Abstract
Coptis chinensis rhizomes (CR) are one important ingredient of traditional Chinese herbal formulas such as San-Huang-Xie-Xin-Tang which is used for treatment of cardiovascular and neurodegenerative diseases. Recent studies suggest that the extract of CR might be a potential therapeutic agent for amelioration of neurological disorders associated with oxidative stress. In the present study we aimed at revealing the main active compound(s) of the CR extract and at investigating the mechanism of action. Four main alkaloids of the CR extract (berberine, coptisine, jatrorrhizine, and palmatine) were selected for this study. Results showed that out of those alkaloids only pretreatment with coptisine significantly attenuated tert-butylhydroperoxide induced reduction of cell viability, increased rate of apoptosis, and declined mitochondrial membrane potential. Elisa assay and quantitative real-time PCR analyses revealed that thioredoxin-interacting protein (TXNIP) gene expression was downregulated by coptisine, which could explain the neuroprotective effect, hypothetically, by strengthening the thioredoxin defense system against oxidative stress and attenuation of apoptosis signal-regulating kinase (Ask1) mediated apoptotic signaling. A comparison between coptisine and CR extract identified coptisine as the main single component responsible for the neuroprotective effect. Based on the results the CR extract and coptisine are promising candidate agents for prevention or improvement of diabetic neuropathy and neurodegenerative disorders.