Lindersin B from Lindernia crustacea induces neuritogenesis by activation of tyrosine kinase A/phosphatidylinositol 3 kinase/extracellular signal-regulated kinase signaling pathway.
BACKGROUND
Neurotrophic factors such as nerve growth factor (NGF) play important roles in nervous system. NGF is a potential therapeutic drug for treatment of neurodegenerative diseases. However, because of physicochemical property, NGF cannot pass through the blood-brain barrier (BBB). Hence, small molecules which exhibit NGF-mimic activity and can pass through the BBB are considered to be promising drug candidates for treatment of such diseases.


OBJECTIVE
The present study was designed to isolate NGF-mimic substance from extract of natural products, determine their structures and investigate mechanism of action of the active substance.


METHODS
Extract of Lindernia crustacean was partitioned between water and ethyl acetate to obtain water layer and ethyl acetate layer samples, respectively, and then evaluated their neuritogenic activity in PC12 cells. The active sample was separated by open columns, followed by HPLC purification to obtain active compound. Then, specific inhibitors were used to investigate signaling pathway of neurite outgrowth induced by the active compound. Finally, western blot analysis was performed to confirm the pathway proposed by inhibitor experiments.


RESULTS
The ethyl acetate layer sample of extract of Lindernia crustacea exhibited significant neuritogenic activity. Two new compounds, named as linderside A and lindersin B, were isolated; their structures were elucidated by spectroscopic and chemical derivatization methods. Linderside A is a cucurbitane glycoside, whereas lindersin B is a cucurbitane triterpenoid. Each compound has an unusual isopentene unit, namely, a double bond bound to an unmodified isopropyl group at the end of cucurbitane triterpenoid side chain. Among them, lindersin B induced significant neurite outgrowth in PC12 cells, while linderside A was inactive against PC12 cells. Western blotting analysis results showed that lindersin B-induced neuritogenic activity depended on the activation of the mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK). Moreover, tyrosine kinase A (TrKA) and phosphatidylinositol 3 kinase (PI3K) were also involved in the signaling pathway.


CONCLUSIONS
Two new cucurbitane triterpenoids, linderside A and lindersin B, were isolated from Lindernia crustacean. Neurite outgrowth induced by lindersin B in PC12 cells depends on activation of TrkA/PI3K/ERK signaling pathway.
College of Pharmaceutical Sciences, Zhejiang University, Yu Hang Tang Road 866, Hangzhou 310058, People's Republic of China.
Lihong
L
Cheng
College of Pharmaceutical Sciences, Zhejiang University, Yu Hang Tang Road 866, Hangzhou 310058, People's Republic of China.
Ying
Y
Ye
College of Pharmaceutical Sciences, Zhejiang University, Yu Hang Tang Road 866, Hangzhou 310058, People's Republic of China.
Lan
L
Xiang
Chemical Biology Research Group, RIKEN Center for Sustainable Resource Science, Wako-shi, Saitama 351-0198, Japan.
Hiroyuki
H
Osada
College of Pharmaceutical Sciences, Zhejiang University, Yu Hang Tang Road 866, Hangzhou 310058, People's Republic of China. Electronic address: qijianhua@zju.edu.cn.
Jianhua
J
Qi
D000818:Animals; D002681:China; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D009414:Nerve Growth Factors / Q000627:therapeutic use*; D019636:Neurodegenerative Diseases / Q000188:drug therapy*; D016716:PC12 Cells / Q000187:drug effects; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D008517:Phytotherapy; D010936:Plant Extracts / Q000494:pharmacology / Q000627:therapeutic use*; D018515:Plant Leaves / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D028083:Scrophulariaceae / Q000737:chemistry*; D015398:Signal Transduction / Q000187:drug effects
D009414:Nerve Growth Factors; D010936:Plant Extracts; D019869:Phosphatidylinositol 3-Kinases; D011505:Protein-Tyrosine Kinases; D048049:Extracellular Signal-Regulated MAP Kinases
Cucurbitane triterpenoid; Lindernia crustacea; Neuritogenic activity; PC12 cells; Scrophulariaceae; Signaling pathway