Abstract
Purpose:
Pathologically, in experimental autoimmune optic neuritis (EAON) microglial activation occurs before T-cell infiltration in the optic nerve and axon degeneration precedes demyelination. The casual relationship between axon damage and microglial activation in EAON is yet to be explored. (Matsunaga Y et al. IOVS, 2012) In this study, we investigated the potential role of microglia in EAON by evaluating the production of glutamate and cytokines in an in vitro co-culture model of microglia with mononuclear cells.
Methods:
EAON was induced by immunizing C57BL/6 mice with myelin oligodendrocyte glycoprotein (MOG). At 14 days after immunization, the mice were killed and mononuclear cells were isolated from the cervical lymph nodes. Mononuclear cells (4 × 105 cells) were co-cultured with different numbers of microglial cells (0, 6 × 103, 1.25 × 104, 2.5 × 104, 5 × 104, 1 × 105, 2 × 105 cells) of mouse origin and stimulated with the MOG antigen (10 μg/ml) for 48 hours. After stimulation, supernatants were collected, and ELISA (n=12) was performed to measure the levels of glutamate and of the following cytokines: IL-1a, IL-1b, IL-2, IL-3, IL-4, IL-5, IL-6, IL-9, IL-10, IL-12(p40), IL-12(p70), IL-13, IL-17, IFN-γ, TNF-α, G-CSF, GM-CSF, Eotaxin, KC, MCP-1, MIP-1a, MIP-1b, and RANTES. Furthermore, cell proliferation assays were performed using supernatants collected at 96 hours of co-culturing.
Results:
MCP-1 production increased proportionally with the increase in the number of microglial cells. On the contrary, production of other cytokines decreased with an increase in microglial cell numbers. Glutamic acid production increased with increasing microglial cell numbers (p < 0.05). The cell proliferation assay showed suppression of, T-cell proliferation when the number of microglial cells was 2 × 105 cells (p < 0.05).
Conclusions:
The increase in glutamic acid production with increasing number of microglia may have resulted in the decreased cytokine production and suppressed cell proliferation.
Keywords: 595 microglia •
629 optic nerve •
613 neuro-ophthalmology: optic nerve