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1 Division of Cardiovascular Surgery, Department of Surgery, 2 Nicotine Research Center, Department of Internal Medicine, 3 Department of Laboratory Medicine, 4 Department of Physiology and Biophysics, 5 Division of Endocrinology, Department of Internal Medicine, and 6 Section of Biostatistics, Mayo Clinic and Foundation, Rochester, Minnesota 55905
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ABSTRACT |
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 TOP
 ABSTRACT
 INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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Smoking is a major risk factor for failure of coronary artery bypass grafts (CABG). Experiments were designed to determine effects of transdermal nicotine, independent of smoking, on structure and function of CABG. Saphenous veins were placed as CABG in untreated dogs (control) or in dogs treated with transdermal nicotine (one 11-mg or two 22-mg patches/day) for 5 wk. Serum nicotine and plasma nitric oxide were measured. Grafts were removed and prepared for organ chamber studies and histology. Serum nicotine averaged 12.1 and 118.7 ng/ml in the 11 mg/day and 44 mg/day groups, respectively. Plasma nitric oxide was higher in dogs treated with 11 mg/day doses compared with controls. In organ chamber studies, endothelium-dependent relaxations to thrombin and A-23187 and endothelium-independent relaxations to nitric oxide were greatest in grafts from dogs treated with 11 mg/day doses. Intimal thickness of the grafts were similar among groups. However, staining for bone sialoprotein was increased in the media of grafts from the 11 mg/day treatment group. These data suggest that transdermal nicotine in doses comparable and double to those used for conventional smoking cessation treatment in humans does not adversely affect early patency of canine CABG up to 4 wk postoperatively. Transdermal nicotine, however, may increase production of and response to nitric oxide in bypass grafts.
endothelium; nitric oxide; saphenous vein; smoking cessation; vascular smooth muscle
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INTRODUCTION |
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TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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CIGARETTE SMOKING IS A RISK factor for failure of coronary artery bypass grafts (CABG) and decreases survival in patients with previous CABG (9, 15, 45). Nicotine is the addictive component of cigarette smoke, and nicotine replacement products, such as patches, gum, inhaler, and nasal spray, are being used to aid smokers in stopping smoking. Two of these products (nicotine patches and gum) are approved by the Food and Drug Administration for over-the-counter use. Despite the known beneficial effects of smoking cessation to reduce the risk of significant coronary events, there is a reluctance on the part of many physicians to prescribe nicotine treatment for smoking cessation in surgical patients because the cardiovascular consequences of nicotine treatment independent of smoking remain unknown. Two prospective clinical studies suggest that nicotine treatment for smoking cessation does not increase the number of primary coronary events in high-risk populations (21, 46). However, there are no controlled pharmacological studies that have examined specifically the effects of transdermal nicotine on function of CABG in the absence of cardiovascular risk factors or smoking. Nicotine is being used clinically to treat non-smoking-related disorders such as ulcerative colitis, Parkinson's disease, Alzheimer's disease, and sleep disorders (12, 14, 37, 39, 41). Therefore, understanding how nicotine affects the structure and function of bypass grafts in the absence of smoking may provide insight into how nicotine might ameliorate symptoms in other conditions. Experiments were designed to characterize effects of transdermal nicotine therapy on function and morphology of reversed saphenous vein CABG in dogs in the subacute postoperative period (4 wk). On the basis of results of clinical trials (21, 46), it was hypothesized that treatment with transdermal nicotine would not decrease patency rates of CABG in dogs in the subacute postoperative period. Furthermore, on the basis of results of effects of nicotine on endothelial function in experimental animals and cultured endothelial cells (3, 6, 28, 35, 42, 43), it was hypothesized that changes in endothelial function would be dependent on the dose of nicotine treatment. Transdermal nicotine was tested at doses within and double to those used for conventional smoking cessation programs (7-22 mg/day) in humans (11).
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METHODS |
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ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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Animals. Sixteen male mongrel dogs (19-27 kg) were used in this study: six were not treated with nicotine patches (control), five were treated with 11 mg/day nicotine patches (Prostep, Elan Pharmaceuticals, Athlone, Ireland), and five were treated with two 22 mg/day patches. Dogs' necks were shaved, and patches were applied to the skin. Loose-fitting leather collars were used to prevent patch removal by scratching. Doses in the 44 mg/day group were sequentially increased by starting at 11 mg/day on the first day of therapy and reaching 44 mg/day on the sixth day of treatment.
One week after the initiation of nicotine patch therapy, reversed saphenous veins were placed as CABG from the left subclavian artery to the circumflex coronary artery without cardiopulmonary bypass, as previously described (32). The bypassed segment of coronary artery was ligated so that blood flow to the distal coronary artery was graft dependent. Anesthesia was induced with methohexital sodium (12-15 mg/kg iv) with isofluorane (1-3%) inhalation anesthesia (positive pressure, tidal volumes of 10-15 ml/kg) with supplemental midazolam (5-10 mg/dose) and fentanyl (50-100 µg/dose). Hydration was maintained with Plasmalyte-A balanced salt solution (10-15 ml · kg
1 · h1). One unit of homologous whole blood (300-400 ml)
was given during placement of the graft. A femoral arterial catheter
was placed percutaneously for monitoring of blood pressure.
Preoperative antibiotics for prophylaxis consisted of gentamicin (80 mg
iv), cefazolin (1 g iv), and penicillin G procaine (1.2 million units, im). Enteric-coated aspirin (325 mg/day) was administered to all dogs
starting 2 days preoperatively and continuing for the duration of the
study, as is standard of care for humans undergoing bypass surgery.
Torbugesic (10 mg/dose) was used for postoperative analgesia, and
acepromazine (2 mg/dose) was used for postoperative sedation. Dogs
received oral cefadroxil (25 mg/kg bid) for 3 days postoperatively. All
animal care was in compliance with the Principles of Laboratory Animal Care formulated by the National Society for Medical
Research and the Guide for the Care and Use of Laboratory
Animals prepared by the National Institutes of Health (NIH
Publication No. 86-23, revised 1985).
In vitro studies. Four weeks postoperatively (5 wk of nicotine patch therapy), animals were anesthetized (pentobarbital sodium 30 mg/kg iv) and exsanguinated via the carotid arteries. Grafts were exposed through a median sternotomy. The heart and great vessels were harvested en bloc with the graft intact. Graft patency was confirmed by transecting the distal anastomosis and by the absence of infarcted lateral myocardium in cross section. Grafts were dissected from connective tissue and quickly placed in chilled modified Krebs-Ringer bicarbonate solution of the following composition (mmol/l): 118.3 NaCl, 4.7 KCl, 1.2 MgSO4, 1.22 KH2PO4, 2.5 CaCl2, 25 NaHCO3, and 11.1 glucose (control solution).
Organ chambers. Rings (5 mm in length) were cut from the middle portion of the grafts. The endothelium was removed intentionally from some rings by gently rubbing the intimal surface with watchman's forceps.
Rings were suspended in organ chambers (25 ml) filled with control solution at 37°C and gassed with 95% O2-5% CO2. Two stainless steel wire stirrups were placed through the lumen of the graft segments. One stirrup was anchored to the bottom of the chamber and the other to a force transducer (Gould UC2, Cleveland, OH) for measurement of isometric force. Rings were placed at the optimal point on the length-tension curve by stepwise stretching and contracting with 20 mM KCl at each level of stretch. Once at optimal length (baseline tension), rings were equilibrated for 30 min, and contractions to 60 mM KCl were measured. Cumulative concentration-response curves were obtained to the
2-adrenergic agonist UK-14304
(1010-106 mol/l) from baseline tension. To
study relaxations, rings were first contracted with PGF2
(2 × 106 mol/l). When contractions plateaued,
cumulative concentration-response curves were obtained to either ADP
(108-104 mol/l), thrombin
(102-1.0 units/ml), or the calcium ionophore A-23187
(1010-106 mol/l) in rings with endothelium
and to nitric oxide (3 × 109-105
mol/l) in rings without endothelium. UK-14304 was studied to assess changes in adrenergic receptor sensitivity associated with denervation of the saphenous veins (16). ADP and thrombin
were studied because endothelium-dependent relaxation to these agonists is preserved in vein grafts in dogs and humans (27,
36) and are associated with release of nitric oxide.
Calcium ionophore releases endothelium-derived factors independent of
receptor activation and, therefore, provides an assessment of
calcium-dependent endothelial function. All experiments were performed
in the presence of the cyclooxygenase inhibitor indomethacin
(105 mol/l) because animals were treated with aspirin
throughout the experimental period. Therefore, changes in
endothelium-dependent responses in vitro were associated with factors
other than prostanoids, including prostacyclin and thromboxane. Rings
with and without endothelium were studied in parallel in the absence
and presence of the arginine analog
NG-monomethyl-L-arginine
(L-NMMA, 104 mol/l) to inhibit production of
nitric oxide. Grafts were incubated with L-NMMA for 30 min
before the initiation of experiments. Rings were washed with control
solution at least three times between dose-response curves and
equilibrated for at least 30 min before initiation of the next curve.
Once L-NMMA was added to the bath, it was readded before
each dose-response curve. Exogenous nicotine was not added to organ
baths in any experiments.
Drugs.
The following drugs were used during the experiment: adenosine
diphosphate, calcium ionophore A-23187, dimethyl sulfoxide, L-NMMA, nicotine, PGF2, indomethacin (Sigma
Chemical, St. Louis, MO), and UK-14304 (Pfizer Central Research,
Sandwich, Kent, UK). Drugs were prepared daily in distilled water and
were kept refrigerated. The calcium ionophore was dissolved in dimethyl sulfoxide (final bath concentration of 8.2 × 103
mol/l) and diluted in distilled water. Indomethacin was prepared with
an equal molar amount of Na2CO3 in distilled
water (105 mol/l). Dimethyl sulfoxide and
Na2CO3 have no effects on response in vein
bypass grafts (7, 25). All concentrations
refer to final molar concentrations (mol/l) of the drug in the organ chamber.
Blood samples.
Venous blood samples were taken before initiation of nicotine patch
therapy (baseline), at 6 and 24 h after patch application 1 day
preoperatively, and on postoperative days 1, 7,
14, 21, and 28. Six hours after patch
application was chosen for sampling because pharmacokinetic studies in
humans showed that peak nicotine levels with this delivery system occur
at about this time point. All blood samples were centrifuged (3,200 g for 15 min at 5°C) immediately. Plasma for the
determination of nitric oxide was drawn into a syringe and transferred
into a siliconized vacuum tube for storage at 
70°C. Cotinine, the
major metabolite of nicotine, was measured in plasma by HPLC
(29). Nicotine was measured in serum by gas
chromatography-mass spectrometry (2). Oxidated products of
nitric oxide (NOx) were measured by chemiluminescence (Sievers nitric
oxide analyzer model 270B, Boulder, CO) (4).
Histological analysis. Rings from proximal, middle, and distal sections of grafts, adjacent to those used in organ chamber studies, were fixed in 10% formalin solution and prepared for light microscopy. Cross sections of grafts (6 µm) were stained with elastin van Gieson's stain.
Adjacent sections of grafts were stained immunohistochemically for smooth muscle-actin (murine monoclonal IgG1 anti-human muscle actin, HHF35, DAKO, Carpinteria, CA), desmin (murine monoclonal IgG1 anti-swine desmin, DE-R-11, DAKO), Ki-67 nuclear
antigen (murine monoclonal IgG1 MIB-1 antibody against
Ki-67 nuclear antigen found only in cells outside G0 phase;
Immunotech, Westbrook, ME) and bone sialoprotein (BSP, polyclonal
rabbit, LF-100; gift from Dr. Larry Fisher, National Institutes of
Dental Research, National Institutes of Health, Bethesda, MD). Actin
and desmin were used to identify differentiated contractile smooth
muscle cells, Ki-67 identifies dividing cells, and bone sialoprotein is
a noncollagenous matrix protein that may be related to vascular
calcification. Vectastatin ELITE ABC kit (Vector Laboratories,
Burlingame, CA) was used for sections stained for BSP. Hematoxylin was
used as counterstain for all other antibodies. To control for
nonspecific staining, adjacent sections were stained with IgG in the
absence of primary antibody. Immunostaining was performed in the
Immunohistochemical Laboratory and Bone Morphometric Laboratory at the
Mayo Clinic. In general, paraffin was removed from the tissue sections
by using xylene (100%). Tissue was rehydrated into descending ethanols and blocked in Tris-buffered saline (0.05 M Tris, 0.01% BSA, 0.9% NaCl, pH 7.5) containing 0.3% casein and 10% normal goat serum. Incubations with primary and secondary antibody (biotynilated goat
anti-rabbit) were performed at room temperature followed by two 15-min
washes in Tris-buffered saline-containing 0.02% Triton X-100.
Endogenous peroxidase activity was inhibited with 1.5%
H2O2 in 0.1% sodium azide and 50% methanol
for 15 min. Bound secondary antibody was detected with
peroxidase-conjugated avidin-biotin complex and visualized with the use
of 0.05% diaminobenzidine and 0.01% H2O2.
Sections were rinsed with tap water, dehydrated with ascending
alcohols, and cleared with xylene.
Statistical analysis.
Data are expressed as means ± SE. The n represents the
number of grafts from different dogs. Contractions to UK-14304 are expressed as a percentage of contractions to 60 mM KCl. Relaxations are
expressed as a percentage of the contraction to PGF2. The concentration of drug causing 50% of maximal relaxation or contraction (ED50) was calculated for individual
dose-response curves, and the mean was reported as the logarithm of the
molar concentration. Areas under individual dose-response curves were calculated and averaged as the mean for all responses in a treatment condition. Maximal response, ED50, and area under the
curves were compared within groups by Student's t-test for
paired observation and among groups by one-way ANOVA. Values were
considered statistically significant if P 
0.05.
0.05.
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RESULTS |
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ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
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Surgical outcome. Fifteen of 16 grafts were patent at 4 wk postoperatively. One graft occluded (dog receiving 44 mg/day dose) as a result of technical problems, which occurred while the proximal anastomosis was being performed. This graft was excluded from the study.
Blood analysis. Nicotine and its major metabolite in humans, cotinine, were not detectable in blood from control dogs (n = 6). Nicotine and cotinine showed dose-dependent increases in serum levels 6 h after application of the patches and decreased by 24 h after application of the patches. Peak steady-state values (6-h values averaged for weeks 2-5 of treatment) for serum nicotine averaged 12.1 ± 6.7 ng/ml (n = 5) and 118.7 ± 38.5 ng/ml (n = 5) in the 11 mg/day and 44 mg/day groups, respectively. Peak steady-state values for plasma cotinine averaged 0.2 ± 2.2 (n = 5) and 35.1 ± 4.1 ng/ml (n = 5) in the 11 mg/day and 44 mg/day respectively over the four postoperative weeks.
Plasma NOx before treatment with nicotine was similar among groups (control 10.7 ± 0.5 nmol/ml, n = 6; 11 mg/day group 11.8 ± 2.5 nmol/ml, n = 5; 44 mg/day group 9.3 ± 0.8 nmol/ml, n = 4). Six hours after patch application, NOx increased significantly 3 wk postoperatively in the 11 mg/day group and decreased toward baseline at the last week of study (Fig. 1). No statistically significant changes in plasma NOx were observed during weeks 1-5 in either the control or 44 mg/day groups (Fig. 1).
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Organ chamber studies. Tension at optimal length (basal tone) did not differ significantly among groups and averaged 3.2 g (range 2.5-3.9) in rings with endothelium and 2.9 g (range 2.1-3.4) in rings without endothelium. L-NMMA caused contractions in three of six grafts with endothelium (0.7 ± 0.5 g; n = 3) from control dogs and in all grafts with endothelium from dogs treated with nicotine patches. These contractions were not significantly different among nicotine-treated dogs and averaged 1.3 ± 0.4 g in rings from both groups (n = 9).
Rings with and without endothelium from all grafts contracted to KCl and PGF2. Contractions of rings with endothelium to both
KCl and PGF2 were not different among groups (Table 1). Contractions of rings without
endothelium to both agonists were significantly greater in grafts from
dogs treated with an 11 mg/day dose compared with those of rings from
either untreated dogs or dogs treated with the 44 mg/day dose.
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2-adrenergic agonist UK-14304 in all groups (Fig.
2). Contractions were significantly
greater in rings without endothelium compared with those with (log
ED50: 7.2 ± 0.3 and 7.6 ± 0.2, respectively; n = 4; Student's t-test for paired
observation) only in rings from dogs treated with the 44 mg/day dose.
This difference was eliminated by L-NMMA (log
ED50 7.5 ± 0.4 vs. 7.7 ± 0.3 in rings with and
without endothelium, respectively; n = 4).
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25.6 ± 5.0% to
14.4 ± 5.2%; n = 5).
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93.5 ± 4.0% vs. 51.4 ± 14%, Fig. 5). Relaxations with
nitric oxide were not altered significantly by L-NMMA (data
not shown, n = 4-6).
Histological analysis.
No differences in neointimal thickness or ratios of intimal to medial
area and intimal to medial thickness (not shown) were found among
grafts from untreated dogs compared with grafts from dogs treated with
nicotine patches (Table 2).
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-actin was present in neointimal
myofibroblasts of all grafts. Stain for desmin was localized to the
media and was not present in the neointima or in neointimal myofibroblasts. No differences in intensity of stain or distribution were observed among groups (Fig. 6).
Positive staining for BSP was observed in sections from all grafts
(Fig. 7). In grafts from control dogs and
dogs treated with a 44 mg/day dose of nicotine, BSP was observed in the
neointima and adventitia. In grafts from dogs treated with an 11 mg/day
dose of nicotine, staining for BSP was more intense and was distributed
in the media in addition to the neointima and adventitia (Fig. 7).
Stain identifying proliferating cells (murine monoclonal antibody
against Ki-67 nuclear antigen) was modest and found only in the
adventitia of grafts, specifically around suture material (not shown).
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DISCUSSION |
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TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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Results of this study identify, for the first time, effects of transdermal nicotine independent of smoking on the function and structure of reverse saphenous vein CABG in an experimental animal. Doses and duration of application of the transdermal nicotine were comparable (11 mg/day) and double (44 mg/day) to those used for conventional smoking cessation programs in humans (11). In humans undergoing nicotine patch therapy for smoking cessation, serum nicotine levels show substantial variability among subjects with levels ranging from 8 to 30 ng/ml with dosing up to 22 mg/day (1, 17, 19). Nicotine levels in smokers immediately after one cigarette per hour reach peak serum venous nicotine levels of 30 ng/ml (38). In this study, dogs treated with a 11 mg/day dose achieved levels similar to average smokers (~12 ng/ml), whereas dogs in the 44 mg/day group achieved concentrations much higher than those of heavy smokers (~118 ng/ml) (19). Cotinine, the major metabolite of nicotine via cytochrome P-450, showed 5- to 10-fold lower levels in the study dogs than in humans using nicotine patches (1, 11, 19). The reasons for this are unclear and may reflect atherosclerotic disease in smokers or other metabolic changes associated with smoking. Alternatively, there may be differences in P-450 enzymes of dogs compared with those of humans.
A positive finding of this study is that low but not high doses of nicotine therapy may stimulate changes in production of endothelium-derived relaxing factors in CABG, in particular nitric oxide. In support of this conclusion are observations that endothelium-dependent relaxations to thrombin and A-23187 were greater in grafts from dogs treated with an 11 mg/day dose of nicotine compared with those treated with a 44 mg/day dose. The fact that relaxations in grafts from the 11 mg/day treatment groups were decreased by L-NMMA suggests, albeit indirectly, that production of nitric oxide by endothelial cells may be increased by this dose of nicotine. The fact that relaxations to both thrombin (receptor activated) and A-23187 (not receptor activated) were increased in the 11 mg/day treatment group suggests a general upregulation of calcium-activated nitric oxide synthase activity rather than one associated with selective receptor activation. Alternatively, increases in endothelium-dependent relaxations may reflect changes in the sensitivity of the smooth muscle to nitric oxide. However, observations that all rings of grafts with endothelium from nicotine-treated dogs contracted to L-NMMA, compared with only 50% of rings with endothelium from control dogs, suggest that nicotine may enhance activity of nitric oxide synthase directly in endothelial cells. Nitric oxide is produced by endothelial cells of reversed saphenous vein CABG in humans (26).
Plasma nitric oxide increased transiently in dogs treated with the 11 mg/day dose after 2-3 wk of treatment. This observation is consistent with sustained increased plasma NOx in human smokers using nicotine nasal spray for smoking cessation (35). Plasma NOx may represent the activity of all three isoenzymes of nitric oxide synthase: neuronal, type I; inducible, type II; or endothelial, type III. All three of these may be affected by nicotine either directly or indirectly. Nicotine stimulates nitroxidergic neurons, leading to the direct release of neurotransmitter nitric oxide. Whether nicotine induces the inducible form of nitric oxide synthase in immunocompetent cells is not known (22). Clearly, definitive pharmacological studies of effects of nicotine on all three isoforms of nitric oxide synthase on transcriptional regulation and enzyme activity are needed. The absence of effect of nicotine on ADP relaxations suggests an agonist specificity for modulation by nicotine.
At first glance, observations of the present study that nicotine
treatment may increase endothelium-dependent relaxations may appear to
contradict observations that endothelium-dependent relaxations are
reduced in human smokers and animals exposed to cigarette smoke
(20, 27, 47). However, nicotine
is only one of many components of cigarette smoke that could affect
endothelial and vascular function (13). This study is the
first to examine effects of nicotine treatment on bypass grafts
independent of smoking. It is important to consider that effects of
nicotine may be time and dose dependent. Indeed, acute infusion of
nicotine (1-2 µg · kg1 · min1 for 45 min) reduced endothelium-dependent
relaxations in microvessels of hamster cheek pouches (30).
On the other hand, chronic treatment (0.18-4.7 µg · kg1 · day1 for 2 wk) did not alter
endothelium-dependent relaxations to acetylcholine in rat mesenteric
arteries (28), but comparable treatment inhibited similar
responses in hamster cheek pouch arterioles (31).
Differences in responses may reflect species differences in metabolism
of nicotine or differences in responsiveness of arteries from various
anatomical locations.
In hamster cheek pouch arteries, endothelium-dependent relaxations could be restored by superoxide dismutase (31). This effect suggests that nicotine either directly or indirectly could affect production of oxygen-derived free radicals, which reduce the bioavailability of nitric oxide.
Several differences exist between these former studies and the present one. First, the present study examined endothelium-dependent responses in vein grafts. These conduits had undergone active remodeling during the nicotine treatment. This is in marked contrast to other studies in which effects of nicotine treatment were tested in previously unmanipulated arteries. Also, in the present study, nicotine was administered via transdermal patches; therefore, absorption and metabolic kinetics of the drug would not be the same as delivery by either intraperitoneal injection or osmotic pump (28, 31). For example, with nicotine delivery by osmotic minipumps, circulating concentrations of nicotine would reach a steady state, whereas, with delivery by transdermal patches, circulating concentrations of nicotine are cyclic peaking at ~6 h after patching and then decaying over the remaining 18 h.
Differences in endothelium-dependent responses with nicotine treatment were expected to show a dose dependency such that increasing doses of nicotine would increase endothelium-dependent responses. This was not the case. On the contrary, with 44 mg/day dosing, endothelium-dependent relaxations were not increased compared with grafts from untreated control dogs. This difference may reflect the multiple sites at which nicotine affects cardiovascular function, including activation of central and peripheral nicotine receptors (33). Indeed, hemodynamics were not measured during the course of this study. Therefore, it is not possible to determine whether effects of nicotine treatment were direct on endothelial cells or indirect because of changes in hemodynamics due to central autonomic output, which affects blood pressure, flow, and resistance.
Nicotine could stimulate endothelial nitric oxide production indirectly
by way of nicotinic stimulation of postganglionic autonomic neurons.
Norepinephrine or acetylcholine released from postsynaptic neurons
could, in turn, stimulate release of endothelium-derived factors, one
of which is nitric oxide (5, 34,
44). Continuous subcutaneous infusion of nicotine in dogs
increases release of catecholamines. However, only a mild (<10
mmHg) transient hypertension results (3, 18).
In humans and nonhuman primates, transdermal delivery also has only
minimal hypertensive effects and may even be hypotensive
(23, 24), suggesting functional
antagonistic actions of nicotine on the cardiovascular system. In
addition, nicotine may affect other endothelium-derived factors, some
of which may cause vasoconstrictions, as do endothelin and thromboxane (6, 40, 42). In the present
study, contractions to 2-adrenergic stimulation were
reduced in rings with endothelium from the 44 mg/day dose group. The
association between nicotine and adrenergic receptors warrants further study.
Another important observation of the present study is that
treatment with transdermal nicotine, which achieved serum
concentrations higher than those found in humans using nicotine patches
for smoking cessation (2, 4), did not
adversely affect immediate or subacute (4-wk) graft patency. This
observation is consistent with observations in human clinical studies
in which using nicotine products for smoking cessation did not increase
primary coronary events in high-risk patients (9,
15, 21, 37, 45,
46). Negative effects of nicotine on graft structure might
be expected on the basis of experimental literature, because, in
cultured endothelial cells, nicotine stimulates proliferation and
synthesis of cytoskeletal proteins (6,
10). In subconfluent cultured human arterial
smooth muscle cells, nicotine and cotinine dose-dependently (109 to 106 mol/l) augment production of
basic fibroblast growth factor, a smooth muscle cell mitogen important
to neointimal formation, and several matrix metalloproteinases critical
to chemotaxis after 12-36 h exposure to nicotine (8).
Increases were observed at 108 and 107
mol/l of nicotine with inhibition at higher concentrations. These observations suggest that nicotine would affect, in a dose- and time-dependent way, proliferation of smooth muscle cells and matrix secretion. These functions are associated with development of intimal
hyperplasia and atherosclerosis, which are the most common causes
of subacute and late graft failure. Unexpectedly, no changes in
proliferation or neointimal thickness were observed in grafts from
nicotine-treated dogs compared with those from control dogs. Differences in proliferation might have been observed if earlier time
points were studied (3-7 days when most cell proliferation and
migration occurs in vein grafts). Although no differences in cell
proliferation were observed in grafts from nicotine-treated dogs,
staining for the noncollagenous matrix protein BSP was greater in the
media of grafts from dogs treated with the 11 mg/day dose of nicotine.
BSP is a highly glycosylated protein that affects integrin interactions
associated with cell adhesion to matrix and migration. The phenotype of
cells producing BSP relative to other functional characteristics of the
cells remains to be determined. However, grafts that expressed greater
staining for BSP also showed increased contractions to KCl and
relaxations to nitric oxide compared with the other grafts. These
results suggest that expression of BSP may be associated with
contractile function of smooth muscle, perhaps related to maintenance
of membrane potential. Consistent with secretion of metalloproteinase
(8), expression of BSP was dependent on but biphasically
related to the dose of nicotine, that is, with stimulation of BSP at
lower (11 mg/day) compared with higher (44 mg/day) doses.
In summary, results of the present study suggest that treatment with transdermal nicotine affects endothelium-dependent relaxations and secretion of BSP in CABG in dogs. These effects are dependent on the dose of nicotine treatment and may be mediated in part by increased production of nitric oxide and depolarization of the smooth muscle. However, despite these functional changes, transdermal nicotine in doses used for smoking cessation does not appear to decrease patency of reversed saphenous vein CABG in dogs in the immediate 4-wk postoperative period.
There are several limitations that should be considered in extrapolating findings of the present study to humans. First, the number of animals studied was small, and the duration of treatment was short. In addition, the grafts were placed in coronary circulation that was not modified by active disease processes such as smoking or atherosclerosis. Furthermore, metabolism of nicotine may differ between humans and dogs. However, despite these limitations, results indicate that transdermal nicotine treatment in the absence of smoking does not decrease graft patency in the subacute postoperative period. These observations, in conjunction with clinical studies in humans (9, 15, 21, 45), support the conclusion that transdermal nicotine to aid smoking cessation (risk reduction) in patients undergoing bypass grafting does not adversely affecting immediate postoperative graft patency.
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ACKNOWLEDGEMENTS |
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We thank Bill Anding and Kevin Rud for excellent technical assistance, Steve Ziesmer and Janis Donovan for performing the immunohistochemistry, and Jim Tarara for assisting with the program to measure intimal areas.
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FOOTNOTES |
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This work was supported in part by grants from the American Heart Association (AHA 96010290) and the Mayo Clinic and Foundation.
Address for reprint requests and other correspondence: V. M. Miller, Dept. of Surgery, Mayo Clinic and Foundation, 200 First St., SW, Rochester, MN 55905 (E-mail: miller.virginia{at}mayo.edu).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Received 23 September 1999; accepted in final form 1 March 2000.
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REFERENCES |
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TOP
ABSTRACT
INTRODUCTION
METHODS
RESULTS
DISCUSSION
REFERENCES
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1.
Bannon, YB,
Corish J,
Corrigan OI,
Devane JG,
Kavanagh M,
and
Mulligan S.
Transdermal delivery of nicotine in normal human volunteers: a single dose and multiple dose study.
Eur J Clin Pharmacol
37:
285-290,
1989[ISI][Medline].
2.
Baskin, LB,
Anderson RW,
Charlson JR,
Hurt RD,
and
Lawson JM.
A solid phase extraction method for determination of nicotine in serum and urine by isotope dilution gas chromatography/mass spectrometry with selected ion monitoring.
Ann Clin Biochem
35:
522-527,
1998.
3.
Bassenge, E,
Holtz J,
and
Strohschein H.
Sympathoadrenal activity and sympathoinhibitory hormones during acute and chronic nicotine application in dogs.
Klin Wochenschr
66:
12-20,
1988.
4.
Braman, RS,
and
Hendrix SA.
Nanogram nitrite and nitrate determination in environmental and biological materials by vanadium (III) reduction with chemiluminescence detection.
Anal Chem
61:
2715-2718,
1989[Medline].
5.
Broten, TP,
Miyashiro JK,
Moncada S,
and
Feigl EO.
Role of endothelium-derived relaxing factor in parasympathetic coronary vasodilation.
Am J Physiol Heart Circ Physiol
262:
H1579-H1584,
1992
6.
Bull, HA,
Pittilo RM,
Woolf N,
and
Machin SJ.
The effect of nicotine on human endothelial cell release of prostaglandins and ultrastructure.
Br J Exp Pathol
69:
413-421,
1988[ISI][Medline].
7.
Cambria, RA,
Lowell RC,
Gloviczki P,
and
Miller VM.
Chronic changes in blood flow alter endothelium-dependent responses in autogenous vein grafts in dogs.
J Vasc Surg
20:
765-773,
1994[ISI][Medline].
8.
Carty, CS,
Soloway PD,
Kayastha S,
Bauer J,
Marsan B,
Ricotta JJ,
and
Dryjski M.
Nicotine and cotinine stimulate secretion of basic fibroblast growth factor and affect expression of matrix metalloproteinases in cultured human smooth muscle cells.
J Vasc Surg
24:
927-934,
1996[ISI][Medline].
9.
Cavender, JB,
Rogers WJ,
Fisher LD,
Gersh BJ,
Coggin CJ,
and
Myers WO.
Effects of smoking on survival and morbidity in patients randomized to medical or surgical therapy in the coronary artery surgery study (CASS): 10-year follow-up.
J Am Coll Cardiol
20:
287-294,
1992[Abstract].
10.
Csonka, E,
Somogyi A,
Augustin J,
Haberbosh W,
Schettler G,
and
Jellinek H.
The effect of nicotine on cultured cells of vascular origin.
Virchows Arch
407:
441-447,
1985.
11.
Dale, LC,
Hurt RD,
Offord KP,
Lawson GM,
Croghan IT,
and
Schroeder DR.
High dose nicotine patch therapy: percent replacement and smoking cessation.
JAMA
27:
1353-1358,
1995.
12.
Davila, DG,
Hurt RD,
Offord KP,
Harris CD,
and
Shepard JW, Jr.
Acute effects of transdermal nicotine on sleep architecture, snoring, and sleep-disordered breathing in nonsmokers.
Am J Respir Crit Care Med
150:
469-474,
1994[Abstract].
13.
Deliconstantinos, G,
Villiotou V,
and
Stavrides JC.
Scavenging effects of hemoglobin and related heme containing compounds on nitric oxide, reactive oxidants and carcinogenic volatile nitrosocompounds of cigarette smoke: a new method for protection against the dangerous cigarette constituents.
Anticancer Res
14:
2717-2726,
1994[ISI][Medline].
14.
Fagerstrom, KO,
Pomerleau O,
Giordani B,
and
Stelson F.
Nicotine may relieve symptoms of Parkinson's disease.
Psychopharmacology (Berl)
116:
117-119,
1994[Medline].
15.
FitzGibbon, GM,
Leach AJ,
and
Kafka HP.
Atherosclerosis of coronary artery bypass grafts and smoking.
Can Med Assoc J
136:
45-47,
1987[Abstract].
16.
Flavahan, NA,
Miller VM,
Aarhus LL,
and
Vanhoutte PM.
Denervation augments alpha-2 but not alpha-1 adrenergic responses in canine saphenous veins.
J Pharmacol Exp Ther
240:
589-593,
1987
17.
Gupta, SK,
Okerholm RA,
Coen P,
Prather RD,
and
Gorsline J.
Single- and multiple-dose pharmacokinetics of Nicoderm (nicotine transdermal system).
J Clin Pharmacol
33:
169-174,
1993[Abstract].
18.
Holtz, J,
Sommer O,
and
Bassenge E.
Development of specific tolerance to nicotine infusions in dogs on chronic nicotine treatment.
Klin Wochenschr
62:
51-57,
1984.
19.
Hurt, RD,
Dale LC,
Offord KP,
Lauger GG,
Baskin LB,
Lawson GM,
Jiang N-S,
and
Hauri PJ.
Serum nicotine and cotinine levels during nicotine-patch therapy.
Clin Pharmacol Ther
54:
98-106,
1993[ISI][Medline].
20.
Jorge, PA,
Ozaki MR,
and
Almeida EA.
Endothelial dysfunction in coronary vessels and thoracic aorta of rats exposed to cigarette smoke.
Clin Exp Pharmacol Physiol
22:
410-413,
1995[ISI][Medline].
21.
Joseph, AM,
Norman SM,
Ferry LH,
Prochazka AV,
Westman EC,
Steele BG,
Sherman SE,
Cleveland M,
Antonnucio DO,
Hartman N,
and
McGovern PG.
The safety of transdermal nicotine as an aid to smoking cessation in patients with cardiac disease.
N Engl J Med
335:
1792-1798,
1996
22.
Jungersten, L,
Edlund A,
Hafstrom LO,
Karlsson L,
Petersson A-S,
and
Wennmalm A.
Plasma nitrate as an index of immune system activation in animals and man.
J Clin Lab Immunol
40:
1-4,
1993[Medline].
23.
Khoury, Z,
Comans P,
Keren A,
Lerer T,
Gavish A,
and
Tzivoni D.
Effects of transdermal nicotine patches on ambulatory ECG monitoring findings: a double-blind study in healthy smokers.
Cardiovasc Drugs Ther
10:
179-184,
1996[ISI][Medline].
24.
Kochak, GM,
Sun JX,
Choi RL,
and
Piraino AJ.
Pharmacokinetic disposition of multiple-dose transdermal nicotine in healthy adult smokers.
Pharmacol Res
9:
1451-1455,
1992.
25.
Komori, K,
Gloviczki P,
Bourchier RG,
Miller VM,
and
Vanhoutte PM.
Endothelium-dependent vasorelaxations in response to aggregating platelets are impaired in reversed vein grafts.
J Vasc Surg
12:
139-147,
1990[ISI][Medline].
26.
Ku, DD,
Caulfield JB,
and
Kirklin JK.
Endothelium-dependent responses in long-term human coronary artery bypass grafts.
Circulation
83:
402-411,
1991
27.
Kugiyama, K,
Yasue H,
Ohgushi M,
Motoyama T,
Kawano H,
Inobe Y,
Hirashima O,
and
Sugiyama S.
Deficiency in nitric oxide bioactivity in epicardial coronary arteries of cigarette smokers.
J Am Coll Cardiol
28:
1161-1167,
1996[Abstract].
28.
Li, Z,
Barrios VE,
Buchholz JN,
Glenn TC,
and
Duckles SP.
Chronic nicotine administration does not affect peripheral vascular reactivity in the rat.
J Pharmacol Exp Ther
271:
1135-1142,
1994
29.
Machacek, DA,
and
Jiang N-S.
Quantification of cotinine in plasma and saliva by liquid chromatography.
Clin Chem
32:
979-982,
1986
30.
Mayhan, WG,
and
Patel KP.
Effect of nicotine on endothelium-dependent arteriolar dilatation in vivo.
Am J Physiol Heart Circ Physiol
272:
H2337-H2342,
1997
31.
Mayhan, WG,
and
Sharpe GM.
Chronic exposure to nicotine alters endothelium-dependent arteriolar dilatation: effect of superoxide dismutase.
J Appl Physiol
86:
1126-1134,
1999
32.
McCarthy, PM,
and
Schaff HV.
A cost-effective technique for experimental coronary artery bypass.
J Thorac Cardiovasc Surg
96:
30-32,
1988[Abstract].
33.
McPhail, I,
Boston U,
Hurt RD,
and
Miller VM.
Mechanisms of cardiovascular effects of nicotine.
Curr Topics Pharmacol
4:
265-280,
1998.
34.
Miller, VM.
Interactions between neural and endothelial mechanisms in the control of vascular tone.
NIPS
6:
60-63,
1991
35.
Miller, VM,
Lewis DA,
Rud KS,
Offord KP,
Croghan IT,
and
Hurt RD.
Plasma nitric oxide before and after smoking cessation with nicotine nasal spray.
J Clin Pharmacol
38:
22-27,
1998[Abstract].
36.
Miller, VM,
Reigel MM,
Hollier LH,
and
Vanhoutte PM.
Endothelium-dependent responses in autogenous femoral veins grafted into the arterial circulation of the dog.
J Clin Invest
80:
1350-1357,
1987.
37.
Pullan, RD,
Rhodes J,
Ganesh S,
Mani V,
Morris JS,
Williams GT,
Newcombe RG,
Russell MAH,
Feyerabend C,
Thomas GAO,
and
Sawe U.
Transdermal nicotine for active ulcerative colitis.
N Engl J Med
330:
811-815,
1994
38.
Russell, MAH,
Feyerabend C,
and
Cole PF.
Plasma nicotine levels after cigarette smoking and chewing nicotine gum.
Circ Res
1:
1043-1046,
1976.
39.
Sandborn, WJ,
Tremaine WJ,
Offord KP,
Lawson GM,
Petersen BT,
Batts KP,
Croghan IT,
Dale LC,
Schroeder DR,
and
Hurt RD.
Transdermal nicotine for mildly to moderately active ulcerative colitis: a randomized, double-blind, placebo-controlled trial.
Ann Intern Med
126:
364-371,
1997
40.
Shirahase, H,
Usui H,
Kurahashi K,
Fujiwara M,
and
Fukui K.
Endothelium-dependent contraction induced by nicotine in isolated canine basilar artery: possible involvement of a thromboxane A2 (TXA2) like substance.
Life Sci
42:
437-445,
1988[ISI][Medline].
41.
Snaedal, J,
Johannesson T,
Jonsson JE,
and
Gylfadottir G.
The effects of nicotine in dermal plaster on cognitive functions in patients with Alzheimer's disease.
Dementia
7:
47-52,
1996.
42.
Suzuki, N,
Ishii Y,
and
Kitamura S.
Effects of nicotine on production of endothelin and eicosanoid by bovine pulmonary artery endothelial cells.
Prostaglandins Leukot Essent Fatty Acids
50:
193-197,
1994[ISI][Medline].
43.
Toda, N,
and
Okamura T.
Reciprocal regulation by putatively nitroxidergic and adrenergic nerves of monkey and dog temporal arterial tone.
Am J Physiol Heart Circ Physiol
261:
H1740-H1745,
1991
44.
Van Bibber, R,
Traub O,
Kroll K,
and
Feigl EO.
EDRF and norepinephrine-induced vasodilation in the canine coronary circulation.
Am J Physiol Heart Circ Physiol
268:
H1973-H1981,
1995
45.
Voors, AA,
van Brussel BL,
Plokker HWT,
Ernst SMPG,
Ernst NM,
Koomen EM,
Tijssen JGP,
and
Vermeulen FEE
Smoking and cardiac events after venous coronary bypass surgery: a 15-year follow-up study.
Circulation
93:
42-47,
1996
46.
Working Group for the Study of Transdermal Nicotine in Patients with Coronary Artery Disease.
. Nicotine replacement therapy for patients with coronary artery disease.
Arch Intern Med
154:
989-995,
1994[Abstract].
47.
Zeiher, AM,
Schachinger V,
and
Minners J.
Long-term cigarette smoking impairs endothelium-dependent coronary arterial vasodilator function.
Circulation
92:
1094-1100,
1995
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