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The Ability of Nitric Oxide to Lower Intraocular Pressure Is Dependent on Guanylyl Cyclase
Journal article   Open access   Peer reviewed

The Ability of Nitric Oxide to Lower Intraocular Pressure Is Dependent on Guanylyl Cyclase

Stefan Muenster, Wolfgang S Lieb, Gregor Fabry, Kaitlin N Allen, Shivani S Kamat, Ann H Guy, Ana C Dordea, Leandro Teixeira, Robert E Tainsh, Binglan Yu, …
Investigative ophthalmology & visual science, Vol.58(11), pp.4826-4835
09/01/2017
DOI: 10.1167/iovs.17-22168
PMCID: PMC5624778
PMID: 28973329
url
https://doi.org/10.1167/iovs.17-22168View
Published (Version of record) Open Access

Abstract

While nitric oxide (NO) donors are emerging as treatments for glaucoma, the mechanism by which NO lowers intraocular pressure (IOP) is unclear. NO activates the enzyme guanylyl cyclase (GC) to produce cyclic guanosine monophosphate. We studied the ocular effects of inhaled and topically applied NO gas in mice and lambs, respectively. IOP and aqueous humor (AqH) outflow were measured in WT and GC-1α subunit null (GC-1-/-) mice. Mice breathed 40 parts per million (ppm) NO in O2 or control gas (N2/O2). We also studied the effect of ocular NO gas exposure (80, 250, 500, and 1000 ppm) on IOP in anesthetized lambs. NO metabolites were measured in AqH and plasma. In awake WT mice, breathing NO for 40 minutes lowered IOP from 14.4 ± 1.9 mm Hg to 10.9 ± 1.0 mm Hg (n = 11, P < 0.001). Comparable results were obtained in anesthetized WT mice (n = 10, P < 0.001). In awake or anesthetized GC-1-/- mice, IOP did not change under similar experimental conditions (P ≥ 0.08, n = 20). Breathing NO increased in vivo outflow facility in WT but not GC-1-/- mice (+13.7 ± 14.6% vs. -12.1 ± 9.4%, n = 4 each, P < 0.05). In lambs, ocular exposure to NO lowered IOP in a dose-dependent manner (-0.43 mm Hg/ppm NO; n = 5 with 40 total measurements; P = 0.04) without producing corneal pathology or altering pulmonary and systemic hemodynamics. After ocular NO exposure, NO metabolites were increased in AqH (n = 8, P < 0.001) but not in plasma. Breathing NO reduced IOP and increased outflow facility in a GC-dependent manner in mice. Exposure of ovine eyes to NO lowers IOP.
Intraocular Pressure - drug effects Nitric Oxide - pharmacology Administration, Inhalation Male Mice, Transgenic Nitric Oxide - administration & dosage Guanylate Cyclase - deficiency Animals Guanylate Cyclase - physiology Female Sheep Mice Administration, Topical Aqueous Humor - physiology Disease Models, Animal

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