Volume 6, Number 2, September 2005

POPULAR
TOPICPAPERCollagen Production in Cardiac Fibroblasts During Inhibition of Aminopeptidase B
Paul J Lijnen, Victor V Petrov, Marisa Turner, Robert H Fagard

Objective. To determine whether the aminopeptidase B inhibitor, arphamenine A, could affect collagen production and expression in control and TGF-ß1-treated cardiac fibroblasts.
Design and Methods. Cardiac fibroblasts from passage 2 from normal male adult rats were cultured to confluency and incubated with and without 600 pmol/l TGF-ß1 for 2 days in serum-free Dulbecco’s modified Eagle’s medium and then incubated with 100 ?mol/l arphamenine A for 1 day in this medium with added ascorbic acid, ß-aminopropionitrile and titriated proline. Soluble collagen was measured in the conditioned medium and non-soluble collagen in the cell layer. Aminopeptidase activity was estimated by spectrophotometric determination of the liberation of p-nitroaniline from alanine- or arginine-p-nitroanilide. Matrix metalloproteinase (MMP) and lysyl oxidase activity were assayed in the conditioned medium. A semi-quantitative reverse transcriptase- polymerase chain reaction was used to examine the expression of lysyl oxidase and collagen type I and III.
Results. Arphamenine A dose-dependently inhibited basal and TGF-ß1-stimulated aminopeptidase activity. Arphamenine A reduced soluble and non-soluble collagen production in control and TGF-ß1-treated cardiac fibroblasts, while it decreased collagen type I and III expression only in TGF-ß1-treated fibroblasts. Lysyl oxidase, MMP-1 and MMP-2 activity were inhibited by arphamenine A in the conditioned media of control and TGF-ß1-treated cardiac fibroblasts.
Conclusions. Our data show that the specific aminopeptidase B inhibitor, arphamenine A, reduces collagen production in cardiac fibroblasts and that this reduction is accompanied by a pronounced inhibition of lysyl oxidase.

JRAAS 2005;6:69-77.

PAPERRenin Release in Response to Renin System Blockade: Activation of the Renin System in Type 1 Diabetes Mellitus
Radomir D Stevanovic, Deborah A Price, M Cecilia Lansang, Naomi DL Fisher, Lori MB Laffel, Norman K Hollenberg

Activation of the renin-angiotensin system (RAS) in diabetes is thought to contribute to nephropathy. This is suggested by findings of an enhanced renovascular (RPF) response to RAS blockade with angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin receptor blockers (ARBs). An alternative approach to assess RAS activation is the evaluation of renin release following RAS blockade.
Forty-four consecutively enrolled Type 1 diabetic patients (28.2 ± 1.5 years) and 37 normal subjects (37 ± 2.6 years) in high salt balance were given 25 mg of captopril and 16 mg of candesartan p.o. on consecutive days. All subjects were Caucasian. All, except one diabetic patient, had normal renal function. Plasma renin activity (PRA) and renal plasma flow (RPF) were measured for four hours after both drugs, and at eight, and 24 hours after candesartan.
As anticipated, both drugs increased PRA. Peak responses (90’ after captopril) were 5.6 ± 1 ng/mL Ang I/hour in diabetic patients, and 1.7 ± 0.9 ng/mL Ang I/hour in normal subjects (p<0.001). Responses to both drugs were correlated in diabetic patients for PRA (r=0.623; p=0.001) and for RPF (r=0.9; p<0.001). When the PRA response to captopril was below the median, the RPF response was limited (22.1 ± 17.6 ml/minute/1.73 m2). When it was above the median, the RPF response was also larger (62.2 ± 13.9 ml/minute/1.73 m2; p=0.006).
Renin response to ACE-I and ARB confirms activation of the RAS in diabetic patients.

JRAAS 2005;6:78-83.

POPULAR
TOPICPAPERComparison of Monotherapy with Irbesartan 150 mg or Amlodipine 5 mg for Treatment of Mild-to-Moderate Hypertension
Joel M Neutel, F Wilford Germino, David Smith

Objective. The primary objective of this study was to compare the antihypertensive efficacy of the angiotensin II receptor blocker irbesartan 150 mg and the calcium channel blocker amlodipine 5 mg in the treatment of patients with seated diastolic blood pressure (DBP) 95–110 mmHg.
Design. Multicentre, randomised, double-blind, comparative pilot study.
Methods. Subjects were 18–65 years of age, with DBP 95–110 mmHg, and of non-African American origin. Following a threeweek, single-blind, placebo lead-in period, 181 subjects were randomised in a 1:1 ratio to receive once-daily irbesartan 150 mg (n=89) or amlodipine 5 mg (n=92) for four weeks. Trough (24±3 hours post-dosing) BP measurements were obtained at baseline and at Weeks 2 and 4 under standardised, controlled conditions. Response was defined as DBP <90 mmHg or a reduction from baseline of ?10 mmHg.
Results. After four weeks of treatment, the mean (±SE) decrease from baseline in DBP was 9.4±0.6 mmHg in the irbesartan group vs. 9.6±0.6 mmHg in the amlodipine group (p=0.806). The mean decrease from baseline in seated systolic BP was 12.2±1.0 mmHg in the irbesartan group vs. 12.0±1.0 mmHg in the amlodipine group (p=0.885). Overall, 62% of subjects in the irbesartan group and 63% in the amlodipine group had a response (p=0.609), and 54% and 56% of patients (p=0.596), respectively, had their DBP normalised (<90 mmHg). Adverse events were reported by 21.3% of patients receiving irbesartan and 20.7% receiving amlodipine.
Conclusions. Irbesartan 150 mg demonstrated comparable efficacy to amlodipine 5 mg, thereby confirming its value as an antihypertensive treatment option in non-African American patients with DBP 95–110 mmHg.

JRAAS 2005;6:84-89.

PAPERAre Multiple Angiotensin Receptor Types Involved in Angiotensin (1-7) Actions on Isolated Rat Portal Vein?
Bogdan Gurzu, Marcel Costuleanu, Simona Mihaela Slatineanu, Aurica Ciobanu, Gheorghe Petrescu

Angiotensin (1-7) [Ang (1-7)] is a bioactive component of the renin angiotensin system. Ang (1-7) may interact with angiotensin type 1 (AT1) or type 2 (AT2) receptors and with Ang (1-7) – specific receptors. We examined the interactions between different doses of Ang (1-7) (1nM-1microM) and angiotensin II (Ang II) (10 and 100nM) on isolated rat portal vein. In endothelium-denuded portal vein rings, Ang (1-7) inhibited contractile effects induced by Ang II. The effects of Ang (1-7) were modified by indomethacin, N(G)-nitro-L-arginine methyl ester (L-NAME), (D-Ala7)-Angiotensin (1-7) (H-2888) and losartan. Our results suggest that on rat isolated portal vein rings without endothelium, Ang (1-7) reduces Ang II–induced contractions by acting mostly on Ang (1-7) specific receptors, and this effect is mediated by vasodilatatory prostaglandins. At high concentrations, Ang (1-7) effects are mediated by AT1-receptors, though to a lesser extent than by Ang (1-7) specific receptors.

JRAAS 2005;6:90-95.

PAPERDoes Angiotensin (1-7) Contribute to the Antiproteinuric Effect of ACE-inhibitors?
Els A van der Wouden, Robert H Henning, Leo E Deelman, Anton JM Roks, Frans Boomsma, Dick de Zeeuw

Angiotensin-converting enzyme inhibitors (ACE-I) reduce proteinuria and protect the kidney in proteinuric renal disease. During ACE-I therapy, circulating levels of angiotensin (1-7) [Ang (1-7)] are increased. As cardiac and renal protective effects of Ang (1-7) have been reported, we questioned whether Ang (1-7) contributes to the antiproteinuric effects of ACE-I treatment.
Therefore, we evaluated whether Ang (1-7) infusion reduces proteinuria in a rat model of adriamycin-induced renal disease. In addition, the effect of a selective Ang (1-7) blocker, [D-Ala7]-Ang (1-7) (A779), was investigated in rats treated with the ACE-I, lisinopril (LIS). Six weeks after induction of proteinuria, therapy was started in four different groups: control, Ang (1-7), LIS, and LIS+A779. After two weeks, the rats were sacrificed.
Six weeks after injection of adriamycin, the rats had developed proteinuria of 323±40 mg/24 hours. The proteinuria remained stable in the control group and in the Ang (1-7) group, but was reduced in both LIS and LIS+A779-treated groups. Similarly, blood pressure (BP) was unchanged in the control and the Ang (1-7) groups, but reduced in both the LIS and the LIS+A779 groups. Plasma levels of Ang (1-7) were increased in the Ang (1-7) and in both LIS-treated groups.
We conclude that systemic Ang (1-7) plays no major role in the antiproteinuric and BPlowering effects of ACE-I in this rat model of adriamycin-induced nephrosis.

JRAAS 2005;6:96-101.

PAPEREffects of Intravenous PD 123319 on Haemodynamic and Arterial Stiffness Indices in Healthy Volunteers
Divina G Brillante, Martina T Johnstone, Laurence G Howes

Relatively little is known about the functional expression of cardiovascular angiotensin type 2 (AT2)-receptors in healthy young adult humans. We performed a randomised, placebo-controlled crossover study of the effects of intravenous administration of the selective AT2-receptor antagonist PD 123319 on haemodynamics and arterial stiffness in normal volunteers.
Sixteen normal subjects aged 29.9 ± 13.8 years (range 18–30 years) received an intravenous infusion of PD 123319 (10 mcg/minute for 5 minutes) and placebo, separated by one week. Haemodynamics (cardiac index, stroke index and systemic vascular resistance) were measured non-invasively using a BioZ.com thoracic impedance detection system. Blood pressure was measured from an arm cuff using oscillometry. Stiffness index, a measure of arterial stiffness, was measured using a PulseTrace recorder.
No significant changes in blood pressure (p=0.92), cardiac index (p=0.52), stroke index (p=0.61), systemic vascular resistance index (p=0.32) or stiffness index (p=0.57) was demonstrated following PD 123319 infusion, compared with placebo.
The results of this study do not support the functional presence of cardiovascular AT2-receptors that mediate acute haemodynamic effects in healthy young adults. It remains possible that higher doses of PD 123319 may be required to demonstrate functional cardiovascular AT2-receptors in this population, if they are present.

JRAAS 2005;6:102-106.

EDITORIAL REVIEWThe Launch of the Renin Academy
Luis M Ruilope

The Renin Academy was launched during the first week of September in Stockholm, at the European Society of Cardiology (ESC) annual congress. The Academy aims to encourage understanding of the renin-angiotensin-aldosterone system (RAAS) and to raise awareness of the benefits of optimising RAAS suppression.

JRAAS 2005;6:49.

POPULAR
TOPICEDITORIAL REVIEWPreventing End-Stage Renal Disease in Diabetic Patients – Dual Blockade of the Renin-Angiotensin System (Part II)
Peter Karl Jacobsen

Diabetic nephropathy is a major cause of diabetes related morbidity and mortality. The first part of the current review was published in the last issue of this journal and discussed the impotant role of the renin-angiotensin system (RAS) in diabetic nephropathy and the genetic influence on development of endstage renal disease (ESRD) in diabetic patients. This second part of the review focus on the potential improvement of the current treatment strategy to slow down the loss of kidney function using dual blockade of the RAS with both ACE-inhibitors (ACE-I) and angiotensin II receptor blockers (ARBs). Substantial evidence from short-term studies using surrogate endpoints indicates a beneficial impact of dual blockade of the RAS, not obtainable with single agent blockade alone, both in diabetic and non-diabetic renal disease. This conclusion has been confirmed and extended in a longterm trial with regard to prevention of ESRD in non-diabetic renal disease. Results indicate that dual blockade of the RAS may further slow down, but not arrest progressive loss of renal function. However, studies defining the optimal dose of ACE-I / ARBs without additional adverse effects are essential to ensure relevant comparison with dual blockade therapy. Trials using primary renal endpoints in diabetic nephropathy are still needed, and will finally establish the role of dual blockade of the RAS in a clinical setting.

JRAAS 2005;6:55-68.

COMMENTARYASCOT a Four Horse Race
Peter Sever

JRAAS 2005;6:51-54.

POPULAR
TOPICRENIN REPORTSpotlight on Renin: Therapeutic opportunities for renin inhibitors
Norman K Hollenberg

JRAAS 2005;6:107-110.