Cardiorenal protective effects of vasopeptidase inhibition with omapatrilat in hypertensive transgenic (mREN-2)27 rats

Influence of renovascular hypertension on the distribution of vasoactive intestinal peptide in the stomach and heart of rats

Arterial hypertension is associated with serious dysfunction of the cardiovascular system and digestive system. Given the relevant role of vasoactive intestinal peptide (VIP) in the regulation of digestion process, control of blood pressure and heart rate as well as cardio- and gastro-protective character of the peptide, it appeared worthwhile to undertake the research aimed at immunohistochemical identification and evaluation of VIP-positive structures in the pylorus and heart of hypertensive rats. Up to now, this issue has not been investigated. The experimental model of hypertension in rats according to Goldblatt (two-kidney one clip model of hypertension) was used in the study. The experimental material (pylorus and heart) was collected in the sixth week of the study. VIP-containing structures were evaluated using immunohistochemical and morphometric methods. The analysis of the results showed a significant increase in the number of immunoreactive VIP structures and in the intensity of immunohistochemical staining in the stomach and in the heart of hypertensive rats. Our findings indicate that VIP is an important regulator of cardiovascular and digestive system in physiological and pathological conditions. However, to better understand the exact role of VIP in hypertension further studies need to be carried out.

Cardiorenal protection in experimental hypertension with renal failure: comparison between vasopeptidase inhibition and angiotensin receptor blockade

OBJECTIVE

The aim of the present study was to compare the preventive impact of treatment with a vasopeptidase inhibitor (VPI) with an angiotensin-receptor blocker (ARB) on left ventricular (LV) function and renal damage in rats with renal failure after 5/6 renal ablation (Nx).

METHODS

Rats (n = 15-20, each group) underwent either sham-operation (Sham) or 5/6 renal ablation (Nx). Two additional groups of Nx-animals (groups Nx-VPI and Nx-ARB) were treated with the VPI ilepatril (AVE7688, 30 mg kg(-1) d(-1)) or with the ARB olmesartan (10 mg kg(-1 )d(-1)). Animals were followed for 4 weeks.

RESULTS

Systolic blood pressure (SBP), LV hypertrophy (LVH) and LV end-diastolic pressure (LVEDP) were increased 4 weeks after Nx (p < 0.05). LV pressure rise (+dP/dt/LVPmax), LV pressure fall (-dP/dt/LVPmax), and creatinine clearance decreased, while albuminuria and renal glomerulosclerosis index (GSI) increased with Nx (p < 0.05, respectively). In comparison to Nx, treatment with both VPI and ARB normalized SBP, LVH, LVEDP, +dP/dt/LVPmax, and -dP/dt/LVPmax to Sham control levels. GSI, but not creatinine clearance, was also normalized in response to both treatments. The significant increase in albuminuria observed in Nx (+230-fold versus Sham, p < 0.0001) was partially reduced in Nx-VPI (+47-fold versus Sham, p < 0.0001) and fully abolished in Nx-ARB.

CONCLUSIONS

Both ilepatril and olmesartan conferred strong cardiorenal protective effects in rats with renal failure. While cardioprotection was clearly comparable with both treatment regimens, the ARB provided a better protection against the increase in albuminuria, although renal function and structural kidney changes were similarly affected by the VIP and ARB.

Vascular and neural dysfunctions in obese Zucker rats: effect of AVE7688

The purpose of this study was to determine whether AVE7688 a drug that inhibits both angiotensin converting enzyme and neutral endopeptidase activity protects vascular and nerve functions in an animal model of metabolic syndrome. Obese Zucker rats at 20 weeks of age were treated for 12 weeks with AVE7688. Vasodilation in epineurial arterioles was measured by videomicroscopy and nerve conduction velocity was measured following electrical stimulation. Treatment with AVE7688 improved vascular relaxation in response to acetylcholine and motor and sensory nerve conduction velocity. In obese Zucker rats superoxide levels and nitrotyrosine staining were elevated in the aorta and treatment corrected both conditions. Obese Zucker rats were hypoalgesic in response to a thermal stimulus and demonstrated signs of impaired tactile response and both conditions were significantly improved with treatment. Even though obese Zucker rats are normoglycemic vascular and neural dysfunctions develop with age and can be improved by treatment with AVE7688.

The renal antifibrotic effects of angiotensin-converting enzyme inhibition involve bradykinin B2 receptor activation in angiotensin II-dependent hypertension

OBJECTIVE

The renoprotective action of angiotensin I-converting enzyme inhibitors (ACE-Is) is well established, but the role played by bradykinin (BK) remains unclear. We therefore investigated whether an enhanced BK effect on B2 receptor subtype mediated the antifibrotic effect of ACE-Is and whether neutral endopeptidase (NEP) inhibition, which can blunt BK degradation more effectively than ACE inhibition, provided further renoprotection in a rat model of angiotensin (Ang) II-dependent renal damage.

METHODS

Five-week-old Ren-2 transgenic rats (TGRen2) received, for 8 weeks, a placebo, ramipril (5 mg/kg body weight) or the dual ACE + NEP inhibitor MDL 100,240 (MDL) (40 mg/kg body weight). After 4 weeks, the B2 receptor antagonist icatibant (0.5 mg/kg body weight) was administered on top of active treatment for 4 weeks to 50% of the TGRen2 rats. Blood pressure was measured weekly by a tail-cuff method and, after sacrifice, kidney weight, glomerular volume, density of glomerular profiles were measured; tubulo-interstitial fibrosis, glomerular and perivascular fibrosis were quantified by histomorphometry.

RESULTS

The development of hypertension and tubulo-interstitial fibrosis was prevented by both ramipril and MDL (P = 0.0001 versus placebo); icatibant annulled the latter effect. Glomerular and perivascular fibrosis were unaffected by either ramipril or MDL alone; however, combined treatment with icatibant enhanced glomerular fibrosis (P = 0.0001 versus placebo).

CONCLUSION

Enhanced BK effect on B2 subtype receptors is essential for the prevention of tubulo-interstitial fibrosis with ACE or dual ACE + NEP inhibition in TGRen2 rats.

Interactions between Angiotensin ll and Atrial Natriuretic Peptide in Renomedullary Interstitial Cells: The Role of Neutral Endopeptidase

BACKGROUND/AIMS

Neutral endopeptidase (NEP) inhibition attenuates renal damage in the diabetic kidney, but little is known about the mechanisms of this renoprotective effect.

METHODS

We examined the interaction between angiotensin II (Ang II) and atrial natriuretic peptide (ANP) under low (5 mM) and high (30 mM) glucose conditions, on cell proliferation and extracellular matrix (ECM) synthesis in renomedullary interstitial cells (RMICs) derived from wild-type (WT) and NEP-deficient (NEP-) mice.

RESULTS

Under high glucose conditions, Ang II (10(-6)M) increased cell proliferation (control, 174.3 +/- 16.9; Ang II, 846.3 +/- 91.0 cpm/well) and ECM synthesis (control, 22.3 +/- 3.1; Ang II, 79.0 +/- 9.6 cpm/cell) in RMICs derived from WT and NEP- mice to a similar extent. ANP (10(-7)M) reduced Ang II-induced cell proliferation and ECM synthesis in RMICs derived from both strains, but more efficiently in RMICs derived from NEP- mice. The Ang II-induced cell proliferation and ECM synthesis was attenuated with AT1 receptor blockade, but more efficiently in RMICs-derived NEP- mice.

CONCLUSIONS

This data shows that ANP and AT1 receptor blockade attenuate Ang II-induced RMIC proliferation and ECM synthesis more efficiently in the absence of NEP. These results support the concept that NEP inhibition is beneficial in attenuating abnormal cell growth and ECM metabolism associated with diabetic nephropathy.

Design, synthesis, and application of azabicyclo[X.Y.0]alkanone amino acids as constrained dipeptide surrogates and peptide mimics

Azabicyclo[X.Y.0]alkanone amino acids are challenging synthetic targets and useful tools for studying structure-activity relationships of native peptide ligands. They have been employed to increase potency and stability in conformationally rigid enzyme inhibitors and receptor ligands. Since last reviewed in 1997, activity in their synthesis and application has increased significantly and access is now available to a wider diversity of these peptide mimics. This review focuses on recent syntheses of these heterocyclic amino acids and their application in the investigation of biologically active peptides and peptide mimics.