Regulation of Interleukin -6 Gene Expression in the Brain of Aged Mice
Ye, Shi-Ming
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Permalink
https://hdl.handle.net/2142/83668
Description
Title
Regulation of Interleukin -6 Gene Expression in the Brain of Aged Mice
Author(s)
Ye, Shi-Ming
Issue Date
2000
Doctoral Committee Chair(s)
Johnson, Rodney W.
Department of Study
Animal Sciences
Discipline
Animal Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Health Sciences, Immunology
Language
eng
Abstract
The occurrence of certain neurodegenerative diseases increases with age. Because over expression of inflammatory cytokines in the brain may establish a state that is permissive to the onset of neurodegenerative diseases, in the present thesis study the effect of aging on the expression of inflammatory cytokine, interleukin-6 (IL-6), was determined. Competitive RT-PCR and ELISA assay showed that IL-6 mRNA and protein concentration were higher in aged brain compared to adult and neonate brain. To begin identifying the cell type responsible for increased IL-6 in the CNS, glial cells were cultured from brains of neonate, adult, and aged mice. Flow cytometric analysis revealed that increased IL-6 production in glia from aged mice is a result of an increase in reactive microglia, which spontaneously secret copious amount of IL-6. To determine the molecular basis responsible for increased IL-6 gene expression in the aged brain, the binding of transcription factors to the major response elements on the IL-6 promoter was evaluated in brains of 1-, 3-, and 24-month old mice by gel mobility shift assay. Whereas NFkappaB activity was increased in aged brain, NF-IL-6, MRE and AP-1 were either unaffected by aging or decreased. Inhibition of increased NFkappaB activity both in vivo and in vitro decrease IL-6 mRNA expression and protein level. These results suggest that increased NFkappaB activity in aged brain contributes to the elevated levels of IL-6. An anti-inflammatory cytokine IL-10 inhibits NFkappaB activity and expression of IL-6. The coronal brain sections and glia from aged mice secreted more IL-6 and less IL-10 than brain sections and glia from adults. Recombinant murine IL-10 decreased NFkappaB DNA binding activity, and therefore, reduced both constitutive and inducible IL-6 mRNA and protein levels in glia from aged mice. However, in glia from adult mice, supplemental IL-10 only decreased inducible, but not constitutive NFkappaB activity, IL-6 mRNA, and IL-6 protein. These data suggest that IL-10 constrains IL-6 gene expression in the adult brain, but in the aged brain it decreases and thus enables a cascade of intracellular events that increase the expression of the IL-6 gene.
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