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Torres Jimenez N, Miller RF, McLoon LK. Effects of D-serine treatment on outer retinal function. Exp Eye Res 2021; 211:108732. [PMID: 34419444 DOI: 10.1016/j.exer.2021.108732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 07/12/2021] [Accepted: 08/16/2021] [Indexed: 11/19/2022]
Abstract
The role of the N-Methyl-D-Aspartate Receptor (NMDAR) in the outer retina is unclear despite expression of the NMDAR-complex and its subunits in the outer retina. The flash-electroretinogram (fERG) offers a non-invasive measurement of the retinal field potentials of the outer retina that can serve to clarify NMDAR contribution to early retinal processing. The role of the NMDAR in retinal function was assessed using a genetic mouse model for NMDAR hypofunction (SR-/-), where the absence of the enzyme serine racemase (SR) results in an 85% reduction of retinal D-serine. NMDAR hypo- and hyperfunction in the retina results in alterations in the components of the fERG. The fERG was examined after application of exogenous D-serine to the eye in order to determine whether pre- and post-topical delivery of D-serine would alter the fERG in SR-/- mice and their littermate WT controls. Amplitude and implicit time of the low-frequency components, the a- and b-wave, were conducted. Reduced NMDAR function resulted in a statistically significantly delayed a-wave and reduced b-wave in SR-/- animals. The effect of NMDAR deprivation was more prominent in male SR-/- mice. A hyperfunction of the NMDAR, through exogenous topical delivery of 5 mM D-serine, in WT mice caused a significantly delayed a-wave implicit time and reduced b-wave amplitude. These changes were not observed in female WT mice. There were temporal delays in the a-wave and amplitude and a decrease in the b-wave amplitude and implicit time in both hypo- and NMDAR hyperfunctional male mice. These results suggest that NMDAR and D-serine are involved in the retinal field potentials of the outer retina that interact based on the animal's sex. This implicates the involvement of gonadal hormones and D-serine in retinal functional integrity.
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Affiliation(s)
- Nathalia Torres Jimenez
- Neuroscience, University of Minnesota, Department of Neuroscience, Minneapolis, MN, USA; Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN, USA
| | - Robert F Miller
- Neuroscience, University of Minnesota, Department of Neuroscience, Minneapolis, MN, USA; Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN, USA
| | - Linda K McLoon
- Neuroscience, University of Minnesota, Department of Neuroscience, Minneapolis, MN, USA; Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, MN, USA.
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2
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Jiang H, Zhang H, Jiang X, Wu S. Overexpression of D-amino acid oxidase prevents retinal neurovascular pathologies in diabetic rats. Diabetologia 2021; 64:693-706. [PMID: 33319325 DOI: 10.1007/s00125-020-05333-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 10/06/2020] [Indexed: 10/22/2022]
Abstract
AIMS/HYPOTHESIS Diabetic retinopathy is characterised by retinal neurodegeneration and retinal vascular abnormalities, affecting one third of diabetic patients with disease duration of more than 10 years. Accumulated evidence suggests that serine racemase (SR) and D-serine are correlated with the pathogenesis of diabetic retinopathy and the deletion of the Srr gene reverses neurovascular pathologies in diabetic mice. Since D-serine content is balanced by SR synthesis and D-amino acid oxidase (DAAO) degradation, we examined the roles of DAAO in diabetic retinopathy and further explored relevant therapy. METHODS Rats were used as a model of diabetes by i.p. injection of streptozotocin at the age of 2 months and blood glucose was monitored with a glucometer. Quantitative real-time PCR was used to examine Dao mRNA and western blotting to examine targeted proteins in the retinas. Bisulphite sequencing was used to examine the methylation of Dao mRNA promoter in the retinas. Intravitreal injection of DAAO-expressing adenovirus (AAV8-DAAO) was conducted one week before streptozotocin administration. Brain specific homeobox/POU domain protein 3a (Brn3a) immunofluorescence was conducted to indicate retinal ganglion cells at 3 months after virus injection. The permeability of the blood-retinal barrier was examined by Evans blue leakage from retinal capillaries. Periodic acid-Schiff staining and haematoxylin counterstaining were used to indicate retinal vasculature, which was further examined with double immunostaining at 7 months after virus injection. RESULTS At the age of 12 months, DAAO mRNA and protein levels in retinas from diabetic animals were reduced to 66.2% and 70.4% of those from normal (control) animals, respectively. The Dao proximal promoter contained higher levels of methylation in diabetic than in normal retinas. Consistent with the observation, DNA methyltransferase 1 was increased in diabetic retinas. Injection of DAAO-expressing virus completely prevented the loss of retinal ganglion cells and the disruption of blood-retinal barrier in diabetic rats. Diabetic retinas contained retinal ganglion cells at a density of 54 ± 4/mm2, which was restored to 68 ± 9/mm2 by DAAO overexpression, similar to the levels in normal retinas. The ratio between the number of endothelial cells and pericytes in diabetic retinas was 6.06 ± 1.93/mm2, which was reduced to 3.42 ± 0.55/mm2 by DAAO overexpression; the number of acellular capillaries in diabetic retinas was 10 ± 5/mm2, which was restored to 6 ± 2/mm2 by DAAO overexpression, similar to the levels in normal retinas. Injection of the DAAO-expressing virus increased the expression of occludin and reduced gliosis, which were examined to probe the mechanism by which the disrupted blood-retinal barrier in diabetic rats was rescued and retinal neurodegeneration was prevented. CONCLUSIONS/INTERPRETATION Altogether, overexpression of DAAO before the onset of diabetes protects against neurovascular abnormalities in retinas from diabetic rats, which suggests a novel strategy for preventing diabetic retinopathy. Graphical abstract.
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Affiliation(s)
- Haiyan Jiang
- School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, People's Republic of China
- State Key Laboratory of Optometry, Ophthalmology, and Visual Science, Wenzhou, Zhejiang, People's Republic of China
| | - He Zhang
- School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, People's Republic of China
- State Key Laboratory of Optometry, Ophthalmology, and Visual Science, Wenzhou, Zhejiang, People's Republic of China
- College of Life and Environmental Sciences, Wenzhou University, Wenzhou, Zhejiang, People's Republic of China
| | - Xue Jiang
- School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, People's Republic of China
- State Key Laboratory of Optometry, Ophthalmology, and Visual Science, Wenzhou, Zhejiang, People's Republic of China
| | - Shengzhou Wu
- School of Optometry and Ophthalmology and the Eye Hospital, Wenzhou Medical University, Wenzhou, Zhejiang, People's Republic of China.
- State Key Laboratory of Optometry, Ophthalmology, and Visual Science, Wenzhou, Zhejiang, People's Republic of China.
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Lockridge A, Gustafson E, Wong A, Miller RF, Alejandro EU. Acute D-Serine Co-Agonism of β-Cell NMDA Receptors Potentiates Glucose-Stimulated Insulin Secretion and Excitatory β-Cell Membrane Activity. Cells 2021; 10:E93. [PMID: 33430405 PMCID: PMC7826616 DOI: 10.3390/cells10010093] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 12/18/2020] [Accepted: 01/04/2021] [Indexed: 02/06/2023] Open
Abstract
Insulin-secreting pancreatic β-cells express proteins characteristic of D-serine regulated synapses, but the acute effect of D-serine co-agonism on its presumptive β-cell target, N-methyl D-aspartate receptors (NMDARs), is unclear. We used multiple models to evaluate glucose homeostasis and insulin secretion in mice with a systemic increase in D-serine (intraperitoneal injection or DAAO mutants without D-serine catabolism) or tissue-specific loss of Grin1-encoded GluN1, the D-serine binding NMDAR subunit. We also investigated the effects of D-serine ± NMDA on glucose-stimulated insulin secretion (GSIS) and β-cell depolarizing membrane oscillations, using perforated patch electrophysiology, in β-cell-containing primary isolated mouse islets. In vivo models of elevated D-serine correlated to improved blood glucose and insulin levels. In vitro, D-serine potentiated GSIS and β-cell membrane excitation, dependent on NMDAR activating conditions including GluN1 expression (co-agonist target), simultaneous NMDA (agonist), and elevated glucose (depolarization). Pancreatic GluN1-loss females were glucose intolerant and GSIS was depressed in islets from younger, but not older, βGrin1 KO mice. Thus, D-serine is capable of acute antidiabetic effects in mice and potentiates insulin secretion through excitatory β-cell NMDAR co-agonism but strain-dependent shifts in potency and age/sex-specific Grin1-loss phenotypes suggest that context is critical to the interpretation of data on the role of D-serine and NMDARs in β-cell function.
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Affiliation(s)
- Amber Lockridge
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN 55455, USA; (A.L.); (E.G.); (A.W.)
| | - Eric Gustafson
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN 55455, USA; (A.L.); (E.G.); (A.W.)
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA;
| | - Alicia Wong
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN 55455, USA; (A.L.); (E.G.); (A.W.)
| | - Robert F. Miller
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA;
| | - Emilyn U. Alejandro
- Department of Integrative Biology and Physiology, University of Minnesota, Minneapolis, MN 55455, USA; (A.L.); (E.G.); (A.W.)
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Jimenez NT, Lines JW, Kueppers RB, Kofuji P, Wei H, Rankila A, Coyle JT, Miller RF, McLoon LK. Electroretinographic Abnormalities and Sex Differences Detected with Mesopic Adaptation in a Mouse Model of Schizophrenia: A and B Wave Analysis. Invest Ophthalmol Vis Sci 2020; 61:16. [PMID: 32053730 PMCID: PMC7326504 DOI: 10.1167/iovs.61.2.16] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2019] [Accepted: 11/02/2019] [Indexed: 12/28/2022] Open
Abstract
Purpose Mesopic flash electroretinography (fERG) as a tool to identify N-methyl-d-aspartate receptor (NMDAR) hypofunction in subjects with schizophrenia shows great potential. We report the first fERG study in a genetic mouse model of schizophrenia characterized by NMDAR hypofunction from gene silencing of serine racemase (SR) expression (SR-/-), an established risk gene for schizophrenia. We analyzed fERG parameters under various background light adaptations to determine the most significant variables to allow for early identification of people at risk for schizophrenia, prior to onset of psychosis. SR is a risk gene for schizophrenia, and negative and cognitive symptoms antedate the onset of psychosis that is required for diagnosis. Methods The scotopic, photopic, and mesopic fERGs were analyzed in male and female mice in both SR-/- and wild-type (WT) mice and also analyzed for sex differences. Amplitude and implicit time of the a- and b-wave components, b-/a-wave ratio, and Fourier transform analysis were analyzed. Results Mesopic a- and b-wave implicit times were significantly delayed, and b-wave amplitudes, b/a ratios, and Fourier transform were significantly decreased in the male SR-/- mice compared to WT, but not in female SR-/- mice. No significant differences were observed in photopic or scotopic fERGs between genotype. Conclusions The fERG prognostic capability may be improved by examination of background light adaptation, a larger array of light intensities, considering sex as a variable, and performing Fourier transform analyses of all waveforms. This should improve the ability to differentiate between controls and subjects with schizophrenia characterized by NMDAR hypofunction.
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Affiliation(s)
- Nathalia Torres Jimenez
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States
| | - Justin W. Lines
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
| | - Rachel B. Kueppers
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States
| | - Paulo Kofuji
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
| | - Henry Wei
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
| | - Amy Rankila
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
| | - Joseph T. Coyle
- Department of Psychiatry, Harvard Medical School, Belmont, Massachusetts, United States
| | - Robert F. Miller
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States
| | - Linda K. McLoon
- Graduate Program in Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
- Department of Neuroscience, University of Minnesota, Minneapolis, Minnesota, United States
- Department of Ophthalmology and Visual Neurosciences, University of Minnesota, Minneapolis, Minnesota, United States
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Ohia SE, Robinson J, Mitchell L, Ngele KK, Heruye S, Opere CA, Njie-Mbye YF. Regulation of Aqueous Humor Dynamics by Hydrogen Sulfide: Potential Role in Glaucoma Pharmacotherapy. J Ocul Pharmacol Ther 2017; 34:61-69. [PMID: 29215951 DOI: 10.1089/jop.2017.0077] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Hydrogen sulfide (H2S) is a gaseous transmitter with well-known biological actions in a wide variety of tissues and organs. The potential involvement of this gas in physiological and pathological processes in the eye has led to several in vitro, ex vivo, and in vivo studies to understand its pharmacological role in some mammalian species. Evidence from literature demonstrates that 4 enzymes responsible for the biosynthesis of this gas (cystathionine β-synthase, CBS; cystathionine γ-lyase, CSE; 3-mercaptopyruvate sulfurtransferase, 3MST; and d-amino acid oxidase) are present in the cornea, iris, ciliary body, lens, and retina. Studies of the pharmacological actions of H2S (using several compounds as fast- and slow-releasing gas donors) on anterior uveal tissues reveal an effect on sympathetic neurotransmission and the ability of the gas to relax precontracted iris and ocular vascular smooth muscles, responses that were blocked by inhibitors of CSE, CBS, and KATP channels. In the retina, there is evidence that H2S can inhibit excitatory amino acid neurotransmission and can also protect this tissue from a wide variety of insults. Furthermore, exogenous application of H2S-releasing compounds was reported to increase aqueous humor outflow facility in an ex vivo model of the porcine ocular anterior segment and lowered intraocular pressure (IOP) in both normotensive and glaucomatous rabbits. Taken together, the finding that H2S-releasing compounds can lower IOP and can serve a neuroprotective role in the retina suggests that H2S prodrugs could be used as tools or therapeutic agents in diseases such as glaucoma.
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Affiliation(s)
- Sunny E Ohia
- 1 Department of Pharmaceutical and Environmental Health Sciences, College of Pharmacy and Health Sciences, Texas Southern University , Houston, Texas
| | - Jenaye Robinson
- 1 Department of Pharmaceutical and Environmental Health Sciences, College of Pharmacy and Health Sciences, Texas Southern University , Houston, Texas
| | - Leah Mitchell
- 1 Department of Pharmaceutical and Environmental Health Sciences, College of Pharmacy and Health Sciences, Texas Southern University , Houston, Texas
| | - Kalu K Ngele
- 2 Department of Biology/Microbiology/Biotechnology, Federal University Ndufu Alike Ikwo , Abakaliki, Nigeria
| | - Segewkal Heruye
- 3 Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University , Omaha, Nebraska
| | - Catherine A Opere
- 3 Department of Pharmacy Sciences, School of Pharmacy and Health Professions, Creighton University , Omaha, Nebraska
| | - Ya Fatou Njie-Mbye
- 1 Department of Pharmaceutical and Environmental Health Sciences, College of Pharmacy and Health Sciences, Texas Southern University , Houston, Texas
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Koga R, Miyoshi Y, Sakaue H, Hamase K, Konno R. Mouse d-Amino-Acid Oxidase: Distribution and Physiological Substrates. Front Mol Biosci 2017; 4:82. [PMID: 29255714 PMCID: PMC5722847 DOI: 10.3389/fmolb.2017.00082] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/14/2017] [Indexed: 01/05/2023] Open
Abstract
d-Amino-acid oxidase (DAO) catalyzes the oxidative deamination of d-amino acids. DAO is present in a wide variety of organisms and has important roles. Here, we review the distribution and physiological substrates of mouse DAO. Mouse DAO is present in the kidney, brain, and spinal cord, like DAOs in other mammals. However, in contrast to other animals, it is not present in the mouse liver. Recently, DAO has been detected in the neutrophils, retina, and small intestine in mice. To determine the physiological substrates of mouse DAO, mutant mice lacking DAO activity are helpful. As DAO has wide substrate specificity and degrades various d-amino acids, many d-amino acids accumulate in the tissues and body fluids of the mutant mice. These amino acids are d-methionine, d-alanine, d-serine, d-leucine, d-proline, d-phenylalanine, d-tyrosine, and d-citrulline. Even in wild-type mice, administration of DAO inhibitors elevates D-serine levels in the plasma and brain. Among the above d-amino acids, the main physiological substrates of mouse DAO are d-alanine and d-serine. These two d-amino acids are most abundant in the tissues and body fluids of mice. d-Alanine derives from bacteria and produces bactericidal reactive oxygen species by the action of DAO. d-Serine is synthesized by serine racemase and is present especially in the central nervous system, where it serves as a neuromodulator. DAO is responsible for the metabolism of d-serine. Since DAO has been implicated in the etiology of neuropsychiatric diseases, mouse DAO has been used as a representative model. Recent reports, however, suggest that mouse DAO is different from human DAO with respect to important properties.
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Affiliation(s)
- Reiko Koga
- Faculty of Pharmaceutical Sciences, Fukuoka University, Fukuoka, Japan
| | - Yurika Miyoshi
- Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Hiroaki Sakaue
- Department of Biochemistry, Tokyo University of Pharmacy and Life Sciences, Hachioji, Japan
| | - Kenji Hamase
- Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan
| | - Ryuichi Konno
- Department of Pharmacological Sciences, International University of Health and Welfare, Ohtawara, Japan
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Zhang H, Song L, Chang Y, Wu M, Kuang X, Jiang H, Wu S. Potential deficit from decreased cerebellar granule cell migration in serine racemase-deficient mice is reversed by increased expression of GluN2B and elevated levels of NMDAR agonists. Mol Cell Neurosci 2017; 85:119-126. [PMID: 28939329 DOI: 10.1016/j.mcn.2017.09.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2017] [Revised: 08/27/2017] [Accepted: 09/14/2017] [Indexed: 12/19/2022] Open
Abstract
Inward migration of cerebellar granule cells (CGCs) after birth is critical for lamination in the cerebellar cortex. N-methyl-d-aspartate (NMDA) subtype of glutamate receptor (NMDAR) tethering CGCs into Bergmann glial fibers mediates the inward movement during the glial-dependent migratory phase. Activation of NMDAR depends on simultaneous binding of the GluN2 subunit by glutamate, and of the GluN1 subunit by d-serine or glycine; d-serine is believed to be an endogenous ligand of NMDAR. We hypothesized that lamination of the cerebellar cortex may be compromised in Srr (the gene for serine racemase (SR)) mutated mice (Srrnull) because of significantly low levels of d-serine per se. Indeed, the external germinal cell layer (EGL) in Srrnull was thicker than in sibling wild-type (WT) mice on postnatal day7 (P7), which accords with decreased CGC migration in Srrnull mice. However, the cerebellar laminar structure in Srrnull mice was normal on P12 and later. Feeding d-serine to pregnant mice abrogated the increased EGL thickness in Srrnull mice on P7. To determine the underlying mechanism of abnormal laminar structure during cerebellar development in Srrnull mice, we examined NMDAR subunits and their ligands. We found increased GluN2B on P10 and increased glycine during P7-12 in the cerebellar homogenates from Srrnull mice compared with the corresponding values from sibling WT mice. In summary, the study revealed how the potential defect in early cerebellar development caused by Srr mutation is circumvented by a compensatory mechanism. This knowledge advances understanding of the adaptation of cerebellar development under the condition of Srr mutation.
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Affiliation(s)
- He Zhang
- School of Optometry and Ophthalmolgy and the Eye Hospital, Wenzhou Medical University, P.R. China; State Key Laboratory of Optometry, Ophthalmology, and Visual Science, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, P.R. China
| | - Liping Song
- School of Optometry and Ophthalmolgy and the Eye Hospital, Wenzhou Medical University, P.R. China; State Key Laboratory of Optometry, Ophthalmology, and Visual Science, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, P.R. China
| | - Yuhua Chang
- School of Optometry and Ophthalmolgy and the Eye Hospital, Wenzhou Medical University, P.R. China; State Key Laboratory of Optometry, Ophthalmology, and Visual Science, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, P.R. China
| | - Mengjuan Wu
- School of Optometry and Ophthalmolgy and the Eye Hospital, Wenzhou Medical University, P.R. China; State Key Laboratory of Optometry, Ophthalmology, and Visual Science, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, P.R. China
| | - Xiuli Kuang
- School of Optometry and Ophthalmolgy and the Eye Hospital, Wenzhou Medical University, P.R. China; State Key Laboratory of Optometry, Ophthalmology, and Visual Science, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, P.R. China
| | - Haiyan Jiang
- School of Optometry and Ophthalmolgy and the Eye Hospital, Wenzhou Medical University, P.R. China; State Key Laboratory of Optometry, Ophthalmology, and Visual Science, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, P.R. China
| | - Shengzhou Wu
- School of Optometry and Ophthalmolgy and the Eye Hospital, Wenzhou Medical University, P.R. China; State Key Laboratory of Optometry, Ophthalmology, and Visual Science, 270 Xueyuan Road, Wenzhou, Zhejiang 325003, P.R. China.
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Lockridge AD, Baumann DC, Akhaphong B, Abrenica A, Miller RF, Alejandro EU. Serine racemase is expressed in islets and contributes to the regulation of glucose homeostasis. Islets 2016; 8:195-206. [PMID: 27880078 PMCID: PMC5161142 DOI: 10.1080/19382014.2016.1260797] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
NMDA receptors (NMDARs) have recently been discovered as functional regulators of pancreatic β-cell insulin secretion. While these excitatory receptor channels have been extensively studied in the brain for their role in synaptic plasticity and development, little is known about how they work in β-cells. In neuronal cells, NMDAR activation requires the simultaneous binding of glutamate and a rate-limiting co-agonist, such as D-serine. D-serine levels and availability in most of the brain rely on endogenous synthesis by the enzyme serine racemase (Srr). Srr transcripts have been reported in human and mouse islets but it is not clear whether Srr is functionally expressed in β-cells or what its role in the pancreas might be. In this investigation, we reveal that Srr protein is highly expressed in primary human and mouse β-cells. Mice with whole body deletion of Srr (Srr KO) show improved glucose tolerance through enhanced insulin secretory capacity, possibly through Srr-mediated alterations in islet NMDAR expression and function. We observed elevated insulin sensitivity in some animals, suggesting Srr metabolic regulation in other peripheral organs as well. Srr expression in neonatal and embryonic islets, and adult deficits in Srr KO pancreas weight and islet insulin content, point toward a potential role for Srr in pancreatic development. These data reveal the first evidence that Srr may regulate glucose homeostasis in peripheral tissues and provide circumstantial evidence that D-serine may be an endogenous islet NMDAR co-agonist in β-cells.
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Affiliation(s)
| | - Daniel C. Baumann
- Department of Integrative Biology & Physiology, Minneapolis, MN, USA
| | - Brian Akhaphong
- Department of Integrative Biology & Physiology, Minneapolis, MN, USA
| | - Alleah Abrenica
- Department of Integrative Biology & Physiology, Minneapolis, MN, USA
| | - Robert F. Miller
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA
| | - Emilyn U. Alejandro
- Department of Integrative Biology & Physiology, Minneapolis, MN, USA
- CONTACT Emilyn U. Alejandro Department of Integrative Biology & Physiology, University of Minnesota, Minneapolis, MN, USA
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Poinsot V, Ong-Meang V, Gavard P, Couderc F. Recent advances in amino acid analysis by capillary electromigration methods, 2013-2015. Electrophoresis 2015; 37:142-61. [DOI: 10.1002/elps.201500302] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/19/2015] [Accepted: 08/19/2015] [Indexed: 12/17/2022]
Affiliation(s)
- Véréna Poinsot
- Université Paul Sabatier, Université de Toulouse, Laboratoire des IMRCP; Toulouse Cedex France
| | - Varravaddheay Ong-Meang
- Université Paul Sabatier, Université de Toulouse, Laboratoire des IMRCP; Toulouse Cedex France
| | - Pierre Gavard
- Université Paul Sabatier, Université de Toulouse, Laboratoire des IMRCP; Toulouse Cedex France
| | - François Couderc
- Université Paul Sabatier, Université de Toulouse, Laboratoire des IMRCP; Toulouse Cedex France
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Sánchez-López E, Marina ML, Crego AL. Improving the sensitivity in chiral capillary electrophoresis. Electrophoresis 2015; 37:19-34. [PMID: 26434566 DOI: 10.1002/elps.201500315] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 09/14/2015] [Accepted: 09/26/2015] [Indexed: 12/16/2022]
Abstract
CE is known for being one of the most powerful analytical techniques when performing enantioseparations due to its numerous advantages such as excellent separation efficiency and extremely low solvents and reagents consumption, all of them derived from the capillary small dimensions. Moreover, it is worth highlighting that unlike in chromatographic techniques, in CE the chiral selector is generally within the separation medium instead of being attached to the separation column which makes the method optimization a more versatile task. Despite its numerous advantages, when using UV-Vis detection, CE lacks of sensitivity detection due to its short optical path length derived from the narrow separation capillary. This issue can be overcome by means of different approaches, either by sample treatment procedures or by in-capillary preconcentration techniques or even by employing detection systems more sensitive than UV-Vis, such as LIF or MS. The present review assembles the latest contributions regarding improvements of sensitivity in chiral CE published from June 2013 until May 2015, which follows the works included in a previous review reported by Sánchez-Hernández et al. [Electrophoresis 2014, 35, 12-27].
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Affiliation(s)
- Elena Sánchez-López
- Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Faculty of Biology, Environmental Sciences and Chemistry, University of Alcalá, Alcalá de Henares, Madrid, Spain
| | - María Luisa Marina
- Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Faculty of Biology, Environmental Sciences and Chemistry, University of Alcalá, Alcalá de Henares, Madrid, Spain
| | - Antonio L Crego
- Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering, Faculty of Biology, Environmental Sciences and Chemistry, University of Alcalá, Alcalá de Henares, Madrid, Spain
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Li X, McCullum C, Zhao S, Hu H, Liu YM. D-serine uptake and release in PC-12 cells measured by chiral microchip electrophoresis-mass spectrometry. ACS Chem Neurosci 2015; 6:582-7. [PMID: 25611520 DOI: 10.1021/cn5003122] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Previous work has established that D-serine (D-Ser) plays important roles in certain neurological processes. Study on its uptake/storage and release by neuronal cells is highly significant for elucidating relevant mechanisms. In this work, PC-12 cells were incubated with racemic Ser (100 μM each enantiomer). After incubation, both intra- and extracellular levels of D-Ser and L-Ser were quantified by chiral microchip electrophoresis with mass spectrometric detection. It was found the cells preferably took up D-Ser over L-Ser. After 120 min incubation, D-Ser percentage ([D-Ser]/([D-Ser] + [L-Ser]) in the culture media changed from 50% to 9% while inside the cells it increased from 13% to 67%. Small neutral amino acids such as threonine impaired D-Ser uptake. Ser release was studied by using PC-12 cells preloaded with D-Ser. KCl, Glu, and Gly evoked Ser release. Interestingly, while depolarization by KCl evoked release of Ser as a D-Ser/L-Ser mixture of 1:1 ratio, the stereoisomeric composition of Ser released due to Glu exposure varied with the exposure time, ranging from 73% D-Ser (i.e., [D-Ser] > [L-Ser]) at 2 min to 44% (i.e., [D-Ser] < [L-Ser]) at 14 min, clearly indicating a stereochemical preference for D-Ser in Ser release from neuronal cells evoked by Glu-receptor activation.
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Affiliation(s)
- Xiangtang Li
- Department
of Chemistry and Biochemistry, Jackson State University, 1400 Lynch
Street, Jackson, Mississippi 39217, United States
| | - Cassandra McCullum
- Department
of Chemistry and Biochemistry, Jackson State University, 1400 Lynch
Street, Jackson, Mississippi 39217, United States
| | - Shulin Zhao
- Department
of Chemistry and Biochemistry, Jackson State University, 1400 Lynch
Street, Jackson, Mississippi 39217, United States
- College
of Chemistry and Chemical Engineering, Guangxi Normal University, Guilin 541004, China
| | - Hankun Hu
- Department
of Chemistry and Biochemistry, Jackson State University, 1400 Lynch
Street, Jackson, Mississippi 39217, United States
- Zhongnan
Hospital, Wuhan University, Wuhan 430071, China
| | - Yi-Ming Liu
- Department
of Chemistry and Biochemistry, Jackson State University, 1400 Lynch
Street, Jackson, Mississippi 39217, United States
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Identity of the NMDA receptor coagonist is synapse specific and developmentally regulated in the hippocampus. Proc Natl Acad Sci U S A 2014; 112:E204-13. [PMID: 25550512 DOI: 10.1073/pnas.1416668112] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
NMDA receptors (NMDARs) require the coagonists D-serine or glycine for their activation, but whether the identity of the coagonist could be synapse specific and developmentally regulated remains elusive. We therefore investigated the contribution of D-serine and glycine by recording NMDAR-mediated responses at hippocampal Schaffer collaterals (SC)-CA1 and medial perforant path-dentate gyrus (mPP-DG) synapses in juvenile and adult rats. Selective depletion of endogenous coagonists with enzymatic scavengers as well as pharmacological inhibition of endogenous D-amino acid oxidase activity revealed that D-serine is the preferred coagonist at SC-CA1 mature synapses, whereas, unexpectedly, glycine is mainly involved at mPP-DG synapses. Nevertheless, both coagonist functions are driven by the levels of synaptic activity as inferred by recording long-term potentiation generated at both connections. This regional compartmentalization in the coagonist identity is associated to different GluN1/GluN2A to GluN1/GluN2B subunit composition of synaptic NMDARs. During postnatal development, the replacement of GluN2B- by GluN2A-containing NMDARs at SC-CA1 synapses parallels a change in the identity of the coagonist from glycine to D-serine. In contrast, NMDARs subunit composition at mPP-DG synapses is not altered and glycine remains the main coagonist throughout postnatal development. Altogether, our observations disclose an unprecedented relationship in the identity of the coagonist not only with the GluN2 subunit composition at synaptic NMDARs but also with astrocyte activity in the developing and mature hippocampus that reconciles the complementary functions of D-serine And Glycine In Modulating Nmdars During The Maturation Of Tripartite Glutamatergic Synapses.
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