Enhanced Neuronal Survival and Neurite Outgrowth Triggered by Novel Small Organic Compounds Mimicking the LewisX Glycan

Abstract

Glycosylation fine-tunes signal transduction of adhesion molecules during neural development and supports synaptic plasticity and repair after injury in the adult nervous system. One abundantly expressed neural glycan is LewisX (LeX). Although it is known that its expression starts at the formation of the neural tube during the second embryonic week in the mouse and peaks during the first postnatal week, its functional relevance is only rudimentarily understood. To gain better insights into the functions of this glycan, we identified small organic compounds that mimic structurally and functionally this glycan glycosidically linked to several neural adhesion molecules. Mimetic compounds were identified by competitive enzyme-linked immunosorbent assay (ELISA) using the LeX-specific monoclonal antibodies L5 and SSEA-1 for screening a library of small organic molecules. In this assay, antibody binding to substrate-coated LeX glycomimetic peptide is measured in the presence of compounds, allowing identification of molecules that inhibit antibody binding and thereby mimic LeX. Gossypol, orlistat, ursolic acid, folic acid, and tosufloxacin inhibited antibody binding in a concentration-dependent manner. With the aim to functionally characterize the molecular consequences of the compounds' actions, we here present evidence that, at nM concentrations, the mimetic compounds enhance neurite outgrowth and promote neuronal survival of cultured mouse cerebellar granule cells via, notably, distinct signal transduction pathways. These findings raise hopes that these LeX mimetics will be powerful tools for further studying the functions of LeX and its effects in acute and chronic nervous system disease models. It is worth mentioning in this context that the LeX compounds investigated in the present study have been clinically approved for different therapies.

Myristoylated alanine‐rich C‐kinase substrate effector domain peptide improves sex‐specific recovery and axonal regrowth after spinal cord injury

“…We then added ED peptide, control peptide (10 µM), or vehicle control (0.1% of DMSO) treatment to the cultures. 34 After 24 hours, cells were fixed, stained, and analyzed for neurite outgrowth as described in the "neurite outgrowth" section above.…”

“…We counted live and apoptotic cells from four images of three wells per condition (12 images/condition), using ImageJ software as described. 34 In brief, with contrast and brightness thresholds set on default, background noise was eliminated using despeckle, erode, and dilate functions of ImageJ. The watershed ImageJ function was used to improve accuracy of counting the cells using the analyze particles function of ImageJ.…”

Glycan Mimetics from Natural Products: New Therapeutic Opportunities for Neurodegenerative Disease

“…Here, we summarize a group of natural products (including semisynthetic compounds) that functionally mimic glycans, have proven neuroprotective functions, and may therefore form a novel class of therapeutics for NDs. These "natural glycomimetics" are classified based on the glycans they mimic including human natural killer-1 (HNK-1) [140], LewisX (LeX) [141], neural cell adhesion molecule L1 (L1CAM) [142], and polysialic acid (PSA) [143]. The glycan-mimicking properties of these compounds have been confirmed by competitive enzyme-linked immunosorbent assay (ELISA) using glycan antibodies.…”

“…Two natural compounds, gossypol and folic acid, have been identified as LeX mimetics [141]. Gossypol is a natural phenolic aldehyde first isolated from the cotton (Gossypium) plant of the family Malvaceae in 1899.…”

“…Multiple studies have linked folate deficiency with dementia, poor cognitive function, and NDs. Melitta et al found that folic acid promotes neuronal survival after hydrogen peroxide treatment [141]. Moreover, folic acid has been used as a supplement for pregnant women to reduce the chance of the neural tube defects (NTDs) in babies [161].…”