St. John's wort對大鼠腸道及肝臟Cytochrome P450活性之影響

Abstract

St. John’s wort（Hypericum perforatum L.）萃取物是目前普遍使用的草藥之一，主要是因為它們有治療輕度至中度憂鬱症活性的報告。然而，在近年的研究中發現，St. John’s wort有影響特定生體轉化第一期單氧酵素cytochrome P450（CYP）的作用，分為長期使用後的CYP促進作用與短期使用後的CYP抑制作用。CYP在藥物代謝中扮演很重要的角色，因此，如對CYP造成促進作用的物質，會造成藥物血中濃度降低，而造成治療失敗，如HIV蛋白酶抑制劑indinavir。 本研究使用週齡14 ± 2（10-20）週以及59 ± 2（54-62）週分別代表年輕與年長的Wistar大鼠，連續餵食低劑量（150 mg/day）或高劑量（300 mg/day）St. John’s wort 15天。藉由分離出肝臟及小腸的微粒體，測定CYP1A的7-ethoxyresorufin O-deethylation（EROD）、CYP2E1的p-nitrophenol hydroxylation（PNPH）及CYP3A的erythromycin N-demethylation（EMND）活性，探討St. John’s wort對CYP活性的作用。實驗發現大鼠肝臟CYP1A的活性在年輕低劑量組有被促進（58.8 ± 11.2 vs. 37.2 ± 12.7 pmol/mg protein/min，p < 0.05），在年長高劑量組也有被促進（109.3 ± 6.8 vs. 57.8 ± 28.8 pmol/mg protein/min，p < 0.05）。肝臟CYP2E1的活性只有在年輕低劑量組會被促進（1.98 ± 0.34 vs. 1.20 ± 0.40 nmol/mg protein/min，p < 0.05）。而大鼠肝臟CYP3A的活性在年輕低劑量組會被促進（0.72 ± 0.11 vs. 0.31 ± 0.07 nmol/mg protein/min，p < 0.001），小腸CYP3A的活性卻不會。本研究進而發現St. John’s wort之促進大鼠肝臟CYP2E1及CYP3A的作用，會受大鼠週齡不同而影響，僅在年輕的大鼠中才有發現促進作用。 以上結果顯示，St. John’s wort確實有促進大鼠肝臟特定CYP的作用，而沒有促進大鼠小腸CYP3A的作用。而在不同週齡與不同劑量時，其促進作用之程度並不相等。綜合本實驗室近年研究St. John’s wort與indinavir的交互作用，推測除了CYP之外還有其他重要因素及機轉，影響此交互作用。

St. John’s wort (Hypericum perforatum L.) extract is one of the most commonly used herbal medications, mainly because of their activity in treating mild to moderate depression. In the recent study, St. John’s wort has the long-term inductive and short-term inhibitive effects of regulating some of the biotransformation phase I monooxygenase, cytochrome P450 (CYP). CYP plays an important role in drug metabolism. Therefore, the matter which has the inductive effects of CYP is able to reduce plasma concentrations of certain drugs, like HIV protease inhibiter, indinavir, to make the treatment fail. Oral administration of either low dose (150 mg/day) or high dose (300 mg/day) St. John’s wort extracts for 15 days was given to the 14±2 (10-20) and 59±2 (54-62) weeks old (representing the young-adult and aged group, respectively) Wistar rats in our research. The activities of 7-ethoxyresorufin O-deethylation (EROD) of CYP1A, p-nitrophenol hydroxylation (PNPH) of CYP2E1, and erythromycin N-demethylation (EMND) of CYP3A in isolated hepatic microsome and intestinal microsome were determined for investigating the effect of St. John’s wort on CYP. We found that the hepatic CYP1A activities were induced in the young-adult low dose group (58.8 ± 11.2 vs. 37.2 ± 12.7 pmol/mg protein/min，p < 0.05) and the aged high dose group (109.3 ± 6.8 vs. 57.8 ± 28.8 pmol/mg protein/min，p < 0.05). The induction of hepatic CYP2E1 activity was only found in young-adult low dose group (1.98 ± 0.34 vs. 1.20 ± 0.40 nmol/mg protein/min，p < 0.05). CYP3A in liver, not intestine, could be induced in young-adult low dose group (0.72 ± 0.11 vs. 0.31 ± 0.07 nmol/mg protein/min，p < 0.001). However, when we discover that St. John’s wort only induces the hepatic CYP in young-adult rats, there are some differences between the inductive effects of St. John’s wort on hepatic CYP, especially CYP2E1 and CYP3A, in young-adult rats and aged rats. According to the results, it demonstrated that St. John’s wort can induce the activity of hepatic CYP but not intestinal CYP3A in rats. Either the age of rats or dosage of St. John’s wort might vary the inductive effect of rat hepatic CYP. We combine the results with the recent research in drug interaction of St. John’s wort and indinavir in our lab. Besides CYP, there might be other important factors and mechanisms in this interaction.