Glycans and Glycan-Binding Proteins in Brain: Galectin-1-Induced Expression of Neurotrophic Factors in Astrocytes

Astrocytes are a major cell type in the central nervous system (CNS). They are considered to act in cooperation with neurons and other glial cells and to participate in the development and maintenance of functions of the CNS. Immature astrocytes possess a polygonal shape and have no processes, and continue to proliferate, while mature astrocytes have a stellate cell morphology, increased glial fibrillary acidic protein expression, and proliferate slowly. Stellate astrocytes, which immediately appear at the site of brain lesions by ischemia or other brain injuries, are thought to produce several neurotrophic factors to protect neurons from delayed post-lesion death. Previously we reported that galectin-1, a member of the family of β-galactoside-binding proteins, induced astrocyte differentiation, and the differentiated astrocytes greatly enhanced their production of brain-derived neurotrophic factor (BDNF). BDNF is known to promote neuronal survival, guide axonal pathfinding, and participate in activity-dependent synaptic plasticity during development. The effect of galectin-1 is astrocyte-specific and does not have any effect on neurons. Prevention of neuronal loss during CNS injuries is important to maintain brain function. Induction of neuroprotective factors in astrocytes by an endogenous mammalian lectin may be a new mechanism for preventing neuronal loss after brain injury, and may be useful for the treatment of neurodegenerative disorders.