Kinins and cardiovascular diseases

Extension of the circulatory half-life of recombinant ecallantide via albumin fusion without loss of anti-kallikrein activity

Ecallantide comprises Kunitz Domain 1 of Tissue Factor Pathway Inhibitor, mutated at seven amino acid positions to inhibit plasma kallikrein (PK). It is used to treat acute hereditary angioedema (HAE). We appended hexahistidine tags to the N- or C-terminus of recombinant Ecallantide (rEcall) and expressed and purified the resulting proteins, with or without fusion to human serum albumin (HSA), using Pichia pastoris. The inhibitory constant (Ki) of rEcall-H6 or H6-rEcall for PK was not increased by albumin fusion. When 125I-labelled rEcall proteins were injected intravenously into mice, the area under the clearance curve (AUC) was significantly increased, 3.4- and 3.6-fold, for fusion proteins H6-rEcall-HSA and HSA-rEcall-H6 versus their unfused counterparts but remained 2- to 3-fold less than that of HSA-H6. The terminal half-life of H6-rEcall-HSA and HSA-H6 did not differ, although that of HSA-rEcall-H6 was significantly shorter than either other protein. Receptor Associated Protein (RAP), a Low-density lipoprotein Receptor-related Protein (LRP1) antagonist, competed H6-rEcall-HSA clearance more effectively than intravenous immunoglobulin (IVIg), a neonatal Fc receptor (FcRn) antagonist. HSA fusion decreases rEcall clearance in vivo, but LRP1-mediated clearance remains more important than FcRn-mediated recycling for rEcall fusion proteins. The properties of H6-rEcall-HSA warrant investigation in a murine model of HAE.

Impaired Kallikrein-Kinin System in COVID-19 Patients' Severity

COVID-19 has emerged as a devastating disease in the last 2 years. Many authors appointed to the importance of kallikrein-kinin system (KKS) in COVID-19 pathophysiology as it is involved in inflammation, vascular homeostasis, and coagulation. We aim to study the bradykinin cascade and its involvement in severity of patients with COVID-19. This is an observational cohort study involving 63 consecutive patients with severe COVID-19 pneumonia and 27 healthy subjects as control group. Clinical laboratory findings and plasma protein concentration of KKS peptides [bradykinin (BK), BK1-8], KKS proteins [high–molecular weight kininogen (HK)], and KKS enzymes [carboxypeptidase N subunit 1 (CPN1), kallikrein B1 (KLKB1), angiotensin converting enzyme 2 (ACE2), and C1 esterase inhibitor (C1INH)] were analyzed. We detected dysregulated KKS in patients with COVID-19, characterized by an accumulation of BK1-8 in combination with decreased levels of BK. Accumulated BK1-8 was related to severity of patients with COVID-19. A multivariate logistic regression model retained BK1-8, BK, and D-dimer as independent predictor factors to intensive care unit (ICU) admission. A Youden’s optimal cutoff value of −0.352 was found for the multivariate model score with an accuracy of 92.9%. Multivariate model score-high group presented an odds ratio for ICU admission of 260.0. BK1-8 was related to inflammation, coagulation, and lymphopenia. Our data suggest that BK1-8/BK plasma concentration in combination with D-dimer levels might be retained as independent predictors for ICU admission in patients with COVID-19. Moreover, we reported KKS dysregulation in patients with COVID-19, which was related to disease severity by means of inflammation, hypercoagulation, and lymphopenia.

Markers for the involvement of endothelial cells and the coagulation system in chronic urticaria: A systematic review

Chronic urticaria (CU) is a chronic inflammatory mast cell-driven disorder. Endothelial cells (ECs) contribute importantly to key features of CU. Several markers of EC (dys)function in CU have been reported, but have not yet been systematically reviewed. In this study, we systematically reviewed and categorized all published markers of EC functions in CU through a comprehensive search in Pubmed, The Cochrane Library, Web of Science, and SCOPUS using the following Mesh terms: CU AND pathogenesis AND (vasculopathy OR microangiopathy OR ECs OR marker). In total, 79 articles were selected and the identified biomarkers were categorized according to EC (dys)function in CU. The most frequent and consistently reported upregulated biomarkers in CU skin were adhesion molecules, TF, and P-selectin. The most frequently reported upregulated and reliable biomarkers in sera of CU patients were F1+2 for coagulation cascade involvement, D-dimers for fibrinolysis, and MMP-9 for vascular permeability. Emerging biomarkers described in the selected articles were endostatin, heat shock proteins, cleaved high molecular weight kininogen, and adipokines. This systematic review contributes to the pool of growing evidence for vascular involvement in CU where EC dysfunction is present in different aspects of cell survival, maintenance of vascular structure, and coagulation/fibrinolysis balance.

Intermittent hypoxia changes the interaction of the kinin-VEGF system and impairs myocardial angiogenesis in the hypertrophic heart

Intermittent hypoxia (IH) is a feature of obstructive sleep apnea (OSA), a condition highly associated with hypertension-related cardiovascular diseases. Repeated episodes of IH contribute to imbalance of angiogenic growth factors in the hypertrophic heart, which is key in the progression of cardiovascular complications. In particular, the interaction between vascular endothelial growth factor (VEGF) and the kallikrein-kinin system (KKS) is essential for promoting angiogenesis. However, researchers have yet to investigate experimental models of IH that reproduce OSA, myocardial angiogenesis, and expression of KKS components. We examined temporal changes in cardiac angiogenesis in a mouse IH model. Adult male C57BI/6 J mice were implanted with Matrigel plugs and subjected to IH for 1-5 weeks with subsequent weekly histological evaluation of vascularization. Expression of VEGF and KKS components was also evaluated. After 3 weeks, in vivo myocardial angiogenesis and capillary density were decreased, accompanied by a late increase of VEGF and its type 2 receptor. Furthermore, IH increased left ventricular myocardium expression of the B2 bradykinin receptor, while reducing mRNA levels of B1 receptor. These results suggest that in IH, an unexpected response of the VEGF and KKS systems could explain the reduced capillary density and impaired angiogenesis in the hypoxic heart, with potential implications in hypertrophic heart malfunction.

A Systematic Review of Molecular Imaging Agents Targeting Bradykinin B1 and B2 Receptors

Kinins, bradykinin and kallidin are vasoactive peptides that signal through the bradykinin B1 and B2 receptors (B1R and B2R). B2R is constitutively expressed in healthy tissues and mediates responses such as vasodilation, fluid balance and retention, smooth muscle contraction, and algesia, while B1R is absent in normal tissues and is induced by tissue trauma or inflammation. B2R is activated by kinins, while B1R is activated by kinins that lack the C-terminal arginine residue. Perturbations of the kinin system have been implicated in inflammation, chronic pain, vasculopathy, neuropathy, obesity, diabetes, and cancer. In general, excess activation and signaling of the kinin system lead to a pro-inflammatory state. Depending on the disease context, agonism or antagonism of the bradykinin receptors have been considered as therapeutic options. In this review, we summarize molecular imaging agents targeting these G protein-coupled receptors, including optical and radioactive probes that have been used to interrogate B1R/B2R expression at the cellular and anatomical levels, respectively. Several of these preclinical agents, described herein, have the potential to guide therapeutic interventions for these receptors.

A Review of the Role of Bradykinin and Nitric Oxide in the Cardioprotective Action of Angiotensin-Converting Enzyme Inhibitors: Focus on Perindopril

The functional integrity of the endothelium is essential for vascular health. In addition to maintaining a delicate balance between vasodilation and vasoconstriction, the endothelium has numerous other complex roles involved in the maintenance of vascular homeostasis. Chronic exposure to cardiovascular risk factors and oxidative stress results in an imbalance in these functions, creating an environment that favors reduced vasodilation and a proinflammatory and prothrombic state. The involvement of endothelial dysfunction in all stages of the cardiovascular continuum makes it an important target for treatment. One of the major endothelial-derived factors involved in the maintenance of endothelial function is nitric oxide (NO). Angiotensin-converting enzyme (ACE) inhibitors increase NO production both directly and indirectly by preventing production of angiotensin II (which diminishes NO production) and inhibiting the degradation of bradykinin (which stimulates local release of NO). Among the ACE inhibitors, perindopril appears to have the greatest effects on bradykinin and has demonstrated efficacy in a number of markers of endothelial dysfunction including arterial stiffness and progression of atherosclerosis. There is also strong evidence supporting the use of perindopril-based therapy for the treatment of hypertension and for reducing the risk of cardiovascular morbidity and mortality in a wide range of patients across the cardiovascular continuum.Funding: The journal's Rapid Service Fee was funded by Servier.

Relaxin-2 in Cardiometabolic Diseases: Mechanisms of Action and Future Perspectives

Despite the great effort of the medical community during the last decades, cardiovascular diseases remain the leading cause of death worldwide, increasing their prevalence every year mainly due to our new way of life. In the last years, the study of new hormones implicated in the regulation of energy metabolism and inflammation has raised a great interest among the scientific community regarding their implications in the development of cardiometabolic diseases. In this review, we will summarize the main actions of relaxin, a pleiotropic hormone that was previously suggested to improve acute heart failure and that participates in both metabolism and inflammation regulation at cardiovascular level, and will discuss its potential as future therapeutic target to prevent/reduce cardiovascular diseases.

Heteromerization Between the Bradykinin B2 Receptor and the Angiotensin-(1-7) Mas Receptor: Functional Consequences

Bradykinin B2 receptor (B2R) and angiotensin-(1-7) Mas receptor (MasR)-mediated effects are physiologically interconnected. The molecular basis for such cross talk is unknown. It is hypothesized that the cross talk occurs at the receptor level. We investigated B2R-MasR heteromerization and the functional consequences of such interaction. B2R fused to the cyan fluorescent protein and MasR fused to the yellow fluorescent protein were transiently coexpressed in human embryonic kidney293T cells. Fluorescence resonance energy transfer analysis showed that B2R and MasR formed a constitutive heteromer, which was not modified by their agonists. B2R or MasR antagonists decreased fluorescence resonance energy transfer efficiency, suggesting that the antagonist promoted heteromer dissociation. B2R-MasR heteromerization induced an 8-fold increase in the MasR ligand-binding affinity. On agonist stimulation, the heteromer was internalized into early endosomes with a slower sequestration rate from the plasma membrane, compared with single receptors. B2R-MasR heteromerization induced a greater increase in arachidonic acid release and extracellular signal-regulated kinase phosphorylation after angiotensin-(1-7) stimulation, and this effect was blocked by the B2R antagonist. Concerning serine/threonine kinase Akt activity, a significant bradykinin-promoted activation was detected in B2R-MasR but not in B2R-expressing cells. Angiotensin-(1-7) and bradykinin elicited antiproliferative effects only in cells expressing B2R-MasR heteromers, but not in cells expressing each receptor alone. Proximity ligation assay confirmed B2R-MasR interaction in human glomerular endothelial cells supporting the interaction between both receptors in vivo. Our findings provide an explanation for the cross talk between bradykinin B2R and angiotensin-(1-7) MasR-mediated effects. B2R-MasR heteromerization induces functional changes in the receptor that may lead to long-lasting protective properties.

Vascular endothelial dysfunction and pharmacological treatment

The endothelium exerts multiple actions involving regulation of vascular permeability and tone, coagulation and fibrinolysis, inflammatory and immunological reactions and cell growth. Alterations of one or more such actions may cause vascular endothelial dysfunction. Different risk factors such as hypercholesterolemia, homocystinemia, hyperglycemia, hypertension, smoking, inflammation, and aging contribute to the development of endothelial dysfunction. Mechanisms underlying endothelial dysfunction are multiple, including impaired endothelium-derived vasodilators, enhanced endothelium-derived vasoconstrictors, over production of reactive oxygen species and reactive nitrogen species, activation of inflammatory and immune reactions, and imbalance of coagulation and fibrinolysis. Endothelial dysfunction occurs in many cardiovascular diseases, which involves different mechanisms, depending on specific risk factors affecting the disease. Among these mechanisms, a reduction in nitric oxide (NO) bioavailability plays a central role in the development of endothelial dysfunction because NO exerts diverse physiological actions, including vasodilation, anti-inflammation, antiplatelet, antiproliferation and antimigration. Experimental and clinical studies have demonstrated that a variety of currently used or investigational drugs, such as angiotensin-converting enzyme inhibitors, angiotensin AT1 receptors blockers, angiotensin-(1-7), antioxidants, beta-blockers, calcium channel blockers, endothelial NO synthase enhancers, phosphodiesterase 5 inhibitors, sphingosine-1-phosphate and statins, exert endothelial protective effects. Due to the difference in mechanisms of action, these drugs need to be used according to specific mechanisms underlying endothelial dysfunction of the disease.

Critical insights into the beneficial and protective actions of the kallikrein-kinin system

Hypertension is characterized by an imbalance between the renin-angiotensin system (RAS) and the kallikrein-kinin system (KKS). Angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II AT-1 receptor antagonists (also known as sartans or ARBs) are potent modulators of these systems and are highly effective as first-line treatments for hypertension, diabetic nephropathies, and diseases of the brain and coronary arteries. However, these agents are mechanistically distinct and should not be considered interchangeable. In this mini-review, we provide novel insights into the often neglected roles of the KKS in the beneficial, protective, and reparative actions of ACEIs. Indeed, ACEIs are the only antihypertensive drugs that properly reduce the imbalance between the RAS and the KKS, thereby restoring optimal cardiovascular homeostasis and significantly reducing morbidity and the risk of all-cause mortality among individuals affected by hypertension and other cardiovascular diseases.

Downregulation of kinin B1 receptor function by B2 receptor heterodimerization and signaling

Signaling through the G protein-coupled kinin receptors B1 (kB1R) and B2 (kB2R) plays a critical role in inflammatory responses mediated by activation of the kallikrein-kinin system. The kB2R is constitutively expressed and rapidly desensitized in response to agonist whereas kB1R expression is upregulated by inflammatory stimuli and it is resistant to internalization and desensitization. Here we show that the kB1R heterodimerizes with kB2Rs in co-transfected HEK293 cells and natively expressing endothelial cells, resulting in significant internalization and desensitization of the kB1R response in cells pre-treated with kB2R agonist. However, pre-treatment of cells with kB1R agonist did not affect subsequent kB2R responses. Agonists of other G protein-coupled receptors (thrombin, lysophosphatidic acid) had no effect on a subsequent kB1R response. The loss of kB1R response after pretreatment with kB2R agonist was partially reversed with kB2R mutant Y129S, which blocks kB2R signaling without affecting endocytosis, or T342A, which signals like wild type but is not endocytosed. Co-endocytosis of the kB1R with kB2R was dependent on β-arrestin and clathrin-coated pits but not caveolae. The sorting pathway of kB1R and kB2R after endocytosis differed as recycling of kB1R to the cell surface was much slower than that of kB2R. In cytokine-treated human lung microvascular endothelial cells, pre-treatment with kB2R agonist inhibited kB1R-mediated increase in transendothelial electrical resistance (TER) caused by kB1R stimulation (to generate nitric oxide) and blocked the profound drop in TER caused by kB1R activation in the presence of pyrogallol (a superoxide generator). Thus, kB1R function can be downregulated by kB2R co-endocytosis and signaling, suggesting new approaches to control kB1R signaling in pathological conditions.

Carboxypeptidase M is a positive allosteric modulator of the kinin B1 receptor

Ligand binding to extracellular domains of G protein-coupled receptors can result in novel and nuanced allosteric effects on receptor signaling. We previously showed that the protein-protein interaction of carboxypeptidase M (CPM) and kinin B1 receptor (B1R) enhances B1R signaling in two ways; 1) kinin binding to CPM causes a conformational activation of the B1R, and 2) CPM-generated des-Arg-kinin agonist is efficiently delivered to the B1R. Here, we show CPM is also a positive allosteric modulator of B1R signaling to its agonist, des-Arg(10)-kallidin (DAKD). In HEK cells stably transfected with B1R, co-expression of CPM enhanced DAKD-stimulated increases in intracellular Ca(2+) or phosphoinositide turnover by a leftward shift of the dose-response curve without changing the maximum. CPM increased B1R affinity for DAKD by ∼5-fold but had no effect on basal B1R-dependent phosphoinositide turnover. Soluble, recombinant CPM bound to HEK cells expressing B1Rs without stimulating receptor signaling. CPM positive allosteric action was independent of enzyme activity but depended on interaction of its C-terminal domain with the B1R extracellular loop 2. Disruption of the CPM/B1R interaction or knockdown of CPM in cytokine-treated primary human endothelial cells inhibited the allosteric enhancement of CPM on B1R DAKD binding or ERK1/2 activation. CPM also enhanced the DAKD-induced B1R conformational change as detected by increased intramolecular fluorescence or bioluminescence resonance energy transfer. Thus, CPM binding to extracellular loop 2 of the B1R results in positive allosteric modulation of B1R signaling, and disruption of this interaction could provide a novel therapeutic approach to reduce pathological B1R signaling.

Different cross-talk sites between the renin-angiotensin and the kallikrein-kinin systems

Targeting the renin-angiotensin system (RAS) constitutes a major advance in the treatment of cardiovascular diseases. Evidence indicates that angiotensin-converting enzyme inhibitors and angiotensin AT1 receptor blockers act on both the RAS and the kallikrein-kinin system (KKS). In addition to the interaction between the RAS and KKS at the level of angiotensin-converting enzyme catalyzing both angiotensin II generation and bradykinin degradation, the RAS and KKS also interact at other levels: 1) prolylcarboxypeptidase, an angiotensin II inactivating enzyme and a prekallikrein activator; 2) kallikrein, a kinin-generating and prorenin-activating enzyme; 3) angiotensin-(1-7) exerts kininlike effects and potentiates the effects of bradykinin; and 4) the angiotensin AT1 receptor forms heterodimers with the bradykinin B2 receptor. Moreover, angiotensin II enhances B1 and B2 receptor expression via transcriptional mechanisms. These cross-talks explain why both the RAS and KKS are up-regulated in some circumstances, whereas in other circumstances both systems change in the opposite manner, expressed as an activated RAS and a depressed KKS. As the cross-talks between the RAS and the KKS play an important role in response to different stimuli, taking these cross-talks between the two systems into account may help in the development of drugs targeting the two systems.

Effects of a novel bradykinin B1 receptor antagonist and angiotensin II receptor blockade on experimental myocardial infarction in rats

Background

The aim of the present study was to evaluate the cardiovascular effects of the novel bradykinin B1 receptor antagonist BI-113823 following myocardial infarction (MI) and to determine whether B1 receptor blockade alters the cardiovascular effects of an angiotensin II type 1 (AT1) receptor antagonist after MI in rats.

Methodology/Principal Findings

Sprague Dawley rats were subjected to permanent occlusion of the left descending coronary artery. Cardiovascular function was determined at 7 days post MI. Treatment with either B1 receptor antagonist (BI-113823) or AT1 receptor antagonist (irbesartan) alone or in combination improved post-MI cardiac function as evidenced by attenuation of elevated left ventricular end diastolic pressure (LVEDP); greater first derivative of left ventricular pressure (± dp/dt max), left ventricle ejection fraction, fractional shorting, and better wall motion; as we as reductions in post-MI up-regulation of matrix metalloproteinases 2 (MMP-2) and collagen III. In addition, the cardiac up-regulation of B1 receptor and AT1 receptor mRNA were markedly reduced in animals treated with BI 113823, although bradykinin B2 receptor and angiotensin 1 converting enzyme (ACE1) mRNA expression were not significantly affected by B1 receptor blockade.

Conclusions/Significance

The present study demonstrates that treatment with the novel B1 receptor antagonist, BI-113823 improves post-MI cardiac function and does not influence the cardiovascular effects of AT1 receptor antagonist following MI.

Renin-angiotensin system inhibitors and angioedema: anesthetic implications

PURPOSE OF REVIEW

Angioedema is a serious complication of renin-angiotensin system inhibitor therapy. The incidence is 0.1-0.7%. It consists of nonpitting edema and involves the face and lips. In severe cases, it extends to pharyngeal and laryngeal structures.

RECENT FINDINGS

Decreased degradation of bradykinin and its metabolites is thought to be a culprit. When the angiotensin-converting enzyme is inhibited, bradykinin metabolism is dependent on degradation by neutral endopeptidase, dipeptidyl peptidase IV, and aminopeptidase P. When these enzymes are inhibited, as in treatment of diabetes or in transplant recipients, the incidence of angioedema increases significantly. African-Americans, people over 65, women, and those with a history of smoking are especially at risk. A fiberoptic laryngeal examination should be performed in all patients. Patients with rapid progression of symptoms are at risk for airway compromise. Supportive treatment with steroids and antihistamines is not very effective. Recently, icatibant, a bradykinin receptor antagonist, has been used to successfully shorten the resolution of edema.

SUMMARY

Trauma of the airway, especially during difficult intubation, may precipitate severe angioedema. In cases with laryngeal involvement, fiberoptic intubation may be necessary. After the episode of angioedema, lifetime discontinuation of all renin-angiotensin inhibitors may be warranted.

Bradykinin restores left ventricular function, sarcomeric protein phosphorylation, and e/nNOS levels in dogs with Duchenne muscular dystrophy cardiomyopathy

AIMS

Cardiomyopathy is a lethal result of Duchenne muscular dystrophy (DMD), but its characteristics remain elusive. The golden retriever muscular dystrophy (GRMD) dogs produce DMD pathology and mirror DMD patient's symptoms, including cardiomyopathy. We previously showed that bradykinin slows the development of pacing-induced heart failure. Therefore, the goals of this research were to characterize dystrophin-deficiency cardiomyopathy and to examine cardiac effects of bradykinin in GRMD dogs.

METHODS AND RESULTS

At baseline, adult GRMD dogs had reduced fractional shortening (28 ± 2 vs. 38 ± 2% in control dogs, P < 0.001) and left ventricular (LV) subendocardial dysfunction leading to impaired endo-epicardial gradient of radial systolic velocity (1.3 ± 0.1 vs. 3.8 ± 0.2 cm/s in control dogs, P < 0.001) measured by echocardiography. These changes were normalized by bradykinin infusion (1 µg/min, 4 weeks). In isolated permeabilized LV subendocardial cells of GRMD dogs, tension-calcium relationships were shifted downward and force-generating capacity and transmural gradient of myofilament length-dependent activation were impaired compared with control dogs. Concomitantly, phosphorylation of sarcomeric regulatory proteins and levels of endothelial and neuronal nitric oxide synthase (e/nNOS) in LV myocardium were significantly altered in GRMD dogs. All these abnormalities were normalized in bradykinin-treated GRMD dogs.

CONCLUSIONS

Cardiomyopathy in GRMD dogs is characterized by profound LV subendocardial dysfunction, abnormal sarcomeric protein phosphorylation, and impaired e/nNOS, which can be normalized by bradykinin treatment. These data provide new insights into the pathophysiological mechanisms accounting for DMD cardiomyopathy and open new therapeutic perspectives.

Vascular endothelial dysfunction in Duchenne muscular dystrophy is restored by bradykinin through upregulation of eNOS and nNOS

Little is known about the vascular function and expression of endothelial and neuronal nitric oxide synthases (eNOS and nNOS) in Duchenne muscular dystrophy (DMD). Bradykinin is involved in the regulation of eNOS expression induced by angiotensin-converting enzyme inhibitors. We characterized the vascular function and eNOS and nNOS expression in a canine model of DMD and evaluated the effects of chronic bradykinin treatment. Vascular function was examined in conscious golden retriever muscular dystrophy (GRMD) dogs with left ventricular dysfunction (measured by echocardiography) and in isolated coronary arteries. eNOS and nNOS proteins in carotid arteries were measured by western blot and cyclic guanosine monophosphate (cGMP) content was analyzed by radioimmunoassay. Compared with controls, GRMD dogs had an impaired vasodilator response to acetylcholine. In isolated coronary artery, acetylcholine-elicited relaxation was nearly absent in placebo-treated GRMD dogs. This was explained by reduced nNOS and eNOS proteins and cGMP content in arterial tissues. Chronic bradykinin infusion (1 μg/min, 4 weeks) restored in vivo and in vitro vascular response to acetylcholine to the level of control dogs. This effect was NO-mediated through upregulation of eNOS and nNOS expression. In conclusion, this study is the first to demonstrate that DMD is associated with NO-mediated vascular endothelial dysfunction linked to an altered expression of eNOS and nNOS, which can be overcome by bradykinin.

Endothelial dysfunction, measured by reactive hyperaemia using strain-gauge plethysmography, is an independent predictor of adverse outcome in heart failure

AIMS

In congestive heart failure (CHF), arterial response is regulated by endothelial molecules. The aim of this study was to evaluate whether endothelial dysfunction (ED) was a predictor of outcome in a cohort of patients with heart failure.

METHODS AND RESULTS

Endothelial function was assessed in 242 patients with CHF by forearm reactive hyperaemia measured with intermittent venous occlusion plethysmography using a mercury strain gauge. The main endpoints were: 'total events' (death, heart attack, angina, stroke, NYHA class IV, or hospitalization due to heart failure) analysed using Cox regression for repeated events and 'death'. Patients were followed-up for 5 years. Post-hyperaemia forearm blood flow (PHFABF) was an independent predictor of total events [P = 0.01; hazard ratio [Exp(B)] 0.665, standard error (SE) 0.182]. Risk stratification by basal forearm blood flow (BFABF) showed that patients with basal blood flow above the median (3.03 mL min(-1) 100 mL(-1)) benefited from an increase in PHFABF, whereas in patients with a BFABF below the median, the increase in PHFABF did not diminish the risk of events. There was no relation between variations in PHFABF and death.

CONCLUSION

Post-hyperaemia forearm blood flow, as a measure of ED, is an independent predictor of major events in patients with CHF. A BFABF below the median is more predictive of an increased risk of complications.

Bradykinin enhances cell migration in human chondrosarcoma cells through BK receptor signaling pathways

Bradykinin (BK) is an inflammatory mediator, and shows elevated levels in regions of severe injury and inflammatory diseases. BK has recently been shown to be involved in carcinogenesis and cancer progression. In this study, we found that BK increased the migration and the expression of alpha2beta1 integrin in human chondrosarcoma cells. We also found that human chondrosarcoma tissues had significantly higher expression of the B1 and B2 receptors comparing to normal cartilage. BK-mediated migration and integrin up-regulation was attenuated by B1 and B2 BK receptor siRNA or antagonist. Activations of phospholipase C (PLC), protein kinase Cdelta (PKCdelta), and NF-kappaB pathways after BK treatment was demonstrated, and BK-induced integrin expression and migration activity was inhibited by the specific inhibitor of PLC, PKCdelta, and NF-kappaB cascades. Taken together, our results indicated that BK enhances the migration of chondrosarcoma cells by increasing alpha2beta1 integrin expression through the BK receptors/PLC/PKCdelta/NF-kappaB signal transduction pathway.

Cardioprotection in ischemia/reperfusion injury: spotlight on sphingosine-1-phosphate and bradykinin signalling

Complex signal-transduction cascades are known to be involved in regulating cardiomyocyte function, death and survival during acute cardiac ischemia-reperfusion process, but detailed survival signalling pathways are not clear. This review presents and discusses the recent findings bearing upon the evidence on the cardioprotective effect of sphingosine-1-phosphate (S1P) and bradykinin in acute cardiac ischemia-reperfusion and underlying signalling mechanisms, particularly, through activation of P21 activated kinase.

Activities of angiotensin-converting enzymes ACE1 and ACE2 and inhibition by bioactive peptides in porcine ocular tissues

PURPOSE

An active local renin-angiotensin system (RAS) has recently been found in the human eye. The aim of the present study was to compare the activities of central RAS enzymes (ACE1 and 2) in porcine ocular tissues, morphologically and physiologically close to the human eye. In addition, the effects of three ACE-inhibitory tripeptides on these enzymes were evaluated.

METHODS

Enucleated fresh porcine eyes were used. Activities of ACE1 and ACE2 and their inhibition by bioactive tripeptides (Ile-Pro-Pro, Val-Pro-Pro, Leu-Pro-Pro) as well as by a standard ACE-inhibitor captopril were assayed in the vitreous body, the retina and the ciliary body using fluorometric detection methods.

RESULTS

Activity of ACE1 as well as ACE2 was found in all tissues evaluated. ACE1 activity was markedly higher in the ciliary body (3.7 +/- 0.7 mU/mg protein) than in retina (0.2 +/- 0.02 mU/mg), whereas ACE2 activities in the ciliary body (0.2 +/- 0.02 mU/mg) and retina (0.2 +/- 0.01 mU/mg) were at the same level. In the vitreous body ACE1 activity (8.2 +/- 0.31 nmol/min/mL) was manifold compared to that of ACE2 (0.1 +/- 0.02 nmol/min/mL). The tripeptides inhibited ACE1 at one-thousandth of the concentration needed to inhibit ACE2. All peptides studied evinced about equal inhibitory activities.

CONCLUSION

To our knowledge the present findings constitute the first evidence of ACE2 activity in the ciliary and vitreous bodies, in addition to previously described activity in the retina. The known favorable effects of ACE2 products vs. those of ACE1 suggest a counterbalancing interaction of these two enzyme homologues in physiological regulation of ocular circulation and pressure and possible protective role in certain ophthalmic disorders such as glaucoma and diabetic retinopathy.

Does the renin-angiotensin system also regulate intra-ocular pressure?

The renin-angiotensin-aldosterone system is known to play an essential role in controlling sodium balance and body fluid volumes, and thus blood pressure. In addition to the circulating system which regulates urgent cardiovascular responses, a tissue-localized renin-angiotensin system (RAS) regulates long-term changes in various organs. Many recognized RAS components have also been identified in the human eye. The highly vasoconstrictive angiotensin II (Ang II) is considered the key peptide in the circulatory RAS. However, the ultimate effect of RAS activation at tissue level is more complex, being based not only on the biological activity of Ang II but also on the activities of other products of angiotensinogen metabolism, often exerting opposite effects to Ang II action. In recent studies, orally administered angiotensin II type 1 receptor blockers and angiotensin-converting enzyme inhibitors lower intra-ocular pressure (IOP), likewise topical application of these compounds, the effect being more prominent in ocular hypertensive eyes. Based on previous findings and our own experimental data, it can strongly be suggested that the RAS not only regulates blood pressure but is also involved in the regulation of IOP.

Modulation by bradykinin and nitric oxide of angiotensin II-induced apoptosis in a vascular smooth muscle cell phenotype

There is evidence for a clinical benefit of ACE inhibitors or AT1 antagonists in cardiovascular diseases with deleterious smooth muscle cells (SMC) apoptosis. We have previously shown that angiotensin II (Ang II) induces a phenotype-dependent SMC apoptosis. We asked whether bradykinin (BK) and nitric oxide (NO) could modulate Ang II-induced SMC apoptosis. BK alone did not induce significant apoptosis in either spindle (Sp-SMC) or epithelioid (Ep-SMC) SMC phenotypes cultured in serum reduction, but phenotype-dependently, reduced cell proliferation. Pretreatment with BK partly impaired Ang II-induced reduction of Ep-SMC culture viability and partly prevented apoptotic features. Pretreatment with sodium nitroprusside completely prevented all Ang II-induced deleterious effects in Ep-SMC, i. e. reduction of culture viability, Annexin V binding, nuclear condensation and cell fragmentation. These findings indicate that the BK-NO system may phenotype-dependently modulate SMC survival and in particular may oppose, mostly by NO, Ang II-induction of apoptosis in the Ep-SMC phenotype.

Participation of kallikrein-kinin system in different pathologies

The general description of kinins refers to these peptides as molecules involved in vascular tone regulation and inflammation. Nevertheless, in the last years a series of evidences has shown that local hormonal systems, such as the kallikrein-kinin system, may be differently regulated and are of pivotal importance to pathophysiological control. The combined interpretations of many recent studies allow us to conclude that the kallikrein-kinin system plays broader and richer roles than those classically described until recently. In this review, we report findings concerning the participation of the kallikrein-kinin system in inflammation, cancer, and in pathologies related to cardiovascular, renal and central nervous systems.