Intraocular pressure regulation via ATP-sensitive potassium channels

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ABSTRACT Elevated intraocular pressure (IOP) is the most prevalent and only treatable risk factor in glaucoma. While the cause of elevated IOP is commonly attributed to increased resistance at the trabecular meshwork/Schlemm's canal interface, an expanding body of evidence highlights the potential resistance created by distal portions of the conventional outflow pathway (Schlemm's canal outer wall, collector channels, and associated deep scleral and intrascleral vasculature). Perturbations within this region have been shown to contribute towards the pathology of glaucoma. We have identified a subset of KATP channel openers as novel ocular hypotensive agents that lower IOP in normotensive animal models (mice, rabbits, non-human primates) by directly affecting the distal portion of the conventional outflow pathway (herein referred to as the distal outflow pathway). This novel mode of action provides us with a unique opportunity to study the role of this region in glaucoma while characterizing in detail the mode of action of this drug class. In addition, we have preliminary data suggesting that KATP channel openers provide neuroprotection to retinal ganglion cells (RGCs). Based on studies completed in our previous funding period, the development of an aqueous soluble, therapy friendly form of this drug class (cromakalim prodrug 1; CKLP1), and new preliminary data presented in this proposal, we hypothesize that KATP channel openers lower IOP by targeting the vasculature in the distal outflow pathway, facilitating fluid flow through an Erk1/2 mediated signaling cascade. Additionally, we hypothesize that KATP channel openers are also neuroprotective agents and can protect RGCs from various glaucomatous insults. To test these hypotheses, we propose to characterize the vasoregulatory role of KATP channels within the distal outflow pathway, define the relevant molecular events pertaining to the Erk1/2 signaling pathway, determine the neuroprotective properties associated with KATP channel opening in RGCs, and examine the ocular hypotensive activity of KATP channel openers in models of glaucoma. New findings from the proposed studies would provide major advancements towards the goal of understanding the pathophysiology of glaucoma, novel mechanisms that enhance RGC survival, and characterization of the KATP channel opener prodrug CKLP1 as a potential therapeutic agent for the management of glaucoma.