The Role of Natriuretic Peptides in Cardiovasuclar System. Zhu MZ et al

Transcription

1 The Role of Natriuretic Peptides in Cardiovasuclar System Zhu MZ et al

2 1. Historical Background 1620s: Harvey. William put forward the theory of Blood Circulation.. From then on, heart was taken as a blood pump,, the organ provides impetus for blood circulation. 1981: For the first time, de Bold et al.. demonstrated the atrial extract contained an extremely powerful inhibitor of renal tubular NaCl reabsorption.. (Life Sciences, 1981) 1983 : The amino acid sequence of the atrial peptide was determined. It is a 28 amino acid peptide with diuretic and natriuretic activity. It was called Atrial natriuretic Peptide(ANP), or atrial natriuretic factor ( ANF), cardionatrin.

3 2.Atrial Natriuretic Peptide Family 1) Members ANP (atrial( natriuretic peptide) BNP (brain natriuretic peptide) CNP (C-type natriuretic peptide) New members: DNP, ventricle natriuretic peptide, VNP (vasonatrin( peptide)

4 2)Chemistry Fig.1. Chemical structures of natriuretic peptides. The common sequences are shaded black.

5 Fig. 2. Amino acid sequences of natriuretic peptides from different species. Note: Identical residues in ANP and BNP are boxed

6 3) Distribution ANP: heart, lungs, aortic arch, brain, kidney, adrenals, gastrointestinal tract, thymus, eye BNP: ventricle,, brain, amnion CNP: vascular endothelium,, brain, kidney

7 3. NPs signal transduction pathway Fig. 4 Receptors for natriuretic peptides

8 Fig. 5 The NP signal transducti on system (2001, cellualr Signalling)

9 Receptor NPR-A NPR-B NPR-C Mol.Weight(kDa) ~ 130 ~140 ~ 60 Receptor structure Extracellular binding domain + single transmembrane domain and a cytoplasmic protein kinase domain Extracellular binding domain + single transmembrane domain and a cytoplasmic protein kinase domain Extracellular binding domain + single transmembrane domain Signalling mechanism GC activation GC activation? AC inhibition Gene/chromosome 1q21-q22 9p12-p21 5p14-p13 Agonist ANP BNP>>CNP CNP>ANP BNP ANP>CNP >BNP Antagonist HS HS C-ANP4-23 Function Pharmacological effects of NPs Pharmacological effects of NPs Elimination of NPs

10 Distribution of NP receptors widely distributed throughout the tissues of the body including kidney, Vascular smooth muscle, Adrenal gland, Intestine, Heart, Brain, Bone, Lung, and others

11 4. Pharmacokinetics Adiministration They could be given as an infusion, but this is seldom the preferred option because of the exorbitant cost. Other drugs that affect the NPs are being investigated.

12 Elimination t 1/2 = 2-4 min (ANP in human) Metabolic clearance rates: ml/min/kg Elimination of NPs occurs by three main mechanisms: enzyme metabolism, clearance receptor and urinary excretion.

13 Enzyme metabolism NEP (neutral endopeptidase) degradative enzyme of all NPs found in: proximal convoluted tubule, lungs, intestine, seminal vesicles, neutrophils,etc. NEP degrades NPs in the rank order: CNP > ANP > BNP Note: ANP is also metabolized by certain other enzymes such as insulin degrading enzyme

14 Clearance receptors Trans-membrane receptor(npr NPR-C) Binding to NPs in the order: ANP > CNP > BNP

15 Urinary excretion Occurs only to a limited extent compared to the other elimination pathways If there is inhibition of other pathways, urinary excretion

16 5. Biological Actions Diuresis and Natriuresis Vasodilatation and antihypertension antimitogenesis and growth inhibition counteract renin-angiotensin angiotensin-aldosterone- system(raas) Endothelin System(ETs) Sympathetic system et al.

17 6. Factors affecting NPs secretion Table Factors affecting NPs secretion Acute release Chronic stimulation Hormonal stimuli: Stretch myocardial cells Increased cardiac transmural pressure Angiotensin II Glucocorticoids Catecholamines Endothelin-1 Thyroid hormones Prostaglandins Vasopression

18 7. Brief Summary (J Hypertension, 2001)

19 8.Physiological Role They are key regulators in the homeostasis of salt and water excretion and in the maintenance of blood pressure and volume. Evidence: iv. HS , Sodium excretion rate Renin Release hyporesponse to acute volume loading coronary vascular resistance coronary blood flow Diastolic Function ANP knockout mice: salt sensitive hypertension ANP over expression:persistent hypotension

20 9.Clinical Roles 1) Pathophysiologic role of the NPs in Chronic Heart failure(chf) NPs are activated in early CHF (asymptom( asymptom) ) and contribute to the maintenance of sodium balance, blood pressure and volume. NPs system play a key role in preserving the compensated state of early heart failure.

21 NPs vasodilatroy and diuretic properties Growth inhibition afterload and pre-load interstitial fibrosis and myocardial hypertrophy Counteract the vasoconstrictor- antinatriuretic system

22 Severe CHF is a syndrome characterized by sodium retention, activation of both NP system and RAAS. The Renal hyporesonsiveness to NPs plays an important role in severe HF, thus contributing to disease progression. Decreased renal perfusion pressure increased sympathetic nerve activity receptor downreguation enhanced enzymatic degradation of NPs by neutral endopeptidase and increased activity of functional antagonists to the NPs such as RAAS, angiotensin II.

23 2) Diagnostic and Prognostic Serum marker in CHF Circulating ANP and BNP correlates with the functional class of CHF and provides prognostic data. N-terminus of pro-anp was more sensitive and specific than C-terminal C ANP. BNP was superior to either N-terminal N or C-terminal C ANP as a marker for ventricular systolic or diastolic dysfunction and ventricular hypertrophy in patients with, or at risk for, cardiac disease.

24 3) Strategies for employing NPs in Pharmacotherapy 对症 强心药 CHF 交感神经 β- 受体阻断剂 对因 RAAS ETs NPs ACEI ET-R 阻断剂 利钠利尿扩血管降压半衰期很短

25 Benefits :Its vasodilatory action without the reflex activation of the sympathetic nervous system and its natriuretic action without the activation of the RAAS. Limiting factors: low oral biovailability short half-life life time NP sensitivity decreasing with age

26 Methods: supply exogenous NPs parenteral infusion nature NPs, NPR-A A analogue such as A68828 and etc. Elevating levels of endogenous NPs preventing the clearance of NPs (NEP( inhibitors) increasing the gene expression of NPs (gene therapy)

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28 10 New members of NPs DNP (Dendroaspis( natriuretic peptide) 38-amino amino-acid acid peptide (7-amino amino-acid acid N-terminus, N a 17-amino amino-acid acid disulfide ring and a 14-amino amino-acid acid C-terminus. C ) from Dendroaspis angusticeps. Dendroaspis angusticeps(green mamba snake), porcine, human Ventricle natriuretic peptide 36-,, 25-amino amino-acid acid peptide eel rainbow trout VNP(vasonatrin peptide) 27-amino amino-acid acid pepitde a man-made made peptide (1993. Wei CM et al.)

29 VNP (Vasonatrin Peptide) Structure: : VNP is a chimera of ANP and CNP Biological Action: VNP possesses the venodilating actions of CNP, the natriuretic actions of ANP and unique arterial vasodilating actions.

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31 Diuresis Natriuresis: : ANP > VNP > CNP Arterial vasodilatation: VNP >ANP >CNP Venous vasodilatation: VNP > CNP >ANP Antiproliferative effects (cardiac fibroblasts, vascular smooth muscle cells) VNP >ANP CNP Other actions: : inhibits hypertrophy and induces apoptosis in cultured cardiac myocytes

32 Therapeutic potential: VNP mimics the pharmacological actions of both a diuretic and nitroglycerin for its potent venodilating and natriuretic actions. It may has long half-life life time and prolonged actions because it is a unique stucture that is not found in nature.

33 The therapeutic role of VNP in hypoxic heart disease Main Results

34 1.NPs has significant inhibitory effects on hypoxia-induced pulmonary hypertension, and VNP is the strongest one.

35 ± ± ± ± ± ±44 44 HR HR ±10 10 a ± ± ± ±10 10 bde bde ±11 11 PVR PVR 24 24± ± ± ± ±4 ac ac 23 23±4 PBF PBF ±0.3a 0.3a ± ± a ± ± bce bce ± mpap mpap after after before before after after before before after after before before ANP ANP CNP CNP VNP VNP Parameters Parameters VNP VNP 等三种钠尿肽对低氧性肺动脉高压大鼠肺循环的影响等三种钠尿肽对低氧性肺动脉高压大鼠肺循环的影响

36 2.VNP has significant vasodilating effects on both artery and vein, which is stronger than both ANP and CNP.

37 VNP 对大鼠肺动脉的舒张作用

38 0 * * * * ** ** ** ** A B Relaxation (%) VNP VNP+MB VNP+HS VNP+TEA * * C 对照 60mV VNP 1500ms Concentration of VNP (log 10 mol/l) 500pA 500ms TEA+VNP -70mV -60mV HS TEA 和 MB 对 VNP 舒张人乳内动脉效应的影响 VNP 增加大鼠肠系膜动脉平滑肌细胞钾电流

39 3.VNP has inhibitory effects on the growth of cardiac myocytes, fibroblasts and smooth muscle cells.

40 VNP 抑制去甲肾上腺素和低氧诱导的心肌细胞肥大 300 * 蛋白含量 (ug/ml) Total protein (ug/well) H-Leu incoporation(cpm/well) 对照组 NE 组 VNP+NE 组 0 0 Concentration of VNP(mol/L) Concentration of VNP(mol/L) VNP 对 NE 诱导的心肌细胞总蛋白质含量的影响 VNP 对中度低氧 (10-12%O 2 ) 诱导的心肌细胞总蛋白质含量和 3 H- 亮氨酸掺入量的影响

41 VNP 抑制低氧诱导的心成纤维细胞的胶原合成 Rate of 3 H-proline incorporation/% b Normoxide b Hypoxia bd Rate of 3 Hproline incorporation/% hypo VNP(mol.L -1 ) b Without serum With serum b c b d 10-6 低氧对心成纤维细胞 3 H-proline 掺入的影响 VNP 抑制低氧诱导的心成纤维细胞 3 H-proline 的掺入

42 VNP 抑制去甲肾上腺素诱导的肺动脉平滑肌细胞的增殖, 作用强于 ANP 和 CNP Total Protein (mg/l) * ** ***VNP CNP ANP *OD Value of MTT * * * ** VNP CNP ANP ** ** ** concentration(m/l) ANP CNP 和 VNP 抑制甲肾上腺素诱导的肺动脉平滑肌细胞增殖作用的比较

43 VNP 通过升高细胞内 cgmp 途径, 抑制细胞增殖 ***VNP *Concentration(M/L)* PVNP 对 PASMCs 胞内 camp 和 campcgm*concentration(pmol/ml) cgmp(pmol/ml) CFs CMs b b b c c VNP(M) HS(10-5 M) cgmp 水平的影响 HS 阻断 VNP 升高心肌细胞和心成纤维细胞内 cgmp 的作用

44 VNP 抑制心肌细胞肥大的作用与其降低低氧诱导的内皮素 -1 升高有关 level of endothelin in the culture medium (pmol/ml) h 24 h ## ## 0 Con MH MH+VNP VNP 降低低氧诱导的培养心肌细胞 ( 左 ) 以及低氧大鼠心肌组织 ( 右 ) 内皮素含量

45 4.VNP can up-regulate the expression of NPR-B and down-regulate the expression of NPR-C

46 VNP 上调血管平滑肌细胞钠尿肽 B 受体的表达 对照 VNP 打点杂交显示 VNP 上调 NPR-B 的表达

47 VNP 下调心肌细胞和心成纤维细胞 NPR-C 的表达 Comparative quantity (C-NPR/β-actin) norm Hyo VNP(M) VNP 下调常氧和低氧条件下 NPR-C 的表达

48 5.VNP could inhibit the calcium transient and twitch amplitude in the rat ventricular myocytes

49 VNP 降低 Iso 诱导的单个心肌细胞钙瞬变和收缩幅度 * ** ** ** Increase of contraction (percentage of maximal effect) VNP(mol/L) ** * ** ** Increase of [Ca 2+ ]i transient (percentage of maximal effect) B VNP(mol/L) VNP 降低 Iso 诱导的心肌细胞钙瞬变 ( 左 ) 以及收缩幅度 ( 右 )

50 6.VNP inhibits L-type L calcium current and sodium current.

51 VNP 降低心室肌细胞 L 型钙电流 A A 500 pa B Increase of calcium current (%Control) 100 ms * ** 10-8 mol/l VNP W ashout Control -40 mv ** ** 0 mv VNP(mol/L) ** 500 pa L-type calcium currents(pa) B 100 ms mv Control VNP+Iso Iso 0 mv Clamp voltage (mv) Control VNP+Iso Iso VNP 降低大鼠心室肌细胞 L 型钙电流 ( 左 ) 和 Iso 增强的 L 型钙电流 ( 右 )

52 VNP 降低心室肌细胞钠电流 A VNP(10-7 m o l/l ) C o n tro l -90 mv -30 mv 5 na 50 ms Increase of calcium current (%Control) B * ** VNP(mol/L) ** ** VNP 降低大鼠心室肌细胞钠电流

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54 Fig.3. Relative proportion of ANP production from heart walls. The width of the narrow is the semi-quantitative indication of ANP release from four chambers of heart.

55 Diuresis and Natriuresis afferent arteriole calibre efferent arteriole calibre glomerular surface area GFR Sodium reabsorption Proximal tubule Distal tubule Renin and aldosterone biosynthesis diuresis natriuresis RAAS, Sympathetic activity Diuresis Natriuresis: ANP >BNP >> CNP

56 Vasodilatation and antihypertension Endothelium independent Arteries: ANP >BNP >>CNP Veins: CNP>>ANP BNP ANP BNP : arteries > veins large vessels > periphery vessels CNP: a potent venodilator

57 Vasodilation Blood pressure Diuresis, natriuresis Vascular permeability extravascular fluid shift Blood volume

58 Growth Inhibition NPs have antiproliferative effects in a variety tissues: Renal mesangial cells, astrocytes,, endothelial cells, cardiac fibroblasts, vscular smooth muslce cells. NPs also inhibits hypertrophy in cultured cardiac myocytes

59 Counteract RAAS ETs Sympathetic system et al. Table The mutually opposing vasodilatory natriuretic and vasoconstrictory antinatriuretic systems Vasodilator-natriuretic systems Natriuretic peptides Prostaglandins Parasympathetic system Nitric oxide Vasoconstrictor- antinatriuretic systems RAAS system ADH Sympathetic system Endothelium