Effects of the Detoxified Extract of Rhus verniciflua on Regulation of Catecholamine Biosynthesis

Abstract

Rhus verniciflua Stokes (RVS) has traditionally been used as a food supplement and traditional herbal medicine for centuries in Korea, despite the fact that it contains the plant allergen, urushiol. Previously, we developed a new biological approach for the removal of urushiol from RVS. In this study, we investigated the effect of detoxified RVS on the expression of catecholamine biosynthetic enzymes in rat brain. Our results showed that RVS is a potent inducer of catecholamine production in rodent brain as indicated by the enhanced expression of the tyrosine hydroxylase (TH), aromatic amino acid decarboxylase (AADC) and dopamine β-hydroxylase (DBH) gene. Induction of TH and AADC in response to RVS was biphasic and transient, and maximal at 10 mg/kg for 4 h. We also detected consistent upregulation of TH and AADC mRNAs and proteins with RVS; however, DBH expression was not detected in the brain by immunostaining. Moreover, we examined the protective effect of detoxified RVS on rotenone induced cell toxicity in the cultured human dopaminergic cell line, SH-SY5Y. We found that rotenone induced cytotoxicity in SH-SY5Y cells was suppressed by treatment with RVS. These results suggest that RVS may serve as an ideal adjuvant in regards to regulating the brain dopaminergic (DArgic) system and may contribute to neuroprotection in neurodegenerative diseases.