Annals of Medicine
ISSN: 0785-3890 (Print) 1365-2060 (Online) Journal homepage: http://www.tandfonline.com/loi/iann20
Platelets, Endothelium-Dependent Responses and Atherosclerosis Andreas Mügge, Ulrich Förstermann & Paul R. Lichtlen To cite this article: Andreas Mügge, Ulrich Förstermann & Paul R. Lichtlen (1991) Platelets, Endothelium-Dependent Responses and Atherosclerosis, Annals of Medicine, 23:5, 545-550, DOI: 10.3109/07853899109150516 To link to this article: http://dx.doi.org/10.3109/07853899109150516
Published online: 08 Jul 2009.
Submit your article to this journal
Article views: 7
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=iann20 Download by: [McMaster University]
Date: 10 April 2016, At: 23:05
SDecial Section: Inflammation and Atheroaenesis
Platelets, Endothelium-Dependent Responses and At herosclerosis
Downloaded by [McMaster University] at 23:05 10 April 2016
Andreas Muggel, Ulrich Forstermann* and Paul R. Lichtlenl
Basal release of endothelium-derived relaxing factor (EDRF) and prostacyclin from intact vascular endothelium may inhibit continuously platelet aggregation. If local platelet aggregation occurs, platelet-derived adenine nucleotides stimulate the release of EDRF. Stimulated EDRF release may override the direct vasoconstrictor effects of other platelet products such as thromboxane and serotonin resulting in local vasodilatation. In addition, stimulation of EDRF release by adenine nucleotides may inhibit further platelet adhesion and aggregation by a feedback mechanism. Thus, intact vascular endothelium may play an important role in the defense against platelet deposition and vasospasm. In atherosclerosis, basal and stimulated release of EDRF is markedly reduced. Endothelial dysfunction will impair this protective mechanism and will favour vasoconstriction and further platelet disposition. Occurrence of occlusive thrombus formation in patients with coronary artery disease may be pathophysiologically related to this impairment of endothelial defense. Key words: atherosclerosis; endothelium-derived relaxing factor; platelets; prostacyclin. (Annals of Medicine 23: 545-550,
1991)
Endothelium-Derived Relaxing Factor Endothelial cells have been found to release a potent vasodilator substance referred to as endothelium-derived relaxing factor (EDRF) (1, 2). EDRF has recently been identified as nitric oxide (NO) (3,4) or a NO-containing compound (e.g. S-nitrosocysteine, 5) which is synthetized by vascular endotheliumfrom the amino acid L-arginine(6). EDRF(N0) relaxes smooth muscle cells through stimulation of soluble guanylatecyclase (7,8) resultingin increased Stimulationofsolubleguanylate levelsof cyclicGMP (9,lO). cyclase by EDRF(N0) resembles the relaxant mechanism of organic nitrates and EDRF(N0)has been proposedto be an “endogenous nitrovasodilator” (1 1 , 12). Various pharmacological and mechanical stimuli are known to release EDRF(N0) from vascular edothelium (2, 13, 14). In addition evidence have been presented that vascular endothelium releases EDRF(N0) continuously and that this basal release contributes to vascular tone in vitro and in vivo (15-1 8).In agreementwith animal models, EDRF(N0)-mediatedrelaxation can also be demonstrated in human arteries in vitro (19-21) and in vivo (22).Infusion of monomethyl-L-arginine,a specific inhibitor of L-arginineFrom the ’Division of Cardiology, Hannover Medical School, Hannover, Germany, and ZAbbottLaboratories, Abbott Park, Chicago, Illinois, USA. Address and reprint requests: A. Mugge, M.D., Division of Cardiology, Hannover Medical School, D-3000 Hannover 61, Germany.
derived EDRF(N0) release, into the brachial artery of volunteers reducedforearm blood flow and attenuatedthe dilator responseto infused acetylcholine but not to glyceryltrinitrate (22).These results suggest that EDRF(N0) contributes to the control of basal and stimulated regional blood flow in man.
EDRF(N0)-Mediated Relaxation in Atherosclerosis Endotheliurn-dependentrelaxation is impaired in animals which were fed an atherogenic diet. This has been demonpigs (25,26), and stratedfor cholesterol-fedrabbits (23,24), primates (27).A similar phenomenonwas demonstratedfor human coronary arteries in vitro which were obtained during heart transplantation from patients with severe atherosclerosis (21,28;Fig. 1). Bioassay studies indicated a reduced release of intact EDRF(N0) from the vascular The precise endotheliumof cholesterol-fed rabbits (29,30). mechanism for reduced release of intact EDRF(N0) in atherosclerosis is not known. One mechanism could be the lack of the precursor L-arginineresulting in reduced synthesis of EDRF(N0). However, incubation of atherosclerotic rabbit aorta in vitro with high concentrationsof L-argininedid not restore impairedacetylcholine-mediatedrelaxation(31). Recent experiments combining bioassay and chemical detection of EDRF(N0) including its degradation product nitrite suggested augmented degradation rather than reduced production of EDRF in atherosclerosis (32).Since
Ann Med 23
Mugge Forstermann Lichtlen
546
b
A-8.7
10min
Downloaded by [McMaster University] at 23:05 10 April 2016
i-SW PGF2a -5.5
PGF2, -5.5
PGF2a -5.5
Figure 1. Original recordings of strips of human coronary arteries. a: non-atherosclerotic preparation taken from the heart of a 24-year-oldpatient, b: atherosclerotic preparation taken form the heart of a 55-year-oldpatient. lndomethacin (10 pM) was present in organ bath. Arteries were preconstricted with prostaglandin F., After reaching contraction plateau, tissues were exposed to endothelium-dependent relaxants substance P (SP), bradykinin (BK), and calcium ionophore A23187. All concentrations are expressed as logarithms of molar concentration. Relaxationswere attenuatedinatherosclerotic preparations. Inthe same preparations,vasodilator responses to the endothelium-independent relaxants isoprenaline and nitroglycerin were of similar magnitude(not shown).W=wash,change of bath solution. Taken with permissionfrom ref. 28.
EDRF(N0) in aequous solutions is highly reactive with oxygen free radicals, e.g., superoxide anions (33, 34), this augmented breakdown of EDRF(N0) in atherosclerosis may be related to an imbalance between radical species and antioxidant defense. In fact, impairment of antioxidant defense in endothelial cells by inhibiting superoxide dismutase activity resulted in the release of degradation products of EDRF (nitrites) which have poor vasorelaxant activity (35). On the other hand, increase of antioxidant defense by chronic pretreatmentwith polyethylenglycolated superoxide dismutase improved impaired acetylcholinemediated relaxationin the aorta of cholesterol-fedrabbits in vitro (36). Although some evidence suggests an association of endothelial dysfunctionwith antioxidantdefense and radical species, other mechanisms may be also involved in the pathogenesis of impaired endothelium-dependentrelaxation in atherosclerosis. Oxidized low density lipoproteins have been reported to cause contraction and inhibition of EDRF-mediated relaxation in pig coronary arteries in vitro (37).Incubationof rabbit aorta in vitro with endothelial cellmodified LDL, but not native LDL, impaired acetylcholinemediated relaxation (38). The latter authors demonstrated that a transfer of lysolecithin from endothelialcell-modified LDL to endothelial membranes produced a unresponsiveness to receptor-regulated endothelium-dependent vasodilators. However, the precise mechanism how oxidized or modified LDL, and in particular lysolecithin, interferes with the L-argininelN0pathway invascular endothelium is unclear.
Ann Med 23
Vascular Responses to Aggregating Platelets: Importance of an Intact Endothelium Aggregating platelets release a number of vasoactive substances. Among these are vasodilators like adenine nucleotides but also vasoconstrictors like serotonin and thrornboxane A, (39). Aggregating canine platelets, when applied to canine coronary arteries, induced endotheliummediatedrelaxation (40). In contrast, arteries mechanically denuded of endothelium contracted. An identical phenomenon could be demonstratedfor aggregating human platelets and human coronary arteries in vitro (41; Fig. 2). The relaxationin response to aggregating platelets was almost abolished and even converted to constriction in the presence of EDRF-inhibitors gossypol, methylene blue, and hemoglobin, but not significantlyimpairedafter pretreatment of the vessel wall with the cyclooxygenaseinhibitor aspirin (41). These results suggest that platelet-inducedrelaxation in intact arteries is mediated by the endothelial release of EDRF. The platelet-derivedsubstanceswhich stimulatethe endothelial release of EDRF are probably adenine nucleotides. This is based on the observation that apyrase which hydrolyzes ATP and ADP to AMP and adenosine abolished platelet-induced relaxation whereas the presence of the serotonin receptor antagonist methysergideor the pretreatmentof platelets with the thromboxane synthesis inhibitor dazmegrel did not affect platelet-induced responses (41). Thus, vascular responses to aggregating platelets are critically dependent on endothelial function.
Platelets, Endothelium-Dependent Responses and Atherosclerosis
-
547
3
a 0
L!Q
20
c
.-0
CL
0
2
0
c
C
sD:
-20
+Endothelium 0 -Endothelium
PI
LL
-40
E
c
-60
.-0
.->*
c
Downloaded by [McMaster University] at 23:05 10 April 2016
Q)
n
8
-80 -9 SP {log MI
107
108 Platelets {l/ml)
Figure 2. Effect of substance P (SP, 1nM), used as afunctional test of endothelial integrity, and human washed platelets (107/ml and 108/ml) on strips of human coronary arteries with the endothelium intact (+Endothehum, 44 strips from 7 patients) or removed (-Endothelium, 22 strips from 4 patients). Response is expressed as percent deviation from the contraction plateau induced by prostaglandin F,= (0.3-3pM). Induced tension was 1.5k0.1 g in endothelium-intact and 1.3f0.1 g in endothelium-denuded preparations. Asteriks denote significant differences between +Endothelium and -Endothelium (P 0
0
t
C
0 ..-
T h r 0.06U
Downloaded by [McMaster University] at 23:05 10 April 2016
In
I
4 min
T hr 0.06U
Thr 0 . 0 6 U
t
T h r 0.06U
WP+B
t
T h r 0.06U
-
.J 10080 -
4 min
60 4020 -
WP +ECB(GOSS)
WP+ECB
w-
0-
t
t
t
Thr 0 . 0 5 U
T h r 0.05U
t
T h r 0.05U Thr 0.05U
WP +ECB +Hb
WP (MB) +
ECB
Thr 0.05U
Figure 3. Measurement of thrombin (Thr)-induced platelet aggregation in a mixture of washed platelets (WP) and empty microcarrier beads (B), or microcarrier beads covered with endothelial cells (ECB). Experiments were performed in the presence of 30 pM indomethacin (a, effects of EDRF), and in the absence of this drug (b, effects of prostacyclin and EDRF). The anti-aggregatory effect of EDRF (a) was 30 pM), after addition of hemoglobin (Hb, 15 pM)to the incubation mixture, or blocked after pretreatment of ECB with gossypol (GOSS, after pretreatment of the platelets with methylene blue (MB, 10 pM,30 min). These inhibitors are specific for EDRF effects as the antiaggregatory effect seen in the absence of indomethacin (b) was not impaired. Therefore, this effect is likely to be mainly due to endothelial prostacyclin. Taken with permission from ref. 58.
intraplatelet negtive feedback mechanism; the PathoPhYsiologicalimportance ofthis system remainsto be established.
Vascular Endothelium as a Defense Mechanism Against Platelet Aggregation and Vasospasm Acute myocardialischemiamanifestedby clinical syndroms
Ann Med 23
of unstable angina pectoris or myocardial infarction usually is the result of an occlusive thrombus formation in the area of atherosclerotic plaques (64). Intact vascular endothelium may play an important role in the defense against platelet aggregation and vasospasm (Fig. 4). Basal release of EDRF and prostacyclin may interfere continuously with platelet aggregation. If local platelet aggregation occurs, platelet-derivedadenine nucleotides stimulate the release of EDRF(N0). Stimulated EDRF(N0) release may override the direct vasoconstrictor effects of other platelet products
Platelets, Endothelium-Dependent Responses and Atherosclerosis INTACT ENDOTHELIUM
ATHEROSCLEROSIS
:elaxation
Downloaded by [McMaster University] at 23:05 10 April 2016
549
Contraction
Figure 4. Schema summarizing the vascular effects of aggregating platelets in patients with normal endothelial function (left) and patients with coronary artery disease (right). In patients with intact endothelium, basal release of endothelium-derived relaxing factor (EDRF) and prostacyclin (PGI,) inhibits continuously platelet aggregation. If local aggregation of platelets occurs, platelet-derived ADP stimulates the endothelial release of EDRF. This increased release of EDRF may override the direct vasoconstrictor effects of other platelet-derived products such as serotonin (5-HT) and thromboxane A, (TxA,) resulting in local vasodilatation. In addition, increased release of EDRF may inhibit further platelet adhesion and aggregation. In patients with atherosclerosis, basal and stimulated release of EDRF is impaired. The EDRF release in response to platelet-derived ADP may not be sufficient to override direct vasoconstrictor effectsof 5-HT and TxA, resulting in local vasoconstriction. Furthermore, anti-aggregatory properties of the endothelium are diminished. Activated platelets may interact with other blood components such as leukocytes. Activated leukocytes may also release potent vasoconstrictors, e.g. TxA,, prostaglandin E, (PGE,), and leukotrienes (LT). EC=endothelial cells, SMC=smooth muscle cells, CSa=complement C5a, PAF=platelet-activating factor.
such as thromboxane and serotonin resulting in local vasodilatation. In addition, stimulation of EDRF(N0) release by adenine nucleotides may inhibit further platelet adhesion and aggregation by a feedback mechanism. It is obvious that endothelial damage or dysfunction would impair this protective mechanism and favor vasoconstriction and further platelet disposition(Fig.4). Since atherosclerosis is a major cause for endothelial dysfunction, occurrence of occlusive thrombus formation in patients with coronary artery disease may be pathophysiologically related to this impairment of endothelial defense. However, the complexity of the interaction between components of the arterial wall, platelets, and other blood components is still far from being fully understood (65).
8.
9. 10. 11. 12. 13. 14.
References 1. Furchgott RF,ZawadzkiJV. The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine. Nature 1980; 288: 3 7 3 - 6 . 2. Furchgott RF. The role of endothelium in the response of vascular smooth muscles todruas. Ann Rev PharmacolToxicol 1984; 24: 175-97. 3. Palmer RMJ. Ferriae AG. Moncada S. Nitric oxide release accounts for’ the bkogical activity of endothelium-derived relaxing factor. Nature 1987; 327. 524-6. 4. lgnarro LJ, Byrns RE, Buga GM, Wood KS, Chaudhuri G. Pharmacological evidence that endothelium-derived relaxing factor is nitricoxide: useof pyrogalloland superoxidedismutase to study endothelium-dependent and nitric oxide-elicited vascular smooth muscle relaxation. J Pharm Exp Ther 1988; 244: 181-9. 5. Myers PR, Minor RL, Guerra R, Bates JN, Harrison DG. Vasorelaxant properties of the endothelium-derived relaxing factor more closely resemble S-nitrosocysteine than nitric oxide. Nature 1990; 345: 161-3. 6. Palmer RMJ, Ashton DS, Moncada S. Vascular endothelial cells synthesize nitric oxide from L-arginine. Nature 1988; 333: 664-6. 7. Forstermann U, Mulsch A, Bohme E, Busse R. Stimulation of soluble guanylate cyclase by an acetylcholine-induced
15.
16.
-
17. 18.
19.
20. 21,
endothelium-derived factor from rabbit and canine arteries. Circ Res 1986; 58: 531-8. lgnarro LJ, Harrison RG, Wood KS, KadowitzPJ.Activation of purified soluble guanylate cyclase by endothelium-derived relaxing factor from intrapulmonary artery and vein: stimulation by acetylcholine, bradykinin, and arachidonic acid. J Pharrn Exp Ther 1986; 237: 893-900. Holzmann S. Endothelium-induced relaxation by acetylcholine associated with larger rises in cyclic GMP in coronary arterial strips. J Cyclic Nucl Res 1982; 8: 409-1 9. Rapoport RM, Murad F. Agonist-induced endothelium-dependent relaxation in rat thoracic aorta may be mediated through cGMP. Circ Res 1983; 52: 352-7. Murad F. Cyclic guanosine monophosphate as a mediator of vasodilation. J Clin Invest 1986; 78: 1-5. Waldman SA, Murad F. Cyclic GMP synthesis and function. Pharmacol Rev 1987; 39: 163-96. Bassenge E, Busse R. Endothelial modulation of coronary tone. Progr Cardiovasc Dis 1988; 30: 349-80. Mugge A, Forstermann U, Lichtlen PR. Endothelial functions in cardiovascular diseases. Z Kardioll989; 78: 147-60. Amezcua JL, Palmer RMJ, de Souza BM, Moncada S. Nitric oxide synthesized from L-arginine regulates vascular tone in the coronary circulation of the rabbit. Br J Pharmacol 1989; 97: 1119-24. Rees DD, Palmer RMJ, Hodson HF, Moncada S. A specific inhibitor of nitric oxide formation from L-arginine attenuates endothelium-dependent relaxation. Br J Pharmacol 1989; 96: 41 8-24. Rees DD, Palmer RMJ, Moncada S. Role of endotheliumderived nitric oxide in the regulation of blood pressure. Proc Natl Acad Sci USA 1989; 86: 3375-8. Mugge A, Lopez JAG, Piegors DJ, Breese KR, Heistad DD. Acetylcholine-induced vasodilatation in rabbit hindlimb in vivo is not inhibited by analogues of L-arginine. Am J Physiol 1991; 260: H242-H247. ForstermannU, Mugge A, FroiichJC. Endothelium-dependent relaxation of human epicardial coronary arteries: frequent lack of effect of acetylcholine. Eur J Pharmacol 1986; 128: 277-81. Luscher T, Cooke JP, Houston DS, Neves RJ, Vanhoutte PM. Endothelium-dependent relaxations in human arteries. Mayo Clin Porc 1987; 62: 6 0 1 4 . Bossaller C, Habib GB, Yamomoto H, Williams C, Wells S, Henry PD. Impaired muscarinic endothelial-dependent relaxation and cyclic guanosine 5-monophosphate formation in atherosclerotic human coronary artery and rabbit aorta. J Clin
Ann Med 23
Downloaded by [McMaster University] at 23:05 10 April 2016
550
Mugge Forstermann Lichtlen
Invest 1987; 79: 1 7 0 4 . 22. Vallance P, Collier J, Moncada S.Effects of endotheliumderived nitric oxide on peripheralarteriolar tone in man. Lancet 1989; II: 997-1000. 23. Jayakody RL, Senaratne, MPJ,Thomson ABR, Kappagoda CT. Cholesterol feeding impairs endothelial-dependent relaxation of rabbit aorta. Can J Physiol Pharmacol 1985, 63: 12069. 24. Verbeuren TJ, Jordaens FH, Zonnekeyn LL, Van Hove CE, Coene MC, Herman AG. Effect of hypercholesterolemia on vascular reactivity in the rabbit. I. Endothelial-dependent and endothelial-independentcontractionsand relaxation in isolated arteries of control and hypercholesterolemic rabbits. Circ Res 1986; 58: 552-64. 25. Cohen RA, Zitnay KM, Haudenschild CC, Cunningham LD. Loss of selective endothelialcell vasoactive functions caused by hypercholesterolemiain pig coronary arteries. Circ Res 1988; 63: 903-1 0. 26. Shimokawa H, Vanhoutte PM. Impaired endothelium-dependent relaxation to aggregating platelets and related vasoactive substances in porcine coronary arteries in hypercholesterolemiaand atherosclerosis. Circ Res 1989;64: 900-1 4. 27. Freiman PC, Mitchell GC, Heistad DD, Armstrong ML, Harrison DG. Atherosclerosisimpairs endothelial-dependent vascular relaxationto acetylcholine and thrombin in primates. Circ Res 1986; 58: 783-9. 28. Farstermann U, Mugge A, Alheid U, Haverich A, Frolich JC. Selectiveattenuation of endothelium-mediatedvasodilation in atherosclerotic human coronary arteries. Circ Res 1988;62: 185-90. 29. Guerra R, Brotherton AFA, Goodwin PJ, Clark CR, Armstrong ML, Harrison DG. Mechanisms of abnormal endothelium-dependent responses in atherosclerosis. Blood Vessels 1989; 26: 300-1 4. 30. Verbeuren TJ, Jordaens FH, Van Hove CE, Van Hoydonck AE, HermanAG. Release and vascular activity of endotheliumderived relaxing factor in atherosclerotic rabbit aorta. Eur J Pharmacoll990; 191: 173434. 31. MuggeA, Harrison DO. L-argininedoes not restoreendothelial dvsfunctionin atheroscleroticrabbit aorta in vitro. Blood Vessels, in press. 32. Minor RL. Mvers PR. Guerra R. Bates JN. Harrison DG. Diet-induceditheroscierosis increases the releasein nitrogen oxides from rabbit aorta. J Clin Invest 1990; 86: 2109-1 6. 33. Gryglewski RJ, Palmer RMJ, Moncada S.Superoxide anion is involved in the breakdownof endothelium-derivedvascular relaxing factor. Nature 1986; 320: 454-6. 34. RubanyiGM, Vanhoutte PM. Superoxideanionsand hyperoxia inactivate endothelium-derivedrelaxing factor. Am J Physiol 1986; 250: H822-H827. 35. Mugge A, Elwell JH, Peterson TE, Harrison DG. Release of intact endothelium-derived relaxing factor depends on endothelial superoxide dismutase activity.Am J Physioll991; 260: C21-225. 36. Mugge A, Elwell JH, Peterson TE, Hofmeyer TG, Heistad DD, Harrison DG. Chronic treatment with polyethylenglycolatedsuperoxidedismutase partiallyrestoresendotheliumdependent vascular relaxationsin cholesterol-fedrabbits. Circ Res, in press. 37. Simon BC, Cunningham LD, Cohen RA. Oxidized low density lipoproteins cause contraction and inhibit endotheliumdependent relaxation in the pig coronary artery. J Clin Invest 1990; 86: 75-9. 38. Kaglyama K, Kerns SA, Morrisett JD, Roberts R, Henry PD. Impairmentof endothelium-dependentrelaxationby lysolecithin in modified low-densitylipoproteins. Nature 1990; 344: 1602. 39. Meyers KM, Holmsen HI Seachord CL. Comparative study of platelet dense granule constituents. Am J Physiol 1982, 243: R454-R461. 40. Houston DS, Shepherd JT, Vanhoutte PM. Adenine nucleotides, serotonin, and endothelium-dependent relaxation to platelets. Am J Physiol 1985; 248: H389-H395. 41. Forstermann U, Mugge A, Bode SM, Frollch JC. Response of human coronary arteries to aggregating platelets: importance of endothelium-derivedrelaxing factor and prostanoids. Circ Res 1988, 63: 306-12. 42. Golino P, Piscione F, Willerson JT, et al. Divergent effects of serotonin on coronary-arterydimensionsand blood flow in
Ann Med 23
patients with coronary atherosclerosisand control patients. N Engl J Med 1991; 324: 641-7. 43. McFadden EP, Clarke JG, Davies GJ, Kaski JC, Haider AW, Maseri A. Effect of intracoronary serotonin on coronary vessels in patients with stable angina and patients with variant angina. N Engl J Med 1991; 324: 648-53. 44. Lopez JAG, Armstrong ML, Piegor DJ, Heistad DD. Effect of early and advancedatherosclerosison vascular responses to serotonin, thromboxane A,, and ADP. Circulation 1989; 79: 698-705. 45. Stuart MJ, Gerrard JM, White JG. Effect of cholesterol on production-ofthromboxane 82 by platelets in vitro. N Engl J Med 1980; 302: 6-1 0. 46. Tremoli E. Maderna P. Colli S. Morazzoni G. Sirtori M. Sirtori CR: Increasedsensitivity and thromboxane 82 formation in type II hyperlipoproteinaemicpatients. Eur J Clin Invest 1984; 14: 329-33. 47. Kaul S, Waack BJ, Mugge A, Brooks RM, Lopez JAG, Heistad DD. Altered vascular responses to activated platelets from hypercholesterolemic humans. Clin Res 1991; 39: 253A. 48. Henson PM. Interactionsbetween neutrophils and platelets. Lab Invest 1990; 62: 391-3. 49. Zatta A, Prosdocimi M, Bertele V, Bazzoni G, Del Maschio A. Inhibition of platelet function by polymorphonuclear leukocytes. J Lab Clin Med 1990; 116: 651-60. 50. Salvernlni D, De Nucci G, Gryglewski RJ, Vane JR. Human neutrophils and mononuclear cells inhibit platelet aggregation by releasing a nitric oxide-likefactor. Proc Natl Acad Sci USA 1989; 86: 6328-32. 51. Lopez JAG, Armstrong ML, Harrison DG, Piegors DJ, Heistad DD. Vascular responses to leukocyte products in atherosclerotic primates. Circ Res 1989; 65: 1078-86. 52. Mugge A, Lopez JAG. Do leukocyteshave a role in hypertension? Hypertension 1991; 17: 331-3. 53. Mugge A, Helstad DD, Padgett RC, Waack BJ, Densen P, Lopez JAG. Mechanisms of contraction induced by human polymorphonuclear and mononuclear leukocytes in normal and atherosclerotic arteries. Circ Res, 1991; 69: 871-80. 54. Gorman RR, Bunting S, Miller OV. Modulation of human platelet adenylatecyclase by prostacylin(PGX). Prostaglandins 1977; 13: 3 7 7 4 8 . 55. Tateson JE, Moncada S, Vane JR. Effects of prostacyclin (PGX) on cyclic AMP concentrations in human platelets. Prostaglandins 1977; 13: 389-97. 56. Mellion BT, lgnarro LJ, Ohlstein EH, Pontecorvo EG, Hyrnan AL, Kadowitz PJ. Evidence for the inhibitory role of guanosine 3 3 monophosphate in ADP-induced human platelet aggregation in the presence of nitric oxide and related vasodilators. Blood 1981; 57: 9 4 6 5 5 . 57. Alheid U, Frdlich JC, Forstermann U. Endothelium-derived relaxing factor from cultured human endothelial cells inhibits aggregation of human platelets.Thromb Res 1987; 47: 56171. 58. Forstermann U, Mugge A, Alheid U, Bode SM, Frolich JC. Endothelium-derivedrelaxingfactor (EDRF): adefense mechanism against platelet aggregationand vasospasm in human coronary arteries. Eur Heart J 1989; 10 (suppl. F): 36-43. 59. Furlona B, HendersonAH. Lewis MJ. Smith JA. Endotheliumderivedrelaxingfactor inhibits in vitroplatelet aggregation.Br J Pharmacol 1987; 90: 687-92. 60. Radomskl MW, Palmer RMJ, Moncada S. The anti-aggregating properties of vascular endothelium: interactions between prostacyclinand nitric oxide. Br J Pharmacol 1987; 92: 639-46. 61. Hogan JC, Lewis MJ, Henderson AH. In vivo EDRF activity influences platelet function. Br J Pharmacoll988; 94: 10202. 62. MacDonald PSI Read MA, Dusting GJ. Synergistic inhibition of platelet aggregationby endothelium-derivedrelaxing factor and prostacyclin. Thromb Res 1988; 49: 437-49. 63. Radomskl MW, Palmer RMJ, Moncada S. An L-arginine/ nitric oxide pathway present in human platelets regulates aggregation. Proc Natl Acad Sci USA 1990; 87: 5193-7. 64. Davies MJ, Thomas A. Thrombosis and acute coronaryartery lesions in sudden cardiac ischemic death. N Engl J Med 1984; 310: 1 1 3 7 4 0 . 65. Dinerman JL, Mehta JL. Endothelial,plateletsand leukocyte interactions in ischemic heart disease: insights into potential mechanisms and their clinical relevance. J Am Colt Cardiol 1990; 16: 207-22.
ISSN: 0785-3890 (Print) 1365-2060 (Online) Journal homepage: http://www.tandfonline.com/loi/iann20
Platelets, Endothelium-Dependent Responses and Atherosclerosis Andreas Mügge, Ulrich Förstermann & Paul R. Lichtlen To cite this article: Andreas Mügge, Ulrich Förstermann & Paul R. Lichtlen (1991) Platelets, Endothelium-Dependent Responses and Atherosclerosis, Annals of Medicine, 23:5, 545-550, DOI: 10.3109/07853899109150516 To link to this article: http://dx.doi.org/10.3109/07853899109150516
Published online: 08 Jul 2009.
Submit your article to this journal
Article views: 7
View related articles
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=iann20 Download by: [McMaster University]
Date: 10 April 2016, At: 23:05
SDecial Section: Inflammation and Atheroaenesis
Platelets, Endothelium-Dependent Responses and At herosclerosis
Downloaded by [McMaster University] at 23:05 10 April 2016
Andreas Muggel, Ulrich Forstermann* and Paul R. Lichtlenl
Basal release of endothelium-derived relaxing factor (EDRF) and prostacyclin from intact vascular endothelium may inhibit continuously platelet aggregation. If local platelet aggregation occurs, platelet-derived adenine nucleotides stimulate the release of EDRF. Stimulated EDRF release may override the direct vasoconstrictor effects of other platelet products such as thromboxane and serotonin resulting in local vasodilatation. In addition, stimulation of EDRF release by adenine nucleotides may inhibit further platelet adhesion and aggregation by a feedback mechanism. Thus, intact vascular endothelium may play an important role in the defense against platelet deposition and vasospasm. In atherosclerosis, basal and stimulated release of EDRF is markedly reduced. Endothelial dysfunction will impair this protective mechanism and will favour vasoconstriction and further platelet disposition. Occurrence of occlusive thrombus formation in patients with coronary artery disease may be pathophysiologically related to this impairment of endothelial defense. Key words: atherosclerosis; endothelium-derived relaxing factor; platelets; prostacyclin. (Annals of Medicine 23: 545-550,
1991)
Endothelium-Derived Relaxing Factor Endothelial cells have been found to release a potent vasodilator substance referred to as endothelium-derived relaxing factor (EDRF) (1, 2). EDRF has recently been identified as nitric oxide (NO) (3,4) or a NO-containing compound (e.g. S-nitrosocysteine, 5) which is synthetized by vascular endotheliumfrom the amino acid L-arginine(6). EDRF(N0) relaxes smooth muscle cells through stimulation of soluble guanylatecyclase (7,8) resultingin increased Stimulationofsolubleguanylate levelsof cyclicGMP (9,lO). cyclase by EDRF(N0) resembles the relaxant mechanism of organic nitrates and EDRF(N0)has been proposedto be an “endogenous nitrovasodilator” (1 1 , 12). Various pharmacological and mechanical stimuli are known to release EDRF(N0) from vascular edothelium (2, 13, 14). In addition evidence have been presented that vascular endothelium releases EDRF(N0) continuously and that this basal release contributes to vascular tone in vitro and in vivo (15-1 8).In agreementwith animal models, EDRF(N0)-mediatedrelaxation can also be demonstrated in human arteries in vitro (19-21) and in vivo (22).Infusion of monomethyl-L-arginine,a specific inhibitor of L-arginineFrom the ’Division of Cardiology, Hannover Medical School, Hannover, Germany, and ZAbbottLaboratories, Abbott Park, Chicago, Illinois, USA. Address and reprint requests: A. Mugge, M.D., Division of Cardiology, Hannover Medical School, D-3000 Hannover 61, Germany.
derived EDRF(N0) release, into the brachial artery of volunteers reducedforearm blood flow and attenuatedthe dilator responseto infused acetylcholine but not to glyceryltrinitrate (22).These results suggest that EDRF(N0) contributes to the control of basal and stimulated regional blood flow in man.
EDRF(N0)-Mediated Relaxation in Atherosclerosis Endotheliurn-dependentrelaxation is impaired in animals which were fed an atherogenic diet. This has been demonpigs (25,26), and stratedfor cholesterol-fedrabbits (23,24), primates (27).A similar phenomenonwas demonstratedfor human coronary arteries in vitro which were obtained during heart transplantation from patients with severe atherosclerosis (21,28;Fig. 1). Bioassay studies indicated a reduced release of intact EDRF(N0) from the vascular The precise endotheliumof cholesterol-fed rabbits (29,30). mechanism for reduced release of intact EDRF(N0) in atherosclerosis is not known. One mechanism could be the lack of the precursor L-arginineresulting in reduced synthesis of EDRF(N0). However, incubation of atherosclerotic rabbit aorta in vitro with high concentrationsof L-argininedid not restore impairedacetylcholine-mediatedrelaxation(31). Recent experiments combining bioassay and chemical detection of EDRF(N0) including its degradation product nitrite suggested augmented degradation rather than reduced production of EDRF in atherosclerosis (32).Since
Ann Med 23
Mugge Forstermann Lichtlen
546
b
A-8.7
10min
Downloaded by [McMaster University] at 23:05 10 April 2016
i-SW PGF2a -5.5
PGF2, -5.5
PGF2a -5.5
Figure 1. Original recordings of strips of human coronary arteries. a: non-atherosclerotic preparation taken from the heart of a 24-year-oldpatient, b: atherosclerotic preparation taken form the heart of a 55-year-oldpatient. lndomethacin (10 pM) was present in organ bath. Arteries were preconstricted with prostaglandin F., After reaching contraction plateau, tissues were exposed to endothelium-dependent relaxants substance P (SP), bradykinin (BK), and calcium ionophore A23187. All concentrations are expressed as logarithms of molar concentration. Relaxationswere attenuatedinatherosclerotic preparations. Inthe same preparations,vasodilator responses to the endothelium-independent relaxants isoprenaline and nitroglycerin were of similar magnitude(not shown).W=wash,change of bath solution. Taken with permissionfrom ref. 28.
EDRF(N0) in aequous solutions is highly reactive with oxygen free radicals, e.g., superoxide anions (33, 34), this augmented breakdown of EDRF(N0) in atherosclerosis may be related to an imbalance between radical species and antioxidant defense. In fact, impairment of antioxidant defense in endothelial cells by inhibiting superoxide dismutase activity resulted in the release of degradation products of EDRF (nitrites) which have poor vasorelaxant activity (35). On the other hand, increase of antioxidant defense by chronic pretreatmentwith polyethylenglycolated superoxide dismutase improved impaired acetylcholinemediated relaxationin the aorta of cholesterol-fedrabbits in vitro (36). Although some evidence suggests an association of endothelial dysfunctionwith antioxidantdefense and radical species, other mechanisms may be also involved in the pathogenesis of impaired endothelium-dependentrelaxation in atherosclerosis. Oxidized low density lipoproteins have been reported to cause contraction and inhibition of EDRF-mediated relaxation in pig coronary arteries in vitro (37).Incubationof rabbit aorta in vitro with endothelial cellmodified LDL, but not native LDL, impaired acetylcholinemediated relaxation (38). The latter authors demonstrated that a transfer of lysolecithin from endothelialcell-modified LDL to endothelial membranes produced a unresponsiveness to receptor-regulated endothelium-dependent vasodilators. However, the precise mechanism how oxidized or modified LDL, and in particular lysolecithin, interferes with the L-argininelN0pathway invascular endothelium is unclear.
Ann Med 23
Vascular Responses to Aggregating Platelets: Importance of an Intact Endothelium Aggregating platelets release a number of vasoactive substances. Among these are vasodilators like adenine nucleotides but also vasoconstrictors like serotonin and thrornboxane A, (39). Aggregating canine platelets, when applied to canine coronary arteries, induced endotheliummediatedrelaxation (40). In contrast, arteries mechanically denuded of endothelium contracted. An identical phenomenon could be demonstratedfor aggregating human platelets and human coronary arteries in vitro (41; Fig. 2). The relaxationin response to aggregating platelets was almost abolished and even converted to constriction in the presence of EDRF-inhibitors gossypol, methylene blue, and hemoglobin, but not significantlyimpairedafter pretreatment of the vessel wall with the cyclooxygenaseinhibitor aspirin (41). These results suggest that platelet-inducedrelaxation in intact arteries is mediated by the endothelial release of EDRF. The platelet-derivedsubstanceswhich stimulatethe endothelial release of EDRF are probably adenine nucleotides. This is based on the observation that apyrase which hydrolyzes ATP and ADP to AMP and adenosine abolished platelet-induced relaxation whereas the presence of the serotonin receptor antagonist methysergideor the pretreatmentof platelets with the thromboxane synthesis inhibitor dazmegrel did not affect platelet-induced responses (41). Thus, vascular responses to aggregating platelets are critically dependent on endothelial function.
Platelets, Endothelium-Dependent Responses and Atherosclerosis
-
547
3
a 0
L!Q
20
c
.-0
CL
0
2
0
c
C
sD:
-20
+Endothelium 0 -Endothelium
PI
LL
-40
E
c
-60
.-0
.->*
c
Downloaded by [McMaster University] at 23:05 10 April 2016
Q)
n
8
-80 -9 SP {log MI
107
108 Platelets {l/ml)
Figure 2. Effect of substance P (SP, 1nM), used as afunctional test of endothelial integrity, and human washed platelets (107/ml and 108/ml) on strips of human coronary arteries with the endothelium intact (+Endothehum, 44 strips from 7 patients) or removed (-Endothelium, 22 strips from 4 patients). Response is expressed as percent deviation from the contraction plateau induced by prostaglandin F,= (0.3-3pM). Induced tension was 1.5k0.1 g in endothelium-intact and 1.3f0.1 g in endothelium-denuded preparations. Asteriks denote significant differences between +Endothelium and -Endothelium (P 0
0
t
C
0 ..-
T h r 0.06U
Downloaded by [McMaster University] at 23:05 10 April 2016
In
I
4 min
T hr 0.06U
Thr 0 . 0 6 U
t
T h r 0.06U
WP+B
t
T h r 0.06U
-
.J 10080 -
4 min
60 4020 -
WP +ECB(GOSS)
WP+ECB
w-
0-
t
t
t
Thr 0 . 0 5 U
T h r 0.05U
t
T h r 0.05U Thr 0.05U
WP +ECB +Hb
WP (MB) +
ECB
Thr 0.05U
Figure 3. Measurement of thrombin (Thr)-induced platelet aggregation in a mixture of washed platelets (WP) and empty microcarrier beads (B), or microcarrier beads covered with endothelial cells (ECB). Experiments were performed in the presence of 30 pM indomethacin (a, effects of EDRF), and in the absence of this drug (b, effects of prostacyclin and EDRF). The anti-aggregatory effect of EDRF (a) was 30 pM), after addition of hemoglobin (Hb, 15 pM)to the incubation mixture, or blocked after pretreatment of ECB with gossypol (GOSS, after pretreatment of the platelets with methylene blue (MB, 10 pM,30 min). These inhibitors are specific for EDRF effects as the antiaggregatory effect seen in the absence of indomethacin (b) was not impaired. Therefore, this effect is likely to be mainly due to endothelial prostacyclin. Taken with permission from ref. 58.
intraplatelet negtive feedback mechanism; the PathoPhYsiologicalimportance ofthis system remainsto be established.
Vascular Endothelium as a Defense Mechanism Against Platelet Aggregation and Vasospasm Acute myocardialischemiamanifestedby clinical syndroms
Ann Med 23
of unstable angina pectoris or myocardial infarction usually is the result of an occlusive thrombus formation in the area of atherosclerotic plaques (64). Intact vascular endothelium may play an important role in the defense against platelet aggregation and vasospasm (Fig. 4). Basal release of EDRF and prostacyclin may interfere continuously with platelet aggregation. If local platelet aggregation occurs, platelet-derivedadenine nucleotides stimulate the release of EDRF(N0). Stimulated EDRF(N0) release may override the direct vasoconstrictor effects of other platelet products
Platelets, Endothelium-Dependent Responses and Atherosclerosis INTACT ENDOTHELIUM
ATHEROSCLEROSIS
:elaxation
Downloaded by [McMaster University] at 23:05 10 April 2016
549
Contraction
Figure 4. Schema summarizing the vascular effects of aggregating platelets in patients with normal endothelial function (left) and patients with coronary artery disease (right). In patients with intact endothelium, basal release of endothelium-derived relaxing factor (EDRF) and prostacyclin (PGI,) inhibits continuously platelet aggregation. If local aggregation of platelets occurs, platelet-derived ADP stimulates the endothelial release of EDRF. This increased release of EDRF may override the direct vasoconstrictor effects of other platelet-derived products such as serotonin (5-HT) and thromboxane A, (TxA,) resulting in local vasodilatation. In addition, increased release of EDRF may inhibit further platelet adhesion and aggregation. In patients with atherosclerosis, basal and stimulated release of EDRF is impaired. The EDRF release in response to platelet-derived ADP may not be sufficient to override direct vasoconstrictor effectsof 5-HT and TxA, resulting in local vasoconstriction. Furthermore, anti-aggregatory properties of the endothelium are diminished. Activated platelets may interact with other blood components such as leukocytes. Activated leukocytes may also release potent vasoconstrictors, e.g. TxA,, prostaglandin E, (PGE,), and leukotrienes (LT). EC=endothelial cells, SMC=smooth muscle cells, CSa=complement C5a, PAF=platelet-activating factor.
such as thromboxane and serotonin resulting in local vasodilatation. In addition, stimulation of EDRF(N0) release by adenine nucleotides may inhibit further platelet adhesion and aggregation by a feedback mechanism. It is obvious that endothelial damage or dysfunction would impair this protective mechanism and favor vasoconstriction and further platelet disposition(Fig.4). Since atherosclerosis is a major cause for endothelial dysfunction, occurrence of occlusive thrombus formation in patients with coronary artery disease may be pathophysiologically related to this impairment of endothelial defense. However, the complexity of the interaction between components of the arterial wall, platelets, and other blood components is still far from being fully understood (65).
8.
9. 10. 11. 12. 13. 14.
References 1. Furchgott RF,ZawadzkiJV. The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine. Nature 1980; 288: 3 7 3 - 6 . 2. Furchgott RF. The role of endothelium in the response of vascular smooth muscles todruas. Ann Rev PharmacolToxicol 1984; 24: 175-97. 3. Palmer RMJ. Ferriae AG. Moncada S. Nitric oxide release accounts for’ the bkogical activity of endothelium-derived relaxing factor. Nature 1987; 327. 524-6. 4. lgnarro LJ, Byrns RE, Buga GM, Wood KS, Chaudhuri G. Pharmacological evidence that endothelium-derived relaxing factor is nitricoxide: useof pyrogalloland superoxidedismutase to study endothelium-dependent and nitric oxide-elicited vascular smooth muscle relaxation. J Pharm Exp Ther 1988; 244: 181-9. 5. Myers PR, Minor RL, Guerra R, Bates JN, Harrison DG. Vasorelaxant properties of the endothelium-derived relaxing factor more closely resemble S-nitrosocysteine than nitric oxide. Nature 1990; 345: 161-3. 6. Palmer RMJ, Ashton DS, Moncada S. Vascular endothelial cells synthesize nitric oxide from L-arginine. Nature 1988; 333: 664-6. 7. Forstermann U, Mulsch A, Bohme E, Busse R. Stimulation of soluble guanylate cyclase by an acetylcholine-induced
15.
16.
-
17. 18.
19.
20. 21,
endothelium-derived factor from rabbit and canine arteries. Circ Res 1986; 58: 531-8. lgnarro LJ, Harrison RG, Wood KS, KadowitzPJ.Activation of purified soluble guanylate cyclase by endothelium-derived relaxing factor from intrapulmonary artery and vein: stimulation by acetylcholine, bradykinin, and arachidonic acid. J Pharrn Exp Ther 1986; 237: 893-900. Holzmann S. Endothelium-induced relaxation by acetylcholine associated with larger rises in cyclic GMP in coronary arterial strips. J Cyclic Nucl Res 1982; 8: 409-1 9. Rapoport RM, Murad F. Agonist-induced endothelium-dependent relaxation in rat thoracic aorta may be mediated through cGMP. Circ Res 1983; 52: 352-7. Murad F. Cyclic guanosine monophosphate as a mediator of vasodilation. J Clin Invest 1986; 78: 1-5. Waldman SA, Murad F. Cyclic GMP synthesis and function. Pharmacol Rev 1987; 39: 163-96. Bassenge E, Busse R. Endothelial modulation of coronary tone. Progr Cardiovasc Dis 1988; 30: 349-80. Mugge A, Forstermann U, Lichtlen PR. Endothelial functions in cardiovascular diseases. Z Kardioll989; 78: 147-60. Amezcua JL, Palmer RMJ, de Souza BM, Moncada S. Nitric oxide synthesized from L-arginine regulates vascular tone in the coronary circulation of the rabbit. Br J Pharmacol 1989; 97: 1119-24. Rees DD, Palmer RMJ, Hodson HF, Moncada S. A specific inhibitor of nitric oxide formation from L-arginine attenuates endothelium-dependent relaxation. Br J Pharmacol 1989; 96: 41 8-24. Rees DD, Palmer RMJ, Moncada S. Role of endotheliumderived nitric oxide in the regulation of blood pressure. Proc Natl Acad Sci USA 1989; 86: 3375-8. Mugge A, Lopez JAG, Piegors DJ, Breese KR, Heistad DD. Acetylcholine-induced vasodilatation in rabbit hindlimb in vivo is not inhibited by analogues of L-arginine. Am J Physiol 1991; 260: H242-H247. ForstermannU, Mugge A, FroiichJC. Endothelium-dependent relaxation of human epicardial coronary arteries: frequent lack of effect of acetylcholine. Eur J Pharmacol 1986; 128: 277-81. Luscher T, Cooke JP, Houston DS, Neves RJ, Vanhoutte PM. Endothelium-dependent relaxations in human arteries. Mayo Clin Porc 1987; 62: 6 0 1 4 . Bossaller C, Habib GB, Yamomoto H, Williams C, Wells S, Henry PD. Impaired muscarinic endothelial-dependent relaxation and cyclic guanosine 5-monophosphate formation in atherosclerotic human coronary artery and rabbit aorta. J Clin
Ann Med 23
Downloaded by [McMaster University] at 23:05 10 April 2016
550
Mugge Forstermann Lichtlen
Invest 1987; 79: 1 7 0 4 . 22. Vallance P, Collier J, Moncada S.Effects of endotheliumderived nitric oxide on peripheralarteriolar tone in man. Lancet 1989; II: 997-1000. 23. Jayakody RL, Senaratne, MPJ,Thomson ABR, Kappagoda CT. Cholesterol feeding impairs endothelial-dependent relaxation of rabbit aorta. Can J Physiol Pharmacol 1985, 63: 12069. 24. Verbeuren TJ, Jordaens FH, Zonnekeyn LL, Van Hove CE, Coene MC, Herman AG. Effect of hypercholesterolemia on vascular reactivity in the rabbit. I. Endothelial-dependent and endothelial-independentcontractionsand relaxation in isolated arteries of control and hypercholesterolemic rabbits. Circ Res 1986; 58: 552-64. 25. Cohen RA, Zitnay KM, Haudenschild CC, Cunningham LD. Loss of selective endothelialcell vasoactive functions caused by hypercholesterolemiain pig coronary arteries. Circ Res 1988; 63: 903-1 0. 26. Shimokawa H, Vanhoutte PM. Impaired endothelium-dependent relaxation to aggregating platelets and related vasoactive substances in porcine coronary arteries in hypercholesterolemiaand atherosclerosis. Circ Res 1989;64: 900-1 4. 27. Freiman PC, Mitchell GC, Heistad DD, Armstrong ML, Harrison DG. Atherosclerosisimpairs endothelial-dependent vascular relaxationto acetylcholine and thrombin in primates. Circ Res 1986; 58: 783-9. 28. Farstermann U, Mugge A, Alheid U, Haverich A, Frolich JC. Selectiveattenuation of endothelium-mediatedvasodilation in atherosclerotic human coronary arteries. Circ Res 1988;62: 185-90. 29. Guerra R, Brotherton AFA, Goodwin PJ, Clark CR, Armstrong ML, Harrison DG. Mechanisms of abnormal endothelium-dependent responses in atherosclerosis. Blood Vessels 1989; 26: 300-1 4. 30. Verbeuren TJ, Jordaens FH, Van Hove CE, Van Hoydonck AE, HermanAG. Release and vascular activity of endotheliumderived relaxing factor in atherosclerotic rabbit aorta. Eur J Pharmacoll990; 191: 173434. 31. MuggeA, Harrison DO. L-argininedoes not restoreendothelial dvsfunctionin atheroscleroticrabbit aorta in vitro. Blood Vessels, in press. 32. Minor RL. Mvers PR. Guerra R. Bates JN. Harrison DG. Diet-induceditheroscierosis increases the releasein nitrogen oxides from rabbit aorta. J Clin Invest 1990; 86: 2109-1 6. 33. Gryglewski RJ, Palmer RMJ, Moncada S.Superoxide anion is involved in the breakdownof endothelium-derivedvascular relaxing factor. Nature 1986; 320: 454-6. 34. RubanyiGM, Vanhoutte PM. Superoxideanionsand hyperoxia inactivate endothelium-derivedrelaxing factor. Am J Physiol 1986; 250: H822-H827. 35. Mugge A, Elwell JH, Peterson TE, Harrison DG. Release of intact endothelium-derived relaxing factor depends on endothelial superoxide dismutase activity.Am J Physioll991; 260: C21-225. 36. Mugge A, Elwell JH, Peterson TE, Hofmeyer TG, Heistad DD, Harrison DG. Chronic treatment with polyethylenglycolatedsuperoxidedismutase partiallyrestoresendotheliumdependent vascular relaxationsin cholesterol-fedrabbits. Circ Res, in press. 37. Simon BC, Cunningham LD, Cohen RA. Oxidized low density lipoproteins cause contraction and inhibit endotheliumdependent relaxation in the pig coronary artery. J Clin Invest 1990; 86: 75-9. 38. Kaglyama K, Kerns SA, Morrisett JD, Roberts R, Henry PD. Impairmentof endothelium-dependentrelaxationby lysolecithin in modified low-densitylipoproteins. Nature 1990; 344: 1602. 39. Meyers KM, Holmsen HI Seachord CL. Comparative study of platelet dense granule constituents. Am J Physiol 1982, 243: R454-R461. 40. Houston DS, Shepherd JT, Vanhoutte PM. Adenine nucleotides, serotonin, and endothelium-dependent relaxation to platelets. Am J Physiol 1985; 248: H389-H395. 41. Forstermann U, Mugge A, Bode SM, Frollch JC. Response of human coronary arteries to aggregating platelets: importance of endothelium-derivedrelaxing factor and prostanoids. Circ Res 1988, 63: 306-12. 42. Golino P, Piscione F, Willerson JT, et al. Divergent effects of serotonin on coronary-arterydimensionsand blood flow in
Ann Med 23
patients with coronary atherosclerosisand control patients. N Engl J Med 1991; 324: 641-7. 43. McFadden EP, Clarke JG, Davies GJ, Kaski JC, Haider AW, Maseri A. Effect of intracoronary serotonin on coronary vessels in patients with stable angina and patients with variant angina. N Engl J Med 1991; 324: 648-53. 44. Lopez JAG, Armstrong ML, Piegor DJ, Heistad DD. Effect of early and advancedatherosclerosison vascular responses to serotonin, thromboxane A,, and ADP. Circulation 1989; 79: 698-705. 45. Stuart MJ, Gerrard JM, White JG. Effect of cholesterol on production-ofthromboxane 82 by platelets in vitro. N Engl J Med 1980; 302: 6-1 0. 46. Tremoli E. Maderna P. Colli S. Morazzoni G. Sirtori M. Sirtori CR: Increasedsensitivity and thromboxane 82 formation in type II hyperlipoproteinaemicpatients. Eur J Clin Invest 1984; 14: 329-33. 47. Kaul S, Waack BJ, Mugge A, Brooks RM, Lopez JAG, Heistad DD. Altered vascular responses to activated platelets from hypercholesterolemic humans. Clin Res 1991; 39: 253A. 48. Henson PM. Interactionsbetween neutrophils and platelets. Lab Invest 1990; 62: 391-3. 49. Zatta A, Prosdocimi M, Bertele V, Bazzoni G, Del Maschio A. Inhibition of platelet function by polymorphonuclear leukocytes. J Lab Clin Med 1990; 116: 651-60. 50. Salvernlni D, De Nucci G, Gryglewski RJ, Vane JR. Human neutrophils and mononuclear cells inhibit platelet aggregation by releasing a nitric oxide-likefactor. Proc Natl Acad Sci USA 1989; 86: 6328-32. 51. Lopez JAG, Armstrong ML, Harrison DG, Piegors DJ, Heistad DD. Vascular responses to leukocyte products in atherosclerotic primates. Circ Res 1989; 65: 1078-86. 52. Mugge A, Lopez JAG. Do leukocyteshave a role in hypertension? Hypertension 1991; 17: 331-3. 53. Mugge A, Helstad DD, Padgett RC, Waack BJ, Densen P, Lopez JAG. Mechanisms of contraction induced by human polymorphonuclear and mononuclear leukocytes in normal and atherosclerotic arteries. Circ Res, 1991; 69: 871-80. 54. Gorman RR, Bunting S, Miller OV. Modulation of human platelet adenylatecyclase by prostacylin(PGX). Prostaglandins 1977; 13: 3 7 7 4 8 . 55. Tateson JE, Moncada S, Vane JR. Effects of prostacyclin (PGX) on cyclic AMP concentrations in human platelets. Prostaglandins 1977; 13: 389-97. 56. Mellion BT, lgnarro LJ, Ohlstein EH, Pontecorvo EG, Hyrnan AL, Kadowitz PJ. Evidence for the inhibitory role of guanosine 3 3 monophosphate in ADP-induced human platelet aggregation in the presence of nitric oxide and related vasodilators. Blood 1981; 57: 9 4 6 5 5 . 57. Alheid U, Frdlich JC, Forstermann U. Endothelium-derived relaxing factor from cultured human endothelial cells inhibits aggregation of human platelets.Thromb Res 1987; 47: 56171. 58. Forstermann U, Mugge A, Alheid U, Bode SM, Frolich JC. Endothelium-derivedrelaxingfactor (EDRF): adefense mechanism against platelet aggregationand vasospasm in human coronary arteries. Eur Heart J 1989; 10 (suppl. F): 36-43. 59. Furlona B, HendersonAH. Lewis MJ. Smith JA. Endotheliumderivedrelaxingfactor inhibits in vitroplatelet aggregation.Br J Pharmacol 1987; 90: 687-92. 60. Radomskl MW, Palmer RMJ, Moncada S. The anti-aggregating properties of vascular endothelium: interactions between prostacyclinand nitric oxide. Br J Pharmacol 1987; 92: 639-46. 61. Hogan JC, Lewis MJ, Henderson AH. In vivo EDRF activity influences platelet function. Br J Pharmacoll988; 94: 10202. 62. MacDonald PSI Read MA, Dusting GJ. Synergistic inhibition of platelet aggregationby endothelium-derivedrelaxing factor and prostacyclin. Thromb Res 1988; 49: 437-49. 63. Radomskl MW, Palmer RMJ, Moncada S. An L-arginine/ nitric oxide pathway present in human platelets regulates aggregation. Proc Natl Acad Sci USA 1990; 87: 5193-7. 64. Davies MJ, Thomas A. Thrombosis and acute coronaryartery lesions in sudden cardiac ischemic death. N Engl J Med 1984; 310: 1 1 3 7 4 0 . 65. Dinerman JL, Mehta JL. Endothelial,plateletsand leukocyte interactions in ischemic heart disease: insights into potential mechanisms and their clinical relevance. J Am Colt Cardiol 1990; 16: 207-22.
