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Lactucopicrin potentiates neuritogenesis and neurotrophic effects by regulating Ca2+/CaMKII/ATF1 signaling pathway

Venkatesan, Ramu, Shim, Won-Sik, Yeo, Eui-Ju, Kim, Sun Yeou
Journal of ethnopharmacology 2017 v.198 pp. 174-183
Cichorium intybus, antidepressants, calcium, calcium-calmodulin-dependent protein kinase, chicory, cholinergic receptors, mice, mitogen-activated protein kinase, neurites, neurodegenerative diseases, neuroprotective effect, neurotrophins, phosphatidylinositol 3-kinase, rats, secretion, signal transduction, traditional medicine, transcription factors, tropomyosins
Lactucopicrin is one of constitutes in Cichorium intybus L, which is commonly known as chicory in worldwide. It has been used for traditional usage such as antianalgesics, antidepressants and antihyperglycemicsWe investigated the neurotrophin-mediated neuroprotective effect of lactucopicrin in in vitro and examined for the underlying mechanism.To verify the neuroprotective effect of lactucopicrin, we investigated the inhibitory AChE activity, neurite outgrowth-related downstream signaling in murine neuroblastoma N2a and neurotrophins secretion in rat C6 glioma cells.Lactucopicrin inhibited the AChE activity and increased intracellular Ca²⁺ levels with a substantial rise in muscarinic acetylcholine receptor M1 (CHRM1) expression in N2a cells. Moreover, lactucopicrin actively promoted neurite outgrowth via Ca²⁺-mediated activation of Ca²⁺/calmodulin-dependent protein kinase-II (CaMKII). It further activates transcription factor 1 (ATF1) along with modulating the levels of tropomyosin receptor kinase A, extracellular signal-regulated kinase 1 and 2, AKT, and synaptophysin 1 in N2a cells. Additionally, the levels of neurotrophins including NGF, BDNF, and NT3 were increased by treatment of lactucopicrin in C6 cells. The effects of lactucopicrin on NGF secretion and neuritogenesis were maintained even in the presence of phosphatidylinositol-3-kinase (PI3K) inhibitor LY294002, indicating that lactucopicrin exerts its effect on neuritogenesis in a PI3K-independent manner.Our results suggest that the natural compound lactucopicrin may be a promising neurotrophin-mediated neuroprotective candidate for neurodegenerative diseases.