The luminal diameter of muscular arteries and arterioles of the microcirculation is the principal site of control of vascular resistance. These small blood vessels are significant regulators of blood pressure and local blood flow distribution, and impaired control of their luminal diameter is a major contributor to cardiovascular-related diseases. Vascular smooth muscle cell membrane potential depolarization is central to the actions of vasoconstrictors, including intravascular pressure. Despite considerable investigation, the mechanisms underlying membrane potential depolarization remain obscure. In this proposal, we will examine the novel concept that activation of the melastatin transient receptor potential (TRP) channel TRPM4 in arterial myocytes integrates signals activated by vasoconstrictor stimuli to cause membrane potential depolarization. Evidence is provided that activation of TRPM4 channels causes membrane depolarization, Ca2+ influx via voltage-dependent Ca2+ channels, and vasoconstriction. Thus, TRPM4 appears to be an important mediator of smooth muscle cell depolarization. As such, an increase in TRPM4 activity or channel number could contribute to vascular pathologies such as hypertension, which are characterized by smooth muscle membrane potential depolarization and vasoconstriction. TRPM4 therefore presents an attractive target for drug-discovery efforts, but currently, little is known about how activity of the channel is controlled under physiological conditions. Phospholipase C (PLC), protein kinase C (PKC), and intracellular Ca2+ dynamics contribute to the control of arterial tone in vivo, and are thought to be important regulators of TRPM4. This proposal will address the central hypothesis that these factors elicit vasoconstriction, in part, by modulating the activity of TRPM4. Experiments are proposed that will use patch-clamp electrophysiology and live-cell confocal imaging experiments to elucidate how TRPM4 activity is regulated by PLC and PKC activity in vascular smooth muscle cells (Specific Aim 1), and by dynamic Ca2+ events involving IP3-mediated Ca2+ release from intracellular stores (Specific Aim 2).
Specific Aim 3 will extend these studies to the level of the intact vasculature and investigate the role of PLC, PKC, and Ca2+-dependent regulation of TRPM4 in pressure and agonist-induced vasoconstriction. These experiments will utilize intact cerebral arteries for intracellular microelectrode recordings of smooth muscle membrane potential confocal Ca2+ imaging, and simultaneous contractile and Ca2+ imaging studies. Additional experiments will employ siRNA technology to suppress TRPM4 expression in intact blood vessels. The outcome of these experiments will significantly enhance our understanding of the role of TRPM4 in blood pressure and blood flow regulation, findings that will contribute to the development of novel therapies for the treatment of cardiovascular-related diseases.

Public Health Relevance

Experiments described in this proposal will examine how TRPM4, an ion channel protein present in smooth muscle cells that line the walls of blood vessels, controls the diameter of small arteries and arterioles. This is important because these small blood vessels regulate blood flow and pressure, and impaired control of their diameter contributes to cardiovascular-related disease, such as hypertension, stroke, and coronary artery disease. The ultimate goal of this project is to improve human health by stimulating the development of new pharmaceuticals that act through TRPM4 to control and prevent cardiovascular-related diseases.

National Institute of Health (NIH)
National Heart, Lung, and Blood Institute (NHLBI)
Research Project (R01)
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Vascular Cell and Molecular Biology Study Section (VCMB)
Program Officer
Thrasher, Terry N
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Colorado State University-Fort Collins
Veterinary Sciences
Schools of Veterinary Medicine
Fort Collins
United States
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Pires, Paulo Wagner; Earley, Scott (2017) Redox regulation of transient receptor potential channels in the endothelium. Microcirculation 24:
Pires, Paulo W; Earley, Scott (2016) No Static at All: Tuning Into the Complexities of Ca2+ Signaling in the Endothelium. Circ Res 118:1042-4
Pires, Paulo Wagner; Earley, Scott (2016) A TRPC3 signalling complex promotes cerebral artery remodelling during hypertension. Cardiovasc Res 109:4-5
Earley, Scott; Brayden, Joseph E (2015) Transient receptor potential channels in the vasculature. Physiol Rev 95:645-90
Pires, Paulo W; Sullivan, Michelle N; Pritchard, Harry A T et al. (2015) Unitary TRPV3 channel Ca2+ influx events elicit endothelium-dependent dilation of cerebral parenchymal arterioles. Am J Physiol Heart Circ Physiol 309:H2031-41
Sullivan, Michelle N; Gonzales, Albert L; Pires, Paulo W et al. (2015) Localized TRPA1 channel Ca2+ signals stimulated by reactive oxygen species promote cerebral artery dilation. Sci Signal 8:ra2
Pires, P W; Earley, S (2015) TRPs in the kidney - location, location, location. Acta Physiol (Oxf) 213:296-7
Zhao, Limin; Sullivan, Michelle N; Chase, Marlee et al. (2014) Calcineurin/nuclear factor of activated T cells-coupled vanilliod transient receptor potential channel 4 ca2+ sparklets stimulate airway smooth muscle cell proliferation. Am J Respir Cell Mol Biol 50:1064-75
Ellinsworth, David C; Earley, Scott; Murphy, Timothy V et al. (2014) Endothelial control of vasodilation: integration of myoendothelial microdomain signalling and modulation by epoxyeicosatrienoic acids. Pflugers Arch 466:389-405
Gonzales, Albert L; Yang, Ying; Sullivan, Michelle N et al. (2014) A PLC?1-dependent, force-sensitive signaling network in the myogenic constriction of cerebral arteries. Sci Signal 7:ra49

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