Rosita Rodriguez-Proteau

Pharmacokinetics of xanthohumol and metabolites in rats after oral and intravenous administration

SCOPE Xanthohumol (XN), a dietary flavonoid found in hops, may have health-protective actions against cardiovascular disease and type 2 diabetes. Yet, there are limited data on the pharmacokinetics (PK) of XN. This study provides PK parameters for XN and its major metabolites in rats. METHODS AND RESULTS A PK study was conducted in male jugular vein-cannulated Sprague-Dawley rats. Rats (n = 12/group) received an intravenous (IV) injection (1.86 mg/kg BW) or an oral gavage of a low (1.86 mg/kg BW), medium (5.64 mg/kg BW), or high (16.9 mg/kg BW) dose of XN. Plasma samples were analyzed for XN and its metabolites using LC-MS/MS. The maximum concentration (C(max) ) and area under the curve (AUC(0-96 h) ) of total XN (free and conjugated) were 2.9±0.1 mg/L and 2.5±0.3 h*  mg/L in IV group, 0.019±0.002 mg/L and 0.84±0.17 h*  mg/L in the oral low group, 0.043±0.002 mg/L and 1.03±0.12 h*  mg/L in the oral medium group, and 0.15±0.01 mg/L and 2.49±0.10 h*  mg/L in the oral high group. CONCLUSION The bioavailability of XN is dose-dependent and approximately 0.33, 0.13, and 0.11 in rats, for the low-, medium-, and high-dose groups, respectively.

Human pharmacokinetics of xanthohumol, an antihyperglycemic flavonoid from hops

SCOPE Xanthohumol (XN) is a bioactive prenylflavonoid from hops. A single-dose pharmacokinetic (PK) study was conducted in men (n = 24) and women (n = 24) to determine dose-concentration relationships. METHODS AND RESULTS Subjects received a single oral dose of 20, 60, or 180 mg XN. Blood was collected at 0, 0.25, 0.5, 1, 2, 4, 8, 12, 24, 48, 72, 96, and 120 h. Plasma levels of XN and its metabolites, isoxanthohumol (IX), 8-prenylnaringenin (8PN), and 6-prenylnaringenin (6PN) were measured by LC-MS/MS. Xanthohumol (XN) and IX conjugates were dominant circulating flavonoids among all subjects. Levels of 8PN and 6PN were undetectable in most subjects. The XN PK profile showed peak concentrations around 1 h and between 4-5 h after ingestion. The maximum XN concentrations (C(max)) were 33 ± 7 mg/L, 48 ± 11 mg/L, and 120 ± 24 mg/L for the 20, 60, and 180 mg dose, respectively. Using noncompartmental modeling, the area under the curves (AUC(0→∞)) for XN were 92 ± 68 h × μg/L, 323 ± 160 h × μg/L, and 863 ± 388 h × μg/L for the 20, 60, and 180 mg dose, respectively. The mean half-life of XN was 20 h for the 60 and 18 h for the 180 mg dose. CONCLUSION XN has a distinct biphasic absorption pattern with XN and IX conjugates being the major circulating metabolites.

Effects of dietary flavonoids on the transport of cimetidine via P-glycoprotein and cationic transporters in Caco-2 and LLC-PK1 cell models

1. The hypotheses tested were to study cimetidine as a substrate of P-glycoprotein (P-gp) and organic cation transport systems and the modulatory effects of eight flavonoid aglycones and glycosides on these transport systems using Caco-2 and LLC-PK1 cells. 2. Transport and uptake experiments of (20 µM) 3H-cimetidine were performed with and without co-exposure to quercetin, quercetrin, rutin, naringenin, naringin, genistein, genistin, and xanthohumol. Co-treatment decreased basolateral to apical (B to A) permeability (Papp) of cimetidine from 2.02 to 1.24 (quercetin), 1.06 (naringenin), 1.24 (genistein), and 0.96 (xanthohumol) × 10−6 cm s−1 in Caco-2 cells and from 10.76 to 1.65 (quercetin), 2.05 (naringenin), 2.88 (genistein), and 1.95 (xanthohumol) × 10−6 cm s−1 in LLC-PK1 cells. Genistin significantly reduced B to A Papp of cimetidine to 1.24 × 10−6 cm s−1 in Caco-2 cells. Basolateral intracellular uptake rate of cimetidine was enhanced 145–295% when co-treated with flavonoids. Co-treatment with P-glycoprotein and organic cation transporter inhibitors, verapamil and phenoxybenzamine, resulted in reduced B to A permeability and slower basolateral intracellular uptake rate of cimetidine. Intracellular uptake rate of 14C-tetraethylammonium (TEA) was reduced in the presence of quercetin, naringenin and genistein in LLC-PK1 cells. 3. In conclusion, quercetin, naringenin, genistein, and xanthohumol reduced P-gp-mediated transport and increased the basolateral uptake rate of cimetidine. Quercetin, naringenin, genistein, but not xanthohumol, reduced intracellular uptake rate of TEA in LLC-PK1 cells. These results suggest that flavonoids may have potential to alter the disposition profile of cimetidine and possibly other therapeutics that are mediated by P-gp and/or cation transport systems.

Plant polyphenols and multidrug resistance: Effects of dietary flavonoids on drug transporters in Caco-2 and MDCKII-MDR1 cell transport models

The hypothesis tested was that specific flavonoids such as epicatechin gallate, epigallocatechin gallate, genistein, genistin, naringenin, naringin, quercetin and xanthohumol will modulate cellular uptake and permeability (Pe) of multidrug-resistant substrates, cyclosporin A (CSA) and digoxin, across Caco-2 and MDCKII-MDR1 cell transport models. 3H-CSA/3H-digoxin transport and uptake experiments were performed with and without co-exposure of the flavonoids. Aglycone flavonoids reduced the Pe of CSA to a greater extent than glycosylated flavonoids with 30 µM xanthohumol producing the greatest effect (7.2 × 10–6 to 6.6 × 10–7 and 17.9 × 10–6 to 4.02 × 10–6 cm s–1 in Caco-2 and MDCKII-MDR1 cells, respectively); while no measurable effects were seen with digoxin. Xanthohumol significantly demonstrated (1) saturable efflux, (2) increased uptake of 3H-digoxin and (3) decreased uptake of 3H-CSA in the Caco-2 cells. The transport data suggests that xanthohumol effects transport of CSA in a manner that is distinct from the digoxin efflux pathway and suggests that intestinal transport of these MDR1 substrates is more complex than previously reported.

Toxicity Evaluation and Human Health Risk Assessment of Surface and Ground Water Contaminated by Recycled Hazardous Waste Materials

Prior to the 1970s, principles involving the fate and transport of hazardous chemicals from either hazardous waste spills or landfills into ground water and/or surface water were not fully understood. In addition, national guidance on proper waste disposal techniques was not well developed. As a result, there were many instances where hazardous waste was not disposed of properly, such as the Love Canal environmental pollution incident. This incident led to the passage of the Resource Conservation and Recovery Act (RCRA) of 1976. This act gave the United States Environmental Protection Agency regulatory control of all stages of the hazardous waste management cycle. Presently, numerous federal agencies provide guidance on methods and approaches used to evaluate potential health effects and assess risks from contaminated source media, i.e., soil, air, and water. These agencies also establish standards of exposure or health benchmark values in the different media, which are not expected to produce environmental or human health impacts. The risk assessment methodology is used by various regulatory agencies using the following steps: i) hazard identification; ii) dose-response (quantitative) assessment; iii) exposure assessment; iv) risk characterization. The overall objectives of risk assessment are to balance risks and benefits; to set target levels; to set priorities for program activities at regulatory agencies, industrial or commercial facilities, or environmental and consumer organizations; and to estimate residual risks and extent of risk reduction. The chapter will provide information on the concepts used in estimating risk and hazard due to exposure to ground and surface waters contaminated from the recycling of hazardous waste and/or hazardous waste materials for each of the steps in the risk assessment process. Moreover, this chapter will provide examples of contaminated water exposure pathway calculations as well as provide information on current guidelines, databases, and resources such as current drinking water standards, health advisories, and ambient water quality criteria. Finally, specific examples of contaminants released from recycled hazardous waste materials and case studies evaluating the human health effects due to contamination of ground and surface waters from recycled hazardous waste materials will be provided and discussed.

Ketoconazole and the modulation of multidrug resistance-mediated transport in Caco-2 and MDCKII-MDR1 drug transport models

The hypothesis tested was that ketoconazole can modulate P-glycoprotein, thereby altering cellular uptake and apparent permeability (Papp) of multidrug-resistant substrates, such as cyclosporin A (CSA) and digoxin, across Caco-2, MDCKII-MDR1, and MDCKII wild-type cell transport models. 3H-CSA/3H-digoxin transport experiments were performed with and without co-exposure to ketoconazole, and 3H-ketoconzole transport experiments were performed with and without co-exposure to dietary flavonoids, epigallocatechin-3-gallate, and xanthohumol. Ketoconazole (3 µM) reduced the Papp efflux of CSA and digoxin from 5.07 × 10−6 to 2.91 × 10−6 cm s−1 and from 2.60 × 10−6 to 1.41 × 10−6 cm s−1, respectively, in Caco-2 cells. In the MDCKII-MDR1 cells, ketoconazole reduced the Papp efflux of CSA and increased the Papp absorption of digoxin. Cellular uptake of ketoconazole in the Caco-2 cells was significantly inhibited by CSA and digoxin, whereas epigallocatechin-3-gallate and xanthohumol exhibited biphasic responses. In conclusion, ketoconazole modulates the Papp of P-glycoprotein substrates by interacting with MDR1 protein. Epigallocatechin-3-gallate and xanthohumol modulate the transport and uptake of ketoconazole.

MDR1 FUNCTION IS SENSITIVE TO THE PHOSPHORYLATION STATE OF MYOSIN REGULATORY LIGHT CHAIN

Multiple drug resistance protein 1 (MDR1) is composed of two homologous halves separated by an intracellular linker region. The linker has been reported to bind myosin regulatory light chain (RLC), but it is not clear how this can occur in the context of a myosin II complex. We characterized MDR1-RLC interactions and determined that binding occurs via the amino terminal of the RLC, a domain that typically binds myosin heavy chain. MDR1-RLC interactions were sensitive to the phosphorylation state of the light chain in that phosphorylation by myosin light chain kinase (MLCK) resulted in a loss of binding in vitro. We used ML-7, a specific inhibitor of MLCK, to study the functional consequences of disrupting RLC phosphorylation in intact cells. Pretreatment of polarized Madin-Darby canine kidney cells stably expressing MDR1 with ML-7 produced a significant increase in apical to basal permeability and a corresponding decrease in the efflux ratio (threefold; p<0.01) of [(3)H]-digoxin, a classic MDR1 substrate. Together these data show that MDR1-mediated transport of [(3)H]-digoxin can be modulated by pharmacological manipulation of myosin RLC, but direct MDR1-RLC interactions are atypical and not explained by the structure of the myosin II holoenzyme.