Characterization of Soluble Guanylate Cyclase in NO-Induced Increases in Aqueous Humor Outflow Facility and in the Trabecular Meshwork

2009 ◽  
Vol 50 (4) ◽  
pp. 1808 ◽  
Author(s):  
Dorette Z. Ellis ◽  
William M. Dismuke ◽  
Binna M. Chokshi
Keyword(s):  
Aqueous Humor ◽  
Guanylate Cyclase ◽  
Trabecular Meshwork ◽  
Soluble Guanylate Cyclase ◽  
Outflow Facility ◽  
Aqueous Humor Outflow

Intracellular Cl regulates Na-K-Cl cotransport activity in human trabecular meshwork cells

1999 ◽  
Vol 277 (3) ◽  
pp. C373-C383 ◽  
Author(s):  
Luanna K. Putney ◽  
Cecile Rose T. Vibat ◽  
Martha E. O’Donnell
Keyword(s):  
Cell Volume ◽  
Aqueous Humor ◽  
Trabecular Meshwork ◽  
Cell Types ◽  
Cellular Mechanisms ◽  
Outflow Facility ◽  
Aqueous Humor Outflow ◽  
Trabecular Meshwork Cells ◽  
Cotransport System ◽  
Stimulation Of

The trabecular meshwork (TM) of the eye plays a central role in modulating intraocular pressure by regulating aqueous humor outflow, although the mechanisms are largely unknown. We and others have shown previously that aqueous humor outflow facility is modulated by conditions that alter TM cell volume. We have also shown that the Na-K-Cl cotransport system is a primary regulator of TM cell volume and that its activity appears to be coordinated with net efflux pathways to maintain steady-state volume. However, the cellular mechanisms that regulate cotransport activity and cell volume in TM cells have yet to be elucidated. The present study was conducted to investigate the hypothesis that intracellular Cl concentration ([Cl]i) acts to regulate TM cell Na-K-Cl cotransport activity, as has been shown previously for some other cell types. We demonstrate here that the human TM cell Na-K-Cl cotransporter is highly sensitive to changes in [Cl]i. Our findings reveal a marked stimulation of Na-K-Cl cotransport activity, assessed as ouabain-insensitive, bumetanide-sensitive K influx, in TM cells following preincubation of cells with Cl-free medium as a means of reducing [Cl]i. In contrast, preincubation of cells with media containing elevated K concentrations as a means of increasing [Cl]i results in inhibition of Na-K-Cl cotransport activity. The effects of reducing [Cl]i, as well as elevating [Cl]i, on Na-K-Cl cotransport activity are concentration dependent. Furthermore, the stimulatory effect of reduced [Cl]i is additive with cell-shrinkage-induced stimulation of the cotransporter. Our studies also show that TM cell Na-K-Cl cotransport activity is altered by a variety of Cl channel modulators, presumably through changes in [Cl]i. These findings support the hypothesis that regulation of Na-K-Cl cotransport activity, and thus cell volume, by [Cl]i may participate in modulating outflow facility across the TM.

Noladin Ether Acts on Trabecular Meshwork Cannabinoid (CB1) Receptors to Enhance Aqueous Humor Outflow Facility

2006 ◽  
Vol 47 (5) ◽  
pp. 1999 ◽  
Author(s):  
Ya Fatou Njie ◽  
Akhilesh Kumar ◽  
Zhuanhong Qiao ◽  
Lichun Zhong ◽  
Zhao-Hui Song
Keyword(s):  
Aqueous Humor ◽  
Trabecular Meshwork ◽  
Cb1 Receptors ◽  
Outflow Facility ◽  
Aqueous Humor Outflow

NO-induced regulation of human trabecular meshwork cell volume and aqueous humor outflow facility involve the BKCa ion channel

2008 ◽  
Vol 294 (6) ◽  
pp. C1378-C1386 ◽  
Author(s):  
William M. Dismuke ◽  
Chigozirim C. Mbadugha ◽  
Dorette Z. Ellis
Keyword(s):  
Cell Volume ◽  
Trabecular Meshwork ◽  
Time Course ◽  
Soluble Guanylate Cyclase ◽  
Anterior Segment ◽  
Drug Application ◽  
Cellular Mechanisms ◽  
No Donors ◽  
Outflow Facility ◽  
Aqueous Humor Outflow

Nitric oxide (NO) donors decrease intraocular pressure (IOP) by increasing aqueous outflow facility in the trabecular meshwork (TM) and/or Schlemm's canal. However, the cellular mechanisms are unknown. Cellular mechanisms known to regulate outflow facility include changes in cell volume and cellular contractility. In this study, we investigated the effects of NO donors on outflow facility and NO-induced effects on TM cell volume. We tested the involvement of soluble guanylate cyclase (sGC), cGMP, PKG, and the large-conductance Ca2+-activated K+ (BKCa) channel using inhibitors and activators. Cell volume was measured using calcein AM fluorescent dye, detected by confocal microscopy, and quantified using NIH ImageJ software. An anterior segment organ perfusion system measured outflow facility. NO increased outflow facility in porcine eye anterior segments (0.4884–1.3956 μl·min−1·mmHg−1) over baseline (0.2373–0.5220 μl·min−1·mmHg−1) within 10 min of drug application. These NO-induced increases in outflow facility were inhibited by the the BKCa channel inhibitor IBTX. Exposure of TM cells to NO resulted in a 10% decrease in cell volume, and these decreases were abolished by the sGC inhibitor 1 H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one and IBTX, suggesting the involvement of sGC and K+ eflux, respectively. NO-induced decreases in cell volume were mimicked by 8-Br-cGMP and abolished by the PKG inhibitor (RP)-8-Br-PET-cGMP-S, suggesting the involvement cGMP and PKG. Additionally, the time course for NO-induced decreases in TM cell volume correlated with NO-induced increases in outflow facility, suggesting that the NO-induced alterations in cell volume may influence outflow facility.

5-Methylurapidil, 8-Iso Prostaglandin E2: New Drugs to Increase Aqueous-Humor Outflow Facility

2000 ◽  
pp. 253-259
Author(s):  
J. B. Serle ◽  
S. M. Podos ◽  
R.-F. Wang ◽  
T. Mittag ◽  
P.-Y. Lee ◽  
...  
Keyword(s):  
Prostaglandin E2 ◽  
Aqueous Humor ◽  
New Drugs ◽  
Outflow Facility ◽  
Aqueous Humor Outflow
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