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Roy Chowdhury U, Pervan-Steel CL, Sheeler R, Sookdeo HK, Rogers B, Casale R, Dosa PI, Htoo T, Wirostko BM, Fautsch MP. Preclinical Pharmacokinetic Profile of Topical Ophthalmic and Intravenous Delivery of QLS-101, a Novel ATP-Sensitive Potassium Channel Opening Ocular Hypotensive Agent. J Ocul Pharmacol Ther 2023; 39:332-346. [PMID: 37200453 PMCID: PMC10398739 DOI: 10.1089/jop.2022.0184] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Accepted: 03/23/2023] [Indexed: 05/20/2023] Open
Abstract
Purpose: To evaluate the pharmacokinetic profiles of the ocular hypotensive agent QLS-101, a novel ATP-sensitive potassium channel opening prodrug, and its active moiety levcromakalim, following topical ophthalmic and intravenous dosing of normotensive rabbits and dogs. Methods: Dutch belted rabbits (n = 85) and beagle dogs (n = 32) were dosed with QLS-101 (0.16-3.2 mg/eye/dose) or formulation buffer for 28 days. Pharmacokinetic profiles of QLS-101 and levcromakalim were evaluated in ocular tissues and blood by LC-MS/MS. Tolerability was assessed by clinical and ophthalmic examinations. Maximum systemic tolerated dose was evaluated in beagle dogs (n = 2) following intravenous bolus administrations of QLS-101 (0.05 to 5 mg/kg). Results: Plasma analysis following topical dosing of QLS-101 (0.8-3.2 mg/eye/dose) for 28 days indicated an elimination half-life (T1/2) of 5.50-8.82 h and a corresponding time (Tmax) range of 2-12 h in rabbits, and a T1/2 of 3.32-6.18 h with a Tmax range of 1-2 h in dogs. Maximum tissue concentration (Cmax) values ranged from 54.8-540 (day 1) to 50.5-777 ng/mL (day 28) in rabbits, and 36.5-166 (day 1) to 47.0-147 ng/mL (day 28) in dogs. Levcromakalim plasma T1/2 and Tmax were similar to QLS-101, while Cmax was consistently lower. Topical ophthalmic delivery of QLS-101 was well tolerated in both species, with sporadic mild ocular hyperemia noted in the group treated with the highest concentration (3.2 mg/eye/dose). Following topical ophthalmic dosing, QLS-101 and levcromakalim were found primarily in the cornea, sclera, and conjunctiva. Maximum tolerated dose was determined to be 3 mg/kg. Conclusions: QLS-101 was converted to its active moiety levcromakalim and showed characteristic absorption, distribution, and safety profiles of a well-tolerated prodrug.
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Affiliation(s)
| | | | | | | | - Brian Rogers
- Pacific BioDevelopment, LLC, Emeryville, California, USA
| | | | - Peter I. Dosa
- Institute for Therapeutics Discovery and Development, Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota, USA
| | | | - Barbara M. Wirostko
- Qlaris Bio, Inc., Dedham, Massachusetts, USA
- Department of Ophthalmology, Moran Eye Center, University of Utah, Salt Lake City, Utah, USA
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Patel S, Mittal R, Sarantopoulos KD, Galor A. Neuropathic ocular surface pain: Emerging drug targets and therapeutic implications. Expert Opin Ther Targets 2022; 26:681-695. [PMID: 36069761 PMCID: PMC9613591 DOI: 10.1080/14728222.2022.2122438] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2021] [Accepted: 09/05/2022] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Dysfunction at various levels of the somatosensory system can lead to ocular surface pain with a neuropathic component. Compared to nociceptive pain (due to noxious stimuli at the ocular surface), neuropathic pain tends to be chronic and refractory to therapies, making it an important source of morbidity in the population. An understanding of the options available for neuropathic ocular surface pain, including new and emerging therapies, is thus an important topic. AREAS COVERED This review will examine studies focusing on ocular surface pain, emphasizing those examining patients with a neuropathic component. Attention will be placed toward recent (after 2017) studies that have examined new and emerging therapies for neuropathic ocular surface pain. EXPERT OPINION Several therapies have been studied thus far, and continued research is needed to identify which individuals would benefit from specific therapies. Gaps in our understanding exist, especially with availability of in-clinic diagnostics for neuropathic pain. A focus on improving diagnostic capabilities and researching gene-modulating therapies could help us to provide more specific mechanism-based therapies for patients. In the meantime, continuing to uncover new modalities and examining which are likely to work depending on pain phenotype remains an important short-term goal.
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Affiliation(s)
- Sneh Patel
- University of Miami Miller School of Medicine, Miami, FL, USA
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Rhiya Mittal
- University of Miami Miller School of Medicine, Miami, FL, USA
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Konstantinos D. Sarantopoulos
- Department of Anesthesiology, Perioperative Medicine, and Pain Management, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
| | - Anat Galor
- University of Miami Miller School of Medicine, Miami, FL, USA
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
- Surgical services, Miami Veterans Affairs Medical Center, Miami, FL, USA
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Yarishkin O, Phuong TTT, Vazquez-Chona F, Bertrand J, van Battenburg-Sherwood J, Redmon SN, Rudzitis CN, Lakk M, Baumann JM, Freichel M, Hwang EM, Overby D, Križaj D. Emergent Temporal Signaling in Human Trabecular Meshwork Cells: Role of TRPV4-TRPM4 Interactions. Front Immunol 2022; 13:805076. [PMID: 35432302 PMCID: PMC9008486 DOI: 10.3389/fimmu.2022.805076] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2021] [Accepted: 03/02/2022] [Indexed: 11/26/2022] Open
Abstract
Trabecular meshwork (TM) cells are phagocytic cells that employ mechanotransduction to actively regulate intraocular pressure. Similar to macrophages, they express scavenger receptors and participate in antigen presentation within the immunosuppressive milieu of the anterior eye. Changes in pressure deform and compress the TM, altering their control of aqueous humor outflow but it is not known whether transducer activation shapes temporal signaling. The present study combines electrophysiology, histochemistry and functional imaging with gene silencing and heterologous expression to gain insight into Ca2+ signaling downstream from TRPV4 (Transient Receptor Potential Vanilloid 4), a stretch-activated polymodal cation channel. Human TM cells respond to the TRPV4 agonist GSK1016790A with fluctuations in intracellular Ca2+ concentration ([Ca2+]i) and an increase in [Na+]i. [Ca2+]i oscillations coincided with monovalent cation current that was suppressed by BAPTA, Ruthenium Red and the TRPM4 (Transient Receptor Potential Melastatin 4) channel inhibitor 9-phenanthrol. TM cells expressed TRPM4 mRNA, protein at the expected 130-150 kDa and showed punctate TRPM4 immunoreactivity at the membrane surface. Genetic silencing of TRPM4 antagonized TRPV4-evoked oscillatory signaling whereas TRPV4 and TRPM4 co-expression in HEK-293 cells reconstituted the oscillations. Membrane potential recordings suggested that TRPM4-dependent oscillations require release of Ca2+ from internal stores. 9-phenanthrol did not affect the outflow facility in mouse eyes and eyes from animals lacking TRPM4 had normal intraocular pressure. Collectively, our results show that TRPV4 activity initiates dynamic calcium signaling in TM cells by stimulating TRPM4 channels and intracellular Ca2+ release. It is possible that TRPV4-TRPM4 interactions downstream from the tensile and compressive impact of intraocular pressure contribute to homeostatic regulation and pathological remodeling within the conventional outflow pathway.
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Affiliation(s)
- Oleg Yarishkin
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, United States
| | - Tam T T Phuong
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, United States
| | - Felix Vazquez-Chona
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, United States
| | - Jacques Bertrand
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | | | - Sarah N Redmon
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, United States
| | - Christopher N Rudzitis
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, United States.,Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, United States
| | - Monika Lakk
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, United States
| | - Jackson M Baumann
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, United States.,Department of Bioengineering, University of Utah, Salt Lake City, United States
| | - Marc Freichel
- Institute of Pharmacology, Heidelberg University, Heidelberg, Germany
| | - Eun-Mi Hwang
- Center for Functional Connectomics, Korea Institute of Science and Technology (KIST), Seoul, South Korea
| | - Darryl Overby
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - David Križaj
- Department of Ophthalmology and Visual Sciences, University of Utah School of Medicine, Salt Lake City, United States.,Interdepartmental Program in Neuroscience, University of Utah, Salt Lake City, United States.,Department of Bioengineering, University of Utah, Salt Lake City, United States.,Department of Neurobiology, University of Utah, Salt Lake City, United States
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Pervan-Steel CL, Roy Chowdhury U, Sookdeo HK, Casale RA, Dosa PI, Htoo TM, Fautsch MP, Wirostko BM. Ocular Hypotensive Properties and Biochemical Profile of QLS-101, a Novel ATP-Sensitive Potassium (KATP) Channel Opening Prodrug. Invest Ophthalmol Vis Sci 2022; 63:26. [PMID: 35486069 PMCID: PMC9055548 DOI: 10.1167/iovs.63.4.26] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 04/10/2022] [Indexed: 11/24/2022] Open
Abstract
Purpose To characterize the ocular hypotensive and pharmacological properties of QLS-101, a novel ATP-sensitive potassium (KATP) channel opening prodrug. Methods Ocular hypotensive properties of QLS-101 were evaluated by measuring IOP with a handheld rebound tonometer after daily topical ocular instillation of 0.2% (n = 5) or 0.4% QLS-101 (n = 10) in C57BL/6J mice. KATP channel specificity was characterized in HEK-293 cells stably expressing human Kir6.2/SUR2B subunits and assessed for off-target interactions using a receptor binding screen. Conversion of QLS-101 prodrug to its active moiety, levcromakalim, was evaluated in vitro using human ocular tissues and plasma samples and after incubation with human phosphatase enzymes (2.0 nM-1.0 µM). Results C57BL/6J mice treated once daily with 0.2% QLS-101 exhibited significant (P < 0.01) IOP reductions of 2.1 ± 0.4 mmHg after five days; however, a daily attenuation of the effect was noted by 23h post-dose. By comparison, treatment with 0.4% QLS-101 lowered IOP by 4.8 ± 0.7 mm Hg (P < 0.0001) which was sustained for 24 hours. Unlike levcromakalim, QLS-101 failed to induce KATP channel activity in HEK-Kir6.2/SUR2B cells consistent with its development as a prodrug. No off-target receptor effects were detected with either compound. In vitro ocular tissue conversion of QLS-101 prodrug was identified in human iris, ciliary body, trabecular meshwork, and sclera. Alkaline phosphatase was found to convert QLS-101 (mean Km = 630 µM, kcat = 15 min-1) to levcromakalim. Conclusions QLS-101 is a novel KATP channel opening prodrug that when converted to levcromakalim shows 24-hour IOP lowering after once-daily topical ocular administration.
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Affiliation(s)
| | - Uttio Roy Chowdhury
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
| | | | | | - Peter I. Dosa
- Institute for Therapeutics Discovery and Development, Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota, United States
| | | | - Michael P. Fautsch
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
| | - Barbara M. Wirostko
- Qlaris Bio, Inc., Wellesley, Massachusetts, United States
- Department of Ophthalmology, Moran Eye Center, University of Utah, Salt Lake City, Utah, United States
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Roy Chowdhury U, Millar JC, Holman BH, Anderson KJ, Dosa PI, Roddy GW, Fautsch MP. Effect of ATP-sensitive Potassium Channel Openers on Intraocular Pressure in Ocular Hypertensive Animal Models. Invest Ophthalmol Vis Sci 2022; 63:15. [PMID: 35129587 PMCID: PMC8822368 DOI: 10.1167/iovs.63.2.15] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Purpose To evaluate the effect of ATP-sensitive potassium channel openers cromakalim prodrug 1 (CKLP1) and diazoxide on IOP in three independent mouse models of ocular hypertension. Methods Baseline IOP was measured in TGFβ2 overexpression, steroid-induced, and iris dispersion (DBA/2J) ocular hypertension mouse models, followed by once daily eyedrop administration with CKLP1 (5 mM) or diazoxide (5 mM). The IOP was measured in conscious animals with a handheld rebound tonometer. Aqueous humor dynamics were assessed by a constant perfusion method. Effect of treatment on ocular tissues was evaluated by transmission electron microscopy. Results CKLP1 decreased the IOP by 20% in TGFβ2 overexpressing mice (n = 6; P < 0.0001), 24% in steroid-induced ocular hypertensive mice (n = 8; P < 0.0001), and 43% in DBA/2J mice (n = 15; P < 0.0001). Diazoxide decreased the IOP by 32% in mice with steroid-induced ocular hypertension (n = 13; P < 0.0001) and by 41% in DBA/2J mice (n = 4; P = 0.005). An analysis of the aqueous humor dynamics revealed that CKLP1 decreased the episcleral venous pressure by 29% in TGFβ2 overexpressing mice (n = 13; P < 0.0001) and by 72% in DBA/2J mice (n = 4 control, 3 treated; P = 0.0002). Diazoxide lowered episcleral venous pressure by 35% in steroid-induced ocular hypertensive mice (n = 3; P = 0.03). Tissue histology and cell morphology appeared normal when compared with controls. Accumulation of extracellular matrix was reduced in CKLP1- and diazoxide-treated eyes in the steroid-induced ocular hypertension model. Conclusions ATP-sensitive potassium channel openers CKLP1 and diazoxide effectively decreased the IOP in ocular hypertensive animal models by decreasing the episcleral venous pressure, supporting a potential therapeutic application of these agents in ocular hypertension and glaucoma.
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Affiliation(s)
| | - J Cameron Millar
- North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, TX, United States
| | - Bradley H Holman
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States
| | | | - Peter I Dosa
- Institute for Therapeutics Discovery and Development, Department of Medicinal Chemistry, University of Minnesota, Minneapolis, MN, United States
| | - Gavin W Roddy
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States
| | - Michael P Fautsch
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States
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Roy Chowdhury U, Kudgus RA, Rinkoski TA, Holman BH, Bahler CK, Hann CR, Reid JM, Dosa PI, Fautsch MP. Pharmacological and pharmacokinetic profile of the novel ocular hypotensive prodrug CKLP1 in Dutch-belted pigmented rabbits. PLoS One 2020; 15:e0231841. [PMID: 32298376 PMCID: PMC7162492 DOI: 10.1371/journal.pone.0231841] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2020] [Accepted: 04/01/2020] [Indexed: 11/19/2022] Open
Abstract
Elevated intraocular pressure is the only treatable risk factor for glaucoma, an eye disease that is the leading cause of irreversible blindness worldwide. We have identified cromakalim prodrug 1 (CKLP1), a novel water-soluble ATP-sensitive potassium channel opener, as a new ocular hypotensive agent. To evaluate the pharmacokinetic and safety profile of CKLP1 and its parent compound levcromakalim, Dutch-belted pigmented rabbits were treated intravenously (0.25 mg/kg) or topically (10 mM; 4.1 mg/ml) with CKLP1. Body fluids (blood, aqueous and vitreous humor) were collected at multiple time points and evaluated for the presence of CKLP1 and levcromakalim using a liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) based assay. Histology of tissues isolated from Dutch-belted pigmented rabbits treated once daily for 90 days was evaluated in a masked manner by a certified veterinary pathologist. The estimated plasma parameters following intravenous administration of 0.25 mg/kg of CKLP1 showed CKLP1 had a terminal half-life of 61.8 ± 55.2 min, Tmax of 19.8 ± 23.0 min and Cmax of 1968.5 ± 831.0 ng/ml. Levcromakalim had a plasma terminal half-life of 85.0 ± 37.0 min, Tmax of 61.0 ± 32.0 min and Cmax of 10.6 ± 1.2 ng/ml. Topical CKLP1 treatment in the eye showed low levels (<0.3 ng/mL) of levcromakalim in aqueous and vitreous humor, and trace amounts of CKLP1 and levcromakalim in the plasma. No observable histological changes were noted in selected tissues that were examined following topical application of CKLP1 for 90 consecutive days. These results suggest that CKPL1 is converted to levcromakalim in the eye and likely to some extent in the systemic circulation.
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Affiliation(s)
- Uttio Roy Chowdhury
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
| | - Rachel A. Kudgus
- Department of Oncology Research, Mayo Clinic, Rochester, MN, United States of America
| | - Tommy A. Rinkoski
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
| | - Bradley H. Holman
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
| | - Cindy K. Bahler
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
| | - Cheryl R. Hann
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
| | - Joel M. Reid
- Department of Oncology Research, Mayo Clinic, Rochester, MN, United States of America
| | - Peter I. Dosa
- Department of Medicinal Chemistry, Institute for Therapeutics Discovery and Development, University of Minnesota, Minneapolis, MN, United States of America
| | - Michael P. Fautsch
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
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Roddy GW, Rosa RH, Viker KB, Holman BH, Hann CR, Krishnan A, Gores GJ, Bakri SJ, Fautsch MP. Diet Mimicking "Fast Food" Causes Structural Changes to the Retina Relevant to Age-Related Macular Degeneration. Curr Eye Res 2019; 45:726-732. [PMID: 31735070 DOI: 10.1080/02713683.2019.1694156] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Introduction: Metabolic syndrome is a disorder characterized by a constellation of findings including truncal obesity, elevated blood pressure, abnormal cholesterol levels, and high blood glucose. Recent evidence suggests that metabolic syndrome may be associated with increased risk of age-related macular degeneration (AMD) and other eye diseases. Recently, C57BL/6J wild-type mice fed with a "fast food" diet consisting of high fat, cholesterol, and fructose-supplemented water showed unique systemic pathology consistent with metabolic syndrome and nonalcoholic steatohepatitis. Additionally, these mice showed higher levels of fibrosis, inflammation, endoplasmic reticulum stress, and mitochondrial dysfunction compared to mice fed with only a high-fat diet alone. Since similar pathways are activated in AMD, we sought to determine whether mice fed a "fast food" diet exhibited retinal changes.Methods: 3-month-old wild-type mice were randomized to a standard chow (n = 11) or a "fast food" (n = 18) diet and fed for 9 months. At 1 year of age, tissues were collected and retinas were analyzed using transmission electron microscopy. Quantitative measures of Bruch's membrane thickness and retinal pigment epithelium (RPE) cell counts were performed.Results: "Fast food" fed mice showed ocular pathology relevant to various stages of AMD including basal laminar deposits, focal thickening of Bruch's membrane, and a significant loss of RPE cells.Discussion/conclusion: A wild-type mouse model of metabolic syndrome fed a "fast food" diet developed changes to the retina similar to some of the pathologic features seen in AMD. Further investigations into this and similar animal models as well as further epidemiological studies are needed to more clearly define the association between metabolic syndrome and AMD.
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Affiliation(s)
- Gavin W Roddy
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, USA
| | - Robert H Rosa
- Department of Ophthalmology, Baylor Scott & White Eye Institute, Temple, Texas, USA
| | - Kimberly B Viker
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, USA
| | - Bradley H Holman
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, USA
| | - Cheryl R Hann
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, USA
| | - Anuradha Krishnan
- Department of Gastroenterology, Mayo Clinic, Rochester, Minnesota, USA
| | - Gregory J Gores
- Department of Gastroenterology, Mayo Clinic, Rochester, Minnesota, USA
| | - Sophie J Bakri
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, USA
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Roy Chowdhury U, Dosa PI, Fautsch MP. ATP sensitive potassium channel openers: A new class of ocular hypotensive agents. Exp Eye Res 2019; 178:225. [PMID: 27353766 PMCID: PMC10518901 DOI: 10.1016/j.exer.2016.06.013] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2016] [Accepted: 06/16/2016] [Indexed: 11/16/2022]
Affiliation(s)
- Uttio Roy Chowdhury
- Department of Ophthalmology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, United States.
| | - Peter I Dosa
- Institute for Therapeutics Discovery and Development, Department of Medicinal Chemistry, University of Minnesota, 717 Delaware Street SE, Minneapolis, MN 55414, United States.
| | - Michael P Fautsch
- Department of Ophthalmology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, United States.
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Bucolo C, Platania CBM, Drago F, Bonfiglio V, Reibaldi M, Avitabile T, Uva M. Novel Therapeutics in Glaucoma Management. Curr Neuropharmacol 2018; 16:978-992. [PMID: 28925883 PMCID: PMC6120119 DOI: 10.2174/1570159x15666170915142727] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 06/26/2017] [Accepted: 09/03/2017] [Indexed: 11/22/2022] Open
Abstract
BACKGROUND Glaucoma is a progressive optic neuropathy characterized by retinal ganglion cell death and alterations of visual field. Elevated intraocular pressure (IOP) is considered the main risk factor of glaucoma, even though other factors cannot be ruled out, such as epigenetic mechanisms. OBJECTIVE An overview of the ultimate promising experimental drugs to manage glaucoma has been provided. RESULTS In particular, we have focused on purinergic ligands, KATP channel activators, gases (nitric oxide, carbon monoxide and hydrogen sulfide), non-glucocorticoid steroidal compounds, neurotrophic factors, PI3K/Akt activators, citicoline, histone deacetylase inhibitors, cannabinoids, dopamine and serotonin receptors ligands, small interference RNA, and Rho kinase inhibitors. CONCLUSIONS The review has been also endowed of a brief chapter on last reports about potential neuroprotective benefits of anti-glaucoma drugs already present in the market.
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Affiliation(s)
- Claudio Bucolo
- Address correspondence to this author at the Department of Biomedical and Biotechnological Sciences, School of Medicine, University of Catania, Via S. Sofia 97, 95123 Catania, Italy; Tel: +39 095 4781196;
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10
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Roy Chowdhury U, Rinkoski TA, Bahler CK, Millar JC, Bertrand JA, Holman BH, Sherwood JM, Overby DR, Stoltz KL, Dosa PI, Fautsch MP. Effect of Cromakalim Prodrug 1 (CKLP1) on Aqueous Humor Dynamics and Feasibility of Combination Therapy With Existing Ocular Hypotensive Agents. Invest Ophthalmol Vis Sci 2017; 58:5731-5742. [PMID: 29114841 PMCID: PMC5678549 DOI: 10.1167/iovs.17-22538] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Purpose Cromakalim prodrug 1 (CKLP1) is a water-soluble ATP-sensitive potassium channel opener that has shown ocular hypotensive properties in ex vivo and in vivo experimental models. To determine its mechanism of action, we assessed the effect of CKLP1 on aqueous humor dynamics and in combination therapy with existing ocular hypotensive agents. Methods Outflow facility was assessed in C57BL/6 mice by ex vivo eye perfusions and by in vivo constant flow infusion following CKLP1 treatment. Human anterior segments with no trabecular meshwork were evaluated for effect on pressure following CKLP1 treatment. CKLP1 alone and in combination with latanoprost, timolol, and Rho kinase inhibitor Y27632 were evaluated for effect on intraocular pressure in C57BL/6 mice and Dutch-belted pigmented rabbits. Results CKLP1 lowered episcleral venous pressure (control: 8.9 ± 0.1 mm Hg versus treated: 6.2 ± 0.1 mm Hg, P < 0.0001) but had no detectable effect on outflow facility, aqueous humor flow rate, or uveoscleral outflow. Treatment with CKLP1 in human anterior segments without the trabecular meshwork resulted in a 50% ± 9% decrease in pressure, suggesting an effect on the distal portion of the conventional outflow pathway. CKLP1 worked additively with latanoprost, timolol, and Y27632 to lower IOP, presumably owing to combined effects on different aspects of aqueous humor dynamics. Conclusions CKLP1 lowered intraocular pressure by reducing episcleral venous pressure and lowering distal outflow resistance in the conventional outflow pathway. Owing to this unique mechanism of action, CKLP1 works in an additive manner to lower intraocular pressure with latanoprost, timolol, and Rho kinase inhibitor Y27632.
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Affiliation(s)
- Uttio Roy Chowdhury
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
| | - Tommy A Rinkoski
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
| | - Cindy K Bahler
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
| | - J Cameron Millar
- North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, Texas, United States
| | - Jacques A Bertrand
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Bradley H Holman
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
| | - Joseph M Sherwood
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Darryl R Overby
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Kristen L Stoltz
- Institute for Therapeutics Discovery and Development, Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota, United States
| | - Peter I Dosa
- Institute for Therapeutics Discovery and Development, Department of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota, United States
| | - Michael P Fautsch
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States
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11
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Han YY, Wang LJ, Zhang L, Zhang WW, Ma KT, Li L, Si JQ. Association between potassium channel SNPs and essential hypertension in Xinjiang Kazak Chinese patients. Exp Ther Med 2017; 14:1999-2006. [PMID: 28962116 PMCID: PMC5609208 DOI: 10.3892/etm.2017.4734] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 05/05/2017] [Indexed: 12/27/2022] Open
Abstract
The aim of the present study was to examine whether single-nucleotide polymorphisms (SNPs) of β1 subunit of large-conductance Ca2+-activated K+ channel (KCNMB1) and inwardly rectifying K+ channel, subfamily J, member-11 (KCNJ11) are associated with essential hypertension (EH) in Xinjiang Kazak Chinese patients. A polymerase chain reaction-restriction fragment length polymorphism technique was applied to detect the distribution of selected alleles and genotype frequencies in a cohort of Xinjiang Kazak Chinese patients. Samples from 267 patients with EH and 259 normotensive (NT) controls were analyzed. An unconditional logistic regression analysis was used to estimate the odds ratio and 95% confidence interval of the risk factors that are associated with the development of EH. Genotype and allele frequency analyses revealed that the frequency of genotypes KCNJ11-rs2285676 and KCNMB1-rs11739136 was not significantly different between the EH and NT groups. Individuals carrying the GG genotype of KCNJ11-rs5219 had a 2.08 times higher risk of having EH than individuals carrying the GA+AA genotype of KCNJ11-rs5219. Furthermore, the G allele frequency of KCNJ11-rs5219 in the EH group was significantly higher than that of the NT group (P=0.048). Additionally, logistic regression analysis revealed that the body weight and GG genotype of KCNJ11-rs5219 were positively associated with EH in Xinjiang Kazak Chinese patients (P<0.01).
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Affiliation(s)
- Yuan-Yuan Han
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Li-Jie Wang
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Liang Zhang
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China.,The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Wen-Wen Zhang
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Ke-Tao Ma
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China.,The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Li Li
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China.,The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China
| | - Jun-Qiang Si
- Department of Physiology, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China.,The Key Laboratory of Xinjiang Endemic and Ethnic Diseases, Medical College of Shihezi University, Shihezi, Xinjiang 832002, P.R. China.,Department of Physiology, Huazhong University of Science and Technology of Basic Medical Sciences, Wuhan, Hubei 430070, P.R. China.,Department of Physiology, Wuhan University School of Basic Medical Sciences, Wuhan, Hubei 430070, P.R. China
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Roy Chowdhury U, Bahler CK, Holman BH, Fautsch MP. ATP-sensitive potassium (KATP) channel openers diazoxide and nicorandil lower intraocular pressure by activating the Erk1/2 signaling pathway. PLoS One 2017; 12:e0179345. [PMID: 28594895 PMCID: PMC5464668 DOI: 10.1371/journal.pone.0179345] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Accepted: 05/26/2017] [Indexed: 01/17/2023] Open
Abstract
Elevated intraocular pressure is the most prevalent and only treatable risk factor for glaucoma, a degenerative disease of the optic nerve. While treatment options to slow disease progression are available, all current therapeutic and surgical treatments have unwanted side effects or limited efficacy, resulting in the need to identify new options. Previous reports from our laboratory have established a novel ocular hypotensive effect of ATP-sensitive potassium channel (KATP) openers including diazoxide (DZ) and nicorandil (NCD). In the current study, we evaluated the role of Erk1/2 signaling pathway in KATP channel opener mediated reduction of intraocular pressure (IOP). Western blot analysis of DZ and NCD treated primary normal trabecular meshwork (NTM) cells, human TM (isolated from perfusion cultures of human anterior segments) and mouse eyes showed increased phosphorylation of Erk1/2 when compared to vehicle treated controls. DZ and NCD mediated pressure reduction (p<0.02) in human anterior segments (n = 7 for DZ, n = 4 for NCD) was abrogated by U0126 (DZ + U0126: -9.7 ± 11.5%, p = 0.11; NCD + U0126: -0.1 ± 11.5%, p = 1.0). In contrast, U0126 had no effect on latanoprostfree acid-induced pressure reduction (-52.5 ± 6.8%, n = 4, p = 0.001). In mice, DZ and NCD reduced IOP (DZ, 14.9 ± 3.8%, NCD, 16.9 ± 2.5%, n = 10, p<0.001), but the pressure reduction was inhibited by U0126 (DZ + U0126, 0.7 ± 3.0%; NCD + U0126, 0.9 ± 2.2%, n = 10, p>0.1). Histologic evaluation of transmission electron micrographs from DZ + U0126 and NCD + U0126 treated eyes revealed no observable morphological changes in the ultrastructure of the conventional outflow pathway. Taken together, the results indicate that the Erk1/2 pathway is necessary for IOP reduction by KATP channel openers DZ and NCD.
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Affiliation(s)
- Uttio Roy Chowdhury
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Cindy K. Bahler
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Bradley H. Holman
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States of America
| | - Michael P. Fautsch
- Department of Ophthalmology, Mayo Clinic, Rochester, Minnesota, United States of America
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13
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Prasanna G, Li B, Mogi M, Rice DS. Pharmacology of novel intraocular pressure-lowering targets that enhance conventional outflow facility: Pitfalls, promises and what lies ahead? Eur J Pharmacol 2016; 787:47-56. [DOI: 10.1016/j.ejphar.2016.03.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Revised: 02/15/2016] [Accepted: 03/01/2016] [Indexed: 12/18/2022]
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14
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Panchal SS, Mehta AA, Santani DD. Effect of potassium channel openers in acute and chronic models of glaucoma. Taiwan J Ophthalmol 2016; 6:131-135. [PMID: 29018728 PMCID: PMC5525614 DOI: 10.1016/j.tjo.2016.05.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 05/09/2016] [Accepted: 05/19/2016] [Indexed: 11/25/2022] Open
Abstract
PURPOSE Glaucoma is characterized by increased intraocular pressure (IOP). The effect of nicorandil and pinacidil on IOP in experimentally induced acute and chronic models of glaucoma and the mechanism of action involved were studied. METHODS New Zealand white rabbits were used for the study. After the measurement of IOP, nicorandil (1%), pinacidil (1%), and pilocarpine as standard (1%) were instilled topically into the left eye. The other eye served as control. Dextrose (5%) was used to induce acute glaucoma. IOP changes were recorded every 15 minutes until the pressure became normal. Freshly prepared α-chymotrypsin solution was introduced in the posterior chamber to induce chronic glaucoma. Rabbits with ocular hypertension were selected for the study. Similar drug solutions were used to study the effect on IOP. Glibenclamide, pilocarpine, and indomethacin (1%) were used to study the mechanism of action of both drugs. The IOPs were measured just prior to drug instillation and at suitable time intervals using a tonometer. RESULTS Pretreatment with topical nicorandil and pinacidil significantly lowered the rise in IOP in the acute model. Nicorandil and pinacidil initially caused rise in IOP for 15-30 minutes in chronic glaucoma. This was followed by reduction in IOP. Pretreatment with indomethacin and pilocarpine did not modify the effect of nicorandil and pinacidil on IOP. Pretreatment with glibenclamide blocked IOP from the lowering effect of nicorandil and pinacidil. CONCLUSION The oculohypotensive effect shown by these drugs appears to be attributable to enhancement of the aqueous humor outflow. This effect is perhaps mediated through potassium channels.
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Affiliation(s)
- Shital S Panchal
- Department of Pharmacology, Institute of Pharmacy, Nirma University, Ahmedabad 382481, Gujarat, India
| | - Anita A Mehta
- Department of Pharmacology, L.M. College of Pharmacy, Navarangpura, Ahmedabad 9, Gujarat, India
| | - Devdas D Santani
- Department of Pharmacy, NIMS University, Shobha Nagar, Jaipure-Delhi Highway (NH-11C), Jaipur 303121, Rajasthan, India
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Roy Chowdhury U, Viker KB, Stoltz KL, Holman BH, Fautsch MP, Dosa PI. Analogs of the ATP-Sensitive Potassium (KATP) Channel Opener Cromakalim with in Vivo Ocular Hypotensive Activity. J Med Chem 2016; 59:6221-31. [PMID: 27367033 DOI: 10.1021/acs.jmedchem.6b00406] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
ATP-sensitive potassium (KATP) channel openers have emerged as potential therapeutics for the treatment of glaucoma, lowering intraocular pressure (IOP) in animal models and cultured human anterior segments. We have prepared water-soluble phosphate and dipeptide derivatives of the KATP channel opener cromakalim and evaluated their IOP lowering capabilities in vivo. In general, the phosphate derivatives proved to be more chemically robust and efficacious at lowering IOP with once daily dosing in a normotensive mouse model. Two of these phosphate derivatives were further evaluated in a normotensive rabbit model, with a significant difference in activity observed. No toxic effects on cell structure or alterations in morphology of the aqueous humor outflow pathway were observed after treatment with the most efficacious compound, (3S,4R)-2, suggesting that it is a strong candidate for development as an ocular hypotensive agent.
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Affiliation(s)
- Uttio Roy Chowdhury
- Department of Ophthalmology, Mayo Clinic , 200 1st St SW, Rochester, Minnesota 55905, United States
| | - Kimberly B Viker
- Department of Ophthalmology, Mayo Clinic , 200 1st St SW, Rochester, Minnesota 55905, United States
| | - Kristen L Stoltz
- Institute for Therapeutics Discovery and Development, Department of Medicinal Chemistry, University of Minnesota , 717 Delaware Street SE, Minneapolis, Minnesota 55414, United States
| | - Bradley H Holman
- Department of Ophthalmology, Mayo Clinic , 200 1st St SW, Rochester, Minnesota 55905, United States
| | - Michael P Fautsch
- Department of Ophthalmology, Mayo Clinic , 200 1st St SW, Rochester, Minnesota 55905, United States
| | - Peter I Dosa
- Institute for Therapeutics Discovery and Development, Department of Medicinal Chemistry, University of Minnesota , 717 Delaware Street SE, Minneapolis, Minnesota 55414, United States
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16
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Roy Chowdhury U, Dosa PI, Fautsch MP. ATP sensitive potassium channel openers: A new class of ocular hypotensive agents. Exp Eye Res 2016; 158:85-93. [PMID: 27130546 DOI: 10.1016/j.exer.2016.04.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 04/22/2016] [Accepted: 04/25/2016] [Indexed: 12/25/2022]
Abstract
ATP sensitive potassium (KATP) channels connect the metabolic and energetic state of cells due to their sensitivity to ATP and ADP concentrations. KATP channels have been identified in multiple tissues and organs of the body including heart, pancreas, vascular smooth muscles and skeletal muscles. These channels are obligatory hetero-octamers and contain four sulfonylurea (SUR) and four potassium inward rectifier (Kir) subunits. Based on the particular type of SUR and Kir present, there are several tissue specific subtypes of KATP channels, each with their own unique set of functions. Recently, KATP channels have been reported in human and mouse ocular tissues. In ex vivo and in vivo model systems, KATP channel openers showed significant ocular hypotensive properties with no appearance of toxic side effects. Additionally, when used in conjunction with known intraocular pressure lowering drugs, an additive effect on IOP reduction was observed. These KATP channel openers have also been reported to protect the retinal ganglion cells during ischemic stress and glutamate induced toxicity suggesting a neuroprotective property for this drug class. Medications that are currently used for treating ocular hypertensive diseases like glaucoma do not directly protect the affected retinal cells, are sometimes ineffective and may show significant side effects. In light of this, KATP channel openers with both ocular hypotensive and neuroprotective properties, have the potential to develop into a new class of glaucoma therapeutics.
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Affiliation(s)
- Uttio Roy Chowdhury
- Dept. of Ophthalmology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, United States.
| | - Peter I Dosa
- Institute for Therapeutics Discovery and Development, Department of Medicinal Chemistry, University of Minnesota, 717 Delaware Street SE, Minneapolis, MN 55414, United States.
| | - Michael P Fautsch
- Dept. of Ophthalmology, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, United States.
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Roy Chowdhury U, Bahler CK, Holman BH, Dosa PI, Fautsch MP. Ocular Hypotensive Effects of the ATP-Sensitive Potassium Channel Opener Cromakalim in Human and Murine Experimental Model Systems. PLoS One 2015; 10:e0141783. [PMID: 26535899 PMCID: PMC4633217 DOI: 10.1371/journal.pone.0141783] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Accepted: 10/13/2015] [Indexed: 11/17/2022] Open
Abstract
Elevated intraocular pressure (IOP) is the most prevalent and only treatable risk factor for glaucoma, a leading cause of irreversible blindness worldwide. Unfortunately, all current therapeutics used to treat elevated IOP and glaucoma have significant and sometimes irreversible side effects necessitating the development of novel compounds. We evaluated the IOP lowering ability of the broad spectrum KATP channel opener cromakalim. Cultured human anterior segments when treated with 2 μM cromakalim showed a decrease in pressure (19.33 ± 2.78 mmHg at 0 hours to 13.22 ± 2.64 mmHg at 24 hours; p<0.001) when compared to vehicle treated controls (15.89 ± 5.33 mmHg at 0 h to 15.56 ± 4.88 mmHg at 24 hours; p = 0.89). In wild-type C57BL/6 mice, cromakalim reduced IOP by 18.75 ± 2.22% compared to vehicle treated contralateral eyes (17.01 ± 0.32 mmHg at 0 hours to 13.82 ± 0.37 mmHg at 24 hours; n = 10, p = 0.002). Cromakalim demonstrated an additive effect when used in conjunction with latanoprost free acid, a common ocular hypotensive drug prescribed to patients with elevated IOP. To examine KATP channel subunit specificity, Kir6.2(-/-) mice were treated with cromakalim, but unlike wild-type animals, no change in IOP was noted. Histologic analysis of treated and control eyes in cultured human anterior segments and in mice showed similar cell numbers and extracellular matrix integrity within the trabecular meshwork, with no disruptions in the inner and outer walls of Schlemm's canal. Together, these studies suggest that cromakalim is a potent ocular hypotensive agent that lowers IOP via activation of Kir6.2 containing KATP channels, its effect is additive when used in combination with the commonly used glaucoma drug latanoprost, and is not toxic to cells and tissues of the aqueous humor outflow pathway, making it a candidate for future therapeutic development.
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Affiliation(s)
- Uttio Roy Chowdhury
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
| | - Cindy K Bahler
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
| | - Bradley H Holman
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
| | - Peter I Dosa
- Institute for Therapeutics Discovery and Development, University of Minnesota, Minneapolis, MN, United States of America
| | - Michael P Fautsch
- Department of Ophthalmology, Mayo Clinic, Rochester, MN, United States of America
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Dalvin LA, Fautsch MP. Analysis of Circadian Rhythm Gene Expression With Reference to Diurnal Pattern of Intraocular Pressure in Mice. Invest Ophthalmol Vis Sci 2015; 56:2657-63. [PMID: 25813988 DOI: 10.1167/iovs.15-16449] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To determine the expression of circadian rhythm clock genes in the iris-ciliary body complex of mice and their association with the diurnal pattern of intraocular pressure (IOP). METHODS Thirty wild-type C57BL/6 mice were acclimated to a 12-hour light-dark cycle. Intraocular pressure was measured with a rebound tonometer at six time points daily (circadian time [CT] 2, 6, 10, 14, 18, and 22 hours) for five consecutive days. On day 6, mice were euthanized at CT 2, 6, 10, 14, 18, and 22. Eyes were flash-frozen or fixed in 4% phosphate-buffered paraformaldehyde. Total RNA was extracted from the iris-ciliary body complex, and RNA expression of circadian rhythm genes Bmal1, Clock, Cry1, Cry2, Per1, and Per2 was assessed by quantitative real-time PCR. Fixed eyes were paraffin embedded, and immunohistochemistry was performed to localize corresponding proteins (BMAL1, CLOCK, CRY1, CRY2, PER1, and PER2). Linear regression analysis was performed to correlate gene expression with IOP. RESULTS Intraocular pressure demonstrated a consistent circadian pattern. The clock genes Bmal1, Clock, Cry1, Cry2, Per1, and Per2 showed a circadian pattern of expression in the iris-ciliary body complex of mice. Bmal1, Clock, Cry1, Per1, and Per2 gene expression demonstrated statistically significant correlations with diurnal variations of IOP. BMAL1, CLOCK, CRY1, CRY2, PER1, and PER2 proteins were found to be expressed locally in the nonpigmented epithelium of the ciliary body. CONCLUSIONS Expression patterns of candidate circadian rhythm genes correlates with the diurnal pattern variation of IOP in mouse eyes, indicating a possible mechanism of IOP regulation through these genes.
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