Studies On The Mechanism Of Antidepressant Effects By 3,6'-disinapoyl Sucrose

3,6′-disinapoyl sucrose (DISS) is the active oligosaccharide ester component found in the root ofPolygala tenuifolia Willd (Radix Polygala). Recorded as"YuanZhi"in the Pharmacopoeia of the People'sRepublic of China, the root has been used in traditional medicine as, among other things, an expectorant, tonic,tranquillizer and antipsychotic agent. Our previous studies indicated that DISS has notable antidepressanteffects in pharmacological depression models, an action closely related to the potentiation of central 5-HT andNE systems. Our recent study also found that DISS increased expression in the hippocampus of threenoradrenergic-regulated plasticity genes (laminin, CAM-L1 and CREB) and one neurotrophic factor (BDNF).This research is aimed to investigate the neuroprotective and nerve regeneration effect and mechanism ofDISS by CREB related upstream and downstream signal pathway and to find the detailed targets and passwayactiving by DISS, which may be useful to the antidepressant new drug development.The effect of DISS on the CREB downstream passway and its antiapoptosis activitySH-SY5Y neuronal cells were pretreated with glutamate (8mM) for 30min followed by co-treatment withDISS for 12 h. Cell viability was determined by (3,4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide(MTT) assay, and apoptosis was confirmed by cell morphology and flow cytometry assay, evaluated withpropidium iodide dye. Treatment with DISS (0.6, 6, and 60μM) increased cell viability dose-dependently,inhibited LDH release and attenuated apoptosis. The mechanisms by which DISS protected neuron cells fromglutamate induced excitotoxicity included the downregulation of proapoptotic gene bax and the upregulationof anti-apoptotic genes bcl-2.The effect of DISS on the CREB downstream passway and its antioxidant activitySH-SY5Y neuronal cells were pretreated with H₂O₂ (300μM) for 30min followed by co-treatment withDISS for 12 h. Cell viability was determined by (3,4,5-dimethylthiazol-2-yl)-2,5-diphenylte-trazolium bromide(MTT) assay, and antioxidant effect was confirmed by SOD,CAT,GSH-PX and MDA level. Treatment withDISS (0.6, 6, and 60μM) increased cell viability dose-dependently, inhibited H₂O₂ induced injurey, increasedthe SOD, CAT, GSH-PX level and decreased the MDA level. The mechanisms by which DISS protectedneuron cells from H₂O₂ induced cell toxicity included its antioxidant activity.The effect of DISS on the CREB upstream passway and its detail targetsThe DISS-induced phosphorylation of CREB was completely blocked by U0126 [a mitogen-activatedprotein (MEK) kinase inhibitor] and KN93 (a CaMK inhibitor), but not by inhibitors of protein kinase A, H89kinase. These results suggest that antidepressants acutely increase CREB activity in CaMK and ERKdependent manners, which might contribute to DISS increased pCREB expression in SY5Y cells. In summary, basing on the results, the present study speculated that the ERK-CREB and CaM-CREBsignal system may be involved in the mechanism that DISS exerts antidepressant actions, and the neuronalmechanism of depression. Moreover the present findings also indicated that DISS exerts the neuroprotectiveeffects by actived CREB phosphorylation and further adjusted its downstream gene (proapoptotic gene bax andanti-apoptotic genes bcl-2.) and antioxidant system proteins, which participant the neural plasticity,differentiation, neurotrophy, apoptotic and oxidative stress function.