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NAC Supplementation of Hyperglycemic Rats Prevents the Development of Insulin Resistance and Improves Antioxidant Status but Only Alleviates General and Salivary Gland Oxidative Stress. OXIDATIVE MEDICINE AND CELLULAR LONGEVITY 2020; 2020:8831855. [PMID: 33274008 PMCID: PMC7683161 DOI: 10.1155/2020/8831855] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Revised: 10/15/2020] [Accepted: 11/02/2020] [Indexed: 12/13/2022]
Abstract
Previous studies based on animal models demonstrated that N-acetylcysteine (NAC) prevents oxidative stress and improves salivary gland function when the NAC supplementation starts simultaneously with insulin resistance (IR) induction. This study is the first to evaluate the effect of a 4-week NAC supply on the antioxidant barrier and oxidative stress in Wistar rats after six weeks of high-fat diet (HFD) intake. Redox biomarkers were evaluated in the parotid (PG) and submandibular (SMG) salivary glands and stimulated whole saliva (SWS), as well as in the plasma and serum. We demonstrated that the activity of salivary peroxidase and superoxide dismutase and total antioxidant capacity were significantly higher in PG, SMG, and SWS of IR rats treated with NAC. It appears that in PG and SMG of rats fed an HFD, N-acetylcysteine supplementation abolishes oxidative modifications to proteins (evidenced by decreased content of advanced oxidation protein products (AOPP) and advanced glycation end products (AGE)). Simultaneously, it does not reverse oxidative modifications of lipids (as seen in increased concentration of 8-isoprostanes and 4-hydroxynonenal vs. the control), although it reduces the peroxidation of salivary lipids in relation to the group fed a high-fat diet alone. NAC administration increased protein levels in PG and SMG but did not affect saliva secretion, which was significantly lower compared to the controls. To sum up, the inclusion of NAC supplementation after six weeks of HFD feeding was effective in improving the general and salivary gland antioxidant status. Nevertheless, NAC did not eliminate salivary oxidative stress and only partially prevented salivary gland dysfunction.
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Vora D, Heruye S, Kumari D, Opere C, Chauhan H. Preparation, Characterization and Antioxidant Evaluation of Poorly Soluble Polyphenol-Loaded Nanoparticles for Cataract Treatment. AAPS PharmSciTech 2019; 20:163. [PMID: 30993475 DOI: 10.1208/s12249-019-1379-y] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Accepted: 03/27/2019] [Indexed: 12/14/2022] Open
Abstract
Cataract, one of the leading causes of blindness worldwide, is a condition in which complete or partial opacity develops in the lens of the eyes, thereby impairing vision. This study aimed to examine the potential therapeutic and protective effects of poorly soluble polyphenols like curcumin, resveratrol, and dibenzoylmethane, known to possess significant antioxidant activity. The polyphenols were loaded into novel lipid-cyclodextrin-based nanoparticles and characterized by particle size, polydispersity index, differential scanning calorimetry, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy (SEM), entrapment efficiency, and release studies. Ferric-reducing ability of plasma and 2,2-diphenyl-1-picrylhydrazyl chemical assays were used to evaluate their antioxidant properties based on their free radical quenching ability. Biochemical in vitro assays were used to examine these polyphenols on hydrogen peroxide-induced formation of cataracts in bovine lenses by estimating total glutathione content and superoxide dismutase activity. Nanoparticles were thermostable and amorphous. Particle size of curcumin, resveratrol, and dibenzoylmethane nanoparticles were 331.0 ± 17.9 nm, 329.9 ± 1.9 nm, and 163.8 ± 3.2 nm, respectively. SEM confirmed porous morphology and XRD confirmed physical stability. Entrapment efficiency for curcumin-, resveratrol-, and dibenzoylmethane-loaded nanoparticles was calculated to be 84.4 ± 2.4%, 72.2 ± 1.5%, and 86.4 ± 0.6%, respectively. In vitro release studies showed an initial burst release followed by a continuous release of polyphenols from nanoparticles. Chemical assays confirmed the polyphenols' antioxidant activity. Superoxide dismutase and glutathione levels were found to be significantly increased (p < 0.05) after treatment with polyphenol-loaded nanoparticles than pure polyphenols; thus, an improved antioxidant activity translational into potential anticataract activity of the polyphenols when loaded into nanoparticles was observed as compared to pure polyphenols.
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Bankhele P, Salvi A, Jamil J, Njie-Mbye F, Ohia S, Opere CA. Comparative Effects of Hydrogen Sulfide-Releasing Compounds on [ 3H]D-Aspartate Release from Bovine Isolated Retinae. Neurochem Res 2018; 43:692-701. [PMID: 29353375 DOI: 10.1007/s11064-018-2471-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2017] [Revised: 12/20/2017] [Accepted: 01/08/2018] [Indexed: 12/31/2022]
Abstract
We investigated the pharmacological actions of a slow-releasing H2S donor, GYY 4137; a substrate for the biosynthesis of H2S, L-cysteine and its precursor, N-acetylcysteine on potassium (K+; 50 mM)-evoked [3H]D-aspartate release from bovine isolated retinae using the Superfusion Method. GYY 4137 (10 nM-10 µM), L-cysteine (100 nM-10 µM) and N-acetylcysteine (10 µM-1 mM) elicited a concentration-dependent decrease in K+-evoked [3H]D-aspartate release from isolated bovine retinae without affecting basal tritium efflux. At equimolar concentration of 10 µM, the rank order of activity was as follows: L-cysteine > GYY 4137 > N-acetylcysteine. A dual inhibitor of the biosynthetic enzymes for H2S, cystathionine β-synthase (CBS) and cystathionine γ-lyase (CSE), amino-oxyacetic acid (AOA; 3 mM) reversed the inhibitory responses caused by GYY 4137, L-cysteine and N-acetylcysteine on K+-evoked [3H]D-aspartate release. Glibenclamide (300 µM), an inhibitor of KATP channels blocked the inhibitory action of GYY 4137 and L-cysteine but not that elicited by N-acetylcysteine on K+-induced [3H]D-aspartate release. The inhibitory effect of GYY 4137 and L-cysteine on K+-evoked [3H]D-aspartate release was reversed by the non-specific inhibitor of nitric oxide synthase (NOS), L-NAME (300 µM). Furthermore, a specific inhibitor of inducible NOS (iNOS), aminoguanidine (10 µM) blocked the inhibitory action of L-cysteine on K+-evoked [3H]D-aspartate release. We conclude that both donors and substrates for H2S production can inhibit amino acid neurotransmission in bovine isolated retinae, an effect that is dependent, at least in part, upon the intramural biosynthesis of this gas, and on the activity of KATP channels and NO synthase.
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Affiliation(s)
- Pratik Bankhele
- Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University, 2500 California Plaza, Omaha, NE, 68178, USA
| | - Ankita Salvi
- Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University, 2500 California Plaza, Omaha, NE, 68178, USA
| | - Jamal Jamil
- Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University, 2500 California Plaza, Omaha, NE, 68178, USA
| | - Fatou Njie-Mbye
- Department of Pharmaceutical & Environmental Health Sciences, College of Pharmacy & Health Sciences, Texas Southern University, 3100 Cleburne Street, Houston, TX, 77004, USA
| | - Sunny Ohia
- Department of Pharmaceutical & Environmental Health Sciences, College of Pharmacy & Health Sciences, Texas Southern University, 3100 Cleburne Street, Houston, TX, 77004, USA
| | - Catherine A Opere
- Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University, 2500 California Plaza, Omaha, NE, 68178, USA.
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Galano JM, Lee YY, Oger C, Vigor C, Vercauteren J, Durand T, Giera M, Lee JCY. Isoprostanes, neuroprostanes and phytoprostanes: An overview of 25years of research in chemistry and biology. Prog Lipid Res 2017; 68:83-108. [PMID: 28923590 DOI: 10.1016/j.plipres.2017.09.004] [Citation(s) in RCA: 114] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2017] [Revised: 09/14/2017] [Accepted: 09/14/2017] [Indexed: 02/07/2023]
Abstract
Since the beginning of the 1990's diverse types of metabolites originating from polyunsaturated fatty acids, formed under autooxidative conditions were discovered. Known as prostaglandin isomers (or isoprostanoids) originating from arachidonic acid, neuroprostanes from docosahexaenoic acid, and phytoprostanes from α-linolenic acid proved to be prevalent in biology. The syntheses of these compounds by organic chemists and the development of sophisticated mass spectrometry methods has boosted our understanding of the isoprostanoid biology. In recent years, it has become accepted that these molecules not only serve as markers of oxidative damage but also exhibit a wide range of bioactivities. In addition, isoprostanoids have emerged as indicators of oxidative stress in humans and their environment. This review explores in detail the isoprostanoid chemistry and biology that has been achieved in the past three decades.
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Affiliation(s)
- Jean-Marie Galano
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS, ENSCM, Université de Montpellier, France
| | - Yiu Yiu Lee
- School of Biological Sciences, The University of Hong Kong, Hong Kong Special Administrative Region
| | - Camille Oger
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS, ENSCM, Université de Montpellier, France
| | - Claire Vigor
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS, ENSCM, Université de Montpellier, France
| | - Joseph Vercauteren
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS, ENSCM, Université de Montpellier, France
| | - Thierry Durand
- Institut des Biomolécules Max Mousseron, UMR 5247 CNRS, ENSCM, Université de Montpellier, France
| | - Martin Giera
- Leiden University Medical Center, Center for Proteomics and Metabolomics, Albinusdreef 2, 2300RC Leiden, The Netherlands
| | - Jetty Chung-Yung Lee
- School of Biological Sciences, The University of Hong Kong, Hong Kong Special Administrative Region.
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Role of the Non-enzymatic Metabolite of Eicosapentaenoic Acid, 5-epi-5-F3t-Isoprostane in the Regulation of [3H]d-Aspartate Release in Isolated Bovine Retina. Neurochem Res 2014; 39:2360-9. [DOI: 10.1007/s11064-014-1436-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 09/05/2014] [Accepted: 09/09/2014] [Indexed: 12/14/2022]
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Davies SS, Guo L. Lipid peroxidation generates biologically active phospholipids including oxidatively N-modified phospholipids. Chem Phys Lipids 2014; 181:1-33. [PMID: 24704586 DOI: 10.1016/j.chemphyslip.2014.03.002] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2014] [Revised: 02/28/2014] [Accepted: 03/18/2014] [Indexed: 12/25/2022]
Abstract
Peroxidation of membranes and lipoproteins converts "inert" phospholipids into a plethora of oxidatively modified phospholipids (oxPL) that can act as signaling molecules. In this review, we will discuss four major classes of oxPL: mildly oxygenated phospholipids, phospholipids with oxidatively truncated acyl chains, phospholipids with cyclized acyl chains, and phospholipids that have been oxidatively N-modified on their headgroups by reactive lipid species. For each class of oxPL we will review the chemical mechanisms of their formation, the evidence for their formation in biological samples, the biological activities and signaling pathways associated with them, and the catabolic pathways for their elimination. We will end by briefly highlighting some of the critical questions that remain about the role of oxPL in physiology and disease.
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Affiliation(s)
- Sean S Davies
- Division of Clinical Pharmacology, Department of Pharmacology, Vanderbilt University, United States.
| | - Lilu Guo
- Division of Clinical Pharmacology, Department of Pharmacology, Vanderbilt University, United States
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Njie-Mbye YF, Kulkarni-Chitnis M, Opere CA, Barrett A, Ohia SE. Lipid peroxidation: pathophysiological and pharmacological implications in the eye. Front Physiol 2013; 4:366. [PMID: 24379787 PMCID: PMC3863722 DOI: 10.3389/fphys.2013.00366] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 11/25/2013] [Indexed: 01/17/2023] Open
Abstract
Oxygen-derived free radicals such as hydroxyl and hydroperoxyl species have been shown to oxidize phospholipids and other membrane lipid components leading to lipid peroxidation. In the eye, lipid peroxidation has been reported to play an important role in degenerative ocular diseases (age-related macular degeneration, cataract, glaucoma, diabetic retinopathy). Indeed, ocular tissues are prone to damage from reactive oxygen species due to stress from constant exposure of the eye to sunlight, atmospheric oxygen and environmental chemicals. Furthermore, free radical catalyzed peroxidation of long chain polyunsaturated acids (LCPUFAs) such as arachidonic acid and docosahexaenoic acid leads to generation of LCPUFA metabolites including isoprostanes and neuroprostanes that may further exert pharmacological/toxicological actions in ocular tissues. Evidence from literature supports the presence of endogenous defense mechanisms against reactive oxygen species in the eye, thereby presenting new avenues for the prevention and treatment of ocular degeneration. Hydrogen peroxide (H2O2) and synthetic peroxides can exert pharmacological and toxicological effects on tissues of the anterior uvea of several mammalian species. There is evidence suggesting that the retina, especially retinal ganglion cells can exhibit unique characteristics of antioxidant defense mechanisms. In the posterior segment of the eye, H2O2 and synthetic peroxides produce an inhibitory action on glutamate release (using [(3)H]-D-aspartate as a marker), in vitro and on the endogenous glutamate and glycine concentrations in vivo. In addition to peroxides, isoprostanes can elicit both excitatory and inhibitory effects on norepinephrine (NE) release from sympathetic nerves in isolated mammalian iris ciliary bodies. Whereas isoprostanes attenuate dopamine release from mammalian neural retina, in vitro, these novel arachidonic acid metabolites exhibit a biphasic regulatory effect on glutamate release from retina and can regulate amino acid neurotransmitter metabolism without inducing cell death in the retina. Furthermore, there appears to be an inhibitory role for neuroprostanes in the release of excitatory amino acid neurotransmitters in mammalian retina. The ability of peroxides and metabolites of LCPUFA to alter the integrity of neurotransmitter pools provides new potential target sites and pathways for the treatment of degenerative ocular diseases.
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Affiliation(s)
- Ya Fatou Njie-Mbye
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Texas Southern University Houston, TX, USA
| | - Madhura Kulkarni-Chitnis
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Texas Southern University Houston, TX, USA
| | - Catherine A Opere
- Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University Omaha, NE, USA
| | - Aaron Barrett
- Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University Omaha, NE, USA
| | - Sunny E Ohia
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Texas Southern University Houston, TX, USA
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Jamil J, Wright A, Harrison N, Kegey E, Flowers AF, Flyod NJ, Kotera C, Guy A, Galano JM, Durand T, Njie-Mbye YF, Ohia SE, Opere CA. Regulation of [³H]d-aspartate release by the 5-F(2t)-isoprostane and its 5-epimer in isolated bovine retina. Neurochem Res 2011; 37:574-82. [PMID: 22081406 DOI: 10.1007/s11064-011-0645-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Revised: 10/25/2011] [Accepted: 11/02/2011] [Indexed: 11/25/2022]
Abstract
We have evidence that 15-F₂-isoprostanes (15-F₂-IsoPs) regulate excitatory neurotransmitter release in ocular tissues. Although 5-F₂-IsoPs are abundantly produced in mammals, their pharmacological actions on neurotransmitter release remain unknown. In the present study, we compared the effect of the 5-F₂-IsoP epimer pair, 5-F(2t)-IsoP (C5-OH in β-position) and 5-epi-5-F(2t)-IsoP (C5-OH in α-position), on K⁺-evoked [³H]D-aspartate release in isolated bovine retina. We further examined the role of prostanoid receptors on the inhibitory action of 5-epi-5-F(2t)-IsoP on [³H]D-aspartate overflow. Isolated bovine retina were prepared for studies of K⁺-evoked release of [³H]D-aspartate using the superfusion method. 5-epi-5-F(2t)-IsoP (0.01 nM to 1 μM), attenuated K⁺-evoked [³H]D-aspartate release in a concentration-dependent manner, with the inhibitory effect of 26.9% (P < 0.001; IC₂₅ = 0.2 μM) being achieved at 1 μM concentration. Its 5-(S)-OH-epimer, 5-F(2t)-IsoP (0.1 nM-1 μM), exhibited an inhibitory biphasic action, yielding a maximal response of 35.7% (P < 0.001) at 10 nM concentration of the drug (IC₂₅ value of 3 nM). Although the prostanoid-receptor antagonists, AH 6809 (10 μM; EP₁₋₃/DP) and BAY-u3405 (10 μM; DP/Tx) exhibited no effect on 5-epi-5-F(2t)-IsoP (10 nM-1 μM)-mediated inhibition, SC-19220 (1 μM; EP₁) completely reversed 5-epi-5-F(2t)-IsoP (0.1 μM and 1 μM)-induced attenuation of K⁺-evoked [³H]D-aspartate release. Similarly, both SC-51322 (10 μM; EP₁ and AH 23848 (1 μM; EP₄) reversed the inhibitory action elicited by 5-epi-5-F(2t)-IsoP (0.1 μM) on the neurotransmitter release. We conclude that the 5-F₂-IsoP epimer pair, 5-F(2t)-IsoP and 5-epi-5-F(2t)-IsoP, attenuate K⁺-induced [³H]D-aspartate release in isolated bovine retina presumably via prostanoid receptor dependent mechanisms. The trans-orientation of the allylic hydroxyl group at position C5 accounts for the apparent biphasic response exhibited by 5-F(2t)-IsoP on excitatory neurotransmitter release.
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Affiliation(s)
- Jamal Jamil
- Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University Medical Center, 2500 California Plaza, Omaha, NE 68178, USA
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Role of prostanoid production and receptors in the regulation of retinal endogenous amino acid neurotransmitters by 8-isoprostaglandin E2, ex vivo. Neurochem Res 2011; 34:2170-80. [PMID: 19513831 DOI: 10.1007/s11064-009-0013-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/21/2009] [Indexed: 12/11/2022]
Abstract
The role of enzymes and receptors of the prostanoid pathway in the inhibitory effect of 8-isoprostaglandin E2 (8-isoPGE2) on endogenous amino acid neurotransmitter levels was examined, ex vivo. Freshly isolated bovine eyeballs were injected intravitreally with IsoPs, incubated in Krebs buffer for 30 min and retina prepared for HPLC-ECD detection of amino acids. 8-isoPGE2 attenuated retinal glutamate and its metabolite, glutamine and glycine in a concentration-dependent manner. The nonselective cyclooxygenase (COX)-inhibitor, flurbiprofen, COX-2 selective inhibitor, NS-398 and thromboxane (Tx) synthase inhibitor, furegrelate had no effect on both basal amino acid levels and the inhibitory effects of 8-isoPGE2 (1-100 μM) on the retinal amino acids. Whereas the TP-receptor antagonist SQ-29548(10 μM) exhibited no effect, SC-19220(EP1; 30 μM), AH-6809(EP(1-3); 30 μM) and AH-23848(EP4; 30 μM) reversed the inhibitory effects of 8-isoPGE2 (0.01-100 μM) on glutamate, glutamine and glycine levels. We conclude that prostanoid EP-receptors regulate the inhibitory effect of 8-isoPGE2 on basal levels of endogenous amino acids in bovine retina, ex vivo.
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Liu H, Zhao M, Opere CA. Prejunctional inhibitory effects of isoprostanes on dopaminergic neurotransmission in bovine retinae, in vitro. Neurochem Res 2007; 33:37-42. [PMID: 17674205 DOI: 10.1007/s11064-007-9404-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2007] [Accepted: 06/05/2007] [Indexed: 11/29/2022]
Abstract
We investigated the effect of isoprostanes (IsoPs) on potassium (K+)-depolarization-evoked release of [3H]dopamine from isolated bovine retinae. Isolated retinae were preloaded with [3H]dopamine and then prepared for studies of [3H]dopamine release using the superfusion method. 8-iso(15R)PGF 2alpha, 8-isoPGE2, 8-isoPGE1 and 8-isoPGF 2alpha attenuated [3H]dopamine release from isolated bovine retinae. At a concentration of 1 microM, the rank order of activity displayed by IsoP agonists was: 8-iso(15R)PGF 2alpha > 8-isoPGE2 > 8-isoPGE1 > 8-isoPGF 2alpha. Inhibition of cyclooxygenase (COX) with flurbiprofen reversed the effects caused by 8-isoPGE2 (10 nM and 10 microM), 8-iso(15R)PGF 2alpha (1 microM) and 8-isoPGE1 (1 microM). Although the EP1/EP2 antagonist, AH 6809 (10 microM) had no significant effect on K+-induced [3H]dopamine release, it blocked the inhibitory effect of both 8-isoPGE1 (10 microM) and 8-isoPGE2 (10 microM). In conclusion, IsoPs attenuate K+-induced [3H]dopamine release in isolated bovine retinae, presumably via an indirect action on COX pathway leading to the production of prostanoids, which in turn, activates EP receptors.
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Affiliation(s)
- Hong Liu
- Department of Ophthalmology, Sichuan Provincial People Hospital, Chengdu, Sichuan 610072, PR China
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Ohia SE, Opere CA, Leday AM. Pharmacological consequences of oxidative stress in ocular tissues. Mutat Res 2005; 579:22-36. [PMID: 16055157 DOI: 10.1016/j.mrfmmm.2005.03.025] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2004] [Revised: 02/26/2005] [Accepted: 03/02/2005] [Indexed: 05/03/2023]
Abstract
The eye is a unique organ because of its constant exposure to radiation, atmospheric oxygen, environmental chemicals and physical abrasion. That oxidative stress mechanisms in ocular tissues have been hypothesized to play a role in diseases such as glaucoma, cataract, uveitis, retrolental fibroplasias, age-related macular degeneration and various forms of retinopathy provides an opportunity for new approaches to their prevention and treatment, In the anterior uvea, both H2O2 and synthetic peroxides exert pharmacological/toxicological actions tissues of the anterior uvea especially on the sympathetic nerves and smooth muscles of the iris-ciliary bodies of several mammalian species. Effects produced by peroxides require the presence of trace amounts of extracellular calcium and the functional integrity of mitochondrial calcium stores. Arachidonic acid metabolites appear to be involved in both the excitatory action of peroxides on sympathetic neurotransmission and their inhibitory effect on contractility of the iris smooth muscle to muscarinic receptor activation. In addition to the peroxides, isoprostanes (products of free radical catalyzed peroxidation of arachidonic acid independent of the cyclo-oxygenase enzyme) can also alter sympathetic neurotransmission in anterior uveal tissues. In the retina, both H2O2 and synthetic peroxides produced an inhibitory action on potassium depolarization induced release of [3H] D-aspartate, in vitro and on the endogenous glutamate and glycine concentrations in vivo. Effects caused by peroxides in the retina are mediated, at least in part, by second messengers such as nitric oxide, prostaglandins and isoprostanes. The ability of H2O2 to alter the integrity of neurotransmitter pools from sympathetic nerves in the anterior uvea and glutaminergic nerves in the retina could underlie its role in the etiology of glaucoma.
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Affiliation(s)
- Sunny E Ohia
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, 141 Science and Research Building 2, University of Houston, Houston, TX 77204, USA.
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