Extracts of Immature Orange (Aurantii fructus immaturus) and Citrus Unshiu Peel (Citri unshiu pericarpium) Induce P-Glycoprotein and Cytochrome P450 3A4 Expression via Upregulation of Pregnane X Receptor

Abstract

P-glycoprotein (P-gp) and cytochrome P450 3A4 (CYP3A4) are expressed in the intestine and are associated with drug absorption and metabolism. Pregnane X receptor (PXR) is the key molecule that regulates the expression of P-gp and CYP3A4. Given that PXR activity is regulated by a variety of compounds, it is possible that unknown PXR activators exist among known medicines. Kampo is a Japanese traditional medicine composed of various natural compounds. In particular, immature orange [Aurantii fructus immaturus (IO)] and citrus unshiu peel [Citri unshiu pericarpium (CP)] are common ingredients of kampo. A previous study reported that kampo containing IO or CP decreased the blood concentration of concomitant drugs via upregulation of CYP3A4 although the mechanism was unclear. Some flavonoids are indicated to alter P-gp and CYP3A4 activity via changes in PXR activity. Because IO and CP include various flavonoids, we speculated that the activity of P-gp and CYP3A4 in the intestine may be altered via changes in PXR activity when IO or CP is administered. We tested this hypothesis by using LS180 intestinal epithelial cells. The ethanol extract of IO contained narirutin and naringin, and that of CP contained narirutin and hesperidin. Ethanol extracts of IO and CP induced P-gp, CYP3A4, and PXR expression. The increase of P-gp and CYP3A4 expression by the IO and CP ethanol extracts was inhibited by ketoconazole, an inhibitor of PXR activation. The ethanol extract of IO and CP decreased the intracellular concentration of digoxin, a P-gp substrate, and this decrease was inhibited by cyclosporine A, a P-gp inhibitor. In contrast, CP, but not IO, stimulated the metabolism of testosterone, a CYP3A4 substrate, and this was inhibited by a CYP3A4 inhibitor. These findings indicate that the ethanol extract of IO and CP increased P-gp and CYP3A4 expression via induction of PXR protein. Moreover, this induction decreased the intracellular substrate concentration.

Safety, Efficacy, and Mechanistic Studies Regarding Citrus aurantium (Bitter Orange) Extract and p‐Synephrine

“…Okada et al . () have shown that an ethanol extract of bitter orange (dried immature fruit) induced expression of cytochrome CYP3A4 and P‐glycoprotein in LS180 cells in culture by upregulating pregnane X receptor. Naringin and narirutin were the primary constituents of the extract.…”

“…The flavonoid content of juice from C. aurantium is about one-fifth the flavonoid content of grapefruit juice (Edwards and Bernier, 1996). Okada et al (2017) have shown that an ethanol extract of bitter orange (dried immature fruit) induced expression of cytochrome CYP3A4 and P-glycoprotein in LS180 cells in culture by upregulating pregnane X receptor. Naringin and narirutin were the primary constituents of the extract.…”

Potential Metabolic Drug–Drug Interaction of Citrus aurantium L. (Rutaceae) Evaluating by Its Effect on 3 CYP450

“…A previous study showed that water extract of FA immature increased CYP3A4 protein expression and ethanol extract of FA immature induced CYP3A4 expression via induction of PXR expression ( Okada et al, 2017 ). They speculated that narirutin might be the key constituent increasing PXR expression and CYP3A4 protein expression.…”

Flavonoids from Aurantii Fructus Immaturus and Aurantii Fructus: promising phytomedicines for the treatment of liver diseases

“…It should also be noted that the amount of these ingredients in AFI and AF vary depending on the harvesting time and geographical distribution. These flavonoids are believed to be major bioactive ingredients and have been reported to have hepatoprotective effects [26]. The chemical structures of major flavonoids in AFI and AF are shown in Fig.…”