Murine microglial cells express functionally active galectin-3 in vitro.

In the present study we have analyzed the expression of galectin-3, a beta-galactoside-specific soluble animal lectin, by microglial cells in vitro. In enriched microglial cell cultures derived from neonatal mouse brain after 2 to 3 weeks in vitro, almost all microglial cells expressed galectin-3 intracellularly and about 90% expressed the molecule on the cell surface. Western blot analyses of lysates from microglial cells using galectin-3-specific antibodies revealed a single band with an apparent molecular weight of 29 kD. The carbohydrate recognition domain of microglia-derived galectin-3 was functional as the molecule could be affinity purified on lactose-agarose. Upon an incubation with lactose-, but not with sucrose-containing buffers the amount of cell surface expressed galectin-3 was strongly reduced, suggesting that the molecule appears to be associated with the plasma membrane via its carbohydrate recognition domain. The total amount as well as the portion of cell surface expressed galectin-3 increased upon treatment with granulocyte-macrophage colony-stimulating factor. Our findings suggest that galectin-3 expression is subject to regulation by growth factors supposed to be involved in the cascade of microglial activation under pathological conditions.