In vitro ischemic tolerance involves upregulation of glutamate transport partly mediated by the TACE/ADAM17-tumor necrosis factor-alpha pathway

• Published in: The Journal of neuroscience Vol. 24; no. 6; pp. 1350 - 1357
• Main Authors: Romera, Cristina, Hurtado, Olivia, Botella, Sofia H, Lizasoain, Ignacio, Cárdenas, Antonio, Fernández-Tomé, Paz, Leza, Juan C, Lorenzo, Pedro, Moro, Maria A
• Format: Journal Article
• Language: English
• Published: United States Society for Neuroscience 11.02.2004
• Subjects: ADAM Proteins; ADAM17 Protein; Amino Acid Transport System X-AG - metabolism; Animals; Antibodies - pharmacology; Astrocytes - cytology; Astrocytes - metabolism; Biological Transport - physiology; Brain Ischemia - metabolism; Caspase 3; Caspases - metabolism; Cell Death - physiology; Cells, Cultured; Coculture Techniques; Enzyme Inhibitors - pharmacology; Excitatory Amino Acid Transporter 2; Excitatory Amino Acid Transporter 3; Glucose - metabolism; Glutamate Plasma Membrane Transport Proteins; Glutamic Acid - metabolism; Glutamic Acid - pharmacokinetics; Hydroxamic Acids - pharmacology; Ischemic Preconditioning; Metalloendopeptidases - antagonists & inhibitors; Metalloendopeptidases - metabolism; Neurobiology of Disease; Neurons - cytology; Neurons - drug effects; Neurons - metabolism; Rats; Rats, Wistar; Signal Transduction - physiology; Symporters - metabolism; Tumor Necrosis Factor-alpha - antagonists & inhibitors; Tumor Necrosis Factor-alpha - pharmacology; Up-Regulation
• ISSN: 0270-6474; 1529-2401
• DOI: 10.1523/JNEUROSCI.1596-03.2004

A short ischemic event [ischemic preconditioning (IPC)] can result in a subsequent resistance to severe ischemic injury (ischemic tolerance). Although tumor necrosis factor-alpha (TNF-alpha) contributes to the brain damage found after cerebral ischemia, its expression and neuroprotective role in models of IPC have also been described. Regarding the role of TNF-alpha convertase (TACE/ADAM17), we have recently shown its upregulation in rat brain after IPC induced by transient middle cerebral artery occlusion and that subsequent TNF-alpha release accounts for at least part of the neuroprotection found in this model. We have now used an in vitro model of IPC using rat cortical cultures exposed to sublethal oxygen-glucose deprivation (OGD) to investigate TACE expression and activity after IPC and the subsequent mechanisms of ischemic tolerance. OGD-induced cell death was significantly reduced in cells exposed to IPC by sublethal OGD 24 hr before, an effect that was inhibited by the TACE inhibitor BB3103 (1 microm) and anti-TNF-alpha antibody (2 microg/ml) and that was mimicked by TNF-alpha (10 pg/ml) preincubation. Western blot analysis showed that TACE expression is increased after IPC. IPC caused TNF-alpha release, an effect that was blocked by the selective TACE inhibitor BB-3103. In addition, IPC diminished the increase in extracellular glutamate caused by OGD and increased cellular glutamate uptake and expression of EAAT2 and EAAT3 glutamate transporters; however, only EAAT3 upregulation was mediated by increased TNF-alpha. These data demonstrate that neuroprotection induced by IPC involves upregulation of glutamate uptake partly mediated by TACE overexpression.