Extracts of Fructus Akebiae:A novel serotonin,norepinephrine and dopamine reuptake inhibitor

OBJECTIVE Fructus Akebiae(FAE) is a traditional Chinese herbal that has been used for the treatment of depressive disorders in China.To determine the content of hederagenin and identify the substance exerting antidepressant activity from the extracts of FAE which was extracted by systemic solvent segregation.To assess pharmacological acute and sub-chronic antidepressant activity of FAE by using behavioural despair animal models.In currently study,we used a series of competitive radio ligand binding and transporter inhibition bioassays to determined FAE affinities at rat and cloned human(h) SERTs,NETs,and DA transporters(DAT).In contrast,we also evaluated the affinity of FAE to numerous other targets(D1,D3,D2,D4,D5,5-HT1A,5-HT1B,5-HT1D,5-HT2a,5-HT2C,5-HT3,5-HT5A,5-HT6,5-HT7,α1A,α1B,α2A,β1,M1,M2,M3,M4,M5,μ,κ,δ,A1,A2A,H1,H2,H3,H4) to determine its selectivity.METHODS As monoaminergic system is one of the most important targets in the pathophysiology and therapy of depression,our current studies were designed to explore the effect of FAE on monoaminergic systems.Here,we used a series of competitive radio ligand binding and transporter inhibition bioassays to determined FAE affinities to the rat and cloned human(h) SERTs,NETs,and DATs.We also evaluated the affinity of FAE to numerous other targets to determine its selectivity.In addition,we tested the effect of FAE on the transport activities of three monoamines,5-HT,NE and DA,using transporter-transfected HEK cell line as well as rat brain synaptosomal preparations.RESULTS We found that FAE showed a high affinity for rat monoamine transporters including SERT,NET and DAT with Ki value 3.89 nmol·L-1,0.22 nmol·L-1 and 2.87 nmol·L-1.FAE showed high affinity to human monoamine transporters with IC50 value 1.65 nmol·L-1,0.14 nmol·L-1 and 1.03 nmol·L-1,consistent with results from rats.Our results showed that FAE inhibited all three transporters(SERT,DAT and NET) in a dose-dependent manner with IC50 value 3.04 nmol·L-1,0.86 nmol·L-1 and 2.08 nmol·L-1.We found FAE also significantly inhibited the activities of NET,SERT and DAT in these transfected cell lines.The Ki values for FAE to inhibit the uptake of -5-HT,-5-NE,and -DA into cells expressing the corresponding human recombinant transporters were 1.34±0.04,0.15±0.02 nmol·L-1 and(1.09±0.12)nmol·L-1,respectively.CONCLUSION In our present study,we found that FAE bound to NET,SERT and DAT with high affinity,and potently inhibited 5-HT,NE and DA reuptake in both rat synaptosomal preparations and intact cell line expressing human transporters,suggesting that FAE is a novel triple reuptake inhibitor.We conducted our assays using both rat brain synaptosomes and human transporter-transfected cell line to evaluate effect of FAE for clarifying whether there would be an issue with species difference.FAE is a novel potent triple reuptake inhibitor that can bind to all three-monoamine transporters(NET,SERT and DAT) with high affinities and selectivity.Our results suggest that FAE may represent a new class of antidepressants with fewer side effects.