title: The polymodal ion channel transient receptor potential vanilloid 4 modulates calcium flux, spiking rate, and apoptosis of mouse retinal ganglion cells.
abstract: Sustained increase in intraocular pressure represents a major risk factor for eye disease, yet the cellular mechanisms of pressure transduction in the posterior eye are essentially unknown. Here we show that the mouse retina expresses mRNA and protein for the polymodal transient receptor potential vanilloid 4 (TRPV4) cation channel known to mediate osmotransduction and mechanotransduction. TRPV4 antibodies labeled perikarya, axons, and dendrites of retinal ganglion cells (RGCs) and intensely immunostained the optic nerve head. Müller glial cells, but not retinal astrocytes or microglia, also expressed TRPV4 immunoreactivity. The selective TRPV4 agonists 4α-PDD and GSK1016790A elevated [Ca2+]i in dissociated RGCs in a dose-dependent manner, whereas the TRPV1 agonist capsaicin had no effect on [Ca2+](RGC). Exposure to hypotonic stimulation evoked robust increases in [Ca2+](RGC). RGC responses to TRPV4-selective agonists and hypotonic stimulation were absent in Ca2+ -free saline and were antagonized by the nonselective TRP channel antagonists Ruthenium Red and gadolinium, but were unaffected by the TRPV1 antagonist capsazepine. TRPV4-selective agonists increased the spiking frequency recorded from intact retinas recorded with multielectrode arrays. Sustained exposure to TRPV4 agonists evoked dose-dependent apoptosis of RGCs. Our results demonstrate functional TRPV4 expression in RGCs and suggest that its activation mediates response to membrane stretch leading to elevated [Ca2+]i and augmented excitability. Excessive Ca2+ influx through TRPV4 predisposes RGCs to activation of Ca2+ -dependent proapoptotic signaling pathways, indicating that TRPV4 is a component of the response mechanism to pathological elevations of intraocular pressure.
authors.affiliation: Department of Ophthalmology & Visual Sciences, John A. Moran Eye Center, Interdepartmental Program in Neuroscience, and Department of Physiology, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Ryskamp
authors.forename: Paul
authors.initials: P
authors.lastname: Witkovsky
authors.forename: Peter
authors.initials: P
authors.lastname: Barabas
authors.forename: Wei
authors.initials: W
authors.lastname: Huang
authors.forename: Christopher
authors.initials: C
authors.lastname: Koehler
authors.forename: Nikolay P
authors.initials: NP
authors.lastname: Akimov
authors.forename: Suk Hee
authors.initials: SH
authors.lastname: Lee
authors.forename: Shiwani
authors.initials: S
authors.lastname: Chauhan
authors.forename: Wei
authors.initials: W
authors.lastname: Xing
authors.forename: René C
authors.initials: RC
authors.lastname: Rentería
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Liedtke
authors.forename: David
authors.initials: D
authors.lastname: Krizaj
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001369:Axons / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002211:Capsaicin / Q000494:pharmacology; D003712:Dendrites / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D007150:Immunohistochemistry; D007930:Leucine / Q000031:analogs & derivatives / Q000494:pharmacology; D040542:Mechanotransduction, Cellular / Q000502:physiology; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012165:Retinal Ganglion Cells / Q000187:drug effects / Q000502:physiology*; D013449:Sulfonamides / Q000494:pharmacology; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: C530602:N-(1-((4-(2-(((2,4-dichlorophenyl)sulfonyl)amino)-3-hydroxypropanoyl)-1-piperazinyl)carbonyl)-3-methylbutyl)-1-benzothiophene-2-carboxamide; D012333:RNA, Messenger; D013449:Sulfonamides; D050916:TRPV Cation Channels; C486576:Trpv4 protein, mouse; D007930:Leucine; D002211:Capsaicin; D002118:Calcium