Effects Of Brucine Combined With Glycyrrhetinic Acid Or Liquiritin On Rat Hepatic Cytochrome P450 MRNA Expression And Activities In Vivo

Strychnos nuxvomica L. (SN) has been widely used in traditional Chinese medicine for the treatment of tumor and rheumatic arthritis disease. Alkaloids are the major active components of this species. Because of the high toxicity of strychnine and brucine existed in SN, the clinical value of SN is limited, and often used by combination with Radix glycyrrhizae and other herbal drug to reduce its toxicity. However, the detoxification mechanism produced by co-administration is still largely unclear. It was reported that the activity of mammalian hepatic cytochrome P450 enzymes (CYPs) can be affected by a wide range of chemicals. In order to minimize potential drug side effects, especially the dugs with a narrow therapeutic window, it is important to ascertain the inhibition or induction on hepatic CYPs activities by drugs. This study investigates the changes of hepatic CYP3A1, CYP1A2, CYP2E1 and CYP2C11 at mRNA expression and enzyme activity levels, as well elucidate the detoxicant mechanism of Radix glycyrrhizae against SN toxicity in vivo through the level phase I metabolism.In the current study, male wistar rats were orally administered by brucine (BR) at three dosage levels (3mg/kg/day,15mg/kg/day and 60mg/kg/day) and the high dose of BR combined with glycyrrhetic acid (GA,25mg/kg/day) or liquiritin (LQ,20mg/kg/day) for 7 consecutive days, then the mRNA expression levels of CYP1A2,2E1,2C11 and 3A1 in rat liver were determined by QRT-PCR, Meanwhile, the activities of four CYP450 enzymes (CYP3A,1A2,2E1 and 2C) were determined by Multifunction Microplate Reader and HPLC. The results revealed that compared with the control, medium and high dose of brucine were up-regulated CYP3A1, CYP2E1 mRNA expression, high dose of brucine caused 34.6%and 24.5%decrease for CYP3A-associated testosterone 6β-hydroxylation (6BTesto-OH) and CYP2C-associated tolbutamide hydroxylation (Tol-OH) respectively,146.1%increase for CYP2E1-associated paranitrophenol hydroxylation (PNP-OH) at the high dose level. On the other hand, compared with the high dose of brucine, (BR+GA) were down-regulated CYP3A1, CYP1A2, CYP2E1 mRNA expression, (BR+LQ) were down-regulated CYP3A1, CYP2E1 mRNA expression; (BR+GA) caused 51.4%and 33.5%decrease respectively for CYP2E1-associated PNP-OH and CYPlA2-associated ethoxyresorufin-O-deethylation (EROD) as compared with the high dose of BR group. Meanwhile, (BR+LQ) caused 41.1% decrease for CYP2E1-associated PNP-OH and 37.7%increase for CYP2C-associated Tol-OH. Taken together, Our results demonstrated that the co-administration of BR with GA or LQ had effect on mRNA expression and activities of the CYP450 enzymes mentioned above in some extent, so the antagonism of LQ on BR-induced CYPs adverse effects, and the inhibitory action of GA on CYP2E1 and CYP1A2 might play an important role in the detoxification of Radix glycyrrhizae against Strychnos nuxvomica L.