Neurite outgrowth induced by spicatoside A, a steroidal saponin, via the tyrosine kinase A receptor pathway.

Although nerve growth factor (NGF) therapy is an available option for the treatment of Alzheimer's disease, several limitations exist in its medical application. In the present study, we examined the neurotrophic effects of spicatoside A isolated from Liriope platyphylla on PC12 cells as well as the mechanisms involved in this process. Spicatoside A (10 microg/mL) induced neurite outgrowth similar to NGF (50 ng/mL). Furthermore, spicatoside A, a steroidal saponin, activated extracellular signal-regulated kinase 1/2 (ERK 1/2) and phosphatidylinositol 3-kinase (PI 3-kinase/Akt) via tyrosine receptor kinase A (TrkA), which is responsible for the induction of the neuritic process. The effects of NGF and spicatoside A on neurite outgrowth disappeared in TrkA knockdown PC12 cells by siRNA. In conclusion, neuritogenic effects resulting from spicatoside A may be involved in TrkA activation.