Tumor necrosis factor modulates transcription of myelin basic protein gene through nuclear factor kappa B in a human oligodendroglioma cell line.

Tumor necrosis factor-alpha (TNF-alpha) is a major mediator of inflammation and it is involved in many neurological disorders such as multiple sclerosis. Levels of TNF-alpha and lymphotoxin-alpha have been found elevated in plaques, bloods, and cerebral spinal fluids from multiple sclerosis patients. The expression of myelin basic protein (MBP), a major protein of the myelin sheath, is affected by cytokines secreted by activated immune cells. To determine the signal transduction pathway involving tumor necrosis factor's action in myelination and demyelination, we have cloned and analyzed cis-elements on promoters of the human and mouse MBP genes. There are two putative nuclear factors kappa-B (NF-kappaB) cis-elements on the human and one on the mouse gene promoter. In an electrophoretic mobility shift assay, all three NF-kappaB cis-elements showed binding to a protein, which was recognized by an antibody against NF-kappaB P65 component. The specificity of the binding was demonstrated in a competitive assay using NF-kappaB consensus oligonucleotides. A two base pair site-directed mutation on the mouse NF-kappaB cis-element abolished its binding activity. We created a DNA construct by linking the mouse MBP gene promoter containing the NF-kappaB cis-element to luciferase gene. Transfection of this construct into a human oligodendroglioma cell line showed TNF-alpha increased the transgene expression. Furthermore the mutation of NF-kappaB site abolished TNF-alpha -induction of the transgene. The data demonstrate that NF-kappaB is the mediator between tumor necrosis factor's action and MBP gene expression. Elucidating the molecular mechanisms underlying TNF-alpha regulation of MBP gene expression provides new scientific bases for the development of therapy against oligodendrocyte-specific and myelin-related disorders such as multiple sclerosis.