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Critical Role of RAAS in Vasculoprotection: New Science
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New aspects of RAAS ACE homologues –ACE2 –Soluble ACE ACE substrates –Ang (1–7) –Ang (1–9) –N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) –Amyloid β-protein Formation of Ang II by non-ACE peptidases ACE signal transduction pathway Fleming I. Circ Res. 2006;98:887-96. RAAS = renin-angiotensin-aldosterone system
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RAAS: Current and potential targets Angiotensinogen Ang I AT 1 RAT 2 RAT 3 RAT 4 RAT (1–7) RmasR Ang (1–9) Ang (1–7)Ang (1–5)Ang II ACE ACE2 NEP Adapted from: Ferrario CM, Strawn WB. Am J Cardiol. 2006;98:121-8. Duprez DA. J Hypertens. 2006;24:983-91. ACE Renin CAGE Cathepsin G Chymase Aldosterone
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Impact of ACEI on ACE signaling pathway Fleming I et al. Physiology. 2005;20:91-5. ACE NH 2 ACE inhibitor Extracellular Cytosol COOH Nucleus Gene expression (ACE, COX-2) CK2 JNK MKK7 P JNK cJun P P P P AP-1 cJun P P Clinical significance of this pathway is under investigation
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ACE metabolism Angiotensin IBradykinin Actions of ACE, kininase II Asp-Arg-Val-Tyr-lie-His-Pro-Phe-His-LeuArg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg Angiotensin II + His-LeuBradykinin 1–7 + Phe-Arg Erdös EG. FASEB J. 2006;20:1034-8.
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ACEI mechanism of benefit: Reduction in clinical events Fleming I et al. Physiology. 2005;20:91-5. Angiotensin I ACE/Kininase II Degradation products Nitric oxide Angiotensin II Angiotensin II ACE inhibitors Bradykinin Bradykinin BP Oxidative stress Endothelial dysfunction Glucose metabolism Plaque growth Fibrous cap stability MMP activity Reduction in clinical events MMP = matrix metalloprotease
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Renin inhibition prevents LVH in animal models *P < 0.05 vs other groups † P < 0.05 vs valsartan 10 mg/kg/d mg/kg/d 10 10.33 ValsartanAliskiren 1010.33 ValsartanAliskiren 9-week-old double transgenic rats (untreated died by week 8) mg/kg/d 0.40 0.20 0.25 0.30 0.35 5 Cardiac hypertrophy index LV wall thickness † 4 3 2 * * cm mg/g * Pilz B et al. Hypertension. 2005;46:569-76.
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Demonstrated benefits of AT 1 R blockade Blood pressure Heart failure symptoms Diabetic renal disease progression Stroke Strauss MH, Hall AS. Circulation. 2006;114:838-54.
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AT 1 R blockade upregulates both Ang II levels and AT 2 R expression Ang I Strauss MH, Hall AS. Circulation. 2006;114:838-54. Ang II AT 2 ACE ARB AT 1 AT 4 Ang I Ang II AT 2 ACE ARB AT 1 AT 4 + Both physiologic and pathologic effects have been proposed for AT 2 R stimulation VasodilationHypertrophy Inflammation
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Postulated role of AT 2 R and MMP-1 in plaque destabilization Strauss MH, Hall AS. Circulation. 2006;114:838-54. Destabilization Rupture ACS Extracellular matrix Leukocyte activation Vascular smooth muscle cells Ang II ARB AT 1 AT 2 MMP-1 Intracellular inflammation Endothelium
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AT 2 R mediates cardiac myocyte enlargement during pressure overload Senbonmatsu T et al. J Clin Invest. 2000;106:R25-9. Agtr2 – /Y AT 2 R-deficient mice and wild-type mice Wild-type Agtr2 – /Y Before2 weeks10 weeks 0 40 80 120 160 200 Aortic-banded mice Control (sham-operated) mice Left ventricular mass (mg) * *P < 0.05
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Sustained decrease in PAI-1 antigen over time with ACEI vs ARB Brown NJ et al. Hypertension. 2002;40:859-65. *BMI = 33.4 ramipril, 31.2 losartan P = 0.043, drug × time interaction PAI-1 antigen (ng/mL) 1346 Weeks 20 10 0 -10 -20 ACEI (ramipril)ARB (losartan) N = 20 obese* patients with hypertension and insulin resistance
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ACEIs and bradykinin oppose Ang II effects Bradykinin B2RB2R Vasodilation NO Prostaglandins EDHF tPA Inactive peptides Ang I Ang II ACE Adapted from Ferrario CM, Strawn WB. Am J Cardiol. 2006;98:121-8. Adapted from Murphey L et al. Eur Heart J Suppl. 2003;5(A):A37-41. ACEI + -- AT 1 R Vasoconstriction Aldosterone secretion Fibrosis Proliferation Oxidative stress Matrix formation Inflammation
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Ang II effect in target organ damage McFarlane SI et al. Am J Cardiol. 2003;91(suppl):30H-7. Angiotensinogen Angiotensin I Angiotensin II Renin ACE Aldosterone (Adrenal/CV tissues) StrokeHF Kidney failure BP VSMC Fat cells Reduced baroreceptor sensitivity
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Potential role of RAAS activation in metabolic syndrome and diabetes Adapted from Henriksen EJ, Jacob S. J Cell Physiol. 2003;196:171-9. Paul M et al. Physiol Rev. 2006;86:747-803. RAAS activation Skeletal musclePancreatic β cells MetS T2DM MetS = metabolic syndrome T2DM = type 2 diabetes Obesity
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RAAS activation in obesity Engeli S et al. Hypertension. 2005;45:356-62. Circulating RAAS, N = 38 menopausal women *P < 0.05 Renin (ng/l) ACE (U/l) Aldosterone (ng/l) Ang II (nmol/l) LeanObese 0 3 6 12 9 0 15 30 60 45 0 90 0.00 0.05 0.10 30 60 LeanObese LeanObeseLeanObese * * *
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Obesity Volume expansion Arterial hypertension Sharma AM. Hypertension. 2004;44:12-19. Leptin Renal medullary compression RAAS activation Sodium reabsorption Renal vasodilation SNS activation SNS = sympathetic nervous system RAAS activation contributes to obesity-related hypertension
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ACEIs: Potential mechanisms of improved glucose metabolism Henriksen EJ, Jacob S. J Cell Physiol. 2003;196:171-9. Angiotensin I ACE/Kininase II Degradation products Nitric oxide Angiotensin II Angiotensin II ACE inhibitors Bradykinin Bradykinin Skeletal muscle blood flow Glucose metabolism
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Role of Ang II in insulin resistance: Focus on signaling pathways Adapted from Henriksen EJ, Jacob S. J Cell Physiol. 2003;196:171-9. BK 2 receptor BK NO NO Glucose transport GLUT-4 trans- location GLUT-4 biosynthesis GLUT-4 Akt1 PI3-KIRS-1 AT 1 receptor Insulin receptor Insulin + + + + + + - - Ang II
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ACEIs improve glucose uptake in peripheral tissue Schiuchi T et al. Hypertension. 2002;40:329-34. *P < 0.05 vs control † P < 0.05 vs temocapril HOE 140 = bradykinin B 2 receptor blocker L -NAME = nitric oxide synthase inhibitor KK-Ay mouse model of T2DM Evidence for bradykinin-mediated effect 500 400 300 200 100 0 Rate constant of 2-[ 3 H]DG uptake ControlTemocaprilTemocapril + HOE 140 Temocapril + L -NAME HOE 140 L -NAME SOLEUS * †
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