Amlodipine increases nitric oxide synthesis in cytokine-stimulated cultured vascualar smooth muscle cells.
OBJECTIVE
If calcium channel blockers affect nitric oxide synthesis in the vascular tissue, they could influence disease progression in coronary arteries. We investigated the effects of the calcium channel blocker amlodipine on nitric oxide synthesis by measuring the production of nitrite, a stable metabolite of nitric oxide, in vascular smooth muscle cells.


METHODS
We measured the production of nitrate in cultured rat vascular smooth muscle cells with the Griess reagent Inducible nitric oxide synthase protein and mRNA expression were assayed by Western blotting and reverse transcription-polymerase chain reaction, respectively. The levels of NF-kappaB proteins in nuclear extracts were analyzed by gel retardation assay.


RESULTS
Incubation of cultures with interleukin-1 , (10 ng/ ml) for 24 h caused a significant increase in nitrite generation. Interleukin-1 l-induced nitrite production by vascular smooth muscle cells was significantly increased by amlodipine in a dose-dependent manner. This augmentative effect of amlodipine was completely abolished in the presence of N(G)-monomethyl-L-arginine or actinomycin D. Amlodipine-induced nitrite production was accompanied by increased inducible nitric oxide synthase mRNA and protein accumulation. Interleukin-1 , induced NF-kappaB activation in vascular smooth muscle cells, and addition of amlodipine further increased this NF-kappaB activation. The effect of amlodipine on nitrite production was maintained in the presence of the calcium channel agonist Bay K 8644.


CONCLUSIONS
Amlodipine enhances nitric oxide synthesis in cytokine-stimulated cultured vascular smooth muscle cells by L-type calcium channel-independent mechanisms.
Ikeda
U
U
Department of Cardiology, Jichi Medical School, Utsunomiya University, Tochigi, Japan. uikeda@jichi.ac.jp
Shimpo
M
M
Ohki
R
R
Takahashi
M
M
Yamamoto
K
K
Ikeda
M
M
Minota
S
S
Shimada
K
K
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D017311:Amlodipine / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology; D002120:Calcium Channel Agonists / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D020746:Calcium Channels, L-Type / Q000378:metabolism; D002478:Cells, Cultured; D004110:Diltiazem / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007375:Interleukin-1 / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D016328:NF-kappa B / Q000378:metabolism; D009543:Nifedipine / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000235:genetics / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D009573:Nitrites / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley
D002120:Calcium Channel Agonists; D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D007375:Interleukin-1; D016328:NF-kappa B; D009573:Nitrites; D012333:RNA, Messenger; D017311:Amlodipine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D004110:Diltiazem; D009543:Nifedipine