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Keskin E, Can EY, Aydın HA, Işık E, Özgen U, Şimşek K, Cengil O, Başar C, Kalaycı M. The preventative effect of of Ro5-4864 (peripheral benzodiazepine receptor agonist) on spinal epidural fibrosis after laminectomy in a rat model. Neurol Res 2021; 43:1107-1115. [PMID: 34461817 DOI: 10.1080/01616412.2021.1949689] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
OBJECTIVE To investigate the histopathological effects of a peripheral benzodiazepine receptor agonist (Ro5-4864) on epidural fibrosis (EF) in an experimental study model (post-laminectomy) in rats. METHODS A total of 32 albino Wistar rats were randomly divided into four equal groups (n = 8). In Group 1, no treatment was applied after laminectomy (control group). In Group 2, hemostasis was achieved after Laminectomy, and the surgical procedure was terminated by placing a 2-mm absorbable gelatin sponge dipped in saline into the epidural space. In Group 3, low-dose (4 mg/kg) Ro5-4864 was administered 30 minutes before the surgery. In Group 4, high-dose (8 mg/kg) Ro5-4864 was administered 30 minutes before the surgery. A histopathological examination was performed to evaluate arachnoidal invasion and EF. RESULTS Our data revealed the EF was significantly reduced in rats treated with high-dose Ro5-4864 (Group 4) compared to the control and saline-soaked Spongostan groups (p = 0.000 and p = 0.006, respectively). There was no significant difference between the groups treated with high- and low-dose Ro5-4864. Arachnoidal invasion was not seen in any of the rats in the high-dose R05-4864 group. However, the arachnoidal invasion results did not significantly differ between the study groups (p = 0.052 = 0.05). CONCLUSIONS Our study showed that Ro5-4864 could be effective in reducing EF in rats after.
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Affiliation(s)
- Emrah Keskin
- Department of Neurosurgery, Faculty of Medicine, Zonguldak Bulent Ecevit University, Zonguldak, Turkey
| | - Emine Yılmaz Can
- Department of Pharmacology, Faculty of Medicine, Zonguldak Bulent Ecevit University, Zonguldak, Turkey
| | - Hasan Ali Aydın
- Department of Neurosurgery, Faculty of Medicine, Zonguldak Bulent Ecevit University, Zonguldak, Turkey
| | - Emre Işık
- Department of Pathology, Faculty of Medicine, Zonguldak Bulent Ecevit University, Zonguldak, Turkey
| | - Utku Özgen
- Department of Neurosurgery, Atatürk State Hospital, Zonguldak, Turkey
| | - Kenan Şimşek
- Department of Neurosurgery, Faculty of Medicine, Zonguldak Bulent Ecevit University, Zonguldak, Turkey
| | - Osman Cengil
- Department of Experimental Animal Research Laboratory, Faculty of Medicine, Zonguldak Bulent Ecevit University, Zonguldak, Turkey
| | - Cansu Başar
- Insurance Information and Monitoring Center, Istanbul, Turkey
| | - Murat Kalaycı
- Department of Neurosurgery, Faculty of Medicine, Zonguldak Bulent Ecevit University, Zonguldak, Turkey
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Grimm A, Lejri I, Hallé F, Schmitt M, Götz J, Bihel F, Eckert A. Mitochondria modulatory effects of new TSPO ligands in a cellular model of tauopathies. J Neuroendocrinol 2020; 32:e12796. [PMID: 31536662 PMCID: PMC7003898 DOI: 10.1111/jne.12796] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 09/09/2019] [Accepted: 09/17/2019] [Indexed: 01/12/2023]
Abstract
Translocator protein 18 kDa (TSPO) is a mitochondrial protein located in the outer membrane and involved in cholesterol translocation, a prerequisite for steroid biosynthesis. TSPO modulation also appears to play a role in other mitochondrial functions, including mitochondrial respiration and cell survival. In the central nervous system, its expression is up-regulated in neuropathology such as Alzheimer's disease (AD). Previously, we demonstrated that two new TSPO ligands, named 2a and 2b, stimulated pregnenolone synthesis and ATP production in a cellular model of AD overproducing β-amyloid peptide. The present study aimed to evaluate the impact of the new TSPO ligands on mitochondrial dysfunction in a cellular model of AD-related tauopathy (human neuroblastoma cells SH-SY5Y stably overexpressing the P301L-mutant Tau) presenting mitochondrial impairments, including a decreased ATP synthesis and mitochondrial membrane potential, as well as a decrease in pregnenolone synthesis compared to control cells. The effects of our new ligands were compared with those of TSPO ligands described in the literature (XBD173, SSR-180,575 and Ro5-4864). The TSPO ligands 2a and 2b exerted beneficial mitochondrial modulatory effects by increasing ATP levels and mitochondrial membrane potential, paralleled by an increase of pregnenolone levels in mutant Tau cells, as well as in control cells. The compounds 2a and 2b showed effects on mitochondrial activity similar to those obtained with the TSPO ligands of reference. These findings indicate that the new TSPO ligands modulate the mitochondrial bioenergetic phenotype as well as the de novo synthesis of neurosteroids in a cellular model of AD-related tauopathy, suggesting that these compounds could be potential new therapeutic tools for the treatment of AD.
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Affiliation(s)
- Amandine Grimm
- Transfaculty Research Platform, Molecular & Cognitive NeuroscienceNeurobiology Laboratory for Brain Aging and Mental HealthUniversity of BaselBaselSwitzerland
- Psychiatric University ClinicsBaselSwitzerland
| | - Imane Lejri
- Transfaculty Research Platform, Molecular & Cognitive NeuroscienceNeurobiology Laboratory for Brain Aging and Mental HealthUniversity of BaselBaselSwitzerland
- Psychiatric University ClinicsBaselSwitzerland
| | - François Hallé
- Laboratoire d’Innovation ThérapeutiqueFaculté de PharmacieUMR7200CNRSUniversité de StrasbourgIllkirchFrance
| | - Martine Schmitt
- Laboratoire d’Innovation ThérapeutiqueFaculté de PharmacieUMR7200CNRSUniversité de StrasbourgIllkirchFrance
| | - Jürgen Götz
- Clem Jones Centre for Ageing Dementia Research (CJCADR)Queensland Brain Institute (QBI)The University of QueenslandSt LuciaQLDAustralia
| | - Frederic Bihel
- Laboratoire d’Innovation ThérapeutiqueFaculté de PharmacieUMR7200CNRSUniversité de StrasbourgIllkirchFrance
| | - Anne Eckert
- Transfaculty Research Platform, Molecular & Cognitive NeuroscienceNeurobiology Laboratory for Brain Aging and Mental HealthUniversity of BaselBaselSwitzerland
- Psychiatric University ClinicsBaselSwitzerland
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Da Pozzo E, Tremolanti C, Costa B, Giacomelli C, Milenkovic VM, Bader S, Wetzel CH, Rupprecht R, Taliani S, Da Settimo F, Martini C. Microglial Pro-Inflammatory and Anti-Inflammatory Phenotypes Are Modulated by Translocator Protein Activation. Int J Mol Sci 2019; 20:ijms20184467. [PMID: 31510070 PMCID: PMC6770267 DOI: 10.3390/ijms20184467] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2019] [Revised: 09/06/2019] [Accepted: 09/09/2019] [Indexed: 12/13/2022] Open
Abstract
A key role of the mitochondrial Translocator Protein 18 KDa (TSPO) in neuroinflammation has been recently proposed. However, little is known about TSPO-activated pathways underlying the modulation of reactive microglia. In the present work, the TSPO activation was explored in an in vitro human primary microglia model (immortalized C20 cells) under inflammatory stimulus. Two different approaches were used with the aim to (i) pharmacologically amplify or (ii) silence, by the lentiviral short hairpin RNA, the TSPO physiological function. In the TSPO pharmacological stimulation model, the synthetic steroidogenic selective ligand XBD-173 attenuated the activation of microglia. Indeed, it reduces and increases the release of pro-inflammatory and anti-inflammatory cytokines, respectively. Such ligand-induced effects were abolished when C20 cells were treated with the steroidogenesis inhibitor aminoglutethimide. This suggests a role for neurosteroids in modulating the interleukin production. The highly steroidogenic ligand XBD-173 attenuated the neuroinflammatory response more effectively than the poorly steroidogenic ones, which suggests that the observed modulation on the cytokine release may be influenced by the levels of produced neurosteroids. In the TSPO silencing model, the reduction of TSPO caused a more inflamed phenotype with respect to scrambled cells. Similarly, during the inflammatory response, the TSPO silencing increased and reduced the release of pro-inflammatory and anti-inflammatory cytokines, respectively. In conclusion, the obtained results are in favor of a homeostatic role for TSPO in the context of dynamic balance between anti-inflammatory and pro-inflammatory mediators in the human microglia-mediated inflammatory response. Interestingly, our preliminary results propose that the TSPO expression could be stimulated by NF-κB during activation of the inflammatory response.
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Affiliation(s)
- Eleonora Da Pozzo
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Chiara Tremolanti
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Barbara Costa
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
- Correspondence:
| | - Chiara Giacomelli
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Vladimir M. Milenkovic
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93059 Regensburg, Germany; (V.M.M.); (S.B.); (C.H.W.); (R.R.)
| | - Stefanie Bader
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93059 Regensburg, Germany; (V.M.M.); (S.B.); (C.H.W.); (R.R.)
| | - Christian H. Wetzel
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93059 Regensburg, Germany; (V.M.M.); (S.B.); (C.H.W.); (R.R.)
| | - Rainer Rupprecht
- Department of Psychiatry and Psychotherapy, Molecular Neurosciences, University of Regensburg, 93059 Regensburg, Germany; (V.M.M.); (S.B.); (C.H.W.); (R.R.)
| | - Sabrina Taliani
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Federico Da Settimo
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
| | - Claudia Martini
- Department of Pharmacy, University of Pisa, 56126 Pisa, Italy; (E.D.P.); (C.T.); (C.G.); (S.T.); (F.D.S.); (C.M.)
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Baez E, Guio-Vega GP, Echeverria V, Sandoval-Rueda DA, Barreto GE. 4'-Chlorodiazepam Protects Mitochondria in T98G Astrocyte Cell Line from Glucose Deprivation. Neurotox Res 2017; 32:163-171. [PMID: 28405935 DOI: 10.1007/s12640-017-9733-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Revised: 03/30/2017] [Accepted: 04/04/2017] [Indexed: 01/12/2023]
Abstract
The translocator protein (TSPO), formerly known as the peripheral-type benzodiazepine receptor (PBR), is considered an important regulator of steroidogenesis and a potential therapeutic target in neurological disorders. Previous evidence suggests that TSPO ligands can protect cells during injury and prevent apoptosis in central nervous system (CNS) cells. However, its actions on astrocytic cells under metabolic injury are not well understood. In this study, we explored whether 4'-chlorodiazepam (Ro5-4864), a TSPO ligand, might protect astrocyte mitochondria under glucose deprivation. Our results showed that 4'-chlorodiazepam preserved cell viability and reduced nuclear fragmentation in glucose-deprived cells. These effects were accompanied by a reduced production of free radicals and maintenance of mitochondrial functions in cells treated with 4'-chlorodiazepam. Finally, our findings suggest that TSPO might be involved in reducing oxidative stress by preserving mitochondrial functions in astrocytic cells exposed to glucose withdrawal.
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Affiliation(s)
- Eliana Baez
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - Gina Paola Guio-Vega
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | | | - Daniel Andres Sandoval-Rueda
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia
| | - George E Barreto
- Departamento de Nutrición y Bioquímica, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá D.C., Colombia. .,Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Santiago, Chile.
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Radin DP, Patel P. Delineating the molecular mechanisms of tamoxifen’s oncolytic actions in estrogen receptor-negative cancers. Eur J Pharmacol 2016; 781:173-80. [DOI: 10.1016/j.ejphar.2016.04.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 04/06/2016] [Accepted: 04/11/2016] [Indexed: 12/15/2022]
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TSPO ligand residence time influences human glioblastoma multiforme cell death/life balance. Apoptosis 2015; 20:383-98. [PMID: 25413799 DOI: 10.1007/s10495-014-1063-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Ligands addressed to the mitochondrial Translocator Protein (TSPO) have been suggested as cell death/life and steroidogenesis modulators. Thus, TSPO ligands have been proposed as drug candidates in several diseases; nevertheless, a correlation between their binding affinity and in vitro efficacy has not been demonstrated yet, questioning the specificity of the observed effects. Since drug-target residence time is an emerging parameter able to influence drug pharmacological features, herein, the interaction between TSPO and irDE-MPIGA, a covalent TSPO ligand, was investigated in order to explore TSPO control on death/life processes in a standardized glioblastoma cell setting. After 90 min irDE-MPIGA cell treatment, 25 nM ligand concentration saturated irreversibly all TSPO binding sites; after 24 h, TSPO de-novo synthesis occurred and about 40 % TSPO binding sites resulted covalently bound to irDE-MPIGA. During cell culture treatments, several dynamic events were observed: (a) early apoptotic markers appeared, such as mitochondrial membrane potential collapse (at 3 h) and externalization of phosphatidylserine (at 6 h); (b) cell viability was reduced (at 6 h), without cell cycle arrest. After digitonin-permeabilized cell suspension treatment, a modulation of mitochondrial permeability transition pore was evidenced. Similar effects were elicited by the reversible TSPO ligand PIGA only when applied at micromolar dose. Interestingly, after 6 h, irDE-MPIGA cell exposure restored cell survival parameters. These results highlighted the ligand-target residence time and the cellular setting are crucial parameters that should be taken into account to understand the drug binding affinity and efficacy correlation and, above all, to translate efficiently cellular drug responses from bench to bedside.
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Yousefi OS, Wilhelm T, Maschke-Neuß K, Kuhny M, Martin C, Molderings GJ, Kratz F, Hildenbrand B, Huber M. The 1,4-benzodiazepine Ro5-4864 (4-chlorodiazepam) suppresses multiple pro-inflammatory mast cell effector functions. Cell Commun Signal 2013; 11:13. [PMID: 23425659 PMCID: PMC3598916 DOI: 10.1186/1478-811x-11-13] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2012] [Accepted: 02/16/2013] [Indexed: 11/25/2022] Open
Abstract
Activation of mast cells (MCs) can be achieved by the high-affinity receptor for IgE (FcεRI) as well as by additional receptors such as the lipopolysaccharide (LPS) receptor and the receptor tyrosine kinase Kit (stem cell factor [SCF] receptor). Thus, pharmacological interventions which stabilize MCs in response to different receptors would be preferable in diseases with pathological systemic MC activation such as systemic mastocytosis. 1,4-Benzodiazepines (BDZs) have been reported to suppress MC effector functions. In the present study, our aim was to analyze molecularly the effects of BDZs on MC activation by comparison of the effects of the two BDZs Ro5-4864 and clonazepam, which markedly differ in their affinities for the archetypical BDZ recognition sites, i.e., the GABAA receptor and TSPO (previously termed peripheral-type BDZ receptor). Ro5-4864 is a selective agonist at TSPO, whereas clonazepam is a selective agonist at the GABAA receptor. Ro5-4864 suppressed pro-inflammatory MC effector functions in response to antigen (Ag) (degranulation/cytokine production) and LPS and SCF (cytokine production), whereas clonazepam was inactive. Signaling pathway analyses revealed inhibitory effects of Ro5-4864 on Ag-triggered production of reactive oxygen species, calcium mobilization and activation of different downstream kinases. The initial activation of Src family kinases was attenuated by Ro5-4864 offering a molecular explanation for the observed impacts on various downstream signaling elements. In conclusion, BDZs structurally related to Ro5-4864 might serve as multifunctional MC stabilizers without the sedative effect of GABAA receptor-interacting BDZs.
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Affiliation(s)
- Omid Sascha Yousefi
- Medical Faculty, Institute of Biochemistry and Molecular Immunology, RWTH Aachen University, Pauwelsstr, 30, 52074, Aachen, Germany.
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The 18 kDa translocator protein influences angiogenesis, as well as aggressiveness, adhesion, migration, and proliferation of glioblastoma cells. Pharmacogenet Genomics 2012; 22:538-50. [PMID: 22547081 DOI: 10.1097/fpc.0b013e3283539cdc] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND It is known that the mitochondrial 18 kDa translocator protein (TSPO) is present in almost all peripheral tissues and also in glial cells in the brain. TSPO levels are typically enhanced in correlation with tumorigenesis of cancer cells including glioblastoma. Relevant for angiogenesis, TSPO is also present in almost all cells of the cardiovascular system. METHODS We studied the effect of TSPO knockdown by siRNA on various aspects of tumor growth of U118MG glioblastoma cells in two in-vivo models: a nude mouse model with intracerebral implants of U118MG glioblastoma cells and implantation of U118MG glioblastoma cells on the chorionallantoic membrane (CAM) of chicken embryos. In vitro, we further assayed the influence of TSPO on the invasive potential of U118MG cells. RESULTS TSPO knockdown increased tumor growth in both in-vivo models compared with the scrambled siRNA control. Angiogenesis was also increased by TSPO knockdown as determined by a CAM assay. TSPO knockdown led to a decrease in adhesion to the proteins of the extracellular matrix, including fibronectin, collagen I, collagen IV, laminin I, and fibrinogen. TSPO knockdown also led to an enhancement in the migratory capability of U118MG cells, as determined in a modified Boyden chamber. Application of the TSPO ligand 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide (PK 11195) at a concentration of 25 µmol/l in the in-vitro models yielded results similar to those obtained on TSPO knockdown. We found no effects of PK 11195 on TSPO protein expression. Interestingly, at low nmol/l concentrations (around 1 nmol/l), PK 11195 enhanced adhesion to collagen I, suggesting a bimodal concentration effect of PK 11195. CONCLUSION Intact TSPO appears to be able to counteract the invasive and angiogenic characteristics related to the aggressiveness of U118MG glioblastoma cells in vivo and in vitro.
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Rupprecht R, Papadopoulos V, Rammes G, Baghai TC, Fan J, Akula N, Groyer G, Adams D, Schumacher M. Translocator protein (18 kDa) (TSPO) as a therapeutic target for neurological and psychiatric disorders. Nat Rev Drug Discov 2011; 9:971-88. [PMID: 21119734 DOI: 10.1038/nrd3295] [Citation(s) in RCA: 715] [Impact Index Per Article: 55.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The translocator protein (18 kDa) (TSPO) is localized primarily in the outer mitochondrial membrane of steroid-synthesizing cells, including those in the central and peripheral nervous system. One of its main functions is the transport of the substrate cholesterol into mitochondria, a prerequisite for steroid synthesis. TSPO expression may constitute a biomarker of brain inflammation and reactive gliosis that could be monitored by using TSPO ligands as neuroimaging agents. Moreover, initial clinical trials have indicated that TSPO ligands might be valuable in the treatment of neurological and psychiatric disorders. This Review focuses on the biology and pathophysiology of TSPO and the potential of currently available TSPO ligands for the diagnosis and treatment of neurological and psychiatric disorders.
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Affiliation(s)
- Rainer Rupprecht
- Department of Psychiatry and Psychotherapy, Ludwig-Maximilians University, Nussbaumstrasse 7, 80336 Munich, Germany.
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Lopes-Costa PV, dos Santos AR, da Silva BB. The effect of raloxifene on Bax protein expression in breast carcinomas of postmenopausal women. Diagn Cytopathol 2010; 40:570-4. [PMID: 22707322 DOI: 10.1002/dc.21580] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2010] [Accepted: 09/29/2010] [Indexed: 01/26/2023]
Abstract
The actual role of Bax protein as a prognostic biomarker that predicts response to therapy remains unclear. The objective of this study was to evaluate the effect of raloxifene on Bax protein expression in breast carcinomas of postmenopausal women. Twenty postmenopausal patients with operable stage II, estrogen receptor-positive, infiltrating ductal breast carcinoma were treated with oral raloxifene at a dose of 60 mg/day for a period of 28 days before definitive surgery. Tumor samples were obtained by incisional biopsy at the time of diagnosis and again at the time of definitive surgical treatment. Immunohistochemical evaluation of Bax expression was assessed semiquantitatively based on the fraction of stained tumor cells and intensity of staining. McNemar's test was used to analyze data (P < 0.05). Eleven of the 20 (55%) patients were classified as positive for Bax expression before raloxifene treatment, whereas 9(45%) were classified as positive after raloxifene treatment (P = 0.479). In conclusion, raloxifene did not alter Bax expression significantly in estrogen receptor-positive breast carcinomas of postmenopausal women.
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Affiliation(s)
- Pedro Vitor Lopes-Costa
- Department of Gynecology, Division of Mastology, Getúlio Vargas Hospital, Universidade Federal do Piauí, Teresina, Piauí, Brazil.
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Leducq-Alet N, Vin V, Savi P, Bono F. TNF-alpha induced PMN apoptosis in whole human blood: Protective effect of SSR180575, a potent and selective peripheral benzodiazepine ligand. Biochem Biophys Res Commun 2010; 399:475-9. [DOI: 10.1016/j.bbrc.2010.07.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2010] [Accepted: 07/03/2010] [Indexed: 10/19/2022]
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Baumann KH, Klusmeier E, Eggemann I, Reinartz S, Almeroth A, Kalder M, Wagner U. Effects of celecoxib and ly117018 combination on human breast cancer cells in vitro. BREAST CANCER-BASIC AND CLINICAL RESEARCH 2009; 3:23-34. [PMID: 21556247 PMCID: PMC3086307 DOI: 10.4137/bcbcr.s2291] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Activation and signalling of estrogen receptor (ER) and COX-2 represent two important pathways in breast cancer cell regulation. Activation of either pathway is associated with breast cancer cell proliferation and eventually malignant progression. Raloxifene analogue, Ly117018, a selective estrogen receptor modulator and celecoxib, a specific COX-2 inhibitor have been shown to inhibit breast cancer cell proliferation when used alone in vitro and in vivo. In this study, the combined drug effects on hormone-dependent MCF-7 and hormone-independent MDA-MB-435 cells in vitro were evaluated. Cell proliferation assays excluded drug antagonism and revealed a moderate synergistic growth inhibitory activity of Ly117018 and celecoxib on both cell lines when combined in specific concentrations. Growth inhibition of either compound was not associated with cell cycle arrest. In MCF-7 cells, western blot analysis revealed a decreased phosphorylation of the AKT protein by either agent alone or in combination. In MDA-MB-435 cells, celecoxib alone induced an increase in AKT phosphorylation relative to total AKT protein; this effect was decreased in the presence of Ly117018. These results indicate that these two drugs are non-antagonistic; and when combined in specific concentrations, moderate synergistic antiproliferative activity of celecoxib and Ly117018 were observed in hormone-dependent MCF-7 and hormone-independent MDA-MB-435 cells associated with changes in cell cycle distribution and regulation of AKT protein and phosphorylation. These findings further support a central role of the ER- and COX-2 pathways in human breast cancer cells.
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Affiliation(s)
- Klaus H Baumann
- University Hospital of Gießen and Marburg, Location Marburg, Dept. of Gynecology, Gynecological Endocrinology and Oncology, 35043 Marburg, Germany
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Ostuni MA, Ducroc R, Péranzi G, Tonon MC, Papadopoulos V, Lacapere JJ. Translocator protein (18 kDa) ligand PK 11195 induces transient mitochondrial Ca2+ release leading to transepithelial Cl- secretion in HT-29 human colon cancer cells. Biol Cell 2008; 99:639-47. [PMID: 17561806 DOI: 10.1042/bc20070048] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND INFORMATION TSPO (translocator protein), known previously as PBR (peripheral-type benzodiazepine receptor), is a 18 kDa protein expressed in the mitochondrial membrane of a variety of tissues. TSPO has been reported to be over-expressed in human colorectal tumours and cancer cell lines, but its function is not well characterized. RESULTS We investigated the expression and function of TSPO in the human colon cancer cells HT-29. Immunohistochemical studies revealed that TSPO is localized in mitochondria, and its endogenous ligand, the polypeptide diazepam-binding inhibitor, in the cytosol. Radioligand binding studies using the specific high-affinity drug ligand [(3)H]PK 11195 and membrane fraction demonstrated saturable binding, with K(d) and B(max) values of 13.5+/-1.5 nM and 10.1+/-1.0 pmol/mg respectively. PK 11195 induced a rapid and transient dose-dependent rise in intracellular [Ca(2+)], which was unaffected by extracellular Ca(2+), but was blocked by the PTP (permeability transition pore) inhibitor, cyclosporin A, and by the TSPO partial agonist, flunitrazepam. Using HT-29 clone 19A cell line, which forms cell monolayers, we demonstrated that TSPO ligand stimulated a Ca(2+)-dependent transepithelial Cl(-) secretion. This secretion was inhibited: (i) after removal of extracellular Cl(-); (ii) by apical addition of the Cl(-) channel blocker NPPB [5-nitro-2-(3-phenylpropylamino)-benzoate]; and (iii) by basolateral addition of the Na(+)-K(+)-2Cl(-) co-transporter inhibitor bumetanide. Furthermore, the intracellular Ca(2+) chelator BAPTA/AM [bis-(o-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid tetrakis(acetoxymethyl ester)] and cyclosporin A abolished the rise in PK 11195-induced Cl(-) secretion. CONCLUSIONS These findings indicate that TSPO is located in mitochondrial membranes of HT-29 and reveal that its activation induces a rise in cytosolic Ca(2+), leading to the stimulation of Cl(-) secretion.
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Affiliation(s)
- Mariano A Ostuni
- Inserm U773, Centre de Recherche Biomédicale Bichat Beaujon CRB3, Université Paris 7 Denis Diderot, F-75018 Paris, France
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Nigam M, Ranjan V, Srivastava S, Sharma R, Balapure AK. Centchroman induces G0/G1 arrest and caspase-dependent apoptosis involving mitochondrial membrane depolarization in MCF-7 and MDA MB-231 human breast cancer cells. Life Sci 2007; 82:577-90. [PMID: 18279897 DOI: 10.1016/j.lfs.2007.11.028] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2007] [Revised: 10/12/2007] [Accepted: 11/27/2007] [Indexed: 12/01/2022]
Abstract
Studies with Centchroman (CC) as a candidate anti-breast cancer agent are into phase III multicentric clinical trial in stage III/IV breast cancer. We have previously demonstrated its anti-neoplastic activity in Estrogen Receptor positive (ER+ve) MCF-7 Human Breast Cancer Cells (HBCCs). We now present the basis for anti-neoplastic activity of CC, mediated through apoptosis in both ER+ve/-ve MCF-7 and MDA MB-231 HBCCs respectively, compared to Tamoxifen (TAM) as a positive control. All the experiments were performed with 48 h estrogen-deprived cells exposed to CC/TAM for the subsequent 48 h. Cytotoxic potential of CC was assessed through SRB assay. Cell-cycle analysis, Time-dependent cytotoxicity, Reactive Oxygen Species (ROS) and Mitochondrial Membrane Permeability were investigated by Flow Cytometry. Early-stage apoptosis was detected by Annexin-PI staining. Caspases were assayed colorimetrically whereas nuclear derangements were assessed morphologically through PI staining and finally by DNA fragmentation analysis. Cell viability studies confirmed the IC50 of CC in MCF-7 and MDA MB-231 cells to be 10 and 20 microM (P < 0.001) respectively, suggesting enhanced susceptibility of the former cell type to CC. FACS data reveals CC mediated G0/G1 arrest (P < 0.01) along with the presence of prominent sub-G0/G1 peak (P < 0.001) in both the cell types suggesting ongoing apoptosis. Phosphatidylserine externalization, mitochondrial events, caspase evaluation and nuclear morphology changes reveal initiation/progression of caspase-dependent apoptosis even at a dose of 1 microM which eventually leads to DNA fragmentation in both the cell types. Results demonstrate that CC induces caspase-dependent apoptosis in MCF-7 and MDA MB-231 cells irrespective of ER status similar to TAM in terms of anti-neoplastic activity.
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Affiliation(s)
- Manisha Nigam
- Tissue and Cell Culture Unit (TCCU), Central Drug Research Institute, Lucknow, 226001, India.
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15
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Maaser K, Sutter AP, Scherübl H. Mechanisms of mitochondrial apoptosis induced by peripheral benzodiazepine receptor ligands in human colorectal cancer cells. Biochem Biophys Res Commun 2005; 332:646-52. [PMID: 15907803 DOI: 10.1016/j.bbrc.2005.05.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2005] [Accepted: 05/03/2005] [Indexed: 10/25/2022]
Abstract
Specific ligands of the peripheral benzodiazepine receptor (PBR) have been shown to induce apoptosis in gastrointestinal cancers. The aim of this study was to characterize the signaling pathways of PBR ligand-induced apoptosis. FGIN-1-27 but not PK 11195-induced apoptosis was associated with a decrease of mitochondrial membrane potential and an increase of mitochondrial volume in HT29 colorectal cancer cells. However, PK 11195-elicited apoptosis was associated with a downregulation of Bcl-2, translocation of Bax to the mitochondria including subsequent oligomerization, and activation of caspase-9, indicating the involvement of mitochondria in PK 11195-induced apoptosis. Moreover, PK 11195-induced apoptosis was associated with the generation of reactive oxygen species. This study demonstrates a novel mechanism of PK 11195-induced mitochondrial apoptosis without alteration of the mitochondrial membrane potential. The characterization of signaling pathways associated with PBR ligand-induced apoptosis will build the base for a future use of these ligands in anti-neoplastic therapeutic approaches.
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Affiliation(s)
- Kerstin Maaser
- Medical Clinic I, Charité-Universitätsmedizin Berlin, Campus Benjamin Franklin, 12200 Berlin, Germany
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16
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Veiga S, Azcoitia I, Garcia-Segura LM. Ro5-4864, a peripheral benzodiazepine receptor ligand, reduces reactive gliosis and protects hippocampal hilar neurons from kainic acid excitotoxicity. J Neurosci Res 2005; 80:129-37. [PMID: 15696538 DOI: 10.1002/jnr.20430] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The peripheral-type benzodiazepine receptor (PBR) is a critical component of the mitochondrial permeability transition pore, which is involved in the regulation of cell survival. Different forms of brain injury result in induction of the expression of the PBR in the areas of neurodegeneration, mainly in reactive glial cells. The consequences of induction of PBR expression after brain injury are unknown. To test whether PBR may be involved in the regulation of neuronal survival after injury, we have assessed the effect of two PBR ligands, Ro5-4864 and PK11195, on neuronal loss induced by kainic acid in the hippocampus. Systemic administration of kainic acid to male rats resulted in the induction of a reactive phenotype in astrocytes and microglia and in a significant loss of hilar neurons in the dentate gyrus. Administration of Ro5-4864, before the injection of kainic acid, decreased reactive gliosis in the hilus and prevented hilar neuronal loss. In contrast, PK11195 was unable to reduce reactive gliosis and did not protect hilar neurons from kainic acid. These findings suggest that the PBR is involved in control of neuronal survival and gliosis after brain injury and identify this molecule as a potential target for neuroprotective interventions.
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17
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Hans G, Wislet-Gendebien S, Lallemend F, Robe P, Rogister B, Belachew S, Nguyen L, Malgrange B, Moonen G, Rigo JM. Peripheral benzodiazepine receptor (PBR) ligand cytotoxicity unrelated to PBR expression. Biochem Pharmacol 2005; 69:819-30. [PMID: 15710359 DOI: 10.1016/j.bcp.2004.11.029] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2004] [Accepted: 11/29/2004] [Indexed: 10/25/2022]
Abstract
Some synthetic ligands of the peripheral-type benzodiazepine receptor (PBR), an 18 kDa protein of the outer mitochondrial membrane, are cytotoxic for several tumor cell lines and arise as promising chemotherapeutic candidates. However, conflicting results were reported regarding the actual effect of these drugs on cellular survival ranging from protection to toxicity. Moreover, the concentrations needed to observe such a toxicity were usually high, far above the affinity range for their receptor, hence questioning its specificity. In the present study, we have shown that micromolar concentrations of FGIN-1-27 and Ro 5-4864, two chemically unrelated PBR ligands are toxic for both PBR-expressing SK-N-BE neuroblastoma cells and PBR-deficient Jurkat lymphoma cells. We have thereby demonstrated that the cytotoxicity of these drugs is unrelated to their PBR-binding activity. Moreover, Ro 5-4864-induced cell death differed strikingly between both cell types, being apoptotic in Jurkat cells while necrotic in SK-N-BE cells. Again, this did not seem to be related to PBR expression since Ro 5-4864-induced death of PBR-transfected Jurkat cells remained apoptotic. Taken together, our results show that PBR is unlikely to mediate all the effects of these PBR ligands. They however confirm that some of these ligands are very effective cytotoxic drugs towards various cancer cells, even for reputed chemoresistant tumors such as neuroblastoma, and, surprisingly, also for PBR-lacking tumor cells.
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Affiliation(s)
- Gregory Hans
- Centre of Cellular and Molecular Neurobiology, Université de Liège, 17 Place Delcour, 4020 Liège 2, Belgium.
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18
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Jordà EG, Jiménez A, Verdaguer E, Canudas AM, Folch J, Sureda FX, Camins A, Pallàs M. Evidence in favour of a role for peripheral-type benzodiazepine receptor ligands in amplification of neuronal apoptosis. Apoptosis 2005; 10:91-104. [PMID: 15711925 DOI: 10.1007/s10495-005-6064-9] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The mitochondrial peripheral benzodiazepine receptor (PBR) is involved in a functional structure designated as the mitochondrial permeability transition (MPT) pore, which controls apoptosis. PBR expression in nervous system has been reported in glial and immune cells. We now show expression of both PBR mRNA and protein, and the appearance of binding of a synthetic ligand fluo-FGIN-1-27 in mitochondria of rat cerebellar granule cells (CGCs). Additionally, the effect of PBR ligands on colchicine-induced apoptosis was investigated. Colchicine-induced neurotoxicity in CGCs was measured at 24 h. We show that, in vitro, PBR ligands 1-(2-chlorophenyl-N-methylpropyl)-3-isoquinolinecarboxamide (PK11195), 7-chloro-5-(4-chlorophenyl)-1,3-dihydro-1-methyl-2H-1,4- benzodiazepin-2-one (Ro5-4864) and diazepam (25- 50 microM) enhanced apoptosis induced by colchicine, as demonstrated by viability experiments, flow cytometry and nuclear chromatin condensation. Enhancement of colchicine-induced apoptosis was characterized by an increase in mitochondrial release of cytochrome c and AIF proteins and an enhanced activation of caspase-3, suggesting mitochondrion dependent mechanism that is involved in apoptotic process. Our results indicate that exposure of neural cells to PBR ligands generates an amplification of apoptotic process induced by colchicine and that the MPT pore may be involved in this process.
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Affiliation(s)
- E G Jordà
- Unitat de Farmacologia i Farmacognòsia, Facultat de Farmàcia, Universitat de Barcelona, Nucli Universitari de Pedralbes, E-08028, Barcelona, Spain
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19
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Karchewski LA, Bloechlinger S, Woolf CJ. Axonal injury-dependent induction of the peripheral benzodiazepine receptor in small-diameter adult rat primary sensory neurons. Eur J Neurosci 2004; 20:671-83. [PMID: 15255978 DOI: 10.1111/j.1460-9568.2004.03530.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
The peripheral benzodiazepine receptor (PBR), a benzodiazepine but not gamma-aminobutyric acid-binding mitochondrial membrane protein, has roles in steroid production, energy metabolism, cell survival and growth. PBR expression in the nervous system has been reported in non-neuronal glial and immune cells. We now show expression of both PBR mRNA and protein, and the appearance of binding of a synthetic ligand, [(3)H]PK11195, in dorsal root ganglion (DRG) neurons following injury to the sciatic nerve. In naïve animals, PBR mRNA, protein expression and ligand binding are undetectable in the DRG. Three days after sciatic nerve transection, however, PBR mRNA begins to be expressed in injured neurons, and 4 weeks after the injury, expression and ligand binding are present in 35% of L4 DRG neurons. PBR ligand binding also appears after injury in the superficial dorsal horn of the spinal cord. The PBR expression in the DRG is restricted to small and medium-sized neurons and returns to naïve levels if the injured peripheral axons are allowed to regrow and reinnervate targets. No non-neuronal PBR expression is detected, unlike its putative endogenous ligand the diazepam binding inhibitor (DBI), which is expressed only in non-neuronal cells, including the satellite cells that surround DRG neurons. DBI expression does not change with sciatic nerve transection. PBR acting on small-calibre neurons could play a role in the adaptive survival and growth responses of these cells to injury of their axons.
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Affiliation(s)
- Laurie A Karchewski
- Neural Plasticity Research Group, Department of Anaesthesia and Critical Care, Massachusetts General Hospital and Harvard Medical School, MGH-East, 149 13th Street, Rm 4309, Charlestown, MA 02129, USA.
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20
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Abstract
Tumor cell targeted therapies, by induction or enhancement of apoptosis, constitute recent promising approaches achieving more specific anti-tumor efficacy. The peripheral benzodiazepine receptor (PBR), which belongs to the permeability transition pore (PTP), the central regulatory complex of apoptosis, is a potential target. A number of findings argue in favor of the development of PBR targeting approaches: (i) overexpression of PBR has been described in a large range of human cancers, (ii) PTP-mediated regulation of programmed cell death is an apoptotic-inducing factor-independent check-point that could be modulated by various conventional cancer therapies, and (iii) PBR ligation enhances apoptosis induction in many types of tumors and reverses Bcl-2 cytoprotective effects. Altogether, these observations support the use of PBR-directed drugs, particularly PBR ligands such as Ro5-4864, in the treatment of human cancers.
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Affiliation(s)
- Didier Decaudin
- Department of Clinical Hematology, Institut Curie, Paris, France.
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Veenman L, Levin E, Weisinger G, Leschiner S, Spanier I, Snyder SH, Weizman A, Gavish M. Peripheral-type benzodiazepine receptor density and in vitro tumorigenicity of glioma cell lines. Biochem Pharmacol 2004; 68:689-98. [PMID: 15276076 DOI: 10.1016/j.bcp.2004.05.011] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2004] [Accepted: 05/04/2004] [Indexed: 11/20/2022]
Abstract
The peripheral-type benzodiazepine receptor is found primarily on the outer mitochondrial membrane and consists of three subunits: the 18kDa isoquinoline binding protein, the 32kDa voltage-dependent anion channel, and the 30kDa adenine nucleotide transporter. The current study evaluates the potential importance of peripheral-type benzodiazepine receptor expression in glioma cell tumorigenicity. While previous studies have suggested that peripheral-type benzodiazepine receptor-binding may be relatively increased in tumor tissue and cells, so far, little is known about the relationships between peripheral-type benzodiazepine receptor density and factors underlying tumorigenicity. In the present study, we found in glioma cell lines (C6, U87MG, and T98G), that peripheral-type benzodiazepine receptor ligand-binding density is relatively high for C6 and low for T98G, while U87MG displays intermediate levels. Cell growth of these cell lines in soft agar indicated that high levels of peripheral-type benzodiazepine receptor-binding were associated with increased colony size, indicative of their ability to establish anchorage independent cell proliferation. Potential causes for differences in tumorigenicity between these cell lines were suggested by various cell death and proliferation assays. Cell death, including apoptosis, appeared to be low in C6, and high in T98G, while U87MG displayed intermediate levels in this respect. Cell proliferation appeared to be high in C6, low in T98G, and intermediate in U87MG. In conclusion, our study suggests that relatively high peripheral-type benzodiazepine receptor-binding density is associated with enhanced tumorigenicity and cell proliferation rate. In particular, apoptosis appears to be an important tumorigenic determinant in these glioma cell lines. Moreover, application of PBR-specific ligands indicated that PBR indeed are functionally involved in apoptosis in glioma cells.
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Affiliation(s)
- Leo Veenman
- Department of Pharmacology, Rappaport Family Institute for Research in the Medical Sciences, Technion-Israel Institute of Technology, P.O.B. 9649, Bat-Galim, Haifa 31096, Israel
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22
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Ostuni MA, Marazova K, Peranzi G, Vidic B, Papadopoulos V, Ducroc R, Lacapere JJ. Functional characterization and expression of PBR in rat gastric mucosa: stimulation of chloride secretion by PBR ligands. Am J Physiol Gastrointest Liver Physiol 2004; 286:G1069-80. [PMID: 14726306 DOI: 10.1152/ajpgi.00290.2003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Previous studies have demonstrated that gastric mucosa contained high levels of the polypeptide diazepam binding inhibitor, the endogenous ligand of the peripheral-type benzodiazepine receptor (PBR). However, the expression and function of this receptor protein in these tissues have not been investigated. Immunohistochemistry identified an intense PBR immunoreactivity in the mucous and parietal cells of rat gastric fundus and in the mucous cells of antrum. Immunoelectron microscopy revealed the mitochondrial localization of PBR in these cells. Binding of isoquinoline PK 11195 and benzodiazepine Ro5-4864 to gastric membranes showed that fundus had more PBR-binding sites than antrum, displaying higher affinity for PK 11195 than Ro5-4864. In a Ussing chamber, PK 11195 and Ro5-4864 increased short-circuit current (I(sc)) in fundic and antral mucosa in a concentration-dependent manner in the presence of GABA(A) and central benzodiazepine receptor (CBR) blockers. This increase in I(sc) was abolished after external Cl(-) substitution and was sensitive to chloride channels or transporter inhibitors. PK 11195-induced chloride secretion was also 1) sensitive to verapamil and extracellular calcium depletion, 2) blocked by thapsigargin and intracellular calcium depletion, and 3) abolished by the mitochondrial pore transition complex inhibitor cyclosporine A. PK 11195 had no direct effect on H(+) secretion, indicating that it stimulates a component of Cl(-) secretion independent of acid secretion in fundic mucosa. These data demonstrate that mucous and parietal cells of the gastric mucosa express mitochondrial PBR functionally coupled to Ca(2+)-dependent Cl(-) secretion, possibly involved in the gastric mucosa protection.
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Affiliation(s)
- M A Ostuni
- Institut National de la Santé et de la Recherche Médicale U410, Neuroendocrinologie et Biologie Cellulaire Digestives, 75870 Paris cedex 18, France
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23
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Delavoie F, Li H, Hardwick M, Robert JC, Giatzakis C, Péranzi G, Yao ZX, Maccario J, Lacapère JJ, Papadopoulos V. In vivo and in vitro peripheral-type benzodiazepine receptor polymerization: functional significance in drug ligand and cholesterol binding. Biochemistry 2003; 42:4506-19. [PMID: 12693947 DOI: 10.1021/bi0267487] [Citation(s) in RCA: 138] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Peripheral-type benzodiazepine receptor (PBR) is an 18 kDa high-affinity drug ligand and cholesterol binding protein involved in various cell functions. Antisera for distinct PBR areas identified immunoreactive proteins of 18, 40, and 56 kDa and occasionally 72, 90, and 110 kDa in testicular Leydig and breast cancer cells. These sizes may correspond to PBR polymers and correlated to the levels of reactive oxygen species. Treatment of Leydig cells with human chorionic gonadotropin rapidly induced free radical, PBR polymer, and steroid formation. UV photoirradiation generates ROS species, which increased the size of intramembraneous particles of recombinant PBR reconstituted into proteoliposomes consistent with polymer formation, determined both by SDS-PAGE and by freeze-fracture electron microscopy. Spectroscopic analysis revealed the formation of dityrosines as the covalent cross-linker between PBR monomers. Moreover, photoirradiation increased PK 11195 drug ligand binding and reduced cholesterol binding capacity of proteoliposomes. Further addition of PK 11195 drug ligand to polymers increased the rate of cholesterol binding. These data indicate that reactive oxygen species induce in vivo and in vitro the formation of covalent PBR polymers. We propose that the PBR polymer might be the functional unit responsible for ligand-activated cholesterol binding and that PBR polymerization is a dynamic process modulating the function of this receptor in cholesterol transport and other cell-specific PBR-mediated functions.
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Affiliation(s)
- Franck Delavoie
- Division of Hormone Research, Department of Cell Biology, Georgetown University Medical Center, Washington, DC 20057, USA
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