Journal Logo

Articles

Molsidomine Improves Flow-Dependent Vasodilation in Brachial Arteries of Patients with Coronary Artery Disease

Belhassen, Laurent; Carville, Claudine; Pelle, Gabriel; Sediame, Said; Benacerraf, Sophie*; Dubois-Randé, Jean-Luc*; Adnot, Serge

Author Information
Journal of Cardiovascular Pharmacology: April 2000 - Volume 35 - Issue 4 - p 560-563
  • Free

Abstract

Nitrovasodilators have been widely used for more than a century in the treatment of acute and chronic coronary artery disease (CAD). However, fundamental understanding of their beneficial effects is more recent and is still being actively studied. Liberation of nitric oxide by endothelial cells mediates vasodilation, and decreases platelet aggregation (1,2). In CAD, NO production is deficient (3), and endothelial function can be impaired at early stages of coronary atherosclerosis (4). Exogenous NO treatment is known to induce arterial vasodilation, especially in atherosclerosis (5). However, whether exogenous NO may affect dynamic regulation of endothelial function through modulation of endothelium-dependent vasodilation has not been determined.

Endothelial function plays an important role in vascular homeostasis, including regulation of vascular tone, regional blood flow, and inhibition of thrombosis. Endothelial function is impaired in most vessels in atherosclerosis, even before the onset of vascular macroscopic lesions (6,7). Because shear stress is believed to be the main physiologic stimulus responsible for basal and stimulated NO formation, flow-mediated vasodilation (FMD) appears to be a good parameter to evaluate endothelial function (8). Many physiologic or pathologic states are responsible for an endothelial dysfunction such as hypercholesterolemia (9), hypertension, heart failure, and diabetes (10-12). One of the most important cause of endothelial dysfunction is oxidative stress, which leads to inactivation of NO and subsequent formation of hydroxyl radicals (13). Indeed, antioxidants, such as vitamins C and E, reverse endothelial dysfunction in smoking, heart failure, and atherosclerosis (14).

Molsidomine is widely used in the symptomatic treatment of CAD and heart failure. It belongs to sydnonimine family and is an exogenous NO donor with specific pharmacologic characteristics. First, NO release by SIN-1, the active metabolite of molsidomine, is nonenzymatic, without the need of any cofactors (15). This feature is thought to explain, at least in part, the absence of tolerance after prolonged administration. Second, NO release is accompanied by superoxide anion release, which could lead to oxidative side reactions and interact with endothelial function (15,16). Thus we evaluated in this study the effect of molsidomine on endothelial function.

METHODS

Subjects

Twenty patients with CAD were included in this study. Inclusion criteria for patients were stable angina pectoris and at least one stenosis on a major coronary vessel (>50%). Exclusion criteria for patients were less than 3-months-old myocardial infarction, heart failure, creatinine clearance <30 ml/min, diabetes, ventricular arrhythmia, and any treatment that could not be discontinued ≥48 h before the beginning of the protocol. For ethical reasons, treatments with β-blockers were not interrupted, and aspirin was interrupted only 48 h before the study (all patients received β-blockers and aspirin). However, patients treated with >300 mg of aspirin a day were not included, because of the known effects of high doses of intravenous aspirin on endothelial function (17). Current smokers (two patients) refrained from smoking 2 days before the beginning of the protocol and until the study was completed. Patients were divided in two groups by a double-blinded randomization, receiving either molsidomine (the molsidomine group) or placebo (the placebo group). All participants gave written informed consent, and the ethics committee of the institution approved the protocol.

Measurement of flow-mediated dilation

A good correlation has been established between endothelial function in coronary arteries and peripheral arteries (18). The brachial artery is readily accessible to vascular ultrasound for stable measurements, and hyperemia reaction can be easily obtained through a short ischemia of the hand. For these reasons, this study was designed to explore the effects of molsidomine on endothelial function in the brachial artery, by using a high-resolution ultrasound Wall Track system (Pie Medical, Maastricht, Neederlands) with a 7.5-Hz linear probe to measure systolic and diastolic internal diameters of distal brachial artery. This echo-tracking system, analyzing the radiofrequency signal, has a precision for diastolic diameter measurements of 30 μm. FMD was measured as a percentage of increase of diastolic diameter of the brachial artery before and after an 8-min ischemia of the homolateral hand performed with an inflatable wrist cuff (hyperemia test). When the wrist cuff is deflated, blood flow and shear stress increase transiently, inducing NO release by the endothelium and FMD. Maximal diameter (DM) was defined as the greatest diastolic diameter after deflation of the cuff, measurements being made at deflation and every 30 s thereafter for 5 min. Measurement at deflation corresponds to the minimal diameter (DB for basal diameter). FMD is expressed as 100 × (DM − DB)/DB. This noninvasive method gives good reproducibility and precision, as it has been previously described (19). We found similar results with an intraobserver intersession coefficient of variability of FMD measured on brachial artery of 6.7%.

Study protocol

The study protocol is shown in Fig. 1. Treatment or placebo was given to patients in a double-blind randomized protocol. After a bed-rest period of ≥30 min, a first FMD measurement was made, just before the first molsidomine intake (H0). Then subjects took orally 4 mg molsidomine or placebo 3 times a day (10 a.m., 4 p.m., 10 p.m.) on day 1 and day 2 and a single dose at 10 a.m. on day 3. Measurements, including diastolic arterial diameters, were performed in the morning on day 1 and 3, before (corresponding to H0 on day one and H48 on day 3), and 2 h after (corresponding to H2 on day 1 and H50 on day 3) molsidomine intake. The 2-h delay between administration of treatment and FMD measurement was chosen in accordance with pharmacologic properties of molsidomine. Blood pressure was measured continuously during each FMD measurement.

FIG. 1
FIG. 1:
Schematic representation of the study. In a double-blinded randomized assay, flow-mediated dilation was measured at the beginning and the end of a 48-h treatment with oral molsidomine or placebo, each time at baseline and 2 h after the intake.

Statistical analysis

Statistical analysis was performed by an independent statistical institute (Versus, Levallois, France). Data are expressed as mean ± SEM. Means are compared by unpaired Student's t test or Scheffé's test. Analysis of variance (ANOVA) was used to compare repeated measures. Statistical significance was accepted at a level α = 0.05.

RESULTS

Study population characteristics

Study population characteristics are provided in Table 1. All subjects included were men. Baseline characteristics did not significantly differ between the placebo and molsidomine groups. Twelve patients (seven in the molsidomine group, five in the placebo group) had a hypercholesterolemia history and long-term treatment with statins, and cholesterol levels were normalized in all patients at the time of inclusion. Two patients in the molsidomine group did not complete the study because of adverse reactions (headaches occurring after molsidomine intake). In these patients, H0 and H2 determinations were performed and used for statistical analysis. Two patients were excluded because of the unreliability of their FMD measurement (patients unable to keep a steady position during measurement).

TABLE 1
TABLE 1:
Clinical characteristics of the patients population

Effect of molsidomine

Treatment with molsidomine improved FMD. As shown in Fig. 2, ANOVA of repeated measures of FMD in the placebo and molsidomine groups showed a significant difference between the two groups (by ANOVA, p = 0.03). FMD was increased by 60% at H2 in the molsidomine group as compared with the placebo group (respectively 4.58 ± 0.7% vs. 2.88 ± 0.6%; p < 0.05 by t test). At H50, molsidomine-treated patients also showed the same trend toward improvement of their endothelial function (a 47% increase). Of note, patients in both groups exhibited a nonsignificant difference in FMD at H0 (3.7 ± 0.8% in molsidomine-receiving patients and 2.7 ± 0.6% in the placebo group; p = 0.4). No significant difference in FMD was observed before the first (H0) and the last (H48) molsidomine intake.

FIG. 2
FIG. 2:
Effect of molsidomine in patients with coronary artery disease (CAD). Flow-mediated dilation at baseline (H0), and after the first (H2) intake, and the last molsidomine intake (H50). *p = 0.02 by ANOVA).

We confirmed that exogenous NO donor molsidomine increased arterial diameter in patients with CAD. At H50, we observed a 7% increase in diastolic diameter (+0.5 ± 0.25 mm in the molsidomine group, −0.06 ± 0.1 mm in the placebo group; p = 0.03; not shown).

DISCUSSION

These results show that molsidomine improves endothelial dysfunction in patients with CAD, in addition to its vasodilator effect.

To evaluate the molsidomine effect on FMD, any treatment other than β-blockers was discontinued 2 days before the beginning of the study, to avoid any interference with other treatment effects on arterial diameter and FMD. For example, members of the statin family and angiotensin-converting enzyme (ACE) inhibitors are known to improve endothelial function (20). In our study, discontinuation of these two treatments may have impaired endothelial function and thus played against reversal by molsidomine. Of note, both groups were homogeneous for treatment with statins (five patients in the placebo group, seven in the molsidomine group), and only one patient had long-term treatment with ACE inhibitors. Current smokers also refrained from smoking. Only two patients were current smokers (one in each group), and smoking discontinuation may have improved endothelial function because smoking is known to impair endothelial function (21).

We measured FMD by using a high-resolution A mode ultrasound determination of brachial artery diameters. Although coronary arteries are the main concern in CAD, the brachial artery is interesting for several reasons. This artery is easily explored with ultrasound, whereas invasive procedures must be used to explore coronary arteries. Moreover, atherosclerosis is general disease, and it has been shown that coronary and brachial artery endothelial function were closely related (18). Study of FMD in coronary arteries also uses drugs that increase blood flow, whereas only mechanical ischemia of the hand is required to increase brachial artery flow. We observed a significant improvement of FMD in the molsidomine-treated group as compared with the placebo group, as assessed by ANOVA analysis. As shown in Fig. 2, 60% at H2 and 47% at H50 increased FMD. The difference in FMD that already exists between the two groups at H0 may interfere with the interpretation of the results. However, this difference is not statistically significant, and most important, the difference between the two curves (Fig. 2) is statistically significant by using repeated measures ANOVA.

When differences between the two groups are analyzed at each time (Scheffé's test), FMD is significantly different between the placebo and the treated groups at H2 but not at H50 (p < 0.05 and p = 0.08, respectively). Thus the improved endothelial function at early time points could remain stable in time, but could also be a transient effect. If molsidomine facilitate endogenous NO bioavailability at the onset of treatment, long-term effects may be weakened by a decreased release and efficacy of endogenous NO after prolonged exposure (22). Further studies are needed to evaluate the effect of molsidomine at later time points.

Molsidomine is a direct NO donor widely used in the treatment of CAD. Specific characteristics of molsidomine are a nonenzymatic release of NO, and the production of superoxide anion (15). NO donors induce arterial vasodilation, especially in atherosclerosis (5). Possible explanations for increased efficiency in atherosclerosis include that endogenous NO decreased production and increased degradation. The first hypothesis is supported by the decreased expression of endothelial NO synthase in atherosclerosis (3), and by the reversibility (although inconstant) of endothelial dysfunction in hypercholesterolemia after L-arginine administration (23). In accordance with the second hypothesis, oxidant stress is known to induce degradation of NO (13), and antioxidant treatment restores endothelial function in many pathologic states (14).

The mechanism involved in molsidomine improvement of FMD remains to be explained. However, this study shows that, at least at the beginning of the treatment, SIN-1 has a positive effect on endothelial function. Restoration of endothelial function may have long-term beneficial effects on thrombosis, progression of atherosclerosis, and more generally cell-to-cell interactions with the endothelium in patients with CAD.

Acknowledgment: This work was supported by a grant from les Laboratoires Hoechst Houdé, France.

REFERENCES

1. Ignarro LJ, Buga GM, Wood KS, Byrns RE, Chaudhuri G. Endothelium-derived relaxing factor produced and released from artery and vein is nitric oxide. Proc Natl Acad Sci U S A 1987;84:9265-9.
2. Moncada S, Radomski MW, Palmer RM. Endothelium-derived relaxing factor: identification as nitric oxide and role in the control of vascular tone and platelet function. Biochem Pharmacol 1988;37:2495-501.
3. Oemar BS, Tschudi MR, Godoy N, Brovkovich V, Malinski T, Luscher TF. Reduced endothelial nitric oxide synthase expression and production in human atherosclerosis. Circulation 1998;97:2494-8.
4. Seiler C, Hess OM, Buechi M, Suter TM, Krayenbuehl HP. Influence of serum cholesterol and other coronary risk factors on vasomotion of angiographically normal coronary arteries. Circulation 1993;88:2139-48.
5. Abrams J. Beneficial actions of nitrates in cardiovascular disease. Am J Cardiol 1996;77:31C-7C.
6. Werns SW, Walton JA, Hsia HH, Nabel EG, Sanz ML, Pitt B. Evidence of endothelial dysfunction in angiographically normal coronary arteries of patients with coronary artery disease. Circulation 1989;79:287-91.
7. Anderson TJ, Gerhard MD, Meredith IT, et al. Systemic nature of endothelial dysfunction in atherosclerosis. Am J Cardiol 1995;75:71B-4B.
8. Dakak N, Husain S, Mulcahy D, et al. Contribution of nitric oxide to reactive hyperemia: impact of endothelial dysfunction. Hypertension 1998;32:9-15.
9. Arcaro G, Zenere BM, Travia D, et al. Non-invasive detection of early endothelial dysfunction in hypercholesterolaemic subjects. Atherosclerosis 1995;114:247-54.
10. van Zwieten PA, Safar M, Laurent S, Pfaffendorf M, Hendriks MG, Bruning TA. New insights into the role of endothelial dysfunction in hypertension [Editorial]. J Hypertens 1995;13:713-6.
11. Ferrari R, Bachetti T, Agnoletti L, Comini L, Curello S. Endothelial function and dysfunction in heart failure [In Process Citation]. Eur Heart J 1998;19(suppl G):G41-7.
12. Johnstone MT, Creager SJ, Scales KM, Cusco JA, Lee BK, Creager MA. Impaired endothelium-dependent vasodilation in patients with insulin-dependent diabetes mellitus [see comments]. Circulation 1993;88:2510-6.
13. Harrison DG, Ohara Y. Physiologic consequences of increased vascular oxidant stresses in hypercholesterolemia and atherosclerosis: implications for impaired vasomotion [see comments]. Am J Cardiol 1995;75:75B-81B.
14. Diaz MN, Frei B, Vita JA, Keaney JF Jr. Antioxidants and atherosclerotic heart disease. N Engl J Med 1997;337:408-16.
15. Feelisch M, Ostrowski J, Noack E. On the mechanism of NO release from sydnonimines. J Cardiovasc Pharmacol 1989;14(suppl 11):S13-22.
16. Hogg N, Darley-Usmar VM, Wilson MT, Moncada S. Production of hydroxyl radicals from the simultaneous generation of superoxide and nitric oxide. Biochem J 1992;281:419-24.
17. Husain S, Andrews NP, Mulcahy D, Panza JA, Quyyumi AA. Aspirin improves endothelial dysfunction in atherosclerosis. Circulation 1998;97:716-20.
18. Anderson TJ, Uehata A, Gerhard MD, et al. Close relation of endothelial function in the human coronary and peripheral circulations. J Am Coll Cardiol 1995;26:1235-41.
19. Kool MJ, van Merode T, Reneman RS, Hoeks AP, Struyker Boudier HA, Van Bortel LM. Evaluation of reproducibility of a vessel wall movement detector system for assessment of large artery properties. Cardiovasc Res 1994;28:610-4.
20. Benacerraf S, Carville C, Adnot S, et al. Improvement of bradykinin endothelium-mediated vasodilation of forearm resistance circulation by quinaprilat in patients with coronary artery disease with or without left ventricular dysfunction [In Process Citation]. J Cardiovasc Pharmacol 1999;34:368-73.
21. Celermajer DS, Sorensen KE, Georgakopoulos D, et al. Cigarette smoking is associated with dose-related and potentially reversible impairment of endothelium-dependent dilation in healthy young adults. Circulation 1993;88:2149-55.
22. Bult H, De Meyer GRY, Jordaens FH, Herman AG. Chronic exposure to exogenous nitric oxide may suppress its endogenous release and efficacy. J Cardiovasc Pharmacol 1991;17:S79-S82.
23. Thorne S, Mullen MJ, Clarkson P, Donald AE, Deanfield JE. Early endothelial dysfunction in adults at risk from atherosclerosis: different responses to L-arginine. J Am Coll Cardiol 1998;32:110-6.
Keywords:

Molsidomine; Flow-mediated vasodilation; Coronary artery disease

© 2000 Lippincott Williams & Wilkins, Inc.