HEK293-APP695 세포에서 coptisine이 아밀로이드 베타 펩타이드 발현에 미치는 영향

Abstract

Alzheimer's disease (AD) is regarded as the main cause of dementia and characterized by neurodegenerative disorder. Amyloid-beta (Aβ) appears in the brain of AD, it's hallmarks in AD pathology and is typically deposited as senile plaques in cerebral. Aβ is generated from amyloid precursor protein (APP) by proteases, β-secretase and γ-secretase. β-site amyloid precursor protein cleaving enzyme 1, called BACE1, it cleaves at the N-terminal domain of APP to release sAPPβ and C99, and C99 converted by γ-secretase to release diverse forms of Aβ. On the other hand, α-secretase, cleaves APP in the center of the Aβ domain, thus it prevents the generation of Aβ. Although the exact mechanism is unknown, Aβ is strongly involved in the etiology of all forms of AD. Thus, compounds that enhance α-secretase, but inhibit β- or γ-secretase activity, have therapeutic potential in the treatment of AD. Coptidis rhizoma (C. rhizoma) and its isolated alkaloids such as berberine, coptisine, palmatine, jateorrhizine, epiberberine, and groenlandicine has been reported to exhibit anti-AD and antioxidant activity through multiple pharmacological effects including cholinesterase inhibitory activity, as well as ONOO-, and ROS scavenging activity. It has also been demonstrated that berberine, a major alkaloid from C. rhizoma can reduce the production of Aβ, which plays a critical role in the pathogenesis of AD. Also, berberine, the potent alkaloid on Aβ production has similar chemical structure with other minor alkaloids from C. rhizoma. However, despite these chemical structure similarity, the inhibitory effect on Aβ secretion of minor alkaloids have not been investigated. Therefore the effect of six alkaloids of Aβ expression were evaluated using HEK293 cells stably transfected with APP695 and its activity was compared with their structure activity relationship. Among these alkaloids, berberine, epiberberine, groenlandicine, and coptisine significantly exhibited Aβ inhibitory effect and also has common structure with dioxymethylene group. On the other hand, palmatine and jateorrhizine showed low inhibition of Aβ peptide on HEK293-APP695 cells and the absence of dioxymethylene group in their structure further helps to predict the structure activity relationship. This result suggests that the presence of dioxymethylene group may attribute for the inhibitory activity of Aβ expression. Among these minor alkaloids, coptisine exhibited strong inhibition of Aβ expression. So, the focus of our investigation was the effect of coptisine on Aβ expression as well as on enzymes responsible in its cleavage using HEK293-APP695 cells. As a result, coptisine dose-, and time- dependently reduced the Aβ and the expression of β-, and γ-secretase in HEK293-APP695 cells. Therefore, coptisine from C. rhizoma seems to have a BACE inhibitor as well as PS1 inhibitor-like activity that β-, and γ-secretase induced APP processing and Aβ secretion. These results indicate that minor alkaloids such as epiberberine, groenlandicine, and coptisine have strong potential of inhibition and prevention of AD. In particular, coptisine may be a promising anti-AD agent due to its potent inhibitory activity of Aβ by inhibiting the expression of BACE1 and PS1. Therefore, coptisine would clearly have beneficial effect in the development of therapeutic and preventive agents for AD.