Articles |
From the Section of Vascular Medicine, Division of Cardiovascular Medicine, Stanford University (Calif).
Correspondence to John P. Cooke, MD, PhD, Division of Cardiovascular Medicine, Stanford University School of Medicine, 300 Pasteur Dr, Stanford, CA 94305-5246.
| Abstract |
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Key Words: endothelium hypercholesterolemia atherosclerosis monocyte
| Introduction |
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Accordingly, the aim of the present study was to determine whether oral administration of L-arginine to hypercholesterolemic rabbits would retard progression of preexisting intimal lesions.
| Methods |
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Animals were then randomized into three dietary treatment groups. Rabbits in two of the groups were exposed to a high-cholesterol diet (0.5% cholesterol chow, Dyets) for 10 weeks. Subsequently, animals received vehicle (CHOL group) or L-arginine (2.25% wt/vol; ARG group) in the drinking water, and cholesterol chow was continued (for a total study duration of 23 weeks). The dose of L-arginine used in this study represents a sixfold increase in the daily arginine intake and in previous studies was associated with a doubling of the plasma arginine concentration.13 14 15
Animals from each of the three experimental groups were randomly selected to be killed at 10, 14, 18, or 23 weeks of dietary treatment (at which time animals in the ARG group had received 0, 4, 8, and 13 weeks of arginine supplementation, respectively). After an overdose of intravenous pentobarbital, blood was obtained for biochemical analysis and the thoracic aortae harvested for physiological and histological studies. Two segments (3 to 4 mm each) from the portion just distal to the subclavian artery were used for vascular reactivity studies, and the rest of the descending thoracic aorta was used for determination of plaque surface area.
Serum Chemistry
Blood samples were obtained at the time of
death from all
animals for determination of total cholesterol, HDL, and
plasma-free arginine. Serum cholesterol and HDL were
analyzed with the use of a modification of the enzymatic method
of Allain et al as developed by Sigma
Diagnostics.13 16 Serum arginine was
determined with the use of an automated amino acid analyzer, as
described previously.13
Vascular Reactivity
The rings (3 to 4 mm each) of thoracic
aorta were dissected free
of connective tissue and immediately placed into oxygenated
PSS that was composed of the following (mmol/L): NaCl 118.3, KCl 4.7,
CaCl2 2.5, MgSO4 1.2,
KH2PO4 1.2, NaHCO3 25.0, and
glucose 11.1. Pairs of rings from each animal were mounted horizontally
on stainless steel wires placed through the lumen and connected to
force transducers. The vascular rings were suspended in the organ
chambers filled with oxygenated PSS at 37°C. Over a
period of 60 minutes, rings were progressively stretched to the optimal
point of their length-tension relation (determined previously to be
4 g).13 Subsequently, the EC50 of
norepinephrine was determined by exposing the tissues to
increasing concentrations of norepinephrine (in
half-log increments from 10-9 to 10-4
mol/L). Once a maximal response was obtained, the rings were washed
repeatedly with fresh PSS for 60 minutes until the tension returned to
the previous baseline value. Response to vasodilating agents
(nitroglycerin, acetylcholine) was studied after the
rings were precontracted with the EC50 concentration of
norepinephrine. After a stable contraction was obtained,
the rings were exposed to increasing doses of the vasodilator.
Histomorphometric Studies
Histology
On
completion of the vascular reactivity studies, the aortic
rings were fixed in 10% buffered formalin, embedded in paraffin,
sectioned, and stained with an elastic van Gieson stain for light
microscopy and histomorphometric measurements. Measurements of intimal
and medial cross-sectional areas (expressed in square millimeters)
were made with the aid of a computerized image analyzer (Image
Analyst, Automatix). At least six sections from each aortic ring were
examined, and the values from each were averaged to derive a value for
each ring.
Lesion Surface Area
The segment of
descending thoracic aorta not used for vascular
reactivity studies was fixed in formalin immediately after dissection.
Subsequently, the aorta was incised longitudinally, opened, and placed
flat under a glass slide for photography. The photographs were
projected and the lesion surface and total surface areas quantified
by planimetry by an observer blinded to the treatment groups.
Measurement of Nitrogen Oxides and Superoxide Anion
A
separate group of rabbits (n=6) was used for determination of
vascular NO and superoxide anion elaboration. Two groups of three
rabbits each were fed 0.5% cholesterol for 10 weeks. At
week 10, one group (ARG) received 2.25% L-arginine in
addition to the cholesterol diet, whereas the other group
continued on the cholesterol diet only (CHOL). The animals
were killed at 12 weeks (at which time the ARG animals had received
L-arginine for a total of 2 weeks).
Before they were killed, the animals were lightly sedated with pentobarbital (200 to 250 mg) and the central ear artery cannulated for measurement of intra-arterial blood pressure. Subsequently, an overdose of intravenous pentobarbital was administered and the thoracic aortae harvested.
For measurement of nitrogen oxides, rings (15 mm) from the arch of the thoracic aorta were removed and placed in ice-cold, oxygenated PSS. After the adventitia was removed, the segment was then carefully opened longitudinally and incubated in 2 mL of Hanks' balanced salt solution (Irvine Scientific), with the endothelial surface exposed to the medium. The medium contained calcium ionophore (1 µmol/L) and L-arginine (100 µmol/L) at 37°C. At selected time points (0, 30, 60, 120 minutes), the medium was collected for measurement of nitrogen oxide and replaced with 2 mL of fresh media. After incubation the aortic segment was blotted dry and weighed. Nitrogen oxide in the incubation medium was measured with a commercially available chemiluminescence apparatus (model 2108, Dasibi Corp), as previously described.15 The samples (100 µL) were injected into boiling acidic vanadium (III). The reaction uses acidic vanadium (III) at 98°C to reduce both NO2- and NO3- to NO, which is then quantified by the chemiluminescence detector after the reaction with ozone. Signals from the detector were analyzed by a computerized integrator and recorded as areas under the curve. Standard curves for NO2/NO3 were linear over the range of 50 pmol to 10 nmol.
For determination of vascular superoxide anion, rings of the suprarenal abdominal aorta 5 mm in length were dissected free of adventitia and transferred to glass vials containing 0.25 mmol lucigenin per 1 mL of phosphate-buffered saline. After a delay of 30 seconds, superoxide release was measured by chemiluminescence at 1-minute intervals at room temperature with the use of a commercially available luminometer (Turner TD-20e Luminometer). Vials containing all components with the exception of aortic rings were counted and these blank values subtracted from the chemiluminescence signals obtained from aortic rings.17
Drugs
All solutions were prepared in distilled water made
fresh the
day of the experiment and stored on ice. Norepinephrine
bitartrate, acetylcholine chloride, and L-arginine were
purchased from Sigma Chemical Co, nitroglycerin from
DuPont Chemicals, and calcium ionophore (A23187) from Calbiochem.
Data Analysis
Data are expressed as mean±SEM.
Concentration-effect curves
to norepinephrine are expressed as contractions in grams
above the resting tension. The concentration-effect curves were
characterized by determining the maximal response and the
EC50. The concentration-effect curves to acetylcholine
or nitroglycerin are expressed as the percentage of
tension attained by precontraction with norepinephrine.
Comparisons between the three experimental groups were made by ANOVA. A
value of P<.05 was considered significant.
| Results |
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At all time points,
the plasma cholesterol level was
markedly elevated in each of the two experimental groups receiving the
atherogenic diet compared with the animals receiving normal chow (Table
1
). The addition of dietary L-arginine supplementation
did
not have a significant effect on the plasma cholesterol
level. There was no difference in plasma HDL levels between the three
experimental groups. Plasma arginine levels were increased by 20% to
65% in the ARG group compared with the CHOL group (Table 2
).
|
Vascular Reactivity
Endothelium-Independent Responses
The response to norepinephrine was not different in
the three experimental groups at any time point, with potency and
maximal tensions that were similar (data not shown).
Endothelium-independent vasorelaxation was also not
different between the experimental groups, with potency and maximal
relaxations that were similar (Table 3
).
|
Endothelium-Dependent Relaxation
NO-dependent
vasodilation to acetylcholine was significantly
impaired in the CHOL group at all time points compared with the animals
receiving normal chow (Fig 1
). In the CHOL group,
endothelium-dependent vasodilation (as expressed by
the maximal response to acetylcholine) became progressively attenuated
over the course of the study (from 53.4% at week 10 to 17.4% at week
23; Fig 1
). By contrast, at 14 and 18 weeks animals in the ARG
group
(hypercholesterolemic animals that had received
L-arginine supplementation for 4 and 8 weeks, respectively)
exhibited significantly improved responses compared with the CHOL
animals at the same time points (Fig 1
, top right and bottom
left
panels). This beneficial effect was lost by week 23 in 4 of the 7
animals ("nonresponders") at this time point (Fig
1
, bottom
right panel). However, despite 23 weeks of persistent
hypercholesterolemia in 3 of the 7 ARG animals,
endothelium-dependent relaxation remained normal
(as judged by a maximal response to acetylcholine that was 2 SDs above
the mean value for the CHOL group at this time point [dashed line in
Fig 2
, top panel]).
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Histomorphometry
Lesion Surface Area
Planimetry
of the lesion within the thoracic aorta was also
performed to determine the amount of surface area involved by lesions.
After 10 weeks on the atherogenic diet, each of the two groups
receiving high-cholesterol chow had a similar
percentage of surface area involved by lesion (30.3% versus 27.3%,
ARG versus CHOL; P=NS; Fig 2
, bottom panel). At
week 14, the
CHOL animals manifested an increase in lesion surface area (to 36.5%),
whereas ARG animals exhibited a reduction in lesion surface area (to
20.9%). This trend was maintained at week 18, with CHOL animals
manifesting a progression in lesion surface area (to 43.7%), whereas
ARG animals exhibited a significant reduction in lesion surface area
(to 18.3%). By week 23, the animals in the CHOL group exhibited a
further increase in lesion surface area (to 56.5%). At this time point
there was a loss of the antiatherogenic effect of arginine in the four
nonresponders that coincided with the loss of the ability of arginine
to restore NO activity in these animals (Fig 2
, top panel).
However, in
3 of the 7 ARG animals, NO activity remained persistently normal
despite 23 weeks on the high-cholesterol diet (dashed
line in Fig 2
, top panel). In these 3 responders, lesion
surface area
was only 5.4% (dotted line in Fig 2
, bottom panel), a
remarkable
finding in view of the persistent
hypercholesterolemia.
The differences in lesion surface between the
responders and
nonresponders could not be accounted for by differences in lipid values
(Table 4
).
|
When all L-arginine-treated
hypercholesterolemic animals (from weeks 14, 18,
and 23) were treated as one group (n=20), their maximal relaxation to
acetylcholine was significantly greater and intimal lesion surface area
significantly less than all hypercholesterolemic
animals not treated with arginine (from weeks 14, 18, and 23; Fig
3
).
|
Cross-Sectional Area
The
cross-sectional area of the media was not different
between the two hypercholesterolemic groups at any
time point (Table 5
).
|
There was no measurable intima in
vessels from
normocholesterolemic animals. There was a
progressive time-dependent increase in aortic intimal area in the
CHOL group. In contrast, in the ARG group intimal lesion area
progressed at a slower rate and was significantly less than that of the
CHOL group at the 18-week time point (Table 5
). The analysis of
intima-media ratios demonstrated a similar pattern, with ARG
animals manifesting a significant reduction in intima-media ratio
at 18 weeks.
Vascular NO and Superoxide Anion
At 12 weeks, vascular
elaboration of nitrogen oxides was
significantly increased in ARG animals compared with CHOL animals
(11.6±3.0 versus 8.5±0.7 pmol/mg tissue per 100 µL buffer;
P<.05).
Aortas from ARG animals also manifested a significant reduction in superoxide anion elaboration compared with CHOL animals at the same time point (2.7±0.4 versus 6.7±2.4 U/mg tissue; P<.05). The ratio of NO generation to superoxide anion release was significantly increased in the ARG animals at this time point (4.3±1.0 versus 1.5±0.4, ARG versus CHOL; P<.05).
| Discussion |
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This is the first demonstration that restoration of vascular NO activity is associated with regression of preexisting lesions. This finding is of scientific interest and potential clinical relevance.
Numerous studies have focused on regression of atherosclerotic lesions in various animal species, including rabbits, pigs, and nonhuman primates. One of the first such studies was by Armstrong and colleagues,18 who induced atherosclerosis in monkeys using a diet high in cholesterol. A reduction in lesion size was seen after the animals were returned to a normal diet. In subsequent studies investigators observed that regression occurred parallel with a restoration of endothelium-dependent relaxation.19 20 21 22 In hypercholesterolemic rabbits, previous studies have documented that angiotensin-converting enzyme inhibitors, calcium antagonists, fish oil, and lipid-lowering agents may slow the progression of disease and even induce regression of preexisting lesions.20 21 22 23 24 Regression was observed only in those studies in which the animals had been returned to a normal chow diet.
What is remarkable about the current findings is that L-arginine administration was associated with a reduction in intimal lesions despite continued intake of the high-cholesterol diet and persistent hypercholesterolemia. The observed regression in intimal lesions at 14 and 18 weeks was not correlated with a change in total cholesterol, as levels remained elevated by 20- and 18-fold, respectively. The three responders at 23 weeks did have a slightly (but not significantly) lower cholesterol level, which was still 16-fold elevated compared with the values in the control animals.
The loss of the effect of L-arginine in the nonresponders at 23 weeks is not explained by either a decreased intake or increased metabolism of L-arginine, since there is no significant difference in plasma arginine levels between the responders and nonresponders. The loss of the antiatherogenic effect of arginine in the nonresponders may be due to an inability to restore NO activity in this group or may even reflect an adverse effect of arginine at later time points.
The mechanism(s) by which restoration of vascular NO activity may induce regression was not elucidated by this study, but recent observations from our laboratory and others provide some clues. Using an ex vivo functional binding assay, we have previously shown that supplemental L-arginine suppresses endothelial adhesiveness for monocytes in the thoracic aorta of hypercholesterolemic rabbits.15 By contrast, when vascular NO synthesis is inhibited (by chronic administration of an NO synthase antagonist), endothelial adhesiveness is markedly increased and lesion formation accelerated.15 25 26
One of the major chemokines mediating monocyte-endothelial cell interaction is MCP-1.27 28 Preliminary studies from our laboratory indicate that the expression of MCP-1 in the thoracic aorta of hypercholesterolemic rabbits is reduced by treatment (2 weeks) with L-arginine. By contrast, treatment of normocholesterolemic animals with the NO synthase antagonist nitro-arginine induces the expression of MCP-1 in the vessel wall (P.T. Tsao and J.P. Cooke, unpublished data, 1995). The mechanism by which vascular NO modulates MCP-1 expression is not fully understood but does appear to involve transcriptional regulation.29
The expression of chemokines and adhesion molecules mediating endothelial-monocyte interaction appears to be regulated by redox-sensitive transcriptional pathways.10 11 12 30 Hypercholesterolemia may activate these transcriptional pathways by increasing endothelial oxidative stress.17 NO may interfere with these transcriptional pathways by virtue of its capability to scavenge superoxide anion, disrupt the autocatalytic chain of lipid peroxidation initiated by oxygen-derived free radicals, or inhibit oxidative enzyme activity.31 32 33 Alternatively, arginine itself may reduce the generation of superoxide anion. LDL cholesterol induces a dysregulation of NO synthase in cultured endothelial cells such that the enzyme begins to generate superoxide anion; this can be reversed by increasing arginine availability to the enzyme.34 The present study reveals that L-arginine treatment in vivo enhances vascular NO activity and reduces generation of superoxide anion by the aorta of the hypercholesterolemic rabbit.
The inhibition by NO of monocyte adherence may fully account for the regression of lesions observed in this study if the accumulation of monocytes depends on a balance between influx and efflux of cells. Lipid-laden foam cells may exit the vessel wall through the endothelium, reenter the circulation, and eventually become enmeshed in the reticuloendothelial system.35 If enhanced vascular NO activity were to inhibit MCP-1 expression, the dissipation of a chemotactic gradient might promote macrophage efflux as well as reduce monocyte adherence.
Programmed cell death, or apoptosis, might be another mechanism by which vascular NO induces regression. NO donors are known to induce apoptosis in macrophages and vascular smooth muscle in vitro.36 37 Therefore, it is possible that the enhanced elaboration of vascular NO could induce apoptosis of cells in the lesion to slow or even reverse lesion growth.
To conclude, this study demonstrates for the first time that enhancement of vascular NO activity can induce regression of preexisting lesions in the thoracic aorta of hypercholesterolemic rabbits. This investigation provides additional support for our hypothesis that endothelium-derived NO is an endogenous antiatherogenic molecule and justifies future clinical studies to determine whether enhancement of endogenous NO activity is a viable therapeutic strategy for individuals afflicted by atherosclerotic vascular disease.
| Selected Abbreviations and Acronyms |
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| Acknowledgments |
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Received May 15, 1995; accepted October 24, 1995.
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J. P. Cooke, K. Sydow, J. Chen, and P. Huang A Peculiar Result and a Fanciful Hypothesis Regarding L-Arginine * Arterioscler. Thromb. Vasc. Biol., June 1, 2003; 23(6): 1128 - 1128. [Full Text] [PDF] |
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M. Weis and J. P. Cooke Cardiac Allograft Vasculopathy and Dysregulation of the NO Synthase Pathway Arterioscler. Thromb. Vasc. Biol., April 1, 2003; 23(4): 567 - 575. [Abstract] [Full Text] [PDF] |
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J. Loscalzo L-Arginine in Atherosclerosis: Consequences of Methylation Stress in a Complex Catabolism? Arterioscler. Thromb. Vasc. Biol., January 1, 2003; 23(1): 3 - 5. [Full Text] [PDF] |
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J. Chen, P. Kuhlencordt, F. Urano, H. Ichinose, J. Astern, and P. L. Huang L-Arginine on Atherosclerosis in ApoE Knockout and ApoE/Inducible NO Synthase Double-Knockout Mice Arterioscler. Thromb. Vasc. Biol., January 1, 2003; 23(1): 97 - 103. [Abstract] [Full Text] [PDF] |
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D. Tousoulis, C. Antoniades, C. Tentolouris, G. Goumas, C. Stefanadis, and P. Toutouzas L-Arginine in cardiovascular disease: dream or reality? Vascular Medicine, August 1, 2002; 7(3): 203 - 211. [Abstract] [PDF] |
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A. J. Maxwell, M. P. Zapien, G. L. Pearce, G. MacCallum, and P. H. Stone Randomized trial of a medical food for the dietary management of chronic, stable angina J. Am. Coll. Cardiol., January 2, 2002; 39(1): 37 - 45. [Abstract] [Full Text] [PDF] |
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M. C. Stuhlinger, P. S. Tsao, J.-H. Her, M. Kimoto, R. F. Balint, and J. P. Cooke Homocysteine Impairs the Nitric Oxide Synthase Pathway: Role of Asymmetric Dimethylarginine Circulation, November 20, 2001; 104(21): 2569 - 2575. [Abstract] [Full Text] [PDF] |
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P. Vermeersch, Z. Nong, E. Stabile, O. Varenne, H. Gillijns, M. Pellens, N. Van Pelt, M. Hoylaerts, I. De Scheerder, D. Collen, et al. L-Arginine Administration Reduces Neointima Formation After Stent Injury in Rats by a Nitric Oxide-Mediated Mechanism Arterioscler. Thromb. Vasc. Biol., October 1, 2001; 21(10): 1604 - 1609. [Abstract] [Full Text] [PDF] |
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J. P. Cooke and P. S. Tsao Go With the Flow Circulation, June 12, 2001; 103(23): 2773 - 2775. [Full Text] [PDF] |
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X.-L. Niu, X. Yang, K. Hoshiai, K. Tanaka, S. Sawamura, Y. Koga, and H. Nakazawa Inducible Nitric Oxide Synthase Deficiency Does Not Affect the Susceptibility of Mice to Atherosclerosis but Increases Collagen Content in Lesions Circulation, February 27, 2001; 103(8): 1115 - 1120. [Abstract] [Full Text] [PDF] |
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Y. Stein and O. Stein Does Therapeutic Intervention Achieve Slowing of Progression or Bona Fide Regression of Atherosclerotic Lesions? Arterioscler. Thromb. Vasc. Biol., February 1, 2001; 21(2): 183 - 188. [Abstract] [Full Text] [PDF] |
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R. H. Boger, S. M. Bode-Boger, P. S. Tsao, P. S. Lin, J. R. Chan, and J. P. Cooke An endogenous inhibitor of nitric oxide synthase regulates endothelial adhesiveness for monocytes J. Am. Coll. Cardiol., December 1, 2000; 36(7): 2287 - 2295. [Abstract] [Full Text] [PDF] |
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J. P. Cooke Does ADMA Cause Endothelial Dysfunction? Arterioscler. Thromb. Vasc. Biol., September 1, 2000; 20(9): 2032 - 2037. [Abstract] [Full Text] [PDF] |
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D. Behr-Roussel, A. Rupin, S. Simonet, E. Bonhomme, S. Coumailleau, A. Cordi, B. Serkiz, J.-N. Fabiani, and T. J. Verbeuren Effect of Chronic Treatment With the Inducible Nitric Oxide Synthase Inhibitor N-Iminoethyl-L-Lysine or With L-Arginine on Progression of Coronary and Aortic Atherosclerosis in Hypercholesterolemic Rabbits Circulation, August 29, 2000; 102(9): 1033 - 1038. [Abstract] [Full Text] [PDF] |
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M. J. Mullen, D. Wright, A. E. Donald, S. Thorne, H. Thomson, and J. E. Deanfield Atorvastatin but not L-arginine improves endothelial function in type I diabetes mellitus: a double-blind study J. Am. Coll. Cardiol., August 1, 2000; 36(2): 410 - 416. [Abstract] [Full Text] [PDF] |
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L. I Romero, D.-N. Zhang, J. P Cooke, H.-K. V Ho, E. Avalos, R. Herrera, and G S. Herron Differential expression of nitric oxide by dermal microvascular endothelial cells from patients with scleroderma Vascular Medicine, August 1, 2000; 5(3): 147 - 158. [Abstract] [PDF] |
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K. M. Channon, H. Qian, and S. E. George Nitric Oxide Synthase in Atherosclerosis and Vascular Injury : Insights From Experimental Gene Therapy Arterioscler. Thromb. Vasc. Biol., August 1, 2000; 20(8): 1873 - 1881. [Abstract] [Full Text] [PDF] |
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Y.-P. Sun, N. C. Lu, W. W. Parmley, and C. B. Hollenbeck Effects of Cholesterol Diets on Vascular Function and Atherogenesis in Rabbits Experimental Biology and Medicine, July 1, 2000; 224(3): 166 - 171. [Abstract] [Full Text] |
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A. Bloodsworth, V. B. O'Donnell, and B. A. Freeman Nitric Oxide Regulation of Free Radical- and Enzyme-Mediated Lipid and Lipoprotein Oxidation Arterioscler. Thromb. Vasc. Biol., July 1, 2000; 20(7): 1707 - 1715. [Abstract] [Full Text] [PDF] |
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J. R. Chan, R. H. Boger, S. M. Bode-Boger, O. Tangphao, P. S. Tsao, T. F. Blaschke, and J. P. Cooke Asymmetric Dimethylarginine Increases Mononuclear Cell Adhesiveness in Hypercholesterolemic Humans Arterioscler. Thromb. Vasc. Biol., April 1, 2000; 20(4): 1040 - 1046. [Abstract] [Full Text] [PDF] |
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J. Y. Jeremy, D. Rowe, A. M. Emsley, and A. C. Newby Nitric oxide and the proliferation of vascular smooth muscle cells Cardiovasc Res, August 15, 1999; 43(3): 580 - 594. [Full Text] [PDF] |
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J. P Cooke The 1998 Nobel prize in Medicine: clinical implications for 1999 and beyond Vascular Medicine, May 1, 1999; 4(2): 57 - 60. [PDF] |
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C. A. D. Nascimento, K. Kauser, and G. M. Rubanyi Effect of 17beta -estradiol in hypercholesterolemic rabbits with severe endothelial dysfunction Am J Physiol Heart Circ Physiol, May 1, 1999; 276(5): H1788 - H1794. [Abstract] [Full Text] [PDF] |
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H. Miyazaki, H. Matsuoka, J. P. Cooke, M. Usui, S. Ueda, S. Okuda, and T. Imaizumi Endogenous Nitric Oxide Synthase Inhibitor : A Novel Marker of Atherosclerosis Circulation, March 9, 1999; 99(9): 1141 - 1146. [Abstract] [Full Text] [PDF] |
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B.-Y. Wang, H.-K. V. Ho, P. S. Lin, S. P. Schwarzacher, M. J. Pollman, G. H. Gibbons, P. S. Tsao, and J. P. Cooke Regression of Atherosclerosis : Role of Nitric Oxide and Apoptosis Circulation, March 9, 1999; 99(9): 1236 - 1241. [Abstract] [Full Text] [PDF] |
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M. Pfeifer, R. Verhovec, B. Zizek, J. Prezelj, P. Poredos, and R. N. Clayton Growth Hormone (GH) Treatment Reverses Early Atherosclerotic Changes in GH-Deficient Adults J. Clin. Endocrinol. Metab., February 1, 1999; 84(2): 453 - 457. [Abstract] [Full Text] |
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R. H. Boger, S. M. Bode-Boger, A. Szuba, P. S. Tsao, J. R. Chan, O. Tangphao, T. F. Blaschke, and J. P. Cooke Asymmetric Dimethylarginine (ADMA): A Novel Risk Factor for Endothelial Dysfunction : Its Role in Hypercholesterolemia Circulation, November 3, 1998; 98(18): 1842 - 1847. [Abstract] [Full Text] [PDF] |
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R. H. Boger, S. M. Bode-Boger, W. Thiele, A. Creutzig, K. Alexander, and J.u. C. Frolich Restoring vascular nitric oxide formation by L-arginine improves the symptoms of intermittent claudication in patients with peripheral arterial occlusive disease J. Am. Coll. Cardiol., November 1, 1998; 32(5): 1336 - 1344. [Abstract] [Full Text] [PDF] |
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B. C. Yang, M. I. Phillips, D. Mohuczy, H. Meng, L. Shen, P. Mehta, and J. L. Mehta Increased Angiotensin II Type 1 Receptor Expression in Hypercholesterolemic Atherosclerosis in Rabbits Arterioscler. Thromb. Vasc. Biol., September 1, 1998; 18(9): 1433 - 1439. [Abstract] [Full Text] [PDF] |
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G. Theilmeier, J. R. Chan, C. Zalpour, B. Anderson, B.-y. Wang, A. Wolf, P. S. Tsao, and J. P. Cooke Adhesiveness of Mononuclear Cells in Hypercholesterolemic Humans Is Normalized by Dietary L-Arginine Arterioscler. Thromb. Vasc. Biol., December 1, 1997; 17(12): 3557 - 3564. [Abstract] [Full Text] |
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X. L. Wang, M. C. Mahaney, A. Siew. Sim, J. Wang, J. Wang, J. Blangero, L. Almasy, R. B. Badenhop, and D. E. L. Wilcken Genetic Contribution of the Endothelial Constitutive Nitric Oxide Synthase Gene to Plasma Nitric Oxide Levels Arterioscler. Thromb. Vasc. Biol., November 1, 1997; 17(11): 3147 - 3153. [Abstract] [Full Text] |
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J. Niebauer, R. Hambrecht, T. Velich, K. Hauer, C. Marburger, B. Kalberer, C. Weiss, E. von Hodenberg, G. Schlierf, G. Schuler, et al. Attenuated Progression of Coronary Artery Disease After 6 Years of Multifactorial Risk Intervention : Role of Physical Exercise Circulation, October 21, 1997; 96(8): 2534 - 2541. [Abstract] [Full Text] |
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W. R. MacLellan and M. D. Schneider Death by Design : Programmed Cell Death in Cardiovascular Biology and Disease Circ. Res., August 19, 1997; 81(2): 137 - 144. [Abstract] [Full Text] |
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R. H. Boger, S. M. Bode-Boger, R. P. Brandes, L. Phivthong-ngam, M. Bohme, R. Nafe, A. Mugge, and J. C. Frolich Dietary L-Arginine Reduces the Progression of Atherosclerosis in Cholesterol-Fed Rabbits : Comparison With Lovastatin Circulation, August 19, 1997; 96(4): 1282 - 1290. [Abstract] [Full Text] |
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J. P. Cooke and P. S. Tsao Arginine: A New Therapy for Atherosclerosis? Circulation, January 21, 1997; 95(2): 311 - 312. [Full Text] |
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W. Aji, S. Ravalli, M. Szabolcs, X.-c. Jiang, R. R. Sciacca, R. E. Michler, and P. J. Cannon L-Arginine Prevents Xanthoma Development and Inhibits Atherosclerosis in LDL Receptor Knockout Mice Circulation, January 21, 1997; 95(2): 430 - 437. [Abstract] [Full Text] |
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