a further decrease of proteinuria. This effect was independent of blood pressure which was normalized in all treated groups. Recent data in non-diabetic CKD, therefore, indicate a new potential for ET(A) antagonists, at least under certain pathological conditions.

ETA receptor activation contributes to T cell accumulation in the kidney following ischemia-reperfusion injury

Renal ischemia-reperfusion (IR) injury and acute kidney injury (AKI) increase the risk of developing hypertension, with T cells suspected as a possible mechanistic link. Endothelin promotes renal T cell infiltration in several diseases, predominantly via the ETA receptor, but its contribution to renal T cell infiltration following renal IR injury is poorly understood. To test whether ETA receptor activation promotes T cell infiltration of the kidney following IR injury, male C57BL/6 mice were treated with the ETA receptor antagonist ABT-627 or vehicle, commencing 2 days prior to unilateral renal IR injury. Mice were sacrificed at 24 h or 10 days post-IR for assessment of the initial renal injury and subsequent infiltration of T cells. Vehicle and ABT-627-treated mice displayed significant upregulation of endothelin-1 (ET-1) in the IR compared to contralateral kidney at both 24 h and 10 days post-IR (P < 0.001). Renal CD3+ T cell numbers were increased in the IR compared to contralateral kidneys at 10 days, but ABT-627-treated mice displayed a 35% reduction in this effect in the outer medulla (P < 0.05 vs. vehicle) and a nonsignificant 23% reduction in the cortex compared to vehicle-treated mice. Whether specific T cell subsets were affected awaits confirmation by flow cytometry, but outer medullary expression of the T helper 17 transcription factor RORγt was reduced by ABT-627 (P = 0.06). These data indicate that ET-1 acting via the ETA receptor contributes to renal T cell infiltration post-IR injury. This may have important implications for immune system-mediated long-term consequences of AKI, an area which awaits further investigation.

Translational science in albuminuria: a new view of de novo albuminuria under chronic RAS suppression

The development of de novo albuminuria during chronic renin–angiotensin system (RAS) suppression is a clinical entity that remains poorly recognized in the biomedical literature. It represents a clear increment in global cardiovascular (CV) and renal risk that cannot be counteracted by RAS suppression. Although not specifically considered, it is clear that this entity is present in most published and ongoing trials dealing with the different forms of CV and renal disease. In this review, we focus on the mechanisms promoting albuminuria, and the predictors and new markers of de novo albuminuria, as well as the potential treatment options to counteract the excretion of albumin. The increase in risk that accompanies de novo albuminuria supports the search for early markers and predictors that will allow practising physicians to assess and prevent the development of de novo albuminuria in their patients.

Oxidative stress and reactive oxygen species in endothelial dysfunction associated with cardiovascular and metabolic diseases

Reactive oxygen species (ROS) are reactive intermediates of molecular oxygen that act as important second messengers within the cells; however, an imbalance between generation of reactive ROS and antioxidant defense systems represents the primary cause of endothelial dysfunction, leading to vascular damage in both metabolic and atherosclerotic diseases. Endothelial activation is the first alteration observed, and is characterized by an abnormal pro-inflammatory and pro-thrombotic phenotype of the endothelial cells lining the lumen of blood vessels. This ultimately leads to reduced nitric oxide (NO) bioavailability, impairment of the vascular tone and other endothelial phenotypic changes collectively termed endothelial dysfunction(s). This review will focus on the main mechanisms involved in the onset of endothelial dysfunction, with particular focus on inflammation and aberrant ROS production and on their relationship with classical and non-classical cardiovascular risk factors, such as hypertension, metabolic disorders, and aging. Furthermore, new mediators of vascular damage, such as microRNAs, will be discussed. Understanding mechanisms underlying the development of endothelial dysfunction is an important base of knowledge to prevent vascular damage in metabolic and cardiovascular diseases.

In vitro characterization studies of self-microemulsified bosentan systems

CONTEXT

Bosentan is a poorly soluble drug and pose challenges in designing of drug delivery systems.

OBJECTIVE

The objective of this study is to enhance the solubility, dissolution and shelf-life of bosentan by formulating it as S-SMEDDS capsules.

MATERIALS AND METHODS

Solubility of bosentan was tested in various liquid vehicles such as oils (rice bran and sunflower), surfactants (span 20 and tween 80) and co-surfactants (PEG 400 and propylene glycol) and microemulsions were developed. Bosentan was incorporated into appropriate microemulsion systems which were previously identified from pseudo ternary phase diagrams. Bosentan-loaded SMEDDS were evaluated for drug content, drug release, zeta potential, and droplet size. The selected liquid SMEDDS were converted into solid SMEDDS by employing adsorption and melt granulation. Solid SMEDDS were characterized for micromeritics and evaluated for drug content, drug release, and shelf-life.

RESULTS

Isotropic systems R5, R13, S5, and S13 with submicron droplet size had exhibited 85.45, 94.12, 81.67, and 96.64% drug release, respectively. Solid SMEDDS of MR13 and AS13 formulations with rapid reconstitution ability, exhibited 84.85 and 86.74% of on par drug release. The formulations were physicochemically intact for 1.02 and 1.56 years.

DISCUSSION

Liquid SMEDDS composed with PEG400 had displayed optimal characters. Solid SMEDDS had high-dissolution profiles than bosentan due to modification in the crystalline structure of drug upon microemulsification.

CONCLUSION

Thus, solid SMEDDS addressed the solubility, dissolution, and stability issues of bosentan and becomes an alternate for clinical convenience.

Candesartan prevents L-NAME-induced cardio-renal injury in spontaneously hypertensive rats beyond hypotensive effects

Our goal was to assess the cardiovascular and renal protection afforded by angiotensin II type 1-receptor blockade against NG-nitro-L-arginine methyl ester (L-NAME)-exacerbated hypertension in young spontaneously hypertensive rats (SHR), in comparison with the antihypertensive drug, hydralazine. Male SHR were assigned to four groups (n=8 per group): no treatment (controls); L-NAME-treated group (20 mg/kg/day, 10 days, orally); co-treatment with L-NAME and hydralazine (15 mg/kg/day, by gavage); co-treatment with L-NAME and candesartan cilexetil (10 mg/kg/day, by gavage), i.e. at a dose that inhibited acute pressor responses to 5—20 ng angiotensin II. One animal died in the L-NAME group, and tail-cuff systolic blood pressure (SBP) increased significantly compared with controls to 201±5 mmHg. Albumin excretion increased 235-fold in L-NAME-treated rats. Heart weight index averaged 3.5±0.1 and 3.8±0.1 mg/g body weight (p<0.05) in control and L-NAME rats, respectively, indicating moderate cardiac hypertrophy induced by L-NAME. Preglomerular vascular lesions affected 63±6% of interlobular arteries and 10±2% of afferent arterioles (vs. 8±3 and 0.8±0.4% in controls, respectively). Hydralazine and candesartan cilexetil treatment similarly reduced SBP to 153±7, and 165±6 mmHg, respectively. However, candesartan provided more protection, in terms of no significant change in albuminuria (vs. 25-fold increase with hydralazine), regression of cardiac hypertrophy, frequency of vascular lesions and histological indices of renal injury maintained within control values. In conclusion, candesartan cilexetil prevented L-NAME-exacerbated hypertension and associated cardio-renal injury in young SHR, the beneficial effects exceeding those of hydralazine.

Impaired Neovascularization and Reduced Capillary Supply in the Malignant vs. Non-malignant Course of Experimental Renovascular Hypertension

Malignant hypertension develops in some cases of hypertension but not in others. We hypothesized that an impaired neovascularization and a reduced capillary supply characterizes the malignant course of experimental hypertension. Two-kidney, one-clip renovascular hypertension was induced in rats; controls (sham) were sham operated. To distinguish malignant hypertension from non-malignant hypertension, we considered two factors: weight loss, and the number of typical vascular lesions (onion skin lesions and fibrinoid necroses) per kidney section of the nonclipped kidney. Animals in the upper half for both criteria were defined as malignant hypertensives. After 5 weeks, mean arterial blood pressure was elevated to the same degree in malignant hypertension and non-malignant hypertension whereas plasma renin and aldosterone were significantly higher in malignant hypertensives. The expression of plasminogen activator inhibitor-1 was elevated (up to 14-fold) in non-malignant but significantly more increased (up to 36-fold) in malignant hypertensive rats, compared to sham. As a bioassay for neovascularization, the area of granulation tissue ingrowth in polyvinyl discs (implanted subcutaneously) was reduced in malignant hypertension compared to non-malignant hypertension and sham, while there was no difference between non-malignant hypertension and sham. The number of renal and left ventricular capillaries was significantly lower in malignant hypertension compared to non-malignant hypertension, as was the number of proliferating endothelial cells. We conclude that an impaired neovascularization and capillarization occurs in malignant renovascular hypertension but not in the non-malignant course of the disease despite comparable blood pressure levels. This might contribute to the unique vascular lesions and progressive target organ damage observed in malignant hypertension.

Angiotensin III increases monocyte chemoattractant protein-1 expression in cultured human proximal tubular epithelial cells

BACKGROUND/AIMS

We investigated whether angiotensin III (Ang III) is involved in monocyte recruitment through regulation of the chemokine monocyte chemoattractant protein-1 (MCP-1) in cultured human proximal tubular epithelial cells (HK-2 cells).

METHODS

We measured MCP-1 levels in HK-2 cells that had been treated with various concentrations of Ang III and Ang II type-1 (AT1) receptor antagonists at various time points. The phosphorylation states of p38, c-Jun N-terminal kinases (JNK), and extracellular-signal-regulated kinases were measured in Ang III-treated cells to explore the mitogen-activated protein kinase (MAPK) pathway. MCP-1 levels in HK-2 cell-conditioned media were measured after pre-treatment with the transcription factor inhibitors curcumin or pyrrolidine dithiocarbamate.

RESULTS

Ang III increased MCP-1 protein production in dose- and time-dependent manners in HK-2 cells, which was inhibited by the AT1 receptor blocker losartan. p38 MAPK activity increased significantly in HK-2 cells exposed to Ang III for 30 minutes, and was sustained at higher levels after 60 minutes (p < 0.05). Total phosphorylated JNK protein levels tended to increase 20 minutes after stimulation with Ang III. Pre-treatment with a p38 inhibitor, a JNK inhibitor, or curcumin significantly inhibited Ang III-induced MCP-1 production.

CONCLUSIONS

Ang III increases MCP-1 synthesis via stimulation of intracellular p38 and JNK MAPK signaling activity and subsequent activated protein-1 transcriptional activity in HK-2 cells.

Understanding and treating hypertension in diabetic populations

Hypertension and diabetes frequently occurs in the same individuals in clinical practice. Moreover, the presence of hypertension does increase the risk of new-onset diabetes, as well as diabetes does promote development of hypertension. Whatever the case, the concomitant presence of these conditions confers a high risk of major cardiovascular complications and promotes the use integrated pharmacological interventions, aimed at achieving the recommended therapeutic targets. While the benefits of lowering abnormal fasting glucose levels in patients with hypertension and diabetes have been consistently demonstrated, the blood pressure (BP) targets to be achieved to get a benefit in patients with diabetes have been recently reconsidered. In the past, randomized clinical trials have, indeed, demonstrated that lowering BP levels to less than 140/90 mmHg was associated to a substantial reduction of the risk of developing macrovascular and microvascular complications in hypertensive patients with diabetes. In addition, epidemiological and clinical reports suggested that "the lower, the better" for BP in diabetes, so that levels of BP even lower than 130/80 mmHg have been recommended. Recent randomized clinical trials, however, designed to evaluate the potential benefits obtained with an intensive antihypertensive therapy, aimed at achieving a target systolic BP level below 120 mmHg as compared to those obtained with less stringent therapy, have challenged the previous recommendations from international guidelines. In fact, detailed analyses of these trials showed a paradoxically increased risk of coronary events, mostly myocardial infarction, in those patients who achieved the lowest BP levels, particularly in the high-risk subsets of hypertensive populations with diabetes. In the light of these considerations, the present article will briefly review the common pathophysiological mechanisms, the potential sites of therapeutic interactions and the currently recommended BP targets to be achieved under pharmacological treatment in hypertension and diabetes.

Brain inflammation and hypertension: the chicken or the egg?

Inflammation of forebrain and hindbrain nuclei controlling the sympathetic nervous system (SNS) outflow from the brain to the periphery represents an emerging concept of the pathogenesis of neurogenic hypertension. Angiotensin II (Ang-II) and prorenin were shown to increase production of reactive oxygen species and pro-inflammatory cytokines (interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α)) while simultaneously decreasing production of interleukin-10 (IL-10) in the paraventricular nucleus of the hypothalamus and the rostral ventral lateral medulla. Peripheral chronic inflammation and Ang-II activity seem to share a common central mechanism contributing to an increase in sympathetic neurogenic vasomotor tone and entailing neurogenic hypertension. Both hypertension and obesity facilitate the penetration of peripheral immune cells in the brain parenchyma. We suggest that renin-angiotensin-driven hypertension encompasses feedback and feedforward mechanisms in the development of neurogenic hypertension while low-intensity, chronic peripheral inflammation of any origin may serve as a model of a feedforward mechanism in this condition.

DC isoketal-modified proteins activate T cells and promote hypertension

Oxidative damage and inflammation are both implicated in the genesis of hypertension; however, the mechanisms by which these stimuli promote hypertension are not fully understood. Here, we have described a pathway in which hypertensive stimuli promote dendritic cell (DC) activation of T cells, ultimately leading to hypertension. Using multiple murine models of hypertension, we determined that proteins oxidatively modified by highly reactive γ-ketoaldehydes (isoketals) are formed in hypertension and accumulate in DCs. Isoketal accumulation was associated with DC production of IL-6, IL-1β, and IL-23 and an increase in costimulatory proteins CD80 and CD86. These activated DCs promoted T cell, particularly CD8+ T cell, proliferation; production of IFN-γ and IL-17A; and hypertension. Moreover, isoketal scavengers prevented these hypertension-associated events. Plasma F2-isoprostanes, which are formed in concert with isoketals, were found to be elevated in humans with treated hypertension and were markedly elevated in patients with resistant hypertension. Isoketal-modified proteins were also markedly elevated in circulating monocytes and DCs from humans with hypertension. Our data reveal that hypertension activates DCs, in large part by promoting the formation of isoketals, and suggest that reducing isoketals has potential as a treatment strategy for this disease.

Angiotensin receptor type 1 and endothelin receptor type A on immune cells mediate migration and the expression of IL-8 and CCL18 when stimulated by autoantibodies from systemic sclerosis patients

INTRODUCTION

Agonistic autoantibodies (Aabs) against the angiotensin II receptor type 1 (AT1R) and the endothelin receptor type A (ETAR) have been identified in patients with systemic sclerosis (SSc). In our present study, we examined the expression of the AT1R and the ETAR in human immune cells and the pathological effects mediated through these receptors by their corresponding Aabs.

METHODS

Protein expression of AT1R and ETAR on peripheral blood mononuclear cells (PBMCs) from healthy individuals and SSc patients was analyzed using flow cytometry, and mRNA expression of both receptors in PBMCs from healthy donors was examined by real-time PCR. In addition, PBMCs from healthy donors were stimulated in vitro with affinity-purified immunoglobulin G (IgG) fractions from SSc patients positive for AT1R and ETAR Aabs, as well as with IgG from healthy donors serving as controls. Alterations in cell surface marker expression, cytokine secretion and chemotactic motility were analyzed using flow cytometry, enzyme-linked immunosorbent assays and chemotaxis assays, respectively. The results were correlated with the characteristics and clinical findings of the IgG donors.

RESULTS

Both AT1R and ETAR were expressed on PBMCs in humans. Protein expression of both receptors was decreased in SSc patients compared with that of healthy donors and declined during the course of disease. IgG fractions of SSc patients positive for AT1R and ETAR Aabs induced T-cell migration in an Aab level-dependent manner. Moreover, IgG of SSc patients stimulated PBMCs to produce more interleukin 8 (IL-8) and chemokine (C-C motif) ligand 18 (CCL18) than did the IgG of healthy donors. All effects were significantly reduced by selective AT1R and ETAR antagonists. Statistical analysis revealed an association of SSc-IgG induced high IL-8 concentrations with an early disease stage and of high CCL18 concentrations with lung fibrosis onset and vascular complications in the respective IgG donors.

CONCLUSION

In our present study, we could demonstrate the expression of both AT1R and ETAR on human peripheral T cells, B cells and monocytes. The decreased receptor expression in SSc patients, the inflammatory and profibrotic effects upon Aab stimulation of PBMCs in vitro and the associations with clinical findings suggest a role for Aab-induced activation of immune cells mediated by the AT1R and the ETAR in the pathogenesis or even the onset of the disease.

The immune system in hypertension

While hypertension has predominantly been attributed to perturbations of the vasculature, kidney, and central nervous system, research for almost 50 yr has shown that the immune system also contributes to this disease. Inflammatory cells accumulate in the kidneys and vasculature of humans and experimental animals with hypertension and likely contribute to end-organ damage. We and others have shown that mice lacking adaptive immune cells, including recombinase-activating gene-deficient mice and rats and mice with severe combined immunodeficiency have blunted hypertension to stimuli such as ANG II, high salt, and norepinephrine. Adoptive transfer of T cells restores the blood pressure response to these stimuli. Agonistic antibodies to the ANG II receptor, produced by B cells, contribute to hypertension in experimental models of preeclampsia. The central nervous system seems important in immune cell activation, because lesions in the anteroventral third ventricle block hypertension and T cell activation in response to ANG II. Likewise, genetic manipulation of reactive oxygen species in the subfornical organ modulates both hypertension and immune cell activation. Current evidence indicates that the production of cytokines, including tumor necrosis factor-α, interleukin-17, and interleukin-6, contribute to hypertension, likely via effects on both the kidney and vasculature. In addition, the innate immune system also appears to contribute to hypertension. We propose a working hypothesis linking the sympathetic nervous system, immune cells, production of cytokines, and, ultimately, vascular and renal dysfunction, leading to the augmentation of hypertension. Studies of immune cell activation will clearly be useful in understanding this common yet complex disease.

New paradigms in inflammatory signaling in vascular endothelial cells

Inflammation is a basic cellular process in innate and adaptive immunity. Vascular endothelial cells play an important role in the initiation, amplification, and resolution of the inflammatory response. Deregulated inflammatory response is implicated in a variety of cardiovascular diseases such as atherosclerosis, obesity, diabetes, and hypertension. Recent studies have made significant progresses in the understanding of the complex molecular pathways that mediate the pro- and anti-inflammatory signaling in endothelial cells (ECs). Specifically, a number of macromolecular complexes termed as signalosomes have been identified to integrate the proinflammatory signaling from the membrane receptors to key transcription factors such as nuclear factor-κB (NF-κB). Inflammasomes are associated with the pattern-recognition receptors such as Toll-like receptors (TLRs), nucleotide-binding oligomerization-domain (NOD)-like receptors (NLRs) to mediate innate immunity responses. Emerging evidence has also revealed that noncoding microRNAs constitute a new class of intra- and intercellular signaling molecules to modulate inflammation in ECs. Thus this article will briefly summarize these new mechanisms with a special emphasis in the context of cardiovascular diseases.

Antihypertensive role of polyphenols

Hypertension is considered the most important risk factor in the development of cardiovascular disease. Considerable evidence suggests that oxidative stress, which results in an excessive generation of reactive oxygen species (ROS), plays a key role in the pathogenesis of hypertension. This phenomenon leads to endothelial dysfunction, an imbalance between endothelium-derived relaxing factors, such as nitric oxide (NO), and contracting factors, such as angiotensin-II and endothelin (ET)-1, favoring the latter. Vascular remodeling also takes place; both processes lead to hypertension establishment. Antioxidant therapies have been evaluated in order to decrease ROS production or increase their scavenging. In this line, polyphenols, widespread antioxidants in fruits, vegetables, and wine, have demonstrated their beneficial role in prevention and therapy of hypertension, by acting as free radical scavengers, metal chelators, and in enzyme modulation and expression. Polyphenols activate and enhance endothelial nitric oxide synthase (eNOS) expression by several signaling pathways, increase glutathione (GSH), and inhibit ROS-producing enzymes such as NADPH and xanthine oxidases. These pathways lead to improved endothelial function, subsequent normalization of vascular tone, and an overall antihypertensive effect. In practice, diets as Mediterranean and the "French paradox" phenomenon, the light and moderate red wine consumption, supplementation with polyphenols as resveratrol or quercetin, and also experimental and clinical trials applying the mentioned have coincided in the antihypertensive effect of polyphenols, either in prevention or in therapy. However, further trials are yet needed to fully assess the molecular mechanisms of action and the appearance of adverse reactions, if a more extensive recommendation of polyphenol introduction in diet wants to be made.

Vascular inflammation and endothelial dysfunction in experimental hypertension

Essential hypertension is characterized by increased peripheral vascular resistance to blood flow. The endothelium is a crucial regulator of vascular tone. Its function is impaired in patients with hypertension, with reduced vasodilation, increased vascular tone associated with a proinflammatory and prothrombotic state. Low-grade inflammation localized in vascular tissue is therefore recognized as an important contributor to the pathophysiology of hypertension, to the initiation and progression of atherosclerosis as well as to the development of cardiovascular diseases.

Macitentan (ACT-064992), a tissue-targeting endothelin receptor antagonist, enhances therapeutic efficacy of paclitaxel by modulating survival pathways in orthotopic models of metastatic human ovarian cancer

Potential treatments for ovarian cancers that have become resistant to standard chemotherapies include modulators of tumor cell survival, such as endothelin receptor (ETR) antagonist. We investigated the therapeutic efficacy of the dual ETR antagonist, macitentan, on human ovarian cancer cells, SKOV3ip1 and IGROV1, growing orthotopically in nude mice. Mice with established disease were treated with vehicle (control), paclitaxel (weekly, intraperitoneal injections), macitentan (daily oral administrations), or a combination of paclitaxel and macitentan. Treatment with paclitaxel decreased tumor weight and volume of ascites. Combination therapy with macitentan and paclitaxel reduced tumor incidence and further reduced tumor weight and volume of ascites when compared with paclitaxel alone. Macitentan alone occasionally reduced tumor weight but alone had no effect on tumor incidence or ascites. Immunohistochemical analyses revealed that treatment with macitentan and macitentan plus paclitaxel inhibited the phosphorylation of ETRs and suppressed the survival pathways of tumor cells by decreasing the levels of pVEGFR2, pAkt, and pMAPK. The dose of macitentan necessary for inhibition of phosphorylation correlated with the dose required to increase antitumor efficacy of paclitaxel. Treatment with macitentan enhanced the cytotoxicity mediated by paclitaxel as measured by the degree of apoptosis in tumor cells and tumor-associated endothelial cells. Collectively, these results show that administration of macitentan in combination with paclitaxel prevents the progression of ovarian cancer in the peritoneal cavity of nude mice in part by inhibiting survival pathways of both tumor cells and tumor-associated endothelial cells.

Combined effects of irbesartan and carvedilol on expression of tissue factor and tissue factor pathway inhibitor in rats after myocardial infarction

The objective of this study was to investigate the effects of irbesartan, carvedilol, and irbesartan plus carvedilol on the expression of tissue factor (TF) and tissue factor pathway inhibitor (TFPI) mRNA and protein in rat myocardium after myocardial infarction (MI). MI was induced in male Wistar rats by ligation of the anterior descending branch of the left coronary artery. Irbesartan at 50 mg/kg/day, carvedilol at 1 mg/kg/day, irbesartan plus carvedilol, or placebo was administered intragastrically; expression of TF and TFPI mRNA and protein was determined by RT-PCR and Western blot analysis. The relative left ventricle weights were lower in all three treatment groups than in the placebo group, with the lowest relative weight in the irbesartan plus carvedilol group (P < 0.001). The size of the infarcted area was lower in the carvedilol and the combined groups than in the placebo group (P < 0.001). The levels of expression of TF and TFPI mRNA and protein were lower in the combined group than in the placebo group or the carvedilol group (P < 0.001). Treatment with irbesartan plus carvedilol reduced the expression of TF and TFPI mRNA and protein after MI in rats, and combined treatment with both agents had greater effects than the single agents alone. These findings suggest that the beneficial effects of these drugs may include anticoagulation and that combined therapy with both agents is an option that should be evaluated further.

Contrasting effects of intervention with ETA and ETB receptor antagonists in hypertension induced by angiotensin II and high-salt diet

Endothelin (ET) receptor antagonists are antihypertensive and renoprotective in angiotensin II (AngII)-induced hypertension if administered when AngII infusion commences, but their effects on established hypertension are poorly understood. We therefore tested the effects of intervening with an ETA (ABT-627) or ETB (A-192621) receptor antagonist after establishing hypertension with AngII (65 ng/min s.c.) plus 8% NaCl diet (AngII-HS) in rats. Prior to administration of ABT-627, AngII-HS and AngII-HS plus ABT-627 groups displayed robust hypertension (mean arterial pressure (MAP), 170 +/- 5 and 165 +/- 5 mm Hg versus 110 +/- 3 mm Hg in normal salt control rats at day 7, P < 0.05). Administering ABT-627 from day 8 of AngII-HS treatment prevented further rises in MAP (168 +/- 5 and 191 +/- 3 mm Hg at day 13 in AngII-HS plus ABT-627 and AngII-HS, P < 0.001), without blunting the significant increases in urinary protein (19-fold), albumin (25-fold), or MCP-1 excretion (6- to 8-fold) or the reduction in creatinine clearance. Administering A-192621 from day 8 mildly exacerbated AngII-HS induced hypertension (P < 0.05 for AngII-HS versus AngII-HS plus A-192621 on days 11 and 12 only) and reduced plasma nitrite/nitrate concentration (P < 0.05), without affecting proteinuria, albuminuria, or creatinine clearance. These results confirm the importance of ETA receptor signaling in maintaining AngII-HS hypertension and suggest that including ETB receptor blockade in therapeutic approaches to treating hypertension would be ineffective or even counterproductive.

At the heart of tissue: endothelin system and end-organ damage

ET (endothelin)-1 was first described as a potent vasoconstrictor. Since then, many other deleterious properties mediated via its two receptors, ETA and ETB, have been described, such as inflammation, fibrosis and hyperplasia. These effects, combined with a wide tissue distribution of the ET system, its up-regulation in pathological situations and a local autocrine/paracrine activity due to a high tissue receptor binding, make the tissue ET system a key local player in end-organ damage. Furthermore, ET-1 interacts in tissues with other systems such as the RAAS (renin-angiotensin-aldosterone system) to exert its effects. In numerous genetically modified animal models, non-specific or organ-targeted ET-1 overexpression causes intense organ damage, especially hypertrophy and fibrosis, in the absence of haemodynamic changes, confirming a local activity of the ET system. ET receptor antagonists have been shown to prevent and sometimes reverse these tissue alterations in an organ-specific manner, leading to long-term benefits and an improvement in survival in different animal models. Potential for such benefits going beyond a pure haemodynamic effect have also been suggested by clinical trial results in which ET receptor antagonism decreased the occurrence of new digital ulcers in patients with systemic sclerosis and delayed the time to clinical worsening in patients with PAH (pulmonary arterial hypertension). The tissue ET system allows therapeutic interventions to provide organ selectivity and beneficial effects in diseases associated with tissue inflammation, hypertrophy or fibrosis.

ACE inhibitors - angiotensin II receptor antagonists: A useful combination therapy for ischemic heart disease

Morbidity and mortality from cardiovascular diseases are still high, even with the use of the best available therapies. There is mounting evidence that excessive renin-angiotensin system activation triggers much of the damaging and progressive nature of cardiovascular and kidney diseases through expression of angiotensin II. Moreover, angiotensin II play a major role in the development of end organ damage through a variety of inflammatory mechanisms. Today, angiotensins-converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists have clearly demonstrated their efficacy in preventing target organ damage and in reducing cardiovascular morbidity and mortality in ischemic heart disease (IHD). Moreover, the development of angiotensin II receptor antagonists has enabled a large gain in tolerability and safety. Several clinical trials have firmly established that these drugs act on the renin–angiotensin system, reducing the incidence of coronary events with monotherapy and combination therapy. In this review we summarize the role mono- and combined therapy of ACE inhibitors and angiotensin II receptor antagonists play in ischemic heart disease. In this respect the review will improve ideas for developing new formulations with combinations of these drugs in the future.

Nephroprotection of lacidipine against gentamycin-induced nephrotoxicity in albino rats

AIM

Gentamycin, a widely-used aminoglycoside antibiotic, is recognized as possessing significant nephrotoxic potential in human beings. Gentamycin-induced nephrotoxicity is suggested to be mediated via reactive oxygen species. The present study investigated the possible antioxidant nephroprotective effect of lacidipine as a calcium-channel blocker in a gentamycin-induced nephrotoxicity model in albino rats.

METHODS

Albino rats were divided into 3 groups. Group 1 received normal saline. Group 2 received gentamycin 80 mg/kg intraperitoneally for 14 days. Group 3 received lacidipine 1 mg/kg intraperitoneally 3 days before and 14 days concurrently with gentamycin. This dose does not affect the blood pressure of rats, as evidenced in the pilot study.

RESULTS

Gentamycin-induced nephrotoxicity was evidenced by a marked reduction in creatinine clearance. Treatment with lacidipine improved creatinine clearance compared to the gentamycin-treated group. In addition, it reduced thiobarbituric acid reactive substance, as an index of lipid peroxidation, with significant increases in superoxide dismutase enzyme in erythrocyte lysates and kidney catalase enzyme activities.

CONCLUSION

This study recommends the use of lacidipine in prophylaxis against gentamycin-induced nephrotoxicity.

The role of aldosterone in mediating the dependence of angiotensin hypertension on IL-6

Knockout (KO) of IL-6 has been shown to attenuate ANG II hypertension, and mineralocorticoid receptors (MR) have been reported to contribute to the increase in IL-6 during acute ANG II infusion. This study determined whether that MR action is sustained with chronic ANG II infusion and whether it plays a role in mediating ANG II hypertension. ANG II infusion (90 ng/min) increased plasma IL-6 from 1.6 +/- 0.6 to 22.7 +/- 2.2 and 19.9 +/- 3.2 pg/ml on days 7 and 14, respectively, and chronic MR blockade with spironolactone attenuated that only at day 7 (7.2 +/- 2.2 pg/ml). ANG II increased MAP (19 h/day with telemetry) approximately 40 mmHg, but in ANG II+spironolactone mice (25 or 50 mg*kg(-1)*day(-1)), mean arterial pressure (MAP) was not significantly different despite a tendency for lower pressure the first 6 days. To isolate further the mineralocorticoid link to IL-6 and blood pressure, DOCA-salt hypertension was induced in IL-6 KO and wild-type (WT) mice. Plasma IL-6 increased from 4.1 +/- 1.7 to 34.5 +/- 7.0 pg/ml by day 7 of DOCA treatment in the WT mice but was back to control levels by day 14. An IL-6 bioassay using the murine B9, B-cell hybridoma cell line demonstrated that plasma IL-6 measurements reflected actual IL-6 bioactivity. The hypertension was not different and virtually superimposable in WT vs. IL-6 KO mice, averaging 145 +/- 2 and 144 +/- 3 mmHg, respectively. Both experiments confirm chronic stimulation of IL-6 by mineralocorticoids but show that it is transient. In addition, IL-6 was not required for mineralocorticoid hypertension. This suggests that aldosterone contributes to the increase in plasma IL-6 in the early stage of ANG II hypertension but that the blood pressure actions of IL-6 in that model are linked most likely to ANG II rather than aldosterone.

Endothelin-A receptor inhibition after cardiopulmonary bypass: cytokines and receptor activation

BACKGROUND

Basic studies have suggested that cross-talk exists between the endothelin-A receptor (ET-AR) and tumor necrosis factor signaling pathway. This study tested the hypothesis that administration of an ET-AR antagonist at the separation from cardiopulmonary bypass would alter the tumor necrosis factor activation in the early postoperative period.

METHODS

Patients (n = 44) were randomly allocated to receive bolus infusion of vehicle, 0.1, 0.5, 1, or 2 mg/kg of the ET-AR antagonist (sitaxsentan), at the separation from cardiopulmonary bypass (n = 9, 9, 9, 9, and 8, respectively). Plasma levels of tumor necrosis factor-alpha and soluble tumor necrosis factor receptor 1 and 2 were measured.

RESULTS

Compared with the vehicle group at 24 hours, plasma levels of tumor necrosis factor-alpha and tumor necrosis factor receptor 2 (indicative of receptor activation) were reduced in the 1 mg/kg ET-AR antagonist group (by approximately 13 pg/mL and approximately 0.5 ng/mL, respectively; p < 0.05). Plasma tumor necrosis factor receptor I levels also decreased (by approximately 1 ng/mL) after infusion of the higher doses of the ET-AR antagonist and remained lower (by approximately 3 ng/mL) at 24 hours after infusion (p < 0.05). In addition, a dose effect was observed between the ET-AR antagonist and these indices of tumor necrosis factor activation (p < 0.01).

CONCLUSIONS

This study demonstrated a mechanistic relationship between the ET-AR and tumor necrosis factor receptor activation in the post-cardiac surgery period. Thus, in addition to the potential cardiovascular effects, a selective ET-AR antagonist can modify other biological processes relevant to the post-cardiac surgery setting.

Angiotensin II modulates CD40 expression in vascular smooth muscle cells

The signalling pathway CD40/CD40L (CD40 ligand) plays an important role in atherosclerotic plaque formation and rupture. AngII (angiotensin II), which induces oxidative stress and inflammation, is also implicated in the progression of atherosclerosis. In the present study, we tested the hypothesis that AngII increases CD40/CD40L activity in vascular cells and that ROS (reactive oxygen species) are part of the signalling cascade that controls CD40/CD40L expression. Human CASMCs (coronary artery smooth muscle cells) in culture exposed to IL (interleukin)-1β or TNF-α (tumour necrosis factor-α) had increased superoxide generation and enhanced CD40 expression, detected by EPR (electron paramagnetic resonance) and immunoblotting respectively. Both phenomena were abolished by previous incubation with membrane-permeant antioxidants or cell transfection with p22phoxantisense. AngII (50–200 nmol/l) induced an early and sustained increase in CD40 mRNA and protein expression in CASMCs, which was blocked by treatment with antioxidants. Increased CD40 expression led to enhanced activity of the pathway, as AngII-treated cells stimulated with recombinant CD40L released higher amounts of IL-8 and had increased COX-2 (cyclo-oxygenase-2) expression. We conclude that AngII stimulation of vascular cells leads to a ROS-dependent increase in CD40/CD40L signalling pathway activity. This phenomenon may be an important mechanism modulating the arterial injury observed in atherosclerosis-related vasculopathy.

Pharmacology of macitentan, an orally active tissue-targeting dual endothelin receptor antagonist

Macitentan, also called Actelion-1 or ACT-064992 [N-[5-(4-bromophenyl)-6-(2-(5-bromopyrimidin-2-yloxy)ethoxy)-pyrimidin-4-yl]-N'-propylaminosulfonamide], is a new dual ET(A)/ET(B) endothelin (ET) receptor antagonist designed for tissue targeting. Selection of macitentan was based on inhibitory potency on both ET receptors and optimization of physicochemical properties to achieve high affinity for lipophilic milieu. In vivo, macitentan is metabolized into a major and pharmacologically active metabolite, ACT-132577. Macitentan and its metabolite antagonized the specific binding of ET-1 on membranes of cells overexpressing ET(A) and ET(B) receptors and blunted ET-1-induced calcium mobilization in various natural cell lines, with inhibitory constants within the nanomolar range. In functional assays, macitentan and ACT-132577 inhibited ET-1-induced contractions in isolated endothelium-denuded rat aorta (ET(A) receptors) and sarafotoxin S6c-induced contractions in isolated rat trachea (ET(B) receptors). In rats with pulmonary hypertension, macitentan prevented both the increase of pulmonary pressure and the right ventricle hypertrophy, and it markedly improved survival. In diabetic rats, chronic administration of macitentan decreased blood pressure and proteinuria and prevented end-organ damage (renal vascular hypertrophy and structural injury). In conclusion, macitentan, by its tissue-targeting properties and dual antagonism of ET receptors, protects against end-organ damage in diabetes and improves survival in pulmonary hypertensive rats. This profile makes macitentan a new agent to treat cardiovascular disorders associated with chronic tissue ET system activation.

Role of the renin-angiotensin system in vascular inflammation

Angiotensin (Ang) II, the main effector of the renin-angiotensin system (RAS), is one of the major mediators of vascular remodeling in hypertension. Besides being a potent vasoactive peptide, Ang II exerts proinflammatory effects on the vasculature by inducing integrins, adhesion molecules, cytokines and growth and profibrotic mediators through activation of redox-sensitive pathways and transcription factors. Clinical findings suggest that inflammation participates in the mechanisms involved in the pathophysiology of hypertension and its complications. Antagonists of the RAS have been shown to exert cardiovascular protection, in part through their vascular anti-inflammatory effects. However, further studies are needed to better understand whether inflammatory biomarkers might be clinically useful for cardiovascular risk stratification and whether targeting inflammation pharmacologically will improve cardiovascular outcomes beyond blood pressure reduction. The present review addresses recent findings regarding the pathophysiology of vascular inflammation in hypertension, focusing specifically on the role of Ang II.