Functional, electrophysiological and molecular docking analysis of the modulation of Cav1.2 channels in rat vascular myocytes by murrayafoline A

• Published in: British journal of pharmacology 2016-01, Vol.173 (2), p.292-304
• Main Authors: Saponara, S, Durante, M, Spiga, O, Mugnai, P, Sgaragli, G, Huong, TT, Khanh, PN, Son, NT, Cuong, NM, Fusi, F
• Format: Article
• Language: English
• Subjects: Aorta; Calcium channels (voltage-gated); Calcium ions; Carbazole; Carbazoles; Cardiomyocytes; Computer simulation; Contractility; Contraction; Coronary vessels; ICA1 protein; Myocytes; Nifedipine; Potassium; Research Paper; Research Papers; Rodents; Stimulation; Vasoactive agents
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1111/bph.13369

Background and Purpose The carbazole alkaloid murrayafoline A (MuA) enhances contractility and the Ca2+ currents carried by the Cav1.2 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 Cav1.2 channels. Experimental Approach Vascular activity was assessed on rat aorta rings mounted in organ baths. Cav1.2 Ba2+ 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 Cav1.2 channel was simulated in silico. Key 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 and Implications Murrayafoline A is a naturally occurring vasoactive agent able to modulate Cav1.2 channels and dock at the α1C subunit central pore in a manner that differed from that of dihydropyridines. © 2015 The British Pharmacological Society