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Sharpe AL, Liter LR, Donohue D, Carter KA, Vangeneugden P, Weaver S, Stout MB, Beckstead MJ. Aged mice exhibit faster acquisition of intravenous opioid self-administration with variable effects on intake. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.03.611052. [PMID: 39282417 PMCID: PMC11398421 DOI: 10.1101/2024.09.03.611052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 09/20/2024]
Abstract
Although opioid abuse is more prevalent in young individuals, opioid use, overdose, and use disorders continue to climb at a rapid rate among the elderly. Little is known about abuse potential in a healthy aged population, in part due to technical and logistical difficulties testing intravenous self-administration in aged rodents. The goal of this study was to address the critical gap in the literature regarding age-dependent differences in opioid (remifentanil and fentanyl) self-administration between old and young mice. Male and female mice were grouped into young (mean: 19 weeks) and old (mean: 101 weeks), and were trained to self-administer intravenous fentanyl or remifentanil in daily sessions. In both old and young mice, acquisition, intake, and cue-responding after forced abstinence were measured for both drugs, and a dose-response curve (remifentanil) and dose-escalation (fentanyl) were conducted. Surprisingly, old mice learned to self-administer both remifentanil and fentanyl faster and more accurately than young mice. Baseline intake of remifentanil was also substantially greater in old mice compared to their young counterparts; however, we did not see increased intake of fentanyl with age at either dose tested. Further, compared to young mice, the old mice showed a greater incubation of responding for cues previously associated with remifentanil after a forced abstinence, but again this was not observed with fentanyl. Together these data suggest that an aged population may have an increased drug-abuse vulnerability for opioids compared to young counterparts and underscore the importance of future work on mechanisms responsible for this increased vulnerability.
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Affiliation(s)
- Amanda L Sharpe
- Department of Pharmaceutical Sciences, University of Oklahoma Health Sciences
| | - Laci R Liter
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation; Graduate Program in Biomedical Sciences, University of Oklahoma Health Sciences
| | - Darius Donohue
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation
| | - Kelsey A Carter
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation
| | | | - Sofia Weaver
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation
| | - Michael B Stout
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation
| | - Michael J Beckstead
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation; Oklahoma City Veterans Affairs Medical Center, Oklahoma City, OK, USA
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2
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Blankenship HE, Carter KA, Cassidy NT, Markiewicz AN, Thellmann MI, Sharpe AL, Freeman WM, Beckstead MJ. VTA dopamine neurons are hyperexcitable in 3xTg-AD mice due to casein kinase 2-dependent SK channel dysfunction. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.16.567486. [PMID: 38014232 PMCID: PMC10680865 DOI: 10.1101/2023.11.16.567486] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
Alzheimer's disease (AD) patients exhibit neuropsychiatric symptoms that extend beyond classical cognitive deficits, suggesting involvement of subcortical areas. Here, we investigated the role of midbrain dopamine (DA) neurons in AD using the amyloid + tau-driven 3xTg-AD mouse model. We found deficits in reward-based operant learning in AD mice, suggesting possible VTA DA neuron dysregulation. Physiological assessment revealed hyperexcitability and disrupted firing in DA neurons caused by reduced activity of small-conductance calcium-activated potassium (SK) channels. RNA sequencing from contents of single patch-clamped DA neurons (Patch-seq) identified up-regulation of the SK channel modulator casein kinase 2 (CK2). Pharmacological inhibition of CK2 restored SK channel activity and normal firing patterns in 3xTg-AD mice. These findings shed light on a complex interplay between neuropsychiatric symptoms and subcortical circuits in AD, paving the way for novel treatment strategies.
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Wüllner U, Borghammer P, Choe CU, Csoti I, Falkenburger B, Gasser T, Lingor P, Riederer P. The heterogeneity of Parkinson's disease. J Neural Transm (Vienna) 2023; 130:827-838. [PMID: 37169935 PMCID: PMC10174621 DOI: 10.1007/s00702-023-02635-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2023] [Accepted: 04/12/2023] [Indexed: 05/13/2023]
Abstract
The heterogeneity of Parkinson's disease (PD), i.e. the various clinical phenotypes, pathological findings, genetic predispositions and probably also the various implicated pathophysiological pathways pose a major challenge for future research projects and therapeutic trail design. We outline several pathophysiological concepts, pathways and mechanisms, including the presumed roles of α-synuclein misfolding and aggregation, Lewy bodies, oxidative stress, iron and melanin, deficient autophagy processes, insulin and incretin signaling, T-cell autoimmunity, the gut-brain axis and the evidence that microbial (viral) agents may induce molecular hallmarks of neurodegeneration. The hypothesis is discussed, whether PD might indeed be triggered by exogenous (infectious) agents in susceptible individuals upon entry via the olfactory bulb (brain first) or the gut (body-first), which would support the idea that disease mechanisms may change over time. The unresolved heterogeneity of PD may have contributed to the failure of past clinical trials, which attempted to slow the course of PD. We thus conclude that PD patients need personalized therapeutic approaches tailored to specific phenomenological and etiologic subtypes of disease.
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Affiliation(s)
- Ullrich Wüllner
- Department of Neurology, University Clinic Bonn and German Center for Neurodegenerative Diseases (DZNE), 53127 Bonn, Germany
| | - Per Borghammer
- Department of Nuclear Medicine and PET, Aarhus University Hospital, Aarhus, Denmark
| | - Chi-un Choe
- Department of Neurology, Klinikum Itzehoe, Robert-Koch-Straße 2, 25524 Itzehoe, Germany
| | - Ilona Csoti
- Fachklinik Für Parkinson, Gertrudis Klinik Biskirchen, Karl-Ferdinand-Broll-Straße 2-4, 35638 Leun-Biskirchen, Germany
| | - Björn Falkenburger
- Department of Neurology, University Hospital Dresden, Fetscherstrasse 74, 01307 Dresden, Germany
| | - Thomas Gasser
- Department of Neurology, Hertie-Institute for Clinical Brain Research, University of Tübingen and German Center for Neurodegenerative Diseases (DZNE), Tübingen, Germany
| | - Paul Lingor
- Department of Neurology, School of Medicine, Klinikum Rechts Der Isar, Technical University of Munich, Munich, Germany
- Department of Neurology and German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Peter Riederer
- University Hospital Wuerzburg, Clinic and Policlinic for Psychiatry, Psychosomatics and Psychotherapy, Margarete-Höppel-Platz 1, 97080 Würzburg, Germany
- Department of Psychiatry, University of Southern Denmark Odense, J.B. Winslows Vey 18, 5000 Odense, Denmark
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4
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Dominguez-Lopez S, Ahn B, Sataranatarajan K, Ranjit R, Premkumar P, Van Remmen H, Beckstead MJ. Long-term methamphetamine self-administration increases mesolimbic mitochondrial oxygen consumption and decreases striatal glutathione. Neuropharmacology 2023; 227:109436. [PMID: 36693561 PMCID: PMC10080784 DOI: 10.1016/j.neuropharm.2023.109436] [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: 09/20/2022] [Revised: 12/26/2022] [Accepted: 01/20/2023] [Indexed: 01/22/2023]
Abstract
Neurotoxic regimens of methamphetamine (METH) are known to increase reactive oxygen species (ROS), affect redox homeostasis, and lead to damage in dopamine neurons. Functional changes induced by long-term METH self-administration on mitochondrial respiratory metabolism and redox homeostasis are less known. To fill this gap, we implanted a jugular catheter into adult male mice and trained them to nose poke for METH infusions. After several weeks of METH exposure, we collected samples of the ventral striatum (vST) and the ventral midbrain (vMB). We used HPLC to determine the levels of the ROS scavenger glutathione in its reduced (GSH) and oxidized forms. Then, we used high-resolution respirometry to determine the oxygen consumption rate (OCR) of mitochondrial complexes. Finally, using in vivo electrophysiology, we assessed changes in dopamine neuron firing activity in the VTA. METH self-administration produced a decrease of the GSH pool in vST, correlating with lifetime METH intake. We observed increased mitochondrial respiration across the two mesolimbic regions. METH self-administration decreases firing rate and burst activity but increases the number of spontaneously active dopamine neurons per track. We conclude that METH self-administration progressively decreased the antioxidant pool in sites of higher dopamine release and produced an increase in mitochondrial metabolism in the mesolimbic areas, probably derived from the increased number of dopamine neurons actively firing. However, dopamine neuron firing activity is decreased by METH self-administration, reflecting a new basal level of dopamine neurotransmission.
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Affiliation(s)
- Sergio Dominguez-Lopez
- Department of Anatomy and Neurobiology, University of Maryland, School of Medicine, Baltimore, MD, 21201, USA; Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA.
| | - Bumsoo Ahn
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | | | - Rojina Ranjit
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Pavithra Premkumar
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA
| | - Holly Van Remmen
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA; Oklahoma City Veterans Affairs Medical Center, Oklahoma City, OK, 73104, USA
| | - Michael J Beckstead
- Aging and Metabolism Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, 73104, USA; Oklahoma City Veterans Affairs Medical Center, Oklahoma City, OK, 73104, USA
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5
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Ledonne A, Massaro Cenere M, Paldino E, D'Angelo V, D'Addario SL, Casadei N, Nobili A, Berretta N, Fusco FR, Ventura R, Sancesario G, Guatteo E, Mercuri NB. Morpho-Functional Changes of Nigral Dopamine Neurons in an α-Synuclein Model of Parkinson's Disease. Mov Disord 2023; 38:256-266. [PMID: 36350188 DOI: 10.1002/mds.29269] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 10/17/2022] [Indexed: 11/11/2022] Open
Abstract
BACKGROUND The accumulation of α-synuclein (α-syn) fibrils in intraneuronal inclusions called Lewy bodies and Lewy neurites is a pathological signature of Parkinson's disease (PD). Although several aspects linked to α-syn-dependent pathology (concerning its spreading, aggregation, and activation of inflammatory and neurodegenerative processes) have been under intense investigation, less attention has been devoted to the real impact of α-syn overexpression on structural and functional properties of substantia nigra pars compacta (SNpc) dopamine (DA) neurons, particularly at tardive stages of α-syn buildup, despite this has obvious relevance to comprehending mechanisms beyond PD progression. OBJECTIVES We aimed to determine the consequences of a prolonged α-syn overexpression on somatodendritic morphology and functions of SNpc DA neurons. METHODS We performed immunohistochemistry, stereological DA cell counts, analyses of dendritic arborization, ex vivo patch-clamp recordings, and in vivo DA microdialysis measurements in a 12- to 13-month-old transgenic rat model overexpressing the full-length human α-syn (Snca+/+ ) and age-matched wild-type rats. RESULTS Aged Snca+/+ rats have mild loss of SNpc DA neurons and decreased basal DA levels in the SN. Residual nigral DA neurons display smaller soma and compromised dendritic arborization and, in parallel, increased firing activity, switch in firing mode, and hyperexcitability associated with hypofunction of fast activating/inactivating voltage-gated K+ channels and Ca2+ - and voltage-activated large conductance K+ channels. These intrinsic currents underlie the repolarization/afterhyperpolarization phase of action potentials, thus affecting neuronal excitability. CONCLUSIONS Besides clarifying α-syn-induced pathological landmarks, such evidence reveals compensatory functional mechanisms that nigral DA neurons could adopt during PD progression to counteract neurodegeneration. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
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Affiliation(s)
- Ada Ledonne
- Department of Experimental Neuroscience, Santa Lucia Foundation IRCCS, Rome, Italy
| | - Mariangela Massaro Cenere
- Department of Experimental Neuroscience, Santa Lucia Foundation IRCCS, Rome, Italy.,Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Emanuela Paldino
- Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy.,Laboratory of Neuroanatomy, Santa Lucia Foundation IRCCS, Rome, Italy
| | - Vincenza D'Angelo
- Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy
| | - Sebastian Luca D'Addario
- Department of Experimental Neuroscience, Santa Lucia Foundation IRCCS, Rome, Italy.,Department of Psychology and Center "Daniel Bovet, University of Rome La Sapienza, Rome, Italy
| | - Nicolas Casadei
- Institute of Medical Genetics and Applied Genomics, University of Tübingen, Tübingen, Germany
| | - Annalisa Nobili
- Department of Experimental Neuroscience, Santa Lucia Foundation IRCCS, Rome, Italy.,Department of Medicine and Surgery, University Campus Bio-Medico, Rome, Italy
| | - Nicola Berretta
- Department of Experimental Neuroscience, Santa Lucia Foundation IRCCS, Rome, Italy
| | - Francesca R Fusco
- Laboratory of Neuroanatomy, Santa Lucia Foundation IRCCS, Rome, Italy
| | - Rossella Ventura
- Department of Experimental Neuroscience, Santa Lucia Foundation IRCCS, Rome, Italy.,Department of Psychology and Center "Daniel Bovet, University of Rome La Sapienza, Rome, Italy
| | | | - Ezia Guatteo
- Department of Experimental Neuroscience, Santa Lucia Foundation IRCCS, Rome, Italy.,Department of Motor Science and Wellness, Parthenope University, Naples, Italy
| | - Nicola Biagio Mercuri
- Department of Experimental Neuroscience, Santa Lucia Foundation IRCCS, Rome, Italy.,Department of Systems Medicine, University of Rome Tor Vergata, Rome, Italy
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6
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Troyano-Rodriguez E, Blankenship HE, Handa K, Branch SY, Beckstead MJ. Preservation of dendritic D2 receptor transmission in substantia nigra dopamine neurons with age. Sci Rep 2023; 13:1025. [PMID: 36658269 PMCID: PMC9852430 DOI: 10.1038/s41598-023-28174-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 01/13/2023] [Indexed: 01/20/2023] Open
Abstract
Substantia nigra pars compacta (SNc) dopamine neurons are required for voluntary movement and reward learning, and advanced age is associated with motor and cognitive decline. In the midbrain, D2-type dopamine receptors located at dendrodendritic synapses between dopamine neurons control cell firing through G protein-activated potassium (GIRK) channels. We previously showed that aging disrupts dopamine neuron pacemaker firing in mice, but only in males. Here we show that the amplitude of D2-receptor inhibitory postsynaptic currents (D2-IPSCs) are moderately reduced in aged male mice. Local application of dopamine revealed a reduction in the amplitude of the D2-receptor currents in old males compared to young, pointing to a postsynaptic mechanism. Further experiments indicated that reduced D2 receptor signaling was not due to a general reduction in GIRK channel currents or degeneration of the dendritic arbor. Kinetic analysis showed no differences in D2-IPSC shape in old versus young mice or between sexes. Potentiation of D2-IPSCs by corticotropin releasing factor (CRF) was also not affected by age, indicating preservation of one mechanism of plasticity. These findings have implications for understanding dopamine transmission in aging, and reduced D2 receptor inhibition could contribute to increased susceptibility of males to SNc dopamine neuron degeneration in Parkinson's disease.
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Affiliation(s)
- Eva Troyano-Rodriguez
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Harris E Blankenship
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Kylie Handa
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA
| | - Sarah Y Branch
- Department of Cellular and Integrative Physiology, University of Texas Health, San Antonio, TX, USA
| | - Michael J Beckstead
- Aging and Metabolism Research Program, Oklahoma Medical Research Foundation, Oklahoma City, OK, USA.
- Oklahoma City VA Medical Center, Oklahoma City, OK, USA.
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7
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Chen XY, Liu C, Xue Y, Chen L. Changed firing activity of nigra dopaminergic neurons in Parkinson's disease. Neurochem Int 2023; 162:105465. [PMID: 36563966 DOI: 10.1016/j.neuint.2022.105465] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2022] [Revised: 12/11/2022] [Accepted: 12/18/2022] [Indexed: 12/24/2022]
Abstract
Parkinson's disease is the second most common neurodegenerative disease which is characterized by selective degeneration of dopaminergic neurons in the substantia nigra pars compacta. The intrinsic neuronal firing activity is critical for the functional organization of brain and the specific deficits of neuronal firing activity may be associated with different brain disorders. It is known that the surviving nigra dopaminergic neurons exhibit altered firing activity, such as decreased spontaneous firing frequency, reduced number of firing neurons and increased burst firing in Parkinson's disease. Several ionic mechanisms are involved in changed firing activity of dopaminergic neurons under parkinsonian state. In this review, we summarize the changes of spontaneous firing activity as well as the possible mechanisms of nigra dopaminergic neurons in Parkinson's disease. This review may let us clearly understand the involvement of neuronal firing activity of nigra dopaminergic neurons in Parkinson's disease.
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Affiliation(s)
- Xin-Yi Chen
- Department of International Medicine, Affiliated Hospital of Qingdao University, Qingdao, China.
| | - Cui Liu
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Yan Xue
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, China
| | - Lei Chen
- Department of Physiology and Pathophysiology, School of Basic Medicine, Qingdao University, Qingdao, China.
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8
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Thirugnanam T, Santhakumar K. Chemically induced models of Parkinson's disease. Comp Biochem Physiol C Toxicol Pharmacol 2022; 252:109213. [PMID: 34673252 DOI: 10.1016/j.cbpc.2021.109213] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Revised: 09/30/2021] [Accepted: 10/14/2021] [Indexed: 12/12/2022]
Abstract
Environmental toxins are harmful substances detrimental to humans. Constant exposure to these fatal neurotoxins can cause various neurodegenerative disorders. Although poisonous, specific neurotoxins at optimal concentrations mimic the clinical features of neurodegenerative diseases in several animal models. Such chemically-induced model systems are beneficial in deciphering the molecular mechanisms of neurodegeneration and drug screening for these disorders. One such neurotoxin is 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a widely used chemical that recapitulates Parkinsonian features in various animal models. Apart from MPTP, other neurotoxins like 6-hydroxydopamine (6-OHDA), paraquat, rotenone also induce specific clinical features of Parkinson's disease in animal models. These chemically-induced Parkinson's disease models are playing a crucial role in understanding Parkinson's disease onset, pathology, and novel therapeutics. In this review, we provide a concise overview of various neurotoxins that can recapitulate Parkinsonian features in different in vivo and in vitro model systems specifically focusing on the different treatment methodologies of neurotoxins.
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Affiliation(s)
- Thilaga Thirugnanam
- Zebrafish Genetics Laboratory, Department of Genetic Engineering, SRM Institute of Science and Technology, Kattankulathur 603 203, Tamil Nadu, India
| | - Kirankumar Santhakumar
- Zebrafish Genetics Laboratory, Department of Genetic Engineering, SRM Institute of Science and Technology, Kattankulathur 603 203, Tamil Nadu, India.
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9
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Wang TF, Wu SY, Pan BS, Tsai SF, Kuo YM. Inhibition of Nigral Microglial Activation Reduces Age-Related Loss of Dopaminergic Neurons and Motor Deficits. Cells 2022; 11:cells11030481. [PMID: 35159290 PMCID: PMC8834087 DOI: 10.3390/cells11030481] [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: 12/31/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 12/17/2022] Open
Abstract
Parkinson's disease (PD) is an age-related neurodegenerative disease caused by a selective loss of dopaminergic (DA) neurons in the substantia nigra (SN). Microglial activation is implicated in the pathogenesis of PD. This study aimed to characterize the role of microglial activation in aging-related nigral DA neuron loss and motor deficits in mice. We showed that, compared to 3-month-old mice, the number of DA neurons in the SN and the expression of dopamine transporter (DAT) in the striatum decreased during the period of 9 to 12 months of age. Motor deficits and microglial activation in the SN were also evident during these months. The number of DA neurons was negatively correlated with the degrees of microglial activation. The inhibition of age-related microglial activation by ibuprofen during these 3 months decreased DA neuron loss in the SN. Eliminating the microglia prevented systemic inflammation-induced DA neuron death. Forcing mice to run during these 3 months inhibited microglial activation and DA neuron loss. Blocking the brain-derived neurotrophic factor (BDNF) signaling eliminated the exercise-induced protective effects. In conclusion, nigral DA neurons were susceptible to local microglial activation. Running exercise upregulated BDNF-TrkB signaling and inhibited microglial activation during aging. Long-term exercise can be considered as a non-pharmacological strategy to ameliorate microglial activation and related neurodegeneration.
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Affiliation(s)
- Tzu-Feng Wang
- Taiwan International Graduate Program in Interdisciplinary Neuroscience, National Cheng Kung University and Academia Sinica, Taipei 11529, Taiwan;
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan;
| | - Shih-Ying Wu
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (S.-Y.W.); (B.-S.P.)
- Department of Cancer Biology, Wake Forest Baptist Medical Center, Wake Forest University, Winston Salem, NC 27157, USA
| | - Bo-Syong Pan
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (S.-Y.W.); (B.-S.P.)
- Department of Cancer Biology, Wake Forest Baptist Medical Center, Wake Forest University, Winston Salem, NC 27157, USA
| | - Sheng-Feng Tsai
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan;
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (S.-Y.W.); (B.-S.P.)
| | - Yu-Min Kuo
- Taiwan International Graduate Program in Interdisciplinary Neuroscience, National Cheng Kung University and Academia Sinica, Taipei 11529, Taiwan;
- Department of Cell Biology and Anatomy, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan;
- Institute of Basic Medical Sciences, College of Medicine, National Cheng Kung University, Tainan 70101, Taiwan; (S.-Y.W.); (B.-S.P.)
- Correspondence: ; Tel.: +886-6-2353535 (ext. 5294); Fax: +886-6-2093007
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10
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Dagra A, Miller DR, Lin M, Gopinath A, Shaerzadeh F, Harris S, Sorrentino ZA, Støier JF, Velasco S, Azar J, Alonge AR, Lebowitz JJ, Ulm B, Bu M, Hansen CA, Urs N, Giasson BI, Khoshbouei H. α-Synuclein-induced dysregulation of neuronal activity contributes to murine dopamine neuron vulnerability. NPJ Parkinsons Dis 2021; 7:76. [PMID: 34408150 PMCID: PMC8373893 DOI: 10.1038/s41531-021-00210-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 07/09/2021] [Indexed: 02/07/2023] Open
Abstract
Pathophysiological damages and loss of function of dopamine neurons precede their demise and contribute to the early phases of Parkinson's disease. The presence of aberrant intracellular pathological inclusions of the protein α-synuclein within ventral midbrain dopaminergic neurons is one of the cardinal features of Parkinson's disease. We employed molecular biology, electrophysiology, and live-cell imaging to investigate how excessive α-synuclein expression alters multiple characteristics of dopaminergic neuronal dynamics and dopamine transmission in cultured dopamine neurons conditionally expressing GCaMP6f. We found that overexpression of α-synuclein in mouse (male and female) dopaminergic neurons altered neuronal firing properties, calcium dynamics, dopamine release, protein expression, and morphology. Moreover, prolonged exposure to the D2 receptor agonist, quinpirole, rescues many of the alterations induced by α-synuclein overexpression. These studies demonstrate that α-synuclein dysregulation of neuronal activity contributes to the vulnerability of dopaminergic neurons and that modulation of D2 receptor activity can ameliorate the pathophysiology. These findings provide mechanistic insights into the insidious changes in dopaminergic neuronal activity and neuronal loss that characterize Parkinson's disease progression with significant therapeutic implications.
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Affiliation(s)
- Abeer Dagra
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Douglas R. Miller
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Min Lin
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Adithya Gopinath
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Fatemeh Shaerzadeh
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Sharonda Harris
- grid.15276.370000 0004 1936 8091Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL USA
| | - Zachary A. Sorrentino
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Jonatan Fullerton Støier
- grid.5254.60000 0001 0674 042XMolecular Neuropharmacology and Genetics Laboratory, Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sophia Velasco
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Janelle Azar
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Adetola R. Alonge
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Joseph J. Lebowitz
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Brittany Ulm
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Mengfei Bu
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Carissa A. Hansen
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Nikhil Urs
- grid.15276.370000 0004 1936 8091Department of Pharmacology and Therapeutics, University of Florida, Gainesville, FL USA
| | - Benoit I. Giasson
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
| | - Habibeh Khoshbouei
- grid.15276.370000 0004 1936 8091Department of Neuroscience, University of Florida, Gainesville, FL USA
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11
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Beckstead MJ, Howell RD. Progressive parkinsonism due to mitochondrial impairment: Lessons from the MitoPark mouse model. Exp Neurol 2021; 341:113707. [PMID: 33753138 PMCID: PMC8169575 DOI: 10.1016/j.expneurol.2021.113707] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 12/21/2022]
Abstract
The cardinal pathophysiological finding of Parkinson's disease (PD) is a chronic, progressive degeneration of dopamine (DA) neurons in the substantia nigra, which is responsible for the motor and some of the non-motor symptomatology. While the primary causes of nigrostriatal degeneration are hotly debated, considerable evidence supports a central role for impaired mitochondrial function. Postmortem analysis of PD patients reveals impaired respiratory chains and increased mutations of mitochondrial DNA (mtDNA), in addition to increased markers of oxidative stress indicative of mitochondrial impairment. Most animal models of PD, both genetic and toxin-based, target some component of mitochondrial function to reproduce aspects of the human disease. One model that continues to gain attention is the MitoPark mouse, created through a cell type-specific knockout of mitochondrial transcription factor A specifically in midbrain DA neurons. This model effectively recapitulates the slowly developing, adult onset motor decline seen in PD due to mass loss of DA neurons. MitoPark mice therefore represent an effective tool for studying the sequence of events that occurs in the early stages of DA neuron degeneration following mitochondrial impairment, as well as for testing the efficacy of potential disease-modifying therapies in a progressive model of neurodegeneration. A targeted review of key findings from MitoPark mice has not been published since the early years following the initial report of the model in 2007. The current review synthesizes findings from several groups that are exploring MitoPark mice and discusses implications for the future identification of disease-modifying treatments for PD.
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Affiliation(s)
- Michael J Beckstead
- Oklahoma Medical Research Foundation, Aging & Metabolism Research Program, USA.
| | - Rebecca D Howell
- Oklahoma Medical Research Foundation, Aging & Metabolism Research Program, USA
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Miller DR, Guenther DT, Maurer AP, Hansen CA, Zalesky A, Khoshbouei H. Dopamine Transporter Is a Master Regulator of Dopaminergic Neural Network Connectivity. J Neurosci 2021; 41:5453-5470. [PMID: 33980544 PMCID: PMC8221606 DOI: 10.1523/jneurosci.0223-21.2021] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 04/19/2021] [Accepted: 05/01/2021] [Indexed: 12/13/2022] Open
Abstract
Dopaminergic neurons of the substantia nigra pars compacta (SNC) and ventral tegmental area (VTA) exhibit spontaneous firing activity. The dopaminergic neurons in these regions have been shown to exhibit differential sensitivity to neuronal loss and psychostimulants targeting dopamine transporter. However, it remains unclear whether these regional differences scale beyond individual neuronal activity to regional neuronal networks. Here, we used live-cell calcium imaging to show that network connectivity greatly differs between SNC and VTA regions with higher incidence of hub-like neurons in the VTA. Specifically, the frequency of hub-like neurons was significantly lower in SNC than in the adjacent VTA, consistent with the interpretation of a lower network resilience to SNC neuronal loss. We tested this hypothesis, in DAT-cre/loxP-GCaMP6f mice of either sex, when activity of an individual dopaminergic neuron is suppressed, through whole-cell patch clamp electrophysiology, in either SNC or VTA networks. Neuronal loss in the SNC increased network clustering, whereas the larger number of hub-neurons in the VTA overcompensated by decreasing network clustering in the VTA. We further show that network properties are regulatable via a dopamine transporter but not a D2 receptor dependent mechanism. Our results demonstrate novel regulatory mechanisms of functional network topology in dopaminergic brain regions.SIGNIFICANCE STATEMENT In this work, we begin to untangle the differences in complex network properties between the substantia nigra pars compacta (SNC) and VTA, that may underlie differential sensitivity between regions. The methods and analysis employed provide a springboard for investigations of network topology in multiple deep brain structures and disorders.
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Affiliation(s)
- Douglas R Miller
- Department of Neuroscience, University of Florida, Gainesville, Florida
| | - Dylan T Guenther
- Department of Neuroscience, University of Florida, Gainesville, Florida
| | - Andrew P Maurer
- Department of Neuroscience, University of Florida, Gainesville, Florida
| | - Carissa A Hansen
- Department of Neuroscience, University of Florida, Gainesville, Florida
| | - Andrew Zalesky
- Melbourne Neuropsychiatry Centre, The University of Melbourne and Melbourne Health, Melbourne, Victoria 3010, Australia
- Department of Biomedical Engineering, Melbourne School of Engineering, The University of Melbourne, Melbourne, Victoria 3010, Australia
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Lin M, Mackie PM, Shaerzadeh F, Gamble-George J, Miller DR, Martyniuk CJ, Khoshbouei H. In Parkinson's patient-derived dopamine neurons, the triplication of α-synuclein locus induces distinctive firing pattern by impeding D2 receptor autoinhibition. Acta Neuropathol Commun 2021; 9:107. [PMID: 34099060 PMCID: PMC8185945 DOI: 10.1186/s40478-021-01203-9] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Accepted: 05/17/2021] [Indexed: 12/12/2022] Open
Abstract
Pathophysiological changes in dopamine neurons precede their demise and contribute to the early phases of Parkinson's disease (PD). Intracellular pathological inclusions of the protein α-synuclein within dopaminergic neurons are a cardinal feature of PD, but the mechanisms by which α-synuclein contributes to dopaminergic neuron vulnerability remain unknown. The inaccessibility to diseased tissue has been a limitation in studying progression of pathophysiology prior to degeneration of dopamine neurons. To address these issues, we differentiated induced pluripotent stem cells (iPSCs) from a PD patient carrying the α-synuclein triplication mutation (AST) and an unaffected first-degree relative (NAS) into dopaminergic neurons. In human-like dopamine neurons α-synuclein overexpression reduced the functional availability of D2 receptors, resulting in a stark dysregulation in firing activity, dopamine release, and neuronal morphology. We back-translated these findings into primary mouse neurons overexpressing α-synuclein and found a similar phenotype, supporting the causal role for α-synuclein. Importantly, application of D2 receptor agonist, quinpirole, restored the altered firing activity of AST-derived dopaminergic neurons to normal levels. These results provide novel insights into the pre-degenerative pathophysiological neuro-phenotype induced by α-synuclein overexpression and introduce a potential mechanism for the long-established clinical efficacy of D2 receptor agonists in the treatment of PD.
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Affiliation(s)
- Min Lin
- Department of Neuroscience, University of Florida, Gainesville, FL, 32611, USA
| | - Phillip M Mackie
- Department of Neuroscience, University of Florida, Gainesville, FL, 32611, USA
| | - Fatima Shaerzadeh
- Department of Neuroscience, University of Florida, Gainesville, FL, 32611, USA
| | | | - Douglas R Miller
- Department of Neuroscience, University of Florida, Gainesville, FL, 32611, USA
| | - Chris J Martyniuk
- Environmental and Human Toxicology, University of Florida Genetics Institute, Interdisciplinary Program in Biomedical Sciences Neuroscience, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA
| | - Habibeh Khoshbouei
- Department of Neuroscience, University of Florida, Gainesville, FL, 32611, USA.
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