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Regazzoni L, Fumagalli L, Artasensi A, Gervasoni S, Gilardoni E, Mazzolari A, Aldini G, Vistoli G. Cyclo(His-Pro) Exerts Protective Carbonyl Quenching Effects through Its Open Histidine Containing Dipeptides. Nutrients 2022; 14:1775. [PMID: 35565743 PMCID: PMC9103439 DOI: 10.3390/nu14091775] [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: 03/11/2022] [Revised: 04/11/2022] [Accepted: 04/19/2022] [Indexed: 12/12/2022] Open
Abstract
Cyclo(His-Pro) (CHP) is a cyclic dipeptide which is endowed with favorable pharmacokinetic properties combined with a variety of biological activities. CHP is found in a number of protein-rich foods and dietary supplements. While being stable at physiological pH, CHP can open yielding two symmetric dipeptides (His-Pro, Pro-His), the formation of which might be particularly relevant from dietary CHP due to the gastric acidic environment. The antioxidant and protective CHP properties were repeatedly reported although the non-enzymatic mechanisms were scantly investigated. The CHP detoxifying activity towards α,β unsaturated carbonyls was never investigated in detail, although its open dipeptides might be effective as already observed for histidine containing dipeptides. Hence, this study investigated the scavenging properties of TRH, CHP and its open derivatives towards 4-hydroxy-2-nonenal. The obtained results revealed that Pro-His possesses a marked activity and is more reactive than l-carnosine. As investigated by DFT calculations, the enhanced reactivity can be ascribed to the greater electrophilicity of the involved iminium intermediate. These findings emphasize that the primary amine (as seen in l-carnosine) can be replaced by secondary amines with beneficial effects on the quenching mechanisms. Serum stability of the tested peptides was also evaluated, showing that Pro-His is characterized by a greater stability than l-carnosine. Docking simulations suggested that its hydrolysis can be catalyzed by serum carnosinase. Altogether, the reported results evidence that the antioxidant CHP properties can be also due to the detoxifying activity of its open dipeptides, which might be thus responsible for the beneficial effects induced by CHP containing food.
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Affiliation(s)
- Luca Regazzoni
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, I-20133 Milano, Italy; (L.R.); (L.F.); (A.A.); (S.G.); (E.G.); (A.M.); (G.A.)
| | - Laura Fumagalli
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, I-20133 Milano, Italy; (L.R.); (L.F.); (A.A.); (S.G.); (E.G.); (A.M.); (G.A.)
| | - Angelica Artasensi
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, I-20133 Milano, Italy; (L.R.); (L.F.); (A.A.); (S.G.); (E.G.); (A.M.); (G.A.)
| | - Silvia Gervasoni
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, I-20133 Milano, Italy; (L.R.); (L.F.); (A.A.); (S.G.); (E.G.); (A.M.); (G.A.)
- Department of Physics, Università di Cagliari, Citt. Universitaria, I-09042 Monserrato, Italy
| | - Ettore Gilardoni
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, I-20133 Milano, Italy; (L.R.); (L.F.); (A.A.); (S.G.); (E.G.); (A.M.); (G.A.)
| | - Angelica Mazzolari
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, I-20133 Milano, Italy; (L.R.); (L.F.); (A.A.); (S.G.); (E.G.); (A.M.); (G.A.)
| | - Giancarlo Aldini
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, I-20133 Milano, Italy; (L.R.); (L.F.); (A.A.); (S.G.); (E.G.); (A.M.); (G.A.)
| | - Giulio Vistoli
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Milano, I-20133 Milano, Italy; (L.R.); (L.F.); (A.A.); (S.G.); (E.G.); (A.M.); (G.A.)
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Grottelli S, Ferrari I, Pietrini G, Peirce MJ, Minelli A, Bellezza I. The Role of Cyclo(His-Pro) in Neurodegeneration. Int J Mol Sci 2016; 17:E1332. [PMID: 27529240 PMCID: PMC5000729 DOI: 10.3390/ijms17081332] [Citation(s) in RCA: 22] [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: 07/04/2016] [Revised: 08/04/2016] [Accepted: 08/08/2016] [Indexed: 02/06/2023] Open
Abstract
Neurodegenerative diseases may have distinct genetic etiologies and pathological manifestations, yet share common cellular mechanisms underpinning neuronal damage and dysfunction. These cellular mechanisms include excitotoxicity, calcium dysregulation, oxidative damage, ER stress and neuroinflammation. Recent data have identified a dual role in these events for glial cells, such as microglia and astrocytes, which are able both to induce and to protect against damage induced by diverse stresses. Cyclo(His-Pro), a cyclic dipeptide derived from the hydrolytic removal of the amino-terminal pyroglutamic acid residue of the hypothalamic thyrotropin-releasing hormone, may be important in regulating the nature of the glial cell contribution. Cyclo(His-Pro) is ubiquitous in the central nervous system and is a key substrate of organic cation transporters, which are strongly linked to neuroprotection. The cyclic dipeptide can also cross the brain-blood-barrier and, once in the brain, can affect diverse inflammatory and stress responses by modifying the Nrf2-NF-κB signaling axis. For these reasons, cyclo(His-Pro) has striking potential for therapeutic application by both parenteral and oral administration routes and may represent an important new tool in counteracting neuroinflammation-based degenerative pathologies. In this review, we discuss the chemistry and biology of cyclo(His-Pro), how it may interact with the biological mechanisms driving neurodegenerative disease, such as amyotrophic lateral sclerosis, and thereby act to preserve or restore neuronal function.
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Affiliation(s)
- Silvia Grottelli
- Dipartimento di Medicina Sperimentale, Università di Perugia, Polo Unico Sant'Andrea delle Fratte, Piazzale Gambuli, 06132 Perugia, Italy.
| | - Ilaria Ferrari
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano ed Istituto di Neuroscienze, Consiglio Nazionale delle Ricerche, Via Vanvitelli 32, 20129 Milano, Italy.
| | - Grazia Pietrini
- Dipartimento di Biotecnologie Mediche e Medicina Traslazionale, Università degli Studi di Milano ed Istituto di Neuroscienze, Consiglio Nazionale delle Ricerche, Via Vanvitelli 32, 20129 Milano, Italy.
| | - Matthew J Peirce
- Dipartimento di Medicina Sperimentale, Università di Perugia, Polo Unico Sant'Andrea delle Fratte, Piazzale Gambuli, 06132 Perugia, Italy.
| | - Alba Minelli
- Dipartimento di Medicina Sperimentale, Università di Perugia, Polo Unico Sant'Andrea delle Fratte, Piazzale Gambuli, 06132 Perugia, Italy.
| | - Ilaria Bellezza
- Dipartimento di Medicina Sperimentale, Università di Perugia, Polo Unico Sant'Andrea delle Fratte, Piazzale Gambuli, 06132 Perugia, Italy.
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Abiram A, Kolandaivel P. Structural analysis and the effect of cyclo(His-Pro) dipeptide on neurotoxins--a dynamics and density functional theory study. J Mol Model 2009; 16:193-202. [PMID: 19554355 DOI: 10.1007/s00894-009-0531-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2009] [Accepted: 04/21/2009] [Indexed: 10/20/2022]
Abstract
The switching propensity and maximum probability of occurrence of the side chain imidazole group in the dipeptide cyclo(His-Pro) (CHP) were studied by applying molecular dynamics simulations and density functional theory. The atomistic behaviour of CHP with the neurotoxins glutamate (E) and paraquat (Pq) were also explored; E and Pq engage in hydrogen bond formation with the diketopiperazine (DKP) ring of the dipeptide, with which E shows a profound interaction, as confirmed further by NH and CO stretching vibrational frequencies. The effect of CHP was found to be greater on E than on Pq neurotoxin. A ring puckering study indicated a twist boat conformation for the six-membered DKP ring. Molecular electrostatic potential (MESP) mapping was also used to explore the hydrogen bond interactions prevailing between the neurotoxins and the DKP ring. The results of this study reveal that the DKP ring of the dipeptide CHP can be expected to play a significant role in reducing effects such as oxidative stress and cell death caused by neurotoxins.
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Krishnamurthi RVM, Mathai S, Kim AH, Zhang R, Guan J. A novel diketopiperazine improves functional recovery given after the onset of 6-OHDA-induced motor deficit in rats. Br J Pharmacol 2009; 156:662-72. [PMID: 19154439 DOI: 10.1111/j.1476-5381.2008.00064.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND AND PURPOSE Cyclo-L-glycyl-L-2-allylproline (NNZ-2591), a modified diketopiperazine, is neuroprotective and improves long-term function after hypoxic-ischaemic brain injury in rats. The present studies were designed to examine both the neuroprotective and neurotrophic actions of NNZ-2591 on neurochemical and behavioural changes in a rat model of Parkinson's disease. EXPERIMENTAL APPROACH To examine its protective effect, either NNZ-2591 (20 ng.day(-1)) or saline was given intracerebroventricularly for 3 days starting 2 h after 6-hydroxydopamine (6-OHDA) induced unilateral striatal lesion. In a subsequent experiment either NNZ-2591 (0.2, 1 and 5 mg.day(-1), s.c.) or saline was administered daily for 14 days starting 2 weeks after the lesion. Behavioural and neurochemical outcomes were examined using the adjusting step test and immunohistochemical staining. KEY RESULTS Cyclo-L-glycyl-L-2-allylproline given 2 h after the lesion reduced the degree of motor deficit compared with the saline-treated group. Delayed treatment with NNZ-2591, initiated after the onset of motor deficit, significantly improved motor function from week 7 onwards compared with the saline-treated group. Neither treatment regime altered nigrostriatal dopamine depletion. NNZ-2591 significantly enhanced the expression of doublecortin-positive neuroblasts in the sub-ventricular zone. CONCLUSIONS AND IMPLICATIONS These studies reveal that early treatment with NNZ-2591 protects against the motor deficit induced by 6-OHDA and that treatment initiated after the establishment of motor impairment significantly improves long-term motor function. These effects of NNZ-2591 on functional recovery were independent of dopamine depletion and also appeared not to be symptomatic as the improved motor function was long-lasting. NNZ-2591 has potential as a therapeutic agent for neurodegenerative disorders.
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Guan J, Mathai S, Harris P, Wen JY, Zhang R, Brimble M, Gluckman P. Peripheral administration of a novel diketopiperazine, NNZ 2591, prevents brain injury and improves somatosensory-motor function following hypoxia-ischemia in adult rats. Neuropharmacology 2007; 53:749-62. [PMID: 17904590 DOI: 10.1016/j.neuropharm.2007.08.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 08/03/2007] [Accepted: 08/06/2007] [Indexed: 11/29/2022]
Abstract
The current study describes the neuroprotective effects of an endogenous diketopiperazine, cyclo-glycyl-proline (cyclic GP), in rats with hypoxic-ischemic brain injury and the pre-clinical development of an analogue, cyclo-L-glycyl-L-2-allylproline (NNZ 2591), modified for improved bioavailability. The compounds were given either intracerebroventricularly or subcutaneously 2h after hypoxia-ischemia. Histology, immunohistochemistry and behavior were used to evaluate treatment effects. The central uptake of NNZ 2591 was also examined in normal and hypoxic-ischemic injured rats by HPLC-mass spectrometry. Central administration of cyclic GP or NNZ 2591 reduced the extent of brain damage in the lateral cortex, the hippocampus and the striatum (p<0.001), with NNZ 2591 being more potent. NNZ 2591 was stable in the plasma and crossed the blood-brain barrier independent of hypoxic-ischemic injury. The level of NNZ 2591 in the CSF was maintained for 2 h after a single subcutaneous dose, and modest neuroprotection was seen after a bolus subcutaneous administration (overall p<0.001). Treatment with NNZ 2591 for 5 d subcutaneously improved somatosensory-motor function (p<0.05) and long-term histological outcome (overall p<0.0001). NNZ 2591 treatment not only reduced both caspase-3 mediated apoptosis and microglial activation but also enhanced astrocytic reactivity, which may mediate its protective effect. The pharmacokinetic profile and potent long-term protective effects of NNZ 2591 suggests its utility for the treatment of ischemic brain injury and other neurological conditions requiring chronic intervention.
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Affiliation(s)
- J Guan
- The Liggins Institute, University of Auckland, Private Bag 92019, Auckland, New Zealand.
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Taubert D, Grimberg G, Stenzel W, Schömig E. Identification of the endogenous key substrates of the human organic cation transporter OCT2 and their implication in function of dopaminergic neurons. PLoS One 2007; 2:e385. [PMID: 17460754 PMCID: PMC1851987 DOI: 10.1371/journal.pone.0000385] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2007] [Accepted: 03/26/2007] [Indexed: 01/11/2023] Open
Abstract
Background The etiology of neurodegenerative disorders, such as the accelerated loss of dopaminergic neurons in Parkinson's disease, is unclear. Current hypotheses suggest an abnormal function of the neuronal sodium-dependent dopamine transporter DAT to contribute to cell death in the dopaminergic system, but it has not been investigated whether sodium-independent amine transporters are implicated in the pathogenesis of Parkinson's disease. Methodology/Principal Findings By the use of a novel tandem-mass spectrometry-based substrate search technique, we have shown that the dopaminergic neuromodulators histidyl-proline diketopiperazine (cyclo(his-pro)) and salsolinol were the endogenous key substrates of the sodium-independent organic cation transporter OCT2. Quantitative real-time mRNA expression analysis revealed that OCT2 in contrast to its related transporters was preferentially expressed in the dopaminergic regions of the substantia nigra where it colocalized with DAT and tyrosine hydroxylase. By assessing cell viability with the MTT reduction assay, we found that salsolinol exhibited a selective toxicity toward OCT2-expressing cells that was prevented by cyclo(his-pro). A frequent genetic variant of OCT2 with the amino acid substitution R400C reduced the transport efficiency for the cytoprotective cyclo(his-pro) and thereby increased the susceptibility to salsolinol-induced cell death. Conclusions/Significance Our findings indicate that the OCT2-regulated interplay between cyclo(his-pro) and salsolinol is crucial for nigral cell integrity and that a shift in transport efficiency may impact the risk of Parkinson's disease.
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Affiliation(s)
- Dirk Taubert
- Department of Pharmacology, Medical Hospital of the University of Cologne, Cologne, Germany.
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Minelli A, Bellezza I, Grottelli S, Pinnen F, Brunetti L, Vacca M. Phosphoproteomic analysis of the effect of cyclo-[His-Pro] dipeptide on PC12 cells. Peptides 2006; 27:105-13. [PMID: 16137790 DOI: 10.1016/j.peptides.2005.07.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2005] [Revised: 07/12/2005] [Accepted: 07/12/2005] [Indexed: 12/23/2022]
Abstract
The effects of dipeptide cyclo-[His-Pro] (CHP), known to participate in the appetite behavior and food intake control, have been investigated using PC12 cells in culture as model system. We found that only in the presence of experimental conditions that cause cellular stress the cyclic dipeptide affect cellular proliferation and protects from apoptosis. It greatly enhances the phosphorylation of hsp27, alpha-B-crystallin, Cdc2, and p-38 MAPK, whereas it decreases the phosphorylation of MEK1, Cav 2, GSK3a, PKB/Akt, PKCdelta, PKCgamma, and Erk2. PKA and PKG are involved in ERK1/2 deactivation via a receptor that appears to be dually coupled to Gs and Gq protein subfamilies.
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Affiliation(s)
- Alba Minelli
- Dipartimento di Medicina Sperimentale e Scienze Biochimiche, Università di Perugia, via del Giochetto, 06123 Perugia, Italy.
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8
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Abstract
Cyclo (His-Pro) or CHP is a cyclic dipeptide endogenous to the brain of a variety of animal species including man. Administration of exogenous peptide to rodents has been shown to exhibit a variety of biological activities some of which appear to be mediated via a dopaminergic mechanism. Since a hypodopaminergic state has been associated with excessive drinking in animal models as well as man, we have explored the potential role of CHP in alcohol-preferring C57BL mice. The results of this study show that the level of CHP, a peptide that mimics dopamine in many of its pharmacologic actions, is lower in brains of alcohol-preferring C57BL mice compared to alcohol non-preferring DBA2 mice. Furthermore, administration of exogenous CHP to C57BL mice caused a pronounced decrease in their voluntary alcohol consumption. In conclusion, endogenous CHP may play a role in risk for developing excessive alcohol use by modulating central dopaminergic tone.
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Affiliation(s)
- C Prasad
- Section of Endocrinology, Department of Medicine, Louisiana State, University Medical Center, New Orleans, LA 70112, USA.
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Prasad C. Limited proteolysis and physiological regulation: an example from thyrotropin-releasing hormone metabolism. Thyroid 1998; 8:969-75. [PMID: 9827668 DOI: 10.1089/thy.1998.8.969] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Proteases like trypsin, elastase, and many others play important regulatory functions by generating new biologically active molecules through limited proteolysis of larger proteins and peptides. The limited proteolysis of thyrotropin-releasing hormone (TRH) by Pyroglutamate aminopeptidase yields cyclo(His-Pro) or CHP, a new biopeptide associated with a variety of pharmacological activities, including regulation of body temperature, inhibition of prolactin secretion, and modulation of motor functions. Although the mechanism by which CHP elicits these biological activities is not well understood, it appears that the cyclic peptide may function at least in part by modulating central amine transport mechanisms.
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Affiliation(s)
- C Prasad
- Department of Medicine, Louisiana State University Medical Center, New Orleans 70112, USA
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Petitto JM, McCarthy DB, Rinker CM, Huang Z, Getty T. Modulation of behavioral and neurochemical measures of forebrain dopamine function in mice by species-specific interleukin-2. J Neuroimmunol 1997; 73:183-90. [PMID: 9058775 DOI: 10.1016/s0165-5728(96)00196-8] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Interleukin-2 (IL-2) has recently been implicated as a modulator of brain neuronal function and in the pathogenesis of several major neuropsychiatric disorders involving the dopamine system (e.g. schizophrenia and Parkinson's disease). Little is known, however, about the effects of IL-2 on dopamine-mediated behaviors. A series of behavioral experiments were performed in mice to examine the hypothesis that species-specific IL-2 could modify behaviors known to be mediated by forebrain dopamine pathways. IL-2 administered subcutaneously produced a robust increase in locomotor activity in an elevated plus-maze. No effects of the cytokine were evident on measures of acoustic startle, prepulse inhibition of the startle response (PPI), or fearfulness. In complementary in vitro neurochemical experiments, to most closely assess physiologically relevant effects of the cytokine on dopamine release from striatal neurons, species-specific IL-2 as well as high performance liquid chromatography (HPLC) were used to measure endogenous dopamine release from striatal slices. IL-2 dose-dependently modulated veratrine-evoked release of endogenous dopamine in a biphasic pattern, increasing release at lower concentrations and inhibiting release at a high concentration of the cytokine. In radioligand competition binding experiments, IL-2 was not active at striatal binding sites for [3H]spiroperidol (D2-like receptors), [3H]mazindol binding (dopamine uptake sites) and [3H]SCH23390 (D1-like receptors), indicating that the neuromodulatory actions of IL-2 are not the result of direct or allosteric effects on dopamine receptors. Knowledge of the mechanisms by which IL-2 influences brain dopamine function could provide new insight into the pathophysiology of forebrain dopamine neurons seen in disorders such as Parkinson's disease and schizophrenia.
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Affiliation(s)
- J M Petitto
- Department of Psychiatry, University of Florida College of Medicine, Gainesville 32610-0256, USA
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Shukla R, Srimal RC, Prasad C. Cyclo (His-Pro) modulation of body temperature at hot ambient temperature in the desert rat (Mastomys natalensis). Peptides 1997; 18:689-93. [PMID: 9213362 DOI: 10.1016/s0196-9781(97)00130-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Cyclo(His-Pro) (CHP) has been shown to facilitate cold-induced hypothermia in the desert rat Mastomys natalensis. In the present study, we examined the role of endogenous CHP in hyperthermia induced by hot ambient temperature (40 degrees C) in the above rodent species. The results of these studies show that housing rodents at 40 degrees C resulted in a altered distribution of CHP in the brain, with a rise in hypothalamic content accompanied by an increase in rectal temperature. While administration of exogenous CHP decreased hyperthermia, immunoneutralization of endogenous CHP increased hyperthermia. The results of these studies show that changes in endogenous CHP levels may affect body temperature regulation.
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Affiliation(s)
- R Shukla
- Division of Pharmacology, Central Drug Research Institute, Lucknow, India
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Frey KA, Koeppe RA, Kilbourn MR, Vander Borght TM, Albin RL, Gilman S, Kuhl DE. Presynaptic monoaminergic vesicles in Parkinson's disease and normal aging. Ann Neurol 1996; 40:873-84. [PMID: 9007092 DOI: 10.1002/ana.410400609] [Citation(s) in RCA: 243] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We present development and human application of a method for determining the regional cerebral density of the type 2 vesicular monoamine transporter (VMAT2) using positron emission tomography (PET) and [11C]dihydrotetrabenazine (DTBZ). Previous animal studies indicate striatal VMAT2 density is linearly related to the integrity of substantia nigra dopamine neurons and is not subject to drug- or lesion-compensatory regulation. In the present studies, kinetic compartmental modeling was employed to estimate blood-brain [11C]DTBZ transport (K1) and VMAT2 binding site density (tissue-to-plasma DTBZ distribution volume, DV) from the cerebral and plasma DTBZ time courses after intravenous tracer injection. In controls, we found reductions of putamen DTBZ DVwith advancing age, corresponding to losses of 0.77% per year in specific VMAT2 binding. Parkinson's disease (PD) patients had reduction in specific DTBZ DV in the putamen (-61%) and in the caudate nucleus (-43%). There was no overlap of lowest specific putamen DTBZ DV between individual elderly controls and PD patients. The present results indicate the suitability of [11C]DTBZ PET for objective quantification of nigrostriatal integrity, including evaluation of PD progression and its possible therapeutic modification.
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Affiliation(s)
- K A Frey
- Department of Internal Medicine (Division of Nuclear Medicine), University of Michigan, Ann Arbor, USA
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Koeppe RA, Frey KA, Vander Borght TM, Karlamangla A, Jewett DM, Lee LC, Kilbourn MR, Kuhl DE. Kinetic evaluation of [11C]dihydrotetrabenazine by dynamic PET: measurement of vesicular monoamine transporter. J Cereb Blood Flow Metab 1996; 16:1288-99. [PMID: 8898703 DOI: 10.1097/00004647-199611000-00025] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
(+)-alpha-[11C]Dihydrotetrabenazine (DTBZ) binds to the vesicular monoamine transporter (VMAT2) located in presynaptic vesicles. The purpose of this work was to evaluate various model configurations for analysis of [11C]DTBZ with the aim of providing the optimal measure of monoamine vesicular transporter density obtainable from a single dynamic PET study. PET studies on seven young normal volunteer subjects, ages 20-35, were performed following i.v. injection of 666 +/- 37 MBq (18 +/- 1 mCi) of (+)-alpha-[11C]DTBZ. Dynamic acquisition consisted of a 15-frame sequence over 1 h. Analysis methods included both creation of pixel-by-pixel functional images of transport (K1) and binding (DVtot) and nonlinear least-squares analysis of volume-of-interest data. Pixel-by-pixel calculations were performed for both two-compartment weighted integral calculations and slope-intercept estimations from Logan plots. Nonlinear least-squares analysis was performed applying model configurations with both two-compartments, estimating K1 and DVtot and three compartments, estimating K1-k4. For the more complex configuration, we examined the stability of various binding-related parameters including k3 (konBmax'), k3/k4 (Bmax'/Kd), DVsp[(K1/k2)(k3/k4)], and DVtot [K1/k2(1 + k3/k4)]. The three-compartment model provided significantly improved goodness-of-fit compared to the two-compartment model, yet did not increase the uncertainty in the estimate of the DVtot. Without constraining parameters in the three-compartment model fits, DVtot was found to provide a more stable estimate of binding density than either k3, k3/k4, or DVsp. The two-compartment least-squares analysis yielded approximately 10% underestimations of the total distribution. However, this bias was found to be very consistent from region to region as well as across subjects as indicated by the correlation between two- and three-compartment DVtot estimates of 0.997. We conclude that (+)-alpha-[11C]DTBZ and PET can provide excellent measures of VMAT2 density in the human brain.
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Affiliation(s)
- R A Koeppe
- Department of Internal Medicine, University of Michigan, Ann Arbor, USA
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Vander Borght T, Kilbourn M, Desmond T, Kuhl D, Frey K. The vesicular monoamine transporter is not regulated by dopaminergic drug treatments. Eur J Pharmacol 1995; 294:577-83. [PMID: 8750721 DOI: 10.1016/0014-2999(95)00594-3] [Citation(s) in RCA: 143] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The number of neuronal synaptic vesicular monoamine transporters (vesicular monoamine transporter type 2; VMAT2) has been recently proposed as an index of monoamine presynaptic terminal density. The present study investigated the possible regulation of the vesicular monoamine transporter. Rats were treated for 2 weeks with drugs known to influence dopaminergic neurotransmission, including those commonly used in the treatment of Parkinson's disease. Autoradiographic assays were performed using [3H]methoxytetrabenazine, [3H]raclopride, and [3H]WIN 35,428 ([3H]2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane) to measure vesicular monoamine transporter, dopamine D2 receptor and synaptic plasma membrane dopamine re-uptake site bindings, respectively. None of the drug treatments significantly modified levels of vesicular monoamine transporter binding. In contrast, both dopamine D2 receptors and dopamine re-uptake sites were altered by some of the treatment regimens. These data extend preliminary results that suggest the vesicular monoamine transporter is not easily regulated and confirm the plasticity of dopamine D2 receptors and the dopamine re-uptake site. Measures of striatal vesicular monoamine transporter density may, thus, provide objective estimates of monoaminergic innervation in neurodegenerative diseases, unaffected by the use of symptomatic therapies.
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Affiliation(s)
- T Vander Borght
- Department of Internal Medicine (Division of Nuclear Medicine), The University of Michigan, Ann Arbor, USA
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Prasad C, Mizuma H, Brock JW, Porter JR, Svec F, Hilton C. A paradoxical elevation of brain cyclo(His-Pro) levels in hyperphagic obese Zucker rats. Brain Res 1995; 699:149-53. [PMID: 8616606 DOI: 10.1016/0006-8993(95)01022-n] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Several studies suggest a role for endogenous cyclo(His-Pro) or CHP in appetite regulation. In the present study, we have examined the regional brain distribution of CHP in hyperphagic obese Zucker rats and their lean littermates. The data show a significant elevation in the levels of CHP in many brain regions, including hypothalamus of the obese rat. Within the hypothalamus, the lateral hypothalamic (LH) nucleus of obese rats had significantly higher levels of CHP when compared to that of the lean littermates. Administration of dehydroepiandrosterone, a steroid hormone known to decrease food intake and body weight gain, to obese rats led to decrease in the levels of CHP in the LH. These data further suggest a role for the endogenous CHP in attenuating food intake.
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Affiliation(s)
- C Prasad
- Department of Medicine, (Section of Endocrinology, LSU Medical Center, New Orleans 70112, USA
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16
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Abstract
Cyclic dipeptides are among the simplest peptide derivatives commonly found in nature. Most cyclic dipeptides found to date appear to have emerged as by-products of fermentation and food processing. However, many are endogenous to members of animal and plant kingdoms; these include cyclo(Pro-Leu), cyclo(Pro-Val), cyclo(Pro-Phe), cyclo(Ala-Leu), cyclo(Pro-Tyr), cyclo(Pro-Trp), and cyclo(His-Pro). Although the five cyclic dipeptides--cyclo(His-Pro), cyclo(Leu-Gly), cyclo(Tyr-Arg), cyclo(Asp-Pro), and cyclo(Pro-Phe)--exhibit interesting physiological and/or pharmacological activities in mammals, only one of these, cyclo(His-Pro), has been conclusively shown to be endogenous to mammals. On the other hand, cyclo(Leu-Gly), cyclo(Tyr-Arg), and cyclo(Asp-Pro) are structurally related to endogenous peptides Pro-Leu-Gly-NH2 (melanocyte-stimulating hormone release inhibiting factor), Tyr-Arg (kyotorphin), and Val-Pro-Asp-Pro-Arg (enterostatin), respectively, which may serve as precursor peptides. It needs to be determined, however, whether these peptides can indeed result from the processing of their respective precursors. In conclusion, it appears that cyclic dipeptides are a relatively unexplored class of bioactive peptides that may hold great promise for the future.
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Affiliation(s)
- C Prasad
- Department of Medicine, Louisiana State University Medical Center, New Orleans 70112, USA
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17
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Boulay D, Leroux-Nicollet I, Duterte-Boucher D, Naudon L, Costentin J. Invariance of the density of dopamine uptake sites and dopamine metabolism in the rat brain after a chronic treatment with the dopamine uptake inhibitor GBR 12783. J Neural Transm (Vienna) 1994; 98:209-15. [PMID: 7748521 DOI: 10.1007/bf01276537] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A chronic treatment (10 mg/kg, twice daily during 9 days) with the dopamine uptake inhibitor GBR 12783 was performed in rats at a dose increasing their locomotor activity. Forty-eight hours after the last administration, animals were sacrificed and 3H mazindol binding was performed on brain slices. Autoradiographic analysis revealed no change in this binding relatively to control animals in regions with high dopamine contents: striatum, nucleus accumbens, olfactory tubercle, substantia nigra and ventral tegmentum area. The treatment did not either modify the levels of dopamine (DA) and metabolites (HVA, DOPAC) both in the striatum and the nucleus accumbens. Thus, early after the end of the treatment, the chronic blockade of the dopamine uptake complex regulates neither the dopamine uptake complex nor the dopamine metabolism.
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Affiliation(s)
- D Boulay
- Unité de Neuropsychopharmacologie Expérimentale E. P. 76 du CNRS, Faculté de Médicine et de Pharmacie de Rouen, Saint Etienne du Rouvray, France
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18
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Wolf GC, Sanborn CR, Thompson DJ, Wagley LM, Mizuma H, Hilton CW. Identification of cyclo(His-Pro)-like immunoreactivity in human follicular fluid: correlation with steroid and peptide hormones. JOURNAL OF THE SOCIETY FOR GYNECOLOGIC INVESTIGATION 1994; 1:220-4. [PMID: 9419775 DOI: 10.1177/107155769400100308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
OBJECTIVE The purpose of this study was to evaluate human follicular fluid (FF) for the presence of cyclo(His-Pro)-like immunoreactivity (CHP-LI). After verifying its presence, we quantitated the levels and investigated correlations with other follicular parameters, including hormone levels. METHODS Follicular fluid was collected from female volunteers undergoing controlled ovarian hyperstimulation. Fluid was collected by follicular puncture, either transvaginally (in vitro fertilization) or laparoscopically (gamete intrafallopian transfer) at the time of oocyte retrieval (N = 137). Follicular size was determined ultrasonographically. Assays for steroid and peptide hormones were determined with commercially available radioimmunoassay kits. CHP-LI was measured using a previously reported assay; parallel dilution curves and column chromatography aided in immunoidentity. RESULTS The mean FF CHP-LI concentration (13.10 +/- 1.83 nmol/L, N = 137) was greater than the corresponding serum values (9.42 +/- 2.45 nmol/L; N = 21) (P < .05). Large follicles (20 mm or greater; 14.45 +/- 1.74 nmol/L) contained significantly more CHP-LI than either medium follicles (16-19 mm; 11.51 +/- 1.88 nmol/L) or small follicles (15 mm or smaller; 10.83 +/- 2.12 nmol/L) (P < .05). Positive correlations were found between FF CHP-LI values and corresponding FF progesterone and prolactin concentrations (r = 0.67 and 0.62, respectively; P < .05). CONCLUSION Mean CHP-LI levels in the FF are greater than those in the corresponding serum. We suggest that the neuropeptide may be originating from either peptidase cleavage of precursor peptides or from granulosa cell production.
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Affiliation(s)
- G C Wolf
- Department of Obstetrics and Gynecology, University of South Carolina School of Medicine, Columbia 29203, USA
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19
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Das D, Rogers J, Michael-Titus AT. Comparative study of the effects of mu, delta and kappa opioid agonists on 3H-dopamine uptake in rat striatum and nucleus accumbens. Neuropharmacology 1994; 33:221-6. [PMID: 8035907 DOI: 10.1016/0028-3908(94)90012-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The effect of the mu opioid agonist DAGO, delta opioid agonist DPDPE and kappa opioid agonist U50,488H on 3H-dopamine (3H-DA) uptake was studied in synaptosomes prepared from rat striatum and nucleus accumbens. Over the range of concentrations tested (1 nM-10 microM) DAGO and DPDPE were devoid of effects on 3H-DA uptake in the striatum and the nucleus acumbens. In contrast, U50,488H significantly decreased 3H-DA uptake in both structures. The inhibition of uptake induced by the kappa agonist was not reversed in the presence of the opiate antagonists naloxone (10 microM) or nor-binaltorphimine (0.1 microM). Dynorphin A (1-13) also induced a significant reduction in 3H-DA uptake in both structures at the concentrations of 10 and 30 microM. This inhibitory effect was not reversed by naloxone (10 microM). These data suggest that kappa opioid agonists modulate dopamine uptake in the striatum and the nucleus accumbens and their effects may not be due to an activation of opioid receptors.
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Affiliation(s)
- D Das
- Department of Pharmacology, Faculty of Medicine Sciences, Queen Mary and Westfield College, University of London, U.K
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20
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Abstract
In many pharmacologic tests, cyclo(His-Pro) (CHP) appears to act like a dopaminergic agonist and augments the actions of amphetamine (AMP). Therefore, to determine whether CHP is an AMP-like peptide, a comparison between CHP and AMP was made using four separate tests known to be AMP-responsive. These include, food intake, locomotor activity, dopamine uptake and modulation of binding sites for amphetamine and mazindol. A decrease in food intake and increase in spontaneous locomotor activity and stereotypy was observed after peripheral administration of amphetamine but not CHP. Chronic CHP administration resulted into a decrease in striatal amphetamine - and increase in mazindol-binding sites; in contrast, chronic amphetamine decreased both amphetamine - and mazindol-binding sites. These results show a clear dissociation between CHP and AMP suggesting that CHP is not an amphetamine-like peptide.
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Affiliation(s)
- H Mizuma
- Department of Medicine, Louisiana State University Medical Center, New Orleans 70112
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21
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Shukla R, Rahmani NH, Mizuma H, Srimal RC, Prasad C. Role of endogenous cyclo(His-Pro) in cold-induced hypothermia in the desert rat (Mastomys natalensis). Peptides 1994; 15:1471-4. [PMID: 7700849 DOI: 10.1016/0196-9781(94)90125-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Central administration of exogenous cyclo(His-Pro) (CHP) is known to produce hypothermia in rodents. In the present study, we examined the role of endogenous CHP in cold-induced hypothermia in the desert rat, Mastomys natalensis. The results of these studies show that a rise in hypothalamic CHP content accompanied a decrease in rectal temperature during cold exposure. Immunoneutralization of endogenous CHP resulted in a significant decline in cold-induced hypothermia. In addition, central administration of cyclo(Ala-Gly), a structural analogue of CHP, also led to a decrease in cold-induced hypothermia. The results of these studies show that changes in endogenous CHP levels may affect body temperature regulation.
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Affiliation(s)
- R Shukla
- Division of Pharmacology, Central Drug Research Institute, Lucknow, India
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22
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Nishikawa Y, Ikegami H, Jikihara H, Koike K, Masumoto N, Kasahara K, Tasaka K, Hirota K, Miyake A, Tanizawa O. Effects of thyrotropin-releasing hormone and phorbol ester on dopamine release from dispersed rat tuberoinfundibular dopaminergic neurons. Peptides 1993; 14:839-44. [PMID: 8234033 DOI: 10.1016/0196-9781(93)90122-w] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
We have investigated the intracellular mechanisms underlying thyrotropin-releasing hormone (TRH)-mediated [3H]dopamine ([3H]DA) release from dispersed rat tuberoinfundibular dopaminergic (TIDA) neurons. The specific binding of [3H]Me-TRH to these cells is characterized by a single, high-affinity binding site (Kd = 1.2 nM) with a Bmax value of 178 fmol/mg protein. Thyrotropin-releasing hormone markedly increased [3H]DA release and intracellular free calcium concentration ([Ca2+]i) in TIDA neurons, and its effect was abolished by treatment with EGTA (5 mM) or chlordiazepoxide, a specific TRH receptor antagonist (10 microM). Furthermore, to examine the involvement of protein kinase C on [3H]DA release, we investigated the effect of phorbol myristate acetate (PMA), which is known to activate protein kinase C directly. Phorbol myristate acetate induced a significant increase in [3H]DA release in a concentration-dependent manner. Treatment with TRH (1 microM) plus PMA (100 nM) resulted in an additive increase in [3H]DA release. Thyrotropin-releasing hormone (1 microM) still increased [3H]DA release even after preincubation with PMA (500 nM) for 24 h, but PMA (100 nM) did not under the same conditions. These results suggest that TRH may induce DA release in dispersed rat TIDA cells by increasing calcium influx and activating the protein kinase C system.
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Affiliation(s)
- Y Nishikawa
- Department of Obstetrics and Gynecology, Osaka University Medical School, Japan
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23
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Kilbourn MR, DaSilva JN, Frey KA, Koeppe RA, Kuhl DE. In vivo imaging of vesicular monoamine transporters in human brain using [11C]tetrabenazine and positron emission tomography. J Neurochem 1993; 60:2315-8. [PMID: 8492135 DOI: 10.1111/j.1471-4159.1993.tb03521.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The pharmacokinetics of [11C]tetrabenazine, a high-affinity radioligand for the monoamine vesicular transporter, were determined in living human brain using in vivo imaging by positron emission tomography (PET). The radiotracer showed high brain uptake and rapid washout from all brain regions with relatively slower clearance from regions of highest concentrations of monoamine vesicular transporters (striatum), resulting in clear differential visualization of these structures at short intervals after injection (10-20 min). As the first human PET imaging study of a vesicular neurotransmitter transporter, these experiments demonstrate that external imaging of vesicular transporters forms a new and valuable approach to the in vivo quantification of monoaminergic neurons, with potential application to the in vivo study of neurodegenerative disorders such as Parkinson's disease.
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Affiliation(s)
- M R Kilbourn
- Department of Internal Medicine, University of Michigan School of Medicine, Ann Arbor
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24
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DaSilva JN, Kilbourn MR, Domino EF. In vivo imaging of monoaminergic nerve terminals in normal and MPTP-lesioned primate brain using positron emission tomography (PET) and [11C]tetrabenazine. Synapse 1993; 14:128-31. [PMID: 8332945 DOI: 10.1002/syn.890140205] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The first successful in vivo imaging of monoamine vesicular transporters in the living primate brain is described, using [11C]tetrabenazine ([11C]TBZ) and Positron Emission Tomography (PET). Radioligand uptake into brain is rapid, and at short time periods (10-30 minutes) the higher uptake and retention of the radiotracer in the more densely dopaminergic innervated striatum is clearly visualized. Specific binding in striatum can be entirely blocked with co-administration of a pharmacological dose (1 mg/kg i.v.) of tetrabenazine. In a unilaterally MPTP-lesioned monkey, specific binding of radioligand was absent in the striatum on the lesioned side, with no effect on radiotracer distribution in the cortex, cerebellum or contralateral striatum. PET imaging with [11C]TBZ provides a new approach to the in vivo study of monoaminergic neurons and their loss in neurodegenerative diseases.
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Affiliation(s)
- J N DaSilva
- Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109
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25
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Morissette M, Di Paolo T. Effect of chronic estradiol and progesterone treatments of ovariectomized rats on brain dopamine uptake sites. J Neurochem 1993; 60:1876-83. [PMID: 8473903 DOI: 10.1111/j.1471-4159.1993.tb13415.x] [Citation(s) in RCA: 112] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Dopamine released from brain nerve terminals is mainly removed from the synaptic cleft by an uptake mechanism. Despite their functional importance, modulation of the dopamine uptake sites is still not well known. Steroid hormones were shown to modulate brain dopamine transmission. The aim of this study was thus to investigate in ovariectomized rats the effects of 17 beta-estradiol and progesterone treatments on brain dopamine uptake sites. Treatments consisted of 17 beta-estradiol (10 micrograms/0.2 ml), progesterone (0.72 mg/0.2 ml), 17 beta-estradiol + progesterone, or the vehicle (0.3% gelatin in saline solution) twice daily for 2 weeks. The steroid treatments left the affinity of [3H]GBR 12935 binding to striatal homogenates unchanged (ovariectomized rats, 0.823 +/- 0.028 nM), whereas the density was increased by these steroids alone or in combination to a similar extent of 16-23%. Chronic treatment of ovariectomized rats with 17 beta-estradiol, progesterone, or their combination increased to the same extent and uniformly [3H]-GBR 12935 binding in the striatum as measured by autoradiography; the increase was similar in the substantia nigra pars compacta, whereas no steroid effect was observed in the nucleus accumbens and in the substantia nigra pars reticulata. In summary, chronic exposure to 17 beta-estradiol and/or progesterone increased dopamine uptake site density in the nigrostriatal dopaminergic system, whereas the nucleus accumbens and the substantia nigra pars reticulata were unaffected.
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Affiliation(s)
- M Morissette
- School of Pharmacy, Laval University, Québec, Canada
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26
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Joyce JN. The dopamine hypothesis of schizophrenia: limbic interactions with serotonin and norepinephrine. Psychopharmacology (Berl) 1993; 112:S16-34. [PMID: 7831438 DOI: 10.1007/bf02245004] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The "dopamine hypothesis" of schizophrenia has been the predominant guiding theoretical construct for driving studies of the neurobiology of schizophrenia. There has, however, been much interest in the contributions of non-dopamine systems to the clinical symptoms of schizophrenia, in particular, norepinephrine and serotonin. However, direct evidence for altered transmission in monoamine systems has been quite limited. In part this reflects a focus on specific brain regions for different transmitters, in contrast to a "neural systems" approach. Thus, evidence for the dopamine hypothesis has been derived from studies of the basal ganglia in schizophrenic cases and infrequently from other (e.g. cortical) regions. Recent studies have suggested that disturbances in the organization or development of the temporal lobe may underlie certain aspects of the symptoms of schizophrenia In particular, the hippocampus may show cellular loss or disturbances in cell orientation. These results are supported by the work that has identified neuropsychological and in vivo brain disturbances in schizophrenia specific to the medial temporal lobe. However, not all cases show such pathology and it is likely that these disorders could, in addition, involve an important afferent and/or efferent system associated with the temporal lobe. This model is based on the currently held view that parallel cortico-striatal-pallidal-thalamo circuits form an important basis for information processing in the brain. One such circuit involves the primary efferent of the hippocampus, the subiculum, and associated cortical regions that project onto the ventral striatum. Many of the cortical regions that project directly to the ventral striatum also project to the hippocampus via the entorhinal cortex. These include the anterior cingulate, posterior cingulate, superior temporal cortex, and inferior temporal cortex. The ventral striatum, made up of the nucleus accumbens, olfactory tubercle, and ventral putamen, has as its target the ventral pallidum. The ventral pallidum projects to the medial dorsal nuclei of the thalamus, which, in turn, projects to the anterior prefrontal cortical area. This loop has been referred to as the limbic loop. The patterns of innervation and expression of monoamine receptors in the brain have been delineated for the non-human primate and are being unraveled in the human. We, and other, have described the patterns of receptor expression in the limbic circuit. However, few studies have been published to date that detail what the neurochemical counterparts of the neuronal and neuropsychological disturbances in the limbic circuit might be. We have explored the possibility that monoamine systems are altered at more than one synaptic station in this circuit.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- J N Joyce
- Department of Psychiatry Research Department, University of Pennsylvania School of Medicine, Philadelphia 19104-6141
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27
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Kaakkola S, Wurtman RJ. Effects of two diketopiperazines, cyclo (His-Pro) and cyclo (Asp-Phe), on striatal dopamine: a microdialysis study. Brain Res Bull 1993; 32:667-72. [PMID: 7693310 DOI: 10.1016/0361-9230(93)90171-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The effects of two diketopiperazines, Cyclo (His-Pro) (CHP) and Cyclo (Asp-Phe) (CAP), on striatal extracellular levels of dopamine (DA), dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) were examined using in vivo microdialysis in anaesthetized rats. Treatment with neither CHP (0.1-10 mg/kg IP and 0.3 mg/kg i.v.) nor CAP (0.1-10 mg/kg IP and 10 mg/kg PO) significantly changed the efflux of DA, DOPAC, HVA, or 5-HIAA when compared to the effects of treatment with saline. Our results suggest that systemic administration of CHP or CAP alone does not modify striatal dopaminergic neurotransmission. The previous findings of enhanced DA release by systemic administration of thyrotropin releasing hormone (TRH) are probably not explained by formation of CHP from TRH.
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Affiliation(s)
- S Kaakkola
- Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge 02139
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28
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Prasad C, Hilton CW, Lohr JB, Robertson HJ. Increased cerebrospinal fluid cyclo(His-Pro) content in schizophrenia. Neuropeptides 1991; 20:187-90. [PMID: 1762668 DOI: 10.1016/0143-4179(91)90130-b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Cyclo(His-Pro) (CHP) is a peptide endogenous to human brain and cerebrospinal fluid (CSF). In animal studies administration of exogenous CHP augments dopaminergic neurotransmission. To explore the role of this peptide in schizophrenia, a disease characterized by a hyperdopaminergic state, we have measured CSF CHP levels in control, never-medicated schizophrenics and medicated schizophrenics. Our data show a 53% increase in CSF levels of CHP in never-medicated schizophrenics (p = 0.015), and a 25% increase in medicated schizophrenics when compared to controls. We speculate that CHP may contribute to the expression of hyperdopaminergic symptoms in schizophrenia.
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Affiliation(s)
- C Prasad
- Department of Medicine, Louisiana State University Medical Center, New Orleans 70112
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29
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Abstract
Cyclic dipeptides or diketopiperazines are readily generated during in vitro hydrolysis of proteins and polypeptides. This led us to examine whether cyclo(His-Pro) (CHP), a diketopiperazine containing histidine and proline, could be formed in vivo from dietary proteins. The data presented here show that at least in rat, neither urinary nor plasma concentration of CHP is elevated by consumption of a diet rich in proteins. Several dietary supplements derived from casein and/or soy protein hydrolysates, however, contain high levels of CHP-LI. Oral intake of one such supplement led to a sharp increase in the plasma level of CHP-LI.
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Affiliation(s)
- C Prasad
- Department of Medicine, Louisiana State University Medical Center, New Orleans 70112
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