Nitric oxide in cardiac transplantation

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Review

Nitric oxide in cardiac transplantation

Wolfgang Dietl, Michael Bauer, Bruno K. Podesser

Ludwig Boltzmann Cluster für Kardiovaskuläre Forschung Medizinische Universität Wien Correspondence: Bruno K. Podesser,e-mail: b.k.podesser@cardiovascular-research.at

Abstract:

The endothelium of coronary arteries has been identified as an important organ locally regulating coronary perfusion and cardiac function by paracrine secretion of nitric oxide (NO) and other vasoactive mediators. Therefore, the established organ procurement in cardiac transplantation using hypothermic storage solutions designed to preserve myocytes but not endothelial cells has to be critically discussed.

Heart transplantation is a prestigious high-end treatment for end-stage heart failure patients with promising survival rates: 84%

one-year and 65% five-year survival. However, these survival rates are still far from being satisfying requiring further research in organ preservation and perioperative management.

This review will focus on possible strategies to improve donor and recipient management in regard to a functional endothelium and NO. The following topics will be addressed: (1) NO and ischemia/reperfusion, to understand the mechanisms that lead to NO depletion and its consequences. (2) NO and hypothermia, to understand the effects of hypothermia on the endothelium. (3) Current status of donor and recipient management, to describe the strategies used today. (4) Possible new approaches: NO-scavenging and NO-substitution, to describe the recent research that is performed in this area including some of our own results. (5) Outlook in donor and recipient management, to give possible new directions, deducted from our current knowledge.

Key words:

nitric oxide, heart transplantation, donor and recipient management

Abbreviations: ACE – angiotensin converting enzyme, ADMA – asymmetrical dimethylarginine, AT II – angiotensin II, cNOS – constitutive nitric oxide synthase, ECMO – extra- corporeal membrane oxygenation, EDRF – endothelial- derived-relaxing-factor, eNOS – endothelial nitric oxide synthase, HTX – heart transplantation, I/R – ischemia/reperfusion, iNOS – inducible nitric oxide synthase, L-NAME – NG-nitro-L- arginine methyl ester, L-NMMA – NG-methyl-L-arginine acetate salt, NO – nitrix oxide, S-NO-HSA – S-NO-human serum albumin

Introduction

Nitric oxide (NO) releasing agents have a long lasting history in cardiovascular medicine. First reports date

back to 1879, when W. Murrell reported that orally administered nitroglycerine relieves angina pectoris [36]. However, the exact mechanisms of its biological action remained unclear.

In 1980, Furchgott and Zawadzki described a potent, endogenous vasodilator [14]. Initially referred to as endothelial-derived-relaxing-factor (EDRF), it took seven more years to identify NO as the primary EDRF [13]. In the forthcoming years, research in NO boomed: It became clear that NO is a central regulator in the cardiovascular system.

This review provides an overview about possible implications of NO substitution for both donor and recipient management in cardiac transplantation.

Pharmacological Reports 2006, 58, suppl., 145152 ISSN 1734-1140

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Re-establishing blood flow to ischemic tissues or organs (reperfusion) is an essential step in many surgi- cal procedures [30]. However, especially after prolonged ischemia, reperfusion can lead to changes in vascular tone and an increase in microvascular perme- ability causing tissue reperfusion edema [57]. These damages are referred to as ischemia/reperfusion (I/R) injury. The consequences of such an injury are massive edema formation and tissue destruction [4, 18].

Constitutive eNOS plays a fundamental role in the pathogenesis of I/R injury. The onset of ischemia leads to elevated intracellular calcium ion concentrations mediated by increased levels of catecholamines.

These increased calcium concentrations activate eNOS to generate nitric oxide and consequently reactive oxygen species and cytotoxic substances [22].

Studies on I/R injury strongly suggest a correlation between initially high NO production during ischemia followed by increasing release of O ^`(decrease in net NO production) and increasing injury to the endothelium, constriction of vessels, and edema formation.

I/R injury is initiated by a massive burst of NO production after ischemia, which depletes local L- arginine concentrations, followed by high production of O ^` after reperfusion and consequently high production of peroxynitrite. The formation of excessive local peroxynitrite concentrations and consequent cleavage products during the initial phase of reperfusion is deleterious. Three of these cleavage products (hydroxyl free radical, nitrogen dioxide free radical, and nitronium cation) are among the most reactive and damaging species and may be major contributors to the severe I/R damage [22].

Endothelial dysfunction is an important factor during and after cardiac transplantation. Both I/R and hypothermia induce endothelial dysfuntion, more commonly known as endothelial stunning: as NO production decreases, vasoconstrictive compounds dominate.

This leads to no-reflow and finally to organ failure. In the heart, this temporary failure is called “myocardial stunning”, which can be characterized as a mechanical dysfunction that persists after reperfusion despite the absence of irreversible damage and despite resto- ration of normal or near-normal coronary blood flow.

Implying that this post ischemic dysfunction is fully reversible, no matter how severe or prolonged [5].

for organ storage until transplantation. The solutions used for this purpose have specific constituents that facilitate a rapid secession of the electrical activity of the organ. They need two meet the following require- ments:

(1) Provision of a physical and biochemical environ- ment that maintains viability of the structural compo- nents of the tissue during hypothermic metabolic arrest and

(2) Minimization of the effects of reperfusion injury.

Though cold ischemic storage is a commonly used and effective method to preserve organs, certain pro- cesses are activated that ultimately can be deleterious to the preserved organ. These include: cellular swelling, extracellular edema, cellular acidosis, depletion of metabolic substrate, reperfusion injury, calcium overload and endothelial injury [24].

Porcine coronary endothelial cells stored in an Uni- versity of Wisconsin solution showed a significant decrease in eNOS activity after storage for more than 6 hours. However, there was no significant decrease stored only for one hour [47].

Current status of donor and recipient management

Donor management

The first step of many leading to successful heart transplantation is adequate organ preservation ensur- ing maintenance of organ viability and function. It is the major challenge to minimize damage to the heart during procurement, storage and implantation, as the heart is always exposed to ischemia and reperfusion during these procedures. The current clinical practice used in heart preservation is based on a single flush induction of cardioplegia and subsequent hypothermic storage in one of a number of storage solutions [66]. These solutions were designed to protect mainly the myocytes against hypothermic swelling, augment energy production on reperfusion, and ablate pathologic damage by reactive oxygen species formed during reperfusion [56].

In this game, time still plays a major roll as the heart only tolerates 4–5 hours of ischemia – longer

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periods lead to a significant increase in acute and chronic organ failure. Consequences are those already described for endothelial stunning.

Besides ischemia, reperfusion and hypothermia there are many other different stimuli that can damage the endothelium during heart transplantation: for instance brain death and mechanical forces from cardioplegic solutions [36].

Recipient management

Short-term management

Registry data from the International Society of Heart and Lung Transplantation shows that despite ad- vances in perioperative management, right ventricular dysfunction accounts for 50% of all cardiac complica- tions and 19% of all early deaths in patients after heart transplantation. There are several factors contributing to right ventricular dysfunction:

Pulmonary hypertension as a result of congestive heart failure is a major risk factor for morbidity and mortality following heart transplantation. In many centers preexisting pulmonary hypertension with a trans- pulmonary gradient over 15 mmHg or a pulmonary vascular resistance greater than 6–8 Woods units is a contraindication for heart transplantation.

During the intraoperative period the elevated pulmonary resistance is further worsened by cardiopulmonary bypass, transfusion of blood, heparin-protamin infusion and other metabolic factors. After a period of cold ischemia the right ventricle of the allograft is not adequately adapted to face a substantial rise in pulmonary vascular resistance [3]. Optimal right ventricular myocardial protection by cardioplegia is difficult due to anatomical limitations in the distribution of the coronary arteries.

Right ventricular failure results in its dilation, ischemia and decreased contractility, leading to a decreased pulmonary blood flow and leftward shift of the septum resulting in a lower LV filling and reduced systemic cardiac output. Treatment of this condition should include: preservation of the coronary perfusion through maintenance of the systemic blood pressure, optimization of the right ventricular preload, reduction of the right ventricular afterload and a limitation of pulmonary vasoconstriction.

Mechanical ways as the implantation of a right ventricular assist device or an extra-corporal membrane oxygenation (ECMO) [58] can be used to lower right ventricular workload. Pharmacologically, potent pulmonary vasodilators as prostaglandin E1 or prosta- cyclin can be used. However, systemic vasodilators bare the problem that they not only affect pulmonary circulation but also systemic circulation and thereby lower systemic blood pressure during this critical perioperative phase.

Inhaled NO has been shown to be a potent, rapidly acting and selective pulmonary vasodilator. Due to its short half life NO is inactivated directly in the lumen of the pulmonary vessels and exerts its action only on the endothelial and smooth muscle cells adjacent the alveolar unit. This is why no or only little effect on the systemic vascular resistance can be observed. How- ever, due to its toxicity and formation of methemoglo- bin, NO and peroxynitrite, the use of inhaled NO should be carried out very carefully [64].

Long-term management

In heart transplant recipients, the alloimmune response and metabolic abnormalities developing as a consequence of the immunosuppressive drugs have deleterious effects on the endothelium. This is not only affecting the early outcome after transplantation but also triggers graft atherosclerosis, which is the leading cause of death in patients surviving the first year after transplantation [62].

NO seems to play a beneficial role in cardiac allograft vasculopathy. After transplantation, the heart and especially the coronary endothelial cells are sub- jected to hypercholesterolemia, hypertriglycerinemia, hyperhomocysteinemia, hyperglycemia and hypertension. All these conditions are associated with endothelial vasodilator dysfunction and mainly triggered by the use of cyclosporine or tacrolimus and steroids for immunosupression. The allograft coronary endothelial cells also serve as potent stimulators as well as targets of allogenic lymphocyte reactivity [65].

The substitution of L-arginine after transplantation has shown to prevent neointimal hyperplasia in allograft coronary arteries via modulating the vascular cell proliferative response to insulin-like growth factor-I and interleukin-6 [34]. Substitution of NOvia

Nitric oxide in cardiac transplantation

Wolfgang Dietl et al.

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plexed to the gene encoding eNOS were infused into the donor coronary circulation before transplantation.

This resulted in an inhibition of NF-kB activation, adhesion molecule expression and the early infiltration of leukocytes [23]. Another novel strategy for the treatment of transplant vasculopathy could be the use of NO-donating aspirin (NCX 4040), which has shown beneficial effects on relaxation, cGMP formation and proliferation of vascular smooth muscle cells in vitro [53].

plexed to the gene encoding eNOS were infused into the donor coronary circulation before transplantation.

This resulted in an inhibition of NF-kB activation, adhesion molecule expression and the early infiltration of leukocytes [23]. Another novel strategy for the treatment of transplant vasculopathy could be the use of NO-donating aspirin (NCX 4040), which has shown beneficial effects on relaxation, cGMP formation and proliferation of vascular smooth muscle cells in vitro [53].

Finally, acute rejection leads to an activation of iNOS with consequent increases in NO concentrations far beyond the physiologic levels in circulation.

NO might have deleterious effects in this setting [1, 7, 40].

Possible new therapeutic approaches

NO-scavenging

Especially concerning iNOS there have been many studies focusing on preventing the induction or inhibiting the activity this enzyme. Moncada’s group and others showed that endotoxin and a variety of cytoki- nes induce iNOS in a variety of cell types, including vascular smooth muscle cells [19]. The induction of this enzyme is prevented by various inhibitors of protein synthesis (actinomycin, cycloheximide) and by dexamethasone [27, 45, 48, 54]. Classical inhibitors of the L-arginine pathway such as NG-nitro-L- arginine methyl ester (L-NAME) and NG-methyl-L- arginine acetate salt (L-NMMA) inhibit both the activity of the inducible enzyme iNOS as well as the activity the constitutive enzymes (eNOS, nNOS). These inhibitors are arginine analogues and principally increase blood pressure and resistance in most vascular beds by inhibiting eNOS and hence reducing basal NO release [16].

Nitric oxide synthase inhibitors have been evaluated both in experimental models as well as in treatment of patients in septic shock. The results gathered in these studies suggest that inhibiting nitric oxide synthase has many detrimental effects: for instance L-NMMA increased pulmonary vascular resistance

L-NMMA increases platelet adhesion to human umbilical vein endothelial cells and platelet accumu- lation in the lungs induced by administration of interleukin-1b and TNF-a administration [46]. Still, there are approaches, describing beneficial effects of NOS inhibition on contractility after cardiopulmonary bypass [10]. Recently, increased blood concentrations of ADMA (asymmetrical dimethylarginine), an endogenous NO inhibitor, have been linked to increased cardiovascular morbidity and mortality and progres- sion of renal disease. Kielstein et al. showed in healthy subjects, that systemic ADMA or L-NAME infusion induces a short-term, dose-related decrease in cardiac output and a subsequent decrease effective renal plasma flow and blood pressure [25].

Growing evidence emerged in the past few years that NO produced by iNOS plays a major role in the etiology of organ rejection. Experimental studies showed increased levels of iNOS in rejected myocardium. Clinical studies confirmed these findings [7, 50]. There are two possible therapeutic approaches:

scavenging of NO and NOS inhibition.

NOX 100, a nitric oxide scavenger, has shown to enhance cardiac allograft survival [49]. This finding was confirmed using a ruthenium based NO scavenger, AMD6221. This effect was explained by an inhibition of nitrosyl protein complex formation [41].

Selective inhibition of iNOS by BBS-1 or BBS-2, both allosteric inhibitors of NOS dimerization, showed to be beneficial for allograft survival in a model of acute rejection. Significantly fewer T- lymphocytes and macrophages were observed in the allografts treated. Furthermore, edema formation and cardiomyocyte damage was reduced [59]. Soto et al., who evaluated Aminoguanidine, a selective iNOS inhibitor [55], confirmed these findings.

However, NO produced by eNOs has been shown be beneficial: inhibition of eNOS by infusion of L-NAME caused a significant increase of intimal thickening in a pig model of heterotopic heart transplantation (HTX) [37].

NO-substitution

Changes to the vascular endothelium have been identified as a precursor to reperfusion damage leading to a decreased release of NO and organ failure [42, 61].

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Substitution of NO – either providing NO directly or substrates for NO formation – appears to be beneficial in myocardial I/R.

Substitution of substrates of NO synthase

Substitution of L-arginine, the substrate of the NO- synthase, has proven to be beneficial in I/R [52]. In a skeletal muscle model, Huk et al. showed that NO levels increase rapidly during early ischemia but drop dramatically during reperfusion. Treatment with L-arginine prevented this drop in NO production. By providing substrates to the eNOS, uncoupling of the enzyme could be prevented and the pathologic production of superoxides was diminished [20].

This beneficial effect has been confirmed in experimental models of cardiac transplantation, when L-arginine was added to the cardioplegic or storage solution [9, 43]. Furthermore, clinical studies using L-arginine in cardioplegia during cardiopulmonary bypass supports this data [2, 8].

Direct NO donors

NO donors increase the bioavailability of NO in the tissue. By direct NO subsititution, endogenous NO synthesis is inhibited, and depletion of L-arginine is prevented. The high L-arginine concentration prevents disarrangement of eNOS and production of superoxide.

Our group is currently evaluating a new NO- Donor, S-NO-human serum albumin (S-NO-HSA), invented by Seth Hallström and Harald Gasser. This special high molecular weight S-nitrosothiol has an exact equimolar S-nitrosation and high S-nitrosograde due to a defined preprocessing [20]. In an experimental setting of two hours of hind limb ischemia and reperfusion Hallström et al. could show that a substitution of NO during I/R preserves the function of eNOS, stabilizes the basal production of NO, decreases production of reactive oxygen species, and therefore has beneficial effects in reduction of I/R injury [20]. In a second study, a simulation of clinical

cold organ procurement and storage, hearts were reperfused after 6 hours of ischemia on an isolated, erythrocyte-perfused working heart model. We could not only show significant beneficial hemodynamic and metabolic effect of S-NO-HSA compared to control, but also compared to a substitution with L-arginine only [51]. In a experimental model of or- thotopical heart transplantation in pigs, including 4 hours of ischemia followed by 3 hours of reperfusion, we observed beneficial hemodynamic and metabolic effects of S-NO-HSA compared to control [17].

Low molecular weight S-nitrosothiols such as S-nitrosoglutathione and S-nitrosocysteine have a short half-life in a range of a few seconds, whereas high molecular weight S-nitrosothiols such as S-nitrosoal- bumin shows a prolonged half-life between 15–20 minin vivo [20].

It has been shown that S-nitroso-N-acetyl-DL- penicillamine induces late preconditioning against myocardial stunning and infarction in rabbits [60]. S- nitrosoglutathione monoethyl ester, another S- nitroso-thiol, has protective effects in isolated rat hearts during cardioplegic ischemic arrest [28]. Fi- nally, S-nitrosoglutathione inhibits platelet activity during coronary angioplasty [32] and suppresses increased nitric oxide activity (i-NOS) after canine cardiopulmonary bypass [35]. In addition, studies have shown that synthetic compounds such as furoxans require thiols for their thiol-mediated generation of nitric oxide [12]. The substitution of NO is controver- sially discussed in literature as there are also studies reporting negative effects: This might result from dif- ferences of both experimental settings and in NO donors as well as methods of substitution.

In a review published in 2001, R.Bolli concludes that endogenous and exogenous NO is beneficial in protecting the not preconditioned, unstressed heart against damage occurring during ischemia and reperfusion [6]. NO plays a critical bifunctional role in late preconditioning, appearing 12–24 hours after an ischemic stimulus and persisting for 72 h. Enhanced production of NO by eNOS is required to trigger iNOS activity and its anti-stunning and anti-infarct actions of late preconditioning.

In the same review, R. Bolli examined the role of NO in modulating the severity of I/R injury. 73% of the reviewed studies showed that NO either endogenous or exogenous has beneficial effects on myocardial protection against infarction or stunning.

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The concept behind the use of angiotensin-converting enzyme (ACE) inhibitors is well understood: ACE is also known as kininase II. This dual enzymatic posi- tion explains its dual action: on the one hand the con- version of angiotensin I to angiotensin II is blocked, leading directly to vasorelaxation, on the other hand the breakdown of bradykinin is blocked, leading to an increase in NO with consequent vasodilation [21].

There have been numerous experimental [26, 29, 31]

and clinical reports [11, 33] on the beneficial action of ACE inhibitors in the setting of I/R. We have recently reported that even in the failing heart, undergoing I/R, myocardial protection can be significantly improved by pre-ischemic ACE-inhibition. The treated rat hearts showed an improvement in postischemic sys- tolic and diastolic function, coronary perfusion as well as higher levels of high-energy phosphates [44].

However, the direct use of ACE-inhibitors in the setting of HTX is rare.

Sasayama and his group report on the effect of captopril and a selective angiotensin II (AT II) receptor blocker in a murine model of graft sclerosis. Both, the ACE-inhibitor and the AT II receptor blocker were able to reduce chronic allograft rejection compared to control [15]. Perrault et al. demonstrated improved coronary endothelial function with Celsior cardioplegia, a solution with a high antioxidant capacity, compared to standard blood and crystalloid solutions. The authors concluded that this preservation of endothelium- dependent relaxation leads to improvements in both short- and long-term outcome in HTX [38].

Outlook in donor and recipient management

From our current experience and in the light of literature we would encourage experimental and clinical transplant scientists to take a more holistic approach in organ preservation. This holistic approach should include:

Improvements in donor procurement. Current do- nor management should be transformed into effective

“donor treatment” to recruit more borderline organs safely into the donor pool. The possible role of pre- ischemic NO-substitution (either as substrate, directly or indirectly), should be considered to guarantee a functional endothelium of the graft after implantation.

with a reduced chance of acute organ failure and pulmonary hypertension. The beneficial role of this peri- and postoperative NO-substitution (substrate, direct or indirect) in chronic rejection is already obvious;

however it needs to be strengthened by larger clinical trials focusing on the development of microvascular disease.

References:

1. Albrecht EW, Stegeman CA, Tiebosch AT, Tegzess AM, van Goor H: Expression of inducible and endothelial nitric oxide synthases, formation of peroxynitrite and reactive oxygen species in human chronic renal transplant failure. Am J Transplant, 2002, 2, 448–453.

2. Andrasi TB, Soos P, Bakos G, Stumpf N, Blazovics A, Hagl S, Szabo G. : L-arginine protects the mesenteric vascular circulation against cardiopulmonary bypass- induced vascular dysfunction. Surgery, 2003, 134, 72–79.

3. Ardehali A, Hughes K, Sadeghi A, Esmailian F, Marelli D, Moriguchi J, Hamilton MA et al.: Inhaled nitric oxide for pulmonary hypertension after heart transplantation.

Transplantation, 2001, 72, 638–641.

4. Baue AE: The horror autotoxicus and multiple-organ failure. Arch Surg, 1992, 127, 1451–1462.

5. Bolli R: Mechanism of myocardial “stunning”. Circula- tion, 1990, 82, 723–738.

6. Bolli R: Cardioprotective function of inducible nitric oxide synthase and role of nitric oxide in myocardial ischemia and preconditioning: an overview of a decade of research. J Mol Cell Cardiol, 2001, 33, 1897–1918.

7. Cannon P, Yang X, Szabolcs MJ, Ravalli S, Sciacca RR, Michler RE: The role of inducible nitric oxide synthase in cardiac allograft rejection. Cardiovasc Res, 1998, 38, 6–15.

8. Carrier M, Pellerin M, Perrault LP, Bouchard D, Page P, Searle N, Lavoie J: Cardioplegic arrest with L-arginine improves myocardial protection: results of a prospective randomized clinical trial. Ann Thorac Surg, 2002, 73, 837–41; discussion 842.

9. Caus T, Desrois M, Izquierdo M, Lan C, LeFur Y, Confort-Gouny S, Metras D et al.: NOS substrate during cardioplegic arrest and cold storage decreases stunning after heart transplantation in a rat model. J Heart Lung Transplant, 2003, 22, 184–191.

10. Chaturvedi RR, Hjortdal VE, Stenbog EV, Ravn HB, White P, Christensen TD, Thomsen AB et al.: Inhibition of nitric oxide synthesis improves left ventricular contractility in neonatal pigs late after cardiopulmonary bypass. Heart, 1999, 82, 740–744.

11. Early and six-month outcome in patients with angina pectoris early after acute myocardial infarction (the GISSI-3

(7)

APPI [angina precoce post-infarto] study). The GISSI-3 APPI Study Group. Am J Cardiol, 1996, 78, 1191–1197.

12. Feelisch M, Schonafinger K, Noack E: Thiol-mediated generation of nitric oxide accounts for the vasodilator action of furoxans. Biochem Pharmacol, 1992, 44, 1149–1157.

13. Fleming I, Busse R: NO: the primary EDRF. J Mol Cell Cardiol, 1999, 31, 5–14.

14. Furchgott RF, Zawadzki JV: The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine. Nature, 1980, 288, 373–376.

15. Furukawa Y, Matsumori A, Hirozane T, Sasayama S:

Angiotensin II receptor antagonist TCV-116 reduces graft coronary artery disease and preserves graft status in a murine model. A comparative study with captopril.

Circulation, 1996, 93, 333–339.

16. Gardiner SM, Kemp PA, March JE, Bennett T: Regional haemodynamic effects of angiotensin II (3–8) in conscious rats. Br J Pharmacol 1993, 110, 159–162.

17. Gottardi R, Szerafin T, Semsroth S: S-nitroso-human serum albumin improves organ preservation in orthotopic heart transplantation in the pig. J Heart Lung Transplan- tation, 2004, 23, 172, abstr.

18. Grace PA: Ischaemia-reperfusion injury. Br J Surg, 1994, 81, 637–647.

19. Guc MO, Furman BL, Paratt JR: Modification of alpha- adrenoceptor-mediated pressor responses by NG-nitro- L-arginine methyl ester and vasopressin in endotoxin- treated pithed rats. Eur J Pharmacol, 1992, 224, 63–69.

20. Hallstrom S, Gasser H, Neumayer C, Fugl A, Nanobash- vili J, Jakubowski A, Huk I et al.: S-nitroso human serum albumin treatment reduces ischemia/reperfusion injury in skeletal musclevia nitric oxide release. Circula- tion, 2002, 105, 3032–3038.

21. Hartman JC: The role of bradykinin and nitric oxide in the cardioprotective action of ACE inhibitors. Ann Tho- rac Surg, 1995, 60, 789–792.

22. Huk I, Nanobashvili J, Neumayer C, Punz A, Mueller M, Afkhampour K, Mittlboeck M et al.: L-arginine treatment alters the kinetics of nitric oxide and superoxide release and reduces ischemia/reperfusion injury in skeletal muscle. Circulation, 1997, 96, 667–675.

23. Iwata A, Sai S, Nitta Y, Chen M, de Fries-Hallstrand R, Dalesandro J, Thomas R et al.: Liposome-mediated gene transfection of endothelial nitric oxide synthase reduces endothelial activation and leukocyte infiltration in trans- planted hearts. Circulation, 2001, 103, 2753–2759.

24. Jahania MS, Sanchez JA, Narayan P, Lasley RD, Mentzer RMJ: Heart preservation for transplantation: principles and strategies. Ann Thorac Surg, 1999, 68, 1983–1987.

25. Kielstein JT, Impraim B, Simmel S, Bode-Boger SM, Tsikas D, Frolich JC, Hoeper MM et al.: Cardiovascular effects of systemic nitric oxide synthase inhibition with asymmetrical dimethylarginine in humans. Circulation, 2004, 109, 172–177.

26. Kitakaze M, Minamino T, Node K, Komamura K, Shino- zaki Y, Mori H, Kosaka H et al.: Beneficial effects of inhibition of angiotensin-converting enzyme on ischemic myocardium during coronary hypoperfusion in dogs.

Circulation, 1995, 92, 950–961.

27. Knowles RG, Salter M, Brooks SL, Moncada S: Anti- inflammatory glucocorticoids inhibit the induction by

endotoxin of nitric oxide synthase in the lung, liver and aorta of the rat. Biochem Biophys Res Commun, 1990, 172, 1042–1048.

28. Konorev EA, Joseph J, Tarpey MM, Kalyanaraman B:

The mechanism of cardioprotection by S-

nitrosoglutathione monoethyl ester in rat isolated heart during cardioplegic ischaemic arrest. Br J Pharmacol, 1996, 119, 511–518.

29. Korn P, Kroner A, Schirnhofer J, Hallstrom S, Bernecker O, Mallinger R, Franz M et al.: Quinaprilat during cardioplegic arrest in the rabbit to prevent ischemia-reperfusion injury. J Thorac Cardiovasc Surg, 2002, 124, 352–360.

30. Korthuis RJ, Granger DN, Townsley MI, Taylor AE: The role of oxygen-derived free radicals in ischemia-induced increases in canine skeletal muscle vascular permeabil- ity. Circ Res, 1985, 57, 599–609.

31. Kupatt C, Habazettl H, Zahler S, Weber C, Becker BF, Messmer K, Gerlach E: ACE-inhibition prevents postischemic coronary leukocyte adhesion and leukocyte- dependent reperfusion injury. Cardiovasc Res, 1997, 36, 386–395.

32. Langford EJ, Brown AS, Wainwright RJ, de Belder AJ, Thomas MR, Smith RE, Radomski MW et al.: Inhibition of platelet activity by S-nitrosoglutathione during coronary angioplasty. Lancet, 1994, 344, 1458–1460.

33. Lazar HL, Volpe C, Bao Y, Rivers S, Vita JA, Keaney JFJ: Beneficial effects of angiotensin-converting enzyme inhibitors during acute revascularization. Ann Thorac Surg, 1998, 66, 487–492.

34. Lou H, Kodama T, Wang YN, Katz N, Ramwell P, Foegh ML: L-arginine prevents heart transplant arteriosclerosis by modulating the vascular cell proliferative response to insulin-like growth factor-I and interleukin-6. J Heart Lung Transplant, 1996, 15, 1248–1257.

35. Mayers I, Salas E, Hurst T, Johnson D, Radomski MW:

Increased nitric oxide synthase activity after canine cardiopulmonary bypass is suppressed by s-nitrosoglutathione.

J Thorac Cardiovasc Surg, 1999, 117, 1009–1016.

36. Murrell W: Nitroglycerine as a remedy for angina pectoris. Lancet 1879, 1, 80–81, 113–115, 151–152, 225–227.

37. Parolari A, Rubini P, Cannata A, Bonati L, Alamanni F, Tremoli E, Biglioli P: Endothelial damage during myocardial preservation and storage. Ann Thorac Surg, 2002, 73, 682–690.

38. Perrault LP, Malo O, Bidouard JP, Villeneuve N, Vilaine JP, Vanhoutte PM: Inhibiting the NO pathway with intra- coronary L-NAME infusion increases endothelial dysfunction and intimal hyperplasia after heart transplantation. J Heart Lung Transplant, 2003, 22, 439–451.

39. Perrault LP, Nickner C, Desjardins N, Dumont E, Thai P, Carrier M: Improved preservation of coronary endothelial function with Celsior compared with blood and crystalloid solutions in heart transplantation. J Heart Lung Transplant, 2001, 20, 549–558.

40. Petros A, Lamb G, Leone A, Moncada S, Bennett D, Val- lance P: Effects of a nitric oxide synthase inhibitor in humans with septic shock. Cardiovasc Res, 1994, 28, 34–39.

41. Pieper GM, Cooper M, Johnson CP, Adams MB, Felix CC, Roza AM: Reduction of myocardial nitrosyl complex formation by a nitric oxide scavenger prolongs car-

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polyaminocarboxylate complex, a novel nitric oxide scavenger, enhances graft survival and decreases nitrosy- lated heme protein in models of acute and delayed cardiac transplant rejection. J Cardiovasc Pharmacol, 2002, 39, 441–448.

43. Pinsky DJ: The vascular biology of heart and lung preservation for transplantation. Thromb Haemost, 1995, 74, 58–65.

44. Pinsky DJ, Oz MC, Koga S, Taha Z, Broekman MJ, Marcus AJ, Liao H et al.: Cardiac preservation is enhanced in a heterotopic rat transplant model by supple- menting the nitric oxide pathway. J Clin Invest, 1994, 93, 2291–2297.

45. Podesser BK, Schirnhofer J, Bernecker OY, Kroner A, Franz M, Semsroth S, Fellner B et al.: Optimizing ischemia/reperfusion in the failing rat heart-improved myocardial protection with acute ACE inhibition. Circula- tion, 2002, 106, I277–1283.

46. Radomski MW, Palmer RM, Moncada S: Glucocorti- coids inhibit the expression of an inducible, but not the constitutive, nitric oxide synthase in vascular endothelial cells. Proc Natl Acad Sci USA, 1990, 87, 10043–10047.

47. Radomski MW, Vallance P, Whitley G, Foxwell N, Mon- cada S: Platelet adhesion to human vascular endothelium is modulated by constitutive and cytokine induced nitric oxide. Cardiovasc Res, 1993, 27, 1380–1382.

48. Redondo J, Manso AM, Pacheco ME, Hernandez L, Sa- laices M, Marin J: Hypothermic storage of coronary endothelial cells reduces nitric oxide synthase activity and expression. Cryobiology, 2000, 41, 292–300.

49. Rees DD, Cellek S, Palmer RM, Moncada S: Dex- amethasone prevents the induction by endotoxin of a nitric oxide synthase and the associated effects on vascular tone: an insight into endotoxin shock. Biochem Biophys Res Commun, 1990, 173, 541–547.

50. Roza AM, Cooper M, Pieper G et al.: NOX 100, a nitric oxide scavenger, enhances cardiac allograft survival and promotes long-term graft acceptance. Transplantation, 2000, 69, 227–231.

51. Russell ME, Wallace AF, Wyner LR, Newell JB, Kar- novsky MJ: Upregulation and modulation of inducible nitric oxide synthase in rat cardiac allografts with chronic rejection and transplant arteriosclerosis. Circula- tion, 1995, 92, 457–464.

52. Semsroth S, Franz M, Fellner B: Nitric oxide substitution during ischemia/reperfusion improves hemodynamic and metabolic outcome of explanted rabbit hearts after long term ischemia. J Heart Lung Transplantation, 2002, 21, 136, abstr.

53. Shiraishi Y, Lee JR, Laks H, Waters PF, Meneshian A, Blitz A, Johnson K et al.: L-arginine administration dur-

drugs for the treatment of saphenous vein graft failure.

Ann Thorac Surg 2003, 75, 1437–1442.

55. Smith RE, Palmer RM, Moncada S: Coronary vasodila- tation induced by endotoxin in the rabbit isolated perfused heart is nitric oxide-dependent and inhibited by dexamethasone. Br J Pharmacol, 1991, 104, 5–6.

56. Soto PF, Jia CX, Rabkin DG, Hart JP, Carter YM, Sardo MJ, Hsu DT et al.: Improvement of rejection-induced diastolic abnormalities in rat cardiac allografts with inducible nitric oxide synthase inhibition. J Thorac Cardio- vasc Surg, 2000, 120, 39–46.

57. Southard JH, Belzer FO: Organ preservation. Annu Rev Med, 1995, 46, 235–247.

58. Sternbergh WC, Makhoul RG, Adelman B: Nitric oxide-mediated, endothelium-dependent vasodilation is selectively attenuated in the postischemic extremity. Sur- gery, 1993, 114, 960–967.

59. Stobierska-Dzierzek B, Awad H, Michler RE: The evolv- ing management of acute right-sided heart failure in cardiac transplant recipients. J Am Coll Cardiol 2001, 38, 923–931.

60. Szabolcs MJ, Sun J, Ma N, Albala A, Sciacca RR, Phil- ips GB, Parkinson J et al.: Effects of selective inhibitors of nitric oxide synthase-2 dimerization on acute cardiac allograft rejection. Circulation, 2002, 106, 2392–2396.

61. Takano H, Tang XL, Qiu Y, Guo Y, French BA, Bolli R:

Nitric oxide donors induce late preconditioning against myocardial stunning and infarction in conscious rabbits via an antioxidant-sensitive mechanism. Circ Res, 1998, 83, 73–84.

62. Tsao PS, Aoki N, Lefer DJ, Johnson Gr, Lefer AM: Time course of endothelial dysfunction and myocardial injury during myocardial ischemia and reperfusion in the cat.

Circulation, 1990, 82, 1402–1412.

63. Valantine HA: Cardiac allograft vasculopathy: central role of endothelial injury leading to transplant

“atheroma”. Transplantation, 2003, 76, 891–899.

64. Wang T, El Kebir D, Blaise G: Inhaled nitric oxide in 2003: a review of its mechanisms of action. Can J An- aesth, 2003, 50, 839–846.

65. Weis M, Cooke JP: Cardiac allograft vasculopathy and dysregulation of the NO synthase pathway. Arterioscler Thromb Vasc Biol, 2003, 23, 567–575.

66. Wheeldon D, Sharples L, Wallwork J, English T: Donor heart preservation survey. J Heart Lung Transplant 1992, 11, 986–993.

Received:

November 23, 2006; in revised form: December 7, 2006