1
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Fontana ACK, Poli AN, Gour J, Srikanth YV, Anastasi N, Ashok D, Khatiwada A, Reeb KL, Cheng MH, Bahar I, Rawls SM, Salvino JM. Synthesis and Structure-Activity Relationships for Glutamate Transporter Allosteric Modulators. J Med Chem 2024; 67:6119-6143. [PMID: 38626917 PMCID: PMC11056993 DOI: 10.1021/acs.jmedchem.3c01909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Revised: 03/23/2024] [Accepted: 03/27/2024] [Indexed: 04/19/2024]
Abstract
Excitatory amino acid transporters (EAATs) are essential CNS proteins that regulate glutamate levels. Excess glutamate release and alteration in EAAT expression are associated with several CNS disorders. Previously, we identified positive allosteric modulators (PAM) of EAAT2, the main CNS transporter, and have demonstrated their neuroprotective properties in vitro. Herein, we report on the structure-activity relationships (SAR) for the analogs identified from virtual screening and from our medicinal chemistry campaign. This work identified several selective EAAT2 positive allosteric modulators (PAMs) such as compounds 4 (DA-023) and 40 (NA-014) from a library of analogs inspired by GT949, an early generation compound. This series also provides nonselective EAAT PAMs, EAAT inhibitors, and inactive compounds that may be useful for elucidating the mechanism of EAAT allosteric modulation.
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Affiliation(s)
- Andréia C. K. Fontana
- Department
of Pharmacology and Physiology, Drexel University
College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Adi N.R. Poli
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Jitendra Gour
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Yellamelli V.V. Srikanth
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Nicholas Anastasi
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Devipriya Ashok
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Apeksha Khatiwada
- Department
of Pharmacology and Physiology, Drexel University
College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Katelyn L. Reeb
- Department
of Pharmacology and Physiology, Drexel University
College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Mary Hongying Cheng
- Laufer
Center for Physical & Quantitative Biology, Stony Brook University, Stony
Brook, New York 11794, United States
| | - Ivet Bahar
- Department
of Biochemistry and Cell Biology, College of Arts & Sciences and
School of Medicine, Stony Brook University, Stony Brook, New York 11794, United States
- Laufer
Center for Physical & Quantitative Biology, Stony Brook University, Stony
Brook, New York 11794, United States
| | - Scott M. Rawls
- Center
for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, Pennsylvania 19140United States
| | - Joseph M. Salvino
- Medicinal
Chemistry, Molecular and Cellular Oncogenesis (MCO) Program, The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
- The
Wistar
Cancer Center Molecular Screening, The Wistar
Institute, Philadelphia, Pennsylvania 19104, United States
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2
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Thoreson WB, Chhunchha B. EAAT5 glutamate transporter rapidly binds glutamate with micromolar affinity in mouse rods. J Gen Physiol 2023; 155:e202313349. [PMID: 37477643 PMCID: PMC10359920 DOI: 10.1085/jgp.202313349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2023] [Revised: 04/17/2023] [Accepted: 07/05/2023] [Indexed: 07/22/2023] Open
Abstract
Light responses of rod photoreceptor cells in the retina are encoded by changes in synaptic glutamate release that is in turn shaped by reuptake involving EAAT5 plasma membrane glutamate transporters. Heterologously expressed EAAT5 activates too slowly upon glutamate binding to support significant uptake. We tested EAAT5 activation in mouse rods in vivo by stimulating glutamate transporter anion currents (IA(glu)) with UV flash photolysis of MNI-glutamate, varying flash intensity to vary glutamate levels. Responses to uncaging rose rapidly with time constants of 2-3 ms, similar to IA(glu) events arising from spontaneous release. Spontaneous release events and IA(glu) evoked by weak flashes also declined with similar time constants of 40-50 ms. Stronger flashes evoked responses that decayed more slowly. Time constants were twofold faster at 35°C, suggesting that they reflect transporter kinetics, not diffusion. Selective EAAT1 and EAAT2 inhibitors had no significant effect, suggesting IA(glu) in rods arises solely from EAAT5. We calibrated glutamate levels attained during flash photolysis by expressing a fluorescent glutamate sensor iGluSnFr in cultured epithelial cells. We compared fluorescence at different glutamate concentrations to fluorescence evoked by photolytic uncaging of MNI-glutamate. The relationship between flash intensity and glutamate yielded EC50 values for EAAT5 amplitude, decay time, and rise time of ∼10 μM. Micromolar affinity and rapid activation of EAAT5 in rods show it can rapidly bind synaptic glutamate. However, we also found that EAAT5 currents are saturated by the synchronous release of only a few vesicles, suggesting limited capacity and a role for glial uptake at higher release rates.
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Affiliation(s)
- Wallace B. Thoreson
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, Omaha, NE, USA
- Department of Pharmacology and Experimental Neuroscience, University of Nebraska Medical Center, Omaha, NE, USA
| | - Bhavana Chhunchha
- Department of Ophthalmology and Visual Sciences, Truhlsen Eye Institute, Omaha, NE, USA
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3
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Temmermand R, Barrett JE, Fontana ACK. Glutamatergic systems in neuropathic pain and emerging non-opioid therapies. Pharmacol Res 2022; 185:106492. [PMID: 36228868 PMCID: PMC10413816 DOI: 10.1016/j.phrs.2022.106492] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 10/05/2022] [Accepted: 10/06/2022] [Indexed: 01/14/2023]
Abstract
Neuropathic pain, a disease of the somatosensory nervous system, afflicts many individuals and adequate management with current pharmacotherapies remains elusive. The glutamatergic system of neurons, receptors and transporters are intimately involved in pain but, to date, there have been few drugs developed that therapeutically modulate this system. Glutamate transporters, or excitatory amino acid transporters (EAATs), remove excess glutamate around pain transmitting neurons to decrease nociception suggesting that the modulation of glutamate transporters may represent a novel approach to the treatment of pain. This review highlights and summarizes (1) the physiology of the glutamatergic system in neuropathic pain, (2) the preclinical evidence for dysregulation of glutamate transport in animal pain models, and (3) emerging novel therapies that modulate glutamate transporters. Successful drug discovery requires continuous focus on basic and translational methods to fully elucidate the etiologies of this disease to enable the development of targeted therapies. Increasing the efficacy of astrocytic EAATs may serve as a new way to successfully treat those suffering from this devastating disease.
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Affiliation(s)
- Rhea Temmermand
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, USA
| | - James E Barrett
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Philadelphia, PA 19140, USA
| | - Andréia C K Fontana
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, PA 19102, USA.
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4
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Tang FS, Yuan HL, Liu JB, Zhang G, Chen SY, Ke JB. Glutamate Transporters EAAT2 and EAAT5 Differentially Shape Synaptic Transmission from Rod Bipolar Cell Terminals. eNeuro 2022; 9:ENEURO.0074-22.2022. [PMID: 35523583 PMCID: PMC9121915 DOI: 10.1523/eneuro.0074-22.2022] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2022] [Revised: 04/26/2022] [Accepted: 05/02/2022] [Indexed: 11/21/2022] Open
Abstract
Excitatory amino acid transporters (EAATs) control visual signal transmission in the retina by rapidly removing glutamate released from photoreceptors and bipolar cells (BCs). Although it has been reported that EAAT2 and EAAT5 are expressed at presynaptic terminals of photoreceptors and some BCs in mammals, the distinct functions of these two glutamate transporters in retinal synaptic transmission, especially at a single synapse, remain elusive. In this study, we found that EAAT2 was expressed in all BC types while coexisting with EAAT5 in rod bipolar (RB) cells and several types of cone BCs from mice of either sex. Our immunohistochemical study, together with a recently published literature (Gehlen et al., 2021), showed that EAAT2 and EAAT5 were both located in RB axon terminals near release sites. Optogenetic, electrophysiological and pharmacological analyses, however, demonstrated that EAAT2 and EAAT5 regulated neurotransmission at RB→AII amacrine cell synapses in significantly different ways: EAAT5 dramatically affected both the peak amplitude and kinetics of postsynaptic responses in AIIs, whereas EAAT2 had either relatively small or opposite effects. By contrast, blockade of EAAT1/GLAST, which was exclusively expressed in Müller cells, showed no obvious effect on AII responses, indicating that glutamate uptake by Müller cells did not influence synaptic transmission from RB terminals. Furthermore, we found that temporal resolution at RB→AII synapses was reduced substantially by blockade of EAAT5 but not EAAT2. Taken together, our work reveals the distinct functions of EAAT2 and EAAT5 in signal transmission at RB ribbon synapses.
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Affiliation(s)
| | | | | | | | | | - Jiang-Bin Ke
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou 510060, China
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5
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Bukke VN, Archana M, Villani R, Romano AD, Wawrzyniak A, Balawender K, Orkisz S, Beggiato S, Serviddio G, Cassano T. The Dual Role of Glutamatergic Neurotransmission in Alzheimer's Disease: From Pathophysiology to Pharmacotherapy. Int J Mol Sci 2020; 21:ijms21207452. [PMID: 33050345 PMCID: PMC7589203 DOI: 10.3390/ijms21207452] [Citation(s) in RCA: 58] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2020] [Revised: 09/28/2020] [Accepted: 10/05/2020] [Indexed: 12/19/2022] Open
Abstract
Alzheimer's disease (AD) is an age-related dementia and neurodegenerative disorder, characterized by Aβ and tau protein deposition impairing learning, memory and suppressing synaptic plasticity of neurons. Increasing evidence suggests that there is a link between the glucose and glutamate alterations with age that down-regulates glucose utilization reducing glutamate levels in AD patients. Deviations in brain energy metabolism reinforce the development of AD by hampering glutamate levels in the brain. Glutamate is a nonessential amino acid and the major excitatory neurotransmitter synthesized from glucose. Alterations in cerebral glucose and glutamate levels precede the deposition of Aβ plaques. In the brain, over 40% of neuronal synapses are glutamatergic and disturbances in glutamatergic function have been implicated in pathophysiology of AD. Nevertheless, targeting the glutamatergic system seems to be a promising strategy to develop novel, improved therapeutics for AD. Here, we review data supporting the involvement of the glutamatergic system in AD pathophysiology as well as the efficacy of glutamatergic agents in this neurodegenerative disorder. We also discuss exciting new prospects for the development of improved therapeutics for this devastating disorder.
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Affiliation(s)
- Vidyasagar Naik Bukke
- Department of Clinical and Experimental Medicine, University of Foggia, 71122 Foggia, Italy;
| | - Moola Archana
- Department of Medical and Surgical Sciences, University of Foggia, 71122 Foggia, Italy; (M.A.); (R.V.); (A.D.R.); (G.S.)
| | - Rosanna Villani
- Department of Medical and Surgical Sciences, University of Foggia, 71122 Foggia, Italy; (M.A.); (R.V.); (A.D.R.); (G.S.)
| | - Antonino Davide Romano
- Department of Medical and Surgical Sciences, University of Foggia, 71122 Foggia, Italy; (M.A.); (R.V.); (A.D.R.); (G.S.)
| | - Agata Wawrzyniak
- Morphological Science Department of Human Anatomy, Medical Faculty University of Rzeszów, 35-310 Rzeszów, Poland; (A.W.); (K.B.); (S.O.)
| | - Krzysztof Balawender
- Morphological Science Department of Human Anatomy, Medical Faculty University of Rzeszów, 35-310 Rzeszów, Poland; (A.W.); (K.B.); (S.O.)
| | - Stanislaw Orkisz
- Morphological Science Department of Human Anatomy, Medical Faculty University of Rzeszów, 35-310 Rzeszów, Poland; (A.W.); (K.B.); (S.O.)
| | - Sarah Beggiato
- Department of Medical, Oral and Biotechnological Sciences, University of Chieti-Pescara, 66100 Chieti, Italy;
| | - Gaetano Serviddio
- Department of Medical and Surgical Sciences, University of Foggia, 71122 Foggia, Italy; (M.A.); (R.V.); (A.D.R.); (G.S.)
| | - Tommaso Cassano
- Department of Clinical and Experimental Medicine, University of Foggia, 71122 Foggia, Italy;
- Correspondence:
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6
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Forster YM, Green JL, Khatiwada A, Liberato JL, Narayana Reddy PA, Salvino JM, Bienz S, Bigler L, dos Santos WF, Karklin Fontana AC. Elucidation of the Structure and Synthesis of Neuroprotective Low Molecular Mass Components of the Parawixia bistriata Spider Venom. ACS Chem Neurosci 2020; 11:1573-1596. [PMID: 32343555 DOI: 10.1021/acschemneuro.0c00007] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The South American social spider Parawixia bistriata produces a venom containing complex organic compounds with intriguing biological activities. The crude venom leads to paralysis in termites and stimulates l-glutamate uptake and inhibits GABA uptake in rat brain synaptosomes. Glutamate is the major neurotransmitter at the insect neuromuscular junction and at the mammalian central nervous system, suggesting a modulation of the glutamatergic system by the venom. Parawixin1, 2, and 10 (Pwx1, 2 and 10) are HPLC fractions that demonstrate this bioactivity. Pwx1 stimulates l-glutamate uptake through the main transporter in the brain, EAAT2, and is neuroprotective in in vivo glaucoma models. Pxw2 inhibits GABA and glycine uptake in synaptosomes and inhibits seizures and neurodegeneration, and Pwx10 increases l-glutamate uptake in synaptosomes and is neuroprotective and anticonvulsant, shown in in vivo epilepsy models. Herein, we investigated the low molecular mass compounds in this venom and have found over 20 small compounds and 36 unique acylpolyamines with and without amino acid linkers. The active substances in fractions Pwx1 and Pwx2 require further investigation. We elucidated and confirmed the structure of the active acylpolyamine in Pwx10. Both fraction Pwx10 and the synthesized component enhance the activity of transporters EAAT1 and EAAT2, and, importantly, offer in vitro neuroprotection against excitotoxicity in primary cultures. These data suggest that compounds with this mechanism could be developed into therapies for disorders in which l-glutamate excitotoxicity is involved.
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Affiliation(s)
- Yvonne M. Forster
- Department of Chemistry, University of Zurich, Zurich, CH 8057, Switzerland
| | - Jennifer Leigh Green
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - Apeksha Khatiwada
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, United States
| | - José Luiz Liberato
- Department of Biology, University of São Paulo, Ribeirão Preto, SP 14040-900, Brazil
| | | | - Joseph M. Salvino
- The Wistar Institute, Philadelphia, Pennsylvania 19104, United States
| | - Stefan Bienz
- Department of Chemistry, University of Zurich, Zurich, CH 8057, Switzerland
| | - Laurent Bigler
- Department of Chemistry, University of Zurich, Zurich, CH 8057, Switzerland
| | | | - Andréia Cristina Karklin Fontana
- Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102, United States
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7
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Ingram NT, Sampath AP, Fain GL. Membrane conductances of mouse cone photoreceptors. J Gen Physiol 2020; 152:e201912520. [PMID: 31986199 PMCID: PMC7054858 DOI: 10.1085/jgp.201912520] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 12/20/2019] [Accepted: 12/20/2019] [Indexed: 12/19/2022] Open
Abstract
Vertebrate photoreceptor cells respond to light through a closure of CNG channels located in the outer segment. Multiple voltage-sensitive channels in the photoreceptor inner segment serve to transform and transmit the light-induced outer-segment current response. Despite extensive studies in lower vertebrates, we do not know how these channels produce the photoresponse of mammalian photoreceptors. Here we examined these ionic conductances recorded from single mouse cones in unlabeled, dark-adapted retinal slices. First, we show measurements of the voltage dependence of the light response. After block of voltage-gated Ca2+ channels, the light-dependent current was nearly linear within the physiological range of voltages with constant chord conductance and a reversal potential similar to that previously determined in lower vertebrate photoreceptors. At a dark resting membrane potential of -45 mV, cones maintain a standing Ca2+ current (iCa) between 15 and 20 pA. We characterized the time and voltage dependence of iCa and a calcium-activated anion channel. After constitutive closure of the CNG channels by the nonhydrolysable analogue GTP-γ-S, we observed a light-dependent increase in iCa followed by a Ca2+-activated K+ current, both probably the result of feedback from horizontal cells. We also recorded the hyperpolarization-activated cyclic nucleotide-gated (HCN) conductance (ih) and measured its current-voltage relationship and reversal potential. With small hyperpolarizations, ih activated with a time constant of 25 ms; activation was speeded with larger hyperpolarizations. Finally, we characterized two voltage-gated K+-conductances (iK). Depolarizing steps beginning at -10 mV activated a transient, outwardly rectifying iK blocked by 4-AP and insensitive to TEA. A sustained iK isolated through subtraction was blocked by TEA but was insensitive to 4-AP. The sustained iK had a nearly linear voltage dependence throughout the physiological voltage range of the cone. Together these data constitute the first comprehensive study of the channel conductances of mouse photoreceptors.
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Affiliation(s)
- Norianne T. Ingram
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, CA
| | - Alapakkam P. Sampath
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, CA
| | - Gordon L. Fain
- Department of Integrative Biology and Physiology, University of California, Los Angeles, CA
- Department of Ophthalmology and Jules Stein Eye Institute, University of California, Los Angeles, CA
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8
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Gao F, Yang Z, Jacoby RA, Wu SM, Pang JJ. The expression and function of TRPV4 channels in primate retinal ganglion cells and bipolar cells. Cell Death Dis 2019; 10:364. [PMID: 31064977 PMCID: PMC6504919 DOI: 10.1038/s41419-019-1576-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 03/25/2019] [Indexed: 12/26/2022]
Abstract
The transient receptor potential vanilloid 4 (TRPV4) channel may be opened by mechanical stimuli to mediate Ca2+ and Na+ influxes, and it has been suggested to mediate glaucoma retinopathy. However, it has been mostly unclear how TRPV4 activities affect the function of primate retinal ganglion cells (RGCs). We studied RGCs and bipolar cells (BCs) in the peripheral retina of the old-world primate using whole-cell current-clamp and voltage-clamp recordings, immunomarkers and confocal microscopy. RGCs were distinguished from displaced amacrine cells (ACs) by the absence of GABA and glycine immunoreactivity and possession of an axon and a large soma in the RGC layer. Strong TRPV4 signal was concentrated in medium to large somas of RGCs, and some TRPV4 signal was found in BCs (including PKCα-positive rod BCs), as well as the end feet, soma and outer processes of Mȕller cells. TRPV4 immunoreactivity quantified by the pixel intensity histogram revealed a high-intensity component for the plexiform layers, a low-intensity component for the soma layers of ACs and Mȕller cells, and both components in the soma layers of RGCs and BCs. In large RGCs, TRPV4 agonists 4α-phorbol 12,13 didecanoate (4αPDD) and GSK1016790A reversibly enhanced the spontaneous firing and shortened the delay of voltage-gated Na+ (Nav) currents under current-clamp conditions, and under voltage-clamp conditions, 4αPDD largely reversibly increased the amplitude and frequency of spontaneous excitatory postsynaptic currents. In BCs, changes in the membrane tension induced by either applying pressure or releasing the pressure both activated a transient cation current, which reversed at ~ -10 mV and was enhanced by heating from 24 °C to 30 °C. The pressure for the half-maximal effect was ~18 mmHg. These data indicate that functional TRPV4 channels are variably expressed in primate RGCs and BCs, possibly contributing to pressure-related changes in RGCs in glaucoma.
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Affiliation(s)
- Fan Gao
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA
| | - Zhuo Yang
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA
| | - Roy A Jacoby
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA
| | - Samuel M Wu
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA
| | - Ji-Jie Pang
- Department of Ophthalmology, Baylor College of Medicine, One Baylor Plaza, NC 205, Houston, TX, 77030, USA.
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9
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Gu Y, Lu J, Sun W, Jin R, Ohira T, Zhang Z, Tian X. Oxymatrine and its metabolite matrine contribute to the hepatotoxicity induced by radix Sophorae tonkinensis in mice. Exp Ther Med 2019; 17:2519-2528. [PMID: 30906440 PMCID: PMC6425122 DOI: 10.3892/etm.2019.7237] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 12/28/2018] [Indexed: 12/13/2022] Open
Abstract
Previous studies by our group demonstrated that radix Sophorae tonkinensis could induce hepatotoxicity. However, it remains unclear which components of this herb may be responsible for its hepatotoxicity. The present study aimed to investigate the hepatic toxicity of treatment with matrine (MT) and oxymatrine (OMT) alone or simultaneously. Furthermore, the current study aimed to identify whether the hepatotoxicity induced by OMT is actually the toxic characterization of its metabolite MT. Hepatotoxicity was evaluated by biochemical and histopathological approaches in subchronic toxicity in mice, as well as via evaluation of cytotoxicity and enzyme leakage in AML12 liver cells. The results indicated that treatment of mice with OMT and MT individually or simultaneously resulted in centrilobular hypertrophy in the liver at doses equivalent to that contained in radix S. tonkinensis at a hepatotoxic dose, suggesting that MT and OMT are likely hepatotoxic components of this herb. OMT-induced hepatotoxicity may be primarily exerted via its metabolite MT in mice. Furthermore, OMT combined with MT was observed to be more toxic compared with OMT or MT alone. These results extend our understanding of the hepatotoxicity of radix S. tonkinensis and its active ingredients.
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Affiliation(s)
- Yingmin Gu
- Center for Drug Safety Evaluation and Research, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China.,Center for Laboratory Animals, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China
| | - Jinyao Lu
- Center for Drug Safety Evaluation and Research, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China.,Center for Laboratory Animals, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China
| | - Wei Sun
- Center for Drug Safety Evaluation and Research, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China.,Center for Laboratory Animals, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China
| | - Ruomin Jin
- Center for Drug Safety Evaluation and Research, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China.,Center for Laboratory Animals, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China
| | - Toko Ohira
- Shanghai Innostar Biotech Co., Ltd., China National Shanghai Center for New Drug Safety Evaluation and Research, Shanghai 201203, P.R. China
| | - Zean Zhang
- Center for Drug Safety Evaluation and Research, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China.,Center for Laboratory Animals, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China
| | - Xuesong Tian
- Center for Drug Safety Evaluation and Research, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China.,Center for Laboratory Animals, Shanghai University of Traditional Chinese Medicine, Shanghai 201203, P.R. China
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10
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Corbetta C, Di Ianni N, Bruzzone MG, Patanè M, Pollo B, Cantini G, Cominelli M, Zucca I, Pisati F, Poliani PL, Finocchiaro G, Pellegatta S. Altered function of the glutamate–aspartate transporter GLAST, a potential therapeutic target in glioblastoma. Int J Cancer 2019; 144:2539-2554. [DOI: 10.1002/ijc.31985] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2018] [Revised: 10/17/2018] [Accepted: 10/31/2018] [Indexed: 01/07/2023]
Affiliation(s)
- Cristina Corbetta
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Natalia Di Ianni
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Maria Grazia Bruzzone
- Experimental Imaging and Neuro‐RadiologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Monica Patanè
- Unit of PathologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Bianca Pollo
- Unit of PathologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Gabriele Cantini
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | | | - Ileana Zucca
- Experimental Imaging and Neuro‐RadiologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Federica Pisati
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | | | - Gaetano Finocchiaro
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
| | - Serena Pellegatta
- Unit of Molecular Neuro‐OncologyFondazione IRCCS Istituto Neurologico Carlo Besta Milan Italy
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11
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Pérez-Mato M, Iglesias-Rey R, Vieites-Prado A, Dopico-López A, Argibay B, Fernández-Susavila H, da Silva-Candal A, Pérez-Díaz A, Correa-Paz C, Günther A, Ávila-Gómez P, Isabel Loza M, Baumann A, Castillo J, Sobrino T, Campos F. Blood glutamate EAAT 2-cell grabbing therapy in cerebral ischemia. EBioMedicine 2018; 39:118-131. [PMID: 30555045 PMCID: PMC6354443 DOI: 10.1016/j.ebiom.2018.11.024] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Revised: 11/13/2018] [Accepted: 11/13/2018] [Indexed: 01/10/2023] Open
Abstract
Background Excitatory amino acid transporter 2 (EAAT2) plays a pivotal role in glutamate clearance in the adult brain, thereby preventing excitotoxic effects. Considering the high efficacy of EAAT2 for glutamate uptake, we hypothesized that the expression of this transporter in mesenchymal stem cells (MSCs) for systemic administration could yield a cell-based glutamate-grabbing therapy, combining the intrinsic properties of these cells with excitotoxic protection. Methods To address this hypothesis, EAAT2-encoding cDNA was introduced into MSCs and human embryonic kidney 293 cells (HEK cells) as the control cell line. EAAT2 expression and functionality were evaluated by in vitro assays. Blood glutamate-grabbing activity was tested in healthy and ischemic rat models treated with 3 × 106 and 9 × 106 cells/animal. Findings The expression of EAAT2 in both cell types conferred the expected glutamate-grabbing activity in in vitro and in vivo studies. The functional improvement observed in ischemic rats treated with EAAT2–HEK at low dose, confirmed that this effect was indeed mediated by the glutamate-grabbing activity associated with EAAT2 functionality. Unexpectedly, both cell doses of non-transfected MSCs induced higher protection than transfected EAAT2–MSCs by another mechanism independent of the glutamate-grabbing capacity. Interpretation Although the transfection procedure most likely interferes with some of the intrinsic protective mechanisms of mesenchymal cells, the results show that the induced expression of EAAT2 in cells represents a novel alternative to mitigate the excitotoxic effects of glutamate and paves the way to combine this strategy with current cell therapies for cerebral ischemia.
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Affiliation(s)
- María Pérez-Mato
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - Ramón Iglesias-Rey
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - Alba Vieites-Prado
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - Antonio Dopico-López
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - Bárbara Argibay
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - Héctor Fernández-Susavila
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - Andrés da Silva-Candal
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - Amparo Pérez-Díaz
- Drug Screening Platform/Biofarma Research Group, Centro Singular de Investigación en Medicina Molecular y Enfermedades Crónicas (CIMUS), Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Clara Correa-Paz
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - Anne Günther
- Institute of Complex Systems-Cellular Biophysics (ICS-4), Forschungszentrum Jülich, Jülich, Germany
| | - Paulo Ávila-Gómez
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - M Isabel Loza
- Drug Screening Platform/Biofarma Research Group, Centro Singular de Investigación en Medicina Molecular y Enfermedades Crónicas (CIMUS), Universidade de Santiago de Compostela, Santiago de Compostela, Spain
| | - Arnd Baumann
- Institute of Complex Systems-Cellular Biophysics (ICS-4), Forschungszentrum Jülich, Jülich, Germany
| | - José Castillo
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain
| | - Tomás Sobrino
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain.
| | - Francisco Campos
- Clinical Neurosciences Research Laboratory (LINC), Department of Neurology, Health Research Institute of Santiago de Compostela (IDIS), Clinical University Hospital, Santiago de Compostela, Spain.
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Rose CR, Felix L, Zeug A, Dietrich D, Reiner A, Henneberger C. Astroglial Glutamate Signaling and Uptake in the Hippocampus. Front Mol Neurosci 2018; 10:451. [PMID: 29386994 PMCID: PMC5776105 DOI: 10.3389/fnmol.2017.00451] [Citation(s) in RCA: 125] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 12/22/2017] [Indexed: 12/22/2022] Open
Abstract
Astrocytes have long been regarded as essentially unexcitable cells that do not contribute to active signaling and information processing in the brain. Contrary to this classical view, it is now firmly established that astrocytes can specifically respond to glutamate released from neurons. Astrocyte glutamate signaling is initiated upon binding of glutamate to ionotropic and/or metabotropic receptors, which can result in calcium signaling, a major form of glial excitability. Release of so-called gliotransmitters like glutamate, ATP and D-serine from astrocytes in response to activation of glutamate receptors has been demonstrated to modulate various aspects of neuronal function in the hippocampus. In addition to receptors, glutamate binds to high-affinity, sodium-dependent transporters, which results in rapid buffering of synaptically-released glutamate, followed by its removal from the synaptic cleft through uptake into astrocytes. The degree to which astrocytes modulate and control extracellular glutamate levels through glutamate transporters depends on their expression levels and on the ionic driving forces that decrease with ongoing activity. Another major determinant of astrocytic control of glutamate levels could be the precise morphological arrangement of fine perisynaptic processes close to synapses, defining the diffusional distance for glutamate, and the spatial proximity of transporters in relation to the synaptic cleft. In this review, we will present an overview of the mechanisms and physiological role of glutamate-induced ion signaling in astrocytes in the hippocampus as mediated by receptors and transporters. Moreover, we will discuss the relevance of astroglial glutamate uptake for extracellular glutamate homeostasis, focusing on how activity-induced dynamic changes of perisynaptic processes could shape synaptic transmission at glutamatergic synapses.
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Affiliation(s)
- Christine R Rose
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Lisa Felix
- Institute of Neurobiology, Faculty of Mathematics and Natural Sciences, Heinrich Heine University Duesseldorf, Duesseldorf, Germany
| | - Andre Zeug
- Cellular Neurophysiology, Hannover Medical School, Hannover, Germany
| | - Dirk Dietrich
- Department of Neurosurgery, University of Bonn Medical School, Bonn, Germany
| | - Andreas Reiner
- Cellular Neurobiology, Faculty of Biology and Biotechnology, Ruhr University Bochum, Bochum, Germany
| | - Christian Henneberger
- Institute of Cellular Neurosciences, University of Bonn Medical School, Bonn, Germany.,German Center for Degenerative Diseases (DZNE), Bonn, Germany.,Institute of Neurology, University College London, London, United Kingdom
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Dai J, Fu Y, Zeng Y, Li S, Qin Yin Z. Improved retinal function in RCS rats after suppressing the over-activation of mGluR5. Sci Rep 2017; 7:3546. [PMID: 28615682 PMCID: PMC5471183 DOI: 10.1038/s41598-017-03702-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2017] [Accepted: 05/03/2017] [Indexed: 01/09/2023] Open
Abstract
Müller cells maintain retinal synaptic homeostasis by taking up glutamate from the synaptic cleft and transporting glutamine back to the neurons. To study the interaction between Müller cells and photoreceptors, we injected either DL-α-aminoadipate or L-methionine sulfoximine–both inhibitors of glutamine synthetase–subretinally in rats. Following injection, the a-wave of the electroretinogram (ERG) was attenuated, and metabotropic glutamate receptor 5 (mGluR5) was activated. Selective antagonism of mGluR5 by 2-methyl-6-(phenylethynyl)-pyridine increased the ERG a-wave amplitude and also increased rhodopsin expression. Conversely, activation of mGluR5 by the agonist, (R,S)-2-chloro-5-hydroxyphenylglycine, decreased both the a-wave amplitude and rhodopsin expression, but upregulated expression of Gq alpha subunit and phospholipase C βIII. Overexpression of mGluR5 reduced the inward-rectifying potassium ion channel (Kir) current and decreased the expression of Kir4.1 and aquaporin-4 (AQP4). Further experiments indicated that mGluR5 formed a macromolecular complex with these two membrane channels. Lastly, increased expression of mGluR5 was found in Royal College of Surgeons rats–a model of retinitis pigmentosa (RP). Inhibition of mGluR5 in this model restored the amplitude of ERG features, and reduced the expression of glial fibrillary acidic protein. These results suggest that mGluR5 may be worth considering as a potential therapeutic target in RP.
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Affiliation(s)
- Jiaman Dai
- Bioengineering College, Chongqing University, Chongqing, 400040, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China
| | - Yan Fu
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University, Chongqing, 400038, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China
| | - Yuxiao Zeng
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University, Chongqing, 400038, China.,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China
| | - Shiying Li
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University, Chongqing, 400038, China. .,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China.
| | - Zheng Qin Yin
- Bioengineering College, Chongqing University, Chongqing, 400040, China. .,Southwest Hospital/Southwest Eye Hospital, Third Military Medical University, Chongqing, 400038, China. .,Key Lab of Visual Damage and Regeneration & Restoration of Chongqing, Chongqing, 400038, China.
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Shaping of Signal Transmission at the Photoreceptor Synapse by EAAT2 Glutamate Transporters. eNeuro 2017; 4:eN-NWR-0339-16. [PMID: 28612046 PMCID: PMC5467398 DOI: 10.1523/eneuro.0339-16.2017] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 05/12/2017] [Accepted: 05/25/2017] [Indexed: 12/30/2022] Open
Abstract
Photoreceptor ribbon synapses tonically release glutamate. To ensure efficient signal transmission and prevent glutamate toxicity, a highly efficient glutamate removal system provided by members of the SLC1 gene family is required. By using a combination of biophysical and in vivo studies, we elucidate the role of excitatory amino acid transporter 2 (EAAT2) proteins in synaptic glutamate homeostasis at the zebrafish photoreceptor synapse. The main glutamate sink is provided by the glial EAAT2a, reflected by reduced electroretinographic responses in EAAT2a-depleted larvae. EAAT2b is located on the tips of cone pedicles and contributes little to glutamate reuptake. However, this transporter displays both a large chloride conductance and leak current, being important in stabilizing the cone resting potential. This work demonstrates not only how proteins originating from the same gene family can complement each other’s expression profiles and biophysical properties, but also how presynaptic and glial transporters are coordinated to ensure efficient synaptic transmission at glutamatergic synapses of the central nervous system.
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15
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Ledolter AA, Holder GE, Ristl R, Schmidt-Erfurth U, Ritter M. Electrophysiological findings show generalised post-photoreceptoral deficiency in macular telangiectasia type 2. Br J Ophthalmol 2017; 102:114-119. [PMID: 28592417 DOI: 10.1136/bjophthalmol-2017-310228] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2017] [Revised: 04/18/2017] [Accepted: 04/23/2017] [Indexed: 11/04/2022]
Abstract
BACKGROUND Photoreceptor damage, reported in single observations, has been suggested to contribute to the disease pathogenesis in macular telangiectasia type 2 (MacTel2). The purpose of this study was to ascertain whether the photoreceptor or post-photoreceptoral function is affected in MacTel2 and could be detected using electrophysiological examination. METHODS Thirty-five eyes from 18 patients (15 men, aged 60.1±9.6 years, range 38-77 years) with MacTel2 were included in the study. All patients underwent standard ophthalmic examination followed by pattern electroretinography (PERG) and full-field ERG. The data were compared against 22 normal control subjects (10 men, age 59.83±6.28 years, range 48-76). RESULTS Mean PERG P50 amplitude and peak time in patients with MacTel2 did not differ significantly from control values (p>0.2) but P50 amplitude was subnormal in three patients. The mean scotopic rod b-wave amplitude was significantly lower in patients than in healthy controls (p=0.027). A lower dark-adapted 10.0 b-wave (p=0.06) but not a-wave amplitude (p=0.58) was present in patients with MacTel2. Photopic single-flash a-wave and b-wave amplitudes did not differ between patient and control groups (p=0.2 and 0.3), but 30 Hz flicker peak time was significantly later in patients with MacTel2 with no effect on amplitude (p=0.04 and 0.7). CONCLUSION Both scotopic (rod system dominated) and photopic ERGs (cone system) are consistent with post-photoreceptoral dysfunction. There was no electrophysiological evidence of dysfunction at the level of the photoreceptor.
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Affiliation(s)
- Anna A Ledolter
- Department of Ophthalmology, Medical University of Vienna, Vienna, Austria
| | - Graham E Holder
- Institute of Ophthalmology, University College London, Moorfields Eye Hospital, London, UK
| | - Robin Ristl
- Section for Medical Statistics, Center for Medical Statistics and Informatics, Medical University of Vienna, Vienna, Austria
| | | | - Markus Ritter
- Department of Ophthalmology, Medical University of Vienna, Vienna, Austria
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Jerath R, Cearley SM, Barnes VA, Nixon-Shapiro E. How lateral inhibition and fast retinogeniculo-cortical oscillations create vision: A new hypothesis. Med Hypotheses 2016; 96:20-29. [PMID: 27959269 DOI: 10.1016/j.mehy.2016.09.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 08/23/2016] [Accepted: 09/21/2016] [Indexed: 12/12/2022]
Abstract
The role of the physiological processes involved in human vision escapes clarification in current literature. Many unanswered questions about vision include: 1) whether there is more to lateral inhibition than previously proposed, 2) the role of the discs in rods and cones, 3) how inverted images on the retina are converted to erect images for visual perception, 4) what portion of the image formed on the retina is actually processed in the brain, 5) the reason we have an after-image with antagonistic colors, and 6) how we remember space. This theoretical article attempts to clarify some of the physiological processes involved with human vision. The global integration of visual information is conceptual; therefore, we include illustrations to present our theory. Universally, the eyeball is 2.4cm and works together with membrane potential, correspondingly representing the retinal layers, photoreceptors, and cortex. Images formed within the photoreceptors must first be converted into chemical signals on the photoreceptors' individual discs and the signals at each disc are transduced from light photons into electrical signals. We contend that the discs code the electrical signals into accurate distances and are shown in our figures. The pre-existing oscillations among the various cortices including the striate and parietal cortex, and the retina work in unison to create an infrastructure of visual space that functionally "places" the objects within this "neural" space. The horizontal layers integrate all discs accurately to create a retina that is pre-coded for distance. Our theory suggests image inversion never takes place on the retina, but rather images fall onto the retina as compressed and coiled, then amplified through lateral inhibition through intensification and amplification on the OFF-center cones. The intensified and amplified images are decompressed and expanded in the brain, which become the images we perceive as external vision. SUMMARY This is a theoretical article presenting a novel hypothesis about the physiological processes in vision, and expounds upon the visual aspect of two of our previously published articles, "A unified 3D default space consciousness model combining neurological and physiological processes that underlie conscious experience", and "Functional representation of vision within the mind: A visual consciousness model based in 3D default space." Currently, neuroscience teaches that visual images are initially inverted on the retina, processed in the brain, and then conscious perception of vision happens in the visual cortex. Here, we propose that inversion of visual images never takes place because images enter the retina as coiled and compressed graded potentials that are intensified and amplified in OFF-center photoreceptors. Once they reach the brain, they are decompressed and expanded to the original size of the image, which is perceived by the brain as the external image. We adduce that pre-existing oscillations (alpha, beta, and gamma) among the various cortices in the brain (including the striate and parietal cortex) and the retina, work together in unison to create an infrastructure of visual space thatfunctionally "places" the objects within a "neural" space. These fast oscillations "bring" the faculties of the cortical activity to the retina, creating the infrastructure of the space within the eye where visual information can be immediately recognized by the brain. By this we mean that the visual (striate) cortex synchronizes the information with the photoreceptors in the retina, and the brain instantaneously receives the already processed visual image, thereby relinquishing the eye from being required to send the information to the brain to be interpreted before it can rise to consciousness. The visual system is a heavily studied area of neuroscience yet very little is known about how vision occurs. We believe that our novel hypothesis provides new insights into how vision becomes part of consciousness, helps to reconcile various previously proposed models, and further elucidates current questions in vision based on our unified 3D default space model. Illustrations are provided to aid in explaining our theory.
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Binda NS, Carayon CPP, Agostini RM, Pinheiro ACDN, Cordeiro MN, Silva MAR, Silva JF, Pereira EMR, da Silva Junior CA, de Castro Junior CJ, Guimarães ALS, Gomez MV. PhTx3-4, a Spider Toxin Calcium Channel Blocker, Reduces NMDA-Induced Injury of the Retina. Toxins (Basel) 2016; 8:toxins8030070. [PMID: 26978403 PMCID: PMC4810215 DOI: 10.3390/toxins8030070] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Revised: 01/26/2016] [Accepted: 03/01/2016] [Indexed: 11/16/2022] Open
Abstract
The in vivo neuroprotective effect of PhTx3-4, a spider toxin N-P/Q calcium channel blocker, was studied in a rat model of NMDA-induced injury of the retina. NMDA (N-Methyl-d-Aspartate)-induced retinal injury in rats reduced the b-wave amplitude by 62% ± 3.6%, indicating the severity of the insult. PhTx3-4 treatment increased the amplitude of the b-wave, which was almost equivalent to the control retinas that were not submitted to injury. The PhTx3-4 functional protection of the retinas recorded on the ERG also was observed in the neuroprotection of retinal cells. NMDA-induced injury reduced live cells in the retina layers and the highest reduction, 84%, was in the ganglion cell layer. Notably, PhTx3-4 treatment caused a remarkable reduction of dead cells in the retina layers, and the highest neuroprotective effect was in the ganglion cells layer. NMDA-induced cytotoxicity of the retina increased the release of glutamate, reactive oxygen species (ROS) production and oxidative stress. PhTx3-4 treatment reduced glutamate release, ROS production and oxidative stress measured by malondialdehyde. Thus, we presented for the first time evidence of in vivo neuroprotection from NMDA-induced retinal injury by PhTx3-4 (-ctenitoxin-Pn3a), a spider toxin that blocks N-P/Q calcium channels.
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Affiliation(s)
- Nancy Scardua Binda
- Institute of Education and Research Santa Casa Belo Horizonte-Laboratory of Toxins, Rua Domingos Vieira 590, Belo Horizonte, Minas Gerais 30150-240, Brazil.
| | - Charles Porto Petruceli Carayon
- Institute of Education and Research Santa Casa Belo Horizonte-Laboratory of Toxins, Rua Domingos Vieira 590, Belo Horizonte, Minas Gerais 30150-240, Brazil.
| | - Rafael Mourão Agostini
- Institute of Education and Research Santa Casa Belo Horizonte-Laboratory of Toxins, Rua Domingos Vieira 590, Belo Horizonte, Minas Gerais 30150-240, Brazil.
| | - Ana Cristina do Nascimento Pinheiro
- Institute of Education and Research Santa Casa Belo Horizonte-Laboratory of Toxins, Rua Domingos Vieira 590, Belo Horizonte, Minas Gerais 30150-240, Brazil.
| | - Marta Nascimento Cordeiro
- Ezequiel Dias Foundation (FUNED), Laboratory of Biochemistry, Rua Conde Pereira Carneiro 80, Belo Horizonte, Minas Gerais 30510-010, Brazil.
| | - Marco Aurélio Romano Silva
- Faculty of Medicine, Minas Gerais Federal University, Neuroscience Laboratory, Av. Alfredo Balena 190, Belo Horizonte, Minas Gerais 30130-100, Brazil.
| | - Juliana Figueira Silva
- Institute of Education and Research Santa Casa Belo Horizonte-Laboratory of Toxins, Rua Domingos Vieira 590, Belo Horizonte, Minas Gerais 30150-240, Brazil.
| | - Elizete Maria Rita Pereira
- Institute of Education and Research Santa Casa Belo Horizonte-Laboratory of Toxins, Rua Domingos Vieira 590, Belo Horizonte, Minas Gerais 30150-240, Brazil.
| | - Claudio Antonio da Silva Junior
- Institute of Education and Research Santa Casa Belo Horizonte-Laboratory of Toxins, Rua Domingos Vieira 590, Belo Horizonte, Minas Gerais 30150-240, Brazil.
| | - Célio José de Castro Junior
- Institute of Education and Research Santa Casa Belo Horizonte-Laboratory of Toxins, Rua Domingos Vieira 590, Belo Horizonte, Minas Gerais 30150-240, Brazil.
| | - Andre Luiz Sena Guimarães
- Department of Dentistry, Montes Claros State University, University Hospital, Health Laboratory Research, Montes Claros, Montes Claros, Minas Gerais 39401-001, Brazil.
| | - Marcus Vinicius Gomez
- Institute of Education and Research Santa Casa Belo Horizonte-Laboratory of Toxins, Rua Domingos Vieira 590, Belo Horizonte, Minas Gerais 30150-240, Brazil.
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RIM1/2-Mediated Facilitation of Cav1.4 Channel Opening Is Required for Ca2+-Stimulated Release in Mouse Rod Photoreceptors. J Neurosci 2015; 35:13133-47. [PMID: 26400943 DOI: 10.1523/jneurosci.0658-15.2015] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Night blindness can result from impaired photoreceptor function and a subset of cases have been linked to dysfunction of Cav1.4 calcium channels and in turn compromised synaptic transmission. Here, we show that active zone proteins RIM1/2 are important regulators of Cav1.4 channel function in mouse rod photoreceptors and thus synaptic activity. The conditional double knock-out (cdko) of RIM1 and RIM2 from rods starting a few weeks after birth did not change Cav1.4 protein expression at rod ribbon synapses nor was the morphology of the ribbon altered. Heterologous overexpression of RIM2 with Cav1.4 had no significant influence on current density when examined with BaCl2 as the charge carrier. Nonetheless, whole-cell voltage-clamp recordings from cdko rods revealed a profound reduction in Ca(2+) currents. Concomitantly, we observed a 4-fold reduction in spontaneous miniature release events from the cdko rod terminals and an almost complete absence of evoked responses when monitoring changes in membrane incorporation after strong step depolarizations. Under control conditions, 49 and 83 vesicles were released with 0.2 and 1 s depolarizations, respectively, which is close to the maximal number of vesicles estimated to be docked at the base of the ribbon active zone, but without RIM1/2, only a few vesicles were stimulated for release after a 1 s stimulation. In conclusion, our study shows that RIM1/2 potently enhance the influx of Ca(2+) into rod terminals through Cav1.4 channels, which is vitally important for the release of vesicles from the rod ribbon. Significance statement: Active zone scaffolding proteins are thought to bring multiple components involved in Ca(2+)-dependent exocytosis into functional interactions. We show that removal of scaffolding proteins RIM1/2 from rod photoreceptor ribbon synapses causes a dramatic loss of Ca(2+) influx through Cav1.4 channels and a correlated reduction in evoked release, yet the channels remain localized to synaptic ribbons in a normal fashion. Our findings strongly argue that RIM1/2 facilitate Ca(2+) entry and in turn Ca(2+) evoked release by modulating Cav1.4 channel openings; however, RIM1/2 are not needed for the retention of Cav1.4 at the synapse. In summary, a key function of RIM1/2 at rod ribbons is to enhance Cav1.4 channel activity, possibly through direct or indirect modulation of the channel.
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