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Martinez-Lozada Z, Robinson MB. Reciprocal communication between astrocytes and endothelial cells is required for astrocytic glutamate transporter 1 (GLT-1) expression. Neurochem Int 2020; 139:104787. [PMID: 32650029 DOI: 10.1016/j.neuint.2020.104787] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2020] [Revised: 05/15/2020] [Accepted: 06/14/2020] [Indexed: 12/12/2022]
Abstract
Astrocytes have diverse functions that are supported by their anatomic localization between neurons and blood vessels. One of these functions is the clearance of extracellular glutamate. Astrocytes clear glutamate using two Na+-dependent glutamate transporters, GLT-1 (also called EAAT2) and GLAST (also called EAAT1). GLT-1 expression increases during synaptogenesis and is a marker of astrocyte maturation. Over 20 years ago, several groups demonstrated that astrocytes in culture express little or no GLT-1 and that neurons induce expression. We recently demonstrated that co-culturing endothelia with mouse astrocytes also induced expression of GLT-1 and GLAST. These increases were blocked by an inhibitor of γ-secretase. This and other observations are consistent with the hypothesis that Notch signaling is required, but the ligands involved were not identified. In the present study, we used rat astrocyte cultures to further define the mechanisms by which endothelia induce expression of GLT-1 and GLAST. We found that co-cultures of astrocytes and endothelia express higher levels of GLT-1 and GLAST protein and mRNA. That endothelia activate Hes5, a transcription factor target of Notch, in astrocytes. Using recombinant Notch ligands, anti-Notch ligand neutralizing antibodies, and shRNAs, we provide evidence that both Dll1 and Dll4 contribute to endothelia-dependent regulation of GLT-1. We also provide evidence that astrocytes secrete a factor(s) that induces expression of Dll4 in endothelia and that this effect is required for Notch-dependent induction of GLT-1. Together these studies indicate that reciprocal communication between astrocytes and endothelia is required for appropriate astrocyte maturation and that endothelia likely deploy additional non-Notch signals to induce GLT-1.
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Affiliation(s)
- Zila Martinez-Lozada
- Departments of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA, 19104-4318
| | - Michael B Robinson
- Departments of Pediatrics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, USA, 19104-4318; Systems Pharmacology and Translational Therapeutics, Children's Hospital of Philadelphia, University of Pennsylvania, Philadelphia, PA, 19104-4318, USA.
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Zhou B, Wang H, Liu R, Wang M, Deng H, Giglio BC, Gill PS, Shan H, Li Z. PET Imaging of Dll4 Expression in Glioblastoma and Colorectal Cancer Xenografts Using (64)Cu-Labeled Monoclonal Antibody 61B. Mol Pharm 2015; 12:3527-34. [PMID: 26288060 DOI: 10.1021/acs.molpharmaceut.5b00105] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Delta-like ligand 4 (Dll4) expressed in tumor cells plays a key role to promote tumor growth of numerous cancer types. Based on a novel antihuman Dll4 monoclonal antibody (61B), we developed a (64)Cu-labeled probe for positron emission tomography (PET) imaging of tumor Dll4 expression. In this study, 61B was conjugated with the (64)Cu-chelator DOTA through lysine on the antibody. Human IgG (hIgG)-DOTA, which did not bind to Dll4, was also prepared as a control. The Dll4 binding activity of the probes was evaluated through the bead-based binding assay with Dll4-alkaline phosphatase. The resulting PET probes were evaluated in U87MG glioblastoma and HT29 colorectal cancer xenografts in athymic nude mice. Our results demonstrated that the 61B-DOTA retained (77.2 ± 3.7) % Dll4 binding activity of the unmodified 61B, which is significantly higher than that of hIgG-DOTA (0.06 ± 0.03) %. Confocal microscopy analysis confirmed that 61B-Cy5.5, but not IgG-Cy5.5, predominantly located within the U87MG and HT29 cells cytoplasm. U87MG cells showed higher 61B-Cy5.5 binding as compared to HT29 cells. In U87MG xenografts, 61B-DOTA-(64)Cu demonstrated remarkable tumor accumulation (10.5 ± 1.7 and 10.2 ± 1.2%ID/g at 24 and 48 h postinjection, respectively). In HT29 xenografts, tumor accumulation of 61B-DOTA-(64)Cu was significantly lower than that of U87MG (7.3 ± 1.3 and 6.6 ± 1.3%ID/g at 24 and 48 h postinjection, respectively). The tumor accumulation of 61B-DOTA-(64)Cu was significantly higher than that of hIgG-DOTA-(64)Cu in both xenografts models. Immunofluorescence staining of the tumor tissues further confirmed that tumor accumulation of 61B-Cy5.5 was correlated well with in vivo PET imaging data using 61B-DOTA-(64)Cu. In conclusion, 61B-DOTA-(64)Cu PET probe was successfully synthesized and demonstrated prominent tumor uptake by targeting Dll4. 61B-DOTA-(64)Cu has great potential to be used for noninvasive Dll4 imaging, which could be valuable for tumor detection, Dll4 expression level evaluation, and Dll4-based treatment monitoring.
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Affiliation(s)
- Bin Zhou
- Department of Radiology, The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou 510630, China.,Biomedical Research Imaging Center, Department of Radiology, University of North Carolina , Chapel Hill, North Carolina 27514, United States
| | - Hui Wang
- Biomedical Research Imaging Center, Department of Radiology, University of North Carolina , Chapel Hill, North Carolina 27514, United States
| | - Ren Liu
- Department of Pathology, University of Southern California , Los Angeles, California 90033, United States
| | - Mengzhe Wang
- Biomedical Research Imaging Center, Department of Radiology, University of North Carolina , Chapel Hill, North Carolina 27514, United States
| | - Huaifu Deng
- Biomedical Research Imaging Center, Department of Radiology, University of North Carolina , Chapel Hill, North Carolina 27514, United States
| | - Benjamin C Giglio
- Biomedical Research Imaging Center, Department of Radiology, University of North Carolina , Chapel Hill, North Carolina 27514, United States
| | - Parkash S Gill
- Department of Pathology, University of Southern California , Los Angeles, California 90033, United States
| | - Hong Shan
- Department of Radiology, The Third Affiliated Hospital of Sun Yat-sen University , Guangzhou 510630, China.,Interventional Radiology Institute, Sun Yat-sen University , Guangzhou 510630, China
| | - Zibo Li
- Biomedical Research Imaging Center, Department of Radiology, University of North Carolina , Chapel Hill, North Carolina 27514, United States
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Klose R, Berger C, Moll I, Adam MG, Schwarz F, Mohr K, Augustin HG, Fischer A. Soluble Notch ligand and receptor peptides act antagonistically during angiogenesis. Cardiovasc Res 2015; 107:153-63. [PMID: 25975260 DOI: 10.1093/cvr/cvv151] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/03/2013] [Accepted: 05/07/2015] [Indexed: 01/06/2023] Open
Abstract
AIMS Notch signalling is essential for blood vessel formation. During angiogenesis, the Notch ligand DLL4 on the leading tip cell activates Notch receptors on the adjacent stalk cells. DLL4-Notch signalling is impaired by the Notch ligand JAG1 in endothelial cells. The Delta/Serrate/Lag2 (DSL) domain of the Notch ligands binds to the EGF-like repeats 11-13 of the Notch receptor. This study aimed to elucidate how soluble proteins containing these short domains interfere with Notch signalling during angiogenesis. METHODS AND RESULTS Adenoviral vectors were generated to express the DSL domains of DLL1, DLL4, JAG1, and the Notch1 EGF-like repeats 11-13 fused to immunoglobulin-G heavy chain. These soluble ligand peptides inhibited Notch signalling in endothelial cells and this caused hyperbranching in cellular angiogenesis assays and in the neonatal mouse retina. The soluble Notch receptor peptides bound stronger to JAG1 than DLL4 ligands, resulting in increased signalling activity. This led to impaired tip cell formation and less vessel sprouting in the retina. CONCLUSION The minimal binding domains of Notch ligands are sufficient to interfere with Notch signalling. The corresponding soluble Notch1 EGF11-13 peptide binds stronger to inhibitory Notch ligands and thereby promotes Notch signalling in endothelial cells.
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Affiliation(s)
- Ralph Klose
- Vascular Signaling and Cancer (A270), German Cancer Research Center (DKFZ-ZMBH Alliance), Heidelberg D-69120, Germany
| | - Caroline Berger
- Vascular Signaling and Cancer (A270), German Cancer Research Center (DKFZ-ZMBH Alliance), Heidelberg D-69120, Germany Vascular Biology and Tumor Angiogenesis, Medical Faculty Mannheim (CBTM), Heidelberg University, Mannheim D-68167, Germany
| | - Iris Moll
- Vascular Signaling and Cancer (A270), German Cancer Research Center (DKFZ-ZMBH Alliance), Heidelberg D-69120, Germany
| | - M Gordian Adam
- Vascular Signaling and Cancer (A270), German Cancer Research Center (DKFZ-ZMBH Alliance), Heidelberg D-69120, Germany Vascular Biology and Tumor Angiogenesis, Medical Faculty Mannheim (CBTM), Heidelberg University, Mannheim D-68167, Germany
| | - Frank Schwarz
- Genomics and Proteomics Core Facilities, German Cancer Research Center, Heidelberg D-69120, Germany
| | - Kerstin Mohr
- Genomics and Proteomics Core Facilities, German Cancer Research Center, Heidelberg D-69120, Germany
| | - Hellmut G Augustin
- Vascular Biology and Tumor Angiogenesis, Medical Faculty Mannheim (CBTM), Heidelberg University, Mannheim D-68167, Germany Vascular Oncology and Metastasis (A190), German Cancer Research Center (DKFZ-ZMBH Alliance), Heidelberg D-69120, Germany
| | - Andreas Fischer
- Vascular Signaling and Cancer (A270), German Cancer Research Center (DKFZ-ZMBH Alliance), Heidelberg D-69120, Germany Vascular Biology and Tumor Angiogenesis, Medical Faculty Mannheim (CBTM), Heidelberg University, Mannheim D-68167, Germany Department of Medicine I and Clinical Chemistry, Heidelberg University, Heidelberg D-69120, Germany
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