9‐Phenanthrol inhibits recombinant and arterial myocyte TMEM16A channels

Background and Purpose In arterial smooth muscle cells (myocytes), intravascular pressure stimulates membrane depolarization and vasoconstriction (the myogenic response). Ion channels proposed to mediate pressure‐induced depolarization include several transient receptor potential (TRP) channels, inc...

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Bibliographic Details
Published in:British journal of pharmacology 2015-05, Vol.172 (10), p.2459-2468
Main Authors: Burris, Sarah K, Wang, Qian, Bulley, Simon, Neeb, Zachary P, Jaggar, Jonathan H
Format: Article
Language:English
Subjects:
Animals
Anoctamin-1
Arteries - cytology
Bestrophins
Calcium - pharmacology
Chloride Channels - antagonists & inhibitors
Chloride Channels - metabolism
Dose-Response Relationship, Drug
HEK293 Cells
Humans
Male
Membrane Potentials - drug effects
Muscle Cells - drug effects
Muscle Cells - metabolism
Neoplasm Proteins - agonists
Neoplasm Proteins - antagonists & inhibitors
Neoplasm Proteins - metabolism
Patch-Clamp Techniques
Phenanthrenes - pharmacology
Rats
Recombinant Proteins - metabolism
Research Papers
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Summary:Background and Purpose In arterial smooth muscle cells (myocytes), intravascular pressure stimulates membrane depolarization and vasoconstriction (the myogenic response). Ion channels proposed to mediate pressure‐induced depolarization include several transient receptor potential (TRP) channels, including TRPM4, and transmembrane protein 16A (TMEM16A), a Ca2+‐activated Cl− channel (CaCC). 9‐Phenanthrol, a putative selective TRPM4 channel inhibitor, abolishes myogenic tone in cerebral arteries, suggesting that either TRPM4 is essential for pressure‐induced depolarization, upstream of activation of other ion channels or that 9‐phenanthrol is non‐selective. Here, we tested the hypothesis that 9‐phenanthrol is also a TMEM16A channel blocker, an ion channel for which few inhibitors have been identified. Experimental Approach Patch clamp electrophysiology was used to measure rat cerebral artery myocyte and human recombinant TMEM16A (rTMEM16A) currents or currents generated by recombinant bestrophin‐1, another Ca2+‐activated Cl− channel, expressed in HEK293 cells. Key Results 9‐Phenanthrol blocked myocyte TMEM16A currents activated by either intracellular Ca2+ or Eact, a TMEM16A channel activator. In contrast, 9‐phenanthrol did not alter recombinant bestrophin‐1 currents. 9‐Phenanthrol reduced arterial myocyte TMEM16A currents with an IC50 of ∼12 μM. Cell‐attached patch recordings indicated that 9‐phenanthrol reduced single rTMEM16A channel open probability and mean open time, and increased mean closed time without affecting the amplitude. Conclusions and Implications These data identify 9‐phenanthrol as a novel TMEM16A channel blocker and provide an explanation for the previous observation that 9‐phenanthrol abolishes myogenic tone when both TRPM4 and TMEM16A channels contribute to this response. 9‐Phenanthrol may be a promising candidate from which to develop TMEM16A channel‐specific inhibitors.
ISSN:0007-1188
1476-5381
DOI:10.1111/bph.13077