Human trabecular meshwork cell volume decrease by NO-independent soluble guanylate cyclase activators YC-1 and BAY-58-2667 involves the BKCa ion channel.
OBJECTIVE
There is a correlation between cell volume changes and changes in the rate of aqueous humor outflow; agents that decrease trabecular meshwork (TM) cell volume increase the rate of aqueous humor outflow. This study investigated the effects of the nitric oxide (NO)-independent activators of soluble guanylate cyclase (sGC), YC-1, and BAY-58-2667 on TM cell volume and the signal transduction pathways and ion channel involved.


METHODS
Cell volume was measured with the use of calcein AM fluorescent dye, detected by confocal microscopy. Inhibitors and activators of sGC, 3',5'-cyclic guanosine monophosphate (cGMP), protein kinase G (PKG), and the BK(Ca) channel were used to characterize their involvement in the YC-1- and BAY-58-2667-induced regulation of TM cell volume. cGMP was assayed by an enzyme immunoassay.


RESULTS
YC-1 (10 nM-200 microM) and BAY-58-2667 (10 nM-100 microM) each elicited a biphasic effect on TM cell volume. YC-1 (1 microM) increased TM cell volume, but higher concentrations decreased TM cell volume. Similarly, BAY-58-2667 (100 nM) increased TM cell volume, but higher concentrations decreased cell volume. The YC-1-induced cell volume decrease was mimicked by 8-Br-cGMP and abolished by the sGC inhibitor ODQ, the PKG inhibitor (RP)-8-Br-PET-cGMP-S, and the BK(Ca) channel inhibitor IBTX. The BAY-58-2667-induced cell volume decrease was mimicked by 8-Br-cGMP and was abolished by the PKG inhibitor and the BK(Ca) channel inhibitor. Unlike the YC-1 response, ODQ potentiated the BAY-58-2667-induced decreases in cell volume.


CONCLUSIONS
These data suggest that the NO-independent decrease in TM cell volume is mediated by the sGC/cGMP/PKG pathway and involves K(+) efflux.
Dismuke
William M
WM
Department of Pharmacodynamics, College of Pharmacy, University of Florida, Gainesville, Florida 32610, USA.
Sharif
Najam A
NA
Ellis
Dorette Z
DZ
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001565:Benzoates / Q000494:pharmacology*; D048429:Cell Size / Q000187:drug effects*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D020536:Enzyme Activators; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005452:Fluoresceins / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism*; D006801:Humans; D007191:Indazoles / Q000494:pharmacology*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D018613:Microscopy, Confocal; D009569:Nitric Oxide / Q000378:metabolism*; D010069:Oxadiazoles / Q000494:pharmacology; D011810:Quinoxalines / Q000494:pharmacology; D014129:Trabecular Meshwork / Q000166:cytology* / Q000378:metabolism
C095284:1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one; D001565:Benzoates; D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D005452:Fluoresceins; D005456:Fluorescent Dyes; D007191:Indazoles; D051036:Large-Conductance Calcium-Activated Potassium Channels; D010069:Oxadiazoles; D011810:Quinoxalines; C085925:calcein AM; C090937:3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; C480588:BAY 58-2667; D017869:Cyclic GMP-Dependent Protein Kinases; D006162:Guanylate Cyclase; D006152:Cyclic GMP