Abstract
The ability of azobenzene trimethylammonium bromide (azoTAB) to sensitize cardiac tissue excitability to light was recently reported. The dark, thermally relaxed trans- isomer of azoTAB suppressed spontaneous activity and excitation propagation speed, whereas the cis- isomer had no detectable effect on the electrical properties of cardiomyocyte monolayers. As the membrane potential of cardiac cells is mainly controlled by activity of voltage-gated ion channels, this study examined whether the sensitization effect of azoTAB was exerted primarily via the modulation of voltage-gated ion channel activity. The effects of trans- and cis- isomers of azoTAB on voltage-dependent sodium (INav), calcium (ICav), and potassium (IKv) currents in isolated neonatal rat cardiomyocytes were investigated using the whole-cell patch-clamp technique. The experiments showed that azoTAB modulated ion currents, causing suppression of sodium (Na+) and calcium (Ca2+) currents and potentiation of net potassium (K+) currents. This finding confirms that azoTAB-effect on cardiac tissue excitability do indeed result from modulation of voltage-gated ion channels responsible for action potential.
Highlights
A remote, reversible, and precise method for controlling excitable biological tissues, such as heart and neural networks, would have enormous potential for biomedical applications
We have recently shown the possibility of photocontrol of excitation waves in cultured monolayers of cardiomyocytes by application of azobenzene trimethylammonium bromide [9,20,21]
Our results show that trans- azobenzene trimethylammonium bromide (azoTAB) suppresses voltage-depended sodium (INav) and calcium (ICav) currents, and potentiates net potassium current (IKv)
Summary
A remote, reversible, and precise method for controlling excitable biological tissues, such as heart and neural networks, would have enormous potential for biomedical applications. Cells may be sensitized to light either through genetic modifications (insertion of the light-sensitive proteins of microbial opsins, such as channelrhodopsin-2 or halorhodopsin [1]) or through application of light-responsive substances that alter the conductance of ion channels [2,3,4,5,6]. A dark, thermally relaxed trans- isomer of azobenzene adopts an extended configuration that is longer than a higher energy cis- or “bent” isomer
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