Inhibitory effects of citrus fruits on cytochrome P450 3A (CYP3A) activity in humans

In Vitro and In Vivo Assessment of Atemoya Fruit (Annona atemoya) for Food-Drug Interactions

BACKGROUND AND OBJECTIVES

Atemoya (Annona atemoya) is increasingly being consumed worldwide because of its pleasant taste. However, only limited information is available concerning possible atemoya-drug interactions. In the present study, the issue of whether atemoya shows food-drug interactions with substrate drugs of the major drug-metabolizing cytochrome P450s (i.e., CYP1A2, CYP2C9, and CYP3A) is addressed.

METHODS

The ability of atemoya juice to inhibit the activities of phenacetin O-deethylase (CYP1A2), diclofenac 4'-hydroxylase (CYP2C9), and midazolam 1'-hydroxylase (CYP3A) was examined in vitro using human and rat liver microsomes. The in vivo pharmacokinetics of phenacetin and metabolites derived from it in rats when atemoya juice or fluvoxamine (a CYP1A2 inhibitor) was preadministered were also investigated.

RESULTS

Atemoya juice significantly inhibited CYP1A2 activity in human liver microsomes, but not the activities of CYP2C9 and CYP3A. In spite of this inhibition, preadministration of atemoya had no effect on the pharmacokinetics of phenacetin, a CYP1A2 substrate, in rats. Meanwhile, preadministration of fluvoxamine significantly extended the time needed for the elimination of phenacetin, possibly due to the inhibition of CYP1A2. This suggests that the intake of an excess amount of atemoya juice is necessary to cause a change in the pharmacokinetics of phenacetin when the IC₅₀ values for CYP1A2 inhibition by atemoya and fluvoxamine are taken into account.

CONCLUSION

The results indicate that a daily intake of atemoya would not change the pharmacokinetics of CYP1A2 substrates such as phenacetin as well as CYP2C9- and CYP3A-substrate drugs.

Processing grapefruit juice with γ-cyclodextrin attenuates its inhibitory effect on cytochrome P450 3A activity

OBJECTIVES

Grapefruit (Citrus paradisi) juice enhances the oral bioavailability of drugs that are metabolized by intestinal cytochrome P450 3A4 (CYP3A4). Patients are advised to avoid drinking grapefruit juice to prevent this drug-grapefruit juice interaction. The aim of this study was to investigate whether processing grapefruit juice with cyclodextrins (CDs) would result in preventing or inhibiting this interaction.

METHODS

Grapefruit juice and the major furanocoumarins found in grapefruit, bergamottin (BG) and 6', 7'-dihydroxy bergamottin (DHBG) were mixed with α, β and γCDs. The effects of these processed juice samples and furanocoumarins on CYP3A activity were compared with the corresponding values for unprocessed juices and furanocoumarins. Interactions between CDs and these furanocoumarins were also investigated by phase solubility and ¹ H NMR studies.

KEY FINDINGS

The inhibition of CYP3A by grapefruit juice was significantly attenuated by processing particularly with γCD. Similar attenuation effects by γCD were observed in the cases of BG and DHBG. Furthermore, BG and DHBG were suggested to be strongly encapsulated in the cavity of γCD.

CONCLUSION

The encapsulation of BG and DHBG by γCD and the resulting attenuation of the inhibition of CYP3A activity by grapefruit juice may be applicable to juice processing for preventing drug-grapefruit juice interactions.

Interaction between phytotherapy and oral anticancer agents: prospective study and literature review

Cancer is becoming more prevalent in elderly patient. Due to polypharmacy, older adults with cancer are predisposed to drug-drug interactions. There is also an increasing interest in the use of complementary and alternative medicine (CAM). Thirty to seventy percent of patients with cancer have used CAM. Through pharmaceutical counseling sessions, we can provide advices on herb-drug interactions (HDI). All the patients seen in pharmaceutical counseling sessions were prospectively included. Information was collected during these sessions: prescribed medication (oral anticancer agents (OAA) and other drugs), CAM (phytotherapy especially), and use of over-the-counter (OTC) drugs. If pharmacist considered an interaction or an intervention clinically relevant, the oncologist was notified. Then, a literature review was realized to identify the potential HDI (no interactions, precautions for use, contraindication). Among 201 pharmacist counseling sessions, it resulted in 104 interventions related to 46 HDI, 28 drug-drug interactions and 30 others (wrong dosage, omission…). To determine HDI, we review 73 medicinal plants which are used by our patients with cancer and 31 OAA. A total of 1829 recommendations were formulated about 59 (75%) medical plants and their interaction with an OAA. Herb-drug interactions should not be ignored by healthcare providers in their management of cancer patients in daily practice.

Inhibitory Effects of Juices Prepared from Individual Vegetables on CYP3A4 Activity in Recombinant CYP3A4 and LS180 Cells

Human intestinal absorption and drug metabolism vary to a large extent among individuals. For example, CYP3A4 activity has large individual variation that cannot be attributed to only genetic differences. Various flavonoids in vegetables, such as kaempferol and quercetin, possess inhibitory effects, and some vegetable and fruit juices have also been found to inhibit CYP3A4 activity. Therefore, differences in daily intake of flavonoid-containing vegetables may induce individual variation in intestinal bioavailability. To identify a vegetable that strongly inhibits CYP3A4, we investigated the effects of juices, prepared from individual vegetables, on CYP3A4 activity using recombinant CYP3A4 and LS180 cells in this study. Nine vegetable juices (cabbage, Japanese radish, onion, tomato, eggplant, carrot, Chinese cabbage, green pepper, and lettuce), were prepared and recombinant CYP3A4 and LS180 cells were used for evaluation of CYP3A4 activity. Metabolism to 6β-hydroxytestosterone by recombinant CYP3A4 was strongly inhibited by cabbage, onion, and green pepper juices, and cabbage and green pepper juices significantly inhibited CYP3A4 activity in a preincubation time-dependent manner. In addition, CYP3A4 activity in LS180 cells was significantly inhibited by cabbage and onion juices. In conclusion, this study showed that juices prepared from some individual vegetables could significantly inhibit CYP3A4 activity. Therefore, variation in the daily intake of vegetables such as cabbage and onion may be one of the factors responsible for individual differences in intestinal bioavailability.

Phytotherapeutic approach: a new hope for polycyclic aromatic hydrocarbons induced cellular disorders, autophagic and apoptotic cell death

Polycyclic aromatic hydrocarbons (PAHs) comprise the major class of cancer-causing chemicals and are ranked ninth among the chemical compounds threatening to humans. Moreover, interest in PAHs has been mainly due to their genotoxic, teratogenic, mutagenic and carcinogenic property. Polymorphism in cytochrome P450 (CYP450) and aryl hydrocarbon receptor (AhR) has the capacity to convert procarcinogens into carcinogens, which is an imperative factor contributing to individual susceptibility to cancer development. The carcinogenicity potential of PAHs is related to their ability to bind to DNA, thereby enhances DNA cross-linking, causing a series of disruptive effects which can result in tumor initiation. They induce cellular toxicity by regulating the generation of reactive oxygen species (ROS), which arbitrate apoptosis. Additionally, cellular toxicity-mediated apoptotic and autophagic cell death and immune suppression by industrial pollutants PAH, provide fertile ground for the proliferation of mutated cells, which results in cancer growth and progression. PAHs play a foremost role in angiogenesis necessary for tumor metastasization by promoting the upregulation of metalloproteinase-9 (MMP-9), vascular endothelial growth factor (VEGF) and hypoxia inducible factor (HIF) in human cancer cells. This review sheds light on the molecular mechanisms of PAHs induced cancer development as well as autophagic and apoptotic cell death. Besides that authors have unraveled how phytotherapeutics is an alternate potential therapeutics acting as a savior from the toxic effects of PAHs for safer and cost effective perspectives.

Revealing the mechanism of in vitro wound healing properties of Citrus tamurana extract

In the present investigation, we examined the effect of Hyuganatsu (Citrus tamurana) extract (HE) on skin fibroblast (TIG-119) proliferation and migration during in vitro wound healing. HE selectively inhibited proliferation of TIG-119 cells at higher concentration (>1.0 mg/mL); at lower concentrations (0.1, 0.25, 0.5, and 0.75 mg/mL), it exhibited linear and time-dependent cell proliferation. In vitro scratch wound healing studies showed that the HE also accelerated the migration of cells towards the wounded region. Cytometric analysis demonstrated that HE extract did not alter G1/0 and S phases of cell cycle in any concentration studied; however, G2/M phases of cell cycle were significantly (P < 0.05) accelerated at 0.75 mg/mL dose. RT-PCR and Western blotting analysis indicated that HE markedly overexpressed levels of Rac-1, Rho-A, and Cdc-42 mRNA and the respective proteins. Cyclin-dependent kinases (Cdk-1 and -2) gene expression activity was significantly (P < 0.05) increased, but protein content decreased during treatment with HE. The induction of Cdk-1 and -2 by HE was abolished by inhibitors, transcription (DRB), and translation (CHX), implying transcriptional regulation that required de novo protein synthesis.

Sorafenib and sunitinib, two anticancer drugs, inhibit CYP3A4-mediated and activate CY3A5-mediated midazolam 1'-hydroxylation

Sorafenib and sunitinib are novel small-molecule molecularly targeted anticancer drugs that inhibit multiple tyrosine kinases. These medicines have shown survival benefits in advanced renal cell carcinomas as well as in advanced hepatocellular carcinomas and gastrointestinal stromal tumors, respectively. The effects of sorafenib and sunitinib on midazolam 1'-hydroxylation catalyzed by human CYP3A4 or CYP3A5 were investigated. Sorafenib and sunitinib inhibited metabolic reactions catalyzed by recombinant CYP3A4. Midazolam hydroxylation was also inhibited in human liver microsomes harboring the CYP3A5*3/*3 genotype (poor CYP3A5 expressor). In contrast, midazolam 1'-hydroxylation catalyzed by recombinant CYP3A5 was enhanced by the coexistence of sorafenib or sunitinib in a concentration-dependent manner, with saturation occurring at approximately 10 μM. Midazolam hydroxylation was also enhanced in human liver microsomal samples harboring the CYP3A5*1/*1 genotype (extensive CYP3A5 expressor). Sorafenib N-oxidation and sunitinib N-deethylation, the primary routes of metabolism, were predominantly catalyzed by CYP3A4 but not by CYP3A5. The preincubation period of sorafenib and sunitinib before the midazolam addition in the reaction mixture did not affect the enhancement of CYP3A5-catalyzed midazolam hydroxylation, indicating that the enhancement was caused by parent sorafenib and sunitinib. Docking studies with a CYP3A5 homology model based on the structure of CYP3A4 revealed that midazolam closely docked to the heme of CYP3A5 compared with sorafenib or sunitinib, suggesting that these anticancer drugs act as enhancers, not as substrates. Our results thus showed that sorafenib and sunitinib activated midazolam 1'-hydroxylation by CYP3A5 but inhibited that by CYP3A4. Unexpected drug interactions involving sorafenib and sunitinib might occur via heterotropic cooperativity of CYP3A5.

Effects of pomegranate juice on human cytochrome p450 3A (CYP3A) and carbamazepine pharmacokinetics in rats

In this study, we investigated whether components of pomegranate could inhibit CYP3A-mediated drug metabolism. The ability of pomegranate to inhibit the carbamazepine 10,11-epoxidase activity of CYP3A was examined using human liver microsomes, and pomegranate juice was shown to be a potent inhibitor of human CYP3A. Addition of 25 microl (5.0% v/v) of pomegranate juice resulted in almost complete inhibition of the carbamazepine 10,11-epoxidase activity of human CYP3A (1.8%). The inhibition potency of pomegranate juice was similar to that of grapefruit juice. In addition, we investigated the in vivo interaction between pomegranate juice and carbamazepine pharmacokinetics using rats. In comparison with water, the area under the concentration-time curve (AUC) of carbamazepine was approximately 1.5-fold higher when pomegranate juice (2 ml) was orally injected 1 h before the oral administration of the carbamazepine (50 mg/kg). On the other hand, the elimination half-life of carbamazepine and the AUC ratio of carbamazepine 10,11-epoxide to carbamazepine were not altered by the injection of pomegranate juice. These data suggest that pomegranate juice component(s) impairs the function of enteric but not hepatic CYP3A. Thus, we discovered that a component(s) of pomegranate inhibits the human CYP3A-mediated metabolism of carbamazepine. Furthermore, pomegranate juice alters the carbamazepine pharmacokinetics in rats.

POTENT INHIBITION BY STAR FRUIT OF HUMAN CYTOCHROME P450 3A (CYP3A) ACTIVITY

There has been very limited information on the capacities of tropical fruits to inhibit human cytochrome P450 3A (CYP3A) activity. Thus, the inhibitory effects of tropical fruits on midazolam 1'-hydroxylase activity of CYP3A in human liver microsomes were evaluated. Eight tropical fruits such as common papaw, dragon fruit, kiwi fruit, mango, passion fruit, pomegranate, rambutan, and star fruit were tested. We also examined the inhibition of CYP3A activity by grapefruit (white) and Valencia orange as controls. The juice of star fruit showed the most potent inhibition of CYP3A. The addition of a star fruit juice (5.0%, v/v) resulted in the almost complete inhibition of midazolam 1'-hydroxylase activity (residual activity of 0.1%). In the case of grape-fruit, the residual activity was 14.7%. The inhibition depended on the amount of fruit juice added to the incubation mixture (0.2-6.0%, v/v). The elongation of the preincubation period of a juice from star fruit (1.25 or 2.5%, v/v) with the microsomal fraction did not alter the CYP3A inhibition, suggesting that the star fruit did not contain a mechanism-based inhibitor. Thus, we discovered filtered extracts of star fruit juice to be inhibitors of human CYP3A activity in vitro.