Effect of Camellia sinensis extract on the expression level of transcription factors and cytochrome P450 genes coding phase I drug-metabolizing enzymes
Abstract
Green tea (Camellia sinensis) is widely used as a popular beverage and dietary supplement
that can significantly reduce the risk of many diseases. Despite the widespread
use of green tea, the data regarding the safety as well as herb-drug interactions are
limited. Therefore, the aim of our study was to assess the influence of standardized
green tea extract (GTE) containing 61% catechins and 0.1% caffeine on the expression
level of rat CYP genes and the corresponding transcription factors expression by realtime
PCR. The findings showed that GTE resulted in a significant decrease of CYP2C6
expression level by 68% (p<0.001). In case of CYP3A1 and CYP3A2, the mRNA levels
were also reduced by extract but in a lesser degree compared to CYP2C6. Simultaneously
the significant increase in the mRNA level of CAR, RXR and GR factors was observed
by 54% (p<0.05), 79% (p<0.001) and 23% (p<0.05), respectively after 10 days
of green tea extract administration. In addition, there was noted a small increase of
CYP1A1 expression level by 21% (p>0.05) was noted. No statistically significant differences
were observed for CYP1A2 and CYP2D1/2. In the same study we observed
an increase in amount of ARNT gene transcript by 27% (p<0.05) in the long-term use.
However, green tea extract showed the ability to stimulate HNF-1α both after 3 and
10 days of treatment by 30% (p<0.05) and 80% (p<0.001), respectively. In contrast,
no change was observed in the concentration of HNF-4α cDNA. These results suggest
that GTE may change the expression of CYP enzymes, especially CYP2C6 (homologue
to human CYP2C9) and may participate in clinically significant interactions with drugs
metabolized by these enzymes.