Kai-Xin-San, a Chinese Herbal Decoction, Accelerates the Degradation of -Amyloid by Enhancing the Expression of Neprilysin in Rats.

This study aimed to investigate the mechanisms of Kai-Xin-San (KXS, a famous Chinese herbal decoction used to treat amnesia) on the degradation of A and further elucidate the mechanism of KXS on A-induced memory dysfunction. After pretreatment with KXS (1.08 g/kg/day) for two weeks, A (2 L, 200 M) was injected into rat hippocampus to induce cognitive dysfunction. Morris water maze (MWM) test was developed to evaluate cognitive performance in rats. Hippocampal neurons were observed by histological staining using Hematoxylin-Eosin (HE) methods. Levels of exogenous A , which was injected into the hippocampus, were continually measured through a special Enzyme-linked immunoassay (ELISA) kit to observe the catabolic process of A in the brain. Similarly, A degradation in PC12 cells was also investigated using the ELISA kit. The expressions of A degeneration enzymes, including neprilysin (NEP), angiotensin-converting enzyme (ACE), and endothelin-converting enzyme (ECE), were detected by western blotting to elucidate A reduction mechanism. Our results showed that KXS prevented A -induced cognitive impairment and attenuated hippocampus neuronal damage caused by A . Moreover, KXS could accelerate A degradation in A injected rats. Furthermore, NEP, an A degradation enzyme, was increased in the hippocampus while ECE and ACE, other two A-degrading enzymes, were not changed. KXS accelerated A degradation in PC12 cells. Our findings revealed that KXS facilitated the degradation of A by increasing the expression of NEP in rat hippocampus. By reducing the A burdens, KXS protected hippocampal neurons, leading to the improvement of cognitive function in rats.