Carvedilol selectively inhibits oscillatory intracellular calcium changes evoked by human alpha1D- and alpha1B-adrenergic receptors.
BACKGROUND
Increasing evidence from clinical trials indicates that carvedilol, an antagonist of alpha1- and beta-adrenergic receptors (ARs), provides an effective treatment for chronic heart failure, whereas nonselective alpha1-AR blockade has an adverse outcome in this disease. It is, however, not clear whether carvedilol exhibits a subtype-dependent impact on three distinct alpha1-adrenergic receptors (alpha1-ARs).


RESULTS
We determined binding properties of human ARs for carvedilol using HEK293 human embryonic kidney cells expressing a single AR subtype. Our results showed that the affinities of alpha1D-AR and alpha1B-AR for carvedilol are higher than that of the beta1-AR subtype, a major target in heart failure treatment. The affinity rank order and pKi values of ARs for carvedilol were as follows: alpha1D-AR (8.9)>alpha1B-AR (8.6)>beta1-AR (8.4)>beta2-AR (8.0)>alpha1A-AR (7.9)?alpha2C-AR (5.9)>alpha2B-AR (5.5)>alpha2A-AR (5.3). Furthermore, temporal kinetics of intracellular calcium signaling mediated via alpha1D- and alpha1B-ARs, but not via alpha1A-AR (P<0.01), showed oscillatory patterns with frequencies ranging from 0.3 to 3 per minute in human smooth muscle and HEK293 cells, which were inhibited by the therapeutic concentrations of carvedilol (10 nM) in a subtype-dependent manner. When oscillatory alpha1B-AR and non-oscillatory alpha1A-AR were co-expressed and heteromer receptors were detected with bioluminescence resonance energy transfer and co-immunoprecipitation, carvedilol suppressed only oscillatory component of global cytosolic free calcium change.


CONCLUSIONS
These results indicate that in addition to beta-ARs, receptor inhibition by carvedilol is directed to alpha1-ARs, preferably to alpha1D- and alpha1B-AR-mediated signaling events, including intracellular calcium oscillations in vascular smooth muscle.
Koshimizu
Taka-Aki
TA
Department of Molecular Pharmacology, National Research Institute for Child Health and Development, 3-35-31, Taishido, Setagaya, Tokyo 154-8567, Japan. tkoshi@nch.go.jp
Tsujimoto
Gozoh
G
Hirasawa
Akira
A
Kitagawa
Yoko
Y
Tanoue
Akito
A
D018674:Adrenergic Antagonists / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D002227:Carbazoles / Q000494:pharmacology*; D000077261:Carvedilol; D002460:Cell Line; D006801:Humans; D007668:Kidney / Q000196:embryology; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology*; D011485:Protein Binding; D018340:Receptors, Adrenergic, alpha-1 / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D013268:Stimulation, Chemical
D018674:Adrenergic Antagonists; D002227:Carbazoles; D011412:Propanolamines; D018340:Receptors, Adrenergic, alpha-1; D011943:Receptors, Adrenergic, beta; D000077261:Carvedilol; D010656:Phenylephrine; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium; D009638:Norepinephrine