| From nearly hundreds of marine organisms, we found the EtOAc layer of the head of Ilisha elongate induced the neurite outgrowth of PC12cells which is the bioassay system for screening the small molecular compounds which have the NGF-mimic activity. Guided by this bioassay, a neuritogenic monoglyceride was isolated by silica gel open column and HPLC. The chemical structure,1-O-(myristoyl) glycerol (MG), was elucidated by analysis of spectral data and comparison with the reference. MG significantly induced42%of the neurite outgrowth of PC12cells at a concentration of10μM through the study of dose-effect relationship.To study the structure-activity relationships of MG, a series of monoglycerides were designed and synthesised. First, by changing the length of the alkyl chain, C10, C12, C14, C16, C17, C18, C19, C20and C22with different alkyl chain lengths were synthesized. Bioassay results indicated that C18has the best activity among these compounds. Based on the result, the groups that link the propane-1,2-diol and alkyl chain were also investigated. Between an ester linkage and an amido one, an ester linkage was found to be optimal for neuritogenic activity. Therefore,1-O(stearoyl) glycerol (SG) which has the best activity among all the synthesized compounds, was determined to be a lead compound for neuritogenic activity.We then investigated the mechanism of action of neurite outgrowth induced by SG on PC12cells using protein specific inhibitors and western bloting assay. The mitogen-activated kinase/ERK kinase (MEK) inhibitor U0126and the phosphatidylinositol-3kinase (PI3K) inhibitor LY294002, at the concentration of30μM, respectively, can significantly inhibite neurite outgrowth. At the protein level, the western bloting verified the above results. Also, SG increased phosphorylation of cAMP responsive element-binding protein (CREB) at the protein level. Thus, SG-induced neuritogenic activity depends on the activation of the ERK/CREB/PI3K signalling pathways in PC12cells. |
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