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Kolko M, Mouhammad ZA, Cvenkel B. Is fat the future for saving sight? Bioactive lipids and their impact on glaucoma. Pharmacol Ther 2023; 245:108412. [PMID: 37037408 DOI: 10.1016/j.pharmthera.2023.108412] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Revised: 04/03/2023] [Accepted: 04/04/2023] [Indexed: 04/12/2023]
Abstract
Glaucoma is characterized by a continuous loss of retinal ganglion cells. The cause of glaucoma is associated with an increase in intraocular pressure (IOP), but the underlying pathophysiology is diverse and, in most cases, unknown. There is an indisputable unmet need to identify new pathways involved in glaucoma pathogenesis. Increasing evidence suggests that bioactive lipids may be critical in the development and progression of glaucoma. Preclinical and clinical bioactive lipid targets exist and are being developed. In this review, we aim to shed light on the potential of bioactive lipids for the prevention, diagnosis, prognosis, and treatment of glaucoma by asking the question "is fat the future for saving sight".
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Affiliation(s)
- Miriam Kolko
- Department of Drug Design and Pharmacology, University of Copenhagen, Denmark; Department of Ophthalmology, Copenhagen University Hospital, Rigshospitalet, Glostrup, Denmark.
| | | | - Barbara Cvenkel
- Department of Ophthalmology, University Medical Centre Ljubljana, Ljubljana, Slovenia; Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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2
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Marando CM, Chen TC. Evidence for Complementary and Alternative Therapies to Treat Glaucoma. Semin Ophthalmol 2023; 38:85-91. [PMID: 36469549 DOI: 10.1080/08820538.2022.2152704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Complementary and alternative medicine is used by approximately 5% of patients with glaucoma, and examples include marijuana, Ginkgo biloba extract, bilberry fruit extract, and acupuncture. Systemic marijuana is not beneficial for glaucoma due to the short duration of action, the lack of evidence that it alters disease progression, and its negative side effect profile. Drops that affect the cannabinoid pathway are still being studied. Ginkgo biloba and bilberry fruit extracts have been shown to decrease oxidative stress and improve perfusion of the optic nerve head. However, these findings are inconsistent throughout the literature and the studies are small, which makes the overall evidence weak. There is no evidence that acupuncture alters glaucoma disease progression or causes a sustained decrease in intraocular pressure. In summary, the literature suggests that there are transient and/or theoretical benefits of complementary and alternative medicine for glaucoma care; however, the overall evidence to support their use is weak.
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Affiliation(s)
- Catherine M Marando
- Harvard Medical School, Department of Ophthalmology, Massachusetts Eye & Ear, Glaucoma Service, Boston, USA
| | - Teresa C Chen
- Harvard Medical School, Department of Ophthalmology, Massachusetts Eye & Ear, Glaucoma Service, Boston, USA
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CB 1R, CB 2R and TRPV1 expression and modulation in in vivo, animal glaucoma models: A systematic review. Biomed Pharmacother 2022; 150:112981. [PMID: 35468582 DOI: 10.1016/j.biopha.2022.112981] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 04/06/2022] [Accepted: 04/14/2022] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND The endocannabinoid system (ECS) is a complex biological regulatory system. Its expression and functionality have been widely investigated in ocular tissues. Recent data have reported its modulation to be valid in determining an ocular hypotensive and a neuroprotective effect in preclinical animal models of glaucoma. AIM This study aimed to explore the available literature on cannabinoid receptor 1 (CB1R), cannabinoid receptor 2 (CB2R), and transient receptor potential vanilloid 1 (TRPV1) expression in the trabecular meshwork (TM), ciliary body (CB), and retina as well as their ocular hypotensive and neuroprotective effects in preclinical, in vivo, animal glaucoma models. MATERIALS AND METHODS The study adhered to both PRISMA and SYRCLE guidelines. Sixty-nine full-length articles were included in the final analysis. RESULTS Preclinical studies indicated a widespread distribution of CB1R, CB2R, and TRPV1 in the TM, CB, and retina, although receptor-, age-, and species-dependent differences were observed. CB1R and CB2R modulation have been shown to exert ocular hypotensive effects in preclinical models via the regulation of inflow and outflow pathways. Retinal cell neuroprotection has been achieved in several experimental models, mediated by agonists and antagonists of CB1R, CB2R, and TRPV1. DISCUSSION Despite the growing body of preclinical data regarding the expression and modulation of ECS in ocular tissues, the mechanisms responsible for the hypotensive and neuroprotective efficacy exerted by this system remain largely elusive. Research on this topic is advocated to further substantiate the hypothesis that the ECS is a new potential therapeutic target in the context of glaucoma.
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Rebibo L, Frušić-Zlotkin M, Ofri R, Nassar T, Benita S. The dose-dependent effect of a stabilized cannabidiol nanoemulsion on ocular surface inflammation and intraocular pressure. Int J Pharm 2022; 617:121627. [PMID: 35245638 DOI: 10.1016/j.ijpharm.2022.121627] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 02/25/2022] [Accepted: 02/26/2022] [Indexed: 12/11/2022]
Abstract
Cannabidiol (CBD) is a phytocannabinoid that has a great clinical therapeutic potential. Few studies have been published on its efficacy in ocular inflammations while its impact on intraocular pressure (IOP), a major risk factor for glaucoma, remains unclear. Moreover, due to its lability and high lipophilicity, its formulation within a prolonged stable topical ophthalmic solution or emulsion able to penetrate the highly selective corneal barrier is challenging. Therefore, various CBD nanoemulsions (NEs) were designed and evaluated for stability in accelerated conditions. Further, the optimal formulation was tested on a murine LPS-induced keratitis inflammation model. Lastly, increasing CBD concentrations were topically applied, for two weeks, on mice eyes, for IOP measurement. CBD NEs exhibited optimal physicochemical characteristics for ocular delivery. A specific antioxidant was required to obtain the stable, final, formulation. In vivo, 0.4 to 1.6% CBD w/v reduced the levels of key inflammatory cytokines, depending on the concentration applied. These concentrations decreased or did not affect the IOP. Our results showed that a well-designed CBD ocular dosage form can be stabilized for an extended shelf life. Furthermore, the significant decrease in inflammatory cytokines levels could be exploited, provided that an adequate therapeutic dosage regimen is identified in humans.
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Affiliation(s)
- Leslie Rebibo
- The Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Ein Kerem, Jerusalem 9112102, Israel
| | - Marina Frušić-Zlotkin
- The Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Ein Kerem, Jerusalem 9112102, Israel
| | - Ron Ofri
- The Koret School of Veterinary Medicine, The Robert H. Smith Faculty of Agricultural, Food & Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel
| | - Taher Nassar
- The Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Ein Kerem, Jerusalem 9112102, Israel
| | - Simon Benita
- The Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, Ein Kerem, Jerusalem 9112102, Israel.
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5
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Mosaed S, Smith AK, Liu JHK, Minckler DS, Fitzgerald RL, Grelotti D, Sones E, Weinreb RN, Marcotte TD. The Relationship Between Plasma Tetrahydrocannabinol Levels and Intraocular Pressure in Healthy Adult Subjects. Front Med (Lausanne) 2022; 8:736792. [PMID: 35111768 PMCID: PMC8801518 DOI: 10.3389/fmed.2021.736792] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 12/24/2021] [Indexed: 11/13/2022] Open
Abstract
BackgroundΔ9-tetrahydrocannabinol (THC) has been shown to decreased intraocular pressure (IOP). This project aims to define the relationship between plasma THC levels and IOP in healthy adult subjects.MethodsEleven healthy subjects received a single dose of inhaled cannabis that was self-administered in negative pressure rooms. Measurements of IOP and plasma THC levels were taken at baseline and every 30 min for 1 h and afterwards every hour for 4 h. IOP reduction and percent change in IOP over time were calculated. Linear regression models were used to measure the relationship between IOP and plasma THC levels. Two line linear regression models with F-tests were used to detect change points in the regression. Then, Pearson correlations were computed based on the change point.ResultsTwenty-two eyes met inclusion criteria. The average peak percentage decrease in IOP was 16% at 60 min. Percent IOP reduction as well as total IOP reduction demonstrated a negative correlation with THC plasma levels showing r-values of −0.81 and −0.70, respectively. F-tests revealed a change point in the regression for plasma levels >20 ng/ml. For levels >20 ng/ml, the correlation coefficients changed significantly with r-values of 0.21 and 0.29 (p < 0.01).ConclusionPlasma THC levels are significantly correlated with IOP reduction up to plasma levels of 20 ng/ml. Plasma levels >20 ng/ml were not correlated with further decrease in IOP. More research is needed to determine the efficacy of THC in reducing IOP for eyes with ocular hypertension and glaucoma.
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Affiliation(s)
- Sameh Mosaed
- Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA, United States
- Irvine School of Medicine, University of California, Irvine, Irvine, CA, United States
| | - Andrew K. Smith
- Gavin Herbert Eye Institute, University of California, Irvine, Irvine, CA, United States
- Irvine School of Medicine, University of California, Irvine, Irvine, CA, United States
- *Correspondence: Andrew K. Smith
| | - John H. K. Liu
- Viterbi Family Department of Ophthalmology, University of California, San Diego, San Diego, CA, United States
| | - Donald S. Minckler
- Irvine School of Medicine, University of California, Irvine, Irvine, CA, United States
| | - Robert L. Fitzgerald
- Department of Pathology, University of California, San Diego, San Diego, CA, United States
| | - David Grelotti
- Department of Psychiatry, University of California, San Diego, San Diego, CA, United States
| | - Emily Sones
- Department of Psychiatry, University of California, San Diego, San Diego, CA, United States
| | - Robert N. Weinreb
- Viterbi Family Department of Ophthalmology, University of California, San Diego, San Diego, CA, United States
| | - Thomas D. Marcotte
- Department of Psychiatry, University of California, San Diego, San Diego, CA, United States
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Garai S, Schaffer PC, Laprairie RB, Janero DR, Pertwee RG, Straiker A, Thakur GA. Design, synthesis, and pharmacological profiling of cannabinoid 1 receptor allosteric modulators: Preclinical efficacy of C2-group GAT211 congeners for reducing intraocular pressure. Bioorg Med Chem 2021; 50:116421. [PMID: 34634617 DOI: 10.1016/j.bmc.2021.116421] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 09/03/2021] [Accepted: 09/14/2021] [Indexed: 11/28/2022]
Abstract
Allosteric modulators of cannabinoid 1 receptor (CB1R) show translational promise over orthosteric ligands due to their potential to elicit therapeutic benefit without cannabimimetic side effects. The prototypic 2-phenylindole CB1R allosteric modulator, GAT211 (1), demonstrates preclinical efficacy in various disease models. The limited systematic structure-activity relationship (SAR) data at the C2 position of the indole ring within GAT211 invites the opportunity for further modifications to improve GAT211's pharmacological profile while serving to amplify and variegate this library of therapeutically attractive agents. These considerations prompted this focused SAR study in which we substituted the GAT211 C2-phenyl ring with heteroaromatic substituents. The synthesized GAT211 analogs were then evaluated in vitro as CB1R allosteric modulators in cAMP and β-arrestin2 assays with CP55,940 as the orthosteric ligand. Furan and thiophene rings (15c-f and 15m) were the best-tolerated substituents at the C2 position of GAT211 for engagement with human CB1R (hCB1R). The SAR around the novel ligands reported allowed direct experimental characterization of the interaction profile of that pharmacophore with its binding domain in functional, human CB1R, thus offering guidance for accessing subsequent-generation hCB1R allosteric modulators as potential therapeutics. The most potent analog, 15d, markedly promoted orthosteric ligand binding to hCB1R. Pharmacological profiling in the GTPγS and mouse vas deferens assays demonstrated that 15d behaves as a CB1R agonist-positive allosteric modulator (ago-PAM), as confirmed electrophysiologically in autoptic neurons. In vivo, 15d was efficacious as a topical agent that significantly reduced intraocular pressure (IOP) in the ocular normotensive murine model of glaucoma. Since elevated IOP is a decisive risk factor for glaucoma and attendant vision loss, our data support the proposition that the 2-phenylindole class of CB1R ago-PAMs has therapeutic potential for glaucoma and other diseases where potentiation of CB1R signaling may be therapeutic.
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Affiliation(s)
- Sumanta Garai
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA 02115, United States
| | - Peter C Schaffer
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA 02115, United States
| | - Robert B Laprairie
- College of Pharmacy and Nutrition, University of Saskatchewan, 104 Clinic Pl, Saskatoon, SK S7N2Z4, Canada
| | - David R Janero
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA 02115, United States
| | - Roger G Pertwee
- School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
| | - Alex Straiker
- Program in Neuroscience, Indiana University, Bloomington, Indiana Gill Center for Biomolecular Science, Bloomington, IN 47405, United States
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, School of Pharmacy and Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, MA 02115, United States
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Garai S, Leo LM, Szczesniak AM, Hurst DP, Schaffer PC, Zagzoog A, Black T, Deschamps JR, Miess E, Schulz S, Janero DR, Straiker A, Pertwee RG, Abood ME, Kelly MEM, Reggio PH, Laprairie RB, Thakur GA. Discovery of a Biased Allosteric Modulator for Cannabinoid 1 Receptor: Preclinical Anti-Glaucoma Efficacy. J Med Chem 2021; 64:8104-8126. [PMID: 33826336 DOI: 10.1021/acs.jmedchem.1c00040] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We apply the magic methyl effect to improve the potency/efficacy of GAT211, the prototypic 2-phenylindole-based cannabinoid type-1 receptor (CB1R) agonist-positive allosteric modulator (ago-PAM). Introducing a methyl group at the α-position of nitro group generated two diastereomers, the greater potency and efficacy of erythro, (±)-9 vs threo, (±)-10 constitutes the first demonstration of diastereoselective CB1R-allosteric modulator interaction. Of the (±)-9 enantiomers, (-)-(S,R)-13 evidenced improved potency over GAT211 as a CB1R ago-PAM, whereas (+)-(R,S)-14 was a CB1R allosteric agonist biased toward G protein- vs β-arrestin1/2-dependent signaling. (-)-(S,R)-13 and (+)-(R,S)-14 were devoid of undesirable side effects (triad test), and (+)-(R,S)-14 reduced intraocular pressure with an unprecedentedly long duration of action in a murine glaucoma model. (-)-(S,R)-13 docked into both a CB1R extracellular PAM and intracellular allosteric-agonist site(s), whereas (+)-(R,S)-14 preferentially engaged only the latter. Exploiting G-protein biased CB1R-allosteric modulation can offer safer therapeutic candidates for glaucoma and, potentially, other diseases.
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Affiliation(s)
- Sumanta Garai
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Luciana M Leo
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania 19140, United States
| | - Anna-Maria Szczesniak
- Department of Pharmacology and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Dow P Hurst
- Center for Drug Discovery, University of North Carolina Greensboro, Greensboro, North Carolina 27402, United States
| | - Peter C Schaffer
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Ayat Zagzoog
- College of Pharmacy and Nutrition, University of Saskatchewan, 104 Clinic Pl, Saskatoon, Saskatchewan S7N2Z4, Canada
| | - Tallan Black
- College of Pharmacy and Nutrition, University of Saskatchewan, 104 Clinic Pl, Saskatoon, Saskatchewan S7N2Z4, Canada
| | - Jeffrey R Deschamps
- Naval Research Laboratory, Code 6930, 4555 Overlook Avenue, Washington, District of Columbia 20375, United States
| | - Elke Miess
- Department of Pharmacology and Toxicology, Jena University Hospital-Friedrich Schiller University Jena, D-07747 Jena, Germany
| | - Stefan Schulz
- Department of Pharmacology and Toxicology, Jena University Hospital-Friedrich Schiller University Jena, D-07747 Jena, Germany
| | - David R Janero
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
| | - Alex Straiker
- The Gill Center and the Department of Psychological & Brain Sciences, Indiana University, 1101 E. 10th St, Bloomington, Indiana 47405, United States
| | - Roger G Pertwee
- School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, U.K
| | - Mary E Abood
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania 19140, United States
| | - Melanie E M Kelly
- Department of Pharmacology and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Patricia H Reggio
- Center for Drug Discovery, University of North Carolina Greensboro, Greensboro, North Carolina 27402, United States
| | - Robert B Laprairie
- College of Pharmacy and Nutrition, University of Saskatchewan, 104 Clinic Pl, Saskatoon, Saskatchewan S7N2Z4, Canada
- Department of Pharmacology and Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, Nova Scotia B3H 4R2, Canada
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Northeastern University, Boston, Massachusetts 02115, United States
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Mosaed S, Liu JHK, Minckler DS, Fitzgerald RL, Grelotti D, Sones E, Shiels CR, Weinreb RN, Marcotte TD. The Effect of Inhaled Cannabis on Intraocular Pressure in Healthy Adult Subjects. Ophthalmology 2021. [DOI: 10.17925/opht.2021.15.1.33] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
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9
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Miller S, Daily L, Dharla V, Gertsch J, Malamas MS, Ojima I, Kaczocha M, Ogasawara D, Straiker A. Endocannabinoid metabolism and transport as targets to regulate intraocular pressure. Exp Eye Res 2020; 201:108266. [PMID: 32979397 DOI: 10.1016/j.exer.2020.108266] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2020] [Revised: 08/17/2020] [Accepted: 09/21/2020] [Indexed: 02/06/2023]
Abstract
Cannabinoids are part of an endogenous signaling system found throughout the body, including the eye. Hepler and Frank showed in the early 1970s that plant cannabinoids can lower intraocular pressure (IOP), an effect since shown to occur via cannabinoid CB1 and GPR18 receptors. Endocannabinoids are synthesized and metabolized enzymatically. Enzymes implicated in endocannabinoids breakdown include monoacylglycerol lipase (MAGL) and fatty acid amide hydrolase (FAAH), but also ABHD12, NAAA, and COX-2. Inhibition of MAGL activity raises levels of the endocannabinoid 2-arachidonoyl glycerol and substantially lowers IOP. Blocking other cannabinoid metabolizing enzymes or cannabinoid transporters may similarly contribute to lowering IOP and so serve as therapeutic targets for treating glaucoma. We have tested blockers for several cannabinoid-metabolizing enzymes and transporters (FABP5 and membrane reuptake) for their ability to alter ocular pressure in a murine model of IOP. Of FAAH, ABHD12, NAAA, and COX2, only FAAH was seen to play a role in regulation of IOP. Only the FAAH blocker URB597 lowered IOP, but in a temporally, diurnally, and sex-specific manner. We also tested two blockers of cannabinoid transport (SBFI-26 and WOBE437), finding that each lowered IOP in a CB1-dependent manner. Though we see a modest, limited role for FAAH, our results suggest that MAGL is the primary cannabinoid-metabolizing enzyme in regulating ocular pressure, thus pointing towards a role of 2-arachidonoyl glycerol. Interestingly, inhibition of cannabinoid transport mechanisms independent of hydrolysis may prove to be an alternative strategy to lower ocular pressure.
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Affiliation(s)
- Sally Miller
- The Gill Center for Biomolecular Science, Program in Neuroscience, Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
| | - Laura Daily
- The Gill Center for Biomolecular Science, Program in Neuroscience, Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
| | - Vijai Dharla
- The Gill Center for Biomolecular Science, Program in Neuroscience, Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA
| | - Juerg Gertsch
- Institute of Biochemistry and Molecular Medicine, NCCR TransCure, University of Bern, Bühlstrasse 28, 3012, Bern, Switzerland
| | - Michael S Malamas
- Center for Drug Discovery and Departments of Chemistry and Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, MA, 02115, USA
| | - Iwao Ojima
- Department of Chemistry, USA; Institute of Chemical Biology and Drug Discovery, USA
| | - Martin Kaczocha
- Institute of Chemical Biology and Drug Discovery, USA; Department of Anesthesiology, Stony Brook University, Stony Brook, NY, 11794, USA
| | - Daisuke Ogasawara
- Department of Chemistry, Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Alex Straiker
- The Gill Center for Biomolecular Science, Program in Neuroscience, Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, 47405, USA.
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10
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Evidence that cannabinoid CB1 receptors regulate intraocular pressure via two opposing mechanisms. Exp Eye Res 2020; 200:108241. [PMID: 32941875 DOI: 10.1016/j.exer.2020.108241] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Revised: 08/14/2020] [Accepted: 09/08/2020] [Indexed: 11/21/2022]
Abstract
The cannabinoid signaling system regulates intraocular pressure (IOP) in the mouse via a complex system that includes three receptors: CB1, GPR18 and GPR119. In each case, activating the receptor lowers IOP, but CB1 receptors are found both at sites of aqueous humor inflow and outflow. As such, knockout mice for any of these receptors would be expected to have higher-than average, or at least unchanged, intraocular pressure. The current study investigates the unexpected observation that CB1 knockout mice have lower pressure than wild type counterparts by testing various regulators of cannabinoid signaling in murine models of IOP. We now report that a CB1 antagonist has differential effects on IOP: SR141716 raises IOP in standard light cycle (SLC) but lowers IOP in reverse light cycle (RLC). This is mimicked by ABD1085, a negative allosteric modulator of CB1. CB1 inhibitors lower IOP in both normotensive and hypertensive mouse eyes. The pressure-lowering effect is absent in CB1 knockout mice. IOP rebounds after the end of treatment but shows no sign of desensitization with daily treatment for a week. Unlike the positive cannabinoid effect, antagonist effects are not sex-dependent. We propose that there are two mechanisms of action for CB1, one that lowers IOP upon activation and a second with inverse sign that lowers IOP when CB1 is antagonized. The relatively lower pressure in CB1 knockout mouse eyes suggests that this second negative regulation of IOP is dominant.
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11
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Garai S, Kulkarni PM, Schaffer PC, Leo LM, Brandt AL, Zagzoog A, Black T, Lin X, Hurst DP, Janero DR, Abood ME, Zimmowitch A, Straiker A, Pertwee RG, Kelly M, Szczesniak AM, Denovan-Wright EM, Mackie K, Hohmann AG, Reggio PH, Laprairie RB, Thakur GA. Application of Fluorine- and Nitrogen-Walk Approaches: Defining the Structural and Functional Diversity of 2-Phenylindole Class of Cannabinoid 1 Receptor Positive Allosteric Modulators. J Med Chem 2020; 63:542-568. [PMID: 31756109 DOI: 10.1021/acs.jmedchem.9b01142] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Cannabinoid 1 receptor (CB1R) allosteric ligands hold a far-reaching therapeutic promise. We report the application of fluoro- and nitrogen-walk approaches to enhance the drug-like properties of GAT211, a prototype CB1R allosteric agonist-positive allosteric modulator (ago-PAM). Several analogs exhibited improved functional potency (cAMP, β-arrestin 2), metabolic stability, and aqueous solubility. Two key analogs, GAT591 (6r) and GAT593 (6s), exhibited augmented allosteric-agonist and PAM activities in neuronal cultures, improved metabolic stability, and enhanced orthosteric agonist binding (CP55,940). Both analogs also exhibited good analgesic potency in the CFA inflammatory-pain model with longer duration of action over GAT211 while being devoid of adverse cannabimimetic effects. Another analog, GAT592 (9j), exhibited moderate ago-PAM potency and improved aqueous solubility with therapeutic reduction of intraocular pressure in murine glaucoma models. The SAR findings and the enhanced allosteric activity in this class of allosteric modulators were accounted for in our recently developed computational model for CB1R allosteric activation and positive allosteric modulation.
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Affiliation(s)
- Sumanta Garai
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Pushkar M Kulkarni
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Peter C Schaffer
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Luciana M Leo
- Center for Substance Abuse Research, Lewis Katz School of Medicine , Temple University , Philadelphia , Pennsylvania 19140 , United States
| | - Asher L Brandt
- College of Pharmacy and Nutrition , University of Saskatchewan , 104 Clinic Pl , Saskatoon , SK S7N2Z4 , Canada
| | - Ayat Zagzoog
- College of Pharmacy and Nutrition , University of Saskatchewan , 104 Clinic Pl , Saskatoon , SK S7N2Z4 , Canada
| | - Tallan Black
- College of Pharmacy and Nutrition , University of Saskatchewan , 104 Clinic Pl , Saskatoon , SK S7N2Z4 , Canada
| | - Xiaoyan Lin
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Dow P Hurst
- Center for Drug Discovery , University of North Carolina Greensboro , Greensboro , North Carolina 27402 , United States
| | - David R Janero
- Department of Pharmaceutical Sciences, Bouvé College of Health Sciences, Department of Chemistry and Chemical Biology, College of Science, and Health Sciences Entrepreneurs , Northeastern University , Boston , Massachusetts 02115 , United States
| | - Mary E Abood
- Center for Substance Abuse Research, Lewis Katz School of Medicine , Temple University , Philadelphia , Pennsylvania 19140 , United States
| | - Anaelle Zimmowitch
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Alex Straiker
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Roger G Pertwee
- School of Medicine, Medical Sciences and Nutrition, Institute of Medical Sciences , University of Aberdeen , Aberdeen AB25 2ZD , Scotland, U.K
| | - Melanie Kelly
- Department of Pharmacology, Faculty of Medicine , Dalhousie University , 5850 College St , Halifax , NS , B3H4R2 , Canada
| | - Anna-Maria Szczesniak
- Department of Pharmacology, Faculty of Medicine , Dalhousie University , 5850 College St , Halifax , NS , B3H4R2 , Canada
| | - Eileen M Denovan-Wright
- Department of Pharmacology, Faculty of Medicine , Dalhousie University , 5850 College St , Halifax , NS , B3H4R2 , Canada
| | - Ken Mackie
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Andrea G Hohmann
- Program in Neuroscience, Psychological and Brain Sciences, and Gill Center for Biomolecular Science , Indiana University , Bloomington , Indiana 47405 , United States
| | - Patricia H Reggio
- Center for Drug Discovery , University of North Carolina Greensboro , Greensboro , North Carolina 27402 , United States
| | - Robert B Laprairie
- College of Pharmacy and Nutrition , University of Saskatchewan , 104 Clinic Pl , Saskatoon , SK S7N2Z4 , Canada.,Department of Pharmacology, Faculty of Medicine , Dalhousie University , 5850 College St , Halifax , NS , B3H4R2 , Canada
| | - Ganesh A Thakur
- Department of Pharmaceutical Sciences, School of Pharmacy, Bouvé College of Health Sciences , Northeastern University , Boston , Massachusetts 02115 , United States
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12
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Affiliation(s)
- Alex Straiker
- Department of Psychological & Brain Sciences, Indiana University, Bloomington, IN, USA
- Program in Neuroscience, Indiana University, Bloomington, IN, USA
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Guglielmi P, Carradori S, Campestre C, Poce G. Novel therapies for glaucoma: a patent review (2013-2019). Expert Opin Ther Pat 2019; 29:769-780. [DOI: 10.1080/13543776.2019.1653279] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Paolo Guglielmi
- Department of Chemistry and Technologies of Drugs, Sapienza University of Rome, Rome, Italy
| | - Simone Carradori
- Department of Pharmacy, University “G. d’Annunzio” of Chieti-Pescara, Chieti, Italy
| | - Cristina Campestre
- Department of Pharmacy, University “G. d’Annunzio” of Chieti-Pescara, Chieti, Italy
| | - Giovanna Poce
- Department of Chemistry and Technologies of Drugs, Sapienza University of Rome, Rome, Italy
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Miller S, Daily L, Leishman E, Bradshaw H, Straiker A. Δ9-Tetrahydrocannabinol and Cannabidiol Differentially Regulate Intraocular Pressure. Invest Ophthalmol Vis Sci 2019; 59:5904-5911. [PMID: 30550613 PMCID: PMC6295937 DOI: 10.1167/iovs.18-24838] [Citation(s) in RCA: 36] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Purpose It has been known for nearly 50 years that cannabis and the psychoactive constituent Δ9-tetrahydrocannabinol (THC) reduce intraocular pressure (IOP). Elevated IOP remains the chief hallmark and therapeutic target for glaucoma, a major cause of blindness. THC likely acts via one of the known cannabinoid-related receptors (CB1, CB2, GPR18, GPR119, GPR55) but this has never been determined explicitly. Cannabidiol (CBD) is a second major constituent of cannabis that has been found to be without effect on IOP in most studies. Methods Effects of topically applied THC and CBD were tested in living mice by using tonometry and measurements of mRNA levels. In addition the lipidomic consequences of CBD treatment were tested by using lipid analysis. Results We now report that a single topical application of THC lowered IOP substantially (∼28%) for 8 hours in male mice. This effect is due to combined activation of CB1 and GPR18 receptors each of which has been shown to lower ocular pressure when activated. We also found that the effect was sex-dependent, being stronger in male mice, and that mRNA levels of CB1 and GPR18 were higher in males. Far from inactive, CBD was found to have two opposing effects on ocular pressure, one of which involved antagonism of tonic signaling. CBD prevents THC from lowering ocular pressure. Conclusions We conclude that THC lowers IOP by activating two receptors—CB1 and GPR18—but in a sex-dependent manner. CBD, contrary to expectation, has two opposing effects on IOP and can interfere with the effects of THC.
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Affiliation(s)
- Sally Miller
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Laura Daily
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Emma Leishman
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Heather Bradshaw
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Alex Straiker
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
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Lafreniere J, Kelly M. Potential for endocannabinoid system modulation in ocular pain and inflammation: filling the gaps in current pharmacological options. Neuronal Signal 2018; 2:NS20170144. [PMID: 32714590 PMCID: PMC7373237 DOI: 10.1042/ns20170144] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 10/18/2018] [Accepted: 10/19/2018] [Indexed: 02/06/2023] Open
Abstract
Challenges in the management of ocular pain are an underappreciated topic. Currently available therapeutics lack both efficacy and clear guidelines for their use, with many also possessing unacceptable side effects. Promising novel agents would offer analgesic, anti-inflammatory, and possibly neuroprotective actions; have favorable ocular safety profiles; and show potential in managing neuropathic pain. Growing evidence supports a link between the endocannabinoid system (ECS) and a range of physiological and disease processes, notably those involving inflammation and pain. Both preclinical and clinical data suggest analgesic and anti-inflammatory actions of cannabinoids and ECS-modifying drugs in chronic pain conditions, including those of neuropathic origin. This review will examine existing evidence for the anatomical and physiological basis of ocular pain, specifically, ocular surface disease and the development of chronic ocular pain. The mechanism of action, efficacy, and limitations of currently available treatments will be discussed, and current knowledge related to ECS-modulation of ocular pain and inflammatory disease will be summarized. A perspective will be provided on the future directions of ECS research in terms of developing cannabinoid therapeutics for ocular pain.
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Affiliation(s)
| | - Melanie E.M. Kelly
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada
- Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, Canada
- Department of Anesthesia, Pain Management and Perioperative Medicine, Dalhousie University, Halifax, NS, Canada
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Maurya N, Velmurugan BK. Therapeutic applications of cannabinoids. Chem Biol Interact 2018; 293:77-88. [PMID: 30040916 DOI: 10.1016/j.cbi.2018.07.018] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Revised: 07/10/2018] [Accepted: 07/20/2018] [Indexed: 12/12/2022]
Abstract
The psychoactive property of cannabinoids is well known and there has been a continuous controversy regarding the usage of these compounds for therapeutic purposes all over the world. Their use for medical and research purposes are restricted in various countries. However, their utility as medications should not be overshadowed by its negative physiological activities. This review article is focused on the therapeutic potential and applications of phytocannabinoids and endocannabinoids. We further highlights their mode of action, overall effects on physiology, various in vitro and in vivo studies that have been done so far and the extent to which these compounds can be useful in different disease conditions such as cancer, Alzheimer's disease, multiple sclerosis, pain, inflammation, glaucoma and many others. Thus, this work is an attempt to make the readers understand the positive implications of these compounds and indicates the significant developments of utilizing cannabinoids as therapeutic agents.
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Affiliation(s)
- Nancy Maurya
- School of Biotechnology, Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal, India
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Miller S, Kulkarni S, Ciesielski A, Nikas SP, Mackie K, Makriyannis A, Straiker A. Controlled-Deactivation CB1 Receptor Ligands as a Novel Strategy to Lower Intraocular Pressure. Pharmaceuticals (Basel) 2018; 11:E50. [PMID: 29786643 PMCID: PMC6027315 DOI: 10.3390/ph11020050] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2018] [Revised: 05/13/2018] [Accepted: 05/18/2018] [Indexed: 12/21/2022] Open
Abstract
Nearly half a century has passed since the demonstration that cannabis and its chief psychoactive component Δ⁸-THC lowers intraocular pressure (IOP). Elevated IOP remains the chief hallmark and therapeutic target for glaucoma, a condition that places millions at risk of blindness. It is likely that Δ⁸-THC exerts much of its IOP-lowering effects via the activation of CB1 cannabinoid receptors. However, the initial promise of CB1 as a target for treating glaucoma has not thus far translated into a credible therapeutic strategy. We have recently shown that blocking monoacylglycerol lipase (MAGL), an enzyme that breaks the endocannabinoid 2-arachidonoyl glycerol (2-AG), substantially lowers IOP. Another strategy is to develop cannabinoid CB1 receptor agonists that are optimized for topical application to the eye. Recently we have reported on a controlled-deactivation approach where the "soft" drug concept of enzymatic deactivation was combined with a "depot effect" that is commonly observed with Δ⁸-THC and other lipophilic cannabinoids. This approach allowed us to develop novel cannabinoids with a predictable duration of action and is particularly attractive for the design of CB1 activators for ophthalmic use with limited or no psychoactive effects. We have tested a novel class of compounds using a combination of electrophysiology in autaptic hippocampal neurons, a well-characterized model of endogenous cannabinoid signaling, and measurements of IOP in a mouse model. We now report that AM7410 is a reasonably potent and efficacious agonist at CB1 in neurons and that it substantially (30%) lowers IOP for as long as 5 h after a single topical treatment. This effect is absent in CB1 knockout mice. Our results indicate that the direct targeting of CB1 receptors with controlled-deactivation ligands is a viable approach to lower IOP in a murine model and merits further study in other model systems.
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Affiliation(s)
- Sally Miller
- The Gill Center for Biomolecular Science, The Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA.
| | - Shashank Kulkarni
- Center for Drug Discovery, Departments of Chemistry & Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, MA 02115, USA.
| | - Alex Ciesielski
- The Gill Center for Biomolecular Science, The Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA.
| | - Spyros P Nikas
- Center for Drug Discovery, Departments of Chemistry & Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, MA 02115, USA.
| | - Ken Mackie
- The Gill Center for Biomolecular Science, The Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA.
| | - Alexandros Makriyannis
- Center for Drug Discovery, Departments of Chemistry & Chemical Biology and Pharmaceutical Sciences, Northeastern University, Boston, MA 02115, USA.
| | - Alex Straiker
- The Gill Center for Biomolecular Science, The Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47405, USA.
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18
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Rapino C, Tortolani D, Scipioni L, Maccarrone M. Neuroprotection by (endo)Cannabinoids in Glaucoma and Retinal Neurodegenerative Diseases. Curr Neuropharmacol 2018; 16:959-970. [PMID: 28738764 PMCID: PMC6120105 DOI: 10.2174/1570159x15666170724104305] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 07/14/2017] [Accepted: 07/21/2017] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Emerging neuroprotective strategies are being explored to preserve the retina from degeneration, that occurs in eye pathologies like glaucoma, diabetic retinopathy, age-related macular degeneration, and retinitis pigmentosa. Incidentally, neuroprotection of retina is a defending mechanism designed to prevent or delay neuronal cell death, and to maintain neural function following an initial insult, thus avoiding loss of vision. METHODS Numerous studies have investigated potential neuroprotective properties of plant-derived phytocannabinoids, as well as of their endogenous counterparts collectively termed endocannabinoids (eCBs), in several degenerative diseases of the retina. eCBs are a group of neuromodulators that, mainly by activating G protein-coupled type-1 and type-2 cannabinoid (CB1 and CB2) receptors, trigger multiple signal transduction cascades that modulate central and peripheral cell functions. A fine balance between biosynthetic and degrading enzymes that control the right concentration of eCBs has been shown to provide neuroprotection in traumatic, ischemic, inflammatory and neurotoxic damage of the brain. RESULTS Since the existence of eCBs and their binding receptors was documented in the retina of numerous species (from fishes to primates), their involvement in the visual processing has been demonstrated, more recently with a focus on retinal neurodegeneration and neuroprotection. CONCLUSION The aim of this review is to present a modern view of the endocannabinoid system, in order to discuss in a better perspective available data from preclinical studies on the use of eCBs as new neuroprotective agents, potentially useful to prevent glaucoma and retinal neurodegenerative diseases.
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Affiliation(s)
- Cinzia Rapino
- Address correspondence to these authors at the Faculty of Veterinary Medicine, University of Teramo, 64100 Teramo, Italy; Tel: +39 0861 266842;, E-mail: and the Department of Medicine, Campus Bio-Medico University of Rome, 00128 Rome, Italy; Tel: +39 06 225419169;, E-mail:
| | | | | | - Mauro Maccarrone
- Address correspondence to these authors at the Faculty of Veterinary Medicine, University of Teramo, 64100 Teramo, Italy; Tel: +39 0861 266842;, E-mail: and the Department of Medicine, Campus Bio-Medico University of Rome, 00128 Rome, Italy; Tel: +39 06 225419169;, E-mail:
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Miller S, Hu SSJ, Leishman E, Morgan D, Wager-Miller J, Mackie K, Bradshaw HB, Straiker A. A GPR119 Signaling System in the Murine Eye Regulates Intraocular Pressure in a Sex-Dependent Manner. Invest Ophthalmol Vis Sci 2017; 58:2930-2938. [PMID: 28593245 PMCID: PMC5469424 DOI: 10.1167/iovs.16-21330] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Purpose GPR119 is a G protein–coupled receptor that may be the endogenous target for 2-oleoylglycerol (2-OG), a lipid related to the endocannabinoid family of neuromodulators. Interest in GPR119 has centered on its role in regulating insulin secretion; however, the role of GPR119 has not been examined in the eye. The purpose of this study was to explore a potential GPR119-based signaling system in the murine eye. Methods We used a combination of RT-PCR, immunohistochemistry, lipid measurement, and IOP measurement in a normotensive mouse model, with GPR119 knockout mice as controls. Results We detected GPR119 mRNA and protein in the anterior eye of the mouse and cow, with GPR119 mRNA levels elevated in female relative to male mice. GPR119 protein expression is most prominent in structures near the angle, including trabecular meshwork, as well as iris and corneal epithelium. We detected 2-OG in the anterior eye and detected alterations in lipid levels in GPR119 knockout versus wild type and also by sex. Last, we found that 2-OG preferentially reduces IOP in female mice in a normotensive model. Conclusions In summary, we offer evidence for a GPR119-based signaling system in the mammalian eye, with receptors, ligands, and function in the form of a reduction in IOP. Notably this reduction in pressure is restricted to female mice.
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Affiliation(s)
- Sally Miller
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Sherry Shu-Jung Hu
- Department of Psychology, National Cheng Kung University, Tainan, Taiwan
| | - Emma Leishman
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Dan Morgan
- Department of Anesthesiology, Penn State University College of Medicine, Hershey, Pennsylvania, United States
| | - Jim Wager-Miller
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Heather B Bradshaw
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Alex Straiker
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
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Cairns EA, Szczesniak AM, Straiker AJ, Kulkarni PM, Pertwee RG, Thakur GA, Baldridge WH, Kelly MEM. The In Vivo Effects of the CB 1-Positive Allosteric Modulator GAT229 on Intraocular Pressure in Ocular Normotensive and Hypertensive Mice. J Ocul Pharmacol Ther 2017; 33:582-590. [PMID: 28719234 DOI: 10.1089/jop.2017.0037] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
PURPOSE Orthosteric cannabinoid receptor 1 (CB1) activation leads to decreases in intraocular pressure (IOP). However, use of orthosteric CB1 agonists chronically has several disadvantages, limiting their usefulness as clinically relevant drugs. Allosteric modulators interact with topographically distinct sites to orthosteric ligands and may be useful to circumvent some of these disadvantages. The purpose of this study was to investigate the effects of the novel CB1-positive allosteric modulator (PAM) GAT229 on IOP. METHODS IOP was measured using rebound tonometry in anesthetized normotensive C57Bl/6 mice and in a genetic model of ocular hypertension [nose, eyes, ears (nee) mice] before drug administration, and at 1, 6, and 12 h thereafter. RESULTS In normotensive mice, topical administration of 5 μL GAT229 alone at either 0.2% or 2% did not reduce IOP. However, a subthreshold dose (0.25%) of the nonselective orthosteric CB1 agonist WIN 55,212-2, when combined with 0.2% GAT229, significantly reduced IOP compared with vehicle at 6 and 12 h. Similarly, combination of subthreshold Δ9-tetrahydrocannabinol (a nonselective orthosteric CB1 agonist; 1 mg/kg) with topical 0.2% GAT229 produced IOP lowering at 6 h. In nee mice, administration of topical 0.2% GAT229 or 10 mg/kg GAT229 alone was sufficient to lower IOP at 6 and 12 h, and 12 h, respectively. CONCLUSIONS The CB1 PAM GAT229 reduces IOP in ocular hypertensive mice and enhanced CB1-mediated IOP reduction when combined with subthreshold CB1 orthosteric ligands in normotensive mice. Administration of CB1 PAMs may provide a novel approach to reduce IOP with fewer of the disadvantages associated with orthosteric CB1 activation.
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Affiliation(s)
- Elizabeth A Cairns
- 1 Department of Pharmacology, Dalhousie University , Halifax, Nova Scotia, Canada
| | | | - Alex J Straiker
- 2 Department of Psychological and Brain Sciences, Indiana University , Bloomington, Indiana
| | - Pushkar M Kulkarni
- 3 Department of Pharmaceutical Sciences School of Pharmacy, Bouvé College of Health Sciences, Northeastern University , Boston, Massachusetts
| | - Roger G Pertwee
- 4 School of Medicine, Medical Sciences, and Nutrition, Institute of Medical Sciences, University of Aberdeen , Aberdeen, Scotland
| | - Ganesh A Thakur
- 3 Department of Pharmaceutical Sciences School of Pharmacy, Bouvé College of Health Sciences, Northeastern University , Boston, Massachusetts
| | - William H Baldridge
- 5 Department of Medical Neuroscience, Dalhousie University , Halifax, Nova Scotia, Canada .,6 Department of Ophthalmology and Visual Sciences, Dalhousie University , Halifax, Nova Scotia, Canada
| | - Melanie E M Kelly
- 1 Department of Pharmacology, Dalhousie University , Halifax, Nova Scotia, Canada .,6 Department of Ophthalmology and Visual Sciences, Dalhousie University , Halifax, Nova Scotia, Canada
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Miller S, Leishman E, Oehler O, Daily L, Murataeva N, Wager-Miller J, Bradshaw H, Straiker A. Evidence for a GPR18 Role in Diurnal Regulation of Intraocular Pressure. Invest Ophthalmol Vis Sci 2017; 57:6419-6426. [PMID: 27893106 PMCID: PMC5132083 DOI: 10.1167/iovs.16-19437] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The diurnal cycling of intraocular pressure (IOP) was first described in humans more than a century ago. This cycling is preserved in other species. The physiologic underpinning of this diurnal variation in IOP remains a mystery, even though elevated pressure is indicated in most forms of glaucoma, a common cause of blindness. Once identified, the system that underlies diurnal variation would represent a natural target for therapeutic intervention. Methods Using normotensive mice, we measured the regulation of ocular lipid species by the enzymes fatty acid amide hydrolase (FAAH) and N-arachidonoyl phosphatidylethanolamine phospholipase (NAPE-PLD), mRNA expression of these enzymes, and their functional role in diurnal regulation of IOP. Results We now report that NAPE-PLD and FAAH mice do not exhibit a diurnal cycling of IOP. These enzymes produce and break down acylethanolamines, including the endogenous cannabinoid anandamide. The diurnal lipid profile in mice shows that levels of most N-acyl ethanolamines and, intriguingly, N-arachidonoyl glycine (NAGly), decline at night: NAGly is a metabolite of arachidonoyl ethanolamine and a potent agonist at GPR18 that lowers intraocular pressure. The GPR18 blocker O1918 raises IOP during the day when pressure is low, but not at night. Quantitative PCR analysis shows that FAAH mRNA levels rise with pressure, suggesting that FAAH mediates the changes in pressure. Conclusions Our results support FAAH-dependent NAGly action at GPR18 as the physiologic basis of the diurnal variation of intraocular pressure in mice.
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Affiliation(s)
- Sally Miller
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Emma Leishman
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Olivia Oehler
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Laura Daily
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Natalia Murataeva
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Jim Wager-Miller
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Heather Bradshaw
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
| | - Alex Straiker
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences, Indiana University, Bloomington, Indiana, United States
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Miller S, Leishman E, Hu SS, Elghouche A, Daily L, Murataeva N, Bradshaw H, Straiker A. Harnessing the Endocannabinoid 2-Arachidonoylglycerol to Lower Intraocular Pressure in a Murine Model. Invest Ophthalmol Vis Sci 2017; 57:3287-96. [PMID: 27333182 PMCID: PMC4961057 DOI: 10.1167/iovs.16-19356] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Purpose Cannabinoids, such as Δ9-THC, act through an endogenous signaling system in the vertebrate eye that reduces IOP via CB1 receptors. Endogenous cannabinoid (eCB) ligand, 2-arachidonoyl glycerol (2-AG), likewise activates CB1 and is metabolized by monoacylglycerol lipase (MAGL). We investigated ocular 2-AG and its regulation by MAGL and the therapeutic potential of harnessing eCBs to lower IOP. Methods We tested the effect of topical application of 2-AG and MAGL blockers in normotensive mice and examined changes in eCB-related lipid species in the eyes and spinal cord of MAGL knockout (MAGL−/−) mice using high performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). We also examined the protein distribution of MAGL in the mouse anterior chamber. Results 2-Arachidonoyl glycerol reliably lowered IOP in a CB1- and concentration-dependent manner. Monoacylglycerol lipase is expressed prominently in nonpigmented ciliary epithelium. The MAGL blocker KML29, but not JZL184, lowered IOP. The ability of CB1 to lower IOP is not desensitized in MAGL−/− mice. Ocular monoacylglycerols, including 2-AG, are elevated in MAGL−/− mice but, in contrast to the spinal cord, arachidonic acid and prostaglandins are not changed. Conclusions Our data confirm a central role for MAGL in metabolism of ocular 2-AG and related lipid species, and that endogenous 2-AG can be harnessed to reduce IOP. The MAGL blocker KML29 has promise as a therapeutic agent, while JZL184 may have difficulty crossing the cornea. These data, combined with the relative specificity of MAGL for ocular monoacylglycerols and the lack of desensitization in MAGL−/− mice, suggest that the development of an optimized MAGL blocker offers therapeutic potential for treatment of elevated IOP.
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Affiliation(s)
- Sally Miller
- Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Emma Leishman
- Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Sherry Shujung Hu
- Department of Psychology, National Cheng Kung University, Tainan, Taiwan
| | - Alhasan Elghouche
- Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Laura Daily
- Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Natalia Murataeva
- Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Heather Bradshaw
- Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Alex Straiker
- Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
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Cairns EA, Toguri JT, Porter RF, Szczesniak AM, Kelly MEM. Seeing over the horizon - targeting the endocannabinoid system for the treatment of ocular disease. J Basic Clin Physiol Pharmacol 2017; 27:253-65. [PMID: 26565550 DOI: 10.1515/jbcpp-2015-0065] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2015] [Accepted: 09/25/2015] [Indexed: 01/09/2023]
Abstract
The observation that marijuana reduces intraocular pressure was made by Hepler and Frank in the 1970s. Since then, there has been a significant body of work investigating cannabinoids for their potential use as therapeutics. To date, no endocannabinoid system (ECS)-modulating drug has been approved for clinical use in the eye; however, recent advances in our understanding of the ECS, as well as new pharmacological tools, has renewed interest in the development of ocular ECS-based therapeutics. This review summarizes the current state-of-affairs for the use of ECS-modulating drugs for the treatment of glaucoma and ocular inflammatory and ischemic disease.
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Kelly MEM, Lehmann C, Zhou J. The Endocannabinoid System in Local and Systemic Inflammation. ACTA ACUST UNITED AC 2017. [DOI: 10.4199/c00151ed1v01y201702isp074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Toguri JT, Caldwell M, Kelly MEM. Turning Down the Thermostat: Modulating the Endocannabinoid System in Ocular Inflammation and Pain. Front Pharmacol 2016; 7:304. [PMID: 27695415 PMCID: PMC5024674 DOI: 10.3389/fphar.2016.00304] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 08/26/2016] [Indexed: 11/13/2022] Open
Abstract
The endocannabinoid system (ECS) has emerged as an important regulator of both physiological and pathological processes. Notably, this endogenous system plays a key role in the modulation of pain and inflammation in a number of tissues. The components of the ECS, including endocannabinoids, their cognate enzymes and cannabinoid receptors, are localized in the eye, and evidence indicates that ECS modulation plays a role in ocular disease states. Of these diseases, ocular inflammation presents a significant medical problem, given that current clinical treatments can be ineffective or are associated with intolerable side-effects. Furthermore, a prominent comorbidity of ocular inflammation is pain, including neuropathic pain, for which therapeutic options remain limited. Recent evidence supports the use of drugs targeting the ECS for the treatment of ocular inflammation and pain in animal models; however, the potential for therapeutic use of cannabinoid drugs in the eye has not been thoroughly investigated at this time. This review will highlight evidence from experimental studies identifying components of the ocular ECS and discuss the functional role of the ECS during different ocular inflammatory disease states, including uveitis and corneal keratitis. Candidate ECS targeted therapies will be discussed, drawing on experimental results obtained from both ocular and non-ocular tissue(s), together with their potential application for the treatment of ocular inflammation and pain.
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Affiliation(s)
- James T. Toguri
- Department of Pharmacology, Dalhousie University, HalifaxNS, Canada
| | - Meggie Caldwell
- Department of Pharmacology, Dalhousie University, HalifaxNS, Canada
| | - Melanie E. M. Kelly
- Department of Pharmacology, Dalhousie University, HalifaxNS, Canada
- Department of Ophthalmology and Visual Sciences, Dalhousie University, HalifaxNS, Canada
- Anesthesia, Pain Management & Perioperative Medicine, Dalhousie University, HalifaxNS, Canada
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van den Heever H, Meyer D. The intraocular pressure-lowering properties of intravenous paracetamol. Clin Ophthalmol 2016; 10:1283-9. [PMID: 27471373 PMCID: PMC4948718 DOI: 10.2147/opth.s87988] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
AIM The aim of this paper was to investigate the intraocular pressure (IOP)-changing properties of a single standard dose of intravenous (IV) paracetamol and compare it to that of topical timolol, oral acetazolamide, and no treatment. METHODS A prospective, randomized, investigator-blind, parallel-group study was conducted in 73 eyes of 52 subjects. Subjects received a single dose of IV paracetamol (1 g), oral acetazolamide (250 mg), topical timolol (0.5%, one drop), or no treatment. Baseline IOP was measured, and the measurement was repeated at 1, 2, 4, and 6 hours after treatment. RESULTS Paracetamol reduced IOP from baseline by -10.8% (95% confidence interval [CI]: -4.9% to -16.8%, P=0.146) at 1 hour, -13.3% (95% CI: -8.3% to -18.4%, P=0.045) at 2 hours, -11.8% (95% CI: -5.5% to -18.4%, P=1.000) at 4 hours, and -23.9% (95% CI: -17.8% to -30.1%, P=0.006) at 6 hours after treatment. In the no-treatment group, the change was -2.9% (95% CI: +1.0% to -6.7%, P= referent) at 1 hour, -2.1% (95% CI: +2.9% to -7.2%, P= referent) at 2 hours, -7.6% (95% CI: -3.9% to -11.2%, P= referent) at 4 hours, and -6.9% (95% CI: -3.6% to -10.2%, P= referent) at 6 hours. Acetazolamide reduced IOP by -18.8% (95% CI: -12.7% to -24.8%, P=0.000) at 1 hour, -26.2% (95% CI: -18.2% to -34.2%, P=0.001) at 2 hours, -24.6% (95% CI: -16.9% to -32.3%, P=0.000) after 4 hours, and -26.9% (95% CI: -19.6% to -34.3%, P=0.000) 6 hours after treatment. Timolol reduced IOP by -31.2% (95% CI: -26.7% to -35.7%, P=0.000) at 1 hour, -27.7% (95% CI: -20.7% to -34.8%, P=0.000) at 2 hours, -28.7% (95% CI: -21.1% to -36.2%, P=0.000) at 4 hours, and -21.3% (95% CI: -13.4% to -30.0%, P=0.030) at 6 hours after treatment. The average change in IOP for the no-treatment group was -4.8% (95% CI: -2.6% to -6.9%, P= referent). It was -15.7% (95% CI: -9.3% to -22.1%, P=0.021) for paracetamol, -23.1% (95% CI: -16.4% to -29.8%, P=0.000) for acetazolamide, and -25.3% for the timolol group (95% CI: -19.4% to -31.2%, P=0.000). The maximal change in IOP for the no-treatment group was -9.2% (95% CI: -3.2% to -15.3%, P= referent). It was -25.9% (95% CI: -16.6% to -35.2%, P=0.009) for paracetamol, -33.8% (95% CI: -25.5% to -42.1%, P=0.000) for acetazolamide, and -36.8% (95% CI: -31.0% to -42.5%, P=0.000) for the timolol group. CONCLUSION Intravenously administered paracetamol shows IOP-lowering properties over the first 6 hours after administration. Clinicians performing IOP measurements in patients who have received IV paracetamol in the preceding 6 hours should interpret these measurements with caution. Further studies are needed to investigate the IOP-changing properties of paracetamol.
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Affiliation(s)
- Henning van den Heever
- Division of Ophthalmology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
| | - David Meyer
- Division of Ophthalmology, Faculty of Medicine and Health Sciences, Stellenbosch University, Cape Town, South Africa
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Cairns EA, Baldridge WH, Kelly MEM. The Endocannabinoid System as a Therapeutic Target in Glaucoma. Neural Plast 2016; 2016:9364091. [PMID: 26881140 PMCID: PMC4737462 DOI: 10.1155/2016/9364091] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Accepted: 11/10/2015] [Indexed: 11/17/2022] Open
Abstract
Glaucoma is an irreversible blinding eye disease which produces progressive retinal ganglion cell (RGC) loss. Intraocular pressure (IOP) is currently the only modifiable risk factor, and lowering IOP results in reduced risk of progression of the disorder. The endocannabinoid system (ECS) has attracted considerable attention as a potential target for the treatment of glaucoma, largely due to the observed IOP lowering effects seen after administration of exogenous cannabinoids. However, recent evidence has suggested that modulation of the ECS may also be neuroprotective. This paper will review the use of cannabinoids in glaucoma, presenting pertinent information regarding the pathophysiology of glaucoma and how alterations in cannabinoid signalling may contribute to glaucoma pathology. Additionally, the mechanisms and potential for the use of cannabinoids and other novel agents that target the endocannabinoid system in the treatment of glaucoma will be discussed.
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Affiliation(s)
- Elizabeth A. Cairns
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada B3H 4R2
| | - William H. Baldridge
- Department of Medical Neuroscience, Dalhousie University, Halifax, NS, Canada B3H 4R2
- Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, Canada B3H 4R2
| | - Melanie E. M. Kelly
- Department of Pharmacology, Dalhousie University, Halifax, NS, Canada B3H 4R2
- Department of Ophthalmology and Visual Sciences, Dalhousie University, Halifax, NS, Canada B3H 4R2
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Murataeva N, Li S, Oehler O, Miller S, Dhopeshwarkar A, Hu SSJ, Bonanno JA, Bradshaw H, Mackie K, McHugh D, Straiker A. Cannabinoid-induced chemotaxis in bovine corneal epithelial cells. Invest Ophthalmol Vis Sci 2015; 56:3304-13. [PMID: 26024113 DOI: 10.1167/iovs.14-15675] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Cannabinoid CB1 receptors are found in abundance in the vertebrate eye, with most tissue types expressing this receptor. However, the function of CB1 receptors in corneal epithelial cells (CECs) is poorly understood. Interestingly, the corneas of CB1 knockout mice heal more slowly after injury via a mechanism proposed to involve protein kinase B (Akt) activation, chemokinesis, and cell proliferation. The current study examined the role of cannabinoids in CEC migration in greater detail. METHODS We determined the role of CB1 receptors in corneal healing. We examined the consequences of their activation on migration and proliferation in bovine CECs (bCECs). We additionally examined the mRNA profile of cannabinoid-related genes and CB1 protein expression as well as CB1 signaling in bovine CECs. RESULTS We now report that activation of CB1 with physiologically relevant concentrations of the synthetic agonist WIN55212-2 (WIN) induces bCEC migration via chemotaxis, an effect fully blocked by the CB1 receptor antagonist SR141716. The endogenous agonist 2-arachidonoylglycerol (2-AG) also enhances migration. Separately, mRNA for most cannabinoid-related proteins are present in bovine corneal epithelium and cultured bCECs. Notably absent are CB2 receptors and the 2-AG synthesizing enzyme diglycerol lipase-α (DAGLα). The signaling profile of CB1 activation is complex, with inactivation of mitogen-activated protein kinase (MAPK). Lastly, CB1 activation does not induce bCEC proliferation, but may instead antagonize EGF-induced proliferation. CONCLUSIONS In summary, we find that CB1-based signaling machinery is present in bovine cornea and that activation of this system induces chemotaxis.
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Affiliation(s)
- Natalia Murataeva
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Shimin Li
- School of Optometry, Indiana University, Bloomington, Indiana, United States
| | - Olivia Oehler
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Sally Miller
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Amey Dhopeshwarkar
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Sherry Shu-Jung Hu
- Department of Psychology, National Cheng Kung University, Tainan, Taiwan
| | - Joseph A Bonanno
- School of Optometry, Indiana University, Bloomington, Indiana, United States
| | - Heather Bradshaw
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Ken Mackie
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
| | - Douglas McHugh
- Frank H. Netter MD School of Medicine, Quinnipiac University, North Haven, Connecticut, United States
| | - Alex Straiker
- The Gill Center for Biomolecular Science and the Department of Psychological and Brain Sciences Indiana University, Bloomington, Indiana, United States
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Caldwell MD, Hu SSJ, Viswanathan S, Bradshaw H, Kelly MEM, Straiker A. A GPR18-based signalling system regulates IOP in murine eye. Br J Pharmacol 2014; 169:834-43. [PMID: 23461720 DOI: 10.1111/bph.12136] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2012] [Revised: 01/17/2013] [Accepted: 02/07/2013] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE GPR18 is a recently deorphaned lipid receptor that is activated by the endogenous lipid N-arachidonoyl glycine (NAGly) as well the behaviourally inactive atypical cannabinoid, abnormal cannabidiol (Abn-CBD). The presence and/or function of any GPR18-based ocular signalling system remain essentially unstudied. The objectives of this research are: (i) to determine the disposition of GPR18 receptors and ligands in anterior murine eye, (ii) examine the effect of GPR18 activation on intraocular pressure (IOP) in a murine model, including knockout mice for CB₁, CB₂ and GPR55. EXPERIMENTAL APPROACH IOP was measured in mice following topical application of Abn-CBD, NAGly or the GPR55/GPR18 agonist O-1602, alone or with injection of the GPR18 antagonist, O-1918. GPR18 protein localization was assessed with immunohistochemistry. Endocannabinoids were measured using LC/MS-MS. KEY RESULTS GPR18 protein was expressed most prominently in the ciliary epithelium and the corneal epithelium and, interestingly, in the trabecular meshwork. The GPR18 ligand, NAGly, was also detected in mouse eye at a level comparable to that seen in the brain. Abn-CBD and NAGly, but not O-1602, significantly reduced IOP in all mice tested. The antagonist, O-1918, blocked the effects of Abn-CBD and NAGly. CONCLUSIONS AND IMPLICATIONS We present evidence for a functional GPR18-based signalling system in the murine anterior eye, including receptors and ligands. GPR18 agonists, Abn-CBD and NAGly, reduce IOP independently of CB₁, CB₂ or GPR55. These findings suggest that GPR18 may serve as a desirable target for the development of novel ocular hypotensive medications.
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Affiliation(s)
- Meggie D Caldwell
- Department of Clinical Vision Science, Dalhousie University, Halifax, NS, Canada
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New therapeutic targets for intraocular pressure lowering. ISRN OPHTHALMOLOGY 2013; 2013:261386. [PMID: 24558600 PMCID: PMC3914177 DOI: 10.1155/2013/261386] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 05/30/2013] [Indexed: 01/08/2023]
Abstract
Primary open-angle glaucoma (POAG) is a leading cause of irreversible and preventable blindness and ocular hypertension is the strongest known risk factor. With current classes of drugs, management of the disease focuses on lowering intraocular pressure (IOP). Despite of their use to modify the course of the disease, none of the current medications for POAG is able to reduce the IOP by more than 25%-30%. Also, some glaucoma patients show disease progression despite of the therapeutics. This paper examines the new described physiological targets for reducing the IOP. The main cause of elevated IOP in POAG is thought to be an increased outflow resistance via the pressure-dependent trabecular outflow system, so there is a crescent interest in increasing trabecular meshwork outflow by extracellular matrix remodeling and/or by modulation of contractility/TM cytoskeleton disruption. Modulation of new agents that act mainly on trabecular meshwork outflow may be the future hypotensive treatment for glaucoma patients. There are also other agents in which modulation may decrease aqueous humour production or increase uveoscleral outflow by different mechanisms from those drugs available for glaucoma treatment. Recently, a role for the ghrelin-GHSR system in the pathophysiology modulation of the anterior segment, particularly regarding glaucoma, has been proposed.
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