從興奮收縮耦聯(lián)機制看心力衰竭正性肌藥物發(fā)展

1、從興奮收縮耦聯(lián)機制看心力衰竭從興奮收縮耦聯(lián)機制看心力衰竭正性肌力藥物發(fā)展正性肌力藥物發(fā)展田野田野 教授教授哈醫(yī)大二院心內(nèi)科哈醫(yī)大二院心內(nèi)科提提 要要3 興奮興奮-收縮耦聯(lián)機制收縮耦聯(lián)機制3 正性肌力藥的循證研究正性肌力藥的循證研究- 洋地黃制劑- -腎上腺素能受體激動劑- 磷酸二酯酶抑制劑 - 鈣增敏劑3 新型正性肌力藥的探索新型正性肌力藥的探索- 亞硝酰氫興奮-收縮耦聯(lián)機制3excitation-contraction (ec) coupling is a excitation-contraction (ec) coupling is a term coined in term coined

2、 in 19521952 to describe the to describe the physiological process of converting an physiological process of converting an electrical stimulus to mechanical responseelectrical stimulus to mechanical response. . sandow a (1952). excitation-contraction coupling in muscular response. yale j biol med 25

3、 (3): 176201. pmid 130159500excitation-contraction coupling3cardiac excitationcontraction coupling is the cardiac excitationcontraction coupling is the process from electrical excitation of the myocyte to process from electrical excitation of the myocyte to contraction of the heart (which propels bl

4、ood out). contraction of the heart (which propels blood out). the ubiquitous the ubiquitous second messenger ca2+second messenger ca2+ is essential is essential in cardiac electrical activity and is the direct in cardiac electrical activity and is the direct activator of the myofilaments, which caus

5、e activator of the myofilaments, which cause contraction. contraction. bers, d. m. excitationcontraction coupling and cardiac contractile force edn 2 (kluwer academic,dordrecht, netherlands, 2001).cardiac excitationcontraction couplingcardiac tissue(guinea-pig ventricular cell)cardiac tissue cardiac

6、 cellsthe action potential moves through sarcolemmat tubeca2+- induced ca2+- releaseca+ca+ca+ca2+plbca2+ca+ca2+ca2+ca2+ca2+ca2+ca2+ca2+ca+ca+ca+ca+ca2+ca+ca+ca+ca+ca2+ca+ca+ca2+ca+ca+ca+ca+ca+ca+ca+ca+ca+ca+ca+ca+ca2+ca+ca+ca+ca+ca+ca+ca+ca+ca+ca2+ca2+ca2+ca2+ca2+ca2+na+na+na+ca2+sercasrryrl-type ca

7、2+channelna+/ca2+ exchangerca+sarcolemmaca2+actintropomyosintroponintitinmyosin myosin-binding-protein c capz tropomodulin cross-linking protein 肌聯(lián)蛋白（titin）將粗肌絲與z-線連接，維持肌原纖維的完整性和穩(wěn)定性，保持舒張肌肉的靜息張力，使粗肌絲處于肌小節(jié)的中央位置，使受牽拉的肌肉可恢復(fù)初始狀態(tài)，以保證肌肉收縮時張力的輸出。zztitin28,000 amino acids (3mda) the largest protein known in

8、mammals.titinthe molecular basis for myocardial contractionthin filament (actin ,tropom-yosin, troponin) thick filament (myosin)other proteinschien, k.r., 1999f-actinz-linez-linethin filament proteinsg to f actin mw 42 kdathe blue and grey molecules are actin monomers (mw 42.000)ken c. holmes: max-p

9、lanck-institute g-actin f-actin 肌動蛋白以兩種形式存在, 即單體和多聚體。單體的肌動蛋白是由一條多肽鏈構(gòu)成的球形分子, 又稱球狀肌動蛋白(globular actin, g-actin),外形類似花生果。肌動蛋白的多聚體形成肌動蛋白絲, 稱為纖維狀肌動蛋白(fibros actin, f-actin)。在電子顯微鏡下, f-肌動蛋白呈雙股螺旋狀, 直徑為8nm, 螺旋間的距離為37nm。 lorenz model of f-actin. a single g-actin monomer with inter-actin contact surfaces is s

10、hown on the right, the entire f-actin on the leftactin filaments are dynamic polymers whose atp-driven assembly in the cell cytoplasm drives shape changes, cell locomotion and chemotactic migration. actin filaments also participate in muscle contraction. the structure of the filament is not known at

11、 atomic resolution, but several models were produced in the laboratory of ken holmes (mpi for medical research, heidelberg, germany) by refinement against x-ray fiber diffraction datatroponinhead-to-tail overlapabtakeda, s. et al. nature 424, 35 41, 2003 hctnchctnihctnttropomyosintropomyosinbinding

12、regionhypervariable regioncrystal structure of human cardiac troponintroponin cc-domainn-domaincentral helixeach tnc domain contains two motifs called ef hands, and it is the ef hands that directly bind calcium ions. thus, the ef hands are tncs way of sensing the calcium concentration; at 100 nm cal

13、cium (the usual cellular concentration) the n-domain ef hands are empty, but if the local concentration rises to 1 m mm, as it does when the muscle contracts, all of the ef hand bind calcium.kca=3 x 105 m-1ca2+-specifickca= 2 x 107 m-1ca2+-mg2+ sitesef handsthick filament proteins myosinmyosin mw 48

14、0 kdaforms thick filamentshydrolyses atpinteracts with f-actin 300-400 myosin molecules per 1 filaments1s1150 nmmyosin重鏈重鏈 -helical coiled-coil輕鏈輕鏈160 nms1s1 - molecular motor of muscle contractionrlcelcmyosin head (s1) molecular motor of muscle contractionrlcelcatp binding siteactin binding siteatp

15、 (myosin) adp + pi + energyf-actincross-bridge actin interactiongordon et al. 2001regulation of thin filament in contraction a b c d efrom craig and lehman, 2001,jmb 311, 1027the reversible binding of calcium to troponin alters the conformation of the thin filament, thereby turning muscle contractio

16、n on and off cross-bridge state: thin filament state:relaxed (off) blockedca2+ activated (weak binding) closed ca2+ and myosin activated (strong binding) open three positions of tropomyosin activated filaments (blue: actin bound end of actively cycling cross-bridges)regulation of muscle contraction:

17、/b/batpca2+muscle contractionpiin the absence of ca2+, the interaction of myosin with actin and consequently contraction is inhibited. upon release of ca2+ from the sr, the regulatory, ca2+ specific sites of tnc bind ca2+ exposing a patch of hydrophobic residues located in the n-terminal domain of t

18、nc and the interaction of the tnc with tni and tnt can take place. these internal tn interactions promote translocation of the tntm complex away from the outer domain of the actin filaments enabling the cyclic interaction between myosin heads (s1) and actin. the myosin head, an actin activated-mg2+-

19、atpase dependent molecular motor, binds to actin and undergoes a power stroke, a phenomenon responsible for the interaction between the thick filament and the thin filaments and force generation. atpase cycle1. a m + atp2. a+ matp3. a m adp pi4. a m adp +pi5. a m +adppiadppi release rate:10-20s-1mus

20、cle contraction pi release rates:1. no tm-tn: 10 20 s-1 ; 2. + tm-tn no ca2+: 0.1- 0.2 s-1 ; 3.+ tm-tn + ca2+:10 20 s-1actin-myosin interactionin vitro motility assay showing the sliding of actin filaments over a myosin surface initiated by flash photolysis of caged atp(clive r. bagshaw)bers dm. car

21、diac excitation-contraction coupling j. nature, 2002, 415(6868): 198-205.excitation-contraction couplingheart failureryanodine receptor(ryr) phosphorylation of ryr increaseca2+ leak atp-dependent pump phospholamban(plb) in hf expression and activation of serca2phosphorylation of plb expression of 1a

22、ratp supplyuptakere-uptake storerelease msrsr ca2+ srore decrease, ca2+ transient delaythe sr ca2+ store123451. reduced ca+ trigger thru l-type channel2. reduced ryr function (calcium leaks from sr)3. decreased sensitivity of tn-c to ca+4. reduced ca+ uptake due to loss of serca function and increas

23、ed plb5. increased na/ca exchanger functionoverview of e-c coupling changes in the failing heart正性肌力藥的循證研究正性肌力藥的循證研究ancient treatment of heart failure洋地黃制劑（洋地黃制劑（200 years） digilis purpureadigilis purpureapurple foxglovepurple foxglovewilliam witheringwilliam withering (1741 - 1799) (1741 - 1799)dig

24、italismechanism of actiondig 試驗試驗(1997)3總死亡率是中性3在3.5年的隨訪中，心衰惡化而死亡的危險性，地高辛組有降低趨勢，地高辛顯著降低了因心衰住院死亡的危險性28%（p0.01）。the effect of digoxin on mortality and morbidity in patients with heart failuren eng1 med,1997;336:525-533總死亡率總死亡率 placebodigoxinthe effect of digoxin on mortality and morbidity in patients

25、with heart failure n eng1 med,1997;336:525-533因心衰住院死亡的發(fā)生率因心衰住院死亡的發(fā)生率28%p0.01placebodigoxinthe effect of digoxin on mortality and morbidity in patients with heart failure n eng1 med,1997;336:525-5333digitalis is digitalis is without question the most without question the most valuable cardiac drug ev

26、er discoveredvaluable cardiac drug ever discovered 3one of one of the most valuable drugs in the ent-irethe most valuable drugs in the ent-ire pharmacopoeiapharmacopoeia. . 3the introduction of digitalis was the introduction of digitalis was one of the one of the landmarkslandmarks in the history of

27、 cardiac disease. in the history of cardiac disease.opie, h. l. drugs for the heart. orlando florida: grune & stratton, inc. 1980.therapeutic use3 各種心臟病引起的充血性心力衰竭。3 快速性室上性心律失常：心房顫動、心房撲動、房性心動過速、陣發(fā)性房室交界區(qū)心動過速、反復(fù)性心動過速。 side effects3action potential recordings from purkinje fiber cells (a)3toxic dose

28、s produce oscillatory after depolorizations (b)3leads to ventricular tachycardia (c)-腎上腺素能受體激動劑腎上腺素能受體激動劑 3 -受體激動劑與心肌細胞膜上-受體結(jié)合3 通過g蛋白偶聯(lián)激活腺苷酸活化酶(ac)3 催化atp生成camp3 camp促使l型鈣通道開放3 ca內(nèi)流增加，細胞內(nèi)ca濃度上升，起到正性肌力作用。direct acting sympathomimeticsdopaminedobutaminetherapeutic use3對維持血壓和心輸出量具有重要意義，但易引起心率加快、心肌耗氧量增加

29、，誘發(fā)心律失常和心肌受體下調(diào), 對生存率有不良影響。3多用于緊急情況的急性心衰、難治性心衰。dies f, et al. circulation 1986;74(suppl ii):ii-39. 磷酸二酯酶抑制劑磷酸二酯酶抑制劑 3 the different forms or subtypes of phosphodiesterase were initially isolated from rat brains by uzunov and weiss in 1972 and were soon afterwards shown to be selectively inhibited in

30、the brain and in other tissues by a variety of drugs3 the potential for selective phosphodisterase inhibitors as therapeutic agents was predicted as early as 1977 by weiss and hait. this prediction meanwhile has proved to be true in a variety of fields.uzunov, p. and weiss, b biochim. biophys. acta

31、284:220-226, 1972 weiss, b. and hait, w.n.: ann. rev. pharmacol. toxicol. 17:441-477, 1977. 3代表藥物為氨力農(nóng)(amrinone)和米力農(nóng)(milrinone)。3增強心肌收縮力，降低后負荷，提高心肌舒張速率phosphodiesterase inhibitorsmechanism of action3pdei為非強心甙非兒茶酚胺類強心藥，通過抑制camp在心肌和平滑肌細胞的降解，而發(fā)揮正性肌力作用。-adr和pdei的作用位點(according to lippincott s pharmacolog

32、y, 2006)promise臨床試驗（臨床試驗（1991）3nyha iii、iv級，ef35% 米力農(nóng) 1000例3結(jié)果結(jié)果- 總死亡率28%- 心血管死亡率的危險性34%- 猝死危險69%3亞組結(jié)論亞組結(jié)論：心功能越差，危險性越高, 試驗提前終止packer m, et al. effect of milrinone on mortality in severe chronic heart failure. n engl j med. 1991;325:1468-1475. therapeutic use3 米力農(nóng)尚不足以作為充血性心衰的首選強心劑和血管擴張劑3 只是作為重癥心衰的輔助用

33、藥或洋地黃中毒患者的二次選擇藥物3 主要用于急性心衰 鈣增敏劑鈣增敏劑3mci-154、左西孟旦（levosimendan）是其中有代表性的藥物。 3作用機制- 增加心肌tnc對ca2的敏感性- 穩(wěn)定ca2-tnc構(gòu)象- 直接增強肌球蛋白和肌動蛋白之間的相互作用mechanism of actionactintropomyosintnitntca2+ctncmyosin head (s1 fragment)atp pocketrlcelc左西孟旦左西孟旦revive-2 研究研究(2005)3rev ive-2 研究共入選600例心力衰竭患者,在常規(guī)治療的基礎(chǔ)上隨機加用levosimendan

34、3研究結(jié)果- 應(yīng)用levosimendan 組心功能改善者比對照組多33%，- 心功能惡化者比對照組少30%packer m. aha scientific sessions, dallas, usa, november, 2005.primary endpoint (n=600)packer m. aha scientific sessions, dallas, usa, november, 2005.33%30%side effects3研究發(fā)現(xiàn)通過增加鈣敏感性的藥物也可減慢心肌的舒張。這是由于增加了肌纖維對舒張時細胞內(nèi)ca2+ 的敏感性，使ca2+從tnc 的解離速度減慢，從而妨礙心肌的

35、舒張，影響心室的充盈。white j ,lee ja , shah n , et al. differential effects of the optical isomers of emd53998 on contraction and cytoplasmic ca2 + in isolated ferret cardiac mus-clej . circ res ,1993 ,73 :61270.lee ja ,allen dg. emd53998 sensitizes the contractile proteins to calcium in intact ferret ventricular musclej . circ res ,1991 ,69 :9272936.therapeutic use3 失代償性急性心力衰竭，伴心輸出量下降和高灌注壓3 心臟