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Modulatory Effects of Clopidogrel on Vascular Response in the Human Internal Mammary Artery: An In Vitro Study
Zeynep Dila Öz1, Emine Kaçar1, İbrahim Murat Özgüler2
1Department of Physiology, Faculty of Medicine, Fırat University, Elazığ, Türkiye.
Insights
Clopidogrel (a P2Y12 inhibitor) directly affects left internal mammary artery (LIMA) vascular tone, attenuating contraction and altering relaxation. These findings suggest clopidogrel influences graft patency beyond its antithrombotic effects in coronary artery bypass grafting (CABG) patients.
Area of Science:
- Vascular Biology
- Pharmacology
- Cardiovascular Surgery
Background:
- Coronary artery disease (CAD) is a leading global cause of mortality, with coronary artery bypass grafting (CABG) often employed for advanced cases.
- The left internal mammary artery (LIMA) is the preferred graft in CABG due to superior long-term patency.
- Clopidogrel, a P2Y12 receptor antagonist, is standard in CABG patients, but its direct vascular effects on LIMA are not well understood.
Purpose of the Study:
- To investigate the direct vascular effects of clopidogrel on isolated left internal mammary artery (LIMA) segments.
- To determine if clopidogrel modulates vascular smooth muscle contractility and relaxation in LIMA grafts.
Main Methods:
- Isolated LIMA segments from 20 CABG patients were used.
- Contractile responses to phenylephrine (PE) and relaxation responses to sodium nitroprusside (SNP) were measured.
- Responses were compared before and after pretreatment with 0.1 μM clopidogrel.
Main Results:
- Clopidogrel significantly attenuated phenylephrine-induced contractions in LIMA segments.
- Clopidogrel enhanced sodium nitroprusside-induced relaxation at low to moderate concentrations.
- The relaxant effect of clopidogrel was diminished at the highest SNP concentration.
Conclusions:
- Clopidogrel exhibits a biphasic effect on LIMA, acting as a direct modulator of vascular tone.
- These findings suggest clopidogrel's role in maintaining graft patency may involve direct vascular effects, not solely antithrombotic action.
- Consideration of clopidogrel's local vascular effects is crucial for optimizing therapeutic strategies in CABG.
Background:
Coronary artery disease (CAD) is one of the leading causes of mortality worldwide, and coronary artery bypass grafting (CABG) is frequently preferred as a surgical approach in advanced cases. The most commonly used graft material in CABG, the left internal mammary artery (LIMA), is considered the gold standard due to its high long-term patency rates. Clopidogrel, an antithrombotic agent widely used in CABG patients that targets P2Y12 receptors on platelets, has also been suggested to influence vascular responses due to the presence of these receptors in vascular smooth muscle cells. However, the direct vascular effects of clopidogrel on LIMA remain unknown.
Methods:
In this study, isolated LIMA segments obtained from 20 patients undergoing CABG were evaluated to compare the contractile responses induced by phenylephrine (PE; 10⁻⁹-10⁻⁴ M) and the endothelium-independent relaxation responses induced by sodium nitroprusside (SNP; 10⁻⁹-10⁻⁴ M), before and after pretreatment with 0.1 μM clopidogrel.
Result:
In clopidogrel-treated LIMA segments, all PE-induced contractile responses were significantly attenuated, whereas SNP-induced relaxation was enhanced at low and moderate concentrations; however, this relaxant effect was diminished at the highest dose.
Conclusion:
This biphasic effect observed in LIMA segments suggests that clopidogrel may act not only as an antithrombotic agent, but also as a direct modulator of vascular tone. These findings indicate that the local vascular effects of clopidogrel should be considered in developing therapeutic strategies aimed at maintaining graft patency following CABG.
