title: Pharmacological inhibition of TRPM4 hyperpolarizes vascular smooth muscle.
abstract: The contractile state of vascular smooth muscle cells is regulated by small changes in membrane potential that gate voltage-dependent calcium channels. The melastatin transient receptor potential (TRP) channel TRPM4 is a critical mediator of pressure-induced membrane depolarization and arterial constriction. A recent study shows that the tricyclic compound 9-phenanthrol inhibits TRPM4, but not the related channel TRPM5. The current study investigated the specificity of 9-phenanthrol and the effects of the compound on pressure-induced smooth muscle depolarization and arterial constriction. Patch-clamp electrophysiology revealed that 9-phenanthrol blocks native TRPM4 currents in freshly isolated smooth muscle cells in a concentration-dependent manner (IC(50) = 10.6 μM). 9-Phenanthrol (30 μM) had no effect on maximum evoked currents in human embryonic kidney cells expressing recombinant TRPC3 or TRPC6 channels. Large-conductance Ca(2+)-activated K(+), voltage-dependent K(+), inwardly rectifying K(+), and voltage-dependent Ca(2+) channel activity in native cerebral artery myocytes was not altered by administration of 9-phenanthrol (30 μM). Using intracellular microelectrodes to record smooth muscle membrane potential in isolated cerebral arteries pressurized to 70 mmHg, we found that 9-phenanthrol (30 μM) reversibly hyperpolarized the membrane from ∼-40 mV to ∼-70 mV. In addition, we found that myogenic tone was reversibly abolished when vessels were exposed to 9-phenanthrol. These data demonstrate that 9-phenanthrol is useful for studying the functional significance of TRPM4 in vascular smooth muscle cells and that TRPM4 is an important regulator of smooth muscle cell membrane depolarization and arterial constriction in response to intraluminal pressure.
authors.affiliation: Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado 80523, USA.
authors.forename: Albert L
authors.initials: AL
authors.lastname: Gonzales
authors.forename: Zarine I
authors.initials: ZI
authors.lastname: Garcia
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Amberg
authors.forename: Scott
authors.initials: S
authors.lastname: Earley
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000378:metabolism; D002536:Cerebral Arteries / Q000033:anatomy & histology / Q000187:drug effects; D006801:Humans; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects*; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D010616:Phenanthrenes / Q000494:pharmacology*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D050053:TRPM Cation Channels / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D010616:Phenanthrenes; D020033:Protein Isoforms; D047428:Protein Kinase Inhibitors; D050053:TRPM Cation Channels; C500239:TRPM4 protein, rat; C091375:9-phenanthrol
references.citation: Circ Res. 1980 Jul;47(1):1-9
references.pmid: 7379260
references.citation: J Physiol. 2000 Aug 15;527 Pt 1:139-48
references.pmid: 10944177
references.citation: Clin Sci (Lond). 2010 Apr 07;119(1):19-36
references.pmid: 20370719
references.citation: Am J Physiol Heart Circ Physiol. 2007 Jun;292(6):H2613-22
references.pmid: 17293488
references.citation: Proc Natl Acad Sci U S A. 2006 Oct 31;103(44):16586-91
references.pmid: 17056714
references.citation: J Physiol. 1998 Apr 1;508 ( Pt 1):199-209
references.pmid: 9490839
references.citation: Circ Res. 2004 Oct 29;95(9):922-9
references.pmid: 15472118
references.citation: Circ Res. 2005 Dec 9;97(12):1270-9
references.pmid: 16269659
references.citation: Cell. 2002 May 3;109(3):397-407
references.pmid: 12015988
references.citation: Physiol Rev. 1989 Apr;69(2):546-604
references.pmid: 2467318
references.citation: Circ Res. 2002 Feb 22;90(3):248-50
references.pmid: 11861411
references.citation: Br J Pharmacol. 2008 Apr;153(8):1697-705
references.pmid: 18297105
references.citation: Endothelium. 2003;10(1):5-15
references.pmid: 12699072
references.citation: Microcirculation. 2010 May;17(4):237-49
references.pmid: 20536737
references.citation: Am J Physiol Cell Physiol. 2010 Aug;299(2):C279-88
references.pmid: 20427713
references.citation: J Physiol. 1902 May 28;28(3):220-31
references.pmid: 16992618
references.citation: Am J Physiol Heart Circ Physiol. 2005 May;288(5):H2055-61
references.pmid: 15604128
references.citation: Cell Calcium. 2003 Sep;34(3):211-29
references.pmid: 12887969
references.citation: Circ Res. 2001 Feb 16;88(3):325-32
references.pmid: 11179201
references.citation: J Physiol. 2008 Feb 15;586(4):1147-60
references.pmid: 18063660
references.citation: Pflugers Arch. 2008 Mar;455(6):1097-103
references.pmid: 17957383
references.citation: Science. 1995 Oct 27;270(5236):633-7
references.pmid: 7570021
references.citation: Am J Physiol. 1995 Apr;268(4 Pt 1):C799-822
references.pmid: 7733230
references.citation: Stroke. 2007 Aug;38(8):2322-8
references.pmid: 17585083