Endothelial function and bradykinin in humans

Characterization of ACE inhibitory activity in Dioscorea alata cv and its implication as a natural antihypertensive extract

ETHNOPHARMACOLOGICAL RELEVANCE

Yam (Dioscorea sp.) extracts have been shown to possess a vast array of medicinal properties such as antihypocholesterolemic, antiatherogenic and antihypertensive bioactivity. However, the compounds conferring its antihypertensive bioactivity have not been fully explored.

AIM OF THE STUDY

The objective of this study was to identify extractable bioactive fractions and associated compounds in Jamaican Renta Yam (Dioscorea alata) that contribute to its antihypertensive properties, using an activity driven chemoinformatic profiling method.

MATERIALS AND METHODS

A diethyl ether extract of Dioscorea alata was obtained by sequential Solid-Liquid extraction coupled to SPE-HPLC fractionation and its chemical composition was analyzed by GC-MS analysis. Its influence on hypertension was evaluated through a combination of in vitro ACE-Inhibitory activity assays and by molecular docking of the identified compounds to the ACE enzyme.

RESULTS

SLE revealed the presence of potent antihypertensive activity (ACE IC50 41.99 μg/mL) in the diethyl ether extract (DR2). GC-MS analysis of DR2 indicated the presence of small organic compounds (95.1 g/mol to 200 g/mol) with 2-Phenyl-1,3-oxazol-2-ine (2PO) being the most predominant small organic compound present in the bioactive extract. The binding affinity of 2PO was assessed using molecular docking of 2PO to the ACE enzyme and showed strong binding affinities forming two (2) hydrogen bonds with Tyr135 and Trp220 in the active site of the enzyme. The in vitro effect of DR2 using human umbilical vein endothelial cell lines (HUVECs) revealed; a significant dose-dependent ACE-Inhibitory activity, a stimulating of nitric oxide (NO) release and no toxicity towards these cells.

CONCLUSION

Overall, this study identified Jamaican Renta Yam (Dioscorea alata) as an alternative source of antihypertensive compounds which may address the toxicity seen with known synthetic antihypertensive agents.

Application of the C3 inhibitor compstatin in a human whole blood model designed for complement research - 20 years of experience and future perspectives

The complex molecular and cellular biological systems that maintain host homeostasis undergo continuous crosstalk. Complement, a component of innate immunity, is one such system. Initially regarded as a system to protect the host from infection, complement has more recently been shown to have numerous other functions, including involvement in embryonic development, tissue modeling, and repair. Furthermore, the complement system plays a major role in the pathophysiology of many diseases. Through interactions with other plasma cascades, including hemostasis, complement activation leads to the broad host-protective response known as thromboinflammation. Most complement research has been limited to reductionistic models of purified components and cells and their interactions in vitro. However, to study the pathophysiology of complement-driven diseases, including the interaction between the complement system and other inflammatory systems, holistic models demonstrating only minimal interference with complement activity are needed. Here we describe two such models; whole blood anticoagulated with either the thrombin inhibitor lepirudin or the fibrin polymerization peptide blocker GPRP, both of which retain complement activity and preserve the ability of complement to be mutually reactive with other inflammatory systems. For instance, to examine the relative roles of C3 and C5 in complement activation, it is possible to compare the effects of the C3 inhibitor compstatin effects to those of inhibitors of C5 and C5aR1. We also discuss how complement is activated by both pathogen-associated molecular patterns, inducing infectious inflammation caused by organisms such as Gram-negative and Gram-positive bacteria, and by sterile damage-associated molecular patterns, including cholesterol crystals and artificial materials used in clinical medicine. When C3 is inhibited, it is important to determine the mechanism by which inflammation is attenuated, i.e., whether the attenuation derives directly from C3 activation products or via downstream activation of C5, since the mechanism involved may determine the appropriate choice of inhibitor under various conditions. With some exceptions, most inflammatory responses are dependent on C5 and C5aR1; one exception is venous air embolism, in which air bubbles enter the blood circulation and trigger a mainly C3-dependent thromboembolism, with the formation of an active C3 convertase, without a corresponding C5 activation. Under such conditions, an inhibitor of C3 is needed to attenuate the inflammation. Our holistic blood models will be useful for further studies of the inhibition of any complement target, not just C3 or C5. The focus here will be on targeting the critical complement component, activation product, or receptor that is important for the pathophysiology in a variety of disease conditions.

Implications of Endothelial Cell-Mediated Dysfunctions in Vasomotor Tone Regulation

Cardiovascular diseases (CVD) constitute the major cause of death worldwide and show a higher prevalence in the adult population. The human umbilical cord consistsof two arteries and one vein, both composed of three tunics. The tunica intima, lined with endothelial cells, regulates vascular tone through the production/release of vasoregulatory substances. These substances can be vasoactive factors released by endothelial cells (ECs) that cause vasodilation (NO, PGI2, EDHF, and Bradykinin) or vasoconstriction (ET1, TXA2, and Ang II) depending on the cell type (ECs or SMC) that reacts to the stimulus. Vascular studies using ECs are important for the analysis of cardiovascular diseases since endothelial dysfunction is an important CVD risk factor. In this paper, we will address the morphological characteristics of the human umbilical cord and its component vessels. the constitution of the vascular endothelium, and the evolution of human umbilical cord-derived endothelial cells when isolated. Moreover, the role played by the endothelium in the vasomotor tone regulation, and how it may be associated with the existence of CVD, were discussed.

Angiotensin-Converting Enzyme 2 in the Pathogenesis of Renal Abnormalities Observed in COVID-19 Patients

Coronavirus disease 2019 (COVID-19) was first reported in late December 2019 in Wuhan, China. The etiological agent of this disease is severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and the high transmissibility of the virus led to its rapid global spread and a major pandemic (ongoing at the time of writing this review). The clinical manifestations of COVID-19 can vary widely from non-evident or minor symptoms to severe acute respiratory syndrome and multi-organ damage, causing death. Acute kidney injury (AKI) has been recognized as a common complication of COVID-19 and in many cases, kidney replacement therapy (KRT) is required. The presence of kidney abnormalities on hospital admission and the development of AKI are related to a more severe presentation of COVID-19 with higher mortality rate. The high transmissibility and the broad spectrum of clinical manifestations of COVID-19 are in part due to the high affinity of SARS-CoV-2 for its receptor, angiotensin (Ang)-converting enzyme 2 (ACE2), which is widely expressed in human organs and is especially abundant in the kidneys. A debate on the role of ACE2 in the infectivity and pathogenesis of COVID-19 has emerged: Does the high expression of ACE2 promotes higher infectivity and more severe clinical manifestations or does the interaction of SARS-CoV-2 with ACE2 reduce the bioavailability of the enzyme, depleting its biological activity, which is closely related to two important physiological systems, the renin-angiotensin system (RAS) and the kallikrein-kinin system (KKS), thereby further contributing to pathogenesis. In this review, we discuss the dual role of ACE2 in the infectivity and pathogenesis of COVID-19, highlighting the effects of COVID-19-induced ACE2 depletion in the renal physiology and how it may lead to kidney injury. The ACE2 downstream regulation of KKS, that usually receives less attention, is discussed. Also, a detailed discussion on how the triad of symptoms (respiratory, inflammatory, and coagulation symptoms) of COVID-19 can indirectly promote renal injury is primary aborded.

Proteomic biomarkers in Gaucher disease

AIMS

The research work was conducted to find new biomarkers and potential drug targets in Gaucher disease type 1 (GDt1) by analysing the serum proteins.

METHODS

This study was an observational, cross-sectional analysis of a group of 12 adult participants: six Gaucher disease (GD) patients and six healthy control. Fasting venous blood underwent proteomics analysis and molecular tests. Over 400 proteins were analysed, and in case of significantly different concentrations between the study and control group, we checked corresponding genes to confirm changes in their expression and consistency with protein alteration.

RESULTS

We found 31 proteins that significantly differed in concentration between GDt1 patients and a control group. These were mostly proteins involved in the regulation of the inflammatory processes and haemostasis. The levels of proteins such as alpha-1-acid glycoprotein 2, S100-A8/A9, adenyl cyclase-associated protein 1, haptoglobin or translationally controlled tumour protein related to inflammation process were significantly higher in GD patients than in control group, whereas the levels of some proteins such as heavy constant mu and gamma 4 or complement C3/C4 complex involved in humoral response like immunoglobulins were significantly decreased in GD patients. Alteration in two proteins concentration was confirmed in RNA analysis.

CONCLUSIONS

The work revealed few new targets for further investigation which may be useful in clinical practice for diagnosis, treatment and monitoring GDt1 patients.

A systems pharmacology approach to investigate the mechanism of Oryeong-san formula for the treatment of hypertension

ETHNOPHARMACOLOGICAL RELEVANCE

Oryeong-san (ORS) is a traditional formula that has long been used for the treatment of dysfunctions of body fluids and electrolyte homeostasis in Korea, China and Japan. Recent reports have shown that ORS may suppress hypertension by controlling the renin-angiotensin-aldosterone system (RAAS) in the kidney, but its action mechanism has not been well defined.

AIM OF THE STUDY

The aim of this study was to decipher the ORS mechanisms in the treatment of hypertension using a systems pharmacology approach.

MATERIALS AND METHODS

The compounds of ORS were obtained from the TM-MC (database of medicinal materials and chemical compounds in Northeast Asian traditional medicine), and the drug-likeness (DL) and oral bioavailability (OB) of the compounds were evaluated. The potential targets of the compounds were identified using various pharmacology databases. To analyze the mechanisms of the ORS for hypertension, a Compound-Target-Disease (C-T-D) network was established with respect to the genes related to hypertension.

RESULTS

A screening evaluation of the DL and OB of the ORS compounds identified a list of 232 active compounds. The pharmacological activity of the targets was investigated by exploring the interaction network between the compounds and the targets. Analysis of the interactions between the compounds and the hypertension-related targets revealed that 14 ORS compounds regulate the RAAS and vasoconstrictors in the kidney.

CONCLUSIONS

This study used the systems pharmacology approach to decipher the mechanisms of action of ORS for the treatment of hypertension. When hypertension drugs and ORS are used in combination for treatment, possible side effects should be considered because most hypertension drugs are related to the RAAS. The results of this study may provide clues to not only analyze the pharmacological activity of ORS for the treatment of hypertension but other diseases as well.

G Protein-Coupled Receptors (GPCRs)-Mediated Calcium Signaling in Ovarian Cancer: Focus on GPCRs activated by Neurotransmitters and Inflammation-Associated Molecules

G-coupled protein receptors (GCPR) involve several signaling pathways, some of them being coupled with intracellular calcium (Ca²⁺) mobilization. GPCRs were involved in migration, invasion and metastasis of different types of cancers, including ovarian cancer. Many studies have discussed the essential contribution of GPCRs activated by steroid hormones in ovarian cancer. However, ovarian cancer is also associated with altered signals coming from the nervous system, the immune system or the inflammatory environment, in which GPCRs are ‘sensing’ these molecular signals. Many studies have been oriented so far on ovarian cell lines (most of them being of human cell lines), and only few studies based on animal models or clinical studies have been devoted to the expression changes or functional role of GPCRs in ovarian cancer. In this paper, we review the alterations of GPCRs activated by neurotransmitters (muscarinic receptors, serotonin receptors, dopamine receptors, adrenoceptors) or inflammation-associated molecules (bradykinin receptors, histamine receptors, chemokine receptors) in ovarian cancer and we discuss their potential as histological biomarkers.

Development of a Novel Diagnostic Biomarker Set for Rheumatoid Arthritis Using a Proteomics Approach

Background

Rheumatoid arthritis (RA) is an autoimmune disease that starts with inflammation of the synovial membrane. Studies have been conducted to develop methods for efficient diagnosis of RA and to identify the mechanisms underlying RA development. Blood samples can be useful for detecting disturbance of homeostasis in patients with RA. Nanoliquid chromatography-tandem mass spectrometry (LC-MS/MS) is an efficient proteomics approach to analyze blood sample and quantify serum proteins.

Methods

Serum samples of 18 healthy controls and 18 patients with RA were analyzed by LC-MS/MS. Selected candidate biomarkers were validated by enzyme-linked immunosorbent assay (ELISA) using sera from 43 healthy controls and 44 patients with RA.

Results

Thirty-eight proteins were significantly differentially expressed by more than 2-fold in healthy controls and patients with RA. Based on a literature survey, we selected six candidate RA biomarkers. ELISA was used to evaluate whether these proteins effectively allow distinguishing patients with RA from healthy controls and monitoring drug efficacy. SAA4, gelsolin, and vitamin D-binding protein were validated as potential biomarkers of RA for screening and drug efficacy monitoring of RA.

Conclusions

We identified a panel of three biomarkers for RA which has potential for application in RA diagnosis and drug efficacy monitoring. Further, our findings will aid in understanding the pathogenesis of RA.

Synergy between sacubitril and valsartan leads to hemodynamic, antifibrotic, and exercise tolerance benefits in rats with preexisting heart failure

Simultaneous neprilysin inhibition (NEPi) and angiotensin receptor blockade (ARB) with sacubitril/valsartan improves cardiac function and exercise tolerance in patients with heart failure. However, it is not known whether these therapeutic benefits are primarily due to NEPi with sacubitril or ARB with valsartan or their combination. Therefore, the aim of the present study was to investigate the potential contribution of sacubitril and valsartan to the benefits of the combination therapy on left ventricular (LV) function and exercise tolerance. Heart failure was induced by volume overload via partial disruption of the aortic valve in rats. Therapy began 4 wk after valve disruption and lasted through 8 wk. Drugs were administered daily via oral gavage [sacubitril/valsartan (68 mg/kg), valsartan (31 mg/kg), and sacubitril (31 mg/kg)]. Hemodynamic assessments were conducted using Millar technology, and an exercise tolerance test was conducted using a rodent treadmill. Therapy with sacubitril/valsartan improved load-dependent indexes of LV contractility (dP/d t_max) and relaxation (dP/d t_min), exercise tolerance, and mitigated myocardial fibrosis, whereas monotherapies with valsartan, or sacubitril did not. Both sacubitril/valsartan and valsartan similarly improved a load-independent index of contractility [slope of the end-systolic pressure-volume relationship ( E_es)]. Sacubitril did not improve E_es. First, synergy of NEPi with sacubitril and ARB with valsartan leads to the improvement of load-dependent LV contractility and relaxation, exercise tolerance, and reduction of myocardial collagen content. Second, the improvement in load-independent LV contractility with sacubitril/valsartan appears to be solely due to ARB with valsartan constituent. NEW & NOTEWORTHY Our data suggest the following explanation for the effects of sacubitril/valsartan: 1) synergy of sacubitril and valsartan leads to the improvement of load-dependent left ventricular contractility and relaxation, exercise tolerance, and reduction of myocardial fibrosis and 2) improvement in load-independent left ventricular contractility is solely due to the valsartan constituent. The findings offer a better understanding of the outcomes observed in clinical studies and might facilitate the continuing development of the next generations of angiotensin receptor neprilysin inhibitors.

CaMKII in Vascular Signalling: "Friend or Foe"?

Signalling mechanisms within and between cells of the vasculature enable function and maintain homeostasis. However, a number of these mechanisms also contribute to the pathophysiology of vascular disease states. The multifunctional signalling molecule calcium/calmodulin-dependent kinase II (CaMKII) has been shown to have critical functional effects in many tissue types. For example, CaMKII is known to have a dual role in cardiac physiology and pathology. The function of CaMKII within the vasculature is incompletely understood, but emerging evidence points to potential physiological and pathological roles. This review discusses the evidence for CaMKII signalling within the vasculature, with the aim to better understand both positive and potentially deleterious effects of CaMKII activation in vascular tissue.

The potential role of angiotensin-converting enzyme inhibition in peripheral arterial disease

Peripheral arterial disease (PAD) is associated with significant morbidity and mortality, and yet remains under-recognized and under-treated. Atherosclerosis is the most common cause of lower extremity PAD and pharmacological interventions that alter this central pathogenic role of atherosclerosis may alter the natural history of PAD. There is growing evidence that the renin-angiotensin system (RAS) is a significant mediator of this disease process and that treatment with angiotensin-converting enzyme (ACE) inhibitors is associated with vasculoprotective effects that are independent of the antihypertensive properties of these agents. Numerous lines of evidence suggest that ACE inhibitors directly inhibit the atherosclerotic process and improve vascular endothelial function. In patients with PAD, ACE inhibitors have been shown to improve peripheral circulation as measured by peripheral arterial blood pressure and by increases in peripheral blood flow. Preliminary evidence suggests that ACE inhibitors might improve clinical symptoms in patients with PAD. Recent evidence has confirmed that ACE inhibition is associated with a decrease in morbidity and mortality in patients with arterial disease without left ventricular dysfunction; this benefit was at least as great for the subset of patients with PAD. Overall, these data support a significant role for the RAS in the pathogenesis of all atherosclerotic diseases (including PAD) and suggest that the benefit is independent of the blood pressure lowering properties of these agents. These studies suggest that ACE inhibitor therapy should be considered in the routine management of individuals with PAD, regardless of whether they have hypertension or left ventricular dysfunction.

Chlamydophila pneumoniae infection induces alterations in vascular contractile responses

Chlamydophila pneumoniae infection has been associated in previous studies with coronary artery disease. The live bacterium has been detected within atherosclerotic plaques and can induce the structural remodeling of the vessel wall. However, the direct effects of infection on the contractile characteristics of the arteries remain unknown. Left anterior descending coronary arteries isolated from porcine hearts were dissected and placed in culture medium for 72 hours before infection with C. pneumoniae. Contractile responses to high molar KCl and u46619 levels and relaxation responses to bradykinin and sodium nitroprusside were assessed at days 5 and 10 postinfection. C. pneumoniae induced decreases in both KCl- and u46619-induced contractile responses at both time points. The altered contractile responses coincided with a down-regulation of L-type Ca(2+) channels at both time points and inositol 1,4,5-triphosphate receptor (IP3R) levels at day 10 postinfection. Infection also induced attenuation of the endothelial-dependent relaxation response to bradykinin at day 10 postinfection. A decrease in endothelial nitric oxide synthase expression levels was noted at day 10 postinfection. Furthermore, an increase in superoxide production combined with an increase in p22phox expression levels was also observed at this time point. These findings indicate that C. pneumoniae infection can directly alter the vascular contractile responses in porcine coronary arteries, providing additional evidence for the role of C. pneumoniae infection in cardiovascular disease.

Bradykinin protects against brain microvascular endothelial cell death induced by pathophysiological stimuli

The morphological and functional integrity of the microcirculation is compromised in many cardiovascular diseases such as hypertension, diabetes, stroke, and sepsis. Angiotensin converting enzyme inhibitors (ACEi), which are known to favor bradykinin (BK) bioactivity by reducing its metabolism, may have a positive impact on preventing the microvascular structural rarefaction that occurs in these diseases. Our study was designed to test the hypothesis that BK, via B2 receptors (B2R), protects the viability of the microvascular endothelium exposed to the necrotic and apoptotic cell death inducers H(2)O(2) and LPS independently of hemodynamics. Expression (RT-PCR and radioligand binding) and functional (calcium mobilization with fura-2AM, and p42/p44MAPK and Akt phosphorylation assays) experiments revealed the presence of functional B2R in pig cerebral microvascular endothelial cells (pCMVEC). In vitro results showed that the cytocidal effects of H(2)O(2) and LPS on pCMVEC were significantly decreased by a BK pretreatment (MTT and crystal violet tests, annexin-V staining/FACS analysis), which was countered by the B2R antagonist HOE 140. BK treatment coincided with enhanced expression of the cytoprotective proteins COX-2, Bcl-2, and (Cu/Zn)SOD. Ex vivo assays on rat brain explants showed that BK impeded (by approximately 40%) H(2)O(2)-induced microvascular degeneration (lectin-FITC staining). The present study proposes a novel role for BK in microvascular endothelial protection, which may be pertinent to the complex mechanism of action of ACEi explaining their long-term beneficial effects in maintaining vascular integrity.

Renal vascular endothelial function in hypertensive patients with type 2 diabetes mellitus

BACKGROUND

Basal nitric oxide (NO) activity has a pivotal role in the regulation of glomerular hemodynamics, and in animal experiments, its alteration has been associated with morphological changes characteristic of diabetic nephropathy.

STUDY DESIGN

Prospective observational-study during a mean follow-up of 2.1 years.

SETTING & PARTICIPANTS

66 hypertensive patients (aged 30 to 80 years) with type 2 diabetes and estimated glomerular filtration rate (GFR) greater than 80 mL/min/1.73 m(2) with normoalbuminuria or microalbuminuria.

PREDICTOR

Mean arterial pressure during follow-up during treatment with telmisartan or ramipril for 9 weeks, followed by treatment according to the discretion of the individual primary care physician.

OUTCOMES & MEASUREMENTS

Renal vascular resistance, renal plasma flow, GFR, and change in renal plasma flow in response to infusion of the NO synthase inhibitor N-monomethyl-L-arginine as an indicator of basal NO activity in the renal vasculature.

RESULTS

50 of 66 patients could be reexamined. At follow-up, mean arterial pressure decreased from 106 +/- 9.1 to 100 +/- 11 mm Hg (P < 0.001). Body mass index and hemoglobin A(1c) levels were unaltered. Renal vascular resistance decreased (from 128 +/- 44 to 103 +/- 30 mm Hg/mL/min/1.73 m(2); P < 0.001), renal plasma flow increased (from 490 +/- 133 to 589 +/- 154 mL/min/1.73 m(2); P < 0.001), and GFR did not change (113 +/- 22 versus 116 +/- 26 mL/min/1.73 m(2); P = 0.4) during follow-up. The decrease in renal plasma flow in response to N-monomethyl-l-arginine infusion was more pronounced at follow-up (-56.7 +/- 39 versus -73.4 +/- 48 mL/min/1.73 m(2); P = 0.02), indicating improved basal NO activity. After adjustment for possible confounders, patients with a marked decrease in mean arterial pressure showed more improved basal NO activity during follow-up than those with a less pronounced decrease in mean arterial pressure (P = 0.04).

LIMITATIONS

Patients were treated according to the discretion of the individual primary care physician.

CONCLUSIONS

During follow-up, renal vascular resistance, renal plasma flow, and renal endothelial function (indicated by basal NO activity) improved. Better blood pressure control was associated with improved endothelial function of the renal vasculature, thereby potentially mediating the changes in renal hemodynamics.

Bradykinin or acetylcholine as vasodilators to test endothelial venous function in healthy subjects

INTRODUCTION

The evaluation of endothelial function has been performed in the arterial bed, but recently evaluation within the venous system has also been explored. Endothelial function studies employ different drugs that act as endothelium-dependent vasodilatory response inductors.

OBJECTIVES

The aim of this study is to compare the endothelium-dependent venous vasodilator response mediated by either acetylcholine or bradykinin in healthy volunteers.

METHODS AND RESULTS

Changes in vein diameter after phenylephrine-induced venoconstriction were measured to compare venodilation induced by acetylcholine or bradykinin (linear variable differential transformer dorsal hand vein technique). We studied 23 healthy volunteers; 31% were male, and the subject had a mean age of 33 +/- 8 years and a mean body mass index of 23 +/- 2 kg/m(2). The maximum endothelium-dependent venodilation was similar for both drugs (p = 0.13), as well as the mean responses for each dose of both drugs (r = 0.96). The maximum responses to acetylcholine and bradykinin also had good agreement.

CONCLUSION

There were no differences between acetylcholine and bradykinin as venodilators in this endothelial venous function investigation.

Endothelial dysfunction: from molecular mechanisms to measurement, clinical implications, and therapeutic opportunities

Endothelial dysfunction has been implicated as a key factor in the development of a wide range of cardiovascular diseases, but its definition and mechanisms vary greatly between different disease processes. This review combines evidence from cell-culture experiments, in vitro and in vivo animal models, and clinical studies to identify the variety of mechanisms involved in endothelial dysfunction in its broadest sense. Several prominent disease states, including hypertension, heart failure, and atherosclerosis, are used to illustrate the different manifestations of endothelial dysfunction and to establish its clinical implications in the context of the range of mechanisms involved in its development. The size of the literature relating to this subject precludes a comprehensive survey; this review aims to cover the key elements of endothelial dysfunction in cardiovascular disease and to highlight the importance of the process across many different conditions.

Nitric oxide and malondialdehyde in human hypertension

Nitric oxide (NO), a multifunctional effector molecule that plays a central role in the maintenance of vascular homeostasis, regulates vascular tone and inhibits platelet and leukocyte adhesion to endothelial cells. NO status is related to the endothelial function. Patients with hypertension have lower levels of NO, increased free radical production, higher oxidative stress, augmented platelet aggregation, and a change in the arachidonic acid cascade metabolism, all leading to the acceleration of the atherosclerotic process. The study subjects included a group of 21 normotensive healthy subjects (8 males and 13 females) with a mean age of 39.2 +/- 1.8 years and a body mass index of 27.9 kg/m, and another group of 42 patients (19 males and 23 females) with untreated essential hypertension with a mean age of 47.6 +/- 1.7 years and a body mass index of 28.3 kg/m. Serum levels and urinary excretion of NO determined as combined nitrate/nitrite (NOx) and serum malondialdehyde (MDA) concentrations were measured in the 2 groups of subjects. The serum levels and 24-hour urinary excretion of NOx were significantly higher and the renal clearance of NO was lower in the normotensive group than in the hypertensive patients, indicating decreased NO status in hypertension. There was a negative correlation between serum NO levels and mean arterial pressure, suggesting that a decrease in NO availability is related to increase in blood pressure. Serum concentrations of MDA were higher in the hypertensive patients as compared with the normotensive individuals, suggesting increased oxidative stress in hypertensive patients. These results are in agreement with previous studies showing decreased NO and increased oxidative stress in hypertension. In conclusion, patients with essential hypertension as compared with normotensive individuals have lower NO status, which may contribute to the endothelial dysfunction in hypertension. Increased serum malondialdehyde in hypertensives suggests an association between increased oxidative stress with higher blood pressure.

Magnesium lithospermate B ameliorates renal cortical microperfusion in rats

AIM

To investigate the effects of magnesium lithospermate B (MLB) isolated from Salviae miltiorrhizae on renal microcirculation, and renal and systemic hemodynamics in Sprague-Dawley rats.

METHODS

MLB (10, 30, and 60 mg/kg) was injected intravenously and renal blood flow (RBF), renal cortical microperfusion (RCM), and systemic hemodynamic function parameters including heart rate (HR), mean arterial pressure (MAP), left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), and maximal velocity of pressure increase (dp/dt(max)) were measured for 45 min after administration.

RESULTS

Intravenous MLB at doses of 10, 30, and 60 mg/kg increased RCM significantly, but had no obvious effects on RBF or systemic hemodynamics. The effect of MLB on RCM reached its peak 15 min after injection and returned to baseline after 45 min. Up to 60 mg/kg MLB increased RCM by 62.4%+/-20.2% (changes from baseline, P<0.01), whereas RBF (3.7%+/-9.7% vs baseline) and renal vascular resistance (-1.4%+/-9.1% vs baseline) did not obviously change.

CONCLUSION

These results indicate that MLB ameliorates renal microcirculation in a dose-dependent manner, which may be related to the renoprotective effects of MLB.

Superiority of combination of thiazide with angiotensin-converting enzyme inhibitor or AT1-receptor blocker over thiazide alone on renoprotection inl-NAME/SHR

The renal and glomerular dynamic effects of combining thiazide and angiotensin antagonists have not been reported. The present study was designed to examine the effects of hydrochlorothiazide (HCTZ) alone or in combination with an angiotensin-converting enzyme inhibitor or ANG II type 1-receptor blocker on renal hemodynamics, glomerular dynamics, renal function, and renal histopathology in the Nω-nitro-l-arginine methyl ester-treated spontaneously hypertensive rat (l-NAME/SHR) model. HCTZ (80 mg·kg−1·day−1) alone or in combination with enalapril (30 mg·kg−1·day−1) or losartan (30 mg·kg−1·day−1) or enalapril (15 mg·kg−1·day−1) plus losartan (15 mg·kg−1·day−1) was administered to l-NAME/SHR (5.0 ± 0.10 mg·kg−1·day−1) for 3 wk. Mean arterial pressure, total peripheral resistance, renal plasma flow, glomerular filtration rate, glomerular hydrostatic pressure, afferent and efferent glomerular arteriolar resistances, single nephron plasma flow, single nephron glomerular filtration rate, serum creatinine concentration, 24-h urinary protein excretion, and glomerular and arteriolar injury scores were determined. HCTZ reduced mean arterial pressure, total peripheral resistance, glomerular hydrostatic pressure, and afferent and efferent glomerular arteriolar resistances ( P < 0.05, at least) but slightly increased renal plasma flow and single nephron plasma flow associated with reduced serum creatinine concentration, urinary protein excretion, and arteriolar injury score compared with l-NAME/SHR control. However, the combination of enalapril and/or losartan with HCTZ markedly improved each of these functions. These results demonstrated minor benefits of HCTZ monotherapy and a marked superiority of its combination with enalapril and/or losartan over HCTZ monotherapy on renoprotection in l-NAME/SHR, thereby providing strong evidence of their clinical benefits for hypertensive patients with renal functional impairment.

Treatment of severe pulmonary hypertension: a bradykinin receptor 2 agonist B9972 causes reduction of pulmonary artery pressure and right ventricular hypertrophy

Bradykinin is an important modulator of endothelial cell function and has also a powerful cardioprotective effect. Here we report that treatment of severely pulmonary hypertensive rats (that recapitulate several of the physiological and pathological characteristics of the human pulmonary vascular disease, including dramatic right ventricular hypertrophy, pericardial effusion and death) with a newly synthesized long-acting bradykinin B2 receptor agonist B9972 caused reduction of the pulmonary artery pressure (PAP=51+/-2.0 versus 68+/-2.8 of untreated animals) and of right ventricular hypertrophy (Rv/Lv+S=0.55+/-0.02 versus 0.73+/-0.03 of untreated rats) and activation of Akt. Long-term stimulation with B9972 in our animal model of SPH resulted in decreased expression of the B2 receptor in lung vasculature. Treatment with B9972 decreased the number of plexiform lesions in the lungs by inducing cell apoptosis in the obliterated vessels and by restoring caveolin-1 expression. B9972 also promoted eNOS activation. In vitro B9972 caused activation of caspase-3 as well as Erk and induction of prostacyclin production in rat pulmonary microvascular EC. Taken together our data suggest that a stable bradykinin B2 agonist B9972 demonstrates the capacity to reduce severe pulmonary hypertension, right ventricular hypertrophy and induce apoptosis of hyperproliferative cells in pre-capillary pulmonary arterioles.

Differential effects of antihypertensive drugs on renal and glomerular hemodynamics and injury in the chronic nitric-oxide-suppressed rat

BACKGROUND/AIMS

Prolonged nitric oxide synthase (NOS) inhibition with N(omega)-nitro-L-arginine methylester in normotensive and hypertensive rats has been demonstrated to produce severe systemic and glomerular hypertension with glomerular sclerosis, and these changes have become a useful experimental model of hypertensive nephrosclerosis. This review summarizes data from our serial studies as well as work of others who are also investigating the effects of the commonly used antihypertensive drugs (including calcium antagonist, angiotensin-converting enzyme inhibitor, angiotensin II type 1 receptor blocker, aldosterone antagonist and thiazide diuretic) on renal and glomerular hemodynamics, renal function and glomerular histopathology using this model.

METHODS

A Medline search was performed to identify the relevant literature describing renal effects of antihypertensive drugs in models of hypertension and nephrosclerosis produced or exacerbated by NOS inhibition.

RESULTS

Existing data have indicated that most of these drug classes have produced dramatic renoprotective effects, structurally or functionally, on nephrosclerosis induced by prolonged NOS inhibition.

CONCLUSION

This review of experimental studies has provided strong evidence supporting the clinical benefits of antihypertensive drugs for hypertensive patients with renal impairment particularly those with endothelial dysfunction associated with NOS deficiency.

Chronic exposure to high glucose impairs bradykinin-stimulated nitric oxide production by interfering with the phospholipase-C-implicated signalling pathway in endothelial cells: evidence for the involvement of protein kinase C

AIMS/HYPOTHESIS

Overwhelming evidence indicates that endothelial cell dysfunction in diabetes is characterised by diminished endothelium-dependent relaxation, but the matter of the underlying molecular mechanism remains unclear. As nitric oxide (NO) production from the endothelium is the major player in endothelium-mediated vascular relaxation, we investigated the effects of high glucose on NO production, and the possible alterations of signalling pathways implicated in this scenario.

METHODS

NO production and intracellular Ca(2+) levels ([Ca(2+)](i)) were assessed using the fluorescent probes 4,5-diaminofluorescein diacetate and fura-2 respectively.

RESULTS

Exposure of cultured bovine aortic endothelial cells to high glucose for 5 or 10 days significantly reduced NO production induced by bradykinin (but not by Ca(2+) ionophore) in a time- and dose-dependent manner. This was probably due to an attenuation in bradykinin-induced elevations of [Ca(2+)](i) under these conditions, since a close correlation between [Ca(2+)](i) increases and NO generation was observed in intact bovine aortic endothelial cells. Both bradykinin-promoted intracellular Ca(2+) mobilisation and extracellular Ca(2+) entry were affected. Moreover, bradykinin-induced formation of Ins(1,4,5)P(3), a phospholipase C product leading to increases in [Ca(2+)](i), was also inhibited following high glucose culture. This abnormality was not attributable to a decrease in inositol phospholipids, but possibly to a reduction in the number of bradykinin receptors. The alterations in NO production, the increases in [Ca(2+)](i), and the bradykinin receptor number due to high glucose could be largely reversed by protein kinase C inhibitors and D: -alpha-tocopherol (antioxidant).

CONCLUSIONS/INTERPRETATION

Chronic exposure to high glucose reduces NO generation in endothelial cells, probably by impairing phospholipase-C-mediated Ca(2+) signalling due to excess protein kinase C activation. This defect in NO release may contribute to the diminished endothelium-dependent relaxation and thus to the development of cardiovascular diseases in diabetes.

Tissue kallikrein attenuates salt-induced renal fibrosis by inhibition of oxidative stress

BACKGROUND

High salt intake induces hypertension, cardiac hypertrophy, and progressive renal damage. Progressive renal injury is the consequence of a process of destructive fibrosis. Using gene transfer approach, we have shown that the tissue kallikrein-kinin system (KKS) plays an important role in protection against renal injury in several hypertensive rat models. In this study, we further investigated the effect and potential mechanisms mediated by kallikrein on salt-induced renal fibrosis.

METHODS

Adenovirus harboring the human tissue kallikrein gene was delivered intravenously into Dahl salt-sensitive (DSS) rats on a high salt diet for 4 weeks. Two weeks after gene delivery, the effect of kallikrein on renal fibrosis was examined by biochemical and histologic analysis.

RESULTS

Kallikrein gene delivery resulted in reduced blood urea nitrogen (BUN), urinary protein and albumin levels in DSS rats on a high salt diet. Expression of recombinant human tissue kallikrein was detected in the sera and urine of rats injected with the kallikrein gene. Histologic investigation showed that kallikrein gene delivery significantly reduced glomerular and tubular fibrosis scores and collagen deposition, as well as renal cell proliferation, compared to rats on a high salt diet injected with control virus. Kallikrein gene transfer significantly increased nitric oxide and cyclic guanosine monophosphate (cGMP) levels in conjunction with reduced salt-induced nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase activity, superoxide production, transforming growth factor-beta1 (TGF-beta1) mRNA and protein levels, and TGF-beta1 immunostaining.

CONCLUSION

These results indicate that tissue kallikrein protects against renal fibrosis in hypertensive DSS rats through increased nitric oxide bioavailability and suppression of oxidative stress and TGF-beta expression.

Hiperreactividad cardiovascular en pacientes con antecedentes familiares de hipertensión arterial

BACKGROUND AND OBJECTIVE

The association between family history of essential high blood pressure (FH of HBP) and the cardiovascular hyperactivity to the isometric exercise is not well known; that is why the aim of this study was to describe this relation and to determine whether it is independent of the presence of cardiovascular risk factors.

PATIENTS AND METHOD

We carried out a correlational descriptive study with a sample of 1855 people of both sexes between 18 and 70 years of age. The cardiovascular hyperactivity, expression of the cardiovascular response to the activity of the sympathetic nervous system (SNS), was determined by means of the test of the sustained weight (TSW). Comparisons of the values of cardiovascular reactivity were developed between individuals with and without FH of HBP and a model of logistical regression. The level of statistical significance was 95%.

RESULTS

The arterial blood pressure at the end of the TSW was higher in individuals with FH of HBP independently of the age group. The cardiovascular hyperactivity, measured by means of they systolic index of cardiovascular reactivity, was also significantly higher in subjects with FH of HBP. Finally, individuals with FH of HBP showed a higher risk (more than 5 times) of having cardiovascular hyperactivity (OR = 5.16; CI 95%, 3.51-7.59), this association being independent of other cardiovascular factors of risk.

CONCLUSIONS

The FH of HBP is independently related to the cardiovascular hyperactivity, to the isometric exercise, of other cardiovascular risks factors. These elements help explain the relationship between cardiovascular hyperactivity, the activity of SNS and essential high blood pressure, at least in an important group of people.

Clinical impact of renin-angiotensin system blockade: angiotensin-converting enzyme inhibitors vs. angiotensin receptor antagonists

Clinical trials have proved that blockade of the renin-angiotensin-aldosterone system (RAAS) offers primary and secondary protection of the cardiovascular system, brain, and kidneys. Drugs that interrupt the RAAS do so by several diverse mechanisms but it remains to be fully proved whether these mechanistic differences are associated with meaningful differences in clinical outcomes. This review summarizes current information about the basic mechanisms of action of three classes of anti-RAAS drugs: angiotensin-converting enzyme (ACE) inhibitors, combined ACE-neutral endopeptidase inhibitors, and angiotensin receptor antagonists as well as results of major clinical outcome trials with these agents. Basic and clinical science information is then blended with insights from the clinical pharmacology of anti-RAAS drugs to address four current controversies in clinical medicine: whether ACE inhibitors and angiotensin receptor antagonists are interchangeable, optimal dosing of available agents, potential justification of ACE inhibitor/angiotensin receptor antagonist combinations, and first-line use of anti-RAAS drugs in antihypertensive therapy.

Impaired endothelium-mediated vasodilation in heart failure: clinical evidence and the potential for therapy

Numerous studies in the last decade have clearly shown an attenuated endothelium-dependent vasodilation in patients with chronic heart failure. This abnormality has been demonstrated in the peripheral, pulmonary, and coronary circulation in patients with both ischemic and nonischemic cardiomyopathy; its magnitude correlates with the severity of symptoms. Endothelial dysfunction in patients with cardiomyopathy and a relatively new onset of symptoms suggests that change in endothelial function occurs early in the course of the disease. In contrast to other circulatory beds, renal circulation has shown significant vasodilatory response to endothelial stimulation. The development of endothelial dysfunction may not be homogeneous, and its magnitude may differ among circulatory systems. Although the clinical implications of the attenuated endothelium-dependent vasodilation in heart failure are not clear, this condition may lead to decreased organ perfusion, impaired exercise tolerance, and progression of disease. Many therapeutic interventions have resulted in improvement of endothelial function in patients with heart failure. Some of these interventions have also proven effective in enhancing exercise capacity, symptoms, and survival in patients with heart failure. This association suggests a therapeutic role for improvement of endothelial function in patients with chronic heart failure.

A synthetic tissue kallikrein inhibitor suppresses cancer cell invasiveness

Serine proteinases modulate the interaction of tumor cells with extracellular matrix components during extravasation and metastasis. The serine proteinase tissue kallikrein has been previously demonstrated in several human adenocarcinomas, and we presently report the localization of immunoreactive kallikrein and its mRNA in pancreatic adenocarcinoma. In addition, a synthetic peptide-based inhibitor specific for tissue kallikrein (FE999024) was used in our studies to explore a possible role for kallikrein in cancer cell invasiveness. Matrigel invasion assays were performed with a human breast-cancer cell line, MDA-MB-231, which expresses tissue kallikrein in culture. In the presence of FE999024 invasion through Matrigel was inhibited in a dose-dependent manner to a maximum of 39%. We also developed a novel ex vivo assay in which breast cancer cells are infused into the pulmonary circulation of artificially ventilated explanted rat lungs. At intervals up to 6 hours after infusion pulmonary invasion was quantified by bronchial alveolar lavage to recover human cancer cells from the airspace. Invading cells in the lung interstitium were also quantified after immunohistochemistry with a monoclonal antibody specific for human cytokeratin 18. The synthetic kallikrein inhibitor attenuates breast cancer cell invasion into the airspace by 33% when quantified by lavage recovery and up to 34% as quantified in the lung interstitium by cytokeratin 18 immunostaining. Our results indicate tissue kallikrein may participate in the invasion and metastasis of human adenocarcinomas. The newly developed explanted rodent lung assay should be useful for the study of cancer cells, neutrophils, or other extravasating cells.

A remarkable medical story: benefits of angiotensin-converting enzyme inhibitors in cardiac patients

The development of angiotensin-converting enzyme inhibitors (ACE inhibitors) has been one of the most remarkable stories in the treatment of cardiovascular diseases. Angiotensin converting enzyme inhibitors have several acute and sustained hemodynamic effects that are beneficial in the presence of left ventricular (LV) dysfunction. They increase cardiac output and stroke volume and reduce systemic vascular resistance as well as pulmonary capillary wedge pressure. The hemodynamic benefits are associated with improvement in the signs and symptoms of congestive heart failure (CHF) as well as decreased mortality, regardless of the severity of CHF. In patients with asymptomatic LV dysfunction, therapy with ACE inhibitors prevented the development of CHF and reduced hospitalization and cardiovascular death. They also increase survival when administered early after an acute myocardial infarction (MI). Most recently, ACE inhibition was associated with improved clinical outcomes in a broad spectrum of high-risk patients with preserved LV function. The mechanism of ACE inhibitors benefits is multifactorial and includes prevention of progressive LV remodeling, prevention of sudden death and arrhythmogenicity and structural stability of the atherosclerotic process. Evidence suggests that ACE inhibitors are underutilized in patients with cardiovascular diseases. Efforts should be directed to prescribe ACE inhibitors to appropriate patients in target doses. It is reasonable to believe that ACE inhibitors have a class effect in the management of LV dysfunction with or without CHF and acute MI. Whether the same is true for ACE inhibitors in the prevention of ischemic events is not known yet.

Bradykinin attenuates the [Ca(2+)](i) response to angiotensin II of renal juxtamedullary efferent arterioles via an EDHF

1. Bradykinin (BK) effect on the [Ca(2+)](i) response to 1 nM angiotensin II was examined in muscular juxtamedullary efferent arterioles (EA) of rat kidney. 2. BK (10 nM) applied during the angiotensin II-stimulated [Ca(2+)](i) increase, induced a [Ca(2+)](i) drop (73+/-2%). This drop was prevented by de-endothelialization and suppressed by HOE 140, a B2 receptor antagonist. It was neither affected by L-NAME or indomethacin, nor mimicked by sodium nitroprusside, 8-bromo-cyclic GMP or PGI(2). The BK effect did not occur when the [Ca(2+)](i) increase was caused by 100 mM KCl-induced membrane depolarization and was abolished by 0.1 microM charybdotoxin, a K(+) channel blocker. 3. Although proadifen prevented the BK-caused [Ca(2+)](i) fall, more selective cytochrome P450 inhibitors, 17-octadecynoic acid (50 microM) and 7-ethoxyresorufin (10 microM) were without effect. 4. Increasing extracellular potassium from 5 to 15 mM during angiotensin II stimulation caused a [Ca(2+)](i) decrease (26+/-4%) smaller than BK which was charybdotoxin-insensitive. Inhibition of inward rectifying K(+) channels by 30 microM BaCl(2) and/or of Na(+)/K(+) ATPase by 1 mM ouabain abolished the [Ca(2+)](i) decrease elicited by potassium but not by BK. 5. A voltage-operated calcium channel blocker, nifedipine (1 microM) did not prevent the BK effect but reduced the [Ca(2+)](i) drop. 6. These results indicate that the BK-induced [Ca(2+)](i) decrease in angiotensin II-stimulated muscular EA is mediated by an EDHF which activates charybdotoxin-sensitive K(+) channels. In these vessels, EDHF seems to be neither a cytochrome P450-derived arachidonic acid metabolite nor K(+) itself. The closure of voltage-operated calcium channels is not the only cellular mechanism involved in this EDHF-mediated [Ca(2+)](i) decrease.

Human tissue kallikrein gene delivery attenuates hypertension, renal injury, and cardiac remodeling in chronic renal failure

BACKGROUND

Tissue kallikrein cleaves kininogen substrate to produce the potent vasodilating peptide kinin, which plays important roles in cardiovascular and renal function. To explore cardiac and renal potential protective effects of kallikrein gene delivery in chronic renal failure, we delivered adenovirus carrying the human tissue kallikrein cDNA (cHK) into rats with 5/6 reduction of renal mass.

METHODS

Expression of human tissue kallikrein in rats was assessed by enzyme-linked immunosorbent assay (ELISA) and reverse transcription-polymerase chain reaction (RT-PCR)/Southern blotting. Physiological parameters monitored in rats included systolic blood pressure, heart rate, and urinary excretion of protein, albumin, kinin, cGMP, cAMP, and nitrate/nitrites. Systemic and regional hemodynamics were measured by fluorescent-labeled microspheres. Heart weight and myocyte diameter were used to assess left ventricular hypertrophy. Quantitative and qualitative morphological analyses were used to evaluate histologic changes in kidney and heart sections.

RESULTS

Active tissue kallikrein reached a peak serum level of 463 +/- 76 ng/mL following gene delivery and returned to control levels within 21 days. A maximal blood pressure reduction of 37 mm Hg was observed within one week in rats receiving kallikrein gene delivery as compared with control rats receiving adenovirus containing the luciferase gene (159 +/- 5 vs. 196 +/- 6 mm Hg, N = 15, P < 0.001), and a significant blood pressure difference continued for five weeks postgene delivery. Kallikrein gene delivery significantly decreased total urinary protein and albumin excretion and increased levels of urinary kinin, nitrite/nitrate, and cGMP levels. Cardiac output and regional blood flow were also increased, while peripheral vascular resistance decreased. Kallikrein gene transfer reduced glomerular sclerotic lesions, tubular damage, lumenal protein cast accumulation, and interstitial inflammation in the kidney. Myocardial hypertrophy and fibrosis were also attenuated in rats receiving kallikrein gene delivery.

CONCLUSIONS

These findings indicated that kallikrein gene delivery attenuates hypertension and protects against renal injury and cardiac remodeling in the rat remnant kidney model of chronic renal failure.

Comparison of zofenopril and lisinopril to study the role of the sulfhydryl-group in improvement of endothelial dysfunction with ACE-inhibitors in experimental heart failure

We evaluated the role of SH-groups in improvement of endothelial dysfunction with ACE-inhibitors in experimental heart failure. To this end, we compared the vasoprotective effect of chronic treatment with zofenopril (plus SH-group) versus lisinopril (no SH-group), or N-acetylcysteine (only SH-group) in myocardial infarcted (MI) heart failure rats. After 11 weeks of treatment, aortas were obtained and studied as ring preparations for endothelium-dependent and -independent dilatation in continuous presence of indomethacin to avoid interference of vasoactive prostanoids, and the selective presence of the NOS-inhibitor L-NMMA to determine NO-contribution. Total dilatation after receptor-dependent stimulation with acetylcholine (ACh) was attenuated (-49%, P<0.05) in untreated MI (n=11), compared to control rats with no-MI (n=8). This was in part due to impaired NO-contribution in MI (-50%, P<0.05 versus no-MI). At the same time the capacity for generation of biologically active NO after receptor-independent stimulation with A23187 remained intact. Chronic treatment with n-acetylcysteine (n=8) selectively restored NO-contribution in total dilatation to ACh. In contrast, both ACE-inhibitors fully normalized total dilatation to ACh, including the part mediated by NO (no significant differences between zofenopril (n=10) and lisinopril (n=8)). Zofenopril, but not lisinopril, additionally potentiated the effect of endogenous NO after A23187-induced release from the endothelium (+100%) as well as that of exogenous NO provided by nitroglycerin (+22%) and sodium nitrite (+36%) (for all P<0.05 versus no-MI). We conclude that ACE-inhibition with a SH-group has a potential advantage in improvement of endothelial dysfunction through increased activity of NO after release from the endothelium into the vessel wall. Furthermore, this is the first study demonstrating the selective normalizing effect of N-actylcysteine on NO-contribution to ACh-induced dilatation in experimental heart failure.

Developmental changes in endothelium-derived vasorelaxant factors in cerebral circulation

Endothelium-derived prostanoids are predominant vasorelaxant factors in the cerebral circulation of newborn pigs in vivo, whereas in older pigs nitric oxide (NO)-mediated responses also contribute to the regulation of cerebral vascular tone. We compared the expression and activities of NO synthase and cyclooxygenase in the cerebral microcirculation of newborn and adult pigs. In adult animals, expression and activity of endothelial NO synthase in cerebral microvessels and in cultured cerebral endothelial cells is two- to threefold higher than in newborn pigs; acetylcholine and bradykinin cause a greater increase in NO production in adult pigs. Expression and activity of cyclooxygenase in cerebral microvascular endothelial cells is similar in newborn and adult pigs; acetylcholine and bradykinin stimulated dilator prostanoid production to the same degree in both age groups. Endothelial prostanoid synthesis in cerebral microvessels and cultured endothelial cells was inhibited 30-70% by NS-398, reflecting a large contribution of COX-2 in both newborn and adult animals. These data indicate that in the cerebral circulation of pigs, NO synthase is age-dependently upregulated, whereas endothelial cyclooxygenase is not altered during postnatal development.

Amlodipine enhances NO production induced by an ACE inhibitor through a kinin-mediated mechanism in canine coronary microvessels

Our previous study found that angiotensin-converting enzyme (ACE) inhibitors and amlodipine induce NO release from coronary microvessels through a kinin-dependent mechanism. The goal of this study was to determine whether amlodipine could potentiate NO formation during ACE inhibition. Coronary microvessels were isolated from 16 mongrel dogs. Nitrite, the hydration product of NO, from coronary microvessels was quantified by using the Griess reaction. Bradykinin and kallikrein all significantly increased nitrite release from coronary microvessels in a concentration-dependent manner. The ACE inhibitor, ramiprilat, potentiated these effects. Amlodipine also markedly potentiated nitrite production by ramiprilat. For instance, amlodipine (10(-10) M) enhanced nitrite release induced by ramiprilat (10(-7) M) from 122 +/- 9 to 168 +/- 14 pmol/mg (p < 0.05 vs. ramiprilat). Nitrite release potentiated by ramiprilat and amlodipine was entirely blocked by N(omega)-nitro-L-arginine methyl ester (L-NAME, an inhibitor of NO synthase), HOE 140 (Icatibant, a specific B2-kinin receptor antagonist), and dichloroisocoumarin (DCIC, a serine protease inhibitor that blocks local kinin formation). These results clearly show that there is a synergistic effect on NO formation when amlodipine is combined with ACE inhibition. Our data suggest that kinin-mediated coronary NO production may contribute importantly to the beneficial therapeutic action of ACE inhibitors, especially in combination with amlodipine in the treatment of heart disease.

Adenovirus-mediated kallikrein gene delivery attenuates hypertension and protects against renal injury in deoxycorticosterone-salt rats

To demonstrate potential therapeutic effects of kallikrein gene delivery in salt-induced hypertension and renal diseases, we delivered adenovirus carrying the human tissue kallikrein gene (Ad.CMV-cHK) into deoxycorticosterone acetate (DOCA)-salt hypertensive rats. A single intravenous injection of Ad.CMV-cHK caused a delay in the rise of blood pressure that began 2 days post gene delivery and lasted for more than 23 days. A maximal blood pressure reduction of 50 mm Hg was observed in rats receiving kallikrein gene delivery, as compared to rats receiving adenovirus containing the luciferase gene (Ad.CMV-Luc) (172 +/- 5 vs. 222 +/- 13 mm Hg, n = 6, P < 0.01). Throughout the experimental period, a blood pressure reduction of at least 32 mm Hg was observed in the DOCA-salt rats injected with Ad.CMV-cHK as compared to DOCA-salt rats receiving control adenovirus. Immunoreactive human tissue kallikrein levels were detected in rat serum and urine post gene delivery. Adenovirus-mediated kallikrein gene delivery caused a significant reduction in urinary excretion, urinary protein levels and body weight. Morphological examination of the kidney showed that kallikrein gene transfer significantly reduced DOCA-salt-induced glomerular sclerotic lesions, brush border disruption of proximal tubules, tubular dilatation and protein cast accumulation. These findings showed that the expression of human tissue kallikrein via gene delivery has protective effects against hypertension and renal injury in DOCA-salt hypertensive rats.

A new experimental approach in endothelium-dependent pharmacological investigations on isolated porcine coronary arteries mounted for impedance planimetry

1. The aim of this study was to investigate whether the balloon-based impedance planimetry technique could be a useful tool in endothelium-dependent investigations. 2. Porcine large coronary arteries contracted with prostaglandin F2alpha (PGF2alpha, 10 microM) did not relax to bradykinin (0.1 nM - 0.1 microM), but did relax to sodium nitroprusside (SNP, 10 microM). However, after eversion of the segments, bradykinin induced relaxations with pD2 values and maximal responses of 8.78+/-0.09 and 75+/-2% (n=6), respectively. 3. Incubation with captopril (1 microM) did not reveal a relaxation to bradykinin in the normal vessel configuration and had no influence on the concentration-relaxation relationship in everted segments. 4. Lowering the luminal pressure in contracted segments from 131+/-5 mmHg (isometric, n=5) to 60 mmHg (isobaric, n=5) did not facilitate the action of bradykinin. 5. Eversion of segments did not influence the concentration-response relationship for K+ (4.7 - 125 mM), PGF2alpha (0.3 - 30 microM), and SNP (30 nM - 30 microM), although the time-courses of responses were faster when the agents were added from the intimal compared to the adventitial side of the preparation. 6. In the same everted segment contracted with PGF2alpha, the concentration-response relationship for bradykinin was not different under isometric and isobaric conditions. 7. These results indicate that, (1) reduced endothelium-dependent relaxations to adventitially administered substances can be ascribed to a diffusion barrier in the vessel wall, while enzymatic degradation, luminal pressure and precontractile responses seem not to play a role, (2) impedance planimetry applied to everted cylindrical segments could be a useful experimental approach in pharmacological studies of endothelium-dependent responses under isobaric and isometric conditions.

Localization and expression of tissue kallikrein and kallistatin in human blood vessels

Tissue kallikrein releases kinins by specific proteolysis, an activity inhibited by kallistatin. In this study, kallikrein and kallistatin were localized to endothelial and smooth muscle cells of large, medium, and small normal blood vessels by immunohistochemical techniques. Immunostaining for both proteins was strong in the endothelium of all sizes of blood vessels and was more intense in medial smooth muscle cells of small and medium-sized blood vessels than in elastic arteries. The sites of synthesis by endothelial and smooth muscle cells were demonstrated in normal blood vessels of all sizes by in situ hybridization histochemistry. Kallikrein and kallistatin levels were measured by immunoassays in homogenates of human aorta, vena cava, and iliac artery and vein. Tissue kallikrein and kallistatin transcripts were identified in human blood vessels by RT-PCR followed by Southern blot analysis with specific oligonucleotide probes. The results demonstrated the expression and co-localization of tissue kallikrein and kallistatin in human vessels and suggest a potential role of kallistatin in regulating tissue kallikrein in blood vessels.

Bradykinin-mediated cardiovascular protective actions of ACE inhibitors. A new dimension in anti-ischaemic therapy?

In addition to being accepted therapy in hypertension and heart failure, ACE inhibitors may well offer a new dimension in anti-ischaemic therapy. Currently, anti-ischaemic properties have been demonstrated by ACE inhibitors in selected patient groups, including patients with left ventricular dysfunction with or without a direct temporal relationship with myocardial infarction. Anti-ischaemic effects of ACE inhibitors become apparent late after initiation of treatment and suggest a structural rather than a functional effect. Underlying mechanisms may include a reduction in ventricular dilatation and (abnormal) cardiac hypertrophy, leading to less myocardial oxygen demand and, possibly, improved subendocardial blood supply, and vasculoprotective effects, i.e. anti-atherosclerotic and antiremodelling properties, a beneficial effect on the fibrinolytic system and an improvement in abnormal endothelial vasodilator function. The latter aspect is most probably the pivotal mode of action where the anti-ischaemic profile of ACE inhibition is concerned. An improvement in endothelial dysfunction has been shown in patients with mild to moderate coronary artery disease [Trial on Reversing ENdothelial Dysfunction (TREND)]. It is of importance that, in both clinical experiments and human studies, the role of bradykinin appears central in the structural and functional cardiovascular effects of ACE inhibition. This is particularly true for the improvement of impaired endothelial function. Myocardial ischaemia evokes vasoconstrictor neurohormonal activation, which may lead to coronary vasoconstriction in diseased coronary segments. The subsequent abnormal endothelial function leads to diminished coronary flow and also increases systemic vasotone and afterload, thus unfavourably altering the myocardial oxygen supply/demand ratio. Under laboratory conditions, acute ACE inhibition counteracts this activation in humans. However, it is speculated that this anti-ischaemic mechanism may become operative and clinically important during long term oral ACE inhibitor therapy when endothelial function improves, and may subsequently protect against the vasoconstrictor effect of neurohormonal activation. As it is unlikely that the mechanisms mentioned above are only relevant in patients with ventricular dysfunction or heart failure, several large controlled trials are currently examining the long term anti-ischaemic and cardiovascular protective effects of ACE inhibition in patients at risk of a cardiovascular event [Heart Outcomes Prevention Evaluation study (HOPE)], with a normal cardiac function [Prevention of Events with ACE inhibition study (PEACE)] or in all patients with coronary artery disease irrespective of cardiac function [EUropean trial of Reduction Of cardiac events with Perindopril in stable coronary Artery disease (EUROPA)].