Click-xylosides overcome neurotoxic effects of reactive astrocytes and promote neuronal growth in a cell culture model of brain injury

Astrocytes, upon activation in response to brain injury, play a critical role in protecting neurons by limiting inflammation through the excessive secretion of many soluble factors, such as, chondroitin sulfate proteoglycans (CSPGs). Unfortunately, excessive CSPGs paradoxically prohibit neuronal recovery and growth, and eventually constitute a scar tissue. Many studies have attempted to overcome this barrier through various molecular approaches including the removal of inhibitory CSPGs by applying chondroitinase enzymes. In this study, we examined whether click-xylosides, which serve as primers of glycosaminoglycan (GAG) biosynthesis, can compete with endogenous inhibitory CSPGs for GAG assembly by serving as decoy molecules and thereby potentially reverse reactive astrocyte mediated neuronal growth inhibition. We investigated the axonal growth of hippocampal neurons in the presence of xyloside treated and untreated reactive astrocyte-conditioned media as a model recapitulating brain injury. Click-xylosides were found to interfere with the GAG biosynthetic machinery in astrocytes and reduced the amount of secreted inhibitory CSPGs by competing with endogenous assembly sites. The extent of underglycosylation was directly related to the outgrowth of hippocampal neurons. Overall, this study suggests that click-xylosides are promising therapeutic agents to treat CNS injuries and warrants further in vivo investigations.