Cathepsin A Mediates Ventricular Remote Remodeling and Atrial Cardiomyopathy in Rats With Ventricular Ischemia/Reperfusion.

After myocardial infarction, remote ventricular remodeling and atrial cardiomyopathy progress despite successful revascularization. In a rat model of ventricular ischemia/reperfusion, pharmacological inhibition of the protease activity of cathepsin A initiated at the time point of reperfusion prevented extracellular matrix remodeling in the atrium and the ventricle remote from the infarcted area. This scenario was associated with preservation of more viable ventricular myocardium and the prevention of an arrhythmogenic and functional substrate for atrial fibrillation. Remote ventricular extracellular matrix remodeling and atrial cardiomyopathy may represent a promising target for pharmacological atrial fibrillation upstream therapy following myocardial infarction.

Inhibition of CatA: an emerging strategy for the treatment of heart failure.

The lysosomal serine carboxypeptidase CatA has a very important and well-known structural function as well as a, so far, less explored catalytic function. A complete loss of the CatA protein results in the lysosomal storage disease galactosialidosis caused by intralysosomal degradation of ß-galactosidase and neuraminidase 1. However, mice with a catalytically inactive CatA enzyme show no signs of this disease. This observation establishes a clear distinction between structural and catalytic functions of the CatA enzyme. Recently, several classes of orally bioavailable synthetic inhibitors of CatA have been identified. Pharmacological studies in rodents indicate a remarkable influence of CatA inhibition on cardiovascular disease progression and identify CatA as a promising novel target for the treatment of heart failure.

Cardioprotective effects of lixisenatide in rat myocardial ischemia-reperfusion injury studies.

BACKGROUND: Lixisenatide is a glucagon-like peptide-1 analog which stimulates insulin secretion and inhibits glucagon secretion and gastric emptying. We investigated cardioprotective effects of lixisenatide in rodent models reflecting the clinical situation. METHODS: The acute cardiac effects of lixisenatide were investigated in isolated rat hearts subjected to brief ischemia and reperfusion. Effects of chronic treatment with lixisenatide on cardiac function were assessed in a modified rat heart failure model after only transient coronary occlusion followed by long-term reperfusion. Freshly isolated cardiomyocytes were used to investigate cell-type specific mechanisms of lixisenatide action. RESULTS: In the acute setting of ischemia-reperfusion, lixisenatide reduced the infarct-size/area at risk by 36% ratio without changes on coronary flow, left-ventricular pressure and heart rate. Treatment with lixisenatide for 10 weeks, starting after cardiac ischemia and reperfusion, improved left ventricular end-diastolic pressure and relaxation time and prevented lung congestion in comparison to placebo. No anti-fibrotic effect was observed. Gene expression analysis revealed a change in remodeling genes comparable to the ACE inhibitor ramipril. In isolated cardiomyocytes lixisenatide reduced apoptosis and increased fractional shortening. Glucagon-like peptide-1 receptor (GLP1R) mRNA expression could not be detected in rat heart samples or isolated cardiomyocytes. Surprisingly, cardiomyocytes isolated from GLP-1 receptor knockout mice still responded to lixisenatide. CONCLUSIONS: In rodent models, lixisenatide reduced in an acute setting infarct-size and improved cardiac function when administered long-term after ischemia-reperfusion injury. GLP-1 receptor independent mechanisms contribute to the described cardioprotective effect of lixisenatide. Based in part on these preclinical findings patients with cardiac dysfunction are currently being recruited for a randomized, double-blind, placebo-controlled, multicenter study with lixisenatide. TRIAL REGISTRATION: (ELIXA, ClinicalTrials.gov Identifier: NCT01147250).

Antihypertensive and laxative effects by pharmacological inhibition of sodium-proton-exchanger subtype 3-mediated sodium absorption in the gut.

High intestinal sodium absorption is one mechanism of hypertension and constipation. The sodium-proton-exchanger subtype 3 (NHE3) is an important mediator of sodium absorption in the gut. SAR218034 (SAR) is an orally nonabsorbable specific NHE3 inhibitor. The effect of SAR (1 mg/kg per day in chow) on feces sodium excretion, systolic blood pressure via tail cuff, and gene expression of NHE3 in the gut were studied in senescent lean hypertensive rats (spontaneously hypertensive rats-lean, loaded with NaCl 0.7% in drinking water) and in hypertensive, obese, and hyperinsulinemic rats (spontaneously hypertensive rats-obese, not loaded with NaCl). In spontaneously hypertensive rats-lean, inhibition of intestinal NHE3 by SAR increased feces sodium excretion and reduced urinary sodium excretion, whereas absolute sodium balance and serum sodium concentration were not changed. This suggests reduced intestinal sodium absorption in SAR-treated animals and was associated with increased feces water content (58% versus 42% in placebo treated animals; P=0.0001) and reduction in systolic blood pressure from 222 ± 7 to 198 ± 2 mm Hg (P=0.0001). Angiotensin-converting enzyme inhibition by ramipril plus NHE3 inhibition resulted in an additive blood pressure-lowering effect. In spontaneously hypertensive rats-obese, SAR lowered systolic blood pressure but did not modify serum insulin or cholesterol levels. Gene expression of NHE3 was upregulated in the ileum and colon but not in the jejunum of SAR-treated rats. Reduction of intestinal sodium absorption by selective NHE3 inhibition in the gut reduces high blood pressure and increases feces water excretion. Intestinal NHE3 blockade could be a new treatment strategy for elderly patients suffering from high blood pressure and constipation.

Cardiac remodeling and myocardial dysfunction in obese spontaneously hypertensive rats.

BACKGROUND: The additive effects of obesity and metabolic syndrome on left ventricular (LV) maladaptive remodeling and function in hypertension are not characterized. METHODS: We compared an obese spontaneously hypertensive rat model (SHR-ob) with lean spontaneously hypertensive rats (SHR-lean) and normotensive controls (Ctr). LV-function was investigated by cardiac magnetic resonance imaging and invasive LV-pressure measurements. LV-interstitial fibrosis was quantified and protein levels of phospholamban (PLB), Serca2a and glucose transporters (GLUT1 and GLUT4) were determined by immunohistochemistry. RESULTS: Systolic blood pressure was similar in SHR-lean and SHR-ob (252 ± 7 vs. 242 ± 7 mmHg, p = 0.398) but was higher when compared to Ctr (155 ± 2 mmHg, p < 0.01 for both). Compared to SHR-lean and Ctr, SHR-ob showed impaired glucose tolerance and increased body-weight. In SHR-ob, LV-ejection fraction was impaired vs. Ctr (46.2 ± 1.1 vs. 59.6 ± 1.9%, p = 0.007). LV-enddiastolic pressure was more increased in SHR-ob than in SHR-lean (21.5 ± 4.1 vs. 5.9 ± 0.81 mmHg, p = 0.0002) when compared to Ctr (4.3 ± 1.1 mmHg, p < 0.0001 for both), respectively. Increased LV-fibrosis together with increased myocyte diameters and ANF gene expression in SHR-ob were associated with increased GLUT1-protein levels in SHR-ob suggestive for an upregulation of the GLUT1/ANF-axis. Serca2a-protein levels were decreased in SHR-lean but not altered in SHR-ob compared to Ctr. PLB-phosphorylation was not altered. CONCLUSION: In addition to hypertension alone, metabolic syndrome and obesity adds to the myocardial phenotype by aggravating diastolic dysfunction and a progression towards systolic dysfunction. SHR-ob may be a useful model to develop new interventional and pharmacological treatment strategies for hypertensive heart disease and metabolic disorders.

Novel ß-amino acid derivatives as inhibitors of cathepsin A.

Cathepsin A (CatA) is a serine carboxypeptidase distributed between lysosomes, cell membrane, and extracellular space. Several peptide hormones including bradykinin and angiotensin I have been described as substrates. Therefore, the inhibition of CatA has the potential for beneficial effects in cardiovascular diseases. Pharmacological inhibition of CatA by the natural product ebelactone B increased renal bradykinin levels and prevented the development of salt-induced hypertension. However, so far no small molecule inhibitors of CatA with oral bioavailability have been described to allow further pharmacological profiling. In our work we identified novel ß-amino acid derivatives as inhibitors of CatA after a HTS analysis based on a project adapted fragment approach. The new inhibitors showed beneficial ADME and pharmacokinetic profiles, and their binding modes were established by X-ray crystallography. Further investigations led to the identification of a hitherto unknown pathophysiological role of CatA in cardiac hypertrophy. One of our inhibitors is currently undergoing phase I clinical trials.

AVE8134, a novel potent PPARα agonist, improves lipid profile and glucose metabolism in dyslipidemic mice and type 2 diabetic rats.

AIM: AVE8134 is a structurally novel potent PPARα agonist. The aim of this study is to investigate the efficacy of AVE8134 on lipid profile and glucose metabolism in dyslipidemic mice and type 2 diabetic rats. METHODS: A cell based PPAR Gal4 transactivation assay was constructed for testing the activities of AVE8134 at 3 different PPAR isoforms in vitro. Transgenic human Apo A1 (hApo A1) mice and insulin-resistant ZDF rats were used to evaluate the effects of AVE8134 in vivo. RESULTS: AVE8134 was a full PPARα dominated PPAR agonist (the values of EC(50) for human and rodent PPARα receptor were 0.01 and 0.3 µmol/L, respectively). AVE8134 was not active at PPARδ receptor. In female hApo A1 mice, AVE8134 (1-30 mg·kg(-1)·d(-1), po for 12 d) dose-dependently lowered the plasma triglycerides, and increased the serum HDL-cholesterol, hApo A1 and mouse Apo E levels. In female ZDF rats, AVE8134 (3-30 mg·kg(-1)·d(-1) for 2 weeks) improved insulin-sensitivity index. In pre-diabetic male ZDF rats (at the age of 7 weeks), AVE8134 (10 mg·kg(-1)·d(-1) for 8 weeks) produced an anti-diabetic action comparable to rosiglitazone, without the PPARγ mediated adverse effects on body weight and heart weight. In male ZDF rats (at the age of 6 weeks), AVE8134 (20 mg·kg(-1)·d(-1) for 12 weeks) increased mRNA levels of the target genes LPL and PDK4 about 20 fold in the liver, and there was no relevant effect with rosiglitazone. CONCLUSION: AVE8134 improves lipid profile and glucose metabolism in dyslipidemic mice and type 2 diabetic rats.

Pharmacological characterization of SAR407899, a novel rho-kinase inhibitor.

Recent advances in basic and clinical research have identified Rho kinase as an important target potentially implicated in a variety of cardiovascular diseases. Rho kinase is a downstream mediator of RhoA that leads to stress fiber formation, membrane ruffling, smooth muscle contraction, and cell motility. Increased Rho-kinase activity is associated with vasoconstriction and elevated blood pressure. We identified a novel inhibitor of Rho kinase (SAR407899) and characterized its effects in biochemical, cellular, tissue-based, and in vivo assays. SAR407899 is an ATP-competitive Rho-kinase inhibitor, equipotent against human and rat-derived Rho-kinase 2 with inhibition constant values of 36 nM and 41 nM, respectively. It is highly selective in panel of 117 receptor and enzyme targets. SAR407899 is approximately 8-fold more active than fasudil. In vitro, SAR407899 demonstrated concentration-dependent inhibition of Rho-kinase-mediated phosphorylation of myosin phosphatase, thrombin-induced stress fiber formation, platelet-derived growth factor-induced proliferation, and monocyte chemotactic protein-1-stimulated chemotaxis. SAR407899 potently (mean IC(50) values: 122 to 280 nM) and species-independently relaxed precontracted isolated arteries of different species and different vascular beds. In vivo, over the dose range 3 to 30 mg/kg PO, SAR407899 lowered blood pressure in a variety of rodent models of arterial hypertension. The antihypertensive effect of SAR407899 was superior to that of fasudil and Y-27632. In conclusion, SAR407899 is a novel and potent selective Rho-kinase inhibitor with promising antihypertensive activity.

The peroxisome proliferator-activated receptor-alpha (PPAR-alpha) agonist, AVE8134, attenuates the progression of heart failure and increases survival in rats.

AIM: To investigate the efficacy of the peroxisome proliferator-activated receptor-alpha (PPARalpha) agonist, AVE8134, in cellular and experimental models of cardiac dysfunction and heart failure. METHODS: In Sprague Dawley rats with permanent ligation of the left coronary artery (post-MI), AVE8134 was compared to the PPARgamma agonist rosiglitazone and in a second study to the ACE inhibitor ramipril. In DOCA-salt sensitive rats, efficacy of AVE8134 on cardiac hypertrophy and fibrosis was investigated. Finally, AVE8134 was administered to old spontaneously hypertensive rats (SHR) at a non-blood pressure lowering dose with survival as endpoint. In cellular models, we studied AVE8134 on hypertrophy in rat cardiomyocytes, nitric oxide signaling in human endothelial cells (HUVEC) and LDL-uptake in human MonoMac-6 cells. RESULTS: In post-MI rats, AVE8134 dose-dependently improved cardiac output, myocardial contractility and relaxation and reduced lung and left ventricular weight and fibrosis. In contrast, rosiglitazone exacerbated cardiac dysfunction. Treatment at AVE8134 decreased plasma proBNP and arginine and increased plasma citrulline and urinary NOx/creatinine ratio. In DOCA rats, AVE8134 prevented development of high blood pressure, myocardial hypertrophy and cardiac fibrosis, and ameliorated endothelial dysfunction. Compound treatment increased cardiac protein expression and phosphorylation of eNOS. In old SHR, treatment with a low dose of AVE8134 improved cardiac and vascular function and increased life expectancy without lowering blood pressure. AVE8134 reduced phenylephrine-induced hypertrophy in adult rat cardiomyocytes. In HUVEC, Ser-1177-eNOS phosphorylation but not eNOS expression was increased. In monocytes, AVE8134 increased the expression of CD36 and the macrophage scavenger receptor 1, resulting in enhanced uptake of oxidized LDL. CONCLUSION: The PPARalpha agonist AVE8134 prevents post-MI myocardial hypertrophy, fibrosis and cardiac dysfunction. AVE8134 has beneficial effects against hypertension-induced organ damages, resulting in decreased mortality. The compound exerts its protective properties by a direct effect on cardiomyocyte hypertrophy, but also indirectly via monocyte signaling and increased endothelial NO production.Acta Pharmacologica Sinica (2009) 30: 935-946; doi: 10.1038/aps.2009.58; published online 8 June 2009.

Inhibition of renin angiotensin system decreases renal protein oxidative damage in diabetic rats.

Renin angiotensin system (RAS) worsens diabetic nephropathy (DN) by increasing oxidative stress. We compared the effect of three different RAS inhibitors: the angiotensin converting enzyme inhibitor Ramipril, the vasopeptidase inhibitor AVE7688 and the angiotensin receptor (AT1) antagonist Losartan on the formation of oxidative and carbonyl stress derived protein modifications in kidney from Zucker obese hyperglycemic rats (ZDFn Gm-fa/fa). Gas chromatography-mass spectrometry was used to measure representative markers of several protein oxidative pathways: direct oxidation [dinitrophenylhydrazine reactive carbonyls (DNP), glutamic (GSA), and aminoadipic (AASA) semialdehydes], mixed glyco- and lipoxidation [N(epsilon)-carboxyethyl-lysine (CEL) and N(epsilon)-(carboxymethyl)-lysine (CML)] and lipoxidation-[N(epsilon)-(malondialdehyde)-lysine-(MDAL)], as well as renal fatty acid composition. Urinary albumin (a marker of DN), DNP, GSA, and MDAL levels, were increased in all obese rats and were dose dependently decreased by AVE7688 whereas Ramipril and Losartan were less efficient. These results show that RAS inhibition improves DN at several levels, independently of its effects on blood pressure and glycemic control, via mechanisms depending of renal oxidative stress.

Blood pressure-independent effect of long-term treatment with the soluble heme-independent guanylyl cyclase activator HMR1766 on progression in a model of noninflammatory chronic renal damage.

Nitric oxide formation is impaired in chronic renal failure. The renoprotective effects of a nonhypotensive dose of HMR1766, a direct activator of the heme enzyme soluble guanylyl cyclase was studied in comparison to an ACE-i in the remnant kidney model. Male Sprague-Dawley rats were subtotally nephrectomized (SNX) or sham operated (sham) and left untreated or started on treatment with HMR1766 or ACE-i in non-hypotensive doses. BP, albumin excretion and parameters of renal damage were analyzed. After a 12-week study, urinary albumin excretion was significantly higher in untreated SNX than in sham; this increase was prevented by ACE-i and ameliorated by HMR1766. Relative kidney and left ventricular weight were significantly higher in untreated SNX compared to sham; these changes were completely prevented by HMR1766. In untreated SNX, glomerulosclerosis (1.02 +/- 0.13) was significantly higher than in sham (0.12 +/- 0.04), SNX+HMR1766 (0.27 +/- 0.04) and SNX+ACE-i (0.46 +/- 0.06). Tubulointerstitial changes went in parallel. Increased glomerular cell number after SNX (71.5 +/- 14 vs. 60 +/- 7.3 in sham) was prevented by HMR1766 (55.7 +/- 7.3), but not by ACE-i (66.6 +/- 9). The results document beneficial BP-independent HMR1766 effects on kidney structure and urinary albumin excretion in a noninflammatory model of renal failure and may argue for a novel therapeutic principle.

Decreased wheel-running activity in hamsters post myocardial infarction.

Reduced exercise capacity is a key symptom and an independent determinant of mortality in patients with heart failure. We analyzed the running activity of hamsters with cardiac dysfunction after myocardial infarction. In 39 male Syrian hamsters aged 10 to 12 weeks, a myocardial infarction (MI) was produced by permanent ligation of the left coronary artery. Spontaneous running activity in a wheel was monitored daily. After four weeks, left ventricular (LV) hemodynamics (catheter tip manometry) were measured at baseline and during inotropic stimulation (isoprenaline 0.03, 0.1 and 0.3 microg/kg/min i.v.). LV infarct size was quantified using planimetry. Four weeks post MI, daily running distance was reduced stepwise in animals with small (4-15% of LV: 9.8 +/- 3.4 km/d) and large (> 15% of LV: 7.5 +/- 3.5 km/d) MI, compared to sham-operated hamsters (11.5 +/- 1.5 km/d). Similar reductions were observed in maximum speed and distance of longest running period. MI size influenced daily running distance, maximum speed, and longest running period (linear correlations, all p < 0.05). MI size also impaired LV systolic and diastolic function under isoprenaline stimulation. The results suggest that myocardial infarction reduces running capacity and isoprenaline stimulated LV function in hamsters, mimicking impaired exercise performance in patients with heart failure. Analysis of running activity in hamsters with myocardial infarction offers a unique opportunity for non-invasive and serial functional assessment of heart failure in the experimental setting.

Vasopeptidase inhibition prevents target organ damage and improves survival in spontaneously hypertensive rats.

BACKGROUND: Vasopeptidase inhibition has been shown to be an effective antihypertensive principle but its long-term effects on hypertensive target organ damage are not known. We investigated the myocardial, vascular and renal effects of chronic vasopeptidase inhibition in arterial hypertension. METHODS AND RESULTS: One hundred and thirty-nine male spontaneously hypertensive rats aged 15 months were treated chronically with either the pure angiotensin-converting enzyme (ACE) inhibitor, ramipril (1 mg/kg/d in drinking water, n=46), or the vasopeptidase inhibitor AVE7688 (30 mg/kg/d in chow, n=46), or placebo (n=47) and followed up until they died. After six months, both ramipril and AVE7688 had markedly reduced plasma ACE activity, normalised blood pressure (BP), reduced left ventricular mass and improved systolic function to similar extents. Acetylcholine mediated relaxation of aortic rings was improved by both ramipril and AVE7688. There was substantial albuminuria in the placebo group (albumin-to-creatinine ratio 107+/-54 microg/mg), which was significantly reduced by ramipril to 57+/-34 microg/mg, and practically abolished in the AVE7688 group (22+/-12 microg/mg, p<0.05 vs. placebo and ramipril). Tubulo-interstitial damage (semi-quantitative score) was significantly reduced by AVE7688 and ramipril. Overall mortality was markedly reduced in the ramipril and AVE7688 groups (13% and 16% at six months, respectively), both p<0.05 vs. placebo (71%). CONCLUSIONS: Vasopeptidase inhibition effectively controls BP and reduces myocardial, vascular and renal target organ damage, resulting in a markedly prolonged survival. At similar degrees of plasma ACE inhibition, AVE7688 compared to ramipril offers superior protection against hypertensive kidney damage.

Impaired left ventricular relaxation in type 2 diabetic rats is related to myocardial accumulation of N(epsilon)-(carboxymethyl) lysine.

Myocardial dysfunction in the absence of myocardial ischemia is frequent in patients with diabetes mellitus but the underlying pathomechanism is unclear. We investigated whether accumulation of advanced glycation end products (AGEs) in the diabetic myocardium is related to its functional abnormalities. In 11 male homozygous Zucker diabetic fatty rats (ZDF/Gmi-fa/fa) aged 37 weeks (OBESE) and 11 non-obese, non-diabetic littermates (LEAN), we measured left ventricular function (pressure-volume catheter) and levels of N(epsilon)-(carboxymethyl) lysine (CML), a prototypical AGE, in serum and the left ventricle (competitive enzyme linked immuno-assay). Overt diabetes mellitus (HbA1c > 9%) was present in all OBESE animals but not in LEAN. Systolic left ventricular function was not different between the groups, but the markers of left ventricular relaxation, dP/dt(min) and the relaxation constant tau, were impaired in OBESE. In parallel, CML levels were increased in serum (273 +/- 15 vs. 197 +/- 10 ng/ml, p<0.05) and in the left ventricle (18.4 +/- 1.1 vs. 12.5 +/- 2.0 ng/mg protein, p < 0.05) in OBESE compared to LEAN. There was a linear correlation between tau and the left ventricular CML levels (r = 0.65; p < 0.05). We conclude that type 2 diabetes is associated with predominant left ventricular diastolic dysfunction. Myocardial accumulation of advanced glycation end products may contribute to relaxation abnormalities in type 2 diabetes.

Biochemistry and pharmacology of novel anthranilic acid derivatives activating heme-oxidized soluble guanylyl cyclase.

The heme-enzyme soluble guanylyl cyclase (sGC) is an ubiquitous NO receptor, which mediates NO downstream signaling by the generation of cGMP. We studied the mechanism of action of the anthranilic acid derivatives 5-chloro-2-(5-chloro-thiophene-2-sulfonylamino-N-(4-(morpholine-4-sulfonyl)-phenyl)-benzamide sodium salt (HMR1766) (proposed international nonproprietary name, ataciguat sodium) and 2-(4-chloro-phenylsulfonylamino)-4,5-dimethoxy-N-(4-(thiomorpholine-4-sulfonyl)-phenyl)-benzamide (S3448) as a new class of sGC agonists. Both compounds activated different sGC preparations (purified from bovine lung, or crude from human corpus cavernosum) in a concentration-dependent and quickly reversible fashion (EC50 = 0.5-10 microM), with mixed-type activation kinetics. Activation of sGC by these compounds was additive to activation by NO donors, but instead of being inhibited, it was potentiated by the heme-iron oxidants 1H-[1,2,4]-oxdiazolo[3,4-a]quinoxalin-1-one (ODQ) and 4H-8-bromo-1,2,4-oxadiazolo(3,4-d) benz(b)(1,4)oxazin-1-one (NS2028), suggesting that the new compounds target the ferric heme sGC isoform. Protoporphyrin IX acted as a competitive activator, and zinc-protoporphyrin IX inhibited activation of heme-oxidized sGC by HMR1766 and S3448, whereas heme depletion of sGC by Tween 20 treatment reduced activation. Both compounds increased cGMP levels in cultured rat aortic smooth muscle cells; induced vasorelaxation of isolated endothelium-denuded rat aorta, porcine coronary arteries, and human corpus cavernosum (EC50 1 to 10 microM); and elicited phosphorylation of the cGMP kinase substrate vasodilator-stimulated phosphoprotein at Ser239. HMR1766 intravenous bolus injection decreased arterial blood pressure in anesthetized pigs. All of these pharmacological responses to the new compounds were enhanced by ODQ and NS2028. Our findings suggest that HMR1766 and S3448 preferentially activate the NO-insensitive heme-oxidized form of sGC, which exists to a variable extent in vascular tissues, and is a pharmacological target for these new vasodilator drugs.

Ramipril prevents extracellular matrix accumulation in cerebral microvessels.

OBJECTIVES: The stroke-prone spontaneously hypertensive rat is a genetic model of severe hypertension with secondary vascular alterations. The aim of this study was to determine the influence of chronic hypertension and ramipril treatment on the extracellular matrix in the cerebral microvasculature. METHODS: The study consisted of three groups: six normotensive Wistar rats, six untreated spontaneously hypertensive rats, and six hypertensive rats treated with an antihypertensive dose of ramipril (1 mg kg(-1)day(-1)) for 6 months. Alterations in the extracellular matrix were examined by western blot, immunohistochemistry, and immunofluorescence using an antibody against collagen type IV. RESULTS: Western blotting showed a reduction of the total amount of collagen type IV by 50% in the ramipril group compared with the untreated hypertensive group (51.0+/-9.3% reduction, p = 0.0004). Compared with the untreated hypertensive rats, ramipril treatment prevented a loss of vessel density in the cortex (23.4+/-1.0 versus 20.4+/-2.0, p < 0.0001) and revealed a reduction of the amount of collagen per vessel (0.54+/-0.04 versus 0.60+/-0.08, p = 0.037). The ratio between the vessel wall and the lumen (0.69+/-0.08 versus 1.31+/-0.13) and the relative collagen intensity was lowered in the ramipril group (18.1+/-4.7% reduction, p < 0.0001). Using these methods the ramipril group showed similar results than the normotensive group. DISCUSSION: Ramipril treatment completely prevented these hypertensive vascular changes. These results may stimulate a therapeutic approach with angiotensin converting enzyme inhibition in human hypertensive small vessel disease.

Restoration of endothelial function via enhanced nitric oxide synthesis after long-term treatment of raloxifene in adult hypertensive rats.

Raloxifene (CAS 84449-90-1, RAL), a selective estrogen receptor modulator (SERM) effective for the prevention of post-menopausal osteoporosis, also has been shown to acutely stimulate nitric oxide (NO) synthesis associated with improved endothelium-dependent relaxation. The effect of a 3-month RAL treatment (10 mg/kg/d) on basal blood pressure, measured via the carotid artery, and its challenge with increasing doses of intravenous bradykinin (1, 3 and 10 nmol/kg) was investigated. Furthermore, aortic NO bioavailability and relaxation in 9-month-old male and female ovarectomized (OVX) spontaneously hypertensive rats (SHR) was tested. Calcium ionophore stimulated NO release from aortic endothelial cells and aortic superoxide (O2-) production was directly assessed by using electrochemical nanosensors. Relaxation studies were performed with acetylcholine (10(-8) to 10(-5) mol/L) following precontraction with phenylephrine (10(-7) mmol/L). Whereas basal blood pressure (BP) was not significantly decreased in RAL treated SHR, the dose-dependent challenge with bradykinin induced an enhanced BP reduction in either gender. In contrast to female animals, aortic segments from RAL treated male animals showed significantly improved relaxaSHR) to 360 +/- 15 nmol/L. Vice versa, O2- was decreased from 110 +/- 15 to 22 +/- 1 nmol/L. In female SHR, ovarectomy led to an increase/decrease of NO/O2- from 130 +/- 5 to 180 +/- 10 nmol/L and 82 +/- 7 to 68 +/- 3 nmol/L, respectively. These effects were significantly amplified by RAL treatment (NO: 370 +/- 10 and O2-: 25 +/- 2 nmol/L). The results show that long-term treatment with RAL has beneficial affects on the cardiovascular system in old male and female OVX SHR via an increased NO bioavailability.

ACE inhibition reduces activity of the plasminogen/plasmin and MMP systems in the brain of spontaneous hypertensive stroke-prone rats.

The spontaneously hypertensive stroke-prone rat (SHR-SP) is an experimental model of malignant hypertension which lead to secondary alterations of the extracellular matrix. Our aim was to determine ACE-inhibitor related changes of proteases involved in the reconstruction of the extracellular matrix in the brain. Twelve SHR-SP rats were randomized into two groups. Each group was treated with either an antihypertensive dose of ramipril or placebo for 6 months. Brain tissue plasminogen activator (t-PA) and urokinase (u-PA) were quantified by using casein-dependent plasminogen zymography, matrix metalloproteinase (MMP)-2 and MMP-9, by MMP-zymography, and tissue inhibitor of MMP (TIMP)-1 and -2, by reverse zymography. The amounts of u-PA, t-PA, and MMPs were significantly reduced in animals treated with ACE inhibitor. Plasminogen zymography showed a 39% reduction of u-PA in the basal ganglia (p < 0.0001); t-PA expression was reduced by 26% in the cortex and by 33% in the basal ganglia (p < 0.0001). MMP-2 expression was reduced by 15% in the cortex (p < 0.05) and by 10% in the basal ganglia (p < 0.05); MMP-9 expression significantly decreased by 37% in the cortex and by 25% in the basal ganglia (p < 0.0001 each). No differences were observed in the amount of TIMP-1 or TIMP-2. These findings provide new insights into the biochemical mechanisms underlying extracellular matrix proliferation and its modulation by ACE inhibitors. Therapeutic alterations that influence the proteolytic systems might prove important in the prevention of extracellular matrix accumulation and secondary microvascular vessel wall changes.

Down-regulation of calpain 9 is linked to hypertensive heart and kidney disease.

Calpains are a family of 14 intracellular calcium-dependent proteases, which have been implicated in cardiovascular diseases. We aimed to analyze specifically the expressional regulation of the different calpain isoforms in hypertensive target organ damage. Using real-time PCR, we found calpain 6 and 9 down-regulated by more than 50% and the endogenous calpain inhibitor calpastatin up-regulated by 225%, respectively, in the hearts of Dahl salt-sensitive rats on a high salt (4% NaCl) compared to normal salt diet. On the protein level, calpain 9 but not calpastatin was regulated in the hypertensive target organs heart and kidney. Moreover, the myocardial expression of calpain 9 protein was inversely linked to left ventricular mass (r= -0.93, p<0.01), and renal expression of calpain 9 protein correlated inversely with albuminuria (r= -0.82, p<0.05). In the aorta, there was no regulation of calpain 9 on the protein level. We conclude that differential regulation of calpain 9 may play a role in hypertensive target organ damage.

Nephroprotection in Zucker diabetic fatty rats by vasopeptidase inhibition is partly bradykinin B2 receptor dependent.

1. Vasopeptidase inhibition (i.e., the simultaneous inhibition of both angiotensin-converting enzyme (ACE) and neutral endopeptidase) can ameliorate diabetic nephropathy. We investigated whether this nephroprotection is mediated by the bradykinin B2 receptor. 2. In all, 43 obese Zucker diabetic fatty (ZDF/Gmi-fa/fa) rats aged 21 weeks were separated into four groups and treated for 26 weeks with either placebo, the bradykinin B2 receptor antagonist icatibant (500 microg kg(-1) day(-1) s.c. infusion), the vasopeptidase inhibitor AVE7688 (45 mg kg(-1) day(-1) in chow), or AVE7688 plus icatibant. Nephropathy was assessed as albuminuria at age 31 and 39 weeks, and by histopathologic scoring at the end of the treatment period. 3. All animals had established diabetes mellitus (blood glucose >20 mmol l(-1)) and marked albuminuria at baseline. Blood glucose was not influenced by any treatment. Icatibant alone did not influence albuminuria (8.6+/-1.6 vs placebo 9.5+/-1.3 mg kg(-1) h(-1)). AVE7688 reduced albuminuria at week 31 markedly to 1.1+/-0.1 mg kg(-1) h(-1) and reduced glomerular and tubulo-interstitial kidney damage at week 47. In the AVE7688 plus icatibant group, proteinuria was significantly higher than in the AVE7688 only group (2.0+/-0.6 mg kg(-1) h(-1)), but still reduced compared to placebo. In addition, icatibant partly antagonized the tubulo-interstitial protection mediated by AVE7688. 4. We conclude that vasopeptidase inhibition provides nephroprotection in rats with type II diabetic nephropathy, which is partly mediated by bradykinin B2 receptor activation.