Dual mechanism of action of amlodipine in human vascular smooth muscle cells.
OBJECTIVE
It has been recently shown that calcium channel blockers (CCBs) could also control smooth muscle cell (SMC) growth/reactivity through mechanisms that were unrelated to their CCB property. Here, we investigated the effects of amlodipine and isradipine on Ca2+ movements and p42/p44 mitogen-activated protein kinase (ERK 1/2) activities, which are two early signalling events triggered by growth factors such as thrombin and basic fibroblast growth factor (bFGF).


METHODS
In cultured human SMCs isolated from internal mammary arteries, Ca2+ movements and ERK 1/2 activation were studied by measurement of the intracellular Ca2+ concentration in Fura 2-labelled SMCs and by Western blots, respectively.


RESULTS
In thrombin- and thapsigargin-stimulated SMCs, amlodipine and not isradipine dose-dependently reduced Ca2+ mobilization (i.e. Ca2+ release from internal stores); these dihydropyridines did not affect either Ca2+ influx or ERK 1/2 activation. In bFGF-stimulated SMCs, amlodipine and isradipine reduced both Ca2+ influx and ERK 1/2 activation without affecting Ca2+ mobilization. ERK 1/2 activation could also be directly stimulated by the l-type channel agonist Bay K 8644, demonstrating the involvement of voltage-gated Ca2+ influx in this process. Most of the observed effects described were obtained with approximately 10 nmol/l amlodipine/isradipine (i.e. concentrations close to the peak plasma level in treated patients).


CONCLUSIONS
In human SMCs, amlodipine can (i) specifically alter Ca2+ mobilization, likely by interacting with the sarcoplasmic reticulum and (ii) inhibit voltage-dependent Ca2+ influx and the resulting ERK 1/2 activation. It is likely that amlodipine exerts its growth-inhibitory potency by interfering with multiple branches of mitogenic signalling pathways.
Stepien
Olivier
O
Department of Pharmacology, CNRS UMR 8604 and University René Descartes, Paris, France.
Zhang
Yuzhen
Y
Zhu
Dingliang
D
Marche
Pierre
P
D017311:Amlodipine / Q000494:pharmacology*; D000959:Antihypertensive Agents / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D005346:Fibroblast Growth Factors / Q000494:pharmacology; D006490:Hemostatics / Q000494:pharmacology; D006801:Humans; D008323:Mammary Arteries / Q000737:chemistry / Q000166:cytology; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000187:drug effects*; D010766:Phosphorylation / Q000187:drug effects; D013917:Thrombin / Q000494:pharmacology
D000959:Antihypertensive Agents; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D006490:Hemostatics; D017311:Amlodipine; D005346:Fibroblast Growth Factors; D020928:Mitogen-Activated Protein Kinases; D013917:Thrombin