Antidepressant and Neuroprotective Effect of the Chinese Herb Kaixinsan against Lentiviral shRNA Knockdown Brain-Derived Neurotrophic Factor-Induced Injury in vitro and in vivo

Depression has been associated with reduced expression of brain-derived neurotrophic factor (BDNF) in the hippocampus. Previous studies have demonstrated that the herbal medicine formula, ‘kaixinsan' (KXS), could ameliorate the severity of depression and increase cAMP response element-binding protein expression. There is direct evidence suggesting that the reduction of the BDNF protein in specific brain sites can provoke depressive-like behaviour or affect neurogenesis in vivo. However, the biological mechanisms between the antidepressant and neuroprotective effect of KXS and the alterations in BDNF levels in in vivo and in vitro models remain unclear. Using BDNF knockdown mediated by lentiviral vectors (LV-shBDNF-3) transfected with primary hippocampal neurons and following injection into the dentate gyrus of the hippocampus, it was demonstrated that a reduction in BDNF expression affects cell viability and animal behaviours associated with depression. During treatment with KXS after the lentiviral shRNA silencing of BDNF in cell and animal, cell viability, body weight, the sucrose preference test (SPT), the open field test (OFT) the Morris Water Maze (MWM) task and BDNF expression were measured. KXS attenuated LV-shBDNF-3-induced cell death in primary hippocampal neurons and also improved the sucrose intake in SPT, ambulatory response in OFT and learning ability in MWM against LV-shBDNF-3-induced depressive-like syndromes. Moreover, immunoblot analysis confirmed that KXS could reverse LV-shBDNF-induced BDNF reduction either in vitro or in vivo. These findings provide substantial evidence for supporting a neurotrophic hypothesis of depression and specify BDNF targets for potential antidepressant interventions. Moreover, the antagonism between LV-shRNA BDNF knockdown and KXS may depend on multiple compounds with synergistic mechanisms that modulate the different signal transduction networks directly or indirectly, increasing BDNF expression and exerting its neuroprotective and antidepressant-like effects.