Capsaicin as an amphipathic modulator of Na_V1.5 mechanosensitivity

ABSTRACT

SCN5A-encoded Na_V1.5 is a voltage-gated Na⁺ channel that drives the electrical excitability of cardiac myocytes and contributes to slow waves of the human gastrointestinal smooth muscle cells. Na_V1.5 is mechanosensitive: mechanical force modulates several facets of Na_V1.5’s voltage-gated function, and some Na_V1.5 channelopathies are associated with abnormal Na_V1.5 mechanosensitivity (MS). A class of membrane-active drugs, known as amphiphiles, therapeutically target Na_V1.5’s voltage-gated function and produce off-target effects including alteration of MS. Amphiphiles may provide a novel option for therapeutic modulation of Na_V1.5’s mechanosensitive operation. To more selectively target Na_V1.5 MS, we searched for a membrane-partitioning amphipathic agent that would inhibit MS with minimal closed-state inhibition of voltage-gated currents. Among the amphiphiles tested, we selected capsaicin for further study. We used two methods to assess the effects of capsaicin on Na_V1.5 MS: (1) membrane suction in cell-attached macroscopic patches and (2) fluid shear stress on whole cells. We tested the effect of capsaicin on Na_V1.5 MS by examining macro-patch and whole-cell Na⁺ current parameters with and without force. Capsaicin abolished the pressure- and shear-mediated peak current increase and acceleration; and the mechanosensitive shifts in the voltage-dependence of activation (shear) and inactivation (pressure and shear). Exploring the recovery from inactivation and use-dependent entry into inactivation, we found divergent stimulus-dependent effects that could potentiate or mitigate the effect of capsaicin, suggesting that mechanical stimuli may differentially modulate Na_V1.5 MS. We conclude that selective modulation of Na_V1.5 MS makes capsaicin a promising candidate for therapeutic interventions targeting MS.

KEYWORDS:

• Amphipathic
• arrhythmia
• capsaicin
• electrophysiology
• functional gastrointestinal disorder
• ion channel
• irritable bowel syndrome
• mechanosensitivity
• mechanotransduction
• voltage-gated sodium channel type 5

Acknowledgments

We thank Kristy Zodrow for administrative assistance and NIH for supporting our work: DK052766 (GF), DK106456, and AT10875 (AB), and GM021342 (OSA). Data is available on request from the authors.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Luke M. Cowan: conceived and designed research, performed experiments, analyzed data, interpreted results of experiments, prepared figures, drafted manuscript, edited and revised manuscript, approved final version of manuscript

Peter R. Strege: conceived and designed research, performed experiments, analyzed data, interpreted results of experiments, prepared figures, edited and revised manuscript, approved final version of manuscript

Radda Rusinova: conceived and designed research, analyzed data, interpreted results of experiments, edited and revised manuscript, approved final version of manuscript

Olaf S. Andersen: conceived and designed research, analyzed data, interpreted results of experiments, edited and revised manuscript, approved final version of manuscript

Gianrico Farrugia: conceived and designed research, edited and revised manuscript, approved final version of manuscript

Arthur Beyder: conceived and designed research, analyzed data, interpreted results of experiments, edited and revised manuscript, approved final version of manuscript

Additional information

Funding

This work was supported by the National Center for Complementary and Integrative Health [AT10875]; National Institute of General Medical Sciences [GM021342]; National Institute of Diabetes and Digestive and Kidney Diseases [DK106456]; National Institute of Diabetes and Digestive and Kidney Diseases [DK052766]; National Institute of Diabetes and Digestive and Kidney Diseases [DK052766].