© 1998 by European Society of Cardiology
Copyright © 1998, European Society of Cardiology
Impairment of forearm vasodilatation to acetylcholine in hypercholesterolemia is reversed by aspirin
Department of Medicine, University of Edinburgh, Western General Hospital, Edinburgh EH4 2XU, UK
* Corresponding author. Tel.: +44 (131) 332 1205; Fax: +44 (131) 343 6017; E-mail: d.j.webb@ed.ac.uk
Received 28 July 1997; accepted 9 December 1997
 |
Abstract |
|---|
 Top Abstract 1 Introduction2 Methods3 Results4 DiscussionReferences |
|---|
Objective: Impaired cholinergic vasodilatation in the forearm in hypertension and hypercholesterolemia has been attributed to impaired nitric oxide bioavailability. However, inhibition of cyclooxygenase reverses the impaired cholinergic dilatation in hypertensive animals and patients. The aim of this study was to examine the effect of aspirin on cholinergic vasodilatation in hypercholesterolemic patients. Methods: We examined responses to brachial artery infusion of acetylcholine and the endothelium-independent vasodilator sodium nitroprusside in the presence or absence of aspirin in 10 hypercholesterolemic patients (7 men/3 women; aged 38–63 yr; systolic blood pressure 133±5 mmHg; diastolic blood pressure 80±3) compared with 10 matched controls (7 men/3 women; aged 38–63 yr; systolic blood pressure 126±2; diastolic blood pressure 77±2). Results: In hypercholesterolemic patients, forearm vasodilatation was impaired in response to acetylcholine (112±20 vs. 346±30% increase in blood flow in controls, at the highest dose [15 µg min–1]; P<0.0001) but not in response to sodium nitroprusside. With the addition of aspirin, baseline forearm blood flow was unaltered. However, forearm vasodilatation to acetylcholine was partially restored in hypercholesterolemics (from 112±20 to 193±30%; P<0.001) though not affected in controls. Vasodilator responses to sodium nitroprusside were unaffected by aspirin in either group. Conclusions: In hypercholesterolemia, an altered balance between vasoconstrictor and dilator prostanoids, favouring constrictors, may contribute to endothelial dysfunction either directly or through an effect on nitric oxide synthesis. Restoration of this imbalance may be a component of the therapeutic benefit of aspirin in cardiovascular disease.
KEYWORDS Acetylcholine; Prostaglandins; Endothelium; Hypercholesterolemia; Human
|
1 Introduction |
|---|
|
TopAbstract1 Introduction2 Methods3 Results4 DiscussionReferences |
|---|
Cholinergic vasodilatation is dependent on a functioning vascular endothelium [1]and may be mediated by generation of nitric oxide, dilator prostanoids, [2]or endothelium-derived hyperpolarising factor [3]. As in animal models, [4–6]patients with essential hypertension [7, 8]and hypercholesterolemia [9, 10]have impaired vasodilatation in forearm and coronary [11, 12]vessels following intra-arterial infusion of acetylcholine. Responses to the endothelium-independent vasodilators, glyceryl trinitrate and sodium nitroprusside, are normal suggesting that vascular smooth muscle sensitivity to nitric oxide is not impaired. In the forearm, by the criterion of lesser vasoconstriction in response to the nitric oxide synthase inhibitor, L-NG-monomethyl-arginine (L-NMMA), basal nitric oxide generation is impaired in essential hypertension [13]but not in hypercholesterolemia [14, 15]. However, nitric oxide generation following acetylcholine stimulation is impaired in both conditions [13–16]. This ‘endothelial dysfunction’ could contribute to both vasospasm and platelet aggregation, and may be important in atherogenesis [17].
There is a contribution of prostanoids to both endothelium dependent vasodilatation and constriction, for example through prostacyclin and thromboxane A2 respectively. In health, aspirin has no effect on basal forearm blood flow or on cholinergic vasodilatation [8]. However, in patients with essential hypertension, indomethacin normalises forearm cholinergic dilatation [18]. This may occur because the balance between dilator and constrictor prostanoids is altered, consistent with work in hypertensive rats, [19, 20]or because prostanoids may act indirectly to impair nitric oxide generation. In the present study, our aim was to establish whether cyclooxygenase inhibition would restore endothelial function in hypercholesterolemic patients.
|
2 Methods |
|---|
|
TopAbstract1 Introduction2 Methods3 Results4 DiscussionReferences |
|---|
2.1 Subjects
Ten hypercholesterolemic patients (total serum cholesterol >7.0 mmol l–1) and 10 healthy control subjects (total serum cholesterol <5.3 mmol l–1) were studied (Table 1). Subjects were not included if they were taking lipid-lowering or anti-hypertensive medication, or had received vasoactive drugs, aspirin, or non-steroidal anti-inflammatory agents during the 2 weeks before the study. All subjects abstained from alcohol for 24 h, and from food, caffeine-containing drinks and cigarettes for at least 4 h before each phase. Subjects rested recumbent during each study in a quiet room maintained at a constant temperature of 22–25°C. All participants gave their written, witnessed, and informed consent to participate in these studies which were approved by the Lothian Research Ethics Committee and conform with the principles outlined in the Declaration of Helsinki [21].
|
2.2 Forearm blood flow methodology
This technique has been described in detail elsewhere [22], [23]. Briefly, subjects lay supine with their arms inclined at approximately 30 degrees to improve venous drainage. Wrist cuffs were applied and, during the recording period, were inflated to 220 mmHg to exclude the hand circulation from the measurements. Upper-arm congesting cuffs were inflated to 40 mmHg and blood flow was recorded for 10 s followed by a 5-s refilling period. Multiple 10 s measurements were made over a three min period and the slopes of the final 5 recordings averaged to determine forearm blood flow. To correct for the effects of non-specific variations in blood flow during the protocol, changes in forearm blood flow during drug infusions are presented in the Figures as the ratio of flow in the infused arm to that in the control arm, expressed as percentage change in this ratio from baseline, as previously validated [22, 23]. After each recording, blood pressure was measured in the non-infused arm using a Takeda UA-751 semi-automated oscillometric sphygmomanometer [24].
For drug infusions, a 27 standard wire gauge needle (Cooper's Needle Works, Birmingham, UK), connected to a 16G epidural catheter (Portex, Hythe, Kent, UK), was introduced into the brachial artery of the non-dominant arm under local anaesthesia of 1% lidocaine (Astra Pharmaceuticals, Kings Langley, UK). Patency was maintained by infusion of physiologic saline (0.9%; Baxter Healthcare, Thetford, Norfolk, UK) or drug solutions (see below) at a rate of 1.0 ml min–1.
2.3 Experimental protocol
Subjects were studied on two occasions in random order separated by a period of at least 14 days. On one occasion, aspirin was administered as an intravenous bolus (600 mg diluted in 5 ml 5% dextrose solution) (Aspegic, Laboratories Synthelabo, Paris, France). On the other occasion saline placebo was injected. After intra-arterial saline had been infused for 20 min, basal forearm blood flow was measured in both arms simultaneously. Then, acetylcholine (Miochol, IOLAB, Bracknell, UK) or sodium nitroprusside (Nipride, Roche Pharmaceutical Products, UK) was infused in physiologic saline at cumulative doses of 7.5 and 15 µg min–1 and 3 and 10 µg min–1 respectively for 6 min at each dose. Saline was then infused to provide a 12 min washout period, then a cumulative dose response was obtained with the other drug (sodium nitroprusside or acetylcholine). Forearm blood flow measurements were obtained during the final 3 min of each dose of drug or saline infusion. The order of administration of acetylcholine and sodium nitroprusside was randomised.
2.4 Statistical analysis
Data were normally distributed within groups and are represented as mean±SEM. Analysis of differences in forearm blood flow was by repeated measures analysis of variance followed by Student's t tests where appropriate. Significance was accepted at P<0.05.
|
3 Results |
|---|
|
TopAbstract1 Introduction2 Methods3 Results4 DiscussionReferences |
|---|
There was a trend toward higher blood pressure in hypercholesterolemic patients, but this did not reach statistical significance (Table 1). Basal forearm blood flows were not different and not affected by aspirin in either group (Table 2). Analyses of relative changes in blood flow showed that the increase in forearm blood flow following intra-arterial infusion of acetylcholine was significantly blunted in hypercholesterolemic patients compared with healthy controls (Fig. 1). Aspirin had no effect on acetylcholine mediated dilatation in controls, but restored the vasodilator response towards normal in hypercholesterolemic patients (Fig. 1). Forearm responses to sodium nitroprusside were not different between groups, and not affected by aspirin (Fig. 2). A similar pattern was confirmed by analysis of absolute changes in blood flow in the infused arm (Table 2), except that in this analysis aspirin had an additional effect which reduced the vasodilator response to both acetylcholine and sodium nitroprusside in controls.
|
|
), expressed as percentage change from baseline, was significantly lower than the vasodilatation in control subjects (
) (P<0.0002). Bolus intravenous injection of aspirin (600 mg) did not affect the response in control subjects (
), but potentiated the response in the patients (
) (P<0.001).
|
|
4 Discussion |
|---|
|
TopAbstract1 Introduction2 Methods3 Results4 DiscussionReferences |
|---|
In keeping with other studies [9, 10, 14, 15], the present findings confirm that cholinergic vasodilatation in the forearm vascular bed is impaired in hypercholesterolemic patients. There were no differences in forearm vasodilatation to sodium nitroprusside between the two groups, suggesting that sensitivity to nitric oxide in forearm resistance vessels was not different in hypercholesterolemia.
Also consistent with other work [8], there was no effect of aspirin on baseline forearm blood flow or on relative cholinergic vasodilatation in healthy subjects. Absolute vasodilatation to both aspirin and sodium nitroprusside was reduced by aspirin. By contrast, the defect in acetylcholine mediated vasodilatation was partially reversed by aspirin in hypercholesterolaemic patients, suggesting that the balance between vasodilator and constrictor prostanoids is altered in favour of vasoconstriction in this vascular bed. This observation is similar to results in hypertensive rats [19, 20]and patients [18]. This might result from enhanced vasoconstrictor prostanoid activity, or impaired vasodilator prostanoid production, and might be mediated directly or indirectly via inhibition of nitric oxide release. The latter possibility is supported by the observation that L-arginine infusion will overcome impaired cholinergic dilatation in the coronary circulation in hypercholesterolaemic patients [25], but this effect of L-arginine is very modest in the forearm circulation [26]. Animal studies suggest that a cyclooxygenase-dependent endothelium-derived contracting factor (probably prostaglandin H2) contributes to the impaired relaxation and that defects in the metabolism of PGH2 may cause upregulation of its synthesis, inhibiting prostacyclin synthase [27].
One potential limitation of this study is that there was a trend for the blood pressure to be higher in the hypercholesterolemic patients. However, no subject was hypertensive by standard criteria, and the magnitude of the difference in blood pressure between groups was very much smaller than that in previous studies in which endothelial dysfunction has been seen [13]. Moreover, endothelial dysfunction has not been observed in all studies in hypertensive patients [28].
In summary, in hypercholesterolemic patients impaired acetylcholine mediated vasodilatation in the forearm may be due, at least in part, to altered generation of prostanoids, directly or indirectly favouring vasoconstriction. Restoration of this imbalance by aspirin may be an important component of its therapeutic benefit in cardiovascular disease.
Time for primary review 42 days.
|
Acknowledgements |
|---|
JPN was supported by the Scottish Home and Health Department and the High Blood Pressure Foundation, Edinburgh. BRW is a British Heart Foundation Senior Research Fellow. MFH was supported by an Allen Postgraduate Research Fellowship from the University of Edinburgh.
|
Notes |
|---|
1 Current address: Postgraduate Division of Nursing, University of Nottingham Medical School, Queen's Medical Centre, Nottingham NG7 2UH, UK.
|
References |
|---|
|
TopAbstract1 Introduction2 Methods3 Results4 DiscussionReferences |
|---|
- Furchgott RF, Zawadzki JV. The obligatory role of endothelial cells in the relaxation of arterial smooth muscle by acetylcholine. Nature (1980) 288:373–376.[CrossRef][Medline]
- Moncada S, Palmer RMJ. The L-arginine:nitric oxide pathway in the vessel wall. In: Moncada S, Higgs EA, editors. Nitric Oxide from L-Arginine: A Bioregulatory System. Amsterdam, Elsevier, 1990:19-33.
- Garland CJ, Plane F, Kemp BK, Cocks TM. Endothelium-dependent hyperpolarisation: a role in the control of vascular tone. Trends Pharmacol Sci (1995) 16:23–30.[CrossRef][Medline]
- Lüscher TF, Vanhoutte PM. Endothelium-dependent contractions of acetylcholine in the aorta of spontaneously hypertensive rats. Hypertension (1986) 8:344–348.
[Abstract/Free Full Text] - Shimokawa H, Vanhoutte PM. Impaired endothelium-dependent relaxation to aggregating platelets and related vasoactive substances in porcine coronary arteries in hypercholesterolemia and atherosclerosis. Circ Res (1989) 64:900–914.
[Abstract/Free Full Text] - Tomita T, Yszac M, Miua M, Nakamura K, Inone Y. Rapid and reversible inhibition by low-density lipoprotein of the endothelium-dependent relaxation to hemostasis substance in porcine coronary arteries. Circ Res (1990) 66:18–27.
[Abstract/Free Full Text] - Panza JA, Quyyumi AA, Brush JE, Epstein SE. Abnormal endothelium-dependent relaxation in patients with essential hypertension. New Engl J Med (1990) 323:22–27.[Abstract]
- Linder L, Kiowski W, Buhler FR, Lüscher TF. Indirect evidence for release of endothelium-derived relaxing factor in human forearm circulation in vivo. Circulation (1990) 81:1762–1767.
[Abstract/Free Full Text] - Chowienczyk PJ, Watts GF, Cockcroft JR, Ritter JM. Impaired endothelium-dependent vasodilation of human forearm resistance vessels in hypercholesterolemia. Lancet (1992) 340:1430–1432.[CrossRef][Web of Science][Medline]
- Casino PR, Kilcoyne CM, Quyyumi AA, Hoeg JM, Panza JA. The role of nitric oxide in endothelium-dependent vasodilatation of hypercholesterolemic patients. Circulation (1993) 88:2541–2547.
[Abstract/Free Full Text] - Drexler H, Zeiher AM. Endothelial function in human coronary arteries in vivo: focus on hypercholesterolemic humans. Hypertension (1991) 18:II90–II99. Suppl II.[Medline]
- Treasure CB, Klein JL, Vita JA, Manoukian SV, Renwick GH, Selwyn AP, Ganz P, Alexander RW. Hypertension and left ventricular hypertrophy are associated with impaired endothelium-mediated relaxation in human coronary resistance vessels. Circulation (1993) 87:86–93.
[Abstract/Free Full Text] - Panza JA, Casino PR, Kilcoyne CM, Quyyumi AA. Role of endothelium-derived nitric oxide in the abnormal endothelium-dependent vascular relaxation in patients with essential hypertension. Circulation (1993) 87:1468–1474.
[Abstract/Free Full Text] - Stroes ESG, Koomans HA, De Bruin TWA, Rabelink TJ. Vascular function in the forearm of hypercholesterolaemic patients off and on lipid-lowering medication. Lancet (1995) 346:467–471.[CrossRef][Web of Science][Medline]
- Casino PR, Kilcoyne CM, Quyyumi AA, Hoeg JM, Panza JA. The role of nitric oxide in endothelium-dependent vasodilation of hypercholesterolemic patients. Circulation (1993) 88:2541–2547.
[Abstract/Free Full Text] - Panza JA, Casino PR, Kilcoyne CM, Quyyumi AA. Impaired endothelium-dependent vasodilatation in patients with essential hypertension: evidence that the abnormality is not at the muscarinic receptor level. Am J Coll Cardiol (1994) 23:1610–1616.[Abstract]
- Ross R. Cell biology of atherosclerosis. Annu Rev Physiol (1995) 57:791–804.[CrossRef][Web of Science][Medline]
- Taddei S, Virdis A, Mattei P, Salvetti A. Vasodilatation to acetylcholine in primary and secondary forms of human hypertension. Hypertension (1993) 21:929–933.
[Abstract/Free Full Text] - Iwama Y, Kato T, Muramatsu M, Asano H, Shimizu K, Toki Y, Miyazaki Y, Okemura K, Hashimoto H, Ito T, Satake T. Correlation with blood pressure of the acetylcholine-induced endothelium-derived contracting factor in the rat aorta. Hypertension (1992) 19:326–332.
[Abstract/Free Full Text] - Diederich D, Yang Z, Bühler FR, Lüscher TF. Impaired endothelium-dependent relaxations in hypertensive resistance arteries involve cyclooxygenase pathway. Am J Physiol (1990) 258:H445–H451.[Web of Science][Medline]
- Anon. World Medical Association Declaration of Helsinki: Recommendations guiding physicians in biomedical research involving human subjects. Cardiovasc Res (1997) 35:2–3.
[Free Full Text] - Benjamin N, Calver A, Collier J, Robinson B, Vallance P, Webb D. Measuring forearm blood flow and interpreting the responses to drugs and mediators. Hypertension (1995) 25:918–923.
[Abstract/Free Full Text] - Haynes WG, Strachan FE, Webb DJ. Endothelin ETA and ETB receptors cause vasoconstriction of human resistance and capacitance vessels in vivo. Circulation (1995) 92:357–363.
[Abstract/Free Full Text] - Wiinberg N, Walter-Larson S, Eriksen C, Nielsen PE. An evaluation of semi-automatic blood pressure manometers against intra-arterial blood pressure. J Amb Monitor (1988) 1:303–309.
- Drexler H, Zeiher AM, Meinzer K, Just H. Correction of endothelial dysfunction in coronary microcirculation of hypercholesterolaemic patients by L-arginine. Lancet (1991) 338:1546–1550.[CrossRef][Web of Science][Medline]
- Casino PR, Kilcoyne CM, Quyyumi AA, Hoeg JM, Panza JA. Investigation of decreased availability of nitric oxide precursor as the mechanism responsible for impaired endothelium-dependent vasodilation in hypercholesterolemic patients. J Am Coll Cardiol (1994) 23:844–850.[Abstract]
- Lin L, Balazy M, Pagano PJ, Nasjletti A. Expression of prostaglandin H2-mediated mechanism of vascular contraction in hypertensive rats: relation to lipoxygenase and prostacyclin synthase activities. Circ Res (1994) 74:197–205.
[Abstract/Free Full Text] - Cockcroft JR, Chowienczyk PJ, Benjamin N, Ritter JM. Preserved endothelium-dependent vasodilatation in patients with essential hypertension. New Engl J Med (1994) 330:1036–1040.
[Abstract/Free Full Text]
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  J. D. Snoep, M. M.C. Hovens, S. M. Pasha, M. Frolich, H. Pijl, J. T. Tamsma, and M. V. Huisman Time-Dependent Effects of Low-Dose Aspirin on Plasma Renin Activity, Aldosterone, Cortisol, and Catecholamines Hypertension, November 1, 2009; 54(5): 1136 - 1142. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. C. Williams, M. J. Coffey, B. Coles, S. Sanchez, J. D. Morrow, J. R. Cockcroft, M. J. Lewis, and V. B. O'Donnell In vivo aspirin supplementation inhibits nitric oxide consumption by human platelets Blood, October 15, 2005; 106(8): 2737 - 2743. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Kojda Direct vasoprotection by aspirin: a significant bonus to antiplatelet activity? Cardiovasc Res, November 1, 2004; 64(2): 192 - 194. [Full Text] [PDF]
|
|
|
|
|
|
J.L. Mehta, J. Chen, F. Yu, and D.Y. Li Aspirin inhibits ox-LDL-mediated LOX-1 expression and metalloproteinase-1 in human coronary endothelial cells Cardiovasc Res, November 1, 2004; 64(2): 243 - 249. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Bogaty, J. M. Brophy, M. Noel, L. Boyer, S. Simard, F. Bertrand, and G. R. Dagenais Impact of Prolonged Cyclooxygenase-2 Inhibition on Inflammatory Markers and Endothelial Function in Patients With Ischemic Heart Disease and Raised C-Reactive Protein: A Randomized Placebo-Controlled Study Circulation, August 24, 2004; 110(8): 934 - 939. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Belhassen, G. Pelle, J.-L. Dubois-Rande, and S. Adnot Improved endothelial function by the thromboxane a2 receptor antagonist s 18886 in patients with coronary artery disease treated with aspirin J. Am. Coll. Cardiol., April 2, 2003; 41(7): 1198 - 1204. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 B.-q. Zhu, R. E Sievers, A. E. Browne, R. J Lee, K. Chatterjee, W. Grossman, J. S Karliner, and W. W Parmley Comparative effects of aspirin with ACE inhibitor or angiotensin receptor blocker on myocardial infarction and vascular function Journal of Renin-Angiotensin-Aldosterone System, March 1, 2003; 4(1): 31 - 37. [Abstract] [PDF]
|
|
|
|
 |
|
 B. A. Kingwell, M. Formosa, M. Muhlmann, S. J. Bradley, and G. K. McConell Type 2 Diabetic Individuals Have Impaired Leg Blood Flow Responses to Exercise: Role of endothelium-dependent vasodilation Diabetes Care, March 1, 2003; 26(3): 899 - 904. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Chenevard, D. Hurlimann, M. Bechir, F. Enseleit, L. Spieker, M. Hermann, W. Riesen, S. Gay, R. E. Gay, M. Neidhart, et al. Selective COX-2 Inhibition Improves Endothelial Function in Coronary Artery Disease Circulation, January 28, 2003; 107(3): 405 - 409. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. J. Irving, M. N. Carson, D. J. Webb, and B. R. Walker Peripheral Vascular Structure and Function in Men with Contrasting GH Levels J. Clin. Endocrinol. Metab., July 1, 2002; 87(7): 3309 - 3314. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. K. Kharbanda, B. Walton, M. Allen, N. Klein, A. D. Hingorani, R. J. MacAllister, and P. Vallance Prevention of Inflammation-Induced Endothelial Dysfunction: A Novel Vasculo-Protective Action of Aspirin Circulation, June 4, 2002; 105(22): 2600 - 2604. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. T. Davidge Prostaglandin H Synthase and Vascular Function Circ. Res., October 12, 2001; 89(8): 650 - 660. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. B. O'Donnell and B. A. Freeman Interactions Between Nitric Oxide and Lipid Oxidation Pathways : Implications for Vascular Disease Circ. Res., January 19, 2001; 88(1): 12 - 21. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. J Duffy, G. New, R. W Harper, and I. T Meredith Metabolic vasodilation in the human forearm is preserved in hypercholesterolemia despite impairment of endothelium-dependent and independent vasodilation Cardiovasc Res, August 15, 1999; 43(3): 721 - 730. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||