Arteriosclerosis, Thrombosis, and Vascular Biology. 2003;23:567-575
Published online before print March 20, 2003,
doi: 10.1161/01.ATV.0000067060.31369.F9
(Arteriosclerosis, Thrombosis, and Vascular Biology. 2003;23:567.)
© 2003 American Heart Association, Inc.
Cardiac Allograft Vasculopathy and Dysregulation of the NO Synthase Pathway
Michael Weis;
John P. Cooke
From the Division of Cardiovascular Medicine (J.P.C., M.W.), Stanford University School of Medicine, Stanford, Calif, and Medizinische Klinik I (M.W.), University Medical Center Munich-Grosshadern, Ludwig-Maximilians University of Munich, Munich, Germany.
Correspondence to John P. Cooke, Stanford University School of Medicine, Division of Cardiovascular Medicine, 300 Pasteur Drive, Stanford, CA 94305-5406. E-mail john.cooke{at}stanford.edu
 |
Abstract
|
|---|
Cardiac allograft vasculopathy is the most aggressive form of
atherosclerosis in humans and is the leading cause of death
after the first year of heart transplantation. Endothelial dysfunction
is a major contributing factor to the acceleration of coronary
vascular disease in these individuals. A reflection of this
endothelial dysfunction is the severe impairment in endothelium-dependent
vasodilation that occurs early after transplantation. The etiology
of this allograft endothelial alteration is multifactorial and
may include preexisting atherosclerosis of the graft vessels,
reperfusion injury during transplantation, denervation, disruption
of the lymphatic system, and acute and chronic immune injury,
as well as traditional risk factors for coronary artery disease
(hyperlipidemia, diabetes, hypertension, or hyperhomocysteinemia)
and pathogens, such as cytomegalovirus. The alteration in endothelial
function affects vasomotor tone of the coronary arteries. Evidence
indicates that there may be an impairment of endothelial production
and/or activity of NO. Because NO is a potent vasodilator, its
deficiency would explain the abnormal vasomotor tone in these
individuals. In addition, because NO inhibits key processes
in vascular inflammation and atherosclerosis, its absence may
contribute to the acceleration of transplant vascular disease.
Recent studies from our group and others have shed light on
the mechanisms of endothelial dysfunction and its importance
in cardiac allograft vasculopathy. In addition, the alteration
in endothelial function contributes to vascular inflammation
and progression of the disease.
Key Words: endothelium coronary transplantation heart inflammation
 |
Introduction
|
|---|
Accelerated graft atherosclerosis is a key feature of most chronic
rejection syndromes.
1 Coronary atherosclerosis frequently limits
the long-term success of cardiac transplantation, is characterized
by intimal proliferation during the early phase of the disease,
and ultimately manifests itself as luminal stenosis of epicardial
branches, occlusion of smaller vessels, and myocardial infarction.
2 The most salient difference between cardiac allograft vasculopathy
(CAV) and typical atherosclerotic coronary artery disease is
the diffuse involvement of the coronary vasculature.
3 Whereas
the structural changes of atherosclerosis largely affect the
proximal epicardial coronary arteries, in CAV, the disease is
much more extensive. Cardiac transplant recipients often manifest
concentric intimal thickening that affects the distal epicardial
vessels, as well as their branches. Intimal thickening and inflammation
may extend into the donor aorta up to the suture lines and,
in some instances, even into the great veins of the allograft.
4,5 Histopathologic analysis reveals that morphological manifestation
of this vasculopathy may range from concentric, diffuse, intimal
hyperplasia to fibrofatty plaques indistinguishable from spontaneously
occurring atherosclerosis.
3 The clinical detection of CAV is
made more difficult by the frequent absence of typical symptoms
of ischemia in the denervated allograft; by the insensitivity
of coronary angiography, which frequently underestimates the
extent and severity of the disease; by the common involvement
of small intramyocardial vessels; and by the occurrence of functional
coronary alterations independent of morphological changes.
46
Immunologic and nonimmunologic factors influence the evolution and progression of transplant vasculopathy.2,7 Allograft coronary endothelial cells serve as potent stimulators as well as targets of allogeneic lymphocyte reactivity.2,8 The recipients dendritic cells are the first and major antigen-presenting cells that recognize foreign major histocompatibility complex molecules on the allograft endothelium.9 After circulating dendritic cells adhere to endothelial cells, they capture foreign antigens, transmigrate, and usually enter the lymphatic vessels and lymph nodes. After heart transplantation, lymphatic disruption may alter this pathway, favoring reentry (reverse transmigration) of dendritic cells into the blood circulation. Subsequently, dendritic cells stimulate T lymphocytes (1 dendritic cell may stimulate up to 1000 T lymphocytes). The activated lymphocytes adhere to graft endothelial cells, enter the vessel wall, and sustain the chronic immune injury. Alterations in endothelial adhesiveness in the graft vasculature contribute to leukocyte invasion. A number of conditions occurring in the context of transplantation stimulate the expression of adhesion molecules and chemokines/cytokines, which participate in the inflammatory process.4,1012 These predisposing conditions may include preservation/injury, ischemia/reperfusion, acute rejection, antibody deposition and complement fixation, hyperglycemia, hyperlipidemia, and pathogens such as cytomegalovirus (CMV).2,1317 As a consequence, endothelial adhesion molecule and chemokine expression is upregulated, and vascular growth factors and thrombogenic molecules are expressed.7,18,19 Indirect alloresponse is likely to be permanently active because of the traffic of recipient dendritic cells through the graft.20 Disruption of the cardiac lymphatic system may result in decreased clearance of graft-infiltrating cells. The ongoing inflammation promotes allograft endothelial dysfunction and accelerates structural changes.12,21
 |
Endothelial Dysfunction: An Early Determinant of CAV
|
|---|
Coronary endothelial vasodilator dysfunction is a common finding
in cardiac transplant recipients and is an early marker for
the development of intimal thickening and graft atherosclerosis.
In 1988, Fish et al
22 observed a paradoxical coronary vasoconstriction
to acetylcholine in allograft recipients with and without angiographic
evidence of CAV. Subsequently, other investigators have observed
abnormal responses (vasoconstriction and/or impairment in coronary
blood flow response) to serotonin, substance P, cold-pressor
testing, and exercise.
2328 The impairment of endothelial
function is time dependent. Early after transplantation, epicardial
vasodilatation is preserved in response to tachycardia (reflecting
the flow-mediated vasomotor response).
29 By contrast, the vasomotor
response to acetylcholine and cold-pressor test are often abnormal
in the earliest period after transplantation.
25,28 During follow-up,
exercise-induced flow-mediated endothelial vasodilation may
become impaired.
30 The prevalence of epicardial endothelial
dysfunction (defined as a paradoxical vasoconstriction of >10%
in response to acetylcholine) is

30% to 40% of patients during
the first year and 35% to 45% at long term follow-up.
31 Notably,
endothelial function in any one subject may not be diffusely
disturbed after cardiac transplantation.
28 The existence of
coronary segments with functioning endothelium indicates that
the coronary endothelium is not globally impaired in all cardiac
transplant recipients and that endothelial function may not
be irreversibly damaged.
28 Indeed, we have reported that intravenous
administration of
L-arginine acutely improves endothelial vasodilator
function of coronary conduit vessels if given at an early stage
of graft atherosclerosis.
32
The prevalence of microvascular endothelial dysfunction is also time dependent.24,30,33 Early after transplantation, microvascular dysfunction is prominent in 20% of the patients and increases to
30% of the patients during long-term follow-up.31 Intriguingly, there is no significant correlation between the degree of epicardial dysfunction and that of microvascular dysfunction.34 Microvascular endothelial dysfunction occurs even in patients with angiographically normal epicardial coronary arteries. Thus, there appear to be some independent determinants of endothelial dysfunction in the epicardial and resistance vessels of the cardiac allograft.35
 |
Consequences of Allograft Vasomotor Dysfunction
|
|---|
The endothelium is the maestro of the circulation, a major determinant
of vascular tone and blood flow. The healthy endothelium releases
a panoply of vasodilator substances, such as NO, prostacyclin,
atrial natriuretic peptide, endothelium-derived hyperpolarizing
factor, and adrenomedullin. Thus, the healthy endothelium increases
vessel diameter and reduces resistance to blood flow. When the
endothelium becomes diseased, the synthesis and bioactivity
of the vasodilators are reduced, and the balance tips in favor
of endothelium-derived vasoconstrictors, such as endothelin
and thromboxane.
36 This derangement in endothelial function
has clinical consequences. As a result of the impairment in
endothelial vasodilator function, there is an increase in coronary
vascular resistance, which can result in ischemia. Hasdai et
al
37 have found that coronary endothelial dysfunction in humans
is associated with reversible myocardial perfusion defects.
In transplant recipients, an impaired coronary flow reserve
has been associated with subsequent reduction in left ventricular
ejection fraction during a 2-year follow-up,
38 suggesting that
repetitive subendocardial ischemia during myocardial stress
can cause a deterioration of ventricular function. Consistently,
heterogeneity of coronary vasodilator reserve is correlated
with a significantly increased risk of cardiovascular events.
39
As discussed below, endothelial vasodilator dysfunction is associated with other vascular abnormalities (eg, expression of adhesion molecules, leukocyte adherence and infiltration, and smooth muscle cell proliferation). Several groups have reported changes in allograft endothelial functions (vasomotor independent) that are correlated with allograft failure.19,4044 Thus, endothelial vasomotor dysfunction might be a marker of endothelial activation, increased adhesiveness and thrombogenicity, and the risk of atherogenesis. Indeed, early epicardial endothelial vasodilator dysfunction predicts the development of visible vasculopathy (as imaged by intravascular ultrasound) 1 year after transplantation.27 This is consistent with reports that coronary endothelial dysfunction in transplant and nontransplant patients is predictive of adverse cardiovascular events.45,46 It is also possible that the loss of the vasodilator contributes directly to the progression of transplant vasculopathy.47 As it turns out, most of the endothelium-derived vasodilators oppose key processes involved in atherogenesis, ie, cell adhesion, proliferation, and inflammation.48 Endothelium-derived NO is paradigmatic of an endothelium-derived antiatherogenic molecule.
 |
Role of Endothelial NOS in Maintaining Vascular Homeostasis
|
|---|
Endothelium-derived NO is the most potent endogenous vasodilator
known.
49 NO induces vasodilation by stimulating soluble guanylate
cyclase to produce cGMP.
50 NO has a short half-life and avidly
interacts with sulfhydryl-containing proteins, heme proteins,
and oxygen-derived free radicals. By virtue of its ability to
nitrosylate proteins, it may change their activity or behavior.
50 The physiological importance of this endothelium-derived vasodilator
is reflected by the significant increase in vascular resistance
that is induced in animals and humans exposed to pharmacological
antagonists of NO synthase (NOS).
51,52
Endothelium-derived NO also inhibits platelet and leukocyte adherence to the vessel wall.53,54 This effect of NO is mediated in part by the activation of cGMP and phosphorylation of intracellular signaling proteins, such as vasodilator-stimulated phosphoprotein.55 In addition, NO suppresses the expression of adhesion molecules and chemokines regulating endothelial interaction with circulating blood elements. Finally, endothelium-derived NO also inhibits vascular smooth muscle cell proliferation.56 This is in part mediated by an effect of NO, an increase in vascular smooth muscle cell apoptosis.57 In contrast, NO is a survival factor for endothelial cells.58 These observations are consistent with the view that NO is an endogenous antiatherogenic molecule.
Impairment of endothelial NOS (eNOS) contributes to the pathological alterations in vascular reactivity and structure that are observed in atherosclerosis.59,60 Pharmacological inhibition or genetic deficiency of NOS inhibits endothelium-dependent vasodilation, impairs tissue blood flow, and raises the blood pressure.59 Furthermore, NO deficiency promotes the adherence and intimal accumulation of mononuclear cells and accelerates lesion formation in animal models of atherosclerosis.59,61 By contrast, enhancing NO production in the vessel wall slows or even reverses atherogenesis or restenosis.6264 As discussed below, endothelial NO bioactivity is also a modulator of CAV.
 |
Does NO Deficiency Play a Role in the Progression of Transplant Vasculopathy?
|
|---|
In organ transplantation, allograft eNOS expression and activity
can be impaired by a number of mechanisms, including preexisting
arteriosclerotic disease in the graft, graft ischemia before
transplantation, immunosuppressive agents such as cyclosporin
A and tacrolimus, classic risk factors (hyperlipidemia, hypertension,
diabetes, and hyperhomocysteinemia), and, possibly, infectious
diseases such as CMV.
In preclinical models of transplant vasculopathy, NO deficiency accelerates the disorder. The inducible form of NOS (iNOS) is expressed in the vessel wall of the aortic allograft. Inhibition of iNOS activity in the aortic allograft significantly increases intimal hyperplasia at 4 weeks.65 Furthermore, early overexpression of iNOS by the use of ex vivo gene transfer completely prevents the development of structural changes in rejecting grafts.65 Furthermore, structural changes are accelerated in iNOS-knockout mice.66 The protective effects of iNOS in these studies may be due to an effect of NO, ie, the inhibition of SMC proliferation and suppression of the adhesion of platelets and leukocytes to the endothelium.56,67 In the context of these observations, it should be noted that there has been some controversy regarding what role iNOS may have in the development of vascular lesions. We hold the view that under the right conditions, iNOS suppresses inflammation and atherogenesis. Specifically, under circumstances in which L-arginine is not rate limiting, the product of iNOS is NO. NO is a survival factor for endothelial cells, but it induces apoptosis of macrophages and proliferating vascular smooth muscle cells.68 Indeed, by increasing vascular NO generation with supplemental L-arginine, apoptosis of macrophages and regression of preexisting lesions is observed in the fat-fed New Zealand White rabbit.69 In this case, the major source of NO in the vessel wall is iNOS. However, under circumstances in which L-arginine becomes rate limiting, the product of iNOS is the superoxide anion (O2·-), which can increase local oxidative stress and exacerbate the inflammatory process. In human cardiac allografts, microvascular endothelial dysfunction is associated with an enhanced endomyocardial iNOS mRNA expression and is accompanied by the expression of nitrotyrosine protein, suggesting peroxynitrite-mediated vessel damage.70 Importantly, dietary L-arginine has been shown to attenuate the structural changes of transplant vasculopathy in vivo associated with downregulation of insulin-like growth factor-I and interleukin-6.71
The literature supports a protective role for eNOS. In a murine chronic-rejection model, transplant atherosclerosis is accelerated in aortic allografts of eNOS-deficient mice.72 Iwata et al73 have demonstrated that intraoperative liposome-mediated gene delivery of eNOS to rabbit donor hearts results in early gene expression sufficient to reduce ischemia/reperfusion injury by inhibiting nuclear factor-
B activation, adhesion molecule expression (intercellular adhesion molecule-1 and vascular cell adhesion molecule-1), and leukocyte infiltration.73 Enhanced eNOS expression extends graft survival without immunosuppression. Most important, eNOS immunoreactivity is gradually lost after human heart transplantation,74 and a reduced myocardial eNOS gene expression has been associated with coronary endothelial dysfunction.75 Thus, eNOS in the endothelium appears to protect allografts from endothelial activation and structural changes.
 |
Is Impairment of the NOS Pathway a Risk Factor for Vascular Disease in Humans?
|
|---|
Do alterations in the NOS pathway contribute to the initiation
and/or progression of atherosclerosis in humans? Several lines
of evidence indicate that impairment of the NOS pathway does
cause human coronary artery disease and vascular events. Genomic
studies of the NOS pathway indicate that genetic alterations
in NO or O
2·- generation contribute to human vascular
disease. Certain eNOS gene polymorphisms are predictive of coronary
artery disease.
76,77 The eNOS gene Glu298Asp polymorphism is
more prevalent in patients with variant angina, essential hypertension,
and acute myocardial infarction.
7880 Similarly, a quadruple
repeat of a 27-bp sequence in intron 4 of the eNOS gene (allele
a) is associated with the risk of coronary artery disease and
acute myocardial infarction.
81 There is an interaction with
smoking, with homozygotes for the eNOSa allele at risk for greater
severity of coronary artery disease. Of note, it has been reported
that the eNOSa allele is associated with a decrease in the level
of plasma nitrogen oxides.
82 These studies suggest that genetically
determined alterations in the NOS pathway could predispose an
individual to atherosclerosis. Recently, several groups have
independently offered evidence that endothelial vasodilator
dysfunction is an independent predictor of vascular events.
8385 These data provide a compelling rationale for understanding
the mechanisms of NO deficiency, with a view toward developing
new therapeutic avenues to prevent coronary artery disease and
its progression.
 |
Mechanisms of NO Deficiency in CAV
|
|---|
Hypercholesterolemia, hypertriglyceridemia, hyperhomocysteinemia,
hypertension, and hyperglycemia are all conditions that are
associated with the posttransplant state, mainly triggered by
the use of cyclosporine or tacrolimus and steroids for immunosuppression.
13,15,86 Each of these conditions is associated with endothelial vasodilator
dysfunction.
Of note, different immunosuppressive strategies have been shown to elicit different expression patterns of vasoactive mediators in the allograft.75 Specifically, the combination of tacrolimus and azathioprine is associated with decreased myocardial eNOS gene expression and endothelial dysfunction early after transplantation.75 In addition, coronary endothelial vasomotor dysfunction is associated with an increased myocardial expression and elaboration of the vasoconstrictor endothelin.87 Significantly, endothelin immunostaining is increased in coronary arteries affected by CAV.88 The early administration of an endothelin antagonist was associated with lower prevalence of functional and morphological abnormalities in a rat transplant model.89 Moreover, inhibition of the endothelin-1converting enzyme significantly improved survival.90 Inasmuch as endothelial dysfunction appears to be a predictor of morphological changes,27 one might conclude that an imbalance between NO and endothelin bioactivity in the allograft may contribute to the development of CAV.
Cardiac cytokine release, a hallmark of allograft inflammatory activity and a common phenomenon early after heart transplantation, is related, at least in part, to endothelial vasomotor dysfunction of the epicardial and microvascular compartment.12 We found an association between an early elevation of coronary sinus levels of inflammatory cytokines and endothelial vasomotor dysfunction during a 1-year follow-up (M. Weis, unpublished data, 2002).
With respect to inflammation and vascular disease, increasing attention has been focused on the role of human CMV, a member of the herpesviruses.9195 CMV can infect human vascular endothelial cells and induce changes relevant to atherogenesis.94 CMV infection increases the expression of endothelial surface adhesion molecules, which upregulate the recruitment of granulocytes.94 Furthermore, CMV infection promotes mononuclear adhesion, activation, and transendothelial migration within the allograft vasculature.96 CMV infection also shifts the balance between endothelial factors mediating blood fluidity so that a procoagulant state is favored.96 It appears that CMV infection of the endothelium promotes processes that favor atherogenesis and vascular lesion formation. Indeed, human CMV is associated with transplant vasculopathy.9698 The most direct evidence of a link between CMV and transplant atherosclerosis was recently produced by Valantine et al.99 In their study, prophylactic treatment of cardiac transplant recipients with ganciclovir reduced the incidence of vasculopathy.99 Thus, a therapy directed toward CMV infection dramatically improves the outcome of patients after transplantation.
These data suggest that CMV may contribute to the initiation and/or progression of transplant vasculopathy. However, the mechanisms by which CMV may trigger atherogenesis are incompletely defined. The immediate-early gene of human CMV can code for a protein that has sequence homology and immunologic cross-reactivity with a domain of human leukocyte antigen-DR.97 Additionally, CMV interferes with the action of p53, a protein that inhibits proliferation and induces apoptosis of vascular smooth muscle cells.98 One of the major mechanisms by which CMV could initiate and/or accelerate transplant vasculopathy is by impairing the NOS pathway. Inflammation impairs endothelium-dependent vasodilation in humans,12,100 and the virus-induced impairment of the eNOS pathway might accelerate atherosclerosis.101 Indeed, in the hypercholesterolemic mouse, infection with murine forms of chlamydia accelerates plaque growth.102
It is possible that CMV infection could downregulate eNOS expression as well as activity. Tumor necrosis factor (TNF)-
has been reported to destabilize mRNA message for eNOS, possibly by inducing the expression of a binding protein for the 3' untranslated region of eNOS mRNA.103 CMV infection of cells stimulates the expression of TNF-
104,105 as well as transcription factors (such as nuclear factor-
B) that stimulate the expression of TNF-
. Parenthetically, NO may inhibit viral replication in the THP-1 monocytic cell line.106 In addition to the effects of TNF-
on eNOS message stability, we and others have found that exposure of endothelial cells to TNF-
reduces NO synthesis and bioactivity.107 These effects appear to be due to the increased elaboration of asymmetric dimethylarginine (ADMA) and O2·-, respectively (see discussion below). Furthermore, TNF-
may induce the endothelial expression of iNOS. The induction of iNOS does not necessarily increase endothelial NO production. This is because in the setting of inflammation and/or metabolic disturbances associated with vascular disease (eg, hypercholesterolemia), there are deficiencies of the cofactor tetrahydrobiopterin as well as the precursor, L-arginine.108,109 In the absence of tetrahydrobiopterin, NOS is no longer capable of transferring electrons to L-arginine to produce NO; instead, the preferred electron acceptor becomes oxygen, to form O2·-, a phenomenon known as eNOS uncoupling.110 These data support the hypothesis that human CMV infection, one of the most common infectious complications in allograft recipients, may contribute to the development of CAV via interaction with the NOS system.
 |
A Role for ADMA?
|
|---|
The impairment in endothelium-dependent vasodilation occurs
early in the course of vascular disease and affects both conduit
and resistance vessels.
111113 The impairment in endothelium-dependent
vasodilation is multifactorial and dependent on the vessel and
species studied, the stage of atherosclerosis, and the associated
metabolic disorders. The mechanism of impairment may include
endothelial generation of O
2·- and increased degradation
of NO, elaboration of vasoconstrictor prostanoids and endothelin,
reduced elaboration of prostacyclin, and/or impaired biosynthesis
of NO.
60,114
Impaired biosynthesis of NO may be due to alterations in NOS affinity for L-arginine, to lipid-induced impairment of the high-affinity cationic amino acid transporter, to reduced availability of the cofactor tetrahydrobiopterin, or to increased levels of ADMA, the competitive inhibitor of NOS.115,116 Our group and others have accumulated extensive data to indicate that O2·- and ADMA are major determinants of endothelial vasodilator dysfunction in humans at risk for atherosclerosis.107,116118 Whereas O2·- degrades NO to reduce its bioactivity, ADMA inhibits NO synthesis. It is also possible that ADMA may "uncouple" eNOS, so that eNOS generates O2·-.119
Intriguingly, plasma levels of ADMA are elevated in a number of conditions associated with endothelial vasodilator dysfunction, including renal failure, hypercholesterolemia, hyperhomocysteinemia, hypertension, diabetes mellitus, and heart failure.120 When ADMA is added to the medium at levels observed in renal failure, it induces vasoconstriction of vascular rings, which is reversible by addition of L-arginine to the medium.121 Dialysis normalizes plasma ADMA levels and improves endothelium-dependent relaxation of peripheral vessels in patients with renal failure.121 It appears that the levels of ADMA observed in patients with hypercholesterolemia and/or atherosclerosis are sufficient to explain the impairment of endothelial function and to explain the observations made repeatedly by multiple investigators that the endothelial dysfunction is reversible by administration of exogenous L-arginine.122124 It is very likely that the L-arginine/ADMA ratio is a regulator of NOS activity that becomes disordered in atherosclerosis and with risk factors for atherosclerosis. Indeed, in hypercholesterolemic individuals, the plasma L-arginine/ADMA ratio is a better predictor of endothelial vasodilator dysfunction than is LDL cholesterol.117 Importantly, several investigations indicate that there is an L-argininereversible impairment of the NOS pathway in atherosclerosis that is at least in part mediated by ADMA.125127 Recent studies from our laboratory indicate that the major mechanism responsible for elevated plasma levels of ADMA is a reduction in its degradation by the oxidant-sensitive enzyme dimethylarginine dimethyl aminohydrolase (DDAH).107,128,129
DDAH is the enzyme most responsible for the degradation of ADMA. We find that its activity is impaired by hypercholesterolemia, hyperglycemia, and hyperhomocysteinemia.107 The reduction in DDAH activity is responsible for accumulation of ADMA, which then inhibits NO synthesis.
To the extent that ADMA is responsible for the impairment of endothelial vasodilator dysfunction, it may be a predictor for vascular events. Indeed, it has been demonstrated in a study of 120 adults with varying levels of risk that ADMA and age were the only independent predictors of intimal-medial thickness of the carotid artery, as measured by ultrasound.130 This finding has recently been confirmed and extended by Zoccali et al.131 They studied >200 individuals with end-stage renal disease. Most intriguingly, in a 5-year follow-up of these patients, the elevation in plasma level of ADMA was the strongest predictor of vascular events, with those in the upper quintile of plasma ADMA level having an odds ratio >10.131 Independently, another group of investigators found that ADMA is an independent predictor of cardiovascular events in patients with coronary artery disease.132 These data provide strong evidence for the crucial role of the NOS pathway in different stages of vascular disease. Of note, preliminary data from our laboratory indicate that ADMA is elevated in cardiac transplant recipients. Intriguingly, the elevation is greater in CMV-positive patients and is correlated with the extent of transplant coronary artery disease. The central role of the disrupted NO pathway after transplantation in the development of cardiovascular morbidity (based on the described studies) is outlined in the Figure.

View larger version (33K):
[in this window]
[in a new window]
|
Central role of impaired NO bioactivity and endothelial dysfunction in allograft failure. Reduced endothelial NO bioactivity is mediated by impaired DDAH activity and peroxynitrite (ONOO·-) formation. Allograft coronary endothelial dysfunction and/or intimal thickening, as well as donor-derived coronary artery disease, may trigger cardiovascular events. AT II indicates angiotensin II; IP3, inositol 1,4,5-tris-phosphate; DAG, diacylglycerol; MAPK, mitogen-activated protein kinase; VCAM-1, vascular cell adhesion molecule-1; ICAM-1, intercellular adhesion molecule-1; MCP-1, monocyte chemotactic protein-1; ET-1, endothelin-1; PDGF, platelet-derived growth factor; and IGF-1, insulin-like growth factor-1; DMA, dimethylarginine; Citr, citrulline.
|
|
 |
Therapeutic Options
|
|---|
These recent insights indicate a significant contribution of
endothelial dysfunction to the initiation and progression of
atherosclerosis and CAV. Strategies to preserve normal endothelial
function are likely to be useful therapies after heart transplantation.
133 For coronary atherosclerosis, endothelial protective agents
such as the 3-hydroxy-3-methylglutaryl coenzyme A reductase
inhibitors (statins) and ACE inhibitors have already been proven
to reduce cardiac mortality in patients with coronary atherosclerosis.
Statin therapy may be associated with a lower prevalence of
graft endothelial dysfunction in humans, independent of lipid-lowering
effects.
134 Enhancement of myocardial eNOS expression, as well
as anti-inflammatory actions of statins, may be particularly
beneficial in the transplant setting.
133 ACE inhibitors have
been shown to reverse coronary endothelial dysfunction in nontransplant
atherosclerosis
135 and partially improve allograft microvascular
endothelial dysfunction.
136 Calcium channel blockers improve
endothelial function in preclinical models but have not been
convincingly shown to reduce the progression of coronary artery
disease in humans. However, the situation is different in cardiac
transplant recipients, inasmuch as the calcium channel blocker
diltiazem appears to slow the progression of transplant coronary
artery disease.
137 Moreover, enhanced nifedipine-induced coronary
vasorelaxation occurs in transplant recipients with coronary
endothelial dysfunction.
138 Other drugs that might have the
potential to restore endothelial vasodilator dysfunction under
circumstances relevant to CAV include antioxidants such as probucol
and vitamins C and E,
139 insulin sensitizers such as rosiglitazone,
phosphodiesterase inhibitors such as cilostazol, and modifiers
of NO synthesis, including
L-arginine and tetrahydrobiopterin.
Another potential strategy is to inhibit the proliferation of infectious particles, such as CMV, that may affect endothelial function. Indeed, ganciclovir treatment appears to reduce the progression of CAV.99 Improvement of cardioplegic solutions and reperfusion strategies could decrease early myocardial oxidative stress and inflammation-induced alterations in the NOS pathway. Moreover, the explanted donor heart may offer a potential for direct vascular/myocardial gene therapy to supplement eNOS or other protective molecules. In the future, therapeutic manipulation of circulating endothelial or smooth muscle progenitor cells140142 or pharmacological induction of tolerance143 and targeting local or circulating dendritic cells9,144 as well as endothelin inactivation145148 may increase our therapeutic options to prevent allograft endothelial dysfunction and structural changes.
 |
Summary
|
|---|
CAV remains the most troublesome long-term complication of heart
transplantation. Allograft coronary endothelial cells, the allogeneic
barrier between a recipients circulating immunoactive
cells and the transplanted organ, can serve as stimulators as
well as targets of inflammatory reactivity. Immunologic and
nonimmunologic factors likely influence the evolution and progression
of transplant vasculopathy, mediated in part by dysregulation
of the eNOS pathway. Activation and dysfunction of the arterial
endothelium predict the development of CAV and may increase
the risk of graft failure.
Received October 23, 2002;
accepted February 5, 2003.
 |
References
|
|---|
- Häyry P, Isoniemi H, Yilmaz S, Mennander A, Lemström K, Räisänen-Sokolowski A, Koskinen P, Ustinov J, Lautenschlager I, Taskinen E, Krogerus L, Aho P, Paavonen T. Chronic allograft rejection. Immunol Rev. 1993; 134: 3381.[CrossRef][Medline]
[Order article via Infotrieve]
- Weis M, von Scheidt W. Coronary atherosclerosis in the transplanted heart. Annu Rev Med. 2000; 51: 81100.[CrossRef][Medline]
[Order article via Infotrieve]
- Billingham ME. Histopathology of graft coronary disease. J Heart Lung Transplant. 1992; 11: S38S44.[Medline]
[Order article via Infotrieve]
- Hosenpud JD, Shipley GD, Wagner CR. Cardiac allograft vasculopathy: current concepts, recent developments, and future directions. J Heart Lung Transplant. 1992; 11: 923.[Medline]
[Order article via Infotrieve]
- Ventura HO, Mehra MR, Smart FW, Stapleton DD. Cardiac allograft vasculopathy: current concepts. Am Heart J. 1995; 129: 791799.[CrossRef][Medline]
[Order article via Infotrieve]
- Weis M, von Scheidt W. Cardiac allograft vasculopathy: a review. Circulation. 1997; 96: 20692077.[Abstract/Free Full Text]
- Andersen H. Heart allograft vascular disease: an obliterative vascular disease in transplanted hearts. Atherosclerosis. 1999; 142: 243263.[CrossRef][Medline]
[Order article via Infotrieve]
- Pober JS. Immunobiology of human vascular endothelium. Immunol Res. 1999; 19: 225232.[Medline]
[Order article via Infotrieve]
- Lechler R, Ng WF, Steinmann RM. Dendritic cells in transplantation: friend or foe? Immunity. 2001; 14: 357368.[CrossRef][Medline]
[Order article via Infotrieve]
- Cunnigham DA, Dunn MJ, Yacoub MH, Rose ML. Local production of cytokines in the human cardiac allograft. Transplantation. 1994; 57: 13331337.[Medline]
[Order article via Infotrieve]
- Deng MC, Bell S, Huie P, Pinto F, Hunt SA, Stinson EB, Sibley R, Hall BM, Valantine HA. Cardiac allograft vascular disease: relationship to microvascular cell surface markers and inflammatory cell phenotypes on endomyocardial biopsy. Circulation. 1995; 91: 16471654.[Abstract/Free Full Text]
- Weis M, Wildhirt SM, Schulze C, Pehlivanli S, Meiser BM, Fraunberger P, Überfuhr P, von Scheidt W. Modulation of coronary vasomotor tone by cytokines in cardiac transplant recipients. Transplantation. 1999; 68: 12631267.[CrossRef][Medline]
[Order article via Infotrieve]
- Johnson MR. Transplant coronary disease: nonimmunologic risk factors. J Heart Lung Transplant. 1992; 11: S124S132.[Medline]
[Order article via Infotrieve]
- Crisp SJ, Dunn MJ, Rose ML, Barbir M, Yacoub MA. Antiendothelial antibodies after heart transplantation: the accelerating factor in transplant-associated coronary artery disease. J Heart Lung Transplant. 1994; 13: 13811392.
- Rickenbacher PR, Kemna MS, Pinto FJ, Hunt SA, Alderman EL, Schroeder JS, Stinson EB, Popp RL, Chen I, Reaven G, Valantine HA. Coronary artery intimal thickening in the transplanted heart: an in vivo intracoronary ultrasound study of immunologic and metabolic risk factors. Transplantation. 1996; 61: 4653.[CrossRef][Medline]
[Order article via Infotrieve]
- Hoang K, Chen I, Reaven G, Zhang L, Ross H, Billingham M, Valantine H. Diabetes and dyslipidemia: a new model for transplant coronary artery disease. Circulation. 1998; 97: 21602168.[Abstract/Free Full Text]
- Hancock WW, Buelow R, Sayegh MH, Turka LA. Antibody-induced transplant arteriosclerosis is prevented by graft expression of anti-oxidant and anti-apoptotic genes. Nat Med. 1998; 4: 13921396.[CrossRef][Medline]
[Order article via Infotrieve]
- Ardehali A, Laks H, Drinkwater DC, Ziv E, Drake TA. Vascular cell adhesion molecule-1 is induced on vascular endothelial and medial smooth muscle cells in experimental cardiac allograft vasculopathy. Circulation. 1995; 92: 450456.[Abstract/Free Full Text]
- Dietrich H, Hu Y, Zou Y, Dirnhofer S, Kleindienst R, Wick G, Xu Q. Mouse model of transplant arteriosclerosis: role of intercellular adhesion molecule-1. Arterioscler Thromb Vasc Biol. 2000; 20: 343352.[Abstract/Free Full Text]
- Rogers NJ, Lechler RI. Allorecognition. Am J Transplant. 2001; 1: 97102.[Medline]
[Order article via Infotrieve]
- Pethig K, Heublein B, Kutschka I, Haverich A. Systemic inflammatory response in cardiac allograft vasculopathy: high-sensitive C-reactive protein is associated with progressive luminal obstruction. Circulation. 2000; 102 (suppl III): III-233III-236.
- Fish RD, Nabel EG, Selwyn AP, Ludmer PL, Mudge GH, Kirsshenbaum JM, Schoen FJ, Alexander RW, Ganz P. Response of coronary arteries of transplant patients to acetylcholine. J Clin Invest. 1988; 81: 2131.
- Mügge A, Heublein B, Kuhn B, Nolte C, Haverich A, Warnecke J, Forrsmann WG, Lichtlen PR. Impaired coronary dilator response to substance P and impaired flow-dependent dilator responses in heart transplant patients with graft vasculopathy. J Am Coll Cardiol. 1993; 21: 163171.[Abstract]
- Hartmann A, Weis M, Olbrich HG, Cieslinski G, Schacherer C, Burger W, Beyersdorf F, Schräder R. Endothelium-dependent and endothelium-independent vasomotion in large coronary arteries and in the microcirculation after cardiac transplantation. Eur Heart J. 1994; 15: 14861493.[Abstract/Free Full Text]
- Benvenutti C, Aptecar E, Mazzucotelli JP, Jouannot P, Loisance D, Nitenberg A. Coronary artery response to cold-pressor test is impaired early after operation in heart transplant recipients. J Am Coll Cardiol. 1995; 26: 446451.[Abstract]
- Preumont N, Lenaers A, Goldman S, Vachiery JL, Wikler D, Damhaut P, Degre S, Berkenboom G. Coronary vasomotility and myocardial blood flow early after heart transplantation. Am J Cardiol. 1996; 78: 550554.[CrossRef][Medline]
[Order article via Infotrieve]
- Davis SF, Yeung AC, Meredith IT, Charbonneau F, Ganz P, Selwyn AP, Anderson TJ. Early endothelial dysfunction predicts the development of transplant coronary artery disease at 1 year posttransplant. Circulation. 1996; 93: 457462.[Abstract/Free Full Text]
- Weis M, Wolf WP, Mazilli N, Olbrich HG, Burger W, Hartmann A. Variations of segmental endothelium dependent and endothelium independent vasomotor tone in the long term follow up after cardiac transplantation (qualitative changes in endothelial function). Am Heart J. 1997; 134: 306315.[CrossRef][Medline]
[Order article via Infotrieve]
- Aptecar E, Dupouy P, Benvenuti C, Mazzucotelli JP, Teiger E, Geschwind H, Castaigne A, Loisance D, Dubois-Rande JL. Sympathetic stimulation overrides flow-mediated endothelium-dependent epicardial coronary vasodilation in transplant patients. Circulation. 1996; 94: 25422550.[Abstract/Free Full Text]
- Vassalli G, Gallino A, Kiowski W, Jiang Z, Turina M, Hess OM. Reduced coronary flow reserve during exercise in heart transplant recipients. Circulation. 1997; 95: 607613.[Abstract/Free Full Text]
- Weis M, Pehlivanli S, von Scheidt W. Cardiac allograft endothelial dysfunction: cause, course, and consequences. Z Kardiol. 2000; 89: IX58IX62.[CrossRef]
- Drexler H, Fischell TA, Pinto FJ, Chenzbraun A, Botas J, Cooke JP, Alderman EL. Effect of L-arginine on coronary endothelial function in cardiac transplant recipients: relation to vessel wall morphology. Circulation. 1994; 89: 16151623.[Abstract/Free Full Text]
- Treasure CB, Vita JA, Ganz P, Ryan TJ Jr, Schoen FJ, Vekshtein V, Yeung AC, Mudge GH, Alexander RW, Selwyn AP, Fish RD. Loss of coronary microvascular response to acetylcholine in cardiac transplant patients. Circulation. 1992; 86: 11561164.[Abstract/Free Full Text]
- Hollenberg SM, Tamburro P, Klein LW, Burns D, Easington C, Costanzo MR, Parrillo JE, Johnson MR. Discordant epicardial and microvascular endothelial responses in heart transplant recipients early after transplantation. J Heart Lung Transplant. 1998; 17: 487494.[Medline]
[Order article via Infotrieve]
- Clausell N, Butany J, Molossi S, Lonn E, Gladstone P, Rabinovitch M, Daly PA. Abnormalities in intramyocardial arteries detected in cardiac transplant biopsy specimens and lack of correlation with abnormal intracoronary ultrasound or endothelial dysfunction in large epicardial coronary arteries. J Am Coll Cardiol. 1995; 26: 110119.[Abstract]
- Cooke JP, Dzau VJ. Nitric oxide synthase: role in the genesis of vascular disease. Annu Rev Med. 1997; 48: 489509.[CrossRef][Medline]
[Order article via Infotrieve]
- Hasdai D, Gibbons RJ, Holmes DR Jr, Higano ST, Lerman A. Coronary endothelial dysfunction in humans is associated with myocardial perfusion defects. Circulation. 1997; 96: 33903395.[Abstract/Free Full Text]
- Weis M, Hartmann A, Olbrich HG, Hör G, Zeiher AM. Prognostic significance of coronary flow reserve on left ventricular ejection fraction in heart transplant recipients. Transplantation. 1998; 65: 103108.[Medline]
[Order article via Infotrieve]
- Wolford TL, Donohue TJ, Bach RG, Drury JH, Caracciolo EA, Kern MJ, Miller LW. Heterogeneity of coronary flow reserve in the examination of multiple individual allograft coronary arteries. Circulation. 1999; 99: 626632.[Abstract/Free Full Text]
- Labarrere CA, Nelson DR, Faulk WP. Endothelial activation and development of coronary artery disease in transplanted human hearts. JAMA. 1997; 278: 11691175.[Abstract]
- Holschermann H, Bohle RM, Zeller H, Schmidt H, Stahl U, Fink L, Grimm H, Tillmanns H, Haberbosch W. In situ detection of tissue factor within the coronary intima in rat cardiac allograft vasculopathy. Am J Pathol. 1999; 154: 211220.[Abstract/Free Full Text]
- Derhaag JG, Duijvestijn AM, Damoiseaux JG, van Breda Vriesman PJ. Effects of antibody reactivity to major histocompatibility complex (MHC) and non-MHC alloantigens on graft endothelial cells in heart allograft rejection. Transplantation. 2000; 69: 18991906.[CrossRef][Medline]
[Order article via Infotrieve]
- Szabolcs MJ, Cannon PJ, Thienel U, Chen R, Michler RE, Chess L, Yellin MJ. Analysis of CD154 and CD40 expression in native coronary atherosclerosis and transplant associated coronary artery disease. Virchows Arch. 2000; 437: 149159.[CrossRef][Medline]
[Order article via Infotrieve]
- Labarrere CA, Lee JB, Nelson DR, Al-Hassani M, Miller SJ, Pitts DE. C-reactive protein, arterial endothelial activation, and development of transplant coronary artery disease: a prospective study. Lancet. 2002; 360: 14621467.[CrossRef][Medline]
[Order article via Infotrieve]
- Hollenberg SM, Klein LW, Parrillo JE, Scherer M, Burns D, Tamburro P, Oberoi M, Johnson MR, Costanzo MR. Coronary endothelial dysfunction after heart transplantation predicts allograft vasculopathy and cardiac death. Circulation. 2001; 104: 30913096.[Abstract/Free Full Text]
- Weis M, Kuebrich A, Pehlivanli S, Muscholl M, Fliri H, Koglin J, Meiser B, von Scheidt W. Prognostic impact of coronary endothelial dysfunction after heart transplantation. Eur Heart J. 2002; 23 (suppl 1): 549.Abstract.
- Davis SF, Yeung AC, Meredith I, Charbonneau F, Ganz P, Selwyn AP, Anderson TJ. Early endothelial dysfunction predicts the development of transplant coronary artery disease at 1 year posttransplant. Circulation. 1996; 93: 457462.
- Cooke JP, Dzau VJ. Derangements of the nitric oxide synthase pathway, L-arginine, and cardiovascular diseases. Circulation. 1997; 96: 379382.
- Furchgott RF, Zawadzki JV. The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine. Nature. 1980; 288: 373376.[CrossRef][Medline]
[Order article via Infotrieve]
- Ignarro L, Burke T, Wood K, Wolin M, Kadowitz P. Association between cyclic GMP accumulation and acetylcholine-elicited relaxation of bovine intrapulmonary artery. J Pharmacol Exp Ther. 1984; 228: 682690.[Abstract/Free Full Text]
- Vallance P, Collier J, Moncada S. Effects of endothelium-derived nitric oxide on peripheral arteriolar tone in man. Lancet. 1989; 2: 9971000.[Medline]
[Order article via Infotrieve]
- Rees DD, Palmer RM, Moncada S. Role of endothelium-derived nitric oxide in the regulation of blood pressure. Proc Natl Acad Sci U S A. 1989; 86: 33753378.[Abstract/Free Full Text]
- Kubes P, Suzuki M, Granger DN. Nitric oxide: an endogenous modulator of leukocyte adhesion. Proc Natl Acad Sci U S A. 1991; 88: 46514655.[Abstract/Free Full Text]
- Tsao P, McEnvoy L, Drexler H, Butcher E, Cooke J. Enhanced endothelial adhesiveness in hypercholesterolemia is attenuated by L-arginine. Circulation. 1994; 89: 21762182.[Abstract/Free Full Text]
- Smolenski A, Burkhardt AM, Eigenthaler M, Butt E, Gambaryan S, Lohmann SM, Walter U. Functional analysis of cGMP-dependent protein kinases I and II as mediators of NO/cGMP effects. Naunyn Schmiedebergs Arch Pharmacol. 1998; 358: 134139.[CrossRef][Medline]
[Order article via Infotrieve]
- Garg UC, Hassid A. Nitric oxide-generating vasodilators and 8-bromo-cyclic guanosine monophosphate inhibit mitogenesis and proliferation of cultured rat vascular smooth muscle cells. J Clin Invest. 1989; 83: 17741777.
- Weidinger F, McLenachan JM, Cybulsky MI, Gordon JB, Rennke HG, Hollenberg NK, Fallon JT, Ganz P, Cooke JP. Persistent dysfunction of regenerated endothelium after balloon angioplasty of rabbit iliac artery. Circulation. 1990; 81: 16671679.[Abstract/Free Full Text]
- Dimmeler S, Rippmann V, Weiland U, Haendeler J, Zeiher AM. Angiotensin II induces apoptosis of human endothelial cells: protective effect of nitric oxide. Circ Res. 1997; 81: 970976.[Abstract/Free Full Text]
- Cooke J, Dzau V. Nitric oxide synthase: role in the genesis of vascular disease. Annu Rev Med. 1997; 48: 489509.
- Vanhoutte PM. Endothelial dysfunction and atherosclerosis. Eur Heart J. 1997; 18 (suppl E): E19E29.
- Gimbrone MA Jr, Cybulsky MI, Kume N, Collins T, Resnick N. Vascular endothelium: an integrator of pathophysiological stimuli in atherogenesis. Ann N Y Acad Sci. 1995; 748: 122132.[Medline]
[Order article via Infotrieve]
- Cooke JP, Singer AH, Tsao P, Zera P, Rowan RA, Billingham ME. Antiatherogenic effects of L-arginine in the hypercholesterolemic rabbit. J Clin Invest. 1992; 90: 11681172.
- von der Leyen HE, Gibbons GH, Morishita R, Lewis NP, Zhang L, Nakajima M, Kaneda Y, Cooke JP, Dzau VJ. Gene therapy inhibiting neointimal vascular lesion: in vivo transfer of endothelial cell nitric oxide synthase gene. Proc Natl Acad Sci U S A. 1995; 92: 11371141.[Abstract/Free Full Text]
- Wang BY, Ho HK, Lin PS, Schwarzacher SP, Pollman