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Oncostatin M promotes excitotoxicity by inhibiting glutamate uptake in astrocytes: implications in HIV-associated neurotoxicity

Moidunny, S., Matos, M., Wesseling, E., Banerjee, S., Volsky, D. J., Cunha, R. A., Agostinho, P., Boddeke, H. W. & Roy, S., 10-Jun-2016, In : Journal of neuroinflammation. 13, 144, 18 p., 144.

Research output: Contribution to journalArticleAcademicpeer-review

Background: Elevated levels of oncostatin M (OSM), an interleukin-6 cytokine family member, have been observed in HIV-1-associated neurocognitive disorders (HAND) and Alzheimer's disease. However, the function of OSM in these disease conditions is unclear. Since deficient glutamate uptake by astrocytes is instrumental in HAND-associated neurotoxicity, we hypothesized that OSM impairs glutamate uptake in astrocytes and thereby promotes neuronal excitotoxicity.

Methods: Primary cultures of mouse cortical astrocytes, neurons, microglia, and BV2 cell line were used. The expression of glutamate transporters (GLAST/EAAT1 and GLT-1/EAAT2) was investigated using real-time PCR and Western blot, and their activity was assessed by measuring H-3-D-aspartate uptake. Neuronal toxicity was measured using the colorimetric MTT (3-(4,5-dimethylthiazol-2-yl-) 2,5-diphenyltetrazolium bromide) assay and immunocytochemistry. A chimeric HIV-1 that infects murine cells (EcoHIV/NL4-3-GFP virus (EcoHIV)) was used to investigate whether the virus induces OSM, OSM receptor (OSMR)-beta, glycoprotein 130 (gp130), GLT-1, GLAST (mRNA and protein), and OSM release (ELISA) in cultured BV2 cells, primary microglia, or astrocytes. Statistical analyses of the data were performed using one-way ANOVA (to allow multiple comparisons) and two-tailed Student's t test.

Results: OSM treatment (10 ng/mL) time-dependently reduced GLAST and GLT-1 expression and inhibited 3H-D-aspartate uptake in cultured astrocytes in a concentration-dependent manner, an effect prevented by the Janus kinase (JAK)/signal transducers and activators of transcription (STAT) 3 inhibitor AG490. Down-regulation of astrocytic glutamate transport by OSM resulted in NMDA receptor-dependent excitotoxicity in cortical neurons. Infection with EcoHIV induced OSM gene expression and protein release in BV2 cells and microglia, but not in astrocytes. Conversely, EcoHIV caused a fivefold increase in OSMR-beta mRNA (but not gp130) and protein in astrocytes, but not in microglia, which did not express OSMR-beta protein. Finally, astrocytic expression of GLAST gene was unaffected by EcoHIV, whereas GLT-1 mRNA was increased by twofold.

Conclusions: We provide first evidence that activation of JAK/STAT3 signaling by OSM inhibits glutamate uptake in astrocytes, which results in neuronal excitotoxicity. Our findings with EcoHIV suggest that targeting OSMR-beta signaling in astrocytes might alleviate HIV-1-associated excitotoxicity.

Original languageEnglish
Article number144
Number of pages18
JournalJournal of neuroinflammation
Volume13
Issue number144
Publication statusPublished - 10-Jun-2016

    Keywords

  • Glutamate, GLAST, GLT-1, Astrocytes, Oncostatin M, Interleukin 6, NMDA, Excitotoxicity, HIV, NECROSIS-FACTOR-ALPHA, AMYOTROPHIC-LATERAL-SCLEROSIS, ACTIVATED PROTEIN-KINASE, ALZHEIMERS-DISEASE, GENE-EXPRESSION, IN-VIVO, LYMPHOMONONUCLEAR CELLS, CULTURED ASTROCYTES, MULTIPLE-SCLEROSIS, ENDOTHELIAL-CELLS

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