Malaria is a global risk to 3.2 billion people. Recently, dried leaves of Artemisia annua (DLA) were shown an effective alternative to current artemisinin combination therapy (ACTs). Oral bioavailability of artemisinin (AN) delivered as DLA in mouse studies was >40 times higher than pure AN resulting partially from increased solubility and significantly higher intestinal permeability than pure AN. The liver is the main site of first-pass drug metabolism, so its role is crucial to understanding bioavailability. The cytochrome P450 (CYP) isoform, CYP2B6, is the major AN metabolizing enzyme in the liver. CYP3A4 plays a lesser role in AN metabolism, but is vital to drug-drug interactions (DDIs). Little information exists on how DLA affects activity and expression of either CYP2B6 or CYP3A4. Using human liver microsomes and HepaRG cells we will compare effects of pure AN with DLA-AN on CYP2B6 and CYP3A4 activity and expression. In vivo information is lacking on how po- delivered AN vs. AN from DLA distributes in the body in response to gender; the LD50 for AN in females is twice that of males.
Our Aims : 1. How do A. annua extracts and phytochemicals inhibit CYP2B6 and CYP3A4 activity? Positing that DLA extracts (DLAe) and individual phytochemicals from DLA inhibit activity of CYP2B6 and/or CYP3A4, we will use human liver microsomes, CYP inhibition assays, DLAe prepared from 3 DLA cultivars in 3 solvents and specific phytochemicals from DLA and measure their ability to inhibit CYP activity. 2. How do A. annua extracts and phytochemicals alter induction of CYP2B6 and CYP3A4? Positing that CYP2B6 expression will decrease when cells are treated with DLAe or the phytochemicals used in Aim 1 we will use HepaRG Cells, CYP induction assays, qPCR, and DLA extracts from Aim 1 to measure transcripts of the 2 target CYPs. 3. Compare DLA with AN on ADME and inflammatory responses in female rats. Hypothesis: We are completing an ADME and inflammation comparison between AN delivered po via DLA or as pure drug in male rats. We will repeat those studies in females to determine if there are gender differences. Most AN in vivo studies are done in male rodents and while there is a gender difference in the AN LD50 of 1,100 mg/kg for males and 2,000 mg/kg for females, data are otherwise scarce. While this Aim is not directly related to liver metabolism, we will measure drug distribution in organs including the liver and beyond. Drug distribution patterns in all male measured organs are significantly different for AN vs. DLA. After po delivery of DLA or AN to female rats, we will compare AN distribution in organs and excretory material. Using LPS to induce an inflammatory response, we also will compare the level of several inflammation markers post drug delivery. Overall these experiments will inform possible mechanisms by which DLA enhances AN bioavailability, potential hepatic DDIs, organ distribution by gender, thereby providing information for clinicians and scientists that will help predict best chemotypes of A. annua most effective for treating malaria.
Artemisinin (AN), from the plant Artemisia annua (sweet annie), is effective in treating malaria other diseases. AN and the plant also have anti-inflammatory effects. Oral consumption of dried leaves of the plant in a malaria mouse model is at least five and three times more effective, respectively, than pure AN vs. the parasite, and in resilience against emergence of AN drug resistance. Here we will compare AN delivered from plant extracts with pure AN in activity and transcript studies of 2 key liver enzymes: CYP3A4 and CYP2B6. We will also complement in female rats our current study in males to compare tissue distribution of AN from pure drug vs. from plant leaves and measure effects on inflammation markers.
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