Inflammatory Cytokine Mediated CNS Damage: Insights Into the Effects of Tnf-Alpha From a Neuronal Cell Line
Sipe, Kimberly Jean
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https://hdl.handle.net/2142/86726
Description
Title
Inflammatory Cytokine Mediated CNS Damage: Insights Into the Effects of Tnf-Alpha From a Neuronal Cell Line
Author(s)
Sipe, Kimberly Jean
Issue Date
1997
Doctoral Committee Chair(s)
James Weyhenmeyer
Department of Study
Microbiology
Discipline
Microbiology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Health Sciences, Immunology
Language
eng
Abstract
Inflammatory cytokine expression is often increased under pathological conditions in the CNS. Tumor necrosis factor-$\alpha$ (TNF) is an inflammatory cytokine that has been identified in directing neuronal response to disease or injury. Results are conflicting as to the role of TNF in mediating neuronal injury. TNF can protect neurons from excitotoxic and metabolic injury but can also mediate neuronal toxicity. We hypothesize that cell state and components of the extracellular milieu determine whether inflammatory cytokines promote neurotoxicity or neuroprotection. The N1E-115 neuroblastoma line (N1E's) was used as a model system to identify factors predisposing neuronal cells to TNF-mediated cell death. The N1E's express mRNA for one of two TNF receptors (TNFR's) and also express membrane-associated TNF. TNF is toxic to both undifferentiated and differentiated N1E's in the presence of the transcriptional inhibitor, actinomycin D and the anti-viral cytokine, interferon-$\alpha/\beta.$ Only undifferentiated N1E's acquire sensitivity to TNF toxicity in the presence of the translational inhibitor, cycloheximide. Differential expression of manganous superoxide dismutase between the two states may explain this finding and could have relevance to neuronal development and tumor biology. Different responses of undifferentiated and differentiated N1E's to TNF in the presence of microglia were observed as well. The anti-apoptotic protein, Bcl-2, is also expressed in differentiated N1E's and may explain their resistance to TNF toxicity. Interaction between the 75 kDa TNFR and membrane-associated TNF appears to induce cell death in the N1E's. Cells were stably transfected with the full length cDNA for the 75 kDa TNFR as demonstrated bv receptor mRNA expression and G418 resistance, however protein expression could not be detected using Western or flow-cytometric analyses. Analysis of cell death indicated increased cell death in 75 kDa TNFR transfected-N1E's 24 hr after transfection. Forty-six percent of cells transfected with empty vector died versus 53% of 75 kDa TNFR-transfected cells, indicating a loss of N1E's on 75 kDa TNFR expression. In conclusion, transcriptional inhibition, 75 kDa TNFR expression, interferon-$\alpha/\beta,$ and microglia increase TNF toxicity in N1E's. The N1E's represent an ideal model for these studies, and similar results are anticipated in other neuronal systems.
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