Echinocystic Acid Facilitates Neurite Outgrowth in Neuroblastoma Neuro2a Cells and Enhances Spatial Memory in Aged Mice

Abstract

Aging leads to functional changes in the brain and decreases ability of learning and memory. Neurite outgrowth is important in learning and memory, therefore regulation of neurite outgrowth might be a candidate for treating aged brain. Echinocystic acid (EA), a pentacyclic triterpene, has shown to exert various neurological effects. However, the effect of EA on neurite outgrowth has not been studied. In this study, we examined if EA is effective on neurite outgrowth and memory in aged mice. The effect of EA on neurite outgrowth was observed by examining neurite processes of Neuro2a cells treated with EA. Western blot analysis was conducted to examine possible mechanisms. Morris water maze test was used to examine the effect of EA on learning and memory in aged mice. Immunohistochemistry was conducted to observe the effect of EA on neurite outgrowth in the hippocampus. EA was shown to induce neurite outgrowth in a concentration dependent manner without affecting cell viability. Moreover, EA treatment increased phosphorylation of c-jun N-terminal kinase (JNK) and JNK inhibitor, SP600125, blocked the effect of EA on neurite outgrowth. These results demonstrated that EA treatment promotes neurite outgrowth through the JNK signaling pathway. In in vivo experiments, EA treatment increased neurite outgrowth in aged mouse hippocampus. Moreover, EA treatment enhanced spatial learning and memory in aged mice. These results suggest that EA can be developed as a new, naturally occurring drug to treat ageing-related neurological diseases.Key words echinocystic acid; neurite outgrowth; aging; spatial memory The ability to remember certain types of information declines with aging.

Effects of Carbazole Derivatives on Neurite Outgrowth and Hydrogen Peroxide-Induced Cytotoxicity in Neuro2a Cells

“…Over the past 2 decades, numerous studies have revealed the molecular mechanisms underlying the regulation of neurite outgrowth by various factors. The representative pathway for neurite outgrowth is the activation of the PI3K/Akt and/or protein kinase A (PKA)/mitogen-activated protein kinase (MAPK)/ERK signaling pathways [16,17,18,19,20,21]. We thus tested by immunoblot analysis whether compound 13 had the ability to promote the phosphorylation of ERK1/2 and/or Akt in neuro2a cells.…”

“…These results suggest that compound 13 -induced neurite outgrowth from neuro2a cells was being regulated through the PI3K/Akt-mediated signaling pathway and not the PKA/MAPK/ERK one. Other various signal pathways such as c-jun N-terminal kinase (JNK) have been reported to be involved in neurite outgrowth of neuro2a cells [19,21]. We will investigate whether not only PI3K/Akt-mediated signaling pathway, but also other signaling pathway(s) underlie the compound 13 -induced neuronal differentiation or not.…”

“…Thus, attention has been recently drawn to compounds promoting neurite outgrowth as being candidates of neuroregenerative drugs [28]. In fact, compounds promoting neurite outgrowth reportedly enhance learning and memory of aged subjects [21,29,30] or exhibit a potent antidepressant effect [31].…”

Terpenoids as Potential Geroprotectors

“…Triterpenoids, for example, ursolic acid, and echinocystic acid, are described to improve learning ability and memory in mice [ 274 , 275 ]. Ginsenoside Rg3 and Rh2 from red ginseng roots have a calming effect [ 276 ].…”

“…Triterpenoids and triterpenoid-containing extracts stimulate expression and enhance enzymatic activity of pro-longevity proteins SIRT1, SIRT6, PGC-1α, and JNK [ 251 , 265 , 275 , 281 , 296 , 297 , 298 ]. Furthermore, in silico, in vitro, and in vivo experiments demonstrated that ursolic acid directly binds to the outer surface of mammalian SIRT1 [ 297 ], as well as links with nematode JNK-1 ATP-binding site [ 250 ].…”