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Lakshmanan Y, Wong FSY, Chan HHL. Long-Term Effects on Retinal Structure and Function in a Mouse Endothelin-1 Model of Retinal Ganglion Cell Degeneration. Invest Ophthalmol Vis Sci 2023; 64:15. [PMID: 37561449 PMCID: PMC10424801 DOI: 10.1167/iovs.64.11.15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 07/22/2023] [Indexed: 08/11/2023] Open
Abstract
Purpose To study the long-term effects of endothelin-1 (ET-1)-induced retinal pathologies in mouse, using clinically relevant tools. Methods Adult C57BL/6 mice (7-9 weeks old) were intravitreally injected with PBS (n = 10) or 0.25 (n = 8), 0.5 (n = 8), or 1 nmol ET-1 (n = 9) and examined using electroretinogram, optical coherence tomography (OCT), and Doppler OCT at baseline and postinjection days 10, 28, and 56. Retinal ganglion cell (RGC) survival in retinal whole mount was quantified at days 28 and 56. Results ET-1 induced immediate retinal arterial constriction. The significantly reduced total blood flow and positive scotopic threshold response in the 0.5- and 1-nmol ET-1 groups at day 10 were recovered at day 28. A-wave magnitude was also significantly reduced at days 10 and 28. While a comparable and significant reduction in retinal nerve fiber layer thickness was detected in all ET-1 groups at day 56, the 1-nmol group was the earliest to develop such change at day 28. All ET-1 groups showed a transient inner retinal layer thinning at days 10 and 28 and a plateaued outer layer thickness at days 10 to 56. The 1-nmol group showed a significant RGC loss over all retinal locations examined at day 28 as compared with PBS control. As for the lower-dosage groups, significant RGC density loss at central and midperipheral retina was detected at day 56 when compared with day 28. Conclusions ET-1 injection in mice resulted in a transient vascular constriction and reduction in retinal functions, as well as a gradual loss of retinal nerve fiber layer and RGC in a dose-dependent manner.
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Affiliation(s)
| | | | - Henry Ho-Lung Chan
- Centre for Eye and Vision Research (CEVR), Hong Kong, Hong Kong
- Laboratory of Experimental Optometry (Neuroscience), School of Optometry, The Hong Kong Polytechnic University, Hong Kong SAR, China
- Research Centre for SHARP Vision (RCSV), The Hong Kong Polytechnic University, Hong Kong SAR, China
- University Research Facilities in Behavioral and Systems Neuroscience (UBSN), The Hong Kong Polytechnic University, Hong Kong SAR, China
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Adeghate J, Rahmatnejad K, Waisbourd M, Katz LJ. Intraocular pressure-independent management of normal tension glaucoma. Surv Ophthalmol 2018; 64:101-110. [PMID: 30300625 DOI: 10.1016/j.survophthal.2018.08.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2017] [Revised: 08/15/2018] [Accepted: 08/20/2018] [Indexed: 11/19/2022]
Affiliation(s)
- Jennifer Adeghate
- Wills Eye Hospital, Glaucoma Research Department, Philadelphia, Pennsylvania, USA; Weill Cornell Medical College, Department of Ophthalmology, New York, New York, USA
| | - Kamran Rahmatnejad
- Wills Eye Hospital, Glaucoma Research Department, Philadelphia, Pennsylvania, USA
| | - Michael Waisbourd
- Wills Eye Hospital, Glaucoma Research Department, Philadelphia, Pennsylvania, USA; Thomas Jefferson University, Department of Ophthalmology, Philadelphia, Pennsylvania, USA; Tel-Aviv University Medical Center, Glaucoma Research Center, Tel-Aviv, Israel
| | - L Jay Katz
- Wills Eye Hospital, Glaucoma Research Department, Philadelphia, Pennsylvania, USA; Thomas Jefferson University, Department of Ophthalmology, Philadelphia, Pennsylvania, USA.
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Shiragami C, Miyake M, Fujiwara A, Morizane Y, Tsujikawa A, Yamashita A, Shiraga F. Effect of topical isopropyl unoprostone on macular atrophy progression in eyes with exudative age-related macular degeneration. Medicine (Baltimore) 2017; 96:e6422. [PMID: 28328847 PMCID: PMC5371484 DOI: 10.1097/md.0000000000006422] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND To evaluate the efficacy and safety of topical isopropyl unoprostone (IU) in treating macular atrophy in age-related macular degeneration (AMD) patients. METHODS Fifty-two AMD patients with macular atrophy were included and randomly assigned (1:1) to the treatment (topical 0.15% IU) or placebo group. Subjects used study eye drops 3 times a day for 54 weeks. The macular atrophy was documented on fundus autofluorescence photographs and measured using RegionFinder. The enlargement rate of macular atrophy and the changes in visual acuity were examined statistically between baseline and 54 weeks. RESULTS Forty-eight subjects were included in the analyses because 4 subjects withdrew from the study. The differences between the IU and placebo groups in mean and median area of macular atrophy were not statistically significant at baseline. The baseline median lesion size of macular atrophy was 2.33 mm in the IU group and 1.63 mm in the placebo group (P = 0.51). The intergroup difference in the enlargement ratio of macular atrophy (21 ± 15% in the IU group and 111 ± 96% in the placebo group) was statistically significant (P < 0.001). Additionally, visual acuity tended to improve over baseline in the IU group. No serious adverse events were observed. CONCLUSIONS Topical IU therapy is safe and effective for treating macular atrophy in AMD patients.
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Affiliation(s)
- Chieko Shiragami
- Department of Ophthalmology, Kagawa University Faculty of Medicine, Kagawa
| | - Masahiro Miyake
- Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto
| | - Atsushi Fujiwara
- Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Yuki Morizane
- Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
| | - Akitaka Tsujikawa
- Department of Ophthalmology, Kagawa University Faculty of Medicine, Kagawa
| | - Ayana Yamashita
- Department of Ophthalmology, Kagawa University Faculty of Medicine, Kagawa
| | - Fumio Shiraga
- Department of Ophthalmology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan
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Nagai N, Iwata S, Kaji H, Sampei K, Katsukura Y, Onami H, Nishizawa M, Nakazawa T, Mashima Y, Abe T. Protective effects of sustained transscleral unoprostone delivery against retinal degeneration in S334ter rhodopsin mutant rats. J Biomed Mater Res B Appl Biomater 2016; 104:1730-1737. [PMID: 27753245 DOI: 10.1002/jbm.b.33522] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Revised: 07/24/2015] [Accepted: 08/30/2015] [Indexed: 01/21/2023]
Abstract
It has been suggested that unoprostone isopropyl (UNO) has potent neuroprotective activity in the retina. The effect of sustained transscleral UNO delivery to the posterior segment of the eye on photoreceptor degeneration was evaluated. UNO was loaded into a device made of poly(ethyleneglycol) dimethacrylate by polydimethylsiloxane mold-based UV-curing. The amount of UNO diffusing from these devices was measured using high-performance liquid chromatography. The polymeric devices that released UNO at 1.8 μg/day were implanted on the sclerae of S334ter rats at postnatal 21 days, and electroretinograms (ERGs) were compared with those of topical application and placebo devices. Retinal thickness was evaluated by histological examination. Western blots of specimens 4 weeks after implantation were performed. ERGs showed that the UNO-loaded device prevented the reduction of ERG amplitudes 2 and 4 weeks after implantation, compared with results using a placebo device or topical application. Histological examination showed that the UNO-loaded device prevented the reduction of retinal thickness, and Western blots of specimens indicated that the UNO-loaded device decreased expression of ERK1/2, phosphorylated ERK1/2, and caspase-3. A device that provided sustained UNO administration protected against retinal degeneration in rhodopsin mutant rats, and thus, may have translational potential as a sustainable method to administer drugs to treat retinitis pigmentosa. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1730-1737, 2016.
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Affiliation(s)
- Nobuhiro Nagai
- Division of Clinical Cell Therapy, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Satoru Iwata
- Division of Clinical Cell Therapy, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Hirokazu Kaji
- Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Kaori Sampei
- Division of Clinical Cell Therapy, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Yuki Katsukura
- Division of Clinical Cell Therapy, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan
| | - Hideyuki Onami
- Division of Clinical Cell Therapy, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan.,Department of Ophthalmology, Tohoku University Graduate School of Medicine, Sendai, 980-8574, Japan
| | - Matsuhiko Nishizawa
- Department of Bioengineering and Robotics, Graduate School of Engineering, Tohoku University, Sendai, 980-8579, Japan
| | - Toru Nakazawa
- Department of Ophthalmology, Tohoku University Graduate School of Medicine, Sendai, 980-8574, Japan
| | | | - Toshiaki Abe
- Division of Clinical Cell Therapy, United Centers for Advanced Research and Translational Medicine (ART), Tohoku University Graduate School of Medicine, Sendai, 980-8575, Japan.
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Abstract
Glaucoma is a progressive optic neuropathy that causes characteristic changes of the optic nerve and visual field in relation to intraocular pressure (IOP). It is now known that glaucoma can occur at statistically normal IOPs and prevalence studies have shown that normal tension glaucoma (NTG) is more common than previously thought. While IOP is believed to be the predominant risk factor in primary open angle glaucoma (POAG), IOP-independent risk factors, such as vascular dysregulation, are believed to play an important part in the pathogenesis of NTG. Though certain distinguishing phenotypic features of NTG have been reported, such as an increased frequency of disc hemorrhages, acquired pits of the optic nerve and characteristic patterns of disc cupping and visual field loss, there is much overlap of the clinical findings in NTG with POAG, suggesting that NTG is likely part of a continuum of open angle glaucomas. However, IOP modification is still the mainstay of treatment in NTG. As in traditional POAG, reduction of IOP can be achieved with the use of medications, laser trabeculoplasty or surgery. Studies now show that the choice of medication may also be important in determining the outcomes of these patients. Though it is likely that future treatment of NTG will involve modification of both IOP and IOP-independent risk factors, current efforts to develop IOP-independent neuroprotective treatments have not yet proven to be effective in humans.
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Affiliation(s)
| | - Joseph Caprioli
- Jules Stein Eye Institute, Department of Ophthalmology, University of California, Los Angeles, USA
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Akiyama M, Ikeda Y, Yoshida N, Notomi S, Murakami Y, Hisatomi T, Enaida H, Ishibashi T. Therapeutic efficacy of topical unoprostone isopropyl in retinitis pigmentosa. Acta Ophthalmol 2014; 92:e229-34. [PMID: 24868583 DOI: 10.1111/aos.12293] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
PURPOSE To evaluate the therapeutic effect of topical unoprostone isopropyl (unoprostone) on patients with retinitis pigmentosa (RP). METHODS Forty patients with typical forms of RP were included in the study.Seventeen of 40 patients were treated with 0.12% topical unoprostone twice daily in a randomly selected eye. Patients underwent follow-up examinations every 3 months after treatment. The efficacy of the treatment was monitored by visual acuity and visual field measurement testing using the Humphrey Field Analyzer (HFA: the central 10-2 programme). Moreover, 12 RP patients who were included this study and 12 normal subjects were evaluated in terms of their macular blood flow of both eyes after instillation of unoprostone using the laser speckle method. RESULTS One year after treatment, the 'macular sensitivity', calculated by HFA as the average sensitivity of the central 12 points, was preserved in the fellow eyes as well as the unoprostone-treated eyes. On the other hand, that in the eyes of the control RP patient was significantly decreased. Moreover, there were significantly greater improvements of the 'macular sensitivity' in the unoprostone-treated eyes than the fellow eyes. The change ratios of macular blood flow obtained from both RP patients and normal subjects were significantly increased in both the treated and the fellow eyes. No severe side-effects were observed. CONCLUSIONS These results demonstrate that topical unoprostone might have a therapeutic efficacy in patients with RP as a consequence of the macular bloodflow improvement as well as its direct neuroprotective effect.
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Affiliation(s)
- Masato Akiyama
- Department of Ophthalmology; Graduate School of Medical Sciences; Kyushu University; Higashi-ku Fukuoka Japan
| | - Yasuhiro Ikeda
- Department of Ophthalmology; Graduate School of Medical Sciences; Kyushu University; Higashi-ku Fukuoka Japan
| | - Noriko Yoshida
- Department of Ophthalmology; Graduate School of Medical Sciences; Kyushu University; Higashi-ku Fukuoka Japan
| | - Shoji Notomi
- Department of Ophthalmology; Graduate School of Medical Sciences; Kyushu University; Higashi-ku Fukuoka Japan
| | - Yusuke Murakami
- Department of Ophthalmology; Graduate School of Medical Sciences; Kyushu University; Higashi-ku Fukuoka Japan
| | - Toshio Hisatomi
- Department of Ophthalmology; Graduate School of Medical Sciences; Kyushu University; Higashi-ku Fukuoka Japan
| | - Hiroshi Enaida
- Department of Ophthalmology; Graduate School of Medical Sciences; Kyushu University; Higashi-ku Fukuoka Japan
| | - Tatsuro Ishibashi
- Department of Ophthalmology; Graduate School of Medical Sciences; Kyushu University; Higashi-ku Fukuoka Japan
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Fung DS, Whitson JT. An evidence-based review of unoprostone isopropyl ophthalmic solution 0.15% for glaucoma: place in therapy. Clin Ophthalmol 2014; 8:543-54. [PMID: 24648719 PMCID: PMC3958522 DOI: 10.2147/opth.s41562] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
Abstract
Glaucoma is a progressive, neurodegenerative optic nerve disease that can cause significant visual morbidity and affects over 60 million people worldwide. The only known modifiable risk factor for glaucoma at this time is elevated intraocular pressure (IOP), which may be treated with medications, laser therapy, and/or incisional surgery. Topical ocular medications are commonly used as first-line therapy for glaucoma, although side effects may limit their use. Unoprostone is a novel 22-carbon ocular hypotensive agent that may be advantageous in treating some patients with open angle glaucoma or ocular hypertension. Unlike the 20-carbon prostanoids, such as latanoprost, that lower IOP primarily through an increase in uveoscleral outflow, unoprostone may lower IOP through increased aqueous outflow via the conventional trabecular meshwork pathway. Although not as efficacious as other prostanoids, unoprostone is effective for IOP reduction both as monotherapy and adjunctive therapy with timolol. Unoprostone has decreased affinity for the prostaglandin F2α receptor, which may explain its well tolerated ocular and systemic side effect profile compared with other prostanoids.
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Affiliation(s)
- Derrick S Fung
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jess T Whitson
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, TX, USA
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Sagawa H, Terasaki H, Nakanishi K, Tokita Y, Watanabe M. Regeneration of optic nerve fibers with unoprostone, a prostaglandin-related antiglaucoma drug, in adult cats. Jpn J Ophthalmol 2013; 58:100-9. [PMID: 24129676 DOI: 10.1007/s10384-013-0282-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2013] [Accepted: 08/26/2013] [Indexed: 01/01/2023]
Abstract
PURPOSE We investigated the effects of unoprostone on neurite extension of cultured retinal pieces and axonal regeneration of retinal ganglion cells in the crushed optic nerve of adult cats. METHODS The retinal pieces were cultured with unoprostone or its primary metabolite, M1, dissolved in DMSO or polysorbate for 14 days, and the number and length of Tau-1-positive neurites and glial processes labeled with anti-glial fibrillary acidic protein antibodies were examined. After the optic nerve was crushed, unoprostone was injected into the vitreous body and the crushed site. On day 12, wheat germ agglutinin-conjugated horseradish peroxidase was injected into the vitreous body to anterogradely label the regenerated axons. On day 14, the optic nerve was excised and longitudinally sectioned. After peroxidase reaction, the number of axons regenerating beyond the crush site was examined. RESULTS The greatest number of neurites protruded from the cultured retinal pieces in 3 μM unoprostone and 3 μM M1. The neurite length was also the longest at 3 μM unoprostone and 3 μM M1, in which no glial processes were detected. After injections of 3 μM unoprostone, the final concentration in the vitreous humor, into the vitreous body and the crush site, the optic nerve fibers regenerated and extended beyond the crush site. In contrast, almost no fibers extended beyond the crush site after injection of phosphate-buffered saline. CONCLUSIONS The results indicate that intravitreal injection of unoprostone promotes regeneration of crushed optic nerve fibers in adult cats.
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Affiliation(s)
- Hiroe Sagawa
- Department of Ophthalmology, Nagoya University Graduate School of Medicine, Nagoya, Japan
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Harms NV, Toris CB. Current status of unoprostone for the management of glaucoma and the future of its use in the treatment of retinal disease. Expert Opin Pharmacother 2012. [PMID: 23199345 DOI: 10.1517/14656566.2013.748038] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION Optic nerve and retinal diseases such as glaucoma, age-related macular degeneration (AMD) and retinitis pigmentosa (RP) are significant public health concerns and have a momentous impact on patients' functional status and quality of life. These diseases are among the most common causes of visual impairment worldwide and account for billions of dollars in healthcare expenditures and lost productivity. The importance of adequate treatment of these conditions and the need for efficacious therapeutic drugs cannot be overstated. Unoprostone continues to be developed as a potential treatment for these debilitating diseases. AREAS COVERED This review provides background information on unoprostone isopropyl (unoprostone), a prostanoid and synthetic docosanoid approved for the treatment of open-angle glaucoma and ocular hypertension, and recapitulates safety and efficacy data as it relates to this indication. Additionally, this review describes potential new uses of unoprostone as therapy for dry AMD and RP. A literature search of peer-reviewed publications was performed utilizing PubMed. Searches were last updated on 10 September 2012. EXPERT OPINION Current data indicate that unoprostone does significantly lower intraocular pressure (IOP) and has a favorable safety and tolerability profile. However, the IOP-lowering effects of unoprostone do not compare with other commercially available prostanoids and it has the disadvantage of a twice-daily rather than once-daily dosing regimen. Nonetheless, recent data suggest that unoprostone may improve neuronal survival and increase ocular blood flow, indicating that it may have some value as a therapy for glaucoma, RP and dry AMD. Further studies are needed to confirm whether unoprostone provides any clinically significant advantage over the other commercially available prostanoids.
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Affiliation(s)
- Nathan V Harms
- University of Nebraska Medical Center, Department of Ophthalmology and Visual Sciences, Omaha, NE 68198-5840, USA
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Yamamoto S, Sugawara T, Murakami A, Nakazawa M, Nao-I N, Machida S, Wada Y, Mashima Y, Myake Y. Topical isopropyl unoprostone for retinitis pigmentosa: microperimetric results of the phase 2 clinical study. Ophthalmol Ther 2012; 1:5. [PMID: 25135585 PMCID: PMC4108136 DOI: 10.1007/s40123-012-0005-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Indexed: 11/26/2022] Open
Abstract
Introduction The purpose of this study was to determine whether topical 0.15% isopropyl unoprostone (IU), a BK-channel activator, could improve or maintain the central retinal sensitivity in patients with middle- to late-stage retinitis pigmentosa (RP). IU was approved for glaucoma and ocular hypertension in 1994. The drug re-profiling strategy is one of the effective ways to develop safe drugs for patients with RP. Methods A randomized, double-blind, and placebo-controlled phase II safety/efficacy trial was conducted. One hundred and nine patients with middle- to late-stage RP having a visual acuity of ≥0.5 were studied at six ophthalmological centers in Japan. The treatments of IU/day were divided into three groups: placebo group; two-drop group; and four-drop group for 24 weeks. The primary outcome measure was changes in the retinal sensitivity from baseline in the central 2° determined by MP-1 microperimetry (MP-1, Nidek, Japan). The secondary outcomes were changes in best-correct visual acuity, contrast sensitivity, retinal sensitivity of the central 10° by MP-1, mean deviation (MD) by a Humphrey field analyzer (HFA; Carl Zeiss Meditec, Dublin, CA, USA) 10-2, and the Visual Functioning Questionnaire 25 (VFQ-25) questionnaire scores. Results There was a tendency for a dose-dependent responsiveness in retinal sensitivity in the central 2°, MD, and total VFQ-25 score after 24 weeks of IU instillation by a simple linear regression analysis. A stratified analysis showed a significant dose-dependent responsiveness of the 2° central retinal sensitivity in more advanced patients (P = 0.028). The number of patients having a ≥4 dB decrease in the primary outcome measure was significantly fewer in the four-drop group than in the placebo group (P = 0.02). No adverse reactions were observed. Conclusions A higher dose of IU can delay progression of the central retinal sensitivity decrease through an improvement of retinal sensitivity.
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Affiliation(s)
- Shuichi Yamamoto
- Department of Ophthalmology and Visual Science, Chiba University Graduate School of Medicine, Chiba, Japan,
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Rosenthal R, Fromm M. Endothelin antagonism as an active principle for glaucoma therapy. Br J Pharmacol 2011; 162:806-16. [PMID: 21054341 DOI: 10.1111/j.1476-5381.2010.01103.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Endothelin, the most potent vasoactive peptide known to date, has been suggested to play a potential role in the pathogenesis of open-angle glaucoma. Open-angle glaucoma is the most common optic nerve head neuropathy and is associated with a loss of retinal ganglion cells and visual field damage. Although an increased intraocular pressure is a major risk factor for glaucomatous optic neuropathy, other factors such as a reduced ocular blood flow play an important role for appearance of the disease. Thus, treatment of glaucoma is focused on lowering of intraocular pressure and preventing the occurrence or progression of glaucomatous optic neuropathy. Endothelin participates in the regulation of intraocular pressure by an effect on trabecular outflow, the main route for aqueous humour outflow from the eye. Trabecular outflow is modulated by trabecular meshwork contractility which is affected by endothelin. In addition to the effects of endothelin in the anterior part of the eye, the vasoconstrictor causes a decrease in ocular blood flow followed by pathological changes in the retina and the optic nerve head which is assumed to contribute to the degeneration of retinal ganglion cells. In sum, inhibition of endothelin signalling leads to lowering of intraocular pressure and exerts neuroprotective effects. Thus, endothelin antagonism in the eye represents a promising approach for pharmacological treatment of glaucoma.
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Affiliation(s)
- Rita Rosenthal
- Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Freie Universität and Humboldt-Universität Berlin, Berlin, Germany
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Abstract
IMPORTANCE OF THE FIELD Glaucoma is the second leading cause of blindness worldwide. To date, treatment of glaucoma has focused on lowering intraocular pressure (IOP) though there are other mechanisms that might damage the optic nerve, leading to characteristic visual field loss. Endothelin, a potent vasoconstrictor, is believed to play a role in the pathogenesis of glaucomatous optic neuropathy. AREAS COVERED IN THIS REVIEW We review the evidence from the last 20 years exploring the action of endothelin in the eye, its association with the pathophysiology of glaucoma, as well as the potential therapeutic role of targeting the endothelin pathway to affect disease progression in glaucomatous eyes. WHAT THE READER WILL GAIN The goal of this paper is to inform readers about endothelin structure, actions, and role in ocular pathology, pharmacology, and potential areas of future research. TAKE HOME MESSAGE Overall, we believe that the body of evidence supports the following conclusions; i) endothelin is a potent vasoconstrictor that plays a role in ocular physiology, ii) endothelin may play a role in the pathophysiology of glaucoma and iii) modulation of the endothelin system with newly discovered potent antagonists holds promise in treating glaucoma through both pressure-dependent and pressure-independent pathways.
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Affiliation(s)
- Travis J Good
- University of Colorado, Denver School of Medicine, Rocky Mountain Lions Eye Institute, Department of Ophthalmology, 1675 Aurora Court, PO Box 6510 Mail Stop F-731, Aurora, CO 80045, USA
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