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Amlodipine inhibition of serum-, thrombin-, or fibroblast growth factor-induced vascular smooth-muscle cell
O Stepien1, J Gogusev, D L Zhu
1Université René Descartes & Department of Pharmacology, CNRS URA 1482, CHU Necker, Paris, France.
Abstract:
Atherosclerosis, like several other vascular diseases, exhibits structural and functional abnormalities resulting partially from an exaggerated proliferation of vascular smooth-muscle cells (VSMCs). Ca2+ channel blockers, such as amlodipine, have been suggested to retard or even prevent the progression of atherosclerosis. To determine the mechanisms involved in these effects, we investigated the influence of amlodipine on VSMC proliferation by using rat aortic VSMCs in culture. Amlodipine (0.1-10 microM) inhibited serum-, basic fibroblast growth factor (bFGF)-, and thrombin-induced VSMC proliferation and DNA synthesis in a concentration-dependent manner, as demonstrated by cell count and bromodeoxyuridine (BrdU)-incorporation measurements, respectively. Delayed addition of amlodipine after VSMC stimulation showed that the drug exerted its effect early in G1 phase of the cell cycle. This observation was confirmed by the finding that amlodipine did not influence DNA synthesis in VSMCs arrested to the G1/S boundary by hydroxyurea treatment. Consistent with its effects on VSMC growth/proliferation, amlodipine also decreased c-myc, c-fos, and c-jun protooncogene expression induced by serum, thrombin, or bFGF within 1 h after cell activation, as assessed by semiquantitative reverse transcriptase (RT)-polymerase chain reaction (PCR) analysis. The calcium channel agonist Bay K 8644, which counteracted the inhibition by nifedipine of bFGF-, thrombin- or serum-induced DNA synthesis, was ineffective to antagonize the inhibitory effect of amlodipine. The aforementioned effects of amlodipine were of similar amplitude, irrespective of the growth-enhancing agent used. This strongly indicates that amlodipine acts downstream of receptor activation to exert its antiproliferative action, probably early in the G1 phase of the cell cycle. Moreover, the lack of antagonistic effect between amlodipine and Bay K 8644 suggests that, in addition to its L-type Ca2+ channel inhibitory effect, amlodipine inhibits other intracellular signaling pathways. Such an interference of amlodipine with mitogenic signaling pathways might contribute to confer a blood vessel-protecting potential on amlodipine.
Insights
Amlodipine inhibits vascular smooth muscle cell proliferation by affecting cell cycle progression and protooncogene expression. This calcium channel blocker may offer blood vessel protection by interfering with mitogenic signaling pathways.
Area of Science:
- Cardiovascular Biology
- Pharmacology
- Cell Biology
Background:
- Atherosclerosis involves vascular smooth muscle cell (VSMC) proliferation.
- Calcium channel blockers, like amlodipine, may prevent atherosclerosis progression.
Purpose of the Study:
- To investigate amlodipine's influence on VSMC proliferation and its underlying mechanisms.
Main Methods:
- Rat aortic VSMCs were cultured and treated with amlodipine.
- Proliferation and DNA synthesis were measured (cell count, BrdU incorporation).
- Protooncogene expression (c-myc, c-fos, c-jun) was assessed via RT-PCR.
Main Results:
- Amlodipine inhibited VSMC proliferation and DNA synthesis in a dose-dependent manner.
- The drug acted early in the G1 phase of the cell cycle.
- Amlodipine reduced c-myc, c-fos, and c-jun expression and did not show antagonism with Bay K 8644.
Conclusions:
- Amlodipine exerts antiproliferative effects on VSMCs, likely acting downstream of receptor activation.
- Its action early in the G1 phase and interference with signaling pathways may contribute to its vascular protective potential.