Effects of 5-hydroxymethyl furfural extracted from Rehmannia glutinosa Libosch on the expression of signaling molecules relevant to learning and memory among hippocampal neurons exposed to high concentration of corticosterone.

Objective: To determine the effects of 5-hydroxymethyl furfural (5-HMF), an extract of Rehmannia glutinosa Libosch, on several down-regulated signaling molecules involved in learning and memory in hippocampal neurons.

Methods: After cultured for 7 days, primary hippocampal neurons were divided into 5 groups: normal, corticosterone model, RU38486, 5-HMF, and donepezil group. Neuron survival rates were calculated 24 h later using SYTO13-PI double-fluorescence staining and an 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. β-galactosidase activity was also assayed. Protein expressed by the glucocorticoid receptor (GCR), brainderived neurotrophic factor (BDNF), and N-methyl-D-aspartate receptor 2B (NR2B), as well as phosphorylationcyclic adenosine monophosphate (cAMP) response element binding protein (p-CREB), phosphorylation-extracellular signal-regulated kinase (p-ERK), and phosphorylation-synapsin (p-synapsin) were quantified with Western blot.

Results: Hippocampal neuron survival rates and the above-mentioned proteins were dramatically decreased (P<0.05), β-galactosidase activity was significantly increased in the model group. but the effect was reversed by 5-HMF, RU38486, and to a lesser extent by donepezil (P<0.05).

Conclusion: 5-HMF extracts from the Chinese herb Rehmannia glutinosa Libosch could protect hippocampal neurons from glucocorticoid injury and from down-regulated signaling molecules in the GCR-BDNF-NR2B-p-ERK-p-CREB-p-synapsin signal transduction pathway.