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Megan E Cavet, Thomas R Vollmer, Karen Harrington, Karl VanDerMeid, Mary Richardson; NO-induced Regulation of Primary Human Trabecular Meshwork Cell Contractility by Latanoprostene Bunod. Invest. Ophthalmol. Vis. Sci. 2014;55(13):546.
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© ARVO (1962-2015); The Authors (2016-present)
Prior in vivo studies demonstrated that latanoprostene bunod (LBN), a nitric oxide (NO)-donating latanoprost, results in greater IOP lowering than latanoprost (Xalatan). This study determined the effect of LBN on primary human trabecular meshwork cell (HTMC) contractility and underlying signaling pathways, to assess whether LBN may mediate this additional IOP lowering via the conventional outflow pathway.
The effect of LBN (1 - 100 µM) on HTMC cGMP levels was determined by ELISA ± the soluble guanylate cyclase (sGC) inhibitor ODQ. Endothelin-1 (100 nM) was used to induce HTMC contractility. To determine the effect of LBN on myosin light chain-2 (MLC-2) phosphorylation, HTMC were pre-treated with 10 - 60 µM LBN for 1 h and then endothelin-1 for 5 min. MLC-2 phosphorylation was determined by western blotting. The effects of LBN (30 and 45 µM) on endothelin-induced actin cytoskeletal stress fibers and the focal adhesion associated protein vinculin were determined by confocal microscopy. Endothelin-1 induced HTMC monolayer resistance in the presence of LBN (1 - 45 µM) was determined by electrical cell substrate impedance sensing, as an indicator of cell contractility. Latanoprost was used as a comparator in all studies.
LBN (1 - 100 µM) significantly increased cGMP levels in a dose dependent manner with an EC50 of 1.54 ± 1.33 µM, while latanoprost caused a minimal increase in cGMP at 100 µM only. The cGMP elevation was abolished by ODQ and was therefore sGC dependent. Effects of LBN on endothelin-1-induced MLC-2 phosphorylation were significantly greater than those of latanoprost. LBN caused a dramatic reduction in endothelin-1 induced actin stress fibers and vinculin localization at focal adhesions, while latanoprost was without effect. LBN significantly reduced endothelin-1 induced HTMC monolayer resistance increases to a greater extent than latanoprost over the dose range studied, indicating a greater reduction in cell contractility with LBN.
Data suggest that LBN mediates HTMC relaxation through activation of the cGMP signaling pathway and a subsequent reduction in MLC-2 phosphorylation. In all cases, effects observed with LBN were of a greater magnitude than those observed with latanoprost. This mechanism may underlie the additional IOP lowering effects of LBN over latanoprost observed in in vivo studies.
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