Effects On Cytochrome P450 Subtype Enzymes Of Chinese Traditional Medicine PNS And TMPz

Panax notoginoside(PNS)and tetramethylpyrazine (TMPz) are two Chinese traditional medicine which are widely applied to treat blood vessel diseases of heart and brain. At present although pharmacology of them has been developed deeply, there is no report of their effects on CYP450 subtype enzymes. Since these two drugs have been used together more and more, the assessment to the drug's safety and the prediction of inter-drug interactions would be more roundly. In this study, the influences of these two drugs on CYP450 enzymes have been investigated, and the result can be a protocol for the design of more suitable drug administration.In human liver, CYP1A2 and CYP3A4 are the most important subtype enzymes of CYP450, which play a critical role in drug metabolism. Many factors can cause the differences of drug effect and their metabolism through affecting CYP450 activity. It is a known fact that the induction or inhibition on CYP450 isomers by some drugs is highly structure dependent. And the variations in molecular skeletons characterized by differences in spatial configuration, steric hindrance and even their physical and/or chemical properties, including hydropathicity or hydrophobicity, etc., also play important roles in modulating enzyme activities.This study was carried out"by probe drug in vitro"method. Caffeine and Dapsone were selected as the probe drugs of CYP1A2 and CYP3A4, respectively,to investigate the two chinese traditional medicines'influences on CYP 1A2 and CYP3A4 enzymes.The experiments showed that liver microsomes preparated in this study are satisfied with the requirement of it in vitro, through detecting the concentration of protein and P450 in liver microsomes.. The incubation time and the incubation protein concentration are determined as 60 minutes and 1mg/ml respectively through the pre-experimentHPLC-UV method of monitering the concentration of Caffeine and Dapsone was established. The reserved time of metronidazole(internal standard),Caffeine and Dapsone is 5.2,7.5 and 9.7 minutes, respectively. This approach was demonstrated to be suitable in this study through the assessment of the HPLC experimental method, which includes the selectivity, intraday and interday reproducibility, and the detection limits.The results showed that PNS had induction effect on CYP1A2 but no effect on CYP3A4. The t1/2 of Caffeine in PNS and control group were 18.71±1.13 min and 25.04±1.86 min(P<0.001), the t1/2 of Dapsone in PNS and control group were 16.62±0.72 min and 16.48±1.08 min(P=0.8214),respectively. TMPz had no effect on both CYP1A2 and CYP3A4, the t1/2 of Caffeine in TMPz and control group were 27.42±1.42 min and 25.04±1.86 min(P=0.1883), while the t1/2 of Dapsone in TMPz and control group were 15.85±1.30 min and 16.48±1.08 min(P=0.4271),respectively.The effects of the drugs on CYP450 subtype enzymes were different,the combined usage of these two drugs with some other drugs, particularly CYP1A2, and CYP3A4 involved drugs, should be carefully considered, so as to avoiding the potential toxicity and adverse effects, and offering a more exact saftey assessment and a more suitable drug administration.