Masahisa Yamada

Interleukin-6 protects cultured rat hippocampal neurons against glutamate-induced cell death.

We examined the effect of interleukin-6 (human recombinant) on glutamate-induced neuronal death of cultured 20-day fetal rat hippocampal neurons. After 7 days in culture, the hippocampal neurons were markedly degenerated by the addition of L-glutamate and also N-methyl-D-aspartate. The neuronal death was prevented by the addition of MK801, a potent N-methyl-D-aspartate antagonist. Interleukin-6 at the concentration of 50 ng/ml has a significant preventive effect on the glutamate-induced neuronal death. Basic fibroblast growth factor at the concentration of 100 ng/ml gave also significant protective effect on hippocampal neurons, but nerve growth factor was ineffective in preventing the toxicity. It has been postulated that glutamate plays an important role in the pathogenesis of neuronal death such as ischemia and the various neurological diseases. Interleukin-6 might have somewhat physiological or pathological role in these events.

Expression of Proteolipid Protein Gene Is Directly Associated with Secretion of a Factor Influencing Oligodendrocyte Development

Abstract: Oligodendroglial cell death in the myelin proteolipid protein (PLP) mutants can be partially rescued by the environment factor(s) supplied by the wild‐type cells in vivo and in vitro. It is possible that the presence of PLP or DM‐20 results in secretion of a factor or factors in the CNS influencing oligodendrocyte development. We previously showed that DM‐20 mRNA is produced in G26 mouse oligodendroglioma, B104 rat neuroblastoma, and B16 mouse melanoma but not in NIH3T3 mouse fibroblast cell lines. Culture supernatants from these cell lines were added to primary glial cell cultures from embryonic day 17 mouse brain. After 4 days, the number of oligodendrocytes present in cultures with supernatants from DM‐20‐producing cells (G26, B104, and B16) was significantly higher than that of control cultures but not with the NIH3T3 supernatant. To investigate more directly whether the PLP gene expression is involved in this process, NIH3T3 cells (nonneural cells) were forced to produce PLP or DM‐20. By addition of the supernatants from the PLP/DM‐20 transformants, the number of oligodendrocytes in the mixed glial cell cultures increased. This clearly demonstrates that the expression of the PLP gene is sufficient for and directly associated with secretion of a factor, which influences the oligodendrocyte development.

S5-2 Development and differentiation of normal and mutant oligodemdrocytes

During embryonic stages, the glutamate transporter GLAST is expressed in the radial glia, whose cell body is localized in the ventricular zone and its radial process extends toward the pial surface of the brain and spinal cord. At embryonic day 15, the GLASTpositive radial glia begins to migrate from ventricular zone. Concomitant with the migration, localization of the GlAST shifts from the radial processes to astrocytic cell membrane. In postnatal development, the GLAST remarkably increases the level of expression in the cerebellar Bergmann astroglia which associates with migrating granule cells and with synapses of Purkinje cells, whereas it is substantially down-regulated in most other astrocytes. Therefore, the GLAST will be a useful molecular marker to investigate the morphodifferentiation from radial glia to astrocyte and also the intimate neuro-glial relationship in the cerebellum.

S1-3 Understanding mechanism governing oligodendrocyte development through analysis of mutant mice

Mutations within the gene coding for myelin proteolipid protein (PLP) result in premature cell death of oligodendrocytes, the myelin-producing cells in the central nervous system. We report that PLP is multi-functional protein. It include: 1) Fragments of PLP is secreted into the medium and increase the number of oligodendrocyte in mixed glial culture. 2) PLP binds to inositol polyphosphate and probably involved in the membrane transport in oligodendrocyte. 3) PLP functions in stabilizing the myelin membrane as has been suggested.