The neuritogenic and synaptogenic effects of the ethanolic extract of radix Puerariae in cultured rat hippocampal neurons

Abstract

Ethnopharmacological relevance: Radix Puerariae, the root of Pueraria montana var. lobata (Willd.) Sanjappa & Pradeep, is used in Korean traditional medicine to treat neuronal disorders including Parkinson's disease, and its active constituent, puerarin has been reported to have a neuroprotective effect in experimental models of Parkinson's and Alzheimer's disease.

Aims of the study: To investigate the neurotrophic effects of these ethnomedicines on the development of central nervous system neurons and the molecular bases of these activities.

Materials and methods: Rat embryonic (E19) brain neurons were cultured in the absence or presence of the ethanolic extract of Radix Puerariae (RPE) or puerarin. At predetermined times, cells were fixed and immunostained to visualize neuronal morphologies, or lysed for protein harvesting. Morphometric analyses of neurite outgrowths and synaptogenesis were performed using Image J software. RPE or puerarin-mediated changes in the protein profiles of cultured neurons were assessed by MALDI-TOF-MS/PMF and measuring immunofluorescent intensities.

Results: RPE and puerarin alone promoted maximum neurite outgrowths at concentrations of 1µg/ml and 5µM, respectively. At these optimal concentrations, RPE and puerarin provided neurotrophic support by promoting axo-dendritic arbors and synapse formation in cultured neurons. Proteomic study revealed that RPE and puerarin both up-regulated a number of proteins, including dynein light chain 2 (DLC2) and elongation factor 2 (EF2), which are associated with neuritogenesis and synaptic potentiation, respectively. Immunofluorescence intensity measurements confirmed the expressions of the DLC2 and Dync1h1 subunits of dynein in RPE or puerarin treated hippocampal neurons were up-regulated when RPE or puerarin induced changes in neuronal cytoarchitecture.

Conclusions: Our study demonstrates that RPE and puerarin should be considered potentially valuable preventative therapeutics for brain disorders due to their abilities to promote the neuronal cytoarchitecture and the synaptic functionality, which are possibly associated with dynein-dependent regulation of cytoskeletal structures and up-regulation of translation machinery.

Keywords: Dynein; Elongation factor 2; Hippocampal neuron; Neuritogenesis; Radix Puerariae; Synaptogenesis.