Functional, electrophysiological and molecular docking analysis of the modulation of Cav 1.2 channels in rat vascular myocytes by murrayafoline A.
OBJECTIVE
The carbazole alkaloid murrayafoline A (MuA) enhances contractility and the Ca(2+) currents carried by the Cav 1.2 channels [ICa1.2 ] of rat cardiomyocytes. As only few drugs stimulate ICa1.2 , this study was designed to analyse the effects of MuA on vascular Cav 1.2 channels.


METHODS
Vascular activity was assessed on rat aorta rings mounted in organ baths. Cav 1.2 Ba(2+) current [IBa1.2 ] was recorded in single rat aorta and tail artery myocytes by the patch-clamp technique. Docking at a 3D model of the rat, α1c central pore subunit of the Cav 1.2 channel was simulated in silico.


RESULTS
In rat aorta rings MuA, at concentrations ≤14.2 μM, increased 30 mM K(+) -induced tone and shifted the concentration-response curve to K(+) to the left. Conversely, at concentrations >14.2 μM, it relaxed high K(+) depolarized rings and antagonized Bay K 8644-induced contraction. In single myocytes, MuA stimulated IBa1.2 in a concentration-dependent, bell-shaped manner; stimulation was stable, incompletely reversible upon drug washout and accompanied by a leftward shift of the voltage-dependent activation curve. MuA docked at the α1C subunit central pore differently from nifedipine and Bay K 8644, although apparently interacting with the same amino acids of the pocket. Neither Bay K 8644-induced stimulation nor nifedipine-induced block of IBa1.2 was modified by MuA.


CONCLUSIONS
Murrayafoline A is a naturally occurring vasoactive agent able to modulate Cav 1.2 channels and dock at the α1C subunit central pore in a manner that differed from that of dihydropyridines.
Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy.
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Saponara
Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy.
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Durante
Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Siena, Italy.
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Spiga
Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy.
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Mugnai
Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy.
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Sgaragli
Institute of Natural Products Chemistry, Vietnam Academy of Science and Technology, Hanoi, Vietnam.
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Huong
Institute of Natural Products Chemistry, Vietnam Academy of Science and Technology, Hanoi, Vietnam.
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Khanh
Institute of Natural Products Chemistry, Vietnam Academy of Science and Technology, Hanoi, Vietnam.
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Son
Institute of Natural Products Chemistry, Vietnam Academy of Science and Technology, Hanoi, Vietnam.
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Cuong
Dipartimento di Scienze della Vita, Università degli Studi di Siena, Siena, Italy.
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Fusi
D000470:Alkaloids / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D020746:Calcium Channels, L-Type / Q000737:chemistry / Q000502:physiology*; D002227:Carbazoles / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D055724:Electrophysiological Phenomena / Q000187:drug effects / Q000502:physiology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D062105:Molecular Docking Simulation / Q000379:methods*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D017208:Rats, Wistar
D000470:Alkaloids; D020746:Calcium Channels, L-Type; D002227:Carbazoles; C419385:L-type calcium channel alpha(1C); C443728:murrayafoline A